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Weatherup RS, Eren B, Hao Y, Bluhm H, Salmeron MB. Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy. J Phys Chem Lett 2016; 7:1622-1627. [PMID: 27082434 DOI: 10.1021/acs.jpclett.6b00640] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Atmospheric pressure X-ray photoelectron spectroscopy (XPS) is demonstrated using single-layer graphene membranes as photoelectron-transparent barriers that sustain pressure differences in excess of 6 orders of magnitude. The graphene serves as a support for catalyst nanoparticles under atmospheric pressure reaction conditions (up to 1.5 bar), where XPS allows the oxidation state of Cu nanoparticles and gas phase species to be simultaneously probed. We thereby observe that the Cu(2+) oxidation state is stable in O2 (1 bar) but is spontaneously reduced under vacuum. We further demonstrate the detection of various gas-phase species (Ar, CO, CO2, N2, O2) in the pressure range 10-1500 mbar including species with low photoionization cross sections (He, H2). Pressure-dependent changes in the apparent binding energies of gas-phase species are observed, attributable to changes in work function of the metal-coated grids supporting the graphene. We expect atmospheric pressure XPS based on this graphene membrane approach to be a valuable tool for studying nanoparticle catalysis.
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Botzem T, McNeil RPG, Mol JM, Schuh D, Bougeard D, Bluhm H. Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs. Nat Commun 2016; 7:11170. [PMID: 27079269 PMCID: PMC4835533 DOI: 10.1038/ncomms11170] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 02/26/2016] [Indexed: 11/17/2022] Open
Abstract
Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using them as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession reduces electron spin coherence by causing faster decorrelation of transverse nuclear fields. However, this effect disappears for appropriate field directions. Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in self-assembled quantum dots and III–V nanowires. Electron spins in semiconductors form a potential basis for quantum information technology however they are strongly affected by interactions with nuclear spins. Here, the authors show how quadrupolar interactions, although suppressing nuclear dynamics, can result in an anisotropic enhancement of electronic decoherence.
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Head AR, Tsyshevsky R, Trotochaud L, Eichhorn B, Kuklja MM, Bluhm H. Electron Spectroscopy and Computational Studies of Dimethyl Methylphosphonate. J Phys Chem A 2016; 120:1985-91. [DOI: 10.1021/acs.jpca.6b01098] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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54
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Eren B, Zherebetskyy D, Patera LL, Wu CH, Bluhm H, Africh C, Wang LW, Somorjai GA, Salmeron M. Activation of Cu(111) surface by decomposition into nanoclusters driven by CO adsorption. Science 2016; 351:475-8. [PMID: 26823421 DOI: 10.1126/science.aad8868] [Citation(s) in RCA: 156] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The (111) surface of copper (Cu), its most compact and lowest energy surface, became unstable when exposed to carbon monoxide (CO) gas. Scanning tunneling microscopy revealed that at room temperature in the pressure range 0.1 to 100 Torr, the surface decomposed into clusters decorated by CO molecules attached to edge atoms. Between 0.2 and a few Torr CO, the clusters became mobile in the scale of minutes. Density functional theory showed that the energy gain from CO binding to low-coordinated Cu atoms and the weakening of binding of Cu to neighboring atoms help drive this process. Particularly for softer metals, the optimal balance of these two effects occurs near reaction conditions. Cluster formation activated the surface for water dissociation, an important step in the water-gas shift reaction.
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Bluhm H. Preface to the Special Issue of Topics in Catalysis on Ambient Pressure X-ray Photoelectron Spectroscopy. Top Catal 2016. [DOI: 10.1007/s11244-015-0514-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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56
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Jovic V, Rettie AJE, Singh VR, Zhou J, Lamoureux B, Buddie Mullins C, Bluhm H, Laverock J, Smith KE. A soft X-ray spectroscopic perspective of electron localization and transport in tungsten doped bismuth vanadate single crystals. Phys Chem Chem Phys 2016; 18:31958-31965. [DOI: 10.1039/c6cp04526j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Polarization dependent V L-edge XAS spectra showing anisotropy in the electronic band structure of a W:BiVO4 single crystal.
