WorldWideScience

Sample records for cell noble metal

  1. Non-noble metal fuel cell catalysts

    CERN Document Server

    Chen, Zhongwei; Zhang, Jiujun

    2014-01-01

    Written and edited by a group of top scientists and engineers in the field of fuel cell catalysts from both industry and academia, this book provides a complete overview of this hot topic. It covers the synthesis, characterization, activity validation and modeling of different non-noble metal and metalfree electrocatalysts for the reduction of oxygen, as well as their integration into acid or alkaline polymer exchange membrane (PEM) fuel cells and their performance validation, while also discussing those factors that will drive fuel cell commercialization. With its well-structured app

  2. Studies on PEM fuel cell noble metal catalyst dissolution

    DEFF Research Database (Denmark)

    Andersen, S. M.; Grahl-Madsen, L.; Skou, E. M.

    2011-01-01

    A combination of electrochemical, spectroscopic and gravimetric methods was carried out on Proton Exchange Membrane (PEM) fuel cell electrodes with the focus on platinum and ruthenium catalysts dissolution, and the membrane degradation. In cyclic voltammetry (CV) experiments, the noble metals were...... catalyst. Other factors like medium acidity, chloride content and oxygen partial pressure all turned out to influence the noble metal dissolution. The degradation of the polyfluorinated sulfonic acid membrane electrolyte was also found to be an important source of increased acidity in the Three......-Phase-Boundary (TPB), and consequently the dissolution of the noble metal catalysts. (C) 2010 Elsevier B.V. All rights reserved....

  3. Studies on PEM Fuel Cell Noble Metal Catalyst Dissolution

    DEFF Research Database (Denmark)

    Ma, Shuang; Skou, Eivind Morten

    Incredibly vast advance has been achieved in fuel cell technology regarding to catalyst efficiency, improvement of electrolyte conductivity and optimization of cell system. With breathtakingly accelerating progress, Proton Exchange Membrane Fuel Cells (PEMFC) is the most promising and most widely....... Membrane Electrode Assembly (MEA) is commonly considered as the heart of cell system [2]. Degradation of the noble metal catalysts in MEAs especially Three-Phase-Boundary (TPB) is a key factor directly influencing fuel cell durability. In this work, electrochemical degradation of Pt and Pt/Ru alloy were...

  4. Noble-Metal Chalcogenide Nanotubes

    Directory of Open Access Journals (Sweden)

    Nourdine Zibouche

    2014-10-01

    Full Text Available We explore the stability and the electronic properties of hypothetical noble-metal chalcogenide nanotubes PtS2, PtSe2, PdS2 and PdSe2 by means of density functional theory calculations. Our findings show that the strain energy decreases inverse quadratically with the tube diameter, as is typical for other nanotubes. Moreover, the strain energy is independent of the tube chirality and converges towards the same value for large diameters. The band-structure calculations show that all noble-metal chalcogenide nanotubes are indirect band gap semiconductors. The corresponding band gaps increase with the nanotube diameter rapidly approaching the respective pristine 2D monolayer limit.

  5. Biomimetic Synthesis of Noble Metal Nanoparticles and Their Applications as Electro-catalysts in Fuel Cells

    OpenAIRE

    Li, Yujing

    2012-01-01

    Today, proton electrolyte membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) are attractive power conversion devices that generate fairly low or even no pollution, and considered to be potential to replace conventional fossil fuel based power sources on automobiles. The operation and performance of PEMFC and DMFC depend largely on electro-catalysts positioned between the electrode and the membranes. The most commonly used electro-catalysts for PEMFC and DMFC are Pt-based noble me...

  6. Synthesis and applications of graphene-based noble metal nanostructures

    Directory of Open Access Journals (Sweden)

    Chaoliang Tan

    2013-01-01

    Full Text Available Graphene and its derivatives, such as graphene oxide (GO and reduced graphene oxide (rGO, are ideal platforms for constructing graphene-based nanostructures for various applications. Hybrid materials of noble metal nanocrystal-decorated GO or rGO with novel or enhanced properties and functions have been extensively explored recently. In this mini-review, various approaches for synthesis of graphene-templated noble metal nanomaterials are discussed. In particular, those novel synthetic strategies and interesting architectures are highlighted. Moreover, the applications of graphene-based noble metal nanostructures in fuel cells, electrochemical sensors, and surface enhanced Raman scattering (SERS will be briefly introduced.

  7. Titanium-Niobium Oxides as Non-Noble Metal Cathodes for Polymer Electrolyte Fuel Cells

    Directory of Open Access Journals (Sweden)

    Akimitsu Ishihara

    2015-07-01

    Full Text Available In order to develop noble-metal- and carbon-free cathodes, titanium-niobium oxides were prepared as active materials for oxide-based cathodes and the factors affecting the oxygen reduction reaction (ORR activity were evaluated. The high concentration sol-gel method was employed to prepare the precursor. Heat treatment in Ar containing 4% H2 at 700–900 °C was effective for conferring ORR activity to the oxide. Notably, the onset potential for the ORR of the catalyst prepared at 700 °C was approximately 1.0 V vs. RHE, resulting in high quality active sites for the ORR. X-ray (diffraction and photoelectron spectroscopic analyses and ionization potential measurements suggested that localized electronic energy levels were produced via heat treatment under reductive atmosphere. Adsorption of oxygen molecules on the oxide may be governed by the localized electronic energy levels produced by the valence changes induced by substitutional metal ions and/or oxygen vacancies.

  8. Incorporation of noble metals into aerogels

    Science.gov (United States)

    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.

  9. 21 CFR 872.3060 - Noble metal alloy.

    Science.gov (United States)

    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,...

  10. Noble metal superparticles and methods of preparation thereof

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Noble Metal Nanoparticles Applications in Cancer

    Directory of Open Access Journals (Sweden)

    João Conde

    2012-01-01

    Full Text Available 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.

  12. Noble metal nanowires incorporated Nafion {sup registered} membranes for reduction of methanol crossover in direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Z.X.; Liao, S.J.; Zeng, J.H. [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Shi, J.Y. [School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2010-09-15

    We electrodeposited noble metal (palladium, platinum) nanowires into the hydrophilic pores of Nafion membrane for mitigating the problem of methanol crossover in direct methanol fuel cells (DMFCs). The DMFC performance result shows that the composite membranes yield lower rate of methanol crossover and better cell performance than the pure Nafion {sup registered} membrane. At low current densities, the Pd nanowire incorporated Nafion membrane shows the best performance. In comparison, the highest performance is achieved at higher current densities with the Pt nanowire modified Nafion membrane. Based on the above findings, we suggest that for the Pd nanowire incorporated Nafion membrane, the mechanism for the suppression of the methanol crossover is mainly the blocking effect due to the 'narrowed' hydrophilic channels in Nafion membrane. For the Pt nanowire modified Nafion membrane, the mechanism includes both increasing the membrane tortuosity and so-called 'on-way consumption' of methanol on the Pt nanowires deposited into the Nafion membrane when the fuel cell is discharging. (author)

  13. Preparation and immobilization of noble metal nanoparticles for plasmonic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ruoli; Pitzer, Martin; Hu, DongZhi; Schaadt, Daniel M. [Institut fuer Angewandte Physik, Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany); DFG Centrum fuer Funktionelle Nanostrukturen (CFN), KIT (Germany); Fruk, Ljiljana [DFG Centrum fuer Funktionelle Nanostrukturen (CFN), KIT (Germany)

    2011-07-01

    Thin-film solar cells are of high interest due to good electrical properties and low material consumption. Traditional thin-film cells, however, have considerable transmission losses because of the reduced absorption volume. A promising way to enhance absorption in the active layer is the light-trapping by plasmonic nanostructures. Metallic nanoparticles have in particular shown large enhancement of the photocurrent in thin-film devices. In this poster, we present preparation of Au,Ag and Pt nanoparticles by polyol method and seed mediated methods for use in plasmonic solar cells. Polyol method typically uses ethylene glycol as the solvent and reducing agent,and in seed-mediated synthesis small nanoparticle seeds are first prepared and then used to promote the growth of different shapes of nanoparticles. We particularly focus on the use of nanocubes and nanospheres for solar cell design. Following the nanoparticle preparation, a new method to immobilize particles on GaAs surfaces via covalent chemical bonds has been developed which prevents agglomerations and allows control of the surface density. Photocurrent spectra of GaAs pin solar cells with and without particles have been recorded. These measurements show the dependence of the photocurrent enhancement on particle material, shape and density.

  14. Electrocatalysis of chemically synthesized noble metal nanoparticles on carbon electrodes

    DEFF Research Database (Denmark)

    Zhang, Ling; Ulstrup, Jens; Zhang, Jingdong

    Noble metal nanoparticles (NPs), such as platinum (Pt) and palladium (Pd) NPs are promising catalysts for dioxygen reduction and oxidation of molecules such as formic acid and ethanol in fuel cells. Carbon nanomaterials are ideal supporting materials for electrochemical catalysts due to their good...... conductivity, chemical inertness and low cost. Improvement of catalytic efficiency and stability of the NPs is, however, essential for their wider applications in electrochemical energy conversion/storage. The activities of noble metal catalysts depend not only on their size, composition, and shapes but also...

  15. One parameter model potential for noble metals

    International Nuclear Information System (INIS)

    A phenomenological one parameter model potential which includes s-d hybridization and core-core exchange contributions is proposed for noble metals. A number of interesting properties like liquid metal resistivities, band gaps, thermoelectric powers and ion-ion interaction potentials are calculated for Cu, Ag and Au. The results obtained are in better agreement with experiment than the ones predicted by the other model potentials in the literature. (author)

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  18. Nanocrystalline Metal Oxides for Methane Sensors: Role of Noble Metals

    Directory of Open Access Journals (Sweden)

    S. Basu

    2009-01-01

    Full Text Available Methane is an important gas for domestic and industrial applications and its source is mainly coalmines. Since methane is extremely inflammable in the coalmine atmosphere, it is essential to develop a reliable and relatively inexpensive chemical gas sensor to detect this inflammable gas below its explosion amount in air. The metal oxides have been proved to be potential materials for the development of commercial gas sensors. The functional properties of the metal oxide-based gas sensors can be improved not only by tailoring the crystal size of metal oxides but also by incorporating the noble metal catalyst on nanocrystalline metal oxide matrix. It was observed that the surface modification of nanocrystalline metal oxide thin films by noble metal sensitizers and the use of a noble metal catalytic contact as electrode reduce the operating temperatures appreciably and improve the sensing properties. This review article concentrates on the nanocrystalline metal oxide methane sensors and the role of noble metals on the sensing properties.

  19. Process for preparing noble metal-containing zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Tsao, Y.-Y.P.

    1989-11-21

    The patent describes a process for preparing noble metal- containing zeolite material of enhanced noble metal dispersion. It comprises: contacting a zeolite material with a cationic noble metal complex; calcining the resulting material in the presence of molecular oxygen at about 300 {degrees} to 375 {degrees} C. for a period of time sufficient to cause decomposition of the noble metal complex into a product containing cationic noble metal species; purging oxygen and water from the resulting material by exposing the material to an atmosphere of inert gas at 200 {degrees} to 350 {degrees} C. and reducing the resulting material with hydrogen at 200 {degrees} to 350 {degrees} C. for a period of time sufficient to reduce the cationic noble metal species to highly dispersed free metal. This paper also describes the same process wherein the zeolite is selected from the group consisting of zeolite beta, ZSM-5, ZSM-11, ZSM-12, ZSM-18, ZSM- 20, ZSM-22, ZSM-23, ZSM-35 and ZSM-48. This paper also describes the same process wherein the noble metal is selected from the group consisting of platinum, palladium, rhodium, ruthenium, silver, rhenium, and iridium.

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

    Science.gov (United States)

    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

  1. Noble Metal/Ceramic Composites in Flame Processes

    DEFF Research Database (Denmark)

    Schultz, Heiko; Madler, Lutz; Strobel, Reto;

    conditions influence the resulting noble metal particles size in those systems [1]. For every specific application the particle size and the metal/metal oxide interaction affect the performance of these nano-composite materials [2]. Recently, aerosol processes have been successfully used to produce platinum...

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

    Energy Technology Data Exchange (ETDEWEB)

    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

  3. Thermodynamic properties of noble metal clusters:molecular dynamics simulation

    Institute of Scientific and Technical Information of China (English)

    WU Zhi-min; WANG Xin-qiang; XIAO Xu-yang; HE Huan-dian; LUO Qiang

    2006-01-01

    The thermodynamics properties of noble metal clusters AuN,AgN,CuN,and PtN (N =80,106,140,180,216,256,312,360,408,500,628,736,and 864) are simulated bymicro-canonical molecular dynamics simulation technique.The potential energy and heat capacities change with temperature are obtained.The results reveal that the phase transition temperature of big noble metal clusters (N≥312 for Au,180 for Ag and Cu,and 360 for Pt) increases linearly with the atom number slowly and approaches gently to bulk crystals.This phenomenon indicates that clusters are intermediate between single atoms and molecules and bulk crystals.But for the small noble clusters,the phase transition temperature changes irregularly with the atom number due to surface effect.All noble metal clusters have negative heat capacity around the solid-liquid phase transition temperature,and hysteresis in the melting/freezing circle is derived in noble metal clusters.

  4. Interaction between Nafion ionomer and noble metal catalyst for PEMFCs

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma

    The implement of polymer impregnation in electrode structure (catalyst layer) decreasing the noble metal catalyst loading by a factor of ten , , is one of the essential mile stones in the evolution of Proton Exchange Membrane Fuel Cells’ development among the application of catalyst support...... and electrode deposition etc. In fuel cell reactions, both electrons and protons are involved. Impregnation of Nafion ionomer in catalyst layer effectively increases the proton-electron contact, enlarge the reaction zone, extend the reaction from the surface to the entire electrode. Therefore, the entire...... catalyst layer conducts both electrons and protons so that catalyst utilization in the layer is improved dramatically. The catalyst layer will in turn generate and sustain a higher current density. One of the generally adapted methods to impregnate Nafion into the catalyst layer is to mix the catalysts...

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

    Science.gov (United States)

    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. Antitumor activity of polyacrylates of noble metals in experiment

    OpenAIRE

    Larisa A. Ostrovskaya; David B. Korman; Natalia V. Bluhterova; Margarita M. Fomina; Valentina A. Rikova; Claudia A. Abzaeva; Larisa V. Zhilitskaya; Nina O. Yarosh

    2014-01-01

    The aim of this research has been the study of the antitumor activity of polymetalacrylate derivatives containing in their structure noble metals. Metallic derivatives of polyacrylic acid were not previously tested as antitumor agents.The antitumor activity of polyacrylates, containing argentum (argacryl), aurum (auracryl) and platinum (platacryl) against experimental models of murine solid tumors (Lewis lung carcinoma and Acatol adenocarcinoma) as well as acute toxicity have been studied. It...

  7. Sintering and ripening resistant noble metal nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    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.

  8. Antitumor activity of polyacrylates of noble metals in experiment

    Directory of Open Access Journals (Sweden)

    Larisa A. Ostrovskaya

    2014-08-01

    Full Text Available The aim of this research has been the study of the antitumor activity of polymetalacrylate derivatives containing in their structure noble metals. Metallic derivatives of polyacrylic acid were not previously tested as antitumor agents.The antitumor activity of polyacrylates, containing argentum (argacryl, aurum (auracryl and platinum (platacryl against experimental models of murine solid tumors (Lewis lung carcinoma and Acatol adenocarcinoma as well as acute toxicity have been studied. It is found that the polyacrylates of noble metals are able to inhibit tumor growth up to 50-90% in comparison with the control. Auracryl induced the inhibition of the Lewis lung carcinoma and Acatol adenocarcinoma by 80 and 90% in comparison with the control, results recommending it for further advanced preclinical studies.

  9. Carbon Nanotubes and Other Nanostructures as Support Material for Nanoparticulate Noble-Metal Catalysts in Fuel Cells

    DEFF Research Database (Denmark)

    Larsen, Mikkel Juul; Veltzé, Sune; Skou, Eivind Morten

    of the fuel-cell electrodes. However, the low concentration of structural defects also poses challenges with regard to anchoring of the catalyst particles on the CNT surface. Thus, activation treatments introducing surface functional groups may be necessary. Also, the surface properties are responsible...... that are relevant for the preparation of fuel-cell electrodes with increased durability. This includes adsorption studies and studies of the role of the surface structure in the generation of materials-deteriorating reaction intermediates during the electrocatalytic processes....

  10. Carbon nanotubes and other nanostructures as support material for nanoparticulate noble-metal catalysts in fuel cells

    DEFF Research Database (Denmark)

    Veltzé, Sune; Larsen, Mikkel Juul; Elina, Yli-Rantala;

    of the fuel-cell electrodes. However, the low concentration of structural defects also poses challenges with regard to anchoring of the catalyst particles on the CNT surface. Thus, activation treatments introducing surface functional groups may be necessary. Also, the surface properties are responsible...... that are relevant for the preparation of fuel-cell electrodes with increased durability. This includes adsorption studies and studies of the role of the surface structure in the generation of materials-deteriorating reaction intermediates during the electrocatalytic processes....

  11. A general approach to mesoporous metal oxide microspheres loaded with noble metal nanoparticles

    KAUST Repository

    Jin, Zhao

    2012-04-26

    Catalytic microspheres: A general approach is demonstrated for the facile preparation of mesoporous metal oxide microspheres loaded with noble metal nanoparticles (see TEM image in the picture). Among 18 oxide/noble metal catalysts, TiO 2/0.1 mol Pd microspheres showed the highest turnover frequency in NaBH 4 reduction of 4-nitrophenol (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Silicon nanocrystal-noble metal hybrid nanoparticles.

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  15. Determination of thin noble metal layers using laser ablation ICP-MS: An analytical tool for NobleChem technology

    International Nuclear Information System (INIS)

    concentration on highly radioactive deposition and crack/crevice monitors or components/fuel surfaces are required. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) is a promising method for this purpose. LA-ICP-MS has gained increasing popularity over the last decade for the direct multi-element determination of major, minor, and trace elements in a variety of solid materials in geology, chemistry, metallurgy and biology. From the early experiments with IR laser, the development moved quickly towards the use of UV lasers. Shorter wavelength improved the laser-sample interaction primarily for transparent samples. Several types of lasers are in use, whereas the most widespread used LA systems are based on Nd:YAG lasers operating at the fourth harmonic at 266 nm. It offers the advantages of high spatial resolution, low sample preparation needs, low limits of detection and good quantification capabilities. A lot of effort has been made in the last years to improve the sensitivity of the technique and to simplify the quantification. Most of the work carried out focused on the sampling in terms of the laser wavelengths, pulse duration, carrier gas and ablation cell design as significant parameters influencing the aerosol generation, transport to the ICP and ionisation therein. Laser ablation ICP-MS has previously been used for thin layer and depth profile analyses. The detection and quantification capabilities for the determination of local noble metal concentrations using LA-ICP-MS were evaluated by the analysis of austenitic stainless steel samples homogeneously coated with platinum. The paper has the following structure: Introduction; Experimental; Sample preparation; Instrumentation; Results; Conclusion. To summarize, in a first series of experiments on platinum coated steel samples the linear dynamic range of the method and the detection limits for platinum within thin layers were determined. The analysis of Pt coated stainless steel samples with

  16. Electrocontact materials, means to save tungsten and noble metals. Review

    Energy Technology Data Exchange (ETDEWEB)

    Minakova, R.V.; Braterskaya, G.N.; Teodorovich, O.K. (AN Ukrainskoj SSR, Kiev. Inst. Problem Materialovedeniya)

    Periodicals, patent literature and firm catalogues are analyzed. It is shown that functional usefulness of the contact pair may be ensured only by means of ..delta..- signing'' heterogenous multicomponent materials whose constituents are chosen by investigating physical and chemical processes, influenced by various factors, and objective choice of criteria to estimate materials for given operating conditions. Certain means are shown expedient for saving tungsten and noble metals.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. Surface Plasmon Waves on noble metals at Optical Wavelengths

    Directory of Open Access Journals (Sweden)

    Niladri Pratap Maity

    2011-05-01

    Full Text Available In this paper the variation of the propagation constant, the attenuation coefficient, penetration depth inside the metal and the dielectric has been evaluated. The propagation characteristics of Surface Plasmon Waves (SPWs which exists on noble metals like gold (Au, silver (Ag and aluminium (Al due to the formation of Surface Plasmon Polaritons (SPPs, have been evaluated theoretically and simulated. It has been found that highly conducting metals Au and Ag provide a strong confinement to the SPWs than Al at optical frequencies. The comparative study reveals that metal having higher conductivity can support a more confined SPW, having a lower penetration depth than metals of lower conductivity at terahertz frequencies when its dielectric constant assumes a negative value.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    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.

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

    Science.gov (United States)

    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.

  4. Steady polarization process modelling of noble metal-electrolyte cermet composite electrode

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Cermet composites containing mixture of noble metal phase and electrolyte phase are the state-of-the-art electrode materials used for electrochemical sensor and solid oxide fuel cell(SOFC). A steady polarization model was developed. The model was based on electronic and ionic transfer process together with the electrochemical reaction regardless of mass transport in the electrode. The modelling results can help to understand the electrochemistry of cermet composite electrode.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Self-assembly of noble metal monolayers on transition metal carbide nanoparticle catalysts.

    Science.gov (United States)

    Hunt, Sean T; Milina, Maria; Alba-Rubio, Ana C; Hendon, Christopher H; Dumesic, James A; Román-Leshkov, Yuriy

    2016-05-20

    We demonstrated the self-assembly of transition metal carbide nanoparticles coated with atomically thin noble metal monolayers by carburizing mixtures of noble metal salts and transition metal oxides encapsulated in removable silica templates. This approach allows for control of the final core-shell architecture, including particle size, monolayer coverage, and heterometallic composition. Carbon-supported Ti(0.1)W(0.9)C nanoparticles coated with Pt or bimetallic PtRu monolayers exhibited enhanced resistance to sintering and CO poisoning, achieving an order of magnitude increase in specific activity over commercial catalysts for methanol electrooxidation after 10,000 cycles. These core-shell materials provide a new direction to reduce the loading, enhance the activity, and increase the stability of noble metal catalysts.

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

    Energy Technology Data Exchange (ETDEWEB)

    Scarselli, M.; Camilli, L.; Castrucci, P.; De Crescenzi, M. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Matthes, L. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Institut fuer Festkoepertheorie und optik, Friedrich Schiller Universitaet, Max-Wien Platz 1, Jena (Germany); Pulci, O. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); ETSF, MIFO, and CNR-ISM, Via del Fosso del Cavaliere, Roma (Italy); Gatto, E.; Venanzi, M. [Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy)

    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.

  8. Supergene mobility of noble metal elements in black rock series

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to discuss the supergene mobility of noble metal elements in black rock series, measurements have been conducted with ICP-MS method for the contents of Ru, Rh, Pd, Ir, Pt, Au and Ag in the primary jordisite-rich black shale ore, in the supergene leached jordisite-rich black shale ore, in the pyrite-rich black shale ore and in the water of pit, well and stream of the mining area near Zhongnan Village, Zunyi District of Guizhou Province. The temperature, pH, electric conductivity, dissolved oxygen of the water were also measured. The pit water is acidic with high electrical conductivity and low dissolved oxygen. The total content of platinum group elements in the primary pyrite-rich black shale ore is only 1/13 of that in the primary jordisite-rich black shale ore. The Ag content in the former is only a half of that in the latter while the Au contents in the two kinds of ores are almost the same. Being leached under supergene condition, the contents of most of the noble metal elements except Au in the jordisite-rich black shale ore greatly decrease; the leaching rates of Rh, Pd, Pt, the total platinum group elements and Ag reach as high as 66.72%~74.79%, revealing that under supergene condition, platinum group elements and Ag can migrate along with water; the ratios of Ag/Au, Pd/Ru, Pt/Ir and(Pt+Pd)/(Ru+Rh+Ir) are remarkably decreased, displaying that Pt and Pd relative to Ru, Rh and Ir, Ag relative to Au bear more active mobility. The noble metal elements in the black rock series near Zhongnan Village might be mobilized and migrate under the procession of "cold water" rich in [SO4]2- with pH value being about 2.4 at a temperature below 50 ℃.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Classical and quantum effects in noble metal and graphene plasmonics

    DEFF Research Database (Denmark)

    Mortensen, N. Asger

    2015-01-01

    Plasmonics — the interaction of light with free electrons in metals — is commonly understood within classical electrodynamics using local-response constitutive laws (such as Ohm's law). However, the tight localization of plasmons to small volumes is revealing intriguing new physics such as noncla......Plasmonics — the interaction of light with free electrons in metals — is commonly understood within classical electrodynamics using local-response constitutive laws (such as Ohm's law). However, the tight localization of plasmons to small volumes is revealing intriguing new physics...... such as nonclassical electrodynamics with a nonlocal response of the plasmons. Nonlocal effects are being explored both theoretically and experimentally in different charge-conducting material systems with examples ranging from sub-10 nanometer noble metal particles to one-atom thin disks of doped graphene....

  12. A New Model Describing the Metal-Support Interaction in Noble Metal Catalysts

    NARCIS (Netherlands)

    Koningsberger, D.C.; Mojet, B.L.; Miller, J.T.; Ramaker, D.E.

    1999-01-01

    The catalytic activity and spectroscopic properties of supported noble metal catalysts are strongly influenced by the acidity/alkalinity of the support but are relatively independent of the metal (Pd or Pt) or the type of support (zeolite LTL or SiO{2}). As the alkalinity of the support increases, t

  13. Optical Properties and Immunoassay Applications of Noble Metal Nanoparticles

    Directory of Open Access Journals (Sweden)

    Shaoli Zhu

    2010-01-01

    Full Text Available Noble metal, especially gold (Au and silver (Ag nanoparticles exhibit unique and tunable optical properties on account of their surface plasmon resonance (SPR. In this paper, we mainly discussed the theory background of the enhanced optical properties of noble metal nanoparticles. Mie theory, transfer matrix method, discrete dipole approximation (DDA method, and finite-difference time domain (FDTD method applied brute-force computational methods for different nanoparticles optical properties. Some important nanostructure fabrication technologies such as nanosphere lithography (NSL and focused ion beam (FIB are also introduced in this paper. Moreover, these fabricated nanostructures are used in the plasmonic sensing fields. The binding signal between the antibody and antigen, amyloid-derived diffusible ligands (ADDLs-potential Alzheimer's disease (AD biomarkers, and staphylococcal enterotixn B (SEB in nano-Moore per liter (nM concentration level are detected by our designed nanobiosensor. They have many potential applications in the biosensor, environment protection, food security, and medicine safety for health, and so forth, fields.

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

    Science.gov (United States)

    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.

  15. Noble metal catalysts in the production of biofuels

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, A.

    2013-11-01

    The energy demand is increasing in the world together with the need to ensure energy security and the desire to decrease greenhouse gas emissions. While several renewable alternatives are available for the production of electricity, e.g. solar energy, wind power, and hydrogen, biomass is the only renewable source that can meet the demand for carbon-based liquid fuels and chemicals. The technology applied in the conversion of biomass depends on the type and complexity of the biomass, and the desired fuel. Hydrogen and hydrogen-rich mixtures (synthesis gas) are promising energy sources as they are more efficient and cleaner than existing fuels, especially when they are used in fuel cells. Hydrotreatment is a catalytic process that can be used in the conversion of biomass or biomass-derived liquids into fuels. In autothermal reforming (ATR), catalysts are used in the production of hydrogen-rich mixtures from conventional fuels or bio-fuels. The different nature of biomass and biomass-derived liquids and mineral oil makes the use of catalysts developed for the petroleum industry challenging. This requires the improvement of available catalysts and the development of new ones. To overcome the limitations of conventional hydrotreatment and ATR catalysts, zirconia-supported mono- and bimetallic rhodium, palladium, and platinum catalysts were developed and tested in the upgrading of model compounds for wood-based pyrolysis oil and in the production of hydrogen, using model compounds for gasoline and diesel. Catalysts were also tested in the ATR of ethanol. For comparative purposes commercial catalysts were tested and the results obtained with model compounds were compared with those obtained with real feedstocks (hydrotreatmet tests with wood-based pyrolysis oil and ATR tests with NExBTL renewable diesel). Noble metal catalysts were active and selective in the hydrotreatment of guaiacol used as the model compound for the lignin fraction of wood-based pyrolysis oil and wood

  16. Investigation of Noble Metals Colloidal Systems Formed by Laser Synthesis at Air

    Directory of Open Access Journals (Sweden)

    Victor Goncharov

    2012-01-01

    Full Text Available The present work is dedicated to the development of formation and diagnostics methods of water colloids of noble metals (Au, Au, Pt. As anoble nanoparticles formation method, the laser synthesis at air conditions is proposed. By the implantation of noble nanoparticles into water media, the colloidal systems of noble metals can be obtained. For the aims of investigation of noble colloid parameters, the complex diagnostics method is used. Such approach deals with direct methods (scanning electron microscopy and the characteristic radiation registration and indirect methods (absorption spectroscopy and extinction modeling by Mie theory.

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

    Science.gov (United States)

    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).

  18. Catastrophic oxidation of Zr-TM (noble metals) glasses

    Energy Technology Data Exchange (ETDEWEB)

    Jastrow, Lioba; Koester, Uwe; Meuris, Monika

    2004-07-15

    Glassy Zr{sub 70}Pd{sub 30} as well as Zr{sub 70}Au{sub 30} prepared by melt-spinning exhibit a 'catastrophic' oxidation behavior in wet as well as synthetic air. For example, at a temperature of 270 deg. C, ribbons (about 30 {mu}m in thickness) are fully oxidized within a few hours. Thermogravimetric analysis reveals an oxidation kinetics by orders of magnitude faster than those in comparable Zr-Pt or Zr-Ni, Zr-Cu as well as related ternary or quaternary glasses. Detailed microstructural investigations, in particular cross-sectional microscopy, revealed details of this reaction and indicate for example for Zr-Au glasses at 25 deg. C an oxygen diffusivity in the developing zirconia scale of about 2x10{sup -17} m{sup 2} s{sup -1}; such a diffusivity is known to occur for stabilized ZrO{sub 2} only at about 300 deg. C. At the as-cast free surface of the ribbon nucleation of the oxidation process starts at defects like scratches or along the grooves at the contact side. The developing 'vulcano' like morphology (with diameters in the range of 10 {mu}m or more) can be explained assuming a diffusion controlled thickening of the scale, but linear lateral growth. It is of interest that the occurrence of extreme fast oxidation is correlated with significant changes in the zirconia microstructure as indicated by a decrease in the intensity of the low-indexed diffraction lines; TEM reveals a nanocrystalline structure with ZrO{sub 2} crystal diameters even below 5 nm. The results will be discussed in detail taking into account for example the different redox potentials of the noble metals, their catalytic activity, the Zr-noble metal bond strength as well as the density of states at the Fermi level of the glasses.

  19. Supported heteronuclear noble metal cluster catalysts and method for preparing same

    International Nuclear Information System (INIS)

    New heteronuclear noble metal cluster complexes have been discovered and synthesized for the first time. These complexes are (pyridine)2Pt(Ir2(CO)15), (pyridine)2 Pt(Ir2(CO)7), (Pyridine)3Pt(Ru3(CO)12), ((C6H5)3P)2Pt(Ir(CO)3(P6H5)3)2, ((C6H5)3P)2Rh(CO)(IR(CO)4), and (pyridine)2Pt(Rh(CO)2(P(C6H5)3)3)2. These new heteronuclear noble metal cluster complexes are useful as supported mixed noble metal catalyst precursors. These new cluster complexes, of known stoichiometry, are deposited on anhydrous refractory inorganic oxide or carbon supports and then reduced resulting in the formation of a supported heteronuclear noble metal catalyst having the same metals stoichiometry as the starting cluster complexes. In this way, precise control can be exercised over the ratio and distribution of multiple metal components in a mixed noble metal catalyst. The usage of preformed heteronuclear noble metal cluster complexes as supported mixed metal catalyst precursors maximizes surface alloy formation and also yields unique mixed-metal cluster structures on the support surface

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

    Science.gov (United States)

    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,...

  1. Nanocrystalline Metal Oxides for Methane Sensors: Role of Noble Metals

    OpenAIRE

    S. Basu; Basu, P. K.

    2009-01-01

    Methane is an important gas for domestic and industrial applications and its source is mainly coalmines. Since methane is extremely inflammable in the coalmine atmosphere, it is essential to develop a reliable and relatively inexpensive chemical gas sensor to detect this inflammable gas below its explosion amount in air. The metal oxides have been proved to be potential materials for the development of commercial gas sensors. The functional properties of the metal oxide-based gas sensors can ...

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

    Science.gov (United States)

    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

  3. Effect of Pressure on the Diffusion Rates in Noble Metals

    International Nuclear Information System (INIS)

    It is possible to find the activation volume, ΔV, for diffusion in solids by the thermodynamic relation (∂ΔG/∂P)T = ΔV , where ΔG is the Gibbs free energy for the process. In noble metals, self-diffusion rate measurement as a function of pressure at a constant temperature will then lead to the determination of the volume of a mole of vacancy in motion, since vacancy mechanism is established for these metals. Employing the standard technique of using a radioactive tracer and lathe sectioning, one can determine the diffusion rates in specimens subjected to diffusion runs at high temperature and at high pressures generated within a vessel containing pressurized gas. The activation volume for self-diffusion in gold was thus found to be 7.2 cm3/mole and that for self-diffusion in silver was found to be 9.3 cm3 /mole. It is possible to apply the same method to study the diffusion of impurities in an otherwise pure crystal. Diffusion of indium and antimony in silver was studied as a function of pressure. The results agree well with the screening theory developed by Lazarus and LeClaire. (author)

  4. Synthesis and self-assembly of thio derivatives of calix[4]arene on noble metal surfaces.

    Science.gov (United States)

    Genorio, Bostjan; He, Tao; Meden, Anton; Polanc, Slovenko; Jamnik, Janko; Tour, James M

    2008-10-21

    Self-assembled monolayers (SAMs) provide a simple route to functionalize electrode surfaces with organic molecules. Herein we use cavity-containing derivatives of calix[4]arenes in SAMs. Bound to noble metal surface, the assembled molecules are candidates to serve as molecular sieves for H 2 molecules and H (+) ions, which could have relevance for fuel cell applications. Tetra- O-alkylated calix[4]arenes with thiolacetate and thiolamide wide-rim anchoring groups in cone and partial-cone conformations were designed, synthesized and self-assembled onto Au, Pt, and Pd surfaces. The resulting SAMs were systematically examined. Single crystal X-ray diffraction of 5,11,17,23-tetrakis(thioacetyl)-25,26,27,28-tetra- i-propoxycalix[4]arene confirmed the cone conformation and revealed the cavity dimensions of the SAMs that were formed by immersing noble metal substrates (Au, Pt and Pd deposited on Si-wafers) in solutions of calix[4]arenes. Surface characterization techniques including ellipsometry, cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) were used, indicating that the metal surface is terminated with a monomolecular layer. Experimental thicknesses obtained from the ellipsometry are consistent with the calculated values. CV results showed 50 to 80% physical passivation against the Fe(CN) 6 (3-/4-) couple, implying an overall relatively low concentration of defects and pinholes in the films. The binding energies of the S2p core level in the XPS were consistent with the literature values and revealed that up to 3.2 out of four anchoring groups were bonded to the noble metal surface.

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

    Science.gov (United States)

    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. Intrinsic therapeutic applications of noble metal nanoparticles: past, present and future.

    Science.gov (United States)

    Arvizo, Rochelle R; Bhattacharyya, Sanjib; Kudgus, Rachel A; Giri, Karuna; Bhattacharya, Resham; Mukherjee, Priyabrata

    2012-04-01

    Biomedical nanotechnology is an evolving field having enormous potential to positively impact the health care system. Important biomedical applications of nanotechnology that may have potential clinical applications include targeted drug delivery, detection/diagnosis and imaging. Basic understanding of how nanomaterials, the building blocks of nanotechnology, interact with the cells and their biological consequences are beginning to evolve. Noble metal nanoparticles such as gold, silver and platinum are particularly interesting due to their size and shape dependent unique optoelectronic properties. These noble metal nanoparticles, particularly of gold, have elicited a lot of interest for important biomedical applications because of their ease of synthesis, characterization and surface functionalization. Furthermore, recent investigations are demonstrating another promising application of these nanomaterials as self-therapeutics. To realize the potential promise of these unique inorganic nanomaterials for future clinical translation, it is of utmost importance to understand a few critical parameters; (i) how these nanomaterials interact with the cells at the molecular level; (ii) how their biodistribution and pharmacokinetics influenced by their surface and routes of administration; (iii) mechanism of their detoxification and clearance and (iv) their therapeutic efficacy in appropriate disease model. Thus in this critical review, we will discuss the various clinical applications of gold, silver and platinum nanoparticles with relevance to above parameters. We will also mention various routes of synthesis of these noble metal nanoparticles. However, before we discuss present research, we will also look into the past. We need to understand the discoveries made before us in order to further our knowledge and technological development (318 references).

  7. Does noble metal modification improve the photocatalytic activity of BiOCl?

    Institute of Scientific and Technical Information of China (English)

    Liang Kong; Zheng Jiang; Henry H.-C. Lai; Tiancun Xiao; Peter P. Edwards

    2013-01-01

    Noble metal-surface-deposited BiOCl photocatalysts were prepared through photo-deposition and used for photodecomposition of Rhodamine B (RhB). The received materials were characterised using X-ray photoemission spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and X-ray diffraction (XRD) to understand the influence of surface deposited noble metals. The results showed that the noble metal species on the surface of BiOCl are in metallic state, which also brought about enhanced light absorption in broad UV-vis region due to plasmonic effects induced by the surface-deposited noble metal species. All the samples showed good activity in photodecomposition of RhB under UV-light irradiation, but only Ag/BiOCl was more active than bulk BiOCl. The mechanism of the different reactivity of these noble-metal modified BiOCl was tentatively proposed based on the band structure and the interactions between noble metals and the BiOCl.

  8. Core shell hybrids based on noble metal nanoparticles and conjugated polymers: synthesis and characterization

    OpenAIRE

    Battocchio Chiara; Polzonetti Giovanni; Cametti Cesare; Fratoddi Ilaria; Venditti Iole; Russo Maria

    2011-01-01

    Abstract Noble metal nanoparticles of different sizes and shapes combined with conjugated functional polymers give rise to advanced core shell hybrids with interesting physical characteristics and potential applications in sensors or cancer therapy. In this paper, a versatile and facile synthesis of core shell systems based on noble metal nanoparticles (AuNPs, AgNPs, PtNPs), coated by copolymers belonging to the class of substituted polyacetylenes has been developed. The polymeric shells cont...

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

    Science.gov (United States)

    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...

  10. Application of noble metals on line in Cofrentes NPP and operation experience; Aplicacion de metales nobles en linea en C.N. Cofrentes y experiencia de operacion

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Zapata, J. D.

    2015-07-01

    Cofrentes NPP implemented in 2010 the Noble Metal Chemistry as a mitigation technique for the Primary System materials protection against IGSCC. the paper describes briefly the technology fundamentals, the implementation of the specific project, the initial application and the operating experience along the last 3 cycles of the plant. (Author)

  11. A novel approach for noble metal deposition on surfaces for IGSCC mitigation of boiling water reactor internals

    International Nuclear Information System (INIS)

    A novel in-situ approach has been developed to deposit noble metals on surfaces of materials commonly used in the nuclear power generating industry. The method involves the injection of a noble metal chemical solution directly into the high temperature water that is in contact with a metal surface to be coated with the noble metal. An effective noble metal coating on a surface can be achieved by maintaining the noble metal concentration at a level of 10 to 100 ppb over a period of 48 hours during the injection process. The surface concentration of the noble metal after the treatment was 2 to 3 atomic %, and the noble metal was present to a depth of 200 to 500 A. The concept of noble metal chemical addition (NMCA) technology was successfully used to create a ''noble metal like'' surface on three of the major nuclear materials, 304 SS, Alloy 600 and Alloy 182. The success of this technology was demonstrated by using constant extension rate tensile (CERT) tests, crack growth rate (CGR) tests and electrochemical corrosion potential (ECP) response tests. The NMCA technology in combination with hydrogen has successfully decreased the ECP of surfaces below the critical cracking potential of -0.230 V(SHE), and prevented both crack initiation and crack propagation in simulated boiling water reactor (BWR) environments

  12. Study of Noble Metal Elements in Lower Cambrian Black Rock Series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Systematic analyses of noble metal elements in the Lower Cambrian black rock series of South China are reported. Correlations of w(Os)/w(Ir), w(Au)/w(Ir), w(Ag)/w(Au), w(Pt+Pd)/w(Os+Ru+Rh+Ir), relations of noble metal and platinum group element (PGE) distribution patterns reveal that the noble metals are not directly from extraterrestrial materials. Studying the data of 9 aspects, the authors conclude that the noble metals were mainly from ultramafic-mafic igneous rocks and their enrichment in black rocks is mainly controlled by hydrothermal fluid.

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

    Energy Technology Data Exchange (ETDEWEB)

    Monreal, R.C., E-mail: r.c.monreal@uam.es [Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Centre (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid (Spain); Goebl, D.; Primetzhofer, D.; Bauer, P. [Institut für Experimentalphysik, Abteilung für Atom-und Oberflächenphysik, Johannes Kepler Universität Linz, 4040 Linz (Austria)

    2013-11-15

    In this work we compare characteristics of Auger neutralization of He{sup +} 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.

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

    International Nuclear Information System (INIS)

    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).

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

    Science.gov (United States)

    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.)

  16. Metal-Free and Noble Metal-Free Heteroatom-Doped Nanostructured Carbons as Prospective Sustainable Electrocatalysts.

    Science.gov (United States)

    Asefa, Tewodros

    2016-09-20

    The large-scale deployment of many types of fuel cells and electrolyzers is currently constrained by the lack of sustainable and efficient catalysts that can replace the less earth-abundant, noble metal-based catalysts, which are commonly used in these renewable energy systems. This burgeoning issue has led to explosive research efforts worldwide to find alternative, metal-free and noble metal-free catalysts that are composed of inexpensive and earth-abundant elements. Hence, the recent discoveries that doping carbon nanomaterials with heteroatoms (such as N, S, B, etc.) can give sustainable materials with good electrocatalytic activity for reactions carried out in fuel cells and electrolyzers have been not only quite exciting but also very promising to address these challenging issues. Interestingly, even though they contain no metals or involve only the inexpensive, more earth-abundant ones, the catalytic activity of some of these materials fares well with those of the commercially used noble metal-based electrocatalysts, such as Pt/C. However, research efforts to improve the catalytic activity, selectivity, and stability of some of these materials for various reactions are still necessary and thus continuing. While some of these efforts have focused on finding synthetic methods that can tune the structures and compositions of already known materials and thereby improve their catalytic properties (activity, selectivity, stability, etc.), others have focused on developing entirely new materials that can exhibit better or superior catalytic properties. In these efforts, additional considerations are also being paid to find facile synthetic routes or renewable and inexpensive precursors that can lead to such types of catalysts in order to make the entire process highly sustainable and widely applicable. In this Account, notable heteroatom-doped carbon catalysts that have been developed for reactions in fuel cells and water electrolyzers, the various synthetic

  17. Metal-Free and Noble Metal-Free Heteroatom-Doped Nanostructured Carbons as Prospective Sustainable Electrocatalysts.

    Science.gov (United States)

    Asefa, Tewodros

    2016-09-20

    The large-scale deployment of many types of fuel cells and electrolyzers is currently constrained by the lack of sustainable and efficient catalysts that can replace the less earth-abundant, noble metal-based catalysts, which are commonly used in these renewable energy systems. This burgeoning issue has led to explosive research efforts worldwide to find alternative, metal-free and noble metal-free catalysts that are composed of inexpensive and earth-abundant elements. Hence, the recent discoveries that doping carbon nanomaterials with heteroatoms (such as N, S, B, etc.) can give sustainable materials with good electrocatalytic activity for reactions carried out in fuel cells and electrolyzers have been not only quite exciting but also very promising to address these challenging issues. Interestingly, even though they contain no metals or involve only the inexpensive, more earth-abundant ones, the catalytic activity of some of these materials fares well with those of the commercially used noble metal-based electrocatalysts, such as Pt/C. However, research efforts to improve the catalytic activity, selectivity, and stability of some of these materials for various reactions are still necessary and thus continuing. While some of these efforts have focused on finding synthetic methods that can tune the structures and compositions of already known materials and thereby improve their catalytic properties (activity, selectivity, stability, etc.), others have focused on developing entirely new materials that can exhibit better or superior catalytic properties. In these efforts, additional considerations are also being paid to find facile synthetic routes or renewable and inexpensive precursors that can lead to such types of catalysts in order to make the entire process highly sustainable and widely applicable. In this Account, notable heteroatom-doped carbon catalysts that have been developed for reactions in fuel cells and water electrolyzers, the various synthetic

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Calculation of phonon spectrum for noble metals by modified analytic embedded atom method (MAEAM)

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiao-Jun; Zhang Jian-Min; Xu Ke-Wei

    2006-01-01

    In the harmonic approximation, the atomic force constants are derived and the phonon dispersion curves along four major symmetry directions [00ζ], [0ζζ], [ζζζ] and [0ζ1] (or △, ∑, A and Z in group-theory notation) are calculated for four noble metals Cu, Ag, Au and Pt by combining the modified analytic embedded atom method (MAEAM) with the theory of lattice dynamics. A good agreement between calculations and measurements, especially for lower frequencies,shows that the MAEAM provides a reasonable description of lattice dynamics in noble metals.

  3. The preparation of primary standard solutions for each of the noble metals

    International Nuclear Information System (INIS)

    A revised method for the preparation of primary standard solutions for each of the noble metals is described. It is now recommended that standard noble-metal solutions should be made from the pure metals and not from salts as previously described. Metals should have a certified purity of 99,95 per cent or better, and the purity should be confirmed by analysis, the techniques of emission spectography or spark-source mass spectrography being used. After the metals have been dissolved, the solutions are made up to volume and the metal content of the standard solutions is checked. For most instrumental techniques for which the standards are intended, the check analysis should be within 0,3 per cent of the certified value

  4. Source tracing of noble metal elements in Lower Cambrian black rock series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-element- ore-deposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.

  5. Source tracing of noble metal elements in Lower Cambrian black rock series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    李胜荣; 高振敏

    2000-01-01

    The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-element-ore-deposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.

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

    Energy Technology Data Exchange (ETDEWEB)

    Smith, M.E. [Westinghouse Savannah River Company, AIKEN, SC (United States); 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.

  7. SULFUR-RESISTANT BIMETALLIC NOBLE METAL CATALYSTS FOR AROMATIC HYDROGENATION OF DIESEL FUEL

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Y zeolite supporting noble metal catalysts, as the important industrial catalysts for aromatics hydrogenation, have received increasing attention in recent years. Pd-M/Y bimetallic catalysts, where M is non-noble metal element, were prepared to investigate the effects of the addition of a second metal. Pd-M/Y catalysts were evaluated under the following conditions: H2 pressure 4.2 MPa, MHSV 4.0 h-1, sulfur content in feed 3000 μg/g. The microreactor results indicated that the second metal remarkably affects the hydrogenation activity of Pd/Y catalysts. Among them, Cr and W improve the sulfur resistance of Pd/Y, but La, Mn, Mo and Ag make the sulfur resistance worse and the second metals have no evident influence on product selectivity and acidic properties of the catalysts.

  8. 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

    Science.gov (United States)

    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

  9. 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.

    Science.gov (United States)

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

    2013-11-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. First-principles calculations of the vacancy formation energy in transition and noble metals

    DEFF Research Database (Denmark)

    Korzhavyi, P.A.; Abrikosov, Igor A.; Johansson, Börje;

    1999-01-01

    Abstract: The vacancy formation energy and the vacancy formation volume of the 3d, 4d, and 5d transition and noble metals have been calculated within the local-density approximation. The calculations employ the order-N locally self-consistent Green's-function method in conjunction with a supercel...

  12. Observation of shell effects in nanowires for the noble metals copper, silver and gold

    OpenAIRE

    Mares, A. I.; van Ruitenbeek, J. M.

    2005-01-01

    We extend our previous shell effect observation in gold nanowires at room temperature under ultra high vacuum to the other two noble metals: silver and copper. Similar to gold, silver nanowires present two series of exceptionally stable diameters related to electronic and atomic shell filling. This observation is in concordance to what was previously found for alkali metal nanowires. Copper however presents only electronic shell filling. Remarkably we find that shell structure survives under ...

  13. Electrical resistivity of noble-metal alloys: Roles of pseudopotential refinements

    International Nuclear Information System (INIS)

    The electrical resistivity of liquid noble-metal alloys i.e. CuAu and AgAu is calculated as a function of concentration. The calculations employ transition-metal-pseudopotentials that include nonlocal effects, hybridization and corrections due to orthogonalization hole and use the hard-sphere structure factors; the optimal values of the hard-sphere diameters are being determined by variational calculations. The calculated resistivities are comparable to the experimental values and to the available theoretical results. (author)

  14. Role of noble metal nanoparticles in DNA base damage and catalysis: a radiation chemical investigation

    International Nuclear Information System (INIS)

    In the emerging field of nanoscience and nanotechnology, tremendous focus has been made by researcher to explore the applications of nanomaterials for human welfare by converting the findings into technology. Some of the examples have been the use of nanoparticles in the field of opto-electronic, fuel cells, medicine and catalysis. These wide applications and significance lies in the fact that nanoparticles possess unique physical and chemical properties very different from their bulk precursors. Numerous methods for the synthesis of noble nanoparticles with tunable shape and size have been reported in literature. The goal of our group is to use different methods of synthesis of noble metal nanoparticles (Au, Ag, Pt and Pd) and test their protective/damaging role towards DNA base damage induced by ionizing radiation (Au and Ag) and to test the catalytic activity of nanoparticles (Pt and Pd) in certain known organic synthesis/electron transfer reactions. Using radiation chemical techniques such as pulse radiolysis and steady state radiolysis complemented by the product analysis using HPLC/LC-MS, a detailed mechanism for the formation of transient species, kinetics leading to the formation of stable end products is studied in the DNA base damage induced by ionizing radiation in presence and absence of Au and Ag nanoparticles. Unraveling the complex interaction between catalysts and reactants under operando conditions is a key step towards gaining fundamental insight in catalysis. The catalytic activity of Pt and Pd nanoparticles in electron transfer and Suzuki coupling reactions has been determined. Investigations are currently underway to gain insight into the interaction between catalysts and reactants using time resolved spectroscopic measurements. These studies will be detailed during the presentation. (author)

  15. Are matrix isolated species really “isolated”? Infrared spectroscopic and theoretical studies of noble gas-transition metal oxide complexes

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this review, we summarize our recent results on matrix isolation infrared spectroscopic studies and theoretical investigations of noble gas-transition metal oxide complexes. The results show that some transition metal oxide species trapped in solid noble gas matrices are chemically coordinated by one or multiple noble gas atoms forming noble gas complexes and, hence, cannot be regarded as isolated species. Noble gas coordination alters the vibrational frequencies as well as the geometric and electronic structures of transition metal oxide species trapped in solid noble gas matrixes. The interactions between noble gas atoms and transition metal oxides involve ion-induced dipole interactions as well as chemical bonding interactions. Periodic trends in the bonding in these noble gas-transition metal complexes are discussed.

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

    International Nuclear Information System (INIS)

    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, Bi2O3, Sb2O3). 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 Sb2O3, Bi2O3, 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 RuO4. 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

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  19. Methane oxidation over noble metal catalysts as related to controlling natural gas vehicle exhaust emissions

    International Nuclear Information System (INIS)

    Natural gas has considerable potential as an alternative automotive fuel. This paper reports on methane, the principal hydrocarbon species in natural-gas engine exhaust, which has extremely low photochemical reactivity but is a powerful greenhouse gas. Therefore, exhaust emissions of unburned methane from natural-gas vehicles are of particular concern. This laboratory reactor study evaluates noble metal catalysts for their potential in the catalytic removal of methane from natural-gas vehicle exhaust. Temperature run-up experiments show that the methane oxidation activity decreases in the order Pd/Al2O3 > Rh/Al2O3 > Pt/Al2O3. Also, for all the noble metal catalysts studied, methane conversion can be maximized by controlling the O2 concentration of the feedstream at a point somewhat rich (reducing) of stoichiometry

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Noble Metal Catalysts for the Hydrocracking of Fischer-Tropsch waxes

    OpenAIRE

    Elorriaga de la Fuente, Ibone

    2012-01-01

    Fischer-Tropsch synthesis enables the production of high quality diesel fuel from biomass derived synthesis gas. In order to increase the overall diesel yield, it is necessary to perform a subsequent hydrocracking of the long-chain linear paraffins. This work is focused on characterization and testing of catalysts for the hydrocracking reaction of Fischer-Tropsch waxes. In particular, noble metal catalyst based on Pt and Pd on amorphous silica-alumina support were tested. Palladium based cata...

  2. Oxidation of ethoxylated fatty alcohols to alkylpolyglycol carboxylic acids using noble metals as catalysts

    Directory of Open Access Journals (Sweden)

    Sagredos, Angelos

    2009-09-01

    Full Text Available The conversion of ethoxylated fatty alcohols to the corresponding carboxylic acids through dehydrogenation/ oxidation using noble-metal catalysts has been studied. Ethoxylated primary aliphatic alcohols, ethoxylated random secondary aliphatic alcohols and ethoxylated alkylphenols have been converted to the corresponding acids in the presence of a base. The noble metal catalysts Palladium and Platinum were used without significant degradation of the ethoxyl chain in yields that exceeded 90%. On the other hand, the catalysts Rhodium and Ruthenium gave yields of about 80% and 60% respectively.La conversión de alcoholes grasos etoxilados a los correspondientes ácidos carboxílicos por deshidrogenación/ oxidación con metales nobles como catalizador ha sido estudiada. Alcoholes primarios alifáticos etoxilados, alcoholes alifáticos secundarios etoxilados al azar y alquilfenoles etoxilados han sido convertidos a los correspondientes ácidos en presencia de base. Los catalizadores paladio y platino fueron usados sin degradación significativa de las cadenas etoxiladas con un rendimiento que excedió del 90%. Por otra parte catalizadores de rodio y rutenio produjeron rendimientos del 80 y 60%, respectivamente.

