Oxidation Of Cu Research Articles

Antibacterial and physicochemical properties of co‐sputtered CuSn thin films

Copper‐tin thin films (CT TFs) were deposited on p‐type Si(100) by radio frequency (RF) magnetron co‐sputtering method. The atomic ratio of Cu and Sn showed complementary tendency with various RF powers on metal targets. Antibacterial test was conducted with Gram‐negative Escherichia coli. The ratio of Cu and Sn ions and the contact time with E. coli affected the antibacterial efficiency. Increasing the ratio of Cu ions and contact time showed higher antibacterial activity. Cu20Sn6 called as bronze structure, metallic Cu, and copper oxide phases were identified from X‐ray diffraction data after sterilization. The lattice strain that was changed due to the substitution of Cu and Sn was also calculated. The surface morphology of CT TFs was entirely grown to round shape when the dominant element was Sn. But, as the content of Cu increased, the surface morphology was changed from ball shape to sharp column shape. When fixed contact time, the intensities of Cu 2p increased but the intensities of Sn 3d decreased as increasing the atomic ratio of Cu. The oxidation of Cu was more sharply progressed as the RF power on Cu target increased. When fixed CT TFs, the intensities of Cu 2p were consistent but the intensities of Sn 3d3/2 decreased as increasing contact time between CT TF and E. coli.

Highly conductive copper films based on submicron copper particles/copper complex inks for printed electronics: Microstructure, resistivity, oxidation resistance, and long-term stability

Submicron Cu particles mixed with Cu complex are used successfully to fabricate highly conductive Cu films for printed electronics. This study investigates the effects of Cu particle size on microstructure, conductivity and on the long-term stability of printed Cu films. In particular, the oxidation behaviors of printed Cu films at high temperatures are studied from the evolutions in microstructure and chemical composition. The submicron Cu particles are sintered efficiently due to the help of in-situ formed Cu nanoparticles from the decomposition of the Cu complex. Low resistivity of 5.8 μΩ cm is easily achieved. At temperatures of 140 °C and 180 °C, the printed Cu films prepared from 800 nm Cu particles are more stable than that from those 350 nm particles, which can be attributed to larger Cu particles possessing higher oxidation resistance. At 220 °C, the result becomes opposite because the loose structure with many large voids in the printed Cu films from large particles provides sufficient space for oxygen and accelerate the break of pathways between adjacent particles by the formation of Cu oxides layers. This indicates the long-term stability of printed Cu films is attributed to not only the intrinsic oxidation of Cu to Cu2O but also the degradation of microstructures. At all events, the printed Cu films from submicron Cu particles with Cu complex exhibit excellent oxidation resistance and are superior to those from Cu nanoparticles. This presents significant potential and favorable prospects for the fabrication of highly reliable and cost-effective printed electronics.

Variation of crystallinity of Cu and Cu2O nanowires arrays grown in various pores of porous alumina membrane

Various pore sizes of a porous alumina membrane were fabricated using H2SO4 and H2C2O4 electrolyte under different ionization voltages. Cu nanowire arrays with high aspect ratios, uniform pore size, and ordered pore arrangement were synthesized using the above porous alumina membrane (PAM). Moreover, Cu2O nanowire arrays were prepared through the oxidization of Cu metal nanowire arrays. From the microstructure and compositional analysis, it was observed that pores of different sizes, i.e. 20~30, 70~90 and 90~100 nm could be obtained by controlling various electrolytes and anodization voltage. The Cu nanowire synthesized with various pore sizes were found to be single crystal (20~90 nm) and polycrystalline (90~100nm) respectively. The single crystal Cu with (111) direction was occurred due to homogeneous current density distribution and relationship between current density (J) and nucleus radius (ro). After oxidation of Cu, the Cu2O nanowires with the pore sizes of 20~100 nm was found to be single crystal. The rearranged of Cu and O2 lattice sites promotes the enhancement of crystalline property.

An Evaluation of Multiple Catalytic Systems for the Cyanation of 2,3-Dichlorobenzoyl Chloride: Application to the Synthesis of Lamotrigine

2,3-Dichlorobenzoyl cyanide is a key intermediate in the synthesis of Lamotrigine. An assessment of various catalytic systems for the cyanation of 2,3-dichlorobenzoyl chloride with cyanide salts is described. High-throughput experimentation identified many conditions for effecting the requisite chemistry, including amine bases and phase-transfer catalysts, as well as catalyst-free conditions utilizing acetonitrile as a polar cosolvent. A novel catalyst, CuBr2, was identified by consideration of the possible oxidation of Cu(I) during high-throughput screening experimentation. CuCN was found to be the best cyanide source for achieving clean conversion; however, the solubility of CuCN was the major factor limiting reaction rate under many conditions. Improving CuCN solubility by using acetonitrile as solvent enhanced the reaction rate even in the absence of the catalysts tested but significantly complicated isolation of the product. With no acetonitrile cosolvent, phase-transfer catalysts such as tetrabutyla...

