Nanocrystalline CuO Research Articles

Evaluation of structural parameters of monoclinic nanocrystalline CuO and study of sunlight-driven photocatalytic dye degradation, antimicrobial and antioxidant potential

Highly pure, crystalline and spherical-shaped Copper oxide nanoparticles (NPs) have been synthesized via facile chemical coprecipitation. Various models including the Scherrer, Monshi-Scherrer, Williamson-Hall, Size-Strain Plot and Halder-Wagner method have been applied to study the crystal structure characteristics. The lattice parameters associated with the monoclinic crystal lattice of CuO NPs were estimated to be a = 4.69 Å, b = 3.41 Å, c = 5.14 Å and β = 99.87(degree), unit cell volume V = 81.35Å3 and cell density dx = 6.49 g/cm3. The photocatalytic dye degradation proficiency at 20 mg/l CuO concentration and 120 min sunlight exposure results the order of percentage dye degradation Malachite Green (88.4%) > Crystal Violet (70.8%) > Eosin Yellow (70.2%) > Methylene Blue (54.08%) dyes. The antimicrobial activity assessment was done against the broad-spectrum pathogenic microbes unveiled the exceptional microbial controlling capability of CuO NPs. Furthermore, the antioxidant activity test demonstrated the potential free radical scavenging activity of CuO NPs with an IC50 value of 47.733 µg/ml. Highlights Synthesis of pure and spherical shaped nanocrystalline CuO was done by using low cost and facile chemical coprecipitation method. XRD, FTIR, FESEM, EDX, UV-Vis, and Raman spectroscopic techniques were used for characterization purpose. The structural and crystallographic parameters of monoclinic crystal structure of CuO NPs were evaluated successfully. The photocatalytic performance of CuO NPs follow the percentage dye degradation order as MG (88.4%) > CV (70.8%) > EY (70.20%) > MB (54.08%) after 120 minutes of sunlight exposure. CuO NPs exhibit promising antifungal activity against COVID-19 associated Pulmonary Aspergillosis (CAPA) causing pathogenic fung. CuO NPs show potential DPPH free radical scavenging activity with an IC50 value of 47.733 µg/ml.

Green synthesis of CuO nanoparticles using Ligustrum lucidum extract, and the antioxidant and antifungal evaluation

Biosynthesis of metal oxide nanoparticles using plant extract is an inexpensive, simple, rapid, and environmentally friendly approach to obtaining nanoparticles for biological applications. Herein, copper oxide nanoparticles (CuO-NPs) were successfully synthesized using an aqueous extract from Ligustrum lucidum leaves. The structural, optical, and morphological characteristics of the nanoparticles were assessed using x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectrophotometer, transmission and scanning electron microscopy (TEM and SEM), and energy-dispersive x-ray (EDX). Nanocrystalline CuO with an average crystalline size of 22.0 nm and a band gap energy of 1.4 eV were confirmed from the XRD and UV-vis spectrophotometer, respectively. Morphological studies showed spherical nanoparticles, whose particle size estimation (30 ± 5 nm) agrees with the crystalline size deduced from the XRD pattern. A free radical scavenging activity of the CuO nanoparticles, evaluated using the 1, 1-diphenhyl-2-picrylhydrazyl (DPPH) assay, showed that it exhibited high antioxidant activity (IC50: 63.35 μg ml−1) that is concentration dependent. Antifungal evaluation using four different fungal strains (Aspergillus flavus, Aspergillus niger, Fusarium oxysporum, and Trichoderma harzianum) indicated a direct relationship between the potency of the particles and their concentration, with 1 ppm solution exhibiting the highest potency. The green synthesized CuO-NPs using Ligustrum lucidum may be potentially used as an antioxidant and antifungal agent for therapeutic applications.

On the structural evolution of nanoporous optically transparent CuO photocathodes upon calcination for photoelectrochemical applications.

