Structure of Adsorption Layer of Silver Nanoparticles in Sodium Bis(2-ethylhexyl) Sulfosuccinate Solutions in n-Decane As Observed by Photon-Correlation Spectroscopy and Nonaqueous Electrophoresis

Photon correlation spectroscopy, nonaqueous electrophoresis, and transmission electron microscopy were used to study the structure of silver nanoparticles (NPs) in n-decane, as a dependence of the concentration of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and temperature. If the concentration of AOT is lower than the critical micelle concentration (CMC), a silver NP is covered with a monolayer of AOT and reveals no electrophoretic mobility. At average concentrations (from CMC to 0.1 M) the hydrodynamic diameter of a NP does not change, but the xi-potential increases from 0 to 110 mV. When the concentration of AOT increases from 0.1 to 1 M, xi potential drops to 13 mV, and the hydrodynamic diameter increases to 90 nm. An increase in temperature to 70 degrees C leads to a reversible decrease in diameter to 40 nm. The hypothesis of clustering (polylayer adsorption) of "empty" micelles on silver NPs is proposed for the qualitative interpretation of the experimental data.