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

    Energy Technology Data Exchange (ETDEWEB)

    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. Visible light active TiO2 films prepared by electron beam deposition of noble metals

    International Nuclear Information System (INIS)

    TiO2 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 TiO2 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 TiO2 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 TiO2 films by this method is affected by the concentration of impregnating solution.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  8. Noble Metal Immersion Spectroscopy of Silica Alcogels and Aerogels

    Science.gov (United States)

    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.

  9. Effect of three-body forces on the lattice dynamics of noble metals

    Indian Academy of Sciences (India)

    P R Vyas; C V Pandya; T C Pandya; V B Gohel

    2001-04-01

    A simple method to generate an effective electron–ion interaction pseudopotential from the energy wave number characteristic obtained by first principles calculations has been suggested. This effective potential has been used, in third order perturbation, to study the effect of three-body forces on the lattice dynamics of noble metals. It is found that three-body forces, in these metals, do play an important role. The inclusion of such three-body forces appreciably improves the agreement between the experimental and theoretical phonon dispersion curves.

  10. Unveiling nickelocene bonding to a noble metal surface

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  13. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Svane, K. L., E-mail: ksvane@inano.au.dk; Hammer, B., E-mail: hammer@phys.au.dk [Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University (Denmark)

    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.

  14. Ice-templated synthesis of multifunctional three dimensional graphene/noble metal nanocomposites and their mechanical, electrical, catalytic, and electromagnetic shielding properties

    OpenAIRE

    Sahoo, P. K.; Radhamanohar Aepuru; Himanshu Sekhar Panda; Bahadur, D.

    2015-01-01

    In-situ homogeneous dispersion of noble metals in three-dimensional graphene sheets is a key tactic for producing macroscopic architecture, which is desirable for practical applications, such as electromagnetic interference shielding and catalyst. We report a one-step greener approach for developing porous architecture of 3D-graphene/noble metal (Pt and Ag) nanocomposite monoliths. The resulting graphene/noble metal nanocomposites exhibit a combination of ultralow density, excellent elasticit...

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

    Science.gov (United States)

    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.

  16. Defense by-products production and utilization program: noble metal recovery screening experiments

    International Nuclear Information System (INIS)

    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

  17. Synthesis of Supported Ultrafine Non-noble Subnanometer-Scale Metal Particles Derived from Metal-Organic Frameworks as Highly Efficient Heterogeneous Catalysts.

    Science.gov (United States)

    Kang, Xinchen; Liu, Huizhen; Hou, Minqiang; Sun, Xiaofu; Han, Hongling; Jiang, Tao; Zhang, Zhaofu; Han, Buxing

    2016-01-18

    The properties of supported non-noble metal particles with a size of less than 1 nm are unknown because their synthesis is a challenge. A strategy has now been created to immobilize ultrafine non-noble metal particles on supports using metal-organic frameworks (MOFs) as metal precursors. Ni/SiO2 and Co/SiO2 catalysts were synthesized with an average metal particle size of 0.9 nm. The metal nanoparticles were immobilized uniformly on the support with a metal loading of about 20 wt%. Interestingly, the ultrafine non-noble metal particles exhibited very high activity for liquid-phase hydrogenation of benzene to cyclohexane even at 80 °C, while Ni/SiO2 with larger Ni particles fabricated by a conventional method was not active under the same conditions.

  18. Optical and structural properties of noble-metal nanoparticles; Optische und strukturelle Eigenschaften von Edelmetallnanopartikeln

    Energy Technology Data Exchange (ETDEWEB)

    Dahmen, C.

    2006-06-23

    Noble-metal nanoparticles exhibit rich optical behavior, such as resonant light scattering and absorption and non-linear signal enhancement. This makes them attractive for a multitude of physical, chemical, and biophysical applications. For instance, recent biomedical experiments demonstrate the suitability of noble-metal nanoparticles for selective photothermal apoptosis by heat transport by laser irradiation. The applications of nanoparticles largely exploit that plasmons, i. e. collective oscillations of the conduction electrons, can be optically excited in these nanoparticles. In optical spectroscopy, these are seen as pronounced resonances. In the first part of this work, model calculations are employed to elucidate how radiation damping in noble-metal nanoparticles, i. e. the transformation of plasmons into photons, depends on particle size, particle shape, and on electromagnetic coupling between individual particles. Exact electrodynamic calculations are carried out for individual spheroidal particles and for pairs of spherical particles. These calculations for spheroidal particles demonstrate for the first time that radiative plasmon decay is determined by both the particle volume and the particle shape. Model calculations for pairs of large spherical particles reveal that the electromagnetic fields radiated by the particles mediate electromagnetic coupling at interparticle distances in the micrometer range. This coupling can lead to immense modulations of the plasmonic linewidth. The question whether this coupling is sufficiently strong to mediate extended, propagating, plasmon modes in nanoparticle arrays is addressed next. Detailed analysis reveals that this is not the case; instead, for the particle spacings regarded here, a non-resonant, purely diffractive coupling is observed, which is identified by steplike signatures in reflection spectra of the particle arrays. In the second part of this work, structural and optical properties of noble-metal

  19. Recent advances in noble metal based composite nanocatalysts: colloidal synthesis, properties, and catalytic applications

    Science.gov (United States)

    Xu, Yong; Chen, Lei; Wang, Xuchun; Yao, Weitang; Zhang, Qiao

    2015-06-01

    This Review article provides a report on progress in the synthesis, properties and catalytic applications of noble metal based composite nanomaterials. We begin with a brief discussion on the categories of various composite materials. We then present some important colloidal synthetic approaches to the composite nanostructures; here, major attention has been paid to bimetallic nanoparticles. We also introduce some important physiochemical properties that are beneficial from composite nanomaterials. Finally, we highlight the catalytic applications of such composite nanoparticles and conclude with remarks on prospective future directions.

  20. Monolithic Catalysts with Low Noble-Metal Content for Exhaust Purification of Small Gasoline Engines

    Institute of Scientific and Technical Information of China (English)

    Zhang Lijuan; Mao Xiaobo; Chen Yaoqiang; Zhong Junbo; Wang Jianli; Zhao Ming; Gong Maochu

    2007-01-01

    A series of low noble-metal content monolithic catalysts for exhaust purification of small gasoline engines was investigated, and it was found that the Pt/Rh-OSM/Al2O3 (where OSM was oxygen storage material) catalyst with Ce0.5Zr0.5-MnOx(3%MnOx) OSM held low light-off temperature for CO, HC, and NO;quite wide three-way window, and outstanding thermal stability. The catalyst could efficiently control exhaust emission of small gasoline engines.

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

    Science.gov (United States)

    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.

  2. Inference on the Nature and the Mass of Earth's Late Veneer from Noble Metals and Gases

    CERN Document Server

    Dauphas, N

    2001-01-01

    Noble metals and gases are very sensitive to the late accretion to the Earth of asteroids and comets. We present mass balance arguments based on these elements that indicate that 0.7E22-2.7E22 kg of extraterrestrial bodies struck the Earth after core formation and that comets comprised less than 1E-5 by mass of the impacting population. These results imply that the dynamics of asteroids and comets changed drastically with time and that biogenic elements and prebiotic molecules were not delivered to the Earth by comets but rather by carbonaceous asteroids.

  3. Expeditious Synthesis of Noble Metal Nanoparticles Using Vitamin B12 under Microwave Irradiation

    Directory of Open Access Journals (Sweden)

    Changseok Han

    2015-08-01

    Full Text Available A greener synthesis protocol for noble nanometals is developed using vitamin B12 as a reducing and capping agent in conjunction with the use of microwaves. Successful assembly of nanoparticles or microparticles with varied shapes and sizes have been demonstrated. The synthesized Ag, Au, and Pd samples were thoroughly characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission microscopy, and UV-visible spectrophotometry, confirming that metallic Ag, Au, and Pd were synthesized by the green chemistry method.

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

    Science.gov (United States)

    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

  5. Core shell hybrids based on noble metal nanoparticles and conjugated polymers: synthesis and characterization

    Directory of Open Access Journals (Sweden)

    Battocchio Chiara

    2011-01-01

    Full Text Available Abstract Noble metal nanoparticles of different sizes and shapes combined with conjugated functional polymers give rise to advanced core shell hybrids with interesting physical characteristics and potential applications in sensors or cancer therapy. In this paper, a versatile and facile synthesis of core shell systems based on noble metal nanoparticles (AuNPs, AgNPs, PtNPs, coated by copolymers belonging to the class of substituted polyacetylenes has been developed. The polymeric shells containing functionalities such as phenyl, ammonium, or thiol pending groups have been chosen in order to tune hydrophilic and hydrophobic properties and solubility of the target core shell hybrids. The Au, Ag, or Pt nanoparticles coated by poly(dimethylpropargylamonium chloride, or poly(phenylacetylene-co-allylmercaptan. The chemical structure of polymeric shell, size and size distribution and optical properties of hybrids have been assessed. The mean diameter of the metal core has been measured (about 10-30 nm with polymeric shell of about 2 nm.

  6. Polyacrylonitrile/noble metal/SiO₂ nanofibers as substrates for the amplified detection of picomolar amounts of metal ions through plasmon-enhanced fluorescence.

    Science.gov (United States)

    Zhang, Han; Cao, Minhua; Wu, Wei; Xu, Haibo; Cheng, Si; Fan, Li-Juan

    2015-01-28

    Electrospun polymer/noble metal hybrid nanofibers have developed rapidly as surface-enhanced Raman scattering (SERS)-active substrates over the last few years. However, polymer/noble metal nanofibers with plasmon-enhanced fluorescence (PEF) activity have received no attention to date. Herein, we show a general and facile approach for the preparation of polyacrylonitrile (PAN)/noble metal/SiO2 nanofibrous mats with PEF activity for the first time by combining electrospinning and controlled silica coatings. These PEF-active nanofibrous mats can selectively improve the fluorescence intensity of conjugated polyelectrolytes (CPEs). Importantly, the CPE solution in the presence of a PAN/noble metal/SiO2 nanofibrous mat showed dramatic fluorescence quenching towards picomolar (pM) amounts of heavy metal ions, while the fluorescence of the CPE solution without the nanofibrous mat had no apparent quenching towards micromolar (μM) amounts of metal ions. The combination of the distance-dependent fluorescence enhancement performance of metal NPs and the ionic characteristics of the CPE solution makes the polymer/noble metal nanofibers promising substrates for greatly improving the detection sensitivity towards metal ions. We believe that this work provides a general strategy for preparing plasmon band-tuned PEF-active substrates with advantages including good selectivity, remarkable sensitivity and recyclability, which make them a preferable choice for practical sensing applications. PMID:25494487

  7. Towards to Extraction of Nanodispersed Noble Metals From Natural Black Graphite Shales

    Directory of Open Access Journals (Sweden)

    Elena A. Mikhailenko

    2012-01-01

    Full Text Available A theoretical approach based on the density functional theory and the pseudopotential method was applied to consider diffusion and accumulation of Au, Pt, and Pd in graphite. It is shown that Pt atoms migrate easily inside graphite. They can stop at structure defects and accumulate there, attracting each other and forming plate clusters. Atoms of gold do not penetrate into graphite but link with edge atoms of broken graphite crystallites, forming three-dimensional metallic particles. Palladium behavior is intermediate between platinum and gold. Addition of silicon into graphite can promote the extraction of noble metals because Si atoms force out Pt, Pd, and Au atoms from their bonded states. Last effect can be used as a mechanism of striking off metals from graphite and their extraction from shales

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  10. Replacing Noble Metals with Alternative Materials in Plasmonics and Metamaterials: how good an idea?

    CERN Document Server

    Khurgin, Jacob B

    2016-01-01

    Noble metals that currently dominate the fields of plasmonics and metamaterials suffer from large ohmic losses. New plasmonic materials, such as doped oxides and nitrides, have smaller material loss, and, using them in place of metals carries promise of reduced-loss plasmonic and metamaterial structures, with sharper resonances and higher field concentration. This promise is put to a rigorous analytical test in this work which reveals that having low material loss is not sufficient to have a reduced modal loss in plasmonic structures. To reduce the modal loss it is absolutely necessary for the plasma frequency to be significantly higher than the operational frequency. Using examples of nanoparticle plasmons and gap plasmons one comes to the conclusion that even in the mid-infrared spectrum metals continue to hold advantage over the alternative media. The new materials may still find application niche where the high absorption loss is beneficial, e.g. in medicine and thermal photovoltaics.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-06

    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.

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

    Science.gov (United States)

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

    2016-06-13

    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

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

    KAUST Repository

    Li, Zhenzhen

    2015-06-12

    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.

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

    Directory of Open Access Journals (Sweden)

    X. H. Liu

    2015-10-01

    Full Text Available 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X. H.; Luo, H.; Qu, T. L., E-mail: qutianliang@nudt.edu.cn; Yang, K. Y.; Ding, Z. C. [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    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.

  16. Tailoring the supercapacitive performances of noble metal oxides, porous carbons and their composites

    Directory of Open Access Journals (Sweden)

    Panić Vladimir V.

    2013-01-01

    Full Text Available Porous electrochemical supercapacitive materials, as an important type of new-generation energy storage devices, require a detailed analysis and knowledge of their capacitive performances upon different charging/discharging regimes. The investigation of the responses to dynamic perturbations of typical representatives, noble metal oxides, carbonaceous materials and RuO2-impregnated carbon blacks, by electrochemical impedance spectroscopy (EIS is presented. This presentation follows a brief description of supercapacitive behavior and origin of pseudocapacitive response of noble metal oxides. For all investigated materials, the electrical charging/discharging equivalent of the EIS response was found to obey the transmission line model envisaged as so-called „resistor/capacitor (RC ladder“. The ladder features are correlated to material physicochemical properties, its composition and the composition of the electrolyte. Fitting of the EIS data of different supercapacitive materials to appropriate RC ladders enables the in-depth profiling of the capacitance and pore resistance of their porous thin-layers and finally the complete revelation of capacitive energy storage issues. [Projekat Ministarstva nauke Republike Srbije, br. 172060

  17. Effect of noble metal treatment to oxide film on SUS 304 under HWC condition

    International Nuclear Information System (INIS)

    Noble metal deposited SUS 304 specimens with an oxide film were exposed to a simulated HWC condition co-existing with Co radioactivity in order to establish a relationship between features of the oxide film such as the weight, composition and morphology, and the accumulation and distribution of Co radioactivity in the oxide film. The accumulated Co radioactivity decreased to about 40% of that of non-deposited sample, and the distribution of Co radioactivity in the outer layer of the oxide film was remarkably decreased. Compared with non-deposited sample, a significant weight loss and decrease in Fe involved in the outer layer of the oxide film occurred. Dissolution of oxide particles on the outer layer was observed by SEM-EDX analysis. From these results, the dissolution of the outer layer of the oxide film is thought to cause the decrease in accumulated Co radioactivity. But in an actual plant, the loss of the outer layer of the oxide film is thought to cause the increase in Co radioactivity in reactor water because the radioactivity, which was accumulated in the oxide film before the noble metal treatment, is released simultaneously. (authors)

  18. Biogalvanic metal oxygen cell. [German patent

    Energy Technology Data Exchange (ETDEWEB)

    Weidlich, E.

    1979-06-04

    The invention concerns a biogalvanic metal-oxygen cell with a silicon rubber membrane around the cell. The following are claimed: a) constructive measures to increase the mechanical stability, b) polyvinyl alcohol membranes which are arranged on the side of the positive electrode facing the metal electrode to prevent the depositing of oxidation products of the metal electrode, c) cathode materials bound to a silver net via polyvinal alcohol which contain nitrogen and noble metal-containing carbon as oxygen reduction catalysts, and d) aluminium as anode material.

  19. Effect of zinc and copper additions on catalytic response of noble metal alloyed 304 SS in high temperature water

    International Nuclear Information System (INIS)

    The effect of zinc (Zn) and copper (Cu) additions on the catalytic behavior of noble metal alloyed 304 stainless steel (SS) in 288 C water understoichiometric excess hydrogen was studied. It was observed that an increase in the Zn or Cu content of the water increased the electrochemical corrosion potential (ECP) of noble metal alloyed 304 SS by ∼ 30 to 50 mV and decreased the recombination efficiency of oxygen (O2)and hydrogen (H2) by ∼ 10%. The change in the ECP and recombination rate was correlated with incorporation of zinc and copper in the oxide film, which, by covering catalytic sites, would alter the redox reaction rate

  20. Shear bond strength of a ceromer to noble and base metal alloys

    Directory of Open Access Journals (Sweden)

    Dorriz H.

    2006-08-01

    Full Text Available Background and Aim: The improvement of the physical and chemical properties of resins as well as great advances achieved in the field of chemical bonding of resin to metal has changed the trend of restorative treatments. Today the second generation of laboratory resins have an important role in the restoration of teeth. The clinical bond strength should be reliable in order to gain successful results. In this study the shear bond strength (SBS between targis (a ceromer and two alloys (noble and base metal was studied and the effect of thermocycling on the bond investigated. Materials and Methods: In this experimental study, alloys samples were prepared according to the manufacturer. After sandblasting of bonding surfaces with 50µ AI2o3 Targis was bonded to the alloy using Targis I link. All of the samples were placed in 37°C water for a period of 24 hours. Then half of the samples were subjected to 1000 cycles of thermocycling at temperatures of 5°C and 55°C. Planear shear test was used to test the bond strength in the Instron machine with the speed rate of 0.5mm/min. Data were analyzed by SPSS software. Two-way analysis of variance was used to compare the bond strength among the groups. T test was used to compare the alloys. The influence of thermocycling and alloy type on bond strength was studied using Mann Whitney test. P<0.05 was considered as the limit of significance. Result: The studied alloys did not differ significantly, when the samples were not thermocycled (P=0.136 but after thermocycling a significant difference was observed in SBS of resin to different alloys (P=000.1. Thermal stress and alloy type had significant interaction, with regard to shear bond strength (P=0.003. There was a significant difference in SBS before and after thermocycling in noble alloys (P=0.009, but this was not true in base metals (P=0.29. Maximum SBS (19.09 Mpa belonged to Degubond 4, before thermocycling. Minimum SBS (8.21 Mpa was seen in Degubond 4

  1. Studies on State and Structure of Noble Metals in Electrocatalyst Made by Coprecipitation Method

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X-ray diffraction and transmission electron microscopy. X-ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals. The results show that the particle size was in nanometer range and the binary metals have come into being an alloy. The platinum in the catalysts existed in zero valency. The valency of the ruthenium on the surface is different from that in the body, while the ruthenium on the surface existed in oxide-form. PtRu/C and Pt/C are of good activity to the electrooxidation of hydrogen except Ru/C. PtRu/C is more tolerant of CO than Pt/C, and CO is only adsorbed on Pt.

  2. Cohesive properties of noble metals by van der Waals-corrected Density Functional Theory

    CERN Document Server

    Ambrosetti, Alberto

    2016-01-01

    The cohesive energy, equilibrium lattice constant, and bulk modulus of noble metals are computed by different van der Waals-corrected Density Functional Theory methods, including vdW-DF, vdW-DF2, vdW-DF-cx, rVV10 and PBE-D. Two specifically-designed methods are also developed in order to effectively include dynamical screening effects: the DFT/vdW-WF2p method, based on the generation of Maximally Localized Wannier Functions, and the RPAp scheme (in two variants), based on a single-oscillator model of the localized electron response. Comparison with results obtained without explicit inclusion of van der Waals effects, such as with the LDA, PBE, PBEsol, or the hybrid PBE0 functional, elucidates the importance of a suitable description of screened van der Waals interactions even in the case of strong metal bonding. Many-body effects are also quantitatively evaluated within the RPAp approach.

  3. The Effect of Novel Mercapto Silane Systems on Resin Bond Strength to Dental Noble Metal Alloys.

    Science.gov (United States)

    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

  4. Noble metal nanowires: from plasmon waveguides to passive and active devices.

    Science.gov (United States)

    Lal, Surbhi; Hafner, Jason H; Halas, Naomi J; Link, Stephan; Nordlander, Peter

    2012-11-20

    Using chemical synthesis, researchers can produce noble metal nanowires with highly regular, crystalline properties unachievable by alternative, top-down nanofabrication methods. Sitting at the intersection of nanochemistry and nanooptics, noble metal nanowires have generated intense and growing research interest. These nanostructures combine subwavelength transverse dimensions (50-100 nm) and longitudinal dimensions that can reach tens of micrometers or more, which makes them an ideal platform to launch surface plasmon waves by direct illumination of one end of the structure. Because of this property, researchers are using noble metal nanowires as a tool for fundamental studies of subwavelength plasmon-based optics and the properties of surface plasmon guided wave propagation in highly confined geometries below the classical optical diffraction limit. In this Account, we review some of the recent developments in plasmonic nanowire fabrication, nanowire plasmon imaging, and nanowire optical components and devices. The addition of an adjacent nanowire, substrate, or other symmetry-breaking defect can enable the direct coupling of light to and from free space to the guided waves on a nanowire structure. Such structures lead to more complex nanowire-based geometries with multiple optical inputs and outputs. Additional nanowire imaging methods are also possible: plasmon propagation on nanowires produces intense near-field diffraction, which can induce fluorescence in nearby quantum dots or photobleach adjacent molecules. When the nanowire is deposited on a dielectric substrate, the plasmon propagation along chemically synthesized nanowires exceeds 10 μm, which makes these structures useful in nonlocal applications such as remote surface-enhanced Raman spectroscopy (SERS) sensing. Nanowires can be used as passive optical devices, which include, for example, polarization manipulators, linear polarization rotators, or even broadband linear-to-circular polarization

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

    Energy Technology Data Exchange (ETDEWEB)

    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

  6. Effect of Mercury-Noble Metal Interactions on SRAT Processing of SB3 Simulants

    International Nuclear Information System (INIS)

    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

  7. Preparation and characterization of noble metal nanocolloids by silk fibroin in situ reduction

    Institute of Scientific and Technical Information of China (English)

    CHEN; Wenxing(陈文兴); WU; Wen(吴雯); CHEN; Haixiang(陈海相); SHEN; Zhiquan(沈之荃)

    2003-01-01

    Noble metal nanocolloids are prepared from their precursors by in situ reduction of a silk fibroin solution at room temperature without any reducing agent. The mechanism, the effects of pH and the molar ratio of the reactants on the reduction reaction are studied by UV-Vis spectroscopy. The structure of the colloids is characterized by FT-IR, TEM and AFM. According to the TEM images, the gold-silk fibroin colloid is a nanostructured bioconjugate with novel core-shell, while the silver-silk fibroin colloid tends to be congregated as clusters having more than ten nanoparticles of silver-silk fibroin. The gold colloid is highly dispersed and stable while the silver colloid is less dispersed and stable than the gold colloid.

  8. Systematic studies of bonding distances of diindenoperylene on noble metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Buerker, Christoph; Gerlach, Alexander; Hosokai, Takuya; Schreiber, Frank [Institut fuer Angewandte Physik, Universitaet Tuebingen, 72076 Tuebingen (Germany); Niederhausen, Jens; Koch, Norbert [Institut fuer Physik, Humboldt-Universitaet zu Berlin, 12489 Berlin (Germany); Detlefs, Blanka [ESRF, 38043 Grenoble Cedex (France)

    2011-07-01

    The interaction of organic semiconducting molecules with different substrates is essential for the understanding of these systems and for possible applications in organic electronic devices. Diindenoperylene (DIP) is one promising semiconductor and has been studied widely in the recent years concerning its growth and ordering behavior on different substrates as well as electronic properties. Despite these efforts the bonding distance d{sub 0} and thus the coupling to the substrate is still an unknown key parameter of DIP adsorption. Here we present a systematic study of d{sub 0} of DIP on Cu(111), Ag(111) and Au(111) surfaces, determined by the X-ray standing wave (XSW) technique. Different bonding distances for different substrates indicate a substrate dependent interaction strength. Our results are compared with the well-established bonding distances and interaction strength of PTCDA on the same noble metal surfaces. Interesting similarities as well as differences between the two molecules are discussed.

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

    Science.gov (United States)

    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.

  10. Synthesis of noble metal nanoparticles and their superstructures; Darstellung von Edelmetallnanopartikeln und deren Ueberstrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Bigall, Nadja-Carola

    2009-08-18

    A modified synthesis procedure for citrate-stabilized gold nanoparticles in aqueous solution is transferred under application of equal concentrations to the systems silver, platinum, and palladium. The nanoparticles are analyzed by means of absorption spectroscopy and electron microscopy. Ordered superstructures of the noble-metal nanoparticles can be synthesized by infiltration of templates of block-copolymer films with aqueous nanoparticle solution. In dependence on the pre-treatment of the polymer films either two-dimensional periodical arrangements with a periodicity of less than 30 nm or fingerprint-like arrangements with a groove distance in the same order of magnitude. By removal of the polymer one- respectively two-dimensional arrangements of platinum nanowires respectively nanoparticles on a silicon waver arise.

  11. Enthalpies of Formation of Noble Metal Binary Alloys Bearing Rh or Ir

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The modified embedded atom method proposed by authors has been applied to calculating the enthalpies of formationof random alloys and the ordered intermetallic compounds for noble metal binary systems bearing Rh or lr. The presentresults are in good agreement with those of Miedema theory, available experiments and the first-principles quantummechanics calculations. The present results indicate that Cu-Rh, Cu-lr, Ag-Rh, Ag-lr, Au-Rh, Au-lr, Pd-Rh and Pd-lrsystems are repulsive, however, Ni-Rh, Ni-lr, Pt-lr, Pt-Rh and Rh-lr systems form solid solutions and Ni-Rh, Ni-lrand Pt-Rh show ordering tendency.

  12. Interactions of noble metal nanoparticles with their environment; Wechselwirkungen von Edelmetallnanopartikeln mit ihrer Umgebung

    Energy Technology Data Exchange (ETDEWEB)

    Reismann, Maximilian

    2009-12-08

    Upon irradiating noble metal nanoparticles with light, unique optical phenomena can occur, such as resonantly enhanced light-scattering and light-absorption, or a tremendous enhancement of the exciting optical field close to the surface of the nanoparticles. These phenomena rely on the excitations of collective oscillations of the conduction electrons within a nanoparticle. The optical properties of a nanoparticle are determined by the resonance frequency of these so-called plasmon oscillations. This resonance frequency and the light-scattering spectrum of a nanoparticle depend (among other effects) on the dielectric environment of the particle. Due to this effect, noble metal nanoparticles can be applied for local optical sensing of chemical substances. The large light-absorption properties of a nanoparticle also enable the usage of light-irradiation to deposit heat in the nanoparticle in a selective and highly localized manner. Therefore, a local temperature increase can be induced in the nanoparticle and its immediate environment. This temperature increase could be used to trigger chemical or biological reactions, or it could be used for a selective hyperthermia of biological material. These and further possible applications rely on the detection or the systematic excitation of interactions between the noble metal nanoparticle and its environment. These interactions are the central subject of this thesis. Particular attention is paid to photothermal interactions. An interesting question is to what extend a nanoparticle-supported, photothermally-induced temperature rise can be applied to trigger a biomolecular reaction in a spatially confined volume. By carefully adjusting the photothermal treatment, one aims at affecting the molecules without damaging their chemical functionality. The photothermal interaction is addressed in two projects: First, networks built up by gold nanoparticles are investigated. In these networks, double-stranded DNA-molecules are used to

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  15. Noble metal catalyzed hydrogen generation from formic acid in nitrite-containing simulated nuclear waste media

    International Nuclear Information System (INIS)

    The Hanford Waste Vitrification Plant (HWVP) is being designed by the U.S. Department of Energy to immobilize high-level nuclear waste. Simulants for the HWVP feed containing the major nonradioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO32-, NO3- and NO2- were used as media to evaluate the stability of formic acid towards hydrogen evolution by the reaction HCO2H→H2+/CO2 catalyzed by the noble metals Ru, Rh, and/or Pd found in significant quantities in uranium fission products. Small-scale experiments using 40-50 mL of feed simulant in closed glass reactors (250-550 mL total volume) at 80-100 degree C were used to study the effect of nitrite and nitrate ion on the catalytic activities of the noble metals for formic acid decomposition. Reactions were monitored using gas chromatography to analyze the CO2, H2, NO, and N2O in the gas phase as a function of time. Rhodium, which was introduced as soluble RhCl3.3H2O, was found to be the most active catalyst for hydrogen generation from formic acid above nearly 80 degree C in the presence of nitrite ion in accord with earlier observations. The apparent homogeneous nature of the nitrite-promoted Rh-catalyzed formic acid decomposition is consistent with the approximate pseudo-first-order dependence of the hydrogen production rate on Rh concentration. 24 refs., 7 figs., 2 tabs

  16. Update on the use of dissolved oxygen addition to monitor the effectiveness of noble metal applications in external manifolds

    International Nuclear Information System (INIS)

    Electrochemical corrosion potential (ECP) measurements in a Mitigation Monitoring System (MMS) ECP manifold have historically been a primary indicator of the effectiveness of an On-Line NobleChem™ (OLNC) application, with the MMS ECP intended to measure the catalytic effect of noble metal deposited on the ECP manifold surface. In some plants ECP measurements made on untreated surfaces prior to an OLNC application were significantly lower than what would be expected for stainless steel under reactor bulk chemistry conditions. This is due to the consumption and depletion of bulk liquid dissolved oxygen (DO) in the lines supplying reactor water to these external ECP measurement locations. This phenomenon degrades the ability to use these external manifolds to confirm noble metal deposition. Previous papers have described how the injection of an oxygen-rich stream to the MMS supply stream (DO Addition) can be used to re-establish the capability of external ECP measurements to monitor the catalytic behavior of platinum deposited during an OLNC injection. This paper will provide an update of how this method is being successfully used in operating BWRs to monitor OLNC injections. The paper will outline the overall approach used to characterize the catalytic behavior of external ECP manifolds before and after the noble metal application and present plant data collected during DO Additions performed under various conditions. (author)

  17. The determination, by x-ray-fluorescence spectrometry, of noble and base metals in matte-leach residues

    International Nuclear Information System (INIS)

    An accurate and precise method is described for the determination of noble and base metals in matte-leach residues. Preparation of the samples essentially involves fusion with sodium peroxide in a zirconium crucible and leaching with hydrochloric and nitric acids. Matrix correction and calibration are achieved by use of the single-standard calibration method with reference solutions prepared from pure metals or from compounds of the element to be determined

  18. Polyacrylonitrile/noble metal/SiO2 nanofibers as substrates for the amplified detection of picomolar amounts of metal ions through plasmon-enhanced fluorescence

    Science.gov (United States)

    Zhang, Han; Cao, Minhua; Wu, Wei; Xu, Haibo; Cheng, Si; Fan, Li-Juan

    2015-01-01

    Electrospun polymer/noble metal hybrid nanofibers have developed rapidly as surface-enhanced Raman scattering (SERS)-active substrates over the last few years. However, polymer/noble metal nanofibers with plasmon-enhanced fluorescence (PEF) activity have received no attention to date. Herein, we show a general and facile approach for the preparation of polyacrylonitrile (PAN)/noble metal/SiO2 nanofibrous mats with PEF activity for the first time by combining electrospinning and controlled silica coatings. These PEF-active nanofibrous mats can selectively improve the fluorescence intensity of conjugated polyelectrolytes (CPEs). Importantly, the CPE solution in the presence of a PAN/noble metal/SiO2 nanofibrous mat showed dramatic fluorescence quenching towards picomolar (pM) amounts of heavy metal ions, while the fluorescence of the CPE solution without the nanofibrous mat had no apparent quenching towards micromolar (μM) amounts of metal ions. The combination of the distance-dependent fluorescence enhancement performance of metal NPs and the ionic characteristics of the CPE solution makes the polymer/noble metal nanofibers promising substrates for greatly improving the detection sensitivity towards metal ions. We believe that this work provides a general strategy for preparing plasmon band-tuned PEF-active substrates with advantages including good selectivity, remarkable sensitivity and recyclability, which make them a preferable choice for practical sensing applications.Electrospun polymer/noble metal hybrid nanofibers have developed rapidly as surface-enhanced Raman scattering (SERS)-active substrates over the last few years. However, polymer/noble metal nanofibers with plasmon-enhanced fluorescence (PEF) activity have received no attention to date. Herein, we show a general and facile approach for the preparation of polyacrylonitrile (PAN)/noble metal/SiO2 nanofibrous mats with PEF activity for the first time by combining electrospinning and controlled silica

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

    Science.gov (United States)

    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.

  20. UV-initiated formation of noble metal nanoparticles on zinc oxide quantum dots

    International Nuclear Information System (INIS)

    Full text: Quantum dots (nanosized semiconductor particles) are a relatively new phenomenon. They exhibit unusual properties as a result of spatial electron confinement within the particles, including an increased band gap energy and blue-shifted fluorescence. Quantum dots and nanoparticles have attracted a lot of academic and industrial interest because of their special properties, including small size and potential as catalysts, 'tunable' fluorescence, and potential use in biomedical applications. Still, there are many properties of quantum dots that need further investigation if they are to be fully utilised. The interaction between nanosized noble metal colloids and zinc oxide quantum dots (Q-ZnO) under UV-irradiation provides valuable information about the electronic structure of Q-ZnO. In a sample containing Q-ZnO and Pt6+, Au+ or Ag+, electrons from excited Q-ZnO were transferred to the metal ions, and consequently, metal particles were reduced onto the Q-ZnO particles. The processes that occur can be followed spectroscopically. The results will be discussed during the presentation. A Transmission Electron Microscope image of a 3nm zinc oxide quantum dot, with lattice planes clearly visible is presented

  1. Attachment of noble metal nanoparticles to conducting polymers containing sulphur - preparation conditions for enhanced electrocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, V.C. [CQB, Departamento de Quimica e Bioquimica, Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); CIQ-UP, Linha 4, Departamento de Quimica, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Melato, A.I. [CQB, Departamento de Quimica e Bioquimica, Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Silva, A.F. [CIQ-UP, Linha 4, Departamento de Quimica, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Abrantes, L.M., E-mail: luisa.abrantes@fc.ul.p [CQB, Departamento de Quimica e Bioquimica, Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal)

    2011-04-01

    Taking advantage of the spontaneous deposition of noble metals on polymers containing sulphur, the inclusion of gold and platinum in poly(3-methylthiophene) and poly(3,4-ehylenedioxythiophene) (PEDOTh) layers, achieved by immersion of the polymer into the metal nanoparticles suspension, is reported in the present work. Platinum and gold nanoparticles (NPs), with diameters between 3 and 17 nm, have been prepared from colloidal methods (citrate or borohydride reduction in the presence of citrate capping agent) and characterized by transmission electron microscopy, ultraviolet-visible spectrophotometry and X-ray diffraction (XRD). The electropolymerization was carried out under potentiostatic and potentiodynamic conditions, imparting distinct morphologies, as revealed by atomic force microscopy. After polymer films immersion in the colloidal solutions, evidence of the NPs confinement and distribution was provided by XRD analysis and scanning electron microscopy. For thin layers, the quantity of attached metal NPs could be estimated from quartz crystal microbalance data collected throughout the films immersion.The influence of the polymer type and morphology, NPs nature, size and incorporated amount on the electrocatalytic activity of the so-prepared modified electrodes towards the hydrazine oxidation, in phosphate buffer solution, has been investigated by cyclic voltammetry. The results clearly show the superior properties of potentiodynamically prepared PEDOTh films attaching very small (3 nm) freshly prepared Pt-NPs.

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

    Science.gov (United States)

    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 [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 with its robustness would make them great candidates for contributing to significant reduction in the overall capital costs of PEM based water electrolyzers. This thesis provides a detailed fundamental study of the synthesis, materials, characterization, theoretical studies and detailed electrochemical response and potential

  3. Interactions of noble metal nanoparticles with their environment; Wechselwirkungen von Edelmetallnanopartikeln mit ihrer Umgebung

    Energy Technology Data Exchange (ETDEWEB)

    Reismann, Maximilian

    2009-12-08

    Upon irradiating noble metal nanoparticles with light, unique optical phenomena can occur, such as resonantly enhanced light-scattering and light-absorption, or a tremendous enhancement of the exciting optical field close to the surface of the nanoparticles. These phenomena rely on the excitations of collective oscillations of the conduction electrons within a nanoparticle. The optical properties of a nanoparticle are determined by the resonance frequency of these so-called plasmon oscillations. This resonance frequency and the light-scattering spectrum of a nanoparticle depend (among other effects) on the dielectric environment of the particle. Due to this effect, noble metal nanoparticles can be applied for local optical sensing of chemical substances. The large light-absorption properties of a nanoparticle also enable the usage of light-irradiation to deposit heat in the nanoparticle in a selective and highly localized manner. Therefore, a local temperature increase can be induced in the nanoparticle and its immediate environment. This temperature increase could be used to trigger chemical or biological reactions, or it could be used for a selective hyperthermia of biological material. These and further possible applications rely on the detection or the systematic excitation of interactions between the noble metal nanoparticle and its environment. These interactions are the central subject of this thesis. Particular attention is paid to photothermal interactions. An interesting question is to what extend a nanoparticle-supported, photothermally-induced temperature rise can be applied to trigger a biomolecular reaction in a spatially confined volume. By carefully adjusting the photothermal treatment, one aims at affecting the molecules without damaging their chemical functionality. The photothermal interaction is addressed in two projects: First, networks built up by gold nanoparticles are investigated. In these networks, double-stranded DNA-molecules are used to

  4. MONTE CARLO SIMULATION STUDY OF SURFACE ELECTRONIC EXCITATION OF NOBLE METALS

    Institute of Scientific and Technical Information of China (English)

    H.M. Li; Z.J. Ding; Q.R. Pu; Z.M. Zhang

    2002-01-01

    In this work we present a numerical simulation of REELS-spectrum for noble metals,Au and Ag. The calculation is based on an electron-surface inelastic scattering modelpreviously developed. The differential inelastic cross section is obtained fron an inho-mogeneous electron self-energy in the surface region, which provides full informationof the dependency of the total and differential cross section on the kinetic energy,the distance from the surface and the moving direction of electrons, accommodatingthe formulation to the practical situation in surface electron spectroscopes. A novelMonte Carlo simulation code of electron interaction with a surface incorporating thelocal scattering mean free path has been developed. The comparison of the simulatedREELS-spectra with the experimental measurements shows a remarkable agreement onthe spectrum shape, which then confirms that the present model for electron-surfaceinelastic .scattering is quite reasonable. The simulation has further shown the compo.nent to surface excitation due to the individual scattering processes along trajectorypart, i.e., the loss in vacuum before reflection, the loss in vacuum after reflection andloss in metal events.

  5. Determination of noble metals by Inductively Coupled Plasma Atomic Emission Spectrometry

    International Nuclear Information System (INIS)

    Full text: It is well known that significant quantities of soluble fission products such as La, Ce, Pr, Eu, Gd, Sm and noble metals such as Ag, Pt, Au, Ru, Rh, Pd are produced in the spent fuel dissolver solutions, in nuclear reactors. The recovery of noble metals from generated high level waste assumes importance in view of their usage in chemical and electronic industries. In the present work, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) technique has been explored to determine six noble metals in aqueous solutions. Synthetic solution standards containing individually Ag, Au, Pt, Pd, Rh and Ru in the range of 1-500 μg/mL were prepared. Individual elemental solutions at 100μg/mL were fed in to the plasma. The instrumental parameters were obtained for positioning of the analytical line with appropriate sensitivity on the photomultiplier tube. The prominent ICP lines reported in literature in decreasing order of sensitivities for Au are 242.745, 267.895, 197.819, 208.219 nm; Ru are 240.272, 245.657, 267.876 nm; for Rh are 233.477, 249.077, 343.419, 252.053 nm and for Pt are 214.423, 203.646, 214.937 nm respectively. Of these the lines shown in bold are only accessible with the axial ICP unit used in these studies. In addition less sensitive lines in the polyscan mode were chosen, where one can access an elemental line 2.2 nm on either side of the analytical channel provided in polychromator of the instrument. The lines chosen in the polyscan are: Pt 306.471, Ru 249.877 and Rh at 343.489 nm. For Ag and Pd the lines at 328.068 nm and 340.458 nm available with the polychromator of the ICP unit were used. A three point standardization containing the analytes in the concentration range of 0.1 to 200 μg/mL was used. The detection limits determined as per the IUPAC convention for these elements are given. The analytical range for Ag and Pd were 0.05-200 μg/mL while for other elements viz: Au, Pt, Rh and Ru it was 0.5-500 μg/mL . Synthetic samples

  6. Understanding the degradation pathway of the pesticide, chlorpyrifos by noble metal nanoparticles.

    Science.gov (United States)

    Bootharaju, M S; Pradeep, T

    2012-02-01

    Application of nanoparticles (NPs) in environmental remediation such as water purification requires a detailed understanding of the mechanistic aspects of the interaction between the species involved. Here, an attempt was made to understand the chemistry of noble metal nanoparticle-pesticide interaction, as these nanosystems are being used extensively for water purification. Our model pesticide, chlorpyrifos (CP), belonging to the organophosphorothioate group, is shown to decompose to 3,5,6-trichloro-2-pyridinol (TCP) and diethyl thiophosphate at room temperature over Ag and Au NPs, in supported and unsupported forms. The degradation products were characterized by absorption spectroscopy and electrospray ionization mass spectrometry (ESI MS). These were further confirmed by ESI tandem mass spectrometry. The interaction of CP with NP surfaces was investigated using transmission electron microscopy, energy dispersive analysis of X-rays, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS reveals no change in the oxidation state of silver after the degradation of CP. It is proposed that the degradation of CP proceeds through the formation of AgNP-S surface complex, which is confirmed by Raman spectroscopy. In this complex, the P-O bond cleaves to yield a stable aromatic species, TCP. The rate of degradation of CP increases with increase of temperature and pH. Complete degradation of 10 mL of 2 ppm CP solution is achieved in 3 h using 100 mg of supported Ag@citrate NPs on neutral alumina at room temperature at a loading of ∼0.5 wt %. The effect of alumina and monolayer protection of NPs on the degradation of CP is also investigated. The rate of degradation of CP by Ag NPs is greater than that of Au NPs. The results have implications to the application of noble metal NPs for drinking water purification, as pesticide contamination is prevalent in many parts of the world. Study shows that supported Ag and Au NPs may be employed in sustainable

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

    Science.gov (United States)

    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

  8. Turning aluminium into a noble-metal-like catalyst for low-temperature activation of molecular hydrogen.

    Science.gov (United States)

    Chopra, Irinder S; Chaudhuri, Santanu; Veyan, Jean François; Chabal, Yves J

    2011-11-01

    Activation of molecular hydrogen is the first step in producing many important industrial chemicals that have so far required expensive noble-metal catalysts and thermal activation. We demonstrate here that aluminium doped with very small amounts of titanium can activate molecular hydrogen at temperatures as low as 90 K. Using an approach that uses CO as a probe molecule, we identify the atomistic arrangement of the catalytically active sites containing Ti on Al(111) surfaces, combining infrared reflection-absorption spectroscopy and first-principles modelling. CO molecules, selectively adsorbed on catalytically active sites, form a complex with activated hydrogen that is removed at remarkably low temperatures (115 K; possibly as a molecule). These results provide the first direct evidence that Ti-doped Al can carry out the essential first step of molecular hydrogen activation under nearly barrierless conditions, thereby challenging the monopoly of noble metals in hydrogen activation. PMID:21946610

  9. Noble metals determination in ancient jewels with portable ED-XRF system

    Energy Technology Data Exchange (ETDEWEB)

    Parreira, Paulo S.; Galvao, Tiago D.; Appoloni, Carlos R. [Universidade Estadual de Londrina (UEL), PR (Brazil). Dept. de Fisica. Lab. de Fisica Nuclear Aplicada ], e-mail: parreira@uel.br, e-mail: tdggalvao@yahoo.com.br, e-mail: appoloni@uel.br

    2009-07-01

    A handmade system of Energy Dispersive X-Ray Fluorescence (ED-XRF) was used to perform the analysis of some jewels of the XIX century, as napkin holder, tobacco case, cigarette case, pen, pendant shrines, bracelets and a crucifix from the collection of the Museu Historico Nacional do Rio de Janeiro (MHN), Brazil. It was possible to verify the presence of Cu, Au and Ag as macro elements of the alloys, besides Hg as contaminant for one silver piece. Some gold and silver coins with well-known concentrations of gold and silver were also analysed, as reference material, to check out the methodology. To determine the concentrations of the metals, a methodology based on the equation of the fundamental parameters was used. For the jewels with silver aspect, it was possible to determine in average 90.4% of Ag for the napkin holder and 46.6% of Ag for one the bracelets, this last one presented also a high concentration of copper. For the jewels with golden aspect, it was possible to determine, in average, 88.6% to 98.9% for the Au content . For one special piece it was observed 62.5% of Au and 37.5% of Cu. For the coins, the obtained values showed a deviation of 0.4 and 7.6 percent for the average concentration of noble metals Ag and Au, respectively. The portable X-ray system showed to be a powerful tool in the investigation of metallic alloys with high concentration of major elements, allowing in situ measurements.(author)

  10. Bond strength of resin cements to noble and base metal alloys with different surface treatments.

    Directory of Open Access Journals (Sweden)

    Farkhondeh Raeisosadat

    2014-10-01

    Full Text Available 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.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.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.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.

  11. Improved ORR activity of non-noble metal electrocatalysts by increasing ligand and metal ratio in synthetic complex precursors

    Energy Technology Data Exchange (ETDEWEB)

    Wang Liucheng [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001 (China); Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada); Zhang Lei, E-mail: lei.zhang@nrc-cnrc.gc.ca [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada); Zhang Jiujun [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada)

    2011-06-30

    Highlights: > Various mole ratios between precursor Fe(II) and nitrogen-containing ligand of tripyridyl triazine (TPTZ) were investigated in order to further improve the ORR activity of Fe-N{sub x}/C catalyst. > The research results revealed that as the Fe to TPTZ mole ratio in the precursor complex was decreased, the catalytic ORR activity of Fe-N{sub x}/C increased monotonically in the mole ratio range of 1:2-1:6. > Increasing the amount of ligand in the precursor metal complex was demonstrated to be an effective way to compress the decomposition of ORR active site density and thereby enhance the ORR activity of Fe-N{sub x}/C. - Abstract: In an effort to improve oxygen reduction reaction (ORR) activity by increasing the catalytic active site density in carbon-supported non-noble metal catalysts, several nitrogen-containing catalysts were synthesized through a heat treatment process at 900 deg. C using precursor complexes of Fe(II) and tripyridyl triazine (TPTZ). Fe to TPTZ mole ratios of 1:2, 1:3, 1:4, 1:5, 1:6, and 1:7 were used to prepare the precursor complexes. X-ray diffraction and surface electrochemical techniques were used to characterize these catalysts (Fe-N{sub x}/C), and revealed that when the amount of TPTZ in the precursor complex was increased, the decomposition of Fe-N{sub x} sites, which are considered active sites for the ORR, was effectively reduced, resulting in higher Fe-N{sub x} site density and thus improving the catalysts' ORR activity. This beneficial effect was validated through rotating disk electrode tests and analysis of the ORR kinetics catalyzed by these catalysts. The obtained results showed that as the Fe to TPTZ mole ratio in the precursor complex was decreased, the catalytic ORR activity of Fe-N{sub x}/C increased monotonically in the mole ratio range of 1:2-1:6. Therefore, increasing the amount of ligand in the precursor metal complex was demonstrated to be an effective way to reduce the decomposition of ORR active site

  12. The effect of noble metals on catalytic methanation reaction over supported Mn/Ni oxide based catalysts

    OpenAIRE

    Wan Azelee Wan Abu Bakar; Rusmidah Ali; Nurul Shafeeqa Mohammad

    2015-01-01

    Carbon dioxide (CO2) in sour natural gas can be removed using green technology via catalytic methanation reaction by converting CO2 to methane (CH4) gas. Using waste to wealth concept, production of CH4 would increase as well as creating environmental friendly approach for the purification of natural gas. In this research, a series of alumina supported manganese–nickel oxide based catalysts doped with noble metals such as ruthenium and palladium were prepared by wetness impregnation method. T...

  13. 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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  17. Non-enzymatic electrochemical immunoassay using noble metal nanoparticles: a review

    International Nuclear Information System (INIS)

    Electrochemical immunodetection has attracted considerable attention due to its high sensitivity, low cost and simplicity. Large efforts have recently made in order to design ultrasensitive assays. Noble metal nanoparticles (NM-NPs) offer advantages such as high conductivity and large surface-to-volume ratio. NM-NPs therefore are excellent candidates for developing electrochemical platforms for immunodetection and as signal tags. The use of biofunctionalized NM-NPs often results in amplified recognition via stronger loading of signal tags, and also in enhanced signal. This review (with 87 references) gives an overview on the current state in the use of NM-NPs in Non-enzymatic electrochemical immunosensing. We discuss the application of NM-NPs as electrode matrices and as electroactive labels (either as a carrier or as electrocatalytic labels), and compare the materials (mainly nanoparticles of gold, platinum, or of bimetallic materials) in terms of performance (for example by increasing sensitivity via label amplification or via high densities of capture molecules). A conclusion covers current challenges and gives an outlook. Rather than being exhaustive, the review focuses on representative examples that illustrate novel concepts and promising applications. NM-NPs based immunosensing opens a series of concepts for basic research and offers new tools for determination of trace amounts of protein-related analytes in environment and clinical applications. (author)

  18. Quantum size effects on the adsorption of rare gases on Ag monolayer covered noble metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Forster, Frank; Nuber, Andreas; Bentmann, Hendrik; Ziroff, Johannes; Reinert, Friedrich [Universtaet Wuerzburg, Experimentelle Physik II, Wuerzburg (Germany)

    2008-07-01

    In the recent past it has been demonstrated that Shockley states on (111) surfaces of Cu,Ag, and Au are a sensitive probe for interactions between surfaces and adsorbates. Their significant change in binding energy, band mass and spin-orbit coupling allows an access to the comprehension of adsorption mechanisms like physisorption. On the example of Xe monolayers on noble metal surfaces we show vice versa that the Shockley states influence the adsorption dynamics of rare gas atoms. For that purpose we present real-time and high resolution ARPES investigations on Xe adsorption on Cu(111) and Au(111) substrates with Shockley states modified by a pre-adsorption of layer-by-layer grown Ag-films of various thickness. In the case of Xe on Ag/Cu(111) we found that the rare gas prefers the adsorption on the thickest Ag film to the disadvantage of thinner layers or the clean substrate. A similar behaviour could be observed for Ag/Au(111) with the exception of a single Ag layer, which is always unfavoured for Xe coverage. Within a simplified model, the local DOS of the Shockley state at the modified surfaces are compared to the obtained ARPES results.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Antonio Tricoli

    2012-05-01

    Full Text Available 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.

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

    Directory of Open Access Journals (Sweden)

    Christopher Knoblauch

    2014-10-01

    Full Text Available 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.

  2. Characterization of the electrochemical behavior of coating by steel welding 308l and in presence of noble metals deposits; Caracterizacion del comportamiento electroquimico de recubrimiento por soldadura de acero 308L y en presencia de depositos de metales nobles

    Energy Technology Data Exchange (ETDEWEB)

    Piedras, P.; Arganis J, C. R., E-mail: pedro.piedras@hotmail.es [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2014-10-15

    In this work the oxide deposits and noble metals deposit were characterized (Ag and Pt) on a coating of stainless steel 308l that were deposited by the shield metal arc welding (SMAW) on steel A36 by means of scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The extrapolation of Tafel technique was also used to obtain the corrosion potential (Ec) for the pre-rusty steel and for the samples with deposits of Pt and Ag under conditions of hydrogen water chemistry (HWC), demonstrating that this parameter diminishes with the presence of this deposits. (Author)

  3. Hartree-Fock ground-state properties for the group 1 alkali metals and the group 11 noble metals

    International Nuclear Information System (INIS)

    In order to use wavefunction-based correlation methods in solids it is necessary to have reliable Hartree-Fock results for the infinite system of interest. Therefore we performed Hartree-Fock calculations for the group 1 alkali metals (Li to Cs) and group 11 noble metals (Cu, Ag and Au). We optimized a basis set of valence-double-ζ quality for the periodic system. For the lighter atoms all-electron basis sets are applied, whereas for the heavier atoms small-core pseudopotentials with the corresponding basis sets were used to deal with the scalar-relativistic effects. We determine the cohesive energy, the lattice constant and the bulk modulus of the systems at the Hartree-Fock level. We use the counterpoise correction for the free atom to minimize the basis set superposition error occurring for finite basis sets. The effects due to the counterpoise correction not only for the cohesive energy but also for the lattice structure and bulk modulus are discussed in detail

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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)

  7. Temperature-programmed oxidation of coked noble metal catalysts after autothermal reforming of n-hexadecane

    Energy Technology Data Exchange (ETDEWEB)

    Kauppi, E.I.; Linnekoski, J.A.; Krause, A.O.I.; Veringa Niemelae, M.K. [Aalto University, School of Science and Technology, Department of Biotechnology and Chemical Technology, Research Group Industrial Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Kaila, R.K. [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1001, FI-02044 VTT (Finland)

    2010-08-15

    Autothermal reforming (ATR) of n-hexadecane was carried out on zirconia-supported mono- and bimetallic noble metal (Rh, Pt) catalysts at 600, 700, and 800 C. After ATR, the reactivity of coke deposits (2.8-9.9 wt%) on the catalysts was investigated by temperature-programmed oxidation (TPO). Analysis of the results obtained from ATR and TPO experiments at various temperatures and on the different catalysts gave information on the reaction conditions where the detrimental coke can be minimized and allows estimating the nature of carbon deposits. H{sub 2} production increased with temperature on the tested Rh-containing catalysts and the ZrO{sub 2} support, but decreased as a function of temperature on the Pt catalyst. The formation of coke was least at 800 C, evidently due to the intensifying reaction of carbon and steam with increasing temperature, as well as to the better activity of the catalysts. The amount of coke formed was highest at 700 C. Comparison of the TPO profiles obtained for the monometallic Rh and Pt catalysts with the bimetallic RhPt revealed differences in the nature of carbon deposits on their surface. At 600 C, the coke formed on the monometallic Rh and Pt catalysts was located mostly on the support, whereas on the bimetallic RhPt catalyst the formation of this type of coke was suppressed. The bimetallic RhPt catalyst also exhibited better tolerance toward coking at 700 C. Therefore, although the selectivity toward hydrogen was not related to the amount of coke formed, the deactivation patterns differed on the mono- and bimetallic catalysts. (author)

  8. Study of interaction of ethylene glycol/PVP phase on noble metal powders prepared by polyol process

    Indian Academy of Sciences (India)

    F Bonet; K Tekaia-Elhsissen; K Vijaya Sarathy

    2000-06-01

    Noble metal powders (Au, Ag, Pt, Pd and Ru) have been synthesized by the polyol process in both the nanometer and submicron scales (sans Pd, Pt and Ru). They have been characterized by both microscopic (TEM and SEM) as well as spectroscopic techniques (FT-IR and XPS). Infrared spectroscopy was employed to study the colloid particles in the presence of ethylene glycol and PVP and the results show that the interaction between the organic phase and the metal particles vary according to the particle size. The role of the solvent, ethylene glycol, during the reduction process was also investigated and we observe formation of >C=O vibration band after the reduction process implying that the solvent reduces the metal ions thereby getting oxidized. XPS measurements carried out on the colloidal sols have shown the presence of the organic phase adsorbed onto the metal particles.