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Stoerzinger KA, Hong WT, Crumlin EJ, Bluhm H, Shao-Horn Y. Insights into electrochemical reactions from ambient pressure photoelectron spectroscopy. Acc Chem Res 2015; 48:2976-83. [PMID: 26305627 DOI: 10.1021/acs.accounts.5b00275] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The understanding of fundamental processes in the bulk and at the interfaces of electrochemical devices is a prerequisite for the development of new technologies with higher efficiency and improved performance. One energy storage scheme of great interest is splitting water to form hydrogen and oxygen gas and converting back to electrical energy by their subsequent recombination with only water as a byproduct. However, kinetic limitations to the rate of oxygen-based electrochemical reactions hamper the efficiency in technologies such as solar fuels, fuel cells, and electrolyzers. For these reactions, the use of metal oxides as electrocatalysts is prevalent due to their stability, low cost, and ability to store oxygen within the lattice. However, due to the inherently convoluted nature of electrochemical and chemical processes in electrochemical systems, it is difficult to isolate and study individual electrochemical processes in a complex system. Therefore, in situ characterization tools are required for observing related physical and chemical processes directly at the places where and while they occur and can help elucidate the mechanisms of charge separation and charge transfer at electrochemical interfaces. X-ray photoelectron spectroscopy (XPS), also known as ESCA (electron spectroscopy for chemical analysis), has been used as a quantitative spectroscopic technique that measures the elemental composition, as well as chemical and electronic state of a material. Building from extensive ex situ characterization of electrochemical systems, initial in situ studies were conducted at or near ultrahigh vacuum (UHV) conditions (≤10(-6) Torr) to probe solid-state electrochemical systems. However, through the integration of differential-pumping stages, XPS can now operate at pressures in the torr range, comprising a technique called ambient pressure XPS (AP-XPS). In this Account, we briefly review the working principles and current status of AP-XPS. We use several recent in situ studies on model electrochemical components as well as operando studies performed by our groups at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory to illustrate that AP-XPS is both a chemically and an electrically specific tool since photoelectrons carry information on both the local chemistry and electrical potentials. The applications of AP-XPS to oxygen electrocatalysis shown in this Account span well-defined studies of (1) the oxide/oxygen gas interface, (2) the oxide/water vapor interface, and (3) operando measurements of half and full electrochemical cells. Using specially designed model devices, we can expose and isolate the electrode or interface of interest to the incident X-ray beam and AP-XPS analyzer to relate the electrical potentials to the composition/chemical state of the key components and interfaces. We conclude with an outlook on new developments of AP-XPS end stations, which may provide significant improvement in the observation of dynamics over a wide range of time scales, higher spatial resolution, and improved characterization of boundary or interface layers (solid/solid and liquid/solid).
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Eren B, Heine C, Bluhm H, Somorjai GA, Salmeron M. Catalyst Chemical State during CO Oxidation Reaction on Cu(111) Studied with Ambient-Pressure X-ray Photoelectron Spectroscopy and Near Edge X-ray Adsorption Fine Structure Spectroscopy. J Am Chem Soc 2015; 137:11186-90. [DOI: 10.1021/jacs.5b07451] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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59
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Mauzeroll J, Thornton G, Rayment T, Maurice V, Williams D, Heberling F, Marcus P, Wren C, Yliniemi K, Lindsay R, Lyth S, Majchrowski T, Hussain H, Hunt G, Renner F, Williams G, Newman R, Frankel G, Lützenkirchen J, Bluhm H. Solid/fluid interface: general discussion. Faraday Discuss 2015; 180:81-96. [PMID: 26125468 DOI: 10.1039/c5fd90044a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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60
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Carenco S, Wu CH, Shavorskiy A, Alayoglu S, Somorjai GA, Bluhm H, Salmeron M. Synthesis and Structural Evolution of Nickel-Cobalt Nanoparticles Under H2 and CO2. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2015; 11:3045-3053. [PMID: 25727527 DOI: 10.1002/smll.201402795] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 11/18/2014] [Indexed: 06/04/2023]
Abstract
Bimetallic nanoparticle (NP) catalysts are interesting for the development of selective catalysts in reactions such as the reduction of CO2 by H2 to form hydrocarbons. Here the synthesis of Ni-Co NPs is studied, and the morphological and structural changes resulting from their activation (via oxidation/reduction cycles), and from their operation under reaction conditions, are presented. Using ambient-pressure X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and transmission electron microscopy, it is found that the initial core-shell structure evolves to form a surface alloy due to nickel migration from the core. Interestingly, the core consists of a Ni-rich single crystal and a void with sharp interfaces. Residual phosphorous species, coming from the ligands used for synthesis, are found initially concentrated in the NP core, which later diffuse to the surface.
