Cupric Oxide Nanowires Research Articles

Synergistic effects on thermal growth of CuO nanowires

Growing cupric oxide (CuO) nanowires (NWs) through thermal oxidation of copper (Cu) in air is a facile and low-cost strategy. In a temperature range of 673–1073 K, single-crystal, bi-crystal NWs and cone-shaped nanostructure usually coexist. As far as the underlying mechanism is concerned, the stress-driven grain-boundary (GB) diffusion mechanism has been the most successful theory up to now. However, it did not include the influence of oxygen partial pressure and cannot explain the growth of long single-crystal CuO NWs of uniform diameters. Thus, the CuO NWs growth mechanism is yet to be fully understood. In this study, we present that synergistic effects of the Kirkendall effect, stress-driven GB diffusion, large surface free energy gap between Cu2O and CuO facets and an effective electric field along the CuO NWs originating from oxygen gradient are mainly involved in the thermal growth of CuO NWs.

Nitrogen dioxide sensing based on multiple-morphology cuprous oxide mixed structures anchored on reduced graphene oxide nanosheets at room temperature

Sensitive detection of trace nitrogen dioxide (NO2) gas at room temperature is of urgent necessity in the fields of healthcare and environment monitoring. To achieve this goal, we report on a porous composite film featuring reduced graphene oxide (rGO) nanosheets as the template platform of nanostructured cuprous oxide (Cu2O) nanowires and nanoparticles via a hydrothermal method. The sensor performance was investigated in terms of sensing response, optimal operation temperature, repeatability, long-term stability, selectivity and humidity effect on NO2 sensing. The sensor response achieved 0.66 towards 50 ppb NO2 gas with a full recovery at room temperature (25 °C ± 2 °C), which was among the best cases of Cu2O-related NO2 detection concerning sensor response and operation temperature. Moreover, a modest repeatability, stability, selectivity as well as a negligible humidity effect on NO2 sensing were exhibited. A mass of interspaces existing within nanostructured composites as well as the synergistic effect between rGO and Cu2O materials endowed the sensing layer with favorable gas accessibility and sufficient gas–solid interaction. Simultaneously, highly conductive rGO nanosheets facilitated an effective electron transfer and collection. In brief, the as-prepared rGO/Cu2O sensors showed a competitive room temperature detection capability for ppb-level NO2 gas, providing a vast potential in the future applications such as the real-time monitoring of ultralow emission.

Toward Robust Photoelectrochemical Operation of Cuprous Oxide Nanowire Photocathodes Using a Strategically Designed Solution-Processed Titanium Oxide Passivation Coating.

To date, TiO2 films prepared by atomic layer deposition are widely used to prepare Cu2O nanowire (NW)-based photocathodes with photoelectrochemical (PEC) durability as this approach enables conformal coating and furnishes chemical robustness. However, this common approach requires complicated interlayers and makes the fabrication of photocathodes with reproducible performance and long-term stability difficult. Although sol-gel-based approaches have been well established for coating surfaces with oxide thin films, these techniques have rarely been studied for oxide passivation in PEC applications, because the sol-gel coating methods are strongly influenced by surface chemical bonding and have been mainly demonstrated on flat substrates. As a unique strategy based on solution processing, herein, we suggest a creative solution for two problems encountered in the conformal coating of surfaces with oxide layers: (i) how to effectively prevent corrosion of materials with hydrophilic surfaces by simply using a single TiO2 surface protection layer instead of a complex multilayer structure and (ii) guaranteeing perfect chemical durability. A Cu(OH)2 NW can be easily prepared as an intermediate phase by anodization of a Cu metal, where the former inherently possesses a hydrophilic hydroxylated surface and thus, enables thorough coating with TiO2 precursor solutions. Chemically robust nanowires are then generated as the final product via the phase transformation of Cu(OH)2 to Cu2O via sintering at 600 °C. The coated NWs exhibit excellent PEC properties and a stable performance. Consequently, the perfect chemical isolation of the Cu2O NWs from the electrolyte allows a remarkable PEC operation with the maintenance of the initial photocurrent for more than one day.

