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Sample records for neutron-deficient au pt

  1. Measurements of electric quadrupole moments of neutron-deficient Au, Pt, and Ir nuclei with NMR-ON in hcp-Co

    CERN Multimedia

    Smolic, E; Hagn, E; Zech, E; Seewald, G

    2002-01-01

    The aim of the experiments is the measurement of $\\,$i) nuclear magnetic moments and electric quadrupole moments of neutron-deficient isotopes in the region Os-Ir-Pt-Au with the methods of quadrupole-interaction-resolved NMR on oriented nuclei " QI-NMR-ON " and modulated adiabatic passage on oriented nuclei " MAPON " and $\\,$ii) the magnetic hyperfine field, electric field gradient (EFG), and spin-lattice relaxation of 5d elements in ferromagnetic Fe, Ni, fcc-Co and hcp-Co.\\\\ The measurements on Au isotopes have been finished successfully. The quadrupole moments of $^{186}$Au, $^{193m}$Au, $^{195}$Au, $^{195m}$Au, $^{197m}$Au, $^{198}$Au and $^{199}$Au were determined with high precision.\\\\ For neutron-deficient Ir isotopes QI-NMR-ON measurements were performed after implantation of Hg precursors. The EFG of Ir in hcp-Co has been calibrated. Thus precise values for the spectroscopic quadrupole mo...

  2. Shape coexistence in the neutron-deficient Pt isotopes in the configuration-mixed IBM

    International Nuclear Information System (INIS)

    Vargas, Carlos E.; Campuzano, Cuauhtemoc; Morales, Irving O.; Frank, Alejandro; Van Isacker, Piet

    2008-01-01

    The matrix-coherent state approach in the IBM with configuration mixing is used to describe the geometry of neutron-deficient Pt isotopes. Employing a parameter set for all isotopes determined previously, it is found that the lowest minimum goes from spherical to oblate and finally acquires a prolate shape when approaching the mid-shell Pt isotopes

  3. Shape coexistence in the neutron-deficient Pt isotopes in a configuration mixing IBM

    International Nuclear Information System (INIS)

    Morales, Irving O.; Vargas, Carlos E.; Frank, Alejandro

    2004-01-01

    The recently proposed matrix-coherent state approach for configuration mixing IBM is used to describe the evolving geometry of the neutron deficient Pt isotopes. It is found that the Potential Energy Surface (PES) of the Platinum isotopes evolves, when the number of neutrons decreases, from spherical to oblate and then to prolate shapes, in agreement with experimental measurements. Oblate-Prolate shape coexistence is observed in 194,192Pt isotopes

  4. β-decay properties of neutron-deficient Pt, Hg, and Pb isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Sarriguren, P., E-mail: p.sarriguren@csic.es [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, E-28006 Madrid (Spain); Boillos, J. M. [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, E-28006 Madrid (Spain); Universidad de Santiago de Compostela, 15706 Santiago de Compostela (Spain); Moreno, O. [Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Moya de Guerra, E. [Departamento de Física Atómica, Molecular y Nuclear, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2015-10-15

    Neutron-deficient isotopes in the lead region are well established examples of the shape coexistence phenomenon in nuclei. In this work, bulk and decay properties, including deformation energy curves, charge mean square radii, Gamow-Teller (GT) strength distributions, and β-decay half-lives, are studied in neutron-deficient Pt, Hg, and Pb isotopes. The nuclear structure involved is described microscopically from deformed quasiparticle random-phase approximation calculations with residual interactions in both particle-hole and particle-particle channels, performed on top of a self-consistent deformed quasiparticle Skyrme Hartree-Fock basis. The sensitivity to deformation of the GT strength distributions in those isotopes is proposed as an additional complementary signature of the nuclear shape. The β-decay half-lives resulting from the GT strength distributions are compared to experiment to demonstrate the ability of the method.

  5. Catalytically favorable surface patterns in Pt-Au nanoclusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2013-01-01

    Motivated by recent experimental demonstrations of novel PtAu nanoparticles with highly enhanced catalytic properties, we present a systematic theoretical study that explores principal catalytic indicators as a function of the particle size and composition. We find that Pt electronic states in the vicinity of the Fermi level combined with a modified electron distribution in the nanoparticle due to Pt-to-Au charge transfer are the origin of the outstanding catalytic properties. From our model we deduce the catalytically favorable surface patterns that induce ensemble and ligand effects. © The Royal Society of Chemistry 2013.

  6. Exotic high activity surface patterns in PtAu nanoclusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2013-05-09

    The structure and chemical ordering of PtAu nanoclusters of 79, 135, and 201 atoms are studied via a combination of a basin hopping atom-exchange technique (to locate the lowest energy homotops at fixed composition), a symmetry orbit technique (to find the high symmetry isomers), and density functional theory local reoptimization (for determining the most stable homotop). The interatomic interactions between Pt and Au are derived from the empirical Gupta potential. The lowest energy structures show a marked tendency toward PtcoreAushell chemical ordering by enrichment of the more cohesive Pt in the core region and of Au in the shell region. We observe a preferential segregation of Pt atoms to (111) facets and Au atoms to (100) facets of the truncated octahedron cluster motif. Exotic surface patterns are obtained particularly for Pt-rich compositions, where Pt atoms are being surrounded by Au atoms. These surface arrangements boost the catalytic activity by creating a large number of active sites. © 2013 American Chemical Society.

  7. Study on the failure temperature of Ti/Pt/Au and Pt5Si2-Ti/Pt/Au metallization systems

    Science.gov (United States)

    Zhang, Jie; Han, Jianqiang; Yin, Yijun; Dong, Lizhen; Niu, Wenju

    2017-09-01

    The Ti/Pt/Au metallization system has an advantage of resisting KOH or TMAH solution etching. To form a good ohmic contact, the Ti/Pt/Au metallization system must be alloyed at 400 °C. However, the process temperatures of typical MEMS packaging technologies, such as anodic bonding, glass solder bonding and eutectic bonding, generally exceed 400 °C. It is puzzling if the Ti/Pt/Au system is destroyed during the subsequent packaging process. In the present work, the resistance of doped polysilicon resistors contacted by the Ti/Pt/Au metallization system that have undergone different temperatures and time are measured. The experimental results show that the ohmic contacts will be destroyed if heated to 500 °C. But if a 20 nm Pt film is sputtered on heavily doped polysilicon and alloyed at 700 °C before sputtering Ti/Pt/Au films, the Pt5Si2-Ti/Pt/Au metallization system has a higher service temperature of 500 °C, which exceeds process temperatures of most typical MEMS packaging technologies. Project supported by the National Natural Science Foundation of China (No. 61376114).

  8. Dynamics of Surface Exchange Reactions Between Au and Pt for HER and HOR

    DEFF Research Database (Denmark)

    Abrams, Billie; Vesborg, Peter Christian Kjærgaard; Bonde, Jacob Lindner

    2009-01-01

    Cyclic voltammetric analysis of the Pt-on-Au system for hydrogen evolution and oxidation reactions (HER/HOR) indicates that dynamic surface exchange reactions occur between Pt and Au. HER/HOR activities depend on the dominant surface species present, which is controllable by the potential applied...... to the system. Bulk Au is not very active for HER/HOR; however, when Pt is deposited onto the Au surface, the system becomes active. The Pt-on-Au system can subsequently be deactivated by cycling to potentials cathodic of the OH-adsorption and Pt-dissolution potentials (~+1.18 V vs normal hydrogen electrode...... reaction is attributed to the lower surface energy of Au relative to Pt causing Au to migrate to the surface. When the system is deactivated, Au is present at the surface. However, Pt migrates back to the surface at higher positive potentials, where PtOx/PtOHx is formed, leading to adsorbate...

  9. Tuning the chemical activity through PtAu nanoalloying: a first principles study

    KAUST Repository

    Mokkath, Junais Habeeb

    2013-06-21

    The electronic structure and adsorption properties of 1.5 nm sized Pt, Au, and PtAu nanoclusters are studied by density functional theory. We explain the recent experimental finding that 20% Au content in PtAu nanoparticles is optimal to induce a dramatically different catalytic behavior. Our results show that the d-band center together with the density of states at the Fermi energy can be used as an indicator of the chemical activity of PtAu nanoclusters. The most favorable adsorption sites on the cluster surfaces as a function of the Pt/Au ratio are identified using atomic H as a probe.

  10. Synthesis of ultrathin face-centered-cubic Au@Pt and Au@Pd core-shell nanoplates from hexagonal-close-packed Au square sheets

    KAUST Repository

    Fan, Zhanxi

    2015-03-17

    The synthesis of ultrathin face-centered-cubic (fcc) Au@Pt rhombic nanoplates is reported through the epitaxial growth of Pt on hexagonal-close-packed (hcp) Au square sheets (AuSSs). The Pt-layer growth results in a hcp-to-fcc phase transformation of the AuSSs under ambient conditions. Interestingly, the obtained fcc Au@Pt rhombic nanoplates demonstrate a unique (101)f orientation with the same atomic arrangement extending from the Au core to the Pt shell. Importantly, this method can be extended to the epitaxial growth of Pd on hcp AuSSs, resulting in the unprecedented formation of fcc Au@Pd rhombic nanoplates with (101)f orientation. Additionally, a small amount of fcc (100)f-oriented Au@Pt and Au@Pd square nanoplates are obtained with the Au@Pt and Au@Pd rhombic nanoplates, respectively. We believe that these findings will shed new light on the synthesis of novel noble bimetallic nanostructures. Phase change: Ultrathin Au@Pt and Au@Pd core-shell nanoplates were prepared from Au square sheets. A phase transformation from hexagonal close-packed (hcp) to face-centered cubic (fcc) is observed upon coating the hcp Au square sheets with Pt or Pd under ambient conditions. The prepared fcc Au@Pt and Au@Pd rhombic nanoplates demonstrate unique (101)f orientation (picture shows a typical fcc Au@Pt rhombic nanoplate). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Ag/Au/Pt trimetallic nanoparticles with defects: preparation, characterization, and electrocatalytic activity in methanol oxidation

    Science.gov (United States)

    Thongthai, Kontee; Pakawanit, Phakkhananan; Chanlek, Narong; Kim, Jun-Hyun; Ananta, Supon; Srisombat, Laongnuan

    2017-09-01

    Two series of Ag x /Au/Pt y trimetallic nanoparticles (Ag x Au1Pt2 with x ranging from 1-5 and Ag4Au1Pt y with y ranging from 1-3) were prepared by a sequential chemical reduction method that involved the deposition of Pt on preformed Ag/Au core-shell particles by systematically controlling the amount of Ag, Au, and Pt metal precursor solutions. The structural changes (the diameters and increased surface roughness from the defective features) and absorption patterns (the significant reduction of the peak intensities) of the nanoparticles examined with TEM and UV-vis spectroscopy indicated the selective incorporation of Pt on the Ag/Au nanoparticles regardless of their compositions. In addition, a combination of WDX, XRD, and XPS analyses quantitatively and qualitatively confirmed the successful formation of the Ag x Au1Pt2 and Ag4Au1Pt y trimetallic nanoparticles. Subsequently, these series of nanoparticles were deposited on multi-wall carbon nanotubes (MWCNTs) to evaluate their electrocatalytic property in the methanol oxidation reaction (MOR) as a function of their metal compositions. The results showed that the electrocatalytic activities of all Ag4/Au1/Pt y systems were higher than those of typical Pt on the MWCNTs. In particular, the Ag4Au1Pt2 nanoparticles exhibited the highest electrocatalytic property for the MOR, suggesting the importance of the proper combination of metal constituents and structures to regulate the activity in electrocatalytic systems.

  12. Study of neutron-deficient Sn isotopes

    International Nuclear Information System (INIS)

    Auger, G.

    1982-05-01

    The formation of neutron deficient nuclei by heavy ion reactions is investigated. The experimental technique is presented, and the results obtained concerning Sn et In isotopes reported: first excited states of 106 Sn, high spin states in 107 Sn and 107 In; Yrast levels of 106 Sn, 107 Sn, 108 Sn; study of neutron deficient Sn and In isotopes formed by the desintegration of the compound nucleus 112 Xe. All these results are discussed [fr

  13. Visible light photoactivity of TiO{sub 2} loaded with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Gołąbiewska, Anna, E-mail: annagolabiewska@o2.pl [Department of Chemical Technology, Gdansk University of Technology, 80-233 Gdańsk (Poland); Lisowski, Wojciech [Mazovia Center for Surface Analysis, Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw (Poland); Jarek, Marcin; Nowaczyk, Grzegorz [NanoBioMedical Center, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Zielińska-Jurek, Anna; Zaleska, Adriana [Department of Chemical Technology, Gdansk University of Technology, 80-233 Gdańsk (Poland)

    2014-10-30

    Graphical abstract: - Highlights: • Au/Pt nanoparticles enhanced TiO{sub 2} photocatalytic activity under visible irradiation. • Higher photoactivity of Au/Pt-TiO{sub 2} resulted from smaller Au/Pt particles. • Intermetallic state of AuPt favors charge transfer between the metals. • TiO{sub 2} obtained by TIP hydrolysis seems to be best matrix for Au/Pt-TiO{sub 2}. - Abstract: TiO{sub 2} modified with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles have been prepared using a water-in-oil microemulsion system (water/AOT/cyclohexane) followed by calcination step. The effect of metal ratio, reducing agent type (NaBH{sub 4} or N{sub 2}H{sub 4}), TiO{sub 2} matrix type (P-25, ST-01, TiO-5, TiO{sub 2} nanotubes or TiO{sub 2} obtained by TIP hydrolysis) as well as calcination temperature (from 350 to 650 °C) were systematically investigated. Obtained photocatalysts were characterized by UV–vis diffuse-reflectance spectroscopy (DRS), BET surface area measurements, scanning transmission microscopy (STEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity under visible light (λ > 420 nm) has been estimated in phenol degradation reaction in aqueous phase. The results showed that phenol degradation rate under visible light in the presence of TiO{sub 2} loaded with Au/Pt nanoparticles differed from 0.7 to 2.2 μmol dm{sup −3} min{sup −1} for samples prepared using different reducing agent. Sodium borohydride (NaBH{sub 4}) favors formation of smaller Au/Pt nanoparticles and higher amount gold in Au/Pt is in the form of electronegative species (Au{sup δ−}) resulted in higher photoactivity. TiO{sub 2} obtained by TIP hydrolysis in microemulsion system seems to be the best support for Au/Pt nanoparticles from all among investigated matrix. It was also observed that enhancement of calcination temperature from 450 to 650 °C resulted in rapid drop of Au/Pt-TiO{sub 2} photoactivity under visible light

  14. Toward hybrid Au nanorods @ M (Au, Ag, Pd and Pt) core-shell heterostructures for ultrasensitive SERS probes

    Science.gov (United States)

    Xie, Xiaobin; Gao, Guanhui; Kang, Shendong; Lei, Yanhua; Pan, Zhengyin; Shibayama, Tamaki; Cai, Lintao

    2017-06-01

    Being able to precisely control the morphologies of noble metallic nanostructures is of essential significance for promoting the surface-enhanced Raman scattering (SERS) effect. Herein, we demonstrate an overgrowth strategy for synthesizing Au @ M (M = Au, Ag, Pd, Pt) core-shell heterogeneous nanocrystals with an orientated structural evolution and highly improved properties by using Au nanorods as seeds. With the same reaction condition system applied, we obtain four well-designed heterostructures with diverse shapes, including Au concave nanocuboids (Au CNs), Au @ Ag crystalizing face central cube nanopeanuts, Au @ Pd porous nanocuboids and Au @ Pt nanotrepangs. Subsequently, the exact overgrowth mechanism of the above heterostructural building blocks is further analysed via the systematic optimiziation of a series of fabrications. Remarkably, the well-defined Au CNs and Au @ Ag nanopeanuts both exhibit highly promoted SERS activity. We expect to be able to supply a facile strategy for the fabrication of multimetallic heterogeneous nanostructures, exploring the high SERS effect and catalytic activities.

  15. High breakdown voltage Au/Pt/GaN Schottky diodes

    International Nuclear Information System (INIS)

    Dang, G. T.; Zhang, A. P.; Mshewa, M. M.; Ren, F.; Chyi, J.-I.; Lee, C.-M.; Chuo, C. C.; Chi, G. C.; Han, J.; Chu, S. N. G.

    2000-01-01

    Au/Pt/GaN Schottky diode rectifiers were fabricated with reverse breakdown voltage (V RB ) up to 550 V on vertically depleting structures and >2000 V on lateral devices. The figure-of-merit (V RB ) 2 /R ON , where R ON is the on-state resistance, had values between 4.2 and 4.8 MW cm -2 . The reverse leakage currents and forward on-voltages were still somewhat higher than the theoretical minimum values, but were comparable to SiC Schottky rectifiers reported in the literature. These devices show promise for use in ultrahigh-power switches. (c) 2000 American Vacuum Society

  16. Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

    KAUST Repository

    Song, Hyon Min

    2012-09-27

    Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

  17. Novel Au Catalysis Strategy for the Synthesis of Au@Pt Core-Shell Nanoelectrocatalyst with Self-Controlled Quasi-Monolayer Pt Skin.

    Science.gov (United States)

    Zhang, Youlin; Li, Xiaokun; Li, Kai; Xue, Bin; Zhang, Chunmei; Du, Cheng; Wu, Zhijian; Chen, Wei

    2017-09-27

    Design of catalytically active Pt-based catalysts with minimizing the usage of Pt is a major issue in fuel cells. Herein, for the first time, we have developed a Au catalytic reduction strategy to synthesize a Au@Pt core-shell electrocatalyst with a quasi-monolayer Pt skin spontaneously formed from the gold surface catalysis. In the presence of presynthesized gold nanocrystals (used as the catalyst and Au seeds) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (used as reductant), under the Au surface catalysis, platinum ions can be reduced and deposited on the gold nanocrystals to form a Pt skin surface with a quasi-monatomic thickness. In the present strategy, Pt ions can be reduced only under the catalysis of gold surface and thus when the surface of Au NPs is covered by a monatomic Pt layer, the reduction reaction of Pt ions will be spontaneously turned off. Therefore, the significant advantage of this synthesis strategy is that the formation of quasi-monolayer Pt skin surface can be self-controlled and is completely free of controlling the dosage of platinum ions and the size distribution of Au cores. The synthesized Au@Pt core@shell structure exhibited enhanced electrocatalytic activities for oxygen reduction reaction and methanol oxidation reaction, which are 6.87 and 10.17 times greater than those of Pt/C catalyst, respectively. The present study provides a new strategy for obtaining high-performance bimetallic/multimetallic electrocatalysts with high utilization of precious metals.

  18. Durable electrocatalytic-activity of Pt-Au/C cathode in PEMFCs.

    Science.gov (United States)

    Selvaganesh, S Vinod; Selvarani, G; Sridhar, P; Pitchumani, S; Shukla, A K

    2011-07-21

    Longevity remains as one of the central issues in the successful commercialization of polymer electrolyte membrane fuel cells (PEMFCs) and primarily hinges on the durability of the cathode. Incorporation of gold (Au) to platinum (Pt) is known to ameliorate both the electrocatalytic activity and stability of cathode in relation to pristine Pt-cathodes that are currently being used in PEMFCs. In this study, an accelerated stress test (AST) is conducted to simulate prolonged fuel-cell operating conditions by potential cycling the carbon-supported Pt-Au (Pt-Au/C) cathode. The loss in performance of PEMFC with Pt-Au/C cathode is found to be ∼10% after 7000 accelerated potential-cycles as against ∼60% for Pt/C cathode under similar conditions. These data are in conformity with the electrochemical surface-area values. PEMFC with Pt-Au/C cathode can withstand >10,000 potential cycles with very little effect on its performance. X-ray diffraction and transmission electron microscopy studies on the catalyst before and after AST suggest that incorporating Au with Pt helps mitigate aggregation of Pt particles during prolonged fuel-cell operations while X-ray photoelectron spectroscopy reflects that the metallic nature of Pt is retained in the Pt-Au catalyst during AST in comparison to Pt/C that shows a major portion of Pt to be present as oxidic platinum. Field-emission scanning electron microscopy conducted on the membrane electrode assembly before and after AST suggests that incorporating Au with Pt helps mitigating deformations in the catalyst layer. This journal is © the Owner Societies 2011

  19. Thermoelectric properties of currently available Au/Pt thermocouples related to the valid reference function

    Directory of Open Access Journals (Sweden)

    Edler F.

    2015-01-01

    Full Text Available Au/Pt thermocouples are considered to be an alternative to High Temperature Standard Platinum Resistance Thermometers (HTSPRTs for realizing temperatures according to the International Temperature Scale of 1990 (ITS-90 in the temperature range between aluminium (660.323 °C and silver (961.78 °C. The original aim of this work was to develop and to validate a new reference function for Au/Pt thermocouples which reflects the properties of presently commercially available Au and Pt wires. The thermoelectric properties of 16 Au/Pt thermocouples constructed at different National Metrological Institutes by using wires from different suppliers and 4 commercially available Au/Pt thermocouples were investigated. Most of them exhibit significant deviations from the current reference function of Au/Pt thermocouples caused by the poor performance of the Au-wires available. Thermoelectric homogeneity was investigated by measuring immersion profiles during freezes at the freezing point of silver and in liquid baths. The thermoelectric inhomogeneities were found to be one order of magnitude larger than those of Au/Pt thermocouples of the Standard Reference Material® (SRM® 1749. The improvement of the annealing procedure of the gold wires is a key process to achieve thermoelectric homogeneities in the order of only about (2–3 mK, sufficient to replace the impracticable HTSPRTs as interpolation instruments of the ITS-90. Comparison measurements of some of the Au/Pt thermocouples against a HTSPRT and an absolutely calibrated radiation thermometer were performed and exhibit agreements within the expanded measurement uncertainties. It has been found that the current reference function of Au/Pt thermocouples reflects adequately the thermoelectric properties of currently available Au/Pt thermocouples.

  20. Electrochemical fabrication of clean dendritic Au supported Pt clusters for electrocatalytic oxidation of formic acid

    International Nuclear Information System (INIS)

    Xia Yue; Liu Jun; Huang Wei; Li Zelin

    2012-01-01

    Highlights: ► A smooth Au surface was rebuilt into clean dendrite via square wave potential pulses. ► It was performed in blank H 2 SO 4 solution without Au(III) species and other additives. ► Dendritic Au provided certain advantage for dispersing Pt due to its unique structure. ► Pt-decorated dendritic Au demonstrated high activity for the HCOOH electrooxidation. - Abstract: We report here the fabrication of clean dendritic gold (DG) directly on a smooth Au electrode via square wave potential pulses (SWPPs) in a blank H 2 SO 4 solution containing no Au(III) species and additives. The effects of potential range, frequency and duration time of SWPPs and H 2 SO 4 concentration on the construction of DG were systematically investigated. A possible mechanism was proposed to explain the growth of DG. The whole process was templateless and surfactantless, and therefore effectively avoided possible contaminations that occurred in other synthetic routes. Further, the prepared DG electrode functioned as a scaffold to support electrodeposited Pt clusters, producing Pt-decorated DG (Pt-DG) electrodes. The electrocatalytic properties of Pt-DG electrodes with various Pt loadings were examined for the oxidation of formic acid. The low Pt loading Pt-DG demonstrated different electrochemical behavior from that on Pt-decorated smooth gold (Pt-SG) and on Pt-decorated gold nanoparticles because there were more defect sites like steps and edges on the DG surface. Ensemble effect, as well as electronic effect, accounts for the improved electrocatalytic activity of low Pt loading Pt-DG.

  1. Au@AuPt nanoparticles embedded in B-doped graphene: A superior electrocatalyst for determination of rutin

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xianlan; Yang, Guangming; Feng, Shaoping; Shi, Ling; Huang, Zhaolong [School of Science, Honghe University (China); Key Laboratory of Natural Pharamaceutical & Chemical Biology of Yunnan Province Mengzi, Yunnan 661100 (China); Pan, Haibo [Fujian Key Lab of Medical Instrument & Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Liu, Wei, E-mail: liuwei4728@126.com [School of Science, Honghe University (China); Key Laboratory of Natural Pharamaceutical & Chemical Biology of Yunnan Province Mengzi, Yunnan 661100 (China)

    2017-04-30

    Highlights: • The formation of B-doped graphene (BG) with high content of a total B species use hydrothermal method with B{sub 2}O{sub 3} as reducing agent and boron source. • BG was exfoliated into monolayer nanosheet impregnated by Au@AuPt NPs because B atom creates a net positive charge to facilitate NPs adsorption. • The dispersed carboxyl units of BG can form hydrogen bonding with the phenolic hydroxyl groups of rutin, making more rutin participate in reaction. • Au@AuPt NPs can form charge accumulation or valence change on prominent part of the surface, improving the catalytic effect to rutin. • More electroactive sites were generated by doping B atoms into graphene structures, which act as multidimensional electron transport pathways. - Abstract: A hydrothermal approach was used to prepare B-doped graphene with B{sub 2}O{sub 3} as reductant and boron source. Results reveal that the boron atoms have been successfully embedded into graphene with a high content of a total B species (2.85 at.%). Then, B-doped graphene was exfoliated further into monolayer nanosheet by impregnating Au@AuPt core-shell nanoparticles (Au@AuPt NPs) because boron atom creates a net positive charge, which facilitates Au@AuPt NPs adsorption to form Au@AuPt NPs/B-doped graphene hybrid nanocatalysts. After that, the Au@AuPt NPs/B-doped hybrid suspension was dropped on glassy carbon electrode for sensing rutin. In this way, the dispersed carboxyl units of B-doped graphene can form hydrogen bonding with the phenolic hydroxyl groups of rutin, making rutin enrich easily on modified electrode surface to enhance the electrochemical response. At the same time, its electrochemical mechanism on the modified electrode was elucidated using cyclic voltammetry. It was found that its electrochemical behavior on modified electrode surface was a surface-controlled quasi-reversible process, and the charge transfer coefficient (α) and electron transfer number (n) were 0.296 and 2, respectively

  2. Pt/Au nanoalloy supported on alumina and chlorided alumina: DFT and experimental analysis

    Science.gov (United States)

    Sharifi, N.; Falamaki, C.; Ghorbanzadeh Ahangari, M.

    2018-04-01

    Density functional theory (DFT) was used to explore the adsorption of Pt/Au nanoalloy onto a pure and chlorided γ-Al2O3(110) surface, which has been applied in numerous catalytic reactions. First, we considered the adsorption properties of Pt clusters (n ≤ 5) onto the Al2O3(110) surface to determine the most stable Pt cluster on alumina surface in reforming processes. After full structural relaxations of Pt clusters at various configurations on alumina, our computed results expressed that the minimum binding energy (‑5.67 eV) is accrued for Pt4 cluster and the distance between the nearest Pt atom in the cluster to the alumina surface is equal to 1.13 Å. Then, we investigated the binding energies, geometries, and electronic properties of adsorbed Aun clusters (n ≤ 6) on the γ-Al2O3(110) surface. Our studied showed that Au5 was the most thermodynamically stable structure on γ-Al2O3. Finally, we inspected these properties for adsorbed Au clusters onto the Pt4-decorated alumina (Aun/Pt4-alumina) system. The binding energy of the Au4/Pt4-alumina system was ‑5.01 eV, and the distance between Au4 cluster and Pt4-alumina was 1.33 Å. The Au4/Pt4alumina system was found to be the most stable nanometer-sized catalyst design. At last, our first-principles calculations predicted that the best position of embedment Cl on the Au4/Pt4-alumina.

  3. Stabilization of Pt nanoparticles by single stranded DNA and the binary assembly of Au and Pt nanoparticles without hybridization

    International Nuclear Information System (INIS)

    Yang, J.; Lee, Jim Yang; Too, Heng-Phon; Chow, Gan-Moog; Gan, Leong M.

    2006-01-01

    The non-specific interaction between single stranded DNA (ssDNA) and 12 nm Pt nanoparticles is investigated in this work. The data show a strong and non-specific interaction between the two which can be exploited for the stabilization of Pt nanoparticles in aqueous solutions. Based on the experimental findings, a non-hybridization based protocol to assemble 17 nm Au and Pt nanoparticles (12 nm cubic and 3.6 nm spherical) by single-stranded DNA was developed. Transmission electron microscopy (TEM) and UV-visible spectroscopy confirmed that Au and Pt nanoparticles could be assembled by the non-specific interaction in an orderly manner. The experimental results also caution against the potential pitfalls in using DNA melting point analysis to infer metal nanoparticle assembly by DNA hybridization

  4. Kinetically controlled synthesis of AuPt bi-metallic aerogels and their enhanced electrocatalytic performances

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Qiurong [School of Mechanical and Materials Engineering; Washington State University; Pullman; USA; Zhu, Chengzhou [School of Mechanical and Materials Engineering; Washington State University; Pullman; USA; Du, Dan [School of Mechanical and Materials Engineering; Washington State University; Pullman; USA; Key Laboratory of Pesticides and Chemical Biology; Bi, Cuixia [Institute of Crystal Materials; Shandong University; Jinan 250100; P. R. China; Xia, Haibing [Institute of Crystal Materials; Shandong University; Jinan 250100; P. R. China; Feng, Shuo [School of Mechanical and Materials Engineering; Washington State University; Pullman; USA; Engelhard, Mark H. [Environmental Molecular Sciences Laboratory; Pacific Northwest National Laboratory; Richland; USA; Lin, Yuehe [School of Mechanical and Materials Engineering; Washington State University; Pullman; USA

    2017-01-01

    Kinetically controlled synthesis of AuPtxbi-metallic hydrogels/aerogels was efficiently achieved for the first timeviatuning the reaction temperature or adding a surfactant.

  5. Large scale structural optimization of trimetallic Cu-Au-Pt clusters up to 147 atoms

    Science.gov (United States)

    Wu, Genhua; Sun, Yan; Wu, Xia; Chen, Run; Wang, Yan

    2017-10-01

    The stable structures of Cu-Au-Pt clusters up to 147 atoms are optimized by using an improved adaptive immune optimization algorithm (AIOA-IC method), in which several motifs, such as decahedron, icosahedron, face centered cubic, sixfold pancake, and Leary tetrahedron, are randomly selected as the inner cores of the starting structures. The structures of Cu8AunPt30-n (n = 1-29), Cu8AunPt47-n (n = 1-46), and partial 75-, 79-, 100-, and 147-atom clusters are analyzed. Cu12Au93Pt42 cluster has onion-like Mackay icosahedral motif. The segregation phenomena of Cu, Au and Pt in clusters are explained by the atomic radius, surface energy, and cohesive energy.

  6. Au-Pt-Au nanoraspberry structures used for mercury ion detection

    Science.gov (United States)

    Huang, Jiang-Hao; Huang, Shuai; Wen, Xiaoyan; Li, Min; Lu, Haifei

    2017-12-01

    Detection of Hg2+ with high sensitivity is of great significance in the biochemical sensing field. Quantitative of Hg2+ was realized based on the influence of Hg2+ on the UV-vis absorption performance of Au-Pt-Au core-shell nanoraspberry (APA)-rhodamine-6G (R6G) structure. First, APA sol was added into R6G indicator solution and the UV-vis absorption signal intensity of R6G was evidently promoted. The signal intensity monotonously increased as more APA sol was added. However, when HgCl2 solution was introduced, the signal intensity declined. A linear relationship between Hg2+ concentration and signal intensity at 527 nm was revealed, based on which quantitative determination of Hg2+ could be realized. Hg2+ detection sensitivity was measured to be 0.031 a.u./M with a limit of detection of 10-7 M and the response time was 20 s. A high Hg2+ detection selectivity over Cu2+, Na+, Li+, and K+ was demonstrated. Due to its simplicity and high sensitivity, the proposed method could find an extensive application prospect in the Hg2+ detection field.

  7. Facile Synthesis of Quasi-One-Dimensional Au/PtAu Heterojunction Nanotubes and Their Application as Catalysts in an Oxygen-Reduction Reaction.

    Science.gov (United States)

    Cai, Kai; Liu, Jiawei; Zhang, Huan; Huang, Zhao; Lu, Zhicheng; Foda, Mohamed F; Li, Tingting; Han, Heyou

    2015-05-11

    An intermediate-template-directed method has been developed for the synthesis of quasi-one-dimensional Au/PtAu heterojunction nanotubes by the heterogeneous nucleation and growth of Au on Te/Pt core-shell nanostructures in aqueous solution. The synthesized porous Au/PtAu bimetallic nanotubes (PABNTs) consist of porous tubular framework and attached Au nanoparticles (AuNPs). The reaction intermediates played an important role in the preparation, which fabricated the framework and provided a localized reducing agent for the reduction of the Au and Pt precursors. The Pt7 Au PABNTs showed higher electrocatalytic activity and durability in the oxygen-reduction reaction (ORR) in 0.1 M HClO4 than porous Pt nanotubes (PtNTs) and commercially available Pt/C. The mass activity of PABNTs was 218 % that of commercial Pt/C after an accelerated durability test. This study demonstrates the potential of PABNTs as highly efficient electrocatalysts. In addition, this method provides a facile strategy for the synthesis of desirable hetero-nanostructures with controlled size and shape by utilizing an intermediate template. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. TUNING OF SIZE AND SHAPE OF AU-PT NANOCATALYST FOR DIRECT METHANOL FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Murph, S.

    2011-04-20

    In this paper, we report the precise control of the size, shape and surface morphology of Au-Pt nanocatalysts (cubes, blocks, octahedrons and dogbones) synthesized via a seed-mediated approach. Gold 'seeds' of different aspect ratios (1 to 4.2), grown by a silver-assisted approach, were used as templates for high-yield production of novel Au-Pt nanocatalysts at a low temperature (40 C). Characterization by electron microscopy (SEM, TEM, HRTEM), energy dispersive X-ray analysis (EDX), UV-Vis spectroscopy, zeta-potential (surface charge), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS) were used to better understand their physico-chemical properties, preferred reactivities and underlying nanoparticle growth mechanism. A rotating disk electrode was used to evaluate the Au-Pt nanocatalysts electrochemical performance in the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) of direct methanol fuel cells. The results indicate the Au-Pt dogbones are partially and in some cases completely unaffected by methanol poisoning during the evaluation of the ORR. The ORR performance of the octahedron particles in the absence of MeOH is superior to that of the Au-Pt dogbones and Pt-black, however its performance is affected by the presence of MeOH.

  9. Heterostructured Au/Pd-M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

    Science.gov (United States)

    Lutz, Patrick S.; Bae, In-Tae; Maye, Mathew M.

    2015-09-01

    The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had high activity attributed to the porous nature of the platinum domains.The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had

  10. Use of PtAu/C electrocatalysts toward formate oxidation: electrochemical and fuel cell considerations

    Directory of Open Access Journals (Sweden)

    Sirlane G. da Silva

    2016-09-01

    Full Text Available Abstract This study reports the use of PtAu/C electrocatalysts with different atomic ratios (90:10, 70:30 and 50:50 supported on Vulcan XC 72 carbon and prepared by the sodium borohydride method toward formate electro-oxidation in alkaline media. The materials were characterized by X-ray diffraction, showing peaks characteristics of Pt and Au face-centered-cubic structures, and also by transmission electron micrographs that show the nanoparticles well dispersed on carbon and a mean particle size between 4 and 5 nm for all electrocatalysts. Electrochemical experiments show PtAu/C as promising catalysts toward formate oxidation, while single cell experiments reveal PtAu/C 90:10 as the best material since it provides a power density higher than Pt/C. The incorporation of Au could increase formate oxidation for more than one reason: (i a facilitated rupture of C–H bond; (ii the Au/oxide interface or (iii by regenerating active sites.

  11. Atomically thin Pt shells on Au nanoparticle cores: facile synthesis and efficient synergetic catalysis

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Seselj, Nedjeljko; Poreddy, Raju

    2016-01-01

    We present a facile synthesis protocol for atomically thin platinum (Pt) shells on top of gold (Au) nanoparticles (NPs) (Au@PtNPs) in one pot under mild conditions. The Au@PtNPs exhibited remarkable stability (> 2 years) at room temperature. The synthesis, bimetallic nanostructures and catalytic ...... activity for the direct production of γ-valerolactone, an alternative biofuel/fuel additive, from levulinic acid and methyl levulinate was finally demonstrated....... in electrooxidation of sustainable fuels (i.e. formic acid, methanol and ethanol), and selective hydrogenation of benzene derivatives. Especially high activity was achieved for formic acid oxidation, 549 mA (mgPt)−1 (at 0.6 V vs. SCE), which is 3.5 fold higher than a commercial

  12. Contribution to the study of Pt197 and Au197 excited states

    International Nuclear Information System (INIS)

    Alves, S.M.C.

    1971-01-01

    The gamma transitions of the Ir 197β- → Pt 197β- → Au 197 decay chain were investigated using three Ge(Li) detectors of high resolution and spectroscopy techniques with one, two and three via of analysis. For the Ir 197β- →Pt 197 decay, four new gamma transitions with energy of 877.6; 938.7; 1049.6 and 1341.8 Kev were observed, presupposing to be energy levels in 877.6; 938.7; 1049.6 and 1347.8 Kev in the Ir 197 population by β- decay of Ir 197 . By the first time, the 299.5 Kev transition was observed, in the Pt 197 m (80min) decay, interpreted as a direct desexcitation of the 299.5Kev level in Pt 197 . A new scheme of Ir 197 β- → Au 197 decay based on the obtained results, is proposed. (M.C.K.) [pt

  13. Seed-mediated synthesis of core/shell FePtM/FePt (M = Pd, Au) nanowires and their electrocatalysis for oxygen reduction reaction.

    Science.gov (United States)

    Guo, Shaojun; Zhang, Sen; Su, Dong; Sun, Shouheng

    2013-09-18

    We report a new seed-mediated growth of FePt over 2.5 nm wide FePtM (M = Pd, Au) nanowires (NWs) into core/shell FePtM/FePt NWs with controlled FePt shell thickness from 0.3 to 1.3 nm. These FePtM/FePt NWs show shell thickness and core composition-dependent electrocatalytic activity for oxygen reduction reaction (ORR) in 0.1 M HClO4. These core/shell FePtM/FePt NWs are generally more active and durable than the corresponding alloy NWs. Among FePtM/FePt NWs, FePt NWs, FePtPd NWs, and commercial Pt studied, the FePtPd/FePt NWs (0.8 nm shell) show the specific activity of 3.47 mA·cm(-2) and the mass activity of 1.68 A/mg Pt at 0.5 V (vs. Ag/AgCl), superior to all other NWs (less than 1.59 mA/cm(2) and 0.82 A/mg Pt for FePtAu/FePt and FePt) as well as the commercial Pt (0.24 mA/cm(2) and 0.141 A/mg Pt). The FePtM/FePt (0.8 nm shell) NWs are also stable in the ORR condition and show no activity decrease after 5000 potential sweeps between 0.4 and 0.8 V (vs Ag/AgCl). They are the most efficient nanocatalyst ever reported for ORR.

  14. Sensitization of Pt/TiO2Using Plasmonic Au Nanoparticles for Hydrogen Evolution under Visible-Light Irradiation.

    Science.gov (United States)

    Wang, Fenglong; Wong, Roong Jien; Ho, Jie Hui; Jiang, Yijiao; Amal, Rose

    2017-09-13

    Au nanoparticles with different sizes (10, 20, 30, and 50 nm) were synthesized using a seed-assisted approach and anchored onto Pt/TiO 2 employing 3-mercaptopropionic acid as the organic linker. The sizes of the Au nanoparticles were controlled within a narrow range so that the size-dependent surface plasmonic resonance effect on sensitizing Pt/TiO 2 can be thoroughly studied. We found that 20 nm Au nanoparticles (Au 20 ) gave the best performance in sensitizing Pt/TiO 2 to generate H 2 under visible-light illumination. Photoelectrochemical measurements indicated that Au 20 -Pt/TiO 2 exhibited the most efficient "hot" electrons separation among the studied catalysts, correlating well with the photocatalytic activity. The superior performance of Au-supported Pt/TiO 2 (Au 20 -Pt/TiO 2 ) compared with Au anchored to TiO 2 (Au 20 /TiO 2 ) revealed the important role of Pt as a cocatalyst for proton reduction. To elucidate how the visible-light excited hot electrons in Au nanoparticles involved in the proton-reduction reaction process, Au 20 /TiO 2 was irradiated by visible light (λ > 420 nm) with the presence of Pt precursor (H 2 PtCl 6 ) in a methanol aqueous solution under deaerated condition. Energy-dispersive X-ray spectroscopy mapping analysis on the recovered sample showed that Pt ions could be reduced on the surfaces of both Au nanoparticles and TiO 2 support. This observation indicated that the generated hot electrons on Au nanoparticles were injected into the TiO 2 conduction band, which were then subsequently transferred to Pt nanoparticles where proton reduction proceeded. Besides, the excited hot electrons could also participate in the proton reduction on Au nanoparticles surface.

  15. AuCu@Pt Nanoalloys for Catalytic Application in Reduction of 4-Nitrophenol

    Directory of Open Access Journals (Sweden)

    Sadia Mehmood

    2016-01-01

    Full Text Available To enhance and optimize nanocatalyst ability for nitrophenol (4-NP reduction reaction we look beyond Au-metal nanoparticles and describe a new class of Au nanoalloys with controlled composition for core of AuCu-metals and Pt-metal shell. The reduction of 4-NP was investigated in aqueous media spectroscopically on 7.8 nm Au nanospheres (AuNSs, 8.3 nm AuCuNSs, and 9.1 nm AuCu@Pt core-shell NSs in diameter. The rate constants of the catalyzed reaction at room temperature, activation energies, and entropies of activation of reactions catalyzed by the AuCu@Pt core-shell NSs are found to have different values to those of the pure metal NSs. The results strongly support the proposal that catalysis by nanoparticles is taking place efficiently on the surface of NSs. These core-shell nanocatalysts exhibited stability throughout the reduction reaction and proved that heterogonous type mechanisms are most likely to be dominant in nanoalloy based catalysis if the surface of the NSs is not defected upon shell incorporation.

  16. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

    2015-01-01

    active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...... driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen...

  17. Sensitive electrochemical detection of nitric oxide based on AuPt and reduced graphene oxide nanocomposites.

    Science.gov (United States)

    Liu, Zhonggang; Forsyth, Heidi; Khaper, Neelam; Chen, Aicheng

    2016-06-20

    Since nitric oxide (NO) plays a critical role in many biological processes, its precise detection is essential toward an understanding of its specific functions. Here we report on a facile and environmentally compatible strategy for the construction of an electrochemical sensor based on reduced graphene oxide (rGO) and AuPt bimetallic nanoparticles. The prepared nanocomposites were further employed for the electroanalysis of NO using differential pulse voltammetry (DPV) and amperometric methods. The dependence of AuPt molar ratios on the electrochemical performance was investigated. Through the combination of the advantages of the high conductivity from rGO and highly electrocatalytic activity from AuPt bimetallic nanoparticles, the AuPt-rGO based NO sensor exhibited a high sensitivity of 7.35 μA μM(-1) and a low detection limit of 2.88 nM. Additionally, negligible interference from common ions or organic molecules was observed, and the AuPt-rGO modified electrode demonstrated excellent stability. Moreover, this optimized electrochemical sensor was practicable for efficiently monitoring the NO released from rat cardiac cells, which were stimulated by l-arginine (l-arg), showing that stressed cells generated over 10 times more NO than normal cells. The novel sensor developed in this study may have significant medical diagnostic applications for the prevention and monitoring of disease.

  18. Exploring the Effect of Au/Pt Ratio on Glycerol Oxidation in Presence and Absence of a Base

    Directory of Open Access Journals (Sweden)

    Alberto Villa

    2018-01-01

    Full Text Available Bimetallic AuPt nanoparticles with different Au:Pt ratios (molar ratio: 9-1, 8-2, 6-4, 2-8, 1-9 and the corresponding Au and Pt monometallic ones were prepared by sol immobilization and immobilized on commercial TiO2 (P25. The catalytic activity was evaluated in the liquid phase glycerol oxidation in presence and absence of a base (NaOH. It was found that the Au:Pt molar ratio and reaction conditions strongly influence the catalytic performance. In the presence of NaOH, Au-rich catalysts were more active than Pt-rich ones, with the highest activity observed for Au9Pt1/TiO2 (6575 h−1. In absence of a base, a higher content of Pt is needed to produce the most active catalyst (Au6Pt4/TiO2, 301 h−1. In terms of selectivity, in presence of NaOH, Au-rich catalysts showed a high selectivity to C3 products (63–72% whereas Pt-rich catalysts promote the formation of formic and glycolic acids. The opposite trend was observed in absence of a base with Pt-rich catalysts showing higher selectivity to C3 products (83–88%.

  19. One-step synthesis of PtPdAu ternary alloy nanoparticles on graphene with superior methanol electrooxidation activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yuzhen; Gu Yonge; Lin Shaoxiong; Wei Jinping; Wang Zaihua [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Wang Chunming, E-mail: wangcm@lzu.edu.cn [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Du Yongling; Ye Weichun [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China)

    2011-10-01

    Highlights: > PtPdAu nanoparticles were synthesized on graphene sheets via chemical reduction method. > The prepared PtPdAu nanoparticles were ternary alloy with fcc structure. > The catalyst exhibited superior catalytic activity and stability for MOR in alkaline. - Abstract: Well-dispersed PtPdAu ternary alloy nanoparticles were synthesized on graphene sheets via a simple one-step chemical reduction method in ethylene glycol (EG) and water system, in which EG served as both reductive and dispersing agent. The electrocatalytic activity of PtPdAu/G was tested by methanol oxidation reaction (MOR). The catalyst was further characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), which indicated that the as-synthesized PtPdAu nanoparticles with alloy structures were successfully dispersed on the graphene sheets. Electrocatalytic properties of the catalyst for MOR in alkaline have been investigated by cyclic voltammetry (CV), chronoamperometry and Tafel curves. The electrocatalytic activity and stability of PtPdAu/G were superior to PtPd/G, PtAu/G and Pt/G. In addition, the anodic peak current on PtPdAu/G catalyst was proportional to the concentration of methanol in the range of 0.05-1.00 M. This study implies that the prepared catalyst have great potential applications in fuel cells.

  20. Effects of different additives on bimetallic Au-Pt nanoparticles electrodeposited onto indium tin oxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ballarin, Barbara, E-mail: ballarin@ms.fci.unibo.i [Dipartimento di Chimica Fisica ed Inorganica, Universita di Bologna, V.le Risorgimento, 4, 40136-Bologna (Italy)] [INSTM, UdR Bologna (Italy); Gazzano, Massimo [ISOF-CNR, V. Selmi, 40126-Bologna (Italy); Tonelli, Domenica [Dipartimento di Chimica Fisica ed Inorganica, Universita di Bologna, V.le Risorgimento, 4, 40136-Bologna (Italy)] [INSTM, UdR Bologna (Italy)

    2010-09-01

    Bimetallic Au-Pt nanoparticles (Au-Pt{sub NPs}) have been synthesized using an electrochemical reduction approach. The effects of the addition of different additives in the electrodeposition bath namely KI, 1-nonanesulfonic acid sodium salt and Triton X-100 have been investigated. The structural characterization of the bimetallic nanoparticles has been carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy, X-ray diffraction (XRD) and cyclic voltammetry (CV). The Au-Pt{sub NPs} prepared in the presence of KI and Triton X-100 characterized by a relatively narrow size distribution as well as a higher particle density and surface coverage whereas no changes in the morphology were observed. These results suggest a dependence of the size and distribution of the bimetallic nanoparticles from the type and concentration of the additives employed.

  1. Laser spectroscopy of neutron deficient Sn isotopes

    CERN Multimedia

    We propose to study the ground state properties of neutron-deficient Sn isotopes towards the doubly-magic nucleus $^{100}$Sn. Nuclear spins, changes in the rms charge radii and electromagnetic moments of $^{101-121}$Sn will be measured by laser spectroscopy using the CRIS experimental beam line. These ground-state properties will help to clarify the evolution of nuclear structure properties approaching the $\\textit{N = Z =}$ 50 shell closures. The Sn isotopic chain is currently the frontier for the application of state-of-the-art ab-initio calculations. Our knowledge of the nuclear structure of the Sn isotopes will set a benchmark for the advances of many-body methods, and will provide an important test for modern descriptions of the nuclear force.

  2. Radiochemical studies of neutron deficient actinide isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Williams, K.E.

    1978-04-01

    The production of neutron deficient actinide isotopes in heavy ion reactions was studied using alpha, gamma, x-ray, and spontaneous fission detection systems. A new isotope of berkelium, /sup 242/Bk, was produced with a cross-section of approximately 10 ..mu..b in reactions of boron on uranium and nitrogen on thorium. It decays by electron capture with a half-life of 7.0 +- 1.3 minutes. The alpha-branching ratio for this isotope is less than 1% and the spontaneous fission ratio is less than 0.03%. Studies of (Heavy Ion, pxn) and (Heavy Ion, ..cap alpha..xn) transfer reactions in comparison with (Heavy ion, xn) compound nucleus reactions revealed transfer reaction cross-sections equal to or greater than the compound nucleus yields. The data show that in some cases the yield of an isotope produced via a (H.I.,pxn) or (H.I.,..cap alpha..xn) reaction may be higher than its production via an xn compound nucleus reaction. These results have dire consequences for proponents of the ''Z/sub 1/ + Z/sub 2/ = Z/sub 1+2/'' philosophy. It is no longer acceptable to assume that (H.I.,pxn) and (H.I.,..cap alpha..xn) product yields are of no consequence when studying compound nucleus reactions. No evidence for spontaneous fission decay of /sup 228/Pu, /sup 230/Pu, /sup 232/Cm, or /sup 238/Cf was observed indicating that strictly empirical extrapolations of spontaneous fission half-life data is inadequate for predictions of half-lives for unknown neutron deficient actinide isotopes.

  3. J /ψ production at low pT in Au + Au and Cu + Cu collisions at √sNN =200 GeV with the STAR detector

    Science.gov (United States)

    Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Anson, C. D.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Averichev, G. S.; Banerjee, A.; Beavis, D. R.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Borowski, W.; Bouchet, J.; Brandin, A. V.; Brovko, S. G.; Bültmann, S.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, L.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chwastowski, J.; Codrington, M. J. M.; Contin, G.; Cramer, J. G.; Crawford, H. J.; Cui, X.; Das, S.; Davila Leyva, A.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Derradi de Souza, R.; di Ruzza, B.; Didenko, L.; Dilks, C.; Ding, F.; Djawotho, P.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Engle, K. S.; Eppley, G.; Eun, L.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Fedorisin, J.; Filip, P.; Fisyak, Y.; Flores, C. E.; Gagliardi, C. A.; Gangadharan, D. R.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Gliske, S.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Haag, B.; Hamed, A.; Han, L.-X.; Haque, R.; Harris, J. W.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, H. Z.; Huang, X.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kesich, A.; Khan, Z. H.; Kikola, D. P.; Kisel, I.; Kisiel, A.; Koetke, D. D.; Kollegger, T.; Konzer, J.; Koralt, I.; Kosarzewski, L. K.; Kotchenda, L.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Kycia, R. A.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, C.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z. M.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, G. L.; Ma, Y. G.; Mahapatra, D. P.; Majka, R.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; McShane, T. S.; Minaev, N. G.; Mioduszewski, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nigmatkulov, G.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Ohlson, A.; Okorokov, V.; Oldag, E. W.; Olvitt, D. L.; Page, B. S.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlak, T.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Planinic, M.; Pluta, J.; Poljak, N.; Poniatowska, K.; Porter, J.; Poskanzer, A. M.; Powell, C. B.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Riley, C. K.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ross, J. F.; Roy, A.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sangaline, E.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Shen, W. Q.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Simko, M.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solanki, D.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stevens, J. R.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Sun, X.; Sun, X. M.; Sun, Y.; Sun, Z.; Surrow, B.; Svirida, D. N.; Symons, T. J. M.; Szelezniak, M. A.; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarnowsky, T.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Trzeciak, B. A.; Tsai, O. D.; Turnau, J.; Ullrich, T.; Underwood, D. G.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Vanfossen, J. A.; Varma, R.; Vasconcelos, G. M. S.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Vossen, A.; Wada, M.; Wang, F.; Wang, G.; Wang, H.; Wang, J. S.; Wang, X. L.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y. F.; Xiao, Z.; Xie, W.; Xin, K.; Xu, H.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y.; Xu, Z.; Yan, W.; Yang, C.; Yang, Y.; Yang, Y.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, J. B.; Zhang, J. L.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, Z. P.; Zhao, F.; Zhao, J.; Zhong, C.; Zhu, X.; Zhu, Y. H.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2014-08-01

    The J /ψ pT spectrum and nuclear modification factor (RAA) are reported for pT<5GeV /c and |y|<1 from 0% to 60% central Au +Au and Cu +Cu collisions at √sNN =200GeV at STAR. A significant suppression of pT-integrated J /ψ production is observed in central Au +Au events. The Cu +Cu data are consistent with no suppression, although the precision is limited by the available statistics. RAA in Au +Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with pT. The data are compared to high-pT STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields at low pT are significantly above hydrodynamic flow predictions but are consistent with models that include color screening and regeneration.

  4. Dipole moments associated with edge atoms; a comparative study on stepped Pt, Au and W surfaces

    International Nuclear Information System (INIS)

    Besocke, K.; Krahl-Urban, B.; Wagner, H.

    1977-01-01

    Work function measurements have been performed on stepped Pt and Au surfaces with (111) terraces and on W surfaces with (110) terraces. In each case the work function decreases linearly with increasing step density and depends on the step orientation. The work function changes are attributed to dipole moments associated with the step edges. The dipole moments per unit step length are larger for open edge structures than for densely packed ones. The dipole moments for Pt are about twice as large as for Au and W. (Auth.)

  5. Final Technical Report: First Principles Investigations for the Ensemble Effects of PdAu and PtAu Bimetallic Nanocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ruqian Wu

    2012-05-18

    Bimetallic surfaces with tunable chemical properties have attracted broad attention in recent years due to their ample potential for heterogeneous catalysis applications. The local chemical properties of constituents are strongly altered from their parent metals by 'ligand effect', a term encompassing the influences of charge transfer, orbital rehybridization and lattice strain. In comparison to the aforementioned, the 'ensemble effect' associated with particular arrangements of the active constituents have received much less attention, despite their notable importance towards the determination of reactivity and selectivity of bimetallic catalysts. We performed theoretical studies for understanding the ensemble effects on bimetallic catalysis: (i) simulations for the formation of different ensembles on PdAu and PtAu nanoclusters; (ii) studies of the size, shape, and substrate dependence of their electronic properties; and (iii) simulations for model reactions such as CO oxidation, methanol, ethylene and water dehydrogenation on PdAu and PtAu nanoclusters. In close collaboration with leading experimental groups, our theoretical research elucidated the fundamentals of Au based bimetallic nanocatalysts.

  6. Characterization of self-assembled electrodes based on Au-Pt nanoparticles for PEMFC application

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, E. [Politecnica Univ. de Chiapas, Tuxtla Gutierrez, Chiapas (Mexico). Energia y Sustentabilidad; Sebastian, P.J. [Politecnica Univ. de Chiapas, Chiapas (Mexico). Energia y Sustentabilidad; Centro de Investigacion en Energia, UNAM, Morelos (Mexico); Gamboa, S.A. [Centro de Investigacion en Energia, UNAM, Morelos (Mexico); Pal, U. [Inst. de Fisica, Universidad Autonoma de Puebla Univ., Puebla (Mexico). Inst. de Fisica; Gonzalez, I. [Autonoma Metropolitana Univ. (Mexico). Dept. de Quimica

    2008-07-01

    This paper reported on a study in which membrane electrode assemblies (MEAs) were fabricated by depositing Au, Pt and AuPt nanoparticles on Nafion 115 membrane for use in a proton exchange membrane fuel cell (PEMFC). A Rotating Disc Electrode (RDE) was used to measure the nanoparticle catalyst activity. After deposition of the nanoparticles on the membrane, the surface was studied by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The membrane proton conduction process was studied by Electrochemical Impedance Spectroscopy (EIS) with the 4 probe technique. The MEAs fabricated with Nafion/Metal membranes were evaluated in a PEMFC under standard conditions. Colloidal solutions were used to prepare self-assembled electrodes with nanoparticles deposited on Nafion membrane. The particles deposited on Nafion showed good stability and had homogeneous distribution along the membrane surface. The impedance results revealed an increase in the membrane proton resistance of the self-assembled electrodes compared to unmodified Nafion. The Au-Pt nanoparticles were obtained by chemical reduction. The nanoparticle size in the three systems was about 2 nm. The self-assembled electrodes performed well in standard conditions. The optimum colloidal concentration and immersion time must be determined in order to obtain good catalytic activity and high membrane conductance. The self-assembled Nafion/AuPt had the best open circuit potential (887 mV). The Au and Pt self-assemblies showed a similar performance in terms of maximum power and maximum current density. The performance of the Nafion/Au self-assembly was influenced more by ohmic losses, particularly in the membrane. The maximum power generation was obtained at 0.35 V. The mass transport losses increased after this value, thereby affecting the efficiency of the PEMFC. 2 figs.

  7. Properties and electrochemical behaviors of AuPt alloys prepared by direct-current electrodeposition for lithium air batteries

    International Nuclear Information System (INIS)

    Zhang, Jinqiu; Li, Da; Zhu, Yiming; Chen, Miaomiao; An, Maozhong; Yang, Peixia; Wang, Peng

    2015-01-01

    AuPt catalyst has a prospective application in a lithium air battery because of its bi-function on catalyzing Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER). Electrodeposition is an in-situ convenient technology for catalyst preparation without chemical residue. In an acid electrolyte, AuPt alloy catalysts were electrodeposited on carbon paper. The effect of main salt concentration, electrodeposition time and current density were studied by deposit micromorphology observation, structure analyses and composition testing. Catalytic abilities of AuPt alloys were measured by cyclic voltammetry (CV) in an ionic liquid of EMI-TFSI/Li-TFSI [1- Ethyl - 3- methylimidazolium–bis (trifluoromethanesulphonyl) imide/lithium–bis (trifluoromethanesulphonyl) imide]. The electrochemical behaviors of Au, Pt and AuPt deposits were also measured. An optimized direct-current electrodeposition process of getting high active AuPt catalyst is concluded, which is an aqueous solution containing 6.7∼10 mmol · L −1 HAuCl 4 , 10∼13.3 mmol · L −1 H 2 PtCl 6 and 0.5 mol · L −1 H 2 SO 4 as the electrolyte, current density of 20mA · cm −2 and electrodeposition time of 8∼34 s. The co-deposition of AuPt alloy is an irregular co-deposition controlled by diffusion, while gold atoms enter the platinum’s crystal lattice in the structure of AuPt alloy. The increase of the concentration of H 2 PtCl 6 in the electrolyte, the extension of the electrodeposition time or the raise of the current density can improve the content of Pt in the deposit. The clusters’ diameters of AuPt catalysts decrease to 150∼250 nm by adjusting current densities during electrodeposition

  8. Highly open bowl-like PtAuAg nanocages as robust electrocatalysts towards ethylene glycol oxidation

    Science.gov (United States)

    Xu, Hui; Yan, Bo; Li, Shumin; Wang, Jin; Song, Pingping; Wang, Caiqin; Guo, Jun; Du, Yukou

    2018-04-01

    A novel combined seed mediated and galvanic replacement method has been demonstrated to synthesize a new class of trimetallic PtAuAg nanocatalysts with highly open bowl-like nanocage structure. The newly-generated PtAuAg nanocages catalysts exhibit superior electrocatalytic performances towards ethylene glycol oxidation with the mass activity of 6357.1 mA mg-1, 5.5 times higher than that of commercial Pt/C (1151.1 mA mg-1). This work demonstrates the first example of designing shape-controlled architectures of trimetallic bowl-like PtAuAg nanocages for liquid fuel electrooxidation.

  9. Au@Pt nanoparticles as catalase mimics to attenuate tumor hypoxia and enhance immune cell-mediated cytotoxicity

    Science.gov (United States)

    Liang, Hong; Wu, Ying; Ou, Xiang-Yu; Li, Jing-Ying; Li, Juan

    2017-11-01

    Hypoxic tumor microenvironment (TME) is closely linked to tumor progression, heterogeneity and immune suppression. Therefore, the development of effective methods to overcome hypoxia and substantially enhance the immunotherapy efficacy remains a desirable goal. Herein, we engineered a biocompatible Au core/Pt shell nanoparticles (Au@Pt NPs) to reoxygenate the TME by reacting with endogenous H2O2. Treatment with Au@Pt NPs appeared to improve oxygen in intracellular environments and decrease hypoxia-inducible factor-1α expression. Furthermore, the integration of high catalytic efficiency of Au@Pt NPs with cytokine-induced killer (CIK) cell immunotherapy, could lead to significantly improve the effect of CIK cell-mediated cytotoxicity. These results suggest great potential of Au@Pt NPs for regulation of the hypoxic TME and enhance immune cell mediated anti-tumor immunity.

  10. Green synthesis of noble nanometals (Au, Pt, Pd) using glycerol under microwave irradiation conditions

    Science.gov (United States)

    A newer application of glycerol in the field of nanomaterials synthesis has been developed from both the economic and environmental points of view. Glycerol can act as a reducing agent for the fabrication of noble nanometals, such as Au, Pt, and Pd, under microwave irradiation. T...

  11. Electrochemical Reduction of CO2 on Compositionally Variant Au-Pt Bimetallic Thin Films

    DEFF Research Database (Denmark)

    Ma, Ming; Hansen, Heine Anton; Valenti, Marco

    2017-01-01

    by a magnetron sputtering co-deposition technique with tunable composition. It was found that the syngas ratio (CO:H2) on the Au-Pt films is able to be tuned by systematically controlling the binary composition. This tunable catalytic selectivity is attributed to the variation of binding strength of COOH and CO...

  12. Stability Studies of a New Design Au/Pt Thermocouple Without a Strain Relieving Coil

    Science.gov (United States)

    Jahan, Ferdouse; Ballico, Mark

    2007-12-01

    The performance of a simple, new design Au/Pt thermocouple developed by NMIA is assessed. This thermocouple is proposed as a more accurate replacement, over the temperature range from 0 to 1,000°C, for the commonly used Type R and S industrial transfer standards, in a robust form familiar to industrial calibration laboratories. Due to the significantly different thermal expansions of the Au and Pt thermoelements, reported designs of the Au/Pt thermocouple incorporate a strain-relieving coil or bridge at the thermocouple junction. As the strain relieving coil is mechanically delicate, these thermocouples are usually mounted in a protective quartz tube assembly, like a standard platinum resistance thermometer (SPRT). Although providing uncertainties at the mK level, they are more delicate than the commonly used Type R and S thermocouples. A new and simple design of the Au/Pt thermocouple was developed in which the differential thermal expansion between Au and Pt is accommodated in the thermocouple leads, facilitated by a special head design. The resulting thermocouple has the appearance and robustness of the traditional Type R and S thermocouples, while retaining stability better than 10 mK up to 961°C. Three thermocouples of this design were calibrated at fixed points and by comparison to SPRTs in a stirred salt bath. In order to assess possible impurity migration, strain effects, and mechanical robustness, sequences of heat treatment up to a total of 500 h together with over 50 thermal cycles from 900°C to ambient were performed. The effect of these treatments on the calibration was assessed, demonstrating the sensors to be robust and stable to better than 10 mK. The effects on the measured inhomogeneity of the thermocouple were assessed using the NMIA thermocouple scanning bath.

  13. Direct ethanol fuel cell, CO and ethanol oxidation on core-shell C/Ni-Au-[Pt and (Pt- Ir)] catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, C.A.D.; Tremiliosi-Filho, G. [Universidade de Sao Paulo (IQSC/USP), Sao Carlos, SP (Brazil). Inst. de Quimica], Email: cesaraug@sc.usp.br; Kokoh, K.B.; Coutanceau, C.; Baranton, S. [Universite de Poitiers (France). Lab. de Catalyse en Chimie Organique (LACCO). Equipe Electrocatalyse

    2010-07-01

    In this paper presents to study of the Pt and Pt-Ir monolayer that were deposited on core-shell Ni-Au nanoparticles supported on carbon. Catalysts with the following molar ratios were prepared: Pt and Pt{sub 65}Ir{sub 35}, Pt{sub 75}Ir{sub 2}5, Pt{sub 80}Ir{sub 20} and Pt{sub 85}Ir{sub 15}. The means particle sizes were in the range of 2 - 6 nm for all catalysts. The electrochemical properties examined in the ethanol and CO oxidation by cyclic voltammetry, and In situ IR spectroscopy measurements (SPAIRS) enabled to determine intermediates and reaction products as a function of the metallic compositions of catalysts. All of the catalysts were tested as anodes of a single direct ethanol fuel cell (DEFC) tests in 1.0 M ethanol solution. As a result, higher power densities were obtained with the core-shell particles in comparison to those issued from the commercial catalyst (Pt-ETEK). Thus, the maximum power densities at 90 deg C for the different systems are: (i) commercial C/Pt catalyst (E-TEK): ca. 0.010 W cm{sup -2}, C/Ni-Au-(Pt{sub 85}Ir{sub 15}): ca. 0.013 W cm{sup -2} and C/Ni-Au-Pt: ca. 0.018 W cm{sup -2} (all core-shell systems were normalization by Pt load). As a result, the performance of the core-shell nanoparticles is much better than that produced for the commercial catalyst and the C/Ni-Au-Pt system showed the best performance. (author)

  14. M-Au/TiO2 (M = Ag, Pd, and Pt) nanophotocatalyst for overall solar water splitting: role of interfaces

    Science.gov (United States)

    Melvin, Ambrose A.; Illath, Kavya; Das, Tanmay; Raja, Thirumalaiswamy; Bhattacharyya, Somnath; Gopinath, Chinnakonda S.

    2015-08-01

    M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2 generation activity by forming a bi-metallic system. Degussa P25 was used as a TiO2 substrate to photodeposit Au followed by Au + M (M = Ag/Pd/Pt). The SWS activity of the M-Au/TiO2 was determined through photocatalytic H2 production in the presence of methanol as a sacrificial agent under one sun conditions with an AM1.5 filter. The highest H2 yield was observed for Pt0.5-Au1/TiO2 and was around 1.3 +/- 0.07 mmol h-1 g-1, with an apparent quantum yield (AQY) of 6.4%. Pt0.5-Au1/TiO2 also demonstrated the same activity for 25 cycles of five hours each for 125 h. Critically, the same Pt0.5-Au1/TiO2 catalyst was active in overall SWS (OSWS) without any sacrificial agent, with an AQY = 0.8%. The amount of Au and/or Pt was varied to obtain the optimum composition and it was found that the Pt0.5-Au1/TiO2 composition exhibits the best activity. Detailed characterization by physico-chemical, spectral and microscopy measurements was carried out to obtain an in-depth understanding of the origin of the photocatalytic activity of Pt0.5-Au1/TiO2. These in-depth studies show that gold interacts predominantly with oxygen vacancies present on titania surfaces, and Pt preferentially interacts with gold for an effective electron-hole pair separation at Pt-Au interfaces and electron storage in metal particles. The Pt in Pt0.5-Au1/TiO2 is electronically and catalytically different from the Pt in Pt/TiO2 and it is predicted that the former suppresses the oxygen reduction reaction.M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2

  15. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

    2015-01-01

    driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen......Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...... active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...

  16. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

    Science.gov (United States)

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-08-01

    Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size.

  17. Electrochemical reduction of O2 and NO on Ni, Pt and Au

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent

    2008-01-01

    the reduction of oxygen. This implies that the triple-phase boundary (3PB) catalyses the reduction of oxygen but not the reduction of nitric oxide, as Au is a catalytic inactive metal. All the materials were more active towards oxidation than towards reduction that is evolution of oxygen or oxidation of nitric......The electrochemical reduction of oxygen and nitric oxide was studied using cyclic voltammetry on point electrodes of Ni, Pt and Au in the temperature range 400-600 degrees C. All the materials were more active towards the reduction of oxygen than towards the reduction of nitric oxide, except Pt...... at 400 degrees C. As a general trend it was observed that the activity of the materials towards the reduction of oxygen increases more than the activity of the materials towards the reduction of nitric oxide with increasing temperature. The Ni wire was covered with a layer of NiO. The NiO layer inhibits...

  18. Isomerization of hexane on PtAu nanoparticles supported on zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Fraissard, Jacques [P. and M. Curie University, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Laboratoire de Physique Quantique, 10 rue Vauquelin, ESPCI, 75231 Paris Cedex 05 (France); Gerda, Vasilyi [Taras Shevchenko National University, 64 Volodymyrskaya str., 01033 Kiev (Ukraine); Patrylak, Kazymyr I.; Voloshyna, Yu.G. [Institute of Biorganic Chemistry and Petrochemistry, Academy of Science, 02660 Kiev (Ukraine)

    2007-04-30

    When lead-based anti-knock additives were withdrawn, petrol was enriched with benzene and benzene derivatives in order to maintain an excellent octane number. However, because of their toxicity, it is planned to eliminate these also and to replace them by methylated alkanes, whence the importance of n-alkane isomerization. Some PtAu-zeolite catalysts tested for n-hexane isomerization reveal that the addition of gold to platinum generally changes the activity and/or the selectivity for methylpentane to the detriment of cracking. The influence of the zeolite structure is also important. At 275 C, the activity and selectivity of PtAu-HZSM5 are about 75%, showing that this catalyst can be useful for such a reaction. (author)

  19. The Precious metals (Au, Ag, Pt, Pd, Rh) adsorption on the Silicon – organic sorbents

    OpenAIRE

    G Burmaa; S Alen; Yu Ganchimeg; I Sukhbaatar

    2014-01-01

    Sorption activity of two types of Silicon-organic sorbents for the previous metals has been studied. A polymer – poly (3- silsesquioxanilpropylthiocarbamate) - 3- silsesquioxanilpropylammonium which was obtained by the hydrolytic poly-condensation reaction and has been determined its physical, chemical characteristics and its sorption activity for the Ag(I), Au(III), Pt(IV), Pd(II), Rh(III). It has been found out that the sorbent shows high static sorption of Gold (III), Mercury (II) at acidi...

  20. Experimental modeling of Au and Pt coupled transport by chloride hydrothermal fluids at 350–450°C and 500–1000 bar

    Science.gov (United States)

    Zotov, A. V.; Tagirov, B. R.; Koroleva, L. A.; Volchenkova, V. A.

    2017-09-01

    The coupled solubility of Au(cr) and Pt(cr) has been measured in acidic chloride solutions at 350-450°C and 0.5 and 1 kb using the autoclave technique with determination of dissolved metal contents after quenching. The constants of the reaction combining the dominant species of Au and Pt in high-temperature hydrothermal fluids ( K (Au-Pt)) have been determined: 2 Au(cr) + PtCl4 2- = Pt(cr) + 2AuCl2 -; log K (Au-Pt) =-1.02 ± 0.25 (450°C, 1 kb), 0.09 ± 0.15 (450°C, 0.5 kb), and -1.31 ± 0.20 (350°C, 1 kb). It has been established that the factors affecting the Au/Pt concentration ratio in hydrothermal fluids and precipitated ores are temperature, pressure, redox potential, and sulfur fugacity. An increase in temperature results in an increase in the Au/Pt concentration ratio (up to 550°C at P = 1 kb). A decrease in pressure and redox potential leads to enrichment of fluid in Au. An increase in sulfur fugacity in the stability field of Pt sulfides results in increase in the Au/Pt concentration ratio. Native platinum is replaced by sulfide mineral in low-temperature systems enriched in Pt (relative to Au).

