X-ray absorption study of PdCu bimetallic alloy nanoparticles containing an average of ∼64 atoms

The synthesis and characterization of PdCu bimetallic nanoparticles and Pd and Cu monometallic nanoparticles, consisting of an average of ∼64 atoms, is described. The bimetallic nanoparticles were prepared by cocomplexation of Pd²⁺ and Cu²⁺ to interior functional groups of a sixth-generation poly(amidoamine) dendrimer template, followed by chemical reduction to yield dendrimer-encapsulated nanoparticles (DENs). Extended X-ray absorption fine structure (EXAFS) spectroscopy indicates that the particles have an alloy structure. TEM studies indicate particle diameters of 1.2-1.3 nm. This is a rare example of a stable nanoparticle in this size range that consists of one reactive metal and one substantially more noble metal. Such materials are predicted by first-principles theory to have interesting catalytic properties.