Application of fluorescence methods to study micellar solutions of perfluorinated surfactants is very scarce because good probes and quenchers could not be found; polycyclic aromatic compounds, the most popular fluorescent probes, are difficult to solubilize into fluorinated surfactant micelles. We have found that the incompatibility of protiated probes with perfluorinated chains of surfactant host may be counterbalanced by positive electrostatic interactions. We present the use of a cationic derivative of pyrene,1-pyrenebutyltrimethylammonium bromide, as a luminophore and cationic quenchers, 1-trimethylammonium-2,2,6,6-tetramethyl-piperidine-1-oxyl iodide (nitroxide radical known as CAT1) and 1,1'-dimethyl-4,4'bipyridinium dichloride (methyl viologen), to examine aqueous solutions of two anionic fluorinated surfactants, ammonium perfluorooctanoate (APFO) and tetraethylammonium perfluorooctyl sulfonate (TEAPFOS). On the basis of the Infelta-Tachiya model, we have determined from time-resolved fluorescence quenching data the micellar aggregation numbers, the rate constants of intramicellar quenching, and the rate constants of the quencher exit from the aggregates. The results indicate formation of ellipsoidal micelles in APFO solution, with the aggregation numbers increasing versus surfactant concentration (from 33 at 0.06 M APFO to 109 at 0.5 M APFO), and threadlike micelles in TEAPFOS solution, which consist of interconnected spherical units each containing at least 52 surfactant molecules.
