Copper Oxide Nanowires Research Articles

Plasma-Enhanced Catalytic CuO Nanowires for CO Oxidation

We report the first experimental study of catalytic CO oxidation over copper oxide (CuO) nanowires (NWs) grown directly on copper meshes. The catalytic activity of CuO NWs is significantly improved by a brief argon or hydrogen radio frequency plasma treatment. The plasma enhancement effect comes from the generation of grain boundaries and the reduction of Cu(II) to the more active oxidation state Cu(I) according to our TEM, XPS, and kinetic study.

Surfactant-free synthesis of novel copper oxide (CuO) nanowire–cobalt oxide (Co3O4) nanoparticle heterostructures and their morphological control

A simple and surfactant-free synthesis of novel heterostructures comprising of copper oxide (CuO) nanowires uniformly decorated with cobalt oxide (Co3O4) nanoparticles was demonstrated by combining thermal growth and wet-coating method. The heterostructures were synthesized by thermally decomposing cobalt salt (cobalt nitrate) into Co3O4 nanoparticles onto vapor–solid (VS)-grown CuO nanowires. X-ray diffraction (XRD) and high resolution transmission electron microscopy (TEM) confirmed the presence of CuO and Co3O4 phases as well as a narrow size distribution of Co3O4 nanoparticles (average diameter ~7.0 ± 1.5 nm) on CuO nanowires (average diameter of nanowire tips ~67.9 ± 18.6 nm). Unique interfacial lattice relationship was observed for (111) Co3O4 nanoparticles on (200) CuO nanowire surface resulting in hemispherical shape of the former. For the first time, further systematic studies were performed to understand the influence of various parameters (cobalt salt concentration and annealing temperature, atmosphere, and time) on the morphological evolution of Co3O4 nanoparticles on CuO nanowires. Interestingly, by varying these parameters, it was possible to grow Co3O4 in different shapes (spherical, triangular, rectangular, cubical, and hexagonal nanoparticles) and forms (shells and nanorods). It was observed that all these parameters play a critical role in influencing the surface migration, nucleation, and growth of Co3O4 nanoparticles on CuO nanowires and this assisted in understanding the involved growth mechanisms. Finally, UV–vis–NIR spectroscopy and band gap energies for these heterostructures were evaluated that showed higher photocatalytic degradation efficiency for Rhodamine B under low-power visible-light illumination.

Direct electrochemistry of hemoglobin immobilized in CuO nanowire bundles

It is one of main challenges to find the suitable materials to enhance the direct electron transfer between the electrode and redox protein for direct electrochemistry field. Nano-structured metal oxides have attracted considerable interest because of unique properties, well biocompatibility, and good stability. In this paper, the copper oxide nanowire bundles (CuO NWBs) were prepared via a template route, and the bioelectrochemical performances of hemoglobin (Hb) on the CuO NWBs modified glass carbon electrodes (denoted as Hb-CuO NWBs/GC) were studied. TEM and XRD were used to characterize the morphology and structure of the as synthesized CuO NWBs. Fourier transform-infrared spectroscopy (FT-IR) proved that Hb in the CuO NWBs matrix could retain its native secondary structure. A pair of well-defined and quasi-reversible redox peaks at approximately −0.325 V (vs. Ag/AgCl saturated KCl) were shown in the cyclic voltammogram curve for the Hb-CuO NWBs/GC electrode, which indicated the direct electrochemical behavior. The Hb-CuO NWBs/GC electrode also displayed a good electrocatalytic activity toward the reduction of hydrogen peroxide. These results indicate that the CuO NWBs are good substrates for immobilization of biomolecules and might be promising in the fields of (bio) electrochemical analysis.

Controllable Synthesis of CuO Nanowires and Cu2O Crystals with Shape Evolution via γ-Irradiation

Copper oxide nanowires and cuprous oxide crystals had been synthesized through gamma-irradiating aqueous CuCl(2)-NaOH-sodium dodecyl sulfate (SDS)-isopropyl alcohol solutions under ambient conditions. The product composition could be changed by modulating the amount of base, NaOH. The morphology of the products could be accurately controlled by altering the amounts of SDS and isopropyl alcohol. A possible formation mechanism was also proposed.

