Science.gov

Sample records for cell noble metal

  1. Noble metals in oncology

    PubMed Central

    Markowska, Anna; Jaszczyńska-Nowinka, Karolina; Lubin, Jolanta; Markowska, Janina

    2015-01-01

    Worldwide research groups are searching for anticancer compounds, many of them are organometalic complexes having platinum group metals as their active centers. Most commonly used cytostatics from this group are cisplatin, carboplatin and oxaliplatin. Cisplatin was used fot the first time in 1978, from this time many platinum derivatives were created. In this review we present biological properties and probable future clinical use of platinum, gold, silver, iridium and ruthenium derivatives. Gold derivative Auranofin has been studied extensively. Action of silver nanoparticles on different cell lines was analysed. Iridium isotopes are commonly used in brachyterapy. Ruthenium compound new anti-tumour metastasis inhibitor (NAMI-A) is used in managing lung cancer metastases. Electroporation of another ruthenium based compound KP1339 was also studied. Most of described complexes have antiproliferative and proapoptotic properties. Further studies need to be made. Nevertheless noble metal based chemotherapheutics and compounds seem to be an interesting direction of research. PMID:26557773

  2. Noble metal ionic catalysts.

    PubMed

    Hegde, M S; Madras, Giridhar; Patil, K C

    2009-06-16

    Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NO(x), and unburned hydrocarbons-need to be fully converted to CO(2), N(2), and H(2)O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al(2)O(3) or SiO(2) promoted by CeO(2). However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce(1-x)M(x)O(2-delta) and Ce(1-x-y)Ti(y)M(x)O(2-delta) (M = Pt, Pd, Rh; x = 0.01-0.02, delta approximately x, y = 0.15-0.25) oxides in fluorite structure. In these oxide catalysts, Pt(2+), Pd(2+), or Rh(3+) ions are substituted only to the extent of 1-2% of Ce(4+) ion. Lower-valent noble metal ion substitution in CeO(2) creates oxygen vacancies. Reducing molecules (CO, H(2), NH(3)) are adsorbed onto electron-deficient noble metal ions, while oxidizing (O(2), NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NO(x) reduction (with >80% N(2) selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO(2) or Ce(1-x)Ti(x)O(2) were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the

  3. Alkaline polymer electrolyte fuel cells completely free from noble metal catalysts

    PubMed Central

    Lu, Shanfu; Pan, Jing; Huang, Aibin; Zhuang, Lin; Lu, Juntao

    2008-01-01

    In recent decades, fuel cell technology has been undergoing revolutionary developments, with fundamental progress being the replacement of electrolyte solutions with polymer electrolytes, making the device more compact in size and higher in power density. Nowadays, acidic polymer electrolytes, typically Nafion, are widely used. Despite great success, fuel cells based on acidic polyelectrolyte still depend heavily on noble metal catalysts, predominantly platinum (Pt), thus increasing the cost and hampering the widespread application of fuel cells. Here, we report a type of polymer electrolyte fuel cells (PEFC) employing a hydroxide ion-conductive polymer, quaternary ammonium polysulphone, as alkaline electrolyte and nonprecious metals, chromium-decorated nickel and silver, as the catalyst for the negative and positive electrodes, respectively. In addition to the development of a high-performance alkaline polymer electrolyte particularly suitable for fuel cells, key progress has been achieved in catalyst tailoring: The surface electronic structure of nickel has been tuned to suppress selectively the surface oxidative passivation with retained activity toward hydrogen oxidation. This report of a H2–O2 PEFC completely free from noble metal catalysts in both the positive and negative electrodes represents an important advancement in the research and development of fuel cells.

  4. Fluorescent noble metal nanoclusters

    NASA Astrophysics Data System (ADS)

    Zheng, Jie

    Water-soluble fluorescent metallic clusters at sizes comparable to the Fermi wavelength of an electron (˜0.5 nm for gold and silver) were created and their photophysical properties were investigated at the bulk and single molecule levels. We employed biocompatible dendrimer and peptide to prepare a series of strong fluorescent gold and silver clusters with chemical or photo reduction methods. Facilitated by the well-defined dendrimer size, electrospray ionization mass spectrometry indicates that the fluorescent silver nanocluster size ranges from 2 to 8 Ag atoms. The correlation of emission energy with the number of atoms, N, in each gold nanocluster is quantitatively fit for the smallest nanoclusters with no adjustable parameters by the simple scaling relation of EFermi/N1/3, in which EFermi is the Fermi energy of bulk gold. The transition energy scaling inversely with cluster radius indicates that electronic structure can be well described with the spherical jellium model and further demonstrates that these nanomaterials are "multi-electron artificial atoms". Fluorescence from these small metal clusters can be considered protoplasmonic, molecular transitions of the free conduction electrons before the onset of collective dipole oscillations occurring when a continuous density of states is reached. In addition, very strong single molecular Stokes and anti-Stokes Raman enhancement by fluorescent silver clusters was observed. Pushing to larger sizes, we also created ˜2nm diameter glutathione encapsulated luminescent gold nanoparticles. Distinct from similarly sized but nonluminescent gold nanoparticles, these 2 nm gold nanoparticles show bright, long lifetime emission but no plasmon absorption. The emission might arise from charge transfer between gold atoms and the thiol ligand. Providing the "missing link" between atomic and nanoparticle behavior in noble metals, these highly fluorescent, water-soluble gold and silver nanoclusters offer complementary transition

  5. Environmentally Friendly Carbon-Preserving Recovery of Noble Metals From Supported Fuel Cell Catalysts.

    PubMed

    Latsuzbaia, R; Negro, E; Koper, G J M

    2015-06-01

    The dissolution of noble-metal catalysts under mild and carbon-preserving conditions offers the possibility of in situ regeneration of the catalyst nanoparticles in fuel cells or other applications. Here, we report on the complete dissolution of the fuel cell catalyst, platinum nanoparticles, under very mild conditions at room temperature in 0.1 M HClO4 and 0.1 M HCl by electrochemical potential cycling between 0.5-1.1 V at a scan rate of 50 mV s(-1) . Dissolution rates as high as 22.5 μg cm(-2) per cycle were achieved, which ensured a relatively short dissolution timescale of 3-5 h for a Pt loading of 0.35 mg cm(-2) on carbon. The influence of chloride ions and oxygen in the electrolyte on the dissolution was investigated, and a dissolution mechanism is proposed on the basis of the experimental observations and available literature results. During the dissolution process, the corrosion of the carbon support was minimal, as observed by X-ray photoelectron spectroscopy (XPS). PMID:25959077

  6. Noble metal/vanadium alloy catalyst and method for making

    SciTech Connect

    Jalan, V.M.

    1980-05-13

    A novel catalyst comprises an alloy of a noble metal and vanadium. The catalyst is particularly useful in an electrochemical cell cathode electrode. The method for making the alloy involves reacting a vanadium compound with sodium dithionite to form a sol of a finely dispersed vanadium sulfite complex, and then reacting noble metal particles with the complex in a reducing environment.

  7. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal... “Class II Special Controls Guidance Document: Dental Noble Metal Alloys.” The devices are exempt from...

  8. 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.

  9. Incorporation of noble metals into aerogels

    DOEpatents

    Hair, L.M.; Sanner, R.D.; Coronado, P.R.

    1998-12-22

    Aerogels or xerogels containing atomically dispersed noble metals for applications such as environmental remediation are disclosed. New noble metal precursors, such as Pt--Si or Pd(Si--P){sub 2}, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

  10. Incorporation of noble metals into aerogels

    DOEpatents

    Hair, Lucy M.; Sanner, Robert D.; Coronado, Paul R.

    1998-01-01

    Aerogels or xerogels containing atomically dispersed noble metals for applications such environmental remediation. New noble metal precursors, such as Pt--Si or Pd(Si--P).sub.2, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

  11. Recovery and use of fission product noble metals

    SciTech Connect

    Jensen, G.A.; Rohmann, C.A.; Perrigo, L.D.

    1980-06-01

    Noble metals in fission products are of strategic value. Market prices for noble metals are rising more rapidly than recovery costs. A promising concept has been developed for recovery of noble metals from fission product waste. Although the assessment was made only for the three noble metal fission products (Rh, Pd, Ru), there are other fission products and actinides which have potential value. (DLC)

  12. 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,...

  13. 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,...

  14. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 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,...

  15. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 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,...

  16. Noble metal superparticles and methods of preparation thereof

    DOEpatents

    Sun, Yugang; Hu, Yongxing

    2016-07-12

    A method comprises heating an aqueous solution of colloidal silver particles. A soluble noble metal halide salt is added to the aqueous solution which undergoes a redox reaction on a surface of the silver particles to form noble metal/silver halide SPs, noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs on the surface of the silver particles. The heat is maintained for a predetermined time to consume the silver particles and release the noble metal/silver halide SPs, the noble metal halide/silver halide SPs or the noble metal oxide/silver halide SPs into the aqueous solution. The aqueous solution is cooled. The noble metal/silver halide SPs, the noble metal halide/silver halide SPs or noble metal oxide/silver halide SPs are separated from the aqueous solution. The method optionally includes adding a soluble halide salt to the aqueous solution.

  17. Inert electrode containing metal oxides, copper and noble metal

    DOEpatents

    Ray, Siba P.; Woods, Robert W.; Dawless, Robert K.; Hosler, Robert B.

    2000-01-01

    A cermet composite material is made by treating at an elevated temperature a mixture comprising a compound of iron and a compound of at least one other metal, together with an alloy or mixture of copper and a noble metal. The alloy or mixture preferably comprises particles having an interior portion containing more copper than noble metal and an exterior portion containing more noble metal than copper. The noble metal is preferably silver. The cermet composite material preferably includes alloy phase portions and a ceramic phase portion. At least part of the ceramic phase portion preferably has a spinel structure.

  18. Inert electrode containing metal oxides, copper and noble metal

    DOEpatents

    Ray, Siba P.; Woods, Robert W.; Dawless, Robert K.; Hosler, Robert B.

    2001-01-01

    A cermet composite material is made by treating at an elevated temperature a mixture comprising a compound of iron and a compound of at least one other metal, together with an alloy or mixture of copper and a noble metal. The alloy or mixture preferably comprises particles having an interior portion containing more copper than noble metal and an exterior portion containing more noble metal than copper. The noble metal is preferably silver. The cermet composite material preferably includes alloy phase portions and a ceramic phase portion. At least part of the ceramic phase portion preferably has a spinel structure.

  19. Synthesis of noble metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Bahadory, Mozhgan

    Improved methods were developed for the synthesis of noble metal nanoparticles. Laboratory experiments were designed for introducing of nanotechnology into the undergraduate curriculum. An optimal set of conditions for the synthesis of clear yellow colloidal silver was investigated. Silver nanoparticles were obtained by borohydride reduction of silver nitrate, a method which produces particles with average size of 12+/-2 nm, determined by Transmission Electron Microscopy (TEM). The plasmon absorbance is at 397 nm and the peak width at half maximum (PWHM) is 70-75 nm. The relationship between aggregation and optical properties was determined along with a method to protect the particles using polyvinylpyrrolidone (PVP). A laboratory experiment was designed in which students synthesize yellow colloidal silver, estimate particle size using visible spectroscopy, and study aggregation effects. The synthesis of the less stable copper nanoparticles is more difficult because copper nanopaticles are easily oxidized. Four methods were used for the synthesis of copper nanoparticles, including chemical reduction with sodium borohydride, sodium borohydride with potassium iodide, isopropyl alcohol with cetyltrimethylammonium bormide (CTAB) and reducing sugars. The latter method was also the basis for an undergraduate laboratory experiment. For each reaction, the dependence of stability of the copper nanoparticles on reagent concentrations, additives, relative amounts of reactants, and temperature is explored. Atomic force microscopy (AFM), TEM and UV-Visible Spectroscopy were used to characterize the copper nanoparticles. A laboratory experiment to produce copper nanoparticles from household chemicals was developed.

  20. Noble Metal Nanoparticles Applications in Cancer

    PubMed Central

    Conde, João; Doria, Gonçalo; Baptista, Pedro

    2012-01-01

    Nanotechnology has prompted new and improved materials for biomedical applications with particular emphasis in therapy and diagnostics. Special interest has been directed at providing enhanced molecular therapeutics for cancer, where conventional approaches do not effectively differentiate between cancerous and normal cells; that is, they lack specificity. This normally causes systemic toxicity and severe and adverse side effects with concomitant loss of quality of life. Because of their small size, nanoparticles can readily interact with biomolecules both at surface and inside cells, yielding better signals and target specificity for diagnostics and therapeutics. This way, a variety of nanoparticles with the possibility of diversified modification with biomolecules have been investigated for biomedical applications including their use in highly sensitive imaging assays, thermal ablation, and radiotherapy enhancement as well as drug and gene delivery and silencing. Here, we review the available noble metal nanoparticles for cancer therapy, with particular focus on those already being translated into clinical settings. PMID:22007307

  1. Noble Metal Nanoparticles for Biosensing Applications

    PubMed Central

    Doria, Gonçalo; Conde, João; Veigas, Bruno; Giestas, Leticia; Almeida, Carina; Assunção, Maria; Rosa, João; Baptista, Pedro V.

    2012-01-01

    In the last decade the use of nanomaterials has been having a great impact in biosensing. In particular, the unique properties of noble metal nanoparticles have allowed for the development of new biosensing platforms with enhanced capabilities in the specific detection of bioanalytes. Noble metal nanoparticles show unique physicochemical properties (such as ease of functionalization via simple chemistry and high surface-to-volume ratios) that allied with their unique spectral and optical properties have prompted the development of a plethora of biosensing platforms. Additionally, they also provide an additional or enhanced layer of application for commonly used techniques, such as fluorescence, infrared and Raman spectroscopy. Herein we review the use of noble metal nanoparticles for biosensing strategies—from synthesis and functionalization to integration in molecular diagnostics platforms, with special focus on those that have made their way into the diagnostics laboratory. PMID:22438731

  2. The Colour of the Noble Metals.

    ERIC Educational Resources Information Center

    Poole, R. T.

    1983-01-01

    Examines the physical basis for colors of noble metals (copper, silver, gold) developed from energy conservation/quantum mechanical view of free electron photoabsorption. Describes production of absorption edges produced by change in density of occupied valence electron states in the d-band, which allows stronger absorption in the visible photon…

  3. 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.

  4. Strategic role of selected noble metal nanoparticles in medicine.

    PubMed

    Rai, Mahendra; Ingle, Avinash P; Birla, Sonal; Yadav, Alka; Santos, Carolina Alves Dos

    2016-09-01

    Noble metals and their compounds have been used as therapeutic agents from the ancient time in medicine for the treatment of various infections. Recently, much progress has been made in the field of nanobiotechnology towards the development of different kinds of nanomaterials with a wide range of applications. Among the metal nanoparticles, noble metal nanoparticles have demonstrated potential biomedical applications. Due to the small size, nanoparticles can easily interact with biomolecules both at surface and inside cells, yielding better signals and target specificity for diagnostics and therapeutics. Noble metal nanoparticles inspired the researchers due to their remarkable role in detection and treatment of dreadful diseases. In this review, we have attempted to focus on the biomedical applications of noble metal nanoparticles particularly, silver, gold, and platinum in diagnosis and treatment of dreaded diseases such as cancer, human immunodeficiency virus (HIV), tuberculosis (TB), and Parkinson disease. In addition, the role of silver nanoparticles (AgNPs) such as novel antimicrobials, gold nanoparticles (AuNPs) such as efficient drug carrier, uses of platinum nanoparticles (PtNPs) in bone allograft, dentistry, etc. have been critically reviewed. Moreover, the toxicity due to the use of metal nanoparticles and some unsolved challenges in the field have been discussed with their possible solutions. PMID:26089024

  5. Oxygen adsorption at noble metal/TiO2 junctions

    NASA Astrophysics Data System (ADS)

    Hossein-Babaei, F.; Alaei-Sheini, Navid; Lajvardi, Mehdi M.

    2016-03-01

    Electric conduction in titanium dioxide is known to be oxygen sensitive and the conductivity of a TiO2 ceramic body is determined mainly by the concentration of its naturally occurring oxygen vacancy. Recently, fabrications and electronic features of a number of noble metal/TiO2-based electronic devices, such as solar cells, UV detectors, gas sensors and memristive devices have been demonstrated. Here, we investigate the effect of oxygen adsorption at the noble metal/TiO2 junction in such devices, and show the potentials of these junctions in chemical sensor fabrication. The polycrystalline, poly-phase TiO2 layers are grown by the selective and controlled oxidation of titanium thin films vacuum deposited on silica substrates. Noble metal thin films are deposited on the oxide layers by physical vapor deposition. Current-voltage (I-V) diagrams of the fabricated devices are studied for Ag/, Au/, and Pt/TiO2 samples. The raw samples show no junction energy barrier. After a thermal annealing in air at 250° C, I-V diagrams change drastically. The annealed samples demonstrate highly non-linear I-V indicating the formation of high Schottky energy barriers at the noble metal/TiO2 junctions. The phenomenon is described based on the effect of the oxygen atoms adsorbed at the junction.

  6. Noble-Metal Nanocrystals with Controlled Facets for Electrocatalysis.

    PubMed

    Hong, Jong Wook; Kim, Yena; Kwon, Yongmin; Han, Sang Woo

    2016-08-19

    Noble-metal nanocrystals (NCs) show excellent catalytic performance for many important electrocatalysis reactions. The crystallographic properties of the facets by which the NCs are bound, closely associated with the shape of the NCs, have a profound influence on the electrocatalytic function of the NCs. To develop an efficient strategy for the synthesis of NCs with controlled facets as well as compositions, understanding of the growth mechanism of the NCs and their interaction with the chemical species involved in NC synthesis is quite important. Furthermore, understanding the facet-dependent catalytic properties of noble-metal NCs and the corresponding mechanisms for various electrocatalysis reactions will allow for the rational design of robust electrocatalysts. In this review, we summarize recently developed synthesis strategies for the preparation of mono- and bimetallic noble-metal NCs by classifying them by the type of facets through which they are enclosed and discuss the electrocatalytic applications of noble-metal NCs with controlled facets, especially for reactions associated with fuel-cell applications, such as the oxygen reduction reaction and fuel (methanol, ethanol, and formic acid) oxidation reactions. PMID:27258679

  7. Noble Metals Would Prevent Hydrogen Embrittlement

    NASA Technical Reports Server (NTRS)

    Paton, N. E.; Frandsen, J. D.

    1987-01-01

    According to proposal, addition of small amounts of noble metals makes iron- and nickel-based alloys less susceptible to embrittlement by hydrogen. Metallurgists demonstrated adding 0.6 to 1.0 percent by weight of Pd or Pt eliminates stress/corrosion cracking in type 4130 steel. Proposal based on assumption that similar levels (0.5 to 1.0 weight percent) of same elements effective against hydrogen embrittlement.

  8. Engineering noble metal nanomaterials for environmental applications

    NASA Astrophysics Data System (ADS)

    Li, Jingguo; Zhao, Tingting; Chen, Tiankai; Liu, Yanbiao; Ong, Choon Nam; Xie, Jianping

    2015-04-01

    Besides being valuable assets in our daily lives, noble metals (namely, gold, silver, and platinum) also feature many intriguing physical and chemical properties when their sizes are reduced to the nano- or even subnano-scale; such assets may significantly increase the values of the noble metals as functional materials for tackling important societal issues related to human health and the environment. Among which, designing/engineering of noble metal nanomaterials (NMNs) to address challenging issues in the environment has attracted recent interest in the community. In general, the use of NMNs for environmental applications is highly dependent on the physical and chemical properties of NMNs. Such properties can be readily controlled by tailoring the attributes of NMNs, including their size, shape, composition, and surface. In this feature article, we discuss recent progress in the rational design and engineering of NMNs with particular focus on their applications in the field of environmental sensing and catalysis. The development of functional NMNs for environmental applications is highly interdisciplinary, which requires concerted efforts from the communities of materials science, chemistry, engineering, and environmental science.

  9. Engineering noble metal nanomaterials for environmental applications.

    PubMed

    Li, Jingguo; Zhao, Tingting; Chen, Tiankai; Liu, Yanbiao; Ong, Choon Nam; Xie, Jianping

    2015-05-01

    Besides being valuable assets in our daily lives, noble metals (namely, gold, silver, and platinum) also feature many intriguing physical and chemical properties when their sizes are reduced to the nano- or even subnano-scale; such assets may significantly increase the values of the noble metals as functional materials for tackling important societal issues related to human health and the environment. Among which, designing/engineering of noble metal nanomaterials (NMNs) to address challenging issues in the environment has attracted recent interest in the community. In general, the use of NMNs for environmental applications is highly dependent on the physical and chemical properties of NMNs. Such properties can be readily controlled by tailoring the attributes of NMNs, including their size, shape, composition, and surface. In this feature article, we discuss recent progress in the rational design and engineering of NMNs with particular focus on their applications in the field of environmental sensing and catalysis. The development of functional NMNs for environmental applications is highly interdisciplinary, which requires concerted efforts from the communities of materials science, chemistry, engineering, and environmental science. PMID:25866322

  10. Non-noble metal based metallization systems

    NASA Technical Reports Server (NTRS)

    Garcia, A., III

    1983-01-01

    The results of efforts to produce a nonsilver metallization system for silicon photovoltaic cells are given. The system uses a metallization system based on molybdenum, tin, and titanium hydride. The initial work in this system was done using the MIDFILM process. The MIDFILM process attains a line resolution comparable to photoresist methods with a process related to screen printing. The surface to be processed is first coated with a thin layer of photopolymer material. Upon exposure to ultraviolet light through a suitable mask, the polymer in the non-pattern area crosslinks and becomes hard. The unexposed pattern areas remain tacky. The conductor material is then applied in the form of a dry mixture of metal which adheres to the tacky pattern area. The assemblage is then fired to ash the photopolymer and sinter the conductor powder.

  11. High temperature, oxidation resistant noble metal-Al alloy thermocouple

    NASA Technical Reports Server (NTRS)

    Smialek, James L. (Inventor); Gedwill, Michael G. (Inventor)

    1994-01-01

    A thermocouple is disclosed. The thermocouple is comprised of an electropositive leg formed of a noble metal-Al alloy and an electronegative leg electrically joined to form a thermocouple junction. The thermocouple provides for accurate and reproducible measurement of high temperatures (600 - 1300 C) in inert, oxidizing or reducing environments, gases, or vacuum. Furthermore, the thermocouple circumvents the need for expensive, strategic precious metals such as rhodium as a constituent component. Selective oxidation of rhodium is also thereby precluded.

  12. Selective Growth of Noble Gases at Metal/Oxide Interface.

    PubMed

    Takahashi, Keisuke; Oka, Hiroshi; Ohnuki, Somei

    2016-02-17

    The locations and roles of noble gases at an oxide/metal interface in oxide dispersed metal are theoretically and experimentally investigated. Oxide dispersed metal consisting of FCC Fe and Y2Hf2O7 (Y2Ti2O7) is synthesized by mechanical alloying under a saturated Ar gas environment. Transmission electron microscopy and density functional theory observes the strain field at the interface of FCC Fe {111} and Y2Hf2O7 {111} whose physical origin emerges from surface reconstruction due to charge transfer. Noble gases are experimentally observed at the oxide (Y2Ti2O7) site and calculations reveal that the noble gases segregate the interface and grow toward the oxide site. In general, the interface is defined as the trapping site for noble gases; however, transmission electron microscopy and density functional theory found evidence which shows that noble gases grow toward the oxide, contrary to the generally held idea that the interface is the final trapping site for noble gases. Furthermore, calculations show that the inclusion of He/Ar hardens the oxide, suggesting that material fractures could begin from the noble gas bubble within the oxides. Thus, experimental and theoretical results demonstrate that noble gases grow from the interface toward the oxide and that oxides behave as a trapping site for noble gases. PMID:26840881

  13. Electrochemical Synthesis of Nanostructured Noble Metal Films for Biosensing

    NASA Astrophysics Data System (ADS)

    Bhattarai, Jay K.

    electrochemical biosensing. We have also discovered a facile electrochemical method to synthesize novel plasmonic noble metal nanostructured films. Plasmonic noble metal nanostructures have promising applications in photovoltaic solar cells, cloaking, and molecular sensing. Here, we used plasmonic noble metal nanostructures as a transducer for biosensing using localized surface plasmon resonance (LSPR) spectroscopy, a label-free biosensing technique. The prepared nanostructured films are not only sensitive for detecting biomolecules, but are stable chemically and physically, and can be easily regenerated. We have compared the sensitivity of three different types of nanostructured films, namely; nanostructured gold film (NGF), nanostructured silver film (NSF), and NPG film, and discussed the advantages and disadvantages of the prepared structures. Finally, we report carbohydrate--lectin, lectin--protein, and layer-by-layer interactions of molecules using LSPR spectroscopy. We have also performed real-time interactions and concentration dependent studies to find the equilibrium dissociation constant of the interactions. The results from these experiments could contribute to the development of cheap and sensitive biosensors that can be used for diagnostic purposes.

  14. Inert anode containing base metal and noble metal useful for the electrolytic production of aluminum

    DOEpatents

    Ray, Siba P.; Liu, Xinghua

    2000-01-01

    An inert anode for production of metals such as aluminum is disclosed. The inert anode comprises a base metal selected from Cu and Ag, and at least one noble metal selected from Ag, Pd, Pt, Au, Rh, Ru, Ir and Os. The inert anode may optionally be formed of sintered particles having interior portions containing more base metal than noble metal and exterior portions containing more noble metal than base metal. In a preferred embodiment, the base metal comprises Cu, and the noble metal comprises Ag, Pd or a combination thereof.

  15. DWPF Hydrogen Generation Study-Form of Noble Metal SRAT Testing

    SciTech Connect

    Bannochie, C

    2005-09-01

    The Defense Waste Processing Facility, DWPF, has requested that the Savannah River National Laboratory, SRNL, investigate the factors that contribute to hydrogen generation to determine if current conservatism in setting the DWPF processing window can be reduced. A phased program has been undertaken to increase understanding of the factors that influence hydrogen generation in the DWPF Chemical Process Cell, CPC. The hydrogen generation in the CPC is primarily due to noble metal catalyzed decomposition of formic acid with a minor contribution from radiolytic processes. Noble metals have historically been added as trim chemicals to process simulations. The present study investigated the potential conservatism that might be present from adding the catalytic species as trim chemicals to the final sludge simulant versus co-precipitating the noble metals into the insoluble sludge solids matrix. Two sludge simulants were obtained, one with co-precipitated noble metals and one without noble metals. Co-precipitated noble metals were expected to better match real waste behavior than using trimmed noble metals during CPC simulations. Portions of both sludge simulants were held at 97 C for about eight hours to qualitatively simulate the effects of long term storage on particle morphology and speciation. The two original and two heat-treated sludge simulants were then used as feeds to Sludge Receipt and Adjustment Tank, SRAT, process simulations. Testing was done at relatively high acid stoichiometries, {approx}175%, and without mercury in order to ensure significant hydrogen generation. Hydrogen generation rates were monitored during processing to assess the impact of the form of noble metals. The following observations were made on the data: (1) Co-precipitated noble metal simulant processed similarly to trimmed noble metal simulant in most respects, such as nitrite to nitrate conversion, formate destruction, and pH, but differently with respect to hydrogen generation: (A

  16. Noble metal abundances in an Early Archean impact deposit.

    PubMed

    Kyte, F T; Zhou, L; Lowe, D R

    1992-01-01

    We report detailed analyses on the concentrations of the noble metals Pd, Os, Ir, Pt, and Au in an early Archean spherule bed (S4) of probable impact origin from the lower Fig Tree Group, Barberton Greenstone Belt, South Africa. Compared to other sedimentary deposits of known or suspected impact origin, some noble metals are present in exceptionally high concentrations. Noble metal abundances are fractionated relative to abundances in chondrites with ratios of Os/Ir, Pt/Ir, Pd/Ir, and Au/Ir at only 80, 80, 41, and 2% of these values in CI chondrites. Although an extraterrestrial source is favored for the noble metal enrichment, the most plausible cause of the fractionation is by regional hydrothermal/metasomatic alteration. PMID:11537203

  17. Noble metal abundances in an early Archean impact deposit

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.; Zhou, Lei; Lowe, Donald R.

    1992-01-01

    Detailed analyses are reported on the concentrations of the noble metals Pd, Os, Ir, Pt, and Au in an early Archean spherule bed (S4) of probably impact origin from the lower Fig Tree Group, Barberton Greenstone Belt, South Africa. Compared to other sedimentary deposits of known or suspected impact origin, some noble metals are present in exceptionally high concentrations. Noble metal abundances are fractionated relative to abundances in chondrites with ratios of Os/Ir, Pt/Ir, Pd/Ir, and Au/Ir at only 80, 80, 41, and 2 percent of these values on CI chondrites. Although an extraterrestrial source is favored for the noble metal enrichment, the most plausible cause of the fractionation is by regional hydrothermal/metasomatic alteration.

  18. DEVELOPMENT OF A NON-NOBLE METAL HYDROGEN PURIFICATION SYSTEM

    SciTech Connect

    Korinko, P; Kyle Brinkman, K; Thad Adams, T; George Rawls, G

    2008-11-25

    Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focus of the reported work was to develop a scaled reactor with a VNi-Ti alloy membrane to replace a production Pd-alloy tube-type purification/diffuser system.

  19. Thermal expansion of noble metals using improved lattice dynamical model

    NASA Astrophysics Data System (ADS)

    Kumar, Priyank; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.

    2013-06-01

    Isothermal bulk modulus and volume thermal expansion for noble metals have been studied on the basis of improved lattice dynamical model proposed by Pandya et al [Physica B 307, 138-149 (2001)]. The present study shows that for all three noble metals the approach gives satisfactory results, when they are compared with experimental findings. The present study thus confirms the use of improved model to study anharmonic property, and can be extended to study temperature dependent properties in high temperature range.

  20. Theoretical study of metal noble-gas positive ions

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Langhoff, Stephen R.

    1989-01-01

    Theoretical calculations have been performed to determine the spectroscopic constant for the ground and selected low-lying electronic states of the transition-metal noble-gas ions Var(+), FeAr(+), CoAr(+), CuHe(+), CuAr(+), and CuKr(+). Analogous calculations have been performed for the ground states of the alkali noble-gas ions LiAr(+), LiKr(+), NaAr(+), and KAr(+) and the alkaline-earth noble-gas ion MgAr(+) to contrast the difference in binding energies between the simple and transition-metal noble-gas ions. The binding energies increase with increasing polarizability of the noble-gas ions, as expected for a charge-induced dipole bonding mechanism. It is found that the spectroscopic constants of the X 1Sigma(+) states of the alkali noble-gas ions are well described at the self-consistent field level. In contrast, the binding energies of the transition-metal noble-gas ions are substantially increased by electron correlation.

  1. Engineering interface and surface of noble metal nanoparticle nanotubes toward enhanced catalytic activity for fuel cell applications.