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Ng ML, Shavorskiy A, Rameshan C, Mikkelsen A, Lundgren E, Preobrajenski A, Bluhm H. Reversible Modification of the Structural and Electronic Properties of a Boron Nitride Monolayer by CO Intercalation. Chemphyschem 2015; 16:923-7. [DOI: 10.1002/cphc.201500031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Indexed: 11/06/2022]
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62
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Mueller DN, Machala ML, Bluhm H, Chueh WC. Redox activity of surface oxygen anions in oxygen-deficient perovskite oxides during electrochemical reactions. Nat Commun 2015; 6:6097. [DOI: 10.1038/ncomms7097] [Citation(s) in RCA: 258] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 12/12/2014] [Indexed: 12/22/2022] Open
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63
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Karslıoğlu O, Nemšák S, Zegkinoglou I, Shavorskiy A, Hartl M, Salmassi F, Gullikson EM, Ng ML, Rameshan C, Rude B, Bianculli D, Cordones AA, Axnanda S, Crumlin EJ, Ross PN, Schneider CM, Hussain Z, Liu Z, Fadley CS, Bluhm H. Aqueous solution/metal interfaces investigated in operando by photoelectron spectroscopy. Faraday Discuss 2015; 180:35-53. [DOI: 10.1039/c5fd00003c] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We describe a new in operando approach for the investigation of heterogeneous processes at solid/liquid interfaces with elemental and chemical specificity which combines the preparation of thin liquid films using the meniscus method with standing wave ambient pressure X-ray photoelectron spectroscopy [Nemšák et al., Nat. Commun., 5, 5441 (2014)]. This technique provides information about the chemical composition across liquid/solid interfaces with sub-nanometer depth resolution and under realistic conditions of solution composition and concentration, pH, as well as electrical bias. In this article, we discuss the basics of the technique and present the first results of measurements on KOH/Ni interfaces.
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64
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Frankel G, Mauzeroll J, Thornton G, Bluhm H, Morrison J, Maurice V, Rayment T, Williams D, Cook A, Joshi G, Davenport A, Gibbon S, Kramer D, Acres M, Tautschnig M, Habazaki H, Marcus P, Shoesmith D, Wren C, Majchrowski T, Lindsay R, Wood M, Todorova M, Scully J, Renner F, Kokalj A, Taylor C, Virtanen S, Wharton J. Corrosion scales and passive films: general discussion. Faraday Discuss 2015; 180:205-32. [DOI: 10.1039/c5fd90045j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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65
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Cook A, Frankel G, Davenport A, Hughes T, Gibbon S, Williams D, Bluhm H, Maurice V, Lyth S, Marcus P, Shoesmith D, Wren C, Wharton J, Hunt G, Lyon S, Majchrowski T, Lindsay R, Williams G, Rico Oller B, Todorova M, Nixon S, Cheng ST, Scully J, Wilson A, Renner F, Chen YH, Taylor C, Habazaki H, Michaelides A, Morsch S, Visser P, Kyhl L, Kokalj A. Corrosion control: general discussion. Faraday Discuss 2015; 180:543-76. [DOI: 10.1039/c5fd90047f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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66
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Newberg JT, Bluhm H. Adsorption of 2-propanol on ice probed by ambient pressure X-ray photoelectron spectroscopy. Phys Chem Chem Phys 2015; 17:23554-8. [DOI: 10.1039/c5cp03821a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The interaction of 2-propanol with ice was examined via ambient pressure X-ray photoelectron spectroscopy (APXPS), a surface sensitive technique that probes the adsorbed 2-propanol directly with submonolayer resolution.
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Schreiber LR, Bluhm H. Quantum computation: Silicon comes back. NATURE NANOTECHNOLOGY 2014; 9:966-968. [PMID: 25305744 DOI: 10.1038/nnano.2014.249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
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68
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Cerfontaine P, Botzem T, DiVincenzo DP, Bluhm H. High-fidelity single-qubit gates for two-electron spin qubits in GaAs. PHYSICAL REVIEW LETTERS 2014; 113:150501. [PMID: 25375696 DOI: 10.1103/physrevlett.113.150501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Indexed: 06/04/2023]
Abstract
Single-qubit operations on singlet-triplet qubits in GaAs double quantum dots have not yet reached the fidelities required for fault-tolerant quantum information processing. Considering experimentally important constraints and using measured noise spectra, we numerically minimize the effect of decoherence (including high-frequency 1/f-like noise) and show, theoretically, that quantum gates with fidelities higher than 99.9% are achievable. We also present a self-consistent tuning protocol which should allow the elimination of individual systematic gate errors directly in an experiment.
