Showing papers on "Copper published in 2010"

How copper catalyzes the electroreduction of carbon dioxide into hydrocarbon fuels

Abstract: Density functional theory calculations explain copper's unique ability to convert CO2 into hydrocarbons, which may open up (photo-)electrochemical routes to fuels.

The Growth Mechanism of Copper Nanowires and Their Properties in Flexible, Transparent Conducting Films

Abstract: Copper nanowires grow from spherical copper seeds in an aqueous solution. Conductive films of copper nanowires have a transmittance of 65% (similar to 15% more than the best values reported for carbon nanotubes), and remain conductive after 1000 bending cycles or one month in air.

Investigations into the antibacterial behavior of copper nanoparticles against Escherichia coli

Abstract: Zerovalent copper nanoparticles (Cu0) of 12 nm size were synthesized using an inert gas condensation method in which bulk copper metal was evaporated into an inert environment of argon with subsequent cooling for nucleation and growth of nanoparticles Crystalline structure, morphology and estimation of size of nanoparticles were carried out by X-ray diffraction and transmission electron microscopy The antibacterial activity of these nanoparticles against the Gram-negative bacterium Escherichia coli was assessed in liquid as well as solid growth media It was observed from scanning electron microscopic analysis that the interaction of copper nanoparticles with E coli resulted in the formation of cavities/pits in the bacterial cell wall The antibacterial property of copper nanoparticles was attributed mainly to adhesion with bacteria because of their opposite electrical charges, resulting in a reduction reaction at the bacterial cell wall Nanoparticles with a larger surface-to-volume ratio provide more efficient means for antibacterial activity

Electrocatalytic CO2 conversion to oxalate by a copper complex.

Abstract: Global warming concern has dramatically increased interest in using CO2 as a feedstock for preparation of value-added compounds, thereby helping to reduce its atmospheric concentration. Here, we describe a dinuclear copper(I) complex that is oxidized in air by CO2 rather than O2; the product is a tetranuclear copper(II) complex containing two bridging CO2-derived oxalate groups. Treatment of the copper(II) oxalate complex in acetonitrile with a soluble lithium salt results in quantitative precipitation of lithium oxalate. The copper(II) complex can then be nearly quantitatively electrochemically reduced at a relatively accessible potential, regenerating the initial dinuclear copper(I) compound. Preliminary results demonstrate six turnovers (producing 12 equivalents of oxalate) during 7 hours of catalysis at an applied potential of –0.03 volts versus the normal hydrogen electrode.

Affinity gradients drive copper to cellular destinations

Abstract: Copper is an essential trace element for eukaryotes and most prokaryotes. However, intracellular free copper must be strictly limited because of its toxic side effects. Complex systems for copper trafficking evolved to satisfy cellular requirements while minimizing toxicity. The factors driving the copper transfer between protein partners along cellular copper routes are, however, not fully rationalized. Until now, inconsistent, scattered and incomparable data on the copper-binding affinities of copper proteins have been reported. Here we determine, through a unified electrospray ionization mass spectrometry (ESI-MS)-based strategy, in an environment that mimics the cellular redox milieu, the apparent Cu(I)-binding affinities for a representative set of intracellular copper proteins involved in enzymatic redox catalysis, in copper trafficking to and within various cellular compartments, and in copper storage. The resulting thermodynamic data show that copper is drawn to the enzymes that require it by passing from one copper protein site to another, exploiting gradients of increasing copper-binding affinity. This result complements the finding that fast copper-transfer pathways require metal-mediated protein-protein interactions and therefore protein-protein specific recognition. Together with Cu,Zn-SOD1, metallothioneins have the highest affinity for copper(I), and may play special roles in the regulation of cellular copper distribution; however, for kinetic reasons they cannot demetallate copper enzymes. Our study provides the thermodynamic basis for the kinetic processes that lead to the distribution of cellular copper.

