Showing papers on "Copper published in 1998"
TL;DR: A range of safe intakes should be defined for the general population, including a lower safe intake and an upper safe intake, to prevent deficiency as well as toxicity for most of the population.
836 citations
TL;DR: In this article, two methods, namely thermal reduction and sonochemical reduction of copper(II) hydrazine carboxylate Cu(N2H3COO)2·2H2O complex in an aqueous medium, are presented.
Abstract: Nanoscale particles of metallic copper clusters have been prepared by two methods, namely the thermal reduction and sonochemical reduction of copper(II) hydrazine carboxylate Cu(N2H3COO)2·2H2O complex in an aqueous medium. Both reduction processes take place under an argon atmosphere over a period of 2−3 h. The FT-IR, powder X-ray diffraction, and UV−visible studies support the reduction products of Cu2+ ions as metallic copper nanocrystallites. The powder X-ray analysis of the thermally derived products show the formation of pure metallic copper, while the sonochemical method yields a mixture of metallic copper and copper oxide (Cu2O). The formation of Cu2O along with the copper nanoparticles in the sonochemical process can be attributed to the partial oxidation of copper by in situ generated H2O2 under the sonochemical conditions. However, the presence of a mixture of an argon/hydrogen (95:5) atmosphere yields pure copper metallic nanoparticles, which could be due to the scavenging action of the hydroge...
575 citations
TL;DR: In this article, the authors discuss the construction of functional solid-state supramolecular metal complexes containing copper (I) and silver (I), which are regarded as extremely soft acids favoring coordination to soft bases, such as ligands containing S and unsaturated N. The most common stereochemistries for both ions are the linear two-coordinate and the tetrahedral four-coordinations with some distortions of the environment, particularly in the presence of chelating type ligands, attributable to the spherical dl0 configuration.
Abstract: Publisher Summary This chapter discusses construction of functional solid-state supramolecular metal complexes containing copper (I) and silver (I). The copper(I) and silver(I) ions are regarded as extremely soft acids favoring coordination to soft bases, such as ligands containing S and unsaturated N. Copper(I) and silver(I) complexes with these soft ligands give rise to an interesting array of stereochemistries and geometric configurations, with the coordination numbers of two to six all occurring. The most common stereochemistries for both ions are the linear two-coordinate and the tetrahedral four-coordinate geometries with some distortions of the environment, particularly in the presence of chelating type ligands, attributable to the spherical dl0 configuration. On the basis of resonance Raman spectra, the lowest excited state in the polymer is assigned to the Cu(I)-topyrazine metal-to-ligand charge-transfer excited state. Successful construction of multidimensional frameworks largely relies on ligand design to suit different geometries and coordination numbers of the metal ions.
420 citations
TL;DR: In this article, the reduction of CuO dispersed on fluorite-type oxide catalysts, namely La-doped CeO2 and Ydoped ZrO2, was studied.
Abstract: The reduction of CuO dispersed on fluorite-type oxide catalysts, namely La-doped CeO2 and Y-doped ZrO2 was studied in this work. On both supports distinct copper species were identified as a function of copper content by temperature-programmed reduction (TPR) by H2 and CH4, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and scanning transmission electron microscopy/energy dispersive X-ray (STEM/EDX) analyses. At low copper loading ( 15 at%), in addition to clusters, larger CuO particles are present which are reduced at higher temperature close to the reduction temperature of bulk CuO. At copper loading lower than ca. 5 at%, copper is present as highly dispersed clusters or isolated Cu ions, which interact strongly with the fluorite-type oxide, thus requiring higher reduction temperature. However, the latter is still below the bulk CuO reduction temperature. Copper is more stabilized when dispersed in Ce(La)O2 than in Zr(Y)O2 matrix, so that reduction of copper oxide species requires lower temperatures on the Zr(Y)O2-based catalysts. The reducibility of the doped ceria is enhanced by the presence of copper in both H2- and CH4-TPR. On the other hand no such interaction is present in CuZr(Y)O2 system. The activity of various copper species for methane oxidation is discussed.
379 citations
TL;DR: Variations in the efficiency of the absorption and excretion of copper appear to reflect variations in the intake of other hepatotoxic or protective factors, differences in the cellular distribution of copper, and Differences in the expression of specific copper transport and storage proteins.
