November 21-25, 2011
Poster Abstracts Book
INDEX - POSTERS
TNT2011
November 21-25, 2011
Canary Islands-Spain
(Please, find your final poster number by looking up your name in the Author Index displayed in the Registration and the Poster Exhibition Areas)
Alphabetical Order (92) Presenting Author
Country
Abdusalyamova
Makhsuda
Tajikistan
Amato
Filippo
Czech Republic
Arias Mediano
Arias Mediano
Biedma Ortiz
Jose Luis
Jose Luis
Rafael
Topic
Student/ Senior
Poster Title
Biosorpsion of antimony, nercury and gold at complex conversion of intractable ores Diamond-Like Carbon (DLC) chemical vapor Low dimensional materials deposition technology: Characterization of DLC nano-layers and Artificial Neural Networks for (nanowires, clusters, process modelling quantum dots, etc.) NanoChemistry
Senior
Student
Spain
Nanomagnetism and Spintronics
Design of Maghemite/Poly(D,L-lactide-coglycolide) Nanoparticles for Magnetic Fluid Hyperthermia
Spain
Nanostructured and nanoparticle based materials
Magnetite/Chitosan Nanocomposite for Magnetic Gemcitabine Targeting to Cancer
Senior
Spain
Nanostructured and nanoparticle based materials
Biodegradable Magnetic Nanomedicine Based on the Antitumor Molecule Tegafur
Student
Magnetosomes for Anticancer Therapies based on 5-Fluorouracil
Student
Senior
Biedma Ortiz
Rafael
Spain
Nanostructured and nanoparticle based materials
Buencuerpo
Jeronimo
Spain
NanoOptics & NanoPhotonics
3D-FDTD Analysis of Absorption Enhancement in Nanostructured Thin Film Solar Cells
Student
Czech Republic
Nanostructured and nanoparticle based materials
Plasma deposition of nanocomposite protective coatings on polymer substrates
Senior
Spain
Nanostructured and nanoparticle based materials
Multifunctional Layers for Safer Aircraft Composites Structures
Student
Bursikova
Chapartegui
Chashchikhin
Chen
Vilma
Maialen
Vladimir
Xuecheng
Russia
Poland
Choi
Seong Soo
Korea
Choi
Seong Soo
Korea
Della Rocca
Maria Luisa
France
Fernandez Martin Eduardo
Spain
Ferrer-Anglada
Spain
NĂşria
TNT2011
Molecular design of a sensor for small analyte Theory and modelling at the molecules based on a dye adsorbed on silica nanoscale nanoclusters and nanopores
Student
Nanostructured and nanoparticle based materials
Template based synthesis of different mesoporous carbon nanostructures
Senior
Nanobiotechnologies
Fabrication and Characteristics of Plasmonic Nanopore on the Pyramid for Ultrafast Genome Sequencing
Senior
Dynamical Formation of Plasmonic Nanopore Nanobiotechnologies and its Optical Characteristics Graphene / Carbon nanotubes based nanoelectronics and field Single-wall carbon nanotubes quantum dots fabricated by controlled electromigration emission Nanostructured and nanoparticle based materials Graphene / Carbon nanotubes based nanoelectronics and field emission
Senior
Senior
Nanostructured GMI multilayers deposited onto flexible substrates for low pressure sensing
Student
Flexible Transparent Electrodes Using Carbon Nanotubes
Senior
November 21-25, 2011
Canary Islands-Spain
Spain
Nanostructured and nanoparticle based materials
Self-Sensing behaviour in glass fiber based epoxy laminates using MWCNT
Senior
Gelinsky-Wersing Dagmar
Germany
Nanobiotechnologies
Nanoporous impedimetric fibre sensor for the detection of acute inflammation in wounds
Student
Gómez
Sacha
Spain
Gómez-Navarro
Cristina
Spain
Gaztelumendi
Gong
Idoia
Hao
González Orive
Alejandro
Singapore
Senior
Spain
Nanostructured and nanoparticle based materials
Electrochemical Synthesis and Delivery of Melanin Covered Gold Nanoparticles and Catalytic Activity
Student
Nanomagnetism and Spintronics
Thermal relaxation and energy barriers near vortex nucleation field in circular permalloy dot arrays
Senior
Application of 3D laser nanolithography to the fabrication of photonic crystals
Senior
Tunable graphene bandgaps from superstrate mediated interactions
Senior
Spain
Haberko
Jakub
Switzerland
Hague
James
United Kingdom
Spain
Hierro Rodríguez Aurelio
Spain
Jones
United Kingdom
Gavin
Kaasbjerg
Kalenczuk
Kristen
Ryszard
Denmark
Poland
Kang
Dae Joon
Korea
Karamitaheri
Hossein
Austria
Kiessling
Anja
Germany
Kim
Duckjong
Korea
Kim
Duckjong
Korea
Knotek
Petr
TNT2011
Senior
The study of indium zinc oxide, a material that can combine with porous silicon to form white light emitting diodes
Konstantin
Cristina
Senior
Nanostructured and nanoparticle based materials
Guslienko
Hermosa
Theory and modelling at the On the use of Artificial Neural Networks in nanoscale Electrostatic Force Microscopy Graphene / Carbon nanotubes based Discriminating chemically derived graphene nanoelectronics and field conductivity through Electrostatic Force emission Microscopy
Czech Republic
NanoOptics & NanoPhotonics Graphene / Carbon nanotubes based nanoelectronics and field emission
Low dimensional materials Highly electrical conductive, ultralarge and well(nanowires, clusters, quantum dots, etc.) ordered MMX nanorods Tailoring the magnetization states in thickness modulated NdCo5 films with perpendicular magnetic anisotropy.
Nanomagnetism and Spintronics Graphene / Carbon nanotubes based nanoelectronics and field Surface Potential Variations in Graphene emission Induced by Crystalline Ionic Substrates
Low dimensional materials (nanowires, clusters, quantum dots, etc.) Phonon-limited mobility in single-layer MoS2 Nanostructured and nanoparticle based materials
Student
Student
Senior
Advances in magnetic silica nanotubes preparation and characterization
Senior
Ferroelectric-gate Field Effect Transistors Based Nonvolatile Memory Devices Using p-type Si Nanowire Conducting Channel
Senior
Other Graphene / Carbon nanotubes based nanoelectronics and field Transport Gap Engineering in Zigzag Graphene emission Nanoribbons Nanostructured and nanoparticle based materials
Student
Student
SiC formation in carbon nanotubes grown from permalloy catalyst particles
Student
Other
Raman characterization of heat spreading in carbon nanotube film
Senior
Other
High power carbon nanotube heater
Senior
SPM
Utilization of Mechanical Properties´ Imaging for Detection of Au-nanospheres Used as Biomarkers
Senior
November 21-25, 2011
Canary Islands-Spain
Kohout
Jaroslav
Czech Republic
Kondov
Ivan
Germany
Kroes
Jaap
Switzerland
Kvashnin
Dmitry
Russia
Lahoz
Fernando
Spain
Nanomagnetism and Spintronics
Effects of surface in epsilon-Fe2O3 nanoparticles
Theory and modelling at the Integrated Services for Multiscale Materials nanoscale Modelling and Simulation Graphene / Carbon nanotubes based nanoelectronics and field DFT studies of hydrogenated and defective carbon nanotubes emission Graphene / Carbon nanotubes based The strong influence of configurations of nanoelectronics and field graphane islands to electronic properties of emission graphene/graphane mixing structure
Senior
Senior
Student
Senior
NanoOptics & NanoPhotonics
Time resolved fluorescence characterization of oligo(p-phenylene ethynylene) based metallic nanorods.
Senior
Senior
Langecker
Jens
Czech Republic
Other
9,12-Dithiol-1,2-dicarba-closo-dodecaborane as building block for ligands for surfaces, nanoparticles and metal complexes
Lebar Bajec
Iztok
Slovenia
Other
Two-layer synchronized ternary quantum-dot cellular automata wire crossings
Senior
Nanostructured and nanoparticle based materials
Carbon Nanoflake/ Tin Oxide Composites Gas Sensors for NH3 Detection
Senior
Netherlands
Nanobiotechnologies
Single Walled Carbon Nanotubes as a Scaffold to Concentrate DNA for Studying DNA-Protein Interactions
Senior
Poland
Nanostructured and nanoparticle based materials
Size of the single domain magnetite particles and MRI parameters
Student
Nanofabrication tools & nanoscale integration
Low energy ion beam fabrication of ultra smooth and sharp AFM nanotips from single crystal diamond rods
Student
Silver-functionalized carbon nanofibers composite electrodes for Ibuprofen detection
Senior
Lee
Soo-Keun
Liu
Zunfeng
Maciejewska
Mahmud
Barbara
Syeda Faria
Korea
Japan
Manea
Florica
Romania
Martin-Gondre
Ludovic
Spain
Matys
Sabine
Germany
Michalska
Martyna
Poland
Mijowska
Ewa
Poland
Miranda
Alvaro
Spain
Mononen
Robert Matias Estonia
Naderi
Fereshteh
Iran
Nikulina
Elizaveta
Spain
TNT2011
Nanostructured and nanoparticle based materials
Theory and modelling at the Energy dissipation channels in the reflection and nanoscale adsorption of nitrogen on Ag(111) Nanostructured and nanoparticle based materials Nanostructured and nanoparticle based materials Graphene / Carbon nanotubes based nanoelectronics and field emission
Bio-sensing of arsenic by S-layer-modified gold nanoparticles
Senior
Dispersion of multiwall carbon nanotubes in aqueous suspensions
Student
Carbon Nanotubes separation techniques Âą efficiency and selectivity.
Senior
Theory and modelling at the NH_3 Molecular Doping of Silicon Nanowires in nanoscale the [112], [110], [100] and [111] directions Nanostructured and nanoparticle based materials
NanoChemistry Nanofabrication tools & nanoscale integration
Senior
Senior
Enhanced tensile strength of thick dielectrophoretic carbon nanotube fibers by TiO2 infiltration
Student
Atomic Structural and electronic properties of some derivatives of C20
Senior
Electron-beam-induced cobalt deposition
Senior
November 21-25, 2011
Canary Islands-Spain
Nowakowska
Sylwia
Switzerland
NanoChemistry
Self Assembly of Acetylene-Appended Porphyrin on Au(111) and cycloaddition of 7,7,8,8Tetracyano-p-quinodimethane (TCNQ) visualized by Scanning Tunneling Microscopy
Nowakowski
Jan
Switzerland
NanoChemistry
Assembly of 2D ionic layers by reaction of alkali halides with an organic electrophile ± TCNQ
Student
Peña-Méndez
Eladia María
Spain
NanoChemistry
Gold (III) and gold nanoparticles interactions with humic acids
Senior
Stability and relaxivity of magnetic particles suspensions improved through a simple structural reorganization
Student
Scanning tunneling microscopy and spectroscopy on edges of epitaxial graphene/Ir(111)
Senior
Direct Observation of Electron Confinement in Epitaxial Graphene Nanoislands
Senior
Nanocalorimetry: a new way to study explosives
Senior
Charge specific CdSe/ZnS quantum dots enhance amyloid fibrillization of human insulin protein in physiological conditions
Student
Pflipsen
Chrystel
Belgium
Phark
Soo-hyon
Germany
Phark
Soo-hyon
Germany
Piazzon
Nelly
France
Poly
Simon
Spain
Pons
Miquel
Spain
Pop
Aniela
Prima Garcia
Puente
Helena
Antonio
Rauwel
Erwan
Romania
Spain
Spain
Nanomagnetism and Spintronics Graphene / Carbon nanotubes based nanoelectronics and field emission Graphene / Carbon nanotubes based nanoelectronics and field emission
Other
Nanobiotechnologies
Theory and modelling at the Generation of Coulomb Matrix Elements for the nanoscale 2D Quantum Harmonic Oscillator
Student
Student
Nanostructured and nanoparticle based materials
Copper-decorated carbon nanotubes based composite electrodes for non-enzymatic detection of glucose
Senior
Nanomagnetism and Spintronics
Prussian Blue Analogue thin films as promising materials of future molecule-based spintronic devices
Senior
Low dimensional materials (nanowires, clusters, Quantum dot addition energies: magnetic field quantum dots, etc.) and interaction screening
Norway
NanoOptics & NanoPhotonics
Unusual photoluminescence of undoped hafnia perovskite nanoparticles synthesized via nonaqueous sol-gel process
Senior
Senior
Rauwel
Erwan
Norway
Nanostructured and nanoparticle based materials
Remes
Adriana
Romania
Nanostructured and nanoparticle based materials
&RQIRUPDO FRDWLQJ RI QDQRSRURXV Ȗ-alumina using Atomic layer deposition: Spinel formation and luminescence induced by rare-earth doping Preparation and application of electrochemical sensor based on Ag-doped synthetic zeolite modified multiwall carbon nanotube electrode for arsenic detection
Nanostructured and nanoparticle based materials
Application of Bare Gold Nanoparticles in OpenTubular CEC Separations of Polyaromatic Hydrocarbons
Senior
Interaction between dipole emitters and 2D plasmonic nanoparticle arrays
Student
Change of geometry of ECAP channel to increase deformation intensity by SPD process AlMn1Cu alloy
Senior
Rezanka
Pavel
Czech Republic
Rodrigues
Sean
United States
Rusz
Stanislav
Sabater Piqueres Carlos
Sato
Yoshiko
TNT2011
Czech Republic
Spain
Japan
NanoOptics & NanoPhotonics Nanostructured and nanoparticle based materials
Low dimensional materials Formation of Stable Metallic Nanocontacts by (nanowires, clusters, mechanical annealing quantum dots, etc.) NanoOptics & NanoPhotonics
Surface smoothening of single crystal diamond chip by 0.50-3.0 keV Oxygen ion beam for XFEL projection optics
November 21-25, 2011
Senior
Student
Student
Student
Canary Islands-Spain
Segura
Rodrigo
Chile
Sorokin
Pavel
Russia
Stassi
Stefano
Italy
Tilocca
Antonio
United Kingdom
Nanostructured and nanoparticle based materials Graphene / Carbon nanotubes based nanoelectronics and field emission Nanostructured and nanoparticle based materials
Filling carbon nanotube membranes with Pd and TiO2
Senior
Ultrathin diamond nanofilms as possible twodimensional insulators for future nanoelectronics
Senior
Evaluation of different conductive nanostructured particles as filler in smart piezoresistive composites
Student
Theory and modelling at the Molecular Dynamics models of a bioactive glass nanoscale nanoparticle
Senior
Optical properties of high-performance liquid crystal-xerogel microcomposite electro-optical films
Student
Timusk
Martin
Estonia
Torrellas
Germán
Spain
Nanobiotechnologies
Twist-radial oscillations resonance effects in double-stranded DNA chains
Student
Umemura
Kazuo
Japan
Nanobiotechnologies
Comparative study of DNA±carbon nanotube hybrids using atomic force microscopy
Senior
Valtr
Miroslav
Czech Republic
SPM
Voice coil based scanning probe microscopy
Senior
Velázquez García José Joaquín Spain
Velázquez García José Joaquín Spain
Other
Low dimensional materials (nanowires, clusters, Photoluminescence of Ag and Li nanoclusters quantum dots, etc.) dispersed in glass host Nanostructured and nanoparticle based materials
Veverková
Lenka
Czech Republic
Villamor
Estitxu
Spain
Nanomagnetism and Spintronics
Yokoyama
Mami
Japan
NanoChemistry
Zaveta
Karel
Czech Republic
Zhukova
Valentina
Spain
Zvatora
Pavel
TNT2011
Czech Republic
NanoChemistry
Multiphase SiO2-SnO2-LaF3 nanostructured glass-ceramics for simultaneous UV and NIR solar spectrum conversion Effect of gold and silver nanoparticles on interactions of porphyrin-brucine conjugates with oxoanions NO3-. H2PO42-, SO42-, ClO3-, ClO4, HCO3-, ReO4-
Student
Student
Student
Optimization of spin injection in Lateral Spin Valves
Student
DFT calculation for OH group around Pd on Smodified Au(111)
Student
Other
Superparamagnetic transition in nanoparticles of iron oxides
Senior
Nanomagnetism and Spintronics
Magnetic and transport properties of granular CoCu glass-coated microwires
Senior
Nanomagnetism and Spintronics
Structural and magnetic properties of nanocrystalline lanthanum ± strontium manganese perovskites
Student
November 21-25, 2011
Canary Islands-Spain
Poster Contributions by Topics (92)
Presenting Author
Country
Poster Title
TOPIC: Carbon Nanotubes Based Nanoelectronics and Field Emission
Della Rocca
Maria Luisa
France
Single-wall carbon nanotubes quantum dots fabricated by controlled electromigration
Ferrer-Anglada
Núria
Spain
Flexible Transparent Electrodes Using Carbon Nanotubes
Gómez-Navarro
Cristina
Spain
Discriminating chemically derived graphene conductivity through Electrostatic Force Microscopy
Hague
James
United Kingdom
Tunable graphene bandgaps from superstrate mediated interactions
Jones
Gavin
United Kingdom
Surface Potential Variations in Graphene Induced by Crystalline Ionic Substrates
Karamitaheri
Hossein
Austria
Transport Gap Engineering in Zigzag Graphene Nanoribbons
Kroes
Jaap
Switzerland
DFT studies of hydrogenated and defective carbon nanotubes
Kvashnin
Dmitry
Russia
The strong influence of configurations of graphane islands to electronic properties of graphene/graphane mixing structure
Mijowska
Ewa
Poland
Carbon Nanotubes separation techniques ± efficiency and selectivity.
Phark
Soo-hyon
Germany
Scanning tunneling microscopy and spectroscopy on edges of epitaxial graphene/Ir(111)
Phark
Soo-hyon
Germany
Direct Observation of Electron Confinement in Epitaxial Graphene Nanoislands
Sorokin
Pavel
Russia
Ultrathin diamond nanofilms as possible two-dimensional insulators for future nanoelectronics
TOPIC: Low-Dimensional Materials
Amato
Filippo
Czech Republic
Diamond-Like Carbon (DLC) chemical vapor deposition technology: Characterization of DLC nano-layers and Artificial Neural Networks for process modelling
Hermosa
Cristina
Spain
Highly electrical conductive, ultralarge and well-ordered MMX nanorods
Kaasbjerg
Kristen
Denmark
Phonon-limited mobility in single-layer MoS2
Puente
Antonio
Spain
Quantum dot addition energies: magnetic field and interaction screening
Sabater Piqueres
Carlos
Spain
Formation of Stable Metallic Nanocontacts by mechanical annealing
TOPIC: Nanobiotechnologies Choi
Seong Soo
Korea
Fabrication and Characteristics of Plasmonic Nanopore on the Pyramid for Ultrafast Genome Sequencing
Choi
Seong Soo
Korea
Dynamical Formation of Plasmonic Nanopore and its Optical Characteristics
TNT2011
November 21-25, 2011
Canary Islands-Spain
Presenting Author
Country
Poster Title
Gelinsky-Wersing
Dagmar
Germany
Nanoporous impedimetric fibre sensor for the detection of acute inflammation in wounds
Liu
Zunfeng
Netherlands
Single Walled Carbon Nanotubes as a Scaffold to Concentrate DNA for Studying DNA-Protein Interactions
Poly
Simon
Spain
Charge specific CdSe/ZnS quantum dots enhance amyloid fibrillization of human insulin protein in physiological conditions
Torrellas
Germán
Spain
Twist-radial oscillations resonance effects in double-stranded DNA chains
Umemura
Kazuo
Japan
Comparative study of DNA±carbon nanotube hybrids using atomic force microscopy
Velázquez García
José Joaquín
Spain
Photoluminescence of Ag and Li nanoclusters dispersed in glass host
TOPIC: Nanochemistry
Abdusalyamova
Makhsuda
Tajikistan
Biosorpsion of antimony, nercury and gold at complex conversion of intractable ores
Naderi
Fereshteh
Iran
Atomic Structural and electronic properties of some derivatives of C20
Nowakowska
Sylwia
Switzerland
Self Assembly of Acetylene-Appended Porphyrin on Au(111) and cycloaddition of 7,7,8,8-Tetracyano-p-quinodimethane (TCNQ) visualized by Scanning Tunneling Microscopy
Nowakowski
Jan
Switzerland
Assembly of 2D ionic layers by reaction of alkali halides with an organic electrophile ± TCNQ
Peña-Méndez
Eladia María
Spain
Gold (III) and gold nanoparticles interactions with humic acids
Veverková
Lenka
Czech Republic
Effect of gold and silver nanoparticles on interactions of porphyrin-brucine conjugates with oxoanions NO3-. H2PO42-, SO42-, ClO3-, ClO4-, HCO3-, ReO4-
Yokoyama
Mami
Japan
DFT calculation for OH group around Pd on S-modified Au(111)
TOPIC: Nanofabrication Tools and Nanoscale Integration Mahmud
Syeda Faria
Japan
Low energy ion beam fabrication of ultra smooth and sharp AFM nanotips from single crystal diamond rods
Nikulina
Elizaveta
Spain
Electron-beam-induced cobalt deposition
TOPIC: Nanomagnetism and Spintronics
Arias Mediano
Jose Luis
Spain
Design of Maghemite/Poly(D,L-lactide-co-glycolide) Nanoparticles for Magnetic Fluid Hyperthermia
Guslienko
Konstantin
Spain
Thermal relaxation and energy barriers near vortex nucleation field in circular permalloy dot arrays
Hierro Rodríguez
Aurelio
Spain
Tailoring the magnetization states in thickness modulated NdCo5 films with perpendicular magnetic anisotropy.
Kohout
Jaroslav
Czech Republic
Effects of surface in epsilon-Fe2O3 nanoparticles
Pflipsen
Chrystel
Belgium
Stability and relaxivity of magnetic particles suspensions improved through a simple structural reorganization
Prima Garcia
Helena
Spain
Prussian Blue Analogue thin films as promising materials of future moleculebased spintronic devices
TNT2011
November 21-25, 2011
Canary Islands-Spain
Presenting Author
Country
Poster Title
Villamor
Estitxu
Spain
Optimization of spin injection in Lateral Spin Valves
Zhukova
Valentina
Spain
Magnetic and transport properties of granular Co-Cu glass-coated microwires
Zvatora
Pavel
Czech Republic
Structural and magnetic properties of nanocrystalline lanthanum Âą strontium manganese perovskites
TOPIC: NanoOptics & NanoPhotonics
Buencuerpo
Jeronimo
Spain
3D-FDTD Analysis of Absorption Enhancement in Nanostructured Thin Film Solar Cells
Haberko
Jakub
Switzerland
Application of 3D laser nanolithography to the fabrication of photonic crystals
Lahoz
Fernando
Spain
Time resolved fluorescence characterization of oligo(p-phenylene ethynylene) based metallic nanorods.
Rauwel
Erwan
Norway
Unusual photoluminescence of undoped hafnia perovskite nanoparticles synthesized via non-aqueous sol-gel process
Rodrigues
Sean
United States
Interaction between dipole emitters and 2D plasmonic nanoparticle arrays
Sato
Yoshiko
Japan
Surface smoothening of single crystal diamond chip by 0.50-3.0 keV Oxygen ion beam for XFEL projection optics
TOPIC: Nanostructured and Nanoparticle Based Materials
Arias Mediano
Jose Luis
Spain
Magnetite/Chitosan Nanocomposite for Magnetic Gemcitabine Targeting to Cancer
Biedma Ortiz
Rafael
Spain
Biodegradable Magnetic Nanomedicine Based on the Antitumor Molecule Tegafur
Biedma Ortiz
Rafael
Spain
Magnetosomes for Anticancer Therapies based on 5-Fluorouracil
Bursikova
Vilma
Czech Republic
Plasma deposition of nanocomposite protective coatings on polymer substrates
Chapartegui
Maialen
Spain
Multifunctional Layers for Safer Aircraft Composites Structures
Chen
Xuecheng
Poland
Template based synthesis of different mesoporous carbon nanostructures
Fernandez Martin
Eduardo
Spain
Nanostructured GMI multilayers deposited onto flexible substrates for low pressure sensing
Gaztelumendi
Idoia
Spain
Self-Sensing behaviour in glass fiber based epoxy laminates using MWCNT
Gong
Hao
Singapore
The study of indium zinc oxide, a material that can combine with porous silicon to form white light emitting diodes
GonzĂĄlez Orive
Alejandro
Spain
Electrochemical Synthesis and Delivery of Melanin Covered Gold Nanoparticles and Catalytic Activity
Kalenczuk
Ryszard
Poland
Advances in magnetic silica nanotubes preparation and characterization
TNT2011
November 21-25, 2011
Canary Islands-Spain
Presenting Author
Country
Poster Title
Kiessling
Anja
Germany
SiC formation in carbon nanotubes grown from permalloy catalyst particles
Lee
Soo-Keun
Korea
Carbon Nanoflake/ Tin Oxide Composites Gas Sensors for NH3 Detection
Maciejewska
Barbara
Poland
Size of the single domain magnetite particles and MRI parameters
Manea
Florica
Romania
Silver-functionalized carbon nanofibers composite electrodes for Ibuprofen detection
Matys
Sabine
Germany
Bio-sensing of arsenic by S-layer-modified gold nanoparticles
Michalska
Martyna
Poland
Dispersion of multiwall carbon nanotubes in aqueous suspensions
Mononen
Robert Matias
Estonia
Enhanced tensile strength of thick dielectrophoretic carbon nanotube fibers by TiO2 infiltration
Pop
Aniela
Romania
Copper-decorated carbon nanotubes based composite electrodes for nonenzymatic detection of glucose
Rauwel
Erwan
Norway
Conformal coatinJ RI QDQRSRURXV Ȗ-alumina using Atomic layer deposition: Spinel formation and luminescence induced by rare-earth doping
Remes
Adriana
Romania
Preparation and application of electrochemical sensor based on Ag-doped synthetic zeolite modified multiwall carbon nanotube electrode for arsenic detection
Rezanka
Pavel
Czech Republic
Application of Bare Gold Nanoparticles in Open-Tubular CEC Separations of Polyaromatic Hydrocarbons
Rusz
Stanislav
Czech Republic
Change of geometry of ECAP channel to increase deformation intensity by SPD process AlMn1Cu alloy
Segura
Rodrigo
Chile
Stassi
Stefano
Italy
Velázquez García
José Joaquin
Spain
Filling carbon nanotube membranes with Pd and TiO2 Evaluation of different conductive nanostructured particles as filler in smart piezoresistive composites Multiphase SiO2-SnO2-LaF3 nanostructured glass-ceramics for simultaneous UV and NIR solar spectrum conversion
TOPIC: Other
Kang
Dae Joon
Korea
Ferroelectric-gate Field Effect Transistors Based Nonvolatile Memory Devices Using p-type Si Nanowire Conducting Channel
Kim
Duckjong
Korea
Raman characterization of heat spreading in carbon nanotube film
Kim
Duckjong
Korea
High power carbon nanotube heater
Langecker
Jens
Czech Republic
9,12-Dithiol-1,2-dicarba-closo-dodecaborane as building block for ligands for surfaces, nanoparticles and metal complexes
Lebar Bajec
Iztok
Slovenia
Two-layer synchronized ternary quantum-dot cellular automata wire crossings
Piazzon
Nelly
France
Nanocalorimetry: a new way to study explosives
TNT2011
November 21-25, 2011
Canary Islands-Spain
Presenting Author
Country
Poster Title
Timusk
Martin
Estonia
Optical properties of high-performance liquid crystal-xerogel microcomposite electro-optical films
Zaveta
Karel
Czech Republic
Superparamagnetic transition in nanoparticles of iron oxides
TOPIC: Scanning Probes Methods Valtr
Miroslav
Czech Republic
Voice coil based scanning probe microscopy
Knotek
Petr
Czech Republic
Utilization of Mechanical Properties麓 Imaging for Detection of Aunanospheres Used as Biomarkers
TOPIC: Theory and Modelling at the Nanoscale
Chashchikhin
Vladimir
Russia
Molecular design of a sensor for small analyte molecules based on a dye adsorbed on silica nanoclusters and nanopores
G贸mez
Sacha
Spain
On the use of Artificial Neural Networks in Electrostatic Force Microscopy
Kondov
Ivan
Germany
Integrated Services for Multiscale Materials Modelling and Simulation
Martin-Gondre
Ludovic
Spain
Energy dissipation channels in the reflection and adsorption of nitrogen on Ag(111)
Miranda
Alvaro
Spain
NH_3 Molecular Doping of Silicon Nanowires in the [112], [110], [100] and [111] directions
Pons
Miquel
Spain
Generation of Coulomb Matrix Elements for the 2D Quantum Harmonic Oscillator
Tilocca
Antonio
United Kingdom
Molecular Dynamics models of a bioactive glass nanoparticle
TNT2011
November 21-25, 2011
Canary Islands-Spain
Biosorpsion of antimony, mercury and gold at complex conversion of intractable ores M.N.Abdusalyamova Institute of Chemistry of Tajik Academy of Science, Ajni Str.299/2,734063 Dushanbe, Tajikistan, amahsuda@mail.ru
With a purpose of new microorganisms extraction, that sorb metals, there was carried out microbiological examination of ore, recieved from this ore concentrates and tails of the lower horizons of Dzhizhikrut deposit. For microorganisms extraction (bacteria, microscopic fungi and actinomycetes) following mediums were used: beef-extract agar (BEA), agarized Ashby medium, Czapek's medium (agarized) and starch-ammonium medium. The method of limiting dilutions was used for quantifying microorganisms. We prepared a suspension of the samples in water, 10 grams of the sample was shaked with 90 ml of sterile water for 5 minutes. There were taken following samples: 1 - Ore initial Sb-3.8%, Hg-0, 4%, Au-2.5g / t:, 2 - Concentrate: 51.5% Sb, 4.1% Hg, Au-6.8g / t, 3-7DLOV 6E • +J J W $X Among them are found bacteria of the genera Bacillus, Mycobacterium, Azotobacter, Pseudomonas and others. Revealed heterotrophic denitrifying bacteria. Dominated among microscopic fungi the genera of Penicillium, Aspergillus, Chaetomium, Fuzarium. Actinomycetes were mostly representatives of the genus of Streptomyces.3 strains of microscopic fungi and 2 strains of actinomycetes were cleaned in a pure culture. Determination of microscopic fungi allowed us to refer them to Aspergillus niger, Aspergillus terreus, Aspergillus fumigatus, and actinomycetes to the genus Streptomyces. These 5 strains were later used in the antimony and mercury biosorption. For the biosorption of antimony and mercury, it was necessary to grow these cultures of microorganisms to produce biomass. Acknowledgements This work was supported by International Science & technology Center(ISTC), #Project T-1598
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Design of Maghemite/Poly(D,L-lactide-co-glycolide) Nanoparticles for Magnetic Fluid Hyperthermia Beatriz Pérez-Artacho, Visitación Gallardo, Mª Adolfina Ruiz, José L. Arias Department of Pharmacy and Pharmaceutical Technology, University of Granada, Spain. jlarias@ugr.es Introduction The interest in using superparamagnetic iron oxide (i.e.., maghemite, -Fe2O3) nanoparticles (NPs) to formulate multifunctional nanoplatforms for biomedical purposes mainly relies in their non-toxic and biodegradable character, and crystalline structure [1]. Crystallinity assures the superparamagnetic behaviour of the nanomaterial, and it will further determine the excellent response of -Fe2O3 towards magnetic gradients which could be used to control the in vivo fate of the nanocomposite (by magnetic guidance), allowing the accumulation of the drug/gene dose into the targeted site. Interestingly, the oscillation of the magnetic moment of such NPs under an alternating electromagnetic gradient will transform them into heaters that could induce a hyperthermia effect against cancer cells [2, 3]. The present investigation is focused on the development of a reproducible technique for the synthesis of maghemite/poly(D,L-lactide-co-glycolide) (core/shell) NPs. Poly(D,L-lactide-co-glycolide) (PLGA) was used as the biocompatible and biodegradable matrix where the -Fe2O3 nanocores were embedded. This FDA-approved polymer will be responsible for the vehiculization of the drug/gene dose. Thus, the therapeutic activity of drug molecules and genes would be significantly enhanced by their incorporation to such magnetic NPs. The coating efficiency of the copolymer around the magnetic cores was analyzed by electron microscopy, infrared absorption spectra, and electrical and thermodynamic surface characterizations of the core/shell NPs, as compared to those of the pure nanomaterials. The internal structure of -Fe2O3/PLGA NPs was characterized by X-ray diffractometry. Finally, the magnetic properties of the nanocomposites were investigated to define its magnetic responsiveness, and their heating property (hyperthermia effect) was also analyzed under the influence of an oscillating electromagnetic gradient. Materials and Methods Superparamagnetic -Fe2O 3 NPs (size 7 nm) were prepared by oxidation of ultrasmall magnetite cores [4]. PLGA NPs were formulated by following a water-in-oil-in-water (w/o/w) double emulsion/solvent evaporation methodology [5]. The synthesis procedure of -Fe2O3/PLGA NPs was equal to the one followed for the preparation of the pure copolymeric NPs, except that the aqueous solution of surfactant agent also contained -Fe2O3 nanocores (6.25 %, w/v). Mean particle diameter was determined in triplicate by PCS. To confirm the size measurements, the nanocomposites were checked by HRTEM and by SEM. FTIR spectrometry was used for the chemical characterization of the NPs. The characterization of the internal structure of -Fe2O3/PLGA NPs was achieved by X-ray diffractometry. Surface electrical properties of the NPs were analyzed by electrophoretic measurements as a function of both pH and KNO3. A surface thermodynamic analysis of the NPs was also carried out using a well-known model [6]. The magnetic properties of the NPs were determined by using a vibrating magnetometer. Finally, the in vitro heating behaviour of the core/shell NPs in a high frequency alternating electromagnetic gradient (frequency and intensity: 250 kHz and 4 kA/m, respectively) was investigated in triplicate at 25.0 0.5 ºC. Results and Discussion -Fe2O3/PLGA nanocomposites were found to be spherical NPs with an average diameter of 135 nm (polydispersity index: 0.283) (figure 1a). It was clear from these pictures that -Fe2O3 cores were satisfactorily embedded into a PLGA matrix. The coating efficiency was further analyzed using FTIR spectrometry, and electrical and thermodynamic surface characterization. For instance, the electrokinetics of the PLGA and -Fe2O3/PLGA NPs were almost indistinguishable, and clearly different from that of -Fe2O3 nanocores (figure 1b). Regarding the thermodynamic analysis, as it is observed in the figure 1c, the hydrophilic nature of -Fe2O3 was modified and the nanocores become hydrophobic (just like the copolymer) when embedded into the PLGA matrix. The comparison of the diffractogram of the core/shell NPs with that of the -Fe2O3 cores confirmed the mineralogical purity of the iron oxide and their high crystallinity, even upon complete coating by the copolymer. This is an important property to assure the superparamagnetic character of the nanocores. Regarding the mechanisms through which the iron oxide nanocores are embedded into the copolymeric network, some arguments could be given if we keep in mind all the information described about the surface characteristics of the NPs. Under the synthesis conditions, we may speak of an attractive electrostatic interaction between the positively charged -Fe2O3 NPs and the negatively charged PLGA matrix. This attraction will tend to concentrate the copolymer in the vicinity of the iron oxide surf ace.
Thermodynamic arguments could also be given: it was determined that the van der Waals and acidbase interactions between -Fe2O3 and the copolymer were neatly attractive. Thus, it would be thermodynamically favorable for the PLGA matrix to remain in contact with the nanocores rather than as isolated entities in water. The magnetic responsiveness and soft magnetic character of the core/shell NPs were determined by the hysteresis cycle. From the linear portions (low field) of the curve we could estimate the initial susceptibility ( i 2.5) and the saturation magnetization ( 206 kA/m). Figure 1d shows the in vitro heating behaviour of a core/shell aqueous magnetofluid in a high frequency alternating electromagnetic gradient. Under the experimental conditions, the oscillation of the magnetic moment of the Fe2O3/PLGA NPs transformed them into heaters. As a result, the temperature of the magnetofluid rose from room temperature to the minimum hyperthermia temperature ( 41 ºC) in 25 min. Interestingly, it has been described that locally heating at this temperature a tumor mass for 30 min is enough to destroy it [3]. Thereafter, the maximum temperature reached 47 ºC after 45 min, being then stabilized until the end of the experiment. Hence, the data proves a good control of the temperature and heat flux, a basic requirement for hyperthermia taking into account that when the temperature rises > 48 ºC, healthy cells surrounding the tumor tissue are expected to be burn and damaged [2]. Conclusions It has been described a reproducible method for preparing magnetically responsive nanocomposites consisting of maghemite nanocores embedded into a poly( D,L-lactide-co-glycolide) matrix. The efficiency of the synthesis procedure is demonstrated by electron microscope analysis, physical chemistry data, and by comparing the thermodynamic and electrophoretic surface properties of the core/shell NPs with those of their components. These nanocomposites may constitute a potential candidate for therapeutic applications, e.g., cancer treatment: they could be tailored to deliver appropriate amounts of a chemotherapy agent specifically into the tumor cells, in combination with a selective hyperthermia effect into the malignant tissue. Acknowledgment Financial support from projects GREIB-PYR 2011-1 (Granada Research of Excellence Initiative on BioHealth, Spain) and PE2008-FQM-3993 (Junta de Andalucía, Spain) is acknowledged. References Weissleder R, Bogdanov A, Neuwelt EA, Papisov M. Adv. Drug Deliv. Rev. 16 (1995) 321. Gonzales M, Krishnan KM. J. Magn. Magn. Mater. 293 (2005) 265. Huber DL. Small 1 (2005) 482. Bee A, Massart R, Neveu S J. Magn. Magn. Mater. 149 (1995) 6. Cózar-Bernal MJ, Holgado MA, Arias JL, Muñoz-Rubio I, Martín-Banderas L, Álvarez-Fuentes J, Fernández-Arévalo M. J. Microencapsul. 28 (2011) 430. [6] van Oss CJ. Interfacial Forces in Aqueous Media, 2nd ed., CRC Press, Boca Raton, USA, 2006. [1] [2] [3] [4] [5]
Figures Figure 1. (a) HRTEM picture of -Fe2O3/PLGA NPs (Inset: SEM photograph of the NPs). (b) Zeta potential ( , mV) of -Fe2O3 -Fe2O3 NPs as a function of KNO3 concentration at pH 4. (c) Solid-liquid interfacial energy of interaction ( GSLS, mJ/m 2) and hydrophobic/hydrophilic character of -Fe2O3, PLGA, and -Fe2O3/PLGA NPs. (d) Heating curve of a -Fe2O3/PLGA magnetofluid (10 mg/mL) exposed to an oscillating electromagnetic gradient.
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3D-FDTD Analysis of Absorption Enhancement in Nanostructured Thin Film Solar Cells J. Buencuerpo, M.L. Dotor, L.E. Mu帽oz and P.A. Postigo IMM-Instituto de Microelectr贸nica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid, Spain
jeronimo.buencuerpo@imm.cnm.csic.es
Summary: Abstract: We investigate 1D-2D photonic crystals for light absorption enhancement on thin film photovoltaics (Si, GaAs and InP) by FDTD. A comparison with RCWA and TMM is presented. The absorption is increased substantially for these systems. OCIS codes: (160.5298) Photonic crystal; (310.6845) Thin film devices and applications; (040.5350) Photovoltaic. Introduction Thin film solar cells solar cells made out of either inorganic/organic material are of an increasin g importance. Despite of their small thickness they can be optimized in order to efficiently use the incident light to improve absorption. Nanostructuration of the surface in form of a periodic pattern like a photonic crystal has been demonstrated to improve them [1]. Nevertheless, a deep understanding on what are the physical mechanisms for the improvement is needed. In order to obtain a deeper insight on these mechanisms, we have developed around the free available software MEEP [2] to model the optical properties of nanostructured solar cells including photonic crystal structures. Three dimensional FDTD simulations have been used to calculate the optical absorption, transmission and reflection on such systems. Comparison with other methods like RCWA and TMM has been also performed. Results The main advantages of using FDTD codes for the modeling of nanostructured solar cells are its rigorous solutions and a higher flexibility for the design of structures. Our calculations have been comp ared with the transfer matrix method (TMM) [3] and the rigorous coupled wave analysis (RCWA) [4], [5] showing compatible results. We have studied nanostructured materials in 1D (nanorods) and in 2D (nanopillars) forming a square lattice photonics crystals, with and without an underlying substrate. Analysis with the polarizations (S-P and pseudo-unpolarized ) and with the angle of incidence has been also evaluated. The materials are simulated realistically using a complex variable refraction index over freq uency. Thicknesses between 100 nm and 1000 nm are studied for crystalline silicon, amorphous silicon, gallium arsenide and indium phosphide. Optical absorption (A=1-R-T) is calculated using monitors for transmission and reflection. As an example, a typical surface-nanostructured layer with a 2D photonic crystal is shown in Fig. 1. The structure in this case is composed of a silicon amorphous substrate with a thickness of 150 nm with nanopillars 150 nm tall. It is compared with the same structure without photonic crystal with a thickness of 300 nm thick and including an anti-reflective coating (ARC) 70 nm thick. There is an improvement in the absorption of the nanopatterned structure despite the mass of absorbing material is only a 60% of the structure without nanostructuration. Absorption is normalized to a perfect absorbing system. For most of the energies of normally incident light the nanopillar photonic crystal surface increases the absorption around a 5% in respect to the same structure without photonic crystal but with an ARC.
References [1] 2009.
, and I. Rey-Stolle, Applied Physics Letters, vol. 94, no. 19, p. 191102,
[2] A. F. Oskooi, D. Roundy, M. Ibanescu, P. Bermel, J. D. Joannopoulos, and S. G. Johnson, Computer Physics Communications, vol. 181, no. 3, pp. 687-702, Mar. 2010. [3] C. Lin and M. L. Povinelli, Optics Express, vol. 17, no. 22, pp. 19371-19381, Oct. 2009. [4] Y. Park et al., Optics Express, vol. 17, no. 16, pp. 14312-14321, 2009. [5] S. Zanotto, M. Liscidini, and L. C. Andreani, Optics Express, vol. 18, no. 5, pp. 4260-4274, Mar. 2010.
Fig. 1. Absorption of the structure shown in the inset (i. Substrate 300 nm with anti-reflective coating d=70nm and metal layer ii. A square lattice of nanopillars with lattice parameter a=450 nm and diameter d=225 nm). (Contribution Poster)
Plasma deposition of nanocomposite protective coatings on polymer substrates 1
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V. Bursikova , J. Lukes , J. Havel , J. Houska , A. Stoica , V. Mocanu
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Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic 2 Praha 6, Czech Republic vilmab@physics.muni.cz
There is a continuing interest in improving methods for deposition of hard coatings having still greater abrasion resistance while also exhibiting improvements in various other physical properties. It is therefore an object of the present work to provide a method for forming protective coatings on the surfaces of plastics such as polycarbonates, having a high level of abrasion resistance, with improved resistance against cracking under exposure to thermal and mechanical stresses. Plasma-chemical methods are generally using a mixture of hard-coating precursors (e.g. organosililicon or organosilazane mixtures with oxygen in the case of transparent coatings) in a high-frequency or corona discharges and depositing the product directly on a plastic substrate as a very thin film. Using this method, thin films with a wide range of mechanical properties can be produced from hard inorganic SiO 2-like to soft polymerlike SiO xCyHz films properties just varying the plasma conditions. Moreover, under specific conditions films with special structures, such nanocomposite SiOCH or nanocomposite SiO 2-containing diamond-like carbon films may be prepared [1-3]. The main objective of the present work was to prepare protective films from hexamethyldisiloxane (C6H18Si20- HMDSO) oxygen mixtures. These types of films are of particular interest in various applications because they exhibit a number of desirable properties: good adherence to polymer substrates, relatively high deposition rate, good transparency to visible radiation, good thermomechanical stability etc. The studied films were prepared by plasma enhanced chemical vapour deposition (PECVD) from HMDSO and oxygen with oxygen-to-HMDSO flow rate ratio (q=Q O2/(QHMDSO+ QO2)) ranging from 0 to 0.95. The substrates were silicon wafers, glass and polycarbonate plates. Capacitive r.f. discharges (13.56 MHz) were generated in a parallel plate reactor . The HMDSO flow rate QHMDSO varied from 3 to 10 sccm, the oxygen flow rate was varied from 0 to 20 sccm. The working pressure was in the range from 1 to 40 Pa depending on q. The applied power P was varied from 50 to 150 W and the negative bias voltage was in the range from 10 to 300 V. The optical properties of the films were studied using ellipsometer. The composition of the films was studied by FTIR, RBS and ERDA techniques. The instrumented indentation technique was used to study the mechanical properties of the films. The morphology of the film surface and the indentation prints was studied by means of Zeiss-Neophot optical microscope, a Nicon SMZ - 2T optical stereomicroscope, a Philips SEM 505 scanning electron microscope and by AFM. The surface energy of the deposited films was calculated from contact angle measurement using See System. Time of flight mass spectrometer equipped with nitrogen laser (337 nm) was used to characterize nanocomposite layers composition via laser desorption ionization (LDI) and/or laser ablation. The stoichiometry of positively or negatively charged species was confirmed via isotopic pattern simulation. The mass spectra of tested material obtained show mainly carbon spectral patterns similar to other carbon -containing materials such as diamond, carbon nanotubes, diamond like carbon, etc. but also several other positively or negatively charged O mSinCoHp species were observed. Inorganic hard-coatings such as silicon dioxide (SiO 2) deposited directly onto plastics such as polycarbonate have performance problems when the system is subjected to stresses produced b y mechanical or thermal effects. These problems are due to the difference in property characteristics of inorganic and plastic materials. We overcame these difficulties developing a very elastic film with nanocomposite character. In Figure 1 there is an example of loading-unloading dependence obtained nanoindentation test. We can see, that the tested film exhibited almost fully elastic behavior, at relatively high indentation depth there was almost no plastic deformation. The deposition conditions suitable for nanocomposite film preparation were achieved due to relatively high HMDSO to oxygen flow rate ratio, which led to the creation of dusty plasma because of the relatively low applied power. The fragmentation of HMDSO molecules during this deposition process was low. The dissociative ionization of the HMDSO molecule and the electron attachment, followed by consecutive ion-neutral reactions led to the creation of high mass anions. These anions were trapped in the plasma and homogeneous reactions finally caused a growth of solid amorphous particles which were incorporated into the growing amorphous SiO xCyHz film. The composite character of the produced film improved its mechanical stability, however the particles embedded in the amorphous SiO xCyHz matrix increased little bit the film roughness as it can be seen on the Figure 2, were an example of AFM
image of the sample surface is shown. The surface energy studies showed that the films have hydrophobic and under optimum plasma conditions even ultrahydrophobic properties. Acknowledgement: The work was supported by the Czech Science Foundation (Project No. 202/07/1669), MSM contract 0021622411, Academy of Science of the Czech Republic and OP R&DI CZ.1.05/2.1.00/03.0086. References [1] L. Martinu, Plasma Pr (1997) 247.
al. Kluwer Academic Publisher
- Surface & coatings technology, 142-144, ( 2001) 449. [3] A.S.S. Sobrinho, N. Sch端hler, J.E. Klemberg-Sapieha, M.R. Wertheimer, M. Andrews and S.C. Gujrathi J. Vac. Sci. Technol. A. 16(4), (1998). Figures
Figure 1 Examples of force-displacement curves obtained using nanoindentation with maximum force of 0.3 mN. the mechanical properties of the sample VI49.
Figure 2 Example of SPM image of the film surface (sample VI49) with sub region roughness analysis indicated by the red square.
Multifunctional Layers for Safer Aircraft Composites Structures M. Chapartegui, A. Iriarte, C. Elizetxea Tecnalia, Mikeletegi 2 E-20009, San Sebastian, Spain maialen.chapartegui@tecnalia.com The objective of the present work is to develop an electrical-thermal conductive material to be used as a heating layer in aircraft ice protection systems. For this purpose, a nanocomposite layer consisting of a polymeric matrix doped with carbon nanotubes (CNT) is developed, which afterwards will be incorporated in the manufacturing process of composite parts. Two alternatives are studied, incorporating different concentrations of multi-walled carbon nanotubes (MWCNT) into epoxy and benzoxazine resins: benzoxazine/MWCNT nanocomposites and epoxy/MWCNT-buckypaper nanocomposites. The materials used for the manufacturing of benzoxazine/MWCNT nanocomposites are Araldite MT35600 benzoxazine resin from Huntsman and Graphistrength C100 multi-walled carbon nanotubes from Arkema. The manufacturing process consists of two main steps: in the first step, MWCNTs are dispersed in benzoxazine resin by means of extrusion with a co-rotating twin-screw extruder; in a second step, the benzoxazine/MWCNT blend is hot-pressed and cured to obtain the nanocomposite film. The MWCNT content of this nanocomposite is 10 wt.%. For the development of epoxy/MWCNT-buckypaper nanocomposites, first a MWCNT buckypaper is manufactured by filtering a nanotube suspension. Graphistrength U100 multi-walled carbon nanotubes from Arkema are used and a 245 buckypaper is obtained. In a second step the buckypaper is infiltrated with epoxy resin in autoclave, using the MTM44-1 epoxy resin film from Advanced Composites Group. A nanocomposite film 40 wt.% MWCNT is obtained. Electrical conductivity and electrothermal heating tests are carried out to evaluate the efficiency of the manufactured nanocomposites as a heating layer. The electrical conductivity is measured using the Van der Pauw four probe method [1-2]. The results reveal that the electrical conductivity of the benzoxazine/MWCNT nanocomposites is in the range of 0.13 to 0.57 S/cm, whereas the electrical conductivity of the epoxy/MWCNT-buckypaper nanocomposites is in the range of 5.2 to 23 S/cm. Therefore, the electrical conductivity of the epoxy/MWCNT-buckypaper nanocomposites is at least one order of magnitude higher than that of the benzoxazine/MWCNT nanocomposites. Electrothermal heating tests are performed at room temperature and at -25 ยบC. The temperature is measured in four points of the specimen using K type thermocouples. In addition, during room temperature tests, an infrared camera is used to capture the distribution of temperatures. The test is performed as follows: an electric current is applied to the specimen, so the temperature starts increasing. When a temperature increase of 35 ยบC is reached, the current is switched off. As can be seen in Figure 1, similar heating rates are observed at -25ยบC and at room temperature. The photographs obtained with the infrared camera and the graphs obtained with the thermocouples reveal that the heat distribution is significantly better for epoxy/MWCNT-buckypaper nanocomposites.
Acknowledgements This work has been carried out within the European Project ACP7-GA-2008-21367, Layers for Safer Aircraft Composites Structures-
References [1] Rosca, I.D, Hoa S.V, Carbon, 47 (2009) 1958-1968. [2] Weiss J.D, Kaplar R.J, Kambour K.E, Solid-State Electron, 52 (2008) 91-98.
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Molecular design of a sensor for small analyte molecules based on a dye adsorbed on silica nanoclusters and nanopores Vladimir Chashchikhin, Elena Rykova, Alexander Bagaturyants Photochemistry Center, ul. Novatorov 7a b.1, Moscow, Russia chashchikhin@gmail.com Quantum-chemical (QC)/molecular dynamics (MD) studies of the interaction of various compounds with fluorescent dyes adsorbed on amorphous silica surfaces are quite important in the design of optical chemical sensors based on adsorbed dyes. Such sensors were proposed for the determination of small molecules by changes in the optical signal (absorption or luminescence spectrum) of a receptor centre (adsorbed dye) upon its interaction with various analytes [1]. QC and MD calculations for such systems can provide an atomic -scale insight into the structure and properties of the receptor centre. The computational results can be used to predict structures; adsorption energies; and changes in the positions, inten sities, and widths of spectral bands of a receptor centre interacting with analyte molecules. We considered a set of both polar and non-polar compounds comprising acetone, ammonia, methanol, ethanol, water, benzene, naphthalene, toluene, and dinitrotoluene. These molecules can form complexes with corresponding sensing components of the sensitive layer (receptor centre). The resulting changes in the absorption or fluorescence spectra provide an output signal of the sensor, so that even rather low concentrations of analytes can be detected [2]. As the indicator dye in this study we used 9-(diphenylamino)acridine (DPAA) adsorbed on a silica substrate, for which we chose different cluster [3] and nanopore models with a diameter from one to several nanometres. Silica clusters were built by MD simulations [4]. To do this, an amorphous SiO2 structure was obtained by simulated annealing of the alpha quartz crystal structure, after which cluster and porous SiO2 structures were cut off from the obtained amorphous struc tuers. We optimised the structures of DPAA/silica/analyte complexes and estimated the interaction energies between the adsorbed dye and analyte molecules and between the dye and the silica surface using a QC DFT-D approach with the PBE0+D functional, including explicit corrections for vdW forces. One of the optimized structures consisting of DPAA , Si 10O 11(OH) 18 (Si10) and ethanol is shown in Figure 1. To determine the effect of silica gel porous surface irregularities on the receptor centre properties, we built model nanopores of different radii. The adsorption of the dye was simulated using genetic algorithms [5]. Next, after cutting off a structure suitable for QC calculations, dye adsorption energies were calculated. The interaction energy of the dye in pores of the lowest investigated diameter reach a maximum value (40 42 kcal/mol, D ~ 1 nm) and decreases with increasing pore size. For pores with a diameter greater than 3 nm, the interaction energies do not differ from similar results for cluster models (25 30 kcal/mol). The construction process is illustrated in Figure 2. The electronic absorption and fluerescencse spectra of molecular complexes were determined by the vertical electron transition energies at the equilibrium geometries of complexes in the ground and excited electronic states. We calculated the positions of the 1st absorption and fluorescence bands in the systems DPAA/silica/analytes and the system without analytes by TDDFT method (PBE0/6-31G**(cc-pVTZ)) [6] and evaluated the displacements of spectra, whose values determine the efficiency of the detecting device. The calculated band shifts are shown in Figure 3 . Another important characteristic of the optical response of a chemical sensor is the shape and the width of the corresponding electronic band. The spectra of adsorbed substances exhibit no rotational structure; therefore, taking into account the vibrational structure should be sufficient in our case. One of the most convenient first-principles approaches to calculating the band shapes in the electronic spectra of complex molecular systems is based on the classical Pekar model [7]. In this model, each electronic transition is broadened into a structureless band of an approximately Gaussian shape due to linear vibronic coupling. In practice, only a single-point evaluation of the excited state gradient is required in this approach. The following data are required from the ground state calculations: equilibrium geometry, nuclear Hessian, harmonic frequencies, and normal modes. These data are calculated by QC methods, such as DFT, DFT-D and TDDFT. The results of calculations of the bands are in good agreement with the experimental data for DPAA in solutions, which leads to the conclusion that the developed approach can be used for the estimation of the shapes of spectral bands in the absorption spectra of organic dyes adsorbed on silica particles and their complexes with analytes . This offers new possibilities for the design of optical chemical sensors on the basis of such systems. The proposed procedure can be used for the preliminary screening of materials (dye + substrate) as receptor centers for optical chemical sensors. It is shown that the DPAA/silica receptor centre can be used to detect compounds in a gas phase by changes in fluorescence and absorption spectra. References
[1] C. McDonagh, C.S. Burke, and B.D. MacCraith, Chem. Rev., 108 (2008) P. 400 422. [2] de Silva A.P., Chem. Rev., 97 (1997) P. 1515 1566. [3] V. Chashchikhin, E. Rykova, and A. Bagaturyants, PCCP., 13 (2011), P. 1440 1447. [4] Feuston B. P. and Garofalini S. H.,Chem. Phys. Lett., 170 (1990), P. 264 270 [5] Grigoriev F.V. et. al., Nanotech. in Russ., 5 (2010), P. 290 298. [6] V. Chashchikhin, E. Rykova, and A. ., Nanotech. in Russ., 6 (2011), P. 579 586 [7] S. I. Pekar, Usp. Fiz. Nauk, 1953, P. 197 252. [8] V. Chashchikhin, E. Rykova, A. Scherbinin, A. Bagaturyants and M. Alfimov, submitted, Jan. 2011
Figure 1. Structure of complexes C2H5OH DPAA Si10. Silicon atoms are given by brown circles; oxygen, by pink; hydrogen, by blue; carbon, by yellow; and nitrogen, by sea-green circles
Figure 3. Band shift of fluorescence (dark blue) and absorption (light purple) spectra of complex DPAA/silica/anaytes corresponded to DPPA/silica system
Figure 2. Stages of modeling complex dye in the pores of the amorphous silica gel: 1) Annealing of alpha quartz, 2) Cutting cylindrical pores (h = 2 nm, R 1 = 0.7 .. 1.5 nm, R 2 = 1 .. 1.8 nm); 3) adsorption of the dye, calculations with using a genetic algorithm and the MD methods; 4) Finding the structure comprising all atoms at a distance from the dye no more than 0.3 nm and subsequent geometry optimization by QC method
Figure 4. Band shapes for complexes (a) analyte DPAA SiH3OH, (b) analyte DPAA Si10 (black line, DPAA Si1(10); red line, complex with ammonia; green line, complex with ethanol; blue line, complex with acetone) and (c) experimental spectrum of DPAA solution in methanol (dark green line) and calculated spectra of isolated DPAA (violet line) and DPAA Si10 complex (black line).
Template based synthesis of different mesoporous carbon nanostructures X. C. Chen, K. Cendrowski, J. Srenscek-Nazzal, R. J. Kalenczuk, Ewa Borowiak-Palen West Pomarina University of Technology, Szczecin, 70-322, Poland xchen@zut.edu.pl Different mesoporous carbon nanomaterials were produced from mesoporous silica templates. In this method, mesoporous carbon nanotube, mesoporous carbon flowers and mesoporous hollow carbon spheres were synthesized with different diameters through CVD reacton in a controlled manner. In these reactions, CTAB was served as carbon seeds for the carbon growth during CVD process. The potential applications such as Lithium ion battery and supercapacitor properties for the mesoporous carbon structures were also studied. The samples have been innestigated via high resolution transmission electron microscopy with EDX, X-Ray Diffraction and BET analysis. References [1] X.C. Chen, K. Cendrowski, J. Srenscek-Nazzal, M. H. R端mmeli, R. J. Kalenczuk, H.M. Chen, P. K. Chu, E. Borowiak-Palen: Colloids and Surfaces A: Physicochemical and Engineering Aspects 377 (2010), 150. [2] S. B. Yoon, J.Y. Kim, J. H. Kim, Y. J. Park, K. R. Yoon, S.K. Park, J.S. Yu: J. Mater. Chem. 17 (2010) 1758. [3] X.C. Chen, K. Kierzek, Z.W. Jiang, H.M. Chen, T. Tang, M. Wojtoniszak, R. J. Kalenczuk, P. K. Chu, E. Borowiak-Palen, J. Phys. Chem. C. 115 (2011), 17717. Figures
Fabrication and Characteristics of Plasmonic Nanopore on the Pyramid For Ultrafast Genome Sequencing a
b
Seong Soo Choi , T. Yamaguchi , M.J. Park
c
a
Department of NanoScience, SunMoon University, Ahsan, Chungnam, 336-708 Korea; b University Instrument Center, SunMoon University, Ahsan, Chungnam c Department of Physics, Korea Military Academy, Seoul,139-799 Korea: sscphy@paran.com
Recently there have been tremendous interests about the nanopore technology due to urgent demands of the ultrafast DNA sequencing device with less than 24 hour diagnosing time and less than $1000 demands by NIH, USA. DNA translocation through a natural hemolysin nanopore with electrical signal detection scheme has been successfully carried out by Dr. Bayley and et al [1, 2]. The solid-state nanopore array using SiN and graphene has also been tried to provide the DNA footprints by others. However, the optical detection technique such as SERS can better characterize the DNA. In this report, the optical characteristics of the nanofabricated plasmonic nanopore with its diameter less than 10 nm will be presented. Initially, the oxide aperture was fabricated followed by metal deposition. The metal 0 2 aperture slit ranging from ~ 10 nm width to 10 nm is obtained. Figure 1 shows the differences of the surface morphology of the FESEM from those of 200 keV TEM due to the nonuniform cylindrical wall. The 5keV FESEM imaging and 200 keV TEM images present the nonuniform structure of the nanopores. In order to get the uniform cyldrical wall of the nanopore, the 30 keV Focused Ga ion beam (FIB) drilling is introduced and the Au diameter of ~50 nm was obtained. In order to better control the size reduction of nanopore less than 10 nm, the electron beam annealing technique is introduced. The pore diameter of ~5 nm or less is obtained using 20 keV electron beam exposure. The probe diameter of the Hitachi S 4800 Type II FESEM is ~ 1 nm and has a maximum current of ~ 2 nA. The temperature rise due to electron beam exposure is linearly dependent upon the electron energy and the current, and inversely proportional to thermal conductivity of the materials [3]. The successive size reduction of the nanopore was also observed for 200 keV using JEOL 2010 TEM [Fig. 2]. [Fig. 3]. This can be atributed to melting of the Au membrane due to electron beam heating effect. In addition, the optical characteristics of the fabricated Au nanopore were measured using Nikon TE inverted microscope with tungsten halogen lamp and Princeton instrument/Acton (Pixie:400, spectroscopic-format CCD). The increasing optical transmittance with decreasing the nanopore size is shown in Fig.4. This extraordinary transmission can be attributed to the optical vortexed photonic flow into the decreasing Au nanoaperture[4]. The nanofabricated device can be utilized as single molecule nanobio sensor and genome sequencing. References [1] G. Maglia, et al, Nature Nanotechnology 4, 437(2009). [2] Cees Dekker and et al, Nature Nanotechnology 2, 209 (2007). Application of electron probes to local chemical and crystallographic analysis , Ph.D. thesis, University of Paris, June 8, 1951. [4] H. F. Schouten, T.D. Visser,, D. Lenstra, H. Blok, Phy.Rev. E 67, 036608(2003)..
Acknowledgements This work has been supported by the Korean Research Foundation under the National Research Laboratory Project, GRL Project (Nanophotonic Integrated Circuits for Ultrafast Processing, K20815000003), and Science Research Center project (Center for Subwavelength Optics).
Figures:
Figure 1. Nanopore images of the samples. The images of the 5 keV SEM for the samples AO5 and A10 does present different images from the images of 200 keV TEM images. This phenomena can be attributed to the nonuniform cylindrical structure of the nanopore, and the different sampling depth for different electron energy of FESEM, and due to the different imaging technique of TEM from that of the SEM.
Figure 2. Dynamic sequence of nanopore closing TEM.(Jeol 2010).
4
Bright Field
(506, 3780)
2
Down 1 ( 560 nm )
using electron beam exposure with 200 keV
(506,
14
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Down 2 ( 6830 nm ) TEM BDP II S10#3-20-1 Date- '11-02-16 Scan time ~ 6 min
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13483) 2
Down 11 (TEM d ~5 nm, S ~ 20 nm ) TEM BDP II S10#3-20-1 Date- '11-05-03 Scan time ~ 6 min
12 10 8
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(506, 252) 0 400
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800
0 400
500
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Figure 3.. Optical transmittance spectra through the Au nano-channel on the pyramid. With decreasing the size from 6830, 580, and 20 nm 2, the peak transmittance has been increased to 252, 3780, and 13483, respectively. The peak position was also shifted.from input peak 678 nm to output peak 550 nm due to surface plasmon resonance.
Dynamical Formation of Plasmonic Nanopore and its Optical Characteristics For Ultrafast Genome Sequencing a
b
c
d
Seong Soo Choi , T. Yamaguchi , M.J. Park , N.K. Park , D.S. Kim
e
a
Department of NanoScience, SunMoon University, Ahsan, Chungnam, 336-708 Korea; b University Instrument Center, SunMoon University, Ahsan, Chungnam c Department of Physics, Korea Military Academy, Seoul,139-799 Korea: d School of Electrical engineering, Seoul National University, Seoul, Korea e School of Physics and Astronomy, Seoul National University, Seoul, Korea sscphy@paran.com, sscphy2010@gmail.com
Recently there have been tremendous interests about the nanopore technology due to urgent demands of the ultrafast DNA sequencing device with less than 24 hour diagnosing time and less than $1000 demands by NIH, USA. DNA translocation through a natural hemolysin nanopore with electrical signal detection scheme has been successfully carried out by Dr. Bayley and et al [1, 2]. The solid -state nanopore array using SiN and graphene has also been tried to provide the DNA footprints by others. However, the optical detection technique such as SERS can better characterize the DNA. In this report, the dynamical sequence of the nanopore formation with video-imaging and the optical characteristics of the nanofabricated plasmonic nanopore will be presented. Initially, the oxide aperture was fabricated 0 2 followed by metal deposition. The metal aperture slit ranging from ~ 10 nm width to 10 nm is obtained. Figure 1 shows the differences of the surface morphology of the FESEM from those of 200 keV TEM due to the nonuniform cylindrical wall. The 5keV FESEM imaging and 200 keV TEM images present the nonuniform structure of the nanopores. In order to get the uniform cyldrical wall of the nanopore, the 30 keV Focused Ga ion beam (FIB) drilling is introduced and the Au diameter of ~50 nm was obtained. In order to better control the size reduction of nanopore less than 10 nm, the electron beam annealing technique is introduced. The pore diameter of ~5 nm or less is obtained using 20 keV electron beam exposure. The probe diameter of the Hitachi S 4800 Type II FESEM is ~ 1 nm and has a maximum current of ~ 2 nA. The temperature rise due to electron beam exposure is line arly dependent upon the electron energy and the current, and inversely proportional to thermal conductivity of the materials [3]. The widening and the reduction of the nanopores depending upon the electron fluences were also observed and videorecorded during 300 keV electron beam exposure. The successive size reduction of the nanopore was also observed for 200 keV using JEOL 2010 TEM [Figure 2]. These can be attributed to melting and evaporation of the Au membrane dependent upon the temperature from electron beam bombardment on the Au membrane. In addition, the optical characteristics of the fabricated Au nanopore were measured using Nikon TE inverted microscope with tungsten halogen lamp and Princeton instrument/Acton (Pixie:400, spectroscopic-format CCD). The increasing optical transmittance with decreasing the nanopore size is shown in Figure 3. The extraordinary transmission can be attributed to the optical vortexed photonic flow into the decreasing the size of the Au nanoaperture[4, 5]. The nanofabricated device can be utilized as single molecule nanobio sensor and genome sequencing. References [1] G. Maglia, et al, Nature Nanotechnology 4, 437(2009). [2] Cees Dekker and et al, Nature Nanotechnology 2, 209 (2007). Application of electron probes to local chemical and crystallographic analysis thesis, University of Paris, June 8, 1951. [4] H. F. Schouten, T.D. Visser,, D. Lenstra, H. Blok, Phy.Rev. E 67, 036608(2003).. [5] M.A. Seo, DaiSik Kim, et al, Nature Photonics 3, 156(2009).
Ph.D.
Acknowledgements This work has been supported by the Korean Research Foundation under the National Research Laboratory Project, GRL Project (Nanophotonic Integrated Circuits for Ultrafast Processing, K 20815000003), and by the National Research Foundation grant (Science Research Center project , 2010-0005839).
Figures:
Figure 1. Nanopore images of the samples. The images of the 5 keV SEM for the samples AO5 and A10 does present different images from the images of 200 keV TEM ima ges. This phenomena can be attributed to the nonuniform cylindrical structure of the nanopore, and the different sampling depth for different electron energy of FESEM, and due to the different imaging technique of TEM from that of the SEM.
Figure 2. Dynamic sequence of nanopore closing TEM(Jeol 2010).
4
Bright Field
(506, 3780)
2
Down 1 ( 560 nm )
using electron beam exposure with 200 keV
(506,
14
TEM BDP II S10#3-20-1 Date- '11-02-16 Scan time ~ 6 min
3
13483)
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Down 11 (TEM d ~5 nm, S ~ 20 nm ) TEM BDP II S10#3-20-1 Date- '11-05-03 Scan time ~ 6 min
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Down 2 ( 6830 nm )
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2 6 4
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(506, 252) 0 400
500
600
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700
800
0 400
500
600
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800
Figure 3. Optical transmittance spectra through the Au nano-channel on the pyramid. With decreasing 2 the size from 6830, 580, and 20 nm , the peak transmittance has been increased to 252, 3780, and 13483, respectively. The peak position was also shifted.from input peak 678 nm to output peak 550 nm due to surface plasmon resonance.
Single-wall carbon nanotubes quantum dots fabricated by controlled electromigration M.L. Della Rocca, P. Petit, C. Feuillet-Palma, C. Sirtori, P. Lafarge Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot-Paris 7, UMR 7162 CNRS 75205 Paris Cedex 13, France maria-luisa.della-rocca@univ-paris-diderot.fr The study of electronic transport in single molecule junctions faces the great difficulty to place a single synthesized molecule between two metallic electrodes. Single-wall carbon nanotubes are giant molecules which can be much more easily manipulated in order to study transport at nanometric scale [1,2]. In this work, we present a new method to fabricate single-wall carbon nanotube (SWNT) quantum dot by a controlled electromigration procedure [3,4]. This offers the possibility to investigate an ultrasmall segment of the nanotube. The device consists of a SWNT coated by a 20 nm-thick, 100 nm-wide metallic wire (Pd) (Fig. 1a). A nanometric sized gap is formed by means of controlled electromigration in the center of the wire resulting in two nanometer spaced electrodes connecting a small portion of SWNT (<10-20 nm) (Fig. 1b). Electronic transport measurements show signatures of quantum dot behavior in the strong coupling limit with a large conductance peak at zero bias which splits at low temperature (Fig. 2). The temperature dependence of such zero bias anomaly indicates that two energy scales are involved. We will discuss the origin of this behavior in the framework of Kondo physics [5]. References [1] J. Nygård, D.H. Cobden, P.E. Lindelof, Nature, 408 (2000) 342. [2] S. Sapmaz, P. Jarillo-Herrero, J. Kong, C. Dekker, L.P. Kouwenhoven, and H.S.J. van der Zant, Phys. Rev. B, 71 (2005) 153402. [3] A. Mangin, A. Anthore, M.L. Della Rocca, E. Boulat, P. Lafarge, Phys. Rev. B, 80 (2009) 235432. [4] J. Moser and A. Batchold, Appl. Phys. Lett., 95 (2009) 173506. [5] L.G.G.V. Dias da Silva, N.P. Sandler, K. Ingersent, and S.E. Ulloa, Phys. Rev. Lett., 97 (2006) 096603. Figures
Fig. 1. a) SWNT coated whit a Pd wire. b) Nanometric sized gap formed by controlled electromigration on the SWNT.
Fig. 2. Zero bias conductance peak splitted at low temperature.
