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Showing papers on "Copper published in 2004"


Journal ArticleDOI
Lei Lu1, Yongfeng Shen1, Xianhua Chen1, Lihua Qian1, Kathy Lu1 
16 Apr 2004-Science
TL;DR: Pure copper samples with a high density of nanoscale growth twins are synthesized and show a tensile strength about 10 times higher than that of conventional coarse-grained copper, while retaining an electrical conductivity comparable to that of pure copper.
Abstract: Methods used to strengthen metals generally also cause a pronounced decrease in electrical conductivity, so that a tradeoff must be made between conductivity and mechanical strength. We synthesized pure copper samples with a high density of nanoscale growth twins. They showed a tensile strength about 10 times higher than that of conventional coarse-grained copper, while retaining an electrical conductivity comparable to that of pure copper. The ultrahigh strength originates from the effective blockage of dislocation motion by numerous coherent twin boundaries that possess an extremely low electrical resistivity, which is not the case for other types of grain boundaries.

2,584 citations


Journal ArticleDOI
TL;DR: The C3-symmetric derivative of polytriazolylamines, TBTA, was shown to be a powerful stabilizing ligand for copper(I), protecting it from oxidation and disproportionation, while enhancing its catalytic activity.

1,344 citations




Journal ArticleDOI
TL;DR: The purpose of this review is to present the information content of spectroscopic methods, which allow one to focus in on the metalloactive site, define its electronic structure, evaluate the role of the protein in determining geometric and Electronic structure, and elucidate the contributions of electronic structure to function.
Abstract: Approximately one-half of all known protein crystal structures in the protein data bank (PDB) contain metal ion cofactors, which play vital roles in charge neutralization, structure, and function.1,2 These proteins range in size from 5000-107 Da with the metal ion corresponding to only on the order of 0.1 wt % of the molecule. Yet, for a wide range of these metalloproteins, the metal ion and its environment are key to the chemistry as these comprise the active site in catalysis. It is the purpose of this review to present the information content of spectroscopic methods, which allow one to focus in on the metalloactive site (Figure 1), define its electronic structure, evaluate the role of the protein in determining geometric and electronic structure, and elucidate the contributions of electronic structure to function. Metalloproteins are simply metal complexes but with remarkably intricate and complex ligands. The metal ion, clusters of metal ions bridged by oxide or sulfide ligands or equatorially chelated by N-heterocyclic ligands (heme, corrin, etc.), are bound to the protein through one or more of the endogenous ligand lone pair donors in Table 1. Note that for most of the donor groups, this requires deprotonation, and the metal ion competition with the proton for the free base lowers the effective pKA by at least several log units from those intrinsic values listed in Table 1. It is important to emphasize that for a number of the ligands in Tables 1 and 2, in particular phenolate, thiolate, oxo and sulfido, and the N-heterocyclic chelates, the metal complex exhibits extremely intense low energy charge transfer (CT) absorption bands, which reflect highly covalent ligand-metal bonds. These make major contributions to the electronic structure of an active site and can be affected by the geometry of the metal site and the orientation of the ligand-metal bond, which in turn can be influenced by the protein matrix. * To whom correspondence should be addressed. † Department of Chemistry, Stanford University. ‡ Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University. 419 Chem. Rev. 2004, 104, 419−458

753 citations


Journal ArticleDOI
TL;DR: The literature dealing with the electrochemical corrosion characteristics of unalloyed copper in aqueous chloride media is examined in this paper, where a wide range of electrode geometries, the importance of the chloride ion and the mass transport of anodic corrosion products on the corrosion behaviour of copper are made clear for both freshly polished and ‘filmed’ surfaces.

609 citations


Journal ArticleDOI
TL;DR: The best fitting of experimental results to the proposed isotherms was observed in models that assume that ionic species bind first at energetically most favorable sites, with multi-layer adsorption taking place subsequently.

531 citations


Journal ArticleDOI
TL;DR: Sorption of copper and nickel on grape stalks released an equivalent amount of alkaline and alkaline earth metals (K+, Mg2+, Ca2+) and protons, indicating that ionic exchange is predominantly responsible for metal ion uptake.

