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 (Kapp) deduced using Benesi–Hildebrand equation from the absorption spectral changes for TSPP-colloidal AuTiO2 nanoparticles (24.69 × 104 M−1) was higher than colloidal TiO2 nanoparticles (4.78 × 104 M−1). Lifetime measurements shows higher rate of electron transfer for colloidal AuTiO2 nanoparticles (4.56 × 108 s−1) compared to colloidal TiO2 nanoparticles (2.54 × 108 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.