Evaluation of hydrophobic properties of sodium dodecylsulfate/γ-alumina admicelles based on fluorescence spectra of N-phenyl-1-naphthylamine Original Research Article

Some molecular probes, whose fluorescence spectra were responsive to the polarity, were tested for monitoring the formation of admicelles. N-Phenyl-1-naphthylamine (PN) was the best choice for evaluating the hydrophobicity of sodium dodecylsulfate (SDS)/γ-alumina admicelles. The fluorescence intensity of PN in the aqueous suspension of the admicelles enhanced in the SDS concentration far below its critical micelle concentration. The intensity was greater than that in the normal SDS micellar system. Additionally, the wavelength at the maximum intensity of the fluorescence in the admicellar system was shorter than that in the micellar solution. These facts strongly suggest that the admicelles provide more hydrophobic environment than conventional micellar media. Comparison of the wavelength with those in several solvents indicated that the admicelles have hydrophobic properties corresponding to 1-octanol or ethyl acetate.