Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 18: Poster Session I - MA 141/144 (Atomic Wires; Size-Selected Clusters; Nanostructures; Metal Substrates: Clean Surfaces+Adsorption of Organic / Bio Molecules+Solid-Liquid Interfaces+Adsorption of O and/or H; Surface or Interface Magnetism; Oxides and Insulators: Clean Surfaces)
O 18.13: Poster
Montag, 25. Februar 2008, 18:30–19:30, Poster F
Oxidation/Reduction of Aun (n=2-13) clusters on SiO2/Si and HOPG — •Rainer Dietsche1, Dong Chan Lim1, Moritz Bubek1, Thorsten Ketterer1, Young Dok Kim2, and Gerd Ganteför1 — 1Dep. of Physics, University of Konstanz, Konstanz, Germany — 2Dep. of Chemistry, Sungkyunkwan University, Suwon, Korea
Gas phase Au clusters with less than 20 atoms show a pronounced even-odd alternation in their oxidation behaviour. This behaviour is due to the unpaired electron in case of even-numbered anions. For clusters deposited on metal oxides this pattern vanishes. In our experiment Au cluster anions are soft-landed on silica and graphite. Oxidation and reduction are studied by X-Ray Photoelectron Spectroscopy (XPS).
For Aun (n=2-13) clusters on Si wafers covered with native oxide layers the even-odd pattern in oxidation behaviour still is observed. This indicates that the cluster-substrate interaction is weak enough to preserve some of the gas phase properties of the clusters [1].
In a second step, the samples are removed from the UHV system and immersed into water or NaOH solution. The samples exposed to water still exhibit similar chemical properties, whereas treatment with NaOH solution results in an inversion of the even-odd alternation.
In case of Aun (n=2-9) clusters on sputtered HOPG an even-odd pattern is not observed. However, Au8 more readily reacts with atomic oxygen compared to the other clusters. STM measurements of Au7 clusters show that this cluster exhibits two layer, 3D structures [2].
[1] D.C. Lim et al., ChemPhysChem 7, 1909 (2006)
[2] D.C. Lim et al., Chem. Phys. Lett. 439, 364 (2007)