The electrocatalysis for CO reduction is interesting for both fundamental understanding of the reaction mechanisms and deriving products of higher values for the electrochemical conversion of CO2. ...Hereby, we report on the development of three-dimensional (3D) Cu nanostructures as advanced electrocatalysts for CO reduction. By thermal oxidation of commercial Cu foams in air, CuO nanowires or porous structures were grown on the 3D frameworks of the foam, which were then reduced to Cu by applying a cathodic electrochemical potential. The derived 3D Cu nanostructures were demonstrated to be highly active and selective for the electroreduction of CO, achieving an improvement in CO reduction current density by a factor of 6 as compared to the 2D counterpart with similar surface roughness factors, 76% Faradaic efficiency (FE) of CO conversion, and >50% FE toward ethanol. The catalytic enhancement mechanisms were further discussed in terms of transport and surface structure effects.
The present study describes the antibacterial behavior and the bacterial resistance analysis of extremophile Pseudomonas aeruginosa in contact with copper nanoparticles (CuNPs). For this purpose, ...green synthesis of CuNPs was performed by combined ultrasound-assisted and chemical reduction methods, obtaining semispherical CuNPs ranging from ca. 4-9 nm. Antibacterial activity (AA) of biosynthesized CuNPs demonstrates an antibacterial inhibition of 85 % (LD85) at 400 μg/mL and a minimum bactericidal concentration (MBC) of 800 μg/mL after 3 h of contact. Bacterial adaptation in contact with CuNPs was observed through the consecutive exposition of microorganisms, presenting a significant increase of LD85 values from 400 μg/mL to 6400 μg/mL after 11 expositions. This behavior demonstrates the bacterial growth adaptation with high-dose of CuNPs. The bacterial resistance mechanism was determined through the overproduction of pyocyanin, associated with oxidative stress events, the genomic polymorphism of resistant bacteria obtained by PCR-RAPDs, and the morphological interaction between P. aeruginosa and CuNPs evidenced by transmission electron microscopy (TEM) micrographs. Our results suggest that under controlled CuNPs exposition, extremophile P. aeruginosa can generate bacterial resistance mechanisms, an important issue for the effective design of antimicrobial nanomaterials.
The development of biopolymer fibers is attracting considerable interest due to the need to reduce the environmental impact of the petroleum-based industry. With the aim to foster the use of ...biopolymer-based antimicrobial fibers, a green and sustainable preparation route for alginate fibers containing copper-based nanostructures is reported. Its strong antimicrobial properties and affinity for alginate make copper the ideal candidate for the preparation of products suitable for various applications. In this work alginate is extruded and crosslinked in a Cu2+ aqueous bath, producing a filiform hydrogel structure. Ascorbic acid was then used to reduce the metal ions and to form the aforementioned nanostructures. This in situ strategy for the reduction of coordinating Cu2+ ions is unprecedented and leads to a homogeneous distribution of the inorganic structures in the polymeric network. The entire process can be monitored through infrared spectroscopy and the performances (e.g., thermal stability, morphology, swelling, water retention, mechanical properties) of the obtained products are tunable as a function of the duration of each preparation step. The great affinity for water and the small amount of Cu2+ released as a function of time suggest promising perspectives for the use of these fibers in antimicrobial applications.
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•Cu2+-alginate fibers obtained through a facile extrusion and crosslinking process.•Ascorbic acid to reduce Cu2+ ions in situ.•Fibers decorated with homogeneously distributed copper-based nanostructures.•Properties of the fibers finely tuned as a function of the preparation conditions.
Precise deuterium incorporation with controllable deuterated sites is extremely desirable. Here, a facile and efficient electrocatalytic deuterodehalogenation of halides using D2O as the deuteration ...reagent and copper nanowire arrays (Cu NWAs) electrochemically formed in situ as the cathode was demonstrated. A cross‐coupling of carbon and deuterium free radicals might be involved for this ipso‐selective deuteration. This method exhibited excellent chemoselectivity and high compatibility with the easily reducible functional groups (C=C, C≡C, C=O, C=N, C≡N). The C−H to C−D transformations were achieved with high yields and deuterium ratios through a one‐pot halogenation–deuterodehalogenation process. Efficient deuteration of less‐active bromide substrates, specific deuterium incorporation into top‐selling pharmaceuticals, and oxidant‐free paired anodic synthesis of high‐value chemicals with low energy input highlighted the potential practicality.
