Cupric Oxide Nanostructures Research Articles

Synthesis of undoped and mixed binary transition metals (Ni-Co)-doped cupric oxide nanostructures: Structural characteristics, optical behavior, and biological activity

In this work, co-precipitation-assisted undoped and various concentrations (1%, 3%, and 5%) Ni-Co-doped CuO nanostructures have been synthesized to test the biomedical applications. The structure, optical band gap, zone of inhibition width, hemocompatibility, and free radical scavenging activity of the CuO are significantly varied by introducing various concentrations of co-dopants compared to the undoped CuO. The single phase of monoclinic and heterogeneous crystal systems (monoclinic CuO, hexagonal Co, cubic NiO, and Co3O4) for undoped CuO and all Ni-Co-doped CuO samples was identified by the powder XRD tools. Microstructural properties were tuned in each dopant concentration of Ni-Co in the CuO, which confirmed through FE-SEM analysis. Heterogeneous structures (spherical particles/sheet-like particles) were noticed in the HR-TEM studies of 5% Ni-Co-doped CuO nanostructures. Synthesized compounds related to the elements (Cu, O, Co, and Ni) were traced with the help of the EDX and XPS study. The photoabsorption spectra and optical band gap values of the undoped CuO and co-doped CuO samples were significantly varied. Antimicrobial studies of the undoped CuO and Ni-Co co-doped CuO against E. coli and S. mutans bacterial strains were performed, and their outcomes of the zone of inhibition (ZOI) values have been discussed in detail. The synthesized undoped and various concentrations of CuO particles were taken to investigate their compatibility via hemolytic study. Hemolysis results showed that both the synthesized undoped CuO and Ni-Co doped CuO nanostructures are highly hemocompatible. In addition, compatibility natures are varied with increasing concentrations from 1% to 5% Ni-Co dopant in the CuO samples. The DPPH assay was employed to evaluate the antioxidant properties of the synthesized particles by determining their free radical scavenging (FRS) activity percentages. It was observed that Ni-Co-doped CuO exhibited better antioxidant properties than undoped CuO due to the higher FRS percentage.

A Comparative Analysis of X-Ray Diffraction, Morphology, and Optical Properties of Sonochemically Synthesized Cupric Oxide Nanostructures

A Comparative Analysis of X-Ray Diffraction, Morphology, and Optical Properties of Sonochemically Synthesized Cupric Oxide Nanostructures

Synthesis and characterization of CuO nanostructures on ZnO nanotubes for non-enzymatic detection of glucose

A non-enzymatic glucose sensing material is investigated on the basis of nanocomposites. Etched zinc oxide (ZnO) nanotubes have been synthesized as base and then dip-coated with various cupric oxide (CuO) nanostructures. Different concentrations of CuO precursor solution formed several sizes and shapes of nanostructures, including nanoparticles and nanoleaves. The fabricated CuO/ZnO nanotubes electrode has high sensitivity of 3.2 mAmM−1cm−2 and superior anti-interference ability towards glucose sensing. It also has good linearity in the range of human pre-meal blood glucose level, which has potential for diabetes monitoring.

Structure–Property–Performance Relationships of Cuprous Oxide Nanostructures for Dielectric Mie Resonance-Enhanced Photocatalysis

Nanostructured metal oxides, such as Cu2O, CeO2, α-Fe2O3, and TiO2, can efficiently mediate photocatalysis for solar-to-chemical energy conversion and pollution remediation. In this contribution, we report a novel approach, dielectric Mie resonance-enhanced photocatalysis, to enhance the catalytic activity of metal oxide photocatalysts. Specifically, we demonstrate that Cu2O nanostructures exhibiting dielectric Mie resonances can exhibit up to an order of magnitude higher photocatalytic rate as compared with Cu2O nanostructures not exhibiting dielectric Mie resonances. Our finite-difference time-domain (FDTD) simulation and experimental results predict a volcano-type relationship between the photocatalytic rate and the size of Cu2O nanospheres and nanocubes. Using transient absorption measurements, we reveal that a coherent electronic process associated with dielectric Mie resonance-mediated charge carrier generation is dominant in Cu2O nanostructures that exhibit higher photocatalytic rates. Although we experimentally demonstrate dielectric Mie resonance-enhanced photocatalysis with only Cu2O nanoparticles here, based on our FDTD simulations, we anticipate the same can be achieved with other metal oxide photocatalysts, including CeO2, α-Fe2O3, and TiO2.

