Sample records for fe ru os

  1. First-principle study of single TM atoms X (X=Fe, Ru or Os) doped monolayer WS2 systems

    NASA Astrophysics Data System (ADS)

    Zhu, Yuan-Yan; Zhang, Jian-Min

    2018-05-01

    We report the structural, magnetic and electronic properties of the pristine and single TM atoms X (X = Fe, Ru or Os) doped monolayer WS2 systems based on first-principle calculations. The results show that the W-S bond shows a stronger covalent bond, but the covalency is obviously weakened after the substitution of W atom with single X atoms, especially for Ru (4d75s1) with the easily lost electronic configuration. The smaller total energies of the doped systems reveal that the spin-polarized states are energetically favorable than the non-spin-polarized states, and the smallest total energy of -373.918 eV shows the spin-polarized state of the Os doped monolayer WS2 system is most stable among three doped systems. In addition, although the pristine monolayer WS2 system is a nonmagnetic-semiconductor with a direct band gap of 1.813 eV, single TM atoms Fe and Ru doped monolayer WS2 systems transfer to magnetic-HM with the total moments Mtot of 1.993 and 1.962 μB , while single TM atom Os doped monolayer WS2 systems changes to magnetic-metal with the total moments Mtot of 1.569 μB . Moreover, the impurity states with a positive spin splitting energies of 0.543, 0.276 and 0.1999 eV near the Fermi level EF are mainly contributed by X-dxy and X-dx2-y2 states hybridized with its nearest-neighbor atom W-dz2 states for Fe, Ru and Os doped monolayer WS2 system, respectively. Finally, we hope that the present study on monolayer WS2 will provide a useful theoretical guideline for exploring low-dimensional spintronic materials in future experiments.

  2. On the Highest Oxidation States of Metal Elements in MO4 Molecules (M = Fe, Ru, Os, Hs, Sm, and Pu).

    PubMed

    Huang, Wei; Xu, Wen-Hua; Schwarz, W H E; Li, Jun

    2016-05-02

    Metal tetraoxygen molecules (MO4, M = Fe, Ru, Os, Hs, Sm, Pu) of all metal atoms M with eight valence electrons are theoretically studied using density functional and correlated wave function approaches. The heavier d-block elements Ru, Os, Hs are confirmed to form stable tetraoxides of Td symmetry in (1)A1 electronic states with empty metal d(0) valence shell and closed-shell O(2-) ligands, while the 3d-, 4f-, and 5f-elements Fe, Sm, and Pu prefer partial occupation of their valence shells and peroxide or superoxide ligands at lower symmetry structures with various spin couplings. The different geometric and electronic structures and chemical bonding types of the six iso-stoichiometric species are explained in terms of atomic orbital energies and orbital radii. The variations found here contribute to our general understanding of the periodic trends of oxidation states across the periodic table.

  3. Electronic, structural and magnetic studies of niobium borides of group 8 transition metals, Nb2MB2 (M=Fe, Ru, Os) from first principles calculations

    NASA Astrophysics Data System (ADS)

    Touzani, Rachid St.; Fokwa, Boniface P. T.

    2014-03-01

    The Nb2FeB2 phase (U3Si2-type, space group P4/mbm, no. 127) is known for almost 50 years, but until now its magnetic properties have not been investigated. While the synthesis of Nb2OsB2 (space group P4/mnc, no. 128, a twofold superstructure of U3Si2-type) with distorted Nb-layers and Os2-dumbbells was recently achieved, "Nb2RuB2" is still not synthesized and its crystal structure is yet to be revealed. Our first principles density functional theory (DFT) calculations have confirmed not only the experimental structures of Nb2FeB2 and Nb2OsB2, but also predict "Nb2RuB2" to crystalize with the Nb2OsB2 structure type. According to chemical bonding analysis, the homoatomic B-B interactions are optimized and very strong, but relatively strong heteroatomic M-B, B-Nb and M-Nb bonds (M=Fe, Ru, Os) are also found. These interactions, which together build a three-dimensional network, are mainly responsible for the structural stability of these ternary borides. The density-of-states at the Fermi level predicts metallic behavior, as expected, from metal-rich borides. Analysis of possible magnetic structures concluded preferred antiferromagnetic ordering for Nb2FeB2, originating from ferromagnetic interactions within iron chains and antiferromagnetic exchange interactions between them.

  4. Muon-spin-relaxation and inelastic neutron scattering investigations of the caged-type Kondo semimetals: CeT2Al10 (T = Fe, Ru and Os)

    NASA Astrophysics Data System (ADS)

    Adroja, D. T.; Hillier, A. D.; Muro, Y.; Takabatake, T.; Strydom, A. M.; Bhattacharyya, A.; Daoud-Aladin, A.; Taylor, J. W.

    2013-12-01

    Recently, Ce-based caged-type compounds with the general formula CeT2Al10 (T = Fe, Ru and Os) have generated considerable interest due to the Kondo semiconducting paramagnetic ground state (down to 40 mK) observed in CeFe2Al10 and anomalously high magnetic ordering temperature with spin gap formation at low temperatures in Kondo semimetals CeRu2Al10 and CeOs2Al10. The formation of long-range magnetic ordering out of the Kondo semiconducting/semimetallic state itself is extraordinary and these are the first examples of this enigmatic coexistence of electronic ground states. These compounds also exhibit strong anisotropy in magnetic and transport properties, which has been explained on the basis of single-ion crystal electric field anisotropy in the presence of strongly anisotropic hybridization between localized 4f-electron and conduction electrons. Furthermore, they also exhibit a remarkable modification of magnetic and transport properties with doping on Ce, or T or Al sites. In this article, we briefly discuss the bulk properties of these compounds, giving a detailed discussion on our muon-spin-relaxation (μSR) investigations and inelastic neutron scattering (INS) results. We present the μSR and the INS results of Ce(Ru1-xFex)2Al10 and CeOs2Al10 as well as the μSR results of NdFe2Al10, NdOs2Al10 and YFe2Al10 for comparison. The zero-field μSR spectra clearly reveal coherent two-frequency oscillations at low temperatures in CeT2Al10 (T = Ru and Os) and Ce(Ru1-xFex)2Al10 (x = 0.3-0.5), which confirms the long-range magnetic ordering with a reduced moment of the Ce. On the other hand, the μSR spectra of Ce(Ru1-xFex)2Al10 (x = 0.8 and 1) down to 1.2 and 0.04 K, respectively, exhibit a temperature independent Kubo-Toyabe (KT) term confirming a paramagnetic ground state. INS measurements on CeT2Al10 (T = Ru and Os) exhibit sharp inelastic excitations at 8 and 11 meV at 5 K due to an opening of a gap in the spin excitation spectrum. A spin gap of 8-12 meV at 7 K

  5. Ruthenium nano-oxide layer in CoFe-Ru-CoFe trilayer system: An x-ray reflectivity study

    NASA Astrophysics Data System (ADS)

    Asgharizadeh, S.; Sutton, M.; Altounian, Z.; Mao, M.; Lee, C. L.

    2008-05-01

    A grazing incidence x-ray reflectivity technique is used to determine the electron density profile as a function of depth in CoFe-Ru-CoFe and CoFe-Ru nano-oxide layer (NOL)-CoFe trilayers. Four trilayers with ruthenium thicknesses of 8, 8.5, and 9Å and one with Ru 8.5Å NOL, prepared by a dc planetary sputtering system, were investigated. For all samples, the electron density profile (EDP) shows a central peak that is related to the Ru layer. Natural oxidation in all of the samples introduces a graded EDP of the top CoFe layers, which decreases gradually to zero. The large surface resistivity of Ru 8.5Å NOL as compared to Ru 8.5Å is related to the remarkable difference between their EDPs. EDP changes have also been investigated in Ru NOL trilayers after annealing at 280°C. The Ru phase in the EDP was observed to confirm the thermal stability of the spacer layer after annealing.

  6. X-ray reflectivity of ruthenium nano-oxide layer in a CoFe-Ru-CoFe trilayer system

    NASA Astrophysics Data System (ADS)

    Asghari Zadeh, Saeid; Sutton, Mark; Altonian, Zaven; Mao, Ming; Lee, Chih-Ling

    2006-03-01

    A grazing incidence X-ray reflectivity technique is used to determine electron density profile(EDP) as a function of depth in CoFe-Ru-CoFe and CoFe-Ru nano oxide layer(NOL)-CoFe trilayers. Four trilayers with ruthenium thicknesses of 8,8.5 and 9 å.08cm and one with Ru8.5.05cmå.05cmNOL, prepared by a dc planetary sputtering system, were investigated. For all samples, EDP shows a central peak which is related to the Ru layer. Natural oxidation in all samples introduces a graded EDP of the top CoFe layer that decreases gradually to zero. The large surface resistivity of Ru8.5 å.05cm NOL compared to Ru 8.5å.08cm can be related to the remarkable difference between their EDP.

  7. Study the Polyol Process of Preparing the ru Doped FePt Nanoparticles

    NASA Astrophysics Data System (ADS)

    Lee, Chih-Hao; Hsu, Jen-Ho; Su, Hui-Chia; Huang, Tzu Wen

    The structure of Ru doped FePt nanoparticles using polyol process was studied. The particle size grown is around 5 nm, and a shell structure might be formed. By selecting the time and temperature of adding the Ru precursors into solution, three different processes to synthesize the FePtRu particles were studied resulting in different growing mechanics. The possible models during the reaction process are also discussed. The phase transition temperature for the as-grown FCC FePt nanoparticle to transform into L10 FePt nanoparticle is about 823 K which is about the same as the one without doping Ru atoms. From the XAS study of each element, the possible scenario is that: although Ru atoms with the size close to the Pt, they do not totally replace the Pt sites in the FePt alloy. Instead, most of Ru formed a shell outside the FePt nanoparticles and Fe atoms are replaced.

  8. Electronic structure of Fe- vs. Ru-based dye molecules

    NASA Astrophysics Data System (ADS)

    Johnson, Phillip S.; Cook, Peter L.; Zegkinoglou, Ioannis; García-Lastra, J. M.; Rubio, Angel; Ruther, Rose E.; Hamers, Robert J.; Himpsel, F. J.

    2013-01-01

    In order to explore whether Ru can be replaced by inexpensive Fe in dye molecules for solar cells, the differences in the electronic structure of Fe- and Ru-based dyes are investigated by X-ray absorption spectroscopy and first-principles calculations. Molecules with the metal in a sixfold, octahedral N cage, such as tris(bipyridines) and tris(phenanthrolines), exhibit a systematic downward shift of the N 1s-to-π* transition when Ru is replaced by Fe. This shift is explained by an extra transfer of negative charge from the metal to the N ligands in the case of Fe, which reduces the binding energy of the N 1s core level. The C 1s-to-π* transitions show the opposite trend, with an increase in the transition energy when replacing Ru by Fe. Molecules with the metal in a fourfold, planar N cage (porphyrins) exhibit a more complex behavior due to a subtle competition between the crystal field, axial ligands, and the 2+ vs. 3+ oxidation states.

  9. Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

    1989-01-01

    Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

  10. Electrochemical and surface analysis of the Fe-Cr-Ru system in non-oxidizing acid solutions

    NASA Astrophysics Data System (ADS)

    Tjong, S. C.

    1990-03-01

    The effect of ruthenium addition on the spontaneous passivation behaviour of Fe-40Cr alloy in 0.5M H 2SO 4 and 0.5M HCl acid solutions has been studied. Auger and XPS techniques were also used to investigate the surface chemistries of the spontaneously passivated film. Electrochemical measurements indicate that the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys exhibit spontaneous passivation upon exposing them in both hydrochloric and sulphuric acid solutions from 25 to 85 ° C. However, the transition time for spontaneous passivation reduces dramatically with an increase in the ruthenium content and solution temperature. Furthermore, this transition time also decreases for the investigated alloys exposed in a less aggressive sulphuric acid solution. AES results show that ruthenium and chromium are enriched in the spontaneous passive films formed on the Fe-40Cr-0.1Ru alloy in both hydrochloric and sulphuric acid solutions at 25 °C, and also in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in hydrochloric acid solution at 25 ° C. AES does not detect the presence of ruthenium in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in sulphuric acid solution. However, XPS analysis shows that ruthenium and chromium are incorporated into the spontaneous passive films formed on the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys in both hydrochloric and sulphuric acid solutions as Ru 4+ and Cr 3+ species.

  11. Electrochemical, spectroscopic, and photophysical properties of structurally diverse polyazine-bridged Ru(II),Pt(II) and Os(II),Ru(II),Pt(II) supramolecular motifs.

    PubMed

    Knoll, Jessica D; Arachchige, Shamindri M; Wang, Guangbin; Rangan, Krishnan; Miao, Ran; Higgins, Samantha L H; Okyere, Benjamin; Zhao, Meihua; Croasdale, Paul; Magruder, Katherine; Sinclair, Brian; Wall, Candace; Brewer, Karen J

    2011-09-19

    Five new tetrametallic supramolecules of the motif [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) and three new trimetallic light absorbers [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) (TL = bpy = 2,2'-bipyridine or phen = 1,10-phenanthroline; M = Ru(II) or Os(II); BL = dpp = 2,3-bis(2-pyridyl)pyrazine, dpq = 2,3-bis(2-pyridyl)quinoxaline, or bpm = 2,2'-bipyrimidine) were synthesized and their redox, spectroscopic, and photophysical properties investigated. The tetrametallic complexes couple a Pt(II)-based reactive metal center to Ru and/or Os light absorbers through two different polyazine BL to provide structural diversity and interesting resultant properties. The redox potential of the M(II/III) couple is modulated by M variation, with the terminal Ru(II/III) occurring at 1.58-1.61 V and terminal Os(II/III) couples at 1.07-1.18 V versus Ag/AgCl. [{(TL)(2)M(dpp)}(2)Ru(BL)](PF(6))(6) display terminal M(dπ)-based highest occupied molecular orbitals (HOMOs) with the dpp(π*)-based lowest unoccupied molecular orbital (LUMO) energy relatively unaffected by the nature of BL. The coupling of Pt to the BL results in orbital inversion with localization of the LUMO on the remote BL in the tetrametallic complexes, providing a lowest energy charge separated (CS) state with an oxidized terminal Ru or Os and spatially separated reduced BL. The complexes [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) and [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) efficiently absorb light throughout the UV and visible regions with intense metal-to-ligand charge transfer (MLCT) transitions in the visible at about 540 nm (M = Ru) and 560 nm (M = Os) (ε ≈ 33,000-42,000 M(-1) cm(-1)) and direct excitation to the spin-forbidden (3)MLCT excited state in the Os complexes about 720 nm. All the trimetallic and tetrametallic Ru-based supramolecular systems emit from the terminal Ru(dπ)→dpp(π*) (3)MLCT state, λ(max)(em) ≈ 750 nm. The tetrametallic systems display complex excited state dynamics with quenching of the (3)MLCT emission at

  12. Spin-orbit torque in Cr/CoFeAl/MgO and Ru/CoFeAl/MgO epitaxial magnetic heterostructures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wen, Zhenchao; Kim, Junyeon; Sukegawa, Hiroaki

    2016-05-15

    We study the spin-orbit torque (SOT) effective fields in Cr/CoFeAl/MgO and Ru/CoFeAl/MgO magnetic heterostructures using the adiabatic harmonic Hall measurement. High-quality perpendicular-magnetic-anisotropy CoFeAl layers were grown on Cr and Ru layers. The magnitudes of the SOT effective fields were found to significantly depend on the underlayer material (Cr or Ru) as well as their thicknesses. The damping-like longitudinal effective field (ΔH{sub L}) increases with increasing underlayer thickness for all heterostructures. In contrast, the field-like transverse effective field (ΔH{sub T}) increases with increasing Ru thickness while it is almost constant or slightly decreases with increasing Cr thickness. The sign of ΔH{submore » L} observed in the Cr-underlayer devices is opposite from that in the Ru-underlayer devices while ΔH{sub T} shows the same sign with a small magnitude. The opposite directions of ΔH{sub L} indicate that the signs of spin Hall angle in Cr and Ru are opposite, which are in good agreement with theoretical predictions. These results show sizable contribution from SOT even for elements with small spin orbit coupling such as 3d Cr and 4d Ru.« less

  13. Electronic and elastic properties of new semiconducting oP(12)-type RuB(2) and OsB(2).

    PubMed

    Hao, Xianfeng; Xu, Yuanhui; Gao, Faming

    2011-03-30

    Using first-principles total energy calculations we investigate the structural, elastic and electronic properties of new hypothetical oP(12)-type phase RuB(2) and OsB(2). The calculations indicate that the oP(12)-type phase RuB(2) and OsB(2) are thermodynamically and mechanically stable. Remarkably, the new phases RuB(2) and OsB(2) are predicted to be semiconductors, and the appearance of band gaps is ascribed to the enhanced B-B covalent hybridization. Compared to metallic oP(6)-type RuB(2) and OsB(2) phases, the new phases possess similar mechanical properties and hardness. The combination of the probability of tunable electronic properties, strong stiffness and high hardness make RuB(2) and OsB(2) attractive and interesting for advanced applications. © 2011 IOP Publishing Ltd

  14. Modifying exchange-spring behavior of CoPt/NiFe bilayer by inserting a Pt or Ru spacer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw; Tsai, C. L.; Lee, C.-M.

    2015-05-07

    We herein explore the possibility of obtaining tunable tilted magnetic anisotropy in ordered-CoPt (5 nm)/NiFe(t{sub NiFe}) bilayers through modifying their exchange spring behavior by inserting Pt and Ru-spacers. The tuning process of tilt angle magnetization of NiFe-layer was systematically investigated by varying the Pt or Ru thickness (t{sub Pt} or t{sub Ru}) from 0 to 8 nm at different thicknesses of NiFe (t{sub NiFe} = 1.5, 4.0, and 6.0 nm). Polar magneto-optic Kerr effect (p-MOKE) studies reveal that the bilayers grown in absence of spacers exhibit almost a rectangular hysteresis loop. With the insertion of Pt-spacer, the loop becomes more and more tilted as t{submore » Pt} increases; whereas, in the case of Ru-spacer, the nature of the loops is not simply changing in one direction. The estimated SQR{sub ⊥} (= θ{sub r}/θ{sub s}) values from the p-MOKE loops are found to monotonically decrease with increasing t{sub Pt} when t{sub Pt} ≦ 4 nm. In contrast, in the case of Ru-spacer, an oscillatory behavior for the SQR{sub ⊥} values is apparent when t{sub Ru} ≦ 4 nm. As a result, an oscillatory tilted angle of NiFe spin configuration was obtained in the case of Ru-spacer; while a decoupling effect was prominent for the Pt-spacer. The results of present study reveal that the insertion of Pt and Ru-spacers as an appropriate means for realizing tunable tilted magnetic anisotropy in the CoPt/NiFe exchange springs.« less

  15. Lattice dynamics of Ru2FeX (X = Si, Ge) Full Heusler alloys

    NASA Astrophysics Data System (ADS)

    Rizwan, M.; Afaq, A.; Aneeza, A.

    2018-05-01

    In present work, the lattice dynamics of Ru2FeX (X = Si, Ge) full Heusler alloys are investigated using density functional theory (DFT) within generalized gradient approximation (GGA) in a plane wave basis, with norm-conserving pseudopotentials. Phonon dispersion curves and phonon density of states are obtained using first-principles linear response approach of density functional perturbation theory (DFPT) as implemented in Quantum ESPRESSO code. Phonon dispersion curves indicates for both Heusler alloys that there is no imaginary phonon in whole Brillouin zone, confirming dynamical stability of these alloys in L21 type structure. There is a considerable overlapping between acoustic and optical phonon modes predicting no phonon band gap exists in dispersion curves of alloys. The same result is shown by phonon density of states curves for both Heusler alloys. Reststrahlen band for Ru2FeSi is found smaller than Ru2FeGe.

  16. The role of the [CpM(CO)2](-) chromophore in the optical properties of the [Cp2ThMCp(CO)2](+) complexes, where M = Fe, Ru and Os. A theoretical view.

    PubMed

    Cantero-López, Plinio; Le Bras, Laura; Páez-Hernández, Dayán; Arratia-Pérez, Ramiro

    2015-12-14

    The chemical bond between actinide and the transition metal unsupported by bridging ligands is not well characterized. In this paper we study the electronic properties, bonding nature and optical spectra in a family of [Cp2ThMCp(CO)2](+) complexes where M = Fe, Ru, Os, based on the relativistic two component density functional theory calculations. The Morokuma-Ziegler energy decomposition analysis shows an important ionic contribution in the Th-M interaction with around 25% of covalent character. Clearly, charge transfer occurs on Th-M bond formation, however the orbital term most likely represents a strong charge rearrangement in the fragments due to the interaction. Finally the spin-orbit-ZORA calculation shows the possible NIR emission induced by the [FeCp(CO)2](-) chromophore accomplishing the antenna effect that justifies the sensitization of the actinide complexes.

  17. Structural, electronic, elastic, thermoelectric and thermodynamic properties of the NbMSb half heusler (M=Fe, Ru, Os) compounds with first principle calculations

    NASA Astrophysics Data System (ADS)

    Abid, O. Miloud; Menouer, S.; Yakoubi, A.; Khachai, H.; Omran, S. Bin; Murtaza, G.; Prakash, Deo; Khenata, R.; Verma, K. D.

    2016-05-01

    The structural, electronic, elastic, thermoelectric and thermodynamic properties of NbMSb (M = Fe, Ru, Os) half heusler compounds are reported. The full-potential linearized augmented plane wave (FP-LAPW) plus local orbital (lo) method, based on the density functional theory (DFT) was employed for the present study. The equilibrium lattice parameter results are in good compliance with the available experimental measurements. The electronic band structure and Boltzmann transport calculations indicated a narrow indirect energy band gap for the compound having electronic structure favorable for thermoelectric performance as well as with substantial thermopowers at temperature ranges from 300 K to 800 K. Furthermore, good potential for thermoelectric performance (thermopower S ≥ 500 μeV) was found at higher temperature. In addition, the analysis of the charge density, partial and total densities of states (DOS) of three compounds demonstrate their semiconducting, ionic and covalent characters. Conversely, the calculated values of the Poisson's ratio and the B/G ratio indicate their ductile makeup. The thermal properties of the compounds were calculated by quasi-harmonic Debye model as implemented in the GIBBS code.

  18. Ordered vs. disordered perovskites; structural studies of Fe-doped SrIrO{sub 3} and SrRuO{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Qasim, Ilyas; Blanchard, Peter E.R.; Liu, Samuel

    2013-10-15

    The structures of the two Fe containing perovskites Sr{sub 2}IrFeO{sub 6} and SrRu{sub 0.5}Fe{sub 0.5}O{sub 3} have been established using a combination of synchrotron and neutron diffraction methods. Sr{sub 2}IrFeO{sub 6} and SrRu{sub 0.5}Fe{sub 0.5}O{sub 3} are shown to be monoclinic I2/m and tetragonal I4/mcm respectively The former exhibits a rock-salt like ordering of the Fe and Ir cations and displays a sequence of phase transitions associated with the loss of the octahedral tilts upon heating; 12/m→I4/m→Fm3{sup ¯}m. The Fe and Ru cations are disordered in SrRu{sub 0.5}Fe{sub 0.5}O{sub 3} and this shows a single structural phase transition upon heatingmore » due to the loss of the in-phase tilts, viz. I4/mcm→Pm3{sup ¯}m. In both cases XANES measurements show partial oxidation of the Fe{sup 3+} to Fe{sup 4+}. The difference in the structures between the two is remarkable given the similar size of Ir{sup 5+} and Ru{sup 5+}, and this is reflected in their magnetic properties. - Graphical abstract: Sr{sub 2}IrFeO{sub 6} and SrRu{sub 0.5}Fe{sub 0.5}O{sub 3} are shown, using a combination of synchrotron and neutron diffraction, to be monoclinic I2/m with cation ordering and tetragonal I4/mcm with disordered Fe and Ir, respectively. Both undergo phase transitions upon heating due to the loss of the octahedral tilts. Display Omitted - Highlights: • Sr{sub 2}IrFeO{sub 6} shown to be monoclinic and shows the transitions upon heating I2/m→I4/m→ Fm3{sup ¯}m. • SrRu{sub 0.5}Fe{sub 0.5}O{sub 3} is tetragonal and shows a single I4/mcm→Pm3m transition upon heating. • The Fe and Ru cations are disordered in SrRu{sub 0.5}Fe{sub 0.5}O{sub 3} but ordered in Sr{sub 2}FeIrO{sub 6}. • XANES measurements show partial oxidation of the Fe{sup 3+} to Fe{sup 4+}.« less

  19. Penta- and tetracarbonyls of Ru, Os, and Hs: Electronic structure, bonding, and volatility

    NASA Astrophysics Data System (ADS)

    Pershina, V.; Iliaš, M.

    2017-05-01

    Calculations of the electronic structures and properties of M(CO)5 and M(CO)4, where M = Ru, Os, and Hs, have been performed using a variety of relativistic methods such as density functional theory and Dirac-Coulomb correlated ones implemented in program packages such as ADF, DIRAC, and ReSpect. The obtained results show that trends in spectroscopic properties of the M(CO)5 species in group 8 follow the same pattern as that of other compounds of group 4 through group 8 elements. The calculated first M-CO bond dissociation energy (FBDE) of Hs(CO)5 turned out to be significantly weaker than that of Os(CO)5. This was obtained both at the scalar relativistic and spin-orbit levels of theory. The reason for that is the relativistic destabilization and the expansion of the 6d AOs, responsible for weaker σ-forth and π-back donations in the Hs compound. Thus, the FBDEs of M(CO)5 have a Λ-shape behavior in the row Ru-Os-Hs. The non-relativistic FBDEs steadily increase in this row. Using the results of the molecular calculations and a molecule-slab dispersion interaction model, the volatility of the group-8 carbonyls was estimated as adsorption enthalpies, ΔHads, on surfaces of quartz and Teflon used in gas-phase chromatography experiments. It was found that Hs(CO)5 should be almost as volatile as the homologs; however, its interaction strength with these surfaces should be somewhat larger than that of both Ru(CO)5 and Os(CO)5, while the M(CO)4 (M = Ru, Os, and Hs) molecules should be non-volatile. It will, therefore, be difficult to distinguish between group-8 M(CO)5 species by measurements of their volatility as ΔHads on inert surfaces with error bars of ˜4 kJ/mol.

  20. Ionic Liquid Gating Control of RKKY Interaction in FeCoB/Ru/FeCoB and (Pt/Co) 2/Ru/(Co/Pt) 2 Multilayers.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Qu; Wang, Lei; Zhou, Ziyao

    To overcome the fundamental challenge of the weak natural response of antiferromagnetic materials under a magnetic field, voltage manipulation of antiferromagnetic interaction is developed to realize ultrafast, high-density, and power efficient antiferromagnetic spintronics. Here, we report a low voltage modulation of Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction via ionic liquid gating in synthetic antiferromagnetic multilayers of FeCoB/Ru/FeCoB and (Pt/Co) 2/Ru/(Co/Pt) 2. At room temperature, the distinct voltage control of transition between antiferromagnetic and ferromagnetic ordering is realized and up to 80% of perpendicular magnetic moments manage to switch with a small-applied voltage bias of 2.5 V. We related this ionic liquid gating-induced RKKYmore » interaction modification to the disturbance of itinerant electrons inside synthetic antiferromagnetic heterostructure and the corresponding change of its Fermi level. Voltage tuning of RKKY interaction may enable the next generation of switchable spintronics between antiferromagnetic and ferromagnetic modes with both fundamental and practical perspectives.« less

  1. Syntheses, structures and redox properties of some complexes containing the Os(dppe)Cp* fragment, including [{Os(dppe)Cp*}2(mu-C triple bondCC triple bond C)].

    PubMed

    Bruce, Michael I; Costuas, Karine; Davin, Thomas; Halet, Jean-François; Kramarczuk, Kathy A; Low, Paul J; Nicholson, Brian K; Perkins, Gary J; Roberts, Rachel L; Skelton, Brian W; Smith, Mark E; White, Allan H

    2007-12-14

    The sequential conversion of [OsBr(cod)Cp*] (9) to [OsBr(dppe)Cp*] (10), [Os([=C=CH2)(dppe)Cp*]PF6 ([11]PF6), [Os(C triple bond CH)(dppe)Cp*] (12), [{Os(dppe)Cp*}2{mu-(=C=CH-CH=C=)}][PF6]2 ([13](PF6)2) and finally [{Os(dppe)Cp*}(2)(mu-C triple bond CC triple bond C)] (14) has been used to make the third member of the triad [{M(dppe)Cp*}2(mu-C triple bond CC triple bond C)] (M = Fe, Ru, Os). The molecular structures of []PF6, 12 and 14, together with those of the related osmium complexes [Os(NCMe)(dppe)Cp*]PF6 ([15]PF6) and [Os(C triple bond CPh)(dppe)Cp*] (16), have been determined by single-crystal X-ray diffraction studies. Comparison of the redox properties of 14 with those of its iron and ruthenium congeners shows that the first oxidation potential E1 varies as: Fe approximately Os < Ru. Whereas the Fe complex has been shown to undergo three sequential 1-electron oxidation processes within conventional electrochemical solvent windows, the Ru and Os compounds undergo no fewer than four sequential oxidation events giving rise to a five-membered series of redox related complexes [{M(dppe)Cp*}2(mu-C4)]n+ (n = 0, 1, 2, 3 and 4), the osmium derivatives being obtained at considerably lower potentials than the ruthenium analogues. These results are complimented by DFT and DT DFT calculations.

  2. Non-Fermi surface nesting driven commensurate magnetic ordering in Fe-doped S r 2 Ru O 4

    DOE PAGES

    Zhu, M.; Shanavas, K. V.; Wang, Y.; ...

    2017-02-10

    Sr 2RuO 4, an unconventional superconductor, is known to possess an incommensurate spin-density wave instability driven by Fermi surface nesting. Here we report a static spin-density wave ordering with a commensurate propagation vector q c = (0.250.250) in Fe-doped Sr 2RuO 4, despite the magnetic fluctuations persisting at the incommensurate wave vectors q ic = (0.30.3L) as in the parent compound. The latter feature is corroborated by the first-principles calculations, which show that Fe substitution barely changes the nesting vector of the Fermi surface. Finally, these results suggest that in addition to the known incommensurate magnetic instability, Sr 2RuO 4more » is also in proximity to a commensurate magnetic tendency that can be stabilized via Fe doping.« less

  3. Electronic energy transfer in bimetallic Ru-Os complexes containing the 3,5-bis(pyridin-2-yl)-1,2,4-triazolate bridging ligand

    NASA Astrophysics Data System (ADS)

    De Cola, Luisa; Barigelletti, Francesco; Balzani, Vincenzo; Hage, Ronald; Haasnoot, Jaap G.; Reedijk, Jan; Vos, Johannes G.

    1991-04-01

    The luminescence and photochemical properties of the two isomeric heterobimetallic [(bpy) 2Ru(bpt)Os(bpy) 2] 3+ and [(bpy) 2Os(bpt)Ru(bpy) 2] 3+ complexes have been investigated (bpy=2,2'-pyridine; bpt -=3,5-bis(pyridin-2-yl)-1,2,4-triazolate ion). The properties of the two isomeric compounds are compared with those of the corresponding dinuclear homometallic inert and exhibit luminescence only from the Os-based component. Excitation in the Ru-based component is followed by ≈ 100% efficient energy transfer to the Os-based component. The energy-transfer mechanism is briefly discussed. The one-electron oxidation products (which contain Os in the 3+ oxidation state) are not luminescent because of the presence of a low-energy intervalence transfer level.

  4. Site preference, magnetism and lattice vibrations of intermetallics Lu₂Fe 17–xT x (T=Cr, Mn, Ru)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Jin-Chun; Qian, Ping, E-mail: qianpinghu@sohu.com; Zhang, Zhen-Feng

    We present an atomistic study on the phase stability, site preference and lattice constants of the rare earth intermetallics Lu₂Fe 17–xT x (T=Cr, Mn, Ru). The calculated preferential occupation site of ternary element T is found to be the 4f site. The order of site preference is given as 4f, 12k, 12j and 6g for Lu₂Fe 17–xT x. The calculated lattice parameters are corresponding to the experimental results. We have calculated the magnetic moments of Lu₂Fe 17–xT x compounds. Results show that the calculated total magnetic moment of Lu₂Fe₁₇ compound is M=37.34 μ B/f.u. In addition, the total and partialmore » phonon densities of states are evaluated first for these complicated structures. - Graphical abstract: The vibrational modes are mostly excited by Fe atoms, Lu contributes to the lower frequencies modes, and the contribution of Ru atoms is the same as Fe atoms. Highlights: • There are no reports on lattice vibrations of Lu₂(Fe, T) 17–x (T=Cr, Mn, Ru) compounds. • The phase stability and site preference are evaluated first for the complex structures of Lu₂(Fe, T) 17–x (T=Cr, Mn, Ru) compounds. • The lattice inversion method to obtain the interatomic pair potential is the unique one.« less

  5. Structural, electronic, magnetic, half-metallic, mechanical, and thermodynamic properties of the quaternary Heusler compound FeCrRuSi: A first-principles study.

    PubMed

    Wang, Xiaotian; Khachai, Houari; Khenata, Rabah; Yuan, Hongkuan; Wang, Liying; Wang, Wenhong; Bouhemadou, Abdelmadjid; Hao, Liyu; Dai, Xuefang; Guo, Ruikang; Liu, Guodong; Cheng, Zhenxiang

    2017-11-23

    In this paper, we have investigated the structural, electronic, magnetic, half-metallic, mechanical, and thermodynamic properties of the equiatomic quaternary Heusler (EQH) compound FeCrRuSi using the density functional theory (DFT) and the quasi-harmonic Debye model. Our results reveal that FeCrRuSi is a half-metallic material (HMM) with a total magnetic moment of 2.0 μ B in agreement with the well-known Slater-Pauling rule M t  = Z t  - 24. Furthermore, the origin of the half-metallic band gap in FeCrRuSi is well studied through a schematic diagram of the possible d-d hybridization between Fe, Cr and Ru elements. The half-metallic behavior of FeCrRuSi can be maintained in a relatively wide range of variations of the lattice constant (5.5-5.8 Å) under uniform strain and the c/a ratio (0.96-1.05) under tetragonal distortion. The calculated phonon dispersion, cohesive and formation energies, and mechanical properties reveal that FeCrRuSi is stable with an EQH structure. Importantly, the compound of interest has been prepared and is found to exist in an EQH type structure with the presence of some B2 disorder. Moreover, the thermodynamic properties, such as the thermal expansion coefficient α, the heat capacity C V , the Grüneisen constant γ, and the Debye temperature Θ D are calculated.

  6. First-principles investigation of competing magnetic interactions in (Mn ,Fe )Ru2Sn Heusler solid solutions

    NASA Astrophysics Data System (ADS)

    Decolvenaere, Elizabeth; Gordon, Michael; Seshadri, Ram; Van der Ven, Anton

    2017-10-01

    Many Heusler compounds possess magnetic properties well suited for applications as spintronic materials. The pseudobinary Mn0.5Fe0.5Ru2Sn , formed as a solid solution of two full Heuslers, has recently been shown to exhibit exchange hardening suggestive of two magnetic phases, despite existing as a single chemical phase. We have performed a first-principles study of the chemical and magnetic degrees of freedom in the Mn1 -xFexRu2Sn pseudobinary to determine the origin of the unique magnetic behavior responsible for exchange hardening within a single phase. We find a transition from antiferromagnetic (AFM) to ferromagnetic (FM) behavior upon replacement of Mn with Fe, consistent with experimental results. The lowest energy orderings in Mn1 -xFexRu2Sn consist of chemically and magnetically uniform (111) planes, with Fe-rich regions preferring FM ordering and Mn-rich regions preferring AFM ordering, independent of the overall composition. Analysis of the electronic structure suggests that the magnetic behavior of this alloy arises from a competition between AFM-favoring Sn-mediated superexchange and FM-favoring RKKY exchange mediated by spin-polarized conduction electrons. Changes in valency upon replacement of Mn with Fe shifts the balance from superexchange-dominated interactions to RKKY-dominated interactions.

  7. Metal-insulator transition in Ba3Fe1 -xRu2 +xO9 : Interplay between site disorder, chemical percolation, and electronic structure

    NASA Astrophysics Data System (ADS)

    Middey, S.; Aich, Payel; Meneghini, C.; Mukherjee, K.; Sampathkumaran, E. V.; Siruguri, V.; Mahadevan, P.; Ray, Sugata

    2016-11-01

    Perovskites containing barium metal at the A site often take up unusual hexagonal structures having more than one type of possible sites for the B cation to occupy. This opens up various different B -B - or B -O-B -type connectivities and consequent physical properties which are naturally missing in cubic perovskites. BaRuO3 is one such system where doping of Ru (4 d4 ) by other transition metals (Mn +) creates similar conditions, giving rise to various M -Ru interactions. Interestingly, the 6 H hexagonal structure of doped barium ruthenate triple perovskite (Ba3M Ru2O9 ) seems to possess some internal checks because within the structure M ion always occupies the 2 a site and Ru goes to the 4 f site, allowing only M -O-Ru 180∘ and Ru-O-Ru 90∘ interactions to occur. The only exception is observed in the case of the Fe dopant, which allows us to study almost the full Ba3Fe1 -xRu2 +xO9 series of compounds with wide ranges of x because here Fe ions have the ability to freely go to the 4 f sites and Ru readily takes up the 2 a positions. Therefore, here one has the opportunity to probe the evolution of electronic and magnetic properties as a function of doping by going from BaRuO3 (paramagnetic metal) to BaFeO3 (ferromagnetic insulator). Our detailed experimental and theoretical results show that the series does exhibit a percolative metal-insulator transition with an accompanying but not coincidental magnetic transition as a function of x .

  8. B11 NMR in the layered diborides OsB2 and RuB2

    NASA Astrophysics Data System (ADS)

    Suh, B. J.; Zong, X.; Singh, Y.; Niazi, A.; Johnston, D. C.

    2007-10-01

    B11 nuclear magnetic resonance (NMR) measurements have been performed on B11 enriched OsB2 and RuB2 polycrystalline powder samples in an external field of 4.7T and in the temperature range, 4.2KOsB2 and RuB2 , respectively. The experimental results indicate that a p character dominates the conduction electron wave function at the B site with a negligibly small s character in both compounds.

  9. Estimation of Δ R/ R values by benchmark study of the Mössbauer Isomer shifts for Ru, Os complexes using relativistic DFT calculations

    NASA Astrophysics Data System (ADS)

    Kaneko, Masashi; Yasuhara, Hiroki; Miyashita, Sunao; Nakashima, Satoru

    2017-11-01

    The present study applies all-electron relativistic DFT calculation with Douglas-Kroll-Hess (DKH) Hamiltonian to each ten sets of Ru and Os compounds. We perform the benchmark investigation of three density functionals (BP86, B3LYP and B2PLYP) using segmented all-electron relativistically contracted (SARC) basis set with the experimental Mössbauer isomer shifts for 99Ru and 189Os nuclides. Geometry optimizations at BP86 theory of level locate the structure in a local minimum. We calculate the contact density to the wavefunction obtained by a single point calculation. All functionals show the good linear correlation with experimental isomer shifts for both 99Ru and 189Os. Especially, B3LYP functional gives a stronger correlation compared to BP86 and B2PLYP functionals. The comparison of contact density between SARC and well-tempered basis set (WTBS) indicated that the numerical convergence of contact density cannot be obtained, but the reproducibility is less sensitive to the choice of basis set. We also estimate the values of Δ R/ R, which is an important nuclear constant, for 99Ru and 189Os nuclides by using the benchmark results. The sign of the calculated Δ R/ R values is consistent with the predicted data for 99Ru and 189Os. We obtain computationally the Δ R/ R values of 99Ru and 189Os (36.2 keV) as 2.35×10-4 and -0.20×10-4, respectively, at B3LYP level for SARC basis set.

  10. Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu1 - x Fe x O3 - δ Thin Films

    NASA Astrophysics Data System (ADS)

    Dash, Umasankar; Acharya, Susant Kumar; Lee, Bo Wha; Jung, Chang Uk

    2017-03-01

    Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu1 - x Fe x O3 - δ epitaxial thin films ( x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu1 - x Fe x O3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR ( 36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies ( δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr1 - x La x )(Ru1 - x Fe x )O3. These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu1 - x Fe x O3 - δ thin films.

  11. Theoretical Study on Structural Stability of Fully Filled p-Type Skutterudites RETM4Sb12 ( RE = Rare Earth; TM = Fe, Ru)

    NASA Astrophysics Data System (ADS)

    Chen, Zhuo; Yang, Jiong; Liu, Ruiheng; Xi, Lili; Zhang, Wenqing; Yang, Jihui

    2013-08-01

    The structural stability of filled p-type skutterudites RETM4Sb12 ( RE = rare earth; TM = Fe, Ru) was studied via ab initio calculations. Most of the RE metals (La-Ho and Yb) could be filled into the cages (voids) of Fe4Sb12 to form stable filled skutterudites. However, only a few RE metals (La-Nd and Eu) could be stably filled into the cage of Ru4Sb12-based skutterudites. Systematic analysis of bonding energy showed that the structural stability could be attributed to ionic radius and effective charge state differences of the RE fillers. Resonant rattling frequencies of the fillers in both Fe4Sb12- and Ru4Sb12-based skutterudites were also studied.

  12. Correlation between microstructure and thermionic electron emission from Os-Ru thin films on dispenser cathodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Swartzentruber, Phillip D.; John Balk, Thomas, E-mail: john.balk@uky.edu; Effgen, Michael P.

    2014-07-01

    Osmium-ruthenium films with different microstructures were deposited onto dispenser cathodes and subjected to 1000 h of close-spaced diode testing. Tailored microstructures were achieved by applying substrate biasing during deposition, and these were evaluated with scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy before and after close-spaced diode testing. Knee temperatures determined from the close-spaced diode test data were used to evaluate cathode performance. Cathodes with a large (10-11) Os-Ru film texture possessed comparatively low knee temperatures. Furthermore, a low knee temperature correlated with a low effective work function as calculated from the close-spaced diode data. It is proposedmore » that the formation of strong (10-11) texture is responsible for the superior performance of the cathode with a multilayered Os-Ru coating.« less

  13. Platinum-group elements fractionation by selective complexing, the Os, Ir, Ru, Rh-arsenide-sulfide systems above 1020 °C

    NASA Astrophysics Data System (ADS)

    Helmy, Hassan M.; Bragagni, Alessandro

    2017-11-01

    The platinum-group element (PGE) contents in magmatic ores and rocks are normally in the low μg/g (even in the ng/g) level, yet they form discrete platinum-group mineral (PGM) phases. IPGE (Os, Ir, Ru) + Rh form alloys, sulfides, and sulfarsenides while Pt and Pd form arsenides, tellurides, bismuthoids and antimonides. We experimentally investigate the behavior of Os, Ru, Ir and Rh in As-bearing sulfide system between 1300 and 1020 °C and show that the prominent mineralogical difference between IPGE (+Rh) and Pt and Pd reflects different chemical preference in the sulfide melt. At temperatures above 1200 °C, Os shows a tendency to form alloys. Ruthenium forms a sulfide (laurite RuS2) while Ir and Rh form sulfarsenides (irarsite IrAsS and hollingworthite RhAsS, respectively). The chemical preference of PGE is selective: IPGE + Rh form metal-metal, metal-S and metal-AsS complexes while Pt and Pd form semimetal complexes. Selective complexing followed by mechanical separation of IPGE (and Rh)-ligand from Pt- and Pd-ligand associations lead to PGE fractionation.

  14. Voltage control of magnetic anisotropy in epitaxial Ru/Co2FeAl/MgO heterostructures

    NASA Astrophysics Data System (ADS)

    Wen, Zhenchao; Sukegawa, Hiroaki; Seki, Takeshi; Kubota, Takahide; Takanashi, Koki; Mitani, Seiji

    2017-03-01

    Voltage control of magnetic anisotropy (VCMA) in magnetic heterostructures is a key technology for achieving energy-efficiency electronic devices with ultralow power consumption. Here, we report the first demonstration of the VCMA effect in novel epitaxial Ru/Co2FeAl(CFA)/MgO heterostructures with interfacial perpendicular magnetic anisotropy (PMA). Perpendicularly magnetized tunnel junctions with the structure of Ru/CFA/MgO were fabricated and exhibited an effective voltage control on switching fields for the CFA free layer. Large VCMA coefficients of 108 and 139 fJ/Vm for the CFA film were achieved at room temperature and 4 K, respectively. The interfacial stability in the heterostructure was confirmed by repeating measurements. Temperature dependences of both the interfacial PMA and the VCMA effect were also investigated. It is found that the temperature dependences follow power laws of the saturation magnetization with an exponent of ~2, where the latter is definitely weaker than that of conventional Ta/CoFeB/MgO. The significant VCMA effect observed in this work indicates that the Ru/CFA/MgO heterostructure could be one of the promising candidates for spintronic devices with voltage control.

  15. Infrared spectra of M-η2-C2H2 and HMsbnd CCH produced in reactions of laser-ablated Fe and Os atoms with acetylene

    NASA Astrophysics Data System (ADS)

    Cho, Han-Gook; Andrews, Lester

    2015-04-01

    The π- and Csbnd H insertion products (M-η2-C2H2 and HMsbnd CCH) are identified in the matrix infrared spectra from reactions of laser-ablated Fe and Os atoms with acetylene isotopomers, but the vinylidene product (H2CCM) is not, in contrast to the recently studied Ru case. The π-complex is produced in deposition and annealing, and it converts to the insertion complex during photolysis. While the vinylidene product is energetically comparable with the two primary products, the energy barrier is considerably higher in contrast to the Ru case. The relatively short Csbnd C bonds of the π-complexes indicate weak back-donations from the group 8 metals to the acetylene π∗ orbitals. The highly bent structure of HOssbnd CCH evidently originates from the high d contributions to the Csbnd Os and Ossbnd H bonds. The C2v structures of the vinylidene products arise from the p-d π bonding between C and M.

  16. The Crystal Structure and Magnetic Behavior of Quinary Osmate and Ruthenate Double Perovskites La ABB'O 6 ( A = Ca, Sr; B = Co, Ni; B' = Ru, Os)

    DOE PAGES

    Morrow, Ryan; McGuire, Michael A.; Yan, Jiaqiang; ...

    2018-02-23

    In this work, six LaABB'O 6 (A = Ca, Sr; B = Co, Ni; B' = Ru, Os) double perovskites were synthesized, several for the first time, and their crystal structures and magnetic behavior were characterized with neutron powder diffraction and direct-current and alternating-current magnetometry. All six compounds crystallize with P2 1/n space group symmetry, resulting from a –a –c + octahedral tilting and complete rock salt ordering of transition-metal ions. Despite the electronic configurations of the transition-metal ions, either d 8–d 3 or d 7–d 3, not one of the six compounds shows ferromagnetism as predicted by the Goodenough–Kanamorimore » rules. LaSrNiOsO 6, LaSrNiRuO 6, and LaCaNiRuO 6 display long-range antiferromagnetic order, while LaCaNiOsO 6, LaCaCoOsO 6, and LaSrCoOsO 6 exhibit spin-glass behavior. These compounds are compared to the previously studied LaCaCoRuO 6 and LaSrCoRuO 6, both of which order antiferromagnetically. Lastly, the observed variations in magnetic properties can be attributed largely to the response of competing superexchange pathways due to changes in B–O–B' bond angles, differences in the radial extent of the 4d (B' = Ru) and 5d (B' = Os) orbitals, and filling of the t 2g orbitals of the 3d ion.« less

  17. The Crystal Structure and Magnetic Behavior of Quinary Osmate and Ruthenate Double Perovskites La ABB'O 6 ( A = Ca, Sr; B = Co, Ni; B' = Ru, Os)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Morrow, Ryan; McGuire, Michael A.; Yan, Jiaqiang

    In this work, six LaABB'O 6 (A = Ca, Sr; B = Co, Ni; B' = Ru, Os) double perovskites were synthesized, several for the first time, and their crystal structures and magnetic behavior were characterized with neutron powder diffraction and direct-current and alternating-current magnetometry. All six compounds crystallize with P2 1/n space group symmetry, resulting from a –a –c + octahedral tilting and complete rock salt ordering of transition-metal ions. Despite the electronic configurations of the transition-metal ions, either d 8–d 3 or d 7–d 3, not one of the six compounds shows ferromagnetism as predicted by the Goodenough–Kanamorimore » rules. LaSrNiOsO 6, LaSrNiRuO 6, and LaCaNiRuO 6 display long-range antiferromagnetic order, while LaCaNiOsO 6, LaCaCoOsO 6, and LaSrCoOsO 6 exhibit spin-glass behavior. These compounds are compared to the previously studied LaCaCoRuO 6 and LaSrCoRuO 6, both of which order antiferromagnetically. Lastly, the observed variations in magnetic properties can be attributed largely to the response of competing superexchange pathways due to changes in B–O–B' bond angles, differences in the radial extent of the 4d (B' = Ru) and 5d (B' = Os) orbitals, and filling of the t 2g orbitals of the 3d ion.« less

  18. L1 0 Fe -Pd Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Zhang, De-Lin; Sun, Congli; Lv, Yang; Schliep, Karl B.; Zhao, Zhengyang; Chen, Jun-Yang; Voyles, Paul M.; Wang, Jian-Ping

    2018-04-01

    Magnetic materials that possess large bulk perpendicular magnetic anisotropy (PMA) are essential for the development of magnetic tunnel junctions (MTJs) used in future spintronic memory and logic devices. The addition of an antiferromagnetic layer to these MTJs was recently predicted to facilitate ultrafast magnetization switching. Here, we report a demonstration of a bulk perpendicular synthetic antiferromagnetic (PSAFM) structure comprised of a (001) textured Fe -Pd /Ru /Fe -Pd trilayer with a face-centered-cubic (fcc) phase Ru spacer. The L1 0 Fe -Pd PSAFM structure shows a large bulk PMA (Ku˜10.2 Merg /cm3 ) and strong antiferromagnetic coupling (-JIEC˜2.60 erg /cm2 ). Full perpendicular magnetic tunnel junctions (PMTJs) with a L1 0 Fe -Pd PSAFM layer are then fabricated. Tunneling magnetoresistance ratios of up to approximately 25% (approximately 60%) are observed at room temperature (5 K) after postannealing at 350 °C . Exhibiting high thermal stabilities and large Ku , the bulk PMTJs with an L1 0 Fe -Pd PSAFM layer could pave a way for next-generation ultrahigh-density and ultralow-energy spintronic applications.

  19. New ternary tantalum borides containing boron dumbbells: Experimental and theoretical studies of Ta2OsB2 and TaRuB

    NASA Astrophysics Data System (ADS)

    Mbarki, Mohammed; Touzani, Rachid St.; Rehorn, Christian W. G.; Gladisch, Fabian C.; Fokwa, Boniface P. T.

    2016-10-01

    The new ternary transition metal-rich borides Ta2OsB2 and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that Ta2OsB2 and TaRuB crystallize in the tetragonal Nb2OsB2 (space group P4/mnc, no. 128) and the orthorhombic NbRuB (space group Pmma, no. 51) structure types with lattice parameters a=5.878(2) Å, c=6.857(2) Å and a=10.806(2) Å, b=3.196(1) Å, c=6.312(2) Å, respectively. Furthermore, crystallographic, electronic and bonding characteristics have been studied by density functional theory (DFT). Electronic structure relaxation has confirmed the crystallographic parameters while COHP bonding analysis indicates that B2-dummbells are the strongest bonds in both compounds. Moreover, the formation of osmium dumbbells in Ta2OsB2 through a Peierls distortion along the c-axis, is found to be the origin of superstructure formation. Magnetic susceptibility measurements reveal that the two phases are Pauli paramagnets, thus confirming the theoretical DOS prediction of metallic character. Also hints of superconductivity are found in the two phases, however lack of single phase samples has prevented confirmation. Furthermore, the thermodynamic stability of the two modifications of AMB (A=Nb, Ta; M =Ru, Os) are studied using DFT, as new possible phases containing either B4- or B2-units are predicted, the former being the most thermodynamically stable modification.

  20. Magnetism and structural chemistry of ternary borides RE2MB 6 ( RE = rare earth, M = Ru, Os)

    NASA Astrophysics Data System (ADS)

    Hiebl, K.; Rogl, P.; Nowotny, H.

    1984-10-01

    The magnetic behavior of the ternary borides RE2RuB 6 and RE2OsB 6 ( RE = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) was studied in the temperature range 1.5 K < T < 1100 K. All compounds crystallize with the Y 2ReB 6-type structure and are characterized by direct RE- RE contacts and the formation of planar infinite two-dimensional rigid boron nets. The magnetic properties reveal a typical Van Vleck paramagnetism of free RE3+-ions at temperatures higher than 200 K with ferromagnetic interaction in the low-temperature range T < 55 K. The ferromagnetic ordering temperatures vary with the De Gennes factor. There is no indication for a magnetic contribution from the Ru(Os)-sublattice. Above 1.8 K none of the samples were found to be superconducting.

  1. Tailoring the composition of ultrathin, ternary alloy PtRuFe nanowires for the methanol oxidation reaction and formic acid oxidation reaction

    DOE PAGES

    Scofield, Megan E.; Koenigsmann, Christopher; Wang, Lei; ...

    2014-11-25

    In the search for alternatives to conventional Pt electrocatalysts, we have synthesized ultrathin, ternary PtRuFe nanowires (NW), possessing different chemical compositions in order to probe their CO tolerance as well as electrochemical activity as a function of composition for both (i) the methanol oxidation reaction (MOR) and (ii) the formic acid oxidation reaction (FAOR). As-prepared ‘multifunctional’ ternary NW catalysts exhibited both higher MOR and FAOR activity as compared with binary Pt₇Ru₃ NW, monometallic Pt NW, and commercial catalyst control samples. In terms of synthetic novelty, we utilized a sustainably mild, ambient wet-synthesis method never previously applied to the fabrication ofmore » crystalline, pure ternary systems in order to fabricate ultrathin, homogeneous alloy PtRuFe NWs with a range of controlled compositions. Thus, these NWs were subsequently characterized using a suite of techniques including XRD, TEM, SAED, and EDAX in order to verify not only the incorporation of Ru and Fe into the Pt lattice but also their chemical homogeneity, morphology, as well as physical structure and integrity. Lastly, these NWs were electrochemically tested in order to deduce the appropriateness of conventional explanations such as (i) the bi-functional mechanism as well as (ii) the ligand effect to account for our MOR and FAOR reaction data. Specifically, methanol oxidation appears to be predominantly influenced by the Ru content, whereas formic acid oxidation is primarily impacted by the corresponding Fe content within the ternary metal alloy catalyst itself.« less

  2. Experimental partitioning of Tc, Mo, Ru, and Re between solid and liquid during crystallization in Fe-Ni-S 1

    NASA Astrophysics Data System (ADS)

    Lazar, C.; Walker, D.; Walker, R. J.

    2004-02-01

    Technetium isotopes 97Tc, 98Tc and 99Tc decay to 97Mo, 98Ru and 99Ru, with half-lives of 2.6 My, 4.1 My, and 0.21 My respectively. If there were early solar system processes that resulted in significant fractionation of Tc from the daughter elements, decay of extant Tc could have led to the creation of Mo and Ru isotopic heterogeneities. To assess the potential of metallic core crystallization to fractionate these elements, we examine the partitioning behavior of Tc relative to Re, Mo and Ru in the Fe-Ni-S system between solid metal and liquid metal alloy. The experimental evidence shows that Tc behaves more like the modestly compatible siderophile element Ru than the more highly compatible siderophile element Re, and that Tc is substantially more compatible than Mo. We also demonstrate a pressure effect in the partitioning of Mo during the crystallization of Fe-Ni-S melts. For a sulfur concentration in the liquid fraction of the core of 10 wt% (16.3 at%), the Jones and Malvin (1990) parameter is -ln(1-2 × 1.09 × 0.163) ≅ 0.44, which yields: D(Re) ≅ 4.1; D(Ru) ≅ 2.3; D(Tc) ≅ 1.7; D(Mo) Lo-P ≅ 1.0;.and D(Mo) Hi-P ≅ 0.5. Our results suggest that detectable Tc-induced isotopic anomalies (≥0.1 ɛ unit) in Ru and Mo could only be produced by unrealistically extreme degrees of crystallization of metal during asteroidal core fractionation, regardless of the time scales and initial Tc abundances involved.

  3. Catalytic performance of M@Ni (M = Fe, Ru, Ir) core-shell nanoparticles towards ammonia decomposition for CO x -free hydrogen production

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Zhou, Junwei; Chen, Shuangjing; Zhang, Hui

    2018-06-01

    To reduce the use of precious metals and maintain the catalytic activity for NH3 decomposition reaction, it is an effective way to construct bimetallic nanoparticles with special structures. In this paper, by using density functional theory methods, we investigated NH3 decomposition reaction on three types of core-shell nanoparticles M@Ni (M = Fe, Ru, Ir) with 13 core M atoms and 42 shell Ni atoms. The size of these three particles is about 1 nm. Benefit from alloying with Ru in this nanocluster, Ru@Ni core-shell nanoparticles exhibit catalytic activity comparable to that of single metal Ru, based on the analysis of the adsorption energy and potential energy diagram of NH3 decomposition, as well as N2 desorption processes. However, as for Fe@Ni and Ir@Ni core-shell nanoparticles, their catalytic activities are still unsatisfactory compared to the active metal Ru. In addition, in order to further explain the synergistic effect of bimetallic core-shell nanoparticles, the partial density of states were also calculated. The results show that d-band electrons provided by the core metal are the main factors affecting the entire catalytic process.

  4. First-principles study on the structure, elastic properties, hardness and electronic structure of TMB4 (TM=Cr, Re, Ru and Os) compounds

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Zheng, W. T.; Guan, W. M.; Zhang, K. H.; Fan, X. F.

    2013-11-01

    The structural formation, elastic properties, hardness and electronic structure of TMB4 (TM=Cr, Re, Ru and Os) compounds are investigated using first-principles approach. The value of C22 for these compounds is almost two times bigger than the C11 and C33. The intrinsic hardness, shear modulus and Young's modulus are calculated to be in a sequence of CrB4>ReB4>RuB4>OsB4, and the Poisson's ratio and B/G ratio of TMB4 follow the order of CrB4RuB4<OsB4. The intrinsic hardness of CrB4 and ReB4 by LDA is bigger than 40 GPa. The high hardness of TMB4 compounds is derived from the feature of B-B bonds cage and higher C22 value. The B-B covalent bonds as bonds cage enhances the resistance to shear deformation and improve the hardness. We predict that the TMB4 compounds with CrB4-type are the potential superhard materials.

  5. Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu1 - x Fe x O3 - δ Thin Films.

    PubMed

    Dash, Umasankar; Acharya, Susant Kumar; Lee, Bo Wha; Jung, Chang Uk

    2017-12-01

    Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu 1 - x Fe x O 3 - δ epitaxial thin films (x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu 1 - x Fe x O 3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR (~36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies (δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr 1 - x La x )(Ru 1 - x Fe x )O 3 . These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu 1 - x Fe x O 3 - δ thin films.

  6. Concerto catalysis--harmonising [NiFe]hydrogenase and NiRu model catalysts.

    PubMed

    Ichikawa, Koji; Nonaka, Kyoshiro; Matsumoto, Takahiro; Kure, Bunsho; Yoon, Ki-Seok; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji

    2010-03-28

    This communication reports the successful merging of the chemical properties of a natural [NiFe]hydrogenase (Desulfovibrio vulgaris Miyazaki F) and our previously reported [NiRu] hydrogenase-mimic. The catalytic activity of both the natural enzyme and the mimic is almost identical, with the exception of working pH ranges, and this allows us to use them simultaneously in the same reaction flask. In such a manner, isotope exchange between D(2) and H(2)O could be conducted over an extended pH range (about 2-10) in one pot under mild conditions at ambient temperature and pressure.

  7. Heterobimetallic Nitrido Complexes of Group 8 Metalloporphyrins.

    PubMed

    Cheung, Wai-Man; Chiu, Wai-Hang; de Vere-Tucker, Matthew; Sung, Herman H-Y; Williams, Ian D; Leung, Wa-Hung

    2017-05-15

    Heterobimetallic nitrido porphyrin complexes with the [(L)(por)M-N-M'(L OEt )Cl 2 ] formula {por 2- = 5,10,15,20-tetraphenylporphyrin (TPP 2- ) or 5,10,15,20-tetra(p-tolyl)porphyrin (TTP 2- ) dianion; L OEt - = [Co(η 5 -C 5 H 5 ){P(O)(OEt) 2 } 3 ] - ; M = Fe, Ru, or Os; M' = Ru or Os; L = H 2 O or pyridine} have been synthesized, and their electrochemistry has been studied. Treatment of trans-[Fe(TPP)(py) 2 ] (py = pyridine) with Ru(VI) nitride [Ru(L OEt )(N)Cl 2 ] (1) afforded Fe/Ru μ-nitrido complex [(py)(TPP)Fe(μ-N)Ru(L OEt )Cl 2 ] (2). Similarly, Fe/Os analogue [(py)(TPP)Fe(μ-N)Os(L OEt )Cl 2 ] (3) was obtained from trans-[Fe(TPP)(py) 2 ] and [Os(L OEt )(N)Cl 2 ]. However, no reaction was found between trans-[Fe(TPP)(py) 2 ] and [Re(L OEt )(N)Cl(PPh 3 )]. Treatment of trans-[M(TPP)(CO)(EtOH)] with 1 afforded μ-nitrido complexes [(H 2 O)(TPP)M(μ-N)Ru(L OEt )Cl 2 ] [M = Ru (4a) or Os (5)]. TTP analogue [(H 2 O)(TTP)Ru(μ-N)Ru(L OEt )Cl 2 ] (4b) was prepared similarly from trans-[Ru(TTP)(CO)(EtOH)] and 1. Reaction of [(H 2 O)(por)M(μ-N)M(L OEt )Cl 2 ] with pyridine gave adducts [(py)(por)M(μ-N)Ru(L OEt )Cl 2 ] [por = TTP, and M = Ru (6); por = TPP, and M = Os (7)]. The diamagnetism and short (por)M-N(nitride) distances in 2 [Fe-N, 1.683(3) Å] and 4b [Ru-N, 1.743(3) Å] are indicative of the M IV ═N═M' IV bonding description. The cyclic voltammograms of the Fe/Ru (2) and Ru/Ru (4b) complexes in CH 2 Cl 2 displayed oxidation couples at approximately +0.29 and +0.35 V versus Fc +/0 (Fc = ferrocene) that are tentatively ascribed to the oxidation of the {L OEt Ru} and {Ru(TTP)} moieties, respectively, whereas the Fe/Os (3) and Os/Ru (5) complexes exhibited Os-centered oxidation at approximately -0.06 and +0.05 V versus Fc +/0 , respectively. The crystal structures of 2 and 4b have been determined.

  8. What is the best bonding model of the (σ-H-BR) species bound to a transition metal? Bonding analysis in complexes [(H)2Cl(PMe3)2M(σ-H-BR)] (M = Fe, Ru, Os).

    PubMed

    Pandey, Krishna K

    2012-03-21

    Density Functional Theory calculations have been performed for the σ-hydroboryl complexes of iron, ruthenium and osmium [(H)(2)Cl(PMe(3))(2)M(σ-H-BR)] (M = Fe, Ru, Os; R = OMe, NMe(2), Ph) at the BP86/TZ2P/ZORA level of theory in order to understand the interactions between metal and HBR ligands. The calculated geometries of the complexes [(H)(2)Cl(PMe(3))(2)Ru(HBNMe(2))], [(H)(2)Cl(PMe(3))(2)Os(HBR)] (R = OMe, NMe(2)) are in excellent agreement with structurally characterized complexes [(H)(2)Cl(P(i)Pr(3))(2)Os(σ-H-BNMe(2))], [(H)(2)Cl(P(i)Pr(3))(2)Os{σ-H-BOCH(2)CH(2)OB(O(2)CH(2)CH(2))}] and [(H)(2)Cl(P(i)Pr(3))(2)Os(σ-H-BNMe(2))]. The longer calculated M-B bond distance in complex [(H)(2)Cl(PMe(3))(2)M(σ-H-BNMe(2))] are due to greater B-N π bonding and as a result, a weaker M-B π-back-bonding. The B-H2 bond distances reveal that (i) iron complexes contain bis(σ-borane) ligand, (ii) ruthenium complexes contain (σ-H-BR) ligands with a stretched B-H2 bond, and (iii) osmium complexes contain hydride (H2) and (σ-H-BR) ligands. The H-BR ligands in osmium complexes are a better trans-directing ligand than the Cl ligand. Values of interaction energy, electrostatic interaction, orbital interaction, and bond dissociation energy for interactions between ionic fragments are very large and may not be consistent with M-(σ-H-BR) bonding. The EDA as well as NBO and AIM analysis suggest that the best bonding model for the M-σ-H-BR interactions in the complexes [(H)(2)Cl(PMe(3))(2)M(σ-H-BR)] is the interaction between neutral fragments [(H)(2)Cl(PMe(3))(2)M] and [σ-H-BR]. This becomes evident from the calculated values for the orbital interactions. The electron configuration of the fragments which is shown for C in Fig. 1 experiences the smallest change upon the M-σ-H-BR bond formation. Since model C also requires the least amount of electronic excitation and geometry changes of all models given by the ΔE(prep) values, it is clearly the most appropriate choice of

  9. Exploring the influence of iron substitution in lithium rich layered oxides Li 2Ru 1–xFe xO 3: triggering the anionic redox reaction

    DOE PAGES

    Satish, Rohit; Lim, Kipil; Bucher, Nicolas; ...

    2017-06-23

    Lithium rich layered materials are an interesting class of materials which exploit both anionic and cationic redox reactions to store energy upwards of 250 mA h g –1. This paper aims to understand the nature of the redox reactions taking place in these compounds. Li 2RuO 3 was used as the base compound, which is then compared with compounds generated by partially substituting Ru with Ti and Fe respectively. Electrochemical tests indicate that Fe substitution in the sample leads to an improvement in capacity, cycle life and reduction of potential decay. To elucidate the reason for this improvement in operandomore » diffraction experiments were carried out, highlighting the formation of a secondary de-lithiated phase. The distortion of the pristine structure eventually induces frontier orbital reorganization leading to the oxygen redox reaction resulting in extra capacity. Local changes at Fe and Ru ions are recorded using in operando X-ray absorption spectroscopy (XAS). It was noted that while Ru undergoes a reversible redox reaction, Fe undergoes a significant irreversible change in its coordination environment during cycling. In conclusion, the changes in the coordination environment of oxygen and formation of O 2 n– type species were probed in situ using soft X-rays.« less

  10. Pressure-induced structural phase transition in transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt): a DFT study

    NASA Astrophysics Data System (ADS)

    Manikandan, M.; Rajeswarapalanichamy, R.; Iyakutti, K.

    2018-03-01

    First-principles calculations based on density functional theory was performed to analyse the structural stability of transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt). It is observed that zinc-blende phase is the most stable one for these carbides. Pressure-induced structural phase transition from zinc blende to NiAs phase is predicted at the pressures of 248.5 GPa, 127 GPa and 142 GPa for OsC, IrC and PtC, respectively. The electronic structure reveals that RuC exhibits a semiconducting behaviour with an energy gap of 0.7056 eV. The high bulk modulus values of these carbides indicate that these metal carbides are super hard materials. The high B/G value predicts that the carbides are ductile in their most stable phase.

  11. Soft magnetic properties of nanocrystalline FeRuGaSi-Hf alloy films and head characteristics for the embedded thin film tape head

    NASA Astrophysics Data System (ADS)

    Ohmori, H.; Shoji, M.; Kobayashi, T.; Yamamoto, T.; Sugiyama, Y.; Hayashi, K.; Hono, K.

    1996-04-01

    The Hf-added FeRuGaSi alloy film has an amorphous structure in the as-deposited state and becomes nanocrystalline after annealing. Due to this structure change from crystalline to amorphous by the addition of Hf, soft magnetic degradation of the film deposited on the slant grooved substrate, which is necessary for the sophisticated embedded thin film (ETF) head structure, is greatly suppressed and the undesirable film stress is relieved. The FeRuGaSi-Hf alloy film has higher resistivity and permeability at high frequencies than those of sendust film, and the read/write characteristics of this alloy film show better performance than sendust film.

  12. Investigation of magnetic order in SmTr2Zn20 (Tr=Fe ,Co,Ru) and SmTr2Cd20 (Tr=Ni ,Pd)

    NASA Astrophysics Data System (ADS)

    Yazici, D.; White, B. D.; Ho, P.-C.; Kanchanavatee, N.; Huang, K.; Friedman, A. J.; Wong, A. S.; Burnett, V. W.; Dilley, N. R.; Maple, M. B.

    2014-10-01

    Single crystals of the "cage compounds" SmTr2Zn20 (Tr=Fe, Co, Ru) and SmTr2Cd20 (Tr=Ni, Pd) have been investigated by means of electrical resistivity, magnetization, and specific-heat measurements. The compounds SmFe2Zn20,SmRu2Zn20, and SmNi2Cd20 exhibit ferromagnetic order with Curie temperatures of TC=47.4, 7.6, and 7.5 K, respectively, whereas SmPd2Cd20 is an antiferromagnet with a Néel temperature of TN=3.4 K. No evidence for magnetic order is observed in SmCo2Zn20 down to 110 mK. The Sommerfeld coefficients γ are found to be 57 mJ /molK2 for SmFe2Zn20,79.5 mJ /molK2 for SmCo2Zn20,258 mJ /molK2 for SmRu2Zn20,165 mJ /molK2 for SmNi2Cd20, and 208 mJ /molK2 for SmPd2Cd20. Enhanced values of γ and a quadratic temperature dependence of the electrical resistivity at low temperature for SmRu2Zn20 and SmPd2Cd20 suggest an enhancement of the quasiparticle masses due to hybridization between localized 4f and conduction electron states.

  13. Comparative Study of Electronic Structure and Magnetic Properties of Osmate Double Perovskites: Ca2FeOsO6 versus Ca2Co(Ni)OsO6

    NASA Astrophysics Data System (ADS)

    Samanta, Kartik; Saha-Dasgupta, Tanusri

    2018-04-01

    Employing density functional theory, we study the trend in the electronic and magnetic properties of 3d-5d double perovskites, upon varying the 3d element for a fixed choice of 5d element, namely Ca2BOsO6 (B = Fe/Co/Ni). While all three compounds are reported to be ferrimagnets, the magnetic transition temperature of Ca2FeOsO6 is reported to be 2-2.4 times larger than that of Ca2CoOsO6 or Ca2NiOsO6. Our first-principles study provides microscopic insight into this trend. This trend is found to be caused by the downward shift in the position of d level energies of the B site element with respect to that of the Os t2g level upon moving across the 3d series from Fe to Co and Ni. This in turn changes the nominal valence of the Os ion from 5+ in Ca2FeOsO6 to 6+ in Ca2CoOsO6 and Ca2NiOsO6, resulting in differing superexchange paths between Ca2FeOsO6 and Ca2Co(Ni)OsO6, and additionally enabling the hybridization-mechanism-driven magnetism in Ca2FeOsO6. These together significantly enhance the magnetic transition temperature in Ca2FeOsO6 compared with that in Ca2Co(Ni)OsO6.

  14. Limits on superconductivity-related magnetization in Sr 2RuO 4 and PrOs 4Sb 12 from scanning SQUID microscopy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Moler, Kathryn

    2010-08-26

    We present scanning SQUID microscopy data on the superconductors Sr{sub 2}RuO{sub 4} (T{sub c} = 1.5 K) and PrOs{sub 4}Sb{sub 12} (T{sub c} = 1.8 K). In both of these materials, superconductivity-related time-reversal symmetry-breaking fields have been observed by muon spin rotation; our aim was to visualize the structure of these fields. However in neither Sr{sub 2}RuO{sub 4} nor PrOs{sub 4}Sb{sub 12} do we observe spontaneous superconductivity-related magnetization. In Sr{sub 2}RuO{sub 4}, many experimental results have been interpreted on the basis of a p{sub x} {+-} ip{sub y} superconducting order parameter. This order parameter is expected to give spontaneous magneticmore » induction at sample edges and order parameter domain walls. Supposing large domains, our data restrict domain wall and edge fields to no more than {approx}0.1% and {approx}0.2% of the expected magnitude, respectively. Alternatively, if the magnetization is of the expected order, the typical domain size is limited to {approx}30 nm for random domains, or {approx} 500 nm for periodic domains.« less

  15. Frustrated magnetism in the double perovskite L a2LiOs O6 : A comparison with L a2LiRu O6

    NASA Astrophysics Data System (ADS)

    Thompson, C. M.; Marjerrison, C. A.; Sharma, A. Z.; Wiebe, C. R.; Maharaj, D. D.; Sala, G.; Flacau, R.; Hallas, A. M.; Cai, Y.; Gaulin, B. D.; Luke, G. M.; Greedan, J. E.

    2016-01-01

    The frustrated double perovskite L a2LiOs O6 , based on O s5 +(5 d3,t23 ) is studied using magnetization, elastic neutron scattering, heat capacity, and muon spin relaxation (μSR) techniques and compared with isostructural (P 21/n ) L a2LiRu O6 ,R u5 +(4 d3,t23 ) . While previous studies of L a2LiOs O6 showed a broad susceptibility maximum (χmax) near 40 K, heat capacity data indicate a sharp peak at 30 K, similar to L a2LiRu O6 with χmax˜30 K and a heat capacity peak at 24 K. Significant differences between the two materials are seen in powder neutron diffraction where the magnetic structure is described by k =(1 /2 1 /2 0 ) for L a2LiOs O6 , while L a2LiRu O6 has been reported with k =(000 ) , structure for face centered lattices. For the k =(1 /2 1 /2 0 ) structure, one has antiferromagnetic layers stacked antiferromagnetically, while for k =(0 0 0 ) structure, ferromagnetic layers are stacked antiferromagnetically. In spite of these differences, both can be considered as type I fcc antiferromagnetic structures. For L a2LiOs O6 , the magnetic structure is best described in terms of linear combinations of basis vectors belonging to irreducible representations Γ2 and Γ4. The combinations Γ2- Γ4 and Γ2+Γ4 could not be distinguished from refinement of the data. In all cases, the O s5 + moments lie in the y z plane with the largest component along y . The total moment is 1.81(4) μB. For L a2LiRu O6 , the R u5 + moments are reported to lie in the x z plane. In addition, while neutron diffraction, μSR and NMR data indicate a unique TN=24 K for L a2LiRu O6 , the situation for L a2LiOs O6 is more complex, with heat capacity, neutron diffraction, and μSR indicating two ordering events at 30 and 37 K, similar to the cases of cubic B a2YRu O6 and monoclinic S r2YRu O6 .

  16. Unusual Phase Diagram of CeOs 4Sb 12

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ho, P. -C.; Goddard, P. A.; Maple, M. B.

    2017-03-01

    Filled skutterudite compounds, with the formula MT 4X 12, where M is an alkali metal, alkaline-earth, lanthanide, or actinide, T is Fe, Ru, or Os, and X is P, As, or Sb, display a wide variety of interesting phenomena caused by strong electron correlations [1]. Among these, the three compounds CeOs 4Sb 12, PrOs 4Sb 12, and NdOs 4Sb 12, formed by employing Periodic Table neighbors for M, span the range from an antiferromagnetic (AFM) semimetal (M = Ce) via a 1.85 K unconventional (quadrupolar-fluctuation mediated) superconductor (M = Pr) to a 1 K ferromagnet (FM; M = Nd). Inmore » the course of an extended study of these compounds, we uncovered an unusual phase diagram for CeOs 4Sb 12.« less

  17. Electronic Structure, Mechanical and Dynamical Stability of Hexagonal Subcarbides M2C (M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt): Ab Initio Calculations

    NASA Astrophysics Data System (ADS)

    Suetin, D. V.; Shein, I. R.

    2018-02-01

    Ab initio calculations were used to study the properties of a series of hexagonal (Fe2N-like) subcarbides M2C, where M = Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt, and to calculate their equilibrium structural parameters, electronic properties, phase stability, elastic constants, compression modulus, shear modulus, Young's modulus, compressibility, Pugh's indicator, Poisson ratio, elastic anisotropy indices, and also hardness, Debye temperature, sound velocity, and low-temperature heat capacity. It is found based on these results that all the subcarbides are mechanically stable; however, their formation energies E form are positive with respect to a mixture of d-metal and graphite. In addition, the calculation of the phonon spectra of these subcarbides shows the existence of negative modes, which indicates their dynamical instability. Thus, a successful synthesis of these subcarbides at normal conditions is highly improbable.

  18. Chemical pressure tuning of URu 2 Si 2 via isoelectronic substitution of Ru with Fe

    DOE PAGES

    Das, Pinaki; Kanchanavatee, N.; Helton, J. S.; ...

    2015-02-26

    We have used specific heat and neutron diffraction measurements on single crystals of URu 2–xFe xSi₂ for Fe concentrations x ≤ 0.7 to establish that chemical substitution of Ru with Fe acts as “chemical pressure” P ch as previously proposed by Kanchanavatee et al. [Phys. Rev. B 84, 245122 (2011)] based on bulk measurements on polycrystalline samples. Neutron diffraction reveals a sharp increase of the uranium magnetic moment at x = 0.1, reminiscent of the behavior at the “hidden order” to large moment antiferromagnetic (LMAFM) phase transition observed at a pressure P x ≈ 0.5-0.7 GPa in URu₂Si₂. Using themore » unit cell volume determined from our measurements and an isothermal compressibility κ T = 5.2×10⁻³ GPa⁻¹ for URu₂Si₂, we determine the chemical pressure P ch in URu 2-xFe xSi₂ as a function of x. The resulting temperature T-chemical pressure P ch phase diagram for URu 2-xFe xSi₂ is in agreement with the established temperature T-external pressure P phase diagram of URu₂Si₂.« less

  19. pH-Dependent isotope exchange and hydrogenation catalysed by water-soluble NiRu complexes as functional models for [NiFe]hydrogenases.

    PubMed

    Kure, Bunsho; Matsumoto, Takahiro; Ichikawa, Koji; Fukuzumi, Shunichi; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji

    2008-09-21

    The pH-dependent hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes and hydrogenation of the carbonyl compounds have been investigated with water-soluble bis(mu-thiolate)(mu-hydride)NiRu complexes, Ni(II)(mu-SR)(2)(mu-H)Ru(II) {(mu-SR)(2) = N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)-1,3-propanediamine}, as functional models for [NiFe]hydrogenases. In acidic media (at pH 4-6), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes has H(+) properties, and the complexes catalyse the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes. A mechanism of the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes through a low-valent Ni(I)(mu-SR)(2)Ru(I) complex is proposed. In contrast, in neutral-basic media (at pH 7-10), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes acts as H(-), and the complexes catalyse the hydrogenation of carbonyl compounds.

  20. Precious metal enrichment at low-redox in terrestrial native Fe-bearing basalts investigated using laser-ablation ICP-MS

    NASA Astrophysics Data System (ADS)

    Howarth, Geoffrey H.; Day, James M. D.; Pernet-Fisher, John F.; Goodrich, Cyrena A.; Pearson, D. Graham; Luo, Yan; Ryabov, Viktor V.; Taylor, Lawrence A.

    2017-04-01

    Primary native Fe is a rare crystallizing phase from terrestrial basaltic magmas, requiring highly reducing conditions (fO2 Fe alloy liquid. If this liquid also contains sufficient sulfur, it can undergo further division into conjugate Fe-C-rich and a Fe-S-rich immiscible melts that can effectively scavenge the highly siderophile elements (HSE: Re, Au, and the platinum group elements [PGE], Pd, Pt, Rh, Ru, Ir, Os), as well as Ni and Cu, to economic abundances. Three localities are known globally where native Fe bearing mafic rocks occur: (1) Paleocene basalts of Disko Island, West Greenland; (2) a Miocene lava of the Bühl basalts, Germany; and (3) mafic intrusions associated with the Late Permian Siberian flood basalts. In this contribution, we report major- and minor-element compositions and HSE concentrations for the main alloy phases (FeNi metal and cohenite) and sulfide, for all three known global occurrences of native Fe bearing basalt. Total HSE abundances in metal grains, obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), are lowest in the Bühl basalt, (∼0.05 ppm), intermediate in the Disko Island basalts (4-8 ppm), and highest the Siberian Khungtukun and Dzhaltul intrusions (10-30 ppm). These differences demonstrate that, while native Fe formation is the result of carbonaceous crustal assimilation, HSE enrichment is not ubiquitous during this process. The Siberian occurrences are characterized by Pt PGE (PPGE: Pt, Pd) enrichment relative to the Ir PGE (IPGE: Rh, Ru, Ir, Os), consistent with models of early stage fractionation of olivine, chromite and metallic IPGE in staging magma reservoirs, prior to the addition of C-rich crustal materials in the shallow crust. Relative to Noril'sk Ni-Cu-PGE sulfide ores

  1. Visualizing ferromagnetic domains in undoped and Fe-doped Sr4Ru3O10

    NASA Astrophysics Data System (ADS)

    Sass, Paul; Wu, Weida; Mao, Zhiqiang; Li, Peigang

    Transition-metal oxides have proven to be a great source of interesting phenomena and new quantum phases of matter with high potential for developing exciting technologies. A remarkable sub-class of these materials with layer dependent properties is the ruthenium perovskites of the Ruddlesden-Popper series, specifically Srn + 1RunO3 n + 1 , exhibiting a range of behavior from ferromagnetism and metamagnetic quantum criticality to p-wave superconductivity. The triple layered oxide Sr4Ru3O10 exhibits coexistence of ferro- (TC < 105 K) and meta- (TM < 50 K) magnetism with strong anisotropy. Despite many studies on bulk magnetic properties of this material, the microscopic nature of the magnetic phase is still unclear. What is lacking is the real space imaging of magnetic domains. To this end, we report our variable temperature magnetic force microscopy studies on floating-zone grown undoped and Fe-doped Sr4Ru3O10 single crystals. Various stripe and branch-like domain patterns were observed below This work is supported by DOE BES under award DE-SC0008147.

  2. Investigation of magnetic order in SmTr2Zn20 (Tr = Fe, Co, Ru) and SmTr2Cd20 (Tr = Ni, Pd)

    NASA Astrophysics Data System (ADS)

    Yazici, Duygu; White, B. D.; Ho, P.-C.; Kanchanavatee, N.; Huang, K.; Dilley, N. R.; Maple, M. B.