    PubMed

    Cui, Chun-Hua; Yu, Shu-Hong

    2013-07-16

    In order for fuel cells to have commercial viability as alternative fuel sources, researchers need to develop highly active and robust fuel cell electrocatalysts. In recent years, the focus has been on the design and synthesis of novel catalytic materials with controlled interface and surface structures. Another goal is to uncover potential catalytic activity and selectivity, as well as understand their fundamental catalytic mechanisms. Scientists have achieved great progress in the experimental and theoretical investigation due to the urgent demand for broad commercialization of fuel cells in automotive applications. However, there are still three main problems: cost, performance, and stability. To meet these targets, the catalyst needs to have multisynergic functions. In addition, the composition and structure changes of the catalysts during the reactions still need to be explored. Activity in catalytic nanomaterials is generally controlled by the size, shape, composition, and interface and surface engineering. As such, one-dimensional nanostructures such as nanowires and nanotubes are of special interest. However, these structures tend to lose the nanoparticle morphology and inhibit the use of catalysts in both fuel cell anodes and cathodes. In 2003, Rubinstein and co-workers proposed the idea of nanoparticle nanotubes (NNs), which combine the geometry of nanotubes and the morphology of nanoparticles. This concept gives both the high surface-to-volume ratio and the size effect, which are both appealing in electrocatalyst design. In this Account, we describe our developments in the construction of highly active NNs with unique surface and heterogeneous interface structures. We try to clarify enhanced activity and stability in catalytic systems by taking into account the activity impact factors. We briefly introduce material structural effects on the electrocatalytic reactivity including metal oxide/metal and metal/metal interfaces, dealloyed pure Pt, and mixed Pt

  2. Field Enhancement using Noble Metal Structures

    NASA Astrophysics Data System (ADS)

    Liu, Benliang

    Resonance may be one of the most fundamental rules of nature. Electromagnetic resonance at nanometer scale could produce a giant field enhancement at optical frequency, providing a way to measure and control the process of atoms and molecules at single molecule scale. For example, the giant field enhancement would provide single molecule sensitivity for Raman scattering, which provides unique tools in measuring the quantity in extremely low concentration. In addition, light-emitting diodes could have high brightness but low input power that would be revolutionary in the optoelectronic industry. Although light enhancement is promising in several key technology areas, there are several challenges remain to be tackled. In particular, since the field enhancement is so strongly geometry dependent that slight modification of the geometry can lead to large variations in the outcome, a thorough understanding in how the geometry of the structure affects the field enhancement and creating proper methods to fabricate these structures reproducibly is of most importance. This thesis is devoted to design, fabrication and characterization of field enhancement generated on the surface of noble metals such as silver or gold with 1D structure. The s-polarized field enhancement arising from one-dimensional metal gratings is designed and optimized by using Rigorous Coupling Wave Analysis (RCWA). After optimization, the strongest enhancement factor is found to be 9.7 for 514nm wavelength light. The theoretical results arc confirmed by angle-dependent reflectivity measurements and the experimental results are found to support the theory. A novel single slit structure employing surface plasmon polaritons (SPPs) for enhancing the electric field is studied. SPPs are first generated on a 50 nm thick metal film using attenuated total reflection coupling, and they are subsequently coupled to the cavity mode induced by the single slit. As a result, the field enhancement is found at least 3

  3. Noble Metal Aerogels—Synthesis, Characterization, and Application as Electrocatalysts

    PubMed Central

    2015-01-01

    Conspectus Metallic and catalytically active materials with high surface area and large porosity are a long-desired goal in both industry and academia. In this Account, we summarize the strategies for making a variety of self-supported noble metal aerogels consisting of extended metal backbone nanonetworks. We discuss their outstanding physical and chemical properties, including their three-dimensional network structure, the simple control over their composition, their large specific surface area, and their hierarchical porosity. Additionally, we show some initial results on their excellent performance as electrocatalysts combining both high catalytic activity and high durability for fuel cell reactions such as ethanol oxidation and the oxygen reduction reaction (ORR). Finally, we give some hints on the future challenges in the research area of metal aerogels. We believe that metal aerogels are a new, promising class of electrocatalysts for polymer electrolyte fuel cells (PEFCs) and will also open great opportunities for other electrochemical energy systems, catalysis, and sensors. The commercialization of PEFCs encounters three critical obstacles, viz., high cost, insufficient activity, and inadequate long-term durability. Besides others, the sluggish kinetics of the ORR and alcohol oxidation and insufficient catalyst stability are important reasons for these obstacles. Various approaches have been taken to overcome these obstacles, e.g., by controlling the catalyst particle size in an optimized range, forming multimetallic catalysts, controlling the surface compositions, shaping the catalysts into nanocrystals, and designing supportless catalysts with extended surfaces such as nanostructured thin films, nanotubes, and porous nanostructures. These efforts have produced plenty of excellent electrocatalysts, but the development of multisynergetic functional catalysts exhibiting low cost, high activity, and high durability still faces great challenges. In this

  4. Noble Metal Nanoparticle-loaded Mesoporous Oxide Microspheres for Catalysis

    NASA Astrophysics Data System (ADS)

    Jin, Zhao

    Noble metal nanoparticles/nanocrystals have attracted much attention as catalysts due to their unique characteristics, including high surface areas and well-controlled facets, which are not often possessed by their bulk counterparts. To avoid the loss of their catalytic activities brought about by their size and shape changes during catalytic reactions, noble metal nanoparticles/nanocrystals are usually dispersed and supported finely on solid oxide supports to prevent agglomeration, nanoparticle growth, and therefore the decrease in the total surface area. Moreover, metal oxide supports can also play important roles in catalytic reactions through the synergistic interactions with loaded metal nanoparticles/nanocrystals. In this thesis, I use ultrasonic aerosol spray to produce hybrid microspheres that are composed of noble metal nanoparticles/nanocrystals embedded in mesoporous metal oxide matrices. The mesoporous metal oxide structure allows for the fast diffusion of reactants and products as well as confining and supporting noble metal nanoparticles. I will first describe my studies on noble metal-loaded mesoporous oxide microspheres as catalysts. Three types of noble metals (Au, Pt, Pd) and three types of metal oxide substrates (TiO2, ZrO2, Al 2O3) were selected, because they are widely used for practical catalytic applications involved in environmental cleaning, pollution control, petrochemical, and pharmaceutical syntheses. By considering every possible combination of the noble metals and oxide substrates, nine types of catalyst samples were produced. I characterized the structures of these catalysts, including their sizes, morphologies, crystallinity, and porosities, and their catalytic performances by using a representative reduction reaction from nitrobenzene to aminobenzene. Comparison of the catalytic results reveals the effects of the different noble metals, their incorporation amounts, and oxide substrates on the catalytic abilities. For this particular

  5. [Polyacrylates of noble metals as potential antitumor drugs].

    PubMed

    Ostrovskaia, L A; Voronkov, M G; Korman, D B; Bliukhterova, N V; Fomina, M M; Rykova, V A; Abzaeva, K A; Zhilitskaia, L V

    2014-01-01

    The antitumor activity of polyacrylates of the noble metals containing argentum (argacryl), aurum (auracryl) and platinum (platacryl) has been studied using experimental murine solid tumor models (Lewis lung carcinoma and Acatol adenocarcinoma). It has been found that polyacrylates of the noble metals are capable of inhibiting tumor development by 50-90% compared to control. Auracryl that inhibites the growth of Lewis lung carcinoma and Acatol adenocarcinoma by 80 and 90%, respectively, compared to control is the most efficient among the tested compounds and can be recommended for the further profound preclinical studies. PMID:25707247

  6. Supported noble metals on hydrogen-treated TiO2 nanotube arrays as highly ordered electrodes for fuel cells.

    PubMed

    Zhang, Changkun; Yu, Hongmei; Li, Yongkun; Gao, Yuan; Zhao, Yun; Song, Wei; Shao, Zhigang; Yi, Baolian

    2013-04-01

    Hydrogen-treated TiO2 nanotube (H-TNT) arrays serve as highly ordered nanostructured electrode supports, which are able to significantly improve the electrochemical performance and durability of fuel cells. The electrical conductivity of H-TNTs increases by approximately one order of magnitude in comparison to air-treated TNTs. The increase in the number of oxygen vacancies and hydroxyl groups on the H-TNTs help to anchor a greater number of Pt atoms during Pt electrodeposition. The H-TNTs are pretreated by using a successive ion adsorption and reaction (SIAR) method that enhances the loading and dispersion of Pt catalysts when electrodeposited. In the SIAR method a Pd activator can be used to provide uniform nucleation sites for Pt and leads to increased Pt loading on the H-TNTs. Furthermore, fabricated Pt nanoparticles with a diameter of 3.4 nm are located uniformly around the pretreated H-TNT support. The as-prepared and highly ordered electrodes exhibit excellent stability during accelerated durability tests, particularly for the H-TNT-loaded Pt catalysts that have been annealed in ultrahigh purity H2 for a second time. There is minimal decrease in the electrochemical surface area of the as-prepared electrode after 1000 cycles compared to a 68 % decrease for the commercial JM 20 % Pt/C electrode after 800 cycles. X-ray photoelectron spectroscopy shows that after the H-TNT-loaded Pt catalysts are annealed in H2 for the second time, the strong metal-support interaction between the H-TNTs and the Pt catalysts enhances the electrochemical stability of the electrodes. Fuel-cell testing shows that the power density reaches a maximum of 500 mWcm(-2) when this highly ordered electrode is used as the anode. When used as the cathode in a fuel cell with extra-low Pt loading, the new electrode generates a specific power density of 2.68 kWg(Pt) (-1) . It is indicated that H-TNT arrays, which have highly ordered nanostructures, could be used as ordered electrode supports

  7. Measuring the noble metal and iodine composition of extracted noble metal phase from spent nuclear fuel using instrumental neutron activation analysis.

    PubMed

    Palomares, R I; Dayman, K J; Landsberger, S; Biegalski, S R; Soderquist, C Z; Casella, A J; Brady Raap, M C; Schwantes, J M

    2015-04-01

    Masses of noble metal and iodine nuclides in the metallic noble metal phase extracted from spent fuel are measured using instrumental neutron activation analysis. Nuclide presence is predicted using fission yield analysis, and radionuclides are identified and the masses quantified using neutron activation analysis. The nuclide compositions of noble metal phase derived from two dissolution methods, UO2 fuel dissolved in nitric acid and UO2 fuel dissolved in ammonium-carbonate and hydrogen-peroxide solution, are compared. PMID:25644079

  8. Size control of noble metal clusters and metallic heterostructures through the reduction kinetics of metal precursors

    NASA Astrophysics Data System (ADS)

    Sevonkaev, Igor V.; Herein, Daniel; Jeske, Gerald; Goia, Dan V.

    2014-07-01

    Eight precious metal salts/complexes were reduced in propylene glycol at temperatures ranging between 110 and 170 °C. We found that the reduction temperature and the size of precipitated metallic nanoparticles formed were significantly affected by the structure and reactivity of the metal precursors. The choice of noble metal precursor offers flexibility for designing, fabricating and controlling the size of metallic heterostructures with tunable properties.Eight precious metal salts/complexes were reduced in propylene glycol at temperatures ranging between 110 and 170 °C. We found that the reduction temperature and the size of precipitated metallic nanoparticles formed were significantly affected by the structure and reactivity of the metal precursors. The choice of noble metal precursor offers flexibility for designing, fabricating and controlling the size of metallic heterostructures with tunable properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03045a

  9. Sintering and ripening resistant noble metal nanostructures

    DOEpatents

    van Swol, Frank B; Song, Yujiang; Shelnutt, John A; Miller, James E; Challa, Sivakumar R

    2013-09-24

    Durable porous metal nanostructures comprising thin metal nanosheets that are metastable under some conditions that commonly produce rapid reduction in surface area due to sintering and/or Ostwald ripening. The invention further comprises the method for making such durable porous metal nanostructures. Durable, high-surface area nanostructures result from the formation of persistent durable holes or pores in metal nanosheets formed from dendritic nanosheets.

  10. Method for low temperature preparation of a noble metal alloy

    DOEpatents

    Even, Jr., William R.

    2002-01-01

    A method for producing fine, essentially contamination free, noble metal alloys is disclosed. The alloys comprise particles in a size range of 5 to 500 nm. The method comprises 1. A method for preparing a noble metal alloy at low temperature, the method comprising the steps of forming solution of organometallic compounds by dissolving the compounds into a quantity of a compatible solvent medium capable of solvating the organometallic, mixing a portion of each solution to provide a desired molarity ratio of ions in the mixed solution, adding a support material, rapidly quenching droplets of the mixed solution to initiate a solute-solvent phase separation as the solvent freezes, removing said liquid cryogen, collecting and freezing drying the frozen droplets to produce a dry powder, and finally reducing the powder to a metal by flowing dry hydrogen over the powder while warming the powder to a temperature of about 150.degree. C.

  11. Noble metal alloy complex nanostructures: controllable synthesis and their electrochemical property.

    PubMed

    Liu, Hui-ling; Nosheen, Farhat; Wang, Xun

    2015-05-21

    Noble metal nanocrystals have been extensively utilized as promising catalysts for chemical transformations and energy conversion. One of their significant applications lies in electrode materials in fuel cells (FCs) due to their superior electrocatalytic performance towards the reactions both on anode and cathode. Nowadays, tremendous efforts have been devoted to improve the catalytic performance and minimize the usage of precious metals. Constructing multicomponent noble metal nanocrystals with complex structures provides the opportunity to reach this goal due to their highly tunable compositions and morphologies, leading to the modification of the related electrochemical properties. In this review, we first highlight the recent advances in the controllable synthesis of noble metal alloy complex nanostructures including nanoframes/nanocages, branched structures, concave/convex structures, core-shell structures and ultrathin structures. Then the effects of the well-defined nanocrystals on the modified and improved electrochemical properties are outlined. Finally, we make a conclusion with the points on the challenges and perspectives of the controllable synthesis of noble metal alloy complex nanostructures and their electrocatalytic performance. PMID:25793455

  12. Noble metal-free hydrazine fuel cell catalysts: EPOC effect in competing chemical and electrochemical reaction pathways.

    PubMed

    Sanabria-Chinchilla, Jean; Asazawa, Koichiro; Sakamoto, Tomokazu; Yamada, Koji; Tanaka, Hirohisa; Strasser, Peter

    2011-04-13

    We report the discovery of a highly active Ni-Co alloy electrocatalyst for the oxidation of hydrazine (N(2)H(4)) and provide evidence for competing electrochemical (faradaic) and chemical (nonfaradaic) reaction pathways. The electrochemical conversion of hydrazine on catalytic surfaces in fuel cells is of great scientific and technological interest, because it offers multiple redox states, complex reaction pathways, and significantly more favorable energy and power densities compared to hydrogen fuel. Structure-reactivity relations of a Ni(60)Co(40) alloy electrocatalyst are presented with a 6-fold increase in catalytic N(2)H(4) oxidation activity over today's benchmark catalysts. We further study the mechanistic pathways of the catalytic N(2)H(4) conversion as function of the applied electrode potential using differentially pumped electrochemical mass spectrometry (DEMS). At positive overpotentials, N(2)H(4) is electrooxidized into nitrogen consuming hydroxide ions, which is the fuel cell-relevant faradaic reaction pathway. In parallel, N(2)H(4) decomposes chemically into molecular nitrogen and hydrogen over a broad range of electrode potentials. The electroless chemical decomposition rate was controlled by the electrode potential, suggesting a rare example of a liquid-phase electrochemical promotion effect of a chemical catalytic reaction ("EPOC"). The coexisting electrocatalytic (faradaic) and heterogeneous catalytic (electroless, nonfaradaic) reaction pathways have important implications for the efficiency of hydrazine fuel cells. PMID:21425793

  13. Noble Metal-Membrane Composites for Electrochemical Applications

    NASA Astrophysics Data System (ADS)

    Millet, Pierre

    1999-01-01

    Composite materials are a new class of materials that combine two or more separate components into a form suitable for structural applications. While each component retains its identity, the new composite material displays macroscopic properties superior to its parent constituents, particularly in terms of mechanical properties and economic value. Perhaps best known for their use in aerospace applications, advanced composites are also used by the automotive, biomedical, and sporting goods markets. In addition, these strong, stiff, lightweight materials are seeing increased use in the rehabilitation, repair, and retrofit of civil infrastructure, including, for example, as replacement bridge decks and wrapping for concrete columns. New composite materials presenting some interesting features which are not directly related to their mechanical properties are appearing. This is the case of noble metal-based polymeric composites, the preparation and characterization of which are considered in this article with regard to their electrochemical properties. These composites are of great practical interest because of potential applications in water electrolysis and H2-O2 fuel cells. Electrolyzers and fuel cells can be used for terrestrial transportation, oxygen generation in submarines, and energy conversion in spacecraft.

  14. Silicon nanocrystal-noble metal hybrid nanoparticles.

    PubMed

    Sugimoto, H; Fujii, M; Imakita, K

    2016-06-01

    We report a novel and facile self-limiting synthesis route of silicon nanocrystal (Si NC)-based colloidally stable semiconductor-metal (gold, silver and platinum) hybrid nanoparticles (NPs). For the formation of hybrid NPs, we employ ligand-free colloidal Si NCs with heavily boron (B) and phosphorus (P) doped shells. By simply mixing B and P codoped colloidal Si NCs with metal salts, hybrid NPs consisting of metal cores and Si NC shells are spontaneously formed. We demonstrate the synthesis of highly uniform and size controllable hybrid NPs. It is shown that codoped Si NCs act as a reducing agent for metal salts and also as a protecting layer to stop metal NP growth. The process is thus self-limiting. The development of a variety of Si NC-based hybrid NPs is a promising first step for the design of biocompatible multifunctional NPs with broad material choices for biosensing, bioimaging and solar energy conversion. PMID:27121127

  15. Preparation and Heat-Treatment of DWPF Simulants With and Without Co-Precipitated Noble Metals

    SciTech Connect

    Koopman, David C.:Eibling, Russel E

    2005-08-01

    The Savannah River National Laboratory is in the process of investigating factors suspected of impacting catalytic hydrogen generation in the Chemical Process Cell of the Defense Waste Processing Facility, DWPF. Noble metal catalyzed hydrogen generation in simulation work constrains the allowable acid addition operating window in DWPF. This constraint potentially impacts washing strategies during sludge batch preparation. It can also influence decisions related to the addition of secondary waste streams to a sludge batch. Noble metals have historically been added as trim chemicals to process simulations. The present study investigated the potential conservatism that might be present from adding the catalytic species as trim chemicals to the final sludge simulant versus co-precipitating the noble metals into the insoluble sludge solids matrix. Parallel preparations of two sludge simulants targeting the composition of Sludge Batch 3 were performed in order to evaluate the impact of the form of noble metals. Identical steps were used except that one simulant had dissolved palladium, rhodium, and ruthenium present during the precipitation of the insoluble solids. Noble metals were trimmed into the other stimulant prior to process tests. Portions of both sludge simulants were held at 97 C for about eight hours to qualitatively simulate the effects of long term storage on particle morphology and speciation. The simulants were used as feeds for Sludge Receipt and Adjustment Tank, SRAT, process simulations. The following conclusions were drawn from the simulant preparation work: (1) The first preparation of a waste slurry simulant with co-precipitated noble metals was successful, based on the data obtained. It appears that 99+% of the noble metals were retained in the simulant. (2) Better control of carbonate, hydroxide, and post-wash trim chemical additions is needed before the new method of simulant preparation will be as reproducible as the old method. (3) The two new

  16. Silicon nanocrystal-noble metal hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Sugimoto, H.; Fujii, M.; Imakita, K.

    2016-05-01

    We report a novel and facile self-limiting synthesis route of silicon nanocrystal (Si NC)-based colloidally stable semiconductor-metal (gold, silver and platinum) hybrid nanoparticles (NPs). For the formation of hybrid NPs, we employ ligand-free colloidal Si NCs with heavily boron (B) and phosphorus (P) doped shells. By simply mixing B and P codoped colloidal Si NCs with metal salts, hybrid NPs consisting of metal cores and Si NC shells are spontaneously formed. We demonstrate the synthesis of highly uniform and size controllable hybrid NPs. It is shown that codoped Si NCs act as a reducing agent for metal salts and also as a protecting layer to stop metal NP growth. The process is thus self-limiting. The development of a variety of Si NC-based hybrid NPs is a promising first step for the design of biocompatible multifunctional NPs with broad material choices for biosensing, bioimaging and solar energy conversion.We report a novel and facile self-limiting synthesis route of silicon nanocrystal (Si NC)-based colloidally stable semiconductor-metal (gold, silver and platinum) hybrid nanoparticles (NPs). For the formation of hybrid NPs, we employ ligand-free colloidal Si NCs with heavily boron (B) and phosphorus (P) doped shells. By simply mixing B and P codoped colloidal Si NCs with metal salts, hybrid NPs consisting of metal cores and Si NC shells are spontaneously formed. We demonstrate the synthesis of highly uniform and size controllable hybrid NPs. It is shown that codoped Si NCs act as a reducing agent for metal salts and also as a protecting layer to stop metal NP growth. The process is thus self-limiting. The development of a variety of Si NC-based hybrid NPs is a promising first step for the design of biocompatible multifunctional NPs with broad material choices for biosensing, bioimaging and solar energy conversion. Electronic supplementary information (ESI) available: Additional TEM images and extinction spectra of Si-metal hybrid NPs are shown in Fig. S1

  17. Noble metal-free hydrogen evolution catalysts for water splitting.

    PubMed

    Zou, Xiaoxin; Zhang, Yu

    2015-08-01

    Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts. PMID:25886650

  18. Ultrafast Hot Carrier Scattering and Generation from Surface Plasmons in Noble Metals

    NASA Astrophysics Data System (ADS)

    Bernardi, Marco; Mustafa, Jamal; Neaton, Jeffrey B.; Louie, Steven G.

    2015-03-01

    Non-equilibrium ``hot''carriers in materials are challenging to study experimentally as they thermalize at subpicosecond time and nanometer length scale. Recent experiments employed hot carriers generated by light absorption or surface plasmon annihilation in noble metals (e.g., Au and Ag) for catalysis and solar cells. The energy distribution and transport of the generated hot carriers play a key role in these experiments. We present ab initio calculations of the energy distribution of hot carriers generated by surface plasmons in noble metals, and the relaxation time and mean free path of the hot carriers along different crystal directions within 5 eV of the Fermi energy. Our calculations show the interplay of the noble metal s and d bands in determining the damping rate of the plasmon and the mean free path of the hot carriers. The trends we find as a function of surface plasmon momentum and frequency allow us to define optimal experimental conditions for hot carrier generation and extraction. Our approach combines density functional theory, GW, and electron-phonon calculations. Our work provides microscopic insight into hot carriers in noble metals, and their ultrafast dynamics in the presence of surface plasmons.

  19. NOBLE METAL CHEMISTRY AND HYDROGEN GENERATION DURING SIMULATED DWPF MELTER FEED PREPARATION

    SciTech Connect

    Koopman, D

    2008-06-25

    Simulations of the Defense Waste Processing Facility (DWPF) Chemical Processing Cell vessels were performed with the primary purpose of producing melter feeds for the beaded frit program plus obtaining samples of simulated slurries containing high concentrations of noble metals for off-site analytical studies for the hydrogen program. Eight pairs of 22-L simulations were performed of the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) cycles. These sixteen simulations did not contain mercury. Six pairs were trimmed with a single noble metal (Ag, Pd, Rh, or Ru). One pair had all four noble metals, and one pair had no noble metals. One supporting 4-L simulation was completed with Ru and Hg. Several other 4-L supporting tests with mercury have not yet been performed. This report covers the calculations performed on SRNL analytical and process data related to the noble metals and hydrogen generation. It was originally envisioned as a supporting document for the off-site analytical studies. Significant new findings were made, and many previous hypotheses and findings were given additional support as summarized below. The timing of hydrogen generation events was reproduced very well within each of the eight pairs of runs, e.g. the onset of hydrogen, peak in hydrogen, etc. occurred at nearly identical times. Peak generation rates and total SRAT masses of CO{sub 2} and oxides of nitrogen were reproduced well. Comparable measures for hydrogen were reproduced with more variability, but still reasonably well. The extent of the reproducibility of the results validates the conclusions that were drawn from the data.

  20. Preparation, Functionality, and Application of Metal Oxide-coated Noble Metal Nanoparticles.

    PubMed

    Liu, Shuhua; Regulacio, Michelle D; Tee, Si Yin; Khin, Yin Win; Teng, Choon Peng; Koh, Leng Duei; Guan, Guijian; Han, Ming-Yong

    2016-08-01

    With their remarkable properties and wide-ranging applications, nanostructures of noble metals and metal oxides have been receiving significantly increased attention in recent years. The desire to combine the properties of these two functional materials for specific applications has naturally prompted research in the design and synthesis of novel nanocomposites, consisting of both noble metal and metal-oxide components. In this review, particular attention is given to core-shell type metal oxide-coated noble metal nanostructures (i.e., metal@oxide), which display potential utility in applications, including photothermal therapy, catalytic conversions, photocatalysis, molecular sensing, and photovoltaics. Emerging research directions and areas are envisioned at the end to solicit more attention and work in this regard. PMID:27291595

  1. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    DOE PAGESBeta

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-06

    We report that identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Furthermore, we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM basedmore » systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.« less

  2. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts.

    PubMed

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S; Kumta, Prashant N

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  3. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    PubMed Central

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  4. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    NASA Astrophysics Data System (ADS)

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

  5. Measuring the Noble Metal and Iodine Composition of Extracted Noble Metal Phase from Spent Nuclear Fuel Using Instrumental Neutron Activation Analysis

    SciTech Connect

    Palomares, R. I.; Dayman, Kenneth J.; Landsberger, Sheldon; Biegalski, Steven R.; Soderquist, Chuck Z.; Casella, Amanda J.; Brady Raap, Michaele C.; Schwantes, Jon M.

    2015-04-01

    Mass quantities of noble metal and iodine nuclides in the metallic noble metal phase extracted from spent fuel are measured using instrumental neutron activation analysis (NAA). Nuclide presence is predicted using fission yield analysis, and mass quantification is derived from standard gamma spectroscopy and radionuclide decay analysis. The nuclide compositions of noble metal phase derived from two dissolution methods, UO2 fuel dissolved in nitric acid and UO2 fuel dissolved in ammonium-carbonate and hydrogen-peroxide solution, are compared. Lastly, the implications of the rapid analytic speed of instrumental NAA are discussed in relation to potential nuclear forensics applications.

  6. Synthesis of graphitic nanostructures on noble metals

    NASA Astrophysics Data System (ADS)

    Parmentier, Amelie

    In this research, two subjects are studied: the growth of graphene from various catalysts with RF-CVD and the growth of graphitic nanostructures from gold-decorated graphene with RF-CVD. In the first topic, various catalysts are made with magnesium oxide and metal nanoparticles: iron, silver and gold. Using a radio-frequency generator, these catalysts are heated and placed in contact with three gases (argon, hydrogen and methane). By controlling various parameters, graphene synthesis can happen. The results are analyzed with Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermo-gravimetrical analysis (TGA), and X-ray diffraction (XRD). In the second topic, commercial graphene is functionalized and decorated with different sizes of gold nanoparticles (1.8nm, 5nm, 10nm and 50nm). Using the RF-CVD process, these samples are heated at different temperatures (500°C, 650°C and 800°C). Depending on the parameters, different kinds of graphitic nanostructures are synthesized. Results are analyzed with Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy.

  7. Noble Metal Arsenides and Gold Inclusions in Northwest Africa 8186

    NASA Technical Reports Server (NTRS)

    Srinivasan, P.; McCubbin, F. M.; Rahman, Z.; Keller, L. P.; Agee, C. B.

    2016-01-01

    CK carbonaceous chondrites are a highly thermally altered group of carbonaceous chondrites, experiencing temperatures ranging between approx.576-867 C. Additionally, the mineralogy of the CK chondrites record the highest overall oxygen fugacity of all chondrites, above the fayalite-magnetite-quartz (FMQ) buffer. Metallic Fe-Ni is extremely rare in CK chondrites, but magnetite and Fe,Ni sulfides are commonly observed. Noble metal-rich inclusions have previously been found in some magnetite and sulfide grains. These arsenides, tellurides, and sulfides, which contain varying amounts of Pt, Ru, Os, Te, As, Ir, and S, are thought to form either by condensation from a solar gas, or by exsolution during metamorphism on the chondritic parent body. Northwest Africa (NWA) 8186 is a highly metamorphosed CK chondrite. This meteorite is predominately composed of NiO-rich forsteritic olivine (Fo65), with lesser amounts of plagioclase (An52), augite (Fs11Wo49), magnetite (with exsolved titanomagnetite, hercynite, and titanohematite), monosulfide solid solution (with exsolved pentlandite), and the phosphate minerals Cl-apatite and merrillite. This meteorite contains coarse-grained, homogeneous silicates, and has 120deg triple junctions between mineral phases, which indicates a high degree of thermal metamorphism. The presence of NiO-rich olivine, oxides phases all bearing Fe3+, and the absence of metal, are consistent with an oxygen fugacity above the FMQ buffer. We also observed noble metal-rich phases within sulfide grains in NWA 8186, which are the primary focus of the present study.

  8. Reversibility of Noble Metal-Catalyzed Aprotic Li-O₂ Batteries.

    PubMed

    Ma, Shunchao; Wu, Yang; Wang, Jiawei; Zhang, Yelong; Zhang, Yantao; Yan, Xinxiu; Wei, Yang; Liu, Peng; Wang, Jiaping; Jiang, Kaili; Fan, Shoushan; Xu, Ye; Peng, Zhangquan

    2015-12-01

    The aprotic Li-O2 battery has attracted a great deal of interest because, theoretically, it can store far more energy than today's batteries. Toward unlocking the energy capabilities of this neotype energy storage system, noble metal-catalyzed high surface area carbon materials have been widely used as the O2 cathodes, and some of them exhibit excellent electrochemical performances in terms of round-trip efficiency and cycle life. However, whether these outstanding electrochemical performances are backed by the reversible formation/decomposition of Li2O2, i.e., the desired Li-O2 electrochemistry, remains unclear due to a lack of quantitative assays for the Li-O2 cells. Here, noble metal (Ru and Pd)-catalyzed carbon nanotube (CNT) fabrics, prepared by magnetron sputtering, have been used as the O2 cathode in aprotic Li-O2 batteries. The catalyzed Li-O2 cells exhibited considerably high round-trip efficiency and prolonged cycle life, which could match or even surpass some of the best literature results. However, a combined analysis using differential electrochemical mass spectrometry and Fourier transform infrared spectroscopy, revealed that these catalyzed Li-O2 cells (particularly those based on Pd-CNT cathodes) did not work according to the desired Li-O2 electrochemistry. Instead the presence of noble metal catalysts impaired the cells' reversibility, as evidenced by the decreased O2 recovery efficiency (the ratio of the amount of O2 evolved during recharge/that consumed in the preceding discharge) coupled with increased CO2 evolution during charging. The results reported here provide new insights into the O2 electrochemistry in the aprotic Li-O2 batteries containing noble metal catalysts and exemplified the importance of the quantitative assays for the Li-O2 reactions in the course of pursuing truly rechargeable Li-O2 batteries. PMID:26535791

  9. Noble Metals and Spinel Settling in High Level Waste Glass Melters

    SciTech Connect

    Sundaram, S. K.; Perez, Joseph M.

    2000-09-30

    In the continuing effort to support the Defense Waste Processing Facility (DWPF), the noble metals issue is addressed. There is an additional concern about the amount of noble metals expected to be present in the future batches that will be considered for vitrification in the DWPF. Several laboratory, as well as melter-scale, studies have been completed by various organizations (mainly PNNL, SRTC, and WVDP in the USA). This letter report statuses the noble metals issue and focuses at the settling of noble metals in melters.

  10. Photoresponse from noble metal nanoparticles-multi walled carbon nanotube composites

    SciTech Connect

    Scarselli, M.; Camilli, L.; Castrucci, P.; De Crescenzi, M.; Matthes, L.; Pulci, O.; Gatto, E.; Venanzi, M.

    2012-12-10

    In this Letter, we investigated the photo-response of multi wall carbon nanotube-based composites obtained from in situ thermal evaporation of noble metals (Au, Ag, and Cu) on the nanotube films. The metal deposition process produced discrete nanoparticles on the nanotube outer walls. The nanoparticle-carbon nanotube films were characterized by photo-electrochemical measurements in a standard three electrode cell. The photocurrent from the decorated carbon nanotubes remarkably increased with respect to that of bare multiwall tubes. With the aid of first-principle calculations, these results are discussed in terms of metal nanoparticle-nanotube interactions and electronic charge transfer at the interface.

  11. Nanoparticles of noble metals in the supergene zone

    NASA Astrophysics Data System (ADS)

    Zhmodik, S. M.; Kalinin, Yu. A.; Roslyakov, N. A.; Mironov, A. G.; Mikhlin, Yu. L.; Belyanin, D. K.; Nemirovskaya, N. A.; Spiridonov, A. M.; Nesterenko, G. V.; Airiyants, E. V.; Moroz, T. N.; Bul'bak, T. A.

    2012-04-01

    Formation of noble metal nanoparticles is related to various geological processes in the supergene zone. Dispersed mineral phases appear during weathering of rocks with active participation of microorganisms, formation of soil, in aqueous medium and atmosphere. Invisible gold and other noble metals are incorporated into oxides, hydroxides, and sulfides, as well as in dispersed organic and inorganic carbonic matter. Sulfide minerals that occur in bedrocks and ores unaltered by exogenic processes and in cementation zone are among the main concentrators of noble metal nanoparticles. The ability of gold particles to disaggregate is well-known and creates problems in technological and analytical practice. When Au and PGE nanoparticles and clusters occur, these problems are augmented because of their unusual reactions and physicochemical properties. The studied gold, magnetite, titanomagnetite and pyrite microspherules from cementation zone and clay minerals of laterites in Republic of Guinea widen the knowledge of their abundance and inferred formation conditions, in particular, in the contemporary supergene zone. Morphology and composition of micrometer-sized Au mineral spherules were studied with SEM and laser microprobe. The newly formed segregations of secondary gold on the surface of its residual grains were also an object of investigation. The character of such overgrowths is the most indicative for nanoparticles. The newly formed Au particles provide evidence for redistribution of ultradispersed gold during weathering. There are serious prerequisites to state that microorganisms substantially control unusual nano-sized microspherical morphology of gold particles in the supergene zone. This is supported by experiments indicating active absorption of gold by microorganisms and direct evidence for participation of Ralstonia metallidurans bacteria in the formation of peculiar corroded bacteriomorphic surface of gold grains. In addition, the areas enriched in carbon

  12. Distributions of noble metal Pd and Pt in mesoporous silica

    NASA Astrophysics Data System (ADS)

    Arbiol, J.; Cabot, A.; Morante, J. R.; Chen, Fanglin; Liu, Meilin

    2002-10-01

    Mesoporous silica nanostructures have been synthesized and loaded with Pd and Pt catalytic noble metals. It is found that Pd forms small nanoclusters (3-5 nm) on the surface of the mesoporous structure whereas Pt impregnation results in the inclusion of Pt nanostructures within the silica hexagonal pores (from nanoclusters to nanowires). It is observed that these materials have high catalytic properties for CO-CH4 combustion, even in a thick film form. In particular, results indicate that the Pt and Pd dispersed in mesoporous silica are catalytically active as a selective filter for gas sensors.

  13. The strong reactions of Lewis-base noble-metals with vanadium and other acidic transition metals

    SciTech Connect

    Ebbinghaus, B.B.