In conclusion, we demonstrate first that excellent GMI response can be obtained from nanostructured multilayers deposited onto a flexible and transparent polymeric substrate. These magnetic nanostructures can be useful for a number of applications as detection of magnetic micro and nano particles in microfluidic chambers that are fabricated using such materials [8]. On the other hand, we have centered in studying the pressure response of the materials deposited. Good pressure sensitivities are obtained at zero magnetic field applied and at MI maximum sensibility magnetic field when the nanostructure element is deposited onto a polymeric substrates. Focusing on possible pressure sensor applications, we have checked that our sensor impedance change due to pressure, is stable when small magnetic field variations are applied. References [1] R. S. Beach and A. E. Berkowitz, Appl. Phys. Lett. 64, 3652 (1994). [2] A. Antonov, S. Gadetsky, A. Granovsky, A. Diachkov, M. Sedova, N. Perov, T. Furmanova, and A. Lagarkov, Physica A, vol. 241, pp. 414 419, 1997. [3] M. A. Correa, F. Bohn, C. Chesman, R. B. da Silva, A. D. C. Viegas and R. L. Sommer , J. Phys. D: Appl. Phys., vol. 43, pp. 295004-7, 2010. [4] L. V. Panina and K. Mohri, Sens. Actuators, A 81, 71 (2000). [5] E. Fernández, A. Garcia-Arribas, S. O. Volchkov, G. V. Kurlyandskaya, and J. M. Barandiaran, IEEE Trans. Magn. 46, 658 (2010). [6] Svalov, A.V. Aseguinolaza, I.R. Garcia-Arribas, A. Orue, I. Barandiaran, J.M. Alonso, J. FernandezGubieda, M.L. Kurlyandskaya, G.V. Magnetics, IEEE Transactions on Magn., vol. 46. pp. 333 336, Feb. 2010. [7] D. de Cos, A. García-Arribas and J. M. Barandiarán, Sens. Actuators A, vol. 115, pp. 368 375, 2004. [8] A. Garcia-Arribas, F. Martínez, E.Fernández, I.Ozaeta, G.V.Kurlyandskaya, A.V. Svalov, J.Berganzo, J.M. Barandiaran, A, in print. Figures: Figure 1
Figure 2
Figure 4
Figure 3
Flexible Transparent Electrodes using Carbon Nanotubes 1
1,2
1
2,3
Núria Ferrer-Anglada , Jordi Pérez-Puigdemont , M.Z. Iqbal , S. Roth 1
Applied Physics Department, Universitat Politècnica de Catalunya, Campus Nort B4, J Girona 1-3, 08034 Barcelona (Catalonia) Spain 2 Max Planck Institute for Solid State research, Heisenbergtrasse 1, 70569 Stuttgart, Germany 3 School of Electrical Engineering, WCU Flexible Nanosystems, Korea University, Seoul, Korea nuria@fa.upc.edu
Flexible conducting thin films are useful for applications in different kind of devices called as sensors, transistors, or transparent electrodes that could be used in photovoltaic solar cells. With this objective we prepared thin single walled carbon nanotubes (SWCNT) networks on a transparent and flexible substrate (PPC) with different SWCNT densities using a very simple spray method [1]. We measured the electric impedance at different frequencies Z(f) in the frequency range from 40 Hz to 20 GHz using two different methods: two-probe method in the range up to 110 MHz and a coaxial (Corvino) [2] method in the range from 10 MHz to 20 GHz, see figure 1. We measured the optical absorption and electrical conductivity in order to optimize the conditions for obtaining optimum performance, films with both high electrical conductivity and transparency , see figure 2. We observe a square resistance from 8,5 to 2 kohm for samples showing 85% to 65% optical transmittance respectively. For some applications we need flexibility and not transparency: for this purpose we deposited a thick film of single walled carbon nanotubes (SWCNT) on a flexible silicone substrate by spray, from an aqueous suspension of SWCNT in SDS, obtaining a flexible conducting electrode. The measured electrical resistance is as low as 200 ohm/square, the impedance is constant from DC up to high frequency. Stretching up to 10% and 20% the electrical resistance increases slightly with the stretching, recovering the initial value for small elongations. The stretching is reversible for elongations up to 10%. We analyzed the stretched and non stretched samples by Raman spectroscopy, and could observe that Raman spectra breathing mode are very sensitive to the stretching. The high energy Raman modes are not changed, then we are not introducing defects when stretching. In both cases, using selected metallic carbon nanotubes could enhance electrical conductivity by a factor from 5 to 10 [4], increasing the film performance. Also previous carbon nanotubes purification will enhance the transparency. Recent results using graphene to obtain flexible transparent electrodes are much successful [5], their obtained samples show sheet resistances as low as125 to 25 ohm/square for 97,4 to 90% transparency respectively. But in our case the films are obtained just using a very simple spray method, from an aqueous suspension of carbon nanotubes and can be deposited on any kind and shape of surface.
References [1] N. Ferrer-Anglada, J. Pérez-Puigdemont, S. Roth, et al. Phys. Statuts Solidi B, 245 (2008) 2276. [2] H. Xu, G.Gruner, et al. Appl. Phys. Lett., 90 (2007) 183119(1-3).. [3] N. Ferrer-Anglada, M. Kaempgen, S. Roth, Phys. Status Solidi B, 243, 13, (2006) 3519. [4] A. A. Green, M.C. Hersam, Nanoletters, 8, 5 (2008) 1417. [5] S. Bae, H. Kim, Y. Lee, X. Xu, J-S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H.R. Kim, Y.I. Song, Y-J. Kim, K.S. Kim, B. Özyilmaz, J-H. Ahn, B.H. Hong, S. Iijima, Nature Nanotechnology 5 (2010) 574. Figures
Figure 1 shows the impedance dependence on frequency Z(f). We can define the cut off frequency fo, at which Z decreases abruptly; we observe that fo increases when increasing the SWCNT density on the substrate.
Figure 2 shows the transparency (%Transmittance at 550nm) versus the sheet resistance, R
Figure 4 Raman spectroscopy on the unstretched and stretched samples show clear shift on the breathing mode
Nanoporous impedimetric fibre sensor for the detection of acute inflammation in wounds Dagmar Gelinsky-Wersing Institute for Materials Science and Max Bergmann Center, Technische Universität Dresden, Budapester Str. 27, 01069 Dresden, Germany dagmar.wersing@nano.tu-dresden.de It is common clinical practice to change wound dressings in a certain time interval of 24 to 48 hours to control possible infections of the wound. This induces stress to the micro environment of the wound. Therefore, effort is made to monitor wound healing by non invasive sensor designs. A multi-parametric sensor integrated in the wound dressing was suggested, that detects an infection and, consequently, avoids stress factors given by frequent and unnecessary changes of bandages [1]. Neutrophils are among the first immune cells to arrive at the site of inflammation and released neutrophil proteases are involved in bacterial killing, tissue degradation and regulation of the inflammatory response [2]. Changes in neutrophil proteases and especially neutrophil elastase activity could be a potent signal for an ongoing wound inflammation in combination with parameters like change of pH value [3], temperature [4] or concentration of reactive oxygen species [5]. The authors have used AC impedance spectroscopy to detect protease activity based on thin film degradation of modified natural enzyme substrates deposited on the surface of interdigitated gold electrodes [6]. These measurements have been used for a redesign to improve the sensor responsivity and selectivity for neutrophil elastase. A nanoporous fiber sensor was designed that would be integrable in wound dressings by automated stitching or weaving processes (Figure 1). The sensor is build up by thin fibrous electrodes embedded in a surrounding nanoporous membrane that will be constructed by a nanoparticle leaching process [7]. The detection principle is based on the change of ionic conductance through the nanopores after binding of neutrophil elastase to its immobilized inhibitor elafin by the mechanism of “volume exclusion” [8]. In a wound with ongoing inflammation neutrophile granulocytes release high amounts of neutrophil elastase. The present elastase binds to elafin immobilized in the nanopores of the sensor surface thereby blocking the ionic flow of wound exudate to the electrode. As a proof of concept impedance measurements were performed with elafin immobilized in aluminum oxide nanomembranes. Gold was directly deposited on commercial anodized aluminum oxide (AAO) filter membranes and placed on a bare gold electrode to function as working electrode. The membrane was placed into the spectrometer flow chamber (Inphaze Impedance Spectrometer, Australia) and the gold wire counter electrode of the flow cell was used for a two electrode system. The AAO membrane has two different pore diameters 20 nm diameter on the top side (1 µm thickness) and 200 nm on the bottom side (60 µm thickness) therefore the orientation of the membrane is of great relevance to the expected blocking of ionic flow to the electrode [9]. Measurements were performed with the 20 nm side of the membrane in close contact to the working electrode to ensure that the exclusion of ions by elastase will be measured. Figure 2 shows the effect of all performed modification steps on the AAO membrane.
References [1] Schröter A, Fritzsche K, Wersing D, Walther A, Rösen-Wolff A, Gerlach G, 3. Dresdner Medizintechnik-Symposium. In: Dresdner Beiträge zur Medizintechnik, Jg. 10 (2010) 59. ISBN: 978-3-942710-02-2 [2] Heutinck KM, Nerge IJM, Hack CE, Hamann J, Rowshani AT, Molecular Immunology 47(2010) 1943. [3] Schneider L, Korber A, Grabbe S, Dissemond J, Arch Dermatol Res 298 (2007), 413. [4] van Pieterson L, Kok MAS de, Koninklijke Phillips electronics N.V. (Eindhoven, NL). US 20090204100 A1 (2009). [5] Lambeth JD, Nature Reviews Immunology 4 (2004), 181.
[6] Application filled for a patent : Schröter A, Gelinsky-Wersing D, Rösen-Wolf A, Gerlach G, Wundsensor (2011). [7] Kellenberger CR, Luechinger NA, Lamprou A, Rossier M, Grass RN, Stark WJ, Journal of Membran Science, (2011) in press. [8] Wang X, Smirnov S, ACS Nano 3 (2009) 1004. [9] Vlassiouk I, Takmakov P, Smirnov S, Langmuire (2005) 4776.
Figure1. Schematic illustration of the fibrous inflammation sensor. (a) Fiber electrodes integrated in a wound dressing. (b) Neutrophile elastase bound to the immobilized inhibitor elafin blocks the ionic flow of the wound exudate.
Figure 2. Cole-Cole (or Nyquist) plot of the capacitance per surface area of AAO membrane with Au film deposited on the 20 nm side measured in PBS buffer at 5 mV. Median of three measurement circles. Black measuring points, bare membrane; green dots, carboxysilane modified membrane; blue dots, membrane with immobilized elafin; red dots, elastase treated elafin-membrane. Acknowledgements We acknowledge the Bundesministerium für Bildung und Forschung for funding the project “ChiBSChip-basierte Biologie für die Sensorik” (project number 45952) within the framework of the WKPotential programme.
et al.
et al. et al.
On the use of Artificial Neural Networks in Electrostatic Force Microscopy E. Castellano-Hernández, F. B. Rodríguez, E. Serrano, P. Varona and Gómez-Moñivas Sacha Grupo de Neurocomputación Biológica. Departamento de Ingeniería Informática. Escuela Politécnica Superior. Universidad Autónoma de Madrid. Spain. sacha.gomez@uam.es We present different applications of Artificial Neural Networks [1] in Electrostatic Force Microscopy [2] [3]. First, a detailed analysis of the electrostatic interaction between an Electrostatic Force Microscope tip and a thin film is presented. By using Artificial Neural Networks, an equivalent semiinfinite sample has been described as an excellent approximation to characterize the whole thin film sample. A useful analytical expression has been also developed. In the case of very small thin film thicknesses (around 1nm), the electric response of the material differs even for very high dielectric constants. This effect can be very important for thin materials where the finite size effect can be described by an ultrahigh thin film dielectric constant. The second application we present is a technique to calculate electrostatic magnitudes such as force and potential in Electrostatic Force Microscopy setups [4]. This technique combines Artificial Neural Networks and the Generalized Image Charge Method [5] to overcome one of the main problems of traditional numerical simulations: the need of many parameters that are difficult to estimate and depend on the geometry of the experimental setup. Using Artificial Neural Networks, our technique is able to estimate the internal parameters of the algorithm and automatically obtain the electric magnitudes with a very high accuracy. This technique has been implemented in the freely distributed software winGICM. [6] The automatic configuration of the software by an Artificial Neural Network allows the users to handle it without being specifically trained in the theoretical background underlying the algorithms. Finally, a technique that combines a theoretical description of the electrostatic interaction and Artificial Neural Networks (ANNs) is used to solve an inverse problem in Scanning Probe Microscopy setups. [7] Electrostatic interaction curves calculated by the Generalized Image Charge Method (GICM) are used to train and validate the ANN in order to estimate unknown magnitudes in highly undetermined setups. To illustrate this technique, we simultaneously estimate the tip-sample distance and the dielectric constant from a system composed of a tip scanning over a metallic nanowire. In a second example, we use this method to quantitatively estimate the dielectric constant in an even more undetermined system where the tip shape (characterized by three free parameters) is not known. Finally, the proposed method is validated with experimental data.
References [1] Haykin S 1999 Neural Networks. Prentice Hall. New Jersey [2] J. Hu, X.-D. Xiao, and M. Salmeron. Appl. Phys. Lett 67, 476 (1995). [3] S. Guriyanova, D. S. Golovko and E. Bonaccurso. Measurement Science and Technology 21, 025502 (2010). [4] G. M. Sacha, F. Rodríguez, E. Serrano and P. Varona. Journal of Electromagnetic Wavesand Applitations 24, 1145 (2010). [5] G. M. Sacha, E. Sahagún and J. J. Sáenz. J. Appl. Phys. 101, 024310, (2007) [6] available at www.ii.uam.es/~sacha [7] G. M. Sacha, F. B. Rodríguez and P. Varona. Nanotechnology 20, 285704 (2009). Figures
FIG. 1.Scheme of the method to obtain the effective dielectric constant of a thin film sample. The electrostatic force of a system composed by a thin film over a dielectric substrate (equipotential lines shown at the top) is used as the input of an Artificial Neural Network. The output value is the effective dielectric constant of an equivalent sample composed by a semiinfinite dielectric substrate (equipotential lines shown at the bottom).
The study of indium zinc oxide, a material that can combine with porous silicon to form white light emitting diodes Hao Gong, Daniel J. Blackwood, Guang Xia Hu and Jian Sun Department of Materials Science and Engineering, National University of Singapore, Engineering Drive 2, Lower Kent Ridge, Singapore msegongh@nus.edu.sgl Indium zinc oxide (IZO) is a transparent semiconductor material that has found unique applications in thin film transistors (TFT), invisible electronics, flexible and large displays.[1] An combination of IZO with porous Si (PS) can form a junction, and white light can be emitted when a voltage is applied across the IZO/PS junction.[2] Figure 1a shows the IV curve of the IZO/PS junction. It is seen that IV curve for IZO/PS is a typical IV curve of a diode. Photoluminescence (PL) spectra of PS and IZO/PS (Figure 1b) reveal that photon excited light emission range of IZO/PS is wider than that of PS, covering the range of visible light wavelengths. Typically, the emitted light intensities at these wavelengths are roughly the same, suggesting that the emitted light can be white. Although PL can be generated by the excitation with high energy photons, it is not necessary that the light can be generated by electrical excitation via applying a voltage across the sample. Figure 1c shows the configuration of the sample for applying a voltage across the IZO/PS junction: two conducting copper pads are on the two sizes of the rectangular grey black IZO/PS/Si sample, and the voltage is applied across the IZO/PS junction via the two conducting plates. When a voltage of about 18 V is applied, white light emission can be observed coming from the IZO/PS/Si sample (Figure 1d). We will discuss in more detail on the properties of indium zinc oxide. A detailed investigation of IZO reveals that the structure, conductivity, band gap, optical transmittance vary with the Zn/In ratio in the sample. Figure 2a shows XRD spectra of IZO samples with different Zn/(Zn+In) ratio. X-ray diffraction patterns of the films reveal that there are no peaks in XRS spectra except for the samples with high indium concentration of In/(Zn+In)>85at% and high zinc concentration of Zn/(Zn+In)>45 at%. The peak observed for the high indium concentration can be assigned to In2O3 (211) and the peak for the sample with high zinc concentration corresponds to ZnO (200). For the other samples, only hump in the range of 29o-35o can be observed, indicating that amorphous IZO phase was obtained. Electrical conductivity of the IZO samples is determined through Hall effect measurement. The band gaps of the samples are obtained from the Tauc plot for the optical absorption data. Figure 2b shows the carrier concentrations and band gaps of the different IZO samples. It is seen that the carrier concentration varies with zinc concentration. For a high indium concentration (or low zinc concentration) and the existence of In2O3 crystallites in the sample, carrier concentration is about twice of those amorphous samples with high zinc concentrations. The optical gaps for both the IZO samples contain crystallite In2O3 (high indium content) and ZnO (high Zn content) are about 3.3-3.4 eV. For the other samples with amorphous structure, the gaps are between 2.6 eV to 3.0 eV. For an amorphous IZO sample, an introduction of Al can cause the structural and electronic property change. Figure 1c shows that an increase in Al to 4 at% (sample Al7), In2O3 precipitation is induced. The increase of Al concentration to 4at% leads to an increase in resistivity as seen in Figure 2d. Interesting, the In2O3 peak disappears but the Al2O3 starts to appear with a further increase in Al concentration (see Figure 2c). More interestingly, a sharp resistivity decrease is accompanied with samples Al9 and Al11 (Al concentrations are 10 at% for sample Al9 and 11 at% for sample Al11) as seen in Figure 2c and 2d. A further increase in Al concentration increases Al2O3 in the IZO sample but the resistivity turns to be higher. Such a phenomena suggests that an insulator (or semiconductor) metal transition by the partial crystallization of an amorphous sample.[3] Analysis and discussion will be made at the presentation. References [1] T. Kamiya, K. Nomura and H. Hosono, Sci. Technol. Adv. Mater., 11 (2010) 044305. [2] G. Hu, H. Gong, D.J. Blackwood et al, J. Phys. Chem. C, 113 (2009) 751. [3] J. Sun and H. Gong, Appl. Phys. Lett, 97 (2010) 092106.
Figure 1 (a) Current-voltage characteristics of an IZO/PS junction, (b) Photoluminescence of PS and IZO/PS, (c) a IZO/PS sample with electrodes below and above, (d) shows white light emission from a part of the IZO/PS sample when 18 V voltage is applied across the IZO/PS junction.
(a)
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(c) (d) Figure 2 (a) XRD of IZOs with increased Zn concentration (from top to bottom); (b) Carrier concentration and band gap variation with Zn concentration in indium zinc oxide; (c) XRD pattern of an amorphous IZO with different Al incorporation; (d) Resistivity and carrier concentration of the Al incorporated IZO samples.
Electrochemical Synthesis and Delivery of Melanin Covered Gold Nanoparticles and Catalytic Activity 1
1*
Alejandro González Orive , Alberto Hernández Creus , Roberto C. Salvarezza
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1
Departamento de Química Física, Universidad de La Laguna, Tenerife, España Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata CONICET, Sucursal 4 Casilla de Correo 16, (1900) La Plata ARGENTINA. *ahcreus@ull.es 2
Melanins are an important class of biopolymers which are present in different regions within living 1 organisms . These polymers have very interesting physical features that are closely related to their biological functions. Eumelanin, in particular, possesses fascinating physicochemical properties: a strong, broad UV-band and visible absorption, extremely low radiative quantum yield, anti-oxidant and free radical scavenging ability, and electrical conductivity and photoconductivity in the condensed phase. These biopolymers are able to coordinate a large number of metallic ions, especially iron. The affinity of melanins for metal cations has been studied in relation to melanome cell targeting by different drugs. Recently we have shown that melanin-iron films can be prepared by electrodeposition on 2,3 4,5 Au(111) and highly oriented pyrolytic graphite (HOPG) surfaces in a controlled way. The preparation of metallic nanoparticles (NPs) modified with organic, bioorganic or oxide coatings is appealing because of their wide range of potential biological and technological applications in the emerging fields of nanoscience and nanotechnology. 6 In this context, the development of new strategies capable of functionalizing NPs with complex molecular systems by using simple and inexpensive methods is a frontier topic that deserves special attention. Thus, thiol-capped and thiol free gold nanoparticles (AuNPs) 2.7 nm in size spontaneously adsorbed on HOPG have been used as cores for deposition of melanin-iron shells by electrochemical methods. Ultrathin nanostructured melanin films on AuNPs have been prepared by using an electrochemical method. 2-5 Film formation takes place at a noticeable rate at E = 1.0 V (vs. SCE) in a melanin containing 0.1 M NaOH solution for 2 hs. The melanin-iron coated AuNPs were characterized by X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopies, small angle X-ray scattering, scanning tunneling microscopy (STM), atomic force microscopy (AFM), and UV-spectroscopy. Direct deposition on the thiol-capped AuNPs decreases the melanin shell thickness with respect to that formed on thiol-free AuNPs. Thiol electrodesorption results in the delivery of a significant amount of melanin-iron coated AuNPs from the HOPG surface to 7 the electrolyte solution. UV spectra of the solutions and XPS data show that NPs preferentially select dihydroxyindole species or small oligomers from the complex polymer during the electrochemical deposition of melanin. This strategy, which integrates electrochemistry and nanotechnology, could be applied to the preparation of efficient Fe-containing organic catalysts for electrically stimulated delivery devices, in analytical separations, in biosensors, and in nanometer sized magnetic storage devices, among others. In addition, we have also shown that the iron melanin coating markedly enhances the catalytic activity of the bare AuNPs for both the hydrogen peroxide electroreduction and hydrogen evolution reaction (HER),8 see fig. 1. Therefore, this procedure, which combines electrochemistry and nanomaterials, could -organic capped AuNP catalysts. References [1] G. Prota, Melanins and Melanogenesis, 1992, Academic Press, San Diego, USA. [2] P. Díaz, Y. Gimeno, P. Carro, S. González, P. Schilardi, G. Benítez, R.C. Salvarezza, A. Hernández Creus, Langmuir, 2005, 21 (13), 5924. [3] A. González Orive, P. Dip, Y. Gimeno, P. Díaz, P. Carro, A. Hernández Creus, G. Benítez, P.L. Schilardi, L. Andrini, F. Requejo, and R.C. Salvarezza, Chemistry A European Journal, 2007, 13 (2), 473-482. [4] A. González Orive, Y. Gimeno, A. Hernández Creus, D. Grumelli, C. Vericat, G. Benitez, and R.C. Salvarezza, Electrochimica Acta, 2009, 54 (5), 1589-1596. [5] A. González Orive, A. Hernández Creus, D. Grumelli, G. A. Benítez, L. Andrini, F. G. Requejo, C. Bonazzola, R. C. Salvarezza, Journal of Physical Chemistry C, 2009, 113(39), 17097-17103. [6] U. Drechsler, B. Erdogan, V. M. Rotello, Chemistry A European Journal, 2004, 10, 5570 05579.
[7] D. Grumelli, C. Vericat, G. Benítez, R. C. Salvarezza, J. M. Ramallo-López, L. Giovanetti, F. G. Requejo, M. Sergio-Moreno, A. González-Orive, A. Hernández-Creus, and R.C. Salvarezza, ChemPhysChem, 2009, 10(2), 370-373. [8] A. González Orive, D. Grumelli, C. Vericat, J. M. Ramallo-López, L. Giovanetti, G. Benitez, J. C. Azcárate, G. Corthey, M. H. Fonticelli, F. G. Requejo, A. Hernández Creus and R. C. Salvarezza, Nanoscale, 2011, 3, 1708-1716. Figures
Figure 1. STM images (200 nm x165 nm) of (a) bare AuNPs on HOPG and (b) AuNPs on HOPG after -1 melanin iron deposition. Cathodic polarization curves recorded at 0.025 V s in 4 mM H2O2 + 0.1 M NaOH (c). Acknowledgments This work was supported by grants CTQ2008-06017/ BQU and ID20100152 from MICINN and ACIISI (Spain), respectively. A. González Orive thanks to ULL for a SEGAI research grant.
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References [1] J.A.J. Burgess et al., Phys. Rev. B, 82 (2010) 144403. [2] G. N. Kakazei et al., Appl. Phys. Lett., 99, (2011) 052512. Figures
Fig. 1. Magnetic viscosity of the permalloy dot array vs. in-plane magnetic field extracted from the magnetization decay experiments by using Eq. (1): black squares (T=200 K), red circles (T=305 K) and green triangles (T=375 K). The dot radius is R = 250 nm and thickness is L=40 nm.
Application of 3D laser nanolithography to the fabrication of photonic crystals a,b
a
J. Haberko , F. Scheffold , J-F Dechezelles
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University of Fribourg, Chemin du MusĂŠe 3, 1700 Fribourg, Switzerland AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland jakub.haberko@unifr.ch
b
3D laser nanolithography is a versatile technique that allows fabricating arbitrary 3D structures with a resolution better than 1 Âľm. In this method ultrasho utilized to induce crosslinking in a polymer photoresist via a two-photon absorption process. The laser light is focused through a high numerical aperture objective. Due to the fact that the probability of the two-photon absorption process is proportional to light intensity squared, the crosslinking only takes place in a small volume of the photoresist around the focal point, where the laser power is the highest. By precisely manipulating the substrate using a 3d piezoelectric stage, one can selectively write a desired pattern into the polymer material and, after dissolving the non-crosslinked photoresist, obtain a free-standing structure. In this work we utilize the technique to manufacture 3D photonic crystals. In order to enhance the refractive index contrast some of the structures were infiltrated with inorganic material by means of atomic layer deposition or chemical vapor deposition. We mainly focus on the so-called woodpile structure, which consists of a series of dielectric rods arranged in layers. For a sufficiently large refractive index of the dielectric material this structure possesses an omnidirectional photonic bandgap [1-3]. Optical characterization of the structures was carried out by means of the FTIR spectroscopy, both in transmission and in reflection mode. As the optical properties of a photonic crystal scale with its size, the position of the bandgap can be tuned by rescaling the structure. Optical spectra of a series of woodpile structures differing in pit ch will be presented here. Furthermore, we will present two types of dual photonic crystals with a double bangap. One of them is a sandwich consisting of two different woodpile structures integrated into one photonic crystal. The other one is a hybrid photonic crystal containing of a woodpile structure and a colloidal crystal. The latter was manufactured by sedimentation of PMMA particles from a suspension. Moreover, a possibility to template the substrate to promote crystallization of the molecular crystal in such a hybrid device will be presented. References [1] [2] [3]
J.D.Joannopoulos et al., Molding the Flow of Light, 2nd ed., Princeton Univ. Press, 2009 M. Deubel, G. von freymann,M. Wegener, S. Pereira, K. Busch, C. M. Soukoulis, Nature Materials, 3 (2004) 444 I. Staude, M. Thiel, S. Essig, C. Wolff, K. Busch, G. von Freymann, M. Wegener, Optics Letters, 35 (2010) 1094
Figures a)
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Fig. 1: a) Optical spectra of a woodpile photonic crystal manufactured by 3D laser nanolithography. b) Scanning electron micrograph of the structure.
Tunable graphene bandgaps from superstrate mediated interactions J.P. Hague Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, UK J.P.Hague@open.ac.uk
A theory is presented for the strong enhancement of graphene-on-substrate bandgaps by attractive interactions mediated through phonons in a polarizable superstrate. It is demonstrated that gaps of up to 1eV can be formed for experimentally achievable values of electron-phonon coupling and phonon frequency [1]. As shown in figure 1, gap enhancements computed using perturbation theory range from 1 to 4, indicating possible benefits to graphene electronics through greater bandgap control for digital applications, through the relatively simple application of polarizable materials. Additionally, polaron spectral functions are computed for heavily doped graphene -on-substrate systems using the diagrammatic quantum Monte Carlo technique to investigate the effects of interaction on spectral functions when the symmetry between graphene sub-lattices is broken by a substrate [2]. Several polaronic features are visible, including band-flattening and changes in particle lifetimes. The difference between energies on each sub-lattice increases with coupling, indicating an augmented transport gap at the K point, while the spectral gap decreases slightly (as shown in figure 2). In the absence of a gap, additional flattening is found around the K point. Results indicate potential difficulties of using ARPES to establish the size of graphene bandgaps in the presence of substrates. References [1] J.P.Hague, Phys. Rev. B, 84 (2011) 155438. [2] J.P.Hague, arXiv:1107.2507 (2011) Figures
Figure 1: Substrate gap enhancement vs superstrate mediated electron phonon coupling the non interacting gap, T the temperature, t the hopping and the phonon frequency.
Figure 2: Spectral function, A(E), for heavily doped graphene at the K point.
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Highly electrical conductive, ultralarge and well-ordered MMX nanorods a
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Cristina Hermosa , Cristina Gómez-Navarro , Julio Gómez-Herrero , Félix Zamora b
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a Departamento de Química Inorgánica, Universidad Autónoma de Madrid, 28049, Madrid, Spain Dpto. de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain cristina.hermosa@uam.es
Infinite structures based on the combination of metals and organic/inorganic ligands by coordination bonds, are known as coordination polymers (CPs). These materials show a rich structural diversity and interesting physic-chemical properties, including electrical conductivity [1, 2]. A novel approach in the search of nanomaterials is the organization of CPs on surfaces with potential technological applications, such as nanoelectronics [3] For this reason, one of the main interests is the formation of electrical conductive 1D nanostructures potentially suitable as molecular wires for the construction of nanocircuits [4] A particular type of CPs called MMX polymers seems to be particularly attractives [5]. A MMX polymer [1] consists of 1D sequence of halides (X) bridging dimetallic (MM) subunits in which metal ions are connected by organic ligands. Here we present electrically conductive fibers of the MMX polymer [Pt2 I (S2CCH3)4]n adsorbed on a SiO 2 surface that we characterize by Atomic Force Microscopy (AFM). The well-ordered 1D nanostructures have been isolated on the surface by direct sublimation from monocrystals of [Pt2I(S2CCH3)4]n. The approach involves the deposition from vapor phase on a substrate of mono or oligomeric species obtained by sublimation of a bulk MMX under high vacuum and their self-organization on the host surface. The advances made in the several parameters that affect the organization experiment of these systems have enabled us to optimize the morphology respect to [5] and obtain longer fibers, with an average length of 8-10 µm and height 10-30 nm. Importantly, we observed a conductance improve of a factor of 100-1000, reaching values in the same order of magnitude to those measured in the macroscopic crystals [6]. We attribute this increment in the conductance to a lower density of defects in the nanorods and put into perspective the importance of the deposition conditions to obtain nanocrystals with high degree of structural perfection. As shown in Fig.2, we have used Conductance Atomic Force Microscopy (C-AFM) to characterize the electrical transport properties of the nanomaterials at room temperature. Further, electrical characterization by three terminal measurements in Field Effect Transistor configuration is currently in progress. These results confirm CPs as excellent candidates for applications in molecular electronics.
References [1] S. Kitagawa and S. Noro, In Comprehensive Coordination Chemistry II, T.J McCleverty, Eselvier, (2004) 231. [2] C.Janiak, Dalton Transactions, 14 (2003) 2781. [3] R. Mas-Balleste, J. Gomez-Herrero and F. Zamora, Chemical Society Reviews, 11 (2010) 4220. [4] R. Mas-Balleste et al., European Journal of Inorganic Chemistry, 20 (2009) 2885. [5] L. Welte, A. Calzolari, R. di Felice, F. Zamora, J. G贸mez-Herrero, Nature Nanotechnology, 5 (2010) 110. [6] H. Kitagawa et al., Journal of the American Chemical Society, 43 (1999) 10068. Figures 25
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100nm Fig.1 AFM topographies of the isolated nanorods on SiO2 and 3D image of one nanorod and its height profile.
Polymer
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V (Voltios) Fig.2 a) Schematic representation of the procedure used to perform electrical measurements on the MMX nanorods using the C-AFM technique in horizontal geometry. b) Example of current versus voltage characteristic curve taken by contacting a fiber 100 nm from the gold electrode.
1.0µm
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Centre for Graphene Science Department of Physics &, University of Bath, Bath BA2 7AY, UK
400nm
(a) Topography, with the edges of various FLG domains and substrate highlighted by a coloured overlay: green, substrate edges; blue, edges of 4-layer graphene domain; the regions in between the two are bi-layer graphene. (b) KP image of a bare ionic substrate: step edges induce sharp variations in the surface potential. (c) Amplitude image of the FLG, corresponding to (d), surface potential image (scale bar, in V). Bilayer domains are more strongly perturbed by the underlying nanostructures of the substrate than the 4-layer ones. (e) Representative potential steps values extracted from (d) and associated with nanostructured features described in the text, taken with the ti p several nanometers away from the surface.
Advances in magnetic silica nanotubes preparation and characterization Ryszard J. Kalenczuk, Xuecheng Chen, Karolina Wilgosz, Ewa Mijowska Westpomeranian University of Technology in Szczecin (Poland)
The application of nanomaterials in medical industry has caused an increase of research interest in recent years. The considerable concern of these materials has achieved the preparation of magnetic silica tubes (r-Fe2O3@SiO2). Components combined with r- Fe2O3@SiO2 have attracted an attention in drug targeted delivery and liquid separation because of their high surface area and magnetic separability. In this contribution the structure of magnetic silica tubes by deposition of Fe2O3 particles onto multi-walled carbon nanotubes surface (MWCNT-Fe2O3) was created. After that MWCNT-Fe2O3 have been coated with silica (MWCNT-Fe2O3@m-SiO2). The final product has been obtained by heating to get rid of MWCNT. Magnetic silica tubes have been characterized in details.
Ferroelectric-gate Field Effect Transistors Based Nonvolatile Memory Devices Using p-type Si Nanowire Conducting Channel 1
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Dae Joon Kang, Ngoc Huynh Van, Jae Hyun Lee , Jung Inn Sohn , Seung Nam Cha , Dong Mok Hwang1, Jongmin Kim 2 BK21 Physics Research Division, Department of Energy Science, Institute of Basic Science, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, Republic of Korea. 1 School of Advanced Materials Science and Engineering, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, Republic of Korea. 2 Frontier Research Lab., Samsung Advanced Institute of Technology, Republic of Korea. djkang@skku.edu Ferroelectric-gate field effect transistor (FEFET) based memory using a nanowire as a conducting channel has many desirable features including small cell size, low-voltage operation, low power consumption, fast programming/erase speed and non-volatility [1]. We successfully fabricated a ferroelectric nonvolatile memory device using a p-type Si nanowire coated with organic ferroelectric PVDF via a low temperature fabrication processing technique [2,3]. The device performance was [3] carefully characterized in terms of their electrical transport, retention and endurance time. . Our FEFET memory devices exhibit excellent memory characteristics with a large modulation in channel 5 4 conductance between ON and OFF states exceeding 10 ; long retention time of over 5x10 s and high endurance of over 105 cycles while maintaining ON/OFF ratio over 10 3 (See Fig. 1, 2 and 3). This result offers a viable way to fabricate a high performance high-density nonvolatile memory device using a low temperature fabrication processing technique, which makes it suitable for future flexible electronics. References [1] Ma, T. P. & Han, J.-Effect Transistor Still IEEE Electron Device Letters, 2002, 23, 386-388 [2] Minghua Tang, Xiaolei Xu, Zhi Ye, Yoshihiro Sugiyama, and Hir buffer layer on data retention characteristics of ferroelectric-gate FET for nonvolatile memory -375, 2011. [3] -gate Si transistors and challenge to ferroelectric-S6, 2009.
