Showing papers on "Copper published in 2013"
TL;DR: The chemistry of copper is extremely rich because it can easily access Cu0, CuI, CuII, and CuIII oxidation states allowing it to act through one-electron or two-Electron processes, which feature confer a remarkably broad range of activities allowing copper to catalyze the oxidation and oxidative union of many substrates.
Abstract: The chemistry of copper is extremely rich because it can easily access Cu0, CuI, CuII, and CuIII oxidation states allowing it to act through one-electron or two-electron processes. As a result, both radical pathways and powerful two-electron bond forming pathways via organmetallic intermediates, similar to those of palladium, can occur. In addition, the different oxidation states of copper associate well with a large number of different functional groups via Lewis acid interactions or π-coordination. In total, these feature confer a remarkably broad range of activities allowing copper to catalyze the oxidation and oxidative union of many substrates.
Oxygen is a highly atom economical, environmentally benign, and abundant oxidant, which makes it ideal in many ways.1 The high activation energies in the reactions of oxygen require that catalysts be employed.2 In combination with molecular oxygen, the chemistry of copper catalysis increases exponentially since oxygen can act as either a sink for electrons (oxidase activity) and/or as a source of oxygen atoms that are incorporated into the product (oxygenase activity). The oxidation of copper with oxygen is a facile process allowing catalytic turnover in net oxidative processes and ready access to the higher CuIII oxidation state, which enables a range of powerful transformations including two-electron reductive elimination to CuI. Molecular oxygen is also not hampered by toxic byproducts, being either reduced to water, occasionally via H2O2 (oxidase activity) or incorporated into the target structure with high atom economy (oxygenase activity). Such oxidations using oxygen or air (21% oxygen) have been employed safely in numerous commodity chemical continuous and batch processes.3
However, batch reactors employing volatile hydrocarbon solvents require that oxygen concentrations be kept low in the head space (typically <5–11%) to avoid flammable mixtures, which can limit the oxygen concentration in the reaction mixture.4,5,6 A number of alternate approaches have been developed allowing oxidation chemistry to be used safely across a broader array of conditions. For example, use of carbon dioxide instead of nitrogen as a diluent leads to reduced flammability.5 Alternately, water can be added to moderate the flammability allowing even pure oxygen to be employed.6 New reactor designs also allow pure oxygen to be used instead of diluted oxygen by maintaining gas bubbles in the solvent, which greatly improves reaction rates and prevents the build up of higher concentrations of oxygen in the head space.4a,7 Supercritical carbon dioxide has been found to be advantageous as a solvent due its chemical inertness towards oxidizing agents and its complete miscibility with oxygen or air over a wide range of temperatures.8 An number of flow technologies9 including flow reactors,10 capillary flow reactors,11 microchannel/microstructure structure reactors,12 and membrane reactors13 limit the amount of or afford separation of hydrocarbon/oxygen vapor phase thereby reducing the potential for explosions.
Enzymatic oxidizing systems based upon copper that exploit the many advantages and unique aspects of copper as a catalyst and oxygen as an oxidant as described in the preceding paragraphs are well known. They represent a powerful set of catalysts able to direct beautiful redox chemistry in a highly site-selective and stereoselective manner on simple as well as highly functionalized molecules. This ability has inspired organic chemists to discover small molecule catalysts that can emulate such processes. In addition, copper has been recognized as a powerful catalyst in several industrial processes (e.g. phenol polymerization, Glaser-Hay alkyne coupling) stimulating the study of the fundamental reaction steps and the organometallic copper intermediates. These studies have inspiried the development of nonenzymatic copper catalysts. For these reasons, the study of copper catalysis using molecular oxygen has undergone explosive growth, from 30 citations per year in the 1980s to over 300 citations per year in the 2000s.