    1991-05-01

    The noble metals often thought of as unreactive solids,react strongly with nearly 40% of the elements in the periodictable: group IIIB-VB transition metals, lanthanides, theactinides, and group IIIA-IVA non-transition metals. These strong reactions arise from increased bonding/electron transfer fromnonbonding electrons d electron pairs on the noble metal tovacant orbitals on V, etc. This effect is a generalized Lewis acid-base interaction. The partial Gibbs energy of V in the noblemetals has been measured as a function of concentration at a temperature near 1000C. Thermodynamics of the intermetallics are determined by ternary oxide equilibria, ternary carbide equilibria, and the high-temperature galvanic cell technique. These experimental methods use equilibrated solid composite mixtures in which grains of V oxides or of V carbides are interspersed with grains of V-NM(noble-metal) alloys. In equilibrium the activity of V in the oxide or the carbide equals the activity in the alloy. Consequently, the thermodynamics available in the literature for the V oxides and V carbides are reviewed. Test runs on the galvanic cell were attempted. The V oxide electrode reacts with CaF[sub 2], ThO[sub 2], YDT(0.85ThO[sub 2]-0.15YO[sub 1.5]), and LDT(0.85ThO[sub 2]- 0.15LaO[sub 1.5]) to interfere with the measured data observed toward the beginning of a galvanic cell experiment are the most accurate. The interaction of vanadium at infinite dilution in the noble-metals was determined.

  14. The strong reactions of Lewis-base noble-metals with vanadium and other acidic transition metals

    SciTech Connect

    Ebbinghaus, B.B.

    1991-05-01

    The noble metals often thought of as unreactive solids,react strongly with nearly 40% of the elements in the periodictable: group IIIB-VB transition metals, lanthanides, theactinides, and group IIIA-IVA non-transition metals. These strong reactions arise from increased bonding/electron transfer fromnonbonding electrons d electron pairs on the noble metal tovacant orbitals on V, etc. This effect is a generalized Lewis acid-base interaction. The partial Gibbs energy of V in the noblemetals has been measured as a function of concentration at a temperature near 1000C. Thermodynamics of the intermetallics are determined by ternary oxide equilibria, ternary carbide equilibria, and the high-temperature galvanic cell technique. These experimental methods use equilibrated solid composite mixtures in which grains of V oxides or of V carbides are interspersed with grains of V-NM(noble-metal) alloys. In equilibrium the activity of V in the oxide or the carbide equals the activity in the alloy. Consequently, the thermodynamics available in the literature for the V oxides and V carbides are reviewed. Test runs on the galvanic cell were attempted. The V oxide electrode reacts with CaF{sub 2}, ThO{sub 2}, YDT(0.85ThO{sub 2}-0.15YO{sub 1.5}), and LDT(0.85ThO{sub 2}- 0.15LaO{sub 1.5}) to interfere with the measured data observed toward the beginning of a galvanic cell experiment are the most accurate. The interaction of vanadium at infinite dilution in the noble-metals was determined.

  15. Functionalized magnetite particles for adsorption of colloidal noble metal nanoparticles.

    PubMed

    Lopes, Joana L; Marques, Karine L; Girão, Ana V; Pereira, Eduarda; Trindade, Tito

    2016-08-01

    Magnetite (inverse spinel type) particles have been surface-modified with siliceous shells enriched in dithiocarbamate groups. The deposition of colloidal noble metal nanoparticles (Au, Ag, Pt, Pd) onto the modified magnetites can be performed by treating the respective hydrosols with the magnetic sorbents, thus allowing their uptake from water under a magnetic gradient. In particular, for Au colloids, these magnetic particles are very efficient sorbents that we ascribe to the strong affinity of sulfur-containing groups at the magnetite surfaces for this metal. Considering the extensive use of Au colloids in laboratorial and industrial contexts, the approach described here might have an impact on the development of nanotechnologies to recover this precious metal. En route to these findings, we varied several operational parameters in order to investigate this strategy as a new bottom-up assembly method for producing plasmonic-magnetic nanoassemblies. PMID:27156089

  16. Photocatalytic water reduction with copper-based photosensitizers: a noble-metal-free system.

    PubMed

    Luo, Shu-Ping; Mejía, Esteban; Friedrich, Aleksej; Pazidis, Alexandra; Junge, Henrik; Surkus, Annette-Enrica; Jackstell, Ralf; Denurra, Stefania; Gladiali, Serafino; Lochbrunner, Stefan; Beller, Matthias

    2013-01-01

    Of noble descent: a fully noble-metal-free system for the photocatalytic reduction of water at room temperature has been developed. This system consists of Cu(I) complexes as photosensitizers and [Fe(3)(CO)(12)] as the water-reduction catalyst. The novel Cu-based photosensitizers are relatively inexpensive, readily available from commercial sources, and stable to ambient conditions, thus making them an attractive alternative to the widely used noble-metal based systems. PMID:23047871

  17. Noble Metal Arsenides and Gold Inclusions in Northwest Africa 8186

    NASA Technical Reports Server (NTRS)

    Srinivasan, P.; McCubbin, F. M.; Rahman, Z.; Keller, L. P.; Agee, C. B.

    2016-01-01

    CK carbonaceous chondrites are a highly thermally altered group of carbonaceous chondrites, experiencing temperatures ranging between approximately 576-867 degrees Centigrade. Additionally, the mineralogy of the CK chondrites record the highest overall oxygen fugacity of all chondrites, above the fayalite-magnetite-quartz (FMQ) buffer. Me-tallic Fe-Ni is extremely rare in CK chondrites, but magnetite and Fe,Ni sulfides are commonly observed. Noble metal-rich inclusions have previously been found in some magnetite and sulfide grains. These arsenides, tellurides, and sulfides, which contain varying amounts of Pt, Ru, Os, Te, As, Ir, and S, are thought to form either by condensation from a solar gas, or by exsolution during metamorphism on the chondritic parent body. Northwest Africa (NWA) 8186 is a highly metamorphosed CK chondrite. This meteorite is predominately composed of NiO-rich forsteritic olivine (Fo65), with lesser amounts of plagioclase (An52), augite (Fs11Wo49), magnetite (with exsolved titanomagnetite, hercynite, and titanohematite), monosulfide solid solution (with exsolved pentlandite), and the phosphate minerals Cl-apatite and merrillite. This meteorite contains coarse-grained, homogeneous silicates, and has 120-degree triple junctions between mineral phases, which indicates a high degree of thermal metamorphism. The presence of NiO-rich olivine, oxides phases all bearing Fe3 plus, and the absence of metal, are consistent with an oxygen fugacity above the FMQ buffer. We also observed noble metal-rich phases within sulfide grains in NWA 8186, which are the primary focus of the present study.

  18. Crystal phase-controlled synthesis, properties and applications of noble metal nanomaterials.

    PubMed

    Fan, Zhanxi; Zhang, Hua

    2016-01-01

    The functional properties of noble metal nanomaterials are determined by their size, shape, composition, architecture and crystal structure/phase. In recent years, the crystal phase control of noble metal nanomaterials has emerged as an efficient and versatile strategy to tune their properties. In this tutorial review, we will give an overview of the latest research progress in the crystal phase-controlled synthesis of noble metal nanomaterials. Moreover, the crystal phase-dependent chemical and physical properties (e.g. chemical stability, magnetic, electrical and optical properties) and catalytic applications (e.g. oxygen reduction reaction, and oxidation reactions of formic acid, methanol and carbon monoxide) of noble metal nanomaterials are also briefly introduced. Finally, based on the current research status of the crystal phase-controlled synthesis of noble metal nanomaterials, we will provide some perspectives on the challenges and opportunities in this emerging research field. PMID:26584059

  19. 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).

  20. Star-like copolymer stabilized noble-metal nanoparticle powders.

    PubMed

    Cao, Peng-Fei; Yan, Yun-Hui; Mangadlao, Joey Dacula; Rong, Li-Han; Advincula, Rigoberto

    2016-03-31

    The amphiphilic star-like copolymer polyethylenimine-block-poly(ε-caprolactone) (PEI-b-PCL) was utilized to transfer the pre-synthesized citrate-capped noble metal nanoparticles (NMNPs) from an aqueous layer to an organic layer without any additional reagents. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were utilized to study the assembly of the polymers coated on the surface of the citrate-capped NMNPs. After removing the organic solvent, the polymer-coated NMNPs in powder form (PCP-NMNPs) were obtained. The excellent solubility of the PEI-b-PCL allows the PCP-NMNPs to be easily dispersed in most of the organic solvents without any significant aggregation. Moreover, the good thermal stability and long-term stability make PCP-NMNPs an excellent NMNP-containing hybrid system for different specific applications, such as surface coating, catalysis and thermoplastic processing of nanocomposite materials. PMID:26659728

  1. Noble metal ionic sites for catalytic hydrogen combustion: spectroscopic insights.

    PubMed

    Deshpande, Parag A; Madras, Giridhar

    2011-01-14

    A catalytic hydrogen combustion reaction was carried out over noble metal catalysts substituted in ZrO(2) and TiO(2) in ionic form. The catalysts were synthesized by the solution combustion technique. The compounds showed high activity and CO tolerance for the reaction. The activity of Pd and Pt ion substituted TiO(2) was comparable and was higher than Pd and Pt ion substituted ZrO(2). The mechanisms of the reaction over the two supports were proposed by making use of the X-ray photoelectron spectroscopy and FT infrared spectroscopic observations. The reaction over ZrO(2) supported catalysts was proposed to take place by the utilization of the surface hydroxyl groups while the reaction over TiO(2) supported catalysts was hypothesized to be a hybrid mechanism utilizing surface hydroxyl groups and the lattice oxygen. PMID:21060910

  2. Alloyed Noble Metal Nanoparticles with Tunable Optical Properties

    NASA Astrophysics Data System (ADS)

    Wessler, Garrett C.; Gong, Chen; Rebello de Sousa Dias, Mariama; Tailon, Joshua A.; Salamanca-Riba, Lourdes G.; Leite, Marina S.

    Noble metal nanoparticles (NPs) have been widely used in sensing, optics, and catalysis applications by taking advantage of surface plasmon resonance (SPR). This response is slightly tuned by varying the size and shape of the NPs; however, a method to obtain truly on-demand plasmonic responses is still lacking due to the intrinsic nature of a metal's dielectric function. Here, we fabricate size and composition controlled metal alloy NP arrays by deposit-and-anneal methods and through-template depositions. We control the composition of the metal NPs by co-sputtering and by alternating electron-beam evaporation of the Ag and Au targets. To characterize the NPs, macroscopic transmission measurements are combined with spectrally dependent near-field scanning optical microscopy to show the local optical properties around the NPs. By varying the atomic fraction of Ag and Au in the alloys, we modulate the optical properties of the NPs for different applications. For example, hot carrier plasmonic devices necessitate high absorption in the visible range, while photovoltaic applications require low absorption by the NPs.

  3. RISK REDUCTION VIA GREENER SYNTHESIS OF NOBLE METAL NANOSTRUCTURES AND NANOCOMPOSITES

    EPA Science Inventory

    Aqueous preparation of nanoparticles using vitamins B2 and C which can function both as reducing and capping agents are described. Bulk and shape-controlled synthesis of noble nanostructures via microwave (MW)-assisted spontaneous reduction of noble metal salts using a-D-glucose,...

  4. Noble metal/functionalized cellulose nanofiber composites for catalytic applications.

    PubMed

    Gopiraman, Mayakrishnan; Bang, Hyunsik; Yuan, Guohao; Yin, Chuan; Song, Kyung-Hun; Lee, Jung Soon; Chung, Ill Min; Karvembu, Ramasamy; Kim, Ick Soo

    2015-11-01

    In this study, cellulose acetate nanofibers (CANFs) with a mean diameter of 325 ± 2.0 nm were electrospun followed by deacetylation and functionalization to produce anionic cellulose nanofibers (f-CNFs). The noble metal nanoparticles (RuNPs and AgNPs) were successfully decorated on the f-CNFs by a simple wet reduction method using NaBH4 as a reducing agent. TEM and SEM images of the nanocomposites (RuNPs/CNFs and AgNPs/CNFs) confirmed that the very fine RuNPs or AgNPs were homogeneously dispersed on the surface of f-CNFs. The weight percentage of the Ru and Ag in the nanocomposites was found to be 13.29 wt% and 22.60 wt% respectively; as confirmed by SEM-EDS analysis. The metallic state of the Ru and Ag in the nanocomposites was confirmed by XPS and XRD analyses. The usefulness of these nanocomposites was realized from their superior catalytic activity. In the aerobic oxidation of benzyl alcohol to benzaldehyde, the RuNPs/CNFs system gave a better yield of 89% with 100% selectivity. Similarly, the AgNPs/CNFs produced an excellent yield of 99% (100% selectivity) in the aza-Michael reaction of 1-phenylpiperazine with acrylonitrile. Mechanism has been proposed for the catalytic systems. PMID:26256382

  5. Fluorescence enhancement in visible light: dielectric or noble metal?

    PubMed

    Sun, S; Wu, L; Bai, P; Png, C E

    2016-07-28

    A high permittivity dielectric gives the impression of outperforming plasmonic noble metal in visible light fluorescence enhancement primarily because of its small loss. Nonetheless, the performances of these two platforms in various situations remain obscure due to the different optical confinement mechanisms as well as the complexity in the fluorescence enhancement process. This study presents a comprehensive comparison between these two platforms based on nanoparticles (NPs) to evaluate their capability and applicability in fluorescence enhancement by taking into account the fluorescence excitation rate, the quantum yield, the fluorophore wavelengths and Stokes shifts as well as the far field intensity. In a low permittivity sensing medium (e.g. air), the dielectric NP can achieve comparable or higher fluorescence enhancement than the metal NP due to its decent NP-enhanced excitation rate and larger quantum yield. In a relatively high permittivity sensing medium (e.g. water), however, there is a significant decrement of the excitation rate of the dielectric NP as the permittivity contrast decreases, leading to a smaller fluorescence enhancement compared to the metallic counterpart. Combining the fluorescence enhancement and the far field intensity studies, we further conclude that for both dielectric and plasmonic NPs, the optimal situation occurs when the fluorescence excitation wavelength, the fluorescence emission wavelength and the electric-dipole-mode of the dielectric NP (or the plasmonic resonance of the metal NP) are the same and all fall in the low conductivity region of the NP material. We also find that the electric-dipole-mode of the dielectric NP performs better than the magnetic-dipole-mode for fluorescence enhancement applications because only the electric-dipole-mode can be strongly excited by the routinely used fluorescent dyes and quantum dots, which behave as electric dipoles by nature. PMID:27374052

  6. Fate of Noble Metals during the Pyroprocessing of Spent Nuclear Fuel

    SciTech Connect

    B.R. Westphal; D. Vaden; S.X. Li; G.L. Fredrickson; R.D. Mariani

    2009-09-01

    During the pyroprocessing of spent nuclear fuel by electrochemical techniques, fission products are separated as the fuel is oxidized at the anode and refined uranium is deposited at the cathode. Those fission products that are oxidized into the molten salt electrolyte are considered active metals while those that do not react are considered noble metals. The primary noble metals encountered during pyroprocessing are molybdenum, zirconium, ruthenium, rhodium, palladium, and technetium. Pyroprocessing of spent fuel to date has involved two distinctly different electrorefiner designs, in particular the anode to cathode configuration. For one electrorefiner, the anode and cathode collector are horizontally displaced such that uranium is transported across the electrolyte medium. As expected, the noble metal removal from the uranium during refining is very high, typically in excess of 99%. For the other electrorefiner, the anode and cathode collector are vertically collocated to maximize uranium throughput. This arrangement results in significantly less noble metals removal from the uranium during refining, typically no better than 20%. In addition to electrorefiner design, operating parameters can also influence the retention of noble metals, albeit at the cost of uranium recovery. Experiments performed to date have shown that as much as 100% of the noble metals can be retained by the cladding hulls while affecting the uranium recovery by only 6%. However, it is likely that commercial pyroprocessing of spent fuel will require the uranium recovery to be much closer to 100%. The above mentioned design and operational issues will likely be driven by the effects of noble metal contamination on fuel fabrication and performance. These effects will be presented in terms of thermal properties (expansion, conductivity, and fusion) and radioactivity considerations. Ultimately, the incorporation of minor amounts of noble metals from pyroprocessing into fast reactor metallic fuel

  7. Star-like copolymer stabilized noble-metal nanoparticle powders

    NASA Astrophysics Data System (ADS)

    Cao, Peng-Fei; Yan, Yun-Hui; Mangadlao, Joey Dacula; Rong, Li-Han; Advincula, Rigoberto

    2016-03-01

    The amphiphilic star-like copolymer polyethylenimine-block-poly(ε-caprolactone) (PEI-b-PCL) was utilized to transfer the pre-synthesized citrate-capped noble metal nanoparticles (NMNPs) from an aqueous layer to an organic layer without any additional reagents. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were utilized to study the assembly of the polymers coated on the surface of the citrate-capped NMNPs. After removing the organic solvent, the polymer-coated NMNPs in powder form (PCP-NMNPs) were obtained. The excellent solubility of the PEI-b-PCL allows the PCP-NMNPs to be easily dispersed in most of the organic solvents without any significant aggregation. Moreover, the good thermal stability and long-term stability make PCP-NMNPs an excellent NMNP-containing hybrid system for different specific applications, such as surface coating, catalysis and thermoplastic processing of nanocomposite materials.The amphiphilic star-like copolymer polyethylenimine-block-poly(ε-caprolactone) (PEI-b-PCL) was utilized to transfer the pre-synthesized citrate-capped noble metal nanoparticles (NMNPs) from an aqueous layer to an organic layer without any additional reagents. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were utilized to study the assembly of the polymers coated on the surface of the citrate-capped NMNPs. After removing the organic solvent, the polymer-coated NMNPs in powder form (PCP-NMNPs) were obtained. The excellent solubility of the PEI-b-PCL allows the PCP-NMNPs to be easily dispersed in most of the organic solvents without any significant aggregation. Moreover, the good thermal stability and long-term stability make PCP-NMNPs an excellent NMNP-containing hybrid system for different specific applications, such as surface coating, catalysis and thermoplastic processing of nanocomposite materials. Electronic supplementary information (ESI) available: Synthesis scheme and the 1H NMR spectrum of PEI

  8. Determination of noble metals in Savannah River Site high-level radioactive sludge

    SciTech Connect

    Coleman, C.J.; Kinard, W.F.; Bibler, N.E.; Bickford, D.F.; Ramsey, W.G.

    1990-01-01

    High-level radioactive sludge at the Savannah River Site (SRS) will be processed at the Defense Waste Processing Facility (DWPF) into durable borosilicate glass wasteforms. The sludges are analyzed for elemental content before processing to ensure compatibility with the glass-making processes. Noble metal fission products in sludge, can under certain conditions, cause problems in the glass melter. Therefore, reliable noble metal determinations are important. The scheme used to measure noble metals in SRS sludges consists of dissolving sludge with hot aqua regia followed by determinations with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ICP-Mass Spectroscopy (ICP-MS) techniques. ICP-MS is the preferred method for measuring trace levels of noble metals in SRS radioactive waste because of superior sensitivity. Analytical results are presented for the two major types of SRS sludge.

  9. Determination of noble metals in Savannah River Site high-level radioactive sludge

    SciTech Connect

    Coleman, C.J.; Kinard, W.F.; Bibler, N.E.; Bickford, D.F.; Ramsey, W.G.

    1990-12-31

    High-level radioactive sludge at the Savannah River Site (SRS) will be processed at the Defense Waste Processing Facility (DWPF) into durable borosilicate glass wasteforms. The sludges are analyzed for elemental content before processing to ensure compatibility with the glass-making processes. Noble metal fission products in sludge, can under certain conditions, cause problems in the glass melter. Therefore, reliable noble metal determinations are important. The scheme used to measure noble metals in SRS sludges consists of dissolving sludge with hot aqua regia followed by determinations with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ICP-Mass Spectroscopy (ICP-MS) techniques. ICP-MS is the preferred method for measuring trace levels of noble metals in SRS radioactive waste because of superior sensitivity. Analytical results are presented for the two major types of SRS sludge.

  10. CO oxidation studies over supported noble metal catalysts and single crystals: A review

    NASA Technical Reports Server (NTRS)

    Boecker, Dirk; Gonzalez, Richard D.

    1987-01-01

    The catalytic oxidation of CO over noble metal catalysts is reviewed. Results obtained on supported noble metal catalysts and single crystals both at high pressures and under UHV conditions are compared. The underlying causes which result in surface instabilities and multiple steady-state oscillations are considered, in particular, the occurrence of hot spots. CO islands of reactivity, surface oxide formation and phase transformations under oscillatory conditions are discussed.

  11. Study of performance characteristics of noble metal thermocouple materials to 2000 C

    NASA Technical Reports Server (NTRS)

    Freeze, P. D.; Thomas, D.; Edelman, S.; Stern, J.

    1972-01-01

    Three performance characteristics of noble metal thermocouples in various environments are discussed. Catalytic effects cause significant errors when noble metal thermocouple materials are exposed to air containing unburned gases in temperature ranges from 25 C to 1500 C. The thermoelectric stability of the iridium 40 rhodium to iridium thermocouple system at 2000 C in an oxidizing medium is described. The effects of large and small temperature gradients on the accuracy and stability of temperature measurements are analyzed.

  12. A new type of noble metal mineralization in the Northern Caucasus

    NASA Astrophysics Data System (ADS)

    Bogush, I. A.; Cherkashin, V. I.; Ryabov, G. V.; Abdullayev, M. Sh.

    2016-01-01

    The weathering crust of the Beden ultrabasite massif (the basin of Big Laba River) is identified and studied. Anomalously high contents of noble metals (Au, Pt, Pd) are revealed in the basal horizon of the Jurassic part of the weathering crust. For this reason we suspect an existence of a belt of noble metal miner-alization in the Paleozoic ultrabasites in the Peredovoi Range of the Northern Caucasus.

  13. Recovery of Noble Metals and Technetium from Nuclear Waste

    SciTech Connect

    Moon, J.K.; Han, Y.J.; Lee, E.H.; Jung, C.H.; Lee, B.C.

    2006-07-01

    An adsorptive separation of Pd, Rh and Tc was tested by using simulated chemical solutions. Pd(NO{sub 3}){sub 2} and Rh(NO{sub 3}){sub 3} were used for the noble metal sources, and Re 203 after dissolving it in 0.5 M nitric acid was used for the technetium substitute, respectively. A felt type ACF (activated carbon fiber) after being pretreated with 1 M NaOH, and an EIR (extractant impregnated resin) which was prepared by impregnating Aliquat 336 onto Amberlite XAD-4 resin were evaluated on their adsorption equilibrium and kinetic performances. As the results, the ACF showed a high selectivity for the palladium ions over the rhodium and rhenium ions. On the other hand, the EIR was shown to be effective for separation of rhenium from the palladium-free two component system of rhenium and rhodium. Column tests were also performed to confirm the separation efficiency of palladium and rhenium using a jacketed glass column (diam. 11 x L 150). The ACF bed showed the complete separation of palladium from rhenium and rhodium. The breakthrough volume, when 1% of breakthrough is considered, was about 140 BV for palladium, while only a small amount of an adsorption of rhenium and rhodium were found in the column. Then the EIR column was applied to separate rhenium from rhodium and showed successful separation performance with about 122 BV of breakthrough volume. The palladium and rhenium with high purity were recovered effectively by eluting the beds with nitric acid. (authors)

  14. Studies of noble-metal thermocouple stability at high temperatures

    NASA Technical Reports Server (NTRS)

    Freeze, P.; Thomas, D. B.

    1976-01-01

    Two investigatory studies on performance characteristics of noble-metal thermocouples are described. (1) thermoelectric stability as affected by preferential oxidation of iridium in the system iridium-40% rhodium versus iridium, and (2) the effects of temperature gradients on the emf stability of the systems platinum-13% rhodium versus platinum and iridium-40% rhodium versus iridium, operating in air. The stability investigation was carried out at three temperatures - 1700, 1850, and 2000 C - by comparing the output of the test thermocouple in air with the output of an identically constructed reference thermocouple in nitrogen. The results show that no calibration shift was observed producing a change in output greater than that corresponding to a 2.0% change in the indicated temperature for all samples tested. The investigation of gradient effects was carried out by subjecting test thermocouples to both severe and mild gradients for periods up to 200 hours. For the platinum system, the operating temperature was 1500 C with gradients of 1475 and 700 C/cm; for the iridium system, 2000 C with gradients of 700, 1500, and 1975 C/cm. Exposure to temperature gradients was found to introduce significant changes in calibration for both systems. In both investigations, the thermoelements were examined by means of electron-probe analysis and by metallographic methods to detect chemical and structural changes. Data and micrographs are presented.

  15. Epsilon Metal Waste Form for Immobilization of Noble Metals from Used Nuclear Fuel

    SciTech Connect

    Crum, Jarrod V.; Strachan, Denis M.; Rohatgi, Aashish; Zumhoff, Mac R.

    2013-10-01

    Epsilon metal (ε-metal), an alloy of Mo, Pd, Rh, Ru, and Tc, is being developed as a waste form to treat and immobilize the undissolved solids and dissolved noble metals from aqueous reprocessing of commercial used nuclear fuel. Epsilon metal is an attractive waste form for several reasons: increased durability relative to borosilicate glass, it can be fabricated without additives (100% waste loading), and in addition it also benefits borosilicate glass waste loading by eliminating noble metals from the glass and thus the processing problems related there insolubility in glass. This work focused on the processing aspects of the epsilon metal waste form development. Epsilon metal is comprised of refractory metals resulting in high reaction temperatures to form the alloy, expected to be 1500 - 2000°C making it a non-trivial phase to fabricate by traditional methods. Three commercially available advanced technologies were identified: spark-plasma sintering, microwave sintering, and hot isostatic pressing, and investigated as potential methods to fabricate this waste form. Results of these investigations are reported and compared in terms of bulk density, phase assemblage (X-ray diffraction and elemental analysis), and microstructure (scanning electron microscopy).

  16. Catalytic activity of noble metals for metal-assisted chemical etching of silicon

    PubMed Central

    2012-01-01

    Metal-assisted chemical etching of silicon is an electroless method that can produce porous silicon by immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias. We have been studying the metal-assisted hydrofluoric acid etching of silicon using dissolved oxygen as an oxidizing agent. Three major factors control the etching reaction and the porous silicon structure: photoillumination during etching, oxidizing agents, and metal particles. In this study, the influence of noble metal particles, silver, gold, platinum, and rhodium, on this etching is investigated under dark conditions: the absence of photogenerated charges in the silicon. The silicon dissolution is localized under the particles, and nanopores are formed whose diameters resemble the size of the metal nanoparticles. The etching rate of the silicon and the catalytic activity of the metals for the cathodic reduction of oxygen in the hydrofluoric acid solution increase in the order of silver, gold, platinum, and rhodium. PMID:22738277

  17. Catalytic activity of noble metals for metal-assisted chemical etching of silicon

    NASA Astrophysics Data System (ADS)

    Yae, Shinji; Morii, Yuma; Fukumuro, Naoki; Matsuda, Hitoshi

    2012-06-01

    Metal-assisted chemical etching of silicon is an electroless method that can produce porous silicon by immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias. We have been studying the metal-assisted hydrofluoric acid etching of silicon using dissolved oxygen as an oxidizing agent. Three major factors control the etching reaction and the porous silicon structure: photoillumination during etching, oxidizing agents, and metal particles. In this study, the influence of noble metal particles, silver, gold, platinum, and rhodium, on this etching is investigated under dark conditions: the absence of photogenerated charges in the silicon. The silicon dissolution is localized under the particles, and nanopores are formed whose diameters resemble the size of the metal nanoparticles. The etching rate of the silicon and the catalytic activity of the metals for the cathodic reduction of oxygen in the hydrofluoric acid solution increase in the order of silver, gold, platinum, and rhodium.

  18. Nanostructured elastomers: From smectic liquid crystals to noble metal nanocomposites

    NASA Astrophysics Data System (ADS)

    Lentz, Daniel M.

    Noble metal/polymer nanocomposites are a desirable and useful class of material due to their combination of the beneficial processibility and mechanical properties of polymers with the optical, electrical, barrier, and other engineering properties of metal nanoparticles. Potential applications of such materials include non-linear optical materials with gold nanoparticles or conductive polymer substrates with percolated silver nanoparticles. A processing approach has been developed whereby metal nanoparticles, especially silver and gold, can be infused into the surface of a thermoplastic elastomer following the melt processing operation. This reaction-diffusion approach (nanoinfusion) allows metal nanoparticles to be introduced at relatively low cost while avoiding the issues of thermal degradation, microphase separation, or agglomeration that can occur at elevated temperatures in the melt state. The nanoinfusion process involves immersion of a molded, cast, or extruded plastic article in an aqueous plasticizer solution (Bayer MaterialScience AURARTM Infusion Technology) containing a metal salt such as HAuCl4 or AgNO 3. Infusion of the metal salt into the plastic surface is achieved well below the melt-processing temperature due to plasticization of a thin surface layer of 10-500 microm. The metal salt is subsequently reduced to produce zero-valent metal nanoparticles by a second infusion of a reducing agent or a thermal or photochemical reduction process. The growth and agglomeration of the nanoparticles is arrested by the high viscosity of the polymer matrix, producing a stable nanocomposite. In order to examine how nanoparticle size distribution and concentration are affected by soak times in the salt and reducing agent solutions, combinatorial, high-throughput screening methods have been applied. Particle size distributions are characterized rapidly by small-angle x-ray scattering (SAXS) using a "dual gradient" nanoinfusion matrix. In addition, an improved

  19. A GREEN CHEMISTRY APPROACH TO PREPARATION OF CORE (FE OR CU)-SHELL (NOBLE METALS) NANOCOMPOSITES USING AQUEOUS ASCORBIC ACID

    EPA Science Inventory

    A greener method to fabricate novel core (Fe or Cu)-shell (noble metals) nanocomposites of transition metals such as Fe and Cu and noble metals such as Au, Pt, Pd, and Ag using aqueous ascorbic acid is described. Transition metal salts such as Cu and Fe were reduced using ascor...

  20. Effects of the atomic level shift in the Auger neutralization rates of noble metal surfaces

    PubMed Central

    Monreal, R.C.; Goebl, D.; Primetzhofer, D.; Bauer, P.

    2013-01-01

    In this work we compare characteristics of Auger neutralization of He+ ions at noble metal and free-electron metal surfaces. For noble metals, we find that the position of the energy level of He with respect to the Fermi level has a non-negligible influence on the values of the calculated Auger rates through the evaluation of the surface dielectric susceptibility. We conclude that even though our calculated rates are accurate, further theoretical effort is needed to obtain realistic values of the energy level of He in front of these surfaces. PMID:25843996

  1. Well-faceted noble-metal nanocrystals with nonconvex polyhedral shapes.

    PubMed

    Chen, Qiaoli; Jia, Yanyan; Xie, Shuifen; Xie, Zhaoxiong

    2016-06-01

    Precise engineering of noble-metal nanocrystals (NCs) is not only an important fundamental research topic, but also has great realistic significance in improving their performances required by the poor reserve and high cost of noble metals. Well-faceted noble-metal NCs with nonconvex polyhedral shapes could be promising candidates to optimize their performance and thus minimize their usage, as they may integrate a well-defined surface structure and a large surface area together, enabling them to have outstanding performance and high efficiency of atomic utilization. Moreover, undesirable aggregation and ripening phenomena could be avoided. This review provides a comprehensive summary of the unique characteristics and corresponding models of well-faceted nonconvex polyhedral noble-metal NCs by classifying the cases into four distinct types, namely the concave polyhedral structure, excavated polyhedral structure, branched structure and nanocage structure, respectively. Due to the complexity of nonconvex morphologies and the thermodynamic antipathy for the growth of nonconvex shaped NCs, we firstly demonstrate the structure characterization and synthetic methodology in detail. Subsequently, typical applications in electrocatalysis and plasmonic fields are presented to demonstrate the unique surface and morphological effects generated from the well-faceted nonconvex NCs. To promote further development in this field, the perspectives and challenges concerning well-faceted noble-metal NCs with nonconvex shapes are put forward in the end. PMID:27086861

  2. Surface treatment of nanoporous silicon with noble metal ions and characterizations

    NASA Astrophysics Data System (ADS)

    Kanungo, J.; Maji, S.; Mandal, A. K.; Sen, S.; Bontempi, E.; Balamurugan, A. K.; Tyagi, A. K.; Uvdal, K.; Sinha, S.; Saha, H.; Basu, S.

    2010-04-01

    A very large surface to volume ratio of nanoporous silicon (PS) produces a high density of surface states, which are responsible for uncontrolled oxidation of the PS surface. Hence it disturbs the stability of the material and also creates difficulties in the formation of a reliable electrical contact. To passivate the surface states of the nanoporous silicon, noble metals (Pd, Ru, and Pt) were dispersed on the PS surface by an electroless chemical method. GIXRD (glancing incidence X-ray diffraction) proved the crystallinity of PS and the presence of noble metals on its surface. While FESEM (field emission scanning electron microscopy) showed the morphology, the EDX (energy dispersive X-ray) line scans and digital X-ray image mapping indicated the formation of the noble metal islands on the PS surface. Dynamic SIMS (secondary ion mass spectroscopy) further confirmed the presence of noble metals and other impurities near the surface of the modified PS. The variation of the surface roughness after the noble metal modification was exhibited by AFM (atomic force microscopy). The formation of a thin oxide layer on the modified PS surface was verified by XPS (X-ray photoelectron spectroscopy).

  3. Nucleation and growth of noble metals on transition-metal di-tellurides

    NASA Astrophysics Data System (ADS)

    Hla, S. W.; Marinković, V.; Prodan, A.

