“…In view of the studies in reverse micelles and micelles, , it is quite pertinent to address the issues concerning the sensitivity of the ESIPT dynamics to micelle hydration, the charge of the surfactant headgroup, and the hydrophobic tail length, which have not yet been explored. This is a particularly interesting topic worth addressing because (i) the interfacial region (Figure ) of the micelles is the preferred site for solubilization, even for hydrophobic molecules, (ii) the hydrogen bond donating abilities are different for the cationic, anionic, and neutral micelles , due to a differential solvation of the ionic or polar headgroups in the Stern or palisade layer of the micelle–water interface, (iii) the Stern layer of the anionic sodium dodecyl sulfate micelles with negatively charged −OSO 3 – headgroups was shown recently by dielectric spectroscopy , to be strongly hydrophilic compared to the essentially hydrophobic surface of the cationic alkyltrimethylammonium halide micelles with positively charged −N(CH 3 ) 3 + headgroups, implying a very strong and poor hydration of the anionic and cationic surfactants, respectively, and (iv) the palisade layer of the nonionic micelles comprises at least two water molecules per ethylene oxide (EO) unit tightly associated with the poly(ethylene oxide) (PEO) chains and thus demonstrates a level of hydration intermediate between those of the cationic and anionic micelles. In this context, the fluorescent dye 2-(2′-furyl)-3-hydroxychromone (N, Figure A) is a potential candidate for sensing micelle hydration through the modulation of its ESIPT dynamics because (i) the ESIPT reaction (Figure A) was found to be sensitive to the hydrogen bond donating ability or H-bond acidity of the polar, protic solvents and (ii) the Stern or palisade layer (Figure a,b) of the micelle–water interface is most likely the preferred site for localization of the FHC dye in micelles, as it is highly polar and possesses hydrophilic 4-carbonyl and 3-hydroxy moieties.…”