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

Abstract

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 ζ-potential increases from 0 to 110 mV. When the concentration of AOT increases from 0.1 to 1 M, ζ potential drops to 13 mV, and the hydrodynamic diameter increases to 90 nm. An increase in temperature to 70 °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.

Synthesis and Electrophoretic Concentration of Cadmium Sulfide Nanoparticles in Reverse Microemulsions of Tergitol NP-4 in n-Decane

“…Many studies showed that micelles can be adsorbed on the surface of NPs, thus forming a developed adsorption layer. 20,33 As a result, PCS gives strongly overestimated diameters, which are the sum of the particle diameter and a double thickness of the adsorption layer of micelles. To get a true value of the particle diameter, the obtained dispersion should be diluted to surfactant concentrations lower than the critical micelle concentration (CMC is commonly equal to 10 −4 −10 −3 M).…”