WorldWideScience

Sample records for pt activated partial

  1. Coupled Oscillator Systems Having Partial PT Symmetry

    CERN Document Server

    Beygi, Alireza; Bender, Carl M

    2015-01-01

    This paper examines chains of $N$ coupled harmonic oscillators. In isolation, the $j$th oscillator ($1\\leq j\\leq N$) has the natural frequency $\\omega_j$ and is described by the Hamiltonian $\\frac{1}{2}p_j^2+\\frac{1}{2}\\omega_j^2x_j^2$. The oscillators are coupled adjacently with coupling constants that are purely imaginary; the coupling of the $j$th oscillator to the $(j+1)$st oscillator has the bilinear form $i\\gamma x_jx_{j+1}$ ($\\gamma$ real). The complex Hamiltonians for these systems exhibit {\\it partial} $\\mathcal{PT}$ symmetry; that is, they are invariant under $i\\to-i$ (time reversal), $x_j\\to-x_j$ ($j$ odd), and $x_j\\to x_j$ ($j$ even). [They are also invariant under $i\\to-i$, $x_j\\to x_j$ ($j$ odd), and $x_j\\to- x_j$ ($j$ even).] For all $N$ the quantum energy levels of these systems are calculated exactly and it is shown that the ground-state energy is real. When $\\omega_j=1$ for all $j$, the full spectrum consists of a real energy spectrum embedded in a complex one; the eigenfunctions correspondi...

  2. Topological states in partially-PT-symmetric azimuthal potentials

    CERN Document Server

    Kartashov, Yaroslav V; Torner, Lluis

    2015-01-01

    We introduce partially-parity-time-symmetric (pPT-symmetric) azimuthal potentials composed from individual PT-symmetric cells located on a ring, where two azimuthal directions are nonequivalent in a sense that in such potentials excitations carrying topological dislo-cations exhibit different dynamics for different directions of energy circulation in the initial field distribution. Such non-conservative ratchet-like structures support rich families of stable vortex solitons in cubic nonlinear media, whose properties depend on the sign of the topological charge due to the nonequivalence of azimuthal directions. In contrast, oppositely charged vortex solitons remain equivalent in similar fully PT-symmetric potentials. The vortex solitons in the pPT- and PT-symmetric potentials are shown to feature qualitatively different internal current distributions, which are described by different discrete rotation symmetries of the intensity profiles.

  3. 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...

  4. Partial oxidation and CO{sub 2} reforming of methane on Pt/Al{sub 2}O{sub 3}, Pt/ZrO{sub 2}, and Pt/Ce-ZrO{sub 2} catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Mattos, L.V.; Noronha, F.B. [Instituto Nacional de Tecnologia-INT, Av. Venezuela 82, Rio de Janeiro CEP 20081-310 (Brazil); Rodino, E.; Passos, F.B. [Departamento de Engenharia Quimica e Programa de Pos-Graduacao em Quimica Organica, Universidade Federal Fluminense, Rua Passos da Patria, 156, Niteroi CEP 24210-230 (Brazil); Resasco, D.E. [School of Chemical Engineering and Materials Science, University of Oklahoma, 100 East Boyd Street, Norman, OK 73019 (United States)

    2003-09-15

    The partial oxidation and CO{sub 2} reforming of methane were studied on Pt/Al{sub 2}O{sub 3}, Pt/ZrO{sub 2}, and Pt/Ce-ZrO{sub 2} catalysts. The reducibility and the oxygen transfer capacity were evaluated by oxygen storage capacity (OSC). The effect of the support on the cleaning mechanism of the catalyst surface was investigated by the sequence of CH{sub 4}/O{sub 2} and CH{sub 4}/CO{sub 2} pulses. The Pt/Ce-ZrO{sub 2} catalyst showed the highest stability on both partial oxidation and CO{sub 2} reforming of methane. The results were explained by the higher reducibility and oxygen storage/release capacity of Pt/Ce-ZrO{sub 2} catalysts, which allowed a continuous removal of carbonaceous deposits from the active sites, favoring the stability of the catalysts, as revealed by the CH{sub 4}/O{sub 2} and CH{sub 4}/CO{sub 2} pulses. For Pt/Al{sub 2}O{sub 3} and Pt/ZrO{sub 2} catalysts, the increase of carbon deposits around or near the metal particle inhibits the CO{sub 2} dissociation on CO{sub 2} reforming of methane. This effect on the CO{sub 2} reforming of methane affects the partial oxidation of methane, which comprehends two steps: combustion of methane and CO{sub 2} and steam reforming of unreacted methane.

  5. Partial oxidation of dimethyl ether to H2/syngas over supported Pt catalyst

    Institute of Scientific and Technical Information of China (English)

    Yazhong Chen; Zongping Shao; Nanping Xu

    2008-01-01

    Dimethyl ether (DME) is a non-toxic fuel with high H/C ratio and high volumetric energy density, and could be served as an ideal source of H2/syngas production for application in solid oxide fuel cells (SOFC). This study presents results of DME partial oxidation over a 1.5 wt% Pt/Ceo.4 Zro.6O2 catalyst under the condition of gas hourly space velocity (GHSV) of 15000-60000 ml/(gh), molar ratio of O2/DME of 0.5 and 500-700 ℃, and this temperature range was also the operation temperature range for intermediate temperature SOFC. The results indicated that the catalyst showed good activity for the selective partial oxidation of DME to H2/syngas. Under the working conditions investigated, DME was completely converted. Increase in reaction temperature enhanced the amount of syngas, but lowered the H2/CO ratio and yield of methane; while increase in reaction GHSV resulted in only slight variation in the distribution of products. The good catalytic activity of Pt supported on Ceo.4Zro.6O2 for the partial oxidation of DME may be directly associated with the good oxygen storage capacity of the support, which is worth of further investigation to develop materials for application in SOFC.

  6. More on PT-Symmetry in (Generalized Effect Algebras and Partial Groups

    Directory of Open Access Journals (Sweden)

    J. Paseka

    2011-01-01

    Full Text Available We continue in the direction of our paper on PT-Symmetry in (Generalized Effect Algebras and Partial Groups. Namely we extend our considerations to the setting of weakly ordered partial groups. In this setting, any operator weakly ordered partial group is a pasting of its partially ordered commutative subgroups of linear operators with a fixed dense domain over bounded operators. Moreover, applications of our approach for generalized effect algebras are mentioned.

  7. Oxygen reduction activity of Pt and Pt-alloys in acid electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Paulus, Ursula A. [Paul Scherrer Inst., CH-5232 Villigen PSI (Switzerland); Schmidt, Thomas J.; Stamenkovic, Vojislav R.; Markovic, Nenad M.; Ross, Philip N. [Material Science Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

    2001-07-01

    The oxygen reduction reaction (ORR) has been studied on polycrystalline (pc) Pt, Pt{sub 3}Ni and Pt{sub 3}Co bulk alloy electrodes and on carbon supported Pt, PtNi and PtCo alloy catalysts. Base voltammetry measurements as well as complementary Auger Electron Spectroscopy (AES) and Low Energy Ion Scattering (LEIS) on bulk electrodes and High Resolution Transmission Electron Microscopy (HRTEM)-analysis on the supported catalysts allow an estimation of the surface composition. By using the rotating ring-disk electrode (RRDE) technique both the kinetic analysis of the ORR and in parallel the detection and quantification of the amount of peroxide produced during the ORR are possible. The activity for the ORR increases in the order Pt < Pt{sub 3}Ni < Pt{sub 3}Co for equally prepared bulk alloys and Pt < Pt{sub 3}Ni {approx} Pt{sub 3}CO < PtCo for the carbon supported catalysts, respectively. It was proposed that the mechanism for the ORR is the same on pure Pt and the PtNi and PtCo alloys. (author)

  8. Highly active Pt3Pb and core-shell Pt3Pb-Pt electrocatalysts for formic acid oxidation.

    Science.gov (United States)

    Kang, Yijin; Qi, Liang; Li, Meng; Diaz, Rosa E; Su, Dong; Adzic, Radoslav R; Stach, Eric; Li, Ju; Murray, Christopher B

    2012-03-27

    Formic acid is a promising chemical fuel for fuel cell applications. However, due to the dominance of the indirect reaction pathway and strong poisoning effects, the development of direct formic acid fuel cells has been impeded by the low activity of existing electrocatalysts at desirable operating voltage. We report the first synthesis of Pt(3)Pb nanocrystals through solution phase synthesis and show they are highly efficient formic acid oxidation electrocatalysts. The activity can be further improved by manipulating the Pt(3)Pb-Pt core-shell structure. Combined experimental and theoretical studies suggest that the high activity from Pt(3)Pb and the Pt-Pb core-shell nanocrystals results from the elimination of CO poisoning and decreased barriers for the dehydrogenation steps. Therefore, the Pt(3)Pb and Pt-Pb core-shell nanocrystals can improve the performance of direct formic acid fuel cells at desired operating voltage to enable their practical application. © 2012 American Chemical Society

  9. Valores de referência do tempo de protrombina (TP e tempo de tromboplastina parcial ativada (TTPa em cães Reference ranges of prothrombin time (PT and activated partial thromboplastin time (aPTT in dogs

    Directory of Open Access Journals (Sweden)

    Sonia Terezinha dos Anjos Lopes

    2005-04-01

    Full Text Available Os fatores de coagulação são parte integrante da hemostasia normal, e tanto as coagulopatias hereditárias como adquiridas que envolvem este sistema são de grande importância veterinária, geralmente evidenciadas por manifestações clínicas, tais como, petéquias, equimoses, hematomas e sangramentos tardios. O presente trabalho teve por objetivo a determinação dos valores de referência do tempo de protrombina (TP e tempo de tromboplastina parcial ativada (TTPa, por métodos manuais. Para tanto, utilizou-se "kits" para dosagens humanas, devido à inexistência de produtos similares de uso específico veterinário. Foram utilizados 40 cães clinicamente sadios, sem raça definida, machos ou fêmeas, de diferentes idades. As amostras sanguíneas foram de 2,5ml cada, colhidas por venopunção cefálica e acondicionadas em tubos de centrífuga contendo 0,25ml de citrato de sódio a 3,8%. O plasma foi imediatamente separado por centrifugação e as determinações de TP e TTPa foram realizadas utilizando-se "kits" comerciais "HemoStat Thromboplastin-SIª" e "HemoStat aPTT-El b", respectivamente. Os resultados obtidos foram de 6,87 ± 1,4 segundos para o TP com valores mínimo e máximo de 4,07 e 9,67, respectivamente, e de 15,10 ± 1,6 segundos para TTPa com valores mínimo e máximo de 11,9 e 18,3, respectivamente. Conclui-se, que os valores obtidos neste trabalho podem ser utilizados como referência. Os reagentes utilizados para plasma humano podem ser empregados para o plasma de cães.The coagulation factors are part of normal hemostasis, and both hereditary and acquired coagulopathies that involve this system have an important role in veterinary medicine, generally evidenced by clinical signs such as: petechias, ecchymosis, hematomas and late hemorrhagies. The objective of this experiment was to determine reference range values of prothrombin time (PT and activated partial thromboplastin time (aPTT, for manual methods. Human commercial

  10. PT AND PT/NI "NEEDLE" ELETROCATALYSTS ON CARBON NANOTUBES WITH HIGH ACTIVITY FOR THE ORR

    Energy Technology Data Exchange (ETDEWEB)

    Colon-Mercado, H.

    2011-11-10

    Platinum and platinum/nickel alloy electrocatalysts supported on graphitized (gCNT) or nitrogen doped carbon nanotubes (nCNT) are prepared and characterized. Pt deposition onto carbon nanotubes results in Pt 'needle' formations that are 3.5 nm in diameter and {approx}100 nm in length. Subsequent Ni deposition and heat treatment results in PtNi 'needles' with an increased diameter. All Pt and Pt/Ni materials were tested as electrocatalysts for the oxygen reduction reaction (ORR). The Pt and Pt/Ni catalysts showed excellent performance for the ORR, with the heat treated PtNi/gCNT (1.06 mA/cm{sup 2}) and PtNi/nCNT (0.664 mA/cm{sup 2}) showing the highest activity.

  11. Superior long-term activity for a Pt-Re alloy compared to Pt in methanol oxidation reactions

    Science.gov (United States)

    Duke, Audrey S.; Xie, Kangmin; Monnier, John R.; Chen, Donna A.

    2017-03-01

    Pt-Re bimetallic catalysts have shown enhanced activity compared to pure Pt for reactions involving oxidation, but the origins of this improved activity are not fully understood. Methanol oxidation on a Pt-Re alloy surface and pure Pt foil was studied in a microreactor coupled to an ultrahigh vacuum chamber. For reaction at 60 °C, the Pt-Re alloy surface exhibits superior long-term activity over a 24 h reaction period compared to pure Pt. The initial activity of Pt is 10-15% higher than on Pt-Re; however, the Pt surface gradually loses activity after 10 h online, whereas the activity of Pt-Re does not diminish. Post-reaction XPS shows that more carbon accumulates on the Pt than on Pt-Re, and the improved long-term activity is attributed to a greater ability of Pt-Re to oxidize the carbonaceous intermediates that eventually poison active sites. Both Pt and Pt-Re surfaces have almost no activity for methanol oxidation until a minimum coverage of oxygen is achieved from O2 dissociation. A comparison with methanol oxidation studies on Pt and Pt-Re in a pressure regime that is 150 times lower than in this work demonstrates that more carbon and less oxygen accumulate on the surfaces during reaction at the lower pressures.

  12. Structure dependence of Pt surface activated ammonia oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Santen, R A van; Offermans, W K [Schuit Institute of Catalysis, Laboratory of Inorganic Chemistry and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Ricart, J M; Novell-Leruth, G [Department of Chemical Physics and Inorganic Chemistry, University Rovira I Virgili, C/ Marcel.lI Domingo s/n, 43007 Tarragona (Spain); Perez-RamIrez, J [Institute of Chemical Research of Catalonia (ICIQ) and Catalan, Institution for Research and Advanced Studies (ICREA), Avinguda Paisos Catalans 16, 43007, Tarragona (Spain)], E-mail: r.a.v.santen@tue.nl

    2008-06-01

    Computational advances that enable the prediction of the structures and the energies of surface reaction intermediates are providing essential information to the formulation of theories of surface chemical reactivity. In this contribution this is illustrated for the activation of ammonia by coadsorbed oxygen and hydroxyl on the Pt(111), Pt(100), and Pt(211) surfaces.

  13. Engineering the Activity and Stability of Pt-Alloy Cathode Fuel-Cell Electrocatalysts by Tuning the Pt-Pt Distance

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Malacrida, Paolo; Vej-Hansen, Ulrik Grønbjerg

    2014-01-01

    with a thickness of few Pt layers is formed. Accordingly, the effect of alloying Pt is to impose strain onto the Pt overlayer [3,4]. It is likely that this strain would be relaxed by defects [6]. Moreover, the activity of the Pt5Ln catalysts vs. the Pt-Pt distance shows a volcano relationship (Fig. A) [5]. Pt5Ln......One of the main obstacles to the commercialisation of low-temperature fuel cells is the slow kinetics of the oxygen reduction reaction (ORR). In order to decrease the ORR overpotential and reduce the Pt loading we need to develop more active and stable electrocatalysts. A fruitful strategy...... for enhancing the cathode activity is to alloy Pt with transition metals [1-2]. However, alloys of Pt and late transition metals are typically unstable under fuel-cell conditions. Herein, we present experimental and theoretical studies showing the trends in activity and stability of novel cathode catalysts...

  14. Engineering the Activity and Stability of Pt-Alloy Cathode Fuel-Cell Electrocatalysts by Tuning the Pt-Pt Distance

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Malacrida, Paolo; Vej-Hansen, Ulrik Grønbjerg

    2014-01-01

    based on alloys of Pt and lanthanides. Sputter-cleaned, polycrystalline Pt5Gd shows a five-fold increase in ORR activity [3], relative to Pt at 0.9 V in 0.1 M HClO4. The rest of the Pt5Ln (Ln = lanthanide) tested present at least a 3-fold enhancement in activity [4,5]. In all cases, a Pt overlayer...

  15. 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.

  16. Electrodeposition and electrocatalytic activity of Pt and Pt-alloy nanoparticles and thin films on highly oriented pyrolytic graphite (HOPG)

    Science.gov (United States)

    Lu, Guojin

    Pt and Pt-based alloy catalysts were synthesized by electrodeposition on HOPG. The nucleation and growth, morphology, composition and crystal structure, and electrocatalytic activity (towards relevant reactions in the frame of PEMFCs and DMFCs) of these model electrodes were systematically investigated. The presence of chlorides inhibits the Pt reduction processes. There is a transition from progressive to instantaneous nucleation with increasing overpotential for the deposition from 1 mM H2PtCl6 electrolytes. The possibility of instantaneous nucleation at large overpotential by using electrolytes with large chloride concentration is advantageous for the growth of small, well dispersed nanoparticles. The electrochemical data were confirmed by AFM and SEM imaging studies. Relatively narrow size distributed nanoparticles can be obtained from the current system. While MOR activity decreases with decreasing particle size, the HER and HOR activity of deposited Pt particles increases with decreasing deposition period. The ORR activity first increases then decreases with increasing deposition time. Interactions between Pt and Ru, or Ni or Co are observed and they form solid solution as verified by XRD. Underpotential deposition occurs for Pt-Ni or Pt-Co co-electrodeposition. Pt-Ru deposition can be described as progressive nucleation at low overpotential and instantaneous nucleation at high overpotentials. Through direct morphological observations, the Pt-Ni or Pt-Co nucleation can be approximately described as progressive. Pt-Ru deposits are superior to Pt towards MOR. The optimum Ru content is about 50 at.%. Pt-Ni and Pt-Co deposits are more active than Pt for ORR. The optimum content is about 30 at.% Ni or 50 at.% Co. Dealloying of Pt-Ru and Pt-Ni or Pt-Co electrodeposit is observed after electrochemical characterization. The extent of dealloying increases with the content of the alloying element.

  17. High Activity of Hexagonal Ag/Pt Nanoshell Catalyst for Oxygen Electroreduction

    Directory of Open Access Journals (Sweden)

    Lee Chien-Liang

    2008-01-01

    Full Text Available Abstract Hexagonal Ag/Pt nanoshells were prepared by using a hexagonal Ag nanoplate as the displacement template and by introducing Pt ions. The prepared Ag/Pt nanoshells played the role of an electrocatalyst in an oxygen reduction process. Compared to spherical Pt and Ag/Pt nanoparticles, the hexagonal Ag/Pt nanoshells showed higher activity for oxygen electroreduction.

  18. Partial Thermodynamic Properties of gamma-(Ni,Pt)3Al in the Ni-Al-Pt System (Preprint)

    Science.gov (United States)

    2006-02-01

    phases belonging to the Cu family, Journal of Alloys and Compounds , 353, 2003, 207. 4. J. Kamm, W. Milligan, Phase stability in (Ni, Pt)3Al alloys...in the Al-Ni-Ru system by direct reaction synthesis calorimetry, Journal of Alloys and Compounds , 403(1-2), 2005, 217-222. 15 Tables Table 1

  19. 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.

  20. 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 ...

  1. Low Temperature Water–gas Shift: Differences in Oxidation States Observed with Partially Reduced Pt/MnOX and Pt/CeOX Catalysts Yield Differences in OH Group Reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, M.; Jacobs, G; Graham, U; Azzam, K; Linganiso, L; Davis, B

    2010-01-01

    The Pt-ceria synergy may be described as the dehydrogenation of formate formed on the surface of the partially reducible oxide (PRO), ceria, by Pt across the interface, with H{sub 2}O participating in the transition state. However, due to the rising costs of rare earth oxides like ceria, replacement by a less expensive partially reducible oxide, like manganese oxide, is desirable. In this contribution, a comparison between Pt/ceria and Pt/manganese oxide catalysts possessing comparable Pt dispersions reveals that there are significant differences and certain similarities in the nature of the two Pt/PRO catalysts. With ceria, partial reduction involves reduction of the oxide surface shell, with Ce{sup 3+} at the surface and Ce{sup 4+} in the bulk. In the case of manganese oxide, partial reduction results in a mixture of Mn{sup 3+} and Mn{sup 2+}, with Mn{sup 2+} located at the surface. With Pt/CeO{sub X}, a high density of defect-associated bridging OH groups react with CO to yield a high density of the formate intermediate. With Pt/MnO{sub X}, the fraction of reactive OH groups is low and much lower formate band intensities result upon CO adsorption; moreover, there is a greater fraction of OH groups that are essentially unreactive. Thus, much lower CO conversion rates are observed with Pt/MnO{sub X} during low temperature water-gas shift. As with ceria, increasing the Pt loading facilitates partial reduction of MnO{sub X} to lower temperature, indicating metal-oxide interactions should be taken into account.

  2. Pd-Pt bimetallic nanodendrites with high activity for oxygen reduction.

    Science.gov (United States)

    Lim, Byungkwon; Jiang, Majiong; Camargo, Pedro H C; Cho, Eun Chul; Tao, Jing; Lu, Xianmao; Zhu, Yimei; Xia, Younan

    2009-06-05

    Controlling the morphology of Pt nanostructures can provide a great opportunity to improve their catalytic properties and increase their activity on a mass basis. We synthesized Pd-Pt bimetallic nanodendrites consisting of a dense array of Pt branches on a Pd core by reducing K2PtCl4 with L-ascorbic acid in the presence of uniform Pd nanocrystal seeds in an aqueous solution. The Pt branches supported on faceted Pd nanocrystals exhibited relatively large surface areas and particularly active facets toward the oxygen reduction reaction (ORR), the rate-determining step in a proton-exchange membrane fuel cell. The Pd-Pt nanodendrites were two and a half times more active on the basis of equivalent Pt mass for the ORR than the state-of-the-art Pt/C catalyst and five times more active than the first-generation supportless Pt-black catalyst.

  3. The activity of ALD-prepared PtCo catalysts for ethanol oxidation in alkaline media

    OpenAIRE

    Santasalo-Aarnio, Annukka; Sairanen, Emma; Arán-Ais, Rosa M.; Figueiredo, Marta C.; Hua, Jiang; Feliu, Juan M.; Lehtonen, Juha; Karinen, Reetta; Kallio, Tanja

    2014-01-01

    Controlled bimetallic catalyst materials can be obtained using atomic layer deposition (ALD) method. In this paper, this method was applied to prepare Pt, PtCo, and PtCoPt nanoparticle catalysts on carbon support. Their activity for ethanol oxidation was studied by various electrochemical methods and the dependency of the reaction on temperature and mass transfer was evaluated. In addition, FTIR analysis was performed to confirm the reaction products. The results showed that bimetallic PtCo e...

  4. Pt-based Bi-metallic Monolith Catalysts for Partial Upgrading of Microalgae Oil

    Energy Technology Data Exchange (ETDEWEB)

    Lawal, Adeniyi [Stevens Inst. of Technology, Hoboken, NJ (United States); Manganaro, James [Anasyn LLC, Princeton, NJ (United States); Goodall, Brian [Valicor Renewables LLC, Dexter, MI (United States); Farrauto, Robert [Columbia Univ., New York, NY (United States)

    2015-03-24

    catalysts, and consumes less hydrogen, if methanation can be mitigated. Our methanation data on Pt and Rh indicate effective suppression of methanation. Our data also show that our catalysts are less susceptible to coking; and unlike NiMo and CoMo, precious metal catalysts are not deactivated by water, a by-product of HDO of algae oil. Finally, our catalysts do not need to be sulfided to be active. A rigorous techno-economic analysis of our process for commercial scale production of 10,000 barrels per day of hydrotreated algae oil, with nutraceuticals co-product claiming only 0.05% of the raw algae oil, indicates an estimated plant gate price of ~$10/gal. Sensitivity analysis shows that critical parameters affecting sale price include (1) algae doubling time (2) biomass oil content (3) CAPEX, and (4) moisture content of post extracted algae residue. Modest improvements in these areas will result in enhanced and competitive economics. Based on a life cycle assessment for greenhouse gas emission, we found that if algae oil replaced 10% of the US consumption, this would result in a CO2e reduction of 210,000 tons per day. Improving the drying process for animal feed by 50% would result in further significant reduction in CO2e.

  5. Removal of Formaldehyde Using Highly Active Pt/TiO2 Catalysts without Irradiation

    Directory of Open Access Journals (Sweden)

    Haibao Huang

    2013-01-01

    Full Text Available Formaldehyde (HCHO is one of the major indoor air pollutants. TiO2 supported Pt catalysts were prepared by sol-gel method and used to eliminate HCHO at room temperature without irradiation. The reduced Pt/TiO2 catalyst (denoted as Pt/TiO2-H2 showed much higher activity than that calcined in air (denoted as Pt/TiO2-air. More than 96% of the conversion of HCHO was obtained over 0.5 wt% Pt/TiO2-H2, on which highly dispersed metallic Pt nanoparticles with very small size (~2 nm were identified. Metallic Pt rather than cationic Pt nanoparticles provide the active sites for HCHO oxidation. Negatively charged metallic Pt nanoparticles facilitate the transfer of charge and oxygen species and the activation of oxygen.

  6. Facile Synthesis of Nanoporous Pt-Y alloy with Enhanced Electrocatalytic Activity and Durability

    Science.gov (United States)

    Cui, Rongjing; Mei, Ling; Han, Guangjie; Chen, Jiyun; Zhang, Genhua; Quan, Ying; Gu, Ning; Zhang, Lei; Fang, Yong; Qian, Bin; Jiang, Xuefan; Han, Zhida

    2017-02-01

    Recently, Pt-Y alloy has displayed an excellent electrocatalytic activity for oxygen reduction reaction (ORR), and is regarded as a promising cathode catalyst for fuel cells. However, the bulk production of nanoscaled Pt-Y alloy with outstanding catalytic performance remains a great challenge. Here, we address the challenge through a simple dealloying method to synthesize nanoporous Pt-Y alloy (NP-PtY) with a typical ligament size of ~5 nm. By combining the intrinsic superior electrocatalytic activity of Pt-Y alloy with the special nanoporous structure, the NP-PtY bimetallic catalyst presents higher activity for ORR and ethanol oxidation reaction, and better electrocatalytic stability than the commercial Pt/C catalyst and nanoporous Pt alloy. The as-made NP-PtY holds great application potential as a promising electrocatalyst in proton exchange membrane fuel cells due to the advantages of facile preparation and excellent catalytic performance.

  7. Evaluation of Prothrombin Time and Activated Partial ...

    African Journals Online (AJOL)

    abnormal PT and APTT in untreated patients with diabetes mellitus. Keywords: Diabetes, Prothrombine ... may in turn enhance cardiovascular risk by increasing the likely hood of .... normalizes PT levels in diabetic patients (Standl et al,. 1996).

  8. Designed nanostructured pt film for electrocatalytic activities by underpotential deposition combined chemical replacement techniques.

    Science.gov (United States)

    Huang, Minghua; Jin, Yongdong; Jiang, Heqing; Sun, Xuping; Chen, Hongjun; Liu, Baifeng; Wang, Erkang; Dong, Shaojun

    2005-08-18

    Multiple-deposited Pt overlayer modified Pt nanoparticle (MD-Pt overlayer/PtNPs) films were deliberately constructed on glassy carbon electrodes through alternately multiple underpotential deposition (UPD) of Ag followed redox replacement reaction by Pt (II) cations. The linear and regular growth of the films characterized by cyclic voltammetry was observed. Atomic force spectroscopy (AFM) provides the surface morphology of the nanostructured Pt films. Rotating disk electrode (RDE) voltammetry and rotating ring-disk electrode (RRDE) voltammetry demonstrate that the MD-Pt overlayer/PtNPs films can catalyze an almost four-electron reduction of O(2) to H(2)O in air-saturated 0.1 M H(2)SO(4). Thus-prepared Pt films behave as novel nanostructured electrocatalysts for dioxygen reduction and hydrogen evolution reaction (HER) with enhanced electrocatalytic activities, in terms of both reduction peak potential and peak current, when compared to that of the bulk polycrystalline Pt electrode. Additionally, it is noted that after multiple replacement cycles, the electrocatalytic activities improved remarkably, although the increased amount of Pt is very low in comparison to that of pre-modified PtNPs due to the intrinsic feature of the UPD-redox replacement technique. In other words, the electrocatalytic activities could be improved markedly without using very much Pt by the technique of tailoring the catalytic surface. These features may provide an interesting way to produce Pt catalysts with a reliable catalytic performance as well as a reduction in cost.

  9. Pd-Pt random alloy nanocubes with tunable compositions and their enhanced electrocatalytic activities.

    Science.gov (United States)

    Yuan, Qiang; Zhou, Zhiyou; Zhuang, Jing; Wang, Xun

    2010-03-07

    Monodisperse, highly-selective sub-10 nm Pd-Pt random alloy nanocubes have been successfully synthesized in aqueous solution, and the electrocatalytic activity of these Pd-Pt alloys towards formic acid oxidation was investigated and compared with the activity of Pd sub-10 nm nanocubes, and the commercial Pd and Pt black.

  10. Molybdenum-Doped PdPt@Pt Core-Shell Octahedra Supported by Ionic Block Copolymer-Functionalized Graphene as a Highly Active and Durable Oxygen Reduction Electrocatalyst.

    Science.gov (United States)

    Cho, Kie Yong; Yeom, Yong Sik; Seo, Heun Young; Kumar, Pradip; Lee, Albert S; Baek, Kyung-Youl; Yoon, Ho Gyu

    2017-01-18

    Development of highly active and durable electrocatalysts that can effectively electrocatalyze oxygen reduction reactions (ORR) still remains one important challenge for high-performance electrochemical conversion and storage applications such as fuel cells and metal-air batteries. Herein, we propose the combination of molybdenum-doped PdPt@Pt core-shell octahedra and the pyrene-functionalized poly(dimethylaminoethyl methacrylate)-b-poly[(ethylene glycol) methyl ether methacrylate] ionic block copolymer-functionalized reduced graphene oxide (Mo-PdPt@Pt/IG) to effectively augment the interfacial cohesion of both components using a tunable ex situ mixing strategy. The rationally designed Mo-PdPt@Pt core-shell octahedra have unique compositional benefits, including segregation of Mo atoms on the vertexes and edges of the octahedron and 2-3 shell layers of Pt atoms on a PdPt alloy core, which can provide highly active sites to the catalyst for ORR along with enhanced electrochemical stability. In addition, the ionic block copolymer functionalized graphene can facilitate intermolecular charge transfer and good stability of metal NPs, which arises from the ionic block copolymer interfacial layer. When the beneficial features of the Mo-PdPt@Pt and IG are combined, the Mo-PdPt@Pt/IG exhibits substantially enhanced activity and durability for ORR relative to those of commercial Pt/C. Notably, the Mo-PdPt@Pt/IG shows mass activity 31-fold higher than that of Pt/C and substantially maintains high activities after 10 000 cycles of intensive durability testing. The current study highlights the crucial strategies in designing the highly active and durable Pt-based octahedra and effective combination with functional graphene supports toward the synergetic effects on ORR.

  11. Enhanced Electrocatalytic Activity of Pt/3D Hierarchical Bimodal Macroporous Carbon Nanospheres.

    Science.gov (United States)

    Balgis, Ratna; Widiyastuti, W; Ogi, Takashi; Okuyama, Kikuo

    2017-07-19

    Proton exchange membrane fuel cells require electrocatalysts with a high platinum (Pt) loading, large active surface area, and favorable hydrodynamic profile for practical applications. Here, we report the design of three-dimensional hierarchical bimodal macroporous carbon nanospheres with an interconnected pore system, which are applied as an electrocatalyst support. Carbon-supported Pt (Pt/C) catalysts were prepared by aerosol spray pyrolysis followed by microwave chemical deposition. The hierarchical porous structures not only increased the dispersion of Pt nanoparticles but also improved catalytic performance. A hierarchical bimodal macroporous Pt/C catalyst with a mixture of 30 and 120 nm size pores showed the best performance. The electrochemical surface area and mass activity values of this support were 96 m(2) g(-1)-Pt and 378 mA mg(-1)-Pt, respectively at a Pt loading of 15 wt %.

  12. Design of Low Pt Concentration Electrocatalyst Surfaces with High Oxygen Reduction Reaction Activity Promoted by Formation of a Heterogeneous Interface between Pt and CeO(x) Nanowire.

    Science.gov (United States)

    Chauhan, Shipra; Mori, Toshiyuki; Masuda, Takuya; Ueda, Shigenori; Richards, Gary J; Hill, Jonathan P; Ariga, Katsuhiko; Isaka, Noriko; Auchterlonie, Graeme; Drennan, John

    2016-04-13

    Pt-CeO(x) nanowire (NW)/C electrocatalysts for the improvement of oxygen reduction reaction (ORR) activity on Pt were prepared by a combined process involving precipitation and coimpregnation. A low, 5 wt % Pt-loaded CeO(x) NW/C electrocatalyst, pretreated by an optimized electrochemical conditioning process, exhibited high ORR activity over a commercially available 20 wt % Pt/C electrocatalyst although the ORR activity observed for a 5 wt % Pt-loaded CeO(x) nanoparticle (NP)/C was similar to that of 20 wt % Pt/C. To investigate the role of a CeO(x) NW promotor on the enhancement of ORR activity on Pt, the Pt-CeO(x) NW interface was characterized by using hard X-ray photoelectron spectroscopy (HXPS), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). Microanalytical data obtained by these methods were discussed in relation to atomistic simulation performed on the interface structures. The combined techniques of HXPS, TEM-EELS, and atomistic simulation indicate that the Pt-CeO(x) NW interface in the electrocatalyst contains two different defect clusters: Frenkel defect clusters (i.e., 2Pt(i)(••) - 4O(i)″ - 4V(o)(••) - V(Ce)″″) formed in the surface around the Pt-CeO(x) NW interface and Schottky defect clusters (i.e., (Pt(Ce)″ - 2V(O)(••) - 2Ce(Ce)') and (Pt(Ce)″ - V(O)(••))) which appear in the bulk of the Pt-CeO(x) NW interface similarly to Pt-CeO(x) NP/C. It is concluded that the formation of both Frenkel defect clusters and Schottky defect clusters at the Pt-CeO(x) NW heterointerface contributes to the promotion of ORR activity and permits the use of lower Pt-loadings in these electrocatalysts.

  13. Oxygen Reduction Reaction Activity and Durability of Pt Catalysts Supported on Titanium Carbide

    Directory of Open Access Journals (Sweden)

    Morio Chiwata

    2015-06-01

    Full Text Available We have prepared Pt nanoparticles supported on titanium carbide (TiC (Pt/TiC as an alternative cathode catalyst with high durability at high potentials for polymer electrolyte fuel cells. The Pt/TiC catalysts with and without heat treatment were characterized by X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, and transmission electron microscopy (TEM. Hemispherical Pt nanocrystals were found to be dispersed uniformly on the TiC support after heat treatment at 600 °C in 1% H2/N2 (Pt/TiC-600 °C. The electrochemical properties (cyclic voltammetry, electrochemically active area (ECA, and oxygen reduction reaction (ORR activity of Pt/TiC-600 °C and a commercial Pt/carbon black (c-Pt/CB were evaluated by the rotating disk electrode (RDE technique in 0.1 M HClO4 solution at 25 °C. It was found that the kinetically controlled mass activity for the ORR on Pt/TiC-600 °C at 0.85 V (507 A g−1 was comparable to that of c-Pt/CB (527 A g−1. Moreover, the durability of Pt/TiC-600 °C examined by a standard potential step protocol (E = 0.9 V↔1.3 V vs. RHE, holding 30 s at each E was much higher than that for c-Pt/CB.

  14. Electrocatalytic activity of PtAu/C catalysts for glycerol oxidation.

    Science.gov (United States)

    Jin, Changchun; Sun, Chao; Dong, Rulin; Chen, Zhidong

    2012-01-01

    The electrocatalytic oxidation of glycerol on PtAu/C catalysts has been investigated by cyclic voltammetry. PtAu bimetallic nanoparticles are prepared by chemical reduction. Carbon-supported PtAu catalysts are found to exhibit high electrocatalytic activity for the oxidation of glycerol in alkaline solution in terms of oxidation potential and current density as well as stability, and PtAu/C catalysts with different Pt:Au composition ratios show no much difference in catalytic activity. In acidic solution, PtAu/C catalysts exhibit similar to Pt/C catalysts in activity, but the advantage of the PtAu/C catalysts in terms of per unit mass of platinum is still obvious. The PtAu/C catalysts, in a wide Pt:Au ratio range, show a remarkable enhancement in the mass specific activity of platinum with decreasing platinum content in both alkaline and acidic solutions. This is of significance for reducing the usage of platinum and indicates that though platinum acts as main active sites, gold also plays an important role in the function of PtAu/C catalysts.

  15. Bactericidal activity of partially oxidized nanodiamonds.

    Science.gov (United States)

    Wehling, Julia; Dringen, Ralf; Zare, Richard N; Maas, Michael; Rezwan, Kurosch

    2014-06-24

    Nanodiamonds are a class of carbon-based nanoparticles that are rapidly gaining attention, particularly for biomedical applications, i.e., as drug carriers, for bioimaging, or as implant coatings. Nanodiamonds have generally been considered biocompatible with a broad variety of eukaryotic cells. We show that, depending on their surface composition, nanodiamonds kill Gram-positive and -negative bacteria rapidly and efficiently. We investigated six different types of nanodiamonds exhibiting diverse oxygen-containing surface groups that were created using standard pretreatment methods for forming nanodiamond dispersions. Our experiments suggest that the antibacterial activity of nanodiamond is linked to the presence of partially oxidized and negatively charged surfaces, specifically those containing acid anhydride groups. Furthermore, proteins were found to control the bactericidal properties of nanodiamonds by covering these surface groups, which explains the previously reported biocompatibility of nanodiamonds. Our findings describe the discovery of an exciting property of partially oxidized nanodiamonds as a potent antibacterial agent.

  16. Antiproliferative Pt(IV) complexes: synthesis, biological activity, and quantitative structure-activity relationship modeling.

    Science.gov (United States)

    Gramatica, Paola; Papa, Ester; Luini, Mara; Monti, Elena; Gariboldi, Marzia B; Ravera, Mauro; Gabano, Elisabetta; Gaviglio, Luca; Osella, Domenico

    2010-09-01

    Several Pt(IV) complexes of the general formula [Pt(L)2(L')2(L'')2] [axial ligands L are Cl-, RCOO-, or OH-; equatorial ligands L' are two am(m)ine or one diamine; and equatorial ligands L'' are Cl- or glycolato] were rationally designed and synthesized in the attempt to develop a predictive quantitative structure-activity relationship (QSAR) model. Numerous theoretical molecular descriptors were used alongside physicochemical data (i.e., reduction peak potential, Ep, and partition coefficient, log Po/w) to obtain a validated QSAR between in vitro cytotoxicity (half maximal inhibitory concentrations, IC50, on A2780 ovarian and HCT116 colon carcinoma cell lines) and some features of Pt(IV) complexes. In the resulting best models, a lipophilic descriptor (log Po/w or the number of secondary sp3 carbon atoms) plus an electronic descriptor (Ep, the number of oxygen atoms, or the topological polar surface area expressed as the N,O polar contribution) is necessary for modeling, supporting the general finding that the biological behavior of Pt(IV) complexes can be rationalized on the basis of their cellular uptake, the Pt(IV)-->Pt(II) reduction, and the structure of the corresponding Pt(II) metabolites. Novel compounds were synthesized on the basis of their predicted cytotoxicity in the preliminary QSAR model, and were experimentally tested. A final QSAR model, based solely on theoretical molecular descriptors to ensure its general applicability, is proposed.

  17. Highly active mesoporous ferrihydrite supported pt catalyst for formaldehyde removal at room temperature.

    Science.gov (United States)

    Yan, Zhaoxiong; Xu, Zhihua; Yu, Jiaguo; Jaroniec, Mietek

    2015-06-01

    Ferrihydrite (Fh) supported Pt (Pt/Fh) catalyst was first prepared by combining microemulsion and NaBH4 reduction methods and investigated for room-temperature removal of formaldehyde (HCHO). It was found that the order of addition of Pt precursor and ferrihydrite in the preparation process has an important effect on the microstructure and performance of the catalyst. Pt/Fh was shown to be an efficient catalyst for complete oxidation of HCHO at room temperature, featuring higher activity than magnetite supported Pt (Pt/Fe3O4). Pt/Fh and Pt/Fe3O4 exhibited much higher catalytic activity than Pt supported over calcined Fh and TiO2. The abundance of surface hydroxyls, high Pt dispersion and excellent adsorption performance of Fh are responsible for superior catalytic activity and stability of the Pt/Fh catalyst. This work provides some indications into the design and fabrication of the cost-effective and environmentally benign catalysts with excellent adsorption and catalytic oxidation performances for HCHO removal at room temperature.

  18. Electrocatalytic activity of porous nanostructured Fe/Pt-Fe electrode for methanol electrooxidation in alkaline media

    Institute of Scientific and Technical Information of China (English)

    Javad Hosseini; Mehdi Abdolmaleki; Hamid Reza Pouretedal; Mohammad Hossein Keshavarz

    2015-01-01

    An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodepo-sition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.

  19. 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.

  20. 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.

  1. Effects of sugammadex on activated partial thromboplastin time and prothrombin time in healthy subjects.

    Science.gov (United States)

    De Kam, Pieter-Jan; Grobara, Peter; Prohn, Marita; Höppener, Floris; Kluft, Cornelis; Burggraaf, Jacobus; Langdon, Ronald B; Peeters, Pierre

    2014-03-01

    To assess the impact of sugammadex on activated partial thromboplastin time (APTT) and international normalized ratio for prothrombin time (PT(INR)) in healthy subjects and characterize the concentration-dependency of sugammadex effects on APTT and prothrombin time (PT) in normal human plasma in vitro. Eight healthy subjects (18 - 45 years of age) were administered intravenous doses of 4 mg/kg sugammadex, 16 mg/kg sugammadex, or placebo in a randomized, placebo-controlled, three period cross-over trial. The primary endpoint was area under the curve from 2 to 60 minutes post-dose (AUC2-60min) for APTT and PT(INR). In vitro, the effects of sugammadex on APTT and PT were assessed in pooled normal human citrate plasma. In subjects dosed with 4 and 16 mg/kg sugammadex, geometric mean ratios (treated vs. placebo) for AUC2-60min were 1.085 (95% confidence interval, 0.888 - 1.325) and 1.019 (0.868 - 1.195), respectively, for APTT, and 1.047 (0.904 - 1.213) and 1.096 (0.953 - 1.261), respectively, for PT(INR). At individual timepoints, mean APTT and PT(INR) increased by up to 22% after 16 mg/kg sugammadex compared with placebo. All such increases occurred within 30 minutes post-dose. Sugammadex was generally well tolerated. In the in vitro experiments, addition of sugammadex to plasma resulted in limited, concentration dependent increases in both APTT and PT. At 200 μg/mL (the mean maximum concentration reached therapeutically), the relative increases were 29% and 19%, respectively. Administration of sugammadex is associated with a dose-related, limited and transient prolongation of APTT and PT(INR) that is unlikely to be of clinical relevance.

  2. Deceptive prothrombin and activated partial thromboplastin times in alcoholic cirrhosis.

    Science.gov (United States)

    Sirikonda, P. R.; Spillert, C. R.; Koneru, B.; Ponnudurai, R.; Wilson, D. J.; Lazaro, E. J.

    1996-01-01

    It is believed that perioperative hemorrhage, in the hepatoportal area, results from a coagulopathy. This study determined if this could be quantitated by a modified recalcification time (MRT) test developed in our laboratory. Unlike prothrombin (PT) and activated partial thromboplastin times (APTT), the MRT is performed with whole blood to ensure the role of blood cells and chemicals (particularly tissue factor, a potent procoagulant) in the coagulation process. Candidates for liver transplantation (n = 11) were studied. Samples (5 mL) of citrated venous blood were obtained from the patients. Aliquots (1 mL) from these samples were divided into groups of vials labeled C, S, and E. Groups C and S received 20 microL saline and group E, 20 microL of saline containing 10 micrograms of Escherichia coli endotoxin (055: B5W). Vial C was incubated for 10 minutes and vials S and E for 120 minutes, all at 37 degrees C. Then, the MRT was determined on 300 microL of blood from each vial after adding 40 microL of 0.1M calcium chloride. Mean MRT values (minutes +/- standard deviation) for C (MRTC), for S (MRTS), and for E (MRTE) were compared with like values from healthy controls (n = 29). Despite prolonged PT and APTT values, MRT values were shortened in patients with cirrhosis. This hypercoagulability detected by the MRT exonerates a hemorrhagic coagulopathy and possibly implicates widened and thinned gaps in the walls of the portal venous tributaries as the cause of perioperative hemorrhage. PMID:8667440

  3. Heterogeneous Au-Pt nanostructures with enhanced catalytic activity toward oxygen reduction.

    Science.gov (United States)

    Ye, Feng; Liu, Hui; Hu, Weiwei; Zhong, Junyu; Chen, Yingying; Cao, Hongbin; Yang, Jun

    2012-03-14

    Heterogeneous Au-Pt nanostructures have been synthesized using a sacrificial template-based approach. Typically, monodispersed Au nanoparticles are prepared first, followed by Ag coating to form core-shell Au-Ag nanoparticles. Next, the galvanic replacement reaction between Ag shells and an aqueous H(2)PtCl(6) solution, whose chemical reaction can be described as 4Ag + PtCl(6)(2-)→ Pt + 4AgCl + 2Cl(-), is carried out at room temperature. Pure Ag shell is transformed into a shell made of Ag/Pt alloy by galvanic replacement. The AgCl formed simultaneously roughens the surface of alloy Ag-Pt shells, which can be manipulated to create a porous Pt surface for oxygen reduction reaction. Finally, Ag and AgCl are removed from core-shell Au-Ag/Pt nanoparticles using bis(p-sulfonatophenyl)phenylphosphane dihydrate dipotassium salt to produce heterogeneous Au-Pt nanostructures. The heterogeneous Au-Pt nanostructures have displayed superior catalytic activity towards oxygen reduction in direct methanol fuel cells because of the electronic coupling effect between the inner-placed Au core and the Pt shell.

  4. Antagonistic Activities of Novel Peptides from Bacillus amyloliquefaciens PT14 against Fusarium solani and Fusarium oxysporum.

    Science.gov (United States)

    Kim, Young Gwon; Kang, Hee Kyoung; Kwon, Kee-Deok; Seo, Chang Ho; Lee, Hyang Burm; Park, Yoonkyung

    2015-12-09

    Bacillus species have recently drawn attention due to their potential use in the biological control of fungal diseases. This paper reports on the antifungal activity of novel peptides isolated from Bacillus amyloliquefaciens PT14. Reverse-phase high-performance liquid chromatography revealed that B. amyloliquefaciens PT14 produces five peptides (PT14-1, -2, -3, -4a, and -4b) that exhibit antifungal activity but are inactive against bacterial strains. In particular, PT14-3 and PT14-4a showed broad-spectrum antifungal activity against Fusarium solani and Fusarium oxysporum. The PT14-4a N-terminal amino acid sequence was identified through Edman degradation, and a BLAST homology analysis showed it not to be identical to any other protein or peptide. PT14-4a displayed strong fungicidal activity with minimal inhibitory concentrations of 3.12 mg/L (F. solani) and 6.25 mg/L (F. oxysporum), inducing severe morphological deformation in the conidia and hyphae. On the other hand, PT14-4a had no detectable hemolytic activity. This suggests PT14-4a has the potential to serve as an antifungal agent in clinical therapeutic and crop-protection applications.

  5. Preparation and characterization of Pt supported on graphene with enhanced electrocatalytic activity in fuel cell

    Science.gov (United States)

    Xin, Yuchen; Liu, Jian-guo; Zhou, Yong; Liu, Wenming; Gao, Jian; Xie, Yun; Yin, Ying; Zou, Zhigang

    Pt nanoparticles are deposited onto graphene sheets via synchronous reduction of H 2PtCl 6 and graphene oxide (GO) suspension using NaBH 4. Lyophilization is introduced to avoid irreversible aggregation of graphene (G) sheets, which happens during conventional drying process. Pt/G catalysts reveal a high catalytic activity for both methanol oxidation and oxygen reduction reaction compared to Pt supported on carbon black (Pt/C). The performance of Pt/G catalysts is further improved after heat treatment in N 2 atmosphere at 300 °C for 2 h, and the peak current density of methanol oxidation for Pt/G after heat treatment is almost 3.5 times higher than Pt/C. Transmission electron microscope (TEM) images show that the Pt particles are uniformly distributed on graphene sheets. X-ray photoelectron spectroscopy (XPS) results demonstrate that the interaction between Pt and graphene is enhanced during annealing. It suggests that graphene has provided a new way to improve electrocatalytic activity of catalyst for fuel cell.

  6. Stellated Ag-Pt bimetallic nanoparticles: An effective platform for catalytic activity tuning

    Science.gov (United States)

    Liu, Hui; Ye, Feng; Yao, Qiaofeng; Cao, Hongbin; Xie, Jianping; Lee, Jim Yang; Yang, Jun

    2014-01-01

    The usefulness of Pt-based nanomaterials for catalysis can be greatly enhanced by coupling morphology engineering to the strategic presence of a second or even third metal. Here we demonstrate the design and preparation of stellated Ag-Pt bimetallic nanoparticles where significant activity difference between the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) may be realized by relegating Ag to the core or by hollowing out the core. In particular the stellated Pt surface, with an abundance of steps, edges, corner atoms, and {111} facets, is highly effective for the ORR but is ineffective for MOR. MOR activity is only observed in the presence of a Ag core through electronic coupling to the stellated Pt shell. The bimetallic Ag-Pt stellates therefore demonstrate the feasibility of tuning a Pt surface for two very different structure sensitive catalytic reactions. Stellated bimetallics may therefore be an effective platform for highly tunable catalyst designs. PMID:24495979

  7. Probing the nanoscale structure of the catalytically active overlayer on Pt alloys with rare earths

    DEFF Research Database (Denmark)

    Pedersen, Anders Filsøe; Ulrikkeholm, Elisabeth Therese; Escribano, Maria Escudero

    2016-01-01

    PtxY and PtxGd exhibit exceptionally high activity for oxygen reduction, both in the polycrystalline form and the nanoparticulate form. In order to understand the origin of the enhanced activity of these alloys, we have investigated thin films of these alloys on bulk Pt(111) crystals, i.e. Y/Pt(1...

  8. Synergistic Effects in CNTs-PdAu/Pt Trimetallic Nanoparticles with High Electrocatalytic Activity and Stability

    Science.gov (United States)

    Cai, Xin-Lei; Liu, Chang-Hai; Liu, Jie; Lu, Ying; Zhong, Ya-Nan; Nie, Kai-Qi; Xu, Jian-Long; Gao, Xu; Sun, Xu-Hui; Wang, Sui-Dong

    2017-10-01

    We present a straightforward physical approach for synthesizing multiwalled carbon nanotubes (CNTs)-PdAu/Pt trimetallic nanoparticles (NPs), which allows predesign and control of the metal compositional ratio by simply adjusting the sputtering targets and conditions. The small-sized CNTs-PdAu/Pt NPs ( 3 nm, Pd/Au/Pt ratio of 3:1:2) act as nanocatalysts for the methanol oxidation reaction (MOR), showing excellent performance with electrocatalytic peak current of 4.4 A mg Pt -1 and high stability over 7000 s. The electrocatalytic activity and stability of the PdAu/Pt trimetallic NPs are much superior to those of the corresponding Pd/Pt and Au/Pt bimetallic NPs, as well as a commercial Pt/C catalyst. Systematic investigation of the microscopic, crystalline, and electronic structure of the PdAu/Pt NPs reveals alloying and charge redistribution in the PdAu/Pt NPs, which are responsible for the promotion of the electrocatalytic performance.

  9. Fabrication of Pt/(Ta2O5+Pt) coated titanium electrodes using combination of partial thermal decomposition and electrolytic reduction of Pt and Ta complex; Tofu-bubun netsubunkai to denkai kangenho wo kumiawaseta hakkin/(sanka tantaru+hakkin) tanji chitan kitai denkyoku no sakusei

    Energy Technology Data Exchange (ETDEWEB)

    Kamegaya, Y. [Ishifuku Metal Industry Co. Ltd., Saitama (Japan); Saito, J.; Kobayashi, H.; Mitamura, T. [Saitama Univ., Saitama (Japan). Faculty of Engineering; Okuyama, M. [Oyama National College of Technology, Tochigi (Japan)

    1996-02-05

    Recently, the authors proposed a new method, a combination of painting/partial thermal decomposition and electrolytic reduction, for the fabrication of Pt coated electrode. When Pt support carbon substrate electrode and Pt support Ti substrate electrode were fabricated using this method, any of these electrode has higher surface area than that of electrode fabricated by conventional painting/partial thermal decomposition method. In this report, in order to make possible to long life for Ti substrate coated electrode, the fabrication of coated electrode structure made of up catalyst layer/interlayer/electrode substrate was carried out using the electrode fabrication method proposed by authors. As a result, the amount of Ta support for including (Ta2O5+Pt) interlayer having sufficient electric conductivity and corrosion resistance into the coated electrode structure was necessary at least 0.4mg.cm{sup -2} if the amount of Pt was 0.4mg.cm{sup -2}. Further, the fabricated Pt/(Ta2O5+Pt)/Ti electrode had higher surface area and electrode life was 2 times longer than that of Pt/Ti electrode and had better stability. 9 refs., 7 figs.

  10. Elucidating the activity of stepped Pt single crystals for oxygen reduction

    DEFF Research Database (Denmark)

    Bandarenka, Aliaksandr S.; Hansen, Heine Anton; Rossmeisl, Jan;

    2014-01-01

    obtained by different groups), a well-defined Sabatier-type volcano is observed for the activities measured for the Pt[n(111) × (111)] and Pt[n(111) × (100)] stepped single crystals, in remarkable agreement with earlier theoretical studies. We propose that the observed destabilisation of *OH species...

  11. Solvothermal synthesis of Pt-Pd alloys with selective shapes and their enhanced electrocatalytic activities

    Science.gov (United States)

    Zhang, Zhi-Cheng; Hui, Jun-Feng; Guo, Zhen-Guo; Yu, Qi-Yu; Xu, Biao; Zhang, Xin; Liu, Zhi-Chang; Xu, Chun-Ming; Gao, Jin-Sen; Wang, Xun

    2012-03-01

    Pt-Pd bimetallic alloy nanostructures with highly selective morphologies such as cube, bar, flower, concave cube, and dendrite have been achieved through a facile one-pot solvothermal synthesis. The effects of shape-controllers (sodium dodecyl sulfate (SDS), ethylenediamine-tetraacetic acid disodium salt (EDTA-2Na), NaI) and solvents (water/DMF) on the morphologies were systematically investigated. The electrocatalytic activities of these Pt-Pd alloy nanostructures toward formic acid oxidation were tested. The results indicated that these alloy nanocrystals exhibited enhanced and shape-dependent electrocatalytic activity toward formic acid oxidation compared to commercial Pt black and Pt/C catalysts.Pt-Pd bimetallic alloy nanostructures with highly selective morphologies such as cube, bar, flower, concave cube, and dendrite have been achieved through a facile one-pot solvothermal synthesis. The effects of shape-controllers (sodium dodecyl sulfate (SDS), ethylenediamine-tetraacetic acid disodium salt (EDTA-2Na), NaI) and solvents (water/DMF) on the morphologies were systematically investigated. The electrocatalytic activities of these Pt-Pd alloy nanostructures toward formic acid oxidation were tested. The results indicated that these alloy nanocrystals exhibited enhanced and shape-dependent electrocatalytic activity toward formic acid oxidation compared to commercial Pt black and Pt/C catalysts. Electronic supplementary information (ESI) available: See DOI: 10.1039/c2nr12135b

  12. Exceptional methanol electro-oxidation activity by bimetallic concave and dendritic Pt-Cu nanocrystals catalysts

    Science.gov (United States)

    Wang, Ying-Xia; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

    2014-01-01

    PtCux (x = 1, 2 and 3) bimetallic nanocrystals with concave surface and dendritic morphology were prepared and used as electrocatalysts in methanol oxidation reaction (MOR) for polymer electrolyte membrane fuel cells. The bimetallic nanocrystals were synthesized via one-pot co-reduction of H2PtCl6 and Cu(acac)2 by oleylamine and polyvinyl pyrrolidone (PVP) in an autoclave at 180 °C. The concave dendritic bimetallic nanostructure consisted of a core rich in Cu and nanodendrites rich in Pt, which was formed via galvanic replacement of Cu by Pt. It was found that PVP played an important role in initiating, facilitating, and directing the replacement reaction. The electrochemical properties of the PtCux were characterized by cyclic voltammetry (CV) and chronoamperometry (CA). The concave dendritic PtCu2/C nanocrystals exhibited exceptionally high activity and strong poisoning resistance in MOR. At 0.75 V (vs. reversible hydrogen electrode, RHE) the mass activity and specific activity of PtCu2/C were 3.3 and 4.1 times higher than those of the commercial Pt/C catalysts, respectively. The enhanced catalytic activity could be attributed to the unique concave dendritic morphology of the bimetallic nanocrystals.

  13. Controlling the Activity and Stability of Pt-Based Electrocatalysts By Means of the Lanthanide Contraction

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Malacrida, Paolo; Vej-Hansen, Ulrik Grønbjerg

    2015-01-01

    In order to reduce the Pt loading at the cathode of proton exchange membrane fuel cells (PEMFCs) more active and stable catalysts are needed to drive the oxygen reduction reaction. Most research has focussed on achieving this by alloying Pt with Fe, Co, Ni or Cu [1,2]. However, these compounds ty...

  14. Synthesis and photocatalytic activity of Pt-ZnO hybrid nanocomposite by solution plasma technology

    Science.gov (United States)

    Hu, Xiulan; Xu, QiuCheng; Ge, Chao; Su, Nan; Zhang, Jianbo; Huang, Huihong; Zhu, Shoufeng; Xu, Yanqiu; Cheng, Jiexu

    2017-01-01

    In this paper, Pt-ZnO hybrid nanocomposites were prepared by solution plasma technology. X-ray diffraction (XRD) and energy dispersive x-ray analysis (EDX) were used to verify their chemical composition. The size and morphology of the Pt-ZnO hybrid nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These results indicate that about 2-3 nm Pt nanoparticles (NPs) were synthesized and dispersed on the pyramid-like ZnO (20-60 nm) surface. Photodegradation of Rhodamine B (RhB) demonstrates that the Pt (5 wt%)-ZnO hybrid nanocomposite has better photocatalytic activity than commercial P25 because Pt NPs restrain the photogenerated electron/hole recombination and increase the catalyst activity.

  15. Fabrication and Characterization of High-activity Pt/C Electrocatalysts for Oxygen Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Borami; Kim, Joung Woon; Hwang, Seung Jun; Yoo, Sung Jong; Cho, Eun Ae; Lim, Tae Hoon; Kim, Soo Kil [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2010-06-15

    A 20 wt % Pt/C is fabricated and characterized for use as the cathode catalyst in a polymer electrolyte membrane fuel cell (PEMFC). By using the polyol method, the fabrication process is optimized by modifying the carbon addition sequence and precursor mixing conditions. The crystallographic structure, particle size, dispersion, and activity toward oxygen reduction of the as-prepared catalysts are compared with those of commercial Pt/C catalysts. The most effective catalyst is obtained by ultrasonic treatment of ethylene glycol-carbon mixture and immediate mixing of this mixture with a Pt precursor at the beginning of the synthesis. The catalyst exhibits very uniform particle size distribution without agglomeration. The mass activities of the as-prepared catalyst are 13.4 mA/mgPt and 51.0 mA/mgPt at 0.9 V and 0.85 V, respectively, which are about 1.7 times higher than those of commercial catalysts.

  16. Synthesis and photocatalytic activity of Pt-ZnO hybrid nanocomposite by solution plasma technology.

    Science.gov (United States)

    Hu, Xiulan; Xu, QiuCheng; Ge, Chao; Su, Nan; Zhang, Jianbo; Huang, Huihong; Zhu, Shoufeng; Xu, Yanqiu; Cheng, Jiexu

    2017-01-27

    In this paper, Pt-ZnO hybrid nanocomposites were prepared by solution plasma technology. X-ray diffraction (XRD) and energy dispersive x-ray analysis (EDX) were used to verify their chemical composition. The size and morphology of the Pt-ZnO hybrid nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These results indicate that about 2-3 nm Pt nanoparticles (NPs) were synthesized and dispersed on the pyramid-like ZnO (20-60 nm) surface. Photodegradation of Rhodamine B (RhB) demonstrates that the Pt (5 wt%)-ZnO hybrid nanocomposite has better photocatalytic activity than commercial P25 because Pt NPs restrain the photogenerated electron/hole recombination and increase the catalyst activity.

  17. Suppression of oxygen reduction reaction activity on Pt-based electrocatalysts from ionomer incorporation

    Energy Technology Data Exchange (ETDEWEB)

    Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.; Kocha, Shyam S.

    2016-09-01

    The impact of Nafion on the oxygen reduction reaction (ORR) activity is studied for Pt/C and Pt-alloy/C catalysts using thin-film rotating disk electrode (TF-RDE) methods in 0.1 M HClO4. Ultrathin uniform catalyst layers and standardized activity measurement protocols are employed to obtain accurate and reproducible ORR activity. Nafion lowers the ORR activity which plateaus with increasing loading on Pt catalysts. Pt particle size is found not to have significant influence on the extent of the SA decrease upon Nafion incorporation. Catalysts using high surface area carbon (HSC) support exhibit attenuated activity loss resulting from lower ionomer coverage on catalyst particles located within the deep pores. The impact of metallic composition on the activity loss due to Nafion incorporation is also discussed.

  18. Electrochemical activation of nanostructured carbon-supported PtRuMo electrocatalyst for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Huerta, M.V., E-mail: mmartinez@icp.csic.e [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Tsiouvaras, N.; Pena, M.A.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Rodriguez, J.L.; Pastor, E. [Departamento de Quimica Fisica, Universidad de La Laguna, Astrofisico Francisco Sanchez s/n, 38071 Tenerife (Spain)

    2010-11-01

    The factors controlling the behavior and the stability of electrocatalysts based on Pt, Ru and Mo nanoparticles during exhaustive electrochemical treatment are examined. Along this treatment, it has been observed that in the case of ternary catalysts there are pronounced changes in the structure of their surface resulting in electrode activation for methanol and CO electrooxidation, whereas the activity of binary PtRu/C and PtMo/C catalysts decreases. Therefore, the role of both Ru and Mo is crucial for the electrochemical activation of the catalyst, though metal losses do occur during electrochemical process. For the first time a detailed study of this phenomenon is presented, including characterization by HRTEM, TXRF, XRD, electrochemical measurements and in situ Fourier transform infrared spectroscopy (FTIR). In order to get a deeper insight into the surface structure, chemical state, and stability of the electrocatalyst under reaction conditions, a combination of cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy (XPS) has been used. By comparing bulk and surface composition, our results point out to the key role of the geometric effect enhanced by previous reduction of the nanoparticles. At the end of the electrochemical treatment, Mo-PtRu/C catalysts surface was restructured with substantial enrichment in Pt and a less pronounced Mo surface enrichment, while Ru is incorporated into the Pt-Mo overlayer. These results underline the possibility of further optimization of the surface structure and composition producing PtRuMo nanoparticles with high methanol and CO oxidation activity.

  19. Fabrication of Supported AuPt Alloy Nanocrystals with Enhanced Electrocatalytic Activity for Formic Acid Oxidation through Conversion Chemistry of Layer-Deposited Pt(2+) on Au Nanocrystals.

    Science.gov (United States)

    Kim, Seong Hyeon; Jeong, Hwakyeung; Kim, Jongwon; Lee, In Su

    2015-10-07

    The exploitation of nanoconfined conversion of Au- and Pt-containing binary nanocrystals for developing a controllable synthesis of surfactant-free AuPt nanocrystals with enhanced formic acid oxidation (FAO) activity is reported, which can be stably and evenly immobilized on various support materials to diversify and optimize their electrocatalytic performance. In this study, an atomic layer of Pt(2+) species is discovered to be spontaneously deposited in situ on the Au nanocrystal generated from a reverse-microemulsion solution. The resulting Au/Pt(2+) nanocrystal thermally transforms into a reduced AuPt alloy nanocrystal during the subsequent solid-state conversion process within the SiO2 nanosphere. The alloy nanocrystals can be isolated from SiO2 in a surfactant-free form and then dispersedly loaded on the carbon sphere surface, allowing for the production of a supported electrocatalyst that exhibits much higher FAO activity than commercial Pt/C catalysts. Furthermore, by involving Fe3O4 nanocrystals in the conversion process, the AuPt alloy nanocrystals can be grown on the oxide surface, improving the durability of supported metal catalysts, and then uniformly loaded on a reduced graphene oxide (RGO) layer with high electroconductivity. This produces electrocatalytic AuPt/Fe3O4/RGO nanocomposites whose catalyst-oxide-graphene triple-junction structure provides improved electrocatalytic properties in terms of both activity and durability in catalyzing FAO. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effects of a TiC substrate on the catalytic activity of Pt for NO reduction.

    Science.gov (United States)

    Chu, Xingli; Fu, Zhaoming; Li, Shasha; Zhang, Xilin; Yang, Zongxian

    2016-05-11

    Density functional theory calculations are used to elucidate the catalytic properties of a Pt monolayer supported on a TiC(001) substrate (Pt/TiC) toward NO reduction. It is found that the compound system of Pt/TiC has a good stability due to the strong Pt-TiC interaction. The diverse dissociation paths (namely the direct dissociation mechanism and the dimeric mechanism) are investigated. The transition state searching calculations suggest that NO has strong diffusion ability and small activation energy for dissociation on the Pt/TiC. For NO reduction on the Pt/TiC surface, we have found that the direct dissociation mechanisms (NO + N + O → NO2 + N and NO + N + O → N2 + O + O) are easier with a smaller dissociation barrier than those on the Pt(111) surface; and the dimeric process (NO + NO → (NO)2 → N2O + O → N2 + O + O) is considered to be dominant or significant with even a lower energy barrier than that of the direct dissociation. The results show that Pt/TiC can serve as an efficient catalyst for NO reduction.

  1. The stability and catalytic activity of W13@Pt42 core-shell structure

    Science.gov (United States)

    Huo, Jin-Rong; Wang, Xiao-Xu; Li, Lu; Cheng, Hai-Xia; Su, Yan-Jing; Qian, Ping

    2016-10-01

    This paper reports a study of the electronic properties, structural stability and catalytic activity of the W13@Pt42 core-shell structure using the First-principles calculations. The degree of corrosion of W13@Pt42 core-shell structure is simulated in acid solutions and through molecular absorption. The absorption energy of OH for this structure is lower than that for Pt55, which inhibits the poison effect of O containing intermediate. Furthermore we present the optimal path of oxygen reduction reaction catalyzed by W13@Pt42. Corresponding to the process of O molecular decomposition, the rate-limiting step of oxygen reduction reaction catalyzed by W13@Pt42 is 0.386 eV, which is lower than that for Pt55 of 0.5 eV. In addition by alloying with W, the core-shell structure reduces the consumption of Pt and enhances the catalytic efficiency, so W13@Pt42 has a promising perspective of industrial application.

  2. The stability and catalytic activity of W13@Pt42 core-shell structure

    Science.gov (United States)

    Huo, Jin-Rong; Wang, Xiao-Xu; Li, Lu; Cheng, Hai-Xia; Su, Yan-Jing; Qian, Ping

    2016-01-01

    This paper reports a study of the electronic properties, structural stability and catalytic activity of the W13@Pt42 core-shell structure using the First-principles calculations. The degree of corrosion of W13@Pt42 core-shell structure is simulated in acid solutions and through molecular absorption. The absorption energy of OH for this structure is lower than that for Pt55, which inhibits the poison effect of O containing intermediate. Furthermore we present the optimal path of oxygen reduction reaction catalyzed by W13@Pt42. Corresponding to the process of O molecular decomposition, the rate-limiting step of oxygen reduction reaction catalyzed by W13@Pt42 is 0.386 eV, which is lower than that for Pt55 of 0.5 eV. In addition by alloying with W, the core-shell structure reduces the consumption of Pt and enhances the catalytic efficiency, so W13@Pt42 has a promising perspective of industrial application. PMID:27759038

  3. The stability and catalytic activity of W13@Pt42 core-shell structure.

    Science.gov (United States)

    Huo, Jin-Rong; Wang, Xiao-Xu; Li, Lu; Cheng, Hai-Xia; Su, Yan-Jing; Qian, Ping

    2016-10-19

    This paper reports a study of the electronic properties, structural stability and catalytic activity of the W13@Pt42 core-shell structure using the First-principles calculations. The degree of corrosion of W13@Pt42 core-shell structure is simulated in acid solutions and through molecular absorption. The absorption energy of OH for this structure is lower than that for Pt55, which inhibits the poison effect of O containing intermediate. Furthermore we present the optimal path of oxygen reduction reaction catalyzed by W13@Pt42. Corresponding to the process of O molecular decomposition, the rate-limiting step of oxygen reduction reaction catalyzed by W13@Pt42 is 0.386 eV, which is lower than that for Pt55 of 0.5 eV. In addition by alloying with W, the core-shell structure reduces the consumption of Pt and enhances the catalytic efficiency, so W13@Pt42 has a promising perspective of industrial application.

  4. Controlled synthesis of Pd-Pt alloy hollow nanostructures with enhanced catalytic activities for oxygen reduction.

    Science.gov (United States)

    Hong, Jong Wook; Kang, Shin Wook; Choi, Bu-Seo; Kim, Dongheun; Lee, Sang Bok; Han, Sang Woo

    2012-03-27

    Pd-Pt alloy nanocrystals (NCs) with hollow structures such as nanocages with porous walls and dendritic hollow structures and Pd@Pt core-shell dendritic NCs could be selectively synthesized by a galvanic replacement method with uniform Pd octahedral and cubic NCs as sacrificial templates. Fine control over the degree of galvanic replacement of Pd with Pt allowed the production of Pd-Pt NCs with distinctly different morphologies. The synthesized hollow NCs exhibited considerably enhanced oxygen reduction activities compared to those of Pd@Pt core-shell NCs and a commercial Pt/C catalyst, and their electrocatalytic activities were highly dependent on their morphologies. The Pd-Pt nanocages prepared from octahedral Pd NC templates exhibited the largest improvement in catalytic performance. We expect that the present work will provide a promising strategy for the development of efficient oxygen reduction electrocatalysts and can also be extended to the preparation of other hybrid or hetero-nanostructures with desirable morphologies and functions. © 2012 American Chemical Society

  5. Size-selective electrocatalytic activity of (Pt)n/MoS2for oxygen reduction reaction

    DEFF Research Database (Denmark)

    Bothra, Pallavi; Pandey, Mohnish; Pati, Swapan K.

    2016-01-01

    In the present work, we have investigated the electrocatalytic activity of the oxygen reduction reaction (ORR), O2 + 4H+ + 4e− → 2H2O, for (Pt)n clusters (n = 1, 2, 3, 5, 7, 10 and 12) adsorbed on semiconducting (2H) and metallic (1T) MoS2 monolayers using first principles density functional theory...... predicting (Pt)7/2H-MoS2 as the best ORR catalyst amongst the (Pt)n/MoS2 heterosystems with an overpotential value of 0.33 V has been established. Our finding proposes a new promising electrocatalyst towards better activity for ORR with very small amount of Pt loading....

  6. Session 6: Highly active Pt/zeolite catalysts for combustion of C{sub 2}-C{sub 4} alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Garetto, T.F.; Rincon, E.; Apesteguia, C.R. [Instituto de Investigaciones en Catalisis y Petroquimica -INCAPE- (UNL-CONICET), Santa Fe (Argentina)

    2004-07-01

    In an attempt for developing more active Pt-based catalysts for lower-alkane combustion, we investigate in this work the deep oxidation of C{sub 2}-C{sub 4} alkanes over Pt-based catalysts. Results show that the lower alkane oxidation turnover rates are more than two orders of magnitude higher on Pt/zeolites compared to Pt/Al{sub 2}O{sub 3} catalyst. (authors)

  7. Activity improvement of Pt/C catalysts by adding CeO2 nanoparticles

    Institute of Scientific and Technical Information of China (English)

    YANG Yuying; ZHANG Ziyu; HU Zhongai

    2011-01-01

    Carbon-supported platinum catalysts were prepared by NaBH4 reduction of metal precursors and the CeO2 nanoparticles were prepared by citric acid sol-gel method. The structure and morphology of two kinds of nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The Pt particles were uniformly dispersed on the carbon surface and showed the rod-like morphology. The CeO2 was spherical in shape. The appropriate amount of CeO2 nanoparticles was added into Pt/C systems to improve activity of the catalysts. Several electrochemical techniques such as cyclic voltammogram (CV), chronoamperometry (I-t)and electrochemical impedance spectroscopy (EIS) were used to investigate the properties of CeO2-Pt/C catalysts for methanol electrooxidation in 1 mol/L CH3OH+0.5H2SO4 aqueous solutions. The results revealed that compared with Pt/C catalysts CeO2-pt/C exhibited a higher activity and stability for methanol electro-oxidation. Moreover, the effect of CeO2 content on the activity of Pt/C catalysts was discussed in detail.

  8. Enhanced Activity of Supported Ni Catalysts Promoted by Pt for Rapid Reduction of Aromatic Nitro Compounds

    Directory of Open Access Journals (Sweden)

    Huishan Shang

    2016-06-01

    Full Text Available To improve the activities of non-noble metal catalysts is highly desirable and valuable to the reduced use of noble metal resources. In this work, the supported nickel (Ni and nickel-platinum (NiPt nanocatalysts were derived from a layered double hydroxide/carbon composite precursor. The catalysts were characterized and the role of Pt was analysed using X-ray diffraction (XRD, high-resolution transmission electron microscopy (HRTEM, energy dispersive X-ray spectroscopy (EDS mapping, and X-ray photoelectron spectroscopy (XPS techniques. The Ni2+ was reduced to metallic Ni0 via a self-reduction way utilizing the carbon as a reducing agent. The average sizes of the Ni particles in the NiPt catalysts were smaller than that in the supported Ni catalyst. The electronic structure of Ni was affected by the incorporation of Pt. The optimal NiPt catalysts exhibited remarkably improved activity toward the reduction of nitrophenol, which has an apparent rate constant (Ka of 18.82 × 10−3 s−1, 6.2 times larger than that of Ni catalyst and also larger than most of the reported values of noble-metal and bimetallic catalysts. The enhanced activity could be ascribed to the modification to the electronic structure of Ni by Pt and the effect of exposed crystal planes.

  9. Oxygen reduction activity of Pt and Pt Co-alloy catalysts: A comparison between kinetic measurements and polymer electrolyte fuel cell experiments

    Energy Technology Data Exchange (ETDEWEB)

    Paulus, U.A.; Draschil, C.; Schmidt, T.J. [PSI and Lawrence Berkeley National Lab (United States); Stamenkovic, V. [Lawrence Berkeley National Lab (United States); Markovic, N.M. [Lawrence Berkeley National Lab (United States); Ross, P.N. [Lawrence Berkeley National Lab (United States); Scherer, G.G.

    2002-03-01

    The oxygen reduction reaction (orr) has been studied on various carbon supported Pt Co alloys in comparison to carbon supported platinum in perchloric acid. The applied thin film rotating ring-disk electrode (rrde) technique allows both the investigation of the orr and their kinetic analysis and in parallel the detection and quantification of the amount of peroxide produced during the orr. Polymer Electrolyte Fuel cell (PEFC) experiments using commercially available gas diffusion electrodes (gdes) with Pt/C and Pt Co/C respectively as active layers were carried out to investigate the above characterized catalysts under real PEFC conditions. (author)

  10. High methanol oxidation activity of well-dispersed pt nanoparticles on carbon nanotubes using nitrogen doping.

    Science.gov (United States)

    Fang, Wei-Chuan

    2009-10-09

    Pt nanoparticles (NPs) with the average size of 3.14 nm well dispersed on N-doped carbon nanotubes (CNTs) without any pretreatment have been demonstrated. Structural properties show the characteristic N bonding within CNTs, which provide the good support for uniform distribution of Pt NPs. In electrochemical characteristics, N-doped CNTs covered with Pt NPs show superior current density due to the fact that the so-called N incorporation could give rise to the formation of preferential sites within CNTs accompanied by the low interfacial energy for immobilizing Pt NPs. Therefore, the substantially enhanced methanol oxidation activity performed by N-incorporation technique is highly promising in energy-generation applications.

  11. High Methanol Oxidation Activity of Well-Dispersed Pt Nanoparticles on Carbon Nanotubes Using Nitrogen Doping

    Directory of Open Access Journals (Sweden)

    Fang Wei-Chuan

    2009-01-01

    Full Text Available Abstract Pt nanoparticles (NPs with the average size of 3.14 nm well dispersed on N-doped carbon nanotubes (CNTs without any pretreatment have been demonstrated. Structural properties show the characteristic N bonding within CNTs, which provide the good support for uniform distribution of Pt NPs. In electrochemical characteristics, N-doped CNTs covered with Pt NPs show superior current density due to the fact that the so-called N incorporation could give rise to the formation of preferential sites within CNTs accompanied by the low interfacial energy for immobilizing Pt NPs. Therefore, the substantially enhanced methanol oxidation activity performed by N-incorporation technique is highly promising in energy-generation applications.

  12. Improved electrocatalytic ethanol oxidation activity in acidic and alkaline electrolytes using size-controlled Pt-Sn nanoparticles.

    Science.gov (United States)

    St John, Samuel; Boolchand, Punit; Angelopoulos, Anastasios P

    2013-12-31

    The promotion of the electrocatalytic ethanol oxidation reaction (EOR) on extended single-crystal Pt surfaces and dispersed Pt nanoparticles by Sn under acidic conditions is well known. However, the correlation of Sn coverage on Pt nanoparticle electrocatalysts to their size has proven difficult. The reason is that previous investigations have typically relied on commercially difficult to reproduce electrochemical treatments of prepared macroscopic electrodes to adsorb Sn onto exposed Pt surfaces. We demonstrate here how independent control over both Sn coverage and particle size can yield a significant enhancement in EOR activity in an acidic electrolyte relative to previously reported electrocatalysts. Our novel approach uses electroless nanoparticle synthesis where surface-adsorbed Sn is intrinsic to Pt particle formation. Sn serves as both a reducing agent and stabilizing ligand, producing particles with a narrow particle size distribution in a size range where the mass-specific electrocatalytic activity can be maximized (ca. 1-4 nm) as a result of the formation of a fully developed Sn shell. The extent of fractional Sn surface coverage on carbon-supported Pt nanoparticles can be systematically varied through wet-chemical treatment subsequent to nanoparticle formation but prior to incorporation into macroscopic electrodes. EOR activity for Pt nanoparticles is found to be optimum at a fractional Sn surface coverage of ca. 0.6. Furthermore, the EOR activity is shown to increase with Pt particle size and correlate with the active area of available Pt (110) surface sites for the corresponding Sn-free nanoparticles. The maximum area- and mass-specific EOR activities for the most active catalyst investigated were 17.9 μA/cm(2)Pt and 12.5 A/gPt, respectively, after 1 h of use at 0.42 V versus RHE in an acidic electrolyte. Such activity is a substantial improvement over that of commercially available Pt, Pt-Sn, and Pt-Ru alloy catalysts under either acidic or alkaline

  13. Relationship between the catalytic activity of Pt/alumina and the relaxation process of the photoexcited electrons

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Junji, E-mail: j-itou@mail.nissan.co.jp [Advanced Materials Laboratory, Nissan Research Center, NISSAN MOTOR CO., LTD., 1 Natsushima-cho, Yokosuka-shi, Kanagawa 237-8523 (Japan); Department of Applied Physics and Chemistry, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Hanaki, Yasunari [Advanced Materials Laboratory, Nissan Research Center, NISSAN MOTOR CO., LTD., 1 Natsushima-cho, Yokosuka-shi, Kanagawa 237-8523 (Japan); Shen, Qing [Department of Applied Physics and Chemistry, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Department of Engineering Science, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Toyoda, Taro [Department of Applied Physics and Chemistry, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Department of Engineering Science, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer We determined the decay time of photoexcited electrons of Pt/Al{sub 2}O{sub 3}. Black-Right-Pointing-Pointer Faster decay of excited electrons in Pt/Al{sub 2}O{sub 3} leads to its faster oxidation rate. Black-Right-Pointing-Pointer Decreasing excited electron lifetime in Pt/Al{sub 2}O{sub 3} may decrease Pt consumption in catalytic convertors. - Abstract: In order to decrease the consumption of precious metals used in the catalytic converters used in automobiles, we studied the relationship between the catalytic activity of Pt/alumina (Pt/Al{sub 2}O{sub 3}) and the relaxation process of photoexcited electrons. Firstly, we studied the relationship between the size of the Pt particles in Pt/Al{sub 2}O{sub 3} and catalytic performance. Secondly, the relationship between the size of the Pt particles in Pt/Al{sub 2}O{sub 3} and the decay time of the excited electrons was studied using an improved transient grating (TG) technique. The results showed that faster decay of the excited electrons leads to greater oxidation rates. The decay time obtained with the improved TG technique gives an indication of the time that the exited electrons take to return to the ground state. According to studies utilizing FT-IR, one of the processes necessary for quickly generating CO{sub 2} with Pt is that the electron in the Pt-O bond moves to the Pt side and that the Pt{sup +} becomes Pt metal. Thus, the decay time obtained with the improved TG technique corresponds to the process whereby Pt{sup +} returns to Pt metal. Thus, we found that the consumption of precious metals can be reduced by increasing the speed of the decay of the excited electrons.

  14. Nanostructured polyaniline-decorated Pt/C@PANI core-shell catalyst with enhanced durability and activity.

    Science.gov (United States)

    Chen, Siguo; Wei, Zidong; Qi, XueQiang; Dong, Lichun; Guo, Yu-Guo; Wan, Lijun; Shao, Zhigang; Li, Li

    2012-08-15

    We have designed and synthesized a polyaniline (PANI)-decorated Pt/C@PANI core-shell catalyst that shows enhanced catalyst activity and durability compared with nondecorated Pt/C. The experimental results demonstrate that the activity for the oxygen reduction reaction strongly depends on the thickness of the PANI shell and that the greatest enhancement in catalytic properties occurs at a thickness of 5 nm, followed by 2.5, 0, and 14 nm. Pt/C@PANI also demonstrates significantly improved stability compared with that of the unmodified Pt/C catalyst. The high activity and stability of the Pt/C@PANI catalyst is ascribed to its novel PANI-decorated core-shell structure, which induces both electron delocalization between the Pt d orbitals and the PANI π-conjugated ligand and electron transfer from Pt to PANI. The stable PANI shell also protects the carbon support from direct exposure to the corrosive environment.

  15. Phase transition in PT symmetric active plasmonic systems

    CERN Document Server

    Mattheakis, M; Molina, M I; Tsironis, G P

    2015-01-01

    Surface plasmon polaritons (SPPs) are coherent electromagnetic surface waves trapped on an insulator-conductor interface. The SPPs decay exponentially along the propagation due to conductor losses, restricting the SPPs propagation length to few microns. Gain materials can be used to counterbalance the aforementioned losses. We provide an exact expression for the gain, in terms of the optical properties of the interface, for which the losses are eliminated. In addition, we show that systems characterized by lossless SPP propagation are related to PT symmetric systems. Furthermore, we derive an analytical critical value of the gain describing a phase transition between lossless and prohibited SPPs propagation. The regime of the aforementioned propagation can be directed by the optical properties of the system under scrutiny. Finally, we perform COMSOL simulations verifying the theoretical findings.

  16. Preparation of Pt/TiO2 hollow nanofibers with highly visible light photocatalytic activity

    Science.gov (United States)

    Yang, Ziling; Lu, Jing; Ye, Weichun; Yu, Chushu; Chang, Yanlong

    2017-01-01

    The Pt/TiO2 hollow nanofibers (HNFs) as a photocatalyst have been successfully prepared by a uniaxial electrospinning method combined with photo-deposition. The as-synthesized photocatalysts were characterized by TEM, XRD, SAED, EDX, XPS, N2 adsorption-desorption, and UV-vis DRS. The TiO2 HNFs were composed of an anatase-rutile mixed phase, with the ratio of ∼70:30. The band gap of TiO2 HNFs decreased from 3.09 down to 2.77 eV with 2 wt.% Pt loading, this led to an enhanced photocatalytic performance under visible light. By evaluating the degradation of azo dye Orange II, the pseudo-first-rate constant (k) of Pt/350-TiO2 HNFs system was 0.0069 min-1, which was 11.5 and 3.63 times higher than for TiO2 HNFs and Pt/P25, respectively. The main factors affecting the photocatalytic activity were further investigated, these included the loading amount of Pt, the calcination temperature of TiO2 HNFs, the pH of initial solution and the light source. The results of repeated use of the Pt/TiO2 HNFs demonstrated that the photocatalysts exhibited an excellent stability even after ten cycles. The possible degradation mechanism was also studied. It was shown that rad O2- radicals were the main reactive oxygen species for the degradation of Orange II.

  17. Ethanol oxidation reaction activity of highly dispersed Pt/SnO{sub 2} double nanoparticles on carbon black

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, Eiji; Miyata, Kazumasa; Takase, Tomonori; Inoue, Hiroshi [Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)

    2011-02-15

    Highly dispersed Pt and SnO{sub 2} double nanoparticles containing different Pt/Sn ratios (denoted as Pt/SnO{sub 2}/CB) were prepared on carbon black (CB) by the modified Boennemann method. The average size of Pt and SnO{sub 2} nanoparticles was 3.1 {+-} 0.5 nm and 2.5 {+-} 0.3 nm, respectively, in Pt/SnO{sub 2}(3:1)/CB, 3.0 {+-} 0.5 nm and 2.6 {+-} 0.3 nm, respectively, in Pt/SnO{sub 2}(1:1)/CB, and 2.8 {+-} 0.5 nm and 2.5 {+-} 0.3 nm, respectively, in Pt/SnO{sub 2}(1:3)/CB. The Pt/SnO{sub 2}(3:1)/CB electrode showed the highest specific activity and lowest overpotential for ethanol oxidation reaction (EOR), and was superior to a Pt/CB electrode. Current density for EOR at 0.40 and 0.60 V vs. reversible hydrogen electrode for the Pt/SnO{sub 2}(3:1)/CB electrode decayed more slowly than that for the Pt/CB electrode because of a synergistic effect between Pt and SnO{sub 2} nanoparticles. The predominant reaction product was acetic acid, and its current efficiency was about 70%, while that for CO{sub 2} production was about 30%. (author)

  18. Activated carbon fibers impregnated with Pd and Pt catalysts for toluene removal.

    Science.gov (United States)

    Liu, Zhen-Shu; Chen, Jian-Yuan; Peng, Yu-Hui

    2013-07-15

    Few studies have investigated the use of activated carbon fibers (ACFs) impregnated with noble metals for the catalytic oxidation of volatile organic compounds (VOCs). This study determined the removal efficiency of toluene as a function of time over ACF-supported metal catalysts. Two catalysts (Pt and Pd), five reaction temperatures (120, 150, 200, 250, and 300°C), and three oxygen contents (6%, 10%, and 21%) were investigated to determine the removal of toluene. To study the effects of the characteristics of the catalysts on toluene removal, the composition and morphology of the ACFs were analyzed using the BET, XPS, ICP, and FE-SEM. The results showed that the 0.42%Pd/ACFs showed greater activity for toluene removal than did 2.68%Pt/ACFs at a reaction temperature of 200°C and an oxygen content of 10%. The main removal mechanism of toluene over the 2.68%Pt/ACFs at reaction temperatures less than 200°C was adsorption. The long-term catalytic activity of the 2.68%Pt/ACFs for toluene removal at a reaction temperature of 250°C and an oxygen content of 10% could be obtained. Furthermore, toluene removal over the 2.68%Pt/ACFs at 200°C could be enhanced with increasing oxygen content.

  19. Surface-Limited Synthesis of Pt Nanocluster Decorated Pd Hierarchical Structures with Enhanced Electrocatalytic Activity toward Oxygen Reduction Reaction.

    Science.gov (United States)

    Yang, Tao; Cao, Guojian; Huang, Qingli; Ma, Yanxia; Wan, Sheng; Zhao, Hong; Li, Na; Sun, Xia; Yin, Fujun

    2015-08-12

    Exploring superior catalysts with high catalytic activity and durability is of significant for the development of an electrochemical device involving the oxygen reduction reaction. This work describes the synthesis of Pt-on-Pd bimetallic heterogeneous nanostructures, and their high electrocatalytic activity toward the oxygen reduction reaction (ORR). Pt nanoclusters with a size of 1-2 nm were generated on Pd nanorods (NRs) through a modified Cu underpotential deposition (UPD) process free of potential control and a subsequent surface-limited redox reaction. The Pt nanocluster decorated Pd nanostructure with a ultralow Pt content of 1.5 wt % exhibited a mass activity of 105.3 mA mg(-1) (Pt-Pd) toward ORR, comparable to that of the commercial Pt/C catalyst but 4 times higher than that of carbon supported Pd NRs. More importantly, the carbon supported Pt-on-Pd catalyst displays relatively small losses of 16% in electrochemical surface area (ECSA) and 32% in mass activity after 10 000 potential sweeps, in contrast to respective losses of 46 and 64% for the commercial Pt/C catalyst counterpart. The results demonstrated that Pt decoration might be an efficient way to improve the electrocatalytic activity of Pd and in turn allow Pd to be a promising substitution for commercial Pt catalyst.

  20. Pt5Gd as a Highly Active and Stable Catalyst for Oxygen Electroreduction

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Verdaguer-Casadevall, Arnau; Verdaguer Casadevall, Arnau

    2012-01-01

    The activity and stability of Pt5Gd for the oxygen reduction reaction (ORR) have been studied, using a combination of electrochemical measurements, angle-resolved X-ray photoelectron spectroscopy (AR-XPS), and density functional theory calculations. Sputter-cleaned, polycrystalline Pt5Gd shows a 5...... can be explained by means of compressive strain effects. Furthermore, these novel bimetallic electrocatalysts are highly stable, which, in combination with their enhanced activity, makes them very promising for the development of new cathode catalysts for fuel cells....

  1. Highly active dealloyed Cu@Pt core-shell electrocatalyst towards 2-propanol electrooxidation in acidic solution

    Science.gov (United States)

    Poochai, Chatwarin

    2017-02-01

    Dealloyed Cu@Pt core-shell electrocatalyst was fabricated by cyclic co-electrodeposition and selective Cu dealloying (CCEd-sCuD) on carbon paper (CP), namely Cu@Pt/CP. The Cu@Pt/CP exhibited a core-shell structure comprising with a Cu-rich core and a Pt-rich shell. The crystalline phases of Pt/CP and Cu@Pt/CP were a face-centered cubic (fcc). The compressive lattice strain approximately 0.85% was found in the Cu@Pt/CP owing to a lattice mismatch between a core and a shell region. In the core-region, Cu was formed Pt-Cu alloy as major and copper oxide and also metallic copper as minor. The morphology and grain size of the Cu@Pt/CP displayed a porous spherical shape with 100 nm in diameter, while those of Pt/CP seemed to be a cubic shape with smaller diameter of 40 nm. In electrochemical and catalytic activity, the surface of Cu@Pt/CP had a larger electrochemical active surface area (ECSA) than that of Pt/CP due to a porous formation caused by Cu dealloying. It is not surprising that the Cu@Pt/CP showed higher catalytic activity and greater stability towards 0.5 M 2-propanol electrooxidation in 0.5 M H2SO4 in terms of peak current density (jp), peak potential (Ep), onset potential (Eonset), diffusion coefficient (D), and charge transfer resistance (Rct) which were caused by electronic structure modification, higher compressive lattice strain, and larger ECSA, compared with Pt/CP.

  2. Electrospun Nb-doped TiO2 nanofiber support for Pt nanoparticles with high electrocatalytic activity and durability.

    Science.gov (United States)

    Kim, MinJoong; Kwon, ChoRong; Eom, KwangSup; Kim, JiHyun; Cho, EunAe

    2017-03-14

    This study explores a facile method to prepare an efficient and durable support for Pt catalyst of polymer electrolyte membrane fuel cell (PEMFC). As a candidate, Nb-doped TiO2 (Nb-TiO2) nanofibers are simply fabricated using an electrospinning technique, followed by a heat treatment. Doping Nb into the TiO2 nanofibers leads to a drastic increase in electrical conductivity with doping level of up to 25 at. % (Nb0.25Ti0.75O2). Pt nanoparticles are synthesized on the prepared 25 at. % Nb-doped TiO2-nanofibers (Pt/Nb-TiO2) as well as on a commercial powdered carbon black (Pt/C). The Pt/Nb-TiO2 nanofiber catalyst exhibits similar oxygen reaction reduction (ORR) activity to that of the Pt/C catalyst. However, during an accelerated stress test (AST), the Pt/Nb-TiO2 nanofiber catalyst retained more than 60% of the initial ORR activity while the Pt/C catalyst lost 65% of the initial activity. The excellent durability of the Pt/Nb-TiO2 nanofiber catalyst can be attributed to high corrosion resistance of TiO2 and strong interaction between Pt and TiO2.

  3. Electrospun Nb-doped TiO2 nanofiber support for Pt nanoparticles with high electrocatalytic activity and durability

    Science.gov (United States)

    Kim, Minjoong; Kwon, Chorong; Eom, Kwangsup; Kim, Jihyun; Cho, Eunae

    2017-03-01

    This study explores a facile method to prepare an efficient and durable support for Pt catalyst of polymer electrolyte membrane fuel cell (PEMFC). As a candidate, Nb-doped TiO2 (Nb-TiO2) nanofibers are simply fabricated using an electrospinning technique, followed by a heat treatment. Doping Nb into the TiO2 nanofibers leads to a drastic increase in electrical conductivity with doping level of up to 25 at. % (Nb0.25Ti0.75O2). Pt nanoparticles are synthesized on the prepared 25 at. % Nb-doped TiO2-nanofibers (Pt/Nb-TiO2) as well as on a commercial powdered carbon black (Pt/C). The Pt/Nb-TiO2 nanofiber catalyst exhibits similar oxygen reaction reduction (ORR) activity to that of the Pt/C catalyst. However, during an accelerated stress test (AST), the Pt/Nb-TiO2 nanofiber catalyst retained more than 60% of the initial ORR activity while the Pt/C catalyst lost 65% of the initial activity. The excellent durability of the Pt/Nb-TiO2 nanofiber catalyst can be attributed to high corrosion resistance of TiO2 and strong interaction between Pt and TiO2.

  4. 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.

  5. Electrospun Nb-doped TiO2 nanofiber support for Pt nanoparticles with high electrocatalytic activity and durability

    Science.gov (United States)

    Kim, MinJoong; Kwon, ChoRong; Eom, KwangSup; Kim, JiHyun; Cho, EunAe

    2017-01-01

    This study explores a facile method to prepare an efficient and durable support for Pt catalyst of polymer electrolyte membrane fuel cell (PEMFC). As a candidate, Nb-doped TiO2 (Nb-TiO2) nanofibers are simply fabricated using an electrospinning technique, followed by a heat treatment. Doping Nb into the TiO2 nanofibers leads to a drastic increase in electrical conductivity with doping level of up to 25 at. % (Nb0.25Ti0.75O2). Pt nanoparticles are synthesized on the prepared 25 at. % Nb-doped TiO2-nanofibers (Pt/Nb-TiO2) as well as on a commercial powdered carbon black (Pt/C). The Pt/Nb-TiO2 nanofiber catalyst exhibits similar oxygen reaction reduction (ORR) activity to that of the Pt/C catalyst. However, during an accelerated stress test (AST), the Pt/Nb-TiO2 nanofiber catalyst retained more than 60% of the initial ORR activity while the Pt/C catalyst lost 65% of the initial activity. The excellent durability of the Pt/Nb-TiO2 nanofiber catalyst can be attributed to high corrosion resistance of TiO2 and strong interaction between Pt and TiO2. PMID:28290503

  6. Scalable Nanoporous (Pt1-xNix)3Al Intermetallic Compounds as Highly Active and Stable Catalysts for Oxygen Electroreduction.

    Science.gov (United States)

    Han, Gao-Feng; Gu, Lin; Lang, Xing-You; Xiao, Bei-Bei; Yang, Zhen-Zhong; Wen, Zi; Jiang, Qing

    2016-12-07

    Author: Bimetallic platinum-nickel (Pt-Ni) alloys as oxygen reduction reaction (ORR) electrocatalysts show genuine potential to boost widespread use of low-temperature fuel cells in vehicles by virtue of their high catalytic activity. However, their practical implementation encounters primary challenges in structural and catalytic durability caused by the low formation heat of Pt-Ni alloys. Here, we report nanoporous (NP) (Pt1-xNix)3Al intermetallic nanoparticles as oxygen electroreduction catalyst NP (Pt1-xNix)3Al, which circumvents this problem by making use of the extraordinarily negative formation heats of Pt-Al and Ni-Al bonds. The NP (Pt1-xNix)3Al nanocatalyst, which is mass-produced by alloying/dealloying and mechanical crushing technologies, exhibits specific activity of 3.6 mA cm(-2)Pt and mass activity of 2.4 A mg(-1)Pt at 0.90 V as a result of both ligand and compressive strain effects, while strong Ni-Al and Pt-Al bonds ensure their exceptional durability by alleviating evolution of Pt, Ni, and Al components and dissolutions of Ni and Al atoms.

  7. Achieving Remarkable Activity and Durability toward Oxygen Reduction Reaction Based on Ultrathin Rh-Doped Pt Nanowires.

    Science.gov (United States)

    Huang, Hongwen; Li, Kan; Chen, Zhao; Luo, Laihao; Gu, Yuqian; Zhang, Dongyan; Ma, Chao; Si, Rui; Yang, Jinlong; Peng, Zhenmeng; Zeng, Jie

    2017-06-21

    The research of active and sustainable electrocatalysts toward oxygen reduction reaction (ORR) is of great importance for industrial application of fuel cells. Here, we report a remarkable ORR catalyst with both excellent mass activity and durability based on sub 2 nm thick Rh-doped Pt nanowires, which combine the merits of high utilization efficiency of Pt atoms, anisotropic one-dimensional nanostructure, and doping of Rh atoms. Compared with commercial Pt/C catalyst, the Rh-doped Pt nanowires/C catalyst shows a 7.8 and 5.4-fold enhancement in mass activity and specific activity, respectively. The combination of extended X-ray absorption fine structure analysis and density functional theory calculations reveals that the compressive strain and ligand effect in Rh-doped Pt nanowires optimize the adsorption energy of hydroxyl and in turn enhance the specific activity. Moreover, even after 10000 cycles of accelerated durability test in O2 condition, the Rh-doped Pt nanowires/C catalyst exhibits a drop of 9.2% in mass activity, against a big decrease of 72.3% for commercial Pt/C. The improved durability can be rationalized by the increased vacancy formation energy of Pt atoms for Rh-doped Pt nanowires.

  8. Promotion of catalytic activity for methanol electro-oxidation on CoPc-Pt/C co-catalysts

    Institute of Scientific and Technical Information of China (English)

    WU JingJie; XU YiMin; PAN Mu; MA WenTao; TANG HaoLin

    2009-01-01

    The catalytic activity for methanol electro-oxidation on CoPc-Pt/C co-catalysts, prepared by impregnation method, was studied in details through electrochemical methods. Cyclic voltammetry (CV) result demonstrates that CoPc has higher forward anodic peak current density and jf/jb value (forward anodic peak current density/backward anodic peak current density) than Pt/C. Chronoamperometry (CA) analysis indicates that CoPc-Pt/C exhibits both excellent transient current density and stable current density for methanol electro-oxidation compared with Pt/C. Two main mechanisms related to the promotion of catalytic activity are as follows: CoPc-Pt/C has the activity of tolerance to carbonaceous intermediates, thus inhibiting the self-poisoning of catalysts; CoPc-Pt/C owns prominent intrinsic catalytic activity indicated by the apparent activation energy for methanol oxidation on CoPc-Pt/C, which is 18 kJ/mol, less than that on Pt and PtRu catalysts as reported.

  9. Effect of Pt Nanoparticles on the Photocatalytic Activity of ZnO Nanofibers

    Science.gov (United States)

    Di Mauro, Alessandro; Zimbone, Massimo; Scuderi, Mario; Nicotra, Giuseppe; Fragalà, Maria Elena; Impellizzeri, Giuliana

    2015-12-01

    For this study, we originally realized ZnO nanofibers (˜50 nm in mean radius) mixed with Pt nanoparticles (˜30 nm in mean radius), prepared by pulsed laser ablation in liquid, and investigated their photocatalytic performance. The material was synthesized by the simple electrospinning method coupled with subsequent thermal treatments. Methylene blue was employed as a representative dye pollutant to evaluate the photocatalytic activity of the nanofibers. It was found that the Pt-ZnO fibers exhibit a photodegradation reaction rate that is ˜40 % higher than the one obtained for reference ZnO fibers. These encouraging results demonstrate that Pt-ZnO nanofibers can be fruitfully applied for environmental applications.

  10. Nickel-doped ceria nanoparticles for promoting catalytic activity of Pt/C for ethanol electrooxidation

    Science.gov (United States)

    Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

    2014-10-01

    This paper reports the facile synthesis of monodispersed nickel-doped ceria nanoparticles by a thermal decomposition method, which is used to promote catalytic properties of Pt/C. The Pt/Ni-doped CeO2/C catalyst obtained exhibits remarkably high activity and stability towards the ethanol electrooxidation in acidic media. This is attributed to higher oxygen releasing capacity and stronger interaction of Ni-doped CeO2 with Pt than pure CeO2 nanoparticles that contribute positively to the removal of poisoning intermediates. We believe that the design concept and synthetic strategy of metal doped oxides used for fuel cell catalysts can be potentially extended to other catalytic fields.

  11. Facile synthesis of PtCu nanowires with enhanced electrocatalytic activity

    Institute of Scientific and Technical Information of China (English)

    Wei Hong[1,2; Jin Wang[1,3; Erkang Wang[1,2

    2015-01-01

    Using Te nanowires as a sacrificial template, We developed a facile wet-chemical method for the synthesis of bimetallic PtCu nanowires. The as-prepared PtCu nanowires possess a porous structure and high aspect ratio. Transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, energy dispersive X-ray spectrum elemental mapping, inductively coupled plasma- mass spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurement techniques are used to analyze the structure and composition of the as-prepared nanowires. The XPS results verify that the incorporation of Cu led to the modified electronic state of Pt. Electrocatalytic results prove that the as-prepared nanowires present superior activity for methanol and ethanol electrooxidation in an alkaline solution.

  12. Anode activation polarization on Pt(h k l) electrodes in dilute sulphuric acid electrolyte

    Science.gov (United States)

    Mann, R. F.; Amphlett, J. C.; Peppley, B. A.; Thurgood, C. P.

    Proton exchange membrane (PEM) fuel cells have been under development for many years and appear to be the potential solution for many electricity supply applications. Modelling and computer simulation of PEM fuel cells have been equally active areas of work as a means of developing better understanding of cell and stack operation, facilitating design improvements and supporting system simulation studies. The prediction of activation polarization in our previous PEM modelling work, as in most PEM models, concentrated on the cathode losses. Anode losses are commonly much smaller and tend to be ignored compared to cathode losses. Further development of the anode activation polarization term is being undertaken in order to broaden the application and usefulness of PEM models in general. Previously published work on the kinetics of the hydrogen oxidation reaction using Pt(h k l) electrodes in dilute H 2SO 4 has been examined and further developed for eventual application to the modelling of PEM fuel cells. New correlations for the exchange current density are developed for Pt(1 0 0), Pt(1 1 0) and Pt(1 1 1) electrodes. Predictive equations for the anode activation polarization are also proposed. In addition, terminology has been modified to make the correlation approach and, eventually, the modelling method more easily understood and used by those without an extensive background in electrochemistry.

  13. AuPt Alloy Nanostructures with Tunable Composition and Enzyme-like Activities for Colorimetric Detection of Bisulfide

    Science.gov (United States)

    He, Weiwei; Han, Xiangna; Jia, Huimin; Cai, Junhui; Zhou, Yunlong; Zheng, Zhi

    2017-01-01

    Tuning the enzyme-like activity and studying the interaction between biologically relevant species and nano-enzymes may facilitate the applications of nanostructures in mimicking natural enzymes. In this work, AuPt alloy nanoparticles (NPs) with varying compositions were prepared through a facile method by co-reduction of Au3+ and Pt2+ in aqueous solutions. The composition could be tuned easily by adjusting the molar ratios of added Pt2+ to Au3+. It was found that both peroxidase-like and oxidase-like activity of AuPt alloy NPs were highly dependent on the alloy compositions, which thus suggesting an effective way to tailor their catalytic properties. By investigating the inhibitory effects of HS- on the enzyme-like activity of AuPt alloy NPs and natural enzyme, we have developed a method for colorimetric detection of HS- and evaluation of the inhibiting effects of inhibitors on natural and artificial enzymes. In addition, the responsive ability of this method was influenced largely by the composition: AuPt alloy NPs show much lower limit of detection for HS- than Pt NPs while Pt NPs show wider linear range than AuPt alloy NPs. This study suggests the facile way not only for synthesis of alloy nanostructures, but also for tuning their catalytic activities and for use in bioanalysis.

  14. Nitric oxide-induced eosinophil apoptosis is dependent on mitochondrial permeability transition (mPT, JNK and oxidative stress: apoptosis is preceded but not mediated by early mPT-dependent JNK activation

    Directory of Open Access Journals (Sweden)

    Ilmarinen-Salo Pinja

    2012-08-01

    Full Text Available Abstract Background Eosinophils are critically involved in the pathogenesis of asthma. Nitric oxide (NO is produced in high amounts in asthmatic lungs and has an important role as a regulator of lung inflammation. NO was previously shown to induce eosinophil apoptosis mediated via c-jun N-terminal kinase (JNK and caspases. Our aim was to clarify the cascade of events leading to NO-induced apoptosis in granulocyte macrophage-colony stimulating factor (GM-CSF-treated human eosinophils concentrating on the role of mitochondria, reactive oxygen species (ROS and JNK. Methods Apoptosis was determined by flow cytometric analysis of relative DNA content, by Annexin-V labelling and/or morphological analysis. Immunoblotting was used to study phospho-JNK (pJNK expression. Mitochondrial membrane potential was assessed by JC-1-staining and mitochondrial permeability transition (mPT by loading cells with calcein acetoxymethyl ester (AM and CoCl2 after which flow cytometric analysis was conducted. Statistical significance was calculated by repeated measures analysis of variance (ANOVA or paired t-test. Results NO-donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP induced late apoptosis in GM-CSF-treated eosinophils. SNAP-induced apoptosis was suppressed by inhibitor of mPT bongkrekic acid (BA, inhibitor of JNK SP600125 and superoxide dismutase-mimetic AEOL 10150. Treatment with SNAP led to late loss of mitochondrial membrane potential. Additionally, we found that SNAP induces early partial mPT (1 h that was followed by a strong increase in pJNK levels (2 h. Both events were prevented by BA. However, these events were not related to apoptosis because SNAP-induced apoptosis was prevented as efficiently when BA was added 16 h after SNAP. In addition to the early and strong rise, pJNK levels were less prominently increased at 20–30 h. Conclusions Here we demonstrated that NO-induced eosinophil apoptosis is mediated via ROS, JNK and late mPT. Additionally

  15. High-activity PtRuPd/C catalyst for direct dimethyl ether fuel cells.

    Science.gov (United States)

    Li, Qing; Wen, Xiaodong; Wu, Gang; Chung, Hoon T; Gao, Rui; Zelenay, Piotr

    2015-06-22

    Dimethyl ether (DME) has been considered as a promising alternative fuel for direct-feed fuel cells but lack of an efficient DME oxidation electrocatalyst has remained the challenge for the commercialization of the direct DME fuel cell. The commonly studied binary PtRu catalyst shows much lower activity in DME than methanol oxidation. In this work, guided by density functional theory (DFT) calculation, a ternary carbon-supported PtRuPd catalyst was designed and synthesized for DME electrooxidation. DFT calculations indicated that Pd in the ternary PtRuPd catalyst is capable of significantly decreasing the activation energy of the CO and CH bond scission during the oxidation process. As evidenced by both electrochemical measurements in an aqueous electrolyte and polymer-electrolyte fuel cell testing, the ternary catalyst shows much higher activity (two-fold enhancement at 0.5 V in fuel cells) than the state-of-the-art binary Pt50 Ru50 /C catalyst (HiSPEC 12100).

  16. Homogeneously embedded Pt nanoclusters on amorphous titania matrix as highly efficient visible light active photocatalyst material

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Vipul; Kumar, Suneel; Krishnan, Venkata, E-mail: vkn@iitmandi.ac.in

    2016-08-15

    A novel and facile technique, based on colloidal synthesis route, has been utilized for the preparation of homogeneously embedded Pt nanoclusters on amorphous titania matrix. The material has been thoroughly characterized using high resolution transmission electron microscopy, energy dispersive x-ray analysis, powder x-ray diffraction, optical and Raman spectroscopic techniques to understand the morphology, structure and other physical characteristics. The photocatalytic activity of the material under visible light irradiation was demonstrated by investigations on the degradation of two organic dyes (methylene blue and rhodamine B). In comparison to other Pt−TiO{sub 2} based nanomaterials (core-shell, doped nanostructures, modified nanotubes, decorated nanospheres and binary nanocomposites), the embedded Pt nanoclusters on titania was found to be highly efficient for visible light active photocatalytic applications. The enhanced catalytic performance could be attributed to the efficient charge separation and decreased recombination of the photo generated electrons and holes at the Pt-titania interface and the availability of multiple metal-metal oxide interfaces due to homogeneous embedment of Pt nanoclusters on amorphous titania. In essence, this work illustrates that homogeneous embedment of noble metal nanoparticles/nanoclusters on semiconductor metal oxide matrices can lead to tuning of the photophysical properties of the final material and eventually enhance its photocatalytic activity. - Highlights: • Homogeneously embedded Pt nanoclusters on amorphous titania matrix has been prepared. • Facile low temperature colloidal synthesis technique has been used. • Enhanced catalytic performance could be observed. • Work can pave way for tuning photocatalytic activity of composite materials.

  17. PdPt bimetallic nanoparticles enabled by shape control with halide ions and their enhanced catalytic activities.

    Science.gov (United States)

    Zhang, Jinfeng; Wan, Lei; Liu, Lei; Deng, Yida; Zhong, Cheng; Hu, Wenbin

    2016-02-21

    In this study, a new and convenient one step approach is described for synthesizing shape controlled PdPt bimetallic nanoparticles. It is found that the resultant morphologies of these PdPt nanoparticles can be well controlled by simply altering the participation of different halide ions that serve as shape controlling agents in the reaction solution. The dendritic core-shell PdPt bimetallic nanoparticles generated with Pt atoms adopt usual island growth pattern in the presence of Cl(-) ions, whereas the introduction of Br(-) ions with a relatively strong adsorption effect facilitate the formation of a layered core-shell structure due to the layered growth mode of Pt atoms on the exterior surface of the central Pd core. Moreover, the stronger adsorption function of I(-) ions and the resulting fast atomic diffusion promoted the generation of mesoporous core-shell PdPt bimetallic nanoparticles with many pore channels. In addition, the size of these synthesized PdPt nanoparticles exhibited a significant dependence on the concentration of the halide ions involved. Due to their specific structural features and synergistic effects, these PdPt catalysts exhibited shape-dependent catalytic performance and drastically enhanced electrocatalytic activities relative to that of commercial Pt black and Pt/C toward methanol oxidation.

  18. Mixed-phase Pd-Pt bimetallic alloy on graphene oxide with high activity for electrocatalytic applications

    Science.gov (United States)

    Khan, Majid; Yousaf, Ammar Bin; Chen, Mingming; Wei, Chengsha; Wu, Xibo; Huang, Ningdong; Qi, Zeming; Li, Liangbin

    2015-05-01

    Bimetallic PdPt alloy nanoparticles on graphene oxide (GO) have been prepared by a simple and facile chemical route, in which the reduction of metal precursors is carried out using CO as a reductant. Structural and morphological characterizations of GO/PdPt composites are performed using X-ray diffraction, X-ray photoelectron spectroscopy analysis and transmission electron microscopy. It is found that PdPt bimetallic nanoparticles are successfully synthesized and uniformly attached on the graphene sheets. The electrocatalytic and electrochemical properties of GO/PdPt composites including methanol oxidation reaction (MOR), oxygen reduction reaction (ORR) and methanol tolerant oxygen reduction reaction (MTORR) are studied in HClO4 aqueous solution. A significant improvement in the electrocatalytic activities is observed by increasing the atomic ratio of Pt in PdPt bimetallic alloys compared to the freestanding Pd nanoparticles on GO. The prepared GO/PdPt composites with an (Pd:Pt) atomic ratio of 40:60 exhibits higher methanol oxidation activity, higher specific ORR activity and better tolerance to CO poisoning. The results can be attributed to the collective effects of the PdPt nanoparticles and the enhanced electron transfer of graphene.

  19. Tuning Pt and Cu sites population inside functionalized UiO-67 MOF by controlling activation conditions.

    Science.gov (United States)

    Braglia, L; Borfecchia, E; Lomachenko, K A; Bugaev, A L; Guda, A A; Soldatov, A V; Bleken, B T L; Øien-Ødegaard, S; Olsbye, U; Lillerud, K P; Bordiga, S; Agostini, G; Manzoli, M; Lamberti, C

    2017-09-08

    The exceptional thermal and chemical stability of the UiO-66, -67 and -68 classes of isostructural MOFs [J. Am. Chem. Soc., 2008, 130, 13850] makes them ideal materials for functionalization purposes aimed at introducing active centres for potential application in heterogeneous catalysis. We previously demonstrated that a small fraction (up to 10%) of the linkers in the UiO-67 MOF can be replaced by bipyridine-dicarboxylate (bpydc) moieties exhibiting metal-chelating ability and enabling the grafting of Pt(ii) and Pt(iv) ions in the MOF framework [Chem. Mater., 2015, 27, 1042] upon interaction with PtCl2 or PtCl4 precursors. Herein we extend this functionalization approach in two directions. First, we show that by controlling the activation of the UiO-67-Pt we can move from a material hosting isolated Pt(ii) sites anchored to the MOF framework with Pt(ii) exhibiting two coordination vacancies (potentially interesting for C-H bond activation) to the formation of very small Pt nanoparticles hosted inside the MOF cavities (potentially interesting for hydrogenation reactions). The second direction consists of the extension of the approach to the insertion of Cu(ii), obtained via interaction with CuCl2, and exhibiting interesting redox properties. All materials have been characterized by in situ X-ray absorption spectroscopy at the Pt L3- and Cu K-edges.

  20. Shortened activated partial thromboplastin time, a hemostatic marker for hypercoagulable state during acute coronary event.

    Science.gov (United States)

    Abdullah, Wan Zaidah; Moufak, Shaimaa K; Yusof, Zurkurnai; Mohamad, Mohd Sapawi; Kamarul, I M

    2010-06-01

    Various factors may contribute to a hypercoagulable state and acute vascular thrombosis. A prospective study was conducted involving 165 coronary heart disease (CHD) patients from the Cardiology Unit, Hospital Universiti Sains Malaysia. The purpose of this study was to investigate the relationship among factor VIII (FVIII), prothrombin time (PT), activated partial thromboplastin time (APTT), and activated protein C resistance (APC-R) state among CHD patients and to look for potential clinical applications from these laboratory findings. There were 110 cases diagnosed as acute coronary syndrome (ACS), whereas another 55 were stable coronary artery disease (SCAD) patients. PT, APTT, FVIII, and APC-R assays were performed on all subjects. There was a significant difference between the FVIII level and the APTT results (P value < 0.0001). A negative relationship was found between the FVIII level and the APTT from linear regression analysis (R(2) = 10%, P value < 0.0001). For each 1% increase in the FVIII level, the APTT was reduced by 0.013 s (95% confidence interval (CI) between -0.019 and -0.007). Interestingly, none of the SCAD patients had abnormally short APTT. Approximately 68.4% of cases with a positive APC-R assay were found to have a high FVIII level. In conclusion, the APTT test is a potential hemostatic marker for hypercoagulable state including in arterial thrombosis.

  1. Instrumental neutron activation analysis of some ayurvedic medicines: Pt. 1

    Energy Technology Data Exchange (ETDEWEB)

    Rajurkar, N.S.; Vinchurkar, M.S. (Poona Univ., Pune (India). Dept. of Chemistry)

    1992-12-01

    Several medicines have been manufactured and prescribed to overcome mineral deficiencies in the human body. Such medicines are mixtures of several components. The present work is undertaken to analyze various Ayurvedic medicines, mainly of herbal origin and used for different purposes, for their elemental contents, by neutron activation analysis. (author).

  2. Asymmetric Volcano Trend in Oxygen Reduction Activity of Pt and Non-Pt Catalysts: In Situ Identification of the Site-Blocking Effect.

    Science.gov (United States)

    Li, Jingkun; Alsudairi, Amell; Ma, Zi-Feng; Mukerjee, Sanjeev; Jia, Qingying

    2017-02-01

    Proper understanding of the major limitations of current catalysts for oxygen reduction reaction (ORR) is essential for further advancement. Herein by studying representative Pt and non-Pt ORR catalysts with a wide range of redox potential (Eredox) via combined electrochemical, theoretical, and in situ spectroscopic methods, we demonstrate that the role of the site-blocking effect in limiting the ORR varies drastically depending on the Eredox of active sites; and the intrinsic activity of active sites with low Eredox have been markedly underestimated owing to the overlook of this effect. Accordingly, we establish a general asymmetric volcano trend in the ORR activity: the ORR of the catalysts on the overly high Eredox side of the volcano is limited by the intrinsic activity; whereas the ORR of the catalysts on the low Eredox side is limited by either the site-blocking effect and/or intrinsic activity depending on the Eredox.

  3. Porous Pt Nanotubes with High Methanol Oxidation Electrocatalytic Activity Based on Original Bamboo-Shaped Te Nanotubes.

    Science.gov (United States)

    Lou, Yue; Li, Chunguang; Gao, Xuedong; Bai, Tianyu; Chen, Cailing; Huang, He; Liang, Chen; Shi, Zhan; Feng, Shouhua

    2016-06-29

    In this report, a facile and general strategy was developed to synthesize original bamboo-shaped Te nanotubes (NTs) with well-controlled size and morphology. On the basis of the as-prepared Te NTs, porous Pt nanotubes (NTs) with excellent property and structural stability have been designed and manufactured. Importantly, we avoided the use of surface stabilizing agents, which may affect the catalytic properties during the templated synthesis process. Furthermore, Pt NTs with different morphology were successfully prepared by tuning the experimental parameters. As a result, transmission electron microscopy (TEM) study shows that both Te NTs and Pt NTs have uniform size and morphology. Following cyclic voltammogram (CV) testing, the as-prepared porous Pt NTs and macroporous Pt NTs exhibited excellent catalytic activities toward electrochemical methanol oxidation reactions due to their tubiform structure with nanoporous framework. Thus, the as-prepared Pt NTs with specific porous structure hold potential usage as alternative anode catalysts for direct methanol fuel cells (DMFCs).

  4. Polyol synthesis of nanosized Pt/C electrocatalysts assisted by pulse microwave activation

    Energy Technology Data Exchange (ETDEWEB)

    Lebegue, E.; Baranton, S.; Coutanceau, C. [Laboratoire de Catalyse en Chimie Organique (LACCO), UMR 6503 CNRS, Universite de Poitiers, 40 av recteur Pineau, F-86000 Poitiers (France)

    2011-02-01

    A polyol process assisted by pulse microwave activation was used to prepare efficient Pt/C electrocatalysts for PEMFC applications with reducing cost. Catalysts from pulsed microwave method were compared with a catalyst issued from a classical method, in terms of active surface area, platinum loading and activity towards the oxygen reduction reaction. A design of experiments (DOE derived from the Taguchi method) has been implemented to optimize experimental parameters only related to pulse microwave activation, the intrinsic synthesis parameters (concentration of platinum salt, platinum/carbon weight ratio and pH) being kept constant. Controlled parameters were duration of microwave pulse, maximum temperature and total duration of the synthesis. Considered responses were catalyst active surface area and the Pt/C loading. An optimized configuration of synthesis parameter was proposed. The confirmation experiment revealed a trend in agreement with that expected. Three catalysts (two from pulsed microwave synthesis method and one prepared by the classical method) were characterized by transmission electron microscopy, cyclic voltammetry and CO stripping. Catalysts from pulsed microwave method display higher characteristics than the one prepared by the classical method. The Pt/C catalyst from the confirmation experiment displays the highest catalytic activity toward oxygen reduction reaction. (author)

  5. Enhanced Catalytic Activity of Pt Supported on Nitrogen-Doped Reduced Graphene Oxide Electrodes for Fuel Cells.

    Science.gov (United States)

    Sun, Qizhong; Park, Soo-Jin; Kim, Seok

    2015-11-01

    We report an efficient method for the synthesis of nitrogen-doped reduced graphene oxide supported Pt nanocatalysts (Pt/N-RGO). Nitrogen-doped reduced graphene oxide (N-RGO) was prepared by pyrolysis of graphene oxide with cyanamide as a nitrogen source. Then, the Pt nanoparticles were deposited over N-RGO by one-step chemical polyol reduction process. The morphology and structure of as-prepared catalysts were characterized by transmission electron microscopy (TEM), and X-ray diffraction (XRD). Subsequently, electrocatalytic activities of the catalysts were evaluated by cyclic voltammetry (CV). As a result, the Pt/N-RGO catalysts exhibit the superior electrochemical activity toward methanol oxidation in compared with that of Pt loaded on undoped reduced graphene oxide (Pt/RGO) and Pt/carbon blacks (Pt/C). This was mainly attributed to the better distribution of Pt nanoparticles as well as the synergistic electrochemical effects of the nitrogen doped supports. These results demonstrate that N-RGO could be a promising candidate as a high performance catalyst support for a fuel cell application.

  6. 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

    Polymer Electrolyte Membrane Fuel Cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the Oxygen Reduction Reaction (ORR) at the PEMFC cathode prevents the commercialisation of this tech...

  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. Preparation of PtSnCu/C and PtSn/C electrocatalysts and activation by dealloying processes for ethanol electrooxidation; Preparacao de eletrocatalisadores PtSnCu/C e PtSn/C e ativacao por processos de dealloying para aplicacao na oxidacao eletroquuimica do etanol

    Energy Technology Data Exchange (ETDEWEB)

    Crisafulli, Rudy

    2013-06-01

    PtSnCu/C (with different Pt:Sn:Cu atomic ratios) and PtSn/C (50:50) electrocatalysts were prepared by borohydride (BR) and alcohol-reduction (AR) processes using H{sub 2}PtCl{sub 6}.6H{sub 2}O, SnCl{sub 2}.2H{sub 2}O and CuCl{sub 2}.2H{sub 2}O as metal sources, NaBH{sub 4} and ethylene glycol as reducing agents, 2-propanol and ethylene glycol/water as solvents and carbon black as support. In a further step, these electrocatalysts were activated by chemical (CD) and electrochemical (ED) dealloying processes through acid treatment and thin porous coating technique, respectively. These materials were characterized by energy dispersive X-ray, Xray diffraction, transmission electron microscopy, line scan energy dispersive Xray and cyclic voltammetry. Electrochemical studies for ethanol electro-oxidation were performed by cyclic voltammetry, chronoamperometry and in single Direct Ethanol Fuel Cell using Membrane Electrode Assembly (MEA). The anodic effluents were analysed by gas chromatography. The X-ray diffractograms of the as-synthesized electrocatalysts showed the typical face-centered cubic structure (FCC) of platinum and its alloys. After dealloying, the X-ray diffractograms showed that the Pt FCC structure was preserved. The crystallite sizes of the assynthesized electrocatalysts were in the range of <=2 nm to 3 nm and after dealloying there were no significant variations in sizes. The energy dispersive Xray analysis of the as-synthesized electrocatalysts showed a Pt:Sn and Pt:Sn:Cu atomic ratios similar to the nominal values. After chemical and electrochemical dealloying of the electrocatalysts the ranged Pt:Sn and Pt:Sn:Cu atomic ratios showed that Cu and Sn atoms were removed. However, chemical dealloying process proved to be more efficient for removing Cu and electrochemical dealloying for removing Sn. The line scan energy dispersive X-ray analysis showed that acid and electrochemical treatments were efficient to dealloying Cu and/or Sn superficial atoms of

  9. Partial characterization of polyphenol oxidase activity in raspberry fruits.

    Science.gov (United States)

    González, E M; de Ancos, B; Cano, M P

    1999-10-01

    A partial characterization of polyphenol oxidase (PPO) activity in raspberry fruits is described. Two early cultivars harvested in May/June (Heritage and Autumm Bliss) and two late cultivars harvested in October-November (Ceva and Rubi) were analyzed for PPO activity. Stable and highly active PPO extracts were obtained using insoluble poly(vinylpyrrolidone) (PVP) and Triton X-100 in sodium phosphate, pH 7.0 buffer. Polyacrylamide gel electrophoresis of raspberry extracts under nondenaturing conditions resolved in one band (R(f)()(1) = 0.25). Raspberry PPO activity has pH optima of 8.0 and 5.5, both with catechol (0.1 M). Maximum activity was with D-catechin (catecholase activity), followed by p-coumaric acid (cresolase activity). Heritage raspberry also showed PPO activity toward 4-methylcatechol. Ceva and Autumm Bliss raspberries showed the higher PPO activity using catechol as substrate.

  10. Au-supported Pt-Au mixed atomic monolayer electrocatalyst with ultrahigh specific activity for oxidation of formic acid in acidic solution.

    Science.gov (United States)

    Huang, Zhao; Liu, Yan; Xie, Fangyun; Fu, Yingchun; He, Yong; Ma, Ming; Xie, Qingji; Yao, Shouzhuo

    2012-12-25

    Au-supported Pt-Au mixed atomic monolayer electrocatalyst was prepared by underpotential deposition of Cu on Au and then redox replacement with noble metal atoms, which shows an ultrahigh Pt-mass (or Pt-area) normalized specific electrocatalytic activity of 102 mA μg(Pt)(-1) (124 mA cm(Pt)(-2)) for oxidation of formic acid in acidic aqueous solution.

  11. Selectivity of Chemisorbed Oxygen in C–H Bond Activation and CO Oxidation and Kinetic Consequences for CH₄–O₂ Catalysis on Pt and Rh Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Ya-Huei; Buda, Corneliu; Neurock, Matthew; Iglesia, Enrique

    2011-10-06

    constants for O₂ dissociation and C–H bond activation elementary steps; the values for this constant are much larger than unity and are higher on larger Pt clusters (1.8–33 nm) at all temperatures (573–1273 K) relevant for CH₄–O₂ reactions. The barriers for the kinetically relevant C–H bond dissociation step increase, while those for CO oxidation remain unchanged as the Pt coordination number and cluster size increase, and lead, in turn, to higher O* selectivities on larger Pt clusters. Oxygen selectivities were much larger on Rh than Pt, because the limiting reactants for CO oxidation were completely consumed in ¹²CO–¹³CH₄–O₂ mixtures, consistent with lower CO/O₂ ratios measured by varying the residence time and O₂/CH₄ ratio independently in CH₄–O₂ reactions. These mechanistic assessments and theoretical treatments for O* selectivity provide rigorous evidence of low intrinsic limits of the maximum CO yields, thus confirming that direct catalytic partial oxidation of CH₄ to CO (and H₂) does not occur at the molecular scale on Pt and Rh clusters. CO (and H₂) are predominantly formed upon complete O₂ depletion from the sequential reforming steps.

  12. Effect of Ni Core Structure on the Electrocatalytic Activity of Pt-Ni/C in Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Vladimir Linkov

    2013-07-01

    Full Text Available Methanol oxidation catalysts comprising an outer Pt-shell with an inner Ni-core supported on carbon, (Pt-Ni/C, were prepared with either crystalline or amorphous Ni core structures. Structural comparisons of the two forms of catalyst were made using transmission electron microscopy (TEM, X-ray diffraction (XRD and X-ray photoelectron spectroscopy (XPS, and methanol oxidation activity compared using CV and chronoamperometry (CA. While both the amorphous Ni core and crystalline Ni core structures were covered by similar Pt shell thickness and structure, the Pt-Ni(amorphous/C catalyst had higher methanol oxidation activity. The amorphous Ni core thus offers improved Pt usage efficiency in direct methanol fuel cells.

  13. Direct Visualization of Catalytically Active Sites at the FeO-Pt(111) Interface

    Energy Technology Data Exchange (ETDEWEB)

    Kudernatsch, Wilhelmine; Peng, Guowen; Zeuthen, Helene; Bai, Yunhai; Merte, L. R.; Lammich, Lutz; Besenbacher, Fleming; Mavrikakis, Manos; Wendt, Stefen

    2015-08-25

    Within the area of surface science, one of the “holy grails” is to directly visualize a chemical reaction at the atomic scale. Whereas this goal has been reached by high-resolution scanning tunneling microscopy (STM) in a number of cases for reactions occurring at flat surfaces, such a direct view is often inhibited for reaction occurring at steps and interfaces. Here we have studied the CO oxidation reaction at the interface between ultrathin FeO islands and a Pt(111) support by in situ STM and density functional theory (DFT) calculations. Time-lapsed STM imaging on this inverse model catalyst in O2 and CO environments revealed catalytic activity occurring at the FeO-Pt(111) interface and directly showed that the Fe-edges host the catalytically most active sites for the CO oxidation reaction. This is an important result since previous evidence for the catalytic activity of the FeO-Pt(111) interface is essentially based on averaging techniques in conjunction with DFT calculations. The presented STM results are in accord with DFTþU calculations, in which we compare possible CO oxidation pathways on oxidized Fe-edges and O-edges. We found that the CO oxidation reaction is more favorable on the oxidized Fe-edges, both thermodynamically and kinetically.

  14. Direct Visualization of Catalytically Active Sites at the FeO-Pt(111) Interface.

    Science.gov (United States)

    Kudernatsch, Wilhelmine; Peng, Guowen; Zeuthen, Helene; Bai, Yunhai; Merte, Lindsay R; Lammich, Lutz; Besenbacher, Flemming; Mavrikakis, Manos; Wendt, Stefan

    2015-08-25

    Within the area of surface science, one of the "holy grails" is to directly visualize a chemical reaction at the atomic scale. Whereas this goal has been reached by high-resolution scanning tunneling microscopy (STM) in a number of cases for reactions occurring at flat surfaces, such a direct view is often inhibited for reaction occurring at steps and interfaces. Here we have studied the CO oxidation reaction at the interface between ultrathin FeO islands and a Pt(111) support by in situ STM and density functional theory (DFT) calculations. Time-lapsed STM imaging on this inverse model catalyst in O2 and CO environments revealed catalytic activity occurring at the FeO-Pt(111) interface and directly showed that the Fe-edges host the catalytically most active sites for the CO oxidation reaction. This is an important result since previous evidence for the catalytic activity of the FeO-Pt(111) interface is essentially based on averaging techniques in conjunction with DFT calculations. The presented STM results are in accord with DFT+U calculations, in which we compare possible CO oxidation pathways on oxidized Fe-edges and O-edges. We found that the CO oxidation reaction is more favorable on the oxidized Fe-edges, both thermodynamically and kinetically.

  15. In-Situ Investigation of Gas Phase Radical Chemistry in the Catalytic Partial Oxidation of Methane on Pt

    OpenAIRE

    Geske, M.; Pelzer, K.; Horn, R.; Jentoft, F.; R. Schlögl

    2009-01-01

    The catalytic partial oxidation of methane on platinum was studied in situ under atmospheric pressure and temperatures between 1000 and 1300 °C. By combining radical measurements using a molecular beam mass spectrometer and threshold ionization with GC, GC-MS and temperature profile measurements it was demonstrated that a homogeneous reaction pathway is opened at temperatures above 1100 °C, in parallel to hetero-geneous reactions which start already at 600 °C. Before ignition of gas phase che...

  16. Electrocatalytic activity of Pt grown by ALD on carbon nanotubes for Si-based DMFC applications

    DEFF Research Database (Denmark)

    Johansson, Alicia Charlotte; Dalslet, Bjarke Thomas; Yang, R.B.

    2012-01-01

    We present an anode design for silicon-based direct methanol fuel cell (DMFC) applications. Platinum was deposited conformally by atomic layer deposition (ALD) onto vertically aligned, nitrogendoped multi-walled carbon nanotubes (MWCNTs) grown on porous silicon. The deposition was carried out...... that ALD could be a MEMS compatible deposition technique for Si-based fuel cell applications. © The Electrochemical Society....... in a top-flow ALD reactor at 250°C, using MeCpPtMe3 and O2 as precursors. The anode was tested for the methanol oxidation reaction (MOR) in a three-electrode electrochemical set-up and it showed improved catalytic activity compared to a reference sample of Pt deposited on flat Si. It is demonstrated...

  17. Polyvinylpyrrolidone (PVP)-capped Pt Nanocubes with Superior Peroxidase-like Activity

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Haihang; Liu, Y.; chhabra, ashima; lilla, emily; xia, xiaohu

    2017-01-01

    Peroxidase mimics of inorganic nanoparticles are expected to circumvent the inherent issues of natural peroxidases, providing enhanced performance in important applications such as diagnosis and imaging. Despite the report of a variety of peroxidase mimics in the past decade, very limited progress has been made on improving their catalytic efficiency. The catalytic efficiencies of most previously reported mimics are only up to one order of magnitude higher than those of natural peroxidases. In this work, we demonstrate a type of highly efficient peroxidase mimic – polyvinylpyrrolidone (PVP)-capped Pt nanocubes of sub-10 nm in size. These PVP-capped Pt cubes are ~200-fold more active than the natural counterparts and exhibit a record-high specific catalytic efficiency. In addition to the superior efficiency, the new mimic shows several other promising features, including excellent stabilities, well-controlled uniformity in both size and shape, controllable sizes, and facile and scalable production.

  18. Ultrathin dendritic Pt3Cu triangular pyramid caps with enhanced electrocatalytic activity.

    Science.gov (United States)

    Kuang, Yun; Cai, Zhao; Zhang, Ying; He, Dongsheng; Yan, Xiuling; Bi, Yongmin; Li, Yaping; Li, Ziyou; Sun, Xiaoming

    2014-10-22

    Here we report on the synthesis of novel dendritic Pt3Cu triangular pyramid caps via a solvothermal coreduction method. These caps had three-dimensional caved structures with ultrathin branches, as evidenced by high-resolution transmission electron microscopy (HRTEM) and HAADF-STEM characterization. Tuning the reduction kinetics of two metal precursors by an iodide ion was believed to be the key for the formation of an alloyed nanostructure. Electro-oxidation of methanol and formic acid showed dramatically improved electrocatalytic activities and poison-tolerance for these nanoalloys as compared to commercial Pt/C catalysts, which was attributed to their unique open porous structure with interconnected network, ultrahigh surface areas, as well as synergetic effect of the two metallic components.

  19. [Trypanocidal activity and plasma kinetics of cis-Pt(II) pentamidine in the parasitized sheep].

    Science.gov (United States)

    Dreyfuss, G; Penicaut, B; Parrondo-Iglesias, E; Craciunescu, D; Dubost, G; Nicolas, J A

    1990-01-01

    The trypanocidal activity of cis-Pt(II) pentamidine had been demonstrated during the first phase of Trypanosoma brucei brucei sheep experimental trypanosomiasis. But a subcutaneous treatment with 5 mg.kg-1 (+2 x 12 mg.kg-1) was not effective during the brain phase of trypanosomiasis. The blood pharmacokinetics of this compound had a plasmatic peak between 45 and 60 min, followed by a low decreasing phase along several days. The curve shape allowed an important interval before the following injection, and showed a compound storage in internal organs and extravascular sites. A model of cis-Pt(II) pentamidine metabolism had been studied: this product could be used as a chemoprophylactic medicine against African trypanosomiasis and American leishmaniasis.

  20. Enhanced electrocatalytic activity of the Au-electrodeposited Pt nanoparticles-coated conducting oxide for the quantum dot-sensitized solar cells

    Science.gov (United States)

    Yoon, Yeung-Pil; Kim, Jae-Hong; Kang, Soon-Hyung; Kim, Hyunsoo; Choi, Chel-Jong; Kim, Kyong-Kook; Ahn, Kwang-Soon

    2014-08-01

    Au was electrodeposited potentiostatically at 0.3 V for 5 min on nanoporous Pt nanoparticle-coated F-doped SnO2 (FTO/Pt) substrates. For comparison, Au-electrodeposited FTO (FTO/Au) and Au-uncoated FTO/Pt were prepared. FTO/Au showed large-sized Au clusters dispersed sparsely over FTO, which resulted in lower electrocatalytic activity than FTO/Pt. In contrast, FTO/Pt exhibited poor stability unlike FTO/Au due to poisoning by the adsorption of sulfur species. The Au-electrodeposited FTO/Pt (FTO/Pt/Au) consisted of small Au clusters deposited over the entire area of Pt due to the effective Au nucleation provided by nanoporous metallic Pt. FTO/Pt/Au exhibited enhanced electrocatalytic activity and excellent stability because the small Au particles well-dispersed over the nanoporous metallic Pt network provided numerous electrochemical reaction sites, and the Pt surface was not exposed to the electrolyte. When FTO/Pt/Au was used as the counter electrode (CE) of a quantum dot-sensitized solar cell, the significantly enhanced electrocatalytic activity of the FTO/Pt/Au CE facilitated the reduction reaction of Sn2- + 2e- (CE) → Sn-12- + S2- at the CE/electrolyte interface, resulting in a significantly hindered recombination reaction, Sn2- + 2e- (TiO2 in the photoanode) → Sn-12- + S2-, and significantly improved overall energy conversion efficiency.

  1. Selectivity loss of Pt/CeO{sub 2} PROX catalysts at low CO concentrations: mechanism and active site study.

    Energy Technology Data Exchange (ETDEWEB)

    Polster, C. S.; Zhang, R.; Cyb, M. T.; Miller, J. T.; Baertsch, C. D. (Chemical Sciences and Engineering Division); (Purdue Univ.)

    2010-07-01

    CO and H{sub 2} oxidation were studied over a series of Pt/CeO{sub 2} catalysts with differing Pt loadings and dispersions. Kinetic rate analysis confirms the presence of dual Langmuir-Hinshelwood (L-H) and Mars and van Krevelen (M-vK) pathways and is used to explain the loss in CO oxidation selectivity at low CO concentrations. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the strong CO coverage dependence on both CO and O{sub 2} concentrations and explains the transition from L-H to M-vK reaction character. Redox site measurements are performed on Pt/CeO{sub 2} catalysts by anaerobic titrations under conditions where the M-vK pathway dominates the reaction rate. Similar redox site densities per interfacial Pt atom suggest that interfacial Pt-O-Ce sites are responsible for M-vK redox activity.

  2. In situ Raman and pulse reaction study on the partial oxidation of methane to synthesis gas over a Pt/Al2O3 catalyst.

    Science.gov (United States)

    Wang, Mei-Liu; Zheng, Hao-Zhuan; Li, Jian-Mei; Weng, Wei-Zheng; Xia, Wen-Sheng; Huang, Chuan-Jing; Wan, Hui-Lin

    2011-02-01

    Catalytic partial oxidation of methane (POM) to synthesis gas (syngas) over Pt/Al(2)O(3) was investigated by in situ microprobe Raman and pulse reaction methods with attention focused on the mechanism of syngas formation in the oxidation zone (i.e., the catalyst zone in which O(2) was still available in the reaction feed). It was found that the amount of platinum oxide in the catalyst under POM conditions was below the detection level of Raman spectroscopy. Raman bands of carbon species that originated from methane dissociation were detected at the entrance of the catalyst bed under working conditions. The results of the pulse reaction study on POM as well as steam and CO(2) reforming of methane at 700 °C with a contact time of less than 1 ms over the catalyst suggest that pyrolysis of methane on reduced platinum sites followed by coupling of two surface hydrogen atoms to H(2) and partial oxidation of surface carbon species to CO are the major reactions responsible for syngas formation in the oxidation zone. Under the experimental conditions, steam and CO(2) reforming of methane play only a minor role in syngas formation in the same reaction zone. The contribution of the last two reactions increases with increasing contact time.

  3. Antitumor activity of [Pt(O,O'-acac)(γ-acac)(DMS)] in mouse xenograft model of breast cancer

    Science.gov (United States)

    Muscella, A; Vetrugno, C; Migoni, D; Biagioni, F; Fanizzi, F P; Fornai, F; De Pascali, S A; Marsigliante, S

    2014-01-01

    The higher and selective cytotoxicity of [Pt(O,O′-acac)(γ-acac)(DMS)] toward cancer cell in both immortalized cell lines and in breast cancer cells in primary cultures, stimulated a pre-clinical study so as to evaluate its therapeutic potential in vivo. The efficacy of [Pt(O,O′-acac)(γ-acac)(DMS)] was assessed using a xenograft model of breast cancer developed by injection of MCF-7 cells in the flank of BALB/c nude mice. Treatment of solid tumor-bearing mice with [Pt(O,O′-acac)(γ-acac)(DMS)] induced up to 50% reduction of tumor mass compared with an average 10% inhibition recorded in cisplatin-treated animals. Thus, chemotherapy with [Pt(O,O′-acac)(γ-acac)(DMS)] was much more effective than cisplatin. We also demonstrated enhanced in vivo pharmacokinetics, biodistribution and tolerability of [Pt(O,O′-acac)(γ-acac)(DMS)] when compared with cisplatin administered in Wistar rats. Pharmacokinetics studies with [Pt(O,O′-acac)(γ-acac)(DMS)] revealed prolonged Pt persistence in systemic blood circulation and decreased nefrotoxicity and hepatotoxicity, major target sites of cisplatin toxicity. Overall, [Pt(O,O′-acac)(γ-acac)(DMS)] turned out to be extremely promising in terms of greater in vivo anticancer activity, reduced nephrotoxicity and acute toxicity compared with cisplatin. PMID:24457958

  4. Calorimetry, activity, and micro-FTIR analysis of CO chemisorption, titration, and oxidation on supported Pt

    Science.gov (United States)

    Sermon, Paul A.; Self, Valerie A.; Vong, Mariana S. W.; Wurie, Alpha T.

    1990-01-01

    The value of in situ analysis on CO chemisorption, titration and oxidation over supported Pt catalysts using calorimetry, catalytic and micro-FTIR methods is illustrated using silica- and titania-supported samples. Isothermal CO-O and O2-CO titrations have not been widely used on metal surfaces and may be complicated if some oxide supports are reduced by CO titrant. However, they can illuminate the kinetics of CO oxidation on metal/oxide catalysts since during such titrations all O and CO coverages are scanned as a function of time. There are clear advantages in following the rates of the catalyzed CO oxidation via calorimetry and gc-ms simultaneously. At lower temperatures the evidence they provide is complementary. CO oxidation and its catalysis of CO oxidation have been extensively studied with hysteresis and oscillations apparent, and the present results suggest the benefits of a combined approach. Silica support porosity may be important in defining activity-temperature hysteresis. FTIR microspectroscopy reveals the chemical heterogeneity of the catalytic surfaces used; it is interesting that the evidence with regard to the dominant CO surface species and their reactivities with regard to surface oxygen for present oxide-supported Pt are different from those seen on graphite-supported Pt.

  5. Structure–activity relationships of Pt/Al2O3 catalysts for CO and NO oxidation at diesel exhaust conditions

    DEFF Research Database (Denmark)

    Boubnov, Alexey; Dahl, Søren; Johnson, Erik

    2012-01-01

    Structure–performance relationships for Pt/Al2O3 catalysts with mean Pt particle sizes of 1, 2, 3, 5 and 10nm are investigated for the catalytic oxidation of CO and NO under lean-burning diesel exhaust conditions. The most active catalysts for CO oxidation exhibit Pt particles of 2–3nm, having...... a large fraction of low-coordinated and reactive surface Pt atoms. Exploiting in situ XAFS, we find that a reversible Pt surface oxidation is connected to high CO conversion. NO oxidation is most efficient over the catalysts with the largest Pt particles mainly exhibiting surface Pt atoms on planar facets....... An irreversible Pt oxide formation observed during NO oxidation is a possible deactivation route and we suggest that the most active sites for NO oxidation are the ones least prone to surface oxidation. When both CO and NO are present in the reaction mixture, activity is increased for both reactions, suggesting...

  6. Nanoporous bimetallic Pt-Au alloy nanocomposites with superior catalytic activity towards electro-oxidation of methanol and formic acid.

    Science.gov (United States)

    Zhang, Zhonghua; Wang, Yan; Wang, Xiaoguang

    2011-04-01

    We present a facile route to fabricate novel nanoporous bimetallic Pt-Au alloy nanocomposites by dealloying a rapidly solidified Al(75)Pt(15)Au(10) precursor under free corrosion conditions. The microstructure of the precursor and the as-dealloyed sample was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray (EDX) analysis. The Al(75)Pt(15)Au(10) precursor is composed of a single-phase Al(2)(Au,Pt) intermetallic compound, and can be fully dealloyed in a 20 wt.% NaOH or 5 wt.% HCl aqueous solution. The dealloying leads to the formation of the nanoporous Pt(60)Au(40) nanocomposites (np-Pt(60)Au(40) NCs) with an fcc structure. The morphology, size and crystal orientation of grains in the precursor can be conserved in the resultant nanoporous alloy. The np-Pt(60)Au(40) NCs consist of two zones with distinct ligament/channel sizes and compositions. The formation mechanism of these np-Pt(60)Au(40) NCs can be rationalized based upon surface diffusion of more noble elements and spinodal decomposition during dealloying. Electrochemical measurements demonstrate that the np-Pt(60)Au(40) NCs show superior catalytic activity towards the electro-oxidation of methanol and formic acid in the acid media compared to the commercial JM-Pt/C catalyst. This material can find potential applications in catalysis related areas, such as direct methanol or formic acid fuel cells. Our findings demonstrate that dealloying is an effective and simple strategy to realize the alloying of immiscible systems under mild conditions, and to fabricate novel nanostructures with superior performance.

  7. The SHORT-ROOT-like gene PtSHR2B is involved in Populus phellogen activity.

    Science.gov (United States)

    Miguel, Andreia; Milhinhos, Ana; Novák, Ondřej; Jones, Brian; Miguel, Célia M

    2016-03-01

    SHORT-ROOT (SHR) is a GRAS transcription factor first characterized for its role in the specification of the stem cell niche and radial patterning in Arabidopsis thaliana (At) roots. Three SHR-like genes have been identified in Populus trichocarpa (Pt). PtSHR1 shares high similarity with AtSHR over the entire length of the coding sequence. The two other Populus SHR-like genes, PtSHR2A and PtSHR2B, are shorter in their 5' ends when compared with AtSHR. Unlike PtSHR1, that is expressed throughout the cambial zone of greenhouse-grown Populus trees, PtSHR2Bprom:uidA expression was detected in the phellogen. Additionally, PtSHR1 and PtSHR2B expression patterns markedly differ in the shoot apex and roots of in vitro plants. Transgenic hybrid aspen expressing PtSHR2B under the 35S constitutive promoter showed overall reduced tree growth while the proportion of bark increased relative to the wood. Reverse transcription-quantitative PCR (RT-qPCR) revealed increased transcript levels of cytokinin metabolism and response-related genes in the transgenic plants consistent with an increase of total cytokinin levels. This was confirmed by cytokinin quantification by LC-MS/MS. Our results indicate that PtSHR2B appears to function in the phellogen and therefore in the regulation of phellem and periderm formation, possibly acting through modulation of cytokinin homeostasis. Furthermore, this work points to a functional diversification of SHR after the divergence of the Populus and Arabidopsis lineages. This finding may contribute to selection and breeding strategies of cork oak in which, unlike Populus, the phellogen is active throughout the entire tree lifespan, being at the basis of a highly profitable cork industry.

  8. Effect of Mo addition on the electrocatalytic activity of Pt-Sn-Mo/C for direct ethanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Eungje; Murthy, Arun [Electrochemical Energy Laboratory and Materials Science and Engineering Program, University of Texas at Austin, Austin, TX 78712 (United States); Manthiram, Arumugam, E-mail: rmanth@mail.utexas.ed [Electrochemical Energy Laboratory and Materials Science and Engineering Program, University of Texas at Austin, Austin, TX 78712 (United States)

    2011-01-01

    Carbon-supported Pt-Sn-Mo electrocatalysts have been synthesized by a polyol reduction method and characterized for ethanol electro-oxidation reaction (EOR). While the percent loading of the synthesized nanoparticles on the carbon support is higher than 35%, energy dispersive spectroscopy (EDS) reveals that the Mo contents in the nanoparticle catalysts are lower than the nominal value, indicating incomplete reduction of the Mo precursor. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses reveal that the Sn and Mo exist as oxide phases at the surface layers of the nanoparticles and the degree of alloying is very low. The electrochemical properties of the electrocatalysts have been evaluated by cyclic voltammetry (CV) and chronoamperometry. The catalytic activity for EOR decreases in the order PtSnMo{sub 0.6}/C > PtSnMo{sub 0.4}/C > PtSn/C. Single cell direct ethanol fuel cell (DEFC) tests also confirm that the PtSnMo{sub 0.6}/C anode catalyst exhibit better performance than the PtSn/C anode catalyst. An analysis of the electrochemical data suggests that the incorporation of Mo to Pt-Sn enhances further the catalytic activity for EOR.

  9. Nanoparticle cluster gas sensor: Pt activated SnO2 nanoparticles for NH3 detection with ultrahigh sensitivity.

    Science.gov (United States)

    Liu, Xu; Chen, Nan; Han, Bingqian; Xiao, Xuechun; Chen, Gang; Djerdj, Igor; Wang, Yude

    2015-09-28

    Pt activated SnO2 nanoparticle clusters were synthesized by a simple solvothermal method. The structure, morphology, chemical state and specific surface area were analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2-sorption studies, respectively. The SnO2 nanoparticle cluster matrix consists of tens of thousands of SnO2 nanoparticles with an ultra-small grain size estimated to be 3.0 nm. And there are abundant random-packed wormhole-like pores, caused by the inter-connection of the SnO2 nanoparticles, throughout each cluster. The platinum element is present in two forms including metal (Pt) and tetravalent metal oxide (PtO2) in the Pt activated SnO2 nanoparticle clusters. The as-synthesized pure and Pt activated SnO2 nanoparticle clusters were used to fabricate gas sensor devices. It was found that the gas response toward 500 ppm of ammonia was improved from 6.48 to 203.44 through the activation by Pt. And the results indicate that the sensor based on Pt activated SnO2 not only has ultrahigh sensitivity but also possesses good response-recovery properties, linear dependence, repeatability, selectivity and long-term stability, demonstrating the potential to use Pt activated SnO2 nanoparticle clusters as ammonia gas sensors. At the same time, the formation mechanisms of the unique nanoparticle clusters and highly enhanced sensitivity are also discussed.

  10. Supported Pt-based nanoparticulate catalysts for the electro-oxidation of methanol: An experimental protocol for quantifying its activity

    DEFF Research Database (Denmark)

    Hernandez-Fernandez, Patricia; Lund, Peter Brilner; Kallesøe, Christian

    2014-01-01

    In here, we propose a simple methodology to evaluate the activity of supported nano-particulate catalysts on the electro-oxidation of methanol in a three-electrode cell. The proof of concept has been made on carbon supported Pt and PtRu commercial catalysts, but the protocol can be extended to all...... kinds of Pt-based nanoparticles. Even though the electro-oxidation of methanol has been studied for many years, there is no established electrochemical procedure for measuring the performance of a catalyst in such reaction. The conditions in which the measurements are carried out differ between research...

  11. Preparation of AuPt alloy foam films and their superior electrocatalytic activity for the oxidation of formic acid.

    Science.gov (United States)

    Liu, Jun; Cao, Ling; Huang, Wei; Li, Zelin

    2011-09-01

    AuPt alloy films with three-dimensional (3D) hierarchical pores consisting of interconnected dendrite walls were successfully fabricated by a strategy of cathodic codeposition utilizing the hydrogen bubble dynamic template. The foam films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Due to the special porous structure, the electronic property, and the assembly effect, the AuPt alloy foam films show superior electrocatalytic activity toward the electrooxidation of formic acid in acidic solution, and the prepared 3D porous AuPt alloy films also show high activity and long stability for the electrocatalytic oxidation of methanol, where synergistic effect plays an important role in addition to the electronic effect and assembly effect. These findings provide more insights into the AuPt bimetallic nanomaterials for electrocatalytic applications.

  12. Low content Pt nanoparticles anchored on N-doped reduced graphene oxide with high and stable electrocatalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Li, Zeyu; Gao, Qiuming; Zhang, Hang; Tian, Weiqian; Tan, Yanli; Qian, Weiwei; Liu, Zhengping

    2017-01-01

    A novel kind of Pt/N-rGO hybrid possessing of low content 5.31 wt.% Pt anchored on the surface of nitrogen doped reduced graphene oxide (N-rGO) evenly was prepared. The Pt has uniformed 2.8 nm diameter and exposed (111) crystal planes; meanwhile, the N works as the bridge between Pt and rGO with the Pt-N and N-C chemical bonds in Pt/N-rGO. The Pt/N-rGO material has a very high electrocatalytic activity in oxygen reduction reaction with the mass catalytic activity more than 1.5 times of the commercial Pt/C due to the synergistic catalytic effect of both N-doped carbon matrix and Pt nanoparticles. Moreover, the Pt/N-rGO exhibits an excellent stability with hardly loss (only 0.4%) after accelerated durability tests of 5000 cycles based on the stable Pt-N-C chemical bonds in Pt/N-rGO, which can prevent the detachment, dissolution, migration and aggregation of Pt nanoparticles on the matrix during the long-term cycling. PMID:28233857

  13. Low content Pt nanoparticles anchored on N-doped reduced graphene oxide with high and stable electrocatalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Li, Zeyu; Gao, Qiuming; Zhang, Hang; Tian, Weiqian; Tan, Yanli; Qian, Weiwei; Liu, Zhengping

    2017-02-01

    A novel kind of Pt/N-rGO hybrid possessing of low content 5.31 wt.% Pt anchored on the surface of nitrogen doped reduced graphene oxide (N-rGO) evenly was prepared. The Pt has uniformed 2.8 nm diameter and exposed (111) crystal planes; meanwhile, the N works as the bridge between Pt and rGO with the Pt-N and N-C chemical bonds in Pt/N-rGO. The Pt/N-rGO material has a very high electrocatalytic activity in oxygen reduction reaction with the mass catalytic activity more than 1.5 times of the commercial Pt/C due to the synergistic catalytic effect of both N-doped carbon matrix and Pt nanoparticles. Moreover, the Pt/N-rGO exhibits an excellent stability with hardly loss (only 0.4%) after accelerated durability tests of 5000 cycles based on the stable Pt-N-C chemical bonds in Pt/N-rGO, which can prevent the detachment, dissolution, migration and aggregation of Pt nanoparticles on the matrix during the long-term cycling.

  14. Photocatalytic activity of Pt-modified Bi{sub 2}WO{sub 6} nanoporous wall under sunlight

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ya-Nan; Lu, Shi-Yu; Bao, Shu-Juan, E-mail: baoshj@swu.edu.cn [Southwest University, Faculty of Material & Energy, Institute for Clean Energy & Advanced Materials (China)

    2015-07-15

    In this work, Bi{sub 2}WO{sub 6} nanoporous wall was synthesized by using Bi{sub 2}O{sub 3} as template and Bi source. Pt nanoparticles whose average size is about 8 nm were further immobilized on the Bi{sub 2}WO{sub 6} nanoporous wall via a simple chemical reduction process. Their photocatalytic activity and the effect of Pt modification were studied by analyzing the degradation of an organic dye, rhodamine 6G (Rh6G), under simulated sunlight. It was found that the photocatalytic ability of Bi{sub 2}WO{sub 6} nanoporous wall was enhanced by introducing Pt nanoparticles. Bare Bi{sub 2}WO{sub 6} shows a degradation efficiency of 78 % after 1 h, while the degradation efficiency of 5 wt% Pt-modified Bi{sub 2}WO{sub 6} was 99 %, and on further increasing the Pt content in the as-prepared Pt-modified Bi{sub 2}WO{sub 6} catalysts, their photocatalytic ability will decrease. The optimal catalyst could be reused without any decrease for five cycles, which may due to Pt be able to help trap the conduction band electrons in the absence of Rh6G. A possible photocatalytic mechanism was proposed and further proved by transient photocurrent response experiment.

  15. On the Superior Activity and Selectivity of PtCo/Nb2O5 Fischer-Tropsch Catalysts

    NARCIS (Netherlands)

    den Otter, J. H.; Yoshida, H.; Ledesma, C.; Chen, D.; de Jong, K. P.

    2016-01-01

    In this study Co/Nb2O5 catalysts and the effect of Pt-promotion thereon are investigated in comparison with γ-Al2O3- and α-Al2O3-supported catalysts for the Fischer-Tropsch (FT) synthesis. Upon Pt-promotion of Co/Nb2O5 the cobalt-weight normalized FT activity was found to increase by a factor of

  16. Direct evidence for active site-dependent formic acid electro-oxidation by topmost-surface atomic redistribution in a ternary PtPdCu electrocatalyst.

    Science.gov (United States)

    Cui, Chun-Hua; Li, Hui-Hui; Cong, Huai-Ping; Yu, Shu-Hong; Tao, Franklin Feng

    2012-12-25

    The active site-dependent electrochemical formic acid oxidation was evidenced by the increased coverage of Pt in the topmost mixed PtPd alloy layer of ternary PtPdCu upon potential cycling, which demonstrated two catalytic pathways only in one catalyst owing to surface atomic redistribution in an acidic electrolyte environment.

  17. One-pot synthesis of Pd-Pt@Pd core-shell nanocrystals with enhanced electrocatalytic activity for formic acid oxidation

    KAUST Repository

    Yuan, Qiang

    2014-01-01

    Well-defined Pd-Pt@Pd core-shell nanocrystals with a Pd-Pt alloy core and a conformal Pd shell of ~2-3 nm were directly synthesized through a one-pot, aqueous solution approach without any preformed Pd or Pt seeds. These Pd-Pt@Pd core-shell nanocrystals show an enhanced electrocatalytic activity for formic acid oxidation compared with commercial Pd black. This journal is © 2014 The Royal Society of Chemistry.

  18. Carbon paper supported Pt/Au catalysts prepared via Cu underpotential deposition-redox replacement and investigation of their electrocatalytic activity for methanol oxidation and oxygen reduction reactions

    Energy Technology Data Exchange (ETDEWEB)

    Khosravi, Mohsen; Amini, Mohammad K. [Chemistry Department, University of Isfahan, Isfahan 81744-73441 (Iran)

    2010-10-15

    Through a simple and rapid method, carbon papers (CPs) were coated with Au and the resulting Au/CP substrates were used for the preparation of Pt/Au/CP by Cu underpotential deposition (Cu UPD) and redox replacement technique. A series of Pt{sub n}/Au/CP catalysts (where n = number of UPD-redox replacement cycles) were synthesized and their electrochemical properties for methanol oxidation reaction (MOR), and oxygen reduction reaction (ORR) were investigated by electrochemical measurements. The Pt{sub n}/Au/CP electrodes show higher electrocatalytic activity and enhanced poison tolerance for the MOR as compared to a commercial Pt/C on CP (Pt/C/CP). The highest mass specific activity and Pt utilization efficiency for MOR was observed on Pt{sub 1}/Au/CP with a thickness close to a monatomic Pt layer. Chronoamperometric tests in methanol solution revealed that Pt{sub n}/Au/CPs have much higher CO tolerance compared to Pt/C/CP. Among the Pt{sub n}/Au/CPs, CO tolerance decreases with increasing the amount of deposited Pt, indicating that the exposed Au atoms in close proximity to Pt plays a positive role against CO poisoning. Compared with the Pt/C/CP, all the Pt{sub n}/Au/CP electrodes show more positive onset potentials and lower overpotentials for ORR. For instance, the onset potential of ORR is 150 mV more positive and the overpotential is {proportional_to}140 mV lower on Pt{sub 4}/Au/CP with respect to Pt/C/CP. (author)

  19. 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...... of Au with mixed Pt/Pd skins. The activity of the binary and ternary catalysts is explained through weakening of the OH binding energy caused by solute elements. However, given the low alloy formation energies it may be difficult to tune and retain the composition under operating conditions....... This is particularly challenging for alloys containing Au due to a high propensity of Au to segregate to the surface. We also show that once Au is on the surface it will diffuse to defect sites, explaining why small amounts of Au retard dissolution of Pt nanoparticles. For the PtPd thin films there is no pronounced...

  20. Proton catalysis with active carbons and partially pyrolyzed carbonaceous materials

    Institute of Scientific and Technical Information of China (English)

    V. V. Strelko; S. S. Stavitskaya; Yu. I. Gorlov

    2014-01-01

    The development of environmentally friendly solid acid catalysts is a priority task. Highly oxidized activated carbon and their ion-substituted (saline) forms are effective proton transfer catalysts in esterification, hydrolysis, and dehydration, and thus are promising candidates as solid acid cata-lysts. Computations by the ab initio method indicated the cause for the enchanced acidity of the carboxylic groups attached to the surface of highly oxidized carbon. The synthesis of phosphorilated carbon was considered, and the proton transfer reactions catalyzed by them in recent studies were analyzed. The development of an amorphous carbon acid catalyst comprising polycyclic carbonaceous (graphene) sheets with-SO3H,-COOH and phenolic type OH-groups was carried out. These new catalysts were synthesized by partial pyrolysis and subsequent sulfonation of carbohydrates, polymers, and other organic compounds. Their high catalytic activities in proton transfere reactions including the processing of bio-based raw materials was demonsrated.

  1. Effect of storage conditions on prothrombin time, activated partial thromboplastin time and fibrinogen concentration on canine plasma samples

    Science.gov (United States)

    Casella, Stefania; Giannetto, Claudia; Giudice, Elisabetta

    2010-01-01

    The present study was to assess the effect of storage conditions on prothrombin time (PT), activated partial thromboplastin time (aPTT) and fibrinogen concentration in blood samples of healthy dogs. Thirty-five dogs of various breeds were included in the study. Citrated blood samples were obtained and plasma was divided into four aliquots to assess selected clotting parameters by means of a coagulometer. The first aliquot was analysed within 1 h after collection, while the remaining 3 were stored at 8℃ for 4, 8 and 24 h, respectively. One-way repeated measures analysis of variance documented a significant decreasing effect on PT at 24 h compared to 8 h and on fibrinogen concentration after 8 and 24 h compared to sampling time and at 4 and 24 h compared to 8 h post sampling. In conclusion, the results of this study indicate that only fibrinogen appears prone to significant decrease. In fact, aPTT is not substantially affected by refrigeration for at least 24 h post sampling and PT showed a statistical difference that does not necessary indicate biological significance as the results obtained were within reference intervals for the dog. PMID:20458152

  2. Tuning the activity of Pt alloy electrocatalysts by means of the lanthanide contraction

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Malacrida, Paolo; Hansen, Martin Hangaard

    2016-01-01

    The high platinum loadings required to compensate for the slow kinetics of the oxygen reduction reaction (ORR) impede the widespread uptake of low-temperature fuel cells in automotive vehicles. We have studied the ORR on eight platinum (Pt)–lanthanide and Pt-alkaline earth electrodes, Pt5M, where...

  3. Preparation and characterization of Pt-CeO2/C and Pt-TiO2/C electrocatalysts with improved electrocatalytic activity for methanol oxidation

    Science.gov (United States)

    Hameed, R. M. Abdel; Amin, R. S.; El-Khatib, K. M.; Fetohi, Amani E.

    2016-03-01

    Pt-TiO2/C and Pt-CeO2/C electrocatalysts were synthesized by solid state reaction of TiO2/C and CeO2/C powders using intermittent microwave heating, followed by chemical reduction of platinum ions using mixed reducing agents of ethylene glycol and sodium borohydride. The crystal structure, surface morphology and chemical composition of prepared electrocatalysts were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The phase angle values of different Pt diffraction planes in Pt-TiO2/C and Pt-CeO2/C were shifted in the positive direction relative to those in Pt/C. Pt particles with diameter values of 3.06 and 2.78 nm were formed in Pt-TiO2/C and Pt-CeO2/C, respectively. The electrochemical performance of prepared electrocatalysts was examined using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Pt-CeO2/C showed an enhanced oxidation current density when compared to Pt/C. Long time oxidation test at Pt-TiO2/C and Pt-CeO2/C revealed their improved stability. Lower charge transfer resistance values were estimated at Pt-metal oxide/C electrocatalysts.

  4. Support-shape Dependent Catalytic Activity in Pt/alumina Systems Using USANS/SANS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Hoon; Han, Sugyeong; Ha, Heonphil; Byun, Jiyoung; Kim, Man-ho [KIST, Seoul (Korea, Republic of)

    2015-10-15

    Pt nanoparticles dispersed on ceramic powder such as alumina and ceria powder are used as catalyst materials to reduce pollution from automobile exhaust, power plant exhaust, etc. Much effort has been put to investigate the relationship between types of catalyst support materials and reactivity of the supported metallic particles. The surface shape of support materials can also be expected to control the catalysts size with the surface shape of support materials. In this presentation, we show our SANS (small angle neutron scattering) -USANS (ultra small angle neutron scattering) analysis on the structural differences of different shapes of the same γ alumina powder with different loadings of Pt nanoparticles. Then, the reactivity of the prepared catalyst materials are presented and discussed based on the investigation of the structure of the support materials by SANS. The shapes of gamma alumina, rod-like or plate-like shape, were determined from nanometer to micrometer with USANS and SANS analysis. We found that the platelet-like alumina consists of an aggregate of 2 - 3 layers, which further reduce specific surface area and catalytic activity compared to rod-like shape. Rod-like shape shows more than 100% enhancement in the catalytic activities in model three-way-catalyst (TWC) reactions of CO, NO, and C{sub 3}H{sub 6} at low temperature around 200 .deg. C.

  5. Effect of BaO on Catalytic Activity of Pt-Rh TWC

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effects of BaO doping on the three-way catalytic activity of Pt-Rh catalyst and on water-gas shift were investigated. The results show that the light-off temperatures of hydrocarbon and carbon monoxide and nitrogen oxides of the fresh catalysts slightly differ from those of the aged catalysts, and the catalysts containing CeO2-ZrO2-BaO have lower lightoff temperature and better catalytic activity than these containing BaO and CeO2-ZrO2 after hydrothermal aging for 5 h at 1000 C. The catalysts were characterized by means of the temperature-programmed reduction (TPR) in hydrogen and the temperature-programmed desorption (TPD) in oxygen. It is confirmed that the suggested route of CeO2-ZrO2-BaO by coprecipitation can improve the catalytic activity of catalysts.

  6. Highly Stable and Active Pt/Nb-TiO2 Carbon-Free Electrocatalyst for Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Shuhui Sun

    2012-01-01

    Full Text Available The current materials used in proton exchange membrane fuel cells (PEMFCs are not sufficiently durable for commercial deployment. One of the major challenges lies in the development of an inexpensive, efficient, and highly durable and active electrocatalyst. Here a new type of carbon-free Pt/Nb-TiO2 electrocatalyst has been reported. Mesoporous Nb-TiO2 hollow spheres were synthesized by the sol-gel method using polystyrene (PS sphere templates. Pt nanoparticles (NPs were then deposited onto mesoporous Nb-TiO2 hollow spheres via a simple wet-chemical route in aqueous solution, without the need for surfactants or potentiostats. The growth densities of Pt NPs on Nb-TiO2 supports could be easily modulated by simply adjusting the experimental parameters. Electrochemical studies of Pt/Nb-TiO2 show much enhanced activity and stability than commercial E-TEK Pt/C catalyst. PtNP/Nb-TiO2 is a promising new cathode catalyst for PEMFC applications.

  7. Enhanced methanol electro-oxidation activity of PtRu catalysts supported on heteroatom-doped carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wu Gang [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: wugang@lanl.gov; Swaidan, Raja [Department of Chemical Engineering, Cooper Union, New York, NY 10003 (United States); Li Deyu; Li Ning [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)

    2008-11-01

    A typical heteroatom (nitrogen)-doped carbon materials were successfully synthesized through the carbonization of a hybrid containing traditional carbon black covered by in situ polymerized polyaniline. The nitrogen content onto carbon can be adjusted up to 5.1 at.% by changing the coverage of polyaniline. The effects of nitrogen doping on the surface physical and electrochemical properties of carbon were studied using XPS, XRD and HRTEM, as well as CV and EIS techniques. With increasing nitrogen doping, the carbon structure became more compact, showing curvatures and dislocations in the graphene stacking. The nitrogen-doped carbon also exhibited a higher accessible surface area in electrochemical reactions, and a lower charge transfer resistance at the carbon/electrolyte interface. Moreover, to investigate the influence of nitrogen doping on the electrocatalytic activity of the PtRu/C catalyst, comparisons in CO stripping and methanol oxidation were carried out on PtRu catalysts supported by non-doped and nitrogen-doped carbon. Since the promotional roles of nitrogen doping, including the high electrochemically accessible surface area, the richness of the disordered nanostructures and defects, and the high electron density on N-doped carbon supports, contribute to the synthesis of well-dispersed PtRu particles with high Pt utilization and stronger metal-support interactions, an enhanced catalytic activity for methanol oxidation was obtained in the case of the PtRu/N-C catalyst in comparison with the traditional PtRu/C catalyst.

  8. Enhanced methanol electro-oxidation activity of PtRu catalysts supported on heteroatom-doped carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Gang; Li, Deyu; Li, Ning [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Swaidan, Raja [Department of Chemical Engineering, Cooper Union, New York, NY 10003 (United States)

    2008-11-01

    A typical heteroatom (nitrogen)-doped carbon materials were successfully synthesized through the carbonization of a hybrid containing traditional carbon black covered by in situ polymerized polyaniline. The nitrogen content onto carbon can be adjusted up to 5.1 at.% by changing the coverage of polyaniline. The effects of nitrogen doping on the surface physical and electrochemical properties of carbon were studied using XPS, XRD and HRTEM, as well as CV and EIS techniques. With increasing nitrogen doping, the carbon structure became more compact, showing curvatures and dislocations in the graphene stacking. The nitrogen-doped carbon also exhibited a higher accessible surface area in electrochemical reactions, and a lower charge transfer resistance at the carbon/electrolyte interface. Moreover, to investigate the influence of nitrogen doping on the electrocatalytic activity of the PtRu/C catalyst, comparisons in CO stripping and methanol oxidation were carried out on PtRu catalysts supported by non-doped and nitrogen-doped carbon. Since the promotional roles of nitrogen doping, including the high electrochemically accessible surface area, the richness of the disordered nanostructures and defects, and the high electron density on N-doped carbon supports, contribute to the synthesis of well-dispersed PtRu particles with high Pt utilization and stronger metal-support interactions, an enhanced catalytic activity for methanol oxidation was obtained in the case of the PtRu/N-C catalyst in comparison with the traditional PtRu/C catalyst. (author)

  9. 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

    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....... This is particularly challenging for alloys containing Au due to a high propensity of Au to segregate to the surface. We also show that once Au is on the surface it will diffuse to defect sites, explaining why small amounts of Au retard dissolution of Pt nanoparticles. For the PtPd thin films there is no pronounced...

  10. A low-temperature synthesis of electrochemical active Pt nanoparticles and thin films by atomic layer deposition on Si(111) and glassy carbon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Rui [Joint Center for Artificial Photosynthesis, California Institute of Technology, Pasadena, CA 91125 (United States); Han, Lihao [Joint Center for Artificial Photosynthesis, California Institute of Technology, Pasadena, CA 91125 (United States); Photovoltaic Materials and Devices (PVMD) Laboratory, Delft University of Technology, P.O. Box 5031, GA Delft 2600 (Netherlands); Huang, Zhuangqun; Ferrer, Ivonne M. [Joint Center for Artificial Photosynthesis, California Institute of Technology, Pasadena, CA 91125 (United States); Division of Chemistry and Chemical Engineering, California Institute of Technology, 210 Noyes Laboratory 127-72, Pasadena, CA 91125 (United States); Smets, Arno H.M.; Zeman, Miro [Photovoltaic Materials and Devices (PVMD) Laboratory, Delft University of Technology, P.O. Box 5031, GA Delft 2600 (Netherlands); Brunschwig, Bruce S., E-mail: bsb@caltech.edu [Beckman Institute, California Institute of Technology, Pasadena, CA 91125 (United States); Lewis, Nathan S., E-mail: nslewis@caltech.edu [Joint Center for Artificial Photosynthesis, California Institute of Technology, Pasadena, CA 91125 (United States); Beckman Institute, California Institute of Technology, Pasadena, CA 91125 (United States); Division of Chemistry and Chemical Engineering, California Institute of Technology, 210 Noyes Laboratory 127-72, Pasadena, CA 91125 (United States); Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125 (United States)

    2015-07-01

    Atomic layer deposition (ALD) was used to deposit nanoparticles and thin films of Pt onto etched p-type Si(111) wafers and glassy carbon discs. Using precursors of MeCpPtMe{sub 3} and ozone and a temperature window of 200–300 °C, the growth rate was 80–110 pm/cycle. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to analyze the composition, structure, morphology, and thickness of the ALD-grown Pt nanoparticle films. The catalytic activity of the ALD-grown Pt for the hydrogen evolution reaction was shown to be equivalent to that of e-beam evaporated Pt on glassy carbon electrode. - Highlights: • Pure Pt films were grown by atomic layer deposition (ALD) using MeCpPtMe3 and ozone. • ALD-grown Pt thin films had high growth rates of 110 pm/cycle. • ALD-grown Pt films were electrocatalytic for hydrogen evolution from water. • Electrocatalytic activity of the ALD Pt films was equivalent to e-beam deposited Pt. • No carbon species were detected in the ALD-grown Pt films.

  11. The effect of antimony-tin and indium-tin oxide supports on the catalytic activity of Pt nanoparticles for ammonia electro-oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Júlio César M. [Department of Chemical & Biological Engineering, Centre for Catalysis Research and Innovation (CCRI), University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada); Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508-900, São Paulo, SP (Brazil); Piasentin, Ricardo M.; Spinacé, Estevam V.; Neto, Almir O. [Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508-900, São Paulo, SP (Brazil); Baranova, Elena A., E-mail: elena.baranova@uottawa.ca [Department of Chemical & Biological Engineering, Centre for Catalysis Research and Innovation (CCRI), University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada)

    2016-09-01

    Platinum nanoparticles supported on carbon (Pt/C) and carbon with addition of ITO (Pt/C-ITO (In{sub 2}O{sub 3}){sub 9}·(SnO{sub 2}){sub 1}) and ATO (Pt/C-ATO (SnO{sub 2}){sub 9}·(Sb{sub 2}O{sub 5}){sub 1}) oxides were prepared by sodium borohydride reduction method and used for ammonia electro-oxidation reaction (AmER) in alkaline media. The effect of the supports on the catalytic activity of Pt for AmER was investigated using electrochemical (cyclic voltammetry and chronoamperometry) and direct ammonia fuel cell (DAFC) experiments. X-ray diffraction (XRD) showed Pt peaks attributed to the face-centered cubic (fcc) structure, as well as peaks characteristic of In{sub 2}O{sub 3} in ITO support and cassiterite SnO{sub 2} phase of ATO support. According to transmission electron micrographs the mean particles sizes of Pt over carbon were 5.4, 4.9 and 4.7 nm for Pt/C, Pt/C-ATO and Pt/C-ITO, respectively. Pt/C-ITO catalysts showed the highest catalytic activity for ammonia electrooxidation in both electrochemical and fuel cell experiments. We attributed this to the presence of In{sub 2}O{sub 3} phase in ITO, which provides oxygenated or hydroxide species at lower potentials resulting in the removal of poisonous intermediate, i.e., atomic nitrogen (N{sub ads}) and promotion of ammonia electro-oxidation. - Highlights: • Oxide support effect on the catalytic activity of Pt towards ammonia electro-oxidation. • Direct ammonia fuel cell (DAFC) performance using Pt over different supports as anode. • Pt/C-ITO shows better catalytic activity for ammonia oxidation than Pt/C and Pt/C-ATO.

  12. CO2 Activation and Hydrogenation by PtHn (-) Cluster Anions.

    Science.gov (United States)

    Zhang, Xinxing; Liu, Gaoxiang; Meiwes-Broer, Karl-Heinz; Ganteför, Gerd; Bowen, Kit

    2016-08-08

    Gas phase reactions between PtHn (-) cluster anions and CO2 were investigated by mass spectrometry, anion photoelectron spectroscopy, and computations. Two major products, PtCO2 H(-) and PtCO2 H3 (-) , were observed. The atomic connectivity in PtCO2 H(-) can be depicted as HPtCO2 (-) , where the platinum atom is bonded to a bent CO2 moiety on one side and a hydrogen atom on the other. The atomic connectivity of PtCO2 H3 (-) can be described as H2 Pt(HCO2 )(-) , where the platinum atom is bound to a formate moiety on one side and two hydrogen atoms on the other. Computational studies of the reaction pathway revealed that the hydrogenation of CO2 by PtH3 (-) is highly energetically favorable.

  13. Sub-4 nm PtZn Intermetallic Nanoparticles for Enhanced Mass and Specific Activities in Catalytic Electrooxidation Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Zhiyuan; Xiao, Chaoxian; Liu, Cong; Goh, Tian Wei; Zhou, Lin; Maligal-Ganesh, Raghu; Pei, Yuchen; Li, Xinle; Curtiss, Larry A.; Huang, Wenyu

    2017-03-22

    Atomically ordered intermetallic nanoparticles (iNPs) have sparked considerable interest in fuel cell applications by virtue of their exceptional electronic and structural properties. However, the synthesis of small iNPs in a controllable manner remains a formidable challenge because of the high temperature generally required in the formation of intermetallic phases. Here we report a general method for the synthesis of PtZn. iNPs (3.2 +/- 0.4 nm) on multiwalled carbon nanotubes (MWNT) via a facile and capping agent free strategy using a sacrificial mesoporous silica (mSiO(2)) shell. The as-prepared PtZn iNPs exhibited ca. 10 times higher mass activity in both acidic and basic solution toward the methanol oxidation reaction (MOR) compared to larger PtZn iNPs synthesized on MWNT without the mSiO2 shell. Density functional theory (DFT) calculations predict that PtZn systems go through a "non-CO" pathway for MOR because of the stabilization of the OH* intermediate by Zn atoms, while a pure Pt system forms highly stable COH* and CO* intermediates, leading to catalyst deactivation. Experimental studies on the origin of the backward oxidation peak of MOR coincide well with DFT predictions. Moreover, the calculations demonstrate that MOR on smaller PtZn iNPs is energetically more favorable than larger iNPs, due to their high density of corner sites and lower-lying energetic pathway. Therefore, smaller PtZn iNPs not only increase the number but also enhance the activity of the active sites in MOR compared with larger ones. This work opens a new avenue for the synthesis of small iNPs with more undercoordinated and enhanced active sites for fuel cell applications.

  14. CATALYTIC AND ELECTROCATALYTIC ACTIVITY OF Pt-Ru/C ELECTRODE FOR HYDROGEN OXIDATION IN ALKALINE

    Directory of Open Access Journals (Sweden)

    D. LABOU

    2008-07-01

    Full Text Available The kinetics of the oxidation of H2 on PtRu/C gas-diffusion electrode was studied by interfacing the electrode with aqueous electrolytes at different pH values. The conducting electrolytes were KOH and HClO4 aqueous solutions with different concentrations. It is shown that the nature of the aqueous electrolyte plays the role of an active catalyst support for the PtRu/C electrode which drastically affects its catalytic properties. During the aforementioned interaction, termed electrochemical metal support interaction (EMSI, the electrochemical potential of the electrons at the catalyst Fermi level is equalised with the electrochemical potential of the solvated electron in the aqueous electrolyte. The electrochemical experiments carried out at various pH values showed that the electrochemical promotion catalysis (EPOC is more intense when the catalyst-electrode is interfaced with electrolytes with high pH values where the OH– ionic conduction prevails. It was concluded that similar to the solid state electrochemical systems EPOC proceeds through the formation of a polar adsorbed promoting layer of , electrochemically supplied by the OH- species, at the three phase boundaries of the gas exposed gas diffusion catalyst-electrode surface.

  15. The Role of OOH Binding Site and Pt Surface Structure on ORR Activities

    Science.gov (United States)

    Jia, Qingying; Caldwell, Keegan; Ziegelbauer, Joseph M.; Kongkanand, Anusorn; Wagner, Frederick T.; Mukerjee, Sanjeev; Ramaker, David E.

    2015-01-01

    We present experimentally observed molecular adsorbate coverages (e.g., O(H), OOH and HOOH) on real operating dealloyed bimetallic PtMx (M = Ni or Co) catalysts under oxygen reduction reaction (ORR) conditions obtained using X-ray absorption near edge spectroscopy (XANES). The results reveal a complex Sabatier catalysis behavior and indicate the active ORR mechanism changes with Pt–O bond weakening from the O2 dissociative mechanism, to the peroxyl mechanism, and finally to the hydrogen peroxide mechanism. An important rearrangement of the OOH binding site, an intermediate in the ORR, enables facile H addition to OOH and faster O–O bond breaking on 111 faces at optimal Pt–O bonding strength, such as that occurring in dealloyed PtM core-shell nanoparticles. This rearrangement is identified by previous DFT calculations and confirmed from in situ measured OOH adsorption coverages during the ORR. The importance of surface structural effects and 111 ordered faces is confirmed by the higher specific ORR rates on solid core vs porous multi-core nanoparticles. PMID:26190857

  16. Improving the Ethanol Oxidation Activity of Pt-Mn Alloys through the Use of Additives during Deposition

    Directory of Open Access Journals (Sweden)

    Mohammadreza Zamanzad Ghavidel

    2015-06-01

    Full Text Available In this work, sodium citrate (SC was used as an additive to control the particle size and dispersion of Pt-Mn alloy nanoparticles deposited on a carbon support. SC was chosen, since it was the only additive tested that did not prevent Mn from co-depositing with Pt. The influence of solution pH during deposition and post-deposition heat treatment on the physical and electrochemical properties of the Pt-Mn alloy was examined. It was determined that careful control over pH is required, since above a pH of four, metal deposition was suppressed. Below pH 4, the presence of sodium citrate reduced the particle size and improved the particle dispersion. This also resulted in larger electrochemically-active surface areas and greater activity towards the ethanol oxidation reaction (EOR. Heat treatment of catalysts prepared using the SC additive led to a significant enhancement in EOR activity, eclipsing the highest activity of our best Pt-Mn/C prepared in the absence of SC. XRD studies verified the formation of the Pt-Mn intermetallic phase upon heat treatment. Furthermore, transmission electron microscopy studies revealed that catalysts prepared using the SC additive were more resistant to particle size growth during heat treatment.

  17. Flowerlike PtCl 4/Bi 2WO 6 composite photocatalyst with enhanced visible-light-induced photocatalytic activity

    Science.gov (United States)

    Duan, Fang; Zheng, Yan; Chen, MingQing

    2011-01-01

    Flowerlike PtCl 4/Bi 2WO 6 composite photocatalyst was successfully synthesized through a simple two-step method involving a template-free hydrothermal process and the following impregnation treatment. The samples were fully characterized by the study of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis absorption spectra. The results indicated that the doping of Pt species did not affect the crystal structure and the morphology of Bi 2WO 6 photocatalyst, but it had great influences on the photocatalytic activity of Bi 2WO 6 towards rhodamine-B (RhB) degradation. Besides, the Pt species was found to be present as PtCl 4 in the composite samples, and also an optimal Pt species content on the surface of Bi 2WO 6 photocatalyst was discovered with the highest photocatalytic ability. The improved photocatalytic performance could be ascribed to the enhanced interfacial charge transfer and the inhibited recombination of electron-hole pairs. Meanwhile, a possible mechanism for RhB photocatalytic degradation over PtCl 4/Bi 2WO 6 catalyst was also proposed.

  18. Prothrombin Time and Activated Partial Thromboplastin Time Testing: A Comparative Effectiveness Study in a Million-Patient Sample.

    Directory of Open Access Journals (Sweden)

    Manu N Capoor

    Full Text Available A substantial fraction of all American healthcare expenditures are potentially wasted, and practices that are not evidence-based could contribute to such waste. We sought to characterize whether Prothrombin Time (PT and activated Partial Thromboplastin Time (aPTT tests of preoperative patients are used in a way unsupported by evidence and potentially wasteful.We evaluated prospectively-collected patient data from 19 major teaching hospitals and 8 hospital-affiliated surgical centers in 7 states (Delaware, Florida, Maryland, Massachusetts, New Jersey, New York, Pennsylvania and the District of Columbia. A total of 1,053,472 consecutive patients represented every patient admitted for elective surgery from 2009 to 2012 at all 27 settings. A subset of 682,049 patients (64.7% had one or both tests done and history and physical (H&P records available for analysis. Unnecessary tests for bleeding risk were defined as: PT tests done on patients with no history of abnormal bleeding, warfarin therapy, vitamin K-dependent clotting factor deficiency, or liver disease; or aPTT tests done on patients with no history of heparin treatment, hemophilia, lupus anticoagulant antibodies, or von Willebrand disease. We assessed the proportion of patients who received PT or aPTT tests who lacked evidence-based reasons for testing.This study sought to bring the availability of big data together with applied comparative effectiveness research. Among preoperative patients, 26.2% received PT tests, and 94.3% of tests were unnecessary, given the absence of findings on H&P. Similarly, 23.3% of preoperative patients received aPTT tests, of which 99.9% were unnecessary. Among patients with no H&P findings suggestive of bleeding risk, 6.6% of PT tests and 7.1% of aPTT tests were either a false positive or a true positive (i.e. indicative of a previously-undiagnosed potential bleeding risk. Both PT and aPTT, designed as diagnostic tests, are apparently used as screening tests

  19. Nanoparticle cluster gas sensor: Pt activated SnO2 nanoparticles for NH3 detection with ultrahigh sensitivity

    Science.gov (United States)

    Liu, Xu; Chen, Nan; Han, Bingqian; Xiao, Xuechun; Chen, Gang; Djerdj, Igor; Wang, Yude

    2015-09-01

    Pt activated SnO2 nanoparticle clusters were synthesized by a simple solvothermal method. The structure, morphology, chemical state and specific surface area were analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2-sorption studies, respectively. The SnO2 nanoparticle cluster matrix consists of tens of thousands of SnO2 nanoparticles with an ultra-small grain size estimated to be 3.0 nm. And there are abundant random-packed wormhole-like pores, caused by the inter-connection of the SnO2 nanoparticles, throughout each cluster. The platinum element is present in two forms including metal (Pt) and tetravalent metal oxide (PtO2) in the Pt activated SnO2 nanoparticle clusters. The as-synthesized pure and Pt activated SnO2 nanoparticle clusters were used to fabricate gas sensor devices. It was found that the gas response toward 500 ppm of ammonia was improved from 6.48 to 203.44 through the activation by Pt. And the results indicate that the sensor based on Pt activated SnO2 not only has ultrahigh sensitivity but also possesses good response-recovery properties, linear dependence, repeatability, selectivity and long-term stability, demonstrating the potential to use Pt activated SnO2 nanoparticle clusters as ammonia gas sensors. At the same time, the formation mechanisms of the unique nanoparticle clusters and highly enhanced sensitivity are also discussed.Pt activated SnO2 nanoparticle clusters were synthesized by a simple solvothermal method. The structure, morphology, chemical state and specific surface area were analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and N2-sorption studies, respectively. The SnO2 nanoparticle cluster matrix consists of tens of thousands of SnO2 nanoparticles with an ultra-small grain size estimated to be 3.0 nm. And there are abundant random-packed wormhole-like pores, caused by the inter

  20. Methanol oxidation reaction activity of microwave irradiated and heat-treated Pt/Co and Pt/Ni nano-electrocatalysts

    CSIR Research Space (South Africa)

    Mathe, NR

    2014-11-01

    Full Text Available Bimetallic Pt nanoparticles were prepared by alloying Pt with the non-noble transition metals, Co and Ni, using a conventional heat-treatment (HT) method and microwaveirradiation (MW). The resulting samples were PteCo-Ht, PteNi-HT, PteCo, MW and Pt...

  1. Partial Agonists Activate PPARgamma Using a Helix 12 Independent Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Bruning, J.B.; Chalmers, M.J.; Prasad, S.; Bushby, S.A.; Kamenecka, T.A.; He, Y.; Nettles, K.W.; Griffin, P.R.

    2009-05-28

    Binding to helix 12 of the ligand-binding domain of PPAR{gamma} is required for full agonist activity. Previously, the degree of stabilization of the activation function 2 (AF-2) surface was thought to correlate with the degree of agonism and transactivation. To examine this mechanism, we probed structural dynamics of PPAR{gamma} with agonists that induced graded transcriptional responses. Here we present crystal structures and amide H/D exchange (HDX) kinetics for six of these complexes. Amide HDX revealed each ligand induced unique changes to the dynamics of the ligand-binding domain (LBD). Full agonists stabilized helix 12, whereas intermediate and partial agonists did not at all, and rather differentially stabilized other regions of the binding pocket. The gradient of PPAR{gamma} transactivation cannot be accounted for solely through changes to the dynamics of AF-2. Thus, our understanding of allosteric signaling must be extended beyond the idea of a dynamic helix 12 acting as a molecular switch.

  2. Combining anti-cancer drugs with artificial sweeteners: synthesis and anti-cancer activity of saccharinate (sac) and thiosaccharinate (tsac) complexes cis-[Pt(sac)2(NH3)2] and cis-[Pt(tsac)2(NH3)2].

    Science.gov (United States)

    Al-Jibori, Subhi A; Al-Jibori, Ghassan H; Al-Hayaly, Lamaan J; Wagner, Christoph; Schmidt, Harry; Timur, Suna; Baris Barlas, F; Subasi, Elif; Ghosh, Shishir; Hogarth, Graeme

    2014-12-01

    The new platinum(II) complexes cis-[Pt(sac)2(NH3)2] (sac=saccharinate) and cis-[Pt(tsac)2(NH3)2] (tsac=thiosaccharinate) have been prepared, the X-ray crystal structure of cis-[Pt(sac)2(NH3)2] x H2O reveals that both saccharinate anions are N-bound in a cis-arrangement being inequivalent in both the solid-state and in solution at room temperature. Preliminary anti-cancer activity has been assessed against A549 human alveolar type-II like cell lines with the thiosaccharinate complex showing good activity.

  3. Investigation of electro-oxidation activity of Pt-CNTs/GC electrodes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The morphology and structure of Pt-CNTs/GC electrodes were characterized via Transmission Electron Microscopy (TEM) and selected area electron diffraction.The electro-oxidation behavior of CO and methanol on Pt-CNTs/GC electrodes were studied with cyclic voltommograms or chronoamperometry.Three oxidation peaks were observed for CO absorbed on PtCNTs/GC electrodes.Methanol was found to be dissociated spontaneously on the electrode to produce a strong absorbed intermediate CO.Among the three oxidation peaks,peak Ⅰ was presumed to be due to the bridged CO absorption while peaks Ⅱ and Ⅲ were attributed to the split in the linear CO which is absorbed on the PtCNTs/GC nanocluster with different particle size and Pt film.The oxidation current of methanol on the Pt-CNTs/GC electrode did not always increase with the increase in the amount of Pt loading,The result indicates that there is an optimal Pt loading for methanol oxidation.It is necesSary to select the catalyst with proper Pt loading when the anode of a direct-methanol fuel cell is prepared.

  4. Design, synthesis and characterization of a Pt-Gd metal-organic framework containing potentially catalytically active sites.

    Science.gov (United States)

    Szeto, Kai C; Kongshaug, Kjell Ove; Jakobsen, Søren; Tilset, Mats; Lillerud, Karl Petter

    2008-04-21

    The heterobimetallic metal-organic framework {[(BPDC)PtCl(2)](3)(Gd(H(2)O)(3))(2)}.5H(2)O (BPDC = 2,2'-bipyridine-5,5'-dicarboxylate) has been designed and synthesized by hydrothermal methods. The new coordination polymer contains subunits of (BPDC)PtCl(2) (1) where both N atoms of the BPDC ligand are attached to a square-planar Pt(II) center. The two remaining cis coordination sites at Pt(II) are occupied by chloride ions. The final structure (2) of the polymeric network is obtained when Gd(III) ions link together the (BPDC)PtCl(2) units, which are organized in sheets, into larger blocks. These blocks are stacked along the crystallographic [010] direction and are held together by a hydrogen bonding scheme that involves carboxylate oxygen atoms and water molecules in the coordination sphere of Gd. The coordination polymer 2 can be obtained in a single-step reaction or in a two-step synthesis where the corresponding Pt complex (1) was first synthesized followed by reacting 1 with Gd(NO(3))(3).6H(2)O. In situ high temperature powder X-ray diffraction shows that the crystalline coordination polymer transforms into an anhydrous modification at 100 degrees C. This modification is stable to 350 degrees C, at which temperature the structure starts to decompose. The coordination sphere around platinum in the polymer closely resembles organometallic Pt complexes that have been previously found to catalytically or stoichiometrically activate and functionalize hydrocarbon C-H bonds in homogeneous systems.

  5. Activation of C-H Bonds in Pt(+) + x CH4 Reactions, where x = 1-4: Identification of the Platinum Dimethyl Cation.

    Science.gov (United States)

    Wheeler, Oscar W; Salem, Michelle; Gao, Amanda; Bakker, Joost M; Armentrout, P B

    2016-08-11

    Activation of C-H bonds in the sequential reactions of Pt(+) + x(CH4/CD4), where x = 1-4, have been investigated using infrared multiple photon dissociation (IRMPD) spectroscopy and theoretical calculations. Pt(+) cations are formed by laser ablation and exposed to controlled amounts of CH4/CD4 leading to [Pt,xC,(4x-2)H/D](+) dehydrogenation products. Irradiation of these products in the 400-2100 cm(-1) range leads to CH4/CD4 loss from the x = 3 and 4 products, whereas PtCH2(+)/PtCD2(+) products do not decompose at all, and x = 2 products dissociate only when formed from a higher order product. The structures of these complexes were explored theoretically at several levels of theory with three different basis sets. Comparison of the experimental and theoretical results indicate that the species formed have a Pt(CH3)2(+)(CH4)x-2/Pt(CD3)2(+)(CD4)x-2 binding motif for x = 2-4. Thus, reaction of Pt(+) with methane occurs by C-H bond activation to form PtCH2(+), which reacts with an additional methane molecule by C-H bond activation to form the platinum dimethyl cation. This proposed reaction mechanism is consistent with theoretical explorations of the potential energy surface for reactions of Pt(+) with one and two methane molecules.

  6. Haemophilus ducreyi partially activates human myeloid dendritic cells.

    Science.gov (United States)

    Banks, Keith E; Humphreys, Tricia L; Li, Wei; Katz, Barry P; Wilkes, David S; Spinola, Stanley M

    2007-12-01

    Dendritic cells (DC) orchestrate innate and adaptive immune responses to bacteria. How Haemophilus ducreyi, which causes genital ulcers and regional lymphadenitis, interacts with DC is unknown. H. ducreyi evades uptake by polymorphonuclear leukocyte and macrophage-like cell lines by secreting LspA1 and LspA2. Many H. ducreyi strains express cytolethal distending toxin (CDT), and recombinant CDT causes apoptosis of DC in vitro. Here, we examined interactions between DC and H. ducreyi 35000HP, which produces LspA1, LspA2, and CDT. In human volunteers infected with 35000HP, the ratio of myeloid DC to plasmacytoid DC was 2.8:1 in lesions, compared to a ratio of 1:1 in peripheral blood. Using myeloid DC derived from monocytes as surrogates for lesional DC, we found that DC infected with 35000HP remained as viable as uninfected DC for up to 48 h. Gentamicin protection and confocal microscopy assays demonstrated that DC ingested and killed 35000HP, but killing was incomplete at 48 h. The expression of LspA1 and LspA2 did not inhibit the uptake of H. ducreyi, despite inactivating Src kinases. Infection of DC with live 35000HP caused less cell surface marker activation than infection with heat-killed 35000HP and lipopolysaccharide (LPS) and inhibited maturation by LPS. However, infection of DC with live bacteria caused the secretion of significantly higher levels of interleukin-6 and tumor necrosis factor alpha than infection with heat-killed bacteria and LPS. The survival of H. ducreyi in DC may provide a mechanism by which the organism traffics to lymph nodes. Partial activation of DC may abrogate the establishment of a full Th1 response and an environment that promotes phagocytosis.

  7. Exploring the Lanthanide Contraction to Tune the Activity and Stability of Pt

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Malacrida, Paolo; Hansen, Martin Hangaard

    2016-01-01

    The high platinum loadings required to compensate for the slow kinetics of the oxygen reduction reaction (ORR) impede the widespread uptake of polymer electrolyte membrane fuel cells. In order to improve the ORR kinetics and reduce the Pt loading, we can tailor the electronic properties of the Pt...

  8. Ternary Pt-Ru-Ni catalytic layers for methanol electrooxidation prepared by electrodeposition and galvanic replacement

    Directory of Open Access Journals (Sweden)

    Athanasios ePapaderakis

    2014-06-01

    Full Text Available Ternary Pt-Ru-Ni deposits on glassy carbon substrates, Pt-Ru(Ni/GC, have been formed by initial electrodeposition of Ni layers onto glassy carbon electrodes, followed by their partial exchange for Pt and Ru, upon their immersion into equimolar solutions containing complex ions of the precious metals. The overall morphology and composition of the deposits has been studied by SEM microscopy and EDS spectroscopy. Continuous but nodular films have been confirmed, with a Pt÷Ru÷Ni % bulk atomic composition ratio of 37÷12÷51 (and for binary Pt-Ni control systems of 47÷53. Fine topographical details as well as film thickness have been directly recorded using AFM microscopy. The composition of the outer layers as well as the interactions of the three metals present have been studied by XPS spectroscopy and a Pt÷Ru÷Ni % surface atomic composition ratio of 61÷12÷27 (and for binary Pt-Ni control systems of 85÷15 has been found, indicating the enrichment of the outer layers in Pt; a shift of the Pt binding energy peaks to higher values was only observed in the presence of Ru and points to an electronic effect of Ru on Pt. The surface electrochemistry of the thus prepared Pt-Ru(Ni/GC and Pt(Ni/GC electrodes in deaerated acid solutions (studied by cyclic voltammetry proves the existence of a shell consisting exclusively of Pt-Ru or Pt. The activity of the Pt-Ru(Ni deposits towards methanol oxidation (studied by slow potential sweep voltammetry is higher from that of the Pt(Ni deposit and of pure Pt; this enhancement is attributed both to the well-known Ru synergistic effect due to the presence of its oxides but also (based on the XPS findings to a modification effect of Pt electronic properties.

  9. Highly active and stable Pt electrocatalysts promoted by antimony-doped SnO2 supports for oxygen reduction reactions

    DEFF Research Database (Denmark)

    Yin, Min; Xu, Junyuan; Li, Qingfeng

    2014-01-01

    supports composed of oxides and carbon and supported platinum catalysts were prepared. Using the pure oxide support, the Pt/ATO catalyst displayed superior specific activity and stability for the oxygen reduction reactions (ORRs). Low surface area of ATO caused poor dispersion of Pt particles compared......Alternative composite supports for platinum catalysts were synthesized from antimony doped tin dioxide (ATO) nanoparticles. In the range of the antimony content from 0 to 11mol%, the highest electrical conductivity of 1.1Scm-1 at 130°C was obtained for the 5mol% Sb ATO, from which composite...

  10. Exploring the Lanthanide Contraction to Tune the Activity and Stability of Pt

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Malacrida, Paolo; Hansen, Martin Hangaard

    2016-01-01

    The high platinum loadings required to compensate for the slow kinetics of the oxygen reduction reaction (ORR) impede the widespread uptake of polymer electrolyte membrane fuel cells. In order to improve the ORR kinetics and reduce the Pt loading, we can tailor the electronic properties of the Pt...... surface atoms by means of alloying Pt with other metals. Researchers have intensively studied alloys of Pt with late transition metals such as Ni and Co during the last decades. However, these compounds typically degrade under fuel cell reaction conditions, due to dealloying. In contrast, alloys of Pt...... and lanthanides present very negative enthalpy of formation [1,2], which should increase their resistance to degradation....

  11. Postassembly Transformation of a Catalytically Active Composite Material, Pt@ZIF-8, via Solvent-Assisted Linker Exchange.

    Science.gov (United States)

    Stephenson, Casey J; Hupp, Joseph T; Farha, Omar K

    2016-02-15

    2-Methylimidazolate linkers of Pt@ZIF-8 are exchanged with imidazolate using solvent-assisted linker exchange (SALE) to expand the apertures of the parent material and create Pt@SALEM-2. Characterization of the material before and after SALE was performed. Both materials are active as catalysts for the hydrogenation of 1-octene, whereas the hydrogenation of cis-cyclohexene occurred only with Pt@SALEM-2, consistent with larger apertures for the daughter material. The largest substrate, β-pinene, proved to be unreactive with H2 when either material was employed as a candidate catalyst, supporting the contention that substrate molecules, for both composites, must traverse the metal-organic framework component in order to reach the catalytic nanoparticles.

  12. 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

    of Au with mixed Pt/Pd skins. The activity of the binary and ternary catalysts is explained through weakening of the OH binding energy caused by solute elements. However, given the low alloy formation energies it may be difficult to tune and retain the composition under operating conditions...

  13. Preparation and Electro-catalytic Activity of Pd@Pt/C Catalyst%低铂催化剂Pd@Pt/C的制备及其电催化活性的研究

    Institute of Scientific and Technical Information of China (English)

    陈容; 黄琦杰

    2016-01-01

    The kinetics of the oxygen reduction reaction in fuel cell cathodes is sluggish that needs using large amounts of Pt to compensate, which mainly leads to the high cost of fuel cell, as well as hider the large scale application of proton exchange membrane fuel cell. In order to overcome these problems, it needs to investigate high performance, low platinum loading, excellent durability electrocatalysts. Core-shell structure catalyst, because of its special structure which can make the Pt dispersion, utilization, and activity be greatly improved as well as reduce Pt loading, has been widely recognized as being among the most promising candidates to achieve the commercialization of proton exchange membrane fuel cell. A novel pulse deposition method was used to prepare a low platinum catalyst Pd@Pt/C. For the cathodic reduction of oxygen, Pd@ Pt/C catalyst demonstrated three times higher mass activity towards the cathodic reduction of oxygen than commercial Pt/C catalyst, exhibiting competitive performance compared with commercial Pt/C catalyst.%燃料电池阴极氧还原动力学缓慢,需要使用大量的铂催化剂,导致电池高昂的成本,制约了质子交换膜燃料电池的大规模产业化。解决这个瓶颈的关键在于研究与制备高性能、低铂载量、耐久性好的燃料电池催化剂。而核壳结构催化剂因其特殊的结构可以使得Pt的分散度、利用率、活性得到很大的提高。本文采用脉冲电流沉积的方法制备了Pd@Pt/C催化剂。电化学测试结果表明, Pd@Pt/C催化剂的氧还原活性可媲美商品的20% Pt/C催化剂, Pd@Pt/C催化剂的Pt质量活性可达JM Pt/C催化剂的3.1倍。

  14. Preparation and Electrocatalytic Activities of Pt-TiO2 Nanotubes Electrode%Pt-TiO2纳米管电极的制备及电催化性能

    Institute of Scientific and Technical Information of China (English)

    雷斌; 薛建军; 秦亮

    2007-01-01

    The Pt-TiO2 nanotubes electrode consisting of Pt nanoparticles dispersed over a nanotubular TiO2 was prepared using the method of electrochemical anodic oxidation followed by cathodic reduction. SEM results show that the nanotubular TiO2 layer consists of average individual tubes of 100 nm diameter, 470 nm length and 20 nm wall thickness. This nanotubular TiO2 support provides a high surface area and the Pt-TiO2 nanotubes electrode owns plenty of active points and well electrocatalytic property based on the exposed platinum particles with very small diameters. It obviously enhances the electrocatalytic activity for methanol oxidation compared to those of pure Pt and Pt-TiO2 electrode (immobilized on a compact TiO2 support with the same Pt loading), and the oxidation current densities on Pt-TiO2 nanotubes electrode are over 20 times than that on pure platinum electrode.%采用电化学阳极氧化-阴极还原法制备Pt-TiO2纳米管电极.扫描电镜(SEM)结果显示TiO2纳米管平均管径100nm,管长470nm,管壁厚20nm,且其比表面积大,同时纳米Pt微粒分散在TiO2纳米管上,且粒径细小,Pt微粒充分裸露,使得Pt-TiO2纳米管电极活性点多,电催化性能高.对甲醇的电催化性能测试表明:同纯Pt电极和Pt-TiO2电极(Pt微粒固定在TiO2致密膜上)相比,Pt-TiO2纳米管电极对甲醇具有更高的电催化活性,其氧化峰电流密度是在纯Pt片电极上的20倍以上.

  15. Promotion effect of manganese oxide on the electrocatalytic activity of Pt/C for methanol oxidation in acid medium

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Hameed, R.M., E-mail: randa311eg@yahoo.com [Chemistry Department, Faculty of Science, Cairo University, Giza (Egypt); Fetohi, Amani E.; Amin, R.S.; El-Khatib, K.M. [Chemical Engineering Department, National Research Center, Dokki, Giza (Egypt)

    2015-12-30

    Graphical abstract: Physical and electrochemical properties of Pt/C, Pt–MnO{sub 2}/C-1 and Pt–MnO{sub 2}/C-2 electrocatalysts. - Highlights: • Adding MnO{sub 2} to Pt/C improved the dispersion of Pt nanoparticles. • The existence of MnO{sub 2} improved the kinetics of methanol oxidation reaction. • R{sub ct} value of Pt–MnO{sub 2}/C was about 10 times as low as that at Pt/C. • The removal of CO{sub ads} poisoning species was facilitated at Pt–MnO{sub 2}/C. - Abstract: The modification of Pt/C by incorporating metal oxides for electrocatalytic oxidation of methanol has gained major attention because of the efficiency loss during the course of long-time operation. This work describes the preparation of Pt–MnO{sub 2}/C electrocatalysts through a chemical route using ethylene glycol or a mixture of ethylene glycol and sodium borohydride as a reducing agent. The crystallite structure and particle size of synthesized electrocatalysts are determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The addition of MnO{sub 2} improves the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt–MnO{sub 2}/C towards methanol oxidation in H{sub 2}SO{sub 4} solution is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The onset potential value of methanol oxidation peak is negatively shifted by 169 mV when MnO{sub 2} is introduced to Pt/C. Moreover, the charge transfer resistance value at Pt–MnO{sub 2}/C is about 10 times as low as that at Pt/C. Chronoamperometry and chronopotentiometry show that CO tolerance is greatly improved at Pt–MnO{sub 2}/C. The increased electrocatalytic activity and enhanced ability to clean platinum surface elect manganese oxide as a suitable promoter for the anode performance in direct methanol fuel cells (DMFCs).

  16. Tuning the Activity of Pt(111) for Oxygen Electroreduction by Subsurface Alloying

    DEFF Research Database (Denmark)

    Stephens, Ifan; Bondarenko, A.S.; Perez-Alonso, F.J.

    2011-01-01

    To enable the development of low temperature fuel cells, significant improvements are required to the efficiency of the Pt electrocatalysts at the cathode, where oxygen reduction takes place. Herein, we study the effect of subsurface solute metals on the reactivity of Pt, using a Cu/Pt(111) near......-surface alloy. Our investigations incorporate electrochemical measurements, ultrahigh vacuum experiments, and density functional theory. Changes to the OH binding energy, ΔEOH, were monitored in situ and adjusted continuously through the subsurface Cu coverage. The incorporation of submonolayer quantities of Cu...

  17. EFFECT OF METHANOLIC SEED EXTRACT OF PERSEA AMERICANA(AVOCADO PEAR ON PROTHROMBIN TIME AND ACTIVATED PARTIAL THROMBOPLASTIN TIME IN MICE

    Directory of Open Access Journals (Sweden)

    2016-11-01

    Full Text Available Twenty (20 adult albino mice were used in the study to determine the effect of methanolic seed extract of Persea Americana on prothrombin time (PT and activated partial thromboplastin time (APTT test. The mice were obtained and kept for 2 weeks to acclimatize. They were weighed and divided into 5 groups. Group A served as control without the extract. Groups B to E were orally administered with graded doses of 200mg, 400 mg, 800 mg and 1600mg/kg body weight per mice daily for 28 days. Blood samples were collected through the median canthus into ti-sodium citrate anticoagulant containers for the analysis of PT and APTT, using standard operative procedure. The analysis was carried out at the Haematology Laboratory of University of Nigeria Teaching Hospital (UNTH Enugu. The results showed a prolonged APTT time at all the doses of the extract when compared with the control (P and lt;0.05. The prothrombin time at the dosage of 200mg/kg did not differ when compared with the control (P and gt;0.05. The increase in PT and APTT was dose dependent. This result pattern suggests that the extract causes prolonged prothrombin time and APTT at various concentrations possibly due to its high potassium content. The extract can be recommended in anticoagulant therapy since it prolongs PT and APTT.

  18. From mixed to three-layer core/shell PtCu nanoparticles: ligand-induced surface segregation to enhance electrocatalytic activity.

    Science.gov (United States)

    Dai, Changqing; Yang, Yang; Zhao, Zheng; Fisher, Adrian; Liu, Zhiping; Cheng, Daojian

    2017-07-06

    Core-shell segregated bimetallic nanoparticles (NPs) exhibit increased enhanced catalytic performance compared to that of mixed bimetallic NPs. Here, we report a simple, yet efficient, one-pot synthetic strategy to synthesize uniform three-layer core/shell PtCu NPs by adding benzyl ether (BE) in the synthesis process of mixed PtCu NPs. In comparison with commercial Pt/C and also mixed PtCu NPs, the three-layer core/shell PtCu NPs exhibit superior activity in catalyzing the oxygen reduction reaction (ORR), formic acid oxidation reaction (FAOR), methanol oxidation reaction (MOR), and ethanol oxidation reaction (EOR), mainly due to the ligand (BE)-induced surface segregation of Pt on the surface of the NPs.

  19. Assessment of the ethanol oxidation activity and durability of Pt catalysts with or without a carbon support using Electrochemical Impedance Spectroscopy

    Science.gov (United States)

    Saleh, Farhana S.; Easton, E. Bradley

    2014-01-01

    We compared the stability and performance of 3 commercially available Johnson Matthey catalysts with various Pt loadings (20, 40 and 100%) using two different accelerated durability testing (ADT) protocols. The various Pt-loaded catalysts were tested by means of a series of intermittent life tests (1, 200, 400, 1000, 2000, 3000 and 4000 cycles). The electrochemical surface area (ECSA) loss of electrode was investigated by electrochemical technique (CV). The use of EIS as an accelerated-testing protocol distinctly elucidates the extent of degradation of Johnson Matthey catalysts with various Pt loading. Using EIS, it was possible to show that Pt-black catalyst layers suffer from increased electronic resistance over the course of ADT which is not observed when a corrosion stable carbon support is present. The effect of Pt loading was further elucidated by comparing the electrocatalytic activity of the catalyst layers towards ethanol oxidation reaction (EOR). The catalyst layer with the lowest Pt loading showed the enhanced EOR performance.

  20. Reproducible fabrication of stable small nano Pt with high activity for sensor applications

    Science.gov (United States)

    Ye, Pingping; Guo, Xiaoyu; Liu, Guiting; Chen, Huifen; Pan, Yuxia; Wen, Ying; Yang, Haifeng

    2013-07-01

    Pt nanoparticles with an average size of 2-3 nm in diameter were reproducibly synthesized by reduction of H2PtCl6 solution containing inositol hexaphosphate (IP6) as the stabilizing agent. Single crystals with Pt(111) faces of the resulting cubic nanoparticles were revealed by the electron diffraction pattern. The PtNPs-IP6 nanoparticles were used to modify an electrode as a nonenzymatic sensor for H2O2 detection, exhibiting a fast response and high sensitivity. A low detection limit of 2.0 × 10-7 M (S/N = 3) with two linear ranges between 2.4 × 10-7 and 1.3 × 10-3 M (R2 = 0.9987) and between 1.3 × 10-3 and 1.3 × 10-2 M (R2 = 0.9980) was achieved. The attractive electrochemical performance of PtNPs-IP6 enables it to be employed as a promising material for the development of Pt-based analytical systems and other applications.

  1. H2/D2 exchange reaction on mono-disperse Pt clusters: enhanced activity from minute O2 concentrations

    DEFF Research Database (Denmark)

    Riedel, Jakob Nordheim; Rötzer, Marian David; Jørgensen, Mikkel;

    2016-01-01

    The H2/D2 exchange reaction was studied on mono-disperse Pt8 clusters in a μ-reactor. The chemical activity was studied at temperatures varying from room temperature to 180 °C using mass spectrometry. It was found that minute amounts of O2 in the gas stream increased the chemical activity...... significantly. XPS and ISS before and after reaction suggest little or no sintering during reaction. A reaction pathway is suggested based on DFT. H2 desorption is identified as the rate-limiting step and O2 is confirmed as the source of the increased activity. The binding energy of platinum atoms in a SiO2...... supported Pt8 cluster is found to be comparable to the interatomic binding energies of bulk platinum, underlining the stability of the model system....

  2. Enhancing the activity and tuning the mechanism of formic acid oxidation at tetrahexahedral Pt nanocrystals by Au decoration.

    Science.gov (United States)

    Liu, Hai-Xia; Tian, Na; Brandon, Michael P; Pei, Jun; Huangfu, Zhi-Chao; Zhan, Chi; Zhou, Zhi-You; Hardacre, Christopher; Lin, Wen-Feng; Sun, Shi-Gang

    2012-12-21

    Tetrahexahedral Pt nanocrystals (THH Pt NCs), bound by high index facets, belong to an emerging class of nanomaterials that promise to bridge the gap between model and practical electrocatalysts. The atomically stepped surfaces of THH Pt NCs are extremely active for the electrooxidation of small organic molecules but they also readily accommodate the dissociative chemisorption of such species, resulting in poisoning by strongly adsorbed CO. Formic acid oxidation is an ideal reaction for studying the balance between these competing catalyst characteristics, since it can proceed by either a direct or a CO mediated pathway. Herein, we describe electrochemical and in situ FTIR spectroscopic investigations of formic acid electrooxidation at both clean and Au adatom decorated THH Pt NC surfaces. The Au decoration leads to higher catalytic currents and enhanced CO(2) production in the low potential range. As the CO oxidation behaviour of the catalyst is not improved by the presence of the Au, it is likely that the role of the Au is to promote the direct pathway. Beyond their fundamental importance, these results are significant in the development of stable, poison resistant anodic electrocatalysts for direct formic acid fuel cells.

  3. Simulation of Stochastic Partial Differential Equations and Stochastic Active Contours

    OpenAIRE

    Lang, Annika

    2007-01-01

    This thesis discusses several aspects of the simulation of stochastic partial differential equations. First, two fast algorithms for the approximation of infinite dimensional Gaussian random fields with given covariance are introduced. Later Hilbert space-valued Wiener processes are constructed out of these random fields. A short introduction to infinite-dimensional stochastic analysis and stochastic differential equations is given. Furthermore different definitions of numerical stability for...

