Copper Oxide Nanostructures Research Articles

Review of Fabrication Methods, Physical Properties, and Applications of Nanostructured Copper Oxides Formed via Electrochemical Oxidation.

Typically, anodic oxidation of metals results in the formation of hexagonally arranged nanoporous or nanotubular oxide, with a specific oxidation state of the transition metal. Recently, the majority of transition metals have been anodized; however, the formation of copper oxides by electrochemical oxidation is yet unexplored and offers numerous, unique properties and applications. Nanowires formed by copper electrochemical oxidation are crystalline and composed of cuprous (CuO) or cupric oxide (Cu2O), bringing varied physical and chemical properties to the nanostructured morphology and different band gaps: 1.44 and 2.22 eV, respectively. According to its Pourbaix (potential-pH) diagram, the passivity of copper occurs at ambient and alkaline pH. In order to grow oxide nanostructures on copper, alkaline electrolytes like NaOH and KOH are used. To date, no systemic study has yet been reported on the influence of the operating conditions, such as the type of electrolyte, its temperature, and applied potential, on the morphology of the grown nanostructures. However, the numerous reports gathered in this paper will provide a certain view on the matter. After passivation, the formed nanostructures can be also post-treated. Post-treatments employ calcinations or chemical reactions, including the chemical reduction of the grown oxides. Nanostructures made of CuO or Cu2O have a broad range of potential applications. On one hand, with the use of surface morphology, the wetting contact angle is tuned. On the other hand, the chemical composition (pure Cu2O) and high surface area make such materials attractive for renewable energy harvesting, including water splitting. While compared to other fabrication techniques, self-organized anodization is a facile, easy to scale-up, time-efficient approach, providing high-aspect ratio one-dimensional (1D) nanostructures. Despite these advantages, there are still numerous challenges that have to be faced, including the strict control of the chemical composition and morphology of the grown nanostructures, their uniformity, and understanding the mechanism of their growth.

Revealing multimode resistive switching in Cu-O nanostructures using conductive atomic force microscopy

We demonstrate the nanoscale multimode resistive switching in copper oxide nanostructures using conductive atomic force microscopy (cAFM). The cross-sectional transmission electron microscopy (XTEM) and scanning tunnelling electron microscopy – high angle angular dark field (STEM-HADDF) imaging confirms the formation of Cu-O nanostructures. In addition, x-ray photoelectron spectroscopy (XPS) is used to study the chemical composition of Cu-O nanostructures. Current-voltage characteristics measured by conductive atomic force microscopy (cAFM) reveals that the filament forms in multistep processes, instead the rapid one, indicating the multimode resistive switching. The presence of multimode RS is corroborated to the defect-induced conduction mechanism across the Cu-O nanostructures. The present study should open up a new avenue to understand the conduction mechanism and to design an advanced nanoscale device.

CO gas sensors based on p-type CuO nanotubes and CuO nanocubes: Morphology and surface structure effects on the sensing performance

Metal oxide nanomaterials have been widely applied in the high-performance gas sensors. For metal oxide semiconductors, high surface-to-volume ratio and the exposed crystal facets are the two key factors for determining their gas sensing performances. In order to study the effect of surface structure on the gas sensing properties, in this work, two types of copper oxide (CuO) nanostructures, CuO nanotubes (CuO NTs) with exposed surface plane of (111) and CuO nanocubes (CuO NCs) with exposed surface plane of (110), were obtained from Cu nanowires (Cu NWs) and Cu2O nanocubes (Cu2O NCs), respectively. The morphologies, crystal and surface structures were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The gas-sensing performances of CuO NTs and CuO NCs for CO gas detection were then studied. The results demonstrated that compared to CuO NCs, the CuO NTs exhibited lower optimum working temperature and higher sensitivity for CO gas detection. At the operating temperature of 175 °C, the prepared CuO NTs exhibited high sensitivity, good selectivity, fast response and recovery times to CO gas. The present study indicates that for the same semiconductor sensing material, the surface crystal structure has significant influence on the sensing performance.

