Spectroscopic behaviour of 8-hydroxy-1,3,6-pyrenetrisulphonate immobilized in ethyl cellulose

Abstract

The spectroscopic behaviour of 8-hydroxy-1,3,6-pyrenetrisulphonate (HPTS) immobilized in an ethyl cellulose film and in aqueous phosphate pH buffers have been studied using fluorescence and electronic absorption spectra. The absorption, excitation and emission peak maxima of the acidic and basic forms of HPTS in ethyl cellulose and aqueous solution have been determined and compared. The deprotonation of the excited acidic form of HPTS is suppressed in ethyl cellulose but not in aqueous solution condition. HPTS in an aqueous solution is more acidic than in an ethyl cellulose film. Less number of water molecules and salt effect in ethyl cellulose are used to explain this observation. The acid dissociation constants of HPTS in an aqueous phosphate solution and an ethyl cellulose film are 7.31 and 8.43, respectively at 25°C.