Copper Coordination in Cu-SSZ-13 and Cu-SSZ-16 Investigated by Variable-Temperature XRD

Abstract: Nitrogen oxides (NOx) are a major atmospheric pollutant produced through the combustion of fossil fuels in internal combustion engines. Copper-exchanged zeolites are promising as selective catalytic reduction catalysts for the direct conversion of NO into N2 and O2, and recent reports have shown the enhanced performance of Cu-CHA catalysts over other zeolite frameworks in the NO decomposition of exhaust gas streams. In the present study, Rietveld refinement of variable-temperature XRD synchrotron data obtained for Cu-SSZ-13 and Cu-SSZ-16 is used to investigate the location of copper cations in the zeolite pores and the effect of temperature on these sites and on framework stability. The XRD patterns show that the thermal stability of SSZ-13 is increased significantly when copper is exchanged into the framework compared with the acid form of the zeolite, H-SSZ-13. Cu-SSZ-13 is also more thermally stable than Cu-SSZ-16. From the refined diffraction patterns, the atomic positions of atoms, copper locations a...

Highly Stabilized and Finely Dispersed Cu2O/TiO2: A Promising Visible Sensitive Photocatalyst for Continuous Production of Hydrogen from Glycerol:Water Mixtures

Abstract: Cu-doped TiO2 with varying amounts of Cu (0.2, 0.3, 0.5, 1, 2, and 5) are prepared by impregnation method and calcined at 350 and 450 °C for 5 h. These catalysts are characterized by X-ray diffraction, diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy energy-dispersive X-ray spectroscopy (EDAX), and transmission electron microscopy (TEM). The DRS studies are clearly showing the expanded photo response of TiO2 into the visible region on impregnation of copper ions. TEM images are depicting the fine dispersion of Cu particles on TiO2 surface. XPS studies are showing change in the binding energy values of Ti 2p, O 1s, and Cu 2p, indicating that copper ions are in interaction with TiO2. XPS results are also confirming that the oxidation state of copper is +2 in samples calcined at 350 °C and +1 in samples calcined at 450 °C. EDAX analysis supports the presence of copper species on the surface layers of TiO2. Photocatalytic hydrogen production activity...

Copper Nanoparticles for Printed Electronics: Routes Towards Achieving Oxidation Stability

Abstract: In the past few years, the synthesis of Cu nanoparticles has attracted much attention because of its huge potential for replacing expensive nano silver inks utilized in conductive printing. A major problem in utilizing these copper nanoparticles is their inherent tendency to oxidize in ambient conditions. Recently, there have been several reports presenting various approaches which demonstrate that copper nanoparticles can resist oxidation under ambient conditions, if they are coated by a proper protective layer. This layer may consist of an organic polymer, alkene chains, amorphous carbon or graphenes, or inorganic materials such as silica, or an inert metal. Such coated copper nanoparticles enable achieving high conductivities by direct printing of conductive patterns. These approaches open new possibilities in printed electronics, for example by using copper based inkjet inks to form various devices such as solar cells, Radio Frequency Identification (RFID) tags, and electroluminescence devices. This paper provides a review on the synthesis of copper nanoparticles, mainly by wet chemistry routes, and their utilization in printed electronics.

Copper recovery combined with electricity production in a microbial fuel cell.

Abstract: A metallurgical microbial fuel cell (MFC) is an attractive alternative for recovery of copper from copper containing waste streams, as the metal is recovered in its metallic form at the cathode, while the energy for metal reduction can be obtained from oxidation of organic materials at the anode with possible additional production of electricity. We studied the recovery of copper in an MFC using a bipolar membrane as a pH separator. Under anaerobic conditions, the maximum power density was 0.43 W/m2 at a current density of 1.7 A/m2. In the presence of oxygen, MFC performance improved considerably to a maximum power density of 0.80 W/m2 at a current density of 3.2 A/m2. Pure copper crystals were formed on the cathode, and no CuO or Cu2O was detected. Removal efficiencies of >99.88% were obtained. The cathodic recovery of copper compared to the produced electricity was 84% (anaerobic) and 43% (aerobic). The metallurgy MFC with the Cu2+ reducing cathode further enlarges the application range of MFCs.

