The photophysics of a hydrophilic molecule in the presence of graphene oxide

Abstract

The photophysics of fluorophore molecule was highly modulated when it was confined inside the nanopool of reverse micelle. By adding some foreign substance such as nanoparticles (in our case graphene oxide) it may interact with the surface active part of the surfactants, polar solvent molecules, and fluorophore present in the reverse micelle. This interaction may modulate photophysics of the fluorophore molecule in the reverse micelles compared to that in reverse micelle without adding foreign substance. The effect of foreign materials (graphene oxide) on the photophysics of 7-(n,n׀-diethylamino)coumarin-3-carboxylic acid (DACCA) in the water/AOT/isooctane reverse micelle was investigated via UV–vis absorption, steady-state and time-resolved fluorescence emission spectroscopy. The stability of the reverse micelle in presence of graphene oxide was investigated via dynamic light scattering (DLS), fluorescence lifetime imaging microscopy (FLIM), field emission scanning electron microscopy (FESEM). In the presence of GO the absorption maxima of DACCA become blue shifted and emission maxima of DACCA become red shifted compared to normal reverse micelle system. The average lifetime of DACCA in GO containing reverse micelle is always less than the normal reverse micelle system (particularly at lower w0 values). The rotational relaxation time in GO containing reverse micelle is faster and solvent relaxation time, particularly at lower w0 values is always slower than the normal reverse micelle. In GO containing reverse micelle, quantum yield, decay time, rotational relaxation time, solvent relaxation time at λex = 375 nm is always higher than λex = 405 nm, shows the excitation wavelength dependent photophysics of DACCA in GO containing reverse micelles. DLS, FLIM and FESEM study revealed that GO does not affect the stability and structure of the reverse micelle.