Multifunctional Fe₃O₄/Au core/satellite nanocubes: an efficient chemical synthesis, characterization and functionalization of streptavidin protein

A novel and efficient chemical approach for the synthesis of Fe₃O₄/Au core/satellite nanocubes is reported. In a one-pot reaction, metallic Au nanodots were successfully deposited on the polyvinylpyrrolidone (PVP) functionalized Fe₃O₄ nanocube surface for the fabrication of a core/satellite structure (Fe₃O₄/Au) by the reduction of HAuCl₄ using ammonia. Transmission electron microscopy and energy dispersive spectroscopy mapping revealed that small Au nanodots of about 2 nm average size decorated the surface of Fe₃O₄ nanocubes. X-ray diffraction data was used to confirm the formation of both the phases of a cubic inverse spinel structure for Fe₃O₄ and a bcc structure for Au in the core/satellite structure of Fe₃O₄/Au nanocubes. The magnetic properties of the seed Fe₃O₄ nanocubes and Fe₃O₄/Au core/satellite nanocubes were measured by using a superconducting quantum interference device at 300 K. For biological application purposes, the as-synthesized Fe₃O₄/Au core/satellite nanocubes were functionalized by cysteamine followed by successful immobilization of streptavidin protein as confirmed through the fluorescence confocal microscopy images.