Showing papers on "Copper published in 2006"

Handbook of metalloproteins

Abstract: Volume 1 IRON Heme Proteins: Oxygen Storage and Oxygen Transport Proteins Heme Proteins: Cytochromes Heme Proteins: Cytochrome Peroxidases Heme Proteins: Cytochrome P-450 Heme Proteins: Oxidoreductases Non-Heme Proteins: Iron-Sulfur Clusters Non-Heme Proteins: Mononuclear Iron Proteins Volume 2 IRON continued Non-Heme Proteins: Dinuclear Iron Proteins Non-Heme Proteins: Iron Storage Non-Heme Proteins: Iron Transport NICKEL MANGANESE COBALT MOLYBDENUM/TUNGSTEN COPPER Cupredoxins (Type-1 Copper Proteins) Type-2 Copper Enzymes Binuclear Copper: Type-3 Copper Enzymes Binuclear Copper: CuA Copper Multicopper Enzymes Copper Storage and Transport VANADIUM.

Single-walled carbon nanotube growth from highly activated metal nanoparticles.

Abstract: We demonstrate that any metal, even gold, silver, and copper, can act as a catalyst for SWCNT synthesis in chemical vapor deposition (CVD). Metal nanoparticles 3 nm or less in diameter, introduced into CVD ambience immediately after heat treatment at 800-950 degrees C in air, produce SWCNTs. The activation method is effective for copper and various noble metals as well as for iron-family elements. This implies that any metal particle may produce SWCNTs when its size becomes 1-3 nm. In other words, carbon atoms can form SWCNTs in a self-assembling fashion on nanoparticles without the specific functions of iron-family elements.

Copper Catalyzing Growth of Single-Walled Carbon Nanotubes on Substrates

Abstract: Metallic copper, which is normally considered as a contaminant in the growth of single-walled carbon nanotubes (SWNTs), was found to be an efficient catalyst to grow SWNTs under suitable conditions. It showed very high catalytic activity for the growth of both random SWNT networks and horizontally aligned SWNT arrays. Especially, high-quality SWNT arrays were obtained when monodispersed copper nanoparticles were used. The catalytic behavior of copper for the growth of SWNTs was discussed. The weaker interaction between the copper and silica surfaces plays an important role in the growth of high-quality horizontally aligned SWNT arrays. This new synthesis process of SWNTs with a non-ferromagnetic catalyst brings more convenience to the study of magnetic properties of SWNTs and gives more insight in structure-controlled synthesis of SWNTs.

Quantitative Analysis of Copper Oxide Nanoparticle Composition and Structure by X-ray Photoelectron Spectroscopy

Abstract: Quantitative determination of oxide nanoparticle composition and structure by X-ray photoelectron spectroscopy (XPS) has proven difficult for metal oxides because of three factors: some oxide nanoparticles are prone to reduction in the XPS instrument under X-ray illumination in the ultrahigh vacuum (UHV) environment; the nanoparticle structure and integral nature of the XPS technique complicate the data analysis; and the composition is not constant during the finite sampling time required for the XPS experiment. In this report, a method for XPS analysis of core−shell nanoparticle composition and structure is developed to account for these factors quantitatively. The method is applied to characterize the copper(II) oxide (CuO) surface layer on copper(I) oxide (Cu2O) nanoparticles as well as the reduction kinetics of Cu2+ when held under X-ray irradiation in the XPS chamber. The XPS analysis is aided by the availability of copper oxide nanoparticles with a narrow size distribution. When corrected for the f...

Large-scale production of carbon-coated copper nanoparticles for sensor applications.

Abstract: Copper nanoparticles with a mean carbon coating of about 1 nm were continuously produced at up to 10 g h−1 using a modified flame spray synthesis unit under highly reducing conditions. Raman spectroscopy and solid state 13C magic angle spinning nuclear magnetic resonance spectroscopy revealed that the thin carbon layer consisted of a sp2-hybridized carbon modification in the form of graphene stacks. The carbon layer protected the copper nanoparticles from oxidation in air. Bulk pills of pressed carbon/copper nanoparticles displayed a highly pressure- and temperature-dependent electrical conductivity with sensitivity at least comparable to commercial materials. These properties suggest the use of thin carbon/copper nanocomposites as novel, low-cost sensor materials and offer a metal-based alternative to the currently used brittle oxidic spinels or perovskites.

Oxygen adsorption and stability of surface oxides on Cu ( 111 ) : A first-principles investigation

Abstract: As a first step towards gaining microscopic understanding of copper-based catalysts, e.g., for the low-temperature water-gas shift reaction and methanol oxidation reactions, we present density-functional theory calculations investigating the chemisorption of oxygen, and the stability of surface oxides on $\mathrm{Cu}(111)$. We report atomic geometries, binding energies, and electronic properties for a wide range of oxygen coverages, in addition to the properties of bulk copper oxide. Through calculation of the Gibbs free energy, taking into account the temperature and pressure via the oxygen chemical potential, we obtain the $(p,T)$ phase diagram of $\mathrm{O}∕\mathrm{Cu}(111)$. Our results show that for the conditions typical of technical catalysis the bulk oxide is thermodynamically most stable. If, however, formation of this fully oxidized surface is prevented due to a kinetic hindering, a thin surface-oxide structure is found to be energetically preferred compared to chemisorbed oxygen on the surface, even at very low coverage. Similarly to the late $4d$ transition metals (Ru, Rh, Pd, Ag), sub-surface oxygen is found to be energetically unfavorable.