Study of CuO Nanowire Growth on Different Copper Surfaces

Cupric oxide (CuO) nanowires were produced by thermal oxidation of copper surfaces at temperatures up to 450 °C. Three different surfaces, namely a copper foil as well as evaporation deposited copper and an application relevant sputtered copper film on Si(100) substrates were characterized ex-situ before and after the experiment. The development of oxide layers and nanowires were monitored in-situ using grazing incidence small angle X-ray scattering. The number density of nanowires is highest for the sputtered surface and lowest for the surface prepared by evaporation deposition. This can be linked to different oxide grain sizes and copper grain boundary diffusions on the different surfaces. Small grains of the copper substrate and high surface roughness thereby lead to promoted growth of the nanowires.

Oriented attachment growth of monocrystalline cuprous oxide nanowires in pure water.

As a crucial mechanism of non-classical crystallization, the oriented attachment (OA) growth of nanocrystals is of great interest in nanoscience and materials science. The OA process occurring in aqueous solution with chemical reagents has been reported many times, but there are limited studies reporting the OA growth in pure water. In this work, we report the temperature-dependent OA growth of cuprous oxide (Cu2O) nanowires in pure water through a reagent-free electrophoretic method. Our experiments demonstrate that Cu2O quantum dots randomly coalesced to form polycrystalline nanowires at room temperature, while they form monocrystalline nanowires at higher temperatures by the OA mechanism. DFT modeling and computations indicate that the water coverage on the Cu2O nanoparticles could affect the particle attachment mechanisms. This study sheds light on the understanding of the effects of water molecules on the OA mechanism and shows new approaches for better controllable non-classical crystallization in pure water.

Material-Independent Nanotransfer onto a Flexible Substrate Using Mechanical-Interlocking Structure.

Nanowire-transfer technology has received much attention thanks to its capability to fabricate high-performance flexible nanodevices with high simplicity and throughput. However, it is still challenging to extend the conventional nanowire-transfer method to the fabrication of a wide range of devices since a chemical-adhesion-based nanowire-transfer mechanism is complex and time-consuming, hindering successful transfer of diverse nanowires made of various materials. Here, we introduce a material-independent mechanical-interlocking-based nanowire-transfer (MINT) method, fabricating ultralong and fully aligned nanowires on a large flexible substrate (2.5 × 2 cm2) in a highly robust manner. For the material-independent nanotransfer, we developed a mechanics-based nanotransfer method, which employs a dry-removable amorphous carbon (a-C) sacrificial layer between a vacuum-deposited nanowire and the underlying master mold. The controlled etching of the sacrificial layer enables the formation of a mechanical-interlocking structure under the nanowire, facilitating peeling off of the nanowire from the master mold robustly and reliably. Using the developed MINT method, we successfully fabricated various metallic and semiconductor nanowire arrays on flexible substrates. We further demonstrated that the developed method is well suited to the reliable fabrication of highly flexible and high-performance nanoelectronic devices. As examples, a fully aligned gold (Au) microheater array exhibited high bending stability (106 cycling) and ultrafast (∼220 ms) heating operation up to ∼100 °C. An ultralong Au heater-embedded cuprous-oxide (Cu2O) nanowire chemical gas sensor showed significantly improved reversible reaction kinetics toward NO2 with 10-fold enhancement in sensitivity at 100 °C.

