Hannover 2003 – wissenschaftliches Programm
MO 6.14: Poster
Dienstag, 25. März 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.