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The Effect of Substrates / Ligands on Metal Nanocatalysts Investigated By Quantitative Z-Contrast Imaging and High Resolution Electron Microscopy

Published online by Cambridge University Press:  15 February 2011

Huiping Xu
Affiliation:
Department of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261. R.J.Lee Group, Inc., Monroeville, PA 15146
Laurent Menard
Affiliation:
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
Anatoly Frenkel
Affiliation:
Department of Physics, Yeshiva University, New York, NY 10016.
Ralph Nuzzo
Affiliation:
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
Duane Johnson
Affiliation:
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Judith Yang
Affiliation:
Department of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261.
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Abstract

Our direct density function-based simulations of Ru-, Pt- and mixed Ru-Pt clusters on carbon-based supports reveal that substrates can mediate the PtRu5 particles [1]. Oblate structure of PtRu5 on C has been found [2]. Nevertheless, the cluster-substrate interface interactions are still unknown. In this work, we present the applications of combinations of quantitative z-contrast imaging and high resolution electron microscopy in investigating the effect of different substrates and ligand shells on metal particles. Specifically, we developed a relatively new and powerful method to determine numbers of atoms in a nanoparticle as well as three-dimensional structures of particles including size and shape of particles on the substrates by very high angle (~96mrad) annular dark-field (HAADF) imaging [2-4] techniques. Recently, we successfully synthesize icosahedra Au13 clusters with mixed ligands and cuboctahedral Au13 cores with thiol ligands, which have been shown by TEM to be of sub-nanometer size (0.84nm) and highly monodisperse narrow distribution. X-ray absorption and UV-visible spectra indicate many differences between icosahedra and cuboctahedral Au13 cores. Particles with different ligands show different emissions and higher quantum efficiency has been found in Au11 (PPH3) SC12)2C12. We plan to deposit those ligands-protected gold clusters onto different substrates, such as, TiO2 and graphite, etc. Aforementioned analysis procedure will be performed for those particles on the substrates and results will be correlated with that of our simulations and activity properties. This approach will lead to an understanding of the cluster-substrates relationship for consideration in real applications.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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References

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