Preparation of magnetite hollow structure for drug delivery application.

Monodispersed Fe3O4 nanospheres with hollow interior and porous shell structures were synthesized without any template by refluxing iron precursor solution in a Teflon-line autoclave at 200 degrees C. Those nanoparticles exhibited a ferromagnetic behavior with a high saturation magnetization of 76 emu/g. The hollow structure was formed based on the assembly of many small particles to form large-sized spheres, followed by chemical conversion coupled with Oswald ripening process. Due to the differences in size, density and/or crystallinity between the outer and interior particles in the spheres, the inner particles migrated to the outer shell, resulting in the formation of the empty space inside nanostructures. The potential application of Fe3O4 hollow nanoparticles as a drug carrier was evaluated with Rhodamine6G as a model drug, showing a pH-dependent release profile due to the difference of proton concentration.