Time-resolved opticalspectroscopy of heterosupramolecular assemblies based on nanostructured TiO_2 films modified by chemisorption of covalently linke druthenium an dviologen complex components

摘要

Described is the preparation of transparent nanostructured TiO_2 (anatase) and Sb-doped SnO_2 films supported on F-doped conducting glass.Also described is the modification of these films by chemisorption of RV,bis(4,4'-bis(phosphonomethyl)-2,2'-bipyridine)(5-(1'-ethyl-4,4'-bipyridinediium-1-yl)butyl)-2,2'-bipyridine)ruthenium(II) tetrakis(hexafluorophosphate),to form the covalent heterosupramolecular assemblies TiO_2-RV and SnO_2-RV,respectively.Visible light excitation of the ruthenium complex component,R,results in electron injection into the TiO_2 or SnO_2:Sb nanocrystal component (60%) and electron transfer to the viologen component (40%),V.In the case of TiO_2-RV,however,long-lived formation of the radical cation of the V component,V~(.+),is observed.In the case of SnO_2-RV,long-lived formation of V~(.+) is not observed.These findings,based on a detailed study of the time-resolved optical spectroscopy of TiO_2-RV and SnO_2:Sb-RV,are accounted for by proposing that long-lived V~(.+) is formed by TiO_2 nanocrystal mediated electron transfer to the V component.