Solvothermal Synthesis of Mesoporous Fe3O4 Nanoparticles in Mixed Solvent of Ethylene Glycol and Water: Structure and Magnetic Properties

Mesoporous Fe3O4 nanoparticles were synthesized by a solvothermal method, via a mixed solvent of ethylene glycol (EG) and deionized water, using iron chloride and urea as the precursors. The phase, morphology, and pore structure are investigated by the characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), and N-2 isotherm adsorption-desorption. The results show that the amount of water in the mixed solvent plays vital role in controlling the size of Fe3O4 nanoparticles, specific surface area, and pore size. Additionally, solid Fe3O4 nanospheres were prepared using only EG as solvent, while alpha-Fe2O3 nanosized polyhedrals were obtained with only water as solvent. The mesoporous Fe3O4 nanoparticles show a ferromagnetic behavior, with saturation magnetizations (Ms) of 78-82 emu g(-1) and coercivities (Hc) ranging from 13-58 Oe. The alpha-Fe2O3 nanoparticles also exhibit a weak-ferrimagnetic character, with a remanent magnetization (Mr) of 0.24 emu g(-1), and Hc of 558 Oe.