Copper oxides are promising photocathode materials for solar hydrogen production due to their narrow optical band gap energy allowing broad visible light absorption. However, they suffer from severe photocorrosion upon illumination, mainly due to copper reduction. Nanostructuring has been proven to enhance the photoresponse of CuO photocathodes; however, there is a lack of precise structural control on the nanoscale upon sol-gel synthesis and calcination for achieving optically transparent CuO thin film photoabsorbers. In this study, nanoporous and nanocrystalline CuO networks were prepared by a soft-templating and dip-coating method utilizing poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic® F-127) as a structure-directing agent, resulting for the first-time in uniformly structured, crack-free, and optically transparent CuO thin films. The photoelectrochemical properties of the nanoporous CuO frameworks were investigated as a function of the calcination temperature and film thickness, revealing important information about the photocurrent, photostability, and photovoltage. Based on surface photovoltage spectroscopy (SPV), the films are p-type and generate up to 60 mV photovoltage at 2.0 eV (0.050 mW cm-2) irradiation for the film annealed at 750 °C. For these high annealing temperatures, the nanocrystalline domains in the thin film structure are more developed, resulting in improved electronic quality. In aqueous electrolytes with or without methyl viologen (as a fast electron acceptor), CuO films show cathodic photocurrents of up to -2.4 mA cm-2 at 0.32 V vs. RHE (air mass (AM) 1.5). However, the photocurrents were found to be entirely due to photocorrosion of the films and decay to near zero over the course of 20 min under AM 1.5 illumination. These fundamental results on the structural and morphological development upon calcination provide a direction and show the necessity for further (surface) treatment of sol-gel derived CuO photocathodes for photoelectrochemical applications. The study demonstrates how to control the size of nanopores starting from mesopore formation at 400 °C to the evolution of macroporous frameworks at 750 °C.

Recyclability and catalytic characteristics of copper oxide nanoparticles derived from bougainvillea plant flower extract for biomedical application

Abstract This work aims to investigate the environmentally sustainable technique to synthesize the copper nanoparticles using bougainvillea flower ethanolic extract at ambient temperature. Copper nanoparticles have considerable potential for reducing the environment’s harmful pigments and nitrogen contaminants. The oxidized copper nanoscale catalysts are enclosed inside nanomaterial, which work as a benign and sustainable resource for capping agents. Ultraviolet spectroscopic, transmission electron microscopy (TEM), and X-ray crystallography (XRD) techniques were used to evaluate the produced oxidized copper nanocrystals. The particles produced have been very robust, are cylindrical in form, and have an outer diameter of 12 nm. Furthermore, under normal conditions, copper oxide (CuO) nanomaterials demonstrated strong photocatalytic efficiency in liquid media for the oxidation of Congo red, bromothymol blue, and 4-nitrophenol in an acidic solution acetic anhydride. Moreover, the CuO nanocrystalline enzyme could be readily vortexed or used for five cycles with an exchange rate of even over 90%. The evaporation process caused around 18% of the loss of weight between 25°C and 190°C, while soil organic breakdown caused almost 31% of the loss of weight around 700°C. As a result, the little reduction in enzymatic effectiveness of the recoverable multilayer CuO substrate might be attributed to catalytic degradation throughout spinning and processing.

Effect on Optical and Antibacterial Activity of SnO<sub>2</sub> and CuO Blended SnO<sub>2</sub> Nanoparticles

Nanocrystalline SnO2 and CuO doped with SnO2 were prepared by the co-precipitation method and characterized for different physiochemical properties and microbiological activity. The composition and morphological formation were characterized by XRD, HRTEM, Raman, FTIR, and UV-vis spectroscopy. The Powder X-ray analysis reveals that Sn4+ ions have substituted the Cu2+ ions without changing the monoclinic structure of SnO2 but the average particle size of the SnO2 and CuO doped SnO2 samples from 11 and 5 nm respectively. However, it exhibits an inhibiting strong bacterial growth against tested bacterial strains.

