Cu-based Nanoparticles Research Articles

Fabrication of H2S gas sensors using ZnxCu1-xFe2O4 nanoparticles

Spinel ferrite nanoparticles can be easily retrieved and utilized for multiple cycles due to their magnetic properties. In this work, nanoparticles of a ZnxCu1-xFe2O4 composition were synthesized by employing a sol–gel auto-combustion technique. The morphology, composition, and crystal structure were examined using scanning electron microscopy, infrared spectroscopy, and X-ray diffraction. The produced nanoparticles are in the range of 30–70 nm and manifest spinel cubic structure. The nanoparticles were tested for their sensitivity to H2 and H2S gases, and the Cu-based spinel ferrite nanoparticles were found the most sensitive and selective to H2S gas. Their enhanced response to H2S gas was attributed to the production of metallic CuFeS2 that manifest higher electrical conductivity as compared with CuFe2O4. The fabricated sensors are functional at low temperatures, and consequently, they need low operational power. They are also simple to fabricate with appropriate cost.

General Synthesis of Ultrafine Cu-Based Alloy Nanoparticles Anchored on Porous N-Doped Carbon Nanofibers for Enhanced Electrocatalytic Performance

Precise size control and general synthesis of ultrafine noble metal-based catalysts are very important in electrochemical energy conversion technologies. Herein, we develop the ultrafine MCu (M = P...

The Role of New Inorganic Materials in Composite Membranes for Water Disinfection.

Today, there is an increasing interest in improving the physicochemical properties of polymeric membranes by merging the membranes with different inorganic materials. These so-called composite membranes have been implemented in different membrane-based technologies (e.g., microfiltration, ultrafiltration, nanofiltration, membrane bioreactors, among others) for water treatment and disinfection. This is because such inorganic materials (such as TiO2-, ZnO-, Ag-, and Cu-based nanoparticles, carbon-based materials, to mention just a few) can improve the separation performance of membranes and also some other properties, such as antifouling, mechanical, thermal, and physical and chemical stability. Moreover, such materials display specific biological activity towards viruses, bacteria, and protozoa, showing enhanced water disinfection properties. Therefore, the aim of this review is to collect the latest advances (in the last five years) in using composite membranes and new hybrid materials for water disinfection, paying particular emphasis on relevant results and new hydride composites together with their preparation protocols. Moreover, this review addresses the main mechanism of action of different conventional and novel inorganic materials toward biologically active matter.

A comparison of the catalytic efficiency of copper-based bimetallic nanoparticles in the click reactions

Compared to monometallic nanoparticles, bimetallic nanoparticles have attracted wide attention due to their physical properties, excellent catalytic activity, high regioselectivity, selectivity, and stability. Here, we have first synthesized 10 different kinds of graphene quantum dot–stabilized Cu-based bimetallic nanoparticles (including CoCu, NiCu, RuCu, RhCu, PdCu, AgCu, IrCu, AuCu, FeCu, and PtCu) and compared their catalytic activities in a CuAAC click reaction. Among them, RhCu provides the highest yield of the desired product in the click reaction (77%). The catalytic activity of these MCu in the click reaction is in the order: RhCu > PdCu > AuCu > CoCu > PtCu > AgCu > NiCu > CuNP > RuCu > FeCu > IrCu.

Photo-transformation of graphene oxide in the presence of co-existing metal ions regulated its toxicity to freshwater algae

Graphene oxide (GO) sheets are unstable in aqueous environments, and the effect of photo-transformation on GO toxicity to freshwater algae (Chlorella pyrenoidosa) was investigated. Our results demonstrated that GO underwent photo-reduction under 25-day sunlight irradiation, and the transformation was generally completed at Day 8. The toxicological investigation showed that 8-day sunlight irradiation significantly increased growth inhibition of GO (25 mg/L) to algal cells by 11.2%, due to enhanced oxidative stress and stronger membrane damage. Low molecular weight (LMW) species were produced during the 8-day GO transformation, and they were identified as two types of aromatic compounds, which played a crucial role in increasing toxicity. The combined toxicity of GO and Cu2+ ions before and after light irradiation was further investigated. Antagonistic effect was observed between the toxicity of pristine GO and co-existing Cu2+ ions. After co-irradiation of GO and Cu2+ ions for 8 days, their combined toxicity was unexpectedly lower or insignificant in comparison with the treatments of pristine GO, or pristine GO in the presence of Cu2+ ions. Two mechanisms were revealed for this finding: (1) Cu2+ ions suppressed the photo-transformation of GO; (2) the toxicity of free Cu2+ ions was decreased through the adsorption/retention of Cu2+ ions and formation of Cu-based nanoparticles (e.g., Cu2O and Cu2S) on the photo-transformed GO. The provided data are helpful for better understanding the environmental process and risk of GO under natural conditions.