    2015-03-01

    Single crystals of the cage compounds Sm Tr 2Zn20 (Tr = Fe, Co, Ru) and Sm Tr 2Cd20 (Tr = Ni, Pd) have been investigated by means of electrical resistivity, magnetization, and specific heat measurements. The compounds SmFe2Zn20, SmRu2Zn20,andSmNi2Cd20 exhibit ferromagnetic order with Curie temperatures of TC = 47.4 K, 7.6 K, and 7.5 K, respectively, whereas SmPd2Cd20 is an antiferromagnet with a Néel temperature of TN = 3.4 K. No evidence for magnetic order is observed in SmCo2Zn20 down to 110 mK. The Sommerfeld coefficients γ are found to be 57 mJ/mol-K2 for SmFe2Zn20, 79.5 mJ/mol-K2 for SmCo2Zn20, 258 mJ/mol-K2 for SmRu2Zn20, 165 mJ/mol-K2 for SmNi2Cd20, and 208 mJ/mol-K2 for SmPd2Cd20. Enhanced values of Sommerfeld coefficients γ and a quadratic temperature dependence of the electrical resistivity at low temperature for SmRu2Zn20andSmPd2Cd20 suggest an enhancement of the quasiparticle masses due to hybridization between localized 4 f and conduction electron states. Research at UCSD was supported by the U.S. DOE under Grant No. DE-FG02-04-ER46105 and the U.S. NSF under Award Grant No. DMR 1206553. Research at California State University, Fresno was supported by the U.S. NSF under Grant No. DMR 1104544.

  3. OsB 2 and RuB 2, ultra-incompressible, hard materials: First-principles electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Chiodo, S.; Gotsis, H. J.; Russo, N.; Sicilia, E.

    2006-07-01

    Recently it has been reported that osmium diboride has an unusually large bulk modulus combined with high hardness, and consequently is a most interesting candidate as an ultra-incompressible and hard material. The electronic and structural properties of the transition metal diborides OsB 2 and RuB 2 have been calculated within the local density approximation (LDA). It is shown that the high hardness is the result of covalent bonding between transition metal d states and boron p states in the orthorhombic structure.

  4. Electron interactions with the heteronuclear carbonyl precursor H2FeRu3(CO)13 and comparison with HFeCo3(CO)12: from fundamental gas phase and surface science studies to focused electron beam induced deposition.

    PubMed

    P, Ragesh Kumar T; Weirich, Paul; Hrachowina, Lukas; Hanefeld, Marc; Bjornsson, Ragnar; Hrodmarsson, Helgi Rafn; Barth, Sven; Fairbrother, D Howard; Huth, Michael; Ingólfsson, Oddur

    2018-01-01

    In the current contribution we present a comprehensive study on the heteronuclear carbonyl complex H 2 FeRu 3 (CO) 13 covering its low energy electron induced fragmentation in the gas phase through dissociative electron attachment (DEA) and dissociative ionization (DI), its decomposition when adsorbed on a surface under controlled ultrahigh vacuum (UHV) conditions and exposed to irradiation with 500 eV electrons, and its performance in focused electron beam induced deposition (FEBID) at room temperature under HV conditions. The performance of this precursor in FEBID is poor, resulting in maximum metal content of 26 atom % under optimized conditions. Furthermore, the Ru/Fe ratio in the FEBID deposit (≈3.5) is higher than the 3:1 ratio predicted. This is somewhat surprising as in recent FEBID studies on a structurally similar bimetallic precursor, HFeCo 3 (CO) 12 , metal contents of about 80 atom % is achievable on a routine basis and the deposits are found to maintain the initial Co/Fe ratio. Low temperature (≈213 K) surface science studies on thin films of H 2 FeRu 3 (CO) 13 demonstrate that electron stimulated decomposition leads to significant CO desorption (average of 8-9 CO groups per molecule) to form partially decarbonylated intermediates. However, once formed these intermediates are largely unaffected by either further electron irradiation or annealing to room temperature, with a predicted metal content similar to what is observed in FEBID. Furthermore, gas phase experiments indicate formation of Fe(CO) 4 from H 2 FeRu 3 (CO) 13 upon low energy electron interaction. This fragment could desorb at room temperature under high vacuum conditions, which may explain the slight increase in the Ru/Fe ratio of deposits in FEBID. With the combination of gas phase experiments, surface science studies and actual FEBID experiments, we can offer new insights into the low energy electron induced decomposition of this precursor and how this is reflected in the relatively

  5. Strain-induced topological transition in SrRu 2O 6 and CaOs 2O 6

    DOE PAGES

    Ochi, Masayuki; Arita, Ryotaro; Trivedi, Nandini; ...

    2016-05-24

    The topological property of SrRumore » $$_2$$O$$_6$$ and isostructural CaOs$$_2$$O$$_6$$ under various strain conditions is investigated using density functional theory. Based on an analysis of parity eigenvalues, we anticipate that a three-dimensional strong topological insulating state should be realized when band inversion is induced at the A point in the hexagonal Brillouin zone. For SrRu$$_2$$O$$_6$$, such a transition requires rather unrealistic tuning, where only the $c$ axis is reduced while other structural parameters are unchanged. However, given the larger spin-orbit coupling and smaller lattice constants in CaOs$$_2$$O$$_6$$, the desired topological transition does occur under uniform compressive strain. Our study paves a way to realize a topological insulating state in a complex oxide, which has not been experimentally demonstrated so far.« less

  6. Photophysics of Ru(II)— and Os(II)—polypyridine complexes in poly(ethyleneoxide) matrices

    NASA Astrophysics Data System (ADS)

    Campagna, Sebastiano; Bartolotta, Antonino; Marco, Gaetano Di

    1993-04-01

    Photophysical properties of Ru(bpy) 32+, Ru(bpy) 2(biq) 2+, and Os(bpy) 32+ (bpy=2,2'-bipyridine; biq=2,2'-biquinoline) in poly(ethyleneoxide) matrices (PEO) constituted by (CH 2CH 2O) repeating units, with average molecular weight 400 (PEO-400, a highly viscous fluid) and 600000 dalton (PEO-600000, a semicrystalline solid) have been studied at room temperature and 77 K. Comparison with similar systems is made. The absorption spectra, luminescence spectra and lifetimes at room temperature of the three complexes in both matrices are in agreement with the typical features reported for the same complexes in fluid solutions, and indicate that fast excited state relaxation via solvent reorganization occurs in both PEO matrices at room temperature. Such behaviour is not usual for solid matrices and is attributed to the microheterogeneous nature of PEO-600000 and to the ability of the solid PEO amorphous region to stabilize polar species within the timescale of radiative relaxation. The results suggest that PEO-600000 is a promising medium for studying electron and energy transfer processes having mild driving forces in the solid state at room temperature.

  7. Dual-mode ferromagnetic resonance in an FeCoB/Ru/FeCoB synthetic antiferromagnet with uniaxial anisotropy

    NASA Astrophysics Data System (ADS)

    Wang, Cuiling; Zhang, Shouheng; Qiao, Shizhu; Du, Honglei; Liu, Xiaomin; Sun, Ruicong; Chu, Xian-Ming; Miao, Guo-Xing; Dai, Youyong; Kang, Shishou; Yan, Shishen; Li, Shandong

    2018-05-01

    Dual-mode ferromagnetic resonance is observed in FeCoB/Ru/FeCoB trilayer synthetic antiferromagnets with uniaxial in-plane magnetic anisotropy. The optical mode is present in the (0-108 Oe) magnetic field range, where the top and bottom layer magnetizations are aligned in opposite directions. The strong acoustic mode appears, when the magnetic field exceeds the 300 Oe value, which corresponds to the flop transition in the trilayer. Magnetic field and angular dependences of resonant frequencies are studied for both optical (low-field) and acoustic (high field) modes. The low-field mode is found to be anisotropic but insensitive to the magnetic field value. In contrast, the high field mode is quasi-isotropic, but its resonant frequency is tunable by the value of the magnetic field. The coexistence of two modes of ferromagnetic resonance as well as switching between them with the increase in the magnetic field originates from the difference in the sign of interlayer coupling energy at the parallel and antiparallel configurations of the synthetic antiferromagnet. The dual-mode resonance in the studied trilayer structures provides greater flexibility in the design and functionalization of micro-inductors in monolithic microwave integrated circuits.

  8. DFT calculations of the structures and vibrational spectra of the [Fe(bpy) 3] 2+ and [Ru(bpy) 3] 2+ complexes

    NASA Astrophysics Data System (ADS)

    Alexander, Bruce D.; Dines, Trevor J.; Longhurst, Rayne W.

    2008-09-01

    Structures of the [M(bpy) 3] 2+ complexes (M = Fe and Ru) have been calculated at the B3-LYP/DZVP level. IR and Raman spectra were calculated using the optimised geometries, employing a scaled quantum chemical force field, and compared with an earlier normal coordinate analysis of [Ru(bpy) 3] 2+ which was based upon experimental data alone, and the use of a simplified model. The results of the calculations provide a highly satisfactory fit to the experimental data and the normal coordinate analyses, in terms of potential energy distributions, allow a detailed understanding of the vibrational spectra of both complexes. Evidence is presented for Jahn-Teller distortion in the 1E MLCT excited state.

  9. Significance of β-dehydrogenation in ethanol electro-oxidation on platinum doped with Ru, Rh, Pd, Os and Ir.

    PubMed

    Sheng, Tian; Lin, Wen-Feng; Hardacre, Christopher; Hu, P

    2014-07-14

    In the exploration of highly efficient direct ethanol fuel cells (DEFCs), how to promote the CO2 selectivity is a key issue which remains to be solved. Some advances have been made, for example, using bimetallic electrocatalysts, Rh has been found to be an efficient additive to platinum to obtain high CO2 selectivity experimentally. In this work, the mechanism of ethanol electrooxidation is investigated using the first principles method. It is found that CH3CHOH* is the key intermediate during ethanol electrooxidation and the activity of β-dehydrogenation is the rate determining factor that affects the completeness of ethanol oxidation. In addition, a series of transition metals (Ru, Rh, Pd, Os and Ir) are alloyed on the top layer of Pt(111) in order to analyze their effects. The elementary steps, α-, β-C-H bond and C-C bond dissociations, are calculated on these bimetallic M/Pt(111) surfaces and the formation potential of OH* from water dissociation is also calculated. We find that the active metals increase the activity of β-dehydrogenation but lower the OH* formation potential resulting in the active site being blocked. By considering both β-dehydrogenation and OH* formation, Ru, Os and Ir are identified to be unsuitable for the promotion of CO2 selectivity and only Rh is able to increase the selectivity of CO2 in DEFCs.

  10. Electron interactions with the heteronuclear carbonyl precursor H2FeRu3(CO)13 and comparison with HFeCo3(CO)12: from fundamental gas phase and surface science studies to focused electron beam induced deposition

    PubMed Central

    P, Ragesh Kumar T; Weirich, Paul; Hrachowina, Lukas; Hanefeld, Marc; Bjornsson, Ragnar; Hrodmarsson, Helgi Rafn; Barth, Sven; Fairbrother, D Howard; Huth, Michael

    2018-01-01

    In the current contribution we present a comprehensive study on the heteronuclear carbonyl complex H2FeRu3(CO)13 covering its low energy electron induced fragmentation in the gas phase through dissociative electron attachment (DEA) and dissociative ionization (DI), its decomposition when adsorbed on a surface under controlled ultrahigh vacuum (UHV) conditions and exposed to irradiation with 500 eV electrons, and its performance in focused electron beam induced deposition (FEBID) at room temperature under HV conditions. The performance of this precursor in FEBID is poor, resulting in maximum metal content of 26 atom % under optimized conditions. Furthermore, the Ru/Fe ratio in the FEBID deposit (≈3.5) is higher than the 3:1 ratio predicted. This is somewhat surprising as in recent FEBID studies on a structurally similar bimetallic precursor, HFeCo3(CO)12, metal contents of about 80 atom % is achievable on a routine basis and the deposits are found to maintain the initial Co/Fe ratio. Low temperature (≈213 K) surface science studies on thin films of H2FeRu3(CO)13 demonstrate that electron stimulated decomposition leads to significant CO desorption (average of 8–9 CO groups per molecule) to form partially decarbonylated intermediates. However, once formed these intermediates are largely unaffected by either further electron irradiation or annealing to room temperature, with a predicted metal content similar to what is observed in FEBID. Furthermore, gas phase experiments indicate formation of Fe(CO)4 from H2FeRu3(CO)13 upon low energy electron interaction. This fragment could desorb at room temperature under high vacuum conditions, which may explain the slight increase in the Ru/Fe ratio of deposits in FEBID. With the combination of gas phase experiments, surface science studies and actual FEBID experiments, we can offer new insights into the low energy electron induced decomposition of this precursor and how this is reflected in the relatively poor performance

  11. Search for the elusive magnetic state of hexagonal iron: The antiferromagnetic Fe71Ru29 hcp alloy

    NASA Astrophysics Data System (ADS)

    Petrillo, C.; Postorino, P.; Orecchini, A.; Sacchetti, F.

    2018-03-01

    The magnetic states of iron and their dependence on crystal structure represent an important case study for the physics of magnetism and its role in fundamental and applied science, including geophysical sciences. hcp iron is the most elusive structure as it exists only at high pressure but, at the same time, it is expected to be stable up to very high temperature. Exploring the magnetic state of pure Fe at high pressure is difficult and no conclusive results have been obtained. Simple binary alloys where the hexagonal phase of Fe is stabilized, offer a more controllable alternative to investigate iron magnetism. We carried out a neutron diffraction experiment on hcp Fe71Ru29 disordered alloy as a function of temperature. Fe in the hexagonal lattice of this specific alloy results to be antiferromagnetically aligned with a rather complex structure and a small magnetic moment. The temperature dependence suggests a Néel temperature TN = 124 ± 10 K, a value consistent with the low magnetic moment of 1.04 ± 0.10 μB obtained from the diffraction data that also suggest a non-commensurate magnetic structure with magnetic moments probably aligned along the c axis. The present data provide evidence for magnetic ordering in hcp Fe and support the theoretical description of magnetism of pure Fe at high pressure.

  12. Magnetic and electronic properties of La3 MO7 and possible polaron formation in hole-doped La3 MO7 (M  =  Ru and Os)

    NASA Astrophysics Data System (ADS)

    Gao, Bin; Weng, Yakui; Zhang, Jun-Jie; Zhang, Huimin; Zhang, Yang; Dong, Shuai

    2017-03-01

    Oxides with 4d/5d transition metal ions are physically interesting for their particular crystalline structures as well as the spin-orbit coupled electronic structures. Recent experiments revealed a series of 4d/5d transition metal oxides R 3 MO7 (R: rare earth; M: 4d/5d transition metal) with unique quasi-one-dimensional M chains. Here first-principles calculations have been performed to study the electronic structures of La3OsO7 and La3RuO7. Our study confirm both of them to be Mott insulating antiferromagnets with identical magnetic order. The reduced magnetic moments, which are much smaller than the expected value for ideal high-spin state (3 t 2g orbitals occupied), are attributed to the strong p  -  d hybridization with oxygen ions, instead of the spin-orbit coupling. The Ca-doping to La3OsO7 and La3RuO7 can not only modulate the nominal carrier density but also affect the orbital order as well as the local distortions. The Coulombic attraction and particular orbital order would prefer to form polarons, which might explain the puzzling insulating behavior of doped 5d transition metal oxides. In addition, our calculations predict that the Ca-doping can trigger ferromagnetism in La3RuO7 but not in La3OsO7.

  13. The series of carbon-chain complexes {Ru(dppe)Cp*}₂{μ-(C≡C )x} (x = 4–8, 11): Synthesis, structures, properties and some reactions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bruce, Michael I.; Cole, Marcus L.; Ellis, Benjamin G.

    The construction of a series of compounds {Ru(dppe)Cp*} 2(μ-C 2x) (Ru*-C2x-Ru*, x = 4–8, 11)) is described. A direct reaction between RuCl(dppe)Cp* and Me 3Si(Ctriple bond; length of mdashC) 4SiMe 3 afforded Ru*-C8-Ru* in 89% yield. The Pd(0)/Cu(I)-catalysed coupling of Ru{Ctriple bond; length of mdashCCtriple bond; length of mdashCAu(PPh 3)}(dppe)Cp*Ru*-C4-Au (2 equiv.) with diiodoethyne gave Ru*-C10-Ru* (64%), or of 1 equiv. with I(Ctriple bond; length of mdashC) 3I gave Ru*-C14-Ru* (36%); similarly, Ru{(Ctriple bond; length of mdashC) 4Au(PPh 3)}(dppe)Cp*Ru*-C8-Au and I(Ctriple bond; length of mdashC) 3I gave Ru*-C22-Ru* (12%). Desilylation (TBAF) of Ru{(Ctriple bond; length of mdashC)xSiMe 3}(dppe)Cp*Ru*-C2x-Si (x =more » 3, 4) followed by oxidative coupling [Cu(OAc) 2/py] gave Ru*-C12-Ru* (82%) and Ru*-C16-Ru* (58%), respectively. Similar oxidative coupling of Ru(Ctriple bond; length of mdashCCtriple bond; length of mdashCH)(dppe)Cp* was a second route to Ru*-C8-Ru* (82%). Appropriate precursors are already known, or obtained by coupling of Ru*-C2x-Si (x = 2, 4) with AuCl(PPh 3)/NaOMe [Ru*-C4-Au, 95%; Ru*-C8-Au, 74%] or from Pd(0)/Cu(I) catalysed coupling of Ru*-C2x-Au (x = 2, 3) with I(Ctriple bond; length of mdashC) 2SiMe 3 (Ru*-C8-Si, 64%; Ru*-C10-Si, 2%). Reactions between Ru*-C2x-Ru* (x = 3, 4) and Fe 2(CO) 9 gave {Fe 3(CO) 9}{μ 3-CCtriple bond; length of mdashC[Ru(dppe)Cp*]} 2Fe(C 3-Ru*) 2 and {Fe 3(CO) 9}{μ 3-CCtriple bond; length of mdashC[Ru(dppe)Cp*]}{μ 3-C(Ctriple bond; length of mdashC) 2[Ru(dppe)Cp*]} Fe(C 3-Ru*)(C 5-Ru*), respectively. The redox properties of the series of complexes with 2x = 2–16 were measured and showed a diminution of the separation of the first two oxidation potentials, ΔE = E 2 - E 1, with increasing carbon chain length. The X-ray-determined molecular structures of Ru*-C8-Si, Ru*-C8-Ru*, Ru*-C14-Ru* (two C 6H 6 solvates), {Ru(PPh 3) 2Cp} 2{μ-(Ctriple bond; length of mdashC) 4}·4CHCl 3Ru-C 8-Ru·4CHCl 3 and of Fe

  14. 186Os-187Os and highly siderophile element abundance systematics of the mantle revealed by abyssal peridotites and Os-rich alloys

    NASA Astrophysics Data System (ADS)

    Day, James M. D.; Walker, Richard J.; Warren, Jessica M.

    2017-03-01

    Abyssal peridotites are oceanic mantle fragments that were recently processed through ridges and represent residues of both modern and ancient melting. To constrain the nature and timing of melt depletion processes, and the composition of the mantle, we report high-precision Os isotope data for abyssal peridotites from three ocean basins, as well as for Os-rich alloys, primarily from Mesozoic ophiolites. These data are complemented by whole-rock highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re), trace- and major-element abundances for the abyssal peridotites, which are from the Southwest Indian (SWIR), Central Indian (CIR), Mid-Atlantic (MAR) and Gakkel Ridges. The results reveal a limited role for melt refertilization or secondary alteration processes in modifying abyssal peridotite HSE compositions. The abyssal peridotites examined have experienced variable melt depletion (2% to >16%), which occurred >0.5 Ga ago for some samples. Abyssal peridotites typically exhibit low Pd/Ir and, combined with high-degrees of estimated total melt extraction, imply that they were relatively refractory residues prior to incorporation into their present ridge setting. Recent partial melting processes and mid-ocean ridge basalt (MORB) generation therefore played a limited role in the chemical evolution of their precursor mantle domains. The results confirm that many abyssal peridotites are not simple residues of recent MORB source melting, having a more complex and long-lived depletion history. Peridotites from the Gakkel Ridge, SWIR, CIR and MAR indicate that the depleted MORB mantle has 186Os/188Os of 0.1198356 ± 21 (2SD). The Phanerozoic Os-rich alloys yield an average 186Os/188Os within uncertainty of abyssal peridotites (0.1198361 ± 20). Melt depletion trends defined between Os isotopes and melt extraction indices (e.g., Al2O3) allow an estimate of the primitive mantle (PM) composition, using only abyssal peridotites. This yields 187Os/188Os (0.1292 ± 25), and 186Os

  15. Anion-cation charge-transfer properties and spectral studies of [M(phen)3][Cd4(SPh)10] (M = Ru, Fe, and Ni).

    PubMed

    Jiang, Jian-Bing; Bian, Guo-Qing; Zhang, Ya-Ping; Luo, Wen; Zhu, Qin-Yu; Dai, Jie

    2011-10-07

    Three anion-cation compounds 1-3 with formula [M(phen)(3)][Cd(4)(SPh)(10)]·Sol (M = Ru(2+), Fe(2+), and Ni(2+), Sol = MeCN and H(2)O) have been synthesized and characterized by single-crystal analysis. Both the cations and anion are well-known ions, but the properties of the co-assembled compounds are interesting. Molecular structures and charge-transfer between the cations and anions in crystal and even in solution are discussed. These compounds are isomorphous and short inter-ion interactions are found in these crystals, such as π···π stacking and C-H···π contacts. Both spectroscopic and theoretical calculated results indicate that there is anion-cation charge-transfer (ACCT) between the Ru-phen complex dye and the Cd-SPh cluster, which plays an important role in their photophysical properties. The intensity of the fluorescent emission of the [Ru(phen)(3)](2+) is enhanced when the cation interacts with the [Cd(4)(SPh)(10)](2-) anion. The mechanism for the enhancement of photoluminescence has been proposed.

  16. Oxygen trapped by rare earth tetrahedral clusters in Nd4FeOS6: Crystal structure, electronic structure, and magnetic properties

    NASA Astrophysics Data System (ADS)

    Lin, Qisheng; Taufour, Valentin; Zhang, Yuemei; Wood, Max; Drtina, Thomas; Bud'ko, Sergey L.; Canfield, Paul C.; Miller, Gordon J.

    2015-09-01

    Single crystals of Nd4FeOS6 were grown from an Fe-S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4MnOSe6-type structure (P63mc, a=9.2693(1) Å, c=6.6650(1)Å, V=495.94(1) Å3, Z=2), featuring parallel chains of face-sharing [FeS6×1/2]4- trigonal antiprisms and interlinked [Nd4OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4MnOSe6-type Nd4FeOS6 and the related La3CuSiS7- and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4FeOS6 suggested the dominance of antiferromagnetic interactions at low temperature, but no magnetic ordering down to 2 K was observed. Spin-polarized electronic structure calculations revealed magnetic frustration with dominant antiferromagnetic interactions.

  17. Exploring the Photovoltaic Properties of Metal Bipyridine Complexes (Metal = Fe, Zn, Cr, and Ru) by Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Irfan, Ahmad; Abbas, Ghulam

    2018-03-01

    The synthesis and characterisation of mononuclear Fe complexes were carried out by using bipyridine (Compound 1) at ambient conditions. Additionally, three more derivatives were designed by substituting the central Fe metal with Zn, Cr, and Ru (Compound 2, Compound 3, and Compound 4), respectively. The ground state geometry calculations were carried out by using density functional theory (DFT) at B3LYP/6-31G** (LANL2DZ) level of theory. We shed light on the frontier molecular orbitals, electronic properties, photovoltaic parameters, and structure-property relationship. The open-circuit voltage is a promising parameter that considerably affects the photovoltaic performance; thus, we have estimated its value by considering the complexes as donors whereas TiO2 and/or Si were used as acceptors. The solar cell performance behaviour was also studied by shedding light on the band alignment and energy level offset.

  18. Modeling of hysteretic Schottky diode-like conduction in Pt/BiFeO3/SrRuO3 switches

    NASA Astrophysics Data System (ADS)

    Miranda, E.; Jiménez, D.; Tsurumaki-Fukuchi, A.; Blasco, J.; Yamada, H.; Suñé, J.; Sawa, A.

    2014-08-01

    The hysteresis current-voltage (I-V) loops in Pt/BiFeO3/SrRuO3 structures are simulated using a Schottky diode-like conduction model with sigmoidally varying parameters, including series resistance correction and barrier lowering. The evolution of the system is represented by a vector in a 3D parameter space describing a closed trajectory with stationary states. It is shown that the hysteretic behavior is not only the result of a Schottky barrier height (SBH) variation arising from the BiFeO3 polarization reversal but also a consequence of the potential drop distribution across the device. The SBH modulation is found to be remarkably lower (<0.07 eV) than previously reported (>0.5 eV). It is also shown that the p-type semiconducting nature of BiFeO3 can explain the large ideality factors (>6) required to simulate the I-V curves as well as the highly asymmetric set and reset voltages (4.7 V and -1.9 V) exhibited by our devices.

  19. Frustration by competing interactions in the highly-distorted double perovskites La2NaRuO6 and La2NaOsO6

    NASA Astrophysics Data System (ADS)

    Aczel, A. A.; Bugaris, D. E.; Li, L.; Yan, J.-Q.; de La Cruz, C.; Zur Loye, H.-C.; Nagler, S. E.

    2013-03-01

    The usual classical behavior of S = 3/2, B-site ordered double perovskites results in simple, commensurate magnetic ground states. In contrast, heat capacity and neutron powder diffraction measurements for the S = 3/2 systems La2NaB'O6 (B' = Ru, Os) reveal an incommensurate magnetic ground state for La2NaRuO6 and a drastically suppressed ordered moment for La2NaOsO6. This behavior is attributed to the large monoclinic structural distortions of these double perovskites. The distortions have the effect of weakening the nearest neighbor superexchange interactions, presumably to an energy scale that is comparable to the next nearest neighbor superexchange. The exotic ground states in these materials can then arise from a competition between these two types of antiferromagnetic interactions, providing a novel mechanism for achieving frustration in the double perovskite family. Work at ORNL is supported by the Division of Scientific User Facilities and the Materials Science and Engineering Division, DOE Basic Energy Sciences. Work at the University of South Carolina is supported by the Heterogeneous Functional Materials Research Center, funded by DOE under award number de-sc0001061.

  20. Unanticipated spin gap measured in the frustrated quasi-FCC d3 double perovskites La2 LiXO6 (X = Ru, Os)

    NASA Astrophysics Data System (ADS)

    Maharaj, Dalini D.; Sala, Gabriele; Marjerrison, Casey A.; Greedan, John; Gaulin, Bruce; Stone, Matthew

    There is much current interest in the influence of strong spin-orbit (SO) interactions on exotic ground state selection in new 4d and 5d magnets, particularly involving 4d5 Ir. Here we consider double perovskites of the form A2 BB'O6 which are based on heavy 4d or 5d magnetic ions, where the SO interaction is expected to be significant as it increases as ~Z4 . The double perovskite structure can accommodate a variety of magnetic ions on the B' site, providing a playground for systematic studies of the exotic ground states stabilized by strong SO coupling. Here, we report inelastic neutron scattering (INS) measurements conducted on the frustrated monoclinic magnets, La2LiXO6 (X = Ru, Os), wherein the magnetic moments decorate a quasi face-centered-cubic lattice. Our results show the development of a spin gap in the spin excitation spectrum of size ΔOs = 8 meV and ΔRu = 2.5meV concomitant with TN, which is unexpected for orbitally quenched d3 systems. We liken these results to INS results obtained for Ba2YXO6 and La2NaXO6, which were also shown to exhibit spin gaps that correlate with TN. We shall discuss trends observed in these three d3 double perovskite families which correlate strong SO coupling, spin gap and TN.

  1. Hidden order signatures in the antiferromagnetic phase of U ( Ru 1 - x Fe x ) 2 Si 2

    DOE PAGES

    Williams, Travis J.; Aczel, Adam A.; Stone, Matthew B.; ...

    2017-03-31

    We present a comprehensive set of elastic and inelastic neutron scattering measurements on a range of Fe-doped samples of U(Ru 1–xFe x) 2Si 2 with 0.01 ≤ x ≤ 0.15. All of the samples measured exhibit long-range antiferromagnetic order, with the size of the magnetic moment quickly increasing to 0.51μB at 2.5% doping and continuing to increase monotonically with doping, reaching 0.69μB at 15% doping. Time-of-flight and inelastic triple-axis measurements show the existence of excitations at (1 0 0) and (1.4 0 0) in all samples, which are also observed in the parent compound. While the excitations in the 1%more » doping are quantitatively identical to the parent material, the gap and width of the excitations change rapidly at 2.5% Fe doping and above. The 1% doped sample shows evidence for a separation in temperature between the hidden order and antiferromagnetic transitions, suggesting that the antiferromagnetic state emerges at very low Fe dopings. Finally, the combined neutron scattering data suggest not only discontinuous changes in the magnetic moment and excitations between the hidden order and antiferromagnetic phases, but that these changes continue to evolve up to at least x = 0.15.« less

  2. Chemical pressure tuning of URu2Si2 via isoelectronic substitution of Ru with Fe

    NASA Astrophysics Data System (ADS)

    Das, Pinaki; Kanchanavatee, N.; Helton, J. S.; Huang, K.; Baumbach, R. E.; Bauer, E. D.; White, B. D.; Burnett, V. W.; Maple, M. B.; Lynn, J. W.; Janoschek, M.

    2015-02-01

    We have used specific heat and neutron diffraction measurements on single crystals of URu2 -xFexSi2 for Fe concentrations x ≤0.7 to establish that chemical substitution of Ru with Fe acts as "chemical pressure" Pc h as previously proposed by Kanchanavatee et al. [Phys. Rev. B 84, 245122 (2011), 10.1103/PhysRevB.84.245122] based on bulk measurements on polycrystalline samples. Notably, neutron diffraction reveals a sharp increase of the uranium magnetic moment at x =0.1 , reminiscent of the behavior at the "hidden order" to large-moment-antiferromagnetic phase transition observed at a pressure Px≈0.5 -0.7 GPa in URu2Si2 . Using the unit-cell volume determined from our measurements and an isothermal compressibility κT=5.2 ×10-3 GPa-1 for URu2Si2 , we determine the chemical pressure Pc h in URu2 -xFexSi2 as a function of x . The resulting temperature (T )-chemical pressure (Pc h) phase diagram for URu2 -xFexSi2 is in agreement with the established temperature (T )-external pressure (P ) phase diagram of URu2Si2 .

  3. The role of the non-magnetic material in spin pumping and magnetization dynamics in NiFe and CoFeB multilayer systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ruiz-Calaforra, A., E-mail: ruiz@physik.uni-kl.de; Brächer, T.; Lauer, V.

    2015-04-28

    We present a study of the effective magnetization M{sub eff} and the effective damping parameter α{sub eff} by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni{sub 81}Fe{sub 19} (NiFe) and Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) in FM/Pt, FM/NM, and FM/NM/Pt systems with the non-magnetic (NM) materials Ru, Cr, Al, and MgO. Moreover, for NiFe layer systems, the influence of interface effects is studied by way of thickness dependent measurements of M{sub eff} and α{sub eff}. Additionally, spin pumping in NiFe/NM/Pt is investigated by means of inverse spin Hall effect (ISHE) measurements. We observe a large dependence ofmore » M{sub eff} and α{sub eff} of the NiFe films on the adjacent NM layer. While Cr and Al do not induce a large change in the magnetic properties, Ru, Pt, and MgO affect M{sub eff} and α{sub eff} in different degrees. In particular, NiFe/Ru and NiFe/Ru/Pt systems show a large perpendicular surface anisotropy and a significant enhancement of the damping. In contrast, the magnetic properties of CoFeB films do not have a large influence of the NM adjacent material and only CoFeB/Pt systems present an enhancement of α{sub eff}. However, this enhancement is much more pronounced in NiFe/Pt. By the introduction of the NM spacer material, this enhancement is reduced. Furthermore, a difference in symmetry between NiFe/NM/Pt and NiFe/NM systems in the output voltage signal from the ISHE measurements reveals the presence of spin pumping into the Pt layer in all-metallic NiFe/NM/Pt and NiFe/Pt systems.« less

  4. Influence of central metalloligand geometry on electronic communication between metals: syntheses, crystal structures, MMCT properties of isomeric cyanido-bridged Fe2Ru complexes, and TDDFT calculations.

    PubMed

    Ma, Xiao; Lin, Chen-Sheng; Hu, Sheng-Min; Tan, Chun-Hong; Wen, Yue-Hong; Sheng, Tian-Lu; Wu, Xin-Tao

    2014-06-02

    To investigate how the central metalloligand geometry influences distant or vicinal metal-to-metal charge-transfer (MMCT) properties of polynuclear complexes, cis- and trans-isomeric heterotrimetallic complexes, and their one- and two-electron oxidation products, cis/trans-[Cp(dppe)Fe(II)NCRu(II)(phen)2CN-Fe(II)(dppe)Cp][PF6]2 (cis/trans-1[PF6]2), cis/trans-[Cp(dppe)Fe(II)NCRu(II)(phen)2CNFe(III)-(dppe)Cp][PF6]3 (cis/trans-1[PF6]3) and cis/trans-[Cp(dppe)Fe(III)NCRu(II)(phen)2CN-Fe(III)(dppe)Cp][PF6]4 (cis/trans-1[PF6]4) have been synthesized and characterized. Electrochemical measurements show the presence of electronic interactions between the two external Fe(II) atoms of the cis- and trans-isomeric complexes cis/trans-1[PF6]2. The electronic properties of all these complexes were studied and compared by spectroscopic techniques and TDDFT//DFT calculations. As expected, both mixed valence complexes cis/trans-1[PF6]3 exhibited different strong absorption signals in the NIR region, which should mainly be attributed to a transition from an MO that is delocalized over the Ru(II)-CN-Fe(II) subunit to a Fe(III) d orbital with some contributions from the co-ligands. Moreover, the NIR transition energy in trans-1[PF6]3 is lower than that in cis-1[PF6]3, which is related to the symmetry of their molecular orbitals on the basis of the molecular orbital analysis. Also, the electronic spectra of the two-electron oxidized complexes show that trans-1[PF6]4 possesses lower vicinal Ru(II) → Fe(III) MMCT transition energy than cis-1[PF6]4. Moreover, the assignment of MMCT transition of the oxidized products and the differences of the electronic properties between the cis and trans complexes can be well rationalized using TDDFT//DFT calculations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Cross sections of X-ray production induced by C and Si ions with energies up to 1 MeV/u on Ti, Fe, Zn, Nb, Ru and Ta

    NASA Astrophysics Data System (ADS)

    Prieto, José Emilio; Zucchiatti, Alessandro; Galán, Patricia; Prieto, Pilar

    2017-09-01

    X-ray production differential cross sections induced by C and Si ions with energies from 1 MeV/u down to 0.25 MeV/u, produced by the CMAM 5 MV tandem accelerator, have been measured for thin targets of Ti, Fe, Zn, Nb, Ru and Ta in a direct way. X-rays have been detected by a fully characterized silicon drift diode and beam currents have been measured by a system of two Faraday cups. Measured cross sections agree in general with previously published results. The ECPSSR theory with the united atoms correction gives absolute values close to the experimental ones for all the studied elements excited by C ions and for Ta, Nb and Ru excited by Si ions. For Ti, Fe and Zn excited by Si, the matching with theory is poor since even the ionization cross section is below the measured data.

  6. CeRuPO: A rare example of a ferromagnetic Kondo lattice

    NASA Astrophysics Data System (ADS)

    Krellner, C.; Kini, N. S.; Brüning, E. M.; Koch, K.; Rosner, H.; Nicklas, M.; Baenitz, M.; Geibel, C.

    2007-09-01

    We have determined the physical ground state properties of the compounds CeRuPO and CeOsPO by means of magnetic susceptibility χ(T) , specific heat C(T) , electrical resistivity ρ(T) , and thermopower S(T) measurements. χ(T) reveals a trivalent 4f1 cerium state in both compounds. For CeRuPO a pronounced decrease of ρ(T) below 50K indicates the onset of coherent Kondo scattering, which is confirmed by enhanced S(T) . The temperature and magnetic field dependence of χ(T) and C(T) evidence ferromagnetic (FM) order at TC=15K . Thus, CeRuPO seems to be one of the rare examples of a FM Kondo lattice. In contrast, CeOsPO shows antiferromagnetic order at TN=4.5K despite only minor changes in lattice parameters and electronic configuration. Additional P31 NMR results support these scenarios. LSDA+U calculations evidence a quasi-two-dimensional electronic band structure, reflecting a strong covalent bonding within the CeO and RuP layers and a weak ioniclike bonding between the layers.

  7. Fabrication of hollow nanorod electrodes based on RuO2//Fe2O3 for an asymmetric supercapacitor.

    PubMed

    Wang, Qiufan; Liang, Xiao; Ma, Yun; Zhang, Daohong

    2018-06-12

    In this work, hollow RuO2 nanotube arrays were successfully grown on carbon cloth by using a facile two-step method to fabricate a binder-free electrode. The well-aligned electrode displays excellent electrochemical performance. By using RuO2 hollow nanotube arrays as the positive electrode and Fe2O3 as the negative electrode, a flexible solid-state asymmetric supercapacitor (ASC) has been fabricated which exhibited excellent electrochemical performance, such as a high capacitance of 4.9 F cm-3, a high energy density of 1.5 mW h cm-3 and a high power density of 9.1 mW cm-3. In addition, the two-electrode SC shows high cycling stability with 97% capacitance retention after 5000 charge-discharge cycles. These excellent electrochemical performances are ascribed to the unique hollow structural design of electrodes, which can shorten the ion diffusion length, provide a fast ion transport channel, and offer a large electrode/electrolyte interface for the charge-transfer reaction. The structural design and the synthesis approach are general and can be extended to synthesizing a broad range of materials systems.

  8. Synthesis of PtRu/Ru heterostructure for efficient methanol electrooxidation: The role of extra Ru

    NASA Astrophysics Data System (ADS)

    Bai, Lei

    2018-03-01

    Platinum-ruthenium (PtRu) nanocubes and PtRu/Ru heterostructure via epitaxial growth were synthesized by varying the amount of Ru precursor. As model catalysts, the PtRu/Ru heterostructure demonstrated the highest catalytic performance in electrooxidation of methanol, which was possibly due to the more hydroxyl species produced from the extra Ru nanoparticles as well as enhanced adsorption of methanol of PtRu alloys in the PtRu/Ru heterostructure. The catalytic performance of the catalysts was closely related with the structure, which was well characterized by a series of methods. It was expected that the present work could provide a new insight for the synthesis of PtRu based nanocatalysts.

  9. Interface Control of Ferroelectricity in an SrRuO3 /BaTiO3 /SrRuO3 Capacitor and its Critical Thickness.

    PubMed

    Shin, Yeong Jae; Kim, Yoonkoo; Kang, Sung-Jin; Nahm, Ho-Hyun; Murugavel, Pattukkannu; Kim, Jeong Rae; Cho, Myung Rae; Wang, Lingfei; Yang, Sang Mo; Yoon, Jong-Gul; Chung, Jin-Seok; Kim, Miyoung; Zhou, Hua; Chang, Seo Hyoung; Noh, Tae Won

    2017-05-01

    The atomic-scale synthesis of artificial oxide heterostructures offers new opportunities to create novel states that do not occur in nature. The main challenge related to synthesizing these structures is obtaining atomically sharp interfaces with designed termination sequences. In this study, it is demonstrated that the oxygen pressure (PO2) during growth plays an important role in controlling the interfacial terminations of SrRuO 3 /BaTiO 3 /SrRuO 3 (SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures are grown by a pulsed laser deposition method. The top SRO/BTO interface, grown at high PO2 (around 150 mTorr), usually exhibits a mixture of RuO 2 -BaO and SrO-TiO 2 terminations. By reducing PO2, the authors obtain atomically sharp SRO/BTO top interfaces with uniform SrO-TiO 2 termination. Using capacitor devices with symmetric and uniform interfacial termination, it is demonstrated for the first time that the FE critical thickness can reach the theoretical limit of 3.5 unit cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Interface Control of Ferroelectricity in an SrRuO 3/BaTiO 3/SrRuO 3 Capacitor and its Critical Thickness

    DOE PAGES

    Shin, Yeong Jae; Kim, Yoonkoo; Kang, Sung -Jin; ...

    2017-03-03

    Here, the atomic-scale synthesis of artificial oxide heterostructures offers new opportunities to create novel states that do not occur in nature. The main challenge related to synthesizing these structures is obtaining atomically sharp interfaces with designed termination sequences. In this study, it is demonstrated that the oxygen pressure (P O2) during growth plays an important role in controlling the interfacial terminations of SrRuO 3/BaTiO 3/SrRuO 3 (SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures are grown by a pulsed laser deposition method. The top SRO/BTO interface, grown at high P O2 (around 150 mTorr), usually exhibits a mixture of RuO 2-BaOmore » and SrO-TiO 2 terminations. By reducing P O2, the authors obtain atomically sharp SRO/BTO top interfaces with uniform SrO-TiO 2 termination. Using capacitor devices with symmetric and uniform interfacial termination, it is demonstrated for the first time that the FE critical thickness can reach the theoretical limit of 3.5 unit cells.« less

  11. Electrochemical oxidation of methanol using dppm-bridged Ru/Pd, Ru/Pt and Ru/Au catalysts.

    PubMed

    Yang, Ying; McElwee-White, Lisa

    2004-08-07

    The electrochemical oxidation of methanol was carried out using a series of dppm-bridged Ru/Pd, Ru/Pt and Ru/Au heterobimetallic complexes as catalysts. The major oxidation products were formaldehyde dimethyl acetal (dimethoxymethane, DMM) and methyl formate (MF). The Ru/Pd and Ru/Pt bimetallic catalysts generally afforded lower product ratios of DMM/MF and higher current efficiencies than the Ru/Au catalysts. The Ru/Au bimetallics exhibited product ratios and current efficiencies similar to those obtained from the Ru mononuclear compound CpRu(PPh(3))(2)Cl. Increasing the methanol concentration afforded higher current efficiencies, while the addition of water to the samples shifted the product distribution toward the more highly oxidized product, MF.

  12. Enhanced interlayer exchange coupling in antiferromagnetically coupled ultrathin (Co70Fe30/Pd) multilayers

    NASA Astrophysics Data System (ADS)

    Meng, Zhaoliang; Qiu, Jinjun; Han, Guchang; Teo, Kie Leong

    2015-12-01

    We report the studies of magnetization reversal and magnetic interlayer coupling in synthetic antiferromagnetic (SAF) [Pd/Co70Fe30]9/Ru(tRu)/Pd(tPd)/[Co70Fe30/Pd]9 structure as functions of inserted Pd layer (tPd) and Ru layer (tRu) thicknesses. We found the exchange coupling field (Hex) and perpendicular magnetic anisotropy (PMA) can be controlled by both the tPd and tRu, The Hex shows a Ruderman-Kittel-Kasuya-Yosida-type oscillatory decay dependence on tRu and a maximum interlayer coupling strength Jex = 0.522 erg/cm2 is achieved at tPd + tRu ≈ 0.8 nm in the as-deposited sample. As it is known that a high post-annealing stability of SAF structure is required for magnetic random access memory applications, the dependence of Hex and PMA on the post-annealing temperature (Ta) is also investigated. We found that both high PMA of the top Co70Fe30/Pd multilayer is maintained and Hex is enhanced with increasing Ta up to 350 °C for tRu > 0.7 nm in our SAF structure.

  13. Magnetic anomalies in self-assembled SrRuO3 -CoFe2O4 nanostructures studied by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Chun; Huang, Yen-Chin; Chien, Chia-Hsien; Liu, Heng-Jui; Chu, Ying-Hao

    2015-03-01

    Self-assembled nanostructures with high interface-to-volume ratio usually possess interesting physical properties through the coupling between neighboring materials. In complex-oxide nanocomposites, the interplay of spin, charge, orbital, and lattice degrees of freedom especially provides various functionalities. Our recent study had shown photo-induced magnetization switching in a self-assembled system, CoFe2O4 (CFO)- SrRuO3(SRO), where the CFO nanopillars were embedded in the SRO matrix. Moreover, this system also has significant magnetoresistance behaviors. In this study, we used Raman spectroscopy to investigate the magnetic coupling mechanisms in CFO-SRO nanostructures. Compared to the pure CFO films, the CFO nano-pillars under out-of-plane compressive strain show a slightly increase of A1g(Co)/A1g(Fe) intensity ratio, which corresponds to a migration of Co ions from O-site (oxygen octahedron) to T-site (oxygen tetrahedron). This behavior can be further tuned by external stimulus, such as magnetic fields and temperatures. A strong increase of A1g(Co)/A1g(Fe) ratio together with a discontinuous A1g frequency shift occur at the SRO magnetic transition temperature. This result indicated that the spin-orbital interaction in CFO can be modulated by the SRO magnetic orderings.

  14. Investigation of energy band alignments and interfacial properties of rutile NMO2/TiO2 (NM = Ru, Rh, Os, and Ir) by first-principles calculations.

    PubMed

    Yang, Chen; Zhao, Zong-Yan

    2017-11-08

    In the field of photocatalysis, constructing hetero-structures is an efficient strategy to improve quantum efficiency. However, a lattice mismatch often induces unfavorable interfacial states that can act as recombination centers for photo-generated electron-hole pairs. If the hetero-structure's components have the same crystal structure, this disadvantage can be easily avoided. Conversely, in the process of loading a noble metal co-catalyst onto the TiO 2 surface, a transition layer of noble metal oxides is often formed between the TiO 2 layer and the noble metal layer. In this article, interfacial properties of hetero-structures composed of a noble metal dioxide and TiO 2 with a rutile crystal structure have been systematically investigated using first-principles calculations. In particular, the Schottky barrier height, band bending, and energy band alignments are studied to provide evidence for practical applications. In all cases, no interfacial states exist in the forbidden band of TiO 2 , and the interfacial formation energy is very small. A strong internal electric field generated by interfacial electron transfer leads to an efficient separation of photo-generated carriers and band bending. Because of the differences in the atomic properties of the components, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures demonstrate band dividing, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures have a pseudo-gap near the Fermi energy level. Furthermore, NMO 2 /TiO 2 hetero-structures show upward band bending. Conversely, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures present a relatively strong infrared light absorption, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures show an obvious absorption edge in the visible light region. Overall, considering all aspects of their properties, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures are more suitable than others for improving the photocatalytic performance of TiO 2 . These findings will provide useful information

  15. Infrared spectra of RuTPP, RuCOTPP, and Ru(CO)2TPP isolated in solid argon.

    PubMed

    Krim, Lahouari; Sorgues, Sébastien; Soep, Benoit; Shafizadeh, Niloufar

    2005-09-22

    Infrared spectra of unstable species such as CO-free ruthenium tetraphenylporphyrin RuTPP and RuCOTPP (species with vacant coordination sites) isolated in solid argon at 8 K have been recorded. Selective deposition conditions allow the isolation of either RuTPP and RuCOTPP or RuCOTPP and Ru(CO)2TPP. This depends on the preparation conditions of the sample. A specific Ru-CO bending mode has been characterized at 590.1 cm(-1) for Ru(CO)2TPP. The behavior of each vibrational mode of RuTPP, RuCOTPP, and Ru(CO)2TPP has been analyzed. Modes such as gamma8 at 721.3 cm(-1) (out-of-plane stretching mode gamma(Cbeta-H)sym) and nu41 at 1342.8 cm(-1) (nuCalpha-N coupled with deltaCalpha-Cm) reflect the charge transfer in the porphyrin. Indeed, the addition of one or two CO ligands to RuTPP reduces the charge transfer between the metal center and the porphyrin, which appears as an increase in the frequency of the nu41 mode and in a decrease in that of the gamma8 mode.

  16. Effects of disordered Ru substitution in BaFe2As2: possible realization of superdiffusion in real materials.

    PubMed

    Wang, Limin; Berlijn, Tom; Wang, Yan; Lin, Chia-Hui; Hirschfeld, P J; Ku, Wei

    2013-01-18

    An unexpected insensitivity of the Fermi surface to impurity scattering is found in Ru substituted BaFe(2)As(2) from first-principles theory, offering a natural explanation of the unusual resilience of transport and superconductivity to a high level of disordered substitution in this material. This robustness is shown to originate from a coherent interference of correlated on-site and intersite impurity scattering, similar in spirit to the microscopic mechanism of superdiffusion in one dimension. Our result also demonstrates a strong substitution dependence of the Fermi surface and carrier concentration and provides a resolution to current discrepancies in recent photoelectron spectroscopy. These effects offer a natural explanation of the diminishing long-range magnetic, orbital, and superconducting orders with high substitution.

  17. Molecule-based magnets formed by bimetallic three-dimensional oxalate networks and chiral tris(bipyridyl) complex cations. The series [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion).

    PubMed

    Coronado, E; Galán-Mascarós, J R; Gómez-García, C J; Martínez-Agudo, J M

    2001-01-01

    The synthesis, structure, and physical properties of the series of molecular magnets formulated as [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion) are presented. All the compounds are isostructural to the [Ru(bpy)3][ClO4][MnCr(ox)3] member whose structure (cubic space group P4(1)32 with a = 15.506(2) A, Z = 4) consists of a three-dimensional bimetallic network formed by alternating MII and CrIII ions connected by oxalate anions. The identical chirality (lambda in the solved crystal) of all the metallic centers determines the 3D chiral structure adopted by these compounds. The anionic 3D sublattice leaves some holes where the chiral [Z(bpy)3]2+ and ClO4- counterions are located. These compounds behave as soft ferromagnets with ordering temperatures up to 6.6 K and coercive fields up to 8 mT.

  18. Characterization and methanol electrooxidation studies of Pt(111)/Os surfaces prepared by spontaneous deposition.

    PubMed

    Johnston, Christina M; Strbac, Svetlana; Lewera, Adam; Sibert, Eric; Wieckowski, Andrzej

    2006-09-12

    Catalytic activity of the Pt(111)/Os surface toward methanol electrooxidation was optimized by exploring a wide range of Os coverage. Various methods of surface analyses were used, including electroanalytical, STM, and XPS methods. The Pt(111) surface was decorated with nanosized Os islands by spontaneous deposition, and the Os coverage was controlled by changing the exposure time to the Os-containing electrolyte. The structure of Os deposits on Pt(111) was characterized and quantified by in situ STM and stripping voltammetry. We found that the optimal Os surface coverage of Pt(111) for methanol electrooxidation was 0.7 +/- 0.1 ML, close to 1.0 +/- 0.1 Os packing density. Apparently, the high osmium coverage Pt(111)/Os surface provides more of the necessary oxygen-containing species (e.g., Os-OH) for effective methanol electrooxidation than the Pt(111)/Os surfaces with lower Os coverage (vs e.g., Ru-OH). Supporting evidence for this conjecture comes from the CO electrooxidation data, which show that the onset potential for CO stripping is lowered from 0.53 to 0.45 V when the Os coverage is increased from 0.2 to 0.7 ML. However, the activity of Pt(111)/Os for methanol electrooxidation decreases when the Os coverage is higher than 0.7 +/- 0.1 ML, indicating that Pt sites uncovered by Os are necessary for sustaining significant methanol oxidation rates. Furthermore, osmium is inactive for methanol electrooxidation when the platinum substrate is absent: Os deposits on Au(111), a bulk Os ingot, and thick films of electrodeposited Os on Pt(111), all compare poorly to Pt(111)/Os. We conclude that a bifunctional mechanism applies to the methanol electrooxidation similarly to Pt(111)/Ru, although with fewer available Pt sites. Finally, the potential window for methanol electrooxidation on Pt(111)/Os was observed to shift positively versus Pt(111)/Ru. Because of the difference in the Os and Ru oxophilicity under electrochemical conditions, the Os deposit provides fewer

  19. QUANTIFYING THE CARBON ABUNDANCES IN THE SECONDARY STARS OF SS CYGNI, RU PEGASI, AND GK PERSEI

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harrison, Thomas E.; Hamilton, Ryan T., E-mail: tharriso@nmsu.edu, E-mail: rthamilton@sofia.usra.edu

    We use a modified version of MOOG to generate large grids of synthetic spectra in an attempt to derive quantitative abundances for three CVs (GK Per, RU Peg, and SS Cyg) by comparing the models to moderate resolution (R ∼ 25,000) K-band spectra obtained with NIRSPEC on Keck. For each of the three systems we find solar, or slightly sub-solar values for [Fe/H], but significant deficits of carbon: for SS Cyg we find [C/Fe] = −0.50, for RU Peg [C/Fe] = −0.75, and for GK Per [C/Fe] = −1.00. We show that it is possible to use lower resolution (Rmore » ∼ 2000) spectra to quantify carbon deficits. We examine realistic veiling scenarios and find that emission from H i or CO cannot reproduce the observations.« less

  20. Relativistic effects in iron-, ruthenium-, and osmium porphyrins

    NASA Astrophysics Data System (ADS)

    Liao, Meng-Sheng; Scheiner, Steve

    2002-12-01

    Nonrelativistic and relativistic DFT calculations are performed on four-coordinate metal porphyrins MP and their six-coordinate adducts MP(py) 2 and MP(py)(CO) (py=pyridine) with M=Fe, Ru, and Os. The electronic structures of the MPs are investigated by considering all possible low-lying states with different configurations of nd-electrons. FeP and OsP have a 3A2 g ground state, while this state is nearly degenerate with 3Eg for RuP. Without relativistic corrections, the ground states of both RuP and OsP would be 3Eg. For the six-coordinate adducts with py and CO, the strong-field axial ligands raise the energy of the M d z2-orbital, thereby making the M II ion diamagnetic. The calculated redox properties of MP(py) 2 and MP(py)(CO) are in agreement with experiment. The difference between RuP(py)(CO) and OsP(py)(CO), in terms of site of oxidation, is due to relativistic effects.

  1. Photomagnetic studies on spin-crossover solid solutions containing two different metal complexes, [Fe(1-bpp)(2)](x)[M(terpy)2](1-x)[BF4]2 (M = Ru or Co).

    PubMed

    Chastanet, Guillaume; Tovee, Clare A; Hyett, Geoffrey; Halcrow, Malcolm A; Létard, Jean-François

    2012-04-28

    The photomagnetic properties of two series of spin-crossover solid solutions, [Fe(1-bpp)(2)](x)[Ru(terpy)(2)](1-x)(BF(4))(2) and [Fe(1-bpp)(2)](x)[Co(terpy)(2)](1-x)(BF(4))(2) (1-bpp = 2,6-bis[pyrazol-1-yl]pyridine), have been investigated. For all the materials, the evolution of the T(LIESST) value, the high-spin → low-spin relaxation parameters and the LITH loops were thoroughly studied. Interestingly in the Fe:Co series, along the photo-excitation, cobalt ions are concomitantly converted from low-spin to high-spin states with the iron centres, and also fully relax after light excitation. This journal is © The Royal Society of Chemistry 2012

  2. Investigation of the synthesis, activation, and isosteric heats of CO2 adsorption of the isostructural series of metal-organic frameworks M3(BTC)2 (M = Cr, Fe, Ni, Cu, Mo, Ru).

    PubMed

    Wade, Casey R; Dincă, Mircea

    2012-07-14

    The synthesis, activation, and heats of CO(2) adsorption for the known members of the M(3)(BTC)(2) (HKUST-1) isostructural series (M = Cr, Fe, Ni, Zn, Ni, Cu, Mo) were investigated to gain insight into the impact of CO(2)-metal interactions for CO(2) storage/separation applications. With the use of modified syntheses and activation procedures, improved BET surface areas were obtained for M = Ni, Mo, and Ru. The zero-coverage isosteric heats of CO(2) adsorption were measured for the Cu, Cr, Ni, Mo, and Ru analogues and gave values consistent with those reported for MOFs containing coordinatively unsaturated metal sites, but lower than for amine functionalized materials. Notably, the Ni and Ru congeners exhibited the highest CO(2) affinities in the studied series. These behaviors were attributed to the presence of residual guest molecules in the case of Ni(3)(BTC)(2)(Me(2)NH)(2)(H(2)O) and the increased charge of the dimetal secondary building unit in [Ru(3)(BTC)(2)][BTC](0.5).

  3. [Phlebotominae: vectors of leishmaniasis in the provinces of Santa Fe and Entre Ríos, Argentina].

    PubMed

    Salomón, Oscar D; Mocarbel, Nicolás J; Pedroni, Elena; Colombo, Javier; Sandillú, Mónica

    2006-01-01

    The transmission of tegumentary leishmaniasis (TL) has increased in 9 provinces of Argentina since 1985. Santa Fe and Entre Ríos did not record in this period autochtonous probed cases: however, an epidemic outbreak took place in 2003 in Bella Vista, Corrientes, located in an area with ecological continuity and contiguous to both provinces. In order to evaluate the potential risk of transmission of LT, Phlebotominae were captured at locations close to and southern from Bella Vista during February 2004. The traps located on the shores of Parana river in Santa Fe (El Rabón, Villa Ocampo, Cayastá), and Entre Ríos (La Paz. La Celina-Villa Urquiza) captured 860 individuals of Lutzomyia neivai (99.5%) and Lu. migonei (0.5 %), both species with vectorial capacity for Leishmania (V.) braziliensis. In Tartagal, Santa Fe, the captures were consistent with the residual "chaco" landscape, 7 individuals of Lu. nerivai, Lu. migonei and Lu. cortelezzii. The risk of LT epidemic transmission in these provinces is highlighted, mainly due to the progressive southern tropicalization of the paranaense gallery forest. Clinical and entomological surveillance is recommended.

  4. Structure and magnetic properties of Fe12X clusters

    NASA Astrophysics Data System (ADS)

    Gutsev, G. L.; Johnson, L. E.; Belay, K. G.; Weatherford, C. A.; Gutsev, L. G.; Ramachandran, B. R.

    2014-02-01

    The electronic and geometrical structures of a Fe12X family of binary clusters Fe12Al, Fe12Sc, Fe12Ti, Fe12V, Fe12Cr, Fe12Mn, Fe12Co, Fe12Ni, Fe12Cu, Fe12Zn, Fe12Y, Fe12Zr, Fe12Nb, Fe12Mo, Fe12Tc, Fe12Ru, Fe12Rh, Fe12Pd, Fe12Ag, Fe12Cd, and Fe12Gd are studied using density functional theory within generalized gradient approximation. It is found that the geometrical structures corresponding to the lowest total energy states found for the Fe12X clusters possess icosahedral shape with the substituent atom occupying the central or a surface site. The only exception presents Fe12Nb where a squeezed cage structure is the energetically most favorable. The substitution of an atom in the Fe13 cluster results in the decrease of its total spin magnetic moment of 44 μB, except for Fe12Mn and Fe12Gd. The Fe12X clusters are more stable than the parent Fe13 cluster when X = Al, Sc, Ti, V, Co, Y, Zr, Nb, Mo, Tc, Ru, and Rh.

  5. Reactivity of O2 on Pd/Ru(0001) and PdRu/Ru(0001) surface alloys

    NASA Astrophysics Data System (ADS)

    Farías, D.; Minniti, M.; Miranda, R.

    2017-05-01

    The reactivity of a Pd monolayer epitaxially grown on Ru(0001) toward O2 has been investigated by molecular beam techniques. O2 initial sticking coefficients were determined using the King and Wells method in the incident energy range of 40-450 meV and for sample temperatures of 100 K and 300 K, and compared to the corresponding values measured on the clean Ru(0001) and Pd(111) surfaces. In contrast to the high reactivity shown by Ru(0001) at 100 K, the Pd/Ru(0001) system exhibits a monotonic decrease in the sticking probability of O2 as a function of normal incident energy. At room temperature, the system was found to be inert. Thermal desorption measurements show that O2 is adsorbed molecularly at 100 K. A completely different behaviour has been measured for the Pd0.95Ru0.05/Ru(0001) surface alloy. On this surface, the O2 sticking probability increases with incident energy and resembles the one observed on the clean Ru(0001) surface, even at 300 K. Thermal desorption measurements point to dissociative adsorption of O2 in this system. Both the charge transfer from the Pd to the Ru substrate and the compressive strain on the Pd monolayer contribute to decrease in the reactivity of the Pd/Ru(0001) system well below those of both Ru(0001) and Pd(111).

  6. The Disposition of Pt, Pd, Ir, Os, and Ru in Marine Sediments and the K/T Boundary

    NASA Technical Reports Server (NTRS)

    Lee, Cin-Ty; Wasserburg, Gerald; Kyte, Frank

    2003-01-01

    The marine record of platinum group elements (PGEs) and Os isotopic compositions provides information on different inputs of PGEs into the oceans. Some studies based on a smaller subset of the PGEs suggest that the PGEs may suffer post-depositional mobility during diagenesis. In some K/T boundary clays, Kyte and others showed that the relative abundances of Pt, Pd, Ir, and Os can differ significantly from chondritic, which is the signature expected from fallout of the meteorite impact. In some K/T boundary sections, elevated Ir concentrations are observed as far as 1 meter from the cm-thick boundary clay containing the meteoritic ejecta. The purpose of this study was to characterize Pt, Pd, Ir, Os, and Ru abundances in zones including the K/T boundary. We determined PGE abundances of boundary clays at two hemipelagic sites (Stevns Klint, Denmark and Caravaca, Spain) in which previous studies by Kyte and others showed that the Ir anomaly is confined to within a few cm. We also analyzed two pelagic Pacific sites: a boundary clay from the north Pacific (Hole 465A) characterized by a 0.5 m thick Ir anomaly and a transect across the K/T boundary from the south Pacific (Hole 596) where the Ir anomaly spans 2 m. The Stevns Klint, Caravaca, and north Pacific sites are characterized by abundant marls and limestones in the section, whereas the south Pacific site is dominated by clays. Samples were spiked with isotopic tracers, mixed with a flux, S and Ni, and equilibrated by fusion. PGEs were extracted from the Ni and analyzed on a Finnigan Element ICP-MS. We find that the narrow Caravaca and Stevns Klint boundary clays have relative PGE abundance patterns indistinguishable from chondritic values. The two Pacific sites were found to have nearly identical PGE patterns but have ratios at the peak, which differ from chondritic values as found earlier by Evans et al. The Pacific sites were found to have nearly identical PGE patterns but are extremely depleted in OS (Os/Ir = 0

  7. Effect of Ru thickness on spin pumping in Ru/Py bilayer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Behera, Nilamani; Singh, M. Sanjoy; Chaudhary, Sujeet

    2015-05-07

    We report the effect of Ru thickness (t{sub Ru}) on ferromagnetic resonance (FMR) line-width of Ru(t{sub Ru})/Py(23 nm) bilayer samples grown on Si(100)/SiO{sub 2} substrates at room temperature by magnetron sputtering. The FMR line-width is found to vary linearly with frequency for all thicknesses of Ru, indicating intrinsic origin of damping. For Ru thicknesses below 15 nm, Gilbert-damping parameter, α is almost constant. We ascribe this behavior to spin back flow that is operative for Ru thicknesses lower than the spin diffusion length in Ru, λ{sub sd}. For thicknesses >15 nm (>λ{sub sd}), the damping constant increases with Ru thickness, indicating spin pumpingmore » from Py into Ru.« less

  8. Demonstration of Ru as the 4th ferromagnetic element at room temperature.

    PubMed

    Quarterman, P; Sun, Congli; Garcia-Barriocanal, Javier; Dc, Mahendra; Lv, Yang; Manipatruni, Sasikanth; Nikonov, Dmitri E; Young, Ian A; Voyles, Paul M; Wang, Jian-Ping

    2018-05-25

    Development of novel magnetic materials is of interest for fundamental studies and applications such as spintronics, permanent magnetics, and sensors. We report on the first experimental realization of single element ferromagnetism, since Fe, Co, and Ni, in metastable tetragonal Ru, which has been predicted. Body-centered tetragonal Ru phase is realized by use of strain via seed layer engineering. X-ray diffraction and electron microscopy confirm the epitaxial mechanism to obtain tetragonal phase Ru. We observed a saturation magnetization of 148 and 160 emu cm -3 at room temperature and 10 K, respectively. Control samples ensure the ferromagnetism we report on is from tetragonal Ru and not from magnetic contamination. The effect of thickness on the magnetic properties is also studied, and it is observed that increasing thickness results in strain relaxation, and thus diluting the magnetization. Anomalous Hall measurements are used to confirm its ferromagnetic behavior.

  9. Constitution and thermodynamics of the Mo-Ru, Mo-Pd, Ru-Pd and Mo-Ru-Pd systems

    NASA Astrophysics Data System (ADS)

    Kleykamp, H.

    1989-09-01

    The constitution of the Mo-Ru, Mo-Pd and Ru-Pd systems was reinvestigated between 800 and 2000°C. The Mo-Ru system is of the eutectic type, a σ-phase Mo 5Ru 3 exists between 1915 and 1143°C. The Mo-Pd system is characterized by an hcp phase Mo 9Pd 11 and by two peritectic reactions, β- Mo( Pd) + L = Mo9Pd11andMo9Pd11 + L = α- Pd( Mo). Mo 9Pd 11 decomposes eutectoidally at 1370°C. The Ru-Pd system is simple peritectic. The continuous series of the hcp solid solutions between Mo 9Pd 11 and ɛ-Ru(Mo, Pd) in the ternary Mo-Ru-Pd system observed at 1700°C are suppressed below 1370°C near the Mo-Pd boundary system by the formation of a narrow α + β + ɛ three-phase field. Relative partial molar Gibbs energies of Mo, Mo and Ru in the respective binary systems and of Mo in the ternary system were measured by the EMF method with a Zr(Ca)O 2 electrolyte. xsΔ ḠMo∞ quantities were evaluated at 1200 K which give -43 kJ/mol Mo in Ru and -94 kJ/mol Mo in Pd at infinite dilution. Gibbs energies of formation of the Mo-Ru and Mo-Pd systems were calculated.

  10. Thermal stability of spin valves based on a synthetic antiferromagnet and Fe50Mn50 alloy

    NASA Astrophysics Data System (ADS)

    Milyaev, M. A.; Naumova, L. I.; Proglyado, V. V.; Chernyshova, T. A.; Blagodatkov, D. V.; Kamenskii, I. Yu.; Ustinov, V. V.

    2015-11-01

    Magnetron sputtering was used to prepare spin valves with the Ta/Ni80Fe20/Co90Fe10/Cu/Co90Fe10/Ru/Co90Fe10/Fe50Mn50/Ta composition. Changes in the functional characteristics of the spin valves were studied in a temperature range of-180 to +160°C. The maximum temperature at which the functional characteristics of spin valve remain unchanged was shown to depend on the relationship of thicknesses of Co90Fe10 layers separated by the Ru interlayer.

  11. Oxygen-participated electrochemistry of new lithium-rich layered oxides Li3MRuO5 (M = Mn, Fe).

    PubMed

    Laha, S; Natarajan, S; Gopalakrishnan, J; Morán, E; Sáez-Puche, R; Alario-Franco, M Á; Dos Santos-Garcia, A J; Pérez-Flores, J C; Kuhn, A; García-Alvarado, F

    2015-02-07

    We describe the synthesis, crystal structure and lithium deinsertion-insertion electrochemistry of two new lithium-rich layered oxides, Li3MRuO5 (M = Mn, Fe), related to rock salt based Li2MnO3 and LiCoO2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m) where Li and (Li0.2Mn0.4Ru0.4) layers alternate along the c-axis, while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R3[combining macron]m) structure where Li and (Li0.2Fe0.4Ru0.4) layers are stacked alternately. Magnetic measurements indicate for Li3MnRuO5 the presence of Mn(3+) and low spin configuration for Ru(4+) where the itinerant electrons occupy a π*-band. The onset of a net maximum in the χ vs. T plot at 9.5 K and the negative value of the Weiss constant (θ) of -31.4 K indicate the presence of antiferromagnetic superexchange interactions according to different pathways. Lithium electrochemistry shows a similar behaviour for both oxides and related to the typical behaviour of Li-rich layered oxides where participation of oxide ions in the electrochemical processes is usually found. A long first charge process with capacities of 240 mA h g(-1) (2.3 Li per f.u.) and 144 mA h g(-1) (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. An initial sloping region (OCV to ca. 4.1 V) is followed by a long plateau (ca. 4.3 V). Further discharge-charge cycling points to partial reversibility (ca. 160 mA h g(-1) and 45 mA h g(-1) for Mn and Fe, respectively). Nevertheless, just after a few cycles, cell failure is observed. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn(3+) and Ru(4+) are partially oxidized to Mn(4+) and Ru(5+) in the sloping region at low voltage, while in the long plateau, O(2-) is also oxidized. Oxygen release likely occurs which may be the cause for failure of cells upon cycling. Interestingly, some other Li-rich layered oxides have been reported to

  12. Heavy-impurity resonance, hybridization, and phonon spectral functions in Fe 1-xM xSi, M=Ir,Os

    DOE PAGES

    Delaire, O.; Al-Qasir, Iyad I.; May, Andrew F.; ...

    2015-03-31

    The vibrational behavior of heavy substitutional impurities (M=Ir,Os) in Fe 1-xM xSi (x = 0, 0.02, 0.04, 0.1) was investigated with a combination of inelastic neutron scattering (INS), transport measurements, and first-principles simulations. In this paper, our INS measurements on single-crystals mapped the four-dimensional dynamical structure factor, S(Q;E), for several compositions and temperatures. Our results show that both Ir and Os impurities lead to the formation of a weakly dispersive resonance vibrational mode, in the energy range of the acoustic phonon dispersions of the FeSi host. We also show that Ir doping, which introduces free carriers and increases electron-phonon coupling,more » leads to softened interatomic force-constants compared to doping with Os, which is isoelectronic to Fe. We analyze the phonon S(Q,E) from INS through a Green's function model incorporating the phonon self-energy based on first-principles density functional theory (DFT) simulations. Calculations of the quasiparticle spectral functions in the doped system reveal the hybridization between the resonance and the acoustic phonon modes. Finally, our results demonstrate a strong interaction of the host acoustic dispersions with the resonance mode, likely leading to the large observed suppression in lattice thermal conductivity.« less

  13. Anisotropic dependence of the magnetic transition on uniaxial pressure in the Kondo semiconductors Ce T2A l10 (T =Ru and Os)

    NASA Astrophysics Data System (ADS)

    Hayashi, K.; Umeo, K.; Takeuchi, T.; Kawabata, J.; Muro, Y.; Takabatake, T.

    2017-12-01

    We have measured the strain, magnetization, and specific heat of the antiferromagnetic (AFM) Kondo semiconductors Ce T2A l10 (T =Ru and Os) under uniaxial pressures applied along the orthorhombic axes. We found a linear dependence of TN on the b -axis parameter for both compounds under uniaxial pressure P ∥b and hydrostatic pressure. This relation indicates that the distance between the Ce-T layers along the b axis is the key structural parameter determining TN. Furthermore, the pressure dependence of the spin-flop transition field indicates that Ce-Ce interchain interactions stabilize the AFM state with the ordered moments pointing to the c axis.

  14. Field-induced magnetic phase transitions and memory effect in bilayer ruthenate Ca 3Ru 2O 7 with Fe substitution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, M.; Hong, Tao; Peng, J.

    Bilayer ruthenate Ca 3(Ru 1-xFe x) 2O 7 (x = 0.05) exhibits an incommensurate magnetic soliton lattice driven by the Dzyaloshinskii–Moriya interaction. Here, in this work, we report complex field-induced magnetic phase transitions and memory effect in this system via single-crystal neutron diffraction and magnetotransport measurements. We observe first-order incommensurate-to-commensurate magnetic transitions upon applying the magnetic field both along and perpendicular to the propagation axis of the incommensurate spin structure. Furthermore, we find that the metastable states formed upon decreasing the magnetic field depend on the temperature and the applied field orientation. Lastly, we suggest that the observed field-induced metastabilitymore » may be ascribable to the quenched kinetics at low temperature.« less

  15. Field-induced magnetic phase transitions and memory effect in bilayer ruthenate Ca 3Ru 2O 7 with Fe substitution

    DOE PAGES

    Zhu, M.; Hong, Tao; Peng, J.; ...

    2018-01-09

    Bilayer ruthenate Ca 3(Ru 1-xFe x) 2O 7 (x = 0.05) exhibits an incommensurate magnetic soliton lattice driven by the Dzyaloshinskii–Moriya interaction. Here, in this work, we report complex field-induced magnetic phase transitions and memory effect in this system via single-crystal neutron diffraction and magnetotransport measurements. We observe first-order incommensurate-to-commensurate magnetic transitions upon applying the magnetic field both along and perpendicular to the propagation axis of the incommensurate spin structure. Furthermore, we find that the metastable states formed upon decreasing the magnetic field depend on the temperature and the applied field orientation. Lastly, we suggest that the observed field-induced metastabilitymore » may be ascribable to the quenched kinetics at low temperature.« less

  16. 155Gd Mössbauer Spectroscopic Study of GdM(CN)6 · 4H2O (M = CrIII, FeIII and CoIII) and KGdM(CN)6 · 3H2O (M = FeII and RuII)

    NASA Astrophysics Data System (ADS)

    Wang, Junhu; Abe, Junko; Kitazawa, Takafumi; Takahashi, Masashi; Takeda, Masuo

    2002-07-01

    155Gd Mössbauer spectroscopic studies of the title complexes have been performed. Although the 155Gd isomer shifts (d) varied scarcely, the quadrupole coupling constants (e2qQ) changed in the range 4.07-4.81 mm s-1. The e2qQ values of KGdM(CN)6 · 3H2O (M = FeII and RuII) are larger than those of GdM(CN)6 · 4H2O (M = CrIII, FeIII, and CoIII), these values increasing with increasing orthorhombic distortion of the crystal structures. A relationship between the e2qQ values and the ionic radii of the transition metal ions has also been recognized

  17. Novel Electronic Structures of Ru-pnictides RuPn (Pn = P, As, Sb)

    NASA Astrophysics Data System (ADS)

    Goto, H.; Toriyama, T.; Konishi, T.; Ohta, Y.

    Density-functional-theory-based electronic structure calculations are made to consider the novel electronic states of Ru-pnictides RuP and RuAs where the intriguing phase transitions and superconductivity under doping of Rh have been reported. We find that there appear nearly degenerate flat bands just at the Fermi level in the high-temperature metallic phase of RuP and RuAs; the flat-band states come mainly from the 4dxy orbitals of Ru ions and the Rh doping shifts the Fermi level just above the flat bands. The splitting of the flat bands caused by their electronic instability may then be responsible for the observed phase transition to the nonmagnetic insulating phase at low temperatures. We also find that the band structure calculated for RuSb resembles that of the doped RuP and RuAs, which is consistent with experiment where superconductivity occurs in RuSb without Rh doping.

  18. Atomistic Modeling of RuAl and (RuNi) Al Alloys

    NASA Technical Reports Server (NTRS)

    Gargano, Pablo; Mosca, Hugo; Bozzolo, Guillermo; Noebe, Ronald D.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Atomistic modeling of RuAl and RuAlNi alloys, using the BFS (Bozzolo-Ferrante-Smith) method for alloys is performed. The lattice parameter and energy of formation of B2 RuAl as a function of stoichiometry and the lattice parameter of (Ru(sub 50-x)Ni(sub x)Al(sub 50)) alloys as a function of Ni concentration are computed. BFS based Monte Carlo simulations indicate that compositions close to Ru25Ni25Al50 are single phase with no obvious evidence of a miscibility gap and separation of the individual B2 phases.

  19. Spectroscopic, Electrochemical and Computational Characterisation of Ru Species Involved in Catalytic Water Oxidation: Evidence for a [Ru(V) (O)(Py2 (Me) tacn)] Intermediate.

    PubMed

    Casadevall, Carla; Codolà, Zoel; Costas, Miquel; Lloret-Fillol, Julio

    2016-07-11

    A new family of ruthenium complexes based on the N-pentadentate ligand Py2 (Me) tacn (N-methyl-N',N''-bis(2-picolyl)-1,4,7-triazacyclononane) has been synthesised and its catalytic activity has been studied in the water-oxidation (WO) reaction. We have used chemical oxidants (ceric ammonium nitrate and NaIO4 ) to generate the WO intermediates [Ru(II) (OH2 )(Py2 (Me) tacn)](2+) , [Ru(III) (OH2 )(Py2 (Me) tacn)](3+) , [Ru(III) (OH)(Py2 (Me) tacn)](2+) and [Ru(IV) (O)(Py2 (Me) tacn)](2+) , which have been characterised spectroscopically. Their relative redox and pH stability in water has been studied by using UV/Vis and NMR spectroscopies, HRMS and spectroelectrochemistry. [Ru(IV) (O)(Py2 (Me) tacn)](2+) has a long half-life (>48 h) in water. The catalytic cycle of WO has been elucidated by using kinetic, spectroscopic, (18) O-labelling and theoretical studies, and the conclusion is that the rate-determining step is a single-site water nucleophilic attack on a metal-oxo species. Moreover, [Ru(IV) (O)(Py2 (Me) tacn)](2+) is proposed to be the resting state under catalytic conditions. By monitoring Ce(IV) consumption, we found that the O2 evolution rate is redox-controlled and independent of the initial concentration of Ce(IV) . Based on these facts, we propose herein that [Ru(IV) (O)(Py2 (Me) tacn)](2+) is oxidised to [Ru(V) (O)(Py2 (Me) tacn)](2+) prior to attack by a water molecule to give [Ru(III) (OOH)(Py2 (Me) tacn)](2+) . Finally, it is shown that the difference in WO reactivity between the homologous iron and ruthenium [M(OH2 )(Py2 (Me) tacn)](2+) (M=Ru, Fe) complexes is due to the difference in the redox stability of the key M(V) (O) intermediate. These results contribute to a better understanding of the WO mechanism and the differences between iron and ruthenium complexes in WO reactions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Buffer layer dependence of magnetoresistance effects in Co2Fe0.4Mn0.6Si/MgO/Co50Fe50 tunnel junctions

    NASA Astrophysics Data System (ADS)

    Sun, Mingling; Kubota, Takahide; Takahashi, Shigeki; Kawato, Yoshiaki; Sonobe, Yoshiaki; Takanashi, Koki

    2018-05-01

    Buffer layer dependence of tunnel magnetoresistance (TMR) effects was investigated in Co2Fe0.4Mn0.6Si (CFMS)/MgO/Co50Fe50 magnetic tunnel junctions (MTJs). Pd, Ru and Cr were selected for the buffer layer materials, and MTJs with three different CFMS thicknesses (30, 5, and 0.8 nm) were fabricated. A maximum TMR ratio of 136% was observed in the Ru buffer layer sample with a 30-nm-thick CFMS layer. TMR ratios drastically degraded for the CFMS thickness of 0.8 nm, and the values were 26% for Cr buffer layer and less than 1% for Pd and Ru buffer layers. From the annealing temperature dependence of the TMR ratios, amounts of interdiffusion and effects from the lattice mismatch were discussed.

  1. Density functional theory calculations on transition metal atoms adsorbed on graphene monolayers

    NASA Astrophysics Data System (ADS)

    Dimakis, Nicholas; Flor, Fernando Antonio; Salgado, Andres; Adjibi, Kolade; Vargas, Sarah; Saenz, Justin

    2017-11-01

    Transition metal atom adsorption on graphene monolayers has been elucidated using periodic density functional theory under hybrid and generalized gradient approximation functionals. More specifically, we examined the adsorption of Cu, Fe, Zn, Ru, and Os on graphene monolayers by calculating, among others, the electronic density-of-states spectra of the adatom-graphene system and the overlap populations of the adatom with the nearest adsorbing graphene carbon atoms. These calculations reveal that Cu form primarily covalent bonds with graphene atoms via strong hybridization between the adatom orbitals and the sp band of the graphene substrate, whereas the interaction of the Ru and Os with graphene also contain ionic parts. Although the interaction of Fe with graphene atoms is mostly covalent, some charge transfer to graphene is also observed. The interaction of Zn with graphene is weak. Mulliken population analysis and charge contour maps are used to elucidate charge transfers between the adatom and the substrate. The adsorption strength is correlated with the metal adsorption energy and the height of the metal adatom from the graphene plane for the geometrically optimized adatom-graphene system. Our analysis shows that show that metal adsorption strength follows the adatom trend RuOs > Fe > Cu > Zn, as verified by corresponding changes in the adsorption energies. The increased metal-carbon orbital overlap for the Ru relative to Os adatom is attributed to hybridization defects.

  2. The End of Monterey Submarine Canyon Incision and Potential River Source Areas-Os, Nd, and Pb Isotope Constraints from Hydrogenetic Fe-Mn Crusts

    NASA Astrophysics Data System (ADS)

    Conrad, T. A.; Nielsen, S.; Ehrenbrink, B. P. E.; Blusztajn, J.; Hein, J. R.; Paytan, A.

    2015-12-01

    The Monterey Canyon off central California is the largest submarine canyon off North America and is comparable in scale to the Grand Canyon. The age and history of the Monterey Canyon are poorly constrained due to thick sediment cover and sediment disruption from turbidity currents. To address this deficit we analyzed isotopic proxies (Os, Pb, Nd) from hydrogenetic ferromanganese (Fe-Mn) crusts, which grow over millions of years on elevated rock surfaces by precipitation of metals from seawater. Fe-Mn crusts were studied from Davidson Seamount near the base of the Monterey submarine fan, the Taney Seamount Chain, and from Hoss Seamount, which serves as a regional control (Fig.). Fe-Mn crusts were dated using Os isotope ratios compared to those that define the Cenozoic Os isotope seawater curve. Four Fe-Mn crust samples from Davidson and Taney Seamounts deviate from the Os isotopic seawater curve towards radiogenic values after 4.5±1 Ma. Osmium is well mixed in the global ocean and is not subject to significant diffusive reequilibration in Fe-Mn crusts. We therefore attribute deviations from the Os isotope seawater curve to large-scale terrestrial input that ended about 4.5±1 Ma. The two Davidson samples also show more radiogenic Nd isotope values from about 4.5±1 Ma. Lead isotopes in one Davidson Seamount crust, measured by LA-ICPMS, deviate from regional values after 4.5±1 Ma for about 500 ka towards terrestrial sources. The Taney Seamount Fe-Mn crust does not deviate from regional Nd nor Pb isotope values due to its greater distance from Monterey Canyon and the shorter marine residence times of Nd and Pb. Isotope plots of our crust data and compiled data for potential source rocks indicate that the river that carved Monterey Canyon carried sediment with values closer to the Sierra Nevada than to a Colorado Plateau source, with cessation of major riverine input occurring approximately 4.5±1 Ma, an age that we interpret as the end of the Monterey Canyon

  3. Photoassisted Synthesis of Mixed-Metal Clusters;(PPN)(CoOs3(CO)13), H2RuOs3(CO13, and H2FeOs3(CO)13.

    DTIC Science & Technology

    1980-05-30

    8 -1 Photoassisted Synthesis of Mixed-Metal Clusters: Interim echnicalfe 0M [PPN][ Cofs (CO) H OP]CC andF F ’ " 13 2 136. PERFORMING ORG. REPORT NUMBER...the reaction conditions.2 A low yield of the unstable protonated derivative HCoOs3 (CO)13 was obtained in a single experiment in which K[Co(CO)4] was...data.1 Apparently [V(CO)6]" is a sufficiently strong reducing agent to reduce both of these trimers to their respective anions, although the 6 proton

  4. Magnetization measurements of Sr2RuO4-Ru eutectic microplates using dc-SQUIDs

    NASA Astrophysics Data System (ADS)

    Nago, Y.; Sakuma, D.; Ishiguro, R.; Kashiwaya, S.; Nomura, S.; Kono, K.; Maeno, Y.; Takayanagi, H.

