The photophysics of 7-(N,N′-diethylamino)coumarin-3-carboxylic acid in water/AOT/isooctane reverse micelles: an excitation wavelength dependent study

Abstract

In this manuscript we have studied the photophysics of 7-(N,N′-diethylamino)coumarin-3-carboxylic acid (7-DCCA) in water/AOT/isooctane reverse micelles. For this purpose we have used steady state absorption and fluorescence emission spectroscopy and time resolved fluorescence spectroscopy. We have studied the spectral behaviour of 7-DCCA inside the water/AOT/isooctane reverse micelles with variation of excitation wavelength. We have studied the dynamics of solvent and rotational relaxation by using two different excitation wavelengths (λ_exi = 375 nm and λ_exi = 405 nm). We have observed the excitation wavelength dependent dynamics of 7-DCCA in the reverse micelles. The fluorescence quantum yield, decay time, solvent relaxation time and rotational relaxation time of 7-DCCA in reverse micelles vary with the excitation wavelength. A two step and wobbling-in-cone model was used to interpret the rotational relaxation dynamics of 7-DCCA in reverse micelles.