A number of elegant reviews on the subject of catalytic copper oxidation chemistry have appeared. Most recently, reviews provide selected coverage of copper catalysts14 or a discussion of their use in the aerobic functionalization of C–H bonds.15 Other recent reviews cover copper and other metal catalysts with a range of oxidants, including oxygen, but several reaction types are not covered.16 Several other works provide a valuable overview of earlier efforts in the field.17 This review comprehensively covers copper catalyzed oxidation chemistry using oxygen as the oxidant up through 2011. Stoichiometric reactions with copper are discussed, as necessary, to put the development of the catalytic processes in context. Mixed metal systems utilizing copper, such as palladium catalyzed Wacker processes, are not included here. Decomposition reactions involving copper/oxygen and model systems of copper enzymes are not discussed exhaustively. To facilitate analysis of the reactions under discussion, the current mechanistic hypothesis is provided for each reaction. As our understanding of the basic chemical steps involving copper improve, it is expected that many of these mechanisms will evolve accordingly.
1,326 citations
TL;DR: Real-time monitoring of a representative cycloaddition process via heat-flow reaction calorimetry revealed that monomeric copper acetylide complexes are not reactive toward organic azides unless an exogenous copper catalyst is added.
Abstract: Copper(I)-catalyzed azide-alkyne cycloaddition has become a commonly employed method for the synthesis of complex molecular architectures under challenging conditions. Despite the widespread use of copper-catalyzed cycloaddition reactions, the mechanism of these processes has remained difficult to establish due to the involvement of multiple equilibria between several reactive intermediates. Real-time monitoring of a representative cycloaddition process via heat-flow reaction calorimetry revealed that monomeric copper acetylide complexes are not reactive toward organic azides unless an exogenous copper catalyst is added. Furthermore, crossover experiments with an isotopically enriched exogenous copper source illustrated the stepwise nature of the carbon-nitrogen bond-forming events and the equivalence of the two copper atoms within the cycloaddition steps.
632 citations
TL;DR: In this article, the reactions of nanomolar concentrations of Cu(I) and Cu(II) with H 2 O 2 have been investigated in 2.0mM NaHCO 3 and 0.7m NaCl at pH 8.0.
475 citations
TL;DR: Carbon nanotube–copper composite is reported, the only material with both high conductivity and high ampacity, making it uniquely suited for applications in microscale electronics and inverters.
Abstract: High electrical conductivity and ampacity are usually mutually exclusive properties. Here, in a carbon nanotube–copper composite, Subramaniam et al. achieve a similar conductivity to copper, but with a hundred fold increase in current carrying capacity.
430 citations
TL;DR: The antibacterial as well as antifungal activity of the nanoparticles were investigated using several microorganisms of interest, including methicillin-resistant Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Salmonella choleraesuis, and Candida albicans.
Abstract: Copper nanoparticle synthesis has been gaining attention due to its availability. However, factors such as agglomeration and rapid oxidation have made it a difficult research area. In the present work, pure copper nanoparticles were prepared in the presence of a chitosan stabilizer through chemical means. The purity of the nanoparticles was authenticated using different characterization techniques, including ultraviolet visible spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The antibacterial as well as antifungal activity of the nanoparticles were investigated using several microorganisms of interest, including methicillin-resistant Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Salmonella choleraesuis, and Candida albicans. The effect of a chitosan medium on growth of the microorganism was studied, and this was found to influence growth rate. The size of the copper nanoparticles obtained was in the range of 2-350 nm, depending on the concentration of the chitosan stabilizer.
373 citations
TL;DR: Platelet-shaped copper sulfide nanocrystals (NCs) with tunable Cu stoichiometry were prepared from Cu-rich covellite through their reaction with a Cu(I) complex at room temperature to access a range of compositions in these NCs, each characterized by a different optical response.
Abstract: Platelet-shaped copper sulfide nanocrystals (NCs) with tunable Cu stoichiometry were prepared from Cu-rich covellite (Cu1.1S) nanoplates through their reaction with a Cu(I) complex ([Cu(CH3CN)4]PF6) at room temperature. Starting from a common sample, by this approach it is possible to access a range of compositions in these NCs, varying from Cu1.1S up to Cu2S, each characterized by a different optical response: from the metallic covellite, with a high density of free carriers and strong localized surface plasmon resonance (LSPR), up to Cu2S NCs with no LSPR. In all these NCs the valency of Cu in the lattice stays always close to +1, while the average −1 valency of S in covellite gradually evolves to −2 with increasing Cu content; i.e., sulfur is progressively reduced. The addition of copper to the starting covellite NCs is similar to the intercalation of metal species in layered transition metal dichalcogenides (TMDCs); i.e., the chalcogen–chalcogen bonds holding the layers are progressively broken to mak...