In situ atomic-scale imaging of the metal/oxide interfacial transformation

Directly probing structure dynamics at metal/oxide interfaces has been a major challenge due to their buried nature. Using environmental transmission electron microscopy, here we report observations of the in-place formation of Cu2O/Cu interfaces via the oxidation of Cu, and subsequently probe the atomic mechanisms by which interfacial transformation and grain rotation occur at the interfaces during reduction in an H2 gas environment. The Cu2O→Cu transformation is observed to occur initially along the Cu2O/Cu interface in a layer-by-layer manner. The accumulation of oxygen vacancies at the Cu2O/Cu interface drives the collapse of the Cu2O lattice near the interface region, which results in a tilted Cu2O/Cu interface with concomitant Cu2O island rotation. These results provide unprecedented microscopic detail regarding the redox reactions of supported oxides, which differs fundamentally from the reduction of bulk or isolated oxides that requires the formation of new interfaces between the parent oxide and the reduced phase.

In situ chemical and morphological characterization of copper under near ambient reduction and oxidation conditions

By using spatially resolved photoelectron spectromicroscopy, we have investigated the formation of Cu(I) oxide phases when a bulk Cu foil is exposed to a near ambient pressure of molecular oxygen. The experiment was performed by using a novel cell for in operando measurements capable to overcome the so called ‘pressure gap’. We have found that the oxidation of Cu proceeds through the formation of Cu(I) oxide domains in the micron and submicron range size, the evolution of which affects the overall morphology of the Cu surface as well. Chemical and morphological changes have been simultaneously detected. It was, surprisingly, found that during the oxidation process in many areas domains having +1 valence state do not spread on the metallic regions which homogenously oxidize; no chemical oxidizing wave was detected by the available lateral resolution and time frame.

Controlled Construction of Supported Cu+ Sites and Their Stabilization in MIL-100(Fe): Efficient Adsorbents for Benzothiophene Capture.

Cu+-containing materials have drawn much attention in various applications because they are versatile, nontoxic, and low-cost. However, the difficulty of selective reduction and the poor stability of Cu+ species are now pretty much the agendas. Here, controlled construction of supported Cu+ sites in MIL-100(Fe) was realized under mild conditions (200 °C, 5 h) via a vapor-reduction strategy (VRS). Remarkably, the yield of Cu+ reaches 100%, which is quite higher than the traditional high-temperature autoreduction method with a yield less than 50% even at 700 °C for 12 h. More importantly, during the treatment via VRS some Fe3+ in MIL-100(Fe) are reduced to Fe2+, which prevent the frequently happened oxidation of Cu+ due to the higher oxidation potential of Fe2+. These properties make Cu+/MIL-100(Fe) efficient in the capture of typical aromatic sulfur, benzothiophene, with regard to both adsorption capacity and stability. To our knowledge, the stabilization of Cu+ using the oxidation tendency of supports is achieved for the first time, which may offer a new idea to utilize active sites with weak stability.

Enhancement of electrochemical oxidation of Cu(CN) 3 2− by the peroxydisulfate oxidation

Abstract In this work, the peroxydisulfate (PDS/K 2 S 2 O 8 ) enhancement of electrochemical oxidation of Cu(CN) 3 2− with the RuO 2 /Ti mesh anode and the stainless steel cathode was investigated. The removal efficiency of cyanide was largely increased with increasing the PDS concentration. When the concentration of K 2 S 2 O 8 was 1.00 mM and the current density was 14.80 A/m 2 , the removal efficiency of cyanide was increased from 34.3% to 89.1% at the initial 10 min. The Cu mass distribution onto the cathode, in the solution, and onto the anode was investigated. With the increase of K 2 S 2 O 8 concentration, the mass of Cu oxides deposition on the anode surface was increased. Combined with the SEM-EDS, XRD and XPS analysis for the anode surface, it was confirmed that the generation of deposition on the anode surface was CuO. The generation of sulfate and hydroxyl radicals was confirmed by the ESR analysis. It was suggested that Cu(I) reacted with S 2 O 8 2− via a Fenton-like process, leading to the formation of SO 4 - radical. OH radical was generated due to the reaction between SO 4 - and OH − /H 2 O. Therefore, these active radicals and anode oxidation were responsible for cyanide removal.