  9. A simple alkali-metal and noble gas ion source for SIMS equipments with mass separation of the primary ions

    International Nuclear Information System (INIS)

    An alkali-metal ion source working without a store of alkali-metals is described. The alkali-metal ions are produced by evaporation of alkali salts and ionization in a low-voltage arc discharge stabilized with a noble gas plasma or in the case of small alkali-metal ion currents on the base of the well known thermic ionization at a hot tungsten wire. The source is very simple in construction and produces a stable ion current of 0.3 μA for more than 100 h. It is possible to change the ion species in a short time. This source is applicable to all SIMS equipments using mass separation for primary ions. (author)

  10. Experimental and computational approaches to evaluate the environmental mitigation effect in narrow spaces by noble metal chemical addition (NMCA)

    International Nuclear Information System (INIS)

    The environmental mitigation effect of NMCA in a narrow space was evaluated by experimental and computational approaches. In the experiment at 8 MPa and 553K, T-tube whose branched line had a narrow space was prepared, and the Zr electrodes were set in the branched line at certain intervals, which were 1, 3, 5, 7, 9, 11, 15 and 29 cm from the opening section of the branched line. Electrochemical corrosion potential (ECP) at the tip of the branched narrow space varied in response to the water chemistry in the main line which was at right angle with the branched line. Computational fluid dynamics (CFD) analysis reproduced the experimental results. It was also confirmed by CFD analysis that the ingress of water from the main line into the narrow space was accelerated by cavity flow and thermal convection. By CFD analysis in a thermal sleeve of actual plant condition, which had a narrow space, the concentration of dissolved oxygen at a tip of the thermal sleeve reached at 250 ppb within 300 sec, which was the same concentration of the main line. Noble metal deposition on the surface of the thermal sleeve was evaluated by mass transfer model. Noble metal deposition was the largest near the opening section of the branched line, and gradually decreased toward the tip section. In light of the consumption of dissolved oxygen in the branched line, noble metal deposition in the thermal sleeve was sufficient to reduce the ECP. It was expected that NMCA could mitigate the corrosion environment in the thermal sleeve. (author)

  11. Ice-templated synthesis of multifunctional three dimensional graphene/noble metal nanocomposites and their mechanical, electrical, catalytic, and electromagnetic shielding properties

    Science.gov (United States)

    Sahoo, P. K.; Aepuru, Radhamanohar; Panda, Himanshu Sekhar; Bahadur, D.

    2015-12-01

    In-situ homogeneous dispersion of noble metals in three-dimensional graphene sheets is a key tactic for producing macroscopic architecture, which is desirable for practical applications, such as electromagnetic interference shielding and catalyst. We report a one-step greener approach for developing porous architecture of 3D-graphene/noble metal (Pt and Ag) nanocomposite monoliths. The resulting graphene/noble metal nanocomposites exhibit a combination of ultralow density, excellent elasticity, and good electrical conductivity. Moreover, in order to illuminate the advantages of the 3D-graphene/noble metal nanocomposites, their electromagnetic interference (EMI) shielding and electrocatalytic performance are further investigated. The as-synthesized 3D-graphene/noble metal nanocomposites exhibit excellent EMI shielding effectiveness when compared to bare graphene; the effectiveness has an average of 28 dB in the 8.2-12.4 GHz X-band range. In the electro-oxidation of methanol, the 3D-graphene/Pt nanocomposite also exhibits significantly enhanced electrocatalytic performance and stability than compared to reduced graphene oxide/Pt and commercial Pt/C.

  12. Expeditious synthesis of noble metal nanoparticles using Vitamin B12 under microwave irradiation

    Science.gov (United States)

    A greener synthesis protocol for noble nanometals is developed using vitamin B12 as a reducing and capping agent in conjunction with the use of microwaves. Successful assembly of nanoparticles or microparticles with varied shapes and sizes have been demonstrated. The synthesized ...

  13. Scattering of low energy noble gas ions from a metal surface

    International Nuclear Information System (INIS)

    Reflection of low energy (0.1-10 keV) noble gas ions can be used to analyse a solid surface. To study charge exchange processes, the ion fractions of neon and of argon, scattered from a Cu(100) surface, have been determined. (Auth.)

  14. Specificity of noble metals dynamic sorption preconcentration on reversed-phase sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Fedyunina, N.N.; Seregina, I.F.; Ossipov, K.; Dubenskiy, A.S. [Chemistry Department, Analytical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow (Russian Federation); Tsysin, G.I. [Chemistry Department, Analytical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow (Russian Federation); Institute for Spectroscopy, Russian Academy of Sciences, 5 Fizicheskaya Street, 142190 Moscow, Troitsk (Russian Federation); Bolshov, M.A., E-mail: mbolshov@mail.ru [Chemistry Department, Analytical Chemistry Division, Lomonosov Moscow State University, 1-3 Leninskie Gory, 119991 Moscow (Russian Federation)

    2013-10-10

    Graphical abstract: -- Highlights: •StrataX and StrataX-AW for PGMs’ preconcentration were used for the first time. •Steric structure of chlorocomplexes plays critical role in the sorption mechanism. •The conditions of quantitative and reversible sorption of Ir on StrataX-AW were found. •The quantitative and reversible schemes for Pd, Pt, Au and Ir are developed. -- Abstract: The reversible sorption preconcentration of noble metals (NMs) using different schemes “sorbent–reagent–eluent” was investigated. The extraction of Au, Pd, Pt, Ir, Rh and Ru chlorocomplexes from hydrochloric acid solutions on hyper-crosslinked polysterene MN-200 in the form of ion associates with tributylamine (TBA) and 4-(n-octyl)diethylenetriamine (ODETA) was investigated. It was found that Pd, Pt and Au were quantitatively and reversibly extracted using TBA on hyper-crosslinked polysterene; the appropriate eluent for desorption was 1 M solution of HCl in ethanol. Ir, Rh and Ru under these conditions were not sorbed quantitatively. It was found that sorbent hydrophobicity is not the main characteristic that defines the efficiency of sorption of a particular NM ion associate. Different efficiencies of hyper-crosslinked polysterene MN-200 for sorption of square-planar chlorcomplexes of Pt, Pd and Au and octahedral complexes of Ir, Rh and Ru were found. For the first time, the sorbents with their own N-atoms – StrataX and StrataX-AW – were used for the sorption of Ir, Rh and Ru. Using these sorbents, the sorption of Ir was increased up to 95%, and the sorption of Ru and Rh was increased to about 40%. We can explain these results by nonspecific interaction of chlorcomplexes of Ir, Rh and Ru with ethylenediamine groups of the sorbent. Weak bases with large anions may be applied for desorption of Ir, Rh and Ru. Two schemes of dynamic sorption preconcentration of NMs from hydrochloric acid solutions were proposed – hyper-crosslinked polysterene MN-200 for the determination

  15. Catalytic pyrolysis of wheat bran for hydrocarbons production in the presence of zeolites and noble-metals by using TGA-FTIR method.

    Science.gov (United States)

    Lazdovica, K; Liepina, L; Kampars, V

    2016-05-01

    Pyrolysis of wheat bran with or without catalysts was investigated using TGA-FTIR method in order to determine the influence of zeolite and noble metal catalysts on the evolution profile and relative yield of the volatile compounds. The addition of all catalysts decreased the volatile matter of wheat bran from 76.3% to 75.9%, 73.9%, 73.5%, 69.7% and increased the solid residue from 18.0% to 18.4%, 20.4%, 20.8%, 24.6% under the catalyst of ZSM-5, 5% Pd/C, MCM-41, and 5% Pt/C. Noble-metal catalysts had higher activity for deoxygenation of compounds containing carbonyl, carboxyl, and hydroxyl groups than zeolites. Degradation of nitrogen containing compounds atom proceeded better in presence of zeolites. Noble-metal catalysts promoted formation of aromatics and changed the profiles of evolved compounds whereas zeolites advanced formation of aliphatics and olefins. PMID:26874441

  16. General Self-Assembly Route toward Sparsely Studded Noble-Metal Nanocrystals inside Graphene Hollow Sphere Network for Ultrastable Electrocatalyst Utilization.

    Science.gov (United States)

    Lou, Xinyuan; Wu, Ping; Zhang, Anping; Zhang, Ruoqing; Tang, Yawen

    2015-09-16

    Herein, we rationally design and construct a novel type of sparsely studded noble-metal nanocrystals inside graphene hollow sphere network (abbreviated as noble-metal@G HSN) through an electrostatic-attraction-directed self-assembly approach. The formation of Pt@G and Pd@G hollow sphere networks have been illustrated as examples using SiO2 spheres as templates. Moreover, the electrocatalytic performance of the Pt@G HSN for methanol oxidation reaction has been examined as a proof-of-concept demonstration of the compositional and structural superiorities of noble-metal@G HSN toward electrocatalyst utilization. The as-prepared Pt@G HSN manifests higher catalytic activity and markedly enhanced long-term durability in comparison with commercial Pt/C catalyst. PMID:26305582

  17. Incorporation of Fines and Noble Metals into HLW Borosilicate Glass: Industrial Responses to a Challenging Issue - 13056

    Energy Technology Data Exchange (ETDEWEB)

    Chauvin, E.; Chouard, N.; Prod' homme, A. [AREVA, AREVA NC, Paris (France); Boudot, E. [AREVA, AREVA NC, La Hague (France); Gruber, Ph.; Pinet, O. [CEA Marcoule LCV, France (France); Grosman, R. [AREVA, SGN, Paris (France)

    2013-07-01

    During the early stages of spent fuel reprocessing, the fuel rods are cut and dissolved to separate the solid metallic parts of the rods (cladding and end pieces) from the radioactive nitric acid solution containing uranium, plutonium, minor actinides and fission products (FP). This solution contains small, solid particles produced during the shearing process. These small particles, known as 'fines', are then separated from the liquid by centrifugation. At the La Hague plant in France, the fines solution is transferred to the vitrification facilities to be incorporated into borosilicate glass along with the highly radioactive FP solution. These fines are also composed of Zr, Mo and other noble metals (i.e. Ru, Pd, Rh, etc.) that are added before vitrification to the the FP solution that already contained noble metals. As noble metals has the potential to modify the glass properties (including viscosity, electrical conductivity, etc.) and to be affected by sedimentation inside the melter, their behavior in borosilicate glass has been studied in depth over the years by the AREVA and CEA teams which are now working together in the Joint Vitrification Laboratory (LCV). At La Hague, the R7 vitrification facility started operation in 1989 using induction-heated metallic melter technology and was quickly followed by the T7 vitrification facility in 1992. Incorporating the fines into glass has been a challenge since operation began, and has given rise to several R and D studies resulting in a number of technological enhancements to improve the mixing capability of the melters (multiple bubbling technology and mechanical stirring in the mid-90's). Nowadays, the incorporation of fines into R7T7 glass is well understood and process adaptations are deployed in the La Hague facilities to increase the operating flexibility of the melters. The paper will briefly describe the fines production mechanisms, give details of the resulting fines characteristics, explain

  18. Synthesis and characterization of fluorescence-labelled silica core-shell and noble metal-decorated ceria nanoparticles

    Directory of Open Access Journals (Sweden)

    Rudolf Herrmann

    2014-12-01

    Full Text Available The present review article covers work done in the cluster NPBIOMEM in the DFG priority programme SPP 1313 and focuses on synthesis and characterization of fluorescent silica and ceria nanoparticles. Synthetic methods for labelling of silica and polyorganosiloxane/silica core–shell nanoparticles with perylenediimide derivatives are described, as well as the modification of the shell with thiol groups. Photometric methods for the determination of the number of thiol groups and an estimate for the number of fluorescent molecules per nanoparticles, including a scattering correction, have been developed. Ceria nanoparticles decorated with noble metals (Pt, Pd, Rh are models for the decomposition products of automobile catalytic converters which appear in the exhaust gases and finally interact with biological systems including humans. The control of the degree of agglomeration of small ceria nanoparticles is the basis for their synthesis. Almost monodisperse agglomerates (40 ± 4–260 ± 40 nm diameter can be prepared and decorated with noble metal nanoparticles (2–5 nm diameter. Fluorescence labelling with ATTO 647N gave the model particles which are now under biophysical investigation.

  19. A highly efficient noble metal free photocatalytic hydrogen evolution system containing MoP and CdS quantum dots

    Science.gov (United States)

    Yin, Shengming; Han, Jianyu; Zou, Yinjun; Zhou, Tianhua; Xu, Rong

    2016-07-01

    We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h-1 can be achieved by the optimized system under visible light (λ >= 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation.We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h-1 can be achieved by the optimized system under visible light (λ >= 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation. Electronic supplementary information (ESI) available: SEM image with EDS, XPS survey spectrum, XRD and TEM images of MoP samples prepared under different conditions; XRD, TEM, UV-vis and photoluminescence spectra of CdS QDs; H2 evolution activity comparison for different MoP/CdS samples; the effect of pH value on H2 evolution activity of a MoP/CdS system; the XPS spectrum of MoP/CdS after photoreaction; table of literature studies on H2 evolution activity by different noble metal free photocatalytic systems

  20. A highly efficient noble metal free photocatalytic hydrogen evolution system containing MoP and CdS quantum dots.

    Science.gov (United States)

    Yin, Shengming; Han, Jianyu; Zou, Yinjun; Zhou, Tianhua; Xu, Rong

    2016-08-14

    We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h(-1) can be achieved by the optimized system under visible light (λ≥ 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation. PMID:27406067

  1. Composition of solar wind noble gases released by surface oxidation of a metal separate from the Weston meteorite

    Science.gov (United States)

    Becker, R. H.; Pepin, R. O.

    1991-01-01

    The paper reports on a set of experiments intended to test the feasibility of determining elemental and isotopic ratios of the noble gases and nitrogen in the solar wind in metal separates from gas-rich ordinary chondrites. Helium, neon, and argon show clear evidence of a solar wind signature, while no solar component could be identified for xenon and nitrogen. Helium, neon, and argon elemental isotopic ratios appear to depend on depth within the metal grains. The ratios derived indicate that the Weston meteorite did not acquire its solar wind gases from a recent exposure to solar wind, but more probably at a time in the past similar to or even earlier than the exposure time of Apollo 17 breccias. The Ar-36/Ar-38 ratio, in tandem with other recent determinations of this value, indicates that the solar and terrestrial values can no longer be assumed to be equivalent.

  2. The potential of operando XAFS for determining the role and structure of noble metal additives in metal oxide based gas sensors

    Science.gov (United States)

    Grunwaldt, Jan-Dierk; Hübner, Michael; Koziej, Dorota; Barsan, Nicolae; Weimar, Udo

    2013-04-01

    Noble metal additives significantly improve the performance of SnO2 based sensors. Recently, it has been found that X-ray absorption spectroscopy is an excellent tool to identify their structure under sensing conditions, despite of the low concentrations and the rather thin (50 μm) and highly porous layers. For this purpose a new in situ approach has been established and here we highlight the potential with an overview on the results of Pd-, Pt-, and Au-additives in SnO2-based sensors at work. Emphasis was laid on recording the structure (by XANES and EXAFS) and performance at the same time. In contrast to earlier studies, Pd- and Pt-additives were observed to be in oxidized and finely dispersed state under sensing conditions excluding a spillover from metallic noble metal particles. However, Au was mainly present as metallic particles in the sensing SnO2-layer. For the Pt- and Au-doped SnO2-layers high energy-resolved fluorescence detected X-ray absorption spectra (HERFD-XAS) were recorded not only to minimize the lifetime-broadening but also to eliminate the Au- and Pt-fluorescence effectively and to record range-extended EXAFS.

  3. The potential of operando XAFS for determining the role and structure of noble metal additives in metal oxide based gas sensors

    International Nuclear Information System (INIS)

    Noble metal additives significantly improve the performance of SnO2 based sensors. Recently, it has been found that X-ray absorption spectroscopy is an excellent tool to identify their structure under sensing conditions, despite of the low concentrations and the rather thin (50 μm) and highly porous layers. For this purpose a new in situ approach has been established and here we highlight the potential with an overview on the results of Pd-, Pt-, and Au-additives in SnO2-based sensors at work. Emphasis was laid on recording the structure (by XANES and EXAFS) and performance at the same time. In contrast to earlier studies, Pd- and Pt-additives were observed to be in oxidized and finely dispersed state under sensing conditions excluding a spillover from metallic noble metal particles. However, Au was mainly present as metallic particles in the sensing SnO2-layer. For the Pt- and Au-doped SnO2-layers high energy-resolved fluorescence detected X-ray absorption spectra (HERFD-XAS) were recorded not only to minimize the lifetime-broadening but also to eliminate the Au- and Pt-fluorescence effectively and to record range-extended EXAFS.

  4. Synthesis of metal-metal oxide catalysts and electrocatalysts using a metal cation adsorption/reduction and adatom replacement by more noble ones

    Science.gov (United States)

    Adzic, Radoslav; Vukmirovic, Miomir; Sasaki, Kotaro

    2010-04-27

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen. The invention also relates to methods of making the metal-metal oxide composites.

  5. Evaluation of HWVP feed preparation chemistry for an NCAW simulant -- Fiscal year 1993: Effect of noble metals concentration on offgas generation and ammonia formation

    Energy Technology Data Exchange (ETDEWEB)

    Patello, G.K.; Wiemers, K.D.; Bell, R.D.; Smith, H.D.; Williford, R.E.; Clemmer, R.G.

    1995-03-01

    The High-Level Waste Vitrification Program is developing technology for the Department of Energy to immobilize high-level and transuranic wastes as glass for permanent disposal. Pacific Northwest Laboratory (PNL) is conducting laboratory-scale melter feed preparation studies using a HWVP simulated waste slurry, Neutralized Current Acid Waste (NCAW). A FY 1993 laboratory-scale study focused on the effects of noble metals (Pd, Rh, and Ru) on feed preparation offgas generation and NH{sub 3} production. The noble metals catalyze H{sub 2} and NH{sub 3} production, which leads to safety concerns. The information gained from this study is intended to be used for technology development in pilot scale testing and design of the Hanford High-Level Waste Vitrification Facility. Six laboratory-scale feed preparation tests were performed as part of the FY 1993 testing activities using nonradioactive NCAW simulant. Tests were performed with 10%, 25%, 50% of nominal noble metals content. Also tested were 25% of the nominal Rh and a repeat of 25% nominal noble metals. The results of the test activities are described. 6 refs., 28 figs., 12 tabs.

  6. Formation of Metal Selenide and Metal-Selenium Nanoparticles using Distinct Reactivity between Selenium and Noble Metals.

    Science.gov (United States)

    Park, Se Ho; Choi, Ji Yong; Lee, Young Hwan; Park, Joon T; Song, Hyunjoon

    2015-07-01

    Small Se nanoparticles with a diameter of ≈20 nm were generated by the reduction of selenium chloride with NaBH4 at -10 °C. The reaction with Ag at 60 °C yielded stable Ag2 Se nanoparticles, which subsequently were transformed into M-Se nanoparticles (M=Cd, Zn, Pb) through cation exchange reactions with corresponding ions. The reaction with Pt formed Pt layers that were evenly coated on the surface of the Se nanoparticles, and the dissolution of the Se cores with hydrazine generated uniform Pt hollow nanoparticles. The reaction with Au generated tiny Au clusters on the Se surface, and eventually formed acorn-shaped Au-Se nanoparticles through heat treatment. These results indicate that small Se nanoparticles with diameters of ≈20 nm can be used as a versatile platform for the synthesis of metal selenide and metal-selenium hybrid nanoparticles with complex structures.

  7. Radiological analysis by the addition of hydrogen and noble metals in the reactors of the Laguna Verde central

    International Nuclear Information System (INIS)

    During the operation of the nuclear power stations there are metals that are subject to condition and agents that cause that these they present indications of intergranular corrosion and for their importance they are subject to a continuous surveillance to assure their integrity. During the time of operation, for the level of indications, it can be necessary the substitution of these. The internal components of the vessel and particularly those of the structure of the reactor core are exposed during the operation to a neutron flow that causes that these they are activated and, in consequence, before an eventual repair it will be necessary to face high radiation levels. At the moment a technique that controls exists and it reduces the growth rate of the indications in the metals and it increases its useful life: the addition of hydrogen. The addition of hydrogen it is an ALARA measure from long term when protecting the internals of the vessel that requires to establish radiological controls in the stage of their application to avoid unnecessary dose to the personnel. The addition of hydrogen to the primary system has as objective to reduce the growth of indications taken place by intergranular corrosion in metals of the reactor core and this is achieved when the electrochemical thresholds are reached. Hydrogen to interacting with the metal surfaces it generates reductive reactions causing in consequence an increment in the concentration of soluble cobalt in the coolant one and an increment in the nitrogen concentration. To reduce the magnitude of the radiological impact that in some NC reach up to factors 10, its are injected to the system noble metals as the rhodium and the platinum, to reduce the concentration of hydrogen to the system and to be below the threshold electrochemical potential necessary to protect the internals of the reactor vessel. The external and internal operational experience generated on this protection technique to the internals of the vessel

  8. A stochastic optimization method based technique for finding out reaction paths in noble gas clusters perturbed by alkali metal ions

    International Nuclear Information System (INIS)

    Graphical abstract: The structure of a minimum in Ar19K+ cluster. Abstract: In this paper we explore the possibility of using stochastic optimizers, namely simulated annealing (SA) in locating critical points (global minima, local minima and first order saddle points) in Argon noble gas clusters perturbed by alkali metal ions namely sodium and potassium. The atomic interaction potential is the Lennard Jones potential. We also try to see if a continuous transformation in geometry during the search process can lead to a realization of a kind of minimum energy path (MEP) for transformation from one minimum geometry to another through a transition state (first order saddle point). We try our recipe for three sizes of clusters, namely (Ar)16M+, (Ar)19M+ and (Ar)24M+, where M+ is Na+ and K+.

  9. Chemical sensing with nanoparticles as optical reporters: from noble metal nanoparticles to quantum dots and upconverting nanoparticles.

    Science.gov (United States)

    Deng, Wei; Goldys, Ewa M

    2014-11-01

    A wide variety of biological and medical analyses are based on the use of optical signals to report specific molecular events. Thanks to advances in nanotechnology, various nanostructures have been extensively used as optical reporters in bio- and chemical assays. This review describes recent progress in chemical sensing using noble metal nanoparticles (gold and silver), quantum dots and upconverting nanoparticles. It provides insights into various nanoparticle-based sensing strategies including fluorescence/luminescence resonance energy transfer nanoprobes as well as activatable probes sensitive to specific changes in the biological environment. Finally we list some research challenges to be overcome in order to accelerate the development of applications of nanoparticle bio- and chemical sensors. PMID:25170528

  10. Photocatalytic Degradation of a Water Soluble Herbicide by Pure and Noble Metal Deposited TiO2 Nanocrystalline Films

    Directory of Open Access Journals (Sweden)

    Katerina Pelentridou

    2008-01-01

    Full Text Available We present the photocatalytic degradation of a water soluble sulfonylurea herbicide: azimsulfuron in the presence of titania nanocrystalline films. Efficient photodegradation of herbicide was achieved by using low-intensity black light tubes emitting in the Near-UV. The degradation of the herbicide follows first-order kinetics according to the Langmuir-Hinshelwood model. Intermediate products were identified by the LC-MS-MS technique during photocatalytic degradation. In order to increase photodegradation rate of the herbicide, we examined the effect of titania modification by depositing noble metals at various quantities and valence states. The presence of platinum at neutral valence state and optimum concentration induced higher photodegradation rates while silver-modified titania exhibited similar photocatalytic rates with those obtained with pure nanocrystalline TiO2 films. Finally, the effect of initial pH value was also examined. Acidic or alkaline media were unfavorable for azimsulfuron photodegradation.

  11. Fano effect in the angle-integrated valence band photoemission of the noble metals Cu, Ag, and Au

    International Nuclear Information System (INIS)

    Results of a combined experimental and theoretical investigation on the Fano-effect in the angle-integrated valence band photoemission of the noble metals are presented. In line with the fact that the Fano-effect is caused by the spin-orbit-coupling, the observed spin polarization of the photocurrent was found to be the more pronounced the higher the atomic number of the element investigated. The ratio of the normalized spin difference curves, however, agreed only for Cu and Ag with the ratio of the corresponding spin-orbit coupling strength parameters. The deviation from this expected behavior in the case of Au could be explained by the properties of individual d-p- and d-f-contributions to the total spin difference curves, that were found to be quite different for Au compared to Cu and Ag

  12. Metallization of bacteria cells

    Institute of Scientific and Technical Information of China (English)

    LI; Xiangfeng; (黎向锋); LI; Yaqin; (李雅芹); CAI; Jun; (蔡军); ZHANG; Deyuan; (张德远)

    2003-01-01

    Bacteria cells with different standard shapes are well suited for use as templates for the fabrication of magnetic and electrically conductive microstructures. In this paper, metallization of bacteria cells is demonstrated by an electroless deposition technique of nickel-phosphorus initiated by colloid palladium-tin catalyst on the surfaces of Citeromyces matritensis and Bacillus cereus. The activated and metallized bacteria cells have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). Results showed that both Citeromyces matritensis and Bacillus cereus had no deformation in shape after metallization; the metallized films deposited on the surfaces of bacteria cells are homogeneous in thickness and noncrystalline in phase structure. The kinetics of colloid palladium-tin solution and electroless plating on bacteria cells is discussed.

  13. A Comparison between Shear Bond Strength of VMK Master Porcelain with Three Base-metal Alloys (Ni-cr-T3, VeraBond, Super Cast) and One Noble Alloy (X-33) in Metal-ceramic Restorations

    OpenAIRE

    Dabaghi Tabriz F.; Epakchi S.; Mousavi N.; Neshati A.; Ahmadzadeh A.; Sarbazi AH.

    2013-01-01

    Statement of Problem: The increase in the use of metal-ceramic restorations and a high prevalence of porcelain chipping entails introducing an alloy which is more compatible with porcelain and causes a stronger bond between the two. This study is to compare shear bond strength of three base-metal alloys and one noble alloy with the commonly used VMK Master Porcelain. Materials and Method: Three different groups of base-metal alloys (Ni-cr-T3, Super Cast, and VeraBond) and one group of noble a...

  14. Determination of noble metals in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry, following cloud point extraction

    Science.gov (United States)

    Andreia Mesquita da Silva, Márcia; Lúcia Azzolin Frescura, Vera; José Curtius, Adilson

    2001-10-01

    A simple separation procedure for noble metals based on cloud point extraction is proposed. The analyte ions in aqueous acidic solution, obtained by the acid digestion of the samples, were complexed with O, O-diethyl-dithiophosphate and Triton X-114 was added as a non-ionic surfactant. By increasing the temperature up to the cloud point, a phase separation occurs, resulting in an aqueous phase and a surfactant-rich phase containing most of the analytes that were complexed. The metals in the surfactant-rich phase were determined by electrothermal vaporization inductively coupled plasma mass spectrometry. The extraction conditions as well as the instrumental parameters were optimized. Enrichment factors ranging from 7 (Rh) to 60 (Pt) and limits of detection from 0.6 (Pt) to 3.0 ng l -1 (Rh) were obtained in the digested samples. The extraction was not efficient for Ir. Among the reference materials analyzed in this work, only one (SRM 2670, urine) presented recommended values for Au and Pt. Due to the non-availability of adequate CRMs, accuracy was assessed by spiking known analyte amounts to the acid digests. Recoveries close to 100% were observed for all the studied elements but Ru. Poor agreement between found and recommended values was observed for non-digested urine sample, probably due to the carrier effect of co-extracted residual matrix components. However, good agreement was reached after urine acid mineralization.

  15. Rational Design of Biomolecular Templates for Synthesizing Multifunctional Noble Metal Nanoclusters toward Personalized Theranostic Applications.

    Science.gov (United States)

    Yu, Yong; Mok, Beverly Y L; Loh, Xian Jun; Tan, Yen Nee

    2016-08-01

    Biomolecule-templated or biotemplated metal nanoclusters (NCs) are ultrasmall (<2 nm) metal (Au, Ag) particles stabilized by a certain type of biomolecular template (e.g., peptides, proteins, and DNA). Due to their unique physiochemical properties, biotemplated metal NCs have been widely used in sensing, imaging, delivery and therapy. The overwhelming applications in these individual areas imply the great promise of harnessing biotemplated metal NCs in more advanced biomedical aspects such as theranostics. Although applications of biotemplated metal NCs as theranostic agents are trending, the rational design of biomolecular templates suitable for the synthesis of multifunctional metal NCs for theranostics is comparatively underexplored. This progress report first identifies the essential attributes of biotemplated metal NCs for theranostics by reviewing the state-of-art applications in each of the four modalities of theranostics, namely sensing, imaging, delivery and therapy. To achieve high efficacy in these modalities, we elucidate the design principles underlying the use of biomolecules (proteins, peptides and nucleic acids) to control the NC size, emission color and surface chemistries for post-functionalization of therapeutic moieties. We then propose a unified strategy to engineer biomolecular templates that combine all these modalities to produce multifunctional biotemplated metal NCs that can serve as the next-generation personalized theranostic agents.

  16. Method and electrochemical cell for synthesis and treatment of metal monolayer electrocatalysts metal, carbon, and oxide nanoparticles ion batch, or in continuous fashion

    Science.gov (United States)

    Adzic, Radoslav; Zhang, Junliang; Sasaki, Kotaro

    2015-04-28

    An apparatus and method for synthesis and treatment of electrocatalyst particles in batch or continuous fashion is provided. In one embodiment, the apparatus comprises a sonication bath and a two-compartment chamber submerged in the sonication bath. The upper and lower compartments are separated by a microporous material surface. The upper compartment comprises a cover and a working electrode (WE) connected to a Pt foil contact, with the foil contact connected to the microporous material. The upper chamber further comprises reference counter electrodes. The lower compartment comprises an electrochemical cell containing a solution of metal ions. In one embodiment, the method for synthesis of electrocatalysts comprises introducing a plurality of particles into the apparatus and applying sonication and an electrical potential to the microporous material connected to the WE. After the non-noble metal ions are deposited onto the particles, the non-noble metal ions are displaced by noble-metal ions by galvanic displacement.

  17. Three-dimensional noble-metal nanostructure: A new kind of substrate for sensitive, uniform, and reproducible surface-enhanced Raman scattering

    International Nuclear Information System (INIS)

    Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique for highly sensitive structural detection of low concentration analyte. The SERS activities largely depend on the topography of the substrate. In this review, we summarize the recent progress in SERS substrate, especially focusing on the three-dimensional (3D) noble-metal substrate with hierarchical nanostructure. Firstly, we introduce the background and general mechanism of 3D hierarchical SERS nanostructures. Then, a systematic overview on the fabrication, growth mechanism, and SERS property of various noble-metal substrates with 3D hierarchical nanostructures is presented. Finally, the applications of 3D hierarchical nanostructures as SERS substrates in many fields are discussed. (invited review — international conference on nanoscience and technology, china 2013)

  18. Release of Implanted Noble Gases from Metallic Glass Vitreloy During Pyrolysis

    Science.gov (United States)

    Meshik, A. P.; Hohenberg, C. M.; Burnett, D. S.; Woolum, D. S.

    2000-01-01

    Vitreloy, a metallic vitreous glass, was examined as a potential target material for the Genesis Mission solar wind collector. Stepped pyrolysis revealed that He and Ne implanted in Vitreloy were efficiently re-trapped during phase transitions.

  19. GREENER PRODUCTION OF NOBLE METAL NANOSTRUCTURES AND NANOCOMPOSITES: RISK REDUCTION AND APPLICATIONS

    Science.gov (United States)

    The synthesis of nanometal/nano metal oxide/nanostructured polymer and their stabilization (through dispersant, biodegradable polymer) involves the use of natural renewable resources such plant material extract, biodegradable polymers, sugars, vitamins and finally efficient and s...

  20. Chronology and shock history of the Bencubbin meteorite: A nitrogen, noble gas, and Ar-Ar investigation of silicates, metal and fluid inclusions

    Science.gov (United States)

    Marty, Bernard; Kelley, Simon; Turner, Grenville

    2010-11-01

    We have investigated the distribution and isotopic composition of nitrogen and noble gases, and the Ar-Ar chronology of the Bencubbin meteorite. Gases were extracted from different lithologies by both stepwise heating and vacuum crushing. Significant amounts of gases were found to be trapped within vesicles present in silicate clasts. Results indicate a global redistribution of volatile elements during a shock event caused by an impactor that collided with a planetary regolith. A transient atmosphere was created that interacted with partially or totally melted silicates and metal clasts. This atmosphere contained 15N-rich nitrogen with a pressure ⩾3 × 10 5 hPa, noble gases, and probably, although not analyzed here, other volatile species. Nitrogen and noble gases were re-distributed among bubbles, metal, and partly or totally melted silicates, according to their partition coefficients among these different phases. The occurrence of N 2 trapped in vesicles and dissolved in silicates indicates that the oxygen fugacity ( fO2) was greater than the iron-wüstite buffer during the shock event. Ar-Ar dating of Bencubbin glass gives an age of 4.20 ± 0.05 Ga, which probably dates this impact event. The cosmic-ray exposure age is estimated at ˜40 Ma with two different methods. Noble gases present isotopic signatures similar to those of "phase Q" (the major host of noble gases trapped in chondrites) but elemental patterns enriched in light noble gases (He, Ne and Ar) relative to Kr and Xe, normalized to the phase Q composition. Nitrogen isotopic data together with 40Ar/ 36Ar ratios indicate mixing between a 15N-rich component (δ 15N = +1000‰), terrestrial N, and an isotopically normal, chondritic N. Bencubbin and related 15N-rich meteorites of the CR clan do not show stable isotope (H and C) anomalies, precluding contribution of a nucleosynthetic component as the source of 15N enrichments. This leaves two possibilities, trapping of an ancient, highly fractionated

  1. Radiolytic model of CN Cofrentes using BWRVIA: analysis of the effectiveness of mitigation in locations of the vessel with application of noble metal son-line; Modelo radiolitico de C. N: Cofrentes utilizando el BWRVIA: analisis de la efectividad de mitigacion en localizaciones de la vasija con aplicacion de metales nobles on-line

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Serrano Ledesma, C.; Sanchez Zapata, J. D.

    2012-07-01

    The effectiveness of mitigation is found from two chemical parameters: electrochemical potential (pm-a hydrogen injection) and Molar Ratio (for the application of noble metals). EPRI code exists, the BWRVIA (BWR Vessel Internals Application,) which enables setting model the impact radiolysis of water, the balance of liquid-vapor phase and recirculation have on the chemical variation of these parameters.

  2. Displacement solid-phase extraction on mercapto-functionalized magnetite microspheres for inductively coupled plasma mass spectrometric determination of trace noble metals

    International Nuclear Information System (INIS)

    A flow injection online displacement solid-phase extraction (DSPE) via magnetic immobilization of mercapto-functionalized magnetite microspheres onto the inner walls of a knotted reactor (KR) coupled with inductively coupled plasma mass spectrometry was developed for selective preconcentration and determination of trace noble metals (Ru, Rh, Pd, Pt, Ir and Au) in complex matrices. Online DSPE of 2.7 mL aqueous solution gave the enhancement factors of 32-46 for the six noble metals in comparison with direct nebulization of aqueous sample solution, and the detection limits (3 s) of 2.1 ng L-1 for Ru, 1.9 ng L-1 for Rh, 2.5 ng L-1 for Pd, 1.8 ng L-1 for Ir, 1.9 ng L-1 for Pt and 1.7 ng L-1 for Au. The sample throughput of the developed method was about 20 samples h-1, and the relative standard deviation for eleven replicate determinations of the noble metals at the 30 ng L-1 level ranged from 1.2% to 2.1%. The recoveries of Ru, Rh, Pd, Pt, Ir and Au still maintained 90% even after successive 140 cycles of DSPE. The developed method was successfully applied to selective determination of trace Ru, Rh, Pd, Pt, Ir and Au in complex matrices.

  3. Production of hydrogen via steam reforming of biofuels on Ni/CeO{sub 2}-Al{sub 2}O{sub 3} catalysts promoted by noble metals

    Energy Technology Data Exchange (ETDEWEB)

    Profeti, Luciene P.R.; Ticianelli, Edson A.; Assaf, Elisabete M. [Universidade de Sao Paulo, Instituto de Quimica de Sao Carlos, C.P. 780, CEP 13560-970, Sao Carlos - SP (Brazil)

    2009-06-15

    The catalytic activity of Ni/CeO{sub 2}-Al{sub 2}O{sub 3} catalysts modified with noble metals (Pt, Ir, Pd and Ru) was investigated for the steam reform of ethanol and glycerol. The catalysts were characterized by the following techniques: Energy-dispersive X-ray, BET, X-ray diffraction, temperature-programmed reduction, UV-vis diffuse reflectance spectroscopy and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive nickel aluminate was prevented by the presence of CeO{sub 2} dispersed on alumina. The promoting effect of noble metals included a decrease in the reduction temperatures of NiO species interacting with the support, due to the hydrogen spillover effect. It was seen that the addition of noble metal stabilized the Ni sites in the reduced state along the reforming reaction, increasing the ethanol and glycerol conversions and decreasing the coke formation. The higher catalytic performance for the ethanol steam reforming at 600 C and glycerol steam reforming was obtained for the NiPd and NiPt catalysts, respectively, which presented an effluent gaseous mixture with the highest H{sub 2} yield with reasonably low amounts of CO. (author)

  4. Noble metal emissions. Final presentation, Hanover, October 17/18, 1996; Edelmetall - Emissionen. Abschlusspraesentation, Hannover, 17. und 18. Oktober 1996. Kurzfassung der Vortraege

    Energy Technology Data Exchange (ETDEWEB)

    Pohl, D. [comp.

    1997-12-31

    The discussion concerning noble metal emissions, in particular platinum emissions, and their environmental effects, started with the introduction of catalytical cleaning of gasoline engine exhaust. The Research Association for Noble Metal Emissions (Forschungsverbund Edelmetallemissionen) ws founded for the purpose of investigating problems concerning the types and volumes of noble metal emissions as well as their toxicological and allergological potential. In order to make valid statements on physiological and toxicological effects, it was necessary to identify the chemical forms of platinum and to develop powerful methods of analysis. Investigations of platinum concentrations in environmental samples suggest a 10 percent bioavailability. [Deutsch] Mit der Einfuehrung der katalytischen Abgasreinigung von Ottomotoren begann gleichzeitig die Diskussion ueber moegliche Emissionen von Edelmetallen, insbesondere von Platin, sowie ueber ihre eventuell moeglichen negativen Wirkungen in der Umwelt. Zur Erforschung der Fragestellungen zur Art und Menge der emittierten Platinmetalle, ihrer Aufnahme und dem Uebergang in den Nahrungskreislauf, sowie zu ihrem toxikologischen und allergologischen Potential wurde der Forschungsverbund ``Edelmetallemissionen`` gegruendet. Um Aussagen ueber physiologische und toxikologische Einfluesse zu machen, war es notwendig, die chemischen Erscheinungsformen des Platins zu identifizieren und nachweisstarke Analysenmethoden zu entwickeln. Untersuchungen zu Platinkonzentrationen in Umweltproben deuten auf eine Bioverfuegbarkeit von ca. 10 % hin. (ABI)

  5. Non-noble metal graphene oxide-copper (II) ions hybrid electrodes for electrocatalytic hydrogen evolution reaction

    KAUST Repository

    Muralikrishna, S.

    2015-08-25

    Non-noble metal and inexpensive graphene oxide-copper (II) ions (GO-Cu2+) hybrid catalysts have been explored for the hydrogen evolution reaction (HER). We were able to tune the binding abilities of GO toward the Cu2+ ions and hence their catalytic properties by altering the pH. We have utilized the oxygen functional moieties such as carboxylate, epoxide, and hydroxyl groups on the edge and basal planes of the GO for binding the Cu2+ ions through dative bonds. The GO-Cu2+ hybrid materials were characterized by cyclic voltammetry in sodium acetate buffer solution. The morphology of the hybrid GO-Cu2+ was characterized by atomic force microscopy. The GO-Cu2+ hybrid electrodes show good electrocatalytic activity for HER with low overpotential in acidic solution. The Tafel slope for the GO-Cu2+ hybrid electrode implies that the primary discharge step is the rate determining step and HER proceed with Volmer step. © 2015 American Institute of Chemical Engineers Environ Prog.

  6. Synthesis and mechanistic study of stable water-soluble noble metal nanostructures

    Science.gov (United States)

    Cai, Ling-Jian; Wang, Min; Hu, Yang; Qian, Dong-Jin; Chen, Meng

    2011-07-01

    Sodium salt of poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA) has been employed to prepare a series of stable nanosized metal colloids such as silver, gold, palladium, platinum, and silver-gold alloy nanostructures. All of the as-synthesized products are very stable in water. The metal nanostructures have been directly confirmed by ultraviolet-visible spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction (SAED), and also characterized by techniques such as Fourier transform infrared spectroscopy (FT-IR) and 1H NMR. Intensive study has found that the metal ions are most probably reduced by organic radicals, generated from the thermal degradation of PSSMA.

  7. Hemoglobin-carbon nanotube derived noble-metal-free Fe5C2-based catalyst for highly efficient oxygen reduction reaction.

    Science.gov (United States)

    Vij, Varun; Tiwari, Jitendra N; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S

    2016-02-03

    High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe5C2 nanoparticles-studded sp(2) carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 °C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm(-2) at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy production.

  8. Hemoglobin-carbon nanotube derived noble-metal-free Fe5C2-based catalyst for highly efficient oxygen reduction reaction

    Science.gov (United States)

    Vij, Varun; Tiwari, Jitendra N.; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S.

    2016-01-01

    High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe5C2 nanoparticles-studded sp2 carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 °C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm−2 at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy production. PMID:26839148

  9. Hemoglobin-carbon nanotube derived noble-metal-free Fe5C2-based catalyst for highly efficient oxygen reduction reaction

    Science.gov (United States)

    Vij, Varun; Tiwari, Jitendra N.; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S.

    2016-02-01

    High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe5C2 nanoparticles-studded sp2 carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 °C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm-2 at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy production.

  10. Properties and modification of two-dimensional electronic states on noble metals; Eigenschaften und Modifikation zweidimensionaler Elektronenzustaende auf Edelmetallen

    Energy Technology Data Exchange (ETDEWEB)

    Forster, F.

    2007-07-06

    In this thesis investigations on two-dimensional electronic structures of (111)-noble metal surfaces and the influence of various adsorbates upon them is presented. It chiefly focuses on the surface-localized Shockley states of Cu, Ag and Au and their band dispersion (binding energy, band mass, and spin-orbit splitting) which turns out to be a sensitive probe for surface modifications induced by adsorption processes. Angular resolved photoelectron spectroscopy enables the observation of even subtle changes in the electronic band structure of these two dimensional systems. Different mechanisms taking place at surfaces and the substrate/adsorbate interfaces influence the Shockley state in a different manner and will be analyzed using suitable adsorbate model systems. The experimental results are matched with appropriate theoretical models like the phase accumulation model and the nearly-free electron model and - if possible - with ab initio calculations based on density functional theory. This allows for the integration of the results into a stringent overall picture. The influence of sub-monolayer adsorption of Na upon the surface state regarding the significant change in surface work function is determined. A systematic study of the physisorption of noble gases shows the effect of the repulsive adsorbate-substrate interaction upon the electrons of the surface state. A step-by-step coverage of the Cu and Au(111) surfaces by monolayers of Ag creates a gradual change in the surface potential and causes the surface state to become increasingly Ag-like. For N=7 ML thick and layer-by-layer growing Ag films on Au(111), new two-dimensional electronic structures can be observed, which are attributed to the quantum well states of the Ag adsorbate. The question whether they are localized within the Ag-layer or substantially within the substrate is resolved by the investigation of their energetic and spatial evolution with increasing Ag-film thicknesses N. For this, beside the

  11. Oxygen permeation through oxygen ion oxide-noble metal dual phase composites

    NARCIS (Netherlands)

    Chen, C.S.; Kruidhof, H.; Bouwmeester, H.J.M.; Verweij, H.; Burggraaf, A.J.

    1996-01-01

    Oxygen permeation behaviour of three composites, yttria-stabilized zirconia-palladium, erbia-stabilized bismuth oxidenoble metal (silver, gold) was studied. Oxygen permeation measurements were performed under controlled oxygen pressure gradients at elevated temperatures. Air was supplied at one side

  12. Temperature-dependence of phonons, solid state properties and liquid structure of noble metals: A comparison of pair-potentials

    Science.gov (United States)

    Januszko, A.; Bose, S. K.

    2015-02-01

    Two groups of effective pair-potentials are studied from the viewpoint of their suitability in being able to describe solid state properties and liquid state structure of noble metals Cu, Ag and Au over a wide temperature range. Since the effective pair-potentials are usually empirical in nature, with parameters obtained by fitting to some reference state properties, the objective of the present study is to determine whether a particular parametrization scheme has any definite advantage over another. We consider Morse potentials with parameters determined by equilibrium lattice parameter, cohesive/sublimation energies as well as bulk modulus values of the solid at low/room temperatures. The other group of potentials considered is Erkoç potentials, where the parameters were determined first by studying dimers and further modified using bulk stability condition and bulk cohesive energy values. The potentials were then used to study the energetics of microclusters containing 3-7 atoms. Quasiharmonic results for the solid obtained at different temperatures and Monte Carlo simulation for the liquid state show that phonon spectra, thermal expansion, temperature-dependence of specific heats and liquid structure are much better described by the latter group. The first group of potentials may have an advantage in reproducing the temperature-dependence of elastic constants and bulk moduli, since they are based on room temperature values of these properties, which show only weak temperature-dependence in general for all metals. It is argued that potentials based on parameters fitted to the properties at a single volume are less versatile in capturing the temperature-dependence of various thermodynamic properties over a wide range. Potentials capable of reproducing the energetics of clusters of different co-ordination numbers and volumes per atom may fare better in this regard.

  13. Organic phase synthesis of noble metal-zinc chalcogenide core-shell nanostructures.

    Science.gov (United States)

    Kumar, Prashant; Diab, Mahmud; Flomin, Kobi; Rukenstein, Pazit; Mokari, Taleb

    2016-10-15

    Multi-component nanostructures have been attracting tremendous attention due to their ability to form novel materials with unique chemical, optical and physical properties. Development of hybrid nanostructures that are composed of metal-semiconductor components using a simple approach is of interest. Herein, we report a robust and general organic phase synthesis of metal (Au or Ag)-Zinc chalcogenide (ZnS or ZnSe) core-shell nanostructures. This synthetic protocol also enabled the growth of more compositionally complex nanostructures of Au-ZnSxSe1-x alloys and Au-ZnS-ZnSe core-shell-shell. The optical and structural properties of these hybrid nanostructures are also presented.

  14. Defect-free nanostructured alumina coating doped with noble metal nanoparticles

    International Nuclear Information System (INIS)

    Nanostructured alumina coatings loaded with platinum or gold nanoparticles were prepared by two different methods. In the first method the alumina coatings were prepared in the presence of metal ions, which were reduced using UV irradiation once the film was deposited. In the second method, polyvinylpyrrolidone-stabilized nanoparticles were first synthesized and then incorporated in the coating. The texturation of the coating occurred in a last step by hot water treatment.

  15. Assaying and smelting noble metals in sixteenth-century Austria: a comparative analytical study

    OpenAIRE

    Mongiatti, A.

    2009-01-01

    This thesis aims primarily at furthering our understanding of the technologies involved in the metallurgy of precious metals during the Renaissance, by combining a critical evaluation of historical texts with the analytical study of contemporary archaeological remains. In particular, this work focuses on high-temperature processes performed in the fire assay and smelting of ores, by investigating two archaeological case studies from sixteenth-century Austria: the small-scale laboratory of Obe...

  16. Non-noble metal vanadium phosphites with broad absorption for photocatalytic hydrogen evolution

    Science.gov (United States)

    Song, Jun-Ling; Zhang, Jian-Han; Mao, Jiang-Gao

    2016-05-01

    We reported the synthesis and crystal structures of alkali metal and alkali-earth metal phosphite, namely, CsV2(H3O)(HPO3)4 (1), and Ba3V2(HPO3)6 (2). Both compounds were prepared by hydrothermal reactions and feature unique new structures. They both exhibit 3D complicated frameworks based on VO6 octahedra which are connected by HPO3 tetrahedra via corner-sharing. Alkali or alkali earth metal cations are filled in the different channels of the frameworks. Topological analysis shows that the framework of CsV2(H3O) (HPO3)4 (1) is a new 3,3,3,4,5-connected network with the Schläfli symbol of {4.62}2{42.66.82}{63}{65.8}. The investigations of X-ray photoelectron spectroscopy (XPS) and magnetic measurement on CsV2(H3O)(HPO3)4 suggest a +3 oxidation state of the vanadium ions in compound 1. Photocatalytic performance was evaluated by photocatalytic H2 evolution and degradation of methylene blue, which shows that both compounds exhibit activity under visible-light irradiation. IR spectrum, UV-vis-NIR spectrum and thermogravimetric analysis (TGA) of compounds were also investigated.

  17. Noble-metal nanoparticles produced with colloidal lithography: fabrication, optical properties and applications

    Energy Technology Data Exchange (ETDEWEB)

    Bocchio, Noelia Laura

    2008-08-15

    In this work, metal nanoparticles produced by nanosphere lithography were studied in terms of their optical properties (in connection to their plasmon resonances), their potential application in sensing platforms - for thin layer sensing and bio-recognition events -, and for a particular case (the nanocrescents), for enhanced spectroscopy studies. The general preparation procedures introduced early in 2005 by Shumaker-Parry et al. to produce metallic nanocrescents were extended to give rise to more complex (isolated) structures, and also, by combining colloidal monolayer fabrication and plasma etching techniques, to arrays of them. The fabrication methods presented in this work were extended not only to new shapes or arrangements of particles, but included also a targeted surface tailoring of the substrates and the structures, using different thiol and silane compounds as linkers for further attachment of, i.e. polyelectrolyte layers, which allow for a controlled tailoring of their nanoenvironment. The optical properties of the nanocrescents were studied with conventional transmission spectroscopy; a simple multipole model was adapted to explain their behaviour qualitatively. In terms of applications, the results on thin film sensing using these particles show that the crescents present an interesting mode-dependent sensitivity and spatial extension. Parallel to this, the penetrations depths were modeled with two simplified schemes, obtaining good agreement with theory. The multiple modes of the particles with their characteristic decay lengths and sensitivities represent a major improvement for particle-sensing platforms compared to previous single resonance systems. The nanocrescents were also used to alter the emission properties of fluorophores placed close to them. In this work, green emitting dyes were placed at controlled distances from the structures and excited using a pulsed laser emitting in the near infrared. The fluorescence signal obtained in this

  18. ARTICLES: Methanol Tolerant Non-noble Metal Co-C-N Catalyst for Oxygen Reduction Reaction Using Urea as Nitrogen Source

    Science.gov (United States)

    Si, Yu-jun; Chen, Chang-guo; Yin, Wei; Cai, Hui

    2010-06-01

    A non-noble metal oxygen reduction reaction (ORR) catalyst labeled as Co-C-N(800) was synthesized by heat-treating a mixture of urea, cobalt chloride and acetylene black for 2 h at 800 °C in an inert nitrogen atmosphere. X-ray diffraction pattern indicates that a metallic β-Co is generated after the heat-treating process. The results from cyclic voltammograms show that the obtained Co-C-N(800) catalyst has good ORR catalytic activity in 0.5 mol/L H2SO4 solution. The catalyst is also good at methanol tolerance and stability in the acidic solution.

  19. Noble Gases

    Science.gov (United States)

    Podosek, F. A.