    1997-04-01

    Transition-metal di-tellurides (α- and β-MoTe 2 and WTe 2) were used as substrates for nucleation and growth studies of noble metals. They represent a group of chemically closely related compounds with different surface topographies. Nucleation and growth of Ag and Au at room temperature were studied by means of UHV-STM, AFM and TEM. The results revealed that the growth and orientation of these metals are influenced by the topography of the substrate surfaces. Contrary to the growth on atomically flat α-MoTe 2, there is an enhanced diffusion and nucleation along the periodic surface troughs on β-MoTe 2 and WTe 2. The topography of their (001) surfaces is responsible for the orientation of metal (112) planes being parallel to the substrate surface.)

  4. Formation of noble metal nanocrystals in the presence of biomolecules

    NASA Astrophysics Data System (ADS)

    Burt, Justin Lockheart

    One of the most promising, yet least studied routes for producing biocompatible nanostructures involves synthesis in the presence of biomolecules. I hypothesized that globular proteins could provide a suitable framework to regulate the formation of noble metal nanocrystals. As proof of concept, I designed two novel synthesis protocols utilizing bovine serum albumin (BSA) protein to regulate the formation of gold nanocrystals. In the first case, the standard protocol for polyol reduction was modified by replacing ethylene glycol with glycerin, replacing synthetic polymers with BSA as protecting agent, and decreasing the reaction temperature. In the second case, the Brust-Schiffrin two-phase reduction was modified by replacing alkylthiols with BSA as protecting agent, which facilitated a strictly aqueous phase synthesis. Due to superior product yield and rapid reduction at room temperature, the aqueous protocol became the foundation for subsequent studies. I extended this approach to produce well-dispersed ˜2nm silver, gold, and platinum nanocrystals. Having demonstrated the feasibility of BSA-functionalized nanocrystals, some potential uses were explored. BSA-functionalized silver nanocrystals were employed in a broader study on the interaction of silver nanocrystals with HIV. BSA-functionalized gold nanocrystals were utilized for in vivo dosage of a contrast enhancing agent to bacteria. BSA-functionalized platinum nanocrystals were studied as hydrogenation catalysts. Since many intriguing uses for protein-functionalized nanocrystals involve incorporation into biosystems, I sought to enhance biocompatibility by using ascorbic acid as reducing agent. Initial experiments revealed elongated and branched nanocrystals. Such structures were not observed in previous synthesis protocols with BSA, so I hypothesized ascorbic acid was driving their formation. To test my assertion, I reduced ionic gold in an aqueous solution of ascorbic acid, thereby discovering a new method

  5. Theory and computation of hot carriers generated by surface plasmon polaritons in noble metals

    PubMed Central

    Bernardi, Marco; Mustafa, Jamal; Neaton, Jeffrey B.; Louie, Steven G.

    2015-01-01

    Hot carriers (HC) generated by surface plasmon polaritons (SPPs) in noble metals are promising for application in optoelectronics, plasmonics and renewable energy. However, existing models fail to explain key quantitative details of SPP-to-HC conversion experiments. Here we develop a quantum mechanical framework and apply first-principles calculations to study the energy distribution and scattering processes of HCs generated by SPPs in Au and Ag. We find that the relative positions of the s and d bands of noble metals regulate the energy distribution and mean free path of the HCs, and that the electron–phonon interaction controls HC energy loss and transport. Our results prescribe optimal conditions for HC generation and extraction, and invalidate previously employed free-electron-like models. Our work combines density functional theory, GW and electron–phonon calculations to provide microscopic insight into HC generation and ultrafast dynamics in noble metals. PMID:26033445

  6. Theory and computation of hot carriers generated by surface plasmon polaritons in noble metals

    NASA Astrophysics Data System (ADS)

    Bernardi, Marco; Mustafa, Jamal; Neaton, Jeffrey B.; Louie, Steven G.

    2015-06-01

    Hot carriers (HC) generated by surface plasmon polaritons (SPPs) in noble metals are promising for application in optoelectronics, plasmonics and renewable energy. However, existing models fail to explain key quantitative details of SPP-to-HC conversion experiments. Here we develop a quantum mechanical framework and apply first-principles calculations to study the energy distribution and scattering processes of HCs generated by SPPs in Au and Ag. We find that the relative positions of the s and d bands of noble metals regulate the energy distribution and mean free path of the HCs, and that the electron-phonon interaction controls HC energy loss and transport. Our results prescribe optimal conditions for HC generation and extraction, and invalidate previously employed free-electron-like models. Our work combines density functional theory, GW and electron-phonon calculations to provide microscopic insight into HC generation and ultrafast dynamics in noble metals.

  7. Theory and computation of hot carriers generated by surface plasmon polaritons in noble metals.

    PubMed

    Bernardi, Marco; Mustafa, Jamal; Neaton, Jeffrey B; Louie, Steven G

    2015-01-01

    Hot carriers (HC) generated by surface plasmon polaritons (SPPs) in noble metals are promising for application in optoelectronics, plasmonics and renewable energy. However, existing models fail to explain key quantitative details of SPP-to-HC conversion experiments. Here we develop a quantum mechanical framework and apply first-principles calculations to study the energy distribution and scattering processes of HCs generated by SPPs in Au and Ag. We find that the relative positions of the s and d bands of noble metals regulate the energy distribution and mean free path of the HCs, and that the electron-phonon interaction controls HC energy loss and transport. Our results prescribe optimal conditions for HC generation and extraction, and invalidate previously employed free-electron-like models. Our work combines density functional theory, GW and electron-phonon calculations to provide microscopic insight into HC generation and ultrafast dynamics in noble metals. PMID:26033445

  8. Recent Advances in Shape-Controlled Synthesis of Noble Metal Nanoparticles by Radiolysis Route.

    PubMed

    Abedini, Alam; Bakar, Ahmad Ashrif A; Larki, Farhad; Menon, P Susthitha; Islam, Md Shabiul; Shaari, Sahbudin

    2016-12-01

    This paper focuses on the recent advances on radiolysis-assisted shape-controlled synthesis of noble metal nanostructures. The techniques and protocols for producing desirable shapes of noble metal nanoparticles are discussed through introducing the critical parameters which can influence the nucleation and growth mechanisms. Nucleation rate plays a vital role on the crystallinity of seeds while growth rate of different seeds' facets determines the final shape of resultant nanoparticles. Nucleation and growth rate both can be altered with factors such as absorbed dose, capping agents, and experimental environment condition to control the final shape. Remarkable physical and chemical properties of synthesized noble metal nanoparticles by controlled morphology have been systematically evaluated to fully explore their applications. PMID:27283051

  9. Functional Application of Noble Metal Nanoparticles In Situ Synthesized on Ramie Fibers

    NASA Astrophysics Data System (ADS)

    Tang, Bin; Yao, Ya; Li, Jingliang; Qin, Si; Zhu, Haijin; Kaur, Jasjeet; Chen, Wu; Sun, Lu; Wang, Xungai

    2015-09-01

    Different functions were imparted to ramie fibers through treatment with noble metal nanoparticles including silver and gold nanoparticles. The in situ synthesis of silver and gold nanoparticles was achieved by heating in the presence of ramie fibers in the corresponding solutions of precursors. The unique optical property of synthesized noble metal nanoparticles, i.e., localized surface plasmon resonance, endowed ramie fibers with bright colors. Color strength (K/S) of fibers increased with heating temperature. Silver nanoparticles were obtained in alkaline solution, while acidic condition was conducive to gold nanoparticles. The optical properties of treated ramie fibers were investigated using UV-vis absorption spectroscopy. Scanning electron microscopy (SEM) was employed to observe the morphologies of silver and gold nanoparticles in situ synthesized on fibers. The ramie fibers treated with noble metal nanoparticles showed remarkable catalytic activity for reduction of 4-nitrophenol (4-NP) by sodium borohydride. Moreover, the silver nanoparticle treatment showed significant antibacterial property on ramie fibers.

  10. Recent Advances in Shape-Controlled Synthesis of Noble Metal Nanoparticles by Radiolysis Route

    NASA Astrophysics Data System (ADS)

    Abedini, Alam; Bakar, Ahmad Ashrif A.; Larki, Farhad; Menon, P. Susthitha; Islam, Md. Shabiul; Shaari, Sahbudin

    2016-06-01

    This paper focuses on the recent advances on radiolysis-assisted shape-controlled synthesis of noble metal nanostructures. The techniques and protocols for producing desirable shapes of noble metal nanoparticles are discussed through introducing the critical parameters which can influence the nucleation and growth mechanisms. Nucleation rate plays a vital role on the crystallinity of seeds while growth rate of different seeds' facets determines the final shape of resultant nanoparticles. Nucleation and growth rate both can be altered with factors such as absorbed dose, capping agents, and experimental environment condition to control the final shape. Remarkable physical and chemical properties of synthesized noble metal nanoparticles by controlled morphology have been systematically evaluated to fully explore their applications.

  11. Nano-structured noble metal catalysts based on hexametallate architecture for the reforming of hydrocarbon fuels

    DOEpatents

    Gardner, Todd H.

    2015-09-15

    Nano-structured noble metal catalysts based on hexametallate lattices, of a spinel block type, and which are resistant to carbon deposition and metal sulfide formation are provided. The catalysts are designed for the reforming of hydrocarbon fuels to synthesis gas. The hexametallate lattices are doped with noble metals (Au, Pt, Rh, Ru) which are atomically dispersed as isolated sites throughout the lattice and take the place of hexametallate metal ions such as Cr, Ga, In, and/or Nb. Mirror cations in the crystal lattice are selected from alkali metals, alkaline earth metals, and the lanthanide metals, so as to reduce the acidity of the catalyst crystal lattice and enhance the desorption of carbon deposit forming moieties such as aromatics. The catalysts can be used at temperatures as high as 1000.degree. C. and pressures up to 30 atmospheres. A method for producing these catalysts and applications of their use also is provided.

  12. Vitrification of noble metals containing NCAW simulant with an engineering scale melter (ESM): Campaign report

    SciTech Connect

    Grunewald, W.; Roth, G.; Tobie, W.; Weisenburger, S.; Weiss, K.; Elliott, M.; Eyler, L.L.

    1996-03-01

    ESM has been designed as a 10th-scale model of the DWPF-type melter, currently the reference melter for nitrification of Hanford double shell tankwaste. ESM and related equipment have been integrated to the existing mockup vitrification plant VA-WAK at KfK. On June 2-July 10, 1992, a shakedown test using 2.61 m{sup 3} of NCAW (neutralized current acid waste) simulant without noble metals was performed. On July 11-Aug. 30, 1992, 14.23 m{sup 3} of the same simulant with nominal concentrations of Ru, Rh, and Pd were vitrified. Objective was to investigate the behavior of such a melter with respect to discharge of noble metals with routine glass pouring via glass overflow. Results indicate an accumulation of noble metals in the bottom area of the flat-bottomed ESM. About 65 wt% of the noble metals fed to the melter could be drained out, whereas 35 wt% accumulated in the melter, based on analysis of glass samples from glass pouring stream in to the canisters. After the melter was drained at the end of the campaign through a bottom drain valve, glass samples were taken from the residual bottom layer. The samples had significantly increased noble metals content (factor of 20-45 to target loading). They showed also a significant decrease of the specific electric resistance compared to bulk glass (factor of 10). A decrease of 10- 15% of the resistance between he power electrodes could be seen at the run end, but the total amount of noble metals accumulated was not yet sufficient enough to disturb the Joule heating of the glass tank severely.

  13. Solid polymer electrolyte composite membrane comprising a porous support and a solid polymer electrolyte including a dispersed reduced noble metal or noble metal oxide

    SciTech Connect

    Liu, Han; Mittelsteadt, Cortney K; Norman, Timothy J; Griffith, Arthur E; LaConti, Anthony B

    2015-02-24

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a thin, rigid, dimensionally-stable, non-electrically-conducting support, the support having a plurality of cylindrical, straight-through pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores are unevenly distributed, with some or no pores located along the periphery and more pores located centrally. The pores are completely filled with a solid polymer electrolyte, the solid polymer electrolyte including a dispersed reduced noble metal or noble metal oxide. The solid polymer electrolyte may also be deposited over the top and/or bottom surfaces of the support.

  14. Noble metal-comparable SERS enhancement from semiconducting metal oxides by making oxygen vacancies

    PubMed Central

    Cong, Shan; Yuan, Yinyin; Chen, Zhigang; Hou, Junyu; Yang, Mei; Su, Yanli; Zhang, Yongyi; Li, Liang; Li, Qingwen; Geng, Fengxia; Zhao, Zhigang

    2015-01-01

    Surface-enhanced Raman spectroscopy (SERS) represents a very powerful tool for the identification of molecular species, but unfortunately it has been essentially restricted to noble metal supports (Au, Ag and Cu). While the application of semiconductor materials as SERS substrate would enormously widen the range of uses for this technique, the detection sensitivity has been much inferior and the achievable SERS enhancement was rather limited, thereby greatly limiting the practical applications. Here we report the employment of non-stoichiometric tungsten oxide nanostructure, sea urchin-like W18O49 nanowire, as the substrate material, to magnify the substrate–analyte molecule interaction, leading to significant magnifications in Raman spectroscopic signature. The enrichment of surface oxygen vacancy could bring additional enhancements. The detection limit concentration was as low as 10−7 M and the maximum enhancement factor was 3.4 × 105, in the rank of the highest sensitivity, to our best knowledge, among semiconducting materials, even comparable to noble metals without ‘hot spots'. PMID:26183467

  15. Noble metal-comparable SERS enhancement from semiconducting metal oxides by making oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Cong, Shan; Yuan, Yinyin; Chen, Zhigang; Hou, Junyu; Yang, Mei; Su, Yanli; Zhang, Yongyi; Li, Liang; Li, Qingwen; Geng, Fengxia; Zhao, Zhigang

    2015-07-01

    Surface-enhanced Raman spectroscopy (SERS) represents a very powerful tool for the identification of molecular species, but unfortunately it has been essentially restricted to noble metal supports (Au, Ag and Cu). While the application of semiconductor materials as SERS substrate would enormously widen the range of uses for this technique, the detection sensitivity has been much inferior and the achievable SERS enhancement was rather limited, thereby greatly limiting the practical applications. Here we report the employment of non-stoichiometric tungsten oxide nanostructure, sea urchin-like W18O49 nanowire, as the substrate material, to magnify the substrate-analyte molecule interaction, leading to significant magnifications in Raman spectroscopic signature. The enrichment of surface oxygen vacancy could bring additional enhancements. The detection limit concentration was as low as 10-7 M and the maximum enhancement factor was 3.4 × 105, in the rank of the highest sensitivity, to our best knowledge, among semiconducting materials, even comparable to noble metals without `hot spots'.

  16. The Behavior and Effects of the Noble Metals in the DWPF Melter System

    SciTech Connect

    Smith, M.E.; Bickford, D.F.

    1997-11-30

    Governments worldwide have committed to stabilization of high-level nuclear waste (HLW) by vitrification to a durable glass form for permanent disposal. All of these nuclear wastes contain the fission-product noble metals: ruthenium, rhodium, and palladium. SRS wastes also contain natural silver from iodine scrubbers. Closely associated with the noble metals are the fission products selenium and tellurium which are chemical analogs of sulfur and which combine with noble metals to influence their behavior and properties. Experience has shown that these melt insoluble metals and their compounds tend to settle to the floor of Joule-heated ceramic melters. In fact, almost all of the major research and production facilities have experienced some operational problem which can be associated with the presence of dense accumulations of these relatively conductive metals and/or their compounds. In most cases, these deposits have led to a loss of production capability, in some cases, to the point that melter operation could not continue. HLW nuclear waste vitrification facilities in the United States are the Department of Energy`s Defense Waste Processing Facility (DWPF) at the Savannah River Site, the planned Hanford Waste Vitrification Plant (HWVP) at the Hanford Site and the operating West Valley Demonstration Project (WVDP) at West Valley, NY. The Integrated DWPF Melter System (IDMS) is a vitrification test facility at the Savannah River Technology Center (SRTC). It was designed and constructed to provide an engineering-scale representation of the DWPF melter and its associated feed preparation and off-gas treatment systems. An extensive noble metals testing program was begun in 1990. The objectives of this task were to explore the effects of the noble metals on the DWPF melter feed preparation and waste vitrification processes. This report focuses on the vitrification portion of the test program.

  17. Ligand-Assisted Co-Assembly Approach toward Mesoporous Hybrid Catalysts of Transition-Metal Oxides and Noble Metals: Photochemical Water Splitting.

    PubMed

    Liu, Ben; Kuo, Chung-Hao; Chen, Jiejie; Luo, Zhu; Thanneeru, Srinivas; Li, Weikun; Song, Wenqiao; Biswas, Sourav; Suib, Steven L; He, Jie

    2015-07-27

    A bottom-up synthetic approach was developed for the preparation of mesoporous transition-metal-oxide/noble-metal hybrid catalysts through ligand-assisted co-assembly of amphiphilic block-copolymer micelles and polymer-tethered noble-metal nanoparticles (NPs). The synthetic approach offers a general and straightforward method to precisely tune the sizes and loadings of noble-metal NPs in metal oxides. This system thus provides a solid platform to clearly understand the role of noble-metal NPs in photochemical water splitting. The presence of trace amounts of metal NPs (≈0.1 wt %) can enhance the photocatalytic activity for water splitting up to a factor of four. The findings can conceivably be applied to other semiconductors/noble-metal catalysts, which may stand out as a new methodology to build highly efficient solar energy conversion systems. PMID:26073465

  18. Electrocatalytic oxidation of small organic molecules in acid medium: enhancement of activity of noble metal nanoparticles and their alloys by supporting or modifying them with metal oxides

    PubMed Central

    Kulesza, Pawel J.; Pieta, Izabela S.; Rutkowska, Iwona A.; Wadas, Anna; Marks, Diana; Klak, Karolina; Stobinski, Leszek; Cox, James A.

    2013-01-01

    Different approaches to enhancement of electrocatalytic activity of noble metal nanoparticles during oxidation of small organic molecules (namely potential fuels for low-temperature fuel cells such as methanol, ethanol and formic acid) are described. A physical approach to the increase of activity of catalytic nanoparticles (e.g. platinum or palladium) involves nanostructuring to obtain highly dispersed systems of high surface area. Recently, the feasibility of enhancing activity of noble metal systems through the formation of bimetallic (e.g. PtRu, PtSn, and PdAu) or even more complex (e.g. PtRuW, PtRuSn) alloys has been demonstrated. In addition to possible changes in the electronic properties of alloys, specific interactions between metals as well as chemical reactivity of the added components have been postulated. We address and emphasize here the possibility of utilization of noble metal and alloyed nanoparticles supported on robust but reactive high surface area metal oxides (e.g. WO3, MoO3, TiO2, ZrO2, V2O5, and CeO2) in oxidative electrocatalysis. This paper concerns the way in which certain inorganic oxides and oxo species can act effectively as supports for noble metal nanoparticles or their alloys during electrocatalytic oxidation of hydrogen and representative organic fuels. Among important issues are possible changes in the morphology and dispersion, as well as specific interactions leading to the improved chemisorptive and catalytic properties in addition to the feasibility of long time operation of the discussed systems. PMID:24443590

  19. Letter Report on the Issue of Noble Metals in the DWPF Melter

    SciTech Connect

    Hutson, N.D.

    2001-09-05

    This report presents some historical data from the radioactive operation of the DWPF melter. Some of the data seem to indication that the melter is displaying symptoms that may be linked to accumulation of noble metal or other conductive material on the melter floor. The complex and often competing effects of waste composition, glass pool temperatures, and operating conditions must also be considered.

  20. Carbonaceous adsorbents from caking coals for the extraction of noble metals

    SciTech Connect

    Kostomarova, M.A.; Surinova, S.I.

    1983-01-01

    The authors examine the sorption and mechanical properties of spherical adsorbents obtained from Kuzbass caking coal using an IGI method. An investigation has also been made of the sorption kinetics of gold and silver. It was found that spherical adsorbent pellets of this kind are capable of extracting noble metals from ore pulps. (1 ref.)

  1. Noble Metal Decoration and Alignment of Carbon Nanotubes in Carboxymethyl Cellulose

    EPA Science Inventory

    A facile microwave (MW) method is described that accomplishes alignment and decoration of noble metals on carbon nanotubes wrapped with carboxymethyl cellulose (CMC). Carbon nanotubes (CNTs) such as single-wall (SWNT), multi-wall (MWNT) and Buckminsterfullerene (C-60) were well ...

  2. Acid Strength and Bifunctional Catalytic Behavior of Alloys Comprised of Noble Metals and Oxophilic Metal Promoters

    SciTech Connect

    Hibbitts, David D.; Tan, Qiaohua; Neurock, Matthew

    2014-06-01

    The promotion of metal catalysts with partially oxidized oxophilic MOx species, such as ReOx-promoted Rh, has been demonstrated to produce Brønsted acid sites that can promote hydrogenolysis of oxygenate intermediates such as those found in biomass-derived species. A wide variety of alloy compositions and structures are examined in this work to investigate strongly acidic promoters by using DFT-calculated deprotonation energies (DPE) as a measure of acid strength. Sites with the highest acid strength had DPE less than 1100 kJ mol-1, similar to DPE values of heteropolyacids or acid-containing zeolites, and were found on alloys composed of an oxophilic metal (such as Re or W) with a noble metal (such as Rh or Pt). NH3 adsorbs more strongly to sites with increasing acid strength and the activation barriers for acid-catalyzed ring opening of a furan ring decrease with increasing acid strength, which was also shown to be stronger for OH acid sites bound to multiple oxophilic metal atoms in a three-fold configuration rather than OH sites adsorbed in an atop configuration on one oxophilic metal, indicating that small MOx clusters may yield sites with the highest acid strength.

  3. Techniques for the quantitative analysis of fission-product noble metals

    SciTech Connect

    Lautensleger, A.W.; Hara, F.T.

    1982-08-01

    Analytical procedures for the determination of ruthenium, rhodium, and palladium in precursor waste, solvent metal, and final glass waste forms have been developed. Two procedures for the analysis of noble metals in the calcine and glass waste forms are described in this report. The first is a fast and simple technique that combines inductively coupled argon plasma atomic emission spectrometry (ICP) and x-ray fluorescence techniques and can only be used on nonradioactive materials. The second procedure is based on a noble metal separation step, followed by an analysis using ICP. This second method is more complicated than the first, but it will work on radioactive materials. Also described is a procedure for the ICP analysis of noble metals in the solvent metal matrix. The only solvent metal addressed in this procedure is lead, but with minor changes the procedure could be applied to any of the solvent metals being considered in the Pacific Northwest Laboratory (PNL) extraction process. A brief explanation of atomic spectroscopy and the ICP analytical process, as well as of certain aspects of ICP performance (interelement spectral line interferences and certain matrix effects) is given.

  4. Noble metal nanodisks epitaxially formed on ZnO nanorods and their effect on photoluminescence

    NASA Astrophysics Data System (ADS)

    Chu, Sheng; Ren, Jingjian; Yan, Dong; Huang, Jian; Liu, Jianlin

    2012-07-01

    Triangular and hexagonal shaped noble metal (Au, Ag, Pt, Pd) nanodisks were synthesized on the top facets of ZnO nanorods via simple deposition-annealing method. Other metals (Ni, Cu, Cr, Pb, Al) only formed irregular shaped nanostructures on ZnO nanorods. The morphology, elemental composition, as well as growth mechanism of the metal nanodisks/ZnO nanorod composite materials were studied. The localized surface plasmon resonant effects from different metal nanodisks on the photoluminescence of ZnO nanorods were investigated. It was demonstrated that the carriers transfer between the metal nanodisks and ZnO can efficiently manipulate the photoluminescence intensities from the nanorods.

  5. Electrodeposited noble metal particles in polyelectrolyte multilayer matrix as electrocatalyst for oxygen reduction studied using SECM.

    PubMed

    Shen, Yan; Träuble, Markus; Wittstock, Gunther

    2008-07-01

    Taking the advantage of the stability and penetrability of polyelectrolyte films formed by layer-by-layer (LbL) deposition, noble metal particles of Pd and Pt were fabricated in a preformed polyeletrolyte multilayer film by galvanic deposition. The metal deposition occurred as metal particles and they were tested for their properties as electrocatalyst for oxygen reduction. Atomic force microscopy (AFM) was used to characterize the morphology of the particle films. The noble metal particles were investigated by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM) with respect to oxygen reduction. The results show that the electrocatalytic properties of the Pd particle film can be adjusted by the electrodeposition time. The hydrogen peroxide formed as an intermediate during electroreduction of dioxygen was conveniently measured in the SECM using the substrate-generation/tip-collection mode. The relevance of the main reduction pathways could be extracted from fitting the current transients to an analytical model. PMID:18563224

  6. Preliminary investigation of a technique to separate fission noble metals from fission product mixtures

    SciTech Connect

    Mellinger, G.B.; Jensen, G.A.

    1982-08-01

    A variation of the gold-ore fire assay technique was examined as a method for recovering Pd, Rh and Ru from fission products. The mixture of fission product oxides is combined with glass-forming chemicals, a metal oxide such as PbO (scavenging agent), and a reducing agent such as charcoal. When this mixture is melted, a metal button is formed which extracts the noble metals. The remainder cools to form a glass for nuclear waste storage. Recovery depended only on reduction of the scavenger oxide to metal. When such reduction was achieved, no difference in noble metal recovery efficiency was found among the scavengers studied (PbO, SnO, CuO, Bi/sub 2/O/sub 3/, Sb/sub 2/O/sub 3/). Not all reducing agents studied, however, were able to reduce all scavenger oxides to metal. Only graphite would reduce SnO and CuO and allow noble metal recovery. The scavenger oxides Sb/sub 2/O/sub 3/, Bi/sub 2/O/sub 3/, and PbO, however, were reduced by all of the reducing agents tested. Similar noble metal recovery was found with each. Lead oxide was found to be the most promising of the potential scavengers. It was reduced by all of the reducing agents tested, and its higher density may facilitate the separation. Use of lead oxide also appeared to have no deterimental effect on the glass quality. Charcoal was identified as the preferred reducing agent. As long as a separable metal phase was formed in the melt, noble metal recovery was not dependent on the amount of reducing agent and scavenger oxide. High glass viscosities inhibited separation of the molten scavenger, while low viscosities allowed volatile loss of RuO/sub 4/. A viscosity of approx. 20 poise at the processing temperature offered a good compromise between scavenger separation and Ru recovery. Glasses in which PbO was used as the scavenging agent were homogeneous in appearance. Resistance to leaching was close to that of certain waste glasses reported in the literature. 12 figures. 7 tables.

  7. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    NASA Astrophysics Data System (ADS)

    Liu, X. H.; Luo, H.; Qu, T. L.; Yang, K. Y.; Ding, Z. C.

    2015-10-01

    We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  8. Highly selective electrodeposition of sub-10 nm crystalline noble metallic nanorods inside vertically aligned multiwall carbon nanotubes.

    PubMed

    Wang, Xuyang; Wang, Ranran; Wu, Qiang; Zhang, Xiaohua; Yang, Zhaohui; Guo, Jun; Chen, Muzi; Tang, Minghua; Cheng, Yajun; Chu, Haibin

    2016-07-01

    In this paper crystalline noble metallic nanorods including Au and Ag with sub-10 nm diameter, are encapsulated within prealigned and open-ended multiwall carbon nanotubes (MWCNTs) through an electrodeposition method. As the external surface of CNTs has been insulated by the epoxy the CNT channel becomes the only path for the mass transport as well as the nanoreactor for the metal deposition. Highly crystallized Au and Ag2O nanorods parallel to the radial direction of CNTs are confirmed by high-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray powder diffraction spectroscopy. The Ag2O nanorods are formed by air oxidation on the Ag metals and show a single crystalline structure with (111) planes. The Au nanorods exhibit a complex crystalline structure including twin-crystal and lattice dislocation with (111) and (200) planes. These crystalline noble metallic nanostructures may have important applications for nanocatalysts for fuel cells as well as nanoelectronic and nanophotonic devices. This method is deemed to benefit the precise deposition of other crystalline nanostructures inside CNTs with a small diameter. PMID:27240546

  9. Highly selective electrodeposition of sub-10 nm crystalline noble metallic nanorods inside vertically aligned multiwall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Xuyang; Wang, Ranran; Wu, Qiang; Zhang, Xiaohua; Yang, Zhaohui; Guo, Jun; Chen, Muzi; Tang, Minghua; Cheng, Yajun; Chu, Haibin

    2016-07-01

    In this paper crystalline noble metallic nanorods including Au and Ag with sub-10 nm diameter, are encapsulated within prealigned and open-ended multiwall carbon nanotubes (MWCNTs) through an electrodeposition method. As the external surface of CNTs has been insulated by the epoxy the CNT channel becomes the only path for the mass transport as well as the nanoreactor for the metal deposition. Highly crystallized Au and Ag2O nanorods parallel to the radial direction of CNTs are confirmed by high-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray powder diffraction spectroscopy. The Ag2O nanorods are formed by air oxidation on the Ag metals and show a single crystalline structure with (111) planes. The Au nanorods exhibit a complex crystalline structure including twin-crystal and lattice dislocation with (111) and (200) planes. These crystalline noble metallic nanostructures may have important applications for nanocatalysts for fuel cells as well as nanoelectronic and nanophotonic devices. This method is deemed to benefit the precise deposition of other crystalline nanostructures inside CNTs with a small diameter.

  10. Cálculo del esfuerzo ideal de metales nobles mediante primeros principios en la dirección <100>

    NASA Astrophysics Data System (ADS)

    Bautista-Hernández, A.; López-Fuentes, M.; Pacheco-Espejel, V.; Rivas-Silva, J. F.

    2005-04-01

    We present calculations of the ideal strength on the < 100 > direction for noble metals (Cu, Ag and Au), by means of first principles calculations. First, we obtain the structural parameters (cell parameters, bulk modulus) for each studied metal. We deform on the < 100 > direction calculating the total energy and the stress tensor through the Hellman-Feynman theorem, by the relaxation of the unit cell in the perpendicular directions to the deformation one. The calculated cell constants differ 1.3 % from experimental data. The maximum ideal strength are 29.6, 17 and 19 GPa for Cu, Ag and Au respectively. Meanwhile, the calculated elastic modulus are 106 (Cu), 71 (Ag), and 45 GPa (Au) and are in agreement with the experimental values for polycrystalline samples. The values of maximum strength are explained by the optimum volume values due to the atomic radius size for each element.

  11. Process for making a noble metal on tin oxide catalyst

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T. (Inventor); Davis, Patricia (Inventor); Miller, Irvin M. (Inventor)

    1989-01-01

    A quantity of reagent grade tin metal or compound, chloride-free, and high-surface-area silica spheres are placed in deionized water, followed by deaerating the mixture by boiling and adding an oxidizing agent, such as nitric acid. The nitric acid oxidizes the tin to metastannic acid which coats the spheres because the acid is absorbed on the substrate. The metastannic acid becomes tin oxide upon drying and calcining. The tin-oxide coated silica spheres are then placed in water and boiled. A chloride-free precious metal compound in aqueous solution is then added to the mixture containing the spheres, and the precious metal compound is reduced to a precious metal by use of a suitable reducing agent such as formic acid. Very beneficial results were obtained using the precious metal compound tetraammine platinum(II) hydroxide.

  12. A review of dry (CO2) reforming of methane over noble metal catalysts.

    PubMed

    Pakhare, Devendra; Spivey, James

    2014-11-21

    Dry (CO2) reforming of methane (DRM) is a well-studied reaction that is of both scientific and industrial importance. This reaction produces syngas that can be used to produce a wide range of products, such as higher alkanes and oxygenates by means of Fischer-Tropsch synthesis. DRM is inevitably accompanied by deactivation due to carbon deposition. DRM is also a highly endothermic reaction and requires operating temperatures of 800-1000 °C to attain high equilibrium conversion of CH4 and CO2 to H2 and CO and to minimize the thermodynamic driving force for carbon deposition. The most widely used catalysts for DRM are based on Ni. However, many of these catalysts undergo severe deactivation due to carbon deposition. Noble metals have also been studied and are typically found to be much more resistant to carbon deposition than Ni catalysts, but are generally uneconomical. Noble metals can also be used to promote the Ni catalysts in order to increase their resistance to deactivation. In order to design catalysts that minimize deactivation, it is necessary to understand the elementary steps involved in the activation and conversion of CH4 and CO2. This review will cover DRM literature for catalysts based on Rh, Ru, Pt, and Pd metals. This includes the effect of these noble metals on the kinetics, mechanism and deactivation of these catalysts. PMID:24504089

  13. Orbital control of Rashba spin orbit coupling in noble metal surfaces

    NASA Astrophysics Data System (ADS)

    Gong, Shi-Jing; Cai, Jia; Yao, Qun-Fang; Tong, Wen-Yi; Wan, Xiangang; Duan, Chun-Gang; Chu, J. H.

    2016-03-01

    Rashba spin orbit coupling (SOC) in noble metal surfaces is of great importance for the application of metal films in spintronic devices. By combining the density-functional theory calculations with our recently developed orbital selective external potential method, we investigate the Rashba SOC in the Shockley surface states of Au(111) and Ag(111). We find that the large Rashba SOC in the sp-character surface states of Au(111) is mainly contributed by the minor d-orbitals in the surface states. While for the sd-character surface states, although they are dominated by the d-orbitals, Rashba splitting is found to be rather small. Band structure analysis reveals that this is mainly because the sd-character surface states are well below the Fermi level and can be less influenced by the asymmetric surface potential. We demonstrate that the Rashba SOC in noble metal surfaces can be effectively manipulated by shifting the d-orbitals in the surface states, which can be physically implemented through surface decoration. Our investigation provides a deep understanding on Rashba SOC in noble metal surfaces and could be helpful to their applications in spintronic devices.

