Fig. 1 a. Ball-and-stick model of the atomic structure of cove-shaped GNRs with different width, edge functionalization and GNR orientation. b. Acoustic region of the Raman spectrum of the GNRs shown in a., where the main feature is attributed to the radial-like breathing mode (RLBM). c, d. Density-functional Perturbation theory simulations of the vibrational properties allow us to understand the relationship of the RLBM position as a function of width (c) and edge functionalization (d). e. Ab initio simulation of the linear optical spectrum of selected cove-shaped GNR (4CNR, top panel in a), as compared to the experimental curve (theory is in blue, exp. in black). f. Femtosecond transient absorption spectroscopy of the 4CNR. The stimulated emission at about 650 nm is attributed to recombination of biexcitons forming by nonlinear exciton–exciton annihilation in the high-excitation regime. g. Tight-binding plus Quantum Monte Carlo simulations are employed to estimate the biexciton binding energy. Comparison with CNTs and with the 2D limit is shown.
Fig. 2 a) Atomically-precise chGNR are grown on a gold surface by surface-synthesis. HREELS vibrational spectra clearly fingerprint the different steps of GNR formation (as schematically shown on the left). The shape of the CH wagging-mode manifold which dominates the chGNR spectrum (red curve) is compared with ab-initio theoretical simulation, providing detailed information on the chGNR edge and termination topology. b) The optical excitation of the precursor polymer and of chGNRs are measured by RDS and HREELS and compared with ab initio calculations based on many-body perturbation theory. The dielectric function of precursor polymer (blue) and ch-AGNR (red), extracted 62
Activity Report 2018