Synthesis of Methyl-Capped TiO₂–SiO₂ Janus Pickering Emulsifiers for Selective Photodegradation of Water-Soluble Dyes

Recently, Pickering emulsion stabilized by Janus particles has received considerable attention for interfacial reactions and droplet manipulation. However, its potential interests have been rarely explored because of the difficulties in designing and fabricating Janus particles for Pickering emulsion with suitable applications. Also, photocatalytic materials are scarcely applied as emulsifiers in Pickering emulsions because of their photogenerated hydrophilicity. This work reports the synthesis of methyl-capped Janus TiO2–SiO2 particles (MJTSs), which can be used as a novel emulsifier and photocatalyst simultaneously. The MJTSs, composed of an anatase TiO2 sphere and silica rod, are prepared by inverse emulsion-based step-by-step growth. We demonstrate that the Pickering emulsion stabilized by MJTSs represents extraordinary ability of emulsification, excellent stability, and tunable emulsion type (water in oil or oil in water). In addition, the MJTSs exhibit photocatalytic activity in decomposition of pollutants in the water phase while maintaining the stability of the Pickering emulsion.