  4. PtNi nanoparticles embedded in porous silica microspheres as highly active catalysts for p-nitrophenol hydrogenation to p-aminophenol

    Indian Academy of Sciences (India)

    HUIJUAN GUAN; CONG CHAO; YANJIE LU; HUISHAN SHANG; YAFEI ZHAO; SIGUO YUAN; BING ZHANG

    2016-09-01

    Supported Pt-based alloy nanoparticles have attracted greater attention in catalysis due to their high activity, reduced cost, and easy recycling in chemical reactions. In this work, mesoporous SiO₂ microspheres were employed as support to immobilize PtNi alloy nanocatalysts with different mass ratios of Pt and Ni (1:0, 3:1, 1:1, 1:3 and 0:1) by a facile in situ one-step reduction in the absence of any capping agent. SEM, EDS, TEM, FTIR, XRD, ICP-AES, XPS and nitrogen adsorption/desorption analysis were employed to systematically investigate the morphology and structure of the obtained SiO2 microspheres and SiO₂/PtNi nanocatalysts. Results show that uniform PtNi nanoparticles can be homogeneously and firmly embedded into the surface of SiO₂ microspheres. When the as-prepared SiO₂/PtNi nanocatalysts were used in the reduction process of pnitrophenol to p-aminophenol, the nanocatalyst with Pt and Ni mass ratio of 1:3 showed the highest catalytic activity (TOF of 5.35 × 10¹⁸ molecules·g⁻¹·s⁻¹) and could transform p-nitrophenol to p-aminophenol completely within 5 min. The SiO₂/PtNi nanocatalyst can also maintain high catalytic activity in the fourth cycle, implying its excellent stability during catalysis.

  5. Revealing the active intermediates in the oxidation of formic acid on Au and Pt(111).

    Science.gov (United States)

    Gao, Wang; Song, Er Hong; Jiang, Qing; Jacob, Timo

    2014-08-25

    The mechanisms of formic acid (HCOOH) oxidation on Au(111) under gas-phase and electrochemical conditions was studied by using density functional theory and then compared with the analogous processes on Pt(111). Our results demonstrate that a mechanism involving a single intermediate molecule is preferred on both Au and Pt(111). Furthermore, under gas-phase conditions, HCOOH oxidation proceeds through the same mechanism (formate pathway) on Au and Pt(111), whereas under electrochemical conditions, it can take place through significantly different mechanisms (formate and/or direct pathways), depending on the applied electrode potential. Our calculations help to rationalize conflicting experimental explanations and are crucial for understanding the mechanism of this fundamental (electro-)catalytic process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Light illuminated α-Fe2O3/Pt nanoparticles as water activation agent for photoelectrochemical water splitting.

    Science.gov (United States)

    Li, Xiaodong; Wang, Zhi; Zhang, Zemin; Chen, Lulu; Cheng, Jianli; Ni, Wei; Wang, Bin; Xie, Erqing

    2015-03-16

    The photoelectrochemical (PEC) water splitting is hampered by strong bonds of H2O molecules and low ionic conductivity of pure water. The photocatalysts dispersed in pure water can serve as a water activation agent, which provides an alternative pathway to overcome such limitations. Here we report that the light illuminated α-Fe2O3/Pt nanoparticles may produce a reservoir of reactive intermediates including H2O2, ·OH, OH(-) and H(+) capable of promoting the pure water reduction/oxidation half-reactions at cathode and highly photocatalytic-active TiO2/In2S3/AgInS2 photoanode, respectively. Remarkable photocurrent enhancement has been obtained with α-Fe2O3/Pt as water activation agent. The use of α-Fe2O3/Pt to promote the reactivity of pure water represents a new paradigm for reproducible hydrogen fuel provision by PEC water splitting, allowing efficient splitting of pure water without adding of corrosive chemicals or sacrificial agent.

  7. Synthesis and Catalytic Activity of Pt Monolayer on Pd Tetrahedral Nanocrystals with CO-adsorption-induced Removal of Surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Gong K.; Vukmirovic M.B.; Ma C.; Zhu Y.; Adzic R.R.

    2011-11-01

    We synthesized the Pt monolayer shell-Pd tetrahedral core electrocatalysts that are notable for their high activity and stable performance. A small number of low-coordination sites and defects, and high content of the (1 1 1)-oriented facets on Pd tetrahedron makes them a suitable support for a Pt monolayer to obtain an active O{sub 2} reduction reaction (ORR) electrocatalyst. The surfactants, used to control size and shape of Pd tetrahedral nanoparticles, are difficult to remove and cause adverse effects on the ORR. We describe a simple and noninvasive method to synthesize high-purity tetrahedral Pd nanocrystals (TH Pd) by combining a hydrothermal route and CO adsorption-induced removal of surfactants. Poly(vinylpyrrolidone) (PVP), used as a protecting and reducing agent in hydrothermal reactions, is strongly bonded to the surface of the resulting nanocrystals. We demonstrate that PVP was displaced efficiently by adsorbed CO. A clean surface was achieved upon CO stripping at a high potential (1.0 V vs RHE). It played a decisive role in improving the activity of the Pt monolayer/TH Pd electrocatalyst for the ORR. Furthermore, the results demonstrate a versatile method for removal of surfactants from various nanoparticles that severely limited their applications.

  8. Formation of a Pt-Decorated Au Nanoparticle Monolayer Floating on an Ionic Liquid by the Ionic Liquid/Metal Sputtering Method and Tunable Electrocatalytic Activities of the Resulting Monolayer.

    Science.gov (United States)

    Sugioka, Daisuke; Kameyama, Tatsuya; Kuwabata, Susumu; Yamamoto, Takahisa; Torimoto, Tsukasa

    2016-05-01

    A novel strategy to prepare a bimetallic Au-Pt particle film was developed through sequential sputter deposition of Au and Pt on a room temperature ionic liquid (RTIL). Au sputter deposition onto an RTIL containing hydroxyl-functionalized cations produced a monolayer of Au particles 4.2 nm in size on the liquid surface. Subsequent Pt sputtering onto the original Au particle monolayer floating on the RTIL enabled decoration of individual Au particles with Pt metals, resulting in the formation of a bimetallic Au-Pt particle monolayer with a Pt-enriched particle surface. The particle size slightly increased to 4.8 nm with Pt deposition for 120 min. The shell layer of a bimetallic particle was composed of Au-Pt alloy, the composition of which was tunable by controlling the Pt sputter deposition time. The electrochemical surface area (ECSA) was determined by cyclic voltammetry of bimetallic Au-Pt particle monolayers transferred onto HOPG electrodes by a horizontal liftoff method. The Pt surface coverage, determined by ECSAs of Au and Pt, increased from 0 to 56 mol % with elapse of the Pt sputter deposition time up to 120 min. Thus-obtained Au-Pt particle films exhibited electrocatalytic activity for methanol oxidation reaction (MOR) superior to the activities of pure Au or Pt particles. Volcano-type dependence was observed between the MOR activity and Pt surface coverage on the particles. Maximum activity was obtained for Au-Pt particles with a Pt coverage of 49 mol %, being ca. 120 times higher than that of pure Pt particles. This method enables direct decoration of metal particles with different noble metal atoms, providing a novel strategy to develop highly efficient multinary particle catalysts.

  9. The size effect of titania-supported Pt nanoparticles on the electrocatalytic activity towards methanol oxidation reaction primarily via the bifunctional mechanism

    Science.gov (United States)

    Ting, Chao-Cheng; Liu, Chung-Hsuan; Tai, Chun-Yen; Hsu, Shih-Chieh; Chao, Chih-Shuan; Pan, Fu-Ming

    2015-04-01

    We prepared Pt nanoparticles of different particle sizes by plasma enhanced atomic layer deposition (PEALD) on the native oxide surface layer of Ti thin films, and investigated the Pt particle size effect on the electrocatalytic activity towards methanol oxidation reaction (MOR) in acidic media. The average Pt nanoparticles size ranges from 3 nm to 7 nm depending on the number of the PEALD reaction cycles. The electronic interaction between Pt nanoparticles and the TiO2 support is insignificant according to x-ray photoelectron spectroscopy analyses, suggesting that the influence of the Pt particle size on the electrocatalytic activity can be mainly described by the bifunctional mechanism. From cyclic voltammetry measurements, Pt particles of smaller size have a better CO tolerance in MOR. We proposed the reaction steps for the electrooxidation of CO adspecies on Pt nanoparticles on the basis of the bifunctional mechanism. The electrode with Pt nanoparticles of ∼5 nm in size shows the best electrocatalytic performance in terms of CO tolerance and electrochemical stability.

  10. Effect of heat treatment on the activity and stability of carbon supported PtMo alloy electrocatalysts for hydrogen oxidation in proton exchange membrane fuel cells

    Science.gov (United States)

    Hassan, Ayaz; Carreras, Alejo; Trincavelli, Jorge; Ticianelli, Edson Antonio

    2014-02-01

    The effect of heat treatment on the activity, stability and CO tolerance of PtMo/C catalysts was studied, due to their applicability in the anode of proton exchange membrane fuel cells (PEMFCs). To this purpose, a carbon supported PtMo (60:40) alloy electrocatalyst was synthesized by the formic acid reduction method, and samples of this catalyst were heat-treated at various temperatures ranging between 400 and 700 °C. The samples were characterized by temperature programmed reduction (TPR), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), cyclic voltammetry (CV), scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDS). Cyclic voltammetry was used to study the stability, and polarization curves were used to investigate the performance of all materials as CO tolerant anode on a PEM single cell text fixture. The catalyst treated at 600 °C, for which the average crystallite size was 16.7 nm, showed the highest hydrogen oxidation activity in the presence of CO, giving an overpotential induced by CO contamination of 100 mV at 1 Acm-2. This catalyst also showed a better stability up to 5000 potential cycles of cyclic voltammetry, as compared to the untreated catalyst. CV, SEM and WDS results indicated that a partial dissolution of Mo and its migration/diffusion from the anode to the cathode occurs during the single cell cycling. Polarization results showed that the catalytic activity and the stability can be improved by a heat treatment, in spite of a growth of the catalyst particles.

  11. CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions

    KAUST Repository

    Michalak, William D.

    2014-04-01

    The barrier to CO oxidation on Pt catalysts is the strongly bound adsorbed CO, which inhibits O2 adsorption and hinders CO2 formation. Using reaction studies and in situ X-ray spectroscopy with colloidally prepared, monodisperse ∼2 nm Pt and PtSn nanoparticle catalysts, we show that the addition of Sn to Pt provides distinctly different reaction sites and a more efficient reaction mechanism for CO oxidation compared to pure Pt catalysts. To probe the influence of Sn, we intentionally poisoned the Pt component of the nanoparticle catalysts using a CO-rich atmosphere. With a reaction environment comprised of 100 Torr CO and 40 Torr O2 and a temperature range between 200 and 300 C, Pt and PtSn catalysts exhibited activation barriers for CO2 formation of 133 kJ/mol and 35 kJ/mol, respectively. While pure Sn is readily oxidized and is not active for CO oxidation, the addition of Sn to Pt provides an active site for O2 adsorption that is important when Pt is covered with CO. Sn oxide was identified as the active Sn species under reaction conditions by in situ ambient pressure X-ray photoelectron spectroscopy measurements. While chemical signatures of Pt and Sn indicated intermixed metallic components under reducing conditions, Pt and Sn were found to reversibly separate into isolated domains of Pt and oxidic Sn on the nanoparticle surface under reaction conditions of 100 mTorr CO and 40 mTorr O2 between temperatures of 200-275 C. Under these conditions, PtSn catalysts exhibited apparent reaction orders in O2 for CO 2 production that were 0.5 and lower with increasing partial pressures. These reaction orders contrast the first-order dependence in O 2 known for pure Pt. The differences in activation barriers, non-first-order dependence in O2, and the presence of a partially oxidized Sn indicate that the enhanced activity is due to a reaction mechanism that occurs at a Pt/Sn oxide interface present at the nanoparticle surface. © 2014 Published by Elsevier Inc.

  12. Ternary Pt9RhFex Nanoscale Alloys as Highly Efficient Catalysts with Enhanced Activity and Excellent CO-Poisoning Tolerance for Ethanol Oxidation.

    Science.gov (United States)

    Wang, Peng; Yin, Shibin; Wen, Ying; Tian, Zhiqun; Wang, Ningzhang; Key, Julian; Wang, Shuangbao; Shen, Pei Kang

    2017-03-22

    To address the problems of high cost and poor stability of anode catalysts in direct ethanol fuel cells (DEFCs), ternary nanoparticles Pt9RhFex (x = 1, 3, 5, 7, and 9) supported on carbon powders (XC-72R) have been synthesized via a facile method involving reduction by sodium borohydride followed by thermal annealing in N2 at ambient pressure. The catalysts are physically characterized by X-ray diffraction, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy, and their catalytic performance for the ethanol oxidation reaction (EOR) is evaluated by cyclic and linear scan voltammetry, CO-stripping voltammograms, and chronopotentiometry. All the Pt9RhFex/C catalysts of different atomic ratios produce high EOR catalytic activity. The catalyst of atomic ratio composition 9:1:3 (Pt/Rh/Fe) has the highest activity and excellent CO-poisoning tolerance. Moreover, the enhanced EOR catalytic activity on Pt9RhFe3/C when compared to Pt9Rh/C, Pt3Fe/C, and Pt/C clearly demonstrates the presence of Fe improves catalytic performance. Notably, the onset potential for CO oxidation on Pt9RhFe3/C (0.271 V) is ∼55, 75, and 191 mV more negative than on Pt9Rh/C (0.326 V), Pt3Fe/C (0.346 V), and Pt/C (0.462 V), respectively, which implies the presence of Fe atoms dramatically improves CO-poisoning tolerance. Meanwhile, compared to the commercial PtRu/C catalyst, the peak potential on Pt9RhFe3/C for CO oxidation was just slightly changed after several thousand cycles, which shows high stability against the potential cycling. The possible mechanism by which Fe and Rh atoms facilitate the observed enhanced performance is also considered herein, and we conclude Pt9RhFe3/C offers a promising anode catalyst for direct ethanol fuel cells.

  13. Effect of Sb Segregation on Conductance and Catalytic Activity at Pt/Sb-Doped SnO2 Interface: A Synergetic Computational and Experimental Study

    DEFF Research Database (Denmark)

    Hu, Qiang; Colmenares Rausseo, Luis César; Martinez, Umberto;

    2015-01-01

    Antimony doped tin dioxide (ATO) is considered a promising support material for Pt-based fuel cell cathodes, displaying enhanced stability over carbon-based supports. In this work, the effect of Sb segregation on the conductance and catalytic activity at Pt/ATO interface was investigated through...... a combined computational and experimental study. It was found that Sb-dopant atoms prefer to segregate toward the ATO/Pt interface. The deposited Pt catalysts, interestingly, not only promote Sb segregation, but also suppress the occurrence of Sb3+ species, a charge carrier neutralizer at the interface...... to support future applications of ATO/Pt-based materials as possible cathodes for PEMFC applications with enhanced durability under practical applications....

  14. In vitro Antifungal, Antioxidant and Cytotoxic Activities of a Partially ...

    African Journals Online (AJOL)

    greater in vitro antioxidant activity than the aqueous extract. SDS-PAGE .... was added to 4 ml of 0.004 % methanol solution of DPPH. After a ... Superoxide anion scavenging activity ... SDS-PAGE was performed to identify the proteins in ...

  15. Direct imaging of thermally-activated grain-boundary diffusion in Cu/Co/IrMn/Pt exchange-bias structures using atom-probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Letellier, F.; Lardé, R.; Le Breton, J.-M., E-mail: jean-marie.lebreton@univ-rouen.fr [Groupe de Physique des Matériaux, UMR 6634 CNRS/Université et INSA de Rouen, F-76801 Saint Etienne du Rouvray (France); Lechevallier, L. [Groupe de Physique des Matériaux, UMR 6634 CNRS/Université et INSA de Rouen, F-76801 Saint Etienne du Rouvray (France); Département de GEII, Université de Cergy-Pontoise, F-95031 Cergy-Pontoise (France); Akmaldinov, K. [SPINTEC, Univ. Grenoble-Alpes/CNRS/INAC-CEA, F-38000 Grenoble (France); CROCUS Technology, F-38025 Grenoble (France); Auffret, S.; Dieny, B.; Baltz, V., E-mail: vincent.baltz@cea.fr [SPINTEC, Univ. Grenoble-Alpes/CNRS/INAC-CEA, F-38000 Grenoble (France)

    2014-11-28

    Magnetic devices are often subject to thermal processing steps, such as field cooling to set exchange bias and annealing to crystallize amorphous magnetic electrodes. These processing steps may result in interdiffusion and the subsequent deterioration of magnetic properties. In this study, we investigated thermally-activated diffusion in Cu/Co/IrMn/Pt exchange biased polycrystalline thin-film structures using atom probe tomography. Images taken after annealing at 400 °C for 60 min revealed Mn diffusion into Co grains at the Co/IrMn interface and along Pt grain boundaries for the IrMn/Pt stack, i.e., a Harrison type C regime. Annealing at 500 °C showed further Mn diffusion into Co grains. At the IrMn/Pt interface, annealing at 500 °C led to a type B behavior since Mn diffusion was detected both along Pt grain boundaries and also into Pt grains. The deterioration of the films' exchange bias properties upon annealing was correlated to the observed diffusion. In particular, the topmost Pt capping layer thickness turned out to be crucial since a faster deterioration of the exchange bias properties for thicker caps was observed. This is consistent with the idea that Pt acts as a getter for Mn, drawing Mn out of the IrMn layer.

  16. Understanding the Effects of Surface Chemistry and Microstructure on the Activity and Stability of Pt Electrocatalysts on Non-Carbon Supports

    Energy Technology Data Exchange (ETDEWEB)

    Mustain, William [Univ. of Conneticut, Storrs, CT (United States)

    2015-02-12

    The objective of this project is to elucidate the effects of the chemical composition and microstructure of the electrocatalyst support on the activity, stability and utilization of supported Pt clusters.

  17. Nonradical oxidation from electrochemical activation of peroxydisulfate at Ti/Pt anode: Efficiency, mechanism and influencing factors.

    Science.gov (United States)

    Song, Haoran; Yan, Linxia; Ma, Jun; Jiang, Jin; Cai, Guangqiang; Zhang, Wenjuan; Zhang, Zhongxiang; Zhang, Jiaming; Yang, Tao

    2017-06-01

    Electrochemical activation of peroxydisulfate (PDS) at Ti/Pt anode was systematically investigated for the first time in this work. The synergistic effect produced from the combination of electrolysis and the addition of PDS demonstrates that PDS can be activated at Ti/Pt anode. The selective oxidation towards carbamazepine (CBZ), sulfamethoxazole (SMX), propranolol (PPL), benzoic acid (BA) rather than atrazine (ATZ) and nitrobenzene (NB) was observed in electrochemical activation of PDS process. Moreover, addition of excess methanol or tert-butanol had negligible impact on CBZ (model compound) degradation, demonstrating that neither sulfate radical (SO4(-)) nor hydroxyl radical (HO) was produced in electrochemical activation of PDS process. Direct oxidation (PDS oxidation alone and electrolysis) and nonradical oxidation were responsible for the degradation of contaminants. The results of linear sweep voltammetry (LSV) and chronoamperometry suggest that electric discharge may integrate PDS molecule with anode surface into a unique transition state structure, which is responsible for the nonradical oxidation in electrochemical activation of PDS process. Adjustment of the solution pH from 1.0 to 7.0 had negligible effect on CBZ degradation. Increase of either PDS concentration or current density facilitated the degradation of CBZ. The presence of chloride ion (Cl(-)) significantly enhanced CBZ degradation, while addition of bicarbonate (HCO3(-)), phosphate (PO4(3-)) and humic acid (HA) all inhibited CBZ degradation with the order of HA > HCO3(-) > PO4(3-). The degradation products of CBZ and chlorinated products were also identified. Electrochemical activation of PDS at Ti/Pt anode may serve as a novel technology for selective oxidation of organic contaminants in water and soil. Copyright © 2017. Published by Elsevier Ltd.

  18. Antibacterial activity of rhizome of curcuma aromatica and partial purification of active compounds

    Directory of Open Access Journals (Sweden)

    S Revathi

    2013-01-01

    Full Text Available The hexane extract of Curcuma aromatica, a plant belonging to the family Zingiberaceae was tested on 10 bacterial strains (clinical isolates and standard strains. Agar diffusion method was adopted for determining the antibacterial activity of the extract. The hexane extract was found to be active against all Gram-positive strains tested, but inactive against Gram-negative strains. The minimum inhibitory concentration and minimum bactericidal concentration were determined and found to be 539 ΅g/ml. The phytochemical analysis of hexane extract by gas chromatography mass spectrometry revealed the presence of 13 compounds. The crude hexane extract was partially purified by thin layer chromatography. The zone showing good antibacterial activity was analysed further by gas chromatography mass spectrometry, UV/Vis spectrophotometry and Fourier transform infrared spectroscopy, which indicated the probable presence of germacrone.

  19. One-step flame synthesis of an active Pt/TiO2 catalyst for SO2 oxidation

    DEFF Research Database (Denmark)

    Johannessen, Tue; Koutsopoulos, Sotiris

    2002-01-01

    size of the platinum particles supported on aggregated nano-particles of TiO2 is approximately 2 nm. The high SO2-oxidation activity of the catalyst proves that platinum is not hidden in the titania matrix. The flame-produced catalyst showed catalytic activity similar to samples prepared by wet......Flame synthesis as a route for production of composite metal oxides has been employed for the one-step synthesis of a supported noble metal catalyst, i.e. a Pt/TiO2 catalyst, by simultaneous combustion of Ti-isopropoxide and platinum acetylacetonate in a quench-cooled flame reactor. The average...

  20. One-step flame synthesis of an active Pt/TiO2 catalyst for SO2 oxidation

    DEFF Research Database (Denmark)

    Johannessen, Tue; Koutsopoulos, Sotiris

    2002-01-01

    Flame synthesis as a route for production of composite metal oxides has been employed for the one-step synthesis of a supported noble metal catalyst, i.e. a Pt/TiO2 catalyst, by simultaneous combustion of Ti-isopropoxide and platinum acetylacetonate in a quench-cooled flame reactor. The average...... size of the platinum particles supported on aggregated nano-particles of TiO2 is approximately 2 nm. The high SO2-oxidation activity of the catalyst proves that platinum is not hidden in the titania matrix. The flame-produced catalyst showed catalytic activity similar to samples prepared by wet...

  1. Partial characterization of Acanthamoeba castellanii (T4 genotype) DNase activity.

    Science.gov (United States)

    Iqbal, Junaid; Panjwani, Shamvil; Siddiqui, Ruqaiyyah; Khan, Naveed Ahmed

    2015-02-01

    The deoxyribonuclease (DNase) activities of Acanthamoeba castellanii belonging to the T4 genotype were investigated. Using zymographic assays, the DNase activities had approximate molecular masses of 25 and 35 kDa. A. castellanii DNases exhibited activity at wide-ranging temperature of up to 60 °C and at pH ranging from 4 to 9. The DNases activities were unaffected by proteinase-K treatment, divalent cations such as Ca(++), Cu(++), Mg(++), and Zn(++), or divalent cation chelating agent ethylenediaminetetraacetic acid (EDTA) or sodium dodecyl sulfate (SDS). The non-reliance on divalent cations and homology data suggests that A. castellanii DNases belong to the class of eukaryotic lysosomal DNase II but exhibit robust properties. The DNases activity in A. castellanii interfered with the genomic DNA extraction. Extraction methods involving EDTA, SDS, and proteinase-K resulted in low yield of genomic DNA. On the other hand, these methods resulted in high yield of genomic DNA from human cells suggesting the robust nature of A. castellanii DNases that are unaffected by reagents normally used in blocking eukaryotic DNases. In contrast, the use of chaotropic agent such as guanidine thiocyanate improved the yield of genomic DNA from A. castellanii cells significantly. Further purification and characterization of Acanthamoeba DNases is needed to study their non-classic distinct properties and to determine their role in the biology, cellular differentiation, cell cycle progression, and arrest of Acanthamoeba.

  2. Sympathoadrenal activity during exercise in partial diabetic and diabetic rats

    NARCIS (Netherlands)

    Houwing, H; Strubbe, J.H.; Bruggink, J.E; Steffens, A.B

    1997-01-01

    Insulin-dependent diabetes mellitus is associated with altered fat and carbohydrate metabolism and disturbed sympathoadrenal functioning. The aim of this study was to investigate whether the short-term diabetic state alters the activity of the sympathoadrenal system and of the adrenal cortex during

  3. Determination of amylase activity of crude extract from partially ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-07-20

    Jul 20, 2009 ... optimum pH and temperature of the crude enzyme were about 6.0 and 60°C respectively. ... Key words: Mango seeds, crude extract, amylase activity. .... from a standard curve of starch (substrate) concentration against.

  4. 不同pH值下Pt-Sn/石墨烯复合材料的电催化性能%Preparation of Pt-Sn/graphene catalysts and their activities for ethanol electrooxidation in polyol synthesis

    Institute of Scientific and Technical Information of China (English)

    王永祯; 王勇

    2014-01-01

    Pt-Sn/graphene catalysts were prepared by heat treatment of a dispersion of graphene oxide, SnCl2 and H2 PtCl6 in eth-ylene glycol at 130℃ for 3 h after its pH value had been adjusted to 12 by NaOH, followed by centrifuging, washing with ethanol and water, and cryodrying. The pH value of the heat-treated dispersion was controlled by adding dilute nitric acid to 2, 4 and 6 to mediate the properties of the catalysts and its effects on the compositions, microstructure and catalytic activities of the resulting cata-lysts in ethanol electrooxidation. These were investigated by XRD, ICP, TEM and cyclic voltammetry. Results indicated that with decreasing pH values the Sn content increased, the Pt/Sn atom ratio decreased and the electrochemical activity increased. The cur-rent density for ethanol electrooxidation was increased by 120% at the pH value of 2 compared for the sample without nitric acid. The improvement of the catalytic activity can be ascribed to an increased loading of Sn and Pt since the oxidative product of ethylene glycol in the heat treatment acted as a chelating agent for metal nanoparticles under high pH values. A very simple acid-treatment-as-sisted polyol route to prepare graphene supported Pt-Sn nanoparticles were developed. To evaluate the composition, microstructure and electrochemical activity of catalysts treated with different pH values of acid solution have been characterized by XRD、ICP、TEM and cyclic voltammetry. And the changes of Pt and Sn metal particles loading on the surface of graphene were discussed. The results show that graphene is a good support. With the increase of pH values, the Sn content of catalysts increased and the electrochemical activity was improved. As the pH values of acid solution was decreased to 2, the synergistic effect of Pt and Sn reached its maxi-mum, and the current densities of ethanol electrooxidation with the catalysts were about 120% higher than that of original Pt-Sn/G catalysts, which also reached the

  5. Synthesis of Pt-Ni Octahedra in Continuous-Flow Droplet Reactors for the Scalable Production of Highly Active Catalysts toward Oxygen Reduction.

    Science.gov (United States)

    Niu, Guangda; Zhou, Ming; Yang, Xuan; Park, Jinho; Lu, Ning; Wang, Jinguo; Kim, Moon J; Wang, Liduo; Xia, Younan

    2016-06-01

    A number of groups have reported the syntheses of nanosized Pt-Ni octahedra with remarkable activities toward the oxygen reduction reaction (ORR), a process key to the operation of proton-exchange membrane fuel cells. However, the throughputs of those batch-based syntheses are typically limited to a scale of 5-25 mg Pt per batch, which is far below the amount needed for commercial evaluation. Here we report the use of droplet reactors for the continuous and scalable production of Pt-Ni octahedra with high activities toward ORR. In a typical synthesis, Pt(acac)2, Ni(acac)2, and W(CO)6 were dissolved in a mixture of oleylamine, oleic acid, and benzyl ether, and then pumped into a polytetrafluoroethylene tube. When the solution entered the reaction zone at a temperature held in the range of 170-230 °C, W(CO)6 quickly decomposed to generate CO gas, naturally separating the reaction solution into discrete, uniform droplets. Each droplet then served as a reactor for the nucleation and growth of Pt-Ni octahedra whose size and composition could be controlled by changing the composition of the solvent and/or adjusting the amount of Ni(acac)2 added into the reaction solution. For a catalyst based on Pt2.4Ni octahedra of 9 nm in edge length, it showed an ORR mass activity of 2.67 A mgPt(-1) at 0.9 V, representing an 11-fold improvement over a state-of-the-art commercial Pt/C catalyst (0.24 A mgPt(-1)).

  6. Synthesis, characterization and evaluation of green catalytic activity of nano Ag-Pt doped silicate

    Energy Technology Data Exchange (ETDEWEB)

    Murugavelu, M. [Department of Chemistry, Annamalai University, Annamalainagar 608 002 (India); Karthikeyan, B., E-mail: bkarthi_au@yahoo.com [Department of Chemistry, Annamalai University, Annamalainagar 608 002 (India)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Nanosized Ag-Pt loaded SiO{sub 2} was prepared by sol-gel method. Black-Right-Pointing-Pointer This catalyst has been characterized by different techniques. Black-Right-Pointing-Pointer Catalyst induces the reaction of condensation of indole and aldehyde in lesser time. Black-Right-Pointing-Pointer The coupled product is confirmed by spectral and DFT theoretical methods. - Abstract: In order to get materials with enhanced adsorption and organic transformation performance, nanosized Ag-Pt nanoparticles loaded SiO{sub 2} was prepared by sol-gel method. This catalyst has been characterized by Fourier transform infrared (FT-IR) spectra, diffuse reflectance spectra (DRS), fluorescence, high-resolution scanning electron microscopy (HR-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Ag-Pt/SiO{sub 2} catalyst induces the reaction of condensation of indole and aldehyde to give bis(indolyl)methanes in striking lesser time under microwave (MW) irradiation and it has been examined with different substituted benzaldehydes. The coupled product is confirmed by FT-IR, {sup 1}H, {sup 13}C NMR and DFT theoretical methods.

  7. 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.

  8. Preparation and characterization of nano-sized Pt-Ru/C catalysts and their superior catalytic activities for methanol and ethanol oxidation.

    Science.gov (United States)

    Şen, Selda; Şen, Fatih; Gökağaç, Gülsün

    2011-04-21

    Carbon-supported PtRu nanoparticles (Ru/Pt: 0.25) were prepared by three different methods; simultaneous reduction of PtCl(4) and RuCl(3) (catalyst I) and changing the reduction order of PtCl(4) and RuCl(3) (catalysts II and III) to enhance the performance of the anodic catalysts for methanol and ethanol oxidation. Structure, microstructure and surface characterizations of all the catalysts were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results of the XRD analysis showed that all catalysts had a face-centered cubic (fcc) structure with different and smaller lattice parameters than that of pure platinum, showing that the Ru incorporates into the Pt fcc structure by different ratios in all the catalysts. The typical particle sizes of all catalysts were in the range of 2-3 nm. The most active and stable catalyst for methanol and ethanol oxidation is catalyst III, in which a large amount (more than 90%) of PtRu alloy formation was observed. It has been found that this catalyst is about 8.0 and 33.4 times more active at ∼0.60 V towards the methanol and ethanol oxidation reactions, respectively, compared to the commercial Pt catalyst.

  9. Density functional theory study on the adsorption and decomposition of the formic acid catalyzed by highly active mushroom-like Au@Pd@Pt tri-metallic nanoparticles.

    Science.gov (United States)

    Duan, Sai; Ji, Yong-Fei; Fang, Ping-Ping; Chen, Yan-Xia; Xu, Xin; Luo, Yi; Tian, Zhong-Qun

    2013-04-07

    Local structures and adsorption energies of a formic acid molecule and its decomposed intermediates (H, O, OH, CO, HCOO, and COOH) on highly electrocatalytically active mushroom-like Au-core@Pd-shell@Pt-cluster nanoparticles with two atomic layers of the Pd shell and stoichiometric Pt coverage of around half-monolayer (Au@2 ML Pd@0.5 ML Pt) have been investigated by first principles calculations. The adsorption sites at the center (far away from the Pt cluster) and the edge (close to the Pt cluster) are considered and compared. Significant repulsive interaction between the edge sites and CO is observed. The calculated potential energy surfaces demonstrate that, with respect to the center sites, the CO2 pathway is considerably promoted in the edge area. Our results reveal that the unique edge structure of the Pt cluster is responsible for the experimentally observed high electrocatalytic activity of the Au@Pd@Pt nanoparticles toward formic acid oxidation. Such microscopic understanding should be useful for the design of new electrochemical catalysts.

  10. 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.

  11. Enhancement of Photocatalytic Activity of ZnO/SiO2 by Nanosized Pt for Photocatalytic Degradation of Phenol in Wastewater

    Directory of Open Access Journals (Sweden)

    R. M. Mohamed

    2012-01-01

    Full Text Available ZnO-SiO2 nanoparticles were synthesized by a sol-gel technique from Zn(NO32⋅6H2O and tetraethyl orthosilicate (TEOS. The synthesized samples were further modified by nanosized Pt from H2PtCl6 solution through photoassisted deposition (PAD and impregnation (Img routes. The obtained samples were characterized by a series of techniques including X-ray diffraction (XRD, UV-Vis diffuse reflectance spectroscopy, N2 adsorption, extended X-ray absorption fine structure (EXAFS, and transmission electron microscopy (TEM. The photocatalytic activity of the Pt-ZnO/SiO2 was evaluated by photocatalytic degradation of phenol in synthetic wastewater under UV-irradiation. Results obtained revealed that the surface area and the photocatalytic activity of the prepared samples were increased in the order ZnO/SiO2 < PAD: Pt-ZnO/SiO2 < img: Pt-ZnO/SiO2. The surface area decreased from 480 to 460 and 450 m2/g, while the efficiency of the phenol degradation increased from 80 to 85 and 100%, with the ZnO/SiO2, Img: Pt-ZnO-SiO2, and PAD: Pt-ZnO-SiO2 samples, respectively.

  12. Ni-, Pd-, or Pt-catalyzed ethylene dimerization: a mechanistic description of the catalytic cycle and the active species.

    Science.gov (United States)

    Roy, Dipankar; Sunoj, Raghavan B

    2010-03-07

    Two key mechanistic possibilities for group 10 transition metal [M(eta(3)-allyl)(PMe(3))](+) catalyzed (where M = Ni(II), Pd(II) and Pt(II)) ethylene dimerization are investigated using density functional theory methods. The nature of the potential active catalysts in these pathways is analyzed to gain improved insights into the mechanism of ethylene dimerization to butene. The catalytic cycle is identified as involving typical elementary steps in transition metal-catalyzed C-C bond formation reactions, such as oxidative insertion as well as beta-H elimination. The computed kinetic and thermodynamic features indicate that a commonly proposed metal hydride species (L(n)M-H) is less likely to act as the active species as compared to a metal-ethyl species (L(n)M-CH(2)CH(3)). Of the two key pathways considered, the active species is predicted to be a metal hydride in pathway-1, whereas a metal alkyl complex serves as the active catalyst in pathway-2. A metal-mediated hydride shift from a growing metal alkyl chain to the ethylene molecule, bound to the metal in an eta(2) fashion, is predicted to be the preferred route for the generation of the active species. Among the intermediates involved in the catalytic cycle, metal alkyls with a bound olefin are identified as thermodynamically stable for all three metal ions. In general, the Ni-catalyzed pathways are found to be energetically more favorable than those associated with Pd and Pt catalysts.

  13. Electrochemical Dealloying of PdCu3 Nanoparticles to Achieve Pt-like Activity for the Hydrogen Evolution Reaction.

    Science.gov (United States)

    Jana, Rajkumar; Bhim, Anupam; Bothra, Pallavi; Pati, Swapan K; Peter, Sebastian C

    2016-10-20

    Manipulating the d-band center of the metal surface and hence optimizing the free energy of hydrogen adsorption (ΔGH ) close to the optimal adsorption energy (ΔGH =0) for hydrogen evolution reaction (HER), is an efficient strategy to enhance the activity for HER. Herein, we report a oleylamine-mediated (acting as the solvent, stabilizer, and reducing agent) strategy to synthesize intermetallic PdCu3 nanoparticles (NPs) without using any external reducing agent. Upon electrochemical cycling, PdCu3 transforms into Pd-rich PdCu (ΔGH =0.05 eV), exhibiting remarkably enhanced activity (with a current density of 25 mA cm(-2) at ∼69 mV overpotential) as an alternative to Pt for HER. The first-principle calculation suggests that formation of low coordination number Pd active sites alters the d-band center and hence optimal adsorption of hydrogen, leading to enhanced activity. This finding may provide guidelines towards the design and development of Pt-free highly active and robust electrocatalysts. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Light-controlled propulsion, aggregation and separation of water-fuelled TiO2/Pt Janus submicromotors and their ``on-the-fly'' photocatalytic activities

    Science.gov (United States)

    Mou, Fangzhi; Kong, Lei; Chen, Chuanrui; Chen, Zhihong; Xu, Leilei; Guan, Jianguo

    2016-02-01

    In this work, water-fuelled TiO2/Pt Janus submicromotors with light-controlled motions have been developed by utilizing the asymmetrical photocatalytic water redox reaction over TiO2/Pt Janus submicrospheres under UV irradiation. The motion state, speed, aggregation and separation behaviors of the TiO2/Pt Janus submicromotor can be reversibly, wirelessly and remotely controlled at will by regulating the ``on/off'' switch, intensity and pulsed/continuous irradiation mode of UV light. The motion of the water-fuelled TiO2/Pt Janus submicromotor is governed by light-induced self-electrophoresis under the local electrical field generated by the asymmetrical water oxidation and reduction reactions on its surface. The TiO2/Pt Janus submicromotors can interact with each other through the light-switchable electrostatic forces, and hence continuous and pulsed UV irradiation can make the TiO2/Pt Janus submicromotors aggregate and separate at will, respectively. Because of the enhanced mass exchange between the environment and active submicromotors, the separated TiO2/Pt Janus submicromotors powered by the pulsed UV irradiation show a much higher activity for the photocatalytic degradation of the organic dye than the aggregated TiO2/Pt submicromotors. The water-fuelled TiO2/Pt Janus submicromotors developed here have some outstanding advantages as ``swimming'' photocatalysts for organic pollutant remediation in the macro or microenvironment (microchannels and microwells in microchips) because of their small size, long-term stability, wirelessly controllable motion behaviors and long life span.In this work, water-fuelled TiO2/Pt Janus submicromotors with light-controlled motions have been developed by utilizing the asymmetrical photocatalytic water redox reaction over TiO2/Pt Janus submicrospheres under UV irradiation. The motion state, speed, aggregation and separation behaviors of the TiO2/Pt Janus submicromotor can be reversibly, wirelessly and remotely controlled at will by

  15. Synthesis Gas Production from Natural Gas on Supported Pt Catalysts

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900 ℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450 ℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800 ℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800 ℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.

  16. Benzaldehyde hydrogenation over titania-covered Pt powder

    Energy Technology Data Exchange (ETDEWEB)

    Vannice, M.A.; Poondi, D. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Chemical Engineering

    1998-08-15

    Titania when used as a support has been found to have a significant effect on the activity and selectivity of Pt during the hydrogenation of aldehydes and ketones. Turnover frequencies based on hydrogen adsorption sites are markedly enhanced, and rates per gram Pt (at similar dispersions) are also often increased. There are several explanations to account for this performance, at least partially. In an effort to determine the validity of these explanations, and hopefully to eliminate them as possibilities, a Pt powder was studied before and after the addition of varying amounts of TiO{sub 2} on its surface, and a physical mixture of this powder plus TiO{sub 2} was also examined and compared both to these catalysts and to Pt dispersed on TiO{sub 2}. The results follow.

  17. 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

  18. One-pot, template-free synthesis of Pd-Pt single-crystalline hollow cubes with enhanced catalytic activity.

    Science.gov (United States)

    Sun, Long; Zhang, Zhicheng; Xu, Biao; Wang, Xun

    2013-07-01

    Hollow structures have attracted ever-growing interest owing to their various excellent properties. However, a facile strategy for their fabrication is still desired. Herein, Pd-Pt alloy with three different morphologies, that is, cubes, hollow cubes, and truncated octahedrons, is synthesized by using a one-pot, template-free method. The mechanism and dynamics of this system is also studied in detail. In particular, the hollow cubic structure represents enhanced catalytic activity in both coupling reactions and in the electrochemical oxidation of formic acid. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. PdM (M = Pt, Au) bimetallic alloy nanowires with enhanced electrocatalytic activity for electro-oxidation of small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Chengzhou; Guo, Shaojun; Dong, Shaojun [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022 (China)

    2012-05-02

    A facile and general method has been developed to synthesize well-defined PdPt and PdAu alloy nanowires, which exhibit significantly enhanced activity towards small molecules, such as ethanol, methanol, and glucose electro-oxidation in an alkaline medium. Considering the important role of one-dimensional alloy nanowires in electrocatalytic systems, the present Pd-based alloy nanostructures could offer a promising new class of advanced electrocatalysts for direct alcohol fuel cells and electrochemical sensors. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Synthesis of Highly Active Sub-Nanometer Pt@Rh Core-Shell Nanocatalyst via a Photochemical Route: Porous Titania Nanoplates as a Superior Photoactive Support.

    Science.gov (United States)

    Zhan, Wen-Wen; Zhu, Qi-Long; Dang, Song; Liu, Zheng; Kitta, Mitsunori; Suenaga, Kazutomo; Zheng, Lan-Sun; Xu, Qiang

    2017-02-02

    Sub-nanometer Pt@Rh nanoparticles highly dispersed on MIL-125-derived porous TiO2 nanoplates are successfully prepared for the first time by a photochemical route, where the porous TiO2 nanoplates with a relatively high specific surface area play a dual role as both effective photoreductant and catalyst support. The resulting Pt@Rh/p-TiO2 can be utilized as a highly active catalyst.

  1. Immunomodulatory Activity and Partial Characterisation of Polysaccharides from Momordica charantia

    Directory of Open Access Journals (Sweden)

    Yuan-Yuan Deng

    2014-08-01

    Full Text Available Momordica charantia Linn. is used as an edible and medicinal vegetable in sub-tropical areas. Until now, studies on its composition and related activities have been confined to compounds of low molecular mass, and no data have been reported concerning the plant’s polysaccharides. In this work, a crude polysaccharide of M. charantia (MCP fruit was isolated by hot water extraction and then purified using DEAE-52 cellulose anion-exchange chromatography to produce two main fractions MCP1 and MCP2. The immunomodulatory effects and physicochemical characteristics of these fractions were investigated in vitro and in vivo. The results showed that intragastric administration of 150 or 300 mg·kg−·d−1 of MCP significantly increased the carbolic particle clearance index, serum haemolysin production, spleen index, thymus index and NK cell cytotoxicity to normal control levels in cyclophosphamide (Cy-induced immunosuppressed mice. Both MCP1 and MCP2 effectively stimulated normal and concanavalin A-induced splenic lymphocyte proliferation in vitro at various doses. The average molecular weights of MCP1 and MCP2, which were measured using high-performance gel permeation chromatography, were 8.55 × 104 Da and 4.41 × 105 Da, respectively. Both fractions exhibited characteristic polysaccharide bands in their Fourier transform infrared spectrum. MCP1 is mainly composed of glucose and galactose, and MCP2 is mainly composed of glucose, mannose and galactose. The results indicate that MCP and its fractions have good potential as immunotherapeutic adjuvants.

  2. Self-assembling behaviour of Pt nanoparticles onto surface of TiO2 and their resulting photocatalytic activity

    Indian Academy of Sciences (India)

    M Qamar; Ashok K Ganguli

    2013-11-01

    In the present study, self-assembling behaviour of guest nanoparticles (platinum) onto the surface of host support (titanium dioxide) during photodeposition process as a function of solution pH has been explored in detail by means of transmission electron microscope (TEM). The photocatalytic activity of the resulting bimetallic nanoassembly (Pt/TiO2) was evaluated by studying the degradation of two organic pollutants viz. triclopyr and methyl orange. Microscopic studies revealed that the deposition and/or distribution of Pt nanoparticles onto the surface of TiO2 were strongly guided by the ionization state of support which in turn was regulated by the solution pH of photodeposition process. A direct relationship between the solution pH of deposition process and the photocatalytic activity of resulting bimetallic catalyst has been observed. A mechanism based on the interparticle interaction between TiO2 and hydrolytic products of metal ions has been proposed for the differences in the photocatalytic activity of the resulting nanocomposite.

  3. Mixed-PtPd-shell PtPdCu nanoparticle nanotubes templated from copper nanowires as efficient and highly durable electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hui-Hui; Cui, Chun-Hua; Zhao, Shuo; Yao, Hong-Bin; Gao, Min-Rui; Fan, Feng-Jia; Yu, Shu-Hong [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026 (China); Div. of Nanomaterials and Chemistry, Heifei National Lab. for Physical, Sciences at Microscale (China)

    2012-10-15

    The controlled synthesis of mixed-PtPd-shell PtPdCu-alloy nanoparticle nanotubes (ANNTs) is demonstrated by galvanic displacement with partially sacrificial copper-nanowire templates, and following the electrochemical leaching of the non-noble metal Cu in the acidic electrolyte. These core-shell catalysts significantly reduce the amount of expensive Pt and highly improve the electrocatalytic activity and durability through their modified electronic structure, atomic distribution, and 1D structure property. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Effect of Pt coverage in Pt-deposited Pd nanostructure electrodes on electrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ah-Reum; Lee, Young-Woo; Kwak, Da-Hee; Park, Kyung-Won [Soongsil University, Seoul (Korea, Republic of)

    2015-06-15

    We have fabricated Pt-deposited Pd electrodes via a two-gun sputtering deposition system by separately operating Pd and Pt target as a function of sputtering time of Pt target. For Pt-deposited Pd electrodes (Pd/Pt-X), Pd were first deposited on the substrates at 20 W for 5min, followed by depositing Pt on the Pd-only electrodes as a function of sputtering time (X=1, 3, 5, 7, and 10min) at 20W on the Pt target. As the sputtering time of Pt target increased, the portion of Pt on the Pd electrodes increased, representing an increased coverage of Pt on the Pd electrodes. The Pd/Pt-7 electrode having an optimized Pt coverage exhibits an excellent electrocatalytic activity for methanol oxidation reaction.

  5. Enhanced Electrocatalytic Activity of Pt Particles Supported on Reduced Graphene Oxide/Poly(3,4-ethylenedioxythiophene RGO/PEDOT Composite towards Ethanol Oxidation

    Directory of Open Access Journals (Sweden)

    Juanito Raphael F. Foronda

    2013-01-01

    Full Text Available Catalysts in fuel cells are normally platinum based because platinum exhibits high electrocatalytic activity towards ethanol oxidation in acidic medium. However, bulk Pt is expensive and rare in nature. To reduce the consumption of Pt, a support material or matrix is needed to disperse Pt on its surface as micro- or nanoparticles with potential application as anode material in direct ethanol fuel cells (DEFCs. In this study, a composite material consisting of platinum particles dispersed on reduced graphene oxide/poly(3,4-ethylenedioxythiophene (RGO/PEDOT support was electrochemically prepared for ethanol oxidation in sulfuric acid electrolyte. PEDOT, a conductive polymer, was potentiodynamically polymerized from the corresponding monomer, 0.10 M EDOT in 0.10 M HClO4 electrolyte. The PEDOT-modified electrode was used as a substrate for exfoliated graphene oxide (EGO which was prepared by electrochemical exfoliation of graphite from carbon rod of spent batteries and subsequently reduced to form RGO. The Pt/RGO/PEDOT composite gave the highest electrocatalytic activity with an anodic current density of 2688.7 mA·cm−2 at E = 0.70 V (versus Ag/AgCl towards ethanol oxidation compared to bare Pt electrode and other composites. Scanning electron microscopy (SEM revealed the surface morphology of the hybrid composites while energy dispersive X-ray (EDX confirmed the presence of all the elements for the Pt/RGO/PEDOT composite.

  6. Mutation on Gly115 and Tyr205 of the cyclic dipeptide C2-prenyltransferase FtmPT1 increases its catalytic activity toward hydroxynaphthalenes.

    Science.gov (United States)

    Zhao, Wei; Fan, Aili; Tarcz, Sylwia; Zhou, Kang; Yin, Wen-Bing; Liu, Xiao-Qing; Li, Shu-Ming

    2017-03-01

    The fungal cyclic dipeptide prenyltransferase FtmPT1 from Aspergillus fumigatus catalyzes a regular C2-prenylation of brevianamide F (cyclo-L-Trp-L-Pro) and is involved in the biosynthesis of a number of biologically active natural products including tryprostatins, spirotryprostatins, verruculogen, and fumitremorgins. FtmPT1, like other members of the dimethylallyltryptophan synthase superfamily, was shown to have high substrate promiscuity for tryptophan-containing cyclic dipeptides and a few other aromatic substrates. A previous study demonstrated the acceptance of 1-naphthol by FtmPT1, but with very low product yield. In this study, we report the significantly increased acceptance of 1-naphthol and other hydroxynaphthalenes by FtmPT1_G115A and six FtmPT1_Y205X single mutants as well as FtmPT1_G115A_Y205C. These results provided an example for creation of biocatalysts with improved catalytic activity by site-directed mutagenesis.

  7. Surface Pourbaix diagrams and oxygen reduction activity of Pt, Ag and Ni(111) surfaces studied by DFT

    DEFF Research Database (Denmark)

    Hansen, Heine Anton; Rossmeisl, Jan; Nørskov, Jens Kehlet

    2008-01-01

    (ORR) on the different surface structures and calculate the free energy of the intermediates. We estimate their catalytic activity for ORR by determining the highest potential at which all ORR reaction steps reduce the free energy. We obtain self-consistency in the sense that the surface is stable...... but not in acidic PEM fuel cells. Based on density functional theory calculations we investigate the electrochemically most stable surface structures as a function of pH and electrostatic potential for Pt(111), Ag(111) and Ni(111), and we construct surface Pourbaix diagrams. We study the oxygen reduction reaction...... of the reactive surface. Oxygen absorbed on the surface shifts the reactivity towards the weak binding region, which in turn increases the activity. The oxidation state of the surface and the ORR potential are constant versus the reversible hydrogen electrode (RHE). The dissolution potential in acidic solution...

  8. Sonochemical/hydration-dehydration synthesis of Pt-TiO2 NPs/decorated carbon nanotubes with enhanced photocatalytic hydrogen production activity.

    Science.gov (United States)

    Abdulrazzak, Firas H; Hussein, Falah H; Alkaim, Ayad F; Ivanova, Irina; Emeline, Alexei V; Bahnemann, Detlef W

    2016-11-02

    Modified Pt-TiO2 NPs/decorated carbon nanotubes were synthesized utilizing sonochemical/hydration-dehydration techniques. Pt was loaded on TiO2 by a photodeposition method keeping in mind the end goal to achieve electron-hole pair separation and promote the surface reaction. The morphological and basic properties of Pt-TiO2/fCNTs were investigated by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and Raman spectroscopy. The selected area electron diffraction (SAED) patterns of Pt-TiO2/fCNTs were obtained utilizing TEM-based energy dispersive X-ray spectroscopy (EDXS) analysis. It was found that the TiO2 nanoparticles were uniformly distributed on the fCNTs, and the Pt particles were decorated on the surface of TiO2/fCNTs. The photocatalytic hydrogen production activity of the Pt(0.5%)-TiO2/fCNTs(0.5%) nanoparticle composites was investigated using a sacrificial agent methanol solution. Pt-loaded TiO2 demonstrated a hydrogen evolution rate around 20 times that of TiO2/fCNTs(0.5%) (fSWCNTs, fMWCNTs). When compared with platinized TiO2 in methanol, which was utilized as a control material, Pt-TiO2/fCNTs demonstrated an almost 2-fold increment in hydrogen generation.

  9. Low content of Pt supported on Ni-MoCx/carbon black as a highly durable and active electrocatalyst for methanol oxidation, oxygen reduction and hydrogen evolution reactions in acidic condition

    Science.gov (United States)

    Zhang, Yan; Zang, Jianbing; Jia, Shaopei; Tian, Pengfei; Han, Chan; Wang, Yanhui

    2017-08-01

    Nickel and molybdenum carbide modified carbon black (Ni-MoCx/C) was synthesized by a two-step microwave-assisted deposition/carbonthermal reduction method and characterized by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The as-prepared Ni-MoCx/C supported Pt (10 wt%) electrocatalyst (10Pt/Ni-MoCx/C) was synthesized through a microwave-assisted reduction method and 10Pt/Ni-MoCx/C exhibited high electrocatalytic activity for methanol oxidation, oxygen reduction and hydrogen evolution reactions. Results showed that 10Pt/Ni-MoCx/C electrocatalyst had better electrocatalytic activity and stability performance than 20 wt% Pt/C (20Pt/C) electrocatalyst. Among them, the electrochemical surface area of 10Pt/Ni-MoCx/C reached 68.4 m2 g-1, which was higher than that of 20Pt/C (63.2 m2 g-1). The enhanced stability and activity of 10Pt/Ni-MoCx/C electrocatalyst were attributed to: (1) an anchoring effect of Ni and MoCx formed during carbonthermal reduction process; (2) a synergistic effect among Pt, Ni, MoOx and MoCx. These findings indicated that 10Pt/Ni-MoCx/C was a promising electrocatalyst for direct methanol fuel cells.

  10. Partial Agonist and Antagonist Activities of a Mutant Scorpion β-Toxin on Sodium Channels*

    OpenAIRE

    Karbat, Izhar; Ilan, Nitza; Zhang, Joel Z.; Cohen, Lior; Kahn, Roy; Benveniste, Morris; Scheuer, Todd; Catterall, William A.; Gordon, Dalia; Gurevitz, Michael

    2010-01-01

    Scorpion β-toxin 4 from Centruroides suffusus suffusus (Css4) enhances the activation of voltage-gated sodium channels through a voltage sensor trapping mechanism by binding the activated state of the voltage sensor in domain II and stabilizing it in its activated conformation. Here we describe the antagonist and partial agonist properties of a mutant derivative of this toxin. Substitution of seven different amino acid residues for Glu15 in Css4 yielded toxin derivatives with both increased a...

  11. Underpinning energetics of lithium bonding and stability in the Li-Pt-Sn system

    Science.gov (United States)

    Matar, Samir F.; Pöttgen, Rainer

    2012-10-01

    Within the Li-Pt-Sn system, we examine the electronic structures and Li-binding of LiPtSn2, Li2PtSn and Li3Pt2Sn3 with fluorite-related crystal structures. The structures with totally de-intercalated lithium keep the characteristics of the pristine ternary compound with a reduction of the volume. In Li3Pt2Sn3 the binding energies of lithium belonging to three crystallographically inequivalent Wyckoff sites are different and point to distinct activities of de-intercalation concomitant with site-selective bonding magnitudes. The derived potentials are within the range of non-oxide binary and ternary lithium based compounds and indicate the possibility of at least partial delithiation.

  12. Study of Hydrogen Adsorption on Pt/WO3-ZrO2 through Pt Sites

    Institute of Scientific and Technical Information of China (English)

    Sugeng Triwahyono; Aishah Abdul Jalil; Hideshi Hattori

    2007-01-01

    The rate determining step and the energy barrier involved in hydrogen adsorption on Pt/WO3ZrO2 were studied based on the assumption that the hydrogen adsorption occurs only through Pt sites.The rate of hydrogen adsorption on Pt/WO3-ZrO2 Was measured in the adsorption temperature range of 323-573 K and an initial hydrogen pressure of 50 Torr.The rates of hydrogen uptake were very high for the initial few minutes and the adsorption continued for more than 5 h below 523 K.The hydrogen uptake far exceeded the H/Pt ratio of unity for all adsorption temperatures,indicating that the adsorption of hydrogen involved the dissociative adsorption of hydrogen on Pt sites to form hydrogen atoms.the spillover of hydrogen atoms onto the surface of the WO3-ZrO2 catalyst.the diffusion of spiltover hydrogen atom over the surface of the WO3-ZrO2 catalyst,and the formation of protonic acid site originated from hydrogen atom by releasing an electron in which the electron may react with a second hydrogen atom to form a hydride near the Lewis acid site.The rate determining step was the spillover with the activation energy of 12.3 kJ/mol.The rate of hydrogen adsorption cannot be expressed by the rate equation based on the assumption that the rate determining step is the surface diffusion.The activity of Pt/WO3-ZrO2 Was examined on n-heptane isomerization in which the increase of hydrogen partial pressure provided positive-effect on the conversion of n-heptane and negative-effect on the selectivity towards iso-heptane.

  13. 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.

  14. Methanol Tolerant PWA-Pt/C Catalyst with Excellent Electrocatalytic Activity for Oxygen Reduction in Direct Methanol Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    It was reported for the first time that phosphorictungstenic acid (PWA) could promote the oxygen reduction reaction (ORR) and inhibit the methanol oxidation reaction at the cathodic Pt/C catalyst in the direct methanol fuel cell (DMFC). When the weight ratio of PWA to Pt/C is 1,the composite catalyst increases the reduction current of oxygen by about 38% and decreases the oxidation current of methanol by about 76% compared with that of the Pt/C catalyst.

  15. Better at work: activation of partially disabled workers in the Netherlands

    NARCIS (Netherlands)

    Knijn, Trudie; van Wel, Frits

    2014-01-01

    This article presents a unique analysis of how activation agen-cies in the Netherlands cope with partially disabled employeeson the basis of tailor-made individual assessments, representingand executing the shift towards a policy paradigm in activationto work–a synchronic instead of diachronic appro

  16. Motor unit activation order during electrically evoked contractions of paralyzed or partially paralyzed muscles

    NARCIS (Netherlands)

    Thomas, CK; Nelson, G; Than, L; Zijdewind, Inge

    The activation order of motor units during electrically evoked contractions of paralyzed or partially paralyzed thenar muscles was determined in seven subjects with chronic cervical spinal cord injury. The median nerve was stimulated percutaneously with pulses of graded intensity to produce

  17. Motor unit activation order during electrically evoked contractions of paralyzed or partially paralyzed muscles

    NARCIS (Netherlands)

    Thomas, CK; Nelson, G; Than, L; Zijdewind, Inge

    2002-01-01

    The activation order of motor units during electrically evoked contractions of paralyzed or partially paralyzed thenar muscles was determined in seven subjects with chronic cervical spinal cord injury. The median nerve was stimulated percutaneously with pulses of graded intensity to produce incremen

  18. Novel high-activity catalysts for partial oxidation of methane to formaldehyde

    CSIR Research Space (South Africa)

    Parmaliana, A

    1993-05-07

    Full Text Available Vanadium oxide-silica catalysts can effect the partial oxidation of methane to formaldehyde with extremely high activities and the space time yield (STY) can reach a value in excess of 800 g kg-1cat h-1; bare silica also shows appreciable STY value...

  19. The role of carbon overlayers on Pt-based catalysts for H2-cleanup by CO-PROX

    Science.gov (United States)

    Romero-Sarria, F.; Garcia-Dali, S.; Palma, S.; Jimenez-Barrera, E. M.; Oliviero, L.; Bazin, P.; Odriozola, J. A.

    2016-06-01

    In this work, we analyze the effect of the activation method on the catalytic activity of Pt-based catalysts supported on alumina in the PROX reaction. For this, model Pt/Al2O3 catalysts with variable amounts of acetic acid were prepared and their thermal evolution studied by FTIR spectroscopy. From the analysis of the nature of the platinum surface upon acetic acid decomposition and the gas phase evolved products, we have demonstrated the formation of partially hydrogenated carbon overlayers that tailor the activity of Pt-based catalysts in the PROX reaction.

  20. Magnetic heating properties and neutron activation of tungsten-oxide coated biocompatible FePt core-shell nanoparticles.

    Science.gov (United States)

    Seemann, K M; Luysberg, M; Révay, Z; Kudejova, P; Sanz, B; Cassinelli, N; Loidl, A; Ilicic, K; Multhoff, G; Schmid, T E

    2015-01-10

    Magnetic nanoparticles are highly desirable for biomedical research and treatment of cancer especially when combined with hyperthermia. The efficacy of nanoparticle-based therapies could be improved by generating radioactive nanoparticles with a convenient decay time and which simultaneously have the capability to be used for locally confined heating. The core-shell morphology of such novel nanoparticles presented in this work involves a polysilico-tungstate molecule of the polyoxometalate family as a precursor coating material, which transforms into an amorphous tungsten oxide coating upon annealing of the FePt core-shell nanoparticles. The content of tungsten atoms in the nanoparticle shell is neutron activated using cold neutrons at the Heinz Maier-Leibnitz (FRMII) neutron facility and thereby transformed into the radioisotope W-187. The sizeable natural abundance of 28% for the W-186 precursor isotope, a radiopharmaceutically advantageous gamma-beta ratio of γβ≈30% and a range of approximately 1mm in biological tissue for the 1.3MeV β-radiation are promising features of the nanoparticles' potential for cancer therapy. Moreover, a high temperature annealing treatment enhances the magnetic moment of nanoparticles in such a way that a magnetic heating effect of several degrees Celsius in liquid suspension - a prerequisite for hyperthermia treatment of cancer - was observed. A rise in temperature of approximately 3°C in aqueous suspension is shown for a moderate nanoparticle concentration of 0.5mg/ml after 15min in an 831kHz high-frequency alternating magnetic field of 250Gauss field strength (25mT). The biocompatibility based on a low cytotoxicity in the non-neutron-activated state in combination with the hydrophilic nature of the tungsten oxide shell makes the coated magnetic FePt nanoparticles ideal candidates for advanced radiopharmaceutical applications.

  1. Inexpensive Ipomoea aquatica Biomass-Modified Carbon Black as an Active Pt-Free Electrocatalyst for Oxygen Reduction Reaction in an Alkaline Medium

    Directory of Open Access Journals (Sweden)

    Yaqiong Zhang

    2015-09-01

    Full Text Available The development of inexpensive and active Pt-free catalysts as an alternative to Pt-based catalysts for oxygen reduction reaction (ORR is an essential prerequisite for fuel cell commercialization. In this paper, we report a strategy for the design of a new Fe–N/C electrocatalyst derived from the co-pyrolysis of Ipomoea aquatica biomass, carbon black (Vulcan XC-72R and FeCl3·6H2O at 900 °C under nitrogen atmosphere. Electrochemical results show that the Fe–N/C catalyst exhibits higher electrocatalytic activity for ORR, longer durability and higher tolerance to methanol compared to a commercial Pt/C catalyst (40 wt % in an alkaline medium. In particular, Fe–N/C presents an onset potential of 0.05 V (vs. Hg/HgO for ORR in an alkaline medium, with an electron transfer number (n of ~3.90, which is close to that of Pt/C. Our results confirm that the catalyst derived from I. aquatica and carbon black is a promising non-noble metal catalyst as an alternative to commercial Pt/C catalysts.

  2. A partially active mutant aldolase B from a patient with hereditary fructose intolerance.

    Science.gov (United States)

    Brooks, C C; Tolan, D R

    1994-01-01

    Hereditary fructose intolerance (HFI) is a potentially fatal autosomal recessive disease of carbohydrate metabolism. HFI patients are deficient in aldolase B, the isozyme expressed in fructose-metabolizing tissues. The eight protein coding exons, including splicing signals, of the aldolase B gene from one American HFI patient were amplified by the polymerase chain reaction (PCR). Single-strand conformational polymorphism (SSCP) analysis and direct sequence determination were applied to the amplified fragments. The mutations in the patient's alleles were identified as a nonsense mutation (R59op) in exon 3 and a missense mutation (C134R) in exon 5. These mutations were confirmed by sequence determination of cloned PCR-amplified exons 3 and 5 from the patient. Allele specific oligonucleotide (ASO) hybridizations of amplified exons 3 and 5 showed the Mendelian inheritance of both mutations. Site-directed mutagenesis was used to generate an expression plasmid for the C134R mutation, and the mutant enzyme was expressed in bacteria. Assays of partially purified enzyme preparations showed that this missense mutation results in an apparently unstable enzyme that retains partial activity. This is the first evidence for a partially active aldolase B from an HFI individual with an identified mutation, and supports the hypothesis that adequate gluconeogenesis/glycolysis is maintained in HFI patients by the presence of partially active enzymes.

  3. Partially resonant active filter using the digital PWM control circuit with the DSP

    Energy Technology Data Exchange (ETDEWEB)

    Matsuo, Hirofumi; Kurokawa, Fujio; Luo, Zongxin; Makino, Yutaka; Ishizuka, Yoichi [Nagasaki Univ. (Japan); Oshikata, Tetsuya [Shindengen Elect. Mfg. Co. Ltd. (Japan)

    2000-07-01

    The partially resonant active filter, as a pre-regulator, using the digital PWM control circuit with the DSP is proposed to improve the power factor and input current harmonic distortion factor. The steady-state and dynamic characteristics of this active filter are analysed and the relationship among the circuit parameters, variables and performance characteristics such as the pre-regulation of the output voltage, input power factor, input current harmonic distortion, boundaries of stability and so forth are defined. Using the partially resonant active filter, the high power efficiency over 91% is obtained and the high frequency switching noise is suppressed. Also, the digital control with the DSP is versatile and consequently, the power factor over 0.99 and total harmonic distortion factor less than 1% are easily realized. (orig.)

  4. Tuning the activity of nanoplatelet MoS{sub 2}-based catalyst for efficient hydrogen evolution via electrochemical decoration with Pt nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Jagminas, Arunas, E-mail: jagmin@ktl.mii.lt [State Research Institute Centre for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius (Lithuania); Naujokaitis, Arnas [State Research Institute Centre for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius (Lithuania); Vilnius University, Faculty of Physics, Sauletekio av. 9, LT-10222 Vilnius (Lithuania); Žalnėravičius, Rokas; Jasulaitiene, Vitalija [State Research Institute Centre for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius (Lithuania); Valušis, Gintaras [State Research Institute Centre for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius (Lithuania); Vilnius University, Faculty of Physics, Sauletekio av. 9, LT-10222 Vilnius (Lithuania)

    2016-11-01

    Highlights: • MoS{sub 2}-based nanoplatelet films on Mo substrate by hydrothermal treatment. • Electrochemical decoration of MoS{sub 2} nanoplatelets with Pt nanoparticles. • Ultra-high efficiency of HER at heterostructured electrode surface. - Abstract: This study establishes a novel methodology for increasing the HER activity of the molybdenum substrate covered with amorphous molybdenum sulfide-oxide nano-structured film up to ultra-high level. We show that utilization of such nanoplatelet/nanoflowered film as electrocatalyst for HER in the sulfuric acidic solution cell with Pt anode and Ag/AgCl,KCl reference leads to obvious structural transformations and nice decoration of nanoplatelet edges with few-nm sized Pt nanoparticles. By this way, a surprising HER efficiency attaining ∼160 mA cm{sup −2} current density at −200 mV and ∼260 mA cm{sup −2} at −300 mV vs RHE overpotentials with the onset of reaction close to the one carried out at the bulk Pt electrode was obtained. To the best of our knowledge, these HER characteristics are among the best reported to date for hybrid MoS{sub 2}-based HER electrocatalysts. The results obtained were confirmed by SEM, XPS, XRD, conductive mode AFM and cyclic voltammetry. It is worth noticing that to achieve this synergetic effect only about 0.5 μg cm{sup −2} of Pt is required.

  5. Electrochemical oxidation of ammonia on carbon-supported bi-metallic PtM (M = Ir, Pd, SnO{sub x}) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lomocso, Thegy L. [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada); Baranova, Elena A., E-mail: elena.baranova@uottawa.ca [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada)

    2011-10-01

    Highlights: > Oxidation of NH{sub 3} is investigated on carbon-supported Pt and PtM (M = Pd, Ir, SnO{sub x}) nanoparticles. > Carbon supported PtPd and PtIr nanoparticles show higher catalytic activity if compared to Pt nanocatalyst. > Pt{sub 7}Ir{sub 3} nanoparticles combine good catalytic activity and enhanced stability for NH{sub 3} oxidation. > Electronic effect between two metals in PtIr is responsible for increase in the catalytic activity. - Abstract: Ammonia electro-oxidation was studied in alkaline solution on carbon-supported Pt and bimetallic Pt{sub y}M{sub 1-y} (M = Pd, Ir, SnO{sub x} and y = 70, 50 at.%) nanoparticles. Catalysts were synthesized using the modified polyol method and deposited on carbon, resulting in 20 wt.% of metal loading. Particle size, structure and surface composition of the particles were investigated using TEM, XRD and XPS. Mean size of PtM bi-metallic nanoparticles varied between 2.0 and 4.7 nm, depending on the second metal (M). XRD revealed the structure of all bi-metallic particles to be face-centered cubic and confirmed alloy formation for Pt{sub y}Pd{sub 1-y} (y = 70, 50 at.%) and Pt{sub 7}Ir{sub 3}nanoparticles, as well as partial alloying between Pt and SnO{sub x}. Electrochemical behaviour of ammonia on Pt and PtM nanoparticles is comparable to that expected for bulk Pt and PtM alloys. Addition of Pd to Pt at the nanoscale decreased the onset potential of ammonia oxidation if compared to pure platinum nanoparticles; however stability of the catalyst was poor. For Pt{sub 7}(SnO{sub x}){sub 3}, current densities were similar to Pt, whereas catalyst stability against deactivation was improved. It is found that carbon supported Pt{sub 7}Ir{sub 3} nanoparticles combine good catalytic activity with enhanced stability for ammonia electro-oxidation. Electronic effect generated between two metals in the bimetallic nanoparticles might be responsible for increase in the catalytic activity of Pd- and Ir-containing catalysts, causing

  6. Self-assembly growth of alloyed NiPt nanocrystals with holothuria-like shape for oxygen evolution reaction with enhanced catalytic activity

    Directory of Open Access Journals (Sweden)

    Tao Ding

    2016-01-01

    Full Text Available Self-assembly growth of alloyed NiPt nanocrystals with holothuria-like wire shape has been achieved via a facile and moderate hydrothermal process at 120 °C for 1 h from the reaction of nickel nitrate and chloroplatinic acid in alkaline solution in the presence of ethanediamine and hydrazine hydrate. The holothuria-like alloyed NiPt wires are Ni-rich in composition (Ni23.6Pt and uniform in diameter with many tiny tips outstretched from the wires surface. The holothuria-like wires are assembled from granular subunits with the assistance of capping molecular of ethanediamine and the wires display an improved oxygen evolution reaction catalytic activity.

  7. Facile Synthesis of Three-Dimensional Pt-TiO2 Nano-networks: A Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Borane.

    Science.gov (United States)

    Khalily, Mohammad Aref; Eren, Hamit; Akbayrak, Serdar; Susapto, Hepi Hari; Biyikli, Necmi; Özkar, Saim; Guler, Mustafa O

    2016-09-26

    Three-dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self-assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt-TiO2 nano-network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO2 by atomic layer deposition (ALD) with angstrom-level thickness precision. The 3D peptide-TiO2 nano-network was further decorated with highly monodisperse Pt nanoparticles by using ozone-assisted ALD. The 3D TiO2 nano-network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia-borane, generating three equivalents of H2 . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Quadratic partial eigenvalue assignment problem with time delay for active vibration control

    Science.gov (United States)

    Pratt, J. M.; Singh, K. V.; Datta, B. N.

    2009-08-01

    Partial pole assignment in active vibration control refers to reassigning a small set of unwanted eigenvalues of the quadratic eigenvalue problem (QEP) associated with the second order system of a vibrating structure, by using feedback control force, to suitably chosen location without altering the remaining large number of eigenvalues and eigenvectors. There are several challenges of solving this quadratic partial eigenvalue assignment problem (QPEVAP) in a computational setting which the traditional pole-placement problems for first-order control systems do not have to deal with. In order to these challenges, there has been some work in recent years to solve QPEVAP in a computationally viable way. However, these works do not take into account of the practical phenomenon of the time-delay effect in the system. In this paper, a new "direct and partial modal" approach of the quadratic partial eigenvalue assignment problem with time-delay is proposed. The approach works directly in the quadratic system without requiring transformation to a standard state-space system and requires the knowledge of only a small number of eigenvalues and eigenvectors that can be computed or measured in practice. Two illustrative examples are presented in the context of active vibration control with constant time-delay to illustrate the success of our proposed approach. Future work includes generalization of this approach to a more practical complex time-delay system and extension of this work to the multi-input problem.

