Systematic investigation on the interaction between SiO2 nanoparticles with different surface affinity and various surfactants

Abstract The effects of both hydrophilic and hydrophobic SiO2 nanoparticles (NPs) on the interfacial activity of three kinds of surfactants (an anionic surfactant sodium dodecyl sulfate (SDS), a cationic surfactant dodecyltrimethylammonium bromide (DTAB), and a nonionic surfactant Triton X-100 (TX-100)) were systematically investigated. The synergistic effects among the electrostatic interaction (attraction and repulsion), the hydrophobic interaction, as well as the hydrogen bond, dominated the interaction between the surfactants and additional SiO2 NPs and the relative IFT variations, which could be reflected by the changes of the zeta potentials in different surfactant/NP dispersions. Furthermore, the measurements of the IFT and the conductivity of the supernatant, the morphology changes of interfacial films, the calculation of the apparent diffusion coefficients were employed to confirm our proposed mechanism.