Electron transfer processes on Au nanoclusters supported on graphite

Shen, Jie; Jia, Juanjuan; Bobrov, K.; Guillemot, L.; Esaulov, Vladimir A.

doi:10.1007/s13404-013-0109-6

Cited by 11 publications

(10 citation statements)

References 34 publications

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“…Such a behavior has been observed in low energy alkali ion scattering from Au and Ag nanoclusters in Refs. [48,50,51], and a decrease of edge atom charge for clusters that are smaller than those considered here may be the reason. Thus, the extrapolation of the model to a cluster diameter of zero in Figs.…”

Section: Modelmentioning

confidence: 77%

“…This is because the alkali LEIS technique is adept for studying surfaces composed of multiple elements and can address questions about the charge state of those elements. Previous results have shown that the ions scattered from Au and Ag nanoclusters on an oxide and other substrates have a much higher neutralization probability than those scattered from the bulk metal, and that neutralization decreases as the cluster size increases [48][49][50][51][52][53][54][55]. Although it is possible that the alkali LEIS neutralization rate and the Au nanocluster catalytic activity are related, such a correlation has not yet been confirmed.…”

Section: Introductionmentioning

confidence: 99%

“…To explain the unusually high neutralization for alkali ions scattered from small Au nanoclusters, a model is developed here based on the notion that the charge associated with each Au atom in a cluster is different. Previously, the charge on the Au clusters had been considered in aggregate when analyzing ion neutralization [48][49][50][51][52][53][54][55], but the present model is dependent on the differences in charge between the atoms and not on the average charge. Density functional theory (DFT) calculations performed for Au nanoclusters supported on TiO2 find that the charge associated with the edge atoms of the nanocluster are noticeably different from the center atoms [27,31].…”

Section: Introductionmentioning

confidence: 99%

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Inhomogeneous charge distribution across gold nanoclusters measured by scattered low energy alkali ions

2018

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The neutralization of low energy Na + and Li + ions scattered from Au nanoclusters formed by deposition onto oxide surfaces decreases as the cluster size increases. An explanation for this behavior is provided here, which is based on the notion that the atoms in the clusters are not uniformly charged, but that the edge atoms are positively charged while the center atoms are nearly neutral. This leads to upward pointing dipoles at the edge atoms that increase the neutralization probability of alkali ions scattered from those atoms. As the clusters increase in size, the number of edge atoms relative to the number of center atoms decreases, so that that the average neutralization also decreases. Calculations employing this model are compared to experimental data and indicate good agreement if the strengths of the dipoles at the edge atoms are assumed to decrease with cluster size. This model also explains differences in the neutralization probabilities of scattered

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Section: Modelmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inhomogeneous charge distribution across gold nanoclusters measured by scattered low energy alkali ions

2018

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“…The Au nanoclusters were grown on sputtered highly ordered pyrolytic graphite (HOPG) 23 and Al 2 O 3 surfaces and on pristine HOPG. We find that significantly more efficient Li + neutralization occurs on small clusters grown on alumina and slightly bombarded HOPG, with neutralization decreasing as the cluster size increased.…”

Section: ■ Introductionmentioning

confidence: 99%

Electron Transfer Processes on Supported Au Nanoclusters and Nanowires and Substrate Effects

et al. 2015

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The catalytic activity of metal nanoclusters is considered to depend on their size, morphology, and substrate type. Here we address this problem by studying changes in electron transfer processes, that are important in surface chemistry, on the example of the interaction of Li ions with gold nanostructures as a function of their sizes and substrate type. The Au nanoclusters were grown on highly ordered pyrolytic graphite (HOPG) and Al 2 O 3 surfaces. In the case of Al 2 O 3 and sputtered HOPG surface, a wide surface coverage distribution of nanoclusters is formed, whereas on pristine HOPG scanning tunneling microscopy (STM) images show that Au clusters nucleate at step edges and can coalesce into "nanowires". We found that electron transfer is much more probable on small clusters than on bulk Au surfaces. For distributed clusters, electron transfer is most probable for lateral size is of the order of 2−3 nm and height is in the 1 nm range, that is, of the order of a few atomic layers. Interestingly, larger electron transfer rates were found on cluster chains or nanowires nucleated on HOPG step edges in the case of pristine HOPG than on isolated clusters on HOPG planes. Our results suggest that the main effects that are observed are largely related to cluster size and morphology.

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“…Bonding to such π orbitals could remove charge from the edge atoms in a similar manner as for Au bonding to a substrate O atom. The NF for low energy Li + scattered from Au nanoclusters supported on HOPG show a similar decrease of the NF as a function of Au coverage [66,67], which suggests that the bonding of the edge atoms to the substrate is via π orbitals for both single layer Gr and bulk graphite surfaces.…”

Section: Discussionmentioning

confidence: 84%