CuO Nanotubes Research Articles

Nanotube Arrays: Joining Copper Oxide Nanotube Arrays Driven by the Nanoscale Kirkendall Effect (Small 15/2013)

Two stacks of nanotube arrays are joined together, driven by the nanoscale Kirkendall effect. The background images show elemental mapping of copper and oxygen. The contrast of colors shown in the maps represents the intensity of the signals. Such mapping analysis reveals that the interface of the joined nanotubes is copper oxide. On page 2546, C. L. Gan and co-workers demonstrate that the transformation from Cu nanowire arrays into copper oxide nanotube arrays can be coupled with the joining of the stacked chips in a single step process. By controlling the environment, temperature, and duration, joined Cu2O or CuO nanotube stacked chips can be achieved, which serve as a platform for the further development of stacked nanostructured devices.

Fabrication of CuO nanotubes by electrospinning, metallisation and annealing

A straightforward combined technology of electrostatic spinning and metallisation was developed to produce novel metallic nanotubes and nanofibres. The metals were deposited onto electrospun poly(vinyl alcohol) (PVA) nanofibres as a template by metallisation method. After removal of the nanofibre template by heat treatment at 400°C for 24 h, the fibrous morphologies were satisfactorily conserved, suggesting the successful deposition of metal layer on the surface of nanofibre template. Wide-angle X-ray diffraction data confirmed that the PVA nanofibres metallised with the copper layer of 200 nm clearly showed typical copper crystalline peaks, whereas after calcination of the nanofibre templates, interestingly, new crystalline peaks were observed at 2θ = 32.5°, 35.5°, 38.7°, 48.7°, 53.4° and 58.4°, corresponding to the (1 1 0), (0 0 2), (1 1 1), ( 0 2), (0 2 0) and (2 0 2) reflections, respectively. The resulting metallic nanotubes and nanofibres were found to show a typical CuO crystalline structure.

CuO Necklace: Controlled Synthesis of a Metal Oxide and Carbon Nanotube Heterostructure for Enhanced Lithium Storage Performance

Metal oxide and nanocarbon heterostructures provide a powerful strategy to materials innovation because judicious combination of different materials may afford collective properties that are otherwise unattainable. However, design and fabrication of spatially patterned heterostructures has been still challenging. Here, we develop a facile approach to synthesize a CuO and carbon nanotube necklace-like heterostructure in solution for enhanced lithium storage performance. Observations confirm that propagative sidewall alkylcarboxylation of carbon nanotubes in liquid ammonia allows the CuO nanospheres to grow on the functional defect sites introduced by the functionalization. Such a method does not require surfactants and is highly scalable. The resulting materials show high lithium ion storage capacities (stable at 500 mAh g–1) and enhanced cycling performance as a lithium-ion battery anode. The improved performance is attributed to the necklace-like nanostructure, which provides an electrical channel as well as excess room to accommodate the volume changes of CuO during electrochemical cycling.

A Simple Fabrication of Interconnected CuO Nanotube Electrodes for High‐Performance Lithium‐Ion Batteries

Staying connected: Robust and interconnected CuO nanotube anodes were fabricated by a thermal oxidation process of spin-coated CuO nanowire networks. The CuO electrodes strongly adhered to the stainless steel foils and exhibited a high specific capacity (ca. 635 mAh g(-1)), a stable cycling (capacity retention of >99 % after 50 cycles), and excellent rate capabilities (315 mAh g(-1) at 20 C rate).

Joining Copper Oxide Nanotube Arrays Driven by the Nanoscale Kirkendall Effect

Various annealing conditions (environment, temperature, and duration) are applied to study the nanoscale Kirkendall effect of copper (Cu) nanowire (NW) arrays on a Si substrate. The results show that an appropriate amount of oxygen supply is crucial for uniform transformation from Cu NWs (average diameter ∼50 nm) into Cu oxide nanotube arrays. An annealing duration of 30 min at 200 °C in a low vacuum environment reveals that the voids are not uniformly distributed at the Cu/Cu oxide interface. This suggests that void growth is due to surface diffusion of Cu along void surfaces. Annealing above 200 °C for 60 min resulted in complete transformation from Cu NWs into Cu oxide nanotubes. X-ray photoelectron spectroscopy characterization indicates that the Cu oxides formed at 200 °C and 300 °C are Cu₂O and CuO, respectively. It is demonstrated that the transformation from Cu NW arrays into Cu oxide nanotube arrays can be combined with the joining of stacked Si chips in a single-process step with reasonable joint shear strength. Transmission electron microscopy-electron energy loss spectroscopy elemental mapping analysis reveals that the joint interface is Cu oxide. The outward diffusion of Cu driven by the nanoscale Kirkendall effect is believed to enhance the joining process. By controlling the environment, temperature, and duration, joined Cu₂O or CuO nanotube stacked chips can be achieved, which serve as a platform for the further development of nanostructured, stacked devices.