  1. Developing an aqueous approach for synthesizing Au and M@Au (M = Pd, CuPt) hybrid nanostars with plasmonic properties

    OpenAIRE

    Du, Jingshan; Yu, Junjie; Xiong, Yalin; Lin, Zhuoqing; Zhang, Hui; Yang, Deren

    2014-01-01

    Anisotropic Au nanoparticles show unique localized surface plasmon resonance (LSPR) properties, which make it attractive in optical, sensing, and biomedical applications. In this contribution, we report a general and facile strategy towards aqueous synthesis of Au and M@Au (M = Pd, CuPt) hybrid nanostars by reducing HAuCl4 with ethanolamine in the presence of cetyltrimethylammonium bromide (CTAB). According to electron microscopic observation and spectral monitoring, we found that the layered...

  2. Characterization of self-assembled electrodes based on Au-Pt nanoparticles for PEMFC application

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, E. [Univ. Politecnica de Chiapas (Mexico). Energia y Sustentabilidad; Sebastian, P.J.; Gamboa, S.A.; Joseph, S. [Univ. Nacional Autonoma de Mexico, Morelos (Mexico). Centrode Investigacion en Energia; Pal, U. [Univ. Autonoma de Puebla, Pue (Mexico). Inst. de Fisica; Gonzalez, I. [Univ. Autonoma Metropolitana, Mexico City (Mexico). Dept. de Quimica

    2010-07-01

    This paper described the synthesis and characterization of gold (Au), platinum (Pt) and Au-Pt nanoparticles impregnated on a Nafion membrane in a proton exchange membrane fuel cell (PEMFC). The aim of the study was to fabricate the membrane electrode assembly (MEA) by depositing the nanoparticles on the membrane using an immersion technique. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to study the deposition process. Electrochemical impedance spectroscopy (EIS) was used to study the membrane proton conduction process. An elemental mapping analysis was performed in order to study the location of the Au and Pt in the self-assemblies. Results of the study showed that the particles deposited on the Nafion had good stability and a homogenous distribution along the membrane surface. The particles showed a direct relation in size and location with the hydrophilic and hydrophobic distribution phases of the membrane. The main membrane resistance was located between the membrane and the electrolyte. The self-assembled electrodes demonstrated a good performance at standard conditions. 33 refs., 4 tabs., 11 figs.

  3. Polymeric carbon nitride/mesoporous silica composites as catalyst support for Au and Pt nanoparticles.

    Science.gov (United States)

    Xiao, Ping; Zhao, Yanxi; Wang, Tao; Zhan, Yingying; Wang, Huihu; Li, Jinlin; Thomas, Arne; Zhu, Junjiang

    2014-03-03

    Small and homogeneously dispersed Au and Pt nanoparticles (NPs) were prepared on polymeric carbon nitride (CNx )/mesoporous silica (SBA-15) composites, which were synthesized by thermal polycondensation of dicyandiamide-impregnated preformed SBA-15. By changing the condensation temperature, the degree of condensation and the loading of CNx can be controlled to give adjustable particle sizes of the Pt and Au NPs subsequently formed on the composites. In contrast to the pure SBA-15 support, coating of SBA-15 with polymeric CNx resulted in much smaller and better-dispersed metal NPs. Furthermore, under catalytic conditions the CNx coating helps to stabilize the metal NPs. However, metal NPs on CNx /SBA-15 can show very different catalytic behaviors in, for example, the CO oxidation reaction. Whereas the Pt NPs already show full CO conversion at 160 °C, the catalytic activity of Au NPs seems to be inhibited by the CNx support. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Bimetallic Pt-Au nanocatalysts electrochemically deposited on graphene and their electrocatalytic characteristics towards oxygen reduction and methanol oxidation.

    Science.gov (United States)

    Hu, Yaojuan; Zhang, Hua; Wu, Ping; Zhang, Hui; Zhou, Bo; Cai, Chenxin

    2011-03-07

    The burgeoning demand for clean and energy-efficient fuel cell system requires electrocatalysts to deliver greater activity and selectivity. Bimetallic catalysts have proven superior to single metal catalysts in this respect. This work reports the preparation, characterization, and electrocatalytic characteristics of a new bimetallic nanocatalyst. The catalyst, Pt-Au-graphene, was synthesized by electrodeposition of Pt-Au nanostructures on the surface of graphene sheets, and characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and voltammetry. The morphology and composition of the nanocatalyst can be easily controlled by adjusting the molar ratio between Pt and Au precursors. The electrocatalytic characteristics of the nanocatalysts for the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) were systematically investigated by cyclic voltammetry. The Pt-Au-graphene catalysts exhibits higher catalytic activity than Au-graphene and Pt-graphene catalysts for both the ORR and the MOR, and the highest activity is obtained at a Pt/Au molar ratio of 2:1. Moreover, graphene can significantly enhance the long-term stability of the nanocatalyst toward the MOR by effectively removing the accumulated carbonaceous species formed in the oxidation of methanol from the surface of the catalyst. Therefore, this work has demonstrated that a higher performance of ORR and the MOR could be realized at the Pt-Au-graphene electrocatalyst while Pt utilization also could be greatly diminished. This method may open a general approach for the morphology-controlled synthesis of bimetallic Pt-M nanocatalysts, which can be expected to have promising applications in fuel cells.

  5. Enzymatic biosensor of horseradish peroxidase immobilized on Au-Pt nanotube/Au-graphene for the simultaneous determination of antioxidants

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Long; Yin, Wenmin; Tang, Kun; Li, Dian; Shao, Kang; Zuo, Yunpeng; Ma, Jing; Liu, Jiawei; Han, Heyou, E-mail: hyhan@mail.hzau.edu.cn

    2016-08-24

    A new electrochemical method has been proposed for the simultaneous determination of butylated hydroxyanisole (BHA) and propyl gallate (PG) in food matrices based on enzymatic biosensors. Spiny Au-Pt nanotubes (SAP NTs) was first synthesized and demonstrated to exhibit intrinsic peroxidase and catalase-like activity. The structure of SAP NTs provides large surface area and favorable medium for electron transfer, on which HRP were immobilized and acted as enzymatic biosensor for the simultaneous detection of BHA and PG. The results revealed that BHA and PG both have well-defined oxidation waves with peak potentials of 624 and 655 mV, respectively. Under the optimal conditions, the method behaved satisfactory analytical performance towards BHA and PG with a wide linear range of 0.3–50 mg L{sup −1} and 0.1–100 mg L{sup −1}, as well as a detection limit of 0.046 mg L{sup −1} and 0.024 mg L{sup −1} (3σ/slope), respectively. Besides, the proposed method exhibits good sensitivity, stability and reproducibility, providing an alternative to fabricate electrode and construct sensitive biosensors. - Highlights: • SAP NTs was synthesized and demonstrated to exhibit intrinsic peroxidase and catalase-like activity. • The structure of SAP NTs provides larger surface area and more favorable medium for electron transfer. • Horseradish peroxidase immobilized on Au-Pt nanotube/Au-graphene acted as enzymatic biosensor. • The simultaneous detection of BHA and PG in food matrices was achieved based on enzymatic biosensors.

  6. Pulse electrodeposition to prepare core-shell structured AuPt@Pd/C catalyst for formic acid fuel cell application

    Science.gov (United States)

    Lu, Xueyi; Luo, Fan; Song, Huiyu; Liao, Shijun; Li, Hualing

    2014-01-01

    A novel core-shell structured AuPt@Pd/C catalyst for the electrooxidation of formic acid is synthesized by a pulse electrodeposition process, and the AuPt core nanoparticles are obtained by a NaBH4 reduction method. The catalyst is characterized with X-ray powder diffraction and transmission electron microscopy, thermogravimetric analysis, cyclic voltammetry, CO stripping and X-ray photoelectron spectroscopy. The core-shell structure of the catalyst is revealed by the increase in particle size resulting from a Pd layer covering the AuPt core, and by a negative shift in the CO stripping peaks. The addition of a small amount of Pt improves the dispersion of Au and results in smaller core particles. The catalyst's activity is evaluated by cyclic voltammetry in formic acid solution. The catalyst shows excellent activity towards the anodic oxidation of formic acid, the mass activity reaches 4.4 A mg-1Pd and 0.83 A mg-1metal, which are 8.5 and 1.6 times that of commercial Pd/C. This enhanced electrocatalytic activity could be ascribed to the good dispersion of Au core particles resulting from the addition of Pt, as well as to the interaction between the Pd shell layer and the Au and Pt in the core nanoparticles.

  7. Electrochemically deposited Pd-Pt and Pd-Au codeposits on graphite electrodes for electrocatalytic H2O2 reduction.

    Science.gov (United States)

    Nagaiah, Tharamani Chikka; Schäfer, Dominik; Schuhmann, Wolfgang; Dimcheva, Nina

    2013-08-20

    Improved electrocatalytic activity and selectivity for the reduction of H2O2 were obtained by electrodepositing Pd-Pt and Pd-Au on spectrographic graphite from solutions containing salts of the two metals at varying ratio. The electrocatalytic activity of the resulting binary codeposits for H2O2 reduction was evaluated by means of the redox-competition mode of scanning electrochemical microscopy (SECM) and voltammetric methods. In a potential range from 0 to -600 mV (vs. Ag/AgCl/3 M KCl) at pH 7.0 in 0.1 M phosphate citrate buffer, the electrocatalytic activity of both Pd-Pt and Pd-Au codeposits was substantially improved as compared with the identically deposited single metals suggesting an electrocatalytic synergy of the codeposits. Pd-Pt and Pd-Au codeposits were characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Codepositing with Au caused a change of hedgehog-like shaped Pd nanoparticles into cauliflower-like nanoparticles with the particle size decreasing with increasing Au concentration. Codepositing Pd with Pt caused the formation of oblong structures with the size initially increasing with increasing Pt content. However, the particle size decreases with further increase in Pt concentration. The improved electrocatalytic capability for H2O2 reduction of the Pd-Pt electrodeposits on graphite was further demonstrated by immobilizing glucose oxidase as a basis for the development of an interference-free amperometric glucose biosensor.

  8. Thermal Stability of Co-Pt and Co-Au Core-Shell Structured Nanoparticles: Insights from Molecular Dynamics Simulations.

    Science.gov (United States)

    Wen, Yu-Hua; Huang, Rao; Shao, Gui-Fang; Sun, Shi-Gang

    2017-09-07

    Co-Pt and Co-Au core-shell nanoparticles were heated by molecular dynamics simulations to investigate their thermal stability. Two core structures, that is, hcp Co and fcc Co, have been addressed. The results demonstrate that the hcp-fcc phase transition happens in the hcp-Co-core/fcc-Pt-shell nanoparticle, while it is absent in the hcp-Co-core/fcc-Au-shell one. The stacking faults appear in both Pt and Au shells despite different structures of the Co core. The Co core and Pt shell concurrently melt and present an identical melting point in both Co-Pt core-shell nanoparticles. However, typical two-stage melting occurs in both Co-Au core-shell nanoparticles. Furthermore, the Au shell in the hcp-Co-core/fcc-Au-shell nanoparticle exhibits a lower melting point than that in the fcc-Co-core/fcc-Au-shell one, while the melting points are closely equal for both hcp and fcc Co cores. All of these observations suggest that their thermal stability strongly depends on the structure of the core and the element of the shell.

  9. Facile synthesis of PtAu nanoparticles supported on polydopamine reduced and modified graphene oxide as a highly active catalyst for methanol oxidation

    International Nuclear Information System (INIS)

    Ren, Fangfang; Zhai, Chunyang; Zhu, Mingshan; Wang, Caiqin; Wang, Huiwen; Bin, Duan; Guo, Jun; Yang, Ping; Du, Yukou

    2015-01-01

    Graphical abstract: A facile and clean method for the synthesis of PtAu nanoparticles with different Pt/Au ratios supported on polydopamine reduced and modified graphene oxide (PtAu/PDA-RGO) is reported, which exhibit higher electro-catalytic performance and stability towards methanol oxidation in alkaline medium. - Highlights: • GO could be reduced and modified simultaneously by PDA without using reducing agents. • PDA plays an important role in enhancing the dispersion and stability of the catalyst. • The bimetallic PtAu/PDA-RGO catalysts exhibits higher catalytic activity than the monometallic Pt/PDA-RGO toward MOR. • The PtAu(3:1)/PDA-RGO catalyst also shows better catalytic activity for MOR than PtAu(3:1)/RGO and PtAu(3:1)/C catalysts. - Abstract: In this paper, a facile strategy for the synthesis of PtAu nanoparticles (NPs) with different Pt/Au ratios supported on polydopamine reduced and modified graphene oxide (PtAu/PDA-RGO) is reported. The as-prepared PtAu/PDA-RGO composites were extensively analyzed by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. It is found that PDA plays an important role in enhancing the dispersion and stability of the catalyst. Moreover, the bimetallic PtAu/PDA-RGO catalysts exhibits higher catalytic activity than the monometallic Pt/PDA-RGO toward methanol oxidation reaction (MOR), with the best performance found for the Pt/Au molar ratio of 3/1. The PtAu(3:1)/PDA-RGO catalyst also shows better catalytic activity for MOR than PtAu(3:1)/RGO and PtAu(3:1)/C catalysts, suggesting that PDA-RGO can be a promising catalyst support for fuel cells. These findings also indicate that the molar ratios of Pt/Au and the catalyst support are the two critical factors to affect the overall performance of the catalyst

  10. Projected shell model study of neutron- deficient 122Ce

    Indian Academy of Sciences (India)

    Recently, Smith et al [1] have communicated the existence of neutron-deficient 122Ce and its excited states have been reported up to spin 14¯h. The band has been as- signed to 122Ce by detecting γ-rays in coincidence with evaporated charged particles and neutrons. The nucleus is believed to have large ground state ...

  11. Variations of color with alloying elements in Pd-free Au-Pt-based high noble dental alloys

    International Nuclear Information System (INIS)

    Shiraishi, Takanobu; Takuma, Yasuko; Miura, Eri; Fujita, Takeshi; Hisatsune, Kunihiro

    2007-01-01

    The effects of alloying addition of a small amount of base metals (In, Sn, Fe, Zn) on color variations in Pd-free Au-Pt-based high noble dental alloys were investigated in terms of rectilinear and polar color coordinates. The ternary Au-Pt-X (X = In, Sn, Fe, Zn) and quaternary Au-Pt-In-Y (Y = Sn, Fe, Zn) alloys were prepared from high purity component metals. The amount of alloying base metals, X and Y, were restricted up to 2 at.%. The alloying addition of a small amount of Fe, In, Sn, to a binary Au-10 at.% Pt alloy (referred to as AP10) effectively increased chroma, C *. On the other hand, the addition of Zn to the parent alloy AP10 did not change color coordinates greatly. The increase in chroma in the present Au-Pt-based high noble alloys was attributed to the increase in the slope of spectral reflectance curve at its absorption edge near 515 nm. It was found that the addition of a small amount of Fe to the parent alloy AP10 markedly increased lightness, L *, and the addition of Sn gave a very light tint of red to the parent alloy. Although red-green chromaticity index a * contributed to chroma to some extent, contribution of yellow-blue chromaticity index b * was much greater in determining chroma in this Pd-free Au-Pt-based multi-component alloys. The present results are expected to be valuable in case color is to be taken into account in designing Pd-free Au-Pt-based high noble dental alloys

  12. Novel synthesis of core-shell Au-Pt dendritic nanoparticles supported on carbon black for enhanced methanol electro-oxidation

    Science.gov (United States)

    Cao, Ribing; Xia, Tiantian; Zhu, Ruizhi; Liu, Zhihua; Guo, Jinming; Chang, Gang; Zhang, Zaoli; Liu, Xiong; He, Yunbin

    2018-03-01

    Core-shell Au-Pt dendritic nanoparticles (Au-Pt NPs) has been synthesized via a facile seed-mediated growth method, in which dendritic Pt nanoparticles as shell grow on the surface of gold nanocores by using ascorbic acid (AA) as "green" reducing reagents. The morphologies and compositions of the as-prepared nanocomposites with core-shell structure are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Electrochemical experiments, including cyclic voltammetry (CV) and chronoamperometry (CA) are performed to investigate the electrocatalytic properties of the Au-Pt NPs loaded carbon black composites (Au-Pt NPs/V) towards methanol oxidation in an alkaline solution. It is found that the reduction time of AA could regulate the thickness and amount of Pt on the Au nanocores, which significantly affect catalytic activity of the Au-Pt NPs/V toward methanol oxidation. Au-Pt NPs/V with optimum reduction time 4 h exhibit 2.3-times higher electrocatalytic activity than that of a commercial catalyst (Pt/carbon black) and an excellent CO tolerance toward methanol oxidation. This behavior is attributed to large active electrochemical area of the bimetallic nanocomposites and the change in the electronic structure of Pt when Au surface modified with fewer Pt nanoparticles.

  13. Unusual Activity Trend for CO Oxidation on Pd(x)Au(140-x)@Pt Core@Shell Nanoparticle Electrocatalysts.

    Science.gov (United States)

    Luo, Long; Zhang, Liang; Henkelman, Graeme; Crooks, Richard M

    2015-07-02

    A theoretical and experimental study of the electrocatalytic oxidation of CO on PdxAu140-x@Pt dendrimer-encapsulated nanoparticle (DEN) catalysts is presented. These nanoparticles are comprised of a core having an average of 140 atoms and a Pt monolayer shell. The CO oxidation activity trend exhibits an unusual koppa shape as the number of Pd atoms in the core is varied from 0 to 140. Calculations based on density functional theory suggest that the koppa-shaped trend is driven primarily by structural changes that affect the CO binding energy on the surface. Specifically, a pure Au core leads to deformation of the Pt shell and a compression of the Pt lattice. In contrast, Pd, from the pure Pd cores, tends to segregate on the DEN surface, forming an inverted configuration having Pt within the core and Pd in the shell. With a small addition of Au, however, the alloy PdAu cores stabilize the core@shell structures by preventing Au and Pd from escaping to the particle surface.

  14. The Precious metals (Au, Ag, Pt, Pd, Rh adsorption on the Silicon – organic sorbents

    Directory of Open Access Journals (Sweden)

    G Burmaa

    2014-09-01

    Full Text Available Sorption activity of two types of Silicon-organic sorbents for the previous metals has been studied. A polymer – poly (3- silsesquioxanilpropylthiocarbamate - 3- silsesquioxanilpropylammonium which was obtained by the hydrolytic poly-condensation reaction and has been determined its physical, chemical characteristics and its sorption activity for the Ag(I, Au(III, Pt(IV, Pd(II, Rh(III. It has been found out that the sorbent shows high static sorption of Gold (III, Mercury (II at acidic condition. The second a net structured silicon-organic copolymer {SiO2*2[O1.5Si(CH23NHC5H4N}n was synthesized by hydrolytic co-poly-condensation reaction. It likely to react as an anionit that adsorbs chloro-complex anion of the Au (III, Pt(IV, Pd(II, Rh(III.DOI: http://dx.doi.org/10.5564/mjc.v12i0.167 Mongolian Journal of Chemistry Vol.12 2011: 29-34

  15. Critical Factors Controlling Pd and Pt Potential in Porphyry Cu–Au Deposits: Evidence from the Balkan Peninsula

    Directory of Open Access Journals (Sweden)

    Demetrios G. Eliopoulos

    2014-03-01

    Full Text Available Porphyry Cu–Au–Pd±Pt deposits are significant Au resources, but their Pd and Pt potential is still unknown. Elevated Pd, Pt (hundreds of ppb and Au contents are associated with typical stockwork magnetite-bornite-chalcopyrite assemblages, at the central parts of certain porphyry deposits. Unexpected high grade Cu–(Pd+Pt (up to 6 ppm mineralization with high Pd/Pt ratios at the Elatsite porphyry deposit, which is found in a spatial association with the Chelopech epithermal deposit (Bulgaria and the Skouries porphyry deposit, may have formed during late stages of an evolved hydrothermal system. Estimated Pd, Pt and Au potential for porphyry deposits is consistent with literature model calculations demonstrating the capacity of aqueous vapor and brine to scavenge sufficient quantities of Pt and Pd, and could contribute to the global platinum-group element (PGE production. Critical requirements controlling potential of porphyry deposits may be from the metals contained in magma (metasomatized asthenospheric mantle wedge as indicated by significant Cr, Co, Ni and Re contents. The Cr content may be an indicator for the mantle input.

  16. From Au to Pt via surface limited redox replacement of Pb UPD in one-cell configuration.

    Science.gov (United States)

    Fayette, M; Liu, Y; Bertrand, D; Nutariya, J; Vasiljevic, N; Dimitrov, N

    2011-05-03

    This work is aimed at developing a protocol based on surface limited redox replacement (SLRR) of underpotentially deposited (UPD) Pb layers for the growth of epitaxial and continuous Pt thin films on polycrystalline and single crystalline Au surfaces. Different from previously reported papers using SLRR in multiple immersion or flow cell setups, this work explores the one-cell configuration setup as an alternative to improve the efficiency and quality of the growth. Open circuit chronopotentiometry and quartz-crystal microbalance experiments demonstrate steady displacement kinetics and a yield that is higher than the stoichiometric Pt(II)-Pb exchange ratio (1:1). This high yield is attributed to oxidative adsorption of OH(ad) taking place on Pt along with the displacement process. Also, ex situ scanning tunneling microscopy surface characterization reveals after the first replacement event the formation of a dense Pt cluster network that homogenously covers the Au surface. The Pt films grow homogenously with no significant changes in the cluster distribution and surface roughness observed up to 10 successive replacement events. X-ray diffraction analysis shows distinct (111) crystallographic orientation of thicker Pt films deposited on (111) textured Au thin films. Coarse energy dispersive spectroscopy measurements and finer X-ray photoelectron spectroscopy suggest at least 4 atom % Pb incorporating into the Pt layer compared to 13 atom % alloyed Cu when the growth is carried out by SLRR of Cu UPD.

  17. Au and Pt co-loaded g-C3N4 nanosheets for enhanced photocatalytic hydrogen production under visible light irradiation

    Science.gov (United States)

    Liang, Shijing; Xia, Yuzhou; Zhu, Shuying; Zheng, Shan; He, Yunhui; Bi, Jinhong; Liu, Minghua; Wu, Ling

    2015-12-01

    Au and Pt have been considered as the active co-catalysts for the enhanced photocatalytic activity of carbon nitride. However, the effects of Au and Pt co-loading on the surface chemical states and activity of carbon nitride were rarely discussed. In this work, a series of carbon nitride samples with Au and Pt loading have been successfully prepared by a traditional photodeposition method. The as-prepared samples have been characterized in detail. The activities of the samples were evaluated by water splitting into hydrogen under visible light irradiation. Results show that the integrity of characteristic structure of carbon nitride is retained before and after deposited Au and Pt. Interestingly, when Pt is firstly loaded on the surface of carbon nitride, Pt species are in the form of PtO with small particle size. While if Pt is loaded on the surface of Au/carbon nitride, the Pt nanoparticles (NPs) are metallic Pt NPs with relatively large particle size. For Au, it is insensitive to the loading order. Among all Au deposited samples, Au species are in the form of metallic Au. Furthermore, the activities of the Au and Pt co-loaded samples exhibited much higher than those of single co-catalyst deposited samples and pure carbon nitride. The dual co-catalysts in the form of metallic state are more active to increase the performance of water splitting over carbon nitride. The enhanced activity of carbon nitride by co-deposited Au and Pt could be well explained by the photoabsorption performance and the separation of photogenerated electron and holes.

  18. Decay-Assisted Laser Spectroscopy of Neutron-Deficient Francium

    Directory of Open Access Journals (Sweden)

    K. M. Lynch

    2014-03-01

    Full Text Available This paper reports on the hyperfine-structure and radioactive-decay studies of the neutron-deficient francium isotopes ^{202–206}Fr performed with the Collinear Resonance Ionization Spectroscopy (CRIS experiment at the ISOLDE facility, CERN. The high resolution innate to collinear laser spectroscopy is combined with the high efficiency of ion detection to provide a highly sensitive technique to probe the hyperfine structure of exotic isotopes. The technique of decay-assisted laser spectroscopy is presented, whereby the isomeric ion beam is deflected to a decay-spectroscopy station for alpha-decay tagging of the hyperfine components. Here, we present the first hyperfine-structure measurements of the neutron-deficient francium isotopes ^{202–206}Fr, in addition to the identification of the low-lying states of ^{202,204}Fr performed at the CRIS experiment.

  19. Decay-Assisted Laser Spectroscopy of Neutron-Deficient Francium

    CERN Document Server

    Lynch, K M; Bissell, M L; Budincevic, I; Cocolios, T E; De Groote, R P; De Schepper, S; Fedosseev, V N; Flanagan, K T; Franchoo, S; Garcia Ruiz, R F; Heylen, H; Marsh, B A; Neyens, G; Procter, T J; Rossel, R E; Rothe, S; Strashnov, I; Stroke, H H; Wendt, K D A

    2014-01-01

    This paper reports on the hyperfine-structure and radioactive-decay studies of the neutron-deficient francium isotopes $^{202-206}$Fr performed with the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the ISOLDE facility, CERN. The high resolution innate to collinear laser spectroscopy is combined with the high efficiency of ion detection to provide a highly-sensitive technique to probe the hyperfine structure of exotic isotopes. The technique of decay-assisted laser spectroscopy is presented, whereby the isomeric ion beam is deflected to a decay spectroscopy station for alpha-decay tagging of the hyperfine components. Here, we present the first hyperfine-structure measurements of the neutron-deficient francium isotopes $^{202-206}$Fr, in addition to the identification of the low-lying states of $^{202,204}$Fr performed at the CRIS experiment.

  20. Decay studies of neutron deficient astatine isotopes, ch. 3

    International Nuclear Information System (INIS)

    Lingeman, E.W.A.

    1975-01-01

    The neutron deficient astatine isotopes were produced using 209 Bi( 3 He, xn) reactions; excitation functions were measured. Singles gamma-ray measurements and level schemes are presented for 207 At, 208 At and 209 At. Energies and relative intensities of gamma-rays belong to decays to Po isotopes are also reported. A special investigation on 206 Po decay was performed. (V.J.C.)

  1. The equation of state of Bi and cross-checking of Au and Pt scales to megabar pressure

    CERN Document Server

    Akahama, Y; Singh, A K

    2002-01-01

    By means of x-ray diffraction experiments using a synchrotron radiation source, the equation of state (EOS) of body-centred cubic Bi has been investigated over a range of multimegabar pressure up to 222 GPa on the basis of the Pt pressure scale and it is proposed as an internal pressure standard over a range of megabar pressures. Pressure scales of the EOS of Au and Pt were cross-checked and the accuracy of the scales is discussed.

  2. Effects of Au content on the structure and magnetic properties of L1{sub 0}-FePt nanoparticles synthesized by the sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Institute of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Jiang, Yuhong [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Kadasala, Naveen [Department of Chemistry, Purdue University, West Lafayette, IN 47907 (United States); Zhang, Xiaolong [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Mao, Chenyi [Department of Chemistry, Purdue University, West Lafayette, IN 47907 (United States); Wang, Yaxin; Liu, Huilian; Liu, Yanqing [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Yang, Jinghai, E-mail: jhyang1@jlnu.edu.cn [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Yan, Yongsheng, E-mail: yanyongsheng215@126.com [Institute of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2014-07-01

    (FePt){sub 100−x}Au{sub x} (x=0, 5, 10, and 20) nanoparticles were synthesized by the sol–gel method, and effects of Au content on the structural and magnetic properties of samples were investigated. Au doping reduced the phase transition temperature from face-centered cubic (FCC) to face-centered tetragonal (FCT) structure. In addition, additive Au promotes the chemical ordering of L1{sub 0} FePt NPs and increases the grain size of L1{sub 0} FePt NPs. When Au content increased from 0 to 10 at%, the coercivity (H{sub c}) increased due to the increase in degree of ordering S and grain size of L1{sub 0} FePt NPs. By increasing the Au content to 20 at%, H{sub c} decreased. - Graphical abstract: (FePt){sub 100}Au{sub 0} NPs are the coexistence of FCT and FCC phases. However, no hints of FCC phase were found for the (FePt){sub 100−x}Au{sub x} NPs (x=5, 10 and 20), which indicates that addition of gold greatly promotes the FCC to FCT phase transition. - Highlights: • (FePt){sub 100−x}Au{sub x} (x=0, 5, 10 and 20) nanoparticles (NPs) were synthesized. • Au addition promotes the chemical ordering of L1{sub 0} FePt NPs. • Au addition reduces ordering temperature of L1{sub 0} FePt NPs from FCC to FCT phase. • (FePt){sub 90}Au{sub 10} NPs show a high coercivity of 9585 Oe at room temperature.

  3. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

    Energy Technology Data Exchange (ETDEWEB)

    Liu Wei; Repo, Eveliina; Sillanpaeae, Mika [Laboratory of Applied Environmental Chemistry, University of Eastern Finland, Patteristonkatu 1, FI-50100 Mikkeli (Finland); Heikkilae, Mikko; Leskelae, Markku, E-mail: weiliuzk@yahoo.cn, E-mail: mika.sillanpaa@uef.fi [Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, PO Box 55 (A.I. Virtasen aukio 1), FI-00014, Helsinki (Finland)

    2010-10-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), {xi}-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH{sub 2}OH{center_dot}HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H{sub 2}PtCl{sub 6} to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  4. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

    International Nuclear Information System (INIS)

    Liu Wei; Repo, Eveliina; Sillanpaeae, Mika; Heikkilae, Mikko; Leskelae, Markku

    2010-01-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), ξ-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH 2 OH·HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H 2 PtCl 6 to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  5. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

    Science.gov (United States)

    Liu, Wei; Repo, Eveliina; Heikkilä, Mikko; Leskelä, Markku; Sillanpää, Mika

    2010-10-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), ξ-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH2OH·HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H2PtCl6 to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  6. Current-voltage curves of atomic-sized transition metal contacts: An explanation of why Au is ohmic and Pt is not

    DEFF Research Database (Denmark)

    Nielsen, S.K.; Brandbyge, Mads; Hansen, K.

    2002-01-01

    We present an experimental study of current-voltage (I-V) curves on atomic-sized Au and Pt contacts formed under cryogenic vacuum (4.2 K). Whereas I-V curves for Au are almost Ohmic, the conductance G=I/V for Pt decreases with increasing voltage, resulting in distinct nonlinear I-V behavior...

  7. Enhanced electrocatalytic activity of pulse deposited Pt particles dispersed on PEDOT-modified Au electrode towards ethanol oxidation

    International Nuclear Information System (INIS)

    Mendoza, Maria Krisandra L.; Tongol, Bernard John V.

    2013-01-01

    Poly(3,4-ethylenedioxythiophene) (PEDOT)-modified Au electrodes were electrochemically prepared via potentiodynamic polymerization using 0.01 M EDOT and 0.10 M HClO 4 on a Au substrate at a potential range from 0.0 to 1.10 V (vs. Ag/AgCl). The PEDOT-modified AU electrode was electrochemically characterized in a monomer-free 0.10M HClO 4 electrolyte. Meanwhile, the surface morphology was probed using Scanning Electron Microscopy (SEM). Platinum particles dispersed on PEDOT-modified Au electrodes were prepared in two steps: (i) aqueous electropolymerization of EDOT and (ii) pulse deposition of platinum. Pulse deposition of Pt nanoparticles was carried out using the following optimized parameters: -30 mA/cm”2 of pulse current with 0.2 s on-time and 0.4 s off-time at 700 pulses. Electrocatalytic activity of the prepared Pt/PEDOT/Au electrode was evaluated towards ethanol oxidation using 1.0 M ethanol in 0.10 M H 2 SO 4 electrolyte solution from E = 0.0 V to E = 0.90 V (vs. Ag/AgCl) at a scan rate of 100 mV s”-“1. The CV profile of the prepared nanocomposite shows an anodic peak at E = +0.700V which is an indication of the presence of the platinum. Examination of the surface morphology of the Pt nanoparticles (Pt NPs)/PEDOT/Au-modified electrode revealed well-dispersed platinum particles on the polymer matrix with a diameter of less than 100 nm. Enhancement of the electrocatalytic activity towards ethanol oxidation was observed in pulse-deposited platinum particles compared to potentiodynamically-deposited platinum particles on PEDOT-modified Au electrode. (author)

  8. Sputter deposition on gas diffusion electrodes of Pt-Au nanoclusters for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Giorgi, L.; Giorgi, R.; Gagliardi, S.; Serra, E. [ENEA Casaccia Research Center, Rome (Italy). Physics Technologies and New Materials; Alvisi, M.; Signore, M.A. [ENEA Brindisi Research Center, Brindisi (Italy). Physics Technologies and New Materials

    2008-07-01

    Polymer electrolyte fuel cells (PEFCs) are suited for use in commercial electrical vehicle and electric power applications. The gas diffusion electrodes of PEFCs are catalyzed by the deposition of platinum (Pt) nanoparticles on carbon powder. The particles must be localized on the electrode surface in order to achieve high electrocatalyst utilization. This study discussed a method of preparing PEFC electrodes using sputter deposition of a Pt-gold (Au) alloy nanoparticles on carbon powders. The method was designed to improve electrode performance and catalyst utilization. The nano-sized alloy clusters were deposited on a gas diffusion electrode at room temperature. The deposits were then characterized using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) in order to examine the effect of the deposition technique on the nano-morphology and electrocatalytic performance of the electrode. Results of the study showed that the technique can be used in the large-scale manufacture of fuel cell electrodes. 3 refs., 1 fig.

  9. Stable structures and potential energy surface of the metallic clusters: Ni, Cu, Ag, Au, Pd, and Pt

    Science.gov (United States)

    Wu, Xia; Sun, Yan

    2017-06-01

    Metallic clusters have been widely studied due to their special electrical, optical, and catalytic properties. The many-body Gupta potential is applied to describe the interatomic interaction of Ni, Cu, Ag, Au, Pd, and Pt clusters, and their global minimal structures within 100 atoms are optimized using dynamic lattice searching (DLS) method. The configurational distribution of global minima is analyzed, and the geometrical difference among these clusters is demonstrated. Results show that the dominant motif of Ni and Cu clusters is the icosahedron, and in Ag and Au clusters the number of decahedra is slightly larger than that of the icosahedra. However, more face-centered cubic (fcc), stacking fault fcc, and amorphous structures are formed in Au clusters than in Ag clusters. Furthermore, the main motif of Pd and Pt clusters is the decahedron. In particular, Ni98 adopts a Leary tetrahedral motif, and Pt54 is a central vacant icosahedron. The difference related to the potential parameters of these metallic clusters is further investigated by energy analysis. Moreover, the potential energy surfaces (PES) of 38-atom metallic clusters is characterized in terms of conformational analysis. It was found that the sequence of the number of local minima on the PES from large to low is Ni, Cu, Ag, Pt, Pd, and Au.

  10. CO Sensing Performance of a Micro Thermoelectric Gas Sensor with AuPtPd/SnO₂ Catalyst and Effects of a Double Catalyst Structure with Pt/α-Al₂O₃.

    Science.gov (United States)

    Goto, Tomoyo; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2015-12-15

    The CO sensing properties of a micro thermoelectric gas sensor (micro-TGS) with a double AuPtPd/SnO₂ and Pt/α-Al₂O₃ catalyst were investigated. While several nanometer sized Pt and Pd particles were uniformly dispersed on SnO₂, the Au particles were aggregated as particles measuring >10 nm in diameter. In situ diffuse reflectance Fourier transform Infrared spectroscopy (DRIFT) analysis of the catalyst showed a CO adsorption peak on Pt and Pd, but no clear peak corresponding to the interaction between CO and Au was detected. Up to 200 °C, CO combustion was more temperature dependent than that of H₂, while H₂ combustion was activated by repeated exposure to H₂ gas during the periodic gas test. Selective CO sensing of the micro-TGS against H₂ was attempted using a double catalyst structure with 0.3-30 wt% Pt/α-Al₂O₃ as a counterpart combustion catalyst. The sensor output of the micro-TGS decreased with increasing Pt content in the Pt/α-Al₂O₃ catalyst, by cancelling out the combustion heat from the AuPtPd/SnO₂ catalyst. In addition, the AuPtPd/SnO₂ and 0.3 wt% Pt/α-Al₂O₃ double catalyst sensor showed good and selective CO detection. We therefore demonstrated that our micro-TGS with double catalyst structure is useful for controlling the gas selectivity of CO against H₂.

  11. Moessbauer effect of 197Au, 99Ru, 193Ir, 195Pt, and 151Eu diluted in hydrogenated palladium

    International Nuclear Information System (INIS)

    Iannarella, L.V.

    1977-01-01

    The study of hidrogenation in transition metals by Moessbauer spectroscopy of 197 Au, 99 Ru, 195 Pt, 193 Ir and 151 Eu diluted in palladium is presented. The measured parameters in the Moessbauer effect are sensitive to hydrogenation and allow to obtain information about phases of hydrogened systems, modifications of electronic structure and effects related to hydrogen mobility. The (Pd 1-x Ag x ) 0.99 Au 0.01 was also investigated by 197 Au Moessbauer effect. The relantioship between α and β phase Debye - Waller factors by Moessbauer effect was estimated. Source and absorber Moessbauer experiments to verifying isomer shift variation in function of hydrogen concentration were done. A proposal for description of the isomer shift of transition (or rare) impurities in transition matrices from state density of each system is presented. The contribution of H + ions bound to IS is discussed qualitatively. (M.C.K.) [pt

  12. Collinear Resonance Ionization Spectroscopy of Neutron-Deficient Francium Isotopes

    CERN Document Server

    Flanagan, K T; Ruiz, R F Garcia; Budincevic, I; Procter, T J; Fedosseev, V N; Lynch, K M; Cocolios, T E; Marsh, B A; Neyens, G; Strashnov, I; Stroke, H H; Rossel, R E; Heylen, H; Billowes, J; Rothe, S; Bissell, M L; Wendt, K D A; de Groote, R P; De Schepper, S

    2013-01-01

    The magnetic moments and isotope shifts of the neutron-deficient francium isotopes Fr202-205 were measured at ISOLDE-CERN with use of collinear resonance ionization spectroscopy. A production-to-detection efficiency of 1\\% was measured for Fr-202. The background from nonresonant and collisional ionization was maintained below one ion in 10(5) beam particles. Through a comparison of the measured charge radii with predictions from the spherical droplet model, it is concluded that the ground-state wave function remains spherical down to Fr-205, with a departure observed in Fr-203 (N = 116).

  13. Developing an aqueous approach for synthesizing Au and M@Au (M = Pd, CuPt) hybrid nanostars with plasmonic properties

    Science.gov (United States)

    Du, Jingshan; Yu, Junjie; Xiong, Yalin; Lin, Zhuoqing; Zhang, Hui; Yang, Deren

    Anisotropic Au nanoparticles show unique localized surface plasmon resonance (LSPR) properties, which make it attractive in optical, sensing, and biomedical applications. In this contribution, we report a general and facile strategy towards aqueous synthesis of Au and M@Au (M = Pd, CuPt) hybrid nanostars by reducing HAuCl4 with ethanolamine in the presence of cetyltrimethylammonium bromide (CTAB). According to electron microscopic observation and spectral monitoring, we found that the layered epitaxial growth mode (i.e., Frank-van der Merwe mechanism) contributes to the enlargement of the core, while, the random attachment of Au nanoclusters onto the cores accounts for the formation of the branches. Both of them are indispensable for the formation of the nanostars. The LSPR properties of the Au nanoparticles have been well investigated with morphology control via precursor amount and growth temperature. The Au nanostars showed improved surface-enhanced Raman spectroscopy (SERS) performance for rhodamine 6G due to their sharp edges and tips, which were therefore confirmed as good SERS substrate to detect trace amount of molecules.

  14. Spallation production of neutron deficient radioisotopes in North America

    International Nuclear Information System (INIS)

    Jamriska, D.J.; Peterson, E.J.; Carty, J.

    1997-01-01

    The United States Department of Energy produces a number of neutron deficient radioisotopes by high energy proton induced spallation reactions in accelerators at Los Alamos National Laboratory in New Mexico and Brookhaven National Laboratory in New York. Research isotopes are also recovered from targets irradiated at TRIUMF in British Columbia, Canada. The radioisotopes recovered are distributed for use in nuclear medicine, environmental research, physics research, and industry worldwide. In addition to the main product line of Sr-82 from either Mo or Rb targets, Cu-67 from ZnO targets, and Ge-68 from RbBr targets, these irradiation facilities also produce some unique isotopes in quantities not available from any other source such as Be-10, Al-26, Mg-28, Si-32, El-44, Fe-52, Gd-248, and Hg-194. We will describe the accelerator irradiation facilities at the Los Alamos and Brookhaven National Laboratories. The high level radiochemical processing facilities at Los Alamos and brief chemical processes from Los Alamos and Brookhaven will be described. Chemical separation techniques have been developed to recover the radioisotopes of interest in both high radiochemical purity and yield and at the same time trying to reduce or eliminate the generation of mixed waste. nearly 75 neutron deficient radioisotopes produced in spallation targets have been produced and distributed to researchers around the world since the inception of the program in 1974

  15. Skin Dose Equivalent Measurement from Neutron-Deficient Isotopes

    International Nuclear Information System (INIS)

    Hsu, Hsiao-Hua; Costigan, Steve A.; Romero, Leonard L.; Whicker, Jeffrey J.

    1997-12-01

    Neutron-deficient-isotopes decay via positron emission and/or electron capture often followed by x-ray, gamma-ray, and 0.511 MeV photons from positron annihilation. For cases of significant area and/or personnel contamination with these isotopes, determination of skin dose equivalent (SDE) is required by 10CFR835. For assessment of SDE, we evaluated the MICROSPEC-2(TM) system manufactured by Bubble Technology Industries of Canada which uses three different probes for dose measurement. We used two probes: (1) the X-probe which measures lower energy (4 - 120 keV) photon energy distributions and determines deep dose equivalent, SDE and dose equivalent to eyes, and (2) the B-probe which measures electron (positron) energy distributions, and determines skin dose equivalent. Also, the measured photon and beta spectra can be used to identify radioactive isotopes in the contaminated area. Measurements with several neutron-deficient sources showed that this system provided reasonably accurate SDE rate measurements when compared with calculated benchmark SDE rates with an average percent difference of 40%. Variations were expected because of differences between the assumed geometries used by MlCROSPEC-2 and the calculations when compared to the measurement conditions

  16. Skin Dose Equivalent Measurement from Neutron-Deficient Isotopes.

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Hsiao-Hua; Costigan, Steve A.; Romero, Leonard L.; Whicker, Jeffrey J.

    1997-12-31

    Neutron-deficient-isotopes decay via positron emission and/or electron capture often followed by x-ray, gamma-ray, and 0.511 MeV photons from positron annihilation. For cases of significant area and/or personnel contamination with these isotopes, determination of skin dose equivalent (SDE) is required by 10CFR835. For assessment of SDE, we evaluated the MICROSPEC-2(TM) system manufactured by Bubble Technology Industries of Canada which uses three different probes for dose measurement. We used two probes: (1) the X-probe which measures lower energy (4 - 120 keV) photon energy distributions and determines deep dose equivalent, SDE and dose equivalent to eyes, and (2) the B-probe which measures electron (positron) energy distributions, and determines skin dose equivalent. Also, the measured photon and beta spectra can be used to identify radioactive isotopes in the contaminated area. Measurements with several neutron-deficient sources showed that this system provided reasonably accurate SDE rate measurements when compared with calculated benchmark SDE rates with an average percent difference of 40%. Variations were expected because of differences between the assumed geometries used by MlCROSPEC-2 and the calculations when compared to the measurement conditions.

  17. CO Sensing Performance of a Micro Thermoelectric Gas Sensor with AuPtPd/SnO2 Catalyst and Effects of a Double Catalyst Structure with Pt/?-Al2O3

    OpenAIRE

    Goto, Tomoyo; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2015-01-01

    The CO sensing properties of a micro thermoelectric gas sensor (micro-TGS) with a double AuPtPd/SnO2 and Pt/α-Al2O3 catalyst were investigated. While several nanometer sized Pt and Pd particles were uniformly dispersed on SnO2, the Au particles were aggregated as particles measuring >10 nm in diameter. In situ diffuse reflectance Fourier transform Infrared spectroscopy (DRIFT) analysis of the catalyst showed a CO adsorption peak on Pt and Pd, but no clear peak corresponding to the interact...

  18. Ultrasensitive colorimetric immunoassay for hCG detection based on dual catalysis of Au@Pt core-shell nanoparticle functionalized by horseradish peroxidase

    Science.gov (United States)

    Wang, Weiguo; Zou, Yake; Yan, Jinwu; Liu, Jing; Chen, Huixiong; Li, Shan; Zhang, Lei

    2018-03-01

    In this paper, an ultrasensitive colorimetric biosensor for human chorionic gonadotrophin (hCG) detection was designed from bottom-up method based on the dual catalysis of the horseradish peroxidase (HRP) and Au@Pt nanoparticles (NPs) relative to H2O2-TEM system. HRP and monoclonal mouse anti-hCG antibody (β-submit, mAb1) were co-immobilized onto the Au@Pt NP surface to improve catalytic efficiency and specificity, which formed a dual functionalized Au@Pt-HRP probe with the mean size of 42.8 nm (D50). The colorimetric immunoassay was developed for the hCG detection, and the Au@Pt-HRP probe featured a higher sensitivity in the concentration range of 0.4-12.8 IU L- 1 with a low limit of detection (LOD) of 0.1 IU L- 1 compared with the LODs of 0.8 IU L- 1 for BA-ELISA and of 2.0 IU L- 1 for Au@Pt, which indicated that the Au@Pt-HRP probe possessed higher catalytic efficiency with 2.8-fold increase over Au@Pt and 33.8-fold increase over HRP. Also, the Au@Pt-HRP probe exhibited good precision and reproducibility, high specificity and acceptable accuracy with CV being less than 15%. The dual functionalized Au@Pt-HRP probe as a type of signal amplified method was firstly applied in the colorimetric immunoassay for the hCG detection.

  19. Au-Pt-Pd-U mineralization in the Coronation Hill-El Sherana region, NT

    International Nuclear Information System (INIS)

    Wyborn, L.

    1992-01-01

    In 1990 BMR's Minerals and Land Use program conducted an geochemical and geophysical survey to provide the best possible basis for estimating the resource potential of the Kakadu Conservation Zone. Combining the old and new data, an integrated model for the deposit types has been developed. Although differing in metal content, all mines and prospects of the Coronation Hill region share similar timing and structural controls, suggesting that they are related to one geochemical system. The presence or absence of U in the Au-Pt-Pd mineralisation appears related to geological differences, primarily in host-rock composition. U-bearing deposits are hosted mainly in carbonaceous shales, although some U is associated with chloritic zones. Deposits lacking U, best developed at Coronation Hill, occur in a broad range of host rocks, including quartz-feldspar porphyry, green tuffaceous shale, diorite, dolomite, and sedimentary breccias. Although seemingly diverse rock types, the common components of these U-poor host units are feldspar and/or carbonate. 1 tab., 3 figs

  20. Anisotropic spin-spin correlations in Mn1/X(111) (X= Pd, Pt, Ag, and Au)

    Science.gov (United States)

    Dos Santos Dias, M.; Staunton, J. B.; Deak, A.; Szunyogh, L.

    2011-02-01

    We present a finite-temperature theory of the anisotropic spin-spin correlations in magnetic metallic monolayers deposited on a suitable substrate. The spins are the local moments set up by the itinerant electrons, and the key concept is the relativistic disordered local moment state, which represents the paramagnetic state of a set of local moments. The spin-spin correlations between these local moments are then extracted using the linear-response formalism. The anisotropy is included in a fully relativistic treatment, based on the Dirac equation, and has a qualitative impact on noncollinear magnetic states by lifting their chiral degeneracy. The theory is applied to Mn monolayers on the hexagonal (111) surfaces of Pd, Pt, Ag, and Au. The presence of competing exchange interactions is highlighted by choosing different substrates, which favor either the row-wise antiferromagnetic state or the chiral triangular Néel state. We correlate the electronic structure with the magnetic properties by comparing filled with partially filled substrate d bands, and low versus high atomic number. The disagreement between theory and experiment for Mn1/Ag(111) is addressed, and the nature of the magnetic domains found experimentally is suggested to be chiral.

  1. Adsorption of Ni, Pd, Pt, Cu, Ag and Au on the Fe3O4(111) surface

    Science.gov (United States)

    Yu, Xiaohu; Tian, Xinxin; Wang, Shengguang

    2014-10-01

    The interaction of Group 10 and 11 transition metals with the magnetite (111) surface has been investigated using the GGA + U density functional theory and periodic slab surface models. It was found that these transition metals adsorb stronger on an oxygen-terminated magnetite (111) surface than on an iron-terminated surface. On an oxygen-terminated surface, the adsorption strength is in the order of Ni > Pt Cu > Pd > Ag Au. In contrast, the order on an iron-terminated surface is Ni > Pt Cu > Au > Pd Ag. The adsorption strength was found to correlate well with the average lengths of metal-oxygen bonds. The magnetite (111) surfaces largely modify the electronic structures of the transition metals. Compared to their density of states in bulk structures, the atomically adsorbed transition metals have narrower d bands, and their d-band centers are closer to the Fermi levels. This implies the higher activities of the atomically adsorbed transition metals.

  2. Spallation production of neutron deficient radioisotopes in North America

    Energy Technology Data Exchange (ETDEWEB)

    Jamriska, D.J.; Peterson, E.J. [Los Alamos National Lab., NM (United States); Carty, J. [Dept. of Energy, Germantown, MD (United States). Office of Isotope Production and Distribution

    1997-12-31

    The US Department of Energy produces a number of neutron deficient radioisotopes by high energy proton induced spallation reactions in accelerators at Los Alamos National Laboratory in New Mexico and Brookhaven National Laboratory in New York. Research isotopes are also recovered from targets irradiated at TRIUMF in British Columbia, Canada. The radioisotopes recovered are distributed for use in nuclear medicine, environmental research, physics research, and industry worldwide. In addition to the main product line of Sr-82 from either Mo or Rb targets, Cu-67 from ZnO targets, and Ge-68 and RbBr targets, these irradiation facilities also produce some unique isotopes in quantities not available from any other source such as Al-26, Mg-28, Si-32, Ti-44, Fe-52, Gd-148, and Hg-194. The authors will describe the accelerator irradiation facilities at the Los Alamos and Brookhaven National Laboratories. The high level radiochemical processing facilities at Los Alamos and brief chemical processes will be described.

  3. Spallation production of neutron deficient radioisotopes in North America

    International Nuclear Information System (INIS)

    Jamriska, D.J.; Peterson, E.J.; Carty, J.

    1997-01-01

    The US Department of Energy produces a number of neutron deficient radioisotopes by high energy proton induced spallation reactions in accelerators at Los Alamos National Laboratory in New Mexico and Brookhaven National Laboratory in New York. Research isotopes are also recovered from targets irradiated at TRIUMF in British Columbia, Canada. The radioisotopes recovered are distributed for use in nuclear medicine, environmental research, physics research, and industry worldwide. In addition to the main product line of Sr-82 from either Mo or Rb targets, Cu-67 from ZnO targets, and Ge-68 and RbBr targets, these irradiation facilities also produce some unique isotopes in quantities not available from any other source such as Al-26, Mg-28, Si-32, Ti-44, Fe-52, Gd-148, and Hg-194. The authors will describe the accelerator irradiation facilities at the Los Alamos and Brookhaven National Laboratories. The high level radiochemical processing facilities at Los Alamos and brief chemical processes will be described

  4. Spectroscopy of neutron-deficient nuclei around 36Ca

    International Nuclear Information System (INIS)

    Buerger, A.; Stanoiu, M.; Azaiez, F.; Bourgeois, Ch.; Franchoo, S.; Ibrahim, F.; Verney, D.; Dombradi, Zs.; Algora, A.; Fueloep, Zs.; Sohler, D.; Al-Khatib, A.; Bringel, P.; Engelhardt, C.; Huebel, H.; Bastin, B.; Benzoni, G.; Borcea, R.; Rotaru, F.; Sorlin, O.

    2006-01-01

    An experiment was performed to extend the knowledge of excited states in neutron-deficient Ca isotopes. In particular, excited states in 36Ca were searched for to allow for a comparison with its stable mirror nucleus, 36S. Secondary beams of 37Ca and 36Ca were produced by fragmentation of a primary 40Ca beam with an energy of 95 · A MeV on the SISSI target at GANIL. A variety of nuclei around 36Ca has been produced in a secondary Be target by neutron and proton-removal at beam energies around 61 · A MeV. The produced nuclei were identified using the spectrometer SPEG, and prompt γ rays were measured with the Chateau de Cristal. A preliminary value for the energy of the first 2+ state of 36Ca has been determined

  5. Mechanism of fission of neutron-deficient actinoids nuclides

    Energy Technology Data Exchange (ETDEWEB)

    Sueki, Keisuke; Nakahara, Hiromichi [Tokyo Metropolitan Univ., Hachioji (Japan). Faculty of Science; Tanase, Masakazu; Nagame, Yuichiro; Shinohara, Nobuo; Tsukada, Kazuaki

    1996-01-01

    A heavy ion reaction ({sup 19}F+{sup 209}Bi) is selected. The reaction produces neutron-deficient {sup 228}U which is compound nucleus with a pair of Rb(z=37) and Cs(Z=55). Energy dissipation problem of nucleus was studied by measuring the isotope distribution of two fissile nuclides. Bismuth metal evaporated on aluminium foil was irradiated by {sup 19}F with the incident energy of 105-128 MeV. We concluded from the results that the excess energy of reaction system obtained with increasing the incident energy is consumed by (1) light Rb much more than Cs and (2) about 60% of energy is given to two fission fragments and the rest 40% to the translational kinetic energy or unknown anomalous {gamma}-ray irradiation. (S.Y.)

  6. Ceramic Defects in Metal-Ceramic Fixed Dental Prostheses Made from Co-Cr and Au-Pt Alloys: A Retrospective Study.

    Science.gov (United States)

    Mikeli, Aikaterini; Boening, Klaus W; Lißke, Benjamin

    2015-01-01

    Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations. In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance. Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance. Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations.

  7. Beta-decay measurements of neutron-deficient cesium isotopes

    International Nuclear Information System (INIS)

    Parry, R.F.

    1983-03-01

    Beta decay endpoint energy measurements of the neutron deficient cesium isotopes were done using an energy spectrum shape fitting technique. This was a departure from the typical method of endpoint energy analysis, the Fermi-Kurie plot. A discussion of the shape fitting procedure and its improved features are discussed. These beta endpoint measurements have led to total decay energies (Q/sub EC/) of the neutron deficient 119 123 Cs isotopes. The total decay energies of /sup 122m/Cs (Q/sub EC/ = 6.95 +- 0.25 MeV) and 119 Cs (Q/sub EC/ = 6.26 +- 0.29 MeV) were new measurements. The total decay energies of 123 Cs (Q/sub EC/ = 4.05 +- 0.18 MeV), /sup 122g/Cs (Q/sub EC/ = 7.05 +- 0.18 MeV), 121 Cs (Q/sub EC/ = 5.21 +- 0.22 MeV), and 120 Cs (Q/sub EC/ = 7.38 +- 0.23 MeV) were measurements with significantly improved uncertainties as compared to the literature. Further, a combination of the energy levels derived from previous literature gamma-gamma coincident measurements and the experimental beta-coincident gamma decay energies has supported an improved level scheme for 121 Xe and the proposal of three new energy levels in 119 Xe. Comparison of the experimental cesium mass excesses (determined with our Q/sub EC/ values and known xenon mass excesses) with both the literature and theoretical predicted values showed general agreement except for 120 Cs. Possible explanations for this deviation are discussed

  8. Folic acid bio-inspired route for facile synthesis of AuPt nanodendrites as enhanced electrocatalysts for methanol and ethanol oxidation reactions

    Science.gov (United States)

    Wang, Ai-Jun; Ju, Ke-Jian; Zhang, Qian-Li; Song, Pei; Wei, Jie; Feng, Jiu-Ju

    2016-09-01

    Folic acid (FA), as an important biomolecule in cell division and growth, is firstly employed as the structure director and stabilizing agent for controlled synthesis of uniform Au65Pt35 nanodendrites (NDs) by a one-pot wet-chemical bio-inspired route at room temperature. No pre-seed, template, organic solvent, polymer, surfactant or complex instrument is involved. The products are mainly characterized by transmission electron microscopy (TEM), high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray diffraction (XRD), and X-Ray photoelectron spectroscopy (XPS). The architectures have enlarged electrochemically active surface area (60.6 m2 gPt-1), enhanced catalytic activity and durability for methanol and ethanol oxidation in contrast with commercial Pt black and the other AuPt alloys by tuning the molar ratios of Au to Pt (e.g., Au31Pt69 and Au82Pt18 nanoparticles). This strategy would be applied to fabricate other bimetallic nanocatalysts in fuel cells.

  9. Investigation of oxygen reduction and methanol oxidation reaction activity of PtAu nano-alloy on surface modified porous hybrid nanocarbon supports

    Science.gov (United States)

    Parambath Vinayan, Bhaghavathi; Nagar, Rupali; Ramaprabhu, Sundara

    2016-09-01

    We investigate the electrocatalytic activity of PtAu alloy nanoparticles supported on various chemically modified carbon morphologies towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The surface-modification of graphene nanosheets (f-G), multi-walled carbon nanotubes (f-MWNTs) and (graphene nanosheets-carbon nanotubes) hybrid support (f-G-MWNTs) were carried out by soft functionalization method using a cationic polyelectrolyte poly-(diallyldimethyl ammonium chloride). The Pt and PtAu alloy nanoparticles were dispersed over chemically modified carbon supports by sodium-borohydride assisted modified polyol reduction method. The electrochemical performance of all electrocatalysts were studied by half- and full-cell proton exchange membrane fuel cell (PEMFC) measurements and PtAu/f-G-MWNTs catalyst comparatively yielded the best catalytic performance. PEMFC full cell measurements of PtAu/f-G-MWNTs cathode electrocatalyst yield a maximum power density of 319 mW cm-2 at 60 °C without any back pressure,which is 2.1 times higher than that of cathode electrocatalyst Pt on graphene support. The high ORR and MOR activity of PtAu/f-G-MWNTs electrocatalyst is due to the alloying effect and inherent beneficial properties of porous hybrid nanocarbon support.

  10. CO Sensing Performance of a Micro Thermoelectric Gas Sensor with AuPtPd/SnO2 Catalyst and Effects of a Double Catalyst Structure with Pt/α-Al2O3

    Directory of Open Access Journals (Sweden)

    Tomoyo Goto

    2015-12-01

    Full Text Available The CO sensing properties of a micro thermoelectric gas sensor (micro-TGS with a double AuPtPd/SnO2 and Pt/α-Al2O3 catalyst were investigated. While several nanometer sized Pt and Pd particles were uniformly dispersed on SnO2, the Au particles were aggregated as particles measuring >10 nm in diameter. In situ diffuse reflectance Fourier transform Infrared spectroscopy (DRIFT analysis of the catalyst showed a CO adsorption peak on Pt and Pd, but no clear peak corresponding to the interaction between CO and Au was detected. Up to 200 °C, CO combustion was more temperature dependent than that of H2, while H2 combustion was activated by repeated exposure to H2 gas during the periodic gas test. Selective CO sensing of the micro-TGS against H2 was attempted using a double catalyst structure with 0.3–30 wt% Pt/α-Al2O3 as a counterpart combustion catalyst. The sensor output of the micro-TGS decreased with increasing Pt content in the Pt/α-Al2O3 catalyst, by cancelling out the combustion heat from the AuPtPd/SnO2 catalyst. In addition, the AuPtPd/SnO2 and 0.3 wt% Pt/α-Al2O3 double catalyst sensor showed good and selective CO detection. We therefore demonstrated that our micro-TGS with double catalyst structure is useful for controlling the gas selectivity of CO against H2.

  11. CO Sensing Performance of a Micro Thermoelectric Gas Sensor with AuPtPd/SnO2 Catalyst and Effects of a Double Catalyst Structure with Pt/α-Al2O3

    Science.gov (United States)

    Goto, Tomoyo; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2015-01-01

    The CO sensing properties of a micro thermoelectric gas sensor (micro-TGS) with a double AuPtPd/SnO2 and Pt/α-Al2O3 catalyst were investigated. While several nanometer sized Pt and Pd particles were uniformly dispersed on SnO2, the Au particles were aggregated as particles measuring >10 nm in diameter. In situ diffuse reflectance Fourier transform Infrared spectroscopy (DRIFT) analysis of the catalyst showed a CO adsorption peak on Pt and Pd, but no clear peak corresponding to the interaction between CO and Au was detected. Up to 200 °C, CO combustion was more temperature dependent than that of H2, while H2 combustion was activated by repeated exposure to H2 gas during the periodic gas test. Selective CO sensing of the micro-TGS against H2 was attempted using a double catalyst structure with 0.3–30 wt% Pt/α-Al2O3 as a counterpart combustion catalyst. The sensor output of the micro-TGS decreased with increasing Pt content in the Pt/α-Al2O3 catalyst, by cancelling out the combustion heat from the AuPtPd/SnO2 catalyst. In addition, the AuPtPd/SnO2 and 0.3 wt% Pt/α-Al2O3 double catalyst sensor showed good and selective CO detection. We therefore demonstrated that our micro-TGS with double catalyst structure is useful for controlling the gas selectivity of CO against H2. PMID:26694397

  12. Construction of Au@Pt core—satellite nanoparticles based on in-situ reduction of polymeric ionic liquid protected gold nanoparticles

    Science.gov (United States)

    Wu, Wenlan; Li, Junbo; Zou, Sheng; Guo, Jinwu; Zhou, Huiyun

    2017-03-01

    A method of in-situ reduction to prepare Au@Pt core-satellite nanoparticles (NPs) is described by using Au NPs coating poly[1-methyl 3-(2-methacryloyloxy propylimidazolium bromine)] (PMMPImB-@-Au NPs) as the template. After electrostatic complex chloroplatinic acid with PMMPImB shell, the composite NP was directly reduced with N2H4 to produce Au@Pt core-satellite NPs. The characterization of composite and core-satellite NPs under different amounts of chloroplatinic acid were studied by DLS, UV-vis absorption spectrum and TEM. The satellite Pt NPs with a small size ( 2 nm) dotted around Au core, and the resulting Au@Pt core-satellite NPs showed a red-shift surface plasmon resonance (SPR) and a good dispersion due to effectively electrostatic repulsion providing by the polymeric ionic liquid (PIL) shell. Finally, Au@Pt core-satellite NPs exhibit an enhanced catalytic activity and cycled catalytic capability for the reduction of p-nitrophenol with NaBH4.

  13. Azimuthal anisotropy of charged and identified high pT hadrons in Au+Au collisions at RHIC

    International Nuclear Information System (INIS)

    Filimonov, K.; STAR Collaboration; STAR-RICH Collaboration

    2002-01-01

    We report new results on v 2 (p T ) for Au+Au collisions at √(S NN ) = 200 GeV for charged hadrons, pions, kaons,(anti)protons, K s 0 , and Lambda. The analysis is extended to p T = 12 GeV/c for charged hadrons and p T = 4 GeV/c for identified particles. A comparison of the azimuthal anisotropy of charged hadrons measured at sqrt √(s NN ) 130 and 200 GeV is presented. The p T -dependence of baryon versus meson elliptic flow is discussed

  14. Study of the visible light activity of Pt and Au-TiO2 photocatalysts in organic pollutants degradation

    Directory of Open Access Journals (Sweden)

    Jairo Antonio Cubillos-Lobo

    2017-01-01

    Full Text Available Los fotocatalizadores Pt-TiO2 y Au-TiO2 se prepararon por fotodeposición del metal noble sobre el TiO2 sulfatado. Se encontró que las propiedades ópticas, el estado de oxidación y el tamaño de partícula de las especies metálicas (Pt o Au juegan un papel fundamental en la actividad fotocatalítica del TiO2 bajo luz visible. La actividad fotocatalítica del TiO2 en la degradación de fenol y naranja de metilo aumentó significativamente a través de los tratamientos de sulfatación y metalización de este óxido. La más alta velocidad de degradación bajo luz UV-Visible y visible, se alcanzó usando el fotocatalizador Pt-S-TiO2; esto se debe principalmente a la modificación de las propiedades ópticas del TiO2 inducidas por la platinización, también a la buena distribución y al pequeño tamaño de las partículas de Pt. Se encontró, además, que este catalizador presenta una buena estabilidad después de dos ciclos de reacción en la degradación de fenol bajo luz UV-Visible. El fotocatalizador Pt-S-TiO2 fue activo también bajo luz solar directa y bajo las condiciones medioambientales de la ciudad de Tunja (Boyacá, Colombia.

  15. Sintered Cr/Pt and Ni/Au ohmic contacts to B{sub 12}P{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Frye, Clint D., E-mail: frye6@llnl.gov [Lawrence Livermore National Laboratory, Livermore, California 94550 and Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506 (United States); Kucheyev, Sergei O.; Voss, Lars F.; Conway, Adam M.; Shao, Qinghui; Nikolić, Rebecca J., E-mail: nikolic1@llnl.gov [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Edgar, James H. [Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506 (United States)

    2015-05-15

    Icosahedral boron phosphide (B{sub 12}P{sub 2}) is a wide-bandgap semiconductor possessing interesting properties such as high hardness, chemical inertness, and the reported ability to self-heal from irradiation by high energy electrons. Here, the authors developed Cr/Pt and Ni/Au ohmic contacts to epitaxially grown B{sub 12}P{sub 2} for materials characterization and electronic device development. Cr/Pt contacts became ohmic after annealing at 700 °C for 30 s with a specific contact resistance of 2 × 10{sup −4} Ω cm{sup 2}, as measured by the linear transfer length method. Ni/Au contacts were ohmic prior to any annealing, and their minimum specific contact resistance was ∼l–4 × 10{sup −4} Ω cm{sup 2} after annealing over the temperature range of 500–800 °C. Rutherford backscattering spectrometry revealed a strong reaction and intermixing between Cr/Pt and B{sub 12}P{sub 2} at 700 °C and a reaction layer between Ni and B{sub 12}P{sub 2} thinner than ∼25 nm at 500 °C.

  16. Dicationic ionic liquid mediated fabrication of Au@Pt nanoparticles supported on reduced graphene oxide with highly catalytic activity for oxygen reduction and hydrogen evolution

    Science.gov (United States)

    Shi, Ya-Cheng; Chen, Sai-Sai; Feng, Jiu-Ju; Lin, Xiao-Xiao; Wang, Weiping; Wang, Ai-Jun

    2018-05-01

    Ionic liquids as templates or directing agents have attracted great attention for shaping-modulated synthesis of advanced nanomaterials. In this work, reduced graphene oxide supported uniform core-shell Au@Pt nanoparticles (Au@Pt NPs/rGO) were fabricated by a simple one-pot aqueous approach, using N-methylimidazolium-based dicationic ionic liquid (1,1-bis(3-methylimadazoilum-1-yl)butylene bromide, [C4(Mim)2]2Br) as the shape-directing agent. The morphology evolution, structural information and formation mechanism of Au@Pt NPs anchored on rGO were investigated by a series of characterization techniques. The obtained nanocomposites displayed superior electrocatalytic features toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) compared with commercial Pt/C catalyst. This approach provides a novel route for facile synthesis of nanocatalysts in fuel cells.

  17. UV-Vis-Induced Degradation of Phenol over Magnetic Photocatalysts Modified with Pt, Pd, Cu and Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    Izabela Wysocka

    2018-01-01

    Full Text Available The combination of TiO2 photocatalyst and magnetic oxide nanoparticles enhances the separation and recoverable properties of nanosized TiO2 photocatalyst. Metal-modified (Me = Pd, Au, Pt, Cu TiO2/SiO2@Fe3O4 nanocomposites were prepared by an ultrasonic-assisted sol-gel method. All prepared samples were characterized by X-ray powder diffraction (XRD analysis, Brunauer-Emmett-Teller (BET method, X-ray photoelectron spectroscopy (XPS, scanning transmission electron microscopy (STEM, Mott-Schottky analysis and photoluminescence spectroscopy (PL. Phenol oxidation pathways of magnetic photocatalysts modified with Pt, Pd, Cu and Au nanoparticles proceeded by generation of reactive oxygen species, which oxidized phenol to benzoquinone, hydroquinone and catechol. Benzoquinone and maleic acid were products, which were determined in the hydroquinone oxidation pathway. The highest mineralization rate was observed for Pd-TiO2/SiO2@Fe3O4 and Cu-TiO2/SiO2@Fe3O4 photocatalysts, which produced the highest concentration of catechol during photocatalytic reaction. For Pt-TiO2/SiO2@Fe3O4 nanocomposite, a lack of catechol after 60 min of irradiation resulted in low mineralization rate (CO2 formation. It is proposed that the enhanced photocatalytic activity of palladium and copper-modified photocatalysts is related to an increase in the amount of adsorption sites and efficient charge carrier separation, whereas the keto-enol tautomeric equilibrium retards the rate of phenol photomineralization on Au-TiO2/SiO2@Fe3O4. The magnetization hysteresis loop indicated that the obtained hybrid photocatalyst showed magnetic properties and therefore could be easily separated after treatment process.

  18. Facile Photochemical Synthesis of Au/Pt/g-C3N4 with Plasmon-Enhanced Photocatalytic Activity for Antibiotic Degradation.

    Science.gov (United States)

    Xue, Jinjuan; Ma, Shuaishuai; Zhou, Yuming; Zhang, Zewu; He, Man

    2015-05-13

    A novel plasmonic photocatalyst, Au/Pt/g-C3N4, was prepared by a facile calcination-photodeposition technique. The samples were characterized by X-ray diffraction, energy-dispersive spectroscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectroscopy, and the results demonstrated that the Au and Pt nanoparticles (7-15 nm) were well-dispersed on the surfaces of g-C3N4. The Au/Pt codecorated g-C3N4 heterostructure displayed enhanced photocatalytic activity for antibiotic tetracycline hydrochloride (TC-HCl) degradation, and the degradation rate was 3.4 times higher than that of pure g-C3N4 under visible light irradiation. The enhancement of photocatalytic activity could be attributed to the surface plasmon resonance effect of Au and electron-sink function of Pt nanoparticles, which improve the optical absorption property and photogenerated charge carriers separation of g-C3N4, synergistically facilitating the photocatalysis process. Finally, a possible photocatalytic mechanism for degrading TC-HCl by Au/Pt/g-C3N4 heterostructure was tentatively proposed.

  19. Electrochemical immunosensor for detecting typical bladder cancer biomarker based on reduced graphene oxide-tetraethylene pentamine and trimetallic AuPdPt nanoparticles.

