Single-Step Nanoengineering of Silica Coated Maghemite Hollow Spheres with Tunable Magnetic Properties

Tunable magnetic hollow spheres of γ-Fe2O3 with a silica-enriched surface layer have been synthesized by aerosol pyrolysis of an iron ammonium citrate/TEOS solution in methanol. Careful temperature control is crucial for an optimum yield of intact spheres. The Figure shows a TEM image of a sphere, revealing the outer layer consisting mainly of silica. The material is potentially interesting for magnetic-fluid applications, e.g., in medicine.