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Transport Gap Engineering in Zigzag Graphene Nanoribbons H. Karamitaheri
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, M. Pourfath3,1, R. Faez2, and H. Kosina1
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Institute for Microelectronics, TU Wien, Vienna, Austria School of Electrical Engineering, Sharif University of Technology, Tehran, Iran 3 Electrical and Computer Engineering Department, University of Tehran, Tehran, Iran karami@iue.tuwien.ac.at 2
Graphene, a recently discovered form of carbon, has received much attention over the past few years due to its excellent electrical, optical, and thermal properties [1]. With an extraordinary carrier mobility and high current density [2], graphene's application in electronic devices is promising. As a zero band gap material, pristine graphene cannot be used as a semi-conducting channel in transistors. However, there are several proposed schemes for opening up a band gap [3,4]. Graphene nanoribbons (GNRs) are thin strips of graphene, where the band gap depends on the chirality of the edge and the width of the ribbon. Zigzag GNRs (ZGNRs) show metallic behavior, whereas armchair GNRs (AGNRs) are semiconductors [3]. In recent years, AGNRs have been extensively studied as channel materials and ZGNRs as metalic electrodes in electronic devices [5,6]. The band-gap of AGNRs is inversely proportional to their width [3]. To obtain a band-gap of nearly 0.5 eV, the width of the ribbon should be around 2nm. On the other hand, it has been shown that line edge roughness and substrate impurities can significantly degrade the ballistic transmission in AGNRs [7]. The effect of these scattering mechanisms is more deteriorative in narrower ribbons. Therefore, high performance AGNR-based transistors can not be achieved. In this work, we suggest a new scheme to open up a transport gap in ZGNRs. In this approach, line edge roughness and substrate impurities are used as mechanisms for band-gap opening. Ballistic transport through ZGNRs is sustained in the presence of line edge roughness and substrate impurities [8]. Very recently, transport properties of ZGNRs with extended line defects along the ribbon's length (ELD-ZGNR) has been studied [8]. In this work, we investigate the transport properties of this structure in the presence of line edge roughness and long-range substrate impurities. This structure is represented by two parameters (n1,n2), where n1 is the index of ZGNR above the line defect and n 2 is the index below the line defect. In addition, we consider another topology of this defect, (see Fig.1 -a), where two line defects parallel to the edges are presented in the ribbons, 2ELD-ZGNR, and represent this structure with three parameters (n 1,n2,n3). To study the transport properties of electrons the non-equilibrium Green functions are used. The electronic Hamiltonian matrix is described by the first nearest-neighbor tight-binding model with a at 0 eV. The band structure of ELD-ZGNR(10,10) and 2ELD-ZGNR(8,4,8) are shown in Fig.1-c and Fig.1-d. For comparison, the folded band structure of ZGNR(20) is also presented in Fig.1-b. The main differences between the band structures of ELD-ZGNR(10,10) and 2ELD-ZGNR(8,4,8) with the original band structure of ZGNR(20) are: i) the asymmetry between electrons and holes around the Fermi level with respect to the extra conduction subbands corresponding to the extended line defects and ii) band folding because of a larger unit cell in ELD-ZGNR and 2ELD-ZGNR. In contrast to ZGNRs, the first subband of ELD-ZGNRs and 2ELD-ZGNR are also sensitive to the long-rang defects because of band folding. However, as shown in Fig.2, the electron current density is confined around the line defects. In fact, a line defect behaves like a quantum wire in the middle of the ribbon. Therefore, the conduct ion bands corresponding to the line defects, indicated by dashed line in Fig.1, are less sensitive to the line edge roughness. As a result, it is possible to suppress transport of carriers through the first valence band and maintain transport along the first conduction band. The average electron transmission probability over many samples is shown in Fig.3 for ELDZGNRs(5,5), ELD-ZGNR(10,10), and 2ELD-ZGNR(8,4,8). The mean free path of electrons in the conduction subbands is higher than that of holes in the valence subband because the quantum wire conduction takes place around the line defect which is far from the edges. Therefore, by increasing the length a transport gap is opened up. As expected, the mean free path is longer in wider ribbons. As a result, ELD-ZGNRs of (5,5) and (10,10), and 2ELD-
References [1] K. Novoselov, A. Geim, S. Morozov, D. Jiang, Y. Zhang, S. Dubonos, I. Grigorieva, and A. Firsov, Science, 306 (2004) 666. [2] A.K. Geim and K.S. Novoseov, Nature Material, 6 (2007) 183. [3] M. Han, B. Ozyilmaz, Y. Zhang, and P. Kim, Phys. Rev. Lett., 98 (2007) 206805. [4] T.G. Pedersen, C. Flindt, J. Pedersen, A.-P. Jauho, N.A. Mortensen, and K. Pedersen, Phys. Rev. B, 77 (2008) 245431. [5] P. Zhao, J. Chauhan, and J. Guo, Nano Letter, 9 (2009) 648. [6] Y. Yoon and J. Guo, App. Phys. Lett., 91 (2007) 073103. [7] D. Areshkin, D. Gunlycke, and C. White, Nano Letter, 7 (2007) 204. [8] D. Bahamon, A. Pereira, and P. Schulz, Phys. Rev. B, 83 (2011) 155436. Figures
Fig.1: (a) The geometrical structure of ELD-ZGNR and 2ELD-ZGNR. The band structure of (b) ZGNR(20), (c) ELD-ZGNR(10,10), and (d) 2ELD-ZGNR(8,4,8). The band structure of ZGNR(20) is also folded for a better comparison. The bands corresponding to the quantum wires are represented with dashed lines. The translation vector length is a = 0.49 nm.
Fig.2: The quantum wire is represented by the current density at E = 0.2 eV for ( a) ELD-ZGNR(10,10) and (b) 2ELD-ZGNR(8,4,8). Fig.3: Electrical conductance of (a) ELD-ZGNR(5,5), (b) ELD- ZGNR(10,10), and (d) 2ELDZGNR(8,4,8).
SiC formation in carbon nanotubes grown from permalloy catalyst particles 1
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A. Kiessling , D.Pohl , C.Täschner , R. Erni , M.H. Rümmeli , L. Schultz and B. Rellinghaus
1
1 Institute for Metallic Materials, IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany 2 Institute for Solid State Research, IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany 3 Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science & Technology, 8600 Dübendorf, Switzerland a.kiessling@ifw-dresden.de We present the formation of SiC nanowires within carbon nanotubes (CNT) that are grown from Ni80Fe20 -enhanced chemical vapour deposition (PE-CVD). The asproduced CNT were characterized by means of aberration-corrected high resolution transmission electron microscopy (using a FEI TITAN³ 80-300 microscope operated at 80kV). Fig. 1a shows a representative scanning electron transmission microscopy (STEM) image of a likewise grown CNT that is attached to an amorphous carbon carrier film. The image reveals a clear contrast difference between the particle, the concentric graphene layers of the CNT and its core, respectively. For a chemical analysis of this nanotube, Electron Energy Loss (EEL) spectra are collected from different positions across the CNT. Whereas these spectra allow us clearly identify the catalyst particle as Ni80Fe20 with no detectable amounts of CNT (as already apparent from the enhanced Z contrast in the STEM image) does not show any signs of Ni nor Fe. Instead, local EEL spectroscopy (EELS) reveals the existence of Si from the occurrence of a Si-L absorption edge at E = 100 eV followed by a broad double-peak type of feature (figure 1b [2]). These spectral features of carry the fingerprint structure of SiC which apparently forms during the CNT growth process. The details of the SiC formation remain to be unveiled, although it is clear that the required Si and C ingredients are largely available through the gaseous carbon feedstock utilized for the CNT growth and the plasma-induced chemical etching of the Si substrate, respectively. The observation of sp³-hybridized carbon in the core of the tubes (which is consistent with the formation of SiC) through cross-sectional EELS lines scans further confirms that the core material is SiC. Moreover, the CNT were found to be coated with a thin layer of amorphous silicon oxide (cf. EELS line scan in figure 1b [3]) which supports the aforementioned assumption that Si is present in the gas phase during (and after) the CNT growth process. This Si vapor apparently forms a thin coating through heterogeneous nucleation and growth on the freshly prepared CNT, and this primarily formed Si layer then oxidizes during the exposure to ambient air upon removal of the sample. As a result, the CNT exhibit a complex core-shell structure with a SiC core and an amorphous SiO2 overcoat, respectively. Fig. 2 shows a HRTEM picture of a CNT grown from a permalloy catalyst particle. Here, the SiC filling is clearly visible. In addition, the graphene layers of the CNT are bent towards the core which indicates a strong correlation between the graphene and the SiC core which is found to form a sharp interface to the permalloy catalyst particle. The amorphous SiO2 overcoat of the CNT is also visible in the HRTEM micrograph. These findings clearly point to a complex mutual interplay between the catalyst particle, the substrate and the carbon feed stock during the CNT growth via PE-CVD. To the best of our knowledge, it is for the first time that such a simultaneous formation of SiC nanowires in the cores of CNT is shown. Previous work in the field is rather dedicated to the production of SiC nanowires, e.g., through the conversion of CNT to carbide rods [1], reactive laser ablation [2] and/or hot filament chemical vapor deposition [3]. Thus, the here reported experimental route renders a novel approach for producing SiC re-inforced CNT or after a SiC nanowires. References [1] Dai et al., Nature, 375 (1995) 769-772. [2] Zhang et al., Science, 281 (1998) 973-975. [3] Zhou et al., APL, 74 (1999) 3942-3944.
Effects of surface in -Fe2O3 nanoparticles 1
2
1
1
J. Kohout , P. Brázda , J. Kuriplach ,
2
,
3
,
, M. Klementová
2
1
Charles University in Prague, Faculty of Mathematics and Physics, V , Czech Republic Institute of Inorganic Chemistry of the ASCR, v.v.i., 250 68 Husinec, Czech Republic 3 Institute of Physics ASCR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
2
kohout@mbox.troja.mff.cuni.cz Maghemite -Fe2O3 and hematite -Fe2O3 are the two well-known polymorphs of ferric oxide [1]. Maghemite is metastable and transforms under heating into hematite, which is thermodynamically stable. No intermediate phase is observed during the thermal treatment of powders, but for particles dispersed in silica matrices [2] or Pd96Fe4 alloy [3], -Fe2O3 was observed as an intermediate phase. The crystal structure of -Fe2O3 is orthorhombic with space group Pna21 [2], lattice parameters at 200 K, a = 5.0885 Å, b = 8.7802 Å, c = 9.4709 Å, and = = = 90° [4], and eight formula units per unit cell. In the structure four cation positions (Fe 1, Fe2, Fe3 and Fe4 [2]) exist. One of them (Fe 4) is tetrahedrally coordinated and the other three positions are octahedrally coordinated, exhibiting various degrees of distortion. From the magnetic point of view, -Fe2O3 is a collinear ferrimagnet with magnetization parallel to a-axis or a canted antiferromagnet with Curie temperature near 490 K [5]. A random canting of the surface spins caused by competing antiferromagnetic interactions between sublattices was proposed by Coey [6] to account for the reduction of Ms in small -Fe2O3 ferrimagnetic particles. We present here application of the core-shell model [6, 7] for Mössbauer and NMR studies of -Fe2O3 57 nanoparticles enriched by isotope Fe in a silica matrix. Samples were prepared by sol-gel technique starting from molecular precursor both for -Fe2O3 and for silica [8] and they were characterized by XRD, TEM, HRTEM and DC magnetic measurement. X-ray powder diffraction pattern of -Fe2O3 was identified and -Fe2O3 and -Fe2O3 as other iron oxide phases present were observed. Mean coherent diffraction domain size ~27 nm was determined. Using the fit of log-normal distribution to the experimental distribution of particles, obtained from the TEM micrographs, the characteristic diameter of particles d0 ~ 24 nm was derived. The hysteresis loops at room temperature and the dependence of magnetization after cooling in zero and non-zero magnetic field, MZFC and MFC, were measured in a SQUID magnetometer. The coercivity of ~2.1 T at room temperature is observed. At external magnetic fields as high as 7 T, magnetization does not reach saturation which may be due to the magnetic structure and behaviour of the surface layer; the non-collinear arrangement of the core moments is the usually used explanation. The temperature dependence of MZFC and MFC show two anomalies: a sharp change of the slope at 124 K, below which the magnetization abruptly decreases down to 100 K, and a much smaller change at 153 K, where a maximum in the magnetization is observed, agreed with the results given in [5]. Table I: Parameters of Mössbauer spectra at room temperature Comp.
-Fe2O3 core -Fe2O3 shell Fe2O3 -Fe2O3
Bhf (T)
IS (mm/s)
EQ (mm/s)
f
RA (%)
S1 S2 S3 S4 S5 S6 S7 S8
45.3 45.0 39.6 26.2 44.1 40.2 35.4 22.0
0.42 0.38 0.40 0.23 0.42 0.38 0.40 0.23
-0.17 -0.31 -0.01 -0.16 0 0 0 0
5.5 5.5 5.5 5.5
0.174 0.174 0.174 0.174 0.043 0.043 0.043 0.043
S9
51.5
D1 D2
-
0.40
-0.2
-
0.081
0.40 0.53
0.72 0.99
-
0.044 0.015
Bh (T)
Orient. of momen ts
random random random random -
Theor
EQ (mm/s)
Cation pos.[2,4]
-0.08 -0.11 0.01 -0.15 -
F1 (FD01) F3 (FRo) F2 (FD02) F4 (FT) -
-
-
57
Transmission Mรถssbauer spectra of the Fe nuclei in -Fe2O3 at room temperature were obtained 57 using Co/Rh source with constant acceleration and calibration by Fe at room temperature. The spectra were fitted by four sextets (S1, S2, S3 and S4) with the same intensities, four sextets (S5, S6, S7 and S8) with distribution of hyperfine field and the same intensities, one sextet S9 and two doublets D1 and D2. We ascribed the sextets S 1 through S4 to Fe in the core of -Fe2O3, the sextets S5 S8 with the distribution of the hyperfine fields to Fe in the surface shell of -Fe2O3, sextet S9 to -Fe2O3 and the two doublets to -Fe2O3. We supposed the same isomer shifts for the corresponding components in the shell and in the core and random canting of the shell spins in -Fe2O3, which means the average quadrupolar shifts in the shell are zero. The parameters of the Mรถssbauer spectra are given in Table 1. The particular sextets from the group S 1-S4 were assigned to cation positions Fe1-Fe4 with the help of the field dependence of Mรถssbauer spectra at temperature of 160 K and by comparison of the experimental and theoretical quadrupolar shifts. These shifts were determined by using the electric field gradient tensor calculated by the WIEN2k ab initio electronic structure program taking the crystal structure from of -Fe2O3 [2] and neglecting the magnetic polarization effects. 57 The NMR spectra of the Fe nuclei were measured by the spin-echo method using the phasecoherent pulse spectrometer with averaging technique and the fast Fourier transformation. The measurements were performed in zero external magnetic field at liquid helium temperature. The signal to-noise ratio was significantly improved by using the Carr-Purcell pulse sequence. The NMR spectra of the 57Fe nuclei in the prepared samples consist of two signals corresponding to -Fe2O3 and -Fe2O3. The NMR spectrum of in -Fe2O3 consists of two broad lines with the ratio of integral intensities equal to 57 Fe4 : (Fe1+Fe2+Fe3) = 1 : 3. The splitting of the NMR spectrum for the Fe nuclei in octahedral sites (Fe1, Fe2, Fe3; 69-72 MHz) is caused by the anisotropy of the hyperfine field which points to the noncollinear orientation of the local moments. Acknowledgement. The authors thank the Ministry of Education of the Czech Republic for the support under the project MSM0021620834 and Grant Agency of the Czech Republic for the support under the grant P204/10/0035 References [1] R. 14 (2002) 969-982 [2] E.Tronc et al., J. Solid State Chem. 139 (1998) 93-104 [3] K. Kelm, W. Mader, Z. Anorg. Allg. Chem. 631 (2005) 2383-2389 [4] M. Gich, et al., Chem. Mater. 18 (2006) 3889-3897 et al., Chem. Mater. 22 (2010) 6483-6505 [6] J.M.D. Coey, Phys. Rev. Lett. 27, (1971) 1140-1142 [7] F. Bodker, S. Morup and S. Linderoth, Phys. Rev. Lett. 72, (1994) 282-285 [8] P. Brรกzda, et al., J. Sol-Gel Sci. Technol. 51 (2009) 78-83
DFT studies of hydrogenated and defective carbon nanotubes Jaap Kroes, Fabio Pietrucci, Wanda Andreoni, Ecole Polytechnique Federale Lausanne, Lausanne, Switzerland Alessandro Curioni IBM Research - Zurich, Rüschlikon, Switzerland Oliver Gröning Laboratories for Materials Testing and Research (EMPA), Dübendorf, Switzerland jaap.kroes@epfl.ch The study of the effects of covalent functionalization on the mechanical properties of real-size carbon nanotubes (CNTs) by means of computer simulations requires the adoption of reliable models and of a robust and accurate methodology. On one hand the correct description of the changes induced by the addition of chemical bonds requires a quantum-mechanical approach; on the other hand the size of the systems (typically 1µm long) imposes the use of classical force fields. The latter however need validation against non-empirical methods. We present the results of two projects: one aimed at identifying the evolution of the pattern of chemisorbed hydrogen on the outer surface of a CNT with increasing concentration [1]; the other at characterizing the stable reconstructions of the CNT after formation of vacancies. These studies include a comparison of results obtained with DFT using several exchange- and correlation-functionals and with the widely-used force-field AIREBO. The system under consideration is a zig-zag semiconducting (10,0) nanotube. DFT calculations show that electron pairing and strain minimization lead hydrogen atoms to cluster. The underlying mechanism is explained as well On the contrary, AIREBO predicts a sparse distribution of the hydrogen atoms on the surface of the tube. We investigate the changes induced by hydrogen in the electronic structure and in the infrared spectrum of the nanotube [1]. Our DFT calculations predict that configurations with double vacancies are thermodynamically favored with respect to single vacancies, as found in previous studies [3]. A number of differences are however found with previous DFT calculations and especially with the results obtained with the AIREBO potential. The only agreement concerns the lowest energy state (5r8r5r) of a double vacancy. References [1] W. Andreoni, A. Curioni; J. Kroes, F. Pietrucci, O. Gröning, "Exohedral Hydrogen Chemisorption on a Carbon Nanotube : The Clustering Effect", JPCC (to appear) [2] S.J. Stuart, A.B. Tutein, J.A. Harrison, J. Chem. Phys., 112 (2000), 6472; D.W. Brenner, O.A. Shenderova, J.A. Harrison, S.J Stuart, B. Ni, S.B. Sinnot, J. Physics: Cond. Matt., 14 (2002), 783. [3] A. Krasheninnikov, P. Lehtinen, A. Foster, R. Nieminen, Chem. Phys. Lett. 418 (2006), 132. Figures
The strong influence of configurations of graphane islands to electronic properties of graphene/graphane mixing structure D. G. Kvashnin, P. B. Sorokin and L. A. Chernozatonskii Emanuel Institute of Biochemical Physics, 4 Kosigin St., Moscow, Russia cvashnini@gmail.com Graphene is one of the most interesting materials synthesized in the last years which two-dimensional nature along with the fascinating electronic properties attracts the great attention from the scientific community. Graphene has an unique electronic properties such as the linear dispersion law leading to zero effective mass for electrons and holes. It already applied as solar cell [1], liquid crystal device [2], molecular sensor [3] and nano-sized transistor prototype [4]. Moreover, electronic properties of graphene can be drastically changes by only partial hydrogenation. It 2 was predicted that adsorption of only one hydrogen atom onto graphene area at ~ 2 nm can open the small band gap of 0.45 eV [5]. Furthermore, adsorption of hydrogen in the periodically arranged lines changes the properties of graphene similarly to graphene ribbons [6]: graphene confined by hydrogen lines displays band gap depended upon the distance between lines and their orientation. We considered the various concentration of the adsorbed hydrogen atoms from 2% to 56.3%. Note that the hydrogen content is not an absolute parameter that determines the electronic properties of the structures, due to the fact that the electronic structure of the superlattices also depends on the particular location of adsorbed atoms. In the Fig. 1 the atomic geometry and electronic structure of graphene with different content of adsorbed hydrogen is shown. We begin our study from considering of the structures with far-arranged (~2 nm) pairs of adsorbed hydrogen atoms (begin of nucleation process, see Fig. 1). Even at such low hydrogen concentration we observed the opening of the band gap. The electronic structure of the partially hydrogenated graphene is sensitive to particular arrangement of adsorbed hydrogen atoms. We studied this effect in more details by considering graphene with concentration of adsorbed hydrogen 56.25% with various distribution of adsorbed hydrogen atoms on the surface. We investigated two different configurations of graphane islands ( significiant difference between their electronic structure.
A A
A A or A B
B ) and didn't find A
References
[1] Xuan Wang, Linjie Zhi, and Klaus M端llen, Nano Lett. 8, (2008), 323
[2] Peter Blake, Paul D. Brimicombe, Rahul R. Nair, Tim J. Booth, Da Jiang, Fred Schedin, Le -onid A. Ponomarenko, Sergey V. Morozov, Helen F. Gleeson, Ernie W. Hill, Andre K. Geim, and Kostya S. Novoselov, Nano Lett. 8, (2008), 1704
[3] Jeremy T. Robinson, F. Keith Perkins, Eric S. Snow, Zhongqing Wei, and Paul E. Sheehan, Nano Lett. 8, (2008), 3137
[4] Antonio H. Castro-Neto, Materials Today 13, (2010), 1
[5] Elizabeth J. Duplock, Matthias Scheffler, and Philip J. D. Lindan, Hallmark of Perfect Gra-phene, Phys. Rev. Lett. 92, (2004), 225502-225505
[6] L. A. Chernozatonskii, P.B. Sorokin and J. Br端ning, Two-dimensional semiconducting na-nostructures based on single graphene sheets with lines of adsorbed hydrogen atoms, Appl. Phys. Lett., 91 (2007), P.183103; Chernozatonskii L.A. Electronic superlattices and waveguides based on graphene: structures, properties and applications / L.A. Chernozatonskii, P.B. Sorokin // Physica Status Solidi B. 245, (2008), P. 2086-2089; Figures Fig. 1 The evolution of the electronic properties of graphene superlattice. Atomic geometry (in the left), band structure (in the center) and density of states (in the right) of graphene superlattice with concentration of hydrogen a) 6.25% (Egap = 0.07 eV) and b) 6.25%, (Egap = 0.43 eV). DOS of superlattice and graphene are marked by solid and dotted lines, respectively. The Fermi energy is marked by horizontal (in the case of band structure) and vertical (in the case of density of states) line
Time resolved fluorescence characterization of oligo(p-phenylene ethynylene) based metallic nanorods. a
a
b
b
b
b
c,
F. Lahoz , D. López , J. Figueira , J. C. Mesquita , N. Oliveira , J. Rodrigues , A. Valkonen K. c c Nättinen , K. Rissanen a
Departamento Física Fundamental y Experimental, Electrónica y Sistemas, Universidad de La Laguna, 38206 La Laguna, Tenerife, SPAIN b CQM-Centro de Química da Madeira, LQCMM/MMRG, Universidade da Madeira, Campus da Penteada, 9000-390 Funchal, PORTUGAL c Nanoscience Center, Department of Chemistry, University of Jyväskylä, P.O. Box 35, 40014 JYU, FINLAND flahoz@ull.es
Highly conjugated molecules are being investigated for their potential applications in nanoelectronics [1] and in optoelectronics [2]. These systems are characterized by a delocalized -electronic density which could provide a pathway through which the movement of electrons is facilitated and, therefore, they could act as a model for molecular wires. Moreover, the excited -electronic density can relax radiatively by emission of a photon in a typical fluorescent process. In particular, organometallic nanorods with robust and redox capable metal centers can offer excellent properties over their organic counterparts by increasing energy throughput. However the determination of the electrical conductivity at the molecular level requires skilled sample preparation and sophisticated equipment. On the other hand, time resolved fluorescence is a powerful technique that provides valuable information about the dynamic processes involved in the relaxation of the excited -electronic states. In this study we analyze the fluorescence emission decays of different Metal-Ligand-Metal where L are oligo(p-phenyleneethynylene)s (OPE) and M are the metal complex moieties PdCl(PEt3)2 and RuCl(dppe)2. We have observed a significant reduction of the emission decay in the organometallic nanorods as compared to the Ligand OPE molecule without metallic termination complexes (example in Fig. 1). This result has been interpreted as an indication of a charge transfer process from the electrons to the metal complexes that can advantageously be used to improve the electrical conductivity of the nanorods. These results show the potential of the Time Resolved Fluorescence technique as a first test to select the best molecules for nanoelectronic applications. In addition to this, two of the obtained crystal structures (example in Fig. 2) will be presented. References [1] J. M. Tour, Molecular Electronics: Commercial Insights, Chemistry, Devices, Architecture and Programming; World Scientific: River Edge, NJ, (2003). [2] C. Ornelas, C. Gandum, J. Mesquita, J. Rodrigues, M. H. García, N. Lopes, M. P. Robalo, K. Nättinen, K. Rissanen, Inorg. Chim. Acta, 358 (2005) 2482.
Figures
10000 (a) no metallic group (b) Pd metallic group (c) Ru metallic group IRF
1000 (b)
100 10 1
(a)
(c)
0
5
10
15
20
25
Time (ns)
30
35
40
Figure 1: Fluorescence decay curves of a OPE nanowire (a) without termination group; (b) with Pd metal complex (Pd metallic termination group); and (c) with Ru metal complex (Ru metallic termination group). Instrumental response function (IRF) of the equipment is also included.
Figure 2: Plot of a PdCl(PEt3)2 tris(phenylene ethynylene) rod (50% probability displacement ellipsoids). Acknowledgments: We gratefully acknowledge the support of Agencia Canaria de Investigaci贸n, Innovaci贸n y Sociedad de la Informaci贸n, Gobierno de Canarias (SolSubC200801000088), the Portuguese Science Foundation (FCT) through the Pluriannual base funding (PEstOE/QUI/UI0674/2011), the research project PTDC/CTM/098451/2008, SFRH/BD/29325/2006 (JF Ph.D. grant) and the NMR and MS Portuguese Networks (PTNMR-REDE/1517/RMN/2005POCI2010/FEDER, REDE/1508/REM/2005). CS Madeira is also gratefully acknowledged for their support.
Two-layer synchronized ternary quantum-dot cellular automata wire crossings Iztok Lebar Bajec, Primo University of Ljubljana,
ilb@fri.uni-lj.si
, Ljubljana, Slovenia
Since the first introduction of Quantum-dot Cellular Automata (QCA), an interesting nano-scale computing paradigm, by C. Lent et al. in 1993 [1], many researchers have embraced its simple concept and potential as a future processing platform. Soon QCAs that implement the functionally complete set of binary logic functions and from there on more and more complex designs were introduced. In recent years a group of researchers have presented a generalization of the basic QCA cell (fig 1), namely the ternary QCA (tQCA) cell (fig 2) [2], which enables ternary computation. Their principal motivator was the premise that future processing platforms should not disregard the advantages of multi-valued processing. These have been extensively researched over the past five decades [3]. The group presented the basic ternary building blocks, the inverter, majority gate, wire, corner-wire and fanout, and more recently also a functionally complete set of ternary logic functions, based on Post Logic, and a memorizing tQCA circuit [4,5]. Due to the specifics of the tQCA cell wire crossings seem to be the principal drawback before a more widespread acceptance of tQCA circuitry. Wire crossings are one of the most used steps in systematic logic design. In the classic, binary QCAs, wires can be crossed either in a coplanar fashion, by using rotated QCA cells for one of the wires, or in a multilayer fashion, where two intermediate layers are used to prevent any possible crosstalk between the two crossing lines. Although the multilayer approach proves to be more robust [6], the majority of designs employ the coplanar one; that is in fact one of the most praised features of classic QCA. Coplanar crossings in tQCA are not possible, but multilayer crossings are, as it has been presented recently [7]. Here we go a step further, by presenting a wire crossing that is synchronized, i.e. the two wires employ such clocking schemes (fig 3) that the outputs have the same effective delay. In addition the clocking schemes allow for a two-layer design, in other words removing the requirement for additional layers, whose sole purpose is to prevent possible crosstalk. Crosstalk is prevented with a clever clocking scheme. Figure 4 presents a two-layer synchronized wire crossing that achieves the most compact wire crossing possible. Typically it will be employed when two wires running parallel to one another have to be swapped. As already stated, there are only two layers in this design, with the inter-layer distance being equal to that between neighbouring cells. Research showed that this inter-layer distance is also the most robust one. The total delay of the crossing is one clock cycle. The four phases are used so as to keep the distance between active cells as large as possible. Active cells on the two layers are never directly one over the other, although this would not present a real issue as long as enough cells are active in the same instant. The lower line, marked X1, travels in a diagonal fashion on the lower layer, achieved in one clock cycle (four phases), with blocks of two cells, so that the same state that is input to the first cell appears on the last cell, marked Y1. The upper line, marked X2, travels fist to the upper layer then in a diagonal fashion downwards and back to the lower layer, all again in one clock cycle. It has to be noted that when moving from one layer to the other, the cell state propagates in an alternating fashion, state A becomes B, and vice versa, as well as state C becomes D and vice versa. When wire crossing is taking place this has no real effect, as eventually the state will be once more alternated upon moving back to the original layer. In the case when processing has to be performed on different layers, however, this fact has to be kept in mind. For states C and D it presents no problem, as they both represent the same logic value and alternating between the two states is achieved through simple addition of another adjacent cell. For states A and B, which represent two opposite logic values (-1 and 1 respectively), this however means adding an inverter (which in its simplest form could be just one cell displaced diagonally) or designing the processing element based on an inverted input value. Our current research is devoted to the study of synchronized two-layer wire crossings that consume fewer clock cycles as well as tile based solutions, what we find to be one of the more promising approaches for QCA design in general.
References [1] C. Lent, P. Tougaw, W. Porod, G. Bernstein, Nanotechnology, 4 (1993) 49. [2] I. Lebar Bajec, N. Zimic, M. Mraz, Nanotechnology, 17 (2006) 1937. [3] M. Fitting, E. Orlowska, (eds.), Beyond two: Theory and applications of multiple-valued logic. Physica-Verlag, Heidelberg (2003). [4] P. Pecar, A. Ramsak, N. Zimic, M. Mraz, I. Lebar Bajec, Nanotechnology, 19 (2008) 495401. [5] P. Pecar, M. Janez, N. Zimic, M. Mraz, I. Lebar Bajec, IEEE Computer Society Annual Symposium on VLSI, (2009) 223 [6] G. Schulhof, K. Walus, G.A. Jullien, ACM Journal on Emerging Technologies in Computing Systems, 3 (2007) 2. [7] P. Pecar, The Fifth International Conference on Quantum, Nano and Micro Technologies, (2011) 80057. Figures
Fig 1. The binary quantum-dot cell, the rotated binary quantum dot cell (a), and the representation of the binary logic values (b).
Fig 2. The ternary quantum-dot cell (a), and the representation of the ternary logic values (b).
Fig 3. The clock cycle governing the pipeline transmission through a quantum-dot cellular automaton. It is based on four phases, switch (0-¼), hold (¼-½), release (½-¾) and relax (¾-1). Indexes 0-3 indicate clock zones, governed by a phase shifted original clock signal C0, so that when a cell in clock zone 0 is in the hold phase, a cell in clock zone 1 is in the switch phase.
Fig 4. The two-layer synchronized wire crossing in ternary quantum-dot cellular automata.
Carbon Nanoflake/ Tin Oxide Composites Gas Sensors for NH3 Detection Soo-Keun Lee, Daeic Chang Daegu Gyeongbuk Institite of Science and Technology(DGIST), 50-1 Sanf-Ri, Hyeonpung-Myeon, Dalseong-Gun, DAEGU, KOREA laser@dgist.ac.kr Recently, functional nanostructured materials such as wires, rods, belts, and tubes, have a great considerable attention because of their unique applications in diverse industrial fields. For industrial applications, the key problem to solve is the development of synthetic process to prepare them economically and control their physico chemical properties easily. In this regards, we have synthesized carbon nano flake(CNFL) by using electrochemical exfoliation method and applied for the detection of NH3 gas. A thin film resistive gas sensor using a composite material(CNFL/SnO2) was manufactured by the drop casting method, and the sensor was evaluated for various ammonia concentrations and operating temperatures. Physical characteristics of the composite material were assessed using SEM and EDS. The composite material having 10% of SnO 2 showed 300% improved response and high repeatability at the optimal temperature of 400 degrees of Celsius compared to a gas sensor fabricated using a pristine SnO2 nano-particle. Besides the fact that these composite films present a high sensitivity to NH 3, it appears that contents of CNFL/SnO 2 play an important role on the sensitivity of the chemical gas sensors. Such behavior still deserves further understanding and the key parameters remain to be elucidated. Acknowledgements: This work was supported by DGIST basic research program of the MEST(11 -NB03). References [1] Ching-Yuan Su, Ang-Yu Lu, Yanping Xu, Fu-Rong Chen, Andrei N. Khlobystov, and Lain-Jong Li, ACS Nano, 5 (2011), 2332. [2] S. Iijima, Nature, 354 (1991) 56. Figures
Figure 1. SEM images showing the morphology of the CNFL/SnO2-NP on an alumina substrate.
Figure 2. Dynamic response of CNFL/SnO 2 gas sensor exposed to 100 ppm NH 3.
Single Walled Carbon Nanotubes as a Scaffold to Concentrate DNA for Studying DNA-Protein Interactions Zunfeng Liu, Remus Th. Dame, Jan Pieter Abrahams Gorlaeus lab, Leiden Institute of Chemistry, 2300RA, Leiden University liuz2@chem.leidenuniv.nl The genomic DNA in bacteria exists in a condensed state, which exhibits different biochemical and biophysical properties from a dilute solution.1 In this paper, DNA was concentrated on streptavidin2,3 coated single walled carbon nanotubes (Strep SWNTs) via biotin-streptavidin interaction. We reasoned that confining DNA within a defined space via mechanical constraints, rather than by manipulating buffer conditions, would more closely resemble physiological conditions. By ensuring a high streptavidin loading on SWNTs of about 1 streptavidin tetramer per 4 nm of SWNT, we were able to achieve dense DNA binding. DNA is bound to Strep SWNTs at a tunable density, and up to as high as 0.5 mg ml-1 in solution and 29 mg ml-1 on 2D surface. This platform allows us to observe aggregation behaviour of DNA at high concentration and the counteracting effects of nucleoid HU protein on the DNA aggregates, as shown in Figure 1. This provides an in vitro model for studying DNADNA and DNA-protein interactions at a high DNA concentration.
Figure 1. AFM images of bio-DNA captured on Strep SWNTs on mica (a) and after incubating with nucleoid HU protein (b). The height analysis shows that DNA has a height of ~0.4 nm, which forms aggregates at high concentration, and the height increases to ~ 2 nm after incubating with HU, and the aggregates dissociate. The diameter increase should be ascribed to the formation of HU DNA complex. References [1] W. M. Gelbart, R. F. Bruinsma, P. A. Pincus, V. A. Parsegian, Phys. Today 2000, 53 38-44. [2] Z. F. Liu, F. Galli, K. G. H. Janssen, L. H. Jiang, H. J. van der Linden, D. C. de Geus, P. Voskamp, M. E. Kuil, R. C. L. Olsthoorn, T. H. Oosterkamp, T. Hankemeier, J. P. Abrahams, J. Phys. Chem. C 2010, 114 4345-4352. [3] Z. F. Liu, L. H. Jiang, F. Galli, I. Nederlof, R. C. L. Olsthoorn, G. E. M. Lamers, T. H. Oosterkamp, J. P. Abrahams, Adv. Funct. Mater. 2010, 20 2857-2865.
