Synthesis of Bimetallic AuPt Clusters with Clean Surfaces via Sequential Displacement-Reduction Processes

Abstract

We report the synthesis of bimetallic AuPt nanoparticles (3.3–4.3 nm) of uniform size and composition using colloidal methods and reagents containing only C, H, O, and N. These clusters were dispersed onto SiO2 and treated at low temperatures in the presence of reductants to remove all surface residues without concomitant agglomeration, thus leading to bimetallic structures suitable for mechanistic inquiries into bimetallic effects on surface reactivity. Synthesis protocols exploit and generalize galvanic displacement-reduction (GDR) processes previously used to prepare AuPd clusters; these routes promote bimetallic mixing but become more challenging for systems (e.g., AuPt) with smaller reduction potential differences and less favorable mixing enthalpies than AuPd. These hurdles are addressed here through procedural modifications that inhibit the formation of large Au-rich clusters, which compromise size and compositional uniformity. In doing so, we extend GDR techniques to endothermic alloys with elemen...