Adsorption of copper, nickel and lead ions from synthetic semiconductor industrial wastewater by palm shell activated carbon

Abstract: Granular activated carbon produced from palm kernel shell was used as adsorbent to remove copper, nickel and lead ions from a synthesized industrial wastewater.Laboratory experimental investigation was carried out to identify the effect of pH and contact time on adsorption of lead, copper and nickel from the mixed metals solution. Equilibrium adsorption experiments at ambient room temperature were carried out and fitted to Langmuir and Freundlich models. Results showed that pH 5 was the most suitable, while the maximum adsorbent capacity was at a dosage of 1 g/L, recording a sorption capacity of 1.337 mg/g for lead, 1.581 mg/g for copper and 0.130 mg/g for nickel. The percentage metal removal approached equilibrium within 30 min for lead, 75 min for copper and nickel, with lead recording 100 %, copper 97 % and nickel 55 % removal, having a trend of Pb 2+ values of 0.977, 0.817 and 0.978 for copper, nickel and lead respectively, which fitted the equilibrium adsorption process more than Freundlich model for the three metals.

Systematic study of synergistic and antagonistic effects on adsorption of tetracycline and copper onto a chitosan

Abstract: Sorption of tetracycline and copper onto chitosan is systematically investigated in this study. The sorption of tetracycline and copper occurs rapidly in the first few hours and 90% of completed uptake occurs in the first 11-12 and 6 h, respectively. The sorption equilibrium of both contaminants is established in 24 h. The solution pH largely affects the sorption of both contaminants. The tetracycline uptake increases as pH is increased from 2.8 to 5.6, and 2.5 to 7 in the absence and the presence of copper, respectively. The presence of copper significantly improves the tetracycline adsorption likely due to the formation of cationic bridging of copper between tetracycline and chitosan. The maximum adsorption capacity and the adsorption affinity constant for tetracycline dramatically increase from 53.82 to 93.04 mmol kg(-1) and from 1.22 to 10.20 L mmol(-1) as the copper concentration is increased from 0 to 0.5 mmol L(-1). The uptake of copper increases with an increase in pH from around 3.5-6.0 in the absence and the presence of tetracycline. The presence of tetracycline decreases the copper adsorption, which may be ascribed to the competition of tetracycline with copper ions for the adsorption sites at the chitosan surface. The adsorption isothermal data of both tetracycline and copper are fit well by the Langmuir equation. The maximum adsorption capacity and adsorption affinity constant of copper ions decrease from 1856.06 to 1486.20 mmol kg(-1) and from 1.80 to 1.68 L mmol(-1) in the absence and the presence of tetracycline. FTIR and XPS studies reveal that amino, hydroxyl, and ether groups in the chitosan are involved in the adsorption of tetracycline and copper. (C) 2009 Elsevier Inc. All rights reserved.

Response of Gram-positive bacteria to copper stress

Abstract: The Gram-positive bacteria Enterococcus hirae, Lactococcus lactis, and Bacillus subtilis have received wide attention in the study of copper homeostasis. Consequently, copper extrusion by ATPases, gene regulation by copper, and intracellular copper chaperoning are understood in some detail. This has provided profound insight into basic principles of how organisms handle copper. It also emerged that many bacterial species may not require copper for life, making copper homeostatic systems pure defense mechanisms. Structural work on copper homeostatic proteins has given insight into copper coordination and bonding and has started to give molecular insight into copper handling in biological systems. Finally, recent biochemical work has shed new light on the mechanism of copper toxicity, which may not primarily be mediated by reactive oxygen radicals.

Graphene Spreads the Heat

Abstract: The reliability and speed of electronic and optoelectronic devices strongly depend on temperature ( 1 , 2 ). Materials with very high thermal conductivities are required to spread the heat generated locally in such devices ( 2 ). Bulk copper, which is widely used as heat spreader in computers, has a thermal conductivity of ∼400 W m−1 K−1 at room temperature, but copper thin films, used as electrical interconnects, can have lower thermal conductivity (below 250 W m−1 K−1) ( 3 ). The search is thus on for materials with thermal conductivities higher than that of copper. On page 213 of this issue, Seol et al. ( 4 ) report that single monolayers of graphite (graphene) in contact with silicon dioxide (SiO2) has a thermal conductivity of ∼600 W m−1 K−1.

