Synthesis, transfer, and characterization of core-shell gold-coated magnetic nanoparticles.

Magnetic separation has gained new popularity as a versatile partitioning method with the recent growth in nanotechnology and related biotechnology applications. In this study, iron oxide magnetic nanoparticles were synthesized via solvothermal methods and directly coated with gold to form core-shell gold-coated magnetic nanoparticles (Fe ₃ O ₄ -AuNPs). High-resolution transmission electron microscopy with Energy dispersive X-ray spectroscopy results suggests that temperature and reaction time play an important role in the formation of small, monodisperse Fe ₃ O ₄ -AuNPs. We also demonstrate that increased 4- dimethyl(amino)pyridine (DMAP) concentrations and vigorous stirring were required to successfully transfer Fe ₃ O ₄ -AuNPs into aqueous solution. The structure and morphology of the synthesized and transferred Fe ₃ O ₄ -AuNPs was further confirmed by UV-vis absorption spectroscopy and solubility experiments. •Direct coating of Fe ₃ O ₄ with Au: Slowly heating by (10 °C/ min) until 180-190 °C without exceeding this reaction temperature and increasing the reaction time to 3 h from 1.5 h•High yield transfer of Fe ₃ O ₄ -AuNPs was achieved using 4- dimethyl(amino)pyridine (DMAP) as phase transfer catalyst.