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 (kq) were calculated from the τo/τ vs. [Q] plots having linear correlation and compared with calculated diffusion-controlled rate constants (kdiff) values. Experimental results were in good agreement with the simultaneous dynamic and static quenching model.