MOLECULAR AGGREGATION OF RHODAMINE 6G PROBED BY OPTICAL AND ELECTROCHEMICAL TECHNIQUES

Emission spectra of rhodamine 6G (R6G) aggregates were observed at 77 K both in water and in alcohols. The temperature behavior of emission and excitation spectra, and their excited state lifetimes illustrated that the transition moment of the tower exciton component, mu, for rhodamine 6G aggregates in alcohols is greater than that in water, but the nonradiative rate, r(NR) (in alcohol) > r(NR)(in water). Cyclic voltammetry analysis revealed that the structural disposition of R6G aggregates in water tends to decrease the pK(a) of the quaternary amine group in rhodamine 6G, which then promotes large changes of current-voltage signal in the reduction of free H+ and oxidation of its counterion, Cl-.