Structure and conductivity of AOT solutions in n-hexadecane-chloroform mixtures.

The structure and conductivity of AOT (sodium bis(2-ethylhexyl) sulfosuccinate) solutions (2.5 × 10-4 -2.5 × 10-1 M) in n-hexadecane-chloroform mixture at the chloroform concentration from 50 to 100 vol% were studied. The diffusion ordered spectroscopy NMR study revealed that in the indicated range, the observed hydrodynamic diameter of micelles depends only on the AOT concentration and does not depend on the chloroform content. Molar fractions of free AOT molecules and those aggregated into micelles were calculated using the Lindman's law: at concentrations above 2.5 × 10-1 М, the solutions contain mostly the micelles, whereas at concentrations below 2.5 × 10-4 M, the solutions contain AOT molecules. The transition region contains both the AOT molecules and the micelles. Conductivity measurements were used to determine free charge carriers in the bulk of solutions and their contributions to conductivity.

The formation of free ions and electrophoretic mobility of Ag and Au nanoparticles in n-hexadecane-chloroform mixtures at low concentrations of AOT.

The electrophoretic mobility of Ag and Au nanoparticles in n-hexadecane-chloroform mixtures was studied as a function of the chloroform content (from 0 to 100 vol%). The nanoparticles were stabilized by sodium bis-(2-ethylhexyl)sulfosuccinate (AOT, Aerosol OT) with a concentration of 2.5 × 10-4 mol L-1. The obtained organosols were characterized by phase analysis light scattering, dynamic light scattering, transmission electron microscopy, diffusion-ordered spectroscopy of nuclear magnetic resonance, spectrophotometry and conductometry. The electrophoretic mobility of the nanoparticles sharply increased from 0 to 3.6 × 10-9 m2 V-1 s-1 with increasing chloroform content. The growth of the mobility was caused by an increase in the concentration of solvated AOT ions, which formed by the disproportionation reaction from uncharged molecules. Low concentrations of AOT and a considerable zeta potential (up to ∼100 mV) made it possible to use the obtained organosols for the formation of electrostatically bound aggregates of Ag and Au with negatively charged SiO2 nanoparticles.