Number Of Cu2 Research Articles

Nanosized Cu-SSZ-13 and Its Application in NH3-SCR

Nanosized SSZ-13 was synthesized hydrothermally by applying N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as a structure-directing agent. In the next step, the quantity of TMAdaOH in the initial synthesis mixture of SSZ-13 was reduced by half. Furthermore, we varied the sodium hydroxide concentration. After ion-exchange with copper ions (Cu2+ and Cu+), the Cu-SSZ-13 catalysts were characterized to explore their framework composition (XRD, solid-state NMR, ICP-OES), texture (N2-sorption, SEM) and acid/redox properties (FT-IR, TPR-H2, DR UV-Vis, EPR). Finally, the materials were tested in the selective catalytic reduction of NOx with ammonia (NH3-SCR). The main difference between the Cu-SSZ-13 catalysts was the number of Cu2+ in the double six-membered ring (6MRs). Such copper species contribute to a high NH3-SCR activity. Nevertheless, all materials show comparable activity in NH3-SCR up to 350 °C. Above 350 °C, NO conversion decreased for Cu-SSZ-13(2–4) due to side reaction of NH3 oxidation.

Exfoliated near infrared fluorescent silicate nanosheets for (bio)photonics

Imaging of complex (biological) samples in the near-infrared (NIR) is beneficial due to reduced light scattering, absorption, phototoxicity, and autofluorescence. However, there are few NIR fluorescent materials known and suitable for biomedical applications. Here we exfoliate the layered pigment CaCuSi4O10 (Egyptian Blue, EB) via ball milling and facile tip sonication into NIR fluorescent nanosheets (EB-NS). The size of EB-NS can be tailored to diameters <20 nm and heights down to 1 nm. EB-NS fluoresce at 910 nm and the fluorescence intensity correlates with the number of Cu2+ ions. Furthermore, EB-NS display no bleaching and high brightness compared with other NIR fluorophores. The versatility of EB-NS is demonstrated by in-vivo single-particle tracking and microrheology measurements in Drosophila melanogaster embryos. EB-NS can be uptaken by plants and remotely detected in a low-cost stand-off detection setup. In summary, EB-NS have the potential for a wide range of bioimaging applications.

Spectroscopic and electrical investigations of copper ions in PbO–GeO2 glasses

Abstract Small concentrations of copper oxide doped PbO–GeO2 glasses were prepared by melt quenching technique. The characteristics of the samples were analyzed by X-ray diffraction, scanning electron microscopy and DSC techniques. The analysis of XRD spectra established the disorderly nature of the glass composition and no specialized crystalline species are observed. The surface morphology of the glass samples has also been systematically investigated by scanning electron microscopy. The optical absorption and ESR spectral studies have revealed probable presence of Cu2+ ions that act as modifiers and induce non-bridging oxygens (NBO’s) in the glass network. The observed decrease in the optical band gap with the increase in the concentration of CuO is attributed to the gradual reduction of Cu2+ ions into Cu+ ions. The presence of GeO4, GeO6, Ge–O–Ge and PbO4 structural blocks has been verified by means of IR spectral bands. The overall inference of optical, ESR and IR studies is that the Cu2+ ions might have changed from ionic environment to covalent environment progressively. The dielectric parameters viz., dielectric constant, e′, loss, tan δ, and ac conductivity, σac, were studied by varying frequency and temperature. The values of e′ and loss tan δ were enhanced where as σac, values are dipped. It is proved that the more is the number of Cu2+ ions in the samples, the higher are the values of dielectric parameters.