Potential Link between Cu Surface and Selective CO2 Electroreduction: Perspective on Future Electrocatalyst Designs.

Electrochemical reduction of carbon dioxide (CO2 RR) product distribution has been identified to be dependent on various surface factors, including the Cu facet, morphology, chemical states, doping, etc., which can alter the binding strength of key intermediates such as *CO and *OCCO during reduction. Therefore, in-depth knowledge of the Cu catalyst surface and identification of the active species under reaction conditions aid in designing efficient Cu-based electrocatalysts. This progress report categorizes various Cu-based electrocatalysts into four main groups, namely metallic Cu, Cu alloys, Cu compounds (Cu + non-metal), and supported Cu-based catalysts (Cu supported by carbon, metal oxides, or polymers). The detailed mechanisms for the selective CO2 RR are presented, followed by recent relevant developments on the synthetic procedures for preparing Cu and Cu-based nanoparticles. Herein, the potential link between the Cu surface and CO2 RR performance is highlighted, especially in terms of the chemical states, but other significant factors such as defective sites and roughened morphology of catalysts are equally considered during the discussion of current studies of CO2 RR with Cu-based electrocatalysts to fully understand the origin of the significant enhancement toward C2 formation. This report concludes by providing suggestions for future designs of highly selective and stable Cu-based electrocatalysts for CO2 RR.

Photocatalytic Activity of Cu-based Nanoparticles Synthesized by Glycine-Nitrate Combustion Technique

The copper based nanoparticles was synthesized by glycine-nitrate process (GNP), using copper nitrate trihydrate [Cu(NO3)2 · 3H2O] as main starting materials and glycine [C2H5NO2] as complexant and incendiary agent. The as-prepared powders were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. Results of the photocatalytic degradation of Nonylphenol polyethoxylates (NP9EO) in a custom-made photoreactor indicated that the maximum degradation (more than 94% and 70% TOD removal) of NP9EO occurred with CuO+Cu2O composite catalyst (dosage of 0.3 g/L) when a combination of ultraviolet (UV) irradiation for 600 min, and a heterogeneous system was used.

La estrategia de los nanomateriales en membranas poliméricas para el tratamiento de agua: membranas nanocompuestas

Membrane-based technologies, such as micro (MF), ultra (UF) and nanofiltration (NF), have been widely applied for water treatment applications; however, the limitations of pure polymeric membranes have encouraged the incorporation of inorganic nanomaterials to enhance their performance. Today, nanocomposite membranes have greatly increased the attention of researchers for different water treatment applications, e.g., water purification, wastewater treatment, removal of microorganisms, chemical compounds and heavy metals. To date, different types of nanomaterials have been incorporated into polymeric membranes, such as carbon nanotubes (CNT), zinc oxide (ZnO), graphene oxide (GO), titanium dioxide (TiO 2 ), Ag and Cu-based nanoparticles, to mention just a few. Thereby, the aim of this paper is to show a brief overview about the effect on embedding these materials into polymeric membranes according to the recent literature inputs in the field of water treatment.

A non-enzymatic sensor based on three-dimensional graphene foam decorated with Cu-xCu2O nanoparticles for electrochemical detection of glucose and its application in human serum.

