CuO Particles Research Articles

Phytonanofabrication of Copper Oxide from Albizia saman and Its Potential as an Antimicrobial Agent and Remediation of Congo Red Dye from Wastewater

Metal nanoparticle fabrication through plant-based green methods is considered the gold standard among the various synthesis techniques owing to its simplicity, eco-friendliness, ease of use, and the huge diversity of plant species. Copper nanoparticles (CuONPs) have proven their potential in the fields of medicine, agriculture, pharmaceutics, and catalysis, and are being synthesized using various physicochemical and biological methods. Here, the authors have reported on the first-ever use of Albizia saman leaf extract for the development of CuONPs. Phytochemical analysis of the methanolic extracts of the plant exhibited the presence of phenols (32.31%), tannins (12.27%), and flavonoids (16.72%). The phytonutrients existing in leaf extract successfully reduced the copper salt in the CuONPs. A detailed investigation of the synthesized CuONPs was performed using advanced instruments. The UV-Vis spectra exhibited an absorbance peak at 290 nm, while the X-ray diffraction pattern (XRD) revealed that the average crystallite size was about 29.86 nm. Dynamic light scattering (DLS) revealed that the average hydrodynamic size of the CuONPs was 72.3 nm in diameter, while its zeta potential was −0.49, with a negative polarity. Fourier transform infrared spectroscopy showed the major bands in the region of 400 to 1000 cm−1, suggesting the formation of CuONPs, while the band in the region of 1100 to 2600 cm−1 shows the association of plant molecules with the phytonanofabricated CuO particles. Transmission and scanning electron microscopy showed the spherical shape of the CuONPs, whose size was about 20–50 nm. The phytonanofabricated CuO exhibited antibacterial activity by forming a zone of inhibition (ZOI) against Escherichia coli, Staphylococcus aureus, and Candida albicans. The removal efficiency of the CuONPs was 33.33% for Congo Red dye. The removal efficiency of the phytonanofabricated CuO for CR dye was reduced to 16% after the 4th cycle.

Strategies to improve the thermal performance of solar collectors

Abstract The paper evaluates a passive method for heat transfer improvement in heat exchangers, which implies the use of nanofluids. All calculations were carried out with a constant volumetric flow rate. The study examines three fluids with 0–4 % volume concentrations of CuO, MgO, and Al2O3 particles. The results indicate an increase in the heat transfer coefficient with increasing temperature. An Al2O3 nanofluid (4 % concentration) contributed to the best thermal performance. The incorporation of a 4 % content of MgO yielded an augmentation in heat transfer ranging from 15 % to 22 %, whereas an analogous concentration of CuO led to a more substantial enhancement of 25 %. Notably, the introduction of nanoparticles of Al2O3 produces a remarkable augmentation in heat transfer performance, with potential improvements of up to 36 %. The Nusselt number increases with increasing particle volume fraction and Reynolds number, according to results obtained for several nanoparticles (Al2O3, CuO, SiO2, and ZnO) with volume percentages in the range of 1–4 % and nanoparticle diameters of 25–70 nm. For all nanofluids, the time-averaged Nusselt number rises with a solid phase volume fraction increase of less than 5 %.

Strategies to improve the thermal performance of solar collectors

Abstract The paper evaluates a passive method for heat transfer improvement in heat exchangers, which implies the use of nanofluids. All calculations were carried out with a constant volumetric flow rate. The study examines three fluids with 0–4 % volume concentrations of CuO, MgO, and Al2O3 particles. The results indicate an increase in the heat transfer coefficient with increasing temperature. An Al2O3 nanofluid (4 % concentration) contributed to the best thermal performance. The incorporation of a 4 % content of MgO yielded an augmentation in heat transfer ranging from 15 % to 22 %, whereas an analogous concentration of CuO led to a more substantial enhancement of 25 %. Notably, the introduction of nanoparticles of Al2O3 produces a remarkable augmentation in heat transfer performance, with potential improvements of up to 36 %. The Nusselt number increases with increasing particle volume fraction and Reynolds number, according to results obtained for several nanoparticles (Al2O3, CuO, SiO2, and ZnO) with volume percentages in the range of 1–4 % and nanoparticle diameters of 25–70 nm. For all nanofluids, the time-averaged Nusselt number rises with a solid phase volume fraction increase of less than 5 %.

Synthesis of CuO, ZnO and SnO2 Coupled TiO2 Photocatalyst Particles for Enhanced Photodegradation of Rhodamine B Dye

Environmental pollution is a global problem and dye pollution is one of the major factors. TiO2 shows promising photocatalytic properties that can degrade organic pollutants such as dye under ultraviolet (UV) irradiation. However, TiO2 possesses some disadvantages such as a wide band gap and a high recombination rate of electron-hole pairs. Coupling TiO2 with various metal oxides can enhance photocatalytic properties. In this work, photodepositon (reduction of metal ions on TiO2) followed by the thermal oxidation method were used for the coupling of TiO2 with CuO, ZnO, or SnO2 under various methanol concentrations (25 vol% or 50 vol%) and deposition duration (1 h or 3 h) to observe the effect of these parameters on the photocatalytic degradation activity on Rhodamine B (RhB) dye (up to 90 min). The rate constant of the photodegradation reaction (k) has improved from 0.0141 min−1 (uncoupled TiO2) to 0.0151~0.0368 min−1. Overall, CuO/TiO2 and SnO2/TiO2 samples have shown similar photocatalytic properties (average rate constants of 0.0341 min−1 and 0.0327 min-1, respectively), and both performed better than ZnO/TiO2 in terms of RhB photodegradation (average rate constants of 0.0197 min−1). The difference in photocatalytic performance can be explained by the bandgap of metal oxides and their relative band positions with TiO2. Lastly, CuO/TiO2 (50 vol%, 3 h) and SnO2/TiO2 (50 vol%, 3 h) have shown the best photocatalytic properties respectively due to a longer deposition time and higher concentration methanol, resulting in more deposited materials. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Scaling preparation of CuO for efficient electrochemical reduction of CO2 to C2+ products

The conversion of CO2 to C2+ products, especially by electrochemical carbon dioxide reduction (ECR), is a promising strategy for the utilization of CO2 and the effective mitigation of the energy crisis and global warming. The development of industrially available catalysts is key to achieving this conversion. In this work, we prepared several CuO catalysts using the ball milling method and evaluated their performance in ECR using an H-type electrolytic cell. Different Cu elemental contents as well as calcination temperatures significantly altered the crystallinity and crystalline phase species of the formed crystals. Among the prepared catalysts, CuO-30 %−350 could achieve 50 % faradaic efficiency of C2+ products (FEC2+) at 20 h of stable operation. Characterization results showed that CuO particles were loaded on the SiO2 surface, and CuO-30 %−350 possessed a large electrochemically active specific surface area, fast electron transport rate, and low kinetic barriers, which was the reason for its high FEC2+. This study provides a green and efficient idea for the large-scale preparation of ECR catalysts.

Mitigating the Recrystallization of a Cold-Worked Cu-Al2O3 Nanocomposite via Enhanced Zener Drag by Nanocrstalline Cu-Oxide Particles.

The strength of metals and alloys at elevated temperatures typically decreases due to the recovery, recrystallization, grain growth, and growth of second-phase particles. We report here a cold-worked Cu-Al2O3 composite did not recrystallize up to a temperature of 0.83Tm of Cu. The composite was manufactured through the internal oxidation process of dilute Cu-0.15 wt.% Al alloy and was characterized by transmission electron microscopy to study the nature of oxide precipitates. As a result of internal oxidation, a small volume fraction (1%) of Al2O3 particles forms. In addition, a high density of extremely fine (2-5 nm) Cu2O particles has been observed to form epitaxially within the elongated Cu grains. These finely dispersed second-phase Cu2O particles enhance the Zener drag significantly by three orders of magnitude as compared to Al2O3 particles and retain their original size and spacing at elevated temperatures. This limits the grain boundary migration and the nucleation of defect-free regions of different orientations and inhibits the recrystallization process at elevated temperatures. In addition, due to the limited grain boundary migration, a bundle of stacking faults appears instead of annealing twins. This investigation has led to a better understanding of how to prevent the recrystallization process of heavily deformed metallic material containing oxide particles.