358 citations
TL;DR: In this article, it was shown that hematite-magnetite intergrowths are commonly found in porphyry copper deposits, suggesting high and fluctuating oxygen fugacity (fO2).
314 citations
TL;DR: It is shown that a graphene coating can, on the contrary, accelerate long-term oxidation of an underlying copper substrate in ambient atmosphere at room temperature.
Abstract: This paper reports the enhancement of long-term oxidation of copper at room temperature by a graphene coating. Previous studies showed that graphene is an effective anticorrosion barrier against short-term thermal and electrochemical oxidation of metals. Here, we show that a graphene coating can, on the contrary, accelerate long-term oxidation of an underlying copper substrate in ambient atmosphere at room temperature. After 6 months of exposure in air, both Raman spectroscopy and energy-dispersive X-ray spectroscopy indicated that graphene-coated copper foil had a higher degree of oxidation than uncoated foil, although X-ray photoelectron spectroscopy showed that the surface concentration of Cu(2+) was higher for the uncoated sample. In addition, we observed that the oxidation of graphene-coated copper foil was not homogeneous and occurred within micrometer-sized domains. The corrosion enhancement effect of graphene was attributed to its ability to promote electrochemical corrosion of copper.
312 citations
TL;DR: In this article, the structural stability and electronic band structure of all three copper oxide compounds were investigated using ab initio methods within the framework of density functional theory and consider different exchange correlation functionals.
Abstract: The $p$-type semiconductor copper oxide has three distinct phases Cu${}_{2}$O, CuO, and Cu${}_{4}$O${}_{3}$ with different morphologies and oxidation states of the copper ions. We investigate the structural stability and electronic band structure of all three copper oxide compounds using ab initio methods within the framework of density functional theory and consider different exchange correlation functionals. While the local density approximation (LDA) fails to describe the semiconducting states of CuO and Cu${}_{4}$O${}_{3}$, the $\mathrm{LDA}+U$ and HSE06 hybrid functional describe both compounds as indirect semiconductors. Using the HSE06 hybrid functional we calculate the electronic band structure in the full Brillouin zone for all three copper oxide compounds.
299 citations
TL;DR: Dual-gradient copper wires' fog-collection ability is demonstrated to be higher than that of conical copper wires with pure hydrophobic surfaces or pure Hydrophilic surfaces, and the underlying mechanism is also analyzed.
Abstract: Inspired by the efficient fog collection on cactus spines, conical copper wires with gradient wettability are fabricated through gradient electrochemical corrosion and subsequent gradient chemical modification. These dual-gradient copper wires' fog-collection ability is demonstrated to be higher than that of conical copper wires with pure hydrophobic surfaces or pure hydrophilic surfaces, and the underlying mechanism is also analyzed.
282 citations
TL;DR: Copper oxide formation on copper during standard antimicrobial testing was measured in situ by spectroscopic ellipsometry and CuO was found to significantly inhibit contact killing, compared to pure copper, meaning that antimicrobial objects will retain their antimicrobial properties even after oxide formation.
