Synergistic Effects Of Cu Research Articles

Structural and optical characteristics, and bacterial decolonization studies on non-reactive RF sputtered Cu–ZnO@ graphene based nanoparticles thin films

Graphene oxide (GO) belongs to carbon family with honeycomb structure having hydroxide, carbonyl, and carboxylic moieties at its basal plane. These functionalities are decreased in reduced graphene oxide (rGO), and this boosts the intrinsic properties of GO. Herein, in this work, the effect on physical and chemical properties of GO and rGO in combination with copper-doped zinc oxide (Cu–ZnO) thin films, prepared via DC/RF sputtering, was investigated for the very first time. The deposition of Cu–ZnO over rGO (Cu–ZnO@rGO) showed remarkably superior properties and presented an extension in d-spacing without preferred plane orientation of Cu–ZnO plane, and this was found to be due to its hydrophobic nature. The decrease in band gap of composite thin films was due to the surface electric charge conducted by GO or rGO. The enhanced dielectric constant is attributed due to increase in electron–hole pairs owing to the increase in sp2 hybridization. However, sp2 network was also found to be responsible to provide the conductivity path way which increases the dielectric loss in Cu–ZnO@rGO thin films as compared to that in Cu–ZnO@GO; this might be due to aggregation of Cu–ZnO nanoparticles over the rGO films in comparison with GO as evident from the morphological analysis by AFM. The change in surface chemistry was ascribed with the ratio of COOH, C=O, C–OH and C–C bonding in the Cu–ZnO@GO and Cu–ZnO@rGO thin films as unveiled in their XPS analysis. The developed thin films exhibited enhanced antimicrobial activity against E. coli and E. faecalis which might be due to the synergistic effects of Cu–ZnO with GO or rGO.

A novel hydrogen peroxide sensor based on electrodeposited copper/cuprous oxide nanocomposites.

In this work, copper/cuprous oxide (Cu/Cu2O) nanocomposites were electrodeposited on a fluorine doped tin oxide (FTO) glass substrate for sensitive determination of hydrogen peroxide (H2O2). The Cu/Cu2O nanocomposites were synthesized on FTO at a constant current density of -0.4 mA cm-2 in 0.3 M CuSO4 (pH 9.5) under magnetic agitation. The composition and morphology of Cu/Cu2O nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. Taking advantage of the synergistic effects of Cu and Cu2O, the fabricated Cu/Cu2O/FTO electrode showed excellent electrocatalytic activity towards the oxidation of H2O2. The electrocatalytic performance of Cu/Cu2O/FTO was evaluated by linear sweep voltammetry and amperometry. Under optimized conditions, the developed sensor exhibited a wide linear range of 0.2-2000 μM for the determination of H2O2 with a detection limit of 0.04 μM (S/N = 3). In addition, the proposed H2O2 sensor was successfully applied for the determination of H2O2 in milk samples, indicating that the electrodeposited Cu/Cu2O nanocomposites are promising nanomaterials for electrochemical sensors.

Improved visible-light photocatalytic activity of TiO2 co-doped with copper and iodine

Cu-I-co-doped TiO2 photocatalysts active to visible light absorption were prepared by hydrothermal method and calcined at various temperatures (350 °C, 450 °C, and 550 °C). The co-doped powders at 350 °C displayed the highest experimental Brunauer–Emmett–Teller surface area and lowest photoluminescence intensity, which demonstrated that a decrease in electron–hole recombination process. The synthesis of co-doped TiO2 was performed at this optimized temperature. In the co-doped sample, the Cu2+ doped TiO2 lattice created a major “red-shift” in the absorption edge due to the presence of the 3d Cu states, whereas the amount of red-shift from the I5+ doping in the TiO2 lattice was minor. Interestingly, the presence of Cu2+ species also boosted the reduction of I5+ ions to the lower multi-valance state I− in the TiO2 lattice by trapping the photogenerated electrons, which resulted in effective separation of the photogenerated charges. The Cu-I-co-doped TiO2 was able to degrade methyl orange dye under visible-light irradiation with improved photocatalytic activity compared with the single metal-doped TiO2 and pure TiO2 because of the strong visible light absorption and effective separation of photogenerated charges caused by the synergistic effects of Cu and I co-dopants.

