PHOTOREDUCTION OF METHYLENE BLUE IN PRESENCE OF UREA

Dyes photochemistry has contributed to the understanding of the mechanism of electron transfer reactions in photochemical devices[ 1-3]. Numerous photoinduced redox reactions of dyes and different reducing agents have been studied in electrochemical cells for the conversion ofsolar energy to electrical energy by chemical means [4]. Methylene blue a member of thiazine dye, is water-soluble cationic dye. Several investigations [5-17], have been made to describe the photo physical properties, spectral studies and structural analysis of the dye molecule since its synthesis, but no attention was made to study the photochemical kinetics of the reduction of methylene blue in the presence of reductants. We report herein the kinetics of photo-reduction of methylene blue (MB) was studied in 1:1 v/v aqueous 2-propanol in the presence of urea as a reducing agent. It was found that the quantum yield (f/J) ofthe reaction at various acidities decreases as the acidity increases. The quantum yield ofthe reaction varies directly with the increase in the concentration of reductant and temperature. Moreover it was also found that the quantum yield of the reaction was independent ofthe concentration ofmethylene blue.