Voltammetric determination of ascorbic acid by using a disposable screen printed electrode modified with Cu(OH)2 nanorods

The authors describe a disposable non-enzymatic sensor for ascorbic acid (AA) that was obtained by modifying a screen printed electrode (SPE) with Cu(OH)2 nanorods (NRs). The NRs were synthesized by a wet chemical process which involves sequential addition of NH3 and NaOH to CuSO4 solution. NR formation was confirmed by thermogravimetric, spectroscopic, microscopic, and diffraction studies. The Cu(OH)2 NRs were mixed with carbon ink and printed onto an SPE. Electrochemical detection of AA was carried out at pH 7.4, at a typical voltage as low as 0 mV versus saturated calomel electrode with a scan rate of 100 mV/s, and is assumed to involve the chemical reduction of Cu(II) by AA followed by electrochemical oxidation of Cu(I). The sensor has a linear response in the 0.0125 to 10 mΜ AA concentration range. Response to AA is free from interference by urea, glucose, uric acid, dopamine, metal ions such as Fe2+, Zn2+ and Ni2+, NaCl, KCl and ethanol. It was applied to the determination of AA in a vitamin C tablet and in urine.

Aluminum‐doped Zn1 − xMgxO as transparent conductive oxide of Cu(In,Ga)(S,Se)2‐based solar cell for minimizing surface carrier recombination

AbstractA 19.5%‐efficient Cu(In,Ga)(S,Se)2 (CIGSSe)‐based solar cell is obtained by replacing traditional CdS/ZnO buffer layers with Cd0.75Zn0.25S/Zn0.79Mg0.21O buffer layers for increasing short‐circuit current density because band‐gap energies of Cd0.75Zn0.25S and Zn0.79Mg0.21O are wider than those of CdS and ZnO, respectively. This yields the increase in external quantum efficiency in a short wavelength range of approximately 320 to 550 nm. Moreover, difference of conduction band minimum (EC) between Zn1 − xMgxO:Al (transparent conductive oxide, TCO) layer and CIGSSe absorber is optimized by varying [Mg]/([Mg] + [Zn]), x. It is revealed that Zn1 − xMgxO:Al films with [Mg]/([Mg] + [Zn]) in a range of 0.10 to 0.12, enhancing Eg from 3.72 to 3.76 eV, are appropriate as TCO because of their enhanced mobility and decreased carrier density. Addition of 12% Mg into ZnO:Al to form Zn0.88Mg0.12O:Al as TCO layer effectively decreases surface carrier recombination and improves photovoltaic parameters, especially open‐circuit voltage and fill factor. This is the first experimental proof of the concept for optimizing EC difference between TCO and absorber to minimize surface carrier recombination. Ultimately, conversion efficiency (η) of CIGSSe solar cell with alternative Cd0.75Zn0.25S/Zn0.79Mg0.21O/Zn0.88Mg0.12O:Al (TCO) layers is enhanced to 20.6%, owing to control of total EC alignment, which is higher η up to 12.6% relative as compared with the solar cell with traditional CdS/ZnO/ZnO:Al layers.

Electrodeposition of CuO from Cu-MOF on glassy carbon electrode: A non-enzymatic sensor for glucose

The present study describes the fabrication of copper oxide (CuO) on glassy carbon (GC) electrode by electrodeposition method using Cu-MOF. The CuO modified GC electrode exhibits a sharp anodic peak at −0.07V corresponding to the oxidation of Cu to Cu oxide and a cathodic peak at −0.18V corresponding to the reduction of Cu oxide. Then, the CuO modified electrode was exploited for the determination of glucose. It was optimized with respect to different concentrations of Cu-MOF, applied potential and deposition time. The GC electrode modified with CuO using 8mg/mL of Cu-MOF at an applied potential of −0.30V for 300s showed higher electrocatalytic activity towards glucose by shifting its oxidation towards less positive potential but also enhanced its oxidation current. The amperometric response of glucose was increased linearly while increasing its concentration from 500nM to 5mM and the limit of detection was found to be 70nM (S/N=3). Finally, the application of the present method was exhibited by determining glucose in human blood serum sample. Further, the present method of glucose determination was validated with the commercially available glucometer.