In the present study, a porous structure consisting of three-dimensional graphene (3DG) decorated with Cu-based nanoparticles (NPs) (Cu or Cu-Cu2O) was synthesized in order to develop an enzyme-free electrochemical glucose sensor. Moreover, the effects of Cu-based nanoparticle concentrations on electrochemical properties and glucose detection were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. Cu-based NPs@3DG showed markedly better electrochemical performance in glucose oxidation in alkaline solution compared to 3DG foam. Moreover, Cu-Cu2O NPs@3DG foam with the lowest concentration of Cu precursor showed excellent performance in glucose detection. A high sensitivity of 230.86 μA mM-1 cm-2 was obtained for this electrode in a linear range of 0.8-10 mM (R2 = 0.9951) and a detection limit of 16 μM. This sensor also showed good repeatability (relative standard deviation of 1.02%) and high selectivity (no observation of significant interference by interfering species such as ascorbic acid, dopamine, urea, and acetaminophen). The results confirmed that this electrode could be applied as a feasible and inexpensive non-enzymatic electrochemical glucose sensor.

Broad Spectrum of Antimicrobial Activity of Cotton Fabric Modified with Oxalic Acid and CuO/Cu2O Nanoparticles

This study discusses the possibility of fabrication of textile nanocomposites with antimicrobial activity against antibiotics-resistant bacterial strains and yeast. Modification of cotton fabric with oxalic acid solutions of different concentrations provided free carboxyl groups for binding of Cu2+ -ions from copper (II) sulfate solution which were further reduced with sodium borohydride in alkaline solution. An increase in the concentration of applied oxalic acid resulted in larger amounts of free carboxyl groups on the cotton fibers, Cu2+ -ions uptake and total amounts of Cu-based nanoparticles after reduction. XPS and XRD analyses suggested that nanoparticles mainly consisted of CuO with fractions of Cu2O. Fabricated textile nanocomposites ensured maximum reduction of Gram-negative E. coli ATCC 25922, E. coli NCTC 13846, E. coli ATCC BAA-2469, K. pneumoniae ATCC-BAA 2146 and P. aeruginosa ATCC 27853, Gram-positive bacteria S. aureus ATCC 25923 and S. aureus ATCC 43300 and yeast C. albicans ATCC 24433. Additionally, controlled release of Cu2+ -ions from fabrics into the physiological saline solution was obtained within 24 hours.

Toward Highly Dispersed Mesoporous Bioactive Glass Nanoparticles With High Cu Concentration Using Cu/Ascorbic Acid Complex as Precursor.

Copper (Cu) ions have a variety of advantageous biological functionalities, such as proangiogenic and bactericidal activities. Given the intrinsic biodegradability and biocompatibility, silicate-based mesoporous bioactive glass nanoparticles (MBGNs) are considered as promising platforms for the delivery of Cu ions. However, effective incorporation of Cu into MBGNs still faces challenges, e.g., particle aggregation, the formation of insoluble crystalline Cu-based nanoparticles, and a low loading amount of Cu. We report a novel method to synthesize chemically homogenous and highly dispersed Cu-containing MBGNs (Cu-MBGNs) with tunable Cu concentration by using ascorbic acid/Cu complexes as the precursor of Cu in a microemulsion-assisted sol-gel approach. Cu-MBGNs exhibited a sphere-like shape with a particle size between 100 and 300 nm while their pore size varied from 2 to 10 nm. The inclusion of Cu, regardless of the incorporated concentration, did not significantly affect the morphology of particles. ICP-AES results indicated that the concentration of Cu in the particles could be conveniently tuned from 0 to ~6 mol% by controlling the amount of ascorbic acid/Cu complexes added, while the formation of crystalline Cu-based nanoparticles was avoided. The amorphous feature of Cu-MBGNs was proved by XRD, while the predominant oxidation state of Cu was evidenced to be Cu2+ by XPS. The incorporation of Cu did not inhibit the apatite-forming ability (bioactivity) of the particles in contact with simulated body fluid. Cu-MBGNs exhibited the capability of releasing Cu, Si, and Ca ions over time in the physiological fluid. The concentration of released Cu ions could be controlled by selecting specific Cu-MBGNs of different Cu contents. The dissolution products of most Cu-MBGNs at the dosage of 1, 0.1, and 0.01 mg/mL did not exhibit cytotoxicity, while only 7Cu-MBGN was cytotoxic at the dosage of 1 mg/mL. This study provided a feasible strategy to synthesize highly dispersed amorphous Cu-MBGNs with high Cu concentrations for biomedical applications. The particles exhibit great potential as building blocks for developing composite 3D scaffolds, coatings, and drug carriers, particularly when a large amount of particles incorporated may compromise the properties of (polymer) matrix materials while a relatively high concentration of released Cu ions is still required.

Electrochemical Performance, Microstructure and Chemical Compositions of Cu-Based Nanoparticles Driven by Exsolution of CuFe2O4 in CO2/H2O and H2O Electrolysis

Use of perovskite as a cathode for solid oxide electrolysis cell is limited by its insufficient electrolysis current density or catalytic activity. Most of present perovskites used has a crucial drawback ─ significant segregation of A-site cations (i.e. SrO), likely resulting in the degradation of performance. In this work, spinel oxide of CuFe2O4, which is an alkline earth metal free oxide, is applied as the cathode material to investigate its electrochemical performance, microstructure and chemical composition in the electrolysis of CO2/H2O, steam and CO2. It was found that the exsolution of Cu nanoparticles was observed in CO2/H2O co-electrolysis and the microstructure of CuFe2O4 influenced significantly by operating in different CO2/H2O compositions. Despite the significantly microstructural variation of the CuFe2O4 layer, the cell performs relatively stable electrochemical performance in CO2/H2O and steam electrolysis.

Structure engineering of Cu-based nanoparticles for electrochemical reduction of CO2

Structure engineering represents a powerful strategy for fine tuning the catalytic activity of catalysts. However, correlating the structural properties with catalytic performance is challenging because it is difficult to characterize the surface structure of catalysts, which restricts the use of structure engineering as a tool to optimize the catalytic performance. Herein, we demonstrate the effects of structural properties (e.g., the coordination number and strain) in CO2 reduction reaction (CRR) by focusing on icosahedral, octahedral and cuboctahedral Cu nanoparticles with the diameters from 1.5 to 2.5 nm by density functional theory calculations. A series of linear relations between the binding energy of CRR intermediates and generalized coordination number (GCN) or surface strain are established. We proposed that GCN and strain can be used as the predictive descriptors correlating the structural properties of Cu-based catalysts to its catalytic performance in CRR. By coupling of GCN and strain effects, we predicted that the octahedral Au@Cu core shell nanoparticle could lower the overpotentials to convert CO2 into CH4. We hoped that the presented structure-activity relations will provide useful insight for the design better Cu-based catalysts for CRR by structure engineering.

Composition effect of Cu-based nanoparticles on phytopathogenic bacteria. Antibacterial studies and phytotoxicity evaluation

Nanotechnology can offer new possibilities to the agrochemical sector providing plant protection products that can reduce the quantities and frequency of their use, by getting maximum effect on the target pest. Herein, copper based nanoparticles (Cu-based NPs) of different composition have been hydrothermally synthesized in the presence of the biocompatible surfactants polyethylene glycol (PEG1000), tetraethylene glycol (TEG) and polysorbate 20 (Tween 20) and tested in vitro and in vivo on plant pathogenic bacterial strains. The obtained NPs, Cu@Tween20, Cu@TEG, Cu2O@TWEEN20 and CuO@PEG1000 with sizes 46, 39, 12 and 18 nm respectively were evaluated in vitro as antibacterial agents, against three phytopathogenic Gram-negative bacterial strains, Erwinia amylovora, Xanthomonas campestris and Pseudomonas syringae. Cu NPs were found the most potent in the in vitro studies against all bacterial strains studied, with the lowest MIC value <3 μg/mL for E. amylovora and MBC value 100 μg/mL for P. syringae always in comparison with the wide used conventional pesticide Kocide 2000 35 WG tested at the registered dose of 1000 μg/mL. Further investigation was performed on testing the antibacterial activity of Cu@TWEEN20 and Cu2O@TWEEN20 nanoparticles in vivo in pot experiments under greenhouse conditions on bean plants (P. vulgaris). The penetration of the nanoparticles, labelled with Alizarin Red S, was investigated in plant tissues under a fluorescence microscope while their possible impact on plant photosynthesis and growth has been estimated. Cu-based NPs were found to penetrate the plant tissues without causing any toxicity.

