Fine tuning of surface properties of SiO2 nanoparticles for the regulation of Pickering emulsions

Pickering emulsions hold great potential in solving the mass transfer limitation in gas-liquid-solid and/or liquid-liquid-solid multiphase systems. In the present study, the surface properties of SiO2 nanoparticles were finely tuned by a novel large-scale production method, which determined the final geometry of the dispersed droplets and their stability. By controlling the amount of KH-570 grafted on the nanoparticles surface the phase inversion of Pickering emulsions was regulated. The addition of stabilizing nanoparticles, the particle size, and the amount of dispersed phase all significantly affected the geometry and stability of the dispersed droplets, mainly attributed to the varying coverage area of dispersed droplets provided by the stabilizing particles at varying grafting degrees. Mechanistic investigation suggested that estimating the value of the solid-oil intermolecular energy provided an indicator measure to predict the type of Pickering emulsions, while the estimate of interfacial tension values gave an additional measure to determine the amount of solid particles needed for forming stable Pickering emulsions.