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Eilert A, Cavalca F, Roberts FS, Osterwalder J, Liu C, Favaro M, Crumlin EJ, Ogasawara H, Friebel D, Pettersson LGM, Nilsson A. Subsurface Oxygen in Oxide-Derived Copper Electrocatalysts for Carbon Dioxide Reduction. J Phys Chem Lett 2017; 8:285-290. [PMID: 27983864 DOI: 10.1021/acs.jpclett.6b02273] [Citation(s) in RCA: 201] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Copper electrocatalysts derived from an oxide have shown extraordinary electrochemical properties for the carbon dioxide reduction reaction (CO2RR). Using in situ ambient pressure X-ray photoelectron spectroscopy and quasi in situ electron energy-loss spectroscopy in a transmission electron microscope, we show that there is a substantial amount of residual oxygen in nanostructured, oxide-derived copper electrocatalysts but no residual copper oxide. On the basis of these findings in combination with density functional theory simulations, we propose that residual subsurface oxygen changes the electronic structure of the catalyst and creates sites with higher carbon monoxide binding energy. If such sites are stable under the strongly reducing conditions found in CO2RR, these findings would explain the high efficiencies of oxide-derived copper in reducing carbon dioxide to multicarbon compounds such as ethylene.
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Niwa K, Ogasawara H, Hasegawa M. Pyrite form of group-14 element pernitrides synthesized at high pressure and high temperature. Dalton Trans 2017; 46:9750-9754. [DOI: 10.1039/c7dt01583f] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The incompressible pyrite form of group 14 elemental pernitrides synthesized at high pressures and high temperatures.
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Hayasaka M, Ogasawara H, Hotta Y, Tsukagoshi K, Kimura O, Kura T, Tarumi T, Muramatsu H, Endo T. Nutritional assessment using stable isotope ratios of carbon and nitrogen in the scalp hair of geriatric patients who received enteral and parenteral nutrition formulas. Clin Nutr 2016; 36:1661-1668. [PMID: 27847116 DOI: 10.1016/j.clnu.2016.10.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 10/14/2016] [Accepted: 10/17/2016] [Indexed: 11/16/2022]
Abstract
BACKGROUND & AIMS The δ13C and δ15N values in the scalp hair of geriatric patients in Japan who received the enteral or parenteral nutrition formula were measured to assess nutritional status. METHODS The relations among δ13C, δ15N, calorie intake, BMI, albumin concentration, total cholesterol (T-CHO) and geriatric nutritional risk index (GNRI) in the patients were investigated. Furthermore, the enrichment of δ13C and δ15N from the nutrients to the hair was investigated. RESULTS The δ13C values in the hair of patients who received enteral nutrition decreased with decreases in the calories received, while the δ15N values increased, suggesting malnutrition in some patients with a low calorie intake due to a negative nitrogen balance. The distribution of patients with a low calorie intake (below 20 kcal/kg/day) when δ13C was plotted against δ15N differed from that of control subjects, but the distribution of patients with a high calorie intake (above 20 kcal/kg/day) was similar to that of control subjects. No significant differences were observed in BMI, albumin concentration, T-CHO or GNRI between the low and high calorie groups. The enrichment of δ13C and δ15N from the enteral nutrients to the hair were inversely correlated with the δ13C and δ15N in the enteral nutrients. The enrichment levels of δ13C and δ15N tended to be higher and lower, respectively, in the high calorie group. On the other hand, the δ13C and δ15N values in the hair of patients who received parenteral nutrition were higher and lower than those in the control subjects and in the patients who received enteral nutrition, respectively, reflecting the higher δ13C and lower δ15N contents of the parenteral nutrients. CONCLUSIONS The δ13C and δ15N values in the hair of patients who received enteral nutrition may be effective indicators for evaluating the long-term nutritional status of geriatric patients. A calorie intake of 20 kcal/kg/day may be a cut-off value for malnutrition in Japanese geriatric patients receiving enteral nutrition. However, caution is necessary when dealing with patients switching from parental nutrition as parenteral nutrition resulted in different changes in δ13C and δ15N. The enrichment levels of δ13C and δ15N from the enteral nutrients to the hair may be inversely correlated with the δ13C and δ15N values of enteral nutrients and vary according to the calorie intake.
