Synthesis of Size-and-Shape-Controlled Iron Oxide Nanoparticles via Coprecipitation and In Situ Magnetic Separation

The purpose of this study was to determine the effect of in situ magnetic separation on the size and shape of iron oxide nanoparticles produced through coprecipitation. A batch reactor system was equipped with a magnetic array comprising neodymium magnets, providing a weak static magnetic field. Iron chloride and sodium hydroxide solutions were contacted at room temperature, producing an iron oxide precipitate. The magnetic array was able to rapidly remove the as-formed iron oxide nanoparticles from the reaction front and prevent further growth and agglomeration, therefore serving as a facile method of controlling the size and shape of the product. Mechanical agitation did not favor this effect, as it resulted in transfer of the precipitating agent from regions of high to low concentration, promoting growth and agglomeration. The method is attractive for large-scale production of iron oxide nanoparticles requiring tuned size and morphology.