Reactivity gold clusters

Fig. 9 Dependence of catalytic activity of MgO-supported catalysts containing cationic gold and (except in the most active catalyst) gold clusters for ethene hydrogenation at 760 Torr and 353 K (reactive mixture of He, ethene, and H2—ethene partial pressure, r ethene. 40 Torr Phydrogen. 160 Torr the balance He). Note the nonlinearity of the scale at the top [53]...

Further dramatic changes can happen in chemical reactivities of gold clusters with diameters smaller than 2nm. The contribution of support materials including metal oxides, carbons, and polymers to the genesis of unique catalytic properties may be much greater than in the case of NPs and therefore may provide an expanding new field of research. 

Prediction of interaction between metal clusters with oxide surface The HSAB principle classifies the interaction between acids and bases in terms of global softness. In the last few years, the reactivity index methodology was well established and had found its application in a wide variety of systems. This study deals with the viability of the reactivity index to monitor metal cluster interaction with oxide. Pure gold cluster of a size between 2 and 12 was chosen to interact with clean alumina (100) surface. A scale was derived in terms of intra- and intermolecular interactions of gold cluster with alumina surface to rationalize the role of reactivity index in material designing [43]. 

Reactivity of metal clusters can be studied using spectroscopic techniques. By means of single molecule luminescence spectroscopy, we can observe individual clusters. Photoreactivity of gold clusters synthesized using a photochemical method... 

Gold clusters were also attached to the Au electrode by dithiols with the reactive bipyridyl group (Bpy) incorporated into... 

The reactivity of Au O clusters to oxygen as a function of n was measured by Salisbury and coworkers using time of flight mass spectroscopy. It was found that odd-n (even-n) clusters have negligible (significant) reactivity, which is explained by the fact that the O2 molecule, acting as a one-electron aceptor, binds to anionic gold clusters, which have an unpaired electron. 

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). 

There have been a number of theoretical studies of small gold clusters and their reactivity with oxygen,1,8,13-21 but because of the different DFT methodologies (see Appendix at the end of this chapter) used it is scarcely surprising that the answers are qualitatively different. Most of the calculations confirm the experimental observations, and add some gloss to them the most recent calculations agree extraordinarily well with experimental... 

Kittredge J. K. Whitesell M. A. Fox, Competitive photochemical reactivity in a self-assembled mono-layer on a colloidal gold cluster. 

The bonding patterns formed between the triangular gold cluster and the ammonia molecule, illustrated in Table 2, differ from those described for Auz-NH3, especially for AU3. This can be anticipated from the more smeared redistribution of the electron charge over the entire cluster and the different shapes of the high occupied and low unoccupied frontier molecular orbitals, which determine its reactivity (see Ref. [26] c). 

Fig. 1.57. Electron binding energies measured as VDEs of gas phase negatively charged gold cluster ions in comparison to the reactivity of the same cluster sizes toward molecular oxygen (adapted from [160])...

Fig. 1.61. Compilation of experimentai resuits from the iiterature on the reiative reactivity of gold cluster anions in the adsorption reaction of one O2 or one CO molecule, respectively, as a function of the ciuster size n. (a) Reactions of Aun with O2 filled squares) data from [370], open triangles) data from [372], open circles) data from [160]. (b) Reactions of An with CO filled squares) data from [372], open circles) data from [352]. For comparison, all data are normalized to the reactivity of Aue toward O2...

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