High-temperature stability of copper nanoparticles through Cu@Ag nanostructures

Copper nanoparticles are promising materials for the development of low-cost, low-temperature processable materials for the interconnection technology. Owing to its low price, copper is expected to replace silver in many applications; however, it suffers from its proneness to oxidation, in particular for nanoparticles due to the high surface-to-volume ratio. In this study, we report the synthesis and the characterization by SEM, TEM-EDS, XRD, and TGA of several Cu-based core-shell nanoparticles. We show that their thermal stability in air towards oxidation can be highly enhanced thanks to a simple core–shell fabrication process. Best results were obtained with thermally post-treated 6-nm-silver-thick shells, which allow to improve the oxidation onset temperature up to 206 °C.

Novel Approach for the Electrosynthesis of Copper Nanoparticles

In recent decades, nanoparticles have become a prominent research topic due to their increased catalytic activity, which is attributed to their high surface areas. Although typical synthesis methods yield highly ordered monodispersed particles, they often require harsh synthesis conditions, such as high pressure or temperatures, and the use of high-purity reagents. Moreover, these syntheses are conducted on a microliter basis and are not easily scaled-up.1 Electrochemistry offers an alternative approach for the synthesis of nanoparticles under mild conditions, since most metal reduction potentials occur at less than 2 V. One of the earliest attempts at the electrosynthesis of nanoparticles was conducted by Reetz et al.2 In their work, a palladium sheet was stripped and then reduced ions at a platinum sheet to form nanoparticles. However, these nanoparticles were not monodispersed, and therefore not ideal for catalysis. In the present work, copper nanoparticles have been synthesized in bulk via oxidation of a copper wire into a 99.7:2.3 nitromethane-water solution in the presence of an acid. A copper wire was stripped into solution and monitored via chronocoulometry. Once oxidized, copper ions were stabilized with polyethylene glycol and diffused to the cathode where they underwent electrochemical reduction with the aid of a sonic probe, which dispersed uniform-sized nanoparticles into solution. The size of these nanospheres can be controlled to range from approximately 2 nm to 250 nm due to different amounts of surfactant and copper in solution. In addition, other nanoparticle shapes, namely nanospheres and nanocubes, were obtained when the acid was changed from perchloric acid to hydrochloric acid. These changes in composition of the electrolyte allow for control over the shape and size of nanoparticles. This new method for electrosynthesis of nanoparticles allows for their shape and size control, which can be useful for large-scale, industrial purposes. References Gawande, M.B., Goswami, A., Felpin, F., Asefa, T., Huang, X., Silva, R., Zou, X., Zboril, R., Varma, R. S., Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis. Rev. 2016, 116, 3722–3811.Reetz, M.T. , Helbig W., Size-Selective Synthesis of Nanostructured Transition Metal Clusters. Am. Chem. Soc. 1994, 116, 7401–7402.

The promotion and stabilization effects of surface nitrogen containing groups of CNT on cu-based nanoparticles in the oxidative carbonylation reaction

N-doped carbon nanotubes (NCNTs) with different contents of N were prepared by pre-oxidation and subsequent N-doping strategy and employed as the supports to fabricate Cu-based catalysts for oxidative carbonylation of methanol. The supports and their corresponding catalysts were characterized thoroughly by BET, XPS, XRD, H2-TPR, TEM, N2O chemisorption, CO-TPD, CH3OH-TPD and ICP-OES measurements. It is found that the increase of oxygen containing groups generated by pre-oxidation can effectively improve the content of the nitrogen containing groups during the subsequent N-doping process. The nitrogen containing groups, especially the pyridine N groups, serving as the preferred anchoring site, significantly promotes the dispersion of Cu species. With the increased content of N from 0 to 5.2%, the dispersion of Cu species increases from 11.0 to 21.6% and the space time yield of DMC increases from 150.5 to 1789.6 mg g−1h−1. Moreover, the incorporation of nitrogen containing groups enhances the interaction between Cu species and CNT support, which suppresses the auto-reduction of Cu2+ to Cu+ and Cu0, while improves the anti-agglomeration, anti-oxidation and anti-leaching properties of Cu species. From the perspective of stability, the space time yield of DMC for Cu/CNT decreases from 150.5 to 86.9 mg g−1 h−1 after four consecutive runs, while that of Cu/NCNT200 slightly decreases from 1789.6 to 1557.9 mg g−1 h−1, and the declined degrees are 42.3% and 12.9%, respectively. The superior dispersion, anti-agglomeration, anti-oxidation and anti-leaching properties of Cu species as well as the promotion effect of pyridine N groups are contributed to the increased activity and stability of the Cu/NCNT200 catalyst.