A Low Charge Transfer Resistance CuO Composite for Efficient Oxygen Evolution Reaction in Alkaline Media.

An efficient, simple, environment-friendly and inexpensive cupric oxide (CuO) electrocatalyst for oxygen evolution reaction (OER) is demonstrated. CuO is chemically deposited on the porous carbon material obtained from the dehydration of common sugar. The morphology of CuO on the porous carbon material is plate-like and monoclinic crystalline phase is confirmed by powder X-ray diffraction. The OER activity of CuO nanostructures is investigated in 1 M KOH aqueous solution. To date, the proposed electrocatalyst has the lowest possible potential of 1.49 V versus RHE (reversible hydrogen electrode) to achieve a current density of 20 mA/cm₂ among the CuO based electrocatalysts and has Tafel slope of 115 mV dec-1. The electrocatalyst exhibits an excellent long-term stability for 6 hours along with significant durability. The enhanced catalytic active centers of CuO on the carbon material are due to the porous structure of carbon as well as strong coupling between CuO-C. The functionalization of metal oxides or other related nanostructured materials on porous carbon obtained from common sugar provides an opportunity for the development of efficient energy conversion and energy storage systems.

Inhibition of pathogenic bacteria by using cupric oxide nanostructures synthesized via CTAB-assisted hydrothermal route

In this research, CuO nanostructures were successfully synthesized via a short-time and low-temperature hydrothermal route without a calcination step. The synthesis of these nanoparticles was accomplished through a hydrothermal reaction of cupric nitrate and sodium hydroxide with different concentrations of cetyltrimethylammonium bromide (CTAB) as the chemical assistant agents. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-DRS), photoluminescence techniques (PL), and Brunauer-Emmett-Teller (BET)-specific surface area analysis. A possible growth mechanism of the CuO nanostructures was proposed, and the photocatalytic activity for the inhibition of pathogenic bacteria was demonstrated under UV light irradiation within 60 min. The best inhibition efficiency of pathogenic bacteria over CuO-CTAB1.0% was 99.40 and 99.01%, with the rate constant of 0.0776 and 0.0666 min-1 for pathogenic Escherichia coli and Staphylococcus aureus bacteria respectively.

Superhydrophobic CuO coating fabricated on cotton fabric for oil/water separation and photocatalytic degradation

Cupric oxide (CuO) nanostructures have attracted great interest and are extensively applied for superhydrophobic coatings and photocatalysis. In this study, leaf-like CuO nanostructures were constructed on the surface of cotton fabric via simple and practical solution immersion processes. The generated CuO nanoleaves can provide the fabric with more interest properties including superhydrophobicity and photocatalysis. Therefore, the CuO coated fabric held superhydrophobicity with a water contact angle of 151.5 ± 1° by further 1-dodecanethiol modification. Due to the simultaneous superhydrophobicity and superoleophilicity, the as-prepared fabric was used for the separation of several oil/water mixtures and exhibited good recyclability. Also, we applied the superhydrophobic fabric to degrade methylene blue aqueous solution under visible light irradiation for assessing its photocatalytic performance. After being exposed to visible light for 120 min, about 99.8% methylene blue was degraded, implying excellent photocatalytic activity. This facile, cost-effective, scalable, environmental-friendly and efficient methodology presented in this study is promising for multicomponent wastewater treatment and oil spill cleaning.

Tuning the activities of cuprous oxide nanostructures via the oxide-metal interaction

Despite tremendous importance in catalysis, the design of oxide-metal interface has been hampered by the limited understanding of the nature of interfacial sites and the oxide-metal interaction (OMI). Through construction of well-defined Cu2O/Pt, Cu2O/Ag and Cu2O/Au interfaces, we find that Cu2O nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same structure. The activities of these interfaces are compared for CO oxidation and follow the order of Cu2O/Pt > Cu2O/Au > Cu2O/Ag. OMI is found to determine the activity and stability of supported Cu2O NSs, which could be described by the formation energy of interfacial oxygen vacancy. Further, electronic interaction between Cu+ and metal substrates is found center to OMI, where the d band center could be used as a key descriptor. Our study provides insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions.

