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 ± 2 nm, respectively, were prepared from gold seeds in the presence of hexadecyltrimethylammonium bromide (CTAB), benzyldimethylammonium chloride (BDAC), NaAuCl 4 , AgNO 3 , 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, AgNO 3 , and ascorbic acid. The CTAB/BDAC molar ratio and the AgNO 3 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 15 min, i.e. as a result of the melting of the BDAC and silver shells.