FLUORESCENCE QUENCHING OF 1,4-BIS [2-(2-METHYLPHENYL) ETHENYL]-BENZENE BY ANILINE IN BENZENE-ACETONITRILE MIXTURES

Life Science-Physics

Abstract

Fluorescence quenching of 1,4-bis [2-(2-methylphenyl) ethenyl]-benzene (Bis-MSB) has been studied in solvent mixtures of benzene (BN) and acetonitrile (ACN) at room temperature with a view to understand the role of dielectric constant on fluorescence quenching. The quenching is found to appreciable and a positive deviation from linearity was observed in Stern-Volmer plot in all the solvent mixtures. The positive deviation is maximum in pure benzene and it decreases with increase in percentage of acetonitrile in benzene. Various rate parameters for the quenching process have been determined by sphere of action static quenching model and finite sink approximation model. The magnitudes of these rate parameters indicate that positive deviation in the Stern-Volmer plot is due to both static and dynamic quenching processes. The Stern-Volmer quenching constant decreases with increase in dielectric constant of solvent mixture. This dependence of Stern-Volmer quenching constant with dielectric constant of solvent mixture is explained based on the possibility of formation of dispersion of Bis-MSB microaggregates which is non-fluorescent in high dielectric constant solvent mixtures.