Electron Diffraction Determination of Nanoscale Structures Page: 2 of 20
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The size-dependent evolutions of the structures and physical and chemical properties of finite
nanoscale materials aggregates have been the subjects of continuing basic and applied research
interests. Structure determination is one of the outstanding challenges of cluster science, and it
has been approached in several ways. Structural determination via analysis of diffraction
measurements is most desirable, since the scattering data is related to the spatial arrangement of
the scattering atoms in a direct manner. However, until the initial measurements' that applied
diffraction measurements to clusters structures such methodology was not practiced because of
experimental technical difficulties, and consequently one resorted to more indirect methods,
mostly through theoretical analysis of photoelectron spectroscopic (PES) data.2-s Electron
diffraction measurements, which may be regarded as a direct structural determination method,6
allow for a comparison between the experimentally measured data and theoretical calculations,
insofar as the measured patterns are the Fourier transform of the pair correlation function and
thus are directly related to atomic positions. Quite recently it has been demonstrated that trapped
ion electron diffraction (TIED) measurements of mass selected metal clusters are particularly
sensitive to changes in local order of silver cluster structures7 and size-dependent changes in the
structural symmetries of gold clusters.8
Analysis of the electron diffraction data, including comparisons between the measured
diffraction patterns and those calculated for theoretically optimized structures, is required in
order to fully determine the atomic arrangement. Consequently, collaborations with theorists
have provided essential contributions to this program. The success of combining TIED
measurements with theoretical calculations to identify the structures of (Aun)- suggested an
approach to study adsorption processes of small molecules which are involved in the initial
kinetics leading to nanocatalytic activity. It was identified by recent experimental and theoretical
investigations of gold cluster anions that these species present a unique opportunity to correlate
sizes and structures with catalytic reactivity on an atom-by-atom level. In these studies,
relationships between cluster structures and catalytic activities have been explored for metal-
oxide supported gold nanoclusters, and for gas-phase (Aun)- clusters.9-12 As a result, we
proceeded to reorient our research emphasis to measure the gas phase adsorption of small gas
phase molecules (02, H20, CO) on gold cluster cations and anions using the structures
determined by diffraction measurements as well as PES and ion mobility methods .
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Parks, Joel H. Electron Diffraction Determination of Nanoscale Structures, report, March 1, 2013; United States. (digital.library.unt.edu/ark:/67531/metadc836528/m1/2/: accessed December 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.