When Gold Is Not Noble:  Nanoscale Gold Catalysts

Sánchez, A.; Abbet, Stéphane; Heiz, Ueli; Schneider, W. D.; Häkkinen, Hannu; Barnett, R. N.; Landman, Uzi

doi:10.1021/jp9935992

Cited by 1,429 publications

(1,450 citation statements)

References 16 publications

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“…[57][58][59][60][61][62] In all of these studies, a common theme has been the cooperative effects of the metal cluster and its support. Related to this, both gas-phase experiments and theory have documented the unusual catalytic activity found for small gold clusters and how this varies with cluster size and charge state.…”

Section: Introductionmentioning

confidence: 99%

IR Photodissociation Spectroscopy and Theory of Au⁺(CO)_n Complexes: Nonclassical Carbonyls in the Gas Phase

et al. 2008

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Au+(CO)n complexes are produced in the gas phase via pulsed laser vaporization, expanded in a supersonic jet, and detected with a reflectron time-of-flight mass spectrometer. Complexes up to n = 12 are observed, with mass channels corresponding to the n = 2 and n = 4 showing enhanced intensity. To investigate coordination and structure, individual complexes are mass-selected and probed with infrared photodissociation spectroscopy. Spectra in the carbonyl stretching region are measured for the n = 3−7 species, but no photodissociation is observed for n = 1, 2 due to the strong metal cation-ligand binding. The carbonyl stretch in these systems is blue-shifted 50−100 cm-1 with respect to the free CO vibration (2143 cm-1), providing evidence that these species are so-called "nonclassical" metal carbonyls. Theory at the MP2 and CCSD(T) levels provides structures for these complexes and predicted spectra to compare to the experiment. Excellent agreement is obtained between experiment and theory, establishing that the n = 3 complex is trigonal planar and the n = 4 complex is tetrahedral. Disciplines Chemistry CommentsReprinted (adapted) ReceiVed: NoVember 21, 2007; In Final Form: December 18, 2007 Au + (CO) n complexes are produced in the gas phase via pulsed laser vaporization, expanded in a supersonic jet, and detected with a reflectron time-of-flight mass spectrometer. Complexes up to n ) 12 are observed, with mass channels corresponding to the n ) 2 and n ) 4 showing enhanced intensity. To investigate coordination and structure, individual complexes are mass-selected and probed with infrared photodissociation spectroscopy. Spectra in the carbonyl stretching region are measured for the n ) 3-7 species, but no photodissociation is observed for n ) 1, 2 due to the strong metal cation-ligand binding. The carbonyl stretch in these systems is blue-shifted 50-100 cm -1 with respect to the free CO vibration (2143 cm -1 ), providing evidence that these species are so-called "nonclassical" metal carbonyls. Theory at the MP2 and CCSD(T) levels provides structures for these complexes and predicted spectra to compare to the experiment. Excellent agreement is obtained between experiment and theory, establishing that the n ) 3 complex is trigonal planar and the n ) 4 complex is tetrahedral.

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Section: Introductionmentioning

confidence: 99%

IR Photodissociation Spectroscopy and Theory of Au⁺(CO)_n Complexes: Nonclassical Carbonyls in the Gas Phase

et al. 2008

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“…It has been particularly important in chemisorption studies of small molecules on oxide surfaces, 7-9 as a prototype oxide in studies of metal adsorption, particle nucleation, and growth on oxide surfaces during metal vapor deposition, [10][11][12][13][14][15][16][17][18][19] and as the prototypical oxide support in preparing model oxidesupported transition metal catalysts used to study metal particle size effects in catalysis. [20][21][22][23] In such studies, it was often found that adsorption, chemical reaction, and metal particle nucleation occur preferentially at defect sites on MgO(100), 14,15,[24][25][26][27][28][29][30][31][32][33][34][35][36] as is generally the case for other oxide surfaces as well. 1, 37,38 Alkaline earth metals like Ca are common promoters in solid catalysts, [39][40][41][42] where they are often thought to reside on the † University of Washington.…”

