Structure and bonding of gold metal clusters, colloids and nanowires studied by EXAFS, XANES and WAXS

Benfield, Robert E. and Grandjean, Didier and Kroll, Michael and Pugin, Raphael and Sawitowski, Thomas and Schmid, Gunter (2001) Structure and bonding of gold metal clusters, colloids and nanowires studied by EXAFS, XANES and WAXS. Journal of Physical Chemistry B, 105 (10). pp. 1961-1970. ISSN 1089-5647. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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The structure and bonding of a series of gold clusters and gold nanomaterials stabilized by ligands or confined within nanoporous alumina have been investigated using EXAFS, XANES, and WAXS. Two gold clusters stabilized by two different ligands, Au-55(PPh3)(12)Cl-6 and AU(55)(T-8-OSS - SH)(12)Cl-6 were confirmed to be of face-centered cubic structure type with metal-metal distances of 2.785 and 2.794 Angstrom, respectively, shorter than in bulk gold. Colloidal gold of 180 Angstrom diameter stabilized by sulfonated phosphine ligands had structural and electronic properties very similar to those of bulk gold but smaller Debye-Waller factors. The cluster Au-55(PPh3)(12)Cl-6 adsorbed into nanoporous alumina membrane was found to retain its integrity inside the membrane but with slightly longer Au-Au bonds due to some aggregation. The same cluster thermally transformed into colloidal gold within the alumina membrane was found to be almost identical structurally and electronically to the bulk. Gold nanowires electrochemically grown within the nanoporous alumina were found to be composed on average of 120 Angstrom diameter crystallites. These have the same structure as the bulk, but with smaller Debye-Waller factors, indicating either a better crystallinity or that the gold atoms are more tightly held than in the bulk. The difference of area method L-3 - kL(2) was used to quantify the d orbital occupancy. The two ligand-stabilized Au-55 clusters both had a smaller value (2.7) than the bulk material (4.1). The nanomaterials inside the membrane also showed smaller L-3 - kL(2) values. The geometrical and electronic structures of these gold materials how a very clear pattern of buildup as the number of gold atoms increases from Au-55 clusters through Au colloids and nanowires to the bulk metal.

Item Type: Article
Projects: [79] EU TMR Network "CLUPOS" FMRX-CT98-0177
Subjects: Q Science > QD Chemistry
Q Science > QC Physics
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences
Depositing User: Robert E Benfield
Date Deposited: 09 Oct 2008 14:48
Last Modified: 09 May 2014 08:26
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