    2018-03-01

    We report magnetization measurements of Sr2RuO4-Ru eutectic microplates using micro-dc-SQUIDs. Sr2RuO4 is considered as a chiral p-wave superconductor and hence Sr2RuO4-Ru eutectic becomes in an unstable state with a superconducting phase frustration between a chiral p-wave state of Sr2RuO4 and a s-wave state of Ru. To compensate the frustration, a single quantum vortex is spontaneously formed at the center of the Ru inclusion at sufficiently low temperatures. However, such a spontaneous vortex state has not been experimentally observed yet. In this study, we prepared a micro-dc-SQUID and a Sr2RuO4-Ru eutectic microplate containing a single Ru-inclusion at the center of the microplate. We performed magnetization measurements down below the superconducting transition temperature of the Ru inclusion to investigate the spontaneous Ru-center vortex state.

  5. Electronically highly cubic conditions for Ru in α -RuCl3

    NASA Astrophysics Data System (ADS)

    Agrestini, S.; Kuo, C.-Y.; Ko, K.-T.; Hu, Z.; Kasinathan, D.; Vasili, H. B.; Herrero-Martin, J.; Valvidares, S. M.; Pellegrin, E.; Jang, L.-Y.; Henschel, A.; Schmidt, M.; Tanaka, A.; Tjeng, L. H.

    2017-10-01

    We studied the local Ru 4 d electronic structure of α -RuCl3 by means of polarization-dependent x-ray absorption spectroscopy at the Ru L2 ,3 edges. We observed a vanishingly small linear dichroism indicating that electronically the Ru 4 d local symmetry is highly cubic. Using full multiplet cluster calculations we were able to reproduce the spectra excellently and to extract that the trigonal splitting of the t2 g orbitals is -12 ±10 meV, i.e., negligible as compared to the Ru 4 d spin-orbit coupling constant. Consistent with our magnetic circular dichroism measurements, we found that the ratio of the orbital and spin moments is 2.0, the value expected for a Jeff=1/2 ground state. We have thus shown that as far as the Ru 4 d local properties are concerned, α -RuCl3 is an ideal candidate for the realization of Kitaev physics.

  6. Electron microscope studies of nano-domain structures in Ru-based magneto-superconductors: RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212).

    PubMed

    Yokosawa, Tadahiro; Awana, V P S Veer Pal Singh; Kimoto, Koji; Takayama-Muromachi, Eiji; Karppinen, Maarit; Yamauchi, Hisao; Matsui, Yoshio

    2004-01-01

    Microstructures of the RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212) magneto-superconductors have been investigated by using selected-area electron diffraction, convergent-beam electron diffraction, dark-field electron microscopy and high-resolution electron microscopy at room temperature. Both Ru-1212 and Ru-1222 consist of nm-size domains stacked along the [Formula: see text] direction, where the domains are formed by two types of superstructures due to ordering of rotated RuO(6) octahedra about the c-axis. In Ru-1212, both primitive-and body-centered tetragonal superstructures (the possible space groups: P4/mbm and I4/mcm) are derived to form the corresponding nm-domains. It is of great interest that Ru-1212 consists of domains of two crystallographically different superstructures, while the similar domains observed in Ru-1222 have crystallographically identical superstructure with an orthorhombic symmetry (possible space group: Aeam), related by 90 degrees rotation around the c-axis (Yokosawa et al., 2003, submitted for publication).

  7. Reconstructing the evolution of the submarine Monterey Canyon System from Os, Nd, and Pb isotopes in hydrogenetic Fe-Mn crusts

    USGS Publications Warehouse

    Conrad, T.A.; Nielsen, S.G.; Peucker-Ehrenbrink, Bernhard; Blusztajn, J.; Winslow, D.; Hein, James; Paytan, A.

    2017-01-01

    The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (± 0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe-Mn crusts from the more remote Taney and Hoss seamounts. At the Taney seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve towards more radiogenic values from 6.8 to 4.5 (± 0.5) Ma. However, none of the isotope systems in Fe-Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (± 0.5) Ma. The isotope ratios recorded in Fe-Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo-location of the Monterey Canyon relative to the paleo-coastline.

  8. Reconstructing the Evolution of the Submarine Monterey Canyon System From Os, Nd, and Pb Isotopes in Hydrogenetic Fe-Mn Crusts

    NASA Astrophysics Data System (ADS)

    Conrad, T. A.; Nielsen, S. G.; Peucker-Ehrenbrink, B.; Blusztajn, J.; Winslow, D.; Hein, J. R.; Paytan, A.

    2017-11-01

    The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (±0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe-Mn crusts from the more remote Taney and Hoss Seamounts. At the Taney Seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve toward more radiogenic values from 6.8 to 4.5 (±0.5) Ma. However, none of the isotope systems in Fe-Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (±0.5) Ma. The isotope ratios recorded in Fe-Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo-location of the Monterey Canyon relative to the paleo-coastline.

  9. Magnetic phase transitions and magnetization reversal in MnRuP

    NASA Astrophysics Data System (ADS)

    Lampen-Kelley, P.; Mandrus, D.

    The ternary phosphide MnRuP is an incommensurate antiferromagnetic metal crystallizing in the non-centrosymmetric Fe2P-type crystal structure. Below the Neel transition at 250 K, MnRuP exhibits hysteretic anomalies in resistivity and magnetic susceptibility curves as the propagation vectors of the spiral spin structure change discontinuously across T1 = 180 K and T2 = 100 K. Temperature-dependent X-ray diffraction data indicate that the first-order spin reorientation occurs in the absence of a structural transition. A strong magnetization reversal (MR) effect is observed upon cooling the system through TN in moderate dc magnetic fields. Positive magnetization is recovered on further cooling through T1 and maintained in subsequent warming curves. The field dependence and training of the MR effect in MnRuP will be discussed in terms of the underlying magnetic structures and compared to anomalous MR observed in vanadate systems. This work is supported by the Gordon and Betty Moore Foundation GBMF4416 and U.S. DOE, Office of Science, BES, Materials Science and Engineering Division.

  10. PGE abundance and Re-Os isotope Systematics of Native-Fe-Bearing Basaltic Rocks and Their Carbonaceous Crustal Contaminants: Insights into magma plumbing-system dynamics in LIPs

    NASA Astrophysics Data System (ADS)

    Howarth, G. H.; Day, J. M.; Goodrich, C. A.; Pernet-Fisher, J.; Pearson, D. G.; Taylor, L. A.

    2014-12-01

    Native-Fe grains form in basaltic melts at highly reducing conditions (Fe-bearing basalts are useful natural analogues for studying PGE pre-concentration mechanisms, and the potential for PGE additions to magmas from crustal sources. Here, we present PGE LA-ICP-MS data for Fe-alloy, cohenite, and sulfide for a suite of Siberian and Disko Island native-Fe basalts, in combination with whole-rock PGE data for all known occurrences. The Siberian native-Fe alloys are characterized by highly variable PGE concentrations (1-30 ppm total PGEs), distinct low Os abundances, and PGE profiles similar to those of the nearby Noril'sk sulfide ores. In contrast, the Disko Island alloys are characterized by total PGE concentrations of 1-10 ppm and distinct positive Os and Re anomalies in extended PGE profiles. The Bühl basalts contain low PGE concentrations (~20 ppb). In order to understand contamination contributions, Os-isotopes analyses have been performed. Preliminary whole-rock 187Os/188Os data for high metal content samples from Siberia (0.33606 ± 37) and Disko (0.15402 ± 15) indicate high-time integrated Re/Os. The Re anomalies observed in extended PGE profiles of the Disko Island samples may reflect a potential crustal contribution to the overall PGE budget, through the addition of carbonaceous material. Whereas the Siberian samples contain abundant carbonaceous xenoliths, there is no apparent PGE contribution from crustal materials. Therefore, the role of crustal contamination is important in forming the native-Fe alloys, but the interaction

  11. The Effect of pH on Slurry Erosion-Corrosion of Tungsten Carbide Overlays Alloyed with Ru

    NASA Astrophysics Data System (ADS)

    Nelwalani, Ndivhuwo B.; van der Merwe, Josias W.

    2018-02-01

    The aim of the study was to determine the effect of Ru additions to WC-Fe overlays when exposed to low pH slurry erosion conditions. These overlays were applied through Plasma Transferred Arc, and the original bulk Ru powder concentrations varied from 0.5 to 5 wt.%. A slurry jet impingement erosion-corrosion test rig was used to evaluate wear, and electrochemical measurements were performed to characterize the corrosion properties. The slurry mixtures contained silica sand and synthetic mine water. The pH was varied between 3 and 6.5 for the slurry erosion tests and lowered further for the corrosion characterization. Samples were examined optically and with a scanning electron microscope using energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the phases present. For the slurry erosion-corrosion results at the pH of 6.5, addition of Ru did not show a decrease in erosion-corrosion rates. However, when the pH was decreased to 3, by the addition of HCl, Ru improved the resistance. From the electrochemistry, it was also clear that Ru additions improved the corrosion resistance, but more than 1 wt.% Ru was required. At very low pH levels, the presence of Ru was not able to prevent corrosion.

  12. Iron deficiency regulated OsOPT7 is essential for iron homeostasis in rice.

    PubMed

    Bashir, Khurram; Ishimaru, Yasuhiro; Itai, Reiko Nakanishi; Senoura, Takeshi; Takahashi, Michiko; An, Gynheung; Oikawa, Takaya; Ueda, Minoru; Sato, Aiko; Uozumi, Nobuyuki; Nakanishi, Hiromi; Nishizawa, Naoko K

    2015-05-01

    The molecular mechanism of iron (Fe) uptake and transport in plants are well-characterized; however, many components of Fe homeostasis remain unclear. We cloned iron-deficiency-regulated oligopeptide transporter 7 (OsOPT7) from rice. OsOPT7 localized to the plasma membrane and did not transport Fe(III)-DMA or Fe(II)-NA and GSH in Xenopus laevis oocytes. Furthermore OsOPT7 did not complement the growth of yeast fet3fet4 mutant. OsOPT7 was specifically upregulated in response to Fe-deficiency. Promoter GUS analysis revealed that OsOPT7 expresses in root tips, root vascular tissue and shoots as well as during seed development. Microarray analysis of OsOPT7 knockout 1 (opt7-1) revealed the upregulation of Fe-deficiency-responsive genes in plants grown under Fe-sufficient conditions, despite the high Fe and ferritin concentrations in shoot tissue indicating that Fe may not be available for physiological functions. Plants overexpressing OsOPT7 do not exhibit any phenotype and do not accumulate more Fe compared to wild type plants. These results indicate that OsOPT7 may be involved in Fe transport in rice.

  13. Ferromagnetism and Ru-Ru distance in SrRuO3 thin film grown on SrTiO3 (111) substrate

    PubMed Central

    2014-01-01

    Epitaxial SrRuO3 thin films were grown on both (100) and (111) SrTiO3 substrates with atomically flat surfaces that are required to grow high-quality films of materials under debate. The following notable differences were observed in the (111)-oriented SrRuO3 films: (1) slightly different growth mode, (2) approximately 10 K higher ferromagnetic transition temperature, and (3) better conducting behavior with higher relative resistivity ratio, than (100)c-oriented SrRuO3 films. Together with the reported results on SrRuO3 thin films grown on (110) SrTiO3 substrate, the different physical properties were discussed newly in terms of the Ru-Ru nearest neighbor distance instead of the famous tolerance factor. PACS 75.70.Ak; 75.60.Ej; 81.15.Fg PMID:24393495

  14. Magnetic impurities in conducting oxides. II. (Sr1-xLax)(Ru1-xCox)O3 system

    NASA Astrophysics Data System (ADS)

    Mamchik, A.; Dmowski, W.; Egami, T.; Chen, I.-Wei

    2004-09-01

    The perovskite solid solution between ferromagnetic SrRuO3 and antiferromagnetic LaCoO3 is studied and its structural, electronic,and magnetic properties are compared with (Sr1-xLax)(Ru1-xFex)O3 . The lower 3d energy levels of Co3+ cause a local charge transfer from 4dRu4+ , a reaction that has the novel feature of being sensitive to the local atomic structure such as cation order. Despite such a complication, Co , like Fe , spin-polarizes the itinerant electrons in SrRuO3 to form a large local magnetic moment that is switchable at high fields. In the spin glass regime when Anderson localization dominates, a large negative magnetoresistance emerges as a result of spin polarization of mobile electronic carriers that occupy states beyond the mobility edge. A phenomenological model predicting an inverse relation between magnetoresistance and saturation magnetization is proposed to explain the composition dependence of magnetoresistance for both (Sr1-xLax)(Ru1-xCOx)O3 and (Sr1-xLax)(Ru1-xFex)O3 systems.

  15. AFLOWLIB.ORG: a Distributed Materials Properties Repository from High-throughput Ab initio Calculations

    DTIC Science & Technology

    2011-11-15

    uncle) fcc (uncle) hcp (uncle) phase-diagram Ag Al Al Au Au Bi Bi Ca Ca Cd Cd Ce Ce Co Co Cr Cr Cu Cu Fe Fe Ga Ga Gd Gd Ge Ge Hf...Hf Hg Hg In In Ir Ir La La Li Li Mg Mg Mn Mn Mo Mo Na Na Nb Nb Ni Ni Os Os Pb Pb Pd Pd Pt Pt Rb Rb Re Re Rh Rh Ru Ru Sb Sb Sc...2 S. Curtarolo, A. N. Kolmogorov, and F. H. Cocks, High-throughput ab initio analysis of the Bi-In, Bi- Mg , Bi-Sb, In- Mg , In-Sb, and Mg -Sb systems

  16. Catalysis of nickel ferrite for photocatalytic water oxidation using [Ru(bpy)3]2+ and S2O8(2-).

    PubMed

    Hong, Dachao; Yamada, Yusuke; Nagatomi, Takaharu; Takai, Yoshizo; Fukuzumi, Shunichi

    2012-12-05

    Single or mixed oxides of iron and nickel have been examined as catalysts in photocatalytic water oxidation using [Ru(bpy)(3)](2+) as a photosensitizer and S(2)O(8)(2-) as a sacrificial oxidant. The catalytic activity of nickel ferrite (NiFe(2)O(4)) is comparable to that of a catalyst containing Ir, Ru, or Co in terms of O(2) yield and O(2) evolution rate under ambient reaction conditions. NiFe(2)O(4) also possesses robustness and ferromagnetic properties, which are beneficial for easy recovery from the solution after reaction. Water oxidation catalysis achieved by a composite of earth-abundant elements will contribute to a new approach to the design of catalysts for artificial photosynthesis.

  17. Syntheses, structures, and physicochemical properties of diruthenium compounds of tetrachlorocatecholate with metal-metal bonded Ru(3+)(mu-OR)(2)Ru(3+) and Ru(3.5+)(mu-OR)(2)Ru(3.5+) cores (R = CH(3) and C(2)H(5)).

    PubMed

    Miyasaka, H; Chang, H C; Mochizuki, K; Kitagawa, S

    2001-07-02

    Metal-metal bonded Ru(3+)(mu-OR)(2)Ru(3+) and Ru(3.5+)(mu-OR)(2)Ru(3.5+) (R = CH(3) and CH(3)CH(2)) compounds with tetrachlorocatecholate (Cl(4)Cat) have been synthesized in the corresponding alcohol, MeOH and EtOH, from a nonbridged Ru(2+)-Ru(3+) compound, Na(3)[Ru(2)(Cl(4)Cat)(4)(THF)].3H(2)O.7THF (1). In alcohol solvents, compound 1 is continuously oxidized by oxygen to form Ru(3+)(mu-OR)(2)Ru(3+) and Ru(3.5+)(mu-OR)(2)Ru(3.5+) species. The presence of a characteristic countercation leads to selective isolation of either Ru(3+)(mu-OR)(2)Ru(3+) or Ru(3.5+)(mu-OR)(2)Ru(3.5+) as a stable adduct species. In methanol, Ph(4)PCl and dibenzo-18-crown-6-ether afford Ru(3+)(mu-OMe)(2)Ru(3+) species, [A](2)[Ru(2)(Cl(4)Cat)(4)(mu-OMe)(2)Na(2)(MeOH)(6)] ([A](+) = Ph(4)P(+) (2), [Na(dibenzo-18-crown-6)(H(2)O)(MeOH)](+) (3)), while benzo-15-crown-5-ether provides a Ru(3.5+)(mu-OMe)(2)Ru(3.5+) species, [Na(benzo-15-crown-5)(2)][Ru(2)(Cl(4)Cat)(4)(mu-OMe)(2)Na(2)(MeOH)(6)] (4). The air oxidation of 1 in a MeOH/EtOH mixed solvent (1:1 v/v) containing benzo-15-crown-5-ether provides a Ru(3.5+)(mu-OMe)(2)Ru(3.5+) species, [Na(benzo-15-crown-5)(H(2)O)][Ru(2)(Cl(4)Cat)(2)(mu-OMe)(2)Na(2)(EtOH)(2)(H(2)O)(2)(MeOH)(2)].(benzo-15-crown-5) (5). Similarly, the oxidation of 1 in ethanol with Ph(4)PCl provides a Ru(3.5+)(mu-OEt)(2)Ru(3.5+) species, (Ph(4)P)[Ru(2)(Cl(4)Cat)(4)(mu-OEt)(2)Na(2)(EtOH)(6)] (7). A selective formation of a Ru(3+)(mu-OEt)(2)Ru(3+) species, (Ph(4)P)(2)[Ru(2)(Cl(4)Cat)(4)(mu-OEt)(2)Na(2)(EtOH)(2)(H(2)O)(2)] (6), is found in the presence of pyrazine or 2,5-dimethylpyrazine. The crystal structures of these compounds, except 2 and 7, have been determined by X-ray crystallography, and all compounds have been characterized by several spectroscopic and magnetic investigations. The longer Ru-Ru bonds are found in the Ru(3+)(mu-OR)(2)Ru(3+) species (2.606(1) and 2.628(2) A for 3 and 6, respectively) compared with those of Ru(3.5+)(mu-OMe)(2)Ru(3.5+) species (2.5260(6) A and 2

  18. Tipping the magnetic instability in paramagnetic S r 3 R u 2 O 7 by Fe impurities [Tipping the magnetic instability in paramagnetic S r 3 R u 2 O 7 by modest Fe substitution

    DOE PAGES

    Zhu, M.; Wang, Y.; Li, P. G.; ...

    2017-05-19

    We report the magnetic and electronic properties of the bilayer ruthenate Sr 3Ru 2O 7 upon Fe substitution for Ru. We find that Sr 3(Ru 1-xFe x) 2O 7 shows spin-glass-like phase below 4 K for x = 0.01 and commensurate E-type antiferromagnetically ordered insulating ground state characterized by the propagation vector q c = (0.25 0.25 0) for x ≥ 0.03, in contrast to the paramagnetic metallic state in the parent compound with strong spin fluctuations occurring at wave vectors q = (0.09 0 0) and (0.25 0 0). The observed antiferromagnetic ordering is quasitwo-dimensional with very short correlationmore » length along the c axis, a feature similar to the Mndoped Sr 3Ru 2O 7. Lastly, our results suggest that this ordered ground state is associated with the intrinsic magnetic instability in the pristine compound, which can be readily tipped by the local magnetic coupling between the 3d orbitals of the magnetic dopants and Ru 4d orbitals.« less

  19. Tipping the magnetic instability in paramagnetic S r 3 R u 2 O 7 by Fe impurities [Tipping the magnetic instability in paramagnetic S r 3 R u 2 O 7 by modest Fe substitution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, M.; Wang, Y.; Li, P. G.

    We report the magnetic and electronic properties of the bilayer ruthenate Sr 3Ru 2O 7 upon Fe substitution for Ru. We find that Sr 3(Ru 1-xFe x) 2O 7 shows spin-glass-like phase below 4 K for x = 0.01 and commensurate E-type antiferromagnetically ordered insulating ground state characterized by the propagation vector q c = (0.25 0.25 0) for x ≥ 0.03, in contrast to the paramagnetic metallic state in the parent compound with strong spin fluctuations occurring at wave vectors q = (0.09 0 0) and (0.25 0 0). The observed antiferromagnetic ordering is quasitwo-dimensional with very short correlationmore » length along the c axis, a feature similar to the Mndoped Sr 3Ru 2O 7. Lastly, our results suggest that this ordered ground state is associated with the intrinsic magnetic instability in the pristine compound, which can be readily tipped by the local magnetic coupling between the 3d orbitals of the magnetic dopants and Ru 4d orbitals.« less

  20. Diversity of Chemical Bonding and Oxidation States in MS 4 Molecules of Group 8 Elements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Wei; Jiang, Ning; Schwarz, W. H. Eugen

    The geometric and electronic ground-state structures of six MS 4 molecules (M = group-8 metals Fe, Ru, Os, Hs, Sm, and Pu) have been studied by using quantum-chemical density-functional and correlated wave-function approaches. The MS 4 species are compared to analogous MO 4 species recently investi-gated (Inorg. Chem. 2016, 55: 4616). Metal oxidation state (MOS) of high value VIII appears in low- spin singlet Td geometric species (Os,Hs)S 4 and (Ru,Os,Hs)O 4, whereas low MOS=II appears in high- spin septet D 2d species Fe(S 2) 2 and (slightly excited) metastable Fe(O 2) 2. The ground states of all other moleculesmore » have intermediate MOS values, containing S 2-, S 2 2-, S2 1- (and resp. O 2--, O 1-, O 2 2-, O 2 1-) ligands, bonded by ionic, covalent and correlative contributions.« less

  1. The Loopy Ultraviolet Line Profiles of RU Lupi: Accretion, Outflows, and Fluorescence

    NASA Astrophysics Data System (ADS)

    Herczeg, Gregory J.; Walter, Frederick M.; Linsky, Jeffrey L.; Gahm, Gösta F.; Ardila, David R.; Brown, Alexander; Johns-Krull, Christopher M.; Simon, Michal; Valenti, Jeff A.

    2005-06-01

    We present far-ultraviolet (FUV) spectra of the classical T Tauri star RU Lup covering the 912-1710 Å spectral range, as observed by the Hubble Space Telescope STIS and the Far Ultraviolet Spectroscopic Explorer satellite. We use these spectra, which are rich in emission and absorption lines, to probe both the accreting and outflowing gas. Absorption in the Lyα profile constrains the extinction to AV~0.07 mag, which we confirm with other diagnostics. We estimate a mass accretion rate of (5+/-2)×10-8 Msolar yr-1 using the optical-NUV accretion continuum. The accreting gas is also detected in bright, broad lines of C IV, Si IV, and N V, which all show complex structures across the line profile. Many other emission lines, including those of H2 and Fe II, are pumped by Lyα. RU Lup's spectrum varies significantly in the FUV; our STIS observations occurred when RU Lup was brighter than several other observations in the FUV, possibly because of a high mass accretion rate.

  2. Spectroscopic studies of three Cepheids with high positive pulsation period increments: SZ Cas, BY Cas, and RU Sct

    NASA Astrophysics Data System (ADS)

    Usenko, I. A.; Klochkova, V. G.

    2015-07-01

    circumstellar envelopes around all three Cepheids. We have determined the atmospheric parameters and chemical composition of the program Cepheids. An appreciable carbon underabundance, a nitrogen overabundance (the result was obtained only for BY Cas), a nearly solar oxygen abundance, a sodium overabundance, and solar magnesium and aluminum abundances have been revealed in all stars, suggesting that these yellow supergiants has already passed the first dredge-up. The abundances of the Fe-peak elements, a-elements, and r- and s-process elements are nearly solar. [Fe/H] = -0.05 dex for SZ Cas and [Fe/H]= +0.05 dex for RU Sct can be used to estimate the metallicities of the open clusters χ and h Per and Trump 35, respectively.

  3. Fragility of ferromagnetic double exchange interactions and pressure tuning of magnetism in 3d–5d double perovskite Sr₂FeOsO₆

    DOE PAGES

    Veiga, L. S. I.; Fabbris, G.; van Veenendaal, M.; ...

    2015-06-19

    The ability to tune exchange (magnetic) interactions between 3d transition metals in perovskite structures has proven to be a powerful route to discovery of novel properties. Here we demonstrate that the introduction of 3d-5d exchange pathways in double perovskites enables additional tunability, a result of the large spatial extent of 5d wave functions. Using x-ray probes of magnetism and structure at high pressure, we show that compression of Sr₂FeOsO₆ drives an unexpected continuous change in the sign of Fe-Os exchange interactions and a transition from antiferromagnetic to ferrimagnetic order. We analyze the relevant electron-electron interactions, shedding light into fundamental differencesmore » with the more thoroughly studied 3d-3d systems.« less

  4. Directed Assembly of Molecules on Graphene/Ru(0001)

    NASA Astrophysics Data System (ADS)

    Zhang, L. Z.; Zhang, H. G.; Sun, J. T.; Pan, Y.; Liu, Q.; Mao, J. H.; Zhou, H. T.; Low, T.; Guo, H. M.; Du, S. X.; Gao, H.-J.

    2012-02-01

    Recently, the graphene monolayers have been seen to adopt a superstructure - moir'e pattern - on Ru(0001). By using low temperature scanning tunneling spectroscopy, we identified the laterally localized electronic states on this system. The individual states are separated by 3 nm and comprise regions of about 90 carbon atoms. This constitutes a highly regular quantum dot-array with molecular precision. It is evidenced by quantum well resonances with energies that relate to the corrugation of the graphene layer. By using scanning tunneling microscopy/spectroscopy, we demonstrate the selective adsorption and formation of ordered molecular arrays of FePc and pentacene molecules on the graphene/Ru(0001) templates. With in-depth investigations of the molecular adsorption and assembly processes we reveal the existence lateral electric dipoles in the epitaxial graphene monolayers and the capability of the dipoles in directing and driving the molecular adsorption and assembly. When increasing the molecular coverage, we observed the formation of regular Kagome lattices that duplicate the lattice of the moir'e pattern of monolayer graphene.

  5. Computational modeling of high-entropy alloys: Structures, thermodynamics and elasticity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gao, Michael C.; Gao, Pan; Hawk, Jeffrey A.

    This study provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if themore » same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.« less

  6. Computational modeling of high-entropy alloys: Structures, thermodynamics and elasticity

    DOE PAGES

    Gao, Michael C.; Gao, Pan; Hawk, Jeffrey A.; ...

    2017-10-12

    This study provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if themore » same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.« less

  7. Sandwich-Type Electrochemiluminescence Sensor for Detection of NT-proBNP by Using High Efficiency Quench Strategy of Fe3O4@PDA toward Ru(bpy)32+ Coordinated with Silver Oxalate.

    PubMed

    Shi, Li; Li, Xiaojian; Zhu, Wenjuan; Wang, Yaoguang; Du, Bin; Cao, Wei; Wei, Qin; Pang, Xuehui

    2017-12-22

    Heart failure (HF) is a burgeoning public health problem trigged by a heart circulation disorder. N-terminal pro-B-type natriuretic peptide (NT-proBNP) has been acknowledged as a prognostic biomarker for cardiac disease. Herein, a sandwich-type electrochemiluminescence (ECL) immunosensor was introduced for sensitive detection of NT-proBNP. Gold nanoparticle modified graphene oxide-Ru(bpy) 3 2+ /Ag 2 C 2 O 4 was used as a luminophore and a desirable platform for immobilization of the captured antibodies. The more stable immobilization of plentiful Ru(bpy) 3 2+ could be implemented by direct covalent bonding chelation with Ag 2 C 2 O 4 . More importantly, significant quenching can be achieved by introducing polydopamine (PDA) coated Fe 3 O 4 onto the electrode via sandwich immunoreactions. The quenching mechanism mainly showed that the excited states of Ru(bpy) 3 2+ could be annihilated by quinone units in PDA via energy transfer. The ECL quenching efficiency was logarithmically related to the concentration of the NT-proBNP in the range from 0.0005 ng/mL to 100.0 ng/mL with a detection limit of 0.28 pg/mL. Furthermore, this specific immunosensor presented good stability and repeatability as well as selectivity, which offers a guiding significance in both fundamental and clinical diagnosis of NT-proBNP.

  8. Dependency of anti-ferro-magnetic coupling strength on Ru spacer thickness of [Co/Pd]{sub n}-synthetic-anti-ferro-magnetic layer in perpendicular magnetic-tunnel-junctions fabricated on 12-inch TiN electrode wafer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chae, Kyo-Suk; Samsung Electronics Co., Ltd., San #16 Banwol-dong, Hwasung-City, Gyeonggi-Do 445-701; Shim, Tae-Hun

    We investigated the Ru spacer-thickness effect on the anti-ferro-magnetic coupling strength (J{sub ex}) of a [Co/Pd]{sub n}-synthetic-anti-ferro-magnetic layer fabricated with Co{sub 2}Fe{sub 6}B{sub 2}/MgO based perpendicular-magnetic-tunneling-junction spin-valves on 12-in. TiN electrode wafers. J{sub ex} peaked at a certain Ru spacer-thickness: specifically, a J{sub ex} of 0.78 erg/cm{sup 2} at 0.6 nm, satisfying the J{sub ex} criteria for realizing the mass production of terra-bit-level perpendicular-spin-transfer-torque magnetic-random-access-memory. Otherwise, J{sub ex} rapidly degraded when the Ru spacer-thickness was less than or higher than 0.6 nm. As a result, the allowable Ru thickness variation should be controlled less than 0.12 nm to satisfy the J{sub ex} criteria. However,more » the Ru spacer-thickness did not influence the tunneling-magneto-resistance (TMR) and resistance-area (RA) of the perpendicular-magnetic-tunneling-junction (p-MTJ) spin-valves since the Ru spacer in the synthetic-anti-ferro-magnetic layer mainly affects the anti-ferro-magnetic coupling efficiency rather than the crystalline linearity of the Co{sub 2}Fe{sub 6}B{sub 2} free layer/MgO tunneling barrier/Co{sub 2}Fe{sub 6}B{sub 2} pinned layer, although Co{sub 2}Fe{sub 6}B{sub 2}/MgO based p-MTJ spin-valves ex-situ annealed at 275 °C achieved a TMR of ∼70% at a RA of ∼20 Ω μm{sup 2}.« less

  9. Substituent-directed structural and physicochemical controls of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

    PubMed

    Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

    2005-05-30

    A family of diruthenium complexes with ligand-unsupported Ru-Ru bonds has been systematically synthesized, and their crystal structures and physical properties have been examined. A simple, useful reaction between Ru2(OAc)4Cl (OAc- = acetate) and catechol derivatives in the presence of bases afforded a variety of diruthenium complexes, generally formulated as [Na(n){Ru2(R4Cat)4}] (n = 2 or 3; R4 = -F4, -Cl4, -Br4, -H4, -3,5-di-t-Bu, and -3,6-di-t-Bu; Cat(2-) = catecholate). The most characteristic feature of the complexes is the formation of short ligand-unsupported Ru-Ru bonds (2.140-2.273 A). These comprehensive studies were carried out to evaluate the effects of the oxidation states and the substituents governing the molecular structures and physicochemical properties. The Ru-Ru bond distances, rotational conformations, and bending structures of the complexes were successfully varied. The results presented in this manuscript clearly demonstrate that the complexes with ligand-unsupported Ru-Ru bonds can sensitively respond to redox reactions and ligand substituents on the basis of the greater degree of freedom in their molecular structures.

  10. An Ru(II)-Fe(III) bimetallic complex as a multifunctional device for detecting, signal amplifying, and degrading oxalate.

    PubMed

    Chow, Cheuk-Fai; Ho, Pui-Yu; Gong, Cheng-Bin

    2014-09-07

    A tetranuclear bimetallic complex, [Ru(II)((t)Bubpy)(CN)4]2-[Fe(III)(H2O)3Cl]2·8H2O (1) has been synthesized and characterized. It was found to be a multifunctional device that can detect, signal amplify, and degrade an organic pollutant, oxalate. Results of the chemosensing studies of 1 toward common anions show that only oxalate selectively induces naked-eye colorimetric and luminometric responses with method detection limits down to 78.7 and 5.5 ppm, respectively from 1. Meanwhile, results of the photo-degradation studies of 1 toward oxalate show that the dissolved organic carbon content of oxalate decreased and reached complete mineralization into CO2 within 6 hours. Complex 1 was also found as the catalyst that amplified the detection signal toward oxalate. Through the photoassisted Fenton reaction by 1, methyl orange, an additional coloring agent, could be degraded so that the visual detection limit of 1 toward oxalate was magnified 50 times from 100 to 2 ppm. The detection, degradation, mineralization and signal amplification were found applicable in real water bodies such as river, pond and underground water with excellent recoveries and relative standard deviation.

  11. Synthesis, characterization, and photophysical properties of a series of supramolecular mixed-valence compounds.

    PubMed

    Pfennig, B W; Fritchman, V A; Hayman, K A

    2001-01-15

    The synthesis and characterization of 10 cyano-bridged trinuclear mixed-valence compounds of the form [(NH3)5M-NC-FeII(CN)4-CN-M'(NH3)5]n+ (M = RuIII, OsIII, CrIII, or PtIV; n = 2, 3, or 4) is reported. The electronic spectra of these supramolecular compounds exhibit a single intervalent (IT) absorption band for each nondegenerate Fe-->M/M' transition. The redox potential of the Fe(II) center is shifted more positive with the addition of each coordinated metal complex, while the redox potentials of the pendant metals vary only slightly from their dinuclear counterparts. As a result, the Fe-->M IT bands are blue-shifted from those in the corresponding dinuclear mixed-valence compounds. The energies of these IT bands show a linear correlation with the ground-state thermodynamic driving force, as predicted by classical electron transfer theory. Estimates of the degree of electronic coupling (Hab) between the metal centers using a theoretical analysis of the IT band shapes indicate that most of these values are similar to those for the corresponding dinuclear species. Notable exceptions occur for the Fe-->M IT transitions in Os-Fe-M (M = Cr or Pt). The enhanced electronic coupling in these two species can be explained as a result of excited state mixing between electron transfer and/or ligand-based charge transfer states and an intensity-borrowing mechanism. Additionally, the possibility of electronic coupling between the remote metal centers in the Ru-Fe-Ru species is discussed in order to explain the observation of two closely spaced redox waves for the degenerate Ru(III) acceptors.

  12. Effect of the strong coupling on the exchange bias field in IrMn/Py/Ru/Co spin valves

    NASA Astrophysics Data System (ADS)

    Tarazona, H. S.; Alayo, W.; Landauro, C. V.; Quispe-Marcatoma, J.

    2018-01-01

    The IrMn/Py/Ru/Co (Py = Ni81Fe19) spin valves have been produced by sputtering deposition and analyzed by magnetization measurements and a theoretical modelling of their exchange interactions, based on the macro-spin model. The Ru thickness was grown between 6 and 22 Å, which is small enough to promote strong indirect coupling between Py and Co. Results of measurements showed a large and gradual change in the shape of hysteresis loops when the Ru thickness was varied. The theoretical analysis, using numerical calculations based on the gradient conjugate method, provides the exchange coupling constants (bilinear and biquadratic), the exchange anisotropy fields and the magnetic anisotropy fields (uniaxial and rotatable). The exchange bias fields of spin valves were compared to that of a IrMn/Py bilayer. We found that the difference between these fields oscillates with Ru thickness in the same manner as the bilinear coupling constants.

  13. Superconductor-Insulator transition in sputtered amorphous MoRu and MoRuN thin films

    NASA Astrophysics Data System (ADS)

    Makise, K.; Shinozaki, B.; Ichikawa, F.

    2018-03-01

    This work shows the experimental results of the superconductor-insulator (S-I) transition for amorphous molybdenum ruthenium (MoRu) and molybdenum ruthenium nitride (MoRuN) films. These amorphous films onto c-plane sapphire substrates have been interpreted to be homogeneous by XRD and AFM measurements. Electrical and superconducting properties measurements were carried out on MoRu and MoRuN thin films deposited by reactive sputtering technique. We have analysed the data on R sq (T) based on excess conductivity of superconducting films by the AL and MT term and weak localization and electron-electron interaction for the conductance. MoRu films which offer the most homogeneous film morphology, showed a critical sheet resistance of transition, Rc, of ∼ 2 kΩ. This values is smaller than those previously our reported for quench-condensed MoRu films on SiO underlayer held at liquid He temperature.

  14. Weathering of PGE sulfides and Pt-Fe alloys in the Freetown Layered Complex, Sierra Leone

    NASA Astrophysics Data System (ADS)

    Bowles, John F. W.; Suárez, Saioa; Prichard, Hazel M.; Fisher, Peter C.

    2017-12-01

    Fresh and weathered rocks and saprolite from Horizon B of the Freetown Layered Complex contain platinum-group minerals (PGM). The PGM in the fresh rocks are 1-7 μm across, including cooperite (PtS), isoferroplatinum (Pt3Fe), minor tetraferroplatinum (PtFe), tulameenite (Pt2FeCu), Os-bearing laurite (RuS2), and other base metal-sulfide (BMS)-bearing PGM. The weathered rocks contain fewer of those PGM but a high proportion of disordered Cu-(±Pd)-bearing Pt-Fe alloys. The saprolite hosts scarce, smaller (1-3 μm) ordered PtFe and disordered PtFe3. The Pt-Fe alloys became increasingly Fe rich as weathering proceeded. Pt-Fe oxides appeared during weathering. Copper sulfides associated with the primary PGM and cooperite (with <3% Pd) were destroyed to provide the minor Cu and Pd found in some of the disordered Pt-Fe alloys. Platinum- and Pd-bearing saprolites have retained the original rock fabric and, to a depth of about 2 m, surround residual rocks that show progressive weathering (corestones). Ground water passing through the saprolite has transported Pt and Pd (and probably Au) in solution down slope into saprolite over unmineralized rocks. Transport is marked by changes in the Pt/Pd ratio indicating that the metals have moved independently. Palladium is present in marginally higher concentrations in the deeper saprolite than in the corestones suggesting some retention of Pd in the deeper saprolite. Platinum and Pd are less concentrated in the upper saprolite than the deeper saprolite indicating surface leaching. Alteration occurred over a long period in an organic and microbial rich environment that may have contributed to the leaching and transport of PGE.

  15. Highly branched RuO2 Nanorods on Electrospun TiO2 Nanofibers toward Electrochemical Catalysts

    NASA Astrophysics Data System (ADS)

    Cho, Yukyung; Kim, Su-Jin; Lee, Nam-Suk; Kim, Myung Hwa; Lee, Youngmi

    2014-03-01

    We report a facile growth route to synthesize hierarchically grown single crystalline metallic RuO2 nanorods on electrospun TiO2 nanofibers via a combination of a simple vapour phase transport process with an electrospinning process. This synthetic strategy could be very useful to design a variety of highly branched network architectures of the functional hetero-nanostructures for electrochemical applications. Particularly, Ruthenium oxide (RuO2) 1-dimensional nanostructures can be used as the effective catalysts or electrochemical electrode materials. Thus, we first synthesize TiO2 nanofibers from mixture of titanium isopropoxide precursor and polymer and then ruthenium hydroxide precursor on TiO2 nanofibers are transformed into RuO2 nanorods by thermal treatment at 250oC in air. The crystalline structures of products are confirmed using scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) spectrum, Raman spectroscopy, and high resolution electron microscopy (HRTEM). The fundamental electrochemical performances are examined using cyclic voltammetry (CV).

  16. Ru-assisted synthesis of Pd/Ru nanodendrites with high activity for ethanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Ke; Bin, Duan; Yang, Beibei; Wang, Caiqin; Ren, Fangfang; Du, Yukou

    2015-07-01

    Due to the specific physical and chemical properties of a highly branched noble metal, the controllable synthesis has attracted much attention. This article reports the synthesis of Pd/Ru nanodendrites by a facile method using an oil bath in the presence of polyvinyl pyrrolidone, potassium bromide and ascorbic acid. The morphology, structure, and composition of the as-prepared catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In the electrochemical measurement, the as-prepared Pd7/Ru1 bimetallic nanodendrites provide a large electrochemically active surface area and exhibit high peak current density in the forward scan toward ethanol electrooxidation, which is nearly four times higher than those of a pure Pd catalyst. The as-prepared Pd7/Ru1 catalysts also exhibit significantly enhanced cycling stability toward ethanol oxidation in alkaline medium, which are mainly ascribed to the synergetic effect between Pd and Ru. This indicates that the Pd7/Ru1 catalysts should have great potential applications in direct ethanol fuel cells.Due to the specific physical and chemical properties of a highly branched noble metal, the controllable synthesis has attracted much attention. This article reports the synthesis of Pd/Ru nanodendrites by a facile method using an oil bath in the presence of polyvinyl pyrrolidone, potassium bromide and ascorbic acid. The morphology, structure, and composition of the as-prepared catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In the electrochemical measurement, the as-prepared Pd7/Ru1 bimetallic nanodendrites provide a large electrochemically active surface area and exhibit high peak current density in the forward scan toward ethanol electrooxidation, which is nearly four times higher than those of a pure Pd catalyst. The as-prepared Pd7/Ru1 catalysts also exhibit significantly

  17. Platinum Group Elements, 187OS/188OS and 87SR/86SR Isotope Systematics in Depleted Fluid-Modified Mariana Fore-Arc Peridotites

    NASA Astrophysics Data System (ADS)

    Harvey, J.; Savov, I. P.; Shirey, S. B.; Horan, M. F.; Mock, T. D.

    2012-12-01

    The serpentine mud volcanoes of the Izu-Bonin-Mariana (IBM) fore-arc, collected during Ocean Drilling Program Leg 195 [1], contain hard-rock clasts of serpentine sampled from close to the décollement, which separates the down-going Pacific slab from the overlying mantle wedge. These clasts preserve evidence for melt depletion (>25 % melt extraction in many instances) in a sub-arc environment, and extensive (40 - 100%) serpentinization due to subsequent fluid / peridotite interaction, e.g. [2]. Platinum-group element (PGE) abundances are not consistent with melt-depletion alone [3]. Fractionation between I-PGE (Os, Ir, Ru) has resulted in groups of IBM serpentinites with either a high chondrite-normalized Os/Ir ratio (OsN/IrN) or a low OsN/IrN ratio. Similarly, fractionation of P-PGE (Pt, Pd) is marked, and distinguishes the IBM serpentinites from worldwide abyssal peridotites. Interaction with high-pH fluids [4] may have partially oxidized mantle sulphide, the major primary host for PGE in these rocks, leading to partial breakdown to sulphate and the selective redistribution of certain PGE (Os, Ru, Pt), a feature normally associated with sub-aerial weathering [5], but which likely prevails in other oxidizing environments. In particular, the Re-Os systematics of the high (OsN/IrN) IBM serpentinites have been disturbed by the addition of Os. Unlike peridotite xenoliths associated with magmatic regions of subduction zones where subduction-related Os-addition is unequivocally radiogenic and derived from crustal material [6][7], where Os has been added to the IBM serpentinites it is unradiogenic and was most likely derived from within the oceanic mantle. IBM serpentinites therefore preserve osmium isotope ratios that are exclusively sub-chondritic (187Os/188Os ≤ 0.127), as previously reported [8]. These serpentinized peridotites were produced by at least a three-step process: melt depletion, serpentinization, and the mobilization of Os, Ru and Pt to produce low Os

  18. Carbon-supported bimetallic Pd–Fe catalysts for vapor-phase hydrodeoxygenation of guaiacol

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sun, Junming; Karim, Ayman M.; Zhang, He

    2013-10-01

    Abstract Carbon supported metal catalysts (Cu/C, Fe/C, Pd/C, Pt/C, PdFe/C and Ru/C) have been prepared, characterized and tested for vapor-phase hydrodeoxygenation (HDO) of guaiacol (GUA) at atmospheric pressure. Phenol was the major intermediate on all catalysts. Over the noble metal catalysts saturation of the aromatic ring was the major pathway observed at low temperature (250 °C), forming predominantly cyclohexanone and cyclohexanol. Substantial ring opening reaction was observed on Pt/C and Ru/C at higher reaction temperatures (e.g., 350 °C). Base metal catalysts, especially Fe/C, were found to exhibit high HDO activity without ring-saturation or ring-opening with the main products being benzene,more » phenol along with small amounts of cresol, toluene and trimethylbenzene (TMB). A substantial enhancement in HDO activity was observed on the PdFe/C catalysts. Compared with Fe/C, the yield to oxygen-free aromatic products (i.e., benzene/toluene/TMB) on PdFe/C increased by a factor of four at 350 °C, and by approximately a factor of two (83.2% versus 43.3%) at 450 °C. The enhanced activity of PdFe/C is attributed to the formation of PdFe alloy as evidenced by STEM, EDS and TPR.« less

  19. Revisiting RuBisCO.

    PubMed

    Yokota, Akiho

    2017-11-01

    Since the discovery of its role in the CO 2 fixation reaction in photosynthesis, RuBisCO has been one of the most extensively researched enzymes in the fields of biochemistry, molecular biology, and molecular genetics as well as conventional plant physiology, agricultural chemistry, and crop science. In addition, the RuBisCO and RuBisCO-like genes of more than 2000 organisms have been sequenced during the past 20 years. During the course of those studies, the origin of the RuBisCO gene began to be discussed. Recent studies have reported that the RuBisCO gene emerged in methanogenic bacteria long before photosynthetic organisms appeared. The origin of similar early genes might have allowed this gene to overcome changes in global environments during ancient and recent eras and to participate in the fixation of 200 GT of CO 2 annually. In this review, I focus on several points that have not been discussed at length in the literature thus far.

  20. Investigation of the Vortex States of Sr2RuO4-Ru Eutectic Microplates Using DC-SQUIDs

    NASA Astrophysics Data System (ADS)

    Sakuma, Daisuke; Nago, Yusuke; Ishiguro, Ryosuke; Kashiwaya, Satoshi; Nomura, Shintaro; Kono, Kimitoshi; Maeno, Yoshiteru; Takayanagi, Hideaki

    2017-11-01

    We investigated the magnetic properties of a Sr2RuO4-Ru eutectic microplate containing a single Ru-inclusion using micrometer-sized DC-SQUIDs (direct-current superconducting quantum interference devices). A phase frustration at the interface between chiral p-wave superconducting Sr2RuO4 and s-wave superconducting Ru is expected to cause novel magnetic vortex states such as the spontaneous Ru-center vortex under zero magnetic field [as reported by H. Kaneyasu and M. Sigrist, J. Phys. Soc. Jpn. 79, 053706 (2010)]. Our experimental results show no positive evidence for such a spontaneous vortex state. However, in an applied field, an abrupt change in the magnetic flux distribution was observed at a superconducting transition of Ru. The flux distribution is clarified by comparing our experimental results with electromagnetic field simulations in our sample geometry. We discuss the transition of the vortex states and the superconducting coupling at the Sr2RuO4/Ru interface.

  1. OsIRO2 is responsible for iron utilization in rice and improves growth and yield in calcareous soil.

    PubMed

    Ogo, Yuko; Itai, Reiko N; Kobayashi, Takanori; Aung, May Sann; Nakanishi, Hiromi; Nishizawa, Naoko K

    2011-04-01

    Iron (Fe) deficiency, a worldwide agricultural problem on calcareous soil with low Fe availability, is also a major human nutritional deficit. Plants induce Fe acquisition systems under conditions of low Fe availability. Previously, we reported that an Fe-deficiency-inducible basic helix-loop-helix (bHLH) transcription factor, OsIRO2, is responsible for regulation of the genes involved in Fe homeostasis in rice. Using promoter-GUS transformants, we showed that OsIRO2 is expressed throughout a plant's lifetime in a spatially and temporally similar manner to the genes OsNAS1, OsNAS2 and TOM1, which is involved in Fe absorption and translocation. During germination, OsIRO2 expression was detected in embryos. OsIRO2 expression in vegetative tissues was restricted almost exclusively to vascular bundles of roots and leaves, and to the root exodermis under Fe-sufficient conditions, and expanded to all tissues of roots and leaves in response to Fe deficiency. OsIRO2 expression was also detected in flowers and developing seeds. Plants overexpressing OsIRO2 grew better, and OsIRO2-repressed plants showed poor growth compared to non-transformant rice after germination. OsIRO2 overexpression also resulted in improved tolerance to low Fe availability in calcareous soil. In addition to increased Fe content in shoots, the overexpression plants accumulated higher amounts of Fe in seeds than non-transformants when grown on calcareous soil. These results suggest that OsIRO2 is synchronously expressed with genes involved in Fe homeostasis, and performs a crucial function in regulation not only of Fe uptake from soil but also Fe transport during germination and Fe translocation to grain during seed maturation.

  2. One-pot process for hydrodeoxygenation of lignin to alkanes using Ru-based bimetallic and bifunctional catalysts supported on zeolite Y

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Hongliang; Ruan, Hao; Feng, Maoqi

    2017-02-22

    Here, the synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbonmore » products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al 2O 3 and HY zeolite.« less

  3. Supergene neoformation of Pt-Ir-Fe-Ni alloys: multistage grains explain nugget formation in Ni-laterites

    NASA Astrophysics Data System (ADS)

    Aiglsperger, Thomas; Proenza, Joaquín A.; Font-Bardia, Mercè; Baurier-Aymat, Sandra; Galí, Salvador; Lewis, John F.; Longo, Francisco

    2017-10-01

    Ni-laterites from the Dominican Republic host rare but extremely platinum-group element (PGE)-rich chromitites (up to 17.5 ppm) without economic significance. These chromitites occur either included in saprolite (beneath the Mg discontinuity) or as `floating chromitites' within limonite (above the Mg discontinuity). Both chromitite types have similar iridium-group PGE (IPGE)-enriched chondrite normalized patterns; however, chromitites included in limonite show a pronounced positive Pt anomaly. Investigation of heavy mineral concentrates, obtained via hydroseparation techniques, led to the discovery of multistage PGE grains: (i) Os-Ru-Fe-(Ir) grains of porous appearance are overgrown by (ii) Ni-Fe-Ir and Ir-Fe-Ni-(Pt) phases which are overgrown by (iii) Pt-Ir-Fe-Ni mineral phases. Whereas Ir-dominated overgrowths prevail in chromitites from the saprolite, Pt-dominated overgrowths are observed within floating chromitites. The following formation model for multistage PGE grains is discussed: (i) hypogene platinum-group minerals (PGM) (e.g. laurite) are transformed to secondary PGM by desulphurization during serpentinization; (ii) at the stages of serpentinization and/or at the early stages of lateritization, Ir is mobilized and recrystallizes on porous surfaces of secondary PGM (serving as a natural catalyst) and (iii) at the late stages of lateritization, biogenic mediated neoformation (and accumulation) of Pt-Ir-Fe-Ni nanoparticles occurs. The evidence presented in this work demonstrates that in situ growth of Pt-Ir-Fe-Ni alloy nuggets of isometric symmetry is possible within Ni-laterites from the Dominican Republic.

  4. Ferromagnetic CaRuO3

    PubMed Central

    Tripathi, Shivendra; Rana, Rakesh; Kumar, Sanjay; Pandey, Parul; Singh, R. S.; Rana, D. S.

    2014-01-01

    The non-magnetic and non-Fermi-liquid CaRuO3 is the iso-structural analog of the ferromagnetic (FM) and Fermi-liquid SrRuO3. We show that an FM order in the orthorhombic CaRuO3 can be established by the means of tensile epitaxial strain. The structural and magnetic property correlations in the CaRuO3 films formed on SrTiO3 (100) substrate establish a scaling relation between the FM moment and the tensile strain. The strain dependent crossover from non-magnetic to FM CaRuO3 was observed to be associated with switching of non-Fermi liquid to Fermi-liquid behavior. The intrinsic nature of this strain-induced FM order manifests in the Hall resistivity too; the anomalous Hall component realizes in FM tensile-strained CaRuO3 films on SrTiO3 (100) whereas the non-magnetic compressive-strained films on LaAlO3 (100) exhibit only the ordinary Hall effect. These observations of an elusive FM order are consistent with the theoretical predictions of scaling of the tensile epitaxial strain and the magnetic order in tensile CaRuO3. We further establish that the tensile strain is more efficient than the chemical route to induce FM order in CaRuO3. PMID:24464302

  5. Reduction of RuVI≡N to RuIII-NH3 by Cysteine in Aqueous Solution.

    PubMed

    Wang, Qian; Man, Wai-Lun; Lam, William W Y; Yiu, Shek-Man; Tse, Man-Kit; Lau, Tai-Chu

    2018-05-21

    The reduction of metal nitride to ammonia is a key step in biological and chemical nitrogen fixation. We report herein the facile reduction of a ruthenium(VI) nitrido complex [(L)Ru VI (N)(OH 2 )] + (1, L = N, N'-bis(salicylidene)- o-cyclohexyldiamine dianion) to [(L)Ru III (NH 3 )(OH 2 )] + by l-cysteine (Cys), an ubiquitous biological reductant, in aqueous solution. At pH 1.0-5.3, the reaction has the following stoichiometry: [(L)Ru VI (N)(OH 2 )] + + 3HSCH 2 CH(NH 3 )CO 2 → [(L)Ru III (NH 3 )(OH 2 )] + + 1.5(SCH 2 CH(NH 3 )CO 2 ) 2 . Kinetic studies show that at pH 1 the reaction consists of two phases, while at pH 5 there are three distinct phases. For all phases the rate law is rate = k 2 [1][Cys]. Studies on the effects of acidity indicate that both HSCH 2 CH(NH 3 + )CO 2 - and - SCH 2 CH(NH 3 + )CO 2 - are kinetically active species. At pH 1, the reaction is proposed to go through [(L)Ru IV (NHSCH 2 CHNH 3 CO 2 H)(OH 2 )] 2+ (2a), [(L)Ru III (NH 2 SCH 2 CHNH 3 CO 2 H)(OH 2 )] 2+ (3), and [(L)Ru IV (NH 2 )(OH 2 )] + (4) intermediates. On the other hand, at pH around 5, the proposed intermediates are [(L)Ru IV (NHSCH 2 CHNH 3 CO 2 )(OH 2 )] + (2b) and [(L)Ru IV (NH 2 )(OH 2 )] + (4). The intermediate ruthenium(IV) sulfilamido species, [(L)Ru IV (NHSCH 2 CHNH 3 CO 2 H)(OH 2 )] 2+ (2a) and the final ruthenium(III) ammine species, [(L)Ru III (NH 3 )(MeOH)] + (5) (where H 2 O was replaced by MeOH) have been isolated and characterized by various spectroscopic methods.

  6. London penetration depth measurements in Ba (Fe 1-xT x) 2As 2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gordon, Ryan T.

    2011-01-01

    The London penetration depth has been measured in various doping levels of single crystals of Ba(Fe 1-xT x) 2As 2 (T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors by utilizing a tunnel diode resonator (TDR) apparatus. All in-plane penetration depth measurements exhibit a power law temperature dependence of the form Δλ ab(T) = CT n, indicating the existence of low-temperature, normal state quasiparticles all the way down to the lowest measured temperature, which was typically 500 mK. Several different doping concentrations from the Ba(Fe 1-xT x) 2As 2 (T=Co,Ni) systems have been measured and the doping dependence of the power law exponent, n, is compared tomore » results from measurements of thermal conductivity and specific heat. In addition, a novel method has been developed to allow for the measurement of the zero temperature value of the in-plane penetration depth, λ ab(0), by using TDR frequency shifts. By using this technique, the doping dependence of λ ab(0) has been measured in the Ba(Fe 1-xCo x) 2As 2 series, which has allowed also for the construction of the doping-dependent superfluid phase stiffness, ρ s(T) = [λ(0)/λ(T)] 2. By studying the effects of disorder on these superconductors using heavy ion irradiation, it has been determined that the observed power law temperature dependence likely arises from pair-breaking impurity scattering contributions, which is consistent with the proposed s±-wave symmetry of the superconducting gap in the dirty scattering limit. This hypothesis is supported by the measurement of an exponential temperature dependence of the penetration depth in the intrinsically clean LiFeAs, indicative of a nodeless superconducting gap.« less

  7. Multiple Pathways for Benzyl Alcohol Oxidation by Ru V =O 3+ and Ru IV =O 2+

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Paul, Amit; Hull, Jonathan F.; Norris, Michael R.

    2011-02-21

    Significant rate enhancements are found for benzyl alcohol oxidation by the RuV=O3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH2)]2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to RuIV=O2+ and for the RuIV=O2+ form with added bases due to a new pathway, concerted hydride proton transfer (HPT).

  8. Multiple Pathways for Benzyl Alcohol Oxidation by Ru V=O 3+ and Ru IV=O 2+

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Paul, Amit; Hull, Jonathan F.; Norris, Michael R.

    2011-01-20

    Significant rate enhancements are found for benzyl alcohol oxidation by the Ru V=O 3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH 2)] 2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to Ru IV=O 2+ and for the Ru IV=O 2+ form with added bases due to a new pathway, concerted hydride proton transfer (HPT).

  9. Fragility of ferromagnetic double exchange interactions and pressure tuning of magnetism in 3 d -5 d double perovskite Sr2FeOsO6

    NASA Astrophysics Data System (ADS)

    Veiga, L. S. I.; Fabbris, G.; van Veenendaal, M.; Souza-Neto, N. M.; Feng, H. L.; Yamaura, K.; Haskel, D.

    2015-06-01

    The ability to tune exchange (magnetic) interactions between 3 d transition metals in perovskite structures has proven to be a powerful route to discovery of novel properties. Here we demonstrate that the introduction of 3 d -5 d exchange pathways in double perovskites enables additional tunability, a result of the large spatial extent of 5 d wave functions. Using x-ray probes of magnetism and structure at high pressure, we show that compression of Sr2FeOsO6 drives an unexpected continuous change in the sign of Fe-Os exchange interactions and a transition from antiferromagnetic to ferrimagnetic order. We analyze the relevant electron-electron interactions, shedding light into fundamental differences with the more thoroughly studied 3 d -3 d systems.

  10. Ru sub 3 (CO) sub 12 and Mo(CO) sub 6 adsorbed on Ru(001) and Au/Ru: An infrared reflection-absorption study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Malik, I.J.; Hrbek, J.

    1990-01-01

    We obtained IRAS and TDS data for Ru{sub 3}(CO){sub 12}/Ru(001) and Mo(CO){sub 6}/Au/Ru systems for metal carbonyl coverages between submonolayer and approximately 20 monolayers. We characterized the C-O stretching mode of both systems (4 cm{sup {minus}1} FWHM) and a deformation mode of Mo(CO){sub 6} at 608 cm{sup {minus}1} (1 cm{sup {minus}1} FWHM). Both IRAS and TDS data suggest adsorption and desorption of metal carbonyls as molecular species with a preferential orientation in the overlayers. The IR intensity of the C-O stretch per a C-O bond projected onto the surface normal is approximately twice (five times) larger for Ru{sub 3}(CO){sub 12}more » (Mo(CO){sub 6}) at submonolayer coverages than for CO/Ru(001) at {theta}{sub CO}=0.68. 31 refs., 4 figs.« less

  11. A [NiFe]hydrogenase model that catalyses the release of hydrogen from formic acid.

    PubMed

    Nguyen, Nga T; Mori, Yuki; Matsumoto, Takahiro; Yatabe, Takeshi; Kabe, Ryota; Nakai, Hidetaka; Yoon, Ki-Seok; Ogo, Seiji

    2014-11-11

    We report the decomposition of formic acid to hydrogen and carbon dioxide, catalysed by a NiRu complex originally developed as a [NiFe]hydrogenase model. This is the first example of H2 evolution, catalysed by a [NiFe]hydrogenase model, which does not require additional energy.

  12. Multiple Pathways for Benzyl Alcohol Oxidation by Ru V=O 3+ and Ru IV=O 2+

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Paul, Amit; Hull, Jonathan F.; Norris, Michael R.

    2011-01-20

    Significant rate enhancements are found for benzyl alcohol oxidation by the Ru V=O 3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH 2)] 2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to Ru IV=O 2+ and for the Ru IV=O 2+ form with added bases due to a new pathway involving concerted hydride proton transfer (HPT).

  13. Paragenesis of multiple platinum-group mineral populations in Shetland ophiolite chromitite: 3D X-ray tomography and in situ Os isotopes

    NASA Astrophysics Data System (ADS)

    Prichard, H. M.; Barnes, Stephen J.; Dale, C. W.; Godel, B.; Fisher, P. C.; Nowell, G. M.

    2017-11-01

    Chromitite from the Harold's Grave locality in the mantle section of the Shetland ophiolite complex is extremely enriched in Ru, Os and Ir, at μg/g concentrations. High-resolution X-ray computed tomography on micro-cores from these chromitites was used to determine the location, size, distribution and morphology of the platinum-group minerals (PGM). There are five generations of PGM in these chromitites. Small (average 5 μm in equivalent sphere diameter, ESD) euhedral laurites, often with Os-Ir alloys, are totally enclosed in the chromite and are likely to have formed first by direct crystallisation from the magma as the chromite crystallised. Also within the chromitite there are clusters of larger (50 μm ESD) aligned elongate crystals of Pt-, Rh-, Ir-, Os- and Ru-bearing PGM that have different orientations in different chromite crystals. These may have formed either by exsolution, or by preferential nucleation of PGMs in boundary layers around particular growing chromite grains. Thirdly there is a generation of large (100 μm ESD) composite Os-Ir-Ru-rich PGM that are all interstitial to the chromite grains and sometimes form in clusters. It is proposed that Os, Ir and Ru in this generation were concentrated in base metal sulfide droplets that were then re-dissolved into a later sulfide-undersaturated magma, leaving PGM interstitial to the chromite grains. Fourthly there is a group of almost spherical large (80 μm ESD) laurites, hosting minor Os-Ir-Ru-rich PGM that form on the edge or enclosed in chromite grains occurring in a sheet crosscutting a chromitite layer. These may be hosted in an annealed late syn- or post magmatic fracture. Finally a few of the PGM have been deformed in localised shear zones through the chromitites. The vast majority of the PGM - including small PGM enclosed within chromite, larger interstitial PGM and elongate aligned PGM - have Os isotope compositions that give Re-depletion model ages approximately equal to the age of the

  14. Diversity of Chemical Bonding and Oxidation States in MS4 Molecules of Group 8 Elements.

    PubMed

    Huang, Wei; Jiang, Ning; Schwarz, W H Eugen; Yang, Ping; Li, Jun

    2017-08-04

    The geometric and electronic ground-state structures of 30 isomers of six MS 4 molecules (M=Group 8 metals Fe, Ru, Os, Hs, Sm, and Pu) have been studied by using quantum-chemical density functional theory and correlated wavefunction approaches. The MS 4 species were compared to analogous MO 4 species recently investigated (W. Huang, W.-H. Xu, W. H. E. Schwarz, J. Li, Inorg. Chem. 2016, 55, 4616). A metal oxidation state (MOS) with a high value of eight appeared in the low-spin singlet T d geometric species (Os,Hs)S 4 and (Ru,Os,Hs)O 4 , whereas a low MOS of two appeared in the high-spin septet D 2d species Fe(S 2 ) 2 and (slightly excited) metastable Fe(O 2 ) 2 . The ground states of all other molecules had intermediate MOS values, with S 2- , S 2 2- , S 2 1- (and O 2- , O 1- , O 2 2- , O 2 1- ) ligands bonded by ionic, covalent, and correlative contributions. The known tendencies toward lower MOS on going from oxides to sulfides, from Hs to Os to Ru, and from Pu to Sm, and the specific behavior of Fe, were found to arise from the different atomic orbital energies and radii of the (n-1)p core and (n-1)d and (n-2)f valence shells of the metal atoms in row n of the periodic table. The comparative results of the electronic and geometric structures of the MO 4 and MS 4 species provides insight into the periodicity of oxidation states and bonding. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Ru-assisted synthesis of Pd/Ru nanodendrites with high activity for ethanol electrooxidation.

    PubMed

    Zhang, Ke; Bin, Duan; Yang, Beibei; Wang, Caiqin; Ren, Fangfang; Du, Yukou

    2015-08-07

    Due to the specific physical and chemical properties of a highly branched noble metal, the controllable synthesis has attracted much attention. This article reports the synthesis of Pd/Ru nanodendrites by a facile method using an oil bath in the presence of polyvinyl pyrrolidone, potassium bromide and ascorbic acid. The morphology, structure, and composition of the as-prepared catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In the electrochemical measurement, the as-prepared Pd7/Ru1 bimetallic nanodendrites provide a large electrochemically active surface area and exhibit high peak current density in the forward scan toward ethanol electrooxidation, which is nearly four times higher than those of a pure Pd catalyst. The as-prepared Pd7/Ru1 catalysts also exhibit significantly enhanced cycling stability toward ethanol oxidation in alkaline medium, which are mainly ascribed to the synergetic effect between Pd and Ru. This indicates that the Pd7/Ru1 catalysts should have great potential applications in direct ethanol fuel cells.

  16. Ru sub 3 (CO) sub 12 and Mo(CO) sub 6 adsorbed on Ru(001) and Au/Ru: An infrared reflection-absorption study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Malik, I.J.; Hrbek, J.

    1990-01-01

    The authors obtained infrared reflection absorption (IRAS) and thermal desorption spectroscopy (TDS) data for Ru{sub 3}(CO){sub 12}/Ru(001) and Mo(CO){sub 6}/Au/Ru systems for metal carbonyl coverages between submonolayer and approximately 20 monolayers. They characterized the C-O stretching mode of both systems (4cm{sup {minus}1}FWHM) and a deformation mode of Mo(CO){sub 6} at 608cm{sup {minus}1} (1 cm{sup {minus}1}FWHM). Both IRAS and TDS data suggest adsorption and desorption of metal carbonyls as molecular species with a preferential orientation in the overlayers. The IR intensity of the C-O stretch per a C-O bond projected onto the surface normal is approximately twice (five times) larger formore » Ru{sub 3}(CO){sub 12} (Mo(CO){sub 6}) at submonolayer coverages than for CO/Ru(001) at {theta}{sub CO}=0.68.« less

  17. Adsorption and diffusion of Ru adatoms on Ru(0001)-supported graphene: Large-scale first-principles calculations

    DOE PAGES

    Han, Yong; Evans, James W.

    2015-10-27

    Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moiré cell, there are three distinct regions: fcc, hcp, and mound, in which the C6-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atom inmore » the fcc region, next strongest in the hcp region, then the fcc-hcp boundary (ridge) between these regions, and the weakest binding in the mound region. Behavior is similar to that observed from small-unit-cell calculations of Habenicht et al. [Top. Catal. 57, 69 (2014)], which differ from previous large-scale calculations. We determine the minimum-energy path for local diffusion near the center of the fcc region and obtain a local diffusion barrier of ~0.48 eV. We also estimate a significantly lower local diffusion barrier in the ridge region. These barriers and information on the adsorption energy variation facilitate development of a realistic model for the global potential energy surface for Ru adatoms. Furthermore, this in turn enables simulation studies elucidating diffusion-mediated directed-assembly of Ru nanoclusters during deposition of Ru on G/Ru(0001).« less

  18. Adsorption and diffusion of Ru adatoms on Ru(0001)-supported graphene: Large-scale first-principles calculations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Han, Yong; Evans, James W.

    2015-10-28

    Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moiré cell, there are three distinct regions: fcc, hcp, and mound, in which the C{sub 6}-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atommore » in the fcc region, next strongest in the hcp region, then the fcc-hcp boundary (ridge) between these regions, and the weakest binding in the mound region. Behavior is similar to that observed from small-unit-cell calculations of Habenicht et al. [Top. Catal. 57, 69 (2014)], which differ from previous large-scale calculations. We determine the minimum-energy path for local diffusion near the center of the fcc region and obtain a local diffusion barrier of ∼0.48 eV. We also estimate a significantly lower local diffusion barrier in the ridge region. These barriers and information on the adsorption energy variation facilitate development of a realistic model for the global potential energy surface for Ru adatoms. This in turn enables simulation studies elucidating diffusion-mediated directed-assembly of Ru nanoclusters during deposition of Ru on G/Ru(0001)« less

  19. One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y.

    PubMed

    Wang, Hongliang; Ruan, Hao; Feng, Maoqi; Qin, Yuling; Job, Heather; Luo, Langli; Wang, Chongmin; Engelhard, Mark H; Kuhn, Erik; Chen, Xiaowen; Tucker, Melvin P; Yang, Bin

    2017-04-22

    The synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al 2 O 3 and HY zeolite. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Positive exchange-bias and giant vertical hysteretic shift in La0.3Sr0.7FeO3/SrRuO3 bilayers

    PubMed Central

    Rana, Rakesh; Pandey, Parul; Singh, R. P.; Rana, D. S.

    2014-01-01

    The exchange-bias effects in the mosaic epitaxial bilayers of the itinerant ferromagnet (FM) SrRuO3 and the antiferromagnetic (AFM) charge-ordered La0.3Sr0.7FeO3 were investigated. An uncharacteristic low-field positive exchange bias, a cooling-field driven reversal of positive to negative exchange-bias and a layer thickness optimised unusual vertical magnetization shift were all novel facets of exchange bias realized for the first time in magnetic oxides. The successive magnetic training induces a transition from positive to negative exchange bias regime with changes in domain configurations. These observations are well corroborated by the hysteretic loop asymmetries which display the modifications in the AFM spin correlations. These exotic features emphasize the key role of i) mosaic disorder induced subtle interplay of competing AFM-superexchange and FM double exchange at the exchange biased interface and, ii) training induced irrecoverable alterations in the AFM spin structure. PMID:24569516

  1. Laser Spectroscopy of Ruthenium Containing Diatomic Molecules: RuH/D and RuP.

    NASA Astrophysics Data System (ADS)

    Adam, Allan G.; Konder, Ricarda M.; Nickerson, Nicole M.; Linton, Colan; Tokaryk, D. W.

    2015-06-01

    In the last few years, the Cheung group in Hong Kong and the Steimle group in Arizona have successfully studied several ruthenium containing diatomic molecules, RuX (X =C, O, N, B, using the laser-ablation molecular jet technique. Based on this success, the UNB spectroscopy group decided to try and find the optical signatures of other RuX molecules. Using CH_3OH and PH_3 as reactant gases, the RuH and RuP diatomic molecules have been detected in surveys of the 420 - 675 nm spectral region. RuD has also been made using fully deuterated methanol as a reactant. Dispersed fluorescence experiments have been performed to determine ground state vibrational frequencies and the presence of any low-lying electronic states. Rotationally resolved spectra for these molecules have also been taken and the analysis is proceeding. The most recent results will be presented. F. Wang et al., Journal of Chemical Physics 139, 174318 (2013). N. Wang et al., Journal of Physical Chemistry A 117, 13279 (2013). T. Steimle et al., Journal of Chemical Physics 119, 12965 (2003). N. Wang et al., Chemical Physics Letters 547, 21 (2012).

  2. Mössbauer analysis of the firing process of the sky-green glaze of the imitative ancient Chinese Ru porcelain

    NASA Astrophysics Data System (ADS)

    Songhua, Chen; Zhengyao, Gao; Guoju, Hu; Xiande, Chen

    1994-12-01

    The variation of the Mössbauer parameters of the imitative ancient Ru porcelain skygreen glaze with the firing conditions is studied in detail in the present paper. The Mössbauer spectra show that the sky-green glaze contains three kinds of iron minerals, i.e. the structural iron (Fe2+ and Fe3+); Fe2O3 and Fe3O4. The relative intensity of the paramagnetic peak Fe2+ increases and the magnetic ratio of the magnetic peak decreases with increasing temperature. Based on the variation of the quadrupole splitting ( QS) of the paramagnetic peak Fe2+, the phase transformation characteristics of the sky-green glaze in the firing process is discussed. The coloring mechanism of the sky-green glaze and the variation of its magnetism in the firing process are also investigated in the present paper.

  3. Re-187-Os-187, Pt-190-Os-186 Isotopic and Highly Siderophile Element Systematics of Group IVA Irons

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; McCoy, T. J.; Schulte, R. F.; McDonough, W. F.; Ash, R. D.

    2005-01-01

    We have recently completed Re-187-Os-187 and Pt-190-Os-186 isotopic and elemental studies of the two largest magmatic iron meteorite groups, IIAB and IIIAB [1]. These studies revealed closed-system behavior of both isotopic systems, but complex trace element behavior for Re, Pt and Os in group IIIAB. Here we examine isotopic and trace elemental systematics of group IVA irons. The IVA irons are not as extensively fractionated as IIAB and IIIAB and their apparently less complex crystallization history may make for more robust interpretation of the relative partitioning behavior of Re, Pt and Os, as well as the other highly siderophile elements (HSE) measured here; Pd, Ru and Ir [e.g. 2]. An additional goal of our continuing research plan for iron meteorites is to assess the possibility of relating certain ungrouped irons with major groups via trace element modeling. Here, the isotopic and trace element systematics of the ungrouped irons Nedagolla and EET 83230 are compared with the IVA irons.

  4. CO2 electroreduction characteristics of Pt-Ru/C powder and Pt-Ru sputtered electrodes under acidic condition

    NASA Astrophysics Data System (ADS)

    Furukawa, Hiroto; Matsuda, Shofu; Tanaka, Shoji; Shironita, Sayoko; Umeda, Minoru

    2018-03-01

    The objective of this study was to overcome the issue about the underpotential adsorption of the CO2 electroreductant on the surface of the Pt electrocatalyst under acidic conditions by the alloying of Pt and Ru. As evaluation parameters, the CO2 reduction onset potential and CO2-reductant reoxidation onset potential were employed. We prepared a porous microelectrode filled with Pt-Ru/C powder and a Pt-Ru sputtered electrode. For the Pt-Ru/C powder electrocatalyst, the CO2 reduction onset potential as well as the CO2-reductant reoxidation onset potential shifted in the direction of the CO2/CO2-reductant standard redox potential dependent on the Ru content, which is indicative of a decrease in the underpotential-adsorption energy of the CO2 reductant. For the Pt-Ru sputtered electrode, only the CO2 reduction onset potential shifted in the direction of the redox potential. Consequently, we demonstrated that the Pt-Ru/C powder electrode improved the reactivity of the CO2/CO2-reductant when discussing the relationship between the CO2 reduction onset potential and the CO2-reductant reoxidation onset potential. Based on our findings, the Pt-Ru/C (1:9) powder is the most effective electrocatalyst for the CO2 reduction, which could minimize the underpotential adsorption.

  5. Mechanism study on inorganic oxidants induced inhibition of Ru(bpy)₃²+ electrochemiluminescence and its application for sensitive determination of some inorganic oxidants.

    PubMed

    Qiu, Bin; Xue, Lingling; Wu, Yanping; Lin, Zhenyu; Guo, Longhua; Chen, Guonan

    2011-07-15

    Inhibited Ru(bpy)(3)(2+) electrochemiluminescence by inorganic oxidants is investigated. Results showed that a number of inorganic oxidants can quench the ECL of Ru(bpy)(3)(2+)/tri-n-propylamine (TPrA) system, and the logarithm of the decrease in ECL intensity (ΔI) was proportional to the logarithm of analyte concentrations. Based on which, a sensitive approach for detection of these inorganic oxidants was established, e.g. the log-log plots of ΔI versus the concentration of MnO(4)(-), Cr(2)O(7)(2-) and Fe(CN)(6)(3-) are linear in the range of 1×10(-7) to 3×10(-4)M for MnO(4)(-) and Cr(2)O(7)(2-), and 1×10(-7) to 1×10(-4)M for Fe(CN)(6)(3-), with the limit of detection (LOD) of 8.0×10(-8)M, 2×10(-8)M, and 1×10(-8)M, respectively. A series of experiments such as a comparison of the inhibitory effect of different compounds on Ru(bpy)(3)(2+)/TPrA ECL, ECL emission spectra, UV-Vis absorption spectra etc. were investigated in order to discover how these inorganic analytes quench the ECL of Ru(bpy)(3)(2+)/TPrA system. A mechanism based on consumption of TPrA intermediate (TPrA(·)) by inorganic oxidants was proposed. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Effect of RuO2 growth temperature on ferroelectric properties of RuO2/Pb(Zr, Ti)O3/RuO2/Pt capacitors

    NASA Astrophysics Data System (ADS)

    Norga, G. J.; Fè, Laura; Wouters, D. J.; Maes, H. E.

    2000-03-01

    We present a promising method for obtaining Pb(Zr, Ti)O3(PZT) layers with excellent endurance and pulse-switching properties on RuO2 electrodes using the sol-gel method. As the substrate temperature during reactive sputtering of the RuO2 bottom electrode layer is reduced, the (111) PZT texture component becomes more pronounced, an effect attributed to the change from columnar to granular RuO2 film morphology. Reducing the residual PZT (100) and (101) texture components was found to be a necessary condition for obtaining optimal pulse switching and endurance properties of the layers. Highly (111)-oriented PZT layers, obtained on RuO2 grown at 150 °C exhibit a net switched charge of >60 μC/cm2 during pulse measurement and <10% degradation after 1011 fatigue cycles.

  7. Direct methanol fuel cell with extended reaction zone anode: PtRu and PtRuMo supported on graphite felt

    NASA Astrophysics Data System (ADS)

    Bauer, Alex; Gyenge, Előd L.; Oloman, Colin W.

    Pressed graphite felt (thickness ∼350 μm) with electrodeposited PtRu (43 g m -2, 1.4:1 atomic ratio) or PtRuMo (52 g m -2, 1:1:0.3 atomic ratio) nanoparticle catalysts was investigated as an anode for direct methanol fuel cells. At temperatures above 333 K the fuel cell performance of the PtRuMo catalyst was superior compared to PtRu. The power density was 2200 W m -2 with PtRuMo at 5500 A m -2 and 353 K while under the same conditions PtRu yielded 1925 W m -2. However, the degradation rate of the Mo containing catalyst formulation was higher. Compared to conventional gas diffusion electrodes with comparable PtRu catalyst composition and load, the graphite felt anodes gave higher power densities mainly due to the extended reaction zone for methanol oxidation.

  8. The knockdown of OsVIT2 and MIT affects iron localization in rice seed.

    PubMed

    Bashir, Khurram; Takahashi, Ryuichi; Akhtar, Shamim; Ishimaru, Yasuhiro; Nakanishi, Hiromi; Nishizawa, Naoko K

    2013-11-20

    The mechanism of iron (Fe) uptake in plants has been extensively characterized, but little is known about how Fe transport to different subcellular compartments affects Fe localization in rice seed. Here, we discuss the characterization of a rice vacuolar Fe transporter 2 (OsVIT2) T-DNA insertion line (osvit2) and report that the knockdown of OsVIT2 and mitochondrial Fe transporter (MIT) expression affects seed Fe localization. osvit2 plants accumulated less Fe in their shoots when grown under normal or excess Fe conditions, while the accumulation of Fe was comparable to that in wild-type (WT) plants under Fe-deficient conditions. The accumulation of zinc, copper, and manganese also changed significantly in the shoots of osvit2 plants. The growth of osvit2 plants was also slow compared to that of WT plants. The concentration of Fe increased in osvit2 polished seeds. Previously, we reported that the expression of OsVIT2 was higher in MIT knockdown (mit-2) plants, and in this study, the accumulation of Fe in mit-2 seeds decreased significantly. These results suggest that vacuolar Fe trafficking is important for plant Fe homeostasis and distribution, especially in plants grown in the presence of excess Fe. Moreover, changes in the expression of OsVIT2 and MIT affect the concentration and localization of metals in brown rice as well as in polished rice seeds.

  9. Role of RuO2(100) in surface oxidation and CO oxidation catalysis on Ru(0001).

    PubMed

    Flege, Jan Ingo; Lachnitt, Jan; Mazur, Daniel; Sutter, Peter; Falta, Jens

    2016-01-07

    We have studied the oxidation of the Ru(0001) surface by in situ microscopy during exposure to NO2, an efficient source of atomic oxygen, at elevated temperatures. In a previous investigation [Flege et al., Phys. Rev. B: Condens. Matter Mater. Phys., 2008, 78, 165407], at O coverages exceeding 1 monolayer, using the combination of intensity-voltage (I(V)) low-energy electron microscopy (LEEM) and multiple scattering calculations for the (00) beam in the very-low-energy range (E≤ 50 eV) we identified three surface components during the initial Ru oxidation: a (1 × 1)-O chemisorption phase, the RuO2(110) oxide phase, and a surface oxide structure characterized by a trilayer O-Ru-O stacking. Here, we use dark-field LEEM imaging and micro-illumination low-energy electron diffraction in the range of 100 to 400 eV to show that this trilayer phase is actually a RuO2(100)-(1 × 1) phase with possibly mixed O and Ru surface terminations. This identification rationalizes the thermodynamic stability of this phase at elevated temperatures and is consistent with the observation of catalytic activity of the phase in CO oxidation.

  10. New polymorphs of Ru IIIP 3O 9: Cyclo-hexaphosphate Ru 2P 6O 18 and metaphosphate Ru(PO 3) 3 with a novel structure

    NASA Astrophysics Data System (ADS)

    Fukuoka, Hiroshi; Imoto, Hideo; Saito, Taro

    1995-10-01

    Two new polymorphs of ruthenium phosphate with RuP 3O 9 composition were prepared and their crystal structures were determined by single-crystal X-ray diffraction. They are cyclo-hexaphosphate Ru 2P 6O 18 and metaphosphate Ru(PO 3) 3. Ru 2P 6O 18 crystallizes in the monoclinic space group P2 1/ c with a = 6.292(2) Å, b = 15.276(2) Å, c = 8.365(2) Å, β = 106.54(2)°, V = 770.6(3) Å 3, Z = 2, R = 0.043, RW = 0.035. The structure contains cyclo-hexaphosphate rings stacking obliquely along the [100] direction and is isotypic with B-form cyclo-phosphates. Ru(PO 3) 3 has a novel structure and crystallizes in the triclinic space group P overline1 with a = 6.957(1) Å, b = 10.324(2) Å, c = 5.030(1) Å, α = 92.45(2)°, β = 92.31(2)°, γ = 98.61(1)°, V = 356.5(1) Å 3, Z = 2, R = 0.030, RW = 0.027. It is built up of a network of infinite [PO 3-] ∞ chains and RuO 6 octahedra. The configuration of the metaphosphate chains is different from that in the C-form Ru(PO 3) 3. While the chains in the C-form consisting of PO 3OPO 3 units are condensed in nearly staggered configurations, the units in the new phosphate are eclipsed.

  11. One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Hongliang; Ruan, Hao; Feng, Maoqi

    2017-03-16

    The synthesis of high-efficiency and low-cost multifunctional catalysts for hydrodeoxygenation (HDO) of waste lignin into advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low molecular weight gaseous side-products. Among all the prepared catalysts, Ru-Cu/HY showed the best HDO performance, giving themore » highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably due to the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all the bifunctional catalysts were proven to be superior over the combination catalysts of Ru/Al2O3 and HY zeolite, and this could be attributed to the “intimacy criterion”. The practical use of the designed catalysts would be promising in lignin valorization.« less

  12. Ni@Ru and NiCo@Ru Core-Shell Hexagonal Nanosandwiches with a Compositionally Tunable Core and a Regioselectively Grown Shell.

