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Showing papers on "Copper published in 2011"


Journal ArticleDOI
TL;DR: In this paper, the authors provide a detailed and up-to-date description of the literature on the subject as well as highlighting challenges that must be overcome for the utilization of graphene deposited on copper substrates by chemical vapour deposition.
Abstract: The discovery of uniform deposition of high-quality single layered graphene on copper has generated significant interest. That interest has been translated into rapid progress in terms of large area deposition of thin films via transfer onto plastic and glass substrates. The opto-electronic properties of the graphene thin films reveal that they are of very high quality with transmittance and conductance values of >90% and 30Ω/sq, both are comparable to the current state-of-the-art indium tin oxide transparent conductor. In this Feature Article, we provide a detailed and up to date description of the literature on the subject as well as highlighting challenges that must be overcome for the utilization of graphene deposited on copper substrates by chemical vapour deposition.

1,405 citations


Journal ArticleDOI
TL;DR: This work has reported several recently reported Cu-catalyzed C-H oxidation reactions that feature substrates that are electron-deficient or appear unlikely to undergo single-electron transfer to copper(II), and evidence has been obtained for the involvement of organocopper(III) intermediates in the reaction mechanism.
Abstract: The selective oxidation of C-H bonds and the use of O(2) as a stoichiometric oxidant represent two prominent challenges in organic chemistry. Copper(II) is a versatile oxidant, capable of promoting a wide range of oxidative coupling reactions initiated by single-electron transfer (SET) from electron-rich organic molecules. Many of these reactions can be rendered catalytic in Cu by employing molecular oxygen as a stoichiometric oxidant to regenerate the active copper(II) catalyst. Meanwhile, numerous other recently reported Cu-catalyzed C-H oxidation reactions feature substrates that are electron-deficient or appear unlikely to undergo single-electron transfer to copper(II). In some of these cases, evidence has been obtained for the involvement of organocopper(III) intermediates in the reaction mechanism. Organometallic C-H oxidation reactions of this type represent important new opportunities for the field of Cu-catalyzed aerobic oxidations.

1,129 citations


Journal ArticleDOI
TL;DR: On the basis of time-resolved spectroscopic studies of core/shell particles, it is concluded that the emission is due to an optical transition that couples a quantized electron state to a localized hole state, which is most likely associated with an internal defect.
Abstract: We report an efficient synthesis of copper indium sulfide nanocrystals with strong photoluminescence in the visible to near-infrared. This method can produce gram quantities of material with a chemical yield in excess of 90% with minimal solvent waste. The overgrowth of as-prepared nanocrystals with a few monolayers of CdS or ZnS increases the photoluminescence quantum efficiency to > 80%. On the basis of time-resolved spectroscopic studies of core/shell particles, we conclude that the emission is due to an optical transition that couples a quantized electron state to a localized hole state, which is most likely associated with an internal defect.

670 citations


Journal ArticleDOI
TL;DR: The NH3-SCR activity of small-pore zeolites, such as Cu-SSZ-13 and Cu-SAPO-34, was investigated using a high-throughput reactor system in this article.
Abstract: The NH3-SCR activity of the small-pore zeolites, Cu-SSZ-13, Cu-SSZ-16, and Cu-SAPO-34, is investigated using a high-throughput reactor system. These copper exchanged small-pore zeolites have high SCR activity between 150 and 500 °C and are shown to be much more hydrothermally stable than the medium-pore zeolite, Cu-ZSM-5. The degree of copper exchange, the dimensionality of the framework, and heteroatom framework substitution all impact the SCR activity and hydrothermal stability of the materials. Of the small-pore zeolites tested, Cu-SSZ-13 and Cu-SAPO-34 display superior SCR performance, both before and after high-temperature hydrothermal treatment.

596 citations


Journal ArticleDOI
TL;DR: FTIR and XPS reveal that Cu(2+) adsorption onto CMCD-MNPs mainly involves the oxygen atoms in CM-β-CD to form surface-complexes and thermodynamic parameters reveal the feasibility, spontaneity and exothermic nature of the Adsorption process.

479 citations


Journal ArticleDOI
TL;DR: In this article, the effects of the nanostructure of the copper surface and compare the effect of the fcc(111, fcc (100) and fcc-211) facets of copper on the energetics of the electroreduction of CO 2.

