Düsseldorf 2007 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 56: Poster: Femtosecond Spectroscopy

MO 56.13: Poster

Donnerstag, 22. März 2007, 16:30–18:30, Poster A

Effects of different bridge/anchor groups on the mechanisms of ultrafast heterogeneous electron transfer in a dye/semiconductor system — •Antje Neubauer, Jodi Szarko, Carlo Dinkel, Guido Morbach, Liana Socaciu-Siebert, Rainer Eichberger, and Frank Willig — Hahn-Meitner-Institut, Glienicker Str. 100, D - 14109 Berlin

Two mechanisms for ultrafast heterogeneous electron transfer are known. For molecules bound to a TiO2 surface via a carboxylic anchor group the standard mechanism for photoinduced electron injection is widely accepted, where the chromophore of the organic dye is excited by light in a first step and the electron is injected from the excited state of the molecule in a second step. For dihydroxy compounds, where the two hydroxy groups bind to one Ti atom an alternative mechanism is known, the direct optical charge transfer.

We investigated new perylene derivatives at nano-porous colloidal TiO2 films in order to clarify the mechanisms for those heterogeneous electron transfer reactions. In these systems the perylene molecule functions as electron donor, and the wide-band gap semiconductor TiO2 functions as electron acceptor. The perylene chromophores are bound via a hydroxyl group, catechol and two hydroxy groups as bridge/anchor groups. The spectral features of the linear absorption spectra in solution and attached to TiO2 give information concerning the dynamics and therefore the mechanisms for the electron transfer, which are supported by the short time constants for the electron injection of less than 30 fs measured with transient absorption spectroscopy.