Cu2O thin films deposited by spray pyrolysis using diethanolamine and L-ascorbic acid as reducing agents

Cu2O thin films are of great interest due to their diverse applications. Spray pyrolysis is a low-cost and straightforward technique among the different methods used to deposit them. Precursor solutions using D-glucose as reducing agent and copper acetate have mainly been used. However, the D-glucose's remaining subproduct can detriment the films' properties and use in devices. In this work, precursor solutions using diethanolamine (DEA) or L-ascorbic acid (AA) as reducing agents to deposit Cu2O thin films are used for the first time. The effect on the structural, morphological, electrical, and optical properties of Cu2O thin films is shown for 0.25 M of DEA and 0.1 M of AA, which were the optimal molar concentrations to obtain homogeneous solutions, with 0.04 M of copper nitrate. The deposition temperature (Td) determines the formation of Cu2O single phase. XRD analysis reveals films only constituted by Cu2O using DEA in the 280°C≤Td≤310°C and AA in the 280°C≤Td≤290°C ranges. These deposition temperatures are lower than the reported values (∼ 330 °C) using the same copper salt and glucose. This fact is associated with the reducing character of both agents since the obtained precursor solutions lead to an in-situ reduction. In addition, the films show minimum organic impurities content associated with the low volatilization temperature of the DEA and AA, which is desirable for their application in devices. The calculated bandgap energy (2.3–2.4 eV) for both types of films corresponds to nanocrystalline Cu2O. However, using L-ascorbic acid resulted in thin films with the lowest resistivity (102Ωcm), attributed to an improvement in the crystallinity.

Structural Analysis of Nanocrystalline Cu2O Prepared by Electrodeposition at Different Temperatures

Structural Analysis of Nanocrystalline Cu2O Prepared by Electrodeposition at Different Temperatures

Hierarchical CuO nanostructured materials for acetaldehyde sensor application

A nanocrystalline CuO with mixed morphologies (nanorods, nanoplates and nanoparticles) were prepared using simple room temperature wet chemical synthesis route. The nanostructured CuO material was characterized using FESEM, TEM, EDS, elemental mapping, UV–visible spectroscopy, and BET surface area techniques for various physicochemical characteristics. The gas sensor device was fabricated using CuO nano-powder and its acetaldehyde gas sensing properties was investigated. The CuO sensor showed excellent sensing response towards 20–100 ppm acetaldehyde. The acetaldehyde response of the CuO sensor was recorded at various operating temperatures as well as concentrations. The responses of 418% and 115% were noted for 100 ppm and 20 ppm acetaldehyde concentration at 180 °C respectively. The higher selectivity of the CuO sensor was observed towards acetaldehyde among various gases. The transient response of the sensor was observed to be consistent with concentrations. The dynamic repetitive response of the sensor was tested at 100 ppm acetaldehyde that revealed to be same. The sensor's stability was tested and observed to be quite stable. A brief acetaldehyde sensing mechanism for CuO sensor was elucidated. The easy and large-scale formation of CuO nanostructures without growth controlling surfactants, and the good selectivity of the high response acetaldehyde sensor at relatively low operating temperatures may pave pathway for future gas sensor technology.

Role of nickel in the phase change from nanocrystalline Cu2O to CuO sputtered films and the formation of a metastable phase of Cu4O3

Copper oxide thin films doped with nickel were prepared by sputtering. The ratio of elements to the silicon substrate was measured by energy- dispersive X-ray spectroscopy. By the change in the power from 20 W to 50 W for sputtering nickel, the content of nickel intercalated in the copper-oxide lattice increased from 2.13 wt% to 7 wt%, respectively. The base sample and 2.13 wt% Ni sample exhibited the cubic Cu2O phase, while the increase in the nickel content to 3.54 wt% and 6.21 wt% led to the change in the tetragonal metastable structure of the Cu4O3 phase. The high doping of Ni at 7 wt% in the copper-oxide lattice transformed the metastable phase to stable monoclinic CuO. The lattice strain and dislocation density of the prepared samples depended on the nickel content. The lattice strain of the 6.21 wt% nickel sample ( ̴ 7.90 ×10−3) was greater than those of the stable phases of Cu2O (~2.5 × 10−3) and CuO (~3.65 × 10−3). The copper-oxide thin film nanostructure was confirmed by atomic-resolution transmission electron microscopy. With the change in the nickel content, the average grain size of the prepared films ranged between 16.57 nm and 20.76 nm. The films roughness was correlated to the nickel content and phase change in the copper-oxide lattice. The optical properties were analyzed and calculated. The optical band gap of the films were affected by the phase change and the nickel content, which decreased from 2.535 eV (Cu2O) to 2.090 eV (CuO).