438 citations


Journal ArticleDOI
TL;DR: In this paper, the copper(I)-catalyzed cycloaddition reaction between azides and alkynes has been employed to make metal-adhesive materials, and the resulting materials were found to possess comparable or superior adhesive strength to standard commercial glues, and structure-activity correlations have identified several important properties of the monomers.
Abstract: The copper(I)-catalyzed cycloaddition reaction between azides and alkynes has been employed to make metal-adhesive materials. Copper and brass surfaces supply the necessary catalytic Cu ions, and thus the polymerization process occurs selectively on these metals in the absence of added catalysts. Alternatively, copper compounds can be added to monomer mixtures and then introduced to reducing metal surfaces such as zinc to initiate polymerization. The resulting materials were found to possess comparable or superior adhesive strength to standard commercial glues, and structure-activity correlations have identified several important properties of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4392–4403, 2004

410 citations


Journal ArticleDOI
TL;DR: In this article, the grain size effect on deformation twinning in nanocrystalline copper is studied, and it is shown that twinning becomes a major deformation mechanism in nano-copper during high-pressure torsion under a very slow strain rate and at room temperature.
Abstract: The grain-size effect on deformation twinning in nanocrystalline copper is studied. It has been reported that deformation twinning in coarse-grained copper occurs only under high strain rate and/or low-temperature conditions. Furthermore, reducing grain sizes has been shown to suppress deformation twinning. Here, we show that twinning becomes a major deformation mechanism in nanocrystalline copper during high-pressure torsion under a very slow strain rate and at room temperature. High-resolution transmission electron microscopy investigation of the twinning morphology suggests that many twins and stacking faults in nanocrystalline copper were formed through partial dislocation emissions from grain boundaries. This mechanism differs from the pole mechanism operating in coarse-grained copper.

402 citations


Journal ArticleDOI
TL;DR: In this article, a modified sol-gel process was used to synthesize copper-loaded titania (Cu/TiO2) catalysts for CO 2 photocatalytic reduction and the yield of methanol was evaluated.

Journal ArticleDOI
TL;DR: This paper presents a novel one-step method for preparing of copper nanofluids by reducing CuSO(4).5H(2)O with NaH( 2)PO(2).


Journal ArticleDOI
G. Liu1, Xiang Li1, B. Qin1, D. Xing1, Y. Guo1, R. Fan1 
TL;DR: In this article, the mending effect of copper nano-particles added to lubricant oil was investigated and it has been shown that the heat generated by friction leads to the diffusion of the nano particles and their subsequent deposition, which finally results in the so-called "mending effect".
Abstract: The mending effect and mechanism of metal nano-particles in an area undergoing wear are quite important for both the fundamental theory of nano-tribology and the development of lubricant additives. This paper presents research on the mending effect of copper nano-particles added to lubricant oil. Pin-on-disk experiments and Scanning Electron Microscopy (SEM) observations show that copper nano-particles do display an excellent mending effect. The observation by Scanning Tunnelling Microscopy (STM) reveals that the mending effect results from the deposition of copper nano-particles onto the wear scar. It has also been disclosed by heating simulation that, due to nano-scale effects, which bring about decrease in the diffusion temperature of copper nano-particles, the heat generated by friction leads to the diffusion of copper nano-particles and their subsequent deposition, which finally results in the so-called mending effect.

Journal ArticleDOI
13 Feb 2004-Langmuir
TL;DR: An intraparticle diffusion model successfully describes the kinetics of copper adsorption onto the carbons and brings about substantial variation in the chemical properties whereas the physical properties remain nearly unchanged.
Abstract: Surface modification of activated carbons by various physicochemical methods directs an attractive approach for improvement of heavy metal uptake from aqueous solutions. Activated carbons were modified with HCl and HNO3 optionally followed by NaOH. The effects of surface modifications on the properties of the carbons were studied by the specific surface area, carbon pH, and total acidity capacity as well as by scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The modifications bring about substantial variation in the chemical properties whereas the physical properties remain nearly unchanged. NaOH causes an increase in the content of hydroxyl groups, while the HCl treatment results in an increase in the amount of single-bonded oxygen functional groups such as phenols, ethers, and lactones. The HNO3 modification generates a large number of surface functional groups such as carbonyl, carboxyl, and nitrate groups. The HNO3 modification significantly increases the copper adsorption, while the HCl treatment slightly reduces the copper uptake. Most of the copper ions are adsorbed rapidly in the first 2 h; the adsorption equilibrium is established in around 8 h. An intraparticle diffusion model successfully describes the kinetics of copper adsorption onto the carbons.

