CuO ZnO Research Articles

Self-powered UV photodetector based on self-assembled CuO and spin-coated ZnO heterostructure

Self-powered UV photodetector based on self-assembled CuO and spin-coated ZnO heterostructure

Fe–Ni–Ce–Zr-modified CuO–ZnO catalyst for methanol steam reforming

Four copper-based catalysts were prepared by co-precipitation method. The catalysts were characterized by scanning electron microscopy, N2 adsorption-desorption, temperature programmed reduction process (H2-TPR), X-ray diffraction (XRD) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) to explore the effects of different components on catalyst activity. The performance of different catalysts for hydrogen production via methanol steam reforming was evaluated on a fixed-bed reactor. The effects of different components, reaction temperature and gas hourly space velocity (GHSV) on the catalytic performance were investigated. The results exhibited that among the investigated catalysts, 1# and 2# catalysts had the higher catalytic activity and stability. Under the conditions of 280 °C, a molar ratio of methanol to water of 1:1.3, and a GHSV of 13.3 L/(g·h), the methanol conversion rate reached 99.9%, the CO concentration was as low as 0.29%, and the selectivity was only 1.16%. The H2 production flow rate per unit mass of catalyst was 270 mL/(min·g). After 60 h of start-stop experiments, the methanol conversion rate remained above 98.4%, the CO concentration was always lower than 0.5%, and the start-up speed was significantly faster than that of the commercial catalyst M650. This study provided an effective method for the preparation of catalysts for methanol steam reforming.

Methanol Synthesis from CO2 Hydrogenation on CuO–ZnO–ZrO2 Prepared by Solvothermal Method: The Influence of Solvent on Catalyst Properties and Catalytic Behavior

Methanol Synthesis from CO2 Hydrogenation on CuO–ZnO–ZrO2 Prepared by Solvothermal Method: The Influence of Solvent on Catalyst Properties and Catalytic Behavior

Field-Effect Passivation of the Cu2O/ZnO Transparent Heterojunction Photovoltaic Device Using Ga2O3 Thin Film

Photovoltaics (PV) would be more promising if light could generate electric power invisibly. This will endow more degrees of freedom to PV cells for wide-range deployment. Transparent photovoltaic (TPV) devices are the groundwork of the building-integrated photovoltaic (BIPV) systems that provide aesthetics to the buildings and solar energy convertor modules. TPV is adequate for the BIPV system of windows. Heterojunctions between p-type Cu2O and n-type ZnO have emerged as one of the most promising TPV devices. However, their inadequate transparency and a deficit of open-circuit voltage (VOC) and short-circuit current density (JSC) remained an open challenge. In this work, we have fabricated a thin Ga2O3 buffer layer embedded transparent ZnO/Cu2O heterojunction photovoltaic device, showing an average visible transmittance of more than 50%. The insertion of the Ga2O3 buffer layer remarkably increases the JSC and VOC to ∼860% and ∼41%, respectively. The TPV device also demonstrated a high JSC of 3.41 mA/cm2 under UV light. The Ga2O3 layer provides a graded conduction band alignment and passivates the interface by the field-effect passivation mechanism. The Ga2O3 buffer layer embedded device also demonstrated a broadband photodetection with remarkably high responsivity and detectivity of 250 mA/W and 5 × 1011 Jones at self-biased conditions.

ZnO-Cu2O Composites for Photocatalytical Removal of Methylene Blue from Aqueous Solution under Visible Light

ZnO-Cu2O composites were prepared by precipitation technique followed by calcination. The prepared composite was characterized by scanning electron microscopy (SEM), energy dispersion X-ray (EDX), Fourier transform infra-red (FT-IR) and X-ray diffraction (XRD). Band gap energy of the composite was determined by UV-visible reflectance measurement. The absorption range of the ZnO-Cu2O composite was shifted to the visible region due to the doping of Cu2O. SEM image represented that composite nanoparticle was smaller in size compared to the pure ZnO. The EDX spectral analysis showed that no elements other than Zn, Cu and O were present in the sample. XRD showed that ZnO-Cu2O composite was made of hexagonal ZnO and cubic Cu2O. The photocatalytic activity of ZnO-Cu2O composite was studied by degrading MB under different experimental conditions. The molar ratios of the composites, amount of the composite, initial concentration of dyes were varied to optimize the conditions for degradation. The experimental result was compared with those of commercial ZnO. It was found that the ZnO-Cu2O composite is a better photocatalyst than ZnO under visible light. Dhaka Univ. J. Sci. 71(1): 42-48, 2023 (Jan)

