Preparation of Silver Nanoparticles in a Water‐in‐Oil Microemulsion Stabilized by Ecosurf EH3 and Determination of Their Electrophoretic Mobility

This work describes a study on the electrophoresis of silver nanoparticles in reverse microemulsions with varying water content. The microemulsion was stabilized using a nonionic ethoxylated surfactant, 2-ethylhexanol triethoxylate (Ecosurf EH3). This study represents the second example of electrophoresis research conducted in media with a low dielectric constant for etoxylated surfactants. The study also determined the boundaries of thermodynamic stability and the conditions required to obtain nanoparticles with a high yield. The hydrodynamic diameter and electrophoretic mobility of nanoparticles were measured using dynamic light scattering and laser Doppler electrophoresis. The study determined the boundary conditions for applying these methods to laser-absorbing samples. The electrophoretic mobility of nanoparticles was found to be dependent on the fraction of water in the range of 2-5% vol. (equivalent to a metal content of 10-25 mM), as determined by electrophoresis in a free medium. The increase in volume fraction of water leads to agglomeration of micelles, which causes a decrease in the electrokinetic potential of nanoparticles, likely due to the blurring of the diffuse part of the electrical double layer.