CuO Nanotubes Research Articles

Synthesis of CuO Nanotubes with Controlled Diameters by Chemical Transformation of Cu Nanowires.

The simple, low-cost, and scalable transformation of Cu nanowires into CuO nanotubes was demonstrated by employing a thermal oxidation processes. The diameter of the Cu nanowires was controlled by utilizing anodic alumina templates with controlled pore sizes and this resulted in CuO nanotubes with various outer and inner diameters after thermal oxidation at 350 °C for 2 h. The morphology, phase, and microstructure of the transformed nanostructures were systematically investigated and it was confirmed that the transformation to the tubular nanostructures resulted from the Kirkendall effect caused by the different diffusion rates of Cu and O in CuxO generated during thermal oxidation. The transformed CuO nanotubes with the controlled diameters have a wide range of applications in photovolatics, catalysis, gas sensors, and field effect transistor because of their dimensionalities and large specific surface areas.

Quantifying bonding strength of CuO nanotubes with substrate using the nano-scratch technique

CuO is a narrow bandgap semiconductor demonstrating applications in/as catalysts, gas sensors, adsorbents, and superconductors, and as electrodes of photocells, super-capacitors, and lithium–ion batteries. One-dimensional (1D) CuO nanostructures are of particular interest in most of these device applications, owing to their huge surface area. Strong bonding between nanomaterials and substrate is essential for extended device life. Hence, knowledge about the strength of the nanomaterial–substrate bond is highly desired. In this research work, CuO nanotubes were synthesized directly on a Cu substrate, and its adhesion strength was quantified using the nano-scratch-based technique. The adhesion energy of CuO nanotubes (for 7 h of reaction period) on the Cu substrate was measured to be 82 Jm−2. The bonding strength can be correlated with the structure of the material. Results of this research will be valuable in analyzing and improving the lifetime of CuO nanotube-based devices, and the technique could be further extended to other 1D transition metal oxide nanostructures.

Improved electrochemical performances of CuO nanotube array prepared via electrodeposition as anode for lithium ion battery

We report a facile strategy to prepared CuO nanotube arrays directly grown on Cu plate through the electrodeposition method. The as-prepared CuO nanotubes show a quasi-cylinder nanostructure with internal diameters of ca. ∼100nm, external diameters of ca. ∼120nm, and average length of ∼3μm. As an anode for lithium ion batteries, the electrochemical properties of the CuO nanotube arrays are investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests. Due to the unique nanotube nanostructure, the as-prepared CuO electrodes exhibit good rate performance (550mAhg−1 at 0.1C and 464mAhg−1 at 1C) and cycling performance (581mAhg−1 at 0.1C and 538mAhg−1 at 0.5C).

Thermal transport and tribological properties of nanogreases for metal-mechanic applications

This study investigates the effect of incorporating nanoparticles – TiO2, Al2O3, CuO, and multi-walled carbon nanotubes (MWNTs) – within greases Mobilgrease 28 and Uniflor 8623B on their thermal transport and tribological properties. Nanoparticle filler fractions, varying from 0.01 to 0.10wt%, were homogeneously dispersed within selected greases. Two tribological tests were performed on a four-ball tribotester; ASTM D5183, and the ITeEPib Polish method for testing lubricants under scuffing conditions. Anti-wear properties resulted in up to 20% wear scar diameter (WSD) reduction using a very low filler fraction of 0.01wt% TiO2. For the extreme pressure test, the increase on the load-carrying capacity was found to be ~19% with a filler fraction of 0.05wt% CuO. A guarded hot-plate method-based apparatus was used in order to characterize thermal conductivity of nanogreases, showing an enhancement of ~28% in thermal conductivity with the addition of 0.10wt% MWNTs. These results demonstrate the potential of nanoparticle additives for improving thermal properties of greases while decreasing friction and wear of mechanical components.

A sandwich-type electrochemical immunosensor based on multiple signal amplification for α-fetoprotein labeled by platinum hybrid multiwalled carbon nanotubes adhered copper oxide

In this work, we designed a novel and ultrasensitive sandwich-type electrochemical immunosensor for quantitative detection of α-fetoprotein (AFP), using β-cyclodextrin functionalized graphene (CD-GS) as the platform and platinum hybrid multiwalled carbon nanotubes adhered copper oxide (Pt@CuO-MWCNTs) as labels. CD-GS has high specific surface area, ideal dispersibility and good biocompatibility, which was used to efficiently capture more primary antibodies (Ab1). Pt, CuO and multiwalled carbon nanotubes (MWCNTs) can be used as catalysts for the decomposition of hydrogen peroxide. The Pt@CuO-MWCNTs realized multiple amplified signals due to their synergy. Therefore, Pt@CuO-MWCNTs was used as the marker, combined with secondary antibodies (Ab2) and this has the effect of multiple amplified signals to catalyze hydrogen peroxide. Under optimal conditions the designed immunosensor exhibited a wide linear range from 1pgmL−1 to 20ngmL−1 with a low detection limit of 0.33pgmL−1 (S/N=3) for AFP. The designed immunosensor showed good selectivity, reproducibility and stability, which could provide potential applications in clinical monitoring of AFP.

Synthesis of Cu(OH)2 and CuO nanotubes arrays on a silicon wafer

Growth of Cu(OH)2 and CuO nanotubes having a diameter of 100 nm on a silicon wafer.

Carbon nanotube based 3-dimensional hierarchical field emitter structure

3-dimensional hierarchical structure of carbon nanotubes on CuO nanotubes offering high field emission current density.

H2S Gas Sensing Properties of CuO Nanotubes

CuO nanotubes are synthesized using TeO₂ nanorod templates for application to H₂S gas sensors. TeO₂ nanorod templates were synthesized by using the VS method through thermal evaporation. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction showed that the synthesized nanotubes were monoclinic-structured polycrystalline CuO with diameter and wall thickness of approximately 100∼300 nm and 5∼10 nm, respectively. The CuO nanotube sensor showed responses of 136∼325% for the H₂S concentration of 0.1∼5 ppm at room temperature. These response values are approximately twice as high as that of the CuO nanowire sensor for the same concentrations of H₂S gas. Along with the investigation of the performance of the sensors, the mechanisms of H₂S gas sensing of the CuO nanotubes are also discussed in this study.

Facile synthesis of CuO nanotubes and their formation mechanism

This paper reports a new facile synthesis method of CuO nanotubes using a three-step process: thermal oxidation of Cu foil in air, dipping in HCl solution, and resuming thermal oxidation in air. This method uses neither any template nor any catalysts. The CuO nanotubes synthesized by this method were 50–150nm in outer diameter and up to 15µm in length and the wall thickness of the nanotubes was ~7nm. The underlying mechanism for the nanotube formation is discussed.

Zeolite-based CuO nanotubes catalysts: investigating the characterization, mechanism, and decolouration process of methylene blue

Novel zeolite-based CuO nanotubes composites were prepared from zeolite-based Cu nanowires by simple thermal oxidation process. The Cu nanowires/zeolite was prepared by reducing a copper–TMEDA complex in an aqueous-cyclohexane bilayer system and using CTAB as a soft template via hydrothermal chemical conversion method. The diameters of the nanowires in the composites are about 300–450 nm with rather smooth surfaces and the diameters of CuO nanotubes in the composites are about 600 nm and their surfaces are rough. It was found that such composites could be used in the photocatalytic decolouration of methylene blue because zeolite bed and CuO form new bands of Cu–O–Si or Cu–O–Al, which act as an electron trapper instead of traditional H2O2 method. Under visible light irradiation, the CuO nanotubes/zeolite showed photocatalytic activities higher than those of pure CuO powder and zeolite. Its decolouration rate has reached 91.5 % within 15 min and the whole decoloration process has completed within 60 min. The as-prepared composites were relatively stable and could be recycled without considering loss of activity.

