Dw. Thompson et al., Sensitization of nanocrystalline TiO2 initiated by reductive quenching of molecular excited states, LANGMUIR, 15(3), 1999, pp. 650-653
An alternative mechanism for dye sensitization of Ride bandgap semiconducto
rs has been realized: reductive quenching of the dye excited state(s) follo
wed by thermal interfacial electron transfer. The processes were identified
using nanosecond-time-resolved absorption and photoluminescence spectrosco
pies after 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 a
nchored to a nanocrystalline (anatase) TiO2 film immersed in a 0.1 M tetrab
utylammonium perchlorate acetonitrile solution with phenothiazine electron
donors. With the electrolyte changed to 0.1 M lithium perchlorate, this sam
e assembly undergoes the generally accepted mechanism for dye sensitization
: the sensitizer excited state(s) transfer an electron to the semiconductor
and is subsequently reduced by the phenothiazine donor.