Section: Introductionmentioning

confidence: 99%

Calcium Adsorption on MgO(100): Energetics, Structure, and Role of Defects

et al. 2008

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Abstract:The adsorption of Ca on the MgO(100) surface at 300 K has been studied using microcalorimetry, in combination with LEED, AES, ISS, work function, sticking probability measurements, and density functional theory (DFT) calculations. The MgO(100) thin films (∼4 nm thick) were grown epitaxially on a 1 µm thick Mo(100) single-crystal. The sticking probability of Ca on MgO(100) at 300 K is unity. On the basis of AES and ISS measurements, it was determined that Ca grows mainly as 3D particles on the MgO(100) surface with a density of ∼1 × 10 12 islands/cm 2 . Ca adsorbs initially at defect sites with a very high heat of adsorption (∼410 kJ/mol). DFT calculations attribute this high initial heat to Ca binding to kink sites (376 kJ/mol), step sites (205 kJ/mol), and lower concentrations of stronger binding sites. The heat of adsorption decreases rapidly with coverage, reaching a minimum of 162 kJ/mol at ∼0.3 ML, where Ca is mainly adding to small 3D Ca clusters. Afterward, it increases to the value of bulk Ca heat of sublimation (178 kJ/mol) at ∼1.2 ML, attributed to the increase in stability with increasing Ca particle size. A 1.0 eV decrease of the work function with Ca coverage from 0 to 0.3 ML indicates that Ca adsorbed at defects is cationic, in agreement with calculations showing that Ca donates electron density to the MgO. Light ion sputtering of the MgO-(100) surface generates point defects, but these do not change the heat of adsorption versus coverage, implying that they do not nucleate Ca particles. Oxygen vacancies are a likely candidate; DFT calculations show that F and F+ center vacancies bind Ca more weakly than terrace sites. More extensive sputtering creates extended defects (such as steps and kinks) that adsorb Ca with heats of adsorption up to ∼400 kJ/mol, similar to that at the intrinsic defect sites.

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“…[5][6][7][8][9] And gas-phase coinage (Ag, Au) clusters are suitable model systems to shed light on reaction mechanisms of Ag-based and Au-based catalysis. [10][11][12] Ag m and Au m (m ) 1-3) are the smallest coinage nanosized catalytic clusters, they are the basic constituent for the larger nanomaterials and nanocatalytic systems.…”

Section: Introductionmentioning

confidence: 99%

Phenyl-Coinage Metal (Ag, Au) Complexes: an Anion Photoelectron Spectroscopy and Density Functional Study

et al. 2005

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The important intermediate phenyl-coinage metal complexes (Ag m C 6 H 5 -, Au m C 6 H 5 -), which are produced from the reactions between coinage metal clusters formed by laser ablation and the benzene molecules seeded in argon carrier gas, are studied by PES (photoelectron spectroscopy) and DFT (density functional theory). The EAs (adiabatic electron affinities) of these complexes are obtained from PES at both 308 and 193 nm photon energies and show odd-even alternation. Calculations with DFT are carried out on the structural and electronic properties of Ag m C 6 H 5 -and Au m C 6 H 5 -; the adiabatic detachment energy and the calculated DOS (density of states) for the ground state of a given anion are in good agreement with the experimental PES results. The observed spectra are also compared with those of the pure coinage metal clusters, which reveal that there are some similarities between them and the phenyl acts like an additional metal atom in the clusters. Furthermore, the bonding between phenyl and metal is analyzed, suggesting that phenyl group binds perpendicularly on metal clusters through C-M σ bond.

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When Gold Is Not Noble: Nanoscale Gold Catalysts

Cited by 1,429 publications

References 16 publications

IR Photodissociation Spectroscopy and Theory of Au⁺(CO)_n Complexes: Nonclassical Carbonyls in the Gas Phase

IR Photodissociation Spectroscopy and Theory of Au⁺(CO)_n Complexes: Nonclassical Carbonyls in the Gas Phase

Calcium Adsorption on MgO(100): Energetics, Structure, and Role of Defects

Phenyl-Coinage Metal (Ag, Au) Complexes: an Anion Photoelectron Spectroscopy and Density Functional Study

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When Gold Is Not Noble: Nanoscale Gold Catalysts

Cited by 1,429 publications

References 16 publications

IR Photodissociation Spectroscopy and Theory of Au+(CO)n Complexes: Nonclassical Carbonyls in the Gas Phase

IR Photodissociation Spectroscopy and Theory of Au+(CO)n Complexes: Nonclassical Carbonyls in the Gas Phase

Calcium Adsorption on MgO(100): Energetics, Structure, and Role of Defects

Phenyl-Coinage Metal (Ag, Au) Complexes: an Anion Photoelectron Spectroscopy and Density Functional Study

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IR Photodissociation Spectroscopy and Theory of Au⁺(CO)_n Complexes: Nonclassical Carbonyls in the Gas Phase

IR Photodissociation Spectroscopy and Theory of Au⁺(CO)_n Complexes: Nonclassical Carbonyls in the Gas Phase