CuO Nanorod Arrays Research Articles

CuO Nanorod Arrays Formed Directly on Cu Foil from MOFs as Superior Binder-Free Anode Material for Lithium-Ion Batteries

In this study, an in situ growth method is developed for the partial conversion of current collector into active materials for lithium ion batteries (LIBs). Through thermal treatment of a metal–organic framework (MOF) precursor, of which the metal ion is provided by a Cu foil current collector, porous CuO nanorod arrays (NRAs) can be directly formed on Cu foil. Importantly, this strategy can avoid the poor contact problem between the current collector and electrode material as well as circumvent the addition of insulating material (binder) and inhomogeneous distribution of conductive carbon material and active material on the current collector. When evaluated as binder-free electrodes for LIBs, porous CuO NRAs deliver a high specific capacity (1341 mA h g–1 at 100 mA g–1) and enhanced rate capability and cycling ability (671 mA h g–1 at 100 mA g–1 after 150 cycles).

Fabrication and Photoelectrochemical Properties of a Cu2O/CuO Heterojunction Photoelectrode for Hydrogen Production from Solar Water Splitting

We report on the fabrication and characterization of a novel Cu2O/CuO heterojunction structure with CuO nanorods embedded in Cu2O thin film as an efficient photocathode for photoelectrochemical (PEC) solar water splitting. A CuO nanorod array was first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method; then, a Cu2O thin film was electrodeposited onto the CuO nanorod array to form an oxide semiconductor heterostructure. The crystalline phases and morphologies of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy, as well as Raman scattering. The PEC properties of the fabricated Cu2O/CuO heterojunction photocathode were evaluated by photocurrent conversion efficiency measurements under white light illumination. From the observed PEC current density versus voltage (J-V) behavior, the Cu2O/CuO photocathode was found to exhibit negligible dark current and high photocurrent density, e.g. −1.05 mA/cm2 at −0.6 V vs. Hg/HgCl2 in 1 mM Na2SO4 electrolyte, revealing the effective operation of the oxide heterostructure. The photocurrent conversion efficiency of the Cu2O/CuO photocathode was estimated to be 1.27% at −0.6 V vs. Hg/HgCl2. Moreover, the PEC current density versus time (J-T) profile measured at −0.5 V vs. Hg/HgCl2 on the Cu2O/CuO photocathode indicated a 3-fold increase in the photocurrent density compared to that of a simple Cu2O thin film photocathode. The improved PEC performance was attributed to a certain synergistic effect of the bilayer heterostructure on the light absorption and electron-hole recombination processes.

Synthesis and photoelectrochemical properties of a novel CuO/ZnO nanorod photocathode for solar hydrogen generation

Here, we present a facile synthesis method and photoelectrochemical characterizations of a p-type CuO-nanorod array photoelectrode with ZnO nanorod branches. Vertically-aligned CuO nanorods were synthesized by using direct oxidation of metallic Cu nanorods grown on a Cu substrate by using a facile template-assisted electrodeposition method. The formed CuONR/ZnONB hierarchically-structured photoelectrode exhibited remarkable photoelectrodechemical performance and outstanding stability compared to the CuO NR photoelectrode without ZnO NR branches. Morphological, optical and electrochemical characterizations were carried out in order to examine the effects of ZnO nanorod branches on the stability and the overall electrochemical performance of the electrode.

Self-assembly of aligned CuO nanorod arrays using nanoporous anodic alumina template by electrodeposition on Si substrate for IR photodetectors

Hexagonally highly-ordered thin nanoporous anodic alumina (AAO) template of pre-deposited Al thin film onto Si substrate was fabricated under controllable conditions through a two-step anodization for the growth of nanostructured materials. The obtained AAO template has approximately 60nm of pore diameter and 1200nm length with 110nm interpore distances within an area of 0.75cm2. A bottom barrier layer of the AAO template was removed by wet etching using phosphoric acid (5wt%) for several minutes at room temperature. As an application, Cu nanorod-arrays embedded in AAO template was prepared by dc electrodeposition. The electrodeposited Cu nanorod-arrays onto Si based AAO template were oxidized at optimized conditions inside a conventional furnace to produce high-quality CuO nanorod arrays. The free-standing CuO nanorod arrays were formed after subsequent removal of AAO template. Fast with high-performance CuO nanorod-arrays IR photodetector based on MSM were fabricated with Al contact electrodes and its optoelectronic properties were examined. The electrical performance and photoelectric response performance were studied and the results showed that IR photodetector exhibited a high sensitivity to 808nm IR laser light. Both the response and recovery time were found to be fast; 0.19 and 0.17s, respectively, which are much shortest time compared to other IR photodetectors reported in the literature.

High Responsivity IR Photodetector Based on CuO Nanorod Arrays/AAO Assembly

Fast with high-performance CuO nanorod arrays IR photodetector was fabricated using CuO nanorod arrays/AAO assembly. The IR photodetector based on MSM with Al contact electrodes and its optoelectronic properties were examined. The CuO nanorod arrays used in the experiment were synthesized by DC electrodeposition method into Si-based/AAO template. The electrical performance and photoelectric response performance were studied, and the results showed that IR photodetector exhibited a high sensitivity to 808nm infrared diode laser source. Both the response and recovery time were found to be fast; 0.19 and 0.15 s, respectively, which are shorter time compared to other IR photodetectors reported in the literature.

Effects of the voltage and time of anodization on modulation of the pore dimensions of AAO films for nanomaterials synthesis

Highly-ordered and hexagonal-shaped nanoporous anodic aluminum oxide (AAO) of 1 μm thickness of Al pre-deposited onto Si substrate using two-step anodization was successfully fabricated. The growth mechanism of the porous AAO film was investigated by anodization current-time behavior for different anodizing voltages and by visualizing the microstructural procedure of the fabrication of AAO film by two-step anodization using cross-sectional and top view of FESEM imaging. Optimum conditions of the process variables such as annealing time of the as-deposited Al thin film and pore widening time of porous AAO film were experimentally determined to obtain AAO films with uniformly distributed and vertically aligned porous microstructure. Pores with diameter ranging from 50 nm to 110 nm and thicknesses between 250 nm and 1400 nm, were obtained by controlling two main influential anodization parameters: the anodizing voltage and time of the second-step anodization. X-ray diffraction analysis reveals amorphous-to-crystalline phase transformation after annealing at temperatures above 800 °C. AFM images show optimum ordering of the porous AAO film anodized under low voltage condition. AAO films may be exploited as templates with desired size distribution for the fabrication of CuO nanorod arrays. Such nanostructured materials exhibit unique properties and hold high potential for nanotechnology devices.

Growth and fabrication method of CdTe and its performance as a radiation detector

We report the nitrogen-monoxide (NO) gas-sensing properties of transparent p-type copper-oxide (CuO) nanorod arrays synthesized by using the hydrothermal method with a CuO nanoparticle seed layer deposited on a glass substrate via sputtering process. We synthesized polycrystalline CuO nanorods measuring 200 to 300 nm in length and 20 to 30 nm in diameter for three controlled molarity ratios of 1:1, 1:2 and 1:4 between copper nitrate trihydrate [Cu(NO2)2·3H2O] and hexamethylenetetramine (C6H12N4). The crystal structures and morphologies of the synthesized CuO nanorod arrays were examined using grazing incidence X-ray diffraction and scanning electron microscopy. The gas-sensing measurements for NO gas in dry air indicated that the CuO nanorodarray-based gas sensors synthesized under hydrothermal condition at a molarity ratio of 1:2 showed the best gas sensing response to NO gas. These CuO nanorod-array gas sensors exhibited a highly sensitive response to NO gas, with a maximum sensitivity of about 650% for 10 ppm NO in dry air at an operating temperature of 100 ℃. These transparent p-type CuO nanorod-array gas sensors have shown a reversible and reliable response to NO gas over a range of operating temperatures. These results indicate certain potential use of p-type oxide semiconductor CuO nanorods as sensing materials for several types of gas sensors, including p — n junction gas sensors.

Synthesis of CuO/Co3O4Coaxial Heterostructures for Efficient and Recycling Photodegradation

The highly efficient CuO/Co3O4composite photocatalyst with different morphologies has been synthesized directly on Cu wire mesh by controlling the composition of cobalt-containing solid precursors via a simple hydrothermal method. The structure morphology and composition of the composite photocatalyst have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectra. The photocatalytic result shows that the CuO/Co3O4coaxial heterostructure is easy to recycle and exhibit enhanced photodegradation activity for methylene blue compared to single CuO nanorod arrays under full spectrum solar light irradiation. The enhanced photocatalytic efficiency of the composite could be ascribed to the synergistic effect of CuO and Co3O4. This study provides a general and effective method in the fabrication of 1D composition NRs with sound heterojunctions that show enhancement of photocatalytic performance and facility of recycling.