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Beye M, Öberg H, Xin H, Dakovski GL, Dell'Angela M, Föhlisch A, Gladh J, Hantschmann M, Hieke F, Kaya S, Kühn D, LaRue J, Mercurio G, Minitti MP, Mitra A, Moeller SP, Ng ML, Nilsson A, Nordlund D, Nørskov J, Öström H, Ogasawara H, Persson M, Schlotter WF, Sellberg JA, Wolf M, Abild-Pedersen F, Pettersson LGM, Wurth W. Chemical Bond Activation Observed with an X-ray Laser. J Phys Chem Lett 2016; 7:3647-3651. [PMID: 27584914 DOI: 10.1021/acs.jpclett.6b01543] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free-electron laser to directly observe the decreased bonding-antibonding splitting following bond-activation using an ultrashort optical laser pulse.
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Ogasawara H. Matching pseudocounts for interval estimation of binomial and Poisson parameters. COMMUN STAT-THEOR M 2016. [DOI: 10.1080/03610926.2014.941492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Öberg H, Gladh J, Marks K, Ogasawara H, Nilsson A, Pettersson LGM, Öström H. Indication of non-thermal contribution to visible femtosecond laser-induced CO oxidation on Ru(0001). J Chem Phys 2015; 143:074701. [PMID: 26298142 DOI: 10.1063/1.4928646] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We studied CO oxidation on Ru(0001) induced by 400 nm and 800 nm femtosecond laser pulses where we find a branching ratio between CO oxidation and desorption of 1:9 and 1:31, respectively, showing higher selectivity towards CO oxidation for the shorter wavelength excitation. Activation energies computed with density functional theory show discrepancies with values extracted from the experiments, indicating both a mixture between different adsorbed phases and importance of non-adiabatic effects on the effective barrier for oxidation. We simulated the reactions using kinetic modeling based on the two-temperature model of laser-induced energy transfer in the substrate combined with a friction model for the coupling to adsorbate vibrations. This model gives an overall good agreement with experiment except for the substantial difference in yield ratio between CO oxidation and desorption at 400 nm and 800 nm. However, including also the initial, non-thermal effect of electrons transiently excited into antibonding states of the O-Ru bond yielded good agreement with all experimental results.
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LaRue JL, Katayama T, Lindenberg A, Fisher AS, Öström H, Nilsson A, Ogasawara H. THz-Pulse-Induced Selective Catalytic CO Oxidation on Ru. PHYSICAL REVIEW LETTERS 2015; 115:036103. [PMID: 26230806 DOI: 10.1103/physrevlett.115.036103] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Indexed: 05/19/2023]
Abstract
We demonstrate the use of intense, quasi-half-cycle THz pulses, with an associated electric field component comparable to intramolecular electric fields, to direct the reaction coordinate of a chemical reaction by stimulating the nuclear motions of the reactants. Using a strong electric field from a THz pulse generated via coherent transition radiation from an ultrashort electron bunch, we present evidence that CO oxidation on Ru(0001) is selectively induced, while not promoting the thermally induced CO desorption process. The reaction is initiated by the motion of the O atoms on the surface driven by the electric field component of the THz pulse, rather than thermal heating of the surface.
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Ng ML, Abild-Pedersen F, Kaya S, Mbuga F, Ogasawara H, Nilsson A. Low Barrier Carbon Induced CO Dissociation on Stepped Cu. PHYSICAL REVIEW LETTERS 2015. [PMID: 26196988 DOI: 10.1103/physrevlett.114.246101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Using x-ray photoelectron spectroscopy we observe the breaking of the strong interatomic bond in molecular CO at low temperature on a stepped Cu surface. Since the electronic structure of Cu does not allow for the splitting of CO at such low temperatures it suggests that there may be a less obvious pathway for the process. Through x-ray photoelectron spectroscopy we can clearly identify products associated with the dissociation of CO and the subsequent formation of stable graphitic carbon on the surface. However, the dissociation of CO can be inhibited when the stepped Cu surface is kept clean from surface carbon. These observations imply that the reaction is driven by the presence of small amounts of weakly bound carbon at the surface. Density-functional theory calculations confirm that carbon atoms on a stepped Cu surface indeed are the preferred adsorption sites for CO, which increases the stabilization of CO on the surface and weakens the C-O bond. This results in the breaking of the C-O bond at the step edge via the Boudouard reaction (2CO(ads)→C(ads)+CO(2)) with a barrier of 0.71 eV.