    Science.gov (United States)

    Ma, Hongmin; Zhang, Xiaoyue; Li, Xiaojian; Li, Rongxia; Du, Bin; Wei, Qin

    2015-10-01

    A highly sensitive electrochemical immunosensor for detection of typical bladder cancer biomarker-nuclear matrix protein 22 (NMP22) was developed by using reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) and trimetallic AuPdPt nanoparticles (NPs). rGO-TEPA was used as the ideal material for signal amplification and AuPdPt NPs immobilization due to its excellent conductivity and large surface area. An effective platform was constructed for antibodies anchoring by using AuPdPt NPs, which kept the antibodies' high stability and bioactivity. Moreover, AuPdPt NPs could accelerate the electron transfer and enhance the signal response, which assisted by the synergistic effect of the three different metals (Au, Pd and Pt). The proposed immunosensor showed satisfied performance such as simple fabrication, low detection limits (0.01 U/mL), wide linear range (from 0.040 to 20 U/mL), short analysis time (2 min), high stability and selectivity in the detection of NMP22. Furthermore, the proposed immunosensor was employed to test real urine samples with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Au/PtO nanoparticle-modified g-C3N4 for plasmon-enhanced photocatalytic hydrogen evolution under visible light.

    Science.gov (United States)

    Jiang, Jing; Yu, Jiaguo; Cao, Shaowen

    2016-01-01

    Photocatalytic hydrogen evolution under visible light is of great potential for renewable energy development. In this work, unalloyed Au/PtO nanoparticle (NP) co-modified graphitic carbon nitride (g-C3N4) photocatalyst is fabricated through a simple photodeposition method. The obtained g-C3N4 composites with co-existed Au and PtO cocatalysts exhibit a considerable enhancement in the photocatalytic hydrogen evolution activity and possess good stability during cycling experiments. The optimal Au-PtO/g-C3N4 photocatalyst shows a H2 production rate of 16.9 μmol h(-1), which exceeds that of PtO/g-C3N4 and Au/g-C3N4 by a factor of 1.5 and 10.6, respectively. Further characterizations demonstrate that the synergetic action of electron-sink and catalytic effects of PtO along with surface plasmon resonance (SPR) effect of Au NPs, greatly improves the photocatalytic performance of g-C3N4 under visible light. Our study should bring in new insight into the design of effective g-C3N4-based photocatalysts for solar-to-fuel conversion. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Study of the oxidation effects on isothermal solidification based high temperature stable Pt/In/Au and Pt/In/Ag thick film interconnections on LTCC substrate

    Science.gov (United States)

    Kumar, Duguta Suresh; Suri, Nikhil; Khanna, P. K.; Sharma, R. P.

    2016-03-01

    The objective of the presented paper is to determine the oxidized phase compositions of indium lead-free solders during solidification at 190 ° C under room environment with the help of X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDX). Many lead-free solders alloys available oxidizes and have poor wetting properties. The oxidation of pure indium solder foil, Au, Pt, and Ag alloys were identified and investigated, in the process of isothermal solidification based solder joints construction at room environment and humidity. Both EDX and XRD characterization techniques were performed to trace out the amount of oxide levels and variety of oxide formations at solder interface respectively. The paper also aims to report the isothermal solidification technique to provide interconnections to pads on Low temperature co-fired ceramic (LTCC) substrate. It also elaborates advantages of isothermal solidification over the other methods of interconnection. Scanning electron microscope (SEM) used to identify the oxidized spots on the surface of Pt, Ag substrates and In solder. The identified oxides were reported.

  2. Study of the oxidation effects on isothermal solidification based high temperature stable Pt/In/Au and Pt/In/Ag thick film interconnections on LTCC substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Duguta Suresh, E-mail: sureshduguta@gmail.com; Khanna, P. K., E-mail: pkk@ceeri.ernet.in [CSIR – Central Electronics Engineering Research Institute, Pilani (India); Academy of Scientific and Innovative Research, New Delhi (India); Suri, Nikhil, E-mail: surinikhil@rediffmail.com [CSIR – Central Electronics Engineering Research Institute, Pilani (India); Sharma, R. P., E-mail: rpsbtti@yahoo.com [BK Birla Institute of Engineering & Technology, Pilani (India)

    2016-03-09

    The objective of the presented paper is to determine the oxidized phase compositions of indium lead-free solders during solidification at 190 ° C under room environment with the help of X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDX). Many lead-free solders alloys available oxidizes and have poor wetting properties. The oxidation of pure indium solder foil, Au, Pt, and Ag alloys were identified and investigated, in the process of isothermal solidification based solder joints construction at room environment and humidity. Both EDX and XRD characterization techniques were performed to trace out the amount of oxide levels and variety of oxide formations at solder interface respectively. The paper also aims to report the isothermal solidification technique to provide interconnections to pads on Low temperature co-fired ceramic (LTCC) substrate. It also elaborates advantages of isothermal solidification over the other methods of interconnection. Scanning electron microscope (SEM) used to identify the oxidized spots on the surface of Pt, Ag substrates and In solder. The identified oxides were reported.

  3. Electrochemical Co-Reduction Synthesis of AuPt Bimetallic Nanoparticles-Graphene Nanocomposites for Selective Detection of Dopamine in the Presence of Ascorbic Acid and Uric Acid

    Directory of Open Access Journals (Sweden)

    Zongya Zhao

    2015-07-01

    Full Text Available In this paper, AuPt bimetallic nanoparticles-graphene nanocomposites were obtained by electrochemical co-reduction of graphene oxide (GO, HAuCl4 and H2PtCl6. The as-prepared AuPt bimetallic nanoparticles-graphene nanocomposites were characterized by scanning electron microscopy (SEM, electrochemical impedance spectroscopy (EIS and other electrochemical methods. The morphology and composition of the nanocomposite could be easily controlled by adjusting the HAuCl4/H2PtCl6 concentration ratio. The electrochemical experiments showed that when the concentration ratio of HAuCl4/H2PtCl6 was 1:1, the obtained AuPt bimetallic nanoparticles-graphene nanocomposite (denoted as Au1Pt1NPs-GR possessed the highest electrocatalytic activity toward dopamine (DA. As such, Au1Pt1NPs-GR nanocomposites were used to detect DA in the presence of ascorbic acid (AA and uric acid (UA using the differential pulse voltammetry (DPV technique and on the modified electrode, there were three separate DPV oxidation peaks with the peak potential separations of 177 mV, 130 mV and 307 mV for DA and AA, DA and UA, AA and UA, respectively. The linear range of the constructed DA sensor was from 1.6 μM to 39.7 μM with a detection limit of 0.1 μM (S/N = 3. The obtained DA sensor with good stability, high reproducibility and excellent selectivity made it possible to detect DA in human urine samples.

  4. X-ray fluorescence determination of Au, Pd and Pt from chloride solutions after preconcentration on cellulose filters

    International Nuclear Information System (INIS)

    Gordeeva, V.P.; Glazkova, S.V.; Tsysin, G.I.; Ivanov, V.M.; Zolotov, Yu. A.

    2003-01-01

    The aim of this work was synthesis of new sorption cellulose filters for dynamic preconcentration of Au, Pd and Pt from chloride solutions and subsequent XRF determination of these elements on the filters. New filters were prepared by impregnation of a filter paper with solution of tri-n-octylamine and paraffin in hexane (TOA-filters). The effect of paraffin and TOA concentration in hexane on a content of nitrogen in a filter was studied. It was found that Au(III), Pd(II) and Pt(IV) were quantitatively recovered on the TOA-filters (filtering surface diameter of 23 mm, thickness of 0.15 mm) from 0.5 - 1 M HCl at a flow rates of 2-5 ml min-1 from 10-100 ml of solution. The mathematical model of sorption dynamics was offered for the estimation of potential possibilities of new impregnated sorbents and for the evaluation of optimum dynamic conditions allowing to achieve of maximum concentration efficiency (CE max ). The elements were determined directly on the filters by XRF spectrometer. Palladium was also determined on the TOA-filters after formation of coloured compounds of metal with 4-(2-pyridylazo)resorcinol (PAR) by diffuse reflectance spectroscopy with the calculation of calorimetric characteristics and using test-scale. (authors)

  5. Tunable thermodynamic stability of Au-CuPt core-shell trimetallic nanoparticles by controlling the alloy composition: insights from atomistic simulations.

    Science.gov (United States)

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua; Sun, Shi-Gang

    2014-11-07

    A microscopic understanding of the thermal stability of metallic core-shell nanoparticles is of importance for their synthesis and ultimately application in catalysis. In this article, molecular dynamics simulations have been employed to investigate the thermodynamic evolution of Au-CuPt core-shell trimetallic nanoparticles with various Cu/Pt ratios during heating processes. Our results show that the thermodynamic stability of these nanoparticles is remarkably enhanced upon rising Pt compositions in the CuPt shell. The melting of all the nanoparticles initiates at surface and gradually spreads into the core. Due to the lattice mismatch among Au, Cu and Pt, stacking faults have been observed in the shell and their numbers are associated with the Cu/Pt ratios. With the increasing temperature, they have reduced continuously for the Cu-dominated shell while more stacking faults have been produced for the Pt-dominated shell because of the significantly different thermal expansion coefficients of the three metals. Beyond the overall melting, all nanoparticles transform into a trimetallic mixing alloy coated by an Au-dominated surface. This work provides a fundamental perspective on the thermodynamic behaviors of trimetallic, even multimetallic, nanoparticles at the atomistic level, indicating that controlling the alloy composition is an effective strategy to realize tunable thermal stability of metallic nanocatalysts.

  6. Synthesis and characterization of FePt/Au core-shell nanoparticles

    International Nuclear Information System (INIS)

    Presa, P. de la; Multigner, M.; Morales, M.P.; Rueda, T.; Fernandez-Pinel, E.; Hernando, A.

    2007-01-01

    In this work, the structural and magnetic properties of the gold-coated FePt nanoparticles synthesized from high-temperature solution phase are presented. The amount of gold was optimized to obtain most of the FePt particles coated. The particle diameter increases from 4 to 10 nm as observed by TEM. The magnetic properties are largely affected by the coating. At low temperature, the coercive field Hc of the coated nanoparticles decreases about three times respect to the uncoated and the blocking temperature reduces to the half. The changes of the magnetic behavior are discussed in terms of the effect of the gold atoms at the FePt core surface

  7. A sensitive sandwich-type immunosensor for the detection of galectin-3 based on N-GNRs-Fe-MOFs@AuNPs nanocomposites and a novel AuPt-methylene blue nanorod.

    Science.gov (United States)

    Tang, Zhiyong; He, Junlin; Chen, Jun; Niu, Yazhen; Zhao, Yilin; Zhang, Yuchan; Yu, Chao

    2018-03-15

    We are presenting an electrochemical immunosensor for the determination of Galectin-3 (Gal-3), a biomarker of heart failure. A glassy carbon electrode (GCE) was modified with a film of a composite made from the N-doped graphene nanoribbons immobilized Fe-based-Metal-organic frameworks deposited with Au nanoparticles (N-GNRs-Fe-MOFs@AuNPs). Primary antibody against Gal-3 (Gal-3-Ab 1 ) was immobilized on the Au nanoparticles on the surface of the modified GCE which then was blocked with bovine serum albumin. Signal amplification is crucial for obtaining low detection limits in biosensors. Here, a relatively simple and ultrasensitive sandwich-type electrochemical immunosensor based on novel signal generation and amplification was developed for the determination of Gal-3. A kind of novel redox-active species, AuPt-Methylene blue (MB) (AuPt-MB) nanocomposites, was synthesized by a one-pot method for the first time. Wherein, MB as a kind of the electron transfer mediators in an amperometric biosensor is responsible for electron production and signal amplification. The rod-like AuPt-MB nanohybrids displayed uniform morphology and good electrochemical activity and can combine with the second antibodies against Gal-3 (Gal-3-Ab 2 ). And the AuPt-MB-Ab 2 coupled with the N-GNRs-Fe-MOFs@AuNPs-Ab 1 to form the sandwich type format that can greatly enhance the biosensor's sensitivity. Under optimal conditions, the designed immunosensor exhibited a linear concentration range from 100fgmL -1 to 50ngmL -1 , with a low detection limit of 33.33fgmL -1 (S/N = 3) for Gal-3 in spiked serum. Additionally, the designed immunosensor showed acceptable selectivity, reproducibility and stability. The satisfactory results in analyzing human serum samples indicated potential application promising in monitoring biomarkers. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Study of Neutron-Deficient $^{202-205}$Fr Isotopes with Collinear Resonance Ionization Spectroscopy

    CERN Document Server

    De Schepper, Stijn; Cocolios, Thomas; Budincevic, Ivan

    The scope of this master’s thesis is the study of neutron-deficient $^{202−205}$Fr isotopes. These isotopes are inside the neutron-deficient lead region, a region that has shown evidence of shape coexistence. For this thesis, this discussion is limited to the phenomenon where a low lying excited state has a different shape than the ground state. Shape coexistence is caused by intruder states. These are single-particle Shell Model states that are perturbed in energy due to the interaction with a deformed core. In the neutron-deficient lead region the main proton intruder orbit is the 3s$_{1/2}$orbit. When going towards more neutron-deficient isotopes, deformation increases. The $\\pi3s_{1/2}$orbit will rise in energy and will eventually become the ground state in odd- A bismuth (Z=83) isotopes. It is also observed in odd-A astatine (Z=85) isotopes, already in less neutron-deficient nuclei. The same phenomenon is expected to be present francium (Z=87) isotopes already at $^{199}$Fr. Although it is currently ...

  9. H2production by the photocatalytic reforming of cellulose and raw biomass using Ni, Pd, Pt and Au on titania.

    Science.gov (United States)

    Caravaca, A; Jones, W; Hardacre, C; Bowker, M

    2016-07-01

    Here, we report a method for sustainable hydrogen production using sunlight and biomass. It is shown that cellulose can be photoreformed to produce hydrogen, even in solid form, by use of metal-loaded titania photocatalysts. The experiments performed verified that the process is enabled by initial hydrolysis via glucose, which itself is shown to be efficiently converted to produce hydrogen by photocatalysis. Importantly, it is shown that not only precious metals such as Pt, Pd and Au can be used as the metal component, but also much more economic and less environmentally damaging Ni is effective. Even more importantly, we show for the first time, to the best our knowledge, that fescue grass as raw biomass can be effective for hydrogen production without significant pre-treatment. This provides additional benefits for the efficiency of biomass hydrogen production, because fewer processing steps for the raw material are required than in the production of purer forms of cellulose, for example.

  10. Ground-state properties of ordered, partially ordered, and random Cu-Au and Ni-Pt alloys

    DEFF Research Database (Denmark)

    Ruban, Andrei; Abrikosov, I. A.; Skriver, Hans Lomholt

    1995-01-01

    We have studied the ground-state properties of ordered, partially ordered, and random Cu-Au and Ni-Pt alloys at the stoichiometric 1/4, 1/2, and 3/4 compositions in the framework of the multisublattice single-site (SS) coherent potential approximation (CPA). Charge-transfer effects in the random ...... for the ordered alloys are in good agreement with experimental data. For all the alloys the calculated ordering energy and the equilibrium lattices parameters are found to be almost exact quadratic functions of the long-range-order parameter....... and the partially ordered alloys are included in the screened impurity model. The prefactor in the Madelung energy is determined by the requirement that the total energy obtained in direct SS CPA calculations should equal the total energy given by the Connolly-Williams expansion based on Green’s function...

  11. Temperature dependence of CO desorption kinetics at a novel Pt-on-Au/C PEM fuel cell anode

    DEFF Research Database (Denmark)

    Pitois, A.; Pilenga, A.; Pfrang, A.

    2010-01-01

    techniques. The temperature dependence of the CO desorption process on this system has been investigated using isotopic exchange experiments. The CO desorption kinetics have been studied as a function of temperature and flow rate. Desorption rate constants have been measured for a temperature range between......A Pt-on-Au/C fuel cell anode catalyst has been obtained by electrochemical deposition of platinum on carbon-supported gold nanoparticles. Its composition, structure and nanoparticle size distribution have been characterised before and after the desorption experiments using microstructural......-modified catalysts, the interactions between underlayer and overlayer materials are worthy of consideration, since they can significantly modify the intrinsic properties of the active sites. The kinetics of the CO desorption process have been discussed with regard to the CO tolerance issue at the PEM fuel cell anode....

  12. Self-consistent linear-muffin-tin-orbitals coherent-potential technique for bulk and surface calculations: Cu-Ni, Ag-Pd, and Au-Pt random alloys

    DEFF Research Database (Denmark)

    Abrikosov, I. A.; Skriver, Hans Lomholt

    1993-01-01

    energies and work functions for three fcc-based alloys (Cu-Ni, Ag-Pd, and Au-Pt) over the complete concentration range. The calculated mixing enthalpies for the Ag-Pd and Au-Pt systems agrees with experimental values, and the calculated concentration dependence of the lattice parameters agrees...

  13. Exploratory catalyst screening studies on the base free conversion of glycerol to lactic acid and glyceric acid in water using bimetallic Au-Pt compounds on acidic zeolites

    NARCIS (Netherlands)

    Pazhavelikkakath Purushothaman, Rajeesh Kumar; van Haveren, J.; Mayoral, A.; Melian Cabrera, I.; Heeres, H.J.

    2014-01-01

    The base free oxidation of glycerol with molecular oxygen in water using bimetallic Au-Pt catalysts on three different acidic zeolite supports (H-mordenite, H-beta and H-USY) was explored in a batch setup. At temperatures between 140 and 180 degrees C, lactic acid formation was significant and

  14. XRD, DRS, and SEM stundies of the effects of metal dopants (Pt and Au) on the structural and optical properties of TiO2

    CSIR Research Space (South Africa)

    Moloantoa, JR

    2011-07-01

    Full Text Available Au and Pt doped TiO2 nanocrystlas were prepared using the sol gel method. Diffuse Reflectance Spectroscopy (DRS) was used to study the characteristics of these precious metals and X-ray diffraction (XRD) with calculated lattice parameters was used...

  15. High Sensitive and Selective Sensing of Hydrogen Peroxide Released from Pheochromocytoma Cells Based on Pt-Au Bimetallic Nanoparticles Electrodeposited on Reduced Graphene Sheets

    Directory of Open Access Journals (Sweden)

    Guangxia Yu

    2015-01-01

    Full Text Available In this study, a high sensitive and selective hydrogen peroxide (H2O2 sensor was successfully constructed with Pt-Au bimetallic nanoparticles (Pt-Au NPs/reduced graphene sheets (rGSs hybrid films. Various molar ratios of Au to Pt and different electrodeposition conditions were evaluated to control the morphology and electrocatalytic activity of the Pt-Au bimetallic nanoparticles. Upon optimal conditions, wide linear ranges from 1 µM to 1.78 mM and 1.78 mM to 16.8 mM were obtained, with a detection limit as low as 0.31 µM. Besides, due to the synergetic effects of the bimetallic NPs and rGSs, the amperometric H2O2 sensor could operate at a low potential of 0 V. Under this potential, not only common anodic interferences induced from ascorbic acid, uric acid and dopamine, but also the cathodic interference induced from endogenous O2 could be effectively avoided. Furthermore, with rat pheochromocytoma cells (PC 12 as model, the proposed sensor had been successfully used in the detection of H2O2 released from the cancer cells. This method with wide linear ranges and excellent selectivity can provide a promising alternative for H2O2 monitoring in vivo in the fields of physiology, pathology and diagnosis.

  16. Signal Amplification Strategy of Triple-Layered Core-Shell Au@Pd@Pt Nanoparticles for Ultrasensitive Immunoassay Detection of Squamous Cell Carcinoma Antigen.

    Science.gov (United States)

    Zhang, Xiaoyue; Du, Bin; Wu, Dan; Ma, Hongmin; Zhang, Yong; Li, He; Wei, Qin

    2015-02-01

    A novel and effective nonenzymatic immunosensor for the sensitive detection of squamous cell carcinoma antigen (SCC- Ag) was described based on triple-layered core-shell Au@Pd@Pt nanoparticles (Au@Pd@Pt NPs). To prepare the immunosensor, primary anti-SCC antibodies (Ab1) were immobilized onto nanoporous gold films (NPGF) of a modified glassy carbon electrode. Au@Pd@Pt NPs that possess strong catalytic activity for the reduction of H2O2 were used as catalytic labels of secondary anti-SCC antibodies (Ab2). Because of the catalytic activities of Au@Pd@Pt NPs and the large surface area of the NPGF, high sensitivity was achieved for the detection of SCC-Ag. The prepared immunosensor showed remarkable results, such as low detection limits (0.6 pg/mL), a wide linear range (0.001-10.0 ng/mL) and high stability and selectivity in the detection of SCC-Ag. Furthermore, the prepared immunosensor exhibited promising properties, which may be useful for real serum sample tests.

  17. The performance and stability of the oxygen reduction reaction on Pt-M (M = Pd, Ag and Au) nanorods: an experimental and computational study.

    Science.gov (United States)

    Liang, Yu-Ting; Lin, Syuan-Pei; Liu, Chen-Wei; Chung, Shu-Ru; Chen, Tsan-Yao; Wang, Jeng-Han; Wang, Kuan-Wen

    2015-04-18

    The ORR activity of Pt3M NRs is related to the oxophilicity (ΔE(ads)). However, their segregation energy when exposed to oxygen containing species (OCS*) determines their stability. Although the ΔE(ads) of Ag is not as weak as that of Au, its structure is relatively stable, thus promoting the ORR stability.

  18. The use of Au and Pt x-ray N lines for correct EDX analysis of C in gold and platinum depositions of micro and nano structures

    NARCIS (Netherlands)

    Mulders, J.J.L.; Botman, A.

    2009-01-01

    One technique to create small Pt and Au nano scale direct structures is Electron Beam Induced Deposition (EBID). These structures however, often suffer from included carbon, as the related precursor often is an organo metallic chemical substance. Research programs focus on optimizing the EBID

  19. Icosahedral Pt-centered Pt13 and Pt19 carbonyl clusters decorated by [Cd5(μ-Br)5Br(5-x)(solvent)x]x+ rings reminiscent of the decoration of Au-Fe-CO and Au-thiolate nanoclusters: a unifying approach to their electron counts.

    Science.gov (United States)

    Femoni, Cristina; Iapalucci, Maria Carmela; Longoni, Giuliano; Zacchini, Stefano; Zarra, Salvatore

    2011-03-02

    The new [Pt(13)(CO)(12){Cd(5)(μ-Br)(5)Br(2)(dmf)(3)}(2)](2-) and [Pt(19)(CO)(17){Cd(5)(μ-Br)(5)Br(3)(Me(2)CO)(2)}{Cd(5)(μ-Br)(5)Br(Me(2)CO)(4)}](2-) clusters have been obtained in good yields by reaction of [Pt(12)(CO)(24)](2-) with CdBr(2)·H(2)O in dmf at 90 °C and structurally characterized by X-ray diffraction. Their structures consist of a Pt-centered Pt(13)(CO)(12) icosahedron and a Pt(19)(CO)(17) interpenetrated double icosahedron, respectively, decorated by two Cd(5)(μ-Br)(5)Br(5-x)(solvent)(x) rings. Their surface decoration may be related to that of Au-Fe-CO clusters as well as to the staple motifs stabilizing gold-thiolates nanoclusters. An oversimplified and unifying approach to interpret their electron count is suggested.

  20. Shape coexistence near the Z-82 closed shell: a study of the excited states of 187Au and 187Pt in the β+ decay of 187Hg and 187Au

    International Nuclear Information System (INIS)

    Grimm, M.A. Jr.

    1978-11-01

    The decays of mass-separated (2.4, 2.2 min)/sup 187m,g/Hg and (8.4 min) 187 Au were studied. Both high- and low-spin states in 187 Au are fed in the (β + , EC) decay of /sup 187m,g/Hg isomers. The h/sub 11/2/, h/sub 9/2/, s/sub 1/2/, d/sub 3/2/, and d/sub 5/2/ collective bands, which are systematically observed throughout the odd-mass gold isotopes, are now extended to 187 Au. In 187 Au, the h/sub 9/2/ bandhead is below the h/sub 11/2/ bandhead, and the transition between the two is found to proceed via a hindered M1 transition due to the change in nuclear shape involved in the transition. One of the most important results of the present study is the discovery of the coupling of the odd proton in an h/sub 9/2/ particle state to the excited O + state of the 186 Pt core. Only the low spin states in 187 Pt appear to be populated in the beta decay of 187 Au. The nature of these low-spin states is not understood at present. One aspect of the levels of 187 Pt not previously reported is a delayed transition of 251 keV energy observed in the present study. 111 references

  1. Surface enhanced vibrational spectroscopy and first-principles study of L-cysteine adsorption on noble trimetallic Au/Pt@Rh clusters.

    Science.gov (United States)

    Loganathan, B; Chandraboss, V L; Senthilvelan, S; Karthikeyan, B

    2015-09-07

    The Rh shell of the Au/Pt/Rh trimetallic nanoparticles induces a wide variety of interesting surface reactions by allowing the adsorption of amino acids like L-cysteine (L-Cys). We present a snapshot of theoretical and experimental investigation of L-Cys adsorption on the surface of noble trimetallic Au/Pt@Rh colloidal nanocomposites. Density functional theoretical (DFT) investigations of L-Cys interaction with the Rhodium (Rh) shell of a trimetallic Au/Pt@Rh cluster in terms of geometry, binding energy (E(B)), binding site, energy gap (E(g)), electronic and spectral properties have been performed. L-Cys establishes a strong interaction with the Rh shell. It binds to Rh by the S1-site, which makes a stable L-Cys-Rh surface complex. DFT can be taken as a valuable tool to assign the vibrational spectra of the adsorption of L-Cys on trimetallic Au/Pt@Rh colloidal nanocomposites and mono-metallic Rh nanoparticles. Surface-enhanced infrared spectroscopy (SEIRS) with L-Cys on a Rh6 cluster surface has been simulated for the first time. Experimental information on the L-Cys-Rh surface complex is included to examine the interaction. The experimental spectral observations are in good agreement with the simulated DFT results. Characterization of the synthesized trimetallic Au/Pt@Rh colloidal nanocomposites has been done by high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED) pattern, energy dispersive X-ray (EDX) spectroscopy, dynamic light scattering (DLS) measurements, zeta potential, zeta deviation analysis and UV-visible (UV-Vis) spectroscopic studies.

  2. Growth of Ag, Au, Cu, and Pt nanostructures on surfaces by micropatterned laser-image formations

    Science.gov (United States)

    Pacheco-Londono, Leonardo C.; Aparicio-Bolaño, Joaquín.; Primera-Pedrozo, Oliva M.; Hernandez-Rivera, Samuel P.

    2011-07-01

    Silver, gold, copper and platinum nanoparticles (NPs) were grown on surfaces in the form of patterns by the exposure of laser radiation onto droplets of metal ion solutions and the aid of a reducing agent. The generation of patterns from metallic NPs was achieved by combining induced growth of NPs and nanostructures by laser incidence directly on surfaces and optical image formation techniques for transferring the patterns. Near-UV (363.8nm) and visible (532nm) laser wavelengths were used for the laser-induced growth of NPs into microstructures on glass, quartz, stainless steel, silicon, and gold-on-silicon substrates. The sizes of the patterns formed were on the micrometer scale and the sizes of the transferred patterns were on the millimeter scale. The patterns formed were generated by optical transference of image and interference of laser beams. Ag and Au substrates were highly active in surface enhanced Raman spectroscopy (SERS). The enhanced Raman activity was measured for SERS probe molecules: 9H-purin-6-amine (adenine) and 1,2-bis (4-pyridyl)-ethane analytes on Ag and Au substrates, respectively. The enhancement factors obtained were 1.8×105 and 6.2×106, respectively.

  3. Nuclear moments and deformation changes in the lightest Pt isotopes measured by laser spectroscopy

    CERN Document Server

    Roussière, B; Crawford, J; Duong, H T; Genevey, J; Girod, M; Huber, G; Ibrahim, F; Krieg, M; Le Blanc, F; Lee, J K P; Obert, J; Oms, J; Peru, S; Pinard, J; Putaux, J C; Sauvage, J; Sebastian, V; Zemlyanoi, S G; Forkel-Wirth, Doris; Lettry, Jacques

    1999-01-01

    Laser spectroscopy measurements are performed with the lightest neutron-deficient platinum isotopes using the experimental setup COMPLIS installed at the ISOLDE-Booster facility. The hyperfine spectra of /sup 182-178/Pt and /sup 183m/Pt are recorded for the first time from the optical transition 5d/sup 9/6s/sup 3/D/sub 3/ to 5d/sup 9/6p/sup 3/P/sub 2/. The variation in the mean-square charge radius of these nuclei and the magnetic and quadrupole (for I>or=1) moments of the odd isotope nuclei are found. A large deformation change between the /sup 183g/Pt and /sup 183m/Pt nuclei, quite large inverted odd-even staggering of the charge radius around the neutron midshell N=104, and a nuclear deformation drop in the region A=179 are revealed. All the results are discussed in terms of nuclear shape variation and are compared with the results of Hartree-Fock- Bogoliubov calculations involving the Gogny force. Comparison of the deformation measured from /sup 183g, m/Pt to the odd-odd isotone /sup 184g, m/Au shows that...

  4. Fabrication of sensitive enzymatic biosensor based on multi-layered reduced graphene oxide added PtAu nanoparticles-modified hybrid electrode.

    Directory of Open Access Journals (Sweden)

    Md Faruk Hossain

    Full Text Available A highly sensitive amperometric glucose sensor was developed by immobilization of glucose oxidase (GOx onto multi-layer reduced graphene oxide (MRGO sheets decorated with platinum and gold flower-like nanoparticles (PtAuNPs modified Au substrate electrode. The fabricated MRGO/PtAuNPs modified hybrid electrode demonstrated high electrocatalytic activities toward oxidation of H2O2, to which it had a wide linear response that ranged from 0.5 to 8 mM (R2 = 0.997, and high sensitivity of 506.25 μA/mMcm2. Furthermore, glucose oxidase-chitosan composite and cationic polydiallyldimethylammonium chloride (PDDA were assembled by a casting method on the surface of MRGO/PtAuNPs modified electrode. This as-fabricated hybrid biosensor electrode exhibited high electrocatalytic activity for the detection of glucose in PBS. It demonstrated good analytical properties in terms of a low detection limit of 1 μM (signal-to-noise ratio of 3, short response time (3 s, high sensitivity (17.85 μA/mMcm2, and a wide linear range (0.01-8 mM for glucose sensing. These results reveal that the newly developed sensing electrode offers great promise for new type enzymatic biosensor applications.

  5. Fabrication of sensitive enzymatic biosensor based on multi-layered reduced graphene oxide added PtAu nanoparticles-modified hybrid electrode.

    Science.gov (United States)

    Hossain, Md Faruk; Park, Jae Y

    2017-01-01

    A highly sensitive amperometric glucose sensor was developed by immobilization of glucose oxidase (GOx) onto multi-layer reduced graphene oxide (MRGO) sheets decorated with platinum and gold flower-like nanoparticles (PtAuNPs) modified Au substrate electrode. The fabricated MRGO/PtAuNPs modified hybrid electrode demonstrated high electrocatalytic activities toward oxidation of H2O2, to which it had a wide linear response that ranged from 0.5 to 8 mM (R2 = 0.997), and high sensitivity of 506.25 μA/mMcm2. Furthermore, glucose oxidase-chitosan composite and cationic polydiallyldimethylammonium chloride (PDDA) were assembled by a casting method on the surface of MRGO/PtAuNPs modified electrode. This as-fabricated hybrid biosensor electrode exhibited high electrocatalytic activity for the detection of glucose in PBS. It demonstrated good analytical properties in terms of a low detection limit of 1 μM (signal-to-noise ratio of 3), short response time (3 s), high sensitivity (17.85 μA/mMcm2), and a wide linear range (0.01-8 mM) for glucose sensing. These results reveal that the newly developed sensing electrode offers great promise for new type enzymatic biosensor applications.

  6. Mechanistic insight into the enhanced photocatalytic activity of single-atom Pt, Pd or Au-embedded g-C3N4

    Science.gov (United States)

    Tong, Tong; Zhu, Bicheng; Jiang, Chuanjia; Cheng, Bei; Yu, Jiaguo

    2018-03-01

    Single atoms of platinum (Pt), palladium (Pd) or gold (Au) trapped by two-dimensional graphitic carbon nitride (g-C3N4) exhibit superior photocatalytic performance. However, the underlying mechanism of single-atom noble metal/g-C3N4 photocatalytic system is still unclear. Herein, the structural, electronic and optical properties of single-atom Pt, Pd and Au loaded on bilayer g-C3N4 (BL-g-C3N4) substrate were investigated by density functional theory (DFT) simulations. The results indicate that single-atom Pt/Pd/Au loading can significantly narrow the band gap of g-C3N4 and thus increase its light absorption in the visible-light region. Rather than being adsorbed on the surface, Pt and Pd atoms tend to be embedded into g-C3N4 interlayer and act as bridges to facilitate the interlayer charge carrier transfer due to the effects of conduction band offset. In particular, an internal electric field is generated in Pt/BL-g-C3N4, which is further beneficial for separating charge carrier of photoexcited g-C3N4. By contrast, Au can only be adsorbed on the g-C3N4 surface (in the six-fold cavity) and deliver a limited amount of charge carrier excited in the N-conjugated aromatic pore of g-C3N4 surface. Our finding is conducive to understanding the interactive relationship between single-atom noble metal co-catalysts and g-C3N4 and to the design of high-efficiency photocatalyst.

  7. One-Pot Polyol Synthesis of Pt/CeO2 and Au/CeO2 Nanopowders as Catalysts for CO Oxidation.

    Science.gov (United States)

    Pilger, Frank; Testino, Andrea; Lucchini, Mattia Alberto; Kambolis, Anastasios; Tarik, Mohammed; El Kazzi, Mario; Arroyo, Yadira; Rossell, Marta D; Ludwig, Christian

    2015-05-01

    The facile one-pot synthesis of CeO2-based catalysts has been developed to prepare a relatively large amount of nanopowders with relevant catalytic activity towards CO oxidation. The method consists of a two-steps process carried out in ethylene glycol: in the first step, 5 nm well-crystallized pure CeO2 is prepared. In a subsequent second step, a salt of a noble metal is added to the CeO2 suspension and the deposition of the noble metal on the nanocrystalline CeO2 is induced by heating. Two catalysts were prepared: Pt/CeO2 and Au/CeO2. The as-prepared catalysts, the thermally treated catalysts, as well as the pure CeO2, are characterized by XRD, TGA, XPS, FTIR, HR-TEM, STEM, particle size distribution, and N2-physisorption. In spite of the identical preparation protocol, Au and Pt behave in a completely different way: Au forms rather large particles, most of them with triangular shape, easily identifiable and dispersed in the CeO2 matrix. In contrast, Pt was not identified as isolated particles. The high resolution X-ray diffraction carried out on the Pt/CeO2 thermally treated sample (500 degrees C for 1 h) shows a significant CeO2 lattice shrinkage, which can be interpreted as an at least partial incorporation of Pt into the CeO2 crystal lattice. Moreover, only Pt2+ and Pt4+ species were identified by XPS. In literature, the incorporation of Pt into the CeO2 lattice is supported by first-principle calculations and experimentally demonstrated only by combustion synthesis methods. To the best of our knowledge this is the first report where ionically dispersed Pt into the CeO2 lattice is obtained via a liquid synthesis method. The thermally treated Pt/CeO2 sample revealed good activity with 50% CO conversion at almost room temperature.

  8. The synthesis of Au@C@Pt core-double shell nanocomposite and its application in enzyme-free hydrogen peroxide sensing

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yayun; Li, Yuhui; Jiang, Yingying [College of Chemistry & Environment, Minnan Normal University, Zhangzhou 363000 (China); Li, Yancai, E-mail: liyancai@mnnu.edu.cn [College of Chemistry & Environment, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China); Li, Shunxing [College of Chemistry & Environment, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China)

    2016-08-15

    Highlights: • A novel Au@C@Pt core-double shell nanocomposite was synthesized and characterized by SEM(*), TEM and EDS, etc. • The synthesized Au@C@Pt core-double shell nanocomposite showed high sensitivity and selectivity to electrocatalytic reduction of hydrogen peroxide (H{sub 2}O{sub 2}) and can be used to fabricate enzyme-free H{sub 2}O{sub 2} electrochemical sensor. • The H{sub 2}O{sub 2} sensor has two linear range of 9.0 μM–1.86 mM and 1.86 mM–7.11 mM, respectively, with a low limit of detection of 0.13 μM. • The H{sub 2}O{sub 2} sensor also displays high anti-interference ability, good stability and reproducibility. - Abstract: A novel Au@C@Pt core-double shell nanocomposite was synthesized and used to fabricate enzyme-free electrochemical sensor for rapid and sensitive detection of hydrogen peroxide (H{sub 2}O{sub 2}). The well-designed Au@C@Pt core-double shell nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and energy-dispersed spectrum (EDS). The Au@C@Pt core-double shell nanocomposite modified glassy carbon electrode (Au@C@Pt/GCE) exhibits good electrocatalytic activity towards H{sub 2}O{sub 2} reduction at 0.0 V and can be used as H{sub 2}O{sub 2} sensor. The sensor displays two wide linear ranges towards H{sub 2}O{sub 2} detection. The one is 9.0 μM–1.86 mM with high sensitivity of 144.7 μA mM{sup −1} cm{sup −2}, and the other is 1.86 mM–7.11 mM with sensitivity of 80.1 μA mM{sup −1} cm{sup −2}. When signal to noise (S/N) is 3, the calculated detection limit (LOD) is 0.13 μM. Furthermore, the interference from the common interfering species such as glucose, ascorbic acid, dopamine and uric acid can be effectively avoided to H{sub 2}O{sub 2} detection. Additionally, the H{sub 2}O{sub 2} sensor also displays good stability and reproducibility.

  9. Multilevel resistance switching effect in Au/La2/3Ba1/3MnO3/Pt heterostructure manipulated by external fields

    Science.gov (United States)

    Wen, Jiahong; Zhao, Xiaoyu; Li, Qian; Zhang, Sheng; Wang, Dunhui; Du, Youwei

    2018-04-01

    Multilevel resistance switching (RS) effect has attracted more and more attention due to its promising potential for the increase of storage density in memory devices. In this work, the transport properties are investigated in an Au/La2/3Ba1/3MnO3 (LBMO)/Pt heterostructure. Taking advantage of the strong interplay among the spin, charge, orbital and lattice of LBMO, the Au/LBMO/Pt device can exhibit bipolar RS effect and magnetoresistance effect simultaneously. Under the coaction of electric field and magnetic field, four different resistance states are achieved in this device. These resistance states show excellent repeatability and retentivity and can be switched between any two states, which suggest the potential applications in the multilevel RS memory devices with enhanced storage density.

  10. Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

    Energy Technology Data Exchange (ETDEWEB)

    Porobova, Svetlana, E-mail: porobova.sveta@yandex.ru; Loskutov, Oleg, E-mail: lom58@mail.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); Markova, Tat’jana, E-mail: patriot-rf@mail.ru [Siberian State Industrial University. 42 Kirov St., Novokuznetsk, 654007 (Russian Federation); Klopotov, Vladimir, E-mail: vdklopotov@mail.ru [Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk, 634050 (Russian Federation); Klopotov, Anatoliy, E-mail: klopotovaa@tsuab.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); National Research Tomsk State University, 36, Lenin Ave., Tomsk, 634050 (Russian Federation); Vlasov, Viktor, E-mail: vik@tsuab.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk, 634050 (Russian Federation)

    2016-01-15

    The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen’s law.

  11. Photochemical synthesis of noble metal (Ag, Pd, Au, Pt) on graphene/ZnO multihybrid nanoarchitectures as electrocatalysis for H2O2 reduction.

    Science.gov (United States)

    Gu, Hui; Yang, Yan; Tian, Jixiang; Shi, Guoyue

    2013-07-24

    For the first time, a series of noble metal (Ag, Au, Pd, and Pt) nanoparticles (NPs) based on new functional graphene were successfully achieved via UV-assisted photocatalytic reduction by ZnO nanorods. The whole preparation strategy for constructing noble metal deposited graphene sheets/ZnO (GS/ZnO) was elucidated in detail in this work. First, graphene oxide based two-dimensional carbon nanostructures served as a support to disperse ZnO nanorods through a hydrothermal route. The ZnO nanorods were self-assembled onto the surface of graphene sheets, forming GS/ZnO nanocomposite, and the graphene oxide was reduced, yielding reduced graphene sheets in this synthetic procedure. Second, the GS/ZnO films were further employed as supporting materials for the dispersion of metal nanoparticles. Photogenerated electrons from UV-irradiated ZnO were transported across GS to stepwise and respectively reduce v μL metal ions (Ag(+), Pd(2+), AuCl4(-), PtCl6(2-), 20 mg/mL) into metal (Ag, Pd, Au, Pt) NPs at a location distinct from the ZnO anchored site, forming five graphene-based hybrid nanocomposites designated as GS/ZnO, GS/ZnO@Agv, GS/ZnO@Pdv, GS/ZnO@Auv, GS/ZnO@Ptv, respectively. The obtained mutihybrid nanoarchitectured materials were clearly characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). According to the diameters and distribution, the four metal NPs on GS/ZnO were divided into two categories: Ag&Au and Pd&Pt. Their difference was rooted in the rival abilities of gathering electron between graphene and different metal islands in the photochemical reduction process. The electrochemical behaviors of the five resultant hybrid nanocomposites were investigated in H2O2 as well as in potassium ferricyanide (Fe(CN)6(3-/4-)) and displayed distinct electrocatalytic activity.

  12. Fluid inclusion and oxygen-isotope evidence for low-temperature Au-Pt-Pd (± U) mineralization at Corronation Hill, NT

    International Nuclear Information System (INIS)

    Mernagh, T.

    1992-01-01

    The fluid inclusion and isotope data have been used to constrain the ore genesis models for the Au-Pt-Pd-U mineralization at Coronation Hill. The fluid inclusions demonstrate that the ore fluid was strongly saline with an unusually high CaCl 2 content, and that the mineralisation was probably formed from a boiling fluid at around 140 deg C. Furthermore, the fluids were highly oxidised and the replacement of earlier chlorite by hematite is common throughout the deposit. It is concluded that both U-rich and U-poor Au-Pt-Pd mineralisation were formed by descending, low-temperature, highly oxidised, very saline, meteoric fluids. The segregation of U was controlled by fluid-rock interaction in the feldspathic or carbonate rocks. Interaction with carbonaceous or chloritic rocks resulted in a reduction in fO 2 , and consequent precipitation of U, Au, Pt and Pd. The other two types of metal associations can be explained by further reaction of the mineralizing fluids. 3 figs

  13. Effect of adsorption site, size, and composition of Pt/Au bimetallic clusters on the CO frequency: a density functional theory study.

    Science.gov (United States)

    Sadek, Mark M; Wang, Lichang

    2006-12-28

    Density functional theory (DFT) calculations were performed to investigate the C-O stretching frequency changes when a CO molecule was adsorbed to Pt/Au clusters of 2-4 atoms. Our calculations show that the adsorption site is the most sensitive quantity to the C-O stretching frequency shifts. All the bridge site adsorptions yield a CO frequency band of 1737-1927 cm-1 with the CO bond distance of 1.167-1.204 A regardless of cluster composition and size, and all the atop site adsorptions yield a CO frequency band of 2000-2091 cm-1 with the CO bond distance of 1.151-1.167 A. More detailed analysis of the two frequency bands shows that each band may consist of two emerging subbands with the lower frequencies corresponding to the CO adsorption to Pt atoms and the higher frequencies to the CO adsorption to Au atoms. The insensitivity of the CO frequency shift to the cluster size indicates that the trend discussed here for small clusters may be used to interpret the experimental observations for nanoparticles. Our results also illustrated that the Fourier transform infrared spectroscopy measurement may be used as a sensitive tool to identify adsorption sites of the Pt/Au nanoparticles using CO adsorption as the probe.

  14. Application of ZnO quantum dots dotted carbon nanotube for sensitive electrochemiluminescence immunoassay based on simply electrochemical reduced Pt/Au alloy and a disposable device

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Deng, Wenping; Zhang, Yan [Key Laboratory of Chemical Sensing and Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022 (China); Ge, Shenguang [Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan, 250022 (China); Yu, Jinghua, E-mail: ujn.yujh@gmail.com [Key Laboratory of Chemical Sensing and Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022 (China); Song, Xianrang, E-mail: sxr@vip.163.com [Cancer Research Center, Shandong Tumor Hospital, Jinan, 250012 (China)

    2014-03-01

    Highlights: • A sandwich-type electrochemluminence immunosensor was fabricated. • Simply electrochemical reduced Pt/Au alloy was selected as immunosensing probes. • ZnO@CNT composite was first employed as signal amplification label. Abstract: We report on a disposable microdevice suitable for sandwich-type electrochemiluminescence (ECL) detection of prostate specific antigen (PSA). The method is making use of ZnO quantum dots dotted carbon nanotube (ZnO@CNT) and simply electrochemical reduced Pt/Au alloy. The latter was selected as immunosensing probe to modify screen-printed carbon electrode, due to its excellent electrical property. For further ultrasensitive, low-potential and stable ECL detection, ZnO@CNT composite was first synthesized using a facile solvothermal method, and employed as signal amplification label. In this work, two working electrodes in one device were used for one determination to obtain more exact results based on screen-print technique. Taking advantage of dual-amplification effects of the Pt/Au and ZnO@CNT, this immunosensor could detect the PSA quantitatively, in the range of 0.001–500 ng mL⁻¹, with a low detection limit of 0.61 pg mL⁻¹. The resulting versatile immunosensor possesses high sensitivity, satisfactory reproducibility and regeneration. This simple and specific strategy has vast potential to be used in other biological assays.

  15. Decay spectroscopy of $^{178}$Au

    CERN Document Server

    Whitmore, B

    In this thesis, the neutron-deficient nucleus $^{178}$Au is investigated through decay spectroscopy. Si and HPGe detectors were used to analyse the decay radiation of $^{178}$Au and its daughter nuclei. Previous studies have been unable to distinguish decay radiation from different isomeric states of this nucleus. This thesis represents the first time such isomeric discrimination has been achieved, and presents tentative spin assignments of both the ground state and an isomer. The neutron-deficient gold isotopes are an area of interest for the study of shape coexistence. This is the phenomenon exhibited by nuclei able to exist at a number of close lying energy minima, each reflecting a distinct type of deformation. It is hoped that studies such as this can help identify the evolution of nuclear deformation in this region of the nuclear chart.

  16. [Quantitative surface analysis of Pt-Co, Cu-Au and Cu-Ag alloy films by XPS and AES].

    Science.gov (United States)

    Li, Lian-Zhong; Zhuo, Shang-Jun; Shen, Ru-Xiang; Qian, Rong; Gao, Jie

    2013-11-01

    In order to improve the quantitative analysis accuracy of AES, We associated XPS with AES and studied the method to reduce the error of AES quantitative analysis, selected Pt-Co, Cu-Au and Cu-Ag binary alloy thin-films as the samples, used XPS to correct AES quantitative analysis results by changing the auger sensitivity factors to make their quantitative analysis results more similar. Then we verified the accuracy of the quantitative analysis of AES when using the revised sensitivity factors by other samples with different composition ratio, and the results showed that the corrected relative sensitivity factors can reduce the error in quantitative analysis of AES to less than 10%. Peak defining is difficult in the form of the integral spectrum of AES analysis since choosing the starting point and ending point when determining the characteristic auger peak intensity area with great uncertainty, and to make analysis easier, we also processed data in the form of the differential spectrum, made quantitative analysis on the basis of peak to peak height instead of peak area, corrected the relative sensitivity factors, and verified the accuracy of quantitative analysis by the other samples with different composition ratio. The result showed that the analytical error in quantitative analysis of AES reduced to less than 9%. It showed that the accuracy of AES quantitative analysis can be highly improved by the way of associating XPS with AES to correct the auger sensitivity factors since the matrix effects are taken into account. Good consistency was presented, proving the feasibility of this method.

  17. Production and novel radiochemical separation of 194Au from Pt for use in multi-modality nanoparticles

    OpenAIRE

    Graves, S.; Goel, S.; Chen, F.; Valdovinos, H.; Barnhart, T.; Cai, W.; Nickles, R.

    2015-01-01

    Introduction Gold nanoparticles (AuNPs) have demonstrated their incredible versatility in applications such as in vitro and in vivo imaging, cancer therapy, and drug delivery.[1-3] These AuNPs come in many shapes including nanospheres, nanorods, nanoshells, and nanocages. Their versatility stems from the ability to construct or label a single AuNP with many functions. Many types of AuNPs are inherently flourescent, allowing for ex vivo utilization as well as small animal fluorescence imagi...

  18. Novel redox species polyaniline derivative-Au/Pt as sensing platform for label-free electrochemical immunoassay of carbohydrate antigen 199

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liyuan; Shan, Jiao; Feng, Feng; Ma, Zhanfang, E-mail: mazhanfang@cnu.edu.cn

    2016-03-10

    A novel electrochemical redox-active nanocomposite was synthesized by a one-pot method using N,N′-diphenyl-p-phenylediamine as monomer, and HAuCl{sub 4} and K{sub 2}PtCl{sub 4} as co-oxidizing agents. The as-prepared poly(N,N′-diphenyl-p-phenylediamine)-Au/Pt exhibited admirable electrochemical redox activity at 0.15 V, excellent H{sub 2}O{sub 2} electrocatalytic ability and favorable electron transfer ability. Based on these, the evaluation of the composite as sensing substrate for label-free electrochemical immunosensing to the sensitive detection of carbohydrate antigen 199 was described. This technique proved to be a prospective detection tool with a wide liner range from 0.001 U mL{sup −1} to 40 U mL{sup −1}, and a low detection limit of 2.3 × 10{sup −4} U mL{sup −1} (S/N = 3). In addition, this method was used for the analysis of human serum sample, and good agreement was obtained between the values and those of enzyme-linked immunosorbent assay, implying the potential application in clinical research. Importantly, the strategy of the present substrate could be extended to other polymer-based nanocomposites such as polypyrrole derivatives or polythiophene derivatives, and this could be of great significance for the electrochemical immunoassay. - Highlights: • A novel electrochemical redox composite PPPD-Au/Pt was synthesized by one-pot method. • PPPD-Au/Pt was used as sensing substrate for label-free electrochemical immunosensor. • The immunosensor showed wide detection range and ultralow detection limit for the detection of CA199.

  19. Operation of ohmic Ti/Al/Pt/Au multilayer contacts to GaN at 600 °C in air

    Science.gov (United States)

    Hou, Minmin; Senesky, Debbie G.

    2014-08-01

    The high-temperature characteristics (at 600 °C) of Ti/Al/Pt/Au multilayer contacts to gallium nitride (GaN) in air are reported. Microfabricated circular-transfer-line-method test structures were subject to 10 h of thermal storage at 600 °C. Intermittent electrical characterization during thermal storage showed minimal variation in the contact resistance after 2 h and that the specific contact resistivity remained on the order of 10-5 Ω-cm2. In addition, the thermally stored multilayer contacts to GaN showed ohmic I-V characteristics when electrically probed at 600 °C. The microstructural analysis with atomic force microscopy showed minimal changes in surface roughness after thermal storage. Observations of the thermochemical reactions after thermal storage using Auger electron spectroscopy chemical depth profiling showed diffusion of Pt and minimal additional Al oxidation. The results support the use of Ti/Al/Pt/Au multilayer metallization for GaN-based sensors and electronic devices that will operate within a high-temperature and oxidizing ambient.

  20. Density functional investigation of the adsorption effects of PH3 and SH2 on the structure stability of the Au55 and Pt55 nanoclusters

    Science.gov (United States)

    Guedes-Sobrinho, Diego; Chaves, Anderson S.; Piotrowski, Maurício J.; Da Silva, Juarez L. F.

    2017-04-01

    Although several studies have been reported for Pt55 and Au55 nanoclusters, our atomistic understanding of the interplay between the adsorbate-surface interactions and the mechanisms that lead to the formation of the distorted reduced core (DRC) structures, instead of the icosahedron (ICO) structure in gas phase, is still far from satisfactory. Here, we report a density functional theory (DFT) investigation of the role of the adsorption effects of PH3 (one lone pair of electrons) and SH2 (two lone pairs) on the relative stability of the Pt55 and Au55 nanoclusters. In gas phase, we found that the DRC structures with 7 and 9 atoms in the core region are about 5.34 eV (Pt55) and 2.20 eV (Au55) lower in energy than the ICO model with Ih symmetry and 13 atoms in the core region. However, the stability of the ICO structure increases by increasing the number of adsorbed molecules from 1 to 18, in which both DRC and ICO structures are nearly degenerate in energy at the limit of 18 ligands, which can be explained as follows. In gas phase, there is a strong compression of the cationic core region by the anionic surface atoms induced by the attractive Coulomb interactions (core+-surface-), and hence, the strain release is obtained by reducing the number of atoms in the cationic core region, which leads to the 55 atoms distorted reduced core structures. Thus, the Coulomb interactions between the core+ and surface- contribute to break the symmetry in the ICO55 structure. On the other hand, the addition of ligands on the anionic surface reduces the charge transfer between the core and surface, which contributes to decrease the Coulomb interactions and the strain on the core region of the ICO structure, and hence, it stabilizes a compact ICO structure. The same conclusion is obtained by adding van der Waals corrections to the plain DFT calculations. Similar results are obtained by the addition of steric effects, which are considered through the adsorption of triphenylphosphine

  1. Comparative Analysis of Cobalt Oxide Nanoisland Stability and Edge Structures on Three Related Noble Metal Surfaces: Au (111), Pt (111) and Ag (111)

    DEFF Research Database (Denmark)

    Fester, Jakob; Bajdich, Michal; Walton, Alexander

    2017-01-01

    Metal oxide nanostructures and thin films grown on metallic substrates have attracted strong attention as model catalysts and as interesting inverse catalyst systems in their own right. In this study, we investigate the role of metal support in the growth and stabilization of cobalt oxide...... nanostructures on the three related (111) surfaces of Au, Pt and Ag, as investigated by means of high-resolution scanning tunneling microscopy and DFT calculations. All three substrates promote the growth of crystalline CoOx (x = 1−2) islands under oxidative conditions, but we find several noteworthy differences...

  2. Characterization of electroless Au, Pt and Pd contacts on CdTe and ZnTe by RBS and SIMS techniques

    International Nuclear Information System (INIS)

    Roumie, M.; Hageali, M.; Zahraman, K.; Nsouli, B.; Younes, G.

    2004-01-01

    Rutherford backscattering spectrometry (RBS) was applied to characterize Au, Pt and Pd contacts on II-VI semiconductor materials, CdTe and ZnTe, used as nuclear detectors. Electroless thin film depositions were prepared by changing the concentration of the reaction solution. Contrary to the deposition reaction time, it was observed that the amount of solution dilution degree had a considerable effect on increasing the thickness of the metal layer. Furthermore, PICTS electrical measurements confirmed the depth profile analysis performed by RBS and SIMS

  3. Observation of new neutron-deficient isotopes with Z≥92 in multinucleon transfer reactions

    Directory of Open Access Journals (Sweden)

    H.M. Devaraja

    2015-09-01

    Full Text Available In deep inelastic multinucleon transfer reactions of 48Ca + 248Cm we observed about 100 residual nuclei with proton numbers between Z=82 and Z=100. Among them, there are five new neutron-deficient isotopes: 216U, 219Np, 223Am, 229Am and 233Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the α decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.

  4. New neutron-deficient isotopes of barium and rare-earth elements

    CERN Document Server

    Bogdanov, D D; Karnaukhov, V A; Petrov, L A; Plochocki, A; Subbotin, V G; Voboril, J

    1976-01-01

    The authors present an investigation of the short-lived neutron- deficient isotopes of barium and rare-earth elements. By using the BEMS-2 isotope separator on a heavy ion beam, 19 new isotopes were produced with mass numbers ranging from 117 to 138. Five of these (/sup 117/Ba, /sup 129,131/Nd and /sup 133,135/Sm) turned out to be delayed proton emitters. The beta -decay probabilities for the new isotopes have been analyzed in terms of the beta -strength function. An analysis of the proton spectrum shape has been performed using the statistical model for delayed proton emission.

  5. Spectroscopy of light neutron deficient nuclei: 31Ar and 27S decays

    International Nuclear Information System (INIS)

    Borrel, V.

    1991-01-01

    Light neutron-deficient nuclei exhibit several interesting decay modes. In some cases, beta-delayed alpha emission becomes possible, and beta-delayed three-proton emission can be allowed. The energy spectra of the emitted protons should give informations on the position of the isobaric analog state and on its deexcitation modes. Experimental results obtained at GANIL with the LISE spectrometer on the decay of the isotopes 31 Ar and 27 S are presented. These data are discussed and compared with the predicted isobaric analog state excitation energies and with shell-model calculations. (G.P.) 13 refs.; 7 figs.; 1 tab

  6. Shape transition and coexistence in neutron-deficient rare earth isotopes

    CERN Multimedia

    We propose to study spectroscopic quadrupole moments of excited states and electromagnetic transition rates between them in the neutron-deficient rare earth nuclei $^{140}$Sm and $^{142}$Gd using projectile Coulomb excitation at energies of 4.7 MeV per nucleon. The rare earth nuclei below the N=82 shell closure form one of the few regions of the nuclear chart where oblate shapes are expected to occur near the ground state. Nuclear shapes are expected to change rapidly in this region, with coexistence of oblate and prolate shapes in some nuclei. The measurement of electromagnetic matrix elements represents therefore a particularly sensitive test of theoretical nuclear structure models.

  7. Study of oblate nuclear shapes and shape coexistence in neutron-deficient rare earth isotopes

    CERN Multimedia

    Guttormsen, M S; Reiter, P; Larsen, A; Korten, W; Clement, E; Siem, S; Renstrom, T; Buerger, A; Jenkins, D G

    We propose to investigate nuclear shapes and shape coexistence in neutron-deficient rare earth nuclei below the N=82 shell closure at the ISOLDE facility by employing Coulomb excitation of Nd, Sm, Gd, and Dy beams from the REX accelerator and the Miniball experiment. Nuclear shapes are expected to change rapidly in this region of the nuclear chart. The measurement of electric quadrupole moments of excited states and the transition rates between them serves as a stringent test of theoretical models and effective nucleon-nucleon interactions.

  8. First observation of excited structures in neutron-deficient 179Hg : evidence for multiple shape coexistence

    International Nuclear Information System (INIS)

    Kondev, F.G.; Carpenter, M.P.; Janssens, R.V.F.; Lister, C.J.; Abu Saleem, K.; Ahmad, I.; Amro, H.; Caggiano, J.; Davids, C.N.; Heinz, A.; Herskind, B.; Khoo, T.L.; Lauristen, T.; Ma, W.C.; Ressler, J.J.; Reviol, W.; Riedinger, L.L.; Sarantites, D.G.; Seweryniak, D.; Siem, S.; Sonzongni, A.A.; Varmette, P.G.; Wiedenhoever, I.

    2002-01-01

    Excited structures in the neutron-deficient nucleus 179 Hg have been established for the first time using the Gammasphere spectrometer in conjunction with the fragment mass analyzer. Competing states originating from three different minima associated with nearly spherical, oblate, and prolate deformations were found. This result can be contrasted with the situation in heavier odd-mass Hg isotopes where only two minima (oblate and prolate) have been seen. The implications of these three shapes at low spin and excitation energy are discussed in the general context of shape coexistence in this mass region.

  9. Measurements of competing structures in neutron-deficient Pb isotopes by employing Coulomb excitation

    CERN Multimedia

    Bastin, B; Kruecken, R; Larsen, A; Rahkila, P J; Srebrny, J; Clement, E; Wadsworth, R; Syed naeemul, H; Peura, P J; Siem, S; Hadynska-klek, K; Habs, D; Napiorkowski, P J; Diriken, J V J; Iwanicki, J S

    Coulomb excitation measurements to study the shape coexistence and quadrupole collectivity of the low-lying levels in neutron-deficient Pb nuclei are proposed. Even-mass $^{188−192}$Pb nuclei will be post-accelerated at REX-ISOLDE in order to measure transition probabilities and quadrupole moments for the first excited states. In combination with results obtained in lifetime measurements, this will allow the sign of the quadrupole deformation parameter to be extracted for the first time for 2$^{+}$ states in the even-mass $^{188−192}$Pb nuclei.

  10. Further studies of neutron-deficient Sn-isotopes using REX-ISOLDE

    CERN Document Server

    Larsen, A; Syed naeemul, H; Siem, S

    2007-01-01

    Encouraged by the committee to submit the latter part of our latest addendum to experiment IS418 under a new heading this proposal focuses on the second physics case mentioned there. We propose to use Coulomb excitation of odd mass neutron-deficient Sn isotopes to study some dominantly "one quasi-particle" states in these nuclei. Due to spin selection rules these states are difficult to populate following either $\\beta$-decay or in a cascade after a fusion-evaporation reactions, whereas the excitation from the ground-state is of E2 character for some of the most interesting cases.

  11. Lifetime limitations of ohmic, contacting RF MEMS switches with Au, Pt and Ir contact materials due to accumulation of ‘friction polymer’ on the contacts

    International Nuclear Information System (INIS)

    Czaplewski, David A; Nordquist, Christopher D; Dyck, Christopher W; Patrizi, Gary A; Kraus, Garth M; Cowan, William D

    2012-01-01

    We present lifetime limitations and failure analysis of many packaged RF MEMS ohmic contacting switches with Au–Au, Au–Ir, and Au–Pt contact materials operating with 100 µN of contact force per contact in hermetically sealed glass wall packages. All metals were tested using the same switch design in a controlled environment to provide a comparison between the performance of the different materials and their corresponding failure mechanisms. The switch lifetimes of the different contact materials varied from several hundred cycles to 200 million cycles with different mechanisms causing failures for different contact materials. Switches with Au–Au contacts failed due to adhesion when thoroughly cleaned while switches with dissimilar metal contacts (Au–Ir and Au–Pt) operated without adhesion failures but failed due to carbon accumulation on the contacts even in a clean, packaged environment as a result of the catalytic behavior of the contact materials. Switch lifetimes correlated inversely with catalytic behavior of the contact metals. The data suggests the path to increase switch lifetime is to use favorable catalytic materials as contacts, design switches with higher contact forces to break through any residual contamination, and use cleaner, probably smaller, packages. (paper)

  12. The Effect of Annealing Treatment and Atom Layer Deposition to Au/Pt Nanoparticles-Decorated TiO₂ Nanorods as Photocatalysts.

    Science.gov (United States)

    Shuang, Shuang; Zhang, Zhengjun

    2018-02-09

    The wide band gap of TiO₂ hinders the utilization of visible light in high-performance photocatalysis. Herein, vertically aligned Ti nanopillar arrays (NPAs) were grown by the glancing angle deposition method (GLAD) and then thermally oxidized into TiO₂ NPAs. The metallic nanoparticles (NPs) were fabricated by successive ion layer adsorption and reaction (SILAR) method. And we covered ultrathin TiO₂ layer on Au/Pt NPs decorated NPA using atomic layer deposition (ALD) method and did annealing process in the end. The photoelectrochemical (PEC) performance and dye degradation have been studied. We find the dye degradation efficiency of best combination reaches up to 1.5 times higher than that of original Au/Pt-TiO₂ sample under visible light irradiation. The TiO₂ ALD layer effectively protects the nanostructure from corrosion and helps the transmission of electrons to the electrolyte. By controlling the annealing temperature we could achieve a matched band gap due to change in noble metal particle size. Our work demonstrates that rational design of composite nanostructures enhances the usage of broader wavelength range light and optimizes photocatalytic degradation of organic pollutants in practical applications.

  13. Pincer-CNC mononuclear, dinuclear and heterodinuclear Au(III) and Pt(II) complexes supported by mono- and poly-N-heterocyclic carbenes: synthesis and photophysical properties.

    Science.gov (United States)

    Gonell, S; Poyatos, M; Peris, E

    2016-04-07

    A family of cyclometallated Au(iii) and Pt(ii) complexes containing a CNC-pincer ligand (CNC = 2,6-diphenylpyridine) supported by pyrene-based mono- or bis-NHC ligands have been synthesized and characterized, together with the preparation of a Pt-Au hetero-dimetallic complex based on a Y-shaped tris-NHC ligand. The photophysical properties of all the new species and of two related Ru(ii)-arene complexes were studied and compared. Whereas the pyrene-based complexes only exhibit emission in solution, those containing the Y-shaped tris-NHC ligand are only luminescent when dispersed in poly(methyl methacrylate) (PMMA). In particular, the pyrene-based complexes were found to be emissive in the range of 373-440 nm, with quantum yields ranging from 3.1 to 6.3%, and their emission spectra were found to be almost superimposable, pointing to the fluorescent pyrene-centered nature of the emission. This observation suggests that the emission properties of the pyrene fragment may be combined with some of the numerous applications of NHCs as supporting ligands allowing, for instance, the design of biological luminescent agents.

  14. Identifying the structure of 4-chlorophenyl isocyanide adsorbed on Au(111) and Pt(111) surfaces by first-principles simulations of Raman spectra.

    Science.gov (United States)

    Hu, Wei; Duan, Sai; Zhang, Yujin; Ren, Hao; Jiang, Jun; Luo, Yi

    2017-12-13

    Surface Raman spectroscopy has become one of the most powerful analytical tools for interfacial structures. However, theoretical modeling for the Raman spectra of molecular adsorbate on metallic surfaces is a long-standing challenge because accurate descriptions of the electronic structure for both the metallic substrates and adsorbates are required. Here we present a quasi-analytical method for high-precision surface Raman spectra at the first principle level. Using this method, we correlate both geometrical and electronic structures of a single 4-chlorophenyl isocyanide (CPI) molecule adsorbed on a Au(111) or Pt(111) surface with its Raman spectra. The "finger-print" frequency shift of the CN stretching mode reveals the in situ configuration of CPI is vertical adsorption on the top site of the Au(111) surface, but a bent configuration when it adsorbs on the hollow site of the Pt(111) surface. Electronic structure calculations reveal that a π-back donation mechanism often causes a red shift to the Raman response of CN stretching mode. In contrast, σ donation as well as a wall effect introduces a blue shift to the CN stretching mode. A clear relationship for the dependence of Raman spectra on the surface electronic and geometrical information is built up, which largely benefits the understanding of chemical and physical changes during the adsorption. Our results highlight that high-precision theoretical simulations are essential for identifying in situ geometrical and electronic surface structures.

  15. Two complexes of Pt(IV) and Au(III) with 2,2'-dipyridylamine and 2,2'-dipyridylaminide ligands.

    Science.gov (United States)

    Chernyshev, Alexander N; Kukushkin, Vadim Yu; Haukka, Matti

    2014-12-01

    Two noble metal complexes involving ancillary chloride ligands and chelating 2,2'-bipyridylamine (Hdpa) or its deprotonated derivative (dpa), namely [bis(pyridin-2-yl-κN)amine]tetrachloridoplatinum(IV), [PtCl4(C10H9N3)], and [bis(pyridin-2-yl-κN)aminido]dichloridogold(III), [AuCl2(C10H8N3)], are presented and structurally characterized. The metal atom in the former has a slightly distorted octahedral coordination environment, formed by four chloride ligands and two pyridyl N atoms of Hdpa, while the metal atom in the latter has a slightly distorted square-planar coordination environment, formed by two chloride ligands and two pyridyl N atoms of dpa. The difference in conjugation between the pyridine rings in normal and deprotonated 2,2'-dipyridylamine is discussed on the basis of the structural features of these complexes. The influence of weak interactions on the supramolecular structures of the complexes, providing one-dimensional chains of [PtCl4(C10H9N3)] and dimers of [AuCl2(C10H8N3)], are discussed.

  16. Tailored Rh surface facilitates, enhancement of Raman scattering in trimetallic AuPt core/Rh shell composites: Experimental and theoretical evidences

    Science.gov (United States)

    Loganathan, B.; Chandraboss, V. L.; Senthilvelan, S.; Karthikeyan, B.

    2016-01-01

    We present a detailed analysis of surface-enhanced Raman scattering of 7-azaindole and L-cysteine adsorbed on a tailored Rh surface by using experimental and density functional theoretical (DFT) calculations. DFT with the B3LYP/Lanl2DZ basis set was used for the optimization of the ground state geometries and simulation of the surface-enhanced Raman spectrum of probe molecules adsorbed on Rh6 cluster. 7-azaindole and L-cysteine adsorption at the shell interface was ascertained from first-principles. In addition, characterization of synthesized trimetallic AuPt core/Rh shell colloidal nanocomposites has been analyzed by UV-visible spectroscopy, high-resolution transmission and scanning electron microscopy, selected area electron diffraction pattern analysis, energy-dispersive X-ray spectroscopy, atomic force, confocal Raman microscopy, FT-Raman and surface-enhanced Raman spectroscopic analysis. This analysis serves as the first step in gaining an accurate understanding of specific interactions at the interface of organic and biomolecules and to gain knowledge on the surface composition of trimetallic Au/Pt/Rh colloidal nanocomposites.

  17. Laser-assisted decay and optical spectroscopy studies of neutron-deficient thallium isotopes

    CERN Document Server

    Van Beveren, Céline; Huyse, Mark

    The neutron-deficient thallium isotopes with one proton less than the Z = 82 shell closure, are situated in an interesting region of the nuclear chart, notorious for intruder states and shape coexistence. Shape coexistence is the remarkable phenomenon in which two or more distinct types of deformation occur at low energy in the same atomic nucleus. Shape coexistence has been studied intensively, experimentally as well as theoretically in different nuclei in the light-lead region and the isomerism in the thallium isotopes was among the first indications of this phenomenon. Different shapes, whose structure has been linked to specific proton orbitals above and below the Z = 82 shell closure, are present at low energy in the neutron-deficient odd-mass thallium nuclei. In the odd-odd nuclei, the coupling of an unpaired proton and unpaired neutron gives rise to multiplets of low-lying states from which some can be isomeric. Since thallium has one proton missing in the major proton shell, and when approaching neutr...

  18. Deformation and mixing of co-existing shapes in the neutron-deficient polonium isotopes

    CERN Document Server

    AUTHOR|(CDS)2078559; Huyse, Mark

    The neutron-deficient polonium isotopes, with only 2 protons outside the Z = 82 shell closure, are situated in an interesting region of the nuclear chart. In the neighboring lead (Z = 82) and mercury (Z = 80) isotopes, experimental and theoretical efforts identified evidence of shape coexistence. Shape coexistence is the remarkable phenomenon in which two or more distinct types of deformation occur in states of the same angular momentum and similar excitation energy in a nucleus. The neutron-deficient polonium isotopes have also been studied intensively, experimentally as well as theoretically. The closed neutron-shell nucleus 210Po (N = 126) manifests itself as a two-particle nucleus where most of the excited states can be explained by considering the degrees of freedom of the two valence protons outside of 208Pb. The near-constant behavior of the yrast 2+1 and 4+1 states in the isotopes with mass 200 ≤ A ≤ 208 can be explained by coupling the two valence protons to a vibrating lead core. 200Po seems to ...

  19. Probing Hot Electron Flow Generated on Pt Nanoparticles with Au/TiO2 Schottky Diodes during Catalytic CO Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jeong Y.; Lee, Hyunjoo; Renzas, J. Russell; Zhang, Yawen; Somorjai, G.A.