435 citations


Journal ArticleDOI
TL;DR: These findings are important first steps for revealing the molecular sensitive targets in cells lethally challenged by exposure to copper surfaces and provide a scientific explanation for the use of copper surfaces as antimicrobial agents for supporting public hygiene.
Abstract: Metallic copper surfaces rapidly and efficiently kill bacteria. Cells exposed to copper surfaces accumulated large amounts of copper ions, and this copper uptake was faster from dry copper than from moist copper. Cells suffered extensive membrane damage within minutes of exposure to dry copper. Further, cells removed from copper showed loss of cell integrity. Acute contact with metallic copper surfaces did not result in increased mutation rates or DNA lesions. These findings are important first steps for revealing the molecular sensitive targets in cells lethally challenged by exposure to copper surfaces and provide a scientific explanation for the use of copper surfaces as antimicrobial agents for supporting public hygiene.

433 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the yield behavior of an electrodeposited cuprous oxide thin film and explore relationships between surface chemistry and reaction behavior relative to air-oxidized and anodized Cu electrodes.
Abstract: The direct reduction of CO2 to CH3OH is known to occur at several types of electrocatalysts including oxidized Cu electrodes. In this work, we examine the yield behavior of an electrodeposited cuprous oxide thin film and explore relationships between surface chemistry and reaction behavior relative to air-oxidized and anodized Cu electrodes. CH3OH yields (43 μmol cm-2 h-1) and Faradaic efficiencies (38%) observed at cuprous oxide electrodes were remarkably higher than air-oxidized or anodized Cu electrodes suggesting Cu(I) species may play a critical role in selectivity to CH3OH. Experimental results also show CH3OH yields are dynamic and the copper oxides are reduced to metallic Cu in a simultaneous process. Yield behavior is discussed in comparison with photoelectrochemical and hydrogenation reactions where the improved stability of Cu(I) species may allow continuous CH3OH generation.

418 citations


Journal ArticleDOI
TL;DR: It is shown that hydrogen acts as an inhibitor for the CH(4) dehydrogenation on copper, contributing to suppress deposition onto the copper substrate, and degrades quality of graphene.
Abstract: Understanding the chemical vapor deposition (CVD) kinetics of graphene growth is important for advancing graphene processing and achieving better control of graphene thickness and properties. In the perspective of improving large area graphene quality, we have investigated in real-time the CVD kinetics using CH4–H2 precursors on both polycrystalline copper and nickel. We highlighted the role of hydrogen in differentiating the growth kinetics and thickness of graphene on copper and nickel. Specifically, the growth kinetics and mechanism is framed in the competitive dissociative chemisorption of H2 and dehydrogenating chemisorption of CH4, and in the competition of the in-diffusion of carbon and hydrogen, being hydrogen in-diffusion faster in copper than nickel, while carbon diffusion is faster in nickel than copper. It is shown that hydrogen acts as an inhibitor for the CH4 dehydrogenation on copper, contributing to suppress deposition onto the copper substrate, and degrades quality of graphene. Additionally, the evidence of the role of hydrogen in forming C–H out of plane defects in CVD graphene on Cu is also provided. Conversely, resurfacing recombination of hydrogen aids CH4 decomposition in the case of Ni. Understanding better and providing other elements to the kinetics of graphene growth is helpful to define the optimal CH4/H2 ratio, which ultimately can contribute to improve graphene layer thickness uniformity even on polycrystalline substrates.

417 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of electrode material, current density, wastewater pH and conductivity on removal performance was explored, and the results showed that metal removal increased with increasing current density and pH.

414 citations


Journal ArticleDOI
TL;DR: The Cu nanoclusters displayed apparent luminescence, with dual emissions at 425 and 593 nm, with quantum yields of 3.5 and 0.9%, respectively, and high electrocatalytic activity in the electoreduction of oxygen.
Abstract: Subnanometer-sized copper nanoclusters were prepared by a one-pot procedure based on wet chemical reduction. The structural characteristics of the 2-mercapto-5-n-propylpyrimidine-protected nanoclusters, Cun (n ≤ 8), were determined by mass spectrometry. The Cu nanoclusters displayed apparent luminescence, with dual emissions at 425 and 593 nm, with quantum yields of 3.5 and 0.9%, respectively, and high electrocatalytic activity in the electoreduction of oxygen.