Abstract: The potential of metallic copper as an intrinsically antibacterial material is gaining increasing attention in the face of growing antibiotics resistance of bacteria. However, the mechanism of the so-called "contact killing" of bacteria by copper surfaces is poorly understood and requires further investigation. In particular, the influences of bacteria-metal interaction, media composition, and copper surface chemistry on contact killing are not fully understood. In this study, copper oxide formation on copper during standard antimicrobial testing was measured in situ by spectroscopic ellipsometry. In parallel, contact killing under these conditions was assessed with bacteria in phosphate buffered saline (PBS) or Tris-Cl. For comparison, defined Cu2O and CuO layers were thermally generated and characterized by grazing incidence X-ray diffraction. The antibacterial properties of these copper oxides were tested under the conditions used above. Finally, copper ion release was recorded for both buffer systems by inductively coupled plasma atomic absorption spectroscopy, and exposed copper samples were analyzed for topographical surface alterations. It was found that there was a fairly even growth of CuO under wet plating conditions, reaching 4-10 nm in 300 min, but no measurable Cu2O was formed during this time. CuO was found to significantly inhibit contact killing, compared to pure copper. In contrast, thermally generated Cu2O was essentially as effective in contact killing as pure copper. Copper ion release from the different surfaces roughly correlated with their antibacterial efficacy and was highest for pure copper, followed by Cu2O and CuO. Tris-Cl induced a 10-50-fold faster copper ion release compared to PBS. Since the Cu2O that primarily forms on copper under ambient conditions is as active in contact killing as pure copper, antimicrobial objects will retain their antimicrobial properties even after oxide formation.
TL;DR: Copper leads to a breakup: simple Cu(II) salts are shown to be highly reactive as water oxidation electrocatalysts in neutral to weakly basic aqueous buffer solutions of CO(2)/HCO(-)/CO(3)(2-) or HPO (4)(2-)/PO(4)(3-).
Abstract: Copper leads to a breakup: simple Cu(II) salts are shown to be highly reactive as water oxidation electrocatalysts in neutral to weakly basic aqueous buffer solutions of CO(2)/HCO(3)(-)/CO(3)(2-) or HPO(4)(2-)/PO(4)(3-). Coordination to the buffer anions under these conditions prevents the precipitation of Cu(OH)(2), CuCO(3), or Cu(3)(PO(4))(2) and appears to stabilize higher oxidation states of copper.
TL;DR: In this paper, the product selectivity in the electrochemical reduction of carbon dioxide and carbon monoxide strongly depends on the atomic configuration of the copper electrode surface, and it was shown that carbon dioxide reduction occurs only on (100) terraces.
Abstract: The product selectivity in the electrochemical reduction of carbon dioxide and carbon monoxide strongly depends on the atomic configuration of the copper electrode surface. On Cu(111), methane formation is favored, whereas on Cu(100), ethylene formation is favored, with selective ethylene formation at low overpotentials. To distinguish the reactivity of (100) terraces vs (100) steps, we have studied carbon monoxide reduction on Cu(322), with the [5(111) × (100)] orientation, and Cu(911), with the [5(100) × (111)] orientation. Only on Cu(911) is the selective ethylene formation at low overpotentials observed, indicating that this reaction pathway occurs only on (100) terraces. We also show that the reduction of ethylene oxide to ethylene is significantly faster on Cu(100) compared with Cu(111), giving further evidence to the importance of the associated intermediate for ethylene formation. On Cu(110), the potential dependence of methane and ethylene formation is similar to Cu(111), and we have observed a p...
TL;DR: In this article, the authors focused mainly on determining the proportions of heterogeneous catalysis in the copper oxidate/persulfate combined system, and the effects of copper oxidates dosage, persulfate concentration, and initial solution pH on the oxidation of p-chloroaniline (PCA) were evaluated.
TL;DR: This redox-neutral reaction allows modular synthesis of a variety of substituted pyridines under mild conditions with tolerance of a broad range of functional groups.
Abstract: We describe here a [3+3]-type condensation reaction of O-acetyl ketoximes and α,β-unsaturated aldehydes that is synergistically catalyzed by a copper(I) salt and a secondary ammonium salt (or amine). This redox-neutral reaction allows modular synthesis of a variety of substituted pyridines under mild conditions with tolerance of a broad range of functional groups. The reaction is driven by a merger of iminium catalysis and redox activity of the copper catalyst, which would initially reduce the oxime N–O bond to generate a nucleophilic copper(II) enamide and later oxidize a dihydropyridine intermediate to the pyridine product.
TL;DR: This nanoreactor, which possesses balanced and stable Cu( 0) and Cu(+) active species, confinement effects, an intrinsically high surface area of Cu(0) andCu(+) and a unique tunable tubular morphology, has potential applications in high-temperature hydrogenation reactions.
