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Crystalline and electronic structure of gold nanoclusters determined by EXAFS, XRD and XPS methods

N. ALDEA1,* , P. MARGINEAN1, V. REDNIC1, S. PINTEA1, B. BARZb2, A. GLUHOI3, B. E. NIEUWENHUYS3, XIE YANING4, F ALDEA5, M. NEUMANN6

Affiliation

  1. National Institute for Research and Development of Isotopic and Molecular Technologies, Romania
  2. University of Missouri-Columbia, 223 Phys Building MO 65211, USA
  3. Leiden Institute of Chemistry, Leiden University, The Netherlands
  4. Beijing Synchrotron Radiation Facilities of Beijing Electron Positron Collider, Coordination Laboratory of National Center for Nanoscience and Nanotechnology, Beijing, People's Republic of China
  5. University of Agriculture Sciences and Veterinary Medicine, Math. Department. Cluj-Napoca, Romania
  6. University of Osnabrück, Fachbereich Physik, 49069 Osnabrück, Germany

Abstract

Gold particles nanoclusters as supported catalysts were analyzed by extended X-ray absorption fine structure, X-ray diffraction and X-ray photoelectron spectroscopy in order to determine their local, global and electronic structure. The present study points out the strong deformation of the local structure of the active metal due to its interaction with oxide supports as well as a possible oxidation state of the gold component. The average particle size and the microstrain parameters of the supported Au nanoclusters were determined by X-ray diffraction method, based on the Fourier transform of the experimental X-ray line profiles. The global structure is obtained with a fitting method using of the generalized Fermi function facilities for the approximation technique. The strong interaction between the metal nanoclusters and oxide supports induces a great change in the local and global microstructures of the catalysts, modifying at the same time the chemisorptions and catalytic processes that occur at the Au-support interface. The following catalyst samples were investigated: Au/ZnO/MgO/Al2O3, Au/CuO/Al2O3 and Au/Li2O/CeO2/Al2O3. The XPS technique was used for determining the electronic states of gold, gold oxide and metal oxides in the oxide supports..

Keywords

Supported gold catalysts, X-ray diffraction, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, Metal support interaction, Local and global structure.

Submitted at: Nov. 14, 2006
Accepted at: May 15, 2007

Citation

N. ALDEA, P. MARGINEAN, V. REDNIC, S. PINTEA, B. BARZb, A. GLUHOI, B. E. NIEUWENHUYS, XIE YANING, F ALDEA, M. NEUMANN, Crystalline and electronic structure of gold nanoclusters determined by EXAFS, XRD and XPS methods, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 5, pp. 1555-1560 (2007)