DETERMINATION OF KINETIC-PARAMETERS OF PROBE MIGRATION IN MICELLES USING SIMULTANEOUS ANALYSIS OF THE FLUORESCENCE DECAY SURFACE

Global analysis with the reference convolution method is applied to study the effect of probe migration between micelles on the fluorescence quenching. AnalYsis of synthetic single-photon timing data based on a modified Infelta-Tachiya equation including probe migration is used to test the capability to discriminate between competing models and determine the accuracy of the recovered model parameters. The applicability of this simultaneous analysis is extended to real experimental data obtained for quenching of the probe sodium 1-pyrenesulfonate by the quencher N-tetradecylpyridinium chloride in aqueous hexadecyltrimethylammonium chloride (CTAC) micelles. Values of the rate constant of quenching and probe migration as well as the mean aggregation number (nu) of CTAC are determined as a function of the surfactant concentration. In the range 0.02-0.07 M surfactant no appreciable variation in the mean aggregation number of CTAC micelles and also in the quenching rate constant (k(q)) was observed. The average values of nu and k(q) were 82 +/-7 and (8.4 +/- 0.5) X 10(7) s-1, respectively. Within this range of surfactant concentration the probe migration rate constant (k) was a linear function of the micelle concentration ([M]) (k = k(m)[M] with k(m) = (3.0 +/- 0.4) X 10(9) L mol-1 s-1). Analysis of the system where the probe sodium 1-pyrenesulfonate was replaced by 1-methylpyrene confirms that this more hydrophobic probe does not migrate between micelles during its excited-state lifetime.