Pure Cupric Oxide Research Articles

Synthesis of CuO nanosheets on Cu foil via one-step wet chemical process at different reaction temperatures and their photoelectrochemical performance

Cupric oxide (CuO) nanostructures were directly grown on copper substrate via a simple one step solution-immersion process. The films were formed by the direct oxidation of copper in aqueous solution containing sodium hydroxide (NaOH) and ammonium persulfate (NH4)2S2O8. The influence of the reaction temperature on the structural, morphological, optical and photoelectrochemical (PEC) properties of the formed copper compounds nanostructures was investigated. The XRD and Raman spectroscopy results revealed the formation of Cu(OH)2/CuO composite for the samples prepared at 3 and 25 °C, and pure CuO was obtained for the samples prepared at 45 and 55 °C. The SEM micrographs showed that the formed Cu(OH)2 and CuO present a nanowire bundles and nanosheet morphology, respectively. The increase of the reaction temperature enhanced the absorbance of the CuO samples in the entire visible region. According to the photoelectrochemical measurements, the increase of the reaction temperature resulted in an improvement of the PEC response. The CuO nanosheets synthesized at 55 °C presents the highest and the most stable PEC response. A reasonable mechanism describing the formation of nanostructured copper compounds at different reaction temperatures is discussed in this paper.

BIOSYNTHESIS AND CHARACTERIZATION OF CuO NANOPARTICLES USING DIFFERENT pH

CuO nanoparticles are synthesized from Ferulago angulate leaf extract under different pH values. The structural, morphological, as well as optical properties of the green synthesized CuO NPs are studied. Besides, the functional groups in the Ferulago angulate stabilizer capping the copper nanoparticles were examined using FTIR spectra. The primary factor that led to the first confirmation of CuO NP production was the reaction mixture's color change. A phytochemical test revealed the presence of proteins, amino acids, carbohydrates, flavonoids, phenols, alkaloids, tannins, and saponins. FTIR spectrum shows a peak at 532.35 cm-1, this may be attributed to CuO's vibrations confirming the presence of copper oxide nanoparticles. XRD analysis shows the presence of crystalline monoclinic cupric oxide (CuO). The morphological study (FESEM) shows different morphology (different shapes and sizes) under different pH values. EDS data shows the O-richness of the prepared CuO NPs extracted from Ferulago angulate [ Schltdl.] BOISS leaf extract shows pure CuO phases. In this investigation, fabricated CuO's estimated energy band gap values were higher than those of bulk CuO. Results show Eg increment with increasing pH values.

Platinum (Pt), gold (Au), and silver (Ag) ohmic contacts to cupric oxide (CuO) films deposited by air-based sputtering and thermal annealing

The present work reports the fabrication of three different ohmic contacts (platinum (Pt)/CuO, gold (Au)/CuO, and silver (Ag)/CuO). Structural properties of the films measured by X-ray diffraction and Raman techniques confirmed that the Cu2O films prepared by DC sputtering using air as a reactive gas, transformed into pure CuO films after thermal annealing. The band gap of the CuO films of 1.33 eV was estimated by reflectance measurements. Hall measurements confirmed the p-type conductivity of the CuO films with an acceptor concentration of 2.04x1016 cm−3.The linear behavior in both directions of polarization observed in the current–voltage measurements confirmed the formation of ohmic contacts between the characterized three metals and CuO. Based on the slope of the current–voltage curve, the best ohmic contact was that fabricated between Au and CuO. The mechanism governing the transport through the interface between the metal/CuO ohmic contact was thermionic emission.

Photocatalytic degradation and electrochemical energy storage properties of CuO/SnO2 nanocomposites via the wet-chemical method

Integrating semiconducting functional materials is a way to enlarge the photoexcitation, energy range, and charge separation, greatly elongating the photocatalytic efficiency to enhance the chemical and physical properties of the materials. This work depicts and investigates the impact of cuprous oxide (CuO) and tin dioxide (SnO2)-based catalysts with various CuO concentrations on photocatalytic and supercapacitor applications. Moreover, three distinct composites were made with varied ratios of CuO (5, 10, and 15% wt. Are designated as AT-1, AT-2, and AT-3) with SnO2 to get an optimized performance. The photocatalytic properties indicate that the CuO/SnO2 nanocomposite outperformed its bulk equivalents in photocatalysis using Methyl blue (MB) dye in a photoreactor. The results were monitored using a UV–visible spectrometer. The AT-1 ratio nanocomposite displayed 96% photocatalytic degradation compared to pure SnO2 and CuO. CV analysis reveals a pseudocapacitive charge storage mechanism from 0.0 to 0.7 V in a potential window in an aqueous medium. The capacitive performance was also investigated for all electrodes, and we observed that a high capacitance of 260/155 F/g at 1/10 A/g was attained for the AT-1 electrode compared to others, specifying good rate performance.

