Heterogeneous electron transfer from a photo-excited molecular donor state to a semiconductor is a unique electron transfer case for a molecular reactant since one can utilize a continuum of electronic acceptor states provided the donor state is located high enough above the bottom of the conduction band. In this case, all the Franck-Condon factors are available for the reaction and only the electronic coupling between the donor orbital and the electronic acceptor states controls the electron transfer time. This situation is particularly attractive for studying the influence of saturated molecular spacer-cum-anchor groups on the electronic coupling between the chromophore part of the attached molecule and the conduction band states in the semiconductor. The chapter investigates the dynamics of electron injection from the aromatic chromophore perylene into the conduction band of colloidal anatase TiO2 by transient absorption spectroscopy under ultra-high vacuum (UHV) conditions for different saturated spacer-cum-anchor groups. Electron injection from perylene directly linked via a carboxylate group to the surface is found to occur with 15 fs time constant. Insertion of saturated spacer groups as well as the exchange of the anchor group can systematically decelerate the electron transfer. For the case of a long rigid spacer molecule, multi-exponential injection dynamics was observed with 4 ps as the largest time constant.
|Original language||English (US)|
|Title of host publication||Femtochemistry and Femtobiology|
|Subtitle of host publication||Ultrafast Events in Molecular Science|
|Number of pages||4|
|State||Published - Apr 16 2004|
All Science Journal Classification (ASJC) codes