Two-Phase Synthesis of Gold-Copper Bimetallic Nanoparticles of Tunable Composition: Toward Optimized Catalytic CO₂ Reduction

Ultrasmall (≤3 nm) bimetallic nanoparticles with controllable compositions and structure are of great interest for their catalytic activity, especially carbon dioxide reduction. Herein is reported a synthesis for bimetallic Au_xCu_1-x nanoparticles of tunable composition that takes advantage of complex-ion chemistry. These Au_xCu_1-x nanoparticles exhibit ultrasmall sizes (∼2 nm), and the observed metal compositions are similar to the nominal metal ratios in the synthesis, roughly 3:1, 1:1, and 1:3 for Au:Cu. The nanoparticles appear to be disordered alloys; no evidence for intermetallic compositions was obtained. Oxidation state analysis of Cu was carried using XPS; after 1 day, only minor oxidation of copper was observed. The original capping agent for the nanoparticles, dodecanethiol, is complexed with sodium dodecyl sulfate to transfer the particles to the aqueous phase.