  9. 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.

  10. Hydrothermal Preparation of Pt/TiO2 Nanotubes and Its Photocatalytic Activity in Generating CO2%Pt/TiO2纳米管水热还原制备及其光催化性能研究

    Institute of Scientific and Technical Information of China (English)

    王栋良; 王騊; 王晟

    2011-01-01

    将商业P25 TiO2纳米粒子经传统水热法制备出钛酸纳米管(HTiNTs),再经水热还原法在其表面沉积Pt,经高温煅烧制备出Pt负载锐钛矿型TiO2纳米管(Pt/TiNTs).采用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)及透射电镜(TEM)、能谱(EDS)对其进行表征,并用气相色谱(GC)研究不同Pt担载量的TiO2纳米管对乙酸溶液的光催化分解效果.结果表明:所制备的Pt/TiNTs为锐钛矿型Ti()2,与P25 TiO2相比,Pt/TiNTs对乙酸的光催化分解效果显著提高.%In this paper hydrogen titanate nanotubes (HTiNTs) are synthesized via a typical hydro-thermal method. Pt loaded titanate nanotubes (Pt/TiNTs) are successfully prepared by loading Pt nanop-articles onto the HTiNTs surface with specific hydrothermal reduction conditions, followed by calcination at 773k. The morphology and structure of Pt/TiNTs are investigated by FESEM, XRD, TEM, and EDS. The relationship between the different loading amount of Pt nanoparticles and the photocatalytic activity of Pt/TiNTs is investigated by the photodecomposition of acetic acid. The results indicate that Pt/TiNTs show the anatase phase, and the photocatalytic activity is proved to be enhanced compared with that of P25 nanoparticles.

  11. Structural characterization and catalytic activity of Pt dendrimer encapsulated nanoparticles supported over Al2O3 for SCR of NOx.

    Science.gov (United States)

    Bae, HyunSook; Rao, Komateedi N; Ha, HeonPhil

    2011-07-01

    Pt/Al2O3 and Pt-Mg/Al2O3 nano composites were successfully prepared by dendrimer templated synthesis route. The obtained dendritic nanoparticles were dispersed in alumina support and they were evaluated for SCR of NOx using methane as reductant. Thermal analysis results of uncalcined samples revealed that the oxygen can accelerate the rate of dendrimer shell decomposition. X-ray diffractograms of 500 degrees C calcined samples disclosed the amorphous nature of materials, whereas 1000 degrees C air calcined samples showed enhanced crystallinity as well as diffraction pattern corresponding to Pt and PtO. HRTEM images of Pt40-G4OH dendritic nanoparticles showed uniform particulate distribution with average particle size of 2.4 nm. The STEM results of 0.5 Pt/Al2O3 sample calcined at 500 degrees C exhibited a wide range of particles between 2 and 20 nm. This indicates the huge segregation of platinum metal particles during impregnation and subsequent calcination. Among the synthesized materials 0.5 wt% Pt/Al2O3 sample showed excellent conversion and selectivity for SCR of NOx.

  12. Active acoustic leak detection for LMFBR steam generators. Pt. 6. Applicability to practical steam generators

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Kazuo; Kumagai, Hiromichi; Kinoshita, Izumi [Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.

    1998-03-01

    It is necessary to develop a reliable water leak detection system for steam generators of liquid metal reactors in order to prevent the expansion of damage and to maintain the structural integrity of the steam generators. The concept of the active acoustic method is to detect the change of the ultrasonic field due to the hydrogen gas bubbles generated by a sodium-water reaction. This method has the potential for improved detection performance compared with conventional passive methods, from the viewpoint of sensitivity, response time and tolerance against the background noise. A feasibility study of the active acoustic leak detection system is being carried out. This report predicts the performance of the active acoustic method in the practical steam generators from the results of the large scale in-water experiments. The results shows that the active acoustic system can detect a 10 g/s leak within a few seconds in large-scale steam generators. (author)

  13. Comparative Analysis Of Conventional Method With Activity Based Costing In PT Mulia Sejati Gallery

    Directory of Open Access Journals (Sweden)

    Irma Nadia Erena

    2016-09-01

    Full Text Available The goal of this research was to provide readers the information about the calculation methods, both traditional and activity-based costing in the application of the cost of production. The method used in this research was the qualitative method. The analysis was done by calculating the amount of the production cost using the traditional system and the magnitude of the production cost when using the activity-based costing system. The amount of each acquisition was then performed into data analysis. The results achieved are massive distortion between the calculations using traditional systems and activity based costing system. The conclusions of the whole thesis are activity-based costing system is considered more relevant than traditional systems that are currently used by the company.

  14. Caving performance through the integration of microseismic activity and numerical modeling at DOZ-PT Freeport, Indonesia

    Institute of Scientific and Technical Information of China (English)

    Rubio Enrique; Napitupulu Daulat

    2009-01-01

    This article describes an undergoing research at PT Freeport,Indonesia,in which the main goal is to use the microseismic information recorded as a result of mining to analyze cave propagation and stress performance on the actual production and fixed in-frastructure.At the moment,several numerical experiments have been conducted to correlate the mining activity with the microseis-mic events using the data collected during year 2005 and 2006.As a result of the preliminary analysis a micro-and a macrocracking envelop were proposed on the basis of computation of stress behavior at the location of the events.Stresses have been computed us-ing standard elastic continuous boundary element models.The correlation between the average source radius and the stress perform-ance has provided a method to propose a macrocracking criterion.Several techniques have been tested to nucleate the microseismic activity around different geological features.This last attempt was aimed to look at potential overstresses induced over the undercut and extraction level drifts.A method was devised to integrate the microseismicity into a 3-dimensional ride distribution model.This model has shown to be very effective to quantify the overstress induced as a result of computing volumetric microseismieity density.The volumetric microseismic model showed to induce overstress up to 10 MPa over a period of two months.The future work will concentrate on the calibration of the integrated model with actual damage observations made at the current mining infrastructure.

  15. Comparative study of ethanol oxidation at Pt: Based nanoalloys and UPD modified Pt nanoparticles

    Directory of Open Access Journals (Sweden)

    Tripković Amalija V.

    2010-01-01

    Full Text Available The activity of two alloys, Pt3Sn/C and Pt3Ru2/C, was compared with the activity of Pt/C modified with corresponding amounts of SnUPD (≈25 % and RuUPD (≈40 % in oxidation of ethanol. Pt3Sn/C, Pt3Ru2/C and Pt/C catalysts were characterized by XRD. To establish the activity and stability of the catalysts, potentiodynamic, quasi steady-state and chronoamperometric measurements were performed. Both alloys are more active than SnUPD or RuUPD modified Pt/C catalysts. Electronic effect determining dominantly the activity of Pt3Sn/C is the main reason for its higher activity compared to Pt3Ru2/C. Since SnUPD and RuUPD do not provoke any significant modification of electronic environment, both modified Pt/C catalysts are less active than corresponding alloys. More pronounced difference in activity between Pt3Sn/C and SnUPD modified Pt/C than between Pt3Ru2/C and RuUPD modified Pt/C is caused by electronic effect in Pt3Sn/C. High activity of Pt3Sn/C modified with small amount of SnUPD (≈10% can be explained by combining the electronic effect, causing less strongly bonded adsorbate on Pt sites and easier mobility of SnUPD, with enhanced amount of oxygen-containing species on Sn sites resulting finally in reinforcement of bifunctional mechanism.

  16. Treatment of partial seizures and seizure-like activity with felbamate in six dogs.

    Science.gov (United States)

    Ruehlmann, D; Podell, M; March, P

    2001-08-01

    Six dogs with partial seizures or partial seizure-like activity were treated with the antiepileptic drug felbamate between 1993 and 1998. All dogs had a history and results of diagnostic testing suggestive of either primary (idiopathic) or occult secondary epilepsy. Dogs ranged between four months and eight years of age at the onset of seizure activity. The median time period between onset of the first seizure and the start of felbamate therapy was 3.8 months (range 0.75 to 36 months). Median duration of therapy was nine months (range two to 22 months). All dogs experienced a reduction in seizure frequency after felbamate administration. Median total number of seizures post-treatment was two (range 0 to 9). Two dogs had an immediate and prolonged cessation of seizure activity. Steady-state trough serum felbamate concentrations measured at two weeks, and one, 12 and 22 months after the commencement of therapy in four dogs ranged between 13 and 55 mg/litre (median 35 mg/litre). Reversible haematological adverse effects were detected in two dogs, with one dog developing concurrent keratoconjunctivitis sicca. These results suggest that felbamate can be an effective antiepileptic drug without life-threatening complications when used as monotherapy for partial seizures in the dog.

  17. Studies of surface processes of electrocatalytic reduction of CO2 on Pt(210), Pt(310) and Pt(510)

    Institute of Scientific and Technical Information of China (English)

    FAN; ChunJie; FAN; YouJun; ZHEN; ChunHua; ZHENG; QingWei; SUN; ShiGang

    2007-01-01

    Surface processes of CO2 reduction on Pt(210), Pt(310), and Pt(510) electrodes were studied by cyclic voltammetry. Different surface structures of these platinum single crystal electrodes were obtained by various treatment conditions. The experimental results illustrated that the electrocatalytic activity of Pt single crystal electrodes towards CO2 reduction is decreased in an order of Pt(210)>Pt(310)>Pt(510), i.e., with the decrease of (110) step density on well-defined surfaces. When the surfaces were reconstructed due to oxygen adsorption, the catalytic activity of all the three electrodes has been enhanced to a certain extent. Although the activity order remains unchanged, the electrocatalytic activity has been enhanced more significantly as the density of (110) step sites is more intensive on the Pt single crystal surface. It has revealed that the more open the surface structure is, the more active the Pt single crystal electrode will be, and the easier for the electrode to be transformed into a surface structure that exhibits higher activity under external inductions. However, the relatively ordered surfaces of Pt single crystal electrode are comparatively stable under the same external inductions. The present study has gained knowledge on the interaction between CO2 and Pt single crystal electrode surfaces at a microscopic level, and thrown new insight into understanding the surface processes of electrocatalytic reduction of CO2.

  18. Active oxygen by Ce–Pr mixed oxide nanoparticles outperform diesel soot combustion Pt catalysts

    OpenAIRE

    Guillén Hurtado, Noelia; Garcia-Garcia, Avelina; Bueno López, Agustín

    2015-01-01

    A Ce0.5Pr0.5O2 mixed oxide has been prepared with the highest surface area and smallest particle size ever reported (125 m2/g and 7 nm, respectively), also being the most active diesel soot combustion catalyst ever tested under realistic conditions if catalysts forming highly volatile species are ruled out. This Ce–Pr mixed oxide is even more active than a reference platinum-based commercial catalyst. This study provides an example of the efficient participation of oxygen species released by ...

  19. Partial Agonist and Antagonist Activities of a Mutant Scorpion β-Toxin on Sodium Channels*

    Science.gov (United States)

    Karbat, Izhar; Ilan, Nitza; Zhang, Joel Z.; Cohen, Lior; Kahn, Roy; Benveniste, Morris; Scheuer, Todd; Catterall, William A.; Gordon, Dalia; Gurevitz, Michael

    2010-01-01

    Scorpion β-toxin 4 from Centruroides suffusus suffusus (Css4) enhances the activation of voltage-gated sodium channels through a voltage sensor trapping mechanism by binding the activated state of the voltage sensor in domain II and stabilizing it in its activated conformation. Here we describe the antagonist and partial agonist properties of a mutant derivative of this toxin. Substitution of seven different amino acid residues for Glu15 in Css4 yielded toxin derivatives with both increased and decreased affinities for binding to neurotoxin receptor site 4 on sodium channels. Css4E15R is unique among this set of mutants in that it retained nearly normal binding affinity but lost its functional activity for modification of sodium channel gating in our standard electrophysiological assay for voltage sensor trapping. More detailed analysis of the functional effects of Css4E15R revealed weak voltage sensor trapping activity, which was very rapidly reversed upon repolarization and therefore was not observed in our standard assay of toxin effects. This partial agonist activity of Css4E15R is observed clearly in voltage sensor trapping assays with brief (5 ms) repolarization between the conditioning prepulse and the test pulse. The effects of Css4E15R are fit well by a three-step model of toxin action involving concentration-dependent toxin binding to its receptor site followed by depolarization-dependent activation of the voltage sensor and subsequent voltage sensor trapping. Because it is a partial agonist with much reduced efficacy for voltage sensor trapping, Css4E15R can antagonize the effects of wild-type Css4 on sodium channel activation and can prevent paralysis by Css4 when injected into mice. Our results define the first partial agonist and antagonist activities for scorpion toxins and open new avenues of research toward better understanding of the structure-function relationships for toxin action on sodium channel voltage sensors and toward potential toxin

  20. Partial agonist and antagonist activities of a mutant scorpion beta-toxin on sodium channels.

    Science.gov (United States)

    Karbat, Izhar; Ilan, Nitza; Zhang, Joel Z; Cohen, Lior; Kahn, Roy; Benveniste, Morris; Scheuer, Todd; Catterall, William A; Gordon, Dalia; Gurevitz, Michael

    2010-10-01

    Scorpion β-toxin 4 from Centruroides suffusus suffusus (Css4) enhances the activation of voltage-gated sodium channels through a voltage sensor trapping mechanism by binding the activated state of the voltage sensor in domain II and stabilizing it in its activated conformation. Here we describe the antagonist and partial agonist properties of a mutant derivative of this toxin. Substitution of seven different amino acid residues for Glu(15) in Css4 yielded toxin derivatives with both increased and decreased affinities for binding to neurotoxin receptor site 4 on sodium channels. Css4(E15R) is unique among this set of mutants in that it retained nearly normal binding affinity but lost its functional activity for modification of sodium channel gating in our standard electrophysiological assay for voltage sensor trapping. More detailed analysis of the functional effects of Css4(E15R) revealed weak voltage sensor trapping activity, which was very rapidly reversed upon repolarization and therefore was not observed in our standard assay of toxin effects. This partial agonist activity of Css4(E15R) is observed clearly in voltage sensor trapping assays with brief (5 ms) repolarization between the conditioning prepulse and the test pulse. The effects of Css4(E15R) are fit well by a three-step model of toxin action involving concentration-dependent toxin binding to its receptor site followed by depolarization-dependent activation of the voltage sensor and subsequent voltage sensor trapping. Because it is a partial agonist with much reduced efficacy for voltage sensor trapping, Css4(E15R) can antagonize the effects of wild-type Css4 on sodium channel activation and can prevent paralysis by Css4 when injected into mice. Our results define the first partial agonist and antagonist activities for scorpion toxins and open new avenues of research toward better understanding of the structure-function relationships for toxin action on sodium channel voltage sensors and toward

  1. Influence of different carbon nanostructures on the electrocatalytic activity and stability of Pt supported electrocatalysts

    DEFF Research Database (Denmark)

    Stamatin, Serban Nicolae; Borghei, Maryam; Andersen, Shuang Ma;

    2014-01-01

    Commercially available graphitized carbon nanofibers and multi-walled carbon nanotubes, two carbon materials with very different structure, have been functionalized in a nitric–sulfuric acid mixture. Further on, the materials have been platinized by a microwave assisted polyol method. The relative...... that the functionalization improves the stability for multi-walled carbon nanotubes, at the cost of decreased activity....

  2. One-pot synthesis of Pd@PtNi core-shell nanoflowers supported on the multi-walled carbon nanotubes with boosting activity toward oxygen reduction in alkaline electrolyte

    Science.gov (United States)

    Liu, Sa; Wang, Yan; Liu, Liwen; Li, Mengli; Lv, Wenjie; Zhao, Xinsheng; Qin, Zhenglong; Zhu, Ping; Wang, Guoxiang; Long, Zhouyang; Huang, Fangmin

    2017-10-01

    Pt-based nanocrystals with controlled morphologies and structures are one of most promising electrocatalysts for oxygen reduction reaction (ORR). Herein, a facile one-pot wet-chemical method is developed to synthesize Pd@PtNi core-shell nanoflowers (CSNFs) supported on the multi-walled carbon nanotubes (MWNCTs). Brij 58 is demonstrated as a structure-directing agent to generate the nanoflower and ascorbic acid acts as a reductant to form a core-shell structure. By tuning the molar ratio of Pd and Pt, Pd@PtNi/MWCNTs CSNFs show obviously improved ORR activity and durability in alkaline electrolyte compared with PtNi/MWCNTs nanoflowers and commercial Pt/C. The results illustrate that the core-shell structure and porous feature of nanoflower are both beneficial to the enhancement of the catalytic properties.

  3. Extraction and partial purification of coagulation active components from common bean seed

    Directory of Open Access Journals (Sweden)

    Šćiban Marina B.

    2006-01-01

    Full Text Available An active coagulation component was extracted from common bean seed by NaCl solution and the obtained crude extract was partially purified through a sequence of steps that included precipitation of protein by ammonium sulphate, desalting by dialysis and anion exchange. A turbid water was treated by protein fractions obtained in the anion- exchange elution process by stepwise increase in NaCl concentration. The jar tests were conducted at various dosages of eluates. Different mode of relation between coagulation activity and applied coagulant dose for each protein fraction indicated the existence of different mechanisms of coagulation/flocculation, depending of characteristics of different proteins in the fractions.

  4. Aqueous solution synthesis of Pt-M (M = Fe, Co, Ni) bimetallic nanoparticles and their catalysis for the hydrolytic dehydrogenation of ammonia borane.

    Science.gov (United States)

    Wang, Shuai; Zhang, Duo; Ma, Yanyun; Zhang, Hui; Gao, Jing; Nie, Yuting; Sun, Xuhui

    2014-08-13

    Platinum-based bimetallic nanocatalysts have attracted much attention due to their high-efficiency catalytic performance in energy-related applications such as fuel cell and hydrogen storage, for example, the hydrolytic dehydrogenation of ammonia borane (AB). In this work, a simple and green method has been demonstrated to successfully prepare Pt-M (M = Fe, Co, Ni) NPs with tunable composition (nominal Pt/M atomic ratios of 4:1, 1:1, and 1:4) in aqueous solution under mild conditions. All Pt-M NPs with a small size of 3-5 nm show a Pt fcc structure, suggesting the bimetallic formation (alloy and/or partial core-shell), examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) analysis. The catalytic activities of Pt-M NPs in the hydrolytic dehydrogenation of AB reveal that Pt-Ni NPs with a ratio of 4:1 show the best catalytic activity and even better than that of pure Pt NPs when normalized to Pt molar amount. The Ni oxidation state in Pt-Ni NPs has been suggested to be responsible for the corresponding catalytic activity for hydrolytic dehydrogenation of AB by XAFS study. This strategy for the synthesis of Pt-M NPs is simple and environmentally benign in aqueous solution with the potential for scale-up preparation and the in situ catalytic reaction.

  5. Electrocatalytic Activity and Durability of Pt-Decorated Non-Covalently Functionalized Graphitic Structures

    Directory of Open Access Journals (Sweden)

    Emanuela Negro

    2015-09-01

    Full Text Available Carbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA and, subsequently, platinum nanoparticles were nucleated on the surface following procedures found in previous studies. Non-covalent functionalization has been proven to be advantageous because it allows for a better control of particle size and monodispersity, it prevents particle agglomeration since particles are bonded to the surface, and it does not affect the chemical and physical resistance of the support. Synthesized electrocatalysts were characterized by electrochemical half-cell studies, in order to evaluate the Electrochemically Active Surface Area (ECSA, ORR activity, and durability to potential cycling and corrosion resistance.

  6. Active acoustic leak detection for LMFBR steam generators. Pt. 7. Potential for small leak detection

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Hiromichi; Yoshida, Kazuo [Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.

    1998-05-01

    In order to prevent the expansion of tube damage and to maintain structural integrity in the steam generators (SGs) of fast breeder reactors (FBR), it is necessary to detect precisely and immediately the leakage of water from heat transfer tubes. Therefore, an active acoustic method, which detects the sound attenuation due to bubbles generated in the sodium-water reactions, is being developed. Previous studies have revealed that the active acoustic method can detect bubbles of 10 l/s (equivalence water leak rate about 10 g/s) within 10 seconds in practical steam generators. In order to prevent the expansion of damage to neighboring tubes, however, it is necessary to detect smaller leakage of water from heat transfer tubes. In this study, in order to evaluate the detection sensitivity of the active method, the signal processing methods for emitter and receiver sound and the detection method for leakage within 1 g/s are investigated experimentally, using an SG full-sector model that simulates the actual SGs. A typical result shows that detection of 0.4 l/s air bubbles (equivalent water leak rate about 0.4 g/s) takes about 80 seconds, which is shorter than the propagation time of damage to neighboring tubes. (author)

  7. Heterogeneous catalysts need not be so "heterogeneous": monodisperse Pt nanocrystals by combining shape-controlled synthesis and purification by colloidal recrystallization.

    Science.gov (United States)

    Kang, Yijin; Li, Meng; Cai, Yun; Cargnello, Matteo; Diaz, Rosa E; Gordon, Thomas R; Wieder, Noah L; Adzic, Radoslav R; Gorte, Raymond J; Stach, Eric A; Murray, Christopher B

    2013-02-20

    Well-defined surfaces of Pt have been extensively studied for various catalytic processes. However, industrial catalysts are mostly composed of fine particles (e.g., nanocrystals), due to the desire for a high surface to volume ratio. Therefore, it is very important to explore and understand the catalytic processes both at nanoscale and on extended surfaces. In this report, a general synthetic method is described to prepare Pt nanocrystals with various morphologies. The synthesized Pt nanocrystals are further purified by exploiting the "self-cleaning" effect which results from the "colloidal recrystallization" of Pt supercrystals. The resulting high-purity nanocrystals enable the direct comparison of the reactivity of the {111} and {100} facets for important catalytic reactions. With these high-purity Pt nanocrystals, we have made several observations: Pt octahedra show higher poisoning tolerance in the electrooxidation of formic acid than Pt cubes; the oxidation of CO on Pt nanocrystals is structure insensitive when the partial pressure ratio p(O2)/p(CO) is close to or less than 0.5, while it is structure sensitive in the O(2)-rich environment; Pt octahedra have a lower activation energy than Pt cubes when catalyzing the electron transfer reaction between hexacyanoferrate (III) and thiosulfate ions. Through electrocatalysis, gas-phase-catalysis of CO oxidation, and a liquid-phase-catalysis of electron transfer reaction, we demonstrate that high quality Pt nanocrystals which have {111} and {100} facets selectively expose are ideal model materials to study catalysis at nanoscale.

  8. Dendrimer Templated Synthesis of One Nanometer Rh and Pt Particles Supported on Mesoporous Silica: Catalytic Activity for Ethylene and Pyrrole Hydrogenation.

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Wenyu; Kuhn, John N.; Tsung, Chia-Kuang; Zhang, Yawen; Habas, Susan E.; Yang, Peidong; Somorjai, Gabor A.

    2008-05-09

    Monodisperse rhodium (Rh) and platinum (Pt) nanoparticles as small as {approx}1 nm were synthesized within a fourth generation polyaminoamide (PAMAM) dendrimer, a hyperbranched polymer, in aqueous solution and immobilized by depositing onto a high-surface-area SBA-15 mesoporous support. X-ray photoelectron spectroscopy indicated that the as-synthesized Rh and Pt nanoparticles were mostly oxidized. Catalytic activity of the SBA-15 supported Rh and Pt nanoparticles was studied with ethylene hydrogenation at 273 and 293 K in 10 torr of ethylene and 100 torr of H{sub 2} after reduction (76 torr of H{sub 2} mixed with 690 torr of He) at different temperatures. Catalysts were active without removing the dendrimer capping but reached their highest activity after hydrogen reduction at a moderate temperature (423 K). When treated at a higher temperature (473, 573, and 673 K) in hydrogen, catalytic activity decreased. By using the same treatment that led to maximum ethylene hydrogenation activity, catalytic activity was also evaluated for pyrrole hydrogenation.

  9. Interfacial Engineering of Bimetallic Ag/Pt Nanoparticles on Reduced Graphene Oxide Matrix for Enhanced Antimicrobial Activity.

    Science.gov (United States)

    Zhang, Mei; Zhao, Yanhua; Yan, Li; Peltier, Raoul; Hui, Wenli; Yao, Xi; Cui, Yali; Chen, Xianfeng; Sun, Hongyan; Wang, Zuankai

    2016-04-06

    Environmental biofouling caused by the formation of biofilm has been one of the most urgent global concerns. Silver nanoparticles (NPs), owing to their wide-spectrum antimicrobial property, have been widely explored to combat biofilm, but their extensive use has raised growing concern because they persist in the environment. Here we report a novel hybrid nanocomposite that imparts enhanced antimicrobial activity and low cytotoxicity yet with the advantage of reduced silver loading. The nanocomposite consists of Pt/Ag bimetallic NPs (BNPs) decorated on the porous reduced graphene oxide (rGO) nanosheets. We demonstrate that the enhanced antimicrobial property against Escherichia coli is ascribed to the intricate control of the interfaces between metal compositions, rGO matrix, and bacteria, where the BNPs lead to a rapid release of silver ions, and the trapping of bacteria by the porous rGO matrix further provides high concentration silver ion sites for efficient bacteria-bactericide interaction. We envision that our facile approach significantly expands the design space for the creation of silver-based antimicrobial materials to achieve a wide spectrum of functionalities.

  10. Longterm Performance Trends Analysis and ManagingExpectation for Active Value1 (Case Study: PT Indocement Tunggal Prakarsa, Tbk

    Directory of Open Access Journals (Sweden)

    Perdana Wahyu Santosa

    2010-01-01

    Full Text Available This research used financial ratio and managing expectations for active value about performance of PT IndocementTunggal Prakarsa, Tbk (INTP as one of largest cement company with a strong brand image at Indonesia Stock Exchange (IDX. Unlike traditional corporate-performance metric, this study use growth value of matrix. INTP is well placed to meet Indonesia’s growing per capita of cement consumption. The financial data sources for this research are the audited annual reports of INTP2002-2008. The analysis focused on compounds annual growth rate (CAGR,  profitability, total assets turnover, cost of capital, market value added & market risk and market perception map. This research also used growth value matrix to analysis the market perception of INTP in 2008 that combined current performance with future growth opportunity. The result of market perception mapping for 2008-2009 shows that INTP was just on market average of current performance index but the future growth opportunity was above the market average level. The conclusion explains that INTP has very good long-term fundamental performance’s trend and the company is indicated has strong capabilityto be excellent value manager in the future.

  11. Non-covalent interactions in water electrolysis: influence on the activity of Pt(111) and iridium oxide catalysts in acidic media.

    Science.gov (United States)

    Ganassin, Alberto; Colic, Viktor; Tymoczko, Jakub; Bandarenka, Aliaksandr S; Schuhmann, Wolfgang

    2015-04-07

    Electrolyte components, which are typically not considered to be directly involved in catalytic processes at solid-liquid electrified interfaces, often demonstrate a significant or even drastic influence on the activity, stability and selectivity of electrocatalysts. While there has been certain progress in the understanding of these electrolyte effects, lack of experimental data for various important systems frequently complicates the rational design of new active materials. Modern proton-exchange membrane (PEM) electrolyzers utilize Pt- and Ir-based electrocatalysts, which are among the very few materials that are both active and stable under the extreme conditions of water splitting. We use model Pt(111) and Ir-oxide films grown on Ir(111) electrodes and explore the effect of alkali metal cations and sulfate-anions on the hydrogen evolution and the oxygen evolution reactions in acidic media. We demonstrate that sulfate anions decrease the activity of Ir-oxide towards the oxygen evolution reaction while Rb(+) drastically promotes hydrogen evolution reaction at the Pt(111) electrodes as compared to the reference HClO4 electrolytes. Issues related to the activity benchmarking for these catalysts are discussed.

  12. Tuning the activity of nanoplatelet MoS2-based catalyst for efficient hydrogen evolution via electrochemical decoration with Pt nanoparticles

    Science.gov (United States)

    Jagminas, Arunas; Naujokaitis, Arnas; Žalnėravičius, Rokas; Jasulaitiene, Vitalija; Valušis, Gintaras

    2016-11-01

    This study establishes a novel methodology for increasing the HER activity of the molybdenum substrate covered with amorphous molybdenum sulfide-oxide nano-structured film up to ultra-high level. We show that utilization of such nanoplatelet/nanoflowered film as electrocatalyst for HER in the sulfuric acidic solution cell with Pt anode and Ag/AgCl,KCl reference leads to obvious structural transformations and nice decoration of nanoplatelet edges with few-nm sized Pt nanoparticles. By this way, a surprising HER efficiency attaining ∼160 mA cm-2 current density at -200 mV and ∼260 mA cm-2 at -300 mV vs RHE overpotentials with the onset of reaction close to the one carried out at the bulk Pt electrode was obtained. To the best of our knowledge, these HER characteristics are among the best reported to date for hybrid MoS2-based HER electrocatalysts. The results obtained were confirmed by SEM, XPS, XRD, conductive mode AFM and cyclic voltammetry. It is worth noticing that to achieve this synergetic effect only about 0.5 μg cm-2 of Pt is required.

  13. Preparation of Highly Active Pt-K/γ-AI203 Catalyst for 0-Phenylphenol Synthesis from 0-Cyclohexenyl-cyclohexanone Dehydrogenation

    Institute of Scientific and Technical Information of China (English)

    DING Jie-lian; LIN Ling; XU Jian-dong; ZENG Chong-yu

    2008-01-01

    0.5%Pt-K/y-Al2O3 catalysts for the synthesis of 0-phenylphenol(OPP) from 0-cyclohexenyl-cyciohexanone (dimer) dehydrogenation were prepared by means of a two subsequent impregnation method.The effects of catalyst preparation parameters,such as K promoters,calcination,and reduction conditions,were investigated.The results showed that the addition of K2SO4 to Pt/y-Al2O3 catalyst notably promoted the selectivity of OPP,and its optimum content was found to be 6% in mass fraction.The higher activity was obtained when Pt/y-Al2O3 catalyst was calcined in nitrogen atmosphere at 400-500℃ and then reduced at the same temperature for 3 h in hydrogen atmosphere.The conversion of the dimer and the selectivity of OPP were always above 99% and 90%,respectively,over 0.5%Pt-6% K2SO4/γ-Al2O3 catalyst during the pilot scale test of 8000 h.

  14. 75 FR 51754 - Certain Activated Carbon from the People's Republic of China: Notice of Partial Rescission of...

    Science.gov (United States)

    2010-08-23

    ... Activated Carbon from the People's Republic of China: Notice of Partial Rescission of Antidumping Duty... of initiation of an administrative review of the antidumping duty order on certain activated carbon... Activated Carbon Plant; Datong Forward Activated Carbon Co., Ltd.; Datong Guanghua Activated Carbon Co.,...

  15. Differential electrochemical mass spectrometry study of Pt and PtSn nanocatalysts for direct ethanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Saidani, F.; Bommersbach, P.; Guay, D.; Mohamedi, M. [Quebec Univ., Institut National de la Recherche Scientifique, Varennes, PQ (Canada). Centre de l' Energie, Materiaux et Telecommunications; Rochefort, D. [Montreal Univ., PQ (Canada). Dept. of Chemistry

    2008-07-01

    This paper reported on a study that investigated Platinum (Pt) and Pt with tin (Sn) nanoparticles prepared under vacuum and under 2 Torr of He by pulsed laser ablation. This method was chosen because it is possible to control size of nanoparticles, structure and morphology of films by varying deposition conditions. The influence of deposition conditions on the electrocatalytic behaviour was determined. In particular, the objective of the study was to better understand the reaction mechanism involved during ethanol oxidation at Pt and PtSn catalysts by means of cyclic voltammetry combined with Differential Electrochemical Mass Spectrometry (DEMS), a powerful technique to elucidate the Ethanol Oxidation Reaction (EOR) mechanism. Ethanol was shown to be a very attractive liquid biofuel for direct-fuelled systems, since its partial oxidation products are less toxic than other alcohols. During pulsed laser ablation, the interaction between an intense laser and a target material resulted in the creation of plasma. This plasma enabled the transfer of matter from the target to the substrate. Highly nanocrystalline films can be prepared when deposition is performed into a moderate pressure gas. The electrochemical investigations showed that Pt deposited under 2 torr have a beneficial effect on the electrocatalytic activity towards ethanol oxidation. 5 refs., 1 fig.

  16. Sequential thrombosis and bleeding in a woman with a prolonged activated partial thromboplastin time

    Directory of Open Access Journals (Sweden)

    Pearce Michael I

    2011-10-01

    Full Text Available Abstract Simultaneous or sequential haemorrhage and thrombosis in the presence of a prolonged activated partial thromboplastin time (aPTT is a rare occurrence: we describe the case a 37 year old lady who developed post-delivery deep vein thrombosis treated with low molecular heparin and warfarin followed a week later by extensive bruising over legs and forearms, a significant drop in haemoglobin and a very prolonged aPTT. Further tests revealed an acquired factor VIII inhibitor at 35 Bethesda Units. We discuss the clinical and laboratory implications and provide a literature review of simultaneous thrombophilia and haemophilia in the presence of a prolonged aPTT.

  17. Increased 99mTc-MDP Activity in a Partially Calcified Malignant Mediastinal Teratoma.

    Science.gov (United States)

    Li, Wei; Zhang, Linqi; Zhang, Rusen

    2016-02-01

    A 41-year-old woman presented with cough and shortness of breath for 3 weeks. Chest x-ray and CT showed a large, partially calcified soft tissue mass adjacent to the right side of the heart. Whole-body bone was acquired to evaluate possible metastases, which showed abnormal accumulation of Tc-MDP in the right chest. Further SPECT/CT imaging that demonstrated intense Tc-MDP activity was mainly in the calcification portion of mass. Histopathological examination from biopsy specimen of the lesion was consistent with malignant teratoma.

  18. Unraveling the photoelectrochemical properties of ionic liquids: cognizance of partially reversible redox activity.

    Science.gov (United States)

    Patel, Dipal B; Chauhan, Khushbu R; Mukhopadhyay, Indrajit

    2014-11-01

    Ionic liquid based electrolytes are gaining great interest in the field of photoenergy conversion. We have found that the ionic liquids namely BMIm Cl, BMIm PF6 and BMIm Tf2N inherently offer redox activity. The device performance of the photoelectrochemical (PEC) cells of the configuration PbOx (0.25 cm(2))|blank ionic liquids|platinum (2 cm(2)) was analyzed in detail to get insights into the working principle of such systems. It was found that partially reversible redox ion pairs diminish the performance of such cells as power generating devices. The partial redox activity of the ionic liquids was confirmed by a number of observations derived from the PEC spectra. The important parameter, Vredox, which determines the performance of any PEC cell was also calculated for all the ionic liquids. The difficulties that arise in high frequency C-V measurements for ionic liquid systems were overcome by choosing the appropriate probing frequency. The evaluated Vredox of BMIm Cl, BMIm PF6 and BMIm Tf2N ionic liquids was found to be -0.30, -0.20 and -0.78 V (vs. NHE), respectively. This study will be beneficial to understand the role of ionic liquids as redox active electrolyte media in several applications.

  19. Influence of CeO2 morphology on the catalytic activity of CeO2-Pt hybrids for CO oxidation.

    Science.gov (United States)

    Singhania, Nisha; Anumol, E A; Ravishankar, N; Madras, Giridhar

    2013-11-21

    Ceria, because of its excellent redox behavior and oxygen storage capacity, is used as a catalyst for several technologically important reactions. In the present study, different morphologies of nano-CeO2 (rods, cubes, octahedra) were synthesized using the hydrothermal route. An ultrafast microwave-assisted method was used to efficiently attach Pt particles to the CeO2 polyhedra. These nanohybrids were tested as catalysts for the CO oxidation reaction. The CeO2/Pt catalyst with nanorods as the support was found to be the most active catalyst. XPS and IR spectroscopy measurements were carried out in order to obtain a mechanistic understanding and it was observed that the adsorbed carbonates with lower stability on the reactive planes of nanorods and cubes are the major contributor to this enhanced catalytic activity.

  20. Electrodeposited Pt and Pt-Sn nanoparticles on Ti as anodes for direct methanol fuel cells

    Institute of Scientific and Technical Information of China (English)

    Hanaa B HASSAN

    2009-01-01

    Electro-oxidation of methanol was studied on titanium supported nanocrystallite Pt and Ptx-Sny catalysts prepared by electrodeposition techniques. Their electro-catalytic activities were studied in 0.5mol/L H2SO4 and compared to those of a smooth Pt, Pt/Pt and Pt-Sn/Pt electrodes. Platinum was deposited on Ti by galvanostatic and potentiostatic techniques. X-ray diffractometer (XRD) and energy dispersive X-ray (EDX) techniques were applied in order to investigate the chemical composition and the phase structure of the modified electrodes. Scanning electron microscopy (SEM) was used to characterize the surface morphology and to correlate the results obtained from the two electrochemical deposition methods. Results show that modified Pt/Ti electrodes prepared by the two methods have comparable performance and enhanced catalytic activity towards methanol electro-oxidation compared to Pt/Pt and smooth Pt electrodes. Steady state Tafel plots experiments show a higher rate of methanol oxidation on a Pt/Ti catalyst than that on a smooth Pt. Introduction of a small amount of Sn deposited with Pt improves the catalytic activity and the stability of prepared electrode with time as indicated from the cyclic votlammetry and the chronoamperometric experiments. The effect of variations in the composition for binary catalysts of the type Ptx-Sny/Ti towards the methanol oxidation reaction is reported. Consequently, the Ptx-Sny/Ti (x∶y (8∶1), molar ratio) catalyst is a very promising one for methanol oxidation.

  1. Disrupted NF-κB activation after partial hepatectomy does not impair hepatocyte proliferation in rats

    Institute of Scientific and Technical Information of China (English)

    Stéphanie Laurent; Yves Horsmans; Peter St(a)rkel; Isabelle Leclercq; Christine Sempoux; Luc Lambotte

    2005-01-01

    AIM: To analyze the effects of NF-κB inhibition by antioxidant pyrrolidine dithiocarbamate (PDTC) or TNF inhibitor pentoxifylline (PTX) on liver regeneration after partial hepatectomy (PH).METHODS: Saline, PDTC or PTX were injected 1 h before PH and rats were killed at 0.5 and 24 h after PH. Several control groups were used for comparison (injection control groups).RESULTS: Compared to saline injected controls, NF-κB activation was absent 0.5 h after PH in rats treated with PDTC or PTX. At 24 h after PH, DNA synthesis and PCNA expression were identical in treated and control rats and thus occurred irrespectively of the status of NF-κB activation at 0.5 h. Signal transducer and activator of transcription 3 (Stat3) activation was observed already 0.5 h after PH in saline, PDTC or PTX group and was similar to Stat3 activation in response to injection without PH.CONCLUSION: These data strongly suggest that (1)NF-κB p65/p50 DNA binding produced in response to PH is not a signal necessary to initiate the liver regeneration,(2) Stat3 activation is a stress response unrelated to the activation of NF-κB. In conclusion, NF-κB activation is not critically required for the process of liver regeneration after PH.

  2. 甲醇在不同结构氧化钨-Pt/C催化剂上的电催化氧化行为%Compared Study of Catalytic Activity for Methanol Oxidation on Different Pt-WO3/C Electrodes

    Institute of Scientific and Technical Information of China (English)

    闫鹏; 徐英明; 赵辉; 霍丽华; 高山

    2011-01-01

    Tungsten oxide-based nano-materials with two different crystal structures were prepared by hydrothermal method and characterized by X-ray diffraction ( XRD) and electron probe micro analyzer (EPMA) , respectively. The electrocatalytic activity for methanol oxidation on Pt-WO3/C electrode was studied by cyclic voltammetry. The results indicate that the electrocatalytic activity of Pt-WO3/C is much higher than that of Pt/C catalyst. For various amount of WO3, the catalyst with 20% mass fraction of WO3 has the best electrocatalytic activity. The electrocatalytic activity of the pyrochlore type tungsten oxide doped Pt/C electrode is higher than that of the tungsten bronze doped electrode, which is likely due to the strong attractions of OH^ on the surface of pyrochlore type tungsten oxide. The current density of the pyrochlore type tungsten oxide doped Pt/C electrode for electro-oxidation of methanol is 87. 2 x 10 "3 A/cm2 in 0. 5 mol/L CH30H + 1 mol/L H2SO4 solution.%采用水热法合成2种氧化钨( WO3)纳米材料,并利用XRD和电子探针显微分析仪(EPMA)进行了表征.利用循环伏安法研究了Pt-WO3/C电极对甲醇氧化的电催化活性.结果表明,Pt-WO#C催化剂对甲醇氧化的电催化活性优于Pt/C催化剂,且氧化钨质量分数为20%的Pt-氧化钨/C催化效果最好.与青铜相氧化钨掺杂的Pt/C电极比较,掺杂焦绿石型氧化钨的Pt/C电极催化性能有很大提高,这是由于焦绿石型氧化钨表面具有较多OH..质量分数20%的Pt-焦绿石型氧化钨/C在0.5mol/LCH3OH+1 mol/L H2SO4溶液中对甲醇氧化的峰电流密度达到87.2×10-3 A/cm2.

  3. Complexes of Pd(II) and Pt(II) with 9-Aminoacridine: Reactions with DNA and Study of Their Antiproliferative Activity

    Science.gov (United States)

    Riera, X.; Moreno, V.; Ciudad, C. J.; Noe, V.; Font-Bardía, M.; Solans, X.

    2007-01-01

    Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin. PMID:18364995

  4. Medium chain fatty acids are selective peroxisome proliferator activated receptor (PPAR γ activators and pan-PPAR partial agonists.

    Directory of Open Access Journals (Sweden)

    Marcelo Vizoná Liberato

    Full Text Available Thiazolidinediones (TZDs act through peroxisome proliferator activated receptor (PPAR γ to increase insulin sensitivity in type 2 diabetes (T2DM, but deleterious effects of these ligands mean that selective modulators with improved clinical profiles are needed. We obtained a crystal structure of PPARγ ligand binding domain (LBD and found that the ligand binding pocket (LBP is occupied by bacterial medium chain fatty acids (MCFAs. We verified that MCFAs (C8-C10 bind the PPARγ LBD in vitro and showed that they are low-potency partial agonists that display assay-specific actions relative to TZDs; they act as very weak partial agonists in transfections with PPARγ LBD, stronger partial agonists with full length PPARγ and exhibit full blockade of PPARγ phosphorylation by cyclin-dependent kinase 5 (cdk5, linked to reversal of adipose tissue insulin resistance. MCFAs that bind PPARγ also antagonize TZD-dependent adipogenesis in vitro. X-ray structure B-factor analysis and molecular dynamics (MD simulations suggest that MCFAs weakly stabilize C-terminal activation helix (H 12 relative to TZDs and this effect is highly dependent on chain length. By contrast, MCFAs preferentially stabilize the H2-H3/β-sheet region and the helix (H 11-H12 loop relative to TZDs and we propose that MCFA assay-specific actions are linked to their unique binding mode and suggest that it may be possible to identify selective PPARγ modulators with useful clinical profiles among natural products.

  5. Bridge-bonded formate: active intermediate or spectator species in formic acid oxidation on a Pt film electrode?

    Science.gov (United States)

    Chen, Y-X; Heinen, M; Jusys, Z; Behm, R J

    2006-12-01

    We present and discuss the results of an in situ IR study on the mechanism and kinetics of formic acid oxidation on a Pt film/Si electrode, performed in an attenuated total reflection (ATR) flow cell configuration under controlled mass transport conditions, which specifically aimed at elucidating the role of the adsorbed bridge-bonded formates in this reaction. Potentiodynamic measurements show a complex interplay between formation and desorption/oxidation of COad and formate species and the total Faradaic current. The notably faster increase of the Faradaic current compared to the coverage of bridge-bonded formate in transient measurements at constant potential, but with different formic acid concentrations, reveals that adsorbed formate decomposition is not rate-limiting in the dominant reaction pathway. If being reactive intermediate at all, the contribution of formate adsorption/decomposition to the reaction current decreases with increasing formic acid concentration, accounting for at most 15% for 0.2 M DCOOH at 0.7 VRHE. The rapid build-up/removal of the formate adlayer and its similarity with acetate or (bi-)sulfate adsorption/desorption indicate that the formate adlayer coverage is dominated by a fast dynamic adsorption-desorption equilibrium with the electrolyte, and that formate desorption is much faster than its decomposition. The results corroborate the proposal of a triple pathway reaction mechanism including an indirect pathway, a formate pathway, and a dominant direct pathway, as presented previously (Chen, Y. X.; et al. Angew. Chem. Int. Ed. 2006, 45, 981), in which adsorbed formates act as a site-blocking spectator in the dominant pathway rather than as an active intermediate.

  6. Partial characterization of peroxidase and polyphenol oxidase activities in blackberry fruits.

    Science.gov (United States)

    González, E M; de Ancos, B; Cano, M P

    2000-11-01

    A partial characterization of peroxidase (POD) and polyphenol oxidase (PPO) activities in blackberry fruits is described. Two cultivars of blackberry (Wild and Thornless) were analyzed for POD and PPO activities. Stable and highly active POD and PPO extracts were obtained using insoluble poly(vinylpyrrolidone) and Triton X-100 in 0.05 M sodium phosphate, pH 7.5, buffer. Blackberry POD and PPO activities have a pH optimum of 6.5, in a reaction mixture of 0.2 M sodium phosphate. Optimal POD activity was found with 3% o-dianisidine. Maximum PPO activity was found with catechol (catecholase activity) followed by 4-methylcatechol. Polyacrylamide gel electrophoresis of blackberry extracts under non-denaturing conditions resolved in various bands. In the POD extracts of Wild fruits, there was only one band with a mobility of 0.12. In the Thornless POD extracts there were three well-resolved bands, with R(f) values of 0.63, 0.36, and 0.09. Both the Wild and Thornless blackberry cultivars produced a single band of PPO, with R(f) values of 0.1 for Wild and 0.06 for Thornless.

  7. The Use of C-MnO2 as Hybrid Precursor Support for a Pt/C-MnxO1+x Catalyst with Enhanced Activity for the Methanol Oxidation Reaction (MOR

    Directory of Open Access Journals (Sweden)

    Alessandro H.A. Monteverde Videla

    2015-07-01

    Full Text Available Platinum (Pt nanoparticles are deposited on a hybrid support (C-MnO2 according to a polyol method. The home-made catalyst, resulted as Pt/C-MnxO1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C. The synthesized catalyst is characterized by means of FESEM, XRD, ICP-MS, XPS and μRS analyses. MnO2 is synthesized and deposited over a commercial grade of carbon (Vulcan XC72 by facile reduction of potassium permanganate in acidic solution. Pt nanoparticles are synthesized on the hybrid support by a polyol thermal assisted method (microwave irradiation, followed by an annealing at 600 °C. The obtained catalyst displays a support constituted by a mixture of manganese oxides (Mn2O3 and Mn3O4 with a Pt loading of 19 wt. %. The electro-catalytic activity towards MOR is assessed by RDE in acid conditions (0.5 M H2SO4, evaluating the ability to oxidize methanol in 1 M concentration. The synthesized Pt/C-MnxO1+x catalyst shows good activity as well as good stability compared to the commercial Pt/C based catalyst.

  8. Amorphous Pt@PdCu/CNT Catalyst for Methanol Electrooxidation ...

    African Journals Online (AJOL)

    A multi-walled carbon nanotube-supported, Pt decorated nano-sized ... alloy cores (denoted as Pt@PdCu/CNT) catalyst with lower Pt loading is synthesized via a ... The electrochemical activity of the Pt@PdCu/CNT catalyst is tested by cyclic ...

  9. Antibacterial activity of rhizome of curcuma aromatica and partial purification of active compounds

    OpenAIRE

    S. Revathi; Malathy, N.S.

    2013-01-01

    The hexane extract of Curcuma aromatica, a plant belonging to the family Zingiberaceae was tested on 10 bacterial strains (clinical isolates and standard strains). Agar diffusion method was adopted for determining the antibacterial activity of the extract. The hexane extract was found to be active against all Gram-positive strains tested, but inactive against Gram-negative strains. The minimum inhibitory concentration and minimum bactericidal concentration were determined and found to be 539 ...

  10. Aggregate size and architecture determine biomass activity for one-stage partial nitritation and anammox

    DEFF Research Database (Denmark)

    Vlaeminck, S.; Terada, Akihiko; Smets, Barth F.

    2010-01-01

    In partial nitritation/anammox systems, aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB) remove ammonium from wastewater. In this process, large granular microbial aggregates enhance the performance, but little is known about this type of granulation so far. In this study......, aggregates of three reactors (A, B, C) with different inoculation and operation were studied. The test objectives were to quantify the AerAOB and AnAOB abundance and the activity balance for the different aggregate sizes, and to relate aggregate morphology, size distribution, and architecture putatively...... to the inoculation and operation of the reactors. Fluorescent in-situ hybridization (FISH) was applied on aggregate sections to quantify AerAOB and AnAOB, as well as to visualize the aggregate architecture. The activity balance of the aggregates was calculated as the nitrite accumulation rate ratio (NARR), i...

  11. The functionalities of Pt/{gamma}-Al{sub 2}O{sub 3} catalysts in simultaneous HDS and HDA reactions

    Energy Technology Data Exchange (ETDEWEB)

    V.G. Baldovino-Medrano; Sonia A. Giraldo; Aristobulo Centeno [Universidad Industrial de Santander (UIS), Bucaramanga (Colombia). Centro de Investigaciones en Catalisis (CICAT)

    2008-08-15

    A Pt/{gamma}-Al{sub 2}O{sub 3} catalyst was tested in simultaneous hydrodesulfurization (HDS) of dibenzothiophene and hydrodearomatization (HDA) of naphthalene reactions. Samples of it were subjected to different pretreatments: reduction, reduction-sulfidation, sulfidation with pure H{sub 2}S and non-activation. The reduced catalyst presented the best performance, even comparable to that of Co(Ni)Mo catalysts. All catalyst samples were selective to the HDS reaction over HDA, and to the direct desulfurization pathway of dibenzothiophene HDS over the hydrogenation reaction pathway of HDS. The effect of H{sub 2}S partial pressure on the functionalities of the reduced Pt/{gamma}-Al{sub 2}O{sub 3} catalyst was studied. The results showed that an increase in H{sub 2}S partial pressure does not cause poisoning, but an inhibition effect, without changing the catalyst selectivity. Accordingly, the activity trends were ascribed to adsorption differences between the different reactive molecules over the same catalytic active site. TPR characterization along with a thermodynamics analysis showed that the active phase of reduced Pt/{gamma}-Al{sub 2}O{sub 3} is constituted by Pt{sup 0} particles. However, presulfidation of the catalyst leads to a mixture of PtS and Pt{sup 0}which has a negative effect on the catalytic performance without changing catalyst functionalities. 61 refs., 4 figs., 1 tab.

  12. 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

    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...

  13. Activation of propane C-H and C-C bonds by gas-phase Pt atom: a theoretical study

    National Research Council Canada - National Science Library

    Li, Fang-Ming; Yang, Hua-Qing; Ju, Ting-Yong; Li, Xiang-Yuan; Hu, Chang-Wei

    2012-01-01

    The reaction mechanism of the gas-phase Pt atom with C(3)H(8) has been systematically investigated on the singlet and triplet potential energy surfaces at CCSD(T)//BPW91/6-311++G(d, p), Lanl2dz level...

  14. Synthesis of carbon supported ordered tetragonal pseudo-ternary Pt 2 M'M'' (M = Fe, Co, Ni) nanoparticles and their activity for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Minh T.; Wakabayashi, Ryo H.; Yang, Minghui; Abruña, Héctor D.; DiSalvo, Francis J.

    2015-04-01

    Alloying Pt with 3d transition metals has attracted much attention due to their reduced Pt content and reports of enhanced electrocatalytic activity for proton exchange membrane fuel cell applications. However, synthesizing ordered nanocrystalline intermetallics in the sub-10 nm range can be challenging. Here, we report on the co-reduction synthesis of ordered ternary Pt-base transition metal intermetallics with particle sizes in the regime of 3–5 nm. Since differences in the activity of PtM (M = Fe, Co, Ni) for oxygen reduction reaction (ORR) have been reported, we explored their combinations: Pt2FeCo, Pt2FeNi, and Pt2CoNi. These ternary intermetallic nanoparticles crystallized in P4/mmm space group upon annealing in a protective KCl matrix. The electrocatalysts were prepared by dispersing these intermetallics onto a carbon support using ethylene glycol and various sonication techniques. A combination of analytical techniques including powder X-ray diffraction, thermogravimetric analysis, electron microscopy and electrochemical methods have been used in this study. The oxygen reduction reaction activity and stability of the catalysts were tested in 0.1 M HClO4 and 0.1 M H2SO4 using cyclic voltammetry and rotating disk electrode voltammetry. The correlations between the composition, structure, morphology and activity of the intermetallics have been established and are discussed.

  15. Selective and regular localization of accessible Pt nanoparticles inside the walls of an ordered silica: Application as a highly active and well-defined heterogeneous catalyst for propene and styrene hydrogenation reactions

    KAUST Repository

    Boualleg, Malika

    2011-12-01

    We describe here an original methodology related to the "build-the-bottle-around-the-ship" approach yielding a highly ordered silica matrix containing regularly distributed Pt nanoparticles (NPs) located inside the silica walls, Pt@{walls}SiO2. The starting colloidal solution of crystalline Pt nanoparticles was obtained from Pt(dba)2 (dba = dibenzylidene acetone) and 3-chloropropylsilane. The resulting nanoparticles (diameter: 2.0 ± 0.4 nm determined by HRTEM) resulted hydrophilic. The NPs present in the THF colloidal solution were incorporated inside the walls of a highly ordered 2D hexagonal mesoporous silica matrix via sol-gel process using a templating route with tetraethylorthosilicate, TEOS, as the silica source, and block copolymer (EthyleneOxide) 20(PropyleneOxide)70(EthyleneOxide)20 (Pluronic P123) as the structure-directing agent. Low-temperature calcination of the crude material at 593 K led to the final solid Pt@{walls}SiO2. Characterization by IR, HRTEM, BF-STEM and HAADF-STEM, SAXS, WAXS, XRD, XPS, H2 chemisorption, etc. of Pt@{walls}SiO2 confirmed the 2D hexagonal structuration and high mesoporosity (870 m2/g) of the material as well as the presence of stable 2-nm-sized crystalline Pt(0) NPs embedded inside the walls of the silica matrix. The material displayed no tendency to NPs sintering or leaching (Pt loading 0.3 wt.%) during its preparation. Pt@{walls}SiO2 was found to be a stable, selective and highly active hydrogenation catalyst. The catalytic performances in propene hydrogenation were tested under chemical regime conditions in a tubular flow reactor (278 K, propene/H2/He = 20/16/1.09 cm3/min, P tot = 1 bar) and were found superior to those of an homologous solid containing Pt NPs along its pore channels Pt@{pores}SiO2 and to those of a classical industrial catalysts Pt/Al2O3, (TOF = 2.3 s-1 vs. TOF = 0.90 and 0.92 s-1, respectively, calculated per surface platinum atoms). Pt@{walls}SiO2 also catalyzes fast and selective styrene

  16. Triterpenoids isolated from apple peels have potent antiproliferative activity and may be partially responsible for apple's anticancer activity.

    Science.gov (United States)

    He, Xiangjiu; Liu, Rui Hai

    2007-05-30

    Bioactivity-guided fractionation of apple peels was used to determine the chemical identity of bioactive constituents. Thirteen triterpenoids were isolated, and their chemical structures were identified. Antiproliferative activities of the triterpenoids against human HepG2 liver cancer cells, MCF-7 breast cancer cells, and Caco-2 colon cancer cells were evaluated. Most of the triterpenoids showed high potential anticancer activities against the three human cancer cell lines. Among the compounds isolated, 2alpha-hydroxyursolic acid, 2alpha-hydroxy-3beta-{[(2E)-3-phenyl-1-oxo-2-propenyl]oxy}olean-12-en-28-oic acid, and 3beta-trans-p-coumaroyloxy-2alpha-hydroxyolean-12-en-28-oic acid showed higher antiproliferative activity toward HepG2 cancer cells. Ursolic acid, 2alpha-hydroxyursolic acid, and 3beta-trans-p-coumaroyloxy-2alpha-hydroxyolean-12-en-28-oic acid exhibited higher antiproliferative activity against MCF-7 cancer cells. All triterpenoids tested showed antiproliferative activity against Caco-2 cancer cells, especially 2alpha-hydroxyursolic acid, maslinic acid, 2alpha-hydroxy-3beta-{[(2E)-3-phenyl-1-oxo-2-propenyl]oxy}olean-12-en-28-oic acid, and 3beta-trans-p-coumaroyloxy-2alpha-hydroxyolean-12-en-28-oic acid, which displayed much higher antiproliferative activities. These results showed the triterpenoids isolated from apple peels have potent antiproliferative activity and may be partially responsible for the anticancer activities of whole apples.

  17. Influence of bismuth on the structure and activity of Pt and Pd nanocatalysts for the direct electrooxidation of NaBH{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Simoes, Mario; Baranton, Steve [Laboratoire de Catalyse en Chimie Organique, Equipe Electrocatalyse, UMR 6503 CNRS, 40 avenue du recteur Pineau, F-86022 Poitiers Cedex (France); Coutanceau, Christophe, E-mail: christophe.coutanceau@univ-poitiers.f [Laboratoire de Catalyse en Chimie Organique, Equipe Electrocatalyse, UMR 6503 CNRS, 40 avenue du recteur Pineau, F-86022 Poitiers Cedex (France)

    2010-12-15

    In the past few years, borohydrides have gathered a lot of attention as an energy carrier for fuel cell application. Numerous investigations on both hydrogen generation and direct oxidation of NaBH{sub 4} have been published. Nonetheless, in our knowledge, only a few catalysts are capable to completely perform the direct oxidation of NaBH{sub 4} at low potentials without hydrogen evolution. In this work, carbon supported Pd{sub 1-x}Bi{sub x}/C and Pt{sub 1-x}Bi{sub x}/C nanocatalysts were synthesized by a 'water in oil' microemulsion method. The influence of surface modifications of Pt and Pd by Bi on the electrooxidation of sodium borohydride in alkaline media was evaluated. Physical and electrochemical methods were applied to characterize the structure and surface of the synthesized catalysts. It was verified that bismuth is present at the surface of the bimetallic catalysts and that hydrogen adsorption/desorption reactions are strongly limited on Pt and Pd surfaces with high bismuth coverage. Although the onset potential for NaBH{sub 4} oxidation on Pd{sub x}Bi{sub 1-x}/C catalysts is ca. 0.2 V higher than that for Pd/C, the presence of bismuth on palladium surface influences the reaction mechanism, limiting hydrogen evolution and oxidation in the case of Pd{sub 0.8}Bi{sub 0.2} catalyst. On Pt{sub 0.9}Bi{sub 0.1} catalyst the onset potential remains unchanged comparing to Pt/C and negligible hydrogen evolution was observed in the whole potential range where the catalyst is active. The number of exchanged electrons was calculated using the Koutecky-Levich equation and it was found that for Pt{sub 0.9}Bi{sub 0.1} catalyst, ca. 8 electrons are exchanged per BH{sub 4}{sup -} ion at low potentials. The presented results are remarkable evidencing that NaBH{sub 4} can be directly oxidized at low potentials with high energy efficiency.

  18. Cerebral blood flow during paroxysmal EEG activation induced by sleep in patients with complex partial seizures

    Energy Technology Data Exchange (ETDEWEB)

    Gozukirmizi, E.; Meyer, J.S.; Okabe, T.; Amano, T.; Mortel, K.; Karacan, I.

    1982-01-01

    Cerebral blood flow (CBF) measurements were combined with sleep polysomnography in nine patients with complex partial seizures. Two methods were used: the 133Xe method for measuring regional (rCBF) and the stable xenon CT method for local (LCBF). Compared to nonepileptic subjects, who show diffuse CBF decreases during stages I-II, non-REM sleep onset, patients with complex partial seizures show statistically significant increases in CBF which are maximal in regions where the EEG focus is localized and are predominantly seen in one temporal region but are also propagated to other cerebral areas. Both CBF methods gave comparable results, but greater statistical significance was achieved by stable xenon CT methodology. CBF increases are more diffuse than predicted by EEG paroxysmal activity recorded from scalp electrodes. An advantage of the 133Xe inhalation method was achievement of reliable data despite movement of the head. This was attributed to the use of a helmet which maintained the probes approximated to the scalp. Disadvantages were poor resolution (7 cm3) and two-dimensional information. The advantage of stable xenon CT method is excellent resolution (80 mm3) in three dimensions, but a disadvantage is that movement of the head in patients with seizure disorders may limit satisfactory measurements.

  19. Anticoagulant activity of native and partially degraded glycoglucuronomannan after chemical sulfation.

    Science.gov (United States)

    de Oliveira Barddal, Helyn Priscila; Gracher, Ana Helena Pereira; Simas-Tosin, Fernanda Fogagnoli; Iacomini, Marcello; Cipriani, Thales Ricardo

    2015-09-01

    Heparin has great clinical importance as anticoagulant and antithrombotic agent. However, because of its risks of causing bleeding and contamination by animal pathogens, several studies aim to obtain alternatives to heparin. In the search for anticoagulant and antithrombotic agents from a non-animal source, a glycoglucuronomannan from the gum exudate of the plant Vochysia thyrsoidea was partially hydrolyzed, and both native and partially degraded polysaccharides were chemically sulfated, yielding VThS and Ph-VThS respectively. Methylation analysis indicated that sulfation occurred preferentially at the O-5 position of arabinose units in the VThS and at the O-6 position of mannose units in Ph-VThS. In vitro aPTT assay showed that VThS and Ph-VThS have anticoagulant activity, which could be controlled by protamine, and ex vivo aPTT assay demonstrated that Ph-VThS is absorbed by subcutaneous route. Like heparin, they were able to inhibit α-thrombin and factor Xa by a serpin-dependent mechanism. In vivo, VThS and Ph-VThS reduced thrombus formation by approximately 50% at a dose of 40 IU/kg, similarly to heparin. The results demonstrated that the chemically sulfated polysaccharides are promising anticoagulant and antithrombotic agents.

  20. Engineering of Recombinant Poplar Deoxy-D-Xylulose-5-Phosphate Synthase (PtDXS) by Site-Directed Mutagenesis Improves Its Activity

    Science.gov (United States)

    Banerjee, Aparajita; Preiser, Alyssa L.

    2016-01-01

    Deoxyxylulose 5-phosphate synthase (DXS), a thiamine diphosphate (ThDP) dependent enzyme, plays a regulatory role in the methylerythritol 4-phosphate (MEP) pathway. Isopentenyl diphosphate (IDP) and dimethylallyl diphosphate (DMADP), the end products of this pathway, inhibit DXS by competing with ThDP. Feedback inhibition of DXS by IDP and DMADP constitutes a significant metabolic regulation of this pathway. The aim of this work was to experimentally test the effect of key residues of recombinant poplar DXS (PtDXS) in binding both ThDP and IDP. This work also described the engineering of PtDXS to improve the enzymatic activity by reducing its inhibition by IDP and DMADP. We have designed and tested modifications of PtDXS in an attempt to reduce inhibition by IDP. This could possibly be valuable by removing a feedback that limits the usefulness of the MEP pathway in biotechnological applications. Both ThDP and IDP use similar interactions for binding at the active site of the enzyme, however, ThDP being a larger molecule has more anchoring sites at the active site of the enzyme as compared to the inhibitors. A predicted enzyme structure was examined to find ligand-enzyme interactions, which are relatively more important for inhibitor-enzyme binding than ThDP-enzyme binding, followed by their modifications so that the binding of the inhibitors can be selectively affected compared to ThDP. Two alanine residues important for binding ThDP and the inhibitors were mutated to glycine. In two of the cases, both the IDP inhibition and the overall activity were increased. In another case, both the IDP inhibition and the overall activity were reduced. This provides proof of concept that it is possible to reduce the feedback from IDP on DXS activity. PMID:27548482

  1. Active vibration control of thin-plate structures with partial SCLD treatment

    Science.gov (United States)

    Lu, Jun; Wang, Pan; Zhan, Zhenfei

    2017-02-01

    To effectively suppress the low-frequency vibration of a thin-plate, the strategy adopted is to develop a model-based approach to the investigation on the active vibration control of a clamped-clamped plate with partial SCLD treatment. Firstly, a finite element model is developed based on the constitutive equations of elastic, piezoelectric and viscoelastic materials. The characteristics of viscoelastic materials varying with temperature and frequency are described by GHM damping model. A low-dimensional real modal control model which can be used as the basis for active vibration control is then obtained from the combined reduction. The emphasis is placed on the feedback control system to attenuate the vibration of plates with SCLD treatments. A modal controller in conjunction with modal state estimator is designed to solve the problem of full state feedback, making it much more feasible to real-time control. Finally, the theoretical model is verified by modal test, and an active vibration control is validated by hardware-in-the-loop experiment under different external excitations. The numerical and experimental study demonstrate how the piezoelectric actuators actively control the lower modes (first bending and torsional modes) using modal controller, while the higher frequency vibration attenuated by viscoelastic passive damping layer.

  2. Synthesis, structure and photocatalytic activity of nano TiO2 and nano Ti1-MO2- (M = Cu, Fe, Pt, Pd, V, W, Ce, Zr)

    Indian Academy of Sciences (India)

    M S Hegde; K Nagaveni; Sounak Roy

    2005-10-01

    We have synthesized 5-7 nm size, highly crystalline TiO2 which absorbs radiation in the visible region of solar spectrum. The material shows higher photocatalytic activity both in UV and visible region of the solar radiation compared to commercial Degussa P25 TiO2. Transition metal ion substitution for Ti4+ creates mid-gap states which act as recombination centers for electron{hole induced by photons thus reducing photocatalytic activity. However, Pt, Pd and Cu ion substituted TiO2 are excellent CO oxidation and NO reduction catalysts at temperatures less than 100°C.

  3. Partial least squares modeling and genetic algorithm optimization in quantitative structure-activity relationships.

    Science.gov (United States)

    Hasegawa, K; Funatsu, K

    2000-01-01

    Quantitative structure-activity relationship (QSAR) studies based on chemometric techniques are reviewed. Partial least squares (PLS) is introduced as a novel robust method to replace classical methods such as multiple linear regression (MLR). Advantages of PLS compared to MLR are illustrated with typical applications. Genetic algorithm (GA) is a novel optimization technique which can be used as a search engine in variable selection. A novel hybrid approach comprising GA and PLS for variable selection developed in our group (GAPLS) is described. The more advanced method for comparative molecular field analysis (CoMFA) modeling called GA-based region selection (GARGS) is described as well. Applications of GAPLS and GARGS to QSAR and 3D-QSAR problems are shown with some representative examples. GA can be hybridized with nonlinear modeling methods such as artificial neural networks (ANN) for providing useful tools in chemometric and QSAR.

  4. Synthesizing Pt nanoparticles in the presence of methylamine: Impact of acetic acid treatment in the electrocatalytic activity of formic acid oxidation

    Science.gov (United States)

    Ooi, M. D. Johan; Aziz, A. Abdul

    2017-05-01

    Surfactant removal from the surface of platinum nanoparticles prepared by solution based method is a prerequisite process to accomplish a high catalytic activity for electrochemical reactions. Here, we report a possible approach of combining acid acetic with thermal treatment for improving catalytic performance of formic acid oxidation. This strategy involves conversion of amine to amide in acetic acid followed by surfactant removal via subsequent thermal treatment at 85 °C. This combined activation technique produced monodisperse nanoparticle with the size of 3 to 5 nm with enhanced formic acid oxidation activity, particularly in perchloric acid solution. Pt treated in 1 h of acetic acid and heat treatment of 9 h shows high electrochemical surface area value (27.6 m2/g) compares to Pt without activation (16.6 m2/g). The treated samples also exhibit high current stability of 0.3 mA/cm2 compares to the as-prepared mA/cm2). Shorter duration of acid wash and longer duration of heating process result in high electrocatalytic activity. This work demonstrates a possible technique in improving catalytic activity of platinum nanoparticles synthesized using methylamine as surfactant.

  5. Carbon supported Pt-Y electrocatalysts for the oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Min Ku; McGinn, Paul J. [Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2011-02-01

    Carbon supported Pt{sub 3}Y (Pt{sub 3}Y/C) and PtY (PtY/C) were investigated as oxygen reduction reaction (ORR) catalysts. After synthesis via reduction by NaBH{sub 4}, the alloy catalysts exhibited 10-20% higher mass activity (mA mg{sub Pt}{sup -1}) than comparably synthesized Pt/C catalyst. The specific activity ({mu}A cm{sub Pt}{sup -2}) was 23 and 65% higher for the Pt{sub 3}Y/C and PtY/C catalysts, respectively, compared to Pt/C. After annealing at 900 C under a reducing atmosphere, Pt{sub 3}Y/C-900 and PtY/C-900 catalysts showed improved ORR activity; the Pt/C and Pt/C-900 (Pt/C catalyst annealed at 900 C) catalysts exhibited specific activities of 334 and 393 {mu}A cm{sub Pt}{sup -2}, respectively, while those of the Pt{sub 3}Y/C-900 and PtY/C-900 catalysts were 492 and 1050 {mu}A cm{sub Pt}{sup -2}, respectively. X-ray diffraction results revealed that both the Pt{sub 3}Y/C and PtY/C catalysts have a fcc Pt structure with slight Y doping. After annealing, XRD showed that more Y was incorporated into the Pt structure in the Pt{sub 3}Y/C-900 catalyst, while the PtY/C-900 catalyst remained unchanged. Although these results suggested that the high ORR activity of the PtY/C-900 catalyst did not originate from Pt-Y alloy formation, it is clear that the Pt-Y system is a promising ORR catalyst which merits further investigation. (author)

  6. Silicide induced surface defects in FePt nanoparticle fcc-to-fct thermally activated phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shu; Lee, Stephen L. [School of Physics and Astronomy, SUPA, University of St Andrews, St Andrews KY16 9SS (United Kingdom); André, Pascal, E-mail: pjpandre@riken.jp [School of Physics and Astronomy, SUPA, University of St Andrews, St Andrews KY16 9SS (United Kingdom); RIKEN, Wako 351-0198 (Japan); Department of Physics, CNRS-Ewha International Research Center (CERC), Ewha W. University, Seoul 120-750 (Korea, Republic of)

    2016-11-01

    Magnetic nanoparticles (MnPs) are relevant to a wide range of applications including high density information storage and magnetic resonance imaging to name but a few. Among the materials available to prepare MnPs, FePt is attracting growing attention. However, to harvest the strongest magnetic properties of FePt MnPs, a thermal annealing is often required to convert face-centered cubic as synthesized nPs into its tetragonal phase. Rarely addressed are the potential side effects of such treatments on the magnetic properties. In this study, we focus on the impact of silica shells often used in strategies aiming at overcoming MnP coalescence during the thermal annealing. While we show that this shell does prevent sintering, and that fcc-to-fct conversion does occur, we also reveal the formation of silicide, which can prevent the stronger magnetic properties of fct-FePt MnPs from being fully realised. This report therefore sheds lights on poorly investigated and understood interfacial phenomena occurring during the thermal annealing of MnPs and, by doing so, also highlights the benefits of developing new strategies to avoid silicide formation.

  7. Partial characterization and anticoagulant activity of a heterofucan from the brown seaweed Padina gymnospora.

    Science.gov (United States)

    Silva, T M A; Alves, L G; de Queiroz, K C S; Santos, M G L; Marques, C T; Chavante, S F; Rocha, H A O; Leite, E L

    2005-04-01

    The brown algae Padina gymnospora contain different fucans. Powdered algae were submitted to proteolysis with the proteolytic enzyme maxataze. The first extract of the algae was constituted of polysaccharides contaminated with lipids, phenols, etc. Fractionation of the fucans with increasing concentrations of acetone produced fractions with different proportions of fucose, xylose, uronic acid, galactose, and sulfate. One of the fractions, precipitated with 50% acetone (v/v), contained an 18-kDa heterofucan (PF1), which was further purified by gel-permeation chromatography on Sephadex G-75 using 0.2 M acetic acid as eluent and characterized by agarose gel electrophoresis in 0.05 M 1,3 diaminopropane/acetate buffer at pH 9.0, methylation and nuclear magnetic resonance spectroscopy. Structural analysis indicates that this fucan has a central core consisting mainly of 3-beta-D-glucuronic acid 1-> or 4-beta-D-glucuronic acid 1 ->, substituted at C-2 with alpha-L-fucose or beta-D-xylose. Sulfate groups were only detected at C-3 of 4-alpha-L-fucose 1-> units. The anticoagulant activity of the PF1 (only 2.5-fold lesser than low molecular weight heparin) estimated by activated partial thromboplastin time was completely abolished upon desulfation by solvolysis in dimethyl sulfoxide, indicating that 3-O-sulfation at C-3 of 4-alpha-L-fucose 1-> units is responsible for the anticoagulant activity of the polymer.

  8. Corticomuscular Activity Modeling by Combining Partial Least Squares and Canonical Correlation Analysis

    Directory of Open Access Journals (Sweden)

    Xun Chen

    2013-01-01

    Full Text Available Corticomuscular activity modeling based on multiple data sets such as electroencephalography (EEG and electromyography (EMG signals provides a useful tool for understanding human motor control systems. In this paper, we propose modeling corticomuscular activity by combining partial least squares (PLS and canonical correlation analysis (CCA. The proposed method takes advantage of both PLS and CCA to ensure that the extracted components are maximally correlated across two data sets and meanwhile can well explain the information within each data set. This complementary combination generalizes the statistical assumptions beyond both PLS and CCA methods. Simulations were performed to illustrate the performance of the proposed method. We also applied the proposed method to concurrent EEG and EMG data collected in a Parkinson’s disease (PD study. The results reveal several highly correlated temporal patterns between EEG and EMG signals and indicate meaningful corresponding spatial activation patterns. In PD subjects, enhanced connections between occipital region and other regions are noted, which is consistent with previous medical knowledge. The proposed framework is a promising technique for performing multisubject and bimodal data analysis.

  9. Partial characterization and anticoagulant activity of a heterofucan from the brown seaweed Padina gymnospora

    Directory of Open Access Journals (Sweden)

    Silva T.M.A.

    2005-01-01

    Full Text Available The brown algae Padina gymnospora contain different fucans. Powdered algae were submitted to proteolysis with the proteolytic enzyme maxataze. The first extract of the algae was constituted of polysaccharides contaminated with lipids, phenols, etc. Fractionation of the fucans with increasing concentrations of acetone produced fractions with different proportions of fucose, xylose, uronic acid, galactose, and sulfate. One of the fractions, precipitated with 50% acetone (v/v, contained an 18-kDa heterofucan (PF1, which was further purified by gel-permeation chromatography on Sephadex G-75 using 0.2 M acetic acid as eluent and characterized by agarose gel electrophoresis in 0.05 M 1,3 diaminopropane/acetate buffer at pH 9.0, methylation and nuclear magnetic resonance spectroscopy. Structural analysis indicates that this fucan has a central core consisting mainly of 3-ß-D-glucuronic acid 1-> or 4-ß-D-glucuronic acid 1 ->, substituted at C-2 with alpha-L-fucose or ß-D-xylose. Sulfate groups were only detected at C-3 of 4-alpha-L-fucose 1-> units. The anticoagulant activity of the PF1 (only 2.5-fold lesser than low molecular weight heparin estimated by activated partial thromboplastin time was completely abolished upon desulfation by solvolysis in dimethyl sulfoxide, indicating that 3-O-sulfation at C-3 of 4-alpha-L-fucose 1-> units is responsible for the anticoagulant activity of the polymer.

  10. Production of high specific activity (195m) Pt-cisplatinum at South African Nuclear Energy Corporation for Phase 0 clinical trials in healthy individual subjects.

    Science.gov (United States)

    Zeevaart, Jan Rijn; Wagener, Judith; Marjanovic-Painter, Biljana; Sathekge, Mike; Soni, Nischal; Zinn, Christa; Perkins, Gary; Smith, Suzanne V

    2013-01-01

    Platinum agents continue to be the main chemotherapeutic agents used in the first-line and second-line treatments of cancer patients. It is important to fully understand the biological profile of these compounds in order to optimize the dose given to each patient. In a joint project with the Australian Nuclear Science and Technology Organisation and the Nuclear Medicine Department at Steve Biko Academic Hospital, South African Nuclear Energy Corporation synthesized and supplied (195m) Pt-cisplatinum (commonly referred to as cisplatin) for a clinical pilot study on healthy volunteers. Enriched (194) PtCl2 was prepared by digestion of enriched (194) Pt metal (>95%) followed by thermal decomposition over a 3 h period. The (194) PtCl2 was then placed in a quartz ampoule, was irradiated in SAFARI-1 up to 200 h, then decay cooled for a minimum of 34 h prior to synthesis of final product. (195m) Pt(NH3 )2 I2 , formed with the addition of KI and NH4 OH, was converted to the diaqua species [(195m) Pt(NH3 )2 (H2 O)2 ](2+) by reaction with AgNO3 . The conversion to (195m) Pt-cisplatinum was completed by the addition of concentrated HCl. The final product yield was 51.7% ± 5.2% (n = 5). The chemical and radionuclidic purity in each case was >95%. The use of a high flux reactor position affords a higher specific activity product (15.9 ± 2.5 MBq/mg at end of synthesis) than previously found (5 MBq/mg). Volunteers received between 108 and 126 MBq of radioactivity, which is equivalent to 6.8-10.0 mg of carrier cisplatinum. Such high specific activities afforded a significant reduction (~50%) in the chemical dose of a carrier cisplatinum, which represents less than 10% of a typical chemotherapeutic dose given to patients. A good manufacturing practice GMP compliant product was produced and was administered to 10 healthy volunteers as part of an ethically approved Phase 0 clinical trial. The majority of the injected activity 27.5% ± 5.8% was excreted

  11. Isotherm-Based Thermodynamic Models for Solute Activities of Organic Acids with Consideration of Partial Dissociation.

    Science.gov (United States)

    Nandy, Lucy; Ohm, Peter B; Dutcher, Cari S

    2016-06-23

    Organic acids make up a significant fraction of the organic mass in atmospheric aerosol particles. The calculation of gas-liquid-solid equilibrium partitioning of the organic acid is therefore critical for accurate determination of atmospheric aerosol physicochemical properties and processes such as new particle formation and activation to cloud condensation nuclei. Previously, an adsorption isotherm-based statistical thermodynamic model was developed for capturing solute concentration-activity relationships for multicomponent aqueous solutions over the entire concentration range (Dutcher et al. J. Phys. Chem. C/A 2011, 2012, 2013), with model parameters for energies of adsorption successfully related to dipole-dipole electrostatic forces in solute-solvent and solvent-solvent interactions for both electrolytes and organics (Ohm et al. J. Phys. Chem. A 2015). However, careful attention is needed for weakly dissociating semivolatile organic acids. Dicarboxylic acids, such as malonic acid and glutaric acid are treated here as a mixture of nondissociated organic solute (HA) and dissociated solute (H(+) + A(-)). It was found that the apparent dissociation was greater than that predicted by known dissociation constants alone, emphasizing the effect of dissociation on osmotic and activity coefficient predictions. To avoid additional parametrization from the mixture approach, an expression was used to relate the Debye-Hückel hard-core collision diameter to the adjustable solute-solvent intermolecular distance. An improved reference state treatment for electrolyte-organic aqueous mixtures, such as that observed here with partial dissociation, has also been proposed. This work results in predictive correlations for estimation of organic acid and water activities for which there is little or no activity data.

  12. Adsorption and activation of methane and methanol on Pt(100) surface: a density functional study; Adsorption et activation du methane et du methanol sur la surface (100) du platine: une etude par la fonctionnelle de la densite

    Energy Technology Data Exchange (ETDEWEB)

    Moussounda, P.S

    2006-11-15

    The activation of methane (CH{sub 4}) and methanol (CH{sub 3}OH) on Pt(100) surface has been investigated using density functional theory calculations based on plane-wave basis and pseudo-potential. We optimised CH{sub 4}/Pt(100) system. The calculated adsorption energies over the top, bridge and hollow sites are small, weakly dependent on the molecular orientation. The nature of the CH{sub 4}-Pt interaction was examined through the electronic structure changes. The adsorption of methyl (CH{sub 3}) and hydrogen (H) and the co-adsorption of CH{sub 3}+H were also calculated. From these results, we examined the dissociation of CH{sub 4} to CH{sub 3}+H, and the activation energies found are in good agreement with the experimental and theoretical values. The activation of CH{sub 3}OH/Pt(100) has been studied. All the sites have almost the same adsorption energy. The adsorption of oxygen (O) and the co-adsorption of CH{sub 4} and O were also examined. In addition, the formation of CH{sub 3}OH assuming a one-step mechanism step via the co-adsorption of CH{sub 4}+O has been studied and the barrier height was found to be high. (authors)

  13. Site-selective Cu deposition on Pt dendrimer-encapsulated nanoparticles: correlation of theory and experiment.

    Science.gov (United States)

    Carino, Emily V; Kim, Hyun You; Henkelman, Graeme; Crooks, Richard M

    2012-03-07

    The voltammetry of Cu underpotential deposition (UPD) onto Pt dendrimer-encapsulated nanoparticles (DENs) containing an average of 147 Pt atoms (Pt(147)) is correlated to density functional theory (DFT) calculations. Specifically, the voltammetric peak positions are in good agreement with the calculated energies for Cu deposition and stripping on the Pt(100) and Pt(111) facets of the DENs. Partial Cu shells on Pt(147) are more stable on the Pt(100) facets, compared to the Pt(111) facets, and therefore, Cu UPD occurs on the 4-fold hollow sites of Pt(100) first. Finally, the structures of Pt DENs having full and partial monolayers of Cu were characterized in situ by X-ray absorption spectroscopy (XAS). The results of XAS studies are also in good agreement with the DFT-optimized models.

  14. 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.

  15. Rational design of orally-active, pyrrolidine-based progesterone receptor partial agonists

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Scott K.; Washburn, David G.; Frazee, James S.; Madauss, Kevin P.; Hoang, Tram H.; Lapinski, Leahann; Grygielko, Eugene T.; Glace, Lindsay E.; Trizna, Walter; Williams, Shawn P.; Duraiswami, Chaya; Bray, Jeffrey D.; Laping, Nicholas J.; (GSKNC); (GSKPA)

    2010-09-03

    Using the X-ray crystal structure of an amide-based progesterone receptor (PR) partial agonist bound to the PR ligand binding domain, a novel PR partial agonist class containing a pyrrolidine ring was designed. Members of this class of N-alkylpyrrolidines demonstrate potent and highly selective partial agonism of the progesterone receptor, and one of these analogs was shown to be efficacious upon oral dosing in the OVX rat model of estrogen opposition.

  16. Tetrahexahedral Pt Nanoparticles: Comparing the Oxygen Reduction Reaction under Transient vs Steady-State Conditions

    DEFF Research Database (Denmark)

    Deng, Yu-Jia; Wiberg, Gustav Karl Henrik; Zana, Alessandro

    2017-01-01

    -state conditions. As a benchmark, the ORR activity is compared with those of polycrystalline Pt and a commercial Pt/C catalyst. The results show that, under transient conditions, the catalytic performance of the THH Pt NPs and Pt/C are approximately the same and about 2 times lower than that of polycrystalline Pt....... However, under steady-state conditions the THH Pt NPs perform considerably better than Pt/C. Under steady-state conditions THH Pt NPs are even slightly more active than polycrystalline Pt...

  17. A comparative study of Pt and Pt-Pd core-shell nanocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Long, Nguyen Viet, E-mail: nguyenviet_long@yahoo.com [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Posts and Telecommunications Institute of Technology, km 10 Nguyen Trai, Thanh Xuan, Ha Dong, Hanoi (Viet Nam); Laboratory for Nanotechnology, Vietnam National University, Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakouen, Kasuga, Fukuoka 816-8580 (Japan); Ohtaki, Michitaka [Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakouen, Kasuga, Fukuoka 816-8580 (Japan); Hien, Tong Duy [Laboratory for Nanotechnology, Vietnam National University, Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Randy, Jalem [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nogami, Masayuki, E-mail: nogami@nitech.ac.jp [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2011-10-30

    Highlights: > The syntheses of Pt (4-8 nm) and Pt-Pd core-shell nanoparticles (15-25 nm) are showed. > Pt-Pd core-shell catalysts possess catalytic property much better than Pt catalysts. > Pt-Pd core-shell catalysts exhibit fast and highly stable catalytic activity. > Fascinatingly, size effect is not as really important as nanostructuring effect. > Fast, stable, sensitive hydrogen adsorption is very crucial for fuel cells. - Abstract: This comparative study characterizes two types of metallic and core-shell bimetallic nanoparticles prepared with our modified polyol method. These nanoparticles consist of Pt and Pt-Pd core-shell nanocatalysts exhibiting polyhedral morphologies. The controlled syntheses of Pt metallic nanoparticles in the 10-nm regime (4-8 nm) and Pt-Pd bimetallic core-shell nanoparticles in the 30-nm regime (15-25 nm) are presented. To realize our ultimate research goals for proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), we thoroughly investigate the dependence of the electrocatalytic properties of the nanoparticles on the structure, size and morphology. Significant differences in the electrocatalysis are also explained in experimental evidences of both Pt and Pt-Pd nanocatalysts. We suggested that the core-shell controlled morphologies and nanostructures of the Pd nanoshell as the Pd atomic monolayers will not only play an important role in producing inexpensive, novel Pt- and Pd-based nanocatalysts but also in designing more efficient Pt- and Pd-based nanocatalysts for practical use in DMFC technology. Our comparative results show that Pt-Pd nanocatalysts with Pd nanoshells exhibited much better electrocatalytic activity and stabilization compared to Pt nanocatalysts. Interestingly, we found that the size effect is not as strong as the nanostructuring effect on the catalytic properties of the researched nanoparticles. A nanostructure effect of the core-shell bimetallic nanoparticles was identified.

  18. Preparation of ternary Pt/Rh/SnO2 anode catalysts for use in direct ethanol fuel cells and their electrocatalytic activity for ethanol oxidation reaction

    Science.gov (United States)

    Higuchi, Eiji; Takase, Tomonori; Chiku, Masanobu; Inoue, Hiroshi

    2014-10-01

    Pt, Rh and SnO2 nanoparticle-loaded carbon black (Pt/Rh/SnO2/CB) catalysts with different contents of Pt and Rh were prepared by the modified Bönnemann method. The mean size and size distribution of Pt, Rh and SnO2 for Pt-71/Rh-4/SnO2/CB (Pt : Rh : Sn = 71 at.%: 4 at.%: 25 at.%) were 3.8 ± 0.7, 3.2 ± 0.7 and 2.6 ± 0.5 nm, respectively, indicating that Pt, Rh and SnO2 were all nanoparticles. The onset potential of ethanol oxidation current for the Pt-65/Rh-10/SnO2/CB and Pt-56/Rh-19/SnO2/CB electrodes was ca. 0.2 V vs. RHE which was ca. 0.2 V less positive than that for the Pt/CB electrode. The oxidation current at 0.6 V for the Pt/Rh/SnO2/CB electrode (ca. 2% h-1) decayed more slowly than that at the Pt/SnO2/CB electrode (ca. 5% h-1), indicating that the former was superior in durability to the latter. The main product of EOR in potentiostatic electrolysis at 0.6 V for the Pt-71/Rh-4/SnO2/CB electrode was acetic acid.

  19. GBF-dependent family genes morphologically suppress the partially active Dictyostelium STATa strain.

    Science.gov (United States)

    Shimada, Nao; Kanno-Tanabe, Naoko; Minemura, Kakeru; Kawata, Takefumi

    2008-02-01

    Transcription factor Dd-STATa, a functional Dictyostelium homologue of metazoan signal transducers and activators of transcription proteins, is necessary for culmination during development. We have isolated more than 18 putative multicopy suppressors of Dd-STATa using genetic screening. One was hssA gene, whose expression is known to be G-box-binding-factor-dependent and which was specific to prestalk A (pstA) cells, where Dd-STATa is activated. Also, hssA mRNA was expressed in pstA cells in the Dd-STATa-null mutant. At least 40 hssA-related genes are present in the genome and constitute a multigene family. The tagged HssA protein was translated; hssA encodes an unusually high-glycine-serine-rich small protein (8.37 kDa), which has strong homology to previously reported cyclic-adenosine-monophosphate-inducible 2C and 7E proteins. Overexpression of hssA mRNA as well as frame-shifted versions of hssA RNA suppressed the phenotype of the partially active Dd-STATa strain, suggesting that translation is not necessary for suppression. Although overexpression of prespore-specific genes among the family did not suppress the parental phenotype, prestalk-specific family members did. Although overexpression of the hssA did not revert the expression of Dd-STATa target genes, and although its suppression mechanism remains unknown, morphological reversion implies functional relationships between Dd-STATa and hssA.

  20. 1D-2D carbon heterostructure with low Pt loading as a superior cathode electrode for dye-sensitized solar cell

    Science.gov (United States)

    Nechiyil, Divya; Ramaprabhu, S.

    2017-02-01

    Cost-effective counter electrode (CE) with high electrocatalytic performance is very much essential for the wide application of dye-sensitized solar cells (DSSC). The 1D-2D carbon heterostructure (Pt/GR@CNT) with low platinum (Pt) loading has been synthesized by a facile in situ microwave-assisted polyol-reduction method. The excellent electrocatalytic activity as well as photovoltaic performance was achieved due to the combination of 2D graphene nanoribbons (GR) and 1D multi-walled carbon nanotubes (CNT) with high catalytically active Pt nanoparticles. Microwave-assisted longitudinal unzipping of few outer layers of CNTs along with co-reduction of Pt nanoparticles is an effective method to create electrochemically active defective edge sites, which have a crucial role in enhancing electrochemical performance. Synergistic effect of ultra-fine Pt nanoparticles, partially unzipped graphene nanoribbons and inner core tubes of CNTs modulates the power conversion efficiency of solar cell to 5.57% ± 0.03 as compared with 4.73% ± 0.13 of CNTs. Pt/GR@CNT CE even with low Pt loading of 14 μg cm-2 showcases equivalent performance with that of pure Pt counter electrode.

  1. Thymus derived inhibitor of lymphocyte proliferation : III—Partial purification and characteristic biological activity

    NARCIS (Netherlands)

    Rijke, E.O.; Ballieux, R.E.

    1980-01-01

    A crude factor isolated from bovine thymus was partially purified using ion exchange chromatography. The resulting fraction was tested for inhibitory properties towards the proliferation of various human and murine lymphoid cells in culture. It was found that this partially purified thymic factor (T

  2. 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 ( ...

  3. $\\mathcal{PT}$-symmetric mode-locking

    CERN Document Server

    Longhi, Stefano

    2016-01-01

    Parity-time ($\\mathcal{PT}$) symmetry is one of the most important accomplishments in optics over the past decade. Here the concept of $\\mathcal{PT}$ mode-locking of a laser is introduced, in which active phase locking of cavity axial modes is realized by asymmetric mode coupling in a complex time crystal. $\\mathcal{PT}$ mode-locking shows a transition from single to double pulse emission as the $\\mathcal{PT}$ symmetry breaking point is crossed. The transition can show a turbulent behavior, depending on a dimensionless modulation parameter that plays the same role as the Reynolds number in hydrodynamic flows.

  4. Influence of method of preparation of Pt Ru/C electrocatalysts on the catalytic activity for the ethanol oxidation reaction in acidic medium; Influencia do metodo de preparacao de eletrocatalisadores PtRu/C sobre a atividade catalitica frente a reacao de oxidacao de etanol em meio acido

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Walber dos Santos; Silva, Uriel Lean Valente; Souza, Jose Pio Iudice de, E-mail: jpio@ufpa.br [Universidade Federal do Para, (UFPA), Belem, PA (Brazil). Instituto de Ciencias Exatas e Naturais. Faculdade de Quimica

    2013-09-01

    In this work the influence of variations in the borohydrate reduction method on the properties of Pt Ru/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH{sub 4} to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that Pt Ru nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The Pt Ru/C electrocatalysts (50:1) obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation. (author)

  5. Simultaneous abrogation of NOS-2 and COX-2 activities is lethal in partially hepatectomised mice.

    Science.gov (United States)

    Zeini, Miriam; Hortelano, Sonsoles; Través, Paqui G; Martín-Sanz, Paloma; Boscá, Lisardo

    2004-06-01

    We have investigated the role of the nitric oxide (NO) and prostaglandins (PGs), respectively, synthesized by nitric oxide synthase 2 (NOS-2) and cyclooxygenase-2 (COX-2), in the outcome of liver regeneration after partial hepatectomy (PH). Liver mass recovery and molecular parameters related to cell proliferation and apoptotic death have been determined. NOS-2 and COX-2 are normally both expressed in the remnant liver after PH, and inhibition of either one delays regeneration. We found, however, that simultaneous suppression of the activities of NOS-2 (by gene knockout) and COX-2 (by pharmacological inhibition) resulted in animal death between 24 and 72 h after PH. Analysis of liver mass recovery and molecular parameters related to cell proliferation and apoptotic death revealed increased liver-cell apoptosis and an insufficient proliferative response. Broad-specificity caspase inhibitors, such as z-Val-Ala-Asp.fmk (z-VAD), or administration of NO-donors, rescued animals from death, revealing a critical apoptotic bias at this stage of proliferation. These findings demonstrate that simultaneous signaling by NO and prostaglandins plays an important role in the mechanism of liver regeneration after PH by protecting the remnant tissue from apoptotic death.

  6. Active vibration control by piezoceramic actuators on a jet aircraft partial frame structure

    Science.gov (United States)

    Lecce, Leonardo; Viscardi, Massimo; Cantoni, Stefania

    1996-04-01

    During the last five years, the Dept. of Aeronautical Engineering of the University of Naples, has carried out a lot of work, especially on the experimental side, focused on assessing the feasibility of an active vibration and noise control approach, based on the use of piezoceramic actuators and sensors bonded to different structural elements. This paper concerns an application of this technique relative to a partially curved stiff frame of a medium civil transport jet aircraft. The general procedure, as previously assessed on different test articles, requires as first step, the dynamic characterization of the test article, to best point out the target of control procedure in terms of deformed shapes relative to the frequency of most interest. The use of PZT piezoactuators to be bonded on the structure guarantee at the same time high actuators forces in front of a low weight increment. The hearth of the MIMO (Multi Input Multi Output) feedforward control algorithm that is usually applied, is then represented by an ANN (Artificial Neural Network) control algorithm that use the evaluation of experimental FRF as measured by reference accelerometer, to calculate the optimum control forces to be applied to the actuators to minimize a target cost function. Experimental results provided over 32 dB of overall vibration level reduction in a single controlled mode shape, without any spillover effect.

  7. Partial ozonation of activated sludge to reduce excess sludge, improve denitrification and control scumming and bulking

    Energy Technology Data Exchange (ETDEWEB)

    Boehler, Marc; Siegrist, Hansruedi

    2003-07-01

    Disposal of sewage sludge is forbidden and agricultural use of stabilized sludge will be banned in 2005 in Switzerland. The sludge has to be dewatered, dried, Incinerated and the ashes disposed in landfills. These processes are cost intensive and lead also to the loss of valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Partial ozonation of the return sludge of an activated sludge system reduces significantly excess sludge production, improves settling properties of the sludge and reduces bulking and scumming. The solubilized COD will also improve denitrification if the treated sludge is recycled to the anoxic zone. But ozonation will partly inhibit and kill nitrifiers and might therefore lead to a decrease of the effective solid retention time of the nitrifier, which reduces the safety of the nitrification. This paper discusses the effect of ozonation on sludge reduction, the operation stability of nitrification, improvement of denitrification and gives also an energy and cost evaluation. (author)

  8. High-performance core-shell PdPt@Pt/C catalysts via decorating PdPt alloy cores with Pt

    Science.gov (United States)

    Wu, Yan-Ni; Liao, Shi-Jun; Liang, Zhen-Xing; Yang, Li-Jun; Wang, Rong-Fang

    A core-shell structured low-Pt catalyst, PdPt@Pt/C, with high performance towards both methanol anodic oxidation and oxygen cathodic reduction, as well as in a single hydrogen/air fuel cell, is prepared by a novel two-step colloidal approach. For the anodic oxidation of methanol, the catalyst shows three times higher activity than commercial Tanaka 50 wt% Pt/C catalyst; furthermore, the ratio of forward current I f to backward current I b is high up to 1.04, whereas for general platinum catalysts the ratio is only ca. 0.70, indicating that this PdPt@Pt/C catalyst has high activity towards methanol anodic oxidation and good tolerance to the intermediates of methanol oxidation. The catalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The core-shell structure of the catalyst is revealed by XRD and TEM, and is also supported by underpotential deposition of hydrogen (UPDH). The high performance of the PdPt@Pt/C catalyst may make it a promising and competitive low-Pt catalyst for hydrogen fueled polymer electrolyte membrane fuel cell (PEMFC) or direct methanol fuel cell (DMFC) applications.

  9. Effects of partial decerebration and hypophyseal allograft in the thymus of chicken embryos: thymostimulin localization and enzymatic activities

    Directory of Open Access Journals (Sweden)

    M Aita

    2009-06-01

    Full Text Available Changes in chicken embryo thymus after partial decerebration (including the hypophysis and hypophyseal allograft were investigated. Chicken embryos were partially decerebrated at 36-40 hr of incubation and on day 12 received a hypophyseal allograft from 18-day-old donor embryos. The embryonic thymuses were collected on day 18 and examined with histological methods, tested for the anti-thymostimulin- like immune-reaction, and for histoenzymatic activities and compared with normal and sham-operated embryos at the same age. After partial decerebration, the thymic cortical and medullary compartments diminished markedly in size. Anti-thymostimulin, succinic dehydrogenase and ATPase enzymatic activities tested, yielded negative reactions. In partially decerebrated hypophyseal allografted embryos, the same thymic compartments improved and anti-thymostimulin-like immune-reaction and enzymatic activities partially recovered. These findings confirmed the key role of hypophysis in thymic ontogenic development and provided new information in metabolic enzymatic pathways and synthesis of a thymostimulin-like substance in the thymus

  10. Identification of PPARgamma partial agonists of natural origin (II: in silico prediction in natural extracts with known antidiabetic activity.

    Directory of Open Access Journals (Sweden)

    Laura Guasch

    Full Text Available BACKGROUND: Natural extracts have played an important role in the prevention and treatment of diseases and are important sources for drug discovery. However, to be effectively used in these processes, natural extracts must be characterized through the identification of their active compounds and their modes of action. METHODOLOGY/PRINCIPAL FINDINGS: From an initial set of 29,779 natural products that are annotated with their natural source and using a previously developed virtual screening procedure (carefully validated experimentally, we have predicted as potential peroxisome proliferators-activated receptor gamma (PPARγ partial agonists 12 molecules from 11 extracts known to have antidiabetic activity. Six of these molecules are similar to molecules with described antidiabetic activity but whose mechanism of action is unknown. Therefore, it is plausible that these 12 molecules could be the bioactive molecules responsible, at least in part, for the antidiabetic activity of the extracts containing them. In addition, we have also identified as potential PPARγ partial agonists 10 molecules from 16 plants with undescribed antidiabetic activity but that are related (i.e., they are from the same genus to plants with known antidiabetic properties. None of the 22 molecules that we predict as PPARγ partial agonists show chemical similarity with a group of 211 known PPARγ partial agonists obtained from the literature. CONCLUSIONS/SIGNIFICANCE: Our results provide a new hypothesis about the active molecules of natural extracts with antidiabetic properties and their mode of action. We also suggest plants with undescribed antidiabetic activity that may contain PPARγ partial agonists. These plants represent a new source of potential antidiabetic extracts. Consequently, our work opens the door to the discovery of new antidiabetic extracts and molecules that can be of use, for instance, in the design of new antidiabetic drugs or functional foods focused

  11. Haploinsufficiency of Def activates p53-dependent TGFβ signalling and causes scar formation after partial hepatectomy.

    Directory of Open Access Journals (Sweden)

    Zhihui Zhu

    Full Text Available The metazoan liver exhibits a remarkable capacity to regenerate lost liver mass without leaving a scar following partial hepatectomy (PH. Whilst previous studies have identified components of several different signaling pathways that are essential for activation of hepatocyte proliferation during liver regeneration, the mechanisms that enable such regeneration to occur without accompanying scar formation remain poorly understood. Here we use the adult zebrafish liver, which can regenerate within two weeks following PH, as a new genetic model to address this important question. We focus on the role of Digestive-organ-expansion-factor (Def, a nucleolar protein which has recently been shown to complex with calpain3 (Capn3 to mediate p53 degradation specifically in the nucleolus, in liver regeneration. Firstly, we show that Def expression is up-regulated in the wild-type liver following amputation, and that the defhi429/+ heteroozygous mutant (def+/- suffers from haploinsufficiency of Def in the liver. We then show that the expression of pro-inflammatory cytokines is up-regulated in the def+/- liver, which leads to distortion of the migration and the clearance of leukocytes after PH. Transforming growth factor β (TGFβ signalling is thus activated in the wound epidermis in def+/- due to a prolonged inflammatory response, which leads to fibrosis at the amputation site. Fibrotic scar formation in def+/- is blocked by the over-expression of Def, by the loss-of-function of p53, and by treatment with anti-inflammation drug dexamethasone or TGFβ-signalling inhibitor SB431542. We finally show that the Def- p53 pathway suppresses fibrotic scar formation, at least in part, through the regulation of the expression of the pro-inflammatory factor, high-mobility group box 1. We conclude that the novel Def- p53 nucleolar pathway functions specifically to prevent a scar formation at the amputation site in a normal amputated liver.

  12. Facile synthesis of polypyrrole functionalized nickel foam with catalytic activity comparable to Pt for the poly-generation of hydrogen and electricity

    Science.gov (United States)

    Tang, Tiantian; Li, Kan; Shen, Zhemin; Sun, Tonghua; Wang, Yalin; Jia, Jinping

    2016-01-01

    Polypyrrole functionalized nickel foam is facilely prepared through the potentiostatic electrodeposition. The PPy-functionalized Ni foam functions as a hydrogen-evolution cathode in a rotating disk photocatalytic fuel cell, in which hydrogen energy and electric power are generated by consuming organic wastes. The PPy-functionalized Ni foam cathode exhibits stable catalytic activities after thirteen continuous runs. Compared with net or plate structure, the Ni foam with a unique three-dimensional reticulate structure is conducive to the electrodeposition of PPy. Compared with Pt-group electrode, PPy-coated Ni foam shows a satisfactory catalytic performance for the H2 evolution. The combination of PPy and Ni forms a synergistic effect for the rapid trapping and removal of proton from solution and the catalytic reduction of proton to hydrogen. The PPy-functionalized Ni foam could be applied in photocatalytic and photoelectrochemical generation of H2. In all, we report a low cost, high efficient and earth abundant PPy-functionalized Ni foam with a satisfactory catalytic activities comparable to Pt for the practical application of poly-generation of hydrogen and electricity.

  13. AN ANIMAL MODEL OF PLATINUM (PT) HYPERSENSITIVITY

    Science.gov (United States)

    Exposure to Pt salts has been associated with occupational asthma. Pt, the most active component and widely used metal in catalytic converters, is released in automobile exhaust and is a proposed diesel fuel additive. Thus, with the potential for widespread environmental distrib...

  14. Hydrogen production for fuel cell by oxidative reforming of diesel surrogate: influence of ceria and/or lanthana over the activity of Pt/Al{sub 2}O{sub 3} catalysts

    Energy Technology Data Exchange (ETDEWEB)

    M.C. Alvarez-Galvan; R.M. Navarro; F. Rosa; Y. Briceno; M.A. Ridao; J.L.G. Fierro [Instituto de Catalisis y Petroleoquimica (CSIC), Madrid (Spain)

    2008-09-15

    A series of Pt catalysts supported on Al{sub 2}O{sub 3} (Pt/A), Al{sub 2}O{sub 3}-CeO{sub 2} (Pt/A-C), Al{sub 2}O{sub 3}-La{sub 2}O{sub 3} (Pt/A-L) and Al{sub 2}O{sub 3}-La{sub 2}O{sub 3}-CeO{sub 2} (Pt/A-L-C) have been prepared and tested in the oxidative reforming of diesel surrogate with the aim of studying the influence of ceria and lanthana additives over the activity and stability toward hydrogen production for fuel cell application. Several characterization techniques, such as adsorption-desorption of N{sub 2}, X-ray diffraction, X-ray photoelectron spectroscopy, temperature programmed reduction, H{sub 2} chemisorption, and thermogravimetric analysis, have been used to define textural, structural, and surface properties of catalysts and to establish relationships with their behaviour in reaction. This physicochemical characterization has shown that lanthana inhibits the formation of {alpha} phase in alumina support and decreases ceria dispersion. Activity results show a better performance of ceria-loaded catalysts, being the Pt/A-C sample the system that offers higher H{sub 2} yields after 8 h of reaction. The greater H{sub 2} production for ceria-loaded catalysts, particularly in the case of the system Pt/A-C, is attributed to the Pt-Ce interaction that may change the electronic properties and/or the dispersion of active metal phase. Also, the Ce{sup III} form of Ce{sup IV}/Ce{sup III} redox pair enhances the adsorption of oxygen and water molecules, thus increasing the catalytic activity and also decreasing coke deposition over surface active Pt phases. Stability tests showed that catalysts in which Pt crystallites are deposited on the alumina substrate covered by a lanthana monolayer, give rise to an increase in stability toward H{sub 2} production. 48 refs., 10 figs., 3 tabs.

  15. Pt-graphene electrodes for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Hoshi, Hajime, E-mail: hoshi@ed.tus.ac.jp; Tanaka, Shumpei; Miyoshi, Takashi

    2014-12-15

    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{sub 3}{sup −}/I{sup −}. • 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{sub 3}{sup −}/I{sup −} 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{sub 3}{sup −}/I{sup −} 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.

  16. 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...... clearly show that the active surface is dominated by Pt with a specific surface area above 45 m2 per gram of Pt. Interactions with the Au core increase the activity of the Pt shell by up to 55% and improve catalytic selectivity compared to pure Pt. The Au@Pt NPs show exciting catalytic activity...

  17. Premature temporal theta (PT theta).

    Science.gov (United States)

    Hughes, J R; Fino, J J; Hart, L A

    1987-07-01

    A distinctive pattern called premature temporal theta (PT theta) was studied in 436 infants, ranging in age from 24 to 46 weeks. The pattern is seen in early prematurity, maximizes at 29-31 weeks and then diminishes and disappears near term. Usually the pattern is found independently on both temporal areas, but with a right-sided preference. Patients without PT theta or with a significantly low amount had either neurological or non-neurological (medical) conditions. With age there is a tendency for an increase in frequency and a decrease in amplitude. Five different peaks in the amount of this pattern are seen at approximately every month. Unilateral PT theta tends to be seen in older babies, more often on the right side and with an abnormal EEG. An abnormal EEG is usually associated with a delay in both the appearance and disappearance of this wave form. PT theta is also associated mainly with REM or active sleep. A polynomial rather than an exponential or power function best describes these data with changes of age. PT theta may arise from the inferior temporal gyrus and/or especially the transverse gyrus.

  18. Differential pathway coupling efficiency of the activated insulin receptor drives signaling selectivity by xmeta, an allosteric partial agonist antibody

    Science.gov (United States)

    XMetA, an anti-insulin receptor (IR) monoclonal antibody, is an allosteric partial agonist of the IR. We have previously reported that XMetA activates the “metabolic-biased” Akt kinase signaling pathway while having little or no effect on the “mitogenic” MAPK signaling pathwayof ERK 1/2. To inves...

  19. Anticoagulant screening of marine algae from Mexico, and partial characterization of the active sulfated polysaccharide from Eisenia arborea

    OpenAIRE

    Muñoz Ochoa, Mauricio; Murillo-Álvarez, Jesús Iván; Rodríguez Montesinos, Yoloxochilt Elizabeth; Hernández Carmona, Gustavo; Arvizu Higuera, Dora Luz; Peralta Cruz, Javier;; Lizardi Mendoza, Jaime

    2009-01-01

    The in vitro anticoagulant activity of 41 water extracts of various seaweeds from Baja California Sur, Mexico was evaluated. In this study, nine extracts exhibited anticoagulant activity in the prothrombin time assay, and 29 extracts were active in the activated partial thromboplastin time assay. The water extract obtained at 25°C from the brown seaweed Eisenia arborea was the most active in both assays, increasing the normal blood clotting-time over 300 s at 100 mg mL-1. The fractionation of...

  20. Catalytic Performance of Activated Carbon Supported Pt-Ni Bimetallic Catalyst for Glycerol in situ Hydrogenolysis%活性炭负载Pt-Ni双金属催化剂上甘油水溶液原位加氢反应性能

    Institute of Scientific and Technical Information of China (English)

    孔丹旎; 江涛; 张一颖; 曹发海

    2016-01-01

    A series of activated carbon supported Pt-M( M=Fe, Ni, Co, Zn, Cu) bimetallic catalysts was prepared via KBH4 reduction method for glycerol in situ hydrogenolysis to produce 1, 2-propanediol. The results showed that Pt-Ni/AC catalyst with a Pt loading ( mass fraction ) of 2. 0% and a Pt/Ni mass ratio of 1:1 displayed excellent performance at 220℃ under 1. 0 MPa of N2 after 8 h reaction time, with a high selec-tivity of 60. 5% and a conversion of 98. 7%. In addition, the prepared Pt-Ni/AC had a good catalytic stabili-ty, which kept a high activity even after five cycles catalytic evaluation. The results from the characterization of catalysts by N2 physisorption, XRD, TEM and XPS indicated that nanoparticles with an average size of ca. 2 nm were uniformly dispersed on the support. And the majority of metals in nanoparticles are present in the zerovalent metallic state. The formation of Pt-Ni phase due to the incorporation of Ni in the Pt lattice was responsible for the strong interaction between Pt and Ni metal. The catalytic performance of Pt-Ni/AC was compared with that of Pt/AC and Ni/AC, it was clearly observed that Pt could promote the aqueous phase reforming of glycerol to hydrogen, and Ni could facilitate the hydrogenolysis of glycerol. The unique perfor-mance of Pt-Ni/AC bimetallic catalysts was attribute to the the synergistic effect between Pt and Ni.%采用KBH4液相还原法制备了系列活性炭( AC)负载的Pt-M( M=Fe, Ni, Co, Zn, Cu)双金属催化剂,考察了该系列催化剂对甘油水溶液原位加氢制备1,2-丙二醇反应的催化性能.结果表明,当Pt负载量(质量分数)为2.0%, Pt/Ni质量比为1:1时,在220℃和1.0 MPa氮气压力下反应8 h,2%Pt-2%Ni/AC催化剂上甘油转化率和1,2-丙二醇选择性分别达到98.7%和60.5%;且在5次重复使用过程中,催化剂保持较高的稳定性.采用氮气物理吸附-脱附实验、X 射线衍射( XRD)、透射电子显微镜( TEM)、选区电子衍射( SAED

  1. 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)

  2. 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)

  3. Antifactor Xa levels versus activated partial thromboplastin time for monitoring unfractionated heparin.

    Science.gov (United States)

    Vandiver, Jeremy W; Vondracek, Thomas G

    2012-06-01

    Intravenous unfractionated heparin (UFH) remains an important therapeutic agent, particularly in the inpatient setting, for anticoagulation. Historically, the activated partial thromboplastin time (aPTT) has been the primary laboratory test used to monitor and adjust UFH. The aPTT test has evolved since the 1950s, and the historical goal range of 1.5-2.5 times the control aPTT, which first gained favor in the 1970s, has fallen out of favor due to a high degree of variability in aPTT readings from one laboratory to another, and even from one reagent to another. As a result, it is now recommended that the aPTT goal range be based on a corresponding heparin concentration of 0.2-0.4 unit/ml by protamine titration or 0.3-0.7 unit/ml by antifactor Xa assay. Given that several biologic factors can influence the aPTT independent of the effects of UFH, many institutions have transitioned to monitoring heparin with antifactor Xa levels, rather than the aPTT. Clinical data from the last 10-20 years have begun to show that a conversion from aPTT to antifactor Xa monitoring may offer a smoother dose-response curve, such that levels remain more stable, requiring fewer blood samples and dosage adjustments. Given the minimal increased acquisition cost of the antifactor Xa reagents, it can be argued that the antifactor Xa is a cost-effective method for monitoring UFH. In this review, we discuss the relative advantages and disadvantages of the aPTT, antifactor Xa, and protamine titration tests, and provide a clinical framework to guide practitioners who are seeking to optimize UFH monitoring within their own institutions.

  4. Differences in neurohormonal activity partially explain the obesity paradox in patients with heart failure: The role of sympathetic activation.

    Science.gov (United States)

    Farré, Núria; Aranyó, Júlia; Enjuanes, Cristina; Verdú-Rotellar, José María; Ruiz, Sonia; Gonzalez-Robledo, Gina; Meroño, Oona; de Ramon, Marta; Moliner, Pedro; Bruguera, Jordi; Comin-Colet, Josep

    2015-02-15

    Obese patients with chronic Heart Failure (HF) have better outcome than their lean counterparts, although little is known about the pathophysiology of this obesity paradox. Our aim was to evaluate the hypothesis that patients with chronic HF and obesity (defined as body mass index (BMI)≥30kg/m(2)), may have an attenuated neurohormonal activation in comparison with non-obese patients. The present study is the post-hoc analysis of a cohort of 742 chronic HF patients from a single-center study evaluating sympathetic activation by measuring baseline levels of norepinephrine (NE). Obesity was present in 33% of patients. Higher BMI and obesity were significantly associated with lower NE levels in multivariable linear regression models adjusted for covariates (p70th percentile) carrying out a separate analysis in obese and non-obese patients we found that in both groups NE remained a significant independent predictor of poorer outcomes, despite the lower NE levels in patients with chronic HF and obesity: all-cause mortality hazard ratio=2.37 (95% confidence interval, 1.14-4.94) and hazard ratio=1.59 (95% confidence interval, 1.05-2.4) in obese and non-obese respectively; and cardiovascular mortality hazard ratio=3.08 (95% confidence interval, 1.05-9.01) in obese patients and hazard ratio=2.08 (95% confidence interval, 1.42-3.05) in non-obese patients. Patients with chronic HF and obesity have significantly lower sympathetic activation. This finding may partially explain the obesity paradox described in chronic HF patients. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  5. Electro-catalytic activity of multiwall carbon nanotube-metal (Pt or Pd) nanohybrid materials synthesized using microwave-induced reactions and their possible use in fuel cells

    Science.gov (United States)

    V, Lakshman Kumar; Ntim, Susana Addo; Sae-Khow, Ornthida; Janardhana, Chelli; Lakshminarayanan, V.; Mitra, Somenath

    2012-01-01

    Microwave induced reactions for immobilizing platinum and palladium nanoparticles on multiwall carbon nanotubes are presented. The resulting hybrid materials were used as catalysts for direct methanol, ethanol and formic acid oxidation in acidic as well as alkaline media. The electrodes are formed by simply mixing the hybrids with graphite paste, thus using a relatively small quantity of the precious metal. We report Tafel slopes and apparent activation energies at different potentials and temperatures. Ethanol electro-oxidation with the palladium hybrid showed an activation energy of 7.64 kJmol−1 which is lower than those observed for other systems. This system is economically attractive because Pd is significantly less expensive than Pt and ethanol is fast evolving as a commercial biofuel. PMID:23118490

  6. Electro-catalytic activity of multiwall carbon nanotube-metal (Pt or Pd) nanohybrid materials synthesized using microwave-induced reactions and their possible use in fuel cells.

    Science.gov (United States)

    V, Lakshman Kumar; Ntim, Susana Addo; Sae-Khow, Ornthida; Janardhana, Chelli; Lakshminarayanan, V; Mitra, Somenath

    2012-11-30

    Microwave induced reactions for immobilizing platinum and palladium nanoparticles on multiwall carbon nanotubes are presented. The resulting hybrid materials were used as catalysts for direct methanol, ethanol and formic acid oxidation in acidic as well as alkaline media. The electrodes are formed by simply mixing the hybrids with graphite paste, thus using a relatively small quantity of the precious metal. We report Tafel slopes and apparent activation energies at different potentials and temperatures. Ethanol electro-oxidation with the palladium hybrid showed an activation energy of 7.64 kJmol(-1) which is lower than those observed for other systems. This system is economically attractive because Pd is significantly less expensive than Pt and ethanol is fast evolving as a commercial biofuel.

  7. Comparison of Pt and Pd Modified TiO2 Gas Sensors

    Directory of Open Access Journals (Sweden)

    Maolin ZHANG

    2014-12-01

    Full Text Available Pt and Pd have been widely used to improve response properties of TiO2 based gas sensors. In this work, differences on response properties, especially the response time of Pt/TiO2 and Pd/TiO2 sensors, were carefully compared. TiO2 sensing films were modified by dipping method using H2PtCl6 and PdCl2, respectively. XRD, XPS and SEM were used to characterize the crystal structure, elemental composition and grain size of the sensing films. The defect state was characterized by the relationship between resistance and oxygen partial pressure. And the response transients to H2 and O2 were tested by voltammetry method. The difference on response properties of modified TiO2 sensors were suggested to arise from their activation energy. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6403

  8. Fabrication of highly electro catalytic active layer of multi walled carbon nanotube/enzyme for Pt-free dye sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Arbab, Alvira Ayoub, E-mail: alvira_arbab@yahoo.com [Department of Organic and Nano Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Sun, Kyung Chul, E-mail: hytec@hanyang.ac.kr [Department of Fuel cells and hydrogen technology, Hanyang University, Seoul 133-791 (Korea, Republic of); Sahito, Iftikhar Ali, E-mail: iftikhar.sahito@faculty.muet.edu.pk [Department of Organic and Nano Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Qadir, Muhammad Bilal, E-mail: bilal_ntu81@hotmail.com [Department of Organic and Nano Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeong, Sung Hoon, E-mail: shjeong@hanyang.ac.kr [Department of Organic and Nano Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2015-09-15

    Graphical abstract: - Highlights: • We prepared three different types of enzyme dispersed multiwall carbon nanotube (E-MWCNT) layer for application in Pt-free dye sensitized solar cell (DSSCs). • E-MWCNT catalysts exhibited an extremely good electro-catalytic activity (ECA), compared with the conventional catalyst, when synthesized with lipase enzyme. • E-MWCNT as counter electrode exhibits a high power conversion efficiency (PCE) of 7.5%, which can be compared to 8% efficiency of Pt catalyst. - Abstract: Highly dispersed conductive suspensions of multi walled carbon nanotubes (MWCNT) can have intrinsic electrical and electrochemical characteristics, which make them useful candidate for platinum (Pt)-free, dye sensitized solar cells (DSSCs). High energy conversion efficiency of 7.52% is demonstrated in DSSCs, based on enzyme dispersed MWCNT (E-MWCNT) layer deposited on fluorine doped tin oxide (FTO) glass. The E-MWCNT layer shows a pivotal role as platform to reduce large amount of iodide species via electro catalytically active layer, fabricated by facile tape casting under air drying technique. The E-MWCNT layer with large surface area, high mechanical adhesion, and good interconnectivity is derived from an appropriate enzyme dispersion, which provides not only enhanced interaction sites for the electrolyte/counter electrode interface but also improved electron transport mechanism. The surface morphology and structural characterization were investigated using field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electronic microscopy techniques. Electro catalytic activity (ECA) and electrochemical properties of E-MWCNT counter electrode (CE) were investigated using cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. The high power conversion efficiency (PCE) of E-MWCNT CE is associated with the low charge transfer

  9. Double-Side Co-Catalytic Activation of Anodic TiO2 Nanotube Membranes with Sputter-Coated Pt for Photocatalytic H2 Generation from Water/Methanol Mixtures.

    Science.gov (United States)

    Cha, Gihoon; Altomare, Marco; Truong Nguyen, Nhat; Taccardi, Nicola; Lee, Kiyoung; Schmuki, Patrik

    2017-02-01

    Self-standing TiO2 nanotube layers in the form of membranes are fabricated by self-organizing anodization of Ti metal and a potential shock technique. The membranes are then decorated by sputtering different Pt amounts i) only at the top, ii) only at the bottom or iii) at both top and bottom of the tube layers. The Pt-decorated membranes are transferred either in tube top-up or in tube top-down configuration onto FTO slides and are investigated, after crystallization, as photocatalysts for H2 generation using either front or back-side light irradiation. Double-side Pt-decoration of the tube membranes leads to higher H2 generation rates (independently of tube and light-irradiation configuration) compared to membranes decorated at only one side with similar overall Pt amounts. The results suggest that this effect cannot be only ascribed to the overall amount of Pt co-catalyst as such but also to its distribution at both tube extremities. This leads to optimized light absorption and electron diffusion/transfer dynamics: the central part of the membranes acts as light-harvesting zone and electrons therein generated can diffuse towards the Pt/TiO2 active zones (tube extremities) where they can react with the environment and generate H2 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Pt3 Co Octapods as Superior Catalysts of CO2 Hydrogenation.

    Science.gov (United States)

    Khan, Munir Ullah; Wang, Liangbing; Liu, Zhao; Gao, Zehua; Wang, Shenpeng; Li, Hongliang; Zhang, Wenbo; Wang, Menglin; Wang, Zhengfei; Ma, Chao; Zeng, Jie

    2016-08-08

    As the electron transfer to CO2 is a critical step in the activation of CO2 , it is of significant importance to engineer the electronic properties of CO2 hydrogenation catalysts to enhance their activity. Herein, we prepared Pt3 Co nanocrystals with improved catalytic performance towards CO2 hydrogenation to methanol. Pt3 Co octapods, Pt3 Co nanocubes, Pt octapods, and Pt nanocubes were tested, and the Pt3 Co octapods achieved the best catalytic activity. Both the presence of multiple sharp tips and charge transfer between Pt and Co enabled the accumulation of negative charges on the Pt atoms in the vertices of the Pt3 Co octapods. Moreover, infrared reflection absorption spectroscopy confirmed that the high negative charge density at the Pt atoms in the vertices of the Pt3 Co octapods promotes the activation of CO2 and accordingly enhances the catalytic activity.

  11. PENGARUH PENERAPAN CORPORATE SOCIAL RESPONSIBILITY ( CSR ) TERHADAP CITRA PERUSAHAAN PADA PT. HADJI KALLA CABANG SULTAN ALAUDDIN

    OpenAIRE

    MAJID, PARAMITA

    2012-01-01

    - This research aims to determine the influence either together or partially between CSR (Corporate Social Responsibility) to corporate image in PT. Hadji Kalla Cabang Sultan Alaudin, Makassar area, that being measured from CSR variables which is Profit, People, and Planet. Expectedly the information obtained from this research can be used by companies to increase CSR activities and quality of CSR programs so that more can enh...

  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. Theoretical investigation of water formation on Rh and Pt Surfaces

    Science.gov (United States)

    Wilke, Steffen; Natoli, Vincent; Cohen, Morrel H.

    2000-06-01

    Catalytic water formation from adsorbed H and O adatoms is a fundamental reaction step in a variety of technologically important reactions involving organic molecules. In particular, the water-formation rate determines the selectivity of the catalytic partial oxidation of methane to syngas. In this report we present a theoretical investigation of the potential-energy diagram for water formation from adsorbed O and H species on Rh(111) and Pt(111) surfaces. The study is based on accurate first-principles calculations applying density-functional theory. Our results are compared to the potential-energy diagram for this reaction inferred from experimental data by Hickman and Schmidt [AIChE. J. 39, 1164 (1993)]. The calculations essentially reproduce the scheme of Hickman and Schmidt for water formation on Rh(111) with the important difference that the OH molecule is significantly more stable than assumed by Hickman and Schmidt. On Pt(111) surfaces, however, the calculations predict a barrier to OH formation very similar to that found on Rh(111). In particular, the calculated barrier to OH formation of about 20 kcal/mol seems to contradict the small 2.5 kcal/mol barrier assumed in the Hickman-Schmidt scheme and the observed large rate of water formation on Pt. A possible explanation for the apparent discrepancy between the large calculated barrier for OH formation on Pt and the experimentally observed rapid formation of water even at low temperatures is that the active sites for water formation on Pt are at "defect" sites and not on the ideally flat terraces. A similar conclusion has been reached by Verheij and co-workers [Surf. Sci. 371, 100 (1997); Chem. Phys. Lett. 174, 449 (1990); Surf. Sci. 272, 276 (1991)], who did detailed experimental work on water formation on Pt surfaces. Analyzing our results, we develop an explicit picture of the interaction processes governing the formation of OH groups. This picture rationalizes the calculated weak dependence of OH

  14. Catalytic Performance and Characterization of Pt-Co/Al2O3Catalysts for CO2 Reforming of CH4 to Synthesis Gas

    Institute of Scientific and Technical Information of China (English)

    HUANG, Chuan-Jing; ZHENG, Xiao-Ming; MO, Liu-Ye; FEI, Jin-Hua

    2001-01-01

    Pt-Co/Al2O3 catalyst has been studied for CO2 reforming of CH4 to synthesis gas. It was found that the catalytic performance of the catalyst was sensitive to calcination temperature.When Co/Al2O3 was calcined at 1473 K prior to adding a small amount of Pt to it, the resulting bimetallic catalyst showed high activity, optimal stability and excellent resistance to carbon deposition, which was more effective to the reaction than Co/Al2O3 and Pt/Al2O3 catalysts. At lower metal loading, catalyst activity decreased in the following order: Pt-Co/Al2O3 > Pt/Al2O3 》 Co/Al2O3. With 9% Co, the Co/Al2O3calcined at 923 K was also active for CO2 reforming of CH4,however, its carbon formation was much more fast than that of the Pt-Co/Al2O3 catalyst. The XRD results indicated that Pt species well dispersed over the bimetallic catalyst. Its high dispersion was related to the presence of CoAl2O4, formed during calcining of Co/Al2O3 at high temperature before Pt addition. Promoted by Pt, CoAl2O4 in the catalyst could be reduced partially even at 923 K, the temperature of pre-re-duction for the reaction, confirmed by TPR. Based on these results, it was considered that the zerovalent platinum with high dispersion over the catalyst surface and the zerovalent cobalt resulting from CoAl2O4 reduction are responsible for high activity of the Pt-Co/Al2O3 catalyst, and the remain CoAl2O4 is beneficial to suppression of carbon deposition over the catalyst.

  15. Pt-Pd nanoelectrocatalyst of ultralow Pt content for the oxidation of formic acid: Towards tuning the reaction pathway

    Indian Academy of Sciences (India)

    Sourov Ghosh; C Retna Raj

    2015-05-01

    Synthesis of highly efficient functional electrocatalyst that favours the electrochemical oxidation of formic acid via CO-free dehydrogenation pathway is required for direct formic acid fuel cells. Traditional catalysts favour the dehydration pathway involving the generation of poisonous CO. Herein we demonstrate the superior electrocatalytic performance of Pt-Pd bimetallic nanoelectrocatalyst of ultralow Pt content and tuning the reaction pathway by controlling the Pt content. Bimetallic nanoparticles of Pt4Pd96, Pt7Pd93 and Pt47Pd53 compositions are synthesized by electrochemical co-deposition method in aqueous solution. The nanoparticles of ultralow Pt content, Pt4Pd96, favour the CO-free dehydrogenation pathway for formic acid oxidation with an onset potential of 0 V (SHE) whereas the Pt47Pd53 nanoparticles favour the dehydration pathway involving the formation of CO at high positive potential. The Pt content of the bimetallic nanoparticles actually controls the oxidation peak potential and catalytic activity. 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 impedance measurements indirectly support the CO-free pathway for the formic acid oxidation on Pt4Pd96 nanoparticles.

  16. The influence of N-acetylcysteine on the measurement of prothrombin time and activated partial thromboplastin time in healthy subjects

    DEFF Research Database (Denmark)

    Jepsen, S; Hansen, A B

    1994-01-01

    The purpose of the study was to evaluate whether the infusion of N-acetylcysteine decreased the measurement of prothrombin time and activated partial thromboplastin time (APTT) in healthy persons. N-acetylcysteine was administered intraveneously 10 mg kg-1 as a loading dose and then at a rate of 10...... mg kg-1 h-1 for 32 h in six male subjects. The intrinsic, extrinsic and common pathway of coagulation were monitored with activated partial thromboplastin time (APTT), and prothrombin time, respectively. In addition, the extrinsic coagulation pathway was monitored with the clotting activity of single...... factors II, VII, and X. No effect on the intrinsic coagulation pathway was observed. There was a significant and rapid decrease in prothrombin time. Coagulation factors II, VII and X, the three components of prothrombin time, decreased significantly to different degrees. We conclude that infusion of N...

  17. The study on carbon nanotubes-supported Pt catalysts for PEMFC

    Institute of Scientific and Technical Information of China (English)

    朱捷; 朱红; 康晓红; 葛奉娟; 杨玉国

    2004-01-01

    Carbon nanotube-supported-platinum (Pt/CNTs) and carbon-supported-platinum (Pt/C) catalysts were prepared by in situ chemical reduction method and analyzed by TEM and XRD. Then the experiments were carried out to test the performance of PEMFCs with the Pt electrodes. The results showed that in both catalyst, Pt was of small particle size (about 4 nm) and Pt/CNTs exhibited higher catalytic activity than Pt/C.

  18. Analysis of Partial Discharge Activity for Evaluation of the State of High Power Electric Generators Stator Windings

    Directory of Open Access Journals (Sweden)

    Dumitrescu Sorin

    2016-08-01

    Full Text Available The paper shows the importance of trending of partial discharge activity in assessing the insulation condition. It is presented the principle of the measurement method and the quantities that characterize partial discharges and also the criteria utilized for the assessement of the insulation condition of the hydrogenerators. Results of the measurements made on several hydrogenerators are presented, like the variation with time of the two main quantities that characterize the partial discharges, maximum magnitude, Qm and the normalized quantity, NQN over a period of about 10 years. Further, a classification of the insulation condition by 3 main and 2 intermediary categories and the definition of these categories are given. The criteria used for the assessment of the insulation condition are presented in the form of a table: quantitative criteria by the ± NQN and ± Qm values and qualitative criteria for the analysis of the 2D and 3D diagrams. At the end of each set of measurements, an analyze of the insulation condition annual evaluation is made, also a verdict is put, and of course, the recommendations made relating to the maintenance and the decisions that have been taken. The paper ends with several considerations on the method of on-line partial discharges and especially, on the conditions for valid trending activity in time.

  19. Multifunctional Pt(II) Reagents: Covalent Modifications of Pt Complexes Enable Diverse Structural Variation and In-Cell Detection.

    Science.gov (United States)

    White, Jonathan D; Haley, Michael M; DeRose, Victoria J

    2016-01-19

    To enhance the functionality of Pt-based reagents, several strategies have been developed that utilize Pt compounds modified with small, reactive handles. This Account encapsulates work done by us and other groups regarding the use of Pt(II) compounds with reactive handles for subsequent elaboration with fluorophores or other functional moieties. Described strategies include the incorporation of substituents for well-known condensation or nucleophilic displacement-type reactions and their use, for example, to tether spectroscopic handles to Pt reagents for in vivo investigation. Other chief uses of displacement-type reactions have included tethering various small molecules exhibiting pharmacological activity directly to Pt, thus adding synergistic effects. Click chemistry-based ligation techniques have also been applied, primarily with azide- and alkyne-appended Pt complexes. Orthogonally reactive click chemistry reactions have proven invaluable when more traditional nucleophilic displacement reactions induce side-reactivity with the Pt center or when systematic functionalization of a larger number of Pt complexes is desired. Additionally, a diverse assortment of Pt-fluorophore conjugates have been tethered via click chemistry conjugation. In addition to providing a convenient synthetic path for diversifying Pt compounds, the use of click-capable Pt complexes has proved a powerful strategy for postbinding covalent modification and detection with fluorescent probes. This strategy bypasses undesirable influences of the fluorophore camouflaged as reactivity due to Pt that may be present when detecting preattached Pt-fluorophore conjugates. Using postbinding strategies, Pt reagent distributions in HeLa and lung carcinoma (NCI-H460) cell cultures were observed with two different azide-modified Pt compounds, a monofunctional Pt(II)-acridine type and a difunctional Pt(II)-neutral complex. In addition, cellular distribution was observed with an alkyne-appended difunctional

  20. Invisibility and PT symmetry

    OpenAIRE

    MOSTAFAZADEH, Ali

    2013-01-01

    PHYSICAL REVIEW A 87, 012103 (2013) Invisibility and PT symmetry Ali Mostafazadeh* Department of Mathematics, Koc¸ University, Sarıyer 34450, Istanbul, Turkey (Received 9 July 2012; published 3 January 2013) For a general complex scattering potential defined on a real line, we show that the equations governing invisibility of the potential are invariant under the combined action of parity and time-reversal (PT ) transformation. We determine the PT -symmetric as well as no...

  1. Tunable Architecture of Rhombic Dodecahedral Pt-Ni Nanoframe Electrocatalysts.

    Energy Technology Data Exchange (ETDEWEB)

    Becknell, Nigel; Son, Yoonkook; Kim, Dohyung; Li, Dongguo; Yu, Yi; Niu, Zhiqiang; Lei, Teng; Sneed, Brian T.; More, Karren L.; Markovic, Nenad M.; Stamenkovic, Vojislav R.; Yang, Peidong

    2017-08-30

    Platinum-based alloys are known to demonstrate advanced properties in electrochemical reactions that are relevant for proton exchange membrane fuel cells and electrolyzers. Further development of Pt alloy electrocatalysts relies on the design of architectures with highly active surfaces and optimized utilization of the expensive elpment, Pt. Here, we show that the three-dimensional Pt anisotropy of Pt-Ni rhombic dodecahedra can be tuned by controlling the ratio between Pt and Ni precursors such that either a completely hollow nanoframe or a new architecture, the excavated nanoframe, can be obtained. The excavated nanoframe showed similar to 10 times higher specific and similar to 6 times higher mass activity for the oxygen reduction reaction than Pt/C, and twice the mass activity of the hollow nanoframe. The high activity is attributed to enhanced Ni content in the near-surface region and the extended two-dimensional sheet structure within the nanoframe that minimizes the number of buried Pt sites.

  2. Hepatitis C virus non-structural protein 3 interacts with cytosolic 5'(3'-deoxyribonucleotidase and partially inhibits its activity.

    Directory of Open Access Journals (Sweden)

    Chiu-Ping Fang

    Full Text Available Infection with hepatitis C virus (HCV is etiologically involved in liver cirrhosis, hepatocellular carcinoma and B-cell lymphomas. It has been demonstrated previously that HCV non-structural protein 3 (NS3 is involved in cell transformation. In this study, a yeast two-hybrid screening experiment was conducted to identify cellular proteins interacting with HCV NS3 protein. Cytosolic 5'(3'-deoxyribonucleotidase (cdN, dNT-1 was found to interact with HCV NS3 protein. Binding domains of HCV NS3 and cellular cdN proteins were also determined using the yeast two-hybrid system. Interactions between HCV NS3 and cdN proteins were further demonstrated by co-immunoprecipitation and confocal analysis in cultured cells. The cellular cdN activity was partially repressed by NS3 protein in both the transiently-transfected and the stably-transfected systems. Furthermore, HCV partially repressed the cdN activity while had no effect on its protein expression in the systems of HCV sub-genomic replicons and infectious HCV virions. Deoxyribonucleotidases are present in most mammalian cells and involve in the regulation of intracellular deoxyribonucleotides pools by substrate cycles. Control of DNA precursor concentration is essential for the maintenance of genetic stability. Reduction of cdN activity would result in the imbalance of DNA precursor concentrations. Thus, our results suggested that HCV partially reduced the cdN activity via its NS3 protein and this may in turn cause diseases.

  3. Charged particle detectors with active detector surface for partial energy deposition of the charged particles and related methods

    Science.gov (United States)

    Gerts, David W; Bean, Robert S; Metcalf, Richard R

    2013-02-19

    A radiation detector is disclosed. The radiation detector comprises an active detector surface configured to generate charge carriers in response to charged particles associated with incident radiation. The active detector surface is further configured with a sufficient thickness for a partial energy deposition of the charged particles to occur and permit the charged particles to pass through the active detector surface. The radiation detector further comprises a plurality of voltage leads coupled to the active detector surface. The plurality of voltage leads is configured to couple to a voltage source to generate a voltage drop across the active detector surface and to separate the charge carriers into a plurality of electrons and holes for detection. The active detector surface may comprise one or more graphene layers. Timing data between active detector surfaces may be used to determine energy of the incident radiation. Other apparatuses and methods are disclosed herein.

  4. THE APPLICATION OF ACTIVITY BASED COSTING ARE: ELIMINATION IN THE CALCULATION OF COST OF PRODUCTION PT SEMEN TONASA (PERSERO, PANGKEP REGENCY

    Directory of Open Access Journals (Sweden)

    Firman Menne

    2013-07-01

    Full Text Available Economic conditions should be viewed as the catalyst for developing the ability to intelligently manage resources so that the people of Indonesia can be out of the condition. Effective management and efficiency is reflected in good planning and good planning requires good information. In order to plan well the utilization of company resources to fold the duplicate spiders, company management requires system information revealed by clearly and precisely the facts relating to the activity. PT Semen Tonasa is a fabrication company doing business in the field of cement industry and produces two types of cement, cement or Portland cement type 1 can (OPC and Portland cement (PPC Pazzolan. The benefits that can be gained if the company implemented the system of Activity-Based Costing are: elimination is obtained more accurate information, among others, to improve the quality of decision making. In the ABC product only burdened costs of resources and activities that are used and does not burdened by the cost of the resources and activities. This method causes the cost per unit of a more stable and consistent with the purposes of the imposition of costs to the product result in activity.

  5. FACILITIES PLANNING WORKSHOP FOR BLASTING SUPPORT THE ACTIVITY OF DEVELOPMENT AND REPAIR SHIP IN PT. JASA MARINA INDAH UNIT II

    Directory of Open Access Journals (Sweden)

    Samuel Samuel

    2012-07-01

    Full Text Available Blasting in the process of planning the workshop production of new building and ship repair to play a role in providing blasting and paint on the block that will be of erection. As a result of blasting workshop facilities that do not have resulted in low production capacity that can be achieved by this workshop, namely three block ships per month. Capacity blasting and paint shop in this low resulted in low productivity process stage (stage the previous workshops which of course result in a decrease in vessel productivity in general.                 In penelitiaan aims to plan for blasting and paint shop facility which has been adjusted to the planned production capacity of PT. JASA MARINA INDAH II units.                 In this study it - thing to note is to understand the data - the data field for research conducted in terms of both technical and economic terms, with the blasting and paint shop facilities on the construction or repair of ships that have been planned, then the effectiveness of the work and production flow at. Jasa Marina Indah II units can be known.                 Based on the analysis and calculation of both technical and economical it can be identified by the workshop on the process of blasting Blasting efficiency is obtained for 2.55 hours, at 10.16 hours during the painting process, while economical in terms of labor costs can be reduced blasting cost is Rp.930000    for          paint       and         Rp.1.23million

  6. 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.

  7. Identification and Characterisation of the Antimicrobial Peptide, Phylloseptin-PT, from the Skin Secretion of Phyllomedusa tarsius, and Comparison of Activity with Designed, Cationicity-Enhanced Analogues and Diastereomers

    Directory of Open Access Journals (Sweden)

    Yitian Gao

    2016-12-01

    Full Text Available Antimicrobial peptides belonging to the phylloseptin family are mainly found in phyllomedusine frogs. These peptides not only possess potent antimicrobial activity but exhibit low toxicity against eukaryotic cells. Therefore, they are considered as promising drug candidates for a number of diseases. In a recent study, potent antimicrobial activity was correlated with the conserved structures and cationic amphiphilic characteristics of members of this peptide family. A phylloseptin peptide precursor was discovered here in the skin secretion of Phyllomedusa tarsius and the mature peptide was validated by MS/MS sequencing, and was subsequently named phylloseptin-PT. The chemically-synthesized and purified phylloseptin-PT displayed activity against Staphylococcus aureus and Candida albicans. Nevertheless, a range of cationicity-enhanced peptide analogues of phylloseptin-PT, which contained amino acid substitutions at specific sites, exhibited significant increases in antimicrobial activity compared to native phylloseptin-PT. In addition, alternative conformers which were designed and chemically-synthesized with d-lysine, showed potent antimicrobial activity and enhanced bioavailability. These data indicate that phylloseptins may represent potential candidates for next-generation antibiotics. Thus, rational design through modification of natural antimicrobial peptide templates could provide an accelerated path to overcoming obstacles en-route to their possible clinical applications.

  8. Spectroscopic, thermal characterization and cytotoxic activity of bi-, tri- and tetra-nuclear Pd(II) and Pt(II) complexes with diSchiff base ligands

    Science.gov (United States)

    Hegazy, Wael Hussein

    2014-10-01

    In this paper; new di-, tri-, and tetra-nuclear Pd(II) and Pt(II) complexes of N,N‧-bis(3,4-dihydroxybenzylidene)ethan-1,2-diamine (EDH4), N,N‧-bis(3,4-dihydroxy-benzylidene)-benzene-1,2-diamine (PDH4) and N,N‧-bis-(3,4-dihydroxybenzylidene)-4,5-dimethyl-1,2-diamine (MPDH4) ligands were synthesized by two different methods. The first method involve the synthesis of the three ligands from condensation reaction of 3,4-dihydroxybenzaldehyde (L‧H2) with ethylenediamine (en), o-phenylenediamine (o-PD), or 4,5-dimethyl-1,2-phenylendiamine (DMPD) in a mole ratio of 2:1 followed by the reaction of the resulting Schiff bases ligands with Pd(II) or Pt(II) ions in the presence of 2,2‧-dipyridyl (L) to form the di- and tri-nuclear metal complexes. The second method involve the condensation of the Pd complex LPd(II)L‧, (L = 2,2‧-dipyridyl, L‧ = 4-formylbenzene-1,2-bis(olate)) with en, o-PD, or DMPD in a mole ratio of 2:1, respectively, followed by reaction with PdCl2 to form di-, tri-, and tetra-nuclear palladium(II) complexes, respectively. Structures of ligands and metal complexes are characterized by physical properties, FT-IR spectra and nuclear magnetic resonance. The geometries of metal complexes are suggested according to elemental analysis, electronic absorption spectra, thermal analysis, atomic absorption, magnetic susceptibility and molar conductance. Cytotoxic activity against lung large cell carcinoma (H460), prostate carcinoma (DU145), breast adenocarcinoma (MCF-7), amelanotic melanoma (M-14), colon adenocarcinoma (HT-29), and chronic myelogenous leukemia (K562) is also reported.

  9. Nb2O5·nH2O—PtRu/C的制备及其对甲醇氧化的催化作用%Preparation and Activity of Nb2O5·nH2O-PtRu/C for Methanol Oxidation

    Institute of Scientific and Technical Information of China (English)

    李伟伟; 张向军; 卢世刚

    2012-01-01

    10%Nb2O5·onH2O-20%Pt10%Ru/C electro-catalyst for methanol oxidation was prepared by deposition method, followed with heat treatment in Ar atmosphere. The effect of heat treatment on morphology, structure and electrochemistry performance of the product was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and chronoamperograms. No diffraction peaks of Ru were observed in the XRD patterns, while all the peaks of Pt were in accordance with the face centered cubic crystal structure. The binding energy of Pt was not affected by NbEO5.nH2O. Compared with 20%Pt10%Ru/C, in 10%Nb2O5.nH2O-20%Pt10%Ru/C samples, the activated particles were uniformly dispersed, and the performances of methanol oxidation and resistance to "CO" were better. The results indicated that the introduction of NbEO5.nH2O inhibited the growth of active particles, and decreased the alloying degree of Pt-Ru during heat treatment. Besides, NbEO5onH2O also provided active "-OH" and improved H+ transfer, leading to easier adsorption-desorption of methanol and its oxidation intermediates.%采用沉淀法制备了甲醇氧化电催化剂10%Nb2O5·nH2O.20%Pt10%Ru/C,并在Ar气氛下对它进行了热处理.用X射线衍射(XRD),透射电子显微镜(TEM)和X射线光电子谱(XPS)研究了热处理对催化剂的结构和形貌的影响,用循环伏安法和计时电流法研究了热处理对催化剂的电化学性能的影响.结果表明:催化剂中看不到Ru的衍射峰存在,Pt晶粒以面心立方体结构存在,Nb2O5·nH2O对Pt的结合能基本无影响;与20%Pt10%Ru/C相比,同温度热处理的条件下,10%Nb2O5.nH2O-20%Pt10%Ru/C催化剂中Pt,Ru合金化程度较差,活性组分颗粒较小、分散均匀,而且催化甲醇氧化性能和抗“CO”毒化性能较好,700℃热处理的10%Nb2O5.nH2O.20%Pt10

  10. Domain wall pinning on strain relaxation defects in FePt(001)/Pt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Attane, J. P.; Samson, Y.; Marty, A.; Halley, D.; Beigne, C.

    2001-08-06

    Thin FePt (001) films, grown by molecular-beam epitaxy on Pt(001), exhibit a very large perpendicular magnetic anisotropy (K{sub u}=5 x 10{sup 6}Jm{sup -3}) and a 100% magnetic remanence in perpendicular field. The lattice misfit between FePt and Pt (1.5%) relaxes through the pileup of a/6 <112> partial dislocations along {l_brace}111{r_brace} planes, leading to the formation of microtwins. Atomic force microscopy images demonstrate that this process induces a spontaneous rectangular nanostructuration of the sample, while magnetic force microscopy shows that the microtwins act as pinning sites for the magnetic walls. This leads to square magnetic domains and explains the large coercivity associated with the domain wall propagation. {copyright} 2001 American Institute of Physics.

  11. Domain wall pinning on strain relaxation defects in FePt(001)/Pt thin films

    Science.gov (United States)

    Attané, J. P.; Samson, Y.; Marty, A.; Halley, D.; Beigné, C.

    2001-08-01

    Thin FePt (001) films, grown by molecular-beam epitaxy on Pt(001), exhibit a very large perpendicular magnetic anisotropy (Ku=5×106J m-3) and a 100% magnetic remanence in perpendicular field. The lattice misfit between FePt and Pt (1.5%) relaxes through the pileup of a/6 partial dislocations along {111} planes, leading to the formation of microtwins. Atomic force microscopy images demonstrate that this process induces a spontaneous rectangular nanostructuration of the sample, while magnetic force microscopy shows that the microtwins act as pinning sites for the magnetic walls. This leads to square magnetic domains and explains the large coercivity associated with the domain wall propagation.

  12. Ternary Pt-Ru-Ni catalytic layers for methanol electrooxidation prepared by electrodeposition and galvanic replacement

    OpenAIRE

    Athanasios ePapaderakis; Nikolaos ePliatsikas; Chara eProchaska; Kalliopi M. Papazisi; Balomenou, Stella P.; Dimitrios eTsiplakides; Panagiotis ePatsalas; Sotiris eSotiropoulos

    2014-01-01

    Ternary Pt-Ru-Ni deposits on glassy carbon substrates, Pt-Ru(Ni)/GC, have been formed by initial electrodeposition of Ni layers onto glassy carbon electrodes, followed by their partial exchange for Pt and Ru, upon their immersion into equimolar solutions containing complex ions of the precious metals. The overall morphology and composition of the deposits has been studied by SEM microscopy and EDS spectroscopy. Continuous but nodular films have been confirmed, with a Pt ÷ Ru ÷ Ni % bulk atomi...

  13. Ion-irradiation induced chemical ordering of FePt and FePtAu nanoparticles

    Science.gov (United States)

    Seetala, Naidu V.; Harrell, J. W.; Lawson, Jeremy; Nikles, David E.; Williams, John R.; Isaacs-Smith, Tamara

    2005-12-01

    We have studied the effect of ion-beam irradiation on reducing the ordering temperature of FePt and FePtAu nanoparticles. FePt and FePt(Au14%) 4 nm particles dispersed on a Si-substrate were irradiated by 300 keV Al-ions with a dose of 1 × 1016 ions/cm2 at 43 °C using a water-cooled flange in order to minimize the vacancy migration and voids formation within the collision cascades. Partial chemical ordering has been observed in as-irradiated particles with coercivity of 60-130 Oe. Post-irradiation annealing at 220 °C enhanced chemical ordering in FePt nanoparticles with coercivity of 3500 Oe, magnetic anisotropy of 1.5 × 107 erg/cc, and thermal stability factor of 130. A much higher 375 °C post-irradiation annealing was required in FePtAu, presumably because Au atoms were trapped at Fe/Pt lattice sites at lower temperatures. As the annealing temperature increased, anomalous features in the magnetization reversal curves were observed that disappeared at higher annealing temperatures.

  14. Ion-irradiation induced chemical ordering of FePt and FePtAu nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Seetala, Naidu V. [Department of Physics, Grambling State University, RWE Jones Drive, Carver Hall 81, Grambling, LA 71245 (United States)]. E-mail: naidusv@gram.edu; Harrell, J.W. [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Lawson, Jeremy [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Nikles, David E. [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Williams, John R. [Department of Physics, Auburn University, Auburn, AL 36849 (United States); Isaacs-Smith, Tamara [Department of Physics, Auburn University, Auburn, AL 36849 (United States)

    2005-12-15

    We have studied the effect of ion-beam irradiation on reducing the ordering temperature of FePt and FePtAu nanoparticles. FePt and FePt(Au14%) 4 nm particles dispersed on a Si-substrate were irradiated by 300 keV Al-ions with a dose of 1 x 10{sup 16} ions/cm{sup 2} at 43 {sup o}C using a water-cooled flange in order to minimize the vacancy migration and voids formation within the collision cascades. Partial chemical ordering has been observed in as-irradiated particles with coercivity of 60-130 Oe. Post-irradiation annealing at 220 {sup o}C enhanced chemical ordering in FePt nanoparticles with coercivity of 3500 Oe, magnetic anisotropy of 1.5 x 10{sup 7} erg/cc, and thermal stability factor of 130. A much higher 375 {sup o}C post-irradiation annealing was required in FePtAu, presumably because Au atoms were trapped at Fe/Pt lattice sites at lower temperatures. As the annealing temperature increased, anomalous features in the magnetization reversal curves were observed that disappeared at higher annealing temperatures.

  15. k178ar.m77t - MGD77 data file for Geophysical data from field activity K-1-78-AR in Barrows to Pt. Barrows, Arctic from 08/18/1978 to 09/18/1978

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Single-beam bathymetry data along with DGPS navigation data was collected as part of field activity K-1-78-AR in Barrows to Pt. Barrows, Arctic from 08/18/1978 to...

  16. k178ar.m77t - MGD77 data file for Geophysical data from field activity K-1-78-AR in Barrows to Pt. Barrows, Arctic from 08/18/1978 to 09/18/1978

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Single-beam bathymetry data along with DGPS navigation data was collected as part of field activity K-1-78-AR in Barrows to Pt. Barrows, Arctic from 08/18/1978 to...

  17. One-Step Synthesis of Pt/Graphene Composites from Pt Acid Dissolved Ethanol via Microwave Plasma Spray Pyrolysis

    Science.gov (United States)

    Jo, Eun Hee; Chang, Hankwon; Kim, Sun Kyung; Choi, Ji-Hyuk; Park, Su-Ryeon; Lee, Chong Min; Jang, Hee Dong

    2016-09-01

    Pt nanoparticles-laden graphene (Pt/GR) composites were synthesized in the gas phase from a mixture of ethanol and Pt precursor by microwave plasma spray pyrolysis. The morphology of Pt/GR composites has the shape of wrinkled sheets of paper, while Pt nanoparticles (Pt NPs) that are less than 2.6 nm in the mean diameter are uniformly well deposited on the surface of GR sheets stacked in only three layers. The Pt/GR composite prepared with 20 wt% of Pt had the highest specific surface area and electrochemical surface area of up to 402 m2 g-1 and 77 m2 g-1 (Pt), respectively. In addition, the composite showed superior electrocatalytic activity compared with commercial Pt-carbon black. The excellent electrocatalytic activity was attributed to the high specific surface area and electrochemical surface area of the Pt/GR composite directly produced by microwave plasma spray pyrolysis. Thus, it is clearly expected that the Pt/GR composite is a promising material for DMFC catalysts.

  18. Reduction of Pt Usage in Fuel Cell Electrocatalysts Using Carbon Nanotubes and Non-Pt Metals

    Institute of Scientific and Technical Information of China (English)

    J. Nakamura; Y. Nagashima; T. Yamazaki; T. Matsumoto; E. Yoo

    2005-01-01

    @@ 1Introduction The high-priced and limited Pt constitutes a high barrier to commercialization of fuel cells. Pt is essential for the electrode catalyst of polymer electrolyte fuel cells (PEFCs). A reduction in Pt usage is one of the key requirements for the commercialization of fuel cells for use in everyday life, because of its high price and limited availability, and the difficulty of finding suitable substitutes. Non-Pt fuel cell catalysts will decrease the demand for Pt by PEFCs, enabling more Pt to be available for use in other essential products, and make fuel cells more popular[1]. The cheaper Mo2C is known to possess similar catalytic activities and electronic structures to Pt[2]. Carbon black (CB) is widely used as the support for Pt nanoparticles. However, we found that when carbon nanotubes (CNTs) rather than CB are used as the support, the performance is improved, especially below 600 mA/cm2[3,4]. Here, we show that a combination of Mo2C catalyst and carbon nanotubes in the anode provides performance as high as half that of the current PEFCs with Pt catalysts below 600mA/cm2.

  19. Synthesis and biological activity of some partially modified retro-inverso analogues of cholecystokinin.

    Science.gov (United States)

    Rodriguez, M; Galas, M C; Lignon, M F; Mendre, C; Laur, J; Aumelas, A; Martinez, J

    1989-10-01

    Syntheses of some partially modified retro-inverso analogues of the C-terminal octa- or heptapeptide of cholecystokinin are described. These analogues (in which the C-terminal carboxamide was deleted or not) were obtained by reverting one or several peptide bonds in the parent molecule. All these compounds were able to inhibit binding of labeled CCK-8 to rat pancreatic acini and guinea pig brain membranes and to stimulate amylase release from rat pancreatic acini with various potencies. Some of these derivatives reproduce only part of the biological response of CCK on amylase release.

  20. Active and Purely Dissipative Nambu Systems in General Thermostatistical Settings Described by Nonlinear Partial Differential Equations Involving Generalized Entropy Measures

    Directory of Open Access Journals (Sweden)

    T. D. Frank

    2016-12-01

    Full Text Available In physics, several attempts have been made to apply the concepts and tools of physics to the life sciences. In this context, a thermostatistic framework for active Nambu systems is proposed. The so-called free energy Fokker–Planck equation approach is used to describe stochastic aspects of active Nambu systems. Different thermostatistic settings are considered that are characterized by appropriately-defined entropy measures, such as the Boltzmann–Gibbs–Shannon entropy and the Tsallis entropy. In general, the free energy Fokker–Planck equations associated with these generalized entropy measures correspond to nonlinear partial differential equations. Irrespective of the entropy-related nonlinearities occurring in these nonlinear partial differential equations, it is shown that semi-analytical solutions for the stationary probability densities of the active Nambu systems can be obtained provided that the pumping mechanisms of the active systems assume the so-called canonical-dissipative form and depend explicitly only on Nambu invariants. Applications are presented both for purely-dissipative and for active systems illustrating that the proposed framework includes as a special case stochastic equilibrium systems.

  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. 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.

  3. The effect of thermal treatment on the atomic structure of core-shell PtCu nanoparticles in PtCu/C electrocatalysts

    Science.gov (United States)

    Pryadchenko, V. V.; Belenov, S. V.; Shemet, D. B.; Volochaev, V. A.; Srabionyan, V. V.; Avakyan, L. A.; Tabachkova, N. Yu.; Guterman, V. E.; Bugaev, L. A.

    2017-08-01

    PtCu/C electrocatalysts with bimetallic PtCu nanoparticles were synthesized by successive chemical reduction of Cu2+ and Pt(IV) in a carbon suspension prepared based on an aqueous ethylene glycol solution. The atomic structure of as-prepared PtCu nanoparticles and nanoparticles subjected to thermal treatment at 350°C was examined using Pt L 3 and Cu K EXAFS spectra, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). The results of joint analysis of TEM microphotographs, XRD profiles, and EXAFS spectra suggest that the synthesized electrocatalysts contain PtCu nanoparticles with a Cu core-Pt shell structure and copper oxides Cu2O and CuO. Thermal treatment of electrocatalysts at 350°C results in partial reduction of copper oxides and fusion of bimetallic nanoparticles with the formation of both homogeneous and ordered PtCu solid solutions.

  4. Mutagenic activity of transition-metal complexes: relation structure-mutagenic and antibacterial activity for some Pd(II), Pt(II) and Rh(I) complexes. [Salmonella typhimurium; Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Aresta, M.; Treglia, S.; Collucia, M.; Correale, M.; Giordano, D.; Moscelli, S.

    1984-01-01

    The inhibitory and mutagenic action of some Pd(II), Pt(II) and Rh(I) complexes towards various bacterial strains has been evaluated, and some correlations have been found between the chemical behavior of the complexes and their selection biological activity; most of the complexes cause only a DNA damage repaired by the excision repair system. Particularly, the Rh(I) complexes used in this work show selective antibacterial effects on defective but no effect on wild-type strains. 19 references, 8 figures, 10 tables.

  5. Effect of P on the electrochemical activity of carbon supported Pt-Ru alloy catalyst for methanol oxidation.

    CSIR Research Space (South Africa)

    Mohlala, M

    2007-11-01

    Full Text Available In polymer electrolyte membrane fuel cell (PEMFC), platinum is recognized to be the most active metal for methanol oxidation, however there is a strong CO adsorption tendency, which blocks the surface for further methanol adsorption and leads...

  6. 76 FR 67142 - Certain Activated Carbon From the People's Republic of China: Final Results and Partial...

    Science.gov (United States)

    2011-10-31

    ... chemicals. Also excluded from the scope is activated carbon cloth. Activated carbon cloth is a woven textile... various types where a woven format is required. Any activated carbon meeting the physical description of...'') Yearbook of Labor Statistics. Additionally, because the Department is now using Chapter 6A to...

  7. Aggregate Size and Architecture Determine Microbial Activity Balance for One-Stage Partial Nitritation and Anammox

    DEFF Research Database (Denmark)

    Vlaeminck, S.E.; Terada, Akihiko; Smets, Barth F.

    2010-01-01

    Aerobic ammonium-oxidizing bacteria (AerAOB) and anoxic ammonium-oxidizing bacteria (AnAOB) cooperate in partial nitritation/anammox systems to remove ammonium from wastewater. In this process, large granular microbial aggregates enhance the performance, but little is known about granulation so far....... In this study, three suspended-growth oxygen-limited autotrophic nitrification-denitrification (OLAND) reactors with different inoculation and operation (mixing and aeration) conditions, designated reactors A, B, and C, were used. The test objectives were (i) to quantify the AerAOB and AnAOB abundance......AOB-rich aggregates (reactors B and C). The hypothesized granulation pathways include granule replication by division and budding and are driven by growth and/or decay based on species-specific physiology and by hydrodynamic shear and mixing....

  8. 用于质子交换膜燃料电池的高活性、高稳定性PtIrFe/C三元合金催化剂∗%Remarkably Active and Durable PtIrFe/C Ternary Alloy Catalysts with Potential Application to Proton Exchange Membrane Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    杜鑫鑫; 王晓霞; 贺阳; 王健农

    2016-01-01

    采用催化裂解法制备了多孔碳,将其作为催化剂载体,利用液相还原和真空热处理工艺制备出PtIrFe/C三元合金催化剂。采用 X射线衍射、透射电子显微镜等手段对样品的结构形貌进行表征。使用电化学测试手段研究了不同热处理温度对其催化性能的影响。实验结果表明,热处理带来的合金化作用使催化剂的催化活性和耐久性得到了极大的提高。经过700℃热处理的样品,其面积比活性和质量比活性分别是传统商业 Pt/C 催化剂的3~4倍。%Using a mesoporous carbon (prepared via catalyzed pyrolysis)as a support material,PtIrFe/C alloy catalysts were synthesized by a liquid reduction and heat treatment method,and characterized by transmission electron microscopy and powder X-ray diffraction to explore and study the morphologies and crystallization properties.The an-nealing of the as prepared catalysts was performed at different temperatures,tested by electrochemical measurements, and proved to be of great importance for the improvement of the catalyst′s activity and durability due to the alloying effect.The catalysts annealed at 700 ℃ exhibited the highest area-specific activity and mass-specific activity which were 3-4 times higher than those of a commercial Pt/C catalyst.

  9. Pneumatic tube system transport does not alter platelet function in optical and whole blood aggregometry, prothrombin time, activated partial thromboplastin time, platelet count and fibrinogen in patients on anti-platelet drug therapy

    Science.gov (United States)

    Enko, Dietmar; Mangge, Harald; Münch, Andreas; Niedrist, Tobias; Mahla, Elisabeth; Metzler, Helfried; Prüller, Florian

    2017-01-01

    Introduction The aim of this study was to assess pneumatic tube system (PTS) alteration on platelet function by the light transmission aggregometry (LTA) and whole blood aggregometry (WBA) method, and on the results of platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen. Materials and methods Venous blood was collected into six 4.5 mL VACUETTE® 9NC coagulation sodium citrate 3.8% tubes (Greiner Bio-One International GmbH, Kremsmünster, Austria) from 49 intensive care unit (ICU) patients on dual anti-platelet therapy and immediately hand carried to the central laboratory. Blood samples were divided into 2 Groups: Group 1 samples (N = 49) underwent PTS (4 m/s) transport from the central laboratory to the distant laboratory and back to the central laboratory, whereas Group 2 samples (N = 49) were excluded from PTS forces. In both groups, LTA and WBA stimulated with collagen, adenosine-5’-diphosphate (ADP), arachidonic acid (AA) and thrombin-receptor-activated-peptide 6 (TRAP-6) as well as platelet count, PT, APTT, and fibrinogen were performed. Results No statistically significant differences were observed between blood samples with (Group 1) and without (Group 2) PTS transport (P values from 0.064 – 0.968). The AA-induced LTA (bias: 68.57%) exceeded the bias acceptance limit of ≤ 25%. Conclusions Blood sample transportation with computer controlled PTS in our hospital had no statistically significant effects on platelet aggregation determined in patients with anti-platelet therapy. Although AA induced LTA showed a significant bias, the diagnostic accuracy was not influenced. PMID:28392742

  10. Passive and Partially Active Fault Tolerance for Massively Parallel Stream Processing Engines

    DEFF Research Database (Denmark)

    Su, Li; Zhou, Yongluan

    2017-01-01

    Fault-tolerance techniques for stream processing engines can be categorized into passive and active approaches. A typical passive approach periodically checkpoints a processing task's runtime states and can recover a failed task by restoring its runtime state using its latest checkpoint....... On the other hand, an active approach usually employs backup nodes to run replicated tasks. Upon failure, the active replica can take over the processing of the failed task with minimal latency. However, both approaches have their own inadequacies in Massively Parallel Stream Processing Engines (MPSPE......, the passive approach is applied to all tasks while only a selected set of tasks will be actively replicated. The number of actively replicated tasks depends on the available resources. If tasks without active replicas fail, tentative outputs will be generated before the completion of the recovery process. We...

  11. Angiotensin I converting enzyme (ACE) inhibitory activity of hetero-chitooligosaccharides prepared from partially different deacetylated chitosans.

    Science.gov (United States)

    Park, Pyo-Jam; Je, Jae-Young; Kim, Se-Kwon

    2003-08-13

    Angiotensin I converting enzyme (ACE) inhibitory activity of hetero-chitooligosaccharides (hetero-COSs) prepared from partially different deacetylated chitosans was investigated. Partially deacetylated chitosans, 90, 75, and 50% deacetylated chitosan, were prepared from crab chitin by N-deacetylation with 40% sodium hydroxide solution for durations. In addition, nine kinds of hetero-COSs with relatively high molecular masses (5000-10 000 Da; 90-HMWCOSs, 75-HMWCOSs, and 50-HMWCOSs), medium molecular masses (1000-5000 Da; 90-MMWCOSs, 75-MMWCOSs, and 50-MMWCOSs), and low molecular masses (below 1000 Da; 90-LMWCOSs, 75-LMWCOSs, and 50-LMWCOSs) were prepared using an ultrafiltration membrane bioreactor system. ACE inhibitory activity of hetero-COSs was dependent on the degree of deacetylation of chitosans. 50-MMWCOSs that are COSs hydrolyzed from 50% deacetylated chitosan, the relatively lowest degree of deacetylation, exhibited the highest ACE inhibitory activity, and the IC(50) value was 1.22 +/- 0.13 mg/mL. In addition, the ACE inhibition pattern of the 50-MMWCOSs was investigated by Lineweaver-Burk plots, and the inhibition pattern was found to be competitive.

  12. Synthesis,characterization,and biological activities of Pt(Ⅱ) and Pd(Ⅱ)complexes with 2',3',4',5,7-pentahydroxy flavone

    Institute of Scientific and Technical Information of China (English)

    TANG Hui'An; WANG Xiaofang; YANG Sheng; WANG Liufang

    2004-01-01

    Pt(Ⅱ) and Pd(Ⅱ) complexes with 2',3',4',5,7-pentahydroxy-flavone were synthesized and characterized by elemental analysis, molar conductance, IR, 1HNMR, TG-DTA, UV-Vis spectroscopic techniques, and fluorescence analysis.The scavenging effect on the superoxide radical ( O-2 ) and the inhibitory effect on lipid peroxides were also investigated.Both the ligand and the complexes exhibit scavenging effect on superoxide radicals, and the effect of the complexes is greater than that of the ligand. The Pt(Ⅱ) complex exhibits the strongest scavenging efficiency. Both Pt(Ⅱ) and Pd(Ⅱ) complexes have the inhibitory effect on lipid peroxides, and the effect of the complexes is greater than that of the ligand, but the Pt(Ⅱ) complex has a high effect of promoting lipid peroxides.

  13. Pt skin on AuCu intermetallic substrate: a strategy to maximize Pt utilization for fuel cells.

    Science.gov (United States)

    Wang, Gongwei; Huang, Bing; Xiao, Li; Ren, Zhandong; Chen, Hao; Wang, Deli; Abruña, Héctor D; Lu, Juntao; Zhuang, Lin

    2014-07-09

    The dependence on Pt catalysts has been a major issue of proton-exchange membrane (PEM) fuel cells. Strategies to maximize the Pt utilization in catalysts include two main approaches: to put Pt atoms only at the catalyst surface and to further enhance the surface-specific catalytic activity (SA) of Pt. Thus far there has been no practical design that combines these two features into one single catalyst. Here we report a combined computational and experimental study on the design and implementation of Pt-skin catalysts with significantly improved SA toward the oxygen reduction reaction (ORR). Through screening, using density functional theory (DFT) calculations, a Pt-skin structure on AuCu(111) substrate, consisting of 1.5 monolayers of Pt, is found to have an appropriately weakened oxygen affinity, in comparison to that on Pt(111), which would be ideal for ORR catalysis. Such a structure is then realized by substituting the Cu atoms in three surface layers of AuCu intermetallic nanoparticles (AuCu iNPs) with Pt. The resulting Pt-skinned catalyst (denoted as Pt(S)AuCu iNPs) has been characterized in depth using synchrotron XRD, XPS, HRTEM, and HAADF-STEM/EDX, such that the Pt-skin structure is unambiguously identified. The thickness of the Pt skin was determined to be less than two atomic layers. Finally the catalytic activity of Pt(S)AuCu iNPs toward the ORR was measured via rotating disk electrode (RDE) voltammetry through which it was established that the SA was more than 2 times that of a commercial Pt/C catalyst. Taking into account the ultralow Pt loading in Pt(S)AuCu iNPs, the mass-specific catalytic activity (MA) was determined to be 0.56 A/mg(Pt)@0.9 V, a value that is well beyond the DOE 2017 target for ORR catalysts (0.44 A/mg(Pt)@0.9 V). These findings provide a strategic design and a realizable approach to high-performance and Pt-efficient catalysts for fuel cells.

  14. A Partial Collection of Observed Activities Fulfilling Career Education in the Penasco Schools: First Edition.

    Science.gov (United States)

    Sullivan, Angelina Romero

    The report contains of collection of career education activities representative of those initiated by teachers of the Penasco and St. Anthony's Schools (Penasco, New Mexico) during the first semester of implementation (second semester, 1974) of an integrated program for grades K-12. Each activity was recorded by the program coordinator following…

  15. A Partial Collection of Observed Activities Fulfilling Career Education in the Penasco Schools: Second Edition.

    Science.gov (United States)

    Sullivan, Angelina Romero

    The report contains a collection of career education activities representative of those initiated by teachers of the Penasco and St. Anthony's Schools (Penasco, New Mexico) during the second year (1974-75) of an integrated program for grades K-12. For each activity, recorded by the program coordinator following classroom visitations, the grade…

  16. 75 FR 70208 - Certain Activated Carbon From the People's Republic of China: Final Results and Partial...

    Science.gov (United States)

    2010-11-17

    ... carbon cloth. Activated carbon cloth is a woven textile fabric made of or containing activated carbon fibers. It is used in masks and filters and clothing of various types where a woven format is required... preliminarily rescinded the review with respect to Lingzhou, the Department now finds that it would be unfair...

  17. Active partial eigenvalue assignment for friction-induced vibration using receptance method

    Science.gov (United States)

    Liang, Y.; Ouyang, H. J.; Yamaura, H.

    2016-09-01

    Generally, a mechanical system always has symmetric system matrices. Nevertheless, when some non-conservative forces are included, such as friction and aerodynamic force, the symmetry of the stiffness matrix or damping matrix or both violated. Moreover, such an asymmetric system is prone to dynamic instability. Distinct from the eigenvalue assignment for symmetric systems to reassign their natural frequencies, the main purpose of eigenvalue assignment for asymmetric systems is to shift the unstable eigenvalues to the stable region. In this research, only the unstable eigenvalues and eigenvalues which are close to the imaginary axis of the complex eigenvalue plane are assigned due to their predominant influence on the response of the system. The remaining eigenvalues remain unchanged. The state-feedback control gains are obtained by solving the constrained linear least-squares problems in which the linear system matrices are deduced based on the receptance method and the constraint is derived from the unobservability condition. The numerical simulation results demonstrate that the proposed method is capable of partially assigning those targeted eigenvalues of the system for stabilisation.

  18. Internal exposure to neutron-activated {sup 56}Mn dioxide powder in Wistar rats. Pt. 1. Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Stepanenko, Valeriy; Kaprin, Andrey; Galkin, Vsevolod; Ivanov, Sergey; Kolyzhenkov, Timofey; Petukhov, Aleksey; Yaskova, Elena; Belukha, Irina; Khailov, Artem; Skvortsov, Valeriy; Ivannikov, Alexander; Akhmedova, Umukusum; Bogacheva, Viktoria [Medical Radiological Research Center (MRRC) named after A.F. Tsyb - National Medical Research Radiological Center of the Health Ministry of the Russian Federation, Obninsk, Kaluga Region (Russian Federation); Rakhypbekov, Tolebay; Dyussupov, Altay; Chaizhunusova, Nailya; Sayakenov, Nurlan; Uzbekov, Darkhan; Saimova, Aisulu; Shabdarbaeva, Dariya; Kairkhanova, Yankar [Semey State Medical University, Semey (Kazakhstan); Otani, Keiko; Endo, Satoru; Satoh, Kenichi; Kawano, Noriyuki; Fujimoto, Nariaki; Hoshi, Masaharu [Hiroshima University, Hiroshima (Japan); Shichijo, Kazuko; Nakashima, Masahiro; Takatsuji, Toshihiro [Nagasaki University, Nagasaki (Japan); Sakaguchi, Aya; Kato, Hiroaki; Onda, Yuichi [University of Tsukuba, Ibaraki (Japan); Toyoda, Shin [Okayama University of Science, Okayama (Japan); Sato, Hitoshi [Ibaraki Prefectural University of Health Science, Ibaraki (Japan); Skakov, Mazhin; Vurim, Alexandr; Gnyrya, Vyacheslav; Azimkhanov, Almas; Kolbayenkov, Alexander [National Nuclear Center of the Republic of Kazakhstan, Kurchatov (Kazakhstan); Zhumadilov, Kasym [Eurasian National University named after L.N. Gumilyov, Astana (Kazakhstan)

    2017-03-15

    There were two sources of ionizing irradiation after the atomic bombings of Hiroshima and Nagasaki: (1) initial gamma-neutron irradiation at the moment of detonation and (2) residual radioactivity. Residual radioactivity consisted of two components: radioactive fallout containing fission products, including radioactive fissile materials from nuclear device, and neutron-activated radioisotopes from materials on the ground. The dosimetry systems DS86 and DS02 were mainly devoted to the assessment of initial radiation exposure to neutrons and gamma rays, while only brief considerations were given for the estimation of doses caused by residual radiation exposure. Currently, estimation of internal exposure of atomic bomb survivors due to dispersed radioactivity and neutron-activated radioisotopes from materials on the ground is a matter of some interest, in Japan. The main neutron-activated radionuclides in soil dust were {sup 24}Na, {sup 28}Al, {sup 31}Si, {sup 32}P, {sup 38}Cl, {sup 42}K, {sup 45}Ca, {sup 46}Sc, {sup 56}Mn, {sup 59}Fe, {sup 60}Co, and {sup 134}Cs. The radionuclide {sup 56}Mn (T{sub 1/2} = 2.58 h) is known as one of the dominant beta- and gamma emitters during the first few hours after neutron irradiation of soil and other materials on ground, dispersed in the form of dust after a nuclear explosion in the atmosphere. To investigate the peculiarities of biological effects of internal exposure to {sup 56}Mn in comparison with external gamma irradiation, a dedicated experiment with Wistar rats exposed to neutron-activated {sup 56}Mn dioxide powder was performed recently by Shichijo and coworkers. The dosimetry required for this experiment is described here. Assessment of internal radiation doses was performed on the basis of measured {sup 56}Mn activity in the organs and tissues of the rats and of absorbed fractions of internal exposure to photons and electrons calculated with the MCNP-4C Monte Carlo using a mathematical rat phantom. The first results of

  19. PT-symmetric strings

    Energy Technology Data Exchange (ETDEWEB)

    Amore, Paolo, E-mail: paolo.amore@gmail.com [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico); Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina); Garcia, Javier [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina); Gutierrez, German [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico)

    2014-04-15

    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)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup 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.

  20. Networks of connected Pt nanoparticles supported on carbon nanotubes as superior catalysts for methanol electrooxidation

    Science.gov (United States)

    Huang, Meihua; Zhang, Jianshuo; Wu, Chuxin; Guan, Lunhui

    2017-02-01

    The high cost and short lifetime of the Pt-based anode catalyst for methanol oxidation reaction (MOR) hamper the widespread commercialization of direct methanol fuel cell (DMFC). Therefore, improving the activity of Pt-based catalysts is necessary for their practical application. For the first time, we prepared networks of connected Pt nanoparticles supported on multi-walled carbon nanotubes with loading ratio as high as 91 wt% (Pt/MWCNTs). Thanks for the unique connected structure, the Pt mass activity of Pt/MWCNTs for methanol oxidation reaction is 4.4 times as active as that of the commercial Pt/C (20 wt%). When carbon support is considered, the total mass activity of Pt/MWCNTs is 20 times as active as that of the commercial Pt/C. The durability and anti-poisoning ability are also improved greatly.

  1. Partial purification of histone H3 proteolytic activity from the budding yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Azad, Gajendra Kumar; Tomar, Raghuvir Singh

    2016-06-01

    The proteolytic clipping of histone tails has recently emerged as a novel form of irreversible post-translational modification (PTM) of histones. Histone clipping has been implicated as a regulatory process leading to the permanent removal of PTMs from histone proteins. However, there is scarcity of literature that describes the identification and characterization of histone-specific proteases. Here, we employed various biochemical methods to report histone H3-specific proteolytic activity from budding yeast. Our results demonstrate that H3 proteolytic activity was associated with sepharose bead matrices and activity was not affected by a variety of stress conditions. We have also identified the existence of an unknown protein that acts as a physiological inhibitor of the H3-clipping activity of yeast H3 protease. Moreover, through protease inhibition assays, we have also characterized yeast H3 protease as a serine protease. Interestingly, unlike glutamate dehydrogenase (GDH), yeast H3 proteolytic activity was not inhibited by Stefin B. Together, our findings suggest the existence of a novel H3 protease in yeast that is different from other reported histone H3 proteases. The presence of histone H3 proteolytic activity, along with the physiological inhibitor in yeast, suggests an interesting molecular mechanism that regulates the activity of histone proteases. Copyright © 2016 John Wiley & Sons, Ltd.

  2. [Protective activity of S-PT84, a heat-killed preparation of Lactobacillus pentosus, against oral and gastric candidiasis in an experimental murine model].

    Science.gov (United States)

    Hayama, Kazumi; Ishijima, Sanae; Ono, Yoshiko; Izumo, Takayuki; Ida, Masayuki; Shibata, Hiroshi; Abe, Shigeru

    2014-01-01

    The effect of S-PT84, a heat-killed preparation of Lactobacillus pentosus on growth of Candida albicans was examined in vitro and in vivo. The mycelial growth was effectively inhibited by S-PT84 and seemed to bind to the hyphae. We assessed the potential of S-PT84 for treatment of oral and gastric candidiasis using a murine model. When 2 mg of S-PT84 was administered three times into the oral cavity of orally Candida infected mice, the score of lesions on the tongue was improved on day 2. When 50 μl and 200 μl of S-PT84 (10 mg/ml) were administered three times into the oral cavity (0.5 mg × 3) and the stomach (2 mg × 3) of the same mouse model, the number of viable Candida cells in the stomach was reduced significantly on day 2. These findings suggest the possibility that S-PT84 has potential as a food ingredient supporting anti-Candida treatment, especially for Candida infection in the gastrointestinal tract.

  3. Isolation and partial characterization of actinomycetes with antimicrobial activity against multidrug resistant bacteria

    Institute of Scientific and Technical Information of China (English)

    Smriti Singh; Pramod Kumar; N Gopalan; Bhuvnesh Shrivastava; RC Kuhad; Hotam Singh Chaudhary

    2012-01-01

    Objective: To isolate strains of Actinomycetes from different locations of Gwalior to evaluate its antimicrobial activity against multidrug resistant pathogenic strains. Method: Soil samples collected from different niche habitats of Gwalior were serially diluted and plated on selective media. Potential colonies were further purified and stored in agar slants and glycerol stocks. Isolates were biochemically characterized and purified isolates were test against pathogenic microorganisms for screening. Isolates with antagonistic properties were inoculated in production media and secondary metabolites or antimicrobial products were extracted. Result: The seven actinomycetes strains showing maximum antibacterial activity were isolated further characterized based on their colony characteristics and biochemical analyses. The isolates were screened for their secondary metabolites activity on three human pathogenic bacteria are Escherichia coli (E. coli), Methicillin-Resistant Staphylococcus aureus (S. aureus) and Vancomycin-Resistant Enterococci (VRE). Discussion: The strain MITS 1005 was found to be more active against the test bacteria.

  4. Purification, partial characterization and antioxidant activity of polysaccharides from Glycyrrhiza uralensis.

    Science.gov (United States)

    Zhang, Ci-Hai; Yu, Yue; Liang, Yi-Zeng; Chen, Xiao-Qing

    2015-08-01

    Glycyrrhiza uralensis, an important Chinese medicine, has a long history of use in China. In this study, three water-soluble polysaccharides fractions (GUPs-1, GUPs-2 and GUPs-3) were isolated and purified from the root of G. uralensis by DEAE-52 and Sephadex G-100 column chromatography. Physicochemical properties and antioxidant activities of the three purified polysaccharides were investigated. The molecular weights of GUPs-1, GUPs-2 and GUPs-3 were 10,160, 11,680 and 13,360 Da, and the ratios of glucose were 23.4%, 14% and 1.13%, respectively. The antioxidant activities of the three purified polysaccharides followed the order: GUPs-1>GUPs-2>GUPs-3. GUPs with lower molecular weight and higher ratio of glucose, basically exhibited higher antioxidant activities at the same concentration. This indicated that the molecular weight and the ratio of monosaccharide composition of the GUPs could affect the antioxidant activities.

  5. Modification of Pt/Co/Pt film properties by ion irradiation

    Science.gov (United States)

    Avchaciov, K. A.; Ren, W.; Djurabekova, F.; Nordlund, K.; Sveklo, I.; Maziewski, A.

    2015-09-01

    We studied the structural modifications of a Pt/Co/Pt trilayer epitaxial film under Ga+ 30-keV ion irradiation by means of classical molecular dynamics and Monte Carlo simulations. The semiclassical tight-binding second-moment approximation potential was adjusted to reproduce the enthalpies of formation, the lattice constants, and the order-disorder transition temperatures for Co-Pt alloys. We found that during irradiation, the sandwich-type Pt(fcc)/Co(hcp)/Pt(fcc) film structure underwent a transition to the new solid solution α -Co /Pt (fcc ) phase. Our analysis of the short-range order indicates the formation, within a nanosecond time scale, of a homogeneous chemically disordered solution. The longer time-scale simulations employing a Monte Carlo algorithm demonstrated that the transition from the disordered phase to the ordered L 10 and L 12 phases was also possible but not significant for the changes in perpendicular magnetic anisotropy (PMA) observed experimentally. The strain analysis showed that the Co layer was under tensile strain in the lateral direction at the fluences of 1.5 ×1014-3.5 ×1014ionscm -2 ; this range of fluences corresponds to the appearance of PMA. This strain was induced in the initially relaxed hcp Co layer due to its partial transformation to the fcc phase and to the influence of atomic layers with larger lattice constants at upper/lower interfaces.

  6. Synthesis and characterization of a monomeric mutant Cu/Zn superoxide dismutase with partially reconstituted enzymic activity.

    Science.gov (United States)

    Banci, L; Bertini, I; Chiu, C Y; Mullenbach, G T; Viezzoli, M S

    1995-12-15

    A monomeric analog of human Cu/Zn superoxide dismutase (F50E/G51E SOD), previously characterized and found to have reduced enzymic activity, was here further modified by replacing Glu133 with Gln. This substitution does not dramatically affect the coordination geometry at the active site, but enhances enzymic activity, and also increases the affinity for anions at the active site. This behavior parallels earlier published results in which this point mutation was made in the dimeric wild-type enzyme. The analog described here has afforded for the first time a monomeric superoxide dismutase with substantial activity. This point mutation does not significantly influence the protein structure but interactions with anions, including superoxide, are altered with respect to the monomeric form. The present monomeric Glu133Gln mutant has partially restored enzymic activity. The diminished activity of the monomeric analogs is discussed in the light of possible minor structural changes and some of their characteristics are compared with those of naturally occurring mutants associated with various neurological diseases.

  7. Activation Energy Calculations for Formamide-TiO2 and Formamide-Pt Interactions in the Presence of Water.

    Science.gov (United States)

    Dushanov, E; Kholmurodov, Kh; Yasuoka, K

    2013-01-01

    Formamide contains the four elements (C, H, O, and N) most required for life and it is attractive as a potential prebiotic starting material for nucleobase synthesis. In the presence of catalysts (for example, TiO2) and with moderate heating, formamide can pass surface energy barriers, yielding a complete set of nucleic bases and acyclonucleosides, and favoring both phosphorylations and transphosphorylations necessary for life. In the reaction mechanism, interaction with water seems to be an essential factor for the formamide molecule to function. In this paper, a formamide-water solution on a TiO$_2$ (anatase) surface is simulated using the molecular dynamics method, and activation energy calculations are performed for the temperature range of T = 250 K to T = 400 K. A correlation is established between the diffusion and density profiles for the formamide and water molecules on an anatase surface. Also, the calculated activation energies of the formamide-water-anatase and formamide-water-platinum systems are compared. A comparative analysis is performed of the behavior of formamide-water and ethanol-water interaction on the same (anatase and platinum) surfaces.

  8. Evaluation, partial characterization and purification of acetylcholine esterase enzyme and antiangiogenic activity from marine sponges

    Institute of Scientific and Technical Information of China (English)

    Maushmi Shailesh Kumar; Sukanya Gopalkrishnan

    2014-01-01

    Objective: To test three marine sponges Halichondria glabrata Keller, 1891; Spirastrellapachyspira (S. pachyspira) Levi, 1958 and Cliona lobata Hancock, 1849 for the presence of the acetylcholinesterase (AChE) in both young and developed samples from western coastal area of India. S. pachyspira methanolic extract was selected for anti/pro angiogenic activity. Methods:They were evaluated for AChE activity using Ellman’s assay based on production of yellow colored 5-thio-2-nitrobenzoate. Purification of the enzyme was planned using ammonium sulphate precipitation and characterization by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Chorioallantoic membrane (ChAM) assay model was used for angiogenic/antiangiogenic testing. Results:All the three sponges showed good specific enzyme activity and S. pachyspira contained maximum specific enzyme activity. Sixty percent of ammonium sulphate precipitation of crude protein sample gave single band at 66 kDa corresponding to the true AChE. ChAM assay was performed at 62.5, 125.0 and 250.0 µg/mL. Dosage beyond 250 µg/mL extract showed toxic response with anti angiogenic activity at all the concentrations. Conclusions:AChE activity was detected in all samples. Extract showed good anti-angiogenic response at 62.5 µg/mL. Extract was highly toxic affecting microvasculature of ChAM as well as normal growth and development of the embryo at 500 µg/mL. With further characterization of bioactive compounds from the extract of S. pachyspira, the compounds can be developed for anti tumor activity.

  9. Partial characterization of a novel amylase activity isolated from Tunisian Ficus carica latex.

    Science.gov (United States)

    Aref, Houda Lazreg; Mosbah, Habib; Louati, Hanen; Said, Khaled; Selmi, Boulbaba

    2011-11-01

    A large number of plants still need to be investigated through screening of amylases suitable for industry. In the present study, and for the first time, we describe the amylolytic activity of Saint Pedro Ficus carica L. (Moraceae) crude latex of Kahli and Bidhi varieties. Effects of temperature, pH, metal ions, and inhibitors and compatibility with some commercial detergents were investigated for amylase activity. Amylase activity was screened in crude latex using the DNS method and potato starch as a substrate. Analyses of amylolytic reaction products by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) were performed. Bidhi and Kahli amylases were active in optimal pH of 6.5 and 7 at 45°C, respectively, displaying a half life of 85 and 60 min, respectively, at 80°C, and they were very stable in a wide range of pH (4-12). Bidhi amylase activity increased to 260% by addition of 10(-3) mM Fe(2+) or 10(-2) mM Cu(2+), and was strongly inhibited by Mg(2+) and EDTA. In the presence of Ca(2+) and Mg(2+), Kahli amylase activity was dramatically enhanced by 220 and 260%, respectively. The compatibility of both amylases with certain commercial detergents was also shown to be good as enzymes retained up to 98% of their activities after 30 min of incubation at 80°C. Analysis of amylolytic reaction products by TLC and HPLC suggested that Kahli amylase was an amyloglucosidase and Bidhi amylase was β-fructose, α(1-4) glucose. Bidhi amylase is a good choice for application in starch, food, detergents and medical industries.

  10. Evaluation, partial characterization and purification of acetylcholine esterase enzyme and antiangiogenic activity from marine sponges

    Directory of Open Access Journals (Sweden)

    Maushmi Shailesh Kumar

    2014-11-01

    Full Text Available Objective: To test three marine sponges Halichondria glabrata Keller, 1891; Spirastrella pachyspira (S. pachyspira Levi, 1958 and Cliona lobata Hancock, 1849 for the presence of the acetylcholinesterase (AChE in both young and developed samples from western coastal area of India. S. pachyspira methanolic extract was selected for anti/pro angiogenic activity. Methods: They were evaluated for AChE activity using Ellman’s assay based on production of yellow colored 5-thio-2-nitrobenzoate. Purification of the enzyme was planned using ammonium sulphate precipitation and characterization by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Chorioallantoic membrane (ChAM assay model was used for angiogenic/ antiangiogenic testing. Results: All the three sponges showed good specific enzyme activity and S. pachyspira contained maximum specific enzyme activity. Sixty percent of ammonium sulphate precipitation of crude protein sample gave single band at 66 kDa corresponding to the true AChE. ChAM assay was performed at 62.5, 125.0 and 250.0 µg/mL. Dosage beyond 250 µg/mL extract showed toxic response with anti angiogenic activity at all the concentrations. Conclusions: AChE activity was detected in all samples. Extract showed good anti-angiogenic response at 62.5 µg/mL. Extract was highly toxic affecting microvasculature of ChAM as well as normal growth and development of the embryo at 500 µg/mL. With further characterization of bioactive compounds from the extract of S. pachyspira, the compounds can be developed for anti tumor activity.

  11. Synthesis and characterisation of estrogenic carriers for cytotoxic Pt(II) fragments: biological activity of the resulting complexes.

    Science.gov (United States)

    Gabano, Elisabetta; Cassino, Claudio; Bonetti, Samuele; Prandi, Cristina; Colangelo, Donato; Ghiglia, Annalisa; Osella, Domenico

    2005-10-07

    This paper describes the synthesis and the spectroscopic characterisation of cis-dichloro[N-(4-(17alpha-ethynylestradiolyl)-benzyl)-ethylenediamine]platinum(II) and cis-diamino[2-(4-(17alpha-ethynylestradiolyl)-benzoylamino)-malonato]platinum(II). These complexes were synthesised in good yield according to multi-step procedures based on the classical and non-classical Sonogashira coupling reaction, respectively. These compounds retain an acceptable degree of relative binding affinity (RBA) for the alpha form of estrogen receptor. Combined treatment of breast cancer cell lines, namely hormone-sensitive MCF-7 and hormone-insensitive MDA-MB-231 cell lines, indicates that these compounds maintain agonistic activity so that the potential advantage in vehiculation of the cytotoxic moiety by means of the receptor system is counteracted by the proliferative effect of the estrogenic component of the entire molecule, especially at low concentrations.

  12. Photocatalytic Ethanol Oxidative Dehydrogenation over Pt/TiO2: Effect of the Addition of Blue Phosphors

    Directory of Open Access Journals (Sweden)

    J. J. Murcia

    2012-01-01

    Full Text Available Ethanol oxidative dehydrogenation over Pt/TiO2 photocatalyst, in the presence and absence of blue phosphors, was performed. The catalyst was prepared by photodeposition of Pt on sulphated TiO2. This material was tested in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. The effect of the addition of blue phosphors into the fluidized bed has been evaluated. The synthesized catalysts were extensively characterized by different techniques. Pt/TiO2 with a loading of 0.5 wt% of Pt appeared to be an active photocatalyst in the selective partial oxidation of ethanol to acetaldehyde improving its activity and selectivity compared to pure TiO2. In the same way, a notable enhancement of ethanol conversion in the presence of the blue phosphors has been obtained. The blue phosphors produced an increase in the level of ethanol conversion over the Pt/TiO2 catalyst, keeping at the same time the high selectivity to acetaldehyde.

  13. Sulfated polysaccharides from Loligo vulgaris skin: potential biological activities and partial purification.

    Science.gov (United States)

    Abdelmalek, Baha Eddine; Sila, Assaâd; Krichen, Fatma; Karoud, Wafa; Martinez-Alvarez, Oscar; Ellouz-Chaabouni, Semia; Ayadi, Mohamed Ali; Bougatef, Ali

    2015-01-01

    The characteristics, biological properties, and purification of sulfated polysaccharides extracted from squid (Loligo vulgaris) skin were investigated. Their chemical and physical characteristics were determined using X-ray diffraction and infrared spectroscopic analysis. Sulfated polysaccharides from squid skin (SPSS) contained 85.06% sugar, 2.54% protein, 1.87% ash, 8.07% sulfate, and 1.72% uronic acid. The antioxidant properties of SPSS were investigated based on DPPH radical-scavenging capacity (IC50 = 19.42 mg mL(-1)), hydrogen peroxide-scavenging activity (IC50 = 0.91 mg mL(-1)), and β-carotene bleaching inhibition (IC50 = 2.79 mg mL(-1)) assays. ACE-inhibitory activity of SPSS was also investigated (IC50 = 0.14 mg mL(-1)). Further antimicrobial activity assays indicated that SPSS exhibited marked inhibitory activity against the bacterial and fungal strains tested. Those polysaccharides did not display hemolytic activity towards bovine erythrocytes. Fractionation by DEAE-cellulose column chromatography showed three major absorbance peaks. Results of this study suggest that sulfated polysaccharides from squid skin are attractive sources of polysaccharides and promising candidates for future application as dietary ingredients.

  14. Solubilization, Activation and Partial Purification of a Sialidase from Horse Liver

    Directory of Open Access Journals (Sweden)

    KRISHNA PURNAWAN CANDRA

    2005-09-01

    Full Text Available Using sialyl-methylumbelliferyl -glycoside as substrate, sialidase in horse liver was detected as a membrane-bound enzyme. A yield of about 50% of sialidase activity was found in supernatant when solubilized in 0.1 M sodium-phosphate buffer pH 5.5, containing 0.15 M NaCl, 0.25 M sucrose, and 0.5% Triton X-100. Sialidase in the solubilisate could be activated by incubating in acidic pH at 37 oC. Incubation of this solubilized enzyme at 37 oC for 1.5 h at pH 5.0 led to 10% increase of activity and to the precipitation of about 50% of contaminating protein. Using cation-exchange chromatography on S-Sepharose FF and affinity chromatography on p-aminophenyl oxamic acid-agarose following solubilization and activation, about 6% of total sialidase activity was recovered with the purification factor of about 500. The pH and temperature optimum were measured at pH 4.3 and between 37-45 oC, respectively. Neu5Ac2en was a strong inhibitor, while p-aminophenyl oxamic acid had only a weak inhibitory effect.

  15. Internal exposure to neutron-activated {sup 56}Mn dioxide powder in Wistar rats. Pt. 2. Pathological effects

    Energy Technology Data Exchange (ETDEWEB)

    Shichijo, Kazuko; Mussazhanova, Zhanna; Niino, Daisuke; Nakashima, Masahiro; Tomonaga, Masao [Nagasaki University, Nagasaki (Japan); Fujimoto, Nariaki; Hoshi, Masaharu [Hiroshima University, Hiroshima (Japan); Uzbekov, Darkhan; Kairkhanova, Ynkar; Saimova, Aisulu; Chaizhunusova, Nailya; Sayakenov, Nurlan; Shabdarbaeva, Dariya; Aukenov, Nurlan; Rakhypbekov, Tolebay [Semey State Medical University, Semey (Kazakhstan); Azimkhanov, Almas; Kolbayenkov, Alexander [National Nuclear Center of the Republic of Kazakhstan, Kurchatov (Kazakhstan); Zhumadilov, Kassym [L.N. Gumilyov Eurasian National University, Astana (Kazakhstan); Stepanenko, Valeriy [A. Tsyb Medical Radiological Research Center, National Medical Research Radiological Center, Ministry of Health of Russian Federation, Obninsk, Kaluga region (Russian Federation)

    2017-03-15

    To fully understand the radiation effects of the atomic bombing of Hiroshima and Nagasaki among the survivors, radiation from neutron-induced radioisotopes in soil and other materials should be considered in addition to the initial radiation directly received from the bombs. This might be important for evaluating the radiation risks to the people who moved to these cities soon after the detonations and probably inhaled activated radioactive ''dust.'' Manganese-56 is known to be one of the dominant radioisotopes produced in soil by neutrons. Due to its short physical half-life, {sup 56}Mn emits residual radiation during the first hours after explosion. Hence, the biological effects of internal exposure of Wistar rats to {sup 56}Mn were investigated in the present study. MnO{sub 2} powder was activated by a neutron beam to produce radioactive {sup 56}Mn. Rats were divided into four groups: those exposed to {sup 56}Mn, to non-radioactive Mn, to {sup 60}Co γ rays (2 Gy, whole body), and those not exposed to any additional radiation (control). On days 3, 14, and 60 after exposure, the animals were killed and major organs were dissected and subjected to histopathological analysis. As described in more detail by an accompanying publication, the highest internal radiation dose was observed in the digestive system of the rats, followed by the lungs. It was found that the number of mitotic cells increased in the small intestine on day 3 after {sup 56}Mn and {sup 60}Co exposure, and this change persisted only in {sup 56}Mn-exposed animals. Lung tissue was severely damaged only by exposure to {sup 56}Mn, despite a rather low radiation dose (less than 0.1 Gy). These data suggest that internal exposure to {sup 56}Mn has a significant biological impact on the lungs and small intestine. (orig.)

  16. Structural basis for PPAR partial or full activation revealed by a novel ligand binding mode

    Science.gov (United States)

    Capelli, Davide; Cerchia, Carmen; Montanari, Roberta; Loiodice, Fulvio; Tortorella, Paolo; Laghezza, Antonio; Cervoni, Laura; Pochetti, Giorgio; Lavecchia, Antonio

    2016-10-01

    The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors involved in the regulation of the metabolic homeostasis and therefore represent valuable therapeutic targets for the treatment of metabolic diseases. The development of more balanced drugs interacting with PPARs, devoid of the side-effects showed by the currently marketed PPARγ full agonists, is considered the major challenge for the pharmaceutical companies. Here we present a structure-based virtual screening approach that let us identify a novel PPAR pan-agonist with a very attractive activity profile and its crystal structure in the complex with PPARα and PPARγ, respectively. In PPARα this ligand occupies a new pocket whose filling is allowed by the ligand-induced switching of the F273 side chain from a closed to an open conformation. The comparison between this pocket and the corresponding cavity in PPARγ provides a rationale for the different activation of the ligand towards PPARα and PPARγ, suggesting a novel basis for ligand design.

  17. Purification, partial characterization and antimicrobial activity of Lectin from Chenopodium Quinoa seeds

    OpenAIRE

    POMPEU,Dávia Guimarães; Marcelo Augusto MATTIOLI; Ribeiro, Rosy Iara Maciel de Azambuja; Gonçalves,Daniel Bonoto; MAGALHÃES,Juliana Teixeira de; Marangoni, Sérgio; Silva,José Antônio da; Paulo Afonso GRANJEIRO

    2015-01-01

    Abstract A novel lectin was isolated from the seeds of Chenopodium quinoa. To achieve this end, the crude extract from the quinoa was submitted to two purification steps, Sephadex G50 and Mono Q. The hemagglutinating activity showed that this lectin agglutinates human erythrocytes. Its activity is inhibited by glucose and mannose, and remained stable under a wide range of pH levels and temperatures. The quinoa lectin was found to be a heterodimeric lectin of approximately 60 kDa, consisting o...

  18. Acid Phosphatase Activity May Affect the Tuber Swelling by Partially Regulating Sucrose-mediated Sugar Resorption in Potato

    Institute of Scientific and Technical Information of China (English)

    Da-Yong Wang; Yong Lian; De-Wei Zhu

    2008-01-01

    APase activity is involved in regulating many physiological and developmental events by affecting the resorption process.In this study, we investigate the role of APase activity in tuber development in potato. APase activities were mainly localized in cytoplasm, gaps among cells and stroma of amyloplasts of parenchyma cells at the stage of tuber swelling. AP1, encoding a putative APase, was also highly expressed in swelling tubers and a low level of expression was observed in elongated stolons and matured tubers. Inhibition of APase activity by applying Brefeldin A, an inhibitor of APase production and secretion, significantly suppressed the tuber swelling and moderately affected the stolon elongation and the tuberization frequency. During tuber development, sucrose serves as the main soluble sugar for long-distance transportation and resorption. Moreover, Inhibition of APase activity by Brefeldin A markedly reduced the sucrose content in tubers and further decreased the starch accumulation, suggesting that the function of APase in regulating the tuber swelling might be at least artially mediated by the sugar resorption. Exogenous sucrose treatments further indicate the important role of sucrose-mediated sugar resorption in tuber swelling. These results suggest that the APase activity might affect the tuber swelling by partially regulating the sucrose-mediated sugar resorption.

  19. PT quantum mechanics.

    Science.gov (United States)

    Bender, Carl M; DeKieviet, Maarten; Klevansky, S P

    2013-04-28

    PT-symmetric quantum mechanics (PTQM) has become a hot area of research and investigation. Since its beginnings in 1998, there have been over 1000 published papers and more than 15 international conferences entirely devoted to this research topic. Originally, PTQM was studied at a highly mathematical level and the techniques of complex variables, asymptotics, differential equations and perturbation theory were used to understand the subtleties associated with the analytic continuation of eigenvalue problems. However, as experiments on PT-symmetric physical systems have been performed, a simple and beautiful physical picture has emerged, and a PT-symmetric system can be understood as one that has a balanced loss and gain. Furthermore, the PT phase transition can now be understood intuitively without resorting to sophisticated mathematics. Research on PTQM is following two different paths: at a fundamental level, physicists are attempting to understand the underlying mathematical structure of these theories with the long-range objective of applying the techniques of PTQM to understanding some of the outstanding problems in physics today, such as the nature of the Higgs particle, the properties of dark matter, the matter-antimatter asymmetry in the universe, neutrino oscillations and the cosmological constant; at an applied level, new kinds of PT-synthetic materials are being developed, and the PT phase transition is being observed in many physical contexts, such as lasers, optical wave guides, microwave cavities, superconducting wires and electronic circuits. The purpose of this Theme Issue is to acquaint the reader with the latest developments in PTQM. The articles in this volume are written in the style of mini-reviews and address diverse areas of the emerging and exciting new area of PT-symmetric quantum mechanics.

  20. Sucrase Activity and Exopolysaccharide Partial Characterization From Three Weissella confusa Strains

    Directory of Open Access Journals (Sweden)

    Amarila Malik

    2015-05-01

    Full Text Available Exopolysaccharides (EPSs produced by lactic acid bacteria have been well known for their important economic value in food, pharmaceutical and health industries. Large extracellular enzyme sucrases are used by lactic acid bacteria to polymerize EPS, i.e. fructansucrase and glucansucrase. This study aimed to characterize sucrase activity of three Weissella confusa strains MBF8-1, MBF8-2 and MBFCNC-2(1, which were isolated previously from local beverages and their EPS products as well. All strains showed ability to form mucoid and slimy colonies by visual inspection on agar plate using raffinose as substrate suggesting that they possessed fructansucrase activity besides glucansucrase. Obtained EPS products were characterized by HPLC analysis after hydrolysis using 3% TCA at 100C for 1 hour, and by viscosity as well. All strains exhibited similar peak patterns, assuming that all of them possessed fructan EPS product. Supernatant and cell pellet were also analyzed by in situ activity assay performing periodic acid Schiff staining after polyacrylamide gel electrophoresis; only cell pellet showed sucrase activity. Viscosity observation showed that EPS products from all strains were able to increase the viscosity slightly.

  1. Synthetic Human β-Globin 5'HS2 Constructs Function as Partially Active Locus Control Regions.

    NARCIS (Netherlands)

    J. Ellis (James); D. Talbot; N.O. Dillon (Niall); F.G. Grosveld (Frank)

    1993-01-01

    textabstractTransgenes linked to the beta-globin locus control region (LCR) are transcribed in a copy-dependent manner that is independent of the integration site. It has previously been shown that the LCR 5'HS2 region does not require its NF-E2 dimer binding site for LCR activity. In this paper we

  2. Antifatigue Activity of Liquid Cultured Tricholoma matsutake Mycelium Partially via Regulation of Antioxidant Pathway in Mouse

    Directory of Open Access Journals (Sweden)

    Quan Li

    2015-01-01

    Full Text Available Tricholoma matsutake has been popular as food and biopharmaceutical materials in Asian countries for its various pharmacological activities. The present study aims to analyze the antifatigue effects on enhancing exercise performance of Tricholoma matsutake fruit body (ABM and liquid cultured mycelia (TM in mouse model. Two-week Tricholoma matsutake treatment significantly enhances the exercise performance in weight-loaded swimming, rotating rod, and forced running test. In TM- and ABM-treated mice, some factors were observed at 60 min after swimming compared with nontreated mice, such as the increased levels of adenosine triphosphate (ATP, antioxidative enzymes, and glycogen and the reduced levels of malondialdehyde and reactive oxygen species in muscle, liver, and/or serum. Further data obtained from western blot show that CM and ABM have strongly enhanced the activation of 5′-AMP-activated protein kinase (AMPK, and the expressions of peroxisome proliferator have activated receptor γ coactivator-1α (PGC-1α and phosphofructokinase-1 (PFK-1 in liver. Our data suggest that both Tricholoma matsutake fruit body and liquid cultured mycelia possess antifatigue effects related to AMPK-linked antioxidative pathway. The information uncovered in our study may serve as a valuable resource for further identification and provide experimental evidence for clinical trials of Tricholoma matsutake as an effective agent against fatigue related diseases.

  3. Synthesis of Pt and Pt-Fe nanoparticles supported on MWCNTs used as electrocatalysts in the methanol oxidation reaction

    Institute of Scientific and Technical Information of China (English)

    J.R.Rodriguez; R.M.F´elix; E.A.Reynoso; Y.Gochi-Ponce; Y.Verde Gómez; S.Fuentes Moyado; G.Alonso-N ´uñez

    2014-01-01

    This work reports a feasible synthesis of highly-dispersed Pt and Pt-Fe nanoparticles supported on multiwall carbon nanotubes (MWCNTs) without Fe and multiwall carbon nanotubes with iron (MWCNTs-Fe) which applied as electrocatalysts for methanol electrooxidation. A Pt coordination complex salt was synthesized in an aqueous solution and it was used as precursor to prepare Pt/MWCNTs, Pt/MWCNTs-Fe, and Pt-Fe/MWCNTs using FeCl2·4H2O as iron source which were named S1, S2 and S3, respectively. The coordination complex of platinum (TOA)2PtCl6 was obtained by the chemical reaction between (NH4)2PtCl6 with tetraoctylammonium bromide (TOAB) and it was characterized by FT-IR and TGA. The materials were characterized by Raman spectroscopy, SEM, EDS, XRD, TEM and TGA. The electrocatalytic activity of Pt-based supported on MWCNTs in the methanol oxidation was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). Pt-Fe/MWCNTs electrocatalysts showed the highest electrocatalytic activity and stability among the tested electrocatalysts due to that the addition of”Fe”promotes the OH species adsorption on the electrocatalyst surface at low potentials, thus, enhancing the activity toward the methanol oxidation reaction (MOR).

  4. Use of Hydrogen Chemisorption and Ethylene Hydrogenation as Predictors for Aqueous Phase Reforming of Lactose over Ni@Pt and Co@Pt Bimetallic Overlayer Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Qinghua; Skoglund, Michael D.; Zhang, Chen; Morris, Allen R.; Holles, Joseph H.

    2016-10-20

    Overlayer Pt on Ni (Ni@Pt) or Co (Co@Pt) were synthesized and tested for H2 generation from APR of lactose. H2 chemisorption descriptor showed that Ni@Pt and Co@Pt overlayer catalysts had reduced H2 adsorption strength compared to a Pt only catalyst, which agree with computational predictions. The overlayer catalysts also demonstrated lower activity for ethylene hydrogenation than the Pt only catalyst, which likely resulted from decreased H2 binding strength decreasing the surface coverage of H2. XAS results showed that overlayer catalysts exhibited higher white line intensity than the Pt catalyst, which indicates a negative d-band shift for the Pt overlayer, further providing evidence for overlayer formation. Lactose APR studies showed that lactose can be used as feedstock to produce H2 and CO under desirable reaction conditions. The Pt active sites of Ni@Pt and Co@Pt overlayer catalysts showed significantly enhanced H2 production selectivity and activity when compared with that of a Pt only catalyst. The single deposition overlayer with the largest d-band shift showed the highest H2 activity. The results suggest that overlayer formation using directed deposition technique could modify the behavior of the surface metal and ultimately modify the APR activity.

  5. Pt/Mesoporous Carbon Counter Electrode with a Low Pt Loading for High-Efficient Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Guiqiang Wang

    2010-01-01

    Full Text Available Pt/Mesoporous carbon counter electrodes with a low Pt loading for dye-sensitized solar cells were fabricated by coating Pt/mesoporous carbon on fluorine-doped tin oxide glass. Pt/mesoporous carbon samples were prepared by reducing H2PtCl6 with NaBH4 in mesoporous carbon and characterized by N2 adsorption analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The Pt particles deposited on mesoporous carbon support were found to be in uniform shape and narrow range of particle size. Low-Pt-loading Pt/mesoporous carbon counter electrode showed a high electrocatalytic activity for triiodide reduction. Electrochemical impedance spectroscopy measurement displayed a low charge-transfer resistance of 1.2 Ωcm2 for 1-Pt/mesoporous carbon counter electrode. Dye-sensitized solar cells based on the 1-Pt/mesoporous carbon counter electrode achieved an overall conversion efficiency of 6.62% under one sun illumination, which is higher than that of the cell with the conventional Pt counter electrode.

  6. Active hydrothermal metamorphism in the Cerro Prieto geothermal system, Baja California, Mexico: a telescoped low P/T facies series. [Abstract only

    Energy Technology Data Exchange (ETDEWEB)

    Schiffman, P. (Univ. of California, Riverside); Elders, W.A.; Williams, A.E.; McDowell, S.D.; Bird, D.K.

    1983-03-01

    In the Cerro Prieto geothermal system, carbonate-cemented, quartzo-feldspathic sediments of the Colorado River delta are being actively recrystallized into calc-silicate metamorphic rocks through intense fluid/rock interaction with alkali chloride brine (1.5 x 10/sup 4/ ppM TDS) at temperatures between 200/sup 0/ and 370/sup 0/C, fluid pressures <0.25 Kb, lithostatic pressures <1.0 Kb, and oxygen fugacities close to the QFM buffer. Petrologic investigations of cuttings and core from more than 50 wells in this field reveal a prograde series of calc-silicate mineral zones with index metamorphic minerals: wairakite (wr), epidote (ep), prehnite (pr), and calcic clinopyrosene (cpx). The compositions of these and other key phases: wr (Ca/Ca + Na + K + 0.97), ep (Fe/Fe + Al/sup vi/ = 0.11 to 0.31), pr (Fe/Fe + Al/sup vi/ = 0.01 to 0.28), cps (close to Wo/sub 50/ and Mg/Mg + Fe + Mn = 0.23 to 0.90), actinolite (0.20 Al/sup iv//15 cations and Mg/Mg + Fe + Mn = 0.67 to 0.82), biotite (Mg/Mg + Fe + Mn = 0.58 to 0.87) and microcline (Or/sub 96 to 100/) reflect recrystallization under low fluid pressures, relatively low f/sub O/sub 2//, and varying brine compositions. Divariant mineral assemblages in this system comprise a very low P/T facies series encompassing the clay-carbonate, zeolite, greenschist, and amphibolite facies and reflect equilibrium occurring in response to both increasing temperature and decreasing CO/sub 2/ pressure. Similar facies series, characterized by telescoped devolatization mineral reactions, are becoming increasingly recognized in other active geothermal systems above 300/sup 0/C. However, close analogues in the fossil geologic record are as yet unidentified.

  7. Selective oxidation of methylamine over zirconia supported Pt-Ru, Pt and Ru catalysts

    Institute of Scientific and Technical Information of China (English)

    Aiying Song; Gongxuan Lu

    2015-01-01

    Pt–Ru, Pt and Ru catalysts supported on zirconia were prepared by impregnation method and were tested in se-lective oxidation of methylamine (MA) in aqueous media. Among three catalysts, Ru/ZrO2 was more active than Pt/ZrO2 while Pt–Ru/ZrO2 demonstrated the best catalytic activity due to the fact that Pt addition efficiently pro-moted the dispersion of active species in bimetallic catalyst. Therefore, the~100%TOC conversion and N2 selec-tivity were achieved over Pt–Ru/ZrO2, Pt/ZrO2 and Ru/ZrO2 catalysts at 190, 220 and 250 °C, respectively.

  8. Fabrication of monometallic (Co, Pd, Pt, Au) and bimetallic (Pt/Au, Au/Pt) thin films with hierarchical architectures as electrocatalysts

    Science.gov (United States)

    Qiu, Cuicui; Zhang, Jintao; Ma, Houyi

    2010-05-01

    Co thin films with novel hierarchical structures were controllably fabricated by simple electrochemical deposition in the absence of hard and soft templates, which were used as sacrificial templates to further prepare noble metal (Pd, Pt, Au) hierarchical micro/nanostructures via metal exchange reactions. SEM characterization demonstrated that the resulting noble metal thin films displayed hierarchical architectures. The as-prepared noble metal thin films could be directly used as the anode catalysts for the electro-oxidation of formic acid. Moreover, bimetallic catalysts (Pt/Au, Au/Pt) fabricated based on the monometallic Au, Pt micro/nanostructures exhibited the higher catalytic activity compared to the previous monometallic catalysts.

  9. Linking mutagenic activity to micropollutant concentrations in wastewater samples by partial least square regression and subsequent identification of variables.

    Science.gov (United States)

    Hug, Christine; Sievers, Moritz; Ottermanns, Richard; Hollert, Henner; Brack, Werner; Krauss, Martin

    2015-11-01

    We deployed multivariate regression to identify compounds co-varying with the mutagenic activity of complex environmental samples. Wastewater treatment plant (WWTP) effluents with a large share of industrial input of different sampling dates were evaluated for mutagenic activity by the Ames Fluctuation Test and chemically characterized by a screening for suspected pro-mutagens and non-targeted software-based peak detection in full scan data. Areas of automatically detected peaks were used as predictor matrix for partial least squares projections to latent structures (PLS) in combination with measured mutagenic activity. Detected peaks were successively reduced by the exclusion of all peaks with lowest variable importance until the best model (high R(2) and Q(2)) was reached. Peaks in the best model co-varying with the observed mutagenicity showed increased chlorine, bromine, sulfur, and nitrogen abundance compared to original peak set indicating a preferential selection of anthropogenic compounds. The PLS regression revealed four tentatively identified compounds, newly identified 4-(dimethylamino)-pyridine, and three known micropollutants present in domestic wastewater as co-varying with the mutagenic activity. Co-variance between compounds stemming from industrial wastewater and mutagenic activity supported the application of "virtual" EDA as a statistical tool to separate toxicologically relevant from less relevant compounds.

  10. Surface structure and catalytic activity of electrodeposited Ni-Fe-Co-Mo alloy electrode by partially leaching Mo and Fe

    Institute of Scientific and Technical Information of China (English)

    LUO Bei-ping; GONG Zhu-qing; REN Bi-ye; YANG Yu-fang; CHEN Meng-jun

    2006-01-01

    Ni-Fe-Mo-Co alloy electrode was prepared in a citrate solution by electrodeposition, and then Mo and Fe were partially leached out from the electrode in 30% KOH solution. The unique surface micromorphology of a hive-like structure was obtained with an average pore size of about 50 nm. The electrode has a very large real surface area and a stable structure. The effects of sodium molybdate concentration on the composition, surface morphology, and structure of electrodes were analyzed by EDS, SEM and XRD. The polarization curves of the different electrodes show that the catalytic activity of electrodes is strongly correlated with the mole fraction of alloy elements (Ni, Fe, Mo, Co), and the addition of cobalt element to Ni-Fe-Mo alloy improves the catalytic activity. The Ni35.63Fe24.67Mo23.52Co16.18 electrode has the best activity for hydrogen evolution reaction(HER), with an over-potential of 66.2 mV, in 30% KOH at 80 ℃ and 200 mA/cm2. The alloy maintains its good catalytic activity for HER during continuous or intermittent electrolysis. Its electrochemical activity and catalytic stability are much higher than the other iron-group with Mo alloy electrodes.

