Abstract
Au-Ag alloy nanostructures with various shapes were synthesized using a successive reduction method in this study. By means of galvanic replacement, twined Ag nanoparticles (NPs) and single-crystalline Ag nanowires (NWs) were adopted as templates, respectively, and alloyed with the same amount of Au+ ions. High angle annular dark field-scanning TEM (HAADF-STEM) images observed from different rotation angles confirm that Ag NPs turned into AuAg alloy rings with an Au/Ag ratio of 1. The shifts of surface plasmon resonance and chemical composition reveal the evolution of the alloy ring formation. On the other hand, single-crystalline Ag NWs became Ag@AuAg core-shell wires instead of hollow nanostructure through a process of galvanic replacement. It is proposed that in addition to the ratio of Ag templates and Au ion additives, the twin boundaries of the Ag templates were the dominating factor causing hollow alloy nanostructures.
Highlights
AuAg alloy nanostructures with zero or one dimension (0-D or 1-D) exhibit unique optical and catalytic properties and have diverse applications, e.g., catalytic converters and electrode catalysts for Li batteries [1,2,3,4,5,6,7,8]
As for the catalytic properties, previous reports show that AuAg alloy nanoparticles (NPs) exhibit superior catalytic activity for CO oxidation compared with pure Au and Ag NPs, due to the synergistic effect [7, 8, 18]
High-resolution TEM (HRTEM) images taken from the near-edge regions of the 1-D Au-Ag nanostructures and corresponding selected area diffraction patterns (SADPs) given in Fig. 5a reveal that the core-shell feature of the 1-D nanostructures, of which the core was singlecrystalline Ag wires, and the shell deposits, compact and attached firmly to the Ag surface, with thickness of 4 ± 0.3 nm comprised nanocrystals showing an interplanar distance of 0.23 nm
Summary
AuAg alloy nanostructures with zero or one dimension (0-D or 1-D) exhibit unique optical and catalytic properties and have diverse applications, e.g., catalytic converters and electrode catalysts for Li batteries [1,2,3,4,5,6,7,8]. As for the catalytic properties, previous reports show that AuAg alloy nanoparticles (NPs) exhibit superior catalytic activity for CO oxidation compared with pure Au and Ag NPs, due to the synergistic effect [7, 8, 18]. AuAg NPs can be reduced from the solution with a mixture of Au and Ag ions containing precursors. In these cases, Ag NPs are usually used as the templates, and Au ions are added for
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