Showing papers on "Copper published in 2012"
TL;DR: Graphene is established as the thinnest known corrosion-protecting coating because it suppresses metal oxidation and oxygen reduction and prevents corrosion of underlying metals.
Abstract: We report the use of atomically thin layers of graphene as a protective coating that inhibits corrosion of underlying metals. Here, we employ electrochemical methods to study the corrosion inhibition of copper and nickel by either growing graphene on these metals, or by mechanically transferring multilayer graphene onto them. Cyclic voltammetry measurements reveal that the graphene coating effectively suppresses metal oxidation and oxygen reduction. Electrochemical impedance spectroscopy measurements suggest that while graphene itself is not damaged, the metal under it is corroded at cracks in the graphene film. Finally, we use Tafel analysis to quantify the corrosion rates of samples with and without graphene coatings. These results indicate that copper films coated with graphene grown via chemical vapor deposition are corroded 7 times slower in an aerated Na2SO4 solution as compared to the corrosion rate of bare copper. Tafel analysis reveals that nickel with a multilayer graphene film grown on it corro...
1,064 citations
TL;DR: It is reported that graphene coatings do not significantly disrupt the intrinsic wetting behaviour of surfaces for which surface-water interactions are dominated by van der Waals forces, and contact angle measurements indicate that a graphene monolayer is wetting-transparent to copper, gold or silicon, but not glass, for which the wettability is dominated by short-range chemical bonding.
Abstract: It is demonstrated that graphene coatings do not alter the wetting behaviour of copper, gold or silicon surfaces Such wetting transparency—shown to occur only for surfaces where surface–water interactions are dominated by van der Waals forces—and graphene’s ability to suppress copper oxidation result in a 30–40% increase in condensation heat transfer on copper The findings have implications for graphene-based coatings with independently tunable electronic and wetting properties
1,007 citations
TL;DR: A method is reported for creating hybrid organic-inorganic nanoflowers using copper (II) ions as the inorganic component and various proteins as the organic component to exhibit enhanced enzymatic activity and stability compared with the free enzyme.
Abstract: Flower-shaped inorganic nanocrystals(1-3) have been used for applications in catalysis(4,5) and analytical science(6,7), but so far there have been no reports of 'nanoflowers' made of organic components(8). Here, we report a method for creating hybrid organic-inorganic nanoflowers using copper (II) ions as the inorganic component and various proteins as the organic component. The protein molecules form complexes with the copper ions, and these complexes become nucleation sites for primary crystals of copper phosphate. Interaction between the protein and copper ions then leads to the growth of micrometre-sized particles that have nanoscale features and that are shaped like flower petals. When an enzyme is used as the protein component of the hybrid nanoflower, it exhibits enhanced enzymatic activity and stability compared with the free enzyme. This is attributed to the high surface area and confinement of the enzymes in the nanoflowers.
893 citations
TL;DR: Electrochemical, electron paramagnetic resonance and other studies indicate that the catalyst is a soluble molecular species, that the dominant species in the catalytically active solutions is (2,2'-bipyridine)Cu(OH)(2) and that this is among the most rapid homogeneous water-oxidation catalysts, with a turnover frequency of ~100 s(-1).
Abstract: The oxidation of water to O(2) is a key challenge in the production of chemical fuels from electricity. Although several catalysts have been developed for this reaction, substantial challenges remain towards the ultimate goal of an efficient, inexpensive and robust electrocatalyst. Reported here is the first copper-based catalyst for electrolytic water oxidation. Copper-bipyridine-hydroxo complexes rapidly form in situ from simple commercially available copper salts and bipyridine at high pH. Cyclic voltammetry of these solutions at pH 11.8-13.3 shows large, irreversible currents, indicative of catalysis. The production of O(2) is demonstrated both electrochemically and with a fluorescence probe. Catalysis occurs at about 750 mV overpotential. Electrochemical, electron paramagnetic resonance and other studies indicate that the catalyst is a soluble molecular species, that the dominant species in the catalytically active solutions is (2,2'-bipyridine)Cu(OH)(2) and that this is among the most rapid homogeneous water-oxidation catalysts, with a turnover frequency of ~100 s(-1).
649 citations
TL;DR: The antibacterial activity of CuO nanoparticles was found to be size-dependent and the highly stable minimum-sized monodispersed copper oxide nanoparticles synthesized during this study demonstrated a significant increase in antibacterial activities against both Gram-positive and -negative bacterial strains.