Cu nanowire arrays formed in situ are efficient catalysts for controllable deuteration of halides using D2O as a cheap and safe deuterated donor. A cross‐coupling of carbon and deuterium free radicals might be involved in this reaction. High compatibility with easily reducible functional groups, one‐pot C−H to C−D transformation, and paired synthesis of valuable chemicals at both electrodes showed the potential utility.
Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The ...nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices.
The electrochemical reduction of CO2 to fuels and value-added chemicals on metallic copper is an attractive strategy for valorizing CO2 emissions. However, favoring the CO2 reduction over hydrogen ...evolution and exclusive control of selectivity towards C1 or C2+ products by restructuring the copper surface is a major challenge. Herein, we exploit the differential orientation of the exposed facets in copper nanostructures that can tune the product selectivity in CO2 electroreduction. The Cu nanostructure with predominant {111} orientation produce C1 products only upon CO2 electroreduction at an applied potential of −1.3 V vs. reversible hydrogen electrodes (RHE), with 66.57% Faradaic efficiency (FE) for methane. Whereas the vertically grown copper nanostructures that are oriented in {110} direction have higher dislocation density and show greater CO2 electroreduction activity (>95%) at the same applied potential, with FE towards ethylene 24.39% and that of oxygenates 41.31%. FIA-DEMS analysis provided experimental evidence of selectivity of methane over methanol at higher overpotentials indicating the mechanism of methane formation occurs via *COH intermediate. The ethylene formation at a potential −1.0 V vs. RHE or more negative to it suggests a common intermediate for methane and ethylene on the vertically grown copper nanostructures. This work advances the understanding between the product selectivity and the surface structure of the copper nanostructures in electrochemical CO2 reduction.
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•Growth direction of copper nanostructures determine the facet formation on the surface.•Higher dislocation density on Cu NsB favored CO2 reduction suppressing H2 evolution.•Cu NsA produced C1 products only on CO2 electroreduction with CH4 as the major product.•The local pH effect on the copper nanostructure is influenced by its exposed facets.•DEMS analysis shows selectivity of methane over methanol at higher overpotentials.
The attachment of nitrogen-doped graphene (NG) on glassy carbon electrode (GCE) followed by electrodeposition of copper nanostructures (CuNSs) is described in this paper. Nitrogen-doped graphene ...oxide (N-GO) was prepared by intercalating melamine into graphene oxide (GO) by sonication. The doping of nitrogen was confirmed from the characteristic peaks at 285.3 and 399 eV in the XPS corresponding to the C–N bond and nitrogen, respectively. The presence of amine groups on the N-GO was exploited to attach them on GCE via Michael’s reaction. Subsequently, N-GO was electrochemically reduced to form NG by reducing the oxygen functionalities present on the N-GO. Then, the CuNSs on the NG modified electrode was prepared by electrodeposition at various applied potentials with different deposition times. The homogeneous deposition of cubic, spherical, quasidendritic, and dendritic NS at the applied potentials of 0, −0.10, −0.30, and −0.40 V, respectively, was evidenced from scanning electron microscopy (SEM) studies. The surface energy of the system can be reduced by the intercalated nitrogen in the graphene layer via doping. Hence, the NG layers with large surface area act as a robust scaffold for the homogeneous deposition of CuNSs. Further, the electrocatalytic activity of the NG-CuNSs modified GCE toward glucose oxidation was studied. In a comparison with NG and CuNSs, the NG-CuNSs exhibited 2-fold higher oxidation current. Further, it was found that the electrocatalytic activity of the composite electrode depends on the shape of the CuNSs. Among the different CuNSs, the NG-dendritic CuNSs electrode exhibited higher electrocatalytic activity. Finally, the practical applicability of the present sensor was demonstrated by fabricating NG-dendritic CuNSs on screen printed carbon electrode for the determination of glucose in human blood serum and urine samples.