Improving the photostability of cupric oxide nanorods

In this study, cupric oxide (CuO) nanorods were grown on a fluorine-doped tin oxide substrate by a modified chemical bath deposition method with various post-annealing temperatures. We investigated the effects of the post-annealing temperature on the morphological, structural, optical, electrical and photoelectrochemical properties of the CuO nanorods. We found that the morphology, light absorbance, and crystallinity of the CuO nanostructures changed with the post-annealing temperature. As the post-annealing temperature increased, CuO showed preferential growth of the (020) plane. In particular, the crystallinity of the (020) plane was substantially greater at post-annealing temperatures of 500 ℃ and 600 ℃ than at other temperatures. In this study, it was found that the preferential growth of the (020) plane and the improved crystallinity of the CuO (020) plane increased the photostability of the CuO nanorod photoelectrodes. As a result, a photocurrent density of −1.13 mA/cm2 (vs. a saturated calomel electrode) and a photostability of approximately 74% were obtained from the sample subjected to a post-annealing temperature of 600 ℃. However, cracks were found in this sample, and further study is necessary to improve the structural and mechanical properties.

Anion-induced morphological regulation of cupric oxide nanostructures and their application as co-catalysts for solar water splitting.

Morphological control of nanomaterials is essential for their properties and potential applications, and many strategies have been developed. In this work, a new strategy for simultaneously preparing and modulating the morphological structure evolution of copper layered hydroxyl salts and oxides is introduced. By changing the nature of the anions in the electroplating solution, significant variations in the size and porosity of nanosheets are achieved. Porous CuO nanosheets with a higher surface area were obtained by the use of copper nitrate as a copper source, while CuO nanoflakes were produced from copper sulfate. Photoanodes combining these porous CuO nanomaterials and a typical light absorber (BiVO4) exhibited good morphology-dependent activities for photoelectrochemical water splitting. The composite electrode displays a negative shift of 180 mV for the onset potential and an approximately 2-fold enhancement in the photocurrent compared to the bare BiVO4. The charge recombination rate in the photoelectrode with the porous CuO nanosheets was significantly lower than the bare photoanode due to the favorable electron diffusion path and effective charge collection. This research offers an effective method for constructing a highly active photoelectrocatalytic system for overall water splitting.

Nanostructured CuO thin film deposited on stainless steel using spray pyrolysis as supercapacitor electrode

We investigated the effects of different annealing temperatures on cupric oxide (CuO) films as supercapacitor electrode. CuO films were grown on stainless steel substrates via spray pyrolysis and annealed for two hours at different temperatures of 160 °C, 250 °C, and 400 °C. X-ray diffractometry (XRD) and micro-Raman spectroscopy (MRS) confirmed the monoclinic phase of CuO films. At higher annealing temperatures, narrower XRD peaks were observed due to reduced defects and increased grain size. The supercapacitive properties of the CuO electrode were evaluated using three-electrode cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1.0 M aqueous sodium sulfate (Na2SO4) electrolyte. At a scan rate of 10 mV s−1, the highest specific capacitance of 87.06 F g−1 was achieved from the CuO electrode annealed at 400 °C. Furthermore, repeated CV scans up to the 1000th cycle revealed that the CV plots have retained its shape and capacitance up to 84.68% of the original value. The obtained results revealed that the CuO nanostructures grown by spray pyrolysis can be used as an electrode for supercapacitors

Cupric Oxide Nanostructures from Plasma Surface Modification of Copper.

