Photosensitization of a colloidal TiO 2 semiconductor system with hypocrellin B

Abstract

The adsorption of hypocrellin B (HB) on the surface of TiO 2 colloidal particles and the electron transfer process from its singlet excited state to the conduction band of TiO 2 were examined by absorption, fluorescence quenching, fluorescence lifetime measurements, laser flash photolysis and pulse radiolysis techniques. Adsorption of HB onto the surface of colloidal TiO 2 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 TiO 2 ( K et= 4.93×10 9 s −1). Laser flash photolysis and pulse radiolysis studies demonstrated the formation of radical cation of HB .