342 citations
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TL;DR: Results were extended to show that even in marginal deficiency, when common indexes of copper are not affected by the diet, the proliferative response and interleukin concentrations are reduced, and neutrophils are predicted to be an effective and valuable tool for assessing nutrient status in human populations.
342 citations
TL;DR: In this paper, the basic mechanisms of irradiation embrittlement in reactor pressure vessel steels are reviewed and a detailed identity and etiology of the matrix defects and manganese-nickel-rich phases are discussed.
Abstract: This paper reviews the current understanding of the basic mechanisms of irradiation embrittlement in reactor pressure vessel steels. Radiation enhanced diffusiona at operating temperatures around 290°C leads to the formation of various ultrafine scale hardening phases, including copper rich and copper catalysed manganese-nickel rich precipitates. Other nanofeatures that do not require copper, so-called matrix defects, include alloy phosphides and carbonitrides as well as defect cluster-solute complexes. Matrix defects that are thermally unstable (anneal) under irradiation play a very important role in mediating flux and temperature effects. The balance of features depends on the composition of the steel and the irradiation conditions. Copper enriched phases, which are the dominant embrittling feature in alloys containing significant trace quantities of this element, are fairly well understood. In contrast, the detailed identity and etiology of the matrix defects and manganese-nickel rich phases t...
330 citations
TL;DR: The addition of polyethylene glycol (PEG) and Cl -to an acid copper electrolyte inhibits the deposition reaction for cathodic overpotentials of up to about 150 mV as mentioned in this paper.
Abstract: The addition of polyethylene glycol (PEG) and Cl - to an acid copper electrolyte inhibits the deposition reaction for cathodic overpotentials of up to about 150 mV. Adding Cl - only promotes the deposition reaction, while adding PEG alone has a relatively small effect on electrode kinetics. Frequency shifts of an electrochemical quartz crystal microbalance suggest the adsorption of a monolayer of PEG molecules that are collapsed into spheres provided chloride ions are present, with little adsorption occurring when Cl - is absent. This behavior is the same for gold and copper surfaces. Transient current measurements suggest that chloride ions affect the PEG adsorption equilibrium rather than adsorption kinetics alone.
329 citations
TL;DR: In this paper, a series of characterizations on the film quality by scanning electron microscope, X-ray photoelectron spectroscopy, Xray diffraction and Fourier transform infrared spectrometer has been made, and the performance of solar thermal conversion are also identified on the produced films.
320 citations
TL;DR: In this article, the redox properties of Cu ions implanted in ZSM-5 and supported on Al2O3, catalysts active in the selective reduction of NO by hydrocarbons such as propane, are investigated.
Abstract: This paper deals with the redox properties of Cu ions implanted in ZSM-5 and supported on Al2O3, catalysts active in the selective reduction of NO by hydrocarbons such as propane. Data on the reducibility of the Cu systems in various atmospheres (vacuum, CO, H2, O2) and on their DeNOx activity are presented. The methods used to obtain informations on the surface and bulk transformations (and their link with catalytic behaviour) are complementary: UV–visible diffuse reflectance spectroscopy being useful to detect the presence of Cu2+ and Cu0, while Cu+ is detected indirectly by the analysis of the IR spectrum of CO bound selectively to this cation. The main contributions to the previous knowledge are the following: it is possible to distinguish CO bound to isolated and non-isolated Cu+ ions; the isolated Cu2+ ions are reducible under vacuum without participation of organic impurities; the more active solids for the NO reduction into N2 are characterized by the presence of isolated Cun+ ions beside the additional influence of the zeolitic framework; after the formation of Cu+ ions the redox cycles are reversible but, after the formation of Cu0, the reversibility or irreversibility of the redox cycles and the restoration of the SCR activity are function of the copper content; the activity decreases after agglomeration into bulk oxides; there is no formation of bulk CuO during the reaction and, with reducing and moderate oxidizing mixtures, part of the copper remains as cuprous ions.
312 citations
Patent•
12 Feb 1998TL;DR: In this paper, a conductive interconnect is formed in a semiconductor device by depositing a dielectric layer (28 ) on the semiconductor substrate, and a tantalum nitride barrier layer is then formed within the interconnect opening.