Multi-branched Cu2O nanowires for photocatalytic degradation of methyl orange

Multi-branched cuprous oxide nanowires (Cu2O NWs) were prepared by one-step hydrothermal method of a facile process. The architecture of these Cu2O NWs was examined by scanning electron microscopy, and the resulting crystal nanowire consists of the trunk growing along [100] plane and the branch growing along [110] plane. Photocatalytic degradation of methyl orange (MO) in the experiment indicates that pure Cu2O NWs prepared at 150 °C have a higher photocatalytic activity (90% MO were degraded within 20 min without the presence of H2O2) compared with the samples obtained at other temperatures. In the photoelectrochemical test, pure Cu2O NWs had outstanding photoelectric response, which corresponds to the catalytic performance. The superior photocatalytic performance can be attributed to the absence of grain boundaries between the small branches and the nanowire trunk, which is conducive to the transport of photo-generated carriers, and the reduction of Cu impurities to reduce the number of recombination centers.

Environment-Modulated Crystallization of Cu2O and CuO Nanowires by Electrospinning and Their Charge Storage Properties.

This article reports the synthesis of cuprous oxide (Cu2O) and cupric oxide (CuO) nanowires by controlling the calcination environment of electrospun polymeric nanowires and their charge storage properties. The Cu2O nanowires showed higher surface area (86 m2 g-1) and pore size than the CuO nanowires (36 m2 g-1). Electrochemical analysis was carried out in 6 M KOH, and both the electrodes showed battery-type charge storage mechanism. The electrospun Cu2O electrodes delivered high discharge capacity (126 mA h g-1) than CuO (72 mA h g-1) at a current density of 2.4 mA cm-2. Electrochemical impedance spectroscopy measurements show almost similar charge-transfer resistance in Cu2O (1.2 Ω) and CuO (1.6 Ω); however, Cu2O showed an order of magnitude higher ion diffusion. The difference in charge storage between these electrodes is attributed to the difference in surface properties and charge kinetics at the electrode. The electrode also shows superior cyclic stability (98%) and Coulombic efficiency (98%) after 5000 cycles. Therefore, these materials could be acceptable choices as a battery-type or pseudocapacitive electrode in asymmetric supercapacitors.

Mechanism for the Formation of Cuprous Oxide Nanowires in AAO template by Electrodeposition

Mechanism for the Formation of Cuprous Oxide Nanowires in AAO template by Electrodeposition

Cupric oxide nanowires on three-dimensional copper foam for application in click reaction

CuO nanowires can be synthesized by facile thermal oxidation of 3D Cu foam in air, which were found to be effective heterogeneous catalysts for the 1,3-dipolar cycloaddition reactions without using any additional support and bases.

The effect of saturation magnetization of nanocatalyst and oscillating magnetic field for green urea synthesis

Hematite and cupric oxide nanowires have been synthesized using the oxidation method for green urea production. Hematite nanowires were obtained by the oxidation of an iron wire at a temperature of 650°C and ambient pressure in the presence of N2 and O2 gases. Cupric oxide nanowires were obtained by the same method at 700°C, using a copper wire. The X-ray diffraction results show the formation of rhombohedral structure of α-Fe2O3 and monoclinic phase of CuO. FE-SEM results reveal the formation of nanowires with dimensions ranging between 5–15µm and 4–12µm in length and a diametere ranging between 50–150nm and 50–250nm for α-Fe2O3 and CuO respectively. The VSM results show that the saturation magnetization values for hematite and cupric oxide were 132.8700 and 0.0124emu/g, respectively. The nanowires were used as catalyst for green urea synthesis in the presence of an oscillating and a static magnetic fields. The use of nanocatalyst with high saturation magnetization gives a higher yield of urea due to the increase in the singlet to triplet conversion. The highest yield of urea 11243ppm was achieved by applying an oscillating magnetic field of frequency 0.5MHz and using α-Fe2O3 nanowires as nanocatalyst.

Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors

Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm2 V−1 s−1.