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Shavorskiy A, Neppl S, Slaughter DS, Cryan JP, Siefermann KR, Weise F, Lin MF, Bacellar C, Ziemkiewicz MP, Zegkinoglou I, Fraund MW, Khurmi C, Hertlein MP, Wright TW, Huse N, Schoenlein RW, Tyliszczak T, Coslovich G, Robinson J, Kaindl RA, Rude BS, Ölsner A, Mähl S, Bluhm H, Gessner O. Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:093102. [PMID: 25273702 DOI: 10.1063/1.4894208] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ~9 ns at a pass energy of 50 eV and ~1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with the retarding ratio can be well approximated by applying Liouville's theorem of constant emittance to the electron trajectories inside the lens system. The performance of the setup is demonstrated by characterizing the laser fluence-dependent transient surface photovoltage response of a laser-excited Si(100) sample.
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Siefermann KR, Pemmaraju CD, Neppl S, Shavorskiy A, Cordones AA, Vura-Weis J, Slaughter DS, Sturm FP, Weise F, Bluhm H, Strader ML, Cho H, Lin MF, Bacellar C, Khurmi C, Guo J, Coslovich G, Robinson JS, Kaindl RA, Schoenlein RW, Belkacem A, Neumark DM, Leone SR, Nordlund D, Ogasawara H, Krupin O, Turner JJ, Schlotter WF, Holmes MR, Messerschmidt M, Minitti MP, Gul S, Zhang JZ, Huse N, Prendergast D, Gessner O. Atomic-Scale Perspective of Ultrafast Charge Transfer at a Dye-Semiconductor Interface. J Phys Chem Lett 2014; 5:2753-9. [PMID: 26277975 DOI: 10.1021/jz501264x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Understanding interfacial charge-transfer processes on the atomic level is crucial to support the rational design of energy-challenge relevant systems such as solar cells, batteries, and photocatalysts. A femtosecond time-resolved core-level photoelectron spectroscopy study is performed that probes the electronic structure of the interface between ruthenium-based N3 dye molecules and ZnO nanocrystals within the first picosecond after photoexcitation and from the unique perspective of the Ru reporter atom at the center of the dye. A transient chemical shift of the Ru 3d inner-shell photolines by (2.3 ± 0.2) eV to higher binding energies is observed 500 fs after photoexcitation of the dye. The experimental results are interpreted with the aid of ab initio calculations using constrained density functional theory. Strong indications for the formation of an interfacial charge-transfer state are presented, providing direct insight into a transient electronic configuration that may limit the efficiency of photoinduced free charge-carrier generation.
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Miller D, Sanchez Casalongue H, Bluhm H, Ogasawara H, Nilsson A, Kaya S. Different Reactivity of the Various Platinum Oxides and Chemisorbed Oxygen in CO Oxidation on Pt(111). J Am Chem Soc 2014; 136:6340-7. [DOI: 10.1021/ja413125q] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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72
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Shavorskiy A, Karslioglu O, Zegkinoglou I, Bluhm H. Synchrotron-based Ambient Pressure X-ray Photoelectron Spectroscopy. ACTA ACUST UNITED AC 2014. [DOI: 10.1080/08940886.2014.889547] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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73
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Nijem N, Bluhm H, Ng ML, Kunz M, Leone SR, Gilles MK. Cu1+ in HKUST-1: selective gas adsorption in the presence of water. Chem Commun (Camb) 2014; 50:10144-7. [DOI: 10.1039/c4cc02327g] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Photo-reduced Cu2+ in HKUST-1 adsorbs NO over water, underscoring the potential of MOFs with mixed oxidation metals for gas separation.
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Neppl S, Shavorskiy A, Zegkinoglou I, Fraund M, Slaughter DS, Troy T, Ziemkiewicz MP, Ahmed M, Gul S, Rude B, Zhang JZ, Tremsin AS, Glans PA, Liu YS, Wu CH, Guo J, Salmeron M, Bluhm H, Gessner O. Capturing interfacial photoelectrochemical dynamics with picosecond time-resolved X-ray photoelectron spectroscopy. Faraday Discuss 2014; 171:219-41. [DOI: 10.1039/c4fd00036f] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Time-resolved core-level spectroscopy using laser pulses to initiate and short X-ray pulses to trace photoinduced processes has the unique potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics in complex systems. Time-domain studies using transient X-ray absorption and emission techniques have proven extremely valuable to investigate electronic and structural dynamics in isolated and solvated molecules. Here, we describe the implementation of a picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS) technique at the Advanced Light Source (ALS) and its application to monitor photoinduced electron dynamics at the technologically pertinent interface formed by N3 dye molecules anchored to nanoporous ZnO. Indications for a dynamical chemical shift of the Ru3d photoemission line originating from the N3 metal centre are observed ∼30 ps after resonant HOMO–LUMO excitation with a visible laser pump pulse. The transient changes in the TRXPS spectra are accompanied by a characteristic surface photovoltage (SPV) response of the ZnO substrate on a pico- to nanosecond time scale. The interplay between the two phenomena is discussed in the context of possible electronic relaxation and recombination pathways that lead to the neutralisation of the transiently oxidised dye after ultrafast electron injection. A detailed account of the experimental technique is given including an analysis of the chemical modification of the nano-structured ZnO substrate during extended periods of solution-based dye sensitisation and its relevance for studies using surface-sensitive spectroscopy techniques.
