One-step synthesis of superparamagnetic monodisperse porous Fe3O4 hollow and core-shell spheres

Monodisperse hollow and core-shell magnetite (Fe3O4) spheres have been prepared by a simple one-pot method based on hydrothermal treatment of FeCl3, citrate, polyacrylamide and urea. The as-prepared samples have been characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption isotherms, superconducting quantum interference device magnetometer. The results of control experiments reveal that citrate and polyacrylamide are crucial for the formation of spherical product and the well known Ostwald ripening process is responsible for the transformation from solid spheres to hollow and core-shell spheres. The hollow and core-shell magnetite spheres are porous and highly water soluble. They exhibit superparamagnetic properties with relatively high saturation magnetization at room temperature. The superparamagnetic properties, high magnetization, high water solubility, together with the hollow interiors will render them ideal candidates for various biomedical applications.