Photophysics of thionine dye in aqueous and liposome media in presence of different reducing agents

The photoelectrochemical and spectral (both absorption and fluorescence) st udies of thionins, a cationic phenothiazine dye, have been carried out in a queous and phosphatidylcholine liposome media in the presence of different reducing agents, such as I, Br-, Cl and Fe2+. The results show that the pho tovoltage generation from photoelectrochemical studies and Stern-Volmer que nching constant studied by fluorescence quenching support the photoinduced electron transfer from the reducing agent to the singlet excited thionine d ye. Moreover, a good correlation between photovoltages/Stern-Volmer quenchi ng constants vs. reduction potentials of the reducing agents also confirms the above electron transfer in the photoexcited state. (C) 2001 Elsevier Sc ience Ireland Ltd. All rights reserved.