Self‐Assembly of Anionic Gemini‐Surfactant‐Assisted Fabrication of Copper Oxide Nanostructures

AbstractA series of anionic gemini surfactants(AGS) were synthesized from N, N‐dimethylaminoethanol(DMEA) and tetracarboxylic acid diester(TAD). TAD was derived from the reactant of 3,3’,4,4’‐biphenyl tetracarboxylic dianhydride with long alkyl alcohol. The surface properties and self‐assembly behaviors of these novel AGS were investigated. These AGS displayed super low critical micelle concentration(cmc) and excellent self‐assembly ability. By changing solution concentration, surfactant molecules self‐assemble into different micellar morphologies, including spherical micelles, threadlike micelles, dendritic micelles and vesicles. Tunable micellar morphology of AGS, which directed the orientated growth of nanocrystals, assisted fabricating copper oxide nanostructures(nano‐CuO). Through reaction, diverse shapes (spherical, linear, branch and multilayer) of nano‐CuO were obtained and confirmed.

Synthesis, characterization and biological studies of copper oxide nanostructures

The development of synthetic methods has been broadly accepted as an area of fundamental importance to the understanding and application of nanoscale materials. It allows the individual to modulate basic parameters such as morphology, particle size, size distributions, and composition. Several methods have been developed to synthesize CuO nanostructures with diverse morphologies, sizes, and dimensions using different chemical and physical based approaches. In this work, CuO nanostructures have been synthesized by aqueous precipitation method and simple chemical deposition method. The characterization of these products has been carried out by the x-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR) and UV–vis spectroscopy. Biological activity such as antibacterial nature of synthesized CuO is also explored. XRD peaks analysis revealed the monoclinic crystalline phase of copper oxide nanostructures. While the rod-like and particle-like morphologies have been observed in SEM results. FTIR spectra have confirmed the formation of CuO nanoparticles by exhibiting its characteristic peaks corresponding to 494 cm−1 and 604 cm−1. The energy band gap of the as-prepared CuO nanostructures determined from UV–vis spectra is found to be 2.18 eV and 2.0 eV for precipitation and chemically deposited samples respectively. The antibacterial activity results described that the synthesized CuO nanoparticles showed better activity against Staphylococcus aureus. The investigated results suggested the synthesis of highly stable CuO nanoparticles with significant antibacterial activities.

N-Type Cu2O/α-Fe2O3 Heterojunctions by Electrochemical Deposition: Tuning of Cu2O Thickness for Maximum Photoelectrochemical Performance

Abstract Here, we report the enhanced photoelectrochemical performance of surface modified hematite thin films with n-type copper oxide nanostructures (Cu2O/Fe2O3) obtained through simple electrochemical deposition method. The thickness and amount of cuprous oxide layer were varied by simply changing the number of electrodeposition cycles (viz. 5, 10, 25, 50 and 100) in order to understand its thermodynamic and kinetic influence on the photoelectrochemical activity of the resultant nano-heterostructures. Structural and morphological characteristics of the obtained Cu2O/Fe2O3 films have been studied by absorption spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analysis. Electrochemical investigations such as linear sweep voltammetry, Mott–Schottky analysis, and electrochemical impedance spectroscopy suggested the formation of n-type Cu2O layers over the hematite films with varying charge-carrier densities, ranging from 0.56×1019 to 3.94×1019 cm−3, that varies with the number of cycles of electrochemical deposition. Besides, the thickness of deposited cuprous oxide layer is noted to alter the net electrochemical and photo-electrochemical response of the base material. An interesting, peak event was recorded for a particular thickness of the cuprous oxide layer (obtained after 25 cycles of electrochemical deposition) below and above which the efficiency of catalyst was impaired. The heterojunction obtained thus, followed well known Z-scheme and gave appreciable increment in the photocurrent response.

Facile preparation of diverse copper oxide nanostructures and their characterization

Copper oxide (CuO) nanostructures, such as nanoshuttles, nanodisks and nanoparticles are synthesized by simple hydrothermal and wet chemical methods. The CuO nanostructures are prepared by thermal dehydration of Cu(OH)2·H2O crystal hydrate without any additives. The CuO nanostructures are characterized by energy dispersive X-ray absorption spectroscopy (EDAS), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, UV-vis spectroscopy and X-ray diffraction (XRD) techniques. The SEM images show that diameter of CuO nanoshuttles ranges from 300–400 nm and length of ∼1 μm. The platelet-like porous CuO nanoparticles have thickness of 0.2–0.4 μm and width of 0.5–1.5 μm. The CuO nanodisks have diameter of 500–700 nm and thickness of 60–120 nm. The EDAS analysis confirms purity of CuO samples. The FTIR spectra of CuO nanostructures exhibit that the vibration peaks correspond to stretching vibrations of CuO bond.