Chitosan bimetallic particles with in-situ ROS driven self-cleaning performance for tetracycline elimination

Adsorption enrichment coupled with oxidative degradation is a promising technique for eliminating tetracycline (TC) from an aqueous environment. However, the high cost associated with this technique limits its applicability. Thus, in this study, we synthesized Cu2O and CuFe2O4 bimetallic-modified chitosan particles (Cu(I)–CuFe2O4@CS) with high adsorption efficiency and self-cleaning performance. The self-cleaning performance was driven by the in-situ generated reactive oxygen species (ROS). Batch experiments and characterization methods indicated that 97.39% of TC was rapidly adsorbed on the particles surface and subsequently degraded by in-situ generated ROS, to achieve a self-cleaning process. The Cu(I)–CuFe2O4@CS/TC system exhibited maximum O2•- and H2O2 concentration of 12.95 μmol/L and 42.05 μmol/L, respectively. Cu2O was the main source of the ROS generation, while CuFe2O4 effectively adsorbed TC and contributed to the synergistic accumulation of ROS. Moreover, the adsorbed TC with reductive functional properties facilitated the reduction of Fe(III)/Fe(II) and Cu(II)/Cu(I) cycles, thereby improving TC elimination efficiency.

Transformation of CuO and Cu2O particles into CuxS within the polymeric matrix of anion exchangers, and its structural and morphological implications

The study demonstrates the process of anion exchanger modification in order to obtain a reactive organic polymer containing CuxS dispersed within its matrix. As starting materials, two strongly basic commercial anion exchangers were used – macroreticular and gel-type – previously modified by deposition of cuprite or tenorite within their structure. The pre-formed composites were sulphidated using an Na2S solution to obtain materials containing CuxS (5.3–6.7 wt% Cu and 4.5–6.7 wt% S), which were further studied using Raman and XPS spectroscopy, and XRD and SEM/EDS analyses. Depending on the sulphidation precursor, Cu2O or CuO, its distribution within the polymeric matrix, and the porous structure of the supporting anion exchanger, products with different CuxS content were obtained. The main sulphidation product – covellite – was accompanied by admixtures of copper-rich phases such as digenite and djurleite, but products of sulphide oxidation were also identified. The conversion of Cu2O into CuS was more efficient and selective in comparison to CuO. The sulphidation process remained within the initial distribution of the precursor particles within the polymeric matrix. The morphology of the obtained covellite particles was strongly dependent on the porous structure of the supporting anion exchanger. The conversion of the Cu2O and CuO within the macroporous matrix led respectively to spiky burr-like CuS and more densely packed elongated needle-shaped CuS particles, while the CuS particles obtained in the gel-type matrix were spherical. The spherical particles obtained from Cu2O conversion exhibited a hollow structure, which was the result of solid-state diffusion during the sulphidation, the so-called Kirkendall effect.

Photocatalytic degradation of fluoroquinolone antibiotics using chitosan biopolymer functionalized copper oxide nanoparticles prepared by facile sonochemical method