Growth Mechanism of the Copper Oxide Nanowires from Copper Thin Films Deposited on CuO-Buffered Silicon Substrate

The growth mechanism of the CuO single-crystal nanowires (NWs) for future device applications has been demonstrated using the copper films deposited on CuO-buffered substrates. The mechanism involves a two-step process: In the first step, hillocks of copper are formed to relieve the compressive stress existing on the copper films at high temperature for a long duration of time in air and then phase is formed by the oxidation of the hillocks in air ambient. The second step involves a continuous supply of copper through the porous seed and then the transformation of the phase to CuO NW. The CuO NW was grown by a continuous supply of both copper from the copper films and oxygen from air. The indispensable requirements for CuO NW growth from the copper films are the presence of compressive stress in the copper films and the presence of the seed phase on the copper films at a high temperature in air.

Synthesis and Characterization of Copper Oxide nanowires by Facile Heating under Static Air Condition

Large-scaled area and aligned copper oxide nanowires have been synthesized by a vapor-phase approach to the facial synthesis of copper oxide nanowires supported on the surface of a copper gasket. The effects of annealing temperature and time were investigated. Long and aligned nanowires can only formed within a narrow temperature range from 400 to <TEX>$500^{\circ}C$</TEX> for 4 hrs. Annealing copper gasket in static air produces large-area, uniform, but not well vertically aligned nanowires along the copper gasket surface. The surface of copper gasket is converted into bicrystal CuO nanowires was observed after the copper gasket is annealed under static air condition.

Electrochemical deposition of copper oxide nanowires for photoelectrochemical applications

We report a two-step electrochemical process to grow copper oxide nanowires without the use of templates and surfactants. The first step is to electrochemically corrode amorphous Cu–W oxides pre-sputtered on fluorine-doped tin oxide (FTO) coated glass substrates under positive potentials. The second step is to use the corroded samples to grow copper oxide nanowires electrochemically under negative potentials. We find that copper oxide nanowires grown by this method exhibit excellent contact with the FTO-coated substrates leading to good charge transfer. The oxidation states, i.e., CuO or Cu2O, and morphology of nanowires can be controlled by the applied potentials. Cu2O nanowires grown using this method reveal moderate photoelectrochemical response and stability under illumination and under cathodic bias.

Physical Vapor Deposition of Copper Oxide Nanowires

Copper oxide nanowires have been successfully prepared by vapor phase transport technique. The deposition conditions strongly influence the morphology of the nanostructures and in turn their electrical and functional properties. Micro-structural investigation and analysis of the electrical properties were performed together with electrical and functional characterization. Transmission electron microscopy confirmed the high crystalline properties and elemental composition of copper oxide nanostructure. P-type semiconductor and sensing behavior has been proved.

Photoelectric Properties of Electrodeposited Copper(I) Oxide Nanowires

Semiconducting copper(I) oxide nanowires were fabricated by electrochemical deposition into porous polycarbonate membranes from a copper lactate electrolyte. Nanowire composition and structure were varied by controlling the deposition potential and deposition rate, respectively. Nanowires formed at more negative potentials had increased metallic Cu content leading to composites. The nanowires were highly resistive but displayed enhanced conductivity under UV/visible light illumination. Optical spectra show both a plasmon resonance due to metallic copper and an interband absorption due to the bandgap of copper(I) oxide, calculated at .

Synthesis of copper oxalate in ether–water bilayer refluxing system and their conversion to copper oxide nanowires

Copper oxalate nanowires with a mean diameter of 100 nm and a length of 10 µm were synthesized via the reaction of copper acetate and dimethyl oxalate in ether–water bilayer refluxing system. The volume ratio of ether to water and the concentration of copper acetate were used to examine the effects on forming copper oxalate nanowires. Copper oxalate nanowires were obtained only in the case of the greater volume ratio of ether to water and the lower concentration of copper acetate. Copper oxalate nanowires with a dense structure (enclosed by a smooth surface) can be further transformed into highly porous copper oxide nanowires by the decomposition of copper oxalate nanowires at 350 °C.