Synthesis and Characterization of CuO Nanotubes (NTs) Formed By Anodization Sonoelectrochemical

The CuO is an important semiconductor material because this presents a narrow bandgap value (~1.2 – 1.7 eV), p-type conductivity, low toxicity and abundance in nature. From comparison of the photoelectrochemical behavior between CuO and others semiconductor, it is concluded that this oxide is sensible to visible radiation whereas others, more widely used such as; TiO2, ZnO, which absorb in UV region.Despite the above, the copper oxide has a low diffusion rate of charge carriers. Therefore, new synthesis routes leading to a nanostructured oxide is required, so that the photogenerated electrons are accumulated in the vicinity of the surface. This is to facilitate the transfer process of charge per on the recombination.This report shows the results concerning the preparation sonoelectrochemical of CuO nanotubes (NTs). Synthesis of CuO NTs is carried out on a copper (Cu) foil in organic media (x% water in ethylene glycol + 0.5 wt % CuC2O4) using the electrochemical anodization method at a constant room temperature. The anodization is carried out for 10 min at an applied potential of 25 V. Cu foil acts as anode and electrode of carbon (C) acts as cathode. The anodized samples are properly washed with distilled water, to remove the occluded ions, and dried in a furnace.The CuO NTs were characterized by sweep electronic microscopy (SEM), energy dispersive X-ray analysis (EDXA) and Raman spectroscopy.The micrographs show an array of nanotubes on the substrate. The composition of the nanotubes immediately formed consisted mainly of copper, when the synthesis was conducted in a solution with a higher % of water. However, when the samples were heat treated in oxygen atmosphere, an array of CuO NTs was obtained.Furthermore, these samples were characterized by Photoelectrochemical Studies. Acknowledgment The financial support of Fondecyt-Chile (Project N° 1140963) and DI-PUCV (Projects N° 037.305/2013) is gratefully acknowledged by the authors.

Nonenzymatic sensing of glucose using a carbon ceramic electrode modified with a composite film made from copper oxide, overoxidized polypyrrole and multi-walled carbon nanotubes

A carbon ceramic electrode was modified with a thin film composed of overoxidized polypyrrole, CuO and multi-walled carbon nanotubes. The surface morphology, electrochemical properties and electrocatalytic activity towards the oxidation of glucose of the modified electrode were studied in detail. Benefiting from the high electrocatalytic activity of CuO, the selectivity of OPpy film, and the fast electron transfer rate promoted by MWCNTs, this modified electrode displays good stability, selectivity, high electrocatalytic activity and a low detection limit for the determination of glucose in pH 13 solution. Under the optimum conditions, the linear range for the determination of glucose by cyclic voltammetry is from 20 μM to 10 mM, and the detection limit is 4.0 μM (at an SNR of 3). The amperometric calibration plot covers the 0.20 μM to 2.0 mM concentration range, and the detection limit is 50 nM. The highest sensitivity for the determination of glucose is 3922.6 μA mM−1 cm2.

Antiwear and Extreme Pressure Properties of Nanofluids for Industrial Applications

This study investigates the effect of CuO, TiO2, Al2O3, and multiwalled nanotube (MWNT) nanoparticles at various treat rates on the tribological properties, namely, wear, coefficient of friction (COF), and pressure of seizure (poz), of metalworking fluids during lubricating processes in diverse industrial applications. Results are reported based on two methods: wear scar diameter (WSD) and COF by ASTM D5183 and poz by the Institute for Sustainable Technologies–National Research Institute (ITEePib) Polish method for testing lubricants under scuffing conditions. Results showed significant improvements with small filler concentrations of nanoparticles. CuO nanofluids showed a diminishment of 86% for WSD at 0.01 wt%, whereas TiO2 resulted in an increase in poz of up to ∼250% at 0.05 wt% compared to pure conventional fluid.

Template-free hydrothermal method for the synthesis of multi-walled CuO nanotubes

Multi-walled CuO nanotubes (NTs) were prepared by a simple hydrothermal method followed by a low temperature thermal oxidation process without the use of any catalysts, surfactants or substrates. Pure multi-walled CuO NTs were obtained after hydrothermal treatment at 100°C followed by a calcination process at 400°C. It was shown that the obtained multi-walled CuO NTs with high purity and crystallinity had 3nm inner and 7nm outer diameters and showed a strong antibacterial effect against Staphylococcus aureus bacteria.