Photocatalytic degradation is an excellent method for removing pharmaceutical residues due to their simplicity, ecological benignity, high efficiency, and exceptional stability. Herein, we demonstrate the sonochemically synthesised chitosan biopolymer functionalized copper oxide nanoparticles as an efficient photocatalyst for the degradation of fluoroquinolone-based antibiotics. The X-ray diffraction Rietveld refinement revealed the formation of single-phase copper oxide (CuO) with a monoclinic structure. The presence of biopolymer functionalization was corroborated by Fourier Transform Infrared spectroscopy by observing the -NH2 and -OH functional groups. The high-resolution transmission electron microscopic images inferred that Chitosan functionalized copper oxide (C-CuO) particles are nano-sized with a smooth texture and aggregation-free particles. The strong absorbance and the broad photoluminescence emission in the ultraviolet-visible region confirm the suitability of CuO and C-CuO nanoparticles for photocatalytic applications. The catalytic activity was studied against fluoroquinolone-based antibiotics such as ciprofloxacin and norfloxacin under direct sunlight illumination. Interestingly, the C-CuO catalyst demonstrated 71.07 % (@140 min.) and 71.9 % (@60 min.) of degradation for ciprofloxacin and norfloxacin, respectively. The obtained photocatalytic activity of the prepared CuO and C-CuO catalysts was superior to the CuO particles prepared by the coprecipitation method (CC-CuO).

Morphological Effect on the Surface Activity and Hydrogen Evolution Catalytic Performance of Cu2O and Cu2O/rGO Composites

Different cuprous oxide (Cu2O) particle forms, including the octahedron, truncated octahedron, cube, and star-like forms, are synthesized through chemical reduction under different reaction conditions. The correlation between the morphology and the catalytic activity of hydrogen evolution reactions (HERs) is investigated. It is discovered that the Cu2O particles with a higher 111/100 facets (r) ratio have a higher oxidation resistance and higher activity in HER catalysis, as supported by the density functional theory (DFT) calculation results. This improvement is attributed to the fact that more Cu+ terminated atoms on facet 111 provide more active sites, as measured using their electroactive area, as well as the lower H2 adsorption energy on that facet. To enhance Cu2O’s HER performance, cuprous oxide particles are deposited on reduced graphene oxide (rGO) through a hydrothermal method. XPS and XRD show a CuO layer on the composite surface, which reduces the Cu2O corrosion in the reaction. Overall, Cu2O/rGO composites exhibit a better particle distribution, increased active sites, and improved charge separation. The best electrocatalyst in this study is the Cu2O/rGO with a star-shaped form, with an overpotential of −458 mV. Its improved performance is attributed to the presence of unsaturated active sites with a higher reactivity, such as the edges and corners. SEM studies of this composite after catalysis indicate that Cu2O undergoes structural reconstruction during the reaction and reaches a more stable structure.

Polyiodo Azole-Based Metal-Organic Framework Energetic Biocidal Material for Synergetic Sterilization Applications.

Biological hazards caused by bacteria, viruses, and toxins have become a major survival and development issue facing the international community. However, the traditional method of disinfection and sterilization is helpless in dealing with viruses that spread quickly and are highly infectious. Metal-organic framework (MOF) biocidal materials hold promise as superior alternatives to traditional sterilization materials because of their stable framework structures and unique properties. Now, we demonstrate for the first time the synthesis of a MOF (TIBT-Cu) containing Cu metal centers and tetraiodo-4,4'-bi-1,2,4-triazole as the main ligand. This novel MOF biocidal material has good thermal stability (Td = 278 °C), excellent mechanical sensitivity, and a high bacteriostatic efficiency (>99.90%). Additionally, the particles produced by the combustion of TIBT-Cu are composed of active iodine substances and CuO particles, which can act synergistically against harmful microorganisms such as bacteria and viruses. This study provides a new perspective for the preparation of highly effective bactericidal materials.

Mineralization of 4-methyl-1-cyclohexane carboxylic acid by heterogeneous catalytic ozonation

