A dye recycled photosensitization system has been designed. As a result of studies in the mechanism of electron transfer reaction of xanthene iodonium salt, it is proposed that the dye-recycled process consists of three-step reactions during the photosensitization: The oxidative fading product(I) of dye is formed through electron transfer under irradiation; In the presence of H-donor, product(I) changes into acidic leuco dye product(II); Product(II) undergoes deprotonization under action of base to regenerate initial dye. The roles of light, H-donor and base are three major factors in the process of dye regeneration. For the efficiency of dye regeneration, it is critical to control the proportion of acidic leuco dye product. For a dye regenerated system composed of eosin ethyl ester iodonium salt (EOEtIPh2) triethylamine (TEA), the efficiency of sensitization is 4 times higher than of single system EOEtIPh2, at mean time the number of active radicals is also multiplicated and thus this system is of importance in practical application.

Key words: PHOTOSENSITIZATION, REACTION MECHANISM, DYES