A facile interfacial reaction route to prepare magnetic hollow spheres with tunable shell thickness.

Magnetic Fe3O4 hollow spheres were successfully synthesized with a water in oil in water (W/O/W) emulsion. During the facile procedure, no high pressure, high temperature, or other complex reaction conditions were required. Transmission electric microscope (TEM) images showed that all the hollow structural products have a good spherical morphology with an average diameter of 160 nm. The average size and the size distribution were further determined with dynamic light scattering (DLS), which reveals that the hollow nanospheres have a narrow size distribution. The average size from DLS was about 180 nm, which approximated that from TEM data. X-ray diffraction (XRD) demonstrates that the products were all Fe3O4 phase without any impurity. By increasing or decreasing the dosage of precipitate and precipitant sources, we controlled the shell thickness successfully in the tens of nanometers range. The formation mechanism of those hollow magnetic nanospheres was discussed by using the "reverse micelle transport" mechanism.