  14. Electrochemical synthesis of elongated noble metal nanoparticles, such as nanowires and nanorods, on high-surface area carbon supports

    SciTech Connect

    Adzic, Radoslav; Blyznakov, Stoyan; Vukmirovic, Miomir

    2015-08-04

    Elongated noble-metal nanoparticles and methods for their manufacture are disclosed. The method involves the formation of a plurality of elongated noble-metal nanoparticles by electrochemical deposition of the noble metal on a high surface area carbon support, such as carbon nanoparticles. Prior to electrochemical deposition, the carbon support may be functionalized by oxidation, thus making the manufacturing process simple and cost-effective. The generated elongated nanoparticles are covalently bound to the carbon support and can be used directly in electrocatalysis. The process provides elongated noble-metal nanoparticles with high catalytic activities and improved durability in combination with high catalyst utilization since the nanoparticles are deposited and covalently bound to the carbon support in their final position and will not change in forming an electrode assembly.

  15. Two types of noble metal mineralization in the Kaalamo massif (Karelia)

    NASA Astrophysics Data System (ADS)

    Ivashchenko, V. I.; Ruchyev, A. M.; Golubev, A. I.

    2016-05-01

    Noble metal mineralization of the syngenetic (Southern Kaalamo) and epigenetic (Surisuo) types are defined in the Kaalamo massif. The ƩPt, Pd, Au content is as high as 0.9-1.1 g/t. Syngenetic mineralization started at the late magmatic stage (at around 800°C) gradually evolving to cease during the hydrothermal-metasomatic stage (<271°C). Epigenetic mineralization was formed at temperatures ranging from 500 to <230°C in zones of intense shear deformations and low-temperature metasomatosis during the collisional stage of the Svecofennian tectono-magmatic cycle (approximately 1.85 Ga ago). Taking into consideration the geological position of the Kaalamo massif in the Raakhe-Ladoga metallogenic zone with widely developed intense shear dislocations, the epigenetic mineralization type seems to be more promising with respect to noble metals.

  16. Ligand-Free Noble Metal Nanocluster Catalysts on Carbon Supports via "Soft" Nitriding.

    PubMed

    Liu, Ben; Yao, Huiqin; Song, Wenqiao; Jin, Lei; Mosa, Islam M; Rusling, James F; Suib, Steven L; He, Jie

    2016-04-13

    We report a robust, universal "soft" nitriding method to grow in situ ligand-free ultrasmall noble metal nanocatalysts (UNMN; e.g., Au, Pd, and Pt) onto carbon. Using low-temperature urea pretreatment at 300 °C, soft nitriding enriches nitrogen-containing species on the surface of carbon supports and enhances the affinity of noble metal precursors onto these supports. We demonstrated sub-2-nm, ligand-free UNMNs grown in situ on seven different types of nitrided carbons with no organic ligands via chemical reduction or thermolysis. Ligand-free UNMNs supported on carbon showed superior electrocatalytic activity for methanol oxidation compared to counterparts with surface capping agents or larger nanocrystals on the same carbon supports. Our method is expected to provide guidelines for the preparation of ligand-free UNMNs on a variety of supports and, additionally, to broaden their applications in energy conversion and electrochemical catalysis. PMID:27014928

  17. Reactive Gas Environment Induced Structural Modification of Noble-Transition Metal Alloy Nanoparticles

    NASA Astrophysics Data System (ADS)

    Petkov, V.; Yang, L.; Yin, J.; Loukrakpam, R.; Shan, S.; Wanjala, B.; Luo, J.; Chapman, K. W.; Zhong, C. J.

    2012-09-01

    Noble-transition metal (noble=Pt,Au; transition=Co,Ni,Cu) alloy particles with sizes of about 5 nm have been studied by in situ high-energy x-ray diffraction while subjected to oxidizing (O2) and reducing (H2) gas atmospheres at elevated temperatures. The different gas atmospheres do not affect substantially the random alloy, face-centered-cubic structure type of the particles but do affect the way the metal atoms pack together. In an O2 atmosphere, atoms get extra separated from each other, whereas, in an H2 atmosphere, they come closer together. The effect is substantial, amounting to 0.1 Å difference in the first neighbor atomic distances, and concurs with a dramatic change of the particle catalytic properties. It is argued that such reactive gas induced “expansion shrinking” is a common phenomenon that may be employed for the engineering of “smart” nanoparticles responding advantageously to envisaged gas environments.

  18. Catalytic activities of noble metal atoms on WO3 (001): nitric oxide adsorption.

    PubMed

    Ren, Xiaoyan; Zhang, Shuai; Li, Chong; Li, Shunfang; Jia, Yu; Cho, Jun-Hyung

    2015-01-01

    Using first-principles density functional theory calculations within the generalized gradient approximation, we investigate the adsorption of NO molecule on a clean WO3(001) surface as well as on the noble metal atom (Cu, Ag, and Au)-deposited WO3(001) surfaces. We find that on a clean WO3 (001) surface, the NO molecule binds to the W atom with an adsorption energy (E ads) of -0.48 eV. On the Cu- and Ag-deposited WO3(001) surface where such noble metal atoms prefer to adsorb on the hollow site, the NO molecule also binds to the W atom with E ads = -1.69 and -1.41 eV, respectively. This relatively stronger bonding of NO to the W atom is found to be associated with the larger charge transfer of 0.43 e (Cu) and 0.33 e (Ag) from the surface to adsorbed NO. However, unlike the cases of Cu-WO3(001) and Ag-WO3(001), Au atoms prefer to adsorb on the top of W atom. On such an Au-WO3(001) complex, the NO molecule is found to form a bond to the Au atom with E ads = -1.32 eV. Because of a large electronegativity of Au atom, the adsorbed NO molecule captures the less electrons (0.04 e) from the surface compared to the Cu and Ag catalysts. Our findings not only provide useful information about the NO adsorption on a clean WO3(001) surface as well as on the noble metal atoms deposited WO3(001) surfaces but also shed light on a higher sensitive WO3 sensor for NO detection employing noble metal catalysts. PMID:25852357

  19. Decoration of diatom biosilica with noble metal and semiconductor nanoparticles (<10 nm): assembly, characterization, and applications.

    PubMed

    Jantschke, Anne; Herrmann, Anne-Kristin; Lesnyak, Vladimir; Eychmüller, Alexander; Brunner, Eike

    2012-01-01

    Diatom-templated noble metal (Ag, Pt, Au) and semiconductor (CdTe) nanoparticle arrays were synthesized by the attachment of prefabricated nanoparticles of defined size. Two different attachment techniques-layer-by-layer deposition and covalent linking-could successfully be applied. The synthesized arrays were shown to be useful for surface-enhanced Raman spectroscopy (SERS) of components, for catalysis, and for improved image quality in scanning electron microscopy (SEM). PMID:22102484

  20. Photocatalytic CO2 conversion over alkali modified TiO2 without loading noble metal cocatalyst.

    PubMed

    Meng, Xianguang; Ouyang, Shuxin; Kako, Tetsuya; Li, Peng; Yu, Qing; Wang, Tao; Ye, Jinhua

    2014-10-01

    Surface modification of TiO2 with NaOH promoted the chemisorption, activation and photocatalytic CO2 reduction. An optimized loading amount of NaOH kept a good balance between CO2 chemisorption quantity and BET surface area of TiO2. This noble metal free method provides a simple pathway for effective multiple H(+)/e(-) CO2 photoreduction. PMID:25130434

  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. Measuring and Predicting Fission Product Noble Metals in SRS HLW Sludges

    SciTech Connect

    Bibler, N

    2005-04-05

    The noble metals Ru, Rh, Pd, and Ag were produced in the Savannah River Site (SRS) reactors as products of the fission of U-235. Consequently they are in the High Level Waste (HLW) sludges that are currently being immobilized into a borosilicate glass in the Defense Waste Processing Facility (DWPF). The noble metals are a concern in the DWPF because they catalyze the decomposition of formic acid used in the process to produce the flammable gas hydrogen. As the concentration of these noble metals in the sludge increases, more hydrogen will be produced when this sludge is processed. In the SRS Tank Farm it takes approximately two years to prepare a sludge batch for processing in the DWPF. This length of time is necessary to mix the appropriate sludges, blend them to form a sludge batch and then wash it to enable processing in the DWPF. This means that the exact composition of a sludge batch is not known for {approx}two years. During this time, studies with simulated nonradioactive sludges must be performed to determine the desired DWPF processing parameters for the new sludge batch. Consequently, prediction of the noble metal concentrations is desirable to prepare appropriate simulated sludges for studies of the DWPF process for that sludge batch. These studies give a measure of the amount of hydrogen that will be produced when that sludge batch is processed. This report describes in detail the measurement of these noble metal concentrations in sludges and a way to predict their concentrations from an estimate of the lanthanum concentration in the sludge. Results for two sludges are presented in this report. These are Sludge Batch 3 (SB3) currently being processed by the DWPF and a sample of unwashed sludge from Tank 11 that will be part of Sludge Batch 4. The concentrations of the noble metals in HLW sludges are measured by using mass spectroscopy to determine concentrations of the isotopes that comprise each noble metal. For example, the noble metal Ru is comprised

  3. The role of van der Waals interactions in the adsorption of noble gases on metal surfaces

    SciTech Connect

    Chen, De-Li; Al-Saidi, W A; Johnson, J Karl

    2012-10-03

    Adsorption of noble gases on metal surfaces is determined by weak interactions. We applied two versions of the nonlocal van der Waals density functional (vdW-DF) to compute adsorption energies of Ar, Kr, and Xe on Pt(111), Pd(111), Cu(111), and Cu(110) metal surfaces. We have compared our results with data obtained using other density functional approaches, including the semiempirical vdW corrected DFT-D2. The vdW-DF results show considerable improvements in the description of adsorption energies and equilibrium distances over other DFTbased methods, giving good agreement with experiments. We have also calculated perpendicular vibrational energies for noble gases on the metal surfaces using vdWDF data and found excellent agreement with available experimental results. Our vdW-DF calculations show that adsorption of noble gases on low-coordination sites is energetically favored over high-coordination sites, but only by a few meV. Analysis of the 2-dimensional potential energy surface shows that the high-coordination sites are local maxima on the 2-dimensional potential energy surface and therefore unlikely to be observed in experiments, which provides an explanation of the experimental observations. The DFT-D2 approach with the standard parameterization was found to overestimate the dispersion interactions, and to give the wrong adsorption site preference for four of the nine systems we studied.

  4. Risk Reduction Via Greener Synthesis of Noble Metal Nanostructures and Nanocomposites

    NASA Astrophysics Data System (ADS)

    Nadagouda, M. N.; Varma, R. S.

    Aqueous preparation of nanoparticles using vitamins B2 and C which can function both as reducing and capping agents are described. Bulk and shape-controlled synthesis of noble nanostructures via microwave (MW)-assisted spontaneous reduction of noble metal salts using α-D-glucose, sucrose, and maltose has been achieved. The MW method also accomplishes the cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic systems such as Pt, Cu, and In; bimetallic systems, namely Pt-In, Ag-Pt, Pt-Fe, Cu-Pd, Pt-Pd and Pd-Fe; and single-walled nanotubes (SWNT), multi-walled nanotubes (MWNT), and Buckmin-sterfullerene (C-60). The strategy is extended to the formation of biodegradable carboxymethyl cellulose (CMC) composite films with noble nanometals; such metal decoration and alignment of carbon nanotubes in CMC is possible using a MW approach. The MW approach also enables the shape-controlled bulk synthesis of Ag and Fe nanorods in poly (ethylene glycol) (PEG).

  5. Role of van der Waals forces in the diffraction of noble gases from metal surfaces

    NASA Astrophysics Data System (ADS)

    del Cueto, M.; Muzas, A. S.; Füchsel, G.; Gatti, F.; Martín, F.; Díaz, C.

    2016-02-01

    The role of van der Waals (vdW) forces in the description of scattering processes of noble gases from metal surfaces is currently under debate. Although features of the potential energy surface such as anticorrugation or adsorption energies are sometimes found to be well described by standard density functional theory (DFT), the performance of DFT to describe diffraction spectra may rely on the accuracy of the vdW functionals used. To analyze the precise role of these vdW forces in noble gas diffraction by metal surfaces, we have thoroughly studied the case of Ne/Ru(0001), for which accurate experimental results are available. We have carried out classical and quantum dynamics calculations by using DFT-based potentials that account for the effect of vdW interactions at different levels of accuracy. From the comparison of our results with experimental data, we conclude that the inclusion of vdW effects is crucial to properly describe diffraction of noble gases from metal surfaces. We show that among the vdW-DFT functionals available in the literature, not all of them can be used to accurately describe this process.

  6. Visible light active TiO 2 films prepared by electron beam deposition of noble metals

    NASA Astrophysics Data System (ADS)

    Hou, Xing-Gang; Ma, Jun; Liu, An-Dong; Li, De-Jun; Huang, Mei-Dong; Deng, Xiang-Yun

    2010-03-01

    TiO 2 films prepared by sol-gel method were modified by electron beam deposition of noble metals (Pt, Pd, and Ag). Effects of noble metals on the chemical and surface characteristics of the films were studied using XPS, TEM and UV-Vis spectroscopy techniques. Photocatalytic activity of modified TiO 2 films was evaluated by studying the degradation of methyl orange dye solution under visible light UV irradiation. The result of TEM reveals that most of the surface area of TiO 2 is covered by tiny particles of noble metals with diameter less than 1 nm. Broad red shift of UV-Visible absorption band of modified photocatalysts was observed. The catalytic degradation of methyl orange in aqueous solutions under visible light illumination demonstrates a significant enhancement of photocatalytic activity of these films compared with the un-loaded films. The photocatalytic efficiency of modified TiO 2 films by this method is affected by the concentration of impregnating solution.

  7. Sol-flame synthesis: a general strategy to decorate nanowires with metal oxide/noble metal nanoparticles.

    PubMed

    Feng, Yunzhe; Cho, In Sun; Rao, Pratap M; Cai, Lili; Zheng, Xiaolin

    2013-03-13

    The hybrid structure of nanoparticle-decorated nanowires (NP@NW) combines the merits of large specific surface areas for NPs and anisotropic properties for NWs and is a desirable structure for applications including batteries, dye-sensitized solar cells, photoelectrochemical water splitting, and catalysis. Here, we report a novel sol-flame method to synthesize the NP@NW hybrid structure with two unique characteristics: (1) large loading of NPs per NW with the morphology of NP chains fanning radially from the NW core and (2) intimate contact between NPs and NWs. Both features are advantageous for the above applications that involve both surface reactions and charge transport processes. Moreover, the sol-flame method is simple and general, with which we have successfully decorated various NWs with binary/ternary metal oxide and even noble metal NPs. The unique aspects of the sol-flame method arise from the ultrafast heating rate and the high temperature of flame, which enables rapid solvent evaporation and combustion, and the combustion gaseous products blow out NPs as they nucleate, forming the NP chains around NWs. PMID:22494023

  8. Lead-Free Halide Double Perovskites via Heterovalent Substitution of Noble Metals.

    PubMed

    Volonakis, George; Filip, Marina R; Haghighirad, Amir Abbas; Sakai, Nobuya; Wenger, Bernard; Snaith, Henry J; Giustino, Feliciano

    2016-04-01

    Lead-based halide perovskites are emerging as the most promising class of materials for next-generation optoelectronics; however, despite the enormous success of lead-halide perovskite solar cells, the issues of stability and toxicity are yet to be resolved. Here we report on the computational design and the experimental synthesis of a new family of Pb-free inorganic halide double perovskites based on bismuth or antimony and noble metals. Using first-principles calculations we show that this hitherto unknown family of perovskites exhibits very promising optoelectronic properties, such as tunable band gaps in the visible range and low carrier effective masses. Furthermore, we successfully synthesize the double perovskite Cs2BiAgCl6, perform structural refinement using single-crystal X-ray diffraction, and characterize its optical properties via optical absorption and photoluminescence measurements. This new perovskite belongs to the Fm3̅m space group and consists of BiCl6 and AgCl6 octahedra alternating in a rock-salt face-centered cubic structure. From UV-vis and photoluminescence measurements we obtain an indirect gap of 2.2 eV. PMID:26982118

  9. Copper-modified covalent triazine frameworks as non-noble-metal electrocatalysts for oxygen reduction.

    PubMed

    Iwase, Kazuyuki; Yoshioka, Tatsuro; Nakanishi, Shuji; Hashimoto, Kazuhito; Kamiya, Kazuhide

    2015-09-14

    The electrochemical oxygen reduction reaction (ORR) is an important cathode reaction of various types of fuel cells. The development of electrocatalysts composed only of abundant elements is a key goal because currently only platinum is a suitable catalyst for ORR. Herein, we synthesized copper-modified covalent triazine frameworks (CTF) hybridized with carbon nanoparticles (Cu-CTF/CPs) as efficient electrocatalysts for the ORR in neutral solutions. The ORR onset potential of the synthesized Cu-CTF/CP was 810 mV versus the reversible hydrogen electrode (RHE; pH 7), the highest reported value at neutral pH for synthetic Cu-based electrocatalysts. Cu-CTF/CP also displayed higher stability than a Cu-based molecular complex at neutral pH during the ORR, a property that was likely as a result of the covalently cross-linked structure of CTF. This work may provide a new platform for the synthesis of durable non-noble-metal electrocatalysts for various target reactions. PMID:26227987

  10. Noninvasive noble metal nanoparticle arrays for surface-enhanced Raman spectroscopy of proteins

    NASA Astrophysics Data System (ADS)

    Inya-Agha, Obianuju; Forster, Robert J.; Keyes, Tia E.

    2007-02-01

    Noble metal nanoparticles arrays are well established substrates for surface enhanced Raman spectroscopy (SERS). Their ability to enhance optical fields is based on the interaction of their surface valence electrons with incident electromagnetic radiation. In the array configuration, noble metal nanoparticles have been used to produce SER spectral enhancements of up to 10 8 orders of magnitude, making them useful for the trace analysis of physiologically relevant analytes such as proteins and peptides. Electrostatic interactions between proteins and metal surfaces result in the preferential adsorption of positively charged protein domains onto metal surfaces. This preferential interaction has the effect of disrupting the native conformation of the protein fold, with a concomitant loss of protein function. A major historic advantage of Raman microspectroscopy has been is its non-invasive nature; protein denaturation on the metal surfaces required for SER spectroscopy renders it a much more invasive technique. Further, part of the analytical power of Raman spectroscopy lies in its use as a secondary conformation probe. The protein structural loss which occurs on the metal surface results in secondary conformation readings which are not true to the actual native state of the analyte. This work presents a method for chemical fabrication of noble metal SERS arrays with surface immobilized layers which can protect protein native conformation without excessively mitigating the electromagnetic enhancements of spectra. Peptide analytes are used as model systems for proteins. Raman spectra of alpha lactalbumin on surfaces and when immobilized on these novel arrays are compared. We discuss the ability of the surface layer to protect protein structure whilst improving signal intensity.

  11. Noble metal (Pd, Ru, Rh, Pt, Au, Ag) doped graphene hybrids for electrocatalysis

    NASA Astrophysics Data System (ADS)

    Giovanni, Marcella; Poh, Hwee Ling; Ambrosi, Adriano; Zhao, Guanjia; Sofer, Zdeněk; Šaněk, Filip; Khezri, Bahareh; Webster, Richard D.; Pumera, Martin

    2012-07-01

    Metal decorated graphene materials are highly important for catalysis. In this work, noble metal doped-graphene hybrids were prepared by a simple and scalable method. The thermal reductions of metal doped-graphite oxide precursors were carried out in nitrogen and hydrogen atmospheres and the effects of these atmospheres as well as the metal components on the characteristics and catalytic capabilities of the hybrid materials were studied. The hybrids exfoliated in nitrogen atmosphere contained a higher amount of oxygen-containing groups and lower density of defects on their surfaces than hybrids exfoliated in hydrogen atmosphere. The metals significantly affected the electrochemical behavior and catalysis of compounds that are important in energy production and storage and in electrochemical sensing. Research in the field of energy storage and production, electrochemical sensing and biosensing as well as biomedical devices can take advantage of the properties and catalytic capabilities of the metal doped graphene hybrids.

  12. Simple and efficient separation of atomically precise noble metal clusters.

    PubMed

    Ghosh, Atanu; Hassinen, Jukka; Pulkkinen, Petri; Tenhu, Heikki; Ras, Robin H A; Pradeep, Thalappil

    2014-12-16

    There is an urgent need for accessible purification and separation strategies of atomically precise metal clusters in order to promote the study of their fundamental properties. Although the separation of mixtures of atomically precise gold clusters Au25L18, where L are thiolates, has been demonstrated by advanced separation techniques, we present here the first separation of metal clusters by thin-layer chromatography (TLC), which is simple yet surprisingly efficient. This method was successfully applied to a binary mixture of Au25L18 with different ligands, as well as to a binary mixture of different cluster cores, Au25 and Au144, protected with the same ligand. Importantly, TLC even enabled the challenging separation of a multicomponent mixture of mixed-monolayer-protected Au25 clusters with closely similar chemical ligand compositions. We anticipate that the realization of such simple yet efficient separation technique will progress the detailed investigation of cluster properties. PMID:25395064

  13. Noble Metal Immersion Spectroscopy of Silica Alcogels and Aerogels

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

    1998-01-01

    We have fabricated aerogels containing gold and silver nanoparticles for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to porous or heterogeneous media. Specifically, we apply the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs further modification for aggregated or surfactant modified systems. Additionally, the kinetics suggest that collective particle interactions in coagulated clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

  14. 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

  15. Unveiling nickelocene bonding to a noble metal surface

    NASA Astrophysics Data System (ADS)

    Bachellier, N.; Ormaza, M.; Faraggi, M.; Verlhac, B.; Vérot, M.; Le Bahers, T.; Bocquet, M.-L.; Limot, L.

    2016-05-01

    The manipulation of a molecular spin state in low-dimensional materials is central to molecular spintronics. The designs of hybrid devices incorporating magnetic metallocenes are very promising in this regard, but are hampered by the lack of data regarding their interaction with a metal. Here, we combine low-temperature scanning tunneling microscopy and density functional theory calculations to investigate a magnetic metallocene at the single-molecule level—nickelocene. We demonstrate that the chemical and electronic structures of nickelocene are preserved upon adsorption on a copper surface. Several bonding configurations to the surface are identified, ranging from the isolated molecule to molecular layers governed by van der Waals interactions.

  16. Electrochemical oxide film formation at noble metals as a surface-chemical process

    NASA Astrophysics Data System (ADS)

    Conway, B. E.

    1995-08-01

    The mechanisms of electrochemical oxide film formation at noble metals are described and exemplified by the cases of Pt and Au, especially in the light of recent experimentation by means of cyclic voltammetry, ellipsometry and vacuum surface-science studies using LEED and AES. Unlike the mechanisms of base-metal oxidation, e.g., in corrosion processes, anodic oxide film formation at noble metals proceeds by surface chemical processes involving, initially, sub-monolayer, through monolayer, formation of 2-dimensional {OH}/{O} arrays. During such 2-d processes, place-exchange between electrosorbed OH or O species on the surface, and Pt or Au atoms within the surface lattice, takes place leading to a quasi-2-d compact film which then grows ultimately to a multilayer hydrous oxide film, probably by continuing injection of ions of the substrate metal and their migration through the growing film under the influence of the field. The initial, sub-monolayer stage of electrosorption of OH involves competitive chemisorption by anions, e.g. HSO 4-, ClO 4-, Cl -, which inhibits onset of the first stage of surface oxidation. These processes are demonstrable in experiments on single-crystal surfaces. The combination of such anion effects with place-exchange during the extension of the film, leads to a general mechanism of noble metal oxide film formation. The formation of the oxide films can be examined in detail by recording the distinguishable stages in the film's electrochemical reduction in linear-sweep voltammetry which is sensitive down to {OH}/{O} fractional coverages as low as 0.5% and over time-scales down to 50μs in experiments on time-evolution and transformation of the states of the oxide films. By means of LEED, AES and STM or AFM experiments, the reconstructions and perturbations (e.g. generation of stepped terraces) which oxide films cause on singlecrystal surfaces can be followed.

  17. Bioactivity of noble metal nanoparticles decorated with biopolymers and their application in drug delivery.

    PubMed

    Rai, Mahendra; Ingle, Avinash P; Gupta, Indarchand; Brandelli, Adriano

    2015-12-30

    The unique properties of nanomaterials can be applied to solve different problems including new ways of drug delivery. Noble metal nanoparticles are most promising because they have been used for medicinal purposes since ancient time. It is evident from the past studies that the metallic nanoparticles are much more effective against various microorganisms when compared to their conventional counterparts. However, decoration of such nanoparticles with biomaterials add more advantages to their antimicrobial activity. Decoration of metal nanoparticles with biopolymers is a quite new area of research. Studies performed hitherto shown that nanoparticles of noble metals like silver, gold and platinum demonstrated better antibacterial, antifungal and antiviral activities when conjugated with biopolymers. The development of such technology has potential to develop materials that are more effective in the field of health science. Considering the importance and uniqueness of this concept, the present review aims to discuss the use of biopolymer-decorated metal nanoparticles for combating various diseases caused by microbial pathogens. Moreover, the nanotoxicity aspect has also been discussed. PMID:26520406

  18. Air- and water-resistant noble metal coated ferromagnetic cobalt nanorods.

    PubMed

    Lentijo-Mozo, Sergio; Tan, Reasmey P; Garcia-Marcelot, Cécile; Altantzis, Thomas; Fazzini, Pier-Francesco; Hungria, Teresa; Cormary, Benoit; Gallagher, James R; Miller, Jeffrey T; Martinez, Herve; Schrittwieser, Stefan; Schotter, Joerg; Respaud, Marc; Bals, Sara; Van Tendeloo, Gustaaf; Gatel, Christophe; Soulantica, Katerina

    2015-03-24

    Cobalt nanorods possess ideal magnetic properties for applications requiring magnetically hard nanoparticles. However, their exploitation is undermined by their sensitivity toward oxygen and water, which deteriorates their magnetic properties. The development of a continuous metal shell inert to oxidation could render them stable, opening perspectives not only for already identified applications but also for uses in which contact with air and/or aqueous media is inevitable. However, the direct growth of a conformal noble metal shell on magnetic metals is a challenge. Here, we show that prior treatment of Co nanorods with a tin coordination compound is the crucial step that enables the subsequent growth of a continuous noble metal shell on their surface, rendering them air- and water-resistant, while conserving the monocrystallity, metallicity and the magnetic properties of the Co core. Thus, the as-synthesized core-shell ferromagnetic nanorods combine high magnetization and strong uniaxial magnetic anisotropy, even after exposure to air and water, and hold promise for successful implementation in in vitro biodiagnostics requiring probes of high magnetization and anisotropic shape. PMID:25734760

  19. Tuning of noble metal work function with organophosphonate nanolayers

    SciTech Connect

    Ramanath, Ganpati Kwan, Matthew; Chow, P. K.; Quintero, Y. Cardona; Ramprasad, R.; Mutin, P. H.

    2014-08-25

    We demonstrate that weak chemical interactions between untethered moieties in molecular nanolayers on metal surfaces can strongly influence the effective work function Φ{sub eff}. Electron spectroscopy shows that nanolayers of mercaptan-anchored organophosphonates on Au and Pt decrease Φ{sub eff}. The measured Φ{sub eff} shifts correlate with the chemical state of phosphonic acid moieties, and scale with molecular length. These results are contrary to predictions of ab initio calculations of monolayer-capped surfaces, but are consistent with calculations of bilayer-capped surfaces with face-to-face hydrogen-bonded phosphonic acid moieties. Our findings indicate that intra-layer bonding and layering in molecular nanolayers can be key to tailoring heterointerfacial electronic properties for applications.

  20. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces

    SciTech Connect

    Svane, K. L. Hammer, B.

    2014-11-07

    The reaction free energy for dehydrogenation of phenol, aniline, thiophenol, benzoic acid, and 1,4-benzenediol on the close packed copper, silver, and gold surfaces has been studied by density functional theory calculations. Dehydrogenation of thiophenol is found to be favourable on all three surfaces while aniline does not dehydrogenate on any of them. For phenol, benzenediol and benzoic acid dehydrogenation is favourable on copper and silver only, following the general trend of an increasing reaction free energy when going form gold to silver to copper. This trend can be correlated with the changes in bond lengths within the molecule upon dehydrogenation. While copper is able to replace hydrogen, leaving small changes in the bond lengths of the aromatic ring, the metal-molecule bond is weaker for silver and gold, resulting in a partial loss of aromaticity. This difference in bond strength leads to pronounced differences in adsorption geometries upon multiple dehydrogenations.

  1. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces

    NASA Astrophysics Data System (ADS)

    Svane, K. L.; Hammer, B.

    2014-11-01

    The reaction free energy for dehydrogenation of phenol, aniline, thiophenol, benzoic acid, and 1,4-benzenediol on the close packed copper, silver, and gold surfaces has been studied by density functional theory calculations. Dehydrogenation of thiophenol is found to be favourable on all three surfaces while aniline does not dehydrogenate on any of them. For phenol, benzenediol and benzoic acid dehydrogenation is favourable on copper and silver only, following the general trend of an increasing reaction free energy when going form gold to silver to copper. This trend can be correlated with the changes in bond lengths within the molecule upon dehydrogenation. While copper is able to replace hydrogen, leaving small changes in the bond lengths of the aromatic ring, the metal-molecule bond is weaker for silver and gold, resulting in a partial loss of aromaticity. This difference in bond strength leads to pronounced differences in adsorption geometries upon multiple dehydrogenations.

  2. Ab Initio Electronic Relaxation Times and Transport in Noble Metals

    NASA Astrophysics Data System (ADS)

    Mustafa, Jamal I.; Bernardi, Marco; Neaton, Jeffrey B.; Louie, Steven G.

    Relaxation times employed to study electron transport in metals are typically assumed to be constants and obtained empirically using the Drude model. Here, we employ ab initio calculations to compute the electron-phonon relaxation times of Cu, Ag, and Au, and find that they vary significantly on the Fermi surface, spanning ~15 -45 fs. We compute room temperature resistivities in excellent agreement with experiment by combining GW bandstructures, Wannier-interpolated band velocities, and ab initio relaxation times. Our calculations are compared to other approximations used for the relaxation times. Additionally, an importance sampling scheme is introduced to speed up the convergence of resistivity and transport calculations by sampling directly points on the Fermi surface. This work was supported by NSF Grant No. DMR15-1508412 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at LBNL's NERSC facility.

  3. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces.

    PubMed

    Svane, K L; Hammer, B

    2014-11-01

    The reaction free energy for dehydrogenation of phenol, aniline, thiophenol, benzoic acid, and 1,4-benzenediol on the close packed copper, silver, and gold surfaces has been studied by density functional theory calculations. Dehydrogenation of thiophenol is found to be favourable on all three surfaces while aniline does not dehydrogenate on any of them. For phenol, benzenediol and benzoic acid dehydrogenation is favourable on copper and silver only, following the general trend of an increasing reaction free energy when going form gold to silver to copper. This trend can be correlated with the changes in bond lengths within the molecule upon dehydrogenation. While copper is able to replace hydrogen, leaving small changes in the bond lengths of the aromatic ring, the metal-molecule bond is weaker for silver and gold, resulting in a partial loss of aromaticity. This difference in bond strength leads to pronounced differences in adsorption geometries upon multiple dehydrogenations. PMID:25381535

  4. A quantitative study of the intracellular concentration of graphene/noble metal nanoparticle composites and their cytotoxicity

    NASA Astrophysics Data System (ADS)

    Zhou, Xiangyan; Dorn, Marco; Vogt, Jürgen; Spemann, Daniel; Yu, Wei; Mao, Zhengwei; Estrela-Lopis, Irina; Donath, Edwin; Gao, Changyou

    2014-07-01

    Noble-metal nanoparticles (NPs) especially prepared from gold and silver have been combined on the surface of graphene to obtain graphene-based nanocomposites for novel functions in enhanced performance in bio-imaging, cancer detection and therapy. However, little is known about their cellular uptake, especially the intracellular quantity which plays a critical role in determining their functions and safety. Therefore, we prepared covalently conjugated GO/Au and GO/Ag composites by immobilizing Au and Ag nanoparticles on GO sheets pre-functionalized with disulfide bonds, respectively. The cellular uptake of these composites was quantitatively studied by means of an ion beam microscope (IBM) to determine the metal content in human lung cancer cells (A549 cells) and liver hepatocellular carcinoma cells (HepG2 cells). The cell uptake was also studied by inductively coupled plasma mass spectrometry (ICP-MS), which is one of the most sensitive techniques being applied to cell suspensions, for comparison. Toxicity, one of the consequences of cellular uptake of GO based composites, was studied as well. The potential toxicity mechanism was also suggested based on the results of intracellular quantification of the nanomaterials.Noble-metal nanoparticles (NPs) especially prepared from gold and silver have been combined on the surface of graphene to obtain graphene-based nanocomposites for novel functions in enhanced performance in bio-imaging, cancer detection and therapy. However, little is known about their cellular uptake, especially the intracellular quantity which plays a critical role in determining their functions and safety. Therefore, we prepared covalently conjugated GO/Au and GO/Ag composites by immobilizing Au and Ag nanoparticles on GO sheets pre-functionalized with disulfide bonds, respectively. The cellular uptake of these composites was quantitatively studied by means of an ion beam microscope (IBM) to determine the metal content in human lung cancer cells (A

  5. Noble metals on the nanoscale: optical and photothermal properties and some applications in imaging, sensing, biology, and medicine.