A new lithium-ion battery: CuO nanorod array anode versus spinel LiNi0.5Mn1.5O4 cathode

Lithium-ion batteries with advanced performances are required to meet the needs for next generation power batteries. In this work, a new lithium-ion battery has been successfully assembled based on high energy CuO nanorod array anode and high voltage spinel LiNi0.5Mn1.5O4 cathode. Electrochemical tests of the CuO nanorod array grown on copper substrate demonstrate that the CuO/Li half cell can deliver discharge capacities of 787 and 560 mAh g−1 at 0.1 and 10C rates. Different from the traditional prelithiation of transition metal oxides anodes, a CuO-limited full cell has been assembled directly by adjusting the positive/negative capacity ratio of 1.2:1, which could deliver a discharge capacity of 660 mAh g−1 with estimated energy density of about 217 Wh kg−1 at 0.1C rate. The CuO/LiNi0.5Mn1.5O4 full cell exhibits good cycle stability (with capacity retention of 84% at 0.5C over 100 cycles) and superior rate capability (about 240 mAh g−1 at a high rate of 10C), which are mainly resulted from CuO arrays directly constructed on copper substrate and the hierarchical structure of LiNi0.5Mn1.5O4 materials. The unique battery may cast new light upon constructing low cost, high energy, high rate capability and high safety full cells.

Facile synthesis of hierarchical CuO nanorod arrays on carbon nanofibers for high-performance supercapacitors

A facile low-temperature solution method combined with a post simple annealing treatment has been used to synthesize one-dimensional hierarchical hybrid nanostructure composed of CuO nanorod arrays grown on carbon nanofibers. The electrochemical properties of this hybrid nanostructure have been evaluated as electrode material for supercapacitor. The material exhibits a high capacitance of 398Fg−1 at 1Ag−1 and even shows a capacitance of 153Fg−1 at an extremely high current density of 50Ag−1, with high power density of 10kWkg−1 in 3M KOH electrolyte. The electrochemical stability of the material for 5000 continuous cycles demonstrates excellent cycling performance at different current densities. This high performance has been related to the structural features, including shape and size of well defined hierarchical nanorod arrays and robust carbon nanofibers backbone. In view of the high electrochemical performance and the facile and cost-effective synthesis, this hierarchical CNF@CuO NR might hold as a promising electrode material for high-performance supercapacitor applications.

An Outward Coating Route to CuO/MnO2 Nanorod Array Films and Their Efficient Catalytic Oxidation of Acid Fuchsin Dye

An outward coating method has been successfully employed to prepare CuO/MnO2 nanorod array films based on the impregnation of Cu(OH)2 nanorod array films with manganese nitrate aqueous solution and heat post-treatment. The as-prepared CuO/MnO2 nanorod array films as heterogeneous catalysts successfully address such issues as easy agglomeration, difficult separation, and possible secondary pollution related to powder catalysts. Furthermore, they exhibit catalytic oxidation activity for the degradation of acid fuchsin (AF) dye in aqueous solution superior to that of bare CuO nanorod array films in the presence of H2O2, because of the synergistic effects of both CuO and MnO2. The effects of the initial concentration of aqueous AF solution and H2O2 dosage on the catalytic oxidation performance were evaluated, indicating that the degradation ratio of AF can reach up to 94.05%. Life-cycle performance and scaleup of the catalytic oxidative degradation process demonstrate the durability and potential engineering application of CuO/MnO2 nanorod array films in dye wastewater treatment.

수열합성법으로 합성된 산화구리 나노막대의 일산화질소 가스 감지 특성

Abstract We report the nitrogen monoxide (NO) gas sensing properties of p-type CuO-nanorod-based gas sensors. Wesynthesized the p-type CuO nanorods with breadth of about 30 nm and length of about 330 nm by a hydrothermal method usingan as-deposited CuO seed layer prepared on a Si/SiO 2 substrate by the sputtering method. We fabricated polycrystalline CuOnanorod arrays at 80 o C under the hydrothermal condition of 1:1 morality ratio between copper nitrate trihydrate[Cu(NO 2 ) 2 ·3H 2 O] and hexamethylenetetramine (C 6 H 12 N 4 ). Structural characterizations revealed that we prepared the pure CuOnanorod array of a monoclinic crystalline structure without any obvious formation of secondary phase. It was found from thegas sensing measurements that the p-type CuO nanorod gas sensors exhibited a maximum sensitivity to NO gas in dry air atan operating temperature as low as 200 o C. We also found that these CuO nanorod gas sensors showed reversible and reliableelectrical response to NO gas at a range of operating temperatures. These results would indicate some potential applicationsof the p-type semiconductor CuO nanorods as promising sensing materials for gas sensors, including various types of p-njunction gas sensors.Key wordsOxide gas sensor, CuO, nanorod, NO gas, hydrothermal method.

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.