Journal ArticleDOI
TL;DR: In this article, copper nanoparticles were synthesized through the chemical reduction of copper sulfate with sodium borohydride in water without inert gas protection, and ascorbic acid was employed as a protective agent to prevent the nascent Cu nanoparticles from oxidation during the synthesis process and in storage.
Abstract: Copper nanoparticles, due to their interesting properties, low cost preparation and many potential applications in catalysis, cooling fluid or conductive inks, have attracted a lot of interest in recent years. In this study, copper nanoparticles were synthesized through the chemical reduction of copper sulfate with sodium borohydride in water without inert gas protection. In our synthesis route, ascorbic acid (natural vitamin C) was employed as a protective agent to prevent the nascent Cu nanoparticles from oxidation during the synthesis process and in storage. Polyethylene glycol (PEG) was added and worked both as a size controller and as a capping agent. Cu nanoparticles were characterized by Fourier transform infrared (FT-IR) spectroscopy to investigate the coordination between Cu nanoparticles and PEG. Transmission electron microscopy (TEM) and UV–vis spectrometry contributed to the analysis of size and optical properties of the nanoparticles, respectively. The average crystal sizes of the particles at room temperature were less than 10 nm. It was observed that the surface plasmon resonance phenomenon can be controlled during synthesis by varying the reaction time, pH, and relative ratio of copper sulfate to the surfactant. The surface plasmon resonance peak shifts from 561 to 572 nm, while the apparent color changes from red to black, which is partly related to the change in particle size. Upon oxidation, the color of the solution changes from red to violet and ultimately a blue solution appears.

Journal ArticleDOI
TL;DR: Although the best monolayer graphene was grown from polished Cu with a low sheet resistance of 260 Ω/sq, a small portion of multilayers were also formed near the impurity particles or locally protruded parts.
Abstract: We report that highly crystalline graphene can be obtained from well-controlled surface morphology of the copper substrate. Flat copper surface was prepared by using a chemical mechanical polishing method. At early growth stage, the density of graphene nucleation seeds from polished Cu film was much lower and the domain sizes of graphene flakes were larger than those from unpolished Cu film. At later growth stage, these domains were stitched together to form monolayer graphene, where the orientation of each domain crystal was unexpectedly not much different from each other. We also found that grain boundaries and intentionally formed scratched area play an important role for nucleation seeds. Although the best monolayer graphene was grown from polished Cu with a low sheet resistance of 260 Ω/sq, a small portion of multilayers were also formed near the impurity particles or locally protruded parts.

Journal ArticleDOI
TL;DR: In this article, the authors synthesize high stable dispersions of nanosized copper particles with an average particle size less than 2 nm using a straightforward, cost-effective, and green method.

Journal ArticleDOI
TL;DR: The human body has an elaborate system for managing and regulating the amount of key trace metals circulating in blood and stored in cells, but when this system fails to function properly, abnormal levels and ratios of trace metals can develop.
Abstract: The human body has an elaborate system for managing and regulating the amount of key trace metals circulating in blood and stored in cells. Nutrient metals from our diet are incorporated into blood if blood levels are depleted, transported into cells if cellular levels are inadequate, or excreted if blood and cell levels are sufficient or overloaded. When this system fails to function properly, abnormal levels and ratios of trace metals can develop. One of the most common trace-metal imbalances is elevated copper and depressed zinc. The ratio of copper to zinc is clinically more important than the concentration of either of these trace metals [1]. There are 2-4 grams of Zn distributed throughout the human body [2]. Most zinc is in the brain, muscle, bones, kidney and liver, with the highest concentrations in the prostate and parts of the eye [3]. It is the second most abundant transition metal in organisms after iron and it is the only metal which appears in all enzyme classes [2,4]. Copper is also a vital dietary nutrient, although only small amounts of the metal are needed for well-being [5]. Although copper is the third most abundant trace metal in the body [behind iron and zinc], the total amount of copper in the body is only 75-100 milligrams [6]. Copper is present in every tissue of the body, but is stored primarily in the liver, with fewer amounts found in the brain, heart, kidney, and muscles.