Physico-chemical Properties of the Molten CuCl–CuCl2 System: Experiment, Thermodynamics and Molecular Dynamics Simulations

The molten CuCl–CuCl2 system was studied by means of the maximum bubble pressure method, thermodynamics and molecular dynamics simulations at temperatures of 835, 866, 905 and 943 K. The equilibrium constant of CuCl2 decomposition has been determined with thermodynamic simulation. The density and molar volume of the CuCl–CuCl2 system were established as a function of composition. Some evidence of ideality of CuCl–CuCl2 solutions was observed. The molar volumes of pure liquid CuCl2 are equal to 44.64, 46.23, 46.55 and 46.81 cm3·mol−1 at 835, 866, 905 and 943 K, correspondingly. Radial distribution functions, coordination numbers, self-diffusion coefficients and trajectories of motion were obtained by molecular dynamics simulation. For this reason a new pair potential for Cu2+–Cl− pair has been designed. The coordination number of Cu2+ by Cl− is about 4. This value corresponds to literature data with regards to this coordination. The self-diffusion coefficients are close to diffusion coefficients measured in molten salts solutions.

Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for NH3-SCR (I): The impact of 950 °c hydrothermal aging time

The hydrothermal stability of Cu/SAPO-34 catalysts under different treatment time (3 h, 6 h, 12 h) at 950 °C has been investigated to understand their framework collapse and deactivation mechanism for NO reduction by ammonia selective catalytic reduction (NH3-SCR). It was seen that SCR activities declined dramatically after 12 h aging, and XRD results showed this treatment led to crystallinity decline since 3 h. Furthermore, zeolites crystal started to transform into SiO2 and AlPO4 phase since 6 h. NMR results further proved the formation of SiO2 and AlPO4·NH3-TPD and ex-situ DRIFTS results revealed the breakage of Si-OH-Al bonds and the decline of the number of Brønsted acid sites, meanwhile, H2-TPR and EPR results proved that the number of Cu2+ species decreased and the location of Cu2+ species changed after this treatment, which were mainly responsible for declined SCR reaction rates.

Understanding of potassium promoter effects on oxychlorination of ethylene by operando spatial-time resolved UV–vis–NIR spectrometry

Obtaining the comprehensive kinetics of elementary reaction steps in catalytic redox cycles remains a challenge. We report here an operando study by combined mass and UV–vis–NIR spectrometry to obtain kinetic data for reduction and oxidation steps in the catalytic cycle of ethylene oxychlorination on potassium-promoted CuCl2/Al2O3 catalysts and understand the catalytic consequences of potassium promotion for ethylene oxychlorination through a comprehensive kinetic analysis of the catalytic cycle. The results demonstrate that the Cu2+ and Cu1+ concentration, the number of active sites, and the activity of the active sites are highly dynamic, depending on the catalyst composition and the operating conditions. A pseudo-steady-state approach was applied to deconvolute the effect of promoters on the oxychlorination reaction into the effects on the individual reduction and oxidation steps, as well as their consequences in steady state in terms of the active site number and the site activity. It has been found that the rate of oxidation of Cu1+ by oxygen is much lower than the rate of reduction of Cu2+ by ethylene at relatively high Cu2+ content. This resulted in CuCl dominating at the surface and thus a low rate in the steady state on the neat CuCl2 catalyst. Potassium promotion increased the reducible Cu2+ content from 0.61mol/molCu of the neat CuCl2 catalyst to 0.8mol/molCu by reducing the interaction between Cu and the alumina support. Further increasing the potassium loading from 0.92 to 1.54wt.% decreases the reducible Cu2+ from about 0.8 to 0.7mol/molCu. Potassium promotion significantly increased the site activity of the Cu1+ oxidation, but decreased the site activity of the Cu2+ reduction by ethylene. The positive effect of potassium promotion is due to the increase in the number of Cu2+ active sites, which was more significant than the negative impact on turnover frequency (TOF); thus, potassium promotion increased the steady-state reaction rate. In addition, owing to the kinetic balance between the higher Cu1+ oxidation rate and the lower Cu2+ reduction rate, potassium promotion yielded an increased Cu oxidation state with Cu2+ dominating the steady-state catalyst surface. This led to remarkably improved stability of CuCl2 catalysts.

