Synthesis of amphipathic superparamagnetic Fe3O4 Janus nanoparticles via a moderate strategy and their controllable self-assembly

Abstract

Recently, amphipathic Janus Fe₃O₄ nanoparticles, with distinct hydrophilic and hydrophobic “faces”, have attracted tremendous attention. However, conventional synthesis methods for these nanoparticles either influenced the superparamagnetism of Fe₃O₄ nanoparticles or failed to endow Fe₃O₄ nanoparticles evident amphipathy, and thus as-prepared amphipathic Janus Fe₃O₄ nanoparticles hardly reveal remarkable self-assembly properties. To address these critical issues, a versatile strategy that combines activators regenerated by electron transfer for atom transfer radical polymerization (ARGET-ATRP) and Pickering emulsions is proposed here to synthesize amphipathic Janus Fe₃O₄ nanoparticles for the first time. Owing to the masterly integration all of the unique features of ARGET-ATRP and Pickering emulsions, Janus Fe₃O₄ nanoparticles with high saturation magnetization and diverse self-assembly behaviors in different solvents are successfully prepared in a gentle, simple and highly controllable reaction condition. Furthermore, these Janus Fe₃O₄ nanoparticles exhibit prominent emulsification in toluene–water model system as their superior amphipathy. These emulsions could not only maintain excellent stability even in an extremely low usage of Janus Fe₃O₄ nanoparticles, but also be easily separated by an external magnetic field because of the intrinsic superparamagnetism of Fe₃O₄. The result implies that the as-received Janus Fe₃O₄ nanoparticles may have extensive application prospects in oil purification from oil–water compounds. This synthesis strategy likewise could be a guidance to synthesize similar Janus materials.