    PubMed

    Jain, Prashant K; Huang, Xiaohua; El-Sayed, Ivan H; El-Sayed, Mostafa A

    2008-12-01

    result of field coupling. A universal scaling model, relating the plasmon resonance frequency to the interparticle distance in terms of the particle size, becomes potentially useful for measuring nanoscale distances (and their changes) in biological systems. The strong plasmon absorption and photothermal conversion of gold nanoparticles has been exploited in cancer therapy through the selective localized photothermal heating of cancer cells. For nanorods or nanoshells, the LSPR can be tuned to the near-infrared region, making it possible to perform in vivo imaging and therapy. The examples of the applications of noble metal nanostructures provided herein can be readily generalized to other areas of biology and medicine because plasmonic nanomaterials exhibit great range, versatility, and systematic tunability of their optical attributes. PMID:18447366

  6. 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.

  7. Solar noble gases revealed by closed system stepped etching of a metal separate from Fayetteville

    NASA Technical Reports Server (NTRS)

    Murer, CH.; Baur, H.; Signer, P.; Wieler, R.

    1993-01-01

    Solar He, Ne, and Ar in a Fe-Ni separate from the chondrite Fayetteville are analyzed by closed system stepped oxidation. We report here data of the first 15 steps comprising 55 percent of the total solar gases. He-4/Ar-36 and Ne-20/Ar-36 are quite constant at values about 20 percent below those of present day solar wind (SWC). In this, Fe-Ni differs from lunar ilmenites where He-4/Ar-36 and Ne-20/Ar-36 in the first steps are several times below SWC. Thus, metal retains SW-noble gases even better than ilmenite, almost without element fractionation. Nevertheless, the isotopic composition of SW-He, -Ne, and -Ar in the first steps of the metal sample are identical to those found in a recently irradiated lunar ilmenite, indicating that ilmenites and chondritic metal both contain isotopically unfractionated SW noble gases. A preliminary analysis of a smaller Fayetteville metal separate shows Ne from solar energetic particles (SEP-Ne) with Ne-20/Ne-22 less than or equal to 11.5.

  8. Delivery of Highly Active Noble-Metal Nanoparticles into Microspherical Supports by an Aerosol-Spray Method.

    PubMed

    Kan, Erjie; Kuai, Long; Wang, Wenhai; Geng, Baoyou

    2015-09-14

    Noble metal nanoparticles (NPs) with 1-5 nm diameter obtained from NaHB4 reduction possess high catalytic activity. However, they are rarely used directly. This work presents a facile, versatile, and efficient aerosol-spray approach to deliver noble-metal NPs into metal oxide supports, while maintaining the size of the NPs and the ability to easily adjust the loading amount. In comparison with the conventional spray approach, the size of the loaded noble-metal nanoparticles can be significantly decreased. An investigation of the 4-nitrophenol hydrogenation reaction catalyzed by these materials suggests that the NPs/oxides catalysts have high activity and good endurance. For 1 % Au/CeO2 and Pd/Al2 O3 catalysts, the rate constants reach 2.03 and 1.46 min(-1) , which is much higher than many other reports with the same noble-metal loading scale. Besides, the thermal stability of catalysts can be significantly enhanced by modifying the supports. Therefore, this work contributes an efficient method as well as some guidance on how to produce highly active and stable supported noble-metal catalysts. PMID:26234910

  9. Assembly of Nanoions via Electrostatic Interactions: Ion-Like Behavior of Charged Noble Metal Nanoclusters

    PubMed Central

    Yao, Qiaofeng; Luo, Zhentao; Yuan, Xun; Yu, Yue; Zhang, Chao; Xie, Jianping; Lee, Jim Yang

    2014-01-01

    The assembly of ultrasmall metal nanoclusters (NCs) is of interest to both basic and applied research as it facilitates the determination of cluster structures and the customization of cluster physicochemical properties. Here we present a facile and general approach to assemble noble metal NCs by selectively inducing electrostatic interactions between negatively-charged metal NCs and divalent cations. The charged metal NCs, which have well-defined sizes, charges and structures; and behave similarly to multivalent anions, can be considered as nanoions. These nanoions exhibit step-like assembly behavior when interacting with the counter cations – assembly only occurs when the solubility product (Ksp) between the carboxylate ions on the NC surface and the divalent cations is exceeded. The assembly here is distinctively different from the random aggregation of colloidal particles by counter ions. The nanoions would assemble into fractal-like monodisperse spherical particles with a high order of regularity that mimic the assembly of ionic crystals. PMID:24457992

  10. Exploring methods for compositional and particle size analysis of noble metal nanoparticles in Daphnia magna.

    PubMed

    Krystek, Petra; Brandsma, Sicco; Leonards, Pim; de Boer, Jacob

    2016-01-15

    The identification and quantification of the bioaccumulation of noble metal engineered nanoparticles (ENPs) by aquatic organisms is of great relevance to understand the exposure and potential toxicity mechanisms of nanoscale materials. Four analytical scenarios were investigated in relation to various sized and composed noble metal (gold (Au), platinum (Pt) and silver (Ag)) ENPs during acute, short-term exposure of Daphnia (D.) magna. Next to the total elemental quantification of absorbed ENPs by D. magna, especially information on the size and particle distribution of ENPs in D. magna is of relevance. Dissolution of the exposed biological material prior to measurement by asymmetric flow field flow fractionation coupled to inductively coupled plasma mass spectrometry (AF4-ICPMS) is challenging because the ENPs must stay stable regarding to particle size and composition. Next to dissolution of exposed D. magna by tetra methyl ammonium hydroxide (TMAH), a new enzymatic dissolution approach was explored by using trypsin. The presence of various sized and composed ENPs has been confirmed by AF4-ICPMS but the chosen dissolution medium was crucial for the results. TMAH and trypsin led to comparable results for medium-sized (50nm) noble metals ENPs in exposed D. magna. But it was also shown that the dissolution of biological materials with smaller (<5nm) ENPs led to different results in particle size and elemental concentration depending on the selected dissolution medium. A significant uptake of Au and Pt ENPs by D. magna or adsorption to particles occurred because only 1-5% of the exposed ENPs remained in the exposure medium. PMID:26592609

  11. Zeolitic BIF Crystal Directly Producing Noble-Metal Nanoparticles in Its Pores for Catalysis

    PubMed Central

    Zhang, Hai-Xia; Liu, Meng; Bu, Xianhui; Zhang, Jian

    2014-01-01

    As an integral part of a porous framework and uniformly distributed throughout the internal pore space, the high density of the exposed B–H bond in zeolite-like porous BIF-20 (BIF = Boron Imidazolate Framework) is shown here to effectively produce nanoparticles within its confined pore space. Small noble-metal nanoparticles (Ag or Au) are directly synthesized into its pores without the need for any external reducing agent or photochemical reactions, and the resulting Ag@BIF-20 (or Au@BIF-20) samples show high catalytic activities for the reduction of 4-nitrophenol. PMID:24473155

  12. Hydrothermal synthesis of nanosize phases based on non-ferrous and noble metals

    NASA Astrophysics Data System (ADS)

    Tupikova, E. N.; Platonov, I. A.; Lykova, T. N.

    2016-04-01

    Research is devoted to reactions of binary complexes containing noble (platinum, palladium) and non-ferrous (cobalt, chrome) metals. Reactions proceed under hydrothermal conditions by the autoclave technique. Initials complexes and products of autoclave thermolysis were characterized by the FT-IR spectroscopy, the transmission electron microscopy (TEM) and the energy-dispersive X-ray spectroscopy (EDX). Comparative catalytic experiments in the test reaction were conducted. The obtained results can form the basis of new methods of nanosize multicomponent phases synthesis under hydrothermal conditions.

  13. Method for localized deposition of noble metal catalysts with control of morphology

    DOEpatents

    Ricco, Antonio J.; Manginell, Ronald P.; Huber, Robert J.

    1998-01-01

    A combustible gas sensor that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac).sub.2 onto microfilaments resistively heated to approximately 500 .degree. C.; Pt deposits only on the hot filament. The filaments tested to date are 2 .mu.m thick .times.10 .mu.m wide .times.100, 250, 500, or 1000 .mu.m-long polycrystalline Si; some are overcoated with a 0.25 .mu.m-thick protective CVD Si.sub.3 N.sub.4 layer.

  14. Noble-Metal-Free Molybdenum Disulfide Cocatalyst for Photocatalytic Hydrogen Production.

    PubMed

    Yuan, Yong-Jun; Lu, Hong-Wei; Yu, Zhen-Tao; Zou, Zhi-Gang

    2015-12-21

    Photocatalytic water splitting using powered semiconductors as photocatalysts represents a promising strategy for clean, low-cost, and environmentally friendly production of H2 utilizing solar energy. The loading of noble-metal cocatalysts on semiconductors can significantly enhance the solar-to-H2 conversion efficiency. However, the high cost and scarcity of noble metals counter their extensive utilization. Therefore, the use of alternative cocatalysts based on non-precious metal materials is pursued. Nanosized MoS2 cocatalysts have attracted considerable attention in the last decade as a viable alternative to improve solar-to-H2 conversion efficiency because of its superb catalytic activity, excellent stability, low cost, availability, environmental friendliness, and chemical inertness. In this perspective, the design, structures, synthesis, and application of MoS2 -based composite photocatalysts for solar H2 generation are summarized, compared, and discussed. Finally, this Review concludes with a summary and remarks on some challenges and opportunities for the future development of MoS2 -based photocatalysts. PMID:26586523

  15. Noble metal nanoparticles embedding into polymeric materials: From fundamentals to applications.

    PubMed

    Prakash, Jai; Pivin, J C; Swart, H C

    2015-12-01

    This review covers some key concepts related to embedding of the noble metal nanoparticles in polymer surfaces. The metal nanoparticles embedded into the polymer matrix can provide high-performance novel materials that find applications in modern nanotechnology. In particular, the origin of various processes that drive the embedding phenomenon, growth of the nanostructure at the surface, factors affecting the embedding including role of surface, interface energies and thermodynamic driving forces with emphasis on the fundamental and technological applications, under different conditions (annealing and ion beams) have been discussed. In addition to the conventional thermal process for embedding which includes the measure of fundamental polymer surface properties with relevant probing techniques, this review discusses the recent advances carried out in the understanding of embedding phenomenon starting from thin metal films to growth of the nanoparticles and embedded nanostructures using novel ion beam techniques. PMID:26584861

  16. Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum

    NASA Astrophysics Data System (ADS)

    Xu, Shao Hui; Fei, Guang Tao; You, Qiao; Gao, Xu Dong; Huo, Peng Cheng; De Zhang, Li

    2016-09-01

    One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10‑5 Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains.

  17. Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals.

    PubMed

    Meyer, Dominik; Schäfer, Tobias; Schulz, Philip; Jung, Sebastian; Rittich, Julia; Mokros, Daniel; Segger, Ingolf; Maercks, Franziska; Effertz, Christian; Mazzarello, Riccardo; Wuttig, Matthias

    2016-09-01

    Tuning the work function of the electrode is one of the crucial steps to improve charge extraction in organic electronic devices. Here, we show that N,N-dialkyl dithiocarbamates (DTC) can be effectively employed to produce low work function noble metal electrodes. Work functions between 3.1 and 3.5 eV are observed for all metals investigated (Cu, Ag, and Au). Ultraviolet photoemission spectroscopy (UPS) reveals a maximum decrease in work function by 2.1 eV as compared to the bare metal surface. Electronic structure calculations elucidate how the complex interplay between intrinsic dipoles and dipoles induced by bond formation generates such large work function shifts. Subsequently, we quantify the improvement in contact resistance of organic thin film transistor devices with DTC coated source and drain electrodes. These findings demonstrate that DTC molecules can be employed as universal surface modifiers to produce stable electrodes for electron injection in high performance hybrid organic optoelectronics. PMID:27504721

  18. Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum.

    PubMed

    Xu, Shao Hui; Fei, Guang Tao; You, Qiao; Gao, Xu Dong; Huo, Peng Cheng; De Zhang, Li

    2016-09-16

    One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10(-5) Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains. PMID:27487089

  19. Abiological catalysis by artificial haem proteins containing noble metals in place of iron.

    PubMed

    Key, Hanna M; Dydio, Paweł; Clark, Douglas S; Hartwig, John F

    2016-06-23

    Enzymes that contain metal ions--that is, metalloenzymes--possess the reactivity of a transition metal centre and the potential of molecular evolution to modulate the reactivity and substrate-selectivity of the system. By exploiting substrate promiscuity and protein engineering, the scope of reactions catalysed by native metalloenzymes has been expanded recently to include abiological transformations. However, this strategy is limited by the inherent reactivity of metal centres in native metalloenzymes. To overcome this limitation, artificial metalloproteins have been created by incorporating complete, noble-metal complexes within proteins lacking native metal sites. The interactions of the substrate with the protein in these systems are, however, distinct from those with the native protein because the metal complex occupies the substrate binding site. At the intersection of these approaches lies a third strategy, in which the native metal of a metalloenzyme is replaced with an abiological metal with reactivity different from that of the metal in a native protein. This strategy could create artificial enzymes for abiological catalysis within the natural substrate binding site of an enzyme that can be subjected to directed evolution. Here we report the formal replacement of iron in Fe-porphyrin IX (Fe-PIX) proteins with abiological, noble metals to create enzymes that catalyse reactions not catalysed by native Fe-enzymes or other metalloenzymes. In particular, we prepared modified myoglobins containing an Ir(Me) site that catalyse the functionalization of C-H bonds to form C-C bonds by carbene insertion and add carbenes to both β-substituted vinylarenes and unactivated aliphatic α-olefins. We conducted directed evolution of the Ir(Me)-myoglobin and generated mutants that form either enantiomer of the products of C-H insertion and catalyse the enantio- and diastereoselective cyclopropanation of unactivated olefins. The presented method of preparing artificial haem

  20. CO-oxidation catalysts: Low-temperature CO oxidation over Noble-Metal Reducible Oxide (NMRO) catalysts

    NASA Technical Reports Server (NTRS)

    Herz, Richard K.

    1990-01-01

    Oxidation of CO to CO2 is an important reaction technologically and environmentally and a complex and interesting reaction scientifically. In most cases, the reaction is carried out in order to remove CO as an environmental hazard. A major application of heterogeneous catalysts is catalytic oxidation of CO in the exhaust of combustion devices. The reaction over catalysts in exhaust gas is fast and often mass-transfer-limited since exhaust gases are hot and O2/CO ratios are high. The main challenges to catalyst designers are to control thermal sintering and chemical poisoning of the active materials. The effect of the noble metal on the oxide is discussed, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form unique catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials.

  1. Noble metals-compatible melter features development Phase 1: Establishing functional and design criteria and design concepts

    SciTech Connect

    Elmore, M.R.; Siemens, D.H.; Chapman, C.C.

    1996-03-01

    Premature failures have occurred in melters at Japan`s Tokai Mockup Facility and at the Federal Republic of Germany (FRG) PAMELA plant during processing of feeds with high levels of noble metals. Melter failure was due to the accumulation of an electrically conductive, noble metals-containing precipitates in the glass, that then resulted in short circuiting of the electrodes. A comparison was made of the anticipated Hanford Waste Vitrification Plant (HWVP) feed with the feeds processed in the FRG and Japanese melters. The evaluation showed that comparable levels of noble metals and other potential precipitate-forming components (e.g. Cr/Fe/Ni-spinels) exist in the HWVP feed. As a result, the HWVP project made a decision to modify the present reference melter design to include features to prevent the precipitation and accumulation or otherwise accommodate precipitated phases on a routine basis without loss of production capacity.

  2. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    SciTech Connect

    Liu, X. H.; Luo, H.; Qu, T. L. Yang, K. Y.; Ding, Z. C.

    2015-10-15

    We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of {sup 87}Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the {sup 87}Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the {sup 87}Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  3. Noble metal nanoparticle-decorated TiO2 nanobelts for enhanced photocatalysis

    NASA Astrophysics Data System (ADS)

    He, Haiyan; Yang, Ping; Jia, Changchao; Miao, Yanping; Zhao, Jie; Du, Yingying

    2014-07-01

    TiO2 nanobelts have been fabricated through a hydrothermal method and subsequently sulfuric-acid-corrosion-treated for a rough surface. Noble metal nanoparticles such as Ag and Au were deposited on the coarse surface of TiO2 nanobelts via a coprecipitation procedure. Ag-TiO2 nanobelts were prepared in ethanolic solution contained silver nitrate (AgNO3) and sodium hydroxide (NaOH). Au-TiO2 nanobelts were obtained in chloroauric acid (HAuCl4) using sodium borohydride (NaBH4) as the reductant. It is confirmed by the results of XRD patterns together with the SEM images that the composite of noble metal and TiO2 nanobelts were obtained successfully and the Ag or Au nanoparticles were well-dispersed on the TiO2 nanobelts. Moreover, the as-prepared Ag and Au nanoparticle-decorated TiO2 nanobelts represent an enhanced photocatalytic activity compared with pure TiO2 nanobelts, which is due to the fact that the Ag and Au nanoparticles on the surface of TiO2 nanobelts act as sinks for the photogenerated electrons and promote the separation of the electrons and holes.

  4. A simple route to diverse noble metal-decorated iron oxide nanoparticles for catalysis.

    PubMed

    Walker, Joan M; Zaleski, Jeffrey M

    2016-01-21

    Developing facile synthetic routes to multifunctional nanoparticles combining the magnetic properties of iron oxides with the optical and catalytic utility of noble metal particles remains an important goal in realizing the potential of hybrid nanomaterials. To this end, we have developed a single route to noble metal-decorated magnetic nanoparticles (Fe3O4@SiO2-M; M = Au, Pd, Ag, and PtAg) and characterized them by HRTEM and STEM/EDX imaging to reveal their nanometer size (16 nm Fe3O4 and 1-5 nm M seeds) and uniformity. This represents one of the few examples of genuine multifunctional particles on the nanoscale. We show that these hybrid structures have excellent catalytic activity for the reduction of 4-nitrophenol (knorm = 2 × 10(7) s(-1) mol(Pd)(-1); 5 × 10(6) s(-1) mol(Au)(-1); 5 × 10(5) s(-1) mol(PtAg)(-1); 7 × 10(5) s(-1) mol(Ag)(-1)). These rates are the highest reported for nano-sized comparables, and are competitive with mesoparticles of similar composition. Due to their magnetic response, the particles are also suitable for magnetic recovery and maintain >99% conversion for at least four cycles. Using this synthetic route, Fe3O4@SiO2-M particles show great promise for further development as a precursor to complicated anisotropic materials or for applications ranging from nanocatalysis to biomedical sensing. PMID:26681072

  5. A simple approach for producing colloidal noble metal nanocrystals: Alternating voltage induced electrochemical synthesis

    NASA Astrophysics Data System (ADS)

    McCann, Kevin

    Intense research has been focused on developing bottom-up nanocrystal synthesis techniques to obtain nanocrystals with sophisticated compositions and enhanced perfomances. Three popular methods are: 1) the reduction of metal complex ions or molecules with selected reducing agents, 2) the decomposition of metal compounds at elevated temperatures, and 3) the electrochemical reduction of metal ions using specialized potentiostats. The first two require expensive metal salt precursors while the last requires specialized potentiostats and either employ a single sacrificial electrode or metal salt precursors. To resolve these issues, we have focused on a facile and generic approach to generate nanocrystals by an alternating voltage induced electrochemical synthesis (AVIES) method. Nanocrystals are produced when an alternating voltage is applied by a common laboratory transformer to two sacrificial electrodes that are inserted in an electrolyte solution containing capping ligands. This work focuses on the ability of the AVIES approach to synthesize Au, Pd, and Pt noble metal nanocrystals. The nanocrystals synthesized were found to be dependent on the electrolyte identity, capping ligand, applied voltage, reaction temperature. The ability of AVIES to produce alloyed nanocrystals starting with alloyed electrodes will be discussed. The AVIES approach requires neither expensive metal compounds nor specialized instruments, is environmentally benign, and can be easily adoptable to any research lab.

  6. Anchoring noble metal nanoparticles on CeO2 modified reduced graphene oxide nanosheets and their enhanced catalytic properties.

    PubMed

    Ji, Zhenyuan; Shen, Xiaoping; Xu, Yuling; Zhu, Guoxing; Chen, Kangmin

    2014-10-15

    The strategy of structurally integrating noble metal, metal oxide, and graphene is expected to offer prodigious opportunities toward emerging functions of graphene-based nanocomposites. In this study, we develop a facile two-step approach to disperse noble metal (Pt and Au) nanoparticles on the surface of CeO2 functionalized reduced graphene oxide (RGO) nanosheets. It is shown that Pt and Au with particle sizes of about 5 and 2nm are well dispersed on the surface of RGO/CeO2. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 was used as a model reaction to quantitatively evaluate the catalytic properties of the as-synthesized RGO/Pt/CeO2 and RGO/Au/CeO2 ternary nanocomposites. In such triple-component catalysts, CeO2 nanocrystals provide unique and critical roles for optimizing the catalytic performance of noble metallic Pt and Au, allowing them to express enhanced catalytic activities in comparison with RGO/Pt and RGO/Au catalysts. In addition, a possible mechanism for the enhanced catalytic activities of the RGO/Pt/CeO2 and RGO/Au/CeO2 ternary catalysts in the reduction of 4-NP is proposed. It is expected that our prepared graphene-based triple-component composites, which inherit peculiar properties of graphene, metal oxide, and noble metal, are attractive candidates for catalysis and other applications. PMID:25080384

  7. Synthesis Of Noble Metal Nanoparticle Composite Glasses Using Low Energy Ion Beam Mixing

    SciTech Connect

    Varma, Ranjana S.; Kothari, D. C.; Mahadkar, A. G.; Kulkarni, N. A.; Kanjilal, D.; Kumar, P.

    2010-12-01

    Carbon coated thin films of Cu or Au on fused silica glasses have been irradiated using 100 keV Ar{sup +} ions at different fluences ranging from 1x10{sup 13} to 1x10{sup 16} ion/cm{sup 2}. In this article, we explore a route to form noble metal nanoparticles in amorphous glass matrices without post irradiation annealing using low energy ion beam mixing where nuclear energy loss process is dominant. Optical and structural properties were studied using UV-Vis-NIR absorbance spectroscopy and Glancing angle X-ray Diffraction (GXRD). Results showed that Cu and Au nanoparticles are formed at higher fluence of 1x10{sup 16} ion/cm{sup 2} used in this work without annealing. The diameters of metal nanoparticles obtained from UV-Vis NIR and GXRD are in agreement.

  8. Study on the Enhanced Contribution in Noble Metals from Positron Annihilation

    NASA Astrophysics Data System (ADS)

    Hamid, A. S.; Ahmed, M. M.; Abu-Elmagd, M. S. M.; Rizk, R. A. M.

    2007-02-01

    Our motivations in the current work were to inspect various enhancement formulae along with to classify the electronic structure of noble metals Cu, Ag and Au. The measurements were performed via the two dimensional angular correlation of annihilation radiation 2D-ACAR apparatus. The electron density in momentum space ρ(p) was reconstructed and it displayed the following features. Initially, the reciprocal lattice points underscored the calculations, and they revealed Fermi surface features. Additionally, enhanced anisotropy exposed nearby Fermi momentum. They attributed to enhancement of the electronic wave function at the position of the positron. Finally, the high momentum contributions, due to interaction of positron with core-like-state, conducted the electronic structure of the metals under investigations. From another viewpoint, the features of Fermi surface of Cu, Ag and Au showed an expected analogous behavior as multiply connected sphere inside the first Brillouin zone.

  9. Self-assembled calixarene aligned patterning of noble metal nanoparticles on graphene.

    PubMed

    Chen, Xianjue; Vimalanathan, Kasturi; Zang, Wenzhe; Slattery, Ashley D; Boulos, Ramiz A; Gibson, Christopher T; Raston, Colin L

    2014-05-01

    Patterns of noble metal nanoparticles (NMNPs) of ruthenium and platinum are formed on p-phosphonic acid calix[8]arene stabilised graphene in water. This involves hydrogen gas induced reduction of metal ions absorbed on the stabilised graphene, with TEM revealing the patterns being comprised of domains of parallel arrays of NMNPs ∼7 nm apart. The domains are orientated in three directions on each graphene sheet at an angle of ∼60° or ∼120° with respect to each other. AFM of self-assembled p-phosphonic acid calix[8]arene on the surface of a highly ordered pyrolytic graphite (HOPG) revealed a similar pattern, implying that the orientation of the assembly of p-phosphonic acid calix[8]arene is governed by the hexagonal motif of graphite/graphene. PMID:24658459

  10. Noble metal nanoclusters and nanoparticles precede mineral formation in magmatic sulphide melts

    PubMed Central

    Helmy, Hassan M.; Ballhaus, Chris; Fonseca, Raúl O.C.; Wirth, Richard; Nagel, Thorsten; Tredoux, Marian

    2013-01-01

    In low temperature aqueous solutions, it has long been recognized by in situ experiments that many minerals are preceded by crystalline nanometre-sized particles and non-crystalline nanophases. For magmatic systems, nanometre-sized precursors have not yet been demonstrated to exist, although the suggestion has been around for some time. Here we demonstrate by high temperature quench experiments that platinum and arsenic self-organize to nanoparticles, well before the melt has reached a Pt–As concentration at which discrete Pt arsenide minerals become stable phases. If all highly siderophile elements associate to nanophases in undersaturated melts, the distribution of the noble metals between silicate, sulphide and metal melts will be controlled by the surface properties of nano-associations, more so than by the chemical properties of the elements. PMID:24008992

  11. First-principles study of the noble metal-doped BN layer

    SciTech Connect

    Zhou, Yungang; Yang, Ping; Sun, Xin; Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei

    2011-04-18

    Intriguing electronic and magnetic properties of BN layer with noble metal (Pd, Pt, Ag and Au) doping are obtained by first-principles calculations. Adsorbed Pd (or Pt) reduces the band gap of BN sheet owing to the induction of impurity states. The unpaired electrons in the Ag (or Au)-adsorbed and the Pd (or Pt)-substituted BN layers are polarized, and thus exhibit a magnetic moment of 1.0 µB, leading to these BN configurations to be magnetic semiconductors. The half-metallic feature of the Ag-substituted BN layer, along with the delocalization of spin states, renders this configuration an excellent spin filter material. Thus, these findings offer a unique opportunity for developing BN-based nanoscale devices.

  12. 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

  13. 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. PMID:26373046

  14. Non-linear conductance in quantum point contacts of noble metals

    NASA Astrophysics Data System (ADS)

    Yoshida, Makoto; Takayanagi, Kunio

    2004-03-01

    We studied the non-linear property of the electronic conductance of the noble metal nanocontact. Specimens were cleaned by Ar ion sputtering in UHV(`2 ˜10|7[Pa]) at room temperature. Current vs voltage curves (I-V curves) were obtained, while the metal contact was stretched by STM. The bias voltage at the contact was changed within 2V (using the triangle wave voltage 3`5kHz). Au, Pt, Ag and Cu quantum point contacts showed non-linear I-V curves. These metallic contacts presented the quantized conductance of the quantum unit G0(=2e2/h). I-V curves are fitted to a cubic function ( IaV+cV3 ). The value of c/a does not depend on the zero-bias conductance value, a. However, c/a values depend on metals (c/a ; Au=0.58 0.02, Ag=0.33 0.02, Cu= 0.40 0.03). The present result indicates that metals of lower resistance (higher mobility) give lower values of c/a.

  15. Effect of Mercury-Noble Metal Interactions on SRAT Processing of SB3 Simulants (U)

    SciTech Connect

    Koopman, D. C.; Baich, M. A.

    2004-12-31

    Controlling hydrogen generation below the Defense Waste Processing Facility (DWPF) safety basis constrains the range of allowable acid additions in the DWPF Chemical Processing Cell. This range is evaluated in simulant tests at the Savannah River National Laboratory (SRNL). A minimum range of allowable acid additions is needed to provide operational flexibility and to handle typical uncertainties in process and analytical measurements used to set acid additions during processing. The range of allowable acid additions is a function of the composition of the feed to DWPF. Feed changes that lead to a smaller range of allowable acid additions have the potential to impact decisions related to wash endpoint control of DWPF feed composition and to the introduction of secondary waste streams into DWPF. A limited program was initiated in SRNL in 2001 to study the issue of hydrogen generation. The program was reinitiated at the end of fiscal year 2004. The primary motivation for the study is that a real potential exists to reduce the conservatism in the range of allowable acid additions in DWPF. Increasing the allowable range of acid additions can allow decisions on the sludge wash endpoint or the introduction of secondary waste streams to DWPF to be based on other constraints such as glass properties, organic carbon in the melter off-gas, etc. The initial phase of the study consisted of a review of site reports and off-site literature related to catalytic hydrogen generation from formic acid and/or formate salts by noble metals. Many things are already known about hydrogen generation during waste processing. This phase also included the development of an experimental program to improve the understanding of hydrogen generation. This phase is being documented in WSRC-TR-2002-00034. A number of areas were identified where an improved understanding would be beneficial. A phased approach was developed for new experimental studies related to hydrogen generation. The first phase

  16. Electric dipole polarizabilities at imaginary frequencies for hydrogen, the alkali-metal, alkaline-earth, and noble gas atoms

    SciTech Connect

    Derevianko, Andrei Porsev, Sergey G. Babb, James F.

    2010-05-15

    The electric dipole polarizabilities evaluated at imaginary frequencies for hydrogen, the alkali-metal atoms, the alkaline-earth atoms, and the noble gases are tabulated along with the resulting values of the atomic static polarizabilities, the atom-surface interaction constants, and the dispersion (or van der Waals) constants for the homonuclear and the heteronuclear diatomic combinations of the atoms.

  17. Hot-Electron Intraband Luminescence from Single Hot Spots in Noble-Metal Nanoparticle Films.

    PubMed

    Haug, Tobias; Klemm, Philippe; Bange, Sebastian; Lupton, John M

    2015-08-01

    Disordered noble-metal nanoparticle films exhibit highly localized and stable nonlinear light emission from subdiffraction regions upon illumination by near-infrared femtosecond pulses. Such hot spot emission spans a continuum in the visible and near-infrared spectral range. Strong plasmonic enhancement of light-matter interaction and the resulting complexity of experimental observations have prevented the development of a universal understanding of the origin of light emission. Here, we study the dependence of emission spectra on excitation irradiance and provide the most direct evidence yet that the continuum emission observed from both silver and gold nanoparticle aggregate surfaces is caused by recombination of hot electrons within the conduction band. The electron gas in the emitting particles, which is effectively decoupled from the lattice temperature for the duration of emission, reaches temperatures of several thousand Kelvin and acts as a subdiffraction incandescent light source on subpicosecond time scales. PMID:26296132

  18. Hot-Electron Intraband Luminescence from Single Hot Spots in Noble-Metal Nanoparticle Films

    NASA Astrophysics Data System (ADS)

    Haug, Tobias; Klemm, Philippe; Bange, Sebastian; Lupton, John M.

    2015-08-01

    Disordered noble-metal nanoparticle films exhibit highly localized and stable nonlinear light emission from subdiffraction regions upon illumination by near-infrared femtosecond pulses. Such hot spot emission spans a continuum in the visible and near-infrared spectral range. Strong plasmonic enhancement of light-matter interaction and the resulting complexity of experimental observations have prevented the development of a universal understanding of the origin of light emission. Here, we study the dependence of emission spectra on excitation irradiance and provide the most direct evidence yet that the continuum emission observed from both silver and gold nanoparticle aggregate surfaces is caused by recombination of hot electrons within the conduction band. The electron gas in the emitting particles, which is effectively decoupled from the lattice temperature for the duration of emission, reaches temperatures of several thousand Kelvin and acts as a subdiffraction incandescent light source on subpicosecond time scales.

  19. Charge transfer and formation of conducting C60 monolayers at C60/noble-metal interfaces

    NASA Astrophysics Data System (ADS)

    Nouchi, Ryo; Kanno, Ikuo

    2005-05-01

    The resistance of a conducting C60 monolayer formed on a polycrystalline Ag film was found to be 0.7±0.1kΩ by in situ resistance measurements. By another series of in situ resistance measurements, the surface scattering cross sections, whose magnitude represents the relative amount of transferred charge, were evaluated as 100Å2 for C60/Au, and 150Å2 for C60/Cu and C60/Ag systems. However, comparison with previous results obtained for monolayers formed on Au and Cu films showed that the resistances of conducting C60 monolayers do not show a simple dependence on the transferred charge. Atomic force microscopy measurements revealed that the grain size of the underlying noble metals also plays an important role.

  20. A simple route to diverse noble metal-decorated iron oxide nanoparticles for catalysis

    NASA Astrophysics Data System (ADS)

    Walker, Joan M.; Zaleski, Jeffrey M.

