Fluorescence quenching of Safranine T by inorganic anions in Tween micelles

The fluorescence quenching of the dye Safranine T by various inorganic anions such as [Fe(CN 6 )] –3 , [Fe(CN 6 )] –4 , I – , Br – , NO 2 – , and N 3 – in aqueous solution and in nonionic micellar solutions of Tweens (Tween 20, Tween 40, and Tween 80) was studied. The Stern–Volmer quenching constants and quenching rate constants were evaluated. Compared to the quenching efficiency in aqueous media, that of the micellar media was found to be lower, except when iodide ion was used as a quencher. With the exception of the iodide ion, it has been established that collisional quenching plays a major role in the photophysical process. In the case of the iodide ion, both static and collisional quenching processes play a major role, owing to the complexation of iodide ion with Tween micelles. The Stern–Volmer quenching constants were found to be dependent on the ionic strength of the medium.Key words: fluorescence, static quenching, Tweens, Stern–Volmer constant, micellar media.