    2008-05-01

    Hot electron flow generated on colloid platinum nanoparticles during exothermic catalytic carbon monoxide oxidation was directly detected with Au/TiO{sub 2} diodes. Although Au/TiO{sub 2} diodes are not catalytically active, platinum nanoparticles on Au/TiO{sub 2} exhibit both chemicurrent and catalytic turnover rate. Hot electrons are generated on the surface of the metal nanoparticles and go over the Schottky energy barrier between Au and TiO{sub 2}. The continuous Au layer ensures that the metal nanoparticles are electrically connected to the device. The overall thickness of the metal assembly (nanoparticles and Au thin film) is comparable to the mean free path of hot electrons, resulting in ballistic transport through the metal. The chemicurrent and chemical reactivity of nanoparticles with citrate, hexadecylamine, hexadecylthiol, and TTAB (Tetradecyltrimethylammonium Bromide) capping agents were measured during catalytic CO oxidation at pressures of 100 Torr O{sub 2} and 40 Torr CO at 373-513 K. We found that chemicurrent yield varies with each capping agent, but always decreases with increasing temperature. We suggest that this inverse temperature dependence is associated with the influence of charging effects due to the organic capping layer during hot electron transport through the metal-oxide interface.

  20. Event-by-event hexb pt hexb fluctuations in Au-Au collisions atsqrt(sNN) = 130 GeV

    Energy Technology Data Exchange (ETDEWEB)

    Adams, J.; Adler, C.; Aggarwal, M.M.; Ahammed, Z.; Amonett, J.; Anderson, B.D.; Anderson, M; Arkhipkin, D.; Averichev, G.S.; Badyal,S.K.; Balewski, J.; Barannikova, O.; Barnby, L.S.; Baudot, J.; Bekele,S.; Belaga, V.V.; Bellwied, R.; Berger, J.; Bezverkhny, B.I.; Bhardwaj,S.; Bhaskar, P.; Bhati, A.K.; Bichsel, H.; Billmeier, A.; Bland, L.C.; Blyth, C.O.; Bonner, B.E.; Botje, M.; Boucham, A.; Brandin, A.; Bravar,A.; Cadman, R.V.; Cai, X.Z.; Caines, H.; Calderon de la Barca Sanchez,M.; Carroll, J.; Castillo, J.; Castro, M.; Cebra, D.; Chaloupka, P.; Chattopadhyay, S.; Chen, H.F.; Chen, Y.; Chernenko, S.P.; Cherney, M.; Chikanian, A.; Choi, B.; Christie, W.; Coffin, J.P.; Cormier, T.M.; Cramer, J.G.; Crawford, H.J.; Das, D.; Das, S.; Derevschikov, A.A.; Didenko, L.; Dietel, T.; Dong, X.; Draper, J.E.; Du, F.; Dubey, A.K.; Dunin, V.B.; Dunlop, J.C.; Dutta Majumdar, M.R.; Eckardt, V.; Efimov,L.G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Fachini, P.; Faine, V.; Faivre, J.; Fatemi, R.; Filimonov, K.; Filip, P.; Finch, E.; Fisyak, Y.; Flierl, D.; Foley, K.J.; Fu, J.; Gagliardi, C.A.; Ganti, M.S.; Gutierrez, T.D.; Gagunashvili, N.; Gans, J.; Gaudichet, L.; Germain, M.; Geurts, F.; Ghazikhanian, V.; Ghosh, P.; Gonzalez, J.E.; Grachov, O.; Grigoriev, V.; Cronstal, S.; Grosnick, D.; Guedon, M.; Guertin, S.M.; Gupta, A.; Gushin, E.; Hallman, T.J.; Hardtke, D.; Harris,J.W.; Heinz, M.; Henry, T.W.; Heppelmann, S.; Herston, T.; Hippolyte, B.; Hirsch, A.; Hjort, E.; Hoffmann, G.W.; Horsley, M.; Huang, H.Z.; Huang,S.L.; Humanic, T.J.; Igo, G.; Ishihara, A.; Jacobs, P.; Jacobs, W.W.; Janik, M.; Johnson, I.; Jones, P.G.; Judd, E.G.; Kabana, S.; Kaneta, M.; Kaplan, M.; Keane, D.; Kiryluk, J.; Kisiel, A.; Klay, J.; Klein, S.R.; Klyachko, A.; Koetke, D.D.; Kollegger, T.; Konstantinov, A.S.; Kopytine,S.M.; Kotchenda, L.; Kovalenko, A.D.; Kramer, M.; Kravtsov, P.; Krueger,K.; Kuhn, C.; Kulikov, A.I.; Kumar, A.; et al.

    2003-09-02

    We present the first large-acceptance measurement of event-wise fluctuations in Au-Au collisions at {radical}s{sub NN} = 130 GeV. Significant nonstatistical fluctuations are observed. The measured fractional r.m.s. width excess of the event-wise distribution for the 15% most-central events for charged hadrons within |{eta}| < 1 and 0.15 {le} p{sub t} {le} 2 GeV/c is 13.7 {+-} 0.1(stat) {+-}1.3(syst)% relative to a statistical reference. The variation of charge-independent fluctuation excess with centrality is non-monotonic but smooth. Charge-dependent nonstatistical fluctuations are also observed.

  1. Penning-trap mass spectrometry and mean-field study of nuclear shape coexistence in the neutron-deficient lead region

    Science.gov (United States)

    Manea, V.; Ascher, P.; Atanasov, D.; Barzakh, A. E.; Beck, D.; Blaum, K.; Borgmann, Ch.; Breitenfeldt, M.; Cakirli, R. B.; Cocolios, T. E.; Day Goodacre, T.; Fedorov, D. V.; Fedosseev, V. N.; George, S.; Herfurth, F.; Kowalska, M.; Kreim, S.; Litvinov, Yu. A.; Lunney, D.; Marsh, B.; Neidherr, D.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Schweikhard, L.; Wienholtz, F.; Wolf, R. N.; Zuber, K.

    2017-05-01

    We present a study of nuclear shape coexistence in the region of neutron-deficient lead isotopes. The midshell gold isotopes 180,185,188,190Au (Z =79 ), the two long-lived nuclear states in 197At (Z =85 ), and the neutron-rich nuclide 219At were produced by the ISOLDE facility at CERN and their masses were determined with the high-precision Penning-trap mass spectrometer ISOLTRAP. The studied gold isotopes address the trend of binding energies in a region of the nuclear chart where the nuclear charge radii show pronounced discontinuities. Significant deviations from the atomic-mass evaluation were found for Au,190188. The new trend of two-neutron separation energies is smoother, although it does reveal the onset of deformation. The origin of this effect is interpreted in connection to the odd-even staggering of binding energies, as well as theoretically by Hartree-Fock-Bogoliubov calculations including quasiparticle blocking. The role of blocking for reproducing the large odd-even staggering of charge radii in the mercury isotopic chain is illustrated.

  2. High $p_{T}$ charged-pion production in Pb-Au collisions at 158 AGeV/c

    CERN Document Server

    Agakichiev, G; Braun-Munzinger, P; Drees, A; Esumi, S C; Faschingbauer, U; Fraenkel, Zeev; Fuchs, C; Glässel, P; Pérez de los Heros, C; Holl, P; Jung, C; Lenkeit, B C; Messer, F; Messer, M; Panebratsev, Yu A; Pfeiffer, A; Rak, J; Ravinovich, I; Razin, S V; Rehak, P; Richter, M; Saveljic, N; Schükraft, Jürgen; Shimansky, S S; Seipp, W; Socol, E; Specht, H J; Stachel, J J; Tel-Zur, G; Tserruya, Itzhak; Ullrich, T S; Voigt, C A; Weber, C; Wessels, J P; Wienold, T; Wurm, J P; Yurevich, V I

    2000-01-01

    The CERES/Na45 experiment at CERN SPS measured transverse momentum spectra ofcharged-pions in the range 1<pt<4GeV/c near mid-rapidity in 158 AGeV/c Pb-Aucollisions. The invariant transverse momentum spectra are exponential over theentire observed range. The average inverse slope is 245+/- 5MeV/c, it shows a2.4 0ncrease with centrality of the collision over the 35most centralfraction of the cross section. The pi-/pi+ ratio is constant at 1.028+/-0.005over the pt interval measured.

  3. Designed synthesis of MOx(M = Zn, Fe, Sn, Ni, Mn, Co, Ce, Mg, Ag), Pt, and Au nanoparticles supported on hierarchical CuO hollow structures.

    Science.gov (United States)

    Zhang, Zailei; Jung, Ji Chul; Yan, Ning

    2016-12-01

    Despite intensive research into support substrates for the dispersal of nanoparticles and their applications, there has been a lack of general methods to produce metal oxide hollow substrates supporting a wide range of metal and metal oxides. Herein, a synthetic protocol for the preparation of CuO hollow structure-supported MO x (M = Zn, Fe, Ni, Sn, Mn, Co, Ce, Mg, and Ag) and noble metals (Pt and Au) with the desired properties and shell structure, such as CuO/Fe 2 O 3 , CuO/ZnO, CuO/SnO 2 , CuO/MgO, CuO/NiO, CuO/Mn 2 O 3 , CuO/CoO, CuO/CeO 2 , CuO/Ag 2 O, CuO/Pt, CuO/Au hollow cubes, CuO/ZnO double-shell hollow cubes, CuO/SnO 2 double-shell hollow octahedra, CuO/SnO 2 /Fe 2 O 3 and CuO/Mn 2 O 3 /NiO double-shell hollow cubes, was developed based on controlled calcination and etching. These hybrid hollow structures were employed not only as support substrates but also as active constituents for catalytic reactions. As an example, we demonstrated that CuO/ZnO hollow cubes are remarkably efficient in converting solid chitin biomass to liquid chemicals in methanol. In addition, CuO/ZnO double-shell hollow cubes were highly effective in the oxidation of benzyl alcohol in the presence of H 2 O 2 , whereas CuO/Pt and CuO/Au hollow cubes promoted the oxidation of benzyl alcohol in pure O 2 . The strategy developed in this work extends the controllable fabrication of high-quality CuO hollow structure-supported nanoparticles using various compositions and shell structures, paving the way to the exploration and systematic comparison of these materials in a wider range of applications.

  4. Amalgams for fluorescent lamps. Pt. II. The systems Bi-Pb-Hg and Bi-Pb-Au-Hg

    Energy Technology Data Exchange (ETDEWEB)

    Lankhorst, M.H.R.; Keur, W.; Hal, H.A.M. van [Philips Research Labs., Eindhoven (Netherlands)

    2000-09-14

    In nowadays compact fluorescent lamps, having coolest spot temperatures in the range 60-130 C, amalgams based on the eutectic Bi-In and Bi-Pb-Sn alloys are used to control the mercury vapour pressure inside the lamp. The consequence of the trend towards smaller and more attractive compact fluorescent lamps is that the amalgam temperature increases. In this paper the materials and thermodynamic properties of the amalgams Bi-Pb-Hg and Bi-Pb-Au-Hg are described. The mercury vapour pressure measurements show that these amalgams can be used for controlling the optimal mercury vapour pressure inside fluorescent lamps at temperatures in the range 60-150 C. In the ternary Bi-Pb-Au system the new ternary compound BiPb{sub 3}Au has been found for which the crystal structure and melting point have been determined. The results of XRD, EPMA, DTA and mercury vapour pressure measurements are combined to formulate a thermodynamic model for the mercury activity in both liquid and solid Bi-Pb-Hg and Bi-Pb-Au-Hg. (orig.)

  5. Coulomb Excitation of Neutron Deficient Sn-Isotopes using REX-ISOLDE

    CERN Multimedia

    Di julio, D D; Kownacki, J M; Marechal, F; Andreoiu, C; Siem, S; Perrot, F; Van duppen, P L E; Napiorkowski, P J; Iwanicki, J S

    2002-01-01

    It is proposed to study the evolution of the reduced transition probabilities, B(E2; 0$^{+} \\rightarrow$ 2$^{+}$), for neutron deficient Sn isotopes by Coulomb excitation in inverse kinematics using REX-ISOLDE and the MINIBALL detector array. Measurements of the reduced transition matrix element for the transition between the ground state and the first excited 2$^{+}$ state in light even-even Sn isotopes provide a means to study e.g. core polarization effects in the $^{100}$Sn core. Previous attempts to measure this quantity have been carried out using the decay of isomeric states populated in fusion evaporation reactions. We thus propose to utilize the unique opportunity provided by REX-ISOLDE, after the energy upgrade to 3.1 MeV/u, to use the more model-independent approach of Coulomb excitation to measure this quantity in a number of isotopes in this region.

  6. Changes in the mean square charge radii and electromagnetic moments of neutron-deficient Bi isotopes

    International Nuclear Information System (INIS)

    Barzakh, A. E.; Batist, L. Kh.; Fedorov, D. V.; Ivanov, V. S.; Molkanov, P. L.; Moroz, F. V.; Orlov, S. Yu.; Panteleev, V. N.; Seliverstov, M. D.; Volkov, Yu. M.

    2015-01-01

    In-source laser spectroscopy experiments for neutron deficient bismuth isotopes at the 306.77 nm atomic transition were carried out at the IRIS (Investigation of Radioactive Isotopes on Synchrocyclotron) facility of Petersburg Nuclear Physics Institute (PNPI). New data on isotope shifts and hyperfine structure for 189–198, 211 Bi isotopes and isomers were obtained. The changes in the mean-square charge radii and the magnetic moment values were deduced. Marked deviation from the nearly spherical behavior for ground states of bismuth isotopes at N < 109 is demonstrated, in contrast to the lead and thallium isotopic chains. The big isomer shift between I = 1/2 (intruder) and I = 9/2 (normal) states for odd Bi isotopes (A = 193, 195, 197) was found

  7. Influence of the concentration of borohydride towards hydrogen production and escape for borohydride oxidation reaction on Pt and Au electrodes - experimental and modelling insights

    Science.gov (United States)

    Olu, Pierre-Yves; Bonnefont, Antoine; Braesch, Guillaume; Martin, Vincent; Savinova, Elena R.; Chatenet, Marian

    2018-01-01

    The Borohydride Oxidation Reaction (BOR), the anode reaction in a Direct borohydride fuel cell (DBFC), is complex and still poorly understood, which impedes the development and deployment of the DBFC technology. In particular, no practical electrocatalyst is capable to prevent gaseous hydrogen generation and escape from its anode upon operation, which lowers the fuel-efficiency of the DBFC and raises safety issues in operation. The nature of the anode electrocatalysts strongly influences the hydrogen escape characteristics of the DBFC, which demonstrates how important it is to isolate the BOR mechanism in conditions relevant to DBFC operation. In this paper, from a selected literature review and BOR experiments performed in differential electrochemical mass spectrometry (DEMS) in a wide range of NaBH4 concentration (5-500 mM), a microkinetic model of the BOR for both Pt and Au surfaces is proposed; this model takes into account the hydrogen generation and escape.

  8. Reacción de ligandos azufrados con el complejo au2pt (ch2p(Sph24,cl2

    Directory of Open Access Journals (Sweden)

    Guillermo Garzón

    2010-07-01

    Full Text Available Se describe la reacción de intercambio del cloro en el complejo au2pt (ch2p(Sph24,cl2 por los ligandos SCH2Ph-,S2CN(CH2CH3,2- y SCN-. Los nuevos derivados azufrados se caracterizan por análisis químico, espectroscopia infrarroja, electrónica y resonancia magnética nuclear protónica. Los ligandos se coordinan por el azufre a los dos átomos sw oro metálico en forma simétrica. El análisis elemental concuerda con las estequiomctrías y estructuras propuestas.

  9. Global optimization of bimetallic cluster structures. II. Size-matched Ag-Pd, Ag-Au, and Pd-Pt systems

    Science.gov (United States)

    Rossi, Giulia; Ferrando, Riccardo; Rapallo, Arnaldo; Fortunelli, Alessandro; Curley, Benjamin C.; Lloyd, Lesley D.; Johnston, Roy L.

    2005-05-01

    Genetic algorithm global optimization of Ag-Pd, Ag-Au, and Pd-Pt clusters is performed. The 34- and 38-atom clusters are optimized for all compositions. The atom-atom interactions are modeled by a semiempirical potential. All three systems are characterized by a small size mismatch and a weak tendency of the larger atoms to segregate at the surface of the smaller ones. As a result, the global minimum structures exhibit a larger mixing than in Ag-Cu and Ag-Ni clusters. Polyicosahedral structures present generally favorable energetic configurations, even though they are less favorable than in the case of the size-mismatched systems. A comparison between all the systems studied here and in the previous paper (on size-mismatched systems) is presented.

  10. The adsorption of CO and NO on the MoS{sub 2} monolayer doped with Au, Pt, Pd, or Ni: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Dongwei, E-mail: dwmachina@126.com [School of Physics, Anyang Normal University, Anyang 455000 (China); Ju, Weiwei [College of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Li, Tingxian; Zhang, Xiwei [School of Physics, Anyang Normal University, Anyang 455000 (China); He, Chaozheng, E-mail: hecz2013@nynu.edu.cn [Physics and Electronic Engineering College, Nanyang Normal University, Nanyang 473061 (China); Ma, Benyuan [Physics and Electronic Engineering College, Nanyang Normal University, Nanyang 473061 (China); Lu, Zhansheng; Yang, Zongxian [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007 (China)

    2016-10-15

    Graphical abstract: The MoS{sub 2} monolayers doped with Au, Pt, Pd, or Ni show enhanced adsorption and sensitivity toward CO or NO molecule. - Highlights: • CO and NO adsorption on the doped MoS{sub 2} monolayers is theoretically studied. • CO and NO are chemisorbed on the doped MoS{sub 2} monolayers. • Charge transfer can be observed between the adsorbed molecule and the substrates. • Molecular adsorption can induce the change in electronic structures of the doped MoS{sub 2} monolayers. - Abstract: By performing the first-principles calculation, the adsorption of CO and NO molecules on the Au, Pt, Pd, or Ni doped MoS{sub 2} monolayer has been studied. The interaction between CO or NO with the doped MoS{sub 2} monolayer is strong and belongs to the chemisorption, as evidenced by the large adsorption energy and the short distance between the adsorbed molecules and the dopants. The charge transfer and the electronic property induced by the molecule adsorption are discussed. It is found that for both CO and NO adsorption, for all the cases charge transfer between the substrates and the adsorbed molecules has been observed. For NO, the adsorption obviously induces new impurity states in the band gap or the redistribution of the original impurity states. These can lead to the change of the transport properties of the doped MoS{sub 2} monolayer, by which the adsorbed CO or NO can be detected. The present work shows that introducing appropriate dopants may be a feasible method to improve the performance of MoS{sub 2}-based gas sensors.

  11. Monte Carlo simulations of segregation at [001] twist boundaries in a Pt(Au) alloy-II

    International Nuclear Information System (INIS)

    Seki, A.; Seidman, D.N.; Oh, Y.

    1991-01-01

    This paper reports on a three dimensional plot of the density of Au atoms versus the position which coordinates for the (002) planes, immediately adjacent to the interface, for a θ = 5 degrees [001] twist boundary, suggests the presence of a hill-and-valley structure in the Au segregation behavior at 850 K. The valleys correspond to the regions of good atomic fit between the regions of misfit; the hills correspond to the cores of the pairs of orthogonal primary grain boundary dislocations. A model for the Monte Carlo simulations is developed that leads to a linear expression for S aver containing a core segregation factor (S core ). For this model S core a single Arrhenius plot and the Gibbs free binding energy of a Au atom to the cores of the primary grain boundary dislocations extracted; the binding enthalpy and entropy of segregation are 0.095 ±0.01 eV and K B (0.49 ± 0.19) respectively

  12. Phosphorescent PtAu2 Complexes with Differently Positioned Carbazole-Acetylide Ligands for Solution-Processed Organic Light-Emitting Diodes with External Quantum Efficiencies of over 20.

    Science.gov (United States)

    Xu, Liang-Jin; Zeng, Xian-Chong; Wang, Jin-Yun; Zhang, Li-Yi; Chi, Yun; Chen, Zhong-Ning

    2016-08-10

    The utilization of phosphorescent metal cluster complexes as new types of emitting materials in organic light-emitting diodes (OLEDs) is becoming an alternative and viable approach for achieving high-efficiency electroluminescence. We report herein the design of cationic PtAu2 cluster complexes with differently positioned 9-phenylcarbazole-acetylides to serve as phosphorescent emitters in OLEDs. The rigid structures of PtAu2 complexes cause intense phosphorescence with quantum yields of over 85%, which originates from (3)[π(phenylcarbazole-acetylide) → π*(dpmp)] ligand-to-ligand and (3)[π(phenylcarbazole-acetylide) → p/s(PtAu2)] ligand-to-metal charge-transfer triplet excited states. When 8 wt % PtAu2 is doped to blended host materials of TCTA and OXD-7 (2:1 weight ratio) as light-emitting layers, solution-processed OLEDs give a current efficiency of 78.2 cd A(-1) and an external quantum efficiency (EQE) of 21.5% at a practical luminance of 1029 cd m(-2) with a slow efficiency roll-off upon increasing luminance. This represents the best device performance and the highest efficiency recorded at practical luminance for solution-processed OLEDs.

  13. Hydration processes of electrolyte anions and cations on pt(111), Ir(111), Ru(001) and Au(111) surfaces: coadsorption of water molecules with electrolyte ions.

    Science.gov (United States)

    Ito, M; Nakamura, M

    2002-01-01

    Water adsorption on Pt( 111) and Ru(001) treated with oxygen, hydrogen chloride and sodium atom at 20 K has been studied by Fourier transform infrared spectroscopy, scanning tunneling microscopy and surface X-ray diffraction. Water molecules chemisorb predominantly on the sites of the electronegative additives, forming hydrogen bonds. Three types of hydration water molecules coordinate to an adsorbed Na atom through an oxygen lone pair. In contrast, water molecules adsorb on electrode surfaces in a simple way in solution. In 1 mM CuSO4 + 0.5 M H2SO4 solution on an Au(111) electrode surface, water molecules coadsorb not only with sulfuric acid anions through hydrogen bonding but also with copper, over wide potential ranges. In the first stage of underpotential deposition (UPD), each anion is accommodated by six copper hexagon (honeycomb) atoms on which water molecules dominate. At any UPD stage water molecules interact with both the copper atom and sulfuric acid anions on the Au(111) surface. Water molecules also coadsorb with CO molecules on the surface of 2 x 2-2CO-Ru(001). All of the hydration water molecules chemisorb weakly on the surfaces. There appears to be a correlation between the orientation of hydrogen bonding water molecules and the electrode potential.

  14. Long-lived high-spin isomers in the neutron-deficient 1g sub(9/2)-shell nuclei

    International Nuclear Information System (INIS)

    Ogawa, K.

    1981-09-01

    The neutron-deficient 1g sub(9/2)-shell nuclei are studied in the framework of the shell model with active nucleons occuping the 1g sub(9/2) and 2p sub(1/2) shells. The calculated result for 95 Pd shows good agreement with the recent experiment by Nolte and Hick. Many ''spin-gap'' Isomers are predicted in the region of A = 76 -- 84 and A = 95 -- 100. (author)

  15. Isolation and characterization of the tertiary amine Alamine 304 hydrochioride. Its application on the extraction of Co(II, Au(III and Pt(IV

    Directory of Open Access Journals (Sweden)

    López-Delgado, Aurora

    2000-06-01

    Full Text Available Amine Alamine 304 dissolved in xylene reacts with hydrochloric acid to form the amine chloride (R3NH+Cl- and the amine dichloride (R3NH2Cl2. The former compound was isolated and characterized by chemical analysis, X-ray powder diffraction, infrared spectroscopy and scanning electron microscopy. Lattice parameters of the isolated amine chloride were determined and refined by least-square numerical treatment (monoclinic cell, with a = 29.017(4 Å, b = 14.564(7 Å, c = 5.043(1 Å, b = 95.68(3 ° and V = 2,120 Å3. The amine chloride is a potential anion-exchanger with metals, thus data on the liquid-liquid extraction of Co(II, Au(III and Pt(IV are also reported.

    La amina Alamine 304 disuelta en xileno reacciona con el ácido clorhídrico para formar el cloruro de la amina (R3NH+Cl- y el dicloruro de amina (R3NH2Cl2. El primero de estos compuestos se aisló y caracterizó mediante análisis químico, difracción de rayos X, espectroscopia de IR y microscopía electrónica de barrido. Se determinaron y refinaron los parámetros de red del cloruro de amina (monoclínico, a = 29,017(4 Å, b = 14,564(7 Å, c = 5,043(1 Å, b = 95,68(3 ° y V = 2.120 Å3. El cloruro de amina actúa como un intercambiador aniónico con ciertos metales, por lo que se incluyen datos sobre la extracción líquido-líquido de Co(II, Au(III y Pt(IV.

  16. Coulomb excitation of $^{182-184}$ Hg: Shape coexistence in the neutron-deficient lead region

    CERN Multimedia

    We put forward a study of the interplay between individual nucleon behavior and collective degrees of freedom in the nucleus, as manifested in shape coexistence in the neutron-deficient lead region. As a first step of this experimental campaign, we propose to perform Coulomb excitation on light mercury isotopes to probe their excited states and determine transitional and diagonal E2 matrix elements, especially reducing the current uncertainties. The results from previous Coulomb excitation measurements in this mass region performed with 2.85 MeV/u beams from REX-ISOLDE have shown the feasibility of these experiments. Based on our past experience and the results obtained, we propose a detailed study of the $^{182-184}$Hg nuclei, that exhibit a pronounced mixing between 2 low-lying excited states of apparently different deformation character, using the higher energy beams from HIE-ISOLDE which are crucial to reach our goal. The higher beam energy should result in an increased sensitivity with respect to the qua...

  17. Electron-capture delayed fission properties of neutron-deficient einsteinium nuclei

    International Nuclear Information System (INIS)

    Shaughnessy, Dawn A.

    2000-01-01

    Electron-capture delayed fission (ECDF) properties of neutron-deficient einsteinium isotopes were investigated using a combination of chemical separations and on-line radiation detection methods. 242 Es was produced via the 233 U( 14 N,5n) 242 Es reaction at a beam energy of 87 MeV (on target) in the lab system, and was found to decay with a half-life of 11 ± 3 seconds. The ECDF of 242 Es showed a highly asymmetric mass distribution with an average pre-neutron emission total kinetic energy (TKE) of 183 ± 18 MeV. The probability of delayed fission (P DF ) was measured to be 0.006 ± 0.002. In conjunction with this experiment, the excitation functions of the 233 U( 14 N,xn) 247-x Es and 233 U( 15 N,xn) 248-x Es reactions were measured for 243 Es, 244 Es and 245 Es at projectile energies between 80 MeV and 100 MeV

  18. Study of the Neutron Deficient Pb and Bi Isotopes by Simultaneous Atomic- and Nuclear-Spectroscopy

    CERN Multimedia

    Kessler, T

    2002-01-01

    We propose to study systematically nuclear properties of the neutron deficient lead $^{183-189}$Pb, $^{191g}$Pb, $^{193g}$Pb and bismuth isotopes $^{188-200}$Bi by atomic spectroscopy with the ISOLDE resonance ionisation laser ion source (RILIS) combined with simultaneous nuclear spectroscopy at the detection set-up. The main focus is the determination of the mean square charge radii of $^{183-190}$Pb and $^{188-193}$Bi from which the influence of low-lying intruder states should become obvious. Also the nuclear spin and magnetic moments of ground-states and long-lived isomers will be determined unambiguously through evaluation of the hyperfine structure, and new isomers could be discovered. The decay properties of these nuclei can be measured by $\\alpha$-$\\gamma$ and $\\beta$-$\\gamma$ spectroscopy. With this data at hand, possible shape transitions around mid-shell at N$\\sim$104 will be studied. This data is crucial for the direct test of nuclear theory in the context of intruder state influence (e.g. energy ...

  19. Shape coexistence in the neutron-deficient mercury isotopes studied through Coulomb excitation

    CERN Document Server

    Bree, Nick

    This thesis describes the analysis and results of a series of Coulomb-excitation experiments on even-even neutron-deficient mercury isotopes aimed at obtaining a more detailed description of shape coexistence. Two experimental campaigns have been undertaken in the Summer of 2007 and 2008. Pure beams of 182,184,186,188Hg were produced and accelerated at the REX-ISOLDE radioactive-beam facility, located at CERN (Geneva, Switzerland). The beams were guided to collide with a stable target to induce Coulomb excitation. The scattered particles were registered by a double-sided silicon strip detector, and the emitted gamma rays by the MINIBALL gamma-ray spectrometer. The motivation to study these mercury isotopes, focused around shape coexistence in atomic nuclei, is addressed in chapter 1, as well as an overview of the knowledge in this region of the nuclear chart. A theoretical description of Coulomb excitation is presented in the second chapter, while the third chapter describes the setup employed for the experim...

  20. Electron-capture delayed fission properties of neutron-deficient einsteinium nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Shaughnessy, Dawn A. [Univ. of California, Berkeley, CA (United States)

    2000-01-01

    Electron-capture delayed fission (ECDF) properties of neutron-deficient einsteinium isotopes were investigated using a combination of chemical separations and on-line radiation detection methods. 242Es was produced via the 233U(14N,5n)242Es reaction at a beam energy of 87 MeV (on target) in the lab system, and was found to decay with a half-life of 11 ± 3 seconds. The ECDF of 242Es showed a highly asymmetric mass distribution with an average pre-neutron emission total kinetic energy (TKE) of 183 ± 18 MeV. The probability of delayed fission (PDF) was measured to be 0.006 ± 0.002. In conjunction with this experiment, the excitation functions of the 233U(14N,xn)247-xEs and 233U(15N,xn)248-xEs reactions were measured for 243Es, 244Es and 245Es at projectile energies between 80 MeV and 100 MeV.

  1. Study of the electrical and nanosecond third order nonlinear optical properties of ZnO films doped with Au and Pt nanoparticles

    International Nuclear Information System (INIS)

    Trejo-Valdez, Martin; Sobral, Hugo; Martínez-Gutiérrez, Hugo; Torres-Torres, Carlos

    2016-01-01

    Zinc oxide films doped with platinum and gold nanoparticles were deposited by the spray pyrolysis technique on glass substrates. A titanium dioxide sol–gel solution containing gold and platinum aqueous ions was employed for synthesizing the nanoparticles by ultraviolet-light irradiation. The conductive properties of the samples were characterized by the electrochemical impedance spectroscopy technique. Our results showed that the impedance of zinc oxide films doped with metallic nanoparticles was, by far, lower than typical measurements in zinc oxide films. A strong enhancement in the nanosecond nonlinear optical response was also obtained in the studied metallic doped films. A vectorial two-mixing experiment performed at 532 nm and 4 ns allowed us to evaluate the sample with a third order optical nonlinearity described by approximately | χ 1111 (3) | = 2.6 × 10 −8 esu. - Highlights: • ZnO films doped with Pt and Au nanoparticles were synthetized. • The inclusion of metallic nanoparticles in the film improves optical nonlinearities. • Conductivity of the films was enhanced by the contribution of the nanoparticles.

  2. STEM nanoanalysis of Au/Pt/Ti-Si3N4 interfacial defects and reactions during local stress of SiGe HBTs

    Directory of Open Access Journals (Sweden)

    Alaeddine Ali

    2011-01-01

    Full Text Available Abstract A new insight on the behavior of metal contact-insulating interfaces in SiGe heterojunction bipolar transistor is given by high-performance aberration-corrected scanning transmission electron microscopy (STEM analysis tools equipped with sub-nanometric probe size. It is demonstrated that the presence of initial defects introduced during technological processes play a major role in the acceleration of degradation mechanisms of the structure during stress. A combination of energy-filtered transmission electron microscopy analysis with high angle annular dark field STEM and energy dispersive spectroscopy provides strong evidence that migration of Au-Pt from the metal contacts to Ti/Si3N4 interface is one of the precursors to species interdiffusion and reactions. High current densities and related local heating effects induce the evolution of the pure Ti initial layer into mixture layer composed of Ti, O, and N. Local contamination of Ti layers by fluorine atoms is also pointed out, as well as rupture of TiN thin barrier layer.

  3. Fabrication of efficient TiO2-RGO heterojunction composites for hydrogen generation via water-splitting: Comparison between RGO, Au and Pt reduction sites

    Science.gov (United States)

    El-Bery, Haitham M.; Matsushita, Yoshihisa; Abdel-moneim, Ahmed

    2017-11-01

    A facile one-step synthesis approach of M/TiO2/RGO (M = Au or Pt) ternary composite by hydrothermal treatment for hydrogen generation via water-splitting was investigated. Photocurrent response measurements revealed that TiO2 (P25) nanoparticles anchored on the reduced graphene oxide (RGO) surface exhibited a p-n heterojunction interface by changing the photocurrent direction with the applied bias from reverse to forward potential. H2 evolution rate of TiO2/RGO (5 wt.%) composite was substantially enhanced by 12-fold in comparison to bare TiO2 under simulated solar light irradiation. Cyclic volatmmetry measurements manifested, that the optimized 0.3 wt.% of platinum metal loaded on TiO2/RGO composite was the most active catalytic reduction sites for hydrogen generation reaction with an initial hydrogen rate of 670 μmol h-1. This study sheds the light on the tunable semiconductor type of TiO2/RGO composite fabricated by solution mixing pathway and its merits to improve the photocatalytic activity.

  4. Freestanding graphene paper decorated with 2D-assembly of Au@Pt nanoparticles as flexible biosensors to monitor live cell secretion of nitric oxide.

    Science.gov (United States)

    Zan, Xiaoli; Fang, Zheng; Wu, Jin; Xiao, Fei; Huo, Fengwei; Duan, Hongwei

    2013-11-15

    We report the development of a new type of flexible electrochemical biosensors based on graphene paper loaded with closely-packed Au@Pt core-shell nanoparticles as a freestanding cell culture substrate for real-time monitoring cell secretion of nitric oxide. The hybrid electrode was fabricated through a modular approach in which 2D-assembly of nanoparticles formed at the oil-water interface was transferred onto graphene paper by dip-coating. We have shown that the independently optimized metal nanostructures and graphene paper were integrated into functional electrodes with high electrocatalytic activity. When used for the detection of nitric oxide, the flexible electrodes have demonstrated high sensitivity, a wide linear range, and a low detection limit, which, in combination with its biocompatibility, offer unique opportunities for the real-time monitoring of nitric oxide secretion by human endothelial vein cells grown on the electrode. These interesting findings collectively demonstrate the potential of our modular approach for designing high-performance flexible electrodes with tailored surface properties. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Trends in the magnetic properties of Fe, Co, and Ni clusters and monolayers on Ir(111), Pt(111), and Au(111)

    Science.gov (United States)

    Bornemann, S.; Šipr, O.; Mankovsky, S.; Polesya, S.; Staunton, J. B.; Wurth, W.; Ebert, H.; Minár, J.

    2012-09-01

    We present a detailed theoretical investigation on the magnetic properties of small single-layered Fe, Co, and Ni clusters deposited on Ir(111), Pt(111), and Au(111). For this, a fully relativistic ab initio scheme based on density functional theory has been used. We analyze the element, size, and geometry specific variations of the atomic magnetic moments and their mutual exchange interactions as well as the magnetic anisotropy energy in these systems. Our results show that the atomic spin magnetic moments in the Fe and Co clusters decrease almost linearly with increasing coordination number on all three substrates, while the corresponding orbital magnetic moments appear to be much more sensitive to the local atomic environment. The isotropic exchange interaction among the cluster atoms is always very strong for Fe and Co exceeding the values for bulk bcc Fe and hcp Co, whereas the anisotropic Dzyaloshinski-Moriya interaction is, in general, one or two orders of magnitude smaller when compared to the isotropic one. For the magnetic properties of Ni clusters, the magnetic properties can show quite a different behavior, and we find in this case a strong tendency towards noncollinear magnetism.

  6. Pull strength evaluation of Sn-Pb solder joints made to Au-Pt-Pd and Au thick film structures on low-temperature co-fired ceramic -final report for the MC4652 crypto-coded switch (W80).

    Energy Technology Data Exchange (ETDEWEB)

    Uribe, Fernando; Vianco, Paul Thomas; Zender, Gary L.

    2006-06-01

    A study was performed that examined the microstructure and mechanical properties of 63Sn-37Pb (wt.%, Sn-Pb) solder joints made to thick film layers on low-temperature co-fired (LTCC) substrates. The thick film layers were combinations of the Dupont{trademark} 4596 (Au-Pt-Pd) conductor and Dupont{trademark} 5742 (Au) conductor, the latter having been deposited between the 4596 layer and LTCC substrate. Single (1x) and triple (3x) thicknesses of the 4596 layer were evaluated. Three footprint sizes were evaluated of the 5742 thick film. The solder joints exhibited excellent solderability of both the copper (Cu) lead and thick film surface. In all test sample configurations, the 5742 thick film prevented side wall cracking of the vias. The pull strengths were in the range of 3.4-4.0 lbs, which were only slightly lower than historical values for alumina (Al{sub 2}O{sub 3}) substrates. General (qualitative) observations: (a) The pull strength was maximized when the total number of thick film layers was between two and three. Fewer that two layers did not develop as strong of a bond at the thick film/LTCC interface; more than three layers and of increased footprint area, developed higher residual stresses at the thick film/LTCC interface and in the underlying LTCC material that weakened the joint. (b) Minimizing the area of the weaker 4596/LTCC interface (e.g., larger 5742 area) improved pull strength. Specific observations: (a) In the presence of vias and the need for the 3x 4596 thick film, the preferred 4596:5742 ratio was 1.0:0.5. (b) For those LTCC components that require the 3x 4596 layer, but do not have vias, it is preferred to refrain from using the 5742 layer. (c) In the absence of vias, the highest strength was realized with a 1x thick 5742 layer, a 1x thick 4596 layer, and a footprint ratio of 1.0:1.0.

  7. Shape coexistence and strong shape changes in very neutron deficient platinum isotopes

    International Nuclear Information System (INIS)

    Cederwall, B.; Wyss, R.; Johnson, A.; Nyberg, J.; Fant, B.; Chapman, R.; Clarke, D.; Khazaie, F.; Lisle, J.C.; Mo, J.N.; Simpson, J.; Thorslund, I.

    1990-01-01

    High spin states of 175,176 Pt have been populated in 144 Sm( 35 Cl, pxn) reactions at beam energies of 175-185 MeV. In-beam γ-ray spectroscopic techniques using the ESSA30 spectrometer array were adopted. Levels up to spin 26 in 176 Pt and tentatively up to spin 45/2 in 175 Pt have been identified. The data are interpreted within the framework of Cranked Shell model calculations using the deformed Woods-Saxon potential and including monopole pairing. (orig.)

  8. Yields of the rare-earth neutron-deficient isotopes in the reactions of Mo isotopes with 40Ca ions

    International Nuclear Information System (INIS)

    Adam, J.; Chaloun, P.; Gangrskij, Yu.P.

    1999-01-01

    The results of the joint Russian-Chinese experiment on the measurements of the reaction cross sections of the rare-earth neutron-deficient isotopes production and the study of their decay scheme are presented. The studied nuclides were obtained in the reactions 92 Mo + 40 Ca and 97 Mo + 40 Ca on the 4-meter cyclotron of the Flerov Laboratory of Nuclear Reactions, JINR. The recoil nuclei were stopped in the inert gas and transported by the gas flow to the detectors. The single and coincidence spectra of γ-, x-rays and delayed protons were measured. The enhanced yield of the reactions with the charge particle evaporation was observed

  9. Deformation of the very neutron-deficient rare-earth nuclei produced with the SPIRAL 76Kr radioactive beam and studied with EXOGAM + DIAMANT

    Science.gov (United States)

    Redon, N.; Prévost, A.; Guinet, D.; Lautesse, Ph.; Meyer, M.; Rossé, B.; Stézowski, O.; Nolan, P. J.; Andreoiu, C.; Boston, A. J.; Descovich, M.; Evans, A. O.; Gros, S.; Norman, J.; Page, R. D.; Paul, E. S.; Rainovski, G.; Sampson, J.; de France, G.; Casandjian, J. M.; Theisen, Ch.; Scheurer, J. N.; Nyakó, B. M.; Gál, J.; Kalinka, G.; Molnár, J.; Dombrádi, Zs.; Timár, J.; Zolnai, L.; Juhász, K.; Astier, A.; Deloncle, I.; Porquet, M. G.; Wadsworth, R.; Raddon, P.; Lee, Y.; Wilkinson, A.; Joshi, P.; Simpson, J.; Appelbe, D.; Joss, D.; Lemmon, R.; Smith, J.; Cullen, D.; Brondi, A.; La Rana, G.; Moro, R.; Vardacci, E.; Girod, M.

    2004-02-01

    The structure of the very neutron-deficient rare-earth nuclei has been investigated in the first experiment with the EXOGAM gamma array coupled to the DIAMANT light charged particle detector using radioactive beam of 76Kr delivered by the SPIRAL facility. Very neutron-deficient Pr, Nd and Pm isotopes have been populated at rather high spin by the reaction 76Kr + 58Ni at a beam energy of 328 MeV. We report here the first results of this experiment.

  10. Experimental investigation of decay properties of neutron deficient $^{116-118}$Ba isotopes and test of $^{112-115}$Ba beam counts

    CERN Multimedia

    We propose to study decay of neutron deficient isotopes $^{116-118}$Ba using Double Sided Silicon Strip Detector (DSSSD). To study delayed-proton and $\\alpha$-decay branching ratios of $^{116-118}$Ba are of special interest because of their vicinity to the proton drip line. The nuclear life-times and properties of the proton unstable states of Cs isotopes, populated through decay of $^{116-118}$Ba isotopes will be measured. In addition to that we propose beam development of $^{112-115}$Ba to study exotic decay properties of these neutron deficient nuclei and to search for super-allowed $\\alpha$-decay in future.

  11. Stage II recovery behavior of a series of ion-irradiated platinum (gold) alloys as studied by field-ion microscopy. [0. 10, 0. 62, and 4. 0 at. percent Au and pure Pt

    Energy Technology Data Exchange (ETDEWEB)

    Wei, C.Y.; Seidman, D.N.

    1976-11-01

    Direct and visible evidence was obtained for long-range migration of self-interstitial atoms (SIAs) in Stage II of three different ion-irradiated platinum (gold) alloys. Field-ion microscope (FIM) specimens of Pt--0.10, 0.62 and 4.0 at. percent Au alloys were irradiated in-situ with 30-keV W/sup +/ or Pt/sup +/ ions at a tip temperature of 35 to 41 K at 2 x 10/sup -9/ torr. Direct observation of the surfaces of the FIM specimens during isochronal warming experiments to 100 K showed that a flux of SIAs crossed the surfaces of the specimens between 40 to 100 K. The spectrum for each alloy consisted of two recovery peaks (substages II/sub B/ and II/sub C/). The results are explained on the basis of an impurity-delayed diffusion mechanism employing a two-level trapping model. The application of this diffusion model to the isochronal recovery spectra yielded a dissociation enthalpy (DELTAh/sub li-Au//sup diss/) and an effective diffusion coefficient for each substage; for substage II/sub B/ DELTAh/sub li-Au//sup diss/ (II/sub B/) = 0.15 eV and for substage II/sub C/ DELTAh/sub li-Au//sup diss/ (II/sub C/) = 0.24 eV. A series of detailed control experiments was also performed to show that the imaging electric field had not caused the observed long-range migration of SIAs and that the observed effects were not the result of surface artifacts. 14 figures, 6 tables.

  12. Insights into electrochemical dealloying of Cu out of Au-doped Pt-alloy nanoparticles at the sub-nano-scale

    Directory of Open Access Journals (Sweden)

    Matija Gatalo

    2018-03-01

    Full Text Available Pt alloy nanoparticles present the most probable candidate to be used as the cathode cathodic oxygen reduction reaction electrocatalyst for achieving commercialization targets of the low-temperature fuel cells. It is therefore very important to understand its activation and degradation processes. Besides the ones known from the pure Pt electrocatalysts, the dealloying phenomena possess a great threat since the leached less-noble metal can interact with the polymer membrane or even poison the electrocatalyst. In this study, we present a solution, supported by in-depth advance electrochemical characterization, on how to suppress the removal of Cu from the Pt alloy nanoparticles.

  13. Study of the odd-${A}$, high-spin isomers in neutron-deficient trans-lead nuclei with ISOLTRAP

    CERN Multimedia

    Herfurth, F; Blaum, K; Beck, D; Kowalska, M; Schwarz, S; Stanja, J; Huyse, M L; Wienholtz, F

    We propose to measure the excitation energy of the $\\frac{13^{+}}{2}$ isomers in the neutron-deficient isotopes $^{193,195,197}$Po with the ISOLTRAP mass spectrometer. The assignment of the low- and high-spin isomers will be made by measuring the energy of the $\\alpha$- particles emitted in the decay of purified beams implanted in a windmill system. Using $\\alpha$-decay information, it is then also possible to determine the excitation energy of the similar isomers in the $\\alpha$-daughter nuclei $^{189,191,193}$Pb, $\\alpha$-parent nuclei $^{197,199,201}$Rn, and $\\alpha$-grand-parent nuclei $^{201,203,205}$Ra. The polonium beams are produced with a UC$_{\\textrm{x}}$ target and using the RILIS.

  14. NEAR-ABSOLUTE EQUATIONS OF STATE OF DIAMOND, Ag, Al, Au, Cu, Mo, Nb, Pt, Ta, AND W FOR QUASI-HYDROSTATIC CONDITIONS

    Directory of Open Access Journals (Sweden)

    Peter I. Dorogokupets

    2012-01-01

    Full Text Available Using the modified formalism of [Dorogokupets, Oganov, 2005, 2007], equations of state are developed for diamond, Ag, Al, Au, Cu, Mo, Nb, Pt, Ta, and W by simultaneous optimization of shock-wave data, ultrasonic, X-ray, dilatometric and thermochemical measurements in the temperature range from ~100 K to the melting temperature and pressures up to several Mbar, depending on the substance. The room-temperature isotherm is given in two forms: (1 the equation from [Holzapfel, 2001, 2010] which is the interpolation between the low pressure (x≥1 and the pressure at infinite compression (x=0; it corresponds to the Thomas-Fermi model, and (2 the equation from [Vinet et al., 1987]. The volume dependence of the Grüneisen parameter is calculated according to equations from [Zharkov, Kalinin, 1971; Burakovsky, Preston, 2004] with adjustable parameters, t and δ. The room-temperature isotherm and the pressure on the Hugoniot adiabat are determined by three parameters, K', t and δ, and K0 is calculated from ultrasonic measurements. In our study, reasonably accurate descriptions of all of the basic thermodynamic functions of metals are derived from a simple equation of state with a minimal set of adjustable parameters.The pressure calculated from room-temperature isotherms can be correlated with a shift of the ruby R1 line. Simultaneous measurements of the shift and unit cell parameters of metals are conducted in mediums containing helium [Dewaele et al., 2004b; 2008; Takemura, Dewaele, 2008; Takemura, Singh, 2006], hydrogen [Chijioke et al., 2005] and argon [Tang et al., 2010]. According to [Takemura, 2001], the helium medium in diamond anvil cells provides for quasi-hydrostatic conditions; therefore, the ruby pressure scale, that is calibrated for the ten substances, can be considered close to equilibrium or almost absolute. The ruby pressure scale is given as P(GPa=1870⋅Δλ/λ0⋅(1+6⋅Δλ/λ0. The room-temperature isotherms corrected with regard

  15. Printing graphene-carbon nanotube-ionic liquid gel on graphene paper: Towards flexible electrodes with efficient loading of PtAu alloy nanoparticles for electrochemical sensing of blood glucose.

    Science.gov (United States)

    He, Wenshan; Sun, Yimin; Xi, Jiangbo; Abdurhman, Abduraouf Alamer Mohamed; Ren, Jinghua; Duan, Hongwei

    2016-01-15

    The increasing demands for portable, wearable, and implantable sensing devices have stimulated growing interest in innovative electrode materials. In this work, we have demonstrated that printing a conductive ink formulated by blending three-dimensional (3D) porous graphene-carbon nanotube (CNT) assembly with ionic liquid (IL) on two-dimensional (2D) graphene paper (GP), leads to a freestanding GP supported graphene-CNT-IL nanocomposite (graphene-CNT-IL/GP). The incorporation of highly conductive CNTs into graphene assembly effectively increases its surface area and improves its electrical and mechanical properties. The graphene-CNT-IL/GP, as freestanding and flexible substrates, allows for efficient loading of PtAu alloy nanoparticles by means of ultrasonic-electrochemical deposition. Owing to the synergistic effect of PtAu alloy nanoparticles, 3D porous graphene-CNT scaffold, IL binder and 2D flexible GP substrate, the resultant lightweight nanohybrid paper electrode exhibits excellent sensing performances in nonenzymatic electrochemical detection of glucose in terms of sensitivity, selectivity, reproducibility and mechanical properties. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. The properties of atomic nuclei at the boundary of proton instability, discussed at the example of very neutron deficient isotopes in the mass range 100-150

    International Nuclear Information System (INIS)

    Roeckl, E.

    1981-10-01

    In this paper it shall be tried to strike the balance after the first years of experimenting at the on-line mass separator of the GSI Darmstadt and to present the main results of the study of very neutron deficient isotopes in the mass range 90-150 as well as the resulting questions for further experiments. First some foundations concerning the properties of neutron deficient nuclei and the measuring method are explained. The results and their interpretation are discussed using examples for the alpha decay, the beta decay, the mass-energy-area, and the proton-drip line. Finally the obtained results are summarized, and an outlook to further studies of nuclear properties far from beta stability is given. (orig.) [de

  17. Synthesis and characterization of Pd@M(x)Cu(1-x) (M = Au, Pd, and Pt) nanocages with porous walls and a yolk-shell structure through galvanic replacement reactions.

    Science.gov (United States)

    Xie, Shuifen; Jin, Mingshang; Tao, Jing; Wang, Yucai; Xie, Zhaoxiong; Zhu, Yimei; Xia, Younan

    2012-11-19

    This paper describes the synthesis of Pd@M(x)Cu(1-x) (M = Au, Pd, and Pt) nanocages with a yolk-shell structure through galvanic replacement reactions that involve Pd@Cu core-shell nanocubes as sacrificial templates and ethylene glycol as the solvent. Compared with the most commonly used templates based on Ag, Cu offers a much lower reduction potential (0.34 versus 0.80 V), making the galvanic reaction more easily to conduct, even at room temperature. Our structural and compositional characterizations indicated that the products were hollow inside, and each one of them contained porous M-Cu alloy walls and a Pd cube in the interior. For the Pd@Au(x)Cu(1-x) yolk-shell nanocages, they displayed broad extinction peaks extending from the visible to the near-IR region. Our mechanistic study revealed that the dissolution of the Cu shell preferred to start from the slightly truncated corners and then progressed toward the interior, because the Cu {100} side faces were protected by a surface capping layer of hexadecylamine. This galvanic approach can also be extended to generating other hollow metal nanostructures by using different combinations of Cu nanostructures and salt precursors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. General synthesis of noble metal (Au, Ag, Pd, Pt) nanocrystal modified MoS2 nanosheets and the enhanced catalytic activity of Pd-MoS2 for methanol oxidation

    Science.gov (United States)

    Yuwen, Lihui; Xu, Fei; Xue, Bing; Luo, Zhimin; Zhang, Qi; Bao, Biqing; Su, Shao; Weng, Lixing; Huang, Wei; Wang, Lianhui

    2014-05-01

    A general and facile method for water-dispersed noble metal (Au, Ag, Pd, Pt) nanocrystal modified MoS2 nanosheets (NM-MoS2 NSs) has been developed. By using sodium carboxymethyl cellulose as a stabilizer, well-dispersed NM-MoS2 NSs with homogeneously deposited noble metal nanocrystals (NM NCs) can be synthesized in aqueous solutions. Due to the transition from the semiconducting 2H phase to the metallic 1T phase, the chemically exfoliated MoS2 (ce-MoS2) NSs have improved electrochemical activity. The partially metallic nature of the ce-MoS2 NSs and the catalytic activity of the NM NCs synergistically make NM-MoS2 NSs a potential electrochemical catalyst. For the first time, Pd-MoS2 NSs were used as an electrocatalyst for methanol oxidation in alkaline media. The results showed that Pd-MoS2 NSs have enhanced catalytic activity with 2.8-fold anodic peak current mass density compared to a commercial Pd/C catalyst, suggesting potential for application in direct methanol fuel cells (DMFCs).A general and facile method for water-dispersed noble metal (Au, Ag, Pd, Pt) nanocrystal modified MoS2 nanosheets (NM-MoS2 NSs) has been developed. By using sodium carboxymethyl cellulose as a stabilizer, well-dispersed NM-MoS2 NSs with homogeneously deposited noble metal nanocrystals (NM NCs) can be synthesized in aqueous solutions. Due to the transition from the semiconducting 2H phase to the metallic 1T phase, the chemically exfoliated MoS2 (ce-MoS2) NSs have improved electrochemical activity. The partially metallic nature of the ce-MoS2 NSs and the catalytic activity of the NM NCs synergistically make NM-MoS2 NSs a potential electrochemical catalyst. For the first time, Pd-MoS2 NSs were used as an electrocatalyst for methanol oxidation in alkaline media. The results showed that Pd-MoS2 NSs have enhanced catalytic activity with 2.8-fold anodic peak current mass density compared to a commercial Pd/C catalyst, suggesting potential for application in direct methanol fuel cells (DMFCs

  19. The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

    Science.gov (United States)

    Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

    2015-05-28

    Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and

  20. β-delayed charged particle decays of neutron-deficient nuclei 20Mg and 23Si and 22Si

    International Nuclear Information System (INIS)

    Babo, Mathieu

    2016-01-01

    The neutron-deficient nuclei 20 Mg, 23 Si and 22 Si were produced by fragmentation at NSCL, at MSU (USA), and implanted into an array of 3 double sided stripped Si detectors, surrounded by 16 high-purity Ge detectors. This novel arrangement allowed the detection of the charged particles emitted by the unbound excited states in coincidence with the γ rays emitted by the de-excitation of the daughter. The βp decay of 20 Mg is very well-known and therefore was used to test and optimize the analysis program. The β-delayed proton transitions to the first 3 excited states in 19 Ne were identified and compared to previous measurements. The half-life, the branching ratio of the transitions and the excitation energies, including the IAS, were measured and are in good agreement with the adopted values. The study of the β+ decay of 23 Si allowed the identification of 14 excited states in 23 Al. The emission of 2 protons from the IAS was unambiguously identified. The measurement of the IAS energy allowed a better determination of the mass excess of 23 Si, giving 23.27 (7) MeV. A possible β3p decay channel was also tentatively identified. Most of the theoretical predictions are in favor of a 2-proton radioactive 22 Si. The β2p decays to the first excited state and the ground state of 20 Na were identified. The branching ratio of the decay to the IAS is 2.05 (44) %, and the IAS excitation energy was measured to be 9040 (54) keV. The additional measurement of the half-life gives T 1/2 = 30.38 (45) ms, and allowed the determination of the partial half-life. In this study, we propose a parameterization of the statistical rate function f for the superallowed Fermi β decays. This allow the first indirect mass measurement of 22 Si ground state, 31.49 (14) MeV. The two-proton threshold is then S2p = 645 (100) keV and does not allow 2p radioactivity. (author) [fr

  1. The Close Relationships between the Crystal Structures of MO and MSO 4 (M = Group 10, 11, or 12 Metal), and the Predicted Structures of AuO and PtSO 4

    KAUST Repository

    Derzsi, Mariana

    2013-08-21

    The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects. The collective Jahn-Teller deformations lead either to tetragonal contraction or (seldom) elongation of the rock salt lattice. On the basis of the rock salt representation of the oxides and sulfates, we show that PdO, CuO, and AgO are metrically related and that the 4d and 5d metal sulfates are close to isostructural with their oxides. These observations guide us towards as yet unknown AuO and PtSO4, for which we predict crystal structures from electronic structure calculations. The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects, as quantified by the c′/a′ ratio. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Shape coexistence measurements in even-even neutron-deficient polonium isotopes by Coulomb excitation, using REX-ISOLDE and the Ge MINIBALL array

    CERN Multimedia

    Butler, P; Bastin, B; Kruecken, R; Voulot, D; Rahkila, P J; Orr, N A; Srebrny, J; Grahn, T; Clement, E; Paul, E S; Gernhaeuser, R A; Dorsival, A; Diriken, J V J; Huyse, M L; Iwanicki, J S

    The neutron-deficient polonium isotopes with two protons outside the closed Z=82 shell represent a set of nuclei with a rich spectrum of nucleus structure phenomena. While the onset of the deformation in the light Po isotopes is well established experimentally, questions remain concerning the sign of deformation and the magnitude of the mixing between different configurations. Furthermore, controversy is present with respect to the transition from the vibrational-like character of the heavier Po isotopes to the shape coexistence mode observed in the lighter Po isotopes. We propose to study this transition in the even-mass neutron-deficient $^{198,200,202}$Po isotopes by using post-accelerated beams from REX-ISOLDE and "safe"-energy Coulomb excitation. $\\gamma$- rays will be detected by the MINIBALL array. The measurements of the Coulomb excitation differential cross section will allow us to deduce both the transition and diagonal matrix elements for these nuclei and, combined with lifetime measurements, the s...

  3. Oxygen Reduction Reaction on Pt Overlayers Deposited onto a Gold Film: Ligand, Strain, and Ensemble Effect

    DEFF Research Database (Denmark)

    Deng, Yu-Jia; Tripkovic, Vladimir; Rossmeisl, Jan

    2016-01-01

    We study the oxygen reduction reaction (ORR), the catalytic process occurring at the cathode in fuel cells, on Pt layers prepared by electrodeposition onto an Au substrate. Using a nominal Pt layer by layer deposition method previously proposed, imperfect layers of Pt on Au are obtained. The ORR...

  4. Performance of the multiple target He/PbI sub 2 aerosol jet system for mass separation of neutron-deficient actinide isotopes

    CERN Document Server

    Ichikawa, S; Asai, M; Haba, H; Sakama, M; Kojima, Y; Shibata, M; Nagame, Y; Oura, Y; Kawade, K

    2002-01-01

    A multiple target He/PbI sub 2 aerosol jet system coupled with a thermal ion source was installed in the isotope separator on line (JAERI-ISOL) at the JAERI tandem accelerator facility. The neutron-deficient americium and curium isotopes produced in the sup 2 sup 3 sup 3 sup , sup 2 sup 3 sup 5 U( sup 6 Li, xn) and sup 2 sup 3 sup 7 Np( sup 6 Li, xn) reactions were successfully mass-separated and the overall efficiency including the ionization of Am atoms was evaluated to be 0.3-0.4%. The identification of a new isotope sup 2 sup 3 sup 7 Cm with the present system is reported.

  5. Effect of the particle-number symmetry restoration on root mean square radii of even–even neutron-deficient nuclei in the isovector pairing case

    International Nuclear Information System (INIS)

    Douici, M.; Allal, N.H.; Fellah, M.; Benhamouda, N.; Oudih, M.R.

    2012-01-01

    The effect of the particle-number symmetry restoration on the root mean square (rms) proton and neutron radii of neutron-deficient nuclei is studied in the isovector pairing case. As a first step, an expression of the nuclear radii which includes the neutron–proton pairing effects and which strictly conserves the particle-number has been established using the SBCS (Sharp BCS) method. It is shown that this expression generalizes the one obtained in the pairing between like-particles case. As a second step, the proton and neutron rms radii are numerically evaluated for even–even nuclei such as 16⩽Z⩽56 and 0⩽(N-Z)⩽4 using the single-particle energies of a Woods–Saxon mean-field. The results are compared with experimental data when available and with the results obtained when one considers only the pairing between like-particles. (author)

  6. Shape coexistence in neutron-deficient Hg isotopes studied via lifetime measurements in $^{184,186}$Hg and two-state mixing calculations

    CERN Document Server

    Gaffney, L P; Page, R.D.; Grahn, T.; Scheck, M.; Butler, P.A.; Bertone, P.F.; Bree, N.; Carroll, R.J.; Carpenter, M.P.; Chiara, C.J.; Dewald, A.; Filmer, F.; Fransen, C.; Huyse, M.; Janssens, R.V.F.; Joss, D.T.; Julin, R.; Kondev, F.G.; Nieminen, P.; Pakarinen, J.; Rigby, S.V.; Rother, W.; Van Duppen, P.; Watkins, H.V.; Wrzosek-Lipska, K.; Zhu, S.

    2014-01-01

    The neutron-deficient mercury isotopes, $^{184,186}$Hg, were studied with the Recoil Distance Doppler Shift (RDDS) method using the Gammasphere array and the K\\"oln Plunger device. The Differential Decay Curve Method (DDCM) was employed to determine the lifetimes of the yrast states in $^{184,186}$Hg. An improvement on previously measured values of yrast states up to $8^{+}$ is presented as well as first values for the $9_{3}$ state in $^{184}$Hg and $10^{+}$ state in $^{186}$Hg. $B(E2)$ values are calculated and compared to a two-state mixing model which utilizes the variable moment of inertia (VMI) model, allowing for extraction of spin-dependent mixing strengths and amplitudes.

  7. Spectroscopy of the long-lived excited state in the neutron-deficient nuclides 195,197,199Po by precision mass measurements

    Science.gov (United States)

    Althubiti, N. A.; Atanasov, D.; Blaum, K.; Cocolios, T. E.; Day Goodacre, T.; Farooq-Smith, G. J.; Fedorov, D. V.; Fedosseev, V. N.; George, S.; Herfurth, F.; Heyde, K.; Kreim, S.; Lunney, D.; Lynch, K. M.; Manea, V.; Marsh, B. A.; Neidherr, D.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Schweikhard, L.; Seliverstov, M. D.; Welker, A.; Wienholtz, F.; Wolf, R. N.; Zuber, K.; Isoltrap Collaboration

    2017-10-01

    Direct mass measurements of the low-spin 3 /2- and high-spin 13 /2+ states in the neutron-deficient isotopes 195Po and 197Po were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the ν i13 /2 orbital in Po,197195. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from α -decay chains. These excitation energies complete the knowledge of the energy systematics in the region and confirm that the 13 /2+ states remain isomeric, independent of the number of valence neutrons.

  8. An analysis of the pull strength behaviors of fine-pitch, flip chip solder interconnections using a Au-Pt-Pd thick film conductor on Low-Temperature, Co-fired Ceramic (LTCC) substrates.

    Energy Technology Data Exchange (ETDEWEB)

    Uribe, Fernando R.; Kilgo, Alice C.; Grazier, John Mark; Vianco, Paul Thomas; Zender, Gary L.; Hlava, Paul Frank; Rejent, Jerome Andrew

    2008-09-01

    The assembly of the BDYE detector requires the attachment of sixteen silicon (Si) processor dice (eight on the top side; eight on the bottom side) onto a low-temperature, co-fired ceramic (LTCC) substrate using 63Sn-37Pb (wt.%, Sn-Pb) in a double-reflow soldering process (nitrogen). There are 132 solder joints per die. The bond pads were gold-platinum-palladium (71Au-26Pt-3Pd, wt.%) thick film layers fired onto the LTCC in a post-process sequence. The pull strength and failure modes provided the quality metrics for the Sn-Pb solder joints. Pull strengths were measured in both the as-fabricated condition and after exposure to thermal cycling (-55/125 C; 15 min hold times; 20 cycles). Extremely low pull strengths--referred to as the low pull strength phenomenon--were observed intermittently throughout the product build, resulting in added program costs, schedule delays, and a long-term reliability concern for the detector. There was no statistically significant correlation between the low pull strength phenomenon and (1) the LTCC 'sub-floor' lot; (2) grit blasting the LTCC surfaces prior to the post-process steps; (3) the post-process parameters; (4) the conductor pad height (thickness); (5) the dice soldering assembly sequence; or (5) the dice pull test sequence. Formation of an intermetallic compound (IMC)/LTCC interface caused by thick film consumption during either the soldering process or by solid-state IMC formation was not directly responsible for the low-strength phenomenon. Metallographic cross sections of solder joints from dice that exhibited the low pull strength behavior, revealed the presence of a reaction layer resulting from an interaction between Sn from the molten Sn-Pb and the glassy phase at the TKN/LTCC interface. The thick film porosity did not contribute, explicitly, to the occurrence of reaction layer. Rather, the process of printing the very thin conductor pads was too sensitive to minor thixotropic changes to ink, which resulted in

  9. Isolation and Structural Characterization of a Mackay 55-Metal-Atom Two-Shell Icosahedron of Pseudo-Ih Symmetry, Pd55L12(μ3-CO)20 (L = PR3, R = Isopropyl): Comparative Analysis with Interior Two-Shell Icosahedral Geometries in Capped Three-Shell Pd145, Pt-Centered Four-Shell Pd-Pt M165, and Four-Shell Au133 Nanoclusters.

    Science.gov (United States)

    Erickson, Jeremiah D; Mednikov, Evgueni G; Ivanov, Sergei A; Dahl, Lawrence F

    2016-02-10

    We present the first successful isolation and crystallographic characterization of a Mackay 55-metal-atom two-shell icosahedron, Pd55L12(μ3-CO)20 (L = PPr(i)3) (1). Its two-shell icosahedron of pseudo-Ih symmetry (without isopropyl substituents) enables a structural/bonding comparison with interior 55-metal-atom two-shell icosahedral geometries observed within the multi-shell capped 145-metal-atom three-shell Pd145(CO)72(PEt3)30 and 165-metal-atom four-shell Pt-centered (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x ≈ 7) nanoclusters, and within the recently reported four-shell Au133(SC6H4-p-Bu(t))52 nanocluster. DFT calculations carried out on a Pd55(CO)20(PH3)12 model analogue, with triisopropyl phosphine substituents replaced by H atoms, revealed a positive +0.84 e charge for the entire Pd55 core, with a highly positive second-shell Pd42 surface of +1.93 e.

  10. Simultaneous spectroscopy of $\\gamma$- rays and conversion electrons: Systematic study of EO transitions and intruder states in close vicinity of mid-shell point in odd-Au isotopes

    CERN Multimedia

    Venhart, M; Grant, A F; Petrik, K

    This proposal focuses on detailed systematic studies of the $\\beta$ /EC-decays of $^{179,181,183,185}$Hg leading to excited states in the neutron-deficient Au isotopes in the vicinity of the N=104 midshell. $\\gamma$-ray, X-ray and conversion electron de-excitations of odd-A Au isotopes will be studied simultaneously. These studies will address important structural questions such as the excitation energies of coexisting states, properties of multiple intruder states (i.e. intruder particles coupled to intruder cores) and mixing of coexisting structures. The unique combination of Hg beam purity and yields make ISOLDE a unique facility for these experiments.

  11. Transverse momentum and centrality dependence of high-ptnon-photonic electron suppression in Au+Au collisions at $\\sqrt{s_{NN}}$= 200 GeV

    Energy Technology Data Exchange (ETDEWEB)

    Abelev, B.I.; Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett,J.; Anderson, B.D.; Anderson, M.; Arkhipkin, D.; Averichev, G.S.; Bai,Y.; Balewski, J.; Barannikova, O.; Barnby, L.S.; Baudot, J.; Bekele, S.; Belaga, V.V.; Bellingeri-Laurikainen, A.; Bellwied, R.; Benedosso, F.; Bhardwaj, S.; Bhasin, A.; Bhati, A.K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L.C.; Blyth, S.-L.; Bonner, B.E.; Botje, M.; Bouchet, J.; Brandin, A.V.; Bravar, A.; Bystersky, M.; Cadman, R.V.; Cai,X.Z.; Caines, H.; Calderon de la Barca Sanchez, M.; Castillo, J.; Catu,O.; Cebra, D.; Chajecki, Z.; Chaloupka, P.; Chattopadhyay, S.; Chen,H.F.; Chen, J.H.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Coffin, J.P.; Cormier, T.M.; Cosentino, M.R.; Cramer, J.G.; Crawford,H.J.; Das, D.; Das, S.; Daugherity, M.; de Moura, M.M.; Dedovich, T.G.; DePhillips, M.; Derevschikov, A.A.; Didenko, L.; Dietel, T.; Djawotho,P.; Dogra, S.M.; Dong, W.J.; Dong, X.; Draper, J.E.; Du, F.; Dunin, V.B.; Dunlop, J.C.; Dutta Mazumdar, M.R.; Eckardt, V.; Edwards, W.R.; Efimov,L.G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Filimonov, K.; Filip, P.; Finch,E.; Fine, V.; Fisyak, Y.; Fu, J.; Gagliardi, C.A.; Gaillard, L.; Ganti,M.S.; Ghazikhanian, V.; Ghosh, P.; Gonzalez, J.S.; Gorbunov, Y.G.; Gos,H.; Grebenyuk, O.; Grosnick, D.; Guertin, S.M.; Guimaraes, K.S.F.F.; Guo,Y.; Gupta, N.; Gutierrez, T.D.; Haag, B.; Hallman, T.J.; Hamed, A.; Harris, J.W.; He, W.; Heinz, M.; Henry, T.W.; Hepplemann, S.; Hippolyte,B.; Hirsch, A.; Hjort, E.; Hoffman, A.M.; Hoffmann, G.W.; Horner, M.J.; Huang, H.Z.; Huang, S.L.; Hughes, E.W.; Humanic, T.J.; Igo, G.; Jacobs,P.; Jacobs, W.W.; Jakl, P.; Jia, F.; Jiang, H.; Jones, P.G.; Judd, E.G.; Kabana, S.; Kang, K.; Kapitan, J.; Kaplan, M.; Keane, D.; Kechechyan, A.; Khodyrev, V.Yu.; Kim, B.C.; Kiryluk, J.; Kisiel, A.; Kislov, E.M.; Klein,S.R.; Kocoloski, A.; Koetke, D.D.; et al.

    2006-07-11

    The STAR collaboration at RHIC reports measurements of theinclusive yield of non-photonic electrons, which arise dominantly fromsemi-leptonic decays of heavy flavor mesons, over a broad range oftransverse momenta (1.2<pt<10 gevc) in pp, dAu, and AuAucollisions at sqrt sNN = 200 GeV. The non-photonic electron yieldexhibits unexpectedly large suppression in central AuAu collisions athigh pt, suggesting substantial heavy quark energy loss at RHIC. Thecentrality and \\pt dependences of the suppression provide constraints ontheoretical models of suppression.

  12. Jets and high pT hadrons in dense matter: recent results from STAR

    International Nuclear Information System (INIS)

    Jacobs, Peter; Klay, Jennifer

    2004-01-01

    We review recent measurements of high transverse momentum (high pT) hadron production in nuclear collisions by the STAR Collaboration at RHIC. The previously observed suppression in central Au+Au collisions has been extended to much higher pT. New measurements from d+Au collisions are presented which help disentangle the mechanisms responsible for the suppression. Inclusive single hadron spectra are enhanced in d+Au relative to p+p, while two-particle azimuthal distributions are observed to be similar in p+p, d+Au and peripheral Au+Au collisions. The large suppression of inclusive hadron production and absence of the away-side jet-like correlations in central Au+Au collisions are shown to be due to interactions of the jets with the very dense medium produced in these collisions

  13. Efficient C-C bond splitting on Pt monolayer and sub-monolayer catalysts during ethanol electro-oxidation: Pt layer strain and morphology effects.

