Directly aqueous synthesis of well-dispersed superparamagnetic Fe3O4 nanoparticles using ionic liquid-assisted co-precipitation method

• Using ionic liquid as templates to prepare the Fe3O4 nanoparticles.
• Ionic liquid can be washed away completely by deionized water and absolute ethyl alcohol.
• The synthesized Fe3O4 nanoparticles are well-dispersed and superparamagnetic.
• The sizes of Fe3O4 nanoparticles can be easily tailored by varying the amount of ionic liquid.

In this paper, well-dispersed superparamagnetic Fe3O4 nanoparticles have been successfully synthesized in aqueous phase by a simple co-precipitation method using ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIN]BF4) as templates. As we studied, the microstructures and magnetic properties of the Fe3O4 nanoparticles were strongly influenced by the addition of ionic liquid. The possible formation mechanisms of Fe3O4 nanoparticles were proposed. It was found that the nanoparticle surface was modified with ionic liquid during the growth of the Fe3O4 nanoparticles, which could prevent the nanoparticles from aggregating effectively. In addition, ionic liquid can be easily removed using deionized water. As a result, well-dispersed Fe3O4 nanoparticles without organic cover can be obtained. Besides, the particle size and magnetic properties of Fe3O4 nanoparticles were strongly depended on the amount of ionic liquid [BMIN]BF4.