Synthesis, size and magnetic properties of controllable MnFe2O4 nanoparticles with versatile surface functionalities

Abstract

Size controllable MnFe₂O₄ superparamagnetic nanoparticles (NPs) were prepared by a solvothermal method using low-cost metal oleate as the source. The particle size, chemical composition and magnetic properties were investigated. The MnFe₂O₄ nanomaterials exhibit high colloidal stabilities and superparamagnetic properties, with an average particle size in the range of 2 to 10 nm by modifying the reaction condition, such as surfactant, reaction temperature and reaction time. By changing Mn²⁺ to different cations, CoFe₂O₄, NiFe₂O₄, and ZnFe₂O₄ with different magnetic properties could be obtained. The hydrophobic MnFe₂O₄ NPs could also be modified with many surfactants, such as cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl benzene sulfonate (SDBS) and sodium dodecylsulfate (SDS), with the aim of achieving high zeta-potential hydrophilic bilayer-coated MnFe₂O₄ NPs. In addition, the water soluble MnFe₂O₄ magnetic NPs can be applied to the removal of Pb(II) from waste water with good recovery under external magnetic field.