Facile synthesis of cuprous oxide nanowires decorated graphene oxide nanosheets nanocomposites and its application in label-free electrochemical immunosensor

In this work, the assembly between one-dimensional (1D) nanomaterials and two-dimensional (2D) nanomaterials was achieved by a simple method. Cuprous oxide nanowires decorated graphene oxide nanosheets (Cu2O@GO) nanocomposites were synthesized for the first time by a simple electrostatic self-assembly process. The nanostructure was well confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM) images. Taking advantages of good electrocatalytic activity and high specific surface area of Cu2O@GO nanocomposites, a label-free electrochemical immunosensor was developed by employing Cu2O@GO as signal amplification platform for the quantitative detection of alpha fetoprotein (AFP). In addition, toluidine blue (TB) was used as the electron transfer mediator to provide the electrochemical signal, which was adsorbed on graphene oxide nanosheets (GO NSs) by electrostatic attraction. The detection mechanism was based on the monitoring of the electrochemical current response change of TB by the square wave voltammetry (SWV) when immunoreaction occurred on the surface of electrode. Under optimal conditions, the proposed immunosensor displayed a high sensitivity and a low detection limit. This designed method may provide an effective method in the clinical diagnosis of AFP and other tumor markers.

Assembly and reaction characterization of a novel thermite consisting aluminum nanoparticles and CuO nanowires

A novel approach for assembling Al/CuO thermite consists of aluminum nanoparticles and cupric oxide nanowires has been successfully developed in this study. Aluminum nanoparticles were driven into gaps in the cupric oxide nanowires layer on a copper wire through electrophoretic deposition in this method. The cupric oxide nanowires along with oxide layers were grown on the copper wire via thermal oxidation, and the remaining copper core was the negative electrode that attracted aluminum particles carrying positive surface charges in the ethanol/water solution during electrophoretic deposition. A nanothermite shell enclosing the copper wire was obtained after the process. Considerable heat release from the thermite wire was observed starting from ∼400°C in differential scanning calorimetry measurements. Exothermic solid–solid thermite reactions were fully ignited at 529°C, and the heat release peaked at 566°C. Above the melting temperature of aluminum, another heat release peak, which could be associated with reactions between liquid aluminum and the remaining oxides, was detected at 760°C. Overall heat release of the nanothermite wire assembled with 80V and 10s electrophoretic deposition was 3108J/g. Reaction propagation speed along the nanothermite wire with 10s electrophoretic deposition was the highest at 43.8cm/s, and longer deposition durations resulted in slower burning speeds.

Simple synthesis of silver nanoparticles functionalized cuprous oxide nanowires nanocomposites and its application in electrochemical immunosensor

In this work, silver nanoparticles functionalized cuprous oxide nanowires (Ag@Cu2O) nanocomposites were synthesized by a simple method. The nanostructure of it could be well confirmed by a scanning electron microscope (SEM) image. Due to the good synergistic effect between silver nanoparticles (Ag NPs) and cuprous oxide nanowires (Cu2O NWs), Ag@Cu2O nanocomposites displayed a good electrocatalytic performance towards the reduction of hydrogen peroxide (H2O2). Cyclic voltammograms (CVs) were employed to investigate electrocatalytic mechanism of it. Using Ag@Cu2O nanocomposites as the labels, a novel and ultrasensitive sandwich-type electrochemical immunosensor was developed for the quantitative detection of carcinoembryonic antigen (CEA). Due to the special electrochemical performance of Ag@Cu2O nanocomposites, the facile and sensitive fabrication of the designed immunosensor was achieved. Under optimal conditions, the designed immunosensor exhibited a wide linear range with a low detection limit. It also displayed an electrochemical performance with good reproducibility, selectivity and stability, which would provide potential applications in the clinical diagnosis of other tumor markers.

Enhanced Field Emission from UV-Illuminated CuO Nanowires Fabricated by Thermal Oxidation of Cu Film

Cupric Oxide (CuO) nanowires have been successfully synthesized by direct thermal oxidation of Cu film in air. The morphologies and structures of the synthesized materials are investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results imply that CuO nanowires with well vertical arrays present very narrow sharp peaks, indicating the nanowires are highly crystalline. The effect of ultraviolet (UV) illumination on the field emission characteristics of the CuO nanowires is investigated. The turn-on electric field of UV-illuminated CuO nanowires decreases and the field enhancement factor enhances.