    2003-12-01

    The noble gases are the group of elements - helium, neon, argon, krypton, xenon - in the rightmost column of the periodic table of the elements, those which have "filled" outermost shells of electrons (two for helium, eight for the others). This configuration of electrons results in a neutral atom that has relatively low electron affinity and relatively high ionization energy. In consequence, in most natural circumstances these elements do not form chemical compounds, whence they are called "noble." Similarly, much more so than other elements in most circumstances, they partition strongly into a gas phase (as monatomic gas), so that they are called the "noble gases" (also, "inert gases"). (It should be noted, of course, that there is a sixth noble gas, radon, but all isotopes of radon are radioactive, with maximum half-life a few days, so that radon occurs in nature only because of recent production in the U-Th decay chains. The factors that govern the distribution of radon isotopes are thus quite different from those for the five gases cited. There are interesting stories about radon, but they are very different from those about the first five noble gases, and are thus outside the scope of this chapter.)In the nuclear fires in which the elements are forged, the creation and destruction of a given nuclear species depends on its nuclear properties, not on whether it will have a filled outermost shell when things cool off and nuclei begin to gather electrons. The numerology of nuclear physics is different from that of chemistry, so that in the cosmos at large there is nothing systematically special about the abundances of the noble gases as compared to other elements. We live in a very nonrepresentative part of the cosmos, however. As is discussed elsewhere in this volume, the outstanding generalization about the geo-/cosmochemistry of the terrestrial planets is that at some point thermodynamic conditions dictated phase separation of solids from gases, and that the

  20. Supported noble metal catalysts in the catalytic wet air oxidation of industrial wastewaters and sewage sludges.

    Science.gov (United States)

    Besson, M; Descorme, C; Bernardi, M; Gallezot, P; di Gregorio, F; Grosjean, N; Minh, D Pham; Pintar, A

    2010-12-01

    This paper reviews some catalytic wet air oxidation (CWAO) investigations of industrial wastewaters over platinum and ruthenium catalysts supported on TiO2 and ZrO2 formulated to be active and resistant to leaching, with particular focus on the stability of the catalyst. Catalyst recycling experiments were performed in batch reactors and long-term stability tests were conducted in trickle-bed reactors. The catalyst did not leach upon treatment of Kraft bleaching plant and olive oil mill effluents, and could be either recycled or used for long periods of time in continuous reactors. Conversely, these catalysts were rapidly leached when used to treat effluents from the production of polymeric membranes containing N,N-dimethylformamide. The intermediate formation of amines, such as dimethylamine and methylamine with a high complexing capacity for the metal, was shown to be responsible for the metal leaching. These heterogeneous catalysts also deactivated upon CWAO of sewage sludges due to the adsorption of the solid organic matter. Pre-sonication of the sludge to disintegrate the flocs and improve solubility was inefficient. PMID:21214003

  1. Simultaneous Elimination of Formaldehyde and Ozone Byproduct Using Noble Metal Modified TiO2 Films in the Gaseous VUV Photocatalysis

    Directory of Open Access Journals (Sweden)

    Pingfeng Fu

    2012-01-01

    Full Text Available Simultaneous removal of low concentration formaldehyde (HCHO and ozone byproduct was investigated in the gaseous VUV (vacuum ultraviolet photocatalysis by using noble metal modified TiO2 films. Noble metal (Pt, Au, or Pd nanoparticles were deposited on TiO2 films with ultrafine particle size and uniform distribution. Under 35 h VUV irradiation, the HCHO gas (ca. 420 ppbv was dynamically degraded to a level of 10~45 ppbv without catalyst deactivation, and over 50% O3 byproduct was in situ decomposed in the reactor. However, under the same conditions, the outlet HCHO concentration remained at 125~178 ppbv in the O3 + UV254 nm photocatalysis process and 190~260 ppbv in the UV254 nm photocatalysis process. And the catalyst deactivation also appeared under UV254 nm irradiation. Metallic Pt or Au could simultaneously increase the elimination of HCHO and ozone, but the PdO oxide seemed to inhibit the HCHO oxidation in the UV254 nm photocatalysis. Deposition of metallic Pt or Au reduces the recombination of h+/e− pairs and thus increases the HCHO oxidation and O3 reduction reactions. In addition, adsorbed O3 may be partly decomposed by photogenerated electrons trapped on metallic Pt or Au nanoparticles under UV irradiation.

  2. Effectiveness of diffusion coatings of noble metals for heat resistance improvement

    International Nuclear Information System (INIS)

    To establish the possibility of palladium coatings substitution for platinum ones a study was made on heat resistance of these coatings for 5VMTs niobium alloy at 1150 deg C. Coatings were applied at 950 deg C by diffusion method in lithium melt with addition of 3 mas% palladium or platinum. Heat resistance tests of samples with coatings were conducted in the air during 100 h. The efficiency of protective coatings was evaluated by gravimetric and metallographic methods. It was established that palladium coating thickness changes less intensively as compared to platinum one and is controlled by the process of formation of dense film of hard oxide preventing evaporation of metallic palladium. It was concluded that substitution of niobium alloy palladization for platinization is possible

  3. Noble metals nanoparticles on titanium dioxide nanostructured films and the influence of their photocatalytic activity

    International Nuclear Information System (INIS)

    Currently, nanoscience and nanotechnology are considered an emerging field and continuously breaking the barrier among various disciplines. The main focus of study involves controlling structures at molecular level, arranging the atoms in order to achieve an understanding and controlling the fundamental properties of matter. In this study, molecular changes on the basis of morphology, optical and crystalline properties of TiO2hin films in order to increase their photon efficiency were proposed. The TiO2 thin films were prepared by sol gel process evaluating the influence of different acids and templates to obtain the nano structured arrangements. Then, metal nanoparticles like Au, Ag, Pd and Pt were incorporated on TiO2 thin films. This incorporation might minimize the electron-hole recombination, so it could improve the photon efficiency. From the several routes studied, the TiO2 thin films prepared with acetic acid showed the best performance by the reason of low agglomeration of TiO2 grains, which favors the exposure of the photoactive sites. The presence of template in the formulation had a slightly effect on photon efficiency, possible due to the higher agglomeration of the grains on the TiO2 thin films. The addition of Pt and Au nanoparticles on TiO2 thin films showed superior photon efficiency. The TiO2 thin films with hexamine and metallic nanoparticles did not show the improvement on photon efficiency except for Pt and Au nanoparticles. On these situations, the improvement on photon efficiency is might be due to a possible decrease at the electron-hole recombination's velocity. Thus, the present work demonstrates the great influence of preparation conditions on the optical, morphological properties and the photon efficiency. In the future, with greater understanding of the mechanism of this influence, the properties of TiO2 thin films will be able tailoring depending on the application. (author)

  4. Catalytic methanation reaction over alumina supported cobalt oxide doped noble metal oxides for the purification of simulated natural gas

    Institute of Scientific and Technical Information of China (English)

    Wan Azelee Wan Abu Bakar; Rusmidah Ali; Abdul Aziz Abdul Kadir; Salmiah Jamal Mat Rosid; Nurul Shafeeqa Mohammad

    2012-01-01

    A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co( 10∶90 )/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co( 10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co( 10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis (EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co( 10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co( 10∶90)/Al2O3 catalyst.

  5. Intriguing structures and magic sizes of heavy noble metal nanoclusters around size 55 governed by relativistic effect and covalent bonding

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, X. J.; Xue, X. L.; Jia, Yu [International Laboratory for Quantum Functional Materials of Henan and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Guo, Z. X. [International Laboratory for Quantum Functional Materials of Henan and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Department of Chemistry and London Centre for Nanotechnology, University College London, London WC1H (United Kingdom); Li, S. F., E-mail: sflizzu@zzu.edu.cn [International Laboratory for Quantum Functional Materials of Henan and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001 (China); ICQD, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zhang, Zhenyu, E-mail: zhangzy@ustc.edu.cn [ICQD, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Gao, Y. F., E-mail: ygao7@utk.edu [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-11-07

    Nanoclusters usually display exotic physical and chemical properties due to their intriguing geometric structures in contrast to their bulk counterparts. By means of first-principles calculations within density functional theory, we find that heavy noble metal Pt{sub N} nanoclusters around the size N = 55 begin to prefer an open configuration, rather than previously reported close-packed icosahedron or core-shell structures. Particularly, for Pt{sub N}, the widely supposed icosahedronal magic cluster is changed to a three-atomic-layered structure with D{sub 6h} symmetry, which can be well addressed by our recently established generalized Wulff construction principle (GWCP). However, the magic number of Pt{sub N} clusters around 55 is shifted to a new odd number of 57. The high symmetric three-layered Pt{sub 57} motif is mainly stabilized by the enhanced covalent bonding contributed by both spin-orbital coupling effect and the open d orbital (5d{sup 9}6s{sup 1}) of Pt, which result in a delicate balance between the enhanced Pt–Pt covalent bonding of the interlayers and negligible d dangling bonds on the cluster edges. These findings about Pt{sub N} clusters are also applicable to Ir{sub N} clusters, but qualitatively different from their earlier neighboring element Os and their later neighboring element Au. The magic numbers for Os and Au are even, being 56 and 58, respectively. The findings of the new odd magic number 57 are the important supplementary of the recently established GWCP.

  6. The effect of noble metals on catalytic methanation reaction over supported Mn/Ni oxide based catalysts

    Directory of Open Access Journals (Sweden)

    Wan Azelee Wan Abu Bakar

    2015-09-01

    Full Text Available Carbon dioxide (CO2 in sour natural gas can be removed using green technology via catalytic methanation reaction by converting CO2 to methane (CH4 gas. Using waste to wealth concept, production of CH4 would increase as well as creating environmental friendly approach for the purification of natural gas. In this research, a series of alumina supported manganese–nickel oxide based catalysts doped with noble metals such as ruthenium and palladium were prepared by wetness impregnation method. The prepared catalysts were run catalytic screening process using in-house built micro reactor coupled with Fourier Transform Infra Red (FTIR spectroscopy to study the percentage CO2 conversion and CH4 formation analyzed by GC. Ru/Mn/Ni(5:35:60/Al2O3 calcined at 1000 °C was found to be the potential catalyst which gave 99.74% of CO2 conversion and 72.36% of CH4 formation at 400 °C reaction temperature. XRD diffractogram illustrated that the supported catalyst was in polycrystalline with some amorphous state at 1000 °C calcination temperature with the presence of NiO as active site. According to FESEM micrographs, both fresh and used catalysts displayed spherical shape with small particle sizes in agglomerated and aggregated mixture. Nitrogen Adsorption analysis revealed that both catalysts were in mesoporous structures with BET surface area in the range of 46–60 m2/g. All the impurities have been removed at 1000 °C calcination temperature as presented by FTIR, TGA–DTA and EDX data.

  7. Sputter fabricated Nb-oxide-Nb josephson junctions incorporating post-oxidation noble metal layers

    International Nuclear Information System (INIS)

    We present an extension, involving other metals, of the work of Hawkins and Clarke, who found that a thin layer of copper prevented the formation of the superconductive shorts which are an inevitable consequence of sputtering niobium counter-electrodes directly on top of niobium oxide. We find gold to be the most satisfactory, and that 0.3 nm is sufficient to guarantee short-free junctions of excellent electrical and mechanical stability, though high excess conductance means they are best suited to shunted-junction applications, as in SQUIDs. We present results for critical current dependence on oxide thickness and on gold thickness. Our data shows that thermal oxide growth is described by the Cabrera-Mott mechanism. We show that the protective effect of the gold layer can be understood in terms of the electro-chemistry of the Nb-oxide-Au structure, and that the reduced quasi-particle resistance of the junctions relative to goldfree junctions with evaporated counterelectrodes can be explained in terms of barrier shape modification, and not by proximity effect mechanisms. The performance of a DC SQUID based on these junctions is described

  8. Noble metal-free reduced graphene oxide-ZnxCd₁-xS nanocomposite with enhanced solar photocatalytic H₂-production performance.

    Science.gov (United States)

    Zhang, Jun; Yu, Jiaguo; Jaroniec, Mietek; Gong, Jian Ru

    2012-09-12

    Design and preparation of efficient artificial photosynthetic systems for harvesting solar energy by production of hydrogen from water splitting is of great importance from both theoretical and practical viewpoints. ZnS-based solid solutions have been fully proved to be an efficient visible-light driven photocatalysts, however, the H(2)-production rate observed for these solid solutions is far from exciting and sometimes an expensive Pt cocatalyst is still needed in order to achieve higher quantum efficiency. Here, for the first time we report the high solar photocatalytic H(2)-production activity over the noble metal-free reduced graphene oxide (RGO)-Zn(x)Cd(1-x)S nanocomposite prepared by a facile coprecipitation-hydrothermal reduction strategy. The optimized RGO-Zn(0.8)Cd(0.2)S photocatalyst has a high H(2)-production rate of 1824 μmol h(-1) g(-1) at the RGO content of 0.25 wt % and the apparent quantum efficiency of 23.4% at 420 nm (the energy conversion efficiency is ca. 0.36% at simulated one-sun (AM 1.5G) illumination). The results exhibit significantly improved photocatalytic hydrogen production by 450% compared with that of the pristine Zn(0.8)Cd(0.2)S, and are better than that of the optimized Pt-Zn(0.8)Cd(0.2)S under the same reaction conditions, showing that the RGO-Zn(0.8)Cd(0.2)S nanocomposite represents one of the most highly active metal sulfide photocatalyts in the absence of noble metal cocatalysts. This work creates a green and simple way for using RGO as a support to enhance the photocatalytic H(2)-production activity of Zn(x)Cd(1-x)S, and also demonstrates that RGO is a promising substitute for noble metals in photocatalytic H(2)-production.

  9. Modeling and simulation of optical properties of noble metals triangular nanoprisms

    Science.gov (United States)

    Alsheheri, Soad

    Gold and silver has gained huge attention across the scientific community for its applications arising from its plasmonic properties. The optical properties achieved by these materials via excitation of plasmons is very unique to these materials and used as diagnostic and therapeutic agents in the field of medicine, and as sensors in a gamut of disciplines such as energy and environmental protection to name a few. Surface plasmon resonance (SPR) properties of the gold and silver are size and shape dependent. Of the various shapes reported in literature, triangular nanoprisms has tunable optical properties in the visible and near IR region by manipulating the structural features such as thickness, edge length, and morphology of tip. To understand the effect of these parameters on dipole surface plasmon resonance we have constructed triangular silver nanoprism and sandwich of gold and triangular nanoprism using Optiwave FDTD. Silver triangular nanoprism has exhibited blue shift on introduction of truncation and the blue shift continued further with depth of truncation. Similar observations were made for increase in thickness of nanoprism. In contrast, increase in edge length of the nanoprism has introduced a blue shift in dipole surface plasmon resonance. Coupling of gold and silver as sandwich with a dielectric material has introduced two plasmon resonance peaks in the visible and near IR region. In contrast to individual silver triangular nanoprism, increasing the edge length and thickness of gold and silver has introduced a red shift. Interestingly, thickness of the dielectric layer controls the wavelength of the dipole plasmon resonance of metals in the sandwich and its strength.

  10. Stabilisation of late transition metal and noble metal films in hexagonal and body centred tetragonal phases by epitaxial growth

    Energy Technology Data Exchange (ETDEWEB)

    Hueger, E.

    2005-08-26

    In this work ultrathin metallic films with a crystal phase different to their natural bulk structure were produced by hetero-epitaxial growth on metallic substrates. A further aim of this work was to understand the initiation, growth and stability of crystal phase modifications of these films. there exist cases where the films turn beyond the pseudomorphic-growth to a crystal phase different from their natural bulk structure. The present work presents and discusses such a case in addition to the general phenomenon of pseudomorphic-growth. In particular it is shown that metals whose natural phase is face centred cubic (fcc) can be grown in body centred tetragonal (bct) or hexagonal close packed (hcp) phases in the form of thin films on (001) surfaces of appropriate substrates. The growth behavior, electron diffraction analysis, appearance conditions, geometric fit considerations, examples and a discussion of the phase stability of non-covered films and superlattices is given reviewing all epitaxial-systems whose diffraction pattern can be explained by the hexagonal or pseudomorphic bct phase. (orig.)

  11. Radiolytic model of Cofrentes NPP using the BWRVIA: analysis of the effectiveness of mitigation in localizations of the vessel with noble metal application on-line; Modelo Radiolitico de C.N. Cofrentes utilizando el BWRVIA: analisis de la efectividad de mitigacion en localizaciones de la vasija con aplicacion de metales nobles on-line

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Zapata, J. D.; Martin-Serrano, C.

    2013-03-01

    Chemistry is one of the principal factors that takes part in IGSCC materials susceptibility. BWR industry has been applying different mitigation techniques against IGSCC: hydrogen injection and noble metals. Mitigation effectiveness is checked by studying chemical parameters: ECP (for hydrogen injection) and Molar Ratio (for noble metal application). There is a software from EPRI called BWRVIA that allows to modelize radiolysis influence in parameters variation and obtain them at different points in the vessel. Recently, this kind of studies have become very relevant within BWR industry because it is the previous step to implement BWRVIP-62-A guidelines in order to get longer inspection intervals at vessel location where mitigation effectiveness is justified, with the cost savings for plants that this means. (Author)

  12. In Situ Studies of Surface Mobility on Noble Metal Model Catalysts Using STM and XPS at Ambient Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Butcher, Derek Robert [Univ. of California, Berkeley, CA (United States)

    2010-06-01

    High Pressure Scanning Tunneling Microscopy (HP-STM) and Ambient Pressure X-ray Photoelectron Spectroscopy were used to study the structural properties and catalytic behavior of noble metal surfaces at high pressure. HP-STM was used to study the structural rearrangement of the top most atomic surface layer of the metal surfaces in response to changes in gas pressure and reactive conditions. AP-XPS was applied to single crystal and nanoparticle systems to monitor changes in the chemical composition of the surface layer in response to changing gas conditions. STM studies on the Pt(100) crystal face showed the lifting of the Pt(100)-hex surface reconstruction in the presence of CO, H2, and Benzene. The gas adsorption and subsequent charge transfer relieves the surface strain caused by the low coordination number of the (100) surface atoms allowing the formation of a (1 x 1) surface structure commensurate with the bulk terminated crystal structure. The surface phase change causes a transformation of the surface layer from hexagonal packing geometry to a four-fold symmetric surface which is rich in atomic defects. Lifting the hex reconstruction at room temperature resulted in a surface structure decorated with 2-3 nm Pt adatom islands with a high density of step edge sites. Annealing the surface at a modest temperature (150 C) in the presence of a high pressure of CO or H2 increased the surface diffusion of the Pt atoms causing the adatom islands to aggregate reducing the surface concentration of low coordination defect sites. Ethylene hydrogenation was studied on the Pt(100) surface using HP-STM. At low pressure, the lifting of the hex reconstruction was observed in the STM images. Increasing the ethylene pressure to 1 Torr, was found to regenerate the hexagonally symmetric reconstructed phase. At room temperature ethylene undergoes a structural rearrangement to form ethylidyne. Ethylidyne preferentially binds at the three-fold hollow sites, which

  13. Poisoning of noble metal catalysts by arsenic and silicon compounds in an oxidizing atmosphere. Die Vergiftung von Edelmetall-Katalysatoren durch Arsen- und Siliziumverbindungen unter oxidierenden Verbindungen

    Energy Technology Data Exchange (ETDEWEB)

    Kaizik, A.

    1984-01-12

    The dissertation deals with the poisoning of noble metal catalysts by arsenic and silicon compounds in an oxidizing atmosphere. The problem was studied in the field of catalytic exhaust and waste air post-combustion, but the findings can be applied to other catalytic processes in which arsenic and silicon compounds may occur as catalyst poisons. The following issues were investigated: 1. Kinetics of arsenic and silicon poisoning of platinum-containing carrier catalysts; 2. Regeneration of poisoned catalysts; 3. mathematical modelling of the poisoning processes.

  14. Axial Changes of Catalyst Structure and Temperature in a Fixed-Bed Microreactor During Noble Metal Catalysed Partial Oxidation of Methane

    DEFF Research Database (Denmark)

    Hannemann, S.; Grunwaldt, Jan-Dierk; Kimmerle, B.;

    2009-01-01

    -heating by the exothermic methane oxidation was too strong. The results indicate that in the oxidized zone mainly combustion of methane occurs, whereas in the reduced part direct partial oxidation and reforming reactions prevail. The results demonstrate how spatially resolved spectroscopy can help in understanding......-line mass spectrometry. This experimental strategy allowed collecting data on the structure of the noble metal (oxidation state) and the temperature along the catalyst bed. The reaction was investigated in a fixed-bed quartz microreactor (1-1.5 mm diameter) following the catalytic performance by on-line gas...... catalytic reactions involving different reaction zones and gradients even in micro scale fixed-bed reactors....

  15. Measurement of the composition of noble-metal particles in high-burnup CANDU fuel by wavelength dispersive X-ray microanalysis

    Energy Technology Data Exchange (ETDEWEB)

    Hocking, W.H.; Szostak, F.J

    1999-09-01

    An investigation of the composition of the metallic inclusions in CANDU fuel, which contain Mo, Tc, Ru, Rh and Pd, has been conducted as a function of burnup by wavelength dispersive X-ray (WDX) microanalysis. Quantitative measurements were performed on micrometer sized particles embedded in thin sections of fuel using elemental standards and the ZAF method. Because the fission yields of the noble metals change with burnup, as a consequence of a shift from almost entirely {sup 235}U fission to mainly {sup 239}Pu fission, their inventories were calculated from the fuel power histories using the WIMS-Origin code for comparison with experiment. Contrary to expectations that the oxygen potential would be buffered by progressive Mo oxidation, little evidence was obtained for reduced incorporation of Mo in the noble-metal particles at high burnup. These surprising results are discussed with respect to the oxygen balance in irradiated CANDU fuels and the likely intrinsic and extrinsic sinks for excess oxygen. (author)

  16. A computational study on structure, stability and bonding in Noble Gas bound metal Nitrates, Sulfates and Carbonates (Metal = Cu, Ag, Au)

    Indian Academy of Sciences (India)

    MANAS GHARA; SUDIP PAN; JYOTIRMOY DEB; ANAND KUMAR; UTPAL SARKAR; PRATIM KUMAR CHATTARAJ

    2016-10-01

    A density functional theory based study is performed to investigate the noble gas (Ng = Ar-Rn) binding ability of nitrates, sulfates and carbonates of noble metal (M). Their ability to bind Ng atoms is assessed through bond dissociation energy and thermochemical parameters like dissociation enthalpy and dissociation free energy change corresponding to the dissociation of Ng bound compound producing Ngand the respective salt. The zero-point energy corrected dissociation energy values per Ng atom for the dissociation process producing Ng atom(s) and the corresponding salts range within 6.0–13.1 kcal/mol in NgCuNO₃, 3.1–9.8 kcal/mol in NgAgNO₃, 6.0–13.2 kcal/mol in NgCuSO₄, 3.2–10.1 kcal/mol in NgAgSO₄, 5.1–11.7 kcal/mol in Ng₂Cu₂SO₄, 2.5–8.6 kcal/mol in Ng₂Ag₂SO₂, 8.1–19.9 kcal/mol in Ng₂Au2SO₂, 5.7–12.4 kcal/mol in NgCuCO₃, 2.3–8.0 kcal/mol in Ng₂Ag₂CO₃ and 7.3–18.2 kcal/mol in Ng₂Au₂CO₃, with a gradual increase in moving from Ar to Rn. For a given type of system, the stability of Ng bound analogues follows the order as Au > Cu > Ag. All dissociation processes are endothermic in nature whereas they become endergonic as well in most of the cases of Kr-Rn bound analogues at 298 K. Natural population analysis along with the computation of Wiberg bond indices, and electron density analyses provide insights into the nature of the Ng-M bonds. The Ng-M bonds can be represented as partial covalent bonds as supported by the different electron density descriptors.

  17. Synthesis, characterization and photocatalytic activity of noble metal-modified TiO{sub 2} nanosheets with exposed {0 0 1} facets

    Energy Technology Data Exchange (ETDEWEB)

    Diak, Magdalena; Grabowska, Ewelina, E-mail: ewelina.grabowska@ug.edu.pl; Zaleska, Adriana

    2015-08-30

    Graphical abstract: - Highlights: • TiO{sub 2} nanosheets with exposed {0 0 1} facets were prepared by hydrothermal method. • Pd and Ag NPs-loaded enhanced the photocatalytic activity under visible irradiation. • Photodeposition is an effective method to obtain noble metal NPs on TiO{sub 2} surface. - Abstract: Pt, Pd, Ag and Au nanoparticles were photodeposited on the {0 0 1} crystal facets of the TiO{sub 2} anatase nanosheets. Morphological and surface characterization of the samples as well as photocatalytic activity were studied. The influence of metal precursor concentration used during photodeposition (0.05−0.5%) on size of formed metal nanoparticles together with UV and vis-mediated activity of Pt, Pd, Ag or Au−TiO{sub 2} was investigated. Generally, samples obtained by photodeposition of noble metal nanoparticles using their 0.2% precursor solutions revealed highest activity in phenol degradation reaction under visible light (λ > 420 nm). The photoactivity of the as-prepared samples with respect to the modified metal species was ordered Ag≅Pd > Au > Pt. TEM analysis showed that photodeposited metal nanoparticles appeared only on {0 0 1} facets of TiO{sub 2}. The average degradation rate of phenol in the presence of Pd and Ag−TiO{sub 2} was 0.5 μmol dm{sup −3} min{sup −1} after 60 min of irradiation under visible light, and was five times higher than that of pure TiO{sub 2} nanosheets.

  18. TLC-SERS Plates with a Built-In SERS Layer Consisting of Cap-Shaped Noble Metal Nanoparticles Intended for Environmental Monitoring and Food Safety Assurance

    Directory of Open Access Journals (Sweden)

    H. Takei

    2015-01-01

    Full Text Available We report on a thin layer chromatograph (TLC with a built-in surface enhanced Raman scattering (SERS layer for in-situ identification of chemical species separated by TLC. Our goal is to monitor mixture samples or diluted target molecules suspended in a host material, as happens often in environmental monitoring or detection of food additives. We demonstrate that the TLC-SERS can separate mixture samples and provide in-situ SERS spectra. One sample investigated was a mixture consisting of equal portions of Raman-active chemical species, rhodamine 6 G (R6G, crystal violet (CV, and 1,2-di(4-pyridylethylene (BPE. The three components could be separated and their SERS spectra were obtained from different locations. Another sample was skim milk with a trace amount of melamine. Without development, no characteristic peaks were observed, but after development, a peak was observed at 694 cm−1. Unlike previous TLC-SERS whereby noble metal nanoparticles are added after development of a sample, having a built-in SERS layer greatly facilitates analysis as well as maintaining high uniformity of noble metal nanoparticles.

  19. Decoration of Micro-/Nanoscale Noble Metal Particles on 3D Porous Nickel Using Electrodeposition Technique as Electrocatalyst for Hydrogen Evolution Reaction in Alkaline Electrolyte.

    Science.gov (United States)

    Qian, Xin; Hang, Tao; Shanmugam, Sangaraju; Li, Ming

    2015-07-29

    Micro-/nanoscale noble metal (Ag, Au, and Pt) particle-decorated 3D porous nickel electrodes for hydrogen evolution reaction (HER) in alkaline electrolyte are fabricated via galvanostatic electrodeposition technique. The developed electrodes are characterized by field emission scanning electron microscopy and electrochemical measurements including Tafel polarization curves, cyclic voltammetry, and electrochemical impedance spectroscopy. It is clearly shown that the enlarged real surface area caused by 3D highly porous dendritic structure has greatly reinforced the electrocatalytic activity toward HER. Comparative analysis of electrodeposited Ag, Au, and Pt particle-decorated porous nickel electrodes for HER indicates that both intrinsic property and size of the noble metal particles can lead to distinct catalytic activities. Both nanoscale Au and Pt particles have further reinforcement effect toward HER, whereas microscale Ag particles exhibit the reverse effect. As an effective 3D hydrogen evolution cathode, the nanoscale Pt-particle-decorated 3D porous nickel electrode demonstrates the highest catalytic activity with an extremely low overpotential of -0.045 V for hydrogen production, a considerable exchange current density of 9.47 mA cm(-2) at 25 °C, and high durability in long-term electrolysis, all of which are attributed to the intrinsic catalytic property and the extremely small size of Pt particles.

  20. PARAMETRIC EFFECTS OF ANTI-FOAM COMPOSITION, SIMULANT PROPERTIES AND NOBLE METALS ON THE GAS HOLDUP AND RELEASE OF A NON-NEWTONIAN WASTE SLURRY SIMULANT

    International Nuclear Information System (INIS)

    Gas holdup tests were performed in bench-scale and small-scale mechanically-agitated mixing systems at the Savannah River National Laboratory (SRNL) for a simulant of waste from the Hanford Tank 241-AZ-101. These featured additions of DOW Corning Q2-3183A anti-foam agent. Results indicated that this anti-foam agent (AFA) increased gas holdup in the waste simulant by about a factor of four and, counter-intuitively, that the holdup increased as the non-newtonian simulant shear strength decreased (apparent viscosity decreased). Such results raised the potential of increased flammable gas retention in Hanford Waste Treatment and Immobilization Plant (WTP) vessels mixed by air sparging and pulse-jet mixers (PJMs) during a Design Basis Event (DBE). Additional testing was performed to determine the effects of simulant properties, composition of alternate AFAs, and presence of trace noble metals. Key results are that: (1) Increased gas holdup resulting from addition of Q2-3183A is due to a decrease in surface tension that supports small bubbles which have low rise velocities. (2) Dow Corning 1520-US AFA shows it to be a viable replacement to Dow Corning Q2-3183A AFA. This alternative AFA, however, requires significantly higher dosage for the same anti-foam function. (3) Addition of noble metals to the AZ-101 waste simulant does not produce a catalytic gas retention effect with the AFA

  1. Proceedings of the 4th seminar of R and D on advanced ORIENT 'strategy and technical requirement for new resource of noble metals in advanced atomic energy science'

    International Nuclear Information System (INIS)

    The 4th Seminar of R and D on advanced ORIENT, 'Strategy and technical requirement for new resource of noble metals in advanced atomic energy science' was held in Swany hall, Rokkasho-Mura, on July 30th, 2010 organized by Japan Atomic Energy Agency. The first meeting of this seminar was held at Oarai, Ibaraki on May, 2007, the second seminar was held at Tokai, on November, 2008, and the third seminar was held at Sendai, on October, 2009. Spent nuclear fuel should be recognized as not only mass of radioactive elements but also potentially useful materials including platinum metals and rare earth elements. Taking the cooperation with universities related companies and research institutes, into consideration, we aimed at expanding and progressing the basic researches. In this seminar, there are many poster presentation included, and the useful discussion with many students are performed. This report records abstracts and figures submitted from the oral speakers in this seminar. (author)

  2. 贵金属/WO3复合纳米晶的气敏与光催化研究进展%Recent progress in noble metal/WO_3 composite nanostructures for gas-sensing and photocatalytic applications

    Institute of Scientific and Technical Information of China (English)

    尹莉; 陈德良; 李涛; 张毅; 张锐

    2012-01-01

    WO3作为新型的气敏材料和光催化剂具有广阔的应用前景,通过贵金属纳米簇修饰后的WO3复合纳米晶比WO3基体材料在性能上大幅提高。本文综述了贵金属修饰对WO3基体气敏和光催化性能的影响,其中气敏性能以不同敏感气体(如NOx、H2S、H2等)为分类依据,而光催化性能以不同贵金属(Au、Ag、Pt等)添加剂为分类依据,系统综述了贵金属/WO3复合纳米晶的气敏和光催化性能研究最新进展,并总结了常见贵金属/WO3的气敏和光催化机理模型,提出了贵金属/WO3在气敏和光催化应用过程中存在的问题及前景展望。%WO3-based composite nanostructures have been used as the promising materials for gas-sensing and photocatalytic applications.The performance of WO3 composite nanostructures modified by noble metals can be greatly improved compared to individual WO3 material.In this paper,the recent progress in the gas-sensing and photocatalytic properties of noble-metal-modified WO3 composite nanostructures is reviewed.Effects of preparation methods and noble metal dopants on the gas-sensing properties to various gases,such as NOx,H2S,H2 and etc.,have been discussed in detail.The gas sensing mechanisms of noble-metal-modified WO3 composite nanostructures have been introduced.The photocatalytic properties of noble-metal-modified WO3 composite nanostructures are reviewed according to the species of noble metal(ssuch as Au,Ag,Pt and Pd nanoclusters).The recent achievements in improving the photocatalytic performance of noble-metal-modified WO3 composite nanocatalysts and the related photocatalytic mechanisms have been summarized.Some existing issues and future trends in development of the noble-metal-modified WO3 composite photocatalysts have been also included.

  3. 4,6-Dimethyl-dibenzothiophene conversion over Al{sub 2}O{sub 3}-TiO{sub 2}-supported noble metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Nunez, Sara [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, Vicentina, Iztapalapa, 09340, Mexico, D.F. (Mexico); Escobar, Jose, E-mail: jeaguila@imp.mx [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas 152, San Bartolo Atepehuacan, Gustavo A. Madero, 07730, Mexico, D.F. (Mexico); Vazquez, Armando; Reyes, Jose Antonio de los [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, Vicentina, Iztapalapa, 09340, Mexico, D.F. (Mexico); Hernandez-Barrera, Melissa [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas 152, San Bartolo Atepehuacan, Gustavo A. Madero, 07730, Mexico, D.F. (Mexico)

    2011-03-15

    Research highlights: {yields} Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3}-TiO{sub 2} (molar ratio Al/Ti = 2, AT2) mixed oxides were pore-filling impregnated to obtain Pd, Pt and Pd-Pt catalysts with {approx}1 wt% nominal metal loading. {yields} Reduced catalysts were tested in the 4,6-dimethyl-dibenzothiophene hydrodesulfurization (HDS). {yields} In Pd-containing materials, TiO{sub 2} incorporation into the alumina support was favorable to the catalytic activity of noble metal catalysts. {yields} Enhanced intrinsic activity (per exposed metallic site) was obtained in Pt-containing catalysts supported on the AT2 mixed oxide. {yields} Yield to different products over various catalysts seemed to be strongly influenced by metallic particles dispersion. - Abstract: Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3}-TiO{sub 2} (molar ratio Al/Ti = 2, AT2) mixed oxides were synthesized using a low-temperature sol-gel method and were further pore-filling impregnated to obtain Pd and Pt catalysts with {approx}1 wt% nominal metal loading. Simultaneous impregnation was used to prepare bimetallic materials at Pd:Pt = 80:20. Solids characterization was carried out by N{sub 2}-physisorption, high-resolution transmission electron microscopy (HR-TEM and E-FTEM), X-ray diffraction, temperature-programmed reduction and CO-chemisorption. Reduced (350 deg. C, H{sub 2} flow) catalysts were tested in the 4,6-dimethyl-dibenzothiophene hydrodesulfurization (HDS) (in n-dodecane, at 300 deg. C and 5.5 MPa, batch reactor). In Pd-containing materials, TiO{sub 2} incorporation into the alumina support was favorable to the catalytic activity of noble metal catalysts, where bimetallic Pd-Pt with AT2 carrier had the highest organo-S compound conversion. Enhanced intrinsic activity (per exposed metallic site) was obtained in Pt-containing catalysts supported on the AT2 mixed oxide (as compared to alumina-supported ones). Yield to different products over various catalysts seemed to be strongly influenced by

  4. Noble-metal-free carbon nanotube-Cd0.1Zn0.9S composites for high visible-light photocatalytic H2-production performance.

    Science.gov (United States)

    Yu, Jiaguo; Yang, Bin; Cheng, Bei

    2012-04-21

    Visible light photocatalytic H(2) production from water splitting using solar light is of great importance from the viewpoint of solar energy conversion and storage. In this study, a novel visible-light-driven photocatalyst multiwalled carbon nanotube modified Cd(0.1)Zn(0.9)S solid solution (CNT/Cd(0.1)Zn(0.9)S) was prepared by a simple hydrothermal method. The prepared samples exhibited enhanced photocatalytic H(2)-production activity under visible light. CNT content had a great influence on photocatalytic activity and an optimum amount of CNT was determined to be ca. 0.25 wt%, at which the CNT/Cd(0.1)Zn(0.9)S displayed the highest photocatalytic activity under visible light, giving an H(2)-production rate of 78.2 μmol h(-1) with an apparent quantum efficiency (QE) of 7.9% at 420 nm, even without any noble metal cocatalysts, exceeding that of pure Cd(0.1)Zn(0.9)S by more than 3.3 times. The enhanced photocatalytic activity was due to CNT as an excellent electron acceptor and transporter, thus reducing the recombination of charge carriers and enhancing the photocatalytic activity. Furthermore, the prepared sample was photostable and no photocorrosion was observed after photocatalytic recycling. Our findings demonstrated that CNT/Cd(0.1)Zn(0.9)S composites were a promising candidate for the development of high-performance photocatalysts in photocatalytic H(2) production. This work not only shows a possibility for the utilization of low cost CNT as a substitute for noble metals (such as Pt) in the photocatalytic H(2)-production but also for the first time shows a significant enhancement in the H(2)-production activity by using metal-free carbon materials as effective co-catalysts. PMID:22422167

  5. Demonstration of neutron detection utilizing open cell foam and noble gas scintillation

    Energy Technology Data Exchange (ETDEWEB)

    Lavelle, C. M., E-mail: christopher.lavelle@jhuapl.edu; Miller, E. C. [The Johns Hopkins University Applied Physics Laboratory, Asymmetric Operations Department, Laurel, Maryland 20723 (United States); Coplan, M. [Institute for Physical Science and Technology, University of Maryland College Park, Maryland 20142 (United States); Thompson, Alan K.; Vest, Robert E.; Yue, A. T. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Kowler, A. L. [Department of Chemical Physics, University of Maryland, College Park, Maryland 20142 (United States); Koeth, T. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20142 (United States); Al-Sheikhly, M. [Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742 (United States); Clark, Charles W. [Institute for Physical Science and Technology, University of Maryland College Park, Maryland 20142 (United States); National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Gaithersburg, Maryland 20899 (United States)

    2015-03-02

    We present results demonstrating neutron detection via a closely spaced converter structure coupled to low pressure noble gas scintillation instrumented by a single photo-multiplier tube (PMT). The converter is dispersed throughout the gas volume using a reticulated vitreous carbon foam coated with boron carbide (B{sub 4}C). A calibrated cold neutron beam is used to measure the neutron detection properties, using a thin film of enriched {sup 10}B as a reference standard. Monte Carlo computations of the ion energy deposition are discussed, including treatment of the foam random network. Results from this study indicate that the foam shadows a significant portion of the scintillation light from the PMT. The high scintillation yield of Xe appears to overcome the light loss, facilitating neutron detection and presenting interesting opportunities for neutron detector design.

  6. Noble gases in meteorites and terrestrial planets

    Science.gov (United States)

    Wacker, J. F.

    1985-01-01

    Terrestrial planets and chondrites have noble gas platforms that are sufficiently alike, especially Ne/Ar, that they may have acquired their noble gases by similar processes. Meteorites presumably obtained their noble gases during formation in the solar nebula. Adsorption onto C - the major gas carrier in chondrites - is the likely mechanism for trapping noble gases; recent laboratory simulations support this hypothesis. The story is more complex for planets. An attractive possibility is that the planets acquired their noble gases in a late accreting veneer of chondritic material. In chondrites, noble gases correlate with C, N, H, and volatile metals; by Occam's Razor, we would expect a similar coupling in planets. Indeed, the Earth's crust and mantle contain chondritic like trace volatiles and PL group metals, respectively and the Earth's oceans resemble C chondrites in their enrichment of D (8X vs 8-10X of the galactic D/H ratio). Models have been proposed to explain some of the specific noble gas patterns in planets. These include: (1) noble gases may have been directly trapped by preplanetary material instead of arriving in a veneer; (2) for Venus, irradiation of preplanetary material, followed by diffusive loss of Ne, could explain the high concentration of AR-36; (3) the Earth and Venus may have initially had similar abundances of noble gases, but the Earth lost its share during the Moon forming event; (4) noble gases could have been captured by planetestimals, possibly leading to gravitational fractionation, particularly of Xe isotopes and (5) noble gases may have been dissolved in the hot outer portion of the Earth during contact with a primordial atmosphere.

  7. Surface Functionalization of g-C3 N4 : Molecular-Level Design of Noble-Metal-Free Hydrogen Evolution Photocatalysts.

    Science.gov (United States)

    Chen, Yin; Lin, Bin; Yu, Weili; Yang, Yong; Bashir, Shahid M; Wang, Hong; Takanabe, Kazuhiro; Idriss, Hicham; Basset, Jean-Marie

    2015-07-13

    A stable noble-metal-free hydrogen evolution photocatalyst based on graphite carbon nitride (g-C3 N4 ) was developed by a molecular-level design strategy. Surface functionalization was successfully conducted to introduce a single nickel active site onto the surface of the semiconducting g-C3 N4 . This catalyst family (with less than 0.1 wt % of Ni) has been found to produce hydrogen with a rate near to the value obtained by using 3 wt % platinum as co-catalyst. This new catalyst also exhibits very good stability under hydrogen evolution conditions, without any evidence of deactivation after 24 h. PMID:26073972

  8. Noble metal nanoparticle-functionalized ZnO nanoflowers for photocatalytic degradation of RhB dye and electrochemical sensing of hydrogen peroxide

    DEFF Research Database (Denmark)

    Hussain, Muhammad; Sun, Hongyu; Karim, Shafqat;

    2016-01-01

    Flower-like hierarchical Zinc oxide nanostructures synthesized by co-precipitation method have been hydrothermally functionalized with 8 nm Au NPs and 15 nm Ag nanoparticles. The photocatalytic and electrochemical performance of these structures are investigated. XPS studies show that the composite...... exhibits a strong interaction between noble metal nanoparticles (NPs) and Zinc oxide nanoflowers. The PL spectra exhibit UV emission arising due to near band edge transition and show that the reduced PL intensities of Au–ZnO and Ag–ZnO composites are responsible for improved photocatalytic activity arising...... due to increase in defects. Moreover, the presence of Au NPs on ZnO surface remarkably enhances photocatalytic activity as compared to Ag–ZnO and pure ZnO due to the higher catalytic activity and stability of Au NPs. On the other hand, Ag–ZnO-modified glassy carbon electrode shows good amperometric...

  9. Surface Functionalization of g-C 3 N 4 : Molecular-Level Design of Noble-Metal-Free Hydrogen Evolution Photocatalysts

    KAUST Repository

    Chen, Yin

    2015-06-12

    A stable noble-metal-free hydrogen evolution photocatalyst based on graphite carbon nitride (g-C3N4) was developed by a molecular-level design strategy. Surface functionalization was successfully conducted to introduce a single nickel active site onto the surface of the semiconducting g-C3N4. This catalyst family (with less than 0.1 wt% of Ni) has been found to produce hydrogen with a rate near to the value obtained by using 3 wt% platinum as co-catalyst. This new catalyst also exhibits very good stability under hydrogen evolution conditions, without any evidence of deactivation after 24h. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Surface modification of g-C3N4 by hydrazine: Simple way for noble-metal free hydrogen evolution catalysts

    KAUST Repository

    Chen, Yin

    2015-11-02

    The graphitic carbon nitride (g-C3N4) usually is thought to be an inert material and it’s difficult to have the surface terminated NH2 groups functionalized. By modifying the g-C3N4 surface with hydrazine, the diazanyl group was successfully introduced onto the g-C3N4 surface, which allows the introduction with many other function groups. Here we illustrated that by reaction of surface hydrazine group modified g-C3N4 with CS2 under basic condition, a water electrolysis active group C(=S)SNi can be implanted on the g-C3N4 surface, and leads to a noble metal free hydrogen evolution catalyst. This catalyst has 40% hydrogen evolution efficiency compare to the 3 wt% Pt photo precipitated g-C3N4, with only less than 0.2 wt% nickel.

  11. Electroless copper on refractory and noble metal substrates with an ultra-thin plasma-assisted atomic layer deposited palladium layer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young-Soon [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Kim, Hyung-Il [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Cho, Joong-Hee [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Seo, Hyung-Kee [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Dar, M.A. [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Shin, Hyung-Shik [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Ten Eyck, Gregory A. [Department of Physics, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Lu, Toh-Ming [Department of Physics, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Senkevich, Jay J. [Brewer Science Inc., Rolla, MO 65401 (United States)]. E-mail: jsenkevich@brewerscience.com

    2006-02-25

    Electroless Cu was investigated on refractory metal, W and TaN {sub X}, and Ir noble metal substrates with a plasma-assisted atomic layer deposited palladium layer for the potential back-end-of-the-line (BEOL) metallization of advanced integrated devices. The sodium and potassium-free Cu electroless bath consisted of: ethylenediamine tetraacetic acid (EDTA) as a chelating agent, glyoxylic acid as a reducing agent, and additional chemicals such as polyethylene glycol, 2,2'-dipyridine and RE-610 as surfactant, stabilizer and wetting agent respectively. The growth and chemical characterization of the Cu films was carried out with a field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). Group VIII metals such as Pt, Pd, etc., are stable in the electroless bath and catalytic towards the oxidation of glyoxylic acid and therefore work well for the electroless deposition of Cu. From RBS analysis, the amount of carbon and oxygen in Cu films were less than 1-3%. The Cu films were electroless deposited at 45-50 deg. C on patterned tantalum nitride with plasma-assisted atomic layer deposited (PA-ALD) Pd as a catalytic layer. Electroless Cu trench fill was successful with ultrasonic vibration, RE-610, and lowering the temperature to 45-50 deg. C on TaN {sub X} with the PA-ALD Pd catalytic layer.

  12. Rechargeable Lithium Metal Cell Project

    Data.gov (United States)

    National Aeronautics and Space Administration — PSI proposes to develop a rechargeable lithium metal cell with energy density >400Wh/kg. This represents a >70% increase as compared to similarly constructed...

  13. Noble metals can have different effects on photocatalysis over metal-organic frameworks (MOFs): a case study on M/NH₂-MIL-125(Ti) (M=Pt and Au).

    Science.gov (United States)

    Sun, Dengrong; Liu, Wenjun; Fu, Yanghe; Fang, Zhenxing; Sun, Fangxiang; Fu, Xianzhi; Zhang, Yongfan; Li, Zhaohui

    2014-04-14

    M-doped NH2-MIL-125(Ti) (M=Pt and Au) were prepared by using the wetness impregnation method followed by a treatment with H2 flow. The resultant samples were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) analyses, N2-sorption BET surface area, and UV/Vis diffuse reflectance spectroscopy (DRS). The photocatalytic reaction carried out in saturated CO2 with triethanolamine (TEOA) as sacrificial agent under visible-light irradiations showed that the noble metal-doping on NH2-MIL-125(Ti) promoted the photocatalytic hydrogen evolution. Unlike that over pure NH2-MIL-125(Ti), in which only formate was produced, both hydrogen and formate were formed over Pt- and Au-loaded NH2-MIL-125(Ti). However, Pt and Au have different effects on the photocatalytic performance for formate production. Compared with pure NH2-MIL-125(Ti), Pt/NH2-MIL-125(Ti) showed an enhanced activity for photocatalytic formate formation, whereas Au has a negative effect on this reaction. To elucidate the origin of the different photocatalytic performance, electron spin resonance (ESR) analyses and density functional theory (DFT) calculations were carried out over M/NH2-MIL-125(Ti).The photocatalytic mechanisms over M/NH2-MIL-125(Ti) (M=Pt and Au) were proposed. For the first time, the hydrogen spillover from the noble metal Pt to the framework of NH2-MIL-125(Ti) and its promoting effect on the photocatalytic CO2 reduction is revealed. The elucidation of the mechanism on the photocatalysis over M/NH2-MIL-125(Ti) can provide some guidance in the development of new photocatalysts based on MOF materials. This study also demonstrates the potential of using noble metal-doped MOFs in photocatalytic reactions involving hydrogen as a reactant, like hydrogenation reactions.

  14. van der Waals-corrected Density Functional Theory simulation of adsorption processes on noble-metal surfaces: Xe on Ag(111), Au(111), and Cu(111)

    CERN Document Server

    Silvestrelli, Pier Luigi

    2016-01-01

    The DFT/vdW-WF2s1 method based on the generation of localized Wannier functions, recently developed to include the van der Waals interactions in the Density Functional Theory and describe adsorption processes on metal surfaces by taking metal-screening effects into account, is applied to the case of the interaction of Xe with noble-metal surfaces, namely Ag(111), Au(111), and Cu(111). The study is also repeated by adopting the DFT/vdW-QHO-WF variant relying on the Quantum Harmonic Oscillator model which describes well many-body effects. Comparison of the computed equilibrium binding energies and distances, and the $C_3$ coefficients characterizing the adatom-surface van der Waals interactions, with available experimental and theoretical reference data shows that the methods perform well and elucidate the importance of properly including screening effects. The results are also compared with those obtained by other vdW-corrected DFT schemes, including PBE-D, vdW-DF, vdW-DF2, rVV10, and by the simpler Local Dens...

  15. Van Der Waals-Corrected Density Functional Theory Simulation of Adsorption Processes on Noble-Metal Surfaces: Xe on Ag(111), Au(111), and Cu(111)

    Science.gov (United States)

    Silvestrelli, Pier Luigi; Ambrosetti, Alberto

    2016-10-01

    The DFT/vdW-WF2s1 method based on the generation of localized Wannier functions, recently developed to include the van der Waals interactions in the density functional theory and describe adsorption processes on metal surfaces by taking metal-screening effects into account, is applied to the case of the interaction of Xe with noble-metal surfaces, namely Ag(111), Au(111), and Cu(111). The study is also repeated by adopting the DFT/vdW-QHO-WF variant relying on the quantum harmonic oscillator model which describes well many body effects. Comparison of the computed equilibrium binding energies and distances, and the C_3 coefficients characterizing the adatom-surface van der Waals interactions, with available experimental and theoretical reference data shows that the methods perform well and elucidates the importance of properly including screening effects. The results are also compared with those obtained by other vdW-corrected DFT schemes, including PBE-D, vdW-DF, vdW-DF2, rVV10, and by the simpler local density approximation and semi-local (PBE) generalized gradient approximation approaches.

  16. Platinum and palladium alloys suitable as fuel cell electrodes

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention concerns electrode catalysts used in fuel cells, such as proton exchange membrane (PEM) fuel cells. The invention is related to the reduction of the noble metal content and the improvement of the catalytic efficiency by low level substitution of the noble metal to provide ne...... and innovative catalyst compositions in fuel cell electrodes. The novel electrode catalysts of the invention comprise a noble metal selected from Pt and Pd alloyed with an alkaline earth metal.......The present invention concerns electrode catalysts used in fuel cells, such as proton exchange membrane (PEM) fuel cells. The invention is related to the reduction of the noble metal content and the improvement of the catalytic efficiency by low level substitution of the noble metal to provide new...

  17. Platinum and palladium alloys suitable as fuel cell electrodes

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention concerns electrode catalysts used in fuel cells, such as proton exchange membrane (PEM) fuel cells. The invention is related to the reduction of the noble metal content and the improvement of the catalytic5 efficiency by low level substitution of the noble metal to provide n...

  18. Applications of Peptides in Noble Metal Nanoparticles (NMNPs) Preparation%多肽在贵金属纳米粒子制备中的应用

    Institute of Scientific and Technical Information of China (English)

    陶凯; 王继乾; 夏道宏; 徐海; 吕建仁; 山红红

    2012-01-01

    由于具有与大块固体相迥异的性能,贵金属纳米粒子的制备与应用已经成为当前纳米、材料技术领域研究的热点。由于组成成分较多、包含各种活性基团、序列可调,并且很多多肽可生物降解、生物兼容、具有生物活性和特异性识别性能,多肽在贵金属纳米粒子制备中的应用也越来越受到人们的重视。本文从多肽作为还原剂还原贵金属盐;多肽作为保护剂/调控剂制备不同尺寸/形貌的贵金属纳米粒子;多肽作为引导剂规则排列贵金属纳米粒子;多肽作为贵金属纳米粒子组装的模板以及多肽在贵金属表面的吸附、多肽的自组装和如何获取所需要的多肽序列等几个方面综述了近年来多肽在贵金属纳米粒子制备中的应用。最后简述了利用多肽制备的贵金属纳米粒子在纳米、材料技术领域中的应用,并提出了当前该领域中存在的一些不足及研究展望。%The preparations and applications of noble metal nanoparticles (NMNPs) have attracted much more interest because of remarkably distinct properties compared with bulky metallic solids. Because peptides have many compositions and active groups, and be degradable, biologically active, biocompatible, specific recognizable, could be used in biological and medical fields, scientists have been trying to prepare NMNPs with peptides in the hope of obtaining more functional and adjustable materials. The recent progress in the applications of peptides in NMNPs preparations is summarized from the following aspects in this review: peptides acting as reducing agents to reduce noble metal salt precursors; peptidcs acting as capping/modulating agents to prepare NMNPs with different sizes/morphologies; peptides acting as directors to array NMNPs to regular superstructures; peptides acting as templates to assemble NMNPs to low-dimensional assemblies. In addition, the adsorption of peptides on surfaces of noble metals

  19. Metal-air electrochemical cell

    Energy Technology Data Exchange (ETDEWEB)

    Sarbacher, R. I.; Fechter, H. R.

    1985-01-01

    An electrochemical cell for which fuel is prepared and introduced under artificial gravity forces. The active metal is deposited through the action of the field on an anode current collecting member, effecting good compaction and reduced cell internal impedance. A microprocessor provides control of the induced gravity, flow rates, temperature, and other variables-enabling the active metal to be controlled in its thickness as well as providing a predetermined separation from the cathode. Abrasion of the cathode and the possibility of shorting are avoided by the presence of outwardly directed radial forces. These forces are induced by rotation of the electrolyte, air cathode, anode collector and the active metal. The forces promote also the passage of moisture laden air through the air cathode elements. Reaction products produced within the cell volume are circulated to an outside container for separation and possible reuse.

  20. Cohesive properties of noble metals by van der Waals-corrected density functional theory: Au, Ag, and Cu as case studies

    Science.gov (United States)

    Ambrosetti, Alberto; Silvestrelli, Pier Luigi

    2016-07-01

    The cohesive energy, equilibrium lattice constant, and bulk modulus of Au, Ag, and Cu noble metals are computed by different van der Waals (vdW)-corrected density functional theory (DFT) methods, including vdW-DF, vdW-DF2, vdW-DF-cx, rVV10, and PBE-D. Two specifically designed methods are also developed in order to effectively include dynamical screening effects: the DFT/vdW-WF2p method, based on the generation of maximally localized Wannier functions, and the RPAp scheme (in two variants), based on a single-oscillator model of the localized electron response. Comparison with results obtained without explicit inclusion of van der Waals effects, such as with the local density approximation (LDA), PBE, PBEsol, or the hybrid PBE0 functional, elucidates the importance of a suitable description of screened van der Waals interactions even in the case of strong metal bonding. Many-body effects are also quantitatively evaluated within the RPAp approach.

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

    Science.gov (United States)

    Anenburg, Michael; Mavrogenes, John A.

    2016-11-01

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

  2. 贵金属纳米材料生物还原制备技术的研究进展%Research Progress on Biosynthetic Technology of Noble Metal Nanomaterials

    Institute of Scientific and Technical Information of China (English)

    郑炳云; 黄加乐; 孙道华; 贾立山; 李清彪

    2011-01-01

    This review provided a brief overview of progress on biosynthetic technology of noble metal nanomaterials and their nanocatalysts. And the future directions of this field were also envisioned.%综述了国内外利用生物还原技术制备贵金属纳米材料及贵金属催化剂的研究进展,并展望了该研究领域的发展方向.

  3. Mo2 C as Non-Noble Metal Co-Catalyst in Mo2 C/CdS Composite for Enhanced Photocatalytic H2 Evolution under Visible Light Irradiation.