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Zhang C, Yu Y, Grass ME, Dejoie C, Ding W, Gaskell K, Jabeen N, Hong YP, Shavorskiy A, Bluhm H, Li WX, Jackson GS, Hussain Z, Liu Z, Eichhorn BW. Mechanistic Studies of Water Electrolysis and Hydrogen Electro-Oxidation on High Temperature Ceria-Based Solid Oxide Electrochemical Cells. J Am Chem Soc 2013; 135:11572-9. [DOI: 10.1021/ja402604u] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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76
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Lampimäki M, Zelenay V, Křepelová A, Liu Z, Chang R, Bluhm H, Ammann M. Ozone-Induced Band Bending on Metal-Oxide Surfaces Studied under Environmental Conditions. Chemphyschem 2013; 14:2419-25. [DOI: 10.1002/cphc.201300418] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Indexed: 11/11/2022]
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77
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Chekhovich EA, Makhonin MN, Tartakovskii AI, Yacoby A, Bluhm H, Nowack KC, Vandersypen LMK. Nuclear spin effects in semiconductor quantum dots. NATURE MATERIALS 2013; 12:494-504. [PMID: 23695746 DOI: 10.1038/nmat3652] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 04/12/2013] [Indexed: 06/02/2023]
Abstract
The interaction of an electronic spin with its nuclear environment, an issue known as the central spin problem, has been the subject of considerable attention due to its relevance for spin-based quantum computation using semiconductor quantum dots. Independent control of the nuclear spin bath using nuclear magnetic resonance techniques and dynamic nuclear polarization using the central spin itself offer unique possibilities for manipulating the nuclear bath with significant consequences for the coherence and controlled manipulation of the central spin. Here we review some of the recent optical and transport experiments that have explored this central spin problem using semiconductor quantum dots. We focus on the interaction between 10(4)-10(6) nuclear spins and a spin of a single electron or valence-band hole. We also review the experimental techniques as well as the key theoretical ideas and the implications for quantum information science.
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Feng Z, Crumlin EJ, Hong WT, Lee D, Mutoro E, Biegalski MD, Zhou H, Bluhm H, Christen HM, Shao-Horn Y. In Situ Studies of the Temperature-Dependent Surface Structure and Chemistry of Single-Crystalline (001)-Oriented La0.8Sr0.2CoO3-δ Perovskite Thin Films. J Phys Chem Lett 2013; 4:1512-1518. [PMID: 26282307 DOI: 10.1021/jz400250t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Perovskites are used to promote the kinetics of oxygen electrocatalysis in solid oxide fuel cells and oxygen permeation membranes. Little is known about the surface structure and chemistry of perovskites at high temperatures and partial oxygen pressures. Combining in situ X-ray reflectivity (XRR) and in situ ambient pressure X-ray photoelectron spectroscopy (APXPS), we report, for the first time, the evolution of the surface structure and chemistry of (001)-oriented perovskite La0.8Sr0.2CoO3-δ (LSC113) and (La0.5Sr0.5)2CoO4+δ (LSC214)-decorated LSC113 (LSC113/214) thin films as a function of temperature. Heating the (001)-oriented LSC113 surface leads to the formation of surface LSC214-like particles, which is further confirmed by ex situ Auger electron spectroscopy (AES). In contrast, the LSC113/214 surface, with activities much higher than that of LSC113, is stable upon heating. Combined in situ XRR and APXPS measurements support that Sr enrichment may occur at the LSC113 and LSC214 interface, which can be responsible for its markedly enhanced activities.
