Local ordering of nanostructured Pt probed by multiple-scattering XAFS

Journal Article · Sat Sep 01 04:00:00 EDT 2007 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.76.104110· OSTI ID:21055147

Witkowska, Agnieszka; Di Cicco, Andrea; Principi, Emiliano ^[1]

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1. Department of Solid State Physics, Gdansk University of Technology, 80-952 Gdansk (Poland)

We present detailed results of a multiple-scattering (MS) extended x-ray absorption fine structure (EXAFS) data analysis of crystalline and nanocrystalline platinum. Advanced MS EXAFS analysis has been applied to raw x-ray absorption data including the background, using the expansion of the absorption cross section in terms of local two-body and three-body configurations. Present EXAFS results on bulk Pt are found to be in agreement with previous structural and vibrational data, and has been used as a reference for reliable structural refinement of nanosized systems. EXAFS structural refinement of Pt nanoparticles has been performed in combination with electron microscopy and x-ray diffraction, showing the importance of considering the actual size distribution and morphology of the samples. Present samples were unsupported and supported Pt nanocrystalline systems with size distributions showing clusters of quasispherical shape in the 1-7 nm range. In particular, EXAFS spectra have been analyzed accounting for the reduction of the coordination number and degeneracy of three-body configurations, resulting from the measured size distribution and expected surface atom contributions. The importance of a correct account of the reduction of the number of neighbors for calculating MS contributions is emphasized in the paper. EXAFS results have been found compatible with x-ray diffraction and transmission electron microscopy investigations. We estimate that EXAFS could be used to study cluster shapes only for sizes below 2 nm using present methods and quality of the experimental data. We have also shown that the local distribution of distances and angles probed by EXAFS is broader than in bulk Pt, with first-neighbor bond length variance and asymmetry increasing upon reducing the particle size. Methods and results presented in this paper have been found to be successful for a robust structural refinement of monatomic nanocrystalline systems and represents a solid starting point for analyzing subtle structural and dynamical local changes occurring during in situ experiments involving nanomaterials for specific applications like supported nanocatalysts.

• OSTI ID: 21055147
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 10 Vol. 76; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ABSORPTION SPECTROSCOPY
BOND LENGTHS
CROSS SECTIONS
CRYSTALS
DISTRIBUTION
FINE STRUCTURE
MORPHOLOGY
MULTIPLE SCATTERING
NANOSTRUCTURES
PARTICLE SIZE
PLATINUM
SURFACES
THREE-BODY PROBLEM
TRANSMISSION ELECTRON MICROSCOPY
TWO-BODY PROBLEM
X RADIATION
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY