Web Release Date: October 4,
Structural Rearrangement of Bimetallic Alloy PdAu Nanoparticles within Dendrimer Templates to Yield Core/Shell Configurations†
Department of Chemistry and Biochemistry, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, and Department of Physics, Yeshiva University, 245 Lexington Avenue, New York, New York 10016
Received July 5, 2007
Revised Manuscript Received August 6, 2007
Abstract:
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 PdCl42− and AuCl4− 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.
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