An investigation on electron transfer quenching of zinc(II) meso-tetraphenylporphyrin (ZnTPP) by colloidal TiO2

The interaction of zinc(II) meso-tetraphenylporphyrin (ZnTPP) with colloidal TiO2 was studied by absorption, steady state and time-resolved fluorescence spectroscopy. The quenching was found to obey the Stern-Volmer equation and the corresponding Stern-Volmer plots were linear in the range of quencher concentration used 0-5 × 10−4 M. The bimolecular quenching rate constants (kq) were 20.5 × 1010 M−1 s−1 (steady-state) and 2.85 × 1010 M−1 s−1 (time resolved). The quenching process is suggested to involve electron transfer from the ZnTPP to TiO2 considering the experimental evidences obtained.