A high-performance nonenzymatic glucose sensor made of CuO–SWCNT nanocomposites

Nanocomposites of CuO and single-wall carbon nanotubes (SWCNTs) were synthesized using an arc-discharging graphite rod that contained copper wires. Simultaneous arc discharges produced a CuO–SWCNT composite network. The crystalline structure and morphology of the CuO–SWCNT composite films were investigated using XRD, Raman spectroscopy, FE-SEM and TEM. The electrochemical properties were investigated by cyclic voltammogram and amperometric measurements in a 0.1M NaOH solution. The CuO content in the CuO–SWCNT nanocomposites was optimized for nonenzymatic glucose detection. The glucose sensing properties of the optimized CuO–SWCNT electrode showed good stability, selectivity, and linear glucose detection that ranged from 0.05 to 1800μM with a higher sensitivity of 1610μAcm−2mM−1, a quick response time of 1–2s, and the lowest limit of detection at 50nM. The sensing performance was better than the pure CuO and SWCNT sensors, and the synergetic effect of the composite sensor was attributed to the high conductivity network of highly porous nanowires. The sensor also showed a good response in a human serum sample, which proves its high potential towards a commercial nonenzymatic glucose sensor.

Controllable synthesis of well‐aligned CuO nanotube arrays using porous alumina templates

AbstractIn order to further enhance the performance of CuO in currently existing applications, well‐aligned CuO nanotube arrays with different diameters were fabricated. During the synthesis process, porous anodic alumina films were fabricated, and then the synthesis of CuO nanotube arrays was realized by using the obtained porous anodic alumina films as templates. The morphology and structure of the obtained products has been confirmed by field‐emission scanning electron microscopy, transmission electron microscopy and X‐ray diffraction measurements. Due to the large surface area of the synthesized products, the prepared CuO nanotube arrays may have potential applications in catalyzing and gas sensing area.

Synthesis of copper(ii) coordination polymers and conversion into CuO nanostructures with good photocatalytic, antibacterial and lithium ion battery performances

Two different nanostructured copper–isonicotinic acid (INA) coordination polymers, Cu(C6H4NO2)2(H2O)4 and [Cu(C6H4NO2)(OH)]H2O have been successfully synthesized under hydrothermal conditions on a large scale without the assistance of surfactants or template. Cu(C6H4NO2)2(H2O)4 has the morphology of 2-dimensional (2D) butterfly-like nanosheet structures, while [Cu(C6H4NO2)(OH)]H2O consists of one-dimensional (1D) nanorods. A possible formation mechanism of the obtained coordination polymer nanostructures is proposed with provision of the crystal structure. After heat treatment, hierarchical CuO butterfly-sheet-like nanostructures and CuO nanotubes were obtained. The photocatalytic and antibacterial studies indicate that the as-obtained CuO samples have great photocatalytic activities for the degradation of Rhodamine B and good bacteriostatic activities. In addition, the electrochemical measurements show that CuO samples exhibit high reversible discharge capacities and stable cyclic performances.

Isopropyl Alcohol Sensors of CuO Nanotubes by Thermal Oxidation of Copper Films on Glass

The growth of CuO nanotubes on Cu/CuO/glass templates is reported. It was found that porous structures were formed at the interface between sputtered CuO film and Cu layer after annealing. The average length of the nanotubes and thickness of the porous structure both increased monotonically as we increased the initial thickness of the copper film. The CuO nanotubes were used to fabricate isopropyl alcohol (IPA) sensors. With a 5-V applied bias, the current became smaller as the IPA was injected into the sealed test chamber. Furthermore, the measured response was larger for the sensors with longer CuO nanotubes.

Cu(OH) 2 and CuO nanotube networks from hexaoxacyclooctadecane-like posnjakite microplates: Synthesis and electrochemical hydrogen storage

Our recent progress shows that Cu(OH) 2 and CuO nanoribbon arrays exhibit notable electrochemical hydrogen storage capacities of 180 and 160 mAh/g, respectively, which also suggests that porous or tubular nanostructures can have a higher ability of hydrogen uptake. Two dimensional (2D) networks consisting of crossed Cu(OH) 2 nanotubes were prepared by a simple topotactic transformation process, including the fabrication of hexaoxacyclooctadecane-like intermediate posnjakite microplates and their subsequent chemical transformation into Cu(OH) 2 nanotube networks, which further dehydrated to produce CuO nanotube networks with partial morphological preservation. The formation of half-tube and half-ribbon structures, nanoribbons, and nanotubes during the transformation processes revealed that the deformations of corrugated posnjakite sheets to give lamellar Cu(OH) 2 with rolling into tubular structures could be responsible for the growth of Cu(OH) 2 nanotube networks from posnjakite microplates. The Cu(OH) 2 and CuO nanotube networks could electrochemically charge and discharge with higher hydrogen storage capacities of 220 and 188 mAh/g than the Cu(OH) 2 and CuO nanoribbon arrays at room temperature, respectively, which made them promising candidates for hydrogen storage, high-energy batteries and catalytic fields. Based on the rolling mechanism of layered structural materials, this simple topotactic transformation route might be extendable to the preparation of novel nanotube networks with higher capacities of hydrogen storage if appropriate precursors of numerous materials with layered structures were treated in solution.

Confined conversion of CuS nanowires to CuO nanotubes by annealing-induced diffusion in nanochannels

Copper oxide (CuO) nanotubes were successfully converted from CuS nanowires embedded in anodic aluminum oxide (AAO) template by annealing-induced diffusion in a confined tube-type space. The spreading of CuO and formation of CuO layer on the nanochannel surface of AAO, and the confinement offered by AAO nanochannels play a key role in the formation of CuO nanotubes.

Tunable Synthesis of Cuprous and Cupric Oxide Nanotubes from Electrodeposited Copper Nanowires

Polycrystalline copper oxide nanostructures with different valence/oxidation states (i.e., Cu2O and CuO) were readily synthesized by thermal oxidation of single crystalline copper nanowires at relative low operating temperature (200 to 300 degrees C). Operating temperature of 200 to 250 degrees C in air oxidized copper to Cu2O and further increased temperature (i.e., 300 degrees C) led to form CuO nanostructures. The morphology of nanostructures significantly altered from nanowires to nanotubes which might be attributed to Kirkendall effect. The electrical resistivity of single copper nanowire, Cu2O and CuO nanotube were determined to be 3.4 x 10(-4), 33, and 211 omega cm, respectively.

Synthesis of TiO<SUB>2</SUB> and CuO Nanotubes and Nanowires

Synthesis of TiO<SUB>2</SUB> and CuO Nanotubes and Nanowires

Synthesis of Sn doped CuO nanotubes from core–shellCu/SnO2 nanowires by the Kirkendall effect

Sn doped CuO nanotubes were synthesized by thermal oxidization ofCu/SnO2 core–shell nanowires in air through the Kirkendall effect. TheCu/SnO2 core–shell nanowires were sequentially electrodeposited by forming aSnO2 shell followed by electrodeposition of the Cu core. After thermal treatment in air, the core–shellCu/SnO2 (13 ± 2 nm thickshell on 128 ± 15 nm in diameter core) nanowires were oxidized to form Sn doped CuO nanotubes with an averagewall thickness and outer diameter of 54 nm and 176 nm, respectively. Room temperatureI–V characterization indicated that the electrical resistivity of the nanostructures was870 ± 85 Ω cm.The methodology that was demonstrated is very general and could be used to synthesize coaxialSnO2 shells with a variety of electrodeposited cores. In addition, doped metal oxide nanotubescan be readily synthesized by thermal oxidization of core–shell nanowires in air where thedopant content can be tuned by controlling the shell thickness through adjusting thedeposition time.

Preparation of CuO Hollow Spheres by Oxidation of Cu Microspheres

Copper oxide (CuO) is a p-type semiconductor with narrow band-gap of 1.2 eV and is widely used as a photoconductive material, and in gas sensors and heterogeneous catalysts. Various morphologies of CuO, such as rods, wires, ribbons, spheres, and even dandelions have been obtained via different synthesis routes. Hollow microparticle CuO structures are probably of most interest due to their potential applications as catalysts, because of their low densities and large surface areas. Hardand soft-templates are commonly used to fabricate hollow copper oxides structures. Hollow CuO microspheres have been prepared hydrothermally from copper acetate as a precursor, and by a hydrothermal reaction using a coppercomplex, in which hexamethyltriethylenetetramine (HMTA) was used as a complexing reagent. Dandelion-like CuO hollow microparticles were also produced, via a donut-like intermediate assembly that consisted of equatorial stacks of rhombic CuO strips, by hydrothermal reaction between copper nitrate and NaOH. The simplest method of making CuO is by the direct oxidation of copper metal in air. Many research groups have prepared CuO nanowires and nanotubes by oxidizing copper nanowires and foils. However, it is difficult to obtain copper metal microspheres for the preparation of hollow CuO microspheres by direct thermal oxidation. Here, we describe a straightforward method for preparing hollow CuO microspheres with radially projecting surface nanorods via the direct thermal oxidation of copper metal microspheres. The morphologies of CuO microspheres and the mechanism of their formation are discussed.