This work studied the mineralization of an aqueous solution of a naphthenic acid model compound, 4-methyl-1-cyclohexane carboxylic acid (4MCH), by heterogenous catalytic ozonation in a semi-batch reactor. A catalyst screening was first conducted by evaluating total organic compound (TOC) removal of Cu, Ce, and Mn (1 and 5 wt%) dispersed on γ-Al2O3, TiO2, ZrO2, and MgO supports. Cu containing catalysts showed the highest TOC removal with Cu/MgO having the best mineralization effectiveness. The Cu/MgO catalysts were characterized by ICP-OES, BET, XRD, XPS, SEM, and TEM. CuO and Cu2O particles were formed on MgO with the majority of them being smaller than 5 nm. pH = 8.5 was identified as the optimum pH for total oxidation of 4MCH due to the right balance between the 4MCH oxidation and ozone decomposition rates. Phosphate and bicarbonate buffers had a different effect on the TOC removal of the Cu/MgO catalysts with better activities in the presence of the phosphate buffer. Mg and Cu leaching was observed during the oxidation of 4MCH, accompanied with an increase in pH. The reusability tests of Cu/MgO (1 wt%) showed that the catalyst retained its activity over 5 cycles with an average Mg and Cu leaching of 44 and 3 mg/L, respectively. The energy consumption cost of the treatment of 4MCH by catalytic ozonation was estimated to be around $13 per cubic meter of the wastewater.

Controlling the Amount of Copper Formate Shells Surrounding Cu Flakes via Wet Method and Thermo-Compression Sinter Bonding between Cu Finishes in Air Using Flakes

To bond a semiconductor power chip on a substrate using the formation of bondlines exhibiting long-term mechanical durability at high temperatures such as 300 °C, compression-assisted sinter bonding between Cu finishes was carried out at 300–350 °C in air. Cu flakes of approximately 7 µm were used as the main filler material; their surfaces were modified by pretreatment using a formic acid solution, and the existing oxide layers were transformed into copper formate shells. To increase the amount of the copper formate shells, the shell transformation reaction was controlled by the deliberate addition of 30 nm Cu2O particles and sustained for 50 min. The formate shells formed decomposed at a peak temperature of 250 °C, forming pure Cu, which rapidly induced sintering between the flakes and at the Cu-finish–flake interfaces. Therefore, the paste containing Cu flakes showed a sufficient shear strength of 26.3 MPa even in air after sinter bonding for only 3 min under 5 MPa at 350 °C. Although the bimodal-type paste presented near-full-density bondline structures within 3 min of adding 350 nm pure Cu particles, the strengths with respect to bonding time showed trends of values less than 26.3 MPa, owing to the excessive oxidation of the 350 nm Cu.

A SP-ICP-MS protocol for the detection of metal nanoparticles composition and size in tattooed ex vivo human skin explants

We developed and validated a protocol based on Single Particle Inductively Coupled Plasma Mass Spectrometry (SP ICP-MS) to detect composition and size of metal nanoparticles (MNPs) in tattoo inks end ex vivo tattooed human skin explants. The explants were tattooed with different inks using an ordinary tattoo machine. Then, 72 hours after tattooing, skin explants were subjected to alkaline extraction by tetramethylammonium hydroxide solution and MNPs of Ag, Al2O3, Au, Cr2O3, CuO, Fe2O3, TiO2 and ZnO were analysed for particle composition and size by SP ICP-MS. The method was validated by assessing the limit of detection, accuracy, precision, and size stability over 72 hours. Particles of Al2O3, Cr2O3, CuO, Fe2O3, TiO2 and ZnO were observed in human skin in the range from 27 nm to 153 nm, and from 26 nm to 228 nm in tattoo inks. Ag and Au NPs were not found neither in inks nor in the skin. Advantages of the protocol were the ability to simultaneously detect the composition of particles and their size, the straightforward sample preparation, the high sensitivity and precision, and the speed of execution of the analysis. The developed methodology can be applied to skin exposed to other consumer products topically applied, such as sunscreens, cosmetics, personal care products and medical devices, which can be all sources of MNPs, in order to improve knowledge and support the human exposure assessment process.

Mesoporous CuO Prepared in a Natural Deep Eutectic Solvent Medium for Effective Photodegradation of Rhodamine B.