Pitch‐Black Nanostructured Copper Oxide as an Alternative to Carbon Black for Autonomous Environments

Light detection and ranging (LiDAR) systems are becoming crucial for measuring the distance and creating a point cloud of the local environment, critical data for artificial intelligence to enable collision‐avoidance mechanisms. However, LiDAR utilizes radiation in the near‐infrared (NIR) region of the electromagnetic spectrum, which is prone to complete absorption by typical dark (such as painted by carbon black) colored objects, leading to loss of timely data points. Till date a very limited number of solutions have been put forward to address this. Herein, nanocrystallites of copper (II) oxide with specific prevalence of crystal facets that create nearly perfect black material at visible wavelengths are proposed. The sharp transition of absorbance near 700 nm wavelength light is attributed to the near‐unity ratio of (−111)/(111) the crystal facets and a crystal size of around 100 Å for the (−111) plane. Although indistinguishable from carbon black and with the same degree of measured blackness (My value 135.5), the nanocrystalline CuO shows 1500% better detectability by LiDAR. The study paves the way for the unconstrained use of dark objects in future society and infrastructure, moving a step closer toward fully autonomous operation of vehicles and robots.

Structural, optical and photoluminescence investigations of nanocrystalline CuO thin films at different microwave powers

Thin films of copper oxide were prepared through two steps: the formation of metallic copper thin films by DC sputtering technique and oxidizing the metallic copper films through microwave plasma chemical vapor deposition technique. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) were used to detect the crystalline phases and the films morphology, respectively. Tenorite CuO phase with interlocking between grains were observed and detected. Optical and photoluminescence properties were investigated by UV–Vis-NIR to detect the optical transparency, optical band gap, and refractive index of the prepared films. The optical transmittance of the studied films was resolved by Swanepoel’s procedure due to the presence of the optical interference in such samples. The optical band gap values were observed to decrease from 2.355 to 1.986 eV as the microwave power increase. A strong UV emission at around 358 nm was observed in all CuO samples. Moreover, weak blue and green emission were also observed in the photoluminescence spectra.

Highly efficient photocatalytic removal of methylene blue by lamellar structured nanocrystalline and amorphous CuO

Photocatalyst microstructure dramatically influences their performance in wastewater treatment applications. In this study, nanocrystalline/amorphous CuO with a three-dimensional flower-like structure was successfully prepared for subsequent degradation of methylene blue (MB). The results illustrate that the photodegradation rate of CuO under visible light can reach 96.41%, which indicates that prepared CuO can be used for the effective removal of organic dye from wastewater. In simulating seawater with NaCl in deionized water, the prepared CuO showed excellent photocatalytic activity. The existence of a crystalline/amorphous phase in the CuO can enhance electron transport via electronic crystalline/amorphous interfacial reconstruction. Moreover, the three-dimensional flower-like structure of CuO is able to shorten the diffusion distance between the electron and the hole, providing significantly improved photoelectric efficiency.

Hesperidin mediated synthesis, structure and optical emission analysis on nanocrystalline CuO

Abstract Nanocrystalline Copper (II) oxide was synthesized through hesperidin mediated phytochemical reduction method and post annealed at 600 °C for 4 hrs. Various analytical results obtained after characteristic measurements such as XRD, FESEM, UV–visible spectroscopy and Photoluminescence studies have been discussed. The crystallographic plane reflections obtained in X-ray diffraction pattern was found to be analogous with the monoclinic end centered phase of copper (II) oxide with Halder-Wagner crystallite size 18 nm. The formation of spherical grains via agglomerated crystallites was apparent from the surface morphology obtained through FESEM images. Tauc’ plot of UV–visible spectrum employing Kubelka-Munk function provided a direct optical band gap of 1.61 eV. The photoluminescence spectrum using 280 nm optimal excitation wavelength and the related CIE plot revealed that the optical emission occurs at blue region as indicated by the chromaticity coordinates.