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79
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Dial OE, Shulman MD, Harvey SP, Bluhm H, Umansky V, Yacoby A. Charge noise spectroscopy using coherent exchange oscillations in a singlet-triplet qubit. PHYSICAL REVIEW LETTERS 2013; 110:146804. [PMID: 25167023 DOI: 10.1103/physrevlett.110.146804] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Indexed: 06/03/2023]
Abstract
Two level systems that can be reliably controlled and measured hold promise as qubits both for metrology and for quantum information science. Since a fluctuating environment limits the performance of qubits in both capacities, understanding environmental coupling and dynamics is key to improving qubit performance. We show measurements of the level splitting and dephasing due to the voltage noise of a GaAs singlet-triplet qubit during exchange oscillations. Unexpectedly, the voltage fluctuations are non-Markovian even at high frequencies and exhibit a strong temperature dependence. This finding has impacts beyond singlet-triplet qubits since nearly all solid state qubits suffer from some kind of charge noise. The magnitude of the fluctuations allows the qubit to be used as a charge sensor with a sensitivity of 2 × 10(-8)e/sqrt[Hz], 2 orders of magnitude better than a quantum-limited rf single electron transistor. Based on these measurements, we provide recommendations for improving qubit coherence, allowing for higher fidelity operations and improved charge sensitivity.
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80
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Rosseler O, Sleiman M, Montesinos VN, Shavorskiy A, Keller V, Keller N, Litter MI, Bluhm H, Salmeron M, Destaillats H. Chemistry of NOx on TiO2 Surfaces Studied by Ambient Pressure XPS: Products, Effect of UV Irradiation, Water, and Coadsorbed K(.). J Phys Chem Lett 2013; 4:536-41. [PMID: 26281751 DOI: 10.1021/jz302119g] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Self-cleaning surfaces containing TiO2 nanoparticles have been postulated to efficiently remove NOx from the atmosphere. However, UV irradiation of NOx adsorbed on TiO2 also was shown to form harmful gas-phase byproducts such as HONO and N2O that may limit their depolluting potential. Ambient pressure XPS was used to study surface and gas-phase species formed during adsorption of NO2 on TiO2 and subsequent UV irradiation at λ = 365 nm. It is shown here that NO3(-), adsorbed on TiO2 as a byproduct of NO2 disproportionation, was quantitatively converted to surface NO2 and other reduced nitrogenated species under UV irradiation in the absence of moisture. When water vapor was present, a faster NO3(-) conversion occurred, leading to a net loss of surface-bound nitrogenated species. Strongly adsorbed NO3(-) in the vicinity of coadsorbed K(+) cations was stable under UV light, leading to an efficient capture of nitrogenated compounds.
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81
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Kaya S, Schlesinger D, Yamamoto S, Newberg JT, Bluhm H, Ogasawara H, Kendelewicz T, Brown GE, Pettersson LGM, Nilsson A. Highly compressed two-dimensional form of water at ambient conditions. Sci Rep 2013; 3:1074. [PMID: 23323216 PMCID: PMC3545261 DOI: 10.1038/srep01074] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 12/27/2012] [Indexed: 12/31/2022] Open
Abstract
The structure of thin-film water on a BaF2(111) surface under ambient conditions was studied using x-ray absorption spectroscopy from ambient to supercooled temperatures at relative humidity up to 95%. No hexagonal ice-like structure was observed in spite of the expected templating effect of the lattice-matched (111) surface. The oxygen K-edge x-ray absorption spectrum of liquid thin-film water on BaF2 exhibits, at all temperatures, a strong resemblance to that of high-density phases for which the observed spectroscopic features correlate linearly with the density. Surprisingly, the highly compressed, high-density thin-film liquid water is found to be stable from ambient (300 K) to supercooled (259 K) temperatures, although a lower-density liquid would be expected at supercooled conditions. Molecular dynamics simulations indicate that the first layer water on BaF2(111) is indeed in a unique local structure that resembles high-density water, with a strongly collapsed second coordination shell.
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82
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Jiang P, Prendergast D, Borondics F, Porsgaard S, Giovanetti L, Pach E, Newberg J, Bluhm H, Besenbacher F, Salmeron M. Experimental and theoretical investigation of the electronic structure of Cu2O and CuO thin films on Cu(110) using x-ray photoelectron and absorption spectroscopy. J Chem Phys 2013; 138:024704. [DOI: 10.1063/1.4773583] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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83
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Křepelová A, Bartels-Rausch T, Brown MA, Bluhm H, Ammann M. Adsorption of Acetic Acid on Ice Studied by Ambient-Pressure XPS and Partial-Electron-Yield NEXAFS Spectroscopy at 230–240 K. J Phys Chem A 2013; 117:401-9. [DOI: 10.1021/jp3102332] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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84
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Fink T, Bluhm H. Noise spectroscopy using correlations of single-shot qubit readout. PHYSICAL REVIEW LETTERS 2013; 110:010403. [PMID: 23383763 DOI: 10.1103/physrevlett.110.010403] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Indexed: 06/01/2023]
Abstract
A better understanding of the noise causing qubit decoherence is crucial for improving qubit performance. The noise spectrum affecting the qubit may be extracted by measuring dephasing under the application of pulse sequences but requires accurate qubit control and sufficiently long relaxation times, which are not always available. Here, we describe an alternative method to extract the spectrum from correlations of single-shot measurement outcomes of successive free induction decays. This method only requires qubit initialization and readout with a moderate fidelity and also allows independent tuning of both the overall sensitivity and the frequency region over which it is sensitive. Thus, it is possible to maintain a good detection contrast over a very wide frequency range. We discuss using our method for measuring both 1/f noise and the fluctuation spectrum of the nuclear bath of GaAs spin qubits.
