Ferrite hollow spheres with tunable magnetic properties

We developed a simple process to prepare monodispersed ferrite hollow spheres with tunable magnetic properties, which were fabricated by coating ferrite nanoparticles on the surface of monodispersed polystyrene spheres and removing of the core polymer subsequently. Transmission electron microscopy images show that magnetic shells of these spheres are composed of ferrite nanoparticles with an average diameter of 15 nm. Scan electron microscopy images show that most of the hollow spheres are complete and structurally intact. Furthermore, the magnetic properties of MFe2O4 ferrite spheres could be tuned by changing the substituted metal cation (M=Mn, Mg, Zn, Ni, Co). The influence of surface modification and calcination on the magnetic properties of ferrite shell was also investigated. It is anticipated that these ferrite hollow spheres can be widely used in various fields of biotechnology and material science. (c) 2006 Elsevier B.V. All rights reserved.