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Donor/Acceptor Adsorbates on the Surface of Metal Oxide Nanoporous Films: A Spectroscopic Probe for Different Electron Transfer Pathways
Author(s) -
Matylitsky Victor V.,
Dworak Lars,
Wachtveitl Josef
Publication year - 2010
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200900991
Subject(s) - acceptor , intermolecular force , electron transfer , nanoporous , chemistry , chemical physics , electron acceptor , ultrafast laser spectroscopy , electron donor , photochemistry , materials science , spectroscopy , molecule , nanotechnology , biochemistry , physics , organic chemistry , quantum mechanics , condensed matter physics , catalysis
Abstract A composite model system which consists of a molecular donor/acceptor pair coupled to the surface of metal oxide nanoporous films is proposed to study the contribution of the surface trap states and their influence on the interfacial ET as well as charge trapping and spatial diffusion processes in films. The photophysics of this donor/acceptor system is investigated by time‐resolved transient absorbance spectroscopy in the UV/Vis (347–675 nm) spectral region. Variation of the band gap allows one to disentangle the ET pathways. Adsorption of the donor/acceptor pair on the nonreactive Al 2 O 3 surface shows that coupling to the surface assists electron transfer between adsorbed donor and acceptor molecules, resulting in ultrafast intermolecular electron transfer of ∼100 fs. On the other hand, a competition between interfacial and intermolecular electron transfer is observed for the donor/acceptor pair coupled to a reactive TiO 2 surface. The subsequent transfer of the conduction band electron to the electron acceptor is examined by monitoring the free charge carrier absorption in the mid‐IR (∼5 μm) spectral region.