Abstract: In one embodiment, a conductive interconnect ( 38 ) is formed in a semiconductor device by depositing a dielectric layer ( 28 ) on a semiconductor substrate ( 10 ). The dielectric layer ( 28 ) is then patterned to form an interconnect opening ( 29 ). A tantalum nitride barrier layer ( 30 ) is then formed within the interconnect opening ( 29 ). A catalytic layer ( 31 ) comprising a palladium-tin colloid is then formed overlying the tantalum nitride barrier layer ( 30 ). A layer of electroless copper ( 32 ) is then deposited on the catalytic layer ( 31 ). A layer of electroplated copper ( 34 ) is then formed on the electroless copper layer ( 32 ), and the electroless copper layer ( 32 ) serves as a seed layer for the electroplated copper layer ( 34 ). Portions of the electroplated copper layer ( 34 ) are then removed to form a copper interconnect ( 38 ) within the interconnect opening ( 29 ).
TL;DR: Regulation is not sufficient with very low amounts of dietary copper and appears to be delayed when copper intake is high, so the use of isotopic tracers and kinetic modeling should aid in elucidating the regulatory mechanisms.
TL;DR: Sunflower stalks as adsorbents for the removal of metal ions such as copper, cadmium, zinc, and chromium ions in aqueous solutions were studied with equilibrium isotherms and kinetic adsorptions as discussed by the authors.
Abstract: Sunflower stalks as adsorbents for the removal of metal ions such as copper, cadmium, zinc, and chromium ions in aqueous solutions were studied with equilibrium isotherms and kinetic adsorptions. The maximum adsorptions of four heavy metals are 29.3 mg/g (Cu2+), 30.73 mg/g (Zn2+), 42.18 mg/g (Cd2+), and 25.07 mg/g (Cr3+), respectively. Particle sizes of sunflower stalks affected the adsorption of metal ions; the finer size of particles showed better adsorption to the ions. Temperature also plays an interesting role in the adsorption of different metal ions. Copper, zinc, and cadmium exhibited lower adsorption on sunflower stalks at higher temperature, while chromium showed the opposite phenomenon. The adsorption rates of copper, cadmium, and chromium are quite rapid. Within 60 min of operation about 60−80% of these ions were removed from the solutions.
TL;DR: In this article, the influence of the physical and chemical deposition parameters on the nanostructure of the deposits and demonstrate that the grain size can be tuned to values between 13 and 93 nm, with rather narrow grain size distribution.
Abstract: Pulsed electrodeposition is a simple, yet versatile method for the production of nanostructured metals. For n-nickel we determine the influence of the physical and chemical deposition parameters on the nanostructure of the deposits and demonstrate that the grain size can be tuned to values between 13 and 93 nm, with rather narrow grain size distribution. The thermal stability of our n-nickel as studied by x-ray diffraction and differential thermal analysis exhibits no detectable grain growth up to temperatures of about 380 K and an initial
$$\sqrt t $$
behavior at 503 K followed by a regime of anomalous grain growth. For nanocrystalline Ni1-x Cux (Monel-metal™) we demonstrate that alloy formation occurs at room temperature and that both chemical composition and grain size can be controlled by the pulse parameters and by appropriate organic additives.
TL;DR: Titania and titania modified with 3 and 12 mu mol Ce/m(2) surface area of the titania were prepared and were used as supports for copper oxide as mentioned in this paper.
TL;DR: In this article, a gamma radiolysis method was used to synthesize capped copper nanoclusters by optimizing various conditions like metal ion concentration, polymer or surfactant concentration and pH.
TL;DR: In this paper, a series of heterocyclic base adducts of copper(II) complexes have been synthesised by the reaction of copper (II) acetate with salicylaldehyde N(4)-phenylthiosemicarbazone in presence of pyridine (py), piperidine (pip), β/γ-picoline (β/γ)-pic), 1,10-phenanthroline (phen) and 2,2′-bipyridine(bipy).
TL;DR: In this article, the authors used ammonium carbonate and nitric acid washing solutions to extract uncombined copper oxide and showed that ammonium-carbonate was only effective for removing dispersed CuO, whereas nitric acids removed both dispersed and crystalline CuO. The results indicated that the active sites are copper species derived from CuAl2O4 and CuCr2O 4 spinels rather than from CuO and indicated that Cu species in tetrahedral coordination lead to higher activity.
TL;DR: Experimental data support the existence of a carrier-mediated transport mechanism with an affinity constant in the micromolar range, and organic acids, other than ascorbic acid, or agents that form low-molecular-weight chelates, are likely to have a positive effect on overall copper absorption.
