Absorption, Fluorescence and Z-Scan Study of Anion and Dianion Structure of Fluorescein Sodium Salt

Abstract

The enhancement of fluorescence intensity and nonlinear absorption of a dye has application in Photodynamic<br><br>therapy and biological detection. In this work, it is shown that the Fluorescein sodium salt -FSS- have<br><br>dianion structure in water and anion structure in microemulsion -ME-. The optical nonlinearity of FSS at<br><br>different concentrations in aqueous solution and ME has been studied. The nonlinear absorption -ß-, nonlinear<br><br>refractive index -n2-, hyperpolarizability -- and the nonlinear susceptibility --3-- were characterized<br><br>by measuring the intensity dependent of open and close aperture. The FSS in water at 1 mM concentration<br><br>exhibited, ß = 9.03×10−8 mW−1, n2<br><br>= 2.88×10−15 m2W−1 and = 5.2×10−26 m−5V−2 was founded at<br><br>0.25 mM concentration showed. Moreover, the value of nonlinear optical properties of FSS-ME is higher than<br><br>an aqueous solution of FSS at below 0.25 mM. By perturbation theory and Raman spectra, it is indicated<br><br>that the formation of ME cannot change the polarity of ME but it can change the ratio of the dipole moment.<br><br>The molecular structure as well as the FSS dipole moment control by different formation of ME.