Abstract: Nanoscale copper catalysts are useful for the selective hydrogenation of carbon–oxygen bonds, although they may be deactivated under harsh conditions. Here the authors report the enhanced activity and stability of core-sheath copper-phyllosilicate nanoreactors due to electronic and morphological effects.
TL;DR: The present lab-scale experimental study presents the process of leaching waste printed circuit boards (WPCBs) in order to recover gold by thioureation, and the effects of sulfuric acid concentration, hydrogen peroxide volume and temperature on the metal extraction yield were studied.
TL;DR: The mechanism by which copper mediates the interplay between the two energy-producing pathways, respiration and glycolysis is described and it is revealed that varying levels of copper serves to regulate oxidative phosphorylation in rapidly proliferating cancer cells inside solid tumors.
Abstract: Copper is an essential trace element, the imbalances of which are associated with various pathological conditions, including cancer, albeit via largely undefined molecular and cellular mechanisms. Here we provide evidence that levels of bioavailable copper modulate tumor growth. Chronic exposure to elevated levels of copper in drinking water, corresponding to the maximum allowed in public water supplies, stimulated proliferation of cancer cells and de novo pancreatic tumor growth in mice. Conversely, reducing systemic copper levels with a chelating drug, clinically used to treat copper disorders, impaired both. Under such copper limitation, tumors displayed decreased activity of the copper-binding mitochondrial enzyme cytochrome c oxidase and reduced ATP levels, despite enhanced glycolysis, which was not accompanied by increased invasiveness of tumors. The antiproliferative effect of copper chelation was enhanced when combined with inhibitors of glycolysis. Interestingly, larger tumors contained less copper than smaller tumors and exhibited comparatively lower activity of cytochrome c oxidase and increased glucose uptake. These results establish copper as a tumor promoter and reveal that varying levels of copper serves to regulate oxidative phosphorylation in rapidly proliferating cancer cells inside solid tumors. Thus, activation of glycolysis in tumors may in part reflect insufficient copper bioavailability in the tumor microenvironment.
TL;DR: In this paper, a robust graphene reinforced composite coating with excellent corrosion resistance by aqueous cathodic electrophoretic deposition (EPD) is reported, at optimum EPD conditions, a coating thickness of around 40nm is obtained at 10V and deposition time of 30 s.
TL;DR: The results suggest that sulfidation may not fully and permanently detoxify copper in biological or environmental compartments that contain reactive oxygen species, and copper sulfide NPs are found to be much less cytotoxic than CuO-NPs.
Abstract: Copper-based nanoparticles are an important class of materials with applications as catalysts, conductive inks, and antimicrobial agents. Environmental and safety issues are particularly important for copper-based nanomaterials because of their potential large-scale use and their high redox activity and toxicity reported from in vitro studies. Elemental nanocopper oxidizes readily upon atmospheric exposure during storage and use, so copper oxides are highly relevant phases to consider in studies of environmental and health impacts. Here we show that copper oxide nanoparticles undergo profound chemical transformations under conditions relevant to living systems and the natural environment. Copper oxide nanoparticle (CuO-NP) dissolution occurs at lysosomal pH (4–5), but not at neutral pH in pure water. Despite the near-neutral pH of cell culture medium, CuO-NPs undergo significant dissolution in media over time scales relevant to toxicity testing because of ligand-assisted ion release, in which amino acid c...
01 Jan 2013
TL;DR: In this paper, various surface preparations for copper and copper alloys including ferric chloride-nitric acid process, ferric sulfate-sulfuric acid/sodium dichromate-Sulfurica acid process and black oxide process are discussed.
Abstract: The chapter discusses various methods used to treat copper and copper alloys for adhesive bonding. The tendency of copper to form brittle amine compounds with the amine curing agents is one of the difficulties in its adhesive bonding. There are numerous reported surface preparations for copper and copper alloys including ferric chloride-nitric acid process, ferric sulfate-sulfuric acid/sodium dichromate-sulfuric acid process and black oxide process. A barrier layer on the surface of the metal can be formed by using the black oxide process. It provides a description on the evaluation of ferric chloride-nitric acid process and the ferric sulfate-sulfuric acid/sodium dichromate-sulfuric acid process with three epoxy type adhesive systems. The epoxy type adhesive system includes a two part polyamide-epoxy consisting of epoxy paste and curing epoxy film adhesive. It is also observed that with the use of ferric chloride-nitric acid process the resulting surfaces appear to be light-sensitive.
