Synthesis and Characterization of Pt Dendrimer-Encapsulated Nanoparticles: Effect of the Template on Nanoparticle Formation

• Published in: Chemistry of materials 2008-08, Vol.20 (16), p.5218-5228
• Main Authors: Knecht, Marc R, Weir, Michael G, Myers, V. Sue, Pyrz, William D, Ye, Heechang, Petkov, Valeri, Buttrey, Douglas J, Frenkel, Anatoly I, Crooks, Richard M
• Format: Article
• Language: English
• Subjects: Nanomaterials (Nanops, Nanotubes, etc.); Templated and Nanoimprinted Materials
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm8004198

In this article, we provide a detailed description of the synthesis and properties of Pt dendrimer-encapsulated nanoparticles (DENs) prepared using sixth-generation, hydroxyl-terminated, poly(amidoamine) (PAMAM) dendrimers (G6−OH) and three different PtCl4 2−/G6−OH ratios: 55, 147, and 240. Results obtained from UV−vis spectroscopy, X-ray photoelectron spectroscopy, electron microscopy, X-ray absorption spectroscopy, and high-energy X-ray diffraction show that only a fraction of the Pt2+/dendrimer precursors are reduced by BH4 − and that the reduction process is highly heterogeneous. That is, after reduction each Pt2+/dendrimer precursor complex is either fully reduced, to yield a DEN having a size and structure consistent with the original PtCl4 2−/dendrimer ratio used for the synthesis, or the precursor is not reduced at all. This result is consistent with an autocatalytic process that entails slow formation of a nascent catalytic Pt seed within the dendrimer, followed by rapid, catalytic reduction of nearby Pt2+ ions. Details concerning the formation of the Pt2+/dendrimer precursor are also discussed.