Fluorescence spectra of thiazine dyes in micellar solution of different surfactants

Centre for Surface Science, Department of Chemistry, Jadavpur University, Kolkata-700 032, India E-mail : bhowmikbbju@yahoo.co.in Fax : 91-33-24146266 Manuscript received 8 October 2002 The fluorescence spectra of thiazine dyes such as thionine, azure A, azure B, azure C and methylene blue have been studied in aqueous solution of different surfactants. The results, which show the enhancement and red-shift of fluorescence bands of these dyes in surfactant solution, account for the interaction of excited dyes with surfactants. An attempt has been made to determine the stability constant of the excited state interaction between thionine and surfactants as well as between Triton X-100 and thiazine dyes from the enhancement of fluorescence intensities and this determination is qualitative. The electrondonating capacities of surfactants interacting with thionine are in the order : Tween 80 > Tween 60 >Tween 40 > Tween 20 >Triton X-100 > SLS. On the other hand, the electron-accepting capacities of thiazine dyes interacting with Triton X-100 are in the order : azure C > thionine >azure A> azure B > methylene blue