One-Pot Template-Free Synthesis of Monodisperse and Single-Crystal Magnetite Hollow Spheres by a Simple Solvothermal Route

Uniform-sized, monodisperse, and single-crystal magnetite hollow spheres with a diameter of 200−300 nm and a shell thickness of ∼50 nm have been successfully synthesized in high yield using a template-free solvothermal route. The reaction duration and the ethylenediamine amount are shown to play important roles in the formation of the magnetite hollow spheres. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier tranform IR, scanning electron microscopy, transmission electron microscopy (TEM), and high-resolution TEM were used to characterize the products. The results show that the prepared single-crystalline hollow spheres are composed of well-aligned magnetite and have a cubic structure. The magnetite hollow spheres show a high saturation magnetization of ca. 68 emu/g, a remnant magnetization of ca. 13 emu/g, and a coercivity of ca. 94 Oe at room temperature. A possible mechanism for the formation of magnetite hollow spherical structures is proposed based on the experimental observations. The prepared magnetite hollow spheres have promising applications in biomedical fields due to their above characteristics.