Analysis of fluorescence quenching of pyronin B and pyronin Y by molecular oxygen in aqueous solution

The fluorescence quenching of pyronin B and pyronin Y molecules by molecular oxygen in aqueous solution was studied by using steady-state and time-resolved fluorescence and UV-Vis absorption spectroscopy techniques. In order to understand the quenching mechanism, fluorescence decays, absorption and fluorescence spectra of the probes were recorded as a function of the oxygen concentration and temperature. The quenching was found to be appreciable and shows positive deviation in the Stern-Volmer representation obtained from the fluorescence intensity ratio. Fluorescence quenching constants (k(q)) were calculated from the tau(o)/tau vs. [Q] plots having linear correlation and compared with calculated diffusion-controlled rate constants (k(diff)) values. Experimental results were in good agreement with the simultaneous dynamic and static quenching model. (C) 2006 Elsevier B.V. All rights reserved.