In-situ oxidation of block copolymer for producing copper oxalate or copper oxide nanowires in mesoporous channels

Copper oxalate nanowires inside the channels of mesoporous SBA-15 are created by in-situ oxidation of block copolymer in as-prepared SBA-15 samples. The pyrolysis of CuC 2O 4/SBA-15 composites under different conditions results in the formation of CuO or Cu 2O nanowires encapsulated in the nanoscale channels. The appearance, structure and composition of these materials are characterized by the X-ray power diffraction, transmission electron microscopy, N 2 adsorption–desorption isotherms, infrared spectra and inductive coupled plasma emission spectra. CuC 2O 4, CuO and Cu 2O nanomaterials filled in the channels of SBA-15 have been proven to possess the electrochemical hydrogen storage capacities of 102, 165 and 231 mAh/g in the second cycle, respectively, and are expected to have a high potential for use in practical applications.

Ferromagnetic behavior of copper oxide-nanowire-covered carbon fibre synthesized by thermal oxidation

Copper oxide nanowires were synthesized on carbon fibre surfaces by annealing of copper thin films at 400 °C for 4 h in air. The nanowires were characterized with field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The magnetic properties of CuO nanowires were measured with a vibrating sample magnetometer (VSM). Its diameters range covered 40–100 nm and lengths range covered 1–3 μm. It is interesting that the CuO nanowires on the carbon fibres showed ferromagnetism at room temperature.

Copper oxide thin film and nanowire as a barrier in ZnO dye-sensitized solar cells

The ZnO dye-sensitized solar cells (DSSCs) with different photoelectrodes were studied on the effect of CuO layer as a barrier layer toward power conversion characteristics. The structures of DSSCs based on ZnO as a photoelectrode, Eosin-Y as a dye sensitizer, iodine/iodide solution as an electrolyte and Pt/FTO as a counterelectrode. CuO powder, nanowire prepared by oxidation reaction of copper powder and CuO thin film prepared by evaporation copper thin film, were used as a layer on the top of ZnO layer to form blocking layer. The photocurrent, photovoltage and power conversion efficiency characteristics for DSSCs were measured under illumination of simulated sunlight obtained from a solar simulator with the radiant power of 100 mW/cm 2. It was found that ZnO DSSCs with CuO thin film exhibited highest current density of 5.10 mA/cm 2 and highest power conversion efficiency of 0.92% than those of CuO powder and nanowire. The enhancement of the power conversion efficiency can be explained in terms of the retardation of the interfacial recombination dynamics of CuO blocking layer.

Vertically Aligned CuO Nanowires Based Electrode for Amperometric Detection of Hydrogen Peroxide

AbstractVertically aligned copper oxide (CuO) nanowires were synthesized by directly heating copper foil on a hotplate under ambient conditions. The as‐grown CuO nanowires film is mechanically stable and was facilely attached to a glassy carbon (GC) electrode, offering an excellent electrochemical sensing platform. The CuO nanowires electrode shows excellent electrocatalytic response to H2O2 with significantly lower overpotentials for its oxidation and reduction and also exhibits a fast response and high sensitivity for the amperometric detection of H2O2. The novel vertically aligned CuO nanowires electrode is readily applicable to other analytes and has great potential applications in the electrochemical detection.

Ionic liquid-assisted synthesis of copper oxalate nanowires and their conversion to copper oxide nanowires

Copper oxalate nanowires were synthesized via the reaction of Cu(CH 3COO) 2·4H 2O and oxalic acid in ethanol solution with the aid of 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF 4) ionic liquid under solvothermal conditions at 180 °C. The as-synthesized nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetric analysis (TG-DSC). The length of the nanowires reaches ∼10 μm, and the width ∼30 nm, giving an aspect ratio of a few hundreds. The formation of the nanowires follows a novel mechanism based on the reorganization of a copper oxalate solid phase. The copper oxalate nanowires can further transform from a dense structure (enclosed by a smooth surface) into highly porous CuO nanowires consisting of interconnected nanocrystallites.