Abstract: Background
CuO is one of the most important transition metal oxides due to its captivating properties. It is used in various technological applications such as high critical temperature superconductors, gas sensors, in photoconductive applications, and so on. Recently, it has been used as an antimicrobial agent against various bacterial species. Here we synthesized different sized CuO nanoparticles and explored the size-dependent antibacterial activity of each CuO nanoparticles preparation.
620 citations
TL;DR: Characterization results indicated that the Cu(0) and Cu(+) were formed during the reduction process, originating from well-dispersed CuO and copper phyllosilicate, respectively, and it is shown that the selectivity for ethanol or ethylene glycol can be tuned simply by regulating the reaction temperature.
Abstract: This paper describes an emerging synthetic route for the production of ethanol (with a yield of ∼83%) via syngas using Cu/SiO2 catalysts. The remarkable stability and efficiency of the catalysts are ascribed to the unique lamellar structure and the cooperative effect between surface Cu0 and Cu+ obtained by an ammonia evaporation hydrothermal method. Characterization results indicated that the Cu0 and Cu+ were formed during the reduction process, originating from well-dispersed CuO and copper phyllosilicate, respectively. A correlation between the catalytic activity and the Cu0 and Cu+ site densities suggested that Cu0 could be the sole active site and primarily responsible for the activity of the catalyst. Moreover, we have shown that the selectivity for ethanol or ethylene glycol can be tuned simply by regulating the reaction temperature.
574 citations
TL;DR: In this paper, photo-induced ATRP was performed with visible light and sunlight in the presence of parts per million (ppm) copper catalysts, and the reaction mixture yielded polymerization in case of 392 and 450 nm light but not for 631 nm light.
Abstract: Photochemically induced ATRP was performed with visible light and sunlight in the presence of parts per million (ppm) copper catalysts. Illumination of the reaction mixture yielded polymerization in case of 392 and 450 nm light but not for 631 nm light. Sunlight was also a viable source for the photoinduced ATRP. Control experiments suggest photoreduction of the CuII complex (ligand to metal charge transfer in the excited state), yielding a CuI complex, and a bromine radical that can initiate polymerization. No photoactivation of CuI complex was detected. This implies that the mechanism of ATRP in the presence of light is a hybrid of ICAR and ARGET ATRP. The method was also used to synthesize block copolymers and polymerizations in water.
487 citations
TL;DR: Application of the auxiliary-assisted, copper catalyzed or promoted sulfenylation of benzoic acid derivative β-C-H bonds and benzylamine derivative γ-C -H bonds to the direct trifluoromethylsulfenylations of C-H Bonds was demonstrated.
Abstract: An auxiliary-assisted, copper catalyzed or promoted sulfenylation of benzoic acid derivative β-C–H bonds and benzylamine derivative γ-C–H bonds has been developed. The method employs disulfide reagents, copper(II) acetate, and DMSO solvent at 90–130 °C. Application of this methodology to the direct trifluoromethylsulfenylation of C–H bonds was demonstrated.
482 citations
TL;DR: Iron copper zeolite (Fe-Cu-ZSM-5) with aqueous hydrogen peroxide is active for the selective oxidation of methane to methanol giving meethanol selectivity and 10 % conversion in a closed catalytic cycle (see scheme).
Abstract: Iron copper zeolite (Fe-Cu-ZSM-5) with aqueous hydrogen peroxide is active for the selective oxidation of methane to methanol. Iron is involved in the activation of the carbon–hydrogen bond, while copper allows methanol to form as the major product. The catalyst is stable, re-usable and activates methane giving >90 % methanol selectivity and 10 % conversion in a closed catalytic cycle (see scheme).
478 citations
TL;DR: The present batch adsorption study describes the effects of solution pH, biochar dose, and contact time on copper and cadmium removal efficiency from single metal ion aqueous solutions.
459 citations
TL;DR: The results demonstrate that copper chalcogenide NCs offer the unique property of holding excitons and highly tunable LSPs on demand, and hence they are envisaged as a unique platform for the evaluation of exciton/LSP interactions.
Abstract: The optical properties of stoichiometric copper chalcogenide nanocrystals (NCs) are characterized by strong interband transitions in the blue part of the spectral range and a weaker absorption onset up to ∼1000 nm, with negligible absorption in the near-infrared (NIR). Oxygen exposure leads to a gradual transformation of stoichiometric copper chalcogenide NCs (namely, Cu2–xS and Cu2–xSe, x = 0) into their nonstoichiometric counterparts (Cu2–xS and Cu2–xSe, x > 0), entailing the appearance and evolution of an intense localized surface plasmon (LSP) band in the NIR. We also show that well-defined copper telluride NCs (Cu2–xTe, x > 0) display a NIR LSP, in analogy to nonstoichiometric copper sulfide and selenide NCs. The LSP band in copper chalcogenide NCs can be tuned by actively controlling their degree of copper deficiency via oxidation and reduction experiments. We show that this controlled LSP tuning affects the excitonic transitions in the NCs, resulting in photoluminescence (PL) quenching upon oxidati...
