Fluorescence probing in aqueous micellar systems: an overview

In this review we discuss the most interesting methods of fluorescence probing related to the study of aqueous micellar systems. It is shown that very important information concerning static and dynamical properties of aggregational colloids, can be obtained from fluorescence experiments. The presentation is focused on application of fluorescence methods to micellar media, rather than on interfacial or aggregational problems themselves. This is also true for the selection of the literature cited, which covers only a number of the most essential publications on fluorescence probing methods in micellar systems. A large part of this article deals with time-resolved fluorescence quenching, since this is the most powerful of all fluorescence probing methods applied in the study of microheterogeneous media. The fluorescence decay of a micelle-bound hydrophobic fluorophor in the presence of different types of quenchers is discussed, and the reliability of the various micellar parameters obtained is evaluated. Systems in which fluorescence quenching must be applied with extreme caution are described and the ambiguities involved are analysed. Steady-state fluorescence, although simple in its experimental aspects, can give valuable information about microproperties in the interior of micellar aggregates, and occasionally, good estimates of their size. However, steady-state fluorescence probing has found only limited use because its results are very often unreliable, and it cannot give information relating to kinetic parameters.