•Nanostructured copper oxide (II) synthesized by direct sonoelectrochemistry method.•An ultrasonic horn with a copper tip is the anode in the direct sonoelectrochemistry.•Nanostructured copper ...generated by ultrasound ablation method.•Copper nanostructures converted to nanostructured copper oxide (II) under heating.•The most main advantages of two methods are fast, high purity, and repeatable.
In this paper, we present two aspects of the ultrasonic for the synthesis of CuO (II) nanostructures. In the first ultrasound application, we made a copper tip for an ultrasonic probe transducer and used it for electrolysis and ultrasound irradiation processes. This method is named direct sonoelectrochemistry and compares with conventional electrochemistry. CuO (II) nanostructures are obtained after sintering for both direct sonoelectrochemistry method and conventional electrochemistry method. In the second application of ultrasound, the copper nanostructures were generated by the ultrasound ablation method, and then, the heating process was performed for oxidation. The formation of the copper and CuO (II) nanostructures is confirmed by the powder X-ray diffraction (XRD), the field emission electron microscopy (FESEM), and transmission electron microscopy (TEM). The results show that the direct sonoelectrochemistry method generates CuO (II) nanostructures 4.2 times more than conventional electrochemistry. The crystallite size in the electrochemistry methods and direct sonoelectrochemistry is 28.44 nm and 26.60 nm, respectively. The direct sonoelectrochemistry way is a very flexible method and parameters in electrochemical, ultrasound, and the relationship between them can play an important role in the process of synthesis of nanostructures. The crystallite size in the ultrasound ablation method is 21.13 nm and 25.23 nm for the copper and CuO (II) nanostructures. The most important advantages of this method are green, fast, and high purity of the produced nanostructures.
In this work, carbon coated copper nanoparticles and nanowires were synthesized as a ligand free nanocatalyst that naturally contains ppm levels of Pd with no post-modification via a two-steps ...reduction-hydrothermal process. Transmittance electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction, inductively coupled plasma optical emission spectrometry (ICP-OES), and Raman spectroscopy were employed for the characterization of the nano-catalyst. The utilization of the synthesized Cu/C nano-catalyst in Suzuki cross coupling reaction showed a high performance in the synthesis of various biaryls in water. Moreover, this catalyst reused successfully with no significant yield decrease even after four subsequently runs.
•Inexpensive copper/carbon nanocomposite for the cross-coupling reaction is proposed.•The Suzuki reactions of various halobenzenes are performed in aqueous media.•High catalytic activity of the copper-based heterogeneous catalyst•The catalyst could be recycled up to four times without loss in activity.
Copper nanostructures were produced as an effective and regioselective catalyst for the synthesis of 1,2,3‐triazoles from a wide range of raw materials, such as sodium azide, epoxides and terminal ...alkynes, in water via a one‐pot three‐component click reaction. The new heterogeneous catalyst was prepared by a simple ball mill reduction of CuO with NaBH4 using a ball‐to‐powder weight ratio of 50:1 under air atmosphere at room temperature. The catalyst was fully characterized using scanning electron microscopy, energy‐dispersive X‐ray analysis, Fourier transform infrared spectroscopy and X‐ray diffraction. The copper nanostructures catalysed both ring opening and triazole cyclization steps. Products were obtained in high yields and short reaction times. The reactions were performed at ambient temperature in water as a green solvent. The Cu/Cu2O nanostructures revealed high reusability and high stability via a simple recycling process.
1,4‐Disubstituted 1,2,3‐triazoles were synthesized from sodium azide, epoxides and terminal alkynes in water via a one‐pot three‐component click reaction. Cu/Cu2O nanostructures as a regioselective and reusable catalyst were used in the synthesis. This method has many advantages including the use of water as a green solvent under mild conditions.
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