Hannover 2003 – scientific programme

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MO: Molekülphysik

MO 6: Poster I

MO 6.14: Poster

Tuesday, March 25, 2003, 16:00–18:30, Lichthof

Experiments on ultrafast electron transfer from perylene into a nanostructured TiO₂ film — •Carsten Zimmermann¹, Ralph Ernstorfer¹, Silke Felber¹, Lars Gundlach¹, Rainer Eichberger¹, Elena Galoppini², Qian Wei², and Frank Willig¹ — ¹Hahn-Meitner-Institut, Glienicker Str. 100, 14109 Berlin — ²Department of Chemistry, Rutgers University, Newark, N.J., USA

Ultrafast photoinduced heterogeneous electron transfer from large molecular adsorbates into a semiconductor is an interesting fundamental case study of interfacial reactions. The electron transfer reaction was measured with fs transient absorption for the perylene chromophore adsorbed on nanocrystals of TiO₂ that formed a sponge-type layer. The transfer time is controlled by the strength of the electronic coupling. The electronic coupling strength can be modified by inserting molecular spacer groups with saturated bonds between the chromophore and the semiconductor surface as well as by attaching the chromophore via different anchor groups to the TiO₂ surface. Different procedures in the preparation of the TiO₂ layers are a further possibility to vary the barrier for the electron transfer reaction. Time constants for the electron injection between sub-15 fs and hundreds of femtoseconds were found with spacer-cum-anchor groups of different length, flexibility and chemical composition. The influence of the environment on the ultrafast electron transfer reaction (injection and recombination) between the photoexcited perylene dye and the TiO₂ was measured using a special designed sample-chamber switchable between ultra high vacuum (10⁻¹⁰ mbar) and different gas or solvent environments.