Studies of structural, optical, and electrical properties associated with defects in sodium-doped copper oxide (CuO/Na) nanostructures

In the present paper, we report a detailed study on the sodium (Na) doping-induced modifications in the copper oxide (CuO) nanostructure and its properties. A facile and sustainable sol–gel synthesis approach was employed for the preparation of high-quality pristine CuO- and Na-doped CuO nanostructures(1.0, 3.0, 5.0 and 7.0 mol% doping levels, CuO/Na) with controlled shape and composition. Due to the remarkable difference in the ionic radii of Cu2+ (0.73 A) and Na+ (1.02 A), Na+ substitution in place of Cu2+ generates strain/distortions in CuO lattice. The XRD analysis reveal the structural alteration from monoclinic to cubic symmetry with increase in doping level and also reveal the phase purity up to 3% doping level, and beyond this (i.e., for 5 and 7% doping level) small amount of impurity phase corresponding to Na2O was observed. The FTIR results further confirmed the presence of the Na–Cu–O stretching vibrations at higher Na-doped samples. Morphology of the samples indicates that the Na-doped CuO nanostructures exhibit less agglomeration compared to pristine CuO nanoparticles. The presence of Na in CuO lattice were found to greatly enhances optical and electrical properties owing to the formation of defects like copper vacancies and oxygen vacancies at the grain boundaries of the nanoparticles with increased doping of Na.

Size Controllable Synthesis and Characterization of CuO Nanostructure

In this study, copper oxide (CuO) nanostructures were successfully prepared by adding EG (ethylene glycol) and PEG (4000, 8000) (polyethylene glycol) via an in-situ chemical precipitation method. EG and PEG (4000, 8000) were effective for changing the particular size of CuO and we examined the effects of drying type such as freeze drying, muffle and horizontal furnace on the size of CuO nanostructure. The structure, morphology and elemental analysis of CuO nanostructure were analyzed by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). Also, the CuO nanostructures showed excellent electrical conductivity by the changing of PEG’s molecular weight and drying processes.

Synergistic effect of metal ion additives on graphitic carbon nitride nanosheet-templated electrodeposition of Cu@CuO for enzyme-free glucose detection

Graphitic carbon nitride nanosheets (g-C3N4 NS) were prepared and used for self-templated electrodeposition of copper and copper oxide nanostructures. The as-prepared g-C3N4 NS can provide a lot of anchoring sites for copper ions in the process of electrodeposition. The electrodeposited CuO@Cu demonstrates high density and good uniformity. During the electrodeposition, the addition of nickel ions had enabled to entrap Ni ions in the lattice of CuO. The CeO2-CuO@Cu/g-C3N4 NS composites have been prepared by the addition of Ce ions in the process of electrodepositing CuO@Cu onto g-C3N4 NS. The cerium and nickel ions, as the additives, can effectively improve the density and uniformity of the electrodeposited CuO@Cu. Furthermore, the successful entrapment of CeO2 and Ni ions greatly improve electrochemical performance of CuO@Cu/g-C3N4 NS/ITO in the non-enzymatic detection of glucose. The Ce and Ni ion additives showed a synergistic effect on improving uniformity and density of the electrodeposited CuO@Cu and electro-catalytic properties of as-prepared composites. The as-prepared CuO@Cu/g-C3N4 NS/ITO, CeO2-CuO@Cu/g-C3N4 NS/ITO and Ni-doped CuO@Cu/g-C3N4 NS/ITO have been respectively used for non-enzymatic detection of glucose. These three proposed electrodes all demonstrate good electrochemical performance in the non-enzymatic detection of glucose. The CeO2−CuO@Cu/g-C3N4 NS/ITO and Ni-doped CuO@Cu/g-C3N4 NS/ITO appear to greatly improve the electro-catalytic activity toward the oxidation of glucose. Among these three electrodes, the Ni-doped CuO@Cu/g-C3N4 NS/ITO demonstrated the best electrochemical performance in the detection of glucose. These three proposed electrodes all demonstrated good stability and anti-interference performance.

