CuO Nanostructures Research Articles

Ethanol Gas Sensors Using Semi-Hedgehog-like CuO Nanostructures: Studying the Role of Oxygen Vacancies, Unsaturated Cu-Sites, and Hole Accumulation Layer

Ethanol Gas Sensors Using Semi-Hedgehog-like CuO Nanostructures: Studying the Role of Oxygen Vacancies, Unsaturated Cu-Sites, and Hole Accumulation Layer

Facile Route to Achieve a Hierarchical CuO/Nickel-Cobalt-Sulfide Electrode for Energy Storage.

Herein, a novel self-supporting CuO/nickel-cobalt-sulfide (NCS) electrode was designed in a two-step electrodeposition technique followed by a calcination process. Three-dimensional copper foam (CF) was exploited as the current collector and spontaneous source for the in situ preparation of the CuO nanostructures, which ensured sufficient deposition space for the subsequent NCS layer, thus forming abundant electrochemical active sites. Such a hierarchical structure is conducive to providing a smooth path for promoting electronic transmission. Therefore, the optimized CuO/NCS electrode exhibits outstanding energy storage capability with extremely superior specific capacitance (Cs) of 7.08 F cm-2 at 4 mA cm-2 and coulombic efficiency of up to 94.83%, as well as excellent cycling stability with capacitance retention of 83.33% after 5000 cycles. The results presented in this work extend our horizons to fabricate novel hierarchical structured electrodes applied to energy storage devices.

Investigation of Glucose Sensing via Controlled Copper Concentration in CuO for Non-Enzymatic Glucose Biosensor

Non-enzymatic glucose sensors have emerged as pivotal tools for monitoring blood glucose levels, offering advantages over traditional enzymatic methods in terms of sensitivity, selectivity, and cost-effectiveness. This study explores the utilization of a simple and low-cost method for preparation of copper oxide (CuO) nanostructures to look for the non-enzymatic glucose sensing. Morphological and structural analysis via Scanning Electron Microscopy and X-ray diffraction of synthesized CuO nanostructures revealed nearly same size, shape, and a pure monoclinic crystal structure. Fourier transform infrared spectroscopy further confirmed the monoclinic phase. More importantly, we employed CuO nanostructures-modified glassy carbon electrodes (GCE) to investigate the glucose sensing and sensing parameters. The electrodes exhibited comparable sensitivity, selectivity, and an extended dynamic range 0.4–0.6 V applied potentials with regard to earlier reports. Amperometric responses of lower concentration based synthesized CuO sample recorded at 0.5 V unveiled a low limit of detection of 5.9 μM, a sensitivity of approximately 10.6 μA/(mM·cm2), and a rapid 2 s response time. Manipulating the CuO-nanostructures and integrating on the GCE can offer a promising opportunity for enhanced non-enzymatic glucose sensing with high sensitivity, selectivity, and broad dynamic range towards utility in real-time glucose monitoring, contributing to improved healthcare diagnostics and diabetes management.

Performances of Nano-Structured Cu2O Thin Films Electrochemically Deposited on ITO Substrates in Lactate Bath as Liquid Petroleum Gas Sensors

The investigations are focused on structural and surface morphological features and their influence on electrical and wetting characteristics against liquid petroleum gas (LPG) sensing of synthesized nanostructured cuprous oxide (Cu2O) thin films grown by electrochemical deposition (ECD) on indium tin oxide (ITO) glass substrates in lactate bath (pH 10). p-Cu2O films revealed a cubical-tetrahedron nano-scale polycrystalline grain distribution (average grain size: 64.2 nm, inter planer spacing: 0.24 nm) that exhibited dominance in the crystallographic plane (111). LPG sensing evaluations of p-Cu2O/ITO done at 70 °C constant temperature with 100% LPG at 5 cc min−1 flow rate, showed excellent gas sensor response, recovery, and stability over time due to its moderate wetting behavior (average contact angle: ∼86°). AC impedance measurements carried out at room temperature demonstrated an ionic to electronic conduction variation from 100 Hz to 1 MHz, due to adsorption/desorption of LPG molecules (CnH2n+2) and oxygen species on the nano-particles surface. Cu2O/ITO flat band potential was found to be higher than its’ ambient state after exposure to LPG with an increment in acceptor density. Overall, this efficient LPG sensing could be attributed to the interfacial properties of Cu2O thin films and ITO substrates, that provide an optimized fabrication process of nano-structured Cu2O thin films.

Augmented Structural and Optical Features of CuO- and Al-Doped CuO Nanostructures

Augmented Structural and Optical Features of CuO- and Al-Doped CuO Nanostructures

Vitex negundo and Euphorbia milii leaf extracts aided green synthesis of copper oxide nanostructures for effective inactivation of pathogenic bacteria

A facile and green route was followed to synthesize copper oxide (CuO) nanostructures using Vitex negundo and Euphorbia milii leaf extracts. Structural, elemental, chemical, spectral and morphological features of the CuO nanostructures were determined by XRD, EDS, FTIR spectroscopy, UV–Vis spectrophotometer and FESEM, respectively. The CuO nanostructures disclosed considerably higher antibacterial activity against selected Gram-positive and Gram-negative pathogenic bacteria over commercial antibiotic (Vancomycin). This enhanced antibacterial activity could be credited to the generation of more ROS associated with oxygen vacancy and size of the CuO nanostructures. Particularly, hierarchical CuO nanoparticles/nanorods prepared using V. negundo leaf extract exhibited the highest antibacterial activity due to their lower size range.

ZnO seed-mediated hydrothermal growth of advanced 1-D ZnO and 2-D CuO nanostructured oxide ceramics for gas sensing applications

ZnO and CuO nanostructured oxide ceramics were synthesized on ZnO-seeded micro-glass substrates (denoted as ZOZO and ZOCO, respectively), and their surface and gas-sensing characteristics were explored. The thin film seed layers were deposited using dip-coating and both ZnO and CuO nanostructures were produced through hydrothermal reactions under similar circumstances. X-ray diffraction patterns showed high crystallinity and texturization of ZOZO (in ZnO hexagonal wurtzite system) compared to ZOCO (in CuO monoclinic system). X-ray photoelectron measurements demonstrated the proper oxidation of Zn into Zn2+ in ZOZO and Cu into Cu2+ in ZOCO. Scanning electron microscope images revealed one-dimensional bundled nanorod-like structures in ZOZO and two-dimensional nano-coffee bean-like structures in ZOCO. The different morphologies induced different wettability features as indicated by water contact angles where the hydrophilic surface nature of ZOZO was more advantageous for NH3 detection compared to ZOCO. Gas sensing measurements in 100 ppm NH3 medium showed initially better results by the ZOCO sensor at a low operating temperature (70 °C, S = 9%) compared to the ZOZO sensor which did not show any credible sensitivity below 90 °C. However, as temperature increased, the ZOZO sensor exhibited an ultra-sensitivity of S = 275% at an optimal operating temperature of 150 °C with a limit of detection of 7 ppb whereas the ZOCO sensor recorded a maximum sensitivity of S = 19% at an operating temperature of 170 °C with a limit of detection of 40 ppb. Both sensors showed good repeatability, long-term stability, and selectivity towards ammonia gas. The variation in the properties of the produced films was discussed based on a seed-mediated approach that is consequently suggested to control the growth and alignment of nanoscale structures and their efficiency in subsequent device applications.

Assessment of Oxidative Stress by Detection of H2O2 in Rye Samples Using a CuO- and Co3O4-Nanostructure-Based Electrochemical Sensor

Hydrogen peroxide is essential for biological processes and normally occurs in low concentrations in living organisms. However, exposure of plants to biotic and abiotic stressors can disrupt their defense mechanisms, resulting in oxidative stress with elevated H2O2 levels. This oxidative stress can damage cell membranes, impair photosynthesis, and hinder crucial plant functions. The primary focus of this article is to investigate the effects of salt and herbicide stress factors on the growth of rye samples. For precise quantification of the released H2O2 concentration caused by these stress factors, a non-enzymatic electrochemical sensor was developed, employing nanostructured CuO and Co3O4 oxides. Nanostructured electrodes exhibit high sensitivity and selectivity towards H2O2, making them suitable for detecting H2O2 in real samples with complex compositions. Rye samples exposed to NaCl- and glyphosate-induced stress demonstrated notable concentrations of released H2O2, displaying an increase of up to 30% compared to the control sample. Moreover, optical absorption measurements revealed a substantial decrease in chlorophyll concentration (up to 35% compared to the control group) in rye samples where elevated H2O2 levels were detected through electrochemical methods. These findings provide further evidence of the harmful effects of elevated H2O2 concentrations on plant vital functions.

