Monday, 23 May 2005 - 3:40 PM

This presentation is part of: Spectroscopy of Biomolecules, Inferfaces and Materials II

Fast Long-range Electron Injection at Molecule-Nanoparticle Interfaces

Piotr Piotrowiak, Rutgers University at Newark, Newark, NJ

Electron transfer processes in heterogeneous materials consisting of semiconductor nanoparticles and molecular components are being investigated. The goal of these efforts is to achieve a similar degree of control over electronic interactions at interfaces between molecules and nanoparticles as it is possible in purely molecular systems. Progress in three areas will be reported: (1)Sub-picosecond electron injection from 'molecular tripods' bearing light absorbing electron donors into the conduction band of TiO2 was observed over distances in excess of 20 Å. The three-point attachment of the tripod to the metal oxide particles allows one to control the distance and orientation of the sensistizer with respect to the surface. The ultrafast injection rates demonstrate the feasibility of 'hot electron' injection over long distances. (2) Novel hybrid systems consisting of amphiphilic host-guest complexes (hemicarceplexes) bound to nanoparticles were prepared. The molecular container spontaneously and reversibly encapsulates a guest and binds it to the surface of a semiconductor nanoparticle. Photoexcitation of the guest results in electron tunneling across the molecular cage to the nanoparticle. (3) Time resolved confocal microscopy experiments revealed a broad range of residual emission lifetimes of surface modified TiO2. The inhomogeneity of the emission depends on the substrate and on the treatment of the sample. Films prepared in the ‘Graetzel cell' fashion display the broadest range of lifetimes reaching hundreds of nanoseconds. In contrast, dilute nanoparticles that were extensively dialyzed prior to the measurement exhibit a much narrower range of lifetimes of only a few nanoseconds .

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