CuO Nanotubes Synthesized by the Thermal Oxidation of Cu Nanowires

Copper oxide (CuO) is a narrow band-gap semiconducting oxide that has been widely used as a cathode in dye-sensitized solar cells, gas sensors and heterogeneous catalysts. Much effort has been devoted to synthesizing unique CuO nanostructures, such as, rods, wires, ribbons, cubes, spheres and dandelions. Unlike nanorods and nanowires, only a few groups have synthesized CuO nanotubes due to fabrication difficulties within hollow nanorods and nanowires. CuO nanotubes were synthesized by pyrolyzing copper acetylacetonate within the pores of the anodic alumina membranes. CuO nanotubes of average length 100 nm were also synthesized by a hydrothermal process involving microemulsified Cu(OH)42−.12 The simplest method of making CuO is from the direct thermal oxidation of copper metal, and many research groups have prepared CuO nanowires and nanorods by oxidizing copper foils. However, due to self aggregation, it is difficult to obtain long copper nanowire or nanorod precursors for the preparation of CuO nanotubes by direct thermal oxidation. Here, we describe the preparation of CuO nanotubes from long copper nanowires by simple thermal oxidation. The morphologies of the CuO nanotubes produced were determined by scanning electron microscopy and transmission electron microscopy.

Tube Formation in Nanoscale Materials

The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas–solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb2O5nanotubes have been prepared by employing sacrificial template strategy based on liquid–solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities.

A comparison of anodically grown CuO nanotube film and Cu2O film as anodes for lithium ion batteries

CuO nanotube film and Cu2O film were anodically grown on Cu substrates through direct oxidation and electrochemical anodic reduction, respectively. The microstructure and morphology of the films were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The obtained CuO is monoclinic crystallization, and the diameters of tubes are about 100–300 nm, while the as-prepared Cu2O has a typical structure with a space group Pn3m and consists of compact faceted crystals. As anodes for Li-ion batteries, the electrochemical properties of the nanostructured CuO and Cu2O films were investigated by cyclic voltammogram and galvanostatic charge–discharge tests. An “apparent charge capacity” was introduced to describe the electrochemical performance. The initial apparent discharge capacity of the CuO and Cu2O film electrode reached to 911 and 570 mAh/g, respectively. Although they exhibited large irreversible capacities attributed to the formation of solid electrolyte interface (SEI) during the first cycle, the CuO nanotube film and Cu2O film had good cyclability and delivered the apparent capacity of 417 and 219 mAh/g after 30 cycles, respectively.

Synthesis and Characterization of Nanostructured CuO Array Films

In this paper, we report a simple and large-scale fabrication of CuO array films with different nanostructures grown on copper foils. CuO nanotube and nanorod array films were synthesized through the dehydration of the nanostructured Cu(OH)2 arrays in flow of N2, which are prepared in an alkali solution at a low temperature without using any templates and surfactants. The obtained CuO nanotube and nanorod array films retain similar morphology to that of the Cu(OH)2 precursors. While CuO nanosheet and nanobelt array films were prepared directly in the alkali solution. The evolution of the nanostructures as a function of the reaction conditions has been revealed, from nanorods of Cu(OH)2 to nanotubes of Cu(OH)2 to nanosheets of CuO to nanobelts of CuO. Experiments show that the growth temperature plays an important role in the formation of well-aligned Cu(OH)2 nanostructured array films on copper foil. The samples are characterized by XRD, SEM and TEM.

Growth of novel nanostructured copper oxide (CuO) films on copper foil

CuO nanotube arrays and nanoflower films have been prepared in large area, respectively. Ordered CuO nanotube arrays were successfully prepared by heating the corresponding Cu(OH) 2 nanotube precursors in N 2, while CuO nanotube arrays with special nanoplate wall structure were obtained by heating the Cu(OH) 2 nanotube precursor in benzene solvent in autoclave solvothermally. Besides, CuO nanoflower film was directly prepared via the oxidation reaction of copper foil in autoclave hydrothermally. The samples have been characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. These novel hierarchical CuO nanoarchitectures may be used as nanobuilding blocks for field emitters and other nanoelectronic devices.