CHANGE IN CONTENT OF GLYCOPROTEINS ON THE SURFACE OF ENDOTHELIAL CELL CULTURE EA.HY 926 AND INTIMA OF INTERNAL CAROTID ARTERIES UNDER THE INFLUENCE OF MAGNESIUM OROTATE

Aim. To study changes in the glycoproteins content in the glycocalyx of endothelial cells under the influence of magnesium orotate. Material and methods. Endotheliocytes of cell culture EA.hy 926 were examined before and after addition of the magnesium orotate to the culture medium. Intimal endothelium of internal carotid arteries, fragments of which were obtained by sequential execution of bilateral resection of the arteries before and after course of treatment with magnesium orotate was also investigated. Anthony’ method (1931), designed for the study of glycoproteins in the bacteria capsule and adapted by L.V. Didenko (2013) for eukaryotes was used to detect glycoproteins. The scanning electron microscopy with simultaneous x-ray microanalysis was applied. Results. Total number of Cu2+-signals per one scanning field in the mapping of samples for Cu2+ as the indirect index of proteoglycan content in EA.hy 926 endothelial cell culture before incubation with magnesium orotate was 6928±124, and after incubation with magnesium orotate – 7592±131. Number of Cu2+-signals on the surface of the internal carotid artery intima before treatment with magnesium orotate was 5015±407, and after treatment – 6100±152 per one scanning field. Conclusion. A significant increase in the content of glycoproteins on the surface of EA.hy926 endothelial cell culture (+10%) and internal carotid artery intima (+22%) under the influence of magnesium orotate was found.

Cation distribution in Cu(Cr2–x Al x )O4 and Cu(Fe2–x Al x )O4 according to neutron-diffraction studies and their catalytic properties in the water-gas shift reaction

The neutron structural analysis of Cu(Cr2 − x Al x )O4 and Cu(Fe2 − x Al x )O4 (0 ≤ x ≤ 2) nanopowders is performed. The samples are prepared by the thermal decomposition of mixed hydroxy compounds at 900°C. Different spinel phases are shown to form in Cu(Cr2 − x Al x )O4: a tetragonally distorted phase when x ≤ 1.0, a cubic phase when x > 1.25, and a mixture of both phases when 1 < x < 1.25. As Al3+ ions substitute Cr3+ ions, a number of Cu2+ ions move from tetrahedral spinel sites to octahedral ones: the degree of inversion δ changes from 0 for CuCr2O4 to ≈0.4 for CuAl2O4. In the Cu(Fe2 − x Al x )O4 system, the cubic spinel forms at all x, except x = 0. The degree of inversion δ varies from 1 for CuFe2O4 to ≈0.4 for CuAl2O4 as Al3+ ions substitute Fe3+ ions. The change in the activation energy of the water-gas shift reaction correlates with the inversion of Cu-containing spinels.

Toxicity Assessment and Selective Leaching Characteristics of Cu-Al-Ni Shape Memory Alloys in Biomaterials Applications

Cu-Al-Ni shape memory alloys (SMAs) possess two-way shape memory effects, superelasticity, and damping capacity. Nonetheless, Cu-Al-Ni SMAs remain promising candidates for use in biomedical applications, as they are more economical and machinable than other SMAs. Ensuring the biocompatibility of Cu-Al-Ni SMAs is crucial to their development for biomedical applications. Therefore, this study aimed to assess the toxicity of Cu-Al-Ni SMAs using a Probit dose-response model and augmented simplex design. In this study, the effects of Cu2+, Al3+ and Ni2+ metal ions on bacteria (Escherichia coli DH5α) using Probit dose-response analysis and augmented simplex design to assess the actual toxicity of the Cu-Al-Ni SMAs. Extraction and repetition of Escherichia coli DH5α solutions with high Cu2+ ion concentrations and 30-hour incubation demonstrated that Escherichia coli DH5α was able to alter its growth mechanisms in response to toxins. Metal ions leached from Cu-Al-Ni SMAs appeared in a multitude of compositions with varying degrees of toxicity, and those appearing close to a saddle region identified in the contour plot of the augmented simplex model were identified as candidates for elevated toxicity levels. When the Cu-13.5Al-4Ni SMA plate was immersed in Ringer's solution, the selective leaching rate of Ni2+ ions far exceeded that of Cu2+ and Al3+. The number of Cu2+, Al3+ and Ni2+ ions leached from Cu-Al-Ni SMAs increased with immersion time; however, at higher ratios, toxicity interactions among the metal ions had the effect of gradually reducing overall toxicity levels with regard to Escherichia coli DH5α. The quantities of Cu2+, Al3+ and Ni2+ ions leached from the Cu-13.5Al-4Ni SMA plate increased with immersion time, the toxicity interactions associated with these compositions reduced the actual toxicity to Escherichia coli DH5α.

