scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Metal clusters and cluster metals

01 Jan 1988-Polyhedron (Pergamon)-Vol. 7, pp 2321-2329
TL;DR: In this article, the authors proposed to remove the ligand sphere together with the outer shell of metal atoms to generate the inner naked M13 nuclei, which are metastable and build up novel structures.
About: This article is published in Polyhedron.The article was published on 1988-01-01. It has received 104 citations till now. The article focuses on the topics: Cluster (physics) & Phenanthroline.
Citations
More filters
Journal ArticleDOI
TL;DR: It is considered more feasible that the rate-deter-mining step is the cleavage of the C-H bond at the R-carbon atom, and the active site consists of an ensemble of metallic Auatoms and a cationic Au.
Abstract: ion from a primary OH group of glyc-erol. 223,231 A similar mechanism was proposed manyyears ago for alcohol oxidation on Pt/C, involving asecond step, the transfer of a hydride ion to the Ptsurface (Scheme 11). 8,87,237 We consider it more feasible that the rate-deter-mining step is the cleavage of the C-H bond at theR-carbon atom. A similar mechanism is now generallyaccepted for Au electrodes (Scheme 12). 238 Despite thestructural differences between Au nanoparticles andan extended Au electrode surface, there are alsosimilarities, such as the critical role of aqueousalkaline medium and the absence of deactivation dueto decomposition products (CO and C x H y frag-ments). 239,240 An important question is the nature of active siteson Au nanoparticles. Electrooxidation of ethanol onAu nanoparticles supported on glassy carbon re-quired the partial coverage of Au surface by oxides. 241 Another analogy might be the model proposed for COoxidation. 219,242,243 According to this suggestion, theactive site consists of an ensemble of metallic Auatoms and a cationic Au

1,784 citations

Journal ArticleDOI
TL;DR: The mean diameter of monodispersed Pd nanoparticles could be controlled from 17 to 30 A in a one-step reaction by changing the amount of protective polymer, poly(N-vinyl-2-pyrrolidone) (PVP) and the kind and/or the concentration of alcohol in the solvent as discussed by the authors.
Abstract: The mean diameter of monodispersed Pd nanoparticles could be controlled from 17 to 30 A in a one-step reaction by changing the amount of protective polymer, poly(N-vinyl-2-pyrrolidone) (PVP) and the kind and/or the concentration of alcohol in the solvent. Although increasing the amount of protective polymer made the size of Pd nanoparticles smaller, the particle size appeared to have a lower limit determined by the kind of alcohol. On the other hand, monodispersed Pd nanoparticles of smaller diameter were obtained in the order methanol > ethanol > 1-propanol, indicating that a faster reduction rate of [PdCl4]2- ions is an important factor to produce the smaller particles. The particle diameter showed a minimum at around 40 vol % of alcohol in solvent. Once the monodispersed Pd nanoparticles were obtained, the larger particles with a narrow size distribution could be easily synthesized by using the stepwise growth reaction. The Pd nanoparticles obtained here had fcc structures like that of bulk Pd, althoug...

823 citations

Journal ArticleDOI
TL;DR: A literature review of modern transition-metal nanoclusters, with an emphasis on those nanclusters which are catalytically active, is presented in this paper, where the authors compare and contrast the syntheses, characterization approaches, and catalytic applications of transition metal nan-clusters.
Abstract: A literature review of modern transition-metal nanoclusters, with an emphasis on those nanoclusters which are catalytically active, is presented in two parts. Part One presents background information on transition-metal nanoclusters, including an overview of common synthetic routes, a description of how nanoclusters are stabilized, and a brief summary of the multiple characterization techniques used (and the type of information that they can provide). In Part Two, five specific nanocluster case studies are presented, case studies which compare and contrast the syntheses, characterization approaches, and catalytic applications of transition-metal nanoclusters.

822 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a synopsis of the wet chemical syntheses of colloidal particles and survey potential applications in catalysis and materials science, but their methods for the characterization of these particles and their surfaces are not reviewed.
Abstract: Mono- and bimetallic colloidal particles have gained increasing attention in science and application throughout the last several years. In this contribution, we present a synopsis of the wet chemical syntheses of these materials and survey potential applications in catalysis and materials science. Methods for the characterization of these particles and their surfaces are not reviewed here.

724 citations

Journal ArticleDOI
26 Dec 1996-Nature
TL;DR: In this paper, it was shown that the properties of small metallic particles depend sensitively on whether they have an odd or even number of electrons, and that the combination of quantum size and Coulomb-charging effects strongly influence the thermodynamic properties.
Abstract: THE properties of nanometre-scale metallic particles differ from those of the same material1,2 in bulk. Conduction electrons, because of their wave-like nature, can have only certain discrete values of kinetic energy or wavelength. Such 'quantum-size' effects have been observed in two-dimensional electron gases in semiconductors3,4, and in atomic-scale metallic point contacts5. Also present are 'Coulomb-charging' effects: these are purely classical in origin, and occur when the energy required to add one electron to a conducting sphere exceeds the mean thermal energy kBT. Thermal fluctuations in the total charge on the particle are then suppressed6. In theory, the combination of quantum-size and Coulomb-charging effects should cause the properties of small metallic particles to depend sensitively on whether they have an odd or even number of electrons7. Odd–even effects have been observed in experiments on tunnelling between discrete electronic levels of single metal particles8, but their influence on thermodynamic properties remains to be demonstrated. Here we report measurements of the heat capacity and electronic magnetic susceptibility of small metallic clusters. Our results show definitive evidence for odd–even effects, thus confirming that quantum and classical size effects strongly influence the thermodynamic properties of small particles.

