SPECTROSCOPIC STUDIES OF METHOXY-3,3,'-DISULFOBUTYL-9-ETHYLTHIACARBOCYANINE (DDTC) IN SOLUTIONS AND IMMOBILIZED IN SOL-GEL MATRICES

Absorption spectra of methoxy-3,3,'-disulfobutyl-9-ethylthiacarbocyani ne (DDTC) in aqueous solutions and immobilized in xerogels prepared by the sol-gel method have been obtained. Influence of pH, detergent (Tr iton X-100), ethanol addition and sol-gel preparation method on the dy e aggregation equilibria and its photostability have been investigated . In liquid solutions lowering of pH, as well as addition of the deter gent, shift the aggregation equilibrium towards the DDTC monomeric for m. However, while more acidic conditions result in a decrease of the d ye stability, addition of the detergent has a slightly stabilizing eff ect on the dye. On the other hand, addition of ethanol drastically red uces the DDTC photodecomposition and shifts the aggregation equilibriu m towards the dye monomer, Entrappment of the thiacarboxycyanine in so l-gel matrix does not prevent the bleaching although the entrapped dye displays significantly increased stability. Lowering of temperature a nd keeping the doped xerogels in the dark further retards the immobili zed dye bleaching and dimer formation. (C) 1998 Elsevier Science B.V.