Photosensitization of Nanocrystalline TiO2 Thin Films by a Polyimide bearing Pendent Substituted Ru(bpy)3+2 Groups

Hiroyuki Osora, Weijin Li, Luis Otero, and Marye Anne Fox*

Contribution from the Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712.


Under visible illumination, a thin film of nanocrystalline TiO2 coated with an adsorbed substituted-Ru(bpy)3+2-labeled polyimide 1 produces a sensitized photocurrent when spin-coated on a conductive ITO support. The magnitude of the observed anodic photocurrent defines the efficiency of charge injection from the adsorbed dye to the nanoparticle and of interparticulate electron hopping to the conductive support. Power characteristics and photocatalytic activity of the sensitized film were investigated. Laser flash photolysis at different applied potentials produced transient absorption spectra that were analyzed as multicomponent charge injections. Lifetime measurements permitted a characterization of the efficiency of electron migration across the semiconductor film. The polymeric dye was also shown to be an effective photosensitizer in inducing the catalytic oxidative decomposition of methylene blue.