The structure of Pt-aggregates on a supported thin aluminum oxide film in comparison with unsupported alumina: a transmission electron microscopy study

Klimenkov, M.; Nepijko, S. A.; Kuhlenbeck, Helmut; Bäumer, Marcus; Schlögl, Robert; Freund, Hans‐Joachim

doi:10.1016/s0039-6028(97)00449-4

Cited by 108 publications

(62 citation statements)

References 16 publications

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“…Such a contraction of small particles is the result of unsaturated bonds of atoms at the particle surface and the interaction with the sp 3 hybridized graphene below the cluster, exhibiting a smaller lattice constant. A comparable nanoparticle contraction was reported for Pt nanoparticles of similar diameter on Al 2 O 3 /NiAl(110) determined from ex-situ transmission electron microscopy diffraction patterns [35].…”

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confidence: 82%

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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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confidence: 82%

“…When reaching the 1-2 nm size regime, a number of fundamental questions arise: 1. How large is the confinement induced compression of the nanoparticles 35 and how does it modify the gas adsorption properties? 2.…”

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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“…35 Furthermore, shift in binding energy is related to the lattice strain that exists because the average bond distances in small clusters are shorter than in the bulk. 36,37 The chemical changes important for the binding energy shift involve an increased d to sp promotion (or hybridization) for shorter bond distances, resulting in the increased binding energy. the bulk value.…”

Section: Methodsmentioning

confidence: 99%

Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

Sengar

Mehta

Govind

2014

Journal of Applied Physics

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Articles you may be interested inTemperature, pressure, and size dependence of Pd-H interaction in size selected Pd-Ag and Pd-Cu alloy nanoparticles: In-situ X-ray diffraction studies J. Appl. Phys. 115, 114308 (2014) In this report, X-ray photoelectron spectroscopy studies have been carried out on Pd, Ag, Cu, PdAg, and Pd-Cu nanoparticles having identical sizes corresponding to mobility equivalent diameters of 60, 40, and 20 nm. The nanoparticles were prepared by the gas phase synthesis method. The effect of size on valence and core levels in metal and alloy nanoparticles has been studied by comparing the values to those with the 60 nm nanoparticles.

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“…As particle size decreases, particle dimensions approach the size of certain physical length scalesssuch as the electron mean-free path and the electron wavelengthsand this results in quantum size effects that alter the electronic structure of the particle (19)(20)(21). For metal particles, quantum effects influence physical and chemical properties when the particle size is less than about 5 nm (18,(22)(23)(24)(25). Similar effects will arise at larger particle sizes (10-150 nm) for materials with lower electron density, such as oxides and semiconductors (26,27).…”

Section: Introductionmentioning

confidence: 99%

Characterization and Properties of Metallic Iron Nanoparticles: Spectroscopy, Electrochemistry, and Kinetics

Nurmi

Tratnyek

Sarathy

et al. 2004

Environ. Sci. Technol.

883

544

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There are reports that nano-sized zero-valent iron (Fe0) exhibits greater reactivity than micro-sized particles of Fe0, and it has been suggested that the higher reactivity of nano-Fe0 may impart advantages for groundwater remediation or other environmental applications. However, most of these reports are preliminary in that they leave a host of potentially significant (and often challenging) material or process variables either uncontrolled or unresolved. In an effort to better understand the reactivity of nano-Fe0, we have used a variety of complementary techniques to characterize two widely studied nano-Fe0 preparations: one synthesized by reduction of goethite with heat and H2 (FeH2) and the other by reductive precipitation with borohydride (FeBH). FeH2 is a two-phase material consisting of 40 nm α-Fe0 (made up of crystals approximately the size of the particles) and Fe3O4 particles of similar size or larger containing reduced sulfur; whereas FeBH is mostly 20−80 nm metallic Fe particles (aggregates of <1.5 nm grains) with an oxide shell/coating that is high in oxidized boron. The FeBH particles further aggregate into chains. Both materials exhibit corrosion potentials that are more negative than nano-sized Fe2O3, Fe3O4, micro-sized Fe0, or a solid Fe0 disk, which is consistent with their rapid reduction of oxygen, benzoquinone, and carbon tetrachloride. Benzoquinonewhich presumably probes inner-sphere surface reactionsreacts more rapidly with FeBH than FeH2, whereas carbon tetrachloride reacts at similar rates with FeBH and FeH2, presumably by outer-sphere electron transfer. Both types of nano-Fe0 react more rapidly than micro-sized Fe0 based on mass-normalized rate constants, but surface area-normalized rate constants do not show a significant nano-size effect. The distribution of products from reduction of carbon tetrachloride is more favorable with FeH2, which produces less chloroform than reaction with FeBH.

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The structure of Pt-aggregates on a supported thin aluminum oxide film in comparison with unsupported alumina: a transmission electron microscopy study

Cited by 108 publications

References 16 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

Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

Characterization and Properties of Metallic Iron Nanoparticles: Spectroscopy, Electrochemistry, and Kinetics

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