TL;DR: It is reported that copper oxide nanoparticles induce DNA damage in agricultural and grassland plants for the first time, and this is the first evidence of multiple DNA lesion formation and accumulation in plants.
Abstract: Engineered nanoparticles, due to their unique electrical, mechanical, and catalytic properties, are presently found in many commercial products and will be intentionally or inadvertently released at increasing concentrations into the natural environment. Metal- and metal oxide-based nanomaterials have been shown to act as mediators of DNA damage in mammalian cells, organisms, and even in bacteria, but the molecular mechanisms through which this occurs are poorly understood. For the first time, we report that copper oxide nanoparticles induce DNA damage in agricultural and grassland plants. Significant accumulation of oxidatively modified, mutagenic DNA lesions (7,8-dihydro-8-oxoguanine; 2,6-diamino-4-hydroxy-5-formamidopyrimidine; 4,6-diamino-5-formamidopyrimidine) and strong plant growth inhibition were observed for radish (Raphanus sativus), perennial ryegrass (Lolium perenne), and annual ryegrass (Lolium rigidum) under controlled laboratory conditions. Lesion accumulation levels mediated by copper ions and macroscale copper particles were measured in tandem to clarify the mechanisms of DNA damage. To our knowledge, this is the first evidence of multiple DNA lesion formation and accumulation in plants. These findings provide impetus for future investigations on nanoparticle-mediated DNA damage and repair mechanisms in plants.
TL;DR: Graphene coating on copper (Cu) is shown to increase the resistance of the metal to electrochemical degradation by one and half orders of magnitude as discussed by the authors, which can bring paradigm changes in the development of anti-corrosion coatings using conformal ultrathin graphene films.
TL;DR: A facile solution synthesis of stoichiometric Cu(2)ZnSnS(4) in size-controlled nanorod form (11 nm × 35 nm), which has a band gap of 1.43 eV and can be assembled into perpendicular aligned arrays by controlled evaporation from solution.
Abstract: The quaternary copper chalcogenide Cu2ZnSnS4 is an important emerging material for the development of low-cost and sustainable solar cells. Here we report a facile solution synthesis of stoichiometric Cu2ZnSnS4 in size-controlled nanorod form (11 nm × 35 nm). The monodisperse nanorods have a band gap of 1.43 eV and can be assembled into perpendicularly aligned arrays by controlled evaporation from solution.
TL;DR: Graphene domains prepared by an atmospheric pressure chemical vapor deposition method with suppressing nucleation on copper foils through an annealing procedure showed that the submillimeter graphene domains were monolayer single crystals.
Abstract: Submillimeter single-crystal monolayer and multilayer graphene domains were prepared by an atmospheric pressure chemical vapor deposition method with suppressing nucleation on copper foils through an annealing procedure. A facile oxidation visualization method was applied to study the nucleation density and morphology of graphene domains on copper foils. Scanning electron microscopy, transmission electron microscopy, atomic force microscopy, polarized optical microscopy, and Raman spectra showed that the submillimeter graphene domains were monolayer single crystals.
TL;DR: The development of copper chalcogenide based nanomaterials as promising candidates for sustainable energy materials, due to their environmental compatibility and low toxicity, is presented and discussed in this article.
Abstract: The development of copper chalcogenide based nanomaterials as promising candidates for sustainable energy materials, due to their environmental compatibility and low toxicity, is presented and discussed in this review. Different solution syntheses have recently been developed for the low-cost preparation of copper chalcogenide nanocrystals, and their unique properties derived from copper deficiencies were investigated with much progress. The notorious compositional instability and defect formation of copper chalcogenide nanocrystals have been healed by forming donor–acceptor pairs in ternary and quaternary chalcogenide based nanocrystals, especially in copper zinc tin sulfides (CZTS). In addition to their use as light absorbers in solar cells, copper chalcogenide nanocrystals have also been utilized in different applications, such as electrode materials in Li ion batteries and high efficiency counter electrodes in dye/quantum dot sensitized solar cells as well as for NIR photothermal therapy. All relate to their unique copper deficiency properties. The copper chalcogenide based nanomaterials are believed to be sustainable materials for future energy applications once the syntheses and property investigations have led to a more complete understanding of their physics.
