Trisodium citrate-assisted synthesis of highly water-dispersible and superparamagnetic mesoporous Fe3O4 hollow microspheres via solvothermal process

Highly water-dispersible and superparamagnetic mesoporous Fe3O4 hollow microspheres were prepared by a facile trisodium citrate-assisted solvothermal method. The composition, morphology and structure of the product were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric (TG) analysis, Brunauer–Emmett–Teller (BET) and vibrating sample magnetometer (VSM). The results showed that the obtained Fe3O4 hollow microspheres were composed of nanoparticles about 21 nm in diameter and exhibited superparamagnetic properties with relatively high saturation magnetization at room temperature. Trisodium citrate played a crucial role as an electrostatic stabilizer in the formation of Fe3O4 hollow microspheres and Ostwald ripening process was responsible for the formation of hollow structures. The Fe3O4 hollow microspheres were mesoporous and highly water-dispersible, indicating that the Fe3O4 hollow microspheres are ideal candidates for various biomedical applications.