Optical Asymmetry and Structural Complexity in Hierarchically Organized Chiral CuO Nanostructures: Insight into the Geometric and Crystallographic Effects on Cooperative Chirality.

Optical asymmetry and structural complexity across different length scales were realized in flower-shaped CuO nanostructures, prepared through refluxing an aqueous solution of copper acetate, sodium hydroxide, and D-tartaric acid, as well as in their toroid-like forms obtained on calcination at 600 °C. Atomic scale chirality in the flower morphology could be visualized as putative Boerdijk-Coexter-Bernal like tetrahelical fragments, while that in the toroid form could be identified as screw dislocation-driven helicity. The fraction of asymmetry in the nanostructures has been evaluated from their chiroptical responses based on Kuhn asymmetry factor (g) from circular dichroism (CD) spectroscopy in the entire UV-vis range. The origin of chirality in the two CuO nanostructures has been assigned to the helical arrangement of the Cu-O-Cu network in accordance with their microscopic and spectroscopic observations. Attempts have been made to interpret the crystallographic and geometric chiralities in the two CuO nanostructures based on the redshift and augmented intensity of the CD signal along with an increase in their corresponding anisotropic factor on calcination. Further, the diverse interaction of the toroid-shaped CuO nanostructures with enantiomeric tryptophan moieties has been illustrated from the measurement of their corresponding thermodynamic parameters.

Facile Fabrication of Cu2O/ZnO/GaN Hierarchical Nanostructure by Solution Process for Multiple Band Detection

In this paper, Cu2O/ZnO/GaN hierarchical nanoarchitectonics was synthesized using a solution process. The hierarchical nanoarchitectonics was assembled from in situ etching and growth Cu2O nanostructures on random distributed ZnO nanotubes/GaN film by hydrothermal process. The device demonstrated multiple wavelength photodetection. It demonstrates that the detector based on Cu2O/ZnO/GaN hierarchical nanoarchitectonics can be used as a low-cost multiple band detection areas.

Comprehensive experimental and theoretical studies on the synthesis and characterization of electrodeposited nanostructured Cu2O thin films

In this study, we present a comprehensive analysis of the morphology, microstructure, and optical properties of electrodeposited Cu2O thin films on SnO2:F (FTO) substrates. The films were synthesized using the galvanostatic method at varying pH levels (9 and 12) and temperatures (40, 45, 50, 55, 60, and 65 °C). Characterization techniques employed include scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman and UV-VIS spectroscopy, photoluminescence (PL), and electrochemical measurements. Additionally, a theoretical study based on Wulff's theorem was conducted to investigate the influence of the synthesis environment on the growth process. The obtained films exhibited uniformity, reproducibility, stability, purity (solely the Pn3m Cu2O phase), and crystallinity. Furthermore, we successfully achieved thin films with various morphologies (cubic and octahedron, truncated or not), growth orientations [111 or 100], with relative high density of cupper vacancies and charge carrier, making a significant contribution to the exploration of multifunctional semiconductor materials for applications in photocatalysis, photovoltaic cells, photoelectrochemistry, and others advanced technologies.

Gas Sensing Properties of CuWO4@WO3 n-n Heterojunction Prepared by Direct Hydrolysis of Mesitylcopper (I) on WO3·2H2O Nanoleaves

The nanometer size Cu2O@WO3·H2O composite material has been prepared by the direct hydrolysis of mesitylcopper (I) on WO3·2H2O nanoleaves. The synthesis has been performed in toluene without the addition of any ancillary ligands. The prepared nanocomposite has been deposited as a gas-sensitive layer on miniaturized silicon devices and heated up gradually to 500 °C in the ambient air. During the heating, the CuWO4 phase is formed upon the reaction of Cu2O with the WO3 support as revealed by the XRD analyses. The as-prepared CuWO4@WO3 sensors have been exposed to 10 ppm of CO or 0.4 ppm of NO2 (RH = 50%). At the operating temperature of 445 °C, a normalized response of 620% towards NO2 is obtained whereas the response to CO is significantly lower (S = 30%). Under these conditions, the sensors prepared either with pristine CuO or WO3 nanostructures are sensitive to only one of the two investigated gases, i.e., CO and NO2, respectively. Interestingly, when the CuWO4@WO3 sensitive layer is exposed to UV light emitted from a 365 nm Schottky diode, its sensitivity towards CO vanishes whereas the response towards NO2 remains high. Thus, the application of UV illumination allowed us to modify the selectivity of the device. This new nanocomposite sensor is a versatile sensitive layer that will be integrated into a gas sensor array dedicated to electronic nose platforms.

Effect of Zn Doping on Antibacterial Efficacy of CuO Nanostructures

AbstractBacterial diseases are causing major health issues across the world. Recent research has revealed that the metal ion discharge of nanomaterials is extremely effective at eradicating bacterial outbreaks and resistance. Reactive oxygen species (ROS) for antibacterial functions have been produced using nanomaterials with high specific surface area, complex structural framework, and spectral properties. In this study, we thoroughly investigated the impact of Zn dopants on copper oxide (CuO) nanostructures and their nanomaterial‐based antibacterial processes. The method of production includes the formation of CuO and Zn‐doped CuO nanostructures via chemical coprecipitation. By using several characterization techniques, the as‐synthesized nanostructures were confirmed. Based on their specific surface area and surface‐active site, the different antibacterial activities of these dopants vary the antibacterial action. The antibacterial activity was evaluated using the agar well diffusion method. A significant antibacterial action was observed in the samples. In the pharmaceutical and food sectors, this CuO and its combined dopants can be a substitute for synthetic antibacterial agents.

Synthesis of Binary Metal Doped CuO Nanoarchitecture for Congo red dye Removal: Synergistic Effects of Adsorption and Mineralization Techniques

Herein, a microwave-assisted fabrication technique has been practiced for the generation of pristine CuO and Cd/Zn co-doped CuO (Cu0.94Cd0.03Zn0.03O) nanopowders with the identical weight ratio of cadmium and zinc metals. The structure, chemical nature, shape, and optical response of CuO and Cu0.94Cd0.03Zn0.03O were assessed by PXRD, FESEM, FTIR, and UV–vis analytical techniques. PXRD results affirmed that CuO and Cu0.94Cd0.03Zn0.03O have developed in a single monoclinic phase; other extra phases are absent. The crystallite sizes of CuO and Cu0.94Cd0.03Zn0.03O were identified as 18.5 nm and 14.39 nm. The FESEM image of the Cu0.94Cd0.03Zn0.03O sample demonstrated a nanosheet-like morphology that was developed after the co-doping of Zn and Cd metal ions. FTIR graphs established the occurrence of Cu–O main bonds in both fabricated nanopowders. The UV–vis examination demonstrated that Cd and Zn co-doping has substantially reduced the energy gap of pristine CuO from 2.0 eV to 1.54 eV. This massive reduction in CuO bandgap assists it in catching extra photons to stimulate valence-band electrons and hence boosts the activity of the catalyst under sunlight irradiations. Moreover, including Cd and Zn has also effectively hindered the e−/h+ recombination in CuO throughout the photocatalysis process. The photocatalytic activities of pristine CuO and Cu0.94Cd0.03Zn0.03O nanosheets were probed against Congo-red (CR) pollutants under sunlight irradiations. The mineralization efficiency was detected as maximum (∼87.88%) for Cu0.94Cd0.03Zn0.03O nanosheets in contrast to pristine CuO nanostructures. Cu0.94Cd0.03Zn0.03O nanosheets, due to their astonishing properties, could be an economical alternative in creating intelligent strategies for mineralizing organic pollutants in industrial effluents.