Journal ArticleDOI
TL;DR: In this paper, the authors synthesized a bi-functional highly dispersed Cu-solid base catalyst for hydrogenolysis of aqueous glycerol using thermal decomposition of the as-synthesized Cu0.4Mg5.6Al2(OH)16CO3 layered double hydroxides.
Abstract: Homogenously dispersed copper on layered solid base (Cu0.4/Mg5.6Al2O8.6-CP, with 80.1% dispersion of copper) was synthesized via thermal decomposition of the as-synthesized Cu0.4Mg5.6Al2(OH)16CO3 layered double hydroxides. This bi-functional highly dispersed Cu-solid base catalyst is extremely effective for hydrogenolysis of aqueous glycerol. The detected conversion of glycerol reached 80.0% with a 98.2% selectivity of 1,2-propanediol at 180 °C, 3.0 MPa H2 and 20 h. But copper dispersed poorly in those catalysts prepared via impregnation and ion-exchange, and their activities were lower. These precursors and catalysts were characterized by N2-adsorption, X-ray diffraction, scanning electronic microscope, transmission electronic microscope, thermo-gravimetry, temperature-programmed reduction with H2, in-situ XRD, dissociative N2O adsorption and CO2 temperature-programmed desorption. It was confirmed that the as-synthesized Cu0.4Mg5.6Al2(OH)16CO3 showed a well crystallized layer-structure of hydrotalcite and copper dispersed homogenously on the layer-structure of hydrotalcite after thermal decomposition and H2 reduction.

Journal ArticleDOI
TL;DR: Stoichiometric copper(I) selenide nanoparticles have been synthesized using the hot injection method and enhanced electronic properties can be explained by the oxidation of Cu(+) and Se(2-) on the nanoparticle surface, ultimately leading to a solid-state conversion of the core from monoclinic Cu(2)Se to cubic Cu(1.8)Se.
Abstract: Stoichiometric copper(I) selenide nanoparticles have been synthesized using the hot injection method. The effects of air exposure on the surface composition, crystal structure, and electronic properties were monitored using X-ray photoelectron spectroscopy, X-ray diffraction, and conductivity measurements. The current−voltage response changes from semiconducting to ohmic, and within a week a 3000-fold increase in conductivity is observed under ambient conditions. The enhanced electronic properties can be explained by the oxidation of Cu+ and Se2− on the nanoparticle surface, ultimately leading to a solid-state conversion of the core from monoclinic Cu2Se to cubic Cu1.8Se. This behavior is a result of the facile solid-state ionic conductivity of cationic Cu within the crystal and the high susceptibility of the nanoparticle surface to oxidation. This regulated transformation is appealing as one could envision using layers of Cu2Se nanoparticles as both semiconducting and conducting domains in optoelectronic...

Journal ArticleDOI
TL;DR: It is shown that under conditions where other copper complexes kill human hepatoma cells, Cu(I)-L-histidine is an effective catalyst for CuAAC labeling of live cells following metabolic incorporation of an alkyne-labeled sugar into glycosylated proteins expressed on the cell surface.
Abstract: Copper toxicity is a critical issue in the development of copper-based catalysts for copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reactions for applications in living systems. The effects and related toxicity of copper on mammalian cells are dependent on the ligand environment. Copper complexes can be highly toxic, can induce changes in cellular metabolism, and can be rapidly taken up by cells, all of which can affect their ability to function as catalysts for CuAAC in living systems. Herein, we have evaluated the effects of a number of copper complexes that are typically used to catalyze CuAAC reactions on four human cell lines by measuring mitochondrial activity based on the metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to study toxicity, inductively coupled plasma mass spectrometry to study cellular uptake, and coherent anti-Stokes Raman scattering (CARS) microscopy to study effects on lipid metabolism. We find that ligand environment around copper influence...

Journal ArticleDOI
12 Aug 2011-ACS Nano
TL;DR: Since leaching did not occur with micrometer-sized CuO, no cytotoxicty effect was observed, thus highlighting the prominence of materials toxicity at the nanoscale.
Abstract: The work investigates the source of toxicity of copper oxide nanoparticles (CuO NPs) with respect to its leaching characteristic and speciation. Complexation-mediated leaching of CuO NPs by amino acids was identified as the source of toxicity toward Escherichia coli, the model microorganism used in the current study. The leached copper-peptide complex induces a multiple-fold increase in intracellular reactive oxygen species generation and reduces the fractions of viable cells, resulting in the overall inhibition of biomass growth. The cytotoxicity of the complex leachate is however different from that of equivalent soluble copper salts (nitrates and sulfates). A pH-dependent copper speciation during the addition of copper salts gives rise to uncoordinated copper ions, which in turn result in greater toxicity and cell lysis, the latter of which was not observed for CuO NPs even at comparable pH. Since leaching did not occur with micrometer-sized CuO, no cytotoxicty effect was observed, thus highlighting the prominence of materials toxicity at the nanoscale.

Journal ArticleDOI
TL;DR: In this paper, microwave assisted chemical reduction in aqueous medium using the biopolymer, starch as a stabilizing agent was used as reducing agent for metallic and bimetallic nanoparticles of copper and silver.

