Magnetite nanoparticles with tunable gold or silver shell

Fe3O4 nanoparticles with size similar to 13 nm have been prepared successfully in aqueous micellar medium at similar to 80 degrees C. To make Fe3O4 nanoparticles resistant to surface poisoning a new route is developed for coating Fe3O4 nanoparticles with noble metals such as gold or silver as shell. The shell thickness of the core-shell particles becomes tunable through the adjustment of the ratio of the constituents. Thus, the route yields well-defined core-shell structures of size from 18 to 30 nm with varying proportion of Fe3O4 to the noble metal precursor salts. These magnetic nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), MR, differential scanning calorimetry (DSC), Raman and temperature-dependent magnetic studies. (c) 2005 Elsevier Inc. All rights reserved.