Quantum Phenomena in Clusters and Nanostructures

Khanna, S.N.; Castleman, A. W.

doi:10.1007/978-3-662-02606-9

Cited by 74 publications

(57 citation statements)

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“…3. What is the explanation for a maximum of the size dependent activity (typically in the 1-2 nm size regime), which is controversially discussed in literature [1,[4][5][6]? These questions directly relate to the atomic structure of small nano-objects in the 1-2 nm size regime, which is a challenge for different experimental techniques: In conventional powder x-ray diffraction the finite particle size gives rise to broad overlapping reflections 40 and in transmission electron microscopy small nanoparticles are often found to be unstable in the electron beam [7].…”

Section: Introductionmentioning

confidence: 99%

Atomic structure of Pt nanoclusters supported by graphene/Ir(111) and reversible transformation under CO exposure

et al. 2016

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We have investigated the atomic structure of graphene/Ir(111) supported platinum clusters with on average fewer than 40 atoms by means of surface x-ray diffraction (SXRD), grazing incidence 15 small angle x-ray scattering (GISAXS) and normal incidence x-ray standing waves (NIXSW) measurements, in comparison with density functional theory calculations (DFT). GISXAS revealed that the clusters with 1.3 nm diameter form a regular array with domain sizes of 90 nm. SXRD shows that the 1-2 monolayer high, (111) oriented Pt nanoparticles grow epitaxially on the graphene support. From the combined analysis of the SXRD and NIXSW data, a 3D structural model of the 20 clusters and the graphene support can be deduced which is in line with the DFT results. For the clusters grown in ultra high vacuum the lattice parameter is reduced by (4.6 ± 0.1) % compared to bulk platinum. The graphene layer undergoes a strong Pt adsorption induced buckling, caused by a re-hybridisation of the carbon atoms below the cluster. In-situ observation of the Pt clusters in CO and O2 environments revealed a reversible change of the clusters' strain state while successively 25 dosing CO at room temperature and O2 at 575 K, pointing to a CO oxidation activity of the Pt clusters.2

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Section: Introductionmentioning

confidence: 99%

Atomic structure of Pt nanoclusters supported by graphene/Ir(111) and reversible transformation under CO exposure

et al. 2016

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“…In particular this behavior has been tested in models where the interaction is restricted to first neighbors [9,10,14], e.g., quantum Ising and X-Y models in an external field, in order to precisely estimate the parameters of the system and to provide useful information about the phase diagram. In view of the attention paid to systems with more sophisticated interaction among lattice sites [15][16][17][18] a question thus naturally arises as to whether criticality may be exploited to enhance metrology in systems with interaction beyond the first-neighbor approximation. * matteo.paris@fisica.unimi.it In this framework, systems described by the Lipkin-Meshkov-Glick (LMG) model provide nontrivial examples to assess quantum criticality as a resource for quantum estimation.…”

Section: Introductionmentioning

confidence: 99%

Quantum metrology in Lipkin-Meshkov-Glick critical systems

2014

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The Lipkin-Meshkov-Glick (LMG) model describes critical systems with interaction beyond the first-neighbor approximation. Here we address the characterization of LMG systems, i.e. the estimation of anisotropy, and show how criticality may be exploited to improve precision. In particular, we provide exact results for the Quantum Fisher Information of small-size LMG chains made of $N=2, 3$ and $4$ lattice sites and analyze the same quantity in the thermodynamical limit by means of a zero-th order approximation of the system Hamiltonian. We then show that the ultimate bounds to precision may be achieved by tuning the external field and by measuring the total magnetization of the system. We also address the use of LMG systems as quantum thermometers and show that: i) precision is governed by the gap between the lowest energy levels of the systems, ii) field-dependent level crossing provides a resource to extend the operating range of the quantum thermometer.Comment: 11 pages, 5 figure