    Science.gov (United States)

    Ma, Baojun; Xu, Haojie; Lin, Keying; Li, Jie; Zhan, Haijuan; Liu, Wanyi; Li, Can

    2016-04-21

    Co-catalysts are a major factor to enhance photocatalytic H2 activity; they are mainly composed of expensive noble metals. Here, we reported a new non-noble-metal co-catalyst Mo2 C that efficiently improves the photocatalytic H2 evolution of CdS under visible light irradiation. Mo2 C is prepared by temperature-programmed reaction with molybdenum oxide as precursor, and the Mo2 C/CdS composite is prepared by deposition of CdS on Mo2 C. The optimum composite 2.0 % Mo2 C/CdS shows a high H2 evolution rate of 161 μmol h(-1) , which is ten times higher than that of CdS alone and 2.3 times higher than the optimum for 1.0 % Pt/CdS. Moreover, the Mo2 C/CdS is stable for 50 h. This study presents a new low-cost non-noble-metal co-catalyst as a photocatalyst to achieve highly efficient H2 evolution.

  4. Synthesis and characterization of a Noble metal Enhanced Optical Nanohybrid (NEON): a high brightness detection platform based on a dye-doped silica nanoparticle.

    Science.gov (United States)

    Roy, Shibsekhar; Dixit, Chandra K; Woolley, Robert; O'Kennedy, Richard; McDonagh, Colette

    2012-05-29

    A highly bright and photostable, fluorescent nanohybrid particle is presented which consists of gold nanoparticles (GNPs) embedded in dye-doped silica in a core-shell configuration. The dye used is the near-infrared emitting 4,5-benzo-5'-(iodoacetaminomethyl)-1',3,3,3',3'-pentamethyl-1-(4-sulfobutyl) indodicarbo cyanine. The nanohybrid architecture comprises a GNP core which is separated from a layer of dye molecules by a 15 nm buffer layer and has an outer protective, undoped silica shell. Using this architecture, a brightness factor of 550 has been achieved compared to the free dye. This hybrid system, referred to as Noble metal Enhanced Optical Nanohybrid (NEON) in this paper, is the first nanohybrid construct to our knowledge which demonstrates such tunable fluorescence property. NEON has enhanced photostability compared to the free dye and compared to a control particle without GNPs. Furthermore, the NEON particle, when used as a fluorescent label in a model bioassay, shows improved performance over assays using a conventional single dye molecule label.

  5. Barrierless growth of precursor-free, ultrafast laser-fragmented noble metal nanoparticles by colloidal atom clusters - A kinetic in situ study.

    Science.gov (United States)

    Jendrzej, Sandra; Gökce, Bilal; Amendola, Vincenzo; Barcikowski, Stephan

    2016-02-01

    Unintended post-synthesis growth of noble metal colloids caused by excess amounts of reactants or highly reactive atom clusters represents a fundamental problem in colloidal chemistry, affecting product stability or purity. Hence, quantified kinetics could allow defining nanoparticle size determination in dependence of the time. Here, we investigate in situ the growth kinetics of ps pulsed laser-fragmented platinum nanoparticles in presence of naked atom clusters in water without any influence of reducing agents or surfactants. The nanoparticle growth is investigated for platinum covering a time scale of minutes to 50days after nanoparticle generation, it is also supplemented by results obtained from gold and palladium. Since a minimum atom cluster concentration is exceeded, a significant growth is determined by time resolved UV/Vis spectroscopy, analytical disc centrifugation, zeta potential measurement and transmission electron microscopy. We suggest a decrease of atom cluster concentration over time, since nanoparticles grow at the expense of atom clusters. The growth mechanism during early phase (Ostwald ripening, validated experimentally by the temperature dependence of Pt nanoparticle size and growth quenching by Iodide anions. PMID:26555960

  6. Barrierless growth of precursor-free, ultrafast laser-fragmented noble metal nanoparticles by colloidal atom clusters - A kinetic in situ study.

    Science.gov (United States)

    Jendrzej, Sandra; Gökce, Bilal; Amendola, Vincenzo; Barcikowski, Stephan

    2016-02-01

    Unintended post-synthesis growth of noble metal colloids caused by excess amounts of reactants or highly reactive atom clusters represents a fundamental problem in colloidal chemistry, affecting product stability or purity. Hence, quantified kinetics could allow defining nanoparticle size determination in dependence of the time. Here, we investigate in situ the growth kinetics of ps pulsed laser-fragmented platinum nanoparticles in presence of naked atom clusters in water without any influence of reducing agents or surfactants. The nanoparticle growth is investigated for platinum covering a time scale of minutes to 50days after nanoparticle generation, it is also supplemented by results obtained from gold and palladium. Since a minimum atom cluster concentration is exceeded, a significant growth is determined by time resolved UV/Vis spectroscopy, analytical disc centrifugation, zeta potential measurement and transmission electron microscopy. We suggest a decrease of atom cluster concentration over time, since nanoparticles grow at the expense of atom clusters. The growth mechanism during early phase (<1day) of laser-synthesized colloid is kinetically modeled by rapid barrierless coalescence. The prolonged slow nanoparticle growth is kinetically modeled by a combination of coalescence and Lifshitz-Slyozov-Wagner kinetic for Ostwald ripening, validated experimentally by the temperature dependence of Pt nanoparticle size and growth quenching by Iodide anions.

  7. Structural changes of noble metal catalysts during ignition and extinction of the partial oxidation of methane studied by advanced QEXAFS techniques

    DEFF Research Database (Denmark)

    Grunwaldt, Jan-Dierk; Beier, M.; Kimmerle, B.;

    2009-01-01

    Pt/Al2O3, the structural changes during ignition were significantly faster in the latter case. The rate of reduction of the catalyst during ignition was also dependent on the axial position in the fixed-bed. The spectroscopic results provide important insight into the ignition and extinction behavior......The dynamics of the ignition and extinction of the catalytic partial oxidation (CPO) of methane to hydrogen and carbon monoxide over Pt-Rh/Al2O3 and Pt/Al2O3 were studied in the subsecond timescale using quick-EXAFS with a novel cam-driven X-ray monochromator employing Si(111) and Si(311) crystals......-significantly faster than during the extinction of the reaction. The dynamic behavior of the catalysts was dependent on the flow conditions and the respective noble metal component(s). Higher reaction gas flow led to a faster ignition process. While the ignition over Pt-Rh/Al2O3 occurred at lower temperature than over...

  8. Noble Metal Decoration and Presulfation on TiO2: Increased Photocatalytic Activity and Efficient Esterification of n-Butanol with Citric Acid

    Directory of Open Access Journals (Sweden)

    Yu Niu

    2016-01-01

    Full Text Available TiO2 has been widely used as a key catalyst in photocatalytic reactions; it also shows good catalytic activity for esterification reactions. Different sulfated M-TiO2 nanoparticles (M = Ag, Au, Rh, and Pt were prepared by photodeposition and ultrasonic methods. The results show that the noble metal nanoparticles, which were loaded onto a TiO2 surface, slightly affected the crystal phase and particle size of TiO2. Among all the catalysts, SO42-/Au-TiO2 exhibited the best catalytic activity in the esterification reaction for the synthesis of citric acid n-butyl acetate and in the decomposition of methyl orange, as confirmed by a high conversion rate of up to 98.2% and 100% degradation rate, respectively. This can be attributed to an increase in the Lewis acidity of the catalyst and increased separation efficiency of electron-hole pairs. This superior catalyst has great potential applications in esterification reactions and wastewater treatments.

  9. Economic Hydrophobicity Triggering of CO2 Photoreduction for Selective CH4 Generation on Noble-Metal-Free TiO2-SiO2.

    Science.gov (United States)

    Dong, Chunyang; Xing, Mingyang; Zhang, Jinlong

    2016-08-01

    On the basis of the fact that the competitive adsorption between CO2 and H2O on the catalyst plays an important role in the CO2 photoreduction process, here we develop an economic NH4F-induced hydrophobic modification strategy to enhance the CO2 competitive adsorption on the mesoporous TiO2-SiO2 composite surface via a simple solvothermal method. After the hydrophobic modification, the CO2 photoreduction for the selective generation of CH4 over the noble-metal-free TiO2-SiO2 composite can be greatly enhanced (2.42 vs 0.10 μmol/g in 4h). The enhanced CO2 photoreduction efficiency is assigned to the rational hydrophobic modification on TiO2-SiO2 surface by replacing Si-OH to hydrophobic Si-F bonds, which will improve the CO2 competitive adsorption and trigger the eight-electron CO2 photoreduction on the reaction kinetics. PMID:27415144

  10. WS2 as an Effective Noble-Metal Free Cocatalyst Modified TiSi2 for Enhanced Photocatalytic Hydrogen Evolution under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Dongmei Chu

    2016-09-01

    Full Text Available A noble-metal free photocatalyst consisting of WS2 and TiSi2 being used for hydrogen evolution under visible light irradiation, has been successfully prepared by in-situ formation of WS2 on the surface of TiSi2 in a thermal reaction. The obtained samples were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive X-ray spectrometry (EDX, transmission electron microscopy (TEM, and X-ray photoelectron spectroscopy (XPS. The results demonstrate that WS2 moiety has been successfully deposited on the surface of TiSi2 and some kind of chemical bonds, such as Ti-S-W and Si-S-W, might have formed on the interface of the TiSi2 and WS2 components. Optical and photoelectrochemical investigations reveal that WS2/TiSi2 composite possesses lower hydrogen evolution potential and enhanced photogenerated charge separation and transfer efficiency. Under 6 h of visible light (λ > 420 nm irradiation, the total amount of hydrogen evolved from the optimal WS2/TiSi2 catalyst is 596.4 μmol·g−1, which is around 1.5 times higher than that of pure TiSi2 under the same reaction conditions. This study shows a paradigm of developing the effective, scalable and inexpensive system for photocatalytic hydrogen generation.

  11. Photocatalytic H2 Production Using Pt-TiO2 in the Presence of Oxalic Acid: Influence of the Noble Metal Size and the Carrier Gas Flow Rate

    Directory of Open Access Journals (Sweden)

    Ákos Kmetykó

    2014-10-01

    Full Text Available The primary objective of the experiments was to investigate the differences in the photocatalytic performance when commercially available Aeroxide P25 TiO2 photocatalyst was deposited with differently sized Pt nanoparticles with identical platinum content (1 wt%. The noble metal deposition onto the TiO2 surface was achieved by in situ chemical reduction (CRIS or by mixing chemically reduced Pt nanoparticle containing sols to the aqueous suspensions of the photocatalysts (sol-impregnated samples, CRSIM. Fine and low-scale control of the size of resulting Pt nanoparticles was obtained through variation of the trisodium citrate concentration during the syntheses. The reducing reagent was NaBH4. Photocatalytic activity of the samples and the reaction mechanism were examined during UV irradiation (λmax = 365 nm in the presence of oxalic acid (50 mM as a sacrificial hole scavenger component. The H2 evolution rates proved to be strongly dependent on the Pt particle size, as well as the irradiation time. A significant change of H2 formation rate during the oxalic acid transformation was observed which is unusual. It is probably regulated both by the decomposition rate of accumulated oxalic acid and the H+/H2 redox potential on the surface of the catalyst. The later potential is influenced by the concentration of the dissolved H2 gas in the reaction mixture.

  12. Free MoS2 Nanoflowers Grown on Graphene by Microwave-Assisted Synthesis as Highly Efficient Non-Noble-Metal Electrocatalysts for the Hydrogen Evolution Reaction

    Science.gov (United States)

    Cao, Jiamu; Zhang, Xuelin; Zhang, Yufeng; Zhou, Jing; Chen, Yinuo; Liu, Xiaowei

    2016-01-01

    Advanced approaches to preparing non-noble-metal electrocatalysts for the hydrogen evolution reaction (HER) are considered to be a significant breakthrough in promoting the exploration of renewable resources. In this work, a hybrid material of MoS2 nanoflowers (NFs) on reduced graphene oxide (rGO) was synthesized as a HER catalyst via an environmentally friendly, efficient approach that is also suitable for mass production. Small-sized MoS2 NFs with a diameter of ca. 190 nm and an abundance of exposed edges were prepared by a hydrothermal method and were subsequently supported on rGO by microwave-assisted synthesis. The results show that MoS2 NFs were distributed uniformly on the remarkably reduced GO and preserved the outstanding original structural features perfectly. Electrochemical tests show that the as-prepared hybrid material exhibited excellent HER activity, with a small Tafel slope of 80 mV/decade and a low overpotential of 170 mV. PMID:27556402

  13. Size characterisation of noble-metal nano-crystals formed in sapphire by ion irradiation and subsequent thermal annealing

    International Nuclear Information System (INIS)

    Highlights: ► Systematic study on the formation of Ag and Au nano-particles in Al2O3. ► Annealing in a reducing atmosphere, below the metal melting point is more suitable. ► Au nano-particles grow up to 15 nm and Ag nano-particles up to 45 nm in radius. ► Ostwald ripening is the mechanism responsible for the formation of large nanoparticles. ► Optical properties of metallic nano-particles in Al2O3 can be related to their size. - Abstract: Metallic nano-particles embedded in transparent dielectrics are very important for new technological applications because of their unique optical properties. These properties depend strongly on the size and shape of the nano-particles. In order to achieve the synthesis of metallic nano-particles it has been used the technique of ion implantation. This is a very common technique because it allows the control of the depth and concentration of the metallic ions inside the sample, limited mostly by straggling, without introducing other contaminant agents. The purpose of this work was to measure the size of the nano-particles grown under different conditions in Sapphire and its size evolution during the growth process. To achieve this goal, α-Al2O3 single crystals were implanted with Ag or Au ions at room temperature with different fluences (from 2 × 1016 ions/cm2 to 8 × 1016 ions/cm2). Afterwards, the samples were annealed at different temperatures (from 600 °C to 1100 °C) in oxidising, reducing, Ar or N2 atmospheres. We measured the ion depth profile by Rutherford Backscattering Spectroscopy (RBS) and the nano-crystals size distribution by using two methods, the surface plasmon resonance in the optical extinction spectrum and the Transmission Electron Microscopy (TEM).

  14. Deactivation of selected noble metal catalysts during CO oxidation: An in-situ IR and kinetic study

    International Nuclear Information System (INIS)

    The deactivation of the oxidation of CO over supported Rh, Ru and Pd as a function of the reactant gas composition is discussed. On supported Rh we have found that the rate of CO oxidation is strongly dependent on the oxidation state of the metal. The rate of CO oxidation over supported Ru is strongly inhibited by the incorporation of sub-surface O2. The oxidation of CO on supported Pd is inhibited by the formation of PdO under conditions in which the CO/O2 reactant gas ratio is net oxidizing and by enhanced CO surface coverage following ignition when the reactant gas ratio is net reducing

  15. Bias dependence of tunneling-electron-induced molecular fluorescence from porphyrin films on noble-metal substrates

    OpenAIRE

    Liu, H.W.; Le, Y.; Nishitani, Ryusuke; Aso, Y; Iwasaki, H.

    2007-01-01

    We investigated scanning tunneling microscope (STM)-excited luminescence from porphyrin (PhTPP and H2TPP) thin films on metal substrate (Au and Ag) under ambient conditions. Molecular fluorescence similar to the corresponding photoluminescence was observed from PhTPP/Au and H2TPP/Ag at both STM bias polarities. We found that at the same experimental condition and parameters, the STM-induced luminescence intensities of maxima peak are similar for PhTPP and H2TPP but weaker by a factor of about...

  16. The rapid and precise determination of noble metals in matte-leach residues by atomic-absorption spectrophotometry

    International Nuclear Information System (INIS)

    A method is proposed for the rapid analysis of platinum-group metals and gold in matte-leach residues. So that the precision of the atomic-absorption measurement is ensured, many measurements are taken (a chart recorder being used) and the calculation is done on a computer. The dissolution of samples was investigated and optimized. Iridium, which is usually present as a minor constituent, is treated on a separate aliquot portion that is concentrated before measurement. The precision of the method ranges from 0,5 per cent for platinum to 2,3 per cent for iridium

  17. Production of mono- and bimetallic nanoparticles of noble metals by pyrolysis of organic extracts on silicon dioxide

    International Nuclear Information System (INIS)

    In the present work the influence of the tri-n-octylammonium (Oct3NH+) salt anion (PtCl62-, PdCl42-, AuCl4−) nature on the phase composition and mean size of crystallites of the extract pyrolysis products on the SiO2 nanopowder has been studied. The XRD phase analysis of the composites (metal loading 2.4 wt.%) made under the same conditions, at the pyrolysis of Pt- and Au-containing extracts has shown the formation of nanoparticles of Pt (dPt = 15 nm) and Au (dAu = 33 nm), respectively. The end-product of the pyrolysis of the Pd-containing extract has an admixture phase of PdO along with the main metal phase (dPd = 21 nm). At the preparation of bimetallic particles (Pt-Pd, Pt-Au, Pd-Au) on the SiO2 nanopowder it has been found that the nanoparticles of the PtPd alloy, Pt and Au or Pd and Au nanoparticles are the products of the thermal decomposition of two-component mixtures of extracts. The investigation of catalytic properties of the produced composites in the reaction of glycerol oxidation by molecular oxygen in alkaline aqueous solutions has shown that all bimetallic composites exhibit catalytic activity in contrast to monometallic ones

  18. Selective extraction and detection of noble metal based on ionic liquid immobilized silica gel surface using ICP-OES

    Indian Academy of Sciences (India)

    HADI M MARWANI; AMJAD E ALSAFRANI; HAMAD A AL-TURAIF; ABDULLAH M ASIRI; SHER BAHADAR KHAN

    2016-08-01

    In this study, an efficiently employed ionic liquid combined with commercially available silica gel (SG–ClPrNTf$_2$) was developed for selective detection of gold(III) by use of inductively coupled plasma–optical emission spectrometry (ICP-OES). The selectivity of SG–ClPrNTf$_2$ was evaluated towards seven metal ions, including Y(III), Mn(II), Zr(IV), Pb(II), Mg(II), Pd(II) and Au(III). Based on pH study and distribution coefficient values, the SG–ClPrNTf$_2$ phase was found to be the most selective towards Au(III) at pH 2 as compared to other metal ions. The adsorption isotherm of Au(III) on the SG–ClPrNTf$_2$ phase followed the Langmuir model with adsorption capacity of 59.48 mg g$^{−1}$, which was highly in agreement with experimental data of adsorption isotherm study. The kinetics study indicated that Au(III) adsorption kinetics data were well fit with the pseudo-second-order kinetic model on the basis of correlation coefficient fitting (0.996) and adsorption capacity agreement (62.26 mg g$^{−1}$). Furthermore, SG–ClPrNTf$_2$ phase was effectively performed for the determination of Au(III) in real water samples with satisfactory results.

  19. Hybrid Coordination Networks Constructed from ɛ-Keggin-Type Polyoxometalates and Rigid Imidazole-Based Bridging Ligands as New Carriers for Noble-Metal Catalysts.

    Science.gov (United States)

    Yang, Xiao-Jian; Sun, Meng; Zang, Hong-Ying; Ma, Yuan-Yuan; Feng, Xiao-Jia; Tan, Hua-Qiao; Wang, Yong-Hui; Li, Yang-Guang

    2016-03-18

    Three hybrid coordination networks that were constructed from ɛ-Keggin polyoxometalate building units and imidazole-based bridging ligands were prepared under hydrothermal conditions, that is, H[(Hbimb)2 (bimb){Zn4 PMo(V8) Mo(VI) 4 O40 }]⋅6 H2 O (1), [Zn(Hbimbp)(bimbp)3 {Zn4 PMo(V8) Mo(VI) 4 O40 }]⋅DMF⋅3.5 H2 O (2), and H[Zn2 (timb)2 (bimba)2 Cl2 {Zn4 PMo(V8) Mo(VI) 4 O40 }]⋅7 H2 O (3) (bimb=1,4-bis(1-imidazolyl)benzene, bimbp=4,4'-bis(imidazolyl)biphenyl, timb=1,3,5-tris(1-imidazolyl)benzene, bimba=3,5-bis(1-imidazolyl)benzenamine). All three compounds were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. The mixed valence of the Mo centers was analyzed by XPS spectroscopy and bond-valence sum calculations. In all three compounds, the ɛ-Keggin polyoxometalate (POM) units acted as nodes that were connected by rigid imidazole-based bridging ligands to form hybrid coordination networks. In compound 1, 1D zigzag chains extended to form a 3D supramolecular architecture through intermolecular hydrogen-bonding interactions. Compound 2 consisted of 2D curved sheets, whilst compound 3 contained chiral 2D networks. Because of the intrinsic reducing properties of ɛ-Keggin POM species, noble-metal nanoparticles were loaded onto these POM-based coordination networks. Thus, compounds 1-3 were successfully loaded with Ag nanoparticles, and the corresponding composite materials exhibited high catalytic activities for the reduction of 4-nitrophenol. PMID:26807960

  20. Three-electrode current-voltage measurements on erbia-stabilized bismuth oxide with sputtered noble metal electrodes

    NARCIS (Netherlands)

    Vinke, I.C.; Boukamp, B.A.; Vries, de K.J.; Burggraaf, A.J.

    1992-01-01

    The anodic and cathodic polarization behaviour of sputtered porous gold electrodes on (Bi2O3)0.75(Er2O3)0.25 (abbreviated BE25) was studied as function of temperature and oxygen partial pressure using a three-electrode cell. The anodic polarization is smaller than the cathodic polarization, allowing

  1. Determination of plasma frequency, damping constant, and size distribution from the complex dielectric function of noble metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza Herrera, Luis J.; Arboleda, David Muñetón [Centro de Investigaciones Ópticas (CIOp), (CONICET La Plata-CIC) (Argentina); Schinca, Daniel C.; Scaffardi, Lucía B., E-mail: lucias@ciop.unlp.edu.ar [Centro de Investigaciones Ópticas (CIOp), (CONICET La Plata-CIC) (Argentina); Departamento de Ciencias Básicas, Facultad de Ingeniería, UNLP (Argentina)

    2014-12-21

    This paper develops a novel method for simultaneously determining the plasma frequency ω{sub P}   and the damping constant γ{sub free} in the bulk damped oscillator Drude model, based on experimentally measured real and imaginary parts of the metal refractive index in the IR wavelength range, lifting the usual approximation that restricts frequency values to the UV-deep UV region. Our method was applied to gold, silver, and copper, improving the relative uncertainties in the final values for ω{sub p} (0.5%–1.6%) and for γ{sub free} (3%–8%), which are smaller than those reported in the literature. These small uncertainties in ω{sub p} and γ{sub free} determination yield a much better fit of the experimental complex dielectric function. For the case of nanoparticles (Nps), a series expansion of the Drude expression (which includes ω{sub p} and γ{sub free} determined using our method) enables size-dependent dielectric function to be written as the sum of three terms: the experimental bulk dielectric function plus two size corrective terms, one for free electron, and the other for bound-electron contributions. Finally, size distribution of nanometric and subnanometric gold Nps in colloidal suspension was determined through fitting its experimental optical extinction spectrum using Mie theory based on the previously determined dielectric function. Results are compared with size histogram obtained from Transmission Electron Microscopy (TEM)

  2. Bifunctional non-noble metal oxide nanoparticle electrocatalysts through lithium-induced conversion for overall water splitting

    Science.gov (United States)

    Wang, Haotian; Lee, Hyun-Wook; Deng, Yong; Lu, Zhiyi; Hsu, Po-Chun; Liu, Yayuan; Lin, Dingchang; Cui, Yi

    2015-06-01

    Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, including oxygen evolution reaction and hydrogen evolution reaction, is important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanoparticles (~20 nm) are electrochemically transformed into ultra-small diameter (2-5 nm) nanoparticles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanoparticles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10 mA cm-2 water-splitting current at only 1.51 V for over 200 h without degradation in a two-electrode configuration and 1 M KOH, better than the combination of iridium and platinum as benchmark catalysts.

  3. Experiments on transmission sputtering with 100-300 keV noble gas ions on metal films

    International Nuclear Information System (INIS)

    The yield and energy spectra of sputtered ions were investigated in the energy range of 100-300 keV with Ne, Ar, Kr ions on aluminium, copper, and silver films of 500-1500 A. The goal of these experiments was to compare the measured yields to Sigmund's theory for transmission sputtering, and to investigate the dependence of the energy spectra on the bombarding ion's energy. The energy dependence of the sputtering yield was studied at one foil thickness for different ion energies, whereby the varying sputtered ion curents were registered. Sigmund's formula S(E1)=const. α' Ssub(n) (E1) (E=exit energy, Ssub(n)=nuclear stopping power of the projectile) proved to be well applicable for sputtered ions in the 100-300 keV range. A scattering experiment and the erosion of a vapor deposited surface on a carrier foil were performed to obtain the factor const. α'. The results of these experiments agreed with Sigmunds theory. The energy spectra of the sputtered ions above E=30eV were fitted by a polynomial with four parameters. At energies above 200 eV, the spectra had the form P(E) approximately Esup(-b), with b approximately 2. No significant change of P(E) with the energy of the projectile was noticed. The following tendency could be noted: beyond the maximum of Ssub(n) (E1), b decreases with decreasing E1 for a fixed projectile, i.e. with increasing stopping power more high energy ions are sputtered. The b values for different metals are approximately equal to those of reflection sputtering experiments. (Auth.)

  4. Autothermal reforming of simulated and commercial fuels on zirconia-supported mono- and bimetallic noble metal catalysts

    OpenAIRE

    Kaila, Reetta

    2008-01-01

    New energy sources are needed if energy supply and demand are to remain in balance. At the same time, the level of emissions needs to be reduced to minimise their contribution to the greenhouse effect. Renewable energy sources, and hydrogen (H2), have been attracting much attention, and more efficient technologies for energy recovery have been developed. Among these are fuel cells. H2 is not a source of energy but an energy carrier, which needs to be produced from a primary fuel (hydroca...

  5. Synthesis of carbon-supported binary FeCo-N non-noble metal electrocatalysts for the oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Li Shang [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada)] [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Zhang Lei, E-mail: lei.zhang@nrc.gc.c [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada); Kim, Jenny [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada); Pan Mu, E-mail: panmu@whut.edu.c [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Shi Zheng; Zhang Jiujun [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada)

    2010-10-01

    In this paper, a carbon-supported binary FeCo-N/C catalyst using tripyridyl triazine (TPTZ) as the complex ligand was successfully synthesized. The FeCo-TPTZ complex was then heat-treated at 600 {sup o}C, 700 {sup o}C, 800 {sup o}C, and 900 {sup o}C to optimize its oxygen reduction reaction (ORR) activity. It was found that the 700 {sup o}C heat-treatment yielded the most active FeCo-N/C catalyst for the ORR. XRD, EDX, TEM, XPS, and cyclic voltammetry techniques were used to characterize the structural changes in these catalysts after heat-treatment, including the total metal loading and the mole ratio of Fe to Co in the catalyst, the possible structures of the surface active sites, and the electrochemical activity. XPS analysis revealed that Co-N{sub x}, Fe-N{sub x}, and C-N were present on the catalyst particle surface. To assess catalyst ORR activity, quantitative evaluations using both RDE and RRDE techniques were carried out, and several kinetic parameters were obtained, including overall ORR electron transfer number, electron transfer coefficient in the rate-determining step (RDS), electron transfer rate constant in the RDS, exchange current density, and mole percentage of H{sub 2}O{sub 2} produced in the catalyzed ORR. The overall electron transfer number for the catalyzed ORR was {approx}3.88, with H{sub 2}O{sub 2} production under 10%, suggesting that the ORR catalyzed by FeCo-N/C catalyst is dominated by a 4-electron transfer pathway that produces H{sub 2}O. The stability of the binary FeCo-N/C catalyst was also tested using single Fe-N/C and Co-N/C catalysts as baselines. The experimental results clearly indicated that the binary FeCo-N/C catalyst had enhanced activity and stability towards the ORR. Based on the experimental results, a possible mechanism for ORR performance enhancement using a binary FeCo-N/C catalyst is proposed and discussed.

  6. MICROWAVE-ASSISTED SYNTHESIS OF NOBLE NANOSTRUCTURES

    Science.gov (United States)

    Microwave-assisted (MW) spontaneous reduction of noble metal salts, silver (Ag), gold (Au), platinum (Pt) and palladium (Pd) is reported using sugar solutions such as -D glucose, sucrose and maltose, etc. to generate nanomaterials. These MW-assisted reactions, conducted in aqueo...

  7. Study and characterization of noble metal deposits on similar rusty surfaces to those of the reactor U-1 type BWR of nuclear power station of Laguna Verde

    International Nuclear Information System (INIS)

    In the present investigation work, were determined the parameters to simulate the conditions of internal oxidation reactor circulation pipes of the nuclear power plant of Laguna Verde in Veracruz. We used 304l stainless steel cylinders with two faces prepared with abrasive paper of No. 600, with the finality to obtain similar surface to the internal circulation piping nuclear reactor. Oxides was formed within an autoclave (Autoclave MEX-02 unit B), which is a device that simulates the working conditions of the nuclear reactor, but without radiation generated by the fission reaction within the reactor. The oxidation conditions were a temperature of 280 C and pressure of 8 MPa, similar conditions to the reactor operating in nuclear power plant of Laguna Verde in Veracruz, Mexico (BWR conditions), with an average conductivity of 4.58 ms / cm and 2352 ppb oxygen to simulate normal water chemistry NWC. Were obtained deposits of noble metal oxides formed on 304l stainless steel samples, in a 250 ml autoclave at a temperature range of 180 to 200 C. The elements that were used to deposit platinum-rhodium (Pt-Rh) with aqueous Na2Pt (OH)6 and Na3Rh (NO2)6, Silver (Ag) with an aqueous solution of AgNO3, zirconium (Zr) with aqueous Zr O (NO3) and ZrO2, and zinc (Zn) in aqueous solution of Zn (NO3)2 under conditions of normal water chemistry. Also there was the oxidation of 304l stainless steel specimens in normal water chemistry with a solution of Zinc (Zn) (NWC + Zn). Oxidation of the specimens in water chemistry with a solution of zinc (Zn + NWC) was prepared in two ways: within the MEX-02 autoclave unit A in a solution of zinc and a flask at constant temperature in zinc solution. The oxides formed and deposits were characterized by scanning electron microscopy, energy dispersive X-ray analysis, elemental field analysis and X-ray diffraction. By other hand was evaluated the electrochemical behavior of the oxides formed on the surface of 304l stainless steel in normal water

  8. Platinum and Palladium Alloys Suitable as Fuel Cell Electrodes

    DEFF Research Database (Denmark)

    2011-01-01

    and innovative catalyst compositions in fuel cell electrodes. The novel electrode catalysts of the invention comprise a noble metal selected from Pt, Pd and mixtures thereof alloyed with a further element selected from Sc, Y and La as well as any mixtures thereof, wherein said alloy is supported on a conductive......The present invention concerns electrode catalysts used in fuel cells, such as proton exchange membrane (PEM) fuel cells. The invention is related to the reduction of the noble metal content and the improvement of the catalytic efficiency by low level substitution of the noble metal to provide new...

  9. NOx Storage-Reduction on Noble Metals/BaO Catalyst%贵金属/BaO催化剂上NOx的储存-还原

    Institute of Scientific and Technical Information of China (English)

    秦宏宇; 鲍晓峰; 李凯; 王猛; 张德满

    2011-01-01

    The storage-reduction behavior of NOx on a Nobel Metals (NM)/BaO catalyst was investigated by means of simulating exhaust gases. The NOx edsorption-desorption performance of the NM/BaO catalyst was studied by TG-DTA (ThermogravimetricDifferential Thermal Analysis). Results showed that NO2 was more likely to be stored on the catalyst than NO, and the presence of O2 greatly promoted the progress of the NOx storage reaction. Temperature had a significant impact on the NOx storage behavior of the catalyst. 300 ℃ was the optimal temperature for NOx storage when φ ( O2 ) was 16% and φ ( NO ) was 5 × 10 -4. At this temperature, the adsorption capacity of NOx on NM/BaO could be up to 15 mg/g, while at 600 ℃ the NOx adsorbed by the catalyst could have complete desorption. In the course of NOx reduction by H2, the reduction rate of NOx changed with the rise of temperature when φ( H2 ) was 1% or 3%. In contrast, there was almost no effect from temperature when φ( H2 ) was 5%.%运用模拟配气方法考察了贵金属(Noble Metals,NM)/BaO催化剂的氮氧化物(NOx)储存-还原性能.采用热重-差热分析(TG-DTA)法对催化剂的NOx吸附-脱附性能进行了研究.结果表明:NO2比NO更易于在催化剂上储存,O2的存在极大地促进了NOx储存反应的进行.温度对催化剂上的NOx储存行为有较大影响,在ψ(O2)为16%,ψ(NO)为5 ×10-4的氧化气氛下,NOx在NM/BaO上储存的适宜温度为300℃.300℃下催化剂的NOx吸附量可达15 mg/g,当温度升到600℃时,催化剂上的NOx能够完全脱附.使用H2在催化剂上进行NOx还原过程中,当ψ(H2)为1%或3%时,还原反应速率随温度的升高而变化;妒(H2)为5%时,还原反应速率几乎不受温度影响.

  10. Planetary noble gases

    Science.gov (United States)

    Zahnle, Kevin

    1993-01-01

    An overview of the history and current status of research on planetary noble gases is presented. The discovery that neon and argon are vastly more abundant on Venus than on earth points to the solar wind rather than condensation as the fundamental process for placing noble gases in the atmospheres of the terrestrial planets; however, solar wind implantation may not be able to fully reproduce the observed gradient, nor does it obviously account for similar planetary Ne/Ar ratios and dissimilar planetary Ar/Kr ratios. More recent studies have emphasized escape rather than accretion. Hydrodynamic escape, which is fractionating, readily accounts for the difference between atmospheric neon and isotopically light mantle neon. Atmospheric cratering, which is nearly nonfractionating, can account for the extreme scarcity of nonradiogenic noble gases (and other volatiles) on Mars.

  11. Heavy metal biosorption by bacterial cells

    Energy Technology Data Exchange (ETDEWEB)

    Vecchio, A.; Finoli, C.; Di Simine, D.; Andreoni, V. [Department of Food Science and Microbiology, State University, Milan (Italy)

    1998-06-01

    Microbial biomass provides available ligand groups on which metal ions bind by different mechanisms. Biosorption of these elements from aqueous solutions represents a remediation technology suitable for the treatment of metal-contaminated effluents. The purpose of the present investigation was the assessment of the capability of Brevibacterium sp. cells to remove bivalent ions, when present alone or in pairs, from aqueous solutions, using immobilized polyacrylamide cells of the microorganism in a flow-through system. The biosorption capacity of Brevibacterium cells was studied for lead, cadmium and copper. The metal cell binding capacity followed the order Cu > Pb > Cd, based on estimated q{sub max}. These values, expressed as mmol metal/g dry weight cells, were 0.54 for Cu, 0.36 for Pb and 0.14 for Cd. Polyacrylamide-gel immobilized cells were effective in Pb, Cu and Cd removal. Lead removal was not affected by the presence of Cd and Cu; lead instead inhibited Cd and Cu removal. The desorption of the metal, by fluxing a chelating solution, restored the metal binding capacity of the cells, thus affording the multiple use of the same biomass in the remediation treatment. (orig.) (orig.) With 5 figs., 4 tabs., 23 refs.

  12. Effect of the energy transfer collision between noble gas and sputtered metal atom on the voltage-current curve of a hollow-cathode discharge

    International Nuclear Information System (INIS)

    The voltage-current curves and the optogalvanic signals of hollow-cathode discharge tubes were measured. Attention was focused on the existence of negative dynamic resistance properties for argon and neon discharges. Three hollow-cathodes, each was made of gadolinium, uranium, and copper, were used with both the noble gases. The negative dynamic resistance regions were observed only in Ar/U, Ar/Gd, and Ne/Cu discharges. These results suggest that resonant Penning ionization is one of the main reactions producing the negative dynamic resistance characteristics in hollow cathode discharges

  13. Osteoblastic cell behavior on nanostructured metal implants.

    NARCIS (Netherlands)

    Guehennec, L Le; Martin, F.; Lopez-Heredia, M.A.; Louarn, G.; Amouriq, Y.; Cousty, J.; Layrolle, P.

    2008-01-01

    AIMS: Surface modifications at the nanometric scale may promote protein adsorption, cell adhesion and thus favor the osseointegration of metal implants. The behavior of osteoblastic cells was studied on mirror-polished (Smooth-SS) and nanostructured (Nano-SS) stainless steel surfaces. MATERIALS & ME

  14. Screen Printed Metallization of Silicon Solar Cells

    OpenAIRE

    Govaerts, R.; Van Overstraeten, R.; Mertens, R.; Ph. Lauwers; Frisson, L.

    1980-01-01

    This paper presents a screen printing process for the metallization of silicon solar cells. The physics and construction of a classical solar cell are reviewed. The results obtained with a screen printing process are comparable with other, more expensive technologies. This technology does not introduce an additional contact resistance on silicon. The process optimization and the influence of different parameters are discussed.

  15. Study and characterization of noble metal deposits on similar rusty surfaces to those of the reactor U-1 type BWR of nuclear power station of Laguna Verde; Estudio y caracterizacion de depositos de metales nobles sobre superficies oxidadas similares a las del reactor de la Central de Laguna Verde (CNLV) U1 del tipo BWR

    Energy Technology Data Exchange (ETDEWEB)

    Flores S, V. H.

    2011-07-01

    In the present investigation work, were determined the parameters to simulate the conditions of internal oxidation reactor circulation pipes of the nuclear power plant of Laguna Verde in Veracruz. We used 304l stainless steel cylinders with two faces prepared with abrasive paper of No. 600, with the finality to obtain similar surface to the internal circulation piping nuclear reactor. Oxides was formed within an autoclave (Autoclave MEX-02 unit B), which is a device that simulates the working conditions of the nuclear reactor, but without radiation generated by the fission reaction within the reactor. The oxidation conditions were a temperature of 280 C and pressure of 8 MPa, similar conditions to the reactor operating in nuclear power plant of Laguna Verde in Veracruz, Mexico (BWR conditions), with an average conductivity of 4.58 ms / cm and 2352 ppb oxygen to simulate normal water chemistry NWC. Were obtained deposits of noble metal oxides formed on 304l stainless steel samples, in a 250 ml autoclave at a temperature range of 180 to 200 C. The elements that were used to deposit platinum-rhodium (Pt-Rh) with aqueous Na{sub 2}Pt (OH){sub 6} and Na{sub 3}Rh (NO{sub 2}){sub 6}, Silver (Ag) with an aqueous solution of AgNO{sub 3}, zirconium (Zr) with aqueous Zr O (NO{sub 3}) and ZrO{sub 2}, and zinc (Zn) in aqueous solution of Zn (NO{sub 3}){sub 2} under conditions of normal water chemistry. Also there was the oxidation of 304l stainless steel specimens in normal water chemistry with a solution of Zinc (Zn) (NWC + Zn). Oxidation of the specimens in water chemistry with a solution of zinc (Zn + NWC) was prepared in two ways: within the MEX-02 autoclave unit A in a solution of zinc and a flask at constant temperature in zinc solution. The oxides formed and deposits were characterized by scanning electron microscopy, energy dispersive X-ray analysis, elemental field analysis and X-ray diffraction. By other hand was evaluated the electrochemical behavior of the oxides

  16. Noble Gas Detectors

    CERN Document Server

    Aprile, Elena; Bolozdynya, Alexander I; Doke, Tadayoshi

    2006-01-01

    This book discusses the physical properties of noble fluids, operational principles of detectors based on these media, and the best technical solutions to the design of these detectors. Essential attention is given to detector technology: purification methods and monitoring of purity, information readout methods, electronics, detection of hard ultra-violet light emission, selection of materials, cryogenics etc.The book is mostly addressed to physicists and graduate students involved in the preparation of fundamental next generation experiments, nuclear engineers developing instrumentation

  17. Trapped noble gases in meteorites

    Science.gov (United States)

    Swindle, Timothy D.

    1988-01-01

    The trapped noble gases in meteorites come in two main varieties, usually referred to as solar and planetary. The solar noble gases are implanted solar-wind or solar-flare materials, and thus their relative elemental abundances provide a good estimate of those of the sun. The planetary noble gases have relative elemental abundances similar to those in the terrestrial atmosphere, but there are also important distinctions. At least one other elemental pattern (subsolar) and several isotopic patterns have also been identified.

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

    Science.gov (United States)

    Gorer, Alexander

    2002-01-01

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

  19. A noble and single source precursor for the synthesis of metal-rich sulphides embedded in an N-doped carbon framework for highly active OER electrocatalysts.

    Science.gov (United States)

    Barman, Barun Kumar; Nanda, Karuna Kar

    2016-04-21

    Here, we demonstrate a green and environment-friendly pyrolysis route for the synthesis of metal-rich sulphide embedded in an N-doped carbon (NC) framework in the absence of sulphide ions (S(2-)). The metal-chelate complex (tris(ethylenediamine) metal(ii) sulfate) serves as a new and single source precursor for the synthesis of earth abundant and non-precious hybrid structures such as metal-rich sulphides Co9S8@NC and Ni3S2@NC when M(II) = Co(2+) and Ni(2+) and counter sulphate (SO4(2-)) ions are the source of S. Both the hybrids show superior OER activity as compared to commercial RuO2.

  20. A noble and single source precursor for the synthesis of metal-rich sulphides embedded in an N-doped carbon framework for highly active OER electrocatalysts.

    Science.gov (United States)

    Barman, Barun Kumar; Nanda, Karuna Kar

    2016-04-12

    Here, we demonstrate a green and environment-friendly pyrolysis route for the synthesis of metal-rich sulphide embedded in an N-doped carbon (NC) framework in the absence of sulphide ions (S(2-)). The metal-chelate complex (tris(ethylenediamine) metal(ii) sulfate) serves as a new and single source precursor for the synthesis of earth abundant and non-precious hybrid structures such as metal-rich sulphides Co9S8@NC and Ni3S2@NC when M(II) = Co(2+) and Ni(2+) and counter sulphate (SO4(2-)) ions are the source of S. Both the hybrids show superior OER activity as compared to commercial RuO2. PMID:26999042

  1. Noble gases solubility in water

    International Nuclear Information System (INIS)

    The available experimental data of solubility of noble gases in water for temperatures smaller than 3300C have been critically surveyed. Due to the unique structure of the solvent, the solubility of noble gases in water decreases with temperature passing through a temperature of minimum solubility which is different for each gas, and then increases at higher temperatures. As aresult of the analysis of the experimental data and of the features of the solute-solvent interaction, a generalized equation is proposed which enables thecalculation of Henry's coefficient at different temperatures for all noble gases. (author)

  2. Carbonates-based noble metal-free lean NOx trap catalysts MOx-K2CO3/K2Ti8O17 (M = Ce, Fe, Cu, Co) with superior catalytic performance

    Science.gov (United States)

    Zhang, Yuxia; You, Rui; Liu, Dongsheng; Liu, Cheng; Li, Xingang; Tian, Ye; Jiang, Zheng; Zhang, Shuo; Huang, Yuying; Zha, Yuqing; Meng, Ming

    2015-12-01

    A series of base metal-based lean NOx trap (LNT) catalysts MOx-K2CO3/K2Ti8O17 (M = Ce, Fe, Cu, Co) were synthesized by successive impregnations and employed for the storage and reduction of NOx in the emissions of lean-burn engines at 350 °C. The XRD and XANES/EXAFS results reveal that the active phases in the corresponding catalysts exist as CeO2, Fe2O3, CuO and Co3O4, respectively. Among all the catalysts, CoOx-K2CO3/K2Ti8O17 exhibits the best performance, which cannot only trap the NOx quickly and completely at lean condition, giving the highest storage capacity (3.32 mmol/g) reported so far, but also reduce the NOx at rich condition, showing a NOx reduction percentage as high as 99.0%. Meanwhile, this catalyst displays an ultralow NOx to N2O selectivity (0.3%) during NOx reduction. The excellent performance of CoOx-K2CO3/K2Ti8O17 results from its largest amount of surface active oxygen species as revealed by XPS, O2-TPD and NO-TPD. HRTEM, FT-IR and CO2-TPD results illustrate that several kinds of K species such as sbnd OK groups, K2O, surface carbonates and bulk or bulk-like carbonates coexist in the catalysts. Based upon the in situ DRIFTS results, the participation of K2CO3 in NOx storage is confirmed, and the predominant NOx storage species is revealed as bidentate nitrites formed via multiple kinetic pathways. The low cost and high catalytic performance of the CoOx-based LNT catalyst make it most promising for the substitution of noble metal-based LNT catalysts.

  3. Process for recycling components of a PEM fuel cell membrane electrode assembly

    Science.gov (United States)

    Shore, Lawrence

    2012-02-28

    The membrane electrode assembly (MEA) of a PEM fuel cell can be recycled by contacting the MEA with a lower alkyl alcohol solvent which separates the membrane from the anode and cathode layers of the assembly. The resulting solution containing both the polymer membrane and supported noble metal catalysts can be heated under mild conditions to disperse the polymer membrane as particles and the supported noble metal catalysts and polymer membrane particles separated by known filtration means.

  4. Understanding the Adsorption of CuPc and ZnPc on Noble Metal Surfaces by Combining Quantum-Mechanical Modelling and Photoelectron Spectroscopy

    Directory of Open Access Journals (Sweden)

    Yu Li Huang

    2014-03-01

    Full Text Available Phthalocyanines are an important class of organic semiconductors and, thus, their interfaces with metals are both of fundamental and practical relevance. In the present contribution we provide a combined theoretical and experimental study, in which we show that state-of-the-art quantum-mechanical simulations are nowadays capable of treating most properties of such interfaces in a quantitatively reliable manner. This is shown for Cu-phthalocyanine (CuPc and Zn-phthalocyanine (ZnPc on Au(111 and Ag(111 surfaces. Using a recently developed approach for efficiently treating van der Waals (vdW interactions at metal/organic interfaces, we calculate adsorption geometries in excellent agreement with experiments. With these geometries available, we are then able to accurately describe the interfacial electronic structure arising from molecular adsorption. We find that bonding is dominated by vdW forces for all studied interfaces. Concomitantly, charge rearrangements on Au(111 are exclusively due to Pauli pushback. On Ag(111, we additionally observe charge transfer from the metal to one of the spin-channels associated with the lowest unoccupied π-states of the molecules. Comparing the interfacial density of states with our ultraviolet photoelectron spectroscopy (UPS experiments, we find that the use of a hybrid functionals is necessary to obtain the correct order of the electronic states.

  5. Estimation of the Patients' Adaptation to Noble Alloy Dentures Relying on the Parameters of Biological Fluids in Oral Cavities

    Institute of Scientific and Technical Information of China (English)

    LEBEDENKO I. Yu.; PARUNOV V. A.; KITKINA T. B.

    2012-01-01

    For the study of the effect of Plagodent and Palladent noble alloy dentures (OJSC "SIC ‘Supermetal’",Russia),the elemental compositions of the fluids obtained from gingival sulcus of abutment teeth of metal-ceramic dentures with frames made of the above-stated dental alloys,have been investigated.Response of white blood cells and fibroblasts in the gingival fluid and the mixed saliva of the patients a long time after prosthetic repair,relying on the content of proinflammatory interleukins IL-1 β and IL-6,anti-inflammatory interleukins IL-4 and IL-10,the factor of tumor necrosis TNF-α and lactoferrin,has been investigated.The results obtained have convincingly proved the biosafety of the Plagodent and Palladent noble alloys.

  6. Metal nanoparticles for thin film solar cells

    DEFF Research Database (Denmark)

    Gritti, Claudia

    Among the different renewable ways to produce energy, photovoltaic cells have a big potential and the research is now focusing on getting higher efficiency and at the same time saving the manufacturing costs improving the performance of thin film solar cells. The spectral distribution in the infr......Among the different renewable ways to produce energy, photovoltaic cells have a big potential and the research is now focusing on getting higher efficiency and at the same time saving the manufacturing costs improving the performance of thin film solar cells. The spectral distribution...... the promotion of electrons from the valence band of the semiconductor. The photoemission would extend the spectral response of the photovoltaic device. Thus, NPs are placed at the metal/semiconductor interface (in order to exploit the localization characteristic of the LSP enhancement) and are used as active...... the solar cell structure (GaAs, SiO2, Si3N4, AZO/Cr), in order to investigate the LSP resonance and tune it to exploit it below the energy band gap of the semiconductor. EBL is a difficult technique when working by lift-off on critical size (20-50 nm) nanoparticles. The optimization of the process saw...

  7. Reducing the Cost and Preserving the Reactivity in Noble-Metal-Based Catalysts: Oxidation of CO by Pt and Al-Pt Alloy Clusters Supported on Graphene.

    Science.gov (United States)

    Koizumi, Kenichi; Nobusada, Katsuyuki; Boero, Mauro

    2016-04-01

    The oxidation mechanisms of CO to CO2 on graphene-supported Pt and Pt-Al alloy clusters are elucidated by reactive dynamical simulations. The general mechanism evidenced is a Langmuir-Hinshelwood (LH) pathway in which O2 is adsorbed on the cluster prior to the CO oxidation. The adsorbed O2 dissociates into two atomic oxygen atoms thus promoting the CO oxidation. Auxiliary simulations on alloy clusters in which other metals (Al, Co, Cr, Cu, Fe, Ni) replace a Pt atom have pointed to the aluminum doped cluster as a special case. In the nanoalloy, the reaction mechanism for CO oxidation is still a LH pathway with an activation barrier sufficiently low to be overcome at room temperature, thus preserving the catalyst efficiency. This provides a generalizable strategy for the design of efficient, yet sustainable, Pt-based catalysts at reduced cost. PMID:26878836

  8. Influence of the noble metals (Pd, Au, Ag) in the thermoluminescent signal induced by radiation in the ZrO2

    International Nuclear Information System (INIS)

    When increasing the use of the ionizing and non ionizing radiations (for example, gamma and ultraviolet radiation) in different areas of the science and technology, there is necessary to apply more accurate safety measures and to avoid over-exposures that could put in risk the life of workers that manipulate radiation sources, patient that are exposed to this under some medical treatment, as well as materials that undergo intentionally to radiation. Also, the UV radiation that arrives to the earth can cause some damages, to the one to weaken the protector layer of ozone the UV radiation increases that arrives to the earth surface being able to affect the alive beings and the materials. By this so much the development of new materials able to take a census of in a more accurate way, fields of gamma and UV radiation is becoming necessary. In this sense, this work presents the obtained results when quantifying radiation fields, through the analysis in the thermoluminescent behavior (TL) induced by the gamma and UV radiation in the zirconium dioxide synthesized by the sol gel method and doped with nanoparticles of Pd, Au and Ag. It is necessary to mention that in reported works in this respect its mention that the zircon has good thermoluminescent sensitivity induced by these radiation types, however it has shown high thermoluminescent instability that is translated in an important lost of the information after the irradiation. For that through the incorporation of the metallic nanoparticles it was intended to stabilize the TL behavior of zircon. The results showed that the doped zircon has a high sensitivity to the gamma and UV radiation. These also show that the ionizing and non ionizing radiation induce a thermoluminescent curve consisting of two TL peaks with maxima located around 65 C and 145 C and that the intensity is increased with the dose, following a lineal behavior in certain interval of dose exposure that is influenced by the presence of the nanoparticles

  9. Comparing Ullmann Coupling on Noble Metal Surfaces: On-Surface Polymerization of 1,3,6,8-Tetrabromopyrene on Cu(111) and Au(111).

    Science.gov (United States)

    Pham, Tuan Anh; Song, Fei; Nguyen, Manh-Thuong; Li, Zheshen; Studener, Florian; Stöhr, Meike

    2016-04-18

    The on-surface polymerization of 1,3,6,8-tetrabromopyrene (Br4 Py) on Cu(111) and Au(111) surfaces under ultrahigh vacuum conditions was investigated by a combination of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Deposition of Br4 Py on Cu(111) held at 300 K resulted in a spontaneous debromination reaction, generating the formation of a branched coordination polymer network stabilized by C-Cu-C bonds. After annealing at 473 K, the C-Cu-C bonds were converted to covalent C-C bonds, leading to the formation of a covalently linked molecular network of short oligomers. In contrast, highly ordered self-assembled two-dimensional (2D) patterns stabilized by both Br-Br halogen and Br-H hydrogen bonds were observed upon deposition of Br4 Py on Au(111) held at 300 K. Subsequent annealing of the sample at 473 K led to a dissociation of the C-Br bonds and the formation of disordered metal-coordinated molecular networks. Further annealing at 573 K resulted in the formation of covalently linked disordered networks. Importantly, we found that the chosen substrate not only plays an important role as catalyst for the Ullmann reaction, but also influences the formation of different types of intermolecular bonds and thus, determines the final polymer network morphology. DFT calculations further support our experimental findings obtained by STM and XPS and add complementary information on the reaction pathway of Br4 Py on the different substrates.

  10. Noble metal recycling. Project 2: Optimization of discontinuous thermal processes (emission reduction). Final report; Edelmetallrecycling. Teilvorhaben 2: Weiterentwicklung der Verfahrenstechnik bei diskontinuierlichen thermischen Prozessen (Emissionsminderung). Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Baumbach, G.; Berger, R.

