Femtosecond fluorescence dynamics of zinc biphenylporphine in nanocrystalline TiO2 films: Evidence for interfacial electron transfer through space

The femtosecond fluorescence dynamics of zinc biphenylporphine (ZnBPP) were investigated in solution and in two solid-state environments – ZnBPP/glass and ZnBPP/TiO2 – with S2 excitation (λex = 410 nm and λem = 630 nm). Our results indicate that the transient in solution involves a persistent component that becomes completely quenched in thin-film samples; for solid films at least three decay coefficients are required to fit the transients. For ZnBPP/TiO2 films, the fluorescence was quenched significantly through J-type aggregation and interfacial electron transfer (IET) through space. Photocurrent measurements were also performed to confirm the existence of IET through space between ZnBPP molecules and TiO2 nanoparticles.