| Abstract
| - An alternative mechanism for dye sensitization of wide bandgap semiconductors has been realized: reductive quenching of the dye excited state(s) followed by thermal interfacial electron transfer. Theprocesses were identified using nanosecond-time-resolved absorption and photoluminescence spectroscopiesafter selective excitation of Ru(deeb)(bpy)2(PF6)2, where bpy is 2,2‘-bipyridine and deeb is 4,4‘-(COOC2H5)2-2,2‘-bipyridine, sensitizers anchored to a nanocrystalline (anatase) TiO2 film immersed in a 0.1 Mtetrabutylammonium perchlorate acetonitrile solution with phenothiazine electron donors. With theelectrolyte changed to 0.1 M lithium perchlorate, this same assembly undergoes the generally acceptedmechanism for dye sensitization: the sensitizer excited state(s) transfer an electron to the semiconductorand is subsequently reduced by the phenothiazine donor.
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