TL;DR: In this article, a new Dimethyl 4, 4′-(o-phenylene)bis(3-thioallophanate) membrane sensor was developed for the quantitative determination of Cu (II) ions both in synthetic and real samples.
TL;DR: In this paper, several copper based catalysts were prepared, characterized and evaluated for the hydrogenation of levulinic acid and its methyl ester in methanol and water respectively.
TL;DR: In this paper, a combination of synchrotron-based and laboratory techniques were used to study the origin of the catalytic activity of Cu-SSZ-13 catalysts and to provide complementary information on the local copper environment under realistic NH3-SCR conditions.
Abstract: NH3-Selective Catalytic Reduction (NH3-SCR) is a widely used technology for NOx reduction in the emission control systems of heavy duty diesel vehicles. Copper-based ion exchanged zeolites and in particular Cu-SSZ-13 (CHA framework) catalysts show both exceptional activity and hydrothermal stability for this reaction. In this work, we have studied the origin of the SCR activity of Cu-SSZ-13 as evidenced from a combination of synchrotron-based and laboratory techniques. Synchrotron-based in situ XAFS/XRD measurements were used to provide complementary information on the local copper environment under realistic NH3-SCR conditions. Crucial then to the catalytic activity of Cu-SSZ-13 is the local environment of the copper species, particularly in the zeolite. Cu-SSZ-13 contains mononuclear Cu2+ species, located in the face of the double-6-ring subunit of the zeolite after calcination where it remains under reaction conditions. At lower temperatures (with low activity), XAFS and XRD data revealed a conformatio...
TL;DR: Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows, and make cupronickel nanoweires a promising alternative for the sustainable, efficient production of transparent conductors.
Abstract: Nanowires of copper can be coated from liquids to create flexible, transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these nanowire films is that copper is prone to oxidation. It was hypothesized that the resistance to oxidation could be improved by coating copper nanowires with nickel. This work demonstrates a method for synthesizing copper nanowires with nickel shells as well as the properties of cupronickel nanowires in transparent conducting films. Time- and temperature-dependent sheet resistance measurements indicate that the sheet resistance of copper and silver nanowire films will double after 3 and 36 months at room temperature, respectively. In contrast, the sheet resistance of cupronickel nanowires containing 20 mol % nickel will double in about 400 years. Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make cupronickel nanowires a promising alternative for the sustainable, efficient production of transparent conductors.
TL;DR: In this paper, the active sites and structure-activity relationships for methanol synthesis from a stoichiometric mixture of CO2 and H2 were investigated for a series of coprecipitated Cu-based catalysts with temperature-programmed reduction (TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Xray photoelectron spectroscopy (XPS), and N2O decomposition.
Abstract: Active sites and structure–activity relationships for methanol synthesis from a stoichiometric mixture of CO2 and H2 were investigated for a series of coprecipitated Cu-based catalysts with temperature-programmed reduction (TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2O decomposition. Experiments in a reaction chamber attached to an XPS instrument show that metallic Cu exists on the surface of both reduced and spent catalysts and there is no evidence of monovalent Cu+ species. This finding provides reassurance regarding the active oxidation state of Cu in methanol synthesis catalysts because it is observed with 6 compositions possessing different metal oxide additives, Cu particle sizes, and varying degrees of ZnO crystallinity. Smaller Cu particles demonstrate larger turnover frequencies (TOF) for methanol formation, confirming the structure sensitivity of this reaction. No correlation between TOF and lattice strain in Cu crystallite...
TL;DR: Analysis of studies from the own lab on model peptides raises an interesting hypothesis that various methionine/histidine/cysteine combinations provide organisms with dynamic, multifunctional domains on copper trafficking proteins that facilitate copper transfer under different extracellular, subcellular, and tissue-specific scenarios of pH, redox environment, and presence of other copper carriers or target proteins.
TL;DR: In this article, a thermoelectric figure-of-merit (ZT) of ∼1.6 at 700°C is achieved in β-phase copper selenide (Cu2Se) made by ball milling and hot pressing.
TL;DR: Copper sees the light of day: [Cu(dap)(2)Cl] proved to be an excellent photoredox catalyst for atom-transfer radical addition reactions, as well as for allylation reactions, providing an attractive alternative to commonly used iridium- and ruthenium-based catalysts.
Abstract: Copper sees the light of day: [Cu(dap)(2)Cl] proved to be an excellent photoredox catalyst for atom-transfer radical addition reactions, as well as for allylation reactions (see scheme), providing an attractive alternative to commonly used iridium- and ruthenium-based catalysts.
