LUMINESCENCE BEHAVIOR OF PHENOSAFRANIN IN REVERSE MICELLES OF AOT IN N-HEPTANE

The absorption and fluorescence properties of the cationic dye phenosa franin (PSF) solubilised in the reverse micelles of the surfactant aer osol OT (AOT) in n-heptane were studied as a function of water content , w(0) = ([H2O]/[AOT]). The room temperature emission of PSF in revers e micelles at w(0) = 0 show a significantly blue shifted maximum as co mpared with that in pure water. A plot of fluorescence polarisation an isotropy (r) against increasing w(0) shows an increase in the rigidity of the dye environment up to w(0) approximate to 10, where it maximis es and then falls off to attain a steady value between w(0) = 25-30. E ven at this high w(0) the anisotropy of the embedded dye molecule is a ppreciably higher than that of the dye in bulk water. Lifetime measure ments at different w(0) values showed single exponential decay charact er. Relevant absorption and luminescence data in representative homoge neous solvents and in low temperature (77 K) glass are also reported. The observations have been interpreted in terms of the location of the dye molecule and changes in its environment with changes in w(0), in the AOT reverse micelles. (C) 1997 Elsevier Science S.A.