In situ Fabrication of Multi-Walled Carbon Nanotubes/Silica Hybrid Colloidosomes by Pickering Emulsion Templating Using Trialkoxysilanes of Opposite Polarity

Abstract

A simple and effective way to prepare multi-walled carbon nanotubes (MWNT)//silica hybrid microcapsules (colloidosomes) is presented. These microcapsules have been generated by emulsion templating in a biphasic oil-in-water (o/w) system. Two trialkoxysilanes of complementary polarity, (3-aminopropyl)triethoxysilane (APTES) and dodecyltriethoxysilane (DTES), were used to chemically immobilize the silica nanoparticles at the o/w interface and stabilize the as-generated Pickering emulsions. The effects of varying the o/w ratio and the concentration of the added solids on the type of emulsion formed, the oil droplet size, as well as the emulsion stability have been investigated. The emulsion phase fraction was dependent on the silica content while the droplet size increased with increasing oil volume percentage. A solid shell emerged around the oil droplets from copolymerization between silane monomers. The thickness of the resulting shells was several hundreds of nm. Although MWNTs and silica nanoparticles both were co-assembled at the o/w interface, silica has shown to be the sole stabilizer, with APTES being crucial for the formation of the shell structure. Drop-casting of the emulsion and air-drying led to hierarchical open porous MWNT-silica nanocomposites. These new structures are promising as electrically conductive thin films for variety of applications, such as electro-optics, encapsulation, or chemical sensing.