    Science.gov (United States)

    Loukrakpam, Rameshwori; Yuan, Qiuyi; Petkov, Valeri; Gan, Lin; Rudi, Stefan; Yang, Ruizhi; Huang, Yunhui; Brankovic, Stanko R; Strasser, Peter

    2014-09-21

    Efficient catalytic C-C bond splitting coupled with complete 12-electron oxidation of the ethanol molecule to CO2 is reported on nanoscale electrocatalysts comprised of a Pt monolayer (ML) and sub-monolayer (sML) deposited on Au nanoparticles (Au@Pt ML/sML). The Au@Pt electrocatalysts were synthesized using surface limited redox replacement (SLRR) of an underpotentially deposited (UPD) Cu monolayer in an electrochemical cell reactor. Au@Pt ML showed improved catalytic activity for ethanol oxidation reaction (EOR) and, unlike their Pt bulk and Pt sML counterparts, was able to generate CO2 at very low electrode potentials owing to efficient C-C bond splitting. To explain this, we explore the hypothesis that competing strain effects due to the Pt layer coverage/morphology (compressive) and the Pt-Au lattice mismatch (tensile) control surface chemisorption and overall activity. Control experiments on well-defined model Pt monolayer systems are carried out involving a wide array of methods such as high-energy X-ray diffraction, pair-distribution function (PDF) analysis, in situ electrochemical FTIR spectroscopy, and in situ scanning tunneling microscopy. The vibrational fingerprints of adsorbed CO provide compelling evidence on the relation between surface bond strength, layer strain and morphology, and catalytic activity.

  14. Pt surface segregation in bimetallic Pt 3M alloys: A density functional theory study

    Science.gov (United States)

    Ma, Yuguang; Balbuena, Perla B.

    A simplified 5-layer slab model is used to study Pt segregation at Pt 3M(1 1 1) surfaces (M = Ag, Au, Co, Cr, Cu, Fe, Ir, Mn, Mo, Ni, Pd, Re, Rh, Ru, Ti, V). The calculated segregation energies are generally in good agreement with the experimental results. However, for Pt 3Ti(1 1 1) and Pt 3Mn(1 1 1), the model is unable to give the correct prediction because the experimental subsurface compositions are very different from those of the model. Pt segregation is found to be correlated with the subsurface atomic structure, the size of metal atoms and the surface energy. Interestingly, the calculations show that the displacement of M atoms at the topmost Pt 3M layer can be used to predict the surface segregation trend. The local geometries for the segregation and non-segregation structures are carefully compared and the surface geometric effect on the oxygen reduction reaction (ORR) activity is discussed. In particular, it is determined that the enhanced ORR activity for the Pt-skin surfaces of Pt 3Ni(1 1 1) and Pt 3Co(1 1 1) alloys are not caused by geometric effects.

  15. Partonic flow and ϕ-meson production in Au+Au collisions at VsNN=200 = GeV

    NARCIS (Netherlands)

    Bai, Y.; Benedosso, F.; Botje, M.A.J.; Grebenyuk, O.; Mischke, A.; Peitzmann, T.; Russcher, M.J.; Snellings, R.J.M.; van der Kolk, N.

    2007-01-01

    We present first measurements of the ϕ-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from √sNN=200  GeV Au+Au collisions at RHIC. In minimum bias collisions the v2 of the ϕ meson is consistent with the trend observed for mesons. The ratio of the yields

  16. Study of neutron deficient iridium isotopes by using laser spectroscopy; Etude des noyaux d'iridium deficients en neutrons par spectroscopie laser

    Energy Technology Data Exchange (ETDEWEB)

    Verney, D

    2000-12-19

    Resonance ionization spectroscopy was performed on neutron deficient iridium isotopes {sup 182-189}Ir, {sup 186}Ir{sup m} and stable isotopes {sup 191,193}Ir. Hyperfine spectra were recorded from the optical transition at 351,7 nm between the 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2} ground state and the 5d{sup 7}6s6p {sup 6}F{sub 11/2} excited state. Radioactive iridium isotopes were obtained from {beta}{sup +}/EC decay of radioactive mercury nuclei deposited on a graphite substrate. The radioactive mercury nuclei were produced at the ISOLDE facility at CERN through spallation reactions, by bombarding a molten lead target with the 1 GeV proton beam delivered by the PS-Booster. Magnetic dipole moments and spectroscopic quadrupole moments were extracted from the hyperfine spectra. The mean square charge radius variations, as deduced from the measured isotopic shift, show a sharp change between {sup 187}Ir and {sup 186}Ir{sup g}, accompanied by a sudden increase in deformation: from {beta}2 {approx} 0,16 to {beta}2 > 0, 2. These results were analysed in the framework of an axial rotor plus one or two quasiparticles. The wave functions of the osmium and platinum cores which are used in order to describe the iridium nuclei were calculated from the HF+BCS method with the Skyrme SIII effective interaction. The cores were constrained to take the deformation parameters extracted from the isotopic shift measurements. One shows then that this sudden deformation change corresponds also to a change in the proton state that describes the odd nuclei ground state or that participates in the coupling with the neutron in odd-odd nuclei. This state is identified with the {pi}3/2{sup +}[402] orbital for the smaller deformations nuclei and with the {pi}1/2{sup -}[541] orbital stemming from the h{sub 9/2} subshell for bigger deformations nuclei. (author)

  17. In vitro corrosion of dental Au-based casting alloys in polyvinylpyrrolidone-iodine solution.

    Science.gov (United States)

    Takasusuki, Norio; Ida, Yusuke; Hirose, Yukito; Ochi, Morio; Endo, Kazuhiko

    2013-01-01

    The corrosion and tarnish behaviors of two Au-based casting alloys (ISO type 1 and type 4 Au alloys) and their constituent pure metals, Au, Ag, Cu, Pt, and Pd in a polyvinylpyrrolidone-iodine solution were examined. The two Au alloys actively corroded, and the main anodic reaction for both was dissolution of Au as AuI₂(-). The amount of Au released from the ISO type 1 Au alloy was significantly larger than that from the ISO type 4 Au alloy (Palloy exhibited higher susceptibility to tarnishing than the type 4 alloy. The corrosion forms of the two Au alloys were found to be completely different, i.e., the type 1 alloy exhibited the corrosion attack over the entire exposed surface with a little irregularity whereas the type 4 alloy exhibited typical intergranular corrosion, which was caused by local cells produced by segregation of Pd and Pt.

  18. Efficient C–C bond splitting on Pt monolayer and sub-monolayer catalysts during ethanol electro-oxidation: Pt layer strain and morphology effects

    Energy Technology Data Exchange (ETDEWEB)

    Loukrakpam, Rameshwori; Yuan, Qiuyi; Petkov, Valeri; Gan, Lin; Rudi, Stefan; Yang, Ruizhi; Huang, Yunhui; Brankovic, Stanko R.; Strasser, Peter (TU Berlin); (Soochow); (CMU); (Huazhong); (Houston)

    2014-07-23

    Efficient catalytic C–C bond splitting coupled with complete 12-electron oxidation of the ethanol molecule to CO2 is reported on nanoscale electrocatalysts comprised of a Pt monolayer (ML) and sub-monolayer (sML) deposited on Au nanoparticles (Au@Pt ML/sML). The Au@Pt electrocatalysts were synthesized using surface limited redox replacement (SLRR) of an underpotentially deposited (UPD) Cu monolayer in an electrochemical cell reactor. Au@Pt ML showed improved catalytic activity for ethanol oxidation reaction (EOR) and, unlike their Pt bulk and Pt sML counterparts, was able to generate CO2 at very low electrode potentials owing to efficient C–C bond splitting. To explain this, we explore the hypothesis that competing strain effects due to the Pt layer coverage/morphology (compressive) and the Pt–Au lattice mismatch (tensile) control surface chemisorption and overall activity. Control experiments on well-defined model Pt monolayer systems are carried out involving a wide array of methods such as high-energy X-ray diffraction, pair-distribution function (PDF) analysis, in situ electrochemical FTIR spectroscopy, and in situ scanning tunneling microscopy. The vibrational fingerprints of adsorbed CO provide compelling evidence on the relation between surface bond strength, layer strain and morphology, and catalytic activity.

  19. Observation of D0 Meson Nuclear Modifications in Au +Au Collisions at √sNN =200 GeV

    Science.gov (United States)

    Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Anson, C. D.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Averichev, G. S.; Banerjee, A.; Beavis, D. R.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Borowski, W.; Bouchet, J.; Brandin, A. V.; Brovko, S. G.; Bültmann, S.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, L.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chwastowski, J.; Codrington, M. J. M.; Contin, G.; Cramer, J. G.; Crawford, H. J.; Cui, X.; Das, S.; Davila Leyva, A.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Derradi de Souza, R.; Dhamija, S.; di Ruzza, B.; Didenko, L.; Dilks, C.; Ding, F.; Djawotho, P.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Engle, K. S.; Eppley, G.; Eun, L.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Fedorisin, J.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Gagliardi, C. A.; Gangadharan, D. R.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Gliske, S.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Haag, B.; Hamed, A.; Han, L.-X.; Haque, R.; Harris, J. W.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, H. Z.; Huang, X.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kesich, A.; Khan, Z. H.; Kikola, D. P.; Kisel, I.; Kisiel, A.; Koetke, D. D.; Kollegger, T.; Konzer, J.; Koralt, I.; Kotchenda, L.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Kycia, R. A.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; LeVine, M. J.; Li, C.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z. M.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, G. L.; Ma, Y. G.; Madagodagettige Don, D. M. M. D.; Mahapatra, D. P.; Majka, R.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; McShane, T. S.; Minaev, N. G.; Mioduszewski, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nigmatkulov, G.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Ohlson, A.; Okorokov, V.; Oldag, E. W.; Olvitt, D. L.; Pachr, M.; Page, B. S.; Pal, S. K.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlak, T.; Pawlik, B.; Pei, H.; Perkins, C.; Peryt, W.; Pile, P.; Planinic, M.; Pluta, J.; Poljak, N.; Porter, J.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Pujahari, P. R.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Riley, C. K.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ross, J. F.; Roy, A.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sangaline, E.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Shen, W. Q.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Singaraju, R. N.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solanki, D.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stevens, J. R.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Sun, X.; Sun, X. M.; Sun, Y.; Sun, Z.; Surrow, B.; Svirida, D. N.; Symons, T. J. M.; Szelezniak, M. A.; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarnowsky, T.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Trzeciak, B. A.; Tsai, O. D.; Turnau, J.; Ullrich, T.; Underwood, D. G.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Vanfossen, J. A.; Varma, R.; Vasconcelos, G. M. S.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Vossen, A.; Wada, M.; Wang, F.; Wang, G.; Wang, H.; Wang, J. S.; Wang, X. L.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y. F.; Xiao, Z.; Xie, W.; Xin, K.; Xu, H.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y.; Xu, Z.; Yan, W.; Yang, C.; Yang, Y.; Yang, Y.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zawisza, Y.; Zbroszczyk, H.; Zha, W.; Zhang, J. B.; Zhang, J. L.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, Z. P.; Zhao, F.; Zhao, J.; Zhong, C.; Zhu, X.; Zhu, Y. H.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2014-10-01

    We report the first measurement of charmed-hadron (D0) production via the hadronic decay channel (D0→K-+π+) in Au +Au collisions at √sNN =200 GeV with the STAR experiment. The charm production cross section per nucleon-nucleon collision at midrapidity scales with the number of binary collisions, Nbin, from p +p to central Au +Au collisions. The D0 meson yields in central Au +Au collisions are strongly suppressed compared to those in p+p scaled by Nbin, for transverse momenta pT>3 GeV /c, demonstrating significant energy loss of charm quarks in the hot and dense medium. An enhancement at intermediate pT is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.

  20. How a gold substrate can increase the reactivity of a Pt overlayer

    DEFF Research Database (Denmark)

    Pedersen, Morten Ø.; Helveg, Stig; Ruban, Andrei

    1999-01-01

    The growth and chemical reactivity of Pt on Au(111) have been studied using scanning tunneling microscopy (STM) and temperature programmed desorption (TPD). Deposition of Pt at coverages from 0.02 ML up to 2.5 ML on Au(111) at room temperature initially leads to the formation of a surface alloy...... to this model, the increased reactivity of the Pt/Au(111) system should hold for other adsorbates and reactions as well. (C) 1999 Elsevier Science B.V. All rights reserved....

  1. Prothrombin time (PT)

    Science.gov (United States)

    PT; Pro-time; Anticoagulant-prothrombin time; Clotting time: protime; INR; International normalized ratio ... PT is measured in seconds. Most of the time, results are given as what is called INR ( ...

  2. PT and INR Test

    Science.gov (United States)

    ... as alcohol, can affect the PT and INR tests. Some antibiotics can increase the PT and INR. Barbiturates, oral ... Time ; Fibrinogen ; Coagulation Factors ; Platelet Count ; Platelet Function Tests ; Thrombin Time ; Warfarin Sensitivity Testing Conditions: Bleeding Disorders , Excessive Clotting Disorders , Vitamin ...

  3. Transition voltages of vacuum-spaced and molecular junctions with Ag and Pt electrodes

    KAUST Repository

    Wu, Kunlin

    2014-07-07

    The transition voltage of vacuum-spaced and molecular junctions constructed with Ag and Pt electrodes is investigated by non-equilibrium Green\\'s function formalism combined with density functional theory. Our calculations show that, similarly to the case of Au-vacuum-Au previously studied, the transition voltages of Ag and Pt metal-vacuum-metal junctions with atomic protrusions on the electrode surface are determined by the local density of states of the p-type atomic orbitals of the protrusion. Since the energy position of the Pt 6p atomic orbitals is higher than that of the 5p/6p of Ag and Au, the transition voltage of Pt-vacuum-Pt junctions is larger than that of both Ag-vacuum-Ag and Au-vacuum-Au junctions. When one moves to analyzing asymmetric molecular junctions constructed with biphenyl thiol as central molecule, then the transition voltage is found to depend on the specific bonding site for the sulfur atom in the thiol group. In particular agreement with experiments, where the largest transition voltage is found for Ag and the smallest for Pt, is obtained when one assumes S binding at the hollow-bridge site on the Ag/Au(111) surface and at the adatom site on the Pt(111) one. This demonstrates the critical role played by the linker-electrode binding geometry in determining the transition voltage of devices made of conjugated thiol molecules. © 2014 AIP Publishing LLC.

  4. Alpha decay of neutron-deficient isotopes with 52

    CERN Document Server

    Schardt, D; Kirchner, R; Klepper, O; Kurcewicz, W; Roeckl, E; Tidemand-Petersson, P

    1981-01-01

    Using /sup 58/Ni(/sup 58/Ni, xpyn) reactions and on-line mass separation, the alpha -decays of very neutron-deficient isotopes of tellurium, iodine, xenon and cesium were studied. The new isotopes /sup 106/Te (T/sub 1/2/=60/sub -10//sup +30/ mu s) and /sup 110/Xe were identified by their alpha -lines of 4160+or-30 keV and 3737+or-30 keV energy, respectively, with the genetic relationship between the two successive alpha -decays being verified experimentally, while for several other alpha -decaying isotopes more precise data were obtained. The observed alpha -decay properties are discussed within the systematics of energy and reduced width. (19 refs).

  5. SiO2-supported Pt particles studied by electron microscopy

    International Nuclear Information System (INIS)

    Wang, D.; Penner, S.; Su, D.S.; Rupprechter, G.; Hayek, K.; Schloegl, R.

    2003-01-01

    Regularly grown Pt particles supported by amorphous SiO 2 were heated in hydrogen at 873 K after an oxidising treatment. The morphological and structural changes were studied by electron microscopy. Platinum silicides Pt 3 Si with L1 2 (Cu 3 Au) structure, monoclinic Pt 3 Si and tetragonal Pt 12 Si 5 were identified after the treatment. The mechanisms of coalescence of the particles and the formation of irregular large particles are suggested. A topotactic structural transformation accompanied with the migration of Si from the substrate to the particles are suggested to take place during Pt 3 Si formation

  6. A partial phase diagram of Pt-rich Pt-Mn alloys

    CERN Document Server

    Sembiring, T; Ohshima, K I; Ota, K; Shishido, T

    2002-01-01

    We have performed the X-ray and electron diffraction studies to reconstruct a partial phase diagram of Pt-rich Pt-Mn alloys in the composition range of 10 to 35 at.% Mn. Electrical resistivity measurement was also used for determining the order-disorder transition temperature in Pt-14.2 at.% Mn alloy. The phase boundary between Cu sub 3 Au type and ABC sub 6 type ordered structures is established, in which the latter has been found recently by the present [J.Phys. Soc. Jpn. 71 (2002) 681]. In the ABC sub 6 type ordered phase, superlattice reflections both at 1/2 1/2 1/2 and its equivalent position (L-point) and at 100, 110 and their equivalent positions (X-point) appear in the composition range from 12.5 to 14.4 at.% Mn below 682degC. In the Cu sub 3 Au type ordered phase, diffuse maxima at L-point appear in the composition range from 15.9 to 19.7 at.% Mn in addition to the superlattice reflections at X-point. The Cu sub 3 Au type ordered structure is found to be stable in the composition range from 19.7 to 3...

  7. Ultralow Pt-loading bimetallic nanoflowers: fabrication and sensing applications.

    Science.gov (United States)

    Wu, Qingqing; Li, Yongxin; Xian, Hongying; Xu, Chaodi; Wang, Lun; Chen, Zhibing

    2013-01-18

    Ultralow Pt-loading Au nanoflowers (AuNFs) were synthesized on a glassy carbon electrode surface by the underpotential deposition (UPD) monolayer redox replacement technique, which involves redox replacement of a copper UPD monolayer by PtCl(4)(2-) that can be reduced and deposited simultaneously. Field-emission scanning electron microscopy, energy dispersive spectroscopy, x-ray photoelectron spectroscopy and the electrochemical method were utilized to characterize the ultralow Pt-loading AuNFs. Cyclic voltammogram results showed that the ultralow Pt-loading AuNFs exhibited excellent electrocatalytic activity towards the reduction of hydrogen peroxide and the oxidation of glucose in neutral media, and the reaction pathway of glucose oxidation was changed from an intermediate process based on the electrosorption of glucose to a direct oxidation process. From chronoamperometric results, it could be obtained that this prepared biosensor had wide linear ranges and very low detection limits (DLs) for H(2)O(2) (0.025-94.3 μM; DL = 0.006 μM) and glucose (0.0028-8.0 mM; DL = 0.8 μM), which were much better than previous results.

  8. Observation of D0 meson nuclear modifications in Au+Au collisions at sqrt[s(NN)] = 200 GeV.

    Science.gov (United States)

    Adamczyk, L; Adkins, J K; Agakishiev, G; Aggarwal, M M; Ahammed, Z; Alekseev, I; Alford, J; Anson, C D; Aparin, A; Arkhipkin, D; Aschenauer, E C; Averichev, G S; Banerjee, A; Beavis, D R; Bellwied, R; Bhasin, A; Bhati, A K; Bhattarai, P; Bichsel, H; Bielcik, J; Bielcikova, J; Bland, L C; Bordyuzhin, I G; Borowski, W; Bouchet, J; Brandin, A V; Brovko, S G; Bültmann, S; Bunzarov, I; Burton, T P; Butterworth, J; Caines, H; Calderón de la Barca Sánchez, M; Cebra, D; Cendejas, R; Cervantes, M C; Chaloupka, P; Chang, Z; Chattopadhyay, S; Chen, H F; Chen, J H; Chen, L; Cheng, J; Cherney, M; Chikanian, A; Christie, W; Chwastowski, J; Codrington, M J M; Contin, G; Cramer, J G; Crawford, H J; Cui, X; Das, S; Davila Leyva, A; De Silva, L C; Debbe, R R; Dedovich, T G; Deng, J; Derevschikov, A A; Derradi de Souza, R; Dhamija, S; di Ruzza, B; Didenko, L; Dilks, C; Ding, F; Djawotho, P; Dong, X; Drachenberg, J L; Draper, J E; Du, C M; Dunkelberger, L E; Dunlop, J C; Efimov, L G; Engelage, J; Engle, K S; Eppley, G; Eun, L; Evdokimov, O; Eyser, O; Fatemi, R; Fazio, S; Fedorisin, J; Filip, P; Finch, E; Fisyak, Y; Flores, C E; Gagliardi, C A; Gangadharan, D R; Garand, D; Geurts, F; Gibson, A; Girard, M; Gliske, S; Greiner, L; Grosnick, D; Gunarathne, D S; Guo, Y; Gupta, A; Gupta, S; Guryn, W; Haag, B; Hamed, A; Han, L-X; Haque, R; Harris, J W; Heppelmann, S; Hirsch, A; Hoffmann, G W; Hofman, D J; Horvat, S; Huang, B; Huang, H Z; Huang, X; Huck, P; Humanic, T J; Igo, G; Jacobs, W W; Jang, H; Judd, E G; Kabana, S; Kalinkin, D; Kang, K; Kauder, K; Ke, H W; Keane, D; Kechechyan, A; Kesich, A; Khan, Z H; Kikola, D P; Kisel, I; Kisiel, A; Koetke, D D; Kollegger, T; Konzer, J; Koralt, I; Kotchenda, L; Kraishan, A F; Kravtsov, P; Krueger, K; Kulakov, I; Kumar, L; Kycia, R A; Lamont, M A C; Landgraf, J M; Landry, K D; Lauret, J; Lebedev, A; Lednicky, R; Lee, J H; LeVine, M J; Li, C; Li, W; Li, X; Li, X; Li, Y; Li, Z M; Lisa, M A; Liu, F; Ljubicic, T; Llope, W J; Lomnitz, M; Longacre, R S; Luo, X; Ma, G L; Ma, Y G; Madagodagettige Don, D M M D; Mahapatra, D P; Majka, R; Margetis, S; Markert, C; Masui, H; Matis, H S; McDonald, D; McShane, T S; Minaev, N G; Mioduszewski, S; Mohanty, B; Mondal, M M; Morozov, D A; Mustafa, M K; Nandi, B K; Nasim, Md; Nayak, T K; Nelson, J M; Nigmatkulov, G; Nogach, L V; Noh, S Y; Novak, J; Nurushev, S B; Odyniec, G; Ogawa, A; Oh, K; Ohlson, A; Okorokov, V; Oldag, E W; Olvitt, D L; Pachr, M; Page, B S; Pal, S K; Pan, Y X; Pandit, Y; Panebratsev, Y; Pawlak, T; Pawlik, B; Pei, H; Perkins, C; Peryt, W; Pile, P; Planinic, M; Pluta, J; Poljak, N; Porter, J; Poskanzer, A M; Pruthi, N K; Przybycien, M; Pujahari, P R; Putschke, J; Qiu, H; Quintero, A; Ramachandran, S; Raniwala, R; Raniwala, S; Ray, R L; Riley, C K; Ritter, H G; Roberts, J B; Rogachevskiy, O V; Romero, J L; Ross, J F; Roy, A; Ruan, L; Rusnak, J; Rusnakova, O; Sahoo, N R; Sahu, P K; Sakrejda, I; Salur, S; Sandweiss, J; Sangaline, E; Sarkar, A; Schambach, J; Scharenberg, R P; Schmah, A M; Schmidke, W B; Schmitz, N; Seger, J; Seyboth, P; Shah, N; Shahaliev, E; Shanmuganathan, P V; Shao, M; Sharma, B; Shen, W Q; Shi, S S; Shou, Q Y; Sichtermann, E P; Singaraju, R N; Skoby, M J; Smirnov, D; Smirnov, N; Solanki, D; Sorensen, P; Spinka, H M; Srivastava, B; Stanislaus, T D S; Stevens, J R; Stock, R; Strikhanov, M; Stringfellow, B; Sumbera, M; Sun, X; Sun, X M; Sun, Y; Sun, Z; Surrow, B; Svirida, D N; Symons, T J M; Szelezniak, M A; Takahashi, J; Tang, A H; Tang, Z; Tarnowsky, T; Thomas, J H; Timmins, A R; Tlusty, D; Tokarev, M; Trentalange, S; Tribble, R E; Tribedy, P; Trzeciak, B A; Tsai, O D; Turnau, J; Ullrich, T; Underwood, D G; Van Buren, G; van Nieuwenhuizen, G; Vandenbroucke, M; Vanfossen, J A; Varma, R; Vasconcelos, G M S; Vasiliev, A N; Vertesi, R; Videbæk, F; Viyogi, Y P; Vokal, S; Vossen, A; Wada, M; Wang, F; Wang, G; Wang, H; Wang, J S; Wang, X L; Wang, Y; Wang, Y; Webb, G; Webb, J C; Westfall, G D; Wieman, H; Wissink, S W; Witt, R; Wu, Y F; Xiao, Z; Xie, W; Xin, K; Xu, H; Xu, J; Xu, N; Xu, Q H; Xu, Y; Xu, Z; Yan, W; Yang, C; Yang, Y; Yang, Y; Ye, Z; Yepes, P; Yi, L; Yip, K; Yoo, I-K; Yu, N; Zawisza, Y; Zbroszczyk, H; Zha, W; Zhang, J B; Zhang, J L; Zhang, S; Zhang, X P; Zhang, Y; Zhang, Z P; Zhao, F; Zhao, J; Zhong, C; Zhu, X; Zhu, Y H; Zoulkarneeva, Y; Zyzak, M

    2014-10-03

    We report the first measurement of charmed-hadron (D(0)) production via the hadronic decay channel (D(0) → K(-) + π(+)) in Au+Au collisions at sqrt[s(NN)] = 200 GeV with the STAR experiment. The charm production cross section per nucleon-nucleon collision at midrapidity scales with the number of binary collisions, N(bin), from p+p to central Au+Au collisions. The D(0) meson yields in central Au + Au collisions are strongly suppressed compared to those in p+p scaled by N(bin), for transverse momenta p(T) > 3 GeV/c, demonstrating significant energy loss of charm quarks in the hot and dense medium. An enhancement at intermediate p(T) is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.

  9. Facile Synthesis of Pt Nanoparticle and Graphene Composite Materials: Comparison of Electrocatalytic Activity with Analogous CNT Composite

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jihye; Jang, Ho Young; Jung, Insub; Yoon, Yeoheung; Jang, Heejeong; Lee, Hyoyoung; Park, Sungho [Sungkyunkwan Univ., Suwon (Korea, Republic of)

    2014-07-15

    Here, we present a facile method to synthesize Pt nanoparticles (NPs) and graphene composite materials (Pt/G) via vacuum filtration. Anodic aluminum oxide (AAO) templates were used to separate Pt/G composite and liquid phase. This method can be used to easily tune the mass ratio of Pt NPs and graphene. Pt NPs, graphene, and carbon nanotubes (CNTs) as building blocks were characterized by a variety of techniques such as scanning electron microscopy, UV-Vis spectroscopy, and Raman spectroscopy. We compared the electrocatalytic activities of Pt/G with Pt NP and CNT films (Pt/CNT) by cyclic voltammetry (CV), CO oxidation, and methanol oxidation. Pt/G was much more stable than pure Pt films. Also, Pt/G had better electrochemical activity, CO tolerance and methanol oxidation than Pt/CNT loaded with the same amount of Pt NPs due to the better dispersion of Pt NPs on graphene flakes without aggregation. We further synthesized Au Pt disk/G and Pt nanorods/G to determine if our synthetic method can be applied to other NP shapes such as nanodisks and nanorods, for further electrocatalysis studies.

  10. Pt, Au and Ag Electrodes on BiCuVOx

    National Research Council Canada - National Science Library

    Boukamp, Bernard

    1998-01-01

    ...) parallel to a resistance with characteristics of a charge transfer resistance. Both elements show strong dependence on pO2 and polarization level. Results are explained with theoretical and observational arguments.

  11. High-precision mass measurements of neutron-deficient Tl isotopes at ISOLTRAP and the development of an ultra-stable voltage source for the PENTATRAP experiment

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, Christine

    2015-01-14

    Atomic masses and hence binding energies of nuclides are of great importance for studies of nuclear structure since they reflect all effective interactions in a nucleus. Within this thesis the masses of seven nuclides, namely {sup 194}Au, {sup 194}Hg, {sup 190,193,198}Tl and {sup 202,208}Pb, were determined at the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The thallium region in the chart of isotopes is of special interest due to the occurrence of nuclear structure effects like low-lying isomers, level inversion, shape coexistence and deformations. These effects are investigated by applying finite-difference mass formulas, such as the two-neutron separation energies or the so-called empirical pairing gaps. The second topic addressed within the present thesis is an ultra-stable voltage source, called StaReP (Stable Reference for Penning Trap Experiments), which was developed at the Max-Planck-Institut fuer Kernphysik. It is one of the key components of the high-precision mass spectrometer PENTATRAP, containing a tower of five Penning traps. A 25-channel voltage source with a relative stability of few 10{sup -8} over a period of 10 minutes in the range of 0 to -100V is mandatory for PENTATRAP aiming for mass measurements with relative mass uncertainties of ≤ 10{sup -11}. Mass values with such a high precision allow for stringent tests of quantum electrodynamics in strong electric fields, testing Einstein's mass-energy relation E = mc{sup 2} as well as measurements of decay energies (Q-values) with applications in neutrino physics.

  12. PT-symmetric strings

    International Nuclear Information System (INIS)

    Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German

    2014-01-01

    We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑ n=1 ∞ 1/E n p , with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities

  13. Ce{sub 2}PdIn{sub 8}, Ce{sub 3}PdIn{sub 11} and Ce{sub 5}Pd{sub 2}In{sub 19}—members of homological series based on AuCu{sub 3}- and PtHg{sub 2}-type structural units

    Energy Technology Data Exchange (ETDEWEB)

    Tursina, A.; Nesterenko, S.; Seropegin, Y. [Department of Chemistry, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Noël, H. [Laboratoire de Chimie du Solide et Matériaux, UMR6226 CNRS-Université de Rennes 1, Avenue du Général Leclerc, Rennes 30542 (France); Kaczorowski, D., E-mail: D.Kaczorowski@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O.Box 1410, Wrocław 50-950 (Poland)

    2013-04-15

    Crystal structures of three members of a unique homological series with the general formula Ce{sub m}Pd{sub n}In{sub 3m+2n} based on the AuCu{sub 3} and PtHg{sub 2} structure types were studied by single-crystal X-ray diffraction. The compounds crystallize with space group P4/mmm (Z=1) and the lattice parameters: a=4.6900(9) Å, c=12.185(6) Å for Ce{sub 2}PdIn{sub 8}, a=4.6846(8) Å, c=16.846(8) Å for Ce{sub 3}PdIn{sub 11}, and a=4.70120(10) Å, c=29.1359(4) Å for Ce{sub 5}Pd{sub 2}In{sub 19}. The crystal structures of Ce{sub 3}PdIn{sub 11} and Ce{sub 5}Pd{sub 2}In{sub 19} represent new types. The three structures constitute of [CeIn{sub 3}] cuboctahedra layers and [PdIn{sub 2}] rectangular polyhedra layers, alternating along the tetragonal c-axis in accordance with the m:n proportion. The magnetic and electrical transport properties of the novel compounds Ce{sub 3}PdIn{sub 11} and Ce{sub 5}Pd{sub 2}In{sub 19} were investigated down to 1.72 K. Both indides are Curie–Weiss paramagnets due to the presence of fairly well localized 4f electrons of trivalent cerium ions. The electrical resistivity of both materials is dominated over an extended temperature range by strong spin–flip Kondo interactions with the characteristic temperature scale of 20–30 K. - Graphical abstract: TOC Figure Crystal structures of Ce{sub 3}PdIn{sub 11}, Ce{sub 2}PdIn{sub 8}, and Ce{sub 5}Pd{sub 2}In{sub 19}. Highlights: ► Large section of Ce–Pd–In phase diagram was examined. ► Three distinct ternary phases were identified, two of them for the first time. ► Crystal structures of two novel compounds constitute new structure types. ► The determined crystal structures show close mutual relationship. ► Ce{sub 3}PdIn{sub 11} and Ce{sub 5}Pd{sub 2}In{sub 19} are paramagnetic Kondo lattices.

  14. Internal Standard Method for the Determination of Au and some ...

    African Journals Online (AJOL)

    Abstract. A method is described for the determination of Au, Pt, Pd, Ru and Rh in a converter matte sample, using inductively coupled plasma optical emission spectrometry (ICP-OES), with Y or Sc as internal standard. The results obtained by this method are discussed and compared with values obtained by an independent ...

  15. Laser-Irradiation-Induced Melting and Reduction Reaction for the Formation of Pt-Based Bimetallic Alloy Particles in Liquids.

    Science.gov (United States)

    Han, Yechuang; Wu, Shouliang; Dai, Enmei; Ye, Yixing; Liu, Jun; Tian, Zhenfei; Cai, Yunyu; Zhu, Xiaoguang; Liang, Changhao

    2017-05-05

    Laser melting in liquids (LML) is one of the most effective methods to prepare bimetallic alloys; however, despite being an ongoing focus of research, the process involved in the formation of such species remains ambiguous. In this paper, we prepared two types of Pt-based bimetallic alloys by LML, including Pt-Au alloys and Pt-iron group metal (iM=Fe/Co/Ni) alloys, and investigated the corresponding mechanisms of alloying process. Detailed component and structural characterizations indicate that laser irradiation induced a quite rapid formation process (not exceeding 10 s) of Pt-Au alloy nanospheres, and the crystalline structures of Pt-Au alloys is determined by the monometallic constituents with higher content. For Pt-iM alloys, we provide direct evidence to support the conclusion that FeO x /CoO x /NiO x colloids can be reduced to elementary Fe/Co/Ni particles by ethanol molecules during laser irradiation, which then react with Pt colloids to form Pt-iM sub-microspheres. These results demonstrate that LML provides an optional route to prepare Pt-based bimetallic alloy particles with tunable size, components, and crystalline phase, which should have promising applications in biological and catalysis studies. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Synthesis of Highly Dispersed and Highly Stable Supported Au–Pt Bimetallic Catalysts by a Two-Step Method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaofeng; Zhao, Haiyan; Wu, Tianpin; Liu, Yuzi; Liang, Xinhua

    2016-11-01

    Highly dispersed and highly stable supported bimetallic catalysts were prepared using a two-step process. Pt nanoparticles (NPs) were first deposited on porous γ-Al2O3 particles by atomic layer deposition (ALD). Au NPs were synthesized by using gold(III) chloride as the Au precursor, and then immobilized on ALD Pt/γ-Al2O3 particles. The Au–Pt bimetallic catalysts were highly active and highly stable in a vigorously stirred liquid phase reaction of glucose oxidation.

  17. Cluster Chemistry in Electron-Poor Ae-Pt-Cd Systems (Ae=Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and Its Known Antitype Er6Pd16Sb8

    Energy Technology Data Exchange (ETDEWEB)

    Samal, Saroj L. [Ames Laboratory; Gulo, Fakhili [Ames Laboratory; Corbett, John D. [Ames Laboratory

    2013-02-18

    Three new ternary polar intermetallic compounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae–Pt–Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) Å) contains a 3D array of separate Cd8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd8[Pt(1)]6/2[Pt(2)]4/8. The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse of the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt2Cd4, Ae = Sr, Ba, are tetragonal (P42/mnm,Z = 2, a ≈ 8.30 Å, c ≈ 4.47 Å) and contain chains of edge-sharing Cd4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt–Cd and Pd–Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt8, and Pd16, and that some terms remain incomparable, Ca–Cd versus Er–Pd.

  18. Significant Broadband Photocurrent Enhancement by Au-CZTS Core-Shell Nanostructured Photocathodes

    Science.gov (United States)

    Zhang, Xuemei; Wu, Xu; Centeno, Anthony; Ryan, Mary P.; Alford, Neil M.; Riley, D. Jason; Xie, Fang

    2016-03-01

    Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap.

  19. Pt, Co–Pt and Fe–Pt alloy nanoclusters encapsulated in virus capsids

    International Nuclear Information System (INIS)

    Okuda, M; Eloi, J-C; Jones, S E Ward; Schwarzacher, W; Verwegen, M; Cornelissen, J J L M

    2016-01-01

    Nanostructured Pt-based alloys show great promise, not only for catalysis but also in medical and magnetic applications. To extend the properties of this class of materials, we have developed a means of synthesizing Pt and Pt-based alloy nanoclusters in the capsid of a virus. Pure Pt and Pt-alloy nanoclusters are formed through the chemical reduction of [PtCl 4 ] − by NaBH 4 with/without additional metal ions (Co or Fe). The opening and closing of the ion channels in the virus capsid were controlled by changing the pH and ionic strength of the solution. The size of the nanoclusters is limited to 18 nm by the internal diameter of the capsid. Their magnetic properties suggest potential applications in hyperthermia for the Co–Pt and Fe–Pt magnetic alloy nanoclusters. This study introduces a new way to fabricate size-restricted nanoclusters using virus capsid. (paper)

  20. High Temperature Characteristics of Pt/TaSi2/Pt/W and Pt/Ti/W Diffusion Barrier Systems for Ohmic Contacts to 4H-SiC

    Science.gov (United States)

    Okojie, Robert S.; Lukco, Dorothy

    2017-01-01

    The degradation of ohmic contacts to 4H-SiC pressure sensors over time at high temperature is primarily due to two failure mechanisms: migrating bond pad Au and atmospheric O toward the ohmic contact SiC interface and the inter-metallic mixing between diffusion barrier systems (DBS) and the underlying ohmic contact metallization. We investigated the effectiveness of Pt/TaSi2/Pt/W (DBS-A) and Pt/Ti/W (DBS-B) in preventing Au and O diffusion through the underlying binary Ti/W or alloyed W50:Ni50 ohmic contacts to 4H-SiC and the DBS ohmic contact intermixing at temperature up to 700 C.

  1. Thermodynamic calculation study on phase structures of Pt-Ir-M(Y, Zr, Mo)

    Science.gov (United States)

    Wang, S. B.; Sun, Y.; Chen, J. L.; Wang, S.; Peng, M. J.; Chen, S.; Liu, MM; Hu, J. Q.; Chen, Y. T.; Zhang, J. M.; Yang, Y. C.; Xie, M.

    2018-01-01

    The energy and electronic structure of the solid solutions of Pt-Ir-M (M=Mo,Y,Zr) alloy systems were investigated using the first-principle pseudo-potential plane-wave method. The results show that, adding the same percentage content, 1% Mo doped in Au-Pd solid solution is the most stable phase structure. When doped with Y and Zr, they are likely to react with Au-Pd to form the corresponding intermetallic compounds.

  2. Single crystalline PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices.

    Science.gov (United States)

    Lin, Yung-Chen; Lu, Kuo-Chang; Wu, Wen-Wei; Bai, Jingwei; Chen, Lih J; Tu, K N; Huang, Yu

    2008-03-01

    We report the formation of PtSi nanowires, PtSi/Si/PtSi nanowire heterostructures, and nanodevices from such heterostructures. Scanning electron microscopy studies show that silicon nanowires can be converted into PtSi nanowires through controlled reactions between lithographically defined platinum pads and silicon nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heterostructure has an atomically sharp interface with epitaxial relationships of Si[110]//PtSi[010] and Si(111)//PtSi(101). Electrical measurements show that the pure PtSi nanowires have low resistivities approximately 28.6 microOmega.cm and high breakdown current densities>1x10(8) A/cm2. Furthermore, using single crystal PtSi/Si/PtSi nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon nanowires, in which the source and drain contacts are defined by the metallic PtSi nanowire regions, and the gate length is defined by the Si nanowire region. Electrical measurements show nearly perfect p-channel enhancement mode transistor behavior with a normalized transconductance of 0.3 mS/microm, field-effect hole mobility of 168 cm2/V.s, and on/off ratio>10(7), demonstrating the best performing device from intrinsic silicon nanowires.

  3. Study of proton and 2 protons emission from light neutron deficient nuclei around A=20; Etude de l'emission proton et de deux protons dans les noyaux legers deficients en neutrons de la region A=20

    Energy Technology Data Exchange (ETDEWEB)

    Zerguerras, T

    2001-09-01

    Proton and two proton emission from light neutron deficient nuclei around A=20 have been studied. A radioactive beam of {sup 18}Ne, {sup 17}F and {sup 20}Mg, produced at the Grand Accelerateur National d'Ions Lourds by fragmentation of a {sup 24}Mg primary beam at 95 MeV/A, bombarded a {sup 9}Be target to form unbound states. Proton(s) and nuclei from the decay were detected respectively in the MUST array and the SPEG spectrometer. From energy and angle measurements, the invariant mass of the decaying nucleus could be reconstructed. Double coincidence events between a proton and {sup 17}F, {sup 16}O, {sup 15}O, {sup 14}O and {sup 18}Ne were registered to obtain excitation energy spectra of {sup 18}Ne, {sup 17}F, {sup 16}F, {sup 15}F et {sup 19}Na. Generally, the masses measures are in agreement with previous experiments. In the case of {sup 18}Ne, excitation energy and angular distributions agree well with the predictions of a break up model calculation. From {sup 17}Ne proton coincidences, a first experimental measurement of the ground state mass excess of {sup 18}Na has been obtained and yields 24,19(0,15)MeV. Two proton emission from {sup 17}Ne and {sup 18}Ne excited states and the {sup 19}Mg ground state was studied through triple coincidences between two proton and {sup 15}O, {sup 16}O and {sup 17}Ne respectively. In the first case, the proton-proton relative angle distribution in the center of mass has been compared with model calculation. Sequential emission from excited states of {sup 17}Ne, above the proton emission threshold, through {sup 16}F is dominant but a {sup 2}He decay channel could not be excluded. No {sup 2}He emission from the 1.288 MeV {sup 17}Ne state, or from the 6.15 MeV {sup 18}Ne state has been observed. Only one coincidence event between {sup 17}Ne and two proton was registered, the value of the one neutron stripping reaction cross section of {sup 20}Mg being much lower than predicted. (author)

  4. New methods of controlled monolayer-to-multilayer deposition of Pt for designing electrocatalysts at an atomic level

    Directory of Open Access Journals (Sweden)

    J. X. WANG

    2001-12-01

    Full Text Available Two new methods for monolayer-to-multileyer Pt deposition are presented. One involves Pt deposition by the replacement of an UPD metal monolayer on an electrode surface and the other the spontaneous deposition of Pt on Ru. The first method, exemplified by the replacement of a Cu monolayer on a Au(111 surface, occurs as a spontaneous irreversible redox reaction in which the Cu monolayer is oxidized by Pt cations, which are reduced and simultaneously deposited. The second method is illustrated by the deposition of Pt on a Ru(0001 surface and on carbon-supported Ru nanoparticles. This deposition takes place upon immersion of a UHV-prepared Ru(0001 crystal or Ru nanoparticles, reduced in H2, in a solution containing PtCl62- ions. The oxidation of Ru to RuOH by a local cell mechanism appears to be coupled with Pt deposition. This method facilitates the design of active Pt-Ru catalysts with ultimately low Pt loadings. Only a quarter of a monolayer of Pt on Ru nanoparticles yields an electrocatalyst with higher activity and CO tolerance for H2/CO oxidation than commercial Pt-Ru alloy electrocatalysts with considerably higher Pt loadings.

  5. Au pair trajectories

    DEFF Research Database (Denmark)

    Dalgas, Karina Märcher

    2015-01-01

    Since 2000, thousands of young Filipino migrants have come to Denmark as au pairs. Officially, they are there to “broaden their cultural horizons” by living temporarily with a Danish host family, but they also conduct domestic labor in exchange for food and money, which allows them to send...... of their Danish host families. Based on their migratory status as au pairs, these young migrants must therefore negotiate the different moral and contractual rights and obligations that characterize the local and transnational family ties in which they are engaged. This study of Filipina au pair migration through...... pair-sending families in the Philippines, this dissertation examines the long-term trajectories of these young Filipinas. It shows how the au pairs’ local and transnational family relations develop over time and greatly influence their life trajectories. A focal point of the study is how au pairs...

  6. Characterization of azo dyes on Pt and Pt/polyaniline/dispersed Pt electrodes

    International Nuclear Information System (INIS)

    Molina, J.; Fernández, J.; Río, A.I. del; Bonastre, J.; Cases, F.

    2012-01-01

    The electrochemical characterization of two organic dyes (amaranth and procion orange MX-2R) has been performed on Pt electrodes and Pt electrodes coated with polyaniline and dispersed Pt. Electrodes with different Pt loads have been synthesized and characterized obtaining that a load of 300 μg cm -2 was the optimum one. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was employed to observe the distribution and morphology of the Pt nanoparticles. The electroactivity of the electrodes has also been characterized by means of scanning electrochemical microscopy (SECM). The chemical characterization of Pt dispersed Pani coated Pt electrodes (Pt-Pani-Pt) was performed by means of X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of the dyes has been performed by means of cyclic voltammetry. Voltammograms have shown that the presence of the dyes diminishes characteristic Pt oxidation and reduction peaks. However, redox processes due to the dyes, appeared in the voltammograms. The different species responsible of these redox processes were generated in the vicinity of the electrode and were not adsorbed on the electrode surface since after stirring, the different redox processes disappeared. Characterization with different scan rates showed that redox processes of both dyes were controlled by diffusion.

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

    Science.gov (United States)

    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.

  8. @AuAg nanostructures

    Science.gov (United States)

    Singh, Rina; Soni, R. K.

    2014-09-01

    Bimetallic and trimetallic nanoparticles have attracted significant attention in recent times due to their enhanced electrochemical and catalytic properties compared to monometallic nanoparticles. The numerical calculations using Mie theory has been carried out for three-layered metal nanoshell dielectric-metal-metal (DMM) system consisting of a particle with a dielectric core (Al@Al2O3), a middle metal Ag (Au) layer and an outer metal Au (Ag) shell. The results have been interpreted using plasmon hybridization theory. We have also prepared Al@Al2O3@Ag@Au and Al@Al2O3@AgAu triple-layered core-shell or alloy nanostructure by two-step laser ablation method and compared with calculated results. The synthesis involves temporal separations of Al, Ag, and Au deposition for step-by-step formation of triple-layered core-shell structure. To form Al@Ag nanoparticles, we ablated silver for 40 min in aluminium nanoparticle colloidal solution. As aluminium oxidizes easily in water to form alumina, the resulting structure is core-shell Al@Al2O3. The Al@Al2O3 particle acts as a seed for the incoming energetic silver particles for multilayered Al@Al2O3@Ag nanoparticles is formed. The silver target was then replaced by gold target and ablation was carried out for different ablation time using different laser energy for generation of Al@Al2O3@Ag@Au core-shell or Al@Al2O3@AgAu alloy. The formation of core-shell and alloy nanostructure was confirmed by UV-visible spectroscopy. The absorption spectra show shift in plasmon resonance peak of silver to gold in the range 400-520 nm with increasing ablation time suggesting formation of Ag-Au alloy in the presence of alumina particles in the solution.

  9. K-shell ionisation cross sections for W, Au and U by low velocity protons

    International Nuclear Information System (INIS)

    Castro Faria, N.V. de; Freire Junior, F.L.; Montenegro, E.C.; Pinho, A.G. de; Silveira, E.F. da.

    1984-01-01

    Proton-induced K-shell ionisation cross section for W, Au and U by low velocity protons were obtained from thick target measurements. For the first time the lowest incident energy reached a value less than 10 times the binding energy of the K-shell electron (less than 9 times in the case of Au). Possible errors are thoroughly examined and a comparison with other available experimental results and theoretical values is presented and discussed. (Author) [pt

  10. Pt-Bi decorated nanoporous gold for high performance direct glucose fuel cell

    Science.gov (United States)

    Guo, Hong; Yin, Huiming; Yan, Xiuling; Shi, Shuai; Yu, Qingyang; Cao, Zhen; Li, Jian

    2016-01-01

    Binary PtBi decorated nanoporous gold (NPG-PtBi) electrocatalyst is specially designed and prepared for the anode in direct glucose fuel cells (DGFCs). By using electroless and electrochemical plating methods, a dense Pt layer and scattered Bi particles are sequentially coated on NPG. A simple DGFC with NPG-PtBi as anode and commercial Pt/C as cathode is constructed and operated to study the effect of operating temperatures and concentrations of glucose and NaOH. With an anode noble metal loading of only 0.45 mg cm−2 (Au 0.3 mg and Pt 0.15 mg), an open circuit voltage (OCV) of 0.9 V is obtained with a maximum power density of 8 mW cm−2. Furthermore, the maximum gravimetric power density of NPG-PtBi is 18 mW mg−1, about 4.5 times higher than that of commercial Pt/C. PMID:27966629

  11. Pt-Bi decorated nanoporous gold for high performance direct glucose fuel cell

    Science.gov (United States)

    Guo, Hong; Yin, Huiming; Yan, Xiuling; Shi, Shuai; Yu, Qingyang; Cao, Zhen; Li, Jian

    2016-12-01

    Binary PtBi decorated nanoporous gold (NPG-PtBi) electrocatalyst is specially designed and prepared for the anode in direct glucose fuel cells (DGFCs). By using electroless and electrochemical plating methods, a dense Pt layer and scattered Bi particles are sequentially coated on NPG. A simple DGFC with NPG-PtBi as anode and commercial Pt/C as cathode is constructed and operated to study the effect of operating temperatures and concentrations of glucose and NaOH. With an anode noble metal loading of only 0.45 mg cm-2 (Au 0.3 mg and Pt 0.15 mg), an open circuit voltage (OCV) of 0.9 V is obtained with a maximum power density of 8 mW cm-2. Furthermore, the maximum gravimetric power density of NPG-PtBi is 18 mW mg-1, about 4.5 times higher than that of commercial Pt/C.

  12. A cast-mold approach to iron oxide and Pt/iron oxide nanocontainers and nanoparticles with a reactive concave surface.

    Science.gov (United States)

    George, Chandramohan; Dorfs, Dirk; Bertoni, Giovanni; Falqui, Andrea; Genovese, Alessandro; Pellegrino, Teresa; Roig, Anna; Quarta, Alessandra; Comparelli, Roberto; Curri, M Lucia; Cingolani, Roberto; Manna, Liberato

    2011-02-23

    We report the synthesis of various iron oxide nanocontainers and Pt-iron oxide nanoparticles based on a cast-mold approach, starting from nanoparticles having a metal core (either Au or AuPt) and an iron oxide shell. Upon annealing, the particles evolve to asymmetric core-shells and then to heterodimers. If iodine is used to leach Au out of these structures, asymmetric core-shells evolve into "nanocontainers", that is, iron oxide nanoparticles enclosing a cavity accessible through nanometer-sized pores, while heterodimers evolve into particles with a concave region. When starting from a metal domain made of AuPt, selective leaching of the Au atoms yields the same iron oxide nanoparticle morphologies but now encasing Pt domains (in their concave region or in their cavity). We found that the concave nanoparticles are capable of destabilizing Au nanocrystals of sizes matching that of the concave region. In addition, for the nanocontainers, we propose two different applications: (i) we demonstrate loading of the cavity region of the nanocontainers with the antitumoral drug cis-platin; and (ii) we show that nanocontainers encasing Pt domains can act as recoverable photocatalysts for the reduction of a model dye.

  13. Preparation of Pt Ag alloy nanoisland/graphene hybrid composites and its high stability and catalytic activity in methanol electro-oxidation

    Directory of Open Access Journals (Sweden)

    Feng Lili

    2011-01-01

    Full Text Available Abstract In this article, PtAg alloy nanoislands/graphene hybrid composites were prepared based on the self-organization of Au@PtAg nanorods on graphene sheets. Graphite oxides (GO were prepared and separated to individual sheets using Hummer's method. Graphene nano-sheets were prepared by chemical reduction with hydrazine. The prepared PtAg alloy nanomaterial and the hybrid composites with graphene were characterized by SEM, TEM, and zeta potential measurements. It is confirmed that the prepared Au@PtAg alloy nanorods/graphene hybrid composites own good catalytic function for methanol electro-oxidation by cyclic voltammograms measurements, and exhibited higher catalytic activity and more stability than pure Au@Pt nanorods and Au@AgPt alloy nanorods. In conclusion, the prepared PtAg alloy nanoislands/graphene hybrid composites own high stability and catalytic activity in methanol electro-oxidation, so that it is one kind of high-performance catalyst, and has great potential in applications such as methanol fuel cells in near future.

  14. Platinum determination by instrumental neutron activation analysis with special reference to the spectral interference of Sc-47 on the platinum indicator nuclide Au-199

    DEFF Research Database (Denmark)

    Alfassi, Z.B.; Probst, T.U.; Rietz, B.

    1998-01-01

    A method of instrumental neutron activation analysis (INAA) is developed for the determination of platinum by the Au-199 daughter of Pt-199 in the presence of the spectral interference from the Sc-47 daughter of Ca-47. The contributions of the Pt and Ca signals to the integral 157-161 keV peak were...

  15. Catalytic activity of Au nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Janssens, Ton V.W.; Clausen, Bjerne

    2007-01-01

    Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change with par......Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change...

  16. Complex {PT}-symmetric extensions of the nonlinear ultra-short light pulse model

    Science.gov (United States)

    Yan, Zhenya

    2012-11-01

    The short pulse equation u_{xt}=u+\\frac{1}{2}(u^2u_x)_x is PT symmetric, which arises in nonlinear optics for the ultra-short pulse case. We present a family of new complex PT-symmetric extensions of the short pulse equation, i[(iu_x)^{\\sigma }]_t=au+bu^m+ic[u^n(iu_x)^{\\epsilon }]_x \\,\\, (\\sigma ,\\, \\epsilon ,\\,a,\\,b,\\,c,\\,m,\\,n \\in {R}), based on the complex PT-symmetric extension principle. Some properties of these equations with some chosen parameters are studied including the Hamiltonian structures and exact solutions such as solitary wave solutions, doubly periodic wave solutions and compacton solutions. Our results may be useful to understand complex PT-symmetric nonlinear physical models. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’.

  17. First principles mechanistic study of borohydride oxidation over the Pt(1 1 1) surface

    International Nuclear Information System (INIS)

    Rostamikia, Gholamreza; Janik, Michael J.

    2010-01-01

    The mechanism of borohydride oxidation and the competing hydrolysis reaction are examined over Pt(1 1 1) using density functional theory (DFT) methods. Adsorption of BH 4 - over Au(1 1 1) and Pt(1 1 1) is examined. Adsorption over Pt(1 1 1) is dissociative and extremely exothermic at potentials of interest, leading to a high surface coverage of H * for which gaseous hydrogen evolution is competitive with oxidation. Elementary surface reactions oxidizing B-containing intermediates are favorable over Pt(1 1 1) at -0.85 V (SHE), consistent with experimental voltammetry results in the literature. The energetics of the initial adsorption step dictate the activity limitation of gold anodes and the selectivity limitation of platinum electrodes. This adsorption energy can be rapidly calculated with DFT methods, enabling screening of pure metals, alloys, poisons, and promoters to optimize borohydride oxidation catalyst design.

  18. Preparation of 198Au free from 199Au

    International Nuclear Information System (INIS)

    Capgras, A.

    1967-01-01

    The necessity of obtaining 198 Au free from 199 Au has led us to carry out irradiations using cadmium. The spectra obtained using irradiated detectors with or without cadmium have confirmed the validity of the method. Under the same irradiation conditions the ratio 199 Au/ 198 Au in the first case is of the order of 8 per cent; in the second case this ratio is less than 0.1 per cent. (author) [fr

  19. Arsitektur Data Pada PT. X

    OpenAIRE

    Gandawidjaja, Agustinus; Dewi, Lily Puspa; Handojo, Andreas

    2015-01-01

    PT. X is a private company that commercially operated since 1991. It becomes the first company which produces Sodium Tripolyphosphate (STPP) in Indonesia. In order to support the business processing, PT. X only have a program holds its warehouse and also the general ledger. The program is lack of information system which is not whole integrated.For this reason, in this thesis, the analysis and design of architecture data information system is made for the company. The process begins by analyz...

  20. Impedance measurements on Au microelectrodes using controlled atmosphere high temperature scanning probe microscope

    DEFF Research Database (Denmark)

    Wu, Yuehua; Hansen, Karin Vels; Jacobsen, Torben

    2011-01-01

    High temperature impedance measurements on Au microelectrodes deposited on polished yttria stabilized zirconia (YSZ) pellets were demonstrated using a newly designed controlled atmosphere high temperature scanning probe microscope (CAHT-SPM). Probes based on Pt0.8Ir0.2 were fabricated and employed...

  1. Pt–Au/C cathode with enhanced oxygen-reduction activity in PEFCs

    Indian Academy of Sciences (India)

    reduction reaction. 1. Introduction. Polymer electrolyte fuel cells ... in recent years due to their attractive stability and activity towards ORR in fuel cells (Li et al .... required amount of Pt/C or. Pt–Au/C was suspended in isopropyl alcohol. The mixture.

  2. Intensity (a.u)

    Indian Academy of Sciences (India)

    Administrator

    Supplementary Information. Fig. S1. Powder X-ray diffraction pattern (Cu Kα) for AlPO-5: (a) as prepared, (b) calcined and (c) simulated [Ref. 27]. 10. 20. 30. 40. 50. Intensity (a.u) b c a. 2θ ...

  3. Au pairs on Facebook

    DEFF Research Database (Denmark)

    Dalgas, Karina Märcher

    2016-01-01

    that engagement with Facebook as a methodological tool can be useful in research among migrants in highly politicised fields. Pointing to a discursive construction of Filipina au pairs as victims of labour exploitation, the article shows how fieldwork on Facebook enables the exploration of the ways in which...

  4. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ohno, S.; Shimakura, H. [Niigata University of Pharmacy and Applied Life Sciences, Higashijima, Akiha-ku, Niigata 956-8603 (Japan); Tahara, S. [Faculty of Science, University of the Ryukyus, Nishihara-cho, Okinawa 903-0213 (Japan); Okada, T. [Niigata College of Technology, Kamishin’eicho, Nishi-ku, Niigata 950-2076 (Japan)

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  5. Pt/C Fuel Cell Catalyst Degradation

    DEFF Research Database (Denmark)

    Zana, Alessandro

    This thesis investigates the degradation behavior of Pt/C catalysts under simulated automotive conditions. By using the “tool box” synthesis method the Pt loading has been changed from low to high Pt loadings, therefore permitting to study the role of Pt on the degradation of high surface area (H...

  6. Pt-decorated nanoporous gold for glucose electrooxidation in neutral and alkaline solutions

    Directory of Open Access Journals (Sweden)

    Yan Xiuling

    2011-01-01

    Full Text Available Abstract Exploiting electrocatalysts with high activity for glucose oxidation is of central importance for practical applications such as glucose fuel cell. Pt-decorated nanoporous gold (NPG-Pt, created by depositing a thin layer of Pt on NPG surface, was proposed as an active electrode for glucose electrooxidation in neutral and alkaline solutions. The structure and surface properties of NPG-Pt were characterized by scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray powder diffraction (XRD, and cyclic voltammetry (CV. The electrocatalytic activity toward glucose oxidation in neutral and alkaline solutions was evaluated, which was found to depend strongly on the surface structure of NPG-Pt. A direct glucose fuel cell (DGFC was performed based on the novel membrane electrode materials. With a low precious metal load of less than 0.3 mg cm-2 Au and 60 μg cm-2 Pt in anode and commercial Pt/C in cathode, the performance of DGFC in alkaline is much better than that in neutral condition.

  7. Pt monolayer shell on hollow Pd core electrocatalysts: Scale up synthesis, structure, and activity for the oxygen reduction reaction

    Directory of Open Access Journals (Sweden)

    Vukmirovic Miomir B.

    2013-01-01

    Full Text Available We report on synthesis, characterization and the oxygen reduction reaction (ORR kinetics of Pt monolayer shell on Pd(hollow, or Pd-Au(hollow core electrocatalysts. Comparison between the ORR catalytic activity of the electrocatalysts with hollow cores and those of Pt solid and Pt hollow nanoparticles has been obtained using the rotating disk electrode technique. Hollow nanoparticles were made using Ni or Cu nanoparticles as sacrificial templates. The Pt ORR specific and mass activities of the electrocatalysts with hollow cores were found considerably higher than those of the electrocatalysts with the solid cores. We attribute this enhanced Pt activity to the smooth surface morphology and hollow-induced lattice contraction, in addition to the mass-saving geometry of hollow particles.

  8. Equilibrium, kinetics and mechanism of Au3+, Pd2+ and Ag+ ions adsorption from aqueous solutions by graphene oxide functionalized persimmon tannin.

    Science.gov (United States)

    Wang, Zhongmin; Li, Xiaojuan; Liang, Haijun; Ning, Jingliang; Zhou, Zhide; Li, Guiyin

    2017-10-01

    In this study, a novel bio-adsorbent (PT-GO) was prepared by functionalization persimmon tannin (PT) with graphene oxide (GO) and the effective adsorption behaviors of Au 3+ , Pd 2+ and Ag + ions from aqueous solution was investigated. The PT-GO was characterized by Fourier transform infrared spectrometer (FTIR), scanning electronic microscope (SEM), thermogravimetric analysis (TGA) and Zeta potential. Many influence factors such as pH value, bio-adsorbent dosage, initial concentration of metal ions and contact time were optimized. The maximum adsorption capacity for Au 3+ , Pd 2+ and Ag + was 1325.09mg/g, 797.66mg/g and 421.01mg/g, respectively. The equilibrium isotherm for the adsorption of Au 3+ and Ag + on PT-GO were found to obey the Langmuir model, while the Freundlich model fitted better for Pd 2+ . The adsorption process of Au 3+ , Pd 2+ presented relatively fast adsorption kinetics with pseudo-second-order equation as the best fitting model, while the pseudo-first-order kinetic model was suitable for describing the adsorption of Ag + . Combination of ion exchange, electrostatic interaction and physical adsorption was the mechanism for adsorption of Au 3+ , Pd 2+ and Ag + onto PT-GO bio-adsorbent. Therefore, the PT-GO bio-adsorbent would be an ideal adsorbent for removal of precious metal ions and broaden the potential applications of persimmon tannin in environmental research. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Production of radio-gold {sup 199}Au for diagnostic and therapeutic applications

    Energy Technology Data Exchange (ETDEWEB)

    Khandaker, Mayeen Uddin, E-mail: mu-khandaker@um.edu.my; Kassim, Hasan Abu, E-mail: hasanak@um.edu.my [Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Haba, Hiromitsu, E-mail: haba@riken.jp [Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0198 (Japan)

    2016-01-22

    Production cross-sections of the {sup nat}Pt(d,x){sup 199}Au reactions have been measured from a 24-MeV deuteron energy down to the threshold by using a stacked-foil activation technique combined with HPGe γ-ray spectrometry. Only a partial agreement is obtained with the existing literature data. Theoretical data extracted from the TENDL-2013 library shows large discrepancy with the measured ones. Physical thick target yield for the {sup 199}Au radionuclide was deduced using the measured cross-sections, and found a general agreement with the directly measured yield available in the literature. This study reveals that a low deuteron energy (<15 MeV) cyclotron and an enriched {sup 198}Pt (100%) target could be used to obtain {sup 199}Au in no carrier added form.

  10. Elliptic flow of electrons from heavy-flavor hadron decays in Au + Au collisions at √{sN N}=200 , 62.4, and 39 GeV

    Science.gov (United States)

    Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, X.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, S.; Gupta, A.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, H. Z.; Huang, X.; Huang, B.; Huang, T.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Kocmanek, M.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, Y.; Li, W.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, P.; Liu, Y.; Liu, F.; Liu, H.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Luo, S.; Ma, Y. G.; Ma, L.; Ma, R.; Ma, G. L.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Saur, M.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, M. K.; Sharma, A.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, X. M.; Sun, X.; Surrow, B.; Svirida, D. N.; Tang, A. H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vasiliev, A. N.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, W.; Xu, Y. F.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, C.; Yang, S.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, Z.; Zhang, X. P.; Zhang, J. B.; Zhang, S.; Zhang, J.; Zhang, Y.; Zhang, J.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, L.; Zhou, C.; Zhu, X.; Zhu, Z.; Zyzak, M.; STAR Collaboration

    2017-03-01

    We present measurements of elliptic flow (v2) of electrons from the decays of heavy-flavor hadrons (eHF) by the STAR experiment. For Au+Au collisions at √{sN N}=200 GeV we report v2, for transverse momentum (pT) between 0.2 and 7 GeV /c , using three methods: the event plane method (v2{EP } ), two-particle correlations (v2{2 } ), and four-particle correlations (v2{4 } ). For Au+Au collisions at √{sN N}=62.4 and 39 GeV we report v2{2 } for pT<2 GeV /c . v2{2 } and v2{4 } are nonzero at low and intermediate pT at 200 GeV, and v2{2 } is consistent with zero at low pT at other energies. The v2{2 } at the two lower beam energies is systematically lower than at √{sN N}=200 GeV for pT<1 GeV /c . This difference may suggest that charm quarks interact less strongly with the surrounding nuclear matter at those two lower energies compared to √{sN N}=200 GeV.

  11. Les technolectes au Maroc

    OpenAIRE

    Messaoudi, Leila

    2017-01-01

    Cette réflexion sur les technolectes au Maroc émane d’un ensemble de travaux menés sur le terrain et conduit à une synthèse permettant de dégager le fonctionnement général et les tendances d’évolution. Nous commencerons par rappeler les traits définitoires du technolecte. Nous aborderons ensuite se : modes de réalisation, en illustrant par des échantillons de corpus recueillis au Maroc. Définition de « technolecte » Par « technolecte », nous entendons l’ensemble des usages lexicaux et discurs...

  12. Le CRDI au Cambodge

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le CRDI a été l'un des premiers bailleurs de fonds à établir des relations avec le Cambodge au début des années 1990, alors que le pays progres- sait vers la paix. Depuis, le Centre aide à reconstruire le Cambodge, qui se remet du régime inhumain des Khmers rouges et de décennies de conflits régionaux. Un État ...

  13. Le CRDI au Vietnam

    International Development Research Centre (IDRC) Digital Library (Canada)

    des agriculteurs trouvent des solutions de rechange à la culture du tabac. □ des responsables de politiques agissent pour réduire la pauvreté. Soutien accordé par le CRDI depuis 1991. 111 activités d'une valeur de 30 millions cad. CRDI. Le CRDI au Vietnam centre de recherches pour le développement international ...

  14. Mise au point

    African Journals Online (AJOL)

    7 mai 2012 ... cervico-thoracique confirme l'existence d'un goitre plon- geant aux dépens du lobe droit restant à 15 mm de la crosse aortique associé à un processus expansif tissulai- ... DU CANCER DIFFERENCIE DE LA ThYROIDE. R. BEN M'hAMED et al. Journal ORL N°26 .ai:Mise au point 07/05/12 09:45 page54 ...

  15. Le CRDI au Ghana

    International Development Research Centre (IDRC) Digital Library (Canada)

    pour prévenir le paludisme, des études ayant démontré que leur utilisation pouvait réduire considérablement la mortalité infantile. Les chercheurs ont également suggéré aux gouvernements différents moyens pour inciter les gens à acheter les moustiquaires et à les utiliser correctement. Les TI au service de la démocratie.

  16. Mise au point

    African Journals Online (AJOL)

    31 mai 2013 ... volumineuse tuméfaction sus claviculaire. Cette masse intéressant toute la partie latérale droite du cou et le quart supérieur du thorax était indolore, mobile par rapport au plan profond et rénitente mesurant 22 cm sur 26 cm de diamètre. On notait la présence de lacis veineux. ailleurs, les poumons étaient ...

  17. Le CRDI au Maroc

    International Development Research Centre (IDRC) Digital Library (Canada)

    démocratiques. Au Maroc, le Centre d'études et de recherches en sciences sociales analyse ce que pourrait être la réaction du gouverne- ment aux pressions exercées par la population en vue d'un changement sur le plan politique. Rabat. Casablanca. Marrakech. Tan-Tan. Bou Arfa. Zagora. Oujda. Tanger. Fès. ALGÉRIE.

  18. Mise au point

    African Journals Online (AJOL)

    et traité à temps, le risque de complications et de morbidité peut être écarté. Les auteurs rapportent 2 cas de kystes de la vallécule. La tomodensitométrie a confirmé la présence d'une formation kystique prenant origine au niveau de la val- lécule. Une laryngoscopie directe a été faite pour les 2 patients sous anesthésie ...