TL;DR: It is found that hydrogen plays dual roles on copper morphology during the whole growth process, that is, removing surface irregularities and, at the same time, etching the copper surface to produce small nanoparticles that have only limited effect on nucleation for graphene growth.
Abstract: Subcentimeter single-crystalline graphene grains, with diameter up to 5.9 mm, have been successfully synthesized by tuning the nucleation density during atmospheric pressure chemical vapor deposition. Morphology studies show the existence of a single large nanoparticle (>∼20 nm in diameter) at the geometric center of those graphene grains. Similar size particles were produced by slightly oxidizing the copper surface to obtain oxide nanoparticles in Ar-only environments, followed by reduction into large copper nanoparticles under H2/Ar environment, and are thus explained to be the main constituent nuclei for graphene growth. On this basis, we were able to control the nanoparticle density by adjusting the degree of oxidation and hydrogen annealing duration, thereby controlling nucleation density and consequently controlling graphene grain sizes. In addition, we found that hydrogen plays dual roles on copper morphology during the whole growth process, that is, removing surface irregularities and, at the same...
TL;DR: In this article, an oxide and corrosion resistant hydrophobic graphene oxide-polymer composite (GOPC) coating was fabricated on the copper by electrophoretic deposition (EPD), and the GOPC coatings were characterized by scanning, and transmission electron microscope (SEM, TEM), thermogravimetric (TGA and electrochemical impedance spectroscopy (EIS).
Abstract: Oxidation and corrosion resistant hydrophobic graphene oxide-polymer composite (GOPC) coating was fabricated on the copper by electrophoretic deposition (EPD). The GOPC coatings were characterized by scanning, and transmission electron microscope (SEM, TEM), thermogravimetric (TGA) and electrochemical impedance spectroscopy (EIS). At optimal EPD conditions of operating voltage 10 V and deposition time 30s, uniform crack free deposit with thickness 45 nm was achieved. Potentiodynamic polarization and EIS investigation demonstrated the efficacy of GOPC coating in shielding copper from corrosion under stringent environment condition. The electrochemical degradation of GOPC coating is more than three orders of magnitude lower than the bare copper substrate. This was due to the impermeability of GOPC coatings to ion diffusion of oxidizing gas and corrosive liquid solution. The procedure employed is fairly facile, inexpensive and less time consuming.
TL;DR: The COMB formalism, which merges variable charge electrostatic interactions with a classical analytical potential, has the capacity to adaptively model metallic, covalent, ionic and van der Waals bonding in the same simulation cell and dynamically determine the charges according to the local environment as mentioned in this paper.
Abstract: Interest in atomic scale computational simulations of multi-phase systems has grown as our ability to simulate nanometer-sized systems has become commonplace. The recently developed charge optimized many body potential (COMB) potentials have significantly enhanced the atomic-scale simulation of heterogeneous material systems, including chemical reactions at surfaces and the physical properties of interfaces. The COMB formalism, which merges variable charge electrostatic interactions with a classical analytical potential, has the capacity to adaptively model metallic, covalent, ionic and van der Waals bonding in the same simulation cell and dynamically determine the charges according to the local environment. Presented here is the theoretical background and evolution of the COMB potential family. The parameterization of the potential is described for several metals, ceramics, a semiconductor, and hydrocarbons, with the intent that the final parameter sets are consistent among materials. The utility of this approach is illustrated with several examples that explore the structure, stability, and mechanical and thermal properties of metallic systems and metal-ceramic and semi-conductor oxide interfaces, including surfaces and/or interfaces of copper and cuprite, copper and silica, silicon and silica, silicon and hafnia, and copper and zinc oxide. The potential is also applied to the simulation of atomic scale processes such as early stage oxidation of copper surfaces, tensile test of polycrystalline zirconium, and hyper-thermal deposition of ethyl radicals on selected copper surfaces.