Aligned CuO nanorod arrays: fabrication and anisotropic ferromagnetism

Copper oxide (CuO) is a p-type semiconductor with a band gap of 1.2 eV, which is well known in high-temperature superconductor and antiferromagnetic (AFM) materials through Cu–O–Cu super-exchange interaction. In this paper, we report the strong anisotropic ferromagnetism (FM) in aligned CuO nanorod arrays synthesized by a microwave-assisted hydrothermal method. The transmission electron microscopy (TEM) image shows that the CuO nanorod consists of a large number of smaller nanorods with almost the same growth direction. The X-ray diffraction (XRD) pattern indicates that the CuO nanorods are well crystallized with highly preferred orientation of the [020] direction. These CuO nanorod arrays show room-temperature ferromagnetism, with strong magnetic anisotropy when the magnetic field is applied perpendicular or parallel to the rod axis. This phenomenon of room-temperature ferromagnetism in those aligned CuO nanorods might originate from uncompensated surface spins and shape anisotropy of the nanorods.

Rapid growth of copper oxide nanorod arrays by a microwave heating approach

High-quality aligned copper oxide (CuO) nanorod arrays have been synthesized using a microwave heating method. The fresh reactants are continuously injected into the reactor in order to accelerate the growth. X-ray diffraction (XRD) results indicate the as-prepared CuO nanorods are well crystallized with preferred growth direction of [020]. It is found that the length of these CuO nanorods increases linearly with an extension of heating time. The growth rate is about 544nm per hour. The formation mechanism of these CuO nanorod arrays synthesized by the microwave heating method is also described. This method shows the potential for growing long CuO nanorods or other one-dimensional nanostructures in a short time.

Morphology-Controlled Fabrication of CuO Architectures

CuO nanorod arrays, networks of nanosheets and pistachio nuts consisting nanorods were prepared via a multi-step synthesis method starting from copper oxalate precursor. CuO nanorod arrays were prepared by solid state thermal calcination of Cu(OH)2 nanorod arrays through the reaction of copper oxalate precursor with NaOH at 40°C. CuO networks of nanosheets were obtained by treatment at 60°C for 90min, and CuO pistachio nuts consisting nanorods were obtained at 80°C for 20min. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).The influences of temperature and reaction time on the synthesis of CuO were investigated. The formation mechanism of CuO nanostructures was discussed.

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.

Patterning and fusion of CuO nanorods with a focused laser beam

We report a simple technique that facilitates the micropatterning of an alignedarray of CuO nanorods on a substrate as well as the fusion of the nanorods intofused junctions. The technique utilizes a focused laser beam from a He–Ne laserwith moderate power to melt away the pointed end of as-grown CuO nanorodsresulting in the formation of microballs at the tips of the truncated nanorods.The size of the microballs and the length of the truncated CuO nanorods werefound to be dependent on the laser power used during the process. The nature ofthe microballs formed was investigated by high-resolution transmission electronmicroscopy and Raman spectroscopy. Such a focused beam provides an effective meansto modify the morphology of the as-grown nanorod array and to pattern thealigned CuO nanorod array into interesting and potentially useful configurations. Inaddition, the focused laser beam was utilized to fuse and join nanorods, which couldpotentially be useful in the fabrication of nanorod circuits and network repair.

Room temperature growth of CuO nanorod arrays on copper and their application as a cathode in dye-sensitized solar cells

Vertically aligned CuO nanorod arrays on copper electrodes with diameters of ∼5 nm and lengths of hundreds of nanometers were synthesized successfully using a simple wet chemical method at room temperature. The composition, morphology, and growth conditions of the nanorods were characterized. We also show that the as-prepared CuO nanorod arrays are promising hole-transport media of dye-sensitized hetero-junctions for solar energy conversion.

Copper-Based Nanowire Materials: Templated Syntheses, Characterizations, and Applications

Well-aligned Cu(OH)2 nanoribbon and CuO nanorod arrays have been prepared on copper substrates by liquid-solid reactions. The effects of temperature, reaction time, solvent, and pH value on the morphology and composition of the products are systematically studied. Using the Cu(OH)2 nanoribbons array as a reactive and sacrificial template, we have successfully synthesized Cu2O, Cu9S8, and Cu nanoribbon/ nanowire arrays, demonstrating the versatility of the template. The extensive series of copper-based one-dimensional nanomaterials have been fully characterized by various structural, microscopic, and spectroscopic techniques. Moreover, the Cu nanowires are demonstrated to be an excellent surface-enhanced Raman scattering substrate with a sensitivity over an order of magnitude higher than that of a common roughened copper electrode.