Titania-Cored Janus Multipods as UV-Protective Pickering Emulsifiers for Sunscreens

Pickering emulsifiers have gained significant interest as alternatives for conventional surfactants in various applications that includes pharmaceutics, food, homecare products, and cosmetics. However, their function is primarily focused on enhancing emulsion stability of which still remains to be resolved. Herein, Janus multipods are presented that simultaneously shield UV while offering high emulsion stability. These particles are prepared by growing multiple silicon dioxide (SiO₂) nanopods using sol-gel method on a spherical titanium dioxide (TiO₂) core with a thin SiO₂ shell. The incorporation of high refractive index TiO₂ in the core is shown to effectively shield UV while the SiO₂ shell suppresses the photocatalytic activity. Moreover, by utilizing wax colloidosomes as templates, these multipod nanoparticles are further modified to exhibit Janus characteristics. This leads to strong adsorption of the Janus multipods at the oil/water emulsion interface where the multipod feature additionally reinforces the interfacial stabilization by interdigitation and interlocking of the Janus multipods to suppress detachment of the highly dense particles from the interface. As these Janus multipods offer effective UV protection as well as excellent emulsion stability, it is envisioned that they have great potential in advanced cosmetic formulations which require both enhanced sunscreen performance and better feeling in skincare products.