Electrochemical Fragmentation of Cu2O Nanoparticles Enhancing Selective C-C Coupling from CO2 Reduction Reaction.

In this study, we demonstrate that the initial morphology of nanoparticles can be transformed into small fragmented nanoparticles, which were densely contacted to each other, during electrochemical CO2 reduction reaction (CO2RR). Cu-based nanoparticles were directly grown on a carbon support by using cysteamine immobilization agent, and the synthesized nanoparticle catalyst showed increasing activity during initial CO2RR, doubling Faradaic efficiency of C2H4 production from 27% to 57.3%. The increased C2H4 production activity was related to the morphological transformation over reaction time. Twenty nm cubic Cu2O crystalline particles gradually experienced in situ electrochemical fragmentation into 2-4 nm small particles under the negative potential, and the fragmentation was found to be initiated from the surface of the nanocrystal. Compared to Cu@CuO nanoparticle/C or bulk Cu foil, the fragmented Cu-based NP/C catalyst achieved enhanced C2+ production selectivity, accounting 87% of the total CO2RR products, and suppressed H2 production. In-situ X-ray absorption near edge structure studies showed metallic Cu0 state was observed under CO2RR, but the fragmented nanoparticles were more readily reoxidized at open circuit potential inside of the electrolyte, allowing labile Cu states. The unique morphology, small nanoparticles stacked upon on another, is proposed to promote C-C coupling reaction selectivity from CO2RR by suppressing HER.

Experimental determination of viscosity of Water-Glycerine based Cu nano-fluids

Abstract Dispersion of nano sized metallic particles in to conventional base fluids, called nano-fluids, is expected to yield enhanced heat transfer properties. Experimental determination and subsequent correlations of thermo-physical properties such as viscosity, thermal conductivity, specific heat capacity etc., of these nano-fluids become necessary to estimate the heat transfer performance of these nano-fluids. Cu nano-fluids in Water-Glycerine base fluids are prepared at different volume concentrations of Cu nano particles. Two step dispersion synthesis method, without using any surfactant, is used to prepare nano-fluids consisting of Cu nano-particles in Water-Glycerine base fluid. Viscosity of these nano-fluids is determined experimentally at different temperatures of 20, 40, 60 and 80 °C using Brookfield Viscometer. Three different volume concentrations of Cu-based nano-particles in the base fluid are taken as 0.2%, 0.6% and 1.0%. SEM and EDS images show the particle size distribution and elemental analysis of Cu nano-particles. It has been observed that viscosity of nano-fluids increased with increase in particle volume concentration and decreased with increase in fluid temperature. Maximum viscosity value of 3.76 cP for 1.0% vol. concentration at 20 °C and minimum viscosity value of 0.94 cP at 80 °C for 0.2% vol. concentration is obtained for copper nano-fluids. Viscosity for Water-Glycerine base fluid also measured at different temperatures of 20, 40, 60 and 80 °C. This viscosity data of will be useful for the aspiring researchers to predict heat transfer properties of copper nano-fluids.

Bio-inspired Cu-alginate to smartly enhance safety performance and the thermal decomposition of ammonium perchlorate

Simultaneous improvement of the safety performance and thermal decomposition properties of ammonium perchlorate (AP) remains a significant challenge. Therefore, based on inspiration from biological materials, we have prepared a novel copper alginate/ammonium perchlorate (Cu-alginate/AP) composite by facile air atomization. The evaluation of the safety performance and thermal decomposition indicates that these properties were significantly improved. In addition, the possible catalytic mechanism of thermal decomposition of AP is proposed herein. It should be noted that Cu-alginate is a three-dimensional network structure and was uniformly coated on the surface and inside of the AP. When the composite is stimulated by external forces, this unique structure plays a buffering role, absorbing energy and greatly improving safety performance. With increasing temperature, the Cu-alginate easily decomposed and renascent Cu-based nanoparticles were generated by in situ growth. These renascent nanoparticles exhibited excellent catalytic activity for the thermal decomposition of AP. As expected, the bio-inspired material can smartly improve both the safety performance and thermal decomposition of AP. Therefore, these findings provide a promising strategy for the development of composite solid propellants.