Hannover 2010 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 21: Femtosecond Spectroscopy III

MO 21.1: Vortrag

Donnerstag, 11. März 2010, 14:00–14:15, F 102

Influence of the Chemical Environment on Perylene/ZnO and Perylene/TiO2 Hybrid Systems Varying the Electronic Coupling — •Antje Neubauer, Andreas Bartelt, Jodi Szarko, Rainer Eichberger, Olaf Lettau, Carlo Fasting, and Thomas Hannappel — Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin

Heterogeneous electron transfer dynamics are determined by the strength of the electronic couplings, the density of states and the energetics of the reaction. Here, we present a study of molecular dye/semiconductor hybrid systems that vary in electronic coupling due to dye structure and in the density of states due to different semiconductor materials. The dye molecules differed in a C-C single bond vs. a C-C double bond between the perylene skeleton and a carboxylic acid anchor group which bounds the dyes chemically to ZnO or TiO2 colloidal films. A detailed study of steady-state absorption and fluorescence spectra for these two dye molecules in different solvents as well as for the hybrid systems showed that the ZnO and TiO2 colloids in the films provide different chemical environments for electron transfer. For the dye with strong electronic coupling this led to a strong broadening of the absorption spectra. This could be explained by a larger dipole moment for the dye with the C-C double bond and a higher intramolecular charge transfer character of the excited state. This has also been shown by excited state spectra measured with femtosecond-resolved transient absorption spectroscopy for the hybrid systems and the dyes in solution.