  19. Measurements of identified particles at intermediate transverse momentum in the STAR experiment from Au+Au collisions at sqrt{s_{NN}}=200 GeV

    CERN Document Server

    Adams, John; Ahammed, Z.; Amonett, J.; Anderson, B.D.; Anderson, M.; Arkhipkin, D.; Averichev, G.S.; Badyal, S.K.; Bai, Y.; Balewski, J.; Barannikova, O.; Barnby, L.S.; Baudot, J.; Bekele, S.; Belaga, V.V.; Bellingeri-Laurikainen, A.; Bellwied, R.; Bezverkhny, B.I.; Bharadwaj, S.; Bhasin, A.; Bhati, A.K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L.C.; Blyth, C.O.; Blyth, S.L.; Bonner, B.E.; Botje, M.; Bouchet, J.; Brandin, A.V.; Bravar, A.; Bystersky, M.; Cadman, R.V.; Cai, X.Z.; Caines, H.; Calderon de la Barca Sancez, M.; Castillo, J.; Catu, O.; Cebra, D.A.; Chajecki, Z.; Chaloupka, P.; Chattopadhyay, S.; Chen, H.F.; Chen, J.H.; Chen, Y.; Cheng, J.; Cherney, Michael G.; Chikanian, A.; Choi, H.A.; Christie, W.; Coffin, J.P.; Cormier, T.M.; Cosentino, M.R.; Cramer, J.G.; Crawford, H.J.; Das, D.; Das, S.; Daugherity, M.; de Moura, M.M.; Dedovich, T.G.; DePhillips, M.; Derevschikov, A.A.; Didenko, L.; Dietel, T.; Djawotho, P.; Dogra, S.M.; Dong, W.J.; Dong, X.; Draper, J.E.; Du, F.; Dunin, V.B.; Dunlop, J.C.; Dutta Mazumdar, M.R.; Eckardt, V.; Edwards, W.R.; Efimov, L.G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Filimonov, K.; Filip, P.; Finch, E.; Fine, V.; Fisyak, Y.; Fornazier, K.S.F.; Fu, J.; Gagliardi, C.A.; Gaillard, L.; Gans, J.; Ganti, M.S.; Ghazikhanian, V.; Ghosh, P.; Gonzalez, J.E.; Gorbunov, Y.G.; Gos, H.; Grebenyuk, O.; Grosnick, D.; Guertin, S.M.; Guo, Y.; Gupta, A.; Gupta, N.; Gutierrez, T.D.; Haag, B.; Hallman, T.J.; Hamed, A.; Harris, J.W.; He, W.; Heinz, M.; Henry, T.W.; Hepplemann, S.; Hippolyte, B.; Hirsch, A.; Hjort, E.; Hoffmann, G.W.; Horner, M.J.; Huang, H.Z.; Huang, S.L.; Hughes, E.W.; Humanic, T.J.; Igo, G.; Jacobs, P.; Jacobs, W.W.; Jakl, P.; Jia, F.; Jiang, H.; Jones, P.G.; Judd, E.G.; Kabana, S.; Kang, K.; Kapitan, J.; Kaplan, M.; Keane, D.; Kechechyan, A.; Khodyrev, V.Yu.; Kim, B.C.; Kiryluk, J.; Kisiel, A.; Kislov, E.M.; Klein, S.R.; Koetke, D.D.; Kollegger, T.; Kopytine, M.; Kotchenda, L.; Kouchpil, V.; Kowalik, K.L.; Kramer, M.; Kravtsov, P.; Kravtsov, V.I.; Krueger, K.; Kuhn, C.; Kulikov, A.I.; Kumar, A.; Kuznetsov, A.A.; Lamont, M.A.C.; Landgraf, J.M.; Lange, S.; LaPointe, S.; Laue, F.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, C.H.; Lehocka, S.; LeVine, Micheal J.; Li, C.; Li, Q.; Li, Y.; Lin, G.; Lindenbaum, S.J.; Lisa, M.A.; Liu, F.; Liu, H.; Liu, J.; Liu, L.; Liu, Z.; Ljubicic, T.; Llope, W.J.; Long, H.; Longacre, R.S.; Lopez-Noriega, M.; Love, W.A.; Lu, Y.; Ludlam, T.; Lynn, D.; Ma, G.L.; Ma, J.G.; Ma, Y.G.; Magestro, D.; Mahajan, S.; Mahapatra, D.P.; Majka, R.; Mangotra, L.K.; Manweiler, R.; Margetis, S.; Markert, C.; Martin, L.; Matis, H.S.; Matulenko, Yu.A.; McClain, C.J.; McShane, T.S.; Melnick, Yu.; Meschanin, A.; Miller, M.L.; Milos, M.; Minaev, N.G.; Mioduszewski, S.; Mironov, C.; Mischke, A.; Mishra, D.K.; Mitchell, J.; Mohanty, B.; Molnar, L.; Moore, C.F.; Morozov, D.A.; Munhoz, M.G.; Nandi, B.K.; Nayak, S.K.; Nayak, T.K.; Nelson, J.M.; Netrakanti, P.K.; Nikitin, V.A.; Nogach, L.V.; Nurushev, S.B.; Odyniec, G.; Ogawa, A.; Okorokov, V.; Oldenburg, M.; Olson, D.; Pal, S.K.; Panebratsev, Y.; Panitkin, S.Y.; Pavlinov, A.I.; Pawlak, T.; Peitzmann, T.; Perevoztchikov, V.; Perkins, C.; Peryt, W.; Petrov, V.A.; Phatak, S.C.; Picha, R.; Planinic, M.; Pluta, J.; Poljak, N.; Porile, N.; Porter, J.; Poskanzer, A.M.; Potekhin, M.; Potrebenikova, E.; Potukuchi, B.V.K.S.; Prindle, D.; Pruneau, C.; Putschke, J.; Rakness, G.; Raniwala, R.; Raniwala, S.; Ray, R.L.; Razin, S.V.; Reinnarth, J.; Relyea, D.; Retiere, F.; Ridiger, A.; Ritter, H.G.; Roberts, J.B.; Rogachevskiy, O.V.; Romero, J.L.; Rose, A.; Roy, C.; Ruan, L.; Russcher, M.J.; Sahoo, R.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarsour, M.; Savin, Igor A.; Sazhin, P.S.; Schambach, J.; Scharenberg, R.P.; Schmitz, N.; Schweda, K.; Seger, J.; Selyuzhenkov, I.; Seyboth, P.; Shabetai, A.; Shahaliev, E.; Shao, M.; Sharma, M.; Shen, W.Q.; Shimanskiy, S.S.; Sichtermann, E; Simon, F.; Singaraju, R.N.; Smirnov, N.; Snellings, R.; Sood, G.; Sorensen, P.; Sowinski, J.; Speltz, J.; Spinka, H.M.; Srivastava, B.; Stadnik, A.; Stanislaus, T.D.S.; Stock, R.; Stolpovsky, A.; Strikhanov, M.; Stringfellow, B.; Suaide, A.A.P.; Sugarbaker, E.; Sumbera, M.; Sun, Z.; Surrow, B.; Swanger, M.; Symons, T.J.M.; Szanto de Toledo, A.; Tai, A.; Takahashi, J.; Tang, A.H.; Tarnowsky, T.; Thein, D.; Thomas, J.H.; Timmins, A.R.; Timoshenko, S.; Tokarev, M.; Trainor, T.A.; Trentalange, S.; Tribble, R.E.; Tsai, O.D.; Ulery, J.; Ullrich, T.; Underwood, David G.; Van Buren, G.; van der Kolk, N.; van Leeuwen, M.; Vander Molen, A.M.; Varma, R.; Vasilevski, I.M.; Vasiliev, A.N.; Vernet, R.; Vigdor, S.E.; Viyogi, Y.P.; Vokal, S.; Voloshin, S.A.; Waggoner, W.T.; Wang, F.; Wang, G.; Wang, J.S.; Wang, X.L.; Wang, Y.; Watson, J.W.; Webb, J.C.; Westfall, G.D.; Wetzler, A.; Whitten, C., Jr.; Wieman, H.; Wissink, S.W.; Witt, R.; Wood, J.; Wu, J.; Xu, N.; Xu, Q.H.; Xu, Z.; Yepes, P.; Yoo, I.K.; Yurevich, V.I.; Zborovsky, I.; Zhan, W.; Zhang, H.; Zhang, W.M.; Zhang, Y.; Zhang, Z.P.; Zhao, Y.; Zhong, C.; Zoulkarneev, R.; Zoulkarneeva, Y.; Zubarev, A.N.; Zuo, J.X.; Braem, A.; Davenport, M.; De Cataldo, G.; Di Bari, D.; Di Mauro, A.; Kunde, G.J.; Martinengo, P.; Nappi, E.; Paic, G.; Posa, E.; Piuz, F.; Schyns, E.

    2006-01-01

    Data for Au+Au collisions at sqrt{s_{NN}}=200 GeV are analyzed to determine the ratios of identified hadrons ($\\pi$, $K$, $p$, $\\Lambda$) as functions of collision centrality and transverse momentum ($p_T$). We find that ratios of anti-baryon to baryon yields are independent of $p_T$ up to 5 GeV/c, a result inconsistent with results of theoretical pQCD calculations that predict a decrease due to a stronger contribution from valence quark scattering. For both strange and non-strange species, strong baryon enhancements relative to meson yields are observed as a function of collision centrality in the intermediate $p_T$ region, leading to $p/\\pi$ and $\\Lambda$/K ratios greater than unity. The increased $p_T$ range offered by the $\\Lambda$/K$^{0}_{S}$ ratio allows a test of the applicability of various models developed for the intermediate $p_{T}$ region. The physics implications of these measurements are discussed with regard to different theoretical models.

  20. Electron transport in a Pt-CO-Pt nanocontact: Density functional theory calculations

    DEFF Research Database (Denmark)

    Strange, Mikkel; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2006-01-01

    We have performed first-principles calculations for the mechanic and electric properties of pure Pt nanocontacts and a Pt contact with a single CO molecule adsorbed. For the pure Pt contacts we see a clear difference between point contacts and short chains in good agreement with experiments. We i...... of the transmission function for the Pt-CO-Pt contact, and show that the conductance is largely determined by the local d band at the Pt apex atoms....

  1. Ab-initio study of the coadsorption of Li and H on Pt(001), Pt(110) and Pt(111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Saad, Farida [Laboratoire de Physique et Chimie Quantique, Faculte des Sciences, Universite Mouloud Mammeri, 15000 Tizi-Ouzou (Algeria); Zemirli, Mourad, E-mail: zemirlimourad@mail.ummto.dz [Laboratoire de Physique et Chimie Quantique, Faculte des Sciences, Universite Mouloud Mammeri, 15000 Tizi-Ouzou (Algeria); Benakki, Mouloud; Bouarab, Said [Laboratoire de Physique et Chimie Quantique, Faculte des Sciences, Universite Mouloud Mammeri, 15000 Tizi-Ouzou (Algeria)

    2012-02-15

    The coadsorption of Li and H atoms on Pt(001), Pt(110) and Pt(111) surfaces is studied using density functional theory with generalised gradient approximation. In all calculations Li, H and the two topmost layers of the metal were allowed to relax. At coverage of 0.25 mono-layer in a p(2 Multiplication-Sign 2) unit cell, lithium adsorption at the hollow site for the three surfaces is favoured over top and bridge sites. The most favoured adsorption sites for H atom on the Pt(001) and Pt(110) surfaces are the top and bridge sites, while on Pt(111) surface the fcc site appears to be slightly favoured over the hcp site. The coadsorption of Li and atomic hydrogen shows that the interaction between the two adsorbates is stabilising when they are far from each other. The analysis of Li, H and Pt local density of states shows that Li strongly interacts with the Pt surfaces.

  2. Mise au point

    African Journals Online (AJOL)

    tomie est replacé et fixé par des fils d'acier, krönlein lais- sait ce fragment pédiculé au fascia temporalis afin d'évi- ter la dépression de la fosse temporale due à la désinser- tion du muscle temporal [20] ; dans notre série, après reconstitution du cadre, le muscle temporal est suturé à son point d'insertion. pour les tumeurs ...

  3. Migration malienne au Cameroun

    OpenAIRE

    Cisse, Pierre

    2013-01-01

    L’attractivité économique du Cameroun à partir des années quatre-vingt a drainé une population d’émigrés maliens. S’appuyant sur un système efficace de réseaux de parenté, la communauté malienne du Cameroun assure sa propre pérennité. En offrant systématiquement un emploi au membre nouvellement venu, elle s’annexe des pans entiers de l’économie camerounaise. Ce faisant, à Yaoundé ou à Douala, elle se met aussi à dos une population autochtone concurrente.

  4. Mise au point

    African Journals Online (AJOL)

    31 mai 2013 ... L'attitude théra- peutique dépend du type de la laryngocèle. en effet, le traitement endoscopique au laser CO2 a gagné beaucoup d'intérêt ces dernières années. MATÉRIEL ET MÉTHOdES. Il s'agit d'une étude rétrospective portant sur 9 patients porteurs d'une laryngocèle colligés sur une période de 14.

  5. Le paludisme au Mexique

    International Development Research Centre (IDRC) Digital Library (Canada)

    Nancy Minogue

    Le paludisme est depuis longtemps un important problème de santé publique au Mexique, où les conditions qui prévalent ... C'est dans les régions côtières que le problème a persisté le plus longtemps, les mesures ... recherche sur l'écologie des moustiques a permis d'en découvrir les raisons. « Les moustiques ne se ...

  6. Charged particle density distributions in Au+ Au collisions at ...

    Indian Academy of Sciences (India)

    Charged particle pseudorapidity distributions have been measured in Au + Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of ...

  7. Charged particle density distributions in Au + Au collisions at ...

    Indian Academy of Sciences (India)

    Charged particle pseudorapidity distributions have been measured in Au + Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of ...

  8. Strategic Alliance Between PT Dirgantara Indonesia and Airbus Millitary (a Case Study of PT Dirgantara Indonesia)

    OpenAIRE

    Indriyanto, Reza Relen; Wandebori, Harimukti; Astuti, Novika Candra

    2013-01-01

    PT Dirgantara Indonesia (PT DI) is one of the aircraft manufacturing companies in Indonesia. The tight of competition in aerospace industry needs to improve its performance to gain niche market. Therefore, Ministry State of Own Enterprises has instructed PT Perusahaan Pengelola Aset (PT PPA) and PT DI to restructure and revitalize company with supported by Airbus Military as a strategic alliance partner, in order to increase the performance of production capacity, aircraft sales, and financia...

  9. Stable and solubilized active Au atom clusters for selective epoxidation of cis-cyclooctene with molecular oxygen

    Science.gov (United States)

    Qian, Linping; Wang, Zhen; Beletskiy, Evgeny V.; Liu, Jingyue; Dos Santos, Haroldo J.; Li, Tiehu; Rangel, Maria Do C.; Kung, Mayfair C.; Kung, Harold H.

    2017-03-01

    The ability of Au catalysts to effect the challenging task of utilizing molecular oxygen for the selective epoxidation of cyclooctene is fascinating. Although supported nanometre-size Au particles are poorly active, here we show that solubilized atomic Au clusters, present in ng ml-1 concentrations and stabilized by ligands derived from the oxidized hydrocarbon products, are active. They can be formed from various Au sources. They generate initiators and propagators to trigger the onset of the auto-oxidation reaction with an apparent turnover frequency of 440 s-1, and continue to generate additional initiators throughout the auto-oxidation cycle without direct participation in the cycle. Spectroscopic characterization suggests that 7-8 atom clusters are effective catalytically. Extension of work based on these understandings leads to the demonstration that these Au clusters are also effective in selective oxidation of cyclohexene, and that solubilized Pt clusters are also capable of generating initiators for cyclooctene epoxidation.

  10. Structure, microstructure and magnetic properties of electrodeposited Co and Co-Pt in different nanoscale geometries

    Energy Technology Data Exchange (ETDEWEB)

    Khatri, Manvendra Singh

    2010-07-09

    Thin films and nanowires of Co-Pt have been prepared by means of electrodeposition. Composition, structure, microstructure and magnetic properties have been intensively studied using X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry and correlated to the deposition parameters such as electrolyte composition, deposition current and/or potential. Co rich Co-Pt films have been deposited at various current densities. A nearly constant composition of Co{sub 70}Pt{sub 30} was achieved for current densities between 18 and 32 mA/cm{sup 2}. Detailed texture measurements confirmed an increasing fraction of the hexagonal phase with its c-axis aligned perpendicular to the film plane with increasing current density. Accordingly, magnetic properties are strongly affected by the magnetocrystalline anisotropy of the hexagonal phase that competes with the shape anisotropy of the thin film geometry. Co-Pt nanowires have been prepared within alumina templates at different deposition potentials between -0.6 and -0.9 V{sub SCE} changing the composition from nearly pure Pt to Co. The composition Co{sub 80}Pt{sub 20} was observed at a deposition potential of -0.7 V{sub SCE}. Co-Pt nanowires are nanocrystalline in the as-deposited state. Magnetic measurements reveal changing fcc and hcp phase fractions within the wires as the effective anisotropy significantly differs from the expected shape anisotropy for nanowires with high aspect ratio. This change in effective anisotropy is attributed to the preferential alignment of the c-axis of hcp Co-Pt phase perpendicular to the nanowires axis. A promising alternative with much smaller feature sizes is the diblock copolymer template. Electrodeposition of Co and Co-Pt into these templates has been carried out. Inhomogeneities in the template thickness as well as a certain substrate roughness have been identified to be the reasons for inhomogeneous template filling. Thus magnetic properties are dominated by large

  11. Rotational high spin structures in doubly-odd in {sup 184}Au

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, F.; Roussiere, B.; Sauvage, J.; Bourgeois, C.; Korichi, A. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Hojman, D.; Kreiner, A.J.; Davidson, J.; Davidson, M.; Debray, M. [Comision Nacional de Energia Atomica, Buenos Aires (Argentina). Dept. de Fisica; Knipper, A. [Strasbourg-1 Univ., 67 (France). Centre de Recherches Nucleaires; Marguier, G. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire] [and others

    1995-12-31

    Excited states in the doubly-odd {sup 184}Au nucleus have been studied by in-beam {gamma}-ray spectroscopy. This nucleus was produced through the fusion-evaporation reactions {sup 165}Ho({sup 24}Mg, 5n), {sup 170}Yb({sup 19}F, 5n) and {sup 161}Dy({sup 27}Al, 4n). Different rotational band structures have been observed and interpreted as specific couplings of proton and neutron single-particle excitations present in neighboring odd Au and Pt nuclei. (author). 34 refs.; Submitted to Physical Review, C (US).

  12. Porous α-Fe2O3 decorated by Au nanoparticles and their enhanced sensor performance

    Science.gov (United States)

    Liu, Xianghong; Zhang, Jun; Guo, Xianzhi; Wu, Shihua; Wang, Shurong

    2010-03-01

    Porous α-Fe2O3 was synthesized by simple calcination of a β-FeOOH precursor derived from a facile hydrothermal method. In the hydrothermal process, only FeCl3·6H2O was used as the source material and no templates or pore-directing agents were needed. The as-prepared porous α-Fe2O3 was further employed as a support for loading Au nanoparticles (AuNPs). Due to the advantages of porous nanostructures (large surface area and facile gas diffusion) and the catalytic capability of AuNPs, the derived AuNP-supported porous α-Fe2O3 was further investigated for gas sensor applications using ethanol as a probe molecule. Obtained results showed that the AuNP-supported porous α-Fe2O3 exhibited a much higher response in comparison to pure α-Fe2O3. The enhanced sensor properties are attributed to the unique porous structures of the α-Fe2O3 support and active AuNPs for promoting sensing reactions, as well as the synergic electronic interaction between Au and α-Fe2O3. It is expected that noble metals such as Ag, Pt and Pd can also be supported on other porous metal oxide semiconductors to explore superior properties of functional nanomaterials.

  13. Dynamics study of green AuNP formation and their basis for Au-Pt core-shell nanostructure synthesis

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Seselj, Nedjeljko; Ulstrup, Jens

    The SAMENS method (saccharide - based approach to metallic nanostructure synthesis) is a synthesis platform for metallic nanostructures. The method has been developed since 2008 and can produce nanostructures of various sizes, shapes and compositions. Recently, a new methodology for studying the ...

  14. Measurement of D^{0} Azimuthal Anisotropy at Midrapidity in Au+Au Collisions at sqrt[s_{NN}]=200  GeV.

    Science.gov (United States)

    Adamczyk, L; Adkins, J K; Agakishiev, G; Aggarwal, M M; Ahammed, Z; Ajitanand, N N; Alekseev, I; Anderson, D M; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, E C; Ashraf, M U; Attri, A; Averichev, G S; Bai, X; Bairathi, V; Behera, A; Bellwied, R; Bhasin, A; Bhati, A K; Bhattarai, P; Bielcik, J; Bielcikova, J; Bland, L C; Bordyuzhin, I G; Bouchet, J; Brandenburg, J D; Brandin, A V; Brown, D; Bunzarov, I; Butterworth, J; Caines, H; Calderón de la Barca Sánchez, M; Campbell, J M; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, X; Chen, J H; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, H J; Das, S; De Silva, L C; Debbe, R R; Dedovich, T G; Deng, J; Derevschikov, A A; Didenko, L; Dilks, C; Dong, X; Drachenberg, J L; Draper, J E; Dunkelberger, L E; Dunlop, J C; Efimov, L G; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Federicova, P; Fedorisin, J; Feng, Z; Filip, P; Finch, E; Fisyak, Y; Flores, C E; Fulek, L; Gagliardi, C A; Garand, D; Geurts, F; Gibson, A; Girard, M; Greiner, L; Grosnick, D; Gunarathne, D S; Guo, Y; Gupta, A; Gupta, S; Guryn, W; Hamad, A I; Hamed, A; Harlenderova, A; Harris, J W; He, L; Heppelmann, S; Heppelmann, S; Hirsch, A; Hoffmann, G W; Horvat, S; Huang, T; Huang, B; Huang, X; Huang, H Z; Humanic, T J; Huo, P; Igo, G; Jacobs, W W; Jentsch, A; Jia, J; Jiang, K; Jowzaee, S; Judd, E G; Kabana, S; Kalinkin, D; Kang, K; Kauder, K; Ke, H W; Keane, D; Kechechyan, A; Khan, Z; Kikoła, D P; Kisel, I; Kisiel, A; Kochenda, L; Kocmanek, M; Kollegger, T; Kosarzewski, L K; Kraishan, A F; Kravtsov, P; Krueger, K; Kulathunga, N; Kumar, L; Kvapil, J; Kwasizur, J H; Lacey, R; Landgraf, J M; Landry, K D; Lauret, J; Lebedev, A; Lednicky, R; Lee, J H; Li, X; Li, C; Li, W; Li, Y; Lidrych, J; Lin, T; Lisa, M A; Liu, H; Liu, P; Liu, Y; Liu, F; Ljubicic, T; Llope, W J; Lomnitz, M; Longacre, R S; Luo, S; Luo, X; Ma, G L; Ma, L; Ma, Y G; Ma, R; Magdy, N; Majka, R; Mallick, D; Margetis, S; Markert, C; Matis, H S; Meehan, K; Mei, J C; Miller, Z W; Minaev, N G; Mioduszewski, S; Mishra, D; Mizuno, S; Mohanty, B; Mondal, M M; Morozov, D A; Mustafa, M K; Nasim, Md; Nayak, T K; Nelson, J M; Nie, M; Nigmatkulov, G; Niida, T; Nogach, L V; Nonaka, T; Nurushev, S B; Odyniec, G; Ogawa, A; Oh, K; Okorokov, V A; Olvitt, D; Page, B S; Pak, R; Pandit, Y; Panebratsev, Y; Pawlik, B; Pei, H; Perkins, C; Pile, P; Pluta, J; Poniatowska, K; Porter, J; Posik, M; Poskanzer, A M; Pruthi, N K; Przybycien, M; Putschke, J; Qiu, H; Quintero, A; Ramachandran, S; Ray, R L; Reed, R; Rehbein, M J; Ritter, H G; Roberts, J B; Rogachevskiy, O V; Romero, J L; Roth, J D; Ruan, L; Rusnak, J; Rusnakova, O; Sahoo, N R; Sahu, P K; Salur, S; Sandweiss, J; Saur, M; Schambach, J; Schmah, A M; Schmidke, W B; Schmitz, N; Schweid, B R; Seger, J; Sergeeva, M; Seyboth, P; Shah, N; Shahaliev, E; Shanmuganathan, P V; Shao, M; Sharma, A; Sharma, M K; Shen, W Q; Shi, Z; Shi, S S; Shou, Q Y; Sichtermann, E P; Sikora, R; Simko, M; Singha, S; Skoby, M J; Smirnov, N; Smirnov, D; Solyst, W; Song, L; Sorensen, P; Spinka, H M; Srivastava, B; Stanislaus, T D S; Strikhanov, M; Stringfellow, B; Sugiura, T; Sumbera, M; Summa, B; Sun, Y; Sun, X M; Sun, X; Surrow, B; Svirida, D N; Szelezniak, M A; Tang, A H; Tang, Z; Taranenko, A; Tarnowsky, T; Tawfik, A; Thäder, J; Thomas, J H; Timmins, A R; Tlusty, D; Todoroki, T; Tokarev, M; Trentalange, S; Tribble, R E; Tribedy, P; Tripathy, S K; Trzeciak, B A; Tsai, O D; Ullrich, T; Underwood, D G; Upsal, I; Van Buren, G; van Nieuwenhuizen, G; Vasiliev, A N; Videbæk, F; Vokal, S; Voloshin, S A; Vossen, A; Wang, G; Wang, Y; Wang, F; Wang, Y; Webb, J C; Webb, G; Wen, L; Westfall, G D; Wieman, H; Wissink, S W; Witt, R; Wu, Y; Xiao, Z G; Xie, W; Xie, G; Xu, J; Xu, N; Xu, Q H; Xu, Y F; Xu, Z; Yang, Y; Yang, Q; Yang, C; Yang, S; Ye, Z; Ye, Z; Yi, L; Yip, K; Yoo, I-K; Yu, N; Zbroszczyk, H; Zha, W; Zhang, Z; Zhang, X P; Zhang, J B; Zhang, S; Zhang, J; Zhang, Y; Zhang, J; Zhang, S; Zhao, J; Zhong, C; Zhou, L; Zhou, C; Zhu, X; Zhu, Z; Zyzak, M

    2017-05-26

    We report the first measurement of the elliptic anisotropy (v_{2}) of the charm meson D^{0} at midrapidity (|y|<1) in Au+Au collisions at sqrt[s_{NN}]=200  GeV. The measurement was conducted by the STAR experiment at RHIC utilizing a new high-resolution silicon tracker. The measured D^{0} v_{2} in 0%-80% centrality Au+Au collisions can be described by a viscous hydrodynamic calculation for a transverse momentum (p_{T}) of less than 4  GeV/c. The D^{0} v_{2} as a function of transverse kinetic energy (m_{T}-m_{0}, where m_{T}=sqrt[p_{T}^{2}+m_{0}^{2}]) is consistent with that of light mesons in 10%-40% centrality Au+Au collisions. These results suggest that charm quarks have achieved local thermal equilibrium with the medium created in such collisions. Several theoretical models, with the temperature-dependent, dimensionless charm spatial diffusion coefficient (2πTD_{s}) in the range of ∼2-12, are able to simultaneously reproduce our D^{0} v_{2} result and our previously published results for the D^{0} nuclear modification factor.

  15. Measurement of D0 Azimuthal Anisotropy at Midrapidity in Au +Au Collisions at √{sN N }=200 GeV

    Science.gov (United States)

    Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, X.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, B.; Huang, X.; Huang, H. Z.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Kocmanek, M.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, W.; Li, Y.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, H.; Liu, P.; Liu, Y.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, G. L.; Ma, L.; Ma, Y. G.; Ma, R.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Saur, M.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Strikhanov, M.; Stringfellow, B.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, X. M.; Sun, X.; Surrow, B.; Svirida, D. N.; Szelezniak, M. A.; Tang, A. H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vasiliev, A. N.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y. F.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, C.; Yang, S.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, Z.; Zhang, X. P.; Zhang, J. B.; Zhang, S.; Zhang, J.; Zhang, Y.; Zhang, J.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, L.; Zhou, C.; Zhu, X.; Zhu, Z.; Zyzak, M.; STAR Collaboration

    2017-05-01

    We report the first measurement of the elliptic anisotropy (v2) of the charm meson D0 at midrapidity (|y |<1 ) in Au +Au collisions at √{sN N}=200 GeV . The measurement was conducted by the STAR experiment at RHIC utilizing a new high-resolution silicon tracker. The measured D0 v2 in 0%-80% centrality Au +Au collisions can be described by a viscous hydrodynamic calculation for a transverse momentum (pT) of less than 4 GeV /c . The D0 v2 as a function of transverse kinetic energy (mT-m0, where mT=√{pT2+m02 }) is consistent with that of light mesons in 10%-40% centrality Au +Au collisions. These results suggest that charm quarks have achieved local thermal equilibrium with the medium created in such collisions. Several theoretical models, with the temperature-dependent, dimensionless charm spatial diffusion coefficient (2 π T Ds) in the range of ˜2 - 12 , are able to simultaneously reproduce our D0 v2 result and our previously published results for the D0 nuclear modification factor.

  16. Measurement of D0 Meson Production and Azimuthal Anisotropy in Au+Au Collisions at √{sNN } = 200 GeV

    Science.gov (United States)

    Xie, Guannan; STAR Collaboration

    2017-08-01

    Due to the large masses, heavy-flavor quarks are dominantly produced in initial hard scattering processes and experience the whole evolution of the medium produced in heavy-ion collisions at RHIC energies. They are also expected to thermalize slower than light-flavor quarks. Thus the measurement of heavy quark production and azimuthal anisotropy can provide important insights into the medium properties through their interactions with the medium. In these proceedings, we report measurements of D0 production and elliptic flow (v2 via topological reconstruction using STAR's recently installed Heavy Flavor Tracker (HFT). The new measurement of the nuclear modification factor (RAA) of D0 mesons in central Au+Au collisions at √{sNN } = 200 GeV confirms the strong suppression at high transverse momenta (pT) reported in the previous publication with much improved precision. We also report the measurement of elliptic flow for D0 mesons in a wide transverse momentum range in 0-80% minimum-bias Au+Au collisions. The D0 elliptic flow is finite for pT > 2 GeV / c and is systematically below that of light hadrons in the same centrality interval. Furthermore, several theoretical calculations are compared to both RAA and v2 measurements, and the charm quark diffusion coefficient is inferred to be between 2 and ∼12.

  17. Reversibility of Pt-Skin and Pt-Skeleton Nanostructures in Acidic Media.

    Science.gov (United States)

    Durst, Julien; Lopez-Haro, Miguel; Dubau, Laetitia; Chatenet, Marian; Soldo-Olivier, Yvonne; Guétaz, Laure; Bayle-Guillemaud, Pascale; Maillard, Frédéric

    2014-02-06

    Following a well-defined series of acid and heat treatments on a benchmark Pt3Co/C sample, three different nanostructures of interest for the electrocatalysis of the oxygen reduction reaction were tailored. These nanostructures could be sorted into the "Pt-skin" structure, made of one pure Pt overlayer, and the "Pt-skeleton" structure, made of 2-3 Pt overlayers surrounding the Pt-Co alloy core. Using a unique combination of high-resolution aberration-corrected STEM-EELS, XRD, EXAFS, and XANES measurements, we provide atomically resolved pictures of these different nanostructures, including measurement of the Pt-shell thickness forming in acidic media and the resulting changes of the bulk and core chemical composition. It is shown that the Pt-skin is reverted toward the Pt-skeleton upon contact with acid electrolyte. This change in structure causes strong variations of the chemical composition.

  18. Measurement of D-meson azimuthal anisotropy in Au + Au 200 GeV collisions at RHIC

    Science.gov (United States)

    Lomnitz, Michael

    2016-12-01

    Heavy quarks are produced through initial hard scatterings and they are affected by the hot and dense medium created in heavy-ion collisions throughout its whole evolution. Due to their heavy mass, charm quarks are expected to thermalize much more slowly than light flavor quarks. The charm quark flow is a unique tool to study the extent of thermalization of the bulk medium dominated by light quarks and gluons. At high pT, D-meson azimuthal anisotropy is sensitive to the path length dependence of charm quark energy loss in the medium, which offers new insights into heavy quark energy loss mechanisms - gluon radiation vs. collisional processes. We present the STAR measurement of elliptic flow (v2) of D0 and D± mesons in Au+Au collisions at √{sNN} = 200 GeV, for a wide transverse momentum range. These results are obtained from the data taken in the first year of physics running of the new STAR Heavy Flavor Tracker detector, which greatly improves open heavy flavor hadron measurements by the topological reconstruction of secondary decay vertices. The D-meson v2 is finite for pT > 2 GeV/c and systematically below the measurement of light particle species at the same energy. Comparison to a series of model calculations favors scenarios where charm flows with the medium and is used to infer a range for the charm diffusion coefficient 2 πTDs.

  19. The neglected Pt-N(sulfonamido) bond in Pt chemistry. New fluorophore-containing Pt(II) complexes useful for assessing Pt(II) interactions with biomolecules.

    Science.gov (United States)

    Christoforou, Anna Maria; Marzilli, Patricia A; Marzilli, Luigi G

    2006-08-21

    Treatment of cis-Pt(Me2SO)2Cl2 with DNSH-tren afforded [Pt(DNSH-tren)Cl]Cl and with DNSH-dienH, under increasingly more basic conditions, led to Pt(DNSH-dienH)Cl(2), Pt(DNSH-dien)Cl, and Pt(DNS-dien). (DNSH = 5-(dimethylamino)naphthalene-1-sulfonyl, linked via a sulfonamide group to tris(2-aminoethyl)amine (DNSH-tren) and diethylenetriamine (DNSH-dienH); the H's in DNSH-dienH designate protons sometimes lost upon Pt binding, i.e., sulfonamide NH for the dienH moiety and H8 for the DNSH moiety). Respectively, the three neutral DNSH-dienH-derived complexes are difunctional, monofunctional, and nonfunctional and exhibit decreasing fluorescence in this order as the dansyl group distance to Pt decreases. 2D NMR data establish that Pt(DNS-dien) has a Pt-C8 bond and a Pt-N(sulfonamido) bond. Pt(DNSH-dien)Cl and [Pt(DNSH-tren)Cl]Cl bind to N7 of 6-oxopurines (e.g., 5'-GMP, 3'-IMP, and 9-ethylguanine) and sulfur of methionine (met). Competition and challenge reactions for Pt(II) with met and 5'-GMP typically reveal that met binding is favored kinetically but that 5'-GMP binding is favored thermodynamically. This common type of behavior was found for [Pt(DNSH-tren)Cl]Cl. In contrast, Pt(DNSH-dien)Cl had reduced kinetic selectivity for met. This unusual behavior undoubtedly arises as a consequence of the bound Pt-N(sulfonamido) group, which donates strongly to Pt (as indicated by relatively upfield dien NH signals) and which places the bulky DNSH moiety close to the monofunctional reaction site. The decrease in the relatively upfield shifts of the DNSH group signals indicates that this group stacks with the purine. This stacking could explain the unprecedented, relatively low reactivity of a Pt complex bearing a dien-type ligand toward met vs 5'-GMP.

  20. Transverse expansion in 197 Au + 197 Au collisions at RHIC

    International Nuclear Information System (INIS)

    Cheng, Y.; Liu, F.; Liu, K.; Schweda, K.; Xu, N.

    2003-01-01

    Using the RQMD model, transverse momentum distributions and particle ratios are studied for 197 Au + 197 Au collisions at √s NN = 200 GeV. In particular, they present results on the mean transverse momentum of charged pions, charged kaons, protons and anti-protons and compare with experimental measurements. They discuss an approach to study early partonic collectivity in high energy nuclear collisions

  1. Centrality dependence of antiproton production in Au+Au collisions

    Energy Technology Data Exchange (ETDEWEB)

    Beavis, D.; Bennett, M.J.; Carroll, J.B.; Chiba, J.; Chikanian, A.; Crawford, H.; Cronqvist, M.; Dardenne, Y.; Debbe, R.; Doke, T.; Engelage, J.; Greiner, L.; Hallman, T.J.; Hayano, R.S.; Heckman, H.H.; Kashiwagi, T.; Kikuchi, J.; Kumar, S.; Kuo, C.; Lindstrom, P.J.; Mitchell, J.W.; Nagamiya, S.; Nagle, J.L.; Pope, J.K.; Stankus, P.; Tanaka, K.H.; Welsh, R.C.; Zhan, W. [Brookhaven National Laboratory, Upton, New York (United States)]|[A.W. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut (United States)]|[University of California at Los Angeles, Los Angeles California (United States)]|[National Laboratory for High Energy Physics (KEK), Tsukuba (Japan)]|[University of California Space Sciences Laboratory, Berkeley California (United States)]|[Waseda University, Tokyo (Japan)]|[University of Tokyo, Tokyo (Japan)]|[Lawrence Berkeley Laboratory, Berkeley California (United States)]|[Universities Space Sciences Research Association/Goddard Space Flight Center, Greenbelt, Maryland (United States)]|[Nevis Laboratory, Columbia University, Irvington, New York (United States)]|[Johns Hopkins University, Baltimore, Maryland (United States); (E878 Collaboration)

    1995-11-13

    We have measured the yields of antiprotons in Au+Au interactions in the rapidity range 1.2{lt}{ital y}{lt}2.8 as a function of centrality using a beam line spectrometer. The shapes of the invariant multiplicity distributions at {ital p}{sub {ital t}}=0 are used to explore the dynamics of antiproton production and annihilation. {copyright} {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.

  2. Direct Determination of the Ionization Energies of PtC, PtO, and PtO2 with VUVRadiation

    Energy Technology Data Exchange (ETDEWEB)

    Citir, Murat; Metz, Ricardo B.; Belau, Leonid; Ahmed, Musahid

    2008-07-21

    Photoionization efficiency curves were measured for gas-phase PtC, PtO, and PtO2 using tunable vacuum ultraviolet (VUV) radiation at the Advanced Light Source. The molecules were prepared by laser ablation of a platinum tube, followed by reaction with CH4 or N2O and supersonic expansion. These measurements providethe first directly measured ionization energy for PtC, IE(PtC) = 9.45 +- 0.05 eV. The direct measurement also gives greatly improved ionization energies for the platinum oxides, IE(PtO) = 10.0 +- 0.1 eV and IE(PtO2) = 11.35 +- 0.05 eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to greatly improved 0 K bond dissociation energies for the neutrals: D0(Pt-C) = 5.95 +- 0.07 eV, D0(Pt-O)= 4.30 +- 0.12 eV, and D0(OPt-O) = 4.41 +- 0.13 eV, as well as enthalpies of formation for the gas-phase molecules Delta H0 f,0(PtC(g)) = 701 +- 7 kJ/mol, Delta H0f,0(PtO(g)) = 396 +- 12 kJ/mol, and Delta H0f,0(PtO2(g)) = 218 +- 11 kJ/mol. Much of the error in previous Knudsen cell measurements of platinum oxide bond dissociation energies is due to the use of thermodynamic second law extrapolations. Third law values calculated using statistical mechanical thermodynamic functions are in much better agreement with values obtained from ionization energies and ion energetics. These experiments demonstrate that laser ablation production with direct VUV ionization measurements is a versatile tool to measure ionization energies and bond dissociation energies for catalytically interesting species such as metal oxides and carbides.

  3. Low Pt content direct methanol fuel cell anode catalyst: nanophase PtRuNiZr

    Science.gov (United States)

    Narayanan, Sekharipuram R. (Inventor); Whitacre, Jay F. (Inventor)

    2010-01-01

    A method for the preparation of a metallic material having catalytic activity that includes synthesizing a material composition comprising a metal content with a lower Pt content than a binary alloy containing Pt but that displays at least a comparable catalytic activity on a per mole Pt basis as the binary alloy containing Pt; and evaluating a representative sample of the material composition to ensure that the material composition displays a property of at least a comparable catalytic activity on a per mole Pt basis as a representative binary alloy containing Pt. Furthermore, metallic compositions are disclosed that possess substantial resistance to corrosive acids.

  4. Face au risque

    CERN Document Server

    Grosse, Christian; November, Valérie

    2007-01-01

    Ce volume collectif sur le risque inaugure la collection L'ÉQUINOXE. Ancré dans l'histoire pour mesurer les continuités et les ruptures, il illustre la manière dont les sciences humaines évaluent et mesurent les enjeux collectifs du risque sur les plans politiques, scientifiques, énergétiques, juridiques et éthiques. Puisse-t-il nourrir la réflexion sur la culture et la prévention du risque. Ses formes épidémiques, écologiques, sociales, terroristes et militaires nourrissent les peurs actuelles, structurent les projets sécuritaires et constituent - sans doute - les défis majeurs à notre modernité. Dans la foulée de la richesse scientifique d'Equinoxe, L'ÉQUINOXE hérite de son esprit en prenant à son tour le pari de contribuer - non sans risque - à enrichir en Suisse romande et ailleurs le champ éditorial des sciences humaines dont notre société a besoin pour forger ses repères. Après Face au risque suivra cet automne Du sens des Lumières. (MICHEL PORRET Professeur Ordinaire à la F...

  5. Fingerprinting ancient gold by measuring Pt with spatially resolved high energy Sy-XRF

    International Nuclear Information System (INIS)

    Guerra, M.F.; Calligaro, T.; Radtke, M.; Reiche, I.; Riesemeier, H.

    2005-01-01

    Trace elements of ancient gold such as Pt, give fundamental information on the circulation of the metal in the past. In the case of objects from the cultural heritage, the determination of trace elements requires non-destructive point analysis in general. These conditions and the need of good detection limits restrain the number of applicable analytical techniques. After the development of a PIXE set-up with a selective Cu or Zn filter of 75 μm and of a PIXE-XRF set-up using a primary target of As, we tested the possibilities of spatially resolved Sy-XRF to determine Pt in gold alloys. With a Zn filter, PIXE showed a detection limit of 1000 ppm in gold while PIXE-XRF lowers this detection limit down to 80 ppm. This last value being constrained by the resonant Raman effect produced on gold. In order to improve the detection limit of Pt keeping the non-destructiveness and access to point analysis, we developed an analytical protocol for XRF with synchrotron radiation at BESSY II, using the BAMline set-up. The L-lines of Pt were excited by a beam of energy above and below 11.564 keV and measured using a Si(Li) detector with a 50 μm Cu filter. A μ-beam of 100-250 μm 2 was used according to the size of the sample. The determination of the Pt content in the samples was carried out by Monte-Carlo simulation and subtraction of Au and Pt spectra obtained on pure standards. The limit of detection for Pt of 20 ppm was determined by using certified standards. The detection limits of a small set of other characteristic elements of gold were also measured using an incident energy of 33 keV

  6. The electrochemical atomic layer deposition of Pt and Pd nanoparticles on Ni foam for the electro oxidation of alcohols

    CSIR Research Space (South Africa)

    Modibedi, RM

    2013-01-01

    Full Text Available need to be lowered for the direct alcohol fuel cells. This can be achieved by increasing Pt utilization and reducing the amount of Pt required in fuel cells [1]. The cost of the proton exchange membrane fuel cells (PEMFC) depends primarily... nanostructures The three electrode flow cell at 25 °C was used for the electrochemical activity studies by means of cyclic voltammetry. An AutoLab PGSTAT302 potentiostat was used for the studies. Au wire and Ag/AgCl/3M KCl (BASF) were used as counter...

  7. Extraction of Source Images in Au+Au and d+Au collisions at RHIC

    International Nuclear Information System (INIS)

    Chung, P.; Taranenko, A.; Lacey, R.; Holzmann, W.; Alexander, J.; Issah, M.

    2005-01-01

    The PHENIX Collaboration has performed a systematic study of two-pion correlations in Au+Au and d+Au collisions at RHIC (s=200AGeV). The correlations have been analyzed using the Imaging technique of Brown and Danielewicz to extract the two-pion source functions as a function of mT and centrality. The source images are characterised by a short-range Gaussian-like core and a long-range exponential-like tail with a characteristic radius about 3 times that of the Gaussian core. The mT and centrality dependence of the source parameters indicate that the two structures are intricately related

  8. Le CRDI au Sri Lanka

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le CRDI appuie la recherche au Sri. Lanka depuis 1973. Il s'est d'abord concentré sur l'amélioration des pratiques agricoles. Par exemple, grâce à la mise au point d'un système de rizi - culture permettant d'exploiter les pluies de mousson, les riziculteurs ont triplé leurs rendements en quatre ans. Ils ont été nombreux à ...

  9. Comparative study of anchoring groups for molecular electronics: structure and conductance of Au-S-Au and Au-NH2-Au junctions

    DEFF Research Database (Denmark)

    Kristensen, Iben Sig; Mowbray, Duncan; Thygesen, Kristian Sommer

    2008-01-01

    of identifying and comparing the intrinsic properties of two commonly used anchoring groups, namely thiol and amine groups, we have calculated the atomic structure and conductance traces of different Au-S-Au and Au-NH2-Au nanojunctions using density functional theory (DFT). Whereas NH2 shows a strong structural...

  10. Exploratory Catalyst Screening Studies on the Base Free Conversion of Glycerol to Lactic Acid and Glyceric Acid in Water Using Bimetallic Au–Pt Nanoparticles on Acidic Zeolites

    NARCIS (Netherlands)

    Purushothaman, R.K.P.; Haveren, van J.; Mayoral, A.; Melian-Cabrera, I.; Heeres, H.J.

    2014-01-01

    The base free oxidation of glycerol with molecular oxygen in water using bimetallic Au-Pt catalysts on three different acidic zeolite supports (H-mordenite, H-beta and H-USY) was explored in a batch setup. At temperatures between 140 and 180 degrees C, lactic acid formation was significant and

  11. On-line nuclear orientation

    International Nuclear Information System (INIS)

    Krane, K.S.

    1990-01-01

    This grant has as its overall goal the pursuit of on-line nuclear orientation experiments for the purpose of eliciting details of nuclear structure from the decays of neutron-deficient nuclei, such as those produced by the Holifield Heavy-Ion Research Facility at Oak Ridge and extracted by the UNISOR Isotope Separator. This paper discusses: refrigerator development; the decay of 184 Au; the decay of 191 Hg to 191 Au; the decay of 189 Pt to 189 Ir; the decays of 109,111 Pd; the decay of 172 Er; and solid angle corrections

  12. Catalytic reduction of NO by methane using a Pt/C/polybenzimidazole/Pt/C fuel cell

    DEFF Research Database (Denmark)

    Petrushina, Irina; Cleemann, Lars Nilausen; Refshauge, Rasmus

    2007-01-01

    The catalytic NO reduction by methane was studied using a (NO,CH4,Ar),Pt|polybenzimidazole(PBI)–H3PO4|Pt,(H2,Ar) fuel cell at 135 and 165°C. It has been found that, without any reducing agent (like CH4), NO can be electrochemically reduced in the (NO, Ar), Pt/C|PBI–H3PO4|Pt/C, (H2,Ar) fuel cell...

  13. Supraconductivity of LaPtSi and LaPtGe

    Science.gov (United States)

    Evers, J.; Oehlinger, G.; Weiss, A.; Probst, C.

    1984-04-01

    In the ternary compounds LaPtSi and LaPtGe with the LaPtSi-type structure we have observed supraconductivity with a sharp transition temperature of T c=3.3 K and T c=3.4 K, respectively. The superconducting properties of these ternary compounds are compared with binary ones which crystallize in the α-ThSi 2-type structure, since the LaPtSi-type structure is a derivative structure of this.

  14. Measurements of electrons from semi-leptonic heavy flavor decays in p+p and Au+Au collisions at √{sNN } = 200 GeV at STAR

    Science.gov (United States)

    Wang, Yaping; STAR Collaboration

    2017-08-01

    In these proceedings, we present recent results on electrons from semi-leptonic decays of open heavy-flavor hadrons (eHF) with the STAR detector at the Relativistic Heavy Ion Collider. We report the updated measurements of eHF production in p+p collisions at √{ s } = 200 GeV with significantly improved precision and wider kinematic coverage than previous measurements. With this new p+p reference, we obtain the nuclear modification factor (RAA) for eHF in Au+Au collisions at √{sNN } = 200 GeV using 2010 data. The RAA shows significant suppression at high pT in most central Au+Au collisions, while the suppression reduces gradually towards more peripheral collisions. We compare eHFRAA in central Au+Au collisions to that in central U+U collisions at √{sNN } = 193 GeV and find that they are consistent within uncertainties. We also show the results of B-hadron contribution to eHF extracted from azimuthal correlations between eHF and charged hadrons in p+p collisions. Finally we report the measurements of eHF from open bottom hadron decays and discuss the prospect of measuring eHF from open bottom and charm hadron decays separately utilizing the Heavy Flavor Tracker in Au+Au collisions.

  15. Rapid, general synthesis of PdPt bimetallic alloy nanosponges and their enhanced catalytic performance for ethanol/methanol electrooxidation in an alkaline medium.

    Science.gov (United States)

    Zhu, Chengzhou; Guo, Shaojun; Dong, Shaojun

    2013-01-14

    We have demonstrated a rapid and general strategy to synthesize novel three-dimensional PdPt bimetallic alloy nanosponges in the absence of a capping agent. Significantly, the as-prepared PdPt bimetallic alloy nanosponges exhibited greatly enhanced activity and stability towards ethanol/methanol electrooxidation in an alkaline medium, which demonstrates the potential of applying these PdPt bimetallic alloy nanosponges as effective electrocatalysts for direct alcohol fuel cells. In addition, this simple method has also been applied for the synthesis of AuPt, AuPd bimetallic, and AuPtPd trimetallic alloy nanosponges. The as-synthesized three-dimensional bimetallic/trimetallic alloy nanosponges, because of their convenient preparation, well-defined sponge-like network, large-scale production, and high electrocatalytic performance for ethanol/methanol electrooxidation, may find promising potential applications in various fields, such as formic acid oxidation or oxygen reduction reactions, electrochemical sensors, and hydrogen-gas sensors. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Pt Skin Versus Pt Skeleton Structures of Pt3Sc as Electrocatalysts for Oxygen Reduction

    DEFF Research Database (Denmark)

    Johansson, Tobias Peter; Ulrikkeholm, Elisabeth Therese; Hernandez-Fernandez, Patricia

    2014-01-01

    . The development of new materials for this reaction is essential in order to increase the overall effeciency of the fuel cell. Herein, we study the effect of ultra high vacuum annealing on the structure and activity of polycrystalline Pt3Sc. Upon annealing in ultra high vacuum a Pt overlayer is formed...

  17. Pt-Pd nanoelectrocatalyst of ultralow Pt content for the oxidation of ...

    Indian Academy of Sciences (India)

    Significant negative shift (∼350 mV) in the oxidation peak potential and remarkable enhancement in the current density (2.6 times) are observed for Pt4Pd96 nanoparticles with respect to Pt47Pd53. The absence of three adjacent Pt and Pd atoms could be the reason for the suppression of CO pathway. The electrochemical ...

  18. Measurement of benzenethiol adsorption to nanostructured Pt, Pd, and PtPd films using Raman spectroelectrochemistry.

    Science.gov (United States)

    Pomfret, Michael B; Pietron, Jeremy J; Owrutsky, Jeffrey C

    2010-05-04

    Raman spectroscopy and electrochemical methods were used to study the behavior of the model adsorbate benzenethiol (BT) on nanostructured Pt, Pd, and PtPd electrodes as a function of applied potential. Benzenethiol adsorbs out of ethanolic solutions as the corresponding thiolate, and voltammetric stripping data reveal that BT is oxidatively removed from all of the nanostructured metals upon repeated oxidative and reductive cycling. Oxidative stripping potentials for BT increase in the order Pt < PtPd < Pd, indicating that BT adsorbs most strongly to nanoscale Pd. Yet, BT Raman scattering intensities, measured in situ over time scales of minutes to hours, are most persistent on the film of nanostructured Pt. Raman spectra indicate that adsorbed BT desorbs from nanoscale Pt at oxidizing potentials via cleavage of the Pt-S bond. In contrast, on nanoscale Pd and PtPd, BT is irreversibly lost due to cleavage of BT C-S bonds at oxidizing potentials, which leaves adsorbed sulfur oxides on Pd and PtPd films and effects the desulfurization of BT. While Pd and PtPd films are less sulfur-resistant than Pt films, palladium oxides, which form at higher potentials than Pt oxides, oxidatively desulfurize BT. In situ spectroelectrochemical Raman spectroscopy provides real-time, chemically specific information that complements the cyclic voltammetric data. The combination of these techniques affords a powerful and convenient method for guiding the development of sulfur-tolerant PEMFC catalysts.

  19. Nonlinear PT-symmetric plaquettes

    International Nuclear Information System (INIS)

    Li Kai; Kevrekidis, P G; Malomed, Boris A; Günther, Uwe

    2012-01-01

    We introduce four basic two-dimensional (2D) plaquette configurations with onsite cubic nonlinearities, which may be used as building blocks for 2D PT-symmetric lattices. For each configuration, we develop a dynamical model and examine its PTsymmetry. The corresponding nonlinear modes are analyzed starting from the Hamiltonian limit, with zero value of the gain–loss coefficient, γ. Once the relevant waveforms have been identified (chiefly, in an analytical form), their stability is examined by means of linearization in the vicinity of stationary points. This reveals diverse and, occasionally, fairly complex bifurcations. The evolution of unstable modes is explored by means of direct simulations. In particular, stable localized modes are found in these systems, although the majority of identified solutions are unstable. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’. (paper)

  20. Platinum determination by instrumental neutron activation analysis with special reference to the spectral interference of Sc-47 on the platinum indicator nuclide Au-199

    DEFF Research Database (Denmark)

    Alfassi, Z.B.; Probst, T.U.; Rietz, B.

    1998-01-01

    A method of instrumental neutron activation analysis (INAA) is developed for the determination of platinum by the Au-199 daughter of Pt-199 in the presence of the spectral interference from the Sc-47 daughter of Ca-47. The contributions of the Pt and Ca signals to the integral 157-161 keV peak were...... separated by calculating the number of disintegrations due to the Sc-47 from the signal of her parent Ca-47 at 1297.1 keV gamma-ray. The method was used to calculate the trace concentrations of Pt in air samples, collected on filters, (C) 1998 Elsevier Science B.V....

  1. Sulfur Resistance of Pt-W Catalysts

    Directory of Open Access Journals (Sweden)

    Carolina P. Betti

    2013-01-01

    Full Text Available The sulfur resistance of low-loaded monometallic Pt catalysts and bimetallic Pt-W catalysts during the partial selective hydrogenation of styrene, a model compound of Pygas streams, was studied. The effect of metal impregnation sequence on the activity and selectivity was also evaluated. Catalysts were characterized by ICP, TPR, XRD, and XPS techniques. Catalytic tests with sulfur-free and sulfur-doped feeds were performed. All catalysts showed high selectivities (>98% to ethylbenzene. Activity differences between the catalysts were mainly attributed to electronic effects due to the presence of different electron-rich species of Pt0 and electron-deficient species of Ptδ+. Pt0 promotes the cleavage of H2 while Ptδ+ the adsorption of styrene. The catalyst successively impregnated with W and Pt (WPt/Al was more active and sulfur resistant than the catalyst prepared with an inverse impregnation order (PtW/Al. The higher poison resistance of WPt/Al was attributed to both steric and electronic effects.

  2. Tuning magnetic properties of non-collinear magnetization configuration in Pt/[Pt/Co]{sub 6}/Pt/Co/Pt multilayer structure

    Energy Technology Data Exchange (ETDEWEB)

    Kalaycı, Taner, E-mail: taner.kalayci@marmara.edu.tr [Department of Physics, Marmara University, 34722, Kadıköy, Istanbul (Turkey); Deger, Caner [Department of Physics, Marmara University, 34722, Kadıköy, Istanbul (Turkey); Akbulut, Salih [Department of Physics, Gebze Technical University, 41400, Gebze, Kocaeli (Turkey); Yildiz, Fikret, E-mail: fyildiz@gtu.edu.tr [Department of Physics, Gebze Technical University, 41400, Gebze, Kocaeli (Turkey)

    2017-08-15

    Highlights: • Effects of Pt spacer and reference layers thickness are investigated by MOKE and FMR. • Controlling of non-collinear states in multilayered thin film systems is studied. • Micromagnetic approach is used for modeling of magnetic multilayered structure. • Magnetic parameters are determined by a simulation based on metropolis algorithm. - Abstract: In this study, effects of Pt spacer and Co reference layers thickness in [Co/Pt]{sub 6}/Pt/Co multilayer have been revealed to tailor magnetization directions in non-collinear configuration. Magneto-optic Kerr effect and ferromagnetic resonance techniques were employed to investigate magnetic properties. Bilinear coupling between [Co/Pt]{sub 6} and Co layers and anisotropy constants were determined by a micromagnetic simulation based on metropolis algorithm. 3 nm spacer causes ferromagnetic coupling while the samples have 4 and 5 nm spacer are coupled anti-ferromagneticaly. Also, tuning magnetic anisotropy of [Co/Pt]{sub 6} layer was accomplished by Co reference layer. It is revealed that controlling of non-collinear states in such systems is possible by variation of thickness of spacer and reference layers and [Co/Pt]{sub 6}/t{sub Pt}/t{sub Co} trilayer system can be used in multilayered magnetic systems.

  3. L’apprentissage au cern

    CERN Multimedia

    2007-01-01

    pour les professions d’électronicien(ne) et de laborantin(e) en physique L’apprentissage au CERN est régi par les lois, règlements et contrats en vigueur dans le canton de Genève. En cas de réussite à l’examen de fin d’apprentissage, les apprentis obtiennent le Certificat fédéral de capacité suisse (CFC). 6 places au total sont ouvertes au recrutement pour les deux professions. L’apprentissage dure 4 ans. Minima requis pour faire acte de candidature : avoir au moins 15 ans et moins de 21 ans à la date de début de l’apprentissage ; avoir terminé la scolarité obligatoire, au minimum 9e du Cycle d’orientation genevois (3e en France) ; être ressortissant d’un pays membre du CERN (Allemagne, Autriche, Belgique, Bulgarie, Danemark, Espagne, Finlande, France, Grèce, Hongrie, Italie, Norvège, Pays-Bas, Pologne, Portugal, Royaume-Uni, République tchèque, République slovaque , Suède, Suisse) ; pour les résidents en Suisse : être ressortissant su...

  4. Studies of Au/SAMs/PEDOT-PSS/Au tunnel junctions

    Science.gov (United States)

    Sun, Nan; Lieberman, Marya; Ruggiero, Steven

    2008-03-01

    We report on tunneling through thin organic films. Junctions of the form: Au/SAMs/Polymer/Au were prepared on electronic-grade Si substrates with Self-Assembled Monolayers (SAMs) including octanedithiol (HS-C8H16-SH) and mercaptohexadecanoic (HS-C15H30-COOH). A transitional conducting polymer film PEDOT-PSS was spun on to the SAMs layer, and junctions were completed with a gold film. X-ray photoelectron spectroscopy (XPS) was employed to monitor the quality of the SAMs films. The electron tunneling properties including dI/dV and d^2I/dV^2 versus bias for the SAMs are discussed.

  5. Structure and magnetic properties of electrodeposited CoPtP/Pt multilayer nanowires

    Science.gov (United States)

    Agarwal, Shivani; Hashmi, S. A.; Nandan, Bhanu; Patra, Ajit Kumar; Singh, Ravi Prakash; Chelvane, J. Arout; Khatri, Manvendra Singh

    2017-09-01

    CoPtP/Pt multilayered nanowires were fabricated by pulse electrodeposition technique into the AAO templates. The electrolyte was based on CoSO4·7H2O, H2PtCl6 and NaHPO2. The morphology and structure of nanowires was studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). The CoPtP/Pt multilayer nanowires exhibit hard magnetic properties with a coercivity of 1.16 kOe, when the applied field is parallel to axis of nanowires. The increase in coercivity is primarily associated with presence of phosphorous, which controls the grain size of nanowires.

  6. Flame-Made Pt-Loaded TiO2 Thin Films and Their Application as H2 Gas Sensors

    Directory of Open Access Journals (Sweden)

    Weerasak Chomkitichai

    2013-01-01

    Full Text Available The hydrogen gas sensors were developed successfully using flame-made platinum-loaded titanium dioxide (Pt-loaded TiO2 nanoparticles as the sensing materials. Pt-loaded TiO2 thin films were prepared by spin-coating technique onto Al2O3 substrates interdigitated with Au electrodes. Structural and gas-sensing characteristics were examined by using scanning electron microscopy (SEM and showed surface morphology of the deposited film. X-ray diffraction (XRD patterns can be confirmed to be the anatase and rutile phases of TiO2. High-resolution transmission electron microscopy (HRTEM showed that Pt nanoparticles deposited on larger TiO2 nanoparticles. TiO2 films loaded with Pt nanoparticles were used as conductometric sensors for the detection of H2. The gas sensing of H2 was studied at the operating temperatures of 300, 350, and 400°C in dry air. It was found that 2.00 mol% Pt-loaded TiO2 sensing films showed higher response towards H2 gas than the unloaded film. In addition, the responses of Pt-loaded TiO2 films at all operating temperatures were higher than that of unloaded TiO2 film. The response increased and the response time decreased with increasing of H2 concentrations.

  7. Electrochemical study of the Pt and Pt-Ni upon multiwalled carbon nanotubes

    Science.gov (United States)

    Mohammed, Norani Muti; Mumtaz, Asad; Ansari, Muhammad Shahid; Ahmad, Riaz

    2016-11-01

    Direct methanol fuel cells have attracted great interest in the recent development of portable devices. New routes are being developed for synthesizing the catalysts used in the methanol oxidation. In this work, the electrochemical behavior of the Pt and Pt-Ni upon multiwalled carbon nanotubes, synthesized via a new modified route, has been studied. The results showed that Pt-Ni 10% has the comparable current density to the Pt 20%-loading which is nearly 3 times greater than 10% Pt loading. The transfer of the polarization curve of Pt-Ni 10% towards lower polarization region following the catalyst with 20% Pt loading indicates the higher activity of the nano-electro-catalysts in the alkaline media. Also the long term efficiency and activity of the Pt-Ni with 10% loading is nearly reaching the 20% Pt-loading which is almost 10 folds greater than the 10% Pt loading. The study revealed that Ni in Pt-based nanoalloy impart not only an enhanced activity but also better durability of catalyst in direct methanol fuel cell applications.

  8. Surface-effect enhanced magneto-electric coupling in FePt/PMN-PT multiferroic heterostructures

    Science.gov (United States)

    Yang, Y. T.; Li, J.; Peng, X. L.; Hong, B.; Wang, X. Q.; Ge, H. L.; Wang, D. H.; Du, Y. W.

    2017-05-01

    A series of FePt films with different film thickness are deposited on Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) substrates. A standard symmetric `Butterfly' shaped Δ M /M -Ed c loops is obtained in 8 nm FePt/PMN-PT heterostrucuture via strain mediated magnetoelectric coupling. For the 3 nm FePt/PMN-PT heterostructure, the loop-like in-plane magnetization (M) -E curve shares a similar shape with the electric polarization of PMN-PT as a function of electric field. The value of MS shows a dramatic change of 30.9% with Edc changing from 0 to 8 kV/cm, this giant magnetoelectric effect in 3 nm FePt/PMN-PT heterostructure results from the remnant polarization induced charge on FePt/PMN-PT interface via the screening charge effect. The enhanced magnetoelectric coupling in thin magnetic/ferroelectric heterostructures opens a promising avenue for the design of ultralow power magnetoelectric devices and information storage devices.

  9. Semihard scattering unraveled from collective dynamics by two-pion azimuthal correlations in 158A GeV/c Pb + Au collisions

    CERN Document Server

    Agakichiev, G; Baur, R; Bielcikova, J; Braun-Munzinger, P; Cherlin, A; Drees, A; Esumi, S I; Filimonov, K; Fraenkel, Zeev; Fuchs, C; Glässel, P; Hering, G; Huovinen, P; Lenkeit, B C; Marin, A; Messer, F; Messer, M; Milosevic, J; Miskowiec, D; Nix, O; Panebratsev, Yu A; Petracek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Razin, S; Rehak, P; Sako, H; Saveljic, N; Schmitz, W; Shimansky, S S; Socol, E; Specht, H J; Stachel, J; Tilsner, H; Tserruya, Itzhak; Voigt, C A; Voloshin, S A; Weber, C; Wessels, J P; Wurm, J P; Yurevich, V

    2004-01-01

    Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-$p_{T}$ pions ($p_{T}>$1 GeV/c) have been measured close to midrapidity in 158A GeV/c Pb + Au collisions by the CERES experiment. Elliptic flow ($v_{2}$) rises linearly with $p_{T}$ to a value of about 10% at 2 GeV/c. Beyond $p_{T} \\approx $1.5 Ge V/c, the slope decreases considerably, possibly indicating a saturation of $v_{2}$ at high $p_{T}$. Two-pion azimuthal anisotropies for $p_{T} >$1.2 GeV/c exceed the elliptic flow values by about 60% in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening.

  10. Elliptic flow of charged pions, protons and strange particles emitted in Pb+Au collisions at top SPS energy

    CERN Document Server

    Adamova, D.; Andronic, A.; Antonczyk, D.; Appelshauser, H.; Belaga, V.; Bielcikova, J.; Braun-Munzinger, P.; Busch, O.; Cherlin, A.; Damjanovic, S.; Dietel, T.; Dietrich, L.; Drees, A.; Dubitzky, W.; Esumi, S.I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glassel, P.; Hering, G.; Holeczek, J.; Kalisky, M.; Krobath, G.; Kushpil, V.; Maas, A.; Marin, A.; Milosevic, J.; Miskowiec, D.; Panebrattsev, Y.; Petchenova, O.; Petracek, V.; Radomski, S.; Rak, J.; Ravinovich, I.; Rehak, P.; Sako, H.; Schmitz, W.; Schuchmann, S.; Sedykh, S.; Shimansky, S.; Stachel, J.; Sumbera, M.; Tilsner, H.; Tserruya, I.; Tsiledakis, G.; Wessels, J.P.; Wienold, T.; Wurm, J.P.; Yurevich, S.; Yurevich, V.

    2012-01-01

    Differential elliptic flow spectra v2(pT) of \\pi-, K0short, p, \\Lambda were measured at \\sqrt(s NN)= 17.3 GeV around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb+Au collisions (10% of \\sigma(geo)). The pT range extends from about 0.1 GeV/c (0.55 GeV/c for \\Lambda ) to more than 2 GeV/c. The proton v2(pT) is extracted from the sample of \\pi+ candidates using particle ratios from NA49 adapted to CERES acceptance and analysis cuts. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis, v2 in the series \\pi- - K0short - p - \\Lambda is seen to fall towards low pT increasingly below the hydro calculations even for kinetic freeze-out at Tf= 160 MeV which effectively suppress the hadronic evolution. The proton v2(pT) shows a downward swing towards low pT with excursions into negative values; the possible impact of a pion-flow isospin asymmetry observed by STAR at RHIC is found not to alter these conclusions. Results are discussed in perspective of recent viscous hydrodyna...

  11. Chiral magnetic effect search in p+Au, d+Au and Au+Au collisions at RHIC

    Science.gov (United States)

    Zhao, Jie

    2018-01-01

    Metastable domains of fluctuating topological charges can change the chirality of quarks and induce local parity violation in quantum chromodynamics. This can lead to observable charge separation along the direction of the strong magnetic field produced by spectator protons in relativistic heavy-ion collisions, a phenomenon called the chiral magnetic effect (CME). A major background source for CME measurements using the charge-dependent azimuthal correlator (Δϒ) is the intrinsic particle correlations (such as resonance decays) coupled with the azimuthal elliptical anisotropy (v2). In heavy-ion collisions, the magnetic field direction and event plane angle are correlated, thus the CME and the v2-induced background are entangled. In this report, we present two studies from STAR to shed further lights on the background issue. (1) The Δϒ should be all background in small system p+Au and d+Au collisions, because the event plane angles are dominated by geometry fluctuations uncorrelated to the magnetic field direction. However, significant Δϒ is observed, comparable to the peripheral Au+Au data, suggesting a background dominance in the latter, and likely also in the mid-central Au+Au collisions where the multiplicity and v2 scaled correlator is similar. (2) A new approach is devised to study Δϒ as a function of the particle pair invariant mass (minv) to identify the resonance backgrounds and hence to extract the possible CME signal. Signal is consistent with zero within uncertainties at high minv. Signal at low minv, extracted from a two-component model assuming smooth mass dependence, is consistent with zero within uncertainties.

  12. Enhanced photocatalytic H2 evolution over CdS/Au/g-C3N4 composite photocatalyst under visible-light irradiation

    OpenAIRE

    Xiaoling Ding; Yingxuan Li; Jie Zhao; Yunqing Zhu; Yan Li; Wenye Deng; Chuanyi Wang

    2015-01-01

    A novel heterojunction structured composite photocatalyst CdS/Au/g-C3N4 has been developed by depositing CdS/Au with a core (Au)-shell (CdS) structure on the surface of g-C3N4. The photocatalytic hydrogen production activity of the developed photocatalyst was evaluated under visible-light irradiation (λ > 420 nm) using methanol as a sacrificial reagent. As a result, its activity is about 125.8 times higher than that of g-C3N4 and is even much higher than that of Pt/g-C3N4. The enhancement in ...

  13. H2 production through steam reforming of ethanol over Pt/ZrO2, Pt/CeO2 and Pt/CeZrO2 catalysts

    OpenAIRE

    Noronha, Fábio Bellot; Silva, Adriana Maria da; Lima, Sonia M. de; Mattos, Lisiane Veiga; Cruz, Ivna O. da; Jacobs, Gary; Davis, Burtron H

    2008-01-01

    The effect of the support nature and metal dispersion on the performance of Pt catalysts during steam reforming of ethanol was studied. H2 and CO production was facilitated over Pt/CeO2 and Pt/CeZrO2, whereas the acetaldehyde and ethene formation was favored on Pt/ZrO2.

  14. Hadron production in Au-Au collisions at RHIC

    International Nuclear Information System (INIS)

    Braun-Munzinger, P.; Magestro, D.; Redlich, K.; Wroclaw Univ.; Stachel, J.

    2001-05-01

    We present an analysis of particle production yields measured in central Au-Au collisions at RHIC in the framework of the statistical thermal model. We demonstrate that the model extrapolated from previous analyses at SPS and AGS energy is in good agreement with the available experimental data at √(s) = 130 GeV implying a high degree of chemical equilibration. Performing a χ 2 fit to the data, the range of thermal parameters at chemical freezeout is determined. At present, the best agreement of the model and the data is obtained with the baryon chemical potential μ B ≅ 51 ± 6 MeV and temperature T ≅ 175 ± 7 MeV. More ratios, such as multistrange baryon to meson, would be required to further constrain the chemical freezeout conditions. Extrapolating thermal parameters to higher energy, the predictions of the model for particle production in Au-Au reactions at √(s) = 200 GeV are also given. (orig.)

  15. Level lifetimes of Au52+ in Au plasma

    International Nuclear Information System (INIS)

    Liu Bo; Zhu Zhiyan; Jiang Gang; Zhu Zhenghe

    2003-01-01

    Based on the extended relativistic multiconfiguration Dirac-Fock theory, the level lifetimes, level widths and wavelengths of Au 52+ have been calculated using the General-purpose Relativistic Atomic Structure Program. The wavelengths obtained are in good agreement with the experimental data available. The relationship between the level lifetimes and the level widths satisfies the Heisenberg uncertainty principle

  16. First principles studies of adsorption of Pd, Ag, Pt, and Au on yttrium disilicide nanowires

    Science.gov (United States)

    Jo, Chulsu; Cao, Juexian; Shinde, Aniketa; Ragan, Regina; Wu, Ruqian

    2008-03-01

    Stability and electronic properties of pristine and metal covered cylindrical yttrium disilicide, YSi 2, nanowires were investigated through first principles calculations. The YSi 2 nanowire prefers Y-rich surface morphology and is attractive toward metal adsorbates such as silver, gold, palladium, and platinum. Strong charge polarization is found from adsorbate to wires, which reduces the work function and alters the chemical activity of the core-shell structures.

  17. Structure determination of Pt-coated Au dumbbells via fluctuation X-ray scattering.

    Science.gov (United States)

    Chen, Gang; Modestino, Miguel A; Poon, Billy K; Schirotzek, André; Marchesini, Stefano; Segalman, Rachel A; Hexemer, Alexander; Zwart, Peter H

    2012-09-01

    A fluctuation X-ray scattering experiment has been carried out on platinum-coated gold nanoparticles randomly oriented on a substrate. A complete algorithm for determining the electron density of an individual particle from diffraction patterns of many particles randomly oriented about a single axis is demonstrated. This algorithm operates on angular correlations among the measured intensity distributions and recovers the angular correlation functions of a single particle from measured diffraction patterns. Taking advantage of the cylindrical symmetry of the nanoparticles, a cylindrical slice model is proposed to reconstruct the structure of the nanoparticles by fitting the experimental ring angular auto-correlation and small-angle scattering data obtained from many scattering patterns. The physical meaning of the refined structure is discussed in terms of their statistical distributions of the shape and electron density profile.

  18. Cage-like effect in Au-Pt nanoparticle synthesis in microemulsions: a simulation study.

    Science.gov (United States)

    Tojo, C; de Dios, M; Buceta, D; López-Quintela, M A

    2014-09-28

    The different distributions of metals in bimetallic nanoparticles synthesized in microemulsions were studied by computer simulation. The simulations demonstrated that if the difference between the reduction potentials of both metals is about 0.15-0.3 V, the compartmentalization of the reaction media causes the accumulation of slower reduction reactants in the microemulsions droplets, which favours the chemical reaction like a cage effect: increasing the local concentration of the slower reduction metal salt gives rise to a faster reduction, so the differences in reduction rates of both metals are attenuated. A more coincidental reduction of both metals deeply affects the nanoparticle structure, causing a better mixed alloy. This effect will be more pronounced when the concentration is higher and the intermicellar exchange rate is faster. This means that for any fixed microemulsion the nanoparticle structure can be modified by changing the reactant concentration: the core can be enriched in the faster reduction metal by lower concentrations, and the shell can be enriched in the slower metal by higher concentrations. Based on these observations, this study suggests a route to help experimentalists better create nanoparticles with a pre-defined structure.