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“…M ass spectrometry has been crucial to the field of cluster research since its inception (1)(2)(3)(4)(5)(6)(7)(8)(9). A variety of cluster formation methods, primarily including laser vaporization (LaVa) (10)(11)(12), pulsed-arc discharge (PACIS) (13)(14)(15), electrospray ionization (ESI) (16), gas aggregation (17)(18), and inert gas sputtering (CORDIS) (18) have enabled the creation of both positively and negatively charged as well as neutral gas-phase clusters across a large size range and with diverse elemental composition.…”

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confidence: 99%

Cluster reactivity experiments: Employing mass spectrometry to investigate the molecular level details of catalytic oxidation reactions

Johnson

Tyo

Castleman

2008

Proc. Natl. Acad. Sci. U.S.A.

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116

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Mass spectrometry is the most widely used tool in the study of the properties and reactivity of clusters in the gas phase. In this article, we demonstrate its use in investigating the molecular-level details of oxidation reactions occurring on the surfaces of heterogeneous catalysts via cluster reactivity experiments. Guided ion beam mass spectrometry (GIB-MS) employing a quadrupole-octopolequadrupole (Q-O-Q) configuration enables mass-selected cluster ions to be reacted with various chemicals, providing insight into the effect of size, stoichiometry, and ionic charge state on the reactivity of catalyst materials. For positively charged tungsten oxide clusters, it is shown that species having the same stoichiometry as the bulk, WO 3 ؉ , W2O 6 ؉ , and W3O 9 ؉ , exhibit enhanced activity and selectivity for the transfer of a single oxygen atom to propylene (C 3H6), suggesting the formation of propylene oxide (C 3H6O), an important monomer used, for example, in the industrial production of plastics. Furthermore, the same stoichiometric clusters are demonstrated to be active for the oxidation of CO to CO 2, a reaction of significance to environmental pollution abatement. The findings reported herein suggest that the enhanced oxidation reactivity of these stoichiometric clusters may be due to the presence of radical oxygen centers (W-O•) with elongated metal-oxygen bonds. The unique insights gained into bulk-phase oxidation catalysis through the application of mass spectrometry to cluster reactivity experiments are discussed.catalysis ͉ tungsten oxide ͉ oxygen radical ͉ carbon monoxide ͉ propylene M ass spectrometry has been crucial to the field of cluster research since its inception (1-9). A variety of cluster formation methods, primarily including laser vaporization (LaVa) (10-12), pulsed-arc discharge (PACIS) (13-15), electrospray ionization (ESI) (16), gas aggregation (17-18), and inert gas sputtering (CORDIS) (18) have enabled the creation of both positively and negatively charged as well as neutral gas-phase clusters across a large size range and with diverse elemental composition. The thermodynamic properties of clusters, including bond-dissociation energies (19-21), endothermic-reaction barriers (22), heat capacities (23), and the enthalpy, entropy, and free-energy changes associated with clustering reactions (24, 25), including those composed of hydrogen-bonded and van der Waals systems, have been widely studied, employing both GIB-MS and flow-tube experiments. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR) (26) along with other linear ion trapping techniques (27) have been used to investigate the time-dependent kinetics of cluster molecule reactions, providing insight into reaction mechanisms, activation energies, and reaction intermediates. The structural properties of clusters, including bonding motifs and collision cross-sections have been examined through collision-induced dissociation (CID) (28) and high-pressure drift cell experiments (29). Time-of-flight (TOF) mass spectrometry...

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Quantum Phenomena in Clusters and Nanostructures

Cited by 74 publications

References 0 publications

Atomic structure of Pt nanoclusters supported by graphene/Ir(111) and reversible transformation under CO exposure

Atomic structure of Pt nanoclusters supported by graphene/Ir(111) and reversible transformation under CO exposure

Quantum metrology in Lipkin-Meshkov-Glick critical systems

Cluster reactivity experiments: Employing mass spectrometry to investigate the molecular level details of catalytic oxidation reactions

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