    2000-10-01

    A batch operated incineration process, used for the recycling of precious metals is described in the report. The development of a new combined pyrolysis/oxidation Process is the main focus of the work. This new process has several remarkable advantages compared to traditionally used techniques. The optimisation of the process with a modern fuzzy based control technique is described in detail. The emissions of the process were reduced considerably applying the new process and the innovative control technique. Furthermore the layout of several components of the new process can be reduced in the future. The developed techniques can also be applied in other thermal processes, especially batch processes. Additionally the application of catalysts for PCDD/PCDF reduction in the flue gas upstream and downstream of the filter was investigated. Whereas the catalyst performed well, as expected, downstream of the filter, no acceptable operation was possible upstream of the filter. As the reheating downstream the filter is economically not feasible the application of catalysts is not applicable for the describe process. (orig.) [German] Die Arbeit beschreibt einen diskontinuierlichen thermischen Prozess, der zur Rueckgewinnung von Edelmetallen eingesetzt wird. Der Schwerpunkt der Arbeit liegt auf der Entwicklung eines neuartigen kombinierten Pyrolyse/Oxidations-Prozesses, der gegenueber den traditionell eingesetzten Anlagen grosse Vorteile aufweist. Die Optimierung dieses Prozesses mit Hilfe modernster Fuzzy-Regelungstechnik wird detailliert beschrieben. Mit dem neuen Verfahren und den innovativen Regelungstechniken konnten die Emissionen des Prozesses merklich gesenkt werden, ohne den Energiebedarf negativ zu beeinflussen. Ausserdem koennen zukuenftige Anlagen kleiner ausgelegt werden. Die entwickelten Verfahren koennen auch auf andere thermische Prozesse uebertragen werden. Weiterhin wurde der Einsatz von Katalysatoren zur PCDD/PCDF-Minderung im Rein- und Rohgas untersucht

  11. The Fundamental Role of Nano-Scale Oxide Films in the Oxidation of Hydrogen and the Reduction of Oxygen on Noble Metal Electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Digby Macdonald

    2005-04-15

    The derivation of successful fuel cell technologies requires the development of more effective, cheaper, and poison-resistant electrocatalysts for both the anode (H{sub 2} oxidation in the presence of small amounts of CO from the reforming of carbonaceous fuels) and the cathode (reduction of oxygen in the presence of carried-over fuel). The proposed work is tightly focused on one specific aspect of electrocatalysis; the fundamental role(s) played by nanoscale (1-2 nm thick) oxide (''passive'') films that form on the electrocatalyst surfaces above substrate-dependent, critical potentials, on charge transfer reactions, particularly at elevated temperatures (25 C < T < 200 C). Once the role(s) of these films is (are) adequately understood, we will then use this information to specify, at the molecular level, optimal properties of the passive layer for the efficient electrocatalysis of the oxygen reduction reaction.

  12. Performance of metal alloys as hydrogen evolution reaction catalysts in a microbial electrolysis cell

    NARCIS (Netherlands)

    Jeremiasse, A.W.; Bergsma, J.; Kleijn, J.M.; Saakes, M.; Buisman, C.J.N.; Cohen Stuart, M.A.; Hamelers, H.V.M.

    2011-01-01

    H2 can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease the energy input and increase the H2 production rate of an MEC, a catalyst is used at the cathode. Platinum is an effective catalyst, but its high costs stimulate searching for alternatives, such as non-nobl

  13. Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors.

    Science.gov (United States)

    McWilliams, R Stewart; Dalton, D Allen; Konôpková, Zuzana; Mahmood, Mohammad F; Goncharov, Alexander F

    2015-06-30

    The noble gases are elements of broad importance across science and technology and are primary constituents of planetary and stellar atmospheres, where they segregate into droplets or layers that affect the thermal, chemical, and structural evolution of their host body. We have measured the optical properties of noble gases at relevant high pressures and temperatures in the laser-heated diamond anvil cell, observing insulator-to-conductor transformations in dense helium, neon, argon, and xenon at 4,000-15,000 K and pressures of 15-52 GPa. The thermal activation and frequency dependence of conduction reveal an optical character dominated by electrons of low mobility, as in an amorphous semiconductor or poor metal, rather than free electrons as is often assumed for such wide band gap insulators at high temperatures. White dwarf stars having helium outer atmospheres cool slower and may have different color than if atmospheric opacity were controlled by free electrons. Helium rain in Jupiter and Saturn becomes conducting at conditions well correlated with its increased solubility in metallic hydrogen, whereas a deep layer of insulating neon may inhibit core erosion in Saturn.

  14. Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors.

    Science.gov (United States)

    McWilliams, R Stewart; Dalton, D Allen; Konôpková, Zuzana; Mahmood, Mohammad F; Goncharov, Alexander F

    2015-06-30

    The noble gases are elements of broad importance across science and technology and are primary constituents of planetary and stellar atmospheres, where they segregate into droplets or layers that affect the thermal, chemical, and structural evolution of their host body. We have measured the optical properties of noble gases at relevant high pressures and temperatures in the laser-heated diamond anvil cell, observing insulator-to-conductor transformations in dense helium, neon, argon, and xenon at 4,000-15,000 K and pressures of 15-52 GPa. The thermal activation and frequency dependence of conduction reveal an optical character dominated by electrons of low mobility, as in an amorphous semiconductor or poor metal, rather than free electrons as is often assumed for such wide band gap insulators at high temperatures. White dwarf stars having helium outer atmospheres cool slower and may have different color than if atmospheric opacity were controlled by free electrons. Helium rain in Jupiter and Saturn becomes conducting at conditions well correlated with its increased solubility in metallic hydrogen, whereas a deep layer of insulating neon may inhibit core erosion in Saturn. PMID:26080401

  15. Molybdenum-tin as a solar cell metallization system

    Science.gov (United States)

    Boyd, D. W.; Radics, C.

    The operations of solar cell manufacture are briefly examined. The formation of reliable, ohmic, low-loss, and low-cost metal contacts on solar cells is a critical process step in cell manufacturing. In a commonly used process, low-cost metallization is achieved by screen printing a metal powder-glass frit ink on the surface of the Si surface and the conductive metal powder. A technique utilizing a molybdenum-tin alloy for the metal contacts appears to lower the cost of materials and to reduce process complexity. The ink used in this system is formulated from MoO3 with Sn powder and a trace amount of titanium resonate. Resistive losses of the resulting contacts are low because the ink contains no frit. The MoO3 is finally melted and reduced in forming gas (N2+H2) to Mo metal. The resulting Mo is highly reactive which facilitates the Mo-Si bonding.

  16. Electrical resistivity of liquid noble metal alloys

    International Nuclear Information System (INIS)

    Calculations of the dependence of the electrical resistivity in liquid Ag-Au, Cu-Ag, Cu-Au binary alloys on composition are reported. The structure of the binary alloy is described as a hard sphere system. A one-parameter local pseudopotential, which incorporates s-d hybridization effects phenomenologically, is employed in the resistivity calculation. A reasonable agreement with experimental trends is observed in cases where experimental information is available. (author)

  17. Aluminium anode for biogalvanic metal--oxygen -cells

    Energy Technology Data Exchange (ETDEWEB)

    Weidlich, E.

    1975-02-20

    The invention deals with an aluminium anode for biogalvanic metal--oxygen cells. The object of the invention is to improve further an aluminium anode for biogalvanic metal--oxygen cells. In particular, the lifetime is to be increased and the Faraday degree of efficiency is to be improved by suppressing an excessive hydrogen development. The anode is thus constructed so as to have a metal net on both sides with aluminium layers, and the surfaces of the aluminium layers not facing the metal net are lapped or sand-blasted and have an anodized layer on their boundary regions.

  18. Negative aluminium electrode for biogalvanic metal-oxygen cells

    Energy Technology Data Exchange (ETDEWEB)

    Weidlich, E.

    1977-03-24

    The invention deals with an aluminium anode for biogalvanic metal-oxygen cells. The object of the invention is to further improve an aluminium anode for biogalvanic metal-oxygen cells. In particular, the service life is to be increased and the Faraday degree of efficiency is to be improved, by suppressing an excessive hydrogen development. The anode is thus constructed so as to have a metal net on both sides with aluminium layers and the surfaces of the aluminium layers not facing the metal net are lapped or sand-blasted and have an eloxal layer on their boundary regions.

  19. A sliding cell technique for diffusion measurements in liquid metals

    OpenAIRE

    Yongliang Geng; Chunao Zhu; Bo Zhang

    2014-01-01

    The long capillary and shear cell techniques are the usual methods for diffusion measurements in liquid metals. Here we present a new “sliding cell technique” to measure interdiffusion in liquid alloys, which combines the merits of these two methods. Instead of a number of shear cells, as used in the shear cell method, only one sliding cell is designed to separate and join the liquid diffusion samples. Using the sliding cell technique, the influence of the heating process (which affects liqui...

  20. Determination of natural in vivo noble-gas concentrations in human blood.

    Directory of Open Access Journals (Sweden)

    Yama Tomonaga

    Full Text Available Although the naturally occurring atmospheric noble gases He, Ne, Ar, Kr, and Xe possess great potential as tracers for studying gas exchange in living beings, no direct analytical technique exists for simultaneously determining the absolute concentrations of these noble gases in body fluids in vivo. In this study, using human blood as an example, the absolute concentrations of all stable atmospheric noble gases were measured simultaneously by combining and adapting two analytical methods recently developed for geochemical research purposes. The partition coefficients determined between blood and air, and between blood plasma and red blood cells, agree with values from the literature. While the noble-gas concentrations in the plasma agree rather well with the expected solubility equilibrium concentrations for air-saturated water, the red blood cells are characterized by a distinct supersaturation pattern, in which the gas excess increases in proportion to the atomic mass of the noble-gas species, indicating adsorption on to the red blood cells. This study shows that the absolute concentrations of noble gases in body fluids can be easily measured using geochemical techniques that rely only on standard materials and equipment, and for which the underlying concepts are already well established in the field of noble-gas geochemistry.

  1. A metal-organic framework-derived bifunctional oxygen electrocatalyst

    Science.gov (United States)

    Xia, Bao Yu; Yan, Ya; Li, Nan; Wu, Hao Bin; Lou, Xiong Wen (David); Wang, Xin

    2016-01-01

    Oxygen electrocatalysis is of great importance for many energy storage and conversion technologies, including fuel cells, metal-air batteries and water electrolysis. Replacing noble metal-based electrocatalysts with highly efficient and inexpensive non-noble metal-based oxygen electrocatalysts is critical for the practical applications of these technologies. Here we report a general approach for the synthesis of hollow frameworks of nitrogen-doped carbon nanotubes derived from metal-organic frameworks, which exhibit higher electrocatalytic activity and stability for oxygen reduction and evolution than commercial Pt/C electrocatalysts. The remarkable electrochemical properties are mainly attributed to the synergistic effect from chemical compositions and the robust hollow structure composed of interconnected crystalline nitrogen-doped carbon nanotubes. The presented strategy for controlled design and synthesis of metal-organic framework-derived functional nanomaterials offers prospects in developing highly active electrocatalysts in electrochemical energy devices.

  2. Ni/CeO{sub 2}-Al{sub 2}O{sub 3} catalysts promoted with noble metals for the hydrogen production by ethanol vapor reforming; Catalisadores de Ni/CeO{sub 2}-Al{sub 2}O{sub 3} promovidos com metais nobres para a producao de hidrogenio por reforma a vapor de etanol

    Energy Technology Data Exchange (ETDEWEB)

    Profeti, Luciene P.R.; Ticianelli, Edson Antonio; Assaf, Elisabete Moreira [Universidade de Sao Paulo (IQSC/USP), Sao Carlos, SP (Brazil). Inst. de Quimica]. E-mail: eassaf@iqsc.usp.br

    2008-07-01

    The catalytic activity of Ni/CeO{sub 2}-Al{sub 2}O{sub 3} catalysts modified with noble metals (Ru, Ir, Pt and Pd) was investigated in the steam reforming of ethanol. The catalysts were characterized by energy dispersive spectroscopy, X-ray diffraction, UV-Vis diffuse reflectance spectroscopy and H{sub 2} temperature-programmed reduction-X-ray absorption fine structure (XANES). The results showed that the formation of inactive nickel aluminate was avoided due to the presence of a CeO{sub 2} dispersed on the alumina. The promoting effect of noble metals included a decrease of the reduction temperatures of NiO species interacting with the support due to the hydrogen spillover effect, leading to an increase of the reducibilities of the promoted catalysts The better catalytic performance for the ethanol steam reforming was obtained for the NiPd/CeAl catalyst, which presented an effluent gaseous mixture with the highest H{sub 2} yield. (author)

  3. Novel fuel cell stack with coupled metal hydride containers

    Science.gov (United States)

    Liu, Zhixiang; Li, Yan; Bu, Qingyuan; Guzy, Christopher J.; Li, Qi; Chen, Weirong; Wang, Cheng

    2016-10-01

    Air-cooled, self-humidifying hydrogen fuel cells are often used for backup and portable power sources, with a metal hydride used as the hydrogen storage material. To provide a stable hydrogen flow to the fuel cell stack, heat must be provided to the metal hydride. Conventionally, the heat released from the exothermic reaction of hydrogen and oxygen in the fuel cell stack to the exhaust air is used to heat a separate metal hydride container. In this case, the heat is only partially used instead of being more closely coupled because of the heat transfer resistances in the system. To achieve better heat integration, a novel scheme is proposed whereby hydrogen storage and single fuel cells are more closely coupled. Based on this idea, metal hydride containers in the form of cooling plates were assembled between each pair of cells in the stack so that the heat could be directly transferred to a metal hydride container of much larger surface-to-volume ratio than conventional separate containers. A heat coupled fuel cell portable power source with 10 cells and 11 metal hydride containers was constructed and the experimental results show that this scheme is beneficial for the heat management of fuel cell stack.

  4. Heavy metal biosorption by bacterial cells

    NARCIS (Netherlands)

    Vecchio, A; Finoli, C; Di Simine, D; Andreoni, [No Value

    1998-01-01

    Microbial biomass provides available ligand groups on which metal ions bind by different mechanisms. Biosorption of these elements from aqueous solutions represents a remediation technology suitable for the treatment of metal-contaminated effluents. The purpose of the present investigation was the a

  5. Back contact to film silicon on metal for photovoltaic cells

    Science.gov (United States)

    Branz, Howard M.; Teplin, Charles; Stradins, Pauls

    2013-06-18

    A crystal oriented metal back contact for solar cells is disclosed herein. In one embodiment, a photovoltaic device and methods for making the photovoltaic device are disclosed. The photovoltaic device includes a metal substrate with a crystalline orientation and a heteroepitaxial crystal silicon layer having the same crystal orientation of the metal substrate. A heteroepitaxial buffer layer having the crystal orientation of the metal substrate is positioned between the substrate and the crystal silicon layer to reduce diffusion of metal from the metal foil into the crystal silicon layer and provide chemical compatibility with the heteroepitaxial crystal silicon layer. Additionally, the buffer layer includes one or more electrically conductive pathways to electrically couple the crystal silicon layer and the metal substrate.

  6. FIB/SEM cell sectioning for intracellular metal granules characterization

    Science.gov (United States)

    Milani, Marziale; Brundu, Claudia; Santisi, Grazia; Savoia, Claudio; Tatti, Francesco

    2009-05-01

    Focused Ion Beams (FIBs) provide a cross-sectioning tool for submicron dissection of cells and subcellular structures. In combination with Scanning Electron Microscope (SEM), FIB provides complementary morphological information, that can be further completed by EDX (Energy Dispersive X-ray Spectroscopy). This study focus onto intracellular microstructures, particularly onto metal granules (typically Zn, Cu and Fe) and on the possibility of sectioning digestive gland cells of the terrestrial isopod P. scaber making the granules available for a compositional analysis with EDX. Qualitative and quantitative analysis of metal granules size, amount and distribution are performed. Information is made available of the cellular storing pattern and, indirectly, metal metabolism. The extension to human level is of utmost interest since some pathologies of relevance are metal related. Apart from the common metal-overload-diseases (hereditary hemochromatosis, Wilson's and Menkes disease) it has been demonstrated that metal in excess can influence carcinogenesis in liver, kidney and breast. Therefore protocols will be established for the observation of mammal cells to improve our knowledge about the intracellular metal amount and distribution both in healthy cells and in those affected by primary or secondary metal overload or depletion.

  7. Environmental tests of metallization systems for terrestrial photovoltaic cells

    Science.gov (United States)

    Alexander, P., Jr.

    1985-01-01

    Seven different solar cell metallization systems were subjected to temperature cycling tests and humidity tests. Temperature cycling excursions were -50 deg C to 150 deg C per cycle. Humidity conditions were 70 deg C at 98% relative humidity. The seven metallization systems were: Ti/Ag, Ti/Pd/Ag, Ti/Pd/Cu, Ni/Cu, Pd/Ni/Solder, Cr/Pd/Ag, and thick film Ag. All metallization systems showed a slight to moderate decrease in cell efficiencies after subjection to 1000 temperature cycles. Six of the seven metallization systems also evidenced slight increases in cell efficiencies after moderate numbers of cycles, generally less than 100 cycles. The copper based systems showed the largest decrease in cell efficiencies after temperature cycling. All metallization systems showed moderate to large decreases in cell efficiencies after 123 days of humidity exposure. The copper based systems again showed the largest decrease in cell efficiencies after humidity exposure. Graphs of the environmental exposures versus cell efficiencies are presented for each metallization system, as well as environmental exposures versus fill factors or series resistance.

  8. Plant Chemistry Response to On-Line NobleChemTM

    International Nuclear Information System (INIS)

    Noble metal chemical addition is widely and successfully used in boiling water reactors (BWRs) as a mitigation method for intergranular stress corrosion cracking (IGSCC). This technology is used to reduce the electrochemical corrosion potential (ECP) of reactor internals and associated piping while maintaining low hydrogen injection rates. Over the past six years, BWRs have started to transition away from applying noble metals during refueling outages to the application of noble metals while the reactor is operating at full power using the On-Line NobleChemTM (OLNC) process. The ability to apply noble metals on-line allows for greater reapplication flexibility and eliminates the impact of an application on the duration of refueling outages. As more plants have begun to perform OLNC applications, the industry has started to accumulate a significant amount of reactor water chemistry and operating experience for periods both during and after injections. The intent of this paper is to summarize changes in chemistry parameters typically observed during and after an OLNC application, such as increases in reactor water conductivity and activated corrosion by product levels. These parameters can therefore be used during an OLNC injection as secondary indicators of application progress. This paper will also discuss methods of monitor an application, including direct ECP measurements and the use of secondary indicators. (authors)

  9. New perspectives for noble gases in oceanography

    Science.gov (United States)

    Aeschbach, Werner

    2016-08-01

    Conditions prevailing in regions of deep water formation imprint their signature in the concentrations of dissolved noble gases, which are conserved in the deep ocean. Such "recharge conditions" including temperature, salinity, and interactions with sea ice are important in view of ocean-atmosphere CO2 partitioning. Noble gases, especially the temperature sensitive Kr and Xe, are well-established tracers to reconstruct groundwater recharge conditions. In contrast, tracer oceanography has traditionally focused on He isotopes and the light noble gases Ne and Ar, which could be analyzed at the required high precision. Recent developments of analytical and data interpretation methods now provide fresh perspectives for noble gases in oceanography.

  10. Preparation of open-cell metal foams by investment cast

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Metal foams are a new kind of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They can be divided into closed and open cell structures. In this paper the open cell structures,called sponges, were treated. A new technique to manufacture sponges by plaster investment casting was described.Experimental results show that it is essential to make a sound plaster mould by casting plaster slurry into the polyurethane foams and infiltrate the open channels of the baked plaster mold by molten metal. The optimal processes include plaster slurry preparation, plaster mold baking, and molten metal infiltration. The sponge sample with porosity of 97% is presented.

  11. Influence of the noble metals (Pd, Au, Ag) in the thermoluminescent signal induced by radiation in the ZrO{sub 2}; Influencia de los metales nobles (Pd, Au, Ag) en la senal termoluminiscente inducida por la radiacion en la ZrO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Villa S, G

    2006-07-01

    When increasing the use of the ionizing and non ionizing radiations (for example, gamma and ultraviolet radiation) in different areas of the science and technology, there is necessary to apply more accurate safety measures and to avoid over-exposures that could put in risk the life of workers that manipulate radiation sources, patient that are exposed to this under some medical treatment, as well as materials that undergo intentionally to radiation. Also, the UV radiation that arrives to the earth can cause some damages, to the one to weaken the protector layer of ozone the UV radiation increases that arrives to the earth surface being able to affect the alive beings and the materials. By this so much the development of new materials able to take a census of in a more accurate way, fields of gamma and UV radiation is becoming necessary. In this sense, this work presents the obtained results when quantifying radiation fields, through the analysis in the thermoluminescent behavior (TL) induced by the gamma and UV radiation in the zirconium dioxide synthesized by the sol gel method and doped with nanoparticles of Pd, Au and Ag. It is necessary to mention that in reported works in this respect its mention that the zircon has good thermoluminescent sensitivity induced by these radiation types, however it has shown high thermoluminescent instability that is translated in an important lost of the information after the irradiation. For that through the incorporation of the metallic nanoparticles it was intended to stabilize the TL behavior of zircon. The results showed that the doped zircon has a high sensitivity to the gamma and UV radiation. These also show that the ionizing and non ionizing radiation induce a thermoluminescent curve consisting of two TL peaks with maxima located around 65 C and 145 C and that the intensity is increased with the dose, following a lineal behavior in certain interval of dose exposure that is influenced by the presence of the nanoparticles

  12. Noble gases in Tagish Lake

    OpenAIRE

    Grady, Monica; Verchovsky, Sasha; Franchi, Ian; Wright, Ian; Pillinger, Colin

    2001-01-01

    From the introduction: Tagish Lake has been classified as a CI2 chondrite [1] with an interstellar grain abundance enhanced over that of CI1 and CM2 chondrites [2]. Noble gases have been used as markers for the presence of exotic, presolar grains in chondritic meteorites: Xe-HL (nanodiamonds) and Xe-s/Ne-E (SiC). We have measured 4He, Ne, Ar and Xe in whole-rock Tagish Lake, and an orthophosphoric acid-resistant residue, in an effort to define more precisely the...

  13. Recycled Cell Phones - A Treasure Trove of Valuable Metals

    Science.gov (United States)

    Sullivan, Daniel E.

    2006-01-01

    This U.S. Geological Survey (USGS) Fact Sheet examines the potential value of recycling the metals found in obsolete cell phones. Cell phones seem ubiquitous in the United States and commonplace throughout most of the world. There were approximately 1 billion cell phones in use worldwide in 2002. In the United States, the number of cell phone subscribers increased from 340,000 in 1985 to 180 million in 2004. Worldwide, cell phone sales have increased from slightly more than 100 million units per year in 1997 to an estimated 779 million units per year in 2005. Cell phone sales are projected to exceed 1 billion units per year in 2009, with an estimated 2.6 billion cell phones in use by the end of that year. The U.S. Environmental Protection Agency estimated that, by 2005, as many as 130 million cell phones would be retired annually in the United States. The nonprofit organization INFORM, Inc., anticipated that, by 2005, a total of 500 million obsolete cell phones would have accumulated in consumers' desk drawers, store rooms, or other storage, awaiting disposal. Typically, cell phones are used for only 1 1/2 years before being replaced. Less than 1 percent of the millions of cell phones retired and discarded annually are recycled. When large numbers of cell phones become obsolete, large quantities of valuable metals end up either in storage or in landfills. The amount of metals potentially recoverable would make a significant addition to total metals recovered from recycling in the United States and would supplement virgin metals derived from mining.

  14. Nobel metal alloyed thin-films with optical properties on demand

    Science.gov (United States)

    Gong, Chen; Leite, Marina S.

    Metallic materials with tunable optical responses can enable the unprecedented control of optoelectronic and nanophotonic devices with enhanced performance, such as thin-film solar cells, metamaterials and metasurfaces for tunable absorbers and optical filters, among others. Here we present the alloying of noble metals, Ag, Au and Cu, to develop a novel class of material with optical response not achieved by pure metals. We fabricate binary mixtures with controlled chemical composition by co-sputtering. Ellipsometry and surface plasmon polariton coupling angle measurements are in excellent agreement when determining the real part of the dielectric function (ɛ1). Surprisingly, in some cases, a mixture provides a material with higher surface plasmon polariton quality factor than the corresponding pure metals. Our approach paves the way to implement metallic nanostructures with tunable absorption/transmission, overcoming the current limitation of the dielectric function of noble metals.

  15. 火焰燃烧法在金属氧化物和贵金属负载型催化剂制备中的应用%The application of flame combustion synthesis in the preparation of metal oxide and supported noble metal catalysts

    Institute of Scientific and Technical Information of China (English)

    李佳琪; 邓昱洲; 刘刚; 岳仁亮; 杨军; 陈运法

    2016-01-01

    Flame combustion synthesis (FCS)is widely used to produce nanoparticles on a large scale,and has been applied in the preparation of carbon black and fumed silica.FCS is a versatile technique to be used but not limited in the specific field of catalyst preparation,gas sensor fabrication,luminant materials and antibacterial materials.In the re-view,we focus on the recent advances in using FCS for the catalyst preparation,including metal oxides and supported noble metals,and in the last section,we make some perspetives for the future developments of this promising synthetic technique.%火焰燃烧法合成纳米颗粒是工业上大规模生产纳米粉体的主要方法。现已经广泛应用于炭黑、颜料等功能粉体的制备,并随着应用领域的拓展逐渐用于催化剂的制备。结合本研究组工作详细综述了近年来国内外火焰燃烧法在催化剂制备方面的研究进展,主要包括金属氧化物催化剂和金属负载催化剂等两方面,并对火焰燃烧法的发展趋势和在催化剂制备相关领域的应用前景进行了展望。

  16. The Chemistry of the noble gases

    Energy Technology Data Exchange (ETDEWEB)

    Chernick, Cedric L. [Agonne National Laboratory

    1967-01-01

    This booklet discusses the 6 noble gases: helium, neon, argon, krypton, xenon, and radon. Until 1962, it was believed that these 6 elements were not able to form chemical compounds. Hence they were called "noble" because they didn't mingle with the common masses of elements.

  17. Noble Gases in the Lunar Regolith

    Institute of Scientific and Technical Information of China (English)

    邹永廖; 徐琳; 欧阳自远

    2003-01-01

    The most fundamental character of lunar soil is its high concentrations of solar-windimplanted dements,and the concentrations and behavior of the noble gases He,Ne,Ar,and Xe,which provide unique and extensive information about a broad range of fundamental problems. In this paper,the authors studied the forming mechanism of lunar regolith,and proposed that most of the noble gases in lunar regolith come from the solar wind. Meteoroid bombardment controls the maturity of lunar soil,with the degree of maturation decreasing with grain size; the concentrations of the noble gases would be of slight variation with the depth of lunar soil but tend to decrease with grain size. In addition,the concentrations of noble gases in lunar soil also show a close relationship with its mineral and chemical compositions. The utilization prospects of the noble gas s He in lunar regolith will be further discussed.

  18. Metal-Insulator-Semiconductor Nanowire Network Solar Cells.

    Science.gov (United States)

    Oener, Sebastian Z; van de Groep, Jorik; Macco, Bart; Bronsveld, Paula C P; Kessels, W M M; Polman, Albert; Garnett, Erik C

    2016-06-01

    Metal-insulator-semiconductor (MIS) junctions provide the charge separating properties of Schottky junctions while circumventing the direct and detrimental contact of the metal with the semiconductor. A passivating and tunnel dielectric is used as a separation layer to reduce carrier recombination and remove Fermi level pinning. When applied to solar cells, these junctions result in two main advantages over traditional p-n-junction solar cells: a highly simplified fabrication process and excellent passivation properties and hence high open-circuit voltages. However, one major drawback of metal-insulator-semiconductor solar cells is that a continuous metal layer is needed to form a junction at the surface of the silicon, which decreases the optical transmittance and hence short-circuit current density. The decrease of transmittance with increasing metal coverage, however, can be overcome by nanoscale structures. Nanowire networks exhibit precisely the properties that are required for MIS solar cells: closely spaced and conductive metal wires to induce an inversion layer for homogeneous charge carrier extraction and simultaneously a high optical transparency. We experimentally demonstrate the nanowire MIS concept by using it to make silicon solar cells with a measured energy conversion efficiency of 7% (∼11% after correction), an effective open-circuit voltage (Voc) of 560 mV and estimated short-circuit current density (Jsc) of 33 mA/cm(2). Furthermore, we show that the metal nanowire network can serve additionally as an etch mask to pattern inverted nanopyramids, decreasing the reflectivity substantially from 36% to ∼4%. Our extensive analysis points out a path toward nanowire based MIS solar cells that exhibit both high Voc and Jsc values.

  19. Metal-Insulator-Semiconductor Nanowire Network Solar Cells.

    Science.gov (United States)

    Oener, Sebastian Z; van de Groep, Jorik; Macco, Bart; Bronsveld, Paula C P; Kessels, W M M; Polman, Albert; Garnett, Erik C

    2016-06-01

    Metal-insulator-semiconductor (MIS) junctions provide the charge separating properties of Schottky junctions while circumventing the direct and detrimental contact of the metal with the semiconductor. A passivating and tunnel dielectric is used as a separation layer to reduce carrier recombination and remove Fermi level pinning. When applied to solar cells, these junctions result in two main advantages over traditional p-n-junction solar cells: a highly simplified fabrication process and excellent passivation properties and hence high open-circuit voltages. However, one major drawback of metal-insulator-semiconductor solar cells is that a continuous metal layer is needed to form a junction at the surface of the silicon, which decreases the optical transmittance and hence short-circuit current density. The decrease of transmittance with increasing metal coverage, however, can be overcome by nanoscale structures. Nanowire networks exhibit precisely the properties that are required for MIS solar cells: closely spaced and conductive metal wires to induce an inversion layer for homogeneous charge carrier extraction and simultaneously a high optical transparency. We experimentally demonstrate the nanowire MIS concept by using it to make silicon solar cells with a measured energy conversion efficiency of 7% (∼11% after correction), an effective open-circuit voltage (Voc) of 560 mV and estimated short-circuit current density (Jsc) of 33 mA/cm(2). Furthermore, we show that the metal nanowire network can serve additionally as an etch mask to pattern inverted nanopyramids, decreasing the reflectivity substantially from 36% to ∼4%. Our extensive analysis points out a path toward nanowire based MIS solar cells that exhibit both high Voc and Jsc values. PMID:27172429

  20. Combined toxicity of heavy metal mixtures in liver cells.

    Science.gov (United States)

    Lin, Xialu; Gu, Yuanliang; Zhou, Qi; Mao, Guochuan; Zou, Baobo; Zhao, Jinshun

    2016-09-01

    With rapid industrialization, China is now facing great challenges in heavy metal contamination in the environment. Human exposure to heavy metals through air, water and food commonly involves a mixture consisting of multiple heavy metals. In this study, eight common heavy metals (Pb, Cd, Hg, Cu, Zn, Mn, Cr, Ni) that cause environmental contamination were selected to investigate the combined toxicity of different heavy metal mixtures in HL7702 cells. Toxicity (24 h LC50 ) of each individual metal on the cells ranked Hg > Cr = Cd > Cu > Zn > Ni > Mn > Pb; toxicity of the different mixtures ranked: M5 > M3PbHgCd > M5+Mn > M5+Cu > M2CdNi > M4A > M8-Mn > M8 > M5+Zn > M4B > M8-Cr > M8-Zn > M8-Cu > M8-Pb > M8-Cd > M8-Hg > M8-Ni > M3PbHgNi > M3CuZnMn. The cytotoxicity data of individual metals were successfully used to build the additive models of two- to eight-component metal mixtures. The comparison between additive model and combination model or partly additive model was useful to evaluate the combined effects in mixture. Synergistic, antagonistic or additive effects of the toxicity were observed in different mixtures. These results suggest that the combined effects should be considered in the risk assessment of heavy metal co-exposure, and more comprehensive investigations on the combined effects of different heavy metal mixtures are needed in the future. Copyright © 2016 John Wiley & Sons, Ltd.

  1. Heavy metals effect in Drosophila melanogaster germinal cells

    International Nuclear Information System (INIS)

    Heavy metals occur naturally and some of them are very important in cellular metabolism. Industrial development has increased metal concentration in the environment and in the living organisms tissues. This increase promotes the human risk to suffer teratogenesis, carcinogenesis and mutagenesis. Different biological systems have been used to proof the genetic effect of heavy metals including Drosophila. In the present work chromium, cadmium, lead, zinc and arsenic salts were administered to Drosophila females and males adults in order to determine the genetic effect produced by these compounds, in both femenine and masculine germinal cells. The mating system used (''Oster males'' and y2wsup(a)/y2wsup(a); e/e females) permited to determine among two succesive generations, the mutagenic effects produced by heavy metals in Drosophila. The salts administration to adult flies was made by injection. Non-disjunction, X-chromosome loss, and sex linked recessive lethals frequency was increased by heavy metals. It was observed a fertility disminution between F 1 descendants from individuals treated with the metalic salts. It was demonstrated that heavy metals can interact with genetic material at different levels in the two types of gametic cells to produce genetic damage. (author)

  2. Advances in Metal Supported Cells in the METSOFC EU Consortium

    DEFF Research Database (Denmark)

    McKenna, B. J.; Christiansen, N.; Schauperl, R.;

    2013-01-01

    The EU‐sponsored project “METSOFC”, completed at the end of 2011, resulted in a number of advancements toward implementing a mechanically robust metal support as the structural element in SOFC. Technical University of Denmark (DTU) Energy Conversion's research into planar metal supported cells (M......, and tolerance to thermal cycles and load cycles. These and other key outcomes of the METSOFC consortium are covered, along with associated work supported by the Danish National Advanced Technology Foundation.......The EU‐sponsored project “METSOFC”, completed at the end of 2011, resulted in a number of advancements toward implementing a mechanically robust metal support as the structural element in SOFC. Technical University of Denmark (DTU) Energy Conversion's research into planar metal supported cells...... (MSCs) has produced an advanced cell design with high performance and mechanical robustness. At low operation temperatures (650 °C), these cells have shown low Area‐specific resistances (ASRs): 0.35 Ω cm2 in cell tests (16 cm2 active area) and under 0.3 Ω cm2 in button cells (0.5 cm2 active area...

  3. PRAGMATIC KNOWLEDGE OR NOBLE KNOWLEDGE?

    Directory of Open Access Journals (Sweden)

    Marian MANOLESCU

    2015-11-01

    Full Text Available Disputes about the opportunity to introduce competence-based education are increasingly present in terms of educational policies and strategies. Obviously, in the last decade and a half, several countries have introduced competence based education. Although specific knowledge acquisition should be an essential component of student learning, assessing such knowledge in adult life depends largely on the individual purchase of more general concepts and skills. The article discusses pragmatic knowledge and noble knowledge. This is a collective dilemma, to the extent that the education system lives in the tension between the two logics. The two positions or divergent attitudes can coexist as long ast hey do not become extremist. Educational dilemma is especially now a priority.

  4. Low Cost PEM Fuel Cell Metal Bipolar Plates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Conghua [TreadStone Technologies, Inc.

    2013-05-30

    Bipolar plate is an important component in fuel cell stacks and accounts for more than 75% of stack weight and volume. The technology development of metal bipolar plates can effectively reduce the fuel cells stack weight and volume over 50%. The challenge is the metal plate corrosion protection at low cost for the broad commercial applications. This project is aimed to develop innovative technological solutions to overcome the corrosion barrier of low cost metal plates. The feasibility of has been demonstrated and patented (US Patent 7,309,540). The plan is to further reduce the cost, and scale up the technology. The project is built on three pillars: 1) robust experimental evidence demonstrating the feasibility of our technology, 2) a team that consists of industrial leaders in fuel cell stack application, design, and manufactures; 3) a low-risk, significant-milestone driven program that proves the feasibility of meeting program objectives The implementation of this project will reduce the fuel cell stack metal bipolar separator plate cost which accounts 15-21% of the overall stack cost. It will contribute to the market adoption of fuel cell technologies. In addition, this corrosion protection technology can be used similar energy devices, such as batteries and electrolyzers. Therefore, the success of the project will be benefit in broad markets.

  5. Dark Matter Search with liquid Noble Gases

    CERN Document Server

    Schumann, Marc

    2012-01-01

    Dark matter detectors using the liquid noble gases xenon and argon as WIMP targets have evolved rapidly in the last decade and will continue to play a major role in the field. Due to the possibility to scale these detectors to larger masses relatively easily, noble liquids will likely be the first technology realizing a detector with a ton-scale target mass. In this article, we summarize the basic concepts of liquid noble gas dark matter detectors and review the current experimental status.

  6. Modification of cell volume and proliferative capacity of Pseudokirchneriella subcapitata cells exposed to metal stress

    International Nuclear Information System (INIS)

    Highlights: •Metals induce morphological alterations on P. subcapitata. •Algal cell cycle consists: mother cell growth; cell division, with two nucleus divisions; release of four autospores. •Cu(II) and Cr(VI) arrest cell growth before the first nuclear division. •Cd(II) arrests cell growth after the second nuclear division but before the cytokinesis. •The approach used can be useful in the elucidation of different modes of action of pollutants. -- Abstract: The impact of metals (Cd, Cr, Cu and Zn) on growth, cell volume and cell division of the freshwater alga Pseudokirchneriella subcapitata exposed over a period of 72 h was investigated. The algal cells were exposed to three nominal concentrations of each metal: low (closed to 72 h-EC10 values), intermediate (closed to 72 h-EC50 values) and high (upper than 72 h-EC90 values). The exposure to low metal concentrations resulted in a decrease of cell volume. On the contrary, for the highest metal concentrations an increase of cell volume was observed; this effect was particularly notorious for Cd and less pronounced for Zn. Two behaviours were found when algal cells were exposed to intermediate concentrations of metals: Cu(II) and Cr(VI) induced a reduction of cell volume, while Cd(II) and Zn(II) provoked an opposite effect. The simultaneous nucleus staining and cell image analysis, allowed distinguishing three phases in P. subcapitata cell cycle: growth of mother cell; cell division, which includes two divisions of the nucleus; and, release of four autospores. The exposure of P. subcapitata cells to the highest metal concentrations resulted in the arrest of cell growth before the first nucleus division [for Cr(VI) and Cu(II)] or after the second nucleus division but before the cytokinesis (release of autospores) when exposed to Cd(II). The different impact of metals on algal cell volume and cell-cycle progression, suggests that different toxicity mechanisms underlie the action of different metals studied

  7. Modification of cell volume and proliferative capacity of Pseudokirchneriella subcapitata cells exposed to metal stress

    Energy Technology Data Exchange (ETDEWEB)

    Machado, Manuela D. [Bioengineering Laboratory-CIETI, Chemical Engineering Department, ISEP-School of Engineering of Polytechnic Institute of Porto, Rua Dr António Bernardino de Almeida, 431, 4200-072 Porto (Portugal); IBB-Institute for Biotechnology and Bioengineering, Centre for Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Soares, Eduardo V., E-mail: evs@isep.ipp.pt [Bioengineering Laboratory-CIETI, Chemical Engineering Department, ISEP-School of Engineering of Polytechnic Institute of Porto, Rua Dr António Bernardino de Almeida, 431, 4200-072 Porto (Portugal); IBB-Institute for Biotechnology and Bioengineering, Centre for Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

    2014-02-15

    Highlights: •Metals induce morphological alterations on P. subcapitata. •Algal cell cycle consists: mother cell growth; cell division, with two nucleus divisions; release of four autospores. •Cu(II) and Cr(VI) arrest cell growth before the first nuclear division. •Cd(II) arrests cell growth after the second nuclear division but before the cytokinesis. •The approach used can be useful in the elucidation of different modes of action of pollutants. -- Abstract: The impact of metals (Cd, Cr, Cu and Zn) on growth, cell volume and cell division of the freshwater alga Pseudokirchneriella subcapitata exposed over a period of 72 h was investigated. The algal cells were exposed to three nominal concentrations of each metal: low (closed to 72 h-EC{sub 10} values), intermediate (closed to 72 h-EC{sub 50} values) and high (upper than 72 h-EC{sub 90} values). The exposure to low metal concentrations resulted in a decrease of cell volume. On the contrary, for the highest metal concentrations an increase of cell volume was observed; this effect was particularly notorious for Cd and less pronounced for Zn. Two behaviours were found when algal cells were exposed to intermediate concentrations of metals: Cu(II) and Cr(VI) induced a reduction of cell volume, while Cd(II) and Zn(II) provoked an opposite effect. The simultaneous nucleus staining and cell image analysis, allowed distinguishing three phases in P. subcapitata cell cycle: growth of mother cell; cell division, which includes two divisions of the nucleus; and, release of four autospores. The exposure of P. subcapitata cells to the highest metal concentrations resulted in the arrest of cell growth before the first nucleus division [for Cr(VI) and Cu(II)] or after the second nucleus division but before the cytokinesis (release of autospores) when exposed to Cd(II). The different impact of metals on algal cell volume and cell-cycle progression, suggests that different toxicity mechanisms underlie the action of

  8. Transition metal catalysis in the mitochondria of living cells

    Science.gov (United States)

    Tomás-Gamasa, María; Martínez-Calvo, Miguel; Couceiro, José R.; Mascareñas, José L.

    2016-09-01

    The development of transition metal catalysts capable of promoting non-natural transformations within living cells can open significant new avenues in chemical and cell biology. Unfortunately, the complexity of the cell makes it extremely difficult to translate standard organometallic chemistry to living environments. Therefore, progress in this field has been very slow, and many challenges, including the possibility of localizing active metal catalysts into specific subcellular sites or organelles, remain to be addressed. Herein, we report a designed ruthenium complex that accumulates preferentially inside the mitochondria of mammalian cells, while keeping its ability to react with exogenous substrates in a bioorthogonal way. Importantly, we show that the subcellular catalytic activity can be used for the confined release of fluorophores, and even allows selective functional alterations in the mitochondria by the localized transformation of inert precursors into uncouplers of the membrane potential.

  9. A review of liquid metal anode solid oxide fuel cells

    Directory of Open Access Journals (Sweden)

    ALIYA TOLEUOVA

    2013-06-01

    Full Text Available This review discusses recent advances in a solid oxide fuel cell (SOFC variant that uses liquid metal electrodes (anodes with the advantage of greater fuel tolerance and the ability to operate on solid fuel. Key features of the approach are discussed along with the technological and research challenges that need to be overcome for scale-up and commercialisation.

  10. Noble Gases and Halogens in Icelandic Basalts

    OpenAIRE

    Weston, Bridget

    2013-01-01

    Noble gas and halogen data from a suite of Icelandic samples are presented. Iceland combines hotspot volcanism, a spreading ridge and abundant subglacially erupted samples. This combination allows for samples that erupted under high enough pressures to retain a measurable mantle volatile content, and also display signatures representing interaction between ocean island basalt (OIB) and mid-ocean ridge basalt (MORB) mantle sources.Erupted samples used to determine the mantle’s halogen and nobl...

  11. Photosensitive dopants for liquid noble gases

    Science.gov (United States)

    Anderson, David F.

    1988-01-01

    In an ionization type detector for high energy radiation wherein the energy of incident radiation is absorbed through the ionization of a liquid noble gas and resulting free charge is collected to form a signal indicative of the energy of the incident radiation, an improvement comprising doping the liquid noble gas with photosensitive molecules to convert scintillation light due to recombination of ions, to additional free charge.

  12. A precious-metal free micro fuel cell accumulator

    Science.gov (United States)

    Bretthauer, C.; Müller, C.; Reinecke, H.

    2011-05-01

    In recent years, integrated fuel cell (FC) type primary and secondary batteries attracted a great deal of attention as integrated on-chip power sources due to their high theoretical power densities. Unfortunately, the costs of these devices have been rather high. This is partially due to the involved clean-room processes, but also due to the fact that these devices generally rely on expensive precious-metals such as Pd and Pt. Therefore we developed a novel integrated FC type accumulator that is based on non-precious-metals only. The key component of the presented accumulator is its alkaline polymer electrolyte membrane that allows not only the usage of a low-cost AB5 type hydrogen storage electrode, but also the usage of La0.6Ca0.4CoO3 as a precious-metal free bifunctional catalyst for the air-breathing electrode. Additionally the presented design requires only comparatively few cleanroom processes which further reduces the overall production costs. Although abdicating precious-metals, the presented accumulator shows an open circuit voltage of 0.81 V and a maximum power density of 0.66 mW cm-2 which is comparable or even superior to former precious-metal based cells.

  13. Oxygen reduction and methanol oxidation behaviour of SiC based Pt nanocatalysts for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Dhiman, Rajnish; Stamatin, Serban Nicolae; Andersen, Shuang Ma;

    2013-01-01

    Research with proton exchange membrane fuel cells has demonstrated their important potential as providers of clean energy. The commercialization of this type of fuel cell needs a breakthrough in electrocatalyst technology to reduce the relatively large amount of noble metal platinum used...

  14. Burp Charging Nickel Metal Hydride Cells

    Science.gov (United States)

    Darcy, Eric; Pollard, Richard

    1997-01-01

    The SKYNET 4 constellation consists of three spacecraft which were launched between December 1988 and August 1990. The spacecraft are three-axis stabilized geostationary earth-orbiting military communications satellites with a design life of seven years on station. With the mission objective achieved all the batteries continue to give excellent performance. This paper presents a review of the history of the six batteries from cell procurement to the end of their design life and beyond. Differences in operational strategies are discussed and the lifetime trends in performance are analyzed. The combination of procurement acceptance criteria and the on-station battery management strategy utilized are presented as the prime factors in achieving completely successful battery performance throughout the mission.

  15. Metallic materials in solid oxide fuel cells

    Directory of Open Access Journals (Sweden)

    Willem Joseph Quadakkers

    2004-03-01

    Full Text Available Fe-Cr alloys with variations in chromium content and additions of different elements were studied for potential application in intermediate temperature Solid Oxide Fuel Cell (SOFC. Recently, a new type of FeCrMn(Ti/La based ferritic steels has been developed to be used as construction material for SOFC interconnects. In the present paper, the long term oxidation resistance of this class of steels in both air and simulated anode gas will be discussed and compared with the behaviour of a number of commercial available ferritic steels. Besides, in-situ studies were carried out to characterize the high temperature conductivity of the oxide scales formed under these conditions. Main emphasis will be put on the growth and adherence of the oxide scales formed during exposure, their contact resistance at service temperature as well as their interaction with various perovskite type contact materials. Additionally, parameters and protection methods in respect to the volatilization of chromia based oxide scales will be illustrated.

  16. Noble gas fractionation during subsurface gas migration

    Science.gov (United States)

    Sathaye, Kiran J.; Larson, Toti E.; Hesse, Marc A.

    2016-09-01

    Environmental monitoring of shale gas production and geological carbon dioxide (CO2) storage requires identification of subsurface gas sources. Noble gases provide a powerful tool to distinguish different sources if the modifications of the gas composition during transport can be accounted for. Despite the recognition of compositional changes due to gas migration in the subsurface, the interpretation of geochemical data relies largely on zero-dimensional mixing and fractionation models. Here we present two-phase flow column experiments that demonstrate these changes. Water containing a dissolved noble gas is displaced by gas comprised of CO2 and argon. We observe a characteristic pattern of initial co-enrichment of noble gases from both phases in banks at the gas front, followed by a depletion of the dissolved noble gas. The enrichment of the co-injected noble gas is due to the dissolution of the more soluble major gas component, while the enrichment of the dissolved noble gas is due to stripping from the groundwater. These processes amount to chromatographic separations that occur during two-phase flow and can be predicted by the theory of gas injection. This theory provides a mechanistic basis for noble gas fractionation during gas migration and improves our ability to identify subsurface gas sources after post-genetic modification. Finally, we show that compositional changes due to two-phase flow can qualitatively explain the spatial compositional trends observed within the Bravo Dome natural CO2 reservoir and some regional compositional trends observed in drinking water wells overlying the Marcellus and Barnett shale regions. In both cases, only the migration of a gas with constant source composition is required, rather than multi-stage mixing and fractionation models previously proposed.

  17. A sliding cell technique for diffusion measurements in liquid metals

    Directory of Open Access Journals (Sweden)

    Yongliang Geng

    2014-03-01

    Full Text Available The long capillary and shear cell techniques are the usual methods for diffusion measurements in liquid metals. Here we present a new “sliding cell technique” to measure interdiffusion in liquid alloys, which combines the merits of these two methods. Instead of a number of shear cells, as used in the shear cell method, only one sliding cell is designed to separate and join the liquid diffusion samples. Using the sliding cell technique, the influence of the heating process (which affects liquid diffusion measurements in the conventional long capillary method can be eliminated. Time-dependent diffusion measurements at the same isothermal temperature were carried out in Al-Cu liquids. Compared with the previous results measured by in-situ X-ray radiography, the obtained liquid diffusion coefficient in this work is believed to be influenced by convective flow. The present work further supports the idea that to obtain accurate diffusion constants in liquid metals, the measurement conditions must be well controlled, and there should be no temperature gradients or other disturbances.

  18. Perspectives on the metallic interconnects for solid oxide fuel cells

    Institute of Scientific and Technical Information of China (English)

    ZHU Wei-zhong; YAN Mi

    2004-01-01

    The various stages and progress in the development of interconnect materials for solid oxide fuel cells (SOFCs) over the last two decades are reviewed. The criteria for the application of materials as interconnects are highlighted. Interconnects based on lanthanum chromite ceramics demonstrate many inherent drawbacks and therefore are only useful for SOFCs operating around 1000 ℃. The advance in the research of anode-supported flat SOFCs facilitates the replacement of ceramic interconnects with metallic ones due to their significantly lowered working temperature. Besides, interconnects made of metals or alloys offer many advantages as compared to their ceramic counterpart. The oxidation response and thermal expansion behaviors of various prospective metallic interconnects are examined and evaluated. The minimization of contact resistance to achieve desired and reliable stack performance during their projected lifetime still remains a highly challenging issue with metallic interconnects. Inexpensive coating materials and techniques may play a key role in pro moting the commercialization of SOFC stack whose interconnects are constructed of some current commercially available alloys. Alternatively, development of new metallic materials that are capable of forming stable oxide scales with sluggish growth rate and sufficient electrical conductivity is called for.

  19. Advances in Metal Supported Cells in the METSOFC EU Consortium

    DEFF Research Database (Denmark)

    McKenna, Brandon J.; Christiansen, Niels; Schauperl, Richard;

    2012-01-01

    Employing a mechanically robust metal support as the structural element in SOFC has been the objective of various development efforts. The EU-sponsored project “METSOFC”, completed at the end of 2011, resulted in a number of advancements towards implementing this strategy. These include robust...... metal supported cells (MSCs) having low ASR at low temperature, incorporation into small stacks of powers approaching ½kW, and stack tolerance to various operation cycles. DTU Energy Conversion's (formerly Risø DTU) research into planar MSCs has produced an advanced cell design with high performance...... outcomes of the METSOFC consortium are covered, along with associated work supported by the Danish National Advanced Technology Foundation....

  20. Neuroprotection (and lack of neuroprotection) afforded by a series of noble gases in an in vitro model of neuronal injury.

    Science.gov (United States)

    Jawad, Noorulhuda; Rizvi, Maleeha; Gu, Jianteng; Adeyi, Olar; Tao, Guocai; Maze, Mervyn; Ma, Daqing

    2009-09-01

    Xenon-induced neuroprotection has been well studied both in vivo and in vitro. In this study, the neuroprotective properties of the other noble gases, namely, krypton, argon, neon and helium, were explored in an in vitro model of neuronal injury. Pure neuronal cultures, derived from foetal BALB/c mice cortices, were provoked into injury by oxygen and glucose deprivation (OGD). Cultures were exposed to either nitrogen hypoxia or noble gas hypoxia in balanced salt solution devoid of glucose for 90min. The cultures were allowed to recover in normal culture medium for a further 24h in nitrogen or noble gas. The effect of noble gases on cell reducing ability in the absence of OGD was also investigated. Cell reducing ability was quantified via an MTT assay and expressed as a ratio of the control. The OGD caused a reduction in cell reducing ability to 0.56+/-0.04 of the control in the absence of noble gas (pNeon and krypton did not have a protective effect under our experimental conditions. Helium had a detrimental effect on the cells. In the absence of OGD, krypton reduced the reducing ability of uninjured cells to 0.84+/-0.09 (p<0.01), but argon showed an improvement in reducing ability to 1.15+/-0.11 (p<0.05). Our data suggest that the cheap and widely available noble gas argon may have potential as a neuroprotectant for the future.

  1. Simulations of atmospheric pressure discharge in a high-voltage nanosecond pulse using the particle-in-cell Monte Carlo collision model in noble gases

    International Nuclear Information System (INIS)

    Atmospheric pressure discharge nonequilibrium plasmas have been applied to plasma processing with modern technology. Simulations of discharge in pure Ar and pure He gases at one atmospheric pressure by a high voltage trapezoidal nanosecond pulse have been performed using a one-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) model coupled with a renormalization and weighting procedure (mapping algorithm). Numerical results show that the characteristics of discharge in both inert gases are very similar. There exist the effects of local reverse field and double-peak distributions of charged particles' density. The electron and ion energy distribution functions are also observed, and the discharge is concluded in the view of ionization avalanche in number. Furthermore, the independence of total current density is a function of time, but not of position

  2. Simulations of atmospheric pressure discharge in a high-voltage nanosecond pulse using the particle-in-cell Monte Carlo collision model in noble gases

    Science.gov (United States)

    Shi, Feng; Wang, Dezhen; Ren, Chunsheng

    2008-06-01

    Atmospheric pressure discharge nonequilibrium plasmas have been applied to plasma processing with modern technology. Simulations of discharge in pure Ar and pure He gases at one atmospheric pressure by a high voltage trapezoidal nanosecond pulse have been performed using a one-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) model coupled with a renormalization and weighting procedure (mapping algorithm). Numerical results show that the characteristics of discharge in both inert gases are very similar. There exist the effects of local reverse field and double-peak distributions of charged particles' density. The electron and ion energy distribution functions are also observed, and the discharge is concluded in the view of ionization avalanche in number. Furthermore, the independence of total current density is a function of time, but not of position.

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

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Cerri, Isotta; Nagami, Tetsuo;

    2013-01-01

    We have analyzed the aptitude of several metal oxide supports (TiO2, SnO2, NbO2, ZrO2, SiO2, Ta2O5 and Nb2O5) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in ...

  4. Nuclear Structure of the Noble Gas

    Science.gov (United States)

    Seong, Nakyeong

    Modern physics usually pictures the nuclear structure as about sphere and treats various detailed situation as perturbative, which may be obscured. In addition, the explanation why 235U undergoes nuclear fission and 238U does not is too difficult and unclear for the people to understand. However, in this paper, we introduce a new approach on the nuclear structure of the noble gas, which simultaneously can explain several phenomena that is obscurely elucidated by modern physics. We consider a 1:1 ratio between protons and neutrons and need the concept of the symmetry of the nuclear structure, because the electron's shell of the noble gas is fully occupied. From these, we can predict the number of neutrons of each noble gas exactly

  5. Lanthanides: new metallic cathode materials for organic photovoltaic cells.

    Science.gov (United States)

    Nikiforov, Maxim P; Strzalka, Joseph; Jiang, Zhang; Darling, Seth B

    2013-08-21

    Organic photovoltaics (OPVs) are compliant with inexpensive, scalable, and environmentally benign manufacturing technologies. While substantial attention has been focused on optimization of active layer chemistry, morphology, and processing, far less research has been directed to understanding charge transport at the interfaces between the electrodes and the active layer. Electrical properties of these interfaces not only impact efficiency, but also play a central role in stability of organic solar cells. Low work function metals are the most widely used materials for the electron transport layer with Ca being the most common material. In bulk heterojunction OPV devices, low work function metals are believed to mirror the role they play in OLEDs, where such metals are used to control carrier selectivity, transport, extraction, and blocking, as well as interface band bending. Despite their advantages, low work function materials are generally prone to reactions with water, oxygen, nitrogen, and carbon dioxide from air leading to rapid device degradation. Here we discuss the search for a new metallic cathode interlayer material that increases device stability and still provides device efficiency similar to that achieved with a Ca interlayer.

