Direct observation of photodriven intermolecular hole transfer across TiO2 nanocrystallites: lateral self-exchange reactions and catalyst oxidation.
Photoselection of Ru(II)-polypyridyl sensitizers with polarized pulsed-light excitation, when anchored to TiO(2) nanocrystallites interconnected in a mesoporous thin film, results in an anisotropic distribution of excited sensitizers. Under conditions where excited-state sensitizers efficiently inject electrons into TiO(2), the resulting oxidized sensitizers exhibit an initial anisotropy in their absorption difference spectra. Over the course of the charge-separated lifetime for many sensitizers, the transient absorption anisotropy signal decays to nearly zero indicative of lateral self-exchange hole-transfer reactions at the interface. When a cobalt metalloporphyrin catalyst was coanchored to the sensitized nanocrystalline TiO(2) film, excited-state injection was followed by lateral hole transfer to oxidize the surface-bound catalyst.
Ardo
Shane
S
Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Meyer
Gerald J
GJ