Patent•
25 Feb 1998TL;DR: In this article, a method and apparatus for improving the adhesion of a copper layer to an underlying layer on a wafer is presented, where the layer of copper is formed over a layer of material on the wafer and the copper layer impacted with ions to improve its adhesion to the underlying layer.
Abstract: A method and apparatus for improving the adhesion of a copper layer to an underlying layer on a wafer. The layer of copper is formed over a layer of material on a wafer and the copper layer impacted with ions to improve its adhesion to the underlying layer.
TL;DR: In this article, the effect of the copper loading and calcination temperature on the structure and performance of Cu/Ni|K|γ-Al2O3 catalysts was examined. But the results were limited to the case of ethanol.
TL;DR: In this article, a model for copper deposition in the presence of polyethylene glycol (PEG) and Cl- ions was proposed. But the model assumes the adsorption of a nearly complete monolayer of PEG in the absence of chloride ions and no adsorptions without Cl- ion.
Abstract: Electrochemical impedance spectroscopy (EIS) results are shown and interpreted with regard to other recent experimental studies for copper deposition in the presence of polyethylene glycol and Cl - . The model assumes the adsorption of a nearly complete monolayer of PEG in the presence of chloride ions and no adsorption without Cl - . The primary effect of PEG adsorption which does not appear to vary with time during an EIS measurement, is a blocking of available surface sites for charge transfer. The model effectively predicts changes in steady-state and EIS results with changes in Cl - concentration and rotation rate on a rotating disk electrode.
TL;DR: Copper-containing enzymes in blood cells, such as erythrocyte superoxide dismutase and platelet cytochrome-c oxidase, may be better indicators of metabolically active copper and copper stores than plasma concentrations of copper or ceruloplasmin because the enzyme activities are sensitive to changes in copper stores and are not as sensitive to factors not related to copper nutriture.
TL;DR: It is demonstrated that the nutritional and toxic copper metalloregulatory transcription factors Mac1p and Ace1p must sense and respond to copper ions in a dynamic fashion to appropriately regulate copper ion homeostasis and establish the requirement for a wild-type Mac1P for survival in the presence of toxic copper levels.
Abstract: The essential yet toxic nature of copper demands tight regulation of the copper homeostatic machinery to ensure that sufficient copper is present in the cell to drive essential biochemical processes yet prevent the accumulation to toxic levels. In Saccharomyces cerevisiae, the nutritional copper sensor Mac1p regulates the copper-dependent expression of the high affinity Cu(I) uptake genes CTR1, CTR3, and FRE1, while the toxic copper sensor Ace1p regulates the transcriptional activation of the detoxification genes CUP1, CRS5, and SOD1 in response to copper. In this study, we characterized the tandem regulation of the copper uptake and detoxification pathways in response to the chronic presence of elevated concentrations of copper ions in the growth medium. Upon addition of CuSO4, mRNA levels of CTR3 were rapidly reduced to eightfold the original basal level whereas the Ace1p-mediated transcriptional activation of CUP1 was rapid and potent but transient. CUP1 expression driven by an Ace1p DNA binding domain-herpes simplex virus VP16 transactivation domain fusion was also transient, demonstrating that this mode of regulation occurs via modulation of the Ace1p copper-activated DNA binding domain. In vivo dimethyl sulfate footprinting analysis of the CUP1 promoter demonstrated transient occupation of the metal response elements by Ace1p which paralleled CUP1 mRNA expression. Analysis of a Mac1p mutant, refractile for copper-dependent repression of the Cu(I) transport genes, showed an aberrant pattern of CUP1 expression and copper sensitivity. These studies (i) demonstrate that the nutritional and toxic copper metalloregulatory transcription factors Mac1p and Ace1p must sense and respond to copper ions in a dynamic fashion to appropriately regulate copper ion homeostasis and (ii) establish the requirement for a wild-type Mac1p for survival in the presence of toxic copper levels.
TL;DR: In this article, amorphous derivatives of kaolinites were prepared by thermal modification followed by acid activation, which improved the exchangeability of kaolinite and showed that the initial 1 h was sufficient to exchange most of the metal ions.
TL;DR: In this paper, the effect of a range of preparation variables are investigated in detail, including the precipitate ageing time, pH and temperature of precipitation, the Cu/Mn ratio of the precipitation solution and the catalyst calcination temperature.