Effect of Pressure on the Behavior of Copper-, Iron-, and Nickel-Based Oxygen Carriers for Chemical-Looping Combustion

Abstract: The combustion process integrated by coal gasification and chemical-looping combustion (CLC) could be used in power plants with a low energy penalty for CO2 capture. This work analyzes the main characteristics related to the CLC process necessary to use the syngas obtained in an integrated gasification combined cycle (IGCC) power plant. The kinetics of reduction with H2 and CO and oxidation with O2 of three high-reactivity oxygen carriers used in the CLC system have been determined in a thermogravimetric analyzer at atmospheric pressure. The iron- and nickel-based oxygen carriers were prepared by freeze-granulation, and the copper-based oxygen carrier was prepared by impregnation. The changing grain size model (CGSM) was used for the kinetic determination, assuming spherical grains for the freeze-granulated particles containing iron and nickel and a platelike geometry for the reacting surface of the copper-based impregnated particles. The dependence of the reaction rates on temperature was low, with the a...

A Low-Power Nonvolatile Switching Element Based on Copper-Tungsten Oxide Solid Electrolyte

Abstract: We describe the materials aspects and electrical characteristics of W-(Cu/WO3)-Cu switching elements. These materials are compatible with back-end-of-line processing in CMOS integrated circuits where both tungsten and copper already play a significant role. Devices based on Cu/WO3 solid electrolytes formed by photodiffusion of copper into tungsten oxide switch via the electrochemical formation of a conducting filament within the high resistance electrolyte film. They are able to switch reversibly between widely spaced nonvolatile resistance states at low voltage ( 125 degC). This difference in behavior was attributed to the observation that the copper tends to oxidize in the plasma-grown oxide whereas the copper in the deposited oxide exists in an unbound state and is, therefore, more able to participate in the switching process

Atomic Layer Deposition of Ultrathin Copper Metal Films from a Liquid Copper(I) Amidinate Precursor

Abstract: We report a method for producing thin, completely continuous and highly conductive copper films conformally inside very narrow holes with aspect ratios over 35:1 by atomic layer deposition (ALD). Pure copper thin films were grown from a novel copper(I) amidinate precursor, copper(I) N,N'-di-sec-butylacetamidinate, and molecular hydrogen gas as the reducing agent. This copper precursor is a liquid during vaporization because its melting point (77°C) is lower than its vaporization temperature (90-120°C). Thus, the transport of the precursor vapor is very reproducible and controllable. Carbon and oxygen impurities were below 1 atom %. The growth per cycle varied from 1.5-2 A/cycle on SiO 2 or Si 3 N 4 surfaces but was only 0.1-0.5 A/cycle on metallic Ru, Cu, and Co surfaces. On oxide surfaces, copper atoms form isolated copper crystallites that merge into rough polycrystalline films after more deposition cycles. On Ru and Co metal surfaces ALD Cu nucleates densely, forming smooth and strongly adherent films that are continuous even for films as thin as 4 atomic layers. With 4 nm Cu deposited on 2 nm Ru substrates, the sheet resistance is below 50 Ω/□, which is low enough for making seed layers for electroplating Cu interconnect wires.

The Atx1-Ccc2 complex is a metal-mediated protein-protein interaction.

Abstract: Cellular systems allow transition-metal ions to reach or leave the cell or intracellular locations through metal transfer between proteins. By coupling mutagenesis and advanced NMR experiments, we structurally characterized the adduct between the copper chaperone Atx1 and the first copper(I)-binding domain of the Ccc2 ATPase. Copper was required for the interaction. This study provides an understanding of metal-mediated protein-protein interactions in which the metal ion is essential for the weak, reversible interaction between the partners.

A sensitized europium complex generated by micromolar concentrations of copper(I): toward the detection of copper(I) in biology.

Abstract: Formation of a luminescent device by the Huisgen 1,3-dipolar cycloaddition reaction between a Eu(III) complex and dansyl azide is reported. This reaction is catalyzed by a common biological copper(I) complex [GS--Cu(I)], and the resultant copper(I) catalytic sensor shows a 10-fold enhancement of europium luminescence emission.

Contact metallization scheme using a barrier layer over a silicide layer

Abstract: Embodiments of the invention generally provide methods of filling contact level features formed in a semiconductor device by depositing a barrier layer over the contact feature and then filing the layer using an PVD, CVD, ALD, electrochemical plating process (ECP) and/or electroless deposition processes. In one embodiment, the barrier layer has a catalytically active surface that will allow the electroless deposition of a metal on the barrier layer. In one aspect, the electrolessly deposited metal is copper or a copper alloy. In one aspect, the contact level feature is filled with a copper alloy by use of an electroless deposition process. In another aspect, a copper alloy is used to from a thin conductive copper layer that is used to subsequently fill features with a copper containing material by use of an ECP, PVD, CVD, and/or ALD deposition process. In one embodiment, a portion of the barrier layer is purposely allowed to react with traces of residual oxide at the silicon junction of the contact level feature to form a low resistance connection.