Metal oxide nanoparticles (NPs) have been widely used as catalysts in the chemical industry, but their preparation is usually limited by strict conditions such as high temperature, elevated pressure, and the use of volatile and highly toxic organic solvents. To solve this problem, this work developed an environmentally benign method using green solvents, i.e., natural deep eutectic solvents (NADESs), as a reaction medium to prepare copper oxide (CuO) particles. The experimental results suggested that the synthesized CuO particles were sheet-like mesoporous NPs, and they exhibited excellent catalytic performance towards the photodegradation of rhodamine B (RhB) in the presence of potassium monopersulfate (PMS). The catalytic activity of the synthesized CuO NPs was better than that of the reported metal oxide-based catalysts. Reactive species such as photoexcited holes, superoxide radicals, and singlet oxygen were involved in the RhB degradation. These results indicated that NADESs are good media for the preparation of CuO NPs, and exhibit the potential for application to the preparation of other metal oxides.

CuO/CeO2 catalysts prepared by modified impregnation method for ethyl acetate oxidation

The impregnation method is one of the most popular methods for preparing various types of supported catalysts. However, the preparation of highly active catalysts by the conventional impregnation method is still a great challenge. In this paper, a modified impregnation method (MI) was developed to prepare CuO/CeO2 catalysts for the catalytic oxidation of ethyl acetate (EA). It was found that the 5 %CuO/CeO2 catalyst (5-MI-500) prepared by MI method achieves 100% EA conversion at a low temperature of 200 °C. However, the temperature for 100% EA conversion over the 5 %CuO/CeO2 catalyst prepared by the conventional method is as high as 300 °C. Notably, the 5-MI-500 catalyst exhibits the highest proportion of well-dispersed CuO and Cu-O-Ce structures, which synergistically enhance catalyst activity. The well-dispersed CuO particles enhance the redox ability of the catalyst, while the Cu-O-Ce structure provides high activated oxygen via oxygen vacancy and better thermal stability during catalytic reaction. Accordingly, the possible reaction mechanism over the 5-MI-500 catalyst for EA oxidation was proposed. This study demonstrates that the MI method reported in this paper can provide a feasible methodology to prepare highly active catalysts with unique structures.

Effects of Al/Ni molar mass ratios and addition of CuO on the microstructure, mechanical properties, and energy release behavior of Al-Ni composites

Reactive Structural Materials (RSMs) are a new class of materials composed of two or more metallic materials with oxide-ceramic particles that are unable to ignite or explode under various types of loadings, such as thermal, mechanical, and electrical. This study aims to investigate the microstructure, thermal, physical and mechanical properties of the Al-Ni composites, as a type of RSMs, produced by mechanical alloying and subsequent hot pressing. In this research, the Al-Ni composites with various molar mass ratios of Al to Ni of 2:1, 1:1, and 1:3 were first produced. After determining the optimum molar mass ratio of Al to Ni concerning mechanical and thermal properties, Al-Ni composites were made by adding different amounts of CuO particles (2, 4, and 6 wt%), and their mechanical and thermal properties were determined. The thermal and mechanical results proved that the 1:1 molar mass ratio of Al to Ni in the Al-Ni composite exhibited optimal properties. The thermal properties of the Al-Ni-CuO composites showed that the general addition of CuO particles had a negative impact on the energy release of the Al-Ni composites. However, the combustion test showed that the presence of a low level of CuO particles (2 wt%) increased the reaction temperature from 1180 °C to 1368 °C. However, the higher content of CuO particles (4 and 6 wt%) reduced the reaction temperature of Al-Ni composites. Similar to the thermal properties, the mechanical tests proved the detrimental influence of CuO particles on the compressive strength and hardness values of Al-Ni composites. In-depth discussions on the affecting factors on the mechanical and thermal properties of the Al-Ni-CuO composites have been provided in this work.