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Sellberg JA, Kaya S, Segtnan VH, Chen C, Tyliszczak T, Ogasawara H, Nordlund D, Pettersson LGM, Nilsson A. Comparison of x-ray absorption spectra between water and ice: new ice data with low pre-edge absorption cross-section. J Chem Phys 2015; 141:034507. [PMID: 25053326 DOI: 10.1063/1.4890035] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The effect of crystal growth conditions on the O K-edge x-ray absorption spectra of ice is investigated through detailed analysis of the spectral features. The amount of ice defects is found to be minimized on hydrophobic surfaces, such as BaF2(111), with low concentration of nucleation centers. This is manifested through a reduction of the absorption cross-section at 535 eV, which is associated with distorted hydrogen bonds. Furthermore, a connection is made between the observed increase in spectral intensity between 544 and 548 eV and high-symmetry points in the electronic band structure, suggesting a more extended hydrogen-bond network as compared to ices prepared differently. The spectral differences for various ice preparations are compared to the temperature dependence of spectra of liquid water upon supercooling. A double-peak feature in the absorption cross-section between 540 and 543 eV is identified as a characteristic of the crystalline phase. The connection to the interpretation of the liquid phase O K-edge x-ray absorption spectrum is extensively discussed.
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Xin H, LaRue J, Öberg H, Beye M, Dell'Angela M, Turner JJ, Gladh J, Ng ML, Sellberg JA, Kaya S, Mercurio G, Hieke F, Nordlund D, Schlotter WF, Dakovski GL, Minitti MP, Föhlisch A, Wolf M, Wurth W, Ogasawara H, Nørskov JK, Öström H, Pettersson LGM, Nilsson A, Abild-Pedersen F. Strong Influence of Coadsorbate Interaction on CO Desorption Dynamics on Ru(0001) Probed by Ultrafast X-Ray Spectroscopy and Ab Initio Simulations. PHYSICAL REVIEW LETTERS 2015; 114:156101. [PMID: 25933322 DOI: 10.1103/physrevlett.114.156101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Indexed: 06/04/2023]
Abstract
We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5σ and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
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Dell'Angela M, Anniyev T, Beye M, Coffee R, Föhlisch A, Gladh J, Kaya S, Katayama T, Krupin O, Nilsson A, Nordlund D, Schlotter WF, Sellberg JA, Sorgenfrei F, Turner JJ, Öström H, Ogasawara H, Wolf M, Wurth W. Vacuum space charge effects in sub-picosecond soft X-ray photoemission on a molecular adsorbate layer. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2015; 2:025101. [PMID: 26798795 PMCID: PMC4711610 DOI: 10.1063/1.4914892] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 03/03/2015] [Indexed: 06/05/2023]
Abstract
Vacuum space charge induced kinetic energy shifts of O 1s and Ru 3d core levels in femtosecond soft X-ray photoemission spectra (PES) have been studied at a free electron laser (FEL) for an oxygen layer on Ru(0001). We fully reproduced the measurements by simulating the in-vacuum expansion of the photoelectrons and demonstrate the space charge contribution of the high-order harmonics in the FEL beam. Employing the same analysis for 400 nm pump-X-ray probe PES, we can disentangle the delay dependent Ru 3d energy shifts into effects induced by space charge and by lattice heating from the femtosecond pump pulse.
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Öström H, Öberg H, Xin H, LaRue J, Beye M, Dell’Angela M, Gladh J, Ng ML, Sellberg JA, Kaya S, Mercurio G, Nordlund D, Hantschmann M, Hieke F, Kühn D, Schlotter WF, Dakovski GL, Turner JJ, Minitti MP, Mitra A, Moeller SP, Föhlisch A, Wolf M, Wurth W, Persson M, Nørskov JK, Abild-Pedersen F, Ogasawara H, Pettersson LGM, Nilsson A. Probing the transition state region in catalytic CO oxidation on Ru. Science 2015; 347:978-82. [DOI: 10.1126/science.1261747] [Citation(s) in RCA: 152] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Sellberg JA, McQueen TA, Laksmono H, Schreck S, Beye M, DePonte DP, Kennedy B, Nordlund D, Sierra RG, Schlesinger D, Tokushima T, Zhovtobriukh I, Eckert S, Segtnan VH, Ogasawara H, Kubicek K, Techert S, Bergmann U, Dakovski GL, Schlotter WF, Harada Y, Bogan MJ, Wernet P, Föhlisch A, Pettersson LGM, Nilsson A. X-ray emission spectroscopy of bulk liquid water in “no-man’s land”. J Chem Phys 2015; 142:044505. [DOI: 10.1063/1.4905603] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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39
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Malacrida P, Sanchez Casalongue HG, Masini F, Kaya S, Hernández-Fernández P, Deiana D, Ogasawara H, Stephens IEL, Nilsson A, Chorkendorff I. Direct observation of the dealloying process of a platinum–yttrium nanoparticle fuel cell cathode and its oxygenated species during the oxygen reduction reaction. Phys Chem Chem Phys 2015; 17:28121-8. [DOI: 10.1039/c5cp00283d] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Size-selected 9 nm PtxY nanoparticles have recently shown an outstanding catalytic activity for the oxygen reduction reaction, representing a promising cathode catalyst for proton exchange membrane fuel cells (PEMFCs).
