Photoinduced electron transfer reactions between meso-tetrakis(4-sulfonatophenyl)porphyrin and colloidal metal-semiconductor nanoparticles

The dynamics of photoinduced electron transfer between meso-tetrakis(4-sulfonatophenyl)porphyrin [TSPP] and colloidal metal-semiconductor nanoparticles (AgTiO2 and AuTiO2) have been studied by using absorption, infra-red, steady state and time resolved fluorescence spectroscopic measurements. The apparent association constant (K-app) deduced using Benesi-Hildebrand equation from the absorption spectral changes for TSPP-colloidal AuTiO2 nanoparticles (24.69 x 10(4) M-1) was higher than colloidal TiO2 nanoparticles (4.78 x 10(4) M-1). Lifetime measurements shows higher rate of electron transfer for colloidal AuTiO2 nanoparticles (4.56 x 10(8) s(-1)) compared to colloidal TiO2 nanoparticles (2.54 x 10(8) s(-1)). The electron transfer mechanism was explained based on the Rehm-Weller equation as well as the energy level diagram. The electrons injected into the TiO2 were quickly transferred to the metal core. Use of metal-semiconductor nanoparticles may provide new ways to modulate charge recombination processes in dye-sensitized solar cells. (C) 2008 Elsevier B.V. All rights reserved.