The influence of negatively charged silica nanoparticles on the surface properties of anionic surfactants: electrostatic repulsion or the effect of ionic strength?
Milad Eftekhari, Karin Schwarzenberger, Aliyar Javadi, Kerstin Eckert
Abstract
) concentration. It is observed that the surface activity of the surfactants is mainly influenced by the change in the system's ionic strength due to the presence of nanoparticles. Several characteristic parameters including the equivalent concentration of the surfactant, the CMC and the apparent partial molar area of the adsorbed surfactant are theoretically calculated and further employed to validate experimental observations. Both the nanoparticles and electrolyte decrease the CMC, while the equivalent concentration of the surfactant remains nearly constant. This paper presents a criterion to estimate the possible influence of such forces for nanoparticles of different sizes and mass fractions.