Ecotoxicological and Interactive Effects of Copper and Chromium on Physiochemical, Ultrastructural, and Molecular Profiling in Brassica napus L.

Heavy metal accumulation causes huge environmental problems, particularly in agricultural ecosystems which have deteriorative effects on the yield and quality of crops. Individual copper (Cu) and chromium (Cr) effects have been investigated extensively in plants; however, co-contamination of Cu and Cr induced stress on Brassica napus L. is still unclear. In the present experiment, the interactive effects of Cu and Cr were studied in two B. napus cultivars (Zheda 622 and ZS 758). Results showed that the application of Cr was more toxic than Cu, and their combined stress had shown a significant adverse effect on plant growth. Biomass and photosynthetic pigment were decreased remarkably under all metal treatments. Individual treatments of Cu and Cr and their combination cause the accumulation of ROS and lipid peroxidation. Moreover, the activities of antioxidant enzymes and their mRNA transcription levels, such as catalase (CAT), ascorbate peroxidase, glutathione reductase, superoxide dismutase, and peroxidase, were increased, especially when treated with Cr alone or under Cu+Cr combined treatment in both cultivars, except for the CAT activity which was decreased in both leaves and roots of sensitive cultivar Zheda 622 as compared with their respective controls. Additionally, nonenzymatic antioxidants like reduced and oxidized glutathione showed a differential activity pattern in roots and leaves of both cultivars. A more pronounced modification in chloroplast ultrastructure was observed in both cultivars under Cu+Cr treatment followed by Cr and Cu alone treatments. Furthermore, synergistic effects of Cu and Cr were prominent; this may be due to the enhanced metals uptake under combined treatment, which suggests that Cr and Cu interaction is not competitive but is rather additive and genotypic-dependent.

Determination of Cu2+ ions release rate from antimicrobial copper bearing stainless steel by joint analysis using ICP-OES and XPS

Antibacterial Cu bearing stainless steels (CuSS) have been developed recently and their performance has attracted significant attention widely in biomedical, healthcare and environmental facilities in cross-disciplines. The antibacterial ability and its efficiency of the CuSS are associated to the rate and concentration of Cu2+ ions releases from its surface. The surface properties such as corrosion resistance are also influenced by the amount and the rate of Cu ions released. Thus, the aim of this study focused on the determination of trace release amount of Cu2+ ions from a typical copper bearing 304 stainless steel (304CuSS). Meanwhile, the release of other key elements in the material such as Cr, Fe, Ni were also examined, and found these multiple elemental releases produced a highly synergistic effect on killing bacterium. The release rate of the metals from 304CuSS was conducted by an inductively coupled plasma optical emission spectrometry (ICP-OES). In this study, the commercial 304 stainless steel (304SS) was served as a control material, while the ICP results showed that the Cu2+ ions released from 304CuSS were maintained a constant level with a release rate as low as 0·8 ppb/day/cm2. This phenomenon could be explained by a coordinating role or synergistic effects of Cu, Fe, Cr, and Ni ions. XPS surface composition analysis showed a releases contribution results in day 1 and day 14 that the reduction trend of Cu quantities in through of the surface depth of 304CuSS is consistent and comprehensible.

Metallomics and NMR-based metabolomics of Chlorella sp. reveal the synergistic role of copper and cadmium in multi-metal toxicity and oxidative stress.