Chemical replacement route to Cu2−xSe-coated CuO nanotube array anode for enhanced performance in lithium ion batteries

The utilization of well-aligned hybrid one-dimensional hollow nanostructured arrays is a promising strategy for the development of transition metal oxides as high-cycle-life stability and high-rate performance electrode materials for lithium ion batteries. Here we report a chemical replacement route to prepare well-aligned Cu2−xSe-coated CuO nanotube arrays with diameters of 400 nm and length of several micrometers, based on Cu(OH)2 nanotube arrays grown on a copper substrate as precursors. As an integrated anode for lithium ion batteries, the Cu2−xSe-coated CuO nanotube array on a copper substrate is capable of delivering a high cycling capacity of 764 mA h g−1 after 100 cycles at a current density of 0.08 mA cm−2 (0.1 C), and retains a discharge capacity of 382.5 mA h g−1 and 94.5 mA h g−1 at current densities of 10 mA cm−2 (12.5 C) and 20 mA cm−2 (25 C), respectively, exhibiting superior performance to the bare CuO nanotube array film. The synergistic effect of the successful integration of the CuO nanotubes with the Cu2−xSe semiconducting coating layer significantly contributes to the enhanced electrochemical properties of the Cu2−xSe-coated CuO nanotube array anode.

Cost-effective CuO nanotube electrodes for energy storage and non-enzymatic glucose detection

Porous CuO nanotube electrodes synthesized by thein situoxidation of copper foils exhibit superior pseudocapacitive and electrocatalytic performances.

A novel method to enhance the conductance of transitional metal oxide electrodes

Transitional metal oxides hold great potential for high capacity anodes. However, the low electron conductivity of such materials leads to poor cycling stability and inferior rate capability. We reported herein the use of a novel hydrogen plasma technology to improve the conductance of metal oxides, which leads great success in improving the rate performance of CuO nanotube based anodes. This method has the potential to be widely adopted in the field of lithium ion batteries and supercapacitors.

One-dimensional copper oxide nanotube arrays: biosensors for glucose detection

One dimensional CuO nanotube (NT) arrays were synthesized by an anodization method and evaluated for glucose detection. The CuO NT arrays electrode showed enhanced activity with a sensitivity of 1.89 mA mM−1 cm−2 and a linear range from 5 μM to 3.0 mM compared with CuO nanorod (NR) arrays due to its larger surface area and faster biomolecule diffusion. Furthermore, the proposed biosensor exhibited excellent stability, high reproducibility and high selectivity for the detection of glucose, and had been successfully applied to determine glucose levels in human plasma samples with satisfactory results. The success of this work indicates the perspective of this kind of CuO electrode for further design and microfabrication of bioelectrochemical nanodevices.

Fabrication and characterisation of CuO nanotubes electrodeposited into aluminium oxide template in ionic liquid

CuO nanotubes are fabricated by direct current electrodeposition within the porous anodic aluminium oxide (AAO) template in urea–NaBr–KBr–CuCl2–acetamide ionic liquid. The AAO membrane is subject to the dual oxidation (two-step) anodising. The composition and morphology of the as prepared products are characterised using X-ray diffraction pattern and scanning electron microscopy images. Results indicate that the CuO nanotubes with 3–4 μm length and 80 nm diameter grow, which is perpendicular to the substrate. The results provide a new method for the synthesis of nanotubes.

Dopant-stimulated CuO nanofibers for electro-oxidation and determination of glucose

We described the preparation of copper oxide composite nanofibers doped with carbon nanotubes (CuO/C-NFs) or nickel oxide(CuO/NiO-NFs) by electrospinning for direct glucose determination. The interest in exploring practical CuO/C-NFs and CuO/NiO-NFs electrode materials for sensor application was fascinated by the possibility of promoting electron transfer for kinetically unfavorable glucose oxidation reactions at a lower overpotential and thus improving the selectivity of the electrode for glucose in electroanalysis. The morphologies of CuO/C-NFs and CuO/NiO-NFs were characterized by scanning electron microscopy(SEM) and X-ray powder diffraction(XRD). The electrocatalytic performances of glucose were evaluated in detail by cyclic voltammetry(CV) and chronoamperometry. Facile charge transport, enhanced current response(at a lower overpotential of +0.35 V), improved stability and selectivity, as well as excellent resistance towards electrode fouling were observed at CuO/C-NFs electrode in direct glucose electroanalysis. These merits are attributed to the highly porous three-dimensional network film structure of CuO/C-NFs electrode materials and the potential synergic catalytic effect of CuO and carbon nanotubes in composite nanofibers. This study may provide a new insight into metal oxide-based composite nanofibers obtained via electrospinning for fabricating novel and high performance sensors and devices.