Fluorescence probe studies on the structure of the adsorbed layer of dodecyl sulfate at the alumina—water interface

Pyrene and dinaphthylpropane (DNP) fluorescence probes were used to investigate the structure of the adsorbed layer of sodium dodecyl sulfate at the alumina-water interface. The fluorescence fine structure of pyrene yielded information on the polarity of the microenvironment in the adsorbed layer. Intramolecular excimer formation of DNP was used to measure the microviscosity of this environment. The results indicate the presence of highly organized surfactant aggregates at the solid—liquid interface, formed by the association of hydrocarbon chains. Fluorescence decay methods enabled the determination of the size of these aggregates and their evolution as a function of surface coverage. The overall spectroscopic investigation reveals a molecular model that is in agreement with the concept of hemimicellization.