Effect of Particle Size on Pickering Emulsion Stability Under Different Homogenization Methods

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Abstract
Pickering emulsions have attracted significant interest due to their superior stability compared to surfactant-stabilized emulsions. Particle size is a key parameter in the stabilization of Pickering emulsions. However, a fundamental understanding of how particle size influences emulsion stabilization across different homogenization methods remains unclear. In this study, the effects of silica nanoparticle size on Pickering emulsion formation and stability were investigated under different processing methods, including rotor-stator homogenization, ultrasonication, and high-pressure homogenization. Emulsion structure and stability were evaluated using droplet size analysis, interfacial adsorption measurements, ζ-potential characterization, and Turbiscan stability analysis. Multivariate Partial Least Squares (PLS) regression was further applied to assess the relative importance of particle size. The results show that the effect of particle size on emulsion stability strongly depends on the processing method. Under rotor-stator homogenization, stability was governed by a balance between droplet size reduction and particle sedimentation, resulting in optimal stability for intermediate-sized nanoparticles. Under ultrasonication, smaller nanoparticles enhanced stability primarily through increased interfacial adsorption. In contrast, for high-pressure homogenization, particle size effects on droplet structure were largely masked, and stability was mainly constrained by limited coalescence during storage and sedimentation of larger particles. These findings show that particle size influences Pickering emulsion stability through distinct mechanisms under different homogenization methods, providing guidance for the rational design of particle-stabilized emulsions.

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