Preparation of Janus Titanium Dioxide Particles via Ultraviolet Irradiation of Pickering Emulsions

Abstract

Pickering emulsions are stabilized by solid particles assembled at an immiscible liquid–liquid interface. In this work, the use of such emulsions to prepare semiconductor Janus particles through UV‐irradiation is explored. Titanium dioxide particles that are prefunctionalized with an alkylsilane or a fluoroalkylsilane are employed to obtain wax‐in‐water emulsion droplets, which consist of the particles partially embedded in the wax core. Different emulsion formation mechanisms are discussed. The emulsified wax droplets are then subjected to ultraviolet irradiation, which photocatalytically degrades the silanes on the exposed portion of the particle surfaces, leading to Janus particles containing partial silane coatings. The particles are finally recovered through dissolution of wax. The Janus particles, which have contrasting wettabilities over their surface, are characterized based on self‐assembly behavior and bulk wetting performance in a compact film, as compared with nonfunctionalized and fully‐functionalized homogeneous particles. Three different types of Janus particles are created and their characters are explained using the concept of the Janus balance. The method has the potential to produce large scale yields in a relatively short time, and can be potentially applied to other semiconductor particles for the generation of Janus particles.

Research Advances in the Synthesis, Application, Assembly, and Calculation of Janus Materials

“…The required area can be chemically modified by aqueous phase chemistry 40,41 or photocatalytic degradation of the exposed portion. 42,43 Finally, Janus particles are obtained through the recovering dissolution of wax. For example, hairy hybrid Janus poly(acrylic acid)/ polystyrene (PAA/PS) particles with hydrophilic and hydrophobic polymer side synthesized through a Pickering emulsion and a combination of "grafting from"/"grafting to" approaches.…”

“…This method typically contains an oil/water (O/W) interface, a wax phase as the oil phase of the emulsion, which is stabilized by silica or titania particles at high temperatures. , Cooling the emulsion causes the uniform particles to be fixed at the interface with the wax. The required area can be chemically modified by aqueous phase chemistry , or photocatalytic degradation of the exposed portion. , Finally, Janus particles are obtained through the recovering dissolution of wax. For example, hairy hybrid Janus poly­(acrylic acid)/ polystyrene (PAA/PS) particles with hydrophilic and hydrophobic polymer side synthesized through a Pickering emulsion and a combination of “grafting from”/“grafting to” approaches .…”

Interfacial Deposition of Titanium Dioxide at the Polarized Liquid–Liquid Interface

“…Another report describes coumarin 343 dye TiO 2 nanoparticles complex interfacial adsorption studied with surface second harmonic generation technique [ 9 ]. The intuitive combination between conventional LLI and TiO 2 nanoparticles are Pickering emulsions that can be frequently found in everyday products (e.g., stabilized sun creams) or the scientific literature [ 10 , 11 , 12 ]. The sol–gel processing of the TiO 2 can occur at the LLI.…”

Janus Particle Preparation through UV-Induced Partial Photodegradation of Spin-Coated Particle Films

“…24 The resulting Janus microspheres formed a superhydrophobic flexible film at the air−water interface, showing their potential as semipermeable membranes. In our previous work, particles prefunctionalized with a hydrophobic coating were assembled at air−water, 25 solid−water, 26 or oil− water 27 interfaces. The assembled particles were then irradiated under UV via a source positioned directly above.…”