Controlling Surfactant Adsorption on Highly Charged Nanoparticles to Stabilize Bijels.

Bicontinuous particle-stabilized emulsions (bijels) are networks of interpenetrating oil/water channels with applications in catalysis, tissue engineering, and energy storage. Bijels can be generated by arresting solvent transfer induced phase separation (STrIPS) via interfacial jamming of nanoparticles. However, until now, STrIPS bijels have only been formed with silica nanoparticles of low surface charge densities, limiting their potential applications in catalysis and fluid transport. Here, we show how strongly charged silica nanoparticles can stabilize bijels. To this end, we carry out a systematic study employing dynamic light scattering, zeta potential, acid/base titrations, turbidimetry, surface tension, and confocal microscopy. We find that moderating the adsorption of oppositely charged surfactants on the particles is crucial to facilitate particle dispersibility in the bijel casting mixture and bijel stabilization. Our results potentially introduce a general understanding for bijel fabrication with different inorganic nanoparticle materials of variable charge density.