Electron paramagnetic resonance, optical absorption and photoluminescence properties of Cu2+ ions in ZnO–Bi2O3–B2O3 glasses

Glass of the composition 23B2O3–5ZnO–72Bi2O3–xCuO (where, x=0.0003, 0.0012 and 0.003at%, in excess) were prepared by a melt-quench technique. The effects of the copper ions on the structural and optical properties of ZnO–Bi2O3–B2O3 glass matrix were analyzed using various spectroscopic techniques. The infrared spectra showed the presence of some bands that are assigned to vibrations of Bi–O bonds from BiO6 octahedral units and B–O bonds from BO3 and BO4 units. The electron paramagnetic resonance spectra revealed the presence of Cu2+ ions in the glass structure in an axially distorted octahedral environment. The number of Cu2+ ions participating in resonance and its paramagnetic susceptibility has been evaluated. The UV–vis spectra show a broad absorption band at 785nm and another band at 438nm which are due to d-d transitions of Cu2+ ions. These glasses are found to exhibit visible and near infrared luminescence bands centered at 548 and 652, and 804nm when excited at 400 and 530nm, respectively. The luminescence centers are supposed to be caused by the lower valence state of bismuth, such as Bi2+ and Bi+ ions, generated during in-situ redox reactions.

Copper and the structural biology of the prion protein

PrP (prion-related protein) is a cell-surface Cu(2+)-binding glycoprotein which, when misfolded, is responsible for a number of transmissible spongiform encephalopathies. The co-ordination geometry, stoichiometry and affinity of Cu(2+) for PrP are the subject of much debate. In the present paper, we review the recent progress we have made in these areas. As many as six Cu(2+) ions bind to PrP with submicromolar affinity. Initially, two Cu(2+) ions bind to full-length PrP in the amyloidogenic region, between the octarepeats and the structured domain, at His(95) and His(110). Only subsequent Cu(2+) ions bind to single histidine residues within the octarepeat region. Competitive chelators have been used to determine the affinity of the first molar equivalent of Cu(2+) bound to full-length PrP; this approach places the affinity in the nanomolar range. The affinity and number of Cu(2+)-binding sites support the suggestion that PrP could act as an antioxidant by binding potentially harmful Cu(2+) ions and sacrificially quenching of free radicals generated as a result of copper redox cycling. Finally, the effect of Cu(2+) on the prion structure and misassembly into oligomers and fibres is discussed.

Rice Albumin N-Terminal (Asp-His-His-Gln) Prevents against Copper Ion-Catalyzed Oxidations

Chromatographic separation of soluble proteins from rice (Oryza sativa L.) yielded a major albumin protein (16 kDa), with the DHHQVYSPGEQ sequence in the N terminus, showing antioxidant action. The rice albumin was more potent than other rice proteins in preventing Cu2+-induced low-density lipoprotein (LDL) oxidation. Additionally, it also exhibited a remarkable suppression of HOCl oxidation. In a further study, albumin inhibited Cu2+-induced oxidation of LDL in a stoichiometric manner with an EC50 value of 4.3 microM, close to that of serum albumins. Moreover, after digestion with trypsin or chymotrypsin, it maintained its antioxidant action. In an experiment to see the involvement of the N terminus in antioxidant action, a synthetic tetrapeptide, equivalent to the N terminus DHHQ, was found to inhibit Cu2+-induced LDL oxidation or degradation of apolipoprotein B, similar to that of rice albumin. In mechanistic analyses, the action of rice albumin or tetrapeptide is primarily due to the removal of Cu2+, as suggested from its inhibitory effect on Cu2+/diphenylcarbohydrazide (DPCH) complex formation. However, despite its similar inhibitory effect on Cu2+-induced oxidation of LDL, rice albumin was less effective than serum albumin in inhibiting Cu2+/DPCH complex formation, suggesting that the number of Cu2+-binding sites in rice albumin may be less than that in serum albumins. Taken together, rice albumin exerts a potent preventive action against Cu2+-induced oxidations, which is due to the Cu2+ binding by DHHQ in the N-terminal sequence. Such a role as a Cu2+ chelator would add up to the application of rice albumin protein.