Taking inspiration from the hydrophilic and superhydrophilic properties observed from the nanostructures present on the leaves of plants such as Alocasia odora, Calathea zebrina, and Ruelia devosiana, we were able to synthesize cupric oxide (CuO) nanostructures from the plasma surface modification of copper (Cu) that exhibits hydrophilic and superhydrophilic properties. The Cu sheets were exposed to oxygen plasma produced from the P300 plasma device (Alliance Concept, Cran-Gevrier, France) at varying power, irradiation times, gas flow rates, and pulsing duty cycles. The untreated and plasma-treated Cu sheets were characterized by contact angle measurements, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to determine the changes in the surface of Cu before and after plasma treatment. Results showed that plasma-treated Cu sheets exhibited enhanced wetting properties compared to untreated Cu. We attributed the decrease in the measured water contact angles after plasma treatment to increased surface roughness, formation of CuO nanostructures, and transformation of Cu to either CuO2 or Cu2O3. The presence of the CuO nanostructures on the surface of Cu is very useful in terms of its possible applications, such as: (1) in antimicrobial and anti-fouling tubing; (2) in the improvement of heat dissipation devices, such as microfluidic cooling systems and heat pipes; and (3) as an additional protection to Cu from further corrosion. This study also shows the possible mechanisms on how CuO, CuO2, and Cu2O3 were formed from Cu based on the varying the plasma parameters.

Facile Synthesis and Phase-Dependent Catalytic Activity of Cabbage-Type Copper Oxide Nanostructures for Highly Efficient Reduction of 4-Nitrophenol

Cabbage-type morphology of cupric oxide (CuO) and cuprous oxide (Cu2O) nanostructures were synthesized via a simple and cost-effective chemical approach. HRTEM, FESEM, XRD, UV–Vis absorption and photoluminescence spectroscopies were used to identify the structural, optical, morphological and catalytic properties of the prepared nanostructures. Phase of the prepared copper oxide nanostructures was well controlled by changing the concentration of glucose. The prepared cabbage-type Cu2O nanostructures showed exceptionally improved catalytic performance towards the reduction of toxic 4-nitrophenol into useful 4-aminophenol as compared to cabbage-type CuO nanostructures. Cabbage-type Cu2O nanostructures completely transformed 4-NP into 4-AP in just 5 min with excellent rate constant (0.587 min−1). The observed excellent catalytic activity of prepared cabbage-type Cu2O nanostructures indicates their potential use in catalytic applications.

Influence of sodium dodecyl sulfate as a surfactant on the microstructural, morphological and optoelectronic characteristics of SILAR deposited CuO thin films

The research was performed aiming to evaluate the impact of sodium dodecyl sulfate (SDS) as a surfactant on the morphological, microstructural, electrical and optical features of nanostructured cupric oxide (CuO) thin films. CuO thin films were grown using successive ionic layer adsorption and reaction (SILAR) technique at room temperature. These as-prepared CuO thin films were thoroughly characterized by scanning electron microscope (SEM), x-ray diffraction (XRD), four-point probe method, UV-Visible spectrophotometer and Fourier transform infrared (FTIR). Surface morphology investigations revealed the uniform and homogeneously distributed CuO nanostructures on the film surfaces. The addition of different concentration of SDS to the growth solution significantly influenced the surface morphological characteristics of the CuO thin films. XRD analysis showed that all deposited CuO thin films were polycrystalline nature having monoclinic crystal system and presented () and (111) preferential orientations. The microstructural parameters, including crystallite size, texture coefficient, microstrain and dislocation density were extracted from XRD data. The resistivity value of CuO thin film prepared without SDS was 1.72 × 106 Ω cm. With SDS concentration of 4.0 M%, the resistivity extraordinarily increased to 3400 × 106 Ω cm. The optical bandgap energy had increased from 1.32 to 1.49 eV as a function of increasing SDS concentration. The CuO bond vibration was confirmed by FTIR analysis.

Interface-controlled two-dimensional cuprous oxide structures

The synthesis, structures and properties of two-dimensional oxides have great fundamental significance and application potentials for the fields of catalysis, electronic devices and superconductors. In this article, the growth and synthesis of two-dimensional cuprous oxide were investigated on the surfaces of Ag(111) and Cu(111) single crystals. The structures of these two-dimensional cuprous oxides were characterized at the atomic scale using scanning tunneling microscopy in ultrahigh vacuum (UHV). On Ag(111), two-dimensional cuprous oxide nanostructures exhibit an ordered honeycomb structure with the lattice distance between six-membered rings at ~6.0 A and the stoichiometry of Cu3O2. The hexagonal lattice of Cu3O2 also contains a small amount of “5-7” defect structure. In comparison, two-dimensional cuprous oxide nanostructures on Cu(111) also exhibit the stoichiometry of Cu3O2, but their surfaces are dominated by the large number of “5-7” defect structure. As a result, their surface lattice does not display the long-range order. Two-dimensional Cu3O2 nanostructures on Ag(111), as well as their zig-zag edges, could remain stable in 10−6 mbar O2 at 400 K or in UHV at 700 K. Under similar oxidation conditions, the Cu3O2 structure without long-range order would grow on Cu(111), due to the continuous oxidation of the exposed Cu surface. The oxidation of the Cu3O2 structure on Cu(111) eventually leads to the formation of the ordered “44”- or “29”-cuprous oxide structure. The comparison of the structure and stability of two-dimensional cuprous oxide on Ag(111) and Cu(111) thus demonstrated that the properties of two-dimensional cuprous oxide could be determined by the interfacial interaction. Our study provides not only a method for the preparation of model catalysts for the interfaces between metal and cuprous oxide, but also a pathway for further exploration of the physical and chemical properties of two-dimensional cuprous oxides.