Fabrication of B–CuO nanostructure and B -CuO/rGO binary nanocomposite: A comparative study in the context of photodegradation and antimicrobial activity assessment

This paper reports the synthesis of a cost-effective, stable, and reproducible Boron-doped copper oxide (B–CuO)/Reduced graphene oxide (rGO) binary nanocomposite. A conventional wet chemical synthetic route was used to fabricate the binary nanocomposite. X-ray diffraction (XRD) studies were performed to check the phase purity and crystallinity, scanning electron microscopic (SEM) technique for structural and morphological analysis, energy dispersive spectroscopy (EDX) for surface composition, and Fourier transform infrared spectroscopy (FT-IR) for functional group identification. The experimental results confirmed the formation of the pure nanocomposite. The photocatalytic activity of B–CuO and B–CuO/rGO binary nanocomposite was tested for Methylene blue (MB) dye degradation under sunlight. The B–CuO/rGO binary nanocomposite exhibited improved photocatalytic competence (98%) as compared to B–CuO (85%) in 90 minutes. The antimicrobial activity was measured against four bacterial strains viz. Escherichia coli (E.Coli), Bacillus amyloliquefaciens (B. amyloliquifaciens), Pseudomonas putida (P. putida), Bacillus subtilis (B. subtilis) and one fungal strains Rhizoctonia solani (R. solani). The minimum inhibitory concentration (MIC) was also calculated and it was found that B–CuO/rGO binary nanocomposite exhibited an excellent MIC of 62.2 μg/mL, against the gram-negative E. Coli.

Transition metal (Zn, Mn, and Ni) incorporated CuO nanostructures for supercapacitor applications

Striking features of cost-effectiveness, eco-friendliness, abundant resources, facile fabrication, and primarily, the high theoretical capacitance of CuO have established it as a smart choice for electrodes in pseudocapacitors, yet its practical utilization is hindered by its low electrical conductivity. Considering this, herein, we have made an effort to improve its conductivity by doping it with various transition metals and investigating each sample's electrochemical performance. Fabrication of pure and TM-doped CuO NPs (Cu1-xTMxO, where TM = Zn, Mn, Ni, and x = 0.05) has been carried out via the coprecipitation method, followed by calcination. The X-ray diffraction technique confirms the monoclinic structure of all the samples. Nanoplate, nanoflake, and nano rod-like morphology are exhibited by CuO, Zn-doped CuO, and Mn-doped CuO, respectively. The maximum value of the surface area is noted for Cu0.95Ni0.05O in BET analysis. Whereas, uniformly distributed arbitrarily shaped nano-particles are observed for Ni-doped CuO. The analysis of electrochemical performance reveals that at 5 mVs−1, 153, 109, 77, and 507 Fg−1 of specific capacitance has been delivered by CuO, Cu0.95Zn0.05O, Cu0.95Mn0.05O, and Cu0.95Ni0.05O, respectively. Ni-doped CuO showed outstanding specific capacitance which is threefold better than pristine CuO. Moreover, it also demonstrated the best cyclic stability with a retained capacitance of 93 % by the end of 2000 cycles, along with the lowest charge transfer and solution resistance amongst all as-prepared samples. Its extraordinary performance is a consequence of its uniformly distributed highly porous morphology and better electrical conductivity. Hence, this study suggests Ni-doped CuO be the most desirable electrode material for pseudocapacitors.

Hydrothermally Synthesized Co- and Mg-doped CuO Nanostructures: Electrical and Dielectric Properties

Hydrothermally Synthesized Co- and Mg-doped CuO Nanostructures: Electrical and Dielectric Properties

Exploration of Bifunctionality in Mn, Co Codoped CuO Nanoflakes for Overall Water Splitting