  6. 贵金属银选择性修饰高能晶面暴露二氧化钛光催化剂的制备及性能%Preparation and photocatalytic activity of noble metal Ag selectively loading on high energy facet of TiO2 single crystal

    Institute of Scientific and Technical Information of China (English)

    刘辉; 刘婷婷; 董晓楠

    2016-01-01

    TiO2 single crystal with high energy facet was successfully synthesized through a simple sintering method by using TBOT (Ti(OC4 H9 )4 ) as Ti source ,and HF acid as facet‐controlling agent .Noble metal Ag was selectively loaded on high energy facet of TiO2 single crystal through sonochemical deposition .The physical and chemical properties of noble metal Ag selectively loading on high energy facet of TiO2 single crystal photocatalyst (Ag‐TiO2 ) was carefully studied by XRD ,SEM ,TEM ,XPS and UV‐vis diffuse reflectance spectra (DRS) .The photocatalytic activity of Ag‐TiO2 was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under simulated sunlight ir‐radiation .The experimental results shown that the high energy (001) facet was successfully exposed in as‐prepared TiO2 nanoparticle and Ag nanoparticles were deposited in (001) fac‐et .The deposition of Ag nanoparticles changed the band gap and valence band position of TiO2 ,and made it can be excited by visible light .Both the exposure of high energy facet and the deposition of noble mental Ag are good for the separation of electron‐hole ,w hich resulted with the good photocatalytic activity of Ag‐TiO2 .%以钛酸丁酯为钛源,以H F酸为表面形貌控制剂,采用烧结方法制备出了高能(001)晶面暴露的TiO2光催化剂,并采用超声沉积方法在其特定晶面(001)晶面上沉积贵金属银。通过XRD、SEM、T EM、XPS和U V‐vis光谱仪等分析手段对样品进行了表征,并测试了该光催化剂在模拟太阳光下对模拟污染物RhB的光催化降解性能。结果表明:所制备的TiO2纳米颗粒成功地暴露了高能(001)晶面,并使贵金属银选择性地沉积在(001)晶面上;贵金属银的沉积改变了TiO2的禁带宽度和价带位置,从而使其可被可见光激发;高能晶面的暴露及贵金属的沉积都有利于TiO2电子空穴对的分

  7. Thermal Conductivity of Metallic Micro-Cell Fuel Pellet with Different Unit Cell Geometry

    International Nuclear Information System (INIS)

    Recently, the metallic micro-cell pellets have been successfully fabricated to increase the thermal conductivities of nuclear fuel pellets with the minimal inclusion of thermal conductive materials (e.g., Mo, W, Cr, etc.) to UO2. Here we numerically characterize the effects of the geometry, such as the size and the aspect ratio, of the UO2-Mo micro-cells on their thermal conductivities. The geometric effects of the metallic (UO2-Mo) micro-cells on their thermal conductivities were numerically investigated in terms of the size and the aspect ratio of the micro-cells. Our simulation results agreed well with the experimental measurements. Under the same contents of the Mo in the UO2, changing the sizes of the micro-cells did not vary their thermal conductivities as long as their aspect ratio was fixed. However, increasing the aspect ratio of the micro-cells greatly increased their thermal conductivities

  8. Angular correlation studies in noble gases

    Science.gov (United States)

    Coleman, P. G.

    1990-01-01

    There has been a recent revival of interest in the measurement of angular correlation of annihilation photons from the decay of positrons and positronium in gases. This revival has been stimulated by the possibility offered by the technique to shed new light on the apparently low positronium formation fraction in the heavier noble gases and to provide information on positronium quenching processes in gases such as oxygen. There is also the potential for learning about positronium slowing down in gases. This review focuses on experimental noble gas work and considers what new information has been, and may be, gained from these studies.

  9. Using 220Rn to calibrate liquid noble gas detectors

    CERN Document Server

    Kobayashi, M; Takeda, A; Kishimoto, K; Moriyama, S

    2016-01-01

    In this paper, we describe 220Rn calibration source that was developed for liquid noble gas detectors. The key advantage of this source is that it can provide 212Bi-212Po consecutive events, which enables us to evaluate the vertex resolution of a detector at low energy by comparing low-energy events of 212Bi and corresponding higher-energy alpha-rays from 212Po. Since 220Rn is a noble gas, a hot metal getter can be used when introduced using xenon as the carrier gas. In addition, no long-life radioactive isotopes are left behind in the detector after the calibration is complete; this has clear advantage over the use of 222Rn which leaves long- life radioactivity, i.e., 210Pb. Using a small liquid xenon test chamber, we developed a system to introduce 220Rn via the xenon carrier gas; we demonstrated the successful introduction of 6 times 10^2 220Rn atoms in our test environment.

  10. Numerical study of metal oxide heterojunction solar cells

    Science.gov (United States)

    Zhu, L.; Shao, G.; Luo, J. K.

    2011-08-01

    Metal oxide (MO) semiconductors have great potential for photovoltaic (PV) application owing to some optimal bandgaps and a variety of possible combinations of the materials. The progress is limited due to lack of high-quality materials, reliable process and theoretical study and models which can guide the development. This paper reports on the numerical modelling of MO semiconductor PV cells. The effects of the bandgap structure, material, doping concentration and layer thickness on the proposed oxide solar cells have been investigated. It was found that, in an ideal case of no defects and no interface states, wide-gap MO, CuO and Cu2O can form a heterostructure n+/p/p+ cell with efficiency up to 28.6%, demonstrating great potential for development.

  11. Multi-metallic anodes for solid oxide fuel cell applications

    International Nuclear Information System (INIS)

    A new method for direct preparation of materials for solid oxide fuel cell anode - Ni- YSZ cermets - based on mechanical alloying (MA) of the original powders is developed, allowing to admix homogeneously any component. Additive metals are selected from thermodynamic criteria, leading to compacts consolidation through sintering by activated surface (SAS). The combined process MA-SSA can reduce the sintering temperature by 300 deg C, yielding porous anodes. Densification mechanisms are discussed from quasi-isothermal sintering kinetics results. Doping with Ag, W, Cu, Mo, Nb, Ta, in descending order, promotes the densification of pellets through liquid phase sintering and evaporation of metals and oxides, which allow reducing the sintering temperature. Powders and pellets characterization by electronic microscopy and X-ray diffraction completes the result analyses. (author)

  12. A Grounded Theory of the Development of Noble Youth Purpose

    Science.gov (United States)

    Bronk, Kendall Cotton

    2012-01-01

    Having a noble purpose in life is an important component of positive youth development; however, little is known about how noble purposes develop over time. Therefore, using three waves of interviews over a 5-year period with 9 adolescents (N = 9) who demonstrated intense commitments to various noble purposes, the present study developed a…

  13. Hydrometallurgical Recovery of Metal Values From Spent Dry Battery Cells

    International Nuclear Information System (INIS)

    This study focuses on the recovery of metal values from spent dry battery cells (DBC) applying a hydro-pyrometallurgical method. A process flow sheet was followed up starting with cutting the DBC with toothed cutter disc followed by water soaking and rinsing. Water soluble ingredients were filtered. Solid residue was assorted with the help of magnetic separation and water flotation.The method utilizes hydrogen peroxide to enhance dissolution of these metals in acidic or alkaline leachants. Parameters affecting the recovery efficiency such as stoichiometric ratio, solid: liquid ratio, temperature, time and ph of the system were investigated. In this concern, experiments were executed with a battery sample weighing up to 15 kg. Atomic absorption analysis showed that the input DBC contain appreciable amounts of metal zinc, zinc chloride and manganese that are recoverable.Results obtained revealed that metallic parts, carbon rods and paper were safely separated for recycling. From the water-soluble salts, pure NH4CI, MnO2 and ZnCI2 salts are obtained meeting the standard specifications. Temperature up to 55 degree enhances the recovery process. Under the optimum conditions, maximum recovery efficiency obtained amounts to 93% for Mn, and 99.5% for Zn and NH4CI. A model for explaining the obtained results was also given. Dissolution of metals concerned increases in the order nitric> hydrochloric acid. Results were explained in the premise of the kinetic and thermodynamic properties of the reactions involved. Cost estimate of the products shows that the prices of the products are competitive to those of the market prices

  14. Different options for noble gas categorization schemes

    Science.gov (United States)

    Kalinowski, Martin

    2010-05-01

    For noble gas monitoring it is crucial to support the decision makers who need to decide whether a decection may indicate a potential nuclear test. Several parameters are available that may help to distinguish a legitimate civilian source from a nuclear explosion. The most promising parameters are: (a) Anomaly observations with respect to the history of concentrations found at that site. (b) Isotopic activity ratios can be used to separate a nuclear reactor domain from the parameter space that is specific for nuclear explosions. (c) Correlation with source-receptor-sensitivities related to known civilian sources as determined by atmospheric transport simulations. A combination of these can be used to categorize an observation. So far, several initial ideas have been presented but the issue of noble gas categorisation has been postponed with the argument that further scientific studies and additional experience have to be awaited. This paper presents the principles of different options for noble gas categorisation and considers how they would meet the interests of different classes of member states. It discusses under different points of view what might be the best approach for the noble gas categorisation scheme.

  15. Cold and trapped metastable noble gases

    NARCIS (Netherlands)

    Vassen, W.; Cohen-Tannoudji, C.; Leduc, M.; Boiron, D.; Westbrook, C.I.; Truscott, A.; Baldwin, K.; Birkl, G.; Cancio, P.; Trippenbach, M.

    2012-01-01

    Experimental work on cold, trapped metastable noble gases is reviewed. The aspects which distinguish work with these atoms from the large body of work on cold, trapped atoms in general is emphasized. These aspects include detection techniques and collision processes unique to metastable atoms. Sever

  16. Voltage effects on cells cultured on metallic biomedical implants

    Science.gov (United States)

    Haerihosseini, Seyed Morteza

    Electrochemical voltage shifts in metallic biomedical implants occur in-vivo due to a number of processes including mechanically assisted corrosion. Surface potential of biomedical implants and excursions from resting open circuit potential (OCP), which is the voltage they attain while in contact with an electrolyte, can significantly change the interfacial properties of the metallic surfaces and alter the behavior of the surrounding cells, compromising the biocompatibility of metallic implants. Voltages can also be controlled to modulate cell function and fate. To date, the details of the physico-chemical phenomena and the role of different biomaterial parameters involved in the interaction between cells and metallic surfaces under cathodic bias have not been fully elucidated. In this work, changes in the interfacial properties of a CoCrMo biomedical alloy (ASTM F-1537) in phosphate-buffered saline (PBS) (pH 7.4) at different voltages was studied. Step polarization impedance spectroscopy technique was used to apply 50 mV voltage steps to samples, and the time-based current transients were recorded. A new equation was derived based on capacitive discharge through a Tafel element and generalized to deal with non-ideal impedance behavior. The new function compared to the KWW-Randles function, better matched the time-transient response. The results also showed a voltage dependent oxide resistance and capacitance behavior. Additionally, the in-vitro effect of static voltages on the behavior of MC3T3-E1 pre-osteoblasts cultured on CoCrMo alloy (ASTM-1537) was studied to determine the range of cell viability and mode of cell death beyond the viable range. Cell viability and morphology, changes in actin cytoskeleton, adhesion complexes and nucleus, and mode of cell death (necrosis, or intrinsic or extrinsic apoptosis) were characterized at different voltages ranging from -1000 to +500 mV (Ag/AgCl). Moreover, electrochemical currents and metal ion concentrations at each

  17. The Biomechanisms of Metal and Metal-Oxide Nanoparticles’ Interactions with Cells

    Directory of Open Access Journals (Sweden)

    Sondra S. Teske

    2015-01-01

    Full Text Available Humans are increasingly exposed to nanoparticles (NPs in medicine and in industrial settings, where significant concentrations of NPs are common. However, NP interactions with and effects on biomolecules and organisms have only recently been addressed. Within we review the literature regarding proposed modes of action for metal and metal-oxide NPs, two of the most prevalent types manufactured. Iron-oxide NPs, for instance, are used as tracers for magnetic resonance imaging of oncological tumors and as vehicles for therapeutic drug delivery. Factors and theories that determine the physicochemical and biokinetic behaviors of NPs are discussed, along with the observed toxicological effects of NPs on cells. Key thermodynamic and kinetic models that explain the sources of energy transfer from NPs to biological targets are summarized, in addition to quantitative structural activity relationship (QSAR modeling efforts. Future challenges for nanotoxicological research are discussed. We conclude that NP studies based on cell culture are often inconsistent and underestimate the toxicity of NPs. Thus, the effect of NPs needs to be examined in whole animal systems.

  18. Computational investigation of noble gas adsorption and separation by nanoporous materials.

    Energy Technology Data Exchange (ETDEWEB)

    Allendorf, Mark D. (Sandia National Laboratories, Livermore, CA); Sanders, Joseph C.; Greathouse, Jeffery A.

    2008-10-01

    Molecular simulations are used to assess the ability of metal-organic framework (MOF) materials to store and separate noble gases. Specifically, grand canonical Monte Carlo simulation techniques are used to predict noble gas adsorption isotherms at room temperature. Experimental trends of noble gas inflation curves of a Zn-based material (IRMOF-1) are matched by the simulation results. The simulations also predict that IRMOF-1 selectively adsorbs Xe atoms in Xe/Kr and Xe/Ar mixtures at total feed gas pressures of 1 bar (14.7 psia) and 10 bar (147 psia). Finally, simulations of a copper-based MOF (Cu-BTC) predict this material's ability to selectively adsorb Xe and Kr atoms when present in trace amounts in atmospheric air samples. These preliminary results suggest that Cu-BTC may be an ideal candidate for the pre-concentration of noble gases from air samples. Additional simulations and experiments are needed to determine the saturation limit of Cu-BTC for xenon, and whether any krypton atoms would remain in the Cu-BTC pores upon saturation.

  19. In-cell NMR: an emerging approach for monitoring metal-related events in living cells.

    Science.gov (United States)

    Li, Hongyan; Sun, Hongzhe

    2014-01-01

    In-cell NMR, an isotope-assisted multi-dimensional NMR technique, has been proven to be successful in the investigation of protein dynamics, folding, conformational changes induced by binding events, posttranslational modification in the complex native environments, as well as in vivo drug screening, even de novo 3D protein structure determination in living cells. This technique was initially applied to bacterial cells, and subsequently has been extended to various other cells including eukaryotic cells. In this review, we briefly summarize the methodology and application of in-cell NMR with a focus on its application in metallomics and metalloproteomics. This emerging technique is anticipated to be an excellent tool for studying metal-associated events in complex native environments of living cells.

  20. High performance, high durability non-precious metal fuel cell catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Thomas E.; Atanasoski, Radoslav; Schmoeckel, Alison K.

    2016-03-15

    This invention relates to non-precious metal fuel cell cathode catalysts, fuel cells that contain these catalysts, and methods of making the same. The fuel cell cathode catalysts are highly nitrogenated carbon materials that can contain a transition metal. The highly nitrogenated carbon materials can be supported on a nanoparticle substrate.

  1. Simulated study of plasmonic coupling in noble bimetallic alloy nanosphere arrays

    Science.gov (United States)

    Bansal, Amit; Verma, S. S.

    2014-05-01

    The plasmonic coupling between the interacting noble metal nanoparticles plays an important role to influence the optical properties of arrays. In this work, we have extended the Mie theory results of our recent communication to include the effect of particle interactions between the alloy nanoparticles by varying interparticle distance and number of particles. The localized surface plasmon resonance (LSPR) peak position, full width at half maxima (FWHM) and scattering efficiency of one dimensional (1D) bimetallic alloy nanosphere (BANS) arrays of earlier optimized compositions i.e. Ag0.75Au0.25, Au0.25Cu0.75 and Ag0.50Cu0.50 have been studied presently by using discrete dipole approximation (DDA) simulations. Studies have been made to optimize size of the nanosphere, number of spheres in the arrays, material and the interparticle distance. It has been found that both the scattering efficiency and FWHM (bandwidth) can be controlled in the large region of the electromagnetic (EM) spectrum by varying the number of interacting particles and interparticle distance. In comparison to other alloy arrays, Ag0.50Cu0.50 BANS arrays (each of particle radius 50 nm) shows larger tunability of LSPR with wide bandwidth (essential condition for plasmonic solar cells).

  2. Experimental determination of noble gas, SF6 and CO2 flow profiles through a porous sandstone

    Science.gov (United States)

    Kilgallon, Rachel; Gilfillan, Stuart; Edlmann, Katriona; McDermott, Chris

    2016-04-01

    The noble gases (He, Ne, Ar, Kr and Xe) and SF6 have recently been used as artificial and inherent tracers of CO2 flow and migration from within[1,2] and from geological reservoirs[3]. However, outstanding questions remain, particularly regarding the flow behaviour of the noble gases compared to CO2. Here we present results from specially constructed experimental equipment, which has been used to determine the factors affecting transport of noble gases relative to CO2 in a porous sandstone. The experimental setup consists of a sample loop that can be loaded with a desired gas mixture. This sample can be released as a pulse into a feeder gas stream through a flow cell. The flow cell consists of a 3.6 cm diameter core, which can be of any length. The sample is surrounded by aluminium foil and treated with epoxy resin inside stainless steel tubing. The flow cell is encased by two purpose designed dispersion end plates. Real-time analysis of the arrival peaks of the gases downstream is recorded using a Quadrupole Mass Spectrometer (QMS). For the experiments, a 0.96 m core of Fell Sandstone was selected to represent a porous media. Noble gases and SF6 pulses were flowed through a CO2 carrier gas at five different pressure gradients (10 - 50 kPa) with arrival profiles measured using the QMS. Surprisingly, peak arrival times of He were slower than the other noble gases at each pressure gradient. The differences in peak arrival times between He and other noble gases increased as pressure decreased and the curve profiles for each noble gas differ significantly. The heavier noble gases (Kr and Xe) along with SF6 show a steeper peak rise at initial appearance, but have a longer duration profile than the He curves. Interestingly, the breakthrough curve profiles for both Kr and Xe were similar to SF6 indicating that Kr and Xe could be substituted for SF6, which is a potent greenhouse gas, in tracing applications. In addition, CO2 pulses were passed through a N2 carrier gas. The

  3. Cold and trapped metastable noble gases

    CERN Document Server

    Vassen, Wim; Leduc, Michèle; Boiron, Denis; Westbrook, Christoph I; Truscott, Andrew; Baldwin, Ken; Birkl, Gerhard; Cancio, Pablo; Trippenbach, Marek

    2011-01-01

    We review experimental and theoretical work on cold, trapped metastable noble gases. We emphasize the aspects which distinguish work with these atoms from the large body of work on cold, trapped atoms in general. These aspects include detection techniques and collision processes unique to metastable atoms. We describe several experiments exploiting these unique features in fields including atom optics and statistical physics. We also discuss precision measurements on these atoms including fine structure splittings, isotope shifts, and atomic lifetimes.

  4. Diffraction of Random Noble Means Words

    Science.gov (United States)

    Moll, Markus

    2014-09-01

    In this paper, several aspects of the random noble means substitution are studied. Beyond important dynamical facets such as the frequency of subwords and the computation of the topological entropy, the important issue of ergodicity is addressed. From the geometrical point of view, we outline a suitable cut and project setting for associated point sets and present results for the spectral analysis of the diffraction measure.

  5. Noble Gases in the Chelyabinsk Meteorites

    Science.gov (United States)

    Haba, Makiko K.; Sumino, Hirochika; Nagao, Keisuke; Mikouchi, Takashi; Komatsu, Mutsumi; Zolensky, Michael E.

    2014-01-01

    The Chelyabinsk meteorite fell in Russia on February 15, 2013 and was classified as LL5 chondrite. The diameter before it entered the atmosphere has been estimated to be about 20 m [1]. Up to now, numerous fragments weighing much greater than 100 kg in total have been collected. In this study, all noble gases were measured for 13 fragments to investigate the exposure history of the Chelyabinsk meteorite and the thermal history of its parent asteroid.

  6. Alpha particles energy straggling in noble gases

    International Nuclear Information System (INIS)

    The comparison of the calculated spectra by the Monte-Carlo simulation with the experimental alpha-particles spectra after their passage through noble gases target has good agreement for Ar, Kr, and Xe and significant deviation for He and Ne. These agreement or disagreement of the calculated and experimental spectra were ascribed to adequacy or inadequacy of the applied Bohr's charged particles energy loss formula for the specific medium. (author)

  7. Brown algae overproduce cell wall polysaccharides as a protection mechanism against the heavy metal toxicity

    International Nuclear Information System (INIS)

    Brown algae are often used as heavy metal biomonitors and biosorbents because they can accumulate high concentrations of metals. Cation-exchange performed by cell wall polysaccharides is pointed out as the main chemical mechanism for the metal sequestration. Here, we biochemically investigated if the brown alga Padina gymnospora living in a heavy metal contaminated area would modify their polysaccharidic content. We exposed non-living biomass to Cd and Pb and studied the metals adsorption and localization. We found that raw dried polysaccharides, sulfate groups, uronic acids, fucose, mannose, and galactose were significantly higher in contaminated algae compared with the control ones. Metal concentrations adsorbed by non-living biomass were rising comparatively to the tested concentrations. Electron microscopy showed numerous granules in the cell walls and X-ray microanalysis revealed Cd as the main element. We concluded that P. gymnospora overproduces cell wall polysaccharides when exposed to high metal concentrations as a defense mechanism.

  8. Prospects of metal research

    International Nuclear Information System (INIS)

    Topical questions about modern metal research are considered covering fundamentals and applications. Many, hitherto undeveloped distinguished properties of metals, such as resistance against particle and quantum radiations, neutrons, very high and very low temperatures , stresses, and chemical agents; memory effects; superconductivity etc. are pointed out. The following topics are treated: subject and methodology of the science of metals, significance of metals; discovery of new properties of metallic materials; theory of metallic alloys; extreme conditions; intermetallic compounds, polymorphic metals; rare metals (rare earth metals, rhenium, noble metals); questions of strength and technology of metals and alloys; temperature zones of brittle fracture in metals and alloys; alloys with particular electrophysical properties; superconductive metalic materials; 'biological' science of metals; and conclusions. The booklet will be useful for students at technical schools and universities as well as for engineers and scientists engaged in metal research

  9. The emerging multiple metal nanostructures for enhancing the light trapping of thin film organic photovoltaic cells.

    Science.gov (United States)

    Choy, Wallace C H

    2014-10-18

    Recently, various metal nanostructures have been introduced into organic solar cells (OSCs) for performance enhancement. Here, we review the recent progress in OSCs incorporated with multiple metal nanostructures including various metal nanopatterns and metal nanomaterials. Multiple physical effects arise from these incorporated nanostructures, which require careful distinction. Changes induced by the metal nanostructures are examined in detail from the optical and electrical aspects. With the comprehensive understanding of the physical mechanisms for various metal nanostructures, further improvement in device performance and emerging applications can be expected for the new class of nanostructure-incorporated OSCs.

  10. Noble metals nanoparticles on titanium dioxide nanostructured films and the influence of their photocatalytic activity; Atividade fotocatalitica de filmes nanoestruturados de dioxido de titanio incorporados com nanoparticulas de metais nobres

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Liana Key Okada

    2012-07-01

    Currently, nanoscience and nanotechnology are considered an emerging field and continuously breaking the barrier among various disciplines. The main focus of study involves controlling structures at molecular level, arranging the atoms in order to achieve an understanding and controlling the fundamental properties of matter. In this study, molecular changes on the basis of morphology, optical and crystalline properties of TiO{sub 2}hin films in order to increase their photon efficiency were proposed. The TiO{sub 2} thin films were prepared by sol gel process evaluating the influence of different acids and templates to obtain the nano structured arrangements. Then, metal nanoparticles like Au, Ag, Pd and Pt were incorporated on TiO{sub 2} thin films. This incorporation might minimize the electron-hole recombination, so it could improve the photon efficiency. From the several routes studied, the TiO{sub 2} thin films prepared with acetic acid showed the best performance by the reason of low agglomeration of TiO{sub 2} grains, which favors the exposure of the photoactive sites. The presence of template in the formulation had a slightly effect on photon efficiency, possible due to the higher agglomeration of the grains on the TiO{sub 2} thin films. The addition of Pt and Au nanoparticles on TiO{sub 2} thin films showed superior photon efficiency. The TiO{sub 2} thin films with hexamine and metallic nanoparticles did not show the improvement on photon efficiency except for Pt and Au nanoparticles. On these situations, the improvement on photon efficiency is might be due to a possible decrease at the electron-hole recombination's velocity. Thus, the present work demonstrates the great influence of preparation conditions on the optical, morphological properties and the photon efficiency. In the future, with greater understanding of the mechanism of this influence, the properties of TiO{sub 2} thin films will be able tailoring depending on the application. (author)

  11. Manufacturing and characterization of metal-supported solid oxide fuel cells

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Hjelm, Johan; Klemensø, Trine;

    2011-01-01

    A metal-supported solid oxide fuel cell design offers competitive advantages, for example reduced material costs and improved robustness. This paper reports the performance and stability of a recently developed metal-supported cell design, based on a novel cermet anode, on a 25cm2 (1cm2/16cm2...

  12. Break-down of Losses in High Performing Metal-Supported Solid Oxide Fuel Cells

    OpenAIRE

    Kromp, Alexander; Nielsen, Jimmi; Blennow Tullmar, Peter; Klemensø, Trine; Weber, André

    2012-01-01

    Metal supported SOFC designs offer competitive advantages such as reduced material costs and improved mechanical robustness. On the other hand, disadvantages might arise due to possible corrosion of the porous metal parts during processing and operation at high fuel utilization. In this paper we present the results of performance and stability improvements for a metal supported cell developed within the European project METSOFC and the Danish National Advanced Technology Foundation. The cells...

  13. Metal Nanowire Networks as Transparent Electrode for Small-Molecule Organic Solar Cells

    OpenAIRE

    Sachse, Christoph

    2015-01-01

    This work focuses on the development of metal nanowire networks for the use as transparent electrodes in small-molecule organic solar cells. Broad adoption of organic solar cells requires inexpensive roll-to-roll processing on flexible, lightweight substrates. Under these conditions, traditional metal oxide electrodes suffer from significant drawbacks such as brittleness and cost. In contrast, metal nanowire networks provide properties more suitable for high-throughput processing and thus...

  14. Fractionated (Martian) Noble Gases — EFA, Experiments and Meteorites

    Science.gov (United States)

    Schwenzer, S. P.; Barnes, G.; Bridges, J. C.; Bullock, M. A.; Chavez, C. L.; Filiberto, J.; Herrmann, S.; Hicks, L. J.; Kelley, S. P.; Miller, M. A.; Moore, J. M.; Ott, U.; Smith, H. D.; Steer, E. D.; Swindle, T. D.; Treiman, A. H.

    2016-08-01

    Noble gases are tracers for physical processes, including adsorption, dissolution and secondary mineral formation. We examine the Martian fractionated atmosphere through literature, terrestrial analogs and experiments.

  15. Thermal modeling and the optimized design of metal plate cooling systems for single concentrator solar cells

    Institute of Scientific and Technical Information of China (English)

    Cui Min; Chen Nuo-Fu; Deng Jin-Xiang

    2012-01-01

    A metal plate cooling model for 400× single concentrator solar cells was established.The effects of the thickness and the radius of the metal plate,and the air environment on the temperature of the solar cells were analyzed in detail.It is shown that the temperature of the solar cells decreased sharply at the beginning,with the increase in the thickness of the metal plate,and then changed more smoothly.When the radius of the metal plate was 4 cm and the thickness increased to 2 mm or thicker,the temperature of the solar cell basically stabilized at about 53 ℃.Increasing the radius of the metal plate and the convective transfer coefficient made the temperature of the solar cell decrease remarkably.The effects of A1 and Cu as the metal plate material on cooling were analyzed contrastively,and demonstrated the superiority of Al material for the cooling system.Furthermore,considering cost reduction,space holding and the stress of the system,we optimized the structural design of the metal plate.The simulated results can be referred to the design of the structure for the metal plate.Finally,a method to devise the structure of the metal plate for single concentrator solar cells was given.

  16. Thermal modeling and the optimized design of metal plate cooling systems for single concentrator solar cells

    International Nuclear Information System (INIS)

    A metal plate cooling model for 400× single concentrator solar cells was established. The effects of the thickness and the radius of the metal plate, and the air environment on the temperature of the solar cells were analyzed in detail. It is shown that the temperature of the solar cells decreased sharply at the beginning, with the increase in the thickness of the metal plate, and then changed more smoothly. When the radius of the metal plate was 4 cm and the thickness increased to 2 mm or thicker, the temperature of the solar cell basically stabilized at about 53 °C. Increasing the radius of the metal plate and the convective transfer coefficient made the temperature of the solar cell decrease remarkably. The effects of Al and Cu as the metal plate material on cooling were analyzed contrastively, and demonstrated the superiority of Al material for the cooling system. Furthermore, considering cost reduction, space holding and the stress of the system, we optimized the structural design of the metal plate. The simulated results can be referred to the design of the structure for the metal plate. Finally, a method to devise the structure of the metal plate for single concentrator solar cells was given. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  17. Mixed noble gas effect on cut green peppers

    Science.gov (United States)

    Raymond, L. V.; Zhang, M.; Karangwa, E.; Chesereka, M. J.

    2013-01-01

    Increasing attempts at using gas which leads to hydrate formation as a preservative tool in fresh-cut fruits and vegetables have been reported. In this study, changes in some physical and biochemical properties of fresh-cut green peppers under compressed noble gas treatments were examined. Mixed argonkrypton and argon treatments were performed before cold storage at 5°C for 15 days. Mass loss and cell membrane permeability were found to be the lowest in mixed argon-krypton samples. Besides, a lower CO2 concentration and vitamin C loss were detected in gastreated samples compared to untreated samples (control). While the total phenol degradation was moderately reduced, the effect of the treatment on polyphenoloxidase activity was better at the beginning of the storage period. The minimum changes in quality observed in cut peppers resulted from both mixed and gas treatment alone.

  18. INGAS: Iranian Noble Gas Analyzing System for radioxenon measurement

    Science.gov (United States)

    Doost-Mohammadi, V.; Afarideh, H.; Etaati, G. R.; Safari, M. J.; Rouhi, H.

    2016-03-01

    In this article, Iranian Noble Gas Analyzing System (INGAS) will be introduced. This system is based on beta-gamma coincidence technique and consists of a well-type NaI(Tl) as gamma or X radiation detector and a cylindrical plastic scintillator to detect beta or conversion electron. Standard NIM modules were utilized to detect coincidence events of detectors. Both the beta and gamma detectors were appropriately calibrated. The efficiency curve of gamma detector for volume geometry was obtained by comparing the results of gamma point sources measurements and simulations of GATE V7.0 Monte Carlo code. The performance of detection system was checked by injection of 222Rn and 131mXe gaseous source in the detection cell. The minimum detectable activity of the system for 133Xe is 1.240±0.024 mBq for 24 h measurement time.

  19. Static Behavior of Chalcogenide Based Programmable Metallization Cells

    Science.gov (United States)

    Rajabi, Saba

    Nonvolatile memory (NVM) technologies have been an integral part of electronic systems for the past 30 years. The ideal non-volatile memory have minimal physical size, energy usage, and cost while having maximal speed, capacity, retention time, and radiation hardness. A promising candidate for next-generation memory is ion-conducting bridging RAM which is referred to as programmable metallization cell (PMC), conductive bridge RAM (CBRAM), or electrochemical metallization memory (ECM), which is likely to surpass flash memory in all the ideal memory characteristics. A comprehensive physics-based model is needed to completely understand PMC operation and assist in design optimization. To advance the PMC modeling effort, this thesis presents a precise physical model parameterizing materials associated with both ion-rich and ion-poor layers of the PMC's solid electrolyte, so that captures the static electrical behavior of the PMC in both its low-resistance on-state (LRS) and high resistance off-state (HRS). The experimental data is measured from a chalcogenide glass PMC designed and manufactured at ASU. The static on- and off-state resistance of a PMC device composed of a layered (Ag-rich/Ag-poor) Ge30Se70 ChG film is characterized and modeled using three dimensional simulation code written in Silvaco Atlas finite element analysis software. Calibrating the model to experimental data enables the extraction of device parameters such as material bandgaps, workfunctions, density of states, carrier mobilities, dielectric constants, and affinities. The sensitivity of our modeled PMC to the variation of its prominent achieved material parameters is examined on the HRS and LRS impedance behavior. The obtained accurate set of material parameters for both Ag-rich and Ag-poor ChG systems and process variation verification on electrical characteristics enables greater fidelity in PMC device simulation, which significantly enhances our ability to understand the underlying physics of

  20. Resonance ionization spectroscopy: Counting noble gas atoms

    International Nuclear Information System (INIS)

    The purpose of this paper is to describe new work on the counting of noble gas atoms, using lasers for the selective ionization and detectors for counting individual particles (electrons or positive ions). When positive ions are counted, various kinds of mass analyzers (magnetic, quadrupole, or time-of-flight) can be incorporated to provide A selectivity. We show that a variety of interesting and important applications can be made with atom-counting techniques which are both atomic number (Z) and mass number (A) selective. (orig./FKS)

  1. Xenon and other noble gases in shergottites

    Science.gov (United States)

    Swindle, T. D.; Caffee, M. W.; Hohenberg, C. M.

    1986-01-01

    The isotopic composition of the xenon component trapped in EETA 79001's lithologies B and C has been determined, and other noble gases were measured in some samples. The Xe component was found to have light isotope ratios indistinguishable from those of the terrestrial atmosphere. The trapped component has a Xe-129/Xe-132 ratio of about 2.4, and is enhanced in Xe-134 and Xe-136 relative to the terrestrial atmosphere or the average carbonaceous chondrite. Similarities between values for Ar-40/Ar-36, Xe-129/Xe-132, and N-15/N-14 and the corresponding Martian atmospheric values suggest Martian origin of the trapped gases.

  2. Constructal Optimization of Top Contact Metallization of a Photovoltaic Solar Cell

    OpenAIRE

    Santanu Bandyopadhyay; Aditya Bhakta

    2005-01-01

    A top contact metallization of a photovoltaic solar cell collects the current generated by incident solar radiation. Several power-loss mechanisms are associated with the current flow through the front contact grid. The design of the top metal contact grid is one of the most important areas of efficient photovoltaic solar cell design. In this paper, an approach based on the constructal theory is proposed to design the grid pattern in a photovoltaic solar cell, minimizing total resistive losse...

  3. Origin of noble gases in the terrestrial planets

    Science.gov (United States)

    Pepin, Robert O.

    1992-01-01

    Current models of the origin of noble gases in the terrestrial planets are reviewed. Primary solar system volatile sources and processes are examined along with the current data base on noble gases and its applications to evolutionary processing. Models of atmospheric evolution by hydrodynamic escape are addressed.

  4. Fullerenes and Noble Gases in the Murchison and Allende Meteorites

    Science.gov (United States)

    Becker, Luann; Poreda, Robert J.; Bunch, Ted E.

    2000-01-01

    In this work we report the detection of fullerenes (C60 to C250) in the Murchison and Allende meteorites. By exploiting the unique ability of these molecules to trap noble gases, we have determined that fullerene is indeed a new carrier phase for noble gases in meteorites.

  5. The Noble Gases in A-Level Chemistry.

    Science.gov (United States)

    Marchant, G. W.

    1983-01-01

    Suggests two methods of developing the study of the noble gases: first, the discovery of the elements and recent discovery of xenon show the human face of chemistry (historical development); second, the properties of noble gas compounds (particularly xenon) can be used to test the framework of conventional chemistry. (Author/JM)

  6. Review of Ni-Cu Based Front Side Metallization for c-Si Solar Cells

    OpenAIRE

    Raval, Mehul C.; Solanki, Chetan S.

    2013-01-01

    Given the high percentage of metal cost in cell processing and concerns due to increasing Ag prices, alternative metallization schemes are being considered. Ni-Cu based front side metallization offers potential advantages of finer grid lines, lower series resistance, and reduced costs. A brief overview of various front side patterning techniques is presented. Subsequently, working principle of various plating techniques is discussed. For electroless plated Ni seed layer, fill factor values n...

  7. Heteroepitaxial Cu2O thin film solar cell on metallic substrates

    OpenAIRE

    Sung Hun Wee; Po-Shun Huang; Jung-Kun Lee; Amit Goyal

    2015-01-01

    Heteroepitaxial, single-crystal-like Cu2O films on inexpensive, flexible, metallic substrates can potentially be used as absorber layers for fabrication of low-cost, high-performance, non-toxic, earth-abundant solar cells. Here, we report epitaxial growth of Cu2O films on low cost, flexible, textured metallic substrates. Cu2O films were deposited on the metallic templates via pulsed laser deposition under various processing conditions to study the influence of processing parameters on the str...

  8. Synergy between metals in bimetallic zeolite supported catalyst for NO-promoted N2O decomposition

    NARCIS (Netherlands)

    Pieterse, J.A.Z.; Mul, G.; Melian-Cabrera, I.; van den Brink, R.W.

    2005-01-01

    The detrimental effect of NO on N2O decomposition over zeolite supported noble metal catalysts can be (partly) eliminated by combining noble metal with iron or cobalt. In the presence of NO, the total conversion of N2O over these bimetallic-zeolites exceeds the sum of conversions over the monometall

  9. Carbon Nanofibers as Catalyst Support for Noble Metals

    NARCIS (Netherlands)

    Toebes, M.L.

    2004-01-01

    In the quest for new and well-defined support materials for heterogeneous catalysts we explored the potential of carbon nanofibers (CNF). CNF belongs to the by now extensive family of synthetic graphite-like carbon materials with advantageous and tunable physico-chemical properties. Aim of the work

  10. Carbon Nanofibers as Catalyst Support for Noble Metals

    OpenAIRE

    Toebes, M.L.

    2004-01-01

    In the quest for new and well-defined support materials for heterogeneous catalysts we explored the potential of carbon nanofibers (CNF). CNF belongs to the by now extensive family of synthetic graphite-like carbon materials with advantageous and tunable physico-chemical properties. Aim of the work described in this thesis has been the exploration of the potential of CNF as catalyst support material, notably for platinum and ruthenium, and its role in the performance of these catalysts in hyd...

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

    Science.gov (United States)

    Suoninen, E; Herø, H; Minni, E

    1985-10-01

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

  12. Noble metal catalysts for the hydrocracking of FT waxes

    OpenAIRE

    Suárez París, Rodrigo

    2012-01-01

    Bifunctional catalysts consisting of palladium or platinum and supported on amorphous silica-alumina were prepared and tested in the hydrocracking of n-hexadecane, which is considered to be representative of n-paraffins in hydrocracker feeds. In addition to the evaluation of the  physicochemical properties, a comprehensive study on catalyst activity and selectivity has been conducted, in the full range of conversions. A theoretical model was proposed to fit the experimental conversion-selecti...

  13. Composite nanomaterials of semiconductors and noble metals as plasmonic photocatalysts

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Law, Matt; Zhang, Jingdong

    behavior, and can be more stable under operating conditions. Composite photocatalysts of semiconductor nanoparticles (SNPs) and PNPs exploit broadly the solar spectrum, provide new catalytic routes and expand the scope of solar photocatalysis. The newly initiated project aims at developing composite...

  14. GREENER SYNTHESIS OF NOBLE METAL NANOSTRUCTURES AND NANOCOMPOSITES

    Science.gov (United States)

    A brief account of a greener preparation of nanoparticles which reduces or eliminates the use and generation of hazardous substances is presented. The utility of vitamins B1 and B2, which can function both as reducing and capping agents, provides an extremely simple, one-pot, gre...

  15. Simplified process for leaching precious metals from fuel cell membrane electrode assemblies

    Science.gov (United States)

    Shore, Lawrence; Matlin, Ramail

    2009-12-22

    The membrane electrode assemblies of fuel cells are recycled to recover the catalyst precious metals from the assemblies. The assemblies are cryogenically embrittled and pulverized to form a powder. The pulverized assemblies are then mixed with a surfactant to form a paste which is contacted with an acid solution to leach precious metals from the pulverized membranes.

  16. Magnetron sputtered gadolinia-doped ceria diffusion barriers for metal-supported solid oxide fuel cells

    DEFF Research Database (Denmark)

    Sønderby, Steffen; Klemensø, Trine; Christensen, Bjarke H.;

    2014-01-01

    Gadolinia-doped ceria (GDC) thin films are deposited by reactive magnetron sputtering in an industrial-scale setup and implemented as barrier layers between the cathode and electrolyte in metal-based solid oxide fuel cells consisting of a metal support, an electrolyte of ZrO2 co-doped with Sc2O3...

  17. Two-dimensional transition metal dichalcogenide nanomaterials for solar water splitting

    Science.gov (United States)

    Andoshe, Dinsefa M.; Jeon, Jong-Myeong; Kim, Soo Young; Jang, Ho Won

    2015-05-01

    Recently, 2-dimensional (2D) transition metal dichalcogenides (TMDs) have received great attention for solar water splitting and electrocatalysis. In addition to their wide variety of electronic and microstructural properties, their promising catalytic activities for hydrogen production make 2D TMDs as earth-abundant and inexpensive catalysts that can replace noble metals. This paper reviews the electronic, structural, and optical properties of 2D TMDs. We highlight the various synthetic methods for 2D TMDs and their applications in hydrogen evolution based on photoelectrochemical and electrocatalytic cells. We also discuss perspectives and challenges of 2D TMDs for hydrogen production and artificial photosynthesis.[Figure not available: see fulltext.

  18. Inorganic and Metallic Nanotubular Materials Recent Technologies and Applications

    CERN Document Server

    Kijima, Tsuyoshi

    2010-01-01

    This book describes the synthesis, characterization and applications of inorganic and metallic nanotubular materials. It cover a wide variety of nanotubular materials excluding carbon nanotubes, ranging from metal oxides, sulfides and nitrides such as titanium oxide, tungsten sulfide, and boron nitride, as well as platinum and other noble-metals to unique nanotubes consisting of water, graphene or fullerene. Based on their structural and compositional characteristics, these nanotubular materials are of importance for their potential applications in electronic devices, photocatalysts, dye-sensitized solar cells, nanothermometers, electrodes for fuel cells and batteries, sensors, and reinforcing fillers for plastics, among others. Such materials are also having a great impact on future developments, including renewable-energy sources as well as highly efficient energy-conversion and energy-saving technologies. This book will be of particular interest to experts in the fields of nanotechnology, material science ...

  19. Tracing Noble Gas Radionuclides in the Environment

    CERN Document Server

    Collon, P; Lu, Z T

    2004-01-01

    Trace analysis of radionuclides is an essential and versatile tool in modern science and technology. Due to their ideal geophysical and geochemical properties, long-lived noble gas radionuclides, in particular, 39Ar (t1/2 = 269 yr), 81Kr (t1/2 = 2.3x10^5 yr) and 85Kr (t1/2 = 10.8 yr), have long been recognized to have a wide range of important applications in Earth sciences. In recent years, significant progress has been made in the development of practical analytical methods, and has led to applications of these isotopes in the hydrosphere (tracing the flow of groundwater and ocean water). In this article, we introduce the applications of these isotopes and review three leading analytical methods: Low-Level Counting (LLC), Accelerator Mass Spectrometry (AMS) and Atom Trap Trace Analysis (ATTA).

  20. Study of Plant Cell Wall Polymers Affected by Metal Accumulation Using Stimulated Raman Scattering Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Shi-You [Harvard Univ., Cambridge, MA (United States)

    2015-03-02

    This project aims to employ newly-developed chemical imaging techniques to measure, in real-time, the concentration, dynamics and spatial distribution of plant cell wall polymers during biomass growth with inoculation of transgenic symbiotic fungi, and to explore a new pathway of delivering detoxified metal to plant apoplast using transgenic symbiotic fungi, which will enhance metal accumulation from soil, and potentially these metals may in turn be used as catalysts to improve the efficiency of biomass conversion to biofuels. The proposed new pathway of biomass production will: 1) benefit metal and radionuclide contaminant mobility in subsurface environments, and 2) potentially improve biomass production and process for bioenergy

  1. Cytochemical characterization of gill and hepatopancreatic cells of the crab Ucides cordatus (Crustacea, Brachyura validated by cell metal transport

    Directory of Open Access Journals (Sweden)

    Priscila Ortega

    2014-09-01

    Full Text Available Ucides cordatus (Linnaeus, 1763 is a hypo-hyper-regulating mangrove crab possessing gills for respiratory and osmoregulatory processes, separated in anterior and posterior sections. They also have hepatopancreas, which is responsible for digestion and absorption of nutrients and detoxification of toxic metals. Each of these organs has specific cells that are important for in vitro studies in cell biology, ion and toxic metals transport. In order to study and characterize cells from gills and hepatopancreas, both were separated using a Sucrose Gradient (SG from 10 to 40% and cells in each gradient were characterized using the vital mitochondrial dye DASPEI (2-(4-dimethylaminostyryl-N- ethylpyridinium iodide and Trichrome Mallory's stain. Both in 20 and 40% SG for gill cells and 30% SG for hepatopancreatic cells, a greater number of cells were colored with DASPEI, indicating a larger number of mitochondria in these cells. It is concluded that the gill cells present in 20% and 40% SG are Thin cells, responsible for respiratory processes and Ionocytes responsible for ion transport, respectively. For hepatopancreatic cells, the 30% SG is composed of Fibrillar cells that possess larger number of membrane ion and nutrient transporters. Moreover, the transport of toxic metal cadmium (Cd by isolated hepatopancreatic cells was performed as a way of following cell physiological integrity after cell separation and to study differences in transport among the cells. All hepatopancreatic cells were able to transport Cd. These findings are the first step for further work on isolated cells of these important exchange epithelia of crabs, using a simple separation method and to further develop successful in vitro cell culture in crabs.

  2. In vitro reactivity to implant metals demonstrates a person-dependent association with both T-cell and B-cell activation.

    Science.gov (United States)

    Hallab, Nadim James; Caicedo, Marco; Epstein, Rachel; McAllister, Kyron; Jacobs, Joshua J

    2010-02-01

    Hypersensitivity to metallic implants remains relatively unpredictable and poorly understood. We initially hypothesized that metal-induced lymphocyte proliferation responses to soluble metal challenge (ions) are mediated exclusively by early T-cell activation (not B-cells), typical of a delayed-type-hypersensitivity response. We tested this by comparing proliferation (6 days) of primary lymphocytes with early T-cell and B-cell activation (48 h) in three groups of subjects likely to demonstrate elevated metal reactivity: group 1 (n = 12) history of metal sensitivity with no implant; group 2a (n = 6) well performing metal-on-metal THRs, and group 2b (n = 20) subjects with poorly performing metal-on-polymer total joint arthroplasties (TJA). Group 1 showed 100% (12/12) metal reactivity (stimulation index > 2) to Ni. Groups 2a and 2b were 83% (5/6) and 75% (15/22) metal reactive (to Co, Cr, or Ni), respectively. Of the n = 32 metal-reactive subjects to Co, Cr, or Ni (SI > 2), n = 22/32 demonstrated >2-fold elevations in % of T-cell or B-cell activation (CD25+, CD69+) to metal challenge when compared with untreated control. 18/22 metal-activated subjects demonstrated an exclusively T-cell or B-cell activation response to metal challenge, where 6/18 demonstrated exclusively B-cell activation and 12/18 demonstrated a T-cell only response, as measured by surface activation markers CD25+ and CD69+. However, there was no direct correlation (R(2) metal reactivity than did subject-dependent results of flow-cytometry analysis of T-cell or B-cell activation. The high incidence of lymphocyte reactivity and activation indicate that more complex than initially hypothesized immune responses may contribute to the etiology of debris-induced osteolysis in metal-sensitive individuals.

  3. Cytotoxicity of Metal Ions Released from Nitinol Alloys on Endothelial Cells

    Science.gov (United States)

    Haider, W.; Munroe, N.; Tek, V.; Gill, P. K. S.; Tang, Y.; McGoron, A. J.

    2011-07-01

    Most implantable medical devices are expected to function in the body over an extended period of time. Therefore, immersion tests under simulated conditions can be useful for assessing the amount of metal ions released in situ. In this investigation, dissolved ions from as-received binary and ternary Nitinol alloys in cell culture media were periodically measured under static and dynamic conditions. Endothelial cells were grown in aliquots of culture media obtained and the effect of dissolved ions on cell proliferation and viability of endothelial cells (HUVEC) was studied by cytotoxicity assays. The concentration of metal ions in the media was measured by inductively coupled plasma mass spectrometry.

  4. Nitride Conversion: A Novel Approach to c-Si Solar Cell Metallization

    Science.gov (United States)

    Hook, David Henry

    Metallization of commercial-grade c-Si solar cells is currently accomplished by screen-printing fine lines of a Ag/PbO-glass paste amalgam (Ag-frit) onto the insulating SiNx antireflective coating (ARC) that lies atop the shallow n-type emitter layer of the cell. Upon annealing, the glass etches SiNx and permits the crystallization of Ag near the electrically-active emitter interface, thus contacting the cell. While entirely functional, the contact interface produced by Ag-frit metallization is non-ideal, and Ag metal itself is expensive; its use adds to overall solar cell costs. The following work explores the use of Ti-containing alloys as metallization media for c-Si solar cells. There is a -176 kJ [mol N]--1 free energy change associated with the conversion of Si3N4 to TiN. By combining Ti with a low-melting point metal, this reaction can take place at temperatures as low as 750°C in the bulk. Combinations of Ti with Cu, Sn, Ag, and Pb ternary and binary systems are investigated. On unmetallized, c-Si textured solar cells it is shown that 900 nm of stoichiometric Ti6Sn 5 is capable of converting the SiNx ARC to TiN and Ti5Si3, both of which are conducting materials with electrically low-barriers to contact with n-type Si. Alongside electron microscopy, specific contact resistivity (rho c) measurements are used to determine the interfacial quality of TiN/Ti5Si3 contacts to n-Si. Circular transmission line model (CTLM) measurements are utilized for the characterization of reacted Ag0.05Cu0.69Ti0.26, Sn0.35 Ag0.27Ti0.38, and Ti6Sn5 contacts. rhoc values as low as 26 muOcm 2 are measured for reacted Ti6Sn5-SiN x on conventional c-Si solar cells. This value is approximately 2-3 orders of magnitude lower than rhoc of contacts produced by traditional Ag-frit metallization. Viable 1x1 cm, Ti6Sn5-metallized solar cells on 5x5 cm substrates were fabricated through a collaboration with the Georgia Institute of Technology (GA Tech). Front-side metallization was performed

  5. Metallomics insights into the programmed cell death induced by metal-based anticancer compounds.

    Science.gov (United States)

    Tan, Cai-Ping; Lu, Yi-Ying; Ji, Liang-Nian; Mao, Zong-Wan

    2014-05-01

    Since the discovery of cisplatin more than 40 years ago, enormous research efforts have been dedicated to developing metal-based anticancer agents and to elucidating the mechanisms involved in the action of these compounds. Abnormal metabolism and the evasion of apoptosis are important hallmarks of malignant transformation, and the induction of apoptotic cell death has been considered to be a main pathway by which cytotoxic metal complexes combat cancer. However, many cancers have cellular defects involving the apoptotic machinery, which results in an acquired resistance to apoptotic cell death and therefore reduced chemotherapeutic effectiveness. Over the past decade, it has been revealed that a growing number of cell death pathways induced by metal complexes are not dependent on apoptosis. Metal complexes specifically triggering these alternative cell death pathways have been identified and explored as novel cancer treatment options. In this review, we discuss recent examples of metallomics studies on the different types of cell death induced by metal-based anticancer drugs, especially on the three major forms of programmed cell death (PCD) in mammalian cells: apoptosis, autophagy and regulated necrosis, also called necroptosis.

  6. Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers.

    Science.gov (United States)

    Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

    2015-01-01

    Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

  7. Metallization improvement on fabrication of interdigitated backside and double sided buried contact solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Jiun-Hua; Cotter, Jeffrey E. [Center of Excellence for Advanced Silicon Photovoltaics and Photonics, University of New South Wales, Sydney NSW 2052 (Australia)

    2005-04-01

    Metallization based on electroless metal plating of nickel and copper is a simple, cost-effective process used in the fabrication of Buried Contact silicon solar cells. Whereas the electroless Ni-Cu metallization scheme works well for metal deposition on early Buried Contact solar cells, in which deposition was required only on phosphorus diffused contact regions, more care is required for advanced Buried Contact solar cell designs that require simultaneous deposition on to both phosphorus and boron diffused contact regions. In this paper, we examine two key issues related to the metallization in these solar cells. Firstly we demonstrate an improved buffered hydrofluoric acid etch process for simultaneous removal of borosilicate and borophosphosilicate glasses from the contact regions prior to electroless deposition of nickel with good etch selectivity against silicon dioxide masking films. Secondly, we demonstrate an improved process for nucleation of the nickel layer on both phosphorus and boron diffused contact areas based on immersion palladium chloride activation of the plating surfaces. N-type double-sided buried contact solar cells metallized by processing introduced in this study show improvement on absolute efficiency of more than 3%.

  8. Nano-electrocatalyst materials for low temperature fuel cells:A review

    Institute of Scientific and Technical Information of China (English)

    K. Vignarooban; J. Lin; A. Arvay; S. Kolli; I. Kruusenberg; K. Tammeveski; L. Munukutla; A. M. Kannan

    2015-01-01

    Low temperature fuel cells are an attractive technology for transportation and residential applica‐tions due to their quick start up and shut down capabilities. This review analyzed the current status of nanocatalysts for proton exchange membrane fuel cells and alkaline membrane fuel cells. The preparation process influences the performance of the nanocatalyst. Several synthesis methods are covered for noble and non‐noble metal catalysts on various catalyst supports including carbon nanotubes, carbon nanofibers, nanowires, and graphenes. Ex situ and in situ characterization methods like scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and fuel cell testing of the nanocatalysts on various supports for both proton exchange and alkaline membrane fuel cells are discussed. The accelerated durability estimate of the nanocat‐alysts, predicted by measuring changes in the electrochemically active surface area using a voltage cycling method, is considered one of the most reliable and valuable method for establishing durabil‐ity.

