In situ dispersion of non-aqueous Fe3O4 nanocolloids by microdroplet coalescence and their use in the preparation of magnetic composite particles

Abstract

Monodispersity and size uniformity are critical issues for nanoparticles, especially for the inorganic particles dispersed in organic carriers serving as the precursor of composites. Herein, for the first time, we have developed a method based on flow-induced droplet coalescence for in situ dispersion of surface-modified Fe₃O₄ nanoparticles to prepare Fe₃O₄/polystyrene (Fe₃O₄/PS) composite particles. A plate-type microchannel was constructed to initiate droplet coalescence for reducing the water–oil interfacial area and for dispersing Fe₃O₄ nanoparticles into the precursor suspensions. Under optimized conditions, the precursor suspensions could be composed of monodispersed Fe₃O₄ nanoparticles with an average size of approximately 12 nm. In this case, the saturation magnetization of the prepared superparamagnetic composites was as high as 4.012 emu g⁻¹ at a magnetite content of 5 wt%. The method is simple and has great potential to be tailored for the preparation of non-aqueous suspensions with uniform and monodispersed nanoparticles.