Gold clusters adsorption

Kruger, D., Fuchs, H., Rousseau, R., Marx, D. and Parinello, M. (2001) Interaction of short-chain alkane thiols and thiolates with small gold clusters Adsorption structures and energetics. Journal of Chemical Physics, 115, 4776-4786. 

Frondelius, P., Honkala, K. and Hakkinen, H. (2007) Adsorption of gold clusters on metal-supported MgO Correlation to electron aflSnity of gold. Physical Revieiv B - Condensed Matter, 76, 073406-1-073406-4. 

Wallace, W.T., Wyrwas, R.B., Whetten, R.L., Mitric, R. and Bonadc-Kouteck, V. (2003) Oxygen adsorption on hydrated gold cluster anions experiment and theory. Journal of the American Chemical Society, 125, 8408-8414. 

Figure 23. Adsorption of oxygen molecule over gold clusters with different sizes [74].

DF calculations were carried out on CO complexes of small neutral, cationic, and anionic gold clusters Au with n= 1-6. The -coordination mode (terminal C-coordination) was found to be the most favorable one irrespective of the charge of the cluster, and cluster planarity is more stable for the bare clusters and their carbonyls. As expected, adsorption energies are greatest for the cationic clusters, and decrease with size. Instead, the adsorption energies of... 

B. Yoon, H. Hakkinen, and U. Landman, Interaction of O2 with gold clusters molecular and dissociative adsorption, J. Phys. Chem. A 107,4066-4071 (2003). 

Gold clusters are stabilized by the adsorption of surfactants. Alkanethiols play an important role in this stabilization. 

DENSITY FUNCTIONAL STUDIES OF NOBLE METAL CLUSTERS. ADSORPTION OF O2 AND CO ON GOLD AND SIIVER CLUSTERS... 

For each cluster size, the few lowest energy equilibrium isomers with molecular adsorption (MA) and two atoms adsorption (TAA) complexes are represented in Fig 8. Most of these structures are planar or near planar. For 4c, 5b, and 5d, only an O atom is not in the plane. Two atom adsorption leads to major structural changes in the gold cluster, particularly for n>5. For example, in the structures 5a, 6a, and 7a, a gold atom breaks the bonds to other Au atoms to form a highly stable linear O-Au-0 unit which bind each 0 atom to one of the remaining Au atoms. On the other hand, molecular adsorption induces only a modest relaxation in the host cluster, and the O2 molecule is attached on top of a Au atom preferably to the bridge position between two Au atoms. 

Gold is one of the least reactive metals in bulk form. However, in recent years a considerable amount of theoretical and experimental works have studied the reactivity of small neutral and charged Au clusters towards different molecules, like H2, O2, CO, and organic radicals " . The reactivity depends on the size and charge state of the cluster. In the previous section we have studied the reactivity towards oxygen adsorption of anionic silver and gold clusters. In this section we study the reactivity of neutral gold clusters towards molecular O2 (subsection 6.1) and CO (subsection 6.2). 

The oxidation of CO is the simplest reaction and has been the most intensively studied since Langmuir first presented a theory of adsorption and catalysis for this reaction [13]. Supported Au NPs such as Au/Ti02, Au/Fe203 and Au/Co304 are extraordinarily active in CO oxidation, even at 200 K, and are much more active than the other noble metals catalysts at temperatures below 400 K [14—16]. Gold clusters composed of several atoms can promote the reaction between CO and 02 to form C02 at as low as 40 K [17]. Most recently, Lahr and Ceyer [18] have extended the temperature range at which the activity for CO oxidation is observed to as low as 70 K by using an Au/Ni surface alloy. 

Lopez-Lozano X, Perez LA, Garzon IL (2006) Enantiospecific adsorption of chiral molecules on chiral gold clusters. Phys Rev Lett 97 233401... 

Mononuclear Au(lll) species supported on ceria powder (averaged 46 nm) is catalytically active for CO oxidation, and would aggregate into gold clusters with even increased catalytic properties, proved by X-ray adsorption study (Aguilar-Guerrero and Gates, 2007). 

Fielicke A, von Helden G, Meijer G, Pederson D, Simard B, Rayner D (2005) Gold cluster carbonyls Saturated adsorption of CO on gold cluster cations, vibrational spectroscopy, and implications for their structures. J Am Chem Soc 127 8416... 

IRAS data (vCO) were reported for CO adsorbed on gold clusters (1.8-3.1 nm) supported on Ti02. vCO was approximately 4 cm-1 higher than for adsorption on to bulk gold.160... 

Fig. 1.55. Schematic representation of collection zone, adlineation, and reverse spillover for the case of a gold cluster supported on a metal-oxide surface. The reactants (red spheres) might either adsorb from the gas phase in the vicinity of the cluster, within the so-called collection zone, and be directly attracted toward the catalytically active cluster. Or the adsorption might be followed by random diffusion and eventually lead to desorption back to the gas phase, if the primary adsorption places are outside the collection zone of the cluster (graphics adapted from [348])...

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