The intramicellar fluorescence quenching in cylindrical micelles. II

Abstract

A theoretical model developed for the intramicellar fluorescence quenching rate constant in cylindrical micelles is used to simulate the fluorescence decay of a probe solubilized in the presence of a solubilized quencher. Different analytical approximations to the simulated fluorescence decay are evaluated for a range of aggregation numbers, diffusion coefficients and quencher concentrations. The fluorescence decay can always be fitted to either a Poisson distribution of quenchers or to the decay law corresponding to a reaction controlled process in an infinite micelle. Using single curve analysis it is often impossible to make a discrimination between those decay laws. The simultaneous analysis of several decays obtained at different quencher concentrations however allows us to make this discrimination when the fluorescence decay time of the probe is long enough (200 ns) and the mutual intramicellar diffusion coefficient is large enough (5.0 × 10 −6 cm 2 s −1). Under those conditions simultaneous analysis of fluorescence decays obtained for different quencher concentrations also allows us to make a discrimination between diffusion transients and mobile quenchers.