Template electrosynthesis of aligned Cu2O nanowires

Large arrays of aligned copper oxide nanowires were produced by electrodeposition, using anodic alumina membranes as template. We have studied the effect of two fundamental parameters involved in fabrication process: potential perturbation and bath composition. Performing electrodeposition from a copper acetate/sodium acetate bath (pH 6.5), we found that chemical composition of nanowires varied in dependence on the shape of the applied potential perturbation: pure copper oxide nanowires were produced by pulsed potential, whilst continuous electrodeposition resulted in a co-deposition of Cu and Cu2O. In a copper lactate bath, buffered at pH 10, the shape of perturbation did not influence the chemical composition of nanowires, consisting of pure copper oxide. Besides, bath composition influenced the crystallographic structure of nanowires: in the acetate bath polycrystalline nanowires, having a maximum length of about 2.5 μm, were obtained whilst in the lactate electrolyte Cu2O nanowires with a preferential orientation along the (2 0 0) plane were deposited. In every case, nanowire diameters were uniform with an average value of about 200 nm. Growth rate of nanowires was influenced by the shape of potential pulse.

Selective growth and kinetic study of copper oxide nanowires from patterned thin-film multilayer structures

Selective growth of CuO nanowires on the etched face of Al2O3/Cu/Al2O3 thin-film multilayer patterns was achieved by ambient oxidation at 400 °C. The nanowires were observed to selectively grow only from the pattern edge with diameter limited by the thickness of Cu thin film. Transmission-electron-microscopy (TEM) characterization confirmed CuO nanowires of a monoclinic CuO growing in the [010] crystallographic direction. Nanowire growth kinetics was studied at 400 °C for different cumulative growth durations with initial growth rates of ∼1 nm/min. A base growth mechanism with kinetics limited by oxygen diffusion through defects of a scaling oxide film is consistent with observed kinetics. The oxygen diffusivity is found to be ∼10−11 cm2/s, consistent with the grain-boundary diffusion of oxygen through polycrystalline copper oxide.

Synthesis of large-area and aligned copper oxide nanowires from copper thin film on siliconsubstrate

Large-area and aligned copper oxide nanowires have been synthesized by thermalannealing of copper thin films deposited onto silicon substrate. The effects of the filmdeposition method, annealing temperature, film thickness, annealing gas, andpatterning by photolithography are systematically investigated. Long and alignednanowires can only be formed within a narrow temperature range from 400 to500 °C. Electroplated copper film is favourable for the nanowire growth, comparedto that deposited by thermal evaporation. Annealing copper thin film instatic air produces large-area, uniform, but not well vertically alignednanowires along the thin film surface. Annealing copper thin film under aN2/O2 gas flow generates vertically aligned, but not very uniform nanowires onlarge areas. Patterning copper thin film by photolithography helps tosynthesize large-area, uniform, and vertically aligned nanowires along thefilm surface. The copper thin film is converted into bicrystal CuO nanowires,Cu2O film, and also perhaps some CuO film after the thermal treatment in static air. Only CuO in theform of bicrystal nanowires and thin film is observed after the copper thin film is annealed under aN2/O2 gas flow.

Enhanced field emission from O 2 and CF 4 plasma-treated CuO nanowires

The effects of tetrafluoro methane (CF 4) and oxygen (O 2) plasmas on the morphology and field emission of copper oxide (CuO) nanowires are investigated. The tip diameter of nanowires is found to be reduced and the tips sharpened by both plasmas. Furthermore, O 2 plasma removes the amorphous layer on the surface of as-grown nanowires, while CF 4 plasma treatment deposits a thick amorphous coating which results in a decrease in the surface work function. All these factors contribute to the large enhancement of the field emission performance after the plasma treatment.