Effect of surfactant structure on the residual fluorescence of micelle-based fluorescent sensors

In the present paper we have investigated some photo-physical characteristics of different micellar-based fluorescent probes containing a fluorophore (pyrene) and a quencher unit (dodecyl-dioxo 2,3,2). The fluorescent response of the probe in the presence of Cu(II) ions was studied using different micellar substrates, and it was found that the pH at which the On-Off jump occurs is not influenced by the chemical structure of surfactant. In addition, the experimental residual fluorescence is not proportionally affected by microviscosity or by the size of the micellar aggregates. The signal of the native fluorescence of pyrene was observed even when the quencher's occupancy number was greater than one. Moreover, we observed discrepancies between experimental values and calculated residual fluorescence using Laplace data. These results were interpreted suggesting that the residual fluorescence has two main components, one that seems to be independent on micellar properties, while the other is directly related to location of molecules inside the surfactant aggregates that serve as substrate