Tailoring Size and Surface Charge in Nanosilica via Microemulsion and Its Synergetic Impact on Pickering Emulsion Stability

Nanosilica with tailored size and surface charge were synthesized via a microemulsion-templated approach, using tetraethyl orthosilicate (TEOS) as the oil phase in a cetyltrimethylammonium bromide (CTAB)/ethanol/water system. The resulting particle size, which ranged from approximately 50 to 1000 nm, correlated directly with the phase behavior of microemulsion, confirming its role as a template. These obtained nanoparticles effectively stabilized Pickering emulsions through a synergistic combination of size and surface charge property. Interfacial dilatational rheology measurements further revealed the formation of an elastic solid-like film with a relatively high modulus (≈32 mN/m) using nanosilica with small size and low surface charge. In contrast to conventional strategies that rely on strong amphiphilicity, this work demonstrates that highly efficient adsorption and stabilization of nanoparticles at the oil-water interface can be achieved through the synergistic control of size and surface charge. This approach offers a controllable pathway for preparation of nanoparticles to construct Pickering emulsion systems. Additionally, the study identified that the synergy between size and surface charge, rather than strong amphiphilicity alone, is the primary mechanism for effective emulsion stabilization.