Construction of an Ultrasensitive and Highly Selective Nitrite Sensor Using Piroxicam-Derived Copper Oxide Nanostructures

In this work, piroxicam-based copper oxide nanostructures (Px-CuO NSs) were synthesized via hydrothermal precipitation in the presence of ammonia. The prepared Px-CuO NSs were subjected to scanning electron microscopy (SEM) and X-ray diffraction (XRD) to obtain morphology and crystallinity, respectively. The SEM study reveals that these Px-CuO NSs are in the form of porous rose-like nanopetals with dotted particles on their surface, while the XRD study confirms their crystalline nature. The Px-CuO NS-based sensors were fabricated by drop-casting them onto the surface of a glassy carbon electrode (GCE) and they were tested for nitrite detection using voltammetry and amperometry. The results show these Px-CuO NSs to be highly stable on the GCE surface with linear amperometric (current vs. time) responses to wide range of nitrite concentrations from 100 to 1800 nM, with limits of detection (LOD) and quantification (LOQ) being 12 nM and 40 nM, respectively. Importantly, the fabricated sensor showed negligible effects for a 10-fold higher concentration of common interfering agents and exhibited excellent selectivity. It was applied successfully for nitrite detection in water samples such as river water, mineral water, and tap water.

Evolution of copper oxide nanoneedle mesh with subtle regulated lyophobicity for high efficiency liquid separation

The relationship between copper oxide nanostructures and lyophobicity has been systematically researched for the design of lyophobic copper materials.

Synthesis of Copper Oxides Nanostructures by an Overstressed Nanosecond Discharge in Atmospheric Pressure Air between Copper Electrodes

The results of study of the characteristics and parameters of plasma of a high-current nanosecond discharge in atmospheric pressure air between copper electrodes under conditions of strong overstress of the discharge gap are presented. Under such conditions, favorable conditions are created for igniting an atmospheric pressure diffuse discharge in an inhomogeneous electric field. The spatial, electrical and optical characteristics of the discharge, as well as the parameters of the air plasma with small additions of copper vapor are studied. It is shown that this type of discharge can be used for the synthesis of copper oxides nanostructures.

Morphological Effects of CuO Nanostructures on Fibrillation of Human Serum Albumin.

The influence of different morphologies of nanostructures on amyloid fibrillation has been investigated by monitoring the fibrillation of human serum albumin (HSA) in the presence of rod-, sphere-, flower-, and star-shaped copper oxide (CuO) nanostructures. The different morphologies of CuO have been synthesized from an aqueous solution-based precipitation method using various organic acids, viz., acetic acid, citric acid, and tartaric acid. The fibrillation process of HSA has been examined using various biophysical techniques, e.g., Thioflavin T fluorescence, Congo red binding studies through UV spectroscopy, circular dichroism spectroscopy, and fluorescence microscopy. The monolayer protein coverage on the CuO nanostructures has been established through DLS studies, and the well-fitted Langmuir isotherm model has been used to interpret the differential adsorption behavior of HSA molecules on the CuO nanostructures. The nanostar-shaped CuO, by virtue of their higher specific surface area (94.45 m2 g-1), presence of high indexed facets {211} and high positive surface charge potential (+16.2 mV at pH 7.0) was found to show the highest adsorption of the HSA monomers and thus was more competent to inhibit the formation of HSA fibrils compared to the other nanostructures of CuO.

Effects of ammonia in the synthesis of copper (II) oxide nanostructures grown via microwave chemical bath deposition

In this study, CuO was grown on fluorine-doped tin oxide (FTO) substrates by depositing a copper (II) oxide seed layer via microwave chemical bath deposition while controlling the ammonia concentration. The morphological, optical, structural, electrical, and photoelectrochemical properties were measured by field emission scanning electron microscopy (FE-SEM), UV–vis spectroscopy (UV–vis), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and three-electrode potentiostat measurements, respectively. The ammonia concentration affected the morphological and structural properties (i.e., the growth and thickness of the CuO nanostructures), the optical properties (i.e., optical energy bandgap), the electrical properties (i.e., the flat-band potential and acceptor density) and the photoelectrochemical properties of the prepared CuO samples. As a result, the highest photocurrent density of 2.05mA/cm2 (at −0.55V vs. SCE) was obtained for the sample with an ammonia concentration of 0.16M.