Size of the single domain magnetite particles and MRI parameters Barbara Maciejewska NanoBioMedical Centre and Department of Macromolecular Physics, Faculty of Physics, Adam Mickiewicz University Umultowska 85, 61bmacieje@amu.edu.pl Magnetic nanostructures are being increasingly used in medical diagnosis and treatment [1]. The properties of these structures depend on their size, shape and crystallographic structure. Among many kinds of nanoparticles that have magnetic properties, iron oxides form a large and diversified group and are of our research interest. One of the representative of this group is magnetite that possesses the most interesting properties. Magnetite has two cations Fe3+ and Fe2+ that create the inverse spinel structure and have ferrimagnetic properties. Magnetite (Fe3O4) magnetic properties depend on the size of its magnetic structure. If we reduce the size of the magnetic particle to the nanoscale, the properties will change from ferrimagnetic to paramagnetic. That behavior is due to the creation of magnetic domain. If the size of a magnetic particle is small enough the probability of the domain walls creation is very low. As a result, single domain state is more energetically favorable compared to multi domain state. Such magnetite nanostructures have superparamagnetic properties. Superparamagnetic nanoparticle has a unique magnetic moment that significantly influences relaxivity in its closest environment. The aim of the study was to examine the effect of the size of single domain magnetite structures on relaxivity of toluene as a selected solvent. The phenomenon is directly related to two different processes that influence the relaxation of the solvent. The first is concerned with the Brownian motion of SPIO (Superparamagnetic Iron Oxide) nanoparticles, the second one is associated with the Neel relaxation. The contribution of Neel and Brownian relaxation strongly depends on magnetite crystal radius [1,2,3]. In our experiment magnetic nanoparticles were suspended in organic solvents in presence of oleic acid (toluene) and polyethylene glycol (water). The nanoparticles size distribution (fig.1) was examined using Transmition Electron Mictoscope (JEOL-JEM 1400, electron accelerating voltage 120kV and JEOL-ARM 200F, electron accelerating voltage 200kV). The chemical characterization of the particles was obtained using Energy Dispersive X-ray Spectroscopy (EDS). Proton relaxivity of toluene with magnetite particles of three different sizes: 5, 10 and 20 nm as well as 10 nm magnetite particles in water was measured using NMR techniques. 1 H spin-lattice (T1) and spin-spin (T2) relaxation times of toluene with magnetite particles of three different sizes were measured using pre-saturation and CPMG sequences respectively. For the particle sizes of 5 and 10 nm the increase of the T 1 relaxation time with increase of particle size was observed. We believe that this size effect is associated with the size of particles for Brownian and Neel processes which have influence on relaxation of the solvent to the same extent. Spin-spin relaxation time for the two smallest sizes behaves like T1 i.e. the smaller size of particles, the shorter T2. Spinspin relaxation time for 20 nm particles is the shortest. We believe that either the 20 nm particles start to have the ferrimagnetic nature or spin-spin interaction is governed by Neel effect. Hence, NMR relaxation dispersion of magnetite nanoparticles was noticed. References [1] A. J. L. Villaraza, A.Bumb, M. W. Breichbiel, , 2010, Chem. Rev. 110, 2921 2959 [2] M.F.Casula, P. Floris, C. Innocenti, A. Lascialfari, M. Masinone, M. Corti, R.E. Sperling, W.J. Parak, C. Sangregorio, 2010, Chem. Mater, 22, 1739 1748 [3] D.Maity, p. Pradhan, P. Chandrasekharan, S.N. Kale, B. Shuter, D. BBahadur, Si-Shen Feng, JunMin Xue, J. Ding, 2011, Journal of Nanoscience and Nanotechnology, 11, 2730 2734 [4] V.Clavio Jordan, M. R. Calpan, K.M. Bennet, 2010, Magnetic Resonance in Medicine, 64, 1260 - 1266
– μm and 2 μm diameter was fabricated by a metallographic etching technique using a Ni film. –
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Silver-functionalized carbon nanofibers composite electrodes for Ibuprofen detection Florica Manea1, Sorina Motoc1, Aniela Pop1, Adriana Remes1, Joop Schoonman2 1 2
”Politehnica” University of Timisoara, Romania Delft University of Technology, The Netherlands florica.manea@chim.upt.ro
Abstract Nanoscale carbonaceous materials, especially carbon nanotube (CNT) and carbon nanofibers (CNF) have attracted great research interests for electroanalysis field. The development of carbon nanofiber based composite electrodes combine the enhanced electrical properties and easy of processing exhibiting attractive electrochemical and economical features [1]. However, the improvement of the electroanalytical signal requires catalyst incorporation into composite matrix, and several studies have been directed to silver-decorated CNT [2]. In this study, two types of silver-functionalized carbon nanofibers composite electrodes, silver-decorated CNF-Epoxy (AgCNF) and silver-modified natural zeolite-CNF-Epoxy (AgZCNF) composites electrodes were prepared, morphologically and electrically characterized and applied for ibuprofen (IBP) detection in aqueous solution. Experimental Carbon nanofibers (CNFs) with average diameter of 60–150 nm and average length of 30– purchased from Applied Sciences Inc., Cedarville, Ohio (Pyrograf III -PR24 AGLD). Silver-modified zeolite was prepared by ion-exchange using natural zeolite (NZ) from Mirsid, Romania, with 68% wt., as we previous described [3]. The two-component epoxy resin used in the study was Araldite®LY5052/ Aradur®5052, purchased from Huntsman Advanced Materials, Switzerland. The decoration of silver nanoparticles into CNF composite was carried out by reducing silver ions in the presence of DMF. 1.1 g of CNF were added into 550 ml of DMF and the mixture was subjected to ultrasonication (Cole-Parmer 8900, USA) for 1 h. 40 ml of AgNO3 solution (0.02 M) was added into the mixture of 60-62 C durin the stirring. After 1h heating the solution was kept without stirring at room temperature for 48 h for Ag deposition, and after filtration and sequentially washed with water, ethanol and acetone resulted silverdecorated CNF. The composite electrodes were prepared by dispersion of CNFs in DMF, 99.9% (DMF, Sigma Aldrich) and epoxy resin (Araldite®LY5052) by ultrasonication, followed by the homogenization of the resulting paste with the zeolite particles and also with the hardener using a two-roll mill. The mixture was then poured into PVC tubes and cured at 60oC for 24 h, obtaining discs electrodes with the surface area of 0.196 cm2. The ratios were chosen to reach 20 % (wt.) CNFs for AgCNF electrode; 20 % (wt.) CNFs and 20 % (wt.) Ag-modified zeolite for AgZCNF electrode. Electrochemical measurements were carried out using an Autolab PGSTAT101 (Metrohm Autolab, The Netherlands) controlled with NOVA 1.6 software and a three-electrode cell, with a Ag/AgCl reference electrode, a platinum counter electrode and the composite working electrodes. Cyclic voltammetry (CV), differential-pulsed voltammetry (DPV), square-wave voltammetry (SWV) and chronoamperometry (CA) were used to assess the electroanalytical performance of the both composite electrodes for IBP detection in the aqueous solution. A preconcentration-detection scheme was proposed for AgCNF composite electrode, which exhibited a greater affinity for IBP sorption on the electrode surface to enhance the electroanalytical parameters. Results Figure 1 a, b shows the series of the cyclic voltammograms (CVs) recorded at silver-decorated CNFEpoxy (AgCNF) and silver-modified natural zeolite-CNF-Epoxy (AgZCNF) composites electrodes in 0.1 M Na2SO4 supporting electrolyte and in the presence of various IBP concentrations. A better sensitivity and correlation coefficient was reached for AgCNF in comparison with AgZCNF electrode. Also, using CA as the simplest electrochemical technique with real practical potential, very good electroanalytical performance for IBP detection at 1.3 V vs. Ag/AgCl was reached, even better than CV. Moreover, the AgCNF composite electrode exhibited useful peculiarities for applying the preconcentrationvoltammetric detection technique, and no electrode fouling occurred. Under these last conditions, a better sensitivity and a lower limit of detection were achieved, this electrode being useful to detect low concentrations of IBP in aqueous solutions.
Acknowledgments This work was partially supported by the PN-II-ID-PCE-2011-3-0582, PNII-72-156/2008 and PNII-RUPD129/2010 Grants and partially by the strategic grants POSDRU/21/1.5/G/13798, POSDRU/88/1.5/S/50783, Project ID 50783, POSDRU/89/1.5/S/57649 Project ID 57649 (PERFORMERA) co-financed by the European Social Fund â&#x20AC;&#x201C; Investing in People, within the Sectoral Operational Programme Human Resources Development 2007-2013. References [1] L. Rassaei, M. Sillanpaa, M.L. Bonne, F. Marken, Electroanalysis, 19(14) (2007), 1461 [2] F. Xin, L. Li, Composites: Part A 42 (2011), 961 [3] C. Orha, F. Manea, A. Pop, G. Burtica, I. Fazekas Todea, Revista de Chimie, 59(2008), 1. Figures
0.025
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Fig. 1. CVs recorded at a) AgCNF, b) AgZCNF electrodes in 0.1M Na2SO4 supporting electrolyte (curve 1) and in the presence of various IBP concentrations: 1-8 mgL-1(curves 2-9); potential scan rate of 50 mV/s. Inset: Calibration plots of peak current vs. IBP concentration. 5.0 0.020
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Fig. 3. Enhancement factor for the oxidation of 1 mgL-1 IBP as function of the accumulation time, with background current subtraction: 1AgZCNF electrode and 2- AgCNF electrode. Detection was performed in 0.1 M Na2SO4 supporting electrolyte by DPVs recorded at 1 Vvs. Ag/AgCl, potential scan rate 0.05 Vs-1.
Bio-sensing of arsenic by S-layer-modified gold nanoparticles Sabine Matys1, Mathias Lakatos1, Beate Katzschner2, Anja Caspari3, Wolfgang Pompe1 1 2
Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, 01062 Dresden, Germany Department of Chemistry and Food Chemistry, Technische Universität Dresden, 01062 Dresden, Germany 3 Leibniz Institute IPF Dresden, 01069 Dresden, Germany sabine.matys@nano.tu-dresden.de
In recent years, there is an increasing interest in the development of rapid, inexpensive and customerfriendly bio-sensing devices for fast detection of critical substances even under field-conditions. Since [1] the first investigations by Mirkin and co-workers , several colorimetric-based systems with gold nanoparticles have been developed. The basic principle of detection utilised the strong dependence of the optical properties of the nanoparticle on their size. Thus, gold nanoparticles are coupled with molecules that target analyte of interest. Upon binding of analytes to corresponding target molecules on the surface of gold nanoparticles, a particle aggregation occurs, which lead to a colour shift from red to purple. In view of this, we investigated, for the first time, the use of bacterial surface layer proteins (Slayers) as target molecules for detection of arsenic in model solutions. The aim of our work was to investigate the capability of several S-layers on gold nanoparticles to detect arsenic (V). S-layers are multifunctional molecules with a remarkable potential for bio- and nanotechnological applications [2]. Using the S-layer of Lysinibacillus sphaericus JG-A12, concentrations of arsenic in the range of 1 mM to 50 µM were detectable. Further, the sensitivity of the system was tunable by changing the nanoparticle size. Acknowledgment This work was supported by grant 03WKP08 from the innovation initiative “Innovative Regional Growth Cores with GC Potential “ (WK Potenzial) from the Federal Ministry of Education and Research (BMBF). References [1] Mirkin, C.A., Letsinger, R.L., Mucic, R.C., Storhoff, J.J., Nature, 382 (1996) 607 [2] Sleytr, U.B., Huber, C., Ilk, N., Pum, D., Schuster, B., Egelseer, E.M., FEMS Microbiol. Lett., 267 (2007) 131 Figures
A) TEM image of an S-layer coated gold nanoparticles at p H 3.5. B) TEM image of uncoated gold nanoparticles at pH 6.
Dispersion of multiwall carbon nanotubes in aqueous suspensions M. Michalska, M. Dobies, M. Grzeszkowiak, S. Jurga Department of Macromolecular Physics and NanoBioMedical Centre, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61m.mich@amu.edu.pl Carbon nanotubes (CNTs) are low density nanostructures built up of graphitic carbon, which exhibit remarkable mechanical properties (i.e. high strength and stiffness, elastic deformability), chemical stability, high electrical and thermal conductivity. These features of CNTs make them very promising and unique systems for new, already implemented, or potential applications in the material science, electronics, optics, biology and medicine [1]. The great obstacle to most applications of individual CNTs is their tendency to bundle up into ropes consisting of several tens of CNTs. These aggregation processes are governed by the strong intertube van der Waals attractions. The superior features of individual nanotubes in the aggregated state are significantly reduced, chemical manipulations limited and bioapplications infeasible. The preparation of aqueous suspensions of CNTs in the presence of appropriate dispersing agents is suggested to avoid these limitations. The interactions of dispersing agents such as surfactants or polysaccharides with carbon nanotubes lead to a separation of their bundles into individual nanotubes. In that way the unique properties of carbon nanotubes can be fully utilized [2 - 4]. The problem of stabilization of multiwall carbon nanotubes in water was the main goal of the study. Multiwall carbon nanotubes (MWCNTs) were suspended in water with addition the Nanosperse AQ surfactant (commercially dedicated) or natural polysaccharide - low methoxyl pectin (LMP). The morphology of studied systems was investigated by Transmission Electron Microscopy (TEM) (JEOL< JEM 1400, instrument with tungsten cathode operating at 120 kV). The chemical composition was evaluated via Energy-Dispersive X-ray Spectroscopy (EDS). The water dynamics in MWCNTs suspensions was analyzed by Nuclear Magnetic Relaxation Dispersion (NMRD) method [5]. The NMRD profiles showing spin-lattice relaxation T1 as a function of Larmor frequency provide information of the nature of a surface nuclear relaxation processes taking place at water-MWCNTs interface. Results of TEM studies have shown that exfoliation of MWCNTs appears due to addition of Nanosperse AQ (0.1% w/w) (Fig.1) and LMP (1% w/w) (Fig. 2). NMRD profiles exhibit the characteristic, logarithmic frequency dependence, terminated by plateau below a given cut-off frequency. With an increase of the MWCNTs concentration in aqueous suspensions the values of spin-lattice relaxation rates (R1) are becoming longer. At the same concentration of MWCNTs more effective relaxation processes were found for suspensions containing the Nanosperse AQ than those containing the LMP. These results suggest the existence of two-dimensional surface diffusion of the proton species in close proximity to paramagnetic impurities in the surface of MWCNTs [6]. The presence of paramagnetic impurities in the studied systems was confirmed by the EDS experiment. The experiment show that LMP is a good alternative for commercially dedicated dispersing agent, Nanosperse AQ, and because of its low toxicity, more usable in bioapplications.
References [1] Pulickel M. Ajayan1 and Otto Z. Zhou., Topics Appl. Phys., 80 (2001) 391 [2] Rausch J., Zhuang R.Composites: Part A, 41 (2010) 1038 [3] Jang B. K., Sakka Y., Woo S. K., J. Phys.: Conf. Ser. 156 012005 (2009) [4] Bandyopadhyaya R., Nativ-Roth E., Regev O. and Yerushalmi-Rozen R., Nano Letters 2, no.1 (2002) 25 [5] Kimmich R. , Anoardo E., Progress in Nuclear Magnetic Resonance Spectroscopy 44 (2004) 257 [6] Godefroy S., Korb J.-P., Fleury M., C. R. Acad. Sci. Paris, Chimie/ Chemistry 4 (2001) 857 Figures
Fig. 1 TEM micrograph of MWCNTs suspended in water with 0.1% w/w Nanosperse AQ
Fig. 2 Cryo TEM micrograph of MWCNTs suspended in water with 1% w/w LMP
Carbon Nanotubes separation techniques
efficiency and selectivity.
Ewa Mijowska, Pawel Lukaszczuk, Ryszard J. Kalenczuk West Pomeranian University of Technology Szczecin, Centre of Knowledge Based Nanomaterials and Technologies,Institute of Chemical and Environment Engineering, Poland emijowska@zut.edu.pl Carbon nanotubes are one of the greatest carbon nanostructures discovered during research on the new materials. Their unique properties arise from one dimensional cylindrical structure, in which diameter is about one nanometer and length exceeds few micrometers. Such a structure exhibits new very desirable electric properties like ballistic electron transport, superconductivity, semiconductivity with narrow band gap and metallic conductivity. Together with these electric properties great mechanical properties like outstanding tensile strength and self-healing in some conditions occur. Beside the electric and mechanical properties, nanotubes demonstrate high thermal conductivity along the axis. Combination of these electric, mechanical and thermal properties gives promising opportunity for new electronic compound production. However, synthesis methods are not sufficient for applications in electronics. As-produced material (raw SWNCTs) is a mixture of different species without specified electric properties. In order to use SWNCTs as a new electronic component, one should separate the semiconducting nanotubes from metallic ones. In this contribution we present the effects of different approaches in the single -walled carbon naotubes separation field. We show the results of dispersion/decantation method, selective destruction of one type of nanotubes and gel permeation chromatography technique. By verifying advantages and disadvantages of proposed method we point out at the most promising for future application. Comparing all separation techniques one can clearly see that some are more efficient but other more selective. Finding the optimal method is very important from economic point of view. Dispersion/decantation method is very energy consuming since it requires ultrasound application in order to disperse nanotubes. Additionally this method use toxic organic solvents which need to be recovered. Selective destruction is the simplest and cheapest method, it can be done via oxidation in air. This method can be carried out in flow reactor on a large scale. However, disadvantage of this process is that it is introduces structural defects. Produced material requires additional treatment since it contains amorphous carbon impurities. The most promising SWCNTs separation method is the gel permeation chromatography. This technique is based on interaction between agarose gel and different surfactants. Chromatography process uses nanotubes water dispersion with surfactant assistance. Preparation of stable suspension is energy consuming, however in this different species of the nanotubes in one process could be obtained. In conclusion, different methods of nanotubes separation were developed and they can be utilized in larger scale. Selective destruction can be promising method for semiconducting nanotubes production. Selective dispersion/decantation can lead to the precise separation according to chiral index. Low cost chromatographic process is the most efficient way to achieve the metallic/semiconducting nanotubes in a large scale.
Molecular Doping on the Electronic Properties of Silicon Nanowires in the [112], [110], [100] and [111] directions 1,3
2
1
A. Miranda , X. Cartoixà , E. Canadell , R. Rurali 1
1
Institut de Ciència de Materiales de Barcelona (ICMAB CSIC), Campus de Bellaterra, 08193 Bellaterra (Barcelona), Spain 2
Campus de Bellaterra, 08193 Bellaterra (Barcelona), Spain 3
Instituto Politécnico Nacional, ESIME-Culhuacan, Av. Santa Ana 1000, 04430 México D.F., México amiranda@icmab.es
We report ab-initio calculations on Silicon Nanowires (SiNWs) oriented along the [112], [110], [100] and [111] directions based on density functional theory (DFT). The influences of the molecular doping and quantum confinement on the electronic properties onto SiNWs are studied [1]. Continuous miniaturization of microelectronic devices requires a corresponding reduction in feature size, and low-dimensional materials have become one of the most active research topics in recent years. In particular, SiNWs are especially attractive for their possible efficient integration in conventional Si-based microelectronics [2,3]; the interest is essentially related to the strong modifications of the basic properties of the material induced by space confinement, with remarkable effects on the optical properties. The possibility that an adsorbed molecule could provide shallow electronic states that could be thermally excited have received less attention than substitutional impurities and could potentially have a high impact in the doping of SiNWs. With such an approach one would simultaneously get rid of two problems that bedevils SiNW doping: (i) the competition between catalyzed and uncatalyze d incorporation of the impurities, often leading to sizeable disuniformities in the dopant concentration [4]; however, this in-situ approach does not always give favorable results [5], (ii) the need to carry out demanding annealing cycle to promote diffusion in ex-situ doping [6,7]. This inconvenience is shared by both conventional in-situ and ex-situ approaches. Here we explore the possibility of obtaining molecular doping of SiNWs. We show that a molecular -based ex-situ doping, where molecules are adsorbed at the sidewall of the NW, can be an alternative path to doping [8]. We discuss the cases of donors. We present results for SiNWs with a diameter of 1.5 nm oriented along the [112], [110], [100] and [111] doped with NH3, whose the band structure are shown in Figs. 1(a), 2(a), 3(a) and 4(a) respectively. It can be seen for all SiNWs that the adsorbed molecule contributes with a localized state close to the conduction band edge, where it pins the Fermi level. Therefore the adsorbed molecule is found to be an efficient donor, as carriers can be thermally excited into the conduction band. More specifically we have found that NH3 requires less energy to adhere to {110} faces, regardless of the growth orientation of the SiNWs. The molecular nature of these states are further supported by the projected electronic density of states, where projections are made on nitrogen, hydrogen and silicon [Fig. 1(b), 2(b), 3(b) and 4(b)]. There it can be seen that the localized states is almost exclusively made up of N and H contribution, thus it is localized at the molecule adsorption site. We acknowledge the financial support Funding under Contract Nos. TEC2009-06986, FIS200912721C04-03, and CSD2007-00041 and Postdoctoral Abroad - Consejo Nacional de Ciencia y Tecnología, México.
References [1] R. Rurali, Rev. Mod. Phys. 82 (2010) 427. [2] J. Chen, Microelectron. J. 39 (2008) 50. [3] W.M. Weber, L. Geelhaar, A.P. Graham, et al., Nano Lett. 6 (2006) 2660. [4] G. Imamura, T. Kawashima, M. Fujii, et al., Nano Lett. 8 (2008) 2620. [5] L. Pan, K.-K. Lew, J.M. Redwing, and E.C. Dickey, J. Cryst. Growth, 277 (2005) 428. [6] S. Ingole, P. Aella, P. Manandhar, S. et al., J. Appl. Phys. 103 (2008) 104302. [7] A. Colli, A. Fasoli, C. Ronning, S. Pisana, S. Piscanec, and A. C. Ferrari, Nano Lett. 8 (2008) 2188. [8] A. Miranda-Durán, X. Cartoixà, M. Cruz-Irisson and Rurali, Nano Lett. 10 (2010) 3590. Figures
Figure 1. SiNW doped with NH3 in the [112] direction (a) Electronic band structures, (b) Projected electronic density of states.
Figure 2. SiNW doped with NH3 in the [110] direction (a) Electronic band structures, (b) Projected electronic density of states.
Figure 3. SiNW doped with NH3 in the [100] direction (a) Electronic band structures, (b) Projected electronic density of states.
Figure 4. SiNW doped with NH 3 in the [111] direction (a) Electronic band structures, (b) Projected electronic density of states.
Enhanced tensile strength of thick dielectrophoretic carbon nanotube fibers by TiO 2 infiltration Robert Matias Mononen, Margo Plaado, Jaan Aa Saal
Ilmar Kink, Kristjan
Institute of Physics, University of Tartu, and Estonian Nanotechnology Competence Centre, 142 Riia Street, 51014 Tartu, Estonia mononen@fi.tartu.ee Carbon nanotube fibers (CNT-fibers) have recently attracted attention because of their potential in developing strong lightweight materials. Research on both neat and those of polymer matrix composite fibers have been increasingly promising. However, there are certain physical restrictions in reinforcing neat CNT-fibers, whereas in the case of composite fibers the lightweight phenomenon and other important mechanical characteristics inherent to these of neat fibers are lost. In this work we demonstrate an alternative method an atomic layer deposition (ALD) of thin TiO 2 film to the porous framework of neat CNT-fibers produced by dielectrophoresis. The performance of treated fibers is outstanding, as the TiO 2 coating of 10 nm thickness provides up to fivefold increase in their tensile of the fibers remains virtually intact. High-resolution electron microscopy and elemental analysis reveal that the ALD parameters can be adjusted so that the TiO 2 coating thoroughly infiltrates the CNT-fiber, yielding thin layer of TiO2 on the CNT framework that constitutes the fiber. Thus, the structure and porosity of the initial fiber is largely maintained. We propose the ALD-coating infiltration method being effective and perspective alternative in developing novel lightweight and mechanically strong CNT based materials. Acknowledgements This work was supported by the Estonian Science Foundation grant no 8420, 8428, Eurocores Fanas Nanoparma Program and by the Estonian Nanotechnology Competence Center. Figures
Figure 1. TEM image of a broken TiO2 infiltrated CNT-fiber (left) and SEM image of a TiO2 infiltrated CNT-fiber (right).
Structural and electronic properties of some derivatives of C20 F. Naderi Department of Chemistry, Shahr-e Qods Branch, Islamic Azad University, Shahr-e Qods, 37541-13115, Tehran, Iran fnaderi2@yahoo.com Full geometry optimizations are accomplished without any symmetry constraints by means of hybrid functional B3LYP [1-3] and the 6-31+G* basis set, as implemented in Gaussian 98 [4]. The applied basis set is comprised of Pople s well known 6-31G* basis set [5,6] and an extra plus due to the importance of diffuse functions [7,8]. Vibrational frequency computations confirm that the fully optimized structures are indeed minima (NIMAG = 0). To obtain more accurate energetic data, single point calculations are performed at B3LYP/6-311++G** level. As a stability criterion of different configurations, binding energies are calculated according to the following expression: Eb = 20EC + 8EX E where E is the total energy of the C20X8 heterofullerene. Systems with larger binding energies are more stable. The electronic conductivity of the fullerenes which is related to the HOMO-LUMO energy gaps were considerably influenced by exohedral derivatives. The NBO population analysis on optimized structures is accomplished at the B3LYP/6-311++G**//B3LYP/6-31+G* level [9]. The smallest possible fullerenes cage, i.e. C20, taken into account of exohedral derivatives through our previously reported isolation strategy. The exohedral derivatives atoms are replaced at eight selected symmetric positions of C20. Probing heterofullerenes C20X8 where X = H, OH, CN, F, Cl and Br reveals that all the systems are true minima. Calculated binding energy of 216.54 eV show C20(CN)8 as the most stable heterofullerene followed by C20(OH)8 with the binding energy of 185.32 eV. The binding energies of the other heterofullerenes ranges from 138.45 to 153.55 eV. Exohedral derivatives leads to a high charge distribution on the surfaces of all heterofullerenes with the highest distribution on C20(OH)8 with +0.197 charged carbons and -0.711 charged O atoms. These high point charges upon the heterofullerenes surface can improve the storage capacity since make them worthy of investigation for hydrogen storage. All exohedral derivatives increase the HOMO-LUMO gap leading to the enhanced stability against electronic excitations. On the other hand, all exohedral derivatives decrease the conductivity of fullerene through increasing their HOMO-LUMO gap. Table1.Point groups (PG), total energies (Etot in a.u.), ranges of C-C and X C bond lengths (Å) and C C X angles (º) for the scrutinized heterofullerenes along with C 20 at the B3LYP/6-31+G* level. Binding energies (B.E.) and the smallest vibrational frequencies ( min) , HOMO-LUMO energy gaps ( EH-L (eV)) at B3LYP/6-311++G**. -1 min (cm )
EH-L (eV)
Species
PG
Etot (a.u.)
C-C
X-C
C-C-X
B.E. (eV)
C20
Ci
-761.6
1.40-1.53
-
-
121.27
32
1.89
C20H8 C20(OH)8 C20(CN)8
Th/C1 Th/C1 Th/C1
-766.7 -1368.6 -1504.7
1.35-1.54 1.35-1.54 1.34-1.54
1.09 1.40 1.16
118.8 120.7 119.2
152.25 185.32 216.54
474 182 85
5.67 5.08 5.60
C20F8 C20Cl8 C20Br8
Th/C1 Th/C1 Th/C1
-1560.8 -4443.7 -21355.1
1.35-1.53 1.35-1.53 1.35-1.52
1.37 1.79 1.96
118.1 118.6 118.3
153.54 142.38 138.44
192 108 61
5.11 5.06 4.74
References [1] A. D. Becke, Phys. Rev. A 38 (1988) 3098. [2] A. D. Becke, J. Chem. Phys. 98 (1993) 5648. [3] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785. [4] M.J. Frisch et al., Gaussian 98; Gaussian, Inc.: Pittsburgh, PA, 1998. See the supporting information for the full reference. [5] P.C. Hariharan, J.A. Pople, Mol. Phys. 27 (1974) 209. [6] M.M. Francl, W.J. Pietro, W.J. Hehre, J.S. Binkley, M.S. Gordon, D.J. DeFrees, J.A. Pople, J. Chem. Phys. 77 (1982) 3654. [7] T. Clark, J. Chandrasekhar, G.W. Spitznagel, P.v.R. Schleyer, J. Comput. Chem. 4 (1983) 294. [8] M.J. Frisch, J.A. Pople, J.S. Binkley, J. Chem. Phys. 80 (1984) 3265. [9] E.D. Glendening, A.E. Reed, J.E. Carpenter, F. Weinhold, NBO Version 3.1.
C20H8
C20F8
C20(OH)8
C20Cl8 Fig. 1. Optimized heterofullerenes at B3LYP/6-31+G.
C20(CN)8
C20Br8
Self Assembly of Acetylene-Appended Porphyrin on Au(111) and cycloaddition of 7,7,8,8-Tetracyano-p-quinodimethane (TCNQ) visualized by Scanning Tunneling Microscopy [a]
[b]
[a]
[a]
Sylwia Nowakowska, Petra Fesser, Cristian Iacovita, Aneliia Shchyrba, Christain Wäckerlin,[c] Saranyan Vijayaraghavan, [a] Nirmalya Ballav,[c] Kara Howes,[b] Jean-Paul Gisselbrecht, [d] Maura Crobu,[e] Corinne Boudon,[d] Meike Stöhr,[f] Thomas A. Jung, *[c] *[b] and Francois Diederich [a]
Institute of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland sylwia.nowakowska@unibas.ch Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg HCI, 8093 Zürich, Switzerland pfesser@student.ethz.ch [c] Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, 5232 Villingen PSI, Switzerland thomas.jung@psi.ch [d] -UMR 7177, C.N.R.S. Université de Strasbourg, 4, rue Blaise Pascal, 67000 Strasbourg ,France [e] Department of Materials (D-MATL), ETH Zürich, Hönggerberg HCI, 8093 Zürich, Switzerland [f] Zernike Institute for Advanced Materials, University of Groningen Nijenborgh 4, 9747 AG Groningen, The Netherlands [b]
The formation of covalenly interlinked two-dimensional structures on surfaces is highly desirable [1] because they feature higher thermal stability and roboustness than their self-assembled analogues. These structures can be equipped with functionalities to provide technologically interesting properties [2] [3] like specific electronic conductivity or high third-order optical nonlinearities. This benefit future applications in nanodevices. Scanning tunneling microscopy (STM) can be used to study the outcome of chemical reactions which occure on single-crystal metal supports with submolecular resolution. Only a few reactions have been [4] observed by STM on metal surfaces, mainly in closed-packed arrangements. The tetra (di-tertiary butyl-phenyl) porphyrin module has been functionalized with electron rich alkyne substituents as functional groups and has been deposited onto atomically clean Au(111) substrates. In detailed STM studies the self organization of these molecules in different 2D phases and structures has been observed to be of characteristic difference from previously observed cases for molecules with other porphyrin based bi-functional architectures. This phenomenon emerges from the complex interplay between the electrophylic and nucleophilic substituents with conformational adaptation. In combination with X-ray photoelectron spectroscopy (XPS) studies, the applicability of a formal [2+2] cycloaddition between electron rich alkynes and electron-deficient TCNQ on an atomically clean Au(111) surface was demonstrated. At low coverage, monomeric and self assembled dimeric species of the initial compounds as well as of the reaction product, a TCNQ-conjugated porphyrin, could be visualized. [5]
References [1] Recent reviews: a) J.A.A.W. Elemans, S.B. Lei, S. De Feyter, Angew. Chem., 121 (2009), 7434-7469; Angew. Chem. Int. Ed. 48 (2009), 7298-7332; b) J.V. Barth, Annu. Rev. Phys. Chem., 58 (2007), 375-407; c) T. Kudernac, S.B. Lei, J.A.A.W. Elemans, S. De Feyter, Chem. Soc. Rev. 38 (2009), 402-421. [2] D.F. Perepichka, F. Rosei, Science 323 (2009), 216-217. [3] a) C. Koos, P. Vorreau, T. Vallaitis, P. Dumon, W. Bogaerts, R.Beats, B. Esembeson, I. Biaggo, T. Michinobu, F. Diederich, W. Freude, J. Leuthold, Nat. Photonics, 3 (2009), 216-219; b) G. de La Torre, P. Vazquez, F. Agullo-Lopez, T. Torres, Chem. Rev., 104 (2004), 3723-3750. [4] Recent reviews: a) A. Gordon, Angew. Chem., 120 (2008), 7056-7059; Angew. Chem. Int. Ed. 47 (2008), 6950-6953; b) J. Sakamoto, J. van Heijst, O. Lukin, A.D. Schluter, Angew. Chem., 121 (2009), 1048-1089; Angew. Chem. Int. Ed., 48 (2009), 1030-1069.
[5] P. Fesser, C. Iacovita, C. Wäckerlin, S. Vijayaraghavan, N. Ballav, K. Howes, J. P. Gisselbrecht, M. Crobu, C. Boudon, M. Stöhr, T. Jung, F. Diederich, Chem. Eur. J., 17 (2011) 5246-5250
Figure
Reaction of Acetylene-Appended Porphyrin molecules with TCNQ on Au(111). The STM zoom depicts the starting material on the left and the reaction product on the right.
Assembly of 2D ionic layers by reaction of alkali halides with an organic electrophile
TCNQ
Jan Nowakowski (1), C. Waeckerlin (1), C. Iacovita (2), D. Chylarecka (1), P. Fesser (3), T. A. Jung (1) N. Ballav (1) (1) Paul Scherrer Institut, Villigen, Switzerland (2) University of Basel, Basel, Switzerland (3) Eidgenoessische Technische Hochschule Zuerich, Zuerich, Switzerland jan.nowakowski@psi.ch The remarkable electron-affinity of TCNQ (7,7,8,8-tetracyano-p-quinodimethane) allows charge-transfer (CT) not only with metals [1-4] and organic electron-donors [5], but also by oxidation of halogens in alkali-halides [6,7]. In the present study NaCl and LiCl have been selected as two alkali-halides to undergo a surface confined CT reaction. Sublimation of NaCl and LiCl onto a pre-assembled hydrogen-bonded layer of TCNQ on Au(111) [8] resulted in the formation of 2D ionic layers via a CT reaction without involvement of the substrate. To demonstrate that CT occurs between the reactants, and not with the Au(111) substrate, spectromicroscopy correlation experiments were performed. They involved scanning tunneling microscopy (STM) (Fig. 1) and photoelectron spectroscopy in the X-ray and UV range (Fig. 2). In case of TCNQ/Au(111) we find that no CT is occurring with the substrate (c.f. [8]) while on Ag(111) TCNQ is found to undergo substrate-to-molecule CT. Our experiments [11] suggest that by choosing various combinations of other salts and electron acceptors similar to TCNQ, ultra-thin ionic layers with tunable electronic and magnetic properties can be prepared without having to rely on i.e. alkali metals, where excess atoms can easily undergo CT with the substrate.
