Controlled Deposition of Size-Selected Silver Nanoclusters

Bromann, Karsten; Félix, Christian; Brune, Harald; Harbich, W.; Monot, R.; Buttet, J.; Kern, Klaus

doi:10.1126/science.274.5289.956

Cited by 307 publications

(241 citation statements)

References 25 publications

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“…This energy is a compromise between the optimum kinetic cluster energy for the quadrupole and soft landing conditions. 34 We adjusted the cluster density to obtain an overall Pt coverage of 0.02 ML, where 1 ML here is defined as an atomic density of Pt(111) of 1.5 × 10 15 atoms/cm 2 . The Pt coverage is obtained from the cluster current density times the deposition time and the cluster size.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Pt_n/TiO₂(110)-(1×1)

et al. 2014

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We determined the CO oxidation rates for sizeselected Pt n (n ∈ {3,7,10}) clusters deposited onto TiO 2 (110). In addition, we investigated the cluster morphologies and their mean sizes before and after the reaction. While the clusters are fairly stable upon annealing in ultrahigh vacuum up to 600 K, increasing the temperature while adsorbing either one of the two reactants leads to ripening already from 430 K on. This coarsening is even more pronounced when both reactants are dosed simultaneously, i.e., running the CO oxidation reaction. Since the ripening depends on the size initially deposited, there is nevertheless a size effect; the catalytic activity decreases monotonically with increasing initial cluster size. ■ INTRODUCTIONIt is well established that small metal clusters have physical and chemical properties distinctively different from those of the bulk. While the properties change rather smoothly in the socalled scalable size regime, each additional atom can substantially change the properties of interest in the nonscalable size range. 1 Metal clusters of well-defined size, shape, and composition, supporting on metal oxide surfaces, provide model catalysts that offer a fundamental understanding of the processes taking place in real catalysts via structure−reactivity correlation at the molecular level. 2 This has been shown for the smallest clusters in numerous examples, three decades ago in the famous photographic experiment by Fayet et al., 3 and more recently in the work of Heiz et al. for metal clusters on MgO(100) 4−9 and of Anderson et al., 10,11 Watanabe et al.,12 and our group 13 for metal clusters on rutile TiO 2 (110). In all these examples, size-selected cluster deposition was employed in order to prepare monodispersed supported clusters which are difficult to obtain by conventional preparation methods. We note that experiments with a finite cluster size distribution also make it possible to study size effects in the scalable regime by varying the mean cluster size. 14 However, to firmly associate a catalytic property with a certain size, one has to probe the cluster morphology not only before but also after the reaction. This information is essentially lacking in most of the experiments cited above.It is fairly well accepted that metal catalysts deactivate, in particular under reaction conditions, as a consequence of morphological changes of the supported clusters, and that this change depends on the cluster size and cluster−support interaction. 2,15−24 This argument is even more important when the smallest entities, with only a handful of atoms, are under investigation. Accordingly, not only in model catalysts with well-defined initial conditions but also in real catalysts, this stability under the reaction conditions sets a clear limitation to the minimum cluster size that can be reasonably employed.Here we present a systematic study of the initial sizedependent reactivity and of the thermal as well as chemical stability of very small Pt clusters on rutile TiO 2 (110)-(1×1) in ...

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Pt_n/TiO₂(110)-(1×1)

et al. 2014

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“…Simple organic cations [7,8], metal clusters [9], polysaccharides [10], a nucleotide [11], and intact viruses [12][13][14] have all been the targets of examination by ion soft-landing. The separation, purification, and storage of chemical species by a completely non-destructive, mass spectrometric approach are the objectives of the studies currently underway in our laboratory.…”

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confidence: 99%

Ion soft-landing into liquids: Protein identification, separation, and purification with retention of biological activity

Gologan

Takáts

Alvarez

et al. 2004

J. Am. Soc. Mass Spectrom.

122

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Protein ions, after mass spectrometric separation, can be soft-landed into liquid surfaces with preservation of their native structures. Retention of biological activity is strongly favored in glycerol-based surfaces but not in self-assembled monolayer solid surfaces. Soft-landing efficiency for multiply-charged hexokinase ions was found to be some four times higher for a glycerol/fructose liquid surface than for a fluorinated self-assembled monolayer surface. Soft-landing into liquid surfaces is also shown to allow (1) protein purification, (2) on-surface identification of the soft-landed material using MALDI, and (3) protein identification by in-surface tryptic digestion. Pure lysozyme was successfully isolated from different mixtures including an oxidized, partially decomposed batch of the protein and a partial tryptic digest. Liquid glycerol/carbohydrate mixtures could be used directly to record MALDI spectra on the soft-landed compounds provided they were fortified in advance with traditional MALDI matrices such as p-nitroaniline and ␣-cyano-4-hydroxycinnamic acid. Various proteins were soft-landed and detected on-target using these types of liquid surface. Soft-landing of multiply-charged lysozyme ions onto fluorinated self-assembled monolayer surfaces was found to occur with a limited amount of neutralization, and trapped multiply-charged ions could be desorbed from the surface by laser desorption. Initial data is shown for a new approach to protein identification that combines top-down and bottom-up approaches by utilizing protein ion soft-landing from a protein mixture, followed by tryptic digestion of the landed material and detection of characteristic tryptic fragments by MALDI. , has been applied in experiments ranging from studies using chemically inert and structurally organized self-assembled monolayers (SAMs) as substrates for ion storage [2], to studies of ion mobility through ice and vapor deposited films [3,4], to experiments aimed at developing a separation method in a form of preparatory mass spectrometry [5,6]. Simple organic cations [7,8] [12][13][14] have all been the targets of examination by ion soft-landing. The separation, purification, and storage of chemical species by a completely non-destructive, mass spectrometric approach are the objectives of the studies currently underway in our laboratory.In a preliminary report [5], we described a method which showed the potential for generating biologically active protein chips from protein mixtures by massselective ion soft-landing. After ionization of the mixture by electrospray (ESI), individual protein ions were mass-selected and soft-landed at predetermined locations on the surface. The results showed that the use of mass spectrometry as a separation method in biology provides high selectivity because components with different molecular formulas can be separated and softlanded. However, retention of the biological activity of a protein or other biomolecule in the course of this (or any mass spectrometry experiment) is a much more chall...

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“…15 We deposited heptamers having the D 5h ͑a pentagonal bipyramid͒ and the C 3v symmetry, the latter corresponding to four coplanar atoms facing one atom on one side and two atoms on the opposite side. These structures resulted from an extended search of equilibrium structures carried out by running molecular-dynamics cycles at temperatures in between Tϭ500 and 800 K, followed by quench at Tϭ0 K. The same approach for the Ag 19 cluster leads to several local minima, from which we selected a highly distorted six-capped icosahedron as initial configuration. We found it instructive to consider also planar Ag 7 structures arranged in the most compact forms compatible with the ͑100͒ and ͑111͒ substrates.…”

Section: Model and Calculationsmentioning

confidence: 99%

“…The Ag atom approaches the surface along the ͓100͔ ͑or ͓111͔͒ direction at zero initial kinetic energy, with the system initially prepared at Tϭ0 K. In the case of Ag 7 and Ag 19 , only one atom is taken to feel the attraction of the surface at tϭ0 ͑atoms have equal heights above the substrate when the heptamer is planar͒. For each cluster-substrate combination 100 depositions are produced for statistical purposes, by varying the atom or cluster location with respect to the ͑100͒ and ͑111͒ planes.…”

Section: Model and Calculationsmentioning

confidence: 99%

Deposition of metallic clusters on a metallic surface at zero initial kinetic energy: Evidence for implantation and site exchanges

1997

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We have investigated the deposition at zero impact kinetic energy of the Ag atom and clusters (Ag 7 ,Ag 19 ) on the ͑100͒ and ͑111͒ surfaces of Pd by molecular-dynamics simulations performed within the embeddedatom-method scheme. Our results elucidate the role played by the adsorption energy in determining the final morphology of the cluster/substrate system when ideal nondestructive deposition conditions are implemented. While implantation of the atom is not observed, we find a finite probability of site Ag-Pd exchanges in the case of clusters. Deposition-assisted mixing occurring at the topmost surface layer appears to be correlated to the size of the cluster and the orientation of the substrate, being higher for Ag 7 /Pd͑100͒ and lower for Ag 19 /Pd͑111͒. Total-energy calculations, combined with an analysis of the atomic motion, indicate that the structural transformation accompanying the deposition of the cluster provides the needed activation energy to induce the observed Ag-Pd atomic exchanges. ͓S0163-1829͑97͒00640-1͔

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Controlled Deposition of Size-Selected Silver Nanoclusters

Abstract: Variable-temperature scanning tunneling microscopy was used to study the effect of kinetic cluster energy and rare-gas buffer layers on the deposition process of size-selected silver nanoclusters on a platinum(111) surface. Clusters with impact energies of Show more

Cited by 307 publications

References 25 publications

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Pt_n/TiO₂(110)-(1×1)

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Pt_n/TiO₂(110)-(1×1)

Ion soft-landing into liquids: Protein identification, separation, and purification with retention of biological activity

Deposition of metallic clusters on a metallic surface at zero initial kinetic energy: Evidence for implantation and site exchanges

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Controlled Deposition of Size-Selected Silver Nanoclusters

Abstract: Variable-temperature scanning tunneling microscopy was used to study the effect of kinetic cluster energy and rare-gas buffer layers on the deposition process of size-selected silver nanoclusters on a platinum(111) surface. Clusters with impact energies of Show more

Cited by 307 publications

References 25 publications

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Ptn/TiO2(110)-(1×1)

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Ptn/TiO2(110)-(1×1)

Ion soft-landing into liquids: Protein identification, separation, and purification with retention of biological activity

Deposition of metallic clusters on a metallic surface at zero initial kinetic energy: Evidence for implantation and site exchanges

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Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Pt_n/TiO₂(110)-(1×1)

Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Pt_n/TiO₂(110)-(1×1)