Abstract: Copper manganese oxides are prepared using a coprecipitation procedure and studied for the oxidation of CO at ambient temperature. In particular, the effect of a range of preparation variables are investigated in detail. The variables investigated include the precipitate ageing time, pH and temperature of precipitation, the Cu/Mn ratio of the precipitation solution and the catalyst calcination temperature. The optimum preparation conditions are identified with respect to the catalyst activity for the oxidation of CO at ambient temperature. The results are interpreted in terms of the structure of the active catalyst. Generally it has been concluded that catalysts containing copper/manganese mixed phases are found to be the most active.
TL;DR: Solution-state absorption and (1)H NMR spectra indicate that the [Cu(dpp)(2)](+) complex is fluxional in solution, rocking between two enantiomeric structures of C(2) molecular symmetry through an intermediate ofC(s)() symmetry.
Abstract: The syntheses, crystal structures, and electronic absorption spectra of the copper(I) and copper(II) complexes of 2,9-diphenyl-1,10-phenanthroline (dpp) are reported. The complex [Cu(dpp)2](PF6) (1) crystallizes in space group P21/c with a = 11.081(4) A, b = 25.491(8) A, c = 14.263(5) A, β = 92.84(3)°, Z = 4, and V = 4024(2) A3. For 4813 unique data with F > 4.0σ(F), R = 5.41% and Rw = 6.43%. The coordination geometry about the copper(I) center in [Cu(dpp)2]+ is best described as distorted tetrahedral with approximate C2 symmetry. The structure of [Cu(dpp)2]+ is largely determined by interligand π-stacking interactions that occur between the phenyl groups of one ligand and the phenanthroline moiety of the other ligand. Solution-state absorption and 1H NMR spectra indicate that the [Cu(dpp)2]+ complex is fluxional in solution, rocking between two enantiomeric structures of C2 molecular symmetry through an intermediate of Cs symmetry. The complex [Cu(dpp)2](ClO4)2 (2) crystallizes in space group P1 with a ...
TL;DR: In this article, the rates of metal aluminate formation in MeOx/Al2O3 systems (Me=Ni, Co, Cu, Fe) at 500-1000°C in O2 or N2atmospheres were compared, using bothα-Al2 o3 andγ-Al 2 o3substrates.
02 Sep 1998
TL;DR: In this paper, the authors investigated intermetallic anode materials based on tin, which can provide a high capacity at a slightly higher voltage than metallic lithium and thus reduce the safety concerns associated with the carbon anode.
Abstract: Lithium batteries are typically constructed from a lithium cobalt oxide cathode and a carbon anode. We have investigated intermetallic anode materials based on tin, which can provide a high capacity at a slightly higher voltage (400 mV) than metallic lithium and thus reduce the safety concerns associated with the carbon anode. In particular, we have investigated the copper-tin system at around the composition Cu{sub 6}Sn{sub 5} and have determined the effect on cycling and capacity of electrodes with various ratios of copper to tin. Anode compositions that are slightly copper rich (Cu{sub 6}Sn{sub 4}) were found to exhibit greater utilization of the tin than those with the stoichiometric bronze ratio (Cu{sub 6}Sn{sub 5}) or those having a slight excess of tin (Cu{sub 6}Sn{sub 6}). The differences in electrochemical behavior are explained in terms of an inert matrix model.
TL;DR: In this paper, thin films of copper sulphide with thickness up to m were deposited at C on glass substrates from a solution containing copper(II) chloride, sodium thiosulphate and dimethylthiourea.
Abstract: Thin films of copper sulphide with thickness up to m were deposited at C on glass substrates from a solution containing copper(II) chloride, sodium thiosulphate and dimethylthiourea. As prepared and after annealing at C in (100 millitorr), these films showed x-ray diffraction patterns matching that of the mineral covellite (CuS). Annealing the films for 1 h each at C and C in nitrogen resulted in their conversion to S (digenite) and S (chalcocite), respectively. The reduction in sulphur content of the films is evident in the x-ray florescence spectra. The sheet resistance of the films varied with annealing temperature. For a film of m thickness, the observed sheet resistance values are: (as prepared), (C), (C) and (C). The low sheet resistance (and thus the high conductivity, ) leads to a high near-infrared reflectance for the films, 65% (CuS) and 40% (S), at a wavelength of 2500 nm. Analyses of the optical band gap of the films indicate an indirect gap of 1.55 eV for CuS and S and 1.4 eV for S.