Photo sensitization of a colloidal TiO2 semiconductor system with hypocrellin B

The adsorption of hypocrellin B (HB) on the surface of TiO2 colloidal particles and the electron transfer process from its singlet excited state to the conduction band of TiO2 were examined by absorption, fluorescence quenching. fluorescence lifetime measurements, laser flash photolysis and pulse radiolysis techniques. Adsorption of HB onto the surface of colloidal TiO2 particle led to red-shifted absorption, and the apparent association constant (K-app) was 3145 (mol/l)(-1) from fluorescence quenching. Exciting HB with visible light could induce electron transfer from its singlet excited state into conduction band of TiO2 (K-et = 4.93 x 10(9) s(-1)). Laser flash photolysis and pulse radiolysis studies demonstrated the formation of radical cation of HB. (C) 2001 Elsevier Science Ltd. All rights reserved.