QUENCHING OF PYRENE FLUORESCENCE BY AMPHIPHILIC NITROXIDE RADICALS EMBEDDED IN CATIONIC MICELLES

Steady-state and nanosecond time-resolved studies have been carried ou t on the fluorescence quenching of excited pyrene by n-doxylstearic me thyl esters (n-DSE, n = 5, 10, 12) in an aqueous solution of cationic micelles of hexadecyltrimethylammonium chloride (HTAC, 0.1 M). The agg regation number (N = 114 +/- 6) and the rate constants of intramicella r quenching (1.4 X 10(7), 1.3 X 10(7) and 1.05 X 10(7) s(-1) for 5-, 1 0- and 12-DSE respectively) have been determined. The results are disc ussed in terms of the average location of the luminophore and the quen cher molecules in the aggregates, considering previous findings of ele ctron spin echo modulation studies of n-doxylstearic acid spin probes in micellar systems.