Aspartic-Acid-Assisted Hydrothermal Growth and Properties of Magnetite Octahedrons

A biomolecule-assisted hydrothermal route to the fabrication of magnetite (Fe 3 O 4 ) with uniform microsized and regular octahedral morphology has been successfully developed by use of toxic-free aspartic acid as reducing reagent and FeCl 3 ·6H 2 O as iron source. The as-prepared magnetite was characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). Altering different experimental parameters showed that pH of the aspartic acid solution, concentration of aspartic acid, and hydrothermal temperature can significantly influence product phase composition. Furthermore, a series of time-course experiments revealed that growth of regular octahedral magnetite is controlled by the Ostwald ripening process. This biomolecule-assisted route may be expected to be applicable for the fabrication of other transition metal oxides with uniform size and morphology. Besides, magnetic properties of the product were characterized on a vibrating sample magnetometer (VSM). The values of saturation magnetization ( M s ), remanent magnetization ( M r ), and coercivity ( H c ) of the magnetite octahedrons are 71.6 emu/g, 9.8 emu/g, and 120 Oe, respectively. The electrochemical performances of the magnetite octahedra exhibit a discharge capacity of ca. 600 mAh/g in the first cycle and a discharge voltage of 0.92 and 0.74 V, respectively.