EXAFS Characterization of Dendrimer‐Derived Pt/γ‐Al₂O₃

Author(s)

A. Siani
Oleg S. Alexeev, University of South Carolina - ColumbiaFollow
Christopher T. Williams, University of South Carolina - ColumbiaFollow
Harry J. Ploehn, University of South Carolina - ColumbiaFollow
Michael D. Amiridis, University of South Carolina - ColumbiaFollow

Document Type

Article

Subject Area(s)

Nanoscience and Nanotechnology, Physics

Abstract

The various steps involved in the preparation of a Pt/γ‐Al₂O₃ material using hydroxyl‐terminated generation four (G4OH) PAMAM dendrimers as templates were monitored by EXAFS. The results indicate that Cl ligands in the Pt precursors (H₂PtCl₆ and K₂PtCl₄) were partially replaced by aquo ligands upon hydrolysis to form [PtCl₃(H₂O)₃]⁺ and [PtCl₂(H₂O)₂] species. After interaction of such species with G4OH, Cl ligands from the first coordination shell of Pt were further replaced by nitrogen atoms from the dendrimer interior, indicating the complexation of Pt with the dendrimer. This process was accompanied by a transfer of the electron density from the dendrimer to Pt, indicating that the former plays the role of a ligand. Following treatment of the H₂PtCl₆/G4OH and K₂PtCl₄/G4OH composites with NaBH₄, no substantial changes were detecteded in the electronic or coordination environment of Pt, and no formation of metal nanoparticles was observed. However, when the reduction treatment was performed with H₂, the formation of extremely small Pt clusters incorporating no more than 4 Pt atoms was observed. These Pt species remained strongly bonded to the dendrimer and their nuclearity depends on the length of the H₂ treatment. Formation of Pt nanoparticles with an average diameter of approximately 10 Å was finally observed after the deposition of H₂PtCl₆/G4OH on γ‐Al₂O₃ and drying, suggesting that their formation may be related to the collapse of the dendrimer structure. The Pt nanoparticles formed appear to have high mobility, since subsequent thermal treatment in O₂/H₂ led to further sintering.

Publication Info

Published in AIP Conference Proceedings, Volume 882, 2007, pages 737-739.

Rights

© AIP Conference Proceedings 2007, American Institute of Physics

Siani, A., Alexeev, O. S., Williams, C. T., Ploehn, H. J., & Amiridis, M. D. (2007). EXAFS characterization of dendrimer-derived Pt/ɣ-Al₂O₃. AIP Conference Proceedings, 882, 737-739.

http://dx.doi.org/10.1063/1.2644648

http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.2644648