Synthesis of monodisperse and single-crystal Fe3O4 hollow spheres by a solvothermal approach

This manuscript reports the solvothermal method for the fabrication of monodisperse and single-crystal Fe3O4 hollow microspheres with a diameter of 200 nm in the presence of Na2CO3. The effects of reaction parameters like the reaction time and the reagent concentration on the structure of the resultant samples are investigated. The amount of water in the reaction system plays an important role during the reaction process. The formation mechanism for Fe3O4 hollow spheres is illustrated by an Ostwald ripening process. X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM and scanning electron microscopy are used to characterize the as-prepared products. The Fe3O4 hollow spheres reveal a ferromagnetic behavior with a saturation magnetization of 75.3 emu g−1, a remnant magnetization of 2.0 emu g−1, and a coercivity of 31.3 Oe at room temperature.