Journal ArticleDOI
TL;DR: In this paper, the performance of a series of N-containing ligands, as well as different copper(II) salt precursors in different solvents are reported, and a reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.
Abstract: A novel and very mild method for the oxidation of primary alcohols to aldehydes with excellent conversions has been developed. The reaction is carried out under air at room temperature and is catalysed using a [copper(II)-(N ligand)n] complex with TEMPO and a base as co-catalysts. In this paper, the performance of a series of N-containing ligands, as well as different copper(II) salt precursors in different solvents are reported. Best results are obtained in acetonitrile/water as solvent using a copper(II) catalyst generated in situ from a Cu(II) salt with weak or non-coordinating anions and bipyridine ligands with electron-donating substituents. A reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.

Journal ArticleDOI
10 Sep 2004-Science
TL;DR: Evidence of analogous molecules for copper transport from methane-oxidizing bacteria is presented, represented by a small fluorescent chromopeptide produced by Methylosinus trichosporium OB3b.
Abstract: Siderophores are extracellular iron-binding compounds that mediate iron transport into many cells. We present evidence of analogous molecules for copper transport from methane-oxidizing bacteria, represented here by a small fluorescent chromopeptide (C45N12O14H62Cu, 1216 daltons) produced by Methylosinus trichosporium OB3b. The crystal structure of this compound, methanobactin, was resolved to 1.15 angstroms. It is composed of a tetrapeptide, a tripeptide, and several unusual moieties, including two 4-thionyl-5-hydroxy-imidazole chromophores that coordinate the copper, a pyrrolidine that confers a bend in the overall chain, and an amino-terminal isopropylester group. The copper coordination environment includes a dual nitrogen- and sulfur-donating system derived from the thionyl imidazolate moieties. Structural elucidation of this molecule has broad implications in terms of organo-copper chemistry, biological methane oxidation, and global carbon cycling.

Journal ArticleDOI
TL;DR: In this article, the adsorption of copper(II) ions on to dehydrated wheat bran (DWB), a byproduct of the flour process, was investigated as a function of initial pH, temperature, initial metal ion concentration and adsorbent dosage.

Journal ArticleDOI
TL;DR: In this article, the fluid flow and heat transfer features of cellular metal lattice structures made from copper by transient liquid phase (TLP) bonding and brazing of plane weave copper meshes (screens) were experimentally characterized under steady-state forced air convection.

Journal ArticleDOI
01 Oct 2004-Geoderma
TL;DR: In this paper, the authors measured the accumulation, distribution and fractionation of copper in contaminated and uncontaminated soils as a step towards understanding copper existence in soils and its potential for availability to flora and fauna.

Journal ArticleDOI
TL;DR: Cox17 represents a novel copper chaperone that delivers copper to two proteins, which is specific because no transfer occurs to heterologous proteins, including bovine serum albumin and carbonic anhydrase.

Journal ArticleDOI
TL;DR: Genetic and nutritional studies have illustrated the essential nature of these copper-binding proteins; alterations in their levels are associated with severe pathology.
Abstract: Copper is an essential cofactor for approximately a dozen cuproenzymes in which copper is bound to specific amino acid residues in an active site. However, free cuprous ions react readily with hydrogen peroxide to yield the deleterious hydroxyl radical. Therefore, copper homeostasis is regulated very tightly, and unbound copper is extremely low in concentration. Copper imported by the plasma membrane transport protein Ctr1 rapidly binds to intracellular copper chaperone proteins. Atox1 delivers copper to the secretory pathway and docks with either copper-transporting ATPase ATP7B in the liver or ATP7A in other cells. ATP7B directs copper to plasma ceruloplasmin or to biliary excretion in concert with a newly discovered chaperone, Murr1, the protein missing in canine copper toxicosis. ATP7A directs copper within the transgolgi network to the proteins dopamine beta-monooxgenase, peptidylglycine alpha-amidating monooxygenase, lysyl oxidase, and tyrosinase, depending on the cell type. CCS is the copper chaperone for Cu,Zn-superoxide dismutase; it delivers copper in the cytoplasm and intermitochondrial space. Cox17 delivers copper to mitochondria to cytochrome c oxidase via the chaperones Cox11, Sco1, and Sco2. Other copper chaperones may exist and might include metallothionein and amyloid precursor protein (APP). Genetic and nutritional studies have illustrated the essential nature of these copper-binding proteins; alterations in their levels are associated with severe pathology.

