Stabilization of Oil-in-Water Pickering Emulsions with Surfactant-Modified SiO2 Nanoparticles

Stabilization of Pickering emulsions with silica nanoparticles modified with nonionic surfactants, namely, Tween 20, Tween 40, and Tween 80; cationic cetyltrimethylammonium bromide; and anionic sodium oleate and oleic acid has been studied. The modification of positively charged Ludox CL nanoparticles and negatively charged Ludox HS-30 nanoparticles with sodium oleate and oleic acid has not led to the formation of stable emulsions at dispersion medium pH values of 2-8. The modification of Ludox CL nanoparticles with Tween 20, Tween 40, Tween 80, and cetyltrimethylammonium bromide also has not increased the stability of the emulsions. The stability of the emulsions stabilized with Ludox HS-30 nanoparticles has increased noticeably in the presence of Tween 20, Tween 40, Tween 80, or cetyltrimethylammonium bromide. These surfactants promote the formation of gel-like networks from aggregated Ludox HS-30 nanoparticles in the dispersion media of the emulsions, thereby leading to the formation of emulsions stable with respect to both coalescence and creaming.