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85
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Starr DE, Liu Z, Hävecker M, Knop-Gericke A, Bluhm H. Investigation of solid/vapor interfaces using ambient pressure X-ray photoelectron spectroscopy. Chem Soc Rev 2013; 42:5833-57. [DOI: 10.1039/c3cs60057b] [Citation(s) in RCA: 313] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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86
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El Gabaly F, McCarty KF, Bluhm H, McDaniel AH. Oxidation stages of Ni electrodes in solid oxide fuel cell environments. Phys Chem Chem Phys 2013; 15:8334-41. [DOI: 10.1039/c3cp50366f] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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87
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Zhang C, Grass ME, Yu Y, Gaskell KJ, DeCaluwe SC, Chang R, Jackson GS, Hussain Z, Bluhm H, Eichhorn BW, Liu Z. Multielement Activity Mapping and Potential Mapping in Solid Oxide Electrochemical Cells through the use of operando XPS. ACS Catal 2012. [DOI: 10.1021/cs3004243] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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88
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Shulman MD, Dial OE, Harvey SP, Bluhm H, Umansky V, Yacoby A. Demonstration of entanglement of electrostatically coupled singlet-triplet qubits. Science 2012; 336:202-5. [PMID: 22499942 DOI: 10.1126/science.1217692] [Citation(s) in RCA: 441] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Quantum computers have the potential to solve certain problems faster than classical computers. To exploit their power, it is necessary to perform interqubit operations and generate entangled states. Spin qubits are a promising candidate for implementing a quantum processor because of their potential for scalability and miniaturization. However, their weak interactions with the environment, which lead to their long coherence times, make interqubit operations challenging. We performed a controlled two-qubit operation between singlet-triplet qubits using a dynamically decoupled sequence that maintains the two-qubit coupling while decoupling each qubit from its fluctuating environment. Using state tomography, we measured the full density matrix of the system and determined the concurrence and the fidelity of the generated state, providing proof of entanglement.
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89
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Knyazev BA, An W, Bluhm H. Stark spectroscopy of a probe lithium beam excited with two dye lasers as a technique to study a high-power ion-beam diode. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:033101. [PMID: 22462900 DOI: 10.1063/1.3690384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A non-disturbing measurement of electric field distributions is a subject of special interest in plasma physics and high-voltage devices. In this paper we describe a diagnostic technique for remote sensing of electric fields via injection of a probe beam of lithium atoms and cascade excitation of resonance fluorescence with two broadband dye lasers. The fluorescence spectrum was recorded using a monochromator equipped with an optical multi-channel analyser. The magnitude of the local electric field was retrieved from the Stark-shifted components of the 3d-2p lithium spectral line. The technique was applied to measurements of the electric field in the applied-B-field high-voltage diode of the 1 TW KALIF ion-beam accelerator.
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90
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Balmes O, Resta A, Wermeille D, Felici R, Messing ME, Deppert K, Liu Z, Grass ME, Bluhm H, van Rijn R, Frenken JWM, Westerström R, Blomberg S, Gustafson J, Andersen JN, Lundgren E. Reversible formation of a PdC(x) phase in Pd nanoparticles upon CO and O2 exposure. Phys Chem Chem Phys 2012; 14:4796-801. [PMID: 22361687 DOI: 10.1039/c2cp22873d] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The structure and chemical composition of Pd nanoparticles exposed to pure CO and mixtures of CO and O(2) at elevated temperatures have been studied in situ by a combination of X-ray Diffraction and X-ray Photoelectron Spectroscopy in pressures ranging from ultra high vacuum to 10 mbar and from room temperature to a few hundred degrees celsius. Our investigation shows that under CO exposure, above a certain temperature, carbon dissolves into the Pd particles forming a carbide phase. Upon exposure to CO and O(2) mixtures, the carbide phase forms and disappears reversibly, switching at the stoichiometric ratio for CO oxidation. This finding opens new scenarios for the understanding of catalytic oxidation of C-based molecules.