362 citations

References
More filters
Journal ArticleDOI
TL;DR: The existence of magic numbers for atomic microclusters has been found experimentally for the first time as mentioned in this paper, and the magic numbers manifest themselves in the mass spectra of free xenon clusters, nucleated in the gas phase.
Abstract: The existence of magic numbers for atomic microclusters has been found experimentally for the first time. The magic numbers ${n}^{*}$ manifest themselves in the mass spectra of free xenon clusters, nucleated in the gas phase. The observed numbers ${n}^{*}=13, 55, \mathrm{and} 147$ coincide with the numbers of spheres required for complete-shell icosahedra. The appearance of further magic numbers (19, 25, 71, and 87) is only partially explained by previous calculations.

653 citations

Journal ArticleDOI
TL;DR: In this article, einfaches Modell, beruhend auf einer Anordnung dichtest gepackter Goldatome, fuhrt zu einem Goldcluster, dessen Aufbau mit der ungewohnlichen chemischen Zusammensetzung in guter Ubereinstimmung ist.
Abstract: Die Reduktion von C6H5)3PAuCl mit B2H6 in Benzol ergibt Au9,2[P(C6H5)3]2Cl, das mittels Molmassebestimmungen als Au55[P(C6H5)3]12Cl6 charakterisiert wurde. Ein einfaches Modell, beruhend auf einer Anordnung dichtest gepackter Goldatome, fuhrt zu einem Goldcluster, dessen Aufbau mit der ungewohnlichen chemischen Zusammensetzung in guter Ubereinstimmung ist. Das Mosbauer-Spektrum der Verbindung zeigt vier Sorten von Goldatomen: einen metallischen Anteil (Au13-Kern), durch P(C6H5)3-bzw. Cl-Liganden Koordinierte Au-Atome, sowie unkoordi-niertes Oberflachengold. Mit Brom und lod las sich der Komplex zu (C6H5)3PAuCl, (C6H5)3 PAuBr(I) und metallischem Gold abbauen. Die Thermolyse bei 50°C fuhrt quantitativ zu [(C6H5)3P]2AuCl und Gold.

532 citations

Journal ArticleDOI
TL;DR: In this article, a single-crystal X-ray analysis of one of these, [Au13-(PMe2Ph)10Cl2](PF6)3, has confirmed a centred icosahedral geometry for the cluster, in agreement with an earlier theoretical prediction.
Abstract: The gold(I) complexes AuCl(PR3)(PR3= PPh3, PMePh2, and PMe2Ph) react with Ti(η-C7H8)2 to form a variety of cationic gold cluster complexes; single-crystal X-ray analysis of one of these, [Au13-(PMe2Ph)10Cl2](PF6)3, has confirmed a centred icosahedral geometry for the cluster, in agreement with an earlier theoretical prediction.

302 citations

Journal ArticleDOI
05 Sep 1985-Nature
TL;DR: In this article, surface profile images were recorded with the electron beam along the 〈110〉 direction with spatial resolution of ∼2.0 A which reveal changes in occupancy of the atom columns often within periods of less than 0.1 s. The motion of atomic columns and the existence of atom clouds revealed here may have important consequences for crystal growth, surface science and catalysis studies.
Abstract: The structure of small metal crystals has been intensively examined by high-resolution electron microscopy (HREM). In particular, multiply-twinned gold and silver crystals have been characterized using the profile-imaging method1,2 at atomic resolution, and reconstructed metal surfaces observed2. Crystal structure images of large gold clusters consisting of 55 gold atoms arranged in a cubeoctahedron have been recorded3 using 2.5 A resolution, and crystal growth, row by row, on a {111} surface has been documented4 using a low-light-level silicon-intensified target television (TV) camera and video system with an on-line image processor. Direct imaging of rearrangements of atomic columns on extended gold surface5 established that profile imaging can provide information about surface self-diffusion. The motion of surface atoms, recorded with a real-time video tape-recorder (VTR) system, and the formation of surface atom steps on {100} surfaces, although not {111}, has also been reported recently6. Dynamic HREM observations at TV rate showing defect motion in gold7 and CdTe (refs. 8, 9) has given information on ‘in-lattice’ rearrangements of columns of atoms. We report here surface profile images recorded with the electron beam along the 〈110〉 direction with spatial resolution of ∼2.0 A which reveal changes in occupancy of the atom columns often within periods of less than 0.1 s. Surfaces with several adjacent atom columns involved in rapid structural changes frequently interacted with a cloud of atoms extending out to 9 A off the crystal and changes in shape and density of the clouds were recorded. Although these clouds have already been described6,10, the present work is the first to analyse these events properly and to describe them in detail. The motion of atomic columns and the existence of atom clouds revealed here may have important consequences for crystal growth, surface science and catalysis studies.

156 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented images that show columns or layers of cluster molecules with a distance of 2.1± 0.1 nm, including the ligand shell and of the naked cluster.

103 citations