Key synthesis of magnetic Janus nanoparticles using a modified facile method

Inorganic/organic poly(methylmethacrylate-acrylic acid-divinylbenzene) iron oxide Janus magnetic nanoparticles (P(MMA-AA-DVB)/Fe₃O₄) with strong magnetic domains and unique surface functionalities were prepared using a solvothermal process. The P(MMA-AA-DVB) nanoparticles were prepared via soap-free emulsion polymerization and used as a precursor for preparing Janus nanoparticles. The morphology and magnetic properties of the magnetic Janus nanoparticles formed were characterized using a laser particle size analyzer, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. The synthesized P(MMA-AA-DVB)/Fe₃O₄ magnetic Janus nanoparticles were characterized by a Janus structure and possessed a stable asymmetric morphology after being dually functionalized. The particle size, magnetic content, and magnetic domain of the P(MMA-AA-DVB)/Fe₃O₄ magnetic Janus nanoparticles were 200 nm, 40%, and 25 emu/g, respectively. The formation mechanism of the Janus nanoparticles was also investigated, and the results revealed that the reduction of Fe³⁺ ions and growth of Fe₃O₄ took place on the surface of the P(MMA-AA-DVB) polymeric precursor particles. The size of the Janus particles could be controlled by narrowing the size distribution of the P(MMA-AA-DVB) precursor nanoparticles.