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40
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Schreck S, Beye M, Sellberg JA, McQueen T, Laksmono H, Kennedy B, Eckert S, Schlesinger D, Nordlund D, Ogasawara H, Sierra RG, Segtnan VH, Kubicek K, Schlotter WF, Dakovski GL, Moeller SP, Bergmann U, Techert S, Pettersson LGM, Wernet P, Bogan MJ, Harada Y, Nilsson A, Föhlisch A. Reabsorption of soft x-ray emission at high x-ray free-electron laser fluences. PHYSICAL REVIEW LETTERS 2014; 113:153002. [PMID: 25375708 DOI: 10.1103/physrevlett.113.153002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Indexed: 05/24/2023]
Abstract
We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.
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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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Sanchez Casalongue HG, Ng ML, Kaya S, Friebel D, Ogasawara H, Nilsson A. In Situ Observation of Surface Species on Iridium Oxide Nanoparticles during the Oxygen Evolution Reaction. Angew Chem Int Ed Engl 2014; 53:7169-72. [DOI: 10.1002/anie.201402311] [Citation(s) in RCA: 316] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 03/27/2014] [Indexed: 11/07/2022]
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Sanchez Casalongue HG, Ng ML, Kaya S, Friebel D, Ogasawara H, Nilsson A. In Situ Observation of Surface Species on Iridium Oxide Nanoparticles during the Oxygen Evolution Reaction. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201402311] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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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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45
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Tokano Y, Ogasawara H, Ando S, Fujii T, Kaneko H, Tamura N, Yano T, Hirokawa K, Fukazawa T, Murashima A, Kobayashi S, Sekigawa I, Takasaki Y, Iida N, Hashimoto H. Cyclosporin A therapy for interstitial pneumonitis associated with rheumatic disease. Mod Rheumatol 2014; 12:305-10. [DOI: 10.3109/s101650200054] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Casalongue HS, Kaya S, Viswanathan V, Miller DJ, Friebel D, Hansen HA, Nørskov JK, Nilsson A, Ogasawara H. Direct observation of the oxygenated species during oxygen reduction on a platinum fuel cell cathode. Nat Commun 2013. [DOI: 10.1038/ncomms3817] [Citation(s) in RCA: 264] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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Rajasekaran S, Abild-Pedersen F, Ogasawara H, Nilsson A, Kaya S. Interlayer carbon bond formation induced by hydrogen adsorption in few-layer supported graphene. PHYSICAL REVIEW LETTERS 2013; 111:085503. [PMID: 24010453 DOI: 10.1103/physrevlett.111.085503] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Indexed: 05/11/2023]
Abstract
We report on the hydrogen adsorption induced phase transition of a few layer graphene (1 to 4 layers) to a diamondlike structure on Pt(111) based on core level x-ray spectroscopy, temperature programed desorption, infrared spectroscopy, and density functional theory total energy calculations. The surface adsorption of hydrogen induces a hybridization change of carbon from the sp2 to the sp3 bond symmetry, which propagates through the graphene layers, resulting in interlayer carbon bond formation. The structure is stabilized through the termination of interfacial sp3 carbon atoms by the substrate. The structural transformation occurs as a consequence of high adsorption energy.
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Schiros T, Andersson KJ, MacNaughton J, Gladh J, Matsuda A, Öström H, Takahashi O, Pettersson LGM, Nilsson A, Ogasawara H. Unique water-water coordination tailored by a metal surface. J Chem Phys 2013; 138:234708. [DOI: 10.1063/1.4809680] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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49
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Beye M, Anniyev T, Coffee R, Dell'Angela M, Föhlisch A, Gladh J, Katayama T, Kaya S, Krupin O, Møgelhøj A, Nilsson A, Nordlund D, Nørskov JK, Öberg H, Ogasawara H, Pettersson LGM, Schlotter WF, Sellberg JA, Sorgenfrei F, Turner JJ, Wolf M, Wurth W, Oström H. Selective ultrafast probing of transient hot chemisorbed and precursor states of CO on Ru(0001). PHYSICAL REVIEW LETTERS 2013; 110:186101. [PMID: 23683223 DOI: 10.1103/physrevlett.110.186101] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 04/03/2013] [Indexed: 05/19/2023]
Abstract
We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process.
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Kaya S, Ogasawara H, Näslund LÅ, Forsell JO, Casalongue HS, Miller DJ, Nilsson A. Ambient-pressure photoelectron spectroscopy for heterogeneous catalysis and electrochemistry. Catal Today 2013. [DOI: 10.1016/j.cattod.2012.08.005] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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