Formation and Characterization of Copper Oxide Nanowires through Thermal Oxidation

In this work, cupric and cuprous oxide nanowires were successfully synthesized through thermal oxidation of copper substrates in a three zone horizontal tube furnace over temperatures ranging from 300 to 800℃. Processing parameters, including temperature, pressure, heating time, type of gas and flow rate, were varied and investigated in terms of their influence on the morphology, aspect ratio, composition and density of the nanowires. Scanning electron microscopy studies show that these nanowires controllably ranged in diameter from 40 to 400 nm with lengths of up to 60 µm and the varying density was a function of the growth temperature and reaction time. High resolution transmission electron microscopy and x-ray diffraction studies were conducted to further identify the chemical composition, crystal structure and growth direction of the nanowires. Additionally, the growth mechanism has been proposed. This study with physical property measurements demonstrates that copper oxide nanowires are attractive choices for future applications in lithium-copper oxide batteries and optoelectronics at nanoscale.

Synthesis of CuO nanowires on Cu-foil using thermal oxidation method, a novel annealing process

Cupric oxide (CuO) nanowires (NWs) on Cu-foils were prepared by thermal oxidation method in air atmosphere using two annealing manners (continuous and steps) in the temperature ranges of 400–500[Formula: see text]C and 400–600[Formula: see text]C. Morphology and microstructure of the NWs was studied using field effect scanning electron microscopy (FESEM), X-ray diffractogram (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Optical reflectance spectrum was used for the optical investigation of the layers. We found the NWs formed have two different morphologies, curved and straight, with diameters between 50 nm and 200 nm and lengths between 5 [Formula: see text]m and 10 [Formula: see text]m. SAED pattern of a single NW revealed as a CuO single crystal with monoclinic structure. The reflectance spectra analysis based on Kubelka–Munk method showed that the band gap energy of the CuO NWs are varying in the range of 1.40–1.47 eV depending on the crystallite sizes of the NWs, a confirmation for the happening of the quantum confined effect in these samples.

Direct growth of CuO/ITO nanowires by the vapor solid oxidation method

In this paper, we report the synthesis results of cupric oxide nanowires (NWs) on the indium tin oxide (ITO) substrate by vapor solid oxidation method. In our study, a Cu layer of thickness 1.4 µm was deposited on ITO thin film substrates through the direct current DC magnetron sputtering method. Cupric oxide NWs grew on ITO after annealing Cu/ITO substrates at the temperatures with range from 350 to 500 °C in air for 3–5 h. The received peak shift of Cu2O to CuO NW phase depending on annealing temperatures was conducted by X-ray diffraction. Chemical atomic elements were obtained from energy dispersive X-ray spectroscopy. The morphology of nanowires were investigated using scanning electron microsope (SEM). The SEM images indicated that the NWs with length about 3–3.5 µm and diameter about 100 nm grew vertically over large area.

The synthesis of cuprous oxide nanowires in the presence of oxygen using a hot tube thermal evaporation method

Cuprous oxide nanowires have been synthesized by heating copper foil in the presence of oxygen rich environment using a hot tube vacuum thermal evaporation method. The effect of growth parameters such as growth time, temperature and oxidative environment on the morphology of the nanowires is investigated. The growth of cuprous oxide nanowires from copper foils thermally oxidized in the presence of oxygen rich at temperatures between 300 and 500 0C. The nanowires were formed within the temperature range of 400 – 500 0C with diameters and length between 25 - 100 nm and length 1 - 4 µm, respectively. This gave an estimate of aspect ratio around 40. Observation from FESEM results revealed the optimal growth of cuprous oxide nanowires which occurred at oxidation times for 1h, 1/2h and 25 minutes and flow rates of oxygen at 0.09 psi, 0.12 psi and 0.08 psi. The atom% of copper and oxygen were measured using EDX and their existence were later confirmed by XRD, essentially indicated by 40% an 60% of copper and oxygen contents, respectively.