References [1] S. L. Tait, Y. Wang, G. Costantini, N. Lin, A. Baraldi, F. Esch, L. Petaccia, S. Lizzit and K. Kern, J. Am. Chem. Soc., 130 (2008), 2108-2113. [2] T. C. Tseng, C. Lin, X. Shi, S. L. Tait, X. Liu, U. Starke, N. Lin, R. Zhang, C. Minot, M. A. Van Hove, J. I. Cerda and K. Kern, Phys. Rev. B, 80 (2009), 155458. [3] S. Stepanow, R. Ohmann, F. Leroy, N. Lin, T. Strunskus, C. Woell and K. Kern, ACS Nano, 4 (2010), 1813-1820. [4] X. Q. Shi, C. Lin, C. Minot, T. C. Tseng, S. L. Tait, N. Lin,R. Q. Zhang, K. Kern, J. I. Cerda and M. A. Van Hove, J. Phys. Chem. C, 114 (2010), 17197-17204. [5] I. Fernรกndez-Torrente, K. Franke, and J. Pascual, Physical Review Letters, 101 (2008), 217203. [6] L. R. Melby, R. J. Harder, W. R. Hertler, W. Mahler, R. E. Benson and W. E. Mochel, J. Am. Chem. Soc., 84 (1962), 3374-3387. [7] J. Ferraris, D. O. Cowan, V. Walatka and J. H. Perlstein, J. Am. Chem. Soc., 95 (1973), 948-949. [8] I. Torrente, K. Franke, and J. Pascual, International Journal of Mass Spectrometry, 277 (2008), 269273. [9] J. M. Lindquist and J. C. Hemminger, J. Phys. Chem., 92 (1988), 1394-1396. [10] J. M. Lindquist and J. C. Hemminger, Chem. Mater., 1 (1989), 72-78. [11] C. Waeckerlin, C. Iacovita, D. Chylarecka, P. Fesser, T. A. Jung, N Ballav, Chem. Commun., 47 (2011), 9146-9148.
Figures
Fig. 1: STM image of the TCNQ layer on Au(111) before and after addition of NaCl.
Fig. 2: N1s and C1s XP spectra show evidence for neutral (TCNQ/Au(111)) and negatively charged TCNQ, accompanied by aromatization (TCNQ + NaCl/Au(111)) and TCNQ/Ag(111)) derived from the characteristic C1s peak shapes [9,10].
Gold (III) and gold nanoparticles interactions with humic acids a
a
a
Eladia María Peña-Méndez , Francisco Jiménez Moreno , Ana Isabel Jimenez Abizanda , Jose Elías Conde Gonzáleza, Juan José Arias Leóna and Josef Havelb,c,d a
Department of Analytical Chemistry, Nutrition and Food Science, Faculty of Chemistry, University of b La Laguna, 38071-La Laguna, Tenerife, Spain; Department of Chemistry, Faculty of Science, c Masaryk University, Kampus Bohunice, Kamenice 5/A14, Brno; Department of Physical Electronics, d Faculty of Science, Masaryk University, 2, 61137 Brno; R&D Center for Low-cost Plasma , Czech Republic E-mail: empena@ull.es The natural organic matter (NOM) is important in the transport, persistence, mobility, and bioavailability of inorganic and/or organic compounds in the environment. As a consequence, the aggregation behavior and surface properties of mineral particles and nanomaterials (e.g. engineered nanoparticles) in the environment is influenced by the adsorption of NOM to their surfaces and/or by their reactivity. Therefore, the understanding of nanoparticles behavior (fate, transport, and toxicity in natural environments) requires better knowledge of nanoparticles and also of their interactions with NOM in nature. Humic acids (HA) are the most important part of NOM and represent a complex mixture of partially "decomposed" and otherwise transformed organic material from different sources. Some of the components of HA do fluorescence. Fluorescence spectroscopy is fast, relatively easy and powerful method to follow such fluorescence structures but also method for providing knowledge about the chemistry and nature of the interactions between gold (III) or nano-gold and HA. The reduction of Au ic groups present in HA, the functional groups which are recognized to be efficient reducing agents for gold cations [1, 2]. Properties of humic acids, separation and applications were recently reviewed [3] and supramolecular complexation of HA with various xenobiotics demonstrated [4].The aim of the work is to study the interaction between i) Au (III) and soil HA and ii) gold nanoparticles and soil HA, applying spectrophotometry, fluorescence spectroscopy, mass spectrometry, etc. methods. The HA soil IHSS standard stock solution (200 mg.l-1) was prepared by dissolving the corresponding weight in 36 mM NaOH. Auric acid, HAuCl4·3H2O, was purchased from Sigma-Aldrich (Steinheim, Germany). Sodium hydroxide was from Merck (Darmstadt, Germany). All other reagents were of analytical grade purity. All aqueous solutions were made using ultrahigh purity water obtained using a Mill-Q Plus system (Millipore Co). Perkin-Elmer (Beaconsfield, Buckinghamshire, UK) spectrofluorimeter equipped with a xenon lamp and quartz cuvetteof 1 cm path length and 4 ml inner volume. Diode Array Detector spectrophotometer Hewlett Packard was used, as well. Mass spectra were acquired using a Bruker Autoflex mass spectrometer (Bruker Daltonics, Bremen, Germany). The mass spectrometer was equipped with a time of flight analyzer (TOF) and nitrogen laser (337 nm). Crison (Barcelona, Spain) digital pH-meter furnished with a combined glass saturated calomel double electrode. Lauda (Königshofen, Germany) MS6 thermostat. Ultrasonic cleaner (Selecta, Seville, Spain) was also used. Mass spectrometric measurements was performed on Axima fromKratos (Manchester, UK). Via spectrophotometry and fluorescence spectroscopy it was proved that Au (III) reacts with HA in several steps and in the final stage metallic nano-gold is formed. The kinetics depends on pH, HA concentration and temperature. We propose that in the first stage Au (III) is bound to HA, and then reduced to Au (0) generating gold nano-particles (GNP) of various size. The redox reaction is pH dependent (Fig. 1). The gold nanoparticles were characterized by scanning electron microscopy (SEM) , mass spectrometry and spectrophotometry. Because the fluorescence of GNP was found to be influenced by HA, the interaction GNP-HA was suggested (Fig. 2). Homogeneous in size gold nanoparticles can be prepared and at different conditions GNP of various size are formed. The results are important to understand gold mobility in the environment.
Acknowledgements E.M.P-M., J.E.C. and F.J. thank the partial support of the University of La Laguna (Spain). Canary Autonomic Government by research project PI 2007/011 is acknowledged. Grant Agency of the Czech Republic, projects no. 525/06/0663 and 202/07/1669, Academy of Sciences of the Czech Republic (project KAN 101630651) and the Ministry of Education, Youth and Sports of the Czech Republic (projects MSM0021622411 and LC 06035) are acknowledged. References [1] E.M.Peña-Méndez, , J. Havel, Chem. & Ecol. 26 (2010) 1672. [2] Talanta 67 (2005) 880. [3] E.M.Peña13 (2005) 13. [4] M. L. Pacheco, E. M. Peña-Méndez, J. Havel, Chemosphere 51, (2003) 95. 160 F l u o r e s c e n c e
pH = 3.02, HA + AuNP
140 120 100
pH = 3.02, HA + Au(III)
80
pH = 3.02, AuNp
60
pH = 5.05, HA + Au(III)
40
pH = 8.58, HA + Au(III) pH = 3.02, HA
20 pH = 3.35, Au(III)
0 250
350
450 550 Wavelength (nm)
650
Figure 1. Fluorescence spectra concerning Au (III) Figure 2. Scheme of redox reaction with HA and interaction between HA and GNP. and complexation of HA with GNP.
Direct Observation of Electron Confinement in Epitaxial Graphene Nanoislands 1
Soo-hyon Phark, Jérôme Borme,
1,2
1
1
1
A. León Vanegas, Marco Corbetta, Dirk Sander, Jürgen 1 Kirschner
1 Max-Planck-Institut fur Mikrostruckturphysik, Weinberg 2, 06120 Halle, Germany Iberian Nanotechnology laboratory, Avenida Mestre José Veiga, 4715-310 Braga, Portugal phark@mpi-halle.mpg.de
2
One leading question for the application of graphene in nanoelectronics is how electronic properties depend on the size at the nanoscale. Direct observation of the quantized electronic states is central to conveying the relationship between electronic structures and local geometry. Scanning tunneling spectroscopy was used to measure differential conductance dI/dV patterns of nanometer -size graphene islands on an Ir(111) surface. Energy resolved dI/dV maps clearly show a spatial modulatio n, indicating a modulated local density of states due to quantum confinement. We extract the electron dispersion relation from a quantitative energy dependent Fourier-analysis of the modulation pattern. We find a linear dispersion relation with E = E0 ± vF|k|, with E0 = -0.09±0.02 eV and Fermi velocity vF = (6.0±0.4) 5 ×10 m/s. This value is smaller as compared to previously published results on graphene/Ir(111),[1-3] 5 (9.0±1.2) ×10 m/s. We discuss possible reasons for this difference. References [1] R. Balog, B. Jørgensen, L. Nilsson, M. Andersen, E. Rienks, M. Bianchi, M. Fanetti, E. Lægsgaard, A. Baraldi, S. Lizzit, Z. Sljivancanin, F. Besenbacher, B. Hammer, R. G. Pedersen, P. Hofmann, and L. Hornekær, Nature Mater. 9 (2010) 315. [2] S. Rusponi, M. Papagno, P. Moras, S. Vlaic, M. Etzkorn, P. M. Sheverdyaeva, D. Pacilé, H. Brune, and C. Carbone, Phys. Rev. Lett. 105 (2010) 246803. [3] M. Kralj, I. Pletikosi , M. Petrovi , P. Pervan, M. Milun, A. T. N'Diaye, C. Busse, T. Michely, J. Fujii, and I. Vobornik, Phys. Rev. B 84, 075427 (2011). Figure (left) Energy-dependent spatial modulations of dI/dV signals in a graphene nanoisland. (right) Electron dispersion E(k) extracted from the wave vectors of the modulation patterns.
Scanning tunneling microscopy and spectroscopy on edges of epitaxial graphene/Ir(111) 1
Soo-hyon Phark, Jérôme Borme,
1,2
1
1
1
A. León Vanegas, Marco Corbetta, Dirk Sander, Jürgen 1 Kirschner
1 Max-Planck-Institut fur Mikrostruckturphysik, Weinberg 2, 06120 Halle, Germany Iberian Nanotechnology laboratory, Avenida Mestre José Veiga, 4715-310 Braga, Portugal phark@mpi-halle.mpg.de
2
We performed scanning tunneling microscopy/spectroscopy (STM/S) on monolayer graphene islands grown on Ir(111). The graphene islands show moiré patterns, which are induced by the lattice mismatch between graphene and Ir(111). The atomic structure at the edge of a graphene island depends on the stacking configurations of the edge atoms, which are correlated with the moiré patterns. The edges of graphene islands terminate with a zigzag carbon configuration and show periodic kinks in the regions of the on-top stacking carbon rings. The periodicity is given by the moiré pattern of the graphene island. The termination of a graphene island at an Ir(111) step also leads to the formation of periodic kinks at the edge. We tentatively ascribe these observations of periodic kinks at the graphene edges to the formation of favorable bonding situations between carbon edge atoms and the underlying Ir lattice. We may speculate that the electronic origin of this bond formation is linked to the int eraction of the broken -bond of graphene with Ir. Spatially resolved tunnel spectroscopy indicates a considerably reduced density of states at the edge as compared to center regions of the island. Figure
(left) A graphene island on Ir(111). (right) Spatially resolved STS data along the perpendicular directions to the edges of graphene/Ir(111).
Generation of Coulomb Matrix Elements for the 2D Quantum Harmonic Oscillator Miquel Pons Viver and Antonio Puente Departament de FĂsica, Universitat de les Illes Balears, E07122 Palma de Mallorca, Spain miquel.pons@uib.es Extant analytic formulas [1] for evaluating electron-electron interaction matrix elements in Fock-Darwin basis suffer from numerical stability problems due to large cancellations in the range of medium to large values of the magnetic quantum numbers. The problem can be bypassed using symbolic calculus software but the computation time is often prohibitive in that regime. The numerical reliability of an existing formula [1] and a novel expression presented in the poster are analyzed using computer-assisted algebraic techniques. We will show that our formula is clearly more stable but nevertheless, the analysis shows that the range of safety parameters is certainly narrow also, even using quadruple precision arithmetic. The main contribution presented here involves a set of recurrence relations which make possible to compute the set of matrix elements by means of any algebraic software at a very high rate. The algorithm devised for using these recurrences is described in detail. Computation time comparison between a Maple implementation of our scheme and previous expressions [1] is presented, showing an overall improvement of two orders of magnitude. Finally we show that the algorithm is even faster than numerical evaluation in calculating all the matrix elements required when working with basis sets of practical size.
References [1] P. Hawrylak, Solid State Communications 88 (1993) 475.
Copper-decorated carbon nanotubes based composite electrodes for non-enzymatic detection of glucose Aniela Pop1, Florica Manea1, Corina Orha2,3, Sorina Motoc1, Elida Ilinoiu1, Nicolae Vaszilcsin1, 4 Joop Schoonman 1
”Politehnica” University of Timisoara, Romania National Institute for Research and Development in Microtechnologies, Bucharest, Romania 3 NIRD in Electrochemistry and Condensed Matter, Timisoara Romania 4 Delft University of Technology, The Netherlands aniela.pop@chim.upt.ro, florica.manea@chim.upt.ro
2
Nowadays, a large community of researchers is focusing on the development of different applications for carbon nanotubes (CNTs), and in the field of electrochemical sensing, CNTs receive considerable attention. The high sensitivity, chemical stability, excellent electrical conductivity, modifiable surface which provide the possibility to fabricate multifunctional electrochemical sensors are only a few important properties that which recommend them for sensing applications [1,2]. Using CNTs in composites gives also the possibility to fabricate sensors with high electroanalytical performances with easy renewable surface and also having a very good mechanical strength. Glucose determination in medical applications by electrocatalytic oxidation is of great interest to electrochemists. Fabrication of high performance sensors for glucose continues to be a provocative challenge. In this paper three types of multi-wall carbon nanotube (CNT)-based composite electrodes, i.e., CNTs embedded in an epoxy matrix (CNT-Epoxy); CNTs – synthetic A-type zeolite (SZ) in an epoxy matrix (SZCNT-Epoxy), CNT – natural clinoptilolite zeolite (NZ) in an epoxy matrix (NZCNT-Epoxy), were prepared, and then modified with copper particles by electrodeposition and tested for direct electrochemical detection of glucose. Experimental Multi-wall carbon nanotubes (MWCNTs) with average diameter of 9.5 nm and average length of 1.5 m were purchased from Nanocyl, Belgium. Synthetic A-type zeolite (SZ) was prepared using natural
clinoptilolite as a silicon source and sodium aluminate as aluminum source, as we previous described [3]. The two-component epoxy resin used in the study was Araldite®LY5052/ Aradur®5052, purchased from Huntsman Advanced Materials, Switzerland. The composite electrodes were prepared by dispersion of MWCNTs in tetrahydrofuran, 99.9% (THF, Sigma Aldrich) and epoxy resin (Araldite®LY5052) by ultrasonication, followed by the homogenization of the resulting paste with the zeolite particles and the hardener using a two-roll mill. The mixture was then poured into PVC tubes and o 2 cured at 60 C for 24 h, obtaining discs electrodes with the surface area of 0.196 cm . The ratios were chosen to reach 20 % (wt.) CNTs for CNT-Epoxy electrode; 20 % (wt.) CNTs and 20 % (wt.) SZ for SZCNT-Epoxy electrode; and 20 % (wt.) CNTs and 20 % (wt.) NZ for NZCNT-Epoxy electrode, respectively. The surface of prepared electrodes was then decorated with copper by electrodeposition at a potential of -0.5 V for 20s in the presence of 0.1 M CuSO4 solution. Electrochemical measurements were carried out using an Autolab PGSTAT101 (Metrohm Autolab, The Netherlands) controlled with NOVA 1.6 software and a three-electrode cell, with an Ag/AgCl reference electrode, a platinum counter electrode and the composite working electrodes. Results
Figure 1 shows the SEM image of SZCNT-Epoxy composite material decorated with Cu particles. The EDX data for the electrode composite material revealed the presence of copper on the composite surface. The electrocatalytic activities of the copper-decorated CNT-Epoxy, SZCNT-Epoxy and NZCNTEpoxy electrodes towards the oxidation of glucose in an alkaline solution were demonstrated. Some examples of the cyclic voltammograms (CVs) recorded in 0.1 M NaOH solution and in the presence of different glucose concentrations are presented in the Figure 2. The differences between the electroanalytical performances of the electrodes are related to composite structure and morphology, which influenced copper particle size and distribution on the surface of the composite material. Best electroanalytical performances obtained for the detection of glucose by cyclic voltammetry were -1 recorded with the copper-decorated CNT-Epoxy electrode, i.e., electrode sensitivity of 8.45 mA and a LOD of 0.2 µM glucose. All copper-decorated composite electrodes exhibited useful properties for the direct oxidation and simple non-enzymatic determination of glucose on tested electrodes surface.
Acknowledgments This work was partially supported by the strategic grants POSDRU/89/1.5/S/57649, Project ID 57649 (PERFORM-ERA), POSDRU/89/1.5/S/63700 and POSDRU/88/1.5/S/50783, Project ID 50783, cofinanced by the European Social Fund â&#x20AC;&#x201C; Investing in People, within the Sectoral Operational Programme Human Resources Development 2007-2013 and partially by the PN-II-ID-PCE-2011-3-0582 and PNII-RU-PD129/2010 Grants. References [1] C. Hu, S. Hu, Journal of Sensors, Article ID 187615 (2009), M. Penza, G. Sberveglieri, W. Wlodarski, Y. Li Guest Eds., Hindawi Publishing Corporation. [2] C.L. Choong, W.I. Milne, K.B.K. Teo, The International Journal of Material Forming, 1 (2008), 117. [3] C. Orha, A. Pop, C. Lazau, I. Grozescu, V. Tiponut, F. Manea, Journal of Optoelectronics and Advanced Materials, 13(5-6) (2011), 544. Figures
Fig. 1. SEM images and EDX quantification of Cu decorated SZCNT-Epoxy electrode material. 1.0 0.8 0.6 0.4 0.2
0.4
y=0.01123+5.718x; 2 R =0.991
0.6
0.3
0.4
0.2
0.2 0.0 0.00
0.04
0.08
0.1
0.12
Glucose concentration / mM
-0.1
-0.2 -1.0
-0.5
0.0
0.5
1.0
1.5
0.1 0.0 0.00
0.03
0.06
0.09
Glucose concentration / mM
a)
0.8
-4
y=8.446x-5.488*10 2 R =0.9998
0.6 0.4 0.2 0.0 0.00
0.04
0.08
0.12
Glucose concentration / mM
0 -1.0
-0.5
0.0
0.5
-0.5
0.0
0.5
1.0
1.5
b) Fig. 2. CVs of a) Cu-SZCNT-Epoxy, b) CuNZCNT-Epoxy, c) Cu-CNT-Epoxy electrodes recorded supporting electrolyte and by 5 successive additions of 0.02 mM glucose in NaOH; potential scan rate 50 mV/s. Insets: calibration plots of peak currents vs. glucose concentrations.
3 1.0
-1.0
E / V vs SSC
E / V vs SSC
1
y=0.011+2.826x; R 2=0.994
0.2
0.0
0.0
2
0.3
1.0
1.5
E / V vs SSC c)
Prussian Blue Analogue thin films as promising materials of future molecule-based spintronic devices 1
1
1
Helena Prima Garcia , Eugenio Coronado , Juan Pablo Prieto , Francisco Romero 1
1
Instituto de Ciencia Molecular, Universidad de Valencia, Catedrático José Beltrán 2, 46980 Paterna (Valencia), Spain
helena.prima@uv.es
The family of Prussian blue analogues (PBA) of general formula CcAa[B(CN)6]b · n H2O (C = alkali cation, A, B = transition metal ions) are molecule-based magnetic materials with interesting properties that rely on: i) the presence of strong magnetic interactions between the spin carriers mediated by the cyanide bridge; and ii) the high dimensionality (3D) and connectivity of the magnetic lattice. As a result, [1,2] PBA showing spontaneous magnetization even above room temperature have been obtained. Due to their transparency in the visible region and their charge-transfer properties, these materials offer many advantages with respect to classical magnets in magneto-optics (i.e., in the study of the crossingeffect between magnetic and optical properties). Magneto-optical effects are used in various optoelectronic devices, such as optical memories, optical insulators, etc.[3] The most studied magnetooptical phenomenon in linear optics is the rotation of the plane of polarization of the incident light when passing through a magnetically ordered material (Faraday and magneto-optic Kerr (MOKE) effects for transmitted and reflected light, respectively). Thin films of PBA can also be interesting materials for the fabrication of future molecule-based spintronic devices[16] combining magnetooptical properties and spin transport. In this context, it has to be noted that a hot topic in molecular spintronics is that of fabricating spin valves [17] in which either the spin collector layer[18,19], or the ferromagnetic electrodes [20] are based on molecule-based materials. PBA magnets may exhibit several advantages with respect to the classical magnets used in spintronics (inorganic metals and metal oxides), such as the processability using solution techniques, the transparency and new added functionalities (like photomagnetism,[21–23] [24] piezomagnetism, etc.). Furthermore, their molecular nature could facilitate the spin injection towards the organic spin collector layer. In view of these applications, it is necessary to scale down the growth of the magnetic films to the nanometer level. A powerful technique like MOKE, with high sensitivity down to monolayer detection and a high spatial resolution limited by the laser spot,[25] seems promising in the study of the magnetic properties of such ultra-thin films and multilayered systems. To summarize, it has been demonstrated in this work that it is possible to reduce the thickness of electrodeposited films of Prussian blue analogues to the nanometer scale. These ultra-thin films possess a smoother surface consisting in homogeneous particles of smaller size. Interestingly, as the thickness of the film is reduced, its magnetic properties are considerably improved (higher coercivity and squareness of the hysteresis loops). It has also been shown that MOKE is a powerful technique for the determination of the magnetic properties of these molecule-based ultra-thin films. These materials offer an outstanding magneto-optical response due to the high intensity of the reflected light from the homogeneous transparent film surface. Further, MOKE yields the possibility of recording magnetic hysteresis loops at relatively high temperatures (just below Tc), a very important fact in terms of future applications. Indeed, the present study shows that is possible to obtain a magnetic hysteretic signal at 200 K from a molecular-based magnetic film with a thickness as small as 80 nm[13]. In view of the versatility of these materials, which include the easy tuning of the magnetic (nature of the magnetic ordering, magnetic anisotropy, critical temperature, coercivity) and electronic properties (redox potential, energy gap) by simply varying the nature of the metal centres, future work will focus on the fabrication and MOKE characterization of PBA magnetic multilayers to study proximity effects, as well as in the use of these films as spin injectors of all-molecular spin valves.
References [1] Authors, Journal, Issue (Year) page. [1] [2] [3] [4] [5]
S. Ferlay, T. Mallah, R. Ouahès, P. Veillet, M. Verdaguer, Nature. 378, (1995) 701–703. R. Garde, F. Villain, M. Verdaguer, J. Am. Chem. Soc. 124, (2002) 10531–10538 S. Sugano , N. Kojima , Magneto-Optics , Springer , Berlin, Germany (2000) J. Z. H. Xiong, D. Wu, Z. V. Vardeny, J. Shi, Nature. 427 (2009), 821–824. V. A. Dediu, L. E. Hueso, I. Bergenti, C. Taliani, Nature Mater. 8, (2009) 707 – 716.
[6] [7] [8] [9] [10] [11] [12] [13]
F. Wang and Z. V. Vardeny, J. Mater. Chem. 19, (2009) 1685. J.W. Yoo, C.Y. Chen, H. W. Jang, C. W. Bark, V. N. Prigodin, C. B. Eom, A. J. Epstein Nature Mater. 9, (2010) 638–642. O. Sato, T. Iyoda, A. Fujishima, K. Hashimoto. Science. 272, (1996) 704–705. N. Shimamoto, S. Ohkoshi, O. Sato, K. Hashimoto, Inorg. Chem. 41, (2002) 678–684. V. Escax, A. Bleuzen, C. Cartier dit Moulin, F. Villain, A. Goujon, F. Varret, M. Verdaguer, J. Am. Chem. Soc. 123, (2001) 12536–12543. E. Coronado, M. C. Giménez-López, T. Korzeniak, G. Levchenko, F. M. Romero, A. Segura, V. García-Baonza, J. C. Cezar, F. M. F. de Groot, A. Milner, M. Paz-Pasternak, J. Am. Chem. Soc. 130,( 2008) 15519–15532. S. D. Bader, J. Magn. Magn. Mater. 100, (1991) 440–454. E. Coronado, * M. Makarewicz, J.P. Prieto-Ruiz, H. Prima-García, * and F. M. Romero, 23, (2011) 4323-4326
Figures
Figure 1. AFM topography images of the surface of thin films of 1 obtained after different times of electrodeposition: 100 s (a, 1500 nm thickness), 50 s (b, 450 nm thickness), 25 s (c, 250 nm thickness), 10 s (d, 80 nm thickness).
Figure 2. Normalized MOKE hysteresis loops obtained in polar configuration for four different thin films of 1 of thickness 1500 nm, 450 nm, 250 nm, 80 nm.
Quantum dot addition energies: magnetic field and interaction screening Antonio Puente, Rashid Nazmitdinov and Miquel Pons Viver Departament de FĂsica, Universitat de les Illes Balears, E07122 Palma de Mallorca, Spain toni.puente@uib.es Quantum dots (QDs) have drawn a great deal of experimental and theoretical attention in recent years. In particular, this interest is due to the fact that QDs may provide a natural realization of quantum bits. It is also related to fundamental aspects of strongly correlated finite systems, which are different from bulk and can be controlled experimentally [1]. A convenient starting point to deal with the theoretical description of finite systems is, in many cases, a mean field treatment like the Hartree-Fock (HF) approach, either in space-restricted (RHF) or spaceunrestricted (UHF) schemes. As the case may require, depending on the model confining potential, post HF projection techniques can be applied to restore broken symmetries [2]. In this framework, selfconsistency between the mean field and the single-particle orbitals and total energy minimization are the basic conditions. The HF energy is a non linear functional of the single-particle states and a careful search for the absolute minimum, particularly important at high magnetic fields, is an essential requirement of the method. Moreover, one of the difficulties encountered in analyzing individual dot data is that energies have to be computed to very high precision. Experimental transport data through these systems, often presented as a difference between the gate voltages for two successive current peaks, can be related to the addition energy, EA(N)=EN+1 EN+EN , the second difference of the total energy with respect to the number of electrons in the dot. In typical QDs, the addition energy is around a few meV while total dot energies can be 1 to 3 orders of magnitude larger so that high precision is needed. This implies not only a good model description, but also as mentioned above a careful search for the ground state energies, which becomes harder in the high magnetic field regime where the density of states around the energy minimum increases. In this work we analyze the role of screening in the electron-electron interaction in the description of addition energies as a function of vertical magnetic field intensity and parabolic confinement, within a RHF formalism. We discuss the evolution of the quantum dot geometry for the ground and first excited states, and the structure of the density of states near the absolute energy minimum. Spin transitions and N-dependent ring shape isomers develop with the intensity of the applied magnetic field at a rate which scales with the interaction strength vs the parabolic confinement ratio, the so called Wigner parameter, RW. A comparison with available experimental data [3] is shown. References [1] S. M. Reimann and M. Manninen, Rev Mod Phys 74 (2002) 1283 1342. [2] C. Yannouleas and Uzi Landman, Rep. Prog. Phys. 70 (2007) 2067 2148. [3] P. A. Maksym, Y. Nishi, D. G. Austing, T. Hatano, L. P. Kouwenhoven, H. Aoki, and S. Tarucha, Phys Rev B 79 (2009) 115314(11).
Unusual photoluminescence of undoped hafnia perovskite nanoparticles synthesized via nonaqueous sol-gel process
Erwan Rauwel
1,2,3
3,4
3,4
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, Augustinas Galeckas , , Protima Rauwel , Mohamed Karmaoui and Helmer 1,3 Fjellvåg
1
Department of Chemistry, University of Oslo, N-0315 Oslo, Norway 2 SFI-inGaP, University of Oslo, N-0315 Oslo, Norway 3 SMN, University of Oslo, N-0315 Oslo, Norway 4 Department of Physics, University of Oslo, N-0316 Oslo, Norway erwan.rauwel@kjemi.uio.nol
Perovskite compounds are among the most interesting mixed metal oxide materials in terms of their optical, magnetic, ferroelectric and multiferroic properties. The synthesis of these compounds as nanoparticles is of fundamental importance as size reduction and shape engineering allow modification 1 and tuning of their fundamental properties, thus opening new possibilities for micro-, opto- and 2 nanoelectronic applications. Hafnia perovskite nanoparticles with size as small as 1.6nm in diameter were synthesized via a non3 aqueous sol-gel process. The synthesis procedures were carried out in a glove box using metallic t strontium (Sr) or calcium methoxide (Ca(OCH 3)2) and hafnium (IV) tert-butoxide (Hf(O Bu)4) mixed into benzyl alcohol. The mixture was transferred into a stainless steel autoclave, carefully sealed and then heated in a furnace at 300ºC for 2 days. An important advantage of this method is the possibility to synthesize pure and highly crystalline nano-sized perovskite (ABO 3)-type oxide nanoparticles without 4 use of surfactant. The structural properties of these nanoparticles were studied by XRD, TGA, SEM, HRTEM, Cs corrected TEM and XPS. High-resolution transmission electron microscopy micrographs presented in Figures 1 reveal high crystallinity of the defect free nanoparticles and that they possess the perovskite structure (power spectrum inset figure 1b). Cs corrected study enabled to differentiate the perovskite phase from the cubic HfO 2 phase. 4 Literature shows that upon cerium or europium doping, these perovskite nanoparticles exhibit certain luminescence from an otherwise optically inactive matrix material. UV-visible diffuse reflectance measurements allowed for the detection of impurity phases (CaCO 3) that were not visible using XRD 5 measurements and HRTEM study (Fig. 2). Under these measurements it was also possible to estimate the optical band gaps of the CaHfO 3 and SrHfO3 nanoparticles. Photoluminescence (PL) study of these undoped perovskite nanoparticles at room temperature revealed two important features. Firstly, an unexpectedly strong luminescence in the UV-visible region was observed for both types of nanoparticles. Secondly, spectral instability under continuous UV illumination became immediately apparent, exhibiting different trends for SrHfO3 and CaHfO3 nanoparticles. To get a better insight into these processes, more systematic PL measurements were carried out as a function of temperature (10 300K) (Fig. 3), UV-exposure time (0-15min) and surrounding ambient (air/vacuum). The influence of these parameters will be discussed and a tentative model will be proposed to explain these phenomena in terms of luminescent centers located at the surface of the nanoparticles. Acknowledgements Financial support from Marie Curie (PERG05-GA-2009-249243), the Research Council Norway project 176740/130 and Statoil through the inGAP project (Innovative Natural Gas Processes and Products) is acknowledged. References [1] L. G. Properties and applications of perovskite-type oxides New York: Dekker (1993) [2] C. Dubourdieu, I. Gélard, O. Salicio, G. Saint-Girons, B. Vilquin, G. Hollinger Int. J. of Nanotechnology 7, 320 (2010). [2] Vioux, A. Chem. Mater. 9, 2292 (1997). [3] Niederberger., M.; Pinna, N. Metal Oxide Nanoparticles in Organic Solvents: Synthesis, Formation, Assembly and Application; Springer, (2009). [4] Ji, Y. M.; Jiang, D. Y.; Wu, Z. H.; Feng, T.; Shi, J. L. Mater. Res. Bull. 40, 1521 (2005). [5] E. Rauwel, A. Galeckas, P. Rauwel and H. Fjellvåg Adv. Func. Mat. DOI: 10.1002/adfm.201101013.
Figures
Figure 1: TEM micrographs of CaHfO3 showing (a) general appearance of these particles, (b) electron diffraction pattern indicating CaHfO 3 cubic structure, (c) HRTEM image of a single particle oriented along <001> zone axis.
Figure 2: Diffuse-reflectance spectra measured in the UV-visible region at 300K for SrHfO3 and CaHfO3 nanoparticles; arrows indicate apparent absorption thresholds. Normalized Tauc plots considering (b) indirect optical transitions for SrHfO 3 and CaHfO3.
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Figure 3: Temperature-dependent PL spectra of CaHfO3 nanoparticles; insets show corresponding evolutions of the integral PL yield as a function of temperature.
-alumina using Atomic layer deposition: Spinel formation and luminescence induced by rare-earth doping
Erwan Rauwel
1,2,3
1,3
3,4
3,4
5
, Ola Nilsen , Augustinas Galeckas , Protima Rauwel , John Walmsley , Erling 6 1,3 Rytter and Helmer Fjellvåg
1
Department of Chemistry, University of Oslo, N-0315 Oslo, Norway 2 SFI-inGaP, University of Oslo, N-0315 Oslo, Norway 3 SMN, University of Oslo, N-0315 Oslo, Norway 4 Department of Physics, University of Oslo, N-0316 Oslo, Norway 5 SINTEF, Dpt. of Physics, Trondheim, Norway 6 Statoil Technol. Centre Trondheim, Trondheim, Norway erwan.rauwel@kjemi.uio.nol
There is presently a real challenge to build nanostructured materials on a large variety of supports and atomic layer deposition (ALD) stands out as the most promising method for coating nanomaterials 1 and more specifically nanoporous materials . There is now increasing interest in nanoporous complex 2 oxides, e.g. ZnO-based spinel type compounds . We have developed a new route towards synthesis of nanoporous spinel using nanoporous -alumina particles ( -ANPs) as a support and by deposition of thin oxide coatings using ALD. For this purpose, a small glass reaction chamber (powder cell) was adapted to a F-120 Sat reactor (ASM) flow type ALD reactor to coat nanoporous micrometer-sized -alumina particles (20 100 m of diameter) (Fig.1a). These kinds of -ANPs are usually used as industrial catalysts supports and more specifically for Fischer-Tropsch process. In this study, the deposition of ZnO thin films using using ZnEt2 and water as precursors at temperature ranging from 170 to 200ºC will be described4. The challenge lies in the capability to completely coat the inside of the particles and the conformity and uniformity characteristics of ALD are essential to the formation of such a smooth coating. In fact, it is possible to fully coat the external surface of -ANPs. However, the common flow type system does not allow complete coating of the interior of the particles due to a nanoporosity of about 16nm. A powder cell is then necessary and a careful control of the gas flow enable to improve the internal coating of these nanoporous particles. The formation of spinel structure was achieved by first depositing a homogeneous and conformal oxide thin film on the surface of the -ANPs, which were then annealed under air in order to induce diffusion of zinc inside the -alumina structure in order to maintain an open porous structure exploiting the Kirkendall effect3.This allowed a spinel structure formation without deteriorating the porosity of the nanoporous structure. XRD data measured as a function of annealing temperature showed that ZnAl 2O4 spinel structure formation occurs above 800ºC. EFTEM demonstrates conformal and homogeneous coating of ZnO without any sealing of the pores during the deposition process 5 (Fig. 2). BET measurements also proved a low reduction in specific surface area subsequent to such annealing. In order to produce highly luminescent robust and inert nanoporous structures that can be used as red-emitting phosphors, the particles were coated with rare earth oxides by ALD using Dy(thd)3, Er(thd)3 or Eu(thd)3 and ozone as precursors at 200ºC. Due to ozone degradation into the pores of the structure, a method of deposition that does not use the powder cell system where only the surface of the particles was coated was employed. However, a high luminescence was observed (Fig. 3) and it is possible to -alumina from the uncoated under UV exposure. Thus a novel synthesis rout for highly porous luminescent spinel particles that can have several potential applications, e.g. as promising tracer, can be used as a component in optoelectronics or as catalyst support will be discussed and. Acknowledgements Authors thank Dr. Maria Rosarìo from University of Aveiro, CICECO for XRD measurements. Financial support from the Norwegian Research Council and Statoil through the inGAP project (Innovative Natural Gas Processes and Products) and Marie Curie (PERG05-GA-2009-249243) is acknowledged.
