Fluorescent probes for structural and distance effect studies in micelles,reversed micelles and microemulsions

The present review is an attempt to highlight the use of fluorescent probes to study the structural parameters and distance effect in micelles, revers ed micelles and microemulsions. Fluorescence quenching has also been used a s a powerful tool to obtain information on the compositional, structural an d dynamic characteristics of these organized assemblies. The work relating to the use of fluorescent probes has been reviewed mostly from the literatu re of the last two decades. The binding constant, critical micelle concentr ation, micellar aggregation number, and distribution of probes and quencher s have been evaluated for micelles by using various probes. Much attention is focused on the nature of the entrapped water within the core of the reve rsed micelle. The presence of four principal microenvironments: an inner 'f ree' water pool, a bound water region, the interface, and the surrounding h ydrocarbon continuum are indicated in reversed micelles. Various studies in microemulsions have been carried out by using mostly pyrene as the fluorop hore. The dielectric constant values, size and polydispersity, aggregation behaviour, photochemical transfer of an electron and a proton have been car ried out by various workers using different probes. These organized assembl ies have a structural advantage of compartmentalizing the fluorophore and q uenchers in their various sites. In view of this situation studies on dista nce effect have been carried out by various workers using different probes and quenchers. The microemulsions separate the oil and water pools clearly by a surfactant membrane and hence distance effect is expected to be notice d very clearly in this system. In the last two decades of the review almost no work in reversed micelles and very few in microemulsions have come to o ur notice. (C) 1999 Elsevier Science B.V. AU rights reserved.