Enhanced Photocatalytic Activity of Cu2O/ZnO/GO Nanocomposites on the Methylene Blue Degradation

This study synthesized nanocomposite photocatalyst materials from a mixture of Cu2O nanoparticles, ZnO nanoparticles, and graphene oxide (GO) through coprecipitation and hydrothermal methods. This study aims to determine the optimum composition of Cu2O/ZnO/GO nanocomposites in degrading methylene blue. The nanocomposite was synthesized in two steps: 1 the synthesis of Cu2O and ZnO nanoparticles through the coprecipitation method and the preparation of GO through the modified Hummer method. 2 The preparation of Cu2O and ZnO nanoparticles mixtures with GO through the hydrothermal method to form Cu2O/ZnO/GO nanocomposites. The adsorption-photocatalysis process of methylene blue was done with UV light from a halogen lamp. The characterization results indicated that the optimum composition was Cu2O/ZnO nanocomposite with a ratio of 1:2 and 10% of GO, which had a specific surface area of 35.874 m2 g-1, a pore radius of 19.073 nm, and a pore volume of 0.092 cm3 g-1, and a diameter crystalline of 31.19 nm. The degradation efficiency of methylene blue under UV light for 120 minutes were 82.0%, 86.0%, 91.4%, and 79.3% using the Cu2O/ZnO nanocomposites with GO of 1%, 3%, 5%, and 10%, respectively. These results indicated that Cu2O/ZnO/GO nanocomposites efficiently degrade methylene blue from textile dye waste.

Photocatalytic performance and solar cell applications of coupled semiconductor CuO– ZnO sprayed thin films: Coupling effect between oxides

In the current study, CuO–ZnO coupled oxide thin films were deposited on glass substrates for the first time by spray pyrolysis technique. The consequences of different synthesis conditions such as molar ratio on structural, morphological, optical, and electrical properties were also studied. These physical studies were carried out by X- Ray Diffraction, scanning electron microscopy, Energy dispersive X-ray analyses (EDX), profilometer analyses, UV-VIS-NIR spectrophotometer, photoluminescence spectra, Hall Effect measurements and impedance spectroscopy. Molar ratio affects the thin films properties mainly the optical and electrical ones. The mechanisms of pure CuO and ZnO oxides and ZnO + CuO coupled oxide thin films for the degradation of methylene blue was discussed. Coupled oxide thin films show higher photocatalytic activity compared to pure oxides and the photodegradation efficiency of copper-zinc coupled oxide was found to be equal to 99% under sun light illumination. Moreover, our thin films show higher stability, recoverability and reusability under cyclic test for 9 h which makes it suitable for industrial applications. as a second applications The performance of FTO/ZnO/CuO–ZnO hetero-junction structure was investigated. This work also represents a comparative study between our synthesized thin films and other binary and coupled oxides thin films catalysis (20 catalysis) for the degradation of metylene blue and the performance of our solar cell with other structures based in ZnO + CuO coupled oxide thin films structures.

Phase equilibria and thermodynamic modelling of the PbO–ZnO-“CuO0.5”-SiO2 system

The phase equilibria of the PbO–ZnO-“CuO0.5“- SiO2 system were studied as part of the investigation of the 19-component PbO–ZnO–Cu2O–FeO–Fe2O3–CaO–SiO2–Al2O3–MgO–S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co as minor elements) slag/matte/metal/speiss/gas system in support of the development and optimization of pyrometallurgical processes. In the experimental study, samples were equilibrated at high temperatures, then quenched, and the lead, zinc, copper and silicon concentration in the phases were directly measured by electron probe X-ray microanalysis (EPMA). The cristobalite (SiO2) primary phase field of the PbO–SiO2 system was experimentally studied between 1575 and 1717 °C. The massicot (PbO), zincite ((Zn,Cu)O), cuprite (Cu2O), copper plumbite (Cu2PbO2) and Pb2SiO4 primary phase fields of the PbO-“CuO0.5”-SiO2, PbO–ZnO-“CuO0.5” and PbO–ZnO–SiO2 systems were studied between 664 and 1100 °C. The cuprite (Cu2O), willemite ((Zn,Cu)2SiO4), larsenite (PbZnSiO4) and melilite (Pb2ZnSi2O4) secondary phase fields of the PbO–ZnO-“CuO0.5”-SiO2 system in equilibrium with metal and tridymite/quartz (SiO2) or zincite ((Zn,Cu)O) were studied between 745 and 1100 °C. The zincite ((Zn,Cu)O), tenorite ((Cu,Zn)O) and willemite ((Zn,Cu)2SiO4) solid solutions in equilibrium with air or pure O2 at 1 atm were studied between 900 and 1100 °C. Using the FactSage thermodynamic calculation software, a self-consistent set of parameters based on the Modified Quasichemical Model (MQM) were developed to describe the newly obtained and existing experimental data.

Effect of Cu or Ni addition to ZnO nanostructures on their n-butanol sensing performance

ZnO nanostructures with two shapes were routinely synthesised using a direct-current heating technique. These structures were coated with metals such as Cu and Ni to enhance the sensor response to n-butanol vapour. The surface modification approach associated with semiconductor materials used in gas sensor applications is essential for improving sensing performance, including the sensor response, selectivity, and stability for specific gases. Previously investigated surface modification approaches mostly involved the addition of noble metals, such as Pd, Pt, and Au. However, these metals are expensive for commercial applications. Herein, surface modification by the addition of non-noble metals is presented as a p–n junction for sensor fabrication. Cu and Ni sputter-coated onto ZnO nanostructures were transformed into CuO and NiO, respectively. The results of the gas-sensing characteristics show that the p–n junction formation of the ZnO–CuO and ZnO–NiO sensors remarkably enhanced the sensor response toward n-butanol. The sensor response of the ZnO–NiO sensor upon exposure to n-butanol at a concentration of 1000 ppm was 1400.0 at a working temperature of 450 °C, whereas that of the ZnO–CuO sensor was 775.9 at the optimum working temperature of 400 °C and an n-butanol concentration of 1000 ppm. Furthermore, these sensors exhibited excellent selectivity toward n-butanol compared to other gases. The sensing mechanism is explained by the large depletion layer width at the boundary of the p–n junction, which improves the sensor response. These results demonstrate a viable approach for manufacturing n-butanol sensors and possibly for constructing a functional active layer in e-nose applications.

Synthesis and characterization of dip-coated ZnO‒CuO composite thin film for room-temperature CO2 gas sensing

In this work, ZnO‒CuO composite thin film is prepared to achieve CO2 gas sensing at room-temperature. To achieve this purpose, a sol-gel dip-coating method was used to prepare the composite ZnO‒CuO thin films on a glass substrate by varying the precursor solution Zn/Cu molar ratio of 0.3, 0.5, and 0.7. The crystal structure of the films was determined by X-ray diffraction, indicating that the films were polycrystalline in nature with the presence of monoclinic CuO and hexagonal wurtzite ZnO phase, which was further confirmed by Raman spectroscopy. The homogeneous and porous surface morphology of the composite films obtained were observed by scanning electron microscopy. Optical properties and band gap measurements were explored by ultra-violet/visible spectroscopy and the direct band gap of synthesized ZnO‒CuO composite film was found to decrease from 1.54 to 1.45 eV, depending on the precursor solution Zn/Cu molar ratio. Various effective parameters on the performance of CO2 gas sensing, including the molar ratio of Zn/Cu, porous surface, water contact angle, film thickness, grain size, optical and electrical properties were investigated. Results demonstrated that the higher molar ratio (0.7) and thicker film (318 ± 5 nm) with the porous surface of ZnO‒CuO composite films exhibited the highest sensing (∼ 48%) response to 10,000 ppm CO2 at room-temperature. The obtained results suggest a direction for room-temperature ZnO–CuO composite-based sensor as efficient, fast as well as sensitive for CO2 detection.

The toxicity of ZnO and CuO nanoparticles on biological wastewater treatment and its detoxification: a review

The wide use of ZnO and CuO nanoparticles in research, medicine, industry, and other fields has raised concerns about their biosafety. It is therefore unavoidable to be discharged into the sewage treatment system. Due to the unique physical and chemical properties of ZnO NPs and CuO NPs, it may be toxic to the members of the microbial community and their growth and metabolism, which in turn affects the stable operation of sewage nitrogen removal. This study summarizes the toxicity mechanism of two typical metal oxide nanoparticles (ZnO NPs and CuO NPs) to nitrogen removal microorganisms in sewage treatment systems. Furthermore, the factors affecting the cytotoxicity of metal oxide nanoparticles (MONPs) are summarized. This review aims to provide a theoretical basis and support for the future mitigating and emergent treatment of the adverse effects of nanoparticles on sewage treatment systems.

Structure and electrochemical properties of CuO-ZnO nanocomposite produced by the one-step novel discharge process

The current study focuses on an alternative strategy for producing nanoparticles (NPs) using one-step electrochemical discharge process (ECDP) in different electrolyte mediums. Current and plasma discharge effects on morphology and mass output rate were examined in detail. FE-SEM and TEM results show dimensional control materials such as rod, flower and rice shapes are produced. The XRD, EDS, UV-vis and Raman characterization techniques confirm the formation of CuO-ZnO NPs with different morphology. The use of two semiconductors (n-type ZnO and p-type CuO) in combination have two different band energies may boost electrochemical performance. From the electrochemical study, the flower-shaped structure has high specific capacity (313 F/g at 2 A/g current density), with 84.1% retention capacitance after 5000 cycles. This study allows us to study the discharge-based composite formation, which could be used in supercapacitors.

Synthesis, structural and optical properties of Cu doped ZnO and CuO–ZnO composite nanoparticles

Hydrothermal synthesis was used to obtain pure, doped and composite semiconductor oxide materials. We synthesized ZnO, CuO, Cu doped ZnO with 1, 2 and 3 wt %, and for Cu additions at 6, 8, 10, 15, 30 and 50 wt% this resulted in ZnO–CuO composites with different morphologies. X-ray diffraction (XRD) showed hexagonal and monoclinic crystalline phases for pure ZnO and CuO, respectively. Electron microscope images showed two-dimensional (2D) shaped particles. The Cu element could dope ZnO up to 3 wt%, whilst above this value, composites of ZnO–CuO were generated, with two segregated phases having flake-like shaped elongated particles. The visible-light absorption increases for the doped samples, being directly proportional to the Cu content for the dopant and the composite particles, showing a broad absorption range between 200 and 800 nm. Two bandgap energy values of 3.22 and 1.45 eV were determined for the ZnO–CuO samples. The samples were studied by X-ray photoelectron spectroscopy (XPS) in order to understand the doping process and composite formation.

Macrocyclic Compounds: Metal Oxide Particles Nanocomposite Thin Films Deposited by MAPLE.

Nanocomposite films based on macrocyclic compounds (zinc phthalocyanine (ZnPc) and 5,10,15,20-tetra(4-pyridyl) 21H,23H-porphyrin (TPyP)) and metal oxide nanoparticles (ZnO or CuO) were deposited by matrix-assisted pulsed laser evaporation (MAPLE). 1,4-dioxane was used as a solvent in the preparation of MAPLE targets that favor the deposition of films with a low roughness, which is a key feature for their integration in structures for optoelectronic applications. The influence of the addition of ZnO nanoparticles (~20 nm in size) or CuO nanoparticles (~5 nm in size) in the ZnPc:TPyP mixture and the impact of the added metal oxide amount on the properties of the obtained composite films were evaluated in comparison to a reference layer based only on an organic blend. Thus, in the case of nanocomposite films, the vibrational fingerprints of both organic compounds were identified in the infrared spectra, their specific strong absorption bands were observed in the UV-Vis spectra, and a quenching of the TPyP emission band was visible in the photoluminescence spectra. The morphological analysis evidenced agglomerated particles on the composite film surface, but their presence has no significant impact on the roughness of the MAPLE deposited layers. The current density-voltage (J-V) characteristics of the structures based on the nanocomposite films deposited by MAPLE revealed the critical role played by the layer composition and component ratio, an improvement in the electrical parameters values being achieved only for the films with a certain type and optimum amount of metal oxide nanoparticles.

CuO–ZnO p-n junctions for accurate prediction of multiple volatile organic compounds aided by machine learning algorithms

Detection and quantification of multiple volatile organic compounds (VOCs) are emerging as critical requirements for several niche applications including healthcare. It is desirable to get multiple gases identified rapidly and using minimum number of sensors. Heterojunctions of metal oxides are still among the top-picks for efficient VOC sensing because they unfold exciting sensing characteristics in addition to enhanced response. This work reports the synthesis of nanostructures of CuO, ZnO, and three CuO–ZnO p-n junctions having different weight percentages (1–0.5, 1-1, and 0.5–1) of CuO and ZnO, using a facile one-pot hydrothermal method. The nanomaterials were characterized using X-ray diffraction, field emission scanning electron microscopy, and UV–Visible spectroscopy. Resistive sensors were fabricated of all five nanomaterials and were tested for 25–200 ppm of four VOCs – isopropanol, methanol, acetonitrile, and toluene. The CuO and CuO–ZnO (1–0.5) sensors showed the highest response for isopropanol (7.5–65.3% and 19–122%, respectively) at 250 °C, CuO–ZnO (1-1) and CuO–ZnO (0.5–1) exhibited the highest responses for methanol (9–60%) and isopropanol (15–120%), respectively at 350 °C, and the intrinsic ZnO showed maximum response to toluene (29–76%) at 400 °C. All the sensing layers were observed to exhibit finite responses to the other three VOCs so, an attempt to classify and quantify the four VOCs accurately was made using support vector machine (SVM) and multiple linear regression (MLR) algorithms. The response and response times of two sensors were observed to be sufficient as inputs to the machine learning algorithms for classifying and quantifying all the four VOCs. The combinations of (CuO–ZnO (1–0.5) & (1-1) and CuO–ZnO (1-1) & (0.5–1) demonstrated the highest classification accuracy of 98.13% with SVM. The combination of CuO–ZnO (1–0.5) & (1-1) demonstrated the best quantification of the four VOCs using MLR.

Effects of nano metal oxide particles on denitrifying phosphorus removal system: Potential stress mechanism and recovery strategy

The accumulation of nano metal oxide particles (NMOPs) in municipal sewage treatment systems harms the microbial community and its metabolism in activated sludge system, resulting in the degradation of its pollutants removal performance. In this work, the stress effect of NMOPs on the denitrifying phosphorus removal system was systematically investigated in terms of pollutants removal performance, key enzyme activities, microbial community diversity and abundances, and intracellular metabolites. Among the ZnO NPs, TiO2 NPs, CeO2 NPs, and CuO NPs, the ZnO NPs showed the most significant impacts with the chemical oxygen demand, total phosphorus, and nitrate nitrogen removal ratio decreased from above 90 % to 66.50 %, 49.13 %, and 57.11 %, respectively. The addition of surfactants and chelating agents could relieve the toxic effect of NMOPs on the denitrifying phosphorus removal system, and the chelating agents were more effective than surfactants in performance recovery. After adding ethylene diamine tetra acetic acid, the removal ratio of chemical oxygen demand, total phosphorus, and nitrate nitrogen under ZnO NPs stress was restored to 87.31 %, 88.79 %, and 90.35 %, respectively. The study provides valuable knowledge to better understand the impacts and stress mechanism of NMOPs on activated sludge systems and provides a solution to recover the nutrients removal performance of denitrifying phosphorus removal system under NMOPs stress.

Production of p-CuO/n-ZnO:Co nanocomposite heterostructure thin films: An optoelectronic study

The p-n junction is the principal mode of optoelectronic semiconductor material. At present, we submit a solution-based attempt at the synthesis of nanostructured p-type CuO and n-type ZnO nanocomposite (NC) heterostructure films. Bare and Cobalt (Co)-doped CuO–ZnO NC films have been produced on glass slides using the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The influence of Co-doping concentration on the physical characteristics of CuO–ZnO NC heterostructure films was investigated. XRD spectrums indicated the phase and structural purity of solution-based synthesized CuO–ZnO NC samples. The surface topographical, as well as optical and electrical properties of heterostructure films were, also investigated. While the bare CuO–ZnO NC film has a ∼38% transmission near 1000 nm wavelength region, the 2.0% Co-doped CuO–ZnO NC film has ∼31% of optical transmission. The sheet resistance value of the grown 2.0% Co:CuO–ZnO NC sample is almost 13 times lower than that of the bare CuO–ZnO NC sample at 400 K temperature. As a consequence, our attempt ensures a novel strategy for the production and performance optimization of CuO–ZnO NC heterostructures in the implementation of optoelectronics.

Design strategy for CuO-ZnO S-scheme heterojunction photocatalysts in the presence of plasmonic Ag and insights into photoexcited carrier generation and interfacial transfer in diverse structural configurations of the heterostructure system

This work demonstrates an exploration of the dynamics of the photogenerated electrons and holes in the S-scheme heterojunctions of CuO nanoparticles and ZnO microrods in the presence of plasmonic Ag nanoparticles. Herein, n-type ZnO microrods developed by the cost-efficient thermal decomposition method are decorated with nanoparticles of CuO and Ag deposited by the direct current magnetron sputtering. Microstructural analyses based on XRD, FESEM, and FETEM measurements reveal interfaces of single crystalline wurtzite ZnO with phase pure CuO and polycrystalline Ag nanoparticles. XPS results complement microstructural information from the FETEM measurements, signifying plasmon loss features of Ag nanoparticles and suggest direct electron transfer from Ag to ZnO, where ZnO microrods constitute the major part of the photocatalysts. The plausible schemes of light collection, carrier generation, and transfer have been presented based on the structural and optical properties, which are utilized to explain the photocatalytic degradation of aqueous cationic Rhodamine 6G under UV-Vis-NIR illumination. The optimized CuO-ZnO heterojunction is highly efficient as a photocatalyst with a degradation rate of 89% due to a greater light collection ability and S-scheme based electron-hole separation at multiple junctions. The plasmonic modulation of the photocatalytic activities of the heterojunction-heterostructure systems is critically governed by the structural organizations of the materials.

The effect of nanocrystalline TiO2 on structure and catalytic activity of CuO–ZnO in combined methanol reforming

CuO–ZnO (CZ) and CuO–ZnO/TiO2 (CZT) catalysts have been prepared by co-precipitation, characterized by X-ray diffraction, surface area measurements and chemical analysis and tested in the combined methanol reforming reaction. Catalytic tests have been performed in the temperature range 200–400 °C with a GHSV = 55.000 h−1, after H2 reducing pretreatment at 250 °C or 450 °C. It is shown that nanocrystalline TiO2 influences the CuO–ZnO nanosized structure, reducibility and reactivity. TiO2 slightly increases ZnO crystallite size of the fresh catalyst. Moreover, it causes the CuO chemical reduction to nanosized Cu2O on exhaust catalyst pretreated in hydrogen at 250 °C, this improves the reaction with higher methanol conversion and hydrogen production. On the contrary, TiO2 reduces CuO to submicron Cu0 and greatly increases ZnO crystallite size on the exhaust catalyst pretreated in hydrogen at 450 °C, this treatment weakens the reaction, with lower methanol conversion and hydrogen production. In both cases, nanocrystalline TiO2 presence is able to decrease the CO formation: independently of the hydrogen pretreatment temperature. This ability of the nanocrystalline TiO2 is ascribed to the presence of the oxygen vacancies, which act as electron donors that contribute to hinder CO2 and H2 surface adsorption for steric, electrostatic and probabilistic factors.

Experimental investigation of bimetallic nanoparticles heat transfer characteristics in automotive radiators

Improvement of the thermal properties of coolants used in automobile radiators increases the cooling performance of the engine. Metallic nanoparticle additives generally improve the thermal properties of the coolant. In this study, the heat transfer characteristics of a nanofluid prepared with bimetallic additives (CuO–ZnO) for automotive radiators were experimentally investigated. Experiments were made for four different fluids under constant heating power. These are water-bimetal mixture fluids with 0.1%, 0.2% and 0.3% particulate additives. UA values of the heat exchanger were calculated using the logarithmic temperature difference method and compared for different concentrations. As a result, it was observed that the 0.3% additive ratio had the highest UA value. In addition, with the increase of the bimetallic nanoparticle additive rate, the heat transfer also increases. Finally, an economic analysis was carried out for the use of nanoparticles in the water cooling system for a single cylinder natural gas engine.