Photophysical features of coumarin 120 in reverse micelles

Abstract

The photophysical properties of 7-amino 4-methyl coumarin (C120) were investigated in the reverse micelle systems by using molecular UV–Vis absorption, steady-state and time-resolved fluorescence spectroscopy techniques. For this purpose, the fluorescence spectra of C120 dye in reverse micelle systems with different values of W0 (from 0 to 45) were examined. The bathochromic shift from 400 nm to 439 nm was observed for the fluorescence maxima of C120. It was found that intramolecular arrangements occurred in the structure of C120 molecule due to specific solute-solvent interactions. Fluorescence lifetime measurements were carried out and quantum yield values, radiative (kr) and non-radiative rate constants (knr) were calculated. The data compared with the values reported in the literature. Steady-state anisotropy (r) studies were done to explain the microenvironment around the C120 molecules. Anisotropy data varying 0.048 to 0.030 with varying W0 displayed that the microenvironment for the C120 dye in water pools of reverse micelles was different than C120 dye in pure water which is 0.009. The microviscosity and rotational relaxation time values were calculated as a function of W0. We have determined that C120 dye is a useful probe for the definition the microviscosity of reverse micelles with different water pool sizes.