  19. Acousto-Plasmonic Sensing Assisted by Nonlinear Optical Interactions in Bimetallic Au-Pt Nanoparticles

    Directory of Open Access Journals (Sweden)

    Eric Abraham Hurtado-Aviles

    2017-10-01

    Full Text Available A strong influence of mechanical action in nonlinear optical transmittance experiments with bimetallic nanoparticles integrated by gold and platinum was observed. The nanostructured samples were synthesized by a sol-gel method and contained in an ethanol suspension. UV-VIS spectroscopy evaluations, Transmission electron microscopy studies and input-output laser experiments were characterized. A two-photon absorption effect was induced by nanosecond pulses at 532 nm wavelength with an important contribution from the plasmonic response of the nanomaterials. All-optical identification of acoustical waves was remarkably improved by optical nonlinearities. High sensitivity for instrumentation of mechano-optical signals sensing particular fluids was demonstrated by using a variable carbon dioxide incorporation to the system.

  20. Development of Pt-Au-Graphene-Carbon Nanotube Composite for Fuel Cells and Biosensors Applications

    Science.gov (United States)

    2011-02-11

    MWNT+f-G) was dispersed in 200 ml of a mixture of ethylene glycol (EG) and water by ultrasonication for 1 h and followed by stirring for 6 hr. After...In this reaction ethylene glycol acts as a reducing, stabilizing and dispersing agent. Finally the solid was filtered and washed with DI water and...with deionized water and filtered using cellulose membrane filters having a pore size of 0.1 μm. The material left out is collected and dried in a

  1. Low-temperature solution synthesis of chemically functional ferromagnetic FePtAu nanoparticles

    NARCIS (Netherlands)

    Kinge, S.S.; Gang, T.; Naber, W.J.M.; Boschker, J.A.; Rijnders, Augustinus J.H.M.; Reinhoudt, David; van der Wiel, Wilfred Gerard

    2009-01-01

    Magnetic nanoparticles are of great scientific and technological interest. The application of ferromagnetic nanoparticles for high-density data storage has great potential, but energy efficient synthesis of uniform, isolated, and patternable nanoparticles that remain ferromagnetic at room

  2. Determination of Au, Pt, Pd in gold ore mineral raw materials by stripping voltammetry

    Directory of Open Access Journals (Sweden)

    Kolpakova N.A.

    2016-01-01

    Full Text Available The paper considers the possibilities of use of the method of stripping voltammetry for finding platinum metals in mineral gold and ore raw material. A review of new options of electro-concentration of platinum metals on the surface of graphite electrode with the following sediment electro-oxidation and receipt of an analytical signal is presented: platinum finding was carried out by picks of selective electro-oxidation of iridium from intermetallic compound with platinum; gold finding was carried out by picks of gold electro-oxidation on the surface of graphite electrode modified by bismuth; palladium finding was performed by picks of palladium electro-oxidation on the surface of graphite electrode. 1M HCL solution was selected as a supporting electrolyte. Gold and hydrogen elimination on the process of palladium electro-oxidation was performed by means of UV irradiation of solution in the process of electro-concentration of palladium sediment. Gold, platinum and palladium determination was carried out in mineral gold and ore raw material of Verkhneamylskiy gold and ore district.

  3. Reduction of Pt2+ species in model Pt-CeO2 fuel cell catalysts upon reaction with methanol

    Science.gov (United States)

    Neitzel, Armin; Johánek, Viktor; Lykhach, Yaroslava; Skála, Tomáš; Tsud, Nataliya; Vorokhta, Mykhailo; Matolín, Vladimír; Libuda, Jörg

    2016-11-01

    The stability of atomically dispersed Pt2+ species on the surface of nanostructured CeO2 films during the reaction with methanol has been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy. The isolated Pt2+ species were prepared at low Pt concentration in Pt-CeO2 film. Additionally, Pt2+ species coexisting with metallic Pt particles were prepared at high Pt concentration. We found that adsorption of methanol yields similar decomposition products regardless of Pt concentration in Pt-CeO2 films. A small number of oxygen vacancies formed during the methanol decomposition can be replenished in the Pt-CeO2 film with low Pt concentration by diffusion of oxygen from the bulk. In the presence of supported Pt particles, a higher number of oxygen vacancies leads to a partial reduction of the Pt2+ species. The isolated Pt2+ species are reduced under rather strongly reducing conditions only, i.e. during annealing under continuous exposure to methanol. Reduction of isolated Pt2+ species results in the formation of ultra-small Pt particles containing around 25 atoms per particle or less. Such ultra-small Pt particles demonstrate excellent stability against sintering during annealing of Pt-CeO2 film with low Pt concentration under reducing conditions.

  4. Perumusan Strategi Bisnis PT XYZ

    Directory of Open Access Journals (Sweden)

    Roy Hutahaean

    2017-09-01

    Full Text Available The purpose of this study is to formulate business strategy of XYZ Company. This study used 4 analysis tool Matrixes i.e. IFE (Internal Factor Evaluation and EFE (External Factor Evaluation, SWOT (Strength, Weaknesses, Opportunities, and Threat, and QPSM (Quantitative Strategic Planning Matrix. The primary and secondary data were used for this study. The IFE and EFE analysis showed weighted values of 2.52; 3.31 in quadrant II, indicating that this company is still in growth and development phase while, through the SWOT analysis, 5 alternative strategies could be concluded i.e. (1 collaboration with government to provide special fleet as domestic transportation to support national shipping industry; (2 collaboration not only with Head company but also with the other multi-stakeholders; (3 Capacity building regarding development of national shipping industry to XYZ employees; (4 establishment of agreement among multi-stakeholders against corruptions, collusion and nepotism; (5 development of a good working mechanism in accordance with the structural organization to increase working efficiency. Lastly, based on QPSM analysis, the main priority in business strategy of XYZ Co. is the capacity building for all of its employees.Keywords: business strategy, IFE,EFE, SWOT Matrix, QSPMAbstrak: Penelitian ini bertujuan memformulasikan strategi bisnis PT. XYZ melalui pendekatan analisis deskriptif. Alat alat analisis yang digunakan, yaitu matrix IFE (Internal factor Evaluation dan EFE (External Factor Evaluation, SWOT (Strength, Weaknesses, Opportunities, and Threat dan QSPM (Quantitative Strategic Planning Matrix. Data yang digunakan adalah data primer dan sekunder. Berdasarkan hasil IFE dan EFE diperoleh nilai tertimbang masing masing sebesar (2,523;3,310 sehingga posisi perusahaan dalam matriks IE berada di kuadran II, yaitu tumbuh dan kembangkan. Berdasarkan hasil analisis SWOT diperoleh lima alternatif strategi (1 bekerja sama dengan pemerintah dalam

  5. Synthesis, shape control, and methanol electro-oxidation properties of Pt-Zn alloy and Pt3Zn intermetallic nanocrystals.

    Science.gov (United States)

    Kang, Yijin; Pyo, Jun Beom; Ye, Xingchen; Gordon, Thomas R; Murray, Christopher B

    2012-06-26

    We report the first synthesis of highly monodisperse Pt(3)Zn nanocrystals (NCs). Shape-controlled synthesis generates cubic and spherical Pt-Zn NCs. Reaction temperature is the key to incorporate Zn into Pt, even in the absence of a strong reducing agent. The Pt-Zn NCs are active toward methanol oxidation, with the spherical NCs exhibiting higher activity than the cubic NCs. The Pt-Zn alloy phase can be transformed into the Pt(3)Zn intermetallic phase, upon annealing. The intermetallic Pt(3)Zn shows better performance than the alloy phase Pt-Zn. Besides the activity toward methanol oxidation, Pt-Zn NCs show excellent poisoning tolerance. With activities comparable to the commercial Pt catalyst, enhanced poisoning tolerance and lower cost, Pt-Zn and Pt(3)Zn NCs are a promising new family of catalysts for direct methanol fuel cells.

  6. Thermodynamic modeling of the Pt-Zr system

    International Nuclear Information System (INIS)

    Gao Yongliang; Guo Cuiping; Li Changrong; Du Zhenmin

    2010-01-01

    By means of the CALPHAD (CALculation of PHAse Diagram) technique, the Pt-Zr system was critically assessed. The solution phases (liquid, bcc, fcc and hcp) are described with the substitutional model. The intermetallic compounds Pt 4 Zr, Pt 4 Zr 3 , αPtZr and Pt 3 Zr 5 are treated as the formula (Pt,Zr) m (Pt,Zr) n by a two-sublattice model with the elements Pt and Zr on the first and the second sublattices, respectively. A two-sublattice model (Pt,Zr) 0.5 (Pt,Zr) 0.5 is applied to describe the compound βPtZr with CsCl-type structure (B2) in order to cope with the order-disorder transition between bcc solution (A2) and βPtZr (B2). Another two-sublattice model (Pt,Zr) 0.75 (Pt,Zr) 0.25 with Ni 3 Ti-type structure (D0 24 ) is applied to describe the compound Pt 3 Zr in order to cope with the order-disorder transition between hexagonal close-packed (A3) and Pt 3 Zr (D0 24 ). The compound Pt 10 Zr 7 is treated as a stoichiometric compound. A set of self-consistent thermodynamic parameters of the Pt-Zr system was obtained. (orig.)

  7. Isotopic fingerprints of Pt-containing luminescence centers in highly enriched Si-28

    CERN Document Server

    Steger, M; Godisov, O N; Alves, E; Kaliteevskii, A K; Saeedi, K; Abrosimov, N V; Churbanov, M F; Gusev, A V; Johnston, K; Thewalt, M L W; Sekiguchi, T; Yang, A; Riemann, H; Henry, M O; Pohl, H -J; Wahl, U

    2010-01-01

    Recently we have shown that the reduction in the photoluminescence linewidth of many deep luminescence centers in highly enriched Si-28 results in well-resolved isotopic fingerprints. This allows for a better characterization of a defect center, as not only the involvement of a specific element but also the number of atoms of that element within the complex can be determined. Surprisingly, we have found that many well-known luminescence centers have a different composition than originally supposed. In addition, we have found a large number of four- and five-atom luminescence centers involving the elements Cu, Au, and Li. Here we introduce series of four- and five-atom deep luminescence centers involving a single Pt atom together with Cu and Li, similar to what has been seen previously for Au-containing luminescence centers.

  8. Direct versus ligand-exchange synthesis of [PtAg28(BDT)12(TPP)4]4-nanoclusters: effect of a single-atom dopant on the optoelectronic and chemical properties.

    Science.gov (United States)

    Bootharaju, Megalamane S; Kozlov, Sergey M; Cao, Zhen; Harb, Moussab; Parida, Manas R; Hedhili, Mohamed N; Mohammed, Omar F; Bakr, Osman M; Cavallo, Luigi; Basset, Jean-Marie

    2017-07-13

    Heteroatom doping of atomically precise nanoclusters (NCs) often yields a mixture of doped and undoped products of single-atom difference, whose separation is extremely difficult. To overcome this challenge, novel synthesis methods are required to offer monodisperse doped NCs. For instance, the direct synthesis of PtAg 28 NCs produces a mixture of [Ag 29 (BDT) 12 (TPP) 4 ] 3- and [PtAg 28 (BDT) 12 (TPP) 4 ] 4- NCs (TPP: triphenylphosphine; BDT: 1,3-benzenedithiolate). Here, we designed a ligand-exchange (LE) strategy to synthesize single-sized, Pt-doped, superatomic Ag NCs [PtAg 28 (BDT) 12 (TPP) 4 ] 4- by LE of [Pt 2 Ag 23 Cl 7 (TPP) 10 ] NCs with BDTH 2 (1,3-benzenedithiol). The doped NCs were thoroughly characterized by optical and photoelectron spectroscopy, mass spectrometry, total electron count, and time-dependent density functional theory (TDDFT). We show that the Pt dopant occupies the center of the PtAg 28 cluster, modulates its electronic structure and enhances its photoluminescence intensity and excited-state lifetime, and also enables solvent interactions with the NC surface. Furthermore, doped NCs showed unique reactivity with metal ions - the central Pt atom of PtAg 28 could not be replaced by Au, unlike the central Ag of Ag 29 NCs. The achieved synthesis of single-sized PtAg 28 clusters will facilitate further applications of the LE strategy for the exploration of novel multimetallic NCs.

  9. Direct versus ligand-exchange synthesis of [PtAg28(BDT)12(TPP)4]4− nanoclusters: effect of a single-atom dopant on the optoelectronic and chemical properties

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2017-06-07

    Heteroatom doping of atomically precise nanoclusters (NCs) often yields a mixture of doped and undoped products of single-atom difference, whose separation is extremely difficult. To overcome this challenge, novel synthesis methods are required to offer monodisperse doped NCs. For instance, the direct synthesis of PtAg28 NCs produces a mixture of [Ag29(BDT)12(TPP)4]3- and [PtAg28(BDT)12(TPP)4]4- NCs (TPP: triphenylphosphine; BDT: 1,3-benzenedithiolate). Here, we designed a ligand-exchange (LE) strategy to synthesize single-sized, Pt-doped, superatomic Ag NCs [PtAg28(BDT)12(TPP)4]4- by LE of [Pt2Ag23Cl7(TPP)10] NCs with BDTH2 (1,3-benzenedithiol). The doped NCs were thoroughly characterized by optical and photoelectron spectroscopy, mass spectrometry, total electron count, and time-dependent density functional theory (TDDFT). We show that the Pt dopant occupies the center of the PtAg28 cluster, modulates its electronic structure and enhances its photoluminescence intensity and excited-state lifetime, and also enables solvent interactions with the NC surface. Furthermore, doped NCs showed unique reactivity with metal ions - the central Pt atom of PtAg28 could not be replaced by Au, unlike the central Ag of Ag29 NCs. The achieved synthesis of single-sized PtAg28 clusters will facilitate further applications of the LE strategy for the exploration of novel multimetallic NCs.

  10. On the noise performance of pt electrodes.

    Science.gov (United States)

    Liu, Xiao; Demosthenous, Andreas; Donaldson, Nick

    2007-01-01

    We measured the noise and impedance from Pt electrode pairs in a frequency band from 100 Hz to 10 kHz, containing the ENG band (500 Hz 5 kHz). The results show that the Pt electrode noise is the same as the thermal noise from the real part of the electrode impedance, which is a summation of the polarisation resistance and the access resistance. This differs from Ag-AgCl electrodes for which the electrode noise has been reported to be higher than the thermal noise. Our study shows that Pt electrodes are suitable for neural recording.

  11. Superconductivity in U-Pt system with low Pt concentrations (≤15 at.%)

    Science.gov (United States)

    Kim-Ngan, N.-T. H.; Havela, L.; Paukov, M.; Drozdenko, D.; Minarik, P.; Chrobak, M.; Tarnawski, Z.; Sowa, S.; Krupska, M.; Duda, A.

    2018-03-01

    We report the study of superconductivity in U-Pt alloys with Pt alloying concentration in the range of 0 - 15 at.%. We have succeed to retain the high-temperature (cubic) γ-U phase down to low temperatures in U-15 at.% Pt alloy by means of splat-cooling technique with a cooling rate better than 106 K/s (U-15 at.% Pt splat). The superconducting phase transitions are revealed below 1 K from electrical resistivity and specific heat measurements in applied magnetic fields for all investigated splat-cooled alloys. We underline the difference in the superconducting transition in U-15at.% Pt splats with that in the as-cast bulk and annealed bulk sample with the same Pt concentration.

  12. Mesoporous Pt and Pt/Ru alloy electrocatalysts for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Franceschini, Esteban A. [Grupo de Celdas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Planes, Gabriel A. [Departamento de Quimica, Facultad de Ciencias Exactas, Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto, Agencia Postal No 3, 5800, Rio Cuarto (Argentina); Williams, Federico J. [Departamento de Quimica Inorganica, Analitica y Quimica-Fisica, INQUIMAE CONICET, Facultad Ciencias Exactas y Naturales, Pabellon 2, Ciudad Universitaria, Buenos Aires (Argentina); Soler-Illia, Galo J.A.A. [Gerencia de Quimica, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Corti, Horacio R. [Grupo de Celdas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Departamento de Quimica Inorganica, Analitica y Quimica-Fisica, INQUIMAE CONICET, Facultad Ciencias Exactas y Naturales, Pabellon 2, Ciudad Universitaria, Buenos Aires (Argentina)

    2011-02-15

    Mesoporous Pt and Pt/Ru catalysts with 2D-hexagonal mesostructure were synthesized using a triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (Pluronic F127 {sup registered}) template, on a gold support. Large electrochemical surface areas were observed for the catalysts prepared at high overpotentials. Compared to the Pt catalyst, the Pt/Ru alloy containing 3 at% of Ru exhibited lower onset potential and more than three times the limit mass activity for methanol oxidation. This behavior is assigned to the larger pore size of the mesoporous Pt and Pt/Ru catalysts obtained with this template that seems to improve the methanol accessibility to the active sites compared to those obtained using lyotropic liquid crystals. (author)

  13. Active Pt3Ni (111) Surface of Pt3Ni Icosahedron for Oxygen Reduction.

    Science.gov (United States)

    Zhu, Jianbing; Xiao, Meiling; Li, Kui; Liu, Changpeng; Zhao, Xiao; Xing, Wei

    2016-11-09

    Highly active, durable oxygen reduction reaction (ORR) electrocatalysts are extremely important for fuel cell applications. Herein, we provide an efficient way to synthesis of activity Pt 3 M icosahedra by the one-pot hydrothermal method in the presence of glucosamine which can well adjust the reduction rate of Pt 4+ and efficiently control the morphology of final catalysts. Compared to Pt/C, the Pt 3 Ni icosahedra show 32-fold and 12-fold enhancement in specific and mass activity, respectively. Furthermore, robust durability was also observed in the accelerated durability test. Thus, this Pt 3 Ni icosahedron is found among the best Pt-based ORR catalysts, moreover, the findings also demonstrate how to mimic active extended surfaces in nanoscale.

  14. Pengukuran Kepuasan Kerja Karyawan APLP & A PT Semen Padang (PT X

    Directory of Open Access Journals (Sweden)

    Shelly Nolandari

    2016-04-01

    Full Text Available Thoughts on employee satisfaction arise because the company believes its employees have a high level of satisfaction will result in a better level of productivity, work more accurate, the fewer the number of absences and higher loyalty than employees with low satisfaction levels.Company's with good productivity will grow and increase revenue. PT Semen Padang has several subsidiaries and affiliates like PT X. PT X will measure employee satisfaction with the company's expectations are always making changes that sustainable about employee satisfaction because companies believe that employee satisfaction level of its high yield levels better productivity, work more accurate, the number of absences are fewer and loyalty higher than employees with low satisfaction levels. Companies with good productivity will experience growth as indicated by the increase in revenue, in line with the increase in the welfare of the employees. PT Semen Padang has several subsidiaries and affiliates PT X. PT Xwill measure employee satisfaction with the Company's expectations.

  15. Filipino au pairs on the move

    DEFF Research Database (Denmark)

    Dalgas, Karina Märcher

    2016-01-01

    Most Filipina au pairs in Denmark send remittances back home, and for many, au pairing forms part of longer-term migration trajectories. This article explores how Filipina au pairs try to carve out a future for themselves abroad. It shows that they navigate within tight webs of financial interdep...

  16. Golden Gate and Pt. Reyes Acoustic Detections

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains detections of acoustic tagged fish from two general locations: Golden Gate (east and west line) and Pt. Reyes. Several Vemco 69khz acoustic...

  17. Event-by-event fluctuations of the mean transverse momentum in 40, 80, and 158 AGeV/c Pb-Au collisions

    CERN Document Server

    AUTHOR|(CDS)2073202; Appelshäuser, H; Belaga, V; Braun-Munzinger, P; Campagnolo, R; Castillo, A; Cherlin, A; Damjanovic, S; Dietel, T; Dietrich, L; Drees, A; Esumi, S; Filimonov, K; Fomenko, K; Fraenkel, Zeev; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kushpil, V; Lenkeit, B C; Ludolphs, W; Maas, A; Marin, A; Milosevic, J; Milov, A; Miskowiec, D; Musa, L; Panebratsev, Yu A; Petchenova, O Yu; Petracek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Rehak, P; Richter, M; Sako, H; Schmitz, W; Schükraft, J; Sedykh, S; Seipp, W; Sharma, A; Shimansky, S S; Slivova, J; Specht, H J; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, Itzhak; Wessels, J P; Wienold, T; Windelband, B; Wurm, J P; Xie, W; Yurevich, S; Yurevich, V

    2003-01-01

    Measurements of event-by-event fluctuations of the mean transverse momentum in Pb-Au collisions at 40, 80, and 158 AGeV/c are presented. A significant excess of mean $p_{T}$ fluctuations at midrapidity is observed over the expectation from statistically independent particle emission. The results are somewhat smaller than recent measurements at RHIC. A possible nonmonotonic behavior of the mean $p_{T}$ fluctuations as function of collision energy, which may have indicated that the system has passed the critical point of the QCD phase diagram in the range of $\\mu_{B}$ under investigation, has not been observed. The centrality dependence of mean $p_{T}$ fluctuations in Pb-Au is consistent with an extrapolation from $pp$ collisions assuming that the nonstatistical fluctuations scale with multiplicity. The results are compared to calculations by the RQMD and URQMD event generators.

  18. Event-by-event fluctuations of the mean transverse momentum in 40, 80, and 158 A GeV/c Pb-Au collisions

    CERN Document Server

    Adamova, D; Appelshäuser, H; Belaga, V V; Braun-Munzinger, P; Campagnolo, R; Castillo, A; Cherlin, A; Damjanovic, S; Dietel, T; Dietrich, L; Drees, A; Esumi, S; Filimonov, K; Fomenko, K; Fraenkel, Zeev; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kushpil, V; Lenkeit, B C; Ludolphs, W; Maas, A; Marin, A; Milosevic, J; Milov, A; Miskowiec, D; Musa, L; Panebratsev, Yu A; Petchenova, O Yu; Petracek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Rehak, P; Richter, M; Sako, H; Schmitz, W; Schükraft, Jürgen; Sedykh, S; Seipp, W; Sharma, A; Shimansky, S S; Slivova, J; Specht, H J; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, Itzhak; Wessels, J P; Wienold, T; Windelband, B; Wurm, J P; Xie, W; Yurevich, S; Yurevich, V I

    2003-01-01

    Measurements of event-by-event fluctuations of the mean transverse momentum in Pb-Au collisions at 40, 80, and 158 A GeV/c are presented. A significant excess of mean p_T fluctuations at mid-rapidity is observed over the expectation from statistically independent particle emission. The results are somewhat smaller than recent measurements at RHIC. A possible non-monotonic behaviour of the mean p_T fluctuations as function of collision energy, which may have indicated that the system has passed the critical point of the QCD phase diagram in the range of mu_B under investigation, has not been observed. The centrality dependence of mean p_T fluctuations in Pb-Au is consistent with an extrapolation from pp collisions assuming that the non-statistical fluctuations scale with multiplicity. The results are compared to calculations by the RQMD and UrQMD event generators.

  19. Dielectron azimuthal anisotropy at mid-rapidity in Au + Au collisions at √{sN N}=200 GeV

    Science.gov (United States)

    Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Anson, C. D.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Averichev, G. S.; Banerjee, A.; Beavis, D. R.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Borowski, W.; Bouchet, J.; Brandin, A. V.; Brovko, S. G.; Bültmann, S.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, L.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chwastowski, J.; Codrington, M. J. M.; Contin, G.; Cramer, J. G.; Crawford, H. J.; Cui, X.; Das, S.; Davila Leyva, A.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Derradi de Souza, R.; Dhamija, S.; di Ruzza, B.; Didenko, L.; Dilks, C.; Ding, F.; Djawotho, P.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Engle, K. S.; Eppley, G.; Eun, L.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Fedorisin, J.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Gagliardi, C. A.; Gangadharan, D. R.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Gliske, S.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Haag, B.; Hamed, A.; Han, L.-X.; Haque, R.; Harris, J. W.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, H. Z.; Huang, X.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kesich, A.; Khan, Z. H.; Kikola, D. P.; Kisel, I.; Kisiel, A.; Koetke, D. D.; Kollegger, T.; Konzer, J.; Koralt, I.; Kotchenda, L.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Kycia, R. A.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; LeVine, M. J.; Li, C.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z. M.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, G. L.; Ma, Y. G.; Madagodagettige Don, D. M. M. D.; Mahapatra, D. P.; Majka, R.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; McShane, T. S.; Minaev, N. G.; Mioduszewski, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nigmatkulov, G.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Ohlson, A.; Okorokov, V.; Oldag, E. W.; Olvitt, D. L.; Pachr, M.; Page, B. S.; Pal, S. K.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlak, T.; Pawlik, B.; Pei, H.; Perkins, C.; Peryt, W.; Pile, P.; Planinic, M.; Pluta, J.; Poljak, N.; Porter, J.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Pujahari, P. R.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Riley, C. K.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ross, J. F.; Roy, A.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sangaline, E.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Shen, W. Q.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Singaraju, R. N.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solanki, D.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stevens, J. R.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Sun, X.; Sun, X. M.; Sun, Y.; Sun, Z.; Surrow, B.; Svirida, D. N.; Symons, T. J. M.; Szelezniak, M. A.; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarnowsky, T.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Trzeciak, B. A.; Tsai, O. D.; Turnau, J.; Ullrich, T.; Underwood, D. G.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Vanfossen, J. A.; Varma, R.; Vasconcelos, G. M. S.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Vossen, A.; Wada, M.; Wang, F.; Wang, G.; Wang, H.; Wang, J. S.; Wang, X. L.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y. F.; Xiao, Z.; Xie, W.; Xin, K.; Xu, H.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y.; Xu, Z.; Yan, W.; Yang, C.; Yang, Y.; Yang, Y.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zawisza, Y.; Zbroszczyk, H.; Zha, W.; Zhang, J. B.; Zhang, J. L.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, Z. P.; Zhao, F.; Zhao, J.; Zhong, C.; Zhu, X.; Zhu, Y. H.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2014-12-01

    We report on the first measurement of the azimuthal anisotropy (v2) of dielectrons (e+e- pairs) at mid-rapidity from √{sN N}=200 GeV Au + Au collisions with the STAR detector at the Relativistic Heavy Ion Collider (RHIC), presented as a function of transverse momentum (pT) for different invariant-mass regions. In the mass region Me e<1.1 GeV /c2 the dielectron v2 measurements are found to be consistent with expectations from π0,η ,ω , and ϕ decay contributions. In the mass region 1.1

  20. The Naimark dilated PT-symmetric brachistochrone

    OpenAIRE

    Guenther, Uwe; Samsonov, Boris F.

    2008-01-01

    The quantum mechanical brachistochrone system with PT-symmetric Hamiltonian is Naimark dilated and reinterpreted as subsystem of a Hermitian system in a higher-dimensional Hilbert space. This opens a way to a direct experimental implementation of the recently hypothesized PT-symmetric ultra-fast brachistochrone regime of [C. M. Bender et al, Phys. Rev. Lett. {\\bf 98}, 040403 (2007)] in an entangled two-spin system.

  1. Naimark-Dilated PT-Symmetric Brachistochrone

    Science.gov (United States)

    Günther, Uwe; Samsonov, Boris F.

    2008-12-01

    The quantum mechanical brachistochrone system with a PT-symmetric Hamiltonian is Naimark-dilated and reinterpreted as a subsystem of a Hermitian system in a higher-dimensional Hilbert space. This opens a way to a direct experimental implementation of the recently hypothesized PT-symmetric ultrafast brachistochrone regime of Bender et al. [Phys. Rev. Lett. 98, 040403 (2007)PRLTAO0031-900710.1103/PhysRevLett.98.040403] in an entangled two-spin system.

  2. Resistive switching in Pt/TiO{sub 2}/Pt

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Doo Seok

    2008-08-15

    Recently, the resistive switching behavior in TiO{sub 2} has drawn attention due to its application to resistive random access memory (RRAM) devices. TiO{sub 2} shows characteristic non-volatile resistive switching behavior, i.e. reversible switching between a high resistance state (HRS) and a low resistance state (LRS). Both unipolar resistive switching (URS) and bipolar resistive switching (BRS) are found to be observed in TiO{sub 2} depending on the compliance current for the electroforming. In this thesis the characteristic current-voltage (I-V) hysteresis in three different states of TiO{sub 2}, pristine, URS-activated, and BRS-activated states, was investigated and understood in terms of the migration of oxygen vacancies in TiO{sub 2}. The I-V hysteresis of pristine TiO{sub 2} was found to show volatile behavior. That is, the temporary variation of the resistance took place depending on the applied voltage. However, the I-V hysteresis of URS- and BRS-activated states showed non-volatile resistive switching behavior. Some evidences proving the evolution of oxygen gas during electroforming were obtained from time-of-flight secondary ion mass spectroscopy analysis and the variation of the morphology of switching cells induced by the electroforming. On the assumption that a large number of oxygen vacancies are introduced by the electroforming process, the I-V behavior in electroformed switching cells was simulated with varying the distribution of oxygen vacancies in electroformed TiO{sub x} (x Pt/TiO{sub x} interface. The oxygen-related reactions given as a function of the applied voltage affect the distribution of oxygen vacancies in TiO{sub x}, consequently, the Schottky barrier height at the cathode/TiO{sub x} interface is influenced by the oxygen vacancy distribution. Therefore, the BRS behavior including the

  3. Decay studies of the highly neutron-deficient indium isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Wouters, J.M.

    1982-02-01

    An extension of the experimentally known nuclidic mass surface to nuclei far from the region of beta-stability is of fundamental interest in providing a better determination of the input parameters for the various nuclear mass formulae, allowing a more accurate prediction of the ultimate limits of nuclear stability. In addition, a study of the shape of the mass surface in the vicinity of the doubly-closed nuclide /sup 100/Sn provides initial information on the behavior of the shell closure to be expected when Z = N = 50. Experiments measuring the decay energies of /sup 103/ /sup 105/In by ..beta..-endpoint measurements are described with special attention focused on the development of a plastic scintillator ..beta..-telescope coupled to the on-line mass separator RAMA (Recoil Atom Mass Analyzer). An attempt to measure the ..beta..-endpoint energy of /sup 102/In is also briefly described. The experimentally determined decay energies and derived masses for /sup 103/ /sup 105/In are compared with the predictions of different mass models to identify which models are more successful in this region. Furthermore, the inclusion in these comparisons of the available data on the neutron-rich indium nuclei permits a systematic study of their ground state mass behavior as a function of the neutron number between the shell closures at N = 50 and N = 82. These analyses indicate that the binding energy of /sup 103/In is 1 MeV larger than predicted by the majority of the mass models. An examination of the Q/sub EC/ surface and the single- and two-neutron separation energies in the vicinity of /sup 103/ /sup 105/In is also performed to investigate further the deviation and other possible systematic variations in the mass surface in a model-independent way.

  4. Spectroscopy of neutron-deficient nuclei around Ca-36

    Czech Academy of Sciences Publication Activity Database

    Burger, A.; Stanoiu, M.; Azaiez, F.; Dombradi, Z.; Algora, A.; Al-Khatib, A.; Bastin, B.; Benzoni, G.; Borcea, R.; Bourgeois, Ch.; Bringel, P.; Clement, E.; Dalouzy, J.-C.; Dlouhý, Zdeněk; Drouart, A.; Engelhardt, C.; Franchoo, S.; Fulop, Zs.; Gorgen, A.; Grévy, S.; Hubel, H.; Ibrahim, F.; Korten, W.; Mrázek, Jaromír; Navin, A.; Rotaru, F.; Roussel-Chomaz, P.; Saint Laurent, M. G.; Sletten, G.; Sohler, D.; Sorlin, O.; Theisen, Ch.; Timis, C.; Verney, D.; Williams, S.

    2007-01-01

    Roč. 150, - (2007), s. 89-91 ISSN 1951-6355. [7th International Conference on Radioactive Nuclear Beams. Cortina, 02.07.2006-07.07.2006] Institutional research plan: CEZ:AV0Z10480505 Keywords : EXOTIC NUCLEI * NUCLEAR SHELL * GANIL Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  5. Nuclear radiation detected optical pumping of neutron deficient Hg isotopes

    International Nuclear Information System (INIS)

    Bonn, J.

    1975-01-01

    The extension of the Nuclear Radiation Detected Optical Pumping method to mass-separated samples of isotopes far off stability is presented for a series of light Hg isotopes produced at the ISOLDE facility at CERN. The isotope under investigation is transferred by an automatic transfer system into the optical pumping apparatus. Zeeman scanning of an isotopically pure Hg spectral lamp is used to reach energetic coincidence with the hyperfine structure components of the 6s 2 1 S 0 -6s6p 3 P 1 (lambda = 2537 A) resonance line of the investigated isotope and the Hg lamp. The orientation build up by optical pumping is monitored via the asymmetry or anisotropy of the nuclear radiation. Nuclear spins, magnetic moments, electric quadrupole moments and isotopic shift are obtained for 181 Hg- 191 Hg using the β-asymmetry as detector. The extension of the method using the γ-anisotropy is discussed and measurements on 193 Hg are presented. (orig./HK)

  6. Decay studies of the highly neutron-deficient indium isotopes

    International Nuclear Information System (INIS)

    Wouters, J.M.

    1982-02-01

    An extension of the experimentally known nuclidic mass surface to nuclei far from the region of beta-stability is of fundamental interest in providing a better determination of the input parameters for the various nuclear mass formulae, allowing a more accurate prediction of the ultimate limits of nuclear stability. In addition, a study of the shape of the mass surface in the vicinity of the doubly-closed nuclide 100 Sn provides initial information on the behavior of the shell closure to be expected when Z = N = 50. Experiments measuring the decay energies of 103 105 In by β-endpoint measurements are described with special attention focused on the development of a plastic scintillator β-telescope coupled to the on-line mass separator RAMA (Recoil Atom Mass Analyzer). An attempt to measure the β-endpoint energy of 102 In is also briefly described. The experimentally determined decay energies and derived masses for 103 105 In are compared with the predictions of different mass models to identify which models are more successful in this region. Furthermore, the inclusion in these comparisons of the available data on the neutron-rich indium nuclei permits a systematic study of their ground state mass behavior as a function of the neutron number between the shell closures at N = 50 and N = 82. These analyses indicate that the binding energy of 103 In is 1 MeV larger than predicted by the majority of the mass models. An examination of the Q/sub EC/ surface and the single- and two-neutron separation energies in the vicinity of 103 105 In is also performed to investigate further the deviation and other possible systematic variations in the mass surface in a model-independent way

  7. Elliptic flow of charged pions, protons and strange particles emitted in Pb + Au collisions at top SPS energy

    Science.gov (United States)

    Adamová, D.; Agakichiev, G.; Andronic, A.; Antończyk, D.; Appelshäuser, H.; Belaga, V.; Bielčíková, J.; Braun-Munzinger, P.; Busch, O.; Cherlin, A.; Damjanović, S.; Dietel, T.; Dietrich, L.; Drees, A.; Dubitzky, W.; Esumi, S. I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glässel, P.; Hering, G.; Holeczek, J.; Kalisky, M.; Krobath, G.; Kushpil, V.; Maas, A.; Marín, A.; Milošević, J.; Miśkowiec, D.; Panebrattsev, Y.; Petchenova, O.; Petráček, V.; Radomski, S.; Rak, J.; Ravinovich, I.; Rehak, P.; Sako, H.; Schmitz, W.; Schuchmann, S.; Sedykh, S.; Shimansky, S.; Stachel, J.; Šumbera, M.; Tilsner, H.; Tserruya, I.; Tsiledakis, G.; Wessels, J. P.; Wienold, T.; Wurm, J. P.; Yurevich, S.; Yurevich, V.; Ceres Collaboration

    Differential elliptic flow spectra v2(pT) of π-, KS0, p, Λ have been measured at √{sNN}=17.3 GeV around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb + Au collisions (10% of σgeo). The pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow is derived as a constituent, besides π+ and K+, of the elliptic flow of positive pion candidates. This retrieval requires additional inputs: (i) of the particle composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios obtained by NA49 are adapted to CERES conditions; for (ii), the measured v2(pT) of negative pions is substituted, assuming π+ and π- elliptic flow magnitudes to be sufficiently close. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π--KS0-p-Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (Tf=160 MeV) leaving not much time for hadronic evolution. The proton v2(pT) data show a downward swing towards low pT with excursions into negative v2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous hydrodynamics studies which focus on late hadronic stages.

  8. Electrocatalysis of fuel cells reaction on Pt and Pt-bimetallic anode catalysts: A selective review

    Directory of Open Access Journals (Sweden)

    Stamenković Vojislav

    2002-01-01

    Full Text Available In this review we selectively summarize recent progress, primarily from our laboratory, in the development of interrelationships between the kinetics of the fuel cells reactions and the structure/composition of anode catalysts. The focus is placed on two types of metallic surfaces: platinum single crystals and bimetallic surfaces based on Pt. In the first part it was illustrated that the hydcogen reaction is structure sensitive process, with Pt(110 being an order of magnitude more active than either of the atomically "flatter" (100 and (111 surfaces. The hydrogen reaction on Pt(hkl modified by pseudomorphic Pd (submonolayers shows the "volcano-like" behavior, having the maximum rate on Pt(111 modified by 1 ML of Pd. The Pt(111-Pd system is used to demonstrate how the energetics of intermediates formed in the hydrogen reaction is affected by interfacial bonding and energetic constraints produced between pseudomorphic Pd films and the Pt(111 substrate. In the second part it was shown that the oxidation of Ha in the presence of CO occurs concurrently with CO oxidation on Pt and Pt bimetallic surfaces. The Pt-Ru system is used to demonstrate that both the bifunctional effect and the ligand effect contribute to the influence of Ru on the CO oxidation rate and for Hz oxidation process in the presence of CO. The knowledge is then used to create the real-life catalyst with the catalytic activities which are, to the greatest extend possible similar to the tailor-made surface.

  9. PT -symmetric model of immune response

    Science.gov (United States)

    Bender, Carl M.; Ghatak, Ananya; Gianfreda, Mariagiovanna

    2017-01-01

    The study of PT -symmetric physical systems began in 1998 as a complex generalization of conventional quantum mechanics, but beginning in 2007 experiments began to be published in which the predicted PT phase transition was clearly observed in classical rather than in quantum-mechanical systems. This paper examines the classical PT phase transition in dynamical-system models that are moderately accurate representations of antigen-antibody systems. A surprising conclusion that can be drawn from these models is that it might be possible treat a serious disease in which the antigen concentration grows out of bounds (and the host dies) by injecting a small dose of a second (different) antigen. In this case a PT -symmetric analysis shows there are two possible favorable outcomes. In the unbroken-PT -symmetric phase the disease becomes chronic and is no longer lethal, while in the appropriate broken-PT -symmetric phase the concentration of lethal antigen goes to zero and the disease is completely cured.

  10. A Novel Conductive Poly(3,4-ethylenedioxythiophene-BSA Film for the Construction of a Durable HRP Biosensor Modified with NanoAu Particles

    Directory of Open Access Journals (Sweden)

    Fangcheng Xu

    2016-03-01

    Full Text Available In this study, we have investigated the contribution of bovine serum albumin (BSA to the durability of the electrochemically synthesized poly(3,4-ethylenedioxythiophene (PEDOT film on a platinum (Pt electrode. The electrode was capable to effectively adsorb the nano Au particles (AuNPs to form a uniform layout, which was then able to immobilize the horseradish peroxidase (HRP to construct a functional HRP/AuNPs/PEDOT(BSA/Pt biosensor. Cyclic voltammetry was employed to evaluate the performance of the biosensor through the measurement of hydrogen peroxide. Our results revealed a satisfied linear correlation between the cathodic current and the concentration of H2O2. Furthermore, the addition of oxidized form of nicotinamide adenine dinucleotide, or NAD+, as the electron transfer mediator in the detection solution could dramatically enhance the sensitivity of detection by about 35.5%. The main advantages of the current biosensor are its durability, sensitivity, reliability, and biocompatibility.

  11. [Studies on Au-Ag-Pd-Cu alloys. (Part 3) Effects of additional elements to Au-Ag-Pd-Cu alloys (author's transl)].

    Science.gov (United States)

    Okazaki, K

    1981-01-01

    In the previous papers, the author pointed out that alloys containing 30 wt% Au, 15-25 wt% Pd and Cu were more favourable for Au-Ag-Pd-Cu quarternary dental alloys. In this paper, the experiments were carried out to find the effects of additional elements and so, Pt, Ir, Os, W, Mo, Cr, Mn, Co, Zn, In, Sn and Si were added to 30 wt% Au-30 wt% Ag-20 wt% Pd-20 wt% Cu alloys ranging 0.1 wt% to 2.0 wt% respectively. Then, tensile strength, elongation, hardness, corrosion resistivity and porosity ratio were tested on these specimen. Results were as follows. 1) The addition of 0.2 wt% Ir, 0.2 wt% Os and 1.0 wt% Co were comparatively effective for the fineness of grain sizes, elongation and tensile strength. 2) The addition of 0.2 wt% W, 1.0 wt% Mo and 0.2 wt% Si showed respectively bad effect for porosities or mechanical properties. 3) The addition of 1.0 wt% Cr, 2.0 wt% Mn, 1.0 wt% Co, 2.0 wt% Zn and 2.0 wt% In were good for the decrease of porosities respectively and showed that the porosity ratio was lower than 0.2%. 4) The additions of 2.0 wt% Zn-1.0 wt% Pt-0.5 wt% Co to Au-Ag-Pd-Cu alloy was especially good and showed 80 kg/mm2 of tensile strength, 5.1% of elongation, 249 of Vicker's hardness number and 0.4% of porosity ratio.

  12. Studying photon-jet correlation in pp, dAu collisions in PHENIX

    Science.gov (United States)

    Jin, Jiamin

    2004-10-01

    PHENIX has measured direct photon production in Au+Au collisions at √s_NN = 200 GeV/c[1]. A large enhancement over the meson decay background is seen in central Au+Au collisions at transverse momentum p_T>6 GeV/c This provides an opportunity to probe the dense medium using jets tagged by direct photons. Most of these direct photons are produced in q +g(barq) arrow γ + q(g) processes. Since photons penetrate the dense medium with greatly reduced interactions compared to hadrons, they will carry roughly the same amount of energy as the scattered quarks, and thus provide an excellent measure of the energy and direction of the tagged jet. However, due to the large amount of underlying background and limited PHENIX acceptance, it is very difficult to identify both the direct photon and tagged jet. We have developed an isolation cut technique to separate direct photon candidates from meson decay photons. These candidates are then correlated with other particles to search for the tagged jet signal, where we use the event mixing technique to subtract the combinatoric background. Results will be shown from a feasibility study of the isolation cuts in giving a clean sample of direct photons. Preliminary results on the properties of the jets tagged by direct photons in p+p and d+Au collisions will also be presented. [1] J. Frantz, "PHENIX Direct Photons in 200 GeV p+p and Au+Au Collisions", nucl-ex/0404006

  13. Synthesis and electrochemical study of Pt-based nanoporous materials

    International Nuclear Information System (INIS)

    Wang Jingpeng; Holt-Hindle, Peter; MacDonald, Duncan; Thomas, Dan F.; Chen Aicheng

    2008-01-01

    In the present work, a variety of Pt-based bimetallic nanostructured materials including nanoporous Pt, Pt-Ru, Pt-Ir, Pt-Pd and Pt-Pb networks have been directly grown on titanium substrates via a facile hydrothermal method. The as-fabricated electrodes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and electrochemical methods. The active surface areas of these nanoporous Pt-based alloy catalysts are increased by over 68 (Pt-Pd), 69 (Pt-Ru) and 113 (Pt-Ir) fold compared to a polycrystalline Pt electrode. All these synthesized nanoporous electrodes exhibit superb electrocatalytic performance towards electrochemical oxidation of methanol and formic acid. Among the five nanoporous Pt-based electrodes, the Pt-Ir shows the highest peak current density at +0.50 V, with 68 times of enhancement compared to the polycrystalline Pt for methanol oxidation, and with 86 times of enhancement in formic acid oxidation; whereas the catalytic activity of the nanoporous Pt-Pb electrode outperforms the other materials in formic acid oxidation at the low potential regions, delivering an enhanced current density by 280-fold compared to the polycrystalline Pt at +0.15 V. The new approach described in this study is suitable for synthesizing a wide range of bi-metallic and tri-metallic nanoporous materials, desirable for electrochemical sensor design and potential application in fuel cells

  14. Synthesis and electrochemical study of Pt-based nanoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jingpeng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Holt-Hindle, Peter; MacDonald, Duncan [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Thomas, Dan F. [Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Chen Aicheng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada)], E-mail: aicheng.chen@lakeheadu.ca

    2008-10-01

    In the present work, a variety of Pt-based bimetallic nanostructured materials including nanoporous Pt, Pt-Ru, Pt-Ir, Pt-Pd and Pt-Pb networks have been directly grown on titanium substrates via a facile hydrothermal method. The as-fabricated electrodes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and electrochemical methods. The active surface areas of these nanoporous Pt-based alloy catalysts are increased by over 68 (Pt-Pd), 69 (Pt-Ru) and 113 (Pt-Ir) fold compared to a polycrystalline Pt electrode. All these synthesized nanoporous electrodes exhibit superb electrocatalytic performance towards electrochemical oxidation of methanol and formic acid. Among the five nanoporous Pt-based electrodes, the Pt-Ir shows the highest peak current density at +0.50 V, with 68 times of enhancement compared to the polycrystalline Pt for methanol oxidation, and with 86 times of enhancement in formic acid oxidation; whereas the catalytic activity of the nanoporous Pt-Pb electrode outperforms the other materials in formic acid oxidation at the low potential regions, delivering an enhanced current density by 280-fold compared to the polycrystalline Pt at +0.15 V. The new approach described in this study is suitable for synthesizing a wide range of bi-metallic and tri-metallic nanoporous materials, desirable for electrochemical sensor design and potential application in fuel cells.0.

  15. Synthesis and electrochemical study of Pt-based nanoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jingpeng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Holt-Hindle, Peter; MacDonald, Duncan; Chen, Aicheng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Thomas, Dan F. [Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada)

    2008-10-01

    In the present work, a variety of Pt-based bimetallic nanostructured materials including nanoporous Pt, Pt-Ru, Pt-Ir, Pt-Pd and Pt-Pb networks have been directly grown on titanium substrates via a facile hydrothermal method. The as-fabricated electrodes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and electrochemical methods. The active surface areas of these nanoporous Pt-based alloy catalysts are increased by over 68 (Pt-Pd), 69 (Pt-Ru) and 113 (Pt-Ir) fold compared to a polycrystalline Pt electrode. All these synthesized nanoporous electrodes exhibit superb electrocatalytic performance towards electrochemical oxidation of methanol and formic acid. Among the five nanoporous Pt-based electrodes, the Pt-Ir shows the highest peak current density at +0.50 V, with 68 times of enhancement compared to the polycrystalline Pt for methanol oxidation, and with 86 times of enhancement in formic acid oxidation; whereas the catalytic activity of the nanoporous Pt-Pb electrode outperforms the other materials in formic acid oxidation at the low potential regions, delivering an enhanced current density by 280-fold compared to the polycrystalline Pt at +0.15 V. The new approach described in this study is suitable for synthesizing a wide range of bi-metallic and tri-metallic nanoporous materials, desirable for electrochemical sensor design and potential application in fuel cells. (author)

  16. d + Au hadron correlation measurements at PHENIX

    Energy Technology Data Exchange (ETDEWEB)

    Sickles, Anne M., E-mail: anne@bnl.gov

    2014-06-15

    In these proceedings, we discuss recent results from d + Au collisions in PHENIX ridge related measurements and their possible hydrodynamic origin. We present the v{sub 2} at midrapidity and measurements of the pseudorapidity dependence of the ridge, distinguishing between the d-going and Au-going directions. We investigate the possible geometrical origin by comparing v{sub 2} in d + Au to that in p + Pb, Au + Au and Pb + Pb collisions. Future plans to clarify the role of geometry in small collision systems at RHIC are discussed.

  17. Study of microstructure and magnetic properties of L10 FePt/SiO2 thin films

    Directory of Open Access Journals (Sweden)

    Giannopoulos G.

    2014-07-01

    Full Text Available Achieving magnetic recording densities in excess of 1Tbit/in2 requires not only perpendicular media with anisotropies larger than 7 MJ/m3, making FePt alloys an ideal choice, but also a narrow distribution below 10 nm for a reduced S/N ratio. Such grain size reduction and shape control are crucial parameters for high density magnetic recording, along with high thermal stability. Previous work has shown that the L10 FePt grain size can be controlled by alloying FePt with materials such as C, Ag, and insulators such as AlOx, MgO. Au and Al2O3 also act to segregate and magnetically decouple the FePt grains. Better results were obtained with C with respect to the uniformity of grains and SiO2 with respect to the shape. We present our results on co-sputtering FePt with C or SiO2 (up to 30 vol % on MgO (001 single crystal substrates at 350 and 500 oC. With C or SiO2 addition we achieved grain size reduction, shape control and isolated structure formation, producing continuous films with high uniformity and a narrow grain size distribution. These additions thus allow us to simultaneously control the coercivity and the S/N ratio. We also will report structural and microstructural properties.

  18. Preparation and electric and photoelectric properties of thin deposits of Fe, Co, Ni, Cu, Ag, Au and Pd

    International Nuclear Information System (INIS)

    Heras, J.M.; Albano, E.V.; Asensio, M.C.; Viscido, L.

    1984-01-01

    The physics chemical properties of desordered metallic thin films of Fe, Co, Ni, Pd, Ag, Cu and Au are of great interest for its catalitic activity and for its application in radiation absorption of solar cells and micro electronic devices. This work has the purpose of reporting the experimental results obtained by evaporated films of these metals, which present desordered characteristics, small crystal size and high surface-volume rate. (A.C.A.S.) [pt

  19. Microwave sinthesys and characterization of Pt and Pt-Rh-Sn electrocatalysts for ethanol oxidation

    Directory of Open Access Journals (Sweden)

    Jovanović Vladislava M.

    2011-01-01

    Full Text Available Carbon supported Pt and Pt-Rh-Sn catalysts were synthesized by microwave-polyol method in ethylene glycol solution and investigated for the ethanol electro-oxidation reaction. The catalysts were characterized in terms of structure, morphology and composition by employing XRD, STM and EDX techniques. STM analysis indicated rather uniform particles and particle size of below 2 nm for both catalysts. XRD analysis of the Pt/C catalyst revealed two phases, one with the main characteristic peaks of face centered cubic crystal structure (fcc of platinum and another related to graphite like structure of carbon support Vulcan XC-72R. However, in XRD pattern of the Pt-Rh-Sn/C catalyst diffraction peaks for Pt, Rh or Sn cannot be resolved, indicating an extremely low crystallinity. The small particle sizes and homogeneous size distributions of both catalysts should be attributed to the advantages of microwave assisted modified polyol process in ethylene glycol solution. Pt-Rh- Sn/C catalyst is highly active for the ethanol oxidation with the onset potential shifted for more than 150 mV to negative values and with currents nearly 5 times higher in comparison to Pt/C catalyst. The stability tests of the catalysts, as studied by the chronoamperometric experiments, reveal that the Pt-Rh-Sn/C catalyst is evidently less poisoned then Pt/C catalyst. The increased activity of Pt-Rh-Sn/C in comparison to Pt/C catalyst is most probably promoted by bifunctional mechanism and the electronic effect of alloyed metals.

  20. Preparation of PtSn/C, PtRu/C, PtRh/C, PtRuRh/C and PtSnRh/C electrocatalysts using an alcohol-reduction process for methanol and ethanol oxidation; Preparacao e caracterizacao de eletrocatalisadores PtRu, PtSn, PtRh, PtRuRh e PtSnRh para oxidacao direta de alcoois em celulas a combustivel tipo PEM utilizando a metodologia da reducao por alcool

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Ricardo Rodrigues

    2009-07-01

    In this work, Pt/C, PtRh (90:10), PtRh/C (50:50), PtSn/C (50:50), PtRu (50:50)/C, PtRuRh/C (50:40:10) and PtSnRh/C (50:40:10) were prepared by an alcohol-reduction process with metal loading of 20 wt.% using H{sub 2}PtCl{sub 6}.6H{sub 2}O (Aldrich), SnCl{sub 2}.2H{sub 2}O (Aldrich),and RhCl{sub 2}.XH{sub 2}O (Aldrich) as metals sources and Vulcan XC72 as support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry (CV). The electro-oxidation of ethanol was studied by CV, chronoamperomety at room temperature in acid medium and tests at 100 deg C on a single cell of a direct methanol or ethanol fuel cell. The EDX analysis showed that the metal atomic ratios of the obtained electrocatalysts were similar to the nominal atomic ratios used in the preparation. The diffractograms of electrocatalysts prepared showed four peaks at approximately 2{theta} =40 deg, 47 deg, 67 deg and 82 deg, which are associated with the (111), (200), (220) and (311) planes, respectively, of a face cubic-centered (fcc) structure characteristic of platinum and platinum alloys. The average crystallite sizes using the Scherrer equation and the calculated values were in the range of 2-3 nm. For Pt Sn/C and PtSnRh/C two additional peaks were observed at 2 = 34 deg and 52 deg that were identified as a SnO{sub 2} phase. Pt Sn/C (50:50) and PtSnRh/C (50:40:10) electro catalyst showed the best performance for ethanol oxidation at room temperature. For methanol oxidation at room temperature Pt Ru/C, Pt Sn/C and PtRuRh/C electrocatalysts showed the best performance. Tests at 100 deg C on a single cell of a direct ethanol fuel cell PtSnRh/C showed the best performance, for methanol oxidation PtRuRh/C showed the best performance. (author)

  1. L’apprentissage au CERN

    CERN Document Server

    Staff Association

    2016-01-01

    En 1961, sur la base du constat que l’évolution du marché du travail nécessitait un besoin croissant de personnel qualifié, le 1er accord entre la République et canton de Genève et le CERN fut signé. Cet accord avait notamment pour objet la formation professionnelle de jeunes électroniciens et techniciens de laboratoires en physique. Le CERN, acteur local économique d’importance, soulignait par cet accord sa volonté de participer au développement économique et social local. Le 1er apprenti arriva au CERN en 1965. En 1971, le centre d’apprentissage fut créé ; il accueille aujourd’hui plus d’une vingtaine d’apprentis au total, à raison d’environ six nouveaux apprentis chaque année. Cet apprentissage est dédié aux jeunes âgés e...

  2. How Does Amino Acid Ligand Modulate Au Core Structure and Characteristics in Peptide Coated Au Nanocluster?

    Science.gov (United States)

    Li, Nan; Li, Xu; Zhao, Hongkang; Zhao, Lina

    2018-03-01

    The atomic structures and the corresponding physicochemical properties of peptide coated Au nanoclusters determine their distinctive biological targeting applications. To learn the modulation of amino acid ligand on the atomic structure and electronic characteristics of coated Au core is the fundamental knowledge for peptide coated Au nanocluster design and construction. Based on our recent coated Au nanocluster configuration study (Nanoscale, 2016, 8, 11454), we built the typically simplified Au13(Cys-Au-Cys) system to more clearly learn the basic modulation information of amino acid ligand on Au core by the density functional theory (DFT) calculations. There are two isomers as ligand adjacent bonding (Iso1) and diagonal bonding (Iso2) to Au13 cores. The geometry optimizations indicate the adjacent bonding Iso1 is more stable than Iso2. More important, the Au13 core of Iso1 distorts much more significantly than that of Iso2 by Cys-Au-Cys bonding through the root-mean-square deviation (RMSD) analysis, which modulate their electronic characteristics in different ways. In addition, the frontier molecular orbital results of Au13(Cys-Au-Cys) isomers confirm that the Au cores mainly determine the blue shifts of Au13(Cys-Au-Cys) systems versus the original Au13 core in their UV-visible absorption spectrum studies. The configuration of Au13 core performs deformation under Cys-Au-Cys ligand modulation to reach new stability with distinct atomic structure and electronic properties, which could be the theory basis for peptide coated AuNCs design and construction.

  3. Synthesis of Supported NiPt Bimetallic Nanoparticles, Methods for Controlling the Surface Coverage of Ni Nanoparticles With Pt, Methods Of Making NiPt Multilayer Core-Shell Structures and Application of the Supported Catalysts for CO2 Reforming

    KAUST Repository

    Li, Lidong

    2015-06-25

    Embodiments of the present disclosure provide for supported Ni/Pt bimetallic nanoparticles, compositions including supported NiPt nanoparticles, methods of making supported NiPt nanoparticles, methods of using supported NiPt nanoparticles, and the like.

  4. Pt skin coated hollow Ag-Pt bimetallic nanoparticles with high catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Fu, Tao; Huang, Jianxing; Lai, Shaobo; Zhang, Size; Fang, Jun; Zhao, Jinbao

    2017-10-01

    The catalytic activity and stability of electrocatalyst is critical for the commercialization of fuel cells, and recent reports reveal the great potential of the hollow structures with Pt skin coat for developing high-powered electrocatalysts due to their highly efficient utilization of the Pt atoms. Here, we provide a novel strategy to prepare the Pt skin coated hollow Ag-Pt structure (Ag-Pt@Pt) of ∼8 nm size at room temperature. As loaded on the graphene, the Ag-Pt@Pt exhibits a remarkable mass activity of 0.864 A/mgPt (at 0.9 V, vs. reversible hydrogen electrode (RHE)) towards oxygen reduction reaction (ORR), which is 5.30 times of the commercial Pt/C catalyst, and the Ag-Pt@Pt also shows a better stability during the ORR catalytic process. The mechanism of this significant enhancement can be attributed to the higher Pt utilization and the unique Pt on Ag-Pt surface structure, which is confirmed by the density functional theory (DFT) calculations and other characterization methods. In conclusion, this original work offers a low-cost and environment-friendly method to prepare a high active electrocatalyst with cheaper price, and this work also discloses the correlation between surface structures and ORR catalytic activity for the hollow structures with Pt skin coat, which can be instructive for designing novel advanced electrocatalysts for fuel cells.

  5. Pt and PtRu catalyst bilayers increase efficiencies for ethanol oxidation in proton exchange membrane electrolysis and fuel cells

    Science.gov (United States)

    Altarawneh, Rakan M.; Pickup, Peter G.

    2017-10-01

    Polarization curves, product distributions, and reaction stoichiometries have been measured for the oxidation of ethanol at anodes consisting of Pt and PtRu bilayers and a homogeneous mixture of the two catalysts. These anode structures all show synergies between the two catalysts that can be attributed to the oxidation of acetaldehyde produced at the PtRu catalyst by the Pt catalyst. The use of a PtRu layer over a Pt layer produces the strongest effect, with higher currents than a Pt on PtRu bilayer, mixed layer, or either catalyst alone, except for Pt at high potentials. Reaction stoichiometries (average number of electrons transferred per ethanol molecule) were closer to the values for Pt alone for both of the bilayer configurations but much lower for PtRu and mixed anodes. Although Pt alone would provide the highest overall fuel cell efficiency at low power densities, the PtRu on Pt bilayer would provide higher power densities without a significant loss of efficiency. The origin of the synergy between the Pt and PtRu catalysts was elucidated by separation of the total current into the individual components for generation of carbon dioxide and the acetaldehyde and acetic acid byproducts.

  6. Reaction mechanisms for the CO oxidation on Au/CeO(2) catalysts: activity of substitutional Au(3+)/Au(+) cations and deactivation of supported Au(+) adatoms.

    Science.gov (United States)

    Camellone, Matteo Farnesi; Fabris, Stefano

    2009-08-05

    Density functional theory calculations that account for the on-site Coulomb interaction via a Hubbard term (DFT+U) reveal the mechanisms for the oxidation of CO catalyzed by isolated Au atoms as well as small clusters in Au/CeO(2) catalysts. Ceria (111) surfaces containing positively charged Au ions, either as supported Au(+) adatoms or as substitutional Au(3+) ions, are shown to activate molecular CO and to catalyze its oxidation to CO(2). In the case of supported single Au(+) adatoms, the limiting rate for the CO oxidation is determined by the adsorbate spillover from the adatom to the oxide support. The reaction then proceeds with the CO oxidation via lattice oxygen and O vacancy formation. These vacancies are shown to readily attract the supported Au(+) adatoms and to turn them into negatively charged Au(delta-) adspecies that deactivate the catalyst, preventing further CO adsorption. Au(3+) ions dispersed into the ceria lattice as substitutional point defects can instead sustain a full catalytic cycle consisting of three individual steps maintaining their activity along the reaction process: Au cations in Au(x)Ce(1-x)O(2) systems promote multiple oxidations of CO without any activation energy via formation of surface O vacancies. Molecular oxygen adsorbs at these vacancies and forms O adspecies that then catalyze the oxidation of molecular CO, closing the catalytic cycle and recovering the stoichiometric Au(x)Ce(1-x)O(2) system. The interplay between the reversible Ce(4+)/Ce(3+) and Au(3+)/Au(+) reductions underpins the high catalytic activity of dispersed Au atoms into the ceria substrate. It is shown that the positive oxidation state of the substitutional Au ions is retained along the catalytic cycle, thus preventing the deactivation of Au(x)Ce(1-x)O(2) catalysts in operation conditions. Finally, although a single Au(+) adatom bound to an O vacancy is shown to deactivate during CO oxidation, the calculations predict that the reactivity of gold nanoparticles

  7. Interface structures in FePt/Fe3Pt hard-soft exchange-coupled magnetic nanocomposites

    International Nuclear Information System (INIS)

    Li Jing; Wang Zhonglin; Zeng Hao; Sun Shouheng; Ping Liu, J.

    2003-01-01

    Self-assembly of FePt and Fe 3 O 4 nanoparticles of different sizes led to various FePt-Fe 3 O 4 nanocomposites. Annealing the composite under reducing atmosphere at 650 and 700 deg. C induced magnetically hard FePt phase and magnetically soft Fe 3 Pt phase. The FePt and Fe 3 Pt phases were either linked by a common interface or coexisted within one grain as domains with sizes <10 nm. This ensures the effective exchange coupling of magnetically hard and soft phases. High-resolution transmission electron microscopy studies provide detailed structural characterization for the FePt based nanocomposites

  8. Fabricating a Homogeneously Alloyed AuAg Shell on Au Nanorods to Achieve Strong, Stable, and Tunable Surface Plasmon Resonances

    KAUST Repository

    Huang, Jianfeng

    2015-08-13

    Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field-enhanced spectroscopies, plasmon-mediated catalysis, etc. Here, a new synthetic strategy is reported that enables the epitaxial growth of a homogeneously alloyed AuAg shell on Au nanorod seeds, circumventing the phase segregation of Au and Ag encountered in conventional synthesis. The resulting core–shell structured bimetallic nanorods (AuNR@AuAg) have well-mixed Au and Ag atoms in their shell without discernible domains. This degree of mixing allows AuNR@AuAg to combine the high stability of Au with the superior plasmonic activity of Ag, thus outperforming seemingly similar nanostructures with monometallic shells (e.g., Ag-coated Au NRs (AuNR@Ag) and Au-coated Au NRs (AuNR@Au)). AuNR@AuAg is comparable to AuNR@Ag in plasmonic activity, but that it is markedly more stable toward oxidative treatment. Specifically, AuNR@AuAg and AuNR@Ag exhibit similarly strong signals in surface-enhanced Raman spectroscopy that are some 30-fold higher than that of AuNR@Au. When incubated with a H2O2 solution (0.5 m), the plasmonic activity of AuNR@Ag immediately and severely decayed, whereas AuNR@AuAg retained its activity intact. Moreover, the longitudinal SPR frequency of AuNR@AuAg can be tuned throughout the red wavelengths (≈620–690 nm) by controlling the thickness of the AuAg alloy shell. The synthetic strategy is versatile to fabricate AuAg alloyed shells on different shaped Au, with prospects for new possibilities in the synthesis and application of plasmonic nanocrystals.

  9. Benchmarking Pt and Pt-lanthanide sputtered thin films for oxygen electroreduction

    DEFF Research Database (Denmark)

    Zamburlini, Eleonora; Jensen, Kim Degn; Stephens, Ifan E.L.

    2017-01-01

    Platinum-lanthanide alloys are very promising as active and stable catalysts for the oxygen reduction reaction (ORR) in low-temperature fuel cells. We have fabricated Pt and Pt5Gd metallic thin films via (co-)sputtering deposition in an ultra-high vacuum (UHV) chamber. The electrochemical ORR...

  10. Electrochemical promotion of catalytic reactions with Pt/C (or Pt/Ru/C)//PBI catalysts

    DEFF Research Database (Denmark)

    Petrushina, Irina; Bjerrum, Niels; Bandur, Viktor

    2007-01-01

    The paper is an overview of the results of the investigation on electrochemical promotion of three catalytic reactions: methane oxidation with oxygen, NO reduction with hydrogen at 135 degrees C and Fischer-Tropsch synthesis (FTS) at 170 degrees C in the [CH4/O-2(or NO/H-2 or CO/H-2)/Ar//Pt(or Pt...

  11. PtxGd alloy formation on Pt(111): Preparation and structural characterization

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese; Pedersen, Anders Filsøe; Vej-Hansen, Ulrik Grønbjerg

    2016-01-01

    Pt x Gd single crystals have been prepared in ultra high vacuum (UHV). This alloy shows promising catalytic properties for the oxygen reduction reaction. The samples were prepared by using vacuum deposition of a thick layer of Gd on a sputter cleaned Pt(111) single crystal, resulting in a ∼63nm...

  12. Cyclic voltammograms for H on Pt(111) and Pt(100) from first principles

    DEFF Research Database (Denmark)

    Karlberg, Gustav; Jaramillo, Thomas; Skulason, Egill

    2007-01-01

    Cyclic voltammetry is a fundamental experimental method for characterizing electrochemical surfaces. Despite its wide use, a way to quantitatively and directly relate cyclic voltammetry to ab initio calculations has been lacking. We derive the cyclic voltammogram for H on Pt(111) and Pt(100), based...

  13. Electrical manipulation of perpendicular magnetic anisotropy in a Pt/Co/Pt trilayer grown on PMN-PT(0 1 1) substrate

    Science.gov (United States)

    Xiao, X.; Sun, L.; Luo, Y. M.; Zhang, D.; Liang, J. H.; Wu, Y. Z.

    2018-03-01

    Strain-induced modulation of perpendicular magnetic anisotropy (PMA) is demonstrated in a wedge-shaped Pt/Co/Pt sandwich grown on PMN-PT(0 1 1) substrate using magnetic torque measurements. An anisotropic in-plane strain is generated by applying an electric field across the PMN-PT substrate and transferred to the ferromagnetic Pt/Co/Pt sandwich. The critical thickness of spin reorientation transition is tuned to the thicker region of the Pt/Co/Pt wedge. The strain-induced change of PMA is quantitatively extracted. Only the first order anisotropy term is tuned by the electric field, while the second order anisotropy term has negligible electric field-dependence. Both of the volume and interface contributions of the first order anisotropy term show tunable electric field modulation. These results may benefit the understanding of strain-mediated magnetoelectric coupling effect in artificial multiferroic structures containing a ferromagnetic layer with PMA.

  14. Preparation and Thermoelectric Characteristics of ITO/PtRh:PtRh Thin Film Thermocouple

    Science.gov (United States)

    Zhao, Xiaohui; Wang, Hongmin; Zhao, Zixiang; Zhang, Wanli; Jiang, Hongchuan

    2017-12-01

    Thin film thermocouples (TFTCs) can provide more precise in situ temperature measurement for aerospace propulsion systems without disturbance of gas flow and surface temperature distribution of the hot components. ITO /PtRh:PtRh TFTC with multilayer structure was deposited on alumina ceramic substrate by magnetron sputtering. After annealing, the TFTC was statically calibrated for multiple cycles with temperature up to 1000 °C. The TFTC with excellent stability and repeatability was realized for the negligible variation of EMF in different calibration cycles. It is believed that owing to oxygen diffusion barriers by the oxidation of top PtRh layer and Schottky barriers formed at the grain boundaries of ITO, the variation of the carrier concentration of ITO film is minimized. Meanwhile, the life time of TFTC is more than 30 h in harsh environment. This makes ITO/PtRh:PtRh TFTC a promising candidate for precise surface temperature measurement of hot components of aeroengines.

  15. Time-invariant PT product and phase locking in PT -symmetric lattice models

    Science.gov (United States)

    Joglekar, Yogesh N.; Onanga, Franck Assogba; Harter, Andrew K.

    2018-01-01

    Over the past decade, non-Hermitian, PT -symmetric Hamiltonians have been investigated as candidates for both a fundamental, unitary, quantum theory and open systems with a nonunitary time evolution. In this paper, we investigate the implications of the former approach in the context of the latter. Motivated by the invariance of the PT (inner) product under time evolution, we discuss the dynamics of wave-function phases in a wide range of PT -symmetric lattice models. In particular, we numerically show that, starting with a random initial state, a universal, gain-site location dependent locking between wave-function phases at adjacent sites occurs in the PT -symmetry-broken region. Our results pave the way towards understanding the physically observable implications of time invariants in the nonunitary dynamics produced by PT -symmetric Hamiltonians.

  16. Electrocatalytic property of PtBi and PtPb line compounds via DFT

    Science.gov (United States)

    Wang, Lin-Lin; Johnson, D. D.

    2007-03-01

    A major obstacle to practical, mass market fuel cell (e.g. hydrogen and direct methanol) technology is CO poisoning of Pt anode. Pt alloys, such as disordered PtxRu(1-x), are known to have an increased CO-tolerance. There has been significant effort to understand the mechanism for increased CO- tolerance and to design better catalyst via alloyed nanoparticles and surface alloys. Alternatively, Pt intermetallic compounds, such as with Bi and Pb, have been observed to improve dramatically the CO-tolerance. [E. Casado- Rivera et al. ChemPhysChem 4, 193 (2003) and J. Am. Chem. Soc. 126, 4043 (2004)] Here we use density functional theory to study the adsorptions of CO, H and OH on these materials. We find that (100) and (110) surfaces of PtBi and PtPb line compounds have lower cleavage energy than (001) surface. Adsorption energies and electronic structure are examined to explain the increased CO-tolerance.

  17. Transport characteristics in Au/pentacene/Au diodes

    Science.gov (United States)

    Hayashi, Toshiaki; Naka, Akiyoshi; Hiroki, Masanobu; Yokota, Tomoyuki; Someya, Takao; Fujiwara, Akira

    2018-03-01

    We have used scanning and transmission electron microscopes (SEM and TEM) to study the structure of a pentacene thin film grown on a Au layer with and shown that it consists of randomly oriented amorphous pentacene clusters. We have also investigated the transport properties of amorphous pentacene in a metal-semiconductor-metal (MSM) diode structure and shown that the current is logarithmically proportional to the square root of the applied voltage, which indicates that transport occurs as the result of hopping between localized sites randomly distributed in space and energy.

  18. PT-symmetry management in oligomer systems

    International Nuclear Information System (INIS)

    Horne, R L; Cuevas, J; Kevrekidis, P G; Whitaker, N; Abdullaev, F Kh; Frantzeskakis, D J

    2013-01-01

    We study the effects of management of the PT-symmetric part of the potential within the setting of Schrödinger dimer and trimer oligomer systems. This is done by rapidly modulating in time the gain/loss profile. This gives rise to a number of interesting properties of the system, which are explored at the level of an averaged equation approach. Remarkably, this rapid modulation provides for a controllable expansion of the region of exact PT-symmetry, depending on the strength and frequency of the imposed modulation. The resulting averaged models are analysed theoretically and their exact stationary solutions are translated into time-periodic solutions through the averaging reduction. These are, in turn, compared with the exact periodic solutions of the full non-autonomous PT-symmetry managed problem and very good agreement is found between the two. (paper)

  19. Centrality dependence of D0 elliptic and triangular flow in Au+Au collisions at √{sNN} = 200GeV at STAR

    Science.gov (United States)

    He, Liang; STAR Collaboration

    2017-11-01

    Due to their large masses, heavy quarks are predominantly produced through initial hard scatterings in heavy-ion collisions and, as such, they experience the entire evolution of the hot and dense medium created in those collisions. They can therefore provide important insights into the properties of the strongly-coupled Quark-Gluon Plasma. For instance, the measurement of the elliptic flow (v2) of charm quarks can provide information on the degree of thermalization for charm quarks in the medium and thus the bulk properties of the system. Furthermore, several models have predicted that fluctuations in the initial conditions, together with strong charm-medium interactions, could lead to a finite triangular flow (v3) for charm quarks, providing another handle to study the dynamics at the early stage of heavy-ion collisions. In these proceedings, we present the measurements of the v2 and v3 of D0 mesons in Au+Au collisions at √{sNN} = 200GeV with the Heavy Flavor Tracker at STAR. Compared to previously reported D0v2 in minimum-bias collisions, the precision of the new results is improved by a factor of 2-4 depending on D0 transverse momentum (pT). The D0v3 as a function of pT is also reported for the first time. The results are compared with the measurements of other particle species and a series of model calculations.

  20. Diffusion and adsorption of dimers on reconstructed Pt(1 1 0) surfaces: First principle and EAM studies

    Science.gov (United States)

    Matrane, I.; Mazroui, M.; Sbiaai, K.

    2018-03-01

    We present a density functional theory (DFT) and embedded atom method (EAM) studies of Pt2 , Au2 and AuPt dimers adsorption and diffusion on the clean Pt (1 1 0) (1 × 1) surface and (1 × 2) (1 × 3) and (1 × 4) missing row reconstructed geometries. As a first step, adsorption energies are calculated for all considered dimers, and their stability is checked by computing the binding energies. Furthermore, the energy barriers for the elementary diffusion mechanisms (concerted jump, dissociation-reassociation and leapfrog) are calculated for dimers diffusion on all considered geometries. The potential energy profile for the leapfrog mechanism is provided for dimers diffusion on the (1 × 2) (1 × 3) and (1 × 4) missing row reconstructed geometries. Our results show that each of the three dimers exhibits a qualitatively different behaviours. In addition, the obtained results provide interesting atomistic information about dimers stability and mobility, which is required for understanding the macroscopic kinetics of crystal growth.

  1. Becoming independent through au pair migration

    DEFF Research Database (Denmark)

    Dalgas, Karina Märcher

    2015-01-01

    . This article argues that, despite this critique, au pairing does play an important formative role for young Filipinas because it opens up for experiences abroad that enable them to be recognised as independent adults in Philippine society. Rather than autonomy, however, au pairs define their independence......Over the past decade, growing numbers of young Filipinas have entered Denmark on the au pair scheme. While its official aim is to broaden the cultural horizons of youth, researchers generally view Filipina au pairing as a form of labour migration using au pairs as inexpensive domestic workers...... in terms of their capacity to assume responsibility for others, thereby achieving a position of social respect. Based on ethnographic fieldwork in Denmark and the Philippines, this article explores how young Filipinas use the social, economic, and cultural resources they gain from their au pair stay abroad...

  2. Colloidal Toolbox Synthesis of Pt Nanoalloys

    DEFF Research Database (Denmark)

    Spanos, Ioannis

    /precipitation technique, which is commonly used in industrial synthesis offuel cell catalysts, will serve as reference. In this particular method, due to the slow rate of themetal precursor reduction and conversion to the metallic state and the even slower diffusion of themetal species on the surface of the carbon......Co1-x nanoalloys, the so-called particledisorder, with the lattice strain. Alloying Pt with increasing amount of Co increases strain andparticle disorder and subsequently both ORR performance and NPs stability. However, excessivealloying and de-alloying, as in the case of PtCo6, leads to particle...

  3. Spontaneous Breaking of Classical PT Symmetry

    OpenAIRE

    Bender, Carl M.; Darg, Daniel W.

    2007-01-01

    The classical trajectories of the family of complex PT-symmetric Hamiltonians $H=p^2+x^2(ix)^\\epsilon$ ($\\epsilon\\geq0$) form closed orbits. All such complex orbits that have been studied in the past are PT symmetric (left-right symmetric). The periods of these orbits exhibit an unusual dependence on the parameter $\\epsilon$. There are regions in $\\epsilon$ of smooth behavior interspersed with regions of rapid variation. It is demonstrated that the onset of rapid variation is associated with ...

  4. Relaxor-PT Single Crystal Piezoelectric Sensors

    Directory of Open Access Journals (Sweden)

    Xiaoning Jiang

    2014-07-01

    Full Text Available Relaxor-PbTiO3 piezoelectric single crystals have been widely used in a broad range of electromechanical devices, including piezoelectric sensors, actuators, and transducers. This paper reviews the unique properties of these single crystals for piezoelectric sensors. Design, fabrication and characterization of various relaxor-PT single crystal piezoelectric sensors and their applications are presented and compared with their piezoelectric ceramic counterparts. Newly applicable fields and future trends of relaxor-PT sensors are also suggested in this review paper.

  5. Rhodium deposition onto a 4-mercaptopyridine SAM on Au(1 1 1)

    Energy Technology Data Exchange (ETDEWEB)

    Manolova, M. [Institute of Electrochemistry, University of Ulm, 89069 Ulm (Germany); Kayser, M. [Institute of Electrochemistry, University of Ulm, 89069 Ulm (Germany); Kolb, D.M. [Institute of Electrochemistry, University of Ulm, 89069 Ulm (Germany)]. E-mail: dieter.kolb@uni-ulm.de; Boyen, H.-G. [Institute of Solid State Physics, University of Ulm, 89069 Ulm (Germany); Ziemann, P. [Institute of Solid State Physics, University of Ulm, 89069 Ulm (Germany); Mayer, D. [BASF Electronic Materials GmbH, 67056 Ludwigshafen (Germany); Wirth, A. [BASF Electronic Materials GmbH, 67056 Ludwigshafen (Germany)

    2007-02-10

    The application of a recently developed method for the deposition of Pd and Pt on top of a SAM, has been successfully extended to Rh, thus proving the versatility of the new concept. Experimental evidence from cyclic voltammetry, in situ STM and ex situ X-ray photoemission spectroscopy is presented for the deposition of monoatomic high rhodium islands onto a 4-mercaptopyridine self-assembled monolayer on a Au(1 1 1) electrode. By repetitive complexation of the Rh ions to the ring-nitrogen and reduction in a Rh-ion free solution, an almost completely covered SAM is obtained. The consequences of making contacts for molecular electronics are briefly discussed.

  6. L’olivier au Maroc

    OpenAIRE

    El Mouhtadi Issam; Agouzzal Mohamed; Guy François

    2014-01-01

    L’olivier est une culture traditionnelle sur le pourtour de la Méditerranée. Il est donc naturel de trouver cet arbre au Maroc où il est présent depuis des siècles. Cultivé surtout traditionnellement jusqu’à ses dernières années, il fait l’objet maintenant d’un plan de valorisation très ambitieux pour non seulement garder le Royaume à son niveau actuel (2e producteur mondial pour l’olive de conserve et 6e pour l’huile d’olive) mais pour conq...

  7. Nuclear structure from radioactive decay. Annual progress report

    International Nuclear Information System (INIS)

    Wood, J.L.

    1982-01-01

    The most exciting development during this year has been the formulation of a unified description of shape coexistence in nuclei. The picture is built on the idea that deformation in nuclei is due to an attractive proton-neutron force acting in the valence shell model space. The excitation of nucleon pairs across closed shells effectively increases the number of valence nucleons, giving rise to a set of coexisting states with larger deformation. The major area of activity is the study of neutron-deficient nuclei around the Z = 82 shell closure, with special emphasis on the levels of the odd-mass Pt, Au, Hg and Tl isotopes. Progress is reported

  8. Pt-Ni and Pt-Co Catalyst Synthesis Route for Fuel Cell Applications

    Science.gov (United States)

    Firdosy, Samad A.; Ravi, Vilupanur A.; Valdez, Thomas I.; Kisor, Adam; Narayan, Sri R.

    2013-01-01

    Oxygen reduction reactions (ORRs) at the cathode are the rate-limiting step in fuel cell performance. The ORR is 100 times slower than the corresponding hydrogen oxidation at the anode. Speeding up the reaction at the cathode will improve fuel cell efficiency. The cathode material is generally Pt powder painted onto a substrate (e.g., graphite paper). Recent efforts in the fuel cell area have focused on replacing Pt with Pt-X alloys (where X = Co, Ni, Zr, etc.) in order to (a) reduce cost, and (b) increase ORR rates. One of these strategies is to increase ORR rates by reducing the powder size, which would result in an increase in the surface area, thereby facilitating faster reaction rates. In this work, a process has been developed that creates Pt-Ni or Pt-Co alloys that are finely divided (on the nano scale) and provide equivalent performance at lower Pt loadings. Lower Pt loadings will translate to lower cost. Precursor salts of the metals are dissolved in water and mixed. Next, the salt mixtures are dried on a hot plate. Finally, the dried salt mixture is heattreated in a furnace under flowing reducing gas. The catalyst powder is then used to fabricate a membrane electrode assembly (MEA) for electrochemical performance testing. The Pt- Co catalyst-based MEA showed comparable performance to an MEA fabri cated using a standard Pt black fuel cell catalyst. The main objective of this program has been to increase the overall efficiencies of fuel cell systems to support power for manned lunar bases. This work may also have an impact on terrestrial programs, possibly to support the effort to develop a carbon-free energy source. This catalyst can be used to fabricate high-efficiency fuel cell units that can be used in space as regenerative fuel cell systems, and terrestrially as primary fuel cells. Terrestrially, this technology will become increasingly important when transition to a hydrogen economy occurs.

  9. Carbon supported nanoparticles Pt Ru (Pt Ru/C electrocatalysts) prepared using electron beam irradiation; Preparacao de nanoparticulas de PtRu suportadas em carbono (eletrocatalisadores PtRu/C) utilizando feixe de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F. da; Oliveira Neto, Almir; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Programa de Celulas a Combustivel], e-mail: espinace@ipen.br, e-mail: dfsilva@ipen.br

    2006-07-01

    Carbon-supported Pt Ru (electrocatalysts PtRu/C nanoparticles) were prepared submitting a water/ethylene glycol mixture containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The PtRu/C electrocatalysts were characterized by EDX, XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C ETEK electrocatalyst at ambient temperature. (author)

  10. Resistive random access memory utilizing ferritin protein with Pt nanoparticles

    International Nuclear Information System (INIS)

    Uenuma, Mutsunori; Kawano, Kentaro; Zheng Bin; Okamoto, Naofumi; Horita, Masahiro; Yoshii, Shigeo; Yamashita, Ichiro; Uraoka, Yukiharu

    2011-01-01

    This study reports controlled single conductive paths found in resistive random access memory (ReRAM) formed by embedding Pt nanoparticles (Pt NPs) in NiO film. Homogeneous Pt NPs produced and placed by ferritin protein produce electric field convergence which leads to controlled conductive path formation. The ReRAM with Pt NPs shows stable switching behavior. A Pt NP density decrease results in an increase of OFF state resistance and decrease of forming voltage, whereas ON resistance was independent of the Pt NP density, which indicates that a single metal NP in a memory cell will achieve low power and stable operation.

  11. High pressure CO hydrogenation over bimetallic Pt-Co catalysts

    DEFF Research Database (Denmark)

    Christensen, Jakob Munkholt; Medford, Andrew James; Studt, Felix

    2014-01-01

    produce mainly methanol in the Pt-rich composition range andmainly hydrocarbons (and to a modest extent higher alcohols) in the Co-rich composition range. The transition between the two types of behavior occurs in a narrow composition range around a molar Pt:Co ratio of 1:1.......The potential of bimetallic Pt-Co catalysts for production of higher alcohols in high pressure CO hydrogenation has been assessed. Two catalysts (Pt3Co/SiO2 and PtCo/SiO2) were tested, and the existing literature on CO hydrogenation over Pt-Co catalysts was reviewed. It is found that the catalysts...

  12. Predicted Habitat Suitability for Montipora Corals in the Au'au Channel Region

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This raster denotes predicted habitat suitability for Montipora in the Au'au Channel region. Maximum Entropy (MaxEnt) modeling software was used to create this...

  13. Predicted Habitat Suitability for All Mesophotic Corals in the Au'au Channel Region

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This raster denotes predicted habitat suitability for all mesophotic corals in the Au'au Channel region. Maximum Entropy (MaxEnt) modeling software was used to...

  14. Predicted Habitat Suitability for Leptoseris in the Au'au Channel Region

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This raster denotes predicted habitat suitability for Leptoseris in the Au'au Channel region. Maximum Entropy (MaxEnt) modeling software was used to create this...

  15. Predicted Habitat Suitability for Porites in the Au'au Channel Region

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This raster denotes predicted habitat suitability for Porites in the Au'au Channel region. Maximum Entropy (MaxEnt) modeling software was used to create this...

  16. Predicted Habitat Suitability for Leptoseris Corals in the Au'au Channel Region

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This raster denotes predicted habitat suitability for Leptoseris in the Au'au Channel region. Maximum Entropy (MaxEnt) modeling software was used to create this...

  17. Synthesis of nir-sensitive Au-Au{sub 2}S nanocolloids for drug delivery

    Energy Technology Data Exchange (ETDEWEB)

    Ren, L.; Chow, G.M

    2003-01-15

    Near IR (NIR) sensitive Au-Au{sub 2}S nanocolloids were prepared by mixing HAuCl{sub 4} and Na{sub 2}S in aqueous solutions. An anti-tumor drug, cis-platin, was adsorbed onto Au-Au{sub 2}S nanoparticle surface via the 11-mercaptoundecanoic acid (MUA) layers. The results show that the degree of adsorption of cis-platin onto Au-Au{sub 2}S nanoparticles was controlled by the solution pH value, and the drug release was sensitive to near-infrared irradiation. The cis-platin-loaded Au-Au{sub 2}S nanocolloids can be potentially applied as NIR activated drug delivery carrier.

  18. Near-side azimuthal and pseudorapidity correlations using neutral strange baryons and mesons in d +Au , Cu + Cu, and Au + Au collisions at √{sN N}=200 GeV

    Science.gov (United States)

    Abelev, B.; Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Barnby, L. S.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bombara, M.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; di Ruzza, B.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Gaillard, L.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, B.; Huang, X.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Jentsch, A.; Jia, J.; Jiang, K.; Jones, P. G.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z. H.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, C.; Li, Y.; Li, W.; Li, X.; Li, X.; Lin, T.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, L.; Ma, R.; Ma, G. L.; Ma, Y. G.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Matis, H. S.; McDonald, D.; McKinzie, S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nattrass, C.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, Z.; Sun, X. M.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, H.; Wang, Y.; Wang, G.; Wang, Y.; Wang, J. S.; Wang, F.; Webb, G.; Webb, J. C.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xin, K.; Xu, Y. F.; Xu, Q. H.; Xu, N.; Xu, J.; Xu, H.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, S.; Yang, Y.; Yang, Y.; Yang, C.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, S.; Zhang, J. B.; Zhang, J.; Zhang, J.; Zhang, Z.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2016-07-01

    We present measurements of the near side of triggered di-hadron correlations using neutral strange baryons (Λ ,Λ ¯) and mesons (KS0) at intermediate transverse momentum (3 < pT <6 GeV /c ) to look for possible flavor and baryon-meson dependence. This study is performed in d +Au , Cu+Cu, and Au+Au collisions at √{sN N}=200 GeV measured by the STAR experiment at RHIC. The near-side di-hadron correlation contains two structures, a peak which is narrow in azimuth and pseudorapidity consistent with correlations from jet fragmentation, and a correlation in azimuth which is broad in pseudorapidity. The particle composition of the jet-like correlation is determined using identified associated particles. The dependence of the conditional yield of the jet-like correlation on the trigger particle momentum, associated particle momentum, and centrality for correlations with unidentified trigger particles are presented. The neutral strange particle composition in jet-like correlations with unidentified charged particle triggers is not well described by PYTHIA. However, the yield of unidentified particles in jet-like correlations with neutral strange particle triggers is described reasonably well by the same model.

  19. Enhanced photocatalytic H2 evolution over CdS/Au/g-C3N4 composite photocatalyst under visible-light irradiation

    Directory of Open Access Journals (Sweden)

    Xiaoling Ding

    2015-10-01

    Full Text Available A novel heterojunction structured composite photocatalyst CdS/Au/g-C3N4 has been developed by depositing CdS/Au with a core (Au-shell (CdS structure on the surface of g-C3N4. The photocatalytic hydrogen production activity of the developed photocatalyst was evaluated under visible-light irradiation (λ > 420 nm using methanol as a sacrificial reagent. As a result, its activity is about 125.8 times higher than that of g-C3N4 and is even much higher than that of Pt/g-C3N4. The enhancement in photocatalytic activity is attributed to efficient separation of the photoexcited charges due to the anisotropic junction in the CdS/Au/g-C3N4 system.

  20. Enhanced photocatalytic H2 evolution over CdS/Au/g-C3N4 composite photocatalyst under visible-light irradiation

    Science.gov (United States)

    Ding, Xiaoling; Li, Yingxuan; Zhao, Jie; Zhu, Yunqing; Li, Yan; Deng, Wenye; Wang, Chuanyi

    2015-10-01

    A novel heterojunction structured composite photocatalyst CdS/Au/g-C3N4 has been developed by depositing CdS/Au with a core (Au)-shell (CdS) structure on the surface of g-C3N4. The photocatalytic hydrogen production activity of the developed photocatalyst was evaluated under visible-light irradiation (λ > 420 nm) using methanol as a sacrificial reagent. As a result, its activity is about 125.8 times higher than that of g-C3N4 and is even much higher than that of Pt/g-C3N4. The enhancement in photocatalytic activity is attributed to efficient separation of the photoexcited charges due to the anisotropic junction in the CdS/Au/g-C3N4 system.

  1. Pt/MOx/SiO2, Pt/MOx/TiO2, and Pt/MOx/Al2O3 Catalysts for CO Oxidation

    Directory of Open Access Journals (Sweden)

    Hongmei Qin

    2015-04-01

    Full Text Available Conventional supported Pt catalysts have often been prepared by loading Pt onto commercial supports, such as SiO2, TiO2, Al2O3, and carbon. These catalysts usually have simple metal-support (i.e., Pt-SiO2 interfaces. To tune the catalytic performance of supported Pt catalysts, it is desirable to modify the metal-support interfaces by incorporating an oxide additive into the catalyst formula. Here we prepared three series of metal oxide-modified Pt catalysts (i.e., Pt/MOx/SiO2, Pt/MOx/TiO2, and Pt/MOx/Al2O3, where M = Al, Fe, Co, Cu, Zn, Ba, La for CO oxidation. Among them, Pt/CoOx/SiO2, Pt/CoOx/TiO2, and Pt/CoOx/Al2O3 showed the highest catalytic activities. Relevant samples were characterized by N2 adsorption-desorption, X-ray diffraction (XRD, transmission electron microscopy (TEM, H2 temperature-programmed reduction (H2-TPR, X-ray photoelectron spectroscopy (XPS, CO temperature-programmed desorption (CO-TPD, O2 temperature-programmed desorption (O2-TPD, and CO2 temperature-programmed desorption (CO2-TPD.

  2. Effect of the applied magnetic field and the layer thickness on the magnon properties in bilayers Co/Pt and symmetrical trilayer Pt/Co/Pt

    International Nuclear Information System (INIS)

    Mehdioui, M.; Fahmi, A.; Lassri, H.; Fahoume, M.; Qachaou, A.

    2014-01-01

    We have studied the elementary magnetic excitations and their dynamics in multilayer Co(t Co)/Pt(t Pt) and Pt(t Pt)/Co(t Co)/Pt(t Pt) under an applied magnetic field. The Heisenberg hamiltonian used takes into account the magneto-crystalline and surface anisotropies, the exchange and dipolar interactions. The calculated excitation spectrum ε N (k) presents a structure with two sub-bands corresponding to the magnons of surface and volume respectively. The existence of a gap of creating these magnons is also highlighted. The lifetimes deduced from these gaps are in good agreement with the results of previous studies. The thermal evolution of the magnetization m z indicates that the system undergoes a dimensional crossover 3D–2D when the temperature increases. The calculated and measured magnetizations are compared and they are in good agreement. The exchange integral and critical temperature values deduced from these adjustments are in very good agreement with the results of previous works. - Highlights: • The magnons of surface and volume exist in Co/Pt and Pt/Co/Pt. • Samples undergo dimensional crossover (3D–2D) when T increases. • A good agreement is obtained between M(T) measured and calculated. • Deduced exchange integrals and critical temperature values are correct. • The magnetism of the sample is reduced by increasing t Pt or capping Co by two Pt layers

  3. Measurements of dielectron production in Au + Au collisions at √{sN N}=200 GeV from the STAR experiment

    Science.gov (United States)

    Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Averichev, G. S.; Banerjee, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandin, A. V.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Cervantes, M. C.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; di Ruzza, B.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, S.; Gupta, A.; Guryn, W.; Hamad, A.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, X.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Jiang, K.; Judd, E. G.; Jung, K.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z. H.; Kikola, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Kycia, R. A.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, W.; Li, Z. M.; Li, Y.; Li, X.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, Y. G.; Ma, G. L.; Ma, L.; Ma, R.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; Meehan, K.; Minaev, N. G.; Mioduszewski, S.; Mohanty, B.; Mondal, M. M.; Morozov, D.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Peterson, A.; Pile, P.; Planinic, M.; Pluta, J.; Poljak, N.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roy, A.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, M. K.; Sharma, B.; Shen, W. Q.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Summa, B.; Sun, X.; Sun, Z.; Sun, X. M.; Sun, Y.; Surrow, B.; Svirida, N.; Szelezniak, M. A.; Tang, A. H.; Tang, Z.; Tarnowsky, T.; Tawfik, A. N.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Wang, H.; Wang, J. S.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y. F.; Xiao, Z. G.; Xie, W.; Xin, K.; Xu, Q. H.; Xu, Z.; Xu, H.; Xu, N.; Xu, Y. F.; Yang, Q.; Yang, Y.; Yang, S.; Yang, Y.; Yang, C.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, X. P.; Zhang, J.; Zhang, Y.; Zhang, J.; Zhang, J. B.; Zhang, S.; Zhang, Z.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2015-08-01

    We report on measurements of dielectron (e+e-) production in Au +Au collisions at a center-of-mass energy of 200 GeV per nucleon-nucleon pair using the STAR detector at BNL Relativistic Heavy Ion Collider. Systematic measurements of the dielectron yield as a function of transverse momentum (pT) and collision centrality show an enhancement compared to a cocktail simulation of hadronic sources in the low invariant-mass region (Me e<1 GeV/c2). This enhancement cannot be reproduced by the ρ -meson vacuum spectral function. In minimum-bias collisions, in the invariant-mass range of 0.30 -0.76 GeV /c2, integrated over the full pT acceptance, the enhancement factor is 1.76 ±0.06 (stat .)±0.26 (sys .)±0.29 (cocktail ) . The enhancement factor exhibits weak centrality and pT dependence in STAR's accessible kinematic regions, while the excess yield in this invariant-mass region as a function of the number of participating nucleons follows a power-law shape with a power of 1.44 ±0.10 . Models that assume an in-medium broadening of the ρ -meson spectral function consistently describe the observed excess in these measurements. Additionally, we report on measurements of ω - and ϕ -meson production through their e+e- decay channel. These measurements show good agreement with Tsallis blast-wave model predictions, as well as, in the case of the ϕ meson, results through its K+K- decay channel. In the intermediate invariant-mass region (1.1

  4. Pt-graphene electrodes for dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Hoshi, Hajime; Tanaka, Shumpei; Miyoshi, Takashi

    2014-01-01

    Highlights: • Graphene films with Pt nanoparticles were prepared from commercial graphene. • Pt consumption can be reduced by using Pt-graphene films. • The film showed improved catalytic activity for the reaction I 3 − /I − . • The film can be used as the counter electrode of dye-sensitized solar cells (DSSCs). • The performance of DSSC was superior to that of the Pt electrode. - Abstract: A simple paste method for fabricating graphene films with Pt nanoparticles was developed. First, graphene pastes with Pt nanoparticles were prepared from commercially available graphene. The resulting films of graphene nanoplatelet aggregates with Pt nanoparticles (Pt-GNA) contained Pt nanoparticles distributed over the entire three-dimensional surface of the GNA. Then, the catalytic activity for the I 3 − /I − redox reaction was evaluated by cyclic voltammetry. The GNA electrode exhibited higher activity than a graphene nanoplatelet electrode because of its higher effective surface area. Addition of Pt nanoparticles to the electrodes improved the catalytic activity. In particular, a large Faradaic current for the I 3 − /I − reaction was observed for the Pt-GNA electrode. As the counter electrodes of dye-sensitized solar cells (DSSCs), their performance was consistent with the cyclic voltammetry results. In particular, the DSSC performance of the Pt-GNA electrode was superior to that of the Pt electrodes commonly used in DSSCs

  5. Activation analysis in food analytics Pt. 2

    International Nuclear Information System (INIS)

    Szabo, A.; Bogancs, J.; Mihalyi, E.

    1979-01-01

    The composition of dried tomato products was examined by activation analysis. The following elements were determined: K, Na, Cl, Br, Mn, Au, Cu, Zn, Sb, As. The deviation of parallel measurements was < 2% in the case of Na, K, Cl, and < 10% in the case of Cu, Zn, Mn and Br. However, the deviation in cases of As, Sb and Au determinations exceeded 50%. The composition of a standard biological sample was also determined, and the results of activation analysis were in good agreement with literature data. (L.E.)

  6. Dynamics of the YSZ-Pt Interface

    DEFF Research Database (Denmark)

    Bay, Lasse; Jacobsen, Torben

    1997-01-01

    Yttria stabilized zirconia (YSZ)-Pt point electrodes were examined by linear potential sweep, potential step and impedance measurements at 1000 degrees C in air. Inductive loops and hysteresis phenomena with long relaxation times were found. Atomic force microscopy showed changes of the interface...

  7. CO on Pt(111): A puzzle revisited

    NARCIS (Netherlands)

    Olsen, R.A.; Philipsen, P.H.T.; Baerends, E.J.

    2003-01-01

    A linear combination of atomic orbitals (LCAO) approach was employed to obtain density functional theory (DFT)/generalized gradient approximation (GGA) results for the CO/Pt(111) system using a slab representation of the surface. Results indicate that the DFT/GGA method correctly predicts the most

  8. Femmes, migration et droits au Mali et au Sénégal | IDRC ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Cette subvention permet au Groupe de recherche sur les femmes et les lois au Sénégal (GREFELS) de lever ces insuffisances. Les chercheurs vont analyser des stratégies migratoires des jeunes filles et des femmes dans les deux pays, étudier les conditions de travail des travailleuses domestiques au Sénégal, ...

  9. O PT e o impeachment de Collor

    Directory of Open Access Journals (Sweden)

    Danilo Enrico Martuscelli

    2010-11-01

    Full Text Available Este artigo analisa a tática política adotada pelo Partido dos Trabalhadores (PT na conjuntura de crise do governo Collor (1990-1992. Considera-se que o PT não tenha fugido à tendência dominante do movimento pró-impeachment, vindo a aderir à campanha pela ética na política e a atacar o presidente Collor a partir de um discurso de cunho moralista que menosprezou a crítica e a denúncia do caráter de classe da política neoliberal, satisfazendo-se apenas com a denúncia da política recessiva do governo. Essa tática se inscreve na luta contra os efeitos da política neoliberal e não propriamente contra essa política, e esse comportamento político pode ser considerado um indicador do processo de aceitação passiva, por parte do PT, das medidas neoliberais.This paper analyzes Collor's government crisis and the political tactics of the Workers' Party (PT at the conjuncture of Collor's government crisis. We consider that the Workers' Party didn't escape of the dominant trend of the pro-impeachment movement, adhering to the campaign for the ethics in politics and attacking president Collor from a moralist point of view, which relegated the critics and denouncement of the class character of the neoliberal politics to the second plan. The Party was limited to join the accusations about the recessionary trend of Collor's government, which meant a tactic inscribed in the fight against the effects of the neoliberal politics but not against its nature. This political behavior can be considered as an indicator of the process of passive acceptation of the neoliberal proposals from the PT.

  10. Hybrid materials based on polymethylsilsesquioxanes containing Fe, Pt, and Fe-Pt metallic nanoparticles

    Science.gov (United States)

    Vasil'kov, A. Yu.; Migulin, D. A.; Naumkin, A. V.; Zubavichus, Ya. V.; Budnikov, A. V.; Ellert, O. G.; Maksimov, Yu. V.; Muzafarov, A. M.

    2017-11-01

    New hybrid materials based on Pt, Fe, and Pt-Fe nanoparticles stabilized in a matrix of polymethylsilsesquioxane nanogel and ultrahigh molecular weight polyethylene (UHMWPE) were prepared. Metal vapor synthesis was used to produce mono- and bimetallic nanoparticles. It was shown that organosilicon nanogel effectively stabilizes Pt nanoparticles with an average size of 0.9 nm. Using the nanogel results in the formation of superparamagnetic Fe particles 3-5 nm in size that consist of ferromagnetic Fe0 core and antiferromagnetic shells of Fe oxides. It is established that using an organosilicon matrix in the formation of Pt-Fe/UHMWPE systems helps reduce the average particle size of Fe in the material from 6.5 to 4.5 nm and narrow their particle size distribution. The composition, magnetic and electronic characteristics of the nanocomposites are studied via transmission electron microscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, XANES, and EXAFS.

  11. Density Functional Theory Applied to Pt and Pt Alloy Clusters and Adsorbate

    National Research Council Canada - National Science Library

    Smotkin, Eugine

    2001-01-01

    ...). Using this advanced and powerful multiprocessor SGI server, we were able to dramatically speed and further advance our computational Density Functional calculations on CO absorbed on Pt and alloy clusters...

  12. Rapid thermal annealing of FePt and FePt/Cu thin films

    Energy Technology Data Exchange (ETDEWEB)

    Brombacher, Christoph

    2011-01-10

    Chemically ordered FePt is one of the most promising materials to reach the ultimate limitations in storage density of future magnetic recording devices due to its high uniaxial magnetocrystalline anisotropy and a corrosion resistance superior to rare-earth based magnets. In this study, FePt and FePt/Cu bilayers have been sputter deposited at room temperature onto thermally oxidized silicon wafers, glass substrates and self-assembled arrays of spherical SiO{sub 2} particles with diameters down to 10 nm. Millisecond flash lamp annealing, as well as conventional rapid thermal annealing was employed to induce the phase transformation from the chemically disordered A1 phase into the chemically ordered L1{sub 0} phase. The influence of the annealing temperature, annealing time and the film thickness on the ordering transformation and (001) texture evolution of FePt films with near equiatomic composition was studied. Whereas flash lamp annealed FePt films exhibit a polycrystalline morphology with high chemical L1{sub 0} order, rapid thermal annealing can lead to the formation of chemically ordered FePt films with (001) texture on amorphous SiO{sub 2}/Si substrates. The resultant high perpendicular magnetic anisotropy and large coercivities up to 40 kOe are demonstrated. Simultaneously to the ordering transformation, rapid thermal annealing to temperatures exceeding 600 C leads to a break up of the continuous FePt film into separated islands. This dewetting behavior was utilized to create regular arrays of FePt nanostructures on SiO{sub 2} particle templates with periods down to 50 nm. The addition of Cu improves the (001) texture formation and chemical ordering for annealing temperatures T{sub a} {<=}600 C. In addition, the magnetic anisotropy and the coercivity of the ternary FePtCu alloy can be effectively tailored by adjusting the Cu content. The prospects of FePtCu based exchange spring media, as well as the magnetic properties of FePtCu nanostructures fabricated

  13. Electrocatalytic properties of Pt/carbon composite nanofibers

    International Nuclear Information System (INIS)

    Lin Zhan; Ji Liwen; Zhang Xiangwu

    2009-01-01

    Pt/carbon composite nanofibers were prepared by electrodepositing Pt nanoparticles directly onto electrospun carbon nanofibers. The morphology and size of Pt nanoparticles were controlled by the electrodeposition time. The resulting Pt/carbon composite nanofibers were characterized by running cyclic voltammograms in 0.20 M H 2 SO 4 and 5.0 mM K 4 [Fe(CN) 6 ] + 0.10 M KCl solutions. The electrocatalytic activities of Pt/carbon composite nanofibers were measured by the oxidation of methanol. Results show that Pt/carbon composite nanofibers possess the properties of high active surface area and fast electron transfer rate, which lead to a good performance towards the electrocatalytic oxidation of methanol. It is also found that the Pt/carbon nanofiber electrode with a Pt loading of 0.170 mg cm -2 has the highest activity.

  14. L’olivier au Maroc

    Directory of Open Access Journals (Sweden)

    El Mouhtadi Issam

    2014-03-01

    Full Text Available L’olivier est une culture traditionnelle sur le pourtour de la Méditerranée. Il est donc naturel de trouver cet arbre au Maroc où il est présent depuis des siècles. Cultivé surtout traditionnellement jusqu’à ses dernières années, il fait l’objet maintenant d’un plan de valorisation très ambitieux pour non seulement garder le Royaume à son niveau actuel (2e producteur mondial pour l’olive de conserve et 6e pour l’huile d’olive mais pour conquérir de nouveaux marchés au niveau mondial et profiter ainsi de l’engouement que connaît cette huile reconnue pour ses bienfaits. Le plan national « Maroc Vert » permet ainsi, grâce à des subventions conséquentes, non seulement de renouveler les vergers existant avec la variété traditionnelle picholine du Maroc, mais également la plantation de nouvelles variétés en super-intensif dans le but d’industrialiser au maximum de nouveaux vergers. Il en est de même pour la transformation des olives en huile de bonne qualité avec la mise en place d’unités de trituration modernes qui doivent supplanter à terme la multitude de « maâsra » et réduire ainsi l’impact environnemental dû aux margines. L’olive ne sera plus dans l’avenir que représentée par son huile et ses formes comestibles, mais les résidus de son extraction seront valorisés soit sous forme de combustible élaboré pour le grignon, soit sous forme d’une base de chimie verte pour les sous-produits du raffinage. D’autres applications sont actuellement à l’étude, car le Maroc à compris, comme tous les autres grands pays producteurs, que l’olive était un nouveau gisement de richesses.

  15. SELECTIVE HYDROGENATION OF CINNAMALDEHYDE WITH Pt AND Pt-Fe CATALYSTS: EFFECTS OF THE SUPPORT

    Directory of Open Access Journals (Sweden)

    A.B. da Silva

    1998-06-01

    Full Text Available Low-temperature reduced TiO2-supported Pt and Pt-Fe catalysts are much more active and selective for the liquid–phase hydrogenation of cinnamaldehyde to unsaturated cinnamyl alcohol than the corresponding carbon-supported catalysts. High-temperature reduced catalysts, where the SMSI effect should be present, are almost inactive for this reaction. There is at present no definitive explanation for this effect but an electronic metal-support interaction is most probably involved.

  16. 22 CFR 62.31 - Au pairs.

    Science.gov (United States)

    2010-04-01

    ... programs under which foreign nationals are afforded the opportunity to live with an American host family and participate directly in the home life of the host family. All au pair participants provide child care services to the host family and attend a U.S. post-secondary educational institution. Au pair...

  17. Study of Au+Au relativistic collisions with the Fopi-Phase I detector; Etude des collisions relativistes Au+Au avec le detecteur Fopi-Phase I

    Energy Technology Data Exchange (ETDEWEB)

    Dupieux, P.

    1995-01-01

    Au+Au relativistic collisions, in a 100-1000 MeV energy domain per nucleon, are described. Experiments have been carried out with the SIS accelerator at GSI/Darmstadt. Data are analysed with the FOPI-phase I detector. These data are compared with IQMD model (Isospin Quantum Molecular Dynamics) Predictions. (S.G). 80 refs., 77 figs., 5 tabs.

  18. AU-EU “Strategic Partnership”

    DEFF Research Database (Denmark)

    Rodt, Annemarie Peen; Okeke, Jide

    2013-01-01

    This article appraises strategic partnership between the African Union (AU) and European Union (EU). It examines the context and nature of AU and EU security relations and explores the conditions under which partnership has a positive impact in this regard. This includes an evaluation...

  19. Travailler avec Windows 7 au CERN (FR)

    CERN Multimedia

    CERN. Geneva

    2010-01-01

    Vue d'ensemble des nouveaux concepts et des changements dans l'interface utilisateur survenus dans Windows 7 depuis les versions antérieures de Windows (XP ou Vista). La mise à disposition de Windows 7 au CERN et son intégration dans l’infrastructure de Windows au CERN seront présentées.

  20. Strongly bound excitons in monolayer PtS2 and PtSe2

    KAUST Repository

    Sajjad, M.

    2018-01-22

    Based on first-principles calculations, the structural, electronic, and optical properties of monolayers PtS2 and PtSe2 are investigated. The bond stiffnesses and elastic moduli are determined by means of the spring constants and strain-energy relations, respectively. Dynamic stability is confirmed by calculating the phonon spectra, which shows excellent agreement with experimental reports for the frequencies of the Raman-active modes. The Heyd-Scuseria-Ernzerhof functional results in electronic bandgaps of 2.66 eV for monolayer PtS2 and 1.74 eV for monolayer PtSe2. G0W0 calculations combined with the Bethe-Salpeter equation are used to predict the optical spectra and exciton binding energies (0.78 eV for monolayer PtS2 and 0.60 eV for monolayer PtSe2). It turns out that the excitons are strongly bound and therefore very stable against external perturbations.

  1. Analisis Motivasi Kerja Karyawan pada PT. Riau Karsa Pelita Pekanbaru

    OpenAIRE

    Yusrizal, Firdaus; Achnes, Syofia; ", Elvi

    2014-01-01

    This research aims to find out how employee motivation at PT. Riau Karsa Pelita and to find out what factors that affect employee motivation at PT. Riau Karsa Pelita.This research uses descriptive quantitative methods to find out how employee motivation at PT. Pelita Pekanbaru Riau Karsa. As for the respondents in use are all employees of PT Riau Karsa Pelita is drawn using census methods. While the data collection technique in this study using observation, interviews, and questionnaires. By ...

  2. Processing of Ni30Pt20Ti50 High-Temperature Shape-Memory Alloy Into Thin Rod Demonstrated

    Science.gov (United States)

    Noebe, Ronald D.; Draper, Susan L.; Biles, Tiffany A.; Leonhardt, Todd

    2005-01-01

    High-temperature shape-memory alloys (HTSMAs) based on nickel-titanium (NiTi) with significant ternary additions of palladium (Pd), platinum (Pt), gold (Au), or hafnium (Hf) have been identified as potential high-temperature actuator materials for use up to 500 C. These materials provide an enabling technology for the development of "smart structures" used to control the noise, emissions, or efficiency of gas turbine engines. The demand for these high-temperature versions of conventional shape-memory alloys also has been growing in the automotive, process control, and energy industries. However these materials, including the NiPtTi alloys being developed at the NASA Glenn Research Center, will never find widespread acceptance unless they can be readily processed into useable forms.

  3. English for au pairs the au pair's guide to learning English

    CERN Document Server

    Curtis, Lucy

    2014-01-01

    English for Au Pairs has interlinked stories about a group of au pairs new to England. Marta, an 18-year-old from Poland arrives in the UK to work as an au pair. Throughout her year-long stay she has many different experiences - some bad, some good - but with the support of her host family she finds new friends and improves her English. English for Au Pairs offers insight into the joys and difficulties of being an au pair while at the same time reinforcing English language learning through grammar explanations and exercises.

  4. Des fluides au grand fleuve

    OpenAIRE

    Arrago-Boruah, Émilie

    2016-01-01

    À Guwahati, capitale de l’Assam, le fleuve Brahmapoutre s’inscrit depuis quelques décennies dans le paysage urbain comme un élément essentiellement esthétique. Avant cela, il a été le théâtre de multiples affrontements, comme avec les Moghols au xviie siècle, puis la voie d’acheminement préférée de l’East India Company pour exporter les richesses de la région jusqu’à Calcutta. Pour retracer cette évolution, la lecture d’un texte ancien en sanskrit permet d’établir une comparaison entre le fle...

  5. Spontaneous breakdown of PT symmetry in the complex Coulomb ...

    Indian Academy of Sciences (India)

    Keywords. Spontaneous breakdown of PT symmetry; Coulomb potential; complex en- ergy eigenvalues. PACS Nos 03.65.Ge; 03.65.Nk; 11.30.Er. 1. Introduction. One of the most intriguing features of PT -symmetric quantum mechanics is the spontaneous breakdown of PT symmetry. This phenomenon was noted in the first.

  6. Amorphous Pt@PdCu/CNT Catalyst for Methanol Electrooxidation ...

    African Journals Online (AJOL)

    A multi-walled carbon nanotube-supported, Pt decorated nano-sized amorphous PdCu alloy cores (denoted as Pt@PdCu/CNT) catalyst with lower Pt loading is synthesized via a galvanic displacement reaction. The structure is examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM).

  7. Amorphous Pt@PdCu/CNT Catalyst for Methanol Electrooxidation

    African Journals Online (AJOL)

    NICO

    A multi-walled carbon nanotube-supported, Pt decorated nano-sized amorphous PdCu alloy cores (denoted as Pt@PdCu/CNT) catalyst with lower Pt loading is synthesized via a galvanic displacement reaction. The structure is examined using X-ray diffrac- tion (XRD) and transmission electron microscopy (TEM).

  8. Fe Stabilization by Intermetallic L10-FePt and Pt Catalysis Enhancement in L10-FePt/Pt Nanoparticles for Efficient Oxygen Reduction Reaction in Fuel Cells.

    Science.gov (United States)

    Li, Junrui; Xi, Zheng; Pan, Yung-Tin; Spendelow, Jacob S; Duchesne, Paul N; Su, Dong; Li, Qing; Yu, Chao; Yin, Zhouyang; Shen, Bo; Kim, Yu Seung; Zhang, Peng; Sun, Shouheng

    2018-02-28

    We report in this article a detailed study on how to stabilize a first-row transition metal (M) in an intermetallic L1 0 -MPt alloy nanoparticle (NP) structure and how to surround the L1 0 -MPt with an atomic layer of Pt to enhance the electrocatalysis of Pt for oxygen reduction reaction (ORR) in fuel cell operation conditions. Using 8 nm FePt NPs as an example, we demonstrate that Fe can be stabilized more efficiently in a core/shell structured L1 0 -FePt/Pt with a 5 Å Pt shell. The presence of Fe in the alloy core induces the desired compression of the thin Pt shell, especially the two atomic layers of Pt shell, further improving the ORR catalysis. This leads to much enhanced Pt catalysis for ORR in 0.1 M HClO 4 solution (at both room temperature and 60 °C) and in the membrane electrode assembly (MEA) at 80 °C. The L1 0 -FePt/Pt catalyst has a mass activity of 0.7 A/mg Pt from the half-cell ORR test and shows no obvious mass activity loss after 30 000 potential cycles between 0.6 and 0.95 V at 80 °C in the MEA, meeting the DOE 2020 target (fuel cell applications.

  9. Gas-phase experiments on Au(III) photochemistry.

    Science.gov (United States)

    Marcum, Jesse C; Kaufman, Sydney H; Weber, J Mathias

    2011-04-14

    Irradiation of AuCl(4)(-) and AuCl(2)(OH)(2)(-) in the gas-phase using ultraviolet light (220-415 nm) leads to their dissociation. Observed fragment ions for AuCl(4)(-) are AuCl(3)(-) and AuCl(2)(-) and for AuCl(2)(OH)(2)(-) are AuCl(2)(-) and AuClOH(-). All fragment channels correspond to photoreduction of the gold atom to either Au(II) or Au(I) depending on the number of neutral ligands lost. Fragment branching ratios of AuCl(4)(-) are observed to be highly energy dependent and can be explained by comparison of the experimental data to calculated threshold energies obtained using density functional theory. The main observed spectral features are attributed to ligand-to-metal charge transfer transitions. These results are discussed in the context of the molecular-level mechanisms of Au(III) photochemistry.

  10. Magnetic depth profiling of Fe/Au multilayer using neutron ...

    Indian Academy of Sciences (India)

    Au multilayer sample for characterizing the layer structure and magnetic moment density profile. Fe/Au multilayer shows strong spin-dependent scattering at interfaces, making it a prospective GMR material. Fe/Au multilayer with bilayer ...

  11. Limit of detection for the determination of Pt in biological material by RNAA using electrolytic separation of gold

    International Nuclear Information System (INIS)

    Xilei, L.; Heydorn, K.; Rietz, B.

    1992-01-01

    Neutron activation analysis based on the 199 Au indicator for platinum requires the separation of gold at high radiochemical purity. The limit of detection is strongly affected by the presence of gold; with a gold content of 50 pg/g, irradiating for 5 days at 5*10 13 n/cm 2 is needed to achieve a limit of detection of approximately 30 pg/g. In this case the nuclear interference from gold will exceeded the level of platium by several orders of magnitude and has to be determined with exceedingly high precision. Preliminary results for SRM 1577 Bovine Liver with 95% yield gave consistent results for Au, but Pt could not be detected. (author) 23 refs.; 3 figs.; 4 tabs

  12. J /ψ production at low transverse momentum in p +p and d + Au collisions at √{sN N}=200 GeV

    Science.gov (United States)

    Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; di Ruzza, B.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, S.; Gupta, A.; Guryn, W.; Hamad, A. I.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, X.; Huang, B.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Jentsch, A.; Jia, J.; Jiang, K.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z. H.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, X.; Li, Y.; Li, W.; Lin, T.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, R.; Ma, G. L.; Ma, Y. G.; Ma, L.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Matis, H. S.; McDonald, D.; McKinzie, S.; Meehan, K.; Mei, J. C.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Powell, C. B.; Pruthi, N. K.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, S.; Raniwala, R.; Ray, R. L.; Reed, R.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, B.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Summa, B.; Sun, Z.; Sun, X. M.; Sun, Y.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, F.; Wang, G.; Wang, J. S.; Wang, H.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xin, K.; Xu, Y. F.; Xu, Q. H.; Xu, N.; Xu, H.; Xu, Z.; Xu, J.; Yang, S.; Yang, Y.; Yang, Y.; Yang, C.; Yang, Y.; Yang, Q.; Ye, Z.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, X. P.; Zhang, Y.; Zhang, J.; Zhang, J.; Zhang, S.; Zhang, S.; Zhang, Z.; Zhang, J. B.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2016-06-01

    We report on the measurement of J /ψ production in the dielectron channel at midrapidity (|y | from the measured J /ψ invariant cross section in p +p and d +Au collisions are evaluated and compared to similar measurements at other collision energies. The nuclear modification factor for J /ψ is extracted as a function of pT and collision centrality in d +Au and compared to model calculations using the modified nuclear parton distribution function and a final-state J /ψ nuclear absorption cross section.

  13. Pelaksanaan Rekrutmen Pegawai Di PT. KAI DAOP 7 Madiun (Studi Kasus Pada PT. KAI DAOP 7 Madiun)

    OpenAIRE

    Pramudi, Ario Nasty

    2015-01-01

    : Implementation of Employee Recruitment PT. KAI DAOP 7 Madiun (Case Study on PT. KAI DAOP 7 Madison). Implementation of recruitment conducted by PT. KAI DAOP 7 Madiun always experience growth in every implementation, it aims to improve the quality of employees resulting from the recruitment process. See vital means of rail transport in Indonesia it is indeed absolutely must be done. With increasing quality of human resources owned by PT. KAI DAOP 7 Madiun will certainly improve the quality o...

  14. Role of Pt(0) in bimetallic (Pt,Fe)-FER catalysts in the N2O decomposition

    Czech Academy of Sciences Publication Activity Database

    Tabor, Edyta; Jíša, Kamil; Nováková, Jana; Bastl, Zdeněk; Vondrová, Alena; Závěta, K.; Sobalík, Zdeněk

    2013-01-01

    Roč. 165, JAN 2013 (2013), s. 40-47 ISSN 1387-1811 R&D Projects: GA ČR GA203/09/1627 Institutional support: RVO:61388955 Keywords : bimetallic Pt,Fe-FER * Pt-FER * Pt(0) clusters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.209, year: 2013

  15. Magma Fertility is the First-Order Factor for the Formation of Porphyry Cu±Au Deposits

    Science.gov (United States)

    Park, J. W.; Campbell, I. H.; Malaviarachchi, S. P. K.; Cocker, H.; Nakamura, E.; Kay, S. M.

    2017-12-01

    Magma fertility, the metal abundance in magma, has been considered to be one of the key factors for the formation of porphyry Cu±Au deposits. In this study we provide clear evidence to support the hypothesis that the platinum group element (PGE) can be used to distinguish barren from ore-bearing Cu±Au felsic suites. We determined the PGE contents of three barren volcanic and subvolcanic suites from Argentina and Japan, and compare the results with two porphyry Cu-bearing subvolcanic suites from Chile and two porphyry Cu-Au-bearing suites from Australia. The barren suites are significantly depleted in PGE abundances by the time of fluid exsolution, which is attributed to early sulfide saturation at mid to lower crust depths or assimilation of chalcophile element-poor crustal materials. Barren magma, produced by melting continental crust, may have been initially deficient in chalcophile elements. In contrast, the Cu±Au ore-bearing suites contain at least an order of magnitude higher PGE contents than those of the barren suites by the time of fluid saturation. They are characterized by late sulfide saturation in a shallow magma chamber, which allows the chalcophile elements to concentrate in the fractionating magma from which they are sequestered by ore-forming fluids. We suggest the Pd/MgO and Pd/Pt ratios of igneous rocks can be used as magma fertility indicators, and to distinguish between barren, porphyry Cu and porphyry Cu-Au magmatic systems.

  16. Crystal phase-based epitaxial growth of hybrid noble metal nanostructures on 4H/fcc Au nanowires

    Science.gov (United States)

    Lu, Qipeng; Wang, An-Liang; Gong, Yue; Hao, Wei; Cheng, Hongfei; Chen, Junze; Li, Bing; Yang, Nailiang; Niu, Wenxin; Wang, Jie; Yu, Yifu; Zhang, Xiao; Chen, Ye; Fan, Zhanxi; Wu, Xue-Jun; Chen, Jinping; Luo, Jun; Li, Shuzhou; Gu, Lin; Zhang, Hua

    2018-03-01

    Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires. Moreover, the method can be extended to the epitaxial growth of Rh, Ru-Rh and Ru-Pt nanorods on the 4H/fcc Au nanowires to form unique hybrid nanowires. Importantly, the Au-Ru hybrid nanowires with tunable compositions exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction in alkaline media.

  17. CoPt nanoparticles by chemical reduction

    International Nuclear Information System (INIS)

    Wang, H.L.; Zhang, Y.; Huang, Y.; Zeng, Q.; Hadjipanayis, G.C.

    2004-01-01

    CoPt nanoparticles with a size of 1-2 nm were synthesized by chemical reduction using the solvents of water and alcohol. A phase transformation from the originally disordered face centered cubic (FCC) structure to an ordered face centered tetragonal L1 0 structure occurred after annealing, which results in the coercivity up to 9 kOe because of the high anisotropy of the tetragonal phase (K∼2-4x10 7 erg/cm 3 ) (Philos. Mag. 13 (1966) 567; IEEE Trans. Magn. 20 (1984) 1625). HREM images of as-grow Co 48 Pt 52 shows the single-crystalline FCC structure with the shape of columnar and spherical

  18. Evaluasi Sistem Informasi Penjualan PT SPNS

    Directory of Open Access Journals (Sweden)

    Anderes Gui

    2010-06-01

    Full Text Available The purpose of this paper is to identify and analyze problems that occur in information systems sales PT SPNS. It also serves to control the management and control of applications running well so it can produce accurate information for decision making. The method used is book study method and field study. Study was done by reading library books, scientific papers and other sources, while the field study was done by observation, interviews, and questionnaires. The result of the evaluation is derived from the respective strengths and weaknesses - each control. Weaknesses are found, the findings presented in the form of a matrix that contains the findings and recommendations as a matter of risk remedial action. Conclusions obtained from the audit for security control, operations, limitations, input and output is good enough because it can satisfy and support the sales activities of PT SPNS.

  19. Half-Lantern Pt(II and Pt(III Complexes. New Cyclometalated Platinum Derivatives

    Directory of Open Access Journals (Sweden)

    Violeta Sicilia

    2014-08-01

    Full Text Available The divalent complex [{Pt(bzq(μ-L}2] (1 [Hbzq = benzo[h]quinolone, HL = CF3C4H2N2SH: 4-(trifluoromethylpyrimidine-2-thiol] was obtained from equimolar amounts of [Pt(bzq(NCMe2]ClO4 and 4-(trifluoromethylpyrimidine-2-thiol with an excess of NEt3. The presence of a low intensity absorption band at 486 nm (CH2Cl2, assignable to a metal-metal-to-ligand charge transfer transition (1MMLCT [dσ*(Pt2→π*(bzq], is indicative of the existence of two platinum centers located in close proximity because the rigidity of the half-lantern structure allows the preservation of these interactions in solution. Compound 1 undergoes two-electron oxidation upon treatment with halogens X2 (X2: Cl2, Br2 or I2 to give the corresponding dihalodiplatinum (III complexes [{Pt(bzq(μ-LX}2] (L = CF3C4H2N2S-κN,S; X: Cl 2, Br 3, I 4. Complexes 2–4 were also obtained by reaction of 1 with HX (molar ratio 1:2, 10% excess of HX in THF with yields of about 80% and compound 2 was also obtained by reaction of [{Pt(bzq(μ-Cl}2] with HL (4-(trifluoromethylpyrimidine-2-thiol in molar ratio 1:2 in THF, although in small yield. The X-ray structures of 2 and 3 confirmed the half-lantern structure and the anti configuration of the molecules. Both of them show Pt–Pt distances (2.61188(15 Å 2, 2.61767(16 Å 3 in the low range of those observed in Pt2(III,IIIX2 half-lantern complexes.

  20. PtRu/C electrocatalysts prepared using electron beam irradiation

    Directory of Open Access Journals (Sweden)

    Dionísio Furtunato da Silva

    2007-12-01

    Full Text Available PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles were prepared submitting water/ethylene glycol mixtures containing Pt(IV and Ru(III ions and the carbon support to electron beam irradiation. The electrocatalysts were characterized by energy dispersive X ray analysis (EDX, X ray diffraction (XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts showed superior performance for methanol electro-oxidation at room temperature compared to commercial PtRu/C electrocatalyst.

  1. Phase transformations during sintering of mechanically alloyed TiPt

    CSIR Research Space (South Africa)

    Nxumalo, S

    2010-10-01

    Full Text Available first and high temperature melting phases form last12. This behaviour is what is observed in this work with the four phases with low melting points being formed which are Ti(Pt), Ti3Pt, TiPt and Ti3Pt5. It is therefore, probable that phase formation.... 1.0 Introduction TiPt is a potential alloy for use as a high temperature shape memory alloy (SMA). Shape memory alloys are alloys that will revert to the shape they had before deformation if the deformed alloy is annealed at a certain temperature...

  2. Hydrophilic Pt nanoflowers: synthesis, crystallographic analysis and catalytic performance.

    Science.gov (United States)

    Mourdikoudis, Stefanos; Altantzis, Thomas; Liz-Marzán, Luis M; Bals, Sara; Pastoriza-Santos, Isabel; Pérez-Juste, Jorge

    2016-05-21

    Water-soluble Pt nanoflowers (NFs) were prepared by diethylene glycol-mediated reduction of Pt acetylacetonate (Pt(acac) 2 ) in the presence of polyethylenimine. Advanced electron microscopy analysis showed that the NFs consist of multiple branches with a truncated cubic morphology and different crystallographic orientations. We demonstrate that the nature of the solvent strongly influences the resulting morphology. The catalytic performance of the Pt NFs in 4-nitrophenol reduction was found to be superior to that of other nanoparticle-based catalysts. Additionally, the Pt NFs display good catalytic reusability with no loss of activity after five consecutive cycles.

  3. Transformace ptDNA Chlamydomonas reinhardtii

    OpenAIRE

    HUSÁKOVÁ, Jana

    2011-01-01

    The aim of this master thesis was to test and compare two available methods of genetic transformation (biolistics, electroporation) of the plastid genome of green algae Chlamydomonas reinhardtii. For biolistic transformation a wide range of experimental parameters which generally influence ptDNA transformation efficiency was optimized: physiological condition of acceptor cells, type and size of microparticles, pressure of propulsion gas (helium), length of projectile trajectory, transformatio...

  4. Domainal fabric development, associated microstructures and PT ...

    Indian Academy of Sciences (India)

    The granulite complex around Jenapore, Orissa, Eastern Ghats granulite belt, bears the imprint of two episodes of strong deformation (D1 and D2) attended with foliation (fabric) development (S1 and S2). Two distinct metamorphic events at P-T conditions of ∼900° C at ∼9 kbar and ∼600° C at ∼6 kbar are correlated with ...

  5. Magnetism of FePt Thin Films

    Science.gov (United States)

    Alqhtany, Norah H.

    Materials with large magnetic anisotropy have received significant attention from the scientific community due to its advantages in technological applications. Equiatomic FePt has been identified as such a material which could possibly be a potential candidate for ultra- high density magnetic recording and other applications like permanent magnets. FePt thin films exhibit ordered L10 texture with high magnetocrystalline anisotropy and high saturation magnetization which seem lucrative for technological applications. This thesis presents an investigation of structural and magnetic properties of granular and epitaxial FePt films with L10 phase prepared by DC sputtering on different substrates (SrTiO3 and glass). X-ray Diffraction (XRD), Atomic Force Microscopy/Magnetic Force Microscopy (AFM/MFM) and Vibrating Sample Magnetometer (VSM) were employed in characterization process. The measurements obtained from these equipment were significant in establishing the relationship between the microstructure and the magnetic properties of these films. The symmetry and magnitude of magnetic anisotropy has also been analyzed and discussed in detail.

  6. Controlled Synthesis of Au@AgAu Yolk-Shell Cuboctahedra with Well-Defined Facets.

    Science.gov (United States)

    Londono-Calderon, Alejandra; Bahena, Daniel; Yacaman, Miguel J

    2016-08-02

    The synthesis of Au@AgAu yolk-shell cuboctahedra nanoparticles formed by galvanic replacement in a seed-mediated method is described. Initially, single-crystal Au seeds are used for the formation of Au@Ag core-shell nanocubes, which serve as the template material for the deposition of an external Au layer. The well-controlled synthesis yields the formation of cuboctahedra nanoparticles with smooth inner and outer Au/Ag surfaces. The deposition/oxidation process is described to understand the formation of cuboctahedra and octahedra nanoparticles. The Au core maintains the initial morphology of the seed and remains static at the center of the yolk-shell because of residual Ag. Structural analysis of the shell indicates intrinsic stacking faults (SFs) near the surface. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) compositional analysis show an Au-Ag nonordered alloy forming the shell. The three-dimensional structure of the nanoparticles presented open facets on the [111] as observed by electron tomography SIRT reconstruction over a stack of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images. The geometrical model was validated by analyzing the direction of streaks in coherent nanobeam diffraction (NBD). The catalytic activity was evaluated using a model reaction based on the reduction of 4-nitrophenol (4-NTP) by NaBH4 in the presence of Au@AgAu yolk-shell nanoparticles.

  7. Density functional theory studies of the adsorption of ethylene and oxygen on Pt(111) and Pt3Sn(111)

    DEFF Research Database (Denmark)

    Watwe, R.M.; Cortright, R.D.; Mavrikakis, Manos

    2001-01-01

    Density functional theory, employing periodic slab calculations, was used to investigate the interactions of ethylene and oxygen with Pt(111) and Pt3Sn(111). The predicted energetics and structures of adsorbed species on Pt(111) are in good agreement with experimental data. The binding energies...... of pi -bonded ethylene, di-sigma -bonded ethylene, and ethylidyne species are weaker on Pt3Sn(111) than on Pt(111) by 21, 31, and 50 kJ/mol, respectively. Hence, the electronic effect of Sn on the adsorption of ethylene depends on the type of adsorption site, with adsorption on three-fold site weakened...

  8. Et pourquoi pas au CERN ?

    CERN Multimedia

    Staff Association

    2015-01-01

    Télétravail ou travail à distance, aménagement des horaires de travail et autres évolutions favorables à un meilleur équilibre vie privée et vie professionnelle sont adoptés par nombre d’entreprises et d’organisations !   Rendu possible grâce au développement de nouvelles technologies dont Internet, le travail à distance séduit de plus en plus de personnels, ainsi que de plus en plus de sociétés qui y trouvent des avantages en matière de gestion de l’espace, de sécurité (moins de trajets domicile-entreprise), de développement durable (moins de pollution), de motivation et de bien-être de leurs personnels. Les horaires aménagés, voire les « core-hours1 », sont également des pratiques de plus e...

  9. Hydrothermal synthesis of size-dependent Pt in Pt/MWCNTs nanocomposites for methanol electro-oxidation

    International Nuclear Information System (INIS)

    Chen Liang; Lu Gongxuan

    2008-01-01

    A hydrothermal method has been developed to prepare size-controlled Pt nanoparticles dispersed highly on multiwalled carbon nanotubes (Pt/MWCNTs). It was found that the size of Pt nanoparticles was strongly dependent on the solution pH in synthesis. The Pt nanoparticles with mean size of 3.0, 4.2 and 9.1 nm were obtained at pHs 13, 12 and 10 separately. After Pt/MWCNTs composites were fabricated, the different properties of cyclic voltammetry and chronoamperometry in electro-oxidation of methanol were found. The results showed that the smaller diameter Pt deposited Pt/MWCNTs nanocomposites exhibited higher electrocatalytic activity for methanol oxidation. By characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), size-dependent activities were identified

  10. Correlating Structure and Oxygen Reduction Activity on Y/Pt(111) and Gd/Pt(111) Single Crystals

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese; Pedersen, Anders Filsøe; Johansson, Tobias Peter

    2015-01-01

    of this technology. Improving the activity of Pt by alloying it with other metals could decrease the loading of Pt at the cathode to a level comparable to Pt-group metal loading in internal combustion engines. PtxY and PtxGd exhibit exceptionally high activity for oxygen reduction, both in the polycrystalline form...... and the nanoparticulate form. [1,2,3,4]. Moreover, their negative alloying energy may make them inherently less prone to degradation via dealloying than the more commonly investigated alloys of Pt and late transition metals such as Ni, Co, Fe and Cu. In order to understand the origin of the enhanced activity...... of these alloys, we have investigated Y/Pt(111) [5] and Gd/Pt(111) single crystals, formed by depositing large amounts of Y and Gd on Pt(111) single crystals under Ultra-High Vacuum (UHV) conditions and annealing to high temperatures. We subsequently characterised the surface using low energy electron diffraction...

  11. Substrate effects on the analysis of biomolecular layers using Au+, Au3+ and C60+ bombardments

    International Nuclear Information System (INIS)

    Kordys, Jeanette; Fletcher, John S.; Lockyer, Nicholas P.; Vickerman, John C.

    2008-01-01

    Effects of platinum silicon, graphite and PET substrates on the secondary ion yield of sub-monolayer and multilayer samples of Cyclosporin A following 20 keV Au + , Au 3 + and C 60 + impacts have been investigated. The obtained results of sub-monolayer samples show that platinum enhances the yield of the pseudo-molecular ion following Au + and Au 3 + impacts due to the high density of the substrate that enables the energy of the primary ions to be deposited near the surface. C 60 + impacts on sub-monolayer samples are less effective, but there is an enhancement on PET substrates. Impacts of 20 keV Au + and Au 3 + are not very efficient on multilayer samples. 20 keV C 60 + impacts enhance the yields significantly, especially for the relatively high molecular weight [M+H] + ion.

  12. Electrochemical Synthesis of Ammonia from Water and Nitrogen using a Pt/GDC/Pt Cell

    International Nuclear Information System (INIS)

    Kim, Jong Nam; Yoo, Chung-Yul; Joo, Jong Hoon; Yu, Ji Haeng; Sharma, Monika; Yoon, Hyung Chul; Jeoung, Hana; Song, Ki Chang

    2014-01-01

    Electrochemical ammonia synthesis from water and nitrogen using a Pt/GDC/Pt cell was experimentally investigated. Electrochemical analysis and ammonia synthesis in the moisture-saturated nitrogen environment were performed under the operating temperature range 400-600 .deg. C and the applied potential range OCV (Open Circuit Voltage)-1.2V. Even though the ammonia synthesis rate was augmented with the increase in the operating temperature (i.e.. increase in the applied current) under the constant potential, the faradaic efficiency was decreased because of the limitation of dissociative chemisorption of nitrogen on the Pt electrode. The maximum synthesis rate of ammonia was 3.67x10 -11 mols -1 cm -2 with 0.1% faradaic efficiency at 600 .deg. C

  13. Intense fluorescence of Au 20

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Chongqi; Harbich, Wolfgang; Sementa, Luca; Ghiringhelli, Luca; Apra, Edoardo; Stener, Mauro; Fortunelli, Alessandro; Brune, Harald

    2017-08-21

    Ligand-protected Au clusters are non-bleaching fluorescence markers in bio- and medical applications. We show that their fluorescence is an intrinsic property of the Au cluster itself. We find a very intense and sharp fluorescence peak located at λ =739.2 nm (1.68 eV) for Au20 clusters in a Ne matrix held at 6 K. The fluorescence reflects the HOMO-LUMO diabatic bandgap of the cluster. The cluster shows a very rich absorption fine structure reminiscent of well defined molecule-like quantum levels. These levels are resolved since Au20 has only one stable isomer (tetrahedral), therefore our sample is mono-disperse in cluster size and conformation. Density-functional theory (DFT) and time-dependent DFT calculations clarify the nature of optical absorptionand predict both main absorption peaks and intrinsic fluorescence in good agreement with experiment.

  14. Amélioration de la nutrition au Cambodge au moyen de l ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Amélioration de la nutrition au Cambodge au moyen de l'aquaculture et des jardins potagers domestiques (FCRSAI). Si l'on produit au Cambodge suffisamment de riz pour nourrir la population, la sous-alimentation maternelle et infantile y demeure quand même élevée en raison de la faible diversification des cultures et du ...

  15. Prévention de la violence chez les jeunes au Guatemala, au ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Prévention de la violence chez les jeunes au Guatemala, au Honduras et au Salvador. La violence chez les jeunes, que ceux-ci en soient victimes ou responsables, est l'un des problèmes les plus importants en Amérique centrale. Ce projet de recherche servira à évaluer les stratégies actuelles de prévention de la violence ...

  16. Proton channeling in Au at low energies

    International Nuclear Information System (INIS)

    Valdes, J.E.; Vargas, P.

    1996-01-01

    The electronic energy loss for low velocity protons channeled in the direction single crystal Au is calculated. The spatial distribution of valence electronic density in Au is calculated using Tight Binding Linear Muffin Tin Method. The proton trajectories are determined by numerical integration of the classical motion equation, and the energy loss is evaluated using the calculated valence electronic density in the friction term. The results allow to describe qualitatively the non linear behavior of energy loss with ion velocity observed experimentally. (author)

  17. Accidents Vasculaires Cerebraux (AVC) au Centre Hospitalier ...

    African Journals Online (AJOL)

    But: décrire les aspects épidémiologiques et évolutifs des AVC au CHU Kara. Méthodologie: Il s'est agi d'une étude prospective transversale monocentrique de cas d'AVC colligés du 1er juillet 2014 au 31 décembre 2015 dans le service de neurologie du CHU- KARA. Résultats: Cent soixante-quatre (164) patients ont ...

  18. Unravelling Thiol’s Role in Directing Asymmetric Growth of Au Nanorod–Au Nanoparticle Dimers

    KAUST Repository

    Huang, Jianfeng

    2015-12-15

    Asymmetric nanocrystals have practical significance in nanotechnologies but present fundamental synthetic challenges. Thiol ligands have proven effective in breaking the symmetric growth of metallic nanocrystals but their exact roles in the synthesis remain elusive. Here, we synthesized an unprecedented Au nanorod-Au nanoparticle (AuNR-AuNP) dimer structure with the assistance of a thiol ligand. On the basis of our experimental observations, we unraveled for the first time that the thiol could cause an inhomogeneous distribution of surface strains on the seed crystals as well as a modulated reduction rate of metal precursors, which jointly induced the asymmetric growth of monometallic dimers. © 2015 American Chemical Society.

  19. Apprentissages techniques : L'apprentissage au CERN

    CERN Multimedia

    2004-01-01

    APPRENTISSAGES TECHNIQUES GESTION ET DEVELOPPEMENT DU PERSONNEL HR/PMD L'APPRENTISSAGE AU CERN pour les professions d'électronicien(ne) et de laborantin(e) en physique L'apprentissage au CERN est régi par les lois, règlements et contrats en vigueur dans le Canton de Genève. En cas de réussite à l'examen de fin d'apprentissage, les apprentis obtiennent le Certificat Fédéral de Capacité Suisse (CFC). 7 places au total sont ouvertes au recrutement pour les deux professions. L'apprentissage dure 4 ans. Minima requis pour faire acte de candidature : • avoir au moins 15 ans et moins de 21 ans à la date de début de l'apprentissage • avoir terminé la scolarité obligatoire, au minimum 9ème du Cycle d'orientation genevois (3ème en France) • être ressortissant d'un pays membre du CERN (Allemagne, Autriche, Belgiqu...

  20. Synchrotron radiation based multi-scale structural characterization of CoPt{sub 3} colloidal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zargham, Ardalan

    2010-08-05

    Bimetallic CoPt{sub 3} nanoparticles represent a category of colloidal nanoparticles with high application potentials in, e.g., heterogeneous catalysis, sensor technology, and magnetic storage media. Deposition of this system on functionalized supports delivers opportunities for controlled immobilization of the nanoparticles. In this work, self-assembled monolayers (SAMs) of n-alkanethiol molecules served as functionalizing material for the Au covered Si substrates. Deposition of the ligand-terminated nanoparticles took place by means of spin and dip coating and has been optimized for each of the mentioned methods so that monolayers of nanoparticles on supports were fabricated with a well-controlled coverage The morphology of the nanoparticle film arranged is addressed by grazing-incidence small angle x-ray scattering (GISAXS). This together with x-ray standing waves in total external reflection (TER-XSW) enables a 3D structural characterization of such nanoparticle films, so that the mean particle size, mean distance of the arranged nanoparticle films to the substrate, as well as the mean particle-particle distance in lateral direction have been determined. TER-XSW, being an element-specific position-sensitive method, also reveals the elemental distribution of the particles which complementary provides a fundamental understanding of their internal structure. The CoPt{sub 3} nanoparticles investigated here exhibit a core-shell-like structure with cores of CoPt{sub 3} and shells mainly comprise Co. The results regarding the internal structure of the nanoparticles were then verified by extended X-ray absorption fine structure (EXAFS) measurements. (orig.)