Synthesis and characterisation of nanocrystalline CuO–Fe2O3/GDC anode powders for solid oxide fuel cells

This paper deals with the development and potential application of a novel mixed ionic-electronic conductive anode composite comprised of copper and iron oxide based on gadolinium-doped ceria (CuO–Fe2O3/GDC) for solid-oxide fuel cell (SOFC). Synthesis of the nanocrystalline CuO–Fe2O3/GDC powders was carried out using a novel co-precipitation method based on ammonium tartrate as the precipitant in a mixed-cationic solution composed of Cu2+, Fe3+, Gd3+, and Ce3+. Thermal decomposition of the resultant precipitate after drying (at 55 °C) was investigated in a wide range of temperature (25–900 °C) using simultaneous DSC/TGA technique in air. The DSC/TGA results suggested the optimal calcination temperature of 500 °C for obtaining the nanocrystalline anode composite from the resultant precipitate. The synthesised CuO–Fe2O3/GDC samples were further characterised using XRD, dilatometry, FESEM, and EDX. Several single cells of SOFCs were fabricated in the anode-supported geometry using the synthesised CuO–Fe2O3/GDC composite as the anode, GDC/CuO composite as the electrolyte, and LSCF/GDC composite as the cathode layer. The fabricated cells were analysed using FESEM imaging and EIS analysis, where an equivalent circuit containing five R-CPE terms was used to interpret the EIS data. The module fitted well the impedance data and allowed for a detailed deconvolution of the total impedance spectra. The catalytic activity and uniformity of the synthesised nanocomposites was further evaluated using TPR analysis, demonstrating excellent activity at temperatures as low as 200 °C.

Recent progress in high pressure X-ray absorption spectroscopy studies at the ODE beamline

ABSTRACTHigh pressure energy-dispersive X-ray absorption spectroscopy is a valuable structural technique, especially, when combined with a nano-polycrystalline diamond anvil cell. Here we present recent results obtained using the dispersive setup of the ODE beamline at SOLEIL synchrotron. The effect of pressure and temperature on the X-ray induced photoreduction is discussed on the example of nanocrystalline CuO. The possibility to follow local environment changes during pressure-induced phase transitions is demonstrated for α-MoO based on the reverse Monte Carlo simulations.

Chemical bath synthesis of CuO-GO-Ag nanocomposites with enhanced antibacterial properties

Copper oxide particles have found applications as strong photocatalytic antibacterial agents in recent years. This paper investigates the facile chemical bath deposition synthesis and antibacterial properties of nanocrystalline CuO, CuO-GO, and CuO-GO-Ag nanocomposites. CuO samples were synthesized through a chemical bath deposition method and the introduction of GO nanosheets and silver nanoparticles into the precursor solutions was used to obtain CuO-GO and CuO-GO-Ag nanocomposites. Scanning electron microscope, energy dispersive spectroscopy, elemental mapping, and Fourier-transform infrared spectroscopy were used to characterize synthesized specimens. Antibacterial properties of the nanocomposites were examined against Gram-positive Staphylococcus aureus ATCC 25923 and Gram-negative Escherichia coli ATCC 25922 by the disc diffusion method and minimum inhibitory concentration (MIC) measurements. CuO particles with monoclinic crystallographic structure and crystallite size of 10 nm were synthesized. Synthesized particles were spherical with a narrow size distribution, between 5 and 10 μm. Minor addition of GO to the precursor solution resulted in less agglomeration of nanocomposite powders. CuO-GO-Ag nanocomposite showed noticeable enhanced antibacterial activities against the tested bacteria under visible light, resulting in MIC of 2.6 ± 0.5 mg/ml against Gram-positive and Gram-negative bacteria and also higher inhabitation zone compared to CuO and CuO-GO nanocomposites.

Flexible CuO–ZnO nano-bulk junction with photovoltaic response

Nano-Bulk junction grown over flexible Cu substrate demonstrating photovoltaic response has been developed. The structure of the device fabricated by us is Cu/CuO/CuO-ZnO/ZnO/Ag with the entire device fabrication sequence taking place at a temperature lower than 330 K. A nano-crystalline p-type CuO layer was deposited on Cu substrate using chemical bath deposition at 300 K. The n-type ZnO was solution grown and spin coated over the blend of CuO-ZnO deposited as a buffer between p-type CuO an n-type ZnO layer. The optimized device exhibited an open circuit voltage of 0.25 V, a short circuit current density of 2 × 10–6 A cm−2, a fill factor of 8% and efficiency of 0.11%. A space charge limited conduction mechanism was identified for the best device structure. The optimized cell structure had a diode ideality factor of 2.11 and work function of 3.28 eV.

Preparation of mesoporous nanocrystalline CuO–ZnO–Al2O3 catalysts for the H2 purification using catalytic preferential oxidation of CO (CO-PROX)

In this article, CuO–ZnO–Al2O3 catalysts with various copper contents were synthesized by a co-precipitation method and employed for the elimination of carbon monoxide from a mixture of 97% H2, 1% CO and 2% O2 at atmospheric pressure via carbon monoxide preferential oxidation (CO-PROX). The influence of the copper and zinc contents on the physicochemical characteristics and catalytic performance was investigated. The prepared samples were characterized using the N2 adsorption-desorption (BET), X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM) and temperature programmed reduction (TPR) techniques. The increment in CuO loading improved the activity of CuO–ZnO–Al2O3 catalysts for CO oxidation reaction. Among the prepared catalysts, the 50%CuO-3% ZnO-47% Al2O3 catalyst calcined at 400 °C with a BET area of 82.3 m2/g exhibited the best activity with a CO conversion of 88.9% at 125 °C. The effects of the presence of CO2 and H2O in the reaction feed stream and gas hourly space velocity (GHSV) were also studied.

Anode-Side Failure of a Cuprous Oxide Semiconductor Caused by High-Density Current Loading

Cuprous oxide (Cu2O) is widely used in thin-film transistors as a p-type semiconductor material, and Cu2O nanowire studies have been actively conducted to enhance device performance and facilitate further scaling down. As scaling down progresses, the device line failure arising from electromigration becomes a constant challenge; however, the characteristics of Cu2O under high-density current have not yet been investigated. Hence, this study performed current loading tests on Cu2O specimens. Dumbbell shaped specimens were fabricated through Cu sputtering, photolithography, and thermal oxidation processes. The main component of the specimen was nanocrystalline Cu2O according to the x-ray diffraction measurement. The relatively high-potential drop specimen often failed at the middle region of the straight section during 1.0 MA/cm2 current loading. The middle-region failure was thought to be the result of the line degradation caused by Joule heating. In contrast, the relatively low-potential drop specimen often failed at the anode-side region because the cross-section area increased at the cathode and middle regions and decreased at the anode regions during current loading. In the usual electromigration phenomenon, atomic transport occurs from the cathode to the anode side; therefore, a lack of atoms can occur on the cathode side. Anode-side failures occurred likely because of the change of nanocrystalline Cu2O to coarse grained material at the middle region from Joule heating during current loading and the difference in atom transportability between the middle region and both end regions of the straight section of the specimen.

Improved photoactivities for CO2 conversion and phenol degradation of α-Fe2O3 nanoparticles by co-coupling nano-sized BiPO4 and CuO to modulate electrons

It's highly desired to design and fabricate effective α-Fe2O3-based photocatalysts by increasing the surface area, promoting the charge separation and providing catalytic function. Herein, specific surface area-enlarged α-Fe2O3 (SE-FO) nanoparticles have been successfully synthesized by a functional molecule-modulated phase-separated hydrothermal method, with high photocatalytic activities for CO2 conversion and phenol degradation. The photocatalytic activities of SE-FO could be greatly improved by coupling nano-sized BiPO4 via an in-situ introduction method. This is attributed to the coupled BiPO4 as a high-energy platform to accept photogenerated electrons from α-Fe2O3 so as to enhance the charge separation mainly by means of surface photovoltage spectra and fluorescence spectra-related to the amount of produced •OH species. Moreover, the photocatalytic activities are further improved by introducing a proper amount of nanocrystalline CuO via a simple impregnation process. It is confirmed based on the temperature-programmed desorption and electrochemical reduction measurements that the improved photoactivity is attributed to the introduced CuO as the co-catalyst for promoting electron-induced reduction reactions. Remarkably, the optimized α-Fe2O3 nanocomposite exhibits about 3-time photoactivity improvement compared with the pristine α-Fe2O3. This work would provide a feasible route to fabricate high-activity α-Fe2O3-based photocatalysts for CO2 conversion and phenol degradation.