    PubMed

    Hwang, Hyeyoun; Kwon, Taehyun; Kim, Ho Young; Park, Jongsik; Oh, Aram; Kim, Byeongyoon; Baik, Hionsuck; Joo, Sang Hoon; Lee, Kwangyeol

    2018-01-01

    The development of highly active electrocatalysts is crucial for the advancement of renewable energy conversion devices. The design of core-shell nanoparticle catalysts represents a promising approach to boost catalytic activity as well as save the use of expensive precious metals. Here, a simple, one-step synthetic route is reported to prepare hexagonal nanosandwich-shaped Ni@Ru core-shell nanoparticles (Ni@Ru HNS), in which Ru shell layers are overgrown in a regioselective manner on the top and bottom, and around the center section of a hexagonal Ni nanoplate core. Notably, the synthesis can be extended to NiCo@Ru core-shell nanoparticles with tunable core compositions (Ni 3 Co x @Ru HNS). Core-shell HNS structures show superior electrocatalytic activity for the oxygen evolution reaction (OER) to a commercial RuO 2 black catalyst, with their OER activity being dependent on their core compositions. The observed trend in OER activity is correlated to the population of Ru oxide (Ru 4+ ) species, which can be modulated by the core compositions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. A search for FeH in M and S giants

    NASA Technical Reports Server (NTRS)

    Davis-Locanthi, D.

    1980-01-01

    The strongest lines of FeH in the visible spectrum fall in the domain of TiO and ZrO bands. Analysis exists for TiO, but nothing is yet available for the weak but important ZrO lines. Using plate measurements and microphotometer tracings, high dispersion spectra of the following cool stars have been searched for FeH lines: Beta Peg, Mu UMa, Alpha Her, Omicron Cet, Chi Cyg, HR 105, HR 8714, R And, R Cyg, R Cam, T Sgr, R CMi, Cy Cyg, and RU Cam. The strongest FeH lines are unimpressive in R Cyg, where the strong infrared bands of FeH have already been identified. Identification of the blue-green FeH lines in other spectra must be considered inconclusive until a rotational analysis of the FeH spectrum is available.

  14. Simulating Ru L3-edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Van Kuiken, Benjamin E.; Valiev, Marat; Daifuku, Stephanie L.

    2013-05-01

    Ruthenium L2,3-edge X-ray absorption (XA) spectroscopy probes transitions from core 2p orbitals to the 4d levels of the atom and is a powerful tool for interrogating the local electronic and molecular structure around the metal atom. However, a molecular-level interpretation of the Ru L2,3-edge spectral lineshapes is often complicated by spin–orbit coupling (SOC) and multiplet effects. In this study, we develop spin-free time-dependent density functional theory (TDDFT) as a viable and predictive tool to simulate the Ru L3-edge spectra. We successfully simulate and analyze the ground state Ru L3-edge XA spectra of a series of RuII and RuIII complexes: [Ru(NH3)6]2+/3+,more » [Ru(CN)6]4-/3-, [RuCl6]4-/3-, and the ground (1A1) and photoexcited (3MLCT) transient states of [Ru(bpy)3]2+ and Ru(dcbpy)2(NCS)2 (termed N3). The TDDFT simulations reproduce all the experimentally observed features in Ru L3-edge XA spectra. The advantage of using TDDFT to assign complicated Ru L3-edge spectra is illustrated by its ability to identify ligand specific charge transfer features in complex molecules. We conclude that the B3LYP functional is the most reliable functional for accurately predicting the location of charge transfer features in these spectra. Experimental and simulated Ru L3-edge XA spectra are presented for the transition metal mixed-valence dimers [(NC)5MII-CN-RuIII(NH3)5]- (where M = Fe or Ru) dissolved in water. We explore the spectral signatures of electron delocalization in Ru L3-edge XA spectroscopy and our simulations reveal that the inclusion of explicit solvent molecules is crucial for reproducing the experimentally determined valencies, highlighting the importance of the role of the solvent in transition metal charge transfer chemistry.« less

  15. Effect of electron irradiation on superconductivity in single crystals of Ba ( Fe 1 – x Ru x ) 2 As 2 ( x = 0.24 )

    DOE PAGES

    Prozorov, R.; Kończykowski, M.; Tanatar, M. A.; ...

    2014-11-18

    A single crystal of isovalently substituted Ba(Fe 1-xRu x) 2As 2 (x=0.24) is sequentially irradiated with 2.5 MeV electrons up to a maximum dose of 2.1×10 19 e -/cm 2. The electrical resistivity is measured in situ at T=22 K during the irradiation and ex situ as a function of temperature between subsequent irradiation runs. Upon irradiation, the superconducting transition temperature T c decreases and the residual resistivity ρ0 increases. We find that electron irradiation leads to the fastest suppression of T c compared to other types of artificially introduced disorder, probably due to the strong short-range potential of themore » pointlike irradiation defects. As a result, a more detailed analysis within a multiband scenario with variable scattering potential strength shows that the observed T c versus ρ 0 is fully compatible with s ± pairing, in contrast to earlier claims that this model leads to a too rapid suppression of T c with scattering.« less

  16. AuRu/AC as an effective catalyst for hydrogenation reactions

    DOE PAGES

    Villa, Alberto; Chan-Thaw, Carine E.; Campisi, Sebastiano; ...

    2015-03-23

    AuRu bimetallic catalysts have been prepared by sequential deposition of Au on Ru or vice versa obtaining different nanostructures: when Ru has been deposited on Au, a Au core–Ru shell has been observed, whereas the deposition of Au on Ru leads to a bimetallic phase with Ru enrichment on the surface. In the latter case, the unexpected Ru enrichment could be attributed to the weak adhesion of Ru on the carbon support, thus allowing Ru particles to diffuse on Au particles. Both structures result very active in catalysing the liquid phase hydrogenolysis of glycerol and levulinic acid but the activity,more » the selectivity and the stability depend on the structure of the bimetallic nanoparticles. Ru@Au/AC core–shell structure mostly behaved as the monometallic Ru, whereas the presence of bimetallic AuRu phase in Au@Ru/AC provides a great beneficial effect on both activity and stability.« less

  17. Nanoscale variations in 187Os isotopic composition and HSE systematics in a Bultfontein peridotite

    NASA Astrophysics Data System (ADS)

    Wainwright, A. N.; Luguet, A.; Schreiber, A.; Fonseca, R. O. C.; Nowell, G. M.; Lorand, J.-P.; Wirth, R.; Janney, P. E.

    2016-08-01

    Understanding the mineralogical controls on radiogenic chronometers is a fundamental aspect of all geochronological tools. As with other common dating tools, it has become increasingly clear that the Re-Os system can be impacted by multiple mineral formation events. The accessory and micrometric nature of the Re-Os-bearing minerals has made assessing this influence complex. This is especially evident in cratonic peridotites, where long residence times and multiple metasomatic events have created a complex melting and re-enrichment history. Here we investigate a harzburgitic peridotite from the Bultfontein kimberlite (South Africa) which contains sub-micron Pt-Fe-alloy inclusions within base metal sulphides (BMS). Through the combination of the focused ion beam lift-out technique and low blank mass spectrometry we were able to remove and analyse the Pt-Fe-alloy inclusions for their Re-Os composition and highly siderophile element (HSE) systematics. Six repeats of the whole-rock yield 187Os/188Os compositions of 0.10893-0.10965, which correspond to Re depletion model ages (TRD) of 2.69-2.79 Ga. The Os, Ir and Pt concentrations are slightly variable across the different digestions, whilst Pd and Re remain constant. The resulting HSE pattern is typical of cratonic peridotites displaying depleted Pt and Pd. The Pt-Fe-alloys have PUM-like 187Os/188Os compositions of 0.1294 ± 24 (2-s.d.) and 0.1342 ± 38, and exhibit a saw-tooth HSE pattern with enriched Re and Pt. In contrast, their BMS hosts have unradiogenic 187Os/188Os of 0.1084 ± 6 and 0.1066 ± 3, with TRD ages of 2.86 and 3.09 Ga, similar to the whole-rock systematics. The metasomatic origin of the BMS is supported by (i) the highly depleted nature of the mantle peridotite and (ii) their Ni-rich sulphide assemblage. Occurrence of Pt-Fe-alloys as inclusions within BMS grains demonstrates the genetic link between the BMS and Pt-Fe-alloys and argues for formation during a single but continuous event of silicate melt

  18. Fe N-Heterocyclic Carbene Complexes as Promising Photosensitizers.

    PubMed

    Liu, Yizhu; Persson, Petter; Sundström, Villy; Wärnmark, Kenneth

    2016-08-16

    The photophysics and photochemistry of transition metal complexes (TMCs) has long been a hot field of interdisciplinary research. Rich metal-based redox processes, together with a high variety in electronic configurations and excited-state dynamics, have rendered TMCs excellent candidates for interconversion between light, chemical, and electrical energies in intramolecular, supramolecular, and interfacial arrangements. In specific applications such as photocatalytic organic synthesis, photoelectrochemical cells, and light-driven supramolecular motors, light absorption by a TMC-based photosensitizer and subsequent excited-state energy or electron transfer constitute essential steps. In this context, TMCs based on rare and expensive metals, such as ruthenium and iridium, are frequently employed as photosensitizers, which is obviously not ideal for large-scale implementation. In the search for abundant and environmentally benign solutions, six-coordinate Fe(II) complexes (Fe(II)L6) have been widely considered as highly desirable alternatives. However, not much success has been achieved due to the extremely short-lived triplet metal-to-ligand charge transfer ((3)MLCT) excited state that is deactivated by low-lying metal-centered (MC) states on a 100 fs time scale. A fundamental strategy to design useful Fe-based photosensitizers is thus to destabilize the MC states relative to the (3)MLCT state by increasing the ligand field strength, with special focus on making eg σ* orbitals on the Fe center energetically less accessible. Previous efforts to directly transplant successful strategies from Ru(II)L6 complexes unfortunately met with limited success in this regard, despite their close chemical kinship. In this Account, we summarize recent promising results from our and other groups in utilizing strongly σ-donating N-heterocyclic carbene (NHC) ligands to make strong-field Fe(II)L6 complexes with significantly extended (3)MLCT lifetimes. Already some of the first

  19. Mechanistic diversity in the RuBisCO superfamily: RuBisCO from Rhodospirillum rubrum is not promiscuous for reactions catalyzed by RuBisCO-like proteins.

    PubMed

    Warlick, Benjamin P E; Imker, Heidi J; Sriram, Jaya; Tabita, F Robert; Gerlt, John A

    2012-11-27

    d-Ribulose 1,5-bisphosphate carboxylase/oxygenases (RuBisCOs) are promiscuous, catalyzing not only carboxylation and oxygenation of d-ribulose 1,5-bisphosphate but also other promiscuous, presumably nonphysiological, reactions initiated by abstraction of the 3-proton of d-ribulose 1,5-bisphosphate. Also, RuBisCO has homologues that do not catalyze carboxylation; these are designated RuBisCO-like proteins or RLPs. Members of the two families of RLPs catalyze reactions in the recycling of 5'-methylthioadenosine (MTA) generated by polyamine synthesis: (1) the 2,3-diketo-5-methylthiopentane 1-phosphate (DK-MTP 1-P) "enolase" reaction in the well-known "methionine salvage" pathway in Bacillus sp. and (2) the 5-methylthio-d-ribulose 1-phosphate (MTRu 1-P) 1,3-isomerase reaction in the recently discovered "MTA-isoprenoid shunt" that generates 1-deoxy-d-xylulose 5-phosphate for nonmevalonate isoprene synthesis in Rhodospirillum rubrum. We first studied the structure and reactivity of DK-MTP 1-P that was reported to decompose rapidly [Ashida, H., Saito, Y., Kojima, C., and Yokota, A. (2008) Biosci., Biotechnol., Biochem. 72, 959-967]. The 2-carbonyl group of DK-MTP 1-P is rapidly hydrated and can undergo enolization both nonenzymatically and enzymatically via the small amount of unhydrated material that is present. We then examined the ability of RuBisCO from R. rubrum to catalyze both of the RLP-catalyzed reactions. Contrary to a previous report [Ashida, H., Saito, Y., Kojima, C., Kobayashi, K., Ogasawara, N., and Yokota, A. (2003) Science 302, 286-290], we were unable to confirm that this RuBisCO catalyzes the DK-MTP 1-P "enolase" reaction either in vitro or in vivo. We also determined that this RuBisCO does not catalyze the MTRu 1-P 1,3-isomerase reaction in vitro. Thus, although RuBisCOs can be functionally promiscuous, RuBisCO from R. rubrum is not promiscuous for either of the known RLP-catalyzed reactions.

  20. Ru sub 3 (CO) sub 12 and Mo (CO) sub 6 overlayers adsorbed on Ru(001) and Au/Ru and their interaction with electrons and photons: An infrared reflection--absorption study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Malik, I.J.; Hrbek, J.

    1991-05-01

    We studied adsorbed Ru{sub 3}(CO){sub 12} and Mo (CO){sub 6} overlayers on Ru(001) and Au/Ru surfaces by infrared reflection--absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). We characterized the C--O stretching mode of both metal carbonyls (4 cm{sup {minus}1} FWHM) and a deformation mode of Mo (CO){sub 6} at 608 cm{sup {minus}1} with an unusually narrow FWHM of 1 cm{sup {minus}1}. Both IRAS and TDS data suggest adsorption and desorption of metal carbonyls as molecular species with a preferential orientation in the overlayers. We discuss annealing experiments of Ru{sub 3}(CO){sub 12}/Ru(001), the interaction of Ru{sub 3}(CO){sub 12} overlayers with electronsmore » of up to 100-eV energy, and the interaction of Mo (CO){sub 6} overlayers with 300-nm photons.« less

  1. Structural and magnetic properties and superconductivity in Ba(Fe 1-xTM x) 2As 2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thaler, Alexander

    2012-01-01

    We studied the effects on structural and magnetic phase transitions and the emergence of superconductivity in transition metal substituted BaFe 2As 2. We grew four series of Ba(Fe 1-xTM 2) 2As 2 (TM=Ru, Mn, Co+Cr and Co+Mn) and characterized them by crystallographic, magnetic and transport measurements. We also subjected Ba(Fe 1-xCr x) 2As 2 and Ba(Fe 1-xCo x) 2As 2 to heat treatment to explore what changes might be induced.

  2. Synthesis science of SrRuO3 and CaRuO3 epitaxial films with high residual resistivity ratios

    NASA Astrophysics Data System (ADS)

    Nair, Hari P.; Liu, Yang; Ruf, Jacob P.; Schreiber, Nathaniel J.; Shang, Shun-Li; Baek, David J.; Goodge, Berit H.; Kourkoutis, Lena F.; Liu, Zi-Kui; Shen, Kyle M.; Schlom, Darrell G.

    2018-04-01

    Epitaxial SrRuO3 and CaRuO3 films were grown under an excess flux of elemental ruthenium in an adsorption-controlled regime by molecular-beam epitaxy (MBE), where the excess volatile RuOx (x = 2 or 3) desorbs from the growth front leaving behind a single-phase film. By growing in this regime, we were able to achieve SrRuO3 and CaRuO3 films with residual resistivity ratios (ρ300 K/ρ4 K) of 76 and 75, respectively. A combined phase stability diagram based on the thermodynamics of MBE (TOMBE) growth, termed a TOMBE diagram, is employed to provide improved guidance for the growth of complex materials by MBE.

  3. Pt and Ru X-ray absorption spectroscopy of PtRu anode catalysts in operating direct methanol fuel cells.

    PubMed

    Stoupin, Stanislav; Chung, Eun-Hyuk; Chattopadhyay, Soma; Segre, Carlo U; Smotkin, Eugene S

    2006-05-25

    In situ X-ray absorption spectroscopy, ex situ X-ray fluorescence, and X-ray powder diffraction enabled detailed core analysis of phase segregated nanostructured PtRu anode catalysts in an operating direct methanol fuel cell (DMFC). No change in the core structures of the phase segregated catalyst was observed as the potential traversed the current onset potential of the DMFC. The methodology was exemplified using a Johnson Matthey unsupported PtRu (1:1) anode catalyst incorporated into a DMFC membrane electrode assembly. During DMFC operation the catalyst is essentially metallic with half of the Ru incorporated into a face-centered cubic (FCC) Pt alloy lattice and the remaining half in an amorphous phase. The extended X-ray absorption fine structure (EXAFS) analysis suggests that the FCC lattice is not fully disordered. The EXAFS indicates that the Ru-O bond lengths were significantly shorter than those reported for Ru-O of ruthenium oxides, suggesting that the phases in which the Ru resides in the catalysts are not similar to oxides.

  4. Skeletal Ru/Cu catalysts prepared from crystalline and quasicrystalline ternary alloy precursors: characterization by X-ray absorption spectroscopy and CO oxidation.

    PubMed

    Highfield, James; Liu, Tao; Loo, Yook Si; Grushko, Benjamin; Borgna, Armando

    2009-02-28

    . Preliminary studies in CO and H(2) oxidation were made in a DRIFTS flow reactor with on-line MS, and their activities and selectivities were compared against skeletal Ru and Cu controls, Ru/Al(2)O(3), and Au/Fe(2)O(3). All samples were active in CO oxidation above approximately 50 degrees C, showing light-off temperatures in the range 60-70 degrees C. Ru(22)Cu(7) and Ru(17)Cu(12.5) also showed good selectivities (vs. H(2) oxidation), attributed tentatively to Ru-modified Cu surfaces of varying thickness. These compositions are promising candidates to test in a (PROX) fuel processor to supply purified (CO-free) H(2) to a PEM fuel cell.

  5. Ultrasound-activated piezoelectric P(VDF-TrFE)/boron nitride nanotube composite films promote differentiation of human SaOS-2 osteoblast-like cells.

    PubMed

    Genchi, Giada Graziana; Sinibaldi, Edoardo; Ceseracciu, Luca; Labardi, Massimiliano; Marino, Attilio; Marras, Sergio; De Simoni, Giorgio; Mattoli, Virgilio; Ciofani, Gianni

    2017-05-26

    Piezoelectric films of poly(vinylidenedifluoride-trifluoroethylene) (P(VDF-TrFE)) and of P(VDF-TrFE)/boron nitride nanotubes (BNNTs) were prepared by cast-annealing and used for SaOS-2 osteoblast-like cell culture. Films were characterized in terms of surface and bulk features, and composite films demonstrated enhanced piezoresponse compared to plain polymeric films (d 31 increased by ~80%). Osteogenic differentiation was evaluated in terms of calcium deposition, collagen I secretion, and transcriptional levels of marker genes (Alpl, Col1a1, Ibsp, and Sparc) in cells either exposed or not to ultrasounds (US); finally, a numerical model suggested that the induced voltage (~20-60 mV) is suitable for cell stimulation. Although preliminary, our results are extremely promising and encourage the use of piezoelectric P(VDF-TrFE)/BNNT films in bone tissue regeneration. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Simulating Ru L 3 -Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Van Kuiken, Benjamin E.; Valiev, Marat; Daifuku, Stephanie L.

    2013-05-30

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of RuII and RuIII complexesmore » in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6]4- and RuII polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5MII-CN-RuIII(NH3)5] (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.« less

  7. Evidence of High-Spin Ru and Universal Magnetic Anisotropy in SrRuO(3) Thin Films

    DTIC Science & Technology

    2012-04-17

    UNIVERSAL . . . PHYSICAL REVIEW B 85, 134429 (2012) (a) (b) FIG. 5. (Color online) (a) Ru M3,2 and (b) O K - edge x-ray absorption ( XA ) and x-ray magnetic...134429-2 EVIDENCE OF HIGH-SPIN Ru AND UNIVERSAL . . . PHYSICAL REVIEW B 85, 134429 (2012) FIG. 1. (Color online) Hysteresis loops taken at 10 K of 60...SQUID magnetometry measurements. a smaller contribution from O2− ions. Typical examples of Ru and O XA spectra can be seen in Fig. 5. As there is no

  8. Round table on RU486.

    PubMed

    Shallat, L

    1993-01-01

    As a non-invasive means of early abortion, RU-486 has the potential to increase women's reproductive options; at the same time, the "abortion pill" has stimulated debate about the ethics and safety of new medical technologies. When combined with a prostaglandin (PG), the success rate for RU-486 is 96% for pregnancies of up to 9 weeks' gestation. In France, over 120,000 women have used RU-486/PG to terminate pregnancy, and this regimen is now used in about 25% of abortions. Clinical trials of RU-486 are underway in Cuba, China, India, Singapore, and Zambia. The Program for Appropriate Technology has identified four considerations for introducing RU-486 to developing countries: whether abortion or menstrual regulation is legal; whether women find the method acceptable and can comply with the multiple visit treatment regimen; whether the health infrastructure can support safe method use, including prevention of misuse and provision of appropriate medical backup personnel and facilities; and whether the cost of the regimen is affordable to individuals and/or programs --conditions unlikely to be met in most such countries. Ideal would be development of a medical abortifacient that is single dose and the lowest possible dose of each drug, provokes miscarriage within a more predictable time frame with less acute and prolonged bleeding, is safe and effective beyond two months, has minimal side effects, and maximizes short-term safety and minimizes long-term effects. Technological advances are being undermined, however, by political and religious attacks on the method. Even some feminists have expressed concerns about potential long-term effects of RU-486 use.

  9. Photoinduced reduction of the medial FeS center in the hydrogenase small subunit HupS from Nostoc punctiforme.

    PubMed

    Raleiras, Patrícia; Hammarström, Leif; Lindblad, Peter; Styring, Stenbjörn; Magnuson, Ann

    2015-07-01

    The small subunit from the NiFe uptake hydrogenase, HupSL, in the cyanobacterium Nostoc punctiforme ATCC 29133, has been isolated in the absence of the large subunit (P. Raleiras, P. Kellers, P. Lindblad, S. Styring, A. Magnuson, J. Biol. Chem. 288 (2013) 18,345-18,352). Here, we have used flash photolysis to reduce the iron-sulfur clusters in the isolated small subunit, HupS. We used ascorbate as electron donor to the photogenerated excited state of Ru(II)-trisbipyridine (Ru(bpy)3), to generate Ru(I)(bpy)3 as reducing agent. Our results show that the isolated small subunit can be reduced by the Ru(I)(bpy)3 generated through flash photolysis. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. NO-binding in {Ru(NO)₂}⁸-type [Ru(NO)₂(PR₃)₂X]BF₄ compounds.

    PubMed

    Gallien, Anna K E; Schaniel, Dominik; Woike, Theo; Klüfers, Peter

    2014-09-21

    Two different structure types were found for a series of mononuclear dinitrosyl complexes of the general formula [RuL2(NO)2X]BF4 (L = monodentate phosphane, X = Cl, Br, I). The {Ru(NO)2}(8)-type target compounds were prepared by the reduction of the respective {RuNO}(6) precursors and subsequent oxidative addition of (NO)BF4. About one half of the new compounds share their molecular structure with the hitherto only representative of this class of dinitrosyls, Pierpont and Eisenberg's [RuCl(NO)2(PPh3)2]PF6·C6H6 (Inorg. Chem., 1972, 11, 1088-1094). The Cs-symmetric cations exhibit both a linear and a bent Ru-N-O fragment, in line with a formal 6 + 2 split of the {Ru(NO)2}(8) electron sum in the sense of a [Ru(II)(NO(+))((1)NO(-))](2+) bonding. The coordination entity's configuration in this subgroup is described by IUPAC's polyhedral symbol SPY-5. Continuous shape measures (CShM) as defined by Alvarez et al. (Coord. Chem. Rev., 2005, 249, 1693-1708) reveal a uniform deviation from the L-M-L angles expected for SPY-5, in a narrower sense, towards a vacant octahedron (vOC-5). DFT calculations confirmed that Enemark and Feltham's analysis (Coord. Chem. Rev., 1974, 13, 339-406) of the electronic situation of the {Ru(NO)2}(8) group remains adequate. The same holds for the second subclass of new compounds the existence of which had been predicted in the same paper by Enemark and Feltham, namely C(2v)-symmetric, TBPY-5-type cations with two almost equally bonded nitrosyl ligands. In agreement with an 8 + 0 distribution of the relevant electrons, the formal [Ru(0)(NO(+))2](2+) entities are found for L/X couples that donate more electron density on the central metal. Two solid compounds (8a/b, 12a/b) were found in both structures including the special case of the P(i)Pr3/Br couple 12a/b, which led to crystals that contained both structure types in the same solid. Conversely, four compounds showed a single form in the solid but both forms in dichloromethane solution in terms

  11. Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

    DOE PAGES

    Manbeck, Gerald F.; Fujita, Etsuko; Brewer, Karen J.

    2017-06-01

    Supramolecular mixed metal complexes combining the trimetallic chromophore [{(bpy) 2Ru(dpp)} 2Ru(dpp)] 6+ (Ru 3) with [Rh(bpy)Cl 2] + or [RhCl 2] + catalytic fragments to form [{(bpy) 2Ru(dpp)} 2Ru(dpp)RhCl 2(bpy)](PF 6) 7 (Ru 3Rh) or [{(bpy) 2Ru(dpp)} 2Ru(dpp)] 2RhCl 2(PF 6) 13 (Ru 3RhRu 3) (bpy = 2,2'-bipyridine and dpp = 2,3-bis(2-pyridyl)pyrazine) catalyze the photochemical reduction of protons to H 2. This first example of a heptametallic Ru,Rh photocatalyst produces over 300 turnovers of H 2 upon photolysis of a solution of acetonitrile, water, triflic acid, and N,N-dimethylaniline as an electron donor. Conversely, the tetrametallic Ru 3Rh produces only 40more » turnovers of H 2 due to differences in the excited state properties and nature of the catalysts upon reduction as ascertained from electrochemical data, transient absorption spectroscopy, and flash-quench experiments. And while the lowest unoccupied molecular orbital of Ru 3Rh is localized on a bridging ligand, it is Rh-centered in Ru 3RhRu 3 facilitating electron collection at Rh in the excited state and reductively quenched state. The Ru → Rh charge separated state of Ru 3RhRu 3 is endergonic with respect to the emissive Ru → dpp 3MLCT excited and cannot be formed by static electron transfer quenching of the 3MLCT state. Instead, a mechanism of subnanosecond charge separation from high lying states is proposed. Multiple reductions of Ru 3 and Ru 3Rh using sodium amalgam were carried out to compare UV–vis absorption spectra of reduced species and to evaluate the stability of highly reduced complexes. Furthermore, the Ru 3 and Ru 3Rh can be reduced by 10 and 13 electrons, respectively, to final states with all bridging ligands doubly reduced and all bpy ligands singly reduced.« less

  12. Effects of countercations on the structures and redox and spectroscopic properties of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

    PubMed

    Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

    2005-05-30

    The molecular structures and physicochemical properties of diruthenium complexes with ligand-unsupported Ru-Ru bonds, generally formulated as [A2{Ru2(DTBCat)4}] (DTB = 3,5- or 3,6-di-tert-butyl; Cat(2-) = catecholate), were studied in detail by changing the countercations. First, the binding structures of the cations in a family of [{A(DME)n}2{Ru2(3,5-DTBCat)4}] (n = 2 for A+ = Li+ and Na+ and n = 1 for A+ = K+ and Rb+) were systematically examined to reveal the effects of the cations on the molecular structures and electrochemical properties. Second, the complex (n-Bu4N)2[Ru2(3,6-DTBCat)4] with a cation-free structure was synthesized using tetra-n-butylammonium cations. The complex clearly demonstrates first that the ligand-unsupported Ru-Ru bonds are essentially stabilized by the dianionic nature of the catecholate derivatives without any other bridging or supporting species. In contrast, the redox potentials and absorption spectra of the complexes can sensitively respond to the countercations depending upon the polarity of the solvents.

  13. Formation of pyroxenite layers in the Totalp ultramafic massif (Swiss Alps) - Insights from highly siderophile elements and Os isotopes

    NASA Astrophysics Data System (ADS)

    van Acken, David; Becker, Harry; Walker, Richard J.; McDonough, William F.; Wombacher, Frank; Ash, Richard D.; Piccoli, Phil M.

    2010-01-01

    Pyroxenitic layers are a minor constituent of ultramafic mantle massifs, but are considered important for basalt generation and mantle refertilization. Mafic spinel websterite and garnet-spinel clinopyroxenite layers within Jurassic ocean floor peridotites from the Totalp ultramafic massif (eastern Swiss Alps) were analyzed for their highly siderophile element (HSE) and Os isotope composition. Aluminum-poor pyroxenites (websterites) display chondritic to suprachondritic initial γOs (160 Ma) of -2 to +27. Osmium, Ir and Ru abundances are depleted in websterites relative to the associated peridotites and to mantle lherzolites worldwide, but relative abundances (Os/Ir, Ru/Ir) are similar. Conversely, Pt/Ir, Pd/Ir and Re/Ir are elevated. Aluminum-rich pyroxenites (clinopyroxenites) are characterized by highly radiogenic 187Os/ 188Os with initial γOs (160 Ma) between +20 and +1700. Their HSE composition is similar to that of basalts, as they are more depleted in Os, Ir and Ru compared to Totalp websterites, along with even higher Pt/Ir, Pd/Ir and Re/Ir. The data are most consistent with multiple episodes of reaction of mafic pyroxenite precursor melts with surrounding peridotites, with the highest degree of interaction recorded in the websterites, which typically occur in direct contact to peridotites. Clinopyroxenites, in contrast, represent melt-dominated systems, which retained the precursor melt characteristics to a large extent. The melts may have been derived from a sublithospheric mantle source with high Pd/Ir, Pt/Ir and Re/Os, coupled with highly radiogenic 187Os/ 188Os compositions. Modeling indicates that partial melting of subducted, old oceanic crust in the asthenosphere could be a possible source for such melts. Pentlandite and godlevskite are identified in both types of pyroxenites as the predominant sulfide minerals and HSE carriers. Heterogeneous HSE abundances within these sulfide grains likely reflect subsolidus processes. In contrast, large grain

  14. Superconductivity in the Nb-Ru-Ge σ phase

    DOE PAGES

    Carnicom, Elizabeth M.; Xie, Weiwei; Sobczak, Zuzanna; ...

    2017-12-07

    Here, we show that the previously unreported ternary σ-phase material Nb 20.4Ru 5.7Ge 3.9 (Nb 0.68Ru 0.19Ge 0.13) is a superconductor with a critical temperature of 2.2 K. Temperature-dependent magnetic susceptibility, resistance, and specific heat measurements were used to characterize the superconducting transition. The Sommerfeld constant γ for Nb 20.4Ru 5.7Ge 3.9 is 91 mJ mol-f.u. -1K -2 (~3 mJ mol-atom -1K -2) and the specific heat anomaly at the superconducting transition, ΔC/γT c, is approximately 1.38. The zero-temperature upper critical field (µ 0Hc 2(0)) was estimated to be 2 T by resistance data. Field-dependent magnetization data analysis estimated µmore » 0Hc 1(0) to be 5.5 mT. Thus, the characterization shows Nb 20.4Ru 5.7Ge 3.9 to be a type II BCS superconductor. This material appears to be the first reported ternary phase in the Nb-Ru-Ge system, and the fact that there are no previously reported binary Nb-Ru, Nb-Ge, or Ru-Ge σ-phases shows that all three elements are necessary to stabilize the material. An analogous σ-phase in the Ta-Ru-Ge system did not display superconductivity above 1.7 K, which suggests that electron count cannot govern the superconductivity observed. Preliminary characterization of a possible superconducting σ-phase in the Nb-Ru-Ga system is also reported.« less

  15. Tuning the Photophysical Properties of Ru(II) Monometallic and Ru(II),Rh(III) Bimetallic Supramolecular Complexes by Selective Ligand Deuteration.

    PubMed

    Wagner, Alec T; Zhou, Rongwei; Quinn, Kevan S; White, Travis A; Wang, Jing; Brewer, Karen J

    2015-07-02

    A series of three new complexes of the design [(TL)2Ru(BL)](2+), two new complexes of the design [(TL)2Ru(BL)Ru(TL)2](4+), and three new complexes of the design [(TL)2Ru(BL)RhCl2(TL)](3+) (TL = bpy or d8-bpy; BL = dpp or d10-dpp; TL = terminal ligand; BL = bridging ligand; bpy = 2,2'-bipyridine; dpp = 2,3-bis(2-pyridyl)pyrazine) were synthesized and the (1)H NMR spectroscopy, electrochemistry, electronic absorbance spectroscopy, and photophysical properties studied. Incorporation of deuterated ligands into the molecular architecture simplifies the (1)H NMR spectra, allowing for complete (1)H assignment of [(d8-bpy)2Ru(dpp)](PF6)2 and partial assignment of [(bpy)2Ru(d10-dpp)](PF6)2. The electrochemistry for the deuterated and nondeuterated species showed nearly identical redox properties. Electronic absorption spectroscopy of the deuterated and nondeuterated complexes are superimposable with the lowest energy transition being Ru(dπ) → BL(π*) charge transfer in nature (BL = dpp or d10-dpp). Ligand deuteration impacts the excited-state properties with an observed increase in the quantum yield of emission (Φ(em)) and excited-state lifetime (τ) of the Ru(dπ) → d10-dpp(π*) triplet metal-to-ligand charge transfer ((3)MLCT) excited state when dpp is deuterated, and a decrease in the rate constant for nonradiative decay (knr). Choice of ligand deuteration between bpy and dpp strongly impacts the observed photophysical properties with BL = d10-dpp complexes showing an enhanced Φ(em) and τ, providing further support that the lowest electronic excited state populated via UV or visible excitation is the photoactive Ru(dπ) → dpp(π*) CT excited state. The Ru(II),Rh(III) complex incorporating the deuterated BL shows increased hydrogen production compared to the variants incorporating the protiated BL, while demonstrating identical dynamic quenching behaviors in the presence of sacrificial electron donor.

  16. Influence of Binders and Solvents on Stability of Ru/RuOx Nanoparticles on ITO Nanocrystals as Li-O2 Battery Cathodes.

    PubMed

    Vankova, Svetoslava; Francia, Carlotta; Amici, Julia; Zeng, Juqin; Bodoardo, Silvia; Penazzi, Nerino; Collins, Gillian; Geaney, Hugh; O'Dwyer, Colm

    2017-02-08

    Fundamental research on Li-O 2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li-O 2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1-2 nm oxygen evolution reaction (OER) catalyst Ru/RuO x nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li-O 2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuO x nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuO x /ITO nanocrystalline materials in DMSO provide efficient Li 2 O 2 decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuO x NPs remain effective OER catalysts for Li 2 O 2 during cycling. The CMC binders avoid PVDF-based side-reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO-EMITFSI [EMITFSI=1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuO x /ITO materials in Li-O 2 cells cycle very well and maintain a consistently very low charge overpotential of 0.5-0.8 V. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Magnetic order and phase transition in the iron oxysulfide La2O2Fe2OS2

    NASA Astrophysics Data System (ADS)

    Oogarah, Reeya K.; Suard, Emmanuelle; McCabe, Emma E.

    2018-01-01

    The Mott-insulating iron oxychalcogenides exhibit complex magnetic behaviour and we report here a neutron diffraction investigation into the magnetic ordering in La2O2Fe2OS2. This quaternary oxysulfide adopts the anti-Sr2MnO2Mn2Sb2-type structure (described by space group I4/mmm) and orders antiferromagnetically below TN = 105 K. We consider both its long-range magnetic structure and its magnetic microstructure, and the onset of magnetic order. It adopts the multi-k vector "2k" magnetic structure (k = (1/2 0 1/2) and k = (0 1/2 1/2) and has similarities with related iron oxychalcogenides, illustrating the robust nature of the "2k" magnetic structure.

  18. Nanoscale decomposition of Nb-Ru-O

    NASA Astrophysics Data System (ADS)

    Music, Denis; Geyer, Richard W.; Chen, Yen-Ting

    2016-11-01

    A correlative theoretical and experimental methodology has been employed to explore the decomposition of amorphous Nb-Ru-O at elevated temperatures. Density functional theory based molecular dynamics simulations reveal that amorphous Nb-Ru-O is structurally modified within 10 ps at 800 K giving rise to an increase in the planar metal - oxygen and metal - metal population and hence formation of large clusters, which signifies atomic segregation. The driving force for this atomic segregation process is 0.5 eV/atom. This is validated by diffraction experiments and transmission electron microscopy of sputter-synthesized Nb-Ru-O thin films. Room temperature samples are amorphous, while at 800 K nanoscale rutile RuO2 grains, self-organized in an amorphous Nb-O matrix, are observed, which is consistent with our theoretical predictions. This amorphous/crystalline interplay may be of importance for next generation of thermoelectric devices.

  19. Re-Os and S isotope evidence for the origin of Platreef mineralization (Bushveld Complex)

    NASA Astrophysics Data System (ADS)

    Yudovskaya, M.; Belousova, E.; Kinnaird, J.; Dubinina, E.; Grobler, D. F.; Pearson, N.

    2017-10-01

    The Bushveld Complex contains the largest platinum-group element (PGE) deposits of the world that are represented by persistent stratiform reefs highly enriched with PGE with respect to underlying and overlying rocks. New Re-Os isotope and elemental LA MC-ICPMS data on platinum-group minerals (PGM) from the mineralized reefs are presented with implications to correlation between the different segments of the Bushveld Complex and a role of superimposed processes at the reef formation. We analyzed laurite (RuS2), hollingworthite (RhAsS), sperrylite (PtAs2) and Pt-Fe alloys from the Merensky Reef, Pseudoreef and the PGE reef of the Platreef. The measured 187Os/188Os value for Platreef laurite is 0.1751 ± 0.0004 whereas the ratios for sperrylite and hollingworthite range to slightly higher values (0.1713-0.1818 and 0.1744-0.1835 respectively). The observed textures of the analyzed PGM, such as Pt-Fe symplectites in base metal sulfides (BMS), laurite inclusions in chromite and sperrylite rims around sulfide-silicate aggregates, are interpreted as features of primary magmatic crystallization whereas hollingworthite overgrowths and exsolutions in sperrylite are likely to have originated from later solid state transformation or metasomatic processes. The Platreef is a composite sill-like body in the northern limb correlative to the Critical Zone in terms of stratigraphic position, whole-rock geochemistry and isotope characteristics. The pristine magmatic character of sulfides and PGM in the stratiform reefs at the top of the Platreef strongly resembles the style of Merensky Reef mineralization. However, the basal part of the Platreef pyroxenitic sequence is variably contaminated and mineralized with a significant hydrothermal overprint. Sulfides from underlying Lower Zone peridotite yield δ34S values varying from +9‰ to +14.2‰ that are much higher than the values for the overlying Platreef and are a consequence of sulfur assimilation from sedimentary sulfates. The

  20. Multiple episodes of mineralization revealed by Re-Os molybdenite geochronology in the Lala Fe-Cu deposit, SW China

    NASA Astrophysics Data System (ADS)

    Zhu, Zhimin; Tan, Hongqi; Liu, Yingdong; Li, Chao

    2018-03-01

    The Lala Fe-Cu deposit is one of the largest iron oxide-copper-gold (IOCG) deposits in the Kangdian copper belt, southwest China. The paragenetic sequence of the Lala deposit includes six hydrothermal stages: pre-ore pervasive Na alteration (I); magnetite stage with K-feldspar and apatite (II); polymetallic disseminated/massive magnetite-sulfide stage (III); banded magnetite-sulfide stage (IV); sulfide vein stage (V); and late quartz-carbonate vein stage (VI). Fifteen molybdenite separates from stages III to VI were analyzed for Re-Os dating. Our new Re-Os data, together with previous studies, identify four distinct hydrothermal events at the Lala deposit. Molybdenite from the stage III disseminated to massive chalcopyrite-magnetite ores yielded a weighted average Re-Os age of 1306 ± 8 Ma (MSWD = 1.1, n = 6) which represents the timing of main ore formation. Molybdenite from the stage IV-banded magnetite-chalcopyrite ores yielded a weighted average Re-Os age of 1086 ± 8 Ma (MSWD = 2.2, n = 7), i.e., a second ore-forming event. Molybdenite from the stage V sulfide veins yielded a weighted average Re-Os age of 988 ± 8 Ma (MSWD = 1.3, n = 7) which represents the timing of a third hydrothermal event. Molybdenite from the quartz-carbonate veins (stage VI) yielded a weighted average Re-Os age at 835 ± 4 Ma (MSWD = 0.66, n = 10) and documented the timing of a late hydrothermal event. Our results indicate that the Lala deposit formed during multiple, protracted mineralization events over several hundred million years. The first three Mesoproterozoic mineralization events are coeval with intra-continental rifting (breakup of the supercontinent Nuna) and share a temporal link to other IOCG-style deposits within the Kangdian Copper Belt, and the last Neoproterozoic hydrothermal event is coeval with the Sibao orogeny which culminated with the amalgamation of the Yangtze Block with the Cathaysia Block at 860-815 Ma.

  1. Activation of H2 over the Ru-Zn Bond in the Transition Metal-Lewis Acid Heterobimetallic Species [Ru(IPr)2(CO)ZnEt](.).

    PubMed

    Riddlestone, Ian M; Rajabi, Nasir A; Lowe, John P; Mahon, Mary F; Macgregor, Stuart A; Whittlesey, Michael K

    2016-09-07

    Reaction of [Ru(IPr)2(CO)H]BAr(F)4 with ZnEt2 forms the heterobimetallic species [Ru(IPr)2(CO)ZnEt]BAr(F)4 (2), which features an unsupported Ru-Zn bond. 2 reacts with H2 to give [Ru(IPr)2(CO)(η(2)-H2)(H)2ZnEt]BAr(F)4 (3) and [Ru(IPr)2(CO)(H)2ZnEt]BAr(F)4 (4). DFT calculations indicate that H2 activation at 2 proceeds via oxidative cleavage at Ru with concomitant hydride transfer to Zn. 2 can also activate hydridic E-H bonds (E = B, Si), and computed mechanisms for the facile H/H exchange processes observed in 3 and 4 are presented.

  2. The influence of metal-support interactions on the accurate determination of Ru dispersion for Ru/TiO{sub 2}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Komaya, Takashi; Bell, A.T.; Weng-Sieh, Zara

    1994-09-01

    Titania-supported Ru catalysts have been characterized by TEM, {sup 1}H NMR, and H{sub 2} chemisorption to determine the metal particle size, the fraction of the metal surface available for H{sub 2} chemisorption, and the H{sub 2} adsorption capacity of the catalyst, as functions of the reduction temperature. TEM micrographs show that as the reduction temperature rises from 573 to 773K, the average particle size of Ru remains the same but the surface of the particles is covered to an increasing extent by an amorphous layer of titania. Quantitative estimates of the fraction of the Ru particle surface available for H{submore » 2} chemisorption were obtained by {sup 1}H NMR. The NMR spectra also show that a fraction of the adsorbed H{sub 2} spills over onto the support and that as a consequence measurements of total H{sub 2} chemisorption overestimate the number of Ru sites available for H{sub 2} adsorption. The implications of these results for the correct calculation of Ru dispersion and the determination of turnover frequencies for reactions carried out over Ru/TiO{sub 2} are discussed. 16 refs., 5 figs., 1 tab.« less

  3. Synthesis and characterization of RuS2 nanostructures.

    PubMed

    Díaz, David; Castillo-Blum, Silvia E; Alvarez-Fregoso, Octavio; Rodríguez-Gattorno, Geonel; Santiago-Jacinto, Patricia; Rendon, Luis; Ortiz-Frade, Luis; León-Paredes, Yolia-Judith

    2005-12-08

    Small naked ruthenium sulfide nanoparticles (NPs) with narrow size distribution (2.5 +/- 0.4 nm of diameter) were synthesized in DMSO colloidal dispersions, under mild reaction conditions and using commercial RuCl3 as precursor. To test the chemical reactivity with soft and hard bases, fresh presynthesized RuS2 colloids were mixed with triethylamine (N(Et)3) and ammonium tetrathiomolybdate ((NH4)2MoS4) dimethyl sulfoxide solutions. Naked N(Et)3 and [MoS4](2-)-capped RuS2 nanoparticle colloids were characterized using UV-visible electronic absorption and emission spectroscopies and high-resolution transmission electron microscopy (HR-TEM). It has also been shown that capped RuS2-[MoS4]2- nanoparticles yield MoO3 crystalline matrix by means of HR-TEM experiments. The emission spectra of RuS2 and N(Et)3-RuS2 dispersions show that both nanosized materials have strong fluorescence. The existence of the ruthenium precursor species in solution was established by cyclic voltammetry. Moreover, naked RuS2 NPs were mixed with a chemical mixture with composition similar to gasoline (dibenzothiophene (Bz2S, 400 ppm), hexane, and toluene (55:45% v/v)). The reaction mixture consisted of two phases; in the polar phase, we found evidences of a strong interaction of Bz2S and toluene with the naked RuS2 NPs. We have also obtained self-organized thin films of capped N(Et)3- and RuS2-[MoS4]2- nanoparticles. In both cases, the shape and thickness of the resulting thin films were controlled by a dynamic vacuum procedure. The thin films have been characterized by atomic force microscopy, scanning electron microscopy, HR-TEM, energy dispersion spectroscopy, X-ray diffraction, and absorbance and fluorescence spectroscopies.

  4. The effects of structural variations of thiophene-containing Ru(II) complexes on the acid-base and DNA binding properties.

    PubMed

    Yuan, Cui-Li; Zhang, An-Guo; Zheng, Ze-Bo; Wang, Ke-Zhi

    2013-03-01

    A phenylthiophenyl-bearing Ru(II) complex of [Ru(bpy)₂(Hbptip)](PF₆)₂ {bpy = 2,2'-bipyridine, Hbptip = 2-(4-phenylthiophen-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline} was synthesized and characterized by elemental analysis, ¹H NMR spectroscopy, and electrospray ionization mass spectrometry. The ground- and excited-state acid-base properties of the complex were studied by UV-visible absorption and photoluminescence spectrophotometric pH titrations and the negative logarithm values of the ground-state acid ionization constants were derived to be pK(a1) = 1.31 ± 0.09 and pK(a2) = 5.71 ± 0.11 with the pK(a2) associated deprotonation/protonation process occurring over 3 pK(a) units more acidic than thiophenyl-free parent complex of [Ru(bpy)₂(Hpip)]²⁺ {Hpip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline}. The calf thymus DNA-binding properties of [Ru(bpy)₂(Hbptip)]²⁺ in Tris-HCl buffer (pH 7.1 and 50 mM NaCl) were investigated by DNA viscosities and density functional theoretical calculations as well as UV-visible and emission spectroscopy techniques of UV-visible and luminescence titrations, steady-state emission quenching by [Fe(CN)₆]⁴⁻, DNA competitive binding with ethidium bromide, DNA melting experiments, and reverse salt effects. The complex was evidenced to bind to the DNA intercalatively with binding affinity being greater than those for previously reported analogs of [Ru(bpy)₂(Hip)]²⁺, [Ru(bpy)₂(Htip)]²⁺, and [Ru(bpy)₂(Haptip)]²⁺ {Hip = 1H-imidazo[4,5-f][1,10]phenanthroline, Htip = 2-thiophenimidazo[4,5-f][1,10]phenanthroline, Haptip = 2-(5-phenylthiophen-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline}.

  5. OsABCB14 functions in auxin transport and iron homeostasis in rice (Oryza sativa L.).

    PubMed

    Xu, Yanxia; Zhang, Saina; Guo, Haipeng; Wang, Suikang; Xu, Ligen; Li, Chuanyou; Qian, Qian; Chen, Fan; Geisler, Markus; Qi, Yanhua; Jiang, De An

    2014-07-01

    Members of the ATP Binding Cassette B/Multidrug-Resistance/P-glyco-protein (ABCB/MDR/PGP) subfamily were shown to function primarily in Oryza sativa (rice) auxin transport; however, none of the rice ABCB transporters have been functionally characterized. Here, we describe that a knock-down of OsABCB14 confers decreased auxin concentrations and polar auxin transport rates, conferring insensitivity to 2,4-dichlorophenoxyacetic acid (2,4-D) and indole-3-acetic acid (IAA). OsABCB14 displays enhanced specific auxin influx activity in yeast and protoplasts prepared from rice knock-down alleles. OsABCB14 is localized at the plasma membrane, pointing to an important directionality under physiological conditions. osabcb14 mutants were surprisingly found to be insensitive to iron deficiency treatment (-Fe). Their Fe concentration is higher and upregulation of Fe deficiency-responsive genes is lower in osabcb14 mutants than in wild-type rice (Nipponbare, NIP). Taken together, our results strongly support the role of OsABCB14 as an auxin influx transporter involved in Fe homeostasis. The functional characterization of OsABCB14 provides insights in monocot auxin transport and its relationship to Fe nutrition. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

  6. RRh2Al10 (R = Ce, Yb): New intermetallic compounds in the 1 : 2 : 10 stoichiometry series

    NASA Astrophysics Data System (ADS)

    Strydom, A. M.; Djoumessi, R. F.; Blinova, M.; Tursina, A.; Nesterenko, S.; Avzuragova, V.

    2018-05-01

    The orthorhombic, space group Cmcm YbFe2Al10 structure type series of compounds are known to form with practically the entire series of rare-earth elements R, but only with the three d - electron elements Fe, Ru, and Os. The Ce-derivatives in particular have been of much interest since the first reports of their highly unusual physical properties. Classified as Kondo insulators, CeRu2Al10 and CeOs2Al10 controversially order magnetically and with uncharacteristically high Néel temperatures of ≃ 28 K. CeFe2Al10 on the other hand shows pronounced semiconducting and Kondo features but remains paramagnetic. As part of our ongoing studies into the rich physics of this class of materials we have succeeded in synthesizing new members of the 1:2:10 stoichiometry involving the chemical element Rh for the first time. CeRh2Al10 is found to crystallize in the tetragonal system with space group I41 / amd . Yb Rh2Al10 on the other hand forms in the serial Cmcm orthorhombic structure type. We discuss important similarities between the two types. At 5.310 Å the shortest Ce-Ce distance is, likewise to the situation in CeRu2Al10 and CeOs2Al10 , also well above the Hill limit of 3.40 Å. Despite the cage-like structure and large rare-earth separation distances, this study reveals the onset of long-range magnetic ordering in CeRh2Al10 at 3.9 K. The magnetic ordering develops out of an incoherent Kondo state that dominates the electrical resistivity below about 40 K.

  7. Electrochemiluminescence resonance energy transfer system between GNRs and Ru(bpy)32+: Application in magnetic aptasensor for β-amyloid.

    PubMed

    Ke, Hong; Sha, Haifeng; Wang, Yinfang; Guo, Weiwei; Zhang, Xin; Wang, Zhiming; Huang, Chusen; Jia, Nengqin

    2018-02-15

    Electrochemiluminescent (ECL) assay has gradually drawn increasing interest in the biomedical analysis. This paper proposed a new methodology for ultrasensitive and facile detection of Alzheimer's disease marker β-amyloid (Aβ) by fabricating a sandwich-type ECL sensing platform. Herein, electrochemiluminescence resonance energy transfer (ECL-RET) was employed to determine Aβ concentration, which can be attributed to the quenching effect from RET between Ru(bpy) 3 2+ and gold nanorods (GNRs) acting as ECL-RET electron donor and acceptor, respectively. In this protocol, mesoporous carbon nanospheres were adopted to immobilize ECL reactant Ru(bpy) 3 2+ and antibody via nafion to acquire the RET donor nanocomposites (MOCs/nafion/Ru(bpy) 3 2+ /antibody), which were tightly interconnected with epoxy group functionalized Fe 3 O 4 nanoparticles. It is of vital importance that GNRs with exquisite rod shape were synthesized and exhibited a typical absorption peak at 650nm to quench ECL signal of Ru(bpy) 3 2+ effectively. In addition, the ECL emission decreased linearly with the logarithm of Aβ concentration in a wide linear range from 1.0 × 10 -5 to 100ng/mL with a detection limit of 4.2 × 10 -6 ng/mL. Furthermore, distinctive and desirable properties were verified to declare the promise for being applicable to analyze the Aβ content in real Alzheimer's cerebrospinal fluid samples with satisfactory results. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Crystal structure of a mononuclear Ru(II) complex with a back-to-back terpyridine ligand: [RuCl(bpy)(tpy-tpy)](.).

    PubMed

    Rein, Francisca N; Chen, Weizhong; Scott, Brian L; Rocha, Reginaldo C

    2015-09-01

    We report the structural characterization of [6',6''-bis-(pyridin-2-yl)-2,2':4',4'':2'',2'''-quaterpyridine](2,2'-bi-pyridine)-chlorido-ruthenium(II) hexa-fluorido-phosphate, [RuCl(C10H8N2)(C30H20N6)]PF6, which contains the bidentate ligand 2,2'-bi-pyridine (bpy) and the tridendate ligand 6',6''-bis-(pyridin-2-yl)-2,2':4',4'':2'',2'''-quaterpyridine (tpy-tpy). The [RuCl(bpy)(tpy-tpy)](+) monocation has a distorted octa-hedral geometry at the central Ru(II) ion due to the restricted bite angle [159.32 (16)°] of the tridendate ligand. The Ru-bound tpy and bpy moieties are nearly planar and essentially perpendicular to each other with a dihedral angle of 89.78 (11)° between the least-squares planes. The lengths of the two Ru-N bonds for bpy are 2.028 (4) and 2.075 (4) Å, with the shorter bond being opposite to Ru-Cl. For tpy-tpy, the mean Ru-N distance involving the outer N atoms trans to each other is 2.053 (8) Å, whereas the length of the much shorter bond involving the central N atom is 1.936 (4) Å. The Ru-Cl distance is 2.3982 (16) Å. The free uncoordinated moiety of tpy-tpy adopts a trans,trans conformation about the inter-annular C-C bonds, with adjacent pyridyl rings being only approximately coplanar. The crystal packing shows significant π-π stacking inter-actions based on tpy-tpy. The crystal structure reported here is the first for a tpy-tpy complex of ruthenium.

  9. Hydrocarbon oxidation by beta-halogenated dioxoruthenium(VI) porphyrin complexes: effect of reduction potential (RuVI/V) and C-H bond-dissociation energy on rate constants.

    PubMed

    Che, Chi-Ming; Zhang, Jun-Long; Zhang, Rui; Huang, Jie-Sheng; Lai, Tat-Shing; Tsui, Wai-Man; Zhou, Xiang-Ge; Zhou, Zhong-Yuan; Zhu, Nianyong; Chang, Chi Kwong

    2005-11-18

    beta-Halogenated dioxoruthenium(VI) porphyrin complexes [Ru(VI)(F(28)-tpp)O(2)] [F(28)-tpp=2,3,7,8,12,13, 17,18-octafluoro-5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato(2-)] and [Ru(VI)(beta-Br(8)-tmp)O(2)] [beta-Br(8)-tmp=2,3,7,8,12,13,17,18-octabromo-5,10,15,20- tetrakis(2,4,6-trimethylphenyl)porphyrinato(2-)] were prepared from reactions of [Ru(II)(por)(CO)] [por=porphyrinato(2-)] with m-chloroperoxybenzoic acid in CH(2)Cl(2). Reactions of [Ru(VI)(por)O(2)] with excess PPh(3) in CH(2)Cl(2) gave [Ru(II)(F(20)-tpp)(PPh(3))(2)] [F(20)-tpp=5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato(2-)] and [Ru(II)(F(28)-tpp)(PPh(3))(2)]. The structures of [Ru(II)(por)(CO)(H(2)O)] and [Ru(II)(por)(PPh(3))(2)] (por=F(20)-tpp, F(28)-tpp) were determined by X-ray crystallography, revealing the effect of beta-fluorination of the porphyrin ligand on the coordination of axial ligands to ruthenium atom. The X-ray crystal structure of [Ru(VI)(F(20)-tpp)O(2)] shows a Ru=O bond length of 1.718(3) A. Electrochemical reduction of [Ru(VI)(por)O(2)] (Ru(VI) to Ru(V)) is irreversible or quasi-reversible, with the E(p,c)(Ru(VI/V)) spanning -0.31 to -1.15 V versus Cp(2)Fe(+/0). Kinetic studies were performed for the reactions of various [Ru(VI)(por)O(2)], including [Ru(VI)(F(28)-tpp)O(2)] and [Ru(VI)(beta-Br(8)-tmp)O(2)], with para-substituted styrenes p-X-C(6)H(4)CH=CH(2) (X=H, F, Cl, Me, MeO), cis- and trans-beta-methylstyrene, cyclohexene, norbornene, ethylbenzene, cumene, 9,10-dihydroanthracene, xanthene, and fluorene. The second-order rate constants (k(2)) obtained for the hydrocarbon oxidations by [Ru(VI)(F(28)-tpp)O(2)] are up to 28-fold larger than by [Ru(VI)(F(20)-tpp)O(2)]. Dual-parameter Hammett correlation implies that the styrene oxidation by [Ru(VI)(F(28)-tpp)O(2)] should involve rate-limiting generation of a benzylic radical intermediate, and the spin delocalization effect is more important than the polar effect. The k(2) values for the oxidation of styrene and

  10. Semiconductor-metal transition of Se in Ru-Se Catalyst Nanoparticles

    NASA Astrophysics Data System (ADS)

    Babu, P. K.; Lewera, Adam; Oldfield, Eric; Wieckowski, Andrzej

    2009-03-01

    Ru-Se composite nanoparticles are promising catalysts for the oxygen reduction reaction (ORR) in fuel cells. Though the role of Se in enhancing the chemical stability of Ru nanoparticles is well established, the microscopic nature of Ru-Se interaction was not clearly understood. We carried out a combined investigation of ^77Se NMR and XPS on Ru-Se nanoparticles and our results indicate that Se, a semiconductor in elemental form, becomes metallic when interacting with Ru. ^77Se spin-lattice relaxation rates are found to be proportional to T, the well-known Korringa behavior characteristic of metals. The NMR results are supported by the XPS binding energy shifts which suggest that a possible Ru->Se charge transfer could be responsible for the semiconductor->metal transition of Se which also makes Ru less susceptible to oxidation during ORR.

  11. Ru nanoframes with an fcc structure and enhanced catalytic properties

    DOE PAGES

    Ye, Haihang; Wang, Qingxiao; Catalano, Massimo; ...

    2016-03-21

    Noble-metal nanoframes are of great interest to many applications due to their unique open structures. Among various noble metals, Ru has never been made into nanoframes. In this study, we report for the first time an effective method based on seeded growth and chemical etching for the facile synthesis of Ru nanoframes with high purity. The essence of this approach is to induce the preferential growth of Ru on the corners and edges of Pd truncated octahedra as the seeds by kinetic control. The resultant Pd–Ru core–frame octahedra could be easily converted to Ru octahedral nanoframes of ~2 nm inmore » thickness by selectively removing the Pd cores through chemical etching. Most importantly, in this approach the face-centered cubic (fcc) crystal structure of Pd seeds was faithfully replicated by Ru that usually takes an hcp structure. Furthermore, the fcc Ru nanoframes showed higher catalytic activities toward the reduction of p-nitrophenol by NaBH 4 and the dehydrogenation of ammonia borane compared with hcp Ru nanowires with roughly the same thickness.« less

  12. Enhanced thermoelectric power and electronic correlations in RuSe₂

    DOE PAGES

    Wang, Kefeng; Wang, Aifeng; Tomic, A.; ...

    2015-03-03

    We report the electronic structure, electric and thermal transport properties of Ru 1-xIr xSe₂ (x ≤ 0.2). RuSe₂ is a semiconductor that crystallizes in a cubic pyrite unit cell. The Seebeck coefficient of RuSe₂ exceeds -200 μV/K around 730 K. Ir substitution results in the suppression of the resistivity and the Seebeck coefficient, suggesting the removal of the peaks in density of states near the Fermi level. Ru 0.8Ir 0.2Se₂ shows a semiconductor-metal crossover at about 30 K. The magnetic field restores the semiconducting behavior. Our results indicate the importance of the electronic correlations in enhanced thermoelectricity of RuSb₂.

  13. Os-187/Os-188 and Highly Siderophile Element Systematics of Apollo 17 Aphanitic Melt Rocks

    NASA Technical Reports Server (NTRS)

    Puchtel, I. S.; Walker, R. J.; James, O. B.

    2005-01-01

    Introduction: Generally chondritic relative abundances and high absolute abundances of the highly siderophile elements (HSE: Ru, Rh, Pd, Re, Os, Ir, Pt, Au) in Earth s upper mantle provide strong evidence that these elements were added to the Earth following the last major interaction between its metallic core and silicate fraction. So called "late accretion" may have added materials comprising as much as 0.8% of the total mass of the Earth and possibly a similar proportion of mass to the Moon. We have begun to study the chemical nature of late accreted materials to the Earth - Moon system by examining the HSE contained in lunar impact-melt rocks. The HSE contained in melt rocks were largely added to the Moon during the period of time from the origin of the lunar highlands crust (4.4- 4.5 Ga) to the end of the late bombardment period (ca. 3.9 Ga). These materials provide the only direct chemical link to the late accretionary period. The chemical fingerprints of the HSE in late accreted materials may enable us to ascertain under what conditions and where in the solar system the late accreted materials formed. The Os-187/Os-188 ratios (reflecting long-term Re/Os), coupled with ratios of other HSE, can be diagnostic for identifying the nature of the impactor. A critical issue, however, will be deconvolving the exogenous from indigenous components.

  14. Structural and functional similarities between a ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO)-like protein from Bacillus subtilis and photosynthetic RuBisCO.

    PubMed

    Saito, Yohtaro; Ashida, Hiroki; Sakiyama, Tomoko; de Marsac, Nicole Tandeau; Danchin, Antoine; Sekowska, Agnieszka; Yokota, Akiho

    2009-05-08

    The sequences classified as genes for various ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBisCO)-like proteins (RLPs) are widely distributed among bacteria, archaea, and eukaryota. In the phylogenic tree constructed with these sequences, RuBisCOs and RLPs are grouped into four separate clades, forms I-IV. In RuBisCO enzymes encoded by form I, II, and III sequences, 19 conserved amino acid residues are essential for CO(2) fixation; however, 1-11 of these 19 residues are substituted with other amino acids in form IV RLPs. Among form IV RLPs, the only enzymatic activity detected to date is a 2,3-diketo-5-methylthiopentyl 1-phosphate (DK-MTP-1-P) enolase reaction catalyzed by Bacillus subtilis, Microcystis aeruginosa, and Geobacillus kaustophilus form IV RLPs. RLPs from Rhodospirillum rubrum, Rhodopseudomonas palustris, Chlorobium tepidum, and Bordetella bronchiseptica were inactive in the enolase reaction. DK-MTP-1-P enolase activity of B. subtilis RLP required Mg(2+) for catalysis and, like RuBisCO, was stimulated by CO(2). Four residues that are essential for the enolization reaction of RuBisCO, Lys(175), Lys(201), Asp(203), and Glu(204), were conserved in RLPs and were essential for DK-MTP-1-P enolase catalysis. Lys(123), the residue conserved in DK-MTP-1-P enolases, was also essential for B. subtilis RLP enolase activity. Similarities between the active site structures of RuBisCO and B. subtilis RLP were examined by analyzing the effects of structural analogs of RuBP on DK-MTP-1-P enolase activity. A transition state analog for the RuBP carboxylation of RuBisCO was a competitive inhibitor in the DK-MTP-1-P enolase reaction with a K(i) value of 103 mum. RuBP and d-phosphoglyceric acid, the substrate and product, respectively, of RuBisCO, were weaker competitive inhibitors. These results suggest that the amino acid residues utilized in the B. subtilis RLP enolase reaction are the same as those utilized in the RuBisCO RuBP enolization reaction.

  15. Evidence that Ribulose 1,5-Bisphosphate (RuBP) Binds to Inactive Sites of RuBP Carboxylase in Vivo and an Estimate of the Rate Constant for Dissociation 1

    PubMed Central

    Cardon, Zoe G.; Mott, Keith A.

    1989-01-01

    The binding of ribulose 1,5-bisphosphate (RuBP) to inactive (noncarbamylated) sites of the enzyme RuBP carboxylase in vivo was investigated in Spinacia oleracea and Helianthus annuus. The concentrations of RuBP and inactive sites were determined in leaf tissue as a function of time after a change to darkness. RuBP concentrations fell rapidly after the change to darkness and were approximately equal to the concentration of inactive sites after 60 s. Variations in the concentration of inactive sites, which were induced by differences in the light intensity before the light-dark transition, correlated with the concentration of RuBP between 60 and 120 s after the change to darkness. These data are discussed as evidence that RuBP binds to inactive sites of RuBP carboxylase in vivo. After the concentration of RuBP fell below that of inactive sites (at times longer than 60 s of darkness), the decline in RuBP was logarithmic with time. This would be expected if the dissociation of RuBP from inactive sites controlled the decline in RuBP concentration. These data were used to estimate the rate constant for dissociation of RuBP from inactive sites in vivo. PMID:16666692

  16. Biochemical characterization of predicted Precambrian RuBisCO

    PubMed Central

    Shih, Patrick M.; Occhialini, Alessandro; Cameron, Jeffrey C.; Andralojc, P John; Parry, Martin A. J.; Kerfeld, Cheryl A.

    2016-01-01

    The antiquity and global abundance of the enzyme, RuBisCO, attests to the crucial and longstanding role it has played in the biogeochemical cycles of Earth over billions of years. The counterproductive oxygenase activity of RuBisCO has persisted over billions of years of evolution, despite its competition with the carboxylase activity necessary for carbon fixation, yet hypotheses regarding the selective pressures governing RuBisCO evolution have been limited to speculation. Here we report the resurrection and biochemical characterization of ancestral RuBisCOs, dating back to over one billion years ago (Gyr ago). Our findings provide an ancient point of reference revealing divergent evolutionary paths taken by eukaryotic homologues towards improved specificity for CO2, versus the evolutionary emphasis on increased rates of carboxylation observed in bacterial homologues. Consistent with these distinctions, in vivo analysis reveals the propensity of ancestral RuBisCO to be encapsulated into modern-day carboxysomes, bacterial organelles central to the cyanobacterial CO2 concentrating mechanism. PMID:26790750

  17. Biochemical characterization of predicted Precambrian RuBisCO.

    PubMed

    Shih, Patrick M; Occhialini, Alessandro; Cameron, Jeffrey C; Andralojc, P John; Parry, Martin A J; Kerfeld, Cheryl A

    2016-01-21

    The antiquity and global abundance of the enzyme, RuBisCO, attests to the crucial and longstanding role it has played in the biogeochemical cycles of Earth over billions of years. The counterproductive oxygenase activity of RuBisCO has persisted over billions of years of evolution, despite its competition with the carboxylase activity necessary for carbon fixation, yet hypotheses regarding the selective pressures governing RuBisCO evolution have been limited to speculation. Here we report the resurrection and biochemical characterization of ancestral RuBisCOs, dating back to over one billion years ago (Gyr ago). Our findings provide an ancient point of reference revealing divergent evolutionary paths taken by eukaryotic homologues towards improved specificity for CO2, versus the evolutionary emphasis on increased rates of carboxylation observed in bacterial homologues. Consistent with these distinctions, in vivo analysis reveals the propensity of ancestral RuBisCO to be encapsulated into modern-day carboxysomes, bacterial organelles central to the cyanobacterial CO2 concentrating mechanism.

  18. Adsorptive Separation of Methanol-Acetone on Isostructural Series of Metal-Organic Frameworks M-BTC (M = Ti, Fe, Cu, Co, Ru, Mo): A Computational Study of Adsorption Mechanisms and Metal-Substitution Impacts.

    PubMed

    Wu, Ying; Chen, Huiyong; Xiao, Jing; Liu, Defei; Liu, Zewei; Qian, Yu; Xi, Hongxia

    2015-12-09

    The adsorptive separation properties of M-BTC isostructural series (M = Ti, Fe, Cu, Co, Ru, Mo) for methanol-acetone mixtures were investigated by using various computational procedures of grand canonical Monte Carlo simulations (GCMC), density functional theory (DFT), and ideal adsorbed solution theory (IAST), following with comprehensive understanding of adsorbate-metal interactions on the adsorptive separation behaviors. The obtained results showed that the single component adsorptions were driven by adsorbate-framework interactions at low pressures and by framework structures at high pressures, among which the mass effects, electrostatics, and geometric accessibility of the metal sites also played roles. In the case of methanol-acetone separation, the selectivity of methanol on M-BTCs decreased with rising pressures due to the pressure-dependent separation mechanisms: the cooperative effects between methanol and acetone hindered the separation at low pressures, whereas the competitive effects of acetone further resulted in the lower selectivity at high pressures. Among these M-BTCs, Ti and Fe analogues exhibited the highest thermodynamic methanol/acetone selectivity, making them promising for adsorptive methanol/acetone separation processes. The investigation provides mechanistic insights on how the nature of metal centers affects the adsorption properties of MOFs, and will further promote the rational design of new MOF materials for effective gas mixture separation.

  19. Intramolecular electron transfer in cyanide bridged adducts comprising Ru(II)/Ru(III) tetracarboxylate and [Mn(I)(CO)(CN)((t)BuNC)(4)] units.

    PubMed

    Imhof, Wolfgang; Sterzik, Anke; Krieck, Sven; Schwierz, Markus; Hoffeld, Thomas; Spielberg, Eike T; Plass, Winfried; Patmore, Nathan

    2010-07-21

    Reaction of mixed valence ruthenium tetracarboxylates [Ru(2)(II,III)(R(1)COO)(2)(R(2)COO)(2)Cl] (R(1) = Me, R(2) = 2,4,6-(i)Pr-Ph or R(1) = R(2) = (t)Bu) with two equivalents of the octahedral manganese complex [Mn(I)(CO)(CN)((t)BuNC)(4)] leads to the formation of cyanide bridged heteronuclear coordination compounds of the general formula {[Ru(2)(II,III)(R(1)COO)(2)(R(2)COO)(2)][Mn(I)(CO)(CN)((t)BuNC)(4)](2)}Cl. In solution an intramolecular electron transfer from manganese towards the multiply bonded Ru(2) core occurs that is verified by EPR and IR spectroscopy, magnetic measurements and DFT calculations. Nevertheless, disproportionation of an initially formed {Mn(I)-Ru(2)(II,III)-Mn(I)}(+) adduct into {Mn(II)-Ru(2)(II,III)-Mn(I)}(2+) and {Mn(I)-Ru(2)(II,II)-Mn(I)} species cannot be completely ruled out.

  20. Re-Os Systematics and HSE Distribution in Metal from Ochansk (H4) Chondrite

    NASA Technical Reports Server (NTRS)

    Smoliar, M. I.; Horan, M. F.; Alexander, C. M. OD.; Walker, R. J.

    2003-01-01

    Previous studies of the Re-Os systematics of chondrites have documented considerable variation in the Re/Os ratios of whole rock samples. For some whole rock chondrites, Re-Os systematics display large deviations from the primitive isochron that are considerably larger than deviations in other isotope systems. Possible interpretation of these facts is that the Re-Os system in chondrites is particularly sensitive to post-formation alteration processes, thus providing a useful tool to examine such processes. Significant variations that have been detected in highly siderophile element (HSE) patterns for ordinary chondrites support this conclusion. We report Re-Os isotope data for metal separates from the Ochansk H4 chondrite coupled with abundance data for Ru, Pd, Ir, and Pt, determined in the same samples by isotope dilution. We chose this meteorite mainly because it is an observed fall with minimal signs of weathering, and its low metamorphic grade (H4) and shock stage (S3).

  1. Optical properties of epitaxial BiFeO3 thin film grown on SrRuO3-buffered SrTiO3 substrate.

    PubMed

    Xu, Ji-Ping; Zhang, Rong-Jun; Chen, Zhi-Hui; Wang, Zi-Yi; Zhang, Fan; Yu, Xiang; Jiang, An-Quan; Zheng, Yu-Xiang; Wang, Song-You; Chen, Liang-Yao

    2014-01-01

    The BiFeO3 (BFO) thin film was deposited by pulsed-laser deposition on SrRuO3 (SRO)-buffered (111) SrTiO3 (STO) substrate. X-ray diffraction pattern reveals a well-grown epitaxial BFO thin film. Atomic force microscopy study indicates that the BFO film is rather dense with a smooth surface. The ellipsometric spectra of the STO substrate, the SRO buffer layer, and the BFO thin film were measured, respectively, in the photon energy range 1.55 to 5.40 eV. Following the dielectric functions of STO and SRO, the ones of BFO described by the Lorentz model are received by fitting the spectra data to a five-medium optical model consisting of a semi-infinite STO substrate/SRO layer/BFO film/surface roughness/air ambient structure. The thickness and the optical constants of the BFO film are obtained. Then a direct bandgap is calculated at 2.68 eV, which is believed to be influenced by near-bandgap transitions. Compared to BFO films on other substrates, the dependence of the bandgap for the BFO thin film on in-plane compressive strain from epitaxial structure is received. Moreover, the bandgap and the transition revealed by the Lorentz model also provide a ground for the assessment of the bandgap for BFO single crystals.

  2. Antiferromagnetism in Bulk Rutile RuO2

    NASA Astrophysics Data System (ADS)

    Berlijn, T.; Snijders, P. C.; Kent, P. R. C.; Maier, T. A.; Zhou, H.-D.; Cao, H.-B.; Delaire, O.; Wang, Y.; Koehler, M.; Weitering, H. H.

    While bulk rutile RuO2 has long been considered to be a Pauli paramagnet, we conclude it to host antiferromagnetism based on our combined theoretical and experimental study. This constitutes an important finding given the large amount of applications of RuO2 in the electrochemical and electronics industry. Furthermore the high onset temperature of the antiferromagnetism around 1000K together with the high electrical conductivity makes RuO2 unique among the ruthenates and among oxide materials in general. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  3. Enhanced interfacial Dzyaloshinskii-Moriya interaction and isolated skyrmions in the inversion-symmetry-broken Ru/Co/W/Ru films

    NASA Astrophysics Data System (ADS)

    Samardak, Alexander; Kolesnikov, Alexander; Stebliy, Maksim; Chebotkevich, Ludmila; Sadovnikov, Alexandr; Nikitov, Sergei; Talapatra, Abhishek; Mohanty, Jyoti; Ognev, Alexey

    2018-05-01

    An enhancement of the spin-orbit effects arising on an interface between a ferromagnet (FM) and a heavy metal (HM) is possible through the strong breaking of the structural inversion symmetry in the layered films. Here, we show that an introduction of an ultrathin W interlayer between Co and Ru in Ru/Co/Ru films enables to preserve perpendicular magnetic anisotropy (PMA) and simultaneously induce a large interfacial Dzyaloshinskii-Moriya interaction (iDMI). The study of the spin-wave propagation in the Damon-Eshbach geometry by Brillouin light scattering spectroscopy reveals the drastic increase in the iDMI value with the increase in W thickness (tW). The maximum iDMI of -3.1 erg/cm2 is observed for tW = 0.24 nm, which is 10 times larger than for the quasi-symmetrical Ru/Co/Ru films. We demonstrate the evidence of the spontaneous field-driven nucleation of isolated skyrmions supported by micromagnetic simulations. Magnetic force microscopy measurements reveal the existence of sub-100-nm skyrmions in the zero magnetic field. The ability to simultaneously control the strength of PMA and iDMI in quasi-symmetrical HM/FM/HM trilayer systems through the interface engineered inversion asymmetry at the nanoscale excites new fundamental and practical interest in ultrathin ferromagnets, which are a potential host for stable magnetic skyrmions.

  4. Preparation, structure and some chemistry of FcC[identically equal to]CC[identically equal to]CC[identically equal to]CRu(dppe)Cp

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bruce, Michael I.; Humphrey, Paul A.; Jevric, Martyn

    The synthesis of Fc(C{triple_bond}C){sub 3}Ru(dppe)Cp (2) from Fc(C{triple_bond}C){sub 3}SiMe{sub 3} and RuCl(dppe)Cp is described, together with its reactions with tcne to give the tetracyano-dienyl FcC{triple_bond}CC{triple_bond}C{l_brace}C[{triple_bond}C(CN){sub 2}]{r_brace}{sub 2}Ru(dppe)Cp (3) and -cyclobutenyl FcC{triple_bond}CC{triple_bond}C{l_brace}C{triple_bond}CC(CN){sub 2}C(CN){sub 2}{r_brace}Ru(dppe)Cp (4), with Co{sub 2}({mu}-dppm){sub n}(CO){sub 8-2n} (n = 0, 1) to give FcC{sub 2}{l_brace}Co{sub 2}(CO){sub 6}{r_brace}C{sub 2}{l_brace}Co{sub 2}(CO){sub 6}{r_brace}CCRu(dppe)Cp (5) and FcC{triple_bond}CC{triple_bond}CC{sub 2}{l_brace}Co{sub 2}({mu}-dppm)(CO){sub 4}{r_brace}Ru(dppe)Cp (6), respectively, and with Os{sub 3}(CO){sub 10}(NCMe){sub 2} to give Os{sub 3}{l_brace}{mu}{sub 3}-C{sub 2}C{triple_bond}CC{triple_bond}C[Ru(dppe)Cp]{r_brace}(CO){sub 10} (7). On standing in solution, the latter isomerises to the cyclo-metallated derivative Os{sub 3}({mu}-H){l_brace}{mu}{sub 3}-C[Ru(dppe)Cp]CCC[({eta}-C{sub 5}H{sub 3})FeCp]{r_brace}(CO){sub 8} (8). X-ray structural determinations of 1, 2, 6 andmore » 7 are reported.« less

  5. Reinforcement of double-exchange ferromagnetic coupling by Ru in La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7} manganite system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumaresavanji, M., E-mail: vanji.hplt@gmail.com; Fontes, M.B.; Lopes, A.M.L.

    2014-03-01

    Highlights: • Effect of Mn-site doping by Ru has been studied in La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7}. • Electrical resistance, magnetoresistance and magnetic properties were measured. • Ru substitution enhances the ferromagnetism and metallicity. • Results were interpreted by the ferromagnetically coupled Ru with Mn ions in Mn–O–Ru network. - Abstract: The effect of Mn-site doping on magnetic and transport properties in the bilayer manganites La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7} (y = 0.0, 0.04, 0.08 and 0.15) has been studied. The undoped compound La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} exhibits a ferromagnetic metal to paramagnetic insulator transition at T{submore » C} = 130 K and the substitution of Ru shifts the transition temperatures to higher temperature values. The increased metal–insulator transition by Ru substitution, obtained from temperature dependence of resistivity measurements, indicates that the Ru substitution enhances the metallic state at low temperature regime and favours the Mn–Ru pairs in the Ru doped samples. Moreover, the activation energy values calculated from the temperature dependence of resistivity curves suggest that the Ru substitution weakens the formation of polarons. The increased magnetoresistance ratio from 108% to 136% by Ru substitution, measured at 5 K, points out that the Ru substitution also enhances the inter-grain tunneling magnetoresistance. Thus, the ferromagnetic order and metallic state in La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} system have been enhanced by the presence of Ru in the Mn-site. These reinforcements of ferromagnetic metallic state and magnetoresistance have been interpreted by the ferromagnetically coupled high spin states of Ru with Mn ions in the Mn–O–Ru network.« less

  6. Into the Modelling of RU Vir

    NASA Astrophysics Data System (ADS)

    Rau, G.; Hron, J.; Paladini, C.; Eriksson, K.; Aringer, B.; Groenewegen, M. A. T.; Mečina, M.

    2015-08-01

    We present an attempt to model the atmosphere of the carbon-rich Mira star RU Vir, using different techniques including spectroscopy, photometry, and interferometry. A radiative transfer code and hydrostatic model atmospheres were used for a preliminary study. To investigate the dynamic processes happening in RU Vir, dynamic model atmospheres were compared to new MIDI/VLTI observations obtained in April 2014, and SiC opacities were added.

  7. Direct penetration of spin-triplet superconductivity into a ferromagnet in Au/SrRuO3/Sr2RuO4 junctions

    NASA Astrophysics Data System (ADS)

    Anwar, M. S.; Lee, S. R.; Ishiguro, R.; Sugimoto, Y.; Tano, Y.; Kang, S. J.; Shin, Y. J.; Yonezawa, S.; Manske, D.; Takayanagi, H.; Noh, T. W.; Maeno, Y.

    2016-10-01

    Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities. Here, we report spin-triplet superconductivity induction into a FM SrRuO3 from a leading TSC candidate Sr2RuO4, by fabricating microscopic devices using an epitaxial SrRuO3/Sr2RuO4 hybrid. The differential conductance, exhibiting Andreev-reflection features with multiple energy scales up to around half tesla, indicates the penetration of superconductivity over a considerable distance of 15 nm across the SrRuO3 layer without help of interfacial complex magnetism. This demonstrates potential utility of FM/TSC devices for superspintronics.

  8. Direct penetration of spin-triplet superconductivity into a ferromagnet in Au/SrRuO3/Sr2RuO4 junctions

    PubMed Central

    Anwar, M. S.; Lee, S. R.; Ishiguro, R.; Sugimoto, Y.; Tano, Y.; Kang, S. J.; Shin, Y. J.; Yonezawa, S.; Manske, D.; Takayanagi, H.; Noh, T. W.; Maeno, Y.

    2016-01-01

    Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities. Here, we report spin-triplet superconductivity induction into a FM SrRuO3 from a leading TSC candidate Sr2RuO4, by fabricating microscopic devices using an epitaxial SrRuO3/Sr2RuO4 hybrid. The differential conductance, exhibiting Andreev-reflection features with multiple energy scales up to around half tesla, indicates the penetration of superconductivity over a considerable distance of 15 nm across the SrRuO3 layer without help of interfacial complex magnetism. This demonstrates potential utility of FM/TSC devices for superspintronics. PMID:27782151

  9. Highly siderophile elements and Os isotope signatures in the K-Pg transition of the Chicxulub peak-ring rocks

    NASA Astrophysics Data System (ADS)

    Sato, H.; Ishikawa, A.; Ferrière, L.; Morgan, J. V.; Gulick, S. P. S.

    2017-12-01

    The Chicxulub impact structure, located in the northern Yucatan Peninsula, Mexico, formed 66 My ago, was drilled by IODP-ICDP 364 expedition in April-May, 2016. A continuous core was successfully recovered from the peak ring from depth between 505.7 and 1334.7 mbsf. In order to determine the distribution and abundance of the projectile component in the Chicxulub peak-ring rocks, we determined highly siderophile elements (HSE: Os, Ir, Ru, Pt, Pd, and Re) concentrations and Os isotope ratio (187Os/188Os) in five samples of Unit 1G from a 75 cm-thick transitional layer between the impactites and early Paleogene rocks (616.59-617.34 mbsf interval). HSE concentrations and 187Os/188Os ratios show systematic variations across the transitional layer. The upper part (616.59-616.63 mbsf) is characterized by about one order of magnitude higher Os, Ir, and Ru contents compared to the average continental crust abundances, but much lower than for the typical Ir-enriched Cretaceous-Paleogene boundary sites (e.g., Gubbio and Caravaca). Relatively flat CI chondrite-normalized HSE patterns are observed in the upper part of the layer. Meanwhile, the HSE concentrations in the lower part of the transitional layer (617.315-617.34 mbsf) are almost equivalent to those of upper continental crust showing pronounced step CI chondrite-normalized HSE patterns (low Ir, and high Pt and Pd). 187Os/188Os and Re/Os ratios in the transitional layer gradually decrease from 0.33 to 0.25 and 35.45 to 1.14, respectively, from bottom to top. These results suggest that the projectile component, with chondritic composition, is enriched in the uppermost part of the transitional layer just below carbonate rocks that are early Paleogene in age, but could be distributed over a thicker interval than for the typical Ir-enriched sites. Further detailed studies of HSE and Os isotope compositions through the stratigraphic sequence will reveal the distribution and dilution effect of the projectile component.

  10. Flux Crystal Growth of the RE 2Ru 3Ge 5 ( RE = La, Ce, Nd, Gd, Tb) Series and Their Magnetic and Metamagnetic Transitions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bugaris, Daniel E.; Malliakas, Christos D.; Bud?ko, Sergey L.

    Previously synthesized only as powders, single crystals of the RE 2Ru 3Ge 5 (RE = La, Ce, Nd, Gd, Tb) series of compounds have been now been obtained from molten In. We report that these materials crystallize with the U 2Co 3Si 5-type structure in orthorhombic space group Ibam with lattice parameters a ~ 10.00-9.77 Å (La-Tb), b ~ 12.51-12.35 Å, and c ~ 5.92-5.72 Å. The structure is a three-dimensional framework consisting of RuGe 5 and RuGe 6 units, as well as Ge-Ge zigzag chains. This structure type, along with the other five (Sc 2Fe 3Si 5, Lu 2Comore » 3Si 5, Y 2Rh 3Sn 5, Yb 2Ir 3Ge 5, and Yb 2Pt 3Sn 5) to compose the RE 2T 3X 5 phase space, are discussed in depth. For the three compounds with RE = Nd, Gd, and Tb, multiple magnetic transitions and metamagnetic behavior are observed. Lastly, electronic band structure calculations performed on La 2Ru 3Ge 5 indicate that these materials have a negative band gap and are semimetallic in nature.« less

  11. Flux Crystal Growth of the RE 2Ru 3Ge 5 ( RE = La, Ce, Nd, Gd, Tb) Series and Their Magnetic and Metamagnetic Transitions

    DOE PAGES

    Bugaris, Daniel E.; Malliakas, Christos D.; Bud?ko, Sergey L.; ...

    2017-11-21

    Previously synthesized only as powders, single crystals of the RE 2Ru 3Ge 5 (RE = La, Ce, Nd, Gd, Tb) series of compounds have been now been obtained from molten In. We report that these materials crystallize with the U 2Co 3Si 5-type structure in orthorhombic space group Ibam with lattice parameters a ~ 10.00-9.77 Å (La-Tb), b ~ 12.51-12.35 Å, and c ~ 5.92-5.72 Å. The structure is a three-dimensional framework consisting of RuGe 5 and RuGe 6 units, as well as Ge-Ge zigzag chains. This structure type, along with the other five (Sc 2Fe 3Si 5, Lu 2Comore » 3Si 5, Y 2Rh 3Sn 5, Yb 2Ir 3Ge 5, and Yb 2Pt 3Sn 5) to compose the RE 2T 3X 5 phase space, are discussed in depth. For the three compounds with RE = Nd, Gd, and Tb, multiple magnetic transitions and metamagnetic behavior are observed. Lastly, electronic band structure calculations performed on La 2Ru 3Ge 5 indicate that these materials have a negative band gap and are semimetallic in nature.« less

  12. Synthesis, Electrochemistry, and Excited-State Properties of Three Ru(II) Quaterpyridine Complexes

    DOE PAGES

    Rudd, Jennifer A.; Brennaman, M. Kyle; Michaux, Katherine E.; ...

    2016-03-09

    The complexes [Ru(qpy)LL']2+ (qpy = 2,2':6',2'':6'',2''-quaterpyridine), with 1: L = acetonitrile, L'= chloride; 2: L = L'= acetonitrile; and 3: L = L'= vinylpyridine, have been prepared from [Ru(qpy) (Cl)2]. Their absorption spectra in CH3CN exhibit broad metal-to-ligand charge transfer (MLCT) absorptions arising from overlapping 1A1 → 1MLCT transitions. Photoluminescence is not observed at room temperature, but all three are weakly emissive in 4:1 ethanol/methanol glasses at 77 K with broad, featureless emissions observed between 600 and 1000 nm consistent with MLCT phosphorescence. Cyclic voltammograms in CH3CN reveal the expected RuIII/II redox couples. In 0.1 M trifluoroacetic acid (TFA), 1more » and 2 undergo aquation to give [RuII(qpy)(OH2)2]2+, as evidenced by the appearance of waves for the couples [RuIII(qpy)(OH2)2]3+/[RuII(qpy)(OH2)2]2+, [RuIV(qpy)(O)(OH2)]2+/[RuIII(qpy)(OH2)2]3+, and [RuVI(qpy)(O)2]2+/[RuIV(qpy)(O)(OH2)]2+ in cyclic voltammograms.« less

  13. Ru/Fe bimetallic complexes: Synthesis, characterization, cytotoxicity and study of their interactions with DNA/HSA and human topoisomerase IB.

    PubMed

    Takarada, Jessica E; Guedes, Adriana P M; Correa, Rodrigo S; Silveira-Lacerda, Elisângela de P; Castelli, Silvia; Iacovelli, Federico; Deflon, Victor Marcelo; Batista, Alzir Azevedo; Desideri, Alessandro

    2017-12-15

    Three ruthenium/iron-based compounds, 1: [Ru(MIm)(bipy)(dppf)]PF 6 (MIm = 2-mercapto-1-methylimidazole anion), 2: [RuCl(Im)(bipy)(dppf)]PF 6 (Im = imidazole), and 3: [Ru(tzdt)(bipy)(dppf)]PF 6 (tzdt = 1,3-thiazolidine-2-thione anion) (dppf = 1,1'-bis(diphenylphosphine)ferrocene and bipy = 2,2'-bipyridine), were synthesized, and characterized by elemental analyses, conductivity, UV/Vis, IR, 1 H, 13 C and 31 P{1H} NMR spectroscopies, and by electrochemical technique. The complex 3 was also characterized by single-crystal X-ray. The three ruthenium(II) complexes show cytotoxicity against DU-145 (prostate carcinoma cells) and A549 (lung carcinoma cells) tumor cells. The free ligands do not exhibit any cytotoxic activity, such as evident by the IC 50 values higher than 200 μM. UV/Vis and viscosity experiments showed that the complexes interact weakly with the DNA molecule, via electrostatic forces. The interaction of the complexes 1-3 with the HSA is moderate, with K b values in range of 10 5 -10 7  M -1 , presenting a static mechanism of interaction stabilized by hydrophobic. Complexes 2 and 3 showed high affinity for the FA7 HSA site as evidenced by fluorescence spectroscopy and molecular docking. Complexes 1-3 were tested as potential human Topoisomerase IB inhibitors by analysing the different steps of the enzyme catalytic cycle. The results indicate that all compounds efficiently inhibit the DNA relaxation and the cleavage reaction, in which the effect increases upon pre-incubation. Complexes 1 and 2 are also able to slow down the religation reaction. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. A negative excursion at 14-16 Ma in seawater osmium isotope record: Implications for paleoceanographic studies using Fe-Mn crusts

    NASA Astrophysics Data System (ADS)

    Goto, K. T.; Tejada, M. L. G.; Suzuki, K.

    2017-12-01

    Osmium isotope stratigraphy is a recently proposed method to determine the depositional age of Fe-Mn crusts [1, 2]. Seawater Os isotope (187Os/188Os) is roughly determined by the balance of riverine Os inputs with radiogenic value (187Os/188Os = 1.4), and mantle-derived and extra-terrestrial Os inputs with non-radiogenic value (187Os/188Os = 0.12) [3]. Secular variation of global seawater Os isotope (seawater Os isotope curve) has been reconstructed by the analysis of pelagic sediments and exhibits large variations ranging from 0.2 to 1.0 with several negative excursions [3]. Hence, the depositional age of Fe-Mn crusts can be approximately estimated by fitting their Os isotope depth profiles to the seawater Os isotope curve (Osmium isotope stratigraphy). However, this method allows multiple interpretations which are partly due to the lack of high-resolution seawater Os isotope curve [1, 2]. For example, the available seawater Os isotope curve does not exhibit negative anomaly during the Miocene, which contrasts with Os isotope records of Fe-Mn crusts [4]. In the present study, we obtained a high-resolution Os isotope record of Miocene seawater using hemipelagic sediments from IODP Expedition 351 SiteU1438. We found a small negative Os isotope anomaly as low as 0.7 from sediments deposited at 14-16 Ma. The magnitude of this anomaly is similar to those reported from Fe-Mn crusts. Although the extrapolation of Be-10 ages for Fe-Mn crust indicate a younger age for the anomaly ( 11 Ma) [4], we could not find any discernable isotope anomaly at 11 Ma. Our finding is consistent with the timing of major eruption of the Columbia River flood basalts (CFRB) which could provide non-radiogenic Os to seawater at 14-16 Ma [5]. Hence, we suggest that the observed isotope anomaly reflect eruption and subsequent weathering of the CFRB. As the similar Os isotope anomaly is commonly found from Fe-Mn crusts, the Os isotope anomaly at 14-16 Ma could be used as a key event to constrain

  15. Distribution and PGE mineralization in the formation of chromitite in ophiolite complexes (Ospina-Kitoi Kharanur and ultrabasic massifs of Eastern Sayan, Sousern Siberia)

    NASA Astrophysics Data System (ADS)

    Kiseleva, Olga; Zhmodik, Sergei

    2015-04-01

    New study of PGE in restitic ultrabasic (Kharanur and Ospin-Kitoi) massifs from North and South branches (Dobretsov et al., 1985) of the ophiolite complexes in south-eastern part of the Eastern Sayan show their presence in chromitites of both branches belonging to the different geodynamic settings. Modern concepts model includes several mechanisms of podiform chromitite origin reflected in the chemistry of Cr-spinels (Arai, Yurimoto, 1994; Ballhaus, 1998; Uysal et al., 2009 et al.): 1) partial melting of upper mantle rocks, 2) mixing of primitive melts with melts enriched in SiO2, 3) melt-rock interaction. We estimated the types of interaction of mafic melts with mantle peridotites, with the formation of chromite bodies. For ore chrome spinelides from northern branch (Al2O3) melt = 8 - 14 wt%, (TiO2) melt = 0 - 0,4 wt%, (Fe/Mg) melt = 0,5 - 2,4; Southern branch (Al2O3) melt = 10 - 13 wt%, (TiO2) melt = 0,1 wt%, (Fe/Mg) melt = 0,3 - 1 (Kiseleva, 2014). There are two types of PGE distribution Os-Ir-Ru (I) and Pt-Pd (II). Type I chromitites (mid-Al#Cr-spinels) revealed only Os-Ir-Ru distributions; type II (low-Al#Cr spinelides) show both Os-Ir-Ru and (Pt-Pd) distributions (Kiseleva et al., 2012, 2014). PGE distribution in ultramafic peridotites and chromitites reflects PGE fractionation during partial melting (Barnes et al., 1985; Rehkämper et al., 1997). Processes bringing to extreme fractionation of PGE, may be associated with fluid-saturated supra subduction environment where melting degree near 20% and above is sufficient for the release of PGE from the mantle source (Dick, Bullen, 1984; Naldrett, 2010). Enrichment in PPGE together with a high content of IPGE in same chromite bodies is attributed to the second step of melting, and formation of S-enriched and saturated in PGE melts (Hamlyn, Keays, 1986; Prichard et al., 1996). For type I chromitites platinum group minerals (PGM) are presented by Os-Ir-Ru system. In type II chromitites PGM are represented by Os-Ir-Ru

  16. Structural investigation of (111) oriented (BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices by X-ray diffraction and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Belhadi, J.; Yousfi, S.; Bouyanfif, H.; El Marssi, M.

    2018-04-01

    (BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices (SLs) with varying x have been grown by pulsed laser deposition on (111) oriented SrTiO3 substrates. In order to obtain good epitaxy and flat samples, a conducting SrRuO3 buffer has been deposited prior to the superlattices to screen the polar mismatch for such (111) SrTiO3 orientation. X-ray diffraction reciprocal space mapping on a different family of planes was collected and evidenced a room temperature structural change at x = 0.5 from a rhombohedral/monoclinic structure for rich BiFeO3 to an orthorhombic symmetry for rich LaFeO3. This symmetry change has been confirmed by Raman spectroscopy and demonstrates the different phase stability compared to similar SLs grown on (100) SrTiO3. The strongly anisotropic strain and oxygen octahedral rotation/tilt system compatibility at the interfaces probably explain the orientation dependence of the phase stability in such superlattices.

  17. Itinerant Antiferromagnetism in RuO 2

    DOE PAGES

    Berlijn, Tom; Snijders, Paul C.; Delaire, Oliver A.; ...

    2017-02-15

    Bulk rutile RuO 2 has long been considered a Pauli paramagnet. Here, in this article, we report that RuO 2 exhibits a hitherto undetected lattice distortion below approximately 900 K. The distortion is accompanied by antiferromagnetic order up to at least 300 K with a small room temperature magnetic moment of approximately 0.05μ B as evidenced by polarized neutron diffraction. Density functional theory plus U(DFT+U) calculations indicate that antiferromagnetism is favored even for small values of the Hubbard U of the order of 1 eV. The antiferromagnetism may be traced to a Fermi surface instability, lifting the band degeneracy imposedmore » by the rutile crystal field. The combination of high Néel temperature and small itinerant moments make RuO 2 unique among ruthenate compounds and among oxide materials in general.« less

  18. Enantioselective light switch effect of Δ- and Λ-[Ru(phenanthroline)2 dipyrido[3,2-a:2', 3'-c]phenazine]2+ bound to G-quadruplex DNA.

    PubMed

    Park, Jin Ha; Lee, Hyun Suk; Jang, Myung Duk; Han, Sung Wook; Kim, Seog K; Lee, Young-Ae

    2018-06-01

    The interaction of Δ- and Λ-[Ru(phen) 2 DPPZ] 2+ (DPPZ = dipyrido[3,2-a:2', 3'-c]phenazine, phen = phenanthroline) with a G-quadruplex formed from 5'-G 2 T 2 G 2 TGTG 2 T 2 G 2-3 '(15-mer) was investigated. The well-known enhancement of luminescence intensity (the 'light-switch' effect) was observed for the [Ru(phen) 2 DPPZ] 2+ complexes upon formation of an adduct with the G-quadruplex. The emission intensity of the G-quadruplex-bound Λ-isomer was 3-fold larger than that of the Δ-isomer when bound to the G-quadruplex, which is opposite of the result observed in the case of double stranded DNA (dsDNA); the light switch effect is larger for the dsDNA-bound Δ-isomer. In the job plot of the G-quadruplex with Δ- and Λ-[Ru(phen) 2 DPPZ] 2+ , a major inflection point for the two isomers was observed at x ≈ .65, which suggests a binding stoichiometry of 2:1 for both enantiomers. When the G base at the 8th position was replaced with 6-methyl isoxanthopterin (6MI), a fluorescent guanine analog, the excited energy of 6-MI transferred to bound Δ- or Λ-[Ru(phen) 2 DPPZ] 2+ , which suggests that at least a part of both Ru(II) enantiomers is close to or in contact with the diagonal loop of the G-quadruplex. A luminescence quenching experiment using [Fe(CN) 6 ] 4- for the G-quadruplex-bound Ru(II) complex revealed downward bending curves for both enantiomers in the Stern-Volmer plot, which suggests the presence of Ru(II) complexes that are both accessible and inaccessible to the quencher and may be related to the 2:1 binding stoichiometry.

  19. Learning from the past: Rare ε-Fe2O3 in the ancient black-glazed Jian (Tenmoku) wares

    PubMed Central

    Dejoie, Catherine; Sciau, Philippe; Li, Weidong; Noé, Laure; Mehta, Apurva; Chen, Kai; Luo, Hongjie; Kunz, Martin; Tamura, Nobumichi; Liu, Zhi

    2014-01-01

    Ancient Jian wares are famous for their lustrous black glaze that exhibits unique colored patterns. Some striking examples include the brownish colored “Hare's Fur” (HF) strips and the silvery “Oil Spot” (OS) patterns. Herein, we investigated the glaze surface of HF and OS samples using a variety of characterization methods. Contrary to the commonly accepted theory, we identified the presence of ε-Fe2O3, a rare metastable polymorph of Fe2O3 with unique magnetic properties, in both HF and OS samples. We found that surface crystals of OS samples are up to several micrometers in size and exclusively made of ε-Fe2O3. Interestingly, these ε-Fe2O3 crystals on the OS sample surface are organized in a periodic two dimensional fashion. These results shed new lights on the actual mechanisms and kinetics of polymorphous transitions of Fe2O3. Deciphering technologies behind the fabrication of ancient Jian wares can thus potentially help researchers improve the ε-Fe2O3 synthesis. PMID:24820819

  20. Preparation and characterization of RuO2/polypyrrole electrodes for supercapacitors

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Wu, Yujiao; Zheng, Feng; Ling, Min; Lu, Fanghai

    2014-11-01

    Polypyrrole (PPy) embedded RuO2 electrodes were prepared by the composite method. Precursor solution of RuO2 was coated on tantalum sheet and annealed at 260 °C for 2.5 h to develop a thin film. PPy particles were deposited on RuO2 films and dried at 80 °C for 12 h to form composite electrode. Microstructure and morphology of RuO2/PPy electrode were characterized using Fourier transform infrared spectrometer, X-ray diffraction and scanning electron microscopy, respectively. Our results confirmed that counter ions are incorporated into RuO2 matrix. Structure of the composite with amorphous phase was verified by X-ray diffraction. Analysis by scanning electron microscopy reveals that during grain growth of RuO2/PPy, PPy particle size sharply increases as deposition time is over 20 min. Electrochemical properties of RuO2/PPy electrode were calculated using cyclic voltammetry. As deposition times of PPy are 10, 20, 25 and 30 min, specific capacitances of composite electrodes reach 657, 553, 471 and 396 F g-1, respectively. Cyclic behaviors of RuO2/PPy composite electrodes are stable.

  1. The valence of Ru, Ce and Eu ions in the magneto-superconductor Eu 1.5Ce 0.5RuSr 2Cu 2O 10

    NASA Astrophysics Data System (ADS)

    Felner, I.; Asaf, U.; Godart, C.; Alleno, E.

    1999-01-01

    The superconducting (T c∼32 K) Eu 1.5Ce 0.5RuSr 2Cu 2O 10 (Ru-2122) material is also magnetically ordered (T M∼122 K) with TM≫ Tc. Superconductivity (SC) is confined to the CuO 2 planes, whereas magnetism is due to the Ru sublattice. Mossbauer spectroscopy performed at 90 and 300 K on 151Eu shows a single narrow line with an isomer shift=0.69(2) and a quadrupole splitting of 1.84 mm/s, indicating that the Eu ions are trivalent with a nonmagnetic J=0 ground state. This is in agreement with X-ray-absorption spectroscopy (XAS) taken at L III edges of Eu, Ce which shows that Eu is trivalent and Ce is tetravalent. XAS experiments at the K edge of Ru indicate that Ru is pentavalent. This indicates, that in the M-2122 system, SC exists only for pentavalent M ions such as Ta, Nb and Ru.

  2. Isonitrile radionuclide complexes for labelling and imaging agents

    DOEpatents

    Jones, Alun G.; Davison, Alan; Abrams, Michael J.

    1984-06-04

    A coordination complex of an isonitrile ligand and radionuclide such as Tc, Ru, Co, Pt, Fe, Os, Ir, W, Re, Cr, Mo, Mn, Ni, Rh, Pd, Nb and Ta, is useful as a diagnostic agent for labelling liposomes or vesicles, and selected living cells containing lipid membranes, such as blood clots, myocardial tissue, gall bladder tissue, etc.

  3. Preparation and characterization of the magnetic superconductor EuSr2RuCu2O8-δ (RuEu-1212) by partial melting

    NASA Astrophysics Data System (ADS)

    Yamaki, K.; Kitagawa, N.; Funahashi, S.; Bamba, Y.; Irie, A.

    2018-07-01

    In this study, fine single crystals of the magnetic superconductor EuSr2RuCu2O8-δ (RuEu-1212) were successfully prepared using the partial melting technique. The obtained single crystals had a cubic shape, which coincides with the results of previous studies of RuGd-1212 single crystals. The single crystals had a typical length of 20-30 μm and the diffraction pattern observed from a sample prepared by partial melting was consistent with patterns of previously reported polycrystalline RuEu-1212 samples. A sample subjected to prolonged sintering, which consisted of a large number of combined micro single crystals prepared by partial melting, exhibited a superconducting transition with Tc-onset of 30.9 K and Tc-zero of 10.5 K.

  4. Effect of the structural characteristics of binary Pt-Ru and ternary Pt-Ru-M fuel cell catalysts on the activity of ethanol electrooxidation in acid medium.

    PubMed

    Antolini, Ermete

    2013-06-01

    In view of their possible use as anode materials in acid direct ethanol fuel cells, the electrocatalytic activity of Pt-Ru and Pt-Ru-M catalysts for ethanol oxidation has been investigated. This minireview examines the effects of the structural characteristics of Pt-Ru, such as the degree of alloying and Ru oxidation state, on the electrocatalytic activity for ethanol oxidation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Infrared vibrational spectroscopy of [Ru(bpy)2(bpm)]2+ and [Ru(bpy)3]2+ in the excited triplet state.

    PubMed

    Mukuta, Tatsuhiko; Fukazawa, Naoto; Murata, Kei; Inagaki, Akiko; Akita, Munetaka; Tanaka, Sei'ichi; Koshihara, Shin-ya; Onda, Ken

    2014-03-03

    This work involved a detailed investigation into the infrared vibrational spectra of ruthenium polypyridyl complexes, specifically heteroleptic [Ru(bpy)2(bpm)](2+) (bpy = 2,2'-bipyridine and bpm = 2,2'-bipyrimidine) and homoleptic [Ru(bpy)3](2+), in the excited triplet state. Transient spectra were acquired 500 ps after photoexcitation, corresponding to the vibrational ground state of the excited triplet state, using time-resolved infrared spectroscopy. We assigned the observed bands to specific ligands in [Ru(bpy)2(bpm)](2+) based on the results of deuterium substitution and identified the corresponding normal vibrational modes using quantum-chemical calculations. Through this process, the more complex vibrational bands of [Ru(bpy)3](2+) were assigned to normal vibrational modes. The results are in good agreement with the model in which excited electrons are localized on a single ligand. We also found that the vibrational bands of both complexes associated with the ligands on which electrons are little localized appear at approximately 1317 and 1608 cm(-1). These assignments should allow the study of the reaction dynamics of various photofunctional systems including ruthenium polypyridyl complexes.

  6. Ru(III) catalyzed permanganate oxidation of aniline at environmentally relevant pH.

    PubMed

    Zhang, Jing; Zhang, Ying; Wang, Hui; Guan, Xiaohong

    2014-07-01

    Ru(III) was employed as catalyst for aniline oxidation by permanganate at environmentally relevant pH for the first time. Ru(III) could significantly improve the oxidation rate of aniline by 5-24 times with its concentration increasing from 2.5 to 15 μmol/L. The reaction of Ru(III) catalyzed permanganate oxidation of aniline was first-order with respect to aniline, permanganate and Ru(III), respectively. Thus the oxidation kinetics can be described by a third-order rate law. Aniline degradation by Ru(III) catalyzed permanganate oxidation was markedly influenced by pH, and the second-order rate constant (ktapp) decreased from 643.20 to 2.67 (mol/L)⁻¹sec⁻¹ with increasing pH from 4.0 to 9.0, which was possibly due to the decrease of permanganate oxidation potential with increasing pH. In both the uncatalytic and catalytic permanganate oxidation, six byproducts of aniline were identified in UPLC-MS/MS analysis. Ru(III), as an electron shuttle, was oxidized by permanganate to Ru(VI) and Ru(VII), which acted the co-oxidants for decomposition of aniline. Although Ru(III) could catalyze permanganate oxidation of aniline effectively, dosing homogeneous Ru(III) into water would lead to a second pollution. Therefore, efforts would be made to investigate the catalytic performance of supported Ru(III) toward permanganate oxidation in our future study. Copyright © 2014. Published by Elsevier B.V.

  7. Reaction mechanism for oxygen evolution on RuO 2, IrO 2, and RuO 2@IrO 2 core-shell nanocatalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ma, Zhong; Zhang, Yu; Liu, Shizhong

    Iridium dioxide, IrO 2, is second to the most active RuO 2 catalyst for the oxygen evolution reaction (OER) in acid, and is used in proton exchange membrane water electrolyzers due to its high durability. In order to improve the activity of IrO 2-based catalysts, we prepared RuO 2@IrO 2 core-shell nanocatalysts using carbon-supported Ru as the template. At 1.48 V, the OER specific activity of RuO 2@IrO 2 is threefold that of IrO 2. While the activity volcano plots over wide range of materials have been reported, zooming into the top region to clarify the rate limiting steps ofmore » most active catalysts is important for further activity enhancement. Here, we verified theory-proposed sequential water dissociation pathway in which the O—O bond forms on a single metal site, not via coupling of two adsorbed intermediates, by fitting measured polarization curves using a kinetic equation with the free energies of adsorption and activation as the parameters. Consistent with theoretical calculations, we show that the OER activities of IrO 2 and RuO 2@IrO 2 are limited by the formation of O adsorbed phase, while the OOH formation on the adsorbed O limits the reaction rate on RuO 2.« less

  8. Reaction mechanism for oxygen evolution on RuO 2, IrO 2, and RuO 2@IrO 2 core-shell nanocatalysts

    DOE PAGES

    Ma, Zhong; Zhang, Yu; Liu, Shizhong; ...

    2017-10-28

    Iridium dioxide, IrO 2, is second to the most active RuO 2 catalyst for the oxygen evolution reaction (OER) in acid, and is used in proton exchange membrane water electrolyzers due to its high durability. In order to improve the activity of IrO 2-based catalysts, we prepared RuO 2@IrO 2 core-shell nanocatalysts using carbon-supported Ru as the template. At 1.48 V, the OER specific activity of RuO 2@IrO 2 is threefold that of IrO 2. While the activity volcano plots over wide range of materials have been reported, zooming into the top region to clarify the rate limiting steps ofmore » most active catalysts is important for further activity enhancement. Here, we verified theory-proposed sequential water dissociation pathway in which the O—O bond forms on a single metal site, not via coupling of two adsorbed intermediates, by fitting measured polarization curves using a kinetic equation with the free energies of adsorption and activation as the parameters. Consistent with theoretical calculations, we show that the OER activities of IrO 2 and RuO 2@IrO 2 are limited by the formation of O adsorbed phase, while the OOH formation on the adsorbed O limits the reaction rate on RuO 2.« less

  9. Depth resolved lattice-charge coupling in epitaxial BiFeO3 thin film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Hyeon Jun; Lee, Sung Su; Kwak, Jeong Hun

    2016-12-01

    For epitaxial films, a critical thickness (t c) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the tc in BiFeO 3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO 3/SrRuO 3/SrTiO 3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO 3 film was resolved into a strained layer with an extremely low piezoelectric coefficientmore » of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical coupling.« less

  10. Depth resolved lattice-charge coupling in epitaxial BiFeO3 thin film

    PubMed Central

    Lee, Hyeon Jun; Lee, Sung Su; Kwak, Jeong Hun; Kim, Young-Min; Jeong, Hu Young; Borisevich, Albina Y.; Lee, Su Yong; Noh, Do Young; Kwon, Owoong; Kim, Yunseok; Jo, Ji Young

    2016-01-01

    For epitaxial films, a critical thickness (tc) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the tc in BiFeO3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO3/SrRuO3/SrTiO3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO3 film was resolved into a strained layer with an extremely low piezoelectric coefficient of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical coupling. PMID:27929103

  11. Electro-oxidation of methanol and ethanol using PtRu/C, PtSn/C and PtSnRu/C electrocatalysts prepared by an alcohol-reduction process

    NASA Astrophysics Data System (ADS)

    Neto, Almir Oliveira; Dias, Ricardo R.; Tusi, Marcelo M.; Linardi, Marcelo; Spinacé, Estevam V.

    PtRu/C, PtSn/C and PtSnRu/C electrocatalysts were prepared by the alcohol reduction process using ethylene glycol as the solvent and reduction agent and Vulcan Carbon XC72 as the support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry. The electrochemical oxidation of methanol and ethanol were studied by chronoamperometry using a thin porous coating technique. The PtSn/C electrocatalyst prepared by this methodology showed superior performance compared to the PtRu/C and PtSnRu/C electrocatalysts for methanol and ethanol oxidation at room temperature.

  12. The Ruthenostannylene Complex [Cp*(IXy)H2 Ru-Sn-Trip]: Providing Access to Unusual Ru-Sn Bonded Stanna-imine, Stannene, and Ketenylstannyl Complexes.

    PubMed

    Liu, Hsueh-Ju; Ziegler, Micah S; Tilley, T Don

    2015-05-26

    Reactivity studies of the thermally stable ruthenostannylene complex [Cp*(IXy)(H)2 Ru-Sn-Trip] (1; IXy=1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene; Cp*=η(5) -C5 Me5 ; Trip=2,4,6-iPr3 C6 H2 ) with a variety of organic substrates are described. Complex 1 reacts with benzoin and an α,β-unsaturated ketone to undergo [1+4] cycloaddition reactions and afford [Cp*(IXy)(H)2 RuSn(κ(2) -O,O-OCPhCPhO)Trip] (2) and [Cp*(IXy)(H)2 RuSn(κ(2) -O,C-OCPhCHCHPh)Trip] (3), respectively. The reaction of 1 with ethyl diazoacetate resulted in a tin-substituted ketene complex [Cp*(IXy)(H)2 RuSn(OC2 H5 )(CHCO)Trip] (4), which is most likely a decomposition product from the putative ruthenium-substituted stannene complex. The isolation of a ruthenium-substituted stannene [Cp*(IXy)(H)2 RuSn(=Flu)Trip] (5) and stanna-imine [Cp*(IXy)(H)2 RuSn(κ(2) -N,O-NSO2 C6 H4 Me)Trip] (6) complexes was achieved by treatment of 1 with 9-diazofluorene and tosyl azide, respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Recent progress in the structure control of Pd–Ru bimetallic nanomaterials

    PubMed Central

    Wu, Dongshuang; Kusada, Kohei; Kitagawa, Hiroshi

    2016-01-01

    Abstract Pd and Ru are two key elements of the platinum-group metals that are invaluable to areas such as catalysis and energy storage/transfer. To maximize the potential of the Pd and Ru elements, significant effort has been devoted to synthesizing Pd–Ru bimetallic materials. However, most of the reports dealing with this subject describe phase-separated structures such as near-surface alloys and physical mixtures of monometallic nanoparticles (NPs). Pd–Ru alloys with homogenous structure and arbitrary metallic ratio are highly desired for basic scientific research and commercial material design. In the past several years, with the development of nanoscience, Pd–Ru bimetallic alloys with different architectures including heterostructure, core-shell structure and solid-solution alloy were successfully synthesized. In particular, we have now reached the stage of being able to obtain Pd–Ru solid-solution alloy NPs over the whole composition range. These Pd–Ru bimetallic alloys are better catalysts than their parent metal NPs in many catalytic reactions, because the electronic structures of Pd and Ru are modified by alloying. In this review, we describe the recent development in the structure control of Pd–Ru bimetallic nanomaterials. Aiming for a better understanding of the synthesis strategies, some fundamental details including fabrication methods and formation mechanisms are discussed. We stress that the modification of electronic structure, originating from different nanoscale geometry and chemical composition, profoundly affects material properties. Finally, we discuss open issues in this field. PMID:27877905

  14. Isonitrile-functionalized ruthenium nanoparticles: intraparticle charge delocalization through Ru=C=N interfacial bonds

    NASA Astrophysics Data System (ADS)

    Zhang, Fengqi; Huang, Lin; Zou, Jiasui; Yang, Jun; Kang, Xiongwu; Chen, Shaowei

    2017-09-01

    Ruthenium nanoparticles (2.06 ± 0.46 nm in diameter) stabilized by 1-hexyl-4-isocyanobenzene (CNBH), denoted as RuCNBH, were prepared by the self-assembly of isonitrile molecules onto the surface of "bare" Ru colloids by virtue of the formation of Ru=C=N- interfacial bonds. FTIR measurements showed that the stretching vibration of the terminal -N≡C bonds at 2119 cm-1 for the monomeric ligands disappeared and concurrently three new bands at 2115, 2043, and 1944 cm-1 emerged with RuCNBH nanoparticles, which was ascribed to the transformation of -N≡C to Ru=C=N- by back donation of Ru-d electrons to the π* orbital of the organic ligands. Metathesis reaction of RuCNBH with vinyl derivatives further corroborated the nature of the Ru=C interfacial bonds. When 1-isocyanopyrene (CNPy) was bounded onto the Ru nanoparticles surface through Ru=C=N interfacial bond (denoted as RuCNPy), the emission maximum was found to red-shift by 27 nm, as compared to that of the CNPy monomers, along with a reduced fluorescence lifetime, due to intraparticle charge delocalization that arose from the conjugated Ru=C=N- interfacial bonds. The results of this study further underline the significance of metal-organic interfacial bonds in the control of intraparticle charge-transfer dynamics and the optical and electronic properties of metal nanoparticles. [Figure not available: see fulltext.

  15. Low leakage Ru-strontium titanate-Ru metal-insulator-metal capacitors for sub-20 nm technology node in dynamic random access memory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Popovici, M., E-mail: Mihaela.Ioana.Popovici@imec.be; Swerts, J.; Redolfi, A.

    2014-02-24

    Improved metal-insulator-metal capacitor (MIMCAP) stacks with strontium titanate (STO) as dielectric sandwiched between Ru as top and bottom electrode are shown. The Ru/STO/Ru stack demonstrates clearly its potential to reach sub-20 nm technology nodes for dynamic random access memory. Downscaling of the equivalent oxide thickness, leakage current density (J{sub g}) of the MIMCAPs, and physical thickness of the STO have been realized by control of the Sr/Ti ratio and grain size using a heterogeneous TiO{sub 2}/STO based nanolaminate stack deposition and a two-step crystallization anneal. Replacement of TiN with Ru as both top and bottom electrodes reduces the amount of electricallymore » active defects and is essential to achieve a low leakage current in the MIM capacitor.« less

  16. Effect of Silicon on the Activity Coefficient of Rhenium in Fe-Si Liquids: Implications for HSE and Os Isotopes in Planetary Mantles

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Yang, S.; Humayun, M.

    2018-01-01

    Metallic cores contain light alloying elements that can be a combination of S, C, Si, and O, all of which have important chemical and physical influences. For Earth, Si may be the most abundant light element in the core. Si dissolved into Fe liquids can have a large effect on the magnitude of the activity coefficient of siderophile elements (SE), and thus the partitioning behavior of those elements between core and mantle. The effect of Si on the highly siderophile elements is only beginning to be studied and the effects on Au, Pd and Pt are significant. Here we report new experiments designed to quantify the effect of Si on the partitioning of Re between metal and silicate melt. A solid understanding of Re partitioning is required for a complete understanding of the Re-Os isotopic systems. The results will be applied to understanding the HSEs and Os isotopic data for planetary mantles, and especially Earth.

  17. OsWRKY74, a WRKY transcription factor, modulates tolerance to phosphate starvation in rice.

    PubMed

    Dai, Xiaoyan; Wang, Yuanyuan; Zhang, Wen-Hao

    2016-02-01

    The WRKY transcription factor family has 109 members in the rice genome, and has been reported to be involved in the regulation of biotic and abiotic stress in plants. Here, we demonstrated that a rice OsWRKY74 belonging to group III of the WRKY transcription factor family was involved in tolerance to phosphate (Pi) starvation. OsWRKY74 was localized in the nucleus and mainly expressed in roots and leaves. Overexpression of OsWRKY74 significantly enhanced tolerance to Pi starvation, whereas transgenic lines with down-regulation of OsWRKY74 were sensitive to Pi starvation. Root and shoot biomass, and phosphorus (P) concentration in rice OsWRKY74-overexpressing plants were ~16% higher than those of wild-type (WT) plants in Pi-deficient hydroponic solution. In soil pot experiments, >24% increases in tiller number, grain weight and P concentration were observed in rice OsWRKY74-overexpressing plants compared to WT plants when grown in P-deficient medium. Furthermore, Pi starvation-induced changes in root system architecture were more profound in OsWRKY74-overexpressing plants than in WT plants. Expression patterns of a number of Pi-responsive genes were altered in the OsWRKY74-overexpressing and RNA interference lines. In addition, OsWRKY74 may also be involved in the response to deficiencies in iron (Fe) and nitrogen (N) as well as cold stress in rice. In Pi-deficient conditions, OsWRKY74-overexpressing plants exhibited greater accumulation of Fe and up-regulation of the cold-responsive genes than WT plants. These findings highlight the role of OsWRKY74 in modulation of Pi homeostasis and potential crosstalk between P starvation and Fe starvation, and cold stress in rice. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  18. Ambipolar thermoelectric power of chemically-exfoliated RuO2 nanosheets

    NASA Astrophysics Data System (ADS)

    Kim, Jeongmin; Yoo, Somi; Moon, Hongjae; Kim, Se Yun; Ko, Dong-Su; Roh, Jong Wook; Lee, Wooyoung

    2018-01-01

    The electrical conductivity and Seebeck coefficient of RuO2 nanosheets are enhanced by metal nanoparticle doping using Ag-acetate solutions. In this study, RuO2 monolayer and bilayer nanosheets exfoliated from layered alkali metal ruthenates are transferred to Si substrates for device fabrication, and the temperature dependence of their conductivity and Seebeck coefficients is investigated. For pristine RuO2 nanosheets, the sign of the Seebeck coefficient changes with temperature from 350-450 K. This indicates that the dominant type of charge carrier is dependent on the temperature, and the RuO2 nanosheets show ambipolar carrier transport behavior. By contrast, the sign of the Seebeck coefficient for Ag nanoparticle-doped RuO2 nanosheets does not change with temperature, indicating that the extra charge carriers from metal nanoparticles promote n-type semiconductor behavior.

  19. Elaboration of a Highly Porous RuII,II Analogue of HKUST-1.

    PubMed

    Zhang, Wenhua; Freitag, Kerstin; Wannapaiboon, Suttipong; Schneider, Christian; Epp, Konstantin; Kieslich, Gregor; Fischer, Roland A

    2016-12-19

    When the dinuclear Ru II,II precursor [Ru 2 (OOCCH 3 ) 4 ] is employed under redox-inert conditions, a Ru II,II analogue of HKUST-1 was successfully prepared and characterized as a phase-pure microcrystalline powder. X-ray absorption near-edge spectroscopy confirms the oxidation state of the Ru centers of the paddle-wheel nodes in the framework. The porosity of 1371 m 2 /mmol of Ru II,II -HKUST-1 exceeds that of the parent compound HKUST1 (1049 m 2 / mmol).

  20. Magnetic Excitations in α-RuCl3

    NASA Astrophysics Data System (ADS)

    Nagler, Stephen; Banerjee, Arnab; Bridges, Craig; Yan, Jiaqiang; Mandrus, David; Stone, Matthew; Aczel, Adam; Li, Ling; Yiu, Yuen; Lumsden, Mark; Knolle, Johannes; Moessner, Roderich; Tennant, Alan

    2015-03-01

    The layered material α-RuCl3 is composed of stacks of weakly coupled honeycomb lattices of octahedrally coordinated Ru3+ ions. The Ru ion ground state has 5 d electrons in the low spin state, with spin-orbit coupling very strong compared to other terms in the single ion Hamiltonian. The material is therefore an excellent candidate for investigating possible Heisenberg-Kitaev physics. In addition, this compound is very amenable to investigation by neutron scattering to explore the magnetic ground state and excitations in detail. Here we discuss new time-of-flight inelastic neutron scattering data on α-RuCl3. A high energy excitation near 200 meV is identified as a transition from the single ion J=1/2 ground state to the J=3/2 excited state, yielding a direct measurement of the spin orbit coupling energy. Higher resolution measurements reveal two collective modes at much lower energy scales. The results are compared with the theoretical expectations for excitations in the Heisenberg - Kitaev model on a honeycomb lattice, and show that Kitaev interactions are important. Research at SNS supported by the DOE BES Scientific User Facilities Division.

  1. Superconductivity and Competing Ordered Phase in RuPn (Pn = As, P)

    NASA Astrophysics Data System (ADS)

    Hirai, Daigorou; Takayama, Tomohiro; Hashizume, Daisuke; Yamamoto, Ayako; Takagi, Hidenori

    2011-03-01

    Unconventional superconductivity likely manifests itself when some competing electronic phases are suppressed down to zero temperature such as cuprates and iron-pnictide superconductors. Therefore, the correlated metallic state neighboring a competing electronic ordering can be a promising playground for unconventional superconductivity. Here we report superconductivity emerging adjacent to electronically ordered phases of RuPn (Pn = As, P). We found that RuAs(P) exhibits phase transitions at 240 (265) K, which is discerned as a drop of magnetic susceptibility or a resistivity upturn. Such anomalies can be suppressed by substituting Rh to the Ru site. Accompanied by the disappearance of the electronic order, superconductivity was found to emerge below 1.8 K and 3.8 K for RuAs and RuP, respectively. The superconductivity in Rh substituted RuPn, which neighbors a competing electronic order, might exhibit an exotic pairing state as seen in the unconventional superconductors known to date.

  2. CaFe interstellar clouds

    NASA Astrophysics Data System (ADS)

    Bondar, A.; Kozak, M.; Gnaciński, P.; Galazutdinov, G. A.; Beletsky, Y.; Krełowski, J.

    2007-07-01

    A new kind of interstellar cloud is proposed. These are rare (just a few examples among ~300 lines of sight) objects with the CaI 4227-Å, FeI 3720-Å and 3860-Å lines stronger than those of KI (near 7699 Å) and NaI (near 3302 Å). We propose the name `CaFe' for these clouds. Apparently they occupy different volumes from the well-known interstellar HI clouds where the KI and ultraviolet NaI lines are dominant features. In the CaFe clouds we have not found either detectable molecular features (CH, CN) or diffuse interstellar bands which, as commonly believed, are carried by some complex, organic molecules. We have found the CaFe clouds only along sightlines toward hot, luminous (and thus distant) objects with high rates of mass loss. In principle, the observed gas-phase interstellar abundances reflect the combined effects of the nucleosynthetic history of the material, the depletion of heavy elements into dust grains and the ionization state of these elements which may depend on irradiation by neighbouring stars. Based on data collected using the Maestro spectrograph at the Terskol 2-m telescope, Russia; and on data collected using the ESO Feros spectrograph; and on data obtained from the ESO Science Archive Facility acquired with the UVES spectrograph, Chile. E-mail: `arctur'@rambler.ru (AB); marizak@astri.uni.torun.pl (MK); pg@iftia.univ.gda.pl (PG); gala@boao.re.kr (GAG); ybialets@eso.org (YB); jacek@astri.uni.torun.pl (JK)

  3. RU 486 in France and England: corporate ethics and compulsory licensing.

    PubMed

    Boland, R

    1992-01-01

    Prospects for the introduction of RU-486 into the US in the foreseeable future are not good. The governments of France and England moved forward expeditiously with testing and approval of the drug. The legal developments surrounding the introduction of RU-486 in France and England as well as American, French, and English legal issues of corporate responsibility for licensing valuable drugs and compulsory licensing are outlined. The French government on October 28, 1988, ordered the company Roussel-Uclaf to resume plans to distribute RU-486 out of concern for public health and stated that RU-486 was the moral property of women. Roussel-Uclaf agreed to resume plans for distribution. RU-486 suits were finally decided in late 1990 and early 1991 by the State Council, France's highest administrative court, which issued a series of significant rulings. The French government issued new rules prohibiting the use of RU-486 by women who are heavy smokers or over 35 years old and modifying the dose of prostaglandin to be administered because of an RU-486-related death of an overweight 31-year old woman. In England, RU-486 was initially approved in July 1991. The conditions set were similar to those in France: the drug would have be used within 9 weeks of amenorrhea, as opposed to 7 in France; women over 35 or moderate to heavy smokers would be ineligible; and visits 36-48 hours later would be necessary to have a prostaglandin administered with check ups 7-10 days later. The hostility of the current US administration to the introduction of RU-486 blocks access to the drug. In 1989, the Food and Drug Administration placed reluctant to enter the American market. Under the Bush administration there is little possibility that the American government will act and take an active role in facilitating access to RU-486.

  4. Adsorption of n-butane on graphene/Ru(0001)—A molecular beam scattering study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sivapragasam, Nilushni; Nayakasinghe, Mindika T.; Burghaus, Uwe, E-mail: uwe.burghaus@ndsu.edu

    2016-07-15

    Adsorption kinetics/dynamics of n-butane on graphene, physical vapor deposited on Ru(0001) (hereafter G/Ru), and bare Ru(0001) (hereafter Ru) are discussed. The chemical activity of the supported-graphene as well as the support was probed by thermal desorption spectroscopy (adsorption kinetics). In addition and to the best of our knowledge, for the first time, molecular beam scattering data of larger molecules were collected for graphene (probing the adsorption dynamics). Furthermore, samples were inspected by x-ray photoelectron spectroscopy and Auger electron spectroscopy. At the measuring conditions used here, n-butane adsorption kinetics/dynamics are molecular and nonactivated. Binding energies of butane on Ru and G/Rumore » are indistinguishable within experimental uncertainty. Thus, G/Ru is “kinetically transparent.” Initial adsorption probabilities, S{sub 0}, of n-butane decrease with increasing impact energy (0.76–1.72 eV) and are adsorption temperature independent for both Ru and G/Ru, again consistent with molecular adsorption. Also, S{sub 0} of Ru and G/Ru are indistinguishable within experimental uncertainty. Thus, G/Ru is “dynamically transparent.” Coverage dependent adsorption probabilities indicate precursor effects for graphene/Ru.« less

  5. The chemistry of (ring)Ru sup 2+ (ring = tetramethylthiophene, p-cymene)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ganja, E.A.; Rauchfuss, T.B.; Stern, C.L.

    1991-01-01

    Described are the compounds ((ring)Ru(OTf){sub 2}){sub x}, where ring = 2,3,4,5-tetramethylthiophene (TMT, 1), and p-cymene (2). These electrophilic reagents serve as precursors to ((ring)RuL{sub 3}){sup 2+}, where L{sub 3} = (H{sub 2}O){sub 3}, (NH{sub 3}){sub 3}, and (PH{sub 3}){sub 3}. Solutions of 1 and 2 react with carbon monoxide to give (ring)Ru(CO)(OTf){sub 2}. The addition of thiophenes to CH{sub 2}Cl{sub 2} solutions of 1 or 2 leads to the precipitation of the sandwich compounds ((ring)(SC{sub 4}R{sub 4})Ru)(OTf){sub 2}, where SC{sub 4}R{sub 4} = thiophene, 2,5-dimethylthiophene, and TMT. ((TMT)Ru(H{sub 2}O){sub 3})(OTf){sub 2} was characterized by single-crystal X-ray crystallography, which established amore » piano-stool geometry with a planar TMT ligand. ((TMT)Ru(D{sub 2}O){sub 3})(OTf){sub 2} decomposes in D{sub 2}O solution at 150C to give ((TMT){sub 2}Ru){sup 2+}, which undergoes selective deuteration at the 2,5-methyl groups. D{sub 2}O solutions of ((TMT){sub 2}Ru){sup 2+} undergo photochemical loss of one TMT ligand in water to give ((TMT)Ru(H{sub 2}O){sub 3}){sup 2+}. A procedure is described for the reversible loading of 1 onto {gamma}-alumina, which in turn was characterized by {sup 13}C CP-MAS NMR spectroscopy.« less

  6. Incorporation of organometallic Ru complexes into apo-ferritin cage.

    PubMed

    Takezawa, Yusuke; Böckmann, Philipp; Sugi, Naoki; Wang, Ziyue; Abe, Satoshi; Murakami, Tatsuya; Hikage, Tatsuo; Erker, Gerhard; Watanabe, Yoshihito; Kitagawa, Susumu; Ueno, Takafumi

    2011-03-14

    Spherical protein cages such as an iron storage protein, ferritin, have great potential as nanometer-scale capsules to assemble and store metal ions and complexes. We report herein the synthesis of a composite of an apo-ferritin cage and Ru(p-cymene) complexes. Ru complexes were efficiently incorporated into the ferritin cavity without degradation of its cage structure. X-Ray crystallography revealed that the Ru complexes were immobilized on the interior surface of the cage mainly by the coordination of histidine residues.

  7. NOVEL RU-NI-S ELECTRODE CATALYST FOR PEMFC

    EPA Science Inventory

    The expected results from this project include:

    • a new formula and preparation procedures for Ru-Ni-S catalyst;
    • demonstration of CO and S tolerance of the new catalyst;
    • a small size PEMFC with Ru-Ni-S catalyst and good performance; an...

    • In situ growth of NiFe alloy nanoparticles embedded into N-doped bamboo-like carbon nanotube as a bifunctional electrocatalyst for Zn-air battery.

      PubMed

      Bin, Duan; Yang, Beibei; Li, Chao; Liu, Yao; Zhang, Xiao; Wang, Yong-Gang; Xia, Yongyao

      2018-06-26

      Developing low-cost catalysts for electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with superior performance in alkaline solution is of significance for large-scale application in aqueous zinc-air batteries (ZABs). Herein, we describe in situ design of embedded NiFe nanoparticles into the N-doped bamboo-like carbon nanotube (NBCNT) with high catalytic performance and stability. The obtained NiFe@NBCNT hybrid exhibits a high electrochemical activity and stability with an unexpectedly low overpotential of ~195 mV for OER at 10 mA cm-2, and an onset potential at 1.03 V for ORR, superior to the state-of-the-art Pt/C and RuO2 catalysts. Additionally, compared to the mixture Pt/C and RuO2 cathode, the ZAB based on the NiFe@NBCNT cathode displays lower overpotential (0.80 V), higher stable round-trip efficiency (58.3%) and improved power density for 200 cycles at 10 mA cm-2. Apparently, the obtained results indicate that NiFe@NBCNT hybird is proven to be one of the best non-noble metal catalysts for achieving commercial implementation of rechargeable ZABs.

    • Direct evidence for double-exchange coupling in Ru- substituted La0.7Pb0.3Mn 1 - x Ru x O3, 0.0 <= x <= 0.4

      NASA Astrophysics Data System (ADS)

      Sundar Manoharan, S.; Sahu, R. K.; Rao, M. L.; Elefant, D.; Schneider, C. M.

      2002-08-01

      The La0.7Pb0.3Mn 1 - x Ru x O3 (0.0 <= x <= 0.4) system shows an innate relationship between Mn and Ru ions by a unique double-exchange mediated transport behavior. This is exonerated by the coexistence of Tp and Tc (range 330 K 245 K for 0.0 <= x <= 0.4). For Ru > 30%, the hole carrier mass influences the transport property. X-ray absorption spectra suggest that the Tc-Tp match is due to the transport mediated by the Mn3+/Mn4+ leftrightarrow Ru4+/Ru5+ redox pair and also due to the broad low-spin Ru:4d conduction band. For x > 0.2, T < 0.5Tc obeys a modified variable-range hopping model, where kT0 propto (M/Ms)2, suggesting a random magnetic potential which localizes the charge carriers.

    • Synthesis of Pd 9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

      DOE Office of Scientific and Technical Information (OSTI.GOV)

      Sun, Yu; Hsieh, Yu -Chi; Chang, Li -Chung

      2014-11-22

      Nanoparticles of PdRu, Pd₃Ru, and Pd₉Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, Pd xRu/C (x=1/3/9), suggest succesful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of Pd xRu/C. Among these samples, the Pd₉Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in anmore » oxygen-saturated 0.1 M aqueous HClO₄ solution. Subsequently, the Pd₉Ru/C undegoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd₉Ru surface (Pd₉Ru@Pt). The Pd₉Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg⁻¹ Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg⁻¹ Pt). Thus, the mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd₉Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.« less

    • Synthesis of Pd9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

      NASA Astrophysics Data System (ADS)

      Sun, Yu; Hsieh, Yu-Chi; Chang, Li-Chung; Wu, Pu-Wei; Lee, Jyh-Fu

      2015-03-01

      Nanoparticles of PdRu, Pd3Ru, and Pd9Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, PdxRu/C (x = 1/3/9), suggest successful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of PdxRu/C. Among these samples, the Pd9Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in an oxygen-saturated 0.1 M aqueous HClO4 solution. Subsequently, the Pd9Ru/C undergoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd9Ru surface (Pd9Ru@Pt). The Pd9Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg-1Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg-1Pt). The mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd9Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.

    • MoRu/Be multilayers for extreme ultraviolet applications

      DOEpatents

      Bajt, Sasa C.; Wall, Mark A.

      2001-01-01

      High reflectance, low intrinsic roughness and low stress multilayer systems for extreme ultraviolet (EUV) lithography comprise amorphous layers MoRu and crystalline Be layers. Reflectance greater than 70% has been demonstrated for MoRu/Be multilayers with 50 bilayer pairs. Optical throughput of MoRu/Be multilayers can be 30-40% higher than that of Mo/Be multilayer coatings. The throughput can be improved using a diffusion barrier to make sharper interfaces. A capping layer on the top surface of the multilayer improves the long-term reflectance and EUV radiation stability of the multilayer by forming a very thin native oxide that is water resistant.

    • Orientation-Dependent Oxygen Evolution on RuO 2 without Lattice Exchange

      DOE Office of Scientific and Technical Information (OSTI.GOV)

      Stoerzinger, Kelsey A.; Diaz-Morales, Oscar; Kolb, Manuel

      RuO2 catalysts exhibit record activities towards the oxygen evolution reaction (OER), which is crucial to enable efficient and sustainable energy storage. Here we examine the RuO2 OER kinetics on rutile (110), (100), (101), and (111) orientations, finding (100) the most active. We assess the potential involvement of lattice oxygen in the OER mechanism with online 3 electrochemical mass spectrometry, which showed no evidence of oxygen exchange on these oriented facets in acidic or basic electrolytes. Similar results were obtained for polyoriented RuO2 films and particles, in contrast to previous work, suggesting lattice oxygen is not exchanged in catalyzing OER onmore » crystalline RuO2 surfaces. This hypothesis is supported by the correlation of activity with the number of active Ru-sites calculated by DFT, where more active facets bind oxygen more weakly. This new understanding of the active sites provides a design strategy to enhance the OER activity of RuO2 nanoparticles by facet engineering.« less

    • Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

      NASA Astrophysics Data System (ADS)

      Grabow, Lars C.; Yuan, Qiuyi; Doan, Hieu A.; Brankovic, Stanko R.

      2015-10-01

      A single layer, bi-metallic RuPt catalyst on Au(111) is synthesized using surface limited red-ox replacement of underpotentially deposited Cu and Pb monolayers though a two-step process. The resulting 2D RuPt monolayer nanoclusters have a unique core-edge structure with a Ru core and Pt at the edge along the perimeter. The activity of this catalyst is evaluated using CO monolayer oxidation as the probe reaction. Cyclic voltammetry demonstrates that the 2D RuPt core-edge catalyst morphology is significantly more active than either Pt or Ru monolayer catalysts. Density functional theory calculations in combination with infra-red spectroscopy data point towards oscillating variations (ripples) in the adsorption energy landscape along the radial direction of the Ru core as the origin of the observed behavior. Both, CO and OH experience a thermodynamic driving force for surface migration towards the Ru-Pt interface, where they adsorb most strongly and react rapidly. We propose that the complex interplay between epitaxial strain, ligand and finite size effects is responsible for the formation of the rippled RuPt monolayer cluster, which provides optimal conditions for a quasi-ideal bi-functional mechanism for CO oxidation, in which CO is adsorbed mainly on Pt, and Ru provides OH to the active Pt-Ru interface.

    • "Job-Sharing" Storage of Hydrogen in Ru/Li₂O Nanocomposites.

      PubMed

      Fu, Lijun; Tang, Kun; Oh, Hyunchul; Manickam, Kandavel; Bräuniger, Thomas; Chandran, C Vinod; Menzel, Alexander; Hirscher, Michael; Samuelis, Dominik; Maier, Joachim

      2015-06-10

      A "job-sharing" hydrogen storage mechanism is proposed and experimentally investigated in Ru/Li2O nanocomposites in which H(+) is accommodated on the Li2O side, while H(-) or e(-) is stored on the side of Ru. Thermal desorption-mass spectroscopy results show that after loading with D2, Ru/Li2O exhibits an extra desorption peak, which is in contrast to Ru nanoparticles or ball-milled Li2O alone, indicating a synergistic hydrogen storage effect due to the presence of both phases. By varying the ratio of the two phases, it is shown that the effect increases monotonically with the area of the heterojunctions, indicating interface related hydrogen storage. X-ray diffraction, Fourier transform infrared spectroscopy, and nuclear magnetic resonance results show that a weak LiO···D bond is formed after loading in Ru/Li2O nanocomposites with D2. The storage-pressure curve seems to favor H(+)/H(-) over H(+)/e(-) mechanism.

    • Magnetic moment in single crystalline BaFe2-xZnxAs2

      NASA Astrophysics Data System (ADS)

      Guo, Yanfeng; Wang, Xia; Li, Jun; Yamaura, Kazunari; Takayama-Muromachi, Eiji

      2012-02-01

      Nature of the magnetism for iron-based superconductors (FeSCs) has been actively studied since the discovery of this new family of compounds in 2008, largely owing to its significance for interpreting the paring mechanism. The approach through impurity substitution to shed light into this issue is always one of major ways. The substitution shows distinct responses to species of impurities, where partially replacement of Fe in parent FeSCs with a variety of d-metals like Co, Ni Ru, Rh, Pd, Ir, and Pt generally results in superconductivity, while recent progress in Zn doped FeSCs gives rather contrary result, where Zn severely degenerates the TC. Herein we show the magnetic and electrical studies on BaFe2-xZnxAs2 single crystals. Nonmagnetic Zn doping progressively suppresses the SDW without resulting in superconductivity, while it alternatively develops the spin-glass state, possibly suggestive of local magnetic moment around the Fe sites induced by Zn. The characterizations by X-ray diffraction, magnetic and electrical transport properties, specific heat capacity, and Hall coefficient have been done and the results will be discussed in detail.

    • Ru-N-C Hybrid Nanocomposite for Ammonia Dehydrogenation: Influence of N-doping on Catalytic Activity

      PubMed Central

      Hien, Nguyen Thi Bich; Kim, Hyo Young; Jeon, Mina; Lee, Jin Hee; Ridwan, Muhammad; Tamarany, Rizcky; Yoon, Chang Won

      2015-01-01

      For application to ammonia dehydrogenation, novel Ru-based heterogeneous catalysts, Ru-N-C and Ru-C, were synthesized via simple pyrolysis of a mixture of RuCl3·6H2O and carbon black with or without dicyandiamide as a nitrogen-containing precursor at 550 °C. Characterization of the prepared Ru-N-C and Ru-C catalysts via scanning transmission electron microscopy, in conjunction with energy dispersive X-ray spectroscopy, indicated the formation of hollow nanocomposites in which the average sizes of the Ru nanoparticles were 1.3 nm and 5.1 nm, respectively. Compared to Ru-C, the Ru-N-C nanocomposites not only proved to be highly active for ammonia dehydrogenation, giving rise to a NH3 conversion of >99% at 550 °C, but also exhibited high durability. X-ray photoelectron spectroscopy revealed that the Ru active sites in Ru-N-C were electronically perturbed by the incorporated nitrogen atoms, which increased the Ru electron density and ultimately enhanced the catalyst activity.

    • RuO2 Thermometer for Ultra-Low Temperatures

      NASA Technical Reports Server (NTRS)

      Hait, Thomas; Shirron, Peter J.; DiPirro, Michael

      2009-01-01

      A small, high-resolution, low-power thermometer has been developed for use in ultra-low temperatures that uses multiple RuO2 chip resistors. The use of commercially available thick-film RuO2 chip resistors for measuring cryogenic temperatures is well known due to their low cost, long-term stability, and large resistance change.

    • Constructing molecular structures on periodic superstructure of graphene/Ru(0001)

      PubMed Central

      Li, Geng; Huang, Li; Xu, Wenyan; Que, Yande; Zhang, Yi; Lu, Jianchen; Du, Shixuan; Liu, Yunqi; Gao, Hong-Jun

      2014-01-01

      We review the way to fabricate large-scale, high-quality and single crystalline graphene epitaxially grown on Ru(0001) substrate. A moiré pattern of the graphene/Ru(0001) is formed due to the lattice mismatch between graphene and Ru(0001). This superstructure gives rise to surface charge redistribution and could behave as an ordered quantum dot array, which results in a perfect template to guide the assembly of organic molecular structures. Molecules, for example iron phthalocyanine and C60, on this template show how the molecule–substrate interaction makes different superstructures. These results show the possibility of constructing ordered molecular structures on graphene/Ru(0001), which is helpful for practical applications in the future. PMID:24615151

    • The search for meaning: RU 486 and the law of abortion.

      PubMed Central

      Banwell, S S; Paxman, J M

      1992-01-01

      The advent of RU 486 (mifepristone), a steroid analogue capable of inducing menses within 8 to 10 weeks of a missed menstrual period, has provoked a firestorm of concern and controversy. When used in conjunction with prostaglandin (RU 486/PG), it is at least 95% effective. Used in France principally to terminate confirmed pregnancies very early in the process of gestation, RU 486 raises many interesting legal questions. This article focuses on whether and how RU 486/PG can be accommodated within the framework of the world's current abortion laws. Four avenues are explored and conclusions drawn. First, it is clear that RU 486/PG can be used readily, if approved, within the regimens established by liberal abortion laws, as has been the experience in France, the United Kingdom, and even China. Second, although unlikely, the introduction of this new technology may inspire a reexamination of restrictive abortion statutes themselves. Third, some of the presently restrictive laws may be interpreted to permit RU 486/PG use as a legal procedure, for a very narrow range of reasons. Finally, in some settings the early use of RU 486/PG (before pregnancy can be confirmed) may fall outside the reach of abortion legislation and hence be acceptable from a legal point of view. PMID:1415870

  1. Estrogen and progesterone receptors in human decidua after RU486 treatment.

    PubMed

    Shi, W L; Wang, J D; Fu, Y; Zhu, P D

    1993-07-01

    To examine RU486 action on decidua at the level of cellular estrogen receptor (ER) and P receptor (PR). Controlled basic study for contragestion mechanism of mifepristone. Normal human volunteers in an academic research environment. Sixty women with 6 to 7 weeks of gestation who voluntarily requested termination of pregnancy were recruited and randomly divided into three groups. A single dose of 200 mg RU486 was orally administered to the two treatment groups 12 and 24 hours, respectively, before surgical interruption of pregnancies. Placebo was used for control group. Decidual tissues were collected right after operation. Immunocytochemical reactions of PR and ER in decidua after RU486 treatment were compared with the control subjects. The differences of the reaction in decidual area with or without trophoblast invasion were noted. RU486 treatment increased PR and ER staining in vessel and stroma of decidua without trophoblast invasion (decidua parietalis) but not in decidua with trophoblast invasion (decidua capsularis or basalis). Chi-squared analysis indicated a significant increase in the number of ER-positive samples after RU486 treatment. The decidua parietalis was the primary target site of RU486. The lack of RU486 effect on decidua capsularis implied that trophoblast invasion prevented against antiprogestin impact.

  2. Gigantic perpendicular magnetic anisotropy of heavy transition metal cappings on Fe/MgO(0 0 1)

    NASA Astrophysics Data System (ADS)

    Taivansaikhan, P.; Odkhuu, D.; Rhim, S. H.; Hong, S. C.

    2017-11-01

    Effects of capping layer by 5d transition metals (TM = Hf, Ta, W, Re, Os, Ir, Pt, and Au) on Fe/MgO(0 0 1), a typical magnetic tunneling junction, are systematically investigated using first-principles calculation for magnetism and magnetocrystalline-anisotropy (MCA). The early TMs having less than half-filled d bands favor magnetization antiparallel to Fe, whereas the late TMs having more than half-filled d bands favor parallel, which is explained in the framework of kinetic exchange energy. The Os capping, isovalent to Fe, enhances MCA significantly to gigantic energy of +11.31 meV/cell, where positive contribution is mostly from the partially filled majority d bands of magnetic quantum number of |m| = 1 along with stronger spin-orbit coupling of Os than Fe. Different TM cappings give different MCA energies as the Fermi level shifts according to the valence of TM: Re and Ir, just one valence more or less than Os, have still large PMCA but smaller than the Os. In the W and Pt cappings, valence difference by two, PMCA are further reduced; MCAs are lowered compared to Fe/MgO(0 0 1) by the cappings of the very early TMs (Hf and Ta), while the very late TM (Au) switches sign to in-plane MCA.

  3. Synthesis, spectral and electrochemical studies of binuclear Ru(III) complexes containing dithiosemicarbazone ligand

    NASA Astrophysics Data System (ADS)

    Kanchana Devi, A.; Ramesh, R.

    2014-01-01

    Synthesis of several new octahedral binuclear ruthenium(III) complexes of the general composition [(EPh3)2(X)Ru-L-Ru(X)(EPh3)2] containing benzene dithiosemicarbazone ligands (where E = P or As; X = Cl or Br; L = binucleating ligands) is presented. All the complexes have been fully characterized by elemental analysis, FT-IR, UV-vis and EPR spectroscopy together with magnetic susceptibility measurements. IR study shows that the dithiosemicarbazone ligands behave as dianionic tridentate ligands coordinating through the oxygen atom of the deprotonated phenolic group, nitrogen atom of the azomethine group and thiolate sulphur. In DMF solution, all the complexes exhibit intense d-d transition and ligand-to-metal charge transfer (LMCT) transition in the visible region. The magnetic moment values of the complexes are in the range 1.78-1.82 BM, which reveals the presence of one unpaired electron on each metal ion. The EPR spectra of the liquid samples at LNT show the presence of three different 'g' values (gx ≠ gy ≠ gz) indicate a rhombic distortion around the ruthenium ion. All the complexes exhibit two quasi-reversible one electron oxidation responses (RuIII-RuIII/RuIII-RuIV; RuIII-RuIV/RuIV-RuIV) within the E1/2 range of 0.61-0.74 V and 0.93-0.98 V respectively, versus Ag/AgCl.

  4. Electron transfer reactivity of the aqueous iron(IV)–oxo complex. Outer-sphere vs proton-coupled electron transfer

    DOE PAGES

    Bataineh, Hajem; Pestovsky, Oleg; Bakac, Andreja

    2016-06-18

    Here, the kinetics of oxidation of organic and inorganic reductants by aqueous iron(IV) ions, Fe IV(H 2O) 5O 2+ (hereafter Fe IV aqO 2+), are reported. The substrates examined include several water-soluble ferrocenes, hexachloroiridate(III), polypyridyl complexes M(NN) 3 2+ (M = Os, Fe and Ru; NN = phenanthroline, bipyridine and derivatives), HABTS–/ABTS 2–, phenothiazines, Co II(dmgBF 2) 2, macrocyclic nickel(II) complexes, and aqueous cerium(III). Most of the reductants were oxidized cleanly to the corresponding one-electron oxidation products, with the exception of phenothiazines which produced the corresponding oxides in a single-step reaction, and polypyridyl complexes of Fe(II) and Ru(II) that generatedmore » ligand-modified products. Fe IV aqO 2+ oxidizes even Ce(III) (E 0 in 1 M HClO 4 = 1.7 V) with a rate constant greater than 10 4 M –1 s –1. In 0.10 M aqueous HClO 4 at 25 °C, the reactions of Os(phen) 3 2+ (k = 2.5 × 10 5 M –1 s –1), IrCl 6 3– (1.6 × 10 6), ABTS 2– (4.7 × 10 7), and Fe(cp)(C 5H 4CH 2OH) (6.4 × 10 7) appear to take place by outer sphere electron transfer (OSET). The rate constants for the oxidation of Os(phen) 3 2+ and of ferrocenes remained unchanged in the acidity range 0.05 < [H+] < 0.10 M, ruling out prior protonation of Fe IV aqO 2+ and further supporting the OSET assignment. A fit to Marcus cross-relation yielded a composite parameter (log k 22 + E 0 Fe/0.059) = 17.2 ± 0.8, where k 22 and E 0 Fe are the self-exchange rate constant and reduction potential, respectively, for the Fe IV aqO 2+/Fe III aqO + couple. Comparison with literature work suggests k 22 < 10 –5 M –1 s –1 and thus E 0(Fe IV aqO 2+/Fe III aqO +) > 1.3 V. For proton-coupled electron transfer, the reduction potential is estimated at E 0 (Fe IV aqO 2+, H +/Fe III aqOH 2+) ≥ 1.95 V.« less

  5. Enhancement of Curie temperature in Mn{sub 2}RuSn by Co substitution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nelson, A.; Huh, Y.; Fuglsby, R.

    2015-04-21

    The Co-substituted Mn{sub 2}RuSn nanomaterials, namely, Mn{sub 2}Ru{sub 0.5}Co{sub 0.5}Sn and Mn{sub 2}Ru{sub 0.35}Co{sub 0.65}Sn have been synthesized and investigated. The presence of Co in the Mn{sub 2}RuSn (a = 6.21 Å) decreased the lattice parameter, where a = 6.14 Å and 6.12 Å for the as prepared Mn{sub 2}Ru{sub 0.5}Co{sub 0.5}Sn and Mn{sub 2}Ru{sub 0.35}Co{sub 0.65}Sn, respectively. The samples show a ferrimagnetic spin order with relatively small coercivities, similar to those of soft magnetic materials. There is a substantial increase in the Curie temperature (T{sub c} = 448 K for Mn{sub 2}Ru{sub 0.5}Co{sub 0.5}Sn and 506 K for Mn{sub 2}Ru{sub 0.35}Co{sub 0.65}Sn) of Mn{sub 2}RuSn (T{sub c} = 272.1 K) due to Comore » substitution, which is a result of strengthening of the positive exchange interaction in this material. These materials are highly stable against heat treatment of up to 450 °C. The first-principles calculations are consistent with our experimentally observed structural and magnetic properties. They also provide insight on how the magnetic and electronic structures change when Ru is replaced with Co in Mn{sub 2}RuSn.« less

  6. Monitoring of RU Peg requested for Swift observations

    NASA Astrophysics Data System (ADS)

    Waagen, Elizabeth O.

    2012-06-01

    Dr. Koji Mukai (Universities Space Research Association/NASA Goddard Space Flight Center) has requested AAVSO observers' assistance in monitoring the SS Cyg-type dwarf nova RU Peg in support of target-of-opportunity observations with the NASA Swift satellite during an outburst. His observations will be targeted during the rise to outburst and during late decline from outburst. Thus, your prompt notification to AAVSO Headquarters of activity in RU Peg will be crucial to the success of this campaign. Dr. Mukai writes: "In the famous AAVSO/EUVE/RXTE campaign on SS Cyg (Mattei et al. 2000JAVSO..28..160M), the hard X-ray flux went up (with a delay) during the rise, then suddenly dropped; there was a corresponding flux enhancement episode during the decline. We know that, during the peak of the outburst, many dwarf novae are hard X-ray fainter than in quiescence (with a few exceptions, like U Gem). However, the hard X-ray enhancement episodes seen in SS Cyg have never been obs! erved in other dwarf novae. We have proposed a hypothesis that this is related to the mass of the accreting white dwarf; only dwarf novae with a relatively massive white dwarf show the hard X-ray enhancement. If that's true, we may well see similar enhancement in RU Peg, which is thought to have a massive white dwarf. Even if this hypothesis is completely wrong, RU Peg is a good target for an SS Cyg-like campaign, since it's X-ray bright during quiescence." Visual and CCD observations (filtered preferred to unfiltered) are appropriate for this campaign. Observers are requested to monitor RU Peg duning minimum, throughout the next outburst, and after return to minimym, and report their observations in a timely manner. If RU Peg appears to be brightening from minimum, please report your observations immediately to the AAVSO. If it is brighter than magnitude 12.3, please also send an email report to Elizabeth Waagen (eowaagen@aavso.org) and Matthew Templeton (matthewt@aavso.org). Please be aware that

  7. Enhanced thermal stability of RuO2/polyimide interface for flexible device applications

    NASA Astrophysics Data System (ADS)

    Music, Denis; Schmidt, Paul; Chang, Keke

    2017-09-01

    We have studied the thermal stability of RuO2/polyimide (Kapton) interface using experimental and theoretical methods. Based on calorimetric and spectroscopic analyses, this inorganic-organic system does not exhibit any enthalpic peaks as well as all bonds in RuO2 and Kapton are preserved up to 500 °C. In addition, large-scale density functional theory based molecular dynamics, carried out in the same temperature range, validates the electronic structure and points out that numerous Ru-C and a few Ru-O covalent/ionic bonds form across the RuO2/Kapton interface. This indicates strong adhesion, but there is no evidence of Kapton degradation upon thermal excitation. Furthermore, RuO2 does not exhibit any interfacial bonds with N and H in Kapton, providing additional evidence for the thermal stability notion. It is suggested that the RuO2/Kapton interface is stable due to aromatic architecture of Kapton. This enhanced thermal stability renders Kapton an appropriate polymeric substrate for RuO2 containing systems in various applications, especially for flexible microelectronic and energy devices.

  8. Multi-band Electronic Structure of Ferromagnetic CeRuPO

    NASA Astrophysics Data System (ADS)

    Takahashi, Masaya; Ootsuki, Daiki; Horio, Masafumi; Arita, Masashi; Namatame, Hirofumi; Taniguchi, Masaki; Saini, Naurang L.; Sugawara, Hitoshi; Mizokawa, Takashi

    2018-04-01

    We have studied the multi-band electronic structure of ferromagnetic CeRuPO (TC = 15 K) by means of angle-resolved photoemission spectroscopy (ARPES). The ARPES results show that three hole bands exist around the zone center and two of them cross the Fermi level (EF). Around the zone corner, two electron bands are observed and cross EF. These hole and electron bands, which can be assigned to the Ru 4d bands, are basically consistent with the band-structure calculation including their orbital characters. However, one of the electron bands with Ru 4d 3z2 - r2 character is strongly renormalized indicating correlation effect due to hybridization with the Ce 4f orbitals. The Ru 4d 3z2 - r2 band changes across TC suggesting that the out-of-plane 3z2 - r2 orbital channel plays essential roles in the ferromagnetism.

  9. Os and HSE of the hot upper mantle beneath southern Tibet: Indian mantle affinity?

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Dale, C. W.; Pearson, D. G.; Niu, Y.; Zhu, D.; Mo, X.

    2011-12-01

    The subduction of the Indian plate (including cratonic continental crust and/or upper mantle) beneath southern Tibet is widely accepted from both geological and geophysical studies. Mantle-derived xenoliths from this region provide a means of directly investigating the mantle underlying the southern part of the plateau. Studies of xenoliths hosted in the Sailipu ultrapotassic volcanic rocks, erupted at ~17 Ma, have indicated that the subcontinental mantle of southern Tibetan Plateau is hot and strongly influenced by metasomatism (Zhao et al., 2008a, b; Liu et al., 2011). Here we report comprehensive EPMA and LA-ICP-MS major and trace element data for the Sailipu xenoliths and also whole rock Os isotope and HSE data in order to constrain the depletion history of the mantle and to identify the presence of any potential Indian cratonic mantle. The xenoliths, ranging in size from 0.5cm to 1.5cm in diameter, are mostly peridotites. The calculated temperatures are 1010-1230°C at the given pressures of ~1.6-2.0 GPa (n=47). These P-T conditions are similar to rift-related upper mantle regimes (e.g. Kenya), indicating the influence of regional extension beneath southern Tibet in the Miocene. A series of compositional discriminations for minerals (Cpx, Opx, Ol, and Phl), e.g. Fo<90, suggest that the xenoliths are non-cratonic spinel-peridotite (cratonic peridotite olivine Fo> ~91), with a clear metasomatic signature We obtained Os isotope data and abundances of highly siderophile elements (HSE, including Os, Ir, Ru, Pt, Pd and Re) on a set of six olivine-dominated peridotite samples from Sailipu volcanics, less than 1 cm in dimension. They allow us to further constrain the nature and state of the upper mantle beneath the southern Tibet. Sailipu samples display low total HSE abundances (Os+Ir+Ru+Pt+Pd+Re) ranging from 8.7 to 25 ppb, with nearly constant Os, Ir , and Ru, but rather varied Pt (2-13), Pd (0.4-5.2), and Re (0.01-0.5). Chondrite-normalised Pd/Ir ratios range from

  10. Mitigation of Cd accumulation in paddy rice (Oryza sativa L.) by Fe fertilization.

    PubMed

    Chen, Zhe; Tang, Ye-Tao; Yao, Ai-Jun; Cao, Jian; Wu, Zhuo-Hao; Peng, Zhe-Ran; Wang, Shi-Zhong; Xiao, Shi; Baker, Alan J M; Qiu, Rong-Liang

    2017-12-01

    Cadmium uptake in rice is believed to be mediated by the Fe transport system. Phyto-available Cd can be changed by Fe fertilization of substrates. This work investigated whether and how Fe fertilization affects mitigation of Cd accumulation in paddy rice. A 90-d soil column experiment was conducted to study the change of Cd and Fe availability in soil after Fe fertilization (ionic and chelated Fe). A low-Cd accumulating cultivar (TY116) and a high-Cd accumulating cultivar (JY841) were grown in two Cd-polluted paddy soils amended with chelated Fe fertilizers. Additionally, both cultivars were grown in hydroponics to compare Fe-related gene expression in EDDHAFe-deficient and EDDHAFe-sufficient roots. The column experiment showed that EDTANa 2 Fe(II) and EDDHAFe(III) fertilization had a better mitigation effect on soil Cd availability compared to FeSO 4 ·7H 2 O. Moreover, the field experiment demonstrated that these two chelated fertilizations could reduce Cd concentrations in brown rice by up to 80%. Iron concentrations in the brown rice were elevated by Fe chelates. Compared to EDDHAFe(III), EDTANa 2 Fe(II) fertilization had a stronger mitigation effect by generating more EDTANa 2 Cd(II) in the soil solution to decrease phyto-available Cd in the soil. While EDDHAFe(III) fertilization could increase soil pH and decrease soil Eh which contributed to decreasing phyto-available Cd in a contaminated soil. In the hydroponic experiment, Fe sufficiency significantly reduced Cd concentrations in above-ground organs. In some cases, the expression of OsIRT1, OsNRAMP1 and OsNRAMP5 was inhibited under Fe sufficiency relative to Fe deficiency conditions. These results suggest that mitigation of rice Cd by Fe chelate fertilization results from a decrease in available Cd in substrates and the inhibition of the expression of several Fe-related genes in the IRT and NRAMP families. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Removal of emerging pollutants by Ru/TiO2-catalyzed permanganate oxidation.

    PubMed

    Zhang, Jing; Sun, Bo; Xiong, Xinmei; Gao, Naiyun; Song, Weihua; Du, Erdeng; Guan, Xiaohong; Zhou, Gongming

    2014-10-15

    TiO2 supported ruthenium nanoparticles, Ru/TiO2 (0.94‰ as Ru), was synthesized to catalyze permanganate oxidation for degrading emerging pollutants (EPs) with diverse organic moieties. The presence of 1.0 g L(-1) Ru/TiO2 increased the second order reaction rate constants of bisphenol A, diclofenac, acetaminophen, sulfamethoxazole, benzotriazole, carbamazepine, butylparaben, diclofenac, ciprofloxacin and aniline at mg L(-1) level (5.0 μM) by permanganate oxidation at pH 7.0 by 0.3-119 times. The second order reaction rate constants of EPs with permanganate or Ru/TiO2-catalyzed permanganate oxidation obtained at EPs concentration of mg L(-1) level (5.0 μM) underestimated those obtained at EPs concentration of μg L(-1) level (0.050 μM). Ru/TiO2-catalyzed permanganate could decompose a mixture of nine EPs at μg L(-1) level efficiently and the second order rate constant for each EP was not decreased due to the competition of other EPs. The toxicity tests revealed that Ru/TiO2-catalyzed permanganate oxidation was effective not only for elimination of EPs but also for detoxification. The removal rates of sulfamethoxazole by Ru/TiO2-catalyzed permanganate oxidation in ten successive cycles remained almost constant in ultrapure water and slightly decreased in Songhua river water since the sixth run, indicating the satisfactory stability of Ru/TiO2. Ru/TiO2-catalyzed permanganate oxidation was selective and could remove selected EPs spiked in real waters more efficiently than chlorination. Therefore, Ru/TiO2-catalyzed permanganate oxidation is promising for removing EPs with electron-rich moieties. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Core-level binding energy shifts in Pt Ru nanoparticles: A puzzle resolved

    NASA Astrophysics Data System (ADS)

    Lewera, Adam; Zhou, Wei Ping; Hunger, Ralf; Jaegermann, Wolfram; Wieckowski, Andrzej; Yockel, Scott; Bagus, Paul S.

    2007-10-01

    Synchrotron measurements of Pt and Ru core-level binding energies, BE's, in Pt-Ru nanoparticles, as a function of Pt content, quantify earlier indications that the Pt 4f BE shift is much larger than the Ru 3d BE shift. A complementary theoretical analysis relates the BE shifts to changes in the metal-metal distances as the composition of the nanoparticle changes. We establish that the large Pt and small Ru BE shifts arise from the different response of these metals to changes in the bond distances, an unexpected result. Our results give evidence that the magnitudes of the BE shifts depend on whether the d band is open, as for Ru, or essentially filled, as for Pt.

  13. Ru-core/Cu-shell bimetallic nanoparticles with controlled size formed in one-pot synthesis.

    PubMed

    Helgadottir, I; Freychet, G; Arquillière, P; Maret, M; Gergaud, P; Haumesser, P H; Santini, C C

    2014-12-21

    Suspensions of bimetallic nanoparticles (NPs) of Ru and Cu have been synthesized by simultaneous decomposition of two organometallic compounds in an ionic liquid. These suspensions have been characterized by Anomalous Small-Angle X-ray Scattering (ASAXS) at energies slightly below the Ru K-edge. It is found that the NPs adopt a Ru-core, a Cu-shell structure, with a constant Ru core diameter of 1.9 nm for all Ru : Cu compositions, while the Cu shell thickness increases with Cu content up to 0.9 nm. The formation of RuCuNPs thus proceeds through rapid decomposition of the Ru precursor into RuNPs of constant size followed by the reaction of the Cu precursor and agglomeration as a Cu shell. Thus, the different decomposition kinetics of precursors make possible the elaboration of core-shell NPs composed of two metals without chemical affinity.

  14. Ru(II) complexes containing chelating phosphine ligands. Synthesis, characterizatin, and x-ray crystal structures of dichlorobis (1,2-bis(diphenylphosphino)ethane)Ru(II) and the coordinatetively unsaturated trigonal-bipyramidal cation, chlorobis(1,2-bis(diphenylphosphino)ethane)Ru(II)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Polam, J.R.; Porter, L.C.

    1993-01-01

    The reaction of trans-RuCl[sub 2](dppe)[sub 2] (1), with AgBF[sub 4] in tetrahydrofuran leads to abstraction of one of the halide ligands to produce the trigonal-bipyrimidal complex. [RuCl(dppe)[sub 2

  15. Hidden order signatures in the antiferromagnetic phase of U (Ru1-xFex) 2Si2

    NASA Astrophysics Data System (ADS)

    Williams, T. J.; Aczel, A. A.; Stone, M. B.; Wilson, M. N.; Luke, G. M.

    2017-03-01

    We present a comprehensive set of elastic and inelastic neutron scattering measurements on a range of Fe-doped samples of U (Ru1-xFex) 2Si2 with 0.01 ≤x ≤0.15 . All of the samples measured exhibit long-range antiferromagnetic order, with the size of the magnetic moment quickly increasing to 0.51 μB at 2.5% doping and continuing to increase monotonically with doping, reaching 0.69 μB at 15% doping. Time-of-flight and inelastic triple-axis measurements show the existence of excitations at (1 0 0) and (1.4 0 0) in all samples, which are also observed in the parent compound. While the excitations in the 1% doping are quantitatively identical to the parent material, the gap and width of the excitations change rapidly at 2.5% Fe doping and above. The 1% doped sample shows evidence for a separation in temperature between the hidden order and antiferromagnetic transitions, suggesting that the antiferromagnetic state emerges at very low Fe dopings. The combined neutron scattering data suggest not only discontinuous changes in the magnetic moment and excitations between the hidden order and antiferromagnetic phases, but that these changes continue to evolve up to at least x =0.15 .

  16. Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system

    NASA Astrophysics Data System (ADS)

    Gossé, S.; Bordier, S.; Guéneau, C.; Brackx, E.; Domenger, R.; Rogez, J.

    2018-03-01

    Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc. In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt. In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T < 1422 K for rhodium sesquioxide and T < 1815 K for ruthenium dioxide), the formed oxides are relatively stable. On the other hand, at high temperatures (T > 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species. A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident. The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.

  17. Magnetic and magnetocaloric properties of Ba and Ti co-doped SrRuO{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal

    2014-12-28

    Temperature evolution of magnetic properties in Ba and Ti doped SrRuO{sub 3} has been investigated to observe the effects of larger ionic radius Ba at Sr site and isovalent nonmagnetic impurity Ti at Ru site. Ionic radius mismatch and different electronic configuration in comparison with Ru modify Sr(Ba)-O and Ru(Ti)-O bond lengths and Ru-O-Ru bond angle. The apical and basal Ru-O-Ru bond angles vary significantly with Ti doping. Ferromagnetic Curie temperature decreases from 161 K to 149 K monotonically with Ba (10%) and Ti (10%) substitutions at Sr and Ru sites. The zero field cooled (ZFC) magnetization reveals a prominent peak whichmore » shifts towards lower temperature with application of magnetic field. The substitution of tetravalent Ti with localized 3d{sup 0} orbitals for Ru with more delocalized 4d{sup 4} orbitals leads to a broad peak in ZFC magnetization. A spontaneous ZFC magnetization becomes negative below 160 K for all the compositions. The occurrence of both normal and inverse magnetocaloric effects in Ba and Ti co-doped SrRuO{sub 3} makes the system more interesting.« less

  18. Conductivity study of thermally stabilized RuO2/polythiophene nanocomposites

    NASA Astrophysics Data System (ADS)

    Hebbar, Vidyashree; Bhajantri, R. F.

    2018-04-01

    The polymer nanocomposites of Ruthenium oxide (RuO2) filled polythiophene (PT) were synthesized by polymerization using chemical method. The purity of the synthesized polymer composite is verified using X-Ray diffraction (XRD). The structural discrepancies of the RuO2 filled PT composites are studied by Fourier transform infrared (FT-IR) spectroscopy. The phase transition and thermal stability of the prepared composite is revised by thermal characterization such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DC conductivity of RuO2 filled PT composite in the form of pellets is calculated using current-voltage (I-V) characterization by two-probe method. The enhancement in conductivity with increased RuO2 content in PT matrix is examined, which is the required property for electrical and electronic applications in supercapacitors.

  19. Optimization of the buffer surface of CoFeB/MgO/CoFeB-based magnetic tunnel junctions by ion beam milling

    NASA Astrophysics Data System (ADS)

    Martins, L.; Ventura, J.; Ferreira, R.; Freitas, P. P.

    2017-12-01

    Due to their high tunnel magnetoresistance (TMR) ratios at room temperature, magnetic tunnel junctions (MTJs) with a crystalline MgO insulating barrier and CoFeB ferromagnetic (FM) layers are the best candidates for novel magnetic memory applications. To overcome impedance matching problems in electronic circuits, the MgO barrier must have an ultra-low thickness (∼1 nm). Therefore, it is mandatory to optimize the MTJ fabrication process, in order to prevent relevant defects in the MgO barrier that could affect the magnetic and electrical MTJ properties. Here, a smoothing process aiming to decrease the roughness of the buffer surface before the deposition of the full MTJ stack is proposed. An ion beam milling process was used to etch the surface of an MTJ buffer structure with a Ru top layer. The morphologic results prove an effective decrease of the Ru surface roughness with the etching time. The electrical and magnetic results obtained for MTJs with smoothed buffer structures show a direct influence of the buffer roughness and coupling field on the improvement of the TMR ratio.

  20. Multicomponent order parameter superconductivity of Sr2RuO4 revealed by topological junctions

    NASA Astrophysics Data System (ADS)

    Anwar, M. S.; Ishiguro, R.; Nakamura, T.; Yakabe, M.; Yonezawa, S.; Takayanagi, H.; Maeno, Y.

    2017-06-01

    Single crystals of the Sr2RuO4 -Ru eutectic system are known to exhibit enhanced superconductivity at 3 K in addition to the bulk superconductivity of Sr2RuO4 at 1.5 K. The 1.5 K phase is believed to be a spin-triplet, chiral p -wave state with a multicomponent order parameter, giving rise to chiral domain structure. In contrast, the 3 K phase is attributable to enhanced superconductivity of Sr2RuO4 in the strained interface region between Ru inclusion of a few to tens of micrometers in size and the surrounding Sr2RuO4 . We investigate the dynamic behavior of a topological junction, where a superconductor is surrounded by another superconductor. Specifically, we fabricated Nb/Ru/Sr2RuO4 topological superconducting junctions, in which the difference in phase winding between the s -wave superconductivity in Ru microislands induced from Nb and the superconductivity of Sr2RuO4 mainly governs the junction behavior. Comparative results of the asymmetry, hysteresis, and noise in junctions with different sizes, shapes, and configurations of Ru inclusions are explained by the chiral domain-wall motion in these topological junctions. Furthermore, a striking difference between the 1.5 and 3 K phases is clearly revealed: the large noise in the 1.5 K phase sharply disappears in the 3 K phase. These results confirm the multicomponent order-parameter superconductivity of the bulk Sr2RuO4 , consistent with the chiral p -wave state, and the proposed nonchiral single-component superconductivity of the 3 K phase.

  1. Local structure distortion induced by Ti dopants boosting the pseudocapacitance of RuO2-based supercapacitors

    NASA Astrophysics Data System (ADS)

    Chen, I.-Li; Wei, Yu-Chen; Lu, Kueih-Tzu; Chen, Tsan-Yao; Hu, Chi-Chang; Chen, Jin-Ming

    2015-09-01

    Binary oxides with atomic ratios of Ru/Ti = 90/10, 70/30, and 50/50 were fabricated using H2O2-oxidative precipitation with the assistance of a cetyltrimethylammonium bromide (CTAB) template, followed by a thermal treatment at 200 °C. The characteristics of electron structure and local structure extracted from X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) analyses indicate that incorporation of Ti into the RuO2 lattice produces not only the local structural distortion of the RuO6 octahedra in (Ru-Ti)O2 with an increase in the central Ru-Ru distance but also a local crystallization of RuO2. Among the three binary oxides studied, (Ru70-Ti30)O2 exhibits a capacitance improvement of about 1.4-fold relative to the CTAB-modified RuO2, mainly due to the enhanced crystallinity of the distorted RuO6 structure rather than the surface area effect. Upon increasing the extent of Ti doping, the deteriorated supercapacitive performance of (Ru50-Ti50)O2 results from the formation of localized nano-clusters of TiO2 crystallites. These results provide insight into the important role of Ti doping in RuO2 that boosts the pseudocapacitive performance for RuO2-based supercapacitors. The present result is crucial for the design of new binary oxides for supercapacitor applications with extraordinary performance.Binary oxides with atomic ratios of Ru/Ti = 90/10, 70/30, and 50/50 were fabricated using H2O2-oxidative precipitation with the assistance of a cetyltrimethylammonium bromide (CTAB) template, followed by a thermal treatment at 200 °C. The characteristics of electron structure and local structure extracted from X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) analyses indicate that incorporation of Ti into the RuO2 lattice produces not only the local structural distortion of the RuO6 octahedra in (Ru-Ti)O2 with an increase in the central Ru-Ru distance but also a local crystallization of RuO2. Among the three binary

  2. Dynamical spin structure factors of α-RuCl3

    NASA Astrophysics Data System (ADS)

    Suzuki, Takafumi; Suga, Sei-ichiro

    2018-03-01

    Honeycomb-lattice magnet α-RuCl3 is considered to be a potential candidate of realizing Kitaev spin liquid, although this material undergoes a phase transition to the zigzag magnetically ordered state at T N ∼ 7 K. Quite recently, inelastic neutron-scattering experiments using single crystal α-RuCl3 have unveiled characteristic dynamical properties. We calculate dynamical spin structure factors of three ab-initio models for α-RuCl3 with an exact numerical diagonalization method. We also calculate temperature dependences of the specific heat by employing thermal pure quantum states. We compare our numerical results with the experiments and discuss characteristics obtained by using three ab-initio models.

  3. Long-time relaxation of photo-induced influence on BiFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Gu, Jun-xing; Jin, Kui-juan; Wang, Le; He, Xu; Guo, Hai-zhong; Wang, Can; He, Meng; Yang, Guo-zhen

    2015-11-01

    An intuitively persistent enhancement of the local surface potential of BiFeO3 layers in both heterostructures of BiFeO3/SrRuO3/SrTiO3 and BiFeO3/Sr0.09Nb0.01TiO3 was observed by the Kelvin probe force microscopy technique after the illumination of 375 nm laser. This photo-induced enhanced surface potential can maintain as long as 15 h after the illumination. We attributed this super-long-time relaxation of photo-induced influence to a photo-induced depolarization in the BiFeO3 thin films, and our first-principles calculation of double-potential well further provides an instinct understanding on this depolarization process. Our findings provide a peculiar understanding into the photo-induced phenomena on the widely researched ferroelectric systems and offer an approach to tune their multifunctionality of the magnetization and polarization not only by applied magnetic and electric fields but also by optical filed.

  4. Geochemical Constraints on Core-Mantle Interaction from Fe/Mn Ratios

    NASA Astrophysics Data System (ADS)

    Humayun, M.; Qin, L.

    2003-12-01

    The greater density of liquid iron alloy, and its immiscibility with silicate, maintains the physical separation of the core from the mantle. There are no a priori reasons, however, why the Earth's mantle should be chemically isolated from the core. Osmium isotopic variations in mantle plumes have been interpreted in terms of interaction between outer core and the source regions of deep mantle plumes. If chemical transport occurs across the core-mantle boundary its mechanism remains to be established. The Os isotope evidence has also been interpreted as the signatures of subducted Mn-sediments, which are known to have relatively high Pt/Os. In the mantle, Fe occurs mainly as the divalent ferrous ion, and Mn occurs solely as a divalent ion, and both behave in a geochemically coherent manner because of similarity in ionic charge and radius. Thus, the Fe/Mn ratio is a planetary constant insensitive to processes of mantle differentiation by partial melting. Two processes may perturb the ambient mantle Fe/Mn of 60: a) the subduction of Mn-sediments should decrease the Fe/Mn ratio in plume sources, while b) chemical transport from the outer core may increase the Fe/Mn ratio. The differentiation of the liquid outer core to form the solid inner core may increase abundances of the light element constituents (FeS, FeO, etc.) to the point of exsolution from the core at the CMB. The exact rate of this process is determined by the rate of inner core growth. Two end-member models include 1) inner core formation mainly prior to 3.5 Ga with heat release dominated by radioactive sources, or 2) inner core formation occurring mainly in the last 1.5 Ga with heat release dominated by latent heat. This latter model would imply large fluxes of Fe into the sources of modern mantle plumes. Existing Fe/Mn data for Gorgona and Hawaiian samples place limits on both these processes. We describe a new procedure for the precise determination of the Fe/Mn ratio in magmatic rocks by ICP-MS. This

  5. Syntheses, Spectroscopic Data, and X-ray Diffraction Structures of the Heterometallic RuRe Face-shared Bioctahedral (eta(6)-cymene)Ru(mu-Cl)(3)Re(CO)(3) and MnRu2 Edge-shared Trioctahedral [fac-ClRu(CO)(3)](2)(mu-Cl)(4)Mn(H2O)(2) Complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Xiaoping; Hunt, Sean W; Richmond, Michael G.

    2009-01-01

    Thermolysis of the diruthenium compound [(eta(6)-cymene)RuCl2](2) (1) with ClRe(CO)(5) (2) leads to the formation of the new confacial bioctahedral compound (eta(6)-cymene) Ru(mu-Cl)(3)Re(CO)(3) (3) in good yields; the same product has also been isolated when a mixture of 1 and 2 is irradiated with near UV-vis light for an extended period of time. Heating 1 and ClMn(CO)(5) (4) does not furnish the corresponding manganese analogue of 3 but rather the trioctahedral halide-bridged product [fac-ClRu(CO)(3)](2)(mu-Cl)(4)Mn(H2O)(2) (5). 3 and 5 have been fully characterized in solution and their molecular structures established by X-ray crystallography.

  6. Spray pyrolysed Ru:TiO2 thin film electrodes prepared for electrochemical supercapacitor

    NASA Astrophysics Data System (ADS)

    Fugare, B. Y.; Thakur, A. V.; Kore, R. M.; Lokhande, B. J.

    2018-04-01

    Ru doped TiO2 thin films are prepared by using 0.06 M aqueous solution of potassium titanium oxalate (pto), and 0.005 M aqueous solution of ruthenium tri chloride (RuCl3) precursors. The deposition was carried on stainless steel (SS) by using well known ultrasonic spray pyrolysis technique (USPT) at 723° K by maintaining the spray rate 12 cc/min and compressed air flow rate 10 Lmin-1. Prepared Ru:TiO2 thin films were characterized by structurally, morphologically and electrochemically. Deposited RuO2 shows amorphous structure and TiO2 shows tetragonal crystal structure with rutile as prominent phase at very low decomposition temperature. SEM micrographs of RuO2 exhibits porous, interconnected, spherical grains type morphology and TiO2 shows porous, nanorods and nanoplates like morphology and also Ru doped TiO2 shows porous, spherical, granular and nanorods type morphology. The electrochemical cyclic voltammetery shows mixed capacitive behavior. The achieved highest value of specific capacitance 2692 F/g was Ru doped TiO2 electrode in 0.5 M H2SO4.

  7. Study on the mechanism of perpendicular magnetic anisotropy in Ta/CoFeB/MgO system

    NASA Astrophysics Data System (ADS)

    Lou, Yongle; Zhang, Yuming; Guo, Hui; Xu, Daqing; Yimen, Zhang

    2017-06-01

    The mechanism of perpendicular magnetic anisotropy (PMA) in a MgO-based magnetic tunnel junction (MTJ) has been studied in this article. By comparing the magnetic properties and elementary composition analysis for different CoFeB-based structures, such as Ta/CoFeB/MgO, Ta/CoFeB/Ta and Ru/CoFeB/MgO structures, it is found that a certain amount of Fe-oxide existing at the interface of CoFeB/MgO is helpful to enhance the PMA and the PMA is originated from the interface of CoFeB/MgO. In addition, Ta film plays an important role to enhance the PMA in Ta/CoFeB/MgO structure. Project supported by the National Defense Advance Research Foundation (No. 9140A08XXXXXX0DZ106), the Basic Research Program of Ministry of Education, China (No. JY10000925005), the Scientific Research Program Funded by Shaanxi Provincial Education Department (No.11JK0912), the Scientific Research Foundation of Xi’an University of Science and Technology (No. 2010011), the Doctoral Research Startup Fund of Xi’an University of Science and Technology (No. 2010QDJ029).

  8. The effect of the surface composition of Ru-Pt bimetallic catalysts for methanol oxidation

    DOE PAGES

    Garrick, Taylor R.; Diao, Weijian; Tengco, John M.; ...

    2016-02-23

    Here, a series of Ru-Pt bimetallic catalysts prepared by the electroless deposition of controlled and variable amounts of Ru on the Pt surface of a commercially-available 20 wt% Pt/C catalyst has been characterized and evaluated for the oxidation of methanol. The activity of each Ru-Pt catalyst was determined as a function of surface composition via cyclic voltammetry. For the Ru-Pt bimetallic catalysts, activity passed through a maximum at approximately 50% monodisperse Ru surface coverage. However, due to the monolayer coverage of Ru on Pt, the amount of metal in the catalyst is minimized compared to a bulk 1:1 atomic ratiomore » of Ru:Pt seen in commercial bimetallic catalysts. Chemisorption and temperature programmed reduction experiments confirmed that the surface had characteristics of a true bimetallic catalyst. On a mass of Pt basis, the activity of this composition for methanol oxidation was 7 times higher than pure Pt and 3.5 times higher than a commercial catalyst with a 1:1 Pt:Ru bulk atomic ratio.« less

  9. Particle size dependence of CO tolerance of anode PtRu catalysts for polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Yamanaka, Toshiro; Takeguchi, Tatsuya; Wang, Guoxiong; Muhamad, Ernee Noryana; Ueda, Wataru

    An anode catalyst for a polymer electrolyte fuel cell must be CO-tolerant, that is, it must have the function of hydrogen oxidation in the presence of CO, because hydrogen fuel gas generated by the steam reforming process of natural gas contains a small amount of CO. In the present study, PtRu/C catalysts were prepared with control of the degree of Pt-Ru alloying and the size of PtRu particles. This control has become possible by a new method of heat treatment at the final step in the preparation of catalysts. The CO tolerances of PtRu/C catalysts with the same degree of Pt-Ru alloying and with different average sizes of PtRu particles were thus compared. Polarization curves were obtained with pure H 2 and CO/H 2 (CO concentrations of 500-2040 ppm). It was found that the CO tolerance of highly dispersed PtRu/C (high dispersion (HD)) with small PtRu particles was much higher than that of poorly dispersed PtRu/C (low dispersion (LD)) with large metal particles. The CO tolerance of PtRu/C (HD) was higher than that of any commercial PtRu/C. The high CO tolerance of PtRu/C (HD) is thought to be due to efficient concerted functions of Pt, Ru, and their alloy.

  10. [Ru/AC catalyzed ozonation of recalcitrant organic compounds].

    PubMed

    Wang, Jian-Bing; Hou, Shao-Pei; Zhou, Yun-Rui; Zhu, Wan-Peng; He, Xu-Wen

    2009-09-15

    Ozonation and Ru/AC catalyzed ozonation of dimethyl phthalate (DMP), phenols and disinfection by-products precursors were studied. It shows that Ru/AC catalyst can obviously enhance the mineralization of organic compounds. In the degradation of DMP, TOC removal was 28.84% by ozonation alone while it was 66.13% by catalytic ozonation. In the oxidation of 23 kinds of phenols, TOC removals were 9.57%-56.08% by ozonation alone while they were 41.81%-82.32% by catalytic ozonation. Compared to ozonation alone, Ru/AC catalyzed ozonation was more effective for the reduction of disinfection by-products formation potentials in source water. The reduction of haloacetic acids formation potentials was more obvious than thichlomethane formation potentials. After the treatment by catalytic ozonation, the haloacetic acids formation potentials decreased from 144.02 microg/L to 58.50 microg/L, which was below the standard value of EPA. However ozonation alone could not make it reach the standard. The treatments of source water by BAC, O3 + BAC, O3/AC + BAC and Ru/AC + O3 + BAC were also studied. In the four processes, TOC removal was 3.80%, 20.14%, 27.45% and 48.30% respectively, COD removal was 4.37%, 27.22%, 39.91% and 50.00% respectively, UV254 removal was 8.16%, 62.24%, 67.03% and 84.95% respectively. Ru/AC + O3 + BAC process is more effective than the other processes for the removal of TOC, COD and UV254 and no ruthenium leaching observed in the solution. It is a promising process for the treatment of micro polluted source water.

  11. Ultrathin Cr added Ru film as a seedless Cu diffusion barrier for advanced Cu interconnects

    NASA Astrophysics Data System (ADS)

    Hsu, Kuo-Chung; Perng, Dung-Ching; Yeh, Jia-Bin; Wang, Yi-Chun

    2012-07-01

    A 5 nm thick Cr added Ru film has been extensively investigated as a seedless Cu diffusion barrier. High-resolution transmission electron microscopy micrograph, X-ray diffraction (XRD) pattern and Fourier transform-electron diffraction pattern reveal that a Cr contained Ru (RuCr) film has a glassy microstructure and is an amorphous-like film. XRD patterns and sheet resistance data show that the RuCr film is stable up to 650 °C, which is approximately a 200 °C improvement in thermal stability as compared to that of the pure Ru film. X-ray photoelectron spectroscopy depth profiles show that the RuCr film can successfully block Cu diffusion, even after a 30-min 650 °C annealing. The leakage current of the Cu/5 nm RuCr/porous SiOCH/Si stacked structure is about two orders of magnitude lower than that of a pristine Ru sample for electric field below 1 MV/cm. The RuCr film can be a promising Cu diffusion barrier for advanced Cu metallization.

  12. RU 486, the FDA and free enterprise.

    PubMed

    Buc, N L

    1992-01-01

    The legal question whether RU-486 can meet the standards for US Food and Drug Administration (FDA) approval for a drug indicated for abortion can be answered in the affirmative. Under the Food, Drug, and Cosmetic Act, efficacy must be demonstrated by evidence consisting of adequate and well-controlled investigations to show that a drug is safe and effective for its intended use. The FDA will approve it if on the basis of the clinical trials it could be concluded that the drug will have the effect it purports as prescribed in the labeling, and if the drug is safe. In congressional hearings and in the newspapers the so-called import alert issued by the FDA to prevent the importing of RU-486 under certain circumstances has been publicized. The import alert is no bar to conducting clinical studies in the US under an investigational new drug application (IND) nor is the import alert a bar to the filing and the pursuit of a new drug application (NDA) to allow marketing in the US. The import alert is no bar to anything except importation without an IND or NDA. The real problem is that there is no seller of RU-486 in the US and no sponsor of an NDA offering clinical evidence of safety and efficacy as well as the ability to manufacture the drug and the necessary prostaglandins properly. In additions to abortion, other uses of RU-486 include contraception, breast cancer, and Cushing syndrome. Some limited research could be done under INDs with small supplies of the drug obtained elsewhere on the world market. There are only 2 solutions to this problem. One is that Roussel must change its mind or have its mind changed as the example of the AIDS community showed, which has managed to induce the development of drugs that were impossible 8 or 10 years ago. The other solution is to found a pharmaceutical company that could induce competition for manufacturing RU-486.

  13. Stable monolayer honeycomb-like structures of RuX2 (X =S,Se)

    NASA Astrophysics Data System (ADS)

    Ersan, Fatih; Cahangirov, Seymur; Gökoǧlu, Gökhan; Rubio, Angel; Aktürk, Ethem

    2016-10-01

    Recent studies show that several metal oxides and dichalcogenides (M X2) , which exist in nature, can be stable in two-dimensional (2D) form and each year several new M X2 structures are explored. The unstable structures in H (hexagonal) or T (octahedral) forms can be stabilized through Peierls distortion. In this paper, we propose new 2D forms of RuS2 and RuSe2 materials. We investigate in detail the stability, electronic, magnetic, optical, and thermodynamic properties of 2D Ru X2 (X =S,Se) structures from first principles. While their H and T structures are unstable, the distorted T structures (T'-Ru X2) are stable and have a nonmagnetic semiconducting ground state. The molecular dynamic simulations also confirm that T'-Ru X2 systems are stable even at 500 K without any structural deformation. T'-RuS2 and T'-RuSe2 have indirect band gaps with 0.745 eV (1.694 eV with HSE) and 0.798 eV (1.675 eV with HSE) gap values, respectively. We also examine their bilayer and trilayer forms and find direct and smaller band gaps. We find that AA stacking is more favorable than the AB configuration. The new 2D materials obtained can be good candidates with striking properties for applications in semiconductor electronic, optoelectronic devices, and sensor technology.

  14. Local structure distortion induced by Ti dopants boosting the pseudocapacitance of RuO2-based supercapacitors.

    PubMed

    Chen, I-Li; Wei, Yu-Chen; Lu, Kueih-Tzu; Chen, Tsan-Yao; Hu, Chi-Chang; Chen, Jin-Ming

    2015-10-07

    Binary oxides with atomic ratios of Ru/Ti = 90/10, 70/30, and 50/50 were fabricated using H2O2-oxidative precipitation with the assistance of a cetyltrimethylammonium bromide (CTAB) template, followed by a thermal treatment at 200 °C. The characteristics of electron structure and local structure extracted from X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) analyses indicate that incorporation of Ti into the RuO2 lattice produces not only the local structural distortion of the RuO6 octahedra in (Ru-Ti)O2 with an increase in the central Ru-Ru distance but also a local crystallization of RuO2. Among the three binary oxides studied, (Ru70-Ti30)O2 exhibits a capacitance improvement of about 1.4-fold relative to the CTAB-modified RuO2, mainly due to the enhanced crystallinity of the distorted RuO6 structure rather than the surface area effect. Upon increasing the extent of Ti doping, the deteriorated supercapacitive performance of (Ru50-Ti50)O2 results from the formation of localized nano-clusters of TiO2 crystallites. These results provide insight into the important role of Ti doping in RuO2 that boosts the pseudocapacitive performance for RuO2-based supercapacitors. The present result is crucial for the design of new binary oxides for supercapacitor applications with extraordinary performance.

  15. A RuBisCO-mediated carbon metabolic pathway in methanogenic archaea

    PubMed Central

    Kono, Takunari; Mehrotra, Sandhya; Endo, Chikako; Kizu, Natsuko; Matusda, Mami; Kimura, Hiroyuki; Mizohata, Eiichi; Inoue, Tsuyoshi; Hasunuma, Tomohisa; Yokota, Akiho; Matsumura, Hiroyoshi; Ashida, Hiroki

    2017-01-01

    Two enzymes are considered to be unique to the photosynthetic Calvin–Benson cycle: ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), responsible for CO2 fixation, and phosphoribulokinase (PRK). Some archaea possess bona fide RuBisCOs, despite not being photosynthetic organisms, but are thought to lack PRK. Here we demonstrate the existence in methanogenic archaea of a carbon metabolic pathway involving RuBisCO and PRK, which we term ‘reductive hexulose-phosphate' (RHP) pathway. These archaea possess both RuBisCO and a catalytically active PRK whose crystal structure resembles that of photosynthetic bacterial PRK. Capillary electrophoresis-mass spectrometric analysis of metabolites reveals that the RHP pathway, which differs from the Calvin–Benson cycle only in a few steps, is active in vivo. Our work highlights evolutionary and functional links between RuBisCO-mediated carbon metabolic pathways in methanogenic archaea and photosynthetic organisms. Whether the RHP pathway allows for autotrophy (that is, growth exclusively with CO2 as carbon source) remains unknown. PMID:28082747

  16. Two-electron oxidation of deoxyguanosine by a Ru(III) complex without involving oxygen molecules through disproportionation.

    PubMed

    Choi, Sunhee; Ryu, DaWeon; DellaRocca, Joseph G; Wolf, Matthew W; Bogart, Justin A

    2011-07-18

    Among the many mechanisms for the oxidation of guanine derivatives (G) assisted by transition metals, Ru(III) and Pt(IV) metal ions share basically the same principle. Both Ru(III)- and Pt(IV)-bound G have highly positively polarized C8-H's that are susceptible to deprotonation by OH(-), and both undergo two-electron redox reactions. The main difference is that, unlike Pt(IV), Ru(III) is thought to require O(2) to undergo such a reaction. In this study, however, we report that [Ru(III)(NH(3))(5)(dGuo)] (dGuo = deoxyguanosine) yields cyclic-5'-O-C8-dGuo (a two-electron G oxidized product, cyclic-dGuo) without O(2). In the presence of O(2), 8-oxo-dGuo and cyclic-dGuo were observed. Both [Ru(II)(NH(3))(5)(dGuo)] and cyclic-dGuo were produced from [Ru(III)(NH(3))(5)(dGuo)] accelerated by [OH(-)]. We propose that [Ru(III)(NH(3))(5)(dGuo)] disproportionates to [Ru(II)(NH(3))(5)(dGuo)] and [Ru(IV)(NH(3))(4)(NH(2)(-))(dGuo)], followed by a 5'-OH attack on C8 in [Ru(IV)(NH(3))(4)(NH(2)(-))(dGuo)] to initiate an intramolecular two-electron transfer from dGuo to Ru(IV), generating cyclic-dGuo and Ru(II) without involving O(2).

  17. PtRu nanoparticles embedded in nitrogen doped carbon with highly stable CO tolerance and durability

    NASA Astrophysics Data System (ADS)

    Ling, Ying; Yang, Zehui; Yang, Jun; Zhang, Yunfeng; Zhang, Quan; Yu, Xinxin; Cai, Weiwei

    2018-02-01

    As is well known, the lower durability and sluggish methanol oxidation reaction (MOR) of PtRu alloy electrocatalyst blocks the commercialization of direct methanol fuel cells (DMFCs). Here, we design a new PtRu electrocatalyst, with highly stable CO tolerance and durability, in which the PtRu nanoparticles are embedded in nitrogen doped carbon layers derived from carbonization of poly(vinyl pyrrolidone). The newly fabricated electrocatalyst exhibits no loss in electrochemical surface area (ECSA) and MOR activity after potential cycling from 0.6-1.0 V versus reversible hydrogen electrode, while commercial CB/PtRu retains only 50% of its initial ECSA. Meanwhile, due to the same protective layers, the Ru dissolution is decelerated, resulting in stable CO tolerance. Methanol oxidation reaction (MOR) testing indicates that the activity of newly fabricated electrocatalyst is two times higher than that of commercial CB/PtRu, and the fuel cell performance of the embedded PtRu electrocatalyst was comparable to that of commercial CB/PtRu. The embedded PtRu electrocatalyst is applicable in real DMFC operation. This study offers important and useful information for the design and fabrication of durable and CO tolerant electrocatalysts.

  18. New isomer and decay half-life of {sup 115}Ru

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kurpeta, J.; Plochocki, A.; Rissanen, J.

    2010-12-15

    Exotic, neutron-rich nuclei of mass A=115 produced in proton-induced fission of {sup 238}U were extracted using the IGISOL mass separator. The beam of isobars was transferred to the JYFLTRAP Penning trap system for further separation to the isotopic level. Monoisotopic samples of {sup 115}Ru nuclei were used for {gamma}and {beta} coincidence spectroscopy. In {sup 115}Ru we have observed excited levels, including an isomer with a half-life of 76(6) ms and (7/2{sup -}) spin and parity. The first excited 61.7-keV level in {sup 115}Ru with spins and parity (3/2{sup +}) may correspond to an oblate 3/2{sup +}[431] Nilsson orbital. A half-lifemore » of 318(19) ms for the {beta}{sup -} decay of the (1/2{sup +}) ground state in {sup 115}Ru has been firmly established in two independent measurements, a value which is significantly shorter than that previously reported.« less

  19. [Population Council responsible for RU486 clinical trials in USA].

    PubMed

    Aguillaume, C J

    1993-04-01

    As a result of the sudden political change that came with the Clinton Administration, RU-486's manufacturer, Roussel-Uclaf, and the Population Council agreed on April 20, 1992, on the manufacture and distribution of RU-486 in the US. In the US, there are less than 1.6 million induced abortions annually. From now on, US women will be able to have a choice between medical and surgical abortion. The Population Council and Roussel-Uclaf have had a contract since 1982. The Council is solely responsible for the phase 2 clinical trial of RU-486 in the US and other countries. It must present to the US Food and Drug Administration (FDA) an amendment allowing it to begin phase 3 clinical trials. The Council will also lead the US medical facilities in this study. It will identify partners for future production of RU-486 and its distribution in the US. It will also submit to FDA a New Drug Application (NDA). FDA will review the scientific literature on RU-486 and evaluate all data submitted by the Population Council. There are still obstacles to be surmounted. The Population Council must demonstrate good judgment when selecting the criteria for choosing a pharmaceutical firm before a Technical Committee which will be part of a group of players promoting women's health, scientific experts, and other interested parties. It must find the necessary funds to conduct the clinical trials and prepare the NDA. Phase 3 clinical trials in the US must have at least 2000 women. They will test RU-486's efficacy, safety, and acceptability among women choosing medical abortion over surgical abortion. Since the Council operates in almost all countries in the world, has innovated contraceptive research and development activities, and has been endorsed by the UN, product approval of RU-486 in the US will affect policy in all countries concerned about abortion.

  20. Brownmillerite-type Ca2 FeCoO5 as a Practicable Oxygen Evolution Reaction Catalyst.

    PubMed

    Tsuji, Etsushi; Motohashi, Teruki; Noda, Hiroyuki; Kowalski, Damian; Aoki, Yoshitaka; Tanida, Hajime; Niikura, Junji; Koyama, Yukinori; Mori, Masahiro; Arai, Hajime; Ioroi, Tsutomu; Fujiwara, Naoko; Uchimoto, Yoshiharu; Ogumi, Zempachi; Habazaki, Hiroki

    2017-07-21

    Here, we report remarkable oxygen evolution reaction (OER) catalytic activity of brownmillerite (BM)-type Ca 2 FeCoO 5 . The OER activity of this oxide is comparable to or beyond those of the state-of-the-art perovskite (PV)-catalyst Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) and a precious-metal catalyst RuO 2 , emphasizing the importance of the characteristic BM structure with multiple coordination environments of transition metal (TM) species. Also, Ca 2 FeCoO 5 is clearly advantageous in terms of expense/laboriousness of the material synthesis. These facts make this oxide a promising OER catalyst used in many energy conversion technologies such as metal-air secondary batteries and hydrogen production from electrochemical/photocatalytic water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Synthesis, molecular structure, and C-C coupling reactions of carbeneruthenium(II) complexes with C5H5Ru(=CRR') and C5Me5Ru(=CRR') as molecular units.

    PubMed

    Braun, Thomas; Münch, Gerhard; Windmüller, Bettina; Gevert, Olaf; Laubender, Matthias; Werner, Helmut

    2003-06-06

    The ethene derivatives [(eta(5)-C(5)R(5))RuX(C(2)H(4))(PPh(3))] with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C(5)R(5))Ru(eta(3)-2-MeC(3)H(4))(PPh(3))] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X=Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C(5)R(5))RuCl(L)(PPh(3))] with L=C(2)(CO(2)Me)(2), Me(3)SiC(2)CO(2)Et, C=CHCO(2)R, and C(3)H(4). The allenylidene complex [(eta(5)-C(5)H(5))RuCl(=C=C=CPh(2))(PPh(3))] is directly accessible from 1 (R=H) in two steps with the propargylic alcohol HC triple bond CC(OH)Ph(2) as the precursor. The reactions of the ethene derivatives [(eta(5)-C(5)H(5))RuX(C(2)H(4))(PPh(3))] (X=Cl, CF(3)CO(2)) with diazo compounds RR'CN(2) yield the corresponding carbene complexes [(eta(5)-C(5)R(5))RuX(=CRR')(PPh(3))], while with ethyl diazoacetate (for X=Cl) the diethyl maleate compound [(eta(5)-C(5)H(5))RuCl[eta(2)-Z-C(2)H(2)(CO(2)Et)(2)](PPh(3))] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C(5)R(5))RuCl(=CHR')(PPh(3))] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C(5)H(5))Ru(=CPh(2))(L)(PPh(3))]X with L=CO and CNtBu and X=AlCl(4) and PF(6), have also been prepared. The neutral compounds [(eta(5)-C(5)H(5))RuCl(=CRR')(PPh(3))] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH(2)=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C(5)H(5))Ru(eta(3)-CH(2)CHCR(2))(PPh(3))] with acetic acid affords the corresponding olefins R(2)C=CHCH(3). The by-product of this process is the acetato

  2. Anomalous perovskite PbRuO3 stabilized under high pressure

    PubMed Central

    Cheng, J.-G.; Kweon, K. E.; Zhou, J.-S.; Alonso, J. A.; Kong, P.-P.; Liu, Y.; Jin, Changqing; Wu, Junjie; Lin, Jung-Fu; Larregola, S. A.; Yang, Wenge; Shen, Guoyin; MacDonald, A. H.; Manthiram, Arumugam; Hwang, G. S.; Goodenough, John B.

    2013-01-01

    Perovskite oxides ABO3 are important materials used as components in electronic devices. The highly compact crystal structure consists of a framework of corner-shared BO6 octahedra enclosing the A-site cations. Because of these structural features, forming a strong bond between A and B cations is highly unlikely and has not been reported in the literature. Here we report a pressure-induced first-order transition in PbRuO3 from a common orthorhombic phase (Pbnm) to an orthorhombic phase (Pbn21) at 32 GPa by using synchrotron X-ray diffraction. This transition has been further verified with resistivity measurements and Raman spectra under high pressure. In contrast to most well-studied perovskites under high pressure, the Pbn21 phase of PbRuO3 stabilized at high pressure is a polar perovskite. More interestingly, the Pbn21 phase has the most distorted octahedra and a shortest Pb—Ru bond length relative to the average Pb—Ru bond length that has ever been reported in a perovskite structure. We have also simulated the behavior of the PbRuO3 perovskite under high pressure by first principles calculations. The calculated critical pressure for the phase transition and evolution of lattice parameters under pressure match the experimental results quantitatively. Our calculations also reveal that the hybridization between a Ru:t2g orbital and an sp hybrid on Pb increases dramatically in the Pbnm phase under pressure. This pressure-induced change destabilizes the Pbnm phase to give a phase transition to the Pbn21 phase where electrons in the overlapping orbitals form bonding and antibonding states along the shortest Ru—Pb direction at P > Pc. PMID:24277807

  3. Structure and magnetic properties of Heusler alloy Co2RuSi melt-spun ribbons

    NASA Astrophysics Data System (ADS)

    Xin, Yuepeng; Ma, Yuexing; Hao, Hongyue; Luo, Hongzhi; Meng, Fanbin; Liu, Heyan; Liu, Enke; Wu, Guangheng

    2017-08-01

    Heusler alloy Co2RuSi has been synthesized by melt-spinning technology successfully. Co2RuSi bulk sample after annealing is composed of an HCP Co-rich phase and a BCC Ru-Si phase, but melt-spinning can suppress the precipitation of the HCP phase and produce a single Co2RuSi Heusler phase. In the XRD pattern, it is found that Ru has a strong preference for the (A, C) sites, though it has fewer valence electrons compared with Co. This site preference is different from the case in Heusler alloys containing only 3d elements and is supported further by first-principles calculations. Melt-spun Co2RuSi has a Ms of 2.67 μB/f.u. at 5 K and a Tc of 491 K. An exothermic peak is observed at 871 K in the DTA curve, corresponding to the decomposition of the Heusler phase. Finally, the site preference and magnetic properties of Co2RuSi were discussed based on electronic structure calculation and charge density difference.

  4. The Behavior of the Ru-bda Water Oxidation Catalysts at Low Oxidation States.

    PubMed

    Matheu, Roc; Ghaderian, Abolfazl; Francas, Laia; Chernev, Petko; Ertem, Mehmed; Benet-Buchholz, Jordi; Batista, Victor; Haumann, Michael; Gimbert-Suriñach, Carolina; Sala, Xavier; Llobet, Antoni

    2018-06-13

    The Ru complex [RuII(bda-κ-N2O2)(N-NH2)2], 1, (bda2- = (2,2'-bipyridine)-6,6'-dicarboxylate; N-NH2 = 4-(pyridin-4-yl)aniline) is used as a synthetic intermediate to prepare Ru-bda complexes that contain the NO+, acetonitrile (MeCN) or H2O ligands at oxidation states II and III. Complex 1 reacts with excess NO+ to form a Ru complex where the aryl amine ligands N-NH2 in 1 are transformed into diazonium salts (N-N2+ = 4-(pyridin-4-yl)benzenediazonium)) together with the formation of a new Ru-NO group at the equatorial zone, to generate [RuII(bda-κ-N2O)(NO)(N-N2)2]3+, 23+. Similarly, complex 1 can also react with a coordinating solvent, such as MeCN, at room temperature leading to complex [RuII(bda-κ-N2O)(MeCN)(N-NH2)2], 3. Finally in acidic aqueous solutions solvent water coordinates the Ru center forming {[RuII(bda-κ-(NO)3)(H2O)(N-NH3)2](H2O)n}2+, 42+, that is strongly hydrogen bonded with additional water molecules at the second coordination sphere. We have additionally characterized the one electron oxidized complex {[RuIII(bda-κ-(NO)3.5)(H2O)(N-NH3)2](H2O)n}3+, 53+. The coordination mode of the complexes has been studied both in the solid state and in solution through single-crystal XRD, X-ray absorption spectroscopy, variable-temperature NMR and DFT calculations. While the κ-N2O is the main coordination mode for 23+ and 3, an equilibrium that involves isomers with κ-N2O and κ-NO2 coordination modes and neighboring hydrogen bonded water molecules is observed for 42+ and 53+. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. New half sandwich-type Ru(II) coordination compounds characterized by the fac-Ru(dmso-S)3 fragment: influence of the face-capping group on the chemical behavior and in vitro anticancer activity.

    PubMed

    Bratsos, Ioannis; Simonin, Camilla; Zangrando, Ennio; Gianferrara, Teresa; Bergamo, Alberta; Alessio, Enzo

    2011-10-07

    The Ru(II) complex fac-[RuCl(dmso-S)(3)(dmso-O)(2)][PF(6)] (P2) was found to be an excellent precursor for the facile preparation in high yield of half sandwich-type compounds of the general formula fac-[RuCl(dmso-S)(3)(N)(2)][PF(6)] (e.g. (N)(2) = 1,2-diaminoethane (en, 4), trans-1,2-diaminocyclohexane (dach, 5), or 2 NH(3) (6)). Neutral half sandwich-type compounds of the general formula fac-[RuCl(dmso-S)(3)(N-O)] where N-O is an anionic chelating ligand (e.g. N-O = picolinate (pic, 7)) are best prepared from the universal Ru(II)-dmso precursor cis-[RuCl(2)(dmso)(4)] (P1). These complexes, that were fully characterized in solution and in the solid state, are structurally similar to the anticancer organometallic compounds [Ru(η(6)-arene)(chel)Cl][PF(6)](n) but, in place of a face-capping arene, have the fac-Ru(dmso-S)(3) fragment. In contrast to what observed for the corresponding arene compounds, that rapidly hydrolyze the Cl ligand upon dissolution in water, compounds 4-6 are very stable and inert in aqueous solution. Probably their inertness is the reason why they showed no significant cytotoxicity against the MDA-MB-231 cancer cell line.

  6. Methanol oxidation on stoichiometric and oxygen-rich RuO2(110).

    PubMed

    Rai, Rahul; Weaver, Jason F

    2017-07-26

    We used temperature-programmed reaction spectroscopy (TPRS) to investigate the adsorption and oxidation of methanol on stoichiometric and O-rich RuO 2 (110) surfaces. We find that the complete oxidation of CH 3 OH is strongly preferred on stoichiometric RuO 2 (110) during TPRS for initial CH 3 OH coverages below ∼0.33 ML (monolayer), and that partial oxidation to mainly CH 2 O becomes increasingly favored with increasing CH 3 OH coverage from 0.33 to 1.0 ML. We present evidence that an adsorbed CH 2 O 2 species serves as the key intermediate to complete oxidation and that CH 2 O 2 formation is intrinsically facile but becomes limited by the availability of bridging O-atoms on stoichiometric RuO 2 (110) at initial CH 3 OH coverages above 0.33 ML. We show that methanol molecules adsorbed in excess of 0.33 ML dehydrogenate to mainly CH 2 O and desorb during TPRS, with adsorbed CH 3 O groups mediating the evolution of both CH 2 O and CH 3 OH. We find that O-rich RuO 2 (110) surfaces are also highly active toward methanol oxidation and that selectivity toward the complete oxidation of methanol increases markedly with increasing coverage of on-top O-atoms (O ot ) on RuO 2 (110). Our results demonstrate that CH 3 OH species adsorbed within O ot -rich domains react efficiently during TPRS, in parallel with reaction of CH 3 OH adsorbed initially on cus-Ru sites. The data suggests that the facile hydrogenation of O ot atoms and the resulting desorption of H 2 O at low-temperature (<∼400 K) provides an efficient pathway for restoring reactive O-atoms and thereby promoting complete oxidation of methanol on the O-rich RuO 2 (110) surface.

  7. Dielectric evidence for possible type-II multiferroicity in α-RuCl3

    NASA Astrophysics Data System (ADS)

    Zheng, JiaCheng; Cui, Yi; Li, TianRun; Ran, KeJing; Wen, JinSheng; Yu, WeiQiang

    2018-05-01

    $\\alpha$-RuCl$_3$ is a Mott insulator with a honeycomb lattice with strong spin-orbit coupling. We report dielectric measurements on $\\alpha$-RuCl$_3$ single crystals under field. At zero field, the dielectric constant, $\\epsilon$, drops rapidly when cooled through the magnetic transition temperature T$_N$. With increasing field, the onset of the drop in $\\epsilon$ tracks the T$_N$. Such behavior is absent with field above a critical value H$_c$ ~ 7.5 T, indicating the onset of a quantum phase transition. Our data suggest that the dielectric constant can be used as a probe of magnetic ordering in $\\alpha$-RuCl$_3$, and $\\alpha$-RuCl$_3$ is a possible type-II multiferroics.

  8. Oxidation of the Ru(0001) surface covered by weakly bound, ultrathin silicate films

    DOE PAGES

    Emmez, Emre; Anibal Boscoboinik, J.; Tenney, Samuel; ...

    2015-06-30

    Bilayer silicate films grown on metal substrates are weakly bound to the metal surfaces, which allows ambient gas molecules to intercalate the oxide/metal interface. In this work, we studied the interaction of oxygen with Ru(0001) supported ultrathin silicate and aluminosilicate films at elevated O 2 pressures (10 -5–10 mbar) and temperatures (450–923 K). The results show that the silicate films stay essentially intact under these conditions, and oxygen in the film does not exchange with oxygen in the ambient. O 2 molecules readily penetrate the film and dissociate on the underlying Ru surface underneath. Also, the silicate layer does howevermore » strongly passivate the Ru surface towards RuO 2(110) oxide formation that readily occurs on bare Ru(0001) under the same conditions. Lastly, the results indicate considerable spatial effects for oxidation reactions on metal surfaces in the confined space at the interface. Moreover, the aluminosilicate films completely suppress the Ru oxidation, providing some rationale for using crystalline aluminosilicates in anti-corrosion coatings.« less

  9. {sup 45}Sc Solid State NMR studies of the silicides ScTSi (T=Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harmening, Thomas; Eckert, Hellmut, E-mail: eckerth@uni-muenster.de; Fehse, Constanze M.

    The silicides ScTSi (T=Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt) were synthesized by arc-melting and characterized by X-ray powder diffraction. The structures of ScCoSi, ScRuSi, ScPdSi, and ScIrSi were refined from single crystal diffractometer data. These silicides crystallize with the TiNiSi type, space group Pnma. No systematic influences of the {sup 45}Sc isotropic magnetic shift and nuclear electric quadrupolar coupling parameters on various structural distortion parameters calculated from the crystal structure data can be detected. {sup 45}Sc MAS-NMR data suggest systematic trends in the local electronic structure probed by the scandium atoms: both the electric field gradients andmore » the isotropic magnetic shifts relative to a 0.2 M aqueous Sc(NO{sub 3}){sub 3} solution decrease with increasing valence electron concentration and within each T group the isotropic magnetic shift decreases monotonically with increasing atomic number. The {sup 45}Sc nuclear electric quadrupolar coupling constants are generally well reproduced by quantum mechanical electric field gradient calculations using the WIEN2k code. Highlights: Black-Right-Pointing-Pointer Arc-melting synthesis of silicides ScTSi. Black-Right-Pointing-Pointer Single crystal X-ray data of ScCoSi, ScRuSi, ScPdSi, and ScIrSi. Black-Right-Pointing-Pointer {sup 45}Sc solid state NMR of silicides ScTSi.« less

  10. Dimerization in honeycomb Na2RuO3 under pressure: a DFT study

    NASA Astrophysics Data System (ADS)

    Gazizova, D. D.; Ushakov, A. V.; Streltsov, S. V.

    2018-04-01

    The structural properties of Na2RuO3 under pressure are studied using density functional theory within the nonmagnetic generalized gradient approximation (GGA). We found that one may expect a structural transition at ˜3 GPa. This structure at the high-pressure phase is exactly the same as the low-temperature structure of Li2RuO3 (at ambient pressure) and is characterized by the P21/m space group. Ru ions form dimers in this phase and one may expect strong modification of the electronic and magnetic properties in Na2RuO3 at pressure higher than 3 GPa.

  11. Neutron diffraction study and anomalous negative thermal expansion in non-superconducting PrFe1-xRuxAsO

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yiu, Yuen; Garlea, Vasile O; McGuire, Michael A

    2012-01-01

    Neutron powder diraction has been used to investigate the structural and magnetic behavior of the isoelectronically doped Fe pnictide material PrFe1-xRuxAsO. Substitution of Ru for Fe sup- presses the structural and magnetic phase transitions that occur in the undoped compound PrFeAsO. Contrary to the behavior usually observed in 1111 pnictide materials, the suppression of both the structural and magnetic transitions does not result in the emergence of superconductivity or any other new ground state. Interestingly, PrFeAsO itself shows an unusual negative thermal expansion (NTE) along the c-axis, from 60K down to at least 4K; this does not occur in superconductingmore » samples such as those formed by doping with fluorine on the oxygen site. We nd that NTE is present for all concentrations of PrFe1-xRuxAsO with x ranging from 0.05 to 0.75. These results suggest that the absence of superconductivity in these materials could be related to the presence of NTE.« less

  12. Nearest-neighbor Kitaev exchange blocked by charge order in electron-doped α -RuCl3

    NASA Astrophysics Data System (ADS)

    Koitzsch, A.; Habenicht, C.; Müller, E.; Knupfer, M.; Büchner, B.; Kretschmer, S.; Richter, M.; van den Brink, J.; Börrnert, F.; Nowak, D.; Isaeva, A.; Doert, Th.

    2017-10-01

    A quantum spin liquid might be realized in α -RuCl3 , a honeycomb-lattice magnetic material with substantial spin-orbit coupling. Moreover, α -RuCl3 is a Mott insulator, which implies the possibility that novel exotic phases occur upon doping. Here, we study the electronic structure of this material when intercalated with potassium by photoemission spectroscopy, electron energy loss spectroscopy, and density functional theory calculations. We obtain a stable stoichiometry at K0.5RuCl3 . This gives rise to a peculiar charge disproportionation into formally Ru2 + (4 d6 ) and Ru3 + (4 d5 ). Every Ru 4 d5 site with one hole in the t2 g shell is surrounded by nearest neighbors of 4 d6 character, where the t2 g level is full and magnetically inert. Thus, each type of Ru site forms a triangular lattice, and nearest-neighbor interactions of the original honeycomb are blocked.

  13. Inner-shell photodetachment of transition metal negative ions

    NASA Astrophysics Data System (ADS)

    Dumitriu, Ileana

    This thesis focuses on the study of inner-shell photodetachment of transition metal negative ions, specifically Fe- and Ru- . Experimental investigations have been performed with the aim of gaining new insights into the physics of negative atomic ions and providing valuable absolute cross section data for astrophysics. The experiments were performed using the X-ray radiation from the Advanced Light Source, Lawrence Berkeley National Laboratory, and the merged-beam technique for photoion spectroscopy. Negative ions are a special class of atomic systems very different from neutral atoms and positive ions. The fundamental physics of the interaction of transition metal negative ions with photons is interesting but difficult to analyze in detail because the angular momentum coupling generates a large number of possible terms resulting from the open d shell. Our work reports on the first inner-shell photodetachment studies and absolute cross section measurements for Fe- and Ru -. In the case of Fe-, an important astrophysical abundant element, the inner-shell photodetachment cross section was obtained by measuring the Fe+ and Fe2+ ion production over the photon energy range of 48--72 eV. The absolute cross sections for the production of Fe+ and Fe2+ were measured at four photon energies. Strong shape resonances due to the 3p→3d photoexcitation were measured above the 3p detachment threshold. The production of Ru+, Ru2+, and Ru3+ from Ru- was measured over 30--90 eV photon energy range The absolute photodetachment cross sections of Ru - ([Kr] 4d75s 2) leading to Ru+, Ru2+, and Ru 3+ ion production were measured at three photon energies. Resonance effects were observed due to interference between transitions of the 4 p-electrons to the quasi-bound 4p54d85s 2 states and the 4d→epsilonf continuum. The role of many-particle effects, intershell interaction, and polarization seems much more significant in Ru- than in Fe- photodetachment.

  14. High antiferromagnetic transition temperature of a honeycomb compound SrRu 2O 6

    DOE PAGES

    Tian, Wei; Svoboda, Chris; Ochi, M.; ...

    2015-09-14

    We study the high-temperature magnetic order in a quasi-two-dimensional honeycomb compound SrRu 2O 6 by measuring magnetization and neutron powder diffraction with both polarized and unpolarized neutrons. SrRu 2O 6 crystallizes into the hexagonal lead antimonate (PbSb 2O 6, space group P31m) structure with layers of edge-sharing RuO6 octahedra separated by Sr 2+ ions. SrRu 2O 6 is found to order at T N = 565 K with Ru moments coupled antiferromagnetically both in plane and out of plane. The magnetic moment is 1.30(2) μ B/Ru at room temperature and is along the crystallographic c axis in the G-type magneticmore » structure. We perform density functional calculations with constrained random-phase approximation (RPA) to obtain the electronic structure and effective intra- and interorbital interaction parameters. The projected density of states shows strong hybridization between Ru 4d and O 2p. By downfolding to the target t 2g bands we extract the effective magnetic Hamiltonian and perform Monte Carlo simulations to determine the transition temperature as a function of interand intraplane couplings. We find a weak interplane coupling, 3% of the strong intraplane coupling, permits three-dimensional magnetic order at the observed T N .« less

  15. Mössbauer study of the Ru porcelain of Chinese Song Dynasty and Yuan Dynasty

    NASA Astrophysics Data System (ADS)

    Zhengyao, Gao; Songhua, Chen; Xiande, Chen

    1994-12-01

    The Mössbauer spectra from the glazes of the Song Dynasty and the Yuan Dynasty Ru porcelains and the imitative ancient Ru porcelain are compared and analyzed. It is determined that the original firing atmosphere of the Yuan Dynasty Ru porcelain was reductive. The firing temperature was 1250±20 ‡C. The original firing atmosphere of the Song Dynasty Ru porcelain was also reductive; the firing temperature was above 1200 ‡C. The coloring mechanism of these glazes is discussed.

  16. Microstructure and dielectric parameters of epitaxial SrRuO3/BaTiO3/SrRuO3 heterostructures

    NASA Astrophysics Data System (ADS)

    Boikov, Yu. A.; Claeson, T.

    2001-05-01

    Epitaxial films of ferroelectric barium titanate are desirable in a number of applications but their properties are inferior to those of bulk material. Relations between microstructure and dielectric properties may give better understanding of limitations. Trilayer heterostructures SrRuO3/BaTiO3/SrRuO3 were grown by laser ablation on (100)LaAlO3 and (100)MgO substrates. The BaTiO3 layer was granular in structure. When grown on (100)SrRuO3/(100)LaAlO3, it was preferentially a-axis oriented due to tensile mechanical stress. Using (100)MgO as a substrate, on the other hand, produced a mixture of about equal value of a-axis and c-axis oriented grains of BaTiO3. The dielectric permittivity, ɛ, of the BaTiO3 layer was almost twice as large, at T>200 K and f=100 kHz, for the LaAlO3 substrate as compared to the MgO one. Its maximum value (ɛ/ɛ0≈6200) depended on temperature of growth, grain size, and electric field and compares well with optimal values commonly used for ceramic material. The maximum in the ɛ(T) shifted from about 370 to 320 K when the grain size in the BaTiO3 film decreased from 100 to 40 nm. At T<300 K, hysteresis loops in polarization versus electric field were roughly symmetric. The BaTiO3 films grown on (100)SrRuO3/(100)MgO exhibit the largest remnant polarizations and coercive fields in the temperature range 100-380 K.

  17. Platinum-group element abundances and Re-Os isotopic systematics of the upper continental crust through time: Evidence from glacial diamictites

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Walker, Richard J.; Rudnick, Roberta L.; Gao, Shan; Gaschnig, Richard M.; Puchtel, Igor S.; Tang, Ming; Hu, Zhao-Chu

    2016-10-01

    The fine-grained matrix of glacial diamictites, deposited periodically by continental ice sheets over much of Earth history, provides insights into the average composition and chemical evolution of the upper continental crust (UCC) (Gaschnig et al., 2016, and references therein). The concentrations of platinum-group elements (PGEs, including Os, Ir, Ru, Pt and Pd) and the geochemically related Re, as well as 187Re/188Os and 187Os/188Os ratios, are reported here for globally-distributed glacial diamictites that were deposited during the Mesoarchean, Paleoproterozoic, Neoproterozoic and Paleozoic eras. The medians and averages of PGE concentrations of these diamictite composites decrease from the Mesoarchean to the Neoproterozoic, mimicking decreases in the concentrations of first-row transition elements (Sc, V, Cr, Co and Ni). By contrast, Re concentrations are highly variable with no discernable trend, owing to its high solubility. Assuming these diamictites are representative of average UCC through time, the new data are fully consistent with the previous inference that the Archean UCC contained a greater proportion of mafic-ultramafic rocks relative to younger UCC. Linear regressions of PGEs versus Cr and Ni concentrations in all the diamictite composites from the four time periods are used to estimate the following concentrations of the PGEs in the present-day UCC: 0.059 ± 0.016 ng/g Os, 0.036 ± 0.008 ng/g Ir, 0.079 ± 0.026 ng/g Ru, 0.80 ± 0.22 ng/g Pt and 0.80 ± 0.26 ng/g Pd (2σ of 10,000 bootstrapping regression results). These PGE estimates are slightly higher than the estimates obtained from loess samples. We suggest this probably results from loess preferentially sampling younger UCC rocks that have lower PGE concentrations, or PGEs being fractionated during loess formation. A Re concentration of 0.25 ± 0.12 ng/g (2σ) is obtained from a regression of Re versus Mo. From this, time-integrated 187Re/188Os and 187Os/188Os ratios for the UCC are

  18. RuO2/Activated Carbon Composite Electrode Prepared by Modified Colloidal Procedure and Thermal Decomposition Method

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Zheng, Feng; Gan, Weiping; Luo, Xun

    2016-01-01

    RuO2/activated carbon (AC) composite electrode was prepared by a modified colloidal procedure and a thermal decomposition method. The precursor for RuO2/AC was coated on tantalum sheet and annealed at 150°C to 190°C for 3 h to develop thin-film electrode. The microstructure and morphology of the RuO2/AC film were characterized by thermogravimetric analysis (TGA), x-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). The TGA results showed the maximum loss of RuO2/AC composite film at 410°C, with residual RuO2 of 23.17 wt.%. The amorphous phase structure of the composite was verified by XRD analysis. SEM analysis revealed that fine RuO2 particles were dispersed in an activated carbon matrix after annealing. The electrochemical properties of RuO2/AC electrode were examined by cycling voltammetry, galvanostatic charge-discharge, and cyclic behavior measurements. The specific capacitance of RuO2/AC electrode reached 245 F g-1. The cyclic behavior of RuO2/AC electrode was stable. Optimal annealing was achieved at 170°C for 3 h.

  19. Preparation of Ru-doped SnO2-supported Pt catalysts and their electrocatalytic properties for methanol oxidation.

    PubMed

    Pang, H L; Zhang, X H; Zhong, X X; Liu, B; Wei, X G; Kuang, Y F; Chen, J H

    2008-03-01

    Ru-doped SnO2 nanoparticles were prepared by chemical precipitation and calcinations at 823 K. Due to high stability in diluted acidic solution, Ru-doped SnO2 nanoparticles were selected as the catalyst support and second catalyst for methanol electrooxidation. The micrograph, elemental composition, and structure of the Ru-doped SnO2 nanoparticles were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, respectively. The electrocatalytic properties of the Ru-doped SnO2-supported Pt catalyst (Pt/Ru-doped SnO2) for methanol oxidation have been investigated by cyclic voltammetry. Under the same loading mass of Pt, the Pt/Ru-doped SnO2 catalyst shows better electrocatalytic performance than the Pt/SnO2 catalyst and the best atomic ratio of Ru to Sn in Ru-doped SnO2 is 1/75. Additionally, the Pt/Ru-doped SnO2 catalyst possesses good long-term cycle stability.

  20. Synthesis and characterization of RuO(2)/poly(3,4-ethylenedioxythiophene) composite nanotubes for supercapacitors.

    PubMed

    Liu, Ran; Duay, Jonathon; Lane, Timothy; Bok Lee, Sang

    2010-05-07

    We report the synthesis of composite RuO(2)/poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes with high specific capacitance and fast charging/discharging capability as well as their potential application as electrode materials for a high-energy and high-power supercapacitor. RuO(2)/PEDOT nanotubes were synthesized in a porous alumina membrane by a step-wise electrochemical deposition method, and their structures were characterized using electron microscopy. Cyclic voltammetry was used to qualitatively characterize the capacitive properties of the composite RuO(2)/PEDOT nanotubes. Their specific capacitance, energy density and power density were evaluated by galvanostatic charge/discharge cycles at various current densities. The pseudocapacitance behavior of these composite nanotubes originates from ion diffusion during the simultaneous and parallel redox processes of RuO(2) and PEDOT. We show that the energy density (specific capacitance) of PEDOT nanotubes can be remarkably enhanced by electrodepositing RuO(2) into their porous walls and onto their rough internal surfaces. The flexible PEDOT prevents the RuO(2) from breaking and detaching from the current collector while the rigid RuO(2) keeps the PEDOT nanotubes from collapsing and aggregating. The composite RuO(2)/PEDOT nanotube can reach a high power density of 20 kW kg(-1) while maintaining 80% energy density (28 Wh kg(-1)) of its maximum value. This high power capability is attributed to the fast charge/discharge of nanotubular structures: hollow nanotubes allow counter-ions to readily penetrate into the composite material and access their internal surfaces, while a thin wall provides a short diffusion distance to facilitate ion transport. The high energy density originates from the RuO(2), which can store high electrical/electrochemical energy intrinsically. The high specific capacitance (1217 F g(-1)) which is contributed by the RuO(2) in the composite RuO(2)/PEDOT nanotube is realized because of the high

  1. Synthesis, structure, and electronic properties of a dimer of Ru(bpy)2 doubly bridged by methoxide and pyrazolate.

    PubMed

    Jude, Hershel; Rein, Francisca N; White, Peter S; Dattelbaum, Dana M; Rocha, Reginaldo C

    2008-09-01

    The heterobridged dinuclear complex cis,cis-[(bpy) 2Ru(mu-OCH 3)(mu-pyz)Ru(bpy) 2] (2+) ( 1; bpy = 2,2'-bipyridine; pyz = pyrazolate) was synthesized and isolated as a hexafluorophosphate salt. Its molecular structure was fully characterized by X-ray crystallography, (1)H NMR spectroscopy, and ESI mass spectrometry. The compound 1.(PF 6) 2 (C 44H 38F 12N 10OP 2Ru 2) crystallizes in the monoclinic space group P2 1/ c with a = 13.3312(4) A, b = 22.5379(6) A, c = 17.2818(4) A, beta = 99.497(2) degrees , V = 5121.3(2) A (3), and Z = 4. The meso diastereoisomeric form was exclusively found in the crystal structure, although the NMR spectra clearly demonstrated the presence of two stereoisomers in solution (rac and meso forms at approximately 1:1 ratio). The electronic properties of the complex in acetonitrile were investigated by cyclic voltammetry and UV-vis and NIR-IR spectroelectrochemistries. The stepwise oxidation of the Ru (II)-Ru (II) complex into the mixed-valent Ru (II)-Ru (III) and fully oxidized Ru (III)-Ru (III) states is fully reversible on the time scale of the in situ (spectro)electrochemical measurements. The mixed-valent species displays strong electronic coupling, as evidenced by the large splitting between the redox potentials for the Ru(III)/Ru(II) couples (Delta E 1/2 = 0.62 V; K c = 3 x 10 (10)) and the appearance of an intervalence transfer (IT) band at 1490 nm that is intense, narrow, and independent of solvent. Whereas this salient band in the NIR region originates primarily from highest-energy of the three IT transitions predicted for Ru(II)-Ru(III) systems, a weaker absorption band corresponding to the lowest-energy IT transition was clearly evidenced in the IR region ( approximately 3200 cm (-1)). The observation of totally coalesced vibrational peaks in the 1400-1650 cm (-1) range for a set of five bpy spectator vibrations in Ru (II)-Ru (III) relative to Ru (II)-Ru (II) and Ru (III)-Ru (III) provided evidence for rapid electron transfer and

  2. Biochemistry of metalocenes. The organ distribution of hydroxyacetyl (/sup 103/Ru)ruthenocene and its glucuronide in mice

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Taylor, A.J.; Macha, J.; Wenzel, M.

    1980-01-01

    Hydroxyacetyl(/sup 103/Ru)ruthenocene and its o-glucuronide were prepared in vitro by incubation of acetyl(/sup 103/Ru)ruthenocene with rat-liver homogenate, NADPH, and UDP-glucuronate. The factors affecting hydroxylation and glucuronidation in vitro were optimized for acetylruthenocene. Hydroxyacetyl(/sup 103/Ru)ruthenocene glucuronide showed no affinity for the adrenal glands, but after iv administration of hydroxyacetyl(/sup 103/Ru)ruthenocene there was a distinct accumulation of Ru-103 in adrenals, similar to that found after administration of acetyl(/sup 103/Ru)ruthenocene.

  3. AuRu/meso-Mn2O3: A Highly Active and Stable Catalyst for Methane Combustion

    NASA Astrophysics Data System (ADS)

    Han, Z.; Fang, J. Y.; Xie, S. H.; Deng, J. G.; Liu, Y. X.; Dai, H. X.

    2018-05-01

    Three-dimensionally ordered mesoporous Mn2O3 (meso-Mn2O3) and its supported Au, Ru, and AuRu alloy (0.49 wt% Au/meso-Mn2O3, 0.48 wt% Ru/meso-Mn2O3, and 0.97 wt% AuRu/meso-Mn2O3 (Au/Ru molar ratio = 0.98)) nanocatalysts were prepared using the KIT-6-templating and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous techniques, and their catalytic activities were evaluated for the combustion of methane. It is found that among all of the samples, 0.48 wt% Ru/meso-Mn 2O3 and 0.97 wt% AuRu/meso-Mn2O3 performed the best (the reaction temperature (T90% ) at 90% methane conversion was 530-540°C), but the latter showed a better thermal stability than the former. The partial deactivation of 0.97 wt% AuRu/meso-Mn2O3 due to H2O or CO2 introduction was reversible. It is concluded that the good catalytic activity and thermal stability of 0.97 wt% AuRu/meso-Mn2O3 was associated with the high dispersion of AuRu alloy NPs (2-5 nm) on the surface of meso-Mn2O3 and good low-temperature reducibility.

  4. Inert anode containing oxides of nickel iron and cobalt useful for the electrolytic production of metals

    DOEpatents

    Ray, Siba P.; Liu, Xinghua; Weirauch, Jr., Douglas A.

    2002-01-01

    An inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode includes a ceramic oxide material preferably made from NiO, Fe.sub.2 O.sub.3 and CoO. The inert anode composition may comprise the following mole fractions of NiO, Fe.sub.2 O.sub.3 and CoO: 0.15 to 0.99 NiO; 0.0001 to 0.85 Fe.sub.2 O.sub.3 ; and 0.0001 to 0.45 CoO. The inert anode may optionally include other oxides and/or at least one metal phase, such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. The Ni--Fe--Co--O ceramic material exhibits very low solubility in Hall cell baths used to produce aluminum.

  5. Inert anode containing oxides of nickel, iron and zinc useful for the electrolytic production of metals

    DOEpatents

    Ray, Siba P.; Weirauch, Jr., Douglas A.; Liu, Xinghua

    2002-01-01

    An inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode includes a ceramic oxide material preferably made from NiO, Fe.sub.2 O.sub.3 and ZnO. The inert anode composition may comprise the following mole fractions of NiO, Fe.sub.2 O.sub.3 and ZnO: 0.2 to 0.99 NiO; 0.0001 to 0.8 Fe.sub.2 O.sub.3 ; and 0.0001 to 0.3 ZnO. The inert anode may optionally include other oxides and/or at least one metal phase, such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. The Ni--Fe--Co--O ceramic material exhibits very low solubility in Hall cell baths used to produce aluminum.

  6. Isolation of high quality graphene from Ru by solution phase intercalation

    NASA Astrophysics Data System (ADS)

    Koren, E.; Sutter, E.; Bliznakov, S.; Ivars-Barcelo, F.; Sutter, P.

    2013-09-01

    We introduce a method for isolating graphene grown on epitaxial Ru(0001)/α-Al2O3. The strong graphene/Ru(0001) coupling is weakened by electrochemically driven intercalation of hydrogen underpotentially deposited in aqueous KOH solution, which allows the penetration of water molecules at the graphene/Ru(0001) interface. Following these electrochemically driven processes, the graphene can be isolated by electrochemical hydrogen evolution and transferred to arbitrary supports. Raman and transport measurements demonstrate the high quality of the transferred graphene. Our results show that intercalation, typically carried out in vacuum, can be extended to solution environments for graphene processing under ambient conditions.

  7. Photochemical Properties and Reactivity of a Ru Compound Containing an NAD/NADH-Functionalized 1,10-Phenanthroline Ligand.

    PubMed

    Kobayashi, Katsuaki; Ohtsu, Hideki; Nozaki, Koichi; Kitagawa, Susumu; Tanaka, Koji

    2016-03-07

    An NAD/NADH-functionalized ligand, benzo[b]pyrido[3,2-f][1,7]-phenanthroline (bpp), was newly synthesized. A Ru compound containing the bpp ligand, [Ru(bpp)(bpy)2](2+), underwent 2e(-) and 2H(+) reduction, generating the NADH form of the compound, [Ru(bppHH)(bpy)2](2+), in response to visible light irradiation in CH3CN/TEA/H2O (8/1/1). The UV-vis and fluorescent spectra of both [Ru(bpp)(bpy)2](2+) and [Ru(bppHH)(bpy)2](2+) resembled the spectra of [Ru(bpy)3](2+). Both complexes exhibited strong emission, with quantum yields of 0.086 and 0.031, respectively; values that are much higher than those obtained from the NAD/NADH-functionalized complexes [Ru(pbn)(bpy)2](2+) and [Ru(pbnHH)(bpy)2](2+) (pbn = (2-(2-pyridyl)benzo[b]-1.5-naphthyridine, pbnHH = hydrogenated form of pbn). The reduction potential of the bpp ligand in [Ru(bpp)(bpy)2](2+) (-1.28 V vs SCE) is much more negative than that of the pbn ligand in [Ru(pbn)(bpy)2](2+) (-0.74 V), although the oxidation potentials of bppHH and pbnHH are essentially equal (0.95 V). These results indicate that the electrochemical oxidation of the dihydropyridine moiety in the NADH-type ligand was independent of the π system, including the Ru polypyridyl framework. [Ru(bppHH)(bpy)2](2+) allowed the photoreduction of oxygen, generating H2O2 in 92% yield based on [Ru(bppHH)(bpy)2](2+). H2O2 production took place via singlet oxygen generated by the energy transfer from excited [Ru(bppHH)(bpy)2](2+) to triplet oxygen.

  8. Synthesis and characterization of bimetallic metal-organic framework Cu-Ru-BTC with HKUST-1 structure.

    PubMed

    Gotthardt, Meike A; Schoch, Roland; Wolf, Silke; Bauer, Matthias; Kleist, Wolfgang

    2015-02-07

    The bimetallic metal-organic framework Cu-Ru-BTC with the stoichiometric formula Cu2.75Ru0.25(BTC)2·xH2O, which is isoreticular to HKUST-1, was successfully prepared in a direct synthesis using mild reaction conditions. The partial substitution of Cu(2+) by Ru(3+) centers in the paddlewheel structure and the absence of other Ru-containing phases was proven using X-ray absorption spectroscopy.

  9. Aqueous-Phase Hydrogenolysis of Glycerol over Re Promoted Ru Catalysts Encapuslated in Porous Silica Nanoparticles

    PubMed Central

    Li, Kuo-Tseng; Yen, Ruey-Hsiang

    2018-01-01

    Activity improvement of Ru-based catalysts is needed for efficient production of valuable chemicals from glycerol hydrogenolysis. In this work, a series of Re promoted Ru catalysts encapuslated in porous silica nanoparticles (denoted as Re-Ru@SiO2) were prepared by coating silica onto the surface of chemically reduced Ru-polyvinylpyrrolidone colloids, and were used to catalyze the conversion of glycerol to diols and alcohols in water. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) were used to characterize these nanoparticles. Effects of Ru/Si atomic ratio, Re addition, glycerol and catalyst concentrations, reaction time, temperature, and hydrogen pressure were investigated. Re addition retarded the reduction of ruthenium oxide, but increased the catalyst reactivity for glycerol hydrogenolysis. Due to its greater Ru content, Re-Ru@ SiO2 showed much better activity (reacted at much lower temperature) and more yields of 1,2-propanediol and overall liquid-phase products than Re-Ru/SiO2 (prepared by conventional impregnation method) reported before. The rate of glycerol disappearance exhibited first-order dependence on glycerol concentration and hydrogen pressure, with an activation energy of 107.8 kJ/mol. The rate constant increased linearly with increasing Ru/Si atomic ratio and catalyst amount. The yield of overall liquid-phase products correlated well with glycerol conversion. PMID:29522432

  10. Plant RuBisCo assembly in E. coli with five chloroplast chaperones including BSD2.

    PubMed

    Aigner, H; Wilson, R H; Bracher, A; Calisse, L; Bhat, J Y; Hartl, F U; Hayer-Hartl, M

    2017-12-08

    Plant RuBisCo, a complex of eight large and eight small subunits, catalyzes the fixation of CO 2 in photosynthesis. The low catalytic efficiency of RuBisCo provides strong motivation to reengineer the enzyme with the goal of increasing crop yields. However, genetic manipulation has been hampered by the failure to express plant RuBisCo in a bacterial host. We achieved the functional expression of Arabidopsis thaliana RuBisCo in Escherichia coli by coexpressing multiple chloroplast chaperones. These include the chaperonins Cpn60/Cpn20, RuBisCo accumulation factors 1 and 2, RbcX, and bundle-sheath defective-2 (BSD2). Our structural and functional analysis revealed the role of BSD2 in stabilizing an end-state assembly intermediate of eight RuBisCo large subunits until the small subunits become available. The ability to produce plant RuBisCo recombinantly will facilitate efforts to improve the enzyme through mutagenesis. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  11. RuO₂ pH Sensor with Super-Glue-Inspired Reference Electrode.

    PubMed

    Lonsdale, Wade; Wajrak, Magdalena; Alameh, Kamal

    2017-09-06

    A pH-sensitive RuO₂ electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO₂ working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO₂ pH-sensitive working electrode and a SiO₂-PVB junction-modified RuO₂ reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices.

  12. Ancient Chemistry "Pharaoh's Snakes" for Efficient Fe-/N-Doped Carbon Electrocatalysts.

    PubMed

    Ren, Guangyuan; Gao, Liangliang; Teng, Chao; Li, Yunan; Yang, Hequn; Shui, Jianglan; Lu, Xianyong; Zhu, Ying; Dai, Liming

    2018-04-04

    The method of fabricating nonprecious metal electrocatalysts with high activity and durability through a facile and eco-friendly procedure is of great significance to the development of low-cost fuel cells and metal-air batteries. Herein, we present that an ancient chemical reaction of "Pharaoh's snakes" can be a fast and convenient technique to prepare Fe-/N-doped carbon (Fe/N-C) nanosheet/nanotube electrocatalysts with sugar, soda, melamine, and iron nitrate as precursors. The resultant Fe/N-C catalyst has a hierarchically porous structure, a large surface area, and uniformly distributed active sites. The catalyst shows high electrocatalytic activities toward both the oxygen reduction reaction with a half-wave potential of 0.90 V (vs reversible hydrogen electrode) better than that of Pt/C and the oxygen evolution reaction with an overpotential of 0.46 V at the current density of 10 mA cm -2 comparable to that of RuO 2 . The activity and stability of the catalyst are also evaluated in primary and rechargeable Zn-air batteries. In both conditions, three-dimensional Fe/N-C exhibited performances superior to Pt/C. Our work demonstrates a success of utilizing an ancient science to make a state-of-the-art electrocatalyst.

  13. Lateral interactions in (NO+O) coadsorbate layers on Ru(001): fundamental and overtone modes

    NASA Astrophysics Data System (ADS)

    Jakob, P.

    1999-06-01

    A systematic investigation of various (NO+O) coadsorbate layers on Ru(001) is presented. By using infrared absorption spectroscopy, fundamental and overtone bands were studied in a wide temperature range to extract dynamical information on lifetime broadening (low-temperature limit) and dephasing behavior (thermal broadening and line shifts). The layers studied were (1) 3NO-(2×2)/Ru(001), (2) (2NO+O)(2×2)/Ru(001) and (3) (NO+2O)(2×2)/Ru(001). It is found that replacing hollow-site NO by oxygen atoms causes characteristic frequency shifts of νRu-NO and νN-O of linearly bond on-top NO which is present for all three layers. In agreement with earlier results on CO/Ru(001) and with theoretical prediction, the νN-O″ overtone band displays rapid broadening with increasing temperature (about four times faster than the respective localized νN-O fundamental band) while the temperature-dependent line shift and the 0 K linewidth is twice as high as observed for νN-O. An unusually large bandwidth close to 100 cm -1 is found for the νN-O mode of the row-like (NO+O)(2×1)/Ru(001) overlayer.

  14. Pt-Ru/CeO2/carbon nanotube nanocomposites: an efficient electrocatalyst for direct methanol fuel cells.

    PubMed

    Sun, Zhenyu; Wang, Xiang; Liu, Zhimin; Zhang, Hongye; Yu, Ping; Mao, Lanqun

    2010-07-20

    Pt-Ru/CeO(2)/multiwalled carbon nanotube (MWNT) electrocatalysts were prepared using a rapid sonication-facilitated deposition method and were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and voltammetry. Morphological characterization by TEM revealed that CeO(2) nanoparticles (NPs) were in intimate contact with Pt-Ru NPs, and both were highly dispersed on the exteriors of nanotubes with a small size and a very narrow size distribution. Compared with the Pt-Ru/MWNT and Pt/MWNT electrocatalysts, the as-prepared Pt-Ru/CeO(2)/MWNT exhibited a significantly improved electrochemically active surface area (ECSA) and a remarkably enhanced activity toward methanol oxidation. The effects of the Pt-Ru loading and the Pt-to-Ru molar ratio on the electrocatalytic activity of Pt-Ru/CeO(2)/MWNT for methanol oxidation were investigated. We found that a maximum activity toward methanol oxidation reached at the 10 wt % of Pt-Ru loading and 1:1 of Pt-to-Ru ratio. Moreover, the role of CeO(2) in the catalysts for the enhancement of methanol oxidation was discussed in terms of both bifunctional mechanism and electronic effects.

  15. Carbon deposition in the Bosch process with ruthenium and ruthenium-iron alloy catalysts. M.S. Thesis. Final Report, Jan. 1981 - Jul. 1982

    NASA Technical Reports Server (NTRS)

    Manning, M. P.; Reid, R. C.; Sophonpanich, C.

    1982-01-01

    The effectiveness of ruthenium and the alloys 50Ru50Fe and 33Ru67Fe as alternatives to iron, nickel, and cobalt catalysts in recovering oxygen from metabolic carbon dioxide was investigated. Carbon deposition boundaries over the unsupported alloys are reported. Experiments were also carried out over 50Ru50Fe and 97Ru3Fe3 catalysts supported on gamma-alumina to determine their performance in the synthesis of low molecular weight olefins. High production of ethylene and propylene would be beneficial for an improvement of an overall Bosch process, as a gas phase containing high olefin content would enhance carbon deposition in a Bosch reactor.

  16. Formation and nitrile hydrogenation performance of Ru nanoparticles on a K-doped Al2O3 surface.

    PubMed

    Muratsugu, Satoshi; Kityakarn, Sutasinee; Wang, Fei; Ishiguro, Nozomu; Kamachi, Takashi; Yoshizawa, Kazunari; Sekizawa, Oki; Uruga, Tomoya; Tada, Mizuki

    2015-10-14

    Decarbonylation-promoted Ru nanoparticle formation from Ru3(CO)12 on a basic K-doped Al2O3 surface was investigated by in situ FT-IR and in situ XAFS. Supported Ru3(CO)12 clusters on K-doped Al2O3 were converted stepwise to Ru nanoparticles, which catalyzed the selective hydrogenation of nitriles to the corresponding primary amines via initial decarbonylation, the nucleation of the Ru cluster core, and the growth of metallic Ru nanoparticles on the surface. As a result, small Ru nanoparticles, with an average diameter of less than 2 nm, were formed on the support and acted as efficient catalysts for nitrile hydrogenation at 343 K under hydrogen at atmospheric pressure. The structure and catalytic performance of Ru catalysts depended strongly on the type of oxide support, and the K-doped Al2O3 support acted as a good oxide for the selective nitrile hydrogenation without basic additives like ammonia. The activation of nitriles on the modelled Ru catalyst was also investigated by DFT calculations, and the adsorption structure of a nitrene-like intermediate, which was favourable for high primary amine selectivity, was the most stable structure on Ru compared with other intermediate structures.

  17. Localized-itinerant dichotomy and unconventional magnetism in SrRu2O6

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Okamoto, Satoshi; Ochi, Masayuki; Arita, Ryotaro

    Electron correlations tend to generate local magnetic moments that usually order if the lattices are not too frustrated. The hexagonal compound SrRumore » $$_2$$O$$_6$$ has a relatively high N{\\'e}el temperature but small local moments, which seem to be at odds with the nominal valence of Ru$$^{5+}$$ in the $$t_{2g}^3$$ configuration. Here, we investigate the electronic and magnetic properties of SrRu$$_2$$O$$_6$$ using density functional theory (DFT) combined with dynamical mean field theory (DMFT). We find that the strong hybridization between Ru $d$ and O $p$ states results in a Ru valence that is closer to $+4$, leading to the small ordered moment, consistent with a DFT prediction. While the agreement with DFT might indicate that SrRu$$_2$$O$$_6$$ is in the weak coupling regime, our DMFT studies provide evidence from the mass enhancement and local moment formation that indicate correlation effects play a significant role. The local moment per Ru site is about a factor 2 larger than the ordered moment at low temperatures and remains finite in the whole temperature range investigated. Our theoretical N{\\'e}el temperature $$\\sim 700$$~K is in reasonable agreement with experimental observations. Due to a small lattice distortion, the degenerate $$t_{2g}$$ manifold is split and the quasiparticle weight is renormalized significantly in the $$a_{1g}$$ state, while correlation effects in $$e_g'$$ states are about a factor of 2--3 weaker. SrRu$$_2$$O$$_6$$ is a unique system in which localized and itinerant electrons coexist with the proximity to an orbitally-selective Mott transition within the $$t_{2g}$$ sector.« less

  18. Antitumor activity of Ru(III) complexes carrying beta-diketonato ligands in vitro and in vivo.

    PubMed

    Arandjelovic, S S; Bjelogrlic, K S; Malesevic, N N; Tesic, Lj Z; Radulovic, S S

    2009-01-01

    To investigate the antitumor activity of two newly synthesized ruthenium(III) [Ru(III)] compounds carrying bidentate ligands: (acac)-acetylacetonate, [Ru(acac)3), and (tfac)-trifluoroacetylacetonate [Ru(tfac)3]. The activity of ruthenium(III) analogues was evaluated on HeLa, B16, and Femx cell lines for cytotoxicity in vitro using MTT assay, and inhibition on tumor invading ability in vitro using cell migration and invasion assays, whereas inhibition of tumor growth in vivo was estimated on advanced B16 murine melanoma model. Both compounds were also investigated in combinations with cisplatin, oxaliplatin, or poly ADP-ribose polymerase- 1 (PARP-1) inhibitor, in order to determine the pattern of mutual interactions. Applied as single drugs, Ru(tfac)3 showed high cytotoxic activity against HeLa and Femx cell lines, while Ru(acac)3 did not reach the IC50 on any of the cell lines tested. In combinations, Ru(acac)3 with cisplatin gained synergistic interaction, antagonistic with oxaliplatin, and of different kind with (PARP-1) inhibitor in concentration-and cell line-dependent manner. Ru(acac)3 exhibited inhibition of HeLa cell migration and gelatinolytic activity of MMP-2 and MMP-9. Ru(tfac)3 complexes did not induce significant reduction of melanoma growth in vivo, whereas Ru(acac)3 did, but the latter failed to contribute in lifespan improvement. The investigated ruthenium complexes showed different levels of antitumor activity in vitro and in vivo, implicating on different mechanisms of their action as well as diverse perspectives in cancer treatment.

  19. Syntheses, structural determinations of [Ru(ROCS2)2(PPh3)2](+/0) pairs, and kinetic analyses of thermal reactions involving transient trans-[Ru(iPrOCS2)2(PPh3)2] species (ROCS2(-) = ethyl- or isopropyldithiocarbonate and PPh3 = triphenylphosphine).

    PubMed

    Noda, Kyoko; Ohuchi, Yuko; Hashimoto, Akira; Fujiki, Masayuki; Itoh, Sumitaka; Iwatsuki, Satoshi; Noda, Toshiaki; Suzuki, Takayoshi; Kashiwabara, Kazuo; Takagi, Hideo D

    2006-02-06

    Controlled-potential electrochemical oxidation of cis-[Ru(ROCS2)2(PPh3)2] (R = Et, iPr) yielded corresponding Ru(III) complexes, and the crystal structures of cis-[Ru(ROCS2)2(PPh3)2] and trans-[Ru(ROCS2)2(PPh3)2](PF6) were determined. Both pairs of complexes exhibited almost identical coordination structures. The Ru-P distances in trans-[Ru(III)(ROCS2)2(PPh3)2](PF6) [2.436(3)-2.443(3) A] were significantly longer than those in cis-[Ru(II)(ROCS2)2(PPh3)2] [2.306(1)-2.315(2) A]: the smaller ionic radius of Ru(III) than that of Ru(II) stabilizes the trans conformation for the Ru(III) complex due to the steric requirement of bulky phosphine ligands while mutual trans influence by the phosphine ligands induces significant elongation of the Ru(III)-P bonds. Cyclic voltammograms of the cis-[Ru(ROCS2)2(PPh3)2] and trans-[Ru(ROCS2)2(PPh3)2]+ complexes in dichloromethane solution exhibited typical dual redox signals corresponding to the cis-[Ru(ROCS2)2(PPh3)2](+/0) (ca. +0.15 and +0.10 V vs ferrocenium/ferrocene couple for R = Et and iPr, respectively) and to trans-[Ru(ROCS2)2(PPh3)2](+/0) (-0.05 and -0.15 V vs ferrocenium/ferrocene for R = Et and iPr, respectively) couples. Analyses on the basis of the Nicholson and Shain's method revealed that the thermal disappearance rate of transient trans-[Ru(ROCS2)2(PPh3)2] was dependent on the concentration of PPh3 in the bulk: the rate constant for the intramolecular isomerization reaction of trans-[Ru(iPrOCS2)2(PPh3)2] was determined as 0.338 +/- 0.004 s(-1) at 298.3 K (deltaH* = 41.8 +/- 1.5 kJ mol(-1) and deltaS* = -114 +/- 7 J mol(-1) K(-1)), while the dissociation rate constant of coordinated PPh3 from the trans-[Ru(iPrOCS2)2(PPh3)2] species was estimated as 0.113 +/- 0.008 s(-1) at 298.3 K (deltaH* = 97.6 +/- 0.8 kJ mol(-1) and deltaS* = 64 +/- 3 J mol(-1) K(-1)), by monitoring the EC reaction (electrode reaction followed by chemical processes) at different concentrations of PPh3 in the bulk. It was found that the trans to cis

  20. The Role of Seven-Coordination in Ru-Catalyzed Water Oxidation

    DOE PAGES

    Matheu, Roc; Ertem, Mehmed Z.; Pipelier, Muriel; ...

    2018-01-19

    A family of Ru complexes based on the pentadentate ligand t5a 3– ((2,5-bis(6-carboxylatopyridin-2-yl)pyrrol-1-ide) and pyridine (py) that includes {Ru II(Ht5a-κ-N 2O)(py) 3} (1H II(κ-N 2O)), {Ru III(t5a-κ-N 3O 1.5)(py) 2} (2 III(κ-N 3O 1.5)), and {Ru IV(t5a-κ-N 3O 2)(py) 2}+ ({2 IV(κ-N3O 2)}+) has been prepared and thoroughly characterized. Complexes 1HII(κ-N 2O), 2 III(κ-N 3O 1.5), and {2 IV(κ-N 3O 2)}+ have been investigated in solution by spectroscopic methods (NMR, UV–vis) and in the solid state by single-crystal X-ray diffraction analysis and complemented by density functional theory (DFT) calculations. The redox properties of complex 2 III(κ-N 3O 1.5) have beenmore » studied by electrochemical methods (CV and DPV), showing its easy access to high oxidation states, thanks to the trianionic nature of the t5a 3– ligand. Under neutral to basic conditions complex {2 IV(κ-N3O 2)}+ undergoes aquation, generating {Ru IV(OH)(t5a-κ-N 2O)(py) 2} (2 IV(OH)(κ-N 2O)). Further oxidation of the complex forms {Ru V(O)(t5a-κ-N 2O)(py) 2} (2 V(O)(κ-N 2O)), which is a very efficient water oxidation catalyst, reaching a TOF MAX value of 9400 s –1 at pH 7.0, as measured via foot of the wave analysis. The key to fast kinetics for the catalytic oxidation of water to dioxygen by 2 V(O)(κ-N 2O) is due not only to the easy access to high oxidation states but also to the intramolecular hydrogen bonding provided by the noncoordinated dangling carboxylate at the transition state, as corroborated by DFT calculations.« less

  1. The Role of Seven-Coordination in Ru-Catalyzed Water Oxidation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Matheu, Roc; Ertem, Mehmed Z.; Pipelier, Muriel

    A family of Ru complexes based on the pentadentate ligand t5a 3– ((2,5-bis(6-carboxylatopyridin-2-yl)pyrrol-1-ide) and pyridine (py) that includes {Ru II(Ht5a-κ-N 2O)(py) 3} (1H II(κ-N 2O)), {Ru III(t5a-κ-N 3O 1.5)(py) 2} (2 III(κ-N 3O 1.5)), and {Ru IV(t5a-κ-N 3O 2)(py) 2}+ ({2 IV(κ-N3O 2)}+) has been prepared and thoroughly characterized. Complexes 1HII(κ-N 2O), 2 III(κ-N 3O 1.5), and {2 IV(κ-N 3O 2)}+ have been investigated in solution by spectroscopic methods (NMR, UV–vis) and in the solid state by single-crystal X-ray diffraction analysis and complemented by density functional theory (DFT) calculations. The redox properties of complex 2 III(κ-N 3O 1.5) have beenmore » studied by electrochemical methods (CV and DPV), showing its easy access to high oxidation states, thanks to the trianionic nature of the t5a 3– ligand. Under neutral to basic conditions complex {2 IV(κ-N3O 2)}+ undergoes aquation, generating {Ru IV(OH)(t5a-κ-N 2O)(py) 2} (2 IV(OH)(κ-N 2O)). Further oxidation of the complex forms {Ru V(O)(t5a-κ-N 2O)(py) 2} (2 V(O)(κ-N 2O)), which is a very efficient water oxidation catalyst, reaching a TOF MAX value of 9400 s –1 at pH 7.0, as measured via foot of the wave analysis. The key to fast kinetics for the catalytic oxidation of water to dioxygen by 2 V(O)(κ-N 2O) is due not only to the easy access to high oxidation states but also to the intramolecular hydrogen bonding provided by the noncoordinated dangling carboxylate at the transition state, as corroborated by DFT calculations.« less

  2. Electrochemiluminescence immunosensor for ultrasensitive detection of biomarker using Ru(bpy)(3)(2+)-encapsulated silica nanosphere labels.

    PubMed

    Qian, Jing; Zhou, Zhenxian; Cao, Xiaodong; Liu, Songqin

    2010-04-14

    Here, we describe a new approach for electrochemiluminescence (ECL) assay with Ru(bpy)(3)(2+)-encapsulated silica nanoparticle (SiO(2)@Ru) as labels. A water-in-oil (W/O) microemulsion method was employed for one-pot synthesis of SiO(2)@Ru nanoparticles. The as-synthesized SiO(2)@Ru nanoparticles have a narrow size distribution, which allows reproducible loading of Ru(bpy)(3)(2+) inside the silica shell and of alpha-fetoprotein antibody (anti-AFP), a model antibody, on the silica surface with glutaraldehyde as linkage. The silica shell effectively prevents leakage of Ru(bpy)(3)(2+) into the aqueous solution due to strong electrostatic interaction between the positively charged Ru(bpy)(3)(2+) and the negatively charged surface of silica. The porous structure of silica shell allowed the ion to move easily through the pore to exchange energy/electrons with the entrapped Ru(bpy)(3)(2+). The as-synthesized SiO(2)@Ru can be used as a label for ultrasensitive detection of biomarkers through a sandwiched immunoassay process. The calibration range of AFP concentration was 0.05-30 ng mL(-1) with linear relation from 0.05 to 20 ng mL(-1) and a detection limit of 0.035 ng mL(-1) at 3sigma. The resulting immunosensors possess high sensitivity and good analytical performance. Copyright 2010 Elsevier B.V. All rights reserved.

  3. Compositional effects in Ru, Pd, Pt, and Rh-doped mesoporous tantalum oxide catalysts for ammonia synthesis.

    PubMed

    Yue, Chaoyang; Qiu, Longhui; Trudeau, Michel; Antonelli, David

    2007-06-11

    A series of early metal-promoted Ru-, Pd-, Pt-, and Rh-doped mesoporous tantalum oxide catalysts were synthesized using a variety of dopant ratios and dopant precursors, and the effects of these parameters on the catalytic activity of NH3 synthesis from H2 and N2 were explored. Previous studies on this system supported an unprecedented mechanism in which N-N cleavage occurred at the Ta sites rather than on Ru. The results of the present study showed, for all systems, that Ba is a better promoter than Cs or La and that the nitrate is a superior precursor for Ba than the isopropoxide or the hydroxide. 15N-labeling studies showed that residual nitrate functions as the major ammonia source in the first hour but that it does not account for the ammonia produced after the nitrate is completely consumed. Ru3(CO)12 proved to be a better Ru precursor than RuCl(3).3H2O, and an almost linear increase in activity with increasing Ru loading level was observed at 350 degrees C (623 K). However, at 175 degrees C (448 K), the increase in Ru had no effect on the reaction rate. Pd functioned with comparable rates to Ru, while Pt and Rh functioned far less efficiently. The surprising activities for the Pd-doped catalysts, coupled with XPS evidence for low-valent Ta in this catalyst system, support a mechanism in which cleavage of the N-N triple bond occurs on Ta rather than the precious metal because the Ea value for N-N cleavage on Pd is 2.5 times greater than that for Ru, and the 9.3 kJ mol-1 Ea value measured previously for the Ru system suggests that N-N cleavage cannot occur at the Ru surface.

  4. Nanoporous Ru as a carbon- and binder-free cathode for Li-O2 batteries.

    PubMed

    Liao, Kaiming; Zhang, Tao; Wang, Yongqing; Li, Fujun; Jian, Zelang; Yu, Haijun; Zhou, Haoshen

    2015-04-24

    Porous carbon-free cathodes are critical to achieve a high discharge capacity and efficient cycling for rechargeable Li-O2 battery. Herein, we present a very simple method to directly grow nanoporous Ru (composed of polycrystalline particles of ∼5 nm) on one side of a current collector of Ni foam via a galvanic replacement reaction. The resulting Ru@Ni can be employed as a carbon- and binder-free cathode for Li-O2 batteries and delivers a specific capacity of 3720 mAh gRu (-1) at a current density of 200 mA gRu (-1) . 100 cycles of continuous discharge and charge are obtained at a very narrow terminal voltage window of 2.75∼3.75 V with a limited capacity of 1000 mAh gRu (-1) . The good performance of the nanoporous Ru@Ni cathode can be mainly attributed to the effective suppression of the by-products related to carbon or binder, the good adhesion of the catalyst to the current collector, and the good permeation of O2 and electrolyte into the active sites of the nanoporous Ru with the open pore system. This new type electrode provides a snapshot toward developing high-performance carbon- and binder-free Li-O2 batteries. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Electronic and magnetic properties in Sr{sub 1-x}La{sub x}RuO{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gupta, Renu; Pramanik, A. K., E-mail: akpramanik@mail.jnu.ac.in

    2016-05-23

    Here we report the structural, magnetic and transport properties in La doped SrRuO{sub 3}. The doping of La{sup 3+} modifies the ionic state of Ru by converting Ru{sup 4+} to Ru{sup +3}. However, there is modification in lattice parameters as La{sup 3+} has smaller ionic radii than that of Sr{sup 2+}. We find La doping weakens the ferromagnetic state in SrRuO{sub 3} in terms of lowering T{sub c} and decreasing the magnetic moment. The electrical resistivity shows metallic behavior in whole temperature range, however, resistivity increases with doping of La.

  6. Magnetic interactions in praseodymium ruthenate Pr{sub 3}RuO{sub 7} with fluorite-related structure

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Inabayashi, Masaki; Doi, Yoshihiro; Wakeshima, Makoto

    2017-06-15

    Solid solutions Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7} (0≤x≤1.0) and (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7} (0≤x≤0.7) were obtained as a single phase compound. They crystallize in an orthorhombic superstructure derived from that of the cubic fluorite with space group Cmcm. The results of the Rietveld analysis for X-ray diffraction profiles of Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7} showed that Ru and Ta atoms are randomly situated at the six-coordinate 4b site. For (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7}, with increasing the concentration of Y ions (x value), the smaller Y ions occupy selectively the seven-coordinate 8g site rather than the eight-coordinate 4a site.more » Through magnetic susceptibility measurements for Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7}, the antiferromagnetic transition temperatures decrease linearly with increasing x value, and at x=0.75 no magnetic ordering was found down to 1.8 K, indicating the magnetic interaction is not one-dimensional, but three-dimensional. On the other hand, the antiferromagnetic transition temperature for (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7} decreases with increasing x value, but above x≥0.50 it becomes constant (~12 K). This result indicates that Pr{sup 3+} ions at the seven-coordinate site greatly contribute to the antiferromagnetic interactions observed in (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7}. Density functional calculations of Pr{sub 3}RuO{sub 7} demonstrate that the electronic structure gives insulating character and that oxygen 2p orbitals hybridize strongly with Ru 4d orbitals in the valence band (VB). Near the top of VB, the Pr 4 f orbitals at the seven-coordinated site also show a weak hybridization with the O(1) 2p orbitals. The Ru-O(1)-Pr superexchange pathway take part in three-dimensional magnetic interaction and play an important role in an enhancement of long-range magnetic ordering. - Graphical abstract: The spin densities and the spin polarization of Pr{sub 3}RuO{sub 7} are shown

  7. Osmium isotope variations in the oceans recorded by Fe-Mn crusts

    USGS Publications Warehouse

    Burton, K.W.; Bourdon, B.; Birck, J.-L.; Allegre, C.J.; Hein, J.R.

    1999-01-01

    This study presents osmium (Os) isotope data for recent growth surfaces of hydrogenetic ferromanganese (Fe-Mn) crusts from the Pacific, Atlantic and Indian Oceans. In general, these data indicate a relatively uniform Os isotopic composition for modern seawater, but suggest that North Atlantic seawater is slightly more radiogenic than that of the Pacific and Indian Oceans. The systematic difference in the Os isotopic composition between the major oceans probably reflects a greater input of old continental material with a high Re/Os ratio in the North Atlantic Ocean, consistent with the distribution of Nd and Pb isotopes. This spatial variation in the Os isotope composition in seawater is consistent with a residence time for Os of between 2 and 60 kyr. Indian Ocean samples show no evidence of a local source of radiogenic Os, which suggests that the present-day riverine input from the Himalaya-Tibet region is not a major source for Os. Recently formed Fe-Mn crusts from the TAG hydrothermal field in the North Atlantic yield an Os isotopic composition close to that of modern seawater, which indicates that, in this area, the input of unradiogenic Os from the hydrothermal alteration of oceanic crust is small. However, some samples from the deep Pacific (???4 km) possess a remarkably unradiogenic Os isotope composition (187Os/186Os ratios as low as 4.3). The compositional control of Os incorporation into the crusts and mixing relationships suggest that this unradiogenic composition is most likely due to the direct incorporation of micrometeoritic or abyssal peridotite particles, rather than indicating the presence of an unradiogenic deep-water mass. Moreover, this unradiogenic signal appears to be temporary, and local, and has had little apparent effect on the overall evolution of seawater. These results confirm that input of continental material through erosion is the dominant source of Os in seawater, but it is not clear whether global Os variations are due to the input

  8. Stress corrosion behavior of Ru-enhanced alpha-beta titanium alloys in methanol solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schutz, R.W.; Horrigan, J.M.; Bednarowicz, T.A.

    1998-12-31

    Conservative, practical guidelines for the minimum water content required to prevent methanolic stress corrosion cracking (SCC) of Ti-6Al-4V-Ru and Ti-3Al-2.5V-Ru alloy tubulars have been developed from slow strain rate testing in plain and acidified NaCl-saturated methanol-water solutions at 25 C. A minimum methanol water content of 10 wt.% is proposed for Ti-6Al-4V-Ru, whereas 2-3 wt.% is sufficient for the lower strength Ti-3Al-2.5V-Ru alloy. Although HCl-acidification aggravated methanolic SCC, intermixing of methanol with crude oil or pure hydrocarbons, H{sub 2}S gas saturation, and/or increasing temperature diminished cracking susceptibility in these alloy tubulars.

  9. Radial mixing and Ru-Mo isotope systematics under different accretion scenarios

    NASA Astrophysics Data System (ADS)

    Fischer, Rebecca A.; Nimmo, Francis; O'Brien, David P.

    2018-01-01

    The Ru-Mo isotopic compositions of inner Solar System bodies may reflect the provenance of accreted material and how it evolved with time, both of which are controlled by the accretion scenario these bodies experienced. Here we use a total of 116 N-body simulations of terrestrial planet accretion, run in the Eccentric Jupiter and Saturn (EJS), Circular Jupiter and Saturn (CJS), and Grand Tack scenarios, to model the Ru-Mo anomalies of Earth, Mars, and Theia analogues. This model starts by applying an initial step function in Ru-Mo isotopic composition, with compositions reflecting those in meteorites, and traces compositional evolution as planets accrete. The mass-weighted provenance of the resulting planets reveals more radial mixing in Grand Tack simulations than in EJS/CJS simulations, and more efficient mixing among late-accreted material than during the main phase of accretion in EJS/CJS simulations. We find that an extensive homogeneous inner disk region is required to reproduce Earth's observed Ru-Mo composition. EJS/CJS simulations require a homogeneous reservoir in the inner disk extending to ≥3-4 AU (≥74-98% of initial mass) to reproduce Earth's composition, while Grand Tack simulations require a homogeneous reservoir extending to ≥3-10 AU (≥97-99% of initial mass), and likely to ≥6-10 AU. In the Grand Tack model, Jupiter's initial location (the most likely location for a discontinuity in isotopic composition) is ∼3.5 AU; however, this step location has only a 33% likelihood of producing an Earth with the correct Ru-Mo isotopic signature for the most plausible model conditions. Our results give the testable predictions that Mars has zero Ru anomaly and small or zero Mo anomaly, and the Moon has zero Mo anomaly. These predictions are insensitive to wide variations in parameter choices.

  10. Radial Mixing and Ru-Mo Isotope Systematics Under Different Accretion Scenarios

    NASA Astrophysics Data System (ADS)

    Fischer, R. A.; Nimmo, F.; O'Brien, D. P.

    2017-12-01

    The Ru-Mo isotopic compositions of inner Solar System bodies may reflect the provenance of accreted material and how it evolved with time, both of which are controlled by the accretion scenario these bodies experienced. Here we use a total of 116 N-body simulations of terrestrial planet accretion, run in the Eccentric Jupiter and Saturn (EJS), Circular Jupiter and Saturn (CJS), and Grand Tack scenarios, to model the Ru-Mo anomalies of Earth, Mars, and Theia analogues. This model starts by applying an initial step function in Ru-Mo isotopic composition, with compositions reflecting those in meteorites, and traces compositional evolution as planets accrete. The mass-weighted provenance of the resulting planets reveals more radial mixing in Grand Tack simulations than in EJS/CJS simulations, and more efficient mixing among late-accreted material than during the main phase of accretion in EJS/CJS simulations. We find that an extensive homogenous inner disk region is required to reproduce Earth's observed Ru-Mo composition. EJS/CJS simulations require a homogeneous reservoir in the inner disk extending to ≥3-4 AU (≥74-98% of initial mass) to reproduce Earth's composition, while Grand Tack simulations require a homogeneous reservoir extending to ≥3-10 AU (≥97-99% of initial mass), and likely to ≥7-10 AU. In the Grand Tack model, Jupiter's initial location (the most likely location for a discontinuity in isotopic composition) is 3.5 AU; however, this step location has only a 33% likelihood of producing an Earth with the correct Ru-Mo isotopic signature for the most plausible model conditions. Our results give the testable predictions that Mars has zero Ru anomaly and small or zero Mo anomaly, and the Moon has zero Mo anomaly. These predictions are insensitive to wide variations in parameter choices.

  11. Towards identifying the active sites on RuO 2 (110) in catalyzing oxygen evolution

    DOE PAGES

    Rao, Reshma R.; Kolb, Manuel J.; Halck, Niels Bendtsen; ...

    2017-11-17

    While the surface atomic structure of RuO 2 has been well studied in ultra high vacuum, much less is known about the interaction between water and RuO 2 in aqueous solution. In this work, in situ surface X-ray scattering measurements combined with density functional theory (DFT) were used to determine the surface structural changes on single-crystal RuO2(110) as a function of potential in acidic electrolyte. The redox peaks at 0.7, 1.1 and 1.4 V vs. reversible hydrogen electrode (RHE) could be attributed to surface transitions associated with the successive deprotonation of –H 2O on the coordinatively unsaturated Ru sites (CUS)more » and hydrogen adsorbed to the bridging oxygen sites. At potentials relevant to the oxygen evolution reaction (OER), an –OO species on the Ru CUS sites was detected, which was stabilized by a neighboring –OH group on the Ru CUS or bridge site. Combining potential-dependent surface structures with their energetics from DFT led to a new OER pathway, where the deprotonation of the –OH group used to stabilize –OO was found to be rate-limiting.« less

  12. The effect of RU 486 and related compounds on cultured macrophage differentiation and function.

    PubMed

    Roberts, C P; Murphy, A A; Santanam, N; Parthasarathy, S

    1996-08-01

    Our purpose was to examine RU 486 and related compounds on macrophage scavenger receptors and cellular adhesion. THP-1 cells were activated with phorbol myristate acetate and treated with dexamethasone, levonorgestrel, and RU 486 alone or in combination. Scavenger receptor activity was determined by counting adhered cells. In addition, fluorescently labeled acetyl low density lipoprotein uptake was determined. Both dexamethasone and RU 486 significantly decreased activated macrophages (81% and 26% of control). Levonorgestrel stimulated adherent cells in activated monocytes (130% of control). RU 486 and dexamethasone were antagonistic when combined (p < 0.001). In contrast, dexamethasone could not overcome the stimulatory effect of levonorgestrel (p < 0.001). Fluorescent studies yielded similar results. RU 486 is a known antiglucocorticoid with novel antioxidant properties. Levonorgestrel has antiglucocorticoid but no antioxidant activity. Glucocorticoids decrease scavenger receptors and antioxidants regulate inflammatory cytokines. RU 486 antagonized the inhibitory effect of dexamethasone on scavenger receptors, whereas levonorgestrel was stimulatory. It is therapeutically important to up-regulate scavenger receptor activity by antiglucocorticoids in the peritoneal cavity of women with endometriosis. However, because these mechanisms also induce inflammatory cytokines, a balance of antioxidants and antiglucocorticoids may prove beneficial.

  13. Catalytic ozonation of dimethyl phthalate and chlorination disinfection by-product precursors over Ru/AC.

    PubMed

    Wang, Jianbing; Zhou, Yunrui; Zhu, Wanpeng; He, Xuwen

    2009-07-15

    Catalytic ozonation of dimethyl phthalate (DMP) in aqueous solution (5mg/L) under various reactions was performed to examine the effect of catalyst dosage, catalyst particle size, ozone dosage, and gas flow rate on the mineralization of DMP. The mineralization of DMP can be achieved via ozonation and the presence of Ru/AC could greatly accelerate the mineralization rate of DMP in ozonation process. In the continuous experiment of the Ru/AC catalyzed ozonation of DMP, total organic carbon (TOC) removals were kept stable around 75% during 42 h reaction. No leaching of ruthenium was observed in the treated water samples. The treatment of natural water using Ru/AC+O(3), Ru/AC+O(2) and ozonation alone was studied. In the Ru/AC+O(3) process, TOC removals, the reductions of the haloacetic acid formation potentials (HAAFPs), and the reductions of the trihalomethane formation potentials (THMFPs) of 11 water samples were 22-44%, 39-61% and 50-65%, respectively. Ru/AC+O(3) process was much more effective than ozonation alone for TOC removal and the reduction of disinfection by-product formation potential (DBPFP) in the treatment of natural water. It is a promising water treatment technology.

  14. Towards identifying the active sites on RuO 2 (110) in catalyzing oxygen evolution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rao, Reshma R.; Kolb, Manuel J.; Halck, Niels Bendtsen

    While the surface atomic structure of RuO 2 has been well studied in ultra high vacuum, much less is known about the interaction between water and RuO 2 in aqueous solution. In this work, in situ surface X-ray scattering measurements combined with density functional theory (DFT) were used to determine the surface structural changes on single-crystal RuO2(110) as a function of potential in acidic electrolyte. The redox peaks at 0.7, 1.1 and 1.4 V vs. reversible hydrogen electrode (RHE) could be attributed to surface transitions associated with the successive deprotonation of –H 2O on the coordinatively unsaturated Ru sites (CUS)more » and hydrogen adsorbed to the bridging oxygen sites. At potentials relevant to the oxygen evolution reaction (OER), an –OO species on the Ru CUS sites was detected, which was stabilized by a neighboring –OH group on the Ru CUS or bridge site. Combining potential-dependent surface structures with their energetics from DFT led to a new OER pathway, where the deprotonation of the –OH group used to stabilize –OO was found to be rate-limiting.« less

  15. Nuclear forward scattering of synchrotron radiation by 99Ru

    DOE PAGES

    Bessas, D.; Merkel, D. G.; Chumakov, A. I.; ...

    2014-10-03

    In this study, we measured nuclear forward scattering spectra utilizing the 99Ru transition, 89.571(3) keV, with a notably mixed E2/M1 multipolarity. The extension of the standard evaluation routines to include mixed multipolarity allows us to extract electric and magnetic hyperfine interactions from 99Ru-containing compounds. This paves the way for several other high-energy Mössbauer transitions, E~90 keV. Lastly, the high energy of such transitions allows for operando nuclear forward scattering studies in real devices.

  16. Magnetic properties of diruthenium(II,III) carboxylate compounds. Crystal structures of Ru2Cl(mu-O2CCH=CHCH=CHMe)4 and Ru2Cl(mu-O2CCH2OMe)4.

    PubMed

    Barral, M C; Jiménez-Aparicio, R; Pérez-Quintanilla, D; Priego, J L; Royer, E C; Torres, M R; Urbanos, F A

    2000-01-10

    The reaction of Ru2Cl(mu-O2CMe)4 with 2,4-hexadienoic and 2-methoxyacetic acids affords the compounds Ru2Cl(mu-O2CR)4 [R = CH=CHCH=CHCH3 (1), CH2OMe (2)]. The structures of both complexes have been determined by X-ray crystallography. 1 crystallizes in the triclinic space group P-1 with a = 9.264(1) A, b = 12.661(8) A, c = 12.839(5) A, alpha = 106.09(3) degrees, beta = 77.89(2) degrees, gamma = 97.73(3) degrees, and Z = 2. 2 crystallizes in the nonstandard monoclinic space group P2(1)/c with a = 12.132(4) A, b = 11.570(2) A, c = 13.674(2) A, beta = 91.18(2) degrees, and Z = 4. Complexes 1 and 2 show [Ru2(mu-O2CR)4]+ units linked by chloride ions, giving zigzag chains with Ru-Cl-Ru angles of 119.43(4) degrees and 110.11(7) degrees, respectively. The Ru-Ru bond distances are 2.2857(9) A (1) and 2.290(1) A (2). A magnetic study, in the 2-300 K temperature range, of the new compounds and the previously described Ru2Cl(mu-O2CR)4 [R = CHMe2 (3), CMe3 (4), C4H4N (5)] is described. The polymeric complexes 1 and 2 and the nonpolymeric 3-5 show a large zero-field splitting which varies from 53.9 to 68.1 cm-1. These complexes also show a weak, but not negligible, through-space intermolecular antiferromagnetic coupling not observed in the previous magnetic studies carried out on these types of compounds.

  17. Conversion of biomass-derived sorbitol to glycols over carbon-materials supported Ru-based catalysts

    PubMed Central

    Guo, Xingcui; Guan, Jing; Li, Bin; Wang, Xicheng; Mu, Xindong; Liu, Huizhou

    2015-01-01

    Ruthenium (Ru) supported on activated carbon (AC) and carbon nanotubes (CNTs) was carried out in the hydrogenolysis of sorbitol to ethylene glycol (EG) and 1,2-propanediol (1,2-PD) under the promotion of tungsten (WOx) species and different bases. Their catalytic activities and glycols selectivities strongly depended on the support properties and location of Ru on CNTs, owning to the altered metal-support interactions and electronic state of ruthenium. Ru located outside of the tubes showed excellent catalytic performance than those encapsulated inside the nanotubes. Additionally, the introduction of WOx into Ru/CNTs significantly improved the hydrogenolysis activities, and a complete conversion of sorbitol with up to 60.2% 1,2-PD and EG yields was obtained on RuWOx/CNTs catalyst upon addition of Ca(OH)2. Stability study showed that this catalyst was highly stable against leaching and poisoning and could be recycled several times. PMID:26578426

  18. Conversion of biomass-derived sorbitol to glycols over carbon-materials supported Ru-based catalysts

    NASA Astrophysics Data System (ADS)

    Guo, Xingcui; Guan, Jing; Li, Bin; Wang, Xicheng; Mu, Xindong; Liu, Huizhou

    2015-11-01

    Ruthenium (Ru) supported on activated carbon (AC) and carbon nanotubes (CNTs) was carried out in the hydrogenolysis of sorbitol to ethylene glycol (EG) and 1,2-propanediol (1,2-PD) under the promotion of tungsten (WOx) species and different bases. Their catalytic activities and glycols selectivities strongly depended on the support properties and location of Ru on CNTs, owning to the altered metal-support interactions and electronic state of ruthenium. Ru located outside of the tubes showed excellent catalytic performance than those encapsulated inside the nanotubes. Additionally, the introduction of WOx into Ru/CNTs significantly improved the hydrogenolysis activities, and a complete conversion of sorbitol with up to 60.2% 1,2-PD and EG yields was obtained on RuWOx/CNTs catalyst upon addition of Ca(OH)2. Stability study showed that this catalyst was highly stable against leaching and poisoning and could be recycled several times.

  19. Constructing hierarchical interfaces: TiO 2-supported PtFe-FeO x nanowires for room temperature CO oxidation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, Huiyuan; Wu, Zili; Dong, Su

    2015-08-05

    This is a report of a facile approach to constructing catalytic active hierarchical interfaces in one-dimensional (1D) nanostructure, exemplified by the synthesis of TiO 2-supported PtFe–FeO x nanowires (NWs). The hierarchical interface, constituting atomic level interactions between PtFe and FeO x within each NW and the interactions between NWs and support (TiO 2), enables CO oxidation with 100% conversion at room temperature. We identify the role of the two interfaces by probing the CO oxidation reaction with isotopic labeling experiments. Both the oxygen atoms (Os) in FeO x and TiO 2 participate in the initial CO oxidation, facilitating the reactionmore » through a redox pathway. Moreover, the intact 1D structure leads to the high stability of the catalyst. After 30 h in the reaction stream, the PtFe–FeO x/TiO2 catalyst exhibits no activity decay. These results provide a general approach and new insights into the construction of hierarchical interfaces for advanced catalysis.« less

  20. Peroxydisulfate activation by [RuII(tpy)(pic)(H2O)]+. Kinetic, mechanistic and anti-microbial activity studies.

    PubMed

    Chatterjee, Debabrata; Banerjee, Priyabrata; Bose, Jagadeesh C K; Mukhopadhyay, Sudit

    2012-03-07

    The oxidation of [Ru(II)(tpy)(pic)H(2)O](+) (tpy = 2,2',6',2''-terpyridine; pic(-) = picolinate) by peroxidisulfate (S(2)O(8)(2-)) as precursor oxidant has been investigated kinetically by UV-VIS, IR and EPR spectroscopy. The overall oxidation of Ru(II)- to Ru(IV)-species takes place in a consecutive manner involving oxidation of [Ru(II)(tpy)(pic)H(2)O](+) to [Ru(III)(tpy)(pic)(OH)](+), and its further oxidation of to the ultimate product [Ru(IV)(tpy)(pic)(O)](+) complex. The time course of the reaction was followed as a function of [S(2)O(8)(2-)], ionic strength (I) and temperature. Kinetic data and activation parameters are interpreted in terms of an outer-sphere electron transfer mechanism. Anti-microbial activity of Ru(II)(tpy)(pic)H(2)O](+) complex by inhibiting the growth of Escherichia coli DH5α in presence of peroxydisulfate has been explored, and the results of the biological studies have been discussed in terms of the [Ru(IV)(tpy)(pic)(O)](+) mediated cleavage of chromosomal DNA of the bacteria.

  1. Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability.

    PubMed

    Jackson, Ariel; Strickler, Alaina; Higgins, Drew; Jaramillo, Thomas Francisco

    2018-01-12

    Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mg Pt -1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications. The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mg Pt -1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s -1 ), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.

  2. Ruthenium (Ru) peeling and predicting robustness of the capping layer using finite element method (FEM) modeling

    NASA Astrophysics Data System (ADS)

    Jang, Il-Yong; John, Arun; Goodwin, Frank; Lee, Su-Young; Kim, Byung-Gook; Kim, Seong-Sue; Jeon, Chan-Uk; Kim, Jae Hyung; Jang, Yong Hoon

    2014-07-01

    Ruthenium (Ru) film used as capping layer in extreme ultraviolet (EUV) mask peeled off after annealing and in-situ UV (IUV) cleaning. We investigated Ru peeling and found out that the mechanical stress caused by the formation of Si oxide due to the penetration of oxygen atoms from ambient or cleaning media to top-Si of ML is the root cause for the problem. To support our experimental results, we developed a numerical model of finite element method (FEM) using commercial software (ABAQUS™) to calculate the stress and displacement forced on the capping layer. By using this model, we could observe that the displacement agrees well with the actual results measured from the transmission electron microscopy (TEM) image. Using the ion beam deposition (IBD) tool at SEMATECH, we developed four new types of alternative capping materials (RuA, RuB, B4C, B4C-buffered Ru). The durability of each new alternative capping layer observed by experiment was better than that of conventional Ru. The stress and displacement calculated from each new alternative capping layer, using modeling, also agreed well with the experimental results. A new EUV mask structure is proposed, inserting a layer of B4C (B4C-buffered Ru) at the interface between the capping layer (Ru) and the top-Si layer. The modeling results showed that the maximum displacement and bending stress observed from the B4C-buffered Ru are significantly lower than that of single capping layer cases. The durability investigated from the experiment also showed that the B4C-buffered structure is at least 3X stronger than that of conventional Ru.

  3. Effects of interfacial alignments on the stability of graphene on Ru(0001) substrate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gao, Lei; Liu, Yanmin; Ma, Tianbao, E-mail: mtb@mail.tsinghua.edu.cn

    2016-06-27

    Structure and electronic properties of two-dimensional materials could be tuned by interfacial misfit or orientation angles. However, graphene grown on Ru(0001) substrate usually shows stable moiré superlattice with a periodicity of 3.0 nm indicating an aligned geometry. The reason for the absence of misaligned structure is still unknown. We have performed first-principles calculation to investigate the microstructure and morphology of graphene on Ru(0001) substrate in both aligned and misaligned geometries with rotation angles of 0°, 7.6°, and 23.4°, respectively. Our results indicate that both the graphene corrugation and moiré superlattice periodicity decrease as the rotation angle increases. Meanwhile the interaction energymore » between graphene and Ru(0001) substrate also becomes weakened with the rotation angle, as the decrease and discretization of intense charge transfer sites at the graphene/Ru interface, which is closely related to the interface stacking structure. Counterintuitively, the strain energy in graphene also increases anomalously with the rotation angle, which is attributed to the highly distorted local deformation of graphene due to the strong but discrete covalent bonding with Ru substrate. The simultaneous increase in both the interaction energy and strain energy in graphene/Ru(0001) heterostructure with rotation angle contributes to the preferred configuration in the aligned state.« less

  4. Ru-Catalyzed Estragole Isomerization under Homogeneous and Ionic Liquid Biphasic Conditions

    PubMed Central

    2017-01-01

    The isomerization of estragole to trans-anethole is an important reaction and is industrially performed using an excess of NaOH or KOH in ethanol at high temperatures with very low selectivity. Simple Ru-based transition-metal complexes, under homogeneous, ionic liquid (IL)-supported (biphasic) and “solventless” conditions, can be used for this reaction. The selectivity of this reaction is more sensitive to the solvent/support used than the ligands associated with the metal catalyst. Thus, under the optimized reaction conditions, 100% conversion can be achieved in the estragole isomerization, using as little as 4 × 10–3 mol % (40 ppm) of [RuHCl(CO)(PPh3)3] in toluene, reflecting a total turnover number (TON) of 25 000 and turnover frequencies (TOFs) of up to 500 min–1 at 80 °C. Using a dimeric Ru precursor, [RuCl(μ-Cl)(η3:η3-C10H16)]2, in ethanol associated with P(OEt)3, a TON of 10 000 and a TOF of 125 min–1 are obtained with 100% conversion and 99% selectivity. These two Ru catalytic systems can be transposed to biphasic IL systems by using ionic-tagged P-ligands such as 1-(3-(diphenylphosphanyl)propyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide immobilized in 1-(3-hydroxypropyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl) imide with up to 99% selectivity and almost complete estragole conversion. However, the reaction is much slower than that performed under solventless or homogeneous conditions. The use of ionic-tagged ligands significantly reduces the Ru leaching to the organic phase, compared to that in reactions performed under homogeneous conditions, where the catalytic system loses catalytic performance after the second recycling. Detailed kinetic investigations of the reaction catalyzed by [RuHCl(CO)(PPh3)3] indicate that a simplified kinetic model (a monomolecular reversible first-order reaction) is adequate for fitting the homogeneous reaction at 80 °C and under biphasic conditions. However, the kinetics of

  5. High-Performance Ru1 /CeO2 Single-Atom Catalyst for CO Oxidation: A Computational Exploration.

    PubMed

    Li, Fengyu; Li, Lei; Liu, Xinying; Zeng, Xiao Cheng; Chen, Zhongfang

    2016-10-18

    By means of density functional theory computations, we examine the stability and CO oxidation activity of single Ru on CeO 2 (111), TiO 2 (110) and Al 2 O 3 (001) surfaces. The heterogeneous system Ru 1 /CeO 2 has very high stability, as indicated by the strong binding energies and high diffusion barriers of a single Ru atom on the ceria support, while the Ru atom is rather mobile on TiO 2 (110) and Al 2 O 3 (001) surfaces and tends to form clusters, excluding these systems from having a high efficiency per Ru atom. The Ru 1 /CeO 2 exhibits good catalytic activity for CO oxidation via the Langmuir-Hinshelwood mechanism, thus is a promising single-atom catalyst. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Characterization of R5020 and RU486 binding to progesterone receptor from calf uterus

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hurd, C.; Moudgil, V.K.

    1988-05-17

    The authors have examined and compared the binding characteristics of the progesterone agonist R5020 (promegestrone, 17,21-dimethylpregna-4,9(10)-diene-3,20-dione) and the progesterone antagonist RU486 (mifepristone, 17..beta..-hydroxy-11..beta..-(4-(dimethylamino)phenyl)-17..cap alpha..-(prop-1-ynyl)-estra-4,9-dien-3-one) in calf uterine cytosol. Both steroids bound cytosol macromolecule(s) with high affinity, exhibiting K/sub d/ values of 5.6 and 3.6 nM for R5020 and RU486 binding, respectively. The binding of the steroids to the macromolecule(s) was rapid at 4/sup 0/C, showing saturation of binding sites at 1-2 h for (/sup 3/H)progesterone and 2-4 h for both (/sup 3/H)R5020 and (/sup 3/H)RU486. Addition of molybdate and glycerol to cytosol increased the extent of (/sup 3/H)R5020 binding. Themore » extent of (/sup 3/H)RU486 binding remained unchanged in the presence of molybdate, whereas glycerol had an inhibitory effect. Molybdate alone or in combination with glycerol stabilized the (/sup 3/H)R5020- and (/sup 3/H)RU486-receptor complexes at 37/sup 0/C. Competitive steroid binding analysis revealed that (/sup 3/H)progesterone, (/sup 3/H)R5020, and (/sup 3/H)RU486 compete for the same site(s) in the uterine cytosol, suggesting that all three bind to the progesterone receptor (PR). Sedimentation rate analysis showed that both steroids were bound to a molecule that sediments in the 8S region. The 8S (/sup 3/H)R5020 and (/sup 3/H)RU486 peaks were abolished by excess radioinert progesterone, RU486, or R5020. The results of this study suggest that, although there are some differences in the nature of their interaction with the PR, both R5020 and RU486 bind to the same 8S receptor in calf uterine cytosol.« less

  7. Collapsed tetragonal phase transition in LaRu2P2

    NASA Astrophysics Data System (ADS)

    Drachuck, Gil; Sapkota, Aashish; Jayasekara, Wageesha T.; Kothapalli, Karunakar; Bud'ko, Sergey L.; Goldman, Alan I.; Kreyssig, Andreas; Canfield, Paul C.

    2017-11-01

    The structural properties of LaRu2P2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu2P2 (I4/mmm) has a tetragonal structure with a bulk modulus of B =105 (2 ) GPa and exhibits superconductivity at Tc=4.1 K. With the application of pressure, LaRu2P2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B =175 (5 ) GPa. At the transition, the c -lattice parameter exhibits a sharp decrease with a concurrent increase of the a -lattice parameter. The cT phase transition in LaRu2P2 is consistent with a second-order transition, and was found to be temperature dependent, increasing from P =3.9 (3 ) GPa at 160 K to P =4.6 (3 ) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K where superconductivity is suppressed. Finally, we compare the effect of physical and chemical pressure in the RRu2P2 (R = Y, La -Er , Yb) isostructural series of compounds and find them to be analogous.

  8. Electronic structure of Rh and Ru doped Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Chikara, Shalinee; Fabbris, Gilberto; Terzic, Jasminka; Qi, Tongfei; Butrouna, Kamal; Veiga, Larissa; Souza Neto, Narcizo; Cao, Gang; Haskel, Daniel

    2014-03-01

    Sr2IrO4 is a spin-orbit interaction(SOI) assisted insulator. It has been proposed that the weaker SOI in the 4 d -substituted Sr2Ir1-x(Ru, Rh)xO4 closes the insulating gap, rendering it a paramagnetic metal. Rh(4d5) is isoelectronic to Ir(5d5) whereas Ru(4d4) has one less electron in the 4 d -band. The AFM-I/PM-M transition takes place at lower x for Ru than Rh, presumably due to the effect of hole doping. X-ray absorption near edge structure (XANES) and x-ray magnetic circular dichroism (XMCD) measurements at the Ir L2 , 3 edges show that < L . S > is non-zero and independent of x. This is indicative of a strong local 5 d spin orbit interaction that is rather insensitive to the 4 d doping. In contrast, measurements at the L2 , 3 edges of Ru and Rh show < L . S > ~ 0 for all x. The results point to the importance of local 4 d / 5 d - 2 p hybridization as opposed to 4 d - 5 d band formation in the Rh and Ru doped Sr2IrO4.

  9. Soft Landing of Bare PtRu Nanoparticles for Electrochemical Reduction of Oxygen

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Johnson, Grant E.; Colby, Robert J.; Engelhard, Mark H.

    2015-08-07

    Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu alloy nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 x 104 ions µm-2 and that their average height is centered at 4 nm. Scanning transmission electron microscopy images obtained in themore » high-angle annular dark field mode (STEM-HAADF) further confirm that the soft-landed PtRu alloy nanoparticles are uniform in size and have a Ru core decorated with small regions of Pt on the surface. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in relative atomic concentrations of ~9% and ~33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt4f and Ru3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the alloy nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He+ and O+ ions. The activity of electrodes containing 7 x 104 ions µm-2 of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the alloy nanoparticles supported on

  10. PdRu/C catalysts for ethanol oxidation in anion-exchange membrane direct ethanol fuel cells

    NASA Astrophysics Data System (ADS)

    Ma, Liang; He, Hui; Hsu, Andrew; Chen, Rongrong

    2013-11-01

    Carbon supported PdRu catalysts with various Pd:Ru atomic ratios were synthesized by impregnation method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electrochemical half-cell tests, and the anion-exchange membrane direct ethanol fuel cell (AEM-DEFC) tests. XRD results suggest that the PdRu metal exists on carbon support in an alloy form. TEM study shows that the bimetallic PdRu/C catalysts have slightly smaller average particle size than the single metal Pd/C catalyst. Lower onset potential and peak potential and much higher steady state current for ethanol oxidation in alkaline media were observed on the bimetallic catalysts (PdxRuy/C) than on the Pd/C, while the activity for ethanol oxidation on the pure Ru/C was not noticeable. By using Pd/C anode catalysts and MnO2 cathode catalysts, AEM-DEFCs free from the expensive Pt catalyst were assembled. The AEM DEFC using the bimetallic Pd3Ru/C anode catalyst showed a peak power density as high as 176 mW cm-2 at 80 °C, about 1.8 times higher than that using the single metal Pd/C catalyst. The role of Ru for enhancing the EOR activity of Pd/C catalysts is discussed.

  11. Diffusion of Zr, Ru, Ce, Y, La, Sr and Ba fission products in UO 2

    DOE PAGES

    Perriot, R.; Liu, X. -Y.; Stanek, C. R.; ...

    2015-01-08

    The diffusivity of the solid fission products (FP) Zr (Zr 4+), Ru (Ru 4+, Ru 3+), Ce (Ce 4+), Y (Y 3+), La (La 3+), Sr (Sr 2+) and Ba (Ba 2+) by a vacancy mechanism has been calculated, using a combination of density functional theory (DFT) and empirical potential (EP) calculations. The activation energies for the solid fission products are compared to the activation energy for Xe fission gas atoms calculated previously. Apart from Ru, the solid fission products all exhibit higher activation energy than Xe. Furthermore, for all solid FPs except Y 3+, the migration of the FPmore » has lower barrier than the migration of a neighboring U atom, making the latter the rate limiting step for direct migration. An indirect mechanism, consisting of two successive migrations around the FP, is also investigated. The calculated diffusivities show that most solid fission products diffuse with rates similar to U self-diffusion. But, Ru, Ba and Sr exhibit faster diffusion than the other solid FPs, with Ru 3+ and Ru 4+ diffusing even faster than Xe for T < 1200 K. The diffusivities correlate with the observed fission product solubility in UO 2, and the tendency to form metallic and oxide second phase inclusions.« less

  12. Reaction mechanism of Ru(II) piano-stool complexes: umbrella sampling QM/MM MD study.

    PubMed

    Futera, Zdeněk; Burda, Jaroslav V

    2014-07-15

    Biologically relevant interactions of piano-stool ruthenium(II) complexes with ds-DNA are studied in this article by hybrid quantum mechanics-molecular mechanics (QM/MM) computational technique. The whole reaction mechanism is divided into three phases: (i) hydration of the [Ru(II) (η(6) -benzene)(en)Cl](+) complex, (ii) monoadduct formation between the resulting aqua-Ru(II) complex and N7 position of one of the guanines in the ds-DNA oligomer, and (iii) formation of the intrastrand Ru(II) bridge (cross-link) between two adjacent guanines. Free energy profiles of all the reactions are explored by QM/MM MD umbrella sampling approach where the Ru(II) complex and two guanines represent a quantum core, which is described by density functional theory methods. The combined QM/MM scheme is realized by our own software, which was developed to couple several quantum chemical programs (in this study Gaussian 09) and Amber 11 package. Calculated free energy barriers of the both ruthenium hydration and Ru(II)-N7(G) DNA binding process are in good agreement with experimentally measured rate constants. Then, this method was used to study the possibility of cross-link formation. One feasible pathway leading to Ru(II) guanine-guanine cross-link with synchronous releasing of the benzene ligand is predicted. The cross-linking is an exergonic process with the energy barrier lower than for the monoadduct reaction of Ru(II) complex with ds-DNA. Copyright © 2014 Wiley Periodicals, Inc.

  13. Graphene-derived Fe/Co-N-C catalyst in direct methanol fuel cells: Effects of the methanol concentration and ionomer content on cell performance

    NASA Astrophysics Data System (ADS)

    Park, Jong Cheol; Choi, Chang Hyuck

    2017-08-01

    Non-precious metal catalysts (typically Fe(Co)-N-C catalysts) have been widely investigated for use as cost-effective cathode materials in low temperature fuel cells. Despite the high oxygen reduction activity and methanol-tolerance of graphene-based Fe(Co)-N-C catalysts in an acidic medium, their use in direct methanol fuel cells (DMFCs) has not yet been successfully implemented, and only a few studies have investigated this topic. Herein, we synthesized a nano-sized graphene-derived Fe/Co-N-C catalyst by physical ball-milling and a subsequent chemical modification of the graphene oxide. Twelve membrane-electrode-assemblies are fabricated with various cathode compositions to determine the effects of the methanol concentration, ionomer (i.e. Nafion) content, and catalyst loading on the DMFC performance. The results show that a graphene-based catalyst is capable of tolerating a highly-concentrated methanol feed up to 10.0 M. The optimized electrode composition has an ionomer content and catalyst loading of 66.7 wt% and 5.0 mg cm-2, respectively. The highest maximum power density is ca. 32 mW cm-2 with a relatively low PtRu content (2 mgPtRu cm-2). This study overcomes the drawbacks of conventional graphene-based electrodes using a nano-sized graphene-based catalyst and further shows the feasibility of their potential applications in DMFC systems.

  14. Characterization of a trinuclear ruthenium species in catalytic water oxidation by Ru(bda)(pic)2 in neutral media.

    PubMed

    Zhang, Biaobiao; Li, Fei; Zhang, Rong; Ma, Chengbing; Chen, Lin; Sun, Licheng

    2016-06-30

    A Ru(III)-O-Ru(IV)-O-Ru(III) type trinuclear species was crystallographically characterized in water oxidation by Ru(bda)(pic)2 (H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; pic = 4-picoline) under neutral conditions. The formation of a ruthenium trimer due to the reaction of Ru(IV)[double bond, length as m-dash]O with Ru(II)-OH2 was fully confirmed by chemical, electrochemical and photochemical methods. Since the oxidation of the trimer was proposed to lead to catalyst decomposition, the photocatalytic water oxidation activity was rationally improved by the suppression of the formation of the trimer.

  15. Thermal stability and electrochemical properties of PVP-protected Ru nanoparticles synthesized at room temperature

    NASA Astrophysics Data System (ADS)

    Kumar, Manish; Devi, Pooja; Shivling, V. D.

    2017-08-01

    Stable ruthenium nanoparticles (RuNPs) have been synthesized by the chemical reduction of ruthenium trichloride trihydrate (RuCl3 · 3H2O) using sodium borohydride (NaBH4) as a reductant and polyvinylpyrrolidone (PVP) as a protecting agent in the aqueous medium at room temperature. The nanoparticles thus prepared were characterized by their morphology and structural analysis from transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-vis spectroscopy, Fourier transformation infrared and thermogravimetric analysis (TGA) techniques. The TEM image suggested a homogeneous distribution of PVP-protected RuNPs having a small average diameter of 2-4 nm with a chain-like network structure. The XRD pattern also confirmed that a crystallite size is around 2 nm of PVP-protected RuNPs having a single broad peak. The thermal stability studied using TGA, indicated good stability and the electrochemical properties of these nanoparticles revealed that saturation current increases for PVP-protected RuNPs/GC.

  16. RuO2 pH Sensor with Super-Glue-Inspired Reference Electrode

    PubMed Central

    Wajrak, Magdalena; Alameh, Kamal

    2017-01-01

    A pH-sensitive RuO2 electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO2 working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO2 pH-sensitive working electrode and a SiO2-PVB junction-modified RuO2 reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices. PMID:28878182

  17. Effects of antiglucocorticoid RU 486 on development of obesity in obese fa/fa Zucker rats.

    PubMed

    Langley, S C; York, D A

    1990-09-01

    The effects of RU 486 (mitepristone), an antagonist of type II glucocorticoid receptors (GR), on the development of obesity in young 5-wk-old obese fa/fa rats has been investigated. After 15 days of treatment, body composition of obese RU 486-treated rats was similar to that of lean-vehicle rats. Analysis of body composition changes showed that RU 486 effectively reversed the obesity. It stopped fat deposition in obese rats but increased protein deposition to the level of lean-vehicle rats. RU 486 prevented the development of hyperphagia and reduced gross energetic efficiency in the obese rats but had little effect on lean rats. Brown adipose tissue mitochondrial GDP binding was increased in obese rats but was reduced in lean rats by RU 486 treatment. RU 486 also reduced the elevated activity of hippocampal glycerophosphate dehydrogenase, a glucocorticoid-responsive enzyme, of obese rats to the level of lean rats. The evidence suggests that abnormal activity of glucocorticoid GR receptors or abnormal cellular responsiveness to corticosterone receptor complexes may be important in the development of obesity in the fa/fa rat.

  18. {beta}-K{sub 4}La{sub 6}I{sub 14}Os: A new structure type for rare-earth-metal cluster compounds that contains discrete tetrahedral K{sub 4}I{sup 3+} units

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Uma, S.; Corbett, J.D.

    1999-08-23

    Suitable reactions of KI, La, LaI{sub 3}, and Os in niobium tubes at 800--850 C result in black, air- and moisture-sensitive crystals of the quaternary title phase. Isostructural K{sub 4}Pr{sub 6}I{sub 14}Z also exist for Z = Fe, Ru. The title phase was characterized by single-crystal X-ray diffraction (tetragonal, P4/ncc (No. 130), Z = 4; a = 13.117(3), c = 25.17(1) {angstrom} at 23 C). The important structural feature is the constitution (K{sub 4}I){sup 3+}(La{sub 6}I{sub 13}Os{sup 3{minus}}) with a new type of 3D anion network of [(La{sub 6}Os)I{sub 8}{sup i}I{sub 4/2}{sup i{minus}a}I{sub 4/2}{sup a{minus}i}I{sub 2/2}{sup a{minus}a}] clusters that aremore » connected into puckered layers through I{sup i{minus}a} and I{sup a{minus}i} atom pairs that bridge diagonally in the a-b plane. These cluster layers are further interlinked along {rvec c} at trans-vertexes through simple bridging I{sup a{minus}a}. The 14th iodine atom occurs in the unique K{sub 4}I{sup 3+} ions which lie in columns that interpenetrate the La{sub 6}OsI{sub 13} network along c. The present 16-e{sup {minus}} clusters, in contrast with the optimal 18-e{sup {minus}} octahedral cluster configuration, exhibit an uncommon tetragonal elongation and evidently become closed shell, with only a small temperature-independent (van Vleck-like) paramagnetism, {approximately}4 x 10{sup {minus}4} emu mol{sup {minus}1}.« less

  19. Boycott threat forces French company to abandon RU486.

    PubMed

    Dorozynski, A

    1997-04-19

    Threatened boycotts by American anti-abortion groups have forced the French pharmaceutical company Roussel-Uclaf, a subsidiary of the German company Hoechst, to stop production and distribution of mifepristone (RU-486), which the protesters call "the abortion pill." All patent rights have been transferred, without charge, to Dr. Edouard Sarkiz, one of the pill's developers. Hoechst, which had acquired Marion Pharmaceuticals to form a new group, Hoechst-Marion-Roussel, had increased its share of the US pharmaceutical market from 1% to 4% in doing so and could not tolerate a boycott. RU-486, which was discovered by Professor Etienne Baulieu, was introduced in France in 1987 as an alternative to surgical abortion. Although Hoechst, then a majority stockholder of Roussel-Uclaf, had asked the French firm to interrupt production of the pill in 1988, the French minister of health and social affairs at that time, Claude Evin, ordered production to be continued. Approximately 25% of French women seeking abortion use RU-486; it is also used in Britain, Sweden, and China (women in China must pay for the drug, while surgical abortion is free). All American firms have refused to buy the drug from Roussel-Uclaf. An offer to the World Health Organization was ignored. The American Population Council obtained the right to use RU-486 in 1993. Dr. Sarkiz has formed Exelgyn, a small nonprofit company, to produce and distribute RU-486; research into other uses for the drug will also be conducted. There has been limited research into its use as an emergency contraceptive and as a treatment for endometriosis, uterine fibroma, and breast cancer. According to Professor Baulieu, the drug could be used in treating wounds and burns because of its antiglucocorticoid and immunosuppressive properties; preliminary research by the professor indicates the drug could also possibly be used as a reversible male contraceptive because of its action on the membranes of spermatozoa. The drug's use in

  20. Electron localization and magnetism in SrRuO3 with non-magnetic cation substitution

    NASA Astrophysics Data System (ADS)

    Tong, W.; Huang, F.-Q.; Chen, I.-W.

    2011-03-01

    The destruction of the ferromagnetism of alloyed SrRuO3 can be caused by electron localization at the substitution sites. Among all the non-magnetic cations that enter the B site, Zr4 + is the least disruptive to conductivity and ferromagnetism. This is because Zr4 + does not cause any charge disorder, and its empty d electron states which are poorly matched in energy with the Ru t2g4 states cause the least resonance scattering of Ru's d electrons. Conducting Sr(Ru, Zr)O3 may be used as an electrode for perovskite-based thin film devices, while its insulating counterpart provides unprecedented magnetoresistance, seldom seen in other non-manganite and non-cobaltite perovskites.

  1. Concave Pd-Ru nanocubes bounded with high active area for boosting ethylene glycol electrooxidation

    NASA Astrophysics Data System (ADS)

    Xiong, Zhiping; Xu, Hui; Li, Shumin; Gu, Zhulan; Yan, Bo; Guo, Jun; Du, Yukou

    2018-01-01

    This paper reported our extensive efforts in the design of concave PdRu nanocubes via a facile wet-chemical strategy. Different from the previously reported PdRu nanostructures, the as-prepared concave PdRu nanocubes combined the advantages of fascinating nanocube structure, synergistic and electronic effect as well as high surface area. All of these beneficial terms endow them to exhibit superior electrocatalytic activity and long-term stability towards ethylene glycol oxidation as compared with commercial Pd/C. Our work highlights the significance of shape-controlled of PdRu nanostructures over the electrocatalytic performances towards the electrooxidation of ethylene glycol (EG), which will pave up a new strategy for boosting the development of renewable and clean energy technology.

  2. Hypotensive effect and vascular relaxation in different arteries induced by the nitric oxide donor RuBPY.

    PubMed

    Pereira, Amanda de Carvalho; Araújo, Alice Valença; Paulo, Michele; Andrade, Fernanda Aparecida de; Silva, Bruno Rodrigues; Vercesi, Juliana Aparecida; da Silva, Roberto Santana; Bendhack, Lusiane Maria

    2017-01-30

    NO donors are compounds that release NO that can be used when the endogenous NO bioavailability is impaired. The compound cis-[Ru(bpy) 2 (py)(NO 2 )](PF 6 ) (RuBPY) is a nitrite-ruthenium, since it has a NO 2 in its molecule. The aim of the present study was to evaluate the effect of RuBPY on arterial pressure, as well as on the vascular relaxation of different vascular arteries in renal hypertensive (2K-1C) and normotensive (2K) rats. We have evaluated the arterial pressure and heart rate changes as well as the RuBPY and SNP-induced relaxation (thoracic aorta, mesenteric resistance, coronary and basilar arteries). The administration of RuBPY in awake rats evoked a smaller but long lasting hypotensive effect when compared to SNP, with no increase in heart rate. The relaxation induced by RuBPY was similar between 2K-1C and 2K rats in thoracic aorta, mesenteric resistance and coronary arteries. However, the relaxation induced by RuBPY was smaller in basilar arteries from 2K-1C than in 2K. Taken together, our results show that RuBPY presents several advantages over SNP, since it does not induce hypotensive effect in normotensive animals, the hypotensive effect is slower, with no reflex tachycardia, and it is long lasting. In addition, RuBPY induces coronary artery relaxation (useful for angina) and presented only a small effect on basilar artery (may not induce headache). Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Ni2P Makes Application of the PtRu Catalyst Much Stronger in Direct Methanol Fuel Cells.

    PubMed

    Chang, Jinfa; Feng, Ligang; Liu, Changpeng; Xing, Wei

    2015-10-12

    PtRu is regarded as the best catalyst for direct methanol fuel cells, but the performance decay resulting from the loss of Ru seriously hinders commercial applications. Herein, we demonstrated that the presence of Ni2 P largely reduces Ru loss, which thus makes the application of PtRu much stronger in direct methanol fuel cells. Outstanding catalytic activity and stability were observed by cyclic voltammetry. Upon integrating the catalyst material into a practical direct methanol fuel cell, the highest maximum power density was achieved on the PtRu-Ni2P/C catalyst among the reference catalysts at different temperatures. A maximum power density of 69.9 mW cm(-2) at 30 °C was obtained on PtRu-Ni2P/C, which is even higher than the power density of the state-of-the-art commercial PtRu catalyst at 70 °C (63.1 mW cm(-2)). Moreover, decay in the performance resulting from Ru loss was greatly reduced owing to the presence of Ni2 P, which is indicative of very promising applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Preparation and characterization of Pt/C and Pt sbnd Ru/C electrocatalysts for direct ethanol fuel cells

    NASA Astrophysics Data System (ADS)

    Liu, Zhaolin; Ling, Xing Yi; Su, Xiaodi; Lee, Jim Yang; Gan, Leong Ming

    Nano-sized Pt and Pt sbnd Ru colloids are prepared by a microwave-assisted polyol process, and transferred to a toluene solution of decanthiol. Vulcan XC-72 is then added to the toluene solution to adsorb the thiolated Pt and Pt sbnd Ru colloids. Transmission electron microscopy examinations show nearly spherical particles and narrow size distributions for both supported and unsupported metals. The carbon-supported Pt and Pt sbnd Ru nanoparticles are activated by thermal treatment to remove the thiol stabilizing shell. All Pt and Pt sbnd Ru catalysts (except Pt 23sbnd Ru 77) give the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Pt 23sbnd Ru 77 alloy is more typical of the hexagonal close packed (hcp) structure. The electro-oxidation of liquid ethanol on these catalysts is investigated at room temperature by cyclic voltammetry. The results demonstrate that the alloy catalyst is catalytically more active than pure platinum. Preliminary tests on a single cell of a direct ethanol fuel cell (DEFC) indicate that a Pt 52sbnd Ru 48/C anode catalyst gives the best electrocatalytic performance among all the carbon-supported Pt and Pt sbnd Ru catalysts.

  5. Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jackson, Ariel; Strickler, Alaina; Higgins, Drew

    Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mg Pt -1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications.more » The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mg Pt -1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s -1), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.« less

  6. Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability

    DOE PAGES

    Jackson, Ariel; Strickler, Alaina; Higgins, Drew; ...

    2018-01-12

    Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mg Pt -1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications.more » The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mg Pt -1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s -1), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.« less

  7. Structural Stability of Diffusion Barriers in Cu/Ru/MgO/Ta/Si

    PubMed Central

    Hsieh, Shu-Huei; Chen, Wen Jauh; Chien, Chu-Mo

    2015-01-01

    Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu film and Si substrate. The various structures of Cu/Ru/MgO/Ta/Si were characterized by four-point probes for their sheet resistances, by X-ray diffractometers for their crystal structures, by scanning electron microscopes for their surface morphologies, and by transmission electron microscopes for their cross-section and high resolution views. The results showed that the ultra-thin tri-layer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is an effective diffusion barrier against the interdiffusion between Cu film and Si substrate. The MgO, and Ta layers as deposited are amorphous. The mechanism for the failure of the diffusion barrier is that the Ru layer first became discontinuous at a high temperature and the Ta layer sequentially become discontinuous at a higher temperature, the Cu atoms then diffuse through the MgO layer and to the substrate at the discontinuities, and the Cu3Si phases finally form. The maximum temperature at which the structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si are annealed and still have low sheet resistance is from 550 to 750 °C for the annealing time of 5 min and from 500 to 700 °C for the annealing time of 30 min. PMID:28347099

  8. Highly efficient bioinspired molecular Ru water oxidation catalysts with negatively charged backbone ligands.

    PubMed

    Duan, Lele; Wang, Lei; Li, Fusheng; Li, Fei; Sun, Licheng

    2015-07-21

    The oxygen evolving complex (OEC) of the natural photosynthesis system II (PSII) oxidizes water to produce oxygen and reducing equivalents (protons and electrons). The oxygen released from PSII provides the oxygen source of our atmosphere; the reducing equivalents are used to reduce carbon dioxide to organic products, which support almost all organisms on the Earth planet. The first photosynthetic organisms able to split water were proposed to be cyanobacteria-like ones appearing ca. 2.5 billion years ago. Since then, nature has chosen a sustainable way by using solar energy to develop itself. Inspired by nature, human beings started to mimic the functions of the natural photosynthesis system and proposed the concept of artificial photosynthesis (AP) with the view to creating energy-sustainable societies and reducing the impact on the Earth environments. Water oxidation is a highly energy demanding reaction and essential to produce reducing equivalents for fuel production, and thereby effective water oxidation catalysts (WOCs) are required to catalyze water oxidation and reduce the energy loss. X-ray crystallographic studies on PSII have revealed that the OEC consists of a Mn4CaO5 cluster surrounded by oxygen rich ligands, such as oxyl, oxo, and carboxylate ligands. These negatively charged, oxygen rich ligands strongly stabilize the high valent states of the Mn cluster and play vital roles in effective water oxidation catalysis with low overpotential. This Account describes our endeavors to design effective Ru WOCs with low overpotential, large turnover number, and high turnover frequency by introducing negatively charged ligands, such as carboxylate. Negatively charged ligands stabilized the high valent states of Ru catalysts, as evidenced by the low oxidation potentials. Meanwhile, the oxygen production rates of our Ru catalysts were improved dramatically as well. Thanks to the strong electron donation ability of carboxylate containing ligands, a seven

  9. Diethyl Ether Production during Catalytic Dehydration of Ethanol over Ru- and Pt- modified H-beta Zeolite Catalysts.

    PubMed

    Kamsuwan, Tanutporn; Praserthdam, Piyasan; Jongsomjit, Bunjerd

    2017-01-01

    In the present study, the catalytic dehydration of ethanol over H-beta zeolite (HBZ) catalyst with ruthenium (Ru-HBZ) and platinum (Pt-HBZ) modification was investigated. Upon the reaction temperature between 200 and 400°C, it revealed that ethanol conversion and ethylene selectivity increased with increasing temperature for both Ru and Pt modification. At lower temperature (200 to 250°C), diethyl ether (DEE) was the major product. It was found that Ru and Pt modification on HBZ catalyst can result in increased DEE yield at low reaction temperature due to increased ethanol conversion without a significant change in DEE selectivity. By comparing the DEE yield of all catalysts in this study, the Ru-HBZ catalyst apparently exhibited the highest DEE yield (ca. 47%) at 250°C. However, at temperature from 350 to 400°C, the effect of Ru and Pt was less pronounced on ethylene yield. With various characterization techniques, the effects of Ru and Pt modification on HBZ catalyst were elucidated. It revealed that Ru and Pt were present in the highly dispersed forms and well distributed in the catalyst granules. It appeared that the weak acid sites measured by NH 3 temperature-programmed desorption technique also decreased with Ru and Pt promotion. Thus, the increased DEE yields with the Ru and Pt modification can be attributed to the presence of optimal weak acid sites leading to increased intrinsic activity of the catalysts. It can be concluded that the modification of Ru and Pt on HBZ catalyst can improve the DEE yields by ca. 10%.

  10. About some processes of replacement of PGM from the placers of Southern Siberia

    NASA Astrophysics Data System (ADS)

    Shvedov, G. I.; Knyazev, V. N.; Nekos, V. V.

    2003-04-01

    Authors observed a series of replacement (conversions) in PGM from gold-bearing placers of southern part of Krasnoyarsk region. These facts have mineralogical and genetic interest. In researched placers primary PGM are presented by solid solutions Os-Ir-Ru with different ratios of main elements from osmium to iridium (by classification of D. Harris and L. Cabri /5 /. At smaller amounts Pt-Fe and sperrylite are presented, and other PGM were found in single cases. In minerals of Os-Ir-Ru system the main typical replacement is the forming of edgings of phase (Os,Ir,Ru)S_2 upon the edges of native Os, Ir, Ru or rutheniridosmine. Usually, the process of transformation takes place in grains in a direction of the best permeability, i.e. along deformational gaps or along planes of cleavage, because the phases of this system are chemically stable. The structures of replacements are diversified: fulfillment of gaps, formation of edgings around the grains, selective replacement, forming of metacrystalls or metagrains. The thickness of forming edgings is not stable; boundaries have corrosion textures with penetration inside of replaced grain. The chemical composition of cations of forming disulfides depends upon the composition of primary mineral first of all, but it cannot be subject to this rule. For example, grains from placer of Bolshoy Khailyk river (Western Sayan) have a composition adequate to ruthenium (tab., No. 1) and are replaced by laurite more often (tab., No. 1-1). In Kuznetsky Alatau (placer of Talanovaya river) authors observed simultaneous replacement of osmium (with admixtures of Ru and Ir) (tab., No. 2) by laurite (tab., No. 2-1) and irarsite (tab., No. 2-2) along gaps. This fact is explained by more affinity of ruthenium to sulfur, then iridium and osmium to sulfur /2/. In conditions of low fugitivity of sulfur the edgings with more rare composition (Ir,Os,Ru)_3S_2 (tab., No. 3-1) are formed. It was observed by the authors on iridium (tab., No. 3) from

  11. DOSE-DEPENDENT EFFECTS OF THE ANTIPROGESTIN, RU486, ON SEXUAL BEHAVIOR OF NATURALLY-CYCLING FISCHER RATS

    PubMed Central

    Uphouse, Lynda

    2015-01-01

    Regularly cycling Fischer female rats were treated with either a low (5 mg/kg) or high (5 mg/RAT; approximately 30 mg/kg) dose of the antiprogestin, RU486, before the morning of proestrus or on the morning of proestrus. The emergence of sexual behavior after treatment with RU486 was examined in a mating test with a sexually active male rat. Lordosis behavior was remarkably resistant to the effects of RU486. Only the high dose of RU486 given the evening before proestrus, approximately 22 hours before mating, reduced lordosis behavior. Independent of dose or time of treatment, proceptivity was reduced and resistance to the male’s attempts to mount was increased by RU486 treatment. In addition, the effect of a 5 min restraint stress on sexual behavior was examined. In contrast to the relative resistance of lordosis behavior of unrestrained rats to RU486 treatment, RU486 treated rats showed a significant decline in lordosis behavior after restraint. These findings allow the suggestion that the emergence of lordosis behavior is relatively resistant to the antiprogestin while the maintenance of lordosis behavior after restraint may require participation of intracellular progesterone receptors. PMID:25591479

  12. Interference removals on Pd, Ru and Au with ICP-QQQ-MS in PGE RM

    NASA Astrophysics Data System (ADS)

    Nadeem Hussain Bokhari, Syed; Meisel, Thomas; Walkner, Christoph

    2015-04-01

    Gold and platinum group elements (PGE) are essential industrial precious metals with high world demand due to their unique properties. Struggle for natural exploration of PGE is on great pace and recycling from industrial wastes, electronics and catalytic convertor is on the rise for PGE supply chain. Along with these developments it is becoming more challenging for analytical chemists to determine gold and PGE out of complex matrix which causes severe interferences. The current state of art is online analysis coupled with chromatographic separation of interferences. The ICP-QQQ-MS Agilent 8800 has the capability of using multi tunes and mass shifts. We aim to remove interferences on Pd+ (for direct and isotope dilution analysis) Au+ and Ru+ in lieu of chemical separations. YO+, SrOH+, ZnAr+, NiAr+, ZrO+, CuAr+, MoO+ , Ru+and Cd+ are expected interferences on Pd+ while Au+ is interfered by TaO+, HfOH+, GdAr+ and 102Ru+ ,104Ru+ by 102Pd+ ,104Pd+ etc. Initial test were performed on pure solutions of 1mg/l (interfering elements): 1 ng/l (Pd, Ru & Au) respectively. The outcomes of initial tests were applied on PGE reference material (RM) WMG-1 and SARM-7 (digested with Na2O2 sintering). The results obtained show that YO+, SrOH+ interfere (104Pd,105Pd), 104 Ru+ on (104Pd), ZnAr+ has slight interference on (104Pd and106Pd), ZrO+, NiAr+, CuAr+ interferences are negligible, MoO+ has severe interference on (108Pd, 110Pd) and that Cd+ has severe isobaric interference on (106Pd,108Pd, 110Pd). These interference have been removed by formation of Pd(NH3)3+complex. The TaO+, HfOH+ and GdAr+ interferences on Au+ are best removed by formation of Au(NH3)+ and Au(NH3)2+ complexes. 102Pd+,104Pd+interference on 102Ru+ ,104Ru+ can be removed by formation of Ru(NH3)4+ and RuO+ compounds. The results obtained comply with certified values of RM. The developed method is being tested on low concentration PGE reference materials. References: Sugiyama, N. " Removal of complex spectral

  13. PtRu catalysts supported on heteropolyacid and chitosan functionalized carbon nanotubes for methanol oxidation reaction of fuel cells.

    PubMed

    Cui, Zhiming; Li, Chang Ming; Jiang, San Ping

    2011-09-28

    A simple self-assembly approach has been developed to functionalize carbon nanotubes (CNTs) with chitosan (CS) and heteropolyacids (HPAs) of phosphomolybdic acid (H(3)PMo(12)O(40), HPMo) and phosphotungstic acid (H(3)PW(12)O(40), HPW). The non-covalent functionalization method, which introduces homogenous surface functional groups with no detrimental effect on graphene structures of CNTs, can be carried out at room temperature without the use of corrosive acids. The PtRu nanoparticles supported on HPAs-CS-CNTs have a uniform distribution and much smaller size as compared to those of the PtRu nanoparticles supported on conventional acid treated CNTs (PtRu/AO-CNTs). The onset and peak potentials for CO(ad) oxidation on PtRu/HPAs-CS-CNTs catalysts are more negative than those on PtRu/AO-CNTs, indicating that HPAs facilitate the electro-oxidation of CO. The PtRu/HPMo-CS-CNTs catalyst has a higher electrocatalytic activity for methanol oxidation and higher tolerance toward CO poisoning than PtRu/HPW-CS-CNTs. The better electrocatalytic enhancement of HPMo on the PtRu/HPAs-CS-CNTs catalyst is most likely related to the fact that molybdenum-containing HPAs such as HPMo have more labile terminal oxygen to provide additional active oxygen sites while accelerating the CO and methanol oxidation in a similar way to that of Ru in the PtRu binary alloy system.

  14. New band structures in Neutron-Rich Mo and Ru Isotopes

    DOE PAGES

    Hamilton, J. H.; Luoa, Y. X.; Zhu, S. J.; ...

    2009-01-01

    Rotational bands in 110,112Ru and 108Mo have been investigated by means of γ-γ-γ and γ-γ(θ) coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. New ΔI = 1 negative parity doublet bands are found. These bands in 110,112Ru and 108Mo have all the properties expected for chiral vibrations. Microscopic calculations that combine the TAC meanfield with random phase approximation support this interpretation.

  15. Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen.

    PubMed

    Johnson, Grant E; Colby, Robert; Engelhard, Mark; Moon, Daewon; Laskin, Julia

    2015-08-07

    Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 × 10(4) ions μm(-2) and that their average height is centered at 4.5 nm. Scanning transmission electron microscopy images obtained in the high-angle annular dark field mode (HAADF-STEM) further confirm that the soft-landed PtRu nanoparticles are uniform in size. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in atomic concentrations of ∼9% and ∼33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt 4f and Ru 3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He(+) and O(+) ions. The activity of electrodes containing 7 × 10(4) ions μm(-2) of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the nanoparticles supported on glassy carbon. The reproducibility of the nanoparticle synthesis and deposition was

  16. Half-metallic ferromagnetism in Sr3Ru2O7

    NASA Astrophysics Data System (ADS)

    Rivero, Pablo; Meunier, Vincent; Shelton, William

    2017-05-01

    The bilayered member of the Ruddesden-Popper family of ruthenates, Sr3Ru2O7 , has received increasing attention due to its interesting properties and phases. By using first principle calculations we find that the ground state is characterized by a ferromagnetic (FM) half-metallic state. This state strongly competes with an antiferromagnetic metallic phase, which indicates the possible presence of a particular state characterized by the existence of different magnetic domains. To drive the system towards a phase transition we studied the electronic and magnetic properties as a function of RuO6 octahedra rotations and found that the magnetic phase does not couple with the rotation angle. Our results provide accurate electronic, structure, and magnetic ground-state properties of Sr3Ru2O7 and stimulate the investigation of other types of octahedra rotations and distortions in the search of phase transitions.

  17. Ultrathin nitrogen-doped graphitized carbon shell encapsulating CoRu bimetallic nanoparticles for enhanced electrocatalytic hydrogen evolution.

    PubMed

    Xu, You; Li, Yinghao; Yin, Shuli; Yu, Hongjie; Xue, Hairong; Li, Xiaonian; Wang, Hongjing; Wang, Liang

    2018-06-01

    Design of highly active and cost-effective electrocatalysts is very important for the generation of hydrogen by electrochemical water-splitting. Herein, we report the fabrication of ultrathin nitrogen-doped graphitized carbon shell encapsulating CoRu bimetallic nanoparticles (CoRu@NCs) and demonstrate their promising feasibility for efficiently catalyzing the hydrogen evolution reaction (HER) over a wide pH range. The resultant CoRu@NC nanohybrids possess an alloy-carbon core-shell structure with encapsulated low-ruthenium-content CoRu bimetallic alloy nanoparticles (10-30 nm) as the core and ultrathin nitrogen-doped graphitized carbon layers (2-6 layers) as the shell. Remarkably, the optimized catalyst (CoRu@NC-2 sample) with a Ru content as low as 2.04 wt% shows superior catalytic activity and excellent durability for HER in acidic, neutral, and alkaline conditions. This work offers a new method for the design and synthesis of non-platium-based electrocatalysts for HER in all-pH.

  18. An Efficient and Reusable Embedded Ru Catalyst for the Hydrogenolysis of Levulinic Acid to γ-Valerolactone.

    PubMed

    Wei, Zuojun; Lou, Jiongtao; Su, Chuanmin; Guo, Dechao; Liu, Yingxin; Deng, Shuguang

    2017-04-22

    To achieve a higher activity and reusability of a Ru-based catalyst, Ru nanoparticles were embedded in N-doped mesoporous carbon through a hard-template method. The catalyst showed excellent catalytic performance (314 h -1 turnover frequency) and recyclability (reusable five times with 3 % activity loss) for the hydrogenolysis of levulinic acid to γ-valerolactone. Compared with the mesoporous carbon without N-doping and conventional activated carbon, the introduction of N-dopant effectively improved the dispersion of Ru nanoparticles, decreased the average size of Ru nanoparticles to as small as 1.32 nm, and improved the adsorption of levulinic acid, which contributed to the increase in the activity of the catalyst. Additionally, the embedding method increased the interaction between Ru nanoparticles and carbon support in contrast with the conventional impregnation method, thus preventing the Ru nanoparticles from migration, aggregation, and leaching from the carbon surface and therefore increasing the reusability of the catalyst. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Ultrathin nitrogen-doped graphitized carbon shell encapsulating CoRu bimetallic nanoparticles for enhanced electrocatalytic hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Xu, You; Li, Yinghao; Yin, Shuli; Yu, Hongjie; Xue, Hairong; Li, Xiaonian; Wang, Hongjing; Wang, Liang

    2018-06-01

    Design of highly active and cost-effective electrocatalysts is very important for the generation of hydrogen by electrochemical water-splitting. Herein, we report the fabrication of ultrathin nitrogen-doped graphitized carbon shell encapsulating CoRu bimetallic nanoparticles (CoRu@NCs) and demonstrate their promising feasibility for efficiently catalyzing the hydrogen evolution reaction (HER) over a wide pH range. The resultant CoRu@NC nanohybrids possess an alloy–carbon core–shell structure with encapsulated low-ruthenium-content CoRu bimetallic alloy nanoparticles (10–30 nm) as the core and ultrathin nitrogen-doped graphitized carbon layers (2–6 layers) as the shell. Remarkably, the optimized catalyst (CoRu@NC-2 sample) with a Ru content as low as 2.04 wt% shows superior catalytic activity and excellent durability for HER in acidic, neutral, and alkaline conditions. This work offers a new method for the design and synthesis of non-platium-based electrocatalysts for HER in all-pH.

  20. N-doped graphene layers encapsulated NiFe alloy nanoparticles derived from MOFs with superior electrochemical performance for oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Feng, Yi; Yu, Xin-Yao; Paik, Ungyu

    2016-09-01

    Water splitting, an efficient approach for hydrogen production, is often hindered by unfavorable kinetics of oxygen evolution reaction (OER). In order to reduce the overpotential, noble metal oxides-based electrocatalysts like RuO2 and IrO2 are usually utilized. However, due to their scarcity, the development of cost-effective non-precious OER electrocatalysts with high efficiency and good stability is urgently required. Herein, we report a facile one-step annealing of metal-organic frameworks (MOFs) strategy to synthesize N-doped graphene layers encapsulated NiFe alloy nanoparticles (NiFe@C). Through tuning the nanoparticle size and calcination temperature, NiFe@C with an average size of around 16 nm obtained at 700 °C exhibits superior OER performance with an overpotential of only 281 mV at 10 mA cm-2 and high durability. The facile synthesis method and excellent electrochemical performance show great potential of NiFe@C in replacing the precious metal-based electrocatalysts in the OER.

  1. Probing the formation mechanism and chemical states of carbon-supported Pt-Ru nanoparticles by in situ X-ray absorption spectroscopy.

    PubMed

    Hwang, Bing Joe; Chen, Ching-Hsiang; Sarma, Loka Subramanyam; Chen, Jiun-Ming; Wang, Guo-Rung; Tang, Mau-Tsu; Liu, Din-Goa; Lee, Jyh-Fu

    2006-04-06

    The understanding of the formation mechanism of nanoparticles is essential for the successful particle design and scaling-up process. This paper reports findings of an X-ray absorption spectroscopy (XAS) investigation, comprised of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions, to understand the mechanism of the carbon-supported Pt-Ru nanoparticles (NPs) formation process. We have utilized Watanabe's colloidal reduction method to synthesize Pt-Ru/C NPs. We slightly modified the Watanabe method by introducing a mixing and heat treatment step of Pt and Ru oxidic species at 100 degrees C for 8 h with a view to enhance the mixing efficiency of the precursor species, thereby one can achieve improved homogeneity and atomic distribution in the resultant Pt-Ru/C NPs. During the reduction process, in situ XAS measurements allowed us to follow the evolution of Pt and Ru environments and their chemical states. The Pt LIII-edge XAS indicates that when H2PtCl6 is treated with NaHSO3, the platinum compound is found to be reduced to a Pt(II) form corresponding to the anionic complex [Pt(SO3)4]6-. Further oxidation of this anionic complex with hydrogen peroxide forms dispersed [Pt(OH)6]2- species. Analysis of Ru K-edge XAS results confirms the reduction of RuIIICl3 to [RuII(OH)4]2- species upon addition of NaHSO3. Addition of hydrogen peroxide to [RuII(OH)4]2- causes dehydrogenation and forms RuOx species. Mixing of [Pt(OH)6]2- and RuOx species and heat treatment at 100 degrees C for 8 h produced a colloidal sol containing both Pt and Ru metallic as well as ionic contributions. The reduction of this colloidal mixture at 300 degrees C in hydrogen atmosphere for 2 h forms Pt-Ru nanoparticles as indicated by the presence of Pt and Ru atoms in the first coordination shell. Determination of the alloying extent or atomic distribution of Pt and Ru atoms in the resulting Pt-Ru/C NPs reveals that the alloying extent of Ru (JRu) is

  2. X-ray diffraction study of the caged magnetic compound DyFe 2 Zn 20 at low temperatures

    NASA Astrophysics Data System (ADS)

    Ohashi, M.; Ohashi, K.; Sawabu, M.; Miyagawa, M.; Maeta, K.; Isikawa, Y.

    2018-05-01

    We have carried out high-angle X-ray powder diffraction measurements of the caged magnetic compound DyFe2Zn20 at low temperature between 14 and 300 K. Even though a strong magnetic anisotropy exists in the magnetization and magnetic susceptibility due to strong exchange interaction between Fe and Dy, almost all X-ray powder diffraction peaks correspond to Bragg reflections of the cubic structural models not only at room temperature paramagnetic state but also at low temperature magnetic ordering state. The Debye temperature is obtained to be 227 K from the results of the volumetric thermal expansion coefficient, which is approximately coincident with that of CeRu2Zn20 (245 K) and that of pure Zn metal (235 K).

  3. Phototoxicity of strained Ru(ii) complexes: is it the metal complex or the dissociating ligand?

    PubMed

    Azar, Daniel F; Audi, Hassib; Farhat, Stephanie; El-Sibai, Mirvat; Abi-Habib, Ralph J; Khnayzer, Rony S

    2017-09-12

    A photochemically dissociating ligand in Ru(bpy) 2 (dmphen)Cl 2 [bpy = 2,2'-bipyridine; dmphen = 2,9-dimethyl-1,10-phenanthroline] was found to be more cytotoxic on the ML-2 Acute Myeloid Leukemia cell line than Ru(bpy) 2 (H 2 O) 2 2+ and prototypical cisplatin. Our findings illustrate the potential potency of diimine ligands in photoactivatable Ru(ii) complexes.

  4. Fluorescence emission and polarization analyses for evaluating binding of ruthenium metalloglycocluster to lectin and tetanus toxin c-fragment

    NASA Astrophysics Data System (ADS)

    Okada, Tomoko; Minoura, Norihiko

    2010-02-01

    We have developed a fluorescent ruthenium metalloglycocluster as a powerful molecular probe for evaluating a binding event between carbohydrates and lectins by fluorescence emission (FE) and fluorescence polarization (FP) analysis. The fluorescent ruthenium metalloglycoclusters, [Ru(bpy-2Gal)3] and [Ru(bpy-2Glc)3], possess clustered galactose and glucose surrounding the ruthenium center. Changes in FE and FP of these metalloglycoclusters were measured by adding each lectin (Peanut agglutinin (PNA), Ricinus communis agglutinin 120 (RCA), Concanavalin A (ConA), or Wheat germ agglutinin (WGA)) or tetanus toxin c-fragment (TCF). Following the addition of PNA, the FE spectrum of [Ru(bpy- 2Gal)3] showed new emission peak and the FP value of [Ru(bpy-2Gal)3] increased. Similarly, the FE spectrum of [Ru(bpy-2Glc)3] showed new emission peak and the FP value increased following the addition of ConA. Since other combinations of the metalloglycoclusters and lectin caused little change, specific bindings of galactose to PNA and glucose to ConA were proved by the FE and FP measurement. From nonlinear least-squares fitting, dissociation constants (Kd) of [Ru(bpy-2Gal)3] to PNA was 6.1 μM, while the Kd values of [Ru(bpy)2(bpy-2Gal)] to PNA was ca. 10-4 M. Therefore, the clustered carbohydrates were proved to increase affinity to lectins. Furthermore, the FP measurements proved specific binding of [Ru(bpy-2Gal)3] to TCF.

  5. Growth, structure, and properties of epitaxial thin films of first-principles predicted multiferroic Bi2FeCrO6

    NASA Astrophysics Data System (ADS)

    Nechache, Riad; Harnagea, Catalin; Pignolet, Alain; Normandin, François; Veres, Teodor; Carignan, Louis-Philippe; Ménard, David

    2006-09-01

    The authors report the structural and physical properties of epitaxial Bi2FeCrO6 thin films on epitaxial SrRuO3 grown on (100)-oriented SrTiO3 substrates by pulsed laser ablation. The 300nm thick films exhibit both ferroelectricity and magnetism at room temperature with a maximum dielectric polarization of 2.8μC /cm2 at Emax=82kV/cm and a saturated magnetization of 20emu/cm3 (corresponding to ˜0.26μB per rhombohedral unit cell), with coercive fields below 100Oe. The results confirm the predictions made using ab initio calculations about the existence of multiferroic properties in Bi2FeCrO6.

  6. Collapsed tetragonal phase transition in LaRu 2 P 2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Drachuck, Gil; Sapkota, Aashish; Jayasekara, Wageesha T.

    Here, the structural properties of LaRu 2P 2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu 2P 2 (I4/ mmm) has a tetragonal structure with a bulk modulus of B = 105(2) GPa and exhibits superconductivity at T c = 4.1 K. With the application of pressure, LaRu 2P 2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B = 175(5) GPa. At the transition, the c-lattice parameter exhibits a sharp decrease with a concurrent increase of themore » a-lattice parameter. The cT phase transition in LaRu 2P 2 is consistent with a second-order transition, and was found to be temperature dependent, increasing from P = 3.9(3) GPa at 160 K to P = 4.6(3) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K where superconductivity is suppressed. Finally, we compare the effect of physical and chemical pressure in the RRu 2P 2 ( R = Y, La–Er, Yb) isostructural series of compounds and find them to be analogous.« less

  7. Collapsed tetragonal phase transition in LaRu 2 P 2

    DOE PAGES

    Drachuck, Gil; Sapkota, Aashish; Jayasekara, Wageesha T.; ...

    2017-11-10

    Here, the structural properties of LaRu 2P 2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu 2P 2 (I4/ mmm) has a tetragonal structure with a bulk modulus of B = 105(2) GPa and exhibits superconductivity at T c = 4.1 K. With the application of pressure, LaRu 2P 2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B = 175(5) GPa. At the transition, the c-lattice parameter exhibits a sharp decrease with a concurrent increase of themore » a-lattice parameter. The cT phase transition in LaRu 2P 2 is consistent with a second-order transition, and was found to be temperature dependent, increasing from P = 3.9(3) GPa at 160 K to P = 4.6(3) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K where superconductivity is suppressed. Finally, we compare the effect of physical and chemical pressure in the RRu 2P 2 ( R = Y, La–Er, Yb) isostructural series of compounds and find them to be analogous.« less

  8. SiO2 decoration dramatically enhanced the stability of PtRu electrocatalysts with undetectable deterioration in fuel cell performance.

    PubMed

    Yu, Xinxin; Xu, Zejun; Yang, Zehui; Xu, Sen; Zhang, Quan; Ling, Ying; Zhang, Yunfeng; Cai, Weiwei

    2018-06-15

    Prevention of Ru dissolution is essential for steady CO tolerance of anodic electrocatalysts in direct methanol fuel cells. Here, we demonstrate a facile way to stabilize Ru atoms by decorating commercial CB/PtRu with SiO 2 , which shows a six-fold higher stability and similar activity toward a methanol oxidation reaction leading to no discernible degradation in fuel cell performance compared to commercial CB/PtRu electrocatalysts. The higher stability and stable CO tolerance of SiO 2 -decorated electrocatalysts originate from the SiO 2 coating, since Ru atoms are partially ionized during SiO 2 decorating, resulting in difficulties in dissolution; while, in the case of commercial CB/PtRu, the dissolved Ru offers active sites for Pt coalescences and CO species resulting in the rapid decay of the electrochemical surface area and fuel cell performance. To the best of our knowledge, this is the first study about the stabilization of Ru atoms by SiO 2 . The highest stability is obtained for a PtRu electrocatalyst with negligible effect on the electrochemical properties.

  9. SiO2 decoration dramatically enhanced the stability of PtRu electrocatalysts with undetectable deterioration in fuel cell performance

    NASA Astrophysics Data System (ADS)

    Yu, Xinxin; Xu, Zejun; Yang, Zehui; Xu, Sen; Zhang, Quan; Ling, Ying; Zhang, Yunfeng; Cai, Weiwei

    2018-06-01

    Prevention of Ru dissolution is essential for steady CO tolerance of anodic electrocatalysts in direct methanol fuel cells. Here, we demonstrate a facile way to stabilize Ru atoms by decorating commercial CB/PtRu with SiO2, which shows a six-fold higher stability and similar activity toward a methanol oxidation reaction leading to no discernible degradation in fuel cell performance compared to commercial CB/PtRu electrocatalysts. The higher stability and stable CO tolerance of SiO2-decorated electrocatalysts originate from the SiO2 coating, since Ru atoms are partially ionized during SiO2 decorating, resulting in difficulties in dissolution; while, in the case of commercial CB/PtRu, the dissolved Ru offers active sites for Pt coalescences and CO species resulting in the rapid decay of the electrochemical surface area and fuel cell performance. To the best of our knowledge, this is the first study about the stabilization of Ru atoms by SiO2. The highest stability is obtained for a PtRu electrocatalyst with negligible effect on the electrochemical properties.

  10. Coverage evolution of the unoccupied Density of States in sulfur superstructures on Ru(0001)

    NASA Astrophysics Data System (ADS)

    Pisarra, M.; Bernardo-Gavito, R.; Navarro, J. J.; Black, A.; Díaz, C.; Calleja, F.; Granados, D.; Miranda, R.; Martín, F.; Vázquez de Parga, A. L.

    2018-03-01

    Sulfur adsorbed on Ru(0001) presents a large number of ordered structures. This characteristic makes S/Ru(0001) the ideal system to investigate the effect of different periodicities on the electronic properties of interfaces. We have performed scanning tunneling microscopy/spectroscopy experiments and density functional theory calculations showing that a sulfur adlayer generates interface states inside the Γ directional gap of Ru(0001) and that the position of such states varies monotonically with sulfur coverage. This is the result of the interplay between band folding effects arising from the new periodicity of the system and electron localization on the sulfur monolayer. As a consequence, by varying the amount of sulfur in S/Ru(0001) one can control the electronic properties of these interfacial materials.

  11. Structure and magnetic ground states of spin-orbit coupled compound alpha-RuCl3

    NASA Astrophysics Data System (ADS)

    Banerjee, Arnab; Bridges, Craig; Yan, Jiaqiang; Mandrus, David; Stone, Matthew; Aczel, Adam; Li, Ling; Yiu, Yuen; Lumsden, Mark; Chakoumakos, Bryan; Tennant, Alan; Nagler, Stephen

    2015-03-01

    The layered material alpha-RuCl3 is composed of stacks of weakly coupled honeycomb lattices of octahedrally coordinated Ru3 + ions. The Ru ion ground state has 5 d electrons in the low spin state, with spin-orbit coupling very strong compared to other terms in the single ion Hamiltonian. The material is therefore an excellent candidate for investigating possible Heisenberg-Kitaev physics. In addition, this compound is very amenable to investigation by neutron scattering to explore the magnetic ground state and excitations in detail. In this talk, we discuss the synthesis of phase-pure alpha-RuCl3 and the characterization of the magnetization, susceptibility, and heat-capacity. We also report neutron diffraction on both powder and single crystal alpha-RuCl3, identifying the low temperature magnetic order observed in the material. The results, when compared to theoretical calculations, shed light on the relative importance of Kitaev and Heisenberg terms in the Hamiltonian. The research is supported by the DOE BES Scientific User Facility Division.

  12. Differences in the binding mechanism of RU486 and progesterone to the progesterone receptor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Skafar, D.F.

    1991-11-12

    The binding mechanism of the antagonist RU486 to the progesterone receptor was compared with that of the agonists progesterone and R5020. Both progesterone and RU486 bound to the receptor with a Hill coefficient of 1.2, indicating the binding of each ligand is positive cooperative. However, when each ligand was used to compete with ({sup 3}H)progesterone for binding to the receptor at receptor concentrations near 8 nM, at which the receptor is likely a dimer, the competition curve for RU486 was significantly steeper than the curves for progesterone and R5020. This indicated that a difference in the binding mechanism of RU486more » and progesterone can be detected when both ligands are present. In contrast, at receptor concentrations near 1 nM, at which the receptor is likely a monomer, the competition curves for all three ligands were indistinguishable. These results indicate that RU486 and agonists have different binding mechanisms for the receptor and further suggest that this difference may be related to site-site interactions within the receptor.« less

  13. A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO2@PEI nanoparticles for NSE analysis

    NASA Astrophysics Data System (ADS)

    Zhou, Limin; Huang, Jianshe; Yu, Bin; You, Tianyan

    2016-02-01

    Poly(ethylenimine) (PEI) and Ru(bpy)32+-doped silica (Ru-SiO2) nanoparticles were simply mixed together to prepare a novel self-enhanced electrochemiluminescence (ECL) composite of Ru-SiO2@PEI. The hollow Ru-SiO2@PEI nanoparticles were used to build an ECL immunosensor for the analysis of neuron specific enolase (NSE). PEI not only assembled on the surface of Ru-SiO2 nanoparticles through the electrostatic interaction to act as co-reactant for Ru(bpy)32+ ECL, but also provided alkaline condition to etch the Ru-SiO2 nanoparticles to form the hollow Ru-SiO2@PEI nanoparticles with porous shell. The unique structure of the Ru-SiO2@PEI nanoparticles loaded both a large amount of Ru(bpy)32+ and its co-reactant PEI at the same time, which shortened the electron-transfer distance, thereby greatly enhanced the luminous efficiency and amplified the ECL signal. The developed immunosensor showed a wide linear range from 1.0 × 10-11 to 1.0 × 10-5 mg mL-1 with a low detection limit of 1.0 × 10-11 mg mL-1 for NSE. When the immunosensor was used for the determination of NSE in clinical human serum, the results were comparable with those obtained by using enzyme-linked immunosorbent assay (ELISA) method. The proposed method provides a promising alternative for NSE analysis in clinical samples.

  14. Influences of Ru-doping on the magnetic properties of Ca0.85Pr0.15Mn1- x Ru x O3

    NASA Astrophysics Data System (ADS)

    Phan, T. L.; Zhang, Y. D.; Yu, S. C.; Thanh, P. Q.; Yen, P. D. H.

    2012-11-01

    CaMnO3 is an antiferromagnet, in which the super-exchange interaction taking place between Mn4+ ions plays an important role. The doping of a small amount of 15% Pr into the Ca site, Ca0.85Pr0.15MnO3, leads to the appearance of Mn3+ ions, and introduces the ferromagnetic (FM) double-exchange interaction between Mn3+ and Mn4+ ions, which is dominant in a narrow temperature range of 90 ˜ 115 K. The FM interaction becomes strong for Ca0.85Pr0.15MnO3 doped with 4 and 8% Ru into the Mn site ( i.e., Ca0.85Pr0.15Mn1- x Ru x O3 with x = 0.04 and 0.08). The Curie temperature obtained for x = 0.04 and 0.08 are about 135 and 180 K, respectively. While the FM interaction in the former is dominant due to Mn3+-Mn4+ exchange pairs, the latter has the contribution of Ru ions. This results in remarkable differences in the features of their FM-paramagnetic phase transitions and their coercive fields H c .

  15. Theoretical study of triaxial shapes of neutron-rich Mo and Ru nuclei

    DOE PAGES

    Zhang, C. L.; Bhat, G. H.; Nazarewicz, W.; ...

    2015-09-10

    Here, whether atomic nuclei can possess triaxial shapes at their ground states is still a subject of ongoing debate. According to theory, good prospects for low-spin triaxiality are in the neutron-rich Mo-Ru region. Recently, transition quadrupole moments in rotational bands of even-mass neutron-rich isotopes of molybdenum and ruthenium nuclei have been measured. The new data have provided a challenge for theoretical descriptions invoking stable triaxial deformations. The purpose of this study is to understand experimental data on rotational bands in the neutron-rich Mo-Ru region, we carried out theoretical analysis of moments of inertia, shapes, and transition quadrupole moments of neutron-richmore » even-even nuclei around 110Ru using self-consistent mean-field and shell model techniques. Methods: To describe yrast structures in Mo and Ru isotopes, we use nuclear density functional theory (DFT) with the optimized energy density functional UNEDF0. We also apply triaxial projected shell model (TPSM) to describe yrast and positive-parity, near-yrast band structures. As a result, our self-consistent DFT calculations predict triaxial ground-state deformations in 106,108Mo and 108,110,112Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative-gamma structure, associated with the aligned ν(h 11/2) 2 pair, becomes energetically favored. The computed transition quadrupole moments vary with angular momentum, which reflects deformation changes with rotation; those variations are consistent with experiment. The TPSM calculations explain the observed band structures assuming stable triaxial shapes. Lastly, the structure of neutron-rich even-even nuclei around Ru-110 is consistent with triaxial shape deformations. Our DFT and TPSM frameworks provide a consistent and complementary description of experimental data.« less

  16. An unusual photosensitizer: dyad of eosin-tris(2,2'-bipyridine)Ru(II).

    PubMed

    Jing, Bingwen; Zhang, Manhua; Shen, Tao

    2003-10-02

    [structure: see text] A dyad of eosin and tris(2,2'-bipyridine)Ru(II) was prepared, and its photophysical properties were investigated. The photosensitization of eosin is greatly enhanced by introduction of tris(2,2'-bipyridine)Ru(II), which is verified via photooxygenation of anthracene derivatives. The electron-transfer mechanism of photosensitization is also discussed.

  17. Enhanced performance of HRGO-RuO 2 solid state flexible supercapacitors fabricated by electrophoretic deposition

    DOE PAGES

    Amir, Fatima Z.; Pham, V. H.; Mullinax, D. W.; ...

    2016-06-07

    Ruthenium oxide (RuO 2) nanomaterials exist as excellent materials for electrochemical capacitors. However, they tend to suffer from low mechanical flexibility when cast into films, which makes them unsuitable for flexible device applications. Herein, we report an environmentally friendly and solution-processable approach to fabricate RuO 2-based composite electrodes for flexible solid state supercapacitors. The composites were produced by anchoring RuO 2 nanoparticles onto holey reduced graphene oxide (HRGO) via a sol-gel method, followed by the electrophoretic deposition (EPD) of the material into thin films. The uniform anchoring of ultra-small RuO 2 nanoparticles on the two-dimensional HRGO sheets resulted in HRGO-RuOmore » 2 hybrid sheets with excellent mechanical flexibility of HRGO. EPD induced a layer-by-layer assembly mechanism for the HRGO-RuO 2 hybrid sheets, which resulted in a binder-free, flexible electrode. The obtained HRGO-RuO 2 flexible supercapacitors exhibited excellent electrochemical capacitive performance in a PVA-H 2SO 4 gel electrolyte with a specific capacitance of 418 F g -1 and superior cycling stability of 88.5% capacitance retention after 10,000 cycles. Additionally, these supercapacitors exhibited high rate performance with capacitance retention of 85% by increasing the current density from 1.0 to 20.0 Ag -1, and excellent mechanical flexibility with only 4.9% decay in the performance when bent 180°.« less

  18. RuO2 supported NaY zeolite catalysts: Effect of preparation methods on catalytic performance during aerobic oxidation of benzyl alcohol

    NASA Astrophysics Data System (ADS)

    Jung, Dasom; Lee, Sunwoo; Na, Kyungsu

    2017-10-01

    The effects of preparation method for RuO2 supported zeolite catalysts on the catalytic consequences during the aerobic oxidation of benzyl alcohol to benzaldehyde were investigated. Three preparation methods, i.e., (i) simultaneous crystallization of the zeolite framework in the presence of RuCl3 (Ru(SC)/NaY), (ii) post ion-exchange with RuCl3 on the zeolite framework (Ru(IE)/NaY), and (iii) post support of preformed Ru metal nanoparticles on the zeolite surface (Ru(PS)/NaY), were used to construct three different RuO2 supported NaY zeolite catalysts. The catalyst performance was investigated as functions of the reaction time and temperature, in correlation with the structural changes of the catalysts, as analyzed by X-ray diffraction (XRD). The results revealed that the catalytic consequences were dramatically affected by the preparation methods. Although similar conversion was achieved with all three catalysts, the turnover frequency (TOF) differed. The Ru(PS)/NaY catalyst exhibited the highest TOF (33-48 h-1), whereas the other catalysts produced much lower TOFs (9-12 h-1). The Ru(PS)/NaY catalyst also had the highest activation energy (Ea) of 48.39 kJ mol-1, whereas the Ru(SC)/NaY and Ru(IE)/NaY catalysts had Ea values of 18.58 and 24.11 kJ mol-1, respectively. Notably, the Ru(PS)/NaY catalyst yielded a significantly higher pre-exponential factor of 5.22 × 105 h-1, which is about 5 orders of magnitude larger than that of the Ru(SC)/NaY catalyst (7.15 × 100 h-1). This suggests that collision between benzyl alcohol and molecular oxygen was very intensive on the Ru(PS)/NaY catalyst, which explains the higher TOF of the Ru(PS)/NaY catalyst relative to the others in spite of the higher Ea value of the former. In terms of recyclability, the pristine crystallinity of the zeolite framework was maintained in the Ru(SC)/NaY catalyst and the RuO2 phase exhibited an insignificant loss of the initial activity up to three catalytic cycles, whereas Ru(PS)/NaY showed slight

  19. Synthesis and characterization of Ru-Ti[sub 4]O[sub 7] microelectrode arrays

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    He, L.; Franzen, H.F.; Vitt, J.E.

    1994-04-01

    A synthesis is described for Ru microelectrode arrays within a conductive Ti[sub 4]O[sub 7] ceramic matrix. Data obtained by X-ray diffractometry and scanning electron microscopy are consistent with the existence of heterogeneous mixtures of Ru particles (ca. 0.8 [mu]m diam) within the Ti[sub 4]O[sub 7] matrices. No mixed metal oxides or other new compounds are detected. Rotated disk electrodes (RDEs) constructed from the Ru-Ti[sub 4]O[sub 7] materials are compared on the basis of their voltammetric response for the oxidations of I[sup [minus

  20. On-line measurements of RuO{sub 4} during a PWR severe accident

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reymond-Laruinaz, S.; Doizi, D.; Manceron, L.

    After the Fukushima accident, it became essential to have a way to monitor in real time the evolution of a nuclear reactor during a severe accident, in order to react efficiently and minimize the industrial, ecological and health consequences of the accident. Among gaseous fission products, the tetroxide of ruthenium RuO{sub 4} is of prime importance since it has a significant radiological impact. Ruthenium is a low volatile fission product but in case of the rupture of the vessel lower head by the molten corium, the air entering into the vessel oxidizes Ru into gaseous RuO{sub 4}, which is notmore » trapped by the Filtered Containment Venting Systems. To monitor the presence of RuO{sub 4} allows making a diagnosis of the core degradation and quantifying the release into the atmosphere. To determine the presence of RuO{sub 4}, FTIR spectrometry was selected. To study the feasibility of the monitoring, high-resolution IR measurements were realized at the French synchrotron facility SOLEIL on the infrared beam line AILES. Thereafter, theoretical calculations were done to simulate the FTIR spectrum to describe the specific IR fingerprint of the molecule for each isotope and based on its partial pressure in the air. (authors)« less

  1. Sol-Gel Process for Making Pt-Ru Fuel-Cell Catalysts

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Valdez, Thomas; Kumta, Prashant; Kim, Y.

    2005-01-01

    A sol-gel process has been developed as a superior alternative to a prior process for making platinum-ruthenium alloy catalysts for electro-oxidation of methanol in fuel cells. The starting materials in the prior process are chloride salts of platinum and ruthenium. The process involves multiple steps, is time-consuming, and yields a Pt-Ru product that has relatively low specific surface area and contains some chloride residue. Low specific surface area translates to incomplete utilization of the catalytic activity that might otherwise be available, while chloride residue further reduces catalytic activity ("poisons" the catalyst). In contrast, the sol-gel process involves fewer steps and less time, does not leave chloride residue, and yields a product of greater specific area and, hence, greater catalytic activity. In this sol-gel process (see figure), the starting materials are platinum(II) acetylacetonate [Pt(C5H7O2)2, also denoted Pt-acac] and ruthenium(III) acetylacetonate [Ru(C5H7O2)3, also denoted Ru-acac]. First, Pt-acac and Ru-acac are dissolved in acetone at the desired concentrations (typically, 0.00338 moles of each salt per 100 mL of acetone) at a temperature of 50 C. A solution of 25 percent tetramethylammonium hydroxide [(CH3)4NOH, also denoted TMAH] in methanol is added to the Pt-acac/Ruacac/ acetone solution to act as a high-molecular-weight hydrolyzing agent. The addition of the TMAH counteracts the undesired tendency of Pt-acac and Ru-acac to precipitate as separate phases during the subsequent evaporation of the solvent, thereby helping to yield a desired homogeneous amorphous gel. The solution is stirred for 10 minutes, then the solvent is evaporated until the solution becomes viscous, eventually transforming into a gel. The viscous gel is dried in air at a temperature of 170 C for about 10 hours. The dried gel is crushed to make a powder that is the immediate precursor of the final catalytic product. The precursor powder is converted to the

  2. Light Makes a Surface Banana-Bond Split: Photodesorption of Molecular Hydrogen from RuO 2 (110)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Henderson, Michael A.; Mu, Rentao; Dahal, Arjun

    The coordination of H2 to a metal center via polarization of its bond electron density, known as a Kubas complex, is the means by which H2 chemisorbs at Ru4+ sites on the rutile RuO2(110) surface. This distortion of electron density off an interatomic axis is often described as a ‘banana-bond.’ We show that the Ru-H2 banana-bond can be destabilized, and split, using visible light. Photodesorption of H2 (or D2) is evident by mass spectrometry and scanning tunneling microscopy. From time-dependent density functional theory, the key optical excitation splitting the Ru-H2 banana-bond involves an interband transition in RuO2 which effectively diminishesmore » its Lewis acidity, and thereby weakening the Kubas complex. Such excitations are not expected to affect adsorbates on RuO2 given its metallic properties. Therefore, this common thermal co-catalyst employed in promoting water splitting is, itself, photo-active in the visible.« less

  3. Raman and electronic transport characterization of few- and single-layer-thick α-RuCl3

    NASA Astrophysics Data System (ADS)

    Zhou, Boyi; Henriksen, Erik

    The layered magnetic semiconductor α-RuCl3, having a honeycomb lattice of spin-1/2 moments, has been identified as a potential candidate material to realize the Kitaev quantum spin liquid. In particular, bulk RuCl3 crystals have been studied and found to be on the cusp of manifesting QSL behavior. As the QSL is primarily a two-dimensional phenomenon, and since the layers of RuCl3 are weakly coupled, we propose to create and study a 2D spin-1/2 honeycomb system by isolating single sheets. Here we report the exfoliation of RuCl3 down to few- and single-layer-thick samples, which we characterize by Raman spectroscopy and atomic force microscopy at room temperature. We will also report our progress on measurements of basic electronic transport properties in the 2D RuCl3 system by controlling the chemical potential via gating in a field-effect configuration.

  4. Methanol decomposition reactions over a boron-doped graphene supported Ru-Pt catalyst.

    PubMed

    Damte, Jemal Yimer; Lyu, Shang-Lin; Leggesse, Ermias Girma; Jiang, Jyh Chiang

    2018-04-04

    The decomposition of methanol is currently attracting research attention due to the potential widespread applications of its end products. In this work, density functional theory (DFT) calculations have been performed to investigate the adsorption and decomposition of methanol on a Ru-Pt/boron doped graphene surface. We find that the most favorable reaction pathway is methanol (CH3OH) decomposition through O-H bond breaking to form methoxide (CH3O) as the initial step, followed by further dehydrogenation steps which generate formaldehyde (CH2O), formyl (CHO), and carbon monoxide (CO). The calculations illustrate that CH3OH and CO groups prefer to adsorb at the Ru-top sites, while CH2OH, CH3O, CH2O, CHO, and H2 groups favor the Ru-Pt bridge sites, indicating the preference of Ru atoms to adsorb the active intermediates or species having lone-pair electrons. Based on the results, it is found that the energy barrier for CH3OH decomposition through the initial O-H bond breaking is less than its desorption energy of 0.95 eV, showing that CH3OH prefers to undergo decomposition to CH3O rather than direct desorption. The study provides in-depth theoretical insights into the potentially enhanced catalytic activity of Ru-Pt/boron doped graphene surfaces for methanol decomposition reactions, thereby contributing to the understanding and designing of an efficient catalyst under optimum conditions.

  5. A novel self-enhanced electrochemiluminescence immunosensor based on hollow Ru-SiO2@PEI nanoparticles for NSE analysis.

    PubMed

    Zhou, Limin; Huang, Jianshe; Yu, Bin; You, Tianyan

    2016-02-26

    Poly(ethylenimine) (PEI) and Ru(bpy)3(2+)-doped silica (Ru-SiO2) nanoparticles were simply mixed together to prepare a novel self-enhanced electrochemiluminescence (ECL) composite of Ru-SiO2@PEI. The hollow Ru-SiO2@PEI nanoparticles were used to build an ECL immunosensor for the analysis of neuron specific enolase (NSE). PEI not only assembled on the surface of Ru-SiO2 nanoparticles through the electrostatic interaction to act as co-reactant for Ru(bpy)3(2+) ECL, but also provided alkaline condition to etch the Ru-SiO2 nanoparticles to form the hollow Ru-SiO2@PEI nanoparticles with porous shell. The unique structure of the Ru-SiO2@PEI nanoparticles loaded both a large amount of Ru(bpy)3(2+) and its co-reactant PEI at the same time, which shortened the electron-transfer distance, thereby greatly enhanced the luminous efficiency and amplified the ECL signal. The developed immunosensor showed a wide linear range from 1.0 × 10(-11) to 1.0 × 10(-5) mg mL(-1) with a low detection limit of 1.0 × 10(-11) mg mL(-1) for NSE. When the immunosensor was used for the determination of NSE in clinical human serum, the results were comparable with those obtained by using enzyme-linked immunosorbent assay (ELISA) method. The proposed method provides a promising alternative for NSE analysis in clinical samples.

  6. Synthesis, characterization, DNA binding and catalytic applications of Ru(III) complexes.

    PubMed

    Shoair, A F; El-Shobaky, A R; Azab, E A

    2015-01-01

    A new series of azodye ligands 5-chloro-3-hydroxy-4-(aryldiazenyl)pyridin-2(1H)-one (HLn) were synthesized by coupling of 5-chloro-3-hydroxypyridin-2(1H)-one with aniline and its p-derivatives. These ligands and their Ru(III) complexes of the type trans-[Ru(Ln)2(AsPh3)2]Cl were characterized by elemental analyses, IR, (1)H NMR and UV-Visible spectra as well as magnetic and thermal measurements. The molar conductance measurements proved that all the complexes are electrolytes. IR spectra show that the ligands (HLn) acts as a monobasic bidentate ligand by coordinating via the nitrogen atom of the azo group (NN) and oxygen atom of the deprotonated phenolic OH group, thereby forming a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The molecular and electronic structures of the investigated compounds (HLn) were also studied using quantum chemical calculations. The calf thymus DNA binding activity of the ligands (HLn) and their Ru(III) complexes were studied by absorption spectra and viscosity measurements. The mechanism and the catalytic oxidation of benzyl alcohol by trans-[Ru(Ln)2(AsPh3)2]Cl with hydrogen peroxide as co-oxidant were described. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Electrons to Reactors Multiscale Modeling: Catalytic CO Oxidation over RuO 2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sutton, Jonathan E.; Lorenzi, Juan M.; Krogel, Jaron T.

    First-principles kinetic Monte Carlo (1p-kMC) simulations for CO oxidation on two RuO 2 facets, RuO 2(110) and RuO 2(111), were coupled to the computational fluid dynamics (CFD) simulations package MFIX, and reactor-scale simulations were then performed. 1p-kMC coupled with CFD has recently been shown as a feasible method for translating molecular scale mechanistic knowledge to the reactor scale, enabling comparisons to in situ and online experimental measurements. Only a few studies with such coupling have been published. This work incorporates multiple catalytic surface facets into the scale-coupled simulation, and three possibilities were investigated: the two possibilities of each facet individuallymore » being the dominant phase in the reactor, and also the possibility that both facets were present on the catalyst particles in the ratio predicted by an ab initio thermodynamics-based Wulff construction. When lateral interactions between adsorbates were included in the 1p-kMC simulations, the two surfaces, RuO 2(110) and RuO 2(111), were found to be of similar order-of-magnitude in activity for the pressure range of 1 × 10 –4 bar to 1 bar, with the RuO 2(110) surface-termination showing more simulated activity than the RuO 2(111) surface-termination. Coupling between the 1p-kMC and CFD was achieved with a lookup table generated by the error-based modified Shepard interpolation scheme. Isothermal reactor scale simulations were performed and compared to two separate experimental studies, conducted with reactant partial pressures of ≤0.1 bar. Simulations without an isothermality restriction were also conducted and showed that the simulated temperature gradient across the catalytic reactor bed is <0.5 K, which validated the use of the isothermality restriction for investigating the reactor-scale phenomenological temperature dependences. The approach with the Wulff construction based reactor simulations reproduced a trend similar to one experimental data set

  8. Electrons to Reactors Multiscale Modeling: Catalytic CO Oxidation over RuO 2

    DOE PAGES

    Sutton, Jonathan E.; Lorenzi, Juan M.; Krogel, Jaron T.; ...

    2018-04-20

    First-principles kinetic Monte Carlo (1p-kMC) simulations for CO oxidation on two RuO 2 facets, RuO 2(110) and RuO 2(111), were coupled to the computational fluid dynamics (CFD) simulations package MFIX, and reactor-scale simulations were then performed. 1p-kMC coupled with CFD has recently been shown as a feasible method for translating molecular scale mechanistic knowledge to the reactor scale, enabling comparisons to in situ and online experimental measurements. Only a few studies with such coupling have been published. This work incorporates multiple catalytic surface facets into the scale-coupled simulation, and three possibilities were investigated: the two possibilities of each facet individuallymore » being the dominant phase in the reactor, and also the possibility that both facets were present on the catalyst particles in the ratio predicted by an ab initio thermodynamics-based Wulff construction. When lateral interactions between adsorbates were included in the 1p-kMC simulations, the two surfaces, RuO 2(110) and RuO 2(111), were found to be of similar order-of-magnitude in activity for the pressure range of 1 × 10 –4 bar to 1 bar, with the RuO 2(110) surface-termination showing more simulated activity than the RuO 2(111) surface-termination. Coupling between the 1p-kMC and CFD was achieved with a lookup table generated by the error-based modified Shepard interpolation scheme. Isothermal reactor scale simulations were performed and compared to two separate experimental studies, conducted with reactant partial pressures of ≤0.1 bar. Simulations without an isothermality restriction were also conducted and showed that the simulated temperature gradient across the catalytic reactor bed is <0.5 K, which validated the use of the isothermality restriction for investigating the reactor-scale phenomenological temperature dependences. The approach with the Wulff construction based reactor simulations reproduced a trend similar to one experimental data set

  9. Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

    NASA Astrophysics Data System (ADS)

    Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

    2018-05-01

    In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

  10. New insights into the chemistry of fac-[Ru(CO)₃]²⁺ fragments in biologically relevant conditions: the CO releasing activity of [Ru(CO)₃Cl₂(1,3-thiazole)], and the X-ray crystal structure of its adduct with lysozyme.

    PubMed

    Santos, M F A; Seixas, J D; Coelho, A C; Mukhopadhyay, A; Reis, P M; Romão, M J; Romão, C C; Santos-Silva, T

    2012-12-01

    Complexes of the general formula fac-[Ru(CO)(3)L(3)](2+), namely CORM-2 and CORM-3, have been successfully used as experimental CO releasing molecules (CO-RMs) but their mechanism of action and delivery of CO remain unclear. The well characterized complex [Ru(CO)(3)Cl(2)(1,3-thiazole)] (1) is now studied as a potential model CO-RM of the same family of complexes using LC-MS, FTIR, and UV-vis spectroscopy, together with X-ray crystallography. The chemistry of [Ru(CO)(3)Cl(2)(1,3-thiazole)] is very similar to that of CORM-3: it only releases residual amounts of CO to the headspace of a solution in PBS7.4 and produces marginal increase of COHb after long incubation in whole blood. 1 also reacts with lysozyme to form Ru adducts. The crystallographic model of the lysozyme-Ru adducts shows only mono-carbonyl Ru species. [Ru(H(2)O)(4)(CO)] is found covalently bound to a histidine (His15) and to two aspartates (Asp18 and Asp119) at the protein surface. The CO release silence of both 1 and CORM-3 and their rapid formation of protein-Ru(CO)(x)(H(2)O)(y) (x=1,2) adducts, support our hypothesis that fac-[Ru(CO)(3)L(3)] CO-RMs deliver CO in vivo through the decay of their adducts with plasma proteins. Copyright © 2012 Elsevier Inc. All rights reserved.

  11. Kinetic modeling and transient DRIFTS–MS studies of CO 2 methanation over Ru/Al 2O 3 catalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Xiang; Hong, Yongchun; Shi, Hui

    CO 2 methanation was investigated on 5% and 0.5% Ru/Al 2O 3 catalysts (Ru dispersions: ~18% and ~40%, respectively) by steady-state kinetic measurements and transient DRIFTS–MS. Methanation rates were higher over 5% Ru/Al 2O 3 than over 0.5% Ru/Al 2O 3. The measured activation energies, however, were lower on 0.5% Ru/Al 2O 3 than on 5% Ru/Al 2O 3. Transient DRIFTS–MS results demonstrated that direct CO 2 dissociation was negligible over Ru. CO 2 has to first react with surface hydroxyls on Al 2O 3 to form bicarbonates, which, in turn, react with adsorbed H on Ru to produce adsorbed formate species. Formates, most likely at the metal/oxide interface, can react rapidly with adsorbed H forming adsorbed CO, only a portion of which is reactive toward adsorbed H, ultimately leading to CH4 formation. The measured kinetics are fully consistent with a Langmuir–Hinshelwood type mechanism in which the H-assisted dissociation of the reactive CO* is the rate-determining step (RDS). The similar empirical rate expressions (r CH4 = kPmore » $$0.1\\atop{CO2}$$P$$0.3-0.5\\atop{H2}$$) and DRIFTS–MS results on the two catalysts under both transient and steady-state conditions suggest that the mechanism for CO 2 methanation does not change with Ru particle size under the studied experimental conditions. Kinetic modeling results further indicate that the intrinsic activation barrier for the RDS is slightly lower on 0.5% Ru/Al 2O 3 than on 5% Ru/Al 2O 3. Due to the presence of unreactive adsorbed CO under reaction conditions, the larger fraction of such surface sites that bind CO too strongly on 0.5% Ru/Al 2O 3 than on 5% Ru/Al 2O 3, as revealed by FTIR measurements, is regarded as the main reason for the lower rates for CO 2 methanation on 0.5% Ru/Al 2O 3. The catalyst preparation and catalytic measurements were supported by a Laboratory Directed Research and Development (LDRD) project. The authors gratefully acknowledge the financial support of this work by the US Department

  12. Initial and steady-state Ru growth by atomic layer deposition studied by in situ Angle Resolved X-ray Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Egorov, Konstantin V.; Lebedinskii, Yury Yu.; Soloviev, Anatoly A.; Chouprik, Anastasia A.; Azarov, Alexander Yu.; Markeev, Andrey M.

    2017-10-01

    The clear substrate-dependent growth and delayed film continuity are essential challenges of Ru atomic layer deposition (ALD) demanding adequate and versatile approaches for their study. Here, we report on the application of in situ Angle Resolved X-ray Phototelectron Spectroscopy (ARXPS) for investigation of initial and steady-state ALD growth of Ru using Ru(EtCp)2 and O2 as precursors. Using ARXPS surface analysis technique we determine such parameters of Ru ALD initial growth as incubation period, fractional coverage and the thickness of islands/film depending on the substrate chemical state, governed by the presence/absence of NH3/Ar plasma pretreatment. It was demonstrated that NH3/Ar plasma pretreatment allows to obtain the lowest incubation period (∼7 ALD cycles) resulting in a continuous ultrathin (∼20 Å) and smooth Ru films after 70 ALD cycles. In situ XPS at UHV was used at steady state Ru growth for analysis of half-cycle reactions that revealed formation of RuOx (x ≈ 2) layer with thickness of ∼8 Å after O2 pulse (first half-cycle). It was also shown that oxygen of RuOx layer combusts Ru(EtCp)2 ligands in the second half-cycle reaction and the observed Ru growth of ∼0.34 Å per cycle is in a good agreement with the amount of oxygen in the RuOx layer.

  13. Transformation of glucocorticoid receptors bound to the antagonist RU 486: Effects of alkaline phosphatase

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gruol, D.J.; Wolfe, K.A.

    1990-08-28

    RU 486 is a synthetic steroid that binds avidly to glucocorticoid receptors without promoting their transformation into activated transcription factors. A significant part of this behavior has been shown to be due to a failure of the RU 486 bound receptor to be efficiently released from a larger (sedimenting at 8-9 S) multimeric complex containing the 90-kDa heat shock protein. The studies have found that in vitro at 15{degree}C the RU 486-receptor was slowly released from the 8-9S complex and converted into a DNA binding protein by a process that could be blocked by sodium fluoride. Moreover, this transition wasmore » significantly accelerated by treatment with alkaline phosphatase. High-resolution anion-exchange chromatography showed that the profile of receptor subspecies released from the 8-9S complex was different for the RU 486 bound receptor when compared to the receptor occupied by the agonist triamcinolone acetonide. Production of the earliest eluting receptor form (peak A) was inhibited with RU 486. Treatment of the Ru 486-receptor with alkaline phosphatase increased the formation of the peak A subspecies as well as the capacity of receptor to bind DNA-cellulose. Taken together, the results indicate that phosphorylation of the receptor or a tightly bound factor contributes to defining the capacity with which individual steroids can promote dissociation of the 8-9S complex and conversion of the glucocorticoid receptor into a DNA-binding protein.« less

  14. Simultaneous optical and IR photometry of the T Tauri star RU LUPI

    NASA Astrophysics Data System (ADS)

    Giovannelli, F.; Errico, L.; Vittone, A. A.; Rossi, C.

    1991-01-01

    Two simultaneous optical and IR photometric observation runs of RU Lupi were carried out at the ESO in February 1983 and in June 1986 within the framework of a large multifrequency coordinated campaign of observations. RU Lupi was found in two different states. In the first case the star was in 'quiescence', in the second it was brighter and showed larger variations due to flare like event (FLE). A positive correlation between luminosity and its variations has been found. A Fourier analysis of the light curve available in literature was performed to point out the rotational period. The analysis of these data excludes any periodicity. The color-color diagnostic diagram clearly shows that RU Lupi variability is mainly due to a strong photospheric and chromospheric activity.

  15. Superconducting and normal-state properties of the layered boride OsB2

    NASA Astrophysics Data System (ADS)

    Singh, Yogesh; Niazi, A.; Vannette, M. D.; Prozorov, R.; Johnston, D. C.

    2007-12-01

    OsB2 crystallizes in an orthorhombic structure (Pmmn) which contains alternate boron and osmium layers stacked along the c axis. The boron layers consist of puckered hexagons as opposed to the flat graphite-like boron layers in MgB2 . OsB2 is reported to become superconducting below 2.1K . We report results of the dynamic and static magnetic susceptibilities, electrical resistivity, Hall effect, heat capacity, and penetration depth measurements on arc-melted polycrystalline samples of OsB2 to characterize its superconducting and normal-state properties. These measurements confirmed that OsB2 becomes a bulk superconductor below Tc=2.1K . Our results indicate that OsB2 is a moderate-coupling type-II superconductor with an electron-phonon coupling constant λep≈0.4-0.5 , a small Ginzburg-Landau parameter κ˜1-2 , and an upper critical magnetic field Hc2(0.5K)˜420Oe for an unannealed sample and Hc2(1K)˜330Oe for an annealed sample. The temperature dependence of the superfluid density ns(T) for the unannealed sample is consistent with an s -wave superconductor with a slightly enhanced zero temperature gap Δ(0)=1.9kBTc and a zero temperature London penetration depth λ(0)=0.38(2)μm . The ns(T) data for the annealed sample show deviations from the predictions of the single-band s -wave BCS model. The magnetic, transport, and thermal properties in the normal state of isostructural and isoelectronic RuB2 , which is reported to become superconducting below 1.6K , are also reported.

  16. Fragment-based Quantum Mechanical/Molecular Mechanical Simulations of Thermodynamic and Kinetic Process of the Ru2+-Ru3+ Self-Exchange Electron Transfer.

    PubMed

    Zeng, Xiancheng; Hu, Xiangqian; Yang, Weitao

    2012-12-11

    A fragment-based fractional number of electron (FNE) approach, is developed to study entire electron transfer (ET) processes from the electron donor region to the acceptor region in condensed phase. Both regions are described by the density-fragment interaction (DFI) method while FNE as an efficient ET order parameter is applied to simulate the electron transfer process. In association with the QM/MM energy expression, the DFI-FNE method is demonstrated to describe ET processes robustly with the Ru 2+ -Ru 3+ self-exchange ET as a proof-of-concept example. This method allows for systematic calculations of redox free energies, reorganization energies, and electronic couplings, and the absolute ET rate constants within the Marcus regime.

  17. Epitaxial BiFeO3 thin films fabricated by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Singh, S. K.; Kim, Y. K.; Funakubo, H.; Ishiwara, H.

    2006-04-01

    Epitaxial BiFeO3 (BFO) thin films were fabricated on (001)-, (110)-, and (111)-oriented single-crystal SrRuO3(SRO )/SrTiO3(STO) structures by chemical solution deposition. X-ray diffraction indicates the formation of an epitaxial single-phase perovskite structure and pole figure measurement confirms the cube-on-cube epitaxial relationship of BFO ‖SRO‖STO. Chemical-solution-deposited BFO films have a rhombohedral structure with lattice parameter of 0.395nm, which is the same structure as that of a bulk single crystal. The remanent polarization of approximately 50μC/cm2 was observed in BFO (001) thin films at 80K.

  18. The control of Pt and Ru nanoparticle size on high surface area supports.

    PubMed

    Liu, Qiuli; Joshi, Upendra A; Über, Kevin; Regalbuto, John R

    2014-12-28

    Supported Ru and Pt nanoparticles are synthesized by the method of strong electrostatic adsorption and subsequently treated under different steaming-reduction conditions to achieve a series of catalysts with controlled particle sizes, ranging from 1 to 8 nm. While in the case of oxidation-reduction conditions, only Pt yielded particles ranging from 2.5 to 8 nm in size and a loss of Ru was observed. Both Ru and Pt sinter faster in air than in hydrogen. This methodology allows the control of particle size using a "production-scalable" catalyst synthesis method which can be applied to high surface area supports with common metal precursors.

  19. Mechanistic analysis of water oxidation catalyst cis-[Ru(bpy) 2(H 2O) 2] 2+: Effect of dimerization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Erdman, Darren; Pineda-Galvan, Yuliana; Pushkar, Yulia

    While the catalytic activity of some Ru-based polypyridine complexes in water oxidation is well established, the relationship between their chemical structure and activity is less known. In this work, the single site Ru complex [Ru(bpy) 2(H 2O) 2] 2+ (bpy = 2,20-bipyridine)—which can exist as either a cis isomer or a trans isomer—is investigated. While a difference in the catalytic activity of these two isomers is well established, with cis-[Ru(bpy) 2(H 2O) 2] 2+ being much more active, no mechanistic explanation of this fact has been presented. The oxygen evolving capability of both isomers at multiple concentrations has been investigated,more » with cis-[Ru(bpy) 2(H 2O) 2] 2+ showing a second-order dependence of O2 evolution activity with increased catalyst concentration. Measurement of the electron paramagnetic resonance (EPR) spectrum of cis-[Ru(bpy) 2(H 2O) 2] 2+, shortly after oxidation with CeIV, showed the presence of a signal matching that of cis,cis-[Ru III(bpy) 2(H 2O)ORu IV(bpy) 2(OH)] 4+, also known as “blue dimer”. The formation of dimers is a concentration-dependent process, which could serve to explain the greater than first order increase in catalytic activity. The trans isomer showed a first-order dependence of O 2 evolution on catalyst concentration. As a result, behavior of [Ru(bpy) 2(H 2O) 2] 2+ isomers is compared with other Ru-based catalysts, in particular [Ru(tpy)(bpy)(H 2O)] 2+ (tpy = 2,20;6,20 0-terpyridine).« less

  20. Mechanistic analysis of water oxidation catalyst cis-[Ru(bpy) 2(H 2O) 2] 2+: Effect of dimerization

    DOE PAGES

    Erdman, Darren; Pineda-Galvan, Yuliana; Pushkar, Yulia

    2017-01-25

    While the catalytic activity of some Ru-based polypyridine complexes in water oxidation is well established, the relationship between their chemical structure and activity is less known. In this work, the single site Ru complex [Ru(bpy) 2(H 2O) 2] 2+ (bpy = 2,20-bipyridine)—which can exist as either a cis isomer or a trans isomer—is investigated. While a difference in the catalytic activity of these two isomers is well established, with cis-[Ru(bpy) 2(H 2O) 2] 2+ being much more active, no mechanistic explanation of this fact has been presented. The oxygen evolving capability of both isomers at multiple concentrations has been investigated,more » with cis-[Ru(bpy) 2(H 2O) 2] 2+ showing a second-order dependence of O2 evolution activity with increased catalyst concentration. Measurement of the electron paramagnetic resonance (EPR) spectrum of cis-[Ru(bpy) 2(H 2O) 2] 2+, shortly after oxidation with CeIV, showed the presence of a signal matching that of cis,cis-[Ru III(bpy) 2(H 2O)ORu IV(bpy) 2(OH)] 4+, also known as “blue dimer”. The formation of dimers is a concentration-dependent process, which could serve to explain the greater than first order increase in catalytic activity. The trans isomer showed a first-order dependence of O 2 evolution on catalyst concentration. As a result, behavior of [Ru(bpy) 2(H 2O) 2] 2+ isomers is compared with other Ru-based catalysts, in particular [Ru(tpy)(bpy)(H 2O)] 2+ (tpy = 2,20;6,20 0-terpyridine).« less

  1. Synthesis and strong photooxidation power of a supramolecular hybrid comprising a polyoxometalate and Ru(II) polypyridyl complex with zinc(II).

    PubMed

    Ohashi, Kenji; Takeda, Hiroyuki; Koike, Kazuhide; Ishitani, Osamu

    2015-01-01

    A novel method for constructing supramolecular hybrids composed of polyoxometalates and photofunctional metal complexes was developed. A Ru(II) complex with phosphonate groups (RuP) strongly interacted with Zn(II) to afford a 2 : 1 trinuclear metal complex ([(RuP)2Zn](3+)). In dimethylsulfoxide, [(RuP)2Zn](3+) strongly interacted with a Keggin-type heteropolyoxometalate (Si-WPOM) to form a 1 : 1 hybrid ([(RuP)2Zn]-POM). Irradiation of [(RuP)2Zn]-POM in the presence of diethanolamine caused rapid accumulation of the one-electron reduced hybrid with a quantum yield of 0.99.

  2. In silico Identification of Ergosterol as a Novel Fungal Metabolite Enhancing RuBisCO Activity in Lycopersicum esculentum.

    PubMed

    Mitra, Joyeeta; Narad, Priyanka; Sengupta, Abhishek; Sharma, P D; Paul, P K

    2016-09-01

    RuBisCO (EC 4.1.1.39), a key enzyme found in stroma of chloroplast, is important for fixing atmospheric CO2 in plants. Alterations in the activity of RuBisCO could influence photosynthetic yield. Therefore, to understand the activity of the protein, knowledge about its structure is pertinent. Though the structure of Nicotiana RuBisCO has been modeled, the structure of tomato RuBisCO is still unknown. RuBisCO extracted from chloroplasts of tomato leaves was subjected to MALDI-TOF-TOF followed by Mascot Search. The protein sequence based on gene identification numbers was subjected to in silico model construction, characterization and docking studies. The primary structure analysis revealed that protein was stable, neutral, hydrophilic and has an acidic pI. The result though indicates a 90 % homology with other members of Solanaceae but differs from the structure of Arabidopsis RuBisCO. Different ligands were docked to assess the activity of RuBisCO against these metabolite components. Out of the number of modulators tested, ergosterol had the maximum affinity (E = -248.08) with RuBisCO. Ergosterol is a major cell wall component of fungi and has not been reported to be naturally found in plants. It is a known immune elicitor in plants. The current study throws light on its role in affecting RuBisCO activity in plants, thereby bringing changes in the photosynthetic rate.

  3. Magnetic order and spin dynamics in La2O2Fe2OSe2 probed by 57Fe Mössbauer, 139La NMR, and muon-spin relaxation spectroscopy

    NASA Astrophysics Data System (ADS)

    Günther, M.; Kamusella, S.; Sarkar, R.; Goltz, T.; Luetkens, H.; Pascua, G.; Do, S.-H.; Choi, K.-Y.; Zhou, H. D.; Blum, C. G. F.; Wurmehl, S.; Büchner, B.; Klauss, H.-H.

    2014-11-01

    We present a detailed local probe study of the magnetic order in the oxychalcogenide La2O2Fe2OSe2 utilizing 57Fe Mössbauer, 139La NMR, and muon-spin relaxation spectroscopy. This system can be regarded as an insulating reference system of the Fe arsenide and chalcogenide superconductors. From the combination of the local probe techniques we identify a noncollinear magnetic structure similar to Sr2F2Fe2OS2 . The analysis of the magnetic order parameter yields an ordering temperature TN=90.1 K and a critical exponent of β =0.133 , which is close to the two-dimensional Ising universality class as reported in the related oxychalcogenide family.

  4. [Clinical use of RU 486: control of the menstrual cycle and effect on the hypophyseal-adrenal axis].

    PubMed

    Gaillard, R C; Herrmann, W

    1983-01-01

    RU 486 is a synthetic 19 norsteroid with a great affinity for progesterone and glucocorticosteroid receptors. The antiprogesterone activity of RU 486 permits interruption of the luteal phase of the menstrual cycle and of early pregnancy, while the antiglucocorticosteroid activity interrupts the feedback mechanisms of cortisol at the hypothalamic-pituitary axis. 11 women aged 18-34 years who were 6-8 weeks pregnant were given daily doses of 200 mg of sensation of lipothymia. Blood pressure and laboratory test results remained normal. The daily increase of beta human chorionic gonadotropin (HCG) and progesterone was stopped by the antiprogesterone. It has been demonstrated in vitro that RU 486 inhibits secretion of beta HCG by cells of trophoblastic origin. 2 weeks after expulsion of the products of conception, the blood levels of beta HCG, progesterone, and estradiol had returned to nonpregnant values and ovarian activity was normal in women not using oral contraceptives. The reason for failure of expulsion in 2 cases was not known. RU 486 was also used to interrupt the luteal phase of normal menstrual cycles in 3 young women. 50 mg/day of RU 486 starting on the 22nd day was sufficient to induce bleeding within 48 hours. Studies using RU 486 50 mg/day beginning on the 10th cycle day indicate that progesterone plays a central and follicular role during the preovulatory period. The antiglucocorticosteroid activity of RU 486 was observed in pregnant women who received the abortifacient dose of 200 mg/day. The 8 a.m. plasma level of ACTH and beta-LPH cortisol remained elevated for thee 4 days of treatment. Nonpregnant women receiving 50 mg of RU 486 for 4 days beginning on the 22nd cycle day had no change in the level of hypophyseal-adrenal hormones.dd Tests in young male volunteers showed that RU 486 amplified circadian rhythms of the hypophysealadrenal axis, affecting specifically the morning hormonal levels without influencing afternoon levels. A test in which RU 486

  5. Benten v. Kessler: the RU 486 import case.

    PubMed

    Pine, R N

    1992-01-01

    On July 1, 1992, the case of Benten v. Kessler was filed in the US District Court in New York. The case arose out of an attempt by abortion rights activist Lawrence Lader to call public attention to the US Food and Drug Administration's (FDA) ban on importation of the abortifacient drug mifepristone known as RU-486. The ban expresses the anti abortion stance of the Reagan and Bush administrations and creates a hostile climate for the development of new drugs related to reproductive health and reproductive choice. Plaintiffs in the Benten case sought public accountability by the FDA for its adoption of a ban of a safe and effective drug for unwanted pregnancy. Although the case did not succeed in retrieving the confiscated RU-486 pills for Leona Benten, in its opinion issued on July 14, 1992, the New York district court judge concluded that the import ban did not appear to be based on concern with the safety or effectiveness of RU-486, describing the FDA's process of adopting the import ban as a sink of illegality. On July 17, 1992, 7 Justices of the Supreme Court, with justices Blackmun and Stevens dissenting, joined in a per curiam opinion denying the application and foreclosing further personal relief for Leona Benten. This was the best result possible short of an all out victory for Leona Benten. The Court ruled against plaintiffs in their argument that notice and comment were required, but left entirely open plaintiffs' claims that the import ban is arbitrary and capricious under the Administrative Procedure Act and that the ban is unconstitutional in that it unduly burdens the right to terminate pregnancy. This backdrop creates a healthy skepticism about the prospects for the introduction of RU-486 into the US in the near future as well as about the fairness of government processes in areas of concern to women. Public health considerations, not politics, should determine access to health care.

  6. Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lu, Junling; Elam, Jeffrey W.

    Thermal atomic layer deposition (ALD) of noble metals is frequently performed using molecular oxygen as the nonmetal precursor to effect a combustion-type chemistry at relatively high temperatures of 300 °C. Bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2) is one of the common used metal precursors for Ru ALD. Using Ru(EtCp)2 and oxygen as reactants, Ru ALD was acheived at near 300 °C. Here, we demonstrate that Ru ALD can proceed at as low as 150 °C by using successive exposures to oxygen and hydrogen as the co-reactants. In situ quartz crystal microbalance (QCM) and quadrupole mass spectroscopy (QMS) measurements both suggest that this ABC-type ALDmore » occurs through dissociative chemisorption, combustion, and reduction for the Ru(EtCp)2, oxygen and hydrogen steps, respectively, in a similar manner to processes using ozone and hydrogen as co-reactants reported previously. Moreover, we believe this molecular O2 and H2 based ABC-type ALD could be exploited for the ALD of other noble metals to decrease the deposition temperature and reduce oxygen impurities.« less

  7. Synthesis of 4‧-substituted-2,2‧;6‧,2″-terpyridine Ru(II) complexes electrochemical, fluorescence quenching and antibacterial studies

    NASA Astrophysics Data System (ADS)

    Ezhilarasu, Tamilarasu; Sathiyaseelan, Anbazhagan; Kalaichelvan, Pudupalayam Thangavelu; Balasubramanian, Sengottuvelan

    2017-04-01

    Three new Ru(II) terpyridine complexes viz. [Ru(BBtpy)2](PF6)2 [Ru(L1)] (BBtpy = 4‧-(4-benzyloxybenzaldehyde)-2,2‧:6‧,2″-terpyridine), [Ru(BMBtpy)2](PF6)2 [Ru(L2)] (BMBtpy = 4‧-(4-benzyloxy-3-methoxybenzaldehyde)-2,2‧:6‧,2″-terpyridine) and [Ru(BEBtpy)2](PF6)2 [Ru(L3)] (BEBtpy = 4‧-(4-benzyloxy-3-ethoxybenzaldehyde)-2,2‧:6‧,2″-terpyridine) have been synthesized and characterized. The MALDI-TOF/MS fragmentation pattern of [Ru(BMBtpy)2](PF6)2 complex exhibits a molecular ion peak at m/z = 987.09 [M-2PF6]2+ fragment. These Ru(II) complexes are redox active, show both metal centered oxidation and ligand centered reduction processes. The peak potential and peak current Ipa and Ipc also undergo definite shift and increase with increase in the scan rate (20-120 mV/s). The fluorescence of Ru(II) complexes [Ru(L1)], [Ru(L2)] and [Ru(L3)] are effectively quenched by 1,4-benzoquinone and 1,4-naphthoquinone in acetonitrile. The antibacterial activity of ruthenium(II) complexes were screened against four human pathogens both gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) and gram negative bacteria (Escherichia coli, Klebsiella pneumonia) by the well diffusion method. The antibacterial activity of Ru(II) complexes is comparable to that of standard antibiotics like tetracycline.

  8. Noble metal abundances in komatiite suites from Alexo, Ontario and Gorgona Island, Colombia

    NASA Astrophysics Data System (ADS)

    Brügmann, G. E.; Arndt, N. T.; Hofmann, A. W.; Tobschall, H. J.

    1987-08-01

    The distribution of the chalcophile and siderophile metals Cu, Ni, Au, Pd, Ir, Os and Ru in an Archaean komatiite flow from Alexo, Ontario and in a Phanerozoic komatiitic suite of Gorgona Island, Colombia, provides new information about the geochemical behaviour of these elements. Copper, Au and Pd behave as incompatible elements during the crystallization of these ultramafic magmas. In contrast, Ni, Ir, Os and Ru concentrations systematically decrease with decreasing MgO contents, a pattern characteristic of compatible elements. These trends are most probably controlled by olivine crystallization, which implies that Ir, Os and Ru are compatible in olivine. Calculated partition coefficients for Ir, Os and Ru between olivine and the melt are about 1.8. Compared to primitive mantle, parental komatiitic liquids are enriched in (incompatible) Cu, Au and Pd and depleted in (compatible) Ir, Os and Ru. Within both Archaean and Phanerozoic komatiites, noble metal ratios such as Au/Pd, Ir/Os, Os/Ru and Ru/Ir and ratios of lithophile and siderophile elements such as Ti/Pd, Ti/Au are constant and similar to primitive mantle values. This implies that Au and Pd are moderately incompatible elements and that there has been no significant fractionation of siderophile and lithophile elements since the Archaean. Platinum-group element abundances of normal MORB are highly variable and always much lower than in komatiites, because MORB magma is saturated with sulfur and a variable but minor amount of sulfide segregated during mantle melting or during the ascent of magma to the surface. Sulfide deposits associated with komatiites display similar chalcophile element patterns to those of komatiites. Noble metal ratios such as Pd/Ir, Au/Ir, Pd/Os and Pd/Ru can be used to determine the composition of the host komatiite at the time of sulfide segregation.

  9. "RU486: Misconceptions, myths and morals." A critique of the criticisms.

    PubMed

    Cottingham, J; Van Look, P

    1993-01-01

    This article was written to counter some of the misinformation contained in the book "RU486: Misconceptions, Myths and Morals." The book concludes that use of RU486 constitutes yet another form of medical violence against women which will have unknown longterm effects. One of the major goals of the women's health movement is to disseminate information about women's health through information networks which also expose abusive reproductive health practices. Critiques about new products and procedures are important because what is considered clinically safe may pose problems for women in practice. While the book on RU486 is important from this viewpoint, it lacks careful scrutiny of its criticisms. Thus, the book suggests that animal testing has been inadequate at 17 months when, in fact, this time frame meets all standards for a single dose drug. The authors also mislabel the exclusion criterion for experimental trials as "contraindications" for use and claim that this incorrectly inflated number of contraindications prohibits the use of RU-486 as a viable alternative to other methods of abortion. In several instances the authors present inaccurate information about the pharmacodynamics and dosages of the drugs involved. The use of prostaglandins is also unjustly criticized by drawing comparisons with other uses of the prostaglandins which involve different doses and delivery periods. The authors act irresponsibly when they suggest that incomplete abortion with Ru-486 may result in uterine cancer or that the simultaneous use of aspirin will result in an almost guaranteed incomplete abortion. Additional ill-founded remarks overemphasize the failure rate, demand unrealistic guarantees about fetal abnormality, and charge that the World Health Organization has "discarded" suction curettage abortion. The book grew out of valid concerns and raises important questions about the best ways to serve women's interests, but these concerns and questions are obfuscated by

  10. Photochemical CVD of Ru on functionalized self-assembled monolayers from organometallic precursors

    NASA Astrophysics Data System (ADS)

    Johnson, Kelsea R.; Arevalo Rodriguez, Paul; Brewer, Christopher R.; Brannaka, Joseph A.; Shi, Zhiwei; Yang, Jing; Salazar, Bryan; McElwee-White, Lisa; Walker, Amy V.

    2017-02-01

    Chemical vapor deposition (CVD) is an attractive technique for the metallization of organic thin films because it is selective and the thickness of the deposited film can easily be controlled. However, thermal CVD processes often require high temperatures which are generally incompatible with organic films. In this paper, we perform proof-of-concept studies of photochemical CVD to metallize organic thin films. In this method, a precursor undergoes photolytic decomposition to generate thermally labile intermediates prior to adsorption on the sample. Three readily available Ru precursors, CpRu(CO)2Me, (η3-allyl)Ru(CO)3Br, and (COT)Ru(CO)3, were employed to investigate the role of precursor quantum yield, ligand chemistry, and the Ru oxidation state on the deposition. To investigate the role of the substrate chemistry on deposition, carboxylic acid-, hydroxyl-, and methyl-terminated self-assembled monolayers were used. The data indicate that moderate quantum yields for ligand loss (φ ≥ 0.4) are required for ruthenium deposition, and the deposition is wavelength dependent. Second, anionic polyhapto ligands such as cyclopentadienyl and allyl are more difficult to remove than carbonyls, halides, and alkyls. Third, in contrast to the atomic layer deposition, acid-base reactions between the precursor and the substrate are more effective for deposition than nucleophilic reactions. Finally, the data suggest that selective deposition can be achieved on organic thin films by judicious choice of precursor and functional groups present on the substrate. These studies thus provide guidelines for the rational design of new precursors specifically for selective photochemical CVD on organic substrates.

  11. GRAIN BOUNDARY STRENGTHENING PROPERTIES OF TUNGSTEN ALLOYS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Setyawan, Wahyu; Kurtz, Richard J.

    2012-10-10

    Density functional theory was employed to investigate grain boundary (GB) properties of W alloys. A range of substitutional solutes across the Periodic Table was investigated to understand the behavior of different electronic orbitals in changing the GB cleavage energy in the Σ27a[110]{525} GB. A number of transition metals were predicted to enhance the GB cohesion. This includes Ru, Re, Os, Ir, V, Cr, Mn, Fe, Co, Ti, Hf, Ta and Nb. While lanthanides, s and p elements were tended to cause GB embrittlement.

  12. A rechargeable hydrogen battery based on Ru catalysis.

    PubMed

    Hsu, Shih-Fan; Rommel, Susanne; Eversfield, Philipp; Muller, Keven; Klemm, Elias; Thiel, Werner R; Plietker, Bernd

    2014-07-01

    Apart from energy generation, the storage and liberation of energy are among the major problems in establishing a sustainable energy supply chain. Herein we report the development of a rechargeable H2 battery which is based on the principle of the Ru-catalyzed hydrogenation of CO2 to formic acid (charging process) and the Ru-catalyzed decomposition of formic acid to CO2 and H2 (discharging process). Both processes are driven by the same catalyst at elevated temperature either under pressure (charging process) or pressure-free conditions (discharging process). Up to five charging-discharging cycles were performed without decrease of storage capacity. The resulting CO2/H2 mixture is free of CO and can be employed directly in fuel-cell technology. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Derivatization of bichromic cyclometalated Ru(II) complexes with hydrophobic substituents.

    PubMed

    Robson, Kiyoshi C D; Koivisto, Bryan D; Berlinguette, Curtis P

    2012-02-06

    The syntheses and physical properties of cyclometalated Ru(II) complexes containing a triphenylamine (TPA) unit bearing aliphatic groups are reported. Each member of the series consists of an octahedral Ru(II) center coordinated by a tridentate polypyridyl ligand and a tridentate cyclometalating ligand. One of the chelating ligands contains electron-deficient methyl ester groups, while a TPA unit is attached to the central ring of the adjacent chelating ligand through a thiophene bridge. This study builds on our previous work (Inorg. Chem. 2011, 50, 6019-6028; Inorg. Chem. 2011, 50, 5494-5508) by (i) outlining a synthetic protocol for installing aliphatic groups on the TPA substituents, (ii) examining the role that terminal -O-hexyl and -S-hexyl groups situated on the TPA have on the electrochemical properties, and (iii) demonstrating the potential benefit of installing the TPA on the neutral chelating ligand rather than the anionic chelating ligand. The results reported herein provide important synthetic advances for our broader goal of developing bis-tridentate cyclometalated Ru(II) complexes for light-harvesting applications.

  14. Paleoceanographic conditions on the São Paulo Ridge, SW Atlantic Ocean, for the past 30 million years inferred from Os and Pb isotopes of a hydrogenous ferromanganese crust

    NASA Astrophysics Data System (ADS)

    Goto, Kosuke T.; Nozaki, Tatsuo; Toyofuku, Takashi; Augustin, Adolpho H.; Shimoda, Gen; Chang, Qing; Kimura, Jun-Ichi; Kameo, Koji; Kitazato, Hiroshi; Suzuki, Katsuhiko

    2017-12-01

    Hydrogenous ferromanganese (Fe-Mn) crusts can provide records of long-term environmental changes during the Cenozoic. To understand the paleoceanographic conditions in the southwestern Atlantic Ocean, we investigated depth profiles of major- and trace-element concentrations as well as Os and Pb isotopic compositions in a Fe-Mn crust collected from the southern flank of the São Paulo Ridge in the southwestern Atlantic. Major and trace element data plotted on ternary Mn-Fe-10×(Ni+Co+Cu) and rare-earth element plus yttrium (REY) discrimination diagrams indicate that the analyzed sample is a typical hydrogenous Fe-Mn crust. The obtained 187Os/188Os data were matched to the Cenozoic seawater Os isotope evolution curve reconstructed from pelagic sediments. The result suggests that the Fe-Mn crust has accreted over 30 Myr with growth rates of 0.5-3 mm/Myr, although the sample likely grew in two directions during the early stage of its growth. We found no evidence of growth hiatus in the sample, which may contrast with the growth histories of many Pacific Fe-Mn crusts. Hence, the conditions favorable for the accretion of hydrogenous Fe-Mn crusts were likely to have developed on the São Paulo Ridge over the past 30 Myr. The Pb isotopic compositions show very limited ranges (e.g., 206Pb/204Pb=18.80-18.85), and are similar to those of pre-anthropogenic seawater in the Southern Ocean. As the São Paulo Ridge is located near the Vema Channel, which is presently a major path of Antarctic Bottom Water, we suggest that a strong northward bottom current has continuously swept detrital and biogenic sediments from the ridge, and played a vital role in the Fe-Mn crust formation since 30 Ma.

  15. Effect of epitaxial strain on ferroelectric polarization in multiferroic BiFeO3 films

    NASA Astrophysics Data System (ADS)

    Kim, Dae Ho; Lee, Ho Nyung; Biegalski, Michael D.; Christen, Hans M.

    2008-01-01

    Multiferroic BiFeO3 epitaxial films with thicknesses ranging from 40to960nm were grown by pulsed laser deposition on SrTiO3 (001) substrates with SrRuO3 bottom electrodes. X-ray characterization shows that the structure evolves from angularly distorted tetragonal with c /a≈1.04 to more bulklike distorted rhombohedral (c/a≈1.01) as the strain relaxes with increasing thickness. Despite this significant structural evolution, the ferroelectric polarization along the body diagonal of the distorted pseudocubic unit cells, as calculated from measurements along the normal direction, barely changes.

  16. The iron-chelate transporter OsYSL9 plays a role in iron distribution in developing rice grains.

    PubMed

    Senoura, Takeshi; Sakashita, Emi; Kobayashi, Takanori; Takahashi, Michiko; Aung, May Sann; Masuda, Hiroshi; Nakanishi, Hiromi; Nishizawa, Naoko K

    2017-11-01

    Rice OsYSL9 is a novel transporter for Fe(II)-nicotianamine and Fe(III)-deoxymugineic acid that is responsible for internal iron transport, especially from endosperm to embryo in developing seeds. Metal chelators are essential for safe and efficient metal translocation in plants. Graminaceous plants utilize specific ferric iron chelators, mugineic acid family phytosiderophores, to take up sparingly soluble iron from the soil. Yellow Stripe 1-Like (YSL) family transporters are responsible for transport of metal-phytosiderophores and structurally similar metal-nicotianamine complexes. Among the rice YSL family members (OsYSL) whose functions have not yet been clarified, OsYSL9 belongs to an uncharacterized subgroup containing highly conserved homologs in graminaceous species. In the present report, we showed that OsYSL9 localizes mainly to the plasma membrane and transports both iron(II)-nicotianamine and iron(III)-deoxymugineic acid into the cell. Expression of OsYSL9 was induced in the roots but repressed in the nonjuvenile leaves in response to iron deficiency. In iron-deficient roots, OsYSL9 was induced in the vascular cylinder but not in epidermal cells. Although OsYSL9-knockdown plants did not show a growth defect under iron-sufficient conditions, these plants were more sensitive to iron deficiency in the nonjuvenile stage compared with non-transgenic plants. At the grain-filling stage, OsYSL9 expression was strongly and transiently induced in the scutellum of the embryo and in endosperm cells surrounding the embryo. The iron concentration was decreased in embryos of OsYSL9-knockdown plants but was increased in residual parts of brown seeds. These results suggested that OsYSL9 is involved in iron translocation within plant parts and particularly iron translocation from endosperm to embryo in developing seeds.

  17. Cytotoxic activity and structural features of Ru(II)/phosphine/amino acid complexes.

    PubMed

    Dos Santos, Edjane R; Graminha, Angelica E; Schultz, Mario S; Correia, Isabel; Selistre-de-Araújo, Heloisa S; Corrêa, Rodrigo S; Ellena, Javier; Lacerda, Elisângela de Paula S; Pessoa, João Costa; Batista, Alzir A

    2018-05-01

    Thirteen new ruthenium amino acid complexes were synthesized and characterized. They were obtained by the reaction of α-amino acids (AA) with [RuCl 2 (P-P)(N-N)], where P-P=1,4-bis(diphenylphosphino)butane (dppb) or 1,3-bis(diphenylphosphino)propane (dppp) and N-N=4,4'-dimethyl-2,2'-bipyridine (4'-Mebipy), 5,5'-dimethyl-2,2'-bipyridine (5'-Mebipy) or 4,4'-Methoxy-2-2'-bipyridine (4'-MeObipy). This afforded a family of complexes formulated as [Ru(AA-H)(P-P)(N-N)]PF 6 , where AA=glycine (Gly), L-alanine (Ala), L-valine (Val), L-tyrosine (Tyr), L-tryptophan (Trp), L-histidine (His) and L-methionine (Met). All compounds were characterized by elemental analysis, spectroscopic and electrochemical techniques. The [Ru(AA-H)(P-P)(N-N)]PF 6 complexes are octahedral (the AA-H ligand binding involves N-amine and O-carboxylate), diamagnetic (low-spin d 6 , S=0) and present bands due to electronic transitions in the visible region. 1 H, 13 C{ 1 H} and 31 P{ 1 H} NMR spectra of the complexes indicate the presence of C 2 symmetry, and the identification of diastereoisomers. In vitro cytotoxicity assays of the compounds and cisplatin were carried out using MDA-MB-231 (human breast) tumor cell line and a non-tumor breast cell line (MCF-10A). Most complexes present promising results with IC 50 values comparable with the reference drug cisplatin and high selectivity indexes were found for the complexes containing L-Trp. The binding of two Ru-precursors of the type [RuCl 2 (dppb)(NN)] (N-N=4'-MeObipy or 4'-Mebipy) to the blood transporter protein human serum albumin (HSA) was evaluated by fluorescence and circular dichroism spectroscopy. Both complexes bind HSA, probably in the hydrophobic pocket near Trp214, and the Ru-complex containing 4'-MeObipy shows higher affinity for HSA than the 4'-Mebipy one. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. The barium iron ruthenium oxide system

    NASA Technical Reports Server (NTRS)

    Kemmler-Sack, S.; Ehmann, A.

    1986-01-01

    In the system BaFe(1-x)Ru(x)O(3-y), three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0 to 0.75) with hexagonal BaTiO3 structure (6H; sequence (hcc)2), a Ru-rich phase (x = 0.9) of hexagonal 4H-type (sequence (hc)2), and the pure Ru compounds BaRuO3 with rhombohedral 9R structure (sequence (hhc)3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich compounds with complete O lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors. The lattice parameters are given.

  19. CuPt and CuPtRu Nanostructures for Ammonia Oxidation Reaction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Manso, R H.; Song, L.; Liang, Z.

    Liquid fuels, such as methanol, ethanol, and ammonia, are attractive alternative to hydrogen for fuel cells due to their lower costs for storage and distribution. However, lack of sufficiently active catalysts for their oxidation reactions is a roadblock. Our previous study found that Pt 3Cu nanodendrites yielded higher activity and durability than Pt nanoparticles for methanol oxidation reaction (MOR) in acid. In this study, we synthesized two types of nanostructures of CuPt and CuPtRu catalysts via seed-mediated growth of Pt and Ru on Cu and tested their performance for ammonia oxidation reaction (AOR) in alkaline solution. Unlike for MOR, themore » nanodendrites do not promote AOR activity - CuPt performs similar to Pt and CuPtRu is less active than Pt. Interestingly, the AOR peak current is increased by 64% on CuPt nanowires and 330% on CuPtRu nanowires as compared to Pt nanoparticles. These results suggest that AOR prefers extended surface on long nanowires, distinctly differing from MOR. This can be contributed to two factors: NH 3 oxidization to N 2 involves dimerization of two N-containing intermediates to form the N-N bond and diffusion batters for adsorbed intermediates are generally lower on terrace than at low-coordination sites. This demonstrated strong effect of surface morphology will be further studied and utilized in developing advanced AOR nanocatalysts.« less

  20. CuPt and CuPtRu Nanostructures for Ammonia Oxidation Reaction

    DOE PAGES

    Manso, R H.; Song, L.; Liang, Z.; ...

    2018-04-01

    Liquid fuels, such as methanol, ethanol, and ammonia, are attractive alternative to hydrogen for fuel cells due to their lower costs for storage and distribution. However, lack of sufficiently active catalysts for their oxidation reactions is a roadblock. Our previous study found that Pt 3Cu nanodendrites yielded higher activity and durability than Pt nanoparticles for methanol oxidation reaction (MOR) in acid. In this study, we synthesized two types of nanostructures of CuPt and CuPtRu catalysts via seed-mediated growth of Pt and Ru on Cu and tested their performance for ammonia oxidation reaction (AOR) in alkaline solution. Unlike for MOR, themore » nanodendrites do not promote AOR activity - CuPt performs similar to Pt and CuPtRu is less active than Pt. Interestingly, the AOR peak current is increased by 64% on CuPt nanowires and 330% on CuPtRu nanowires as compared to Pt nanoparticles. These results suggest that AOR prefers extended surface on long nanowires, distinctly differing from MOR. This can be contributed to two factors: NH 3 oxidization to N 2 involves dimerization of two N-containing intermediates to form the N-N bond and diffusion batters for adsorbed intermediates are generally lower on terrace than at low-coordination sites. This demonstrated strong effect of surface morphology will be further studied and utilized in developing advanced AOR nanocatalysts.« less