    2016-01-01

    Developing facile synthetic routes to multifunctional nanoparticles combining the magnetic properties of iron oxides with the optical and catalytic utility of noble metal particles remains an important goal in realizing the potential of hybrid nanomaterials. To this end, we have developed a single route to noble metal-decorated magnetic nanoparticles (Fe3O4@SiO2-M M = Au, Pd, Ag, and PtAg) and characterized them by HRTEM and STEM/EDX imaging to reveal their nanometer size (16 nm Fe3O4 and 1-5 nm M seeds) and uniformity. This represents one of the few examples of genuine multifunctional particles on the nanoscale. We show that these hybrid structures have excellent catalytic activity for the reduction of 4-nitrophenol (knorm = 2 × 107 s-1 mol(Pd)-1 5 × 106 s-1 mol(Au)-1 5 × 105 s-1 mol(PtAg)-1 7 × 105 s-1 mol(Ag)-1). These rates are the highest reported for nano-sized comparables, and are competitive with mesoparticles of similar composition. Due to their magnetic response, the particles are also suitable for magnetic recovery and maintain >99% conversion for at least four cycles. Using this synthetic route, Fe3O4@SiO2-M particles show great promise for further development as a precursor to complicated anisotropic materials or for applications ranging from nanocatalysis to biomedical sensing.Developing facile synthetic routes to multifunctional nanoparticles combining the magnetic properties of iron oxides with the optical and catalytic utility of noble metal particles remains an important goal in realizing the potential of hybrid nanomaterials. To this end, we have developed a single route to noble metal-decorated magnetic nanoparticles (Fe3O4@SiO2-M M = Au, Pd, Ag, and PtAg) and characterized them by HRTEM and STEM/EDX imaging to reveal their nanometer size (16 nm Fe3O4 and 1-5 nm M seeds) and uniformity. This represents one of the few examples of genuine multifunctional particles on the nanoscale. We show that these hybrid structures have excellent catalytic

  1. Visible-light-driven hydrogen production in a dye sensitized polyoxometalate system without noble metals

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Li, Yuexiang; Peng, Shaoqin; Lai, Hua; Yi, Zhengji

    2016-05-01

    In this work, a noble-metal-free homogeneous system was constructed in one step with Keggin-type polyoxometalate (POM) SiW12O404- as a catalyst, Eosin Y as a photosensitizer, and triethanolamine (TEOA) as a sacrificial electron donor for water splitting to produce hydrogen under visible-light irradiation. A two-electron reduced heteropoly blue SiW12O406- is produced by photosensitization under visible-light irradiation. The effect of various component concentrations and POMs with different central atoms (PW12O403-, GeW12O404-, etc.) on hydrogen production was discussed. This simple system made of earth-abundant elements is expected to contribute toward the development of functional and efficient artificial photosynthetic system.

  2. Highly Sensitive and Reproducible SERS Performance from Uniform Film Assembled by Magnetic Noble Metal Composite Microspheres.

    PubMed

    Niu, Chunyu; Zou, Bingfang; Wang, Yongqiang; Cheng, Lin; Zheng, Haihong; Zhou, Shaomin

    2016-01-26

    To realize highly sensitive and reproducible SERS performance, a new route was put forward to construct uniform SERS film by using magnetic composite microspheres. In the experiment, monodisperse Fe3O4@SiO2@Ag microspheres with hierarchical surface were developed and used as building block of SERS substrate, which not only realized fast capturing analyte through dispersion and collection under external magnet but also could be built into uniform film through magnetically induced self-assembly. By using R6G as probe molecule, the as-obtained uniform film exhibited great improvement on SERS performance in both sensitivity and reproducibility when compared with nonuniform film, demonstrating the perfect integration of high sensitivity of hierarchal noble metal microspheres and high reproducibility of ordered microspheres array. Furthermore, the as-obtained product was used to detect pesticide thiram and also exhibited excellent SERS performance for trace detection. PMID:26731200

  3. Elucidation of noble metal/formic acid chemistry during DWPF feed preparation

    SciTech Connect

    Landon, L.F.

    1991-01-01

    Eleven reports are included: evaluation of noble metal compounds as catalysts for aerobic decomposition of formic acid; reaction of NaNO[sub 3] and NaNO[sub 2] with formic acid under argon; effects of Ru, Rh, Pd chlorides on formic acid decomposition in presence of IDMS (pH=11.0) sludge; effects of additives on catalysts on decomposition of formic acid to hydrogen; Rh-catalyzed decomposition of formic acid; the question of whether this decomposition can be heterogeneous catalysis; inhibition of this reaction by additives; nitrilotriacetic acid inhibitor; uses of gelatin and other water soluble polymers to control flocculation rate; comparison of catalytic activities of Rh, Ru, Pd in Purex and HM sludges; experiments on homogeneous vs heterogeneous nature of Rh catalyst. Figs, refs, tabs.

  4. Elucidation of noble metal/formic acid chemistry during DWPF feed preparation. Revision 1

    SciTech Connect

    Landon, L.F.

    1991-12-31

    Eleven reports are included: evaluation of noble metal compounds as catalysts for aerobic decomposition of formic acid; reaction of NaNO{sub 3} and NaNO{sub 2} with formic acid under argon; effects of Ru, Rh, Pd chlorides on formic acid decomposition in presence of IDMS (pH=11.0) sludge; effects of additives on catalysts on decomposition of formic acid to hydrogen; Rh-catalyzed decomposition of formic acid; the question of whether this decomposition can be heterogeneous catalysis; inhibition of this reaction by additives; nitrilotriacetic acid inhibitor; uses of gelatin and other water soluble polymers to control flocculation rate; comparison of catalytic activities of Rh, Ru, Pd in Purex and HM sludges; experiments on homogeneous vs heterogeneous nature of Rh catalyst. Figs, refs, tabs.

  5. High density decoration of noble metal nanoparticles on polydopamine-functionalized molybdenum disulphide.

    PubMed

    Hussain, Muhammad Asif; Yang, MinHo; Lee, Tae Jae; Kim, Jung Won; Choi, Bong Gill

    2015-08-01

    Here, we report a highly stable colloidal suspension of nanoparticles (i.e., Pt and Au)-deposited MoS2 sheets, in which polydopamine (PD) serves as surface functional groups. The adoption of polydopamine coating onto the MoS2 surface enables homogeneous deposition of nanoparticles in an aqueous solution. As-synthesized nanohybrids are thoroughly characterized by transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD) measurement. These intensive investigations reveal that noble metal nanocrystals are uniformly distributed on the surface of ultrathin MoS2 sheets (∼4 layers). Moreover, as-prepared Au/PD/MoS2 nanohybrids can be applied as a heterogeneous catalyst for reduction of 4-nitrophenol to 4-aminophenol, and they exhibit an excellent catalytic activity. PMID:25898116

  6. Deposition behavior of UO2 and noble-metal elements in oxide-electrowinning reprocessing

    NASA Astrophysics Data System (ADS)

    Kosugi, K.; Fukushima, M.; Myochin, M.; Mizuguchi, K.; Oomori, T.

    2005-02-01

    As a candidate process for future reprocessing technology of nuclear spent fuel, oxide-electrowinning method has been studied. In this method, the uranium is collected on the cathode in the form of UO2 by electrolysis in the molten chloride. Thereby, the noble metal (NM) elements accompany the uranium deposition, because of very close redox potential between NM elements and UO2. To clarify the electrolysis behavior of the uranium and NM elements in the low-current-density electrolysis, the laboratory scale experiments were performed under various conditions of cathode current density and solutes concentration in the chloride melt, and the separation efficiency and the morphology of the deposition were investigated. It was found that the separation of Pd from uranium was more difficult than that of Rh. The presence of U4+ greatly influenced current efficiency of the electrolysis process.

  7. Structure and optical properties of noble metal and oxide nanoparticles dispersed in various polysaccharide biopolymers

    NASA Astrophysics Data System (ADS)

    Djoković, V.; Božanic, D. K.; Vodnik, V. V.; Krsmanović, R. M.; Trandafilovic, L. V.; Dimitrijević-Branković, S.

    2011-10-01

    We present the results on the structure and the optical properties of noble metal (Ag, Au) and oxide (ZnO) nanoparticles synthesized by various methods in different polysaccharide matrices such as chitosan, glycogen, alginate and starch. The structure of the obtained nanoparticles was studied in detail with microscopic techniques (TEM, SEM), while the XPS spectroscopy was used to investigate the effects at the nanoparticle-biomolecule interfaces. The antimicrobial activity of the nanocomposite films with Ag nanoparticles was tested against the Staphylococcus aureus, Escherichia coli and Candida albicans pathogens. In addition, we will present the results on the structure and optical properties of the tryptophan amino acid functionalized silver nanoparticles dispersed in water soluble polymer matrices.

  8. Incipient hydrous oxide species as inhibitors of reduction processes at noble metal electrode

    SciTech Connect

    Burke, L.D.; O'Sullivan, J.F.; O'Dwyer, K.J.; Scannell, R.A.; Ahern, M.J.G.; McCarthy, M.M. )

    1990-08-01

    Evidence is presented to illustrate the important role of hydrous oxide in noble metal electrocatalysis. It was demonstrated, for instance, that in the case of gold in acid the onset/termination potential, under potential sweep conditions, for hydrazine oxidation and persulfate or iodate reduction occurred at the end of the hydrous oxide reduction peak (recorded for a thick film growth grown by potential multicycling); there was also a maximum in the faradaic ac response for gold in acid in the same region. Both gold and platinum were investigated in acid and base electrolytes. In some cases a range of potential, rather than a discrete value, was found to be involved, different species react with (or are inhibited by) different types (or coverages) of these submonolayer species. In some, possibly electrocatalytically nondemanding, reduction reactions the hydrous oxide seemed to have little effect.

  9. Characterization of small noble metal electrodes by voltammetry and energy dispersive x ray analysis

    NASA Astrophysics Data System (ADS)

    Strein, Timothy G.; Ewing, Andrew G.

    1993-01-01

    Construction and characterization of platinum and gold electrodes with total structural diameters of 1-2 micrometers is described. These small voltammetric probes have been constructed by direct electroreduction of noble metals onto the tips of etched carbon fiber microdisk electrodes. Voltammetry, electron microscopy, energy-dispersive x-ray analysis, and pulsed amperometric detection have been used to characterize these electrodes. Dopamine concentrations have been determined over a range of 10(exp -4) to 10(exp -3) M in the biological buffer system which contains 25 mM glucose, a compound known to adsorb strongly to electrodes. Amperometric monitoring at a constant potential with these small results in signal decay of 20% to 40% in a ten minute experiment. Pulsed amperometric detection minimizes electrode fouling, resulting in 5% or less signal decay over the same ten minute period.

  10. Synthesis and characterization of ZnO nanostructures on noble-metal coated substrates

    NASA Astrophysics Data System (ADS)

    Dikovska, A. Og.; Atanasova, G. B.; Avdeev, G. V.; Nedyalkov, N. N.

    2016-06-01

    In this work, ZnO nanostructures were fabricated on noble-metal (Au, Ag and Au-Ag alloys) coated silicon substrates by applying pulsed laser deposition. The samples were prepared at a substrate temperature of 550 °C, an oxygen pressure of 5 Pa, and a laser fluence of 2 J cm-2 - process parameters usually used for deposition of smooth and dense thin films. The metal layer's role is substantial for the preparation of nanostructures. Heating of the substrate changed the morphology of the metal layer and, subsequently, nanoparticles were formed. The use of different metal particles resulted in different morphologies and properties of the ZnO nanostructures synthesized. The morphology of the ZnO nanostructures was related to the Au-Ag alloy's content of the catalyst layer. It was found that the morphology of the ZnO nanostructures evolved from nanorods to nanobelts as the ratio of Au/Ag in the alloy catalyst was varied. The use of a small quantity of Ag in the Au-Ag catalyst (Au3Ag) layer resulted predominantly in the deposition of ZnO nanorods. A higher Ag content in the catalyst alloy (AuAg2) layer resulted in the growth of a dense structure of ZnO nanobelts.

  11. Measurement of the Inhomogeneity in Type B and Land-Jewell Noble-Metal Thermocouples

    NASA Astrophysics Data System (ADS)

    Webster, E. S.; Greenen, A.; Pearce, J.

    2016-07-01

    Inhomogeneity is the largest contributor to uncertainty in temperature measurements made with thermocouples, and the knowledge of inhomogeneity is essential if low-uncertainty measurements are required. Inhomogeneity is a particular problem for long-term applications at temperatures near or above 1500 ^{circ }hbox {C}, where pairs of alloyed noble-metal thermocouples must be used and the alloy components and potential contaminants become very mobile and cause large deviations in the Seebeck coefficient. While changes in inhomogeneity are a known and well-studied problem in noble-metal alloys at temperatures below 1100 ^{circ }hbox {C}, the effects are not well quantified at higher temperatures. This paper reports the first detailed measurements of inhomogeneity in a number of Type B and Land-Jewell thermocouples exposed to either short-term calibration up to 1600 ^{circ }hbox {C} or long-term in situ measurements for a period of approximately 3000 h at 1600 ^{circ }hbox {C}. The inhomogeneity is measured in a high-resolution scanner operating over the range from 600 ^{circ }hbox {C} to 900 ^{circ }hbox {C}. The results show that drifts of between 0.2 % and 0.6 % can be expected for reversible crystallographic and oxidation effects, whereas drift caused by irreversible contamination effects can be expected to be between 0.6 % and 1.1 %. It is also shown that the deviations in emfs caused by irreversible homogeneities in these thermocouples scale approximately linearly with temperature. This scalability allows uncertainties assessed at one temperature, to be extrapolated to other temperatures. Additionally it is shown that a preconditioning anneal at 1100 ^{circ }hbox {C} should be applied both before and after calibration to remove undesirable crystallographic and rhodium-oxidation effects.

  12. The effect of ceramic supports on partial oxidation of hydrocarbons over noble metal coated monoliths

    SciTech Connect

    Bodke, A.S.; Bharadwaj, S.S.; Schmidt, L.D.

    1998-10-01

    Support effects on the production of synthesis gas and olefins by the partial oxidation of light hydrocarbons has been examined on noble metal catalysts at contact times of {approximately}5 ms. The authors consider the effect of the following parameters on selectivities and conversions: adding a washcoat, varying pore size, ceramic support material, and loading of noble metal. In oxidation of methane on rhodium-coated monoliths, maximum hydrogen selectivity improves from 89 to 95% on the addition of a washcoat. It is also a strong function of the catalyst pore size, changing from 83% on a catalyst with 20 ppi (pores per inch) to 93% on a catalyst with 80 ppi. It varies from 86 to 91% on adding a washcoat and changes from 70 to 95% on changing the pore size. In the oxidation of ethane on platinum-coated monoliths, the addition of a washcoat reduces ethylene selectivity from 63 to 35%, while changing the pore size results in minor variations. On different ceramic supports, the ethylene selectivity varies from 60 to 64% with mullite giving the best results. The authors find that washcoat addition, decreasing pore size, and replacement of zirconia for alumina as the support material increase syngas selectivity and reduce olefin selectivity irrespective of the fuel, catalyst, or amount of diluent used. Most of these results can be explained on the basis of differences in mass transfer rates to the catalytic site between catalysts of different support geometries. It is argued that homogeneous reactions play a minor role in these short contact time processes.

  13. New technique for the determination of trace noble metal content in geological and process materials

    NASA Astrophysics Data System (ADS)

    Mitkin, V. N.; Zayakina, S. B.; Anoshin, G. N.

    2003-02-01

    A new two-step sample preparation technique is proposed for the instrumental determination of trace quantities of noble metals (NM) in refractory geological and process materials. The decomposition procedure is based on the oxidizing fluorination of samples with subsequent sulfatization (OFS) of the sample melt or cake. Fluorination of samples is accomplished using a mixture of KHF 2+KBrF 4 or KHF 2+BrF 3 depending on the ratio of sample mass to oxidizing mixture. Both cakes and melts can result using this procedure. Sulfatization of resulting fluorides is completed using concentrated sulfuric acid heated to 550 °C. Validation studies using certified geostandard reference materials (GSO VP-2, ZH-3, Matte RTP, HO-1, SARM-7) have shown that the proposed method is fast, convenient and most often produces non-hygroscopic homogeneous residues suitable for analysis by atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES). Results obtained for NM concentrations in reference materials agreed with certified concentration ranges and results obtained using other methods of analysis. The OFS procedure combined with direct current plasma d.c. plasma AES achieved the following limits of detection (LOD) for the noble metals: Ag, Au, Pd, 1-2×10 -6; Pt, 5×10 -6; and Ru, Rh, Ir, Os, 1-3×10 -7 wt.%. Using graphite furnace AAS (GFAAS) combined extraction pre-concentration the following LODs for NMs were achieved: Pt, Ru, 1×10 -6; Pd, Rh, 1×10 -7; and Au, Ag, 1-2×10 -8 wt.%. The relative standard deviation for NM determinations ( Sr) was dependent on NM concentration and sample type, but commonly was in the range of 3-15% for d.c. plasma AES and 5-30% for GFAAS.

  14. Conversion of ion-exchange resins, catalysts and sludges to glass with optional noble metal recovery using the GMODS process

    SciTech Connect

    Forsberg, C.W.; Beahm, E.C.

    1996-11-01

    Chemical processing and cleanup of waste streams (air and water) typically result in products, clean air, clean water, and concentrated hazardous residues (ion exchange resins, catalysts, sludges, etc.). Typically, these streams contain significant quantities of complex organics. For disposal, it is desirable to destroy the organics and immobilize any heavy metals or radioactive components into stable waste forms. If there are noble metals in the residues, it is desirable to recover these for reuse. The Glass Material Oxidation and Dissolution System (GMODS) is a new process that directly converts radioactive and hazardous chemical wastes to borosilicate glass. GMODS oxidizes organics with the residue converted to glass; converts metals, ceramics, and amorphous solids to glass; converts halides (eg chlorides) to borosilicate glass and a secondary sodium halide stream; and recovers noble metals. GMODS has been demonstrated on a small laboratory scale (hundreds of grams), and the equipment needed for larger masses has been identified.

  15. Magnetic properties of ZnS doped with noble metals (X = Ru, Rh, Pd, and Ag)

    NASA Astrophysics Data System (ADS)

    Tan, Zhiyun; Xiao, Wenzhi; Wang, Lingling; Yang, Youchang

    2012-12-01

    Density functional theory calculations are carried out to study the electronic structures and magnetic properties in zinc-blende structure ZnS doped with nonmagnetic noble metals (X = Ru, Rh, Pd, and Ag). Results show robust magnetic ground states for X-doped ZnS. The total magnetic moments are about 2.0, 3.0, and 2.0 μB per supercell for the Ru-, Rh-, and Pd-doped ZnS, respectively. As the atomic number of X element increases, the local magnetic moment tends toward delocalize and the hybridization between X-4d and S-3p states become stronger. This trend is strongly related to the difference in electronegativity between the substitutional X and the cation in the ZnS host. For Ag-doped ZnS, both non-spin- and spin-polarized calculations yield nearly equal total energy. The substitution of Zn in ZnS parent material by the nonmagnetic 4d transition-metals may lead to half-metallic ferromagnetism which stems from the hybridization between X-4d and S-3p states and could be attributed to a double-exchange mechanism. Curie temperature values are estimated using mean-field approximation.

  16. Fundamental study of nanostructured electro-catalysts with reduced noble metal content for PEM based water electrolysis

    NASA Astrophysics Data System (ADS)

    Kadakia, Sandeep Karan

    Identification and development of non-noble metal based electro-catalysts or electro-catalysts with significant reduction of expensive noble metal contents (E.g. IrO2, Pt) with comparable electrochemical performance as the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would constitute a major breakthrough in the generation of hydrogen by water electrolysis. Accomplishing such a system would not only result reduction of the overall capital costs of PEM based water electrolyzers, but also help attain the targeted hydrogen production cost [< $ 3.0 / gallon gasoline equivalent (gge)] comparable to conventional liquid fuels. In line with these goals, it was demonstrated that fluorine doped IrO 2 thin films and nanostructured high surface area powders display remarkably higher electrochemical activity, and comparable durability as pure IrO 2 electro-catalyst for the oxygen evolution reaction (OER) in PEM based water electrolysis. Furthermore, corrosion resistant SnO2 and NbO 2 support has been doped with F and coupled with IrO2 or RuO2 for use as an OER electro-catalyst. A solid solution of SnO 2:F or NbO2:F with only 20 - 30 mol.% IrO2 or RuO2 yielding a rutile structure in the form of thin films and bulk nanoparticles displays similar electrochemical activity and stability as pure IrO2/RuO2. This would lead to more than 70 mol.% reduction in the noble metal oxide content. Novel nanostructured ternary (Ir,Sn,Nb)O 2 thin films of different compositions have also been studied. It has been shown that (Ir0.40Sn0.30Nb 0.30)O2 shows similar electrochemical activity and enhanced chemical robustness as compared to pure IrO2. F doping of the ternary (Ir,Sn,Nb)O2 catalyst helps in further decreasing the noble metal oxide content of the catalyst. As a result, these reduced noble metal oxide catalyst systems would potentially be preferred as OER electro-catalysts for PEM electrolysis. The excellent performance of the catalysts coupled

  17. Thermalization time of noble metal nanoparticles: effects of the electron density profile

    NASA Astrophysics Data System (ADS)

    López-Bastidas, C.

    2012-02-01

    The lack of d-electron screening in the s-electron spill-out region at the surface of Ag nanoparticles increases the electron-electron interaction in this region compared to the bulk. Therefore when comparing the electron-electron interaction contribution to the thermalization time of nanoparticles of varying radius, smaller particles thermalize faster due to the increased surface to bulk ratio. One aspect which has not been addressed is the effect of the spatial distribution of charge at the surface of the nanoparticle. In this work it is shown that the size dependence of the thermalization time is very sensitive to the surface density profile. The electron thermalization time of conduction electrons in noble metal nanoparticles as a function of the radius is calculated. The sensitivity of the scattering rate to the spatial distribution of charge at the surface of the nanostructure is analyzed using several model surface profiles. The change in surface charge distribution via charging or coating of the nanospheres is shown to be a tool for control and probing of the ultra-fast electron-electron dynamics in metallic nanoparticles.

  18. Noble-transition metal nanoparticle breathing in a reactive gas atmosphere.

    PubMed

    Petkov, Valeri; Shan, Shiyao; Chupas, Peter; Yin, Jun; Yang, Lefu; Luo, Jin; Zhong, Chuan-Jian

    2013-08-21

    In situ high-energy X-ray diffraction coupled to atomic pair distribution function analysis is used to obtain fundamental insight into the effect of the reactive gas environment on the atomic-scale structure of metallic particles less than 10 nm in size. To substantiate our recent discovery we investigate a wide range of noble-transition metal nanoparticles and confirm that they expand and contract radially when treated in oxidizing (O2) and reducing (H2) atmospheres, respectively. The results are confirmed by supplementary XAFS experiments. Using computer simulations guided by the experimental diffraction data we quantify the effect in terms of both relative lattice strain and absolute atomic displacements. In particular, we show that the effect leads to a small percent of extra surface strain corresponding to several tenths of Ångström displacements of the atoms at the outmost layer of the particles. The effect then gradually decays to zero within 4 atomic layers inside the particles. We also show that, reminiscent of a breathing type structural transformation, the effect is reproducible and reversible. We argue that because of its significance and widespread occurrence the effect should be taken into account in nanoparticle research. PMID:23828235

  19. A System for High-Temperature Homogeneity Scanning of Noble-Metal Thermocouples

    NASA Astrophysics Data System (ADS)

    Webster, E.; Mason, R.; Greenen, A.; Pearce, J.

    2015-11-01

    Noble-metal thermocouples are amongst the most widely used thermocouples for high-temperature process measurement and as references. Although they are less susceptible to inhomogeneity effects than the more-common base-metal thermocouples, inhomogeneity is still the major source of uncertainty. Currently, most estimates of the uncertainty due to inhomogeneity are based on thermocouple specifications or historical performance of similar thermocouples. It is not common for the inhomogeneity to be measured directly, in part because there is no accepted method for measuring the inhomogeneities, and in part because there is no conclusive evidence linking the magnitude of inhomogeneities determined at the scanning temperature to the effects of the same inhomogeneities at other temperatures. This paper describes an inhomogeneity scanner able to be fitted to sodium heat-pipe furnaces to operate between 600°C and 1000°C. Comparison of scans made at 100°C demonstrates the scalability of some types of inhomogeneity in Type S and R thermocouples. It is concluded that for Type R and S thermocouples, a robust uncertainty assessment can be obtained from a scan made at a single temperature.

  20. Solar wind noble gases and nitrogen in metal from lunar soil 68501

    NASA Technical Reports Server (NTRS)

    Becker, Richard H.; Pepin, Robert O.

    1994-01-01

    Noble gases and N were analyzed in handpicked metal separates from lunar soil 68501 by a combination of step-wise combustions and pyrolyses. Helium and Ne were found to be unfractionated with respect to one another when normalized to solar abundances, for both the bulk sample and for all but the highest temperature steps. However, they are depleted relative to Ar, Kr and Xe by at least a factor of 5. The heavier gases exhibit mass-dependent fractionation relative to solar system abundance ratios but appear unfractionated, both in the bulk metal and in early temperature steps, when compared to relative abundances derived from lunar ilmenite 71501 by chemical etching, recently put forward as representing the abundance ratios in solar wind. Estimates of the contribution of solar energetic particles (SEP) to the originally implanted solar gases, derived from a basic interpretation of He and Ne isotopes, yield values of about 10%. Analysis of the Ar isotopes requires a minimum of 20% SEP, and Kr isotopes, using our preferred composition for solar wind Kr, yield a result that overlaps both these values. It is possible to reconcile the data from these gases if significant loss of solar wind Ar, Kr and presumably Xe has occurred relative to the SEP component, most likely by erosive processes that are mass independent, although mass-dependent losses (Ar greater than Kr greater than Xe) cannot be excluded. If such losses did occur, the SEP contribution to the solar implanted gases must have been no more than a few percent. Nitrogen is a mixture of indigenous meteoritic N, whose isotopic composition is inferred to be relatively light, and implanted solar N, which has probably undergone diffusive redistribution and fractionation. If the heavy noble gases have not undergone diffusive loss, then N/Ar in the solar wind can be inferred to be at least several times the accepted solar ratio. The solar wind N appears, even after correction for fractionation effects, to have a minimum

  1. Noble metal based plasmonic nanomaterials and their application for bio-imaging and photothermal therapy

    NASA Astrophysics Data System (ADS)

    Zhu, Dewei

    During the past two decades, researchers have gained more and more insight into the manipulation of nanomaterials to create useful technologies. Numerous classes of nanomaterials have been produced and studied based upon their intriguing chemical and physical properties and their potential applications in diverse fields, ranging from electronics to renewable energy and biomedicine. In this dissertation, we describe the synthesis and potential biomedical applications of several types of noble metal-based nanomaterials in which we control size, shape, and coupling to other materials to tune their localized surface plasmon resonance (LSPR) interaction with light. We demonstrate the application of these novel nanostructures as contrast agents for photoacoustic imaging and as photosensitizers for photothermal therapy. Chapter one first presents protocols for producing monodisperse spherical nanoparticles of gold and silver. The diameter of the nanospheres can be adjusted from less than 2 nm to greater than 10 nm by controlling the reaction conditions, including ligands that cap the nanosphere surfaces, reaction time, and reaction temperature. Next, we describe the synthesis of multi-branched Au nanocrystals with predominantly tripodal, tetrapodal and star-shaped morphologies. We demonstrate tuning of the LSPR energy in these materials by changing the branch length. In the third part of this chapter, we present a novel method for coupling heavily-doped p-type copper selenide (Cu2-xSe) NPs with Au NPs by seeded nanocrystal growth to form a new type of semiconductor-metal heterogeneous nanostructure. This new class of plasmonic nanomaterials can simultaneously exhibit two types of LSPR in a single system, producing a broad optical absorbance that is nearly flat across the near infrared (NIR) spectral region (750-1150nm), along with a small shoulder at 566 nm that originates from the Au NP. We conclude this first chapter by demonstrating the use of self-doped copper sulfide

  2. Effect of residual gases in high vacuum on the energy-level alignment at noble metal/organic interfaces

    SciTech Connect

    Helander, M. G.; Wang, Z. B.; Lu, Z. H.

    2011-10-31

    The energy-level alignment at metal/organic interfaces has traditionally been studied using ultraviolet photoelectron spectroscopy (UPS) in ultra-high vacuum (UHV). However, since most devices are fabricated in high vacuum (HV), these studies do not accurately reflect the interfaces in real devices. We demonstrate, using UPS measurements of samples prepared in HV and UHV and current-voltage measurements of devices prepared in HV, that the small amounts of residual gases that are adsorbed on the surface of clean Cu, Ag, and Au (i.e., the noble metals) in HV can significantly alter the energy-level alignment at metal/organic interfaces.

  3. Corrosion potential behavior in high-temperature water of noble metal-doped alloy coatings deposited by underwater thermal spraying

    SciTech Connect

    Kim, Y.J.; Andresen, P.L.; Gray, D.M.; Lau, Y.C.; Offer, H.P.

    1996-06-01

    Intergranular stress corrosion cracking (IGSCC) of sensitized stainless steel (SS) components in boiling water reactors (BWR) is a major concern. The SCC susceptibility of structural materials in high-temperature water is affected by the electrochemical corrosion potential (ECP). The ECP of type 304 stainless steel coated under water by hyper-velocity oxy-fuel (HVOF) and plasma-spray (PS) techniques using noble metal-doped powders was measured to evaluate the catalytic behavior in high-temperature water under various water chemistry conditions. Thermal-spray coatings of noble metal-doped powders exhibited catalytic behavior for the recombination of oxygen and hydrogen in high-temperature water, which caused ECP to decrease well below a critical value of {minus}230 mV{sub SHE} for intergranular stress corrosion cracking protection in water. This was observed in water containing various amounts of oxygen and hydrogen peroxide when stoichiometric excess hydrogen was present.

  4. Nature of graphitization and noble metal mineralization in metamorphic rocks of the northern Khanka Terrane, Primorye

    NASA Astrophysics Data System (ADS)

    Khanchuk, A. I.; Plyusnina, L. P.; Ruslan, A. V.; Likhoidov, G. G.; Barinov, N. N.

    2013-07-01

    Elevated contents of noble metals (NM) have been established in the Riphean-Cambrian graphite-bearing complexes of the northern Khanka Terrane, which metamorphosed under conditions of greenschist to granulite facies. At the previously known graphite deposits of the Turgenevo-Tamga group, NM comprise (ppm): Pt (0.04-62.13), Au (0.021-26), Ag (0.56-4.41), Pd (0.003-5.67), Ru (0.007-0.2), Rh (0.001-0.74), Ir (0.002-0.55), and Os (0.011-0.09). Analyses of graphitized rocks carried out with various methods (IMS, INAA, AAS, AES, fire assay) reveal a wide scatter of the results related to the specifics of sample preparation, in particular, due to a significant loss of NM by thermal oxidation decomposition. Analysis of a low-soluble graphite residue obtained by treatment of graphitized rocks allowed us to establish genetic links between NM mineralization and carbonic alteration of various igneous, granulite- and amphibolitefacies metamorphic rocks, which occur over a vast area. The nonuniform distribution of graphite and NM in rocks, their fine dispersivity, and compositional variability of NM indicate that their origin is related largely to endogenic processes with the participation of deep reduced fluids. In greenschist-facies rocks, fluorine, bromine, and iodine are associated both with ore minerals and graphite, providing evidence for transport of NM by halogene- and carbon-bearing fluids. The inhomogeneous distribution of metals in graphite, microglobular structure, and carbon isotopic composition are the guides for its gas-condensate crystallization. At the same time, thermal analysis and Raman spectroscopy show that graphite formed by metamorphism of carbonaceous matter contained in sedimentary rocks also occurs. It is concluded that the predominant mass of NM is of fluid-magmatic origin with the participation of exogenic and metamorphic sources of metals.

  5. Bond Strength of Resin Cements to Noble and Base Metal Alloys with Different Surface Treatments

    PubMed Central

    Raeisosadat, Farkhondeh; Ghavam, Maryam; Hasani Tabatabaei, Masoomeh; Arami, Sakineh; Sedaghati, Maedeh

    2014-01-01

    Objectives: The bond strength of resin cements to metal alloys depends on the type of the metal, conditioning methods and the adhesive resins used. The purpose of this study was to evaluate the bond strength of resin cements to base and noble metal alloys after sand blasting or application of silano-pen. Materials and Method: Cylinders of light cured Z 250 composite were cemented to “Degubond 4” (Au Pd) and “Verabond” (Ni Cr) alloys by either RelyX Unicem or Panavia F2, after sandblasting or treating the alloys with Silano-Pen. The shear bond strengths were evaluated. Data were analyzed by three-way ANOVA and t tests at a significance level of P<0.05. Results: When the alloys were treated by Silano-Pen, RelyX Unicem showed a higher bond strength for Degubond 4 (P=0.021) and Verabond (P< 0.001). No significant difference was observed in the bond strength of Panavia F2 to the alloys after either of surface treatments, Degubond 4 (P=0.291) and Verabond (P=0.899). Panavia F2 showed a higher bond strength to sandblasted Verabond compared to RelyX Unicem (P=0.003). The bond strength of RelyX Unicem was significantly higher to Silano-Pen treated Verabond (P=0.011). The bond strength of the cements to sandblasted Degubond 4 showed no significant difference (P=0.59). RelyX Unicem had a higher bond strength to Silano-Pen treated Degubond 4 (P=0.035). Conclusion: The bond strength of resin cements to Verabond alloy was significantly higher than Degubond 4. RelyX Unicem had a higher bond strength to Silano-Pen treated alloys. Surface treatments of the alloys did not affect the bond strength of Panavia F2. PMID:25628687

  6. Ab initio investigation of the oxygen reduction reaction activity on noble metal (Pt, Au, Pd), Pt3M (M = Fe, Co, Ni, Cu) and Pd3M (M = Fe, Co, Ni, Cu) alloy surfaces, for Lisbnd O2 cells

    NASA Astrophysics Data System (ADS)

    Sankarasubramanian, Shrihari; Singh, Nikhilendra; Mizuno, Fuminori; Prakash, Jai

    2016-07-01

    First principles, density functional theory (DFT) modelling of the oxygen reduction reaction (ORR) on noble metal (Pt, Au, Pd), Pt3M (M = Fe, Co, Ni, Cu) and Pd3M (M = Fe, Co, Ni, Cu) alloy surfaces, was carried out. Periodic models of close-packed (111) surfaces were constructed, their geometry was optimized and the most stable geometric surface configuration was identified. The correlation between the intermediate species binding energy and the favored reaction pathway from amongst 1e-, 2e-, and 4e- mechanisms were studied by calculating the binding energies of a 1/4 monolayer of O, O2, LiO, LiO2, Li2O2, and Li2O on various sites and orientations. The reaction free energies (ΔGrxn) were calculated and used to compute the catalytic activity of the surfaces using molecular kinetics theory. Plots of the catalytic activity vs. Oxygen binding energy (EBinding (O)) showed a typical "volcano" profile. The insights gained from this study can be used to guide the choice of cathode catalysts in Lisbnd O2 cells.

