Solvent‐free synthesis of propargylamines catalyzed by an efficient recyclable ZnO‐supported CuO/Al2O3 nanocatalyst

An efficient nanocatalyst of ZnO‐supported CuO/Al₂O₃ (CuO/ZnO/Al₂O₃ nanocatalyst) was prepared by the co‐precipitation method and characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray powder diffraction and Brunauer–Emmett–Teller surface area analysis. CuO/ZnO/Al₂O₃ nanocatalyst proved to be a very efficient catalyst on the synthesis of propargylamines under solvent‐free conditions in high yields. Moreover, the catalyst can be recyclable without reducing catalytic activity up to five times.     

ZnO/Co3O4 Porous Nanocomposites Derived from MOFs: Room‐Temperature Ferromagnetism and High Catalytic Oxidation of CO

ZnO/Co₃O₄ porous nanocomposites were successfully fabricated by the thermal decomposition of Prussian Blue analogue (PBA) Zn₃[Co(CN)₆]₂ nanospheres obtained at room temperature. Interestingly, ZnO/Co₃O₄ porous nanocomposites exhibit room‐temperature ferromagnetism. Moreover, the ZnO/Co₃O₄ porous nanocomposites show good catalytic activity for CO oxidation, and the CO conversion rate reaches 100 % at 250 °C. It is suggested that the synergistic effect of each component, relative high surface area (32 m² g^?1) and porous structure lead to the promising catalytic properties.     

Visible light driven photocatalytic activity of ZnO/CuO nanocomposites coupled with rGO heterostructures synthesized by solid-state method for RhB dye degradation

Metal oxide frame works along with carbon materials have been attracting tremendous attention of researches as the potential materials for energy and environmental remediation. In the present work heterostructures of (ZnO/CuO)/rGO ternary nanocomposites were synthesized by solid-state method. The crystalline structure of the nanoparticles was obtained from the XRD analysis. Optical band gap of the ZnO nanoparticles (3.1 eV) is tuned to 2.8 eV in the synthesized (ZnO/CuO)/rGO ternary nanocomposites. Field emission scanning electron microscope images of the (ZnO/CuO)/rGO ternary nanocomposites revealed formation of well-developed flowers like morphology of (ZnO/CuO) nanoparticles on rGO sheets. Photoluminescence spectroscopy analysis of (ZnO/CuO)/rGO ternary nanocomposites show enhancement in the electron-hole pair separation and thereby diminishing electron-hole pairs recombination rates effectively. In the present work, the photocatalytic activity of the ZC₃G₁₅ ternary nanocomposites show 99% and 93% of degradation efficiency respectively against RhB dye and 4-chlorophenol for 20 min under visible light irradiation. Thus, the simple solid-state method provides the effective ternary nanocomposites heterostructures light harvesting material for energy and environmental remediation.     

负载于HZSM-5上的CuO-ZnO-Al2O3纳米粒子：尿素－硝酸盐燃烧合成和理化表征

用尿素-硝酸盐燃烧法制备了一系列的负载于HZSM-5上的CuO-ZnO-Al2O3纳米复合材料(CZA/HZSM-5)。研究了燃料与氧化物的比率对所合成的复合材料的理化性质的影响。用TGA/DTG,FTIR和XRD等研究了尿素-硝酸盐凝胶的热分解和煅烧粉体的相演变过程。FESEM结果表明在燃烧过程中燃料的用量对CZA/HZSM-5的性质有重大影响。CuO和ZnO的晶粒首先随尿素量的增加而增大,然后随尿素量的增加而减小。CuO和ZnO的相对结晶度随燃料量的增加表现为非单调趋势。随着燃料与硝酸盐的比率的增加,CZA/HZSM-5不仅形貌变得超细和均一,而且表面孔隙率也显著增加。FTIR结果表明HZSM-5的结构甚至在负载了CuO-ZnO-Al2O3纳米粒子后也未被破坏,而且在CuO和ZnO与HZSM-5之间还有表面的键合。TGA/DTG结果指出燃烧合成法是一种由若干过程组合起来的方法,例如前驱体的热分解和前驱体间的放热反应等。另外,提出了CuO-ZnO-Al2O3负载在HZSM-5上的生成机理。     

Synthesis of Fe3O4/CuO/ZnO/RGO and its catalytic degradation of dye wastewater using dielectric barrier discharge plasma

The design of an efficient and green dye degradation technology is of great significance to mitigate water pollution as well as ecological damage. Fe₃O₄/CuO/ZnO/RGO was prepared by solvothermal synthesis and homogeneous precipitation. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), and vibrating-sample magnetometry (VSM) were used to characterize the samples, to explore the morphology and structural composition of the composites. To enhance the degradation efficiency, a dielectric barrier discharge (DBD)–Fe₃O₄/CuO/ZnO/RGO co-catalytic system was created based on the DBD plasma technology. Response surface methodology analysis results demonstrate that the degradation effect of DBD–Fe₃O₄/CuO/ZnO/RGO is optimal and the decolorization rate is 95.06 % when the solution pH is 3, conductivity is 0.5 mS/cm, the input voltage is 90 V, and Fe₃O₄/CuO/ZnO/RGO concentration is 0.18 g/L. Therefore, this study offers a novel method for dye degradation and confirms the viability of a DBD–Fe₃O₄/CuO/ZnO/RGO synergistic catalytic system.     

Generation of Methyl Vinyl Ketone from Oxidation of Levulinic Acid Oxidized by Cupric Oxide Complex

Methyl vinyl ketone (MVK) is a kind of high‐value chemical which has been widely used in many fields. In this paper, it is formed from oxidation of levulinic acid–a hydrolysis product of biomass. Copper oxide supported on cerium dioxide (CuO/CeO₂) and alumina (CuO/Al₂O₃) were prepared and used for the oxidation of levulinic acid (LA). The oxidants were characterized by means of X‐ray diffraction (XRD), H₂‐temperature programmed reduction (H₂‐TPR) and atomic force microscope (AFM) techniques. CuO/CeO₂ and CuO/Al₂O₃ show a different behavior with respect to pure CuO. The experiments revealed that CuO/CeO₂ and CuO/Al₂O₃ can oxidize LA and get methyl vinyl ketone [yield of 15.5% detected by head space‐gas chromatograph‐mass spectrometer (HS‐GC‐MS)] under mild reactive conditions, while pure CuO oxidizes LA to produce butanone (MEK).     

Synthesis and Characterization of β‐Co(OH)2, CuO and ZnO Nanostructures by Solvothermal Method without Any Additive

β‐Co(OH)₂, CuO and ZnO nanostructures with plate‐like, particle‐like and flower‐like morphologies were prepared through the use of simple solvothermal method using of melt salt and 1,10‐phenanthroline as complexing agent and sodium hydroxide. β‐Co(OH)₂ consisted of a plate‐like structure, and the nanoplates size was about 29 nm. The structure was comprised of regular sheets which were assembled together. Furthermore, the as‐obtained β‐Co(OH)₂ nanoplates can be easily converted into Co₃O₄ nanoplates by calcining in air at 500 °C for 2 h. The results indicate that ZnO powder is of hexagonal wurtzite structure and well crystallized with high purity. CuO powder is pure monoclinic‐structured crystalline. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT‐IR) spectra. Possible formation mechanism of the nanostructures is proposed.     