CuO:Se composite films and its photovoltaic application

Cupric oxide (CuO) and selenium (Se) are old photoelectric materials, and their photovoltaic properties have always received attention. However, CuO has a high melting point (1026℃) and will decompose near its melting point, so it is difficult to prepare high crystallinity CuO films. Selenium (Se) can not efficiently absorb sunlight because of its large optical band gap (1.9 eV). Here, a CuO:Se composite film was prepared by radio frequency magnetron co-sputtering of CuO and Se and low temperature annealing (200℃). The experimental results show that this composite material film has the advantages of CuO and Se, and overcome their disadvantages. The material has strong absorption of light in the entire solar spectral range (250-2500 nm, average absorptance ~80%). A prototype solar cell based on this composite film was fabricated and its power conversion efficiency (PCE) is up to 2.05%, which is much higher than that of the pure CuO (0.007%) or pure Se (1.05%) film solar cells. This material should be promising for photovoltaic and other photo-electrical application.

Enhanced Thermoelectric Efficiency of Cement-Based Materials with Cuprous Oxide for Sustainable Buildings

The thermoelectric effect of plain cement paste is usually weak. To improve the thermoelectric performance of cement composites, functional components, such as carbon fibers, steel fibers, carbon nanotubes, and graphene, are often added to cement paste. In view of the advantage of metal oxides with a higher band gap, pure cuprous oxide crystals with different particle sizes were synthesized by a hydrothermal method and incorporated into the cement matrix to improve the thermoelectric efficiency of cement composites in this study. Pure cuprous oxide crystals with different particle sizes (15 μm, 1.5 μm, and 100 nm) were prepared by controlling the reaction temperature and time, pH value, amount of reducing agent, and polyvinylpyrrolidone in the reaction system. The Seebeck coefficient, electrical conductivity, and thermal conductivity of the cement composites with 5.0 wt.% nanostructured Cu2O powder increased to 3966 ± 54 μV/K, (2.68 ± 0.12) × 10−4 S/m, and 0.69 ± 0.007 W/(m·K), respectively. Thereby, a high figure of merit value of 1.93 × 10−6 was obtained for the cement composites, which made future application of cement composites in energy harvesting for buildings possible.

A new efficient synthesis of CuO thin films using modified SILAR method

Due to its direct band gap and high absorption coefficient, Cupric Oxide (CuO) is widely used as an absorbent material for solar cells, yet most of the available deposition methods are expensive and complex. For this reason, this paper is concerned with the elaboration of CuO thin films using the simple and inexpensive modified successive ionic layer adsorption and reaction method, i.e., modified SILAR method. To that end, glass slide substrates and an aqueous solution of hydrated copper chloride (CuCl $$_{2}$$ ·2H $$_{2}$$ O) complexed with aqueous ammonia (NH $$ _{3} $$ ) (25–28%) were used, then the growth conditions were carefully evaluated to reduce the presence of the remaining phases other than CuO. The elaborated thin films are studied from four perspectives: (1) structural decomposition, (2) morphological decomposition, (3) chemical decomposition and (4) optical properties. It is found that the deposited films are polycrystalline and crystallized in a pure CuO monoclinic structure without any other secondary phase. Raman and X-ray photoelectron spectroscopy confirmed the pure phase obtained and the scanning electron microscopy images showed that the resulting films were dense, smooth and homogeneous. The energy dispersive X-ray spectrum and the elemental mapping scan corroborate the uniform distribution of Cu and O elements on the film surface. Furthermore, UV–visible spectra exhibited a negative correlation between optical transmission and deposition cycles—if the deposition cycles increased, optical transmission decreased similarly the optical band gap. As well as the refractive index and Urbach energy were determined. As a result, the synthesis technique is very simple and low cost, CuO thin films could be appropriate for solar cells applications.

Preparation and Characteristic of Ultrafine Copper-Based Powders Reduced by a Two-Step Reduction Method

In this study, the ultrafine copper-based powders were fabricated by a facile two-step chemical reduction method. Glucose (C6H12O6) and ascorbic acid (AA) were taken as a pre-reductant and a second reductant, respectively. Polyvinylpyrrolidone (PVP) was applied as the capping agent. Effects of parameters, such as glucose content, PVP content and PH value on the ultimate reduction products were analyzed. Microstructure and composition of the products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). It was found that when the amount of glucose was increased from half to full and then excessive, the powder gradually changed from flaky to spherical, from pure copper powder to a mixture of copper and cuprous oxide (Cu2O). With the amount of PVP increasing from 0g to 0.64 g, the shape of the pure copper powder changed from cubic to spherical or HYPERLINK "javascript:void (0);" icosahedron. When the PH value changed from 10-14, the powder changed from spherical to regular octahedron and Irregular polyhedron, from pure copper powder to pure cuprous oxide powder. Therefore, copper-based powders with different morphologies and different compositions can be prepared by changing PH value and the amount of reductant.

Carbon dots-stabilized Cu4O3 for a multi-responsive nanozyme with exceptionally high activity

A novel nanocomposite of carbon dots-stabilized paramelaconite (CDs@Cu4O3) is firstly reported and investigated as a stimuli-responsive nanozyme. The CDs@Cu4O3 is a more robust catalyst without incurring the burden of easy denaturation or decomposition and behaves as oxidase and peroxidase mimetics. The activity of CDs@Cu4O3 is up to 3.6 times higher than that of pure cuprous oxide nanoparticles and can be boosted by multiple kinds of external stimuli including of light irradiation, temperature, pH and oxidizing agent. We find that carbon dots play the key roles in facilitating the generation of Cu4O3 and sustaining Cu2+/Cu+ redox couples that are required for the catalytic reaction to proceed quickly. This nanocomposite endowed with ease of preparation, versatility and high stability is expected to be wide uses for biotechnology, environmental treatment, and organic synthesis.

A Low Cost Synthesis and Characterization of CuO Nanoparticles for Photovoltaic Applications

A simple low cost chemical route has been used to synthesize cupric oxide nanoparticles. The synthesized CuO nanoparticles were characterized using XRD, TEM and UV-absorption. X-ray diffraction analysis showed the synthesized nanoparticles to be a pure cupric oxide. EDAX analysis showed the presence of copper and Oxygen in the as prepared CuO nano particles, with the AAS indicating that Cu2+ represented 53.5% of the sample. The particle size and particle size distribution of the cupric oxide nanoparticles were obtained by transmission electron microscopy (TEM) whereas the crystallite size and crystallite size distribution were obtained by X-ray diffraction. The particle size was found to be between 20 nm and 60 nm. The particle size distribution obtained from cumulative percentage frequency plots features a log-normal function. Absorbance measurements and analysis showed that the material has an absorbance peak at 314 nm and energy bandgap of 1.48 eV, making it a good candidate for photovoltaic applications.

Thermal oxidation of copper over a broad temperature range: towards the formation of cupric oxide (CuO)

P-type semiconducting cupric oxide (CuO) was formed by thermal oxidation of copper (Cu) sheets. Oxidation variables such as temperature, oxidation time, and oxidation atmosphere were controlled with the aim of form the single phase of CuO. Structural, morphological, and electrical properties of copper oxide were measured with x-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), and Hall effect techniques, respectively. Oxidation at temperatures lower than 200 °C showed that a thin layer of copper oxide, mainly of cuprous oxide (Cu2O), is grown on the surface of Cu. Oxidation at 300 °C promoted growth of a passivating oxide layer composed by CuO and Cu2O, even when Cu is oxidized during 24 h. In the range of temperatures from 400 to 700 °C, copper oxide layer was fragile and showed poor adherence to the Cu surface. Further Cu oxidation at higher temperatures promoted complete oxidation of the Cu sheets. However, the bulk was found to be composed by a mixture of Cu2O and CuO. Oxidation at 1000 °C for 24 h in flow of air or for 8 h in ambient of oxygen allowed formation of pure and high cristallinity CuO. Carrier concentration and mobility charge carriers of CuO estimated from Hall measurements for the CuO sample oxidized in oxygen atmosphere were found to be 7.64 × 1012 cm−3 and 1.1164 × 102 cm2 V−1 s−1, respectively.

A Facile Synthesis of Cu2O and CuO Nanoparticles Via Sonochemical Assisted Method

Background: During past two decades, functional nanomaterials have received great attention for many technological applications such as catalysis, energy, environment, medical and sensor due to their unique properties at nanoscale. However, copper oxide nanoparticles (NPs) such as CuO and Cu2O have most widely investigated for many potential applications due to their wide bandgap, high TC, high optical absorption and non-toxic in nature. The physical and chemical properties of CuO and Cu2O NPs are critically depending on their size, morphology and phase purity. Therefore, lots of efforts have been done to prepare phase CuO and Cu2O NPs with different morphology and size. Method: The synthesis of cupric oxide (CuO) and cuprous oxide (Cu2O) NPs using copper acetate as a precursor by varying the reducing agents such as hydrazine sulphate and hydrazine hydrate via sonochemical method. The phase, morphology and crystalline structure of a prepared CuO and Cu2O NPs were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDS) and UV-Visible Diffuse reflectance spectroscopy (DRS). Results: The phase of NPs was tuned as a function of reducing agents.XRD patterns confirmed the formation of pure phase crystalline CuO and Cu2O NPs. FTIR peak at 621 cm-1 confirmed Cu(I)-O vibrations, while CuO vibrations confirmed by the presence of two peaks at 536 and 586 cm-1. Further investigation was done by Raman, which clearly indicates the presence of peaks at 290, 336, 302 cm-1 and 173, 241 cm-1 for CuO and Cu2O NPs, respectively. The FESEM images revealed rod-like morphology of the CuO NPs while octahedral like shape for Cu2O NPs. The presence of elemental Cu and O in stoichiometric ratios in EDS spectra confirms the formation of both CuO and Cu2O NPs. Conclusion: In summary, CuO and Cu2O NPs were successfully synthesized by a sonochemical method using copper acetate as a precursor at different reducing agents. The bandgap of CuO and Cu2O NPs was 2.38 and 1.82, respectively. Furthermore, the phase purity critically depends on reducing agents.

Исследование процесса релаксации напряжений в деформированном композите с эпоксидной матрицей

The present paper gives results from a study of the relaxation of internal stresses in a granular composite with an epoxy matrix. We studied samples of ED-20 epoxy resins cured by polyethylene polyamine. As the filler we used powdered copper oxide with a volumetric concentration 0 . 064–0 . 35. The samples had the shape of cylinders of diameter 8 mm and height 30 mm. The experiments are performed with the use of nuclear quadrupole resonance (NQR). Measurements are made of the 63-Cu NQR-frequencies in samples as of epoxy resin containing cuprous oxide powder as control sample – pure cuprous oxide powder. In the description of the results of the NQR experiments, the value of internal stresses is given in frequency units. We held experimental research on cylindrical samples of granular composite with epoxy matrix hardened at high temperature. These samples were subjected to uniaxial compression at room temperature. Deformation of the samples led to an increase NQR frequency of the filler. The change in the value of internal stresses during heating of deformed samples of a granular composite was experimentally investigated. Measurements were made of the frequency difference for copper oxide in the polymer and control samples in the temperature range 393–293 K at 10 K intervals. Stresses in the matrix and the frequency difference decreases with increasing temperature. The observed nonlinearity of the temperature dependences of the NQR frequencies for the filler indicates the presence of relaxation processes in the stressed matrix of the samples at temperatures below the glass transition temperature. It is shown that the process of relaxation of stresses caused by the deformation of the sample is well described by an exponential dependence. The activation energy of this process was 105 kJ / mol. Comparison of the calculation results with the experimental data has shown their satisfactory comparability. Similar experiments were conducted with samples having an epoxy matrix cured at room temperature. It was found that stress relaxation occurs at temperatures well below the glass-transition temperatures.

Cu2O epitaxial films with domain structures prepared on Y-stabilized ZrO2 substrates by pulsed laser deposition

Abstract Copper oxide films have been deposited on the Y-stabilized ZrO2 (YSZ) (100) substrates by pulsed laser deposition and the effect of oxygen pressure (PO2) on the film properties was investigated in detail. The phase, crystallinity, and surface morphology of the films were strongly influenced by PO2 and the film prepared at 0.09 Pa was pure cuprous oxide (Cu2O) having the best film crystallinity. An out-of-plane epitaxial relationship of Cu2O (110)∥YSZ (100) with six different kinds of domain structure were observed for the 0.09 Pa-deposited sample and the corresponding in-plane epitaxial relationships were deduced. The lowest resistivity of 13.4 Ω cm and highest Hall mobility of 16.3 cm2 v−1 s−1 were also obtained for the film deposited at 0.09 Pa. The optical band gap of the as-prepared copper oxide films varied from 2.37 to 2.57 eV.

Synthesis and characterization of CuO thin films grown by chemical spray pyrolysis

In this study, nanostructured cupric oxide (CuO) thin films were deposited using simple spray pyrolysis technique on glass substrates with a fixed temperature at 375 $$^{\circ }$$ C. The films were deposited at different precursor molarities 0.035, 0.05 and 0.1 M using (CuCl $$_{2}\cdot 2$$ H $$_{2}$$ O) as precursor. The characterizations used such as X-ray diffraction (XRD) shows the formation of pure polycrystalline CuO with tenorite phase which belongs to a monoclinic structure. Raman spectroscopy confirms what we obtained in XRD. The films deposited with 0.1 M show high absorbance. The gap energy decreased from 1.58 to 1.53 eV with increasing precursor concentration from 0.035 to 0.1 M. Other optical parameters such as refractive index, extinction coefficient and dielectric constants were calculated through absorbance/transmittance data extracted from spectrophotometry.

Morphologically tailored CuO photocathode using aqueous solution technique for enhanced visible light driven water splitting

Abstract Cupric oxide (CuO) nanostructures are grown on fluorine doped tin oxide (FTO) coated glass substrate using aqueous solution approach. The concentration of precursor’s solution has significant impact on morphology of CuO nanostructure. By varying concentration of precursor, the growth of two different morphologies (oriented nanosheets and nanoleaves) is achieved. X-ray diffraction pattern and X-ray photoelectron spectroscopy reveals formation of pure CuO crystalline phase. Mott-Schottky characteristic confirms the p-type semiconducting nature. Ultrathin structures of nanoleaves lead to higher light trapping and light absorption in visible-NIR region. The nanoleaves film has lower bandgap in comparison with nanosheets film. Photoelectrochemical measurements result in 1.5 mA/cm2 photocurrent for nanoleaves electrode and 1.1 mA/cm2 for nanosheets electrode at a potential of 0 V v/s RHE. The photocurrent conversion efficiency is 1.8% and 1.4% in nanoleaves and nanosheets electrodes, respectively. Electrochemical impedance analyses endorse more efficient collection and separation of charge carriers in nanoleaves film.

Multi-shelled copper oxide hollow spheres and their gas sensing properties

In this work, multi-shelled copper oxide hollow composite microspheres with tunable shell number and composition were successfully synthesized by means of hard template method. The source for the carbonaceous microspheres templates affects the compositions of the final copper oxides spheres critically. When changing the sucrose to glucose, the composite hollow spheres of cupric oxide (CuO) and cuprous oxide (Cu2O) were synthesized instead of the pure CuO hollow spheres. The structure of products can be tuned from single-, double- to triple-shelled hollow spheres by precisely increasing the calcination rate. The pure CuO hollow-shell spheres had uniform diameters of about 900nm and an average shell thickness of 45nm. While the diameters and thicknesses of Cu2O/CuO composite hollow-shell spheres are 90–500nm and 15–35nm, respectively. Both of these two kinds of hollow-shell spheres showed much improved response to ethanol gas as gas sensors, the triple-shelled CuO/Cu2O hollow spheres exhibited the highest response at 140°C, 1000ppm.

ELECTROCATALYTIC OXIDATION OF ALCOHOLS ON Cu2O/Cu THIN FILM ELECTRODEPOSITED ON TITANIUM SUBSTRATE

A novel class of nanomaterials consisting of a composite thin film of cooper metal nanoparticles and cuprous oxide (Cu2O/Cu) for the catalytic electrooxidation of methanol, ethanol and ethylene glycol is considered here. The material was prepared by electrochemical deposition under a potentiostatic condition of [Formula: see text][Formula: see text]mV vs saturated calomel electrode (SCE) from acetate bath at titanium substrate. The effect of electrodeposition time on the structure, composition and morphology of the deposit was investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated the formation of pure cuprous oxide Cu2O thin film at low electrodeposition time (5 min) and Cu2O oxide thin film decorated with Cu nanoparticles (Cu2O/Cu) at high electrodeposition time. The obtained Cu2O and Cu2O/Cu thin films were explored for the electrochemical oxidation of alcohols in 1 M NaOH alkaline medium using cyclic voltammetry (CV) method. The Cu2O/Cu thin film grown at electrodeposition time of 15 min shows the best electrocatalytic performance toward ethanol oxidation. The effect of concentration of alcohols on the oxidation reaction was studied by CV and chronoamperometry. It was found that the reaction is governed by an irreversible diffusion process. The promising electrocatalytic activity of the Cu2O/Cu electrode provides a new platform for the fabrication of high-performance thin films for alcohols oxidation in alkaline medium. Therefore, the Cu2O/Cu electrode is a suitable as a less expensive electrocatalyst for alcohols oxidation.

Wet Chemically Synthesized CuO Bipods and their Optical Properties.

Metal oxide nanostructures are being investigated widely due to their strong optical absorption, efficient photoluminescence, abundant of availability and structural stability which lead them as a possible substitute of Si based solar cells and many optoelectronic and sensor devices. Due to their non-toxic nature they are supposed to be promising materials for drug delivery and medical research. Among several metal oxides, cupric oxide (CuO) is being investigated nowadays due to their high transparency and visible luminescence. It is a p-type semiconductor of band gap varying from 1.3 eV to 2.1 eV depending of the structure and process of fabrication. This low band gap of CuO nanostructures leads its application in photoconductive and photothermal applications. This leads rigorous investigations on CuO nanostructures. A simple wet chemical methods has been used to synthesize CuO bipods. Predetermined amount of Copper sulphate penta-hydrate (CuSO4, 5H2O) was dissolved in double distilled de-ionized water to prepare 0.5 M solution. Predetermined amount of Lithium hydroxide (LiOH) was dissolved in de-ionized water to prepare 1 M solution. Under rigorous magnetic stirring of the LiOH solution CuSO4 solution was added drop by drop for five minutes and the stirring was maintained for 2 hours at room temperature (30°C). After the reaction a white precipitate was observed at the bottom of the flask. This solution was then aged for 24 hours. The color of the precipitate solution was turned into grey. The precipitate was filtered and subsequently washed with distilled de-ionized water thrice for the removal of unreacted salts if any. The precipitate was then dried in an ordinary furnace at 150°C for further characterization. X-ray diffraction data confirmed the formation of well crystalline CuO having monoclinic unit cell structure. The crystallite size was ~ 12 nm as calculated from the XRD pattern. Transmission electron microscope images revealed that the bipod-like structure is composed of several crystallites. The lengths of the bipods are ~ 300 nm with a waist size ~ 100 nm. The UV-visible spectroscopic data revealed a strong absorption at ~ 376 nm and the band gap was calculated to be 2.51 eV. FTIR spectrum revealed the existence of only Cu=O bonds. In the Raman shift data two strong peaks were found at 273 cm-1, and 608 cm-1 that owe to the Ag mode and Bg mode respectively. Room temperature photoluminescence spectroscopy revealed that the CuO nanoparticles exhibit broad strong emission at ~ 472 nm. After decomposing we observed three peaks at 436, 469 and 495 nm. The emission peak at 469 nm arises due to near band edge transition. The emission peak at 495 nm arises due to shallow level defect states related transitions. In conclusion, we have fabricated CuO nano-bipods using a simple wet chemical method. XRD pattern indicates the formation of well crystalline and pure CuO without any impurity. The nano-bipods exhibit sharp absorption peak at ~ 376 nm with optical band gap energy of 2.51 eV. FTIR spectrum and Raman shift data confirms the formation of CuO with the presence of Ag mode (273 cm-1) and Bg mode (608 cm-1). The fabricated CuO nano-bipods exhibit strong PL emission at 469 nm owing to the recombination of free excitons at the absorption band edge in the UV region associated with other low intense deep level emission. Few relevant patents to the topic have been reviewed and cited.

Synthesis of octahedral and cubic Cu2O microcrystals in sub- and super-critical methanol and their photocatalytic performance

A simple and potentially scalable sub- and super-critical methanol technique was applied to synthesize cuprous oxide. Cu2O microcrystals with two morphologies were obtained in methanol of subcritical domain by adjusting the feeding methods. The effects of the reaction time, temperature, pressure, and feeding method on the formation of Cu2O microcrystals were investigated. XRD, SEM, and XPS were applied to analyze the composition and morphology of products. Results showed that pure cuprous oxide could be obtained in subcritical methanol of 230 °C, 7.8 MPa for 15 min. The two as-obtained products displayed octahedral and cubic morphology with an average edge length of 4 and 2 μm by solution and solid feeding methods, respectively. The formation and crystal growth mechanism of Cu2O in subcritical methanol were also proposed on the basis of above results. Furthermore, the two microcrystals were employed as catalysts in the photodecomposition of negatively charged molecule methyl orange. Results showed that both microcrystals possessed excellent photocatalytic activities. However, the obvious difference between cubic and octahedral in photocatalytic performance was not found in the scale of micrometer (2–4 μm).