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From: sotheeswaran@hotmail.com To: p.m.jayaweera@gmail.com Subject: RE: Abstract 2012 Date: Sun, 19 Feb 2012 17:22:09 +1200 Dear Professor Jayaweera, Your abstract titled " A Kinetic Study of Photodegradation of β-carotene

in Water/Ethanol Solutions" has been accepted for an oral presentation at the International Conference on Chemical Sciences to be held during 20-22 June 2012 in Colombo. I have attached a conference brochure. All participants and the presenter should register for the conference by completing the attached registration form. I have also attached a conference brochure. Please follow the guideline and ask all the participants to pay the appropriate registration fees. If the participants are below the age of 40 yrs, they can apply for IUPAC/NSF funds to obtain re-imbursements of the conference registration fees. To be eligible for such re-imbursements, participants should register in the formal manner, obtain a certificate of participation and then claim the re-imbursements. Professor S. Sotheeswaran

A Kinetic Study of Photodegradation of β-Carotene in Water/Ethanol Solutions T. S. Guruge1, L. A. Jayaweera1, U. G. Chandrika2 and P. M. Jayaweera3* 1. B. Pharmacy Unit, University of Sri Jayewardenepura, Nugegoda, Sri Lanka 2. Dept. of Biochemistry, University of Sri Jayewardenepura, Nugegoda, Sri Lanka 3. Dept. of Chemistry, University of Sri Jayewardenepura, Nugegoda, Sri Lanka

Carotenes (Car) are excellent quencher of Reactive Oxygen Species (ROS). Living cells are sensitive towards oxidative stresses, such as exposure to UV light which leads to generation of ROS. The formed ROS interfere with the normal function of biological molecules. In this study photodegradation of β-carotene was investigated under three very important conditions such as exposure to UV irradiation, presence of water and dissolved oxygen in an attempt to fully understand the of photo-induced degradation of β-carotene. Analysis of data confirms that nitrogen purged photodegradation data obeys the second-order kinetics, whereas air purged photodegradation data obeys the first-order kinetics. This confirms that dissolved molecular O2 plays a very significant role in the photodegradation mechanism. In order to understand the effect of water, studies were extended to water/ethanol mixtures. Further, the effect of Fe2+, redox active ion, was investigated on the photodecomposition kinetics in this work. The change in the kinetic behavior could be explained in this manner. In the presence of proton acceptors Car•+ under goes deprotonation to form β-carotene radical Car•, which dimerizes to form Car2, 2Car• → Car2. However, in the presence of O2, Car2 formation is inhibited by the reactions O2 + e- → O2•− and Car•+ + O2•− → CarO2.

Further, the reaction of O2•− +2H2O → 2OH• +2OH− + O2 enhances the

photodegradation of β-carotene via OH• to form carbonyl products such as apo-β-carotenal and apo-βcarotenone. Therefore, it is clear that in the presence of O2 photo-induced decomposition follows a 1


different mechanism. In the absence of O2 photodecomposition proceed via β-carotene dimmer formation, explaining the observed second order kinetics. The observed first order kinetics in the presence O2 indicate that product giving step may well be the degradation of CarO2 and it is most likely the rate determining step. Addition of Fe2+ ions into the medium further slow down the degradation rate. Fe2+ ions act as an electron acceptor from Car•+ to generate Car back. Car•+ + Fe2+− → Car + Fe3+. Furthermore, e− generated by the reaction Fe2+(aq) + hυ → Fe3+(aq) + e− again can form the Car back for its radical cation Car•+ + e− → Car. These reactions may well slow down the rate of photodecomposition of β-carotene in the presence of electron accepting species like Fe2+ ions. However, it is still not clear why the presence of small amounts of water in the mixture, absences of O2, slow down the rate of photodecomposition. Perhaps, the stabilization of π→π* in polar solvents as observed by 10 nm red shift in the UV-Vis. absorption spectrum in water/ethanol mixtures could influence the photodegradation rate.

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COLL 329-Surface chemistry and photochemistry of nitrogen oxides on metal oxide particle surfaces

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Author(s): Baltrusaitis, J (Baltrusaitis, Jonas)1 ; Jayaweera, PM (Jayaweera, Pradeep M.)1 ; Grassian, VH (Grassian, Vicki H.)1

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Source: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Volume: 238 Meeting Abstract: 329-COLL Published: AUG 16 2009

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Times Cited: 0 (from Web of Science) Cited References: 0 Accession Number: WOS:000207861903315 Document Type: Meeting Abstract

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Language: English Addresses: 1. Univ Iowa, Dept Chem, Iowa City, IA 52242 USA Publisher: AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA Web of Science Category: Chemistry, Multidisciplinary Subject Category: Chemistry

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4/25/12

APS -76th Annual Meeting of the Southeastern Section of APS - Event - Ultraviolet-Infrared dual band …

Bulletin of the American Physical Society 76th Annual Meeting of the Southeastern Section of APS Volume 54, Number 16 Wednesday–Saturday, November 11–14, 2009; Atlanta, Georgia

Session PA: Optics 10:45 AM–12:33 PM, Saturday, November 14, 2009 Room: Brussels Chair: Brian Thoms, Georgia State University Abstract ID: BAPS.2009.SES.PA.9

Abstract: PA.00009 : Ultraviolet-Infrared dual band detector using ZnO/PbS composite nanostructure 12:21 PM–12:33 PM Preview Abstract Authors: P.K.D.D.P. Pitigala (Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303, USA ) P.V.V. Jayaweera (Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303, USA) J. Shao (Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303, USA) K. Tennakone (Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303, USA) A.G.U. Perera (Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303, USA) P.M. Jayaweera (Department of Chemistry, University of Sri Jayewardenepura, Nugegoda, Sri Lanka) J. Baltrusaitis (Central Microscopy Research Facility, University of Iowa, Iowa City, Iowa 52242, USA) meetings.aps.org/Meeting/SES09/Event/112848

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4/25/12

APS -76th Annual Meeting of the Southeastern Section of APS - Event - Ultraviolet-Infrared dual band â&#x20AC;Ś

Sensors for detecting ultraviolet (UV) and near-infrared (NIR) photons, fabricated by complex epitaxial methods are costly. A low cost UV-NIR detector is fabricated using ZnO nonporous powder and PbS quantum size particles is demonstrated. A nonporous film of ZnO was fabricated on Fluorine doped Tin Oxide (FTO) glass with a scribe, separating the FTO layer in to two electrodes. PbS quantum particles were composites on the ZnO film by wetting the film using a solution of lead acetate in ethanol and passing a stream of H$_{2}$S gas on top of the film. When a bias voltage is applied across the electrodes the device shows two response peaks, around 380nm (UV) and 800nm (NIR). These two responses are resulted due to bandgap excitation of ZnO ($\sim $3.2 eV) and PbS ($\sim $0.9 eV) quantum particles. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.SES.PA.9

APS Home | APS Meetings | Join APS | Help | Contact APS Meetings Š 2012 American Physical Society

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