Magnetically separable ZnO/ZnFe2O4 and ZnO/CoFe2O4 photocatalysts supported onto nitrogen doped graphene for photocatalytic degradation of toxic dyes

Advanced oxidation processes (AOPs) counting heterogeneous photocatalysis has confirmed as one of the preeminent method for waste water remediation. In the present work, we have successfully fabricated novel visible-light-driven nitrogen-doped graphene (NG) supported magnetic ZnO/ZnFe₂O₄ (ZnO/ZF/NG) and ZnO/CoFe₂O₄ (ZnO/CF/NG) nanocomposites. ZnO synthesized via direct precipitation method. Hydrothermal method was used for the preparation of nitrogen-doped graphene supported magnetic ZnO/ZF (ZnO/ZnFe₂O₄) and ZnO/CF (ZnO/CoFe₂O₄) nanocomposites. The procured materials were scrutinized by assorted characterizations to acquire information on their chemical composition, crystalline structure and photosensitive properties. The absorption and photocatalytic performance of photocatalysts were studied via UV–Visible spectra. Photodegradation performance of the synthesized nanocomposites was estimated toward mineralization of methyl orange (MO) and malachite green (MG) dyes in aqueous solution. The high surface area of ZnO/ZF/NG and ZnO/CF/NG was suitable for adsorptive removal of MO and MG dyes. The photodegradation performance of heterojunction photocatalysts was superior to bare photocatalyst in 140 min under visible-light irradiation. Spectrophotometer, GC–MS (Gas chromatography–mass spectrometry) elucidation was carried out to expose the possible intermediates formed. Both ZnO/ZF/NG and ZnO/CF/NG were rapidly isolated from the aqueous phase by applying an external magnetic field in 20 sec and 2 min, respectively. The photocatalytic performance and stability of ZnO/ZF/NG and ZnO/CF/NG nanocomposites were confirmed by conducting 10 consecutive regeneration cycles. Owing to recyclability of ZnO/ZF/NG and ZnO/CF/NG, these heterogeneous nanocomposites might be used as cost-effective for treatment of discarded water. The observations endorse that the synthesized ternary heterogeneous nanocomposites facilitates wastewater decontamination using photocatalytic technology.     

Vapour phase synthesis of quinoline from aniline and glycerol over mixed oxide catalysts

The vapour phase synthesis of quinoline from aniline and glycerol (1:2 mole ratio) in a single step was investigated over ZnO–Cr₂O₃, CuO–ZnO/Al₂O₃, MoO₃–V₂O₅/Al₂O₃ and NiO–MoO₃/Al₂O₃ catalysts in the presence of air at 623–723 K under normal atmospheric pressure. Among these catalysts investigated, the CuO–ZnO/Al₂O₃ combination effectively performed this reaction with high activity and selectivity.     

Inactivation of Escherichia coli on Immobilized CuO/CoFe2O4‐TiO2 Thin‐Film under Simulated Sunlight Irradiation

Composite photocatalysts of CuO/CoFe₂O₄‐TiO₂ were successfully synthesized by a sol‐gel method and fixed on ordinary tiles. The photosterilization of Escherichia coli was examined on CuO/CoFe₂O₄‐TiO₂ thin films under a xenon lamp irradiation. The film was characterized by XRD, and the morphology was observed by SEM. Disinfection data indicated that CuO/CoFe₂O₄‐TiO₂ composite photocatalysts have the much better photocatalytic activity than CuO/CoFe₂O₄ and TiO₂. The optimized composition of the nanocomposites has been found to be m_CuO/CoFe2O4:m_TiO2=3:7, with loadings ranging from 790 to 1400 mg/m². The photocatalytic inactivated rate of E. coli (10⁵ CFU/mL) reached 98.4% under the xenon lamp of 150 W within 30 min.     

