Structural Rearrangement of Bimetallic Alloy PdAu Nanoparticles within Dendrimer Templates to Yield Core/Shell Configurations

Here we present evidence for an oxidation-driven structural conversion of quasi-alloy PdAu dendrimer-encapsulated nanoparticles (DENs) to a Au-core/Pd-shell configuration. The initial quasialloy was prepared by co-complexation of PdCl 4 2− and AuCl 4 − within a sixth-generation, poly(amidoamine) dendrimer template followed by chemical reduction. Exposure to air resulted in selective reoxidation of the Pd atoms and subsequent re-reduction led to deposition of a Pd-rich shell on the surface of the remaining Au core. The core/shell nanoparticles were extracted as monolayer-protected clusters (MPCs) from within the dendrimer templates using dodecanethiol. The resulting materials were characterized by UV−vis spectroscopy, transmission electron microscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy.