Science.gov

Sample records for metals palladium platinum

  1. Noble Metal Catalysts for Mercury Oxidation in Utility Flue Gas: Gold, Palladium and Platinum Formulations

    SciTech Connect

    Presto, A.A.; Granite, E.J

    2008-07-01

    The use of noble metals as catalysts for mercury oxidation in flue gas remains an area of active study. To date, field studies have focused on gold and palladium catalysts installed at pilot scale. In this article, we introduce bench-scale experimental results for gold, palladium and platinum catalysts tested in realistic simulated flue gas. Our initial results reveal some intriguing characteristics of catalytic mercury oxidation and provide insight for future research into this potentially important process.

  2. Fluorometric imaging methods for palladium and platinum and the use of palladium for imaging biomolecules.

    PubMed

    Tracey, Matthew P; Pham, Dianne; Koide, Kazunori

    2015-07-21

    Neither palladium nor platinum is an endogenous biological metal. Imaging palladium in biological samples, however, is becoming increasingly important because bioorthogonal organometallic chemistry involves palladium catalysis. In addition to being an imaging target, palladium has been used to fluorometrically image biomolecules. In these cases, palladium species are used as imaging-enabling reagents. This review article discusses these fluorometric methods. Platinum-based drugs are widely used as anticancer drugs, yet their mechanism of action remains largely unknown. We discuss fluorometric methods for imaging or quantifying platinum in cells or biofluids. These methods include the use of chemosensors to directly detect platinum, fluorescently tagging platinum-based drugs, and utilizing post-labeling to elucidate distribution and mode of action.

  3. Monodisperse colloidal metal particle from nonaqueous solutions: catalytic behavior in hydrogenation of but-1-ene of platinum, palladium, and rhodium particles supported on pumice

    SciTech Connect

    Boutonnet, M.; Kizling, J.; Mintsa-Eya, V.; Choplin, A.; Touroude, R.; Maire, G.; Stenius, P.

    1987-01-01

    Metal catalysts have been prepared by depositing monodisperse particles of platinum (2-3 nm), rhodium (2-3 nm), or palladium (5 nm) prepared in reversed micellar solutions on pumice. The particles are well dispersed on the support whereas particles deposited from aqueous or alcoholic solution give large aggregates. The catalytic properties of these different catalysts in the deuteration, isomerization, and hydrogen-deuterium exchange of but-1-ene have been compared. The activities calculated per metal surface atom are similar. However, platinum prepared from microemulsions show unusually high selectivity in the isomerization reaction, and for such particles dehydrogenated species are active in the exchange reaction. The specificity of rhodium and palladium catalysts is independent of the mode of preparation. The reaction mechanisms are discussed.

  4. Mineral resource of the month: platinum-group metals

    USGS Publications Warehouse

    Hilliard, Henry

    2003-01-01

    The precious metals commonly referred to as platinum-group metals (PGM) include iridium, osmium, palladium, platinum, rhodium and ruthenium. PGM are among the rarest of elements, and their market values — particularly for palladium, platinum and rhodium — are the highest of all precious metals.

  5. Platinum-ruthenium-palladium fuel cell electrocatalyst

    DOEpatents

    Gorer, Alexander

    2006-02-07

    A catalyst suitable for use in a fuel cell, especially as an anode catalyst, that contains platinum at a concentration that is between about 20 and about 60 atomic percent, ruthenium at a concentration that is between about 20 and about 60 atomic percent, palladium at a concentration that is between about 5 and about 45 atomic percent, and having an atomic ratio of platinum to ruthenium that is between about 0.7 and about 1.2. Alternatively, the catalyst may contain platinum at a concentration that is between about 25 and about 50 atomic percent, ruthenium at a concentration that is between about 25 and about 55 atomic percent, palladium at a concentration that is between about 5 and about 45 atomic percent, and having a difference between the concentrations of ruthenium and platinum that is no greater than about 20 atomic percent.

  6. Platinum and palladium oxalates: positive-tone extreme ultraviolet resists

    NASA Astrophysics Data System (ADS)

    Sortland, Miriam; Hotalen, Jodi; Re, Ryan Del; Passarelli, James; Murphy, Michael; Kulmala, Tero S.; Ekinci, Yasin; Neisser, Mark; Freedman, Daniel A.; Brainard, Robert L.

    2015-10-01

    Here, we present platinum and palladium mononuclear complexes with EUV photosensitivity and lithographic performance. Many platinum and palladium complexes show little or no EUV sensitivity; however, we have found that metal carbonates and metal oxalates (L2M(CO3) and L2M(C2O4); M=Pt or Pd) are sensitive to EUV. The metal carbonates give negative-tone behavior. The most interesting result is that the metal oxalates give the first positive-tone EUV resists based on mononuclear organometallic compounds. In particular, (dppm)Pd(C2O4) (dppm=1,1-bis(diphenylphosphino)methane) (23) prints 30-nm dense lines with E of 50 mJ/cm2. Derivatives of (23) were synthesized to explore the relationship between the core metal and the resist sensitivity. The study showed that palladium-based resists are more sensitive than platinum-based resists. The photoreaction has been investigated for two of our most promising resists, (dppm)Pd(C2O4) (23) and EtPPdC2O4 (27). Our experiments suggest the loss of CO2 and the formation of a zerovalent L4Pd complex upon exposure to light. We have identified dppm2Pd(δ(P)23.6) as the main photoproduct for (23) and EtPPd (δ(P)32.7) as the main photoproduct for (27).

  7. Platinum-ruthenium-palladium alloys for use as a fuel cell catalyst

    DOEpatents

    Gorer, Alexander

    2002-01-01

    A noble metal alloy composition for a fuel cell catalyst, a ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  8. Simultaneous determination of palladium, platinum and rhodium in crude platinum samples by activation analysis and high-resolution gamma spectrometry.

    PubMed

    Turkstra, J; de Wet, W J

    1969-08-01

    Instrumental neutron-activation analysis using a Ge(Li) detector has been investigated for the simultaneous determination of platinum, palladium and rhodium in crude platinum samples contained in lead cupels. This technique proved feasible and appears promising for extension to the determination of most of the noble metals.

  9. Determination of palladium and platinum by atomic absorption

    USGS Publications Warehouse

    Schnepfe, M.M.; Grimaldi, F.S.

    1969-01-01

    Palladium and platinum are determined by atomic absorption after fire-assay concentration into a gold bead. The limit of determination is ~0??06 ppm in a 20-g sample. Serious depressive interelement interferences are removed by buffering the solutions with a mixture of cadmium and copper sulphates with cadmium and copper concentrations each at 0??5%. Substantial amounts of Ag, Al, Au, Bi, Ca, Co, Cr, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn, and the platinum metals do not interfere in the atomic-absorption determination. ?? 1969.

  10. Platinum- and platinum alloy-coated palladium and palladium alloy particles and uses thereof

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir Branko

    2010-04-06

    The present invention relates to particle and nanoparticle composites useful as oxygen-reduction electrocatalysts. The particle composites are composed of a palladium or palladium-alloy particle or nanoparticle substrate coated with an atomic submonolayer, monolayer, bilayer, or trilayer of zerovalent platinum atoms. The invention also relates to a catalyst and a fuel cell containing the particle or nanoparticle composites of the invention. The invention additionally includes methods for oxygen reduction and production of electrical energy by using the particle and nanoparticle composites of the invention.

  11. Luminescent Cyclometalated Platinum and Palladium Complexes with Novel Photophysical Properties

    NASA Astrophysics Data System (ADS)

    Turner, Eric

    Organic light emitting diodes (OLEDs) is a rapidly emerging technology based on organic thin film semiconductors. Recently, there has been substantial investment in their use in displays. In less than a decade, OLEDs have grown from a promising academic curiosity into a multi-billion dollar global industry. At the heart of an OLED are emissive molecules that generate light in response to electrical stimulation. Ideal emitters are efficient, compatible with existing materials, long lived, and produce light predominantly at useful wavelengths. Developing an understanding of the photophysical processes that dictate the luminescent properties of emissive materials is vital to their continued development. Chapter 1 and Chapter 2 provide an introduction to the topics presented and the laboratory methods used to explore them. Chapter 3 discusses a series of tridentate platinum complexes. A synthetic method utilizing microwave irradiation was explored, as well as a study of the effects ligand structure had on the excited state properties. Results and techniques developed in this endeavor were used as a foundation for the work undertaken in later chapters. Chapter 4 introduces a series of tetradentate platinum complexes that share a phenoxy-pyridyl (popy) motif. The new molecular design improved efficiency through increased rigidity and modification of the excited state properties. This class of platinum complexes were markedly more efficient than those presented in Chapter 3, and devices employing a green emitting complex of the series achieved nearly 100% electron-to-photon conversion efficiency in an OLED device. Chapter 5 adapts the ligand structure developed in Chapter 4 to palladium. The resulting complexes exceed reported efficiencies of palladium complexes by an order of magnitude. This chapter also provides the first report of a palladium complex as an emitter in an OLED device. Chapter 6 discusses the continuation of development efforts to include carbazolyl

  12. Extractive separation and spectrophotometric determination of palladium and platinum with dithizone in the presence of stannous chloride.

    PubMed

    Marczenko, Z; Kuś, S; Mojski, M

    1984-11-01

    The conditions [acid used, presence of chloride and tin(II)] for the extractive separation and spectrophotometric determination of palladium and platinum as the dithizonates Pd(HDz)(2) and Pt(HDz)(2) have been examined. In the absence of stannous chloride platinum does not undergo extraction. Conditions for the separation and determination of these metals in the presence of mercury, gold and copper, which are also extracted with dithizone into carbon tetrachloride or chloroform under the conditions suitable for palladium (1M sulphuric acid/0.1M hydrochloric acid), have been defined. The mercury and gold dithizonates are formed quickly and can be removed before the palladium and platinum compounds have had time to form. They can be decomposed with iodide. Copper dithizonate is decomposed by reduction with tin(II). The proposed procedure has been applied to the determination of palladium in technical platinum metal.

  13. Superlattices of platinum and palladium nanoparticles

    SciTech Connect

    MARTIN,JAMES E.; WILCOXON,JESS P.; ODINEK,JUDY G.; PROVENCIO,PAULA P.

    2000-04-06

    The authors have used a nonionic inverse micelle synthesis technique to form nanoclusters of platinum and palladium. These nanoclusters can be rendered hydrophobic or hydrophilic by the appropriate choice of capping ligand. Unlike Au nanoclusters, Pt nanoclusters show great stability with thiol ligands in aqueous media. Alkane thiols, with alkane chains ranging from C{sub 6} to C{sub 18} were used as hydrophobic ligands, and with some of these they were able to form 2-D and/or 3-D superlattices of Pt nanoclusters as small as 2.7 nm in diameter. Image processing techniques were developed to reliably extract from transmission electron micrographs (TEMs) the particle size distribution, and information about the superlattice domains and their boundaries. The latter permits one to compute the intradomain vector pair correlation function of the particle centers, from which they can accurately determine the lattice spacing and the coherent domain size. From these data the gap between the particles in the coherent domains can be determined as a function of the thiol chain length. It is found that as the thiol chain length increases, the gaps between particles within superlattice domains increases, but more slowly than one might expect, possibly indicating thiol chain interdigitation.

  14. Fate of platinum metals in the environment.

    PubMed

    Pawlak, Justyna; Łodyga-Chruścińska, Elżbieta; Chrustowicz, Jakub

    2014-07-01

    For many years now automotive exhaust catalysts have been used to reduce the significant amounts of harmful chemical substances generated by car engines, such as carbon monoxide, nitrogen oxides, and aromatic hydrocarbons. Although they considerably decrease environmental contamination with the above-mentioned compounds, it is known that catalysts contribute to the environmental load of platinum metals (essential components of catalysts), which are released with exhaust fumes. Contamination with platinum metals stems mainly from automotive exhaust converters, but other major sources also exist. Since platinum group elements (PGEs): platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and iridium (Ir) seem to spread in the environment and accumulate in living organisms, they may pose a threat to animals and humans. This paper discusses the modes and forms of PGE emission as well as their impact on the environment and living organisms.

  15. Evidence for a late chondritic veneer in the Earth's mantle from high-pressure partitioning of palladium and platinum

    PubMed

    Holzheid; Sylvester; O'Neill; Rubie; Palme

    2000-07-27

    The high-pressure solubility in silicate liquids of moderately siderophile 'iron-loving' elements (such as nickel and cobalt) has been used to suggest that, in the early Earth, an equilibrium between core-forming metals and the silicate mantle was established at the bottom of a magma ocean. But observed concentrations of the highly siderophile elements--such as the platinum-group elements platinum, palladium, rhenium, iridium, ruthenium and osmium--in the Earth's upper mantle can be explained by such a model only if their metal-silicate partition coefficients at high pressure are orders of magnitude lower than those determined experimentally at one atmosphere (refs 3-8). Here we present an experimental determination of the solubility of palladium and platinum in silicate melts as a function of pressure to 16 GPa (corresponding to about 500 km depth in the Earth). We find that both the palladium and platinum metal-silicate partition coefficients, derived from solubility, do not decrease with pressure--that is, palladium and platinum retain a strong preference for the metal phase even at high pressures. Consequently the observed abundances of palladium and platinum in the upper mantle seem to be best explained by a 'late veneer' addition of chondritic material to the upper mantle following the cessation of core formation. PMID:10935633

  16. Operation of platinum-palladium catalysts with leaded gasoline.

    PubMed

    Teague, D M; Clougherty, L B; Speca, A N

    1975-04-01

    The effect of various fuel additives on the ability of platinum-palladium catalytic converters to remove the carbon monoxide and hydrocarbon components of automotive exhaust has been examined. Engine dynamometer studies suggest that these catalysts may be successfully used in conjunction with fuels of relatively high tetraethyllead concentrations, provided the ethylene dibromide portion of the scavenger is excluded. PMID:50929

  17. Operation of platinum-palladium catalysts with leaded gasoline.

    PubMed Central

    Teague, D M; Clougherty, L B; Speca, A N

    1975-01-01

    The effect of various fuel additives on the ability of platinum-palladium catalytic converters to remove the carbon monoxide and hydrocarbon components of automotive exhaust has been examined. Engine dynamometer studies suggest that these catalysts may be successfully used in conjunction with fuels of relatively high tetraethyllead concentrations, provided the ethylene dibromide portion of the scavenger is excluded. PMID:50929

  18. Operation of platinum-palladium catalysts with leaded gasoline.

    PubMed

    Teague, D M; Clougherty, L B; Speca, A N

    1975-04-01

    The effect of various fuel additives on the ability of platinum-palladium catalytic converters to remove the carbon monoxide and hydrocarbon components of automotive exhaust has been examined. Engine dynamometer studies suggest that these catalysts may be successfully used in conjunction with fuels of relatively high tetraethyllead concentrations, provided the ethylene dibromide portion of the scavenger is excluded.

  19. Metal-support interaction in platinum and palladium nanoparticles loaded on nitrogen-doped mesoporous carbon for oxygen reduction reaction.

    PubMed

    Perini, Lorenzo; Durante, Christian; Favaro, Marco; Perazzolo, Valentina; Agnoli, Stefano; Schneider, Oliver; Granozzi, Gaetano; Gennaro, Armando

    2015-01-21

    Mesoporous carbons are highly porous materials, which show large surface area, chemical inertness and electrochemical performances superior to traditional carbon material. In this study, we report the preparation of nitrogen-doped and undoped mesoporous carbons by an optimized hard template procedure employing silica as template, sucrose and ammonia as carbon and nitrogen source, respectively. Surface area measurements assert a value of 900 and 600 m(2) g(-1) for the best doped and undoped samples, respectively. Such supports were then thoroughly characterized by surface science and electron microscopy tools. Afterward, they were decorated with Pt and Pd nanoparticles, and it was found that the presence of nitrogen defects plays a significant role in improving the metal particles dimension and dispersion. In fact, when doped supports are used, the resulting metal nanoparticles are smaller (2-4 nm) and less prone to aggregation. Photoemission measurements give evidence of a binding energy shift, which is consistent with the presence of an electronic interaction between nitrogen atoms and the metal nanoparticles, especially in the case of Pd. The catalytic properties of electrodes decorated with such catalyst/support systems were investigated by linear sweep voltammetry and by rotating disk electrode measurements, revealing excellent stability and good activity toward oxygen reduction reaction (ORR). In particular, although Pd nanoparticles always result in lower activity than Pt ones, both Pt and Pd electrodes based on the N-doped supports show an increased activity toward ORR with respect to the undoped ones. At the same mass loading, the Tafel slope and the stability test of the Pt@N-doped electrocatalysts indicate superior performances to that of a commercial Pt@C catalysts (30 wt % Pt on Vulcan XC-72, Johnson Matthey). PMID:25525718

  20. Biosorption of platinum and palladium for their separation/preconcentration prior to graphite furnace atomic absorption spectrometric determination

    NASA Astrophysics Data System (ADS)

    Godlewska-Żyłkiewicz, Beata

    2003-08-01

    Inexpensive baker's yeast Saccharomyces cerevisiae and green algae Chlorella vulgaris, either free or immobilized on silica gel have been shown to selectively accumulate platinum and palladium from water samples in acidic medium (pH 1.6-1.8). Optimization of conditions of metals biosorption (sample pH, algae and yeast masses, adsorption time, temperature) was performed in batch mode. The procedure of matrix separation based on biosorption of platinum and palladium on algae C. vulgaris covalently immobilized on silica gel in flow mode was developed. The use of algae in flow procedure offers several advantages compared with its use in the batch mode. The procedure shows better reproducibility (<2%), improved efficiency of platinum retention on the column (93.3±1.6%), is less laborious and less time consuming. The best recovery of biosorbed metals from column (87.7±3.3% for platinum and 96.8±1.1 for palladium) was obtained with solution of 0.3 mol l -1 thiourea in 1 mol l -1 hydrochloric acid. The influence of thiourea on analytical signals of examined metals during GFAAS determination is discussed. The procedure has been applied for separation of noble metals from tap and waste water samples spiked with platinum and palladium.

  1. Determination of palladium, platinum and rhodium in geologic materials by fire assay and emission spectrography

    USGS Publications Warehouse

    Hapfty, J.; Riley, L.B.

    1968-01-01

    A method is described for the determination of palladium down to 4ppb (parts per billion, 109), platinum down to 10 ppb and rhodium down to 5 ppb in 15 g of sample. Fire-assay techniques are used to preconcentrate the platinum metals into a gold bead, then the bead is dissolved in aqua regia and diluted to volume with 1M hydrochloric acid. The solution is analysed by optical emission spectrography of the residue from 200 ??l of it evaporated on a pair of flat-top graphite electrodes. This method requires much less sample handling than most published methods for these elements. Data are presented for G-1, W-1, and six new standard rocks of the U.S. Geological Survey. The values for palladium in W-1 are in reasonable agreement with previously published data. ?? 1968.

  2. Mineral resource of the month: platinum group metals

    USGS Publications Warehouse

    Loferski, Patricia J.

    2010-01-01

    The article focuses on platinum group metals (PGMs) and their properties. According to the author, PGMs, which include iridium, osmium, palladium, platinum, rhodium, and ruthenium, are among the rarest mineral commodities in the Earth's crust. PGMs are primarily used as catalytic converters that clean harmful exhaust from vehicle engines. They are also used in the chemical industry as catalysts in the production of nitric acid and in the petroleum refining industry.

  3. Bulk synthesis of nanoporous palladium and platinum powders

    DOEpatents

    Robinson, David B.; Fares, Stephen J.; Tran, Kim L.; Langham, Mary E.

    2012-04-17

    Disclosed is a method for providing nanoporous palladium and platinum powders. These materials were synthesized on milligram to gram scales by chemical reduction of tetrahalo-complexes with ascorbate in a concentrated aqueous surfactant at temperatures between -20.degree. C. and 30.degree. C. The prepared particles have diameters of approximately 50 nm, wherein each particle is perforated by pores having diameters of approximately 3 nm, as determined by electron tomography. These materials are of potential value for hydrogen and electrical charge storage applications.

  4. Bulk synthesis of nanoporous palladium and platinum powders

    DOEpatents

    Robinson, David B; Fares, Stephen J; Tran, Kim L; Langham, Mary E

    2014-04-15

    Disclosed is a method for providing nanoporous palladium and platinum powders. These materials were synthesized on milligram to gram scales by chemical reduction of tetrahalo-complexes with ascorbate in a concentrated aqueous surfactant at temperatures between -20.degree. C. and 30.degree. C. The prepared particles have diameters of approximately 50 nm, wherein each particle is perforated by pores having diameters of approximately 3 nm, as determined by electron tomography. These materials are of potential value for hydrogen and electrical charge storage applications.

  5. 48 CFR 252.208-7000 - Intent to furnish precious metals as Government-furnished material.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Offeror shall cite the type (silver, gold, platinum, palladium, iridium, rhodium, and ruthenium) and... metal* Quantity Deliverable item (NSN and nomenclature)!!rs *If platinum or palladium, specify...

  6. 48 CFR 252.208-7000 - Intent to furnish precious metals as Government-furnished material.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Offeror shall cite the type (silver, gold, platinum, palladium, iridium, rhodium, and ruthenium) and... metal* Quantity Deliverable item (NSN and nomenclature)!!rs *If platinum or palladium, specify...

  7. 48 CFR 252.208-7000 - Intent to furnish precious metals as Government-furnished material.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Offeror shall cite the type (silver, gold, platinum, palladium, iridium, rhodium, and ruthenium) and... metal* Quantity Deliverable item (NSN and nomenclature)!!rs *If platinum or palladium, specify...

  8. 48 CFR 252.208-7000 - Intent to furnish precious metals as Government-furnished material.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Offeror shall cite the type (silver, gold, platinum, palladium, iridium, rhodium, and ruthenium) and... metal* Quantity Deliverable item (NSN and nomenclature)!!rs *If platinum or palladium, specify...

  9. 48 CFR 252.208-7000 - Intent to furnish precious metals as Government-furnished material.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Offeror shall cite the type (silver, gold, platinum, palladium, iridium, rhodium, and ruthenium) and... metal* Quantity Deliverable item (NSN and nomenclature)!!rs *If platinum or palladium, specify...

  10. Recent strikes in South Africa’s platinum-group metal mines: effects upon world platinum-group metal supplies

    USGS Publications Warehouse

    Yager, Thomas R.; Soto-Viruet, Yadira; Barry, James J.

    2012-01-01

    The recent labor disputes over wages and working conditions that have affected South Africa’s three leading platinum-group metal (PGM) producers have affected an industry already plagued by market pressures and labor unrest and raised the specter of constraints in the world’s supply of these metals. Although low demand for these metals in 2011 and 2012 helped to offset production losses of recent years, and particularly those losses caused by the strikes in 2012, a prolonged resumption of strikes could cause severe shortages of iridium, platinum, rhodium, ruthenium, and, to a lesser extent, palladium.

  11. Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles

    DOEpatents

    Wang, Jia X.; Adzic, Radoslav R.

    2009-03-24

    The present invention relates to methods for producing metal-coated palladium or palladium-alloy particles. The method includes contacting hydrogen-absorbed palladium or palladium-alloy particles with one or more metal salts to produce a sub-monoatomic or monoatomic metal- or metal-alloy coating on the surface of the hydrogen-absorbed palladium or palladium-alloy particles. The invention also relates to methods for producing catalysts and methods for producing electrical energy using the metal-coated palladium or palladium-alloy particles of the present invention.

  12. Biaxially textured metal substrate with palladium layer

    DOEpatents

    Robbins, William B [Maplewood, MN

    2002-12-31

    Described is an article comprising a biaxially textured metal substrate and a layer of palladium deposited on at least one major surface of the metal substrate; wherein the palladium layer has desired in-plane and out-of-plane crystallographic orientations, which allow subsequent layers that are applied on the article to also have the desired orientations.

  13. Determination of platinum and palladium in geological materials by neutron-activation analysis after fire-assay preconcentration

    USGS Publications Warehouse

    Rowe, J.J.; Simon, F.O.

    1971-01-01

    Fire-asay preconcentration followed by neutron-activation analysis permits the determination of as little as 0.5 ppM of platinum and 0.5 ppM of palladium on a 20-g sample. Platinum and palladium are separated with carriers and beta-counted. Results for the platinum and palladium content of seven U.S.G.S. standard rocks are presented. ?? 1971.

  14. Endohedral nickel, palladium, and platinum atoms in 10-vertex germanium clusters: competition between bicapped square antiprismatic and pentagonal prismatic structures.

    PubMed

    King, R B; Silaghi-Dumitrescu, I; Uţa, M M

    2009-01-22

    Density functional theory predicts significant differences in the preferred structures of endohedral M@Ge10z (M = Ni, Pd, Pt; z = 0, 2-, 4-) clusters upon a change of the central metal atom in otherwise isoelectronic systems. For the neutral clusters M@Ge10 the global minima are singlet bicapped square antiprisms. However, triplet regular pentagonal prismatic structures become increasingly energetically competitive in the series Ni --> Pd -> Pt. The pentagonal prismatic dianions M@Ge10(2-) (M = Ni, Pd, Pt) appear to have closed shell structures and are the global minima for palladium and platinum. However, the global minimum for Ni@Ge102- is the capped square antiprism suggested by the Wade-Mingos rules. A number of singlet low-energy unsymmetrical structures are found for the tetraanions M@Ge10(4-). However, for the palladium and platinum tetraanions triplet pentagonal prismatic structures are energetically competitive with the unsymmetrical structures.

  15. Mechanistic insights on platinum- and palladium-pincer catalyzed coupling and cyclopropanation reactions between olefins.

    PubMed

    Rajeev, Ramanan; Sunoj, Raghavan B

    2012-07-21

    The mechanism of M(II)-PNP-pincer catalyzed reaction between (i) ethene, (ii) trans-butene with 2-methylbut-2-ene, 2,3-dimethylbut-2-ene and tert-butylbutene is examined by using density functional theory methods (where M = Pt or Pd). All key intermediates and transition states involved in the reaction are precisely located on the respective potential energy surfaces using the popular DFT functionals such as mPW1K, M06-2X, and B3LYP in conjunction with the 6-31+G** basis set. The reaction between these olefins can lead to a linear coupling product or a substituted cyclopropane. The energetic comparison between coupling as well as cyclopropanation pathways involving four pairs of olefins for both platinum (1-4) and palladium (5-8) catalyzed reactions is performed. The key events in the lower energy pathway in the mechanistic course involves (i) a C-C bond formation between the metal bound olefin (ethene or trans-butene) and a free olefin, and (ii) two successive [1,2] hydrogen migrations in the ensuing carbocationic intermediates (1c-4c, and 1d-4d), toward the formation of the coupling product. The computed barriers for these steps in the reaction of metal bound ethene to free tert-butylbutene (or other butenes) are found to be much lower than the corresponding steps when trans-butene is bound to the metal pincer. The Gibbs free energy differences between the transition states leading to the coupling product (TS(d-e)) and that responsible for cyclopropanated product (TS(d-g)) are found to be diminishingly closer in the case of the platinum pincer as compared to that in the palladium system. The computed energetics indicate that the coupled product prefers to remain as a metal olefin complex, consistent with the earlier experimental reports.

  16. Structures of polynuclear complexes of palladium(II) and platinum(II) formed by slow hydrolysis in acidic aqueous solution.

    PubMed

    Torapava, Natallia; Elding, Lars I; Mändar, Hugo; Roosalu, Kaspar; Persson, Ingmar

    2013-06-01

    The aqua ions of palladium(II) and platinum(II) undergo extremely slow hydrolysis in strongly acidic aqueous solution, resulting in polynuclear complexes. The size and structures of these species have been determined by EXAFS and small angle X-ray scattering, SAXS. For palladium(II), the EXAFS data show that the Pd-O and Pd···Pd distances are identical to those of crystalline palladium(II) oxide, but the intensities of the Pd···Pd distances in the Fourier transform at 3.04 and 3.42 Å are significantly lower compared to those of crystalline PdO. Furthermore, no Pd···Pd distances beyond 4 Å are observed. These observations strongly indicate that the polynuclear palladium(II) complexes are oxido- and hydroxido-bridged species with the same core structure as solid palladium(II) oxide. Based on the number of Pd···Pd distances, as derived from the EXAFS data, their size can be estimated to be approximately two unit cells, or ca. 1.0 nm(3). For platinum(II), EXAFS data of the polynuclear species formed in the slow hydrolysis process show Pt-O and Pt···Pt distances identical to those of amorphous platinum(II) oxide, precipitating from the solution studied. The Pt···Pt distances are somewhat different from those reported for crystalline platinum(II) oxide. The polynuclear platinum(II) complexes have a similar structure to the palladium ones, but they are somewhat larger, with an estimated diameter of 1.5-3.0 nm. It has not been possible to precipitate any of these species by ultracentrifugation. They are detectable by SAXS, indicating diameters between 0.7 and 2 nm, in excellent agreement with the EXAFS observations. The number of oxido- relative to hydroxido bridges will increase with increasing size of the complex. The charge of the complexes will remain about the same, +4, at growth, with approximate formulas [Pd10O4(OH)8(H2O)12](4+) and [Pt14O8(OH)8(H2O)12](4+) for complexes with a size of 2 and 3 unit cells of the corresponding solid metal oxide

  17. Determination of platinum, palladium, and lead in biological samples by atomic absorption spectrophotometry.

    PubMed Central

    Tillery, J B; Johnson, D E

    1975-01-01

    A flameless atomic absorption method for the coextraction of platinum and palladium from biological and environmental samples by high molecular weight amine (HMWA) is given. Also, methods for lead determination in biological samples by use of extraction flameless analysis and direct aspiration-flame analysis are reported. A study of lead contamination of Vacutainer tubes is given. PMID:1227857

  18. Method for producing electricity using a platinum-ruthenium-palladium catalyst in a fuel cell

    DOEpatents

    Gorer, Alexander

    2004-01-27

    A method for producing electricity using a fuel cell that utilizes a ternary alloy composition as a fuel cell catalyst, the ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  19. High-pressure/high-temperature synthesis and characterization of the first palladium or platinum containing lithium transition-metal sulfides Li2M3S4 (M=Pd, Pt)

    NASA Astrophysics Data System (ADS)

    Heymann, Gunter; Niehaus, Oliver; Krüger, Hannes; Selter, Philipp; Brunklaus, Gunther; Pöttgen, Rainer

    2016-10-01

    The new lithium transition-metal sulfides Li2M3S4 (M=Pd, Pt) were obtained via multianvil high-pressure/high-temperature syntheses at 8 GPa and 1150 °C starting from a stoichiometric mixture of lithium nitride, sulfur, and palladium or platinum. Single crystal structure analyses indicated the space group P21/c (no. 14) with the following lattice parameters and refinement results: a=492.9(1), b=1005.9(2), c=614.9(2) pm, β=110.9 (1)°, R1=0.0165, wR2=0.0308 (all data) for Li2Pd3S4 and a=498.2(1), b=1005.5(2), c=613.0(2) pm, β=110.8(1)°, R1=0.0215, wR2=0.0450 (all data) for Li2Pt3S4. The crystal structures are built up from two distinct Pd/Pt sites, one of which is a special position (0,0,0), two sulfur sites, and one lithium site. The atoms Pd2/Pt2 form isolated square planar PdS4/PtS4 units, whereas the Pd1/Pt1 atoms form pairs of square planar PdS4/PtS4 units, which are connected via a common edge. These two structural motives built up a three-dimensional network structure by linking through common corners. The lithium atoms are positioned inside of the so formed channels. Li2M3S4 (M=Pd, Pt) are isostructural to the minerals jaguéite, Cu2Pd3Se4 and chrisstanleyite, Ag2Pd3Se4, which are up to now the only representatives of this structure type. Both compounds were studied with respect to their magnetic properties and can be classified as Pauli paramagnetic or diamagnetic. Regarding the possibility of lithium mobility inside the channels, of the structure, solid state 7Li NMR and high-temperature single crystal investigations revealed localization of the lithium atoms on their crystallographic sites.

  20. Nickel and platinum group metal nanoparticle production by Desulfovibrio alaskensis G20.

    PubMed

    Capeness, M J; Edmundson, M C; Horsfall, L E

    2015-12-25

    Desulfovibrio alaskensis G20 is an anaerobic sulfate reducing bacteria. While Desulfovibrio species have previously been shown to reduce palladium and platinum to the zero-state, forming nanoparticles in the process; there have been no reports that D. alaskensis is able to form these nanoparticles. Metal nanoparticles have properties that make them ideal for use in many industrial and medical applications, such as their size and shape giving them higher catalytic activity than the bulk form of the same metal. Nanoparticles of the platinum group metals in particular are highly sought after for their catalytic ability and herein we report the formation of both palladium and platinum nanoparticles by D. alaskensis and the biotransformation of solvated nickel ions to nanoparticle form.

  1. The adsorption of gold, palladium and platinum from acidic chloride solutions on mesoporous carbons.

    DOE PAGESBeta

    Zalupski, Peter R.; McDowell, Rocklan; Dutech, Guy

    2014-08-05

    Studies on the adsorption characteristics of gold, palladium and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II) and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of hydrogen ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces.more » The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.« less

  2. The adsorption of gold, palladium and platinum from acidic chloride solutions on mesoporous carbons.

    SciTech Connect

    Zalupski, Peter R.; McDowell, Rocklan; Dutech, Guy

    2014-08-05

    Studies on the adsorption characteristics of gold, palladium and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II) and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of hydrogen ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces. The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.

  3. Copper, Palladium, and Platinum-Containing Complexes of an Asymmetric Dinucleating Ligand

    PubMed Central

    Halvagar, Mohammad Reza; Neisen, Benjamin

    2013-01-01

    The coordination chemistry of an asymmetric dinucleating hexadentate ligand LH2 comprising neutral alkyltriamine and potentially dianionic dicarboxamido-pyridyl donor sets with copper, palladium, and platinum has been explored. Monometallic, dicopper, and heterodinuclear Cu-Pd and -Pt complexes have been prepared and characterized, including by NMR, EPR, UV-vis, and IR spectroscopy and X-ray crystallography. For example, the monometallic complexes [(LH2)MCl]X (M = Cu, X = OTf; M = Pd or Pt, X = Cl) were prepared, wherein the metal(II) ions is coordinated to the triamine portion and the pyridyldicarboxamide is unperturbed. Treatment of LH2 with [MesCu]x (Mes = mesityl) provided a monocopper(I) complex, again with the metal coordinated only to the trialkylamine donor set. Reaction of [(LH2)CuCl]OTf with NaOMe resulted in an unexpected migration of the copper(II)-chloride fragment to the pyridyldicarboxamide site to yield Na[LCuCl], from which a dicopper complex LCu2Cl2 and mixed-metal complexes LCu(Cl)M(Cl) (M = Pd, Pt) were prepared by addition of CuCl2 or MCl2, respectively. The heterodinuclear complexes were also prepared by addition of CuCl2 to [(LH2)MCl]Cl. PMID:23268657

  4. Bioaccessibility of palladium and platinum in urban aerosol particulates

    NASA Astrophysics Data System (ADS)

    Puls, Christoph; Limbeck, Andreas; Hann, Stephan

    2012-08-01

    To evaluate potential health hazards caused by environmental Platinum Group Elements (PGEs), bioaccessibility of the metals in question needs to be assessed. To gain appropriate data, airborne particulate matter samples of different size fractions (total suspended particles as well as PM10 and PM2.5) were taken in downtown Vienna, an urban site primarily polluted by traffic. Total PGE concentrations in these samples were in the low picogram per cubic meter range, as determined by ID-ICP-MS after microwave digestion. For elimination of elements interfering with the accurate quantification, the digested samples were subjected to a cleaning procedure involving cation exchange. For determination of the bioaccessible fraction, it was assumed that inhaled particles are removed from the respiratory system by mucociliary clearance and subsequently ingested. Accordingly, the solubility of PGE in synthetic gastric juice was investigated by batch extraction of particulate matter samples followed by microwave assisted UV-digestion, cation exchange cleanup and ID-ICP-MS. The acquired data was used to calculate the bioaccessible fraction of Pd and Pt in airborne particulate matter. Average GIT-extractable fractions for Pd and Pt in TSP were 41% and 27%, in PM10 34% and 26%, respectively, thus exceeding previously determined values for bioaccessibility of PGE from ground catalyst materials by up to an order of magnitude.

  5. Californium--palladium metal neutron source material

    DOEpatents

    Dahlen, B.L.; Mosly, W.C. Jr.; Smith, P.K.; Albenesius, E.L.

    1974-01-22

    Californium, as metal or oxide, is uniformly dispersed throughout a noble metal matrix, provided in compact, rod or wire form. A solution of californium values is added to palladium metal powder, dried, blended and pressed into a compact having a uni-form distribution of californium. The californium values are decomposed to californium oxide or metal by heating in an inert or reducing atmosphere. Sintering the compact to a high density closes the matrix around the dispersed californium. The sintered compact is then mechanically shaped into an elongated rod or wire form. (4 claims, no drawings) (Official Gazette)

  6. Chelated bis-N-heterocyclic carbene platinum and palladium units as tunable components of multinuclear complexes.

    PubMed

    Maeda, Yuri; Hashimoto, Hideki; Kinoshita, Isamu; Nishioka, Takanori

    2015-01-20

    Heterometallic trinuclear M2M' complexes (M = Rh, Ir; M' = Pt, Pd) containing a platinum or palladium moiety with chelated bis-N-heterocyclic carbene ligands, [(MCp*)2{M'(bisNHC-Cn-R)}(μ3-S)2](BPh4)2 (M = Rh, Ir; M' = Pt, Pd; bisNHC-Cn-R = methylene-, ethylene-, or propylene-bridged bis(N-alkyl-imidazolylidene)), were synthesized by reacting bis(hydrosulfido)platinum(II) or palladium(II) complexs with bisNHC-Cn-R and hydroxo-bridged dinuclear complexes [(MCp*)2(μ-OH)3](BPh4), whose dinuclear structures remained intact during the formation of the trinuclear complexes, which was confirmed by using electrospray mass spectrometry and NMR spectroscopy. The heterometallic trinuclear M2M' complexes with a variety of alkylene bridges in bisNHC-Cn-R showed two reversible reduction waves in the cyclic voltammogram, and the second reduction potentials were affected by the alkylene chain lengths, which caused different dihedral angles between the imidazolylidene rings and the coordination plane of the platinum or palladium center. The M2M' complexes, except for those containing the platinum unit with the ethylene-bridged bisNHC ligands, showed dynamic behavior in solution due to the flapping wing motion of the NHC ligand moieties. Although activation parameters obtained from line-shape analyses on variable-temperature NMR spectra of the complexes suggested that the flapping wing motion occurred without bond cleavage, large negative ΔS(‡) values were obtained for the complexes with the palladium unit with the ethylene-bridged ligand, suggesting that the Pd-Ccarbene bond cleavage, accompanied by coordination of solvent molecules, occurred.

  7. Imino-phosphine palladium(II) and platinum(II) complexes: synthesis, molecular structures and evaluation as antitumor agents.

    PubMed

    Motswainyana, William M; Onani, Martin O; Madiehe, Abram M; Saibu, Morounke; Thovhogi, Ntevheleni; Lalancette, Roger A

    2013-12-01

    The imino-phosphine ligands L1 and L2 were prepared via condensation reaction of 2-(diphenylphosphino)benzaldehyde with substituted anilines and obtained in very good yields. An equimolar reaction of L1 and L2 with either PdCl2(cod) or PtCl2(cod) gave new palladium(II) and platinum(II) complexes 1-4. The compounds were characterized by elemental analysis, IR, (1)H and (31)P NMR spectroscopy. The molecular structures of 2, 3 and 4 were confirmed by X-ray crystallography. All the three molecular structures crystallized in monoclinic C2/c space system. The coordination geometry around the palladium and platinum atoms in respective structures exhibited distorted square planar geometry at the metal centers. The complexes were evaluated in vitro for their cytotoxic activity against human breast (MCF-7) and human colon (HT-29) cancer cells, and they exhibited growth inhibitory activities and selectivity that were superior to the standard compound cisplatin.

  8. Structural characterization and comparison of iridium, platinum and gold/palladium ultra-thin film coatings for STM of biomolecules

    SciTech Connect

    Sebring, R.; Arendt, P.; Imai, B.; Bradbury, E.M.; Gatewood, J.; Panitz, J.; Yau, P.

    1997-10-30

    Scanning tunneling microscopy (STM) is capable of atomic resolution and is ideally suited for imaging surfaces with uniform work function. A biological sample on a conducting substrate in air does not meet this criteria and requires a conductive coating for stable and reproducible STM imaging. In this paper, the authors describe the STM and transmission electron microscopy (TEM) characterization of ultra-thin ion-beam sputtered films of iridium and cathode sputtered gold/palladium and platinum films on highly ordered pyrolytic graphite (HOPG) which were developed for use as biomolecule coatings. The goals were the development of metal coatings sufficiently thin and fine grained that 15--20 {angstrom} features of biological molecules could be resolved using STM, and the development of a substrate/coating system which would allow complementary TEM information to be obtained for films and biological molecules. The authors demonstrate in this paper that ion-beam sputtered iridium on highly ordered pyrolytic graphite (HOPG) has met both these goals. The ion-beam sputtered iridium produced a very fine grained (< 10 {angstrom}) continuous film at 5--6 {angstrom} thickness suitable for stable air STM imaging. In comparison, cathode sputtered platinum produced 16 {angstrom} grains with the thinnest continuous film at 15 {angstrom} thickness, and the sputtered gold/palladium produced 25 {angstrom} grains with the thinnest continuous film at 18 {angstrom} thickness.

  9. Phonon anharmonicity and components of the entropy in palladium and platinum

    NASA Astrophysics Data System (ADS)

    Shen, Yang; Li, Chen W.; Tang, Xiaoli; Smith, Hillary L.; Fultz, B.

    2016-06-01

    Inelastic neutron scattering was used to measure the phonon density of states in fcc palladium and platinum metal at temperatures from 7 K to 1576 K. Both phonon-phonon interactions and electron-phonon interactions were calculated by methods based on density functional theory (DFT) and were consistent with the measured shifts and broadenings of phonons with temperature. Unlike the longitudinal modes, the characteristic transverse modes had a nonlinear dependence on temperature owing to the requirement for a population of thermal phonons for upscattering. Kohn anomalies were observed in the measurements at low temperature and were reproduced by calculations based on DFT. Contributions to the entropy from phonons and electrons were assessed and summed to obtain excellent agreement with prior calorimetric data. The entropy from thermal expansion is positive for both phonons and electrons but larger for phonons. The anharmonic phonon entropy is negative in Pt, but in Pd it changes from positive to negative with increasing temperature. Owing to the position of the Fermi level on the electronic DOS, the electronic entropy was sensitive to the adiabatic electron-phonon interaction in both Pd and Pt. The adiabatic EPI depended strongly on thermal atom displacements.

  10. Palladium and platinum nanoparticles attenuate aging-like skin atrophy via antioxidant activity in mice.

    PubMed

    Shibuya, Shuichi; Ozawa, Yusuke; Watanabe, Kenji; Izuo, Naotaka; Toda, Toshihiko; Yokote, Koutaro; Shimizu, Takahiko

    2014-01-01

    Cu-Zn superoxide dismutase (Sod1) loss causes a redox imbalance as it leads to excess superoxide generation, which results in the appearance of various aging-related phenotypes, including skin atrophy. Noble metal nanoparticles, such as palladium (Pd) and platinum (Pt) nanoparticles, are considered to function as antioxidants due to their strong catalytic activity. In Japan, a mixture of Pd and Pt nanoparticles called PAPLAL has been used to treat chronic diseases over the past 60 years. In the present study, we investigated the protective effects of PAPLAL against aging-related skin pathologies in mice. Transdermal PAPLAL treatment reversed skin thinning associated with increased lipid peroxidation in Sod1-/- mice. Furthermore, PAPLAL normalized the gene expression levels of Col1a1, Mmp2, Has2, Tnf-α, Il-6, and p53 in the skin of the Sod1-/- mice. Pt nanoparticles exhibited marked SOD and catalase activity, while Pd nanoparticles only displayed weak SOD and catalase activity in vitro. Although the SOD and catalase activity of the Pt nanoparticles significantly declined after they had been oxidized in air, a mixture of Pd and Pt nanoparticles continued to exhibit SOD and catalase activity after oxidation. Importantly, a mixture of Pd and Pt nanoparticles with a molar ratio of 3 or 4 to 1 continued to exhibit SOD and catalase activity after oxidation, indicating that Pd nanoparticles prevent the oxidative deterioration of Pt nanoparticles. These findings indicate that PAPLAL stably suppresses intrinsic superoxide generation both in vivo and in vitro via SOD and catalase activity. PAPLAL is a potentially powerful tool for the treatment of aging-related skin diseases caused by oxidative damage. PMID:25333617

  11. Palladium and platinum nanoparticles attenuate aging-like skin atrophy via antioxidant activity in mice.

    PubMed

    Shibuya, Shuichi; Ozawa, Yusuke; Watanabe, Kenji; Izuo, Naotaka; Toda, Toshihiko; Yokote, Koutaro; Shimizu, Takahiko

    2014-01-01

    Cu-Zn superoxide dismutase (Sod1) loss causes a redox imbalance as it leads to excess superoxide generation, which results in the appearance of various aging-related phenotypes, including skin atrophy. Noble metal nanoparticles, such as palladium (Pd) and platinum (Pt) nanoparticles, are considered to function as antioxidants due to their strong catalytic activity. In Japan, a mixture of Pd and Pt nanoparticles called PAPLAL has been used to treat chronic diseases over the past 60 years. In the present study, we investigated the protective effects of PAPLAL against aging-related skin pathologies in mice. Transdermal PAPLAL treatment reversed skin thinning associated with increased lipid peroxidation in Sod1-/- mice. Furthermore, PAPLAL normalized the gene expression levels of Col1a1, Mmp2, Has2, Tnf-α, Il-6, and p53 in the skin of the Sod1-/- mice. Pt nanoparticles exhibited marked SOD and catalase activity, while Pd nanoparticles only displayed weak SOD and catalase activity in vitro. Although the SOD and catalase activity of the Pt nanoparticles significantly declined after they had been oxidized in air, a mixture of Pd and Pt nanoparticles continued to exhibit SOD and catalase activity after oxidation. Importantly, a mixture of Pd and Pt nanoparticles with a molar ratio of 3 or 4 to 1 continued to exhibit SOD and catalase activity after oxidation, indicating that Pd nanoparticles prevent the oxidative deterioration of Pt nanoparticles. These findings indicate that PAPLAL stably suppresses intrinsic superoxide generation both in vivo and in vitro via SOD and catalase activity. PAPLAL is a potentially powerful tool for the treatment of aging-related skin diseases caused by oxidative damage.

  12. Electron photoemission from platinum and palladium microdeposits on glassy carbon into the solution

    SciTech Connect

    Yakushev, V.V.; Bagotskii, V.S.; Skundin, A.M.

    1984-08-01

    It was of interest to the authors to compare the electrocatalytic and photoemission properties of microdeposits in other systems. Platinum and palladium microdeposits on glassy carbon were selected as such systems in the present work. The procedure used in the photoemission measurements has been previously described. All measurements were conducted in 1 N KOH. A mercury-mercuric oxide electrode served as reference electrode. The true surface areas of the platinum microdeposits were measured potentiodynamically in terms of hydrogen adsorption and oxygen desorption, while that of the palladium microdeposits was measured in terms of oxygen desorption. The results of the present work yield the important conclusion that the changes which occur in the density of electronic states in the microdeposits because of their contact with the support depend on potential, i.e., on the position of the Fermi level. It is found that the enhancement of the photoemission currents is attended by an increase, and the depression of the photoemission currents is attended by a decrease in electrocatalytic activity.

  13. Reactivity studies of pincer bis-protic N-heterocyclic carbene complexes of platinum and palladium under basic conditions

    PubMed Central

    Marelius, David C; Moore, Curtis E; Rheingold, Arnold L

    2016-01-01

    Summary Bis-protic N-heterocyclic carbene complexes of platinum and palladium (4) yield dimeric structures 6 when treated with sodium tert-butoxide in CH2Cl2. The use of a more polar solvent (THF) and a strong base (LiN(iPr)2) gave the lithium chloride adducts monobasic complex 7 or analogous dibasic complex 8. PMID:27559382

  14. Reactivity studies of pincer bis-protic N-heterocyclic carbene complexes of platinum and palladium under basic conditions.

    PubMed

    Marelius, David C; Moore, Curtis E; Rheingold, Arnold L; Grotjahn, Douglas B

    2016-01-01

    Bis-protic N-heterocyclic carbene complexes of platinum and palladium (4) yield dimeric structures 6 when treated with sodium tert-butoxide in CH2Cl2. The use of a more polar solvent (THF) and a strong base (LiN(iPr)2) gave the lithium chloride adducts monobasic complex 7 or analogous dibasic complex 8. PMID:27559382

  15. Highly Unsaturated Platinum and Palladium Carbenes PtC3 and PdC3 Isolated and Characterized in the Gas Phase

    PubMed Central

    Bittner, Dror M.; Zaleski, Daniel P.; Tew, David P.

    2016-01-01

    Abstract Carbenes of platinum and palladium, PtC3 and PdC3, were generated in the gas phase through laser vaporization of a metal target in the presence of a low concentration of a hydrocarbon precursor undergoing supersonic expansion. Rotational spectroscopy and ab initio calculations confirm that both molecules are linear. The geometry of PtC3 was accurately determined by fitting to the experimental moments of inertia of twenty‐six isotopologues. The results are consistent with the proposal of an autogenic isolobal relationship between O, Au+, and Pt atoms. PMID:27478275

  16. Highly Unsaturated Platinum and Palladium Carbenes PtC3 and PdC3 Isolated and Characterized in the Gas Phase

    PubMed Central

    Bittner, Dror M.; Zaleski, Daniel P.; Tew, David P.

    2016-01-01

    Abstract Carbenes of platinum and palladium, PtC3 and PdC3, were generated in the gas phase through laser vaporization of a metal target in the presence of a low concentration of a hydrocarbon precursor undergoing supersonic expansion. Rotational spectroscopy and ab initio calculations confirm that both molecules are linear. The geometry of PtC3 was accurately determined by fitting to the experimental moments of inertia of twenty‐six isotopologues. The results are consistent with the proposal of an autogenic isolobal relationship between O, Au+, and Pt atoms. PMID:26879473

  17. Highly Unsaturated Platinum and Palladium Carbenes PtC3 and PdC3 Isolated and Characterized in the Gas Phase

    DOE PAGESBeta

    Bittner, Dror M.; Zaleski, Daniel P.; Tew, David P.; Walker, Nicholas R.; Legon, Anthony C.

    2016-02-16

    Carbenes of platinum and palladium, PtC3 and PdC3 , were generated in the gas phase through laser vaporization of a metal target in the presence of a low concentration of a hydrocarbon precursor undergoing supersonic expansion. Rotational spectroscopy and abinitio calculations confirm that both molecules are linear. The geometry of PtC3 was accurately determined by fitting to the experimental moments of inertia of twenty-six isotopologues. In conclusion, the results are consistent with the proposal of an autogenic isolobal relationship between O, Au+ , and Ptatoms.

  18. Platinum metals magmatic sulfide ores.

    PubMed

    Naldrett, A J; Duke, J M

    1980-06-27

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example.

  19. Electrocatalysts having platium monolayers on palladium, palladium alloy, and gold alloy core-shell nanoparticles, and uses thereof

    DOEpatents

    Adzic, Radoslav; Mo, Yibo; Vukmirovic, Miomir; Zhang, Junliang

    2010-12-21

    The invention relates to platinum-coated particles useful as fuel cell electrocatalysts. The particles are composed of a noble metal or metal alloy core at least partially encapsulated by an atomically thin surface layer of platinum atoms. The invention particularly relates to such particles having a palladium, palladium alloy, gold alloy, or rhenium alloy core encapsulated by an atomic monolayer of platinum. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

  20. Anthropogenic platinum and palladium in the sediments of Boston Harbor

    USGS Publications Warehouse

    Tuit, C.B.; Ravizza, G.E.; Bothner, Michael H.

    2000-01-01

    Anthropogenic activity has increased recent sediment concentrations of Pt and Pd in Boston Harbor by approximately 5 times background concentrations. Surface sediments and downcore profiles were investigated to evaluate Pt and Pd accumulation and behavior in urban coastal sediments. There is no clear correlation between temporal changes in Pt and Pd consumption and sediment concentration. However, Pt/Pb and Pd/Pb ratios suggest that Pt and Pd flux into the Harbor may not be decreasing with cessation of sludge input as rapidly as other metals. This is supported by the large discrepancy between fluxes associated with sludge and effluent release and those calculated from surface sediment concentrations. This evidence supports catalytic converters as a major source of Pd and Pt to Boston Harbor but cannot preclude other sources. Pd does not exhibit signs of post-burial remobilization below the mixed layer in the sediment cores, although near-surface variability in Pd concentrations may indicate a labile Pd component. Pt displays an inverse correlation with Mn above the oxic/suboxic transition, similar to behavior seen in pristine sediments where Pt is thought to be chemically mobile. This study does not support the use of Pd and Pt as tracers of recent contaminated sedimentation. However, the possibility of a labile Pt and Pd in these sediments highlights the need for further study of the biological uptake of these metals.Anthropogenic activity has increased recent sediment concentrations of Pt and Pd in Boston Harbor by approximately 5 times background concentrations. Surface sediments and downcore profiles were investigated to evaluate Pt and Pd accumulation and behavior in urban coastal sediments. There is no clear correlation between temporal changes in Pt and Pd consumption and sediment concentration. However, Pt/Pb and Pd/Pb ratios suggest that Pt and Pd flux into the Harbor may not be decreasing with cessation of sludge input as rapidly as other metals. This is

  1. Palladium(II) and platinum(II) derivatives of benzothiazoline ligands: Synthesis, characterization, antimicrobial and antispermatogenic activity

    NASA Astrophysics Data System (ADS)

    Sharma, Krishna; Singh, R. V.; Fahmi, Nighat

    2011-01-01

    A series of Pd(II) and Pt(II) complexes with two N ∩S donor ligands, 5-chloro-3-(indolin-2-one)benzothiazoline and 6-nitro-3-(indolin-2-one)benzothiazoline, have been synthesized by the reaction of metal chlorides (PdCl 2 and PtCl 2) with ligands in 1:2 molar ratios. All the synthesized compounds were characterized by elemental analyses, melting point determinations and a combination of electronic, IR, 1H NMR and 13C NMR spectroscopic techniques for structure elucidation. In order to evaluate the effect of metal ions upon chelation, both the ligands and their complexes have been screened for their antimicrobial activity against the various pathogenic bacterial and fungal strains. The metal complexes have shown to be more antimicrobial against the microbial species as compared to free ligands. One of the ligands, 5-chloro-3-(indolin-2-one)benzothiazoline and its corresponding palladium and platinum complexes have been tested for their antifertility activity in male albino rats. The marked reduction in sperm motility and density resulted in infertility by 62-90%. Significant alterations were found in biochemical parameters of reproductive organs in treated animals as compared to control group. It is concluded that all these effects may finally impair the fertility of male rats.

  2. Platinum metals magmatic sulfide ores.

    PubMed

    Naldrett, A J; Duke, J M

    1980-06-27

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. PMID:17796685

  3. Stripping voltammetric determination of palladium, platinum and rhodium in freshwater and sediment samples from South African water resources.

    PubMed

    van der Horst, C; Silwana, B; Iwuoha, E; Somerset, V

    2012-01-01

    Stripping voltammetry as technique has proved to be very useful in the analysis of heavy and other metal ions due to its excellent detection limits and its sensitivity in the presence of different metal species or interfering ions. Recent assessments of aquatic samples have shown increased levels of platinum group metals (PGMs) in aquatic ecosystems, caused by automobile exhaust emissions and mining activities. The development of an analytical sensor for the detection and characterisation of PGMs were investigated, since there is an ongoing need to find new sensing materials with suitable recognition elements that can respond selectively and reversibly to specific metal ions in environmental samples. The work reported shows the successful application of another mercury-free sensor electrode for the determination of platinum group metals in environmental samples. The work reported in this study entails the use of a glassy carbon electrode modified with a bismuth film for the determination of platinum (Pt(2+)), palladium (Pd(2+)) or rhodium (Rh(2+)) by means of adsorptive cathodic stripping voltammetry. Optimised experimental conditions included composition of the supporting electrolyte, complexing agent concentration, deposition potential, deposition time and instrumental voltammetry parameters for Pt(2+), Pd(2+) and Rh(2+) determination. Adsorptive differential pulse stripping voltammetric measurements for PGMs were performed in the presence of dimethylglyoxime (DMG) as complexing agent. The glassy carbon bismuth film electrode (GC/BiFE) employed in this study exhibit good and reproducible sensor characteristics. Application of GC/BiFE sensor exhibited well-defined peaks and highly linear behaviour for the stripping analysis of the PGMs in the concentration range between 0 and 3.5 μg/L. The detection limit of Pd, Pt and Rh was found to be 0.12 μg/L, 0.04 μg/L and 0.23 μg/L, respectively for the deposition times of 90 s (Pd) and 150 s (for both Pt and Rh). Good

  4. Stripping voltammetric determination of palladium, platinum and rhodium in freshwater and sediment samples from South African water resources.

    PubMed

    van der Horst, C; Silwana, B; Iwuoha, E; Somerset, V

    2012-01-01

    Stripping voltammetry as technique has proved to be very useful in the analysis of heavy and other metal ions due to its excellent detection limits and its sensitivity in the presence of different metal species or interfering ions. Recent assessments of aquatic samples have shown increased levels of platinum group metals (PGMs) in aquatic ecosystems, caused by automobile exhaust emissions and mining activities. The development of an analytical sensor for the detection and characterisation of PGMs were investigated, since there is an ongoing need to find new sensing materials with suitable recognition elements that can respond selectively and reversibly to specific metal ions in environmental samples. The work reported shows the successful application of another mercury-free sensor electrode for the determination of platinum group metals in environmental samples. The work reported in this study entails the use of a glassy carbon electrode modified with a bismuth film for the determination of platinum (Pt(2+)), palladium (Pd(2+)) or rhodium (Rh(2+)) by means of adsorptive cathodic stripping voltammetry. Optimised experimental conditions included composition of the supporting electrolyte, complexing agent concentration, deposition potential, deposition time and instrumental voltammetry parameters for Pt(2+), Pd(2+) and Rh(2+) determination. Adsorptive differential pulse stripping voltammetric measurements for PGMs were performed in the presence of dimethylglyoxime (DMG) as complexing agent. The glassy carbon bismuth film electrode (GC/BiFE) employed in this study exhibit good and reproducible sensor characteristics. Application of GC/BiFE sensor exhibited well-defined peaks and highly linear behaviour for the stripping analysis of the PGMs in the concentration range between 0 and 3.5 μg/L. The detection limit of Pd, Pt and Rh was found to be 0.12 μg/L, 0.04 μg/L and 0.23 μg/L, respectively for the deposition times of 90 s (Pd) and 150 s (for both Pt and Rh). Good

  5. Simultaneous nondestructive analysis of palladium, rhodium, platinum, and gold nanoparticles using energy dispersive X-ray fluorescence.

    PubMed

    Fiedler, Haidi D; Drinkel, Emma E; Orzechovicz, Beatriz; Leopoldino, Elder C; Souza, Franciane D; Almerindo, Gizelle I; Perdona, Cristian; Nome, Faruk

    2013-11-01

    A selective method is proposed for the determination of palladium, gold, and sulfur in catalytic systems, by direct liquid analysis using energy dispersive X-ray fluorescence (EDXRF), under an atmosphere of helium or air. This method allows a nondestructive analysis of palladium, rhodium, platinum, and gold nanoparticulate catalysts stabilized by imidazolium propane sulfonate based zwitterionic surfactants, allowing the samples to be reused for catalytic studies. The signals from palladium, rhodium, platinum, and gold samples in the presence of imidazolium propane sulfonate-based zwitterionic surfactants obtained using EDXRF before (Pd(2+), Rh(2+), Pt(2+), and Au(3+)) and after (Pd(0), Rh(0), Pt(0), and Au(0)) formation of nanoparticles are essentially identical. The results show that the EDXRF method is nondestructive and allows detection and quantification of the main components of platinum, gold, rhodium, and palladium NPs, including the surfactant concentration, with detection and quantification limits in the range of 0.4-3 mg L(-1). The matrices used in such samples present no problems, even allowing the detection and quantification of interfering elements.

  6. Chemical Forms and Distribution of Platinum Group Metals and Technetium During Spent Fuel Reprocessing

    SciTech Connect

    Pokhitonov, Y.

    2007-07-01

    Amongst the fission products present in spent nuclear fuel of Nuclear Power Plants there are considerable quantities of platinum group metals (PGMs): ruthenium, rhodium and palladium. At the same time there are considerable amounts of technetium in the spent fuel, the problem of its removal at radiochemical plants being in operation encountering serious difficulties. Increased interest in this radionuclides is due not only to its rather large yield, but to higher mobility in the environment as well. However, the peculiarities of technetium chemistry in nitric acid solutions create certain problems when trying to separate it as a single product in the course of NPP's spent fuel reprocessing. The object of this work was to conduct a comprehensive analysis of platinum group metals and technetium behavior at various stages of spent fuel reprocessing and to seek the decisions which could make it possible to separate its as a single product. The paper will report data on platinum metals (PGM) and technetium distribution in spent fuel reprocessing products. The description of various techniques for palladium recovery from differing in composition radioactive solutions arising from reprocessing is given. (authors)

  7. Spectroscopic and structural properties of 2,2'-dipyridylamine and its palladium and platinum complexes

    NASA Astrophysics Data System (ADS)

    Yurdakul, Ş.; Bilkana, M. T.

    2015-10-01

    The structural features such as geometric parameters, vibration frequencies and intensities of the vibrational bands of 2,2'-dipyridylamine ligand (DPA), its palladium (Pd(DPA)Cl2) and platinum (Pt(DPA)Cl2) complexes were studied by the density functional theory (DFT). The calculations were carried out by DFT / B3LYP method with 6-311++G(d,p) and LANL2DZ basis sets. All vibrational frequencies assigned in detail with the help of total energy distribution analysis (TED). Optimized geometric bond lengths and bond angles were compared with experimental X-ray data. Using DPA, K2PtCl4, and Na2PdCl4, the synthesized complex structures were characterized by the combination of elemental analysis, FT-IR (mid and far IR) and Raman spectroscopy.

  8. Novel platinum-palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities.

    PubMed

    Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

    2015-01-01

    Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum-palladium bimetallic nanoparticles (Pt-PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2-5 nm, while PdNPs and Pt-PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88% ± 1.73% elemental Pt and 68.96% ± 1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm(-1), attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm(-1), associated with C-H stretching, N-H bending in primary amines, N-O stretching in nitro group, and C-C stretch, respectively. Anticancer activity against HeLa cells showed that Pt-PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt-PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals.

  9. Novel platinum-palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities.

    PubMed

    Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

    2015-01-01

    Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum-palladium bimetallic nanoparticles (Pt-PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2-5 nm, while PdNPs and Pt-PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88% ± 1.73% elemental Pt and 68.96% ± 1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm(-1), attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm(-1), associated with C-H stretching, N-H bending in primary amines, N-O stretching in nitro group, and C-C stretch, respectively. Anticancer activity against HeLa cells showed that Pt-PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt-PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals. PMID:26719690

  10. Syntheses and spectroscopic studies of some platinum group metal complexes with oxazepam as ligand

    NASA Astrophysics Data System (ADS)

    Benedetti, Adriano; Preti, Carlo; Tosi, Giuseppe

    1984-05-01

    The preparation and characterization of some rhodium(III), iridium(III), palladium(II) and platinum(II) halide complexes with oxazepam, 7-chloro-1,3-dihydro-5-phenyl-3-hydroxy-2H-1,4-benzodiazepin-2-one are reported. The obtained complexes of the type ML 3X 3 (M = Rh, Ir) and ML 2X 2 (M = Pd, Pt) with the exception of the rhodium and palladium iododerivatives which have 1:6 and 1:4 metal:ligand ratios, respectively, have been studied and characterized through vibrational and electronic spectra, 1H and 13C NMR studies, conductivity measurements and magnetic susceptibility data. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of the crystal field theory and the various parameters have been calculated. The most convincing structural evidence supports an octahedral stereochemistry for the rhodium and iridium derivatives and a square planar geometry for the palladium and platinum compounds with terminal halides and terminal ligands, acting as monodentate only in all the metal complexes through the nitrogen atom in the 4-position.

  11. Exhaust system having a gold-platinum group metal catalyst

    DOEpatents

    Ragle, Christie Susan; Silver, Ronald G.; Zemskova, Svetlana Mikhailovna; Eckstein, Colleen J.

    2012-08-07

    A method of providing an exhaust treatment device is disclosed. The method includes applying a catalyst including gold and a platinum group metal to a particulate filter. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide.

  12. Exhaust system having a gold-platinum group metal catalyst

    DOEpatents

    Ragle, Christie Susan; Silver, Ronald G.; Zemskova, Svetlana Mikhailovna; Eckstein, Colleen J.

    2011-12-06

    A method of providing an exhaust treatment device is disclosed. The method includes applying a catalyst including gold and a platinum group metal to a particulate filter. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide.

  13. Thermodynamic ground states of platinum metal nitrides

    SciTech Connect

    Aberg, D; Sadigh, B; Crowhurst, J; Goncharov, A

    2007-10-09

    We have systematically studied the thermodynamic stabilities of various phases of the nitrides of the platinum metal elements using density functional theory. We show that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability can extend up to 17 GPa for PtN{sub 2}. Furthermore, we show that according to calculations using the local density approximation, these new compounds are also thermodynamically stable at ambient pressure and thus may be the ground state phases for these materials. We further discuss the fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures.

  14. Gold/palladium and silver/palladium colloids as novel metallic substrates for surface-enhanced Raman scattering.

    PubMed

    Pergolese, Barbara; Bigotto, Adriano; Muniz-Miranda, Maurizio; Sbrana, Giuseppe

    2005-02-01

    New surface-enhanced Raman scattering (SERS) substrates, composed of gold or silver colloidal nanoparticles doped with palladium, were prepared. These novel colloids are stable and maintain a satisfactory SERS efficiency, even after long aging. The interest in doping the coinage metal nanoparticles with palladium is due to the well-known catalytic activity of this metal. Transmission electron microscopy (TEM) and ultraviolet-visible absorption spectroscopy were used to characterize the shape and size of the metal particles. It was found that these bimetallic colloidal nanoparticles have a core-shell structure, with gold or silver coated with palladium clusters.

  15. The influence of ethylenediamine tetra acetic acid (EDTA) on the transformation and solubility of metallic palladium and palladium(II) oxide in the environment.

    PubMed

    Zereini, Fathi; Wiseman, Clare L S; Vang, My; Albers, Peter; Schneider, Wolfgang; Schindl, Roland; Leopold, Kerstin

    2015-05-01

    The environmental occurrence of elevated concentrations of platinum (Pt), palladium (Pd) and rhodium (Rh) from automotive catalytic converters has been well-documented. Limited information exists regarding their chemical behavior post-emission, however, especially in the presence of commonly occurring complexing agents. The purpose of this study is to examine the influence of ethylenediamine tetra acetic acid (EDTA) on the possible environmental transformation and solubility of Pd by conducting batch experiments using metallic palladium (Pd black) and palladium(ii) oxide (PdO). Changes in the particle surface chemistry of treated samples were analyzed using X-ray Photoelectron Spectroscopy (XPS) and Transition Electron Microscopy/Energy Dispersive X-ray Spectrometry (TEM/EDX) techniques. Metallic palladium was partially transformed into PdOx (x < 1), while PdO remained largely unaffected. The pH of EDTA solutions was observed to modulate Pd solubility, with Pd black demonstrating a higher solubility compared to PdO. Solubility was also found to increase with a corresponding increase in the strength of EDTA solution concentrations, as well as with the length of extraction time. The overall solubility of Pd remained relatively low for most samples (<1 wt%). A dissolution rate of 2.01 ± 0.17 nmol m(-2) h(-1) was calculated for Pd black in 0.1 M EDTA (pH 7). In contrast to previously held assumptions about the environmental immobility of Pd, small amounts of this element emitted in metallic form are likely to be soluble in the presence of complexing agents such as EDTA.

  16. Triphenyl phosphine adducts of platinum(IV) and palladium(II) dithiocarbamates complexes: a spectral and in vitro study

    NASA Astrophysics Data System (ADS)

    Manav, N.; Mishra, A. K.; Kaushik, N. K.

    2004-11-01

    Triphenyl phosphine adducts of dithiocarbamate complexes of platinum(IV) and palladium(II) of the type [Pt(L) 2PPh 3Cl 2] and [Pd(L) 2PPh 3] [L: morpholine dithiocarbamate (L 1), aniline dithiocarbamate (L 2) and N-(methyl, cyclohexyl) dithiocarbamate (L 3)] were prepared and characterized by elemental analysis, electronic, IR, 1H NMR and 13C NMR spectral studies. Thermal studies of the complexes were carried out. In vitro antitumor activity has been screened towards human adenocarcinoma cell lines and showed significant inhibition even at very low concentration.

  17. Preparation and characterization of platinum (Pt) and palladium (Pd) nanoparticle decorated graphene sheets and their utilization for the elimination of basic fuchsin and indigo carmine dyes

    NASA Astrophysics Data System (ADS)

    Kurt, Belma Zengin; Durmus, Zehra; Durmus, Ali

    2016-01-01

    In this study, graphene nano sheets, prepared with chemical oxidation and reduction routes via modified-Hummer method, were successfully decorated with platinum (Pt) and palladium (Pd) nanoparticles. Structural and morphological features of resulted graphene-metal nanocomposites were characterized with FT-IR, XRD, SEM and TEM methods. Anti-oxidant activity (AOA) values of nanocomposites were determined. The IC50 values of Pt-graphene and Pd-graphene nanocomposites were found to be 46.1 and 90.2 μg/mL, respectively based on the ABTS method and 80.2 and 143.7 μg/mL according to the DPPH method. It was found that the graphene-metal nanocomposites exhibited superior free radical scavenging activity compared to several types of noble metal nano particles although the nanocomposites consist of much lower amount of active metal sites than the nano-crystalline metal powders. It was consequently reported that the graphene-metal nanocomposites could be successfully used for the photocatalytic elimination of fuchsin and indigo carmine dyes under light irradiation.

  18. Microwave assisted synthesis, characterization and biological evaluation of palladium and platinum complexes with azomethines

    NASA Astrophysics Data System (ADS)

    Sharma, Krishna; Singh, Ritu; Fahmi, Nighat; Singh, R. V.

    2010-01-01

    Reactions of 3-acetyl-2,5-dimethylthiophene with thiosemicarbazide and semicarbazide hydrochloride resulted in the formation of new heterocyclic ketimines, 3-acetyl-2,5-dimethylthiophene thiosemicarbazone (C 9H 13N 3OS 2 or L 1H) and 3-acetyl-2,5- dimethylthiophene semicarbazone (C 9H 13N 3OS or L 2H), respectively. The Pd(II) and Pt(II) complexes have been synthesized by mixing metal salts in 1:2 molar ratios with these ligands by using microwave as well as conventional heating method for comparison purposes. The authenticity of these ligands and their complexes has been established on the basis of elemental analysis, melting point determinations, molecular weight determinations, IR, 1H NMR and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a monobasic bidentate manner and square planar environment around the metal atoms has been proposed to the complexes. Both the ligands and their complexes have been screened for their antimicrobial activities. The antiamoebic activity of both the ligands and their palladium compounds against the protozoan parasite Entamoeba histolytica has been tested.

  19. Platinum and Palladium Overlayers Dramatically Enhance the Activity of Ruthenium Nanotubes for Alkaline Hydrogen Oxidation

    SciTech Connect

    St. John, Samuel; Atkinson, Robert W.; Unocic, Kinga A.; Unocic, Raymond R.; Zawodzinski, Thomas A.; Papandrew, Alexander B.

    2015-10-18

    Templated vapor synthesis and thermal annealing were used to synthesize unsupported metallic Ru nanotubes with Pt or Pd overlayers. By controlling the elemental composition and thickness of these overlayers, we obtain nanostructures with very high alkaline hydrogen oxidation activity. For nanotubes with a nominal atomic composition of Ru0.90Pt0.10 display a surface-specific activity (2.4 mA/cm2) that is 35 times greater than that of pure Ru nanotubes at a 50 mV overpotential and 2.5 times greater than that of pure Pt nanotubes (0.98 mA/cm2). The surface-segregated structure also confers dramatically increased Pt utilization efficiency. We find a platinum-mass-specific activity of 1240 A/gPt for the optimized nanotube versus 280 A/gPt for carbon-supported Pt nanoparticles and 109 A/gPt for monometallic Pt nanotubes. Here, we attribute the enhancement of both area- and platinum-mass-specific activity to the atomic-scale homeomorphism of the nanotube form factor with adlayer-modified polycrystals. Subsurface ligand and bifunctional effects previously observed on segregated, adlayer-modified polycrystals are translated to nanoscale catalysts.

  20. Platinum and Palladium Overlayers Dramatically Enhance the Activity of Ruthenium Nanotubes for Alkaline Hydrogen Oxidation

    DOE PAGESBeta

    St. John, Samuel; Atkinson, Robert W.; Unocic, Kinga A.; Unocic, Raymond R.; Zawodzinski, Thomas A.; Papandrew, Alexander B.

    2015-10-18

    Templated vapor synthesis and thermal annealing were used to synthesize unsupported metallic Ru nanotubes with Pt or Pd overlayers. By controlling the elemental composition and thickness of these overlayers, we obtain nanostructures with very high alkaline hydrogen oxidation activity. For nanotubes with a nominal atomic composition of Ru0.90Pt0.10 display a surface-specific activity (2.4 mA/cm2) that is 35 times greater than that of pure Ru nanotubes at a 50 mV overpotential and 2.5 times greater than that of pure Pt nanotubes (0.98 mA/cm2). The surface-segregated structure also confers dramatically increased Pt utilization efficiency. We find a platinum-mass-specific activity of 1240 A/gPtmore » for the optimized nanotube versus 280 A/gPt for carbon-supported Pt nanoparticles and 109 A/gPt for monometallic Pt nanotubes. Here, we attribute the enhancement of both area- and platinum-mass-specific activity to the atomic-scale homeomorphism of the nanotube form factor with adlayer-modified polycrystals. Subsurface ligand and bifunctional effects previously observed on segregated, adlayer-modified polycrystals are translated to nanoscale catalysts.« less

  1. A combined experimental and theoretical investigation of a new imineoxime and its palladium(II) and platinum(II) complexes: Synthesis, structural characterization and spectroscopic properties

    NASA Astrophysics Data System (ADS)

    Kaya, Yunus; Icsel, Ceyda; Yilmaz, Veysel T.; Buyukgungor, Orhan

    2014-12-01

    A new imineoxime compound {(1E,2E)-(2-hydroxy-ethylimino)-naphthalene-2yl-ethanal oxime (heineoH)} and its palladium(II) and platinum(II) complexes ([M(heineo)2]) have been synthesized and characterized by IR, NMR, UV-vis, elemental analysis, mass spectra and X-ray single crystal diffraction. [Pt(heineo)2] was obtained as a single crystal, while [Pd(heineo)2] was synthesized as a polycrystalline powder. The X-ray diffraction analysis of the [Pt(heineo)2] indicated that the platinum(II) ion is coordinated by two heineo ligands in a distorted square-planar geometry. DFT (B3LYP/6-311++G(d,p) and LANL2DZ) calculations on the ligand and its complexes were carried out to correlate the geometry and vibrational and electronic properties. Additionally, heineoH is fluorescent in EtOH at room temperature, but the fluorescence is quenched in the case of the metal complexes.

  2. A combined experimental and theoretical investigation of a new imineoxime and its palladium(II) and platinum(II) complexes: synthesis, structural characterization and spectroscopic properties.

    PubMed

    Kaya, Yunus; Icsel, Ceyda; Yilmaz, Veysel T; Buyukgungor, Orhan

    2014-12-10

    A new imineoxime compound {(1E,2E)-(2-hydroxy-ethylimino)-naphthalene-2yl-ethanal oxime (heineoH)} and its palladium(II) and platinum(II) complexes ([M(heineo)2]) have been synthesized and characterized by IR, NMR, UV-vis, elemental analysis, mass spectra and X-ray single crystal diffraction. [Pt(heineo)2] was obtained as a single crystal, while [Pd(heineo)2] was synthesized as a polycrystalline powder. The X-ray diffraction analysis of the [Pt(heineo)2] indicated that the platinum(II) ion is coordinated by two heineo ligands in a distorted square-planar geometry. DFT (B3LYP/6-311++G(d,p) and LANL2DZ) calculations on the ligand and its complexes were carried out to correlate the geometry and vibrational and electronic properties. Additionally, heineoH is fluorescent in EtOH at room temperature, but the fluorescence is quenched in the case of the metal complexes. PMID:24929321

  3. MONTANA PALLADIUM RESEARCH INITIATIVE

    SciTech Connect

    Peters, John; McCloskey, Jay; Douglas, Trevor; Young, Mark; Snyder, Stuart; Gurney, Brian

    2012-05-09

    Project Objective: The overarching objective of the Montana Palladium Research Initiative is to perform scientific research on the properties and uses of palladium in the context of the U.S. Department of Energy's Hydrogen, Fuel Cells and Infrastructure Technologies Program. The purpose of the research will be to explore possible palladium as an alternative to platinum in hydrogen-economy applications. To achieve this objective, the Initiatives activities will focus on several cutting-edge research approaches across a range of disciplines, including metallurgy, biomimetics, instrumentation development, and systems analysis. Background: Platinum-group elements (PGEs) play significant roles in processing hydrogen, an element that shows high potential to address this need in the U.S. and the world for inexpensive, reliable, clean energy. Platinum, however, is a very expensive component of current and planned systems, so less-expensive alternatives that have similar physical properties are being sought. To this end, several tasks have been defined under the rubric of the Montana Palladium Research Iniative. This broad swath of activities will allow progress on several fronts. The membrane-related activities of Task 1 employs state-of-the-art and leading-edge technologies to develop new, ceramic-substrate metallic membranes for the production of high-purity hydrogen, and develop techniques for the production of thin, defect-free platinum group element catalytic membranes for energy production and pollution control. The biomimetic work in Task 2 explores the use of substrate-attached hydrogen-producing enzymes and the encapsulation of palladium in virion-based protein coats to determine their utility for distributed hydrogen production. Task 3 work involves developing laser-induced breakdown spectroscopy (LIBS) as a real-time, in situ diagnostic technique to characterize PGEs nanoparticles for process monitoring and control. The systems engineering work in task 4 will

  4. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  5. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  6. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  7. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  8. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a...,” and “osmium,” or any abbreviation to mark or describe all or part of an industry product if such... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  9. Platinum and palladium incorporation into phosphate/viologen-phosphonates of zirconium and hafnium: synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Dokoutchaev, Alexandre; Krishnan, Venkatesan V.; Thompson, Mark E.; Balasubramanian, Mahalingam

    1998-10-01

    We have continued previous efforts to synthesize and characterize a microporous metal phosphate/viologen-phosphonate compound, [(ZrF) 2(PO 4)(O 3PCH 2CH 2-4,4'-bipyridinium-CH 2CH 2PO 3)] ṡF·2H 2O, ZrPO PV. A derivative of this material has been shown to be an efficient catalyst for the production of hydrogen peroxide from hydrogen and oxygen. This paper has two objectives—one is to optimize the synthetic routes leading to the preparation of MPO PV (M=zirconium or hafnium) and the second is to characterize MPO PV and the derivatives formed by Pt or Pd incorporation by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray absorption fine structure analysis (XAFS). Powder XRD data have shown much higher crystallinity in MPO PV samples prepared by hydrothermal methods than those prepared by reflux methods. In the hydrothermal synthesis, the amount of mineralizer (HF) present controlled the crystallite size (as determined from TEM micrographs). The larger the quantity of HF in the bomb, the larger the size of the crystals but the lower the yield of the MPO PV material. Crystal sizes of about 2.5 μm in length and 0.15 μm in diameter have been made with very large quantities of HF as mineralizer (10 times the required stoichiometric amount). Ion exchange of the material by PdCl 42- has resulted in the incorporation of the PdCl 42- ions in place of X - in the material. This has been confirmed by XAFS studies that demonstrate the oxidation state of Pd is 2+ and show four Cl atoms bound to Pd. Upon reduction it has been confirmed (by XAFS) that the palladium exists as metal with oxidation state of zero. Ion exchange by PdCl 42- and PtCl 42- and subsequent reduction of the material suspension by hydrogen result in the formation of separate Pt and Pd colloids in the close vicinity of the crystallites. TEM micrographs show clearly that the Pt metal

  10. Concentration of some platinum-group metals in coal

    USGS Publications Warehouse

    Finkelman, R.B.; Aruscavage, P. J.

    1981-01-01

    New data on some platinum group metals in coal indicate that the concentration of Pt is generally less than about 5 ppb, that of Pd is generally less than 1 ppb, and that of Rh is generally less than 0.5 ppb. No conclusive evidence was obtained concerning the mode of occurrence of these elements in coal. ?? 1981.

  11. Enhancement of Platinum Cathode Catalysis by Addition of Transition Metals

    ERIC Educational Resources Information Center

    Duong, Hung Tuan

    2009-01-01

    The sluggish kinetics of oxygen reduction reaction (ORR) contributes significantly to the loss of cathode overpotential in fuel cells, thus requiring high loadings of platinum (Pt), which is an expensive metal with limited supply. However, Pt and Pt-based alloys are still the best available electrocatalysts for ORR thus far. The research presented…

  12. Palladium-platinum core-shell electrocatalysts for oxygen reduction reaction prepared with the assistance of citric acid

    DOE PAGESBeta

    Zhang, Lulu; Su, Dong; Zhu, Shangqian; Chang, Qiaowan; Yue, Jeffrey; Du, Zheng; Shao, Minhua

    2016-04-26

    Core–shell structure is a promising alternative to solid platinum (Pt) nanoparticles as electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). A simple method of preparing palladium (Pd)–platinum (Pt) core–shell catalysts (Pd@Pt/C) in a gram-batch was developed with the assistance of citric acid. The Pt shell deposition involves three different pathways: galvanic displacement reaction between Pd atoms and Pt cations, chemical reduction by citric acid, and reduction by negative charges on Pd surfaces. The uniform ultrathin (~0.4 nm) Pt shell was characterized by in situ X-ray diffraction (XRD) and high-angle annular dark-field scanning transmission electron microscopymore » (HAADF-STEM) images combined with electron energy loss spectroscopy (EELS). Compared with state-of-the-art Pt/C, the Pd@Pt/C core–shell catalyst showed 4 times higher Pt mass activity and much better durability upon potential cycling. As a result, both the mass activity and durability were comparable to that of Pd@Pt/C synthesized by a Cu-mediated-Pt-displacement method, which is more complicated and difficult for mass production.« less

  13. Composite metal membrane

    DOEpatents

    Peachey, N.M.; Dye, R.C.; Snow, R.C.; Birdsell, S.A.

    1998-04-14

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  14. Composite metal membrane

    DOEpatents

    Peachey, Nathaniel M.; Dye, Robert C.; Snow, Ronny C.; Birdsell, Stephan A.

    1998-01-01

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  15. Bio‐palladium: from metal recovery to catalytic applications

    PubMed Central

    De Corte, Simon; Hennebel, Tom; De Gusseme, Bart; Verstraete, Willy; Boon, Nico

    2012-01-01

    Summary While precious metals are available to a very limited extent, there is an increasing demand to use them as catalyst. This is also true for palladium (Pd) catalysts and their sustainable recycling and production are required. Since Pd catalysts exist nowadays mostly under the form of nanoparticles, these particles need to be produced in an environment‐friendly way. Biological synthesis of Pd nanoparticles (‘bio‐Pd’) is an innovative method for both metal recovery and nanocatalyst synthesis. This review will discuss the different bio‐Pd precipitating microorganisms, the applications of the catalyst (both for environmental purposes and in organic chemistry) and the state of the art of the reactors based on the bio‐Pd concept. In addition, some main challenges are discussed, which need to be overcome in order to create a sustainable nanocatalyst. Finally, some outlooks for bio‐Pd in environmental technology are presented. PMID:21554561

  16. Palladium(II) and platinum(II) complexes with tridentate iminophosphine ligands; synthesis and structural studies.

    PubMed

    Ní Dhubhghaill, Orla M; Lennon, Joanne; Drew, Michael G B

    2005-10-01

    The previously synthesised Schiff-base ligands 2-(2-Ph(2)PC(6)H(4)N[double bond, length as m-dash]CH)-R'-C(6)H(3)OH (R'= 3-OCH(3), HL(1); 5-OCH(3), HL(2); 5-Br, HL(3); 5-Cl, HL(4)) were prepared by a faster, more efficient route involving a microwave assisted co-condensation of 2-(diphenylphosphino)aniline with the appropriate substituted salicylaldehyde. HL(1-4) react directly with M(II)Cl(2)(M = Pd, Pt) or Pt(II)I(2)(cod) affording neutral square-planar complexes of general formula [M(II)Cl(eta(3)-L(1-4))](M = Pd, Pt, 1-8) and [Pt(II)I(eta(3)-L(1-4))](M = Pd, Pt, 9-12). Reaction of complexes 1-4 with the triarylphosphines PR(3)(R = Ph, p-tolyl) gave the novel ionic complexes [Pd(II)(PR(3))(eta(3)-L(1-4))]ClO(4)(13-20). Substituted platinum complexes of the type [Pt(II)(PR(3))(eta(3)-L(1-4))]ClO(4)(R = P(CH(2)CH(2)CN)(3)21-24) and [Pt(II)(P(p-tolyl)(3))(eta(3)-L(3,4))]ClO(4)( 25 and 26 ) were synthesised from the appropriate [Pt(II)Cl(eta(3)-L(1-4))] complex (5-8) and PR(3). The complexes are characterised by microanalytical and spectroscopic techniques. The crystal structures of 3, 6, 10, 15, 20 and 26 were determined and revealed the metal to be in a square-planar four-coordinate environment containing a planar tridentate ligand with an O,N,P donor set together with one further atom which is trans to the central nitrogen atom. PMID:16172647

  17. The preparation of well-defined dendrimer-encapsulated palladium and platinum nanoparticles and their catalytic evaluation in the oxidation of morin

    NASA Astrophysics Data System (ADS)

    Ncube, Phendukani; Hlabathe, Thaane; Meijboom, Reinout

    2015-12-01

    The preparation of dendrimer-encapsulated platinum (Pt-DENs) and palladium (Pd-DENs) nanoparticles using generation 6-hydroxyl-terminated poly(amidoamine) (PAMAM) dendrimers as a templating agent is described. These nanoparticles were characterized using UV-vis spectrophotometry, spectrofluorophotometry, Fourier transform infrared spectrometry (FTIR), and high resolution transmission electron microscopy (HRTEM). The UV-vis spectra of palladium and platinum dendrimer-encapsulated nanoparticles gave a clear proof that nanoparticles were formed. It was found from FTIR spectra that there are shifts of peaks from higher wave numbers to lower wave numbers after reduction with sodium borohydride and these confirm the encapsulation of nanoparticles inside the voids of the dendrimer. The particle diameters were found to be 1.4 ± 0.2 and 1.6 ± 0.2 nm in diameter for palladium and platinum respectively from HRTEM. These nanoparticles were evaluated as catalysts in the oxidation of morin by hydrogen peroxide. The kinetic data was modeled to the Langmuir-Hinshelwood equation. The model allows relating apparent rate constant to the total surface area (S) of the nanoparticle. The Langmuir-Hinshelwood model also allows a direct relationship between the kinetic constant (k) and Kmorin and KH2O2 . The Arrhenius and Eyring equations were used to determine thermodynamic parameters for the oxidation of morin.

  18. Global exploration and production capacity for platinum-group metals from 1995 through 2015

    USGS Publications Warehouse

    Wilburn, David R.

    2012-01-01

    Platinum-group metals (PGMs) are required in a variety of commercial, industrial, and military applications for many existing and emerging technologies, yet the United States is highly dependent on foreign sources of PGMs. Information on global exploration for PGMs since 1995 has been used in this study as a basis for identifying locations where the industry has determined that exploration has provided data sufficient to warrant development of a new mine or expansion of an existing operation or where a significant increase in capacity for PGMs is anticipated by 2015. Discussions include an overview of the industry and the selected sites, factors affecting mineral supply, and circumstances leading to the development of mineral properties with the potential to affect mineral supply. Of the 52 sites or regional operations that were considered in this analysis, 16 sites were producing before 1995, 28 sites commenced production from 1995 through 2010, and 8 sites were expected to begin production from 2011 through 2015 if development plans came to fruition. The United States imports PGMs primarily from Canada, Russia, South Africa, and Zimbabwe to meet increasing demand for these materials in a variety of specialized and high-tech applications. Feed sources of PGMs are changing in South Africa and Russia, which together accounted for about 89 percent of platinum production and 82 percent of palladium production in 2009. A greater amount of South African PGM capacity is likely to come from deeper, higher cost Upper Group Reef seam 2 deposits and deposits in the Eastern Bushveld area. Future Russian PGM capacity is likely to come from ore zones with generally lower PGM content and different platinum-to-palladium ratios than the nickel-rich ore that dominated PGM supply in the 1990s. Because PGM supply from Canada and Russia is derived as a byproduct of copper and nickel mining, the PGM supply from these countries is influenced by economic, environmental, political, and

  19. Global exploration and production capacity for platinum-group metals from 1995 through 2015

    USGS Publications Warehouse

    Wilburn, David R.

    2012-01-01

    Platinum-group metals (PGMs) are required in a variety of commercial, industrial, and military applications for many existing and emerging technologies, yet the United States is highly dependent on foreign sources of PGMs. Information on global exploration for PGMs since 1995 has been used in this study as a basis for identifying locations where the industry has determined that exploration has provided data sufficient to warrant development of a new mine or expansion of an existing operation or where a significant increase in capacity for PGMs is anticipated by 2015. Discussions include an overview of the industry and the selected sites, factors affecting mineral supply, and circumstances leading to the development of mineral properties with the potential to affect mineral supply. Of the 52 sites or regional operations that were considered in this analysis, 16 sites were producing before 1995, 28 sites commenced production from 1995 through 2010, and 8 sites were expected to begin production from 2011 through 2015 if development plans came to fruition. The United States imports PGMs primarily from Canada, Russia, South Africa, and Zimbabwe to meet increasing demand for these materials in a variety of specialized and high-tech applications. Feed sources of PGMs are changing in South Africa and Russia, which together accounted for about 89 percent of platinum production and 82 percent of palladium production in 2009. A greater amount of South African PGM capacity is likely to come from deeper, higher cost Upper Group Reef seam 2 deposits and deposits in the Eastern Bushveld area. Future Russian PGM capacity is likely to come from ore zones with generally lower PGM content and different platinum-to-palladium ratios than the nickel-rich ore that dominated PGM supply in the 1990s. Because PGM supply from Canada and Russia is derived as a byproduct of copper and nickel mining, the PGM supply from these countries is influenced by economic, environmental, political, and

  20. Palladium, platinum, and rhodium contents of rocks near the lower margin of the Stillwater complex, Montana.

    USGS Publications Warehouse

    Zientek, M.L.; Foose, M.P.; Leung, Mei

    1986-01-01

    Statistical summaries are reported for Pd, Pt and Rh contents of rocks from the lower part of the Stillwater complex, the underlying contact-metamorphosed sediments, and post-metamorphic dykes and sills wholly within the hornfelses. Variability of the data among the rock types is attributed largely to differences in sulphide content. Non-correlation of sulphur with platinum-group assays of many rock types leads to the suggestion that the immiscible sulphide and silicate liquids did not completely equilibrate with respect to platinum-group elements. -G.J.N.

  1. Separation of platinum group metal ions by Donnan dialysis

    SciTech Connect

    Brajter, K.; Slonawska, K.; Cox, J.A.

    1985-10-01

    Separations of metal ions on the basis of Donnan dialysis across anion-exchange membranes should be possible if the receiver electrolyte composition favors the formation of selected anionic complexes of the sample metal ions. Moreover, such a separation has the possibility of being better suited from some applications than batch or column experiments with anion-exchange resins. The above hypothesis are tested on the platinum-group metal ions, Pt(IV), Rh(III), Pd(II), Ir(III), and Ir(IV). 13 references, 4 tables.

  2. International strategic minerals inventory summary report: platinum-group metals

    USGS Publications Warehouse

    Sutphin, David M.; Page, Norman J

    1986-01-01

    Major world resources of platinum-group metals are described in this summary report of information in the International Strategic Minerals Inventory {ISMI}. ISMI is a cooperative data-collection effort of earth-science and mineral-resource agencies in Australia, Canada, the Federal Republic of Germany, the Republic of South Africa, and the United States of America. This report, designed to be of benefit to policy analysts, contains two parts. Part I presents an overview of the resources and potential supply of platinum-group metals on the basis of inventory information. Part II contains tables of some of the geologic information and mineral-resource and production data that were collected by ISMI participants.

  3. Platinum metals in magmatic sulfide ores

    USGS Publications Warehouse

    Naldrett, A.J.; Duke, J.M.

    1980-01-01

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. Copyright ?? 1980 AAAS.

  4. Platinum redispersion on metal oxides in low temperature fuel cells.

    PubMed

    Tripković, Vladimir; Cerri, Isotta; Nagami, Tetsuo; Bligaard, Thomas; Rossmeisl, Jan

    2013-03-01

    We have analyzed the aptitude of several metal oxide supports (TiO(2), SnO(2), NbO(2), ZrO(2), SiO(2), Ta(2)O(5) and Nb(2)O(5)) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum dissolution at high potentials and the interference of redispersion with normal working potential of the PEMFC cathode. We have calculated the PtO(x) (x = 0, 1, 2) adsorption energies on different metal oxides' surface terminations as well as inside the metal oxides' bulk, and we have concluded that NbO(2) might be a good support for platinum redispersion at PEMFC cathodes. PMID:23358311

  5. First determination of the levels of platinum group metals in Manta birostris (manta ray) caught along the Ghanaian coastline.

    PubMed

    Essumang, D K

    2010-06-01

    Tissues from Manta birostris caught by fishermen from Dixcove in the western part of Ghana were analyzed for their Platinum, palladium and rhodium concentrations (PGM). The use of chondrichthyan fish has permitted the study of trace levels of Platinum group metals (PGMs) which have travelled very far into the sea. The analysis showed that Ghana's coastline is fairly polluted with these platinum group metals (PGMs). PGM concentration in manta ray recorded a range of (0.15-0.85) microg/g for Pt, (0.033-0.67) microg/g for Pd and (0.007-0.145) microg/g for Rh. Comparing these values to the UK dietary intake of 0.2 microg/day for Pt and Rh and 1.0 microg/day for Pd, its indicates that the values obtained from the analysis for Pt was above the required level. This is the first study to show the accumulation of PGM in chondrichthyan fish, although the sources of this pollution are not clear as manta birostris is migratory and therefore need to be investigated further. The presence of the PGM is very significant, since manta ray meat is consumed in Ghana. This may presents a health risk, due to a possible accumulation of PGMs in humans.

  6. Fuel cell performance of palladium-platinum core-shell electrocatalysts synthesized in gram-scale batches

    DOE PAGESBeta

    Khateeb, Siddique; Su, Dong; Guerreo, Sandra; Darling, Robert M.; Protsailo, Lesia V.; Shao, Minhua

    2016-05-03

    This article presents the performance of palladium-platinum core-shell catalysts (Pt/Pd/C) for oxygen reduction synthesized in gram-scale batches in both liquid cells and polymer-electrolyte membrane fuel cells. Core-shell catalyst synthesis and characterization, ink fabrication, and cell assembly details are discussed. The Pt mass activity of the Pt/Pd core-shell catalyst was 0.95 A mg–1 at 0.9 V measured in liquid cells (0.1 M HClO4), which was 4.8 times higher than a commercial Pt/C catalyst. The performances of Pt/Pd/C and Pt/C in large single cells (315 cm2) were assessed under various operating conditions. The core-shell catalyst showed consistently higher performance than commercial Pt/Cmore » in fuel cell testing. A 20–60 mV improvement across the whole current density range was observed on air. Sensitivities to temperature, humidity, and gas composition were also investigated and the core-shell catalyst showed a consistent benefit over Pt under all conditions. However, the 4.8 times activity enhancement predicated by liquid cell measurements was not fully realized in fuel cells.« less

  7. Investigation of platinum and palladium as potential anodic catalysts for direct borohydride and ammonia borane fuel cells

    NASA Astrophysics Data System (ADS)

    Olu, Pierre-Yves; Deschamps, Fabien; Caldarella, Giuseppe; Chatenet, Marian; Job, Nathalie

    2015-11-01

    Platinum and palladium are investigated as anodic catalysts for direct borohydride and direct ammonia borane fuel cells (DBFC and DABFC). Half-cell characterizations performed at 25 °C using NH3BH3 or NaBH4 alkaline electrolytes demonstrate the lowest open-circuit potential and highest electrocatalytic activity for the NH3BH3 alkaline electrolyte for Pd and Pt rotating disk electrodes, respectively. Voltammograms performed in fuel cell configuration at 25 °C confirm this trend: the highest open circuit voltage (1.05 V) and peak power density (181 mW·cm-2) are monitored for DABFC using Pd/C and Pt/C anodes, respectively. Increasing the temperature heightens the peak power density (that reaches 420 mW·cm-2 at 60 °C for DBFC using Pt/C anodes), but strongly generates gas from the fuel hydrolysis, hindering the overall fuel cells performances. The anode texture strongly influences the fuel cell performances, highlighting: (i) that an open anode texture is required to efficiently circulate the anolyte and (ii) the difficulty to compare potential anodic catalysts characterized using different fuel cell setups within the literature. Furthermore, TEM imaging of Pt/C and Pd/C catalysts prior/post DBFC and DABFC operation shows fast degradation of the carbon-supported nanoparticles.

  8. Palladium and platinum catalyzed addition of allylstannanes to aldehydes and imines

    SciTech Connect

    Nakamura, Hiroyuki; Yamamoto, Yoshinori

    1995-12-31

    The reaction of allylstannanes with aldehydes in THF was catalyzed by Pd(II) or Pt(II) complexes (10 mole %) either at room temperature or at reflux, giving the corresponding homoallyl alcohols in high to good yields. Among the catalysts examined, PtCl{sub 2}(PPh{sub 3}){sub 2} gave the best result. Aromatic, aliphatic, and {alpha},{beta}-unsaturated aldehydes can be utilized and even cyclohexanone undergoes the allylation reaction. Allyl and methallyltributylstannane reacted very smoothly. Crotyltributylstannane also reacted with aldehydes to give the branched homoallyl alcohols in good yields, but the reaction speed was slower than that of allylstannane. Detailed mechanistic studies of the Pd(II) catalyzed allylation, using NMR spectra, revealed that bis-{pi}-allyl palladium 5 is a key intermediate for the catalytic cycle and it exhibits nucleophilic reactivity.

  9. The separation of platinum, palladium and gold from silicate rocks by the anion exchange separation of chloro complexes after a sodium peroxide fusion: an investigation of low recoveries.

    PubMed

    Enzweiler, J; Potts, P J

    1995-10-01

    A series of experiments was undertaken to measure the recovery efficiency of platinum, palladium and gold from silicate rocks using a sodium peroxide fusion followed by anion exchange separation of the analytes as chloro complexes. Results obtained by graphite furnace atomic absorption spectrometric analysis of standard solutions prepared in dilute HCl or HCl-acidified sodium peroxide solution showed that recoveries were near quantitative. However, when standard solutions were added to an alkaline sodium peroxide solution, which was then acidified, low results were obtained for platinum and gold (46% and 76% respectively). Low and variable results were also obtained when standard solutions were added to a peridotite sample that had been dissolved by the state procedure, and in the analysis of the South African Bureau of Standards certified reference material, SARM 7. Various experiments were undertaken to investigate these low recoveries, but the reason proposed here is the formation of hydroxychloro compounds in alkaline solution which are not, on acidification with HCl, converted quantitatively to the chloro complex necessary for quantitative anion exchange separation. It is concluded that a sodium peroxide fusion followed by an anion-exchange separation does not appear to form the basis of a successful technique for the determination of platinum, palladium and gold in silicate rocks. PMID:18966370

  10. The separation of platinum, palladium and gold from silicate rocks by the anion exchange separation of chloro complexes after a sodium peroxide fusion: an investigation of low recoveries.

    PubMed

    Enzweiler, J; Potts, P J

    1995-10-01

    A series of experiments was undertaken to measure the recovery efficiency of platinum, palladium and gold from silicate rocks using a sodium peroxide fusion followed by anion exchange separation of the analytes as chloro complexes. Results obtained by graphite furnace atomic absorption spectrometric analysis of standard solutions prepared in dilute HCl or HCl-acidified sodium peroxide solution showed that recoveries were near quantitative. However, when standard solutions were added to an alkaline sodium peroxide solution, which was then acidified, low results were obtained for platinum and gold (46% and 76% respectively). Low and variable results were also obtained when standard solutions were added to a peridotite sample that had been dissolved by the state procedure, and in the analysis of the South African Bureau of Standards certified reference material, SARM 7. Various experiments were undertaken to investigate these low recoveries, but the reason proposed here is the formation of hydroxychloro compounds in alkaline solution which are not, on acidification with HCl, converted quantitatively to the chloro complex necessary for quantitative anion exchange separation. It is concluded that a sodium peroxide fusion followed by an anion-exchange separation does not appear to form the basis of a successful technique for the determination of platinum, palladium and gold in silicate rocks.

  11. Palladium(II)-catalyzed direct alkoxylation of arenes: evidence for solvent-assisted concerted metalation deprotonation.

    PubMed

    Anand, Megha; Sunoj, Raghavan B

    2011-09-16

    Density functional theory investigations on the mechanism of palladium acetate catalyzed direct alkoxylation of N-methoxybenzamide in methanol reveal that the key steps involve solvent-assisted N-H as well as C-H bond activations. The transition state for the critical palladium-carbon bond formation through a concerted metalation deprotonation (CMD) process leading to a palladacycle intermediate has been found to be more stable in the methanol-assisted pathway as compared to an unassisted route.

  12. PALLADIUM, PLATINUM, RHODIUM, RUTHENIUM AND IRIDIUM IN PERIDOTITES AND CHROMITITES FROM OPHIOLITE COMPLEXES IN NEWFOUNDLAND.

    USGS Publications Warehouse

    Page, Norman J; Talkington, Raymond W.

    1984-01-01

    Samples of spinel lherzolite, harzburgite, dunite, and chromitite from the Bay of Islands, Lewis Hills, Table Mountain, Advocate, North Arm Mountain, White Hills Periodite Point Rousse, Great Bend and Betts Cove ophiolite complexes in Newfoundland were analyzed for the platinum-group elements (PGE) Pd, Pt, Rh, Ru and Ir. The ranges of concentration (in ppb) observed for all rocks are: less than 0. 5 to 77 (Pd), less than 1 to 120 (Pt), less than 0. 5 to 20 (Rh), less than 100 to 250 (Ru) and less than 20 to 83 (Ir). Chondrite-normalized PGE ratios suggest differences between rock types and between complexes. Samples of chromitite and dunite show relative enrichment in Ru and Ir and relative depletion in Pt and Pd.

  13. Effect of palladium on sulfide tarnishing of noble metal alloys.

    PubMed

    Suoninen, E; Herø, H; Minni, E

    1985-10-01

    Electron spectroscopic studies of Au-Ag-Cu alloys of the type used for dental castings show that small additions (less than or equal to 3 wt%) of palladium reduce essentially the thickness of the sulfide layer formed on surfaces of samples treated in aqueous Na2S solutions. Relative to silver, palladium does not enrich in the sulfide, but statistically significant enrichment is found immediately below the sulfide layer. This enrichment probably takes place during the exposure of the substrate surface to atmosphere before the sulfiding treatment. The mechanism of the impeding effect of palladium on sulfiding is assumed to be a decrease in diffusion from the bulk alloy to the surface due to the enriched layer. The effect cannot be explained by changes in the electronic structure of the alloy due to palladium alloying.

  14. Palladium, platinum, rhodium, iridium and ruthenium in chromite- rich rocks from the Samail ophiolite, Oman.

    USGS Publications Warehouse

    Page, N.J.; Pallister, J.S.; Brown, M.A.; Smewing, J.D.; Haffty, J.

    1982-01-01

    30 samples of chromitite and chromite-rich rocks from two stratigraphic sections, 250 km apart, through the basal ultramafic member of the Samail ophiolite were spectrographically analysed for platinum-group elements (PGE) and for Co, Cu, Ni and V. These data are reported as are Cr/(Cr + Al), Mg/(Mg + Fe) and wt.% TiO2 for most samples. The chromitite occurs as pods or lenses in rocks of mantle origin or as discontinuous layers at the base of the overlying cumulus sequence. PGE abundances in both sections are similar, with average contents in chromite-rich rocks: Pd 8 ppb, Pt 14 ppb, Rh 6 ppb, Ir 48 ppb and Ru 135 ppb. The PGE data, combined with major-element and petrographic data on the chromitite, suggest: 1) relatively larger Ir and Ru contents and highest total PGE in the middle part of each section; 2) PGE concentrations and ratios do not correlate with coexisting silicate and chromite abundances or chromite compositions; 3) Pd/PGE, on average, increases upward in each section; 4) Samail PGE concentrations, particularly Rh, Pt and Pd, are lower than the average values for chromite-rich rocks in stratiform intrusions. 2) suggests that PGEs occur in discrete alloy or sulphide phases rather than in the major oxides or silicates, and 4) suggests that chromite-rich rocks from the oceanic upper mantle are depleted in PGE with respect to chondrites. L.C.C.

  15. Tritium production from a low voltage deuterium discharge on palladium and other metals

    SciTech Connect

    Claytor, T.N.; Jackson, D.D.; Tuggle, D.G.

    1995-09-01

    Over the past year the authors have been able to demonstrate that a plasma loading method produces an exciting and unexpected amount of tritium from small palladium wires. In contrast to electrochemical hydrogen or deuterium loading of palladium, this method yields a reproducible tritium generation rate when various electrical and physical conditions are met. Small diameter wires (100--250 microns) have been used with gas pressures above 200 torr at voltages and currents of about 2,000 V at 3--5 A. By carefully controlling the sputtering rate of the wire, runs have been extended to hundreds of hours allowing a significant amount (> 10`s nCi) of tritium to accumulate. they show tritium generation rates for deuterium-palladium foreground runs that are up to 25 times larger than hydrogen-palladium control experiments using materials from the same batch. They illustrate the difference between batches of annealed palladium and as received palladium from several batches as well as the effect of other metals (Pt, Ni, Nb, Zr, V, W, Hf) to demonstrate that the tritium generation rate can vary greatly from batch to batch.

  16. Evidence for the Formation of Nitrogen-Rich Platinum and Palladium Nitride Nanoparticles

    SciTech Connect

    Veith, Gabriel M.; Lupini, Andrew R.; Baggetto, Loïc; Browning, James F.; Keum, Jong K.; Villa, Alberto; Prati, Laura; Papandrew, Alexander B.; Goenaga, Gabriel A.; Mullins, David R.; Bullock, Steven E.; Dudney, Nancy J.

    2013-12-03

    Here, we report evidence for the formation of nitrogen-rich precious metal nanoparticles (Pt, Pd) prepared by reactive sputtering of the pure metal in a N2 plasma. The composition of the nanoparticles varies as a function of particle size and growth conditions. For the smallest particles the nitrogen content appears to be as high as 6.7 N atoms for each Pd atom or 5.9 N atoms for each Pt atom whereas bulk films have nominal compositions of Pt7.3N and Pd2.5N. The nanoparticles are metastable in air and moisture, slowly decomposing over several years. This paper describes the synthesis of these materials along with experimental evidence of the composition, oxidation state, and growth modes. Moreover, the catalytic properties of these N-rich nanoparticles were accessed by rotating disk electrode electrochemical studies, the liquid phase oxidation of benzyl alcohol and gas phase CO oxidation and support the experimental evidence for the materials composition.

  17. Evidence for the Formation of Nitrogen-Rich Platinum and Palladium Nitride Nanoparticles

    DOE PAGESBeta

    Veith, Gabriel M.; Lupini, Andrew R.; Baggetto, Loïc; Browning, James F.; Keum, Jong K.; Villa, Alberto; Prati, Laura; Papandrew, Alexander B.; Goenaga, Gabriel A.; Mullins, David R.; et al

    2013-12-03

    Here, we report evidence for the formation of nitrogen-rich precious metal nanoparticles (Pt, Pd) prepared by reactive sputtering of the pure metal in a N2 plasma. The composition of the nanoparticles varies as a function of particle size and growth conditions. For the smallest particles the nitrogen content appears to be as high as 6.7 N atoms for each Pd atom or 5.9 N atoms for each Pt atom whereas bulk films have nominal compositions of Pt7.3N and Pd2.5N. The nanoparticles are metastable in air and moisture, slowly decomposing over several years. This paper describes the synthesis of these materialsmore » along with experimental evidence of the composition, oxidation state, and growth modes. Moreover, the catalytic properties of these N-rich nanoparticles were accessed by rotating disk electrode electrochemical studies, the liquid phase oxidation of benzyl alcohol and gas phase CO oxidation and support the experimental evidence for the materials composition.« less

  18. A rapid and practical strategy for the determination of platinum, palladium, ruthenium, rhodium, iridium and gold in large amounts of ultrabasic rock by inductively coupled plasma optical emission spectrometry combined with ultrasound extraction

    NASA Astrophysics Data System (ADS)

    Zhang, Gai; Tian, Min

    2015-04-01

    This proposed method regulated the determination of platinum, palladium, ruthenium, rhodium, iridium and gold in platinum-group ores by nickel sulfide fire assay—inductively coupled plasma optical emission spectrometry (ICP-OES) combined with ultrasound extraction for the first time. The quantitative limits were 0.013-0.023μg/g. The samples were fused to separate the platinum-group elements from matrix. The nickel sulfide button was then dissolved with hydrochloric acid and the insoluble platinum-group sulfide residue was dissolved with aqua regia by ultrasound bath and finally determined by ICP-OES. The proposed method has been applied into the determination of platinum-group element and gold in large amounts of ultrabasic rocks from the Great Dyke of Zimbabwe.

  19. Preliminary studies on the toxicity and metabolism of palladium and platinum.

    PubMed Central

    Moore, W; Hysell, D; Hall, L; Campbell, K; Stara, J

    1975-01-01

    Preliminary data are given on the LD50 of PdCl2 following different routes of exposure and on the LD50 of PtCl4 following intravenous exposure. The retention, tissue distribution, and excretion of 103Pd and 191Pt in rats was determined following oral, intravenous, intratracheal, and inhalation exposure. The highest retention for both 103Pd and 191Pt was obtained following intravenous dosing, and the lowest retention occurred after oral dosing. Following a single oral dose, almost all of the 103Pd and 191Pt was excreted in the feces due to nonabsorption, whereas after intravenous dosing, similar quantities were excreted in both the urine and feces. Tissues containing the highest concentrations of these metals were the kidney, spleen and liver. Following intravenous dosing of pregnant rats, a small amount of 103Pd and 191Pt was found in the fetuses. PMID:50942

  20. Electrocatalysis of formic acid on palladium and platinum surfaces: from fundamental mechanisms to fuel cell applications.

    PubMed

    Jiang, Kun; Zhang, Han-Xuan; Zou, Shouzhong; Cai, Wen-Bin

    2014-10-14

    Formic acid as a natural biomass and a CO2 reduction product has attracted considerable interest in renewable energy exploitation, serving as both a promising candidate for chemical hydrogen storage material and a direct fuel for low temperature liquid fed fuel cells. In addition to its chemical dehydrogenation, formic acid oxidation (FAO) is a model reaction in the study of electrocatalysis of C1 molecules and the anode reaction in direct formic acid fuel cells (DFAFCs). Thanks to a deeper mechanistic understanding of FAO on Pt and Pd surfaces brought about by recent advances in the fundamental investigations, the "synthesis-by-design" concept has become a mainstream idea to attain high-performance Pt- and Pd-based nanocatalysts. As a result, a large number of efficient nanocatalysts have been obtained through different synthesis strategies by tailoring geometric and electronic structures of the two primary catalytic metals. In this paper, we provide a brief overview of recent progress in the mechanistic studies of FAO, the synthesis of novel Pd- and Pt-based nanocatalysts as well as their practical applications in DFAFCs with a focus on discussing studies significantly contributing to these areas in the past five years.

  1. Electrocatalysis of formic acid on palladium and platinum surfaces: from fundamental mechanisms to fuel cell applications.

    PubMed

    Jiang, Kun; Zhang, Han-Xuan; Zou, Shouzhong; Cai, Wen-Bin

    2014-10-14

    Formic acid as a natural biomass and a CO2 reduction product has attracted considerable interest in renewable energy exploitation, serving as both a promising candidate for chemical hydrogen storage material and a direct fuel for low temperature liquid fed fuel cells. In addition to its chemical dehydrogenation, formic acid oxidation (FAO) is a model reaction in the study of electrocatalysis of C1 molecules and the anode reaction in direct formic acid fuel cells (DFAFCs). Thanks to a deeper mechanistic understanding of FAO on Pt and Pd surfaces brought about by recent advances in the fundamental investigations, the "synthesis-by-design" concept has become a mainstream idea to attain high-performance Pt- and Pd-based nanocatalysts. As a result, a large number of efficient nanocatalysts have been obtained through different synthesis strategies by tailoring geometric and electronic structures of the two primary catalytic metals. In this paper, we provide a brief overview of recent progress in the mechanistic studies of FAO, the synthesis of novel Pd- and Pt-based nanocatalysts as well as their practical applications in DFAFCs with a focus on discussing studies significantly contributing to these areas in the past five years. PMID:25144896

  2. Near Infrared Phosphorescent, Non-oxidizable Palladium and Platinum Perfluoro-phthalocyanines.

    PubMed

    Łapok, Łukasz; Obłoza, Magdalena; Gorski, Alexandr; Knyukshto, Valeri; Raichyonok, Tamara; Waluk, Jacek; Nowakowska, Maria

    2016-04-18

    New Pd(II) and Pt(II) complexes with a highly electron-deficient ligand (H2 PcF64 ) were conveniently prepared in a three-step synthesis. This is the first time that the phosphorescence of phthalocyanines with a H2 PcF64 framework has been measured. Based on these measurements, the triplet-state energies (ET ) were directly determined. Transient absorption experiments revealed broad T1 →Tn absorption spanning from ca. 350 to ca. 1000 nm and allowed determination of the triplet-state lifetimes. Removal of the Pd or Pt from the perfluoro-phthalocyanine resulted in a significant increase of the triplet lifetime for H2 PcF64 . The very efficient intersystem crossing observed for both PdPcF64 and PtPcF64 leads to residual fluorescence and suppresses the fluorescence lifetimes to less than 50 ps. The absence of Pd and Pt in the perfluoro-phthalocyanine ligand, viz. H2 PcF64 , led to a recovery of fluorescence. Cyclic voltamperometry studies pointed to complete resistance of PdPcF64 and PtPcF64 to oxidation and very strong electron affinity, which rendered these materials very good electron acceptors (n-type materials). The presence of d-orbital metals such as Pd(II) and Pt(II) in the phthalocyanine ring stabilizes their reduced forms, as indicated by the spectroelectrochemical experiments. PdPcF64 and PtPcF64 easily sensitize singlet oxygen production with very high quantum yields. Both phthalocyanines presented resistance to photodegradation in the solid state under aerobic conditions and under intense irradiation.

  3. Donnan dialysis of bromocomplexes of some platinum group metal ions

    SciTech Connect

    Brajter, K.; Slonawska, K. ); Cox, J.A. )

    1989-03-01

    The separation of bromocomplexes of platinum group metals by Donnan dialysis is demonstrated with both anion and cation exchange membranes. The inclusion of ethylenediamine (en) in the sample improves the separation of Pd(II) from Pt(IV) with experiments performed with an anion exchange membrane and decreases the amount of metal retained on the membrane phase. With a cation exchange membrane, the addition of a ligand such as en is required for transport. With 5.6 mM en in the sample at pH 10, 74% of Pd(II) is transported across an anion exchange membrane into 0.5 M NH{sub 4} Br after 6 hours while only 8% of the Pt(IV) is dialyzed. Rhodium(III) and iridium(III) behave like Pt(IV). Using a cation exchange membrane under the same conditions except with a 1 hour dialysis results in a 30-fold preferential preconcentration of Pd(II) relative to Pt(IV), and, based on the amount retained in the membrane, a preconcentration of Ir(III) which exceeds that of Pd(II) and Pt(IV) by factors of 40 and 20, respectively.

  4. Complexes of platinum and palladium with β-diketones and DMSO: Synthesis, characterization, molecular modeling, and biological studies

    NASA Astrophysics Data System (ADS)

    do Couto Almeida, J.; Marzano, I. M.; de Paula, F. C. Silva; Pivatto, M.; Lopes, N. P.; de Souza, P. C.; Pavan, F. R.; Formiga, A. L. B.; Pereira-Maia, E. C.; Guerra, W.

    2014-10-01

    This work reports on the synthesis and characterization of new complexes of the type [MCl(L)DMSO], where L = 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HTPB) or 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (HTTA) and M = Pt2+ or Pd2+. These complexes were characterized by elemental analyses, conductivity measurements, FT-IR, UV-Vis, high-resolution mass spectra (HRESIMS) and TG/DTA. In the complexes, the metallic ions bind to β-diketone via the oxygen atoms and to DMSO molecule via sulfur atom. The structures of complexes were optimized and theoretical data showed good agreement with the experimental results. The cytotoxic activity of the compounds was evaluated in a chronic myelogenous leukemia cell line. The platinum complexes were more cytotoxic than the free ligands and carboplatin and are promising candidates for further investigations. As example, the compound [PtCl(TPB)(DMSO)] inhibits the growth of K562 cells with an IC50 value equal to 2.5 μM. Furthermore, microbiological assays against Mycobacterium tuberculosis showed that all complexes exhibit low cytotoxicity against this bacterial strain while the free ligands exhibited MIC values of approximately 10 μg mL-1.

  5. Temporal and spatial studies of autocatalyst-derived platinum, rhodium, and palladium and selected vehicle-derived trace elements in the environment.

    PubMed

    Jarvis, K E; Parry, S J; Piper, J M

    2001-03-15

    The distribution of platinum, rhodium, and palladium (platinum-group elements; PGEs) adjacent to two major U.K. roads shows a rapid decrease (more than 1 order of magnitude) away from the road and reflects patterns shown by other traffic-derived trace elements such as Pb and Zn. However, ratios of Pt:Rh remain relatively constant from 0 to 10 m distance, suggesting that at least some of the PGEs are transported away from the source. A temporal study over a 12-month period, of road dust and surface samples, reveals elevated concentrations above background levels, with maximum values of Pt >500 ng g(-1), Rh 70 ng g(-1), and Pd 70 ng g(-1). Concentrations vary considerably throughout the year and show some tentative correlation with rainfall. Element speciation, an essential control on mobility and hence distribution, was investigated, and the results of solubility experiments show that up to 30% of the Pd present dissolves in acid solutions. This indicates that at least some of the Pd is present in a soluble form and is therefore potentially highly mobile.

  6. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination

    NASA Astrophysics Data System (ADS)

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-06-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon-nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation.

  7. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination.

    PubMed

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-06-10

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon-nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation.

  8. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination.

    PubMed

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-01-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon-nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation. PMID:26059552

  9. Friction behavior of members of the platinum metals group with gold

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1975-01-01

    The adhesion and friction behavior of the platinum metals group was examined with clean surfaces and surfaces selectively contaminated with oxygen, vinyl chloride (C2H3Cl), and methyl mercaptan (CH3SH). A pin or disk specimen configuration was used with the pin being a single crystal of gold of the (111) orientation and with the platinum metal disks also being single crystals of the (111) or (0001) orientation. Loads applied ranged from 1 to 10 g and a sliding velocity of 0.7 mm/min was employed. Results indicate adhesion and transfer of gold to all of the platinum metals. Despite this observation friction differences existed among the metals in the group. These differences are related to surface chemical activity. Adsorption of various friction reducing species was selective. With some adsorbates present strong adhesive forces between metals were still observed.

  10. The platinum group metals in Younger Dryas Horizons are terrestrial

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Wikes, E.; Kennett, J.; West, A.; Sharma, M.

    2009-12-01

    The Younger Dryas (YD) event, which began 12,900 years ago, was a period of abrupt and rapid cooling in the Northern Hemisphere whose primary cause remains unclear. The prevalent postulated mechanism is a temporary shutdown of the thermohaline circulation following the breakup of an ice dam in North America. Firestone et al. (2007) proposed that the cooling was triggered by multiple cometary airbursts and/or impacts that engendered enormous environmental changes and disrupted the thermohaline circulation. The evidence in support for this hypothesis is a black layer in North America and in Europe marking the YD boundary containing charcoal, soot, carbon spherules and glass-like carbon suggesting extensive and intense forest fires. This layer is also enriched in magnetic grains high in iridium, magnetic microspherules, fullerenes containing extraterrestrial He-3, and nanodiamonds. Whereas the nanodiamonds could be produced in an impact or arrive with the impactor, the cometary burst/impact hypothesis remains highly controversial as the YD horizon lacks important impact markers such as craters, breccias, tektites and shocked minerals. Firestone et al. (2007) contend that bulk of Ir found at the YD boundary is associated with magnetic grains. The key issue is whether this Ir is meteorite derived. We used Ir and Os concentrations and Os isotopes to investigate the provenance of the platinum group metals in the YD horizon. The bulk sediment samples from a number of North American YD sites (Blackwater Draw, Murray Springs, Gainey, Sheriden Cave, and Myrtle Beach) and a site in Europe (Lommel) do not show any traces of meteorite derived Os and Ir. The [Os] = 2 to 45 pg/g in these sediments and the 187Os/188Os ratios are similar to the upper continental crustal values (~1.3), much higher than those in meteorites (0.13). Higher [Os] is observed in Blackwater Draw (= 194 pg/g). However, the Os/Ir ratio in Blackwater Draw is 5 (not 1 as expected for a meteorite) and 187Os/188

  11. Coating Carbon Fibers With Platinum

    NASA Technical Reports Server (NTRS)

    Effinger, Michael R.; Duncan, Peter; Coupland, Duncan; Rigali, Mark J.

    2007-01-01

    A process for coating carbon fibers with platinum has been developed. The process may also be adaptable to coating carbon fibers with other noble and refractory metals, including rhenium and iridium. The coated carbon fibers would be used as ingredients of matrix/fiber composite materials that would resist oxidation at high temperatures. The metal coats would contribute to oxidation resistance by keeping atmospheric oxygen away from fibers when cracks form in the matrices. Other processes that have been used to coat carbon fibers with metals have significant disadvantages: Metal-vapor deposition processes yield coats that are nonuniform along both the lengths and the circumferences of the fibers. The electrical resistivities of carbon fibers are too high to be compatible with electrolytic processes. Metal/organic vapor deposition entails the use of expensive starting materials, it may be necessary to use a furnace, and the starting materials and/or materials generated in the process may be hazardous. The present process does not have these disadvantages. It yields uniform, nonporous coats and is relatively inexpensive. The process can be summarized as one of pretreatment followed by electroless deposition. The process consists of the following steps: The surfaces of the fiber are activated by deposition of palladium crystallites from a solution. The surface-activated fibers are immersed in a solution that contains platinum. A reducing agent is used to supply electrons to effect a chemical reduction in situ. The chemical reduction displaces the platinum from the solution. The displaced platinum becomes deposited on the fibers. Each platinum atom that has been deposited acts as a catalytic site for the deposition of another platinum atom. Hence, the deposition process can also be characterized as autocatalytic. The thickness of the deposited metal can be tailored via the duration of immersion and the chemical activity of the solution.

  12. Neutron emission and the tritium content associated with deuterium-loaded palladium and titanium metals

    NASA Astrophysics Data System (ADS)

    Wolf, K. L.; Packham, N. J. C.; Lawson, D.; Shoemaker, J.; Cheng, F.; Wass, J. C.

    1990-06-01

    An experimental investigation has been conducted on samples of palladium and titanium metals which have been loaded with deuterium through the electrolysis of D2O and by absorption of D2 gas. In approximately 200 experiments on 25 cells, statistically significant evidence for neutron emission was obtained in three separate experiments from one palladium cathode. Observed rates are 3-4 times the background rate and correspond to source strengths up to 50 neutrons/min. The pulse height response of the NE213 liquid scintillator-based detectors corresponds to that expected for 2.45 MeV neutrons. Tritium has been identified in nine Pd-Ni electrolytic cells, at levels corresponding 1012-1016 atoms. Activity buildup curves indicate that the apparent production occurs over a time period as short as a few hours.

  13. Biological role in the transformation of platinum-group mineral grains

    NASA Astrophysics Data System (ADS)

    Reith, Frank; Zammit, Carla M.; Shar, Sahar S.; Etschmann, Barbara; Bottrill, Ralph; Southam, Gordon; Ta, Christine; Kilburn, Matthew; Oberthür, Thomas; Ball, Andrew S.; Brugger, Joël

    2016-04-01

    Platinum-group elements are strategically important metals. Finding new deposits is becoming increasingly difficult owing to our limited understanding of the processes that affect their mobility in surface environments. Microorganisms have been shown to promote the mobility of metals around ore deposits. Here we show that microorganisms influence the mobility of platinum-group elements in mineral grains collected from Brazil, Australia and Colombia. Scanning electron microscopy showed biofilms covering the platinum-group mineral grains. The biofilms contained abundant platinum-group element nanoparticles and microcrystalline aggregates, and were dominated by Proteobacteria, many of which were closely related to known metal-resistant species. Some platinum-group mineral grains contained carbon, nitrogen, sulfur, selenium and iodine, suggesting the grains may be biogenic in origin. Molecular analyses show that Brazilian platinum-palladium grains hosted specific bacterial communities, which were different in composition from communities associated with gold grains, or communities in surrounding soils and sediments. Nano-phase metallic platinum accumulated when a metallophillic bacterium was incubated with a percolating platinum-containing medium, suggesting that biofilms can cause the precipitation of mobile platinum complexes. We conclude that biofilms are capable of forming or transforming platinum-group mineral grains, and may play an important role for platinum-group element dispersion and re-concentration in surface environments.

  14. Combined homogeneous and heterogeneous catalysts. Rhodium and platinum isocyanide complexes tethered on silica-supported metal heterogeneous catalysts: Arene and cyclohexanone hydrogenation

    SciTech Connect

    Gao, H.; Angelici, R.J. |

    1999-03-15

    Rhodium and platinum isocyanide complexes RhCl(CO)[CN(CH{sub 2}){sub 3}Si(OC{sub 2}H{sub 5}){sub 3}]{sub 2} (Rh-CNR{sub 2}), RhCl[CN(CH{sub 2}){sub 3}Si(OC{sub 2}H{sub 5}){sub 3}]{sub 3} (Rh-CNR{sub 3}), and PtCl{sub 2}[CN(CH{sub 2}){sub 3}Si(OC{sub 2}H{sub 5}){sub 3}]{sub 2} (Pt-CNR{sub 2}) were tethered to the silica-supported metal heterogeneous catalysts M-SiO{sub 2} (M = Pd, Pt, Ru) to give the TCSM (tethered complex on supported metal) catalysts Rh-CNR{sub 2}/Pd-SiO{sub 2}, Rh-CNR{sub 3}/M-SiO{sub 2} (M = Pd, Pt, Ru), and Pt-CNR{sub 2}/Pd-SiO{sub 2}. These TCSM catalysts were used to catalyze the hydrogenation of arenes (Rh-CNR{sub 2}/Pd-SiO{sub 2} and Rh-CNR{sub 3}/M-SiO{sub 2}) and cyclohexanone (Pt-CNR{sub 2}/Pd-SiO{sub 2}) under the mild conditions of 40 C and 1 atm. They exhibit activities that are higher than those of the separate homogeneous rhodium (or platinum) isocyanide complex, the separate silica-supported metal heterogeneous catalyst, or the rhodium (or platinum) complex catalyst tethered on just SiO{sub 2}. The activities of the TCSM catalysts are strongly affected by the nature and loading of the supported metal in the catalyst. Among the three silica-supported metal M-SiO{sub 2} (M = Pd, Pt, Ru) catalysts, the rhodium complex Rh-CNR{sub 3} tethered on Pd-SiO{sub 2} exhibits the highest activity for the hydrogenation of toluene (TOF = 5.5 mol H{sub 2}/(mol Rh min) and TO = 2,420 mol H{sub 2}/mol Rh during 8.5 h). The Rh-CNR{sub 3}/Pd-SiO{sub 2} catalyst with 10 wt % Pd is more active than its counterparts with higher or lower palladium loadings. IR (DRIFT) spectral studies of the TCSM catalysts before and after being used for toluene hydrogenation show that the isocyanide ligands remain coordinated to the rhodium (or platinum) center even after extended use. Atomic emission spectroscopic analysis of hydrogenation solutions shows that there is no rhodium (or platinum) leaching into the solutions.

  15. Electrochemical metallization switching with a platinum group metal in different oxides

    NASA Astrophysics Data System (ADS)

    Wang, Zhongrui; Jiang, Hao; Hyung Jang, Moon; Lin, Peng; Ribbe, Alexander; Xia, Qiangfei; Yang, J. Joshua

    2016-07-01

    In a normal electrochemical metallization (ECM) switch, electrochemically active metals, such as Ag and Cu are used to provide mobile ions for the conducting filament. In both ECM and valence change memory (VCM) devices, platinum group metals, such as Pt and Pd, are typically used as the counter electrode and assumed to be chemically and physically inert. In this study, we explore whether the so-called inert metal itself can form a conducting filament and result in repeatable resistance switching. Pd and different oxide host matrices are used for this purpose. We have observed that the transport of oxygen anions dominates over Pd metal cations in ALD deposited AlOx and HfOx. However, in sputtered SiOx, Pd cation transport was revealed, accompanied by the formation of nano-crystalline Pd filament(s) in the junctions. Based on these observations, memristors with reversible and repeatable switching were obtained by using Pd doped SiOx as the switching material.In a normal electrochemical metallization (ECM) switch, electrochemically active metals, such as Ag and Cu are used to provide mobile ions for the conducting filament. In both ECM and valence change memory (VCM) devices, platinum group metals, such as Pt and Pd, are typically used as the counter electrode and assumed to be chemically and physically inert. In this study, we explore whether the so-called inert metal itself can form a conducting filament and result in repeatable resistance switching. Pd and different oxide host matrices are used for this purpose. We have observed that the transport of oxygen anions dominates over Pd metal cations in ALD deposited AlOx and HfOx. However, in sputtered SiOx, Pd cation transport was revealed, accompanied by the formation of nano-crystalline Pd filament(s) in the junctions. Based on these observations, memristors with reversible and repeatable switching were obtained by using Pd doped SiOx as the switching material. Electronic supplementary information (ESI) available

  16. Doped palladium containing oxidation catalysts

    DOEpatents

    Mohajeri, Nahid

    2014-02-18

    A supported oxidation catalyst includes a support having a metal oxide or metal salt, and mixed metal particles thereon. The mixed metal particles include first particles including a palladium compound, and second particles including a precious metal group (PMG) metal or PMG metal compound, wherein the PMG metal is not palladium. The oxidation catalyst may also be used as a gas sensor.

  17. Effective and selective recovery of gold and palladium ions from metal wastewater using a sulfothermophilic red alga, Galdieria sulphuraria.

    PubMed

    Ju, Xiaohui; Igarashi, Kensuke; Miyashita, Shin-Ichi; Mitsuhashi, Hiroaki; Inagaki, Kazumi; Fujii, Shin-Ichiro; Sawada, Hitomi; Kuwabara, Tomohiko; Minoda, Ayumi

    2016-07-01

    The demand for precious metals has increased in recent years. However, low concentrations of precious metals dissolved in wastewater are yet to be recovered because of high operation costs and technical problems. The unicellular red alga, Galdieria sulphuraria, efficiently absorbs precious metals through biosorption. In this study, over 90% of gold and palladium could be selectively recovered from aqua regia-based metal wastewater by using G. sulphuraria. These metals were eluted from the cells into ammonium solutions containing 0.2M ammonium salts without other contaminating metals. The use of G. sulphuraria is an eco-friendly and cost-effective way of recovering low concentrations of gold and palladium discarded in metal wastewater. PMID:27118429

  18. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Noble metal alloy. 872.3060 Section 872.3060 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver,...

  19. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Noble metal alloy. 872.3060 Section 872.3060 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver,...

  20. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Noble metal alloy. 872.3060 Section 872.3060 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver,...

  1. Metal-enhanced intrinsic fluorescence of nucleic acids using platinum nanostructured substrates

    NASA Astrophysics Data System (ADS)

    Akbay, Nuriye; Mahdavi, Farhad; Lakowicz, Joseph R.; Ray, Krishanu

    2012-10-01

    We investigated the feasibility of using platinum nanostructures to accomplish the metal-enhanced fluorescence (MEF) in the UV spectral region. We examine the possibility for detection of the intrinsic fluorescence from nucleotides and G-quadruplex DNA on platinum nanoparticles. Guanosine monophosphate (GMP) showed significant increases (˜20-fold) in fluorescence intensities in the presence of platinum nanostructures when compared to quartz controls. G-quadruplex DNA demonstrated ˜5-fold increase in fluorescence intensity and higher photostability in the presence of Pt nanostructures. We performed Finite Element Method simulations to explore how Pt nanoparticles interact with plane waves and conformed that the Pt nanostructures are promising for enhancing the fluorescence emission in the UV region.

  2. Making A Noble-Metal-On-Metal-Oxide Catalyst

    NASA Technical Reports Server (NTRS)

    Miller, Irvin M.; Davis, Patricia P.; Upchurch, Billy T.

    1989-01-01

    Catalyst exhibits superior performance in oxidation of CO in CO2 lasers. Two-step process developed for preparing platinum- or palladium-on-tin-oxide catalyst for recombination of CO and O2, decomposition products that occur in high-voltage discharge region of closed-cycle CO2 laser. Process also applicable to other noble-metal/metal-oxide combinations.

  3. Photophysical investigation of palladium(II) ortho-metalated complexes

    SciTech Connect

    Craig, C.A.; Watts, R.J. )

    1989-01-25

    Syntheses and structural characterizations of four complexes of Pd(II) with ortho-metalated 2-phenylpyridinate (ppy{sup minus}) are reported. These complexes include a parent dimer, (Pd(ppy)Cl){sub 2}, and three derivative monomers, (Pd(ppy)(bpy))Cl, (Pd(ppy)(en))Cl, and (Pd(ppy)(CO)Cl), whereby = 2,2'-bipyridine and en = ethylenediamine. Photophysical characterizations of these species indicate low-energy absorption bands ({approximately}360 nm) and emission bands at 77 K ({approximately}460 nm) that are assigned to transitions located on the ppy{sup {minus}} ligand. Some evidence for low-energy charge-transfer states is found in trends in luminescence lifetimes. 2 tabs., 5 figs., 21 refs.

  4. In vitro investigations of platinum, palladium, and rhodium mobility in urban airborne particulate matter (PM10, PM2.5, and PM1) using simulated lung fluids.

    PubMed

    Zereini, Fathi; Wiseman, Clare L S; Püttmann, Wilhelm

    2012-09-18

    Environmental concentrations of platinum group elements (PGE) have been increasing since the introduction of automotive catalytic converters to control harmful emissions. Assessments of the human health risks of exposures to these elements, especially through the inhalation of PGE-associated airborne particulate matter (PM), have been hampered by a lack of data on their bioaccessibility. The purpose of this study is to apply in vitro methods using simulated human lung fluids [artificial lysosomal fluid (ALF) and Gamble's solution] to assess the mobility of the PGE, platinum (Pt), palladium (Pd), and rhodium (Rh) in airborne PM of human health concern. Airborne PM samples (PM(10), PM(2.5), and PM(1)) were collected in Frankfurt am Main, Germany. For comparison, the same extraction experiments were conducted using the standard reference material, Used Auto Catalyst (monolith) (NIST 2557). Pt and Pd concentrations were measured using isotope dilution ICP-Q-MS, while Rh was measured directly with ICP-Q-MS (in collision mode with He), following established matrix separation and enrichment procedures, for both solid (filtered residues) and extracted sample phases. The mobilized fractions measured for PGE in PM(10), PM(2.5), and PM(1) were highly variable, which can be attributed to the heterogenic nature of airborne PM and its composition. Overall, the mobility of PGE in airborne PM samples was notable, with a mean of 51% Rh, 22% Pt, and 29% Pd present in PM(1) being mobilized by ALF after 24 h. For PM(1) exposed to Gamble's solution, a mean of 44% Rh, 18% Pt, and 17% Pd was measured in solution after 24 h. The mobility of PGE associated with airborne PM was also determined to be much higher compared to that measured for the auto catalyst standard reference material. The results suggest that PGE emitted from automotive catalytic converters are likely to undergo chemical transformations during and/or after being emitted in the environment. This study highlights the need

  5. In vitro investigations of platinum, palladium, and rhodium mobility in urban airborne particulate matter (PM10, PM2.5, and PM1) using simulated lung fluids.

    PubMed

    Zereini, Fathi; Wiseman, Clare L S; Püttmann, Wilhelm

    2012-09-18

    Environmental concentrations of platinum group elements (PGE) have been increasing since the introduction of automotive catalytic converters to control harmful emissions. Assessments of the human health risks of exposures to these elements, especially through the inhalation of PGE-associated airborne particulate matter (PM), have been hampered by a lack of data on their bioaccessibility. The purpose of this study is to apply in vitro methods using simulated human lung fluids [artificial lysosomal fluid (ALF) and Gamble's solution] to assess the mobility of the PGE, platinum (Pt), palladium (Pd), and rhodium (Rh) in airborne PM of human health concern. Airborne PM samples (PM(10), PM(2.5), and PM(1)) were collected in Frankfurt am Main, Germany. For comparison, the same extraction experiments were conducted using the standard reference material, Used Auto Catalyst (monolith) (NIST 2557). Pt and Pd concentrations were measured using isotope dilution ICP-Q-MS, while Rh was measured directly with ICP-Q-MS (in collision mode with He), following established matrix separation and enrichment procedures, for both solid (filtered residues) and extracted sample phases. The mobilized fractions measured for PGE in PM(10), PM(2.5), and PM(1) were highly variable, which can be attributed to the heterogenic nature of airborne PM and its composition. Overall, the mobility of PGE in airborne PM samples was notable, with a mean of 51% Rh, 22% Pt, and 29% Pd present in PM(1) being mobilized by ALF after 24 h. For PM(1) exposed to Gamble's solution, a mean of 44% Rh, 18% Pt, and 17% Pd was measured in solution after 24 h. The mobility of PGE associated with airborne PM was also determined to be much higher compared to that measured for the auto catalyst standard reference material. The results suggest that PGE emitted from automotive catalytic converters are likely to undergo chemical transformations during and/or after being emitted in the environment. This study highlights the need

  6. In vitro heavy-atom effect of palladium(II) and platinum(II) complexes of pyrrolidine-fused chlorin in photodynamic therapy.

    PubMed

    Obata, Makoto; Hirohara, Shiho; Tanaka, Rika; Kinoshita, Isamu; Ohkubo, Kei; Fukuzumi, Shunichi; Tanihara, Masao; Yano, Shigenobu

    2009-05-14

    Introduction of a heavy atom into photosensitizers generally facilitates intersystem crossing and improves the quantum yield (Phi(Delta)) of singlet oxygen ((1)O(2)), which is a key species in photodynamic therapy (PDT). However, little information is available about the physiological importance of this heavy-atom effect. The aim of this study is to examine the heavy-atom effect in simple metallochlorins in vitro at the cellular level. 1,3-Dipolar cycloaddition of azomethine ylide to 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato palladium(II) and platinum(II) afforded metallochlorins 4b and 4c in yields of 17.1 and 12.9%, respectively. The Phi(Delta) values increased in the order of 4a (0.28) < 4b (0.89) < 4c (0.92) in C(6)D(6). The photocytotoxicity of 4a, 4b, and 4c was evaluated in HeLa cells at a light dose of 16 J x cm(-2) with lambda > 500 nm and increased in the order of 4a < 4b < 4c at the concentration of 0.5 microM. The photocytotoxicity of 4b and 4c was significantly inhibited by addition of sodium azide, but not D-mannitol, suggesting that (1)O(2) is the major species causing cell death. Our results clearly indicate that 4b and 4c act as efficient (1)O(2) generators due to the heavy-atom effect in a cellular microenvironment as well as in nonphysiological media. PMID:19378972

  7. Platinum Group Metal Recycling Technology Development - Final Report

    SciTech Connect

    Lawrence Shore

    2009-08-19

    BASF Catalysts LLC, formerly Engelhard Corporation, has completed a project to recover Pt from PEM fuel cell membrane electrode assemblies. The project, which began in 2003, has met the project objective of an environmentally-friendly, cost-effective method for recovery of platinum without release of hydrogen fluoride. This has been achieved using a combination of milling, dispersion and acid leaching. 99% recovery of Pt was achieved, and this high yield can be scaled up using one vessel for a single leach and rinse. Leaching was been successfully achieved using a 10% solids level, double the original target. At this solids content, the reagent and utility costs represent ~0.35% of the Pt value of a lot, using very conservative assumptions. The main cost of the process is capital depreciation, followed by labor.

  8. Core-Protected Platinum Monolayer Shell High-Stability Electrocatalysts for Fuel-Cell Cathodes

    SciTech Connect

    Adzic, R.R.; Sasaki, K.; Naohara, H.; Cai, Y.; Choi, Y.M.; Liu, P.; Vukmirovic, M.B.; Wang, J.X.

    2010-11-08

    More than skin deep: Platinum monolayers can act as shells for palladium nanoparticles to lead to electrocatalysts with high activities and an ultralow platinum content, but high platinum utilization. The stability derives from the core protecting the shell from dissolution. In fuel-cell tests, no loss of platinum was observed in 200?000 potential cycles, whereas loss of palladium was significant.

  9. Core-Protected Platinum Monolayer Shell High-Stability Electrocatalysts for Fuel-Cell Cathodes

    SciTech Connect

    K Sasaki; H Naohara; Y Cai; Y Choi; P Liu; M Vukmirovic; J Wang; R Adzic

    2011-12-31

    Platinum monolayers can act as shells for palladium nanoparticles to lead to electrocatalysts with high activities and an ultralow platinum content, but high platinum utilization. The stability derives from the core protecting the shell from dissolution. In fuel-cell tests, no loss of platinum was observed in 200,000 potential cycles, whereas loss of palladium was significant.

  10. Mechanism of pH-switchable peroxidase and catalase-like activities of gold, silver, platinum and palladium.

    PubMed

    Li, Junnan; Liu, Wenqi; Wu, Xiaochun; Gao, Xingfa

    2015-04-01

    Despite being increasingly used as artificial enzymes, little has been known for the origin of the pH-switchable peroxidase-like and catalase-like activities of metals. Using calculations and experiments, we report the mechanisms for both activities and their pH-switchability for metals Au, Ag, Pd and Pt. The calculations suggest that both activities are intrinsic properties of metals, regardless of the surfaces and intersections of facets exposed to environments. The pre-adsorbed OH groups on the surfaces, which are only favorably formed in basic conditions, trigger the switch between both activities and render the pH-switchability. The adsorption energies between H2O2 and metals can be used as convenient descriptors to predict the relative enzyme-like activities of the metals with similar surface morphologies. The results agree with the enzyme-mimic activities that have been experimentally reported for Au, Ag, Pt and predict that Pd should have the similar properties. The prediction, as well as the predicted activity order for the four metals, has been verified by the experimental tests. The results thus provide an in-depth insight into the peroxidase-like and catalase-like activities of the metals and will guide the de novo design, synthesis and application of artificial enzymes based on inorganic materials.

  11. Hydrogen storage studies on palladium-doped carbon materials (AC, CB, CNMs) @ metal-organic framework-5.

    PubMed

    Viditha, V; Srilatha, K; Himabindu, V

    2016-05-01

    Metal organic frameworks (MOFs) are a rapidly growing class of porous materials and are considered as best adsorbents for their high surface area and extraordinary porosity. The MOFs are synthesized by using various chemicals like triethylamine, terepthalic acid, zinc acetate dihydrate, chloroform, and dimethylformamide (DMF). Synthesized MOFs are intercalated with palladium/activated carbon, carbon black, and carbon nanomaterials by chemical reduction method for the purpose of enhancing the hydrogen adsorption capacities. We have observed that the palladium doped activated carbon on MOF-5 showed high hydrogen storage capacity. This may be due to the affinity of the palladium toward hydrogen molecule. The samples are characterized by X-ray diffraction, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. We have observed a clear decrease in the BET surface area and pore volume. The obtained results show a better performance for the synthesized sample. To our best knowledge, no one has reported the work on palladium-doped carbon materials (activated carbon, carbon black, carbon nanomaterials) impregnated to the metal-organic framework-5. We have attempted to synthesize carbon nanomaterials using indigenously fabricated chemical vapor deposition (CVD) unit as a support. We have observed an increase in the hydrogen storage capacities.

  12. Hydrothermal synthesis of platinum-group-metal nanoparticles by using HEPES as a reductant and stabilizer.

    PubMed

    So, Man-Ho; Ho, Chi-Ming; Chen, Rong; Che, Chi-Ming

    2010-06-01

    Platinum-group-metal (Ru, Os, Rh, Ir, Pd and Pt) nanoparticles are synthesized in an aqueous buffer solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (200 mM, pH 7.4) under hydrothermal conditions (180 degrees C). Monodispersed (monodispersity: 11-15%) metal nanoparticles were obtained with an average particle size of less than 5 nm (Ru: 1.8+/-0.2, Os: 1.6+/-0.2, Rh: 4.5+/-0.5, Ir: 2.0+/-0.3, Pd: 3.8+/-0.4, Pt: 1.9+/-0.2 nm). The size, monodispersity, and stability of the as-obtained metal nanoparticles were affected by the HEPES concentration, pH of the HEPES buffer solution, and reaction temperature. HEPES with two tertiary amines (piperazine groups) and terminal hydroxyl groups can act as a reductant and stabilizer. The HEPES molecules can bind to the surface of metal nanoparticles to prevent metal nanoparticles from aggregation. These platinum-group-metal nanoparticles could be deposited onto the surface of graphite, which catalyzed the aerobic oxidation of alcohols to aldehydes. PMID:20512785

  13. Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy

    SciTech Connect

    Liotta, L.F.; Deganello, G.; Delichere, P.

    1996-12-01

    Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminates, obtained by sol-gel techniques, with a different amount of sodium, and R equal to 2.1 and 6.1 respectively. LEIS experiments and electron microscopy demonstrate a different location of alkali metal ions in the first two series: in the Na-Pd/SiO{sub 2} catalysts sodium is distributed in a way which is not uniform on the support and on the palladium metal, which is partly decorated with Na ions, whereas in the Pd/natural-pumice series the palladium surface is sodium-free. The results on the third series of catalysts, Pd/model pumice, are not definitive on the basis of the LEIS and TEM analyses, but by FTIR study of CO and CO{sub 2} adsorption, the decoration of palladium by sodium ions could be excluded. The results confirm the importance of the alkali metal ion location in alkali-promoted palladium catalysts and open new possibilities in the design of palladium-supported catalysts by a better control of promoter location. 18 refs., 5 figs., 2 tabs.

  14. Synthesis of nanoscaled platinum particles (NSPP): their role in performance improvement of ionic polymer-metal composite (IPMC) artificial muscles

    NASA Astrophysics Data System (ADS)

    Kim, Kwang J.; Shahinpoor, Mohsen

    2001-07-01

    In this work the synthesis of nano-scaled platinum particles by a chemical reducing technique within an ion-exchange membrane has been performed. It is desirable to gain a fundamental knowledge and understanding of the properties of small nano-scaled platinum particles within ion-exchange membranes, which can affect the performance of Ionic Polymer-Metal Composite (IPMC) artificial muscles. In IPMC artificial muscle applications, the finite size of platinum particles is believed to strongly influence their properties. This might be related to a platinum surface effect originating from the electronic surface states of platinum particles that differ from the bulk states. In order to address this issue, we have attempted to synthesize small platinum particles having different size distributions by using protective agents. Further, we have characterized them as well. For IPMC artificial muscles, the presence of such nano-scale platinum particles minimizes the solvent- leakage from the surface electrodes. This in turn improves their performance dramatically. A successfully fabricated IPMC artificial muscle with nano-Platinum particles has shown a significantly improved force density as much as 100% than that of the conventional IPMC.

  15. Platinum and palladium nano-structured catalysts for polymer electrolyte fuel cells and direct methanol fuel cells.

    PubMed

    Long, Nguyen Viet; Thi, Cao Minh; Yong, Yang; Nogami, Masayuki; Ohtaki, Michitaka

    2013-07-01

    In this review, we present the synthesis and characterization of Pt, Pd, Pt based bimetallic and multi-metallic nanoparticles with mixture, alloy and core-shell structure for nano-catalysis, energy conversion, and fuel cells. Here, Pt and Pd nanoparticles with modified nanostructures can be controllably synthesized via chemistry and physics for their uses as electro-catalysts. The cheap base metal catalysts can be studied in the relationship of crystal structure, size, morphology, shape, and composition for new catalysts with low cost. Thus, Pt based alloy and core-shell catalysts can be prepared with the thin Pt and Pt-Pd shell, which are proposed in low and high temperature proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs). We also present the survey of the preparation of Pt and Pd based catalysts for the better catalytic activity, high durability, and stability. The structural transformations, quantum-size effects, and characterization of Pt and Pd based catalysts in the size ranges of 30 nm (1-30 nm) are presented in electro-catalysis. In the size range of 10 nm (1-10 nm), the pure Pt catalyst shows very large surface area for electro-catalysis. To achieve homogeneous size distribution, the shaped synthesis of the polyhedral Pt nanoparticles is presented. The new concept of shaping specific shapes and morphologies in the entire nano-scale from nano to micro, such as polyhedral, cube, octahedra, tetrahedra, bar, rod, and others of the nanoparticles is proposed, especially for noble and cheap metals. The uniform Pt based nanosystems of surface structure, internal structure, shape, and morphology in the nanosized ranges are very crucial to next fuel cells. Finally, the modifications of Pt and Pd based catalysts of alloy, core-shell, and mixture structures lead to find high catalytic activity, durability, and stability for nano-catalysis, energy conversion, fuel cells, especially the next large-scale commercialization of next

  16. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal–nitrogen coordination

    PubMed Central

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-01-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon–nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation. PMID:26059552

  17. Carbon-carbon cross coupling reactions in ionic liquids catalysed by palladium metal nanoparticles.

    PubMed

    Prechtl, Martin H G; Scholten, Jackson D; Dupont, Jairton

    2010-05-12

    A brief summary of selected pioneering and mechanistic contributions in the field of carbon-carbon cross-coupling reactions with palladium nanoparticles (Pd-NPs) in ionic liquids (ILs) is presented. Five exemplary model systems using the Pd-NPs/ILs approach are presented: Heck, Suzuki, Stille, Sonogashira and Ullmann reactions which all have in common the use of ionic liquids as reaction media and the use of palladium nanoparticles as reservoir for the catalytically active palladium species.

  18. Luminescence of ortho-metallated platinum(II) complexes

    NASA Astrophysics Data System (ADS)

    Maestri, Mauro; Sandrini, Diana; Balzani, Vincenzo; Chassot, Laurent; Jolliet, Philippe; von Zelewsky, Alex

    1985-12-01

    The absorption spectra, emission spectra, and emission lifetimes of Pt(Phpy) 2, Pt(Thpy) 2, and Pt(Bhq) 2 complexes (Phpy -, Thpy -, and Bhq - are the ortho C-deprotonated forms of 2-phenylpyridine, 2-(2-thienyl)-pyridine, and benzo(h)quinoline) have been studied and compared with those of the C-protonated neutral ligands. For all complexes examined the low-energy absorption bands in the near UV and visible region are assigned to metal-to-ligand charge-transfer transitions. The strong and structured luminescence emissions observed in the 500-600 nm region (lifetime in the microsecond range at 77 K) are assigned to metal-to-ligand charge-transfer excited states.

  19. High Temperature Strength of YSZ Joints Brazed with Palladium Silver Copper Oxide Filler Metals

    SciTech Connect

    Darsell, Jens T.; Weil, K. Scott

    2010-06-09

    The Ag-CuOx system is being investigated as potential filler metals for use in air brazing high-temperature electrochemical devices such as solid oxide fuel cells and gas concentrators. The current study examines the effects of palladium addition on the high temperature joint strength of specimens prepared from yttria stabilized zirconia (YSZ) bars brazed with the binary Ag-CuOx, and 15Pd-Ag-CuO. It was found that while the binary Ag-CuOx system exhibits stronger room temperature strength than the 15Pd system the strength is reduced to values equivalent of the 15Pd system at 800°C. The 15Pd system exhibits a lower ambient temperature strength that is retained at 800°C. In both systems the failure mechanism at high temperature appears to be peeling of the noble metal component from the oxide phases and tearing through the noble metal phase whereas sufficient adhesion is retained at lower temperatures to cause fracture of the YSZ substrate.

  20. Platinum metallization for MEMS application. Focus on coating adhesion for biomedical applications.

    PubMed

    Guarnieri, Vittorio; Biazi, Leonardo; Marchiori, Roberto; Lago, Alexandre

    2014-01-01

    The adherence of Platinum thin film on Si/SiO2 wafer was studies using Chromium, Titanium or Alumina (Cr, Ti, Al2O3) as interlayer. The adhesion of Pt is a fundamental property in different areas, for example in MEMS devices, which operate at high temperature conditions, as well as in biomedical applications, where the problem of adhesion of a Pt film to the substrate is known as a major challenge in several industrial applications health and in biomedical devices, such as for example in the stents. We investigated the properties of Chromium, Titanium, and Alumina (Cr, Ti, and Al2O3) used as adhesion layers of Platinum (Pt) electrode. Thin films of Chromium, Titanium and Alumina were deposited on Silicon/Silicon dioxide (Si/SiO2) wafer by electron beam. We introduced Al2O3 as a new adhesion layer to test the behavior of the Pt film at higher temperature using a ceramic adhesion thin film. Electric behaviors were measured for different annealing temperatures to know the performance for Cr/Pt, Ti/Pt, and Al2O3/Pt metallic film in the gas sensor application. All these metal layers showed a good adhesion onto Si/SiO2 and also good Au wire bondability at room temperature, but for higher temperature than 400 °C the thin Cr/Pt and Ti/Pt films showed poor adhesion due to the atomic inter-diffusion between Platinum and the metal adhesion layers. The proposed Al2O3/Pt ceramic-metal layers confirmed a better adherence for the higher temperatures tested.

  1. Platinum metallization for MEMS application: focus on coating adhesion for biomedical applications.

    PubMed

    Guarnieri, Vittorio; Biazi, Leonardo; Marchiori, Roberto; Lago, Alexandre

    2014-01-01

    The adherence of Platinum thin film on Si/SiO 2 wafer was studies using Chromium, Titanium or Alumina (Cr, Ti, Al 2O 3) as interlayer. The adhesion of Pt is a fundamental property in different areas, for example in MEMS devices, which operate at high temperature conditions, as well as in biomedical applications, where the problem of adhesion of a Pt film to the substrate is known as a major challenge in several industrial applications health and in biomedical devices, such as for example in the stents. (1)(-) (4) We investigated the properties of Chromium, Titanium, and Alumina (Cr, Ti, and Al 2O 3) used as adhesion layers of Platinum (Pt) electrode. Thin films of Chromium, Titanium and Alumina were deposited on Silicon/Silicon dioxide (Si/SiO 2) wafer by electron beam. We introduced Al 2O 3 as a new adhesion layer to test the behavior of the Pt film at higher temperature using a ceramic adhesion thin film. Electric behaviors were measured for different annealing temperatures to know the performance for Cr/Pt, Ti/Pt, and Al 2O 3/Pt metallic film in the gas sensor application. All these metal layers showed a good adhesion onto Si/SiO 2 and also good Au wire bondability at room temperature, but for higher temperature than 400 °C the thin Cr/Pt and Ti/Pt films showed poor adhesion due to the atomic inter-diffusion between Platinum and the metal adhesion layers. (5) The proposed Al 2O 3/Pt ceramic-metal layers confirmed a better adherence for the higher temperatures tested.

  2. Materials discovery by crystal growth: Lanthanide metal containing oxides of the platinum group metals (Ru, Os, Ir, Rh, Pd, Pt) from molten alkali metal hydroxides

    SciTech Connect

    Mugavero, Samuel J.; Gemmill, William R.; Roof, Irina P.; Loye, Hans-Conrad zur

    2009-07-15

    This review addresses the process of materials discovery via crystal growth, specifically of lanthanide metal containing oxides of the platinum group metals (Ru, Os, Ir, Rh, Pd, Pt). It provides a detailed overview of the use of hydroxide fluxes for crystal growth. The melt chemistry of hydroxide fluxes, specifically, the extensive acid base chemistry, the metal cation solubility, and the ability of hydroxide melts to oxidize metals are described. Furthermore, a general methodology for the successful crystal growth of oxides is provided, including a discussion of experimental considerations, suitable reaction vessels, reaction profiles and temperature ranges. Finally, a compilation of complex platinum group metal oxides recently synthesized using hydroxide melts, focusing on their crystal growth and crystal structures, is included. - Graphical abstract: A review that addresses the process of materials discovery via crystal growth using hydroxide fluxes. It provides a detailed overview of the use of hydroxide fluxes for crystal growth and describes the melt chemistry of hydroxide fluxes, specifically, the extensive acid base chemistry, the metal cation solubility, and the ability of hydroxide melts to oxidize metals. In addition, a compilation of complex platinum group metal oxides recently synthesized using hydroxide melts is included.

  3. Fractionation of palladium and platinum in a Mesozoic diabase sheet, Gettysburg basin, Pennsyvania: implications for mineral exploration

    USGS Publications Warehouse

    Gottfried, D.; Froelich, A.J.; Rait, N.; Aruscavage, P. J.

    1990-01-01

    The York Haven diabase sheet displays clear-cut evidence of fractionation of Pd and Pt during differentiation of a high-Ti (about 1.1%) quartz-normative tholeiitic magma (York Haven type). At York Haven the sheet is about 750 m thick. It is characterized by abundant cumulus MgO-rich orthopyroxene (bronzite), and is markedly depleted in incompatible elements relative to the chilled margins. In contrast, at Reesers Summit, 16 km to the northwest, the sheet is about 500 m thick and consists of evolved rocks that have contents of incompatible elements two to three times greater than in the enclosing chilled margins. These evolved rocks represent complementary fractions to the cumulate rocks at York Haven. Mineralogic, petrologic and geochemical variations suggest considerable lateral migration and fractionation of the initial magma. Chilled margins of both sections have essentially the same Pd and Pt contents (10 ppb each) and similar Pd to Pt ratios (1.2). During differentiation, the cumulate rocks at York Haven were enriched in Pt and depleted in Pd, whereas at Reesers Summit, the low-MgO diabase and ferrogabbro zone were enriched in Pd relative to Pt. Anomalously high contents of Pd (to 165 ppb), Au (to 54 ppb), and Te (to 26 ppb) were found in an iron- (to 18%) and chlorine- (to 0.44%) rich ferrogabbro at Reesers Summit, suggesting possible late or post-magmatic enrichment of precious metals. Field relations, geochemical and petrographic data provide guides for further exploration for Pd and Pt in differentiated high-Ti quartz-normative diabase sheets. Based on present information, the most favorable sites for economic deposits are late-stage differentiates enriched in Fe and Cl. ?? 1990.

  4. Clinical utility of platinum chromium bare-metal stents in coronary heart disease

    PubMed Central

    Jorge, Claudia; Dubois, Christophe

    2015-01-01

    Coronary stents represent a key development for the treatment of obstructive coronary artery disease since the introduction of percutaneous coronary intervention. While drug-eluting stents gained wide acceptance in contemporary percutaneous coronary intervention practice, further developments in bare-metal stents remain crucial for patients who are not candidates for drug-eluting stents, or to improve metallic platforms for drug elution. Initially, stent platforms used biologically inert stainless steel, restricting stent performance due to limitations in flexibility and strut thickness. Later, cobalt chromium stent alloys outperformed steel as the material of choice for stents, allowing latest generation stents to be designed with significantly thinner struts, while maintaining corrosion resistance and radial strength. Most recently, the introduction of the platinum chromium alloy refined stent architecture with thin struts, high radial strength, conformability, and improved radiopacity. This review will provide an overview of the novel platinum chromium bare-metal stent platforms available for coronary intervention. Mechanical properties, clinical utility, and device limitations will be summarized and put into perspective. PMID:26345228

  5. Clinical utility of platinum chromium bare-metal stents in coronary heart disease.

    PubMed

    Jorge, Claudia; Dubois, Christophe

    2015-01-01

    Coronary stents represent a key development for the treatment of obstructive coronary artery disease since the introduction of percutaneous coronary intervention. While drug-eluting stents gained wide acceptance in contemporary percutaneous coronary intervention practice, further developments in bare-metal stents remain crucial for patients who are not candidates for drug-eluting stents, or to improve metallic platforms for drug elution. Initially, stent platforms used biologically inert stainless steel, restricting stent performance due to limitations in flexibility and strut thickness. Later, cobalt chromium stent alloys outperformed steel as the material of choice for stents, allowing latest generation stents to be designed with significantly thinner struts, while maintaining corrosion resistance and radial strength. Most recently, the introduction of the platinum chromium alloy refined stent architecture with thin struts, high radial strength, conformability, and improved radiopacity. This review will provide an overview of the novel platinum chromium bare-metal stent platforms available for coronary intervention. Mechanical properties, clinical utility, and device limitations will be summarized and put into perspective. PMID:26345228

  6. Stable optical oxygen sensing materials based on click-coupling of fluorinated platinum(II) and palladium(II) porphyrins—A convenient way to eliminate dye migration and leaching

    PubMed Central

    Koren, Klaus; Borisov, Sergey M.; Klimant, Ingo

    2012-01-01

    Nucleophilic substitution of the labile para-fluorine atoms of 2,3,4,5,6-pentafluorophenyl groups enables a click-based covalent linkage of an oxygen indicator (platinum(II) or palladium(II) 5,10,15,20-meso-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin) to the sensor matrix. Copolymers of styrene and pentafluorostyrene are chosen as polymeric materials. Depending on the reaction conditions either soluble sensor materials or cross-linked microparticles are obtained. Additionally, we prepared Ormosil-based sensors with linked indicator, which showed very high sensitivity toward oxygen. The effect of covalent coupling on sensor characteristics, stability and photophysical properties is studied. It is demonstrated that leaching and migration of the dye are eliminated in the new materials but excellent photophysical properties of the indicators are preserved. PMID:23576845

  7. Noble metal alloy clusters in the gas phase derived from protein templates: unusual recognition of palladium by gold.

    PubMed

    Baksi, Ananya; Pradeep, T

    2013-12-21

    Matrix assisted laser desorption ionization of a mixture of gold and palladium adducts of the protein lysozyme (Lyz) produces naked alloy clusters of the type Au24Pd(+) in the gas phase. While a lysozyme-Au adduct forms Au18(+), Au25(+), Au38(+) and Au102(+) ions in the gas phase, lysozyme-Pd alone does not form any analogous cluster. Addition of various transition metal ions (Ag(+), Pt(2+), Pd(2+), Cu(2+), Fe(2+), Ni(2+) and Cr(3+)) in the adducts contributes to drastic changes in the mass spectrum, but only palladium forms alloys in the gas phase. Besides alloy formation, palladium enhances the formation of specific single component clusters such as Au38(+). While other metal ions like Cu(2+) help forming Au25(+) selectively, Fe(2+) catalyzes the formation of Au25(+) over all other clusters. Gas phase cluster formation occurs from protein adducts where Au is in the 1+ state while Pd is in the 2+ state. The creation of alloys in the gas phase is not affected whether a physical mixture of Au and Pd adducts or a Au and Pd co-adduct is used as the precursor. The formation of Au cores and AuPd alloy cores of the kind comparable to monolayer protected clusters implies that naked clusters themselves may be nucleated in solution. PMID:24146135

  8. Noble metal alloy clusters in the gas phase derived from protein templates: unusual recognition of palladium by gold.

    PubMed

    Baksi, Ananya; Pradeep, T

    2013-12-21

    Matrix assisted laser desorption ionization of a mixture of gold and palladium adducts of the protein lysozyme (Lyz) produces naked alloy clusters of the type Au24Pd(+) in the gas phase. While a lysozyme-Au adduct forms Au18(+), Au25(+), Au38(+) and Au102(+) ions in the gas phase, lysozyme-Pd alone does not form any analogous cluster. Addition of various transition metal ions (Ag(+), Pt(2+), Pd(2+), Cu(2+), Fe(2+), Ni(2+) and Cr(3+)) in the adducts contributes to drastic changes in the mass spectrum, but only palladium forms alloys in the gas phase. Besides alloy formation, palladium enhances the formation of specific single component clusters such as Au38(+). While other metal ions like Cu(2+) help forming Au25(+) selectively, Fe(2+) catalyzes the formation of Au25(+) over all other clusters. Gas phase cluster formation occurs from protein adducts where Au is in the 1+ state while Pd is in the 2+ state. The creation of alloys in the gas phase is not affected whether a physical mixture of Au and Pd adducts or a Au and Pd co-adduct is used as the precursor. The formation of Au cores and AuPd alloy cores of the kind comparable to monolayer protected clusters implies that naked clusters themselves may be nucleated in solution.

  9. Palladium Nanoparticle Incorporated Porous Activated Carbon: Electrochemical Detection of Toxic Metal Ions.

    PubMed

    Veerakumar, Pitchaimani; Veeramani, Vediyappan; Chen, Shen-Ming; Madhu, Rajesh; Liu, Shang-Bin

    2016-01-20

    A facile method has been developed for fabricating selective and sensitive electrochemical sensors for the detection of toxic metal ions, which invokes incorporation of palladium nanoparticles (Pd NPs) on porous activated carbons (PACs). The PACs, which were derived from waste biomass feedstock (fruit peels), possess desirable textural properties and porosities favorable for dispersion of Pd NPs (ca. 3-4 nm) on the graphitic PAC substrate. The Pd/PAC composite materials so fabricated were characterized by a variety of different techniques, such as X-ray diffraction, field-emission transmission electron microscopy, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. The Pd/PAC-modified glassy carbon electrodes (GCEs) were exploited as electrochemical sensors for the detection of toxic heavy metal ions, viz., Cd(2+), Pb(2+), Cu(2+), and Hg(2+), which showed superior performances for both individual as well as simultaneous detections. For simultaneous detection of Cd(2+), Pb(2+), Cu(2+), and Hg(2+), a linear response in the ion concentration range of 0.5-5.5, 0.5-8.9, 0.5-5.0, and 0.24-7.5 μM, with sensitivity of 66.7, 53.8, 41.1, and 50.3 μA μM(-1) cm(-2), and detection limit of 41, 50, 66, and 54 nM, respectively, was observed. Moreover, the Pd/PAC-modified GCEs also show perspective applications in detection of metal ions in real samples, as illustrated in this study for a milk sample.

  10. Versatile Oxidation Methods for Organic and Inorganic Substrates Catalyzed by Platinum-Group Metals on Carbons.

    PubMed

    Sawama, Yoshinari; Asai, Shota; Monguchi, Yasunari; Sajiki, Hironao

    2016-02-01

    Platinum-group metals on activated carbon catalysts, represented by Pd/C, Ru/C, Rh/C, etc., are widely utilized to accomplish green and sustainable organic reactions due to their favorable features, such as easy handling, recoverability, and reusability. The efficient oxidation methods of various organic compounds using heterogeneous platinum-group metals on carbons with or without added oxidants are summarized in this Personal Account. The oxidation of internal alkynes into diketones was effectively catalyzed by Pd/C in the presence of dimethyl sulfoxide and molecular oxygen or pyridine N-oxide. The Pd/C-catalyzed mild combustion of gaseous hydrogen with molecular oxygen provided hydrogen peroxide, which could be directly utilized for the oxidation of sulfide derivatives into sulfoxides. Furthermore, the Ru/C-catalyzed aerobic oxidation of primary and secondary alcohols gave the corresponding aldehydes and ketones, respectively. On the other hand, the dehydrogenative oxidation of secondary alcohols into ketones was achieved using Rh/C in water, and primary alcohols were effectively dehydrogenated by Pd/C in water under mildly reduced pressure to produce carboxylic acids. PMID:26666634

  11. Platinum group metal particles aggregation in nuclear glass melts under the effect of temperature

    NASA Astrophysics Data System (ADS)

    Hanotin, Caroline; Puig, Jean; Neyret, Muriel; Marchal, Philippe

    2016-08-01

    The viscosity of simulated high level radioactive waste glasses containing platinum group metal particles is studied over a wide range of shear stress, as a function of the particles content and the temperature, thanks to a stress imposed rheometer, coupled to a high-temperature furnace. The system shows a very shear thinning behavior. At high shear rate, the system behaves as a suspension of small clusters and individual particles and is entirely controlled by the viscosity of the glass matrix as classical suspensions. At low shear rate, above a certain fraction in platinum group metal particles, the apparition of macroscopic aggregates made up of chains of RuO2 particles separated by thin layers of glass matrix strongly influences the viscosity of the nuclear glass and leads, in particular, to the apparition of yield stress and thixotropic effects. The maximum size of these clusters as well as their effective volume fraction have been estimated by a balance between Van der Waals attractive forces and hydrodynamic forces due to shear flow. We showed experimentally and theoretically that this aggregation phenomenon is favored by an increase of the temperature, owing to the viscosity decrease of the glass matrix, leading to an unusual increase of the suspension viscosity.

  12. Aurum and Platinum as Metal Contact to Amorphous Carbon Thin Films

    NASA Astrophysics Data System (ADS)

    Mohamad, F.; Suriani, A. B.; Noor, U. M.; Rusop, M.

    2010-07-01

    Amorphous carbon (a-C) thin films have been deposited on quartz substrates at different deposition temperatures ranging from 700 °C-800 °C. The objective of this work is to investigate several electrical contacts on a-C thin films and to find the suitable method to fabricate ohmic contact on a-C thin films that prepared from a natural product, camphor (C10H16O). The a-C thin films were prepared with a simple thermal CVD method. In this study, Aurum (Au) and Platinum (Pt) were selected as the metal contact to a-C thin films. I-V characteristics measurement was carried out to study the contact between metal and a-C thin films. It was found that increasing deposition temperature also contributes to the variation I-V characteristics of a-C thin films.

  13. CONTROL ROD ALLOY CONTAINING NOBLE METAL ADDITIONS

    DOEpatents

    Anderson, W.K.; Ray, W.E.

    1960-05-01

    Silver-base alloys suitable for use in the fabrication of control rods for neutronic reactors are given. The alloy consists of from 0.5 wt.% to about 1.5 wt.% of a noble metal of platinum, ruthenium, rhodium, osmium, or palladium, up to 10 wt.% of cadmium, from 2 to 20 wt.% indium, the balance being silver.

  14. Alkene epoxidation employing metal nitro complexes

    DOEpatents

    Andrews, M.A.; Cheng, C.W.; Kelley, K.P.

    1982-07-15

    Process for converting alkenes to form epoxides utilizes transition metal nitro complexes of the formula: M(RCN)/sub 2/XNO/sub 2/ wherein M is palladium or platinum, R is an alkyl or aryl group containing up to 12 carbon atoms, and X is a monoanionic, monodentate ligand such as chlorine, optionally in the presence of molecular oxygen.

  15. Virus templated metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Aljabali, Alaa A. A.; Barclay, J. Elaine; Lomonossoff, George P.; Evans, David J.

    2010-12-01

    Plant viruses are considered as nanobuilding blocks that can be used as synthons or templates for novel materials. Cowpea mosaic virus (CPMV) particles have been shown to template the fabrication of metallic nanoparticles by an electroless deposition metallization process. Palladium ions were electrostatically bound to the virus capsid and, when reduced, acted as nucleation sites for the subsequent metal deposition from solution. The method, although simple, produced highly monodisperse metallic nanoparticles with a diameter of ca. <=35 nm. CPMV-templated particles were prepared with cobalt, nickel, iron, platinum, cobalt-platinum and nickel-iron.Plant viruses are considered as nanobuilding blocks that can be used as synthons or templates for novel materials. Cowpea mosaic virus (CPMV) particles have been shown to template the fabrication of metallic nanoparticles by an electroless deposition metallization process. Palladium ions were electrostatically bound to the virus capsid and, when reduced, acted as nucleation sites for the subsequent metal deposition from solution. The method, although simple, produced highly monodisperse metallic nanoparticles with a diameter of ca. <=35 nm. CPMV-templated particles were prepared with cobalt, nickel, iron, platinum, cobalt-platinum and nickel-iron. Electronic supplementary information (ESI) available: Additional experimental detail, agarose gel electrophoresis results, energy dispersive X-ray spectra, ζ-potential measurements, dynamic light scattering data, nanoparticle tracking analysis and an atomic force microscopy image of Ni-CPMV. See DOI: 10.1039/c0nr00525h

  16. Distribution of platinum and other traffic related metals in sediments and clams (Corbicula sp.).

    PubMed

    Ruchter, Nadine; Sures, Bernd

    2015-03-01

    Platinum is part of traffic-emitted metals since the introduction of automotive catalyst converters. Still, automobile emissions are one of the major sources for metals in European river systems. However, field data on Pt is scarce and there is a lack of knowledge concerning the distribution and biological availability of Pt. Therefore, the distribution of traffic related metals (Cd, Cr, Cu, Ni, Pb, Pt, and Zn) was analyzed in sediment samples and in the Asian clam Corbicula sp. Samples were taken from three transects following road runoff inlets. Pt was introduced into the river by road runoff. The highest Pt concentrations in sediments were analyzed in the silt/clay fraction (45 ng/g), while the highest total Pt burden was obtained for the sand fraction, that makes up more than 60% of the sediment. Metal concentrations were related to the area of the drained street section as well as to their distance from the discharge point, and to grain size distribution within the sediment. Pt and other traffic related metals were accumulated by clams. Due to the feeding behavior of the freshwater mussel Corbicula sp. Pt concentrations in the soft tissue remain relatively low (max Pt concentration: 1.3 ng/g freeze dried soft tissue) and acute lethal or toxic effects therefore appear to be unlikely. Nonetheless, chronic exposure effects still have to be examined.

  17. Distribution of platinum and other traffic related metals in sediments and clams (Corbicula sp.).

    PubMed

    Ruchter, Nadine; Sures, Bernd

    2015-03-01

    Platinum is part of traffic-emitted metals since the introduction of automotive catalyst converters. Still, automobile emissions are one of the major sources for metals in European river systems. However, field data on Pt is scarce and there is a lack of knowledge concerning the distribution and biological availability of Pt. Therefore, the distribution of traffic related metals (Cd, Cr, Cu, Ni, Pb, Pt, and Zn) was analyzed in sediment samples and in the Asian clam Corbicula sp. Samples were taken from three transects following road runoff inlets. Pt was introduced into the river by road runoff. The highest Pt concentrations in sediments were analyzed in the silt/clay fraction (45 ng/g), while the highest total Pt burden was obtained for the sand fraction, that makes up more than 60% of the sediment. Metal concentrations were related to the area of the drained street section as well as to their distance from the discharge point, and to grain size distribution within the sediment. Pt and other traffic related metals were accumulated by clams. Due to the feeding behavior of the freshwater mussel Corbicula sp. Pt concentrations in the soft tissue remain relatively low (max Pt concentration: 1.3 ng/g freeze dried soft tissue) and acute lethal or toxic effects therefore appear to be unlikely. Nonetheless, chronic exposure effects still have to be examined. PMID:25543241

  18. Transition-metal-catalyzed Suzuki-Miyaura cross-coupling reactions: a remarkable advance from palladium to nickel catalysts.

    PubMed

    Han, Fu-She

    2013-06-21

    In the transition-metal-catalyzed cross-coupling reactions, the use of the first row transition metals as catalysts is much more appealing than the precious metals owing to the apparent advantages such as cheapness and earth abundance. Within the last two decades, particularly the last five years, explosive interests have been focused on the nickel-catalyzed Suzuki-Miyaura reactions. This has greatly advanced the chemistry of transition-metal-catalyzed cross-coupling reactions. Most notably, a broad range of aryl electrophiles such as phenols, aryl ethers, esters, carbonates, carbamates, sulfamates, phosphates, phosphoramides, phosphonium salts, and fluorides, as well as various alkyl electrophiles, which are conventionally challenging, by applying palladium catalysts can now be coupled efficiently with boron reagents in the presence of nickel catalysts. In this review, we would like to summarize the progress in this reaction.

  19. Platinum and platinum based nanoalloys synthesized by wet chemistry.

    PubMed

    Salzemann, Caroline; Kameche, Farid; Ngo, Anh-Tu; Andreazza, Pascal; Calatayud, Monica; Petit, Christophe

    2015-01-01

    Platinum nanocrystals and their derivatives with palladium and cobalt are of fundamental interest due to their wide field of application in chemistry and physics. Their properties are strongly dependent on their shape and composition. However the chemical route is far from allowing control of both shape and composition. In this paper, we show both experimentally and theoretically the important role of the interaction of small adsorbed molecules on the shape but also on the composition. This has been studied by comparing the case of pure palladium and platinum nanocrystals and the case of PtPd and PtCo nanoalloys synthesized by the liquid-liquid phase transfer method.

  20. Polyhydrides of Platinum Group Metals: Nonclassical Interactions and σ-Bond Activation Reactions.

    PubMed

    Esteruelas, Miguel A; López, Ana M; Oliván, Montserrat

    2016-08-10

    The preparation, structure, dynamic behavior in solution, and reactivity of polyhydride complexes of platinum group metals, described during the last three decades, are contextualized from both organometallic and coordination chemistry points of view. These compounds, which contain dihydrogen, elongated dihydrogen, compressed dihydride, and classical dihydride ligands promote the activation of B-H, C-H, Si-H, N-H, O-H, C-C, C-N, and C-F, among other σ-bonds. In this review, it is shown that, unlike other more mature areas, the chemistry of polyhydrides offers new exciting conceptual challenges and at the same time the possibility of interacting with other fields including the conversion and storage of regenerative energy, organic synthetic chemistry, drug design, and material science. This wide range of possible interactions foresees promising advances in the near future.

  1. Polyhydrides of Platinum Group Metals: Nonclassical Interactions and σ-Bond Activation Reactions.

    PubMed

    Esteruelas, Miguel A; López, Ana M; Oliván, Montserrat

    2016-08-10

    The preparation, structure, dynamic behavior in solution, and reactivity of polyhydride complexes of platinum group metals, described during the last three decades, are contextualized from both organometallic and coordination chemistry points of view. These compounds, which contain dihydrogen, elongated dihydrogen, compressed dihydride, and classical dihydride ligands promote the activation of B-H, C-H, Si-H, N-H, O-H, C-C, C-N, and C-F, among other σ-bonds. In this review, it is shown that, unlike other more mature areas, the chemistry of polyhydrides offers new exciting conceptual challenges and at the same time the possibility of interacting with other fields including the conversion and storage of regenerative energy, organic synthetic chemistry, drug design, and material science. This wide range of possible interactions foresees promising advances in the near future. PMID:27268136

  2. Life cycle benefits of using nanotechnology to stabilize platinum-group metal particles in automotive catalysts.

    PubMed

    Lloyd, Shannon M; Lave, Lester B; Matthews, H Scott

    2005-03-01

    Due to advances in nanotechnology, the approach to catalytic design is transitioning from trial-and-error to planned design and control. Expected advances should enable the design and construction of catalysts to increase reaction speed, yield, and catalyst durability while also reducing active species loading levels. Nanofabrication techniques enabling precise control over the shape, size, and position of nanoscale platinum-group metal (PGM) particles in automotive catalysts should result in reduced PGM loading levels. These reductions would decrease energy consumption, improve environmental quality, and contribute to sustainable resource usage. We estimate the amount of PGM required to meet U.S. vehicle emissions standards through 2030 based on current catalysttechnology. We then estimate the range of PGM that could be saved from potential nanotechnology advances. Finally, we employ economic input-output and process-based life cycle assessment models to estimate the direct and life cycle benefits from reducing PGM mining and refining.

  3. Platinum nanoparticles encapsulated metal-organic frameworks for the electrochemical detection of telomerase activity.

    PubMed

    Ling, Pinghua; Lei, Jianping; Jia, Li; Ju, Huangxian

    2016-01-21

    A simple and rapid electrochemical sensor is constructed for the detection of telomerase activity based on the electrocatalysis of platinum nanoparticle (Pt NP) encapsulated metal-organic frameworks (MOFs), which are synthesized by one-pot encapsulation of Pt NPs into prototypal MOFs, UiO-66-NH2. Integrating with the efficient electrocatalysis of Pt@MOFs towards NaBH4 oxidation, this biosensor shows the wide dynamic correlation of telomerase activity from 5 × 10(2) to 10(7) HeLa cells mL(-1) and the telomerase activity in a single HeLa cell was calculated to be 2.0 × 10(-11) IU, providing a powerful platform for detecting telomerase activity.

  4. The catalytic inactivation of cellulase enzyme components by palladium complexes

    SciTech Connect

    Woodward, J.; Gooch, M.G.; Shultz, M.D.

    1993-10-01

    It has been discovered that sodium hexachloropalladate is a strong inhibitor of cellobiohydrolase I (CBH I) from Trichoderma reesei having an I{sub 50} of <50 {mu}M with p-nitrophenylcellobioside (PNPC) as the substrate. Similar complexes of the metals platinum, osmium, iridium, and rhodium have little effect on CBH I. Other cellulase activities (Avicelase, {beta}-glucanase) are also inhibited by the palladium complex, suggesting that inhibition of two major types of catalytic activity in cellulase are affected. Preliminary data on the kinetics of inhibition of CBH I by sodium hexachloropalladate indicate that the inhibition is reversible and, possibly, uncompetitive. It is anticipated that sodium hexachloropalladate and other palladium complexes will be useful for determining the effect of the binding of catalytically inactivated CBH I and other cellulase components on the structure of cellulose fibers.

  5. Recent progress in fluorescent and colorimetric chemosensors for detection of precious metal ions (silver, gold and platinum ions).

    PubMed

    Zhang, Jun Feng; Zhou, Ying; Yoon, Juyoung; Kim, Jong Seung

    2011-07-01

    Due to the wide range of applications and biological significance, the development of optical probes for silver, gold and platinum ions has been an active research area in the past few years. This tutorial review focuses on the recent contributions concerning the fluorescent or colorimetric sensors for these metal ions, and is organized according to their structural classifications (for Ag(+) detection) and unique mechanisms between the sensors and metal ions (for Au(3+) and Pt(2+) detection).

  6. The calculated solubility of platinum and gold in oxygen-saturated fluids and the genesis of platinum-palladium and gold mineralization in the unconformity-related uranium deposits

    NASA Astrophysics Data System (ADS)

    Jaireth, S.

    1992-01-01

    Thermodynamic calculations on the solubility of platinum and gold indicate that saline (1 m NaCl), fluids saturated with atmospheric oxygen can transport geologically realistic concentrations of platinum-group-elements (PGE), gold, and uranium as chloro-complexes. A number of calculations involving fluid-rock interaction suggest that the oxygen-saturated fluids flowing through rocks containing quartz, muscovite, kaolinite, magnetite and hematite, initially oxidize any magnetite to hematite, allowing subsequent batches of ore fluids to retain their high oxidation state. During their migration through the aquifer, the oxidizing fluids would move the oxidation-reduction interface deeper into the aquifer, leaching and redepositing platinum and gold. The redissolution of earlier precipitated platinum and gold depends on the fluid/ rock ratio and the associated increase in the oxidation state. Therefore, lowering of fluid/rock ratios and/or mixing of the oxidized fluids with a large amount of reduced fluid will precipitate uranium, PGE, and gold. It is suggested that this model can explain the genesis of gold and PGE mineralization in the unconformity-related uranium deposits of the Alligator Rivers Uranium Field in the Northern Territory, Australia.

  7. Thermally tolerant multilayer metal membrane

    DOEpatents

    Dye, Robert C.; Snow, Ronny C.

    2001-01-01

    A composite metal membrane including a first metal layer of a Group IVB or Group VB metal sandwiched between two layers of a Group VIIIB metal selected from the group consisting of palladium, platinum, nickel, rhodium, iridium, cobalt, and alloys thereof, and a non-continuous layer of a metal chalcogenide upon one layer of the Group VIIIB metal is disclosed together with a process for the recovery of hydrogen from a gaseous mixture using such a composite membrane and a process for forming such a composite metal membrane.

  8. Changes in physical and chemical properties of a dental palladium-silver alloy during metal-porcelain bonding.

    PubMed

    Payan, J; Moya, G E; Meyer, J M; Moya, F

    1986-07-01

    The hardening ability of a dental palladium-silver (Pd-Ag-Sn-In) bonding alloy has been investigated, and the distribution of the elements along the metal-ceramic interface have been studied by microprobe analysis. The alloy was found to be highly heterogeneous in its 'as-cast' condition, but homogenized alloy was obtained after heating the alloy at 1000 degrees C for 2 h. Hardening occurred after annealing at 650 degrees C for 1 h. A longer thermal treatment caused the hardness to decrease (over-ageing). The change in hardness could be attributed to an internal oxidation phenomenon. The additional elements tin and indium segregated towards the ceramic-metal interface, with a diffusion of indium only into the porcelain. Diffusion of silver in the ceramics, supposed to be the cause of the 'greening' of dental porcelains baked on silver-rich alloys, has not been detected by the microprobe across the interface. PMID:3531444

  9. Testing the metal of ERCC2 in predicting the response to platinum-based therapy.

    PubMed

    Turchi, John J; Woods, Derek S; VanderVere-Carozza, Pamela

    2014-10-01

    DNA repair has been shown to affect the cellular response to platinum-based therapy in a variety of cancers; however, translating this knowledge to the clinic has proven difficult and yielded mixed results. In this issue of Cancer Discovery, Van Allen and colleagues have analyzed responders and nonresponders to neoadjuvant platinum-based therapy with locally advanced urothelial cancer and identified a series of mutations in the nucleotide excision repair (NER) gene ERCC2 that correlate with the response to platinum-based therapy. This work provides evidence that defects in NER can be exploited to maximize the efficacy of conventional platinum-based chemotherapy.

  10. XAFS Study of Platinum Group Metals Occluded in LaScO3-BASED Perovskite Oxide by Solid-Phase Reaction at High Temperatuers

    NASA Astrophysics Data System (ADS)

    Kageyama, Hiroyuki; Nomura, Katsuhiro; Ohmi, Kentaro; Fujita, Mitsuharu; Ueda, Tetsuya

    2013-07-01

    We have recently found a new preparation route for platinum group metal containing LaScO3-based perovskite oxides. Sr and Ba containing perovskite powder, (La0.7Sr0.2Ba0.1)ScO3-δ (LSBS) reacted with the solid-state platinum group metals at temperatures from 1623 to 1898K in air, and formed platinum group metal containing perovskite oxides without changing the perovskite structure. In this study we made X-ray absorption fine structure (XAFS) analysis of platinum group metals (M = Ir, Pd, Pt, Rh and Ru) occluded in the LSBS perovskite oxide by the solid-phase reaction at high temperatures. The results of the analysis for XANES regions and the radial structure functions showed that the platinum group metals exist not in the metallic but rather in an ionic state in the LSBS perovskite oxide and that the platinum group metals are mainly introduced into the ScO6 octahedral sites in LSBS perovskite structure, respectively.

  11. A Capped Octahedral MHC6 Compound of a Platinum Group Metal.

    PubMed

    Eguillor, Beatriz; Esteruelas, Miguel A; Lezáun, Virginia; Oliván, Montserrat; Oñate, Enrique; Tsai, Jui-Yi; Xia, Chuanjun

    2016-06-27

    A MHC6 complex of a platinum group metal with a capped octahedral arrangement of donor atoms around the metal center has been characterized. This osmium compound OsH{κ(2) -C,C-(PhBIm-C6 H4 )}3 , which reacts with HBF4 to afford the 14 e(-) species [Os{κ(2) -C,C-(PhBIm-C6 H4 )}(Ph2 BIm)2 ]BF4 stabilized by two agostic interactions, has been obtained by reaction of OsH6 (PiPr3 )2 with N,N'-diphenylbenzimidazolium chloride ([Ph2 BImH]Cl) in the presence of NEt3 . Its formation takes place through the C,C,C-pincer compound OsH2 {κ(3) -C,C,C-(C6 H4 -BIm-C6 H4 )}(PiPr3 )2 , the dihydrogen derivative OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(η(2) -H2 )(PiPr3 )2 , and the five-coordinate osmium(II) species OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(PiPr3 )2 .

  12. A Capped Octahedral MHC6 Compound of a Platinum Group Metal.

    PubMed

    Eguillor, Beatriz; Esteruelas, Miguel A; Lezáun, Virginia; Oliván, Montserrat; Oñate, Enrique; Tsai, Jui-Yi; Xia, Chuanjun

    2016-06-27

    A MHC6 complex of a platinum group metal with a capped octahedral arrangement of donor atoms around the metal center has been characterized. This osmium compound OsH{κ(2) -C,C-(PhBIm-C6 H4 )}3 , which reacts with HBF4 to afford the 14 e(-) species [Os{κ(2) -C,C-(PhBIm-C6 H4 )}(Ph2 BIm)2 ]BF4 stabilized by two agostic interactions, has been obtained by reaction of OsH6 (PiPr3 )2 with N,N'-diphenylbenzimidazolium chloride ([Ph2 BImH]Cl) in the presence of NEt3 . Its formation takes place through the C,C,C-pincer compound OsH2 {κ(3) -C,C,C-(C6 H4 -BIm-C6 H4 )}(PiPr3 )2 , the dihydrogen derivative OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(η(2) -H2 )(PiPr3 )2 , and the five-coordinate osmium(II) species OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(PiPr3 )2 . PMID:27123555

  13. Platinum-coated non-noble metal-noble metal core-shell electrocatalysts

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir

    2015-04-14

    Core-shell particles encapsulated by a thin film of a catalytically active metal are described. The particles are preferably nanoparticles comprising a non-noble core with a noble metal shell which preferably do not include Pt. The non-noble metal-noble metal core-shell nanoparticles are encapsulated by a catalytically active metal which is preferably Pt. The core-shell nanoparticles are preferably formed by prolonged elevated-temperature annealing of nanoparticle alloys in an inert environment. This causes the noble metal component to surface segregate and form an atomically thin shell. The Pt overlayer is formed by a process involving the underpotential deposition of a monolayer of a non-noble metal followed by immersion in a solution comprising a Pt salt. A thin Pt layer forms via the galvanic displacement of non-noble surface atoms by more noble Pt atoms in the salt. The overall process is a robust and cost-efficient method for forming Pt-coated non-noble metal-noble metal core-shell nanoparticles.

  14. Evaluating the abnormal ossification in tibiotarsi of developing chick embryos exposed to 1.0ppm doses of platinum group metals by spectroscopic techniques.

    PubMed

    Stahler, Adam C; Monahan, Jennifer L; Dagher, Jessica M; Baker, Joshua D; Markopoulos, Marjorie M; Iragena, Diane B; NeJame, Britney M; Slaughter, Robert; Felker, Daniel; Burggraf, Larry W; Isaac, Leon A C; Grossie, David; Gagnon, Zofia E; Sizemore, Ioana E Pavel

    2013-04-01

    Platinum group metals (PGMs), i.e., palladium (Pd), platinum (Pt) and rhodium (Rh), are found at pollutant levels in the environment and are known to accumulate in plant and animal tissues. However, little is known about PGM toxicity. Our previous studies showed that chick embryos exposed to PGM concentrations of 1mL of 5.0ppm (LD50) and higher exhibited severe skeletal deformities. This work hypothesized that 1.0ppm doses of PGMs will negatively impact the mineralization process in tibiotarsi. One milliliter of 1.0ppm of Pd(II), Pt(IV), Rh(III) aqueous salt solutions and a PGM-mixture were injected into the air sac on the 7th and 14th day of incubation. Control groups with no-injection and vehicle injections were included. On the 20th day, embryos were sacrificed to analyze the PGM effects on tibiotarsi using four spectroscopic techniques. 1) Micro-Raman imaging: Hyperspectral Raman data were collected on paraffin embedded cross-sections of tibiotarsi, and processed using in-house-written MATLAB codes. Micro-Raman univariate images that were created from the ν1(PO4(3-)) integrated areas revealed anomalous mineral inclusions within the bone marrow for the PGM-mixture treatment. The age of the mineral crystals (ν(CO3(2-))/ν1(PO4(3-))) was statistically lower for all treatments when compared to controls (p≤0.05). 2) FAAS: The percent calcium content of the chemically digested tibiotarsi in the Pd and Pt groups changed by ~45% with respect to the no-injection control (16.1±0.2%). 3) Micro-XRF imaging: Abnormal calcium and phosphorus inclusions were found within the inner longitudinal sections of tibiotarsi for the PGM-mixture treatment. A clear increase in the mineral content was observed for the outer sections of the Pd treatment. 4) ICP-OES: PGM concentrations in tibiotarsi were undetectable (<5ppb). The spectroscopic techniques gave corroborating results, confirmed the hypothesis, and explained the observed pathological (skeletal developmental abnormalities

  15. Metallization Process of a Polyimide Surface with Palladium-Free Activation for Electronic Field Applications

    NASA Astrophysics Data System (ADS)

    Li, Libo; Ma, Yue; Xie, Jingchen; Yang, Xiuchun; Wang, Heng; Tian, Haiyan; Mu, Hongjing; Wang, Wentao

    2015-10-01

    A new copper plating bath without Pd activation for electroless deposition on polyimide (PI) film is reported. The characteristics of Cu coatings on the PI via electroless plating and the effects of operating parameters on the coating coverage are discussed. The pre-treatment and plating processes are further optimized based on orthogonal experiment methods, involving variations of multiple process parameters. The electroless copper coating was characterized by scanning electron microscopy and atomic force microscopy, while the composition and crystalline structure are estimated by energy dispersive spectrometer and x-ray diffraction, respectively. These results show that the crystalline copper layer on the PI surface after electroless plating is dense, continuous and uniform. The joint tensile experiment is used to measure the adhesive strength of the coating with palladium-free and palladium activation, and the former is higher. Furthermore, the pre-treatment method proposed in this work without using palladium compounds is considered to be environmentally friendly. In addition, it provides a new concept of electroless Cu plating on the PI, which is generally difficult to plate due to its hydrophobic nature.

  16. 76 FR 67793 - Notification of Expanded Pricing Grid for Precious Metals Products Containing Platinum and Gold...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-02

    ... and Gold--Excluding Commemorative Gold Coins AGENCY: United States Mint, Department of the Treasury..., 2009, outlining the new pricing methodology for numismatic products containing platinum and gold. Since that time, the price of platinum and gold has increased considerably, and is approaching the...

  17. Platinum-nickel frame within metal-organic framework fabricated in situ for hydrogen enrichment and molecular sieving

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Yu, Rong; Huang, Jinglu; Shi, Yusheng; Zhang, Diyang; Zhong, Xiaoyan; Wang, Dingsheng; Wu, Yuen; Li, Yadong

    2015-09-01

    Developing catalysts that provide the effective activation of hydrogen and selective absorption of substrate on metal surface is crucial to simultaneously improve activity and selectivity of hydrogenation reaction. Here we present an unique in situ etching and coordination synthetic strategy for exploiting a functionalized metal-organic framework to incorporate the bimetallic platinum-nickel frames, thereby forming a frame within frame nanostructure. The as-grown metal-organic framework serves as a `breath shell' to enhance hydrogen enrichment and activation on platinum-nickel surface. More importantly, this framework structure with defined pores can provide the selective accessibility of molecules through its one-dimensional channels. In a mixture containing four olefins, the composite can selectively transport the substrates smaller than its pores to the platinum-nickel surface and catalyse their hydrogenation. This molecular sieve effect can be also applied to selectively produce imines, which are important intermediates in the reductive imination of nitroarene, by restraining further hydrogenation via cascade processes.

  18. The Bioaccumulation and Toxicity of Platinum Group Metals in Developing Chick Embryos

    NASA Astrophysics Data System (ADS)

    Pavel, Ioana; Monahan, Jennifer; Markopoulos, Marjorie; Gagnon, Zofia; Nejame, Britney; Cawley, Jacob; Reens, David

    2008-10-01

    Recent studies showed that platinum group metals (PGMs) such as Pt, Pd, and Rh from automobile catalytic converters, can accumulate in the soft tissues of a variety of living organisms. However, the effects of PGMs on bone and organs development of animals are not clearly understood. To examine these aspects, developing chick embryos were injected with 0.1, 1.0, 5, or 10 ppm solutions of Pt, Rh, Pd, or with a PGMs mixture. 1) Pathological Changes: were observed for all PGM treatments above 1 ppm. Bone Cells Assesment: Chondrocyte cells in thibiotarsus showed decreased diameter and length. 2) PGMs Accumulation in Tissues: was quantified by GFAAS spectrometry on finely ground tissue powder. 3) Bone Demineralization: was detected by micro-Raman spectroscopy imaging on paraffin embedded bone sections. 4) DNA Damage in Cells: was determined by using a Comet assay and fluorescence spectroscopy. Oxidative Damage in Tissues: was analyzed using a glutathione peroxidase assay. The overall results indicated that PGMs presence in our environment raises concerns about their long-term health effects on all organisms.

  19. Communication: Photoactivation of nucleobase bound platinumII metal complexes: Probing the influence of the nucleobase

    NASA Astrophysics Data System (ADS)

    Sen, Ananya; Dessent, Caroline E. H.

    2014-12-01

    We present UV laser action spectra (220-300 nm) of isolated nucleobase-bound PtII(CN)42- complexes, i.e., Pt(CN)42-ṡM, where M = uracil, thymine, cytosine, and adenine. These metal complex-nucleobase clusters represent model systems for identifying the fundamental photophysical and photochemical processes occurring in photodynamic platinum (II) drug therapies that target DNA. This is the first study to explore the specific role of the nucleobase in the photophysics of the aggregate complex. Each of the complexes studied displays a broadly similar absorption spectra, with a strong λmax ˜ 4.7 eV absorption band (nucleobase localized chromophore) and a subsequent increase in the absorption intensity towards higher spectral-energy (Pt(CN)42- localized chromophore). However, strikingly different band widths are observed across the series of complexes, decreasing in the order Pt(CN)42-ṡThymine > Pt(CN)42-ṡUracil > Pt(CN)42-ṡAdenine > Pt(CN)42-ṡCytosine. Changes in the bandwidth of the ˜4.7 eV band are accompanied by distinctive changes in the photofragment product ions observed following photoexcitation, with the narrower-bandwidth complexes showing a greater propensity to decay via electron detachment decay. We discuss these observations in the context of the distinctive nucleobase-dependent excited state lifetimes.

  20. Platinum porous nanoparticles hybrid with metal ions as probes for simultaneous detection of multiplex cancer biomarkers.

    PubMed

    Wang, Zifeng; Liu, Na; Ma, Zhanfang

    2014-03-15

    In this work, platinum porous nanoparticles (PtPNPs) absorbed metal ions as electrochemical signals were fabricated. Clean-surface PtPNPs were prepared by a surfactant-free method and decorated with amino groups via 2-aminoethanethiol. Amino capped PtPNPs complexation with Cd(2+) and Cu(2+) to form PtPNPs-Cd(2+) and PtPNPs-Cu(2+) hybrids, respectively. Anti-CEA and Anti-AFP separately labeled with PtPNPs-Cd(2+) and PtPNPs-Cu(2+) were used as distinguishable signal tags for capturing antigens. The metal ions were detected in a single run through differential pulse voltammetry (DPV) without acid dissolution, electric potentials and peak heights of which reflected the identity and concentrations of the corresponding antigen. Ionic liquid reduced graphene oxide (IL-rGO) modified glassy carbon electrode (GCE) was used as a substrate, which was rich in amino groups to immobilize antibodies by glutaraldehyde through cross-link between aldehyde groups and amino groups. Using the proposed probes and platform, a novel sandwich-type electrochemical immunosensor for simultaneous detecting carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) was successfully developed. This immunoassay possessed good linearity from 0.05 ng mL(-1) to 200 ng mL(-1) for both CEA and AFP. The detection limit of CEA was 0.002 ng mL(-1) and that of AFP was 0.05 ng mL(-1) (S/N=3). Furthermore, analysis of clinical serum samples using this immunosensor was well consistent with the data determined by the enzyme-linked immunosorbent assay (ELISA). It suggested that the proposed electrochemical immunoassay provided a potential application of clinical screening for early-stage cancers.

  1. Platinum porous nanoparticles hybrid with metal ions as probes for simultaneous detection of multiplex cancer biomarkers.

    PubMed

    Wang, Zifeng; Liu, Na; Ma, Zhanfang

    2014-03-15

    In this work, platinum porous nanoparticles (PtPNPs) absorbed metal ions as electrochemical signals were fabricated. Clean-surface PtPNPs were prepared by a surfactant-free method and decorated with amino groups via 2-aminoethanethiol. Amino capped PtPNPs complexation with Cd(2+) and Cu(2+) to form PtPNPs-Cd(2+) and PtPNPs-Cu(2+) hybrids, respectively. Anti-CEA and Anti-AFP separately labeled with PtPNPs-Cd(2+) and PtPNPs-Cu(2+) were used as distinguishable signal tags for capturing antigens. The metal ions were detected in a single run through differential pulse voltammetry (DPV) without acid dissolution, electric potentials and peak heights of which reflected the identity and concentrations of the corresponding antigen. Ionic liquid reduced graphene oxide (IL-rGO) modified glassy carbon electrode (GCE) was used as a substrate, which was rich in amino groups to immobilize antibodies by glutaraldehyde through cross-link between aldehyde groups and amino groups. Using the proposed probes and platform, a novel sandwich-type electrochemical immunosensor for simultaneous detecting carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) was successfully developed. This immunoassay possessed good linearity from 0.05 ng mL(-1) to 200 ng mL(-1) for both CEA and AFP. The detection limit of CEA was 0.002 ng mL(-1) and that of AFP was 0.05 ng mL(-1) (S/N=3). Furthermore, analysis of clinical serum samples using this immunosensor was well consistent with the data determined by the enzyme-linked immunosorbent assay (ELISA). It suggested that the proposed electrochemical immunoassay provided a potential application of clinical screening for early-stage cancers. PMID:24176967

  2. Noble metals in mid-ocean ridge volcanism: A significant fractionation of gold with respect to platinum group metals

    NASA Technical Reports Server (NTRS)

    Crocket, James H.

    1988-01-01

    Hydrothermal precipitates, black smoker particulate, and massive sulphide dredge samples from the Explorer Ridge on the Juan de Fuca Plate and the TAG hydrothermal area on the Mid-Atlantic Ridge were analyzed for selected noble metals including Au, Ir and Pd by radiochemical neutron activation analysis. The preliminary results indicate that gold contents may reach the ppm range although values in the neighborhood of 100 to 200 ppb are more typical. The platinum group elements (PGE) represented by Ir and Pd are typically less than 0.02 ppb and less than 2 ppb respectively. These abundances represent a significant enrichment of gold relative to the PGE in comparison with average noble metal abundances in mid-ocean ridge basalts (MORB). A partial explanation of this distinctive fractionation can be found in the concepts of sulfur-saturation of basic magma in mid-ocean ridge (MOR) settings, and the origin of MOR hydrothermal fluids. Experimental and petrological data suggest that MORBs are sulfur-saturated at the time of magma generation and that an immiscible sulfide component remains in the mantle residue. Hence, MORBs are noble metal-poor, particularly with respect to PGE. Consequently, black smoker fluids can be expected to reflect the low Ir and Pd contents of the rock column. The average Au content of MORB is 1.3 ppb, and so the rock column is not significantly enriched in Au. The generation of fluids which precipitate solids with 200 ppb Au is apparently dependent on highly efficient fluid chemistry to mobilize Au from the rock column, high Au solubility in seawater hydrothermal fluids and efficient precipitation mechanisms to coprecipitate Au on Fe, Zn and Cu sulfides. Significant differences in these parameters appear to be the ultimate cause of the strong Au-PGE fractionation in the MOR setting. It does not appear from the current data base that MOR hydrothermal fluids are significant contributors to the Ir enrichment seen in Cretaceous-Tertiary boundary

  3. Extended Platinum Nanotubes as Fuel Cell Catalysts

    SciTech Connect

    Alia, S.; Pivovar, B. S.; Yan, Y.

    2012-01-01

    Energy consumption has relied principally on fossil fuels as an energy source; fuel cells, however, can provide a clean and sustainable alternative, an answer to the depletion and climate change concerns of fossil fuels. Within proton exchange membrane fuel cells, high catalyst cost and poor durability limit the commercial viability of the device. Recently, platinum nanotubes (PtNTs) were studied as durable, active catalysts, providing a platform to meet US Department of Energy vehicular activity targets.[1] Porous PtNTs were developed to increase nanotube surface area, improving mass activity for oxygen reduction without sacrificing durability.[2] Subsurface platinum was then replaced with palladium, forming platinum-coated palladium nanotubes.[3] By forming a core shell structure, platinum utilization was increased, reducing catalyst cost. Alternative substrates have also been examined, modifying platinum surface facets and increasing oxygen reduction specific activity. Through modification of the PtNT platform, catalyst limitations can be reduced, ensuring a commercially viable device.

  4. Global flows of critical metals necessary for low-carbon technologies: the case of neodymium, cobalt, and platinum.

    PubMed

    Nansai, Keisuke; Nakajima, Kenichi; Kagawa, Shigemi; Kondo, Yasushi; Suh, Sangwon; Shigetomi, Yosuke; Oshita, Yuko

    2014-01-01

    This study, encompassing 231 countries and regions, quantifies the global transfer of three critical metals (neodymium, cobalt, and platinum) considered vital for low-carbon technologies by means of material flow analysis (MFA), using trade data (BACI) and the metal contents of trade commodities, resolving the optimization problem to ensure the material balance of the metals within each country and region. The study shows that in 2005 international trade led to global flows of 18.6 kt of neodymium, 154 kt of cobalt, and 402 t of platinum and identifies the main commodities and top 50 bilateral trade links embodying these metals. To explore the issue of consumption efficiency, the flows were characterized according to the technological level of each country or region and divided into three types: green ("efficient use"), yellow ("moderately efficient use"), and red ("inefficient use"). On this basis, the shares of green, yellow, and red flows in the aggregate global flow of Nd were found to be 1.2%, 98%, and 1.2%, respectively. For Co, the respective figures are 53%, 28%, and 19%, and for Pt 15%, 84%, and 0.87%. Furthermore, a simple indicator focusing on the composition of the three colored flows for each commodity was developed to identify trade commodities that should be prioritized for urgent technical improvement to reduce wasteful use of the metals. Based on the indicator, we discuss logical, strategic identification of the responsibilities and roles of the countries involved in the global flows.

  5. Material and Energy Flows Associated with Select Metals in GREET 2. Molybdenum, Platinum, Zinc, Nickel, Silicon

    SciTech Connect

    Benavides, Pahola T.; Dai, Qiang; Sullivan, John L.; Kelly, Jarod C.; Dunn, Jennifer B.

    2015-09-01

    In this work, we analyzed the material and energy consumption from mining to production of molybdenum, platinum, zinc, and nickel. We also analyzed the production of solar- and semiconductor-grade silicon. We described new additions to and expansions of the data in GREET 2. In some cases, we used operating permits and sustainability reports to estimate the material and energy flows for molybdenum, platinum, and nickel, while for zinc and silicon we relied on information provided in the literature.

  6. Palladium/kieselguhr composition and method

    DOEpatents

    Mosley, W.C. Jr.

    1993-09-28

    A hydrogen-absorbing composition and method for making such a composition are described. The composition comprises a metal hydride, preferably palladium, deposited onto a porous substrate such as kieselguhr, for use in hydrogen-absorbing processes. The composition is made by immersing a substrate in a concentrated solution containing palladium, such as tetra-amine palladium nitrate. Palladium from the solution is deposited onto the porous substrate, which is preferably in the form of kieselguhr particles. The substrate is then removed from the solution, calcined, and heat treated. This process is repeated until the desired amount of palladium has been deposited onto the substrate.

  7. Palladium/kieselguhr composition and method

    DOEpatents

    Mosley, Jr., Wilbur C.

    1993-01-01

    A hydrogen-absorbing composition and method for making such a composition. The composition comprises a metal hydride, preferably palladium, deposited onto a porous substrate such as kieselguhr, for use in hydrogen-absorbing processes. The composition is made by immersing a substrate in a concentrated solution containing palladium, such as tetra-amine palladium nitrate. Palladium from the solution is deposited onto the porous substrate, which is preferably in the form of kieselguhr particles. The substrate is then removed from the solution, calcined, and heat treated. This process is repeated until the desired amount of palladium has been deposited onto the substrate.

  8. Novel Di- and Trinuclear Palladium Complexes Supported by N,N'-Diphosphanyl NHC Ligands and N,N'-Diphosphanylimidazolium Palladium, Gold, and Mixed-Metal Copper-Gold Complexes.

    PubMed

    Ai, Pengfei; Gourlaouen, Christophe; Danopoulos, Andreas A; Braunstein, Pierre

    2016-02-01

    The reaction of the trinuclear complex [Ag3(μ3-PC(NHC)P,κP,κC(NHC),κP)2](OTf)3 (Ag3; PC(NHC)P = N,N'-bis(di-tert-butylphosphanyl)imidazol-2-ylidene) with [Pd(dba)2] afforded the trinuclear palladium complex [Pd3(μ3-PC(NHC)P,κP,κC(NHC),κP)2](OTf)2 (Pd3) and the dinuclear palladium(I) complex [Pd2(μ2-PC(NHC)P,κP,κC(NHC),κP)2](OTf)2 (Pd2). The assignment of the oxidation state of the metals in the mixed-valence Pd3 chain as Pd(0)-Pd(II)-Pd(0) was based on the reactivity of the complex with 2,6-dimethylphenyl isocyanide and density functional theory calculations. Reaction of PCNHCP with [PdMe2(tmeda)] afforded the palladium(II) complex [PdMe2(PC(NHC)P,κP,κC(NHC))] (Pd-Me2), with PC(NHC)P acting as a bidentate ligand. The reaction of PC(NHC)P with [Pd(dba)2] led to a dinuclear palladium(0) complex [Pd2(μ2-PC(NHC)P,κP,κC(NHC),κP)](dba) (Pd2-dba); attempted replacement of the remaining dba by PC(NHC)P failed. The imidazolium triflate PCHP, precursor to PC(NHC)P, was reacted with [Pd2(dba)3]·CHCl3 to give the (2 + 2) metalla-mesocyclic cationic palladium(0) complex [Pd2(μ2-PCHP,κP,κP)2] (PCHP-Pd2), which resisted further deprotonation of the imidazolium cation. In contrast, PCHP reacted with [AuCl(tht)] to give [Au2Cl2(μ2-PCHP,κP,κP)] (PCHP-Au2), in which one Au-Cl moiety is bound to each P donor. Further reaction of PCHP-Au2 with [Au{N(SiMe3)2}(PPh3)] afforded a mixture of the trinuclear [Au3(μ3-PC(NHC)P,κP,κC(NHC),κP)2](OTf)3 (Au3) and [AuCl(PPh3)], while reaction with [CuMes]5, where Mes = 2,4,6-trimethylphenyl, resulted in a novel, centrosymmetric, heterometallic complex [Au2Mes2(Cu4Cl4)(PCHP,κP,κP)2] (PCHP-AuCu) featuring a new PCHP-AuMes metalloligand bridging a Cu···Cu diagonal of a Cu4Cl4 cubane via the P and AuMes functionalities.

  9. Copper-Based Electrochemical Sensor with Palladium Electrode for Cathodic Stripping Voltammetry of Manganese

    PubMed Central

    2015-01-01

    In this work, we report on the development of a palladium-based, microfabricated point-of-care electrochemical sensor for the determination of manganese using square wave cathodic stripping voltammetry. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Voltammetry offers an attractive approach to metal detection on the microscale, but traditional carbon, gold, or platinum electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor uses palladium working and auxiliary electrodes and integrates them with a copper-based reference electrode for simple fabrication and compatibility with microfabrication and printed circuit board processing, while maintaining competitive performance in electrochemical detection. Copper electrodes were prepared on glass substrate using a combination of microfabrication procedures followed by electrodeposition of palladium. The disposable sensor system was formed by bonding a poly(dimethylsiloxane) (PDMS) well to the glass substrate. Cathodic stripping voltammetry of manganese using our new disposable palladium-based sensors exhibited 334 nM (18.3 ppb) limit of detection in borate buffer. The sensor was used to demonstrate manganese determination in natural water samples from a pond in Burnet Woods, located in Cincinnati, OH, and the Ohio River. PMID:25476591

  10. Bulk Modulus of Spherical Palladium Nanoparticles by Chen-Mobius Lattice Inversion Method

    NASA Astrophysics Data System (ADS)

    Abdul-Hafidh, Esam

    2015-03-01

    Palladium is a precious and rare element that belongs to the Platinum group metals (PGMS) with the lowest density and melting point. Numerous uses of Pd in dentistry, medicine and industrial applications attracted considerable investment. Preparation and characterization of palladium nanoparticles have been conducted by many researchers, but very little effort has taken place on the study of Pd physical properties, such as, mechanical, optical, and electrical. In this study, Chen-Mobius lattice inversion method is used to calculate the cohesive energy and modulus of palladium. The method was employed to calculate the cohesive energy by summing over all pairs of atoms within palladium spherical nanoparticles. The modulus is derived from the cohesive energy curve as a function of particles' sizes. The cohesive energy has been calculated using the potential energy function proposed by (Rose et al., 1981). The results are found to be comparable with previous predictions of metallic nanoparticles. This work is supported by the Royal commission at Yanbu- Saudi Arabia.

  11. Copper-based electrochemical sensor with palladium electrode for cathodic stripping voltammetry of manganese.

    PubMed

    Kang, Wenjing; Pei, Xing; Bange, Adam; Haynes, Erin N; Heineman, William R; Papautsky, Ian

    2014-12-16

    In this work, we report on the development of a palladium-based, microfabricated point-of-care electrochemical sensor for the determination of manganese using square wave cathodic stripping voltammetry. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Voltammetry offers an attractive approach to metal detection on the microscale, but traditional carbon, gold, or platinum electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor uses palladium working and auxiliary electrodes and integrates them with a copper-based reference electrode for simple fabrication and compatibility with microfabrication and printed circuit board processing, while maintaining competitive performance in electrochemical detection. Copper electrodes were prepared on glass substrate using a combination of microfabrication procedures followed by electrodeposition of palladium. The disposable sensor system was formed by bonding a poly(dimethylsiloxane) (PDMS) well to the glass substrate. Cathodic stripping voltammetry of manganese using our new disposable palladium-based sensors exhibited 334 nM (18.3 ppb) limit of detection in borate buffer. The sensor was used to demonstrate manganese determination in natural water samples from a pond in Burnet Woods, located in Cincinnati, OH, and the Ohio River.

  12. Copper-based electrochemical sensor with palladium electrode for cathodic stripping voltammetry of manganese.

    PubMed

    Kang, Wenjing; Pei, Xing; Bange, Adam; Haynes, Erin N; Heineman, William R; Papautsky, Ian

    2014-12-16

    In this work, we report on the development of a palladium-based, microfabricated point-of-care electrochemical sensor for the determination of manganese using square wave cathodic stripping voltammetry. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Voltammetry offers an attractive approach to metal detection on the microscale, but traditional carbon, gold, or platinum electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor uses palladium working and auxiliary electrodes and integrates them with a copper-based reference electrode for simple fabrication and compatibility with microfabrication and printed circuit board processing, while maintaining competitive performance in electrochemical detection. Copper electrodes were prepared on glass substrate using a combination of microfabrication procedures followed by electrodeposition of palladium. The disposable sensor system was formed by bonding a poly(dimethylsiloxane) (PDMS) well to the glass substrate. Cathodic stripping voltammetry of manganese using our new disposable palladium-based sensors exhibited 334 nM (18.3 ppb) limit of detection in borate buffer. The sensor was used to demonstrate manganese determination in natural water samples from a pond in Burnet Woods, located in Cincinnati, OH, and the Ohio River. PMID:25476591

  13. Osmium isotope constraints on ore metal recycling in subduction zones

    PubMed

    McInnes; McBride; Evans; Lambert; Andrew

    1999-10-15

    Veined peridotite xenoliths from the mantle beneath the giant Ladolam gold deposit on Lihir Island, Papua New Guinea, are 2 to 800 times more enriched in copper, gold, platinum, and palladium than surrounding depleted arc mantle. Gold ores have osmium isotope compositions similar to those of the underlying subduction-modified mantle peridotite source region, indicating that the primary origin of the metals was the mantle. Because the mantle is relatively depleted in gold, copper, and palladium, tectonic processes that enhance the advective transport and concentration of these fluid soluble metals may be a prerequisite for generating porphyry-epithermal copper-gold deposits. PMID:10521343

  14. Osmium isotope constraints on ore metal recycling in subduction zones

    PubMed

    McInnes; McBride; Evans; Lambert; Andrew

    1999-10-15

    Veined peridotite xenoliths from the mantle beneath the giant Ladolam gold deposit on Lihir Island, Papua New Guinea, are 2 to 800 times more enriched in copper, gold, platinum, and palladium than surrounding depleted arc mantle. Gold ores have osmium isotope compositions similar to those of the underlying subduction-modified mantle peridotite source region, indicating that the primary origin of the metals was the mantle. Because the mantle is relatively depleted in gold, copper, and palladium, tectonic processes that enhance the advective transport and concentration of these fluid soluble metals may be a prerequisite for generating porphyry-epithermal copper-gold deposits.

  15. Metal-support interactions during the adsorption of CO on thin layers and islands of epitaxial palladium

    NASA Technical Reports Server (NTRS)

    Park, C.; Poppa, H.; Soria, F.

    1984-01-01

    Islands and continuous layers of palladium were grown in an ultrahigh vacuum on substrates of Mo(110)c(14 x 7)-O, designated MoO(x), and of clean Mo(110). It was found that as-deposited islands and layers exhibited bulk palladium adsorption properties for CO when deposited at room temperature and for palladium thicknesses in excess of about 3 monolayers. CO adsorption was drastically reduced, however, on annealing. For islands, annealing temperatures of as low as 400 K led to some reduction in CO adsorption whereas more severe reductions were found to occur at 600 K for islands and at 800 K for continuous multilayers. The deactivation depended on the palladium thickness, the substrate species and the extent of thermal treatments. Auger electron spectroscopy, temperature-programmed desorption and Delta-Phi measurements were combined to interpret the deactivation behavior in terms of substrate-support interactions involving the diffusion of substrate species towards the palladium surface.

  16. Thin metal bilayer for surface plasmon resonance sensors in a multimode plastic optical fiber: the case of palladium and gold metal films

    NASA Astrophysics Data System (ADS)

    Cennamo, Nunzio; Zuppella, Paola; Bacco, Davide; Corso, Alain J.; Pelizzo, Maria G.; Pesavento, Maria; Zeni, Luigi

    2016-05-01

    A novel sensing platform based on thin metal bilayer for surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF) has been designed, implemented and tested. The experimental results are congruent with the numerical studies. This platform has been properly optimized to work in the 1.38 -1.42 refractive index range and it exhibits excellent sensitivity. This refractive index range is very interesting for bio-chemical applications, where the polymer layer are used as receptors (e.g. molecularly imprinted polymer) or to immobilize the bio-receptor on the metal surface. The proposed metallic bilayer is based on palladium and gold films and replaces the traditional gold by exhibiting higher performances. Furthermore, the deposition of the thin bilayer is a single process and no further manufacturing step is required. In fact, in this case the photoresist buffer layer between the POF core and the metal layer, usually required to increase the refractive index range, is no longer necessary.

  17. Liquid-liquid extraction of metal ions by the 6-membered N-containing macrocycle hexacyclen.

    PubMed

    Arpadjan, S; Mitewa, M; Bontchev, P R

    1987-11-01

    The nitrogen-containing analogue of 18-crown-6, 1,4,7,10,13,16-hexa-azaoctadecane (hexacyclen)] was studied as a reagent for complexation and extraction of some metal ions. It was found that with this reagent and methyl isobutyl ketone, metal ions such as silver(I), mercury(II), copper(II), platinum(II) and palladium(II) can be quantitatively extracted and separated from iron(III) and some other metal ions.

  18. Experimental partitioning of Zr, Ti, and Nb between silicate liquid and a complex noble metal alloy and the partitioning of Ti between perovskite and platinum metal

    NASA Technical Reports Server (NTRS)

    Jurewicz, Stephen R.; Jones, John H.

    1993-01-01

    El Goresy et al.'s observation of Nb, Zr, and Ta in refractory platinum metal nuggets (RPMN's) from Ca-Al-rich inclusions (CAI's) in the Allende meteorite led them to propose that these lithophile elements alloyed in the metallic state with noble metals in the early solar nebula. However, Grossman pointed out that the thermodynamic stability of Zr in the oxide phase is vastly greater than metallic Zr at estimated solar nebula conditions. Jones and Burnett suggested this discrepancy may be explained by the very non-ideal behavior of some lithophile transition elements in noble metal solutions and/or intermetallic compounds. Subsequently, Fegley and Kornacki used thermodynamic data taken from the literature to predict the stability of several of these intermetallic compounds at estimated solar nebula conditions. Palme and Schmitt and Treiman et al. conducted experiments to quantify the partitioning behavior of certain lithophile elements between silicate liquid and Pt-metal. Although their results were somewhat variable, they did suggest that Zr partition coefficients were too small to explain the observed 'percent' levels in some RPMN's. Palme and Schmitt also observed large partition coefficients for Nb and Ta. No intermetallic phases were identified. Following the work of Treiman et al., Jurewicz and Jones performed experiments to examine Zr, Nb, and Ti partitioning near solar nebula conditions. Their results showed that Zr, Nb, and Ti all have an affinity for the platinum metal, with Nb and Ti having a very strong preference for the metal. The intermetallic phases (Zr,Fe)Pt3, (Nb,Fe)Pt3, and (Ti,Fe)Pt3 were identified. Curiously, although both experiments and calculations indicate that Ti should partition strongly into Pt-metal (possibly as TiPt3), no Ti has ever been observed in any RPMN's. Fegley and Kornacki also noticed this discrepancy and hypothesized that the Ti was stabilized in perovskite which is a common phase in Allende CAI's.

  19. Method of synthesizing metal doped diamond-like carbon films

    NASA Technical Reports Server (NTRS)

    Ueno, Mayumi (Inventor); Sunkara, Mahendra Kumar (Inventor)

    2003-01-01

    A method of synthesizing metal doped carbon films by placing a substrate in a chamber with a selected amount of a metalorganic compound. An electron cyclotron resonance is applied to the chamber in order to vaporize the metalorganic compound. The resonance is applied to the chamber until a metal doped carbon film is formed. The metalorganic compound is preferably selected from the group consisting of an organic salt of ruthenium, palladium, gold or platinum.

  20. Global Flows of Critical Metals Necessary for Low-Carbon Technologies: The Case of Neodymium, Cobalt, and Platinum

    PubMed Central

    2014-01-01

    This study, encompassing 231 countries and regions, quantifies the global transfer of three critical metals (neodymium, cobalt, and platinum) considered vital for low-carbon technologies by means of material flow analysis (MFA), using trade data (BACI) and the metal contents of trade commodities, resolving the optimization problem to ensure the material balance of the metals within each country and region. The study shows that in 2005 international trade led to global flows of 18.6 kt of neodymium, 154 kt of cobalt, and 402 t of platinum and identifies the main commodities and top 50 bilateral trade links embodying these metals. To explore the issue of consumption efficiency, the flows were characterized according to the technological level of each country or region and divided into three types: green (“efficient use”), yellow (“moderately efficient use”), and red (“inefficient use”). On this basis, the shares of green, yellow, and red flows in the aggregate global flow of Nd were found to be 1.2%, 98%, and 1.2%, respectively. For Co, the respective figures are 53%, 28%, and 19%, and for Pt 15%, 84%, and 0.87%. Furthermore, a simple indicator focusing on the composition of the three colored flows for each commodity was developed to identify trade commodities that should be prioritized for urgent technical improvement to reduce wasteful use of the metals. Based on the indicator, we discuss logical, strategic identification of the responsibilities and roles of the countries involved in the global flows. PMID:24387330

  1. Automated on-line preconcentration of palladium on different sorbents and its determination in environmental samples.

    PubMed

    Sánchez Rojas, Fuensanta; Bosch Ojeda, Catalina; Cano Pavón, José Manuel

    2007-01-01

    The determination of noble metals in environmental samples is of increasing importance. Palladium is often employed as a catalyst in chemical industry and is also used with platinum and rhodium in motor car catalytic converters which might cause environmental pollution problems. Two different sorbents for palladium preconcentration in different samples were investigated: silica gel functionalized with 1,5-bis(di-2-pyridyl)methylene tbiocarbohydrazide (DPTH-gel) and [1,5-Bis(2-pyridyl)-3-sulphophenyI methylene thiocarbonohydrazide (PSTH) immobilised on an anion-exchange resin (Dowex lx8-200)]. The sorbents were tested in a micro-column, placed in the auto-sampler arm, at the flow rate 2.8 mL min(-1). Elution was performed with 4 M HCl and 4 M HNO3, respectively. Satisfactory results were obtained for two sorbents.

  2. Encapsulation of palladium porphyrin photosensitizer in layered metal oxide nanoparticles for photodynamic therapy against skin melanoma

    NASA Astrophysics Data System (ADS)

    Chen, Zih-An; Kuthati, Yaswanth; Kankala, Ranjith Kumar; Chang, Yu-Chuan; Liu, Chen-Lun; Weng, Ching-Feng; Mou, Chung-Yuan; Lee, Chia-Hung

    2015-10-01

    We designed a biodegradable nanocarrier of layered double hydroxide (LDH) for photodynamic therapy (PDT) based on the intercalation of a palladium porphyrin photosensitizer (PdTCPP) in the gallery of LDH for melanoma theragnosis. Physical and chemical characterizations have demonstrated the photosensitizer was stable in the layered structures. In addition, the synthesized nanocomposites rendered extremely efficacious therapy in the B16F10 melanoma cell line by improving the solubility of the hydrophobic PdTCPP photosensitizer. The detection of singlet oxygen generation under irradiation at the excitation wavelength of a 532 nm laser was indeed impressive. Furthermore, the in vivo results using a tumour xenograft model in mice indicated the apparent absence of body weight loss and relative organ weight variation to the liver and kidney demonstrated that the nanocomposites were biosafe with a significant reduction in tumour volume for the anti-cancer efficacy of PDT. This drug delivery system using the nanoparticle-photosensitizer hybrid has great potential in melanoma theragnosis.

  3. Elemental characterization of PM2.5 and PM10 emitted from light duty vehicles in the Washburn Tunnel of Houston, Texas: release of rhodium, palladium, and platinum.

    PubMed

    Bozlaker, Ayşe; Spada, Nicholas J; Fraser, Matthew P; Chellam, Shankararaman

    2014-01-01

    We report the elemental composition, including Rh, Pd, and Pt, of total (i.e., tailpipe and nontailpipe) PM2.5 and PM10 emissions from predominantly gasoline-driven light-duty vehicles (LDVs) traversing the Washburn Tunnel in Houston, Texas during November and December, 2012. Using a novel sample preparation and dynamic reaction cell-quadrupole-inductively coupled plasma-mass spectrometry technique, we quantify the emission of numerous representative, transition, and lanthanoid elements. Two sets of time integrated PM samples were collected over 3-4week duration both inside the tunnel as well as from the tunnel ventilation air supply to derive accurate LDV source profiles incorporating three platinum group elements (PGEs) for the first time. Average Rh, Pd, and Pt concentrations from the tunnel ventilation air supply were 1.5, 11.1, and 4.5pgm(-3) in PM2.5 and 3.8, 23.1, and 15.1pgm(-3) in PM10, respectively. Rh, Pd, and Pt levels were elevated inside the Washburn Tunnel reaching 12.5, 91.1, and 30.1pgm(-3) in PM2.5 and 36.3, 214, and 61.1pgm(-3) in PM10, respectively. Significantly higher enrichment factors of Cu, Zr, Rh, Pd, Sb, and Pt (referenced to Ti in the upper continental crust) inside the tunnel compared with the ventilation air supply suggested that they are unique elemental tracers of PM derived from gasoline-driven LDVs. This highlights the importance of advancing methods to quantify the trace level PGE emissions as a technique to more accurately estimate LDVs' contributions to airborne PM. Using the emission profile based on PGEs and ambient quantification, mass balancing revealed that approximately half the fine PM mass in the tunnel could be attributed to tailpipe emissions, approximately one-quarter to road dust, with smaller contributions from brake (7%) and tire (3%) wear. On the other hand, PM10 mostly originated from resuspended road dust (∼50%), with progressively lower contributions from tailpipe emissions (14%), brake wear (9%), and tire

  4. Well-defined coinage metal transfer agents for the synthesis of NHC-based nickel, rhodium and palladium macrocycles.

    PubMed

    Andrew, Rhiann E; Storey, Caroline M; Chaplin, Adrian B

    2016-06-01

    With a view to use as carbene transfer agents, well-defined silver(i) and copper(i) complexes of a macrocyclic NHC-based pincer ligand, bearing a central lutidine donor and a dodecamethylene spacer [CNC-(CH2)12, 1], have been prepared. Although the silver adduct is characterised by X-ray diffraction as a dinuclear species anti-[Ag(μ-1)]2(2+), variable temperature measurements indicate dynamic structural interchange in solution involving fragmentation into mononuclear [Ag(1)](+) on the NMR time scale. In contrast, a mononuclear structure is evident in both solution and the solid-state for the analogous copper adduct partnered with the weakly coordinating [BAr(F)4](-) counter anion. A related copper derivative, bearing instead the more coordinating cuprous bromide dianion [Cu2Br4](2-), is notable for the adoption of an interesting tetranuclear assembly in the solid-state, featuring two cuprophilic interactions and two bridging NHC donors, but is not retained on dissolution. Coinage metal precursors [M(1)]n[BAr(F)4]n (M = Ag, n = 2; M = Cu, n = 1) both act as carbene transfer agents to afford palladium, rhodium and nickel complexes of 1 and the effectiveness of these precursors has been evaluated under equivalent reaction conditions. PMID:27157720

  5. Well-defined coinage metal transfer agents for the synthesis of NHC-based nickel, rhodium and palladium macrocycles.

    PubMed

    Andrew, Rhiann E; Storey, Caroline M; Chaplin, Adrian B

    2016-06-01

    With a view to use as carbene transfer agents, well-defined silver(i) and copper(i) complexes of a macrocyclic NHC-based pincer ligand, bearing a central lutidine donor and a dodecamethylene spacer [CNC-(CH2)12, 1], have been prepared. Although the silver adduct is characterised by X-ray diffraction as a dinuclear species anti-[Ag(μ-1)]2(2+), variable temperature measurements indicate dynamic structural interchange in solution involving fragmentation into mononuclear [Ag(1)](+) on the NMR time scale. In contrast, a mononuclear structure is evident in both solution and the solid-state for the analogous copper adduct partnered with the weakly coordinating [BAr(F)4](-) counter anion. A related copper derivative, bearing instead the more coordinating cuprous bromide dianion [Cu2Br4](2-), is notable for the adoption of an interesting tetranuclear assembly in the solid-state, featuring two cuprophilic interactions and two bridging NHC donors, but is not retained on dissolution. Coinage metal precursors [M(1)]n[BAr(F)4]n (M = Ag, n = 2; M = Cu, n = 1) both act as carbene transfer agents to afford palladium, rhodium and nickel complexes of 1 and the effectiveness of these precursors has been evaluated under equivalent reaction conditions.

  6. Linking structure to function: The search for active sites in non-platinum group metal oxygen reduction reaction catalysts

    DOE PAGESBeta

    Holby, Edward F.; Zelenay, Piotr

    2016-05-17

    Atomic-scale structures of oxygen reduction reaction (ORR) active sites in non-platinum group metal (non-PGM) catalysts, made from pyrolysis of carbon, nitrogen, and transition-metal (TM) precursors have been the subject of continuing discussion in the fuel cell electrocatalysis research community. We found that quantum chemical modeling is a path forward for understanding of these materials and how they catalyze the ORR. Here, we demonstrate through literature examples of how such modeling can be used to better understand non-PGM ORR active site relative stability and activity and how such efforts can also aid in the interpretation of experimental signatures produced by thesemore » materials.« less

  7. Nanostructured metal foams: synthesis and applications

    SciTech Connect

    Luther, Erik P; Tappan, Bryce; Mueller, Alex; Mihaila, Bogdan; Volz, Heather; Cardenas, Andreas; Papin, Pallas; Veauthier, Jackie; Stan, Marius

    2009-01-01

    Fabrication of monolithic metallic nanoporous materials is difficult using conventional methodology. Here they report a relatively simple method of synthesizing monolithic, ultralow density, nanostructured metal foams utilizing self-propagating combustion synthesis of novel metal complexes containing high nitrogen energetic ligands. Nanostructured metal foams are formed in a post flame-front dynamic assembly with densities as low as 0.011 g/cc and surface areas as high as 270 m{sup 2}/g. They have produced metal foams via this method of titanium, iron, cobalt, nickel, zirconium, copper, palladium, silver, hafnium, platinum and gold. Microstructural features vary as a function of composition and process parameters. Applications for the metal foams are discussed including hydrogen absorption in palladium foams. A model for the sorption kinetics of hydrogen in the foams is presented.

  8. Determination of platinum group metal catalyst residues in active pharmaceutical ingredients by means of total reflection X-ray spectrometry

    NASA Astrophysics Data System (ADS)

    Marguí, Eva; Queralt, Ignasi; Hidalgo, Manuela

    2013-08-01

    The control of metal catalyst residues (i.e., platinum group metals (PGMs)) in different stages of the manufacturing processes of the active pharmaceutical ingredients (APIs) and, especially, in the final product is crucial. For API specimens, there are strict guidelines to limit the levels of metal residues based on their individual levels of safety concern. For PGMs the concentration limit has been established at 10 mg/kg in the API. Therefore great effort is currently being devoted to the development of new and simple procedures to control metals in pharmaceuticals. In the present work, an analytical methodology based on benchtop total reflection X-ray fluorescence spectrometry (TXRF) has been developed for the rapid and simple determination of some PGM catalyst impurities (Rh, Pd, Ir and Pt) in different types of API samples. An evaluation of different sample treatments (dissolution and digestion of the solid pharmaceutical samples) has been carried out and the developed methodologies have been validated according to the analytical parameters to be considered and acceptance criteria for PGM determination according to the United States Pharmacopeia (USP). Limits of quantification obtained for PGM metals were in the range of 2-4 mg/kg which are satisfactory according to current legislation. From the obtained results it is shown that the developed TXRF method can be implemented in the pharmaceutical industries to increase productivity of the laboratory; offering an interesting and complementary analytical tool to other atomic spectroscopic methods.

  9. The new insight into oral drug delivery system based on metal drugs in colon cancer therapy through β-lactoglobulin/oxali-palladium nanocapsules.

    PubMed

    Ghalandari, Behafarid; Divsalar, Adeleh; Saboury, Ali Akbar; Parivar, Kazem

    2014-11-01

    Many efforts have been made to improve the targeting and potential applications of oral drug delivery systems. In this paper, we have demonstrated and investigated how biopolymer nanocapsules can be used as a novel oral drug delivery system for metal-based drug delivery in colon cancer therapy. In this work, β-lactoglobulin nanocapsules containing oxali-palladium were chosen to be synthesized and investigated for the use in colon cancer therapy. These nanocapsules were fabricated in three different pHs (3, 4.5 and 7) and investigated both in the presence and absence of low methoxyl pectin. The results obtained from these experiments indicated that the soluble and stable β-lactoglobulin nanocapsules which contained oxali-palladium had the ability to be formed at a size smaller than 200 nm when in the presence of low methoxyl pectin and at pH 4.5. The in vitro release data indicated that the maximum release occurs at pH 7.0 and 7.5. There lease mechanism demonstrated an anomalous diffusion with a predominant contribution from erosion. Finally, it can be concluded that the β-LG nanocapsules containing oxali-palladium complexed with low methoxyl pectin can be a very promising candidate for the use in oral drug delivery for colon cancer treatment. PMID:25190224

  10. NMR studies of chiral P,S-chelate platinum, rhodium, and iridium complexes and the X-ray structure of a palladium(II) allyl derivative

    SciTech Connect

    Albinati, A.; Eckert, J.; Pregosin, P.; Ruegger, H.; Salzmann, R.; Stoessel, C.

    1997-02-18

    Several Rh(I), Ir(III), and Pt(II) complexes of the chiral P,S-bidentate ligand 2 have been prepared and characterized. Detailed two-dimensional NMR studies show that (i) the boat-type chelate ring and the stereogenic sulfur center can invert rapidly at ambient temperature and (ii) the sulfur donor may dissociate, essentially destroying the chiral pocket. The solid-state structure of [Pt({eta}{sup 3}-C{sub 3}H{sub 5})(2)]PF{sub 6} (3) has been determined and the sulfur substituent shown to have an axial orientation. The six-membered chelate ring takes up a boat-like conformation. As shown by an X-ray diffraction study for 3, and via incoherent inelastic neutron scattering (IINS) measurements for the Pd analog, 4, the OH group is remote from the metal atom. 42 refs., 11 figs., 6 tabs.

  11. The influence of alkali metal ions in the chemisorption of CO and CO{sub 2} on supported palladium catalysts: A Fourier transform infrared spectroscopic study

    SciTech Connect

    Liotta, L.F.; Deganello, G.; Martin, G.A.

    1996-12-01

    Two series of palladium-based catalysts were compared on the basis of the adsorption of CO and CO{sub 2}, monitored by Fourier transform infrared spectroscopy. The first series is represented by a silica-supported palladium catalyst and by some catalysts derived from it by addition of different amounts of sodium ion 0 {le} R {le} 25.6, where R is the atomic ratio Na/Pd. The second series consists of palladium catalysts supported on {open_quotes}model{close_quotes} and natural pumices. The model pumices, obtained by sol-gel techniques, are silico-aluminates containing variable amounts of sodium so that the corresponding Pd catalysts have an R value in the range 0{le}R{le}6.1. In the Pd/natural pumice catalysts, changes of the atomic ratio R{prime} = (Na + K)/Pd are achieved with different palladium loadings. Despite the analogous behaviour of the catalysts of both series when R=0, the presence of increasing alkali metal ions induces different behaviour towards the adsorption of CO. On increasing R in the Na-Pd/SiO{sub 2} series there is a progressive weakening of the C-O bond to produce eventually carbonates, whereas only a decrease of the amount of adsorbed CO occurs in the Pd/model pumice series (R{le}6.1). Furthermore, only physisorbed CO bands are observed in Pd/natural pumice catalysts (R{prime}{le}17). Different behaviour is also noticed towards the adsorption of CO{sub 2}: the equilibrium CO{sub 2}(gas){r_equilibrium}CO{sub ads}+O{sub ads} occurs in the Pd/SiO{sub 2} series, in contrast to the Pd/pumice series where only carbonate species on the surface of the support are detected. 83 refs., 12 figs., 4 tabs.

  12. Direct oxidation of L-sorbose to 2-keto-L-gulonic acid with molecular oxygen on platinum- and palladium-based catalysts

    SciTech Connect

    Broennimann, C.; Bodnar, Z.; Mallat, T.; Baiker, A.; Hug, P.

    1994-11-01

    The selective oxidation of the C1 hydroxyl group of L-sorbose to a carboxylic group without protection of the four other hydroxyl functions was investigated. The reactions were performed in slightly alkaline aqueous solutions with molecular oxygen over various alumina- and carbon-supported Pt and Pd catalysts. Optimum reaction conditions were 50{degrees}C, pH 7.3, and a catalyst:reactant ratio of 1:4 (wt/wt). The lower the pH and the temperature, the higher the selectivity toward 2-keto-L-gluonic acid. Catalyst deactivation was also found to increase with lower pH and temperature. A 5 wt% Pt/alumina catalyst showed the best catalytic performance (67% selectivity at 58% conversion). Promotion with Bi or Pb had a detrimental effect on selectivity for 2-keto-L-gulonic acid. Electrochemical measurements indicated that the reaction occurs in a rather narrow potential range, which corresponds to a moderate oxygen coverage of Pt or Pd. Four types of catalyst deactivation processes were identified, based on XPS and ICP-AES analysis and on the in situ determination of the oxidation state by monitoring the catalyst potential during reaction. A significant chemical poisoning of the active noble metal sites occurred during the initial, destructive adsorption of L-sorbose and during the oxidation reaction. The successive contamination of active sites resulted in overoxidation (too high oxygen coverage of Pt or Pd). The partially oxidized promoters and noble metals were corroded and dissolved in the presence of 2-keto-L-gulonic acid, resulting in an irreversible deactivation. 66 refs., 11 figs., 2 tabs.

  13. Dissolution Process of Palladium in Hydrochloric Acid: A Route via Alkali Metal Palladates

    NASA Astrophysics Data System (ADS)

    Kasuya, Ryo; Miki, Takeshi; Morikawa, Hisashi; Tai, Yutaka

    2015-12-01

    To improve the safety of the Pd recovery processes that use toxic oxidizers, dissolution of Pd in hydrochloric acid with alkali metal palladates was investigated. Alkali metal palladates were prepared by calcining a mixture of Pd black and alkali metal (Li, Na, and K) carbonates in air. Almost the entire amount of Pd was converted into Li2PdO2 after calcination at 1073 K (800 °C) using Li2CO3. In contrast, PdO was obtained by calcination at 1073 K (800 °C) using Na and K carbonates. Our results indicated that Li2CO3 is the most active reagent among the examined alkali metal carbonates for the formation of palladates. In addition, dissolution of the resulting Li2PdO2 in HCl solutions was evaluated under various conditions. In particular, Li2PdO2 rapidly dissolved in diluted (0.1 M) HCl at ambient temperature. Solubility of Pd of Li2PdO2 was found to be 99 pct or larger after dissolution treatment at 353 K (80 °C) for 5 minutes; in contrast, PdO hardly dissolved in 0.1 M HCl. The dissolution mechanism of Li2PdO2 in HCl was also elucidated by analysis of crystal structures and particulate properties. Since our process is completely free from toxic oxidizers, the dissolution process via alkali metal palladates is much safer than currently employed methods.

  14. A Generic Wet Impregnation Method for Preparing Substrate-Supported Platinum Group Metal and Alloy Nanoparticles with Controlled Particle Morphology.

    PubMed

    Zhang, Changlin; Oliaee, Shirin Norooz; Hwang, Sang Youp; Kong, Xiangkai; Peng, Zhenmeng

    2016-01-13

    Mass production of shape-controlled platinum group metal (PGM) and alloy nanoparticles is of high importance for their many fascinating properties in catalysis, electronics, and photonics. Despite of successful demonstrations at milligram scale using wet chemistry syntheses in many fundamental studies, there is still a big gap between the current methods and their real applications due to the complex synthetic procedures, scale-up difficulty, and surface contamination problem of the made particles. Here we report a generic wet impregnation method for facile, surfactant-free, and scalable preparation of nanoparticles of PGMs and their alloys on different substrate materials with controlled particle morphology and clean surface, which bridges the outstanding properties of these nanoparticles to practical important applications. The underlying particle growth and shape formation mechanisms were investigated using a combination of ex situ and in situ characterizations and were attributed to their different interactions with the applied gas molecules.

  15. Substituent effects in heterogeneous catalysis. VIII. Reactions of 2-methyl- and 2-ethylcyclohexanone with deuterium catalyzed by platinum metals

    SciTech Connect

    Teratani, S.; Tanaka, K.; Ogawa, H.; Taya, K.

    1981-08-01

    2-Methyl and 2-ethyl derivatives of cyclohexanone were allowed to react with deuterium in t-BuOD using platinum group metals as catalysts. The product alcohols and the remaining ketone were examined by mass spectrometry. Over Ru, Os, and Ir, the simple addition of two deuterium atoms to the carbonyl linkage was predominant, accompanied by little isotopic exchange. Over Pt, however, isotopic exchange was significant and over Rh and Pd quite extensive. The samples obtained over Rh and Pd were further analyzed by NMR spectroscopy to determine the loci of the incorporated deuterium atoms. Deuterium exchange over Pd was almost entirely confined to the C(2) and C(6) positions, while that over Rh was smeared beyond these positions. These results can be accounted for by assuming the intermediacy of ..pi..-absorbed ..pi..-oxaallylic species on Pd and of ..beta..-diadsorbed species on Rh.

  16. Contamination from gold and platinum-group metals mining in the Gulf of Darién, Colombia

    NASA Astrophysics Data System (ADS)

    Vasquez-Bedoya, L.; Palacio Baena, J.

    2013-12-01

    Gulf of Darién, triangular southernmost extension of the Caribbean Sea, bounded by Panama on the southwest and by Colombia on the southeast and east. The Gulf is made up of 17 municipalities in the department of Choco and Antioquia. The Gulf of Darién is a geostrategic region, rich in biodiversity, known for its natural resources of minerals, oil, lumber as well as its water and fertile land. The Darién also acts as the bridge between South America and Central America and has access to the Pacific Ocean and the Caribbean Sea. The economy in the region is based mainly on agribusinesses, tourism and mining activities, mainly the 'mining of gold and platinum-group metals'. In our study we determined the degree of trace element contamination in estuarine sediment samples originated from mining activities and municipal waste water discharges of effluents on the gulf of Darién. . Surface samples were taken from 17 locations through the entire Gulf. Grain size, Corg, Ag, Al, Ca , Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb and Zn concentrations were analyzed, and enrichment factors (EF) as well as geo-accumulation indices (Igeo) were calculated. Concentrations of Pb, Zn, Ni, Cu and Cr show levels that are consistent with those typically found in urbanized marine environments. EF and Igeo values revealed that the Gulf is extremely contaminated with Ag and moderately contaminated with Cr and Zn. The sources of Cr, Ag, Hg and Zn are associated with the development of mining activities in the Atrato River basin. The observed enrichment of Ag may be explained as a residue of the extraction of gold and platinum-group metals.

  17. Gold and palladium adsorption from leached electronic scrap using ordered mesoporous carbon nanoscaffolds

    SciTech Connect

    McDowell, Rocklan; Dutech, Guy

    2014-09-01

    Ordered mesoporous carbon (OMC) nanoscaffolds are engineered agglomerates of carbon nanotubes held together by small carbon nanofibers with uniform pore sizes, high pore volume, and high channel permeability. These materials exhibit very high affinity for the adsorption of gold from aqueous acidic mixtures. The efficiency of gold recovery is comparable to those typically accomplished using biopolymer-based adsorbents. The adsorption efficiency for other precious metals such as palladium and platinum is lower. Studies on the precious metal (Au, Pd) adsorption on OMC materials from actual liquors of leached electronics will be presented. Adsorption properties will be compared for several different sorbents used for the recovery of precious metals. The leach liquor compositions for three different types of electronic scrap materials (personal computer board, cell phone and tv input/output board) will be presented. The sorption efficiencies for Au, Pd, together with a spectrum of competing and non-competing metals, from such leach mixtures will be compared.

  18. Development of palladium nanowires

    NASA Astrophysics Data System (ADS)

    Cheng, Chuanding

    Inherent limitations of traditional lithography have prompted the search for means of achieving self-assembly of nano-scale structures and networks for the next generation of electronic and photonic devices. The nanowire, the basic building block of a nanocircuit, has recently become the focus of intense research. Reports on nanowire synthesis and assembly have appeared in the scientific literature, which include Vapor-Liquid-Solid mechanism, template-based electrochemical fabrication, solvothermal or wet chemistry, and assembly by fluid alignment or microchannel networks. An ideal approach for practical application of nanowires would circumvent technical and economic constraints of templating. Here we report on the self-assembly of highly-ordered metallic nanowires directly from a palladium acetate solution under an applied alternating current (AC) electric field of relatively high intensity and frequency. DNA-templated nanowires are first presented here. DNA molecules were stretched and positioned by electric field, followed by metallization by palladium acetate solution. Palladium nanowire arrays have been found to grow directly between microelectrodes without any template, under an alternating electric field of relatively high intensity and frequency. The wires grew spontaneously along the direction of the electric field and have high uniformity and conductivity. Single 75 nm-diameter palladium nanowires have also been self-assembled from aqueous solution at predefined locations between 15 mum-gap electrodes built on a SiO2 substrate. Nanowire assembly was initiated by application an electric field, and it occurred only along the direction of field lines where the field is strongest. Related metals did not support single nanowire assembly under comparable conditions. Current-limiting circuits for controlled nanowire synthesis, electric field simulation, and growth mechanism were studied. The simple and straightforward approach to nanowire assembly outlined here

  19. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    PubMed Central

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A.; Xin, Huolin L.; Abruña, Héctor D.

    2016-01-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications. PMID:27336795

  20. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A.; Xin, Huolin L.; Abruña, Héctor D.

    2016-06-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd-Co-Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.

  1. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    DOE PAGESBeta

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; et al

    2016-06-23

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. Themore » uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.« less

  2. DFT study of adsorption of CO2 on palladium cluster doped by transition metal

    NASA Astrophysics Data System (ADS)

    Saputro, A. G.; Agusta, M. K.; Wungu, T. D. K.; Suprijadi; Rusydi, F.; Dipojono, H. K.

    2016-08-01

    We report on a theoretical study of CO2 adsorption on Pd6-M (M: Ni, Cu, Pt, Rh) cluster using first-principles density functional theory (DFT) calculations. We find that CO2 molecule is adsorbed with a bidendate configuration on Pd7 and on most of Pd6M clusters. The bidendate adsorption configuration is formed due to the filling of the unoccupied n* orbital of CO2 molecule upon its interaction with d-orbitals of the cluster. We find that transition metal doping could modify the adsorption energy, adsorption site and adsorption configuration of CO2 molecule on Pd7 cluster. We also predict that the usage of Pd6M clusters as CO2 hydrogenation catalysts might facilitate the formations of HCOO/COOH.

  3. Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores.

    PubMed

    El-Safty, Sherif A; Shenashen, Mohamed A; Sakai, Masaru; Elshehy, Emad; Halada, Kohmei

    2015-12-06

    Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

  4. Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores.

    PubMed

    El-Safty, Sherif A; Shenashen, Mohamed A; Sakai, Masaru; Elshehy, Emad; Halada, Kohmei

    2015-01-01

    Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals. PMID:26709467

  5. Synthesis of hindered biphenyls by sequential non-transition metal-catalyzed reaction/palladium-catalyzed cross-couplings.

    PubMed

    He, Ping; Dong, Cheng-Guo; Hu, Qiao-Sheng

    2008-03-17

    The sequential reaction of 1,2-dihalobenzenes with aryl lithiums followed by palladium-catalyzed cross-coupling reactions with Grignard reagents and arylboronic acids is described. This sequential reaction provides a convenient and expeditious access to tri-ortho substituted biaryl derivatives.

  6. Epitaxial Overgrowth of Platinum on Palladium Nanocrystals

    SciTech Connect

    Jiang, M.; Zhu, Y.; Lim, B.; Tao, J.; Camargo, P.H.C.; Ma, C.; Xia, Y.

    2010-11-01

    This paper describes a systematic study on the epitaxial overgrowth of Pt on well-defined Pdnanocrystals with different shapes (and exposed facets), including regular octahedrons, truncated octahedrons, and cubes. Two different reducing agents, i.e., citric acid and L-ascorbic acid, were evaluated and compared for the reduction of K{sub 2}PtCl{sub 4} in an aqueous solution in the presence of Pdnanocrystal seeds. When citric acid was used as a reducing agent, conformal overgrowth of octahedral Pt shells on regular and truncated octahedrons of Pd led to the formation of Pd-Pt core-shell octahedrons, while non-conformal overgrowth of Pt on cubic Pd seeds resulted in the formation of an incomplete octahedral Pt shell. On the contrary, localized overgrowth of Pt branches was observed when L-ascorbic acid was used as a reducing agent regardless of the facets expressed on the surface of Pdnanocrystal seeds. This work shows that both the binding affinity of a reducing agent to the Pt surface and the reduction kinetics for a Pt precursor play important roles in determining the mode of Pt overgrowth on Pdnanocrystal surface.

  7. Ultrafine Metal-Organic Right Square Prism Shaped Nanowires.

    PubMed

    Otake, Ken-Ichi; Otsubo, Kazuya; Sugimoto, Kunihisa; Fujiwara, Akihiko; Kitagawa, Hiroshi

    2016-05-23

    We report the structural design and control of electronic states of a new series of ultrafine metal-organic right square prism-shaped nanowires. These nanowires have a very small inner diameter of about 2.0 Å, which is larger than hydrogen and similar to xenon atomic diameters. The electronic states of nanowires can be widely controlled by substitution of structural components. Moreover, the platinum homometallic nanowire shows a 100 times higher proton conductivity than a palladium/platinum heterometallic one depending on the electronic states.

  8. Ultrafine Metal-Organic Right Square Prism Shaped Nanowires.

    PubMed

    Otake, Ken-Ichi; Otsubo, Kazuya; Sugimoto, Kunihisa; Fujiwara, Akihiko; Kitagawa, Hiroshi

    2016-05-23

    We report the structural design and control of electronic states of a new series of ultrafine metal-organic right square prism-shaped nanowires. These nanowires have a very small inner diameter of about 2.0 Å, which is larger than hydrogen and similar to xenon atomic diameters. The electronic states of nanowires can be widely controlled by substitution of structural components. Moreover, the platinum homometallic nanowire shows a 100 times higher proton conductivity than a palladium/platinum heterometallic one depending on the electronic states. PMID:27080935

  9. Method of forming supported doped palladium containing oxidation catalysts

    SciTech Connect

    Mohajeri, Nahid

    2014-04-22

    A method of forming a supported oxidation catalyst includes providing a support comprising a metal oxide or a metal salt, and depositing first palladium compound particles and second precious metal group (PMG) metal particles on the support while in a liquid phase including at least one solvent to form mixed metal comprising particles on the support. The PMG metal is not palladium. The mixed metal particles on the support are separated from the liquid phase to provide the supported oxidation catalyst.

  10. Assessing Economic Modulation of Future Critical Materials Use: The Case of Automotive-Related Platinum Group Metals.

    PubMed

    Zhang, Jingshu; Everson, Mark P; Wallington, Timothy J; Field, Frank R; Roth, Richard; Kirchain, Randolph E

    2016-07-19

    Platinum-group metals (PGMs) are technological and economic enablers of many industrial processes. This important role, coupled with their limited geographic availability, has led to PGMs being labeled as "critical materials". Studies of future PGM flows have focused on trends within material flows or macroeconomic indicators. We complement the previous work by introducing a novel technoeconomic model of substitution among PGMs within the automotive sector (the largest user of PGMs) reflecting the rational response of firms to changing prices. The results from the model support previous conclusions that PGM use is likely to grow, in some cases strongly, by 2030 (approximately 45% for Pd and 5% for Pt), driven by the increasing sales of automobiles. The model also indicates that PGM-demand growth will be significantly influenced by the future Pt-to-Pd price ratio, with swings of Pt and Pd demand of as much as 25% if the future price ratio shifts higher or lower even if it stays within the historic range. Fortunately, automotive catalysts are one of the more effectively recycled metals. As such, with proper policy support, recycling can serve to meet some of this growing demand. PMID:27285880

  11. First-principles study of spin-dependent thermoelectric properties of half-metallic Heusler thin films between platinum leads

    NASA Astrophysics Data System (ADS)

    Comtesse, Denis; Geisler, Benjamin; Entel, Peter; Kratzer, Peter; Szunyogh, László

    2014-03-01

    The electronic and magnetic bulk properties of half-metallic Heusler alloys such as Co2FeSi,Co2FeAl, Co2MnSi, and Co2MnAl are investigated by means of ab initio calculations in combination with Monte Carlo simulations. The electronic structure is analyzed using the plane-wave code quantum espresso and the magnetic exchange interactions are determined using the Korringa-Kohn-Rostoker (KKR) method. From the magnetic exchange interactions, the Curie temperature is obtained via Monte Carlo simulations. In addition, electronic transport properties of trilayer systems consisting of two semi-infinite platinum leads and a Heusler layer in-between are obtained from the fully relativistic screened KKR method by employing the Kubo-Greenwood formalism. The focus is on thermoelectric properties, namely, the Seebeck effect and its spin dependence. It turns out that already thin Heusler layers provide highly spin-polarized currents. This is attributed to the recovery of half-metallicity with increasing layer thickness. The absence of electronic states of spin-down electrons around the Fermi level suppresses the contribution of this spin channel to the total conductance, which strongly influences the thermoelectric properties and results in a spin polarization of thermoelectric currents.

  12. Assessing Economic Modulation of Future Critical Materials Use: The Case of Automotive-Related Platinum Group Metals.

    PubMed

    Zhang, Jingshu; Everson, Mark P; Wallington, Timothy J; Field, Frank R; Roth, Richard; Kirchain, Randolph E

    2016-07-19

    Platinum-group metals (PGMs) are technological and economic enablers of many industrial processes. This important role, coupled with their limited geographic availability, has led to PGMs being labeled as "critical materials". Studies of future PGM flows have focused on trends within material flows or macroeconomic indicators. We complement the previous work by introducing a novel technoeconomic model of substitution among PGMs within the automotive sector (the largest user of PGMs) reflecting the rational response of firms to changing prices. The results from the model support previous conclusions that PGM use is likely to grow, in some cases strongly, by 2030 (approximately 45% for Pd and 5% for Pt), driven by the increasing sales of automobiles. The model also indicates that PGM-demand growth will be significantly influenced by the future Pt-to-Pd price ratio, with swings of Pt and Pd demand of as much as 25% if the future price ratio shifts higher or lower even if it stays within the historic range. Fortunately, automotive catalysts are one of the more effectively recycled metals. As such, with proper policy support, recycling can serve to meet some of this growing demand.

  13. Photobiomolecular metallic particles and films

    DOEpatents

    Hu, Zhong-Cheng

    2003-05-06

    The method of the invention is based on the unique electron-carrying function of a photocatalytic unit such as the photosynthesis system I (PSI) reaction center of the protein-chlorophyll complex isolated from chloroplasts. The method employs a photo-biomolecular metal deposition technique for precisely controlled nucleation and growth of metallic clusters/particles, e.g., platinum, palladium, and their alloys, etc., as well as for thin-film formation above the surface of a solid substrate. The photochemically mediated technique offers numerous advantages over traditional deposition methods including quantitative atom deposition control, high energy efficiency, and mild operating condition requirements.

  14. Barrier Modification of Metal-contact on Silicon by Sub-2 nm Platinum Nanoparticles and Thin Dielectrics

    PubMed Central

    Zheng, Haisheng; Mahajan, Bikram K.; Su, Sheng C.; Mukherjee, Somik; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

    2016-01-01

    We report metal/p-Si contact barrier modification through the introduction of either “isolated” or “nonisolated” tilted-target-sputtered sub-2 nm platinum nanoparticles (Pt NPs) in combination with either a 0.98 nm Atomic Layer Deposited Al2O3 or a 1.6 nm chemically grown SiO2 dielectric layer, or both. Here, we study the role of these Pt NP’s size dependent properties, i.e., the Pt NP-metal surface dipole, the Coulomb blockade and quantum confinement effect in determining the degree of Fermi level depinning observed at the studied metal/p-Si interfaces. By varying only the embedded Pt NP size and its areal density, the nature of the contact can also be modulated to be either Schottky or Ohmic upon utilizing the same gate metal. 0.74 nm Pt NPs with an areal density of 1.1 × 1013 cm−2 show ~382 times higher current densities compared to the control sample embedded with similarly sized Pt NPs with ~1.6 times lower areal densities. We further demonstrate that both Schottky (Ti/p-Si) and poor Ohmic (Au/p-Si) contact can be modulated into a good Ohmic contact with current density of 18.7 ± 0.6 A/cm2 and 10.4 ± 0.4 A/cm2, respectively, showing ~18 and ~30 times improvement. A perfect forward/reverse current ratio of 1.041 is achieved for these low doped p-Si samples. PMID:27121605

  15. Supporting palladium metal on gold nanoparticles improves its catalysis for nitrite reduction.

    PubMed

    Qian, Huifeng; Zhao, Zhun; Velazquez, Juan C; Pretzer, Lori A; Heck, Kimberly N; Wong, Michael S

    2014-01-01

    Nitrate (NO3(-)) and nitrite (NO2(-)) anions are often found in groundwater and surface water as contaminants globally, especially in agricultural areas due to nitrate-rich fertilizer use. One popular approach to studying the removal of nitrite/nitrate from water has been their degradation to dinitrogen via Pd-based reduction catalysis. However, little progress has been made towards understanding how the catalyst structure can improve activity. Focusing on the catalytic reduction of nitrite in this study, we report that Au NPs supporting Pd metal ("Pd-on-Au NPs") show catalytic activity that varies with volcano-shape dependence on Pd surface coverage. At room temperature, in CO2-buffered water, and under H2 headspace, the NPs were maximally active at a Pd surface coverage of 80%, with a first-order rate constant (k(cat) = 576 L g(Pd)(-1) min(-1)) that was 15x and 7.5x higher than monometallic Pd NPs (~4 nm; 40 L g(Pd)(-1) min(-1)) and Pd/Al2O3 (1 wt% Pd; 76 L g(Pd)(-1) min(-1)), respectively. Accounting only for surface Pd atoms, these NPs (576 L g(surface-Pd)(-1) min(-1)) were 3.6x and 1.6x higher than monometallic Pd NPs (160 L g(surface-Pd)(-1) min(-1)) and Pd/Al2O3 (361 L g(surface-Pd)(-1) min(-1)). These NPs retained ~98% of catalytic activity at a chloride concentration of 1 mM, whereas Pd/Al2O3 lost ~50%. The Pd-on-Au nanostructure is a promising approach to improve the catalytic reduction process for nitrite and, with further development, also for nitrate anions.

  16. Synthesis and characterization of nanostructured palladium-based alloy electrocatalysts

    NASA Astrophysics Data System (ADS)

    Sarkar, Arindam

    Low temperature fuel cells like proton exchange membrane fuel cells (PEMFC) are expected to play a crucial role in the future hydrogen economy, especially for transportation applications. These electrochemical devices offer significantly higher efficiency compared to conventional heat engines. However, use of exotic and expensive platinum as the electrocatalyst poses serious problems for commercial viability. In this regard, there is an urgent need to develop low-platinum or non-platinum electrocatalysts with electrocatalytic activity for the oxygen reduction reaction (ORR) superior or comparable to that of platinum. This dissertation first investigates non-platinum, palladium-based alloy electrocatalysts for ORR. Particularly, Pd-M (M = Mo and W) alloys are synthesized by a novel thermal decomposition of organo-metallic precursors. The carbon-supported Pd-M (M = Mo, W) electrocatalyts are then heat treated up to 900°C in H2 atmosphere and investigated for their phase behavior. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo or W significantly enhances the catalytic activity for ORR as well as the stability (durability) of the electrocatalysts. Additionally, both the alloy systems exhibit high tolerance to methanol, which is particularly advantageous for direct methanol fuel cells (DMFC). The dissertation then focuses on one-pot synthesis of carbon-supported multi-metallic Pt-Pd-Co nanoalloys by a rapid microwave-assisted solvothermal (MW-ST) method. The multi-metallic alloy compositions synthesized by the MW-ST method show much higher catalytic activity for ORR compared to their counterparts synthesized by the conventional borohydride reduction method. Additionally, a series of Pt encapsulated Pd-Co nanoparticle electrocatalysts are synthesized by the MW-ST method and characterized to understand their phase behavior, surface composition, and electrocatalytic activity for ORR. Finally, the dissertation

  17. Platinum group element and cerium concentrations in roadside environments in Toronto, Canada.

    PubMed

    Wiseman, Clare L S; Hassan Pour, Zahra; Zereini, Fathi

    2016-02-01

    Platinum (Pt), palladium (Pd) and rhodium (Rh) are accumulating globally in the environment, due to their use as catalysts to control automotive exhaust emissions. While environmental increases in platinum metal concentrations have been well documented for a number of countries, published data for Canada have been missing to date. The aim of this study is to examine the concentrations of Pt, Pd and Rh, as well as Ce, in soils and dust as a function of traffic volume in Toronto, Ontario. Soils and road and underpass dust were collected from two sites with medium and high volumes of traffic. Samples were acid digested and co-precipitated with Hg (for Pd) and Te (for Pt and Rh), prior to measurement using ICP-Q-MS. Palladium occurred at the highest levels in samples, followed by Pt and Rh. Median concentrations for all soil samples were 63 μg Pd/kg, 8.7 μg Pt/kg, 1.7 μg Rh/kg and 41 mg Ce/kg. The results support existing data regarding PGE accumulation trends in urban and roadside environments, due to their use as catalysts in automotive catalytic converters. This study also confirms a shift toward the heavier use of Pd as the catalyst of choice in recent years, as reflected in the higher concentrations measured for this metal relative to Pt and Rh. The results highlight a need to continue monitoring the accumulation of PGE, most notably Pd, in urban environments.

  18. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    SciTech Connect

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-07-02

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. Ultimately, these results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

  19. Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

    PubMed Central

    El-Safty, Sherif A.; Shenashen, Mohamed A.; Sakai, Masaru; Elshehy, Emad; Halada, Kohmei

    2015-01-01

    Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobaltmetals. PMID:26709467

  20. Batch leaching tests of motherboards to assess environmental contamination by bromine, platinum group elements and other selected heavy metals.

    PubMed

    Almeida, César; Grosselli, Melina; González, Patricia; Martínez, Dante; Gil, Raúl

    2016-02-01

    In this study, a batch leaching test was executed to evaluate the toxicity associated with chemicals contained in motherboards. The leaching solutions used were distilled water, nitric acid, acetic acid and synthetic acid rain solution. A total of 21 elements including Ag, As, Au, Br, Cd, Co, Cr, Cu, Hf, Ir, Mn, Ni, Os, Pb, Pd, Pt, Rd, Rh, Se, U and Zn were analyzed. In this study, the pH values of all the leachates fell within the range of 2.33-4.88. The highest concentrations of metals were obtained from the acid rain solution, whilst the maximum value of bromine was achieved with solution of acetic acid. Appreciable concentrations of platinum group elements were detected with concentrations around 3.45, 1.43, 1.21 and 22.19 µg L(-1) for Ir, Pd, Pt and Rh, respectively. The different leaching of the motherboards revealed the predominant presence of the toxic substances in the leached from the e-waste.

  1. Batch leaching tests of motherboards to assess environmental contamination by bromine, platinum group elements and other selected heavy metals.

    PubMed

    Almeida, César; Grosselli, Melina; González, Patricia; Martínez, Dante; Gil, Raúl

    2016-02-01

    In this study, a batch leaching test was executed to evaluate the toxicity associated with chemicals contained in motherboards. The leaching solutions used were distilled water, nitric acid, acetic acid and synthetic acid rain solution. A total of 21 elements including Ag, As, Au, Br, Cd, Co, Cr, Cu, Hf, Ir, Mn, Ni, Os, Pb, Pd, Pt, Rd, Rh, Se, U and Zn were analyzed. In this study, the pH values of all the leachates fell within the range of 2.33-4.88. The highest concentrations of metals were obtained from the acid rain solution, whilst the maximum value of bromine was achieved with solution of acetic acid. Appreciable concentrations of platinum group elements were detected with concentrations around 3.45, 1.43, 1.21 and 22.19 µg L(-1) for Ir, Pd, Pt and Rh, respectively. The different leaching of the motherboards revealed the predominant presence of the toxic substances in the leached from the e-waste. PMID:26343021

  2. Platinum-group element, Gold, Silver and Base Metal distribution in compositionally zoned sulfide droplets from the Medvezky Creek Mine, Noril'sk, Russia

    NASA Astrophysics Data System (ADS)

    Barnes, Sarah-Jane; Cox, R. A.; Zientek, M. L.

    2006-08-01

    Concentrations of Ag, Au, Cd, Co, Re, Zn and Platinum-group elements (PGE) have been determined in sulfide minerals from zoned sulfide droplets of the Noril’sk 1 Medvezky Creek Mine. The aims of the study were; to establish whether these elements are located in the major sulfide minerals (pentlandite, pyrrhotite, chalcopyrite and cubanite), to establish whether the elements show a preference for a particular sulfide mineral and to investigate the model, which suggests that the zonation in the droplets is caused by the crystal fractionation of monosulfide solid solution (mss). Nickel, Cu, Ag, Re, Os, Ir, Ru, Rh and Pd, were found to be largely located in the major sulfide minerals. In contrast, less than 25% of the Au, Cd, Pt and Zn in the rock was found to be present in these sulfides. Osmium, Ir, Ru, Rh and Re were found to be concentrated in pyrrhotite and pentlandite. Palladium and Co was found to be concentrated in pentlandite. Silver, Cd and Zn concentrations are highest in chalcopyrite and cubanite. Gold and platinum showed no preference for any of the major sulfide minerals. The enrichment of Os, Ir, Ru, Rh and Re in pyrrhotite and pentlandite (exsolution products of mss) and the low levels of these elements in the cubanite and chalcopyrite (exsolution products of intermediate solid solution, iss) support the mss crystal fractionation model, because Os, Ir, Ru, Rh and Re are compatible with mss. The enrichment of Ag, Cd and Zn in chalcopyrite and cubanite also supports the mss fractionation model these minerals are derived from the fractionated liquid and these elements are incompatible with mss and thus should be enriched in the fractionated liquid. Gold and Pt do not partition into either iss or mss and become sufficiently enriched in the final fractionated liquid to crystallize among the iss and mss grains as tellurides, bismithides and alloys. During pentlandite exsolution Pd appears to have diffused from the Cu-rich portion of the droplet into

  3. Transition metal oxides deposited on rhodium and platinum: Surface chemistry and catalysis

    SciTech Connect

    Boffa, A B

    1994-07-01

    The surface chemistry and catalytic reactivity of transition metal oxides deposited on Rh and Pt substrates has been examined in order to establish the role of oxide-metal interactions in influencing catalytic activity. The oxides investigated included titanium oxide (TiOx), vanadium oxide (VOx), iron oxide (FeOx), zirconium oxide (ZrOx), niobium oxide (NbOx), tantalum oxide (TaOx), and tungsten oxide (WOx). The techniques used to characterize the sample included AES, XPS, LEED, TPD, ISS, and STM. After characterization of the surface in UHV, the sample was enclosed in an atmospheric reaction cell to measure the influence of the oxide deposits on the catalytic activity of the pure metal for CO and CO{sub 2} hydrogenation. The oxide deposits were found to strongly enhance the reactivity of the Rh foil. The rates of methane formation were promoted by up to 15 fold with the maximum in rate enhancement occurring at oxide coverages of approximately 0.5 ML. TiOx TaOx, and NbOx were the most effective promoters and were stable in the highest oxidation states during both reactions (compared to VOx, WOx, and FeOx). The trend in promoter effectiveness was attributed to the direct relationship between oxidation state and Lewis acidity. Bonding at the metal oxide/metal interface between the oxygen end of adsorbed CO and the Lewis acidic oxide was postulated to facilitate C-O bond dissociation and subsequent hydrogenation. 192 refs.

  4. Direct functionalization processes: a journey from palladium to copper to iron to nickel to metal-free coupling reactions.

    PubMed

    Mousseau, James J; Charette, André B

    2013-02-19

    The possibility of finding novel disconnections for the efficient synthesis of organic molecules has driven the interest in developing technologies to directly functionalize C-H bonds. The ubiquity of these bonds makes such transformations attractive, while also posing several challenges. The first, and perhaps most important, is the selective functionalization of one C-H bond over another. Another key problem is inducing reactivity at sites that have been historically unreactive and difficult to access without prior inefficient prefunctionalization. Although remarkable advances have been made over the past decade toward solving these and other problems, several difficult tasks remain as researchers attempt to bring C-H functionalization reactions into common use. The functionalization of sp(3) centers continues to be challenging relative to their sp and sp(2) counterparts. Directing groups are often needed to increase the effective concentration of the catalyst at the targeted reaction site, forming thermodynamically stable coordination complexes. As such, the development of removable or convertible directing groups is desirable. Finally, the replacement of expensive rare earth reagents with less expensive and more sustainable catalysts or abandoning the use of catalysts entirely is essential for future practicality. This Account describes our efforts toward solving some of these quandaries. We began our work in this area with the direct arylation of N-iminopyridinium ylides as a universal means to derivatize the germane six-membered heterocycle. We found that the Lewis basic benzoyl group of the pyridinium ylide could direct a palladium catalyst toward insertion at the 2-position of the pyridinium ring, forming a thermodynamically stable six-membered metallocycle. Subsequently we discovered the arylation of the benzylic site of 2-picolonium ylides. The same N-benzoyl group could direct a number of inexpensive copper salts to the 2-position of the pyridinium ylide

  5. Reactions of organometallic compounds catalyzed by transition metal complexes. XIII. Comparison of the reactivity of organometallic compounds in aryldemetallation reactions catalyzed by palladium complexes

    SciTech Connect

    Bumagin, N.A.; Ponomarev, A.B.; Beletskaya, I.P.

    1987-12-10

    The effect of the nature of the metal M and the organic group R on the reaction of organometallic compounds RM (R = Ph, PhC triple bond C, C/sub 3/H/sub 7/, Allyl; M = Li, Mg, Zn, Cd, Cu Al), produced in situ from Grignard reagents or organolithium compounds and the respective salts, with p-iodoanisole in the presence of palladium complexes PdCl/sub 2/L/sub 2/ (L = PPh/sub 3/, MeCN, dppf) was studied. The organozinc and organoaluminum compounds react with a high degree of selectivity. In the reactions of C/sub 3/H/sub 7/M with p-MeOC/sub 6/H/sub 4/I the highest yield from cross-coupling is obtained with catalysis by the PdCl/sub 2/ (dppf) complex. The mechanism of the formation of the homocoupling products is discussed.

  6. Palladium contamination in silicon

    NASA Astrophysics Data System (ADS)

    Polignano, M. L.; Mica, I.; Ceresoli, M.; Codegoni, D.; Somaini, F.; Bianchi, I.; Volonghi, D.

    2015-04-01

    In this work palladium is characterized as a silicon contaminant by recombination lifetime, DLTS, C-V and C-t measurements of palladium-implanted wafers. Palladium introduced by ion implantation is found to remain in the solid solution in silicon after rapid thermal treatments, and to be a very effective recombination center. For this reason recombination lifetime measurements are the most sensitive method to detect palladium in silicon. Two palladium-related levels were found by DLTS in p-type material. One of these levels corresponds to a level reported in the literature as the single donor level of substitutional palladium. For what concerns MOS capacitors, palladium is responsible for negative oxide charge and for degradation of the generation lifetime. In addition, palladium is confirmed to be a very fast diffuser, which segregates at the wafer surface even with low temperature treatments (250 °C). Microscopy inspections showed that palladium precipitates and surface defects were formed upon segregation.

  7. Method for forming porous platinum films

    DOEpatents

    Maya, Leon

    2000-01-01

    A method for forming a platinum film includes providing a substrate, sputtering a crystalline platinum oxide layer over at least a portion of the substrate, and reducing the crystalline platinum oxide layer to form the platinum film. A device includes a non-conductive substrate and a platinum layer having a density of between about 2 and 5 g/cm.sup.3 formed over at least a portion of the non-conductive substrate. The platinum films produced in accordance with the present invention provide porous films suitable for use as electrodes, yet require few processing steps. Thus, such films are less costly. Such films may be formed on both conductive and non-conductive substrates. While the invention has been illustrated with platinum, other metals, such as noble metals, that form a low density oxide when reactively sputtered may also be used.

  8. Synthesis of Platinum Nanotubes and Nanorings via Simultaneous Metal Alloying and Etching.

    PubMed

    Huang, Zhiqi; Raciti, David; Yu, Shengnan; Zhang, Lei; Deng, Lin; He, Jie; Liu, Yijing; Khashab, Niveeen M; Wang, Chao; Gong, Jinlong; Nie, Zhihong

    2016-05-25

    Metallic nanotubes represent a class of hollow nanostructures with unique catalytic properties. However, the wet-chemical synthesis of metallic nanotubes remains a substantial challenge, especially for those with dimensions below 50 nm. This communication describes a simultaneous alloying-etching strategy for the synthesis of Pt nanotubes with open ends by selective etching Au core from coaxial Au/Pt nanorods. This approach can be extended for the preparation of Pt nanorings when Saturn-like Au core/Pt shell nanoparticles are used. The diameter and wall thickness of both nanotubes and nanorings can be readily controlled in the range of 14-37 nm and 2-32 nm, respectively. We further demonstrated that the nanotubes with ultrathin side walls showed superior catalytic performance in oxygen reduction reaction. PMID:27090384

  9. Characterization of T Cell Receptors of Th1 Cells Infiltrating Inflamed Skin of a Novel Murine Model of Palladium-Induced Metal Allergy

    PubMed Central

    Kobayashi, Hiroshi; Eguchi, Takanori; Shigematsu, Hiroaki; Kitaura, Kazutaka; Kawano, Mitsuko; Horikawa, Tatsuya; Suzuki, Satsuki; Matsutani, Takaji; Ogasawara, Kouetsu; Hamada, Yoshiki

    2013-01-01

    Metal allergy is categorized as a delayed-type hypersensitivity reaction, and is characterized by the recruitment of lymphocytes into sites of allergic inflammation. Because of the unavailability of suitable animal models for metal allergy, the role of T cells in the pathogenesis of metal allergy has not been explored. Thus, we developed a novel mouse model for metal allergy associated with infiltration of T cells by multiple injections of palladium (Pd) plus lipopolysaccharide into the footpad. Using this model, we characterized footpad-infiltrating T cells in terms of phenotypic markers, T cell receptor (TCR) repertoires and cytokine expression. CD3+ CD4+ T cells accumulated in the allergic footpads 7 days after Pd challenge. The expression levels of CD25, interleukin-2, interferon-γ and tumor necrosis factor, but not interleukin-4 and interleukin-5, increased in the footpads after challenge, suggesting CD4+ T helper 1 (Th1) cells locally expanded in response to Pd. Infiltrated T cells in the footpads frequently expressed AV18-1 and BV8-2 T cell receptor (TCR) chains compared with T cells in the lymph nodes and exhibited oligoclonality. T-cell clones identified from Pd-allergic mouse footpads shared identical CDR3 sequences containing AV18-1 and BV8-2. These results suggest that TCR AV18-1 and BV8-2 play dominant and critical parts in the antigen specificity of Pd-specific Th1 cells. PMID:24098486

  10. Synthesis, structure, and spectroscopic properties of ortho-metalated platinum(II) complexes

    SciTech Connect

    Mdleleni, M.M.; Bridgewater, J.S.; Watts, R.J.; Ford, P.C.

    1995-04-26

    The ortho-metalated Pt(II) complexes Pt(ppy)(CO)Cl (1), Pt(ptpy)(CO)Cl (2), and Pt(ppy)(Hppy)Cl (3) (where ppy and ptpy are respectively the ortho-C-deprotonated forms of 2-phenylpyridine and 2-p-tolylpyridine and Hppy is 2-phenylpyridine) have been prepared. The CO ligand is coordinated trans to the nitrogen atom of the ortho-metalated ligand and exerts a strong trans effect resulting in a relatively long Pt-N bond [2.114(19) {angstrom}]. This structure shows both the bidentate ppy ligand and the monodentate Hppy with the nitrogens of these ligands trans to each other. The UV/vis electronic absorption spectra of 1-3 have intense bands in the near-UV region ({approximately}375 nm) which have been assigned as metal to ligand charge transfer (MLCT) transitions, and higher energy bands were assigned as ligand-centered transitions. Each complex exhibits relatively long-lived structured emissions in the solid state at ambient temperature and at 77 K and 77 K glassy toluene solutions. These emissions are proposed to originate from triplet MLCT states. Notably, in solution both the lifetime and spectrum of 2 proved to be a function of the concentration, a phenomenon interpreted in terms of the propensity of square planar d{sup 8} complexes to oligomerize. In contrast, the more sterically hindered complex 3 displayed no such tendency toward oligomerization.

  11. Assessment of exposure to platinum-group metals in urban children

    NASA Astrophysics Data System (ADS)

    Caroli, S.; Alimonti, A.; Petrucci, F.; Bocca, B.; Krachler, M.; Forastiere, F.; Sacerdote, M. T.; Mallone, S.

    2001-07-01

    Catalytic converters for automotive traction raise some concern for human health and the environment, due to the release of Pd, Pt and Rh (Pt-Group Metals, PGMs). In fact, the thermal and mechanical conditions under which such devices work (including abrasion effects and hot-temperature chemical reactions with oil fumes) can cause significant release of the PGMs to the environment and eventually affect human health. A pilot investigation was performed to assess the exposure to these metals of 310 schoolchildren aged between 6 and 10 years from the urban and suburban area of Rome. All determinations were performed by high-resolution magnetic-sector inductively-coupled plasma-mass spectrometry after UV irradiation of the samples. The mean concentration values of these metals in urine were found to be (in ng/g creatinine) 7.5±5.4 for Pd, 0.9±1.1 for Pt and 8.5±8.0 for Rh. Urine concentrations of Pd and Rh (but not Pt) were found to be strongly associated with traffic density in the area of residence.

  12. Cytotoxic properties of a new organometallic platinum(II) complex and its gold(I) heterobimetallic derivatives.

    PubMed

    Serratrice, Maria; Maiore, Laura; Zucca, Antonio; Stoccoro, Sergio; Landini, Ida; Mini, Enrico; Massai, Lara; Ferraro, Giarita; Merlino, Antonello; Messori, Luigi; Cinellu, Maria Agostina

    2016-01-14

    A novel platinum(ii) organometallic complex, [Pt(pbi)(Me)(DMSO)], bearing the 2-(2'-pyridyl)-benzimidazole (pbiH) ligand, was synthesized and fully characterized. Interestingly, the reaction of this organometallic platinum(ii) complex with two distinct gold(i) phosphane compounds afforded the corresponding heterobimetallic derivatives with the pbi ligand bridging the two metal centers. The antiproliferative properties in vitro of [Pt(pbi)(Me)(DMSO)] and its gold(i) derivatives as well as those of the known coordination platinum(ii) and palladium(ii) complexes with the same ligand, of the general formula [MCl2(pbiH)], were comparatively evaluated against A2780 cancer cells, either sensitive or resistant to cisplatin. A superior biological activity of the organometallic compound clearly emerged compared to the corresponding platinum(ii) complex; the antiproliferative effects are further enhanced upon attaching the gold(i) triphenylphosphine moiety to the organometallic Pt compound. Remarkably, these novel metal species are able to overcome nearly complete resistance to cisplatin. Significant mechanistic insight into the study compounds was gained after investigating their reactions with a few representative biomolecules by electrospray mass spectrometry and X-ray crystallography. The obtained results are comprehensively discussed.

  13. Process for Making a Noble Metal on Tin Oxide Catalyst

    NASA Technical Reports Server (NTRS)

    Davis, Patricia; Miller, Irvin; Upchurch, Billy

    2010-01-01

    To produce a noble metal-on-metal oxide catalyst on an inert, high-surface-area support material (that functions as a catalyst at approximately room temperature using chloride-free reagents), for use in a carbon dioxide laser, requires two steps: First, a commercially available, inert, high-surface-area support material (silica spheres) is coated with a thin layer of metal oxide, a monolayer equivalent. Very beneficial results have been obtained using nitric acid as an oxidizing agent because it leaves no residue. It is also helpful if the spheres are first deaerated by boiling in water to allow the entire surface to be coated. A metal, such as tin, is then dissolved in the oxidizing agent/support material mixture to yield, in the case of tin, metastannic acid. Although tin has proven especially beneficial for use in a closed-cycle CO2 laser, in general any metal with two valence states, such as most transition metals and antimony, may be used. The metastannic acid will be adsorbed onto the high-surface-area spheres, coating them. Any excess oxidizing agent is then evaporated, and the resulting metastannic acid-coated spheres are dried and calcined, whereby the metastannic acid becomes tin(IV) oxide. The second step is accomplished by preparing an aqueous mixture of the tin(IV) oxide-coated spheres, and a soluble, chloride-free salt of at least one catalyst metal. The catalyst metal may be selected from the group consisting of platinum, palladium, ruthenium, gold, and rhodium, or other platinum group metals. Extremely beneficial results have been obtained using chloride-free salts of platinum, palladium, or a combination thereof, such as tetraammineplatinum (II) hydroxide ([Pt(NH3)4] (OH)2), or tetraammine palladium nitrate ([Pd(NH3)4](NO3)2).

  14. Photobiomolecular deposition of metallic particles and films

    DOEpatents

    Hu, Zhong-Cheng

    2005-02-08

    The method of the invention is based on the unique electron-carrying function of a photocatalytic unit such as the photosynthesis system I (PSI) reaction center of the protein-chlorophyll complex isolated from chloroplasts. The method employs a photo-biomolecular metal deposition technique for precisely controlled nucleation and growth of metallic clusters/particles, e.g., platinum, palladium, and their alloys, etc., as well as for thin-film formation above the surface of a solid substrate. The photochemically mediated technique offers numerous advantages over traditional deposition methods including quantitative atom deposition control, high energy efficiency, and mild operating condition requirements.

  15. Nickel, cobalt, chromium, palladium and gold induce a mixed Th1- and Th2-type cytokine response in vitro in subjects with contact allergy to the respective metals.

    PubMed

    Minang, J T; Areström, I; Troye-Blomberg, M; Lundeberg, L; Ahlborg, N

    2006-12-01

    Nickel (Ni), the main cause of contact allergy to metals, induces in vitro production of both Th1- and Th2-type cytokines in peripheral blood mononuclear cells (PBMC) from allergic subjects. Because the knowledge of the cellular immune response to other metals involved in contact allergy has been limited, we investigated the cytokine profile induced by Ni, cobalt (Co), chromium (Cr), palladium (Pd) and gold (Au) in PBMC from patients with patch test reactivity to the respective metals. PBMC from patients with patch test reactivity to Ni, Co, Cr, Au and/or Pd (n = 31) and non-allergic controls (n = 5) were stimulated in vitro with corresponding metal salts. Th1- [interleukin (IL)-2 and interferon (IFN)-gamma] and Th2- (IL-4 and IL-13) type cytokine responses were measured by enzyme-linked immunospot (ELISpot) and/or enzyme-linked immunosorbent assay (ELISA). All metals induced a mixed Th1- and Th2-type cytokine production in PBMC from individual patients with patch test reactivity to the corresponding metal, but not in control PBMC. Significantly higher responses in the patient versus controls were found for Cr (IL-2 and IL-13), Pd (IL-2 and IL-4), Au (IL-13 and IFN-gamma) (all P < 0.05) and Ni (all four cytokines; P < 0.01) but not Co. Overall, 71% (37/52) and 89% (81/91) of the positive and negative patch test reactivities to metals, respectively, were matched by the in vitro reactivity. In conclusion, our data suggest that sensitization to Co, Cr, Pd and Au results in a cellular immune response of a character similar to the mixed Th1- and Th2-type cytokine profile shown previously to be induced by Ni.

  16. Electrodeposition of Metals in Catalyst Synthesis: The Case of Platinum Monolayer Electrocatalysts

    SciTech Connect

    Vukmirovic, M.B.; Bliznakov, S.T.; Sasaki, K.; Wang, J.X.; Adzic, R.R.

    2011-07-01

    The concern about energy sources, their availability, and related environmental effects, is at an all time high. Proton Exchange Membrane Fuel Cells (PEMFCs) - with an efficiency higher than that of internal combustion engines, light weight, low operating temperature, and fast-start-up capability - are strong candidates for automotive applications. Transportation applications could be especially important in shaping up the new energy economy since they may entail a substantial decrease in the adverse environmental effects linked to the use of fossil fuels and prolong their availability. The largest portion of the cost of PEMFCs reflects the large amount of Pt needed in the cathode's catalytic layer due to the low catalytic activity of Pt for the oxygen reduction reaction (ORR). Recently, considerable advances have been made in fuel cell electrocatalysis yielding improved electrocatalysts, and increasing our understanding of the kinetics of the ORR in combination with significant advances in theoretical treatments. Some of these studies involved: (1) alloying Pt to synthesize bi-metallic catalysts, (2) core-shell nanoparticles catalysts, (3) the role of size, structure, and shape of nanoparticles, and (4) de-alloying of bimetallic alloys. However, a complete understanding of the ORR kinetics on Pt, the best single element catalyst, and of its low efficiency, is yet to be achieved. These problems, compounded with the high Pt content in current cathode catalysts, and with their gradual loss of performance under operating conditions, still hamper commercialization of fuel cells. In order to minimize the amount of noble metal electrocatalysts and maximize their utilization, while achieving high catalytic activity, numerous synthetic approaches have been attempted. The electrocatalysts were prepared using vacuum deposition methods, wet chemistry methods, or electrodeposition techniques. Electrodeposition in particular has several attractive features with respect to the

  17. Gold and platinum in shales with evidence against extraterrestrial sources of metals

    USGS Publications Warehouse

    Coveney, R.M.; Murowchick, J.B.; Grauch, R.I.; Glascock, M.D.; Denison, J.R.

    1992-01-01

    Few black shales contain concentrations of precious metals higher than average continental crust (i.e. ???5 ppb Au). Yet Au and Pt alloys have been reported from the Kupferschiefer in Poland. Moreover, thin sulfide beds in certain Chinese and Canadian shales contain several hundred ppb Au, Pd and Pt and average ???4% Mo and ???2.5% Ni in an association that is difficult to explain. Volcanic and non-volcanic exhalations, hydrothermal epigenesis involving either igneous or sedex fluids, biogenic processes and low-temperature secondary enrichment are among the possible factors involved in deriving Ni, PGE and Au for black shales and sulfide beds in black shales. Extraterrestrial sources have been invoked in some cases (e.g., the Cambrian of China). However, available data on abundances of PGE indicate relatively low values for Ir (<0.02-2 ppb) in comparison with amounts for other PGE (up to 700 ppb Pt and 1255 ppb Pd). These data and high contents for Mo are not consistent with extraterrestrial sources of metals for Chinese shales and Ni-Mo-sulfide beds. Data are less complete for the U.S. shales, but nevertheless are suggestive of earthly origins for PGE. ?? 1992.

  18. Further studies on the ability of different metal salts to influence the DNA synthesis of human lymphoid cells.

    PubMed

    Nordlind, K

    1986-01-01

    In a further study on the ability of different metal salts to influence the DNA synthesis of human lymphoid cells, aluminum chloride, beryllium chloride, cadmium chloride, cupric sulfate, ferric chloride, manganese chloride, palladium chloride, platinum chloride and silver nitrate, were tested regarding effect on thymocytes and peripheral blood lymphocytes in children. At certain concentrations in the range of 10(-4)-10(-5)M, all tested compounds but aluminum chloride and ferric chloride, were inhibitory, the latter compounds inhibited at 4.8 X 10(-3)M. A slight stimulation mainly on the thymocytes was obtained with beryllium chloride, cadmium chloride, palladium chloride, platinum chloride and silver nitrate, at certain concentrations in the range of 10(-5)-10(-6)M, while ferric chloride gave a slight stimulation at 1.2 X 10(-3)M. Thus, the tested metal salts should be suitable for use in lymphocyte transformation tests for diagnosis of contact allergy.

  19. Communication: Photoactivation of nucleobase bound platinum{sup II} metal complexes: Probing the influence of the nucleobase

    SciTech Connect

    Sen, Ananya; Dessent, Caroline E. H.

    2014-12-28

    We present UV laser action spectra (220-300 nm) of isolated nucleobase-bound Pt{sup II}(CN){sub 4}{sup 2−} complexes, i.e., Pt(CN){sub 4}{sup 2−}⋅M, where M = uracil, thymine, cytosine, and adenine. These metal complex-nucleobase clusters represent model systems for identifying the fundamental photophysical and photochemical processes occurring in photodynamic platinum (II) drug therapies that target DNA. This is the first study to explore the specific role of the nucleobase in the photophysics of the aggregate complex. Each of the complexes studied displays a broadly similar absorption spectra, with a strong λ{sub max} ∼ 4.7 eV absorption band (nucleobase localized chromophore) and a subsequent increase in the absorption intensity towards higher spectral-energy (Pt(CN){sub 4}{sup 2−} localized chromophore). However, strikingly different band widths are observed across the series of complexes, decreasing in the order Pt(CN){sub 4}{sup 2−}⋅Thymine > Pt(CN){sub 4}{sup 2−}⋅Uracil > Pt(CN){sub 4}{sup 2−}⋅Adenine > Pt(CN){sub 4}{sup 2−}⋅Cytosine. Changes in the bandwidth of the ∼4.7 eV band are accompanied by distinctive changes in the photofragment product ions observed following photoexcitation, with the narrower-bandwidth complexes showing a greater propensity to decay via electron detachment decay. We discuss these observations in the context of the distinctive nucleobase-dependent excited state lifetimes.

  20. Magnesium, zinc, arsenic, selenium and platinum urinary excretion from cancer patients of Antofagasta region, Chile: multi-metal approach

    PubMed Central

    Pizarro, I; Rivera, L; Ávila, J; Cortés, P

    2016-01-01

    Objectives To evaluate the short-term 24 h urinary excretion of platinum, arsenic, selenium, magnesium and zinc in patients with lung cancer and with cancer other than lungs treated with cisplatin or/and carboplatin from Antofagasta, Chile. Design Urine measurements of Pt and Se were made by inductively coupled plasma optical emission spectrometry, As by hydride-generation atomic absorption spectrometry and Mg and Zn by means of flame furnace atomic absorption spectrometry. Setting All samples were provided by the Oncological Centre of Antofagasta Regional Hospital (Region of Antofagasta, Chile). Participants Ninety 24-h urine samples from cancer patients after the infusion of Pt-base drugs and 10 24-h urine samples from cancer patients not treated with metal-base drugs. Main outcome measures Concentrations of Pt, Se, As, Zn and Mg coming from 24-h urine samples. Results Pt excreted was not significantly different between patients with lung and other cancers treated with cisplatin. The excretion of Mg, Zn and Se was greater than As. Then, Pt favours the excretion of essential elements. For lung and other types of cancers treated with drugs without Pt, excretion of Mg, Zn and Se was also greater than that of As, suggesting antagonism Mg-Zn-Se–anti-cancer drug relationship. Conclusions The amounts of Mg, Zn and Se excreted were greater than for As either with or without Pt-containing drugs, suggesting antagonist Mg-Zn-Se–anti-cancer drug relationships. The excretion of As, Mg, Zn and Se is induced by Pt. Knowledge obtained can contribute to understanding the arsenic cancer mechanism and the As-Mg-Zn-Se-Pt inter-element association for lung cancer and other types of cancer. PMID:27757244

  1. Alloys of platinum and early transition metals as oxygen reduction electrocatalysts.

    PubMed

    Greeley, J; Stephens, I E L; Bondarenko, A S; Johansson, T P; Hansen, H A; Jaramillo, T F; Rossmeisl, J; Chorkendorff, I; Nørskov, J K

    2009-10-01

    The widespread use of low-temperature polymer electrolyte membrane fuel cells for mobile applications will require significant reductions in the amount of expensive Pt contained within their cathodes, which drive the oxygen reduction reaction (ORR). Although progress has been made in this respect, further reductions through the development of more active and stable electrocatalysts are still necessary. Here we describe a new set of ORR electrocatalysts consisting of Pd or Pt alloyed with early transition metals such as Sc or Y. They were identified using density functional theory calculations as being the most stable Pt- and Pd-based binary alloys with ORR activity likely to be better than Pt. Electrochemical measurements show that the activity of polycrystalline Pt(3)Sc and Pt(3)Y electrodes is enhanced relative to pure Pt by a factor of 1.5-1.8 and 6-10, respectively, in the range 0.9-0.87 V. PMID:21378936

  2. Influence of Metal Oxides on Platinum Activity towards Methanol Oxidation in H2SO4 solution.

    PubMed

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

    2016-04-01

    Pt-CeO2 /C, Pt-TiO2 /C, and Pt-ZrO2 /C electrocatalysts were prepared by using a modified microwave-assisted polyol process. Physical characterization was performed by using XRD, TEM, and EDX analyses. The incorporation of different metal oxides increased the dispersion degree of Pt nanoparticles and reduced their diameter to 2.50 and 2.33 nm when TiO2 and ZrO2 were introduced to Pt/C, respectively. The electrocatalytic activity of various electrocatalysts was examined towards methanol oxidation in H2 SO4 solution by using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Among the studied composites, Pt-ZrO2 /C was selected to be a candidate electrocatalyst for better electrochemical performance in direct methanol fuel cells.

  3. Platinum partitioning between metal and silicate melts: Core formation, late veneer and the nanonuggets issue

    NASA Astrophysics Data System (ADS)

    Médard, Etienne; Schmidt, Max W.; Wälle, Markus; Keller, Nicole S.; Günther, Detlef

    2015-08-01

    High-pressure, high-temperature experiments have been performed at ∼1.2 GPa and 1360-2100 °C to investigate the partitioning of Pt between a silicate melt and a metallic melt. Our experiments indicate that nanonuggets encountered in previous experiments are experimental artifacts, formed at high temperature by oversaturation caused by high oxygen fugacity during the initial stages of an experiment. Experiments at high-acceleration using a centrifuging piston-cylinder show that nanonuggets can be removed by gravity during the experiment. Formation of nanonuggets can also be avoided by using initially reduced starting materials. The presence of iron is also a key element in reducing the formation of nanonuggets. Our nanonugget-free data are broadly consistent with previous nanonuggets-filtered data, and suggest that Pt partitioning becomes independent of oxygen fugacity below an oxygen fugacity of at least IW+2. Pt is thus possibly dissolved as a neutral species (or even an anionic species) at low fO2, instead of the more common Pt2+ species present at higher fO2. Due to low concentration, the nature of this species cannot be determined, but atomic Pt or Pt- are possible options. Under core-formation conditions, Pt partitioning between metal and silicate is mostly independent of oxygen fugacity, silicate melt composition, and pressure. Partition coefficient during core formation can be expressed by the following equation: log DPtMmetal/silicate = 1.0348 + 14698 / T (in weight units). Calculations indicate that the Pt content (and by extension the Highly Siderophile Elements content) of the Earth's mantle cannot be explained by equilibrium partitioning during core formation, requiring further addition of HSE to the mantle. The mass of this late veneer is approximately 0.4% of the total mass of the Earth (or 0.6% of the mass of the mantle).

  4. Recovery of Elemental Palladium by Shewanella putrefaciens

    NASA Astrophysics Data System (ADS)

    Akasaka, S.; Xia, X.; Sawada, K.; Enokida, Y.; Yamamoto, I.; Ohnuki, T.

    2006-12-01

    Microbial reduction of metals plays an important role in environmental behavior and provides a technique for the recovery of metals from industrial wastewater. Recently, demand for platinum group metals (PGMs) increases by their catalytic properties. The extreme rarity of PGMs have led to a growing interest in their recovery. Palladium, one of PGMs, has different oxidation states of Pd(II) and Pd(0). The oxidized form of Pd(II) is soluble, while the reduced form of Pd(0) is insoluble. In this study, microbial reduction of palladium by Fe(III)- reducing bacterium, Shewanella putrefaceins was conducted. This bacterium is known to be capable of reducing metals, such as Mn(IV), U(VI), or Tc(VII) with organic C or H2 as an electron donor. In order to investigate the potential of S. putrefaciens to reduce Pd(II) in solution, resting cells or heat-killed cells were suspended under anaerobic conditions with lactate or H2 as an electron donor. The cells of S. putrefaciens (NBRC3908) were grown in aerobic medium, harvested by centrifugation, and then washed with 25 mmol/dm3 HEPES and 100 mmol/dm3 NaCl (HEPES-NaCl) solution (pH 7.0). The heat-killed cells were autoclaved for 20 min at 121 degrees C. The cell suspension (21.5 mg in dry weight) was resuspended in the HEPES-NaCl solution which contained 1.0 mmol/dm3 Na2PdCl4 (Wako Pure chemical Industries, Ltd). The suspensions were bubbled with N2 for 15 min before 10 mmol/dm3 lactate or 4.8 v/v% H2 was added. The suspensions were then incubated at 30 degrees C. Redox potential (Eh) and pH of the solutions were measured in an inert glove box with Ar gas. Concentration of Pd(II) was measured by Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). Deposited Pd and cells were analyzed by X-ray powder diffraction (XRD) and Scanning Electron Microscope (SEM) with Energy-Dispersive Spectroscopy (EDS). Approximately 86% of Pd(II) of the initial concentration was removed from solution by the resting cells within 24 h when

  5. Development of novel low-temperature selective hydrogen gas sensors made of palladium/oxide or nitride capped Magnesium-transition metal hydride films

    NASA Astrophysics Data System (ADS)

    Tang, Yu Ming

    Palladium capped Mg-based transition metal alloy film (Pd/Mg-TM) is a potentially useful hydrogen gas (H2) sensing material, which can operate at low temperature for detection of H2 leakage in an environment to ensure safe use and storage of the gas. The Pd layer catalytically dissociates hydrogen molecules, and the hydrogen atoms produced can enter (hydridation) or be detached (dehydridation) from the alloy layer. These processes are reversible, such that the film is switchable between a metal state and a hydride state, giving rise to substantial changes in its optical transmittance/reflectance and electrical resistivity. Unlike a conventional metal-oxide (MOx) H2 sensor, hydridation of an Mg-TM film is associated with relatively low enthalpy, and hence can perform at temperature much lower than the operation temperature of an MOx sensor (typically around 500°C or above). As such, an Mg-TM based sensor does not experience undesired annealing effect during operation, and hence is much more stable and durable. Furthermore, the detection selectivity of a Pd/Mg-TM film versus other reducing gases is superior to most conventional MOx-type hydrogen sensors. In this project, we systematically investigated the H2 sensing properties of Pd/Mg-TM films.

  6. Dependence of the adsorption and catalytic properties of a copper-platinum catalyst on the structure of metal particles and the composition of the catalyst surface

    NASA Astrophysics Data System (ADS)

    Yagodovskii, V. D.; Lobanov, N. N.; Bratchikova, I. G.; Galimova, N. A.; Platonov, E. A.; Eremina, O. V.

    2011-10-01

    The kinetics of H2 desorption from the surface of a copper-platinum catalyst deposited on silica gel ([1 wt % Pt + 0.15 wt % Cu]/SiO2) and the kinetics of C6H12 dehydrogenation were studied. The effects of copper introduction in a platinum catalyst on the structural characteristics of platinum particles, the composition of their surface, and the effects of plasmochemical treatments on these parameters were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The metal-H atom bond energies ( E Pt-H) and the catalytic activity were found to increase in the presence of Cu. This was explained by the formation of new hydrogen adsorption centers (due to the Cu+δ adatoms) and catalytic centers composed of Cu+δ adatoms and carbon atoms. The mean diameter of Pt particles ( D) increased twofold. The microstresses (ɛ) in the particles increased after the catalyst was treated with glow discharge plasma in Ar and O2 and with high-frequency plasma in H2 (HF-H2). The observed changes in the bond energy E Pt-H and kinetic parameters were explained by the increase in microstresses in Pt particles.

  7. Ni-BaTiO3-Based Base-Metal Electrode (BME) Ceramic Capacitors for Space Applications

    NASA Technical Reports Server (NTRS)

    Liu, Donhang; Fetter, Lula; Meinhold, Bruce

    2015-01-01

    A multi-layer ceramic capacitor (MLCC) is a high-temperature (1350C typical) co-fired ceramic monolithic that is composed of many layers of alternately stacked oxide-based dielectric and internal metal electrodes. To make the dielectric layers insulating and the metal electrode layers conducting, only highly oxidation-resistant precious metals, such as platinum, palladium, and silver, can be used for the co-firing of insulating MLCCs in a regular air atmosphere. MLCCs made with precious metals as internal electrodes and terminations are called precious-metal electrode (PME) capacitors. Currently, all military and space-level applications only address the use of PME capacitors.

  8. Probing Interaction Between Platinum Group Metal (PGM) and Non-PGM Support Through Surface Characterization and Device Performance

    NASA Astrophysics Data System (ADS)

    Saha, Shibely

    High cost and limited abundance of Platinum (Pt) have hindered effective commercialization of Proton Exchange Membrane Fuel Cell and Electrolyzer. Efforts have been undertaken to reduce precious group metal (PGM) requirement for these devices without compromising the activity of the catalyst by using transition metal carbides (TMC) as non-PGM support thanks to their similar electronic and geometric structures as Pt. In this work Mo2C was selected as non-PGM support and Pt was used as the PGM of interest. We hypothesize that the hollow nanotube morphology of Mo2C support combined with Pt nano particles deposited on it via atomic layer deposition (ALD) technique would allow increased interaction between them which may increase the activity of Pt and Mo2C as well as maximize the Pt active surface area. Specifically, a rotary ALD equipment was used to grow Pt particles from atomic level to 2--3 nanometers by simply adjusting number of ALD cycles in order to probe the interaction between the deposited Pt nanoparticles and Mo2C nanotube support. Interaction between the Pt and Mo2 C was analyzed via surface characterization and electrochemical characterization. Interaction between Pt and Mo2C arises due to the lattice mismatch between Pt and Mo2C as well as electron migration between them. Lattice spacing analysis using high resolution transmission electron microscopy (HRTEM) images, combined with Pt binding energy shift in XPS results, clearly showed strong bonding between Pt nanoparticles and the Mo2C nanotube support in all the resultant Pt/Mo2C samples. We postulate that this strong interaction is responsible for the significantly enhanced durability observed in our constant potential electrolysis (CPE) and accelerated degradation testing (ADT). Of the three samples from different ALD cycles (15, 50 and 100), Mo2C nanotubes modified by 50 (1.07 wt% Pt loading) and 100 cycles (4.4 wt% Pt) of Pt deposition, showed higher HER and HOR activity per Pt mass than commercial

  9. Platinum-group elements: so many excellent properties

    USGS Publications Warehouse

    Zientek, Michael L.; Loferski, Patricia J.

    2014-01-01

    The platinum-group elements (PGE) include platinum, palladium, rhodium, ruthenium, iridium, and osmium. These metals have similar physical and chemical properties and occur together in nature. The properties of PGE, such as high melting points, corrosion resistance, and catalytic qualities, make them indispensable to many industrial applications. PGE are strategic and critical materials for many nations because they are essential for important industrial applications but are mined in a limited number of places and have no adequate substitutes. Exploration and mining companies have found approximately 104,000 metric tons of PGE (with minor gold) in mineral deposits around the world that could be developed. For PGE, almost all known production and resources are associated with three geologic features: the Bushveld Complex, a layered mafic-to-ultramafic intrusion in South Africa; the Great Dyke, a layered mafic-to-ultramafic intrusion in Zimbabwe; and sill-like intrusions associated with flood basalts in the Noril’sk-Talnakh area, Russia. To help predict where PGE supplies might be located, USGS scientists study how and where PGE resources are concentrated in the Earth's crust and use that knowledge to assess the likelihood that undiscovered PGE deposits may exist. Techniques used for assessing mineral resources were developed by the USGS to support the stewardship of Federal lands and evaluate mineral resource availability in a global context. The USGS also compiles statistics and information on the worldwide supply, demand, and flow of PGE. These data are all used to inform U.S. national policymakers.

  10. Global mining risk footprint of critical metals necessary for low-carbon technologies: the case of neodymium, cobalt, and platinum in Japan.

    PubMed

    Nansai, Keisuke; Nakajima, Kenichi; Kagawa, Shigemi; Kondo, Yasushi; Shigetomi, Yosuke; Suh, Sangwon

    2015-02-17

    Meeting the 2-degree global warming target requires wide adoption of low-carbon energy technologies. Many such technologies rely on the use of precious metals, however, increasing the dependence of national economies on these resources. Among such metals, those with supply security concerns are referred to as critical metals. Using the Policy Potential Index developed by the Fraser Institute, this study developed a new footprint indicator, the mining risk footprint (MRF), to quantify the mining risk directly and indirectly affecting a national economy through its consumption of critical metals. We formulated the MRF as a product of the material footprint (MF) of the consuming country and the mining risks of the countries where the materials are mined. A case study was conducted for the 2005 Japanese economy to determine the MF and MRF for three critical metals essential for emerging energy technologies: neodymium, cobalt and platinum. The results indicate that in 2005 the MFs generated by Japanese domestic final demand, that is, the consumption-based metal output of Japan, were 1.0 × 10(3) t for neodymium, 9.4 × 10(3) t for cobalt, and 2.1 × 10 t for platinum. Export demand contributes most to the MF, accounting for 3.0 × 10(3) t, 1.3 × 10(5) t, and 3.1 × 10 t, respectively. The MRFs of Japanese total final demand (domestic plus export) were calculated to be 1.7 × 10 points for neodymium, 4.5 × 10(-2) points for cobalt, and 5.6 points for platinum, implying that the Japanese economy is incurring a high mining risk through its use of neodymium. This country's MRFs are all dominated by export demand. The paper concludes by discussing the policy implications and future research directions for measuring the MFs and MRFs of critical metals. For countries poorly endowed with mineral resources, adopting low-carbon energy technologies may imply a shifting of risk from carbon resources to other natural resources, in particular critical metals, and a trade

  11. Platinum Element Group and Other Metal Element Variations at the Permo-Triassic Boundary in Kashmir and British Columbia and Their Significance

    NASA Astrophysics Data System (ADS)

    Brookfield, M. E.; Schnellnutt, G.; Qi, L.; Hannigan, R.; Bhat, G. M.; Wignall, P.

    2009-05-01

    The end Permian marks the greatest extinction in the geological record, but there is little consensus on whether it was caused by terrestrial or extraterrestrial factors. We report here detailed analyses of platinum group element(PGE) and other metals from relatively narrowly spaced (30 cm. in Kashmir) intervals in two expanded sections from the Permo-Triassic northern and southern hemispheres that confirm a terrestrial volcanic source for the elements. But a mechanism is required that can distribute such elements world-wide from their volcanic sources, currently only exposed in the Permo-Triassic northern hemisphere.

  12. Dynamics of palladium on nanocarbon in the direct synthesis of H2O2.

    PubMed

    Arrigo, Rosa; Schuster, Manfred E; Abate, Salvatore; Wrabetz, Sabine; Amakawa, Kazuhiko; Teschner, Detre; Freni, Maria; Centi, Gabriele; Perathoner, Siglinda; Hävecker, Michael; Schlögl, Robert

    2014-01-01

    This work aims to clarify the nanostructural transformation accompanying the loss of activity and selectivity for the hydrogen peroxide synthesis of palladium and gold-palladium nanoparticles supported on N-functionalized carbon nanotubes. High-resolution X-ray photoemission spectroscopy (XPS) allows the discrimination of metallic palladium, electronically modified metallic palladium hosting impurities, and cationic palladium. This is paralleled by the morphological heterogeneity observed by high-resolution TEM, in which nanoparticles with an average size of 2 nm coexisted with very small palladium clusters. The morphological distribution of palladium is modified after reaction through sintering and dissolution/redeposition pathways. The loss of selectivity is correlated to the extent to which these processes occur as a result of the instability of the particle at the carbon surface. We assign beneficial activity in the selective hydrogenation of oxygen to palladium clusters with a modified electronic structure compared with palladium metal or palladium oxides. These beneficial species are formed and stabilized on carbons modified with nitrogen atoms in substitutional positions. The formation of larger metallic palladium particles not only reduces the number of active sites for the synthesis, but also enhances the activity for deep hydrogenation to water. The structural instability of the active species is thus detrimental in a dual way. Minimizing the chance of sintering of palladium clusters by all means is thus the key to better performing catalysts.

  13. An Examination of the Surface and Sub-Surface of Modern and Historical Platinum Photographic Prints Using Low Vacuum High-Resolution Scanning Electron Microscopy.

    PubMed

    Ravines, Patrick; Erdman, Natasha; McElroy, Rob

    2016-08-01

    Photographic prints of platinum metal on paper supports are some of the most exquisite and expressive in the world of fine art photography. Platinum prints were produced from about 1890 to 1920 in the USA and Europe. The chemical and material nature of these valuable prints is of great interest to many who are interested in their long-term preservation, in the intersection of science and art, and in the scientific and technical study of cultural heritage. This paper presents the results of a characterization study using newer electron microscopy techniques. In this study, a low vacuum high-resolution scanning electron microscope was used to study the surface and sub-surface of historic and modern platinum and/or palladium print samples. Using environmental SEM pressures allowed us to investigate the actual top surface and sub-surface with cross-sections without any preparation; no coatings of carbon or other material. Cross-sections were prepared using an argon plasma cross-polishing system. This study shows that the photographic image of platinum prints is composed of platinum nanoparticles embedded in the upper layers of the paper's cellulosic fibers.

  14. An Examination of the Surface and Sub-Surface of Modern and Historical Platinum Photographic Prints Using Low Vacuum High-Resolution Scanning Electron Microscopy.

    PubMed

    Ravines, Patrick; Erdman, Natasha; McElroy, Rob

    2016-08-01

    Photographic prints of platinum metal on paper supports are some of the most exquisite and expressive in the world of fine art photography. Platinum prints were produced from about 1890 to 1920 in the USA and Europe. The chemical and material nature of these valuable prints is of great interest to many who are interested in their long-term preservation, in the intersection of science and art, and in the scientific and technical study of cultural heritage. This paper presents the results of a characterization study using newer electron microscopy techniques. In this study, a low vacuum high-resolution scanning electron microscope was used to study the surface and sub-surface of historic and modern platinum and/or palladium print samples. Using environmental SEM pressures allowed us to investigate the actual top surface and sub-surface with cross-sections without any preparation; no coatings of carbon or other material. Cross-sections were prepared using an argon plasma cross-polishing system. This study shows that the photographic image of platinum prints is composed of platinum nanoparticles embedded in the upper layers of the paper's cellulosic fibers. PMID:27459309

  15. Selective extraction of palladium(II) with theophylline derivatives.

    PubMed

    Kaikake, K; Baba, Y

    2001-03-01

    Theophylline derivatives with some kinds of alkyl chains were synthesized and used in extraction experiments involving metal ions. Theophylline derivatives have exhibited a high selectivity for palladium over other precious metals and base metals. The extraction of palladium from acidic chloride media has been investigated using theophylline derivatives (= RN) as extractants. Palladium(II) was found to be extracted with 7-octyltheophylline according to the following reaction: PdCl2 + 2RN <==> PdCl2(RN)2. The extraction equilibrium constant was determined to be K = 2.67 x 10(8) ( moldm(-3))(-2). In addition, the stripping of palladium was performed to an extent of 100% by a single batchwise treatment with a 1.0 mol dm(-3) ammonia solution. The stoichiometric relation in the extraction of palladium was supported by an analysis using mass spectrometry.

  16. Platinum-group element, Gold, Silver and Base Metal distribution in compositionally zoned sulfide droplets from the Medvezky Creek Mine, Noril'sk, Russia

    USGS Publications Warehouse

    Barnes, S.-J.; Cox, R.A.; Zientek, M.L.

    2006-01-01

    Concentrations of Ag, Au, Cd, Co, Re, Zn and Platinum-group elements (PGE) have been determined in sulfide minerals from zoned sulfide droplets of the Noril'sk 1 Medvezky Creek Mine. The aims of the study were; to establish whether these elements are located in the major sulfide minerals (pentlandite, pyrrhotite, chalcopyrite and cubanite), to establish whether the elements show a preference for a particular sulfide mineral and to investigate the model, which suggests that the zonation in the droplets is caused by the crystal fractionation of monosulfide solid solution (mss). Nickel, Cu, Ag, Re, Os, Ir, Ru, Rh and Pd, were found to be largely located in the major sulfide minerals. In contrast, less than 25% of the Au, Cd, Pt and Zn in the rock was found to be present in these sulfides. Osmium, Ir, Ru, Rh and Re were found to be concentrated in pyrrhotite and pentlandite. Palladium and Co was found to be concentrated in pentlandite. Silver, Cd and Zn concentrations are highest in chalcopyrite and cubanite. Gold and platinum showed no preference for any of the major sulfide minerals. The enrichment of Os, Ir, Ru, Rh and Re in pyrrhotite and pentlandite (exsolution products of mss) and the low levels of these elements in the cubanite and chalcopyrite (exsolution products of intermediate solid solution, iss) support the mss crystal fractionation model, because Os, Ir, Ru, Rh and Re are compatible with mss. The enrichment of Ag, Cd and Zn in chalcopyrite and cubanite also supports the mss fractionation model these minerals are derived from the fractionated liquid and these elements are incompatible with mss and thus should be enriched in the fractionated liquid. Gold and Pt do not partition into either iss or mss and become sufficiently enriched in the final fractionated liquid to crystallize among the iss and mss grains as tellurides, bismithides and alloys. During pentlandite exsolution Pd appears to have diffused from the Cu-rich portion of the droplet into

  17. Biogenic metals in advanced water treatment.

    PubMed

    Hennebel, Tom; De Gusseme, Bart; Boon, Nico; Verstraete, Willy

    2009-02-01

    Microorganisms can change the oxidation state of metals and concomitantly deposit metal oxides and zerovalent metals on or into their cells. The microbial mechanisms involved in these processes have been extensively studied in natural environments, and researchers have recently gained interest in the applications of microbe-metal interactions in biotechnology. Because of their specific characteristics, such as high specific surface areas and high catalytic reactivity, biogenic metals offer promising perspectives for the sorption and (bio)degradation of contaminants. In this review, the precipitation of biogenic manganese and iron species and the microbial reduction of precious metals, such as palladium, platinum, silver and gold, are discussed with specific attention to the application of these biogenic metals in innovative remediation technologies in advanced water treatment.

  18. Catalytic Activity of Platinum Monolayer on Iridium and Rhenium Alloy Nanoparticles for the Oxygen Reduction Reaction

    SciTech Connect

    Karan, Hiroko I.; Sasaki, Kotaro; Kuttiyiel, Kurian; Farberow, Carrie A.; Mavrikakis, Manos; Adzic, Radoslav R.

    2012-05-04

    A new type of electrocatalyst with a core–shell structure that consists of a platinum monolayer shell placed on an iridium–rhenium nanoparticle core or platinum and palladium bilayer shell deposited on that core has been prepared and tested for electrocatalytic activity for the oxygen reduction reaction. Carbon-supported iridium–rhenium alloy nanoparticles with several different molar ratios of Ir to Re were prepared by reducing metal chlorides dispersed on Vulcan carbon with hydrogen gas at 400 °C for 1 h. These catalysts showed specific electrocatalytic activity for oxygen reduction reaction comparable to that of platinum. The activities of PtML/PdML/Ir2Re1, PtML/Pd2layers/Ir2Re1, and PtML/Pd2layers/Ir7Re3 catalysts were, in fact, better than that of conventional platinum electrocatalysts, and their mass activities exceeded the 2015 DOE target. Our density functional theory calculations revealed that the molar ratio of Ir to Re affects the binding strength of adsorbed OH and, thereby, the O2 reduction activity of the catalysts. The maximum specific activity was found for an intermediate OH binding energy with the corresponding catalyst on the top of the volcano plot. The monolayer concept facilitates the use of much less platinum than in other approaches. Finally, the results with the PtML/PdML/Ir2Re electrocatalyst indicate that it is a promising alternative to conventional Pt electrocatalysts in low-temperature fuel cells.

  19. Cinchonidine adsorption on gold and gold-containing bimetallic platinum metal surfaces: an attenuated total reflection infrared and density functional theory study.

    PubMed

    Behzadi, Bahar; Vargas, Angelo; Ferri, Davide; Ernst, Karl-Heinz; Baiker, Alfons

    2006-08-31

    Adsorption of cinchonidine on monometallic Au and bimetallic Pt-Au and Pd-Au thin model films prepared by physical vapor deposition has been investigated with attenuated total reflection infrared (ATR-IR) spectroscopy. On Au the alkaloid forms an adsorbed layer that shows higher stability against desorption than the corresponding adsorption on Pt. In this adsorption layer the intermolecular interactions dominate over metal-adsorbate interactions as indicated by the absence of the spectroscopic features attributed to strongly flat adsorbed species. This behavior is further supported by Density Functional Theory (DFT) calculations indicating that flat and tilted orientations of the quinoline ring have comparable adsorption energy on Au but lower (7-10 kcal/mol) compared to adsorption on Pt (ca. 40 kcal/mol). As a consequence, the creation of a metal surface with isolated chiral sites is prevented by formation of an adsorbed structure formed by intermolecularly bound cinchonidine molecules on Au. While the binding to Pt is due to the formation of sigma-bonds to surface atoms, such aggregates are bound to Au mainly by van der Waals forces. Given this different nature of bonding of cinchonidine to Au and Pt, addition of Au to Pt and Pd films could be used to probe the changes of fractional coverage of the different adsorbed species of cinchonidine on the platinum metals. It is demonstrated that the lowering of the domain size of the platinum group metal by Au can simulate the effect of particle size on the distribution of the surface conformations of the alkaloid on a metal surface.

  20. Gold–promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

    SciTech Connect

    Kuttiyiel, Kurian A.; Sasaki, Kotaro; Su, Dong; Wu, Lijun; Zhu, Yimei; Adzic, Radoslav R.

    2014-11-06

    Considerable efforts to make palladium and palladium alloys active catalysts and a possible replacement for platinum have had a marginal success. Here, we report on a structurally ordered Au₁₀Pd₄₀Co₅₀ catalyst that exhibits comparable activity to conventional platinum catalysts in both acid and alkaline media. Electron microscopic techniques demonstrate that via addition of gold atoms PdCo nanoparticles undergo at elevated temperatures an atomic structural transition from core-shell to a rare intermetallic ordered structure with twin boundaries forming stable {111}, {110} and {100} facets. The superior stability of this catalyst compared to platinum after 10,000 potential cycles in alkaline media is attributed to the atomic structural order of PdCo nanoparticles along with protective effect of clusters of gold atoms on the surface. This strategy of making ordered palladium intermetallic alloy nanoparticles can be used in diverse heterogeneous catalysis where particle size and structural stability matters.

  1. Preparation of benzyne complexes of group 10 metals by intramolecular suzuki coupling of ortho-metalated phenylboronic esters: molecular structure of the first benzyne-palladium(0) complex.

    PubMed

    Retbøll, Mikael; Edwards, Alison J; Rae, A David; Willis, Anthony C; Bennett, Martin A; Wenger, Eric

    2002-07-17

    A series of nickel(II) and palladium(II) aryl complexes substituted in the ortho position of the aromatic ring by a (pinacolato)boronic ester group, [MBr[o-C(6)H(4)B(pin)]L(2)] (M = Ni, L(2) = 2PPh(3) (2a), 2PCy(3) (2b), 2PEt(3) (2c), dcpe (2d), dppe (2e), and dppb (2f); M = Pd, L(2) = 2PPh(3) (3a), 2PCy(3) (3b), and dcpe (3d)), has been prepared. Many of these complexes react readily with KO(t)Bu to form the corresponding benzyne complexes [M(eta(2)-C(6)H(4))L(2)] (M = Ni, L(2) = 2PPh(3) (4a), 2PCy(3) (4b), 2PEt(3) (4c), dcpe (4d); M = Pd, L(2) = 2PCy(3) (5b)). This reaction can be regarded as an intramolecular version of a Suzuki cross-coupling reaction, the driving force for which may be the steric interaction between the boronic ester group and the phosphine ligands present in the precursors 2 and 3. Complex 3d also reacts with KO(t)Bu, but in this case disproportionation of the initially formed eta(2)-C(6)H(4) complex (5d) leads to a 1:1 mixture of a novel dinuclear palladium(I) complex, [(dcpe)Pd(mu(2)-C(6)H(4))Pd(dcpe)] (6), and a 2,2'-biphenyldiyl complex, [Pd(2,2'-C(6)H(4)C(6)H(4))(dcpe)] (7d). Complexes 2a, 3b, 3d, 4b, 5b, 6, and 7d have been structurally characterized by X-ray diffraction; complex 5b is the first example of an isolated benzyne-palladium(0) species.

  2. Electrothermal atomisation atomic absorption conditions and matrix modifications for determining antimony, arsenic, bismuth, cadmium, gallium, gold, indium, lead, molybdenum, palladium, platinum, selenium, silver, tellurium, thallium and tin following back-extraction of organic aminohalide extracts

    USGS Publications Warehouse

    Clark, J.R.

    1986-01-01

    A multi-element organic-extraction and back-extraction procedure, that had been developed previously to eliminate matrix interferences in the determination of a large number of trace elements in complex materials such as geological samples, produced organic and aqueous solutions that were complex. Electrothermal atomisation atomic absorption conditions and matrix modifications have been developed for 13 of the extracted elements (Ag, As, Au, Bi, Cd, Ga, In, Pb, Sb, Se, Sn, Te and Tl) that enhance sensitivity, alleviate problems resulting from the complex solutions and produce acceptable precision. Platinum, Pd and Mo can be determined without matrix modification directly on the original unstripped extracts.

  3. Noble metals: a toxicological appraisal of potential new environmental contaminants.

    PubMed Central

    Brubaker, P E; Moran, J P; Bridbord, K; Hueter, F G

    1975-01-01

    The public health benefits expected by reducing known hazardous emissions from mobile sources should not be compromised by increasing levels of other potentially hazardous unregulated emissions. Catalytic converters are going to be used to meet the statutory requirements on carbon monoxide and hydrocarbon emissions from light duty motor vehicles. Platinum and palladium metals are the catalytic materials to be used in these emission control devices. Preliminary experimental evidence and analysis of the impact of these control devices on the future use and demand for platinum indicates that this metal may appear at detectable levels in the environment by the end of this decade. At the present time, platinum and palladium are not present in the public environment and represent potentially new environmental contaminants as a consequence of use of this new abatement control technology. There is relatively little information available to adequately assess the potential health hazards that may be associated with exposure to these metals and their compounds. Analysis of the environmental problems and concerns associated with possible new environmental contaminants are discussed. Limited estimates are made on community exposure by use of a meteorological dispersion model. Biodegradation potential and attention is also given to the limited toxicological information available. PMID:50939

  4. Simultaneous determination of dopamine and its oxidized product (aminochrom), by hydrodynamic amperometry and anodic stripping voltammetry, using the metallic palladium and uranalyl hexacyanoferrate coated aluminum electrodes.

    PubMed

    Pournaghi-Azar, M H; Dastangoo, H; Fadakar bajeh baj, R

    2010-02-15

    In the present work, the development of an effective electroanalytical strategy for the simultaneous determination of dopamine (DA) and aminochrom (AC) using hydrodynamic amperometry and anodic stripping voltammetry (ASV) on the Al modified electrodes is described. For this purpose the Al electrode is plated with metallic palladium (Pd-Al) by simple dipping procedure and subsequently the uranyl hexacyanoferrate (K(2)UO(2)[Fe(CN)(6)]) is deposited electrochemically on the Pd-Al electrode from a UO(2)(2+)+Fe(CN)(6)(3-) solution. The Pd-Al electrode is used for hydrodynamic amperometric measurement of DA at constant electrode potential of 0.35 V in a stirred electrolyte solution. At fixed operational conditions, the calibration graph for amperometry was linear over the DA concentration range 1x10(-6) to 50x10(-6)M. The detection limit of DA was 4.1x10(-7) M. Whereas the decrease of the ASV current of the K(2)UO(2)[Fe(CN)(6)]/Pd-Al electrode prepared in the presence of AC was the principal of the AC determination. This decrease was proportional to the AC concentration in the solution, during K(2)UO(2)[Fe(CN)(6)]/Pd-Al electrode preparation and the calibration graph was linear over the concentration range 1x10(-6) to 35x10(-6) M of AC. The detection limit was 4.5x10(-7) M AC. PMID:19963367

  5. Electronic transitions of palladium dimer

    SciTech Connect

    Qian, Yue; Ng, Y. W.; Chen, Zhihua; Cheung, A. S.-C.

    2013-11-21

    The laser induced fluorescence spectrum of palladium dimer (Pd{sub 2}) in the visible region between 480 and 700 nm has been observed and analyzed. The gas-phase Pd{sub 2} molecule was produced by laser ablation of palladium metal rod. Eleven vibrational bands were observed and assigned to the [17.1] {sup 3}II{sub g} - X{sup 3}Σ{sub u}{sup +} transition system. The bond length (r{sub o}) and vibrational frequency (ΔG{sub 1/2}) of the ground X{sup 3}Σ{sub u}{sup +} state were determined to be 2.47(4) Å and 211.4(5) cm{sup −1}, respectively. A molecular orbital energy level diagram was used to understand the observed ground and excited electronic states. This is the first gas-phase experimental investigation of the electronic transitions of Pd{sub 2}.

  6. Failure mechanism characterization of platinum alloy

    NASA Technical Reports Server (NTRS)

    Rosen, J. M.; Mcfarlen, W. T.

    1986-01-01

    This article describes procedures and results of testing performed on a platinum/10-percent rhodium, thin-wall tubular product. The purpose of the testing was to develop exemplar SEM fractographs to be used to characterize failures under various environmental conditions. Conditions evaluated for the platinum alloys included high temperature, hydrogen environment, braze metal contamination, and cyclic loading.

  7. Direct deposition of gold nanoplates and porous platinum on substrates through solvent-free chemical reduction of metal precursors with ethylene glycol vapor.

    PubMed

    Cho, Swee Jen; Mei, Xiaoguang; Ouyang, Jianyong

    2012-12-01

    Deposition of nanostructured metals on substrates is important for the fundamental study and practical application, such as in optics and catalysis. In this paper, we report the deposition of gold (Au) nanoplates and porous platinum (Pt) structures on substrates through solvent-free chemical reductions of chloroauric acid (HAuCl(4)) and chloroplatinic acid (H(2)PtCl(6)) with ethylene glycol (EG) vapor at temperatures below 200 °C. The process includes two steps. The first step is the formation of a thin layer of a metal precursor on substrates by coating solution of a metal precursor. The thin metal precursor layer is subsequently dried by annealing. The second step is the chemical reduction of the metal precursor with EG vapor at 160 or 180 °C in the absence of solvent. Both the Au and Pt nanostructures deposited by this method have good adhesion to substrates, but they have different morphologies. The Au nanostructures appear as separate two-dimensional islands on the substrates, and up to 70% of them can be triangular nanoplates with the (111) crystal plane as the basal plane. In contrast, the reduction of H(2)PtCl(6) gives rise to a 3-dimensional porous Pt structure on substrates. The different morphologies of nanostructured Au and Pt are tentatively related to the different surface energies of Au and Pt.

  8. Which Density Functional Is the Best in Computing C-H Activation Energies by Pincer Complexes of Late Platinum Group Metals?

    PubMed

    Lai, Wenzhen; Yao, Jiannian; Shaik, Sason; Chen, Hui

    2012-09-11

    Using the recently proposed corrective LCCSD(T) method as a reference, we systematically assess the widely used approximate density functionals to reproduce C-H bond activation barriers by pincer complexes of the late platinum group transition metals (TMs) (TM = Rh, Pd, Ir, Pt). The pincer ligands explored here cover a wide range of PNP, PCP, POCOP, NCN, and SCS types. Interestingly, B3LYP is found to be the most accurate functional, followed by several others previously identified as well-performing functionals, like B2GP-PLYP, B2-PLYP, and PBE0. However, all tested functionals were found to exhibit the following uniform trends: (1) the DFT barriers for reactions of group 9 TM (Rh and Ir) pincer complexes show higher accuracy compared with those for group 10 TM (Pd and Pt) reactions; (2) within the same group, 5d TM pincer complexes have higher accuracy than 4d TM ones. Consequently, the barriers for C-H activation by Pd(II) pincer complexes were found to be the least accurate among the four TMs in almost all functionals tested here. The DFT empirical dispersion correction (DFT-D3) is shown to have a very small effect on barrier height. This study has some implications for other σ-bond activations like H-H, C-C, and C-halogen bonds by late platinum group pincer complexes.

  9. Experimental observations on noble metal nanonuggets and Fe-Ti oxides, and the transport of platinum group elements in silicate melts

    NASA Astrophysics Data System (ADS)

    Anenburg, Michael; Mavrogenes, John A.

    2016-11-01

    Platinum group element (PGE) nanonuggets are a nuisance in experimental studies designed to measure solubility or partitioning of noble metals in silicate melts. Instead of treating nanonuggets as experimental artifacts, we studied their behaviour motivated by recent discoveries of PGE nanonuggets in a variety of natural settings. We used an experimental setup consisting of AgPd, Pt or AuPd capsules and Fe(-Ti) oxide-saturated hydrous peralkaline silicate melts to maximise nanonugget production. TABS (Te, As, Bi, Sb, Sn) commonly occur in PGM (platinum group minerals), prompting addition of Bi to our experiments to investigate its properties as well. Three-dimensional optical examination by 100× objective and immersion oil reveals variable colour which correlates with nanonugget size and shape due to plasmon resonance effects. We observe two textural types: (1) intermediate-sized nanonuggets dispersed in the glass and adhering to oxides, and (2) abundant fine nanonuggets dispersed in the glass with coarse euhedral crystals in contact with oxides. Slow cooling removes dispersed nanonuggets and greatly coarsens existing oxide-associated metal crystals. Nanonugget-free halos are commonly observed around oxide grains. All metal phases are composed of major (Ag, Pd) and trace (Pt, Ir, Au) capsule material. Our results show reduction processes, imposed by growing oxides, causing local metal saturation in the oxide rich zones with preferential nucleation on smaller oxide grains. The redox gradient then blocks additional metals from diffusing into oxide rich zones, forming halos. As the entire experimental charge is reduced throughout the run, nanonuggets form in the distal glass. Bismuth contents of metal phases do not depend on Bi2O3 amounts dissolved in the melt. Further PGM crystallisation consumes nanonuggets as feedstock. We conclude that the appearance of metallic PGE phases happens in two stages: first as nanonuggets and then as larger PGM. Once formed

  10. Near-UV phosphorescent emitters: N-heterocyclic platinum(ii) tetracarbene complexes.

    PubMed

    Unger, Yvonne; Zeller, Alexander; Taige, Maria A; Strassner, Thomas

    2009-06-28

    Although examples of nickel(ii), palladium(ii) and platinum(ii) N-heterocyclic tetracarbene complexes are known in the literature, particularly platinum(ii) tetracarbene complexes are rare. We developed a new synthetic route via biscarbene acetate complexes, which make homoleptic as well as heteroleptic platinum(ii) tetracarbene complexes accessible. The reported photoluminescence data show that these complexes have good quantum yields and photostability and are a promising class of emitters for PhOLEDs. Characterization of the compounds includes a solid-state structure of the homoleptic complex bis(1,1'-diisopropyl-3,3'-methylenediimidazoline-2,2'-diylidene)platinum(ii) dibromide. PMID:19513490

  11. Accumulation and distribution characteristics of platinum group elements in roadside dusts in Beijing, China.

    PubMed

    Gao, Bo; Yu, Yanke; Zhou, Huaidong; Lu, Jin

    2012-06-01

    The concentrations, distribution, and accumulation of platinum group elements (PGEs) were investigated in roadside dusts collected in four different foundational areas in Beijing during February to May 2010. The results showed that PGE levels in all samples were above the average upper crust values, with mean concentrations of 57.5 ng · g(-1) Pd, 28.2 ng · g(-1) Pt, and 9.8 ng · g(-1) Rh, respectively. Palladium concentration has increased rapidly in recent years. The rank of PGE levels in four different functional regions for roadside dusts was: heavy density traffic area > residential area > educational area > tourism area. Palladium, Pt, and Rh concentrations in dusts showed strong positive correlations, indicating a common traffic-related source of these metals. Meanwhile, PGEs in these samples were not correlated with other traffic-related metals except for Cr. The average PGE ratios of road dusts from Beijing were consistent with those in Germany and Western Australia, but lower than those in the United States and Mexico, indicating that various catalyst productions were used in different countries. In addition, grain-size partitioning of PGEs in dusts indicated that concentrations of PGEs differed from one particle size to another. The coarse fraction had higher PGE concentrations than the fine fraction in roadside dusts. These results showed that autocatalyst PGE contamination estimates in the environment would be significantly underestimated if only a fine-grain size fraction (<0.063 mm) is analyzed.

  12. Luminescent metallogels of platinum(II) terpyridyl complexes: interplay of metal...metal, pi-pi and hydrophobic-hydrophobic interactions on gel formation.

    PubMed

    Tam, Anthony Yiu-Yan; Wong, Keith Man-Chung; Wang, Guoxin; Yam, Vivian Wing-Wah

    2007-05-28

    A series of platinum(II) terpyridyl complexes has been demonstrated to show gelation properties driven by Pt...Pt and pi-pi interactions in addition to hydrophobic-hydrophobic interactions; counter-anions have been found to affect strongly the colour of the metallogel.

  13. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy

    PubMed Central

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-01-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER. PMID:27034988

  14. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy.

    PubMed

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-03-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER.

  15. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy.

    PubMed

    Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

    2016-03-01

    Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER. PMID:27034988

  16. Facile preparation of an immobilized surfactant-free palladium nanocatalyst for metal hydride trapping: a novel sensing platform for TXRF analysis

    NASA Astrophysics Data System (ADS)

    Romero, V.; Costas-Mora, I.; Lavilla, I.; Bendicho, C.

    2015-01-01

    In this work, a simple route for the synthesis of surfactant-free immobilized palladium nanoparticles (Pd NPs) and their use as effective nanocatalysts for metal hydride decomposition is described. A mixture of ethanol : water was used as the reducing agent. Ethanol was added in a large excess to reduce the ionic Pd and stabilize the obtained Pd NPs. Ethanol is adsorbed on the surface of Pd allowing steric stabilization. Freshly prepared Pd NPs were immobilized onto quartz substrates modified with 3-mercaptopropyltrimethoxysilane. Pd interacts with the thiol group of the alkoxysilane that is adsorbed on the surface of NPs without the dissociation of the S-H bond. Different parameters affecting the synthesis of Pd NPs and their immobilization onto quartz substrates were evaluated. A comprehensive characterization of the synthesized Pd NPs was carried out by transmission electron microscopy (TEM), whereas total reflection X-ray fluorescence (TXRF) spectrometry was applied in order to evaluate their catalytic activity for solid-gas reactions. Immobilized Pd NPs were applied as nanocatalysts for the dissociative chemisorption of arsine at room temperature, yielding the formation of As-Pd bonds. Quartz substrates coated with nanosized Pd could be used as novel sensing platforms for total reflection X-ray fluorescence analysis. Arsenic can be detected in situ in natural water with a limit of detection of 0.08 μg L-1.In this work, a simple route for the synthesis of surfactant-free immobilized palladium nanoparticles (Pd NPs) and their use as effective nanocatalysts for metal hydride decomposition is described. A mixture of ethanol : water was used as the reducing agent. Ethanol was added in a large excess to reduce the ionic Pd and stabilize the obtained Pd NPs. Ethanol is adsorbed on the surface of Pd allowing steric stabilization. Freshly prepared Pd NPs were immobilized onto quartz substrates modified with 3-mercaptopropyltrimethoxysilane. Pd interacts with the thiol

  17. Influence of group 10 metals on the growth and subsequent Coulomb explosion of small silicon clusters under strong light pulses.

    PubMed

    Ross, Matt W; Castleman, A W

    2013-03-18

    Growth and ionization patterns of small silicon clusters are studied using ultrafast pulses centered at 624 nm by varying the metal electron source for cluster formation using group 10 transition metals. The silicon-cluster size was observed to change as the electron source was varied from Pdpalladium system is attributed to the higher work function of palladium metal, producing less collisions of the laser-induced plasma with the silane. This shows that changing the metal electron source while holding the laser intensity constant affects the degree of dehydrogenation of SiH4 due to the number of collisions in the cluster source. The saturation intensities of each atomic charge state of silicon, resulting from Coulomb explosion of pure silicon clusters, formed with each metal are measured and compared to those calculated by using semi-classical tunneling theory assuming sequential ionization. The ion signal of silicon atomic charge states produced when using palladium as electron source for cluster formation shows a greater degree of ionization enhancement than that observed for the nickel and platinum systems. This is reflected by the smaller-size clusters formed in the palladium system. Based on a plot of the ion signal as a function of laser intensity compared to the simulated ion signal from tunneling theory, the ionization enhancement of silicon high-charge states is found to increase by varying the electron source from Ni

  18. The friction behavior of semiconductors Si and GaAs in contact with pure metals

    NASA Technical Reports Server (NTRS)

    Mishina, H.

    1984-01-01

    The friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals was studied. Five transition and two nontransition metals, titanium, tantalum, nickel, palladium, platinum, copper, and silver, slid on a single crystal silicon (111) surface. Four metals, indium, nickel, copper and silver, slid on a single crystal gallium arsenide (100) surface. Experiments were conducted in room air and in a vacuum of 10 to the minus 7th power N/sq cm (10 to the minus 9th power torr). The results indicate that the sliding of silicon on the transition metals exhibits relatively higher friction than for the nontransition metals in contact with silicon. There is a clear correlation between friction and Schottky barrier height formed at the metal silicon interface for the transition metals. Transition metals with a higher barrier height on silicon had a lower friction. The same effect of barrier height was found for the friction of gallium arsenide in contact with metals.

  19. Levels of platinum group metals in selected species (Sarotherodon melanotheron, Chonophorus lateristriga, Macrobrachium vollenhovenii and Crassostrea tulipa) in some estuaries and lagoons along the coast of Ghana.

    PubMed

    Essumang, D K; Adokoh, C K; Boamponsem, L

    2010-10-12

    The use of some biota as bioindicators of heavy metal pollution has been demonstrated as particularly adequate due to their capacity of bioconcentration. This study evaluated the levels of platinum group metals (PGMs) in some selected species along the coastal belt of Ghana, using the neutron activation analysis (NAA) method. The result was processed to evaluate pollution indices in order to map the distribution of the metals in those species in the lagoons and estuaries along the costal belt of Ghana. The analysis showed significant levels of all PGMs in blackchin tilapia (Sarotherodon melanotheron Cichlidae), brown goby (Chonophorus lateristriga Gobiidae), shrimp (Macrobrachium vollenhovenii Palaemonidae), and mangrove oysters (Crassostrea tulipa Ostreidae) in the lagoons and river Pra estuary. However, the oysters showed an elevated mean concentration of 0.13 μg/g (dry weight) Pd. From the pollution indices, most of the sampling sites registered mean contamination factor (CF) values between 1.20 and 3.00 for Pt, Pd, and Rh. The pollution load index (PLI) conducted also gave an average pollution index between 0.79 and 2.37, indicating progressive contamination levels. The results revealed that anthropogenic sources, industrial and hospital effluent, etc., together with vehicular emissions, could be the contributing factors to the deposition of PGMs along the Ghanaian coast.

  20. Palladium/nickel bifunctional electrocatalyst for hydrogen oxidation reaction in alkaline membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Alesker, Maria; Page, Miles; Shviro, Meital; Paska, Yair; Gershinsky, Gregory; Dekel, Dario R.; Zitoun, David

    2016-02-01

    Investigation of the hydrogen oxidation reaction (HOR) in alkaline media has been pursued in the past few years side by side with the development of alkaline membrane fuel cells (AMFCs), also called anion exchange membrane fuel cells (AEM-FCs). In this communication, we present the synthesis, electrochemistry and AMFC test of a platinum-free HOR catalyst. The anode catalyst is prepared by growing palladium nanoparticles onto nanoparticles of an oxophilic metal (nickel), resulting in nano-dispersed, interconnected crystalline phases of Ni and Pd. When used in the anode of a hydrogen/air AMFC, such Pd/Ni catalyst exhibits high HOR activity, resulting in record high performance for a platinum-free AMFC (0.4 A cm-2 at 0.6 V vs RHE). The enhancement of HOR catalytic activity vs. that observed at Pd (or Ni) alone is revealed directly in rotating disc electrode tests of this Pd/Ni catalyst that shows a significant negative shift (200 mV) of the onset potential for the HOR current vs. the case of Pd.

  1. Synthesis of metal silicide at metal/silicon oxide interface by electronic excitation

    SciTech Connect

    Lee, J.-G.; Nagase, T.; Yasuda, H.; Mori, H.

    2015-05-21

    The synthesis of metal silicide at the metal/silicon oxide interface by electronic excitation was investigated using transmission electron microscopy. A platinum silicide, α-Pt{sub 2}Si, was successfully formed at the platinum/silicon oxide interface under 25–200 keV electron irradiation. This is of interest since any platinum silicide was not formed at the platinum/silicon oxide interface by simple thermal annealing under no-electron-irradiation conditions. From the electron energy dependence of the cross section for the initiation of the silicide formation, it is clarified that the silicide formation under electron irradiation was not due to a knock-on atom-displacement process, but a process induced by electronic excitation. It is suggested that a mechanism related to the Knotek and Feibelman mechanism may play an important role in silicide formation within the solid. Similar silicide formation was also observed at the palladium/silicon oxide and nickel/silicon oxide interfaces, indicating a wide generality of the silicide formation by electronic excitation.

  2. Study on separation of platinum group metals from high level liquid waste using macroporous (MOTDGA-TOA)/SiO{sub 2}-P silica-based absorbent

    SciTech Connect

    Ito, Tatsuya; Kim, Seong-Yun; Xu, Yuanlai; Hitomi, Keitaro; Ishii, Keizo; Nagaishi, Ryuji; Kimura, Takaumi

    2013-07-01

    The recovery of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO{sub 2}-P has been developed by impregnating two extractants of N,N'-dimethyl-N,N'-di-n-octyl-thio-diglycolamide (MOTDGA) and tri-n-octylamine (TOA) into a silica/polymer composite support (SiO{sub 2}-P). The adsorption of Ru(III), Rh(III) and Pd(II) have been investigated in simulated HLLW by batch method. The adsorbent has shown good uptake property for Pd(II). In addition, the combined use of MOTDGA and TOA improved the adsorption of Ru(III) and Rh(III) better than the individual use of them. The usability of adsorbent in radiation fields was further confirmed by irradiation experiments. The adsorbent remained to have the uptake capability for PGMs over the absorbed dose of 100 kGy, corresponding with one really adsorbed by the adsorbent, and showed good retention capability for Pd(II) even at the absorbed dose of 800 kGy. The chromatographic separation of metal ions was demonstrated with the adsorbent packed column, there is no influence of Re(VII) (instead of Tc) on the excellent separation behavior of Pd(II). (authors)

  3. Platinum recycling in the United States in 1998

    USGS Publications Warehouse

    Hilliard, Henry E.

    2001-01-01

    In the United States, catalytic converters are the major source of secondary platinum for recycling. Other sources of platinum scrap include reforming and chemical process catalysts. The glass industry is a small but significant source of platinum scrap. In North America, it has been estimated that in 1998 more than 20,000 kilograms per year of platinum-group metals from automobile catalysts were available for recycling. In 1998, an estimated 7,690 kilograms of platinum were recycled in the United States. U.S. recycling efficiency was calculated to have been 76 percent in 1998; the recycling rate was estimated at 16 percent.

  4. Structural Preferences in Phosphanylthiolato Platinum(II) Complexes.

    PubMed

    Duran, Josep; Polo, Alfonso; Real, Julio; Benet-Buchholz, Jordi; Solà, Miquel; Poater, Albert

    2016-02-01

    The transition-metal complexes of heterotopic phosphanylthiolato ligands are useful in various reactions which depend on the stereochemistry of the complexes. Bis-chelate complex [Pt(SCH2CH2PPh2-κ(2) P,S)2] (1) was obtained in good yields by direct base-free substitution reaction of the corresponding phosphanylthiol (HSCH2CH2PPh2) with K2PtCl4 or by oxidative addition of the same phosphanylthiol to Pt(PPh3)4. In agreement with the antisymbiosis rule, complex 1 shows a cis-P,P arrangement in solid state crystallizing in the monoclinic system (C2/c). Density functional theory (DFT) calculations on 1 reveal the right characteristics for the preferred cis-P,P arrangement, rationalizing its formation. Direct base-free reaction of [PtCl2(1,5-cyclooctadiene)] with one equivalent of the same phosphanylthiol produce the trinuclear complex [PtCl(μ-SCH2CH2PPh2-κ(2) P,S)]3 (2) instead of the binuclear structure common in palladium and nickel derivatives. Crystals of 2 are triclinic (P 1‾ ) showing a sulfur-bridging edge-sharing cyclic trinuclear complex with square-planar coordination geometry around the platinum atoms and a Pt3S3 cycle in skew-boat conformation. This preference for the trinuclear structure was rationalized mechanistically and through conceptual DFT. PMID:27308212

  5. Structural Preferences in Phosphanylthiolato Platinum(II) Complexes

    PubMed Central

    Duran, Josep; Real, Julio; Benet‐Buchholz, Jordi; Solà, Miquel

    2015-01-01

    Abstract The transition‐metal complexes of heterotopic phosphanylthiolato ligands are useful in various reactions which depend on the stereochemistry of the complexes. Bis‐chelate complex [Pt(SCH2CH2PPh2‐κ2 P,S)2] (1) was obtained in good yields by direct base‐free substitution reaction of the corresponding phosphanylthiol (HSCH2CH2PPh2) with K2PtCl4 or by oxidative addition of the same phosphanylthiol to Pt(PPh3)4. In agreement with the antisymbiosis rule, complex 1 shows a cis‐P,P arrangement in solid state crystallizing in the monoclinic system (C2/c). Density functional theory (DFT) calculations on 1 reveal the right characteristics for the preferred cis‐P,P arrangement, rationalizing its formation. Direct base‐free reaction of [PtCl2(1,5‐cyclooctadiene)] with one equivalent of the same phosphanylthiol produce the trinuclear complex [PtCl(μ‐SCH2CH2PPh2‐κ2 P,S)]3 (2) instead of the binuclear structure common in palladium and nickel derivatives. Crystals of 2 are triclinic (P 1‾ ) showing a sulfur‐bridging edge‐sharing cyclic trinuclear complex with square‐planar coordination geometry around the platinum atoms and a Pt3S3 cycle in skew‐boat conformation. This preference for the trinuclear structure was rationalized mechanistically and through conceptual DFT. PMID:27308212

  6. Control of Metal Nanocrystal Size Reveals Metal-Support Interface Role for Ceria Catalysts

    SciTech Connect

    Cargnello, M; Doan-Nguyen, VVT; Gordon, TR; Diaz, RE; Stach, EA; Gorte, RJ; Fornasiero, P; Murray, CB

    2013-08-15

    Interactions between ceria (CeO2) and supported metals greatly enhance rates for a number of important reactions. However, direct relationships between structure and function in these catalysts have been difficult to extract because the samples studied either were heterogeneous or were model systems dissimilar to working catalysts. We report rate measurements on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals. We found that carbon monoxide oxidation in ceria-based catalysts is greatly enhanced at the ceria-metal interface sites for a range of group VIII metal catalysts, clarifying the pivotal role played by the support.

  7. Combination of three metals for the treatment of cancer: gallium, rhenium and platinum. 1. Determination of the optimal schedule of treatment.

    PubMed

    Collery, Philippe; Mohsen, Ahmed; Kermagoret, Anthony; D'Angelo, Jean; Morgant, Georges; Desmaele, Didier; Tomas, Alain; Collery, Thomas; Wei, Ming; Badawi, Abdelfattah

    2012-07-01

    Platinum is well known for its anticancer activity, firstly used as cis-diaminedichloroplatinum (II) (CDDP), with a wide range of activity. Its main mechanism of action involves its binding to DNA. Gallium, another metal, has also demonstrated apoptotic effects on malignant cells, but through interaction with targets other than DNA, such as the membrane, cytoskeleton and proteasome, and on enzyme activities. An antitumor synergism between CDDP and both gallium and rhenium compounds has been demonstrated. For these reasons, we proposed to combine these three metals and to determine at which doses each compound could be administered without major toxicity. CDDP, tetrakis(1-octanol) tris(5-aminosalicylate)gallium(III), and a diseleno-ether rhenium(I) complex were used in this experimental study in breast cancer MCF-7 tumor-bearing mice. CDDP was administered intraperitoneally (i.p.) twice a week at the dose of 3 mg/kg. Tetrakis(1-octanol) tris(5-aminosalicylate) gallium (III) and rhenium(I) diseleno-ether complexes were administered orally, daily, five days a week for three weeks, at doses ranging from 20 to 100 mg/kg for the gallium compound and from 10 to 50 mg/kg for the rhenium compound. Doses of 10 mg/kg of rhenium(I) diseleno-ether, and 100 mg/kg of the salicylate gallium compound, in combination with CDDP induced a significant decrease of 50% of the tumor volume, by comparison with the control group. In contrast, the decrease of the tumor volume in mice treated by CDDP alone was less than 25%. Changes in the sequence of administration of the three metals will be discussed to improve the therapeutic index.

  8. Growth of transition metals on cerium tungstate model catalyst layers

    NASA Astrophysics Data System (ADS)

    Skála, T.; Tsud, N.; Stetsovych, V.; Mysliveček, J.; Matolín, V.

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed.

  9. Growth of transition metals on cerium tungstate model catalyst layers.

    PubMed

    Skála, T; Tsud, N; Stetsovych, V; Mysliveček, J; Matolín, V

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed. PMID:27494195

  10. Stabilizing platinum in phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Remick, R. J.

    1981-01-01

    The cathode of the phosphoric acid fuel cell uses a high surface area platinum catalyst supported on a carbon substrate. During operation, the small platinum crystallites sinter, causing loss in cell performance. A support was developed that stabilizes platinum in the high surface area condition by retarding or preventing the sintering process. The approach is to form etch pits in the carbon by oxidizing the carbon in the presence of a metal oxide catalyst, remove the metal oxide by an acid wash, and then deposit platinum in these pits. Results confirm the formation of etch pits in each of the three supports chosen for investigation: Vulcan XC-72R, Vulcan XC-72 that was graphized at 2500 C, and Shawinigan Acetylene Black.

  11. Concentrations of platinum group elements in 122 U.S. coal samples

    USGS Publications Warehouse

    Oman, C.L.; Finkelman, R.B.; Tewalt, S.J.

    1997-01-01

    Analysis of more than 13,000 coal samples by semi-quantitative optical emission spectroscopy (OES) indicates that concentrations of the platinum group elements (iridium, palladium, platinum, osmium, rhodium, and ruthenium) are less than 1 ppm in the ash, the limit of detection for this method of analysis. In order to accurately determine the concentration of the platinum group elements (PGE) in coal, additional data were obtained by inductively coupled plasma mass spectroscopy, an analytical method having part-per-billion (ppb) detection limits for these elements. These data indicate that the PGE in coal occur in concentrations on the order of 1 ppb or less.

  12. Morphology of the base of the J-M Reef Package and its bearing on the localization of platinum group metal mineralization in the Stillwater Complex, Montana

    SciTech Connect

    Wolfgram, D. . Dept. of Geological Engineering); Evans-Holmgren, J.A.

    1993-04-01

    Economic concentrations of platinum group metals (PGM) in the Stillwater Complex are typically localized within a unique lithologic sequence, the J-M Reef Package. The J-M Reef Package is generally believed to be the result of the influx of a pulse of undifferentiated' magma into the chamber subsequent to the appearance of plagioclase as a cumulus mineral in the more differentiated resident melt. Underground workings of Stillwater Mining Company, together with over 3,000 underground core holes on 50-foot centers, facilitate the definition of the igneous stratigraphy below the J-M Reef Package and the relationship of its base to it. As much as 350 feet of consolidated footwall igneous cumulates were removed by thermochemical ablation in terraced channels prior to the accumulation of the J-M Reef Package. Distribution of PGM mineralization within the J-M Reef Package, as well as the differential accumulation of the Reef Package itself, is related to channel morphology. Models of ore genesis must account for a new magma pulse that debouched with vigor along the top of the pre-existing cumulus pile.

  13. Facet effects of palladium nanocrystals for oxygen reduction in ionic liquids and for sensing applications

    NASA Astrophysics Data System (ADS)

    Tang, Yongan; Chi, Xiaowei; Zou, Shouzhong; Zeng, Xiangqun

    2016-03-01

    Palladium nanocrystals enclosed by {100} and {110} crystal facets, were successfully synthesized through an aqueous one-pot synthesis method. A new thermal annealing approach was developed for fabricating these palladium nanocrystals as a working electrode on a gas permeable membrane to study the facet effects of the oxygen reduction process in an ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Bmpy][NTf2]). Results were compared with the same processes at a conventional platinum electrode. Our study shows that the structural difference between the two facets of Pd nanocrystals has little effect on the oxygen reduction process but significantly affects the oxidation process of the superoxide. It is found that the Pd{110}/IL interface can better stabilize superoxide radicals revealed by a more positive oxidation potential compared to that of Pd{100}. In addition, the analytical characteristic of utilizing both palladium nanocrystals as electrodes for oxygen sensing is comparable with a polycrystal platinum oxygen sensor, in which Pd{110} presents the best sensitivity and lowest detection limit. Our results demonstrate the facet-dependence of oxygen reduction in an ionic liquid medium and provide the fundamental information needed to guide the applications of palladium nanocrystals in electrochemical gas sensor and fuel cell research.Palladium nanocrystals enclosed by {100} and {110} crystal facets, were successfully synthesized through an aqueous one-pot synthesis method. A new thermal annealing approach was developed for fabricating these palladium nanocrystals as a working electrode on a gas permeable membrane to study the facet effects of the oxygen reduction process in an ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Bmpy][NTf2]). Results were compared with the same processes at a conventional platinum electrode. Our study shows that the structural difference between the two facets of Pd

  14. Platinum-group element signatures in the North Atlantic Igneous Province: Implications for mantle controls on metal budgets during continental breakup

    NASA Astrophysics Data System (ADS)

    Hughes, Hannah S. R.; McDonald, Iain; Kerr, Andrew C.

    2015-09-01

    The North Atlantic Igneous Province (NAIP) is a large igneous province (LIP) that includes a series of lava suites erupted from the earliest manifestations of the (proto)-Icelandic plume, through continental rifting and ultimate ocean opening. The lavas of one of these sub-provinces, the British Palaeogene Igneous Province (BPIP), were some of the first lavas to be erupted in the NAIP and overlie a thick crustal basement and sedimentary succession with abundant S-rich mudrocks. We present the first platinum-group element (PGE) and Au analyses of BPIP flood basalts from the main lava fields of the Isle of Mull and Morvern and the Isle of Skye, in addition to a suite of shallow crustal dolerite volcanic plugs on Mull, and other minor lavas suites. BPIP lavas display both S-saturated and S-undersaturated trends which, coupled with elevated PGE abundances (> MORB), suggest that the BPIP is one of the most prospective areas of the NAIP to host Ni-Cu-PGE-(Au) mineralisation in conduit systems. Platinum-group element, Au and chalcophile element abundances in lavas from West and East Greenland, and Iceland, are directly comparable to BPIP lavas, but the relative abundances of Pt and Pd vary systematically between lavas suites of different ages. The oldest lavas (BPIP and West Greenland) have a broadly chondritic Pt/Pd ratio (~ 1.9). Lavas from East Greenland have a lower Pt/Pd ratio (~ 0.8) and the youngest lavas from Iceland have the lowest Pt/Pd ratio of the NAIP (~ 0.4). Hence, Pt/Pd ratio of otherwise equivalent flood basalt lavas varies temporally across the NAIP and appears to be coincident with the changing geodynamic environment of the (proto)-Icelandic plume through time. We assess the possible causes for such systematic Pt/Pd variation in light of mantle plume and lithospheric controls, and suggest that this reflects a change in the availability of lithospheric mantle Pt-rich sulphides for entrainment in ascending plume magmas. Hence the precious metal

  15. PLATINUM AND FUEL CELLS

    EPA Science Inventory

    Platinum requirements for fuel cell vehicles (FCVS) have been identified as a concern and possible problem with FCV market penetration. Platinum is a necessary component of the electrodes of fuel cell engines that power the vehicles. The platinum is deposited on porous electrodes...

  16. Combine palladium with iron for enhanced dechlorination

    SciTech Connect

    1995-07-01

    Research Corporation Technologies (RCT; Tucson, Arizona) is completing bench-scale testing of a new groundwater-treatment process that uses particles of palladium-coated iron to dechlorinate organic compounds. The palladized-iron process, developed by a research team at the University of Arizona, dechlorinates low-molecular-weight hydrocarbons by converting the chlorinated organics to chloride ions and either methane or ethane gas. A three-month test of an above-ground treatment unit is scheduled to begin in September. The key to the new process is the palladium. When elemental iron is immersed in water, it oxidizes and releases electrons, which create a reducing environment. This reducing environment breaks down chlorinated and fluorinated organic compounds. Unfortunately, a layer of metal oxide (rust) forms on the iron surface. This layer ultimately impedes the flow of electrons into the water and makes the reduction process slow and inefficient. To overcome this, RCT deposits a small amount (0.05 wt%) of palladium as discrete islands on the iron particles. This palladium prevents rust from coating the iron but does not impede the steady flow of the electrons needed to sustain a reducing environment.

  17. Preparation and characterization of magnetic nanoparticles for the on-line determination of gold, palladium, and platinum in mine samples based on flow injection micro-column preconcentration coupled with graphite furnace atomic absorption spectrometry.

    PubMed

    Ye, Juanjuan; Liu, Shuxia; Tian, Miaomiao; Li, Wanjun; Hu, Bin; Zhou, Weihong; Jia, Qiong

    2014-01-01

    A simple and highly selective procedure for on-line determination of trace levels of Au, Pd, and Pt in mine samples has been developed using flow injection-column adsorption preconcentration coupled with graphite furnace atomic absorption spectrophotometry (FI-column-GFAAS). The precious metals were adsorbed on the as-synthesized magnetic nanoparticles functionalized with 4'-aminobenzo-15-crown-5-ether packed into a micro-column and then eluted with 2% thiourea + 0.1 mol L(-1) HCl solution prior to the determination by GFAAS. The properties of the magnetic adsorbents were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Various experimental parameters affecting the preconcentration of Au, Pd, and Pt were investigated and optimized. Under the optimal experimental conditions, the detection limits of the developed technique were 0.16 ng mL(-1) for Au, 0.28 ng mL(-1) for Pd, and 1.01 ng mL(-1) for Pt, with enrichment factors of 24.3, 13.9, and 17.8, respectively. Precisions, evaluated as repeatability of results, were 1.1%, 3.9%, and 4.4% respectively for Au, Pd, and Pt. The developed method was validated by the analysis of Au, Pd, and Pt in certified reference materials and mine samples with satisfactory results.

  18. The Solid Phase Extraction of Some Metal Ions Using Palladium Nanoparticles Attached to Silica Gel Chemically Bonded by Silica-Bonded N-Propylmorpholine as New Sorbent prior to Their Determination by Flame Atomic Absorption Spectroscopy

    PubMed Central

    Ghaedi, M.; Rezakhani, M.; Khodadoust, S.; Niknam, K.; Soylak, M.

    2012-01-01

    In this research at first palladium nanoparticle attached to a new chemically bonded silica gel has been synthesized and has been characterized with different techniques such as X-ray diffraction (XRD), fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Then, this new sorbent (chemically modified silica gel with N-propylmorpholine (PNP-SBNPM)) was efficiently used for preconcentration of some metal ions in various food samples. The influence of effective variables including mass of sorbent, flow rate, pH of sample solutions and condition of eluent such as volume, type and concentration on the recoveries of understudy metal ions were investigated. Following the optimization of variables, the interfering effects of some foreign ions on the preconcentration and determination of the investigated metal ions described. At optimum values of variables, all investigated metal ions were efficiently recovered with efficiency more than 95%, relative standard deviation (RSD) between 2.4 and 2.8, and detection limit in the range of 1.4–2.7 ng mL−1. The present method is simple and rapidly applicable for the determination of the understudied metal ions (ng mL−1) in different natural food samples. PMID:22666150

  19. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    PubMed Central

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-01-01

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability. PMID:26133469

  20. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    DOE PAGESBeta

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; et al

    2015-07-02

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can bemore » attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. Ultimately, these results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.« less

  1. Characterization of electrochemically modified polycrystalline platinum surfaces

    SciTech Connect

    Krebs, L.C.; Ishida, Takanobu.

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between {minus}0.24 and +1.25 V{sub SCE} while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-{rho}-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  2. Aptamer selection for fishing of palladium ion using graphene oxide-adsorbed nanoparticles.

    PubMed

    Cho, Yea Seul; Lee, Eun Jeong; Lee, Gwan-Ho; Hah, Sang Soo

    2015-12-01

    A new aptamer selection method using graphene oxide (GO)-adsorbed nanoparticles (GO-adsorbed NPs) was employed for specific fishing of palladium ion. High affinity ssDNA aptamers were isolated through 13 rounds of selection and the capacity of the selected DNA aptamers for palladium ion uptake was measured, clarifying that DNA01 exhibits the highest affinity to palladium ion with a dissociation constant (Kd) of 4.60±1.17 μM. In addition, binding ability of DNA01 to palladium ion was verified against other metal ions, such as Li(+), Cs(+), Mg(2+), and Pt(2+). Results of the present study suggest that future modification of DNA01 may improve palladium ion-binding ability, leading to economic recovery of palladium from water solution.

  3. Rational Design of Porous Conjugated Polymers and Roles of Residual Palladium for Photocatalytic Hydrogen Production.

    PubMed

    Li, Lianwei; Cai, Zhengxu; Wu, Qinghe; Lo, Wai-Yip; Zhang, Na; Chen, Lin X; Yu, Luping

    2016-06-22

    Developing highly efficient photocatalyts for water splitting is one of the grand challenges in solar energy conversion. Here, we report the rational design and synthesis of porous conjugated polymer (PCP) that photocatalytically generates hydrogen from water splitting. The design mimics natural photosynthetics systems with conjugated polymer component to harvest photons and the transition metal part to facilitate catalytic activities. A series of PCPs have been synthesized with different light harvesting chromophores and transition metal binding bipyridyl (bpy) sites. The photocatalytic activity of these bpy-containing PCPs can be greatly enhanced due to the improved light absorption, better wettability, local ordering structure, and the improved charge separation process. The PCP made of strong and fully conjugated donor chromophore DBD (M4) shows the highest hydrogen production rate at ∼33 μmol/h. The results indicate that copolymerization between a strong electron donor and weak electron acceptor into the same polymer chain is a useful strategy for developing efficient photocatalysts. This study also reveals that the residual palladium in the PCP networks plays a key role for the catalytic performance. The hydrogen generation activity of PCP photocatalyst can be further enhanced to 164 μmol/h with an apparent quantum yield of 1.8% at 350 nm by loading 2 wt % of extra platinum cocatalyst. PMID:27254306

  4. Rational Design of Porous Conjugated Polymers and Roles of Residual Palladium for Photocatalytic Hydrogen Production.

    PubMed

    Li, Lianwei; Cai, Zhengxu; Wu, Qinghe; Lo, Wai-Yip; Zhang, Na; Chen, Lin X; Yu, Luping

    2016-06-22

    Developing highly efficient photocatalyts for water splitting is one of the grand challenges in solar energy conversion. Here, we report the rational design and synthesis of porous conjugated polymer (PCP) that photocatalytically generates hydrogen from water splitting. The design mimics natural photosynthetics systems with conjugated polymer component to harvest photons and the transition metal part to facilitate catalytic activities. A series of PCPs have been synthesized with different light harvesting chromophores and transition metal binding bipyridyl (bpy) sites. The photocatalytic activity of these bpy-containing PCPs can be greatly enhanced due to the improved light absorption, better wettability, local ordering structure, and the improved charge separation process. The PCP made of strong and fully conjugated donor chromophore DBD (M4) shows the highest hydrogen production rate at ∼33 μmol/h. The results indicate that copolymerization between a strong electron donor and weak electron acceptor into the same polymer chain is a useful strategy for developing efficient photocatalysts. This study also reveals that the residual palladium in the PCP networks plays a key role for the catalytic performance. The hydrogen generation activity of PCP photocatalyst can be further enhanced to 164 μmol/h with an apparent quantum yield of 1.8% at 350 nm by loading 2 wt % of extra platinum cocatalyst.

  5. Palladium(II)-Catalyzed Annulation between ortho-Alkenylphenols and Allenes. Key Role of the Metal Geometry in Determining the Reaction Outcome

    PubMed Central

    2016-01-01

    2-Alkenylphenols react with allenes, upon treatment with catalytic amounts of Pd(II) and Cu(II), to give benzoxepine products in high yields and with very good regio- and diastereoselectivities. This contrasts with the results obtained with Rh catalysts, which provided chromene-like products through a pathway involving a β-hydrogen elimination step. Computational studies suggest that the square planar geometry of the palladium is critical to favor the reductive elimination process required for the formation of the oxepine products. PMID:27807509

  6. Method for the preparation of metal colloids in inverse micelles and product preferred by the method

    DOEpatents

    Wilcoxon, Jess P.

    1992-01-01

    A method is provided for preparing catalytic elemental metal colloidal particles (e.g. gold, palladium, silver, rhodium, iridium, nickel, iron, platinum, molybdenum) or colloidal alloy particles (silver/iridium or platinum/gold). A homogeneous inverse micelle solution of a metal salt is first formed in a metal-salt solvent comprised of a surfactant (e.g. a nonionic or cationic surfactant) and an organic solvent. The size and number of inverse micelles is controlled by the proportions of the surfactant and the solvent. Then, the metal salt is reduced (by chemical reduction or by a pulsed or continuous wave UV laser) to colloidal particles of elemental metal. After their formation, the colloidal metal particles can be stabilized by reaction with materials that permanently add surface stabilizing groups to the surface of the colloidal metal particles. The sizes of the colloidal elemental metal particles and their size distribution is determined by the size and number of the inverse micelles. A second salt can be added with further reduction to form the colloidal alloy particles. After the colloidal elemental metal particles are formed, the homogeneous solution distributes to two phases, one phase rich in colloidal elemental metal particles and the other phase rich in surfactant. The colloidal elemental metal particles from one phase can be dried to form a powder useful as a catalyst. Surfactant can be recovered and recycled from the phase rich in surfactant.

  7. Ozone sensing based on palladium decorated carbon nanotubes.

    PubMed

    Colindres, Selene Capula; Aguir, Khalifa; Cervantes Sodi, Felipe; Vargas, Luis Villa; Salazar, José Moncayo; Febles, Vicente Garibay

    2014-04-14

    Multiwall carbon nanotubes (MWCNTs) were easily and efficiently decorated with Pd nanoparticles through a vapor-phase impregnation-decomposition method starting from palladium acetylacetonates. The sensor device consisted on a film of sensitive material (MWCNTs-Pd) deposited by drop coating on platinum interdigitated electrodes on a SiO₂ substrate. The sensor exhibited a resistance change to ozone (O₃) with a response time of 60 s at different temperatures and the capability of detecting concentrations up to 20 ppb. The sensor shows the best response when exposed to O3 at 120 °C. The device shows a very reproducible sensor performance, with high repeatability, full recovery and efficient response.

  8. Ceramic-metal composite article and joining method

    DOEpatents

    Kang, Shinhoo; Selverian, John H.; Kim, Hans J.; Dunn, Edmund M.; Kim, Kyung S.

    1992-01-01

    A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof.

  9. Ceramic-metal composite article and joining method

    DOEpatents

    Kang, S.; Selverian, J.H.; Kim, H.J.; Dunn, E.M.; Kim, K.S.

    1992-04-28

    A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod is described. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof. 4 figs.

  10. Organometallic palladium reagents for cysteine bioconjugation.

    PubMed

    Vinogradova, Ekaterina V; Zhang, Chi; Spokoyny, Alexander M; Pentelute, Bradley L; Buchwald, Stephen L

    2015-10-29

    Reactions based on transition metals have found wide use in organic synthesis, in particular for the functionalization of small molecules. However, there are very few reports of using transition-metal-based reactions to modify complex biomolecules, which is due to the need for stringent reaction conditions (for example, aqueous media, low temperature and mild pH) and the existence of multiple reactive functional groups found in biomolecules. Here we report that palladium(II) complexes can be used for efficient and highly selective cysteine conjugation (bioconjugation) reactions that are rapid and robust under a range of bio-compatible reaction conditions. The straightforward synthesis of the palladium reagents from diverse and easily accessible aryl halide and trifluoromethanesulfonate precursors makes the method highly practical, providing access to a large structural space for protein modification. The resulting aryl bioconjugates are stable towards acids, bases, oxidants and external thiol nucleophiles. The broad utility of the bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody-drug conjugates. These palladium complexes show potential as benchtop reagents for diverse bioconjugation applications.

  11. Synthesis, optical properties and ultrafast electronic relaxation of metal (silver, gold, platinum) and manganese(2+)-doped zinc sulfide nanoparticles

    NASA Astrophysics Data System (ADS)

    Smith, Brian Ampere

    Ultrafast transient absorption and time-dependent luminescence spectroscopy have been performed on metal (Ag, Au, Pt) and semiconductor (Mn2+ doped ZnS) nanoparticles respectively. In metal nanoparticles it was found that the decay dynamics exhibit a complex size and surface dependence. Specifically, the photoinduced dynamics show an exponential time constant that is longer than the same in bulk for particle sizes of 4-40 nm. When particle size is reduced further the plasmon band is drastically broadened and the relaxation time constant is similar to bulk. Upon reducing the size still further to only 13 atoms per cluster a much longer electronic relaxation is observed. These results are attributed to an intrinsic size dependent reduction in the electron-phonon coupling when particle size is reduced. This slows down the electronic relaxation compared to bulk. The increase in the number of surface collisions for very small particles increases the rate of electronic relaxation relative to larger particles. For particles on the order of 13 atoms the excitation is more singular in nature and the long relaxation is attributed to the fact that the excited species is a molecular as opposed to a fermi system. Also, the synthesis and luminescence decay kinetics of 1.2 nm Mn 2+ doped ZnS nanoclusters grown in reverse micelles are reported. The preparation method produces small particles with narrow size distribution and fluorescence bands near 400-450 nm and 585 nm. Time-dependent fluorescence decay measurements using picosecond, nanosecond and millisecond techniques reveal relaxation processes on all three time scales. In the doped sample, the red emission detected at 600 nm exhibits an 1-2 ms decay in addition to faster decays with time constants on the order of hundreds of ps, a few ns and tens of μs. While the slow decay is the same as that of bulk Mn 2+ doped ZnS, the fast decays are present for both doped and undoped samples and are unique to nanocluster ZnS, which are

  12. Hydrogenation of cottonseed oil with nickel, palladium and platinum catalysts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A number of commercial catalysts have been used to study hydrogenation of cottonseed oil, with the goal of minimizing trans fatty acid (TFA) content. Despite the different temperatures used, catalyst levels, and reaction times, the data from each catalyst type fall on the same curve when the TFA le...

  13. Ages and sources of components of Zn-Pb, Cu, precious metal, and platinum group element deposits in the goodsprings district, clark county, Nevada

    USGS Publications Warehouse

    Vikre, P.; Browne, Q.J.; Fleck, R.; Hofstra, A.; Wooden, J.

    2011-01-01

    The Goodsprings district, Clark County, Nevada, includes zinc-dominant carbonate replacement deposits of probable late Paleozoic age, and lead-dominant carbonate replacement deposits, copper ?? precious metal-platinum group element (PGE) deposits, and gold ?? silver deposits that are spatially associated with Late Triassic porphyritic intrusions. The district encompasses ??500 km2 although the distribution of all deposits has been laterally condensed by late Mesozoic crustal contraction. Zinc, Pb, and Cu production from about 90 deposits was ??160,000 metric tons (t) (Zn > Pb >> Cu), 2.1 million ounces (Moz) Ag, 0.09 Moz Au, and small amounts of PGEs-Co, V, Hg, Sb, Ni, Mo, Mn, Ir, and U-were also recovered. Zinc-dominant carbonate replacement deposits (Zn > Pb; Ag ?? Cu) resemble Mississippi Valley Type (MVT) Zn-Pb deposits in that they occur in karst and fault breccias in Mississippian limestone where the southern margin of the regional late Paleozoic foreland basin adjoins Proterozoic crystalline rocks of the craton. They consist of calcite, dolomite, sphalerite, and galena with variably positive S isotope compositions (??34S values range from 2.5-13%), and highly radiogenic Pb isotope compositions (206Pb/204Pb >19), typical of MVT deposits above crystalline Precambrian basement. These deposits may have formed when southward flow of saline fluids, derived from basinal and older sedimentary rocks, encountered thinner strata and pinch-outs against the craton, forcing fluid mixing and mineral precipitation in karst and fault breccias. Lead-dominant carbonate replacement deposits (Pb > Zn, Ag ?? Cu ?? Au) occur among other deposit types, often near porphyritic intrusions. They generally contain higher concentrations of precious metals than zinc-dominant deposits and relatively abundant iron oxides after pyrite. They share characteristics with copper ?? precious metal- PGE and gold ?? silver deposits including fine-grained quartz replacement of carbonate minerals in

  14. Petrology, geochemistry and the mechanisms determining the distribution of platinum-group element and base metal sulphide mineralisation in the Platreef at Overysel, northern Bushveld Complex, South Africa

    NASA Astrophysics Data System (ADS)

    Holwell, David A.; McDonald, Iain

    2006-09-01

    Platinum-group element (PGE) mineralisation within the Platreef at Overysel is controlled by the presence of base metal sulphides (BMS). The floor rocks at Overysel are Archean basement gneisses, and unlike other localities along the strike of the Platreef where the floor is comprised of Transvaal Supergroup sediments, the intimate PGE-BMS relationship holds strong into the footwall rocks. Decoupling of PGE from BMS is rare and the BMS and platinum-group mineral assemblages in the Platreef and the footwall are almost identical. There is minimal overprinting by hydrothermal fluids; therefore, the mineralisation style present at Overysel may represent the most ‘primary’ style of Platreef mineralisation preserved anywhere along the strike. Chondrite-normalised PGE profiles reveal a progressive fractionation of the PGE with depth into the footwall, with Ir, Ru and Rh dramatically depleted with depth compared to Pt, Pd and Au. This feature is not observed at Sandsloot and Zwartfontein, to the south of Overysel, where the footwall rocks are carbonates. There is evidence from rare earth element abundances and the amount of interstitial quartz towards the base of the Platreef pyroxenites that contamination by a felsic melt derived from partial melting of the gneissic footwall has taken place. Textural evidence in the gneisses suggests that a sulphide liquid percolated down into the footwall through a permeable, inter-granular network that was produced by partial melting around grain boundaries in the gneisses that was induced by the intrusion of the Platreef magma. PGE were originally concentrated within a sulphide liquid in the Platreef magma, and the crystallisation of monosulphide solid solution from the sulphide liquid removed the majority of the IPGE and Rh from it whilst still within the mafic Platreef. Transport of PGE into the gneisses, via downward migration of the residual sulphide liquid, fractionated out the remaining IPGE and Rh in the upper parts of the

  15. The influence of metal and carrier natures on the effectiveness of catalysts of the deoxygenation of fatty acids into hydrocarbons

    NASA Astrophysics Data System (ADS)

    Berenblyum, A. S.; Shamsiev, R. S.; Podoplelova, T. A.; Danyushevsky, V. Ya.

    2012-08-01

    The activity and selectivity of palladium, copper, platinum, and nickel catalysts in the decarbonylation of stearic acid into hydrocarbons were studied at a 14 atm hydrogen pressure and temperatures of 300-350°C. If γ-alumina was used as a carrier, the catalysts formed the series Pd > Cu > Pt > Ni according to desired product yields. Quantum-chemical simulation was performed to show that the free energy of activation increased in the same series. The same metals deposited on mixed tungsten and zirconium oxides catalyzed decarbonylation with a low yield of C17 hydrocarbons, likely because such a superacidic carrier could catalyse cracking of olefins or their oligomers formed.

  16. Platinum Metal-Free Catalysts for Selective Soft Oxidative Methane → Ethylene Coupling. Scope and Mechanistic Observations.

    PubMed

    Peter, Matthias; Marks, Tobin J

    2015-12-01

    Using abundant soft oxidants, a high methane-to-ethylene conversion might be achievable due to the low thermodynamic driving force for over-oxidation. Here we report on the oxidative coupling of methane by gaseous S2 (SOCM). The catalytic properties of Pd/Fe3O4 are compared with those of Fe3O4, and it is found that high ethylene selectivities can be achieved without noble metals; conversion and selectivity on Fe3O4 are stable for at least 48 h at SOCM conditions. SOCM data for 10 oxides are compared, and ethylene selectivities as high as 33% are found; the C2H4/C2H6 ratios of 9-12 observed at the highest S2 conversions are significantly higher than the C2H4/C2H6 ratios usually found in the CH4 coupling with O2. Complementary in-detail analytical studies show that, on Mg, Zr, Sm, W, and La catalysts, which strongly coke during the reaction, lower ethylene selectivities are observed than on Fe, Ti, and Cr catalysts, which only coke to a minor extent. Further catalyst-dependent changes during SOCM in surface area, surface composition, and partial conversion to oxysulfides and sulfides are discussed. Evidence concerning the reaction mechanism is obtained taking into account the selectivity for the different reaction products versus the contact time. CH4 coupling proceeds non-oxidatively with the evolution of H2 on some catalysts, and evidence is presented that C2H4 and C2H2 formation occur via C2H6 and C2H4 dehydrogenation, respectively. PMID:26551955

  17. Platinum stable isotopes in ferromanganese crust and nodules

    NASA Astrophysics Data System (ADS)

    Corcoran, Loretta; Seward, Terry; Handler, Monica R.

    2015-04-01

    Hydrogenetic ferromanganese (Fe-Mn) crust and nodules are slow-growing chemical sediments that form by direct precipitation from seawater, resulting in a record of changing seawater chemistry. These sediments are the primary sink for platinum in the modern oxic marine environment, hosting well-documented enrichments over other platinum-group elements (PGEs): the Pt anomaly [1]. Platinum is a non-bio-essential, highly siderophile, transition metal with six stable isotopes (190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt) with several oxidation states (Pt0, Pt2+ and Pt4+). Platinum is generally considered to exist in the hydrosphere as Pt2+ although its behaviour in the marine environment is poorly constrained, and Pt4+may also be present. Variations in ocean redox state, together with changes in source fluxes to the oceans, may therefore lead to small variations (< ±1) in the stable isotopic composition of marine platinum, raising the potential of adding platinum to the growing arsenal of paleoceanographic tracers. A method has been developed to measure the platinum isotopic composition using double spike MC-ICPMS analysis [2]and applied to a global suite of modern Fe-Mn crust and nodules. Combining synchrotron XAFS analyses of platinum adsorbed onto Fe-Mn oxide and oxyhydroxide surfaces to determine oxidation state and bonding environment, with platinum stable isotopic measurements allowing us to evaluate both platinum incorporation onto these sediments and the associated degree of platinum isotopic fractionation. Leaching experiments conducted on platinum rich terrestrial materials underwent platinum stable isotopic measurement as an analogue for the Pt isotopic fractionation associated with continental weathering. [1] Hodge, V.F. et al. (1985) Earth and Planetary Science Letters, 72, 158-162. [2] Creech, J. et al. (2013) Journal of Analytical Atomic Spectrometry, 28. 853-865.

  18. Molecular studies of model surfaces of metals from single crystals to nanoparticles under catalytic reaction conditions. Evolution from prenatal and postmortem studies of catalysts.

    PubMed

    Somorjai, Gabor A; Aliaga, Cesar

    2010-11-01

    Molecular level studies of metal crystal and nanoparticle surfaces under catalytic reaction conditions at ambient pressures during turnover were made possible by the use of instruments developed at the University of California at Berkeley. Sum frequency generation vibrational spectroscopy (SFGVS), owing to its surface specificity and sensitivity, is able to identify the vibrational features of adsorbed monolayers of molecules. We identified reaction intermediates, different from reactants and products, under reaction conditions and for multipath reactions on metal single crystals and nanoparticles of varying size and shape. The high-pressure scanning tunneling microscope (HP-STM) revealed the dynamics of a catalytically active metallic surface by detecting the mobility of the adsorbed species during catalytic turnover. It also demonstrated the reversible and adsorbate-driven surface restructuring of platinum when exposed to molecules such as CO and ethylene. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) detected the reversible changes of surface composition in rhodium-palladium, platinum-palladium, and other bimetallic nanoparticles as the reactant atmosphere changed from oxidizing to reducing. It was found that metal nanoparticles of less than 2 nm in size are present in higher oxidation states, which alters and enhances their catalytic activity. The catalytic nanodiode (CND) confirmed that a catalytic reaction-induced current flow exists at oxide-metal interfaces, which correlates well with the reaction turnover.

  19. Biomonitoring of traffic police officers exposed to airborne platinum

    PubMed Central

    Iavicoli, I; Bocca, B; Petrucci, F; Senofonte, O; Carelli, G; Alimonti, A; Caroli, S

    2004-01-01

    Background: Over the past two decades there has been a substantial increase in environmental levels of palladium, platinum, and rhodium, the platinum group elements (PGEs), due to the widespread use of catalytic converters for automotive traction. Aim: To evaluate urinary platinum levels in occupationally exposed subjects. Methods: A total of 161 employees from the Rome City Police Force were studied; 103 were traffic police involved in controlling streets with an average flow of vehicles, while the remaining 58 were control subjects engaged only in office work. Platinum quantification in the urine samples of these subjects was carried out by sector field inductively coupled plasma mass spectrometry. Results: There were no statistically significant differences between platinum levels in the group of subjects engaged in traffic control and the control group (4.45 (2.42) ng/l v 4.56 (2.84) ng/l, respectively). Conclusions: Urinary levels were found to be higher than those reported for other urban populations, thus showing a progressive increase in human exposure to Pt. PMID:15208381

  20. Platinum(II)-Oligonucleotide Coordination Based Aptasensor for Simple and Selective Detection of Platinum Compounds.

    PubMed

    Cai, Sheng; Tian, Xueke; Sun, Lianli; Hu, Haihong; Zheng, Shirui; Jiang, Huidi; Yu, Lushan; Zeng, Su

    2015-10-20

    Wide use of platinum-based chemotherapeutic regimens for the treatment for carcinoma calls for a simple and selective detection of platinum compound in biological samples. On the basis of the platinum(II)-base pair coordination, a novel type of aptameric platform for platinum detection has been introduced. This chemiluminescence (CL) aptasensor consists of a designed streptavidin (SA) aptamer sequence in which several base pairs were replaced by G-G mismatches. Only in the presence of platinum, coordination occurs between the platinum and G-G base pairs as opposed to the hydrogen-bonded G-C base pairs, which leads to SA aptamer sequence activation, resulting in their binding to SA coated magnetic beads. These Pt-DNA coordination events were monitored by a simple and direct luminol-peroxide CL reaction through horseradish peroxidase (HRP) catalysis with a strong chemiluminescence emission. The validated ranges of quantification were 0.12-240 μM with a limit of detection of 60 nM and selectivity over other metal ions. This assay was also successfully used in urine sample determination. It will be a promising candidate for the detection of platinum in biomedical and environmental samples.

  1. Fabrication, characteristics and electrical model of an ionic polymer metal-carbon nanotube composite

    NASA Astrophysics Data System (ADS)

    He, Qingsong; Song, Linlin; Yu, Min; Dai, ZhenDong

    2015-07-01

    We develop an ionic polymer metal-carbon nanotube composite (IPMCC) actuator composed of a multiwalled carbon nanotube (MWCNT)/Nafion membrane sandwiched between two hybrid electrodes, composed of palladium, platinum and MWCNTs. The surface morphology and cross-sectional structure of the metal-carbon nanotube hybrid electrode were observed using scanning electron microscopy (SEM). SEM investigation indicated that the MWCNT layer can adhere very well with the platinum-palladium metal electrode, fill the cracks in the metal surface, and prevent the oxidation of nanoscale platinum particles. These observations show that the surface resistance of the total electrode is retained and the stability of electrode property is maintained. The displacement, blocking force and nonlinear current versus voltage (V-I) characteristics were measured. Compared with an ionic polymer metal composite (IPMC), the IPMCC shows a more stable displacement and blocking force under 1, 1.2 and 2 V at 0.1 Hz, and 2.34-3.29 times higher effective air-operating time under 3 V at 0.1 Hz. It can be observed from the V-I characteristics that the change in shape becomes significant at amplitudes higher than 1.2 V. An equivalent circuit is used to model the nonlinear behavior of the IPMCC, in which the leakage current was taken into account and analyzed. The values of the components in the circuit are estimated and electrical behavior is simulated by using the Pspice software. Compared with the model with no consideration of the leakage current, the simulations obtained by the model considering leakage current showed better agreement with the experimental results. The impressive leakage current (20 mA), which is successfully simulated by the proposed model with the nonlinear circuit, is shown to play an important role in the total current.

  2. New silylated iminophosphorano(amino)phosphines Me(3)SiN=PPh(2)N(R)PPh(2) (R = Et, (n)Pr, (n)Bu). Crystal and molecular structure of trimethylsilyliminophosphorano(propylamino)diphenylphosphine Me(3)SiN=PPh(2)N((n)Pr)PPh(2). Further oxidative derivatization with S, Se, and azides, titanium(IV) transmetalation of the imine, and syntheses of rhodium(I), palladium(II), and platinum(II) complexes of these iminophosphorano(amino)phosphines.

    PubMed

    Balakrishna, M S; Teipel, S; Pinkerton, A A; Cavell, R G

    2001-04-01

    Bis(phosphino)amines Ph(2)PN(R)PPh(2) (R = Et, (n)Pr, (n)Bu) react with stoichiometric amounts of trimethylsilyl azide to give the trimethylsilyliminophosphorano(amino)phosphines Me(3)SiN=PPh(2)N(R)PPh(2) (1, R = Et; 2, R = (n)Pr; 3, R = (n)Bu) as crystalline compounds. The structure of 2 has been determined by single-crystal X-ray analysis. (Crystal data for 2: monoclinic, P2(1)/c, a = 10.235(1) A, b = 16.802(2) A, c = 17.075(2) A, beta = 101.05(1) degrees, V = 2882.9(5) A(3), Z = 4.) The structure of 2, which is the first example of an iminophosphoranophosphine with the P(III)-N-P(V)=N skeleton, was solved by direct methods and refined to R = 0.044. Compound 2 readily reacts with elemental sulfur, selenium, or phosphoryl azide to give fully oxidized phosphinimines Ph(2)P(E)N((n)()Pr)Ph(2)P=NSiMe(3) (4, E = S; 5, E = Se; 6, E = NP(O)(OPh)(2)). Compounds 4-6 are very sensitive to moisture and readily undergo desilylation to give the parent phosphinimines Ph(2)P(E)N((n)()Pr)Ph(2)P=NH, which can be isolated as moderately stable crystalline solids. The phosphiniminophosphine 2 and the oxidized phosphinimines (4 and 5) react with CpTiCl(3) to give new nitrogen-bound Ti(IV) derivatives Ph(2)P(E)N((n)Pr)Ph(2)P=NTi(Cp)Cl(2) (10, E = lone pair; 11, E = S; 12, E = Se). Compounds 1-3 readily react with rhodium(I), palladium(II), and platinum(II) complexes to give five-membered metallacycles via phosphorus(III) and imine nitrogen coordination. PMID:11312734

  3. Uptake of platinum by zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis) and resulting effects on early embryogenesis.

    PubMed

    Osterauer, Raphaela; Haus, Nadine; Sures, Bernd; Köhler, Heinz-R

    2009-11-01

    Platinum group elements (PGEs), platinum, palladium and rhodium are widely used in automobile catalytic converters. PGEs are emitted into the environment and enter the aquatic ecosystem via runoff rainwater. The present study investigated the bioavailability of platinum chloride for the zebrafish (Danio rerio) and the ramshorn snail (Marisa cornuarietis) and determined the bioaccumulation rate of platinum. Applying the fish early life stage assay for D. rerio (DarT) and the Marisa embryo toxicity test ("Mariett") for M. cornuarietis, effects of platinum chloride on the embryonic development were investigated. Platinum concentrations tested in this study ranged from environmentally relevant concentrations of 38 ng L(-1) up to a concentration of 74.2 microg L(-1) for D. rerio and of 200 ngL(-1) up to 98.7 microg L(-1) for M. cornuarietis. Platinum was found to be accumulated in both organisms. Bioaccumulation factors (BAFs) were in the range of 5-55 for D. rerio and of 218.4-723.9 for M. cornuarietis, depending on the tested Pt concentrations. During the embryonic development, platinum was shown to alter the heart rate of both organisms already at the lowest tested concentration. At higher concentrations, platinum decelerated the hatching rate of the embryos of both species. Additionally, a retardation of the general development and a loss of weight due to platinum exposure was observed in M. cornuarietis. Results of this study contribute important data on the ecotoxicity of a rarely studied element.

  4. Strategies for the fabrication of porous platinum electrodes.

    PubMed

    Kloke, Arne; von Stetten, Felix; Zengerle, Roland; Kerzenmacher, Sven

    2011-11-16

    Porous platinum is of high technological importance due to its various applications in fuel cells, sensors, stimulation electrodes, mechanical actuators and catalysis in general. Based on a discussion of the general principles behind the reduction of platinum salts and corresponding deposition processes this article discusses techniques available for platinum electrode fabrication. The numerous, different strategies available to fabricate platinum electrodes are reviewed and discussed in the context of their tuning parameters, strengths and weaknesses. These strategies comprise bottom-up approaches as well as top-down approaches. In bottom-up approaches nanoparticles are synthesized in a fi rst step by chemical, photochemical or sonochemical means followed by an electrode formation step by e.g. thin fi lm technology or network formation to create a contiguous and conducting solid electrode structure. In top-down approaches fabrication starts with an already conductive electrode substrate. Corresponding strategies enable the fabrication of substrate-based electrodes by e.g. electrodeposition or the fabrication of self-supporting electrodes by dealloying. As a further top-down strategy, this review describes methods to decorate porous metals other than platinum with a surface layer of platinum. This way, fabrication methods not performable with platinum can be applied to the fabrication of platinum electrodes with the special benefit of low platinum consumption. PMID:22180890

  5. Gold–promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

    DOE PAGESBeta

    Kuttiyiel, Kurian A.; Sasaki, Kotaro; Su, Dong; Wu, Lijun; Zhu, Yimei; Adzic, Radoslav R.

    2014-11-06

    Considerable efforts to make palladium and palladium alloys active catalysts and a possible replacement for platinum have had a marginal success. Here, we report on a structurally ordered Au₁₀Pd₄₀Co₅₀ catalyst that exhibits comparable activity to conventional platinum catalysts in both acid and alkaline media. Electron microscopic techniques demonstrate that via addition of gold atoms PdCo nanoparticles undergo at elevated temperatures an atomic structural transition from core-shell to a rare intermetallic ordered structure with twin boundaries forming stable {111}, {110} and {100} facets. The superior stability of this catalyst compared to platinum after 10,000 potential cycles in alkaline media is attributedmore » to the atomic structural order of PdCo nanoparticles along with protective effect of clusters of gold atoms on the surface. This strategy of making ordered palladium intermetallic alloy nanoparticles can be used in diverse heterogeneous catalysis where particle size and structural stability matters.« less

  6. STRONTIUM AS AN EFFICIENT PROMOTER FOR SUPPORTED PALLADIUM HYDROGENATION CATALYSTS

    EPA Science Inventory

    The effect of strontium promotion is studied for a series of supported palladium catalysts such as Pd/zeolite-β, Pd/Al2O3, Pd/SiO2, Pd/hydrotalcite and Pd/MgO. Strontium is found to be an effective promoter for enhancing the metal area, perce...

  7. Silver-palladium braze alloy recovered from masking materials

    NASA Technical Reports Server (NTRS)

    Cierniak, R.; Colman, G.; De Carlo, F.

    1966-01-01

    Method for recovering powdered silver-palladium braze alloy from an acrylic spray binder and rubber masking adhesive used in spray brazing is devised. The process involves agitation and dissolution of masking materials and recovery of suspended precious metal particles on a filter.

  8. Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation

    NASA Astrophysics Data System (ADS)

    Primo, Ana; Neatu, Florentina; Florea, Mihaela; Parvulescu, Vasile; Garcia, Hermenegildo

    2014-10-01

    Catalysis makes possible a chemical reaction by increasing the transformation rate. Hydrogenation of carbon-carbon multiple bonds is one of the most important examples of catalytic reactions. Currently, this type of reaction is carried out in petrochemistry at very large scale, using noble metals such as platinum and palladium or first row transition metals such as nickel. Catalysis is dominated by metals and in many cases by precious ones. Here we report that graphene (a single layer of one-atom-thick carbon atoms) can replace metals for hydrogenation of carbon-carbon multiple bonds. Besides alkene hydrogenation, we have shown that graphenes also exhibit high selectivity for the hydrogenation of acetylene in the presence of a large excess of ethylene.

  9. Separation of metallic residues from the dissolution of a high-burnup BWR fuel using nitrogen trifluoride

    SciTech Connect

    McNamara, Bruce K.; Buck, Edgar C.; Soderquist, Chuck Z.; Smith, Frances N.; Mausolf, Edward J.; Scheele, Randall D.

    2014-03-23

    Nitrogen trifluoride (NF3) was used to fluorinate the metallic residue from the dissolution of a high burnup, boiling water reactor fuel (~70 MWd/kgU). The metallic residue included the noble metal phase (containing ruthenium, rhodium, palladium, technetium, and molybdenum), and smaller amounts of zirconium, selenium, tellurium, and silver. Exposing the noble metal phase to 10% NF3 in argon between 400 and 550°C, removed molybdenum and technetium near 400°C as their volatile fluorides, and ruthenium near 500C as its volatile fluoride. The events were thermally and temporally distinct and the conditions specified are a recipe to separate these transition metals from each other and from the noble metal phase nonvolatile residue. Depletion of the volatile fluorides resulted in substantial exothermicity. Thermal excursion behavior was recorded under non-adiabatic, isothermal conditions that typically minimize heat release. Physical characterization of the metallic noble phase and its thermal behavior are consistent with high kinetic velocity reactions encouraged by the nanoparticulate phase or perhaps catalytic influences of the mixed platinum metals with nearly pure phase structure. Post-fluorination, only two phases were present in the residual nonvolatile fraction. These were identified as a nano-crystalline, metallic palladium cubic phase and a hexagonal rhodium trifluoride (RhF3) phase. The two phases were distinct as the sub-µm crystallites of metallic palladium were in contrast to the RhF3 phase, which grew from the parent nano-crystalline noble-metal phase during fluorination, to acicular crystals exceeding 20-µm in length.

  10. 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

    PubMed Central

    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

  11. 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.

    PubMed

    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.

  12. High-Valent Organometallic Copper and Palladium in Catalysis

    PubMed Central

    Hickman, Amanda J.; Sanford, Melanie S.

    2015-01-01

    Preface Copper and palladium catalysts are critically important for numerous commercial chemical processes. Improvements in the activity, selectivity, and scope of these catalysts have the potential to dramatically reduce the environmental impact and increase the sustainability of chemical reactions. One rapidly emerging strategy to achieve these goals is to exploit “high-valent” copper and palladium intermediates in catalysis. This review describes exciting recent advances involving both the fundamental chemistry and the applications of these high-valent metal complexes in numerous synthetically useful catalytic transformations. PMID:22498623

  13. Carbon monoxide adsorption on platinum-osmium and platinum-ruthenium-osmium mixed nanoparticles.

    PubMed

    Dimakis, Nicholas; Navarro, Nestor E; Smotkin, Eugene S

    2013-05-01

    Density functional calculations (DFT) on carbon monoxide (CO) adsorbed on platinum, platinum-osmium, and platinum-ruthenium-osmium nanoclusters are used to elucidate changes on the adsorbate internal bond and the carbon-metal bond, as platinum is alloyed with osmium and ruthenium atoms. The relative strengths of the adsorbate internal bond and the carbon-metal bond upon alloying, which are related to the DFT calculated C-O and C-Pt stretching frequencies, respectively, cannot be explained by the traditional 5σ-donation/2π*-back-donation theoretical model. Using a modified π-attraction σ-repulsion mechanism, we ascribe the strength of the CO adsorbate internal bond to changes in the polarization of the adsorbate-substrate hybrid orbitals towards carbon. The strength of the carbon-metal bond is quantitatively related to the CO contribution to the adsorbate-substrate hybrid orbitals and the sp and d populations of adsorbing platinum atom. This work complements prior work on corresponding slabs using periodic DFT. Similarities and differences between cluster and periodic DFT calculations are discussed. PMID:23656149

  14. Quantitative bioimaging of platinum group elements in tumor spheroids.

    PubMed

    Niehoff, Ann-Christin; Grünebaum, Jonas; Moosmann, Aline; Mulac, Dennis; Söbbing, Judith; Niehaus, Rebecca; Buchholz, Rebecca; Kröger, Sabrina; Wiehe, Arno; Wagner, Sylvia; Sperling, Michael; von Briesen, Hagen; Langer, Klaus; Karst, Uwe

    2016-09-28

    Limited drug penetration into tumor tissue is a significant factor to the effectiveness of cancer therapy. Tumor spheroids, a 3D cell culture model system, can be used to study drug penetration for pharmaceutical development. In this study, a method for quantitative bioimaging of platinum group elements by laser ablation (LA) coupled to inductively coupled plasma mass spectrometry (ICP-MS) is presented. Different matrix-matched standards were used to develop a quantitative LA-ICP-MS method with high spatial resolution. To investigate drug penetration, tumor spheroids were incubated with platinum complexes (Pt(II)acetylacetonate, cisplatin) and the palladium tagged photosensitizer 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (mTHPP). Distribution and accumulation of the pharmaceuticals were determined with the developed method. PMID:27619092

  15. Quantitative bioimaging of platinum group elements in tumor spheroids.

    PubMed

    Niehoff, Ann-Christin; Grünebaum, Jonas; Moosmann, Aline; Mulac, Dennis; Söbbing, Judith; Niehaus, Rebecca; Buchholz, Rebecca; Kröger, Sabrina; Wiehe, Arno; Wagner, Sylvia; Sperling, Michael; von Briesen, Hagen; Langer, Klaus; Karst, Uwe

    2016-09-28

    Limited drug penetration into tumor tissue is a significant factor to the effectiveness of cancer therapy. Tumor spheroids, a 3D cell culture model system, can be used to study drug penetration for pharmaceutical development. In this study, a method for quantitative bioimaging of platinum group elements by laser ablation (LA) coupled to inductively coupled plasma mass spectrometry (ICP-MS) is presented. Different matrix-matched standards were used to develop a quantitative LA-ICP-MS method with high spatial resolution. To investigate drug penetration, tumor spheroids were incubated with platinum complexes (Pt(II)acetylacetonate, cisplatin) and the palladium tagged photosensitizer 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (mTHPP). Distribution and accumulation of the pharmaceuticals were determined with the developed method.

  16. Metallization of Large Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Pryor, R. A.

    1978-01-01

    A metallization scheme was developed which allows selective plating of silicon solar cell surfaces. The system is comprised of three layers. Palladium, through the formation of palladium silicide at 300 C in nitrogen, makes ohmic contact to the silicon surface. Nickel, plated on top of the palladium silicide layer, forms a solderable interface. Lead-tin solder on the nickel provides conductivity and allows a convenient means for interconnection of cells. To apply this metallization, three chemical plating baths are employed.

  17. Solar abundance of platinum

    PubMed Central

    Burger, Harry; Aller, Lawrence H.

    1975-01-01

    Three lines of neutral platinum, located at λ 2997.98 Å, λ 3064.71 Å, and λ 3301.86 Å have been used to determine the solar platinum abundance by the method of spectral synthesis. On the scale, log A(H) = 12.00, the thus-derived solar platinum abundance is 1.75 ± 0.10, in fair accord with Cameron's value of log A(Pt) = 1.69 derived by Mason from carbonaceous chondrites and calculated on the assumption that log A(Si) = 7.55 in the sun. PMID:16592278

  18. Electrocatalyst for oxygen reduction with reduced platinum oxidation and dissolution rates

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Vukmirovic, Miomir

    2011-11-22

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen.

  19. Electrocatalyst for oxygen reduction with reduced platinum oxidation and dissolution rates

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Vukmirovic, Miomir

    2012-11-13

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen.

  20. Molecularly doped metals.

    PubMed

    Avnir, David

    2014-02-18

    The many millions of organic, inorganic, and bioorganic molecules represent a very rich library of chemical, biological, and physical properties that do not show up among the approximately 100 metals. The ability to imbue metals with any of these molecular properties would open up tremendous potential for the development of new materials. In addition to their traditional features and their traditional applications, metals would have new traits, which would merge their classical virtues such as conductivity and catalytic activity with the diverse properties of these molecules. In this Account, we describe a new materials methodology, which enables, for the first time, the incorporation and entrapment of small organic molecules, polymers, and biomolecules within metals. These new materials are denoted dopant@metal. The creation of dopant@metal yields new properties that are more than or different from the sum of the individual properties of the two components. So far we have developed methods for the doping of silver, copper, gold, iron, palladium, platinum, and some of their alloys, as well as Hg-Ag amalgams. We have successfully altered classical metal properties (such as conductivity), induced unorthodox properties (such as rendering a metal acidic or basic), used metals as heterogeneous matrices for homogeneous catalysts, and formed new metallic catalysts such as metals doped with organometallic complexes. In addition, we have created materials that straddle the border between polymers and metals, we have entrapped enzymes to form bioactive metals, we have induced chirality within metals, we have made corrosion-resistant iron, we formed efficient biocidal materials, and we demonstrated a new concept for batteries. We have developed a variety of methods for synthesizing dopant@metals including aqueous homogeneous and heterogeneous reductions of the metal cations, reductions in DMF, electrochemical entrapments, thermal decompositions of zerovalent metal carbonyls

  1. Molecularly doped metals.

    PubMed

    Avnir, David

    2014-02-18

    The many millions of organic, inorganic, and bioorganic molecules represent a very rich library of chemical, biological, and physical properties that do not show up among the approximately 100 metals. The ability to imbue metals with any of these molecular properties would open up tremendous potential for the development of new materials. In addition to their traditional features and their traditional applications, metals would have new traits, which would merge their classical virtues such as conductivity and catalytic activity with the diverse properties of these molecules. In this Account, we describe a new materials methodology, which enables, for the first time, the incorporation and entrapment of small organic molecules, polymers, and biomolecules within metals. These new materials are denoted dopant@metal. The creation of dopant@metal yields new properties that are more than or different from the sum of the individual properties of the two components. So far we have developed methods for the doping of silver, copper, gold, iron, palladium, platinum, and some of their alloys, as well as Hg-Ag amalgams. We have successfully altered classical metal properties (such as conductivity), induced unorthodox properties (such as rendering a metal acidic or basic), used metals as heterogeneous matrices for homogeneous catalysts, and formed new metallic catalysts such as metals doped with organometallic complexes. In addition, we have created materials that straddle the border between polymers and metals, we have entrapped enzymes to form bioactive metals, we have induced chirality within metals, we have made corrosion-resistant iron, we formed efficient biocidal materials, and we demonstrated a new concept for batteries. We have developed a variety of methods for synthesizing dopant@metals including aqueous homogeneous and heterogeneous reductions of the metal cations, reductions in DMF, electrochemical entrapments, thermal decompositions of zerovalent metal carbonyls

  2. Recommended values of clean metal surface work functions

    SciTech Connect

    Derry, Gregory N. Kern, Megan E.; Worth, Eli H.

    2015-11-15

    A critical review of the experimental literature for measurements of the work functions of clean metal surfaces of single-crystals is presented. The tables presented include all results found for low-index crystal faces except cases that were known to be contaminated surfaces. These results are used to construct a recommended value of the work function for each surface examined, along with an uncertainty estimate for that value. The uncertainties are based in part on the error distribution for all measured work functions in the literature, which is included here. The metals included in this review are silver (Ag), aluminum (Al), gold (Au), copper (Cu), iron (Fe), iridium (Ir), molybdenum (Mo), niobium (Nb), nickel (Ni), palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru), tantalum (Ta), and tungsten (W)

  3. Optimization of carbon-supported platinum cathode catalysts for DMFC operation.

    SciTech Connect

    Zhu, Y.; Brosha, E. L.; Zelenay, P.

    2002-01-01

    In this paper, we describe performance and optimization of carbon-supported cathode catalysts at low platinum loading. We find that at a loading below 0.6 mg cm-2 carbon-supported platinum outperforms platinum black as a DMFC cathode catalyst. A catalyst with a 1:1 volume ratio of the dry NafionTM to the electronically conducting phase (platinum plus carbon support) provides the best performance in oxygen reduction reaction. Thanks to improved catalyst utilization, carbon-supported catalysts with a platinum content varying from 40 wt% to 80 wt% deliver very good DMFC performance, even at relatively modest precious metal loadings investigated in this work.

  4. Platinum hypersensitivity and desensitization.

    PubMed

    Miyamoto, Shingo; Okada, Rika; Ando, Kazumichi

    2015-09-01

    Platinum agents are drugs used for various types of cancer. With increased frequency of administration of platinum agents, hypersensitivity reactions appear more frequently, occurring in over 25% of cases from the seventh cycle or second line onward. It then becomes difficult to conduct treatment using these agents. Various approaches have been investigated to address hypersensitivity reactions to platinum agents. Desensitization, which gradually increases the concentration of the anticancer drug considered to be the antigen until the target dosage, has been reported as being particularly effective, with a success rate of 80-100%. The aims of this paper are to present the current findings regarding hypersensitivity reactions to platinum agents and to discuss attempts of using desensitization against hypersensitivity reactions worldwide.

  5. Platinum and associated elements at the New Rambler mine and vicinity, Albany and Carbon Counties, Wyoming

    USGS Publications Warehouse

    Theobald, P.K.; Thompson, Charles Emmet

    1968-01-01

    Platinum-group metals in the Medicine Bow Mountains were first identified by W. C. Knight in 1901. In the Medicine Bow Mountains, these metals are commonly associated with copper, silver, or gold in shear zones that cut a series of mafic igneous and metamorphic rocks. At the New Rambler mine, where the initial discovery was made, about 50,000 tons of mine and mill waste contain an average of 0.3 percent copper, 7 ppm (parts per million) silver, 1 ppm platinum plus palladium, and 0.7 ppm gold. This material is believed to be from a low-grade envelope around the high-grade pod of complex ore that was mined selectively in the old workings. Soil samples in the vicinity of the New Rambler mine exhibit a wide range of content of several elements associated with the ore. Most of the variation can be attributed to contamination, from the mine workings. Even though soil samples identify a low-level copper anomaly that persists to the limit of the area sampled, soils do not offer a promising medium for tracing mineralization owing to the blanket of transported overburden. Stream sediments, if preconcentrated for analysis, do reveal anomalies not only in the contaminated stream below the New Rambler mine, but in adjacent drainage and on Dave Creek. Examination of a spectrum of elements in heavy-mineral concentrates from stream sediment may contribute to knowledge of the nature of the mineralization and of the basic geology of the environment. The sampling of bedrock exposures is not particularly fruitful because outcrops are sparse and the exposed rocks are the least altered and mineralized. Bedrock sampling does, however, provide information on the large size and provincial nature of the platinum-rich area. We feel that a properly integrated program of geological, geophysical, and geochemical exploration in the Medicine Bow Mountains and probably in the Sierra Madre to the west has a reasonable probability of successfully locating a complex ore body.

  6. Partial oxidation of step-bound water leads to anomalous pH effects on metal electrode step-edges.

    PubMed

    Schwarz, Kathleen; Xu, Bingjun; Yan, Yushan; Sundararaman, Ravishankar

    2016-06-28

    The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how this as-yet unreported change in net surface charge due to this water explains the anomalous pH variations of the hydrogen underpotential deposition (Hupd) and the potentials of zero total charge (PZTC) observed in published experimental data. This partial oxidation of water is not limited to platinum metal step edges, and we report the charge of the water on metal step edges of commonly used catalytic metals, including copper, silver, iridium, and palladium, illustrating that this partial oxidation of water broadly influences the reactivity of metal electrodes. PMID:27250359

  7. Effect of barrier height on friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals

    NASA Technical Reports Server (NTRS)

    Mishina, H.; Buckley, D. H.

    1984-01-01

    Friction experiments were conducted for the semiconductors silicon and gallium arsenide in contact with pure metals. Polycrystalline titanium, tantalum, nickel, palladium, and platinum were made to contact a single crystal silicon (111) surface. Indium, nickel, copper, and silver were made to contact a single crystal gallium arsenide (100) surface. Sliding was conducted both in room air and in a vacuum of 10 to the minus 9th power torr. The friction of semiconductors in contact with metals depended on a Schottky barrier height formed at the metal semiconductor interface. Metals with a higher barrier height on semiconductors gave lower friction. The effect of the barrier height on friction behavior for argon sputtered cleaned surfaces in vacuum was more specific than that for the surfaces containing films in room air. With a silicon surface sliding on titanium, many silicon particles back transferred. In contrast, a large quantity of indium transferred to the gallium arsenide surface.

  8. Teaching the Chemistry of Platinum.

    PubMed

    Anderson, Robert G W

    2015-01-01

    Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. PMID:26924332

  9. Study of palladium plating components

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Palladium deposits were prepared by electrolysis for evaluation as catalytic materials. Electrolysis was carried out in acidic solutions consisting of either 1.0 M in NaCl and 0.01 M PdCl2 or 1.0 M NaCl and 0.04 M PdCl2. It was during the preparation of the palladium deposits that unexpected observations were made that led to the request for analytical services. The analyses did not, nor were they intended to, answer all of the questions. They did, however, shed light on the nature and magnitude of some of the contaminants in the solutions and in the palladium electrodes, as well as characterize the forms of the palladium deposits. Results of analyses are grouped into solution, deposit, and electrode categories for comparison purposes.

  10. Interfacial electronic effects control the reaction selectivity of platinum catalysts

    NASA Astrophysics Data System (ADS)

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

  11. In{sub 3}Ir{sub 3}B, In{sub 3}Rh{sub 3}B and In{sub 5}Ir{sub 9}B{sub 4}, the first indium platinum metal borides

    SciTech Connect

    Kluenter, Wilhelm; Jung, Walter . E-mail: walter.jung@uni-koeln.de

    2006-09-15

    The first indium platinum metal borides have been synthesized and structurally characterized by single crystal X-ray diffraction data. In{sub 3}Ir{sub 3}B and In{sub 3}Rh{sub 3}B are isotypic. They crystallize with the hexagonal space group P6-bar 2m and Z=1. The lattice constants are a=685.78(1)pm, c=287.30(1)pm for In{sub 3}Ir{sub 3}B and a=678.47(3)pm, c=288.61(6)pm for In{sub 3}Rh{sub 3}B. The structure which is derived from the Fe{sub 2}P type is characterized by columns of boron centered triangular platinum metal prisms inserted in a three-dimensional indium matrix. The indium atoms are on split positions. In{sub 5}Ir{sub 9}B{sub 4} (hexagonal, space group P6-bar 2m, a=559.0(2)pm, c=1032.6(3)pm, Z=1) crystallizes with a structure derived from the CeCo{sub 3}B{sub 2} type. The structure can be interpreted as a layer as well as a channel structure. In part the indium atoms are arranged at the vertices of a honeycomb net (Schlaefli symbol 6{sup 3}) separating slabs consisting of double layers of triangular Ir{sub 6}B prisms, and in part they form a linear chain in a hexagonal channel formed by iridium prisms and indium atoms of the honeycomb lattice.

  12. Low-cost method for fabricating palladium and palladium-alloy thin films on porous supports

    DOEpatents

    Lee, Tae H; Park, Chan Young; Lu, Yunxiang; Dorris, Stephen E; Balachandran, Uthamalingham

    2013-11-19

    A process for forming a palladium or palladium alloy membrane on a ceramic surface by forming a pre-colloid mixture comprising a powder palladium source, carrier fluid, dispersant and a pore former and a binder. Ultrasonically agitating the precolloid mixture and applying to a substrate with an ultrasonic nozzle and heat curing the coating form a palladium-based membrane.

  13. Direct and quinone-mediated palladium reduction by Geobacter sulfurreducens: mechanisms and modeling.

    PubMed

    Pat-Espadas, Aurora M; Razo-Flores, Elías; Rangel-Mendez, J Rene; Cervantes, Francisco J

    2014-01-01

    Palladium(II) reduction to Pd(0) nanoparticles by Geobacter sulfurreducens was explored under conditions of neutral pH, 30 °C and concentrations of 25, 50, and 100 mg of Pd(II)/L aiming to investigate the effect of solid species of palladium on their microbial reduction. The influence of anthraquinone-2,6-disulfonate was reported to enhance the palladium reaction rate in an average of 1.7-fold and its addition is determining to achieve the reduction of solid species of palladium. Based on the obtained results two mechanisms are proposed: (1) direct, which is fully described considering interactions of amide, sulfur, and phosphoryl groups associated to proteins from bacteria on palladium reduction reaction, and (2) quinone-mediated, which implies multiheme c-type cytochromes participation. Speciation analysis and kinetic results were considered and integrated into a model to fit the experimental data that explain both mechanisms. This work provides elements for a better understanding of direct and quinone-mediated palladium reduction by G. sulfurreducens, which could facilitate metal recovery with concomitant formation of valuable palladium nanoparticles in industrial processes.

  14. [Platinum antitumor complexes].

    PubMed

    Bonetti, Andrea; Giuliani, Jacopo; Muggia, Franco

    2015-12-01

    In the last 50 years the oncology has experienced remarkable changes resulting in transforming malignant germ-cell testicular tumors from highly fatal to nearly uniformly cured neoplasms. This clinical landmark was justly attributed to the identification of cisplatin by Barnett Rosenberg in his experiments dating to 1965. On this 50th anniversary of this discovery, one is reminded of the following key aspects in cancer therapeutics: 1) the life-story of Barnett Rosenberg and his legacy that included organizing nearly quadrennial "platinum" meetings incorporating advances in cancer biology into evolving therapeutic strategies; 2) the search for less toxic analogs of cisplatin leading to the development of carboplatin; 3) clinical research into attenuation of cisplatin toxicities; 4) oxaliplatin and the expansion of the therapeutic spectrum of platinum compounds; and 5) the ongoing multifaceted investigations into the problem of "platinum resistance".

  15. Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution

    PubMed Central

    Hodnik, Nejc; Baldizzone, Claudio; Polymeros, George; Geiger, Simon; Grote, Jan-Philipp; Cherevko, Serhiy; Mingers, Andrea; Zeradjanin, Aleksandar; Mayrhofer, Karl J. J.

    2016-01-01

    The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors. However, due to its resistance to corrosion, platinum-leaching techniques rely on high reagent consumption and hazardous processes, for example, boiling aqua regia; a mixture of concentrated nitric and hydrochloric acid. Here we demonstrate that complete dissolution of metallic platinum can be achieved by induced surface potential alteration, an ‘electrode-less' process utilizing alternatively oxidative and reductive gases. This concept for platinum recycling exploits the so-called transient dissolution mechanism, triggered by a repetitive change in platinum surface oxidation state, without using any external electric current or electrodes. The effective performance in non-toxic low-concentrated acid and at room temperature is a strong benefit of this approach, potentially rendering recycling of industrial catalysts, including but not limited to platinum-based systems, more sustainable. PMID:27767178

  16. PALLADIUM/COPPER ALLOY COMPOSITE MEMBRANES FOR HIGH TEMPERATURE HYDROGEN SEPARATION FROM COAL-DERIVED GAS STREAMS

    SciTech Connect

    J. Douglas Way

    2003-01-01

    For hydrogen from coal gasification to be used economically, processing approaches that produce a high purity gas must be developed. Palladium and its alloys, nickel, platinum and the metals in Groups 3 to 5 of the Periodic Table are all permeable to hydrogen. Hydrogen permeable metal membranes made of palladium and its alloys are the most widely studied due to their high hydrogen permeability, chemical compatibility with many hydrocarbon containing gas streams, and infinite hydrogen selectivity. Our Pd composite membranes have demonstrated stable operation at 450 C for over 70 days. Coal derived synthesis gas will contain up to 15000 ppm H{sub 2}S as well as CO, CO{sub 2}, N{sub 2} and other gases. Highly selectivity membranes are necessary to reduce the H{sub 2}S concentration to acceptable levels for solid oxide and other fuel cell systems. Pure Pd-membranes are poisoned by sulfur, and suffer from mechanical problems caused by thermal cycling and hydrogen embrittlement. Recent advances have shown that Pd-Cu composite membranes are not susceptible to the mechanical, embrittlement, and poisoning problems that have prevented widespread industrial use of Pd for high temperature H{sub 2} separation. These membranes consist of a thin ({le} 5 {micro}m) film of metal deposited on the inner surface of a porous metal or ceramic tube. With support from this DOE Grant, we have fabricated thin, high flux Pd-Cu alloy composite membranes using a sequential electroless plating approach. Thin, Pd{sub 60}Cu{sub 40} films exhibit a hydrogen flux more than ten times larger than commercial polymer membranes for H{sub 2} separation, resist poisoning by H{sub 2}S and other sulfur compounds typical of coal gas, and exceed the DOE Fossil Energy target hydrogen flux of 80 ml/cm{sup 2} {center_dot} min = 0.6 mol/m{sup 2} {center_dot} s for a feed pressure of 40 psig. Similar Pd-membranes have been operated at temperatures as high as 750 C. We have developed practical electroless plating

  17. Functionalization of Platinum Complexes for Biomedical Applications.

    PubMed

    Wang, Xiaoyong; Wang, Xiaohui; Guo, Zijian

    2015-09-15

    Platinum-based anticancer drugs are the mainstay of chemotherapy regimens in clinic. Nevertheless, the efficacy of platinum drugs is badly affected by serious systemic toxicities and drug resistance, and the pharmacokinetics of most platinum drugs is largely unknown. In recent years, a keen interest in functionalizing platinum complexes with bioactive molecules, targeting groups, photosensitizers, fluorophores, or nanomaterials has been sparked among chemical and biomedical researchers. The motivation for functionalization comes from some of the following demands: to improve the tumor selectivity or minimize the systemic toxicity of the drugs, to enhance the cellular accumulation of the drugs, to overcome the tumor resistance to the drugs, to visualize the drug molecules in vitro or in vivo, to achieve a synergistic anticancer effect between different therapeutic modalities, or to add extra functionality to the drugs. In this Account, we present different strategies being used for functionalizing platinum complexes, including conjugation with bisphosphonates, peptides, receptor-specific ligands, polymers, nanoparticles, magnetic resonance imaging contrast agents, metal chelators, or photosensitizers. Among them, bisphosphonates, peptides, and receptor-specific ligands are used for actively targeted drug delivery, polymers and nanoparticles are for passively targeted drug delivery, magnetic resonance imaging contrast agents are for theranostic purposes, metal chelators are for the treatment or prevention of Alzheimer's disease (AD), and photosensitizers are for photodynamic therapy of cancers. The rationales behind these designs are explained and justified at the molecular or cellular level, associating with the requirements for diagnosis, therapy, and visualization of biological processes. To illustrate the wide range of opportunities and challenges that are emerging in this realm, representative examples of targeted drug delivery systems, anticancer conjugates

  18. Nanoscale platinum printing on insulating substrates.

    PubMed

    O'Connell, C D; Higgins, M J; Sullivan, R P; Jamali, S S; Moulton, S E; Wallace, G G

    2013-12-20

    The deposition of noble metals on soft and/or flexible substrates is vital for several emerging applications including flexible electronics and the fabrication of soft bionic implants. In this paper, we describe a new strategy for the deposition of platinum electrodes on a range of materials, including insulators and flexible polymers. The strategy is enabled by two principle advances: (1) the introduction of a novel, low temperature strategy for reducing chloroplatinic acid to platinum using nitrogen plasma; (2) the development of a chloroplatinic acid based liquid ink formulation, utilizing ethylene glycol as both ink carrier and reducing agent, for versatile printing at nanoscale resolution using dip-pen nanolithography (DPN). The ink formulation has been printed and reduced upon Si, glass, ITO, Ge, PDMS, and Parylene C. The plasma treatment effects reduction of the precursor patterns in situ without subjecting the substrate to destructively high temperatures. Feature size is controlled via dwell time and degree of ink loading, and platinum features with 60 nm dimensions could be routinely achieved on Si. Reduction of the ink to platinum was confirmed by energy dispersive x-ray spectroscopy (EDS) elemental analysis and x-ray diffraction (XRD) measurements. Feature morphology was characterized by optical microscopy, SEM and AFM. The high electrochemical activity of individually printed Pt features was characterized using scanning electrochemical microscopy (SECM).

  19. Spectrometric determination of platinum with methoxypromazine maleate

    SciTech Connect

    Thimmegowda, A.; Sankegowda, H.; Gowda, N.M.M.

    1984-03-01

    A simple, rapid, and sensitive spectrophotometric method has been developed for the determination of platinum in solution. The chromogenic reagent, methoxypromazine maleate, reacts with platinum(IV) almost instantaneously in phosphoric acid medium containing copper(II) catalyst to form a bluish pink 1:1 complex with an absorption maximum at 562 nm. The complexation is complete within 1 min. A 30-fold molar excess of the reagent over metal ion is necessary for completion of the reaction. Beer's law is obeyed over the concentration range of 0.4-9.8 ppm of platinum(IV) with an optimal range of 1.5-8.6 ppm. The molar absorptivity is 1.71 x 10/sub 4/ L mol/sup -1/ cm/sup -1/ and the Sandell sensitivity is 11.4 ng cm/sup -2/. The apparent stability constant of the complex is log K = 5.58 +/- 0.1 at 27/sup 0/C. The effects of acid concentration, time, temperature, concentration of the reagent and copper, order of addition of reagents, and the interferences from various ions are investigated. The method has been used for the determination of platinum in synthetic solutions that approximate the composition of some alloys and minerals. 25 references, 1 figure, 2 tables.

  20. Nanoscale platinum printing on insulating substrates.

    PubMed

    O'Connell, C D; Higgins, M J; Sullivan, R P; Jamali, S S; Moulton, S E; Wallace, G G

    2013-12-20

    The deposition of noble metals on soft and/or flexible substrates is vital for several emerging applications including flexible electronics and the fabrication of soft bionic implants. In this paper, we describe a new strategy for the deposition of platinum electrodes on a range of materials, including insulators and flexible polymers. The strategy is enabled by two principle advances: (1) the introduction of a novel, low temperature strategy for reducing chloroplatinic acid to platinum using nitrogen plasma; (2) the development of a chloroplatinic acid based liquid ink formulation, utilizing ethylene glycol as both ink carrier and reducing agent, for versatile printing at nanoscale resolution using dip-pen nanolithography (DPN). The ink formulation has been printed and reduced upon Si, glass, ITO, Ge, PDMS, and Parylene C. The plasma treatment effects reduction of the precursor patterns in situ without subjecting the substrate to destructively high temperatures. Feature size is controlled via dwell time and degree of ink loading, and platinum features with 60 nm dimensions could be routinely achieved on Si. Reduction of the ink to platinum was confirmed by energy dispersive x-ray spectroscopy (EDS) elemental analysis and x-ray diffraction (XRD) measurements. Feature morphology was characterized by optical microscopy, SEM and AFM. The high electrochemical activity of individually printed Pt features was characterized using scanning electrochemical microscopy (SECM). PMID:24270681

  1. Nanoscale platinum printing on insulating substrates

    NASA Astrophysics Data System (ADS)

    O'Connell, C. D.; Higgins, M. J.; Sullivan, R. P.; Jamali, S. S.; Moulton, S. E.; Wallace, G. G.

    2013-12-01

    The deposition of noble metals on soft and/or flexible substrates is vital for several emerging applications including flexible electronics and the fabrication of soft bionic implants. In this paper, we describe a new strategy for the deposition of platinum electrodes on a range of materials, including insulators and flexible polymers. The strategy is enabled by two principle advances: (1) the introduction of a novel, low temperature strategy for reducing chloroplatinic acid to platinum using nitrogen plasma; (2) the development of a chloroplatinic acid based liquid ink formulation, utilizing ethylene glycol as both ink carrier and reducing agent, for versatile printing at nanoscale resolution using dip-pen nanolithography (DPN). The ink formulation has been printed and reduced upon Si, glass, ITO, Ge, PDMS, and Parylene C. The plasma treatment effects reduction of the precursor patterns in situ without subjecting the substrate to destructively high temperatures. Feature size is controlled via dwell time and degree of ink loading, and platinum features with 60 nm dimensions could be routinely achieved on Si. Reduction of the ink to platinum was confirmed by energy dispersive x-ray spectroscopy (EDS) elemental analysis and x-ray diffraction (XRD) measurements. Feature morphology was characterized by optical microscopy, SEM and AFM. The high electrochemical activity of individually printed Pt features was characterized using scanning electrochemical microscopy (SECM).

  2. Monofunctional and Higher-Valent Platinum Anticancer Agents

    PubMed Central

    Johnstone, Timothy C.; Wilson, Justin J.

    2013-01-01

    Platinum compounds represent one of the great success stories of metals in medicine. Following the serendipitous discovery of the anticancer activity of cisplatin by Rosenberg, a large number of cisplatin variants have been prepared and tested for their ability to kill cancer cells and inhibit tumor growth. These efforts continue today with increased realization that new strategies are needed to overcome issues of toxicity and resistance inherent to treatment by the approved platinum anticancer agents. One approach has been the use of so-called “non-traditional” platinum(II) and platinum(IV) compounds that violate the structure-activity relationships that governed platinum drug-development research for many years. Another is the use of specialized drug delivery strategies. Here we describe recent developments from our laboratory involving monofunctional platinum(II) complexes together with an historical account of the manner by which we came to investigate these compounds and their relationship to previously studied molecules. We also discuss work carried out using platinum(IV) prodrugs and the development of nanoconstructs designed to deliver them in vivo. PMID:23738524

  3. Defense by-products production and utilization program: noble metal recovery screening experiments

    SciTech Connect

    Hazelton, R.F.; Jensen, G.A.; Raney, P.J.

    1986-03-01

    Isotopes of the platinum metals (rutheium, rhodium, and palladium) are produced during uranium fuel fission in nuclear reactors. The strategic values of these noble metals warrant considering their recovery from spent fuel should the spent fuel be processed after reactor discharge. A program to evaluate methods for ruthenium, rhodium, and palladium recovery from spent fuel reprocessing liquids was conducted at Pacific Northwest Laboratory (PNL). The purpose of the work reported in this docuent was to evaluate several recovery processes revealed in the patent and technical literature. Beaker-scale screening tests were initiated for three potential recovery processes: precipitation during sugar denitration of nitric acid reprocessing solutions after plutonium-uranium solvent extraction, adsorption using nobe metal selective chelates on active carbon, and reduction forming solid noble metal deposits on an amine-borane reductive resin. Simulated reprocessing plant solutions representing typical nitric acid liquids from defense (PUREX) or commercial fuel reprocessing facilities were formulated and used for evaluation of the three processes. 9 refs., 3 figs., 9 tabs.

  4. Oxidation of methane over palladium catalysts: effect of the support.

    PubMed

    Escandón, Lara S; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

    2005-01-01

    This work is focused on the deep catalytic oxidation of methane over supported palladium catalysts. The influences of the metal loading, oxidation state of palladium, nature of supports, presence of promoters in the supports (for zirconia-based supports), and thermal stability have been studied experimentally. Catalysts were prepared by incipient wetness of commercially available supports with aqueous solutions of palladium nitrate. For gamma-alumina support, it was observed that the optimal amount of palladium is between 0.5% and 2%, with higher amounts leading to a loss in specific activity. Concerning the oxidation state of the catalyst, it is concluded that for all the supports tested in the present work, a reduction of the catalyst is not needed, yielding the same conversion at steady state catalysts reduced and oxidised. The thermal stability of various supported catalysts were also studied, zirconia supports being the most active. These supports, specially Y-modified zirconia support, do not suffer appreciable deactivation below 500 degrees C.

  5. Ozone Sensing Based on Palladium Decorated Carbon Nanotubes

    PubMed Central

    Colindres, Selene Capula; Aguir, Khalifa; Sodi, Felipe Cervantes; Vargas, Luis Villa; Moncayo Salazar, José A.; Febles, Vicente Garibay

    2014-01-01

    Multiwall carbon nanotubes (MWCNTs) were easily and efficiently decorated with Pd nanoparticles through a vapor-phase impregnation-decomposition method starting from palladium acetylacetonates. The sensor device consisted on a film of sensitive material (MWCNTs-Pd) deposited by drop coating on platinum interdigitated electrodes on a SiO2 substrate. The sensor exhibited a resistance change to ozone (O3) with a response time of 60 s at different temperatures and the capability of detecting concentrations up to 20 ppb. The sensor shows the best response when exposed to O3 at 120 °C. The device shows a very reproducible sensor performance, with high repeatability, full recovery and efficient response. PMID:24736133

  6. Palladium Decorated Graphene-Nanoribbon Network for Enhanced Gas Sensing.

    PubMed

    Kuru, Cihan; Choi, Duyoung; Choi, Chulmin; Kim, Young Jin; Jin, Sungho

    2015-03-01

    The fabrication of large-scale graphene nanoribbon (GNR) network and its application for gas sensing are reported. A large area, nanoscale GNR network was produced by a facile approach of silver nanowires (Ag NWs) templated graphene masking and subsequent 02 plasma etching. GNR network shows significantly enhanced sensitivity to ammonia gas compared to pristine graphene layer. The gas detection sensitivity of the nanoscale GNR network is even further improved by decorating GNR network with palladium (Pd) or platinum (Pt) nanoparticles, which show a relative resistance response of 65% and 45%, respectively to 50 ppm (parts per million) of ammonia (NH3) in nitrogen (N2) at room temperature as well as good reversibility in air.

  7. METHOD TO TEST ISOTOPIC SEPARATION EFFICIENCY OF PALLADIUM PACKED COLUMNS

    SciTech Connect

    Heung, L; Gregory Staack, G; James Klein, J; William Jacobs, W

    2007-06-27

    The isotopic effect of palladium has been applied in different ways to separate hydrogen isotopes for many years. At Savannah River Site palladium deposited on kieselguhr (Pd/k) is used in a thermal cycling absorption process (TCAP) to purify tritium for over ten years. The need to design columns for different throughputs and the desire to advance the performance of TCAP created the need to evaluate different column designs and packing materials for their separation efficiency. In this work, columns with variations in length, diameter and metal foam use, were tested using an isotope displacement method. A simple computer model was also developed to calculate the number of theoretical separation stages using the test results. The effects of column diameter, metal foam and gas flow rate were identified.

  8. 77 FR 43620 - Self-Regulatory Organizations; NYSE Arca, Inc.; Order Instituting Proceedings to Determine...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-25

    ... Commission.\\102\\ According to V&F, gold, silver, platinum, and palladium are all precious metals that have... available on the LME.\\108\\ Senator Levin states that gold, silver, platinum, and palladium are substantially... holding platinum, palladium, silver, or gold had on their respective markets and the broader...

  9. Reduction of FCCI effects in lanthanide-iron diffusion couples by doping with palladium

    NASA Astrophysics Data System (ADS)

    Egeland, G. W.; Mariani, R. D.; Hartmann, T.; Porter, D. L.; Hayes, S. L.; Kennedy, J. R.

    2013-09-01

    Fast-reactor metallic fuels produce lanthanide fission products which have been shown to diffuse to the fuel periphery. Lanthanides interacting with the cladding is one cause of fuel-cladding chemical interaction. To test the viability of reducing the interaction by pinning these lanthanides, palladium was chosen as a fuel dopant based on the lanthanide-palladium intermetallic thermodynamic stability and fuel compatibility. Three lanthanides were tested, neodymium, cerium, and praseodymium, along with their 1:1 palladium compounds, against iron using diffusion couples. These experiments show the direct contact effect on iron of each lanthanide and its respective palladium compound at temperatures from 580 °C to 700 °C for 100 h.

  10. Testing of a 7-tube palladium membrane reactor for potential use in TEP

    SciTech Connect

    Carlson, Bryan J; Trujillo, Stephen; Willms, R. Scott

    2010-01-01

    A Palladium Membrane Reactor (PMR) consists of a palladium/silver membrane permeator filled with catalyst (catalyst may be inside or outside the membrane tubes). The PMR is designed to recover tritium from the methane, water, and other impurities present in fusion reactor effluent. A key feature of a PMR is that the total hydrogen isotope content of a stream is significantly reduced as (1) methane-steam reforming and/or water-gas shift reactions proceed on the catalyst bed and (2) hydrogen isotopes are removed via permeation through the membrane. With a PMR design matched to processing requirements, nearly complete hydrogen isotope removals can be achieved. A 3-tube PMR study was recently completed. From the results presented in this study, it was possible to conclude that a PMR is appropriate for TEP, perforated metal tube protectors function well, platinum on aluminum (PtA) catalyst performs the best, conditioning with air is probably required to properly condition the Pd/Ag tubes, and that CO/CO{sub 2} ratios maybe an indicator of coking. The 3-tube PMR had a permeator membrane area of 0.0247 m{sup 2} and a catalyst volume to membrane area ratio of 4.63 cc/cm{sup 2} (with the catalyst on the outside of the membrane tubes and the catalyst only covering the membrane tube length). A PMR for TEP will require a larger membrane area (perhaps 0.35 m{sup 2}). With this in mind, an intermediate sized PMR was constructed. This PMR has 7 permeator tubes and a total membrane area of 0.0851 m{sup 2}. The catalyst volume to membrane area ratio for the 7-tube PMR was 5.18 cc/cm{sup 2}. The total membrane area of the 7-tube PMR (0.0851 m{sup 2}) is 3.45 times larger than total membrane area of the 3-tube PMR (0.0247 m{sup 2}). The following objectives were identified for the 7-tube PMR tests: (1) Refine test measurements, especially humidity and flow; (2) Refine maintenance procedures for Pd/Ag tube conditioning; (3) Evaluate baseline PMR operating conditions; (4) Determine PMR

  11. Computer simulation on the water/platinum interface

    SciTech Connect

    Spohr, E. )

    1989-08-10

    A molecular model for the water/platinum interface has been devised. It includes the surface corrugation of the metal and orientationally anisotropic water-metal interactions obtained from quantum chemical cluster calculations. Barriers for the surface diffusion and for the reorientation of a single water molecule on the quadratic (100) face of the face-centered-cubic platinum crystal are discussed. The flexible Bopp-Jancso-Heinzinger water model describes the water-water interactions, and the platinum-platinum interactions are described by a single force constant. Molecular dynamics simulations of a water lamina confined by (100) platinum surfaces have been performed using these interaction potentials. The structure is discussed on the basis of one-particle density profiles and solvent pair correlation functions. The surface-induced structural inhomogeneity ranges up to distances of 10 {angstrom}. In the center of the lamina water properties are bulklike. Hydrogen bonding in the vicinity of the interface is only slightly reduced relative to the bulk. The orientational structure of water is strongly influenced by water-water interactions and is considerably different from the preferential orientation according to the water-platinum interaction potential. It leads to a dipolar potential drop across the interface of 1.1 V.

  12. In vitro permeation of platinum and rhodium through Caucasian skin.

    PubMed

    Franken, A; Eloff, F C; Du Plessis, J; Badenhorst, C J; Jordaan, A; Du Plessis, J L

    2014-12-01

    During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace.

  13. Transition Metal Dithiolene Near-IR Dyes and Thier Applications in Liquid Crystal Devices

    SciTech Connect

    Marshall, K.L.; Painter, G.; Lotito, K.; Noto, A.G.; Chang, P.

    2006-08-18

    Numerous commercial and military applications exist for guest–host liquid crystal (LC) devices operating in the near- to mid-IR region. Progress in this area has been hindered by the severe lack of near-IR dyes with good solubility in the LC host, low impact on the inherent order of the LC phase, good thermal and chemical stability, and a large absorbance maximum tunable by structural modification over a broad range of the near-IR region. Transition metal complexes based on nickel, palladium, or platinum dithiolene cores show substantial promise in meeting these requirements. In this paper, we overview our past and present activities in the design and synthesis of transition metal dithiolene dyes, show some specific applications examples for these materials as near-IR dyes in LC electro-optical devices, and present our most recent results in the computational modeling of physical and optical properties of this interesting class of organometallic optical materials.

  14. Platinum blue staining of cells grown in electrospun scaffolds.

    PubMed

    Yusuf, Mohammed; Millas, Ana Luiza G; Estandarte, Ana Katrina C; Bhella, Gurdeep K; McKean, Robert; Bittencourt, Edison; Robinson, Ian K

    2014-01-01

    Fibroblast cells grown in electrospun polymer scaffolds were stained with platinum blue, a heavy metal stain, and imaged using scanning electron microscopy. Good contrast on the cells was achieved compared with samples that were gold sputter coated. The cell morphology could be clearly observed, and the cells could be distinguished from the scaffold fibers. Here we optimized the required concentration of platinum blue for imaging cells grown in scaffolds and show that a higher concentration causes platinum aggregation. Overall, platinum blue is a useful stain for imaging cells because of its enhanced contrast using scanning electron microscopy (SEM). In the future it would be useful to investigate cell growth and morphology using three-dimensional imaging methods.

  15. An analytical technique to extract surface information of negatively stained or heavy-metal shadowed organic materials within the TEM.

    PubMed

    Matsko, Nadejda B; Letofsky-Papst, Ilse; Albu, Mihaela; Mittal, Vikas

    2013-06-01

    Using a series of uranyl acetate stained or platinum-palladium shadowed organic samples, an empirical analytical method to extract surface information from energy-filtered transmission electron microscopy (EFTEM) images is described. The distribution of uranium or platinum-palladium atoms, which replicate the sample surface topography, have been mathematically extracted by dividing the image acquired in the valence bulk plasmon energy region (between 20 and 30 eV) by the image acquired at the carbon K ionization edge (between 284 and 300 eV). The resulting plasmon-to-carbon ratio (PCR) image may be interpreted as a precise metal replica of the sample surface. In contrast to conventional EFTEM elemental mapping, including an absolute quantification approach, this technique can be applied to 200-600 nm thick organic samples. A combination of conventional TEM and PCR imaging allows one to detect complementary transmission and topographical information with nanometer precision of the same area of carbon-based samples. The advantages and limitations of PCR imaging are highlighted. PMID:23570815

  16. Selective ligandless cloud point extraction of palladium from water and dust samples.

    PubMed

    Mohammadi, Sayed Zia; Mohammadnezhad, Mohsen

    2015-01-01

    In this study, the phase-separation phenomenon of non-ionic surfactants was used for separation and preconcentration of Pd(II). The cloud point extraction (CPE) method is based on the formation of PdI2 which is then entrapped in the non-ionic surfactant Triton X-114. Ethanol acidified with 0.5 M HNO3 was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry. The main factors affecting CPE efficiency, such as sample solution pH, concentration of iodide ion and Triton X-114, equilibration temperature and time, were all investigated and optimized. At optimum conditions, a calibration curve was constructed for the determination of palladium according to the ligandless CPE procedure. Linearity was maintained between 1.0 to 500.0 ng/mL. The LOD based on three times the SD of the blank divided by the slope of analytical curve, (3Sb/m) was 0.3 ng/mL. Seven replicate determinations of a solution containing of 4.0 μg palladium gave a mean absorbance of 0.359 with RSD±1.85%. The high efficiency of CPE to carry out the determination of palladium in complex matrixes was demonstrated. The proposed method has been applied to the determination of trace amounts of palladium in a platinum-iridium alloy, water, and dust samples, with satisfactory results.

  17. Levitation calorimetry. IV - The thermodynamic properties of liquid cobalt and palladium.

    NASA Technical Reports Server (NTRS)

    Treverton, J. A.; Margrave, J. L.

    1971-01-01

    Some of the thermodynamic properties of liquid cobalt and palladium investigated by means of levitation calorimetry are reported and discussed. The presented data include the specific heats and heats of fusion of the liquid metals, and the emissivities of the liquid metal surfaces.

  18. Nanometer-Size Effect on Hydrogen Sites in Palladium Lattice.

    PubMed

    Akiba, Hiroshi; Kofu, Maiko; Kobayashi, Hirokazu; Kitagawa, Hiroshi; Ikeda, Kazutaka; Otomo, Toshiya; Yamamuro, Osamu

    2016-08-17

    Nanometer-sized materials attract much attention because their physical and chemical properties are substantially different from those of bulk materials owing to their size and surface effects. In this work, neutron powder diffraction experiments on the nanoparticles of palladium hydride, which is the most popular metal hydride, have been performed at 300, 150, and 44 K to investigate the positions of the hydrogen atoms in the face-centered cubic (fcc) lattice of palladium. We used high-quality PdD0.363 nanocrystals with a diameter of 8.0 ± 0.9 nm. The Rietveld analysis revealed that 30% of D atoms are located at the tetrahedral (T) sites and 70% at the octahedral (O) sites. In contrast, only the O sites are occupied in bulk palladium hydride and in most fcc metal hydrides. The temperature dependence of the T-site occupancy suggested that the T-sites are occupied only in a limited part, probably in the subsurface region, of the nanoparticles. This is the first study to determine the hydrogen sites in metal nanoparticles. PMID:27462875

  19. Addition of platinum and silver nanoparticles to toughen dental porcelain.

    PubMed

    Fujieda, Tokushi; Uno, Mitsunori; Ishigami, Hajime; Kurachi, Masakazu; Wakamatsu, Nobukazu; Doi, Yutaka

    2012-01-01

    Several studies have investigated toughening porcelain that is layered over a frame or a core. The introduction of residual compressive stress to the surface of porcelain has been shown to be effective to strengthen it. In the present study, nanoparticles of precious metals of silver and platinum (rather than non-precious metals) were used to evaluate if they could increase the fracture resistance of porcelain. The addition of silver and platinum nanoparticles was found to improve the mechanical properties of porcelain since it increased both the Young's modulus and the fracture toughness of commercial porcelain.

  20. Bio-inspired routes for synthesizing efficient nanoscale platinum electrocatalysts

    SciTech Connect

    Cha, Jennifer N.; Wang, Joseph

    2014-08-31

    controlled, the nanocrystals boast a defined shape, morphology, orientation and size and are synthesized at benign reaction conditions. Adapting the methods of biomineralization towards the synthesis of platinum nanocrystals will allow effective control at a molecular level of the synthesis of highly active metal electrocatalysts, with readily tailored properties, through tuning of the biochemical inputs. The proposed research will incorporate many facets of biomineralization by: (1) isolating peptides that selectively bind particular crystal faces of platinum (2) isolating peptides that promote the nucleation and growth of particular nanocrystal morphologies (3) using two-dimensional DNA scaffolds to control the spatial orientation and density of the platinum nucleating peptides, and (4) combining bio-templating and soluble peptides to control crystal nucleation, orientation, and morphology. The resulting platinum nanocrystals will be evaluated for their electrocatalytic behavior (on common carbon supports) to determine their optimal size, morphology and crystal structure. We expect that such rational biochemical design will lead to highly uniform and efficient platinum nanocrystal catalysts for fuel cell applications.

  1. Synthesis of Bimetallic Platinum Nanoparticles for Biosensors

    PubMed Central

    Leteba, Gerard M.; Lang, Candace I.

    2013-01-01

    The use of magnetic nanomaterials in biosensing applications is growing as a consequence of their remarkable properties; but controlling the composition and shape of metallic nanoalloys is problematic when more than one precursor is required for wet chemistry synthesis. We have developed a successful simultaneous reduction method for preparation of near-spherical platinum-based nanoalloys containing magnetic solutes. We avoided particular difficulties in preparing platinum nanoalloys containing Ni, Co and Fe by the identification of appropriate synthesis temperatures and chemistry. We used transmission electron microscopy (TEM) to show that our particles have a narrow size distribution, uniform size and morphology, and good crystallinity in the as-synthesized condition. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) confirms the coexistence of Pt with the magnetic solute in a face-centered cubic (FCC) solid solution. PMID:23941910

  2. Palladium Catalyzed Reduction of Nitrobenzene.

    ERIC Educational Resources Information Center

    Mangravite, John A.

    1983-01-01

    Compares two palladium (Pd/C) reducing systems to iron/tin-hydrochloric acid (Fe/HCl and Sn/HCl) reductions and suggests an efficient, clean, and inexpensive procedures for the conversion of nitrobenzene to aniline. Includes laboratory procedures used and discussion of typical results obtained. (JN)

  3. Growth of platinum nanocrystals

    SciTech Connect

    2009-01-01

    Movie showing the growth of platinum nanocrystals in a liquid cell observed in situ using the JEOL 3010 TEM at the National Center for Electron Microscopy. This is the first ever-real time movie showing nucleation and growth by monomer attachment or by smaller nanocrystals coalescing to form larger nanocrystals. All the nanocrystals end up being roughly the same shape and size. http://newscenter.lbl.gov/feature-stories/2009/08/04/growth-spurts/

  4. Synthesis and characterization of palladium nanoparticles using Catharanthus roseus leaf extract and its application in the photo-catalytic degradation.

    PubMed

    Kalaiselvi, Aasaithambi; Roopan, Selvaraj Mohana; Madhumitha, Gunabalan; Ramalingam, C; Elango, Ganesh

    2015-01-25

    The potential effect of Catharanthus roseus leaf extract for the formation of palladium nanoparticles and its application on dye degradation was discussed. The efficiency of C.roseus leaves are used as a bio-material for the first time as reducing agent. Synthesized palladium nanoparticles were supported by UV-vis spectrometry, XRD, FT-IR and TEM analysis. The secondary metabolites which are responsible for the formation of nanoparticles were identified by GC-MS. The results showed that effect of time was directly related to synthesized nanoparticles and functional groups has a critical role in reducing the metal ions and stabilizing the palladium nanoparticles in an eco-friendly process.

  5. Development of palladium-based nanocatalysts on carbon support for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Arroyo Ramirez, Lisandra

    Direct methanol fuel cell (DMFC) promises to be a power source for space application, transportation and portable devices. However, platinum catalysts, the methanol crossover and the sluggish kinetics of the oxygen reduction reaction (ORR) limit their commercialization. DMFC has the challenge to find a catalyst with high methanol tolerance and simple synthesis methodology. We proposed the development of palladium-based nanostructures on carbon supports as electrocatalyst for the oxygen reduction reaction. The working hypothesis is that the use of different methodologies and carbon supports will lead the formation of different palladium catalytic nanostructures with high methanol tolerance. A new single source approach was used to synthesize Pd-Co nanostructures on a highly ordered pyrolytic graphite (HOPG) surface using a bimetallic molecular precursor. Then, synthesis of palladium and palladium-cobalt nanoparticles on Vulcan XC-72R by chemical and thermal reduction using organometallic complexes as precursors was done. The palladium thin films and nanoshells were synthesized on HOPG and carbon cloth using sputtering deposition and electrospinning techniques. The morphology and composition were characterized by surface analysis techniques, such as: atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscope with energy-dispersive X-ray fluorescence spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), among others. ORR electrocatalytic activity and methanol tolerance was determined for the Pd/C, Pd2Co/C and PdCo 2/C catalysts. The rotating ring-disk electrode technique was used to determine the ORR mechanism and kinetics. Pd2Co nanorings were formed on a HOPG surface by self-assembly with humidity control. Also, a single precursor was used for the synthesis of palladium-cobalt nanocatalysts on carbon supports by thermal reduction with ORR electrocatalytic activity and higher methanol

  6. The use of palladium to obtain reproducible boundary conditions for permeability measurements using galvanostatic charging

    NASA Astrophysics Data System (ADS)

    Bowker, J.; Piercy, G. R.

    1985-05-01

    The diffusion current of hydrogen through palladium in an electrochemical cell initially rises linearly with the charging current, reaches a steady “plateau” value, and then rises again. The diffusivity of hydrogen in palladium was measured using standard transient techniques in the initial region of low current density. Combining this value with the measured value of diffusion current at the plateau level gave a concentration of hydrogen at the entrance surface of the palladium that was the same for three different palladium thicknesses, and was equal to the saturation value in α palladium. It is proposed that this can be used as a known and reproducible effective hydrogen pressure (0.019 atm) if palladium is plated onto other metals before measuring their permeability in an electrochemical cell. Experimental evidence for this was obtained from permeability measurements made on several thicknesses of iron. Permeation studies were also made on AISI 410 stainless steel and tin plated mild steel. The measured value for electrolytic tinplate was 107 times that expected from extrapolation of high temperature data. This could be attributed to grain boundaries or porosity covering 0.003 pct of the area. The permeability values of iron and stainless steel are 8.4 x 1012 and 2.8 x 1013 H atom/cm • s • √atm, respectively.

  7. Formation of iron oxides in a highly alkaline medium in the presence of palladium ions

    NASA Astrophysics Data System (ADS)

    Krehula, Stjepko; Musić, Svetozar

    2009-04-01

    The effect of the presence of palladium ions in a highly alkaline precipitation system on the formation of iron oxides was investigated using X-ray powder diffraction (XRPD), Mössbauer and FT-IR spectroscopies, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Acicular α-FeOOH particles precipitated in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH) were used as reference material. The initial addition of palladium ions to that precipitation system had a significant effect on the formation of iron oxide phases and their properties. In the presence of palladium ions, the initially formed α-FeOOH has been transformed to α-Fe 2O 3 crystals in the form of hexagonal bipyramids via a dissolution-reprecipitation mechanism with a simultaneous formation of metallic palladium nanoparticles. These palladium nanoparticles acted as a catalyst for the reductive dissolution of α-Fe 2O 3 particles and the formation of Fe 3O 4 crystals in the form of octahedrons. Increase in the initial concentration of palladium ions in the precipitation system accelerated the transformation process α-FeOOH → α-Fe 2O 3 → Fe 3O 4 and influenced changes in the shape of α-Fe 2O 3 and Fe 3O 4 particles.

  8. Highly dispersed palladium nanoparticles anchored on UiO-66(NH2) metal-organic framework as a reusable and dual functional visible-light-driven photocatalyst

    NASA Astrophysics Data System (ADS)

    Shen, Lijuan; Wu, Weiming; Liang, Ruowen; Lin, Rui; Wu, Ling

    2013-09-01

    Proper design and preparation of high-performance and stable dual functional photocatalytic materials remains a significant objective of research. In this work, highly dispersed Pd nanoparticles of about 3-6 nm in diameter are immobilized in the metal-organic framework (MOF) UiO-66(NH2) via a facile one-pot hydrothermal method. The resulting Pd@UiO-66(NH2) nanocomposite exhibits an excellent reusable and higher visible light photocatalytic activity for reducing Cr(vi) compared with UiO-66(NH2) owing to the high dispersion of Pd nanoparticles and their close contact with the matrix, which lead to the enhanced light harvesting and more efficient separation of photogenerated electron-hole pairs. More significantly, the Pd@UiO-66(NH2) could be used for simultaneous photocatalytic degradation of organic pollutants, like methyl orange (MO) and methylene blue (MB), and reduction of Cr(vi) with even further enhanced activity in the binary system, which could be attributed to the synergetic effect between photocatalytic oxidation and reduction by individually consuming photogenerated holes and electrons. This work represents the first example of using the MOFs-based materials as dual functional photocatalyst to remove different categories of pollutants simultaneously. Our finding not only proves great potential for the design and application of MOFs-based materials but also might bring light to new opportunities in the development of new high-performance photocatalysts.Proper design and preparation of high-performance and stable dual functional photocatalytic materials remains a significant objective of research. In this work, highly dispersed Pd nanoparticles of about 3-6 nm in diameter are immobilized in the metal-organic framework (MOF) UiO-66(NH2) via a facile one-pot hydrothermal method. The resulting Pd@UiO-66(NH2) nanocomposite exhibits an excellent reusable and higher visible light photocatalytic activity for reducing Cr(vi) compared with UiO-66(NH2) owing to the

  9. Coordination of two high-affinity hexamer peptides to copper(II) and palladium(II) models of the peptide-metal chelation site on IMAC resins

    SciTech Connect

    Chen, Y.; Pasquinelli, R.; Ataai, M.; Koepsel, R.R.; Kortes, R.A.; Shepherd, R.E.

    2000-03-20

    The coordination of peptides Ser-Pro-His-His-Gly-Gly (SPHHGG) and (His){sub 6} (HHHHHH) to [Pd{sup II}(mida)(D{sub 2}O)] (mida{sup 2{minus}} = N-methyliminodiacetate) was studied by {sup 1}H NMR as model reactions for Cu{sup II}(iminodiacetate)-immobilized metal affinity chromatography (IMAC) sites. This is the first direct physical description of peptide coordination for IMAC. A three-site coordination is observed which involves the first, third, and fourth residues along the peptide chain. The presence of proline in position 2 of SPHHGG achieves the best molecular mechanics and bonding angles in the coordinated peptide and enhances the interaction of the serine amino nitrogen. Histidine coordination of H{sub 1}, H{sub 3}, and H{sub 4} of (His){sub 6} and H{sub 3} and H{sub 4} of SPHHGG was detected by {sup 1}H NMR contact shifts and H/D exchange of histidyl protons. The EPR spectra of SPHHGG and HHHHHH attached to the [Cu{sup II}(mida)] unit were obtained for additional modeling of IMAC sites. EPR parameters of the parent [Cu(mida)(H{sub 2}O){sub 2}] complex are representative: g{sub zz} = 2.31; g{sub yy} = 2.086; g{sub xx} = 2.053; A{sub {vert_bar}{vert_bar}} = 161 G; A{sub N} = 19G (three line, one N coupling). Increased rhombic distortion is detected relative to the starting aqua complex in the order of [Cu(mida)L] for distortion of HHHHHH > SPHHGG > (H{sub 2}O){sub 2}. The lowering of symmetry is also seen in the decrease in the N-shf coupling, presumably to the imino nitrogen of mida{sup 2{minus}} in the order 19 G (H{sub 2}O), 16 G (SPHHGG) and 11 G (HHHHHH). Visible spectra of the [Cu(mida)(SPHHGG)] and [Cu(mida)(HHHHHH)] as a function of pH indicate coordination of one histidyl donor at ca. 4.5, two in the range of pH 5--7, and two chelate ring attachments involving the terminal amino donor for SPHHGG or another histidyl donor of HHHHHH in the pH domain of 7--8 in agreement with the [Pd{sup II}(mida)L] derivatives which form the two

  10. Metal/ceramic composites with high hydrogen permeability

    DOEpatents

    Dorris, Stephen E.; Lee, Tae H.; Balachandran, Uthamalingam

    2003-05-27

    A membrane for separating hydrogen from fluids is provided comprising a sintered homogenous mixture of a ceramic composition and a metal. The metal may be palladium, niobium, tantalum, vanadium, or zirconium or a binary mixture of palladium with another metal such as niobium, silver, tantalum, vanadium, or zirconium.

  11. Optical, spectroscopic, and electrochemical properties of cyclometalated complexes of platinum metals based on 2-tolylpyridine and benzo[h]quinoline in ethylenediamine

    NASA Astrophysics Data System (ADS)

    Katlenok, E. A.; Balashev, K. P.

    2013-10-01

    Cyclometalated [M(C∧N)En]PF6 (M = Pd(II), Pt(II)) and [M(C∧N)2En]PF6 (M = Rh(III), Ir(III)) complexes ((C∧N)- corresponds to the deprotonated forms of 2-tolylpyridine and benzo[h]quinoline, and En is ethylenediamine) are studied by 1H NMR spectroscopy, electronic absorption and emission spectroscopy, and voltammetry. Metalation of heterocyclic ligands leads to the formation of five-membered {M(C∧N)} cycles in the composition of square planar and octahedral complexes of the cis-C,C structure. Correlation of the energy positions of the long-wavelength metal-to-ligand charge-transfer absorption bands with the difference between the potentials of one-electron waves of metal-centered oxidation and ligand-centered reduction of complexes is shown. The phosphorescence of the complexes in the visible region of 469-524 nm is attributed to the radiative transition from the metal-modified intraligand excited state. The temperature quenching of the phosphorescence of complexes is attributed to the thermally activated population of metal-centered electronically excited states with subsequent nonradiative deactivation.

  12. Palladium as electrode in DNA sequencing

    NASA Astrophysics Data System (ADS)

    Chen, Xiang

    2013-08-01

    We construct a molecular junction comprising two identical "reader" molecules that are each linked on one end to a DNA single base via hydrogen bonds and on the other end to a palladium electrode. The structure of the junction is thus palladium-reader-base-reader-palladium. The palladium-reader contacts occur via Pd-S bonds. We calculated the electronic structure and conductance of the molecular junctions. Compared with the performance of molecular junctions with gold or titanium nitride electrodes, the current-voltage characteristics of the molecular junctions with palladium electrodes show higher sensitivity to the identity of the bridging DNA base, allowing the DNA bases to be distinguished more easily. Therefore, palladium is a superior electrode for molecular electronics and DNA sequencing.

  13. Electrically conductive palladium containing polyimide films

    NASA Technical Reports Server (NTRS)

    Taylor, L. T.; St.clair, A. K.; Carver, V. C.; Furtsch, T. A. (Inventor)

    1982-01-01

    Lightweight, high temperature resistant, electrically conductive, palladium containing polyimide films and methods for their preparation are described. A palladium (II) ion-containing polyamic acid solution is prepared by reacting an aromatic dianhydride with an equimolar quantity of a palladium II ion-containing salt or complex and the reactant product is cast as a thin film onto a surface and cured at approximately 300 C to produce a flexible electrically conductive cyclic palladium containing polyimide. The source of palladium ions is selected from the group of palladium II compounds consisting of LiPdCl4, PdS(CH3)2Cl2Na2PdCl4, and PdCl2. The films have application to aerodynamic and space structures and in particular to the relieving of space charging effects.

  14. In situ electrical characterization of palladium-based single electron transistors made by electromigration technique

    SciTech Connect

    Arzubiaga, L.; Llopis, R.; Golmar, F.; Casanova, F.; Hueso, L. E.

    2014-11-15

    We report the fabrication of single electron transistors (SETs) by feedback-controlled electromigration of palladium and palladium-nickel alloy nanowires. We have optimized a gradual electromigration process for obtaining devices consisting of three terminals (source, drain and gate electrodes), which are capacitively coupled to a metallic cluster of nanometric dimensions. This metal nanocluster forms into the inter-electrode channel during the electromigration process and constitutes the active element of each device, acting as a quantum dot that rules the electron flow between source and drain electrodes. The charge transport of the as-fabricated devices shows Coulomb blockade characteristics and the source to drain conductance can be modulated by electrostatic gating. We have thus achieved the fabrication and in situ measurement of palladium-based SETs inside a liquid helium cryostat chamber.

  15. Understanding Palladium Acetate from a User Perspective.

    PubMed

    Carole, William A; Colacot, Thomas J

    2016-06-01

    The behavior of palladium acetate is reviewed with respect to its synthesis, characterization, structure (in both solution and solid state), and activation pathways. In addition, comparisons of catalytic activities between pure palladium acetate and two common byproducts, Pd3 (OAc)5 (NO2 ) and polymeric [Pd(OAc)2 ]n , typically present in commercially available material are reviewed. Hence, this minireview serves as a concise guide for the users of palladium acetate from both academia and industry. PMID:27125630

  16. Transition-metal chromophore as a new, sensitive spectroscopic tag for proteins. Selective covalent labeling of histidine residues in cytochromes c with chloro(2,2':6',2''-terpyridine)platinum(II) chloride

    SciTech Connect

    Ratilla, E.M.A.; Brothers, H.M. II; Kostic, N.M.

    1987-07-22

    Reactivity and selectivity of Pt(trpy)Cl/sup +/ toward proteins are studied with cytochromes c from horse and tuna as examples. The new transition-metal reagent is specific for histidine residues at pH 5. The reaction, facile one-step displacement of the Cl/sup -/ ligand by imidazole, produces good yield. The binding sites, His 26 and His 33 in the horse protein and His 26 in the tuna protein, are identified by UV-vis spectrophotometry and by peptide-mapping experiments. Model complexes with imidazole, histidine, histidine derivatives, and histidine-containing peptides are prepared and characterized. The covalently attached Pt(trpy)/sup 2 +/ labels allow easy separation of the protein derivatives by cation-exchange chromatography. The labels do not perturb the conformation and reduction potential of cytochrome c, as shown by UV-vis spectrophotometry, cyclic voltammetry, differential-pulse voltammetry, EPR spectroscopy, and /sup 1/H NMR spectroscopy. The selectivity of Pt(trpy)Cl/sup +/ is entirely opposite from that of PtCl/sub 4//sup 2 -/ although both of them are platinum(II)-chloro complexes. Owing to an interplay between the steric and electronic effects of the terpyridyl ligand, the new reagent is unreactive toward methionine (a thio ether) and cystine (a disulfide), which are otherwise highly nucleophilic ligands, but very reactive toward imidazole, which is otherwise a relatively weak ligand. Unusual and useful selectivity of preformed transition-metal complexes toward proteins evidently can be achieved by a judicious choice of ancillary ligands.

  17. Geochemical behaviour of palladium in soils and Pd/PdO model substances in the presence of the organic complexing agents L-methionine and citric acid.

    PubMed

    Zereini, Fathi; Wiseman, Clare L S; Vang, My; Albers, Peter; Schneider, Wolfgang; Schindl, Roland; Leopold, Kerstin

    2016-01-01

    Risk assessments of platinum group metal (PGE) emissions, notably those of platinum (Pt), palladium (Pd) and rhodium (Rh), have been mostly based on data regarding the metallic forms used in vehicular exhaust converters, known to be virtually biologically inert and immobile. To adequately assess the potential impacts of PGE, however, data on the chemical behaviour of these metals under ambient conditions post-emission is needed. Complexing agents with a high affinity for metals in the environment are hypothesized to contribute to an increased bioaccessibility of PGE. The purpose of this study is to examine the modulating effects of the organic complexing agents, L-methionine and citric acid, on the geochemical behavior of Pd in soils and model substances (Pd black and PdO). Batch experimental tests were conducted with soils and model substances to examine the impacts of the concentration of complexing agents, pH and length of extraction period on Pd solubility and its chemical transformation. Particle surface chemistry was examined using X-ray photoelectron spectroscopy (XPS) on samples treated with solutions under various conditions, including low and high O2 levels. Pd was observed to be more soluble in the presence of organic complexing agents, compared to Pt and Rh. Pd in soils was more readily solubilized with organic complexing agents compared to the model substances. After 7 days of extraction, L-methionine (0.1 M) treated soil and Pd black samples, for instance, had mean soluble Pd fractions of 12.4 ± 5.9% and 0.554 ± 0.024%, respectively. Surface chemistry analyses (XPS) confirmed the oxidation of metallic Pd surfaces when treated with organic complexing agents. The type of organic complexing agent used for experimental purposes was observed to be the most important factor influencing solubility, followed by solution pH and time of extraction. The results demonstrate that metallic Pd can be transformed into more bioaccessible species in the presence of

  18. Platinum in Earth surface environments

    NASA Astrophysics Data System (ADS)

    Reith, F.; Campbell, S. G.; Ball, A. S.; Pring, A.; Southam, G.

    2014-04-01

    Platinum (Pt) is a rare precious metal that is a strategic commodity for industries in many countries. The demand for Pt has more than doubled in the last 30 years due to its role in the catalytic conversion of CO, hydrocarbons and NOx in modern automobiles. To explore for new Pt deposits, process ores and deal with ecotoxicological effects of Pt mining and usage, the fundamental processes and pathways of Pt dispersion and re-concentration in surface environments need to be understood. Hence, the aim of this review is to develop a synergistic model for the cycling of Pt in Earth surface environments. This is achieved by integrating the geological/(biogeo)chemical literature, which focuses on naturally occurring Pt mobility around ore deposits, with the environmental/ecotoxicological literature dealing with anthropogenic Pt dispersion. In Pt deposits, Pt occurs as sulfide-, telluride- and arsenide, native metal and alloyed to other PGEs and iron (Fe). Increased mining and utilization of Pt combined with the burning of fossil fuels have led to the dispersion of Pt-containing nano- and micro-particles. Hence, soils and sediments in industrialized areas, urban environments and along major roads are now commonly Pt enriched. Platinum minerals, nuggets and anthropogenic particles are transformed by physical and (bio)geochemical processes. Complexation of Pt ions with chloride, thiosulfate, ammonium, cyanide, low- and high molecular weight organic acids (LMWOAs and HMWOAs) and siderophores can facilitate Pt mobilization. Iron-oxides, clays, organic matter and (micro)biota are known to sequester Pt-complexes and -particles. Microbes and plants are capable of bioaccumulating and reductively precipitating mobile Pt complexes. Bioaccumulation can lead to toxic effects on plants and animals, including humans. (Bio)mineralization in organic matter-rich sediments can lead to the formation of secondary Pt particles and -grains. Ultimately, Pt is enriched in oceanic sediments

  19. A gold/platinum thermocouple reference table

    NASA Astrophysics Data System (ADS)

    Gotoh, M.; Hill, K. D.; Murdock, E. G.

    1991-11-01

    The thermoelectric voltage of the gold/platinum thermocouple has been measured over the range 0-962 °C by comparison with calibrated platinum resistance thermometers. From 0 to 500 °C, the measurements were carried out in stirred liquid baths; from 660 to 964 °C, they were carried out in a pressure-controlled sodium-filled heat pipe furnace that provided an isothermal intercomparison environment. Measurements were also made in the metal freezing points of indium, tin, zinc, antimony, and silver, at the melting point of gallium, and at the liquidus point of the silver-copper eutectic. By fitting the measured thermoelectric voltages to a single eighth-degree polynomial in temperature by the method of least squares, a reference function is obtained for the Au/Pt thermocouple that provides emf as a function of temperature (ITS-90) to within ±10 mK from 0 to 962 °C. The Au/Pt thermocouple merits serious consideration for precise temperature measurements as its stability approaches that of the high-temperature platinum resistance thermometer.

  20. Atomistic potentials for palladium-silver hydrides

    NASA Astrophysics Data System (ADS)

    Hale, L. M.; Wong, B. M.; Zimmerman, J. A.; Zhou, X. W.

    2013-06-01

    New embedded-atom method potentials for the ternary palladium-silver-hydrogen system are developed by extending a previously developed palladium-hydrogen potential. The ternary potentials accurately capture the heat of mixing and structural properties associated with solid solution alloys of palladium-silver. Stable hydrides are produced with properties that smoothly transition across the compositions. Additions of silver to palladium are predicted to alter the properties of the hydrides by decreasing the miscibility gap and increasing the likelihood of hydrogen atoms occupying tetrahedral interstitial sites over octahedral interstitial sites.

  1. Titanium(IV) oxide photocatalysts with palladium

    SciTech Connect

    Papp, J.; Shen, H.S.; Kershaw, R.; Dwight, K.; Wold, A. )

    1993-03-01

    Samples of palladium decomposed onto TiO[sub 2] particles were prepared by two methods: the dispersion of a PdCl[sub 2] solution followed by thermal decomposition, and the photodecomposition of PdCl[sub 2]. The addition of palladium to all samples increased their photocatalytic activity toward the degradation of 1,4-dichlorobenzene. This increase was optimized and compared for these two preparative methods. Palladium was also decomposed onto TiO[sub 2] thin films by the photodecomposition of PdCl[sub 2]. The addition of palladium to the films increased their photocatalytic activity toward the degradation of salicylic acid. 35 refs., 4 figs., 4 tabs.

  2. The Effect of Novel Mercapto Silane Systems on Resin Bond Strength to Dental Noble Metal Alloys.

    PubMed

    Lee, Yangho; Kim, Kyo-Han; Kim, Young Kyung; Son, Jun Sik; Lee, Eunkyung; Kwon, Tae-Yub

    2015-07-01

    Self-assembled monolayers of thiols (RSH), which are key elements in nanoscience and nanotechnology, have been used to link a range of materials to planar gold surfaces or gold nanoparticles. In this study, the adhesive performance of mercapto silane systems to dental noble metal alloys was evaluated in vitro and compared with that of commercial dental primers. Dental gold-palladium-platinum (Au-Pd-Pt), gold-palladium-silver (Au-Pd-Ag), and palladium-silver (Pd-Ag) alloys were used as the bonding substrates after air-abrasion (sandblasting). One of the following primers was applied to each alloy: (1) no primer treatment (control), (2) three commer- cial primers: V-Primer, Metal Primer II, and M.L. Primer, and (3) two experimental silane primer systems: 2-step application with 3-mercaptopropyltrimethoxysilane (SPS) (1.0 wt%) and then 3-methacryloxypropyltrimethoxysilane (MPS) (1.0 wt%), and a silane blend consisting of SPS and MPS (both 1.0 wt%). Composite resin cylinders with a diameter of 2.38 mm were bonded to the surfaces and irradiated for 40 sec using a curing light. After storage in water at 37 °C for 24 h, all the bonded specimens were thermocycled 5000 times before the shear bond strength test. Regardless of the alloy type, the mercapto silane systems (both the 2-step and blend systems) consistently showed superior bonding performance than the commercial primers. Contact angle analysis of the primed surfaces indicated that higher resin bond strengths were produced on more hydrophilic alloy surfaces. These novel mercapto silane systems are a promising alternative for improving resin bonding to dental noble metal alloys.

  3. Lithographically patterned nanowire electrodeposition: a method for patterning electrically continuous metal nanowires on dielectrics.

    PubMed

    Xiang, Chenxiang; Kung, Sheng-Chin; Taggart, David K; Yang, Fan; Thompson, Michael A; Güell, Aleix G; Yang, Yongan; Penner, Reginald M

    2008-09-23

    Lithographically patterned nanowire electrodeposition (LPNE) is a new method for fabricating polycrystalline metal nanowires using electrodeposition. In LPNE, a sacrificial metal (M(1)=silver or nickel) layer, 5-100 nm in thickness, is first vapor deposited onto a glass, oxidized silicon, or Kapton polymer film. A (+) photoresist (PR) layer is then deposited, photopatterned, and the exposed Ag or Ni is removed by wet etching. The etching duration is adjusted to produce an undercut approximately 300 nm in width at the edges of the exposed PR. This undercut produces a horizontal trench with a precisely defined height equal to the thickness of the M(1) layer. Within this trench, a nanowire of metal M(2) is electrodeposited (M(2)=gold, platinum, palladium, or bismuth). Finally the PR layer and M(1) layer are removed. The nanowire height and width can be independently controlled down to minimum dimensions of 5 nm (h) and 11 nm (w), for example, in the case of platinum. These nanowires can be 1 cm in total length. We measure the temperature-dependent resistance of 100 microm sections of Au and Pd wires in order to estimate an electrical grain size for comparison with measurements by X-ray diffraction and transmission electron microscopy. Nanowire arrays can be postpatterned to produce two-dimensional arrays of nanorods. Nanowire patterns can also be overlaid one on top of another by repeating the LPNE process twice in succession to produce, for example, arrays of low-impedance, nanowire-nanowire junctions. PMID:19206435

  4. Lithographically patterned nanowire electrodeposition: a method for patterning electrically continuous metal nanowires on dielectrics.

    PubMed

    Xiang, Chenxiang; Kung, Sheng-Chin; Taggart, David K; Yang, Fan; Thompson, Michael A; Güell, Aleix G; Yang, Yongan; Penner, Reginald M

    2008-09-23

    Lithographically patterned nanowire electrodeposition (LPNE) is a new method for fabricating polycrystalline metal nanowires using electrodeposition. In LPNE, a sacrificial metal (M(1)=silver or nickel) layer, 5-100 nm in thickness, is first vapor deposited onto a glass, oxidized silicon, or Kapton polymer film. A (+) photoresist (PR) layer is then deposited, photopatterned, and the exposed Ag or Ni is removed by wet etching. The etching duration is adjusted to produce an undercut approximately 300 nm in width at the edges of the exposed PR. This undercut produces a horizontal trench with a precisely defined height equal to the thickness of the M(1) layer. Within this trench, a nanowire of metal M(2) is electrodeposited (M(2)=gold, platinum, palladium, or bismuth). Finally the PR layer and M(1) layer are removed. The nanowire height and width can be independently controlled down to minimum dimensions of 5 nm (h) and 11 nm (w), for example, in the case of platinum. These nanowires can be 1 cm in total length. We measure the temperature-dependent resistance of 100 microm sections of Au and Pd wires in order to estimate an electrical grain size for comparison with measurements by X-ray diffraction and transmission electron microscopy. Nanowire arrays can be postpatterned to produce two-dimensional arrays of nanorods. Nanowire patterns can also be overlaid one on top of another by repeating the LPNE process twice in succession to produce, for example, arrays of low-impedance, nanowire-nanowire junctions.

  5. METAL COMPOSITIONS

    DOEpatents

    Seybolt, A.U.

    1959-02-01

    Alloys of uranium which are strong, hard, and machinable are presented, These alloys of uranium contain bctween 0.1 to 5.0% by weight of at least one noble metal such as rhodium, palladium, and gold. The alloys may be heat treated to obtain a product with iniproved tensile and compression strengths,

  6. Selective recovery of palladium from waste printed circuit boards by a novel non-acid process.

    PubMed

    Zhang, Zhiyuan; Zhang, Fu-Shen

    2014-08-30

    An environmental benign, non-acid process was successfully developed for selective recovery of palladium from waste printed circuit boards (PCBs). In the process, palladium was firstly enriched during copper recovery procedure and dissolved in a special solution made of CuSO4 and NaCl. The dissolved palladium was then extracted by diisoamyl sulfide (S201). It was found that 99.4% of Pd(II) could be extracted from the solution under the optimum conditions (10% S201, A/O ratio 5 and 2min extraction). In the whole extraction process, the influence of base metals was negligible due to the relatively weak nucleophilic substitution of S201 with base metal irons and the strong steric hindrance of S201 molecular. Around 99.5% of the extracted Pd(II) could be stripped from S201/dodecane with 0.1mol/L NH3 after a two-stage stripping at A/O ratio of 1. The total recovery percentage of palladium was 96.9% during the dissolution-extraction-stripping process. Therefore, this study established a benign and effective process for selective recovery of palladium from waste printed circuit boards.

  7. Tritium Production from Palladium Alloys

    SciTech Connect

    Claytor, T.N.; Schwab, M.J.; Thoma, D.J.; Teter, D.F.; Tuggle, D.G.

    1998-04-19

    A number of palladium alloys have been loaded with deuterium or hydrogen under low energy bombardment in a system that allows the continuous measurement of tritium. Long run times (up to 200 h) result in an integration of the tritium and this, coupled with the high intrinsic sensitivity of the system ({approximately}0.1 nCi/l), enables the significance of the tritium measurement to be many sigma (>10). We will show the difference in tritium generation rates between batches of palladium alloys (Rh, Co, Cu, Cr, Ni, Be, B, Li, Hf, Hg and Fe) of various concentrations to illustrate that tritium generation rate is dependent on alloy type as well as within a specific alloy, dependent on concentration.

  8. Mixed-metal chloro sulfido cluster complex of molybdenum and platinum, (Mo sub 3 Pt sub 2 S sub 4 Cl sub 4 (PEt sub 3 ) sub 6 )

    SciTech Connect

    Saito, Taro; Tsuboi, Toshio; Kajitani, Yoshimichi; Yamagata, Tsuneaki; Imoto, Hideo )

    1991-09-04

    In the authors recent publication, syntheses of mixed-metal chloro sulfido and chloro selenido complexes of molybdenum and nickel were reported. They were prepared by the reaction of (Mo{sub 3}X{sub 4}Cl{sub 4}(PEt{sub 3}){sub 3}(MeOH){sub 2}) (X = S, Se){sup 2} with Ni(cod){sub 2} (cod = 1,5-cyclooctadiene). In the present study, another excellent building block compound, Pt(cot){sub 2}, was reacted with the same trinuclear molybdenum complex, and the mixed-metal cluster complex (Mo{sub 3}Pt{sub 2}S{sub 4}Cl{sub 4}(PEt{sub 3}){sub 6}) (1) with an unexpected structure was obtained.

  9. Physicochemical and catalytic properties of palladium supported on poly(o-methoxyaniline)

    SciTech Connect

    Drelinkiewicz, A. . E-mail: drelinki@chemia.uj.edu.pl; Hasik, M.; Sobczak, J.W.; Sobczak, E.; Bernasik, A.; Bielanska, E.

    2005-05-18

    Palladium was introduced into a conjugated polymer poly(o-methoxyaniline) (POM) by reacting the powdered polymer with aqueous solution of PdCl{sub 2} of low acidity (PdCl{sub 2}: 2.3 x 10{sup -3} mol/dm{sup 3}, HCl: 0.66 x 10{sup -3} mol/dm{sup 3}). Various Pd{sup 2+} complexes with Cl{sup -}, H{sub 2}O, OH{sup -} ligands coexisted in this solution but predominated [PdCl{sub 2}(H{sub 2}O){sub 2}] ones. Several techniques like X-ray powder diffraction, scanning electron microscopy, X-ray photoelectron and Raman spectroscopy, extended X-ray absorption fine structure have been used to characterize the poly(o-methoxyaniline)-Pd systems. In particular, the state of Pd species in the Pd/POM of various content of palladium (2-8 wt.% Pd) and chemical changes in the polymer matrix induced by insertion of palladium were studied. The protonation and redox reactions involved on palladium incorporation resulted in palladium ions and Pd metal in the final samples. Metallic Pd produced due to spontaneous reduction of palladium ions by the polymer formed large crystalline particles 200-1000 nm in size. The Pd{sup 2+} species in the form of anionic complexes like [PdCl{sub 4}]{sup 2-} acted as the counterions at low content of palladium (2-4 wt.% Pd). At high palladium content (8 wt.% Pd), several atoms like Cl, N and/or O were identified by extended X-ray absorption fine structure (EXAFS) technique in the nearest environment of Pd atoms. The structural groups of POM (like N groups and/or OCH{sub 3}) as well as H{sub 2}O, OH{sup -} molecules are, therefore, considered as probable species in the coordination sphere of palladium. The catalytic properties were studied for the as-prepared Pd/POM and the samples additionally reduced with aqueous solution of NaH{sub 2}PO{sub 2}. They were used in the hydrogenation of C=C bonds in maleic acid (MAC) and C=O groups in 2-ethylanthraquinone (eAQ) at 60 deg. C and atmospheric pressure of hydrogen using xylene-octanol-2 or water medium. The

  10. Antimicrobial Properties of Diamondlike Carbon-Silver-Platinum Nanocomposite Thin Films

    SciTech Connect

    CHRISTOPHER, BERRY

    2005-03-07

    Silver and platinum were incorporated within diamondlike carbon (DLC) thin films using a multicomponent target pulsed laser deposition process. Transmission electron microscopy of the DLC-silver and DLC-platinum composite films reveals that the metals self-assemble into particulate nanocomposite structures. Nanoindentation testing has shown that diamondlike carbon-silver films exhibit hardness and Young's modulus values of approximately 37 GPa and 333 GPa, respectively. DLC-silver-platinum films exhibited antimicrobial properties against Staphylococcus bacteria. Diamondlike carbon-biofunctional metal nanocomposite films have a variety of potential medical and antimicrobial applications.

  11. Therapeutic gold, silver, and platinum nanoparticles.

    PubMed

    Yamada, Miko; Foote, Matthew; Prow, Tarl W

    2015-01-01

    There are an abundance of nanoparticle technologies being developed for use as part of therapeutic strategies. This review focuses on a narrow class of metal nanoparticles that have therapeutic potential that is a consequence of elemental composition and size. The most widely known of these are gold nanoshells that have been developed over the last two decades for photothermal ablation in superficial cancers. The therapeutic effect is the outcome of the thickness and diameter of the gold shell that enables fine tuning of the plasmon resonance. When these metal nanoparticles are exposed to the relevant wavelength of light, their temperature rapidly increases. This in turn induces a localized photothermal ablation that kills the surrounding tumor tissue. Similarly, gold nanoparticles have been developed to enhance radiotherapy. The high-Z nature of gold dramatically increases the photoelectric cross-section. Thus, the photoelectric effects are significantly increased. The outcome of these interactions is enhanced tumor killing with lower doses of radiation, all while sparing tissue without gold nanoparticles. Silver nanoparticles have been used for their wound healing properties in addition to enhancing the tumor-killing effects of anticancer drugs. Finally, platinum nanoparticles are thought to serve as a reservoir for platinum ions that can induce DNA damage in cancer cells. The future is bright with the path to clinical trials is largely cleared for some of the less complex therapeutic metal nanoparticle systems.

  12. Therapeutic gold, silver, and platinum nanoparticles.

    PubMed

    Yamada, Miko; Foote, Matthew; Prow, Tarl W

    2015-01-01

    There are an abundance of nanoparticle technologies being developed for use as part of therapeutic strategies. This review focuses on a narrow class of metal nanoparticles that have therapeutic potential that is a consequence of elemental composition and size. The most widely known of these are gold nanoshells that have been developed over the last two decades for photothermal ablation in superficial cancers. The therapeutic effect is the outcome of the thickness and diameter of the gold shell that enables fine tuning of the plasmon resonance. When these metal nanoparticles are exposed to the relevant wavelength of light, their temperature rapidly increases. This in turn induces a localized photothermal ablation that kills the surrounding tumor tissue. Similarly, gold nanoparticles have been developed to enhance radiotherapy. The high-Z nature of gold dramatically increases the photoelectric cross-section. Thus, the photoelectric effects are significantly increased. The outcome of these interactions is enhanced tumor killing with lower doses of radiation, all while sparing tissue without gold nanoparticles. Silver nanoparticles have been used for their wound healing properties in addition to enhancing the tumor-killing effects of anticancer drugs. Finally, platinum nanoparticles are thought to serve as a reservoir for platinum ions that can induce DNA damage in cancer cells. The future is bright with the path to clinical trials is largely cleared for some of the less complex therapeutic metal nanoparticle systems. PMID:25521618

  13. Thermoregulated Coacervation, Metal-Encapsulation and Nanoparticle Synthesis in Novel Triazine Dendrimers.

    PubMed

    Ramírez-Crescencio, Fermín; Enciso, Alan E; Hasan, Mirza; da Costa, Viviana C P; Annunziata, Onofrio; Redón, Rocío; Coffer, Jeffery L; Simanek, Eric E

    2016-01-01

    The synthesis and solubility behaviors of four generation five (G5) triazine dendrimers are studied. While the underivatized cationic dendrimer is soluble in water, the acetylated and propanoylated derivatives undergo coacervation in water upon increasing temperature. Occurring around room temperature, this behavior is related to a liquid-liquid phase transition with a lower critical solution temperature (LCST) and is explained by differences in composition, notably, the hydrophobic nature of the terminal groups. Interestingly, the water solubility of the acetylated dendrimer is affected by the addition of selected metal ions. Titrating solutions of acetylated dendrimer at temperatures below the LCST with gold or palladium ions promoted precipitation, but platinum, iridium, and copper did not. Gold nanoparticles having diameters of 2.5 ± 0.8 nm can be obtained from solutions of the acetylated dendrimer at concentrations of gold less than that required to induce precipitation by treating the solution with sodium borohydride. PMID:27187331

  14. Controllable nanoimprinting of metallic glasses: effect of pressure and interfacial properties.

    PubMed

    Kumar, Golden; Blawzdziewicz, Jerzy; Schroers, Jan

    2013-03-15

    The quantitative model proposed here for nanoimprinting by thermoplastic compression molding is focused on bulk metallic glasses (BMGs), but it is also applicable to polymers and other thermoplastic materials. In our model the flow and pressure fields are evaluated using the lubrication theory, and the effect of molding pressure, BMG viscosity, and capillary pressure on the spatial distribution of nanoimprinted features is determined. For platinum-based BMG the theory that takes into account capillary pressure but no other surface stresses agrees very well with experimental results. For palladium-based BMG (prone to oxidation) the extended theory includes an additional threshold pressure required to break the oxide layer that forms on the BMG surface. Our analysis provides important insights into flow behavior of BMG supercooled liquids. In particular, a new method for measuring surface tension and viscosity of BMGs and evaluating the strength of the surface oxide layer is demonstrated.

  15. Thermodynamics of the hybrid interaction of hydrogen with palladium nanoparticles

    NASA Astrophysics Data System (ADS)

    Griessen, Ronald; Strohfeldt, Nikolai; Giessen, Harald

    2016-03-01

    Palladium-hydrogen is a prototypical metal-hydrogen system. It is therefore not at all surprising that a lot of attention has been devoted to the absorption and desorption of hydrogen in nanosized palladium particles. Several seminal articles on the interaction of H with Pd nanocubes and nanoparticles have recently been published. Although each article provides for the first time detailed data on specific aspects of hydrogen in nanoparticles, they individually do not contain enough information to draw firm conclusions about the involved mechanisms. Here, we show that the large body of data available so far in literature exhibits general patterns that lead to unambiguous conclusions about the processes involved in H absorption and desorption in Pd nanoparticles. On the basis of a remarkably robust scaling law for the hysteresis in absorption-desorption isotherms, we show that hydrogen absorption in palladium nanoparticles is consistent with a coherent interface model and is thus clearly different from bulk Pd behaviour. However, H desorption occurs fully coherently only for small nanoparticles (typically smaller than 50 nm) at temperatures sufficiently close to the critical temperature. For larger particles it is partially incoherent, as in bulk, where dilute α-PdHx and high concentration β-PdHx phases coexist.

  16. Thermodynamics of the hybrid interaction of hydrogen with palladium nanoparticles.

    PubMed

    Griessen, Ronald; Strohfeldt, Nikolai; Giessen, Harald

    2016-03-01

    Palladium-hydrogen is a prototypical metal-hydrogen system. It is therefore not at all surprising that a lot of attention has been devoted to the absorption and desorption of hydrogen in nanosized palladium particles. Several seminal articles on the interaction of H with Pd nanocubes and nanoparticles have recently been published. Although each article provides for the first time detailed data on specific aspects of hydrogen in nanoparticles, they individually do not contain enough information to draw firm conclusions about the involved mechanisms. Here, we show that the large body of data available so far in literature exhibits general patterns that lead to unambiguous conclusions about the processes involved in H absorption and desorption in Pd nanoparticles. On the basis of a remarkably robust scaling law for the hysteresis in absorption-desorption isotherms, we show that hydrogen absorption in palladium nanoparticles is consistent with a coherent interface model and is thus clearly different from bulk Pd behaviour. However, H desorption occurs fully coherently only for small nanoparticles (typically smaller than 50 nm) at temperatures sufficiently close to the critical temperature. For larger particles it is partially incoherent, as in bulk, where dilute α-PdHx and high concentration β-PdHx phases coexist.

  17. Thermodynamics of the hybrid interaction of hydrogen with palladium nanoparticles.

    PubMed

    Griessen, Ronald; Strohfeldt, Nikolai; Giessen, Harald

    2016-03-01

    Palladium-hydrogen is a prototypical metal-hydrogen system. It is therefore not at all surprising that a lot of attention has been devoted to the absorption and desorption of hydrogen in nanosized palladium particles. Several seminal articles on the interaction of H with Pd nanocubes and nanoparticles have recently been published. Although each article provides for the first time detailed data on specific aspects of hydrogen in nanoparticles, they individually do not contain enough information to draw firm conclusions about the involved mechanisms. Here, we show that the large body of data available so far in literature exhibits general patterns that lead to unambiguous conclusions about the processes involved in H absorption and desorption in Pd nanoparticles. On the basis of a remarkably robust scaling law for the hysteresis in absorption-desorption isotherms, we show that hydrogen absorption in palladium nanoparticles is consistent with a coherent interface model and is thus clearly different from bulk Pd behaviour. However, H desorption occurs fully coherently only for small nanoparticles (typically smaller than 50 nm) at temperatures sufficiently close to the critical temperature. For larger particles it is partially incoherent, as in bulk, where dilute α-PdHx and high concentration β-PdHx phases coexist. PMID:26569476

  18. Platinum group nuggets in deep sea sediments

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.; Bates, B. A.; Wheelock, M. M.

    1984-01-01

    The existence of iron meteor oblation spheres in deep sea sediments was known for over a century. These spheres generally were believed to be composed of either pure magnetite and wustite or an oxide shell surrounding a NiFe metal core. A large number of 300 micron to 600 micron spheres found were pure oxide spheres, usually containing a solitary 10 micron platinum group nugget (pgn) composed almost entirely of group VIII metals. Twelve PGN's were analyzed and most had chondritic abundances with some depletions that correlate with element volatility. PGN formation by oxidation of a molten metal sphere entering the atmosphere cannot occur if the oxygen abundance in the atmosphere is less than half of its present value. The first appearance of PGN's in the geological record should mark when, in the Earth's history, oxygen rose to this level.

  19. Remarkable effect of bimetallic nanocluster catalysts for aerobic oxidation of alcohols: combining metals changes the activities and the reaction pathways to aldehydes/carboxylic acids or esters.

    PubMed

    Kaizuka, Kosuke; Miyamura, Hiroyuki; Kobayashi, Shū

    2010-11-01

    Selective oxidation of alcohols catalyzed by novel carbon-stabilized polymer-incarcerated bimetallic nanocluster catalysts using molecular oxygen has been developed. The reactivity and the selectivity were strongly dependent on the combination of metals and solvent systems; aldehydes and ketones were obtained by the gold/platinum catalyst in benzotrifluoride, and esters were formed by the gold/palladium catalyst in methanol. To the best of our knowledge, this is the first example that the reaction pathway has been changed dramatically in gold catalysis by combining with a second metal. The differences in the activity and the selectivity are considered to be derived from the difference in the structure of the bimetallic clusters.

  20. Assessment of metallic mineral resources in the Humboldt River Basin, Northern Nevada, with a section on Platinum-Group-Element (PGE) Potential of the Humboldt Mafic Complex

    USGS Publications Warehouse

    Wallace, Alan R.; Ludington, Steve; Mihalasky, Mark J.; Peters, Stephen G.; Theodore, Ted G.; Ponce, David A.; John, David A.; and Berger, Byron R.; Zientek, Michael L.; Sidder, Gary B.; Zierenberg, Robert A.

    2004-01-01

    The Humboldt River Basin is an arid to semiarid, internally drained basin that covers approximately 43,000 km2 in northern Nevada. The basin contains a wide variety of metallic and nonmetallic mineral deposits and occurrences, and, at various times, the area has been one of the Nation's leading or important producers of gold, silver, copper, mercury, and tungsten. Nevada currently (2003) is the third largest producer of gold in the world and the largest producer of silver in the United States. Current exploration for additional mineral deposits focuses on many areas in northern Nevada, including the Humboldt River Basin.

  1. The Mechanochemical Reaction of Palladium(II) Chloride with a Bidentate Phosphine

    ERIC Educational Resources Information Center

    Berry, David E.; Carrie, Philippa; Fawkes, Kelli L.; Rebner, Bruce; Xing, Yao

    2010-01-01

    This experiment describes the reaction of palladium(II) chloride with 1,5-bis(diphenylphosphino)pentane by grinding the two powders together in the solid state. The product is the precursor for the metalation reaction at one of the methylene carbon atoms of the ligand's backbone. The final product is known to be a catalyst for Suzuki-Miyaura…

  2. GREEN SYNTHESIS OF SILVER AND PALLADIUM NANOPARTICLES AT ROOM TEMPERATURE USING COFFEE AND TEA EXTRACT

    EPA Science Inventory

    An extremely simple green approach that generates bulk quantities of nanocrystals of noble metals such as silver (Ag) and palladium (Pd) using coffee and tea extract at room temperature is described. The single-pot method uses no surfactant, capping agent, and/or template. The ob...

  3. Regioselective Allene Hydrosilylation Catalyzed by NHC Complexes of Nickel and Palladium

    PubMed Central

    Miller, Zachary D.; Li, Wei; Belderrain, Tomás R.; Montgomery, John

    2013-01-01

    Regioselective methods for allene hydrosilylation have been developed, with regioselectivity being governed primarily by choice of metal. Alkenylsilanes are produced via nickel catalysis with larger N-heterocyclic carbene ligands, and allylsilanes are produced via palladium catalysis with smaller N-heterocyclic carbene ligands. These complementary methods allow either regioisomeric product to be obtained with exceptional regiocontrol. PMID:24079389

  4. Preparation of low-sulfur platinum and platinum aluminide layers in thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Spitsberg, Irene T. (Inventor); Walston, William S. (Inventor); Schaeffer, Jon C. (Inventor)

    2003-01-01

    A method for preparing a coated nickel-base superalloy article reduces the sulfur content of the surface region of the metallic coating layers to low levels, thereby improving the adhesion of the coating layers to the article. The method includes depositing a first layer of platinum overlying the surface of a substrate, depositing a second layer of aluminum over the platinum, and final desulfurizing the article by heating the article to elevated temperature, preferably in hydrogen, and removing a small amount of material from the surface that was exposed during the step of heating. A ceramic layer may be deposited over the desulfurized article. The article may also be similarly desulfurized at other points in the fabrication procedure.

  5. Palladium-Catalyzed Direct Cyclopropylation of Heterocycles.

    PubMed

    Wu, Xiaojin; Lei, Chuanhu; Yue, Guizhou; Zhou, Jianrong Steve

    2015-08-10

    Many 1,3-azoles and thiophenes are directly cyclopropylated in the presence of a simple palladium catalyst. The relative configuration on the three-membered rings is retained in the products. Thus, the cyclopropyl-halide bond undergoes concerted oxidative addition to palladium(0) and cyclopropyl radicals are not involved in the productive pathway.

  6. Metal and Precursor Effect during 1-Heptyne Selective Hydrogenation Using an Activated Carbon as Support

    PubMed Central

    Lederhos, Cecilia R.; Badano, Juan M.; Carrara, Nicolas; Coloma-Pascual, Fernando; Almansa, M. Cristina; Liprandi, Domingo; Quiroga, Mónica

    2013-01-01

    Palladium, platinum, and ruthenium supported on activated carbon were used as catalysts for the selective hydrogenation of 1-heptyne, a terminal alkyne. All catalysts were characterized by temperature programmed reduction, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. TPR and XPS suggest that the metal in all catalysts is reduced after the pretreatment with H2 at 673 K. The TPR trace of the PdNRX catalyst shows that the support surface groups are greatly modified as a consequence of the use of HNO3 during the catalyst preparation. During the hydrogenation of 1-heptyne, both palladium catalysts were more active and selective than the platinum and ruthenium catalysts. The activity order of the catalysts is as follows: PdClRX > PdNRX > PtClRX ≫ RuClRX. This superior performance of PdClRX was attributed in part to the total occupancy of the d electronic levels of the Pd metal that is supposed to promote the rupture of the H2 bond during the hydrogenation reaction. The activity differences between PdClRX and PdNRX catalysts could be attributed to a better accessibility of the substrate to the active sites, as a consequence of steric and electronic effects of the superficial support groups. The order for the selectivity to 1-heptene is as follows: PdClRX = PdNRX > RuClRX > PtClRX, and it can be mainly attributed to thermodynamic effects. PMID:24348168

  7. Investigation of the interaction between a novel unnatural chiral ligand and reactant on palladium for asymmetric hydrogenation.

    PubMed

    Jeon, Eun Hee; Yang, Sena; Kang, Sung Ho; Kim, Sehun; Lee, Hangil

    2015-07-21

    We report about the mechanistic studies of the reaction between a newly synthesized (S)-2-((R)-3H-dinaphtho[2,1-c:1',2'-e]azepin-4(5H)-yl)-2-phenylethanol based on the binaphthyl skeleton and (E)-2-methyl-5-phenylpent-2-enoic acid for the asymmetric hydrogenation of α,β-unsaturated acids with heterogeneous palladium catalysts. The specific interactions between the chiral ligand and reactant were investigated in solution with palladium nanoparticles, as well as under ultrahigh vacuum (UHV) conditions on the palladium metal surface in the absence of hydrogen. The reactions were explored using nuclear magnetic resonance (NMR) spectroscopy, scanning tunneling microscopy (STM), and high-resolution photoemission spectroscopy (HRPES) combined with density functional theory (DFT) calculations. A NMR study identified the interaction between both molecules with palladium nanoparticles in solution. In addition, STM and HRPES studies revealed the spatial distribution and configuration of both compounds on the palladium metal surface under UHV conditions. The theoretical results support the experimental results with respect to the interaction energy value. It was found that the reaction between the ligand and reactant occurs with hydrogen bonding on palladium surface, simultaneously. The present study provides mechanistic details of the asymmetric hydrogenation reaction, which bears a correlation between the ligand, reactant, and catalyst during the reaction.

  8. Palladium and gold nanotubes as oxygen reduction reaction and alcohol oxidation reaction catalysts in base.

    PubMed

    Alia, Shaun M; Duong, Kathlynne; Liu, Toby; Jensen, Kurt; Yan, Yushan

    2014-06-01

    Palladium (PdNTs) and gold nanotubes (AuNTs) were synthesized by the galvanic displacement of silver nanowires. PdNTs and AuNTs have wall thicknesses of 6 nm, outer diameters of 60 nm, and lengths of 5-10 and 5-20 μm, respectively. Rotating disk electrode experiments showed that the PdNTs and AuNTs have higher area normalized activities for the oxygen reduction reaction (ORR) than conventional nanoparticle catalysts. The PdNTs produced an ORR area activity that was 3.4, 2.2, and 3.7 times greater than that on carbon-supported palladium nanoparticles (Pd/C), bulk polycrystalline palladium, and carbon-supported platinum nanoparticles (Pt/C), respectively. The AuNTs produced an ORR area activity that was 2.3, 9.0, and 2.0 times greater than that on carbon-supported gold nanoparticles (Au/C), bulk polycrystalline gold, and Pt/C, respectively. The PdNTs also had lower onset potentials than Pd/C and Pt/C for the oxidation of methanol (0.236 V), ethanol (0.215 V), and ethylene glycol (0.251 V). In comparison to Pt/C, the PdNTs and AuNTs further demonstrated improved alcohol tolerance during the ORR.

  9. Characterization of the Sukinda and Nausahi ultramafic complexes, Orissa, India by platinum-group element geochemistry

    USGS Publications Warehouse

    Page, N.J.; Banerji, P.K.; Haffty, J.

    1985-01-01

    Samples of 20 chromitite, 14 ultramafic and mafic rock, and 9 laterite and soil samples from the Precambrian Sukinda and Nausahi ultramafic complexes, Orissa, India were analyzed for platinum-group elements (PGE). The maximum concentrations are: palladium, 13 parts per billion (ppb); platinum, 120 ppb; rhodium, 21 ppb; iridium, 210 ppb; and ruthenium, 630 ppb. Comparison of chondrite-normalized ratios of PGE for the chromitite samples of lower Proterozoic to Archean age with similar data from Paleozoic and Mesozoic ophiolite complexes strongly implies that these complexes represent Precambrian analogs of ophiolite complexes. This finding is consistent with the geology and petrology of the Indian complexes and suggests that plate-tectonic and ocean basin developement models probably apply to some parts of Precambrian shield areas. ?? 1985.

  10. Method of making sulfur-resistant composite metal membranes

    DOEpatents

    Way, J Douglas [Boulder, CO; Lusk, Mark [Golden, CO; Thoen, Paul [Littleton, CO

    2012-01-24

    The invention provides thin, hydrogen-permeable, sulfur-resistant membranes formed from palladium or palladium-alloy coatings on porous, ceramic or metal supports. Also disclosed are methods of making these membranes via sequential electroless plating techniques, wherein the method of making the membrane includes decomposing any organic ligands present on the substrate, reducing the palladium crystallites on the substrate to reduced palladium crystallites, depositing a film of palladium metal on the substrate and then depositing a second, gold film on the palladium film. These two metal films are then annealed at a temperature between about 200.degree. C. and about 1200.degree. C. to form a sulfur-resistant, composite PdAu alloy membrane.

  11. One-pot palladium-catalyzed borrowing hydrogen synthesis of thioethers.

    PubMed

    Corma, Avelino; Navas, Javier; Ródenas, Tania; Sabater, María J

    2013-12-16

    Palladium on magnesium oxide is able to allow a one-pot reaction to synthesize thioethers from thiols and aldehydes formed in situ from the respective alcohol by means of a borrowing hydrogen method. The reaction is initiated by dehydrogenation of the alcohol to give a palladium hydride intermediate and an aldehyde. The latter reacts with a thiol involving most probably the intermediacy of a thionium ion RCH=S(+)R, which can be reduced in situ by the metal hydride to afford thioethers. PMID:24259460

  12. Palladium-Catalyzed Intramolecular Carbene Insertion into C(sp(3) )-H Bonds.

    PubMed

    Solé, Daniel; Mariani, Francesco; Bennasar, M-Lluïsa; Fernández, Israel

    2016-05-23

    A palladium-catalyzed carbene insertion into C(sp(3) )-H bonds leading to pyrrolidines was developed. The coupling reaction can be catalyzed by both Pd(0) and Pd(II) , is regioselective, and shows a broad functional group tolerance. This reaction is the first example of palladium-catalyzed C(sp(3) )-C(sp(3) ) bond assembly starting from diazocarbonyl compounds. DFT calculations revealed that this direct C(sp(3) )-H bond functionalization reaction involves an unprecedented concerted metalation-deprotonation step.

  13. One-dimensional Magnus-type platinum double salts

    PubMed Central

    Hendon, Christopher H.; Walsh, Aron; Akiyama, Norinobu; Konno, Yosuke; Kajiwara, Takashi; Ito, Tasuku; Kitagawa, Hiroshi; Sakai, Ken

    2016-01-01

    Interest in platinum-chain complexes arose from their unusual oxidation states and physical properties. Despite their compositional diversity, isolation of crystalline chains has remained challenging. Here we report a simple crystallization technique that yields a series of dimer-based 1D platinum chains. The colour of the Pt2+ compounds can be switched between yellow, orange and blue. Spontaneous oxidation in air is used to form black Pt2.33+ needles. The loss of one electron per double salt results in a metallic state, as supported by quantum chemical calculations, and displays conductivity of 11 S cm−1 at room temperature. This behaviour may open up a new avenue for controllable platinum chemistry. PMID:27320502

  14. Metal oxide films on metal

    DOEpatents

    Wu, Xin D.; Tiwari, Prabhat

    1995-01-01

    A structure including a thin film of a conductive alkaline earth metal oxide selected from the group consisting of strontium ruthenium trioxide, calcium ruthenium trioxide, barium ruthenium trioxide, lanthanum-strontium cobalt oxide or mixed alkaline earth ruthenium trioxides thereof upon a thin film of a noble metal such as platinum is provided.

  15. Development of Platinum(iv) Complexes as Anticancer Prodrugs: the Story so Far

    NASA Astrophysics Data System (ADS)

    Wong, Daniel Yuan Qiang; Ang, Wee Han

    2012-06-01

    The serendipitous discovery of the antitumor properties of cisplatin by Barnett Rosenberg some forty years ago brought about a paradigm shift in the field of medicinal chemistry and challenged conventional thinking regarding the role of potentially toxic heavy metals in drugs. Platinum(II)-based anticancer drugs have since become some of the most effective and widely-used drugs in a clinician's arsenal and have saved countless lives. However, they are limited by high toxicity, severe side-effects and the incidence of drug resistance. In recent years, attention has shifted to stable platinum(IV) complexes as anticancer prodrugs. By exploiting the unique chemical and structural attributes of their scaffolds, these platinum(IV) prodrugs offer new strategies of targeting and killing cancer cells. This review summarizes the development of anticancer platinum(IV) prodrugs to date and some of the exciting strategies that utilise the platinum(IV) construct as targeted chemotherapeutic agents against cancer.

  16. Effect of recasting on the oxidation layer of a palladium-silver porcelain alloy

    SciTech Connect

    Hong, J.M.; Razzoog, M.E.; Lang, B.R.

    1988-04-01

    The oxidation zone of a commercial palladium-silver porcelain alloy was compared after repeated casting with and without the addition of new alloy. The intensity of palladium, silver, tin, indium, and O K-alpha near the oxidation zone was analyzed with XMA. The intensity curves of tin, silver, and oxygen increased progressively through each generation despite the addition of new alloy. The thickness of the oxidation zone and the microporosities at the internal oxidation zone increased through each generation without the addition of new alloy. Although the findings indicated that the oxidation zone was favorably formed by adding new alloy, 50% by weight, for four generations, the silver and metallic oxides of the oxidation zone increased through each generation. The reuse of the palladium-silver porcelain alloy remains questionable.

  17. Mechanistic Studies of Gold and Palladium Cooperative Dual-Catalytic Cross-Coupling Systems

    PubMed Central

    Al-Amin, Mohammad; Roth, Katrina E.; Blum, Suzanne A.

    2014-01-01

    Double-label crossover, modified-substrate, and catalyst comparison experiments in the gold and palladium dual-catalytic rearrangement/cross-coupling of allenoates were performed in order to probe the mechanism of this reaction. The results are consistent with a cooperative catalysis mechanism whereby 1) gold activates the substrate prior to oxidative addition by palladium, 2) gold acts as a carbophilic rather than oxophilic Lewis acid, 3) competing olefin isomerization is avoided, 4) gold participates beyond the first turnover and therefore does not serve simply to generate the active palladium catalyst, and 5) single-electron transfer is not involved. These experiments further demonstrate that the cooperativity of both gold and palladium in the reaction is essential because significantly lower to zero conversion is achieved with either metal alone in comparison studies that examined multiple potential gold, palladium, and silver catalysts and precatalysts. Notably, employment of the optimized cocatalysts, PPh3AuOTf and Pd2dba3, separately (i.e., only Au or only Pd) results in zero conversion to product at all monitored time points compared to quantitative conversion to product when both are present in cocatalytic reactions. PMID:24757581

  18. Synthesis and characterization of chitosan and grape polyphenols stabilized palladium nanoparticles and their antibacterial activity.

    PubMed

    Amarnath, Kanchana; Kumar, Jayanthi; Reddy, Tejesh; Mahesh, Vakka; Ayyappan, Senniyanallur Rathakrishnan; Nellore, Jayshree

    2012-04-01

    Based on enhanced effectiveness, the new age drugs are nanoparticles of polymers, metals or ceramics, which can combat conditions like cancer and fight human pathogens like bacteria. In this present study we aimed for a green approach to synthesize palladium nanoparticles by reducing palladium chloride salts with nontoxic and biodegradable polymeric chitosan and grape polyphenols and confirmed by FTIR, TEM, SEM and UV-spectroscopy. We also extended our study to show the efficacy of the grape and chitosan impregnated palladium nanoparticles as an antibacterial agent against Escherichia coli. Antibacterial assays were carried out with a representative gram-negative bacterium, E. coli and a gram-positive bacterium, Staphylococcus aureus. Commendable efforts have been made to explore this property using electron microscopy, which has revealed size dependent interaction of palladium nanoparticles conjugates with bacteria by disrupting cell membranes and the leakage of cytoplasm. Therefore, the observed results imply that grape and chitosan-based nano palladium conjugates prepared in our present system are promising candidates for a wide range of biomedical and general applications. PMID:22225943

  19. Platinum-Free Counter Electrode Comprised of Metal-Organic-Framework (MOF)-Derived Cobalt Sulfide Nanoparticles for Efficient Dye-Sensitized Solar Cells (DSSCs)

    PubMed Central

    Hsu, Shao-Hui; Li, Chun-Ting; Chien, Heng-Ta; Salunkhe, Rahul R.; Suzuki, Norihiro; Yamauchi, Yusuke; Ho, Kuo-Chuan; Wu, Kevin C.-W.

    2014-01-01

    We fabricated a highly efficient (with a solar-to-electricity conversion efficiency (η) of 8.1%) Pt-free dye-sensitized solar cell (DSSC). The counter electrode was made of cobalt sulfide (CoS) nanoparticles synthesized via surfactant-assisted preparation of a metal organic framework, ZIF-67, with controllable particle sizes (50 to 320 nm) and subsequent oxidation and sulfide conversion. In contrast to conventional Pt counter electrodes, the synthesized CoS nanoparticles exhibited higher external surface areas and roughness factors, as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM) element mapping, and electrochemical analysis. Incident photon-to-current conversion efficiency (IPCE) results showed an increase in the open circuit voltage (VOC) and a decrease in the short-circuit photocurrent density (Jsc) for CoS-based DSSCs compared to Pt-based DSSCs, resulting in a similar power conversion efficiency. The CoS-based DSSC fabricated in the study show great potential for economically friendly production of Pt-free DSSCs. PMID:25382139

  20. Gold, palladium, and gold-palladium alloy nanoshells on silica nanoparticle cores.

    PubMed

    Kim, Jun-Hyun; Bryan, William W; Chung, Hae-Won; Park, Chan Young; Jacobson, Allan J; Lee, T Randall

    2009-05-01

    The synthesis of gold, palladium, and gold-palladium alloy nanoshells (approximately 15-20 nm thickness) was accomplished by the reduction of gold and palladium ions onto dielectric silica core particles (approximately 100 nm in diameter) seeded with small gold nanoparticles (approximately 2-3 nm in diameter). The size, morphology, elemental composition, and optical properties of the nanoshells were characterized using field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. The results demonstrate the successful growth of gold, palladium, and gold-palladium alloy nanoshells, where the optical properties systematically vary with the relative content of gold and palladium. The alloy nanoshells are being prepared for use in applications that stand to benefit from photoenhanced catalysis. PMID:20355892

  1. Influence of Dose on Particle Size and Optical Properties of Colloidal Platinum Nanoparticles

    PubMed Central

    Gharibshahi, Elham; Saion, Elias

    2012-01-01

    Attempts to produce colloidal platinum nanoparticles by using steady absorption spectra with various chemical-based reduction methods often resulted in the fast disappearance of the absorption maxima leaving reduced platinum nanoparticles with little information on their optical properties. We synthesized colloidal platinum nanoparticles in an aqueous solution of polyvinyl pyrrolidone by gamma radiolytic reduction method, which produced steady absorption spectra of fully reduced and highly pure platinum nanoparticles free from by-product impurities or reducing agent contamination. The average particle size was found to be in the range of 3.4–5.3 nm and decreased with increasing dose due to the domination of nucleation over ion association in the formation of metal nanoparticles by the gamma radiolytic reduction method. The platinum nanoparticles exhibit optical absorption spectra with two absorption peaks centered at about 216 and 264 nm and the peaks blue shifted to lower wavelengths with decreasing particle size. The absorption spectra of platinum nanoparticles were also calculated using quantum mechanical treatment and coincidently a good agreement was obtained between the calculated and measured absorption peaks at various particle sizes. This indicates that the 216 and 264-nm absorption peaks of platinum nanoparticles conceivably originated from the intra-band transitions of conduction electrons of (n = 5, l = 2) and (n = 6, l = 0) energy states respectively to higher energy states. The absorption energies, i.e., conduction band energies of platinum nanoparticles derived from the absorption peaks increased with increasing dose and decreased with increasing particle size. PMID:23203091

  2. Silica-metal core-shell nanostructures.

    PubMed

    Jankiewicz, B J; Jamiola, D; Choma, J; Jaroniec, M

    2012-01-15

    Silica-metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica-noble metal core-shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the Stöber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100 nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica-metal core-shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core-shell nanostructures. Silica-metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed

  3. A Pd/C-CeO2 Anode Catalyst for High-Performance Platinum-Free Anion Exchange Membrane Fuel Cells.

    PubMed

    Miller, Hamish A; Lavacchi, Alessandro; Vizza, Francesco; Marelli, Marcello; Di Benedetto, Francesco; D'Acapito, Francesco; Paska, Yair; Page, Miles; Dekel, Dario R

    2016-05-10

    One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm(-2) . PMID:27062251

  4. A Pd/C-CeO2 Anode Catalyst for High-Performance Platinum-Free Anion Exchange Membrane Fuel Cells.

    PubMed

    Miller, Hamish A; Lavacchi, Alessandro; Vizza, Francesco; Marelli, Marcello; Di Benedetto, Francesco; D'Acapito, Francesco; Paska, Yair; Page, Miles; Dekel, Dario R

    2016-05-10

    One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm(-2) .

  5. Porous platinum-based catalysts for oxygen reduction

    DOEpatents

    Erlebacher, Jonah D; Snyder, Joshua D

    2014-11-25

    A porous metal that comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A fuel cell includes a first electrode, a second electrode spaced apart from the first electrode, and an electrolyte arranged between the first and the second electrodes. At least one of the first and second electrodes is coated with a porous metal catalyst for oxygen reduction, and the porous metal catalyst comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A method of producing a porous metal according to an embodiment of the current invention includes producing an alloy consisting essentially of platinum and nickel according to the formula Pt.sub.xNi.sub.1-x, where x is at least 0.01 and less than 0.3; and dealloying the alloy in a substantially pH neutral solution to reduce an amount of nickel in the alloy to produce the porous metal.

  6. Well-defined N-heterocyclic carbenes-palladium(II) precatalysts for cross-coupling reactions.

    PubMed

    Marion, Nicolas; Nolan, Steven P

    2008-11-18

    Metal-catalyzed cross-coupling reactions, notably those permitting C-C bond formation, have witnessed a meteoritic development and are now routinely employed as a powerful synthetic tool both in academia and in industry. In this context, palladium is arguably the most studied transition metal, and tertiary phosphines occupy a preponderant place as ancillary ligands. Seriously challenging this situation, the use of N-heterocyclic carbenes (NHCs) as alternative ligands in palladium-catalyzed cross-coupling reactions is rapidly gaining in popularity. These two-electron donor ligands combine strong sigma-donating properties with a shielding steric pattern that allows for both stabilization of the metal center and enhancement of its catalytic activity. As a result, the number of well-defined NHC-containing palladium(II) complexes is growing, and their use in coupling reactions is witnessing increasing interest. In this Account, we highlight the advantages of this family of palladium complexes and review their synthesis and applications in cross-coupling chemistry. They generally exhibit high stability, allowing for indefinite storage and easy handling. The use of well-defined complexes permits a strict control of the Pd/ligand ratio (optimally 1/1), avoiding the use of excess costly ligand that usually requires end-game removal. Furthermore, it partly removes the "black box" character often associated with cross-coupling chemistry and catalyst formation. In the present Account, four main classes of NHC-containing palladium(II) complexes will be presented: palladium dimers with bridging halogens, palladacycles, palladium acetates and acetylacetonates, and finally pi-allyl complexes. These additional ligands are best described as a protecting shell that will be discarded going from the palladium(II) precatalyst to the palladium(0) true catalyst. The synthesis of all these precatalysts generally requires simple and short synthetic procedures. Their catalytic activity in

  7. New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

    SciTech Connect

    Qinhua Huang

    2004-12-19

    The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I{sub 2}, ICl, PhSeCl, PhSCl and p-O{sub 2}NC{sub 6}H{sub 4}SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This methodology accommodates a variety of iminoalkynes and affords the anticipated heterocycles in moderate to excellent yields. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellent yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. The process involves arylpalladation of the alkyne, followed by intramolecular Heck olefination and double bond isomerization. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migratiodarylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement with the idea that

  8. Surface decorated platinum carbonyl clusters

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters.Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters. CCDC 867747 and 867748. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30400g

  9. Pumice-supported palladium catalysts. II. Selective hydrogenation of 1,3-cyclooctadiene

    SciTech Connect

    Deganello, G.; Duca, D.; Martorana, A.; Fagherazzi, G.; Benedetti, A.

    1994-11-01

    Two series of pumice-supported palladium catalysts (W and U) have been tested in the liquid-phase selective hydrogenation of 1,3-cyclooctadiene (1,3-COD) to cyclooctene (COE). The two series of catalysts, obtained via organometallic precursors, differ in the preparation procedure. In the W series the reduced metal derives only from Pd intermediates anchored to pumice; in the U series the metal originates also from unreacted Pd(allyl){sub 2} species in solution. The U catalysts present agglomerated metal particles. The hydrogenations, free of any diffusion problems, were performed at constant pressure of hydrogen (1 atm). Analysis of the data suggests that the rate-determining step is a surface reaction involving activated 1,3-COD. Selectivity is very high since cyclooctane (COA) is detected only when all 1,3-COD is consumed. The turnover frequencies (TOF{sub 1}) of the first semihydrogenation do not change with palladium dispersion, determined from the Porod diameter D{sub p} up to D{sub x} < 35%, but thereafter they slowly decrease. Experimental evidence, such as the absence of oxidation when exposed to air and the negative shift of binding energy of the Pd 3d level in XPS measurements, indicate a different behavior of the present catalysts in comparison with other supported palladium catalysts. These differences are attributed to the presence of alkali metal ions (Na{sup +}, K{sup +}) on the pumice surface and are explained on the basis of the change in electron density and/or in the ensemble size of the supported palladium. Several interesting features and differences in activity and selectivity between the two series of catalysts can be accounted for by the presence of agglomerated palladium particles in the U series and are discussed in terms of the evolution of parameters with dispersion. 40 refs., 8 figs., 2 tabs.

  10. Platinum Recovery from Synthetic Extreme Environments by Halophilic Bacteria.

    PubMed

    Maes, Synthia; Props, Ruben; Fitts, Jeffrey P; Smet, Rebecca De; Vilchez-Vargas, Ramiro; Vital, Marius; Pieper, Dietmar H; Vanhaecke, Frank; Boon, Nico; Hennebel, Tom

    2016-03-01

    Metal recycling based on urban mining needs to be established to tackle the increasing supply risk of critical metals such as platinum. Presently, efficient strategies are missing for the recovery of platinum from diluted industrial process streams, often characterized by extremely low pHs and high salt concentrations. In this research, halophilic mixed cultures were employed for the biological recovery of platinum (Pt). Halophilic bacteria were enriched from Artemia cysts, living in salt lakes, in different salt matrices (sea salt mixture and NH4Cl; 20-210 g L(-1) salts) and at low to neutral pH (pH 3-7). The main taxonomic families present in the halophilic cultures were Halomonadaceae, Bacillaceae, and Idiomarinaceae. The halophilic cultures were able to recover >98% Pt(II) and >97% Pt(IV) at pH 2 within 3-21 h (4-453 mg Ptrecovered h(-1) g(-1) biomass). X-ray absorption spectroscopy confirmed the reduction to Pt(0) and transmission electron microscopy revealed both intra- and extracellular Pt precipitates, with median diameters of 9-30 nm and 11-13 nm, for Pt(II) and Pt(IV), respectively. Flow cytometric membrane integrity staining demonstrated the preservation of cell viability during platinum recovery. This study demonstrates the Pt recovery potential of halophilic mixed cultures in acidic saline conditions.

  11. Platinum Recovery from Synthetic Extreme Environments by Halophilic Bacteria.

    PubMed

    Maes, Synthia; Props, Ruben; Fitts, Jeffrey P; Smet, Rebecca De; Vilchez-Vargas, Ramiro; Vital, Marius; Pieper, Dietmar H; Vanhaecke, Frank; Boon, Nico; Hennebel, Tom

    2016-03-01

    Metal recycling based on urban mining needs to be established to tackle the increasing supply risk of critical metals such as platinum. Presently, efficient strategies are missing for the recovery of platinum from diluted industrial process streams, often characterized by extremely low pHs and high salt concentrations. In this research, halophilic mixed cultures were employed for the biological recovery of platinum (Pt). Halophilic bacteria were enriched from Artemia cysts, living in salt lakes, in different salt matrices (sea salt mixture and NH4Cl; 20-210 g L(-1) salts) and at low to neutral pH (pH 3-7). The main taxonomic families present in the halophilic cultures were Halomonadaceae, Bacillaceae, and Idiomarinaceae. The halophilic cultures were able to recover >98% Pt(II) and >97% Pt(IV) at pH 2 within 3-21 h (4-453 mg Ptrecovered h(-1) g(-1) biomass). X-ray absorption spectroscopy confirmed the reduction to Pt(0) and transmission electron microscopy revealed both intra- and extracellular Pt precipitates, with median diameters of 9-30 nm and 11-13 nm, for Pt(II) and Pt(IV), respectively. Flow cytometric membrane integrity staining demonstrated the preservation of cell viability during platinum recovery. This study demonstrates the Pt recovery potential of halophilic mixed cultures in acidic saline conditions. PMID:26854514

  12. In Vitro Permeation of Metals through Human Skin: A Review and Recommendations.

    PubMed

    Franken, Anja; Eloff, Frederik C; Du Plessis, Jeanetta; Du Plessis, Johannes L

    2015-12-21

    During the last few decades, the interest in skin permeation of, specifically, metals has increased with the in vitro method utilizing diffusion cells as the prominent method of investigating permeability. This review provides a systematic synopsis focused on an in vitro diffusion cell method utilizing human skin and examines the differences in experimental design as this could influence the results obtained. The permeation of metals such as chromium, cobalt, copper, gold, lead, mercury, nickel, palladium, platinum, rhodium, silver, titanium, and zinc are discussed. The metals included in this review, except for titanium and zinc, can permeate through intact human skin under physiological conditions. On the basis of flux values, the order of permeability could be summarized as Cu > Pb > Cr > Ni > Co > Pt > Hg > Rh (excluding nanoparticles). Permeability of metals through human skin is highly variable with the different methodologies as a contributing factor. Furthermore, metals are retained in the skin which could lead to reservoir (depot) formation and extended exposure even after the removal thereof from the outer surface of the skin. Finally, recommendations are provided on the standardization of experimental design and format of data reporting to enable the comparison of results from future in vitro metal permeation studies. PMID:26555458

  13. In Vitro Permeation of Metals through Human Skin: A Review and Recommendations.

    PubMed

    Franken, Anja; Eloff, Frederik C; Du Plessis, Jeanetta; Du Plessis, Johannes L

    2015-12-21

    During the last few decades, the interest in skin permeation of, specifically, metals has increased with the in vitro method utilizing diffusion cells as the prominent method of investigating permeability. This review provides a systematic synopsis focused on an in vitro diffusion cell method utilizing human skin and examines the differences in experimental design as this could influence the results obtained. The permeation of metals such as chromium, cobalt, copper, gold, lead, mercury, nickel, palladium, platinum, rhodium, silver, titanium, and zinc are discussed. The metals included in this review, except for titanium and zinc, can permeate through intact human skin under physiological conditions. On the basis of flux values, the order of permeability could be summarized as Cu > Pb > Cr > Ni > Co > Pt > Hg > Rh (excluding nanoparticles). Permeability of metals through human skin is highly variable with the different methodologies as a contributing factor. Furthermore, metals are retained in the skin which could lead to reservoir (depot) formation and extended exposure even after the removal thereof from the outer surface of the skin. Finally, recommendations are provided on the standardization of experimental design and format of data reporting to enable the comparison of results from future in vitro metal permeation studies.

  14. Highly selective monitoring of metals by using ion-imprinted polymers.

    PubMed

    Hande, Pankaj E; Samui, Asit B; Kulkarni, Prashant S

    2015-05-01

    Ion imprinting technology is one of the most promising tools in separation and purification sciences because of its high selectivity, good stability, simplicity and low cost. It has been mainly used for selective removal, preconcentration, sensing and few miscellaneous fields. In this review article, recent methodologies in the synthesis of IIPs have been discussed. For several applications, different parameters of IIP including complexing and leaching agent, pH, relative selectivity coefficient, detection limit and adsorption capacity have been evaluated and an attempt has been made to generalize. Biomedical applications mostly include selective removal of toxic metals from human blood plasma and urine samples. Wastewater treatment involves selective removal of highly toxic metal ions like Hg(II), Pb(II), Cd(II), As(V), etc. Preconcentration covers recovery of economically important metal ions such as gold, silver, platinum and palladium. It also includes selective preconcentration of lanthanides and actinides. In sensing, various IIP-based sensors have been fabricated for detection of toxic metal ions. This review article includes almost all metal ions based on the ion-imprinted polymer. At the end, the future outlook section presents the discussion on the advancement, corresponding merits and the need of continued research in few specific areas. Graphical Abstract IIPs for the selective monitoring of metals. PMID:25663338

  15. The Next Generation of Platinum Drugs: Targeted Pt(II) Agents, Nanoparticle Delivery, and Pt(IV) Prodrugs

    PubMed Central

    Johnstone, Timothy C.; Suntharalingam, Kogularamanan; Lippard, Stephen J.

    2016-01-01

    The platinum drugs, cisplatin, carboplatin, and oxaliplatin, prevail in the treatment of cancer,, but new platinum agents have been very slow to enter the clinic. Recently, however, there has been a surge of activity, based on a great deal of mechanistic information, aimed at developing non-classical platinum complexes that operate via mechanisms of action distinct from those of the approved drugs. The use of nanodelivery devices has also grown and many different strategies have been explored to incorporate platinum warheads into nanomedicine constructs. In this review, we discuss these efforts to create the next generation of platinum anticancer drugs. The introduction provides the reader with a brief overview of the use, development, and mechanism of action of the approved platinum drugs to provide the context in which more recent research has flourished. We then describe approaches that explore non-classical platinum(II) complexes with trans geometry and with a monofunctional coordination mode, polynuclear platinum(II) compounds, platinum(IV) prodrugs, dual-treat agents, and photoactivatable platinum(IV) complexes. Nanodelivery particles designed to deliver platinum(IV) complexes will also be discussed, including carbon nanotubes, carbon nanoparticles, gold nanoparticles, quantum dots, upconversion nanoparticles, and polymeric micelles. Additional nanoformulations including supramolecular self-assembled structures, proteins, peptides, metal-organic frameworks, and coordination polymers will then be described. Finally, the significant clinical progress made by nanoparticle formulations of platinum(II) agents will be reviewed. We anticipate that such a synthesis of disparate research efforts will not only help to generate new drug development ideas and strategies, but also reflect our optimism that the next generation of platinum cancer drugs is about to arrive. PMID:26865551

  16. Separation preconcentration method for platinum and rhodium from environmental samples using a chelating resin.

    PubMed

    Bosch Ojeda, C; Sánchez Rojas, F; Cano Pavón, J M

    2006-01-01

    A method of determining trace levels of platinum and rhodium in different samples was investigated. The method involves separation and preconcentration of the platinum and rhodium from the matrix by flow injection (FI) on-line coupled with electrothermal atomic absorption spectrometry (ETAAS) with Zeeman effect background correction. Platinum and rhodium were adsorbed on a microcolumn packed with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The sorbed metals were directly eluted with nitric acid into the graphite furnace and determined by AAS.

  17. Electrocatalysts having gold monolayers on platinum nanoparticle cores, and uses thereof

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang

    2010-04-27

    The invention relates to gold-coated particles useful as fuel cell electrocatalysts. The particles are composed of an electrocatalytically active core at least partially encapsulated by an outer shell of gold or gold alloy. The invention more particularly relates to such particles having a noble metal-containing core, and more particularly, a platinum or platinum alloy core. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

  18. Synthesis, Characterization, and Application of Metal-Chelating Polymers for Mass Cytometric Bioassays

    NASA Astrophysics Data System (ADS)

    Majonis, Daniel

    This thesis describes the synthesis, characterization, and application of metal-chelating polymers for mass-cytometric bioassays. Mass cytometry is a cell characterization technique in which cells are injected individually into an ICP-MS detector. Signal is provided by staining cell-surface or intracellular antigens with metal-labeled antibodies (Abs). These Abs are labeled through the covalent attachment of metal-chelating polymers which carry multiple copies of a lanthanide isotope. In this work, my first goal was to develop a facile, straightforward synthesis of a new generation of metal-chelating polymers. The synthesis began with reversible addition-fragmentation chain transfer polymerization, and was followed by numerous post-polymerization pendant group transformations to introduce DTPA lanthanide chelators to every repeat unit, and a maleimide at the end of the chain. The second goal was to apply these metal-chelating polymers in bioassay experiments. The DTPA groups were loaded with lanthanide ions, and the maleimide group was used to covalently attach the polymer to an Ab. This goat anti-mouse conjugate was found to carry an average of 2.4 +/- 0.3 polymer chains. Then, primary Ab conjugates were prepared and used in an 11-plex mass cytometry assay in the characterization of umbilical cord blood cells. The third goal was to expand the multiplexity of the assay. In current technology, the number of Abs that can be monitored simultaneously is limited to the 31 commercially available, stable lanthanide isotopes. Thus, I had an interest in preparing metal-chelating polymers that could carry other metals in the 100-220 amu range. I synthesized polymers with four different polyaminocarboxylate ligands, and investigated the loading of palladium and platinum ions into these polymers. Polymer-Ab conjugates prepared with palladium- and platinum-loaded polymers gave curious results, in that only dead cells were recognized. The fourth goal was to create dual

  19. Activation of amide N-H bonds by organotransition metal complexes

    SciTech Connect

    Schaad, D.R.

    1992-01-01

    This research was aimed at developing new homogeneous transition metal hydroamination catalysts, specifically for hydroamination reactions involving the addition of amides to olefins. New iron-, ruthenium-, palladium- and platinum-amido complexes were formed via amide N-H bond activation reactions to zerovalent and divalent organotransition metal complexes. Complexes of the general formula trans-MW(amido) (diphosphine)[sub 2] were synthesized by reaction of amides with FeH(C[sub 6]H[sub 4]PPhCH[sub 2]CH[sub 2]PPh[sub 2]) (dppe) and cis-RuHNp(dmpe)[sub 2]. Photolysis of cis-FeH[sub 2](dmpe)[sub 2] or Pt(C[sub 2]O[sub 4] (PEt[sub 3])[sub 2] in the presence of amides yielded trans-FeH(amido)(dmple)[sub 2] and trans-PtH (amido) IPEt[sub 3]) products. Reactions of amides with cis-M(PEtt[sub 3])[sub 2]Me[sub 2] yielded compounds with the general formula M(amido)Me(PEt[sub 3])[sub 2] (M = Pd, Pt). The reaction of M(diphosphine)Me[sub 2] complexes with amides produced compounds with the general formula M(amido)Me(diphosphine) (M = Pd, Pt). Reaction of amides with PtMe[sub 2](COD) yielded complexes with the general formula PtMe(amido)(COD). The compounds were characterized by multinuclear NMR spectroscopy. The reactions were proposed to occur by two routes: oxidative addition of the amid eN-H bond to the metal complex or direct protonation of the metal complex by the N-H bond of the amide. The rate of formation and the stability of the metal-amido products depended on the nature of the metal complex and the amide employed. Only acidic amides reacted with the iron complexes. For the thermal reactions of amides with the metal complexes, the reactions proceeded to completion faster as the acidity of the amide was increased. The new iron-, ruthenium-, palladium- and platinum-amido complexes were inert to further reaction.

  20. Mechanistic study of the hydrothermal reduction of palladium on the Tobacco mosaic virus.

    PubMed

    Adigun, Oluwamayowa O; Freer, Alexander S; Miller, Jeffrey T; Loesch-Fries, L Sue; Kim, Bong Suk; Harris, Michael T

    2015-07-15

    The fundamental mechanisms governing reduction and growth of palladium on the genetically engineered Tobacco mosaic virus in the absence of an external reducer have been elucidated via in situ X-ray absorption spectroscopy. In recent years, many virus-inorganic materials have been synthesized as a means to produce high quality nanomaterials. However, the underlying mechanisms involved in virus coating have not been sufficiently studied to allow for directed synthesis. We combined XAS, via XANES and EXAFS analysis, with TEM to confirm an autocatalytic reduction mechanism mediated by the TMV1Cys surface. This reduction interestingly proceeds via two first order regimes which result in two linear growth regimes as spherical palladium nanoparticles are formed. By combining this result with particle growth data, it was discovered that the first regime describes growth of palladium nanoparticles on the virion while the second regime describes a second layer of larger particles which grew sporadically on the first palladium nanoparticle layer. Subsequent aggregation of free solution based spherical particles and metallized nanorods characterize a third and final regime. At the end of the second reduction regime, the average particle diameter of particles tethered to the TMV1Cys surface are approximately 4.5 nm. The use of XAS to simultaneously monitor the kinetics of biotemplated reactions along with growth of metal nanoparticles will provide insight into the pertinent reduction and growth mechanisms so that nanorod properties can be controlled through their populating nanoparticles.