Abstract
This paper focuses on the photophysical studies of 7-(diethylamino)coumarin-3-carboxylic acid N-succinimidyl ester (7-DCCAE) in aqueous reverse micelles using steady state absorption, fluorescence emission and picosecond time resolved emission spectroscopy. We used sodium dioctylsulfosuccinate (AOT) as surfactant to prepare reverse micelles. We have observed excitation wavelength dependent photophysics of 7-DCCAE in the reverse micelles. The red edge excitation shift (REES) was found in the reverse micelles, at different w0 values. The REES gradually decreases with increase in size of the water pool. The rotational relaxation time of the dye molecule decreases with increasing the mole ratio of water to surfactant (w0) inside the reverse micelles. The fluorescence anisotropy decays were found biexponential in nature with fast and slow reorientation times, which is explained by two steps and “wobbling-in-cone model”. We have observed the excitation wavelength dependent dynamics of 7-DCCAE in the reverse micelles. We have observed the difference in the photophysics 7-DCCAE with its acid form.
Highlights
Reverse micelles are used as template for bio-mimicking media
Where h is the viscosity of isooctane, rh is the hydrodynamic radius of the as received. Sodium dioctylsulfosuccinate (AOT) reverse micelles. k and T are the Boltzmann constant and the absolute temperature, respectively
The hydrodynamic radius of the AOT reverse micelles is given by the following equation[58,59] rh 1⁄4 0.5dwp + 1.0 nm dwp is the diameter of the water pool inside the isooctane/ water/AOT reverse micelles
Summary
Reverse micelles are used as template for bio-mimicking media. It is a microheterogeneous system, and used as effective stabilisers for nanomaterials, biological membrane, drug-delivery systems, and have diverse applications.[1,2,3,4,5,6,7] The most important feature of this system is its ability to encapsulate a fairly large amount of water molecules in the core of the reverse micelles.[8]. These dyes undergo a large Stokes shi as well as a substantial change in the dipole moment between ground and excited state.[33,34] With this in mind, our special interest concerns the photophysical investigation of 7-(diethylamino)coumarin-3-carboxylic acid N-succinimidyl ester (7-DCCAE) in the presence of water reverse micelles. The chemistry in con ned media mimics the extremely efficient chemical or biological processes occurring in nature.[38] The photophysical properties of coumarin dyes in different con ned media such as cyclodextrins, micelles and reverse micelles have been reported in the literature.[19,20,21,22,23,24,25,39,40,41,42,43,44,45,46,47,48,49] To know the effect of con nement on the photodynamics of 7-DCCAE we have used isooctane/AOT/water reverse micelles. To the best of our knowledge this is the rst report of the dynamics of 7-DCCAE in con ned media
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