Effect of solvents on the dipole moments and fluorescence quantum yield of rhodamine dyes

ABSTRACT

This study aims to investigate the effects of solvents of various polarities on the electronic absorption and fluorescence spectra of RhB and Rh6G. The singlet-state excited dipole moments [micro e] and ground state dipole moments [micro g] were estimated from the equations of Bakshiev-Kawski and Chamma-Viallet using the variation of Stokes shift along with the solvent's dielectric constant [e] and refractive indexes [n]. The observed singlet-state excited dipole moments were found to be larger than the ground-state ones. Moreover, the obtained fluorescence quantum yield values were influenced by the environment of the fluorescing molecule. Consequently, the concentration of the dye solution, excited singlet state absorption and aggregate of dye molecules has been found to affect the values of the fluorescence quantum yield.