  7. Noble metal based plasmonic nanomaterials and their application for bio-imaging and photothermal therapy

    NASA Astrophysics Data System (ADS)

    Zhu, Dewei

    During the past two decades, researchers have gained more and more insight into the manipulation of nanomaterials to create useful technologies. Numerous classes of nanomaterials have been produced and studied based upon their intriguing chemical and physical properties and their potential applications in diverse fields, ranging from electronics to renewable energy and biomedicine. In this dissertation, we describe the synthesis and potential biomedical applications of several types of noble metal-based nanomaterials in which we control size, shape, and coupling to other materials to tune their localized surface plasmon resonance (LSPR) interaction with light. We demonstrate the application of these novel nanostructures as contrast agents for photoacoustic imaging and as photosensitizers for photothermal therapy. Chapter one first presents protocols for producing monodisperse spherical nanoparticles of gold and silver. The diameter of the nanospheres can be adjusted from less than 2 nm to greater than 10 nm by controlling the reaction conditions, including ligands that cap the nanosphere surfaces, reaction time, and reaction temperature. Next, we describe the synthesis of multi-branched Au nanocrystals with predominantly tripodal, tetrapodal and star-shaped morphologies. We demonstrate tuning of the LSPR energy in these materials by changing the branch length. In the third part of this chapter, we present a novel method for coupling heavily-doped p-type copper selenide (Cu2-xSe) NPs with Au NPs by seeded nanocrystal growth to form a new type of semiconductor-metal heterogeneous nanostructure. This new class of plasmonic nanomaterials can simultaneously exhibit two types of LSPR in a single system, producing a broad optical absorbance that is nearly flat across the near infrared (NIR) spectral region (750-1150nm), along with a small shoulder at 566 nm that originates from the Au NP. We conclude this first chapter by demonstrating the use of self-doped copper sulfide

  8. Quasi-noble-metal graphene quantum dots deposited stannic oxide with oxygen vacancies: Synthesis and enhanced photocatalytic properties.

    PubMed

    Quan, Bin; Liu, Wei; Liu, Yousong; Zheng, Ying; Yang, Guangcheng; Ji, Guangbin

    2016-11-01

    Quasi-noble-metal graphene quantum dots (GQDs) deposited stannic oxide (SnO2) with oxygen vacancies (VOs) were prepared by simply sintering SnO2 and citric acid (CA) together. The redox process between SnO2 and GQDs shows the formation of oxygen vacancy states below the conduction band of stannic oxide. The produced VOs obviously extend the optical absorption region of SnO2 to the visible-light region. Meanwhile, GQDs can effectively improve the charge-separation efficiency via a quasi function like noble metal and promote the visible-light response to some degree. In addition, the samples calcinated at 450°C reveals the best performance because of its relatively high concentrations of VOs. What is more, the possible degradation mechanism has been inferred as extended visible-light response as well as raised charge-separation efficiency has also been put forward. Our work may offer a simple strategy to combine the defect modulation and noble metal deposition simultaneously for efficient photocatalysis. PMID:27450887

  9. Ab initio study of the trapping of polonium on noble metals

    NASA Astrophysics Data System (ADS)

    Rijpstra, Kim; Van Yperen-De Deyne, Andy; Maugeri, Emilio Andrea; Neuhausen, Jörg; Waroquier, Michel; Van Speybroeck, Veronique; Cottenier, Stefaan

    2016-04-01

    In the future MYRRHA reactor, lead bismuth eutectic (LBE) will be used both as coolant and as spallation target. Due to the high neutron flux a small fraction of the bismuth will transmute to radiotoxic 210Po. Part of this radiotoxic element will evaporate into the gas above the coolant. Extracting it from the gas phase is necessary to ensure a safe handling of the reactor. An issue in the development of suitable filters is the lack of accurate knowledge on the chemical interaction between a candidate filter material and either elemental polonium or polonium containing molecules. Experimental work on this topic is complicated by the high radiotoxicity of polonium. Therefore, we present in this paper a first-principles study on the adsorption of polonium on noble metals as filter materials. The adsorption of monoatomic Po is considered on the candidate filter materials palladium, platinum, silver and gold. The case of the gold filter is looked upon in more detail by examining how bismuth pollution affects its capability to capture polonium and by studying the adsorption of the heavy diatomic molecules Po2, PoBi and PoPb on this gold filter.

  10. Fabrication of Mo pyramidal-shape single atom tips covered by a noble metal

    NASA Astrophysics Data System (ADS)

    Lin, Rung-Jiun; Chen, Yi-Ju; Chen, Hsiao-Chi; Fu, Tsu-Yi

    2014-08-01

    The effect of annealing temperature on the faceting phenomena has been studied for pure molybdenum (Mo) and Mo tips covered with palladium (Pd), platinum (Pt), rhodium (Rh), or iridium (Ir) by field ion microscopy (FIM). For these Mo samples, three {2 1 1} facets were found to expand to {1 1 1} facets and form pyramidal structures after annealing at the temperature of 1100-1300 K. The pyramidal single atom tips (SATs) were formed on Pd-, Pt- and Rh-covered Mo tips. Two types of pyramidal structure, stacked by either 1, 3, 10 or 1, 6, 15 atoms for the top three layers were found. However, no SATs were found on pure Mo and Ir-covered tips. This indicates that noble metal adsorption, which can increase the difference of surface-free-energy anisotropy, indeed benefits the formation of SATs on Mo systems. Additionally, an SAT cannot be obtained for the Ir-covered Mo systems, because Ir is easily alloyed with Mo.

  11. Spin-Orbit Effects in the Quasiparticle Bandstructure of Noble Metals

    NASA Astrophysics Data System (ADS)

    Mustafa, Jamal; Louie, Steven

    2014-03-01

    Applications of the GW approximation to the electron self-energy have proven quite successful for calculating the quasiparticle properties of materials. We find that for the noble metals, in line with previous work in such calculations, the semicore states need to be taken into account. We show that, with these semicore states, a large cutoff must be used to describe the screening and, in turn, a large number of empty states must be included. Taking all of this into account, and carefully checking convergence, shows G0W0 can describe experimental results from angle-resolved photoemission spectroscopy quite well when the effects of spin-orbit coupling is also included. We compare our results to recent self-consistent GW calculations on gold. This work was supported by NSF grant No. DMR10-1006184 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at LBNL's NERSC facility.

  12. Structural Stability and Performance of Noble Metal-Free SnO2-Based Gas Sensors

    PubMed Central

    Tricoli, Antonio

    2012-01-01

    The structural stability of pure SnO2 nanoparticles and highly sensitive SnO2-SiO2 nanocomposites (0–15 SiO2 wt%) has been investigated for conditions relevant to their utilization as chemoresistive gas sensors. Thermal stabilization by SiO2 co-synthesis has been investigated at up to 600 °C determining regimes of crystal size stability as a function of SiO2-content. For operation up to 400 °C, thermally stable crystal sizes of ca. 24 and 11 nm were identified for SnO2 nanoparticles and 1.4 wt% SnO2-SiO2 nanocomposites, respectively. The effect of crystal growth during operation (TO = 320 °C) on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms. In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration. Furthermore, the effect of SiO2 cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO2-based gas sensors was assessed. PMID:25585712

  13. Sedimentation behavior of noble metal particles in simulated high-level waste borosilicate glasses

    SciTech Connect

    Nakajima, M.; Ohyama, K.; Morikawa, Y.; Miyauchi, A.; Yamashita, T.; Komamine, S.; Ochi, E.

    2013-07-01

    Solubility of noble metal elements (NME) in the melted borosilicate glass is much smaller than its normal concentration of the high level liquid waste. Thus most of NME show small particles in the melted glass and tend to sediment in the bottom region of the vitrification melter due to their higher density than that of glass. Experiments of the sedimentation of NME particles in the melted glass were carried out under static condition. Three conditions of initial NME concentration (1.1, 3.0, 6.1 wt % with an equivalent for each oxide) in the simulated glass were set and held at 1100 C. degrees up to 2880 hours. The specimen with 1.1 wt % initial NME concentration indicated zone settling, and the settling rate of the interface is constant: 2.4 mm/h. This sedimentation behavior is the type of rapid settling. Following the rapid settling, the settling rate goes gradually slower; this is the type of compressive settling. The specimens with 3.0 wt % and 6.1 wt % initial NME concentration showed compression settling from the beginning. From the settling curve of the interface, the maximum concentration of NME in sediment was estimated to be around 23- 26 wt %. Growth of NME particles was observed by holding at 1100 C. degrees for up to 2880 hours. The viscosity becomes higher as NME concentration increases and the dependence on shear rate becomes simultaneously stronger. The effect of the particle growth to viscosity appears to be not significant.

  14. Catalytic conversion of CHx and CO2 on non-noble metallic impurities in graphene.

    PubMed

    Tang, Yanan; Liu, Zhiyong; Chen, Weiguang; Ma, Dongwei; Chang, Shanshan; Dai, Xianqi

    2016-06-22

    Density functional theory (DFT) was applied to investigate the geometric, electronic, and magnetic properties of CHx (x = 0, 1, 2, 3, 4) species on non-noble metal embedded graphene (NNM-graphene). It was found that the different stabilities of CHx species can modify the electronic structures and magnetic properties of NNM-graphene systems. The carbonaceous reforming reactions include conversion of CHx (x = 0, 1, 2 and 3) species by hydrogen molecules (H2) to form CHx+2 species or oxidation of C atoms by oxygen molecules to form CO2. In the hydrogenation reactions, deposited C atoms can be converted easily into CHx species overcoming small energy barriers. In comparison, coadsorption of C and O2 to generate CO2 encounters relatively larger energy barriers on the NNM-graphene. Hence, the coadsorption of CHx and H2 as the starting state is energetically more favorable and formation of CHx species can reduce amounts of carbon deposition. Among the NNM-graphene substrates studied, moderate adsorption energies and low reaction barriers of CHx species are more likely to occur on the Co-graphene surface, thus the hydrogenation reaction is able to inhibit carbon deposition on the NNM-graphene surface while maintaining high activity. PMID:27296782

  15. Hydrocracking naphthas using mildly steamed, noble metal-containing zeolite beta

    SciTech Connect

    Hickey, K.J. Jr.; Morrison, R.A.

    1989-03-14

    A method is described for hydrocracking a naphtha which comprises contacting the naphtha with a noble metal-containing zeolite beta naphtha hydrocracking catalyst at a pressure of about 0 to about 2000 psig, a temperature of about 400/sup 0/ to about 650/sup 0/F, a hydrogen or hydrocarbon molar ratio of about 0.1 to 1 to about 15 to 1 and a weight hourly space velocity of about 0.5 to about 20. Naphtha hydrocracking activity of the catalyst is enhanced by mild steaming of the zeolite beta catalyst prior to the contacting, the mild steaming being accomplished by steaming the zeolite catalyst in its fresh state under controlled conditions of temperature, time and steam partial pressure so as to initially increase the alpha activity of the catalyst and produce a steamed catalyst having a peak alpha activity, and subsequently reduce the alpha activity from the peak alpha activity to an alpha activity substantially the same as the alpha activity of the fresh catalyst and no more than 25% below the initial alpha activity of the fresh catalyst.

  16. Enhancing spectral shifts of plasmon-coupled noble metal nanoparticles for sensing applications.

    PubMed

    Göeken, Kristian L; Subramaniam, Vinod; Gill, Ron

    2015-01-01

    Noble metal nanoparticles possess very large scattering cross-sections, which make them useful as tags in biosensing assays with the potential to detect even single binding events. In this study, we investigated the effects of nanoparticle size on the shift in the light scattering spectrum following formation of Au-Au, Ag-Ag or Ag-Au dimers using FDTD simulations. We discuss the use of a color camera to detect these spectral changes for application in a target-induced dimerization sensing assay. Dimerization of Au nanoparticles induced a larger shift in color compared to Ag nanoparticles. Heterodimers composed of 60 nm Ag and 40 nm Au demonstrated an even larger spectral shift and color response compared to the best homodimer pair (80-40 nm Au). The increased spectral shift of the Ag-Au heterodimer was subsequently observed experimentally for the DNA-induced dimerization of nanoparticles, showing that careful selection of nanoparticle size and composition can significantly enhance recognition of nanoparticle dimerization events for use in (color) sensing assays. PMID:25406679

  17. A noble-metal-free system for photocatalytic hydrogen production from water.

    PubMed

    Mejía, Esteban; Luo, Shu-Ping; Karnahl, Michael; Friedrich, Aleksej; Tschierlei, Stefanie; Surkus, Annette-Enrica; Junge, Henrik; Gladiali, Serafino; Lochbrunner, Stefan; Beller, Matthias

    2013-11-18

    A series of heteroleptic copper(I) complexes with bidentate PP and NN chelate ligands was prepared and successfully applied as photosensitizers in the light-driven production of hydrogen, by using [Fe3(CO)12] as a water-reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble-metal-free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton-reduction systems. Within these experiments, considerably long excited-state lifetimes of up to 54 μs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway. PMID:24123302

  18. Recent Advances in the Field of Bionanotechnology: An Insight into Optoelectric Bacteriorhodopsin, Quantum Dots, and Noble Metal Nanoclusters

    PubMed Central

    Knoblauch, Christopher; Griep, Mark; Friedrich, Craig

    2014-01-01

    Molecular sensors and molecular electronics are a major component of a recent research area known as bionanotechnology, which merges biology with nanotechnology. This new class of biosensors and bioelectronics has been a subject of intense research over the past decade and has found application in a wide variety of fields. The unique characteristics of these biomolecular transduction systems has been utilized in applications ranging from solar cells and single-electron transistors (SETs) to fluorescent sensors capable of sensitive and selective detection of a wide variety of targets, both organic and inorganic. This review will discuss three major systems in the area of molecular sensors and electronics and their application in unique technological innovations. Firstly, the synthesis of optoelectric bacteriorhodopsin (bR) and its application in the field of molecular sensors and electronics will be discussed. Next, this article will discuss recent advances in the synthesis and application of semiconductor quantum dots (QDs). Finally, this article will conclude with a review of the new and exciting field of noble metal nanoclusters and their application in the creation of a new class of fluorescent sensors. PMID:25340449

  19. Graphene-based non-noble-metal Co/N/C catalyst for oxygen reduction reaction in alkaline solution

    NASA Astrophysics Data System (ADS)

    Niu, Kexing; Yang, Baoping; Cui, Jinfeng; Jin, Jutao; Fu, Xiaogang; Zhao, Qiuping; Zhang, Junyan

    2013-12-01

    This study develops a promising catalyst for oxygen reduction reaction (ORR) via a simple two-step heat treatment of a mixture of cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O), polyethyleneimine (PEI), and graphene oxide (GO), firstly in argon atmosphere and then in ammonia atmosphere. X-ray photoemission spectroscopy (XPS) result reveals that the catalyst has pyridinic N-dominant (46% atomic concentration among all N components) on the surface. The kinetics measurement of the catalyst in 0.1 M KOH solution using a rotating disk electrode (RDE) reveals that the catalyst (Co/N/rGO(NH3)) has high activity. Furthermore, the number of electrons exchanged during the ORR with the catalyst is determined to be ˜3.9, suggesting that the ORR is dominated by a 4e- reduction of O2 to H2O. The catalyst has good stability, and its performance is superior to the commercial Pt/C(20%) catalyst in alkaline condition, making the material a promising substitute to noble metal ORR electrocatalyst on the cathode side of fuel cells.

  20. Rational design of binder-free noble metal/metal oxide arrays with nanocauliflower structure for wide linear range nonenzymatic glucose detection

    PubMed Central

    Li, Zhenzhen; Xin, Yanmei; Zhang, Zhonghai; Wu, Hongjun; Wang, Peng

    2015-01-01

    One-dimensional nanocomposites of metal-oxide and noble metal were expected to present superior performance for nonenzymatic glucose detection due to its good conductivity and high catalytic activity inherited from noble metal and metal oxide respectively. As a proof of concept, we synthesized gold and copper oxide (Au/CuO) composite with unique one-dimensional nanocauliflowers structure. Due to the nature of the synthesis method, no any foreign binder was needed in keeping either Au or CuO in place. To the best of our knowledge, this is the first attempt in combining metal oxide and noble metal in a binder-free style for fabricating nonenzymatic glucose sensor. The Au/CuO nanocauliflowers with large electrochemical active surface and high electrolyte contact area would promise a wide linear range and high sensitive detection of glucose with good stability and reproducibility due to its good electrical conductivity of Au and high electrocatalytic activity of CuO. PMID:26068705

  1. Rational design of binder-free noble metal/metal oxide arrays with nanocauliflower structure for wide linear range nonenzymatic glucose detection.

    PubMed

    Li, Zhenzhen; Xin, Yanmei; Zhang, Zhonghai; Wu, Hongjun; Wang, Peng

    2015-01-01

    One-dimensional nanocomposites of metal-oxide and noble metal were expected to present superior performance for nonenzymatic glucose detection due to its good conductivity and high catalytic activity inherited from noble metal and metal oxide respectively. As a proof of concept, we synthesized gold and copper oxide (Au/CuO) composite with unique one-dimensional nanocauliflowers structure. Due to the nature of the synthesis method, no any foreign binder was needed in keeping either Au or CuO in place. To the best of our knowledge, this is the first attempt in combining metal oxide and noble metal in a binder-free style for fabricating nonenzymatic glucose sensor. The Au/CuO nanocauliflowers with large electrochemical active surface and high electrolyte contact area would promise a wide linear range and high sensitive detection of glucose with good stability and reproducibility due to its good electrical conductivity of Au and high electrocatalytic activity of CuO. PMID:26068705

  2. Non-noble electrocatalysts for alkaline fuel cells

    NASA Technical Reports Server (NTRS)

    Sarangapani, S.; Lessner, P.; Manoukian, M.; Giner, J.

    1989-01-01

    Carbons activated with macrocyclics have attracted increasing attention as alternative electrocatalysts for oxygen reduction. Initial activity of these catalysts is good, but performance declines rapidly. Pyrolyzing the macrocyclic on the carbon support leads to enhanced stability and the catalysts retain good activity. The approach described is designed to develop bulk doped catalysts with similar structures to pyrolyzed macrocyclic catalysts. The transition metal and coordinated ligands are dispersed throughout the bulk of the conductive carbon skeleton. Two approaches to realizing this concept are being pursued, both involving the doping of carbon precursors. In one approach, the precursor is a solid phase carbon-containing ion-exchange resin. The precursor is doped with a transition metal and/or nitrogen, and the resulting mixture is pyrolyzed. In the other approach, the precursor is a gas-phase hydrocarbon. This is introduced with a transition metal species and nitrogen species into a reactor and pyrolyzed. Several studies have been conducted to determine if there is a synergistic effect between the transition metal and nitrogen and the effect of different methods of introducing the metal-nitrogen (M-N) coordination on performance. One approach was to introduce the metal and nitrogen separately, for example, by sequentially doping FeCl3 and NH4OH into the resin. Catalysts were prepared from an undoped ion-exchange resin, a resin doped only with N, a resin doped only with Fe, and a resin doped with both Fe and N. Introduction of nitrogen alone has no beneficial effect on the performance of the catalysts. The introduction of the Fe alone significantly improves the performance in both the high and low current density regions. When both Fe and N are introduced, the performance at lower current densities (catalytic activity) is increased beyond that of the Fe-doped carbon, but the performance at higher current densities is similar to the carbon containing only Fe

  3. Noble metal nanoparticle-induced oxidative stress modulates tumor associated macrophages (TAMs) from an M2 to M1 phenotype: An in vitro approach.

    PubMed

    Pal, Ramkrishna; Chakraborty, Biswajit; Nath, Anupam; Singh, Leichombam Mohindro; Ali, Mohammed; Rahman, Dewan Shahidur; Ghosh, Sujit Kumar; Basu, Abhishek; Bhattacharya, Sudin; Baral, Rathindranath; Sengupta, Mahuya

    2016-09-01

    Diagnosis of cancer and photothermal therapy using optoelectronic properties of noble metal nanoparticles (NPs) has established a new therapeutic approach for treating cancer. Here we address the intrinsic properties of noble metal NPs (gold and silver) as well as the mechanism of their potential antitumor activity. For this, the study addresses the functional characterization of tumor associated macrophages (TAMs) isolated from murine fibrosarcoma induced by a chemical carcinogen, 3-methylcholanthrene (MCA). We have previously shown antitumor activity of both gold nanoparticles (AuNPs) and silver nanoparticle (AgNPs) in vivo in a murine fibrosarcoma model. In the present study, it has been seen that AuNPs and AgNPs modulate the reactive oxygen species (ROS) and reactive nitrogen species (RNS) production, suppressing the antioxidant system of cells (TAMs). Moreover, the antioxidant-mimetic action of these NPs maintain the ROS and RNS levels in TAMs which act as second messengers to activate the proinflammatory signaling cascades. Thus, while there is a downregulation of tumor necrosis factor-α (TNF-α) and Interleukin-10 (IL-10) in the TAMs, the proinflammatory cytokine Interleukin-12 (IL-12) is upregulated resulting in a polarization of TAMs from M2 (anti-inflammatory) to M1 (pro-inflammatory) nature. PMID:27344639

  4. Structure Determination of Noble Metal Clusters by Trapped Ion Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Schooss, Detlef

    2006-03-01

    The structures of noble metal cluster ions have been studied by the recently developed technique of trapped ion electron diffraction (TIED)^1. In brief, cluster ions are generated by a magnetron sputter source and injected into a cooled (95 K) quadrupole ion trap. After mass selection and thermalization, the trapped ions are irradiated with a 40 keV electron beam. The resulting diffraction pattern is integrated with a CCD detector. The assignment of the structural motif is done via a comparison of the experimental and simulated scattering function, calculated from density functional theory structure calculations. The structures of mass selected silver cluster cations Ag19^+, Ag38^+, Ag55^+, Ag59^+, Ag75^+ and Ag79^+ have been investigated^2. The resulting experimental data are best described by structures based on the icosahedral motif, while closed packed structures could be ruled out. Additionally, we present a comparison of the structures of Cu20^+/-, Ag20^+/- and Au20^+/-. Our findings show unambiguously that the structure of Au20^- is predominantly given by a tetrahedron in agreement with the results of L.S. Wang et al.^3 In contrast, structures of Ag20^- and Cu20^- based on the icosahedral motif agree best with the experimental data. Small structural differences between the charge states are observed. The possibilities and limitations of the TIED method are discussed. (1) M. Maier-Borst, D. B. Cameron, M. Rokni, and J. H. Parks, Physical Review A 59 (5), R3162 (1999); S. Krückeberg, D. Schooss, M. Maier-Borst, and J. H. Parks, Physical Review Letters 85 (21), 4494 (2000). (2) D. Schooss, M.N. Blom, B. v. Issendorff, J. H. Parks, and M.M. Kappes, Nano Letters 5 (10), 1972 (2005). (3) J. Li, X. Li, H. J. Zhai, and L. S. Wang, Science 299, 864 (2003)

  5. Noble metals (Ag, Au) nanoparticles addition effects on superconducting properties of CuTl-1223 phase

    NASA Astrophysics Data System (ADS)

    Jabbar, Abdul; Mumtaz, Muhammad; Nadeem, Kashif

    2015-03-01

    Low anisotropic (Cu0.5Tl0.5) Ba2Ca2Cu3O10 - δ (CuTl-1223) high temperature superconducting phase was synthesized by solid-state reaction, silver (Ag) nanoparticles were prepared by sol-gel method and gold (Au) nanoparticles were extracted from colloidal solution. We added Ag and Au nanoparticles in CuTl-1223 matrix separately with same concentration during the final sintering process to get (M)x/CuTl-1223; M = Ag nanoparticles or Au nanoparticles (x = 0 and 1.0 wt.%) nano-superconductor composites. We investigated and compared the effects of these noble metals nanoparticles addition on structural, morphological and superconducting transport properties of CuTl-1223 phase. The crystal structure of the host CuTl-1223 superconducting phase was not affected significantly after the addition of these nanoparticles. The enhancement of superconducting properties was observed after the addition of both Ag and Au nanoparticles, which is most probably due to improved inter-grains weak-links and reduction of defects such as oxygen deficiencies, etc. The reduction of normal state room temperature resistivity is the finger prints of the reduction of barriers and facilitation to the carriers transport across the inter-crystallite sites due to improved inter-grains weak-links. The greater improvement of superconducting properties in Ag nanoparticles added samples is attributed to the higher conductivity of silver as compared to gold, which also suits for practical applications due to lower cost and easy synthesis of Ag nanoparticles as compared to Au nanoparticles.

  6. Enantioselectivity of (321) chiral noble metal surfaces: A density functional theory study of lactate adsorption

    SciTech Connect

    Franke, J.-H.; Kosov, D. S.

    2013-12-14

    The adsorption of the chiral molecule lactate on the intrinsically chiral noble metal surfaces Pt(321), Au(321), and Ag(321) is studied by density functional theory calculations. We use the oPBE-vdW functional which includes van der Waals forces on an ab initio level. It is shown that the molecule binds via its carboxyl and the hydroxyl oxygen atoms to the surface. The binding energy is larger on Pt(321) and Ag(321) than on Au(321). An analysis of the contributions to the binding energy of the different molecular functional groups reveals that the deprotonated carboxyl group contributes most to the binding energy, with a much smaller contribution of the hydroxyl group. The Pt(321) surface shows considerable enantioselectivity of 0.06 eV. On Au(321) and Ag(321) it is much smaller if not vanishing. The chiral selectivity of the Pt(321) surface can be explained by two factors. First, it derives from the difference in van der Waals attraction of L- and D-lactate to the surface that we trace to differences in the binding energy of the methyl group. Second, the multi-point binding pattern for lactate on the Pt(321) surface is sterically more sensitive to surface chirality and also leads to large binding energy contributions of the hydroxyl group. We also calculate the charge transfer to the molecule and the work function to gauge changes in electronic structure of the adsorbed molecule. The work function is lowered by 0.8 eV on Pt(321) with much smaller changes on Au(321) and Ag(321)

  7. Enantioselectivity of (321) chiral noble metal surfaces: a density functional theory study of lactate adsorption.

    PubMed

    Franke, J-H; Kosov, D S

    2013-12-14

    The adsorption of the chiral molecule lactate on the intrinsically chiral noble metal surfaces Pt(321), Au(321), and Ag(321) is studied by density functional theory calculations. We use the oPBE-vdW functional which includes van der Waals forces on an ab initio level. It is shown that the molecule binds via its carboxyl and the hydroxyl oxygen atoms to the surface. The binding energy is larger on Pt(321) and Ag(321) than on Au(321). An analysis of the contributions to the binding energy of the different molecular functional groups reveals that the deprotonated carboxyl group contributes most to the binding energy, with a much smaller contribution of the hydroxyl group. The Pt(321) surface shows considerable enantioselectivity of 0.06 eV. On Au(321) and Ag(321) it is much smaller if not vanishing. The chiral selectivity of the Pt(321) surface can be explained by two factors. First, it derives from the difference in van der Waals attraction of L- and D-lactate to the surface that we trace to differences in the binding energy of the methyl group. Second, the multi-point binding pattern for lactate on the Pt(321) surface is sterically more sensitive to surface chirality and also leads to large binding energy contributions of the hydroxyl group. We also calculate the charge transfer to the molecule and the work function to gauge changes in electronic structure of the adsorbed molecule. The work function is lowered by 0.8 eV on Pt(321) with much smaller changes on Au(321) and Ag(321). PMID:24329084

  8. Synthesis, characterization and application of noble-metal nanoparticles and their Langmuir films

    NASA Astrophysics Data System (ADS)

    Sun, Yuan

    Noble-metal nanoparticles and their Langmuir films have attracted remarkable research interest due to their unique properties and potential applications in catalysis, hydrogen storage materials, and optical, magnetic and electronic devices. The properties of nanoparticles are affected not only by the size, but also by the shape. In this dissertation, highly crystalline rectangular palladium nanoparticles have been successfully synthesized via the reduction of K2PdCl 4 by ascorbic acid in the presence of a surfactant cetyltrimethylammonium bromide under room temperature. Trisodium citrate is a key factor for high yield of nanocubes and nanorods. The average length and aspect ratio of the nanorods can be tuned by varying the concentration of trisodium citrate. These rectangular nanoparticles were stable for months as colloids. However, after being exposed to air for about 100 days, the dry nanoparticles on TEM grids were oxidized to form shells of 1.6--3.8 nm thick covering the nanoparticle surfaces. This procedure is conducted under room temperature and requires no seed-mediated growth or nanoporous rigid template so that it is easier and more practical for large-scale synthesis. Alkanethiolate palladium nanoparticles can be synthesized by two routes: a one-phase method and a two-phase method. In order to understand the electronic and chemical properties of dodecanethiolate palladium nanoparticles, a systematic comparison between the particles obtained by these two synthetic techniques was conducted. From transmission electron microscopy (TEM) we determined that the particle sizes were 46 +/- 10 A and 20 +/- 5 A for the 1- and 2-phase particles, respectively. Electron diffraction confirmed that their structure was face-centered cubic (FCC). High-resolution TEM (HRTEM) showed that the 1-phase particles had an ordered core surrounded by a disordered shell structure while the 2-phase particles appeared to be crystalline throughout. The particles were also analyzed with

  9. Strategies and applications of combinatorial methods and high throughput screening to the discovery of non-noble metal catalyst

    NASA Astrophysics Data System (ADS)

    Bricker, Maureen L.; Sachtler, J. W. Adriaan; Gillespie, Ralph D.; McGonegal, Charles P.; Vega, Honorio; Bem, Dave S.; Holmgren, Jennifer S.

    2004-02-01

    The integrated End-to-End™ combinatorial process for catalyst preparation and screening, with emphasis on its capability to vary both process and compositional parameters will be demonstrated. Additionally, each step of the combinatorial screening process has been validated against results from traditional screening methods. The greatest challenge of all has been the adherence to the core concepts of the combinatorial approach. Catalyst libraries have been made and tested for naphthalene dehydrogenation chemistry. The preparation of these libraries has included the application of high throughput techniques for: metal impregnation; catalyst finishing; catalyst screening. The catalyst screening system has been used to find a non-noble metal catalyst system that can replace Pt in dehydrogenation applications in the petroleum industry. A proprietary catalytic composition was developed for the dehydrogenation of methylcyclohexane (MCH) to toluene starting with four non-noble metals of different proportions and four different supports (alumina, titania, zirconia and silica) prepared in different ways and applying a statistical design of experiments. These data demonstrate that all steps of catalyst preparation and screening are performed in a rapid, useful, high throughput manner. Data will be presented from the catalyst screening efforts will demonstrate that optimized metal composition is dependent on the support type.

  10. Localized surface plasmon mediated photochemistry and charge transfer in noble metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Wu, Xiaomu

    This thesis addresses the fundamental physical and chemical processes of localized surface plasmon mediated photochemistry and charge transfer in noble metal nanoparticles. The first chapter introduces the theory and application of surface plasmons. It includes a discussion of propagating and localized surface plasmons, plasmon decay dynamics, factors governing plasmon excitation of metal nanoparticles, near-field enhanced photochemistry and plasmon mediated charge transfer. The second chapter presents a photovoltage mechanism for room light conversion of citrate stabilized silver nanocrystal seeds to large nanoprisms. The process relies on the excitation of silver surface plasmons and requires citrate and oxygen. The transformation rate is first-order in seed concentration. The mechanism involves oxidative etching of seeds and subsequent photoreduction of aqueous silver ions preferentially onto silver prisms that have a cathodic photovoltage resulting from plasmon hot hole citrate photo- oxidation. This idea also explains several previously reported experiments including single and dual wavelength irradiation and the core/shell synthesis of silver layers on gold seeds. The third chapter explores the photo-driven growth of citrate stabilized silver nanoparticles. Under plasmon excitation, particles that absorb/scatter light weakly reduce dioxygen and lose silver ions, whereas particles with resonant plasmons build up a high photovoltage due to citrate photo-oxidation and reduce silver ions. Overall, growth is favored for on-resonant particles. Compared to the borohydride reduction method, more monodisperse, round 10-20 nm diameter silver nanoparticles are obtained by plasmon mediated approaches. Adding a trace amount of potassium chloride can speed up the growth and inhibit the formation of Ag aggregates. The fourth chapter investigates the plasmon induced photochemical charge separation in gold nanoparticles on a transparent indium tin oxide (ITO) substrate