Anisotropic syntheses of boat-shaped core-shell Au-Ag nanocrystals and nanowires

This paper describes the syntheses of boat-shaped core-shell Au-Ag bimetallic nanoparticles (NPs) and Au-Ag bimetallic nanowires (NWs). Initially, gold nanorods (AuNRs) having lengths and widths of 70 18 and 12 2nm, respectively, were prepared from gold seeds in the presence of hexadecyltrimethylammonium bromide (CTAB), benzyldimethylammonium chloride (BDAC), NaAuCl₄, AgNO₃, and ascorbic acid. The thus-prepared AuNRs were then used to prepare boat-shaped core-shell Au-Ag bimetallic NPs in a glycine solution (pH 8.0) containing CTAB, AgNO₃, and ascorbic acid. The CTAB/BDAC molar ratio and the AgNO₃ concentration were important parameters affecting the anisotropy of the products. Silver atoms were deposited at both ends of the AuNRs to form the boat-shaped core-shell Au-Ag bimetallic NPs. Upon coalescence of the NPs at 88 2 °C, the boat-shaped core-shell Au-Ag bimetallic NPs assembled into the form of NWs. These NWs, which were stable in solution at room temperature for at least 3 weeks, formed nanomaterials containing AuNRs after being heated at 210 °C for 15min, i.e.as a result of the melting of the BDAC and silver shells.