Copper stress affects iron homeostasis by destabilizing iron-sulfur cluster formation in Bacillus subtilis.

Abstract: Copper and iron are essential elements for cellular growth. Although bacteria have to overcome limitations of these metals by affine and selective uptake, excessive amounts of both metals are toxic for the cells. Here we investigated the influences of copper stress on iron homeostasis in Bacillus subtilis, and we present evidence that copper excess leads to imbalances of intracellular iron metabolism by disturbing assembly of iron-sulfur cofactors. Connections between copper and iron homeostasis were initially observed in microarray studies showing upregulation of Fur-dependent genes under conditions of copper excess. This effect was found to be relieved in a csoR mutant showing constitutive copper efflux. In contrast, stronger Fur-dependent gene induction was found in a copper efflux-deficient copA mutant. A significant induction of the PerR regulon was not observed under copper stress, indicating that oxidative stress did not play a major role under these conditions. Intracellular iron and copper quantification revealed that the total iron content was stable during different states of copper excess or efflux and hence that global iron limitation did not account for copper-dependent Fur derepression. Strikingly, the microarray data for copper stress revealed a broad effect on the expression of genes coding for iron-sulfur cluster biogenesis (suf genes) and associated pathways such as cysteine biosynthesis and genes coding for iron-sulfur cluster proteins. Since these effects suggested an interaction of copper and iron-sulfur cluster maturation, a mutant with a conditional mutation of sufU, encoding the essential iron-sulfur scaffold protein in B. subtilis, was assayed for copper sensitivity, and its growth was found to be highly susceptible to copper stress. Further, different intracellular levels of SufU were found to influence the strength of Fur-dependent gene expression. By investigating the influence of copper on cluster-loaded SufU in vitro, Cu(I) was found to destabilize the scaffolded cluster at submicromolar concentrations. Thus, by interfering with iron-sulfur cluster formation, copper stress leads to enhanced expression of cluster scaffold and target proteins as well as iron and sulfur acquisition pathways, suggesting a possible feedback strategy to reestablish cluster biogenesis.

Palladium nanoparticles supported on MOF-5: A highly active catalyst for a ligand- and copper-free Sonogashira coupling reaction

Abstract: Palladium nanoparticles supported on MOF-5 (Pd/MOF-5), have been prepared by a chemical method at room temperature. MOF-5 and Pd/MOF-5 were characterized by X-ray diffraction, N 2 sorption, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. The catalyst consists of highly dispersed palladium nanoparticles (about 3–6 nm) on MOF-5 with a high surface area (533 m 2 /g). It exhibits efficient catalytic activity for the Sonogashira coupling reaction between aryl iodides and terminal acetylenes without the assistance of ligand and copper.

Hydrogen Sulfide Adsorption on MOFs and MOF/Graphite Oxide Composites

Abstract: Composites of a copper-based metal-organic framework (MOF) and graphite oxide (GO) were tested for hydrogen sulfide removal at ambient conditions. In order to understand the mechanisms of adsorption, the initial and exhausted samples were analyzed by various techniques including X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses, and sorption of nitrogen. Compared to the parent materials, an enhancement in hydrogen sulfide adsorption was found. It was the result of physical adsorption of water and H(2)S in the pore space formed at the interface between the MOF units and the graphene layers where the dispersive forces are the strongest. Besides physisorption, reactive adsorption was found as the main mechanism of retention. H(2)S molecules bind to the copper centers of the MOF. They progressively react with the MOF units resulting in the formation of copper sulfide. This leads to the collapse of the MOF structure. Water enhances adsorption in the composites as it allows the dissolution of hydrogen sulfide.