Thermal stability of low-temperature sintered joint using Sn-coated Cu particles during isothermal aging at 250 °C

In this paper, we investigate the microstructural stability of a Cu–Cu joint sintered with microscale Cu particles and Sn-coated Cu (Cu@Sn) particles during an isothermal aging. Using Cu particles and Cu@Sn particles as die attach materials, pure Cu discs were bonded at 200 °C for 20 min with an applied pressure of 10 MPa in a formic acid atmosphere. After the bonding, the Cu sintered joint showed a loosely sintered structure, while the Cu@Sn sintered joint exhibited a microstructure comprised of a Cu3Sn network with a dispersion of Cu particles. The isothermal aging test was conducted at 250 °C in an air atmosphere. Debonding of the Cu sintered joint happened after the aging for only 100 h, due to a severe oxidation of the sintered Cu layer and Cu substrate. On the other hand, the Cu@Sn sintered joints showed better thermal stability. The joint presented nearly 20 MPa shear strength after the aging for 1000 h. The Cu3Sn IMC network suppressed the oxidation of Cu both in the sintered layer and on the substrate, thereby maintaining the microstructural integrity of the Cu@Sn sintered joint.

Role of Graphene in Water-Assisted Oxidation of Copper in Relation to Dry Transfer of Graphene

The process of oxidation of a copper surface coated by a layer of graphene in water-saturated air at 50 °C was studied where it was observed that oxidation started at the graphene edge and was complete after 24 h. Isotope labeling of the oxygen gas and water showed that the oxygen in the formed copper oxides originated from water and not from the oxygen in air for both Cu and graphene-coated Cu, and this has interesting potential implications for graphene as a protective coating for Cu in dry air conditions. We propose a reaction pathway where surface hydroxyl groups formed at graphene edges and defects induce the oxidation of Cu. DFT simulation shows that the binding energy between graphene and the oxidized Cu substrate is smaller than that for the bare Cu substrate, which facilitates delamination of the graphene. Using this process, dry transfer is demonstrated using poly(bisphenol A carbonate) (PC) as the support layer. The high quality of the transferred graphene is demonstrated from Raman maps, XPS, ...

X-ray Absorption and Electron Paramagnetic Resonance Guided Discovery of the Cu-Catalyzed Synthesis of Multiaryl-Substituted Furans from Aryl Styrene and Ketones Using DMSO as the Oxidant.

The first example of DMSO serving not only as a solvent but also as an oxidant to promote the oxidation of Cu(I) to Cu(II) has been demonstrated. X-ray absorption and electron paramagnetic resonance evidence revealed a single-electron redox process where DMSO could oxidize Cu(I) to Cu(II). The novel discovery guided the rational design of copper-catalyzed oxidative cyclization of aryl ketones with styrenes to furans, providing a new method for the synthesis of multiaryl-substituted furans from cheap and readily available starting materials.

Suppression of conductivity deterioration of copper thin films by coating with atomic-layer materials

Theoretical calculations are performed to explore the electronic structures and electron conducting properties of copper (Cu) thin films coated with graphene or h-boron-nitride (h-BN) layers. The Shockley surface states of Cu surfaces are preserved by the graphene and h-BN coatings which prevent the surface oxidation of Cu because of the weak interaction between the Cu surface and graphene or the h-BN layers. Furthermore, the Shockley surface states in Cu thin films possess quasi-two dimensional free-electron characteristics and exhibit a high conductivity of 1.62 × 107 (Ωm)−1 at room temperature. These hybrid structures may be suitable as interconnects in memory devices that can stably store data for long periods.

Synthesis of Copper–Silica Core–Shell Nanostructures with Sharp and Stable Localized Surface Plasmon Resonance

Copper nanoparticles exhibit intense and sharp localized surface plasmon resonance (LSPR) in the visible region; however, the LSPR peaks become weak and broad when exposed to air due to the oxidation of Cu. In this work, the Cu nanoparticles are successfully encapsulated in SiO2 by employing trioctyl-n-phosphine (TOP)-capped Cu nanoparticles for the sol–gel reaction, yielding an aqueous Cu–SiO2 core–shell suspension with stable and well-preserved LSPR properties of the Cu cores. With the TOP capping, the oxidation of the Cu cores in the microemulsion was significantly reduced, thus allowing the Cu cores to sustain the sol–gel process used for coating the SiO2 protection layer. It was found that the self-assembled TOP-capped Cu nanoparticles were spontaneously disassembled during the sol–gel reaction, thus recovering the LSPR of individual particles. During the disassembling progress, the extinction spectrum of the nanocube agglomerates evolved from a broad extinction profile to a narrow and sharp peak. Fo...

