Physicochemical Investigation of Nanostructures in Liquid Phases: Ytterbium Nitrate Ionic Clusters Confined in Ytterbium Bis(2-ethylhexyl) Sulfosuccinate Reversed Micelles and Liquid Crystals

The confinement of finite amounts of ytterbium nitrate in the nanoscopic space of ytterbium bis(2-ethylhexyl)sulfosuccinate (Yb(DEHSS)3) reversed micelles dispersed in n-heptane has been investigated by UV-vis-NIR, FT-IR, and SAXS. The analysis of the experimental data is consistent with the hypothesis that Yb(NO3)3 is distributed among reversed micelles as small size ionic clusters surrounded by the Yb3+ surfactant counterions and anionic heads while the surfactant alkyl chains point toward the solvent medium. As a consequence of confinement and interfacial effects, the ionic clusters display photophysical properties different from those in the bulk state or isolated species. Moreover, the entrapment of Yb(NO3)3 involves some changes in the structural properties of reversed micelles attributable to the increase of the volume fraction of the hydrophilic matter confined in the micellar core. Preliminary WAXS experiments on Yb(NO3)3/Yb(DEHSS)3 composites obtained by complete evaporation of volatile components (water and organic solvent) of the liquid Yb(NO3)3,water/Yb(DEHSS) 3/n-heptane samples showed that also in these systems Yb(NO 3)3 is dispersed in the hydrophilic domains of the surfactant matrix as very small clusters.