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

The interaction of zinc(II) rneso-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 x 10(-4) M. The bimolecular quenching rate constants (k(q)) were 20.5 x 10(10) M-1 s(-1) (steady-state) and 2.85 x 10(10) 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. (C) 2008 Elsevier B.V. All rights reserved.