Enhancement of linear and non-linear optical properties of erythrosin b by nano-droplet

Abstract

Erythrosine B dye has found applications as photosensitizers in photodynamic therapy, fluorescent probes in chemistry and biology. In this study, we have investigated the effect of nano-droplets, concentration and size on linear and nonlinear optical characteristics of Erythrosine B (EryB) by Z-Scan, UV–Vis spectroscopy and spectrofluorometer techniques. Two-photon absorption coefficient (β) of EryB was measured using the Z-Scan technique at two molar ratios of water to AOT surfactant (W = 3 and 8) for two types of Oil (n-decane and n-heptane) and different nano-droplet concentrations as well as nonlinear refractive index (n 2) of EryB in bulk water. Our results showed that two-photon absorption coefficient (β) was enhanced in nano-droplet as compared with bulk water. Moreover, the fluorescence peaks of EryB was enhanced by nano-droplets (microemulsion). The excited to ground state dipole moment ratio (μ e /μ g ) was calculated through quantum–mechanical second order perturbation theory for different nano-droplet concentrations. The results indicated that μ e /μ g of EryB in bulk water is higher than that of in water nano-droplets. It is demonstrated that for the equal concentration of EryB in the microemulsion, the peak of fluorescence intensity varied by changing the concentration of nano-droplets. Moreover, the fluorescence peak intensity enhanced when the continuous phase of microemulsion changed from n-decane to n-heptane.