Industrial wastewaters often contain high levels of metal mixtures, in which metal mixtures may have synergistic or antagonistic effects on aquatic organisms. A combination of metallomics and nuclear magnetic resonance spectroscopy (NMR)-based metabolomics was employed to understand the consequences of multi-metal systems (Cu, Cd, Pb) on freshwater microalgae. Morphological characterization, cell viability and chlorophyll a determination of metal-spiked Chlorella sp. suggested synergistic effects of Cu and Cd on growth inhibition and toxicity. While Pb has no apparent effect on Chlorella sp. metabolome, a substantial decrease of sucrose, amino acid content and glycerophospholipid precursors in Cu-spiked microalgae revealed Cu-induced oxidative stress. Addition of Cd to Cu-spiked cultures induced more drastic metabolic perturbations, hence we confirmed that Cu and Cd synergistically influenced photosynthesis inhibition, oxidative stress and membrane degradation. Total elemental analysis revealed a significant decrease in K, and an increase in Na, Mg, Zn and Mn concentrations in Cu-spiked cultures. This indicated that Cu is more toxic to Chlorella sp. as compared to Cd or Pb, and the combination of Cu and Cd has a strong synergistic effect on Chlorella sp. oxidative stress induction. Oxidative stress is confirmed by liquid chromatography tandem mass spectrometry analysis, which demonstrated a drastic decrease in the GSH/GSSG ratio solely in Cu-spiked cultures. Interestingly, we observed Cu-facilitated Cd and Pb bioconcentration in Chlorella sp. The absence of phytochelatins and an increment of extracellular polymeric substances (EPS) yields in Cu-spiked cultures suggested that the mode of bioconcentration of Cd and Pb is through adsorption of free metals onto the algal EPS rather than intracellular chelation to phytochelatins.

The selective hydrogenation of ethyl stearate to stearyl alcohol over Cu/Fe bimetallic catalysts

Bimetallic and monometallic catalysts including Cu and/or Fe species were prepared by a co-precipitation method and their catalytic performance was tested for the selective hydrogenation of ethyl stearate to stearyl alcohol. The bimetallic catalysts were observed to be even more active for this selective hydrogenation compared to the monometallic catalysts and their physical mixtures. With a bimetallic catalyst of Cu/Fe (4/1 in mole ratio) reduced at 200°C, a selectivity to the alcohol reached to above 99% at a conversion of 97% in reaction for 4h at 230°C, 3.0MPa. Effects of composition and reduction temperature on the catalytic performance were studied and the properties of catalysts prepared under different conditions were examined by XRD, TPR, N2 physisorption, and SEM. The relationship of the performance with the properties of the catalysts was discussed, along with the conditions under which synergistic effects of Cu and Fe species appeared and caused the enhancement of the catalytic performance.

Effect of anions on the structure and catalytic properties of a La-doped Cu-Mn catalyst in the water-gas shift reaction

AbstractEffects of the anion type on the structure, thermal stability, and catalytic performance of La-doped Cu-Mn catalysts prepared by co-precipitation were characterized by X-ray diffraction, Brunauer-Emmett-Teller, temperature-programmed reduction, temperature-programmed reduction of oxidized surfaces, and temperature-programmed desorption. The Cu-Mn catalyst was tested for the water-gas shift (WGS) reaction. The main crystalline phase of samples prepared with sulfate, acetate, chloride, and nitrate as the starting materials was a Cu1.5Mn1.5O4 spinel structure, following the WGS reaction, the main crystalline phases were transformed into Cu and MnO. The sample prepared with acetate as the starting material showed the most obvious MnCO3 characteristic diffraction peaks, with better synergistic effects of Cu and MnO, increased adsorption of CO2 and improved dispersion of Cu on the catalyst surface; also, the best thermal stability and the highest low temperature catalytic activity were observed. The sample prepared with nitrate as the starting material maintained high thermal stability and catalytic performance in the range of 400°C to 450°C, but CO conversion decreased below 350°C. Catalytic performance of the sample prepared with sulfate and chloride as the starting materials was poor, ranging from 200°C to 450°C.