  9. Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance

    Science.gov (United States)

    Walsworth, Ronald L.

    2003-01-01

    We pursued advanced technology development of laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This new multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation-as well as studies of tissue perfusion. In addition, laser-polarized noble gases (3He and 129Xe) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We pursued two technology development specific aims: (1) development of low-field (less than 0.01 T) noble gas MRI of humans; and (2) development of functional MRI of the lung using laser-polarized noble gas and related techniques.

  10. The metal wrap through solar cell. Developement and characterisation; Die metal wrap through Solarzelle. Entwicklung und Charakterisierung

    Energy Technology Data Exchange (ETDEWEB)

    Clement, Florian

    2009-03-20

    This work focuses on the development and the optimization of the metal wrap through (MWT) solar cell. Primary goal of this work has been the development of an appropriate process flow for MWT solar cells, which generates only insignificant extra costs compared to the conventional process flow, however, achieves a significant efficiency increase for MWT cells compared to conventionally processed cells. The latter was one of the main challenges of this work. For this purpose MWT solar cells have been studied and characterized in detail. Loss mechanisms have been detected and improvements evaluated as well as transferred to the cell process. Furthermore, the assembling process for MWT solar cells in the module has been optimized focusing on less series resistance losses. A comparison with the conventional module assembling process is presented. A process flow similar to the one for the conventional process has been developed for MWT solar cells. Merely two additional laser process steps for hole drilling and rear contact isolation as well as one screen printing step for the through connection turn out to be necessary. It is shown that the additional screen printing process can be omitted without significant efficiency losses, if the through connection and solder pad metallization is done in a single process step. Furthermore, a fast and reliable through connection process has been developed and characterized in detail. Moreover, a gauge mounting block for MWT solar cells has been constructed, analyzed and calibrated for current-voltage-characteristic measurements. With multi crystalline MWT silicon solar cells an efficiency gain up to 0.5% absolute has been achieved compared to conventionally processed solar cells - thereby reaching a maximum cell efficiency of more than 16.7%. Due to a novel MWT module technology developed in this work the efficiency compared to the conventional technology could be improved further by another 0.3% absolute. The primary loss

  11. High Voltage in Noble Liquids for High Energy Physics

    Energy Technology Data Exchange (ETDEWEB)

    Rebel, B. [Fermilab; Bernard, E. [Yale U.; Faham, C. H. [LBL, Berkeley; Ito, T. M. [Los Alamos; Lundberg, B. [Maryland U.; Messina, M. [Columbia U.; Monrabal, F. [Valencia U., IFIC; Pereverzev, S. P. [LLNL, Livermore; Resnati, F. [Zurich, ETH; Rowson, P. C. [SLAC; Soderberg, M. [Fermilab; Strauss, T. [Bern U.; Tomas, A. [Imperial Coll., London; Va' vra, J. [SLAC; Wang, H. [UCLA

    2014-08-22

    A workshop was held at Fermilab November 8-9, 2013 to discuss the challenges of using high voltage in noble liquids. The participants spanned the fields of neutrino, dark matter, and electric dipole moment physics. All presentations at the workshop were made in plenary sessions. This document summarizes the experiences and lessons learned from experiments in these fields at developing high voltage systems in noble liquids.

  12. High Voltage in Noble Liquids for High Energy Physics

    CERN Document Server

    Rebel, Edited by B; Faham, C H; Ito, T M; Lundberg, B; Messina, M; Monrabal, F; Pereverzev, S P; Resnati, F; Rowson, P C; Soderberg, M; Strauss, T; Tomas, A; Va'vra, J; Wang, H

    2014-01-01

    A workshop was held at Fermilab November 8-9, 2013 to discuss the challenges of using high voltage in noble liquids. The participants spanned the fields of neutrino, dark matter, and electric dipole moment physics. All presentations at the workshop were made in plenary sessions. This document summarizes the experiences and lessons learned from experiments in these fields at developing high voltage systems in noble liquids.

  13. Assessment of a 42 metal salts chemical library in mouse embryonic stem cells

    Science.gov (United States)

    The developmental effects of xenobiotics on differentiation can be profiled using mouse embryonic stem cells (mESCs). The adherent cell differentiation and cytotoxicity (ACDC) technique was used to evaluate a library of 42 metal and metaloid salts. Jl mESCs were allowed to prolif...

  14. Topology optimization: An effective method for designing front metallization patterns of solar cells

    NARCIS (Netherlands)

    Gupta, D.K.; Langelaar, M.; Barink, M.; Keulen, F. van

    2014-01-01

    Optimal front electrode design is one of the approaches to improve the performance of solar cells. This work introduces the application of topology optimization (TO) to design complex front metallization patterns for solar cells. TO optimizes the distribution of electrode material on the front surfa

  15. Patterned 3-dimensional metal grid electrodes as alternative electron collectors in dye-sensitized solar cells.

    Science.gov (United States)

    Chua, Julianto; Mathews, Nripan; Jennings, James R; Yang, Guangwu; Wang, Qing; Mhaisalkar, Subodh G

    2011-11-21

    We describe the application of 3-dimensional metal grid electrodes (3D-MGEs) as electron collectors in dye-sensitized solar cells (DSCs) as a replacement for fluorinated tin oxide (FTO) electrodes. Requirements, structure, advantages, and limitations of the metal grid electrodes are discussed. Solar conversion efficiencies of 6.2% have been achieved in 3D-MGE based solar cells, comparable to that fabricated on FTO (7.1%). The charge transport properties and collection efficiencies in these novel solar cells have been studied using electrochemical impedance spectroscopy.

  16. Development of hyperpolarized noble gas MRI

    Science.gov (United States)

    Albert, M. S.; Balamore, D.

    1998-02-01

    Magnetic resonance imaging using the MR signal from hyperpolarized noble gases 129Xe and 3He may become an important new diagnostic technique. Alex Pines (adapting the hyperpolarization technique pioneered by William Happer) presented MR spectroscopy studies using hyperpolarized 129Xe. The current authors recognized that the enormous enhancement in the detectability of 129Xe, promised by hyperpolarization, would solve the daunting SNR problems impeding their attempts to use 129Xe as an in vivo MR probe, especially in order to study the action of general anesthetics. It was hoped that hyperpolarized 129Xe MRI would yield resolutions equivalent to that achievable with conventional 1H 2O MRI, and that xenon's solubility in lipids would facilitate investigations of lipid-rich tissues that had as yet been hard to image. The publication of hyperpolarized 129Xe images of excised mouse lungs heralded the emergence of hyperpolarized noble-gas MRI. Using hyperpolarized 3He, researchers have obtained images of the lung gas space of guinea pigs and of humans. Lung gas images from patients with pulmonary disease have recently been reported. 3He is easier to hyperpolarize than 129Xe, and it yields a stronger MR signal, but its extremely low solubility in blood precludes its use for the imaging of tissue. Xenon, however, readily dissolves in blood, and the T1 of dissolved 129Xe is long enough for sufficient polarization to be carried by the circulation to distal tissues. Hyperpolarized 129Xe dissolved-phase tissue spectra from the thorax and head of rodents and humans have been obtained, as have chemical shift 129Xe images from the head of rats. Lung gas 129Xe images of rodents, and more recently of humans, have been reported. Hyperpolarized 129Xe MRI (HypX-MRI) may elucidate the link between the structure of the lung and its function. The technique may also be useful in identifying ventilation-perfusion mismatch in patients with pulmonary embolism, in staging and tracking the

  17. Monitoring of noble gas radioisotopes in nuclear power plant effluents

    International Nuclear Information System (INIS)

    Monitoring of gaseous radionuclides in the effluents of nuclear facilities is an essential requirement in effluent management programs. Since there is no practical way of removing noble gas radioisotopes from air at release pathways, their accurate monitoring is essential for providing appropriate environmental protection. Emitted γ dose-rate is the limiting factor for concentration-time integral of noble gas in gaseous effluents of reactor facilities. The external exposure to the public from a semi-infinite cloud is directly proportional to both the noble gas isotope concentration and the integrated γ energy per disintegration. Both can be directly measured in gaseous effluent pathways with a suitable detector. The capability of NaI(T1), CaF2(Eu) and plastic scintillation detectors to measure the γ-Ci.MeV content of noble gas releases was experimentally evaluated. The combination of CaF2(Eu) detector in a pressurized through-flow chamber, with a charge integrating scaler well complied with both γ energy response and detection sensitivity requirements. Noble gas source terms and effluent monitoring criteria are discussed, theoretical and experimental results are presented and a practical, on-line noble gas monitoring system is described

  18. The diverse biological properties of the chemically inert noble gases.

    Science.gov (United States)

    Winkler, David A; Thornton, Aaron; Farjot, Géraldine; Katz, Ira

    2016-04-01

    The noble gases represent an intriguing scientific paradox. They are extremely inert chemically but display a remarkable spectrum of clinically useful biological properties. Despite a relative paucity of knowledge of their mechanisms of action, some of the noble gases have been used successfully in the clinic. Studies with xenon have suggested that the noble gases as a class may exhibit valuable biological properties such as anaesthesia; amelioration of ischemic damage; tissue protection prior to transplantation; analgesic properties; and a potentially wide range of other clinically useful effects. Xenon has been shown to be safe in humans, and has useful pharmacokinetic properties such as rapid onset, fast wash out etc. The main limitations in wider use are that: many of the fundamental biochemical studies are still lacking; the lighter noble gases are likely to manifest their properties only under hyperbaric conditions, impractical in surgery; and administration of xenon using convectional gaseous anaesthesia equipment is inefficient, making its use very expensive. There is nonetheless a significant body of published literature on the biochemical, pharmacological, and clinical properties of noble gases but no comprehensive reviews exist that summarize their properties and the existing knowledge of their models of action at the molecular (atomic) level. This review provides such an up-to-date summary of the extensive, useful biological properties of noble gases as drugs and prospects for wider application of these atoms. PMID:26896563

  19. Increasing the solar cell power output by coating with transition metal-oxide nanorods

    International Nuclear Information System (INIS)

    Highlights: → Nanoparticles enhance solar cell efficiency. → Solar cell power increase by nanorod coating. → Metal-oxide nanorods are prepared in flames. → Molybdenum oxide nanorods effectively scatter light on solar cell surface. → Scattering efficiency depends on coating density. -- Abstract: Photovoltaic cells produce electric current through interactions among photons from an ambient light source and electrons in the semiconductor layer of the cell. However, much of the light incident on the panel is reflected or absorbed without inducing the photovoltaic effect. Transition metal-oxide nanoparticles, an inexpensive product of a process called flame synthesis, can cause scattering of light. Scattering can redirect photon flux, increasing the fraction of light absorbed in the thin active layer of silicon solar cells. This research aims to demonstrate that the application of transition metal-oxide nanorods to the surface of silicon solar panels can enhance the power output of the panels. Several solar panels were coated with a nanoparticle-methanol suspension, and the power outputs of the panels before and after the treatment were compared. The results demonstrate an increase in power output of up to 5% after the treatment. The presence of metal-oxide nanorods on the surface of the coated solar cells is confirmed by electron microscopy.

  20. Cell overcharge testing inside sodium metal halide battery

    Science.gov (United States)

    Frutschy, Kris; Chatwin, Troy; Bull, Roger

    2015-09-01

    Testing was conducted to measure electrical performance and safety of the General Electric Durathon™ E620 battery module (600 V class 20 kWh) during cell overcharge. Data gathered from this test was consistent with SAE Electric Vehicle Battery Abuse Testing specification J2464 [1]. After cell overcharge failure and 24 A current flow for additional 60 minutes, battery was then discharged at 7.5 KW average power to 12% state of charge (SOC) and recharged back to 100% SOC. This overcharging test was performed on two cells. No hydrogen chloride (HCl) gas was detected during front cell (B1) test, and small amount (6.2 ppm peak) was measured outside the battery after center cell (F13) overcharge. An additional overcharge test was performed per UL Standard 1973 - Batteries for Use in Light Electric Rail (LER) Applications and Stationary Applications[2]. With the battery at 11% SOC and 280 °C float temperature, an individual cell near the front (D1) was deliberately imbalanced by charging it to 62% SOC. The battery was then recharged to 100% SOC. In all three tests, the battery cell pack was stable and individual cell failure did not propagate to other cells. Battery discharge performance, charge performance, and electrical isolation were normal after all three tests.

  1. Nitrogen and light noble gases in Shergotty

    Science.gov (United States)

    Becker, R. H.; Pepin, R. O.

    1986-01-01

    Two samples of Shergotty and a sample of EETA 79001's lithology A have been analyzed for N, He, Ne, and Ar abundances and isotopic composition. After correcting for spallogenic nitrogen, the nitrogen isotopic ratios were found to be close to that of the terrestrial atmosphere. The spallogenic noble gas data are consistent with cosmic ray irradiation of both Shergotty and EETA 79001 at shallow shielding depths. Cosmic ray exposure ages were estimated to be in the range of 0.5-0.8 Myr for EETA 79001, and of 2.0-5.2 Myr for Shergotty, depending on the choice of object size and shielding. Among the two Shergotty samples, the contents of Ar-40 differed by a factor of 3. This difference can be attributed to either a small-scale mineralogical inhomogeneity or a significant variation in the degree of degassing of minerals during shock, although the presence of trapped argon with a high Ar-40/Ar-36 ratio and its heterogeneous distribution cannot be ruled out.

  2. Noble gases in E-chondrites

    Science.gov (United States)

    Crabb, J.; Anders, E.

    1981-01-01

    The combination of noble gas data for 12 E-chondrites with literature data shows K-Ar ages greater than 4 AE for 14 out of 18 meteorites, while U, Th-He ages are often shorter. Cosmic ray exposure ages are found to differ systematically between types E4 and E6, with the respective, below-16 Myr and above-30 Myr values implying that the E-chondrite parent body predominantly contains a single petrologic type on the 1 km scale of individual impacts in contrast to the mixed parent bodies of the ordinary chondrites. Amounts of planetary gas in E4-E6 chondrites fall in the range for ordinary chondrites of types 4-6, but fail to correlate with petrologic type or volatile trace element contents, in contrast to the ordinary chondrites. Analyses of mineral separates show that the planetary gases are concentrated in an HFand HCl-insoluble mineral, similar to phase Q. The subsolar gases are located in an HCl- and HNO3-resistant phase.

  3. Noble gas atmospheric monitoring at reprocessing facilities

    Energy Technology Data Exchange (ETDEWEB)

    Nakhleh, C.W.; Perry, R.T. Jr.; Poths, J.; Stanbro, W.D.; Wilson, W.B.; Fearey, B.L.

    1997-05-01

    The discovery in Iraq after the Gulf War of the existence of a large clandestine nuclear-weapon program has led to an across-the-board international effort, dubbed Programme 93+2, to improve the effectiveness and efficiency of International Atomic Energy Agency (IAEA) safeguards. One particularly significant potential change is the introduction of environmental monitoring (EM) techniques as an adjunct to traditional safeguards methods. Monitoring of stable noble gas (Kr, Xe) isotopic abundances at reprocessing plant stacks appears to be able to yield information on the burnup and type of the fuel being processed. To estimate the size of these signals, model calculations of the production of stable Kr, Xe nuclides in reactor fuel and the subsequent dilution of these nuclides in the plant stack are carried out for two case studies: reprocessing of PWR fuel with a burnup of 35 GWd/tU, and reprocessing of CAND fuel with a burnup of 1 GWd/tU. For each case, a maximum-likelihood analysis is used to determine the fuel burnup and type from the isotopic data.

  4. Engineered metal nanoparticles in the sub-nanomolar levels kill cancer cells

    Directory of Open Access Journals (Sweden)

    Vodyanoy V

    2016-04-01

    Full Text Available Vitaly Vodyanoy,1 Yasmine Daniels,2 Oleg Pustovyy,1 William A MacCrehan,2 Shin Muramoto,2 Gheorghe Stan21Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL, 2Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MA, USA Background: Small metal nanoparticles obtained from animal blood were observed to be toxic to cultured cancer cells, whereas noncancerous cells were much less affected. In this work, engineered zinc and copper metal nanoparticles were produced from bulk metal rods by an underwater high-voltage discharge method. The metal nanoparticles were characterized by atomic force microscopy and X-ray photoelectron spectroscopy. The metal nanoparticles, with estimated diameters of 1 nm–2 nm, were determined to be more than 85% nonoxidized. A cell viability assay and high-resolution light microscopy showed that exposure of RG2, cultured rat brain glioma cancer cells, to the zinc and copper nanoparticles resulted in cell morphological changes, including decreased cell adherence, shrinking/rounding, nuclear condensation, and budding from cell bodies. The metal-induced cell injuries were similar to the effects of staurosporine, an active apoptotic reagent. The viability experiments conducted for zinc and copper yielded values of dissociation constants of 0.22±0.08 nmol/L (standard error [SE] and 0.12±0.02 nmol/L (SE, respectively. The noncancerous astrocytes were not affected at the same conditions. Because metal nanoparticles were lethal to the cancer cells at sub-nanomolar concentrations, they are potentially important as nanomedicine.Purpose: Lethal concentrations of synthetic metal nanoparticles reported in the literature are a few orders of magnitude higher than the natural, blood-isolated metal nanoparticles; therefore, in this work, engineered metal nanoparticles were examined to mimic the properties of endogenous metal

  5. Biosorption characteristics of Spirulina and Chlorella cells to accumulate heavy metals

    OpenAIRE

    Kőnig-Péter Anikó; Kilár Ferenc; Felinger Attila; Pernyeszi Tímea

    2015-01-01

    The heavy metal biosorption of dried Chlorella vulgaris and Spirulina platensis-Spirulina maxima cells was studied under various experimental conditions. The effect of biosorbent dosage, pH, adsorption time, temperature, initial metal concentration on biosorption was studied. Biosorption process can be divided into two parts: the first part follows zero-order, the second part pseudo second-order kinetics. Characterization of biosorption equilibrium was eval...

  6. Topology optimization of front metallization patterns for solar cells

    NARCIS (Netherlands)

    Gupta, D.K.; Langelaar, M.; Barink, M.; Keulen, F. van

    2015-01-01

    This paper presents the application of topology optimization (TO) for designing the front electrode patterns for solar cells. Improving the front electrode design is one of the approaches to improve the performance of the solar cells. It serves to produce the voltage distribution for the front surfa

  7. Performance evaluation and characterization of metallic bipolar plates in a proton exchange membrane (PEM) fuel cell

    Science.gov (United States)

    Hung, Yue

    Bipolar plate and membrane electrode assembly (MEA) are the two most repeated components of a proton exchange membrane (PEM) fuel cell stack. Bipolar plates comprise more than 60% of the weight and account for 30% of the total cost of a fuel cell stack. The bipolar plates perform as current conductors between cells, provide conduits for reactant gases, facilitate water and thermal management through the cell, and constitute the backbone of a power stack. In addition, bipolar plates must have excellent corrosion resistance to withstand the highly corrosive environment inside the fuel cell, and they must maintain low interfacial contact resistance throughout the operation to achieve optimum power density output. Currently, commercial bipolar plates are made of graphite composites because of their relatively low interfacial contact resistance (ICR) and high corrosion resistance. However, graphite composite's manufacturability, permeability, and durability for shock and vibration are unfavorable in comparison to metals. Therefore, metals have been considered as a replacement material for graphite composite bipolar plates. Since bipolar plates must possess the combined advantages of both metals and graphite composites in the fuel cell technology, various methods and techniques are being developed to combat metallic corrosion and eliminate the passive layer formed on the metal surface that causes unacceptable power reduction and possible fouling of the catalyst and the electrolyte. The main objective of this study was to explore the possibility of producing efficient, cost-effective and durable metallic bipolar plates that were capable of functioning in the highly corrosive fuel cell environment. Bulk materials such as Poco graphite, graphite composite, SS310, SS316, incoloy 800, titanium carbide and zirconium carbide were investigated as potential bipolar plate materials. In this work, different alloys and compositions of chromium carbide coatings on aluminum and SS316

  8. Summary of the 4th Workshop on Metallization for Crystalline Silicon Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Beaucarne, G. [Dow Corning, Parc Industriel, Zone C, Rue Jules Bordet, 7180 Seneffe (Belgium); Schubert, G. [Sunways AG, Macairestrasse 3 - 5, D - 78467 Konstanz (Germany); Hoornstra, J. [Energy research Centre of the Netherlands ECN, POBox 1, 1755 ZG Petten (Netherlands)

    2013-07-01

    The 4th Metallization Workshop held in May 2013 in Constance, Germany, enabled experts in metallization for crystalline silicon solar cells to obtain a clear view on the status of the technology, as well as to exchange and generate new ideas and insights. From the contributions on the workshop, it was clear that the traditional metallization technique of screenprinting Ag paste has been improved in a dramatic way over the last two years, accelerating the decrease of Ag consumption per cell while improving solar cell efficiency. This was achieved through enhanced understanding of screenprinted contacts, improving Ag pastes and evolutionary modifications to the screenprinting technique. Alternatives to screenprinting, including electroplating of Ni and Cu contacts, also continue to progress, though not quite at the same impressive rate of improvement as Ag printing.

  9. Numerical simulation of current distribution in metal pad of aluminum reduction cells

    Institute of Scientific and Technical Information of China (English)

    QI Xi-quan; FENG Nai-xiang; CUI Jian-zhong

    2005-01-01

    Based on the numerical calculation of 3-D potential distribution in aluminum reduction cells, current distribution in the metal pad is calculated under the following conditions: 1) pot ledge ideally formed; 2) ledge extension to below anode; 3) different metal heights; 4) AC and 5) Spike. It is found that Jy in metal pad increases first to a highest point and then decreases along anode length. At normal status, the largest Jy is about 0. 4 A/cm2 and it locates at about 2/3 of anode length. With longer ledge, the maximum value of Jy decreases and its position movescenter-ward. The longer the side ledge, the larger the negative current flowing center-ward at side channel. Jz in metal pad increases with anode length and it is not affected by metal height; while Jy increases with metal height. At AC, current flows toward metal under new anode. At spike, current concentrates at spike rather than evenly distributes. Normally, Jx is almost negligible in metal pad.

  10. Review of Ni-Cu Based Front Side Metallization for c-Si Solar Cells

    Directory of Open Access Journals (Sweden)

    Mehul C. Raval

    2013-01-01

    Full Text Available Given the high percentage of metal cost in cell processing and concerns due to increasing Ag prices, alternative metallization schemes are being considered. Ni-Cu based front side metallization offers potential advantages of finer grid lines, lower series resistance, and reduced costs. A brief overview of various front side patterning techniques is presented. Subsequently, working principle of various plating techniques is discussed. For electroless plated Ni seed layer, fill factor values nearing 80% and efficiencies close to 17.5% have been demonstrated, while for Light Induced Plating deposited layers, an efficiency of 19.2% has been reported. Various methods for qualifying adhesion and long term stability of metal stack are discussed. Adhesion strengths in the range of 1–2.7 N/mm have been obtained for Ni-Cu contacts tabbed with conventional soldering process. Given the significance of metallization properties, different methods for characterization are outlined. The problem of background plating for Ni-Cu based metallization along with the various methods for characterization is summarized. An economic evaluation of front side metallization indicates process cost saving of more than 50% with Ni-Cu-Sn based layers. Recent successful commercialization and demonstration of Ni-Cu based metallization on industrial scale indicate a potential major role of Ni-Cu based contacts in near future.

  11. Investigation of metal oxide/cuprous oxide heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Herion, J.; Neikisch, E.A.; Scharl, G.

    1980-12-01

    ZnO/Cu/sub 2/O heterojunction solar cells can be prepared by means of rf sputter deposition of In-doped ZnO layers on Cu/sub 2/O. The temperature at which ZnO is deposited is found to be of crucial importance for the photovoltaic performance of the cells. Maxima of the open-circuit voltage, the short-circuit current, and the dark resistance are observed for deposition temperatures between 230 and 240/sup 0/C. Auger sputter profiles show an oxygen depletion zone at the ZnO/Cu/sub 2/O interface which can be attributed to a very thin copper layer. The oxygen depletion and, correspondingly, the copper enrichment are apparently correlated with the photovoltaic effects. A relatively small copper enrichment has also been observed in CuO/Cu/sub 2/O cells. However, the nature of copper enrichment seems to be different in both types of cells.

  12. Molecular solution processing of metal chalcogenide thin film solar cells

    OpenAIRE

    Yang, Wenbing

    2013-01-01

    The barrier to utilize solar generated electricity mainly comes from their higher cost relative to fossil fuels. However, innovations with new materials and processing techniques can potentially make cost effective photovoltaics. One such strategy is to develop solution processed photovoltaics which avoid the expensive vacuum processing required by traditional solar cells. The dissertation is mainly focused on two absorber material system for thin film solar cells: chalcopyrite CuIn(S,Se)2 (C...

  13. Switching Characteristics of Phase Change Memory Cell Integrated with Metal-Oxide Semiconductor Field Effect Transistor

    Institute of Scientific and Technical Information of China (English)

    XU Cheng; CHEN Bomy; LIU Bo; CHEN Yi-Feng; LIANG Shuang; SONG Zhi-Tang; FENG Song-Lin; WAN Xu-Dong; YANG Zuo-Ya; XIE Joseph

    2008-01-01

    A Ge2Sb2Te5 based phase change memory device cell integrated with metal-oxide semiconductor field effect transistor (MOSFET) is fabricated using standard 0.18 μm complementary metal-oxide semiconductor process technology.It shows steady switching characteristics in the dc current-voltage measurement.The phase changing phenomenon from crystalline state to amorphous state with a voltage pulse altitude of 2.0 V and pulse width of 50 ns is also obtained.These results show the feasibility of integrating phase change memory cell with MOSFET.

  14. Autophagy as an ultrastructural marker of heavy metal toxicity in human cord blood hematopoietic stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Di Gioacchino, Mario [Aging Research Center, ' G. d' Annunzio' University Foundation, Via Colle dell' Ara, 66100 Chieti (Italy); Medicine and Science of Ageing University of Chieti-Pescara, Via dei Vestini 1, 66100 Chieti (Italy)], E-mail: m.digioacchino@unich.it; Petrarca, Claudia; Perrone, Angela [Aging Research Center, ' G. d' Annunzio' University Foundation, Via Colle dell' Ara, 66100 Chieti (Italy); Medicine and Science of Ageing University of Chieti-Pescara, Via dei Vestini 1, 66100 Chieti (Italy); Farina, Massimo; Sabbioni, Enrico; Hartung, Thomas [Oncology and Neurosciences University of Chieti-Pescara, Via dei Vestini 1, 66100 Chieti (Italy); Martino, Simone [Department of Experimental Medicine, University La Sapienza, Viale Regina Elena 324, 00161 Rome (Italy); Esposito, Diana L. [Aging Research Center, ' G. d' Annunzio' University Foundation, Via Colle dell' Ara, 66100 Chieti (Italy); Oncology and Neurosciences University of Chieti-Pescara, Via dei Vestini 1, 66100 Chieti (Italy); Lotti, Lavinia Vittoria [Department of Experimental Medicine, University La Sapienza, Viale Regina Elena 324, 00161 Rome (Italy); Mariani-Costantini, Renato [Aging Research Center, ' G. d' Annunzio' University Foundation, Via Colle dell' Ara, 66100 Chieti (Italy); Oncology and Neurosciences University of Chieti-Pescara, Via dei Vestini 1, 66100 Chieti (Italy)

    2008-03-15

    Stem cells are a key target of environmental toxicants, but little is known about their toxicological responses. We aimed at developing an in-vitro model based on adult human stem cells to identify biomarkers of heavy metal exposure. To this end we investigated the responses of human CD34+ hematopoietic progenitor cells to hexavalent chromium (Cr[VI]) and cadmium (Cd). Parallel cultures of CD34+ cells isolated from umbilical cord blood were exposed for 48 h to 0.1 {mu}M and 10 {mu}M Cr(VI) or Cd. Cultures treated with 10 {mu}M Cr(VI) or Cd showed marked cell loss. Ultrastructural analysis of surviving cells revealed prominent autophagosomes/autophagolysosomes, which is diagnostic of autophagy, associated with mitochondrial damage and replication, dilatation of the rough endoplasmic reticulum and Golgi complex, cytoplasmic lipid droplets and chromatin condensation. Treated cells did not show the morphologic hallmarks of apoptosis. Treatment with 0.1 {mu}M Cr(VI) or Cd did not result in cell loss, but at the ultrastructural level cells showed dilated endoplasmic reticulum and evidence of mitochondrial damage. We conclude that autophagy is implicated in the response of human hematopoietic stem cells to toxic concentrations of Cr(VI) and Cd. Autophagy, which mediates cell survival and death under stress, deserves further evaluation to be established as biomarker of metal exposure.

  15. Galvanic cells including cobalt-chromium alloys.

    Science.gov (United States)

    Gjerdet, N R

    1980-01-01

    Galvanic cells may be created when dentures made of cobalt-chromium alloys are placed on teeth with metallic restorations. The power of such cells was evaluated in an in vitro galvanic using amalgams, gold alloy, and nickel-chromium alloys. The amalgams and one of the nickel-chromium alloys revealed high corrosion currents when placed in contact with cobalt-chromium alloy, the conventional amalgam showing the highest values. The gold alloy and another nickel-chromium alloy exhibited low corrosion currents and they were noble with respect to cobalt-chromium.

  16. POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

    DEFF Research Database (Denmark)

    2001-01-01

    thermoplastic polymers for high temperature polymer electrolyte fuel cells have also been developed. Miscible blends are used for solution casting of polymer membranes (solid electrolytes). High conductivity and enhanced mechanical strength were obtained for the blend polymer solid electrolytes....... With the thermally resistant polymer, e.g., polybenzimidazole or a mixture of polybenzimidazole and other thermoplastics as binder, the carbon-supported noble metal catalyst is tape-cast onto a hydrophobic supporting substrate. When doped with an acid mixture, electrodes are assembled with an acid doped solid...

  17. Mechanism for resistive switching in chalcogenide-based electrochemical metallization memory cells

    Directory of Open Access Journals (Sweden)

    Fei Zhuge

    2015-05-01

    Full Text Available It has been reported that in chalcogenide-based electrochemical metallization (ECM memory cells (e.g., As2S3:Ag, GeS:Cu, and Ag2S, the metal filament grows from the cathode (e.g., Pt and W towards the anode (e.g., Cu and Ag, whereas filament growth along the opposite direction has been observed in oxide-based ECM cells (e.g., ZnO, ZrO2, and SiO2. The growth direction difference has been ascribed to a high ion diffusion coefficient in chalcogenides in comparison with oxides. In this paper, upon analysis of OFF state I–V characteristics of ZnS-based ECM cells, we find that the metal filament grows from the anode towards the cathode and the filament rupture and rejuvenation occur at the cathodic interface, similar to the case of oxide-based ECM cells. It is inferred that in ECM cells based on the chalcogenides such as As2S3:Ag, GeS:Cu, and Ag2S, the filament growth from the cathode towards the anode is due to the existence of an abundance of ready-made mobile metal ions in the chalcogenides rather than to the high ion diffusion coefficient.

  18. [Advance in the bioavailability monitoring of heavy metal based on microbial whole-cell sensor].

    Science.gov (United States)

    Hou, Qi-Hui; Ma, An-Shou; Zhuang, Xiu-Liang; Zhuang, Guo-Qiang

    2013-01-01

    Microbial whole-cell biosensor is an excellent tool to assess the bioavailability of heavy metal in soil and water. However, the traditional physicochemical instruments are applied to detect the total metal. Furthermore, microbial whole-cell biosensor is simple, rapid and economical in manipulating, and is thus a highly qualified candidate for emergency detection of pollution incidents. The biological component of microbial whole-cell biosensor mostly consists of metalloregulatory proteins and reporter genes. In detail, metalloregulatory proteins mainly include the MerR family, ArsR family and RS family, and reporter genes mainly include gfp, lux and luc. Metalloregulatory protein and reporter gene are related to the sensitivity, specificity and properties in monitoring. The bioavailability of heavy metals is alterable under different conditions, influenced by pH, chelate and detection methods and so on. Increasing the accumulation of intracellular heavy metal, modifying the metalloregulatory proteins and optimizing the detecting conditions are important for improving the sensitivity, specificity and accuracy of the microbial whole-cell biosensor. The future direction of microbial whole-cell biosensor is to realize the monitoring of pollutions in situ and on line. PMID:23487961

  19. Cytotoxic mechanism related to dihydrolipoamide dehydrogenase in Leydig cells exposed to heavy metals

    International Nuclear Information System (INIS)

    Heavy metals are common environmental toxicants with adverse effects on steroid biosynthesis. The importance of mitochondria has been recognized in cytotoxic mechanism of heavy metals on Leydig cells these years. But it is still poorly known. Our previous study reported that dihydrolipoamide dehydrogenase (DLD) located on the mitochondria was significantly decreased in Leydig cells exposed to cadmium, which suggested that DLD might be involved in the cytotoxic effects. Therefore, the altered expression of DLD was validated in rats and R2C cells exposed to cadmium, manganese and lead, and the role of DLD in the steroid synthesis pathway cAMP/PKA-ERK1/2 was investigated in this study. With a low expression of DLD, heavy metals dramatically reduced the levels of steroid hormone by inhibiting the activation of cAMP/PKA, PKC signaling pathway and the steroidogenic enzymes StAR, CYP11A1 and 3β-HSD. After knockdown of DLD in R2C cells, progesterone synthesis was reduced by 40%, and the intracellular concentration of cAMP, protein expression of StAR, 3β-HSD, PKA, and the phosphorylation of ERK1/2 were also decreased. These results highlight that DLD is down-regulation and related to steroid biosynthesis in Leyig cells exposed to heavy metals; cAMP/PKA act as downstream effector molecules of DLD, which activate phosphorylation of ERK1/2 to initiate the steroidogenesis

  20. Metal-air cell with performance enhancing additive

    Energy Technology Data Exchange (ETDEWEB)

    Friesen, Cody A; Buttry, Daniel

    2015-11-10

    Systems and methods drawn to an electrochemical cell comprising a low temperature ionic liquid comprising positive ions and negative ions and a performance enhancing additive added to the low temperature ionic liquid. The additive dissolves in the ionic liquid to form cations, which are coordinated with one or more negative ions forming ion complexes. The electrochemical cell also includes an air electrode configured to absorb and reduce oxygen. The ion complexes improve oxygen reduction thermodynamics and/or kinetics relative to the ionic liquid without the additive.

  1. Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

    Directory of Open Access Journals (Sweden)

    M. M. Aliyu

    2012-01-01

    Full Text Available This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears the most favorable candidate, while close spaced sublimation (CSS, electrodeposition (ED, magnetic sputtering (MS, and high vacuum thermal evaporation (HVE have been found to be most common deposition technologies used for CdTe on metal foils. The advantages of these techniques include large grain size (CSS, ease of constituent control (ED, high material incorporation (MS, and low temperature process (MS, HVE, ED. These invert-structured thin film CdTe solar cells, like their superstrate counterparts, suffer from problems of poor ohmic contact at the back electrode. Thus similar strategies are applied to minimize this problem. Despite the challenges faced by flexible structures, efficiencies of up to 13.8% and 7.8% have been achieved in superstrate and substrate cell, respectively. Based on these analyses, new strategies have been proposed for obtaining cheaper, more efficient, and viable flexible CdTe solar cells of the future.

  2. Laser-polarized noble gases: a powerful probe for biology, medicine, and subatomic physics

    Science.gov (United States)

    Cates, Gordon

    2010-03-01

    For over a decade, laser-polarized noble gases such as ^3He and ^129Xe have proven useful for a wide range of scientific inquiries. These include investigations of pulmonary disease using the polarized gas as a signal source for magnetic resonance imaging (MRI), measurements of various aspects of nucleon structure, and tests of fundamental symmetries. Early efforts were often limited by expensive and bulky laser systems, but ongoing advancements in solid-state lasers have enabled increasingly large volumes of polarized gas to be produced with steadily improved polarization. Equally important have been advances in the fundamental understanding of spin exchange. This has led, for example, to the introduction of hybrid mixtures of alkali metals that can increase the efficiency of spin exchange by an order of magnitude. As a consequence of these advances, the figure of merit for polarized nuclear targets has increased by roughly three orders of magnitude in comparison to early accelerator-based experiments. And in MRI applications, it has become possible to pursue increasingly sophisticated imaging protocols that provide a wide range of diagnostic information. Even the earliest noble-gas MR images of the gas space of the human lung provided unprecedented resolution. More recent work includes the use of diffusion-sensitizing pulse sequences to study lung microstructure, and tagging techniques that enable the visualization (in real-time MRI movies) of gas flow during breathing. The range of applications of laser-polarized noble gases is continuing to grow, and it is notable that with an improved understanding of the underlying physics, it is quite likely that the capabilities of this useful technology will expand for some time to come.

  3. Possible Immune Regulation of Natural Killer T Cells in a Murine Model of Metal Ion-Induced Allergic Contact Dermatitis

    Directory of Open Access Journals (Sweden)

    Kenichi Kumagai

    2016-01-01

    Full Text Available Metal often causes delayed-type hypersensitivity reactions, which are possibly mediated by accumulating T cells in the inflamed skin, called irritant or allergic contact dermatitis. However, accumulating T cells during development of a metal allergy are poorly characterized because a suitable animal model is unavailable. We have previously established novel murine models of metal allergy and found accumulation of both metal-specific T cells and natural killer (NK T cells in the inflamed skin. In our novel models of metal allergy, skin hypersensitivity responses were induced through repeated sensitizations by administration of metal chloride and lipopolysaccharide into the mouse groin followed by metal chloride challenge in the footpad. These models enabled us to investigate the precise mechanisms of the immune responses of metal allergy in the inflamed skin. In this review, we summarize the immune responses in several murine models of metal allergy and describe which antigen-specific responses occur in the inflamed skin during allergic contact dermatitis in terms of the T cell receptor. In addition, we consider the immune regulation of accumulated NK T cells in metal ion–induced allergic contact dermatitis.

  4. Possible Immune Regulation of Natural Killer T Cells in a Murine Model of Metal Ion-Induced Allergic Contact Dermatitis.

    Science.gov (United States)

    Kumagai, Kenichi; Horikawa, Tatsuya; Shigematsu, Hiroaki; Matsubara, Ryota; Kitaura, Kazutaka; Eguchi, Takanori; Kobayashi, Hiroshi; Nakasone, Yasunari; Sato, Koichiro; Yamada, Hiroyuki; Suzuki, Satsuki; Hamada, Yoshiki; Suzuki, Ryuji

    2016-01-12

    Metal often causes delayed-type hypersensitivity reactions, which are possibly mediated by accumulating T cells in the inflamed skin, called irritant or allergic contact dermatitis. However, accumulating T cells during development of a metal allergy are poorly characterized because a suitable animal model is unavailable. We have previously established novel murine models of metal allergy and found accumulation of both metal-specific T cells and natural killer (NK) T cells in the inflamed skin. In our novel models of metal allergy, skin hypersensitivity responses were induced through repeated sensitizations by administration of metal chloride and lipopolysaccharide into the mouse groin followed by metal chloride challenge in the footpad. These models enabled us to investigate the precise mechanisms of the immune responses of metal allergy in the inflamed skin. In this review, we summarize the immune responses in several murine models of metal allergy and describe which antigen-specific responses occur in the inflamed skin during allergic contact dermatitis in terms of the T cell receptor. In addition, we consider the immune regulation of accumulated NK T cells in metal ion-induced allergic contact dermatitis.

  5. Possible Immune Regulation of Natural Killer T Cells in a Murine Model of Metal Ion-Induced Allergic Contact Dermatitis

    Science.gov (United States)

    Kumagai, Kenichi; Horikawa, Tatsuya; Shigematsu, Hiroaki; Matsubara, Ryota; Kitaura, Kazutaka; Eguchi, Takanori; Kobayashi, Hiroshi; Nakasone, Yasunari; Sato, Koichiro; Yamada, Hiroyuki; Suzuki, Satsuki; Hamada, Yoshiki; Suzuki, Ryuji

    2016-01-01

    Metal often causes delayed-type hypersensitivity reactions, which are possibly mediated by accumulating T cells in the inflamed skin, called irritant or allergic contact dermatitis. However, accumulating T cells during development of a metal allergy are poorly characterized because a suitable animal model is unavailable. We have previously established novel murine models of metal allergy and found accumulation of both metal-specific T cells and natural killer (NK) T cells in the inflamed skin. In our novel models of metal allergy, skin hypersensitivity responses were induced through repeated sensitizations by administration of metal chloride and lipopolysaccharide into the mouse groin followed by metal chloride challenge in the footpad. These models enabled us to investigate the precise mechanisms of the immune responses of metal allergy in the inflamed skin. In this review, we summarize the immune responses in several murine models of metal allergy and describe which antigen-specific responses occur in the inflamed skin during allergic contact dermatitis in terms of the T cell receptor. In addition, we consider the immune regulation of accumulated NK T cells in metal ion–induced allergic contact dermatitis. PMID:26771600

  6. Metallic Nickel Hydroxide Nanosheets Give Superior Electrocatalytic Oxidation of Urea for Fuel Cells.

    Science.gov (United States)

    Zhu, Xiaojiao; Dou, Xinyu; Dai, Jun; An, Xingda; Guo, Yuqiao; Zhang, Lidong; Tao, Shi; Zhao, Jiyin; Chu, Wangsheng; Zeng, Xiao Cheng; Wu, Changzheng; Xie, Yi

    2016-09-26

    The direct urea fuel cell (DUFC) is an important but challenging renewable energy production technology, it offers great promise for energy-sustainable developments and mitigating water contamination. However, DUFCs still suffer from the sluggish kinetics of the urea oxidation reaction (UOR) owing to a 6 e(-) transfer process, which poses a severe hindrance to their practical use. Herein, taking β-Ni(OH)2 nanosheets as the proof-of-concept study, we demonstrated a surface-chemistry strategy to achieve metallic Ni(OH)2 nanosheets by engineering their electronic structure, representing a first metallic configuration of transition-metal hydroxides. Surface sulfur incorporation successfully brings synergetic effects of more exposed active sites, good wetting behavior, and effective electron transport, giving rise to greatly enhanced performance for UOR. Metallic nanosheets exhibited a much higher current density, smaller onset potential and stronger durability. PMID:27572334

  7. Metallic Nickel Hydroxide Nanosheets Give Superior Electrocatalytic Oxidation of Urea for Fuel Cells.

    Science.gov (United States)

    Zhu, Xiaojiao; Dou, Xinyu; Dai, Jun; An, Xingda; Guo, Yuqiao; Zhang, Lidong; Tao, Shi; Zhao, Jiyin; Chu, Wangsheng; Zeng, Xiao Cheng; Wu, Changzheng; Xie, Yi

    2016-09-26

    The direct urea fuel cell (DUFC) is an important but challenging renewable energy production technology, it offers great promise for energy-sustainable developments and mitigating water contamination. However, DUFCs still suffer from the sluggish kinetics of the urea oxidation reaction (UOR) owing to a 6 e(-) transfer process, which poses a severe hindrance to their practical use. Herein, taking β-Ni(OH)2 nanosheets as the proof-of-concept study, we demonstrated a surface-chemistry strategy to achieve metallic Ni(OH)2 nanosheets by engineering their electronic structure, representing a first metallic configuration of transition-metal hydroxides. Surface sulfur incorporation successfully brings synergetic effects of more exposed active sites, good wetting behavior, and effective electron transport, giving rise to greatly enhanced performance for UOR. Metallic nanosheets exhibited a much higher current density, smaller onset potential and stronger durability.

  8. Plasmonic metallic nanostructures for efficient absorption enhancement in ultrathin CdTe-based photovoltaic cells

    International Nuclear Information System (INIS)

    The effects of incorporating metal nanodiscs (NDs) and nanospheres on optical absorptions of a CdTe solar cell are theoretically investigated by finite-difference time-domain calculations. Significant broadband absorption enhancements have been demonstrated in CdTe layers with various metals, among which Al-ND arrays result in the best photon absorption performance of up to 50% enhancement with respect to bare CdTe materials. The origins of increased absorptions are believed to be the effects of the enormous electric field enhancement and increased scattering upon the excitation of localized surface plasmon resonance. The geometrical dependences of photon absorption in plasmonic CdTe thin films are also studied, from which the relatively optimal geometrical parameters leading to the ultimate solar cell efficiency of ∼36% are extracted. Besides, this work offers a clue to using low-cost plasmonic metals for potential photovoltaic applications.

  9. Magnetometry with millimeter-scale anti-relaxation-coated alkali-metal vapor cells

    CERN Document Server

    Balabas, M V; Kitching, J; Schwindt, P D D; Stalnaker, J E

    2005-01-01

    Dynamic nonlinear magneto-optical-rotation signals with frequency- and amplitude-modulated laser light have been observed and investigated with a spherical glass cell of 3-mm diameter containing Cs metal with inner walls coated with paraffin. Intrinsic Zeeman relaxation rates of $\\gamma/(2\\pi)\\approx 20 $Hz and lower have been observed. Favorable prospects of using millimeter-scale coated cells in portable magnetometers and secondary frequency references are discussed.

  10. The use of additive manufacture for metallic bipolar plates in polymer electrolyte fuel cell stacks

    OpenAIRE

    Dawson, Richard; Patel, Anant; Rennie, Allan; White, Simon

    2014-01-01

    The bipolar plate is of critical importance to the efficient and long lasting operation of a polymer electrolyte fuel cell (PEMFC) stack. With advances in membrane electrode assembly (MEA) design greater attention has been focused on the bipolar plate and the important role it plays in performance and durability. Although carbon composite plates are a likely candidate for the mass introduction of fuel cells, it is metallic plates made from thin strip materials (typically 0.2 mm thick stainles...

  11. Recent Experimental Advances to Determine (noble) Gases in Waters

    Science.gov (United States)

    Kipfer, R.; Brennwald, M. S.; Huxol, S.; Mächler, L.; Maden, C.; Vogel, N.; Tomonaga, Y.

    2013-12-01

    In aquatic systems noble gases, radon, and bio-geochemically conservative transient trace gases (SF6, CFCs) are frequently applied to determine water residence times and to reconstruct past environmental and climatic conditions. Recent experimental breakthroughs now enable ● to apply the well-established concepts of terrestrial noble gas geochemistry in waters to the minute water amounts stored in sediment pore space and in fluid inclusions (A), ● to determine gas exchange processes on the bio-geochemical relevant time scales of minutes - hours (B), and ● to separate diffusive and advective gas transport in soil air (C). A. Noble-gas analysis in water samples (10.1021/es401698p. [4] Mächler et al. (2012) Environ. Sci. Technol., 47, 7060-7066. [5] Huxol et al. Environ. Sci. Technol., in revision.

  12. International Conference on LIght Detection in Noble Elements

    CERN Document Server

    2016-01-01

    The objective of the Light Detection in Noble Elements (LIDINE) 2015 conference is to promote discussion between the members of the particle and nuclear physics communities about light and charge collection in detectors based on liquid or gaseous noble elements, xenon and argon being the most common, but neon and helium also in use, and represented at this conference. The neutrino physics, ultra-cold neutron study, dark matter search, and medical physics communities all utilize noble-based detector technologies, recording UV scintillation and/or ionization. Therefore, this will be an interdisciplinary opportunity for information exchange, and a chance for each of these communities enumerated above, in the U.S. as well as abroad, to expand their technical knowledge bases.

  13. Modified Electrodes Used for Electrochemical Detection of Metal Ions in Environmental Analysis

    Directory of Open Access Journals (Sweden)

    Gregory March

    2015-04-01

    Full Text Available Heavy metal pollution is one of the most serious environmental problems, and regulations are becoming stricter. Many efforts have been made to develop sensors for monitoring heavy metals in the environment. This review aims at presenting the different label-free strategies used to develop electrochemical sensors for the detection of heavy metals such as lead, cadmium, mercury, arsenic etc. The first part of this review will be dedicated to stripping voltammetry techniques, on unmodified electrodes (mercury, bismuth or noble metals in the bulk form, or electrodes modified at their surface by nanoparticles, nanostructures (CNT, graphene or other innovative materials such as boron-doped diamond. The second part will be dedicated to chemically modified electrodes especially those with conducting polymers. The last part of this review will focus on bio-modified electrodes. Special attention will be paid to strategies using biomolecules (DNA, peptide or proteins, enzymes or whole cells.

  14. Fabrication of Polymer Solar Cells Using Aqueous Processing for All Layers Including the Metal Back Electrode

    DEFF Research Database (Denmark)

    Søndergaard, Roar; Helgesen, Martin; Jørgensen, Mikkel;

    2011-01-01

    The challenges of printing all layers in polymer solar cells from aqueous solution are met by design of inks for the electron-, hole-, active-, and metallic back electrode-layers. The conversion of each layer to an insoluble state after printing enables multilayer formation from the same solvent...

  15. Dual-color encoded DNAzyme nanostructures for multiplexed detection of intracellular metal ions in living cells.

    Science.gov (United States)

    Zhou, Wenjiao; Liang, Wenbing; Li, Daxiu; Yuan, Ruo; Xiang, Yun

    2016-11-15

    The detection of intracellular metal ions is of great importance in understanding metal homeostasis in cells and related diseases, and yet it remains a significant challenge to achieve this goal. Based on a new self-assembled and dual-color encoded DNAzyme nanostructure, we describe here an approach for multiplexed sensing of UO2(2+) and Pb(2+) in living cells. The fluorescently quenched nanoprobes can be prepared by simple thermal annealing of four ssDNAs containing the metal ion-dependent enzymatic and substrate sequences. The self-assembly formation of the nanostructures are verified by native polyacrylamide gel electrophoresis. The target metal ions can cleave the substrate sequences in the DNAzyme nanostructures to recover fluorescent emissions at different wavelengths for sensitive and selective in vitro multiplexed detection of UO2(2+) and Pb(2+) with the detection limits of 0.6nM and 3.9nM, respectively. Importantly, we demonstrate that these nanoprobes are stable in cell lysates and can enter cells without the aid of any transfection agents for simultaneous imaging intracellular UO2(2+) and Pb(2+). Moreover, the nanoprobes offer excellent biocompatibility and non-cytotoxicity. With these unique features, the dual-color encoded nanostructures presented here can thus offer new opportunities for multiplexed detection of specific intracellular species. PMID:27236722

  16. Dual-color encoded DNAzyme nanostructures for multiplexed detection of intracellular metal ions in living cells.

    Science.gov (United States)

    Zhou, Wenjiao; Liang, Wenbing; Li, Daxiu; Yuan, Ruo; Xiang, Yun

    2016-11-15

    The detection of intracellular metal ions is of great importance in understanding metal homeostasis in cells and related diseases, and yet it remains a significant challenge to achieve this goal. Based on a new self-assembled and dual-color encoded DNAzyme nanostructure, we describe here an approach for multiplexed sensing of UO2(2+) and Pb(2+) in living cells. The fluorescently quenched nanoprobes can be prepared by simple thermal annealing of four ssDNAs containing the metal ion-dependent enzymatic and substrate sequences. The self-assembly formation of the nanostructures are verified by native polyacrylamide gel electrophoresis. The target metal ions can cleave the substrate sequences in the DNAzyme nanostructures to recover fluorescent emissions at different wavelengths for sensitive and selective in vitro multiplexed detection of UO2(2+) and Pb(2+) with the detection limits of 0.6nM and 3.9nM, respectively. Importantly, we demonstrate that these nanoprobes are stable in cell lysates and can enter cells without the aid of any transfection agents for simultaneous imaging intracellular UO2(2+) and Pb(2+). Moreover, the nanoprobes offer excellent biocompatibility and non-cytotoxicity. With these unique features, the dual-color encoded nanostructures presented here can thus offer new opportunities for multiplexed detection of specific intracellular species.

  17. NRF2 Oxidative Stress Induced by Heavy Metals is Cell Type Dependent

    Science.gov (United States)

    Exposure to metallic environmental toxicants has been demonstrated to induce a variety of oxidative stress responses in mammalian cells. The transcription factor Nrf2 is activated in response to oxidative stress and coordinates the expression of antioxidant gene products. In this...

  18. Absorption enhancement in metal nanoparticles for photoemission current for solar cells

    DEFF Research Database (Denmark)

    Gritti, Claudia; Novitsky, Andrey; Malureanu, Radu;

    2012-01-01

    In order to improve the photoconversion efficiency, we consider the possibility of increasing the photocurrent in solar cells exploiting the electron photoemission from small metal nanoparticles into a semiconductor. The effect is caused by the absorption of photons and generation of local surfac...

  19. The microstructural origin of strain hardening in two-dimensional open-cell metal foams

    NARCIS (Netherlands)

    Mangipudi, K. R.; van Buuren, S. W.; Onck, P. R.

    2010-01-01

    This paper aims at elucidating the microstructural origin of strain hardening in open-cell metal foams. We have developed a multiscale model that allows to study the development of plasticity at two length scales: (i) the development of plastic zones inside individual struts (microscopic scale) and

  20. Compatibility of copper-electroplated cells with Metal Wrap Through module materials

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, I.J.; Geerligs, L.J.; Olson, C.L.; Goris, M.J.A.A. [ECN Solar Energy, Petten (Netherlands)

    2013-10-16

    As part of the European FP7 RandD project 'Cu-PV', the compatibility of copper-electroplated metal wrapthrough (MWT) cells with conductive adhesives has been investigated. The objectives of this project include to reduce, by the use of copper plating, the amount of silver utilized in cell manufacturing, and to demonstrate the compatibility of high-power n-type back-contact module technology with copper-plated cells. The overall goal is to reduce the impact on the environment of cell and module manufacture. MWT module technology as developed by ECN uses conductive adhesive to make the interconnection between cells and a conductive backsheet foil. These adhesives have been proved to result in very reliable modules in the case of cells with fired silver metallization. To determine the compatibility of conductive adhesive with copper-plated cells, component tests were performed, followed by the manufacture of modules with copperplated cells and conductive adhesive interconnections. Climate chamber testing of these modules showed that the adhesive is compatible with the copper-plated cells. The next steps include further optimization of the plating process and additional testing at the module level.