Investigation on transport properties, heat transfer characteristics and pressure drop of CuO enhanced R1234yf based refrigerant

In refrigeration systems, one of the potential heat transfer fluids is nano-refrigerant. It can boost the performance of air conditioning and vapour compression refrigeration systems. In this investigation, the heat transfer characteristics and pressure drop of CuO/R1234yf are analysed by mathematical and simulation methods. Appropriate mathematical models were adopted from the previous studies to evaluate the heat transfer characteristics and the transport properties of the novel nano-refrigerant. The analysis was carried out with the volume fraction of nano-sized CuO particles in R1234yf refrigerant ranging from 0.2 to 1% and the temperature varying from 0 °C to 65 °C. From the investigation, it is seen that the viscosity, thermal conductivity and density are augmented with nanoparticle inclusion. However, the specific heat capacity of the nano-enhanced refrigerant is diminished with intensify in the nanoparticles’ concentration. The heat transfer coefficient and pressure drop of the nano-refrigerant are enhanced by 45.36% and 35.69% respectively. There is a 3.91% average absolute deviation observed between the results obtained from the mathematical and simulation method.

Molecular-level understanding of interfacial carbonates in stabilizing CuO-ZnO(Al2O3) catalysts

A descriptor of active CuO-ZnO(Al2O3) methanol-synthesis and water–gas-shift catalysts is the presence of high-temperature carbonates (HT-CO3) in the oxidic catalyst precursor. Previous reports have shown that such HT-CO3 lead to an appropriate interaction between the oxides; as a result, a high Cu surface area (or Cu-Zn or Cu/ZnO interphase areas) can be achieved. Yet, their nature is not well understood. In this study, the nature of these carbonates was investigated by experimental and theoretical methods in the oxidic precatalyst. A calcined Cu-Zn-Al hydrotalcite model compound revealed to have well-dispersed ZnO and CuO phases, together with highly stable HT-CO3. It was hypothesized that these HT-CO3 groups may be placed at critical locations at nano-scale as a glue, thus avoiding the growth of the oxide crystallites during calcination. This is an excellent pre-condition to achieve a high Cu surface area (or Cu-Zn or Cu/ZnO interphase areas) upon reduction, and therefore a high activity. To prove that, first-principles calculations were carried out based on the density functional theory (DFT); alumina was not considered in the model as the experimental data showed it to be amorphous but it may still have an effect. Comprehensive calculations provided evidence that such carbonate groups favourably bind the CuO and ZnO together at the interface, rather than being isolated on the individual oxide surfaces. The results strongly suggest that the HT-CO3 groups are part of the structure, in the calcined precatalyst, where they would prevent thermal sintering through a bonding mechanism between CuO and ZnO particles, which is a novel interpretation of this important catalyst descriptor.

Visible-Light-driven Photocatalytic Properties of Copper(I) Oxide (Cu2O) and Its Graphene-based Nanocomposites

In this study, an improved process was proposed for the synthesis of structure-controlled Cu2O nanoparticles, using a simplified wet chemical method at room temperature. A chemical solution route was established to synthesize Cu2O crystals with various sizes and morphologies. The structure, morphology, and optical properties of Cu2O nanoparticles were analyzed by X-ray diffraction, SEM (scanning electron microscope), and UV-Vis spectroscopy. By adjusting the aqueous mixture solutions of NaOH and NH2OH•HCl, the synthesis of Cu2O crystals with different morphology and size could be realized. Strangely, it was found that the change in the ratio of de-ionized water and NaOH aqueous solution led to the synthesis of Cu2O crystals of different sizes, while the morphology of Cu2O crystals was not affected. The synthesized Cu2O crystal samples were used as photocatalysts for methyl orange (MO) dye decomposition, as a model molecule, to evaluate the photocatalytic activities. However, under 200 watts of a visible light source, there are four samples with and without graphene-based nanocomposite of Cu2O NPs. The results showed that, compared with roughly spherical, irregular but thick plates, brick and small granule spheres shaped Cu2O nanoparticles provided better activity. The Cu2O sample with irregular but thick platelet-like shapes, having an average particle size of 0.53 µm, exhibited excellent photocatalytic activity (99.08% degradation). In addition, by reducing the size of Cu2O particles and preparing their graphene composition, one can fabricate a sample (Cu2-Cu2Gr) with the highest efficiency which has significantly better photocatalytic activity in comparison to the others. This work represents an innovative strategy for pre-the-case production of nanomaterials with shapes and sizes, that is, Cu2O crystals, with excellent photocatalytic activity through compositing with graphene