Photophysics of 7-(diethylamino)coumarin-3-carboxylic acid in cationic micelles: effect of chain length and head group of the surfactants and urea

Abstract

In this work, we have studied the effects of chain length and the head group of different cationic surfactants on the photophysics of an anionic dye, 7-(diethylamino)coumarin-3-carboxylic acid (7-DCCA), using steady state absorption and fluorescence emission spectroscopy, and time resolved emission spectroscopy. We have observed pronounced effects on the photophysics of 7-DCCA, by varying the chain length and the head group of the surfactants. The fluorescence quantum yield, decay time, solvent relaxation time, and rotational relaxation time changes with chain length and the head group of the surfactants. We have studied the effect of urea on the photophysics of 7-DCCA bound to the micellar media and found that urea causes increases in the fluorescence quantum yield, fluorescence decay time, and solvent relaxation time. These aspects clearly demonstrate that the addition of urea does not cause the removal of the dye from the micellar surface.