Synthesis and growth mechanism of Au@Cu core–shell nanorods having excellent antioxidative properties

Abstract

Au@Cu core–shell nanorods (NRs) were prepared using Au NRs as seeds. The resultant crystal structures were characterized using transmission electron microscopy (TEM), TEM-energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). When Cu shells were grown over Au NRs as seeds by reducing CuCl₂·2H₂O in an aqueous solution in the presence of hexadecylamine (HDA) and D-(+)-glucose (GLC) at 97 °C, Au@Cu NRs with {110} side facets were grown epitaxially as major side facets through a single island-growth mechanism. In this mechanism, crystal growth of Cu shells over Au core NRs starts from the formation of single semi-spherical nuclei on a wide side facet, followed by growth to neighbouring facets, with eventual full coverage by rectangular Cu shells with {110} side facets. When CuCl₂·2H₂O was replaced with Cu(OAc)₂·H₂O, layered growth of Cu shells was observed. Effects of the addition of NaCl to Cu(OAc)₂·H₂O show that Cl⁻ ions play an important role in the single-island growth of Cu shells. The Au@Cu NRs exhibited much stronger antioxidative properties than spherical Cu particles.