OXIDES-STABILIZED PICKERING EMULSIONS: INFLUENCE OF SURFACE PROPERTIES, IN-SITU FUNCTIONALIZATION, AND STIMULI-INDUCED RESPONSIVENESS

Pickering emulsions are gaining significant interest as a superior alternative to conventional surfactant-stabilized emulsions, offering promising applications across various fields, including medicine, pharmaceuticals, cosmetics, the food industry, and cultural heritage preservation [1,2]. In this study, we investigate the role of oxide surface properties in the stabilization of Pickering emulsions, specifically focusing on ZnO and TiO2 nanoparticles as solid emulsifiers – chosen for their broad range of applications arising from their UV-blocking, photocatalytic and antibacterial properties. The resulting emulsions display excellent stability over time and against temperature variations, mechanical stress and increased ionic strength. We explore the interplay between the oxide surface features and in situ functionalization with fatty acids in determining key emulsion characteristics, including type, droplet size, stability, and the responsiveness to external stimuli (acidification by mineral and organic acids, UV and sunlight irradiation, addition of multivalent cations and CO2 bubbling) [3]. The switching behavior of oxides-stabilized Pickering emulsions can be controlled by various stimuli, with reversibility achieved through pH adjustment, gas bubbling, or darkness. While stable emulsions can be recovered after multiple cycles, irreversible destabilization occurs with excess acid or multivalent cations. The inversion mechanism is attributed to surface charge-mediated flocculation rather than wetting changes [4]. Our work offers valuable insights for enhancing the design of sustainable, surfactant-free emulsions that can be optimized for practical applications, such as stable UV protection or controlled destabilization in photocatalytic processes.