Mixed alkali effect in Li2O–Na2O–B2O3 glasses containing CuO – An EPR and optical study

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of 0.5mol% CuO doped xLi2O–(30−x)Na2O–69.5B2O3 (5⩽x⩽25) mixed alkali glasses have been investigated. The EPR spectra of all the investigated samples exhibit resonance signals characteristic of Cu2+ ions in octahedral sites with tetragonal distortion. It is found that the spin-Hamiltonian parameters do not vary much with x. It is interesting to observe that the number of Cu2+ ions participating in resonance (N) and its paramagnetic susceptibility (χ) exhibits the mixed alkali effect with composition. It is observed that the temperature dependence of paramagnetic susceptibility (χ) obeys Curie–Weiss law. The paramagnetic Curie temperature (θp) is negative for the investigated sample, which suggests that the copper ions are antiferromagnetically coupled by negative super exchange interactions at very low temperatures. A broad band corresponding to the transition 2B1g→2B2g in the optical absorption spectrum shows a blue shift with x. By correlating the EPR and optical absorption data, the molecular orbital coefficients α2 and β12 have been evaluated. It is interesting to observe that the optical band gap (Eopt) and Urbach energies (ΔE) exhibit the mixed alkali effect. The theoretical values of optical basicity (Λth) have also been evaluated.

PURIFICATION AND CHARACTERIZATION OF POLYPHENOL OXIDASE FROM POTATO: I. PURIFICATION AND PROPERTIES

Polyphenol oxidase (Isozyme I) from potato was extracted and purified with ammonium sulfate, cation-exchange (Bio-Rad Bio-Scale S2) and Sephadex G-100 column chromatography. The enzyme was purified 11.8 fold resulting in a specific activity of 250.3 units/mg. Optimum pH of the enzyme was 6.6. Optimum temperature of the enzyme was 40C and its half-life was 0.8 min at 70C. The Kmfor catechol, pyrogallol, 4-methyl catechol, caffeic acid and L-DOPA were 4.11 mM, 0.61 mM, 0.78 mM, 0.50 mM and 32 mM, respectively. However, monophenols such as tyrosine, p-cresol and 1-naphtol did not show any activity. Data for Vmax/Km which represents catalytic efficiency show that 4-methyl catechol has the highest value. The molecular weight of the active enzyme was 86,000 Da, composed of two identical subunits. The number of Cu2+ ions bound was found to be 2 per enzyme molecule.

Ion transport in copper boromolybdate glasses

Copper ion conducting glasses with mixed glass formers and having composition CuI+Cu2O+MoO3+B2O3 have been studied. The variation of room-temperature conductivity with glass composition has been found to be controlled by the variation in mobility of the mobile species and the number of Cu2+ ions present in the glass samples. The temperature variation of conductivity has been found to follow an Arrhenius relation.

Paramagnetic resonance studies of Cu2+ doped in NH4Br

Electron Paramagnetic Resonance studies of Cu2+ doped in NH4Br single crystals have been carried out for the first time. The room temperature data reveal that Cu2+ ions go predominantly to interstitial sites having square planar co-ordination of four Br− ions. For this type of complexes the bromine: superhyperfine structure: is observed on the normal hyperfine structure lines of copper. Existence of other weak spectra indicates that a relatively few Cu++ ions go substitutionally to (NH4)+ ions, and are probably associated with a first or a second nearest neighbour cation vacancy, among the two, the latter being more predominant. However, the low temperature studies corresponding to the tetragonal phase of NH4Br indicate that a number of Cu2+ ions at interstitial sites get readjusted to the lattice sites after phase transformation. The spectra in both the phases are analysed by the usual spin Hamiltonian method.