Study on CuO/Al2O3 catalytic ozone treatment of acid red B solution

A CuO/Al₂O₃ catalyst was prepared using the impregnation method. The catalytic activity of CuO/Al₂O₃ for the ozonation of acid red B (ARB) in aqueous solution was studied, the chemical oxygen demand (COD) removal rate was an indicator for catalytic activity evaluation. The effects of initial ARB concentration, solution pH, and different oxidative degradation systems on oxidative degradation of ARB solution were studied. The CuO/Al₂O₃ catalyst was characterized using X‐ray diffractometry (XRD), N₂ adsorption desorption test, X‐ray photoelectron spectroscopy (XPS), and zero‐point charge (pH_zpc). The results show that copper species on the carrier were in the form of CuO and highly dispersed on the carrier. CuO can increase the alkalinity of the Al₂O₃ surface, and the CuO/Al₂O₃ catalyst facilitates the decomposition of O₃ into ·OH, which was beneficial for the catalytic O₃ oxidation degradation reaction. With the increase of the initial concentration of simulated wastewater, the CuO/Al₂O₃ catalytic reaction still has a high COD removal rate. Alkaline solution was of benefit to catalyze the degradation of ARB solution. When the ARB solution pH = 8.93, the degradation reaction was carried out for 40 min, the COD removal rate reached 83.2%. The degradation reaction was dominated by the hydroxyl radical (·OH) reaction.     

CuO–ZnO Micro/Nanoporous Array‐Film‐Based Chemosensors: New Sensing Properties to H2S

CuO–ZnO micro/nanoporous array‐films are synthesized by transferring a solution‐dipped self‐organized colloidal template onto a device substrate and sequent heat treatment. Their morphologies and structures are characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectrum analysis. Based on the sensing measurement, it is found that the CuO–ZnO films prepared with the composition of [Cu²⁺]/[Zn²⁺]=0.005, 0.01, and 0.05 all show a nice sensitivity to 10 ppm H₂S. Interestingly, three different zones exist in the patterns of gas responses versus H₂S concentrations: a platform zone, a rapidly increasing zone, and a slowly increasing zone. Further experiments show that the hybrid CuO–ZnO porous film sensor exhibits shorter recovery time and better selectivity to H₂S gas against other interfering gases at a concentration of 10 ppm. These new sensing properties may be due to a depletion layer induced by p–n junction between p‐type CuO and n‐type ZnO and high chemical activity of CuO to H₂S. This work will provide a new construction route of ZnO‐based sensing materials, which can be used as H₂S sensors with high performances.     

溶剂极性对微波辐射老化制备前驱体及CuO/ZnO/Al2O3催化剂结构的影响

在制备CuO/ZnO/Al2O3催化剂的老化过程中,采用微波辐射老化技术,着重研究了溶剂极性对前躯体物相组成,烧后CuO/ZnO/Al2O3催化剂结构及其在浆态床合成甲醇工艺中催化性能的影响。通过XRD、DTG、H2-TPR,FTIR、HR-TEM和XPS对前驱体及催化剂表征表明,沉淀母液在微波辐射条件下进行老化,溶剂的极性对前躯体物相组成及催化剂结构影响显著。随着溶剂极性的增大,Zn2+/Cu2+取代Cu2(CO3)(OH)2/Zn5(CO3)2(OH)6中Cu2+/Zn2+的取代反应增强,使得前躯体中(Cu,Zn)5(CO3)2(OH)6和(Cu,Zn)2(CO3)(OH)2物相的含量增多,结晶度提高,导致烧后CuO/ZnO/Al2O3催化剂中CuO-ZnO协同作用增强,且CuO晶粒减小,表面Cu含量增加,催化剂活性和稳定性提高。水溶剂的极性最大,制备的催化剂活性和稳定性最好,甲醇的时空收率(STY)和平均失活率分别为320 mg.g-1.h-1和0.11%.d-1。     

Preparation and characterization of novel polyimide/functionalized ZnO bionanocomposite for gas separation and study of their antibacterial activity

