A temperature-controlled method to produce Janus nanoparticles using high internal interface systems: Experimental and theoretical approaches

Abstract

This work presents a unique method to produce large amounts of very small Janus nanoparticles (<50nm) using Pickering emulsions of paraffin-in-water, known as desymmetrization process in high internal interface systems. Unlike other similar works, applying a thermal shock in cooling stage allowed surfactants to be not used in the process besides stabilizing nanoparticles. This provided better modification efficiency after coverage of solid paraffin droplets with small nanoparticles as well as controlling limited and partial coalescences. Two types of silica nanoparticles with different size (<50nm) were used and (3-aminopropyl)triethoxysilane was also applied in order to modify their exposed surface after preparation of stabilized emulsion. Besides SEM images, some other new experimental/analytical procedures are proposed in order to investigate the presence of nanoparticles on the surface of provided solid paraffin droplets. Produced Janus nanoparticles were characterized using FTIR, TGA and EDX tests in order to confirm the chemical modification. Furthermore, a chloroform/water mixture was used to demonstrate the differences of Janus nanoparticles with similar uniformly modified nanoparticles. The results revealed the amphiphilic properties of Janus nanoparticles which led them to be placed at the interface while uniformly modified particles were placed in chloroform phase.