Synthesis of nanometer-size maghemite particles from magnetite

Magnetite (Fe3O4) nanoparticles with mean diameter of about 7 and 13 nm were prepared by partial reduction coprecipitation method and modified Massart method, respectively. Then the maghemite (γ-Fe2O3) nanoprticles were obtained by aeration oxidizing of acidified magnetite nanoparticles aqueous suspension. The transition from magnetite to maghemite nanoparticles was confirmed by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) and electron diffraction (ED) photography. And the stable maghemite nanoparticles may be used in magnetic ferrofluids hyperthermia (MFH) application because of their satisfactory heating property in ac magnetic field.