TL;DR: In this paper, the effect of background pressure and synthesis temperature on the graphene crystal sizes in chemical vapor deposition (CVD) on copper catalyst was quantitatively demonstrated and provided the activation energy for graphene nucleation in atmospheric pressure CVD (9 eV).
Abstract: In this paper we discuss the effect of background pressure and synthesis temperature on the graphene crystal sizes in chemical vapor deposition (CVD) on copper catalyst. For the first time, we quantitatively demonstrate a fundamental role of the background pressure and provide the activation energy for graphene nucleation in atmospheric pressure CVD (9 eV), which is substantially higher than for the low pressure CVD (4 eV). We attribute the difference to a greater importance of copper sublimation in the low pressure CVD, where severe copper evaporation likely dictates the desorption rate of active carbon from the surface. At atmospheric pressure, where copper evaporation is suppressed, the activation energy is assigned to the desorption energy of carbon clusters instead. The highest possible temperature, close to the melting point of copper, should be used for large single crystal graphene synthesis. Using these conditions, we have synthesized graphene single crystals with sizes over 0.5 mm. Single crysta...
TL;DR: In this article, a series of highly luminescent, heteroleptic copper(I) complexes has been synthesized using a modular approach based on easily accessible P^N ligands, triphenylphosphine, and copper halides, allowing for an independent tuning of the emission wavelength with low synthetic efforts.
Abstract: A series of highly luminescent, heteroleptic copper(I) complexes has been synthesized using a modular approach based on easily accessible P^N ligands, triphenylphosphine, and copper(I) halides, allowing for an independent tuning of the emission wavelength with low synthetic efforts. The molecular structure has been investigated via X-ray analysis, confirming a dinuclear copper(I) complex consisting of a butterfly shaped metal-halide cluster and two different sets of ligands. The bidentate P^N ligand bridges the two metal centers and can be used to tune the energy of the frontier orbitals and therefore the photophysical characteristics, as confirmed by emission spectroscopy and theoretical investigations, whereas the two monodentate triphenylphosphine ligands on the periphery of the cluster core mainly influence the solubility of the complex. By using electron-rich or electron-poor heterocycles as part of the bridging ligand, emission colors can be adjusted, respectively, between yellow (581 nm) and deep b...
TL;DR: The results of EIS indicate that the value of CPEs tends to decrease and both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration, and the investigated inhibitor has shown good inhibition efficiency in 0.5 M HCl.
TL;DR: In this article, the authors introduced boron species by impregnation into silica-supported copper catalysts prepared by an ammonia evaporation hydrothermal method and investigated their catalytic activity and thermal stability for hydrogenation of dimethyl oxalate.
TL;DR: It is shown that copper telluride NCs with well-defined morphologies (spheres, rods, tetrapods) can be prepared via cation exchange of preformed CdTe NCs while retaining their original shape, suggesting that holes in the valence band of Cu(2-x)Te cannot be described as fully free particles and that the effects of localization of holes are important.
Abstract: Size- and shape-controlled synthesis of copper chalcogenide nanocrystals (NCs) is of paramount importance for a careful engineering and understanding of their optoelectronic properties and, thus, for their exploitation in energy- and plasmonic-related applications. From the copper chalcogenide family copper telluride NCs have remained fairly unexplored as a result of a poor size-, shape-, and monodispersity control that is achieved via one-step syntheses approaches. Here we show that copper telluride (namely Cu2–xTe) NCs with well-defined morphologies (spheres, rods, tetrapods) can be prepared via cation exchange of preformed CdTe NCs while retaining their original shape. The resulting copper telluride NCs are characterized by pronounced plasmon bands in the near-infrared (NIR), in analogy to other copper-deficient chalcogenides (Cu2–xS, Cu2–xSe). We demonstrate that the extinction spectra of the as-prepared NCs are in agreement with theoretical calculations based on the discrete dipole approximation and ...
TL;DR: In this article, the migration of copper species in Cu/SAPO-34 during hydrothermal aging and its role in selective catalytic reduction (SCR) of NOx was reported.