Graphene : Functionalization and Application of Its Composites

The ionic liquid (IL) 1-butyl-3-methylimidazolium octyl sulfate, [C4mim][C8SO4]mediated micelle to vesicle transition in aqueous solution of a cationic Gemini surfactant(tetramethylene-1,4-bis(dimethylpentadecylammonium bromide) (14-5-14) has beeninvestigated by applying dynamic light scattering (DLS), viscosity, steady state and timeresolved fluorescence and HRTEM measurement for different mole fractions of IL i.e. (XIL =0.0, 0.1, 0.2, 0.3, 0.35, 0.4, 0.45, and 0.5). Phase transfer of the mixture can be visualized byoptical micrographs and the turbidity of the mixed solution increases with increasing themole fraction of IL and it is maximum at XIL = 0.5. Steady state fluorescence anisotropy ofDPH in the investigated solutions also increases with increasing the mole fraction of IL andthe anisotropy value also indicates the transformation of a micelle (XIL=0.1, and 0.2) toelongated micelle (XIL=0.3, 0.35, and 0.4) to vesicle (XIL=0.45, and 0.5). A viscosity peakhas been observed at XIL=0.3 indicating the formation of elongated micelle at intermediatestage of micelle to vesicle transition. The hydrodynamic diameter of the solution graduallyincreases with increasing the mole fraction of IL and the vesicular solution shows theapparent hydrodynamic diameter ~ 190 nm, corroborated by HRTEM measurement. Themicropolarity and stability of the vesicular solution are also understood by using the Pyreneprobe through I1/I3 measurement and anisotropy measurements by using the DPH probe withvarious temperatures which indicates that it is stable within the biological temperature range.The steady state and time resolved fluorescence measurements have been carried out usingC153, a 8 nm spectral shift occurs in the blue region indicating the residence of the probe inhighly non polar region probably inside the hydrophobic bilayer of vesicle. The rotationalrelaxation time of the probe molecule C153 (Coumarin 153) gradually increases with