In the present investigation novel Polyimide/functionalized ZnO (PI/ZnO) bionanocomposites containing amino acid (Methionine) and benzimidazole pendent groups with different amounts of modified ZnO nanoparticles (ZnO NPs) were successfully prepared through ultrasonic irradiation technique. Due to the high surface energy and tendency for agglomeration, the surface ZnO NPs was modified by a coupling agent as 3- methacryloxypropyl-trimethoxysilane (MPS) to form MPS-ZnO nanoparticles. The ultrasonic irradiation effectively changes the rheology and the glass transition temperature and the crystallinity of the composite polymer. PI/ZnO nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). TEM analysis showed that the modified ZnO nanoparticles were homogeneously dispersed in polymer matrix. The TGA results of PI/ZnO nanocomposites showed that the thermal stability is obviously improved the presence of MPS-ZnO NPs in comparison with the pure PI and that this increase is higher when the NP content increases. The permeabilities of pure H₂, CH₄, O₂, and N₂ gases through prepared membranes were determined at room temperature (25 °C) and 20 bar feed pressure. The membranes having 20% ZnO showed higher values of H₂ permeability, and H₂/CH₄ and H₂/N₂ ideal selectivities (the ratio of pair gas permeabilities) compared with other membranes. The antibacterial activity of bionanocomposite films was tested against gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Further, it was observed that antibacterial activity of the resulting hybrid biofilms showed somewhat higher for gram-positive bacteria compared to gram-negative bacteria.     

Porous ZnO/Co3O4/N‐doped carbon nanocages synthesized via pyrolysis of complex metal–organic framework (MOF) hybrids as an advanced lithium‐ion battery anode

Metal oxides have a large storage capacity when employed as anode materials for lithium‐ion batteries (LIBs). However, they often suffer from poor capacity retention due to their low electrical conductivity and huge volume variation during the charge–discharge process. To overcome these limitations, fabrication of metal oxides/carbon hybrids with hollow structures can be expected to further improve their electrochemical properties. Herein, ZnO‐Co₃O₄ nanocomposites embedded in N‐doped carbon (ZnO‐Co₃O₄@N‐C) nanocages with hollow dodecahedral shapes have been prepared successfully by the simple carbonizing and oxidizing of metal–organic frameworks (MOFs). Benefiting from the advantages of the structural features, i.e. the conductive N‐doped carbon coating, the porous structure of the nanocages and the synergistic effects of different components, the as‐prepared ZnO‐Co₃O₄@N‐C not only avoids particle aggregation and nanostructure cracking but also facilitates the transport of ions and electrons. As a result, the resultant ZnO‐Co₃O₄@N‐C shows a discharge capacity of 2373 mAh g^?1 at the first cycle and exhibits a retention capacity of 1305 mAh g^?1 even after 300 cycles at 0.1 A g^?1. In addition, a reversible capacity of 948 mAh g^?1 is obtained at a current density of 2 A g^?1, which delivers an excellent high‐rate cycle ability.     

X-ray absorption near edge structures (xanes) of Cu/ZnO/Al2O3 Co shift catalysts

X-ray absorption near edge structures (XANES) of some Cu/ZnO/Al₂O₃CO shift catalysts have been measured at high resolution using synchrotron radiation, and compared to reference compounds Prior to reduction. CuO and ZnO are present, after reduction ZnO and highly dispersed Cu, no indication was found for Cu₂O or the presence of spinels. The results are qualitatively confirmed by preliminary analysis of EXAFS spectra.     

Low‐Temperature Transformation of Methane to Methanol on Pd1O4 Single Sites Anchored on the Internal Surface of Microporous Silicate

Direct conversion of methane to chemical feedstocks such as methanol under mild conditions is a challenging but ideal solution for utilization of methane. Pd₁O₄ single‐sites anchored on the internal surface of micropores of a microporous silicate exhibit high selectivity and activity in transforming CH₄ to CH₃OH at 50–95 °C in aqueous phase through partial oxidation of CH₄ with H₂O₂. The selectivity for methanol production remains at 86.4 %, while the activity for methanol production at 95 °C is about 2.78 molecules per Pd₁O₄ site per second when 2.0 wt % CuO is used as a co‐catalyst with the Pd₁O₄@ZSM‐5. Thermodynamic calculations suggest that the reaction toward methanol production is highly favorable compared to formation of a byproduct, methyl peroxide.     