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91
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El Gabaly F, McDaniel AH, Grass M, Chueh WC, Bluhm H, Liu Z, McCarty KF. Electrochemical intermediate species and reaction pathway in H2 oxidation on solid electrolytes. Chem Commun (Camb) 2012; 48:8338-40. [PMID: 22781193 DOI: 10.1039/c2cc33229a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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92
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Butcher DR, Grass ME, Zeng Z, Aksoy F, Bluhm H, Li WX, Mun BS, Somorjai GA, Liu Z. In Situ Oxidation Study of Pt(110) and Its Interaction with CO. J Am Chem Soc 2011; 133:20319-25. [DOI: 10.1021/ja207261s] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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93
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Miller DJ, Öberg H, Kaya S, Sanchez Casalongue H, Friebel D, Anniyev T, Ogasawara H, Bluhm H, Pettersson LGM, Nilsson A. Oxidation of Pt(111) under near-ambient conditions. PHYSICAL REVIEW LETTERS 2011; 107:195502. [PMID: 22181624 DOI: 10.1103/physrevlett.107.195502] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Indexed: 05/31/2023]
Abstract
The oxidation of Pt(111) at near-ambient O2 pressures has been followed in situ using x-ray photoelectron spectroscopy (XPS) and ex situ using x-ray absorption spectroscopy (XAS). Polarization-dependent XAS signatures at the O K edge reveal significant temperature- and pressure-dependent changes of the Pt-O interaction. Oxide growth commences via a PtO-like surface oxide that coexists with chemisorbed oxygen, while an ultrathin α-PtO2 trilayer is identified as the precursor to bulk oxidation. These results have important implications for understanding the chemical state of Pt in catalysis.
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94
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Merte LR, Knudsen J, Eichhorn FM, Porsgaard S, Zeuthen H, Grabow LC, Lægsgaard E, Bluhm H, Salmeron M, Mavrikakis M, Besenbacher F. CO-Induced Embedding of Pt Adatoms in a Partially Reduced FeOx Film on Pt(111). J Am Chem Soc 2011; 133:10692-5. [DOI: 10.1021/ja2015923] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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95
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Shavorskiy A, Aksoy F, Grass ME, Liu Z, Bluhm H, Held G. A Step toward the Wet Surface Chemistry of Glycine and Alanine on Cu{110}: Destabilization and Decomposition in the Presence of Near-Ambient Water Vapor. J Am Chem Soc 2011; 133:6659-67. [PMID: 21473591 DOI: 10.1021/ja110910y] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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96
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Porsgaard S, Jiang P, Borondics F, Wendt S, Liu Z, Bluhm H, Besenbacher F, Salmeron M. Charge State of Gold Nanoparticles Supported on Titania under Oxygen Pressure. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201005377] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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97
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Porsgaard S, Jiang P, Borondics F, Wendt S, Liu Z, Bluhm H, Besenbacher F, Salmeron M. Charge State of Gold Nanoparticles Supported on Titania under Oxygen Pressure. Angew Chem Int Ed Engl 2011; 50:2266-9. [DOI: 10.1002/anie.201005377] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 12/01/2010] [Indexed: 11/10/2022]
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98
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Kroll JH, Donahue NM, Jimenez JL, Kessler SH, Canagaratna MR, Wilson KR, Altieri KE, Mazzoleni LR, Wozniak AS, Bluhm H, Mysak ER, Smith JD, Kolb CE, Worsnop DR. Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol. Nat Chem 2011; 3:133-9. [DOI: 10.1038/nchem.948] [Citation(s) in RCA: 686] [Impact Index Per Article: 52.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 11/11/2010] [Indexed: 11/09/2022]
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99
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de Smit E, van Schooneveld MM, Cinquini F, Bluhm H, Sautet P, de Groot FMF, Weckhuysen BM. On the Surface Chemistry of Iron Oxides in Reactive Gas Atmospheres. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201005282] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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100
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de Smit E, van Schooneveld MM, Cinquini F, Bluhm H, Sautet P, de Groot FMF, Weckhuysen BM. On the Surface Chemistry of Iron Oxides in Reactive Gas Atmospheres. Angew Chem Int Ed Engl 2011; 50:1584-8. [DOI: 10.1002/anie.201005282] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 10/09/2010] [Indexed: 11/06/2022]
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