Sonochemical synthesis, structure and magnetic properties of air-stable Fe3O4/Au nanoparticles

Air-stable nanoparticles of Fe 3 O 4 / Au were prepared via sonolysis of a solution mixture of hydrogen tetrachloroaureate(III) trihydrate (HAuCl 4 ) and (3-aminopropyl)triethoxysilane (APTES)-coated Fe 3 O 4 nanoparticles with further drop-addition of sodium citrate. The Fe 3 O 4 / Au nanoparticles were characterized by x-ray powder diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) magnetometry. Nanoparticles of Fe 3 O 4 / Au obtained under appropriate conditions possess a very high saturation magnetization of about 63 emu g −1 and their average diameter is about 30 nm.