Journal ArticleDOI
TL;DR: In this paper, Nafion, a perfluorosulfonated polymer, was used to solubilize single-wall carbon nanotubes (SWCNTs) to fabricate electrochemical sensors.

Journal ArticleDOI
TL;DR: This work is the first report on the physiological function of copper transport in Arabidopsis thaliana and reveals striking plant growth and development roles for copper acquisition by high affinity copper transporters.

Journal ArticleDOI
TL;DR: In this paper, the feasibility of friction stir welding (FSW) for joining of copper was demonstrated on 4 mm thick copper plate at travel speed of 61 mm/min and tool rotation speed of 1250 rpm using a general tool steel as the welding tool.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the performance of catalysts for preferential oxidation of CO in hydrogen-rich steam reformates using a high surface area (SBET=117-172 m2/g).

Journal ArticleDOI
TL;DR: To measure dissolved copper contributions from recreational vessel antifouling coatings for both passive leaching and hull cleaning activities, three coating formulations, including hard vinyl, modified epoxy and a biocide free bottom paint were applied on fiberglass panels and placed in a harbor environment.

Journal ArticleDOI
TL;DR: In this article, the nucleation and growth of the cerium-based conversion coating on AA2024 was studied using complementary surface analysis techniques, as atomic force microscopy in the Kelvin probe mode (SKPFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).
Abstract: The chemical conversion treatment for aluminium alloys based on the immersion in cerium chloride/hydrogen peroxide solutions is one of the possible alternatives to the chromate conversion process for the corrosion protection of aluminium alloys. The nucleation and growth of the cerium-based conversion coating on AA2024 was studied using complementary surface analysis techniques, as atomic force microscopy in the Kelvin probe mode (SKPFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The influence of both the intermetallic particles and the copper in solid solution was considered. According to this aim, different surface preparation procedures prior to the conversion process were investigated. Acid pickling and Ce-based deoxidising, as well, were found to cause the formation of copper or copper oxide deposits, i.e. copper smut, on the AA2024 surface. While the intermetallics do not act as preferential nucleation sites, the deposition of copper on the surface is a necessary condition in order to form a thick cerium oxide film. On the other hand, the copper smut strongly decreases the adherence of the conversion layer to the aluminium substrate.

Journal ArticleDOI
TL;DR: In this article, copper-doped zinc oxide nanowires were fabricated on a copper-coated silicon substrate by sintering a mixture of zinc oxide and graphite powders at high temperature.
Abstract: Copper-doped zinc oxide nanowires were fabricated on copper-coated silicon substrate by sintering a mixture of zinc oxide and graphite powders at high temperature. Copper functioned as a catalyst in the zinc oxide nanowire growth and was incorporated during the growth as a dopant. The size of copper-doped zinc oxide nanowires ranges from 30 to 100 nm in diameter and tens to hundreds of microns in length. The photoluminescent excitation spectra showed multiple absorption peaks in the ultraviolet and blue/green region. Correspondingly, broad and continuous photoluminescence spectra were observed extending from the ultraviolet to the red region with shoulder peaks at room temperature, which is different from that of the bulk. The x-ray photoelectron spectroscopy and low temperature photoluminescence were employed to analyse the luminescent mechanism.

Journal ArticleDOI
TL;DR: This article discusses the impact of the differences in the material properties and integration process on reliability of copper interconnects, including dielectric breakdown, temperature cycle, and stability within packages.