Preparation and application of electrochemical sensor based on Ag-doped synthetic zeolite modified multiwall carbon nanotube electrode for arsenic detection 1
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Adriana Remes , Anamaria Baciu , A. Pop , Florica Manea , Stephen J. Picken , Joop 3 Schoonman 1Politehnica University of Timisoara, Sqr. Victoriei, no.2, 300006 Timisoara, Romania 2NanoStructured Materials, Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL, Delft, The Netherlands 3Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628BL, Delft, The Netherlands adriana.remes@chim.upt.ro; florica.manea@chim.upt.ro Introduction Carbon nanotubes (CNTs) have extensively been used for electroanalytical applications due to their unique structure, mechanical strength and electronic properties. Because of their enhanced electrochemical properties and large surface area, CNT are used to fabricate highly sensitive electrodes for detection of different kinds of pollutants. With regard to detection of heavy metals, several authors have reported the use of different forms of CNT composite electrode material for the detection of different heavy metals with enhanced sensitivity and/or selectivity [1-6]. Arsenic (As) is an environmentally and toxicologically important element known to cause a variety of adverse health effects, including dermal changes and respiratory, cardiovascular, gastrointestinal, genotoxic, mutagenic, and carcinogenic effects. Till now, the commonly employed techniques for the determination of arsenic in drinking water are based on spectrometry [7]. Since these techniques have expensive instrumentation, running costs and most of them cannot detect arsenic below 10 ppb, the use of simpler, faster, and cheaper, yet sensitive, electrochemical techniques can be interesting alternatives, especially those based on electroanalytical techniques. In this work, we are developing a new approach to prepare Ag- doped synthetic zeolitemultiwall carbon nanotubes- epoxy composite electrode. The composite material was characterized by microscopic and electrochemical techniques. Furthermore, the electrode was tested for the detection of arsenic in aqueous solutions. Experimental The composite electrode used in this study was made of multiwall carbon nanotubes 300 m2/g ; produced by catalytic carbon vapor deposition method (CCVD)), supplied by Nanocyl, Belgium and from the epoxy resin Araldite®LY5052/ Aradur®5052 produced by Huntsman Corporation. Tetrahydrofuran (THF 99.9%), used as dispersing agent was obtained from Sigma- Aldrich. Synthetic zeolites (ZA) were synthesized from natural clinoptilolite as Si source and the details regarding the synthesis method were presented in our previous work [8]. A dilute suspension of nanotubes in THF was sonicated using a Cole-Parmer® 750-Watt Ultrasonic Processor for 10 min to spread out the nanotubes. First step in achieving high level of dispersion was to mix the suspension and the liquid epoxy resin (without hardener). The mixture was left overnight in a vacuum oven at 60°C in order to extract the solvent. In the processing step, the resulting mixture was then mixed with Ag-doped synthetic zeolite, and the batch was two-roll milled for several times on a laboratory scale two-row mill (Collin) at different shear intensities and then the hardener was added and mixed again to ensure a uniform homogeneity. Finally, the mixture was poured into PVC tubes and cured in an oven at 80°C for 24 h, which after it was left to cool down at room temperature for 24 hrs. Electrochemical measurements were recorded using a computer controlled Autolab potentiostat/galvanostat PGSTAT 302 (ECO CHEMIE, The Netherlands) with a standard three electrode configuration. A MWCNTs-ZA-Ag electrode with a geometric area of 0.196 cm2 was used as working electrode, a platinum wire as counter electrode and a saturated calomel reference electrode (SCE). Scanning electron microscopy (SEM) imaging of the electrode surfaces was carried out using a (SEM XL20, Philips) with an acceleration voltage of 15 kV. Raman spectra were recorded using a Renishaw In- Via spectrometer (Renishaw PLC, UK) equipped with a high power 785 nm line-focus NIR laser (100mWpower at sample). Results and Discussion
SEM microscopy was used to gain the surface characteristics of the modified electrode. Fig. 1 shows the SEM image of the MWCNTs-ZA-Ag- epoxy composite electrode, and a good dispersion of CNTs and Ag-doped synthetic zeolite within the polymer matrix is revealed.
Fig 1. - SEM image of the MWCNTs-ZA-Ag- epoxy composite electrode surface The electrochemical behaviour of the modified electrode was studied by cyclic voltammetry (CV) in 0.09 M Na2SO4 and 0.01 M H2SO4 supporting electrolyte solution, and in the presence of different arsenic concentrations: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 ppm (curves 2-11) in the potential range from 0-1.0 V (vs.SCE), scan rate of 50 mVs-1 (Fig. 2) Based on Fig. 2, two main oxidation peaks are observed on the CVs, where peak at +0.30 V is attributed to the oxidation of As (0) to As (III) and the second peak at +0.5 V corresponds to the oxidation of As (III) to As (V). The reduction peak observed at 0.2 V is typically due to the reduction of Ag oxide layer formed on the surface of Ag nanoparticles during the anodic scan.
Figure 2. (a) (b) Conclusions MWCNTs-ZA-Ag-epoxy composite electrode was successfully prepared. The electroanalytical performance of this electrode for arsenic detection together with the very easy preparation and surface regeneration give the potential for practical applications. Acknowledgements This work was partially supported by a grant of Romanian National Authority for Scientific Research, CNCS-UEFISCDI, project number PN-II-ID-PCE-2011-3-0582; PN-II-72-156/2008 and by the strategic grant, Contract POSDRU/6/1.5/S/13 Proiect ID 6998; POSDRU/88/1.5/S/50783; POSDRU/89/1.5/S/57649, Project ID 57649 (PERFORM-ERA) co-financed by the European Social Fund Investing in People, within the Sectoral Operational Programme Human Resources Development 2007-2013. References [1] J.-H. Yoon, G. Muthuraman, J. Yang, Y.-B. Shim, M.-S. Won, Electroanalysis 19 (2007) 1160. [2] S. Liu, J. Li, X. Mao, P. Gao, Anal. Lett. 36 (2003) 1381. [3] H.-H. Frey, C.J. McNeil, R.W. Keay, J.V. Bannister, Electroanalysis 10 (1998) 480. [4] S.B. Khoo, J. Zhu, Analyst (Cambridge United Kingdom) 121 (1996) 1983. [5] B. Hoyer, T.M. Florence, G.E. Batley, Anal.Chem. 59 (1987) 1608. [6] D.R. Kendall, Anal. Lett. 5 (1972) 867. -Zavala, M. Svobod, L. Langrovรก, B.M. Adair, Z. Drobnรก, D.J. Thomas, 406. [8] C. Orha, A. Pop, C. Lazau, I. Grozescu, V. Tiponut, F. Manea, Journal of Optoelectronics and Advanced Materials 13 (5-6) (2011) 544.
Figures Fig.1- SEM image of the MWCNTs-ZA-Ag- epoxy composite electrode surface Fig. 2- (a) CV curves of MWCNTs-ZA-Ag- epoxy composite electrode in 0.09 M Na2SO4 and 0.01 M H2SO4 supporting electrolyte (1) and in the presence of: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 ppm As (curves 2- 11); potential range from 0-1.0 V/SCE; scan rate 0.05 Vs-1 with pre-treatment at - 0.5V/SCE for 60 s. (b) Calibration plot of the currents recorded at E= +0.50 V/SCE vs. Arsenic concentrations.
Application of Bare Gold Nanoparticles in Open-Tubular CEC Separations of Polyaromatic Hydrocarbons
Dept. of Analytical Chemistry, Institute of Chemical Technology Prague, Technickรก 5, 166 28 Prague 6, Czech Republic pavel.rezanka@vscht.cz Nanoparticles (NPs) are objects of variable shapes with the dimensions in the range of units to hundreds of nanometers possessing unique physical and chemical properties [1, 2]. Typical features of NPs are a large surface-to2]. NPs have significantly influenced many fields of science including analytical separation and preconcentration of a variety of analytes. The potential of gold NPs (GNPs) in separation science has been recognized at the beginning of this century and since then a bunch of interesting papers on this topic has been published as further documented by several cited papers. In cap illary electromigration techniques, the GNPs can serve either as permanent or dynamic inner surface coatings in open -tubular capillary electrochromatography (OT-CEC) [3 5] or as pseudostationary phases in partial filling or continuous filling mode in micellar electrokinetic chromatography (MEKC) [6]. Lately, also the potential of the GNPs for sample preconcentration have been distinguished and this area undergoes a dynamic progress [7, 8]. Recently, several detailed review papers devoted specifically to the applications of GNPs in separation science have been published [9, 10]. In OT-CEC mode, GNPs modified with alkylthiols of various chain lengths are used in applications where hydrophobic compounds are separated in reversed-phase (RP) mode [3-6, 11]. While the use of bare GNPs for the preconcentration of various compounds has been successfully demonstrated elsewhere [9, 10], to the best of our knowledge, the separations utilizing bare GNPs immobilized on pretreated sol-gel FS capillary as stationary phase in OT-CEC mode is described for the first time. In this study, bare gold nanoparticles (GNPs) immobilized in the sol-gel pretreated fused silica (FS) capillary as a stationary phase for open-tubular capillary electrochromatography (OT-CEC) are for the first time shown to be able to separate hydrophobic polyaromatic hydrocarbons (PAHs). Model mixture of four PAHs, naphthalene, fluorene, phenanthrene, and anthracene, was resolved by OT -CEC in the GNPs modified FS capillaries using the hydro-organic background electrolyte (BGE) composed of 20 mmol/L podium phosphate buffer, pH 7, modified with acetonitrile at 8/2 (v/v) ratio. Acknowledgement: Financial support from the Czech Science Foundation, projects no. 203/09/0675 and 203/08/1428, and from the Academy of Sciences of the Czech Republic, Research Projects AV0Z40550506 and AV0Z50110509, is gratefully acknowledged. References: [1] Boisselier, E., Astruc, D., Chem. Soc. Rev. 2009, 38, 1759-82. [2] Daniel, M. C., Astruc, D., Chem. Rev. 2004, 104, 293-346. [3] O'Mahony, T., Owens, V. P., Murrihy, J. P., Guihen, E., Holmes, J. D., Glennon, J. D., J. Chromatogr. A 2003, 1004, 181-93. [4] Yang, L., Guihen, E., Holmes, J. D., Loughran, M., O'Sullivan, G. P., Glennon, J. D., Anal. Chem. 2005, 77, 1840-46. [5] Qu, Q. S., Zhang, X. X., Shen, M., Liu, Y., Hu, X. Y., Yang, G. J., Wang, C. Y., Zhang, Y. K., Yan, C., Electrophoresis 2008, 29, 901-09. [6] Yan, H. T., Li, T., Guo, Y. L., Chin. J. Chem. 2009, 27, 759-62. [7] Feng, J. J., Sun, M., Liu, H. M., Li, J. B., Liu, X., Jiang, S. X., J. Chromatogr. A 2010, 1217, 8079-86. [8] Wang, H. Y., Knobel, G., Wilson, W. B., Calimag-Williams, K., Campiglia, A. D., Electrophoresis 2011, 32, 720-27. [9 J. Sep. Sci. 2010, 33, 372-87. [10] Wu, C. S., Liu, F. K., Ko, F. H., Anal. Bioanal. Chem. 2011, 399, 103-18. [11] Qu, Q., Liu, D., Mangelings, D., Yang, C., Hu, X., J. Chromatogr. A 2010, 1217, 6588-94.
Change of geometry of ECAP channel to increase deformation intensity by SPD process AlMn1Cu alloy *
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Stanislav Rusz , Lubomir Cizek , Stanislav Tylsar , Michal Salajka , Jan Kedron , Karel Malanik *
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Technical University of Ostrava, Faculty of Mechanical Engineering, CZ 708 33 Ostrava Poruba, Czech Republic Research Institute of Iron and Metallurgy Dobra, CZ 738 01 Dobra, Czech Republic stanislav.rusz@vsb.cz, lubomir.cizek@vsb.cz, stanislav.tylsar@vsb.cz, michal.salajka@vsb.cz, jan.kedron@vsb.cz, malanik@vuhz.cz,
The article presents a simulation of the ECAP process with new geometry of horizontal channel, which increases substantially its efficiency. Process ECAP, based on severe plastic deformations, is at present developed in great detail. Semi-products with UFG and NANO structure, particularly made of non-ferrous metals, are used in aviation, in electrical and automotive industries, as well as in medicine. Achievement of UFG structure requires higher number o passes through the forming to ol, which greatly limits use of the ECAP process in practice [1]. Efficiency of the SPD process is low. Design of the channel was modified. A helix was built into horizontal part of the channel with higher angle of lead, which enables much greater distortion of materials during individual passes. This modification also induces a counter-pressure in the channel, which increases flow stress in forming process [2]. This leads to a more uniform deformation in the whole volume of the formed semi-product, and consequently to substantial increase in homogeneity of structure in the formed semi-product. At the same time new ECAP tool was manufactured with this modification of design and it was built into the forming device itself. Mathematical simulation based on the program SimufactForming was used for calculation of deformation intensity and strain intensity at individual passes through the ECAP tool. These values were continuously compared with the values achieved with classical geometry of the ECAP tool. Altogether 6 passes were performed through the forming tool. It was also performed experimental verification of the results of simulations. He evaluated the influence of passage on the size of the hardness and metallographic analysis of samples taken. At first part a mathematical simulation based on the program SimufactForming was used for calculation of deformation intensity and strain intensity at individual passes through the ECAP tool with new geometry- helix matrix in horizontal part of channel. Results of simulations are given in Fig.1. As experimental materials AlMn1Cu alloy for ECAP process with new geometry was used. Influence number of passes on stress values is given in Fig.2 [3]. Metallographic analysis on light microscopy NEOPHOT 2 was performed. Results of metallographic analysis of samples AlMn1Cu alloy are shown in Fig.3. Results from the simulations and from experiments have confirmed the original assumption of substantial increase of efficiency of the ECAP process with new geometry. References [1] Zhilyaev, A. P., Langdon, T. G., Progress in Materials Science, Vol. 53, 2008, Issue 6, p. 893-979. [2] Perez, l., Irigoyen, L., Gaston-Ochoa, D., Journal of Materials Processing Technology, 2004. p. 153 154, 846 852. [3] Rusz, S., Dutkiewicz , L., HluchnĂk., Proceedings of 18th International Conference METAL nd 2009, 19.-21. May 2009, symposium B, publ.. Tanger, s. r. o., 2 part, p. 99-105
Formation of Stable Metallic Nanocontacts by mechanical annealing 1
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C. Sabater, C.Untiedt, J.J. Palacios, and M.J. Caturla , 1
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Departamento de Física Aplicada, Universidad de Alicante, Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid.
carlos.sabater@ua.es Metallic nanocontacts can be fabricated using a Scanning Tunneling Microscope or related techniques. In these experiments the evolution of the lateral size of the nanocontact can be followed, down to the atomic contact, by measuring its electrical conductance. Such evolution, shown as a trace of conductance, will normally differ for each experimental realization and therefore conductance histograms are normally used to identify preferential configurations. However it can be shown that occasionally there are some atomic configurations that can be repeated during consecutive cycles of mechanical deformation of the contacts. Here we report experiments for gold nanocontacts where the same trace of conductance can be obtained for hundreds of cycles of formation and rupture of the contact. We have studied the process leading to such repetitiveness of the traces and found that this is obtained when limiting the indentation depth betw een the two surfaces to a conductance value of approximately 5 or 6 G 0. Using molecular dynamics simulations we have obtained the same behavior and observed how, after repeated indentations, the two metallic contacts are shaped into a stable configuration by mechanical annealing. This confirms and explains the fact that repeated indentation of a tip into a metallic substrate can be used as a method to sharpen or clean STM tips, but only when such indentation does not exceed a limit which here is characterized for the case of gold. References
[1] N. Agrait, A. Levy-Yeyati, J. M. van Ruitenbeek, Phys. Rep 377, 81 (2003) [2] L. Olesen,E. Lagsgaard, I. Stensgaard, F. Besenbacher,J. Schiotz, P. Stoltze, K. W. Jacobsen, J. K. Norskov, Phys.Rev. Lett.74, 2147 (1995) [3] J. M. Krans, J. M. van Ruitenbeek, V. V. Fisun, I. K.Yanson, L. J. de Jongh, Nature 375, 767 (1995) [4] Zhou et al, Act. Met. 49, 4005 (2001) [5] M. R. Sorensen, M. Brandbyge, and K.W. Jacob-sen,Phys. Rev. B 57, 3283 (1998) [6] C. Untiedt, G. Rubio, S. Vieira and N. Agrait, Phys. Rev.B 56, 2154 (1997) [7] A. Hasmy, E. Medina, P. Serena, Phys. Rev. Lett.86,5574 (2001) [8] P. Garcia-Mochales, X. Pelaez, P. A. Serena, E. Medina,A. Hasmy, Appl. Phys. A-Materials Science and Processing 81, 1545 (2005) [9] M. Dreher, F. Pauly, J. Heurich, J. C. Cuevas, E. Scheer,P. Nielaba, Phys. Rev. B 72, 075435 (2005) [10] F. Pauly, M. Dreher, J.K. Viljas, M. Hafer, J.C. Cuevas,P. Nielaba, Phys. Rev. B 74, 235106 (2006) [11] A. R. Calvo, M. J. Caturla, D. Jacob, C. Untiedt, J.J. Palacios, IEEE TRANSACTIONS ON NANOTECHNOLOGY 7, 165 (2008)
Figures
Fgure 3. Geometry, Ab-initio calculations and Molecular Dynamic during the proces formation of stable metallic nanocontact.
Surface smoothening of single crystal diamond chip by 0.50-3.0 keV Oxygen ion beam for XFEL projection optics Y. Sato, S. F. Mahmud*, S. A. Pahlovy, and I. Miyamoto Applied Electronics Department, Tokyo University of Science, 2641 Yamazaki, Japan sf.mahmud19@yahoo.com Introduction Single crystal diamond has exceptional properties such as ultrahigh hardness, ultra high tensile strength and high thermal conductivity in materials on the earth, and chemical inertness. Therefore, single crystal diamond chips with high quality surface may be used as molds for nano-imprint. Moreover, diamond has high X-ray reflectivity (>0.95) and high crystal perfection (need to increase more), and it can be one of the strong candidates for the optics of X-ray free electron laser [1, 2] and so on. Generally, diamond tools and devices are mechanically polished using lap plate of soft material and fine diamond powder. However, the conventional mechanical process cannot be applied to engrave nm-patterns into a diamond chip and also Ion beam is considered as one of the strong tools for smoothening of almost all materials. Smoothening of diamond was performed by Ar + ion beam [3], however the processing speed was very slow. Therefore, we proposed a high speed smoothening technique of single crystal diamond by 0.50-3.0 keV Oxygen ion beam. Experiment and results The experiment was performed by an ECR type ion beam machining apparatus to generate Ar+ ion beam. +
After generating the ion, the diamond sample was bombarded by 0.50-3.0 keV Ar ion beam at different angles of ion incidence and selected 0.5 keV oxygen, 0ยบ ion incidence for the ultra smooth optics fabrication. Then, the un-processed and processed surfaces were observed by an atomic force microscope for the measurement of surface roughness. The fabrication process of 10-50
thick mirror is shown in Fig. 1. Fig. 2
shows the dependence of surface roughness on ion incidence angle. Fig. 3 shows the AFM images of processed diamond substrate at different angles of ion incidence. As shown in the figures, the smooth surface with the roughness value of 0.096 nm rms was obtained by 0.5 keV oxygen ion beam at 0ยบ ion incidence. Fig. +
4 shows the comparison of roughness vs. machined depth curve for Ar and oxygen ion beam. As shown in +
the figure, the machining rate of oxygen is almost three times higher than that of Ar due to presents of both physical and chemical sputtering. In the case of oxygen processing, the surface roughness increases with increasing the machine depth and it becomes 0.21 nm rms at 15 increase further if the machined depth exceeds 30
machined depth. The roughness may
. Therefore, after machined depth of 25
apply the same process on lower part of the sample and can get ultra smooth mirror with 10-50
, we will thickness
(Fig.1). The smoothening and roughening mechanism will be discussed by height height correlation and PSD analysis of the processed samples.
Conclusion By our proposed technique, it is possible to btain an ultra smooth diamond substrate with the surface roughness of about 0.20 nm rms and thickness of 10References [1] B. Sonntag, Nucl. Instr. Meth. Phys. Res A 467, 8 (2001). [2] W. M. Chen et al. Phys. Stat. Sol. (a) 186, 365 (2001). [3] T. Nagase et al, Vacuum 84, 1423(2010).
R=0.096
0.00053 [nm rms]
(a) R=0.26
0.015 [nm rms]
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R=1.2 0.085 [nm rms]
R=1.2 0.015 [nm rms]
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Fig.3. AFM images of unprocessed and processed Fig.1.
Fabrication
processed
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diamond substrate at different angles of ion
XFEL
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diamond optics by low energy oxygen ion beam. 1.4
Unprocessed surface roughness : 0.26 Ion dose: 4.0 1018 (ions/cm2)
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Fig.2. Dependence of surface roughness of the diamond chips with ion incident angle at ion dose of 4.0Ă&#x2014;1018 ions/cm2.
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Fig.4. Dependence of surface roughness of the diamond chips on machined depth.
Filling carbon nanotube membranes with Pd and TiO2 Rodrigo Segura1, Verónica Núñez1, Claudia Contreras1, Pia Homm2, Samuel Hevia2 1
Depto. de Química y Bioquímica, Universidad de Valparaíso, Valparaíso, Chile. 2 Depto. de Física, Pontificia Universidad Católica de Chile, Santiago, Chile rodrigo.segura@uv.cl
The design of novel hybrid nanostructures, with specific functionalities and well defined dimensions are among the desired properties of many emerging applications. Learning how to grow nanostructures, in specific locations with certain morphology and functionality, remains, in many areas, a challenge for the continuous progress of technology. With the aim of contribute in this subject we will present the synthesis and characterization of palladium and titanium dioxide nanostructures grown selectively inside carbon nanotubes. Carbon Nanotubes were synthesized by decomposition of acetylene inside the pores of anodized aluminum oxide (AAO). Two types of membranes were used: one prepared by the anodization of an Aluminum foil to obtain a self-supported material ( 50 m thick), the other one was prepared by the anodization of a thin Aluminum film deposited on silicon chip by e-beam evaporation ( 1 m thick). The grow of CNTs was performed at 650 ºC with a mixture of Argon/acetylene (200/25 sccm) by periods of 10-30 min. Figure 1(a) show a SEM image of the obtained CNTs after a partial AAO removal. Figure 1(d) shows a TEM image of the CNTs obtained using AAO-Si membrane after total removal of AAO. Since the tubes outside walls are initially completely covered by the template, we can very easily access the inside the tubes by molecules or metals precursors in liquid dissolutions, while the outside wall remains free of any molecules or particles. As an example of the potential uses of these membranes as nanoreactors, we have explored the possibility to form palladium and TiO2 nanostructures inside the carbon nanotubes. To prepare palladium composites we have used PdCl2 and Pd(NO3)2 dissolutions to impregnate the CNT-AAO membranes by dip-coating or by drop-casting. After impregnation the membranes were calcinated (350 ºC) in an O2/Ar mixture and reduced (450 ºC) in H2/Ar atmosphere. The AAOs were finally removed with a NaOH solution, leaving behind nanotubes filled with nanoparticles (see figure 1 b and c). Preliminary results of the electrical characterization of these Pd@CNT nanohybrid films deposited over interdigitated microelectrodes indicate that these materials could be used as gas sensors since their resistivity change considerably with different gas mixtures. On the other hand, TiO2-CNT composites were prepared by Chemical Vapour Deposition (CVD) of a conventional titanium precursor [1], Titanium Tetraisopropoxide (TTIP), over CNT-AAO-Si membranes. The TTIP was introduced to the tube furnace by bubbling Argon through a vessel with the titanium precursor previously thermalized at 100 ºC, and then decomposed at 400 or 500 ºC. The TEM results show that TiO2 effectively cover the inner cavity carbon nanotubes (see figure 1 e and f). The results show that the use of AAO membranes is very useful to prepare nanostructures selectively inside carbon nanotubes at difference of other methods used by our group [2, 3]. The authors want to acknowledge Dr. A. Cortes by supply part of the AAO membranes. This research was possible thanks to the financial support of the following grants: Fondecyt 11080232, 11110352 and Mecesup UVA 0604, Chile. References [1] Chien-Sheng Kuo, Yao-Hsuan Tseng, Chia-Hung Huang, Yuan-Yao Li, Journal of Molecular Catalysis A: Chemical 270 (2007) 93–100. [2] Tello A, Cárdenas G, Häberle P, Segura R A, Carbon 46 (2008) 884-889. [3] Segura, R., IJMR 2011 (in press).
(a)
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50 nm 0.2 Âľm
Figure 1. Electron microscopy Images of (a) CNTs with AAO partially dissolved, (b) Pd@CNTs prepared by dip-coating in PdCl2 precursor, (c) Pd@CNTs prepared by drop-casting with PdCl2 precursor, (d) CNTs prepared in AAO-Si membrane, (e, f) TiO2-CNTs nanohybrids.
Ultrathin diamond nanofilms as possible two-dimensional insulators for future nanoelectronics Pavel B. Sorokin, Alexander G. Kvashnin and Leonid A. Chernozatonskii Technological Institute of Superhard and Novel Carbon Materials, 7a Centralnaya Street, T roitsk, Moscow region, Russian Federation Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygin st., Moscow, Russian Federation PBSorokin@gmail.com Hydrogenation of graphene [1] enlarges its potential application in nanoelectronics. Total hydrogenation of graphene changes the nature of electronic states due to changing of sp2 hybridization of C-C bonds to sp3 one and opens the dielectric band gap. Such two-dimensional insulator was called as graphane [2]. 3
Graphane is only first member in a series of sp bonded diamond films with nanometer thickness (or diamanes) consist of a number of adjusted 111 oriented layers which display unique physical properties [3]. The consequent study of graphene, graphane and proposed diamanes can be considered as bottom-up nanotechnological approach opposite to ordinary top-down paradigm. The main goal of this work is the theoretically study of diamane physical properties. We considered diamanes with different thickness; we investigated their stability and compared them with known data for sp3-hybridized hydrocarbon clusters. We studied the elastic properties of the structures and obtained phonon dispersion (as well as Raman spectra), wave velocities and elastic constants of the films. We calculated phase diagram depended upon the diamond film thickness and discussed possible ways of synthesis of the considered structures and their application in nanoelectronics and nanooptics.
References [1] D. C. Elias, R.R. Nair, T.M.G. Mohiuddin, S.V. Morozov, P. Blake, M P. Halsall, A.C. Ferrari, D.W. Boukhvalov, M.I. Katsnelson, A.K. Geim and K.S. Novoselov, Science 320 (2009) 610 [2] J.O. Sofo, A.S. Chaudhari, G.D. Barber, Phys. Rev. B 75 (2007) 153401 [3] L.A. Chernozatonskii, P.B. Sorokin, A.A. Kuzubov, B.P. Sorokin, A.G. Kvashnin, D.G. Kvashnin, P.V. Avramov, and B.I. Yakobson, J. Phys. Chem. C 115 (2011) 132 Figures
Evaluation of different conductive nanostructured particles as filler in smart piezoresistive composites 1,2
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S. Stassi , G. Canavese , S. Marasso , C. Bignardi , C.F. Pirri 1) 2) 3) 4)
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Center for Space Human Robotics, IIT Istituto Italiano di Tecnologia @ PoliTo, C.so Trento 21,10129 Torino, Italy Department of Physics, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy Department of Materials Science and Chemical Engineering, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy Department of Mechanics, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy
stefano.stassi@polito.it In the last decades, piezoresistive composite materials have found extensive potential application in the fields of micro-sensors, electromechanical device, circuit breakers, touchable sensitive screen and tactile sensors for robotics, providing cheaper, accurate and faster alternatives to devices alread y present on the market. The properties of these materials could be tuned varying the kind and the shape of the particles, used as functional filler, and the type of matrix[1, 2]. This work presents the investigation of the piezoresistive response of composite materials based on nanostructured conductive fillers in a polydimetihylsiloxane (PDMS) insulating elastomeric matrix for tactile sensor application. Three different metal fillers were tested: the nickel and the copper powders were purchased by Vale Inco (Type 123) and Pometon (LT10) respectively, while the highly multibranched gold nanostars were synthesized with a room temperature wet synthesis[3]. These particles were chosen because of the elevate conductivity and most of all for the presence of nanosized sharp tips on their surface. Whereas PDMS was chosen as insulating matrix in order to assure a good flexibility and conformability of the final material to be capable of covering any irregular surface. The peculiarity of these metal-polymer composites is the conduction mechanism based on quantum tunnelling phenomenon between closed particles that originates variation of electrical resistivity of several orders of magnitude. Lacking any mechanical stress, the material presents an insulating electric behavior. While upon the application of a deformation to the sample the electrical conduction drastically increases as a function of load. In fact under compression, the insulating layer between the particles is reduced causing an increase of the probability of the electrons to tunnel. Consequently the resistivity of the sample decrease exponentially. The morphology of the particles, presenting very sharp nanometric spikes on the surface, enhances this effect, because the charges injected in the composite will reside on the fillers, generating very large electric local field at the tips on the surface. This phenomenon was observed for the first time by Bloor et al.[4] in composite prepared with nickel powder and different elastomeric matrices. We developed a similar material[5] and compared it with composites with copper and gold particles. The aim was to obtain better performances, lower process cost, thinner composite layer for integration in MEMS technology and the reduction of safety risk for the human body related to the materials used in the preparation of composite samples. In fact inhalation of nickel powder may cause cancer and sensitizing effect. The composites were prepared dispersing the metal particles in the PDMS copolymer. The blend was gently mixed in order to not modify the electric behavior of the composite preventing the destruction of the tips on the particles surface. Then the PDMS curing agent was added to the blend and the mixture was gently mixed at room temperature. The resulting paste was outgassed for 1 hour, poured in PMMA molds with different hollow cavity shapes, realized by milling techniques and then cured in oven at 70째C for three hours. Different composites were prepared varying the copper/PDMS ratio, the copolymer/curing agent ratio and the thickness of the final samples. All the tested composites presented a huge piezoresistive response. When a pressure from zero to 2 MPa was applied to the samples the electrical resistance showed a reduction from six to nine orders of magnitude. The encouraging results obtained in the preliminary piezoresistive characterization demonstrate the possibility to replace the nickel materials as functional filler in piezoresistive composite material based on quantum tunneling conduction with other nanostructured particles more safe for health.
References [1] Fu S-Y, Feng X-Q, Lauke B, and Mai Y-W, Composites Part B: Engineering, 39 (2008) 933-961. [2] Strumpler R and Glatz-Reichenbach, Journal of Electroceramics, 3 (1999) 329-346. [3] Khoury CG and Vo-Dinh T., Journal of Physical Chemistry C, 112 (2008) 18849-18859. [4] Bloor D, Donnelly K, J Hands P, Laughlin P, and Lussey D., Journal Of Physics D:Applied Physics, 38 (2005) 2851-2860. [5] Stassi S, Canavese G, Lombardi M, Guerriero A, and Fabrizio Pirri C., MRS Online Proceedings Library, (2011) 1299. Figures
Fig1. FESEM image of the nickel particles. The scale bar corresponds to 1 Âľm.
Fig1. FESEM image of the copper particles. The scale bar corresponds to 2 Âľm.
Fig3. FESEM image of the gold particles. The scale bar corresponds to 200 nm.
Fig4. Piezoresistive response of the composite prepared with nickel powder in PDMS matrix.
Molecular Dynamics models of a bioactive glass nanoparticle Antonio Tilocca Department of Chemistry, University College London, U.K.
Bioactive glasses such as the 45S5 composition (BG45) are clinically employed as bone defect fillers in orthopaedic and dental applications. Their potential in regenerative medicine has also been highlighted but not exploited as yet, due to the lack of fundamental understanding of their composition-structureactivity relations. For instance, nanosized BG45 particles have shown enhanced biological activity and antibacterial properties, which could be the key towards developing a new generation of biomaterials for regenerative medicine. However, the rational development of these materials requires a better understanding of the origin of the superior properties of BG45 nanoparticles. Molecular dynamics simulations of a Bioglass spherical nanoparticle (approximately 6 nm diameter) have been carried out to investigate how the reduced size affect structural and dynamical features, which could enhance the bioreactivity of these systems. Compared to the bulk glass or to the 2D-flat surface of BG45, the simulations reveal that the reduced size leads to a further slight reduction in the already low silicate connectivity on the nanoparticle surface, to a ring size distribution shifted towards three-membered rings, and to a higher Na+/Ca2+ ratio in close proximity of the surface. A higher mobility of Na cations in the external regions of the nanoparticle has also been detected. The possible ways in which these effects can translate into higher bioreactivity of BG45 nanoparticles are discussed.