Herein, bimetal (Mn, Co) codoping on a CuO host is aimed at enhancing oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity. Codoping of Mn and Co on CuO to enhance bifunctional action in electrochemical water splitting has not yet been investigated to the best of our knowledge. Literatures are focused on unary Mn-doped CuO or Co-doped CuO nanostructures. Mn, Co codoped CuO through an easy chemical coprecipitation method has been successfully attempted and is more beneficial which is the novelty of the present work. Defect-enriched ample active sites (Mn2+/Mn3+ and Co2+/Co3+) along with Cu2+ in the host CuO achieved high current density (100 mA/cm2) in OER and HER with low overpotential such as 468 mV and 271 mV, respectively. Faster charge transfer and diffusion ability was stimulated by the bimetal codoping CuO. Reasonable Tafel plot values (OER: 199 mV/dec, and HER: 21 mV/dec) with improved water-splitting reaction kinetics were achieved for the Mn, Co codoped CuO nanoflakes. The double-layer capacitance ( C dl ) value of 27.5 mF/cm2 for Mn, Co codoped CuO nanoflakes was achieved. Similarly, the increasing order of an electrochemically active surface area (EASA) was exhibited by the consequent addition of bimetal doping on CuO, denoted as Mn , Co / CuO > Co / CuO > Mn / CuO > CuO . The evidence shows that the codoping strategy could facilitate rapid reaction kinetics to develop overall water splitting. The charge transfer resistances ( R ct ) of 3.6 Ω and 1.2 Ω for the Mn, Co codoped CuO nanostructure corresponding to the OER and HER, respectively, were reported. The long-term stability over 16 h with negligible loss was reported for both the OER and the HER performance. Thus, this work contributes to better insight and analysis of the successful codoping of bimetal elements in earth-abundant electrocatalysts to enhance and make practical the electrocatalytic water-splitting activity.

Visible light photo-Fenton catalytic properties of starch functionalized α-FeOOH/β-FeOOH/Cu2O p-n-p heterojunction nanostructures

Photocatalysts with p-n-p heterojunctions can result in efficient charge separation. This idea motivated the synthesis of starch functionalized α-FeOOH/β-FeOOH/Cu2O heterojunction nanocomposites. All components in the composite have visible range band gaps. In a step-wise procedure, Cu2O nanostructures were precipitated on starch functionalized α-FeOOH/β-FeOOH nanocomposites. Mott Schottky plots confirmed p-n-p heterojunction formation. It enhanced charge separation and slowed down recombination resulting in efficient visible-light photocatalytic activity. The activity of this photocatalyst was evaluated for the photo-Fenton degradation of p-nitrophenol (PNP) and methyl orange (MO). Both degradation reactions follow zero-order kinetics. The photocatalyst remained stable during the organic pollutant degradation process even after repeated use.

Waste remediation: Low-temperature synthesis of hybrid Cu(OH)2/CuO and CuO nanostructures from spent printed circuit boards and their dye degradation studies.

The demand for environmentally friendly and sustainable resource utilization techniques for recycling waste printed circuit boards is significant due to their status as valuable secondary resources, containing high-purity copper and precious metals. In this context, Cu(OH)2/CuO and CuO nanostructures were fabricated using alkaline precipitation and low-temperature aging methods using the strip solution originated from laboratory-scale spent mobile phone printed circuit board recovery process. XRD, FTIR, FESEM-EDX, and TEM were utilized to characterize the as-recovered nanoproducts. A hybrid structure of Cu(OH)2/CuO was formed at 70°, and monoclinic CuO phase was formed at 80°C aging time. The results show that Cu(OH)2/CuO nanoflakes have an average crystallite size of 24.06nm and a particle width of 22 ± 3nm. Cu(OH)2/CuO nanoflakes formed at 70°C aging temperature and 24-h residence time have finer crystallite and particle sizes than CuO-ridged nanospheres formed at 80°C aging temperature. The optical band gap energy of Cu(OH)2/CuO and CuO nanostructures formed was found to be 2.28eV and 2.22eV, respectively. The hybrid Cu(OH)2/CuO nanostructure photocatalyzed the decomposed 97.28% rhodamine blue using a visible light source, whereas the CuO nanostructure degraded only 14.64% rhodamine blue dye under similar conditions. A surfactant-less hybrid structure is developed without the use of any chemical precursor. Thus, a high value-added product is produced using one waste material to remove another waste in wastewater treatment.