Copper Oxide Nanostructures; Syntheses and Characterization

Copper oxide (CuO) nanoparticles are synthesized by pulse laser ablation (Nd:YAG, λ=1064nm,) of cupper (Cu) in pure water (DDDW). The synthesized nanomaterial is characterized with UV-Visible spectroscopy; atomic force microscopy AFM, in combination with FTIR.AFM image shows that the CuO are spherical in shape with average diameter 51 nm and FTIR spectrum confirm the formation of CuO nanoparticles. The UV–vis spectrum of the colloidal nanoparticles shows maximum absorbance around the UV region at ~270nm and in Vis region at~600nm, indicating the formation of CuO nanoparticles with a direct bandgap energy of~ 3.2eV.

Synthesis, characterisation and applications of nanostructured copper oxide

Synthesis, characterisation and applications of nanostructured copper oxide

Nanostructuring of anodic copper oxides in fluoride-containing ethylene glycol media

We demonstrate that the anodization of copper in alkaline water/ethylene glycol media containing fluoride ions generates nanostructured copper oxide films. By modifying the anodization conditions (fluoride and OH– concentrations, applied voltage and anodization time), nanofibrillar Cu2O as well as highly rough nanofibrillar network or nanoporous mixed Cu2O/CuO films are obtained. Raman and X-ray Photoemission Spectroscopy (XPS) results indicate that in fluoride presence, Cu(I) oxide is obtained when anodization takes place applying low voltages at a relatively low OH– concentration. In comparison, the subsequent oxidation to obtain Cu(II) species (CuO and Cu(OH)2) is promoted by increasing the OH– contents. According to the present results, an oxidation reaction scheme is proposed in order to gain a deeper understanding in the preparation of controlled nanostructured copper oxide films.

Silica template electrodeposition of copper oxide nanostructures on Ni foam as an ultrasensitive non-enzymatic glucose sensor

Abstract Silica templated copper oxide nanostructures were prepared on Ni foam electrode and presented as an enzyme-free glucose sensor. X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and field emission scanning electron microscopy (FE-SEM) techniques were used to characterize the presented electrode. A good synergistic effect between Cu and Ni for glucose determination caused a high sensitivity of 5.45 mA/mM/cm2, the linear range up to 22.5 mM and low practical detection limit of 4.81 nM. The electrochemical properties of the proposed sensor such as electrochemical active surface area, diffusion coefficient, and catalytic rate constant of glucose electro-oxidation were reported. The presented sensor showed good long term stability and reproducibility. It has excellent selectivity and it was applied for accurate determination of glucose in the real serum samples.

A non-enzymatic glucose sensor based on CuO-nanostructure modified carbon ceramic electrode

Mesoporous silica-graphite composite (SiO2/C-graphite) was synthesized by the sol-gel technique. The surface area (SBET=98.93m2/g), pore volume (0.30cm3/g) and pore size (12.16nm) were characterized by BET. The novelty of this work lays in the fabrication of material in which ceramic material (SiO2/C-graphite) was decorated with copper oxide (CuO) nanostructure. SEM images revealed material compactness without phase segregation and EDX mapping showed a homogenous structure. Pressed disk electrode fabricated with SiO2/C/CuO nanocomposite material was evaluated as an amperometric non-enzymatic glucose sensor in 0.1M NaOH solution. The linear response range, sensitivity, detection limit, and quantification limit were 0.02–20.0mmolL−1, 0.06μmolL−1, 472μA mmol−1L−1cm−2, and 0.76mmolL−1, respectively. The electrode response time is <1s with the addition of 0.02mmolL−1 glucose. The electrode is chemically stable, exhibits rapid and excellent sensitivity and does not show any interference from coexisting species present in the blood samples. The proposed sensor repeatability was assessed as 1.9% RSD for ten measurements of 13.0mmolL−1 glucose solution. The sensor tested to ascertain glucose in blood serum showed to be a promising tool for the future evolution of non-enzymatic glucose sensors.