Optical properties of high-performance liquid crystal-xerogel microcomposite electro-optical films Martin Timusk, Martin Järvekülg, Aigi Salundi, Rünno Lõhmus and Kristjan Saal Institute of Physics, University of Tartu, Riia 142, Tartu, Estonia martin.timusk@ut.ee Sol-gel method in combination with phase separation enables to fabricate hierarchically porous metal and silicon oxides [1]. When highly polar solvent is used in sol-gel process instead of or in combination with classical alcohol solvents, polycondensation leads to phase separation in form of spinodal decomposition or nucleation growth. In such materials, in addition to micro- and in some occasion mesopores that are characteristic to xerogels prepared by sol-gel method, macropores can be obtained. First systematic study of the macroporous monolithic silica prepared using sol-gel method together with phase separation was published in 1991 [2]. The same year, Levy et. al. used 4-cyano-4'-pentylbiphenyl liquid crystal as polar solvent to achieve phase separation [3]. Obtained material is called gel-glass dispersed liquid crystal (GDLC). GDLC is a hybrid electro-optical film material composing of LC microdroplets encapsulated in inorganic or organically modified silica or mixed oxide matrix. Due to the dielectrical and optical anisotropy of liquid crystal phase inside amorphous oxide matrix the material can be switched from opaque to transparent state by applying an electric field in a similar manner to parallel plate capacitor whereas dielectric layer between electrodes is replaced by microcomposite GDLC film and transparent conductive films (usually indium-tin oxide) on transparent substrates are used as electrodes. The electro-optical quality (difference between transmittance with applied electric field and without the applied field) is mainly determined by the film thickness and the magnitude of mismatch between refractive index of the matrix and the ordinary refractive index of liquid crystal. In this work we report the significant improvement compared to our previously reported results [4]. GDLC film preparation process was elaborated to incorporate titanium alkoxides in synthesis process. This enabled the adjustment of the refractive index of silica glass matrix without having destructive influence on macroscopic liquid crystal phase separation at the same time. That is a fundamental problem with the use of titanium alkoxides since the orders of magnitude greater hydrolysis and polycondensation rates of titanium alkoxides lead to too rapid gelation. High performance films that exhibit remarkable 78% change in transmittance as an electric field is applied were prepared. An original setup was developed that enables measurement of transmittance dependence on applied voltage at different temperatures in full visible and near-IR spectral range. For the first time, function of change of transmittance vs. wavelength of light was measured for GDLC film, showing the distinct maxima in the mid-visible range. Transmittance vs. applied voltage measurements at different temperatures demonstrate electro-optical effects at least down to -13 °C which means that liquid crystal must be in molten (liquid crystal) state at these temperatures in the microscopic volume confined in xerogel matrix. That is remarkable since it is known that liquid crystal 4-cyano-4'-pentylbiphenyl crystallizes in macroscopic volume at 24.5 °C [5]. References [1] K. Nakanishi, N. Tanaka, Acc. Chem. Res. 40 (2007) 863 873. [2] K. Nakanishi, N. Soga, J. Am. Ceram. Soc. 74 (1991) 2518 2530. [3] D. Levy, C.J. Serna, J.M. Otón, Mater. Lett. 10 (1991) 470 476. [4] M. Timusk, M. Järvekülg, R. Lõhmus, I. Kink, K. Saal, Mater. Sci. Eng. B. 172 (2010) 1-5. [5] M. Boussoualem, F. Roussel, M. Ismaili, Physical Review 69 (2004) 031702. Figures
Fig. 1. SEM image of a cross section of GDLC film
Twist-radial oscillations resonance effects in double-stranded DNA chains 1
Germán Torrellas , Enrique Maciá
2
1
Dpto. Física de Materiales, Fac. CC. Físicas, Universidad Complutense de Madrid, 28040 - Madrid; german_torrellas@hotmail.com Dpto. Física de Materiales, Fac. CC. Físicas, Universidad Complutense de Madrid, 28040 - Madrid; emaciaba@fis.ucm.es
2
Studying the dynamics of the DNA double helix is a very complicated task, due to its complex structure and interactions between the nucleobases, the sugar-phosphate backbone and the environment [1]. In this work we study the canonical equations of motion and normal modes of a duplex DNA chain at low temperatures, taking into account the coupling between the H-bond radial oscillations and the twisting motion of each base pair through the helical backbone structure. This coupling is mediated by the stacking interaction between adjacent base pairs along the helix, as prescribed by the PeyrardDauxois-Bishop model [2]. This kind of coupling has been shown to be very important in biological processes (such as denaturation and transcription), given that an untwisting of the helix can cause the local aperture of the molecule (figure 2). In order to provide a more realistic treatment, we explicitly consider different mass values for different nucleotides, hence properly extending previous works where the masses for A, T, G and C nucleobases were assumed to be identical [3]. A schematic view of the model is shown in figure 1. In this way, we disclose several resonance conditions, which can be achieved via fine-tuning of the effective masses of the different nucleobases (which can be modified through metilation processes or the attachment of heavier molecules to the backbone), which lead to interesting particular solutions of the dynamical equations. The role of these dynamical effects on the DNA chain charge transport properties is discussed.
References [1] Chakarborty, T. Editor. Charge Migration in DNA: Perspectives from Physics, Chemistry and Biology. Springer, Berlin (2007) 1-288 [2] Peyrard M., Nonlinearity, 17 (2004) R1
R40
[3] Maciá E., Physical Review B, 80 (2009) 125102-1
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Figures
Figure 1. Schematic view of the model and detail of one of the base pair planes, where the mass difference effect is clearly visible.
Figure 2. Radial opening of the molecule is only possible if accompanied by an untwisting.
Comparative study of DNA carbon nanotube hybrids using atomic force microscopy Kazuo Umemura, Takuya Hayashida, Shigeyuki Hirayama Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan meicun2006@163.com Carbon nanotubes (CNTs) are one of the promising nanomaterials that can be used in nanodevices and biosensors and for drug delivery. [1] However, the insolubility of CNTs makes the realization of such applications difficult. To solve this problem, the attachment of biomolecules on CNT surfaces is one of the effective approaches. For example, the preparation of DNA CNT hybrids has been intensively examined by many research groups. When DNA molecules attach to and cover the CNT surface, the DNA CNT hybrids become water soluble owing to the hydrophilic nature of DNA. Recently, it was reported that specific DNA molecules with a specific sequence tend to bind with CNTs having specific chirality. [2] Although the preparation of DNA CNT has become popular as a method to solubilize CNT, the detailed structures of DNA CNT hybrids have not yet been clarified. Thus, characterization of the structures and physicochemical properties of DNA CNT hybrids is being studied intensively these days. Spectrum analyses such as Raman spectroscopy and photoluminescence are a major approach for estimating the structures of dispersed CNTs. For example, the diameters and chirality of dispersed CNTs have been determined using spectroscopic studies. [3] Another approach is the direct observation of DNA-CNT hybrids using an atomic force microscope (AFM) or a transmission electron microscope (TEM). In this manner, the morphologies of individual DNA CNT hybrids are visualized, and any unevenness in the structures of DNA CNT hybrids can be discussed in detail. For instance, distributions of the diameters of individual DNA CNT hybrids have been precisely characterized using the results of cross-section analysis of individual molecules observed with an AFM. [4] There are several different CNT synthesis methods such as chemical vapor deposition (CVD), highpressure Carbon monooxide (HiPco), and arc discharge. Single-walled CNTs (SWNT), double-walled CNTs (DWNT), and multi-walled CNTs (MWNT) that are synthesized via the abovementioned methods probably have various different structures and physicochemical properties. Furthermore, single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) contain various sequences. Although many papers about structures and physicochemical properties of DNA-CNT hybrids have been published recently, comparative studies of the various types of DNA CNT hybrids are few. Researchers have employed types of various DNA molecules and CNTs without systematic comparison. Therefore, it is hard to simply summarize the knowledge about structures and properties of DNA CNT hybrids. In this paper, we carried out a comparative study of several types of DNA CNT hybrids. First, hybrids of ssDNA or dsDNA with HiPco-synthesized SWNTs or CVD-synthesized SWNTs were fabricated sequentially. Four types of hybrids, ssDNA HiPco SWNT, ssDNA CVD SWNT, dsDNA HiPco SWNT, and dsDNA CVD SWNT, were comparatively characterized using AFM. For AFM observation, a certain amount of the hybrids was dropped on a 3-(Aminopropyl)triethoxysilane (APS) treated mica surface, and then, the sample was rinsed with water. After drying, AFM observations of the samples were performed in air. As a result, surfaces of ssDNA-CVD and dsDNA-CVD showed very smooth features as compared to those of ssDNA HiPco and dsDNA HiPco (Figure 1). Although there is only one previous report that employed CVD SWNT for hybridization with DNA [5], in most of papers, HiPco SWNT was employed to prepare DNA CNT hybrids. Furthermore, there is no previous report on the hybridization of dsDNA molecules with CVD-synthesized CNTs. Our data clearly indicated that CVD SWNT is also suitable for preparing DNA CNT hybrids. As for the diameters of the hybrids, when dsDNA was employed, as expected, the diameters of the hybrids were larger than when ssDNA was employed. However, the increase in the diameter with the use of dsDNA was less than twice that with the use of ssDNA. This finding suggests that the increase in diameter was not necessarily proportional to the number of DNA strands. Second, we employed 1% sodium dodecyl sulfate (SDS) instead of DNA for comparison. It is known that SDS is an effective CNT-solubilizing compound. [6] In this case, AFM observation was difficult even after rinsing the sample with water. Without rinsing, it was not possible to obtain the AFM images. When the SWNT dispersed with the 1% SDS was dialyzed against pure water using 100x volumes to remove excess SDS, the AFM observation became much more stable. We confirmed that dialysis using 1000x and 1000000x volumes of water were also effective for stable AFM imaging. Although the dialysis treatment was effective, the dispersion with DNA was convenient for depositing the hybrids on the APS-
treated mica surface. This is the first example of the direct comparison of SDS CNT with DNA CNT using the same CNT compound. Finally, we examined a SWNT that was functionalized with polyethyleneglycol (PEG-SWNT). Usually, when insoluble CNT is dispersed using DNA, a mixture of DNA and CNT is sonicated to promote dispersion and the sonicated mixture is centrifuged to remove aggregates. However, in the case of PEG SWNT, these powerful treatments can be avoided because PEG SWNT is water soluble. We mixed ssDNA with PEG-SWNT without sonication and centrifugation, and then observed the mixture using an AFM to evaluate interaction between ssDNA and PEG SWNT. The AFM images showed both smooth and rough filamentous structures depending on the mixing conditions. The result suggests that the AFM observation of DNA and PEG SWNT may provide useful information to verify DNA CNT interaction. We compared several types of DNA CNT hybrids using AFM sequentially. We opine that our comparative study provided useful information for understanding the DNA CNT interaction in detail. We hope that our results will be the basis for establishing industrial applications of CNT. Acknowledgements This work was partially supported by the Grants-in-Aid for Scientific Research (23540479) from the Japan Society for the Promotion of Science (JSPS). The authors thank the Green Light Project of Tokyo University of Science for the use of Raman micro-spectroscopy. References [1] S. Iijima, T. Ichihashi, Nature 363, (1993) 603-605. [2] X. Tu, S. Manohar, A. Jagota, M. Zheng, Nature 460, (2009) 250-253. [3] H. Kawamoto, T. Uchida, K. Kojima, M. Tachibana, Chem. Phys. Lett. 432, 1-3 (2006) 172-176. [4] S. Wang, Z. Liang, B. Wang, C. Zhang, Nanotechnology 17, 3 (2006) 634-639. [5] B. Koh, J. B. Park, X. Hou, W. Cheng, J. Phys. Chem. B 115, (2011) 2627-2633. [6] P. Angelikopoulos, A. Gromov, A. Leen, O. Nerushev, H. Bock, E. E. B. Campbell, J. Phys. Chem. C 114, 1 (2010) 2-9. Figures
Figure 1 AFM images of ssDNA SWNT hybrids. (A) SWNT synthesized via CVD. (B) SWNT synthesized via HiPco. Scan area was 500 nm 2.
Photoluminescence of Ag and Li nanoclusters dispersed in glass host J.J. Velázquez1,2, V.K. Tikhomirov1, V.D. Rodríguez2, J. Méndez-Ramos2, V.V. Moshchalkov1 1 2
INPAC Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Belgium Departamento de Fisica Fundamental y Experimental, Electrónica y Systemas, Universidad de La Laguna, Tenerife, Spain josvel@ull.es Victor.Tikhomirov@fys.kuleuven.be
Photoluminescence of silver (Ag) and Lithium (Li) nanoclusters embedded in different hosts has recently been attracted substantial interest because of the promising applications in optical nanolabels, visible light sources, optical recording, and also in down conversion of solar spectrum [1,2]. Bulk oxyfluoride glasses doped with Ag nanoclusters have been prepared using the melt quenching technique, for the first time to our knowledge. When pumped in the absorption band of Ag nanoclusters between 300 to 500 nm, these glasses emit a very broad luminescence band covering all the visible range with a weak tail extending into the near infrared. The maximum of the luminescence band and its color shifts to the blue with a shortening of the excitation wavelength and an increasing ratio of oxide to fluoride components, resulting in white color luminescence at a particular ratio of oxide to fluoride; with a quantum yield above 20%. Preliminary data has been published in [3]. Li-Yb3+ co-doped nano-crystalline ZnO have been synthesized by a method of thermal growth from the salt mixtures. X-ray diffraction, transmission electron microscopy, atomic absorption spectroscopy and optical spectroscopy confirm the doping and indicate that the dopants may form Li-Li and Yb3+-Li based nanoclusters. When pumped into the conduction and exciton absorption bands of ZnO between 250 to 425 nm, broad emission bands of about 100 nm half-height-width are excited around 770 and 1000 nm, due to Li and Yb3+ dopants, respectively. These emission bands are activated by energy transfer from the ZnO host mostly by quantum cutting processes, which generate pairs of quanta in Li (770 nm) and Yb3+ (1000 nm) emission bands, respectively, out of one quantum absorbed by the ZnO host. These quantum cutting phenomena have great potential for application in the downconversion layers coupled to the Si solar cells [2,4]. References [1] Z. Shen, H. Duan, and H. Frey, Adv. Mater. 19, 349-352 (2007). [2] S. Ye, N. Jiang, F. He, X. Liu, B. Zhu, Y. Teng and J. R. Qiu, Opt. Express. 18, 639 (2010). [3] V.K. Tikhomirov, V.D. Rodríquez, A. Kuznetsov, D. Kirilenko, G. Van Tendeloo, and V.V. Moshchalkov, Opt. Express, 18, 22032 (2010). [4] Ü. Özgür, Y.I. Alivov, C. Liu, A. Teke, M.A. Reshchikov, and S. Do an, J. Appl. Phys. 98, 041301 (2005). Figures C
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Fig.1. (a) Daylight picture of as-prepared glass samples: 1 is the basic glass doped with 10 wt% AgNO3; 2 is the basic glass doped with 1 wt% AgNO3; 3 is the oxygen-enriched glass 51(SiO2)14(AlO1.5)22.5(CdF2)10(PbF2)2.5(ZnF2), mol%, doped with 5 wt% AgNO3; 4 is the undoped basic glass. b) Luminescence image of the same glass samples, marked respectively, excited with a UV lamp CAMAG at 366 nm. c) Energy filtered transmission electron microscope image of a piece of the basic glass doped with 1 wt% AgNO3 and 3.5 mol% of YbF3: the red color represents Ag and the green color represents Yb, respectively. d) TEM image of a single Ag nanoparticle grown by intentional heattreatment of the basic glass doped with 1 wt% AgNO3: the glass was treated at 350ºC for 1 hour.
Emission spectra excited at 320 nm excited at 355 nm excited at 380 nm excited at 457 nm
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Fig. 2. Normalized emission and excitation spectra of the basic glass doped with 5 wt% AgNO3. Emission and excitation wavelengths are post-signed, respectively.
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Fig. 3. (a) TEM image and (b) TEM EDX spectrum of ZnO:Li-Yb nanopowder. The Yb-M4,5 peaks between 1.50 and 2.00 keV are indicated and zoomed. Other peaks corresponding to the Yb, Zn and O are also labeled. Cu and C peaks are due to the sample holder. a)
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Fig. 4. (a) A piece of ZnO:Li-Yb nanopowder pellet showing a bright luminescent spot when illuminated by an invisible laser beam of Ar laser at 355 nm. (b,c,d) Excitation (left side) and emission (right side, black curves) spectra of ZnO (b), ZnO:Li (c) and ZnO:Li-Yb (d) nanopowders; in excitation spectra the green curves correspond to detection at 550 nm (intrinsic defect emission), red curves to detection at 770 nm (Li emission) and blue curve to detection at 980 nm (Yb emission).
Multiphase SiO2-SnO2-LaF3 nanostructured glass-ceramics for simultaneous UV and NIR solar spectrum conversion J.J. Velázquez1, A.C. Yanes2, J. Méndez-Ramos1, J. Del-Castillo2, A. Aguirretxu-Comerón1,2, A. Hernández-Suárez1,2, C. Rodero1,2, and V.D. Rodríguez1 1
Departamento Física Fundamental y Experimental, Electrónica y Sistemas, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain 2
Departamento Física Básica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain josvel@ull.es, ayanesh@ull.es.
In the last few decades, the possibility of increasing of solar efficiency has been extensively investigated. It is well known that the spectral response of commercial silicon solar cells to the solar spectrum constitutes one of the main losses of photovoltaic technology1. In order to avoid these losses many efforts have been carried out to enhance the solar cells efficiency by photon conversion from the UV-blue (down-shifting) or NIR (up-conversion) photon to green-red radiation where the Si solar cells response is maximum. This solar spectrum conversion could be obtained by means of rare earth ions (RE) doped nanostructured glass-ceramics as luminescent layers, without interference with the solar cell active media2. These ions show luminescent high quantum efficiencies when they are located in low phonon energy environments related with low non-radiative rates, although with the drawback of low absorption coefficients. This would be resolved by using a “like-antenna” specie which much stronger absorption capacity with subsequent very efficient energy transfer to the emitting RE ions. In this work we present nanostructured glass-ceramics comprising two nanocrystalline phases, SnO2 and LaF3, doped with RE ions and embedded in a silica glass matrix for an efficient photon conversion from UV and NIR into visible. These photon conversion processes would be obtained by means of a strong UV absorption of SnO2 semiconductor nanocrystals (quantum dots), following with an efficient 3+ 3 energy transfer from the host to the Sm ions yielding green and red emissions . In particular, as it can bee seen in Fig. 1(a) a broad excitation UV band, correspond to SnO2 nanocrystals, is observed together with a narrow and weaker peaks, mainly at 401 and 463 nm, related with Sm3+ ions. Corresponding emission spectra exciting at the maximum of the SnO2 broad band give rise to luminescent down-shifting from the UV and blue irradiation into the wanted reddish-orange spectral range, see Fig. 1(b). On the other hand, efficient NIR to visible up-conversion emissions will be obtained by using pairs of RE ions co-doped LaF3 nanocrystals. These nanocrystals are an exceptional host material for RE ions due to considerable solubility and low phonon energy (300-400 cm-1), which 4,5 reduces multiphonon relaxation increasing the radiative emissions . Particularly, efficient upconversion processes will be obtained by using the couples Ho3+-Yb3+ and Er3+-Yb3+ as a co-dopant in LaF3 nanocrystals, see Fig. 1(c). These materials co-doped with Sm 3+-Ho3+-Yb3+ and Sm3+-Er3+-Yb3+, present luminescence features that could be used to enhance the efficiency of photovoltaic solar cells. References [1] Richards, B.S.; Solar Energy Materials and Solar Cells, 90, (2006) 1189. [2] Shalav, A.; Richards, B.S.; Green, M.A.; Solar Energy Materials and Solar Cells, 91, (2007) 829. [3] A.C. Yanes, J.J. Velázquez, J. Del-Castillo, J. Méndez-Ramos and V.D. Rodríguez, Nanotech. 19, (2008) 295707. [4] J.J. Velázquez, A.C. Yanes, J. del Castillo, J. Méndez-Ramos and V.D. Rodríguez, Phys. Status Solidi A, 204, (2007) 1762. [5] Biswas, A; Maciel, G.S.; Friends, C.S.; Prasad, P.N.; J Non-Cryst Solids 316, (2003) 393.
Figures (a) detec. at 614 nm
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Fig. 1 (a) UV-visible excitation spectra of 90SiO2-5SnO2-5LaF3 co-doped with 0.4Sm3+-0.1Er3+-0.3Yb3+ (black) and 0.4Sm3+-0.1Ho3+-0.3Yb3+ (red), in mol%, heat-treated at 900 ยบC during 4 h, detecting at 614 nm and normalized to the maximum of the UV band. (b) Emission spectra under excitation at 328 nm, corresponding to the maximum of the excitation band of SnO2 nanocrystals and normalized to the maximum of the VIS emission. (c) Up-conversion emission spectra of Sm3+-Er3+-Yb3+ and Sm3+-Ho3+Yb3+ samples obtained under 980 nm infrared excitation with 200 mW pump power, both normalized to the maximum of green emission. RE ion transitions are indicated by labels.
Effect of gold and silver nanoparticles on interactions of porphyrin-brucine conjugates with oxoanions NO3-. H2PO42-, SO42-, ClO3-, ClO4-, HCO3-, ReO4Lenka Veverková, Kamil Záruba, Vladimír Král Institute of Chemical Technology, Department of Analytical Chemistry, Technicka 5, 166 28 Prague 6, Czech Republic, Lenka.Veverkova@vscht.cz The development of molecular sensors for detecting selectively chemically and biologically important anionic species has become a major research project in supramolecular chemistry. It is still a challenge to find and study materials capable of recognizing and sensing anions in aqueous media [1]. The possible use of modified porphyrins as selectors is based on formation of non-covalent - complexes between the flat porphyrin core and planar analytes together with additional binding modes, like H-bonding, coulombic interactions etc. [2] Immobilization of porphyrin derivatives on the surface of nanoparticles allows studying interaction in environment in which the selector is insoluble [3]. The goal of this work was to study the interaction between oxoanions and porphyrin-brucine conjugates [4] in methanol-water solution and water, the influence of gold and silver nanoparticles on the interactions was also studied. Nowadays, gold nanoparticles are often prepared by chemical reduction of Au(III), silver nanoparticles by chemical reduction of Ag(I) [5]. Sodium citrate belongs to the most usable reducing agents [6] to prepare citrate stabilized nanoparticles. Mercapto-derivatives have been commonly used as modifiers of nanoparticles in recent years and 3-mercaptopropionic acid (3-MPA) used here belongs this group. At basic pH nanoparticles modified by 3-MPA have negative charge on the surface due to carboxylate groups. This allowed immobilization of porphyrin conjugates which have positive charge due to quaternary nitrogen atoms by ionic interaction. The method based on the reduction of K[AuCl4] and AgNO3 by citrate was used to prepare 15 nm average size gold nanoparticles [5] and 45 nm average size silver nanoparticles. The immobilization of porphyrin conjugates was carried out by two different ways of ionic interaction. Direct immobilization of conjugates on nanoparticles and immobilization of conjugates on 3-MPA premodified nanoparticles were applied. Interactions of oxoanions (NO3-. H2PO42-, SO42-, ClO3-, ClO4-, HCO3-, ReO4-) with porphyrin-brucine conjugates in methanolwater solution and water were studied by UV-Vis and ECD spectroscopy [7]. The financial support from the MSMT No 21/2011, MSMT6046137307, KAN200100801, BIOMEDREG and KAN200200651 is gratefully acknowledged. References: [1] Boldyrev, A. I.; Gutowski, M.; J. Acc. Chem. Res., 29 (1996) 497. [2] Záruba K., Setni ka V.,Charvátová J., Rusin O., Tománková Z., Hrdli ka J., Sýkora D., Král V., Collect. Czech. Chem. Commun., 66 (2001) 693. [3] ezanka P., Záruba K., Král V., Tetrahedron Lett., 49 (2008) 644. [4] Král V., Pataridis S., Setni ka V., Záruba K., Urbanová M., Volka K., Tetrahedron, 61 (2005) 5506. [5] Shipway N. A., Katz E., Willner I., Chem. Phys. Chem., 1 (2000) 1655.
[6] Turkevitch J., Stevenson P. C., Hillier J., Discuss. Faraday Soc., 11 (1951) 55. [7] Veverkovรก L., Zรกruba K., Koukolovรก J., Krรกl V., New J. Chem., 34 (2010) 117. Figures: H3CO OCH3 O
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DFT calculation for OH group around Pd on S-modified Au(111) 1
1,*
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Mami Yokoyama , Akira Ishii , Mituhiro Arisawa ,and Satoshi Shuto
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Department of Applied Mathematics and Physics, Tottori University, Tottori, Japan
2
Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12, Nishi 6, Kita-ku, Sapporo 060-0812 Japan. * ishii@damp.tottori-u.ac.jp
Transition metal catalyzed reactions have played an important role in synthetic and process chemistry. The homogeneous catalyst surely causes effective reaction; however, a lot of efforts and energy are required for reusing the catalyst. From this viewpoint, development of the easily treatable heterogeneous catalyst is strongly desired for reducing the waste of expensive rare metal. Although the polymer supported catalyst has been developed, it cannot tolerate under severe conditions such as high temperature and it is restricted to use in organic solvents. On the other hand, Pd acetate (Pd(OAc)2) molecules immobilized on the S-terminated GaAs(001) has high catalytic activity and stability for Heck reaction [1]. However, the GaAs substrates including toxic As, it is not suitable for mass productions. To solve this problem, a new type catalyst was reported recently [2], which transition metals were supported on the S-modified Au(111). In order to develop more effective catalysts, it is essential to understand the function of the Pd catalyst of the S-modified Au(111). Therefore, in this study, we tried to find the stable structure of Pd catalyst on the S -modified Au(111) by DFT calculations using the program package VASP [3]. The S atom is easier to be desorbed from the Au(111) substrate than the Pd atom during catalyst reaction. The binding energy of Pd atom is stronger due to the co-adsorption of S, the role of S is to make the binding of Pd stronger. We found that the stable position of Pd is lower place than S. We compared Pd on S-supported Au(111) with Pd on S-terminated GaAs(001)/GaN(0001), then we found that this kind of catalyst have a lot in common. [4,5]
References [1] I. Takamiya, S. Tsukamoto, M. Shimoda, M. Arisawa, A.Nishida and Y.Arakawa, Japanese Journal of Applied Physics.vol.45,No.18, 2006, L475-L477. [2] Hoshiya N, Shimoda M, Yoshikawa H, Yamashita Y, Shuto S, Arisawa M. J Am Chem Soc. 2010 Jun 2;132(21):7270-2. [3] G.Kresse and J.Hafner, Phys.Rev.B 47, RC558 (1993). [4] A.Ishii, H.Asano, M.Yokoyama, S.Tsukamoto, S.Shuto and M.Arisawa, phys.stat.sol. (c) 7 359-361 (2010) [5] Mami Yokoyama, Shiro Tsukamoto and Akira Ishii, e-JSSNT Surf. Sci. Vol. 8, pp. 377-380 (13 November, 2010)
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time window the blocking temperature derived from the DC magnetic measurements is about four times lower than that determined from the behaviour of the Mössbauer spectra, if Keff remains constant. In real situations we deal with a system of particles displaying a distribution of sizes and consequently the blocking temperatures also possess a distribution. A meaningful estimate of this distribution from DC magnetic measurement may be done from the temperature dependences of the magnetization after cooling the system in zero (ZFC) or non-zero magnetic field (FC). Lu et al. [3] have shown that the
distribution p of TB should be proportional to the derivative by T of the difference between the MZFC and MFC moments:
p (TB) = d (MZFC MFC ) / dT . (5) For the relevant value of the blocking temperature of the system we may then use the temperature at which the function p (TB) passes through its maximum. . On the other end of the time scale stands the Moessbauer spectroscopy with the characteristic time of -7 ~10 s. For the rather frequent case of alloys and compounds of iron, we may exploit the Mössbauer 57 spectroscopy of the Fe isotope. From the spectra acquired at various temperatures we may estimate the relative number of Fe moments that are either in the blocked or superparamagnetic state and accept for the average blocking temperature that one where these two quantities are approximately equal. In our work [4] we applied this approach to the system of particles of iron oxides predominantly -Fe2O3 locking temperatures for the two rather different observation times (DC magnetic measurements and Mössbauer spectroscopy) we had the unique possibility to derive the ranges of both relevant quantities -8 -11 from relation (3): the energy barrier Keff V and the constant 0 . For 0 we obtained 5x10 s 2x10 s in good agreement with the usual estimates of this quantity. . -25 3 With the average particle size of about 5 nm which gives for the volume ~10 m , we obtained for the 4 5 3 absolute value of Keff 3.6x10 J/m . This value compares well with the magnitude of the first 4 3 constant of magnetocrystalline anisotropy of bulk cubic maghemite equal to -2.5x10 J/m [5]. We may thus conclude that in this case the relevant anisotropy constituting the energy barrier for spontaneous change of the direction of particle moment is of the magnetocrystalline origin. Acknowledgement. The authors thank the Ministry of Industry and Trade of the Czech Republic for the support under the grant FR-TI3/521 and Grant Agency of the Czech Republic for the support under the grant P204/10/0035
References [1] C. Kittel, Rev. Mod . Phys., 21 (1949), 541. [2] L. Néel: Ann. Geoph. 5 (1949) 99. [3] J.J. Lu, H.Y. Deng, and H.L. Huang: J. Mag. Mag. Mat. 209 (2000) 37. [5] E.P. Valstyn, J.P. Hanton, Morish: Phys. Rev. 128 (1962) 2078
E90.
Magnetic and transport properties of granular Co-Cu glass-coated microwires V. Zhukova1, M Ilyn1, C. Garcia2, R. Varga3, J. J. del Val1, A. Granovsky1,4and A. Zhukov1,5 1
Dpto. de Física de Materiales, Fac. Químicas, UPV/EHU, 20018, San Sebastián, Spain 2 Bogazici Univ, Dept Phys, TR-34342 Istanbul, Turkey 3 Inst. Phys., Fac..Sci., UPJS, Park Angelinum 9, Kosice, Slovakia 4 Moscow State University, Moscow, 119991, Russian Federation 5 IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain valentina.zhukova@ehu.es
During last years studies of glass-coated magnetic microwires attracted considerable attention owing to a number of outstanding magnetic properties suitable for various technological applications [1-2]. These microwires with typical metallic nucleus diameters 1 - 30 m and the thickness of the glass coating 0,5 20 m are produced by so-called Taylor-Ulitovsky method allowing fast quenching from the melt and therefore fabrication of microwires with amorphous, nanocrystalline, microcrystalline or granular structure [1,2]. Amorphous and nanocrystalline microwires usually exhibit excellent soft magnetic properties such as the magnetic bistability (MB) and the giant magnetoimpedance (GMI) effects [1-3]. On the other hand, rapid solidification allows further expand the limits for obtaining of novel magnetic materials, since it may lead to textures, amorphous to crystalline transitions and nanocrystalline structures [3]. Recently Taylor- Ulitovski technique allowed preparation of granular microwires [3,4], microwires with magnetocaloric effect, MCE, [5] and even Heusler type microwires [6]. It is well established, that the microstructure of such Co-Cu granular alloys consists of small (few nm) Co grains embedded in paramagnetic Cu matrix. The Giant Magneto-resistance (GMR) effect in granular alloys is interpreted considering mixed ferromagnetic-paramagnetic microstructure and spindependent scattering of the electrons on grain boundaries between these two phases [7]. Consequently in this paper we present results on fabrication of Co-Cu glass-coated microwires with granular structure and GMR effect and on their structural and magnetic properties. Cox-Cu100-x (5 x 40 at %). Structure and phase composition have been checked by using a Siemens-500 X-ray diffractometer with Cu K ( =1.54 Å) radiation. Magnetic and magneto-transport properties have been measured within 5 - 400 K using suitable options of PPMS by Quantum Design and using SQUID Quantum Design MPMS XL. Heat treatment has been performed in a conventional furnace up to 1073K. Magnetoresistance (MR) has been defined as: R/R(%) = (R(H)-R(0))x100/R(0) Typical magnetic field, H, dependence of R/R of studied microwires is shown in the Fig 1a. R/R(H) dependence showing monotonous decay with H should be attributed to the GMR, related with the existence of a single domain ferromagnetic particles embedded in an immiscible medium. We observed considerable MR in Co10Cu90, Co20Cu80 and Co30Cu70 microwires (Figs. 1a, 1b and 2). In most cases, cooling resulted in increasing of R/R, indicating, that GMR is a major contribution in total MR. As previously reported elsewhere [2,3,8] ratio affects strength of internal stresses induced during the rapid solidification of composite wire and also quenching rate when using Taylor-Ulitovsky method. Therefore, we measured R/R(H) in CoxCu100-x microwires as a function of temperature with chemical composition and -ratio ( d/D) as a parameters (see Fig 2). For the samples with concentration of cobalt x=20 and 30 R/R(H) dependences showed non-monotonic behavior, exhibiting R/R increase with H at low H values (up to 10 kOe), as was also previously reported for Co29Ni25Mn1Cu45 microwires [3,4]. We assumed that the anisotropic contribution should be attributed to the ferromagnetic nature of Co-rich phase while the negative longitudinal MR should be related with the single domain ferromagnetic particles embedded in an immiscible metallic medium [4]. This assumption has been recently confirmed by studying the contrast of bulk CuCo ribbons made by melt spinning through TEM [8]. Such results, confirm, that the structure of these materials is not exactly granular (as many works assume) but of a spinodal decomposed material [9]. That is, Co atoms in these materials are mainly distributed on a periodic profile within the Cu phase. Additionally, we recently observed that glass-coated microwires exhibit a contrast very similar to that seen in the ribbons, but with smaller wavelength due to internal stresses induced by the fabrication technique [8] and anomalous temperature dependence, observed in some Co-Cu microwires has been attributed to such effects [3]. Consequently, variation of MR with ratio should be attributed to the corresponding changes of the microwire structure. Experimental data obtained using measurements of ZFC and FC magnetization M on temperature T dependences: we did not observe any difference for Co5Cu95 microwires, and significant difference on ZFC and FC curves for Co20Cu80. For Co10Cu90 microwires small difference has been observed at quite low temperatures, indicating possibility of existence of some amount of small Co-grains.
In our opinion it means that vast majority of Co is dissolved in matrix or aggregated in rather small clusters. X-ray diffraction (XRD) results reveal that the structure of the metallic core is granular with two phases: the main one, fcc Cu (lattice parameter 3.61 ), found in all samples and fcc -Co (lattice parameter 3.54 ) which presents in microwires with higher Co content. In the case of low Co content XRD indicates that Co atoms are distributed within the Cu crystals. The quantity and the crystallite size of the formed phases strongly depend on the geometry of the microwire. From XRD we can see that in Co40Cu60 -Co phase has been observed. At the same time we did not observe this phase in the sample Co10Cu90 (Fig.3). Consequently observed experimental data on structure and properties of CoxCu100-x microwires allows us to consider, that since Co and Cu are almost immiscible at room temperature rapid quenching of molten solution gives rise to formation of supersaturated solid solutions and partial precipitation of fine Co grains in as-prepared state. The residual concentration of Co dissolved in the Cu matrix and size of Co grains depends on the quenching rate and on internal stresses determined by the ratio. References [1] M. Vazquez, H. Chiriac, A. Zhukov, L. Panina and T. Uchiyama, Phys. Status Solidi A, A 208 (2011) 493 [2] V. Zhukova, M. Ipatov and A Zhukov, Sensors 9 (2009) 9216. [3] A. Zhukov and V. Zhukova, «Magnetic properties and applications of ferromagnetic microwires with amorphous and nanocrystalline structure , Nova Science Publishers, Inc. 400 Oser Avenue, Suite 1600 Hauppauge, NY 11788, 162 p. 2009, ISBN: 978-1-60741-770-5. [4] A. Zhukov, J. Gonzalez and V. Zhukova, J. Magn. and Magn., Mater. 294 (2005) 165 [5] M. I. Ilyn, V. Zhukova, J. D. Santos, M. L. Sánchez, V. M. Prida, B. Hernando, V. Larin, J. González, A. M. Tishin, and A. Zhukov: Phys. Stat. Sol. (a), 205 (2008) 1378. [6] C.M. Craciunescu, A. Ercuta, I. Mitelea, M. Valeanu, V.S. Teodorescu, N. Lupu, and H. Chiriac, Eur. Phys. J. Special Topics 158(2008) 161 [7] J.Q. Xiao, J.S. Jiang and C.L. Chien, Phys.Rev.Let., 68 (1992) 3749. [8] H. Chiriac, T.-A- Ovari and A. Zhukov, J. Magn. Magn. Mater., 254-255 (2003) 469 [9] M.N. Baibich , G. Martínez, M.G.M. Miranda , A.T. da Rosa, J. González , A. Zhukov, J. Magn. Magn. Mater. 320 (2008) e29 Figures 0
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Cu95Co5 ( =0.787)
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Fig.1 R/R (H) of CoxCu100-x microwires for x=20 (a) and x=30 (b)
Fig. 3 XRD spectra of CoxCu100-x (x = 10 and x=40)
The authors thank the Ministry of Industry and Trade of the Czech Republic for the support under the grant FR-TI3/521
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