TL;DR: Evidence that animals use copper as an antimicrobial weapon and that microbes have developed mechanisms to counteract the toxic effects of copper are reviewed.
22 May 2012
TL;DR: In this article, a simple one-step method is presented for synthesizing large single crystal graphene domains on melted copper using atmospheric pressure chemical vapour deposition (CVD), achieved by performing the reaction above the melting point of copper (1090 °C) and using a molybdenum support to prevent the copper from dewetting.
Abstract: A simple one-step method is presented for synthesizing large single crystal graphene domains on melted copper using atmospheric pressure chemical vapour deposition (CVD). This is achieved by performing the reaction above the melting point of copper (1090 °C) and using a molybdenum support to prevent balling of the copper from dewetting. By controlling the amount of hydrogen during growth, individual single crystal domains of monolayer graphene greater than 200 µm are produced, determined by electron diffraction mapping. Angular resolved photoemission spectroscopy is used to show the graphene grown on copper exhibits a linear dispersion relationship and has no sign of doping.
TL;DR: Results suggest that copper alloy surface-mediated killing of E. coli is triggered by nonenzymatic oxidative damage of membrane phospholipids that ultimately results in the loss of membrane integrity and cell death.
Abstract: Copper alloy surfaces are passive antimicrobial sanitizing agents that kill bacteria, fungi, and some viruses. Studies of the mechanism of contact killing in Escherichia coli implicate the membrane as the target, yet the specific component and underlying biochemistry remain unknown. This study explores the hypothesis that nonenzymatic peroxidation of membrane phospholipids is responsible for copper alloy-mediated surface killing. Lipid peroxidation was monitored with the thiobarbituric acid-reactive substances (TBARS) assay. Survival, TBARS levels, and DNA degradation were followed in cells exposed to copper alloy surfaces containing 60 to 99.90% copper or in medium containing CuSO(4). In all cases, TBARS levels increased with copper exposure levels. Cells exposed to the highest copper content alloys, C11000 and C24000, exhibited novel characteristics. TBARS increased immediately at a very rapid rate but peaked at about 30 min. This peak was associated with the period of most rapid killing, loss in membrane integrity, and DNA degradation. DNA degradation is not the primary cause of copper-mediated surface killing. Cells exposed to the 60% copper alloy for 60 min had fully intact genomic DNA but no viable cells. In a fabR mutant strain with increased levels of unsaturated fatty acids, sensitivity to copper alloy surface-mediated killing increased, TBARS levels peaked earlier, and genomic DNA degradation occurred sooner than in the isogenic parental strain. Taken together, these results suggest that copper alloy surface-mediated killing of E. coli is triggered by nonenzymatic oxidative damage of membrane phospholipids that ultimately results in the loss of membrane integrity and cell death.
TL;DR: A new bronze age: the described copper-mediated cross-coupling with double C-H activation can provide a convergent access to indole-containing biheteroaryls that are of high interest in pharmaceutical and medicinal chemistry.
Abstract: A new bronze age: the described copper-mediated cross-coupling with double C-H activation can provide a convergent access to indole-containing biheteroaryls that are of high interest in pharmaceutical and medicinal chemistry. In this strategy an easily attachable and detachable 2-pyrimidyl directing group is used. Moreover, a variant that is catalytic in copper is achieved by using atmospheric oxygen as an ideal co-oxidant.
TL;DR: The dissolution of elemental Se in oleylamine by alkylthiol reduction at room temperature, which generates soluble alkylammonium selenide, which is highly reactive for hot-injection synthesis of selenides semiconductor NCs, such as Cu(2)ZnSnSe(4), Cu(InGa)Se(2), and CdSe.
Abstract: Enhancement of Se solubility in organic solvents without the use of alkylphosphine ligands is the key for phosphine-free synthesis of selenide semiconductor nanocrystals (NCs). In this communication, we demonstrate the dissolution of elemental Se in oleylamine by alkylthiol reduction at room temperature, which generates soluble alkylammonium selenide. This Se precursor is highly reactive for hot-injection synthesis of selenide semiconductor NCs, such as Cu2ZnSnSe4, Cu(InGa)Se2, and CdSe. In the case of Cu2ZnSnSe4, for example, the as-synthesized NCs possessed small size, high size monodispersity, strong absorbance in the visible region, and in particular a promising increase in photocurrent under AM1.5 illumination. The current preparation of the Se precursor is simple and convenient, which will promote the synthesis and practical applications of selenide NCs.
TL;DR: This review is devoted to silica-noble metal core-shell nanostructures and outlines the main methods used for the preparation and surface modification ofsilica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles.