PHOTOSENSITIZATION OF COLLOIDAL TIO2 WITH A CYANINE DYE

Fluorescence quenching studies have been carried out to elucidate the processes of electron injection from the excited ,1'-diethyl-3,3'-disu lfobutyl-5,5'-dicyanimidazolo carbocyanine hydroxide (dye) into the co nduction band of TiO2 semiconductor colloid. The dye adsorbed strongly on colloidal TiO2 with an apparent association constant of 3478 M-1, and its fluorescence emission was quenched by TiO2 colloid with an eff iciency of 92%. Fluorescence lifetime measurements gave the rate const ant for the electron injection process from the excited singlet state of the dye into the conduction band of the semiconductor as 4 x 10(9) s(-1). (C) 1997 Elsevier Science S.A.