Preventing Alkyne-Alkyne (i.e., Glaser) Coupling Associated with the ATRP Synthesis of Alkyne-Functional Polymers/Macromonomers and for Alkynes under Click (i.e., CuAAC) Reaction Conditions.

Alkyne-functional polymers synthesized by ATRP exhibit bimodal molecular weight distributions indicating the occurrence of some undesirable side reaction. By modeling the molecular weight distributions obtained under various reaction conditions, we show that the side reaction is alkyne-alkyne (i.e., Glaser) coupling. Glaser coupling accounts for as much as 20% of the polymer produced, significantly compromising the polymer functionality and undermining the success of subsequent click reactions in which they are used. Glaser coupling does not occur during ATRP but during postpolymerization workup upon first exposure to air. Two strategies are reported that effectively eliminate these coupling reactions without the need for a protecting group for the alkyne-functional initiator: (1) maintaining low temperature post-ATRP upon exposure to air followed by immediate removal of copper catalyst; (2) adding excess reducing agents post-ATRP which prevent the oxidation of Cu(I) catalyst required by the Glaser coupling mechanism. Post-ATRP Glaser coupling was also influenced by the ATRP synthesis ligand used. The order of ligand activity for catalyzing Glaser coupling was: linear bidentate > tridentate > tetradentate. We find that Glaser coupling is not problematic in ARGET-ATRP of alkyne-terminated polymers because a reducing agent is present during polymerization, however the molecular weight distribution is broadened compared to ATRP due to the presence of oxygen. Glaser coupling can also occur for alkynes held under CuAAC reaction conditions but again can be eliminated by adding appropriate reducing agents.

Cu2+/Cu+ Redox Battery Utilizing Low-Potential External Heat for Recharge

We viewed a redox galvanic cell with copper and platinum electrodes in an electrolyte of copper(II) sulfate and studied the chemical equilibrium between the Cu1+ and Cu2+. The basis of the work of the cell is the ability to continuously generate electromotive force (EMF) by absorbing external heat. The cell is charged by an endothermic reaction, accumulating the reduced form of copper (Cu1+), the number of which is limited thermodynamically, and is discharged by oxidation of Cu1+ to Cu2+ on the surface of copper electrode. In this work we investigated the dependence of the electromotive force of the temperature and a long continuous operation with a voltage of 1.5 mV and thermodynamic efficiency of 45%.

Aggregation enhanced luminescent detection of homocysteine in water with terpyridine-based Cu2+ complexes

Four terpyridine–based Cu2+ complexes with different hydrophilic or hydrophobic groups were synthesized and developed for the detection of Hcy in water based on the aggregation of copper complexes. It is found that these terpyridine–based Cu2+ complexes were reduced by homocysteine (Hcy) along with generation of luminescent four–coordinated Cu+ species. Terpyridine–based Cu2+ complexes bearing hydrophilic groups such as [Ru(bpy)3]+ exhibited turn–on luminescence at 635nm in the presence of Hcy and then the luminescence would be quenched in 1min due to rapid oxidation of Cu+ species by dissolved oxygen in water, resulting in cyclic detection of Hcy. However, complexes bearing more hydrophobic groups exhibited stronger and much more durable luminescence over 10min upon addition of Hcy in water because of aggregation of generated Cu+ species which were beneficial to enhance inhibition of oxygen–induced quenching. A 1500–fold luminescence intensity enhancement at 603nm was observed in the detection of Hcy using the [Ir(ppy)2(bpy)]+ modified terpyridine–based Cu2+ complex. The detection process was fast within 2min and limit of detection (LOD) was found to be ∼10.1nM. Finally, terpyridine–based Cu2+ complexes were successfully applied in cell imaging.

Trimesic acid on Cu in ethanol: Potential-dependent transition from 2-D adsorbate to 3-D metal-organic framework

We report the potential-dependent interactions of trimesic acid with Cu surfaces in EtOH. CV experiments and electrochemical surface-enhanced Raman spectroscopy show the presence of an adsorbed trimesic acid layer on Cu at potentials lower than 0V vs Cu. The BTC coverage increases as the potential increases, reaching a maximum at 0V. Based on molecular dynamics simulations, we report adsorption geometries and possible structures of the organic adlayer. We find that, depending on the crystal facet, trimesic acid adsorbs either flat or with one or two of the carboxyl groups facing the metal surface. At higher coverages, a multi-layer forms that is composed mostly of flat-lying trimesic acid molecules. Increasing the potential beyond 0V activates the Cu-adsorbate interface in such a way that under oxidation of Cu to Cu2+, a 3-D metal-organic framework forms directly on the electrode surface.