  11. The pretranslocation ribosome is targeted by GTP-bound EF-G in partially activated form

    Science.gov (United States)

    Hauryliuk, Vasili; Mitkevich, Vladimir A.; Eliseeva, Natalia A.; Petrushanko, Irina Yu.; Ehrenberg, Måns; Makarov, Alexander A.

    2008-01-01

    Translocation of the tRNA·mRNA complex through the bacterial ribosome is driven by the multidomain guanosine triphosphatase elongation factor G (EF-G). We have used isothermal titration calorimetry to characterize the binding of GDP and GTP to free EF-G at 4°C, 20°C, and 37°C. The binding affinity of EF-G is higher to GDP than to GTP at 4°C, but lower at 37°C. The binding enthalpy and entropy change little with temperature in the case of GDP binding but change greatly in the case of GTP binding. These observations are compatible with a large decrease in the solvent-accessible hydrophobic surface area of EF-G on GTP, but not GDP, binding. The explanation we propose is the locking of the switch 1 and switch 2 peptide loops in the G domain of EF-G to the γ-phosphate of GTP. From these data, in conjunction with previously reported structural data on guanine nucleotide-bound EF-G, we suggest that EF-G enters the pretranslocation ribosome as an “activity chimera,” with the G domain activated by the presence of GTP but the overall factor conformation in the inactive form typical of a GDP-bound multidomain guanosine triphosphatase. We propose that the active overall conformation of EF-G is attained only in complex with the ribosome in its “ratcheted state,” with hybrid tRNA binding sites. PMID:18836081

  12. Surface Chemistry of Aromatic Reactants on Pt- and Mo-Modified Pt Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, Allison M.; Mark, Lesli; Rasmussen, Mathew J.; Hensley, Jesse E.; Medlin, J. Will

    2016-11-01

    Supported catalysts containing an oxophilic metal such as Mo and a noble metal such as Pt have shown promising activity and selectivity for deoxygenation of biomass-derived compounds. Here, we report that PtMo catalysts also promote hydrogenolysis of the model compound benzyl alcohol, while decarbonylation is most prevalent over unmodified Pt. A combination of single crystal surface science studies, density functional theory (DFT) calculations, and vapor phase upgrading experiments using supported catalysts was carried out to better understand the mechanism by which Mo promotes deoxygenation. Molybdenum was deposited in submonolayer quantities on a Pt(111) surface and reduced at high temperature. Temperature-programmed desorption (TPD) experiments using benzyl alcohol as a reactant showed greatly enhanced yields of the deoxygenation product toluene at moderate Mo coverages. To understand how the interaction of the aromatic group with the surface influenced this reactivity, we investigated the adsorption of toluene as a probe molecule. We found that the addition of Mo to Pt(111) resulted in a significant decrease in toluene decomposition. DFT calculations indicated that this decrease was consistent with decreased aromatic adsorption strengths that accompany incorporation of Mo into the Pt subsurface. The weaker aromatic-surface interaction on Pt/Mo surfaces led to a tilted adsorption geometry for benzyl alcohol, which presumably promotes hydrogenolysis to produce toluene instead of decarbonylation to produce benzene and CO. Alumina-supported Pt and PtMo catalysts were also tested for benzyl alcohol deoxygenation. PtMo catalysts had a higher rate of toluene production and lower rates of benzene and benzaldehyde production. Additionally, when benzaldehyde was used as the reactant to measure decarbonylation activity the mass-normalized rate of benzene production was 2.5 times higher on Pt than PtMo. Overall, the results of TPD, DFT, and supported catalyst experiments

  13. Neurite-promoting activity from fetal skeletal muscle: partial purification of a high-molecular-weight form.

    Science.gov (United States)

    Steele, J G; Hoffman, H

    1986-01-01

    Neurite extension from sensory neuroblasts dissociated from chick embryo dorsal root ganglia can be stimulated by precoating the polylysine culture surface with extracts of skeletal muscle from bovine fetuses. The active factor(s) may be partially purified from cytosolic extracts of muscle by chromatography on Sepharose 6B and affinity chromatography on wheat germ agglutinin or Helix pomatia agglutinin columns. Extract concentrations of 10-50 micrograms protein per 1 ml were active in promoting neurite extension when the neurons were cultured without serum or nerve growth factor (beta NGF). However, levels of 1-10 micrograms/ml produced dramatic neurite extension when 10% (v/v) fetal or newborn calf serum or 0.5 ng/ml beta NGF was added to the medium. The biological activity was not blocked by antiserum that was raised against purified mouse laminin and that abolished the neurite-promoting activity of mouse laminin. The activity of the muscle extract was destroyed by trypsin or heparitinase, in contrast to the biological activity of purified mouse laminin, which was not abolished by heparitinase treatment. The activity could be resolved into two broad peaks on a Sepharose 2B column (apparent Mr between 2 X 10(6) and in 10 X 10(6) in native form). Treatment with dithiothreitol was necessary to dissociate the factor for electrophoresis in 4.25% polyacrylamide-SDS gels, revealing three major polypeptide bands at Mr = 160,000, 195,000 and 200,000. This preliminary characterization indicates that the neurite-promoting activity from bovine skeletal muscle tissue consists of a high-molecular-weight complex, one essential component of which is a heparan sulfate.

  14. Simple preparation of Pd-Pt nanoalloy catalysts for methanol-tolerant oxygen reduction

    Science.gov (United States)

    He, Wei; Liu, Juanying; Qiao, Yongjin; Zou, Zhiqing; Zhang, Xiaogang; Akins, Daniel L.; Yang, Hui

    Carbon-supported Pd-Pt bimetallic nanoparticles of different atomic ratios (Pd-Pt/C) have been prepared by a simple procedure involving the complexing of Pd and Pt species with sodium citrate followed by ethylene glycol reduction. As-prepared Pd-Pt alloy nanoparticles evidence a single-phase fcc disordered structure, and the degree of alloying is found to increase with Pd content. Both X-ray diffraction and transmission electron microscopy characterizations indicate that all the Pd-Pt/C catalysts possess a similar mean particle size of ca. 2.8 nm. The highest mass and specific activity of the oxygen reduction reaction (ORR) using the Pd-Pt/C catalysts are found with a Pd:Pt atomic ratio of 1:2. Moreover, all Pd-Pt alloy catalysts exhibit significantly enhanced methanol tolerance during the ORR than the Pt/C catalyst, ensuring a higher ORR performance while diminishing Pt utilization.

  15. The electrocatalytic properties of carbon supported PtRu/C nanoalloys in oxidation of small organic molecules: Comparison with Pt/C catalyst

    Directory of Open Access Journals (Sweden)

    Lović Jelena D.

    2012-01-01

    Full Text Available The electrocatalytic activity of carbon supported PtRu/C catalysts, with different composition, toward the electrooxidation of methanol, CO and formic acid were examined in acid and alkaline solution at ambient temperature using thin-film rotating disk electrode (RDE method and compared with activity of Pt/C. The catalysts were characterized by XRD, AFM and STM techniques. XRD pattern revealed that PtRu-1/C catalyst is consisted of two structures e.g. Pt-Ru-fcc and Ru-hcp (the solid solution of Ru in Pt and the small amount of Ru or solid solution of Pt in Ru, as opposed to PtRu-2/C catalyst which is consisted of one structure mostly, Pt-Ru-fcc. According to STM images, PtRu as well as Pt, particles size were between 2 and 6 nm, which is in a good agreement with the mean particles size determined by XRD. To establish the activity and stability of the catalysts potentiodynamic and quasi steady-state measurements were performed. It was found that the activity of Pt and PtRu for CO and methanol oxidation is a strong function of pH of solution. The kinetics are much higher in alkaline than in acid solution and the difference between Pt/C and PtRu/C is much less pronounced in alkaline media. Results presented in this work indicate that activity of PtRu catalysts depends on catalyst composition, e.g. on Pt/Ru atomic ratio, as well as on alloying degree of catalysts. Comparison of CO, methanol and formic acid oxidation on PtRu-2/C, PtRu-1/C and Pt/C catalysts revealed that PtRu-2/C is the most active one. It was shown that the PtRu-2/C catalyst, due to fact that it is consisted of only one phase, with high alloying degree, through the bifunctional mechanism improved by electronic effect, achieve the activity two times higher related to PtRu-1/C in the oxidation of all organic molecules investigated, and about three times higher compared to Pt/C in the oxidation of methanol and CO, and five times higher in formic acid oxidation.

  16. Preparation of Pt/K2La2Ti3O10 and its photo-catalytic activity for hydrogen evolution from methanol water solution

    Institute of Scientific and Technical Information of China (English)

    CUI; Wenquan

    2006-01-01

    ):A new series of layered perovskites exhibiting ion exchange,Inorg.Chem.,1987,26:4299-4301.[12]Takata,T.,Shinohara,K.,Tanaka,A.,Hara,M.,Kondo,J.N.,Domen,K.,A highly active photocatalyst for overall water splitting with a hydrated layered perovskite structure,J.Photochem.Photobiol.A:Chem.,1997,106(1-3):45-49.[13]Cui,W.Q.,Feng,L.R.,Xu,C.H.,Lü,S.J.,Qiu,F.L.,Hydrogen production by photocatalytic decomposition of methanol gas on Pt/TiO2 nano-film,Catal.Comm.,2004(5):533-536.[14]Herrmann,J.M.,Disdier,J.,Pichat,P.,Photoassisted platinum deposition on TiO2 powder using various platinum complexes,J.Phys.Chem.,1986,90:6028-6034.[15]Cui,W.Q.,Feng,L.R.,Xu,C.H.,Lü,S.J.,Qiu,F.L.,Studies on the photo-catalytic decomposition of methanol vapor on Pt-loaded nano-TiO2 particles,Acta Chim.Sinica (in Chinese),2005,63(3):203-209.[16]Ikeda,S.,Hara,M.,Kondo,J.N.,Domen,K.,Preparation of K2La2Ti3O10 by polymerized complex method and photocatalytic decomposition of water,Chem.Mater.,1998,10(1):72-77.[17]Yang,X.Y.,Per,Z.F.,Bai,R.Q.,Studies on dispersion of Pt by HOT,Petrochemical Technology,1978,7(4):352.[18]Fox,M.A.,Dulay,M.Y.,Heterogeneous photocatalysis,Chem.Rev.,1993,93(1):341-357.[19]Kudo,A.,Sakata,T.,Luminescent properties of nondoped and rare earth metal ion-doped K2La2Ti3O10 with layered perovskite structures:Importance of the hole trap process,J.Phys.Chem.,1995,99:15963-15967.

  17. Activity Enhancement of Pt/Ba/Al2O3 Mixed with Mn/Ba/Al2O3 for NOx Storage-reduction by Hydrogen

    Institute of Scientific and Technical Information of China (English)

    Jian Hua XIAO; Xue Hui LI; Sha DENG; Fu Rong WANG; Le Fu WANG

    2006-01-01

    Mn/Ba/Al2O3 catalyst for NO oxidation-storage and Pt/Ba/Al2O3 catalyst mixed with Mn/Ba/Al2O3 for NOx storage-reduction by hydrogen were investigated. The results showed that Mn/Ba/Al2O3 had large nitrogen oxides storage capacity (397.9 μmolg-1) under lean bum condition.When Pt/Ba/Al2O3 catalyst was mixed with Mn/Ba/Al2O3 in equal weight proportion, the NOx conversion increased between 250 ℃ and 500 ℃ under the dynamic lean-rich bum conditions, and the maximum NOx conversion increased from 95.4% to 98.2%. Mn/Ba/Al2O3 has promoted NOx storing in the lean stage and improved NOx reduction efficiency in the rich stage, these might result in higher NOx conversion over the low Pt loading content catalyst.

  18. Radiolytic Preparation of Electrocatalysts with Pt-Co and Pt-Sn Nanoparticles for a Proton Exchange Membrane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Sang Kyum Kim

    2014-01-01

    Full Text Available Nanosized Pt-Sn/VC and Pt-Co/VC electrocatalysts were prepared by a one-step radiation-induced reduction (30 kGy process using distilled water as the solvent and Vulcan XC72 as the supporting material. While the Pt-Co/VC electrodes were compared with Pt/VC (40 wt%, HiSpec 4000, in terms of their electrocatalytic activity towards the oxidation of H2, the Pt-Co/VC electrodes were evaluated in terms of their activity towards the hydrogen oxidation reaction (HOR and compared with Pt/VC (40 wt%, HiSpec 4000, Pt-Co/VC, and Pt-Sn/VC in a single cell. Additionally, the prepared electrocatalyst samples (Pt-Co/VC and Pt-Sn/VC were characterized by transmission electron microscopy (TEM, scanning electron microscope (SEM, thermogravimetric analysis (TGA, X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, electrochemical surface area (ECSA, and fuel cell polarization performance.

  19. The role of the cationic Pt sites in the adsorption properties of water and ethanol on the Pt4/Pt(111) and Pt4/CeO2(111) substrates: A density functional theory investigation

    Science.gov (United States)

    Seminovski, Yohanna; Tereshchuk, Polina; Kiejna, Adam; Da Silva, Juarez L. F.

    2016-09-01

    Finite site platinum particles, Ptn, supported on reduced or unreduced cerium oxide surfaces, i.e., CeO2-x(111) ( 0 CeO2-x has been improved in the last years; however, the identification of the active sites on the Ptn/CeO2-x(111) substrates is still far from complete. In this work, we applied density functional theory based calculations with the addition of the on-site Coulomb interactions (DFT+U) for the investigation of the active sites and the role of the Pt oxidation state on the adsorption properties of water and ethanol (probe molecules) on four selected substrates, namely, Pt(111), Pt4/Pt(111), CeO2(111), and Pt4/CeO2(111). Our results show that water and ethanol preferentially bind in the cationic sites of the base of the tetrahedron Pt4 cluster instead of the anionic lower-coordinated Pt atoms located on the cluster-top or in the surface Ce (cationic) and O (anionic) sites. The presence of the Pt4 cluster contributes to increase the adsorption energy of both molecules on Pt(111) and CeO2(111) surfaces; however, its magnitude increases less for the case of Pt4/CeO2(111). Thus, the cationic Pt sites play a crucial role in the adsorption properties of water and ethanol. Both water and ethanol bind to on-top sites via the O atom and adopt parallel and perpendicular configurations on the Pt(111) and CeO2(111) substrates, respectively, while their orientation is changed once the Pt4 cluster is involved, favoring H binding with the surface sites.

  20. Partial chemical composition and antimicrobial activity of Daucus crinitus Desf. extracts

    Energy Technology Data Exchange (ETDEWEB)

    Dib, M. A.; Bendahou, M.; Bendiabdellah, A.; Djabou, N.; Allali, H.; Tabti, B.; Paolini, J.; Costa, J.

    2010-07-01

    The chemical composition of fatty acids and the unsaponifiable fraction of the roots, leaves and stems from Daucus crinitus Desf. were, determined using gas chromatography (GC) and gas chromatography-Mass Spectrometry (GC-MS). The fatty acid fractions of different organs (leaves, stems and roots) were characterized by lauric acid (17.9, 17.5 and 18.1 % respectively) and other long chain fatty acids (until C22). Qualitative and quantitative differences were reported between the unsaponifiable fractions of different organs from D. crinitus. The unsaponifiable fractions of the leaves, roots and stem showed high amounts of aliphatic components (83.4%, 87.2% and 91.4%, respectively). The monoterpen, diterpen and sesquiterpen components were only present in small percentages. The antimicrobial properties of the D. critinus extracts were tested on four different microorganisms. These extracts were found to be active against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Candida albicans. (Author) 35 refs.

  1. Partial Activation of SA- and JA-Defensive Pathways in Strawberry upon Colletotrichum acutatum Interaction.

    Science.gov (United States)

    Amil-Ruiz, Francisco; Garrido-Gala, José; Gadea, José; Blanco-Portales, Rosario; Muñoz-Mérida, Antonio; Trelles, Oswaldo; de Los Santos, Berta; Arroyo, Francisco T; Aguado-Puig, Ana; Romero, Fernando; Mercado, José-Ángel; Pliego-Alfaro, Fernando; Muñoz-Blanco, Juan; Caballero, José L

    2016-01-01

    Understanding the nature of pathogen host interaction may help improve strawberry (Fragaria × ananassa) cultivars. Plant resistance to pathogenic agents usually operates through a complex network of defense mechanisms mediated by a diverse array of signaling molecules. In strawberry, resistance to a variety of pathogens has been reported to be mostly polygenic and quantitatively inherited, making it difficult to associate molecular markers with disease resistance genes. Colletotrichum acutatum spp. is a major strawberry pathogen, and completely resistant cultivars have not been reported. Moreover, strawberry defense network components and mechanisms remain largely unknown and poorly understood. Assessment of the strawberry response to C. acutatum included a global transcript analysis, and acidic hormones SA and JA measurements were analyzed after challenge with the pathogen. Induction of transcripts corresponding to the SA and JA signaling pathways and key genes controlling major steps within these defense pathways was detected. Accordingly, SA and JA accumulated in strawberry after infection. Contrastingly, induction of several important SA, JA, and oxidative stress-responsive defense genes, including FaPR1-1, FaLOX2, FaJAR1, FaPDF1, and FaGST1, was not detected, which suggests that specific branches in these defense pathways (those leading to FaPR1-2, FaPR2-1, FaPR2-2, FaAOS, FaPR5, and FaPR10) were activated. Our results reveal that specific aspects in SA and JA dependent signaling pathways are activated in strawberry upon interaction with C. acutatum. Certain described defense-associated transcripts related to these two known signaling pathways do not increase in abundance following infection. This finding suggests new insight into a specific putative molecular strategy for defense against this pathogen.

  2. Partial activation of SA- and JA-defensive pathways in strawberry upon Colletotrichum acutatum interaction

    Directory of Open Access Journals (Sweden)

    FRANCISCO AMIL-RUIZ

    2016-07-01

    Full Text Available Understanding the nature of pathogen host interaction may help improve strawberry (Fragaria × ananassa cultivars. Plant resistance to pathogenic agents usually operates through a complex network of defense mechanisms mediated by a diverse array of signaling molecules. In strawberry, resistance to a variety of pathogens has been reported to be mostly polygenic and quantitatively inherited, making it difficult to associate molecular markers with disease resistance genes. Colletotrichum acutatum spp. is a major strawberry pathogen, and completely resistant cultivars have not been reported. Moreover, strawberry defense network components and mechanisms remain largely unknown and poorly understood. Assessment of the strawberry response to C. acutatum included a global transcript analysis, and acidic hormones SA and JA measurements were analyzed after challenge with the pathogen. Induction of transcripts corresponding to the SA and JA signaling pathways and key genes controlling major steps within these defense pathways was detected. Accordingly, SA and JA accumulated in strawberry after infection. Contrastingly, induction of several important SA, JA, and oxidative stress-responsive defense genes, including FaPR1-1, FaLOX2, FaJAR1, FaPDF1, and FaGST1, was not detected, which suggests that specific branches in these defense pathways (those leading to FaPR1-2, FaPR2-1, FaPR2-2, FaAOS, FaPR5 and FaPR10 were activated. Our results reveal that specific aspects in SA and JA dependent signaling pathways are activated in strawberry upon interaction with C. acutatum. Certain described defense-associated transcripts related to these two known signaling pathways do not increase in abundance following infection. This finding suggests new insight into a specific putative molecular strategy for defense against this pathogen.

  3. Partial Activation of SA- and JA-Defensive Pathways in Strawberry upon Colletotrichum acutatum Interaction

    Science.gov (United States)

    Amil-Ruiz, Francisco; Garrido-Gala, José; Gadea, José; Blanco-Portales, Rosario; Muñoz-Mérida, Antonio; Trelles, Oswaldo; de los Santos, Berta; Arroyo, Francisco T.; Aguado-Puig, Ana; Romero, Fernando; Mercado, José-Ángel; Pliego-Alfaro, Fernando; Muñoz-Blanco, Juan; Caballero, José L.

    2016-01-01

    Understanding the nature of pathogen host interaction may help improve strawberry (Fragaria × ananassa) cultivars. Plant resistance to pathogenic agents usually operates through a complex network of defense mechanisms mediated by a diverse array of signaling molecules. In strawberry, resistance to a variety of pathogens has been reported to be mostly polygenic and quantitatively inherited, making it difficult to associate molecular markers with disease resistance genes. Colletotrichum acutatum spp. is a major strawberry pathogen, and completely resistant cultivars have not been reported. Moreover, strawberry defense network components and mechanisms remain largely unknown and poorly understood. Assessment of the strawberry response to C. acutatum included a global transcript analysis, and acidic hormones SA and JA measurements were analyzed after challenge with the pathogen. Induction of transcripts corresponding to the SA and JA signaling pathways and key genes controlling major steps within these defense pathways was detected. Accordingly, SA and JA accumulated in strawberry after infection. Contrastingly, induction of several important SA, JA, and oxidative stress-responsive defense genes, including FaPR1-1, FaLOX2, FaJAR1, FaPDF1, and FaGST1, was not detected, which suggests that specific branches in these defense pathways (those leading to FaPR1-2, FaPR2-1, FaPR2-2, FaAOS, FaPR5, and FaPR10) were activated. Our results reveal that specific aspects in SA and JA dependent signaling pathways are activated in strawberry upon interaction with C. acutatum. Certain described defense-associated transcripts related to these two known signaling pathways do not increase in abundance following infection. This finding suggests new insight into a specific putative molecular strategy for defense against this pathogen. PMID:27471515

  4. Nanocrystalline Fe-Fe2O3 particle-deposited N-doped graphene as an activity-modulated Pt-free electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Dhavale, Vishal M.; Singh, Santosh K.; Nadeema, Ayasha; Gaikwad, Sachin S.; Kurungot, Sreekumar

    2015-11-01

    The size-controlled growth of nanocrystalline Fe-Fe2O3 particles (2-3 nm) and their concomitant dispersion on N-doped graphene (Fe-Fe2O3/NGr) could be attained when the mutually assisted redox reaction between NGr and Fe3+ ions could be controlled within the aqueous droplets of a water-in-oil emulsion. The synergistic interaction existing between Fe-Fe2O3 and NGr helped the system to narrow down the overpotential for the oxygen reduction reaction (ORR) by bringing a significant positive shift to the reduction onset potential, which is just 15 mV higher than its Pt-counterpart. In addition, the half-wave potential (E1/2) of Fe-Fe2O3/NGr is found to be improved by a considerable amount of 135 mV in comparison to the system formed by dispersing Fe-Fe2O3 nanoparticles on reduced graphene oxide (Fe-Fe2O3/RGO), which indicates the presence of a higher number of active sites in Fe-Fe2O3/NGr. Despite this, the ORR kinetics of Fe-Fe2O3/NGr are found to be shifted significantly to the preferred 4-electron-transfer pathway compared to NGr and Fe-Fe2O3/RGO. Consequently, the H2O2% was found to be reduced by 78.3% for Fe-Fe2O3/NGr (13.0%) in comparison to Fe-Fe2O3/RGO (51.2%) and NGr (41.0%) at -0.30 V (vs. Hg/HgO). This difference in the yield of H2O2 formed between the systems along with the improvements observed in terms of the oxygen reduction onset and E1/2 in the case of Fe-Fe2O3/NGr reveals the activity modulation achieved for the latter is due to the coexistence of factors such as the presence of the mixed valancies of iron nanoparticles, small size and homogeneous distribution of Fe-Fe2O3 nanoparticles and the electronic modifications induced by the doped nitrogen in NGr. A controlled interplay of these factors looks like worked favorably in the case of Fe-Fe2O3/NGr. As a realistic system level validation, Fe-Fe2O3/NGr was employed as the cathode electrode of a single cell in a solid alkaline electrolyte membrane fuel cell (AEMFC). The system could display an open

  5. Preparation of Pd/Pt Bimetallic Electrodes and Its Activity Toward Oxygen Reduction Reaction%Pd/Pt二元合金电极的制备及氧还原性能

    Institute of Scientific and Technical Information of China (English)

    方兰兰; 廖玲文; 刘少雄; 蔡俊; 李明芳; 陈艳霞

    2011-01-01

    bimetallic electrodes toward oxygen reduction reaction (ORR) increase with x up to 4 and remains unchanged at x≥4 as revealed by cyclic voltammetric studies in a flow cell. For Pd/Ptx electrode(with x >3), its ORR activity is higher(with the half wave potential of ca. 25 mV more positive) than that of polycrystalline Pt. This is attributed to the reduction of adsorption energy of O or OH containing species on the surface Pt atoms induced by adjacent Pd atoms at the surface or by Pd atoms under the surface Pt layer.

  6. The HEART mobile phone trial: The partial mediating effects of self-efficacy on physical activity among cardiac patients

    Directory of Open Access Journals (Sweden)

    Ralph eMaddison

    2014-05-01

    Full Text Available Background: The ubiquitous use of mobile phones provides an ideal opportunity to deliver interventions to increase physical activity levels. Understanding potential mediators of such interventions is needed to increase their effectiveness. A recent randomized controlled trial of a mobile phone and Internet (mHealth intervention was conducted in New Zealand to determine the effectiveness on exercise capacity and physical activity levels in addition to current cardiac rehabilitation (CR services for people (n=171 with ischaemic heart disease (IHD. Significant intervention effect was observed for self-reported leisure time physical activity and walking, but not peak oxygen uptake (PVO2 at 24 weeks. There was also significant improvement in self-efficacy.Objective: To evaluate the mediating effect of self-efficacy on physical activity levels in an mHealth delivered exercise CR programme. Methods: Treatment evaluations were performed on the principle of intention to treat (ITT. Adjusted regression analyses were conducted to evaluate the main treatment effect on leisure time physical activity and walking at 24 weeks, with and without change in self-efficacy as the mediator of interest. Results: Change in self-efficacy at 24 weeks significantly mediated the treatment effect on leisure time physical activity by 13%, but only partially mediated the effect on walking by 4% at 24 weeks. Conclusion: An mHealth intervention involving text messaging and Internet support had a positive treatment effect on leisure time physical activity and walking at 24 weeks, and this effect was likely mediated through changes in self-efficacy. Future trials should examine other potential mediators related to this type of intervention.

  7. Effect of Pt:Sn atomic ratio on the preparation of PtSn/C electrocatalysts using electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F.; Oliveira Neto, Almir; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V., E-mail: dfsilva@ipen.b, E-mail: espinace@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    PtSn/C electrocatalysts were prepared with Pt:Sn atomic ratios of 3:1, 1:1 and 1:3 in water/2-propanol using electron beam irradiation. The obtained materials were characterized by EDX, XRD and cyclic voltammetry. The ethanol electro-oxidation was studied by chronoamperometry. The XRD diffractograms of the PtSn/C electrocatalysts showed typical face-centered cubic (fcc) structure of platinum and the presence of a SnO{sub 2} phase (cassiterite). The mean crystallite sizes of Pt fcc phase was in the range of 3.0-3.5 nm. The PtSn/C electrocatalysts were active for ethanol electro-oxidation at room temperature and the material prepared with Pt:Sn atomic ratio of 1:1 showed the best activity. (author)

  8. Computing partial transposes and related entanglement functions

    CERN Document Server

    Maziero, Jonas

    2016-01-01

    The partial transpose (PT) is an important function for entanglement testing and quantification and also for the study of geometrical aspects of the quantum state space. In this article, considering general bipartite and multipartite discrete systems, explicit formulas ready for the numerical implementation of the PT and of related entanglement functions are presented and the Fortran code produced for that purpose is described. What is more, we obtain an analytical expression for the Hilbert-Schmidt entanglement of two-qudit systems and for the associated closest separable state. In contrast to previous works on this matter, we only use the properties of the PT, not applying Lagrange multipliers.

  9. Computing Partial Transposes and Related Entanglement Functions

    Science.gov (United States)

    Maziero, Jonas

    2016-10-01

    The partial transpose (PT) is an important function for entanglement testing and quantification and also for the study of geometrical aspects of the quantum state space. In this article, considering general bipartite and multipartite discrete systems, explicit formulas ready for the numerical implementation of the PT and of related entanglement functions are presented and the Fortran code produced for that purpose is described. What is more, we obtain an analytical expression for the Hilbert-Schmidt entanglement of two-qudit systems and for the associated closest separable state. In contrast to previous works on this matter, we only use the properties of the PT, not applying Lagrange multipliers.

  10. Unusual Initial Manifestation of Acquired Hemophilia A: A Normal Activated Partial Thromboplastin Time, Intramuscular Hematoma and Cerebral Hemorrhage

    Science.gov (United States)

    Tsuyama, Nobuaki; Ichiba, Toshihisa; Naito, Hiroshi

    2016-01-01

    We herein present a case of acquired hemophilia A with a normal activated partial thromboplastin (aPTT), intramuscular hematoma and cerebral hemorrhage occurring in a 73-year-old man. The patient visited our emergency department with gait disturbance, pain and swelling in his right leg. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed intramuscular hematoma and intracranial hemorrhage. The results of initial coagulation studies were normal, but repeated coagulation studies revealed an isolated prolongation of the aPTT. Additional laboratory tests confirmed the diagnosis of acquired hemophilia A. If the initial aPTT is normal, we should therefore repeat the aPTT and also perform other coagulation studies including a mixing study, factor VIII level and inhibitor, to investigate the underlying diseases in elderly patients with spontaneous hemorrhaging of unknown etiology. PMID:27853081

  11. Electro-oxidation of ethanol on ternary non-alloyed Pt-Sn-Pr/C catalysts

    Science.gov (United States)

    Corradini, Patricia G.; Antolini, Ermete; Perez, Joelma

    2015-02-01

    Ternary Pt-Sn-Pr/C (70:10:20), (70:15:15) and (45:45:10) electro-catalysts were prepared by a modified formic acid method, and their activity for the ethanol oxidation reaction (EOR) was compared with that of Pt-Pr/C catalysts prepared by the same methods and that of commercial Pt-Sn/C (75:25) and Pt/C catalysts. Among all the catalysts, the Pt-Sn-Pr/C (45:45:10) catalyst presented both the highest mass activity and the highest specific activity. The steady state electrochemical stability of ternary Pt-Sn-Pr catalysts increased with the surface Sn/Pt atomic ratio. Following repetitive potential cycling (RPC), the activity for ethanol oxidation of Pt-Sn-Pr/C catalysts with high surface Sn/Pt atomic ratio was considerably higher than that of the corresponding as-prepared catalysts, and increased with increasing the Sn/Pt ratio. The increase of the EOR mass activity following RPC was ascribed to the increase of either the specific activity (for the Pt-Sn-Pr/C (70:15:15) catalyst) or the electrochemically active surface area (for the Pt-Sn-Pr/C (45:45:10) catalyst). Dissolution of Sn and Pr oxides from Pt-Sn-Pr/C catalyst surface was observed following RPC.

  12. Partial characterization of cold active amylases and proteases of Streptomyces sp. from Antarctica

    Directory of Open Access Journals (Sweden)

    Mihaela Cotârleţ

    2011-09-01

    Full Text Available The aim of this study was to isolate novel enzyme-producing bacteria from vegetation samples from East Antarctica and also to characterize them genetically and biochemically in order to establish their phylogeny. The ability to grow at low temperature and to produce amylases and proteases cold-active was also tested. The results of the 16S rRNA gene sequence analysis showed that the 4 Alga rRNA was 100% identical to the sequences of Streptomyces sp. rRNA from Norway and from the Solomon Islands. The Streptomyces grew well in submerged system at 20ºC, cells multiplication up to stationary phase being drastically increased after 120 h of submerged cultivation. The beta-amylase production reached a maximum peak after seven days, while alpha-amylase and proteases were performing biosynthesis after nine days of submerged cultivation at 20ºC. Newly Streptomyces were able to produce amylase and proteases in a cold environment. The ability to adapt to low temperature of these enzymes could make them valuable ingredients for detergents, the food industry and bioremediation processes which require low temperatures.

  13. Tissue localization and partial characterization of pheromone biosynthesis activating neuropeptide in Achaea janata

    Indian Academy of Sciences (India)

    V S Ajitha; D Muraleedharan

    2005-03-01

    Female sex pheromone production in certain moth species have been shown to be regulated by a cephalic endocrine peptidic factor: pheromone biosynthesis activating neuropeptide (PBAN), having 33 amino acid residues. Antisera against synthetic Heliothis zea-PBAN were developed. Using these polyclonals, immunoreactivity was mapped in the nervous system of Achaea janata. Three distinct groups of immunopositive secretory neurons were identified in the suboesophageal ganglion; and immunoreactivity was observed in the corpora cardiaca, thoracic and in the abdominal ganglia. From about 6000 brain sub-oesophageal ganglion complexes, the neuropeptide was isolated; and purified sequentially by Sep-pak and reversed phase high performance liquid chromatographic methods. Identity of purified PBAN fraction was confirmed with polyclonal antibody by immunoblotting. Molecular mass of the isolated peptide was determined by matrix-assisted laser desorption/ionization mass spectrometry, and was found to be 3900 Da, same as that of known H. zea-PBAN. Radiochemical bioassay confirmed the pheromonotropic effect of the isolated neuropeptide in this insect.

  14. Partial priapism

    DEFF Research Database (Denmark)

    Høyerup, Peter; Dahl, Claus; Azawi, Nessn Htum

    2014-01-01

    Partial priapism, also called partial segmental thrombosis of the corpus cavernosum, is a rare urological condition. Factors such as bicycle riding, drug usage, penile trauma and haematological diseases have been associated with the condition. Medical treatment with low molecular weight heparin (...... (LMWH) or acetylsalicylic acid is first choice treatment, and surgery is preserved for patients unresponsive to analgesics. In this report we describe the case of a 70-year-old man with partial priapism after blood transfusions treated successfully with LMWH....

  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. Partial antiviral activities detection of chicken Mx jointing with neuraminidase gene (NA against Newcastle disease virus.

    Directory of Open Access Journals (Sweden)

    Yani Zhang

    Full Text Available As an attempt to increase the resistance to Newcastle Disease Virus (NDV and so further reduction of its risk on the poultry industry. This work aimed to build the eukaryotic gene co-expression plasmid of neuraminidase (NA gene and myxo-virus resistance (Mx and detect the gene expression in transfected mouse fibroblasts (NIH-3T3 cells, it is most important to investigate the influence of the recombinant plasmid on the chicken embryonic fibroblasts (CEF cells. cDNA fragment of NA and mutant Mx gene were derived from pcDNA3.0-NA and pcDNA3.0-Mx plasmid via PCR, respectively, then NA and Mx cDNA fragment were inserted into the multiple cloning sites of pVITRO2 to generate the eukaryotic co-expression plasmid pVITRO2-Mx-NA. The recombinant plasmid was confirmed by restriction endonuclease treatment and sequencing, and it was transfected into the mouse fibroblasts (NIH-3T3 cells. The expression of genes in pVITRO2-Mx-NA were measured by RT-PCR and indirect immunofluorescence assay (IFA. The recombinant plasmid was transfected into CEF cells then RT-PCR and the micro-cell inhibition tests were used to test the antiviral activity for NDV. Our results showed that co-expression vector pVITRO2-Mx-NA was constructed successfully; the expression of Mx and NA could be detected in both NIH-3T3 and CEF cells. The recombinant proteins of Mx and NA protect CEF cells from NDV infection until after 72 h of incubation but the individually mutagenic Mx protein or NA protein protects CEF cells from NDV infection till 48 h post-infection, and co-transfection group decreased significantly NDV infection compared with single-gene transfection group (P<0. 05, indicating that Mx-NA jointing contributed to delaying the infection of NDV in single-cell level and the co-transfection of the jointed genes was more powerful than single one due to their synergistic effects.

  17. Partial chemical composition and antimicrobial activity of Daucus crinitus Desf. extracts

    Directory of Open Access Journals (Sweden)

    Paolini, J.

    2010-09-01

    Full Text Available The chemical composition of fatty acids and the unsaponifiable fraction of the roots, leaves and stems from Daucus crinitus Desf. were, determined using gas chromatography (GC and gas chromatography-Mass Spectrometry (GC-MS. The fatty acid fractions of different organs (leaves, stems and roots were characterized by lauric acid (17.9, 17.5 and 18.1 % respectively and other long chain fatty acids (until C22. Qualitative and quantitative differences were reported between the unsaponifiable fractions of different organs from D. crinitus. The unsaponifiable fractions of the leaves, roots and stem showed high amounts of aliphatic components (83.4%, 87.2% and 91.4%, respectively. The monoterpen, diterpen and sesquiterpen components were only present in small percentages. The antimicrobial properties of the D. critinus extracts were tested on four different microorganisms. These extracts were found to be active against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Candida albicans.La composición química de los ácidos grasos y la fracción insaponificable de raíces, hojas, y tallos de Daucus crinitus Desf. fueron establecidas utilizando cromatografía de gases (GC y cromatografía de gases-espectrometría de masas (GC-MS. La fracción de ácidos grasos de los diferentes órganos (hojas, tallos y raíces se caracterizó por el ácido láurico (17.9, 17.5 y 18.1% respectivamente y otros ácidos grasos de cadena larga (hasta C22. Diferencias cualitativas y cuantitativas se registraron entre las fracciones insaponificable de los diferentes órganos de D. crinitus. De hecho, las fracciones insaponificable de la raíz, de la hoja y del tallo mostraron cantidades altas de componentes alifáticos (83.4%, 87.2% y 91.4%, respectivamente. Los componentes monoterpénicos, diterpénicos y sesquiterpénicos solo estuvieron presentes en un pequeño porcentaje. Las propiedades antimicrobianas de los extractos de D. critinus fueron ensayadas en cuatro

  18. Medium chain fatty acids are selective peroxisome proliferator activated receptor (PPAR) γ activators and pan-PPAR partial agonists

    NARCIS (Netherlands)

    Liberato, Marcelo Vizoná; Nascimento, Alessandro S; Ayers, Steven D; Lin, Jean Z; Cvoro, Aleksandra; Silveira, Rodrigo L; Martínez, Leandro; Souza, Paulo C T; Saidemberg, Daniel; Deng, Tuo; Amato, Angela Angelica; Togashi, Marie; Hsueh, Willa A; Phillips, Kevin; Palma, Mário Sérgio; Neves, Francisco A R; Skaf, Munir S; Webb, Paul; Polikarpov, Igor

    2012-01-01

    Thiazolidinediones (TZDs) act through peroxisome proliferator activated receptor (PPAR) γ to increase insulin sensitivity in type 2 diabetes (T2DM), but deleterious effects of these ligands mean that selective modulators with improved clinical profiles are needed. We obtained a crystal structure of

  19. PT symmetry and supersymmetry

    CERN Document Server

    Znojil, M

    2002-01-01

    A re-formulated, non-Hermitian version of the Witten's supersymmetric quantum mechanics is presented. Its use of pseudo-Hermitian (so called PT symmetric) Hamiltonians is reviewed and illustrated via several forms of an innovated supersymmetric partnership between strongly singular ("spiked") harmonic oscillators.

  20. Thrombelastography is Better Than PT, aPTT, and Activated Clotting Time in Detecting Clinically Relevant Clotting Abnormalities After Hypothermia, Hemorrhagic Shock and Resuscitation in Pigs

    Science.gov (United States)

    2008-09-01

    samples were taken for measurements of coagulation and hemodynamics. Animals were euthanized afterward with an overdose of a veterinary euthanasia ...clinical outcomes.34–38 Thus, although the insensitivity of PT or aPTT under some circumstances is not appreciated, it should be recognized that

  1. The effect of Rhδ+ dopant in SrTiO3 on the active oxidation state of co-catalytic Pt nanoparticles in overall water splitting

    NARCIS (Netherlands)

    Zoontjes, M.G.C.; Han, K.; Huijben, M.; Wiel, van der W.G.; Mul, G.

    2016-01-01

    We report on the oxidation state of Pt nanoparticles when deposited on SrTiO3 or Rh-doped SrTiO3 under realistic solar water-splitting conditions. The oxidation state was investigated using state-of-the-art analysis of the reaction in a continuously stirred tank reactor (CSTR) connected to a micro g

  2. Pt Ru/C electrocatalysts prepared using electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F.; Oliveira Neto, Almir; Pino, Eddy S.; Brandalise, Michele; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mails: dfsilva@ipen.br; espinace@ipen.br

    2007-07-01

    Pt Ru/C electrocatalysts (carbon-supported Pt Ru nanoparticles) were prepared submitting water/ethylene glycol solutions containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The water/ethylene glycol ratio (v/v) was evaluated as synthesis parameters. The Pt Ru/C electrocatalysts were prepared with a nominal Pt:Ru atomic ratio of 50:50 and were characterized by energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) and tested for methanol electro-oxidation using cyclic voltammetry and chronoamperometry. The obtained Pt Ru/C electrocatalysts showed the typical fcc structure of platinum-ruthenium alloys and the electrocatalytic activity depends on the water/ethylene glycol ratio used in the preparation.

  3. Partially Deglycosylated Equine LH Preferentially Activates β-Arrestin-Dependent Signaling at the Follicle-Stimulating Hormone Receptor

    Science.gov (United States)

    Wehbi, Vanessa; Tranchant, Thibaud; Durand, Guillaume; Musnier, Astrid; Decourtye, Jérémy; Piketty, Vincent; Butnev, Vladimir Y.; Bousfield, George R.; Crépieux, Pascale; Maurel, Marie-Christine; Reiter, Eric

    2010-01-01

    Deglycosylated FSH is known to trigger poor Gαs coupling while efficiently binding its receptor. In the present study, we tested the possibility that a deglycosylated equine LH (eLHdg) might be able to selectively activate β-arrestin-dependent signaling. We compared native eLH to an eLH derivative [i.e. truncated eLHβ (Δ121-149) combined with asparagine56-deglycosylated eLHα (eLHdg)] previously reported as an antagonist of cAMP accumulation at the FSH receptor (FSH-R). We confirmed that, when used in conjunction with FSH, eLHdg acted as an antagonist for cAMP accumulation in HEK-293 cells stably expressing the FSH-R. Furthermore, when used alone at concentrations up to 1 nm, eLHdg had no detectable agonistic activity on cAMP accumulation, protein kinase A activity or cAMP-responsive element-dependent transcriptional activity. At higher concentrations, however, a weak agonistic action was observed with eLHdg, whereas eLH led to robust responses whatever the concentration. Both eLH and eLHdg triggered receptor internalization and led to β-arrestin recruitment. Both eLH and eLHdg triggered ERK and ribosomal protein (rp) S6 phosphorylation at 1 nm. The depletion of endogenous β-arrestins had only a partial effect on eLH-induced ERK and rpS6 phosphorylation. In contrast, ERK and rpS6 phosphorylation was completely abolished at all time points in β-arrestin-depleted cells. Together, these results show that eLHdg has the ability to preferentially activate β-arrestin-dependent signaling at the FSH-R. This finding provides a new conceptual and experimental framework to revisit the physiological meaning of gonadotropin structural heterogeneity. Importantly, it also opens a field of possibilities for the development of selective modulators of gonadotropin receptors. PMID:20107152

  4. Partially deglycosylated equine LH preferentially activates beta-arrestin-dependent signaling at the follicle-stimulating hormone receptor.

    Science.gov (United States)

    Wehbi, Vanessa; Tranchant, Thibaud; Durand, Guillaume; Musnier, Astrid; Decourtye, Jérémy; Piketty, Vincent; Butnev, Vladimir Y; Bousfield, George R; Crépieux, Pascale; Maurel, Marie-Christine; Reiter, Eric

    2010-03-01

    Deglycosylated FSH is known to trigger poor Galphas coupling while efficiently binding its receptor. In the present study, we tested the possibility that a deglycosylated equine LH (eLHdg) might be able to selectively activate beta-arrestin-dependent signaling. We compared native eLH to an eLH derivative [i.e. truncated eLHbeta (Delta121-149) combined with asparagine56-deglycosylated eLHalpha (eLHdg)] previously reported as an antagonist of cAMP accumulation at the FSH receptor (FSH-R). We confirmed that, when used in conjunction with FSH, eLHdg acted as an antagonist for cAMP accumulation in HEK-293 cells stably expressing the FSH-R. Furthermore, when used alone at concentrations up to 1 nM, eLHdg had no detectable agonistic activity on cAMP accumulation, protein kinase A activity or cAMP-responsive element-dependent transcriptional activity. At higher concentrations, however, a weak agonistic action was observed with eLHdg, whereas eLH led to robust responses whatever the concentration. Both eLH and eLHdg triggered receptor internalization and led to beta-arrestin recruitment. Both eLH and eLHdg triggered ERK and ribosomal protein (rp) S6 phosphorylation at 1 nM. The depletion of endogenous beta-arrestins had only a partial effect on eLH-induced ERK and rpS6 phosphorylation. In contrast, ERK and rpS6 phosphorylation was completely abolished at all time points in beta-arrestin-depleted cells. Together, these results show that eLHdg has the ability to preferentially activate beta-arrestin-dependent signaling at the FSH-R. This finding provides a new conceptual and experimental framework to revisit the physiological meaning of gonadotropin structural heterogeneity. Importantly, it also opens a field of possibilities for the development of selective modulators of gonadotropin receptors.

  5. Comparison of formic acid oxidation at supported Pt catalyst and at low-index Pt single crystal electrodes in sulfuric acid solution

    Directory of Open Access Journals (Sweden)

    AMALIJA V. TRIPKOVIC

    2003-11-01

    Full Text Available The oxidation of formic acid was studied at supported Pt catalyst (47.5 wt%. Pt and a low-index single crystal electrodes in sulfuric acid. The supported Pt catalyst was characterized by the TEM and HRTEM techniques. The mean Pt particle diameter, calculated from electrochemical measurements, fits well with Pt particle size distribution determined by HRTEM. For the mean particle diameter the surface averaged distribution of low-index single crystal facets was established. Comparison of the activities obtained at Pt supported catalyst and low-index Pt single crystal electrodes revealed that Pt(111 plane is the most active in the potential region relevant for fuel cell applications.

  6. Pt-Ni and Pt-M-Ni (M = Ru, Sn Anode Catalysts for Low-Temperature Acidic Direct Alcohol Fuel Cells: A Review

    Directory of Open Access Journals (Sweden)

    Ermete Antolini

    2017-01-01

    Full Text Available In view of a possible use as anode materials in acidic direct alcohol fuel cells, the electro-catalytic activity of Pt-Ni and Pt-M-Ni (M = Ru, Sn catalysts for methanol and ethanol oxidation has been widely investigated. An overview of literature data regarding the effect of the addition of Ni to Pt and Pt-M on the methanol and ethanol oxidation activity in acid environment of the resulting binary and ternary Ni-containing Pt-based catalysts is presented, highlighting the effect of alloyed and non-alloyed nickel on the catalytic activity of these materials.

  7. Partial Sleep Restriction Activates Immune Response-Related Gene Expression Pathways: Experimental and Epidemiological Studies in Humans

    Science.gov (United States)

    Rantanen, Ville; Kronholm, Erkki; Surakka, Ida; van Leeuwen, Wessel M. A.; Lehto, Maili; Matikainen, Sampsa; Ripatti, Samuli; Härmä, Mikko; Sallinen, Mikael; Salomaa, Veikko; Jauhiainen, Matti; Alenius, Harri; Paunio, Tiina; Porkka-Heiskanen, Tarja

    2013-01-01

    Epidemiological studies have shown that short or insufficient sleep is associated with increased risk for metabolic diseases and mortality. To elucidate mechanisms behind this connection, we aimed to identify genes and pathways affected by experimentally induced, partial sleep restriction and to verify their connection to insufficient sleep at population level. The experimental design simulated sleep restriction during a working week: sleep of healthy men (N = 9) was restricted to 4 h/night for five nights. The control subjects (N = 4) spent 8 h/night in bed. Leukocyte RNA expression was analyzed at baseline, after sleep restriction, and after recovery using whole genome microarrays complemented with pathway and transcription factor analysis. Expression levels of the ten most up-regulated and ten most down-regulated transcripts were correlated with subjective assessment of insufficient sleep in a population cohort (N = 472). Experimental sleep restriction altered the expression of 117 genes. Eight of the 25 most up-regulated transcripts were related to immune function. Accordingly, fifteen of the 25 most up-regulated Gene Ontology pathways were also related to immune function, including those for B cell activation, interleukin 8 production, and NF-κB signaling (P<0.005). Of the ten most up-regulated genes, expression of STX16 correlated negatively with self-reported insufficient sleep in a population sample, while three other genes showed tendency for positive correlation. Of the ten most down-regulated genes, TBX21 and LGR6 correlated negatively and TGFBR3 positively with insufficient sleep. Partial sleep restriction affects the regulation of signaling pathways related to the immune system. Some of these changes appear to be long-lasting and may at least partly explain how prolonged sleep restriction can contribute to inflammation-associated pathological states, such as cardiometabolic diseases. PMID:24194869

  8. Partial sleep restriction activates immune response-related gene expression pathways: experimental and epidemiological studies in humans.

    Directory of Open Access Journals (Sweden)

    Vilma Aho

    Full Text Available Epidemiological studies have shown that short or insufficient sleep is associated with increased risk for metabolic diseases and mortality. To elucidate mechanisms behind this connection, we aimed to identify genes and pathways affected by experimentally induced, partial sleep restriction and to verify their connection to insufficient sleep at population level. The experimental design simulated sleep restriction during a working week: sleep of healthy men (N = 9 was restricted to 4 h/night for five nights. The control subjects (N = 4 spent 8 h/night in bed. Leukocyte RNA expression was analyzed at baseline, after sleep restriction, and after recovery using whole genome microarrays complemented with pathway and transcription factor analysis. Expression levels of the ten most up-regulated and ten most down-regulated transcripts were correlated with subjective assessment of insufficient sleep in a population cohort (N = 472. Experimental sleep restriction altered the expression of 117 genes. Eight of the 25 most up-regulated transcripts were related to immune function. Accordingly, fifteen of the 25 most up-regulated Gene Ontology pathways were also related to immune function, including those for B cell activation, interleukin 8 production, and NF-κB signaling (P<0.005. Of the ten most up-regulated genes, expression of STX16 correlated negatively with self-reported insufficient sleep in a population sample, while three other genes showed tendency for positive correlation. Of the ten most down-regulated genes, TBX21 and LGR6 correlated negatively and TGFBR3 positively with insufficient sleep. Partial sleep restriction affects the regulation of signaling pathways related to the immune system. Some of these changes appear to be long-lasting and may at least partly explain how prolonged sleep restriction can contribute to inflammation-associated pathological states, such as cardiometabolic diseases.

  9. Telmisartan protects against diabetic vascular complications in a mouse model of obesity and type 2 diabetes, partially through peroxisome proliferator activated receptor-{gamma}-dependent activity

    Energy Technology Data Exchange (ETDEWEB)

    Toyama, Kensuke; Nakamura, Taishi; Kataoka, Keiichiro [Department of Pharmacology and Molecular Therapeutics, Kumamoto University Graduate School of Medical Sciences, Kumamoto (Japan); Yasuda, Osamu [Department of Cardiovascular Clinical and Translational Research, Kumamoto University Hospital, Kumamoto (Japan); Fukuda, Masaya; Tokutomi, Yoshiko; Dong, Yi-Fei [Department of Pharmacology and Molecular Therapeutics, Kumamoto University Graduate School of Medical Sciences, Kumamoto (Japan); Ogawa, Hisao [Department of Cardiovascular Medicine, Kumamoto University Graduate School of Medical Sciences, Kumamoto (Japan); Kim-Mitsuyama, Shokei, E-mail: kimmitsu@gpo.kumamoto-u.ac.jp [Department of Pharmacology and Molecular Therapeutics, Kumamoto University Graduate School of Medical Sciences, Kumamoto (Japan)

    2011-07-08

    Highlights: {yields} Telmisartan, an angiotensin receptor blocker, acts as a partial PPAR{gamma} agonist. {yields} The protective effects of telmisartan against diabetic vascular injury were associated with attenuation of vascular NF{kappa}B activation and TNF {alpha}. {yields} PPAR{gamma} activity of telmisartan was involved in the normalization of vascular PPAR{gamma} downregulation in diabetic mice. {yields} We provided the first evidence indicating that PPAR{gamma} activity of telmisartan contributed to the protective effects of telmisartan against diabetic vascular complication. -- Abstract: Experimental and clinical data support the notion that peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) activation is associated with anti-atherosclerosis as well as anti-diabetic effect. Telmisartan, an angiotensin receptor blocker (ARB), acts as a partial PPAR{gamma} agonist. We hypothesized that telmisartan protects against diabetic vascular complications, through PPAR{gamma} activation. We compared the effects of telmisartan, telmisartan combined with GW9662 (a PPAR{gamma} antagonist), and losartan with no PPAR{gamma} activity on vascular injury in obese type 2 diabetic db/db mice. Compared to losartan, telmisartan significantly ameliorated vascular endothelial dysfunction, downregulation of phospho-eNOS, and coronary arterial remodeling in db/db mice. More vascular protective effects of telmisartan than losartan were associated with greater anti-inflammatory effects of telmisartan, as shown by attenuation of vascular nuclear factor kappa B (NF{kappa}B) activation and tumor necrosis factor {alpha}. Coadministration of GW9662 with telmisartan abolished the above mentioned greater protective effects of telmisartan against vascular injury than losartan in db/db mice. Thus, PPAR{gamma} activity appears to be involved in the vascular protective effects of telmisartan in db/db mice. Moreover, telmisartan, but not losartan, prevented the downregulation of

  10. Tailoring the morphology of Pt3Cu1 nanocrystals supported on graphene nanoplates for ethanol oxidation

    Science.gov (United States)

    Zhang, Genlei; Yang, Zhenzhen; Zhang, Wen; Hu, Hongwei; Wang, Chunzhen; Huang, Chengde; Wang, Yuxin

    2016-01-01

    In the search for alternatives to conventional Pt electrocatalysts, we synthesized a series of graphene nanoplate (GNP)-supported Pt3Cu1 nanocrystals (NCs), possessing almost the same composition but different morphologies to probe their electrochemical properties as a function of morphology for the ethanol oxidation reaction. The morphology of the Pt3Cu1 catalysts could be systematically evolved from dendritic (D-Pt3Cu1/GNPs) to wire-like (W-Pt3Cu1/GNPs) and spherical (Pt3Cu1/GNPs) by only varying pH of the reaction solution. The as-prepared Pt3Cu1 catalysts were subsequently characterized using a suite of techniques including transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS) to verify not only their morphologies and chemical compositions but also the incorporation of Cu into the Pt lattice, as well as physical structure and integrity. Gratifyingly, the three Pt3Cu1 catalysts exhibited superior electrocatalytic properties for the ethanol oxidation compared to the monometallic Pt/GNPs and Pt/C-JM (Johnson Matthey), with the activities, durabilities and anti-poisonous abilities following the order Pt3Cu1/GNPs chemical compositions but also the incorporation of Cu into the Pt lattice, as well as physical structure and integrity. Gratifyingly, the three Pt3Cu1 catalysts exhibited superior electrocatalytic properties for the ethanol oxidation compared to the monometallic Pt/GNPs and Pt/C-JM (Johnson Matthey), with the activities, durabilities and anti-poisonous abilities following the order Pt3Cu1/GNPs < W-Pt3Cu1/GNPs < D-Pt3Cu1/GNPs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08013d

  11. EFEKTIVITAS IMPLEMENTASI CORPORATE SOCIAL RESPOSIBILITY PT. ABC

    Directory of Open Access Journals (Sweden)

    Rizkiaji Rikky Djunaedi

    2015-12-01

    Full Text Available The purposes of this study were 1 to analyze public perceptions on the effectiveness of the implementation of CSR of PT. A B C; 2 to analyze the implementation of CSR activities by PT. A B C; 3 to formulate strategies to improve the effectiveness of the implementation of CSR of PT. A B C. The method used in this research was descriptive analysis with a survey approach to measure expectations and performance assessment on the CSR implemented programs by the public, and there were respondents 104 respondents involved in this study. This study used the Importance-Performance Analysis (IPA aiming to determine the effectiveness of the programs that have been implemented and to map the relationship between the expectations and the performance of each variable. Furthermore, using a SWOT analysis of the data processing and of the objectives of the program made by CSR is expected to provide recommendations to develop strategies in order to increase the effectiveness of CSR program of ABC Company.Keywords: corporate social responsibility (CSR, mining industry, implementation analysis, IPA, SWOTAbstrakTujuan dari  penelitian ini adalah 1 menganalisis persepsi masyarakat teradap efektivitas implementasi CSR PT. ABC; 2 menganalisis pelaksanaan  kegiatan CSR oleh PT. ABC; 3 merumuskan strategi untuk meningkatkan efektivitas implementasi CSR PT. ABC. Metode yang digunakan dalam penelitian ini adalah analisis deskriptif dengan pendekatan survey untuk mengukur harapan dan penilaian kinerja oleh masyarakat atas program CSR yang diterapkan. Jumlah responden sebanyak 104 orang.  Dalam penelitian ini digunakan Analisis Importance-Performance Analysis (IPA bertujuan untuk mengetahui efektifitas dari program-program yang telah dijalankan serta  memetakan hubungan antara harapan dengan kinerja dari masing-masing variabel. Selanjutnya menggunakan analisis SWOT dari hasil pengolahan data dan dari tujuan program dibuat oleh CSR sehingga dapat memberikan rekomendasi

  12. Vibration reduction in helicopter rotors using an actively controlled partial span trailing edge flap located on the blade

    Science.gov (United States)

    Millott, T. A.; Friedmann, P. P.

    1994-01-01

    This report describes an analytical study of vibration reduction in a four-bladed helicopter rotor using an actively controlled, partial span, trailing edge flap located on the blade. The vibration reduction produced by the actively controlled flap (ACF) is compared with that obtained using individual blade control (IBC), in which the entire blade is oscillated in pitch. For both cases a deterministic feedback controller is implemented to reduce the 4/rev hub loads. For all cases considered, the ACF produced vibration reduction comparable with that obtained using IBC, but consumed only 10-30% of the power required to implement IBC. A careful parametric study is conducted to determine the influence of blade torsional stiffness, spanwise location of the control flap, and hinge moment correction on the vibration reduction characteristics of the ACF. The results clearly demonstrate the feasibility of this new approach to vibration reduction. It should be emphasized than the ACF, used together with a conventional swashplate, is completely decoupled from the primary flight control system and thus it has no influence on the airworthiness of the helicopter. This attribute is potentially a significant advantage when compared to IBC.

  13. The Mechanism of Direct Formic Acid Fuel Cell Using Pd, Pt and Pt-Ru

    Science.gov (United States)

    Kamiya, Nobuyuki; Liu, Yan; Mitsushima, Shigenori; Ota, Ken-Ichiro; Tsutsumi, Yasuyuki; Ogawa, Naoya; Kon, Norihiro; Eguchi, Mika

    The electro-oxidation of formic acid, 2-propanol and methanol on Pd black, Pd/C, Pt-Ru/C and Pt/C has been investigated to clear the reaction mechanism. It was suggested that the formic acid is dehydrogenated on Pd surface and the hydrogen is occluded in the Pd lattice. Thus obtained hydrogen acts like pure hydrogen supplied from the outside and the cell performance of the direct formic acid fuel cell showed as high as that of a hydrogen-oxygen fuel cell. 2-propanol did not show such dehydrogenation reaction on Pd catalyst. Platinum and Pt-Ru accelerated the oxidation of C-OH of 2-propanol and methanol. Slow scan voltammogram (SSV) and chronoamperometry measurements showed that the activity of formic acid oxidation increased in the following order: Pd black > Pd 30wt.%/C > Pt50wt.%/C > 27wt.%Pt-13wt.%Ru/C. A large oxidation current for formic acid was found at a low overpotential on the palladium electrocatalysts. These results indicate that formic acid is mainly oxidized through a dehydrogenation reaction. For the oxidation of 2-propanol and methanol, palladium was not effective, and 27wt.%Pt-13wt.%Ru/C showed the best oxidation activity.

  14. Characterization and single cell testing of Pt/C electrodes prepared by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Martin, A.J.; Chaparro, A.M.; Gallardo, B.; Folgado, M.A. [CIEMAT, Department of Energy, Avda. Complutense 22, 28040 Madrid (Spain); Daza, L. [CIEMAT, Department of Energy, Avda. Complutense 22, 28040 Madrid (Spain); Instituto de Catalisis y Petroleoquimica (CSIC), C/. Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain)

    2009-07-01

    Electrodes for proton exchange membrane fuel cells (PEMFC) have been prepared by the electrodeposition method. For this task, the electrodeposition of platinum is carried out on a carbon black substrate impregnated with an ionomer, proton conducting, medium. Before electrodeposition, the substrate is submitted to an activation process to increase the hydrophilic character of the surface to a few microns depth. Electrodeposition of platinum takes place inside the generated surface hydrophilic layer, resulting in a continuous phase covering totally or partially carbon substrate grains. Cross sectional images show a decay profile of platinum towards the interior of the substrate, reflecting a deposition process limited by diffusion of PtCl{sub 6}{sup 2-} through the porous substrate. Electrodes with different platinum loads have been prepared, and membrane electrode assemblies (MEA) have been mounted with the electrodeposited electrodes as cathode and other standard components (commercial anode and Nafion{sup R} 117 membrane). The electrochemically active surface area determined from hydrogen underpotential deposition charge, is lower on the electrodeposited electrodes than on standard electrodes. However, single cell testing shows higher mass specific activity on electrodeposited cathodes with low and intermediate Pt load (below 0.05 mg Pt cm{sup -2}). (author)

  15. Characterization and single cell testing of Pt/C electrodes prepared by electrodeposition

    Science.gov (United States)

    Martín, A. J.; Chaparro, A. M.; Gallardo, B.; Folgado, M. A.; Daza, L.

    Electrodes for proton exchange membrane fuel cells (PEMFC) have been prepared by the electrodeposition method. For this task, the electrodeposition of platinum is carried out on a carbon black substrate impregnated with an ionomer, proton conducting, medium. Before electrodeposition, the substrate is submitted to an activation process to increase the hydrophilic character of the surface to a few microns depth. Electrodeposition of platinum takes place inside the generated surface hydrophilic layer, resulting in a continuous phase covering totally or partially carbon substrate grains. Cross sectional images show a decay profile of platinum towards the interior of the substrate, reflecting a deposition process limited by diffusion of PtCl 6 2- through the porous substrate. Electrodes with different platinum loads have been prepared, and membrane electrode assemblies (MEA) have been mounted with the electrodeposited electrodes as cathode and other standard components (commercial anode and Nafion R 117 membrane). The electrochemically active surface area determined from hydrogen underpotential deposition charge, is lower on the electrodeposited electrodes than on standard electrodes. However, single cell testing shows higher mass specific activity on electrodeposited cathodes with low and intermediate Pt load (below 0.05 mg Pt cm -2).

  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

    In order for low temperature polymer electrolyte membrane fuel cells to become economically viable Pt catalyst loading must be significantly reduced. The cathode of the polymer electrolyte membrane fuel cell, where oxygen reduction takes place, is responsible for the main activity loss. The devel...

  17. Thermal memory effects at the Pt vertical bar YSZ interface

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Bay, Lasse

    2002-01-01

    A current induced activation mechanism in the oxygen reaction on the Pt \\ YSZ interface at 1000 degreesC is demonstrated by impedance measurements. It is shown that Pt point electrodes conditioned at high temperature retain their initial reactivity when cooled to 600 degreesC. At this temperature...

  18. Mechanisms of self-diffusion on Pt(110)

    DEFF Research Database (Denmark)

    Lorensen, Henrik Qvist; Nørskov, Jens Kehlet; Jacobsen, Karsten Wedel

    1999-01-01

    The self-diffusion of Pt on the missing row reconstructed Pt(110) surface is discussed based on density functional calculations of activation energy barriers. Different competing diffusion mechanisms are considered and we show that several different diffusion paths along the reconstruction troughs...

  19. The Synthesis of Glycosyl Phosphite-Pt(Ⅱ) Complexes

    Institute of Scientific and Technical Information of China (English)

    Ling Hua CAO; Hong Yun GAO; Chuan Jian ZHOU; Yu Ting LIU

    2004-01-01

    Ethylene glycol phosphorochloridite 1 or catechol phosphorochloridite 2 reacted with isopropylidene derivatives of D-glucose, D-galactose, D-mannose and D-fructose, a series of glycosyl phosphites were obtained. These glycosyl phosphites form optically active complexes with simple Pt (Ⅱ) salts. Pt (Ⅱ) is coordinated to the phosphorus atom, most of the metal complexes are quite stable.

  20. Halogen poisoning effect of Pt-TiO2 for formaldehyde catalytic oxidation performance at room temperature

    Science.gov (United States)

    Zhu, Xiaofeng; Cheng, Bei; Yu, Jiaguo; Ho, Wingkei

    2016-02-01

    Catalytic decomposition of formaldehyde (HCHO) at room temperature is an important method for HCHO removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. However, the stability of this catalyst remains unexplored. In this study, Pt-TiO2 (Pt-P25) catalysts with and without adsorbed halogen ions (including F-, Cl-, Br-, and I-) were prepared through impregnation and ion modification. Pt-TiO2 samples with adsorbed halogen ions exhibited reduced catalytic activity for formaldehyde decomposition at room temperature compared with the Pt-TiO2 sample; the catalytic activity followed the order of F-Pt-P25, Cl-Pt-P25, Br-Pt-P25, and I-Pt-P25. Characterization results (including XRD, TEM, HRTEM, BET, XPS, and metal dispersion) showed that the adsorbed halogen ions can poison Pt nanoparticles (NPs), thereby reducing the HCHO oxidation activity of Pt-TiO2. The poison mechanism is due to the strong adsorption of halogen ions on the surface of Pt NPs. The adsorbed ions form coordination bonds with surface Pt atoms by transferring surplus electrons into the unoccupied 5d orbit of the Pt atom, thereby inhibiting oxygen adsorption and activation of the Pt NP surface. Moreover, deactivation rate increases with increasing diameter of halogen ions. This study provides new insights into the fabrication of high-performance Pt-based catalysts for indoor air purification.

  1. Microwave-assisted synthesis of high-loading, highly dispersed Pt/carbon aerogel catalyst for direct methanol fuel cell

    Indian Academy of Sciences (India)

    Zhijun Guo; Hong Zhu; Xinwei Zhang; Fanghui Wang; Yubao Guo; Yongsheng Wei

    2011-06-01

    A Pt supported on carbon aerogel catalyst has been synthesized by the microwave-assisted polyol process. The Pt supported on carbon aerogel catalyst was characterized by high resolution transmission electron microscopy and X-ray diffraction. The results show a uniform dispersion of spherical Pt nanoparticles 2.5–3.0 nm in diameter. Cyclic voltammetry and chronoamperometry were used to evaluate the electrocatalytic activity of the Pt/carbon aerogel catalyst for methanol oxidation at room temperature. The Pt/carbon aerogel catalyst shows higher electrochemical catalytic activity and stability for methanol oxidation than a commercial Pt/C catalyst of the same Pt loading.

  2. Resistance switching mode transformation in SrRuO3/Cr-doped SrZrO3/Pt frameworks via a thermally activated Ti out-diffusion process.

    Science.gov (United States)

    Jo, Yongcheol; Jung, Kyooho; Kim, Jongmin; Woo, Hyeonseok; Han, Jaeseok; Kim, Hyungsang; Hong, Jinpyo; Lee, Jeon-Kook; Im, Hyunsik

    2014-12-08

    This work reports on a mechanism for irreversible resistive switching (RS) transformation from bipolar to unipolar RS behavior in SrRuO3 (SRO)/Cr-doped SrZrO3 (SZO:Cr)/Pt capacitor structures prepared on a Ti/SiO2/Si substrate. Counter-clockwise bipolar RS memory current-voltage (I-V) characteristics are observed within the RS voltage window of -2.5 to +1.9 V, with good endurance and retention properties. As the bias voltage increases further beyond 4 V under a forward bias, a forming process occurs resulting in irreversible RS mode transformation from bipolar to unipolar mode. This switching mode transformation is a direct consequence of thermally activated Ti out-diffusion from a Ti adhesion layer. Transition metal Ti effectively out-diffuses through the loose Pt electrode layer at high substrate temperatures, leading to the unintended formation of a thin titanium oxide (TiO(x) where x < 2) layer between the Pt electrode and the SZO:Cr layer as well as additional Ti atoms in the SZO:Cr layer. Cross-sectional scanning electron microscopy, transmission electron microscopy and Auger electron spectroscopy depth-profile measurements provided apparent evidence of the Ti out-diffusion phenomenon. We propose that the out-diffusion-induced additional Ti atoms in the SZO:Cr layer contributes to the creation of the metallic filamentary channels.

  3. High pressure organic colloid method for the preparation of high performance carbon nanotube-supported Pt and PtRu catalysts for fuel cell applications

    Institute of Scientific and Technical Information of China (English)

    WANG; KateNing; Viola; BIRSS

    2010-01-01

    Highly dispersed,high performance Pt and PtRu catalysts,supported on multiwalled carbon nanotubes(CNTs),were prepared by a high pressure organic colloid method.The particle sizes of the active components were as small as 1.2 nm for Pt and 1.1 nm for PtRu,and the active Pt surface areas were 295 and 395 m2/g,respectively.The catalysts showed very high activities toward the anodic oxidation of methanol,evaluated by cyclic voltammetry,being up to 4 times higher than that of commercial Johnson Matthey Hispec 2000 Pt/XC-72R and 5 times better than Hispec 5000 PtRu/XC-72R catalysts.In a full air/hydrogen fuel cell,a membrane-electrode assembly prepared using our Pt/CNT and PtRu/CNT catalysts showed 50% and 100% higher performances than those prepared with commercial Johnson Matthey Pt/XC-72R and PtRu/XC-72R catalysts for the same Pt loading and operating conditions.

  4. CLOUD COMPUTING ADOPTION STRATEGIES AT PT TASPEN INDONESIA, Tbk

    Directory of Open Access Journals (Sweden)

    Julirzal Sarmedy

    2014-10-01

    Full Text Available PT. Taspen as Indonesian institution, is responsible for managing social insuranceprograms of civil servants. With branch offices and business partners who are geographicallydispersed throughout Indonesia, information technology is very important to support thebusiness processes. Cloud computing is a model of information technology services that couldpotentially increase the effectiveness and efficiency of PT. Taspen information system. Thisstudy examines the phenomenon exists at PT. Taspen in order to adopt cloud computing inthe information system, by using the framework of Technology-Organization-Environment,Diffusion of Innovation theory, and Partial Least Square method. Organizational factor isthe most dominant for PT. Taspen to adopt cloud computing. Referring to these findings,then a SWOT analysis and TOWS matrix are performed, which in this study recommendsthe implementation of a strategy model of cloud computing services that are private andgradually in process.

  5. Preparation of Pt Au/C and Pt Au Bi/C electrocatalysts using electron beam irradiation for ethanol electro-oxidation in alkaline medium

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F.; Geraldes, Adriana N.; Cardoso, Elisangela S.Z.; Gomes, Thiago B.; Linardi, Marcelo; Oliveira Neto, Almir; Spinace, Estevam V., E-mail: dfsilva@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    Pt Au/C (50:50) and PtAuBi/C electrocatalysts with Pt:Au:Bi atomic ratios of 50:40:10, 50:30:20 and 50:10:40 were prepared in water/2-propanol using electron beam irradiation. The materials were characterized by X-ray diffraction (XRD) and the electro-oxidation of ethanol was studied by chronoamperometry at room temperature. The X-ray diffraction measurements for all electrocatalysts prepared showed four peaks, which are associated with the planes of the face-center