Preparation of New Magnetic Nanocatalysts Based on TiO2 and ZnO and Their Application in Improved Photocatalytic Degradation of Dye Pollutant Under Visible Light

Photocatalytic degradation of methyl orange (MO) as a model of an organic pollution was accomplished with magnetic and porous TiO₂/ZnO/Fe₃O₄/PANI and ZnO/Fe₃O₄/PANI nanocomposites under visible light irradiation. The structures of nanocomposites were characterized by various techniques including UV–Vis absorption spectroscopy, XRD, SEM, EDS, BET and TGA. Optical absorption investigations show two λ_max at 450 and 590 nm for TiO₂/ZnO/Fe₃O₄/PANI nanocomposites respectively possessing optical band gaps about 2.75 and 2.1 eV smaller than that of the neat TiO₂ and ZnO nanoparticles. Due to these optical absorptions, the nanocomposites can be considered promising candidates as visible light photocatalysts to produce more electron‐hole pairs. The degradation of MO, extremely increased using polymeric photocatalysts and decolorization in the presence of visible light achieved up to 90% in less than 20 min in comparison with the neat nanoparticles (about 10%). All these advantages promise a bright future for these composites as useful photocatalysts. The degradation efficiency of MO using stable nanocomposites was still over 70% after ten times reusing. The highest decolorizing efficiencies were achieved with 0.75 g L^?1 of catalyst and 10 mg L^?1 of MO at natural pH under visible light irradiation in less than 20 min.     

Corallocarpus epigaeus mediated synthesis of ZnO/CuO integrated ZrO2 nanoparticles for enhanced in-vitro antibacterial,antifungal and antidiabetic activities

Zirconia based nanocomposites have attracted much research attention in recent years due to their exceptional biomedicinal activities. Rhizome extracts of Corallocarpus epigaeus based ZrO₂/CuO–ZnO nanocomposite were green synthesized in a facile synthesis strategy. The nanocomposites were examined with XRD technique for their structural information and FT-IR technique for surface functional group analysis. Electron microscopic images aided to elucidate the CuO and ZnO nanoparticles decorated ZrO₂ nanostructures. UV–vis absorption spectroscopic studies of the nanocomposite revealed the characteristic UV absorption of ZrO₂ and enhanced visible region absorption for the incorporated nanoparticles. Antibacterial and antifungal studies indicated enhanced activity of nanocomposites over the pristine zirconia nanoparticles. ZrO₂/CuO–ZnO nanocomposite had exhibited about 75% of α-amylase inhibition activity, whereas pristine ZrO₂ nanoparticles had exhibited only 57% suggesting the worthwhile application in the antidiabetic activity of the nanocomposite.     

Supported Intermetallic PdZn Nanoparticles as Bifunctional Catalysts for the Direct Synthesis of Dimethyl Ether from CO‐Rich Synthesis Gas

The single‐step syngas‐to‐dimethyl ether (STD) process entails economic and technical advantages over the current industrial two‐step process. Pd/ZnO‐based catalysts have recently emerged as interesting alternatives to currently used Cu/ZnO/Al₂O₃ catalysts, but the nature of the active site(s), the reaction mechanism, and the role of Pd and ZnO in the solid catalyst are not well established. Now, Zn‐stabilized Pd colloids with a size of 2 nm served as the key building blocks for the methanol active component in bifunctional Pd/ZnO‐γ‐Al₂O₃ catalysts. The catalysts were characterized by combining high‐pressure operando X‐ray absorption spectroscopy and DFT calculations. The enhanced stability, longevity, and high dimethyl ether selectivity observed makes Pd/ZnO‐γ‐Al₂O₃ an effective alternative system for the STD process compared to Cu/ZnO/γ‐Al₂O₃.