The Bingham Canyon Porphyry Cu-Mo-Au Deposit. III. Zoned Copper-Gold Ore Deposition by Magmatic Vapor Expansion

Abstract: Fluid inclusion microthermometry and laser-ablation ICPMS microanalysis are combined with geological and textural observations to reconstruct the spatial and temporal evolution of magmatic fluids that formed the subvolcanic porphyry Cu-Au(-Mo) ore deposit at Bingham Canyon, Utah. The Bingham Canyon orebody is exposed over ~1.6 km vertically and has the shape of an inverted cup with distinct metal zoning. Fluid inclusions in the barren but highly veined and potassically altered deep center of the system have intermediate density (~0.6 g cm−3) and a salinity of ~7 wt percent NaCl equiv. They have subequal concentrations of Na, K, Fe, and Cu and contain minor CO2. The intermediate-density fluids were trapped as a single phase, mostly at >500°C and >800 bars. The Au-Cu-rich center near the top of the orebody contains low-density vapor inclusions (~0.2 g cm−3) coexisting with brine inclusions containing ~45 wt percent NaCl equiv. The vertical transition of different inclusion types indicates phase separation of the single-phase input fluid upon volume expansion associated with a pressure drop to 200 ± 100 bars. Mass-balance calculation based on all analyzed inclusion components indicates that the mass of the vapor phase exceeded that of the brine by ~9/1. The vapor contained Cu as its dominant cation (~1.5 wt %) and contributed about 95 percent of the total amount of copper transported to the base of the orebody. Bornite, chalcopyrite, and native gold were precipitated in a narrow temperature interval from 430° to 350°C, into secondary pore space created by local redissolution of vein quartz as a result of retrograde quartz solubility in the vapor-dominated fluid system. Intermediate-density fluid inclusions in the deepest parts of the peripheral copper ore zone have identical density and composition, including similar gold contents, as those in the deep center. Microthermometry and statistical estimation of phase proportions in the inclusions show that the vapor in the peripheral Cu-rich but Au-poor ore zone remained denser, and the separating brine was less saline (~36 wt % NaCl equiv), compared to vapor and brine in the central Au-Cu ore zone. This indicates that the peripheral fluids experienced a lower degree of phase separation, due to slightly higher fluid pressure at equivalent temperature, compared to more strongly expanding fluids in the center of the system. The systematic zoning of Au/Cu within the ore shell, despite compositionally similar input fluids, is interpreted to have resulted from slightly different pressure-temperature-density evolution paths of magmatic fluids. Copper was selectively precipitated in the peripheral ore zone, in contrast to complete coprecipitation of Au and Cu in the central upflow zone of the vapor plume. The formation of particularly rich Cu-Au ore in the center of the upward-expanding fluid plume is consistent with published experimental data, showing that the solubility of metals in hydrous vapor decreases sharply with falling pressure, due to destabilization of the hydration shell around metal complexes in expanding vapor. This interpretation supports the classic vapor plume model for porphyry copper ore formation but additionally emphasizes the role of sulfur-bearing complexes as a key chemical control on magmatic-hydrothermal metal transport and the deposition of Cu and Au in porphyry ores. Our interpretation of selective Cu ± Au precipitation as a function of vapor density can explain the more general observation that most gold-rich porphyry copper deposits are formed in shallow sub-volcanic environments, whereas deeper seated porphyry Cu-(Mo) deposits are generally gold poor.

Multicomponent Synthesis of 1,2,3‐Triazoles in Water Catalyzed by Copper Nanoparticles on Activated Carbon

Abstract: Copper nanoparticles on activated carbon have been found to effectively catalyze the multicomponent synthesis of 1,2,3-triazoles from different azide precursors, such as organic halides, diazonium salts, anilines and epoxides in water. The first one-pot transformation of an olefin into a triazole is also described. The catalyst is easy to prepare, very versatile and reusable at a low copper loading.

High capacity and excellent stability of lithium ion battery anode using interface-controlled binder-free multiwall carbon nanotubes grown on copper.

Abstract: We present a novel binder-free multiwall carbon nanotube (MWCNT) structure as an anode in Li ion batteries. The interface-controlled MWCNT structure, synthesized through a two-step process of catalyst deposition and chemical vapor deposition (CVD) and directly grown on a copper current collector, showed very high specific capacity, almost three times as that of graphite, excellent rate capability even at a charging/discharging rate of 3 C, and no capacity degradation up to 50 cycles. Significantly enhanced properties of this anode could be related to high Li ion intercalation on the carbon nanotube walls, strong bonding with the substrate, and excellent conductivity.