Quenching of fluorescence from pyrene in micellar solutions by cationic quenchers

The fluorescence from the S₁ state of pyrene solubilized within the hydrophobic region of sodium dodecyl sulfate micelles has been studied as a function of concentration of some cationic additives to the aqueous phase. At concentrations of added quencher below ca. 10^?3 mol dm^?3 the fluorescence decay follows a complex rate law; at long time, the decay is exponential with the same time constant as that of pyrene (S₁) without added quencher. The initial slope of the decay curve depends linearly on the concentration of added cation. These results are discussed in terms of the recently proposed model which requires the water-hydrocarbon interface to penetrate the micelle in the region of the probe. An analytical treatment is presented which, on the premises stated, serves to explain the observed kinetic features.