A novel surfactant-like fluorophore and its probing ability to the aggregation of amphiphilic compounds

A novel surfactant-like non-ionic fluorophore, 3-(bis(2-hydroxyethyl)amino)-N-(4-(pyrene-1-sulfonamido)butyl) propanamide (PSDA-DEA), was designed and prepared. Fluorescence and surface tension studies revealed that the fluorophore aggregates in aqueous medium, and its critical aggregation concentration (CAC) is ∼3.3 × 10−5 M. Cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements demonstrated that the diameter of the aggregates as formed is of a few hundred nano-meters. It was also shown that the profile of the emission spectrum of the compound is well dependent upon the polarity of its medium, as indicated by a change up to 53% of its intensity ratio at 399 nm and 380 nm (I399/I380) when the solvent changed from water to ethanol. It is of the polarity sensitive property that the fluorophore can be used for monitoring micelle formation of several anionic, cationic and non-ionic surfactants. Furthermore, PSDA-DEA is also a valuable probe for sensing transition of different aggregates such as micelles to vesicles. Comparative studies demonstrated that the present probe is more versatile than pyrene when it is used as a fluorescence probe.