Effects of Five Metals on the Evolution of Hydrogen Sulfide, Methanethiol, and Dimethyl Sulfide during Anaerobic Storage of Chardonnay and Shiraz Wines

The synergistic effects of Cu, Fe, Mn, Zn, and Al on the evolution of different volatile sulfur compounds (VSCs) in a Chardonnay and a Shiraz wine have been investigated. The evolution of H2S, MeSH, and DMS were influenced by metal addition, and in some instances, a combination of metals was responsible for the largest variation in the concentration of VSCs. The metals and metal combinations associated with significant changes in VSC concentrations in both Chardonnay and Shiraz samples after anaerobic storage were Cu, Fe, Zn, Al, Cu*Fe, Cu*Mn*Al, and Cu*Zn*Al for H2S; Cu, Zn, Fe*Mn, and Cu*Fe*Mn for MeSH; and Al and Zn*Al for DMS. The effect of Cu addition on the evolution of VSCs has previously been shown; however, this investigation has demonstrated that metals other than Cu could also be involved in the catalytic release of VSCs and that the interactions and combinations of metals are important. In some instances, the metal effect was reversed, associated with significant decreases during high oxygen conditions and with significant increases during low oxygen conditions.

Synergistic effects of Cu and Ni on nanoscale precipitation and mechanical properties of high-strength steels

There is an increasing demand for ultrahigh-strength ferritic steels strengthened by nanoprecipitates. Improvement of the precipitation strengthening response requires an understanding of the nanoscale precipitation mechanisms. In this study, the synergistic effects of Cu and Ni on nanoscale precipitation and mechanical properties of ferritic steels were thoroughly investigated, and new steels with ultrahigh strength and high ductility have been developed. Our results indicate that Ni effectively increases the number density of Cu-rich nanoprecipitates by more than an order of magnitude, leading to a substantial increase in yield strength. It appears that Ni decreases both the strain energy for nucleation and the interfacial energy between the nucleus and the matrix, thereby decreasing the critical energy for nucleation of Cu-rich nanoprecipitates. Cu and Ni are also found to be beneficial to grain-size refinement, resulting from lowering the austenite-to-ferrite transformation temperature, as determined from thermodynamic calculations. In addition, the strengthening mechanisms of Cu and Ni were quantitatively evaluated in terms of precipitation strengthening, grain refinement strengthening and solid-solution strengthening. The current findings shed light on the composition–microstructure–property relationships in nanoprecipitate-strengthened ferritic steels.

Effects of copper and sulfur additions on machinability behavior of high performance austenitic stainless steel

Flank wear, cutting force, the number and area of sulfides, and shear strain rate were measured to elucidate the synergistic effects of Cu and S additions on machinability of high-performance austenitic stainless steels with a basic composition of Fe-18 %Cr-21 %Ni-3.2 %Mo-1.6 %W-0.2 %N. As Cu and S content increased, flank wear and cutting force decreased. While Cu and S content increased, shear strain rate and shear angle increased. The tool life for an alloy with 3.1 %Cu + 0.091 %S was about four times longer than that of an alloy with 0.06%Cu + 0.005 %S due to high shear strain rate generated by Cu addition, lubricating films of ductile (Mn, Cr)S sulfides adhering to tool surface and low cutting force resulting from thinly and lengthily continuous sulfides formed in chips during machining.

Synergistic effects of Cu(II) and dimethylammonium 2,4-dichlorophenoxyacetate (U46 D fluid) on PM2 DNA and mechanism of DNA damage.

Dimethylammonium 2,4-dichlorophenoxyacetate (2,4-D . DMA) induced strand breaks in PM2 DNA when incubated with CuCl2, whereas 2,4-D . DMA alone or CuCl2 alone did not show any or only a negligible effect. The formation of single strand breaks increased linearly with time and concentration of 2,4-D . DMA. Neocuproine, a specific Cu(I) chelator totally prevented strand break formation. So did catalase (up to 100 mM 2,4-D . DMA), but DMSO had only a small protective effect. 2,4-Dichlorophenol, CO2 and formaldehyde were detected as reaction products of 2,4-D and CuCl2. From these results a redox reaction of Cu(II) and 2,4-D is proposed, which could explain the DNA damaging properties of CuCl2/2,4-D . DMA.