Janus-like particles prepared through partial UV irradiation at the water/oil interface and their encapsulation capabilities

Abstract

Janus particles are the ones whose surfaces have more than one distinct physical and/or chemical properties, which endow them the ability to self-assemble at interface of dissimilar media. However, existing methods to produce good yields of Janus particles are difficult to scale up. In this work, amphiphobic-amphiphilic Janus-like particles are prepared through the ultraviolet irradiation of Pickering emulsions. By assembling at the water/oil interface, pre-functionalized amphiphobic titanium dioxide particles were found to stabilize water-in-oil Pickering emulsions for at least a month. Subjecting emulsion droplets to UV irradiation induces photocatalytic degradation of the coating on exposed particle surfaces. The process is feasible for scaling up to generate larger yields. Even on a lab scale, hundreds of milligrams of Janus-like particles were prepared. The obtained Janus-like particles showed larger affinity for an oil/water interface than their homogeneous counterparts. When employed as encapsulators for the release of molecules in different pH environments, the Janus-like particles provided a slow and controllable release of the cargo throughout a month, opening the possibility for the tailored release of drugs and other molecules. For practical applications, this work demonstrates that high Janus uniformity is not necessary if the particles collectively exhibit an overall Janus behavior. The conceived method is applicable for other particles with photocatalytic properties to create various particle-coating combinations.