Journal ArticleDOI
01 Feb 2011-Carbon
TL;DR: In this paper, a copper-based metal-organic framework and graphite oxide were synthesized with different ratios of HKUST-1 (also called MOF-199) and Graphite oxide.

Journal ArticleDOI
TL;DR: The obtained enthalpy value indicates that the chelation of copper ions among the aminated polyacrylonitrile can be regarded as a chemical adsorption process and fit well with the Langmuir isotherm.

Journal ArticleDOI
TL;DR: Copper sorption isotherms were obtained for soils having distinct characteristics: clay-rich, alkaline San Joaquin soil with significant heavy metal sorption capacity, and eroded, acidic Norfolk sandy loam soil having low capacity to retain copper.

Journal ArticleDOI
TL;DR: In this article, copper, chromium and mercury ions were adsorbed on natural and crosslinked (glutaraldehyde and epichlorohydrin) chitosan matrices, which present diverse functional groups and may induce different adsorption mechanisms.

Journal ArticleDOI
TL;DR: Al( 2)O(3) and TiO(2) atomic layer deposition (ALD) were employed to develop an ultrathin barrier film on copper to prevent water corrosion and were found to be much more resilient to dissolution in water and prevented the water corrosion of copper.
Abstract: Al2O3 and TiO2 atomic layer deposition (ALD) were employed to develop an ultrathin barrier film on copper to prevent water corrosion. The strategy was to utilize Al2O3 ALD as a pinhole-free barrier and to protect the Al2O3 ALD using TiO2 ALD. An initial set of experiments was performed at 177 °C to establish that Al2O3 ALD could nucleate on copper and produce a high-quality Al2O3 film. In situ quartz crystal microbalance (QCM) measurements verified that Al2O3 ALD nucleated and grew efficiently on copper-plated quartz crystals at 177 °C using trimethylaluminum (TMA) and water as the reactants. An electroplating technique also established that the Al2O3 ALD films had a low defect density. A second set of experiments was performed for ALD at 120 °C to study the ability of ALD films to prevent copper corrosion. These experiments revealed that an Al2O3 ALD film alone was insufficient to prevent copper corrosion because of the dissolution of the Al2O3 film in water. Subsequently, TiO2 ALD was explored on copper...

Journal ArticleDOI
TL;DR: In this paper, the best hydrophobic coating sol was prepared with methyltriethoxysilane (MTES), methanol (MeOH), and water at a molar ratio of 1:19.1:4.

Journal ArticleDOI
TL;DR: In this paper, in situ techniques including XRD, EPR, XANES, and FT-IR were employed to reveal the structural changes of the Au-Cu bimetallic particles during different pretreatment and reaction conditions, and to clarify the essence of the synergistic effect between gold and copper.

Journal ArticleDOI
TL;DR: Evidence obtained in humans and non-human primates presented here suggest that current copper UL should be re evaluated and developing the scientific basis for a copper UL and evaluating the relevance of copper deficiency globally are future key challenges for copper researchers.

Journal ArticleDOI
TL;DR: In this article, the oxidation of 5-hydroxymethyl-2-furfural was studied under mild reaction conditions using TiO2-supported Au and Au-Cu catalysts synthesized from pre-formed nanoparticles.

Journal ArticleDOI
TL;DR: In this paper, the IPL process successfully removed the oxide shells of copper nanoparticles, leaving a conductive, pure copper film in a short period of time (2 ms) under ambient conditions.
Abstract: Most commercial copper nanoparticles are covered with an oxide shell and cannot be sintered into conducting lines/films by conventional thermal sintering. To address this issue, past efforts have utilized complex reduction schemes and sophisticated chambers to prevent oxidation, thereby rendering the process cost ineffective. To alleviate these problems, we demonstrate a reactive sintering process using intense pulsed light (IPL) in the present study. The IPL process successfully removed the oxide shells of copper nanoparticles, leaving a conductive, pure copper film in a short period of time (2 ms) under ambient conditions. The in situ copper oxide reduction mechanism was studied using several different experiments and analyses. We observed instant copper oxide reduction and sintering through poly(N-vinylpyrrolidone) functionalization of copper nanoparticles, followed by IPL irradiation. This phenomenon may be explained by oxide reduction either via an intermediate acid created by ultraviolet (UV) light irradiation or by hydroxyl (-OH) end groups, which act like long-chain alcohol reductants.