A neutron scattering and electron microscopy study of the structure, wetting, and freezing behavior of water near hydrophilic CuO-nanostructured surfaces

Oscillating heat pipes (OHPs) provide a promising heat transfer device for a variety of applications, including the cooling of electronic devices. Recently, it has been shown that a hydrophilic, nanostructured cupric oxide (CuO) coating can significantly enhance the thermal performance of copper OHPs that use water as the working fluid. Motivated by these results, we report neutron scattering and electron microscopy (EM) measurements to investigate the interaction of water with copper-oxide surfaces on the nanoscale. Our measurements confirm earlier observations of a thin cuprous oxide (Cu2O) layer growing on a bare copper substrate followed by “grass-like” CuO nanostructures. New evidence of the nanostructure hydrophilicity is provided by EM measurements of wetting and by our high-energy-resolution elastic neutron scattering measurements, showing a continuous freezing and melting of the water in our samples over a temperature range of ∼80 K. In addition, our neutron diffraction measurements are consistent with water closest to the CuO nanostructures freezing into an amorphous solid at low levels of hydration and hexagonal ice at higher hydration. In short, our findings support a strong interaction of water with the CuO nanostructures, which could significantly affect the operation of an OHP.

Complexing agent triethanolamine mediated synthesis of nanocrystalline CuO thin films at room temperature via SILAR technique

In the present work, nanostructured cupric oxide (CuO) thin films have been successfully deposited on glass substrates by successive ionic layer adsorption and reaction (SILAR) technique at room temperature. The influence of complexing agent as triethanolamine (TEA) on the structural, morphological, optical and electrical characteristics of nanocrystalline CuO thin films have been examined in detail. Structural studies confirm that all the films were polycrystalline nature having a monoclinic crystalline form and displayed (1¯11) and (111) preferential orientations. The estimated crystallite values ranged from 17.47 to 19.95 nm. The surface morphology of CuO thin films was examined through scanning electron microscopy and materials microscope studies. Surface studies revealed that homogeneously distributed CuO nanostructures on the film surfaces. The optical studies showed that band gap energy values of the CuO thin films were increased from 1.33 to 2.00 eV as a function of increasing TEA concentration. Meanwhile, the average transmittance of all the films had increased from 2.5 to 42.5% with the increasing TEA concentration. FTIR studies identified the formation of single phase CuO and chemical bonding of the complexing agent. The resistivity value of CuO thin film synthesized without TEA was 3.74 × 105 Ω cm and the resistivity consequently increased to 509 × 105 Ω cm with TEA concentration of 1.0 M%. A high figure of merit (786 × 10−12 Ω−1) was obtained for complexing agent concentration of 0.25 M%.

Impact of ablation time on Cu oxide nanoparticle green synthesis via pulsed laser ablation in liquid media

Large-scale commercial production of nanoparticles via efficient, economical, and environmentally friendly methods is a challenging endeavour. The laser ablation method being a green and potential route of nanoparticles synthesis can be exploited to achieve this end. In this work, we report the ablation of a copper target submerged in distilled water by pulsed Nd:YAG laser. The influence of ablation time on the structure and optical properties of grown copper oxide nanoparticles are studied. Such nanoparticle composition and structure is determined by X-ray diffraction (XRD), Fourier transform infrared, and Raman analyses. Results from transmission electron microscopy images established that synthesised nanoparticles are a spherical shape with average sizes of 24–37 nm. Fluorescence spectra revealed the enhancement of nanoparticle concentration and reduction in the sizes with increasing ablation time, where the optimum ablation time is demonstrated to be 60 min. Photoluminescence spectra exhibited a prominent visible peak (green), which blueshifted from 542 to 537 nm, confirming the shrinkage of copper oxide particle size at higher ablation time. The XRD pattern showed that the prepared nanoparticles possess a single phase of monocline cupric oxide nanostructure.

Plasma Deposited Metal-Oxide Nanosensors for Amine Detection

The metal-oxides have raised significant scientific interest in recent years, due to their sensing properties. In is notable that the gas sensing properties can be enhanced by structural and morphological manipulation of the sensor. Previously was demonstrated that increasing the sensor surface to volume ratio during synthesis with formation of sheet-like structures or nanowires can enhance the sensor sensitivity [1,2]. Among different oxides, cuprous oxide is interesting due to its wide band gap and stability [3]. Cuprous oxide nanostructures can be synthesized by different methods ranging from solution based chemical methods to thermal and plasma synthesis [4]. However one of most optimal in terms of time, simplicity and quality of synthesized nanostructures is plasma processing, especially at atmospheric pressures. For this reason, the atmospheric DC plasma source was used for deposition of CuO nano-sheets on the surface of copper electrodes [5,6]. The prepared samples were then used to detect different amines (diethylamine, trietylamine, cyclohexanamine) which are present in vapours generated in spoiled food and many industrial processes. These chemical substances are cancerogenious and represent serious health hazards to humans. The developed gas-vapour sensor exhibited an excellent resistive sensitivity for these chemicals even at temperatures below 100 °C. In performed evaluation analysis, the morphology of the CuO nanostructures was changed, but results demonstrated that sensitivity is preserved during morphological changes as long as crystallinity remains similar, and the sensor material is of nanosize-dimension at least in one direction. The obtained results were explained by theoretical investigation of sensor performance. [1] S. Steinhauer et al., Sensors and Actuators B: Chemical, 187 (2013), 50-57 [2] C. Yang et al., Sensors and Actuators B: Chemical, 207 (2015), 177-185 [3] M. Hübner et al., Sensors and Actuators B: Chemical, 153 (2011), 347-353 [4] G. Filipič et al., Nanotechnology, 23 (2012), 194001 [5] J. Gruenwald et al., Plasma Processes and Polymers, 13 (2016), 946-954. [6 ] J. Gruenwald et al., Plasma Processes and Polymers, 13 (2016), 766-774

Cuprous oxide nanostructures tuned by histidine-containing peptides and their photocatalytic activities

Peptides have been used as modifiers and templates in the fabrication of a variety of inorganic nanostructures including noble metals, silica oxide, and metal oxides. In this work, three peptides, including HGGGHGHGGGHG (HG12), HGGGHG (HG6) and RHTDGLRRIAAR (CN225), were used to tune the morphologies of cuprous oxide (Cu2O) nanoparticles. Unlike the morphologies of modified octahedron with polyvinylpyrrolidone (PVP) and truncated cube with cetyltrimethyl ammonium bromide (CTAB), the Cu2O nanoparticles regulated by peptides showed completely different shapes and size. In the presence of HG12, the nanoparticles still showed octahedral morphology with the edge length of 84 nm, but there were distinct defects on the (1 1 1) facets. The Cu2O nanoparticles were sphere-like with the diameter of ∼86 nm under the regulation of HG6. In the presence of CN225, the Cu2O sample was spherical aggregates of smaller nanoparticles, and the diameter of the aggregates was about 128 nm. The interactions between Cu2+ and peptides have been investigated through UV–Vis spectrometer, circular dichroism spectrometer (CD) and isothermal titration calorimetry (ITC). The different coordinating structures of peptide molecules to Cu2+ ions dominated the nucleation and succedent crystal growth. The cuprous oxide synthesized with CN225 showed the best photocatalytic activity among the synthesized Cu2O particles, and about 67% methyl orange could be removed within 2 h under UV–Vis irradiation. The high photocatalytic activity of Cu2O-CN225 was attributed to the relatively small size and the (1 1 1) crystal planes on the primary particles.