Ratio Of Cu Research Articles

Room temperature ferromagnetism in Cu2+ doped TiO2 nanocrystals: The impact of their size, shape and dopant concentration

Cu2+ doped TiO2 nanocrystals were synthesized using dispersions of titania nanotubes in the presence of Cu2+ ions as a precursors. The morphologies of nanotubular titania precursors and resulted Cu2+ doped TiO2 nanocrystals were characterized by TEM. Structural and optical properties were studied by XRPD analysis and UV–vis spectroscopy in reflectance mode, respectively. Their magnetic properties were investigated using SQUID magnetometer. Tetragonal anatase crystalline structure was confirmed in all synthesized samples. Polygonal (d∼15nm) and spheroid like (length, up to 90nm) Cu2+ doped TiO2 nanocrystals in samples synthesized at different pHs were observed by TEM. Ferromagnetic ordering with almost closed loop (Hc∼200Oe) was detected in all Cu2+ doped TiO2 nanoparticle films. The saturation magnetization values varied depending on the Cu2+ concentration, nanoparticles shape, size and consequently different number of oxygen vacancies. This study revealed possibility to control magnetic ordering by changing the shape/aspect ratio of Cu2+ doped TiO2 nanocrystals.

Oleylamine‐Assisted Phase‐Selective Synthesis of Cu2−xS Nanocrystals and the Mechanism of Phase Control

Environmentally friendly Cu2−x S compounds exist in many different mixed phases in nature, while their nanoscale counterparts can be pure phase with interesting localized surface plasmon resonance properties. Because of the complexity of composition and phase, controllable synthesis of Cu2−x S nanocrystals becomes an important scientific issue in colloidal chemistry. In this work, a hot‐injection method is developed to synthesize Cu2−x S nanocrystals by injecting a sulfur precursor into a copper precursor using oleylamine and octadecene as solvents. By varying the reaction parameters (temperature, volume ratio of oleylamine/octadecene, molar ratio of Cu/S in the precursors), hexagonal CuS, monoclinic Cu1.75S, and rhombohedral Cu1.8S, nanocrystals can be selectively synthesized, providing a platform to illustrate the mechanism of crystal phase control. The crystal phase control of Cu2−x S nanocrystals is oleylamine‐determined by controlling the molar ratio of Cu/S in the reaction precursors as well as the ratio of Cu2−x S clusters/Cu+ in the subsequent reaction. More importantly, temperature plays an important role in varying the molar ratio of Cu/S and Cu2−x S clusters/Cu+ in the reaction system, which significantly influences the crystal phase of the resulting Cu2−x S nanocrystals. The understanding into crystal control provides a guideline to realize reproducible phase‐selective synthesis and obtain well‐defined high‐quality materials with precise control.

Preparation of Cu<sub>2</sub>O/TiO<sub>2</sub> Heterostructure with High Visible-Light Photocatalytic Activity

The Cu2O/TiO2heterostructure nanocomposites photocatalysts with different molar ratios of Cu2+/Ti4+were successfully synthesized by a simple hydrothermal procedure. The obtained samples were characterized by XRD, SEM, UV-vis DRS in order to detect the composition, the shape and the property. The photocatalytic activity of Cu2O/TiO2nanocomposites was evaluated by the degradation of methyl orange (MO) as a model compound. The experimental results showed that the prepared Cu2O/TiO2nanocomposites exhibited higher photocatalytic activity for the degradation of MO than the pure Cu2O and the commercial anatase TiO2under visible light irradiation.

Dendritic copper-cobalt nanostructures/reduced graphene oxide-chitosan modified glassy carbon electrode for glucose sensing

A novel nonenzymatic glucose sensor was developed by electrodepositing dendritic copper-cobalt nanostructures (Cu-Co NSs) on glassy carbon electrode (GCE) which was modified by reduced grapheme oxide-chitosan (RGO-CHIT) nanocomposites. The electrochemical behaviors and electrocatalytic performances of the sensor towards oxidation of glucose were evaluated by cyclic voltammograms, chronoamperometry and amperometric method. Compared to sensors based on monometal Cu or Co NSs, the sensor based on bimetal Cu-Co NSs exhibits good electrocatalytic activity towards oxidation of glucose. The effects of electrodeposition time and the ratio of Cu2+ and Co2+ in an electrodeposition solution on the electrocatalytic performance of the Cu-Co NSs sensor were explored in detail. The best catalytic activity towards oxidation of glucose can be achieved under an optimized condition: electrodepositing time of 2600 s and the Cu2+/Co2+ molar ratio of 2:1. The catalytic current density is linear to the glucose concentration in the range of 0.015–6.95mM (r=0.9947) with a sensitivity of 1921μAcm−2mM−1, and a detection limit of 10μM. The good catalytic activity, high sensitivity and good stability indicate that the newly developed sensor based on the dendritic Cu-Co NSs/RGO-CHIT/GCE is a promising sensor for application in real samples.

Synthesis of Cu-Poor Copper-Indium-Gallium-Diselenide Nanoparticles by Solvothermal Route for Solar Cell Applications

Copper-indium-gallium-diselenide (CIGS) thin films were fabricated using precursor nanoparticle ink and sintering technology. The precursor was a Cu-poor quaternary compound with constituent ratios ofCu/(In+Ga)=0.603,Ga/(In+Ga)=0.674, andSe/(Cu+In+Ga)=1.036. Cu-poor CIGS nanoparticles of chalcopyrite for solar cells were successfully synthesized using a relatively simple and convenient elemental solvothermal route. After a fixed reaction time of 36 h at 180°C, CIGS nanocrystals with diameters in the range of 20–70 nm were observed. The nanoparticle ink was fabricated by mixing CIGS nanoparticles, a solvent, and an organic polymer. Analytical results reveal that the Cu-poor CIGS absorption layer prepared from a nanoparticle-ink polymer by sintering has a chalcopyrite structure and a favorable composition. For this kind of sample, its mole ratio of Cu : In : Ga : Se is equal to 0.617 : 0.410 : 0.510 : 2.464 and related ratios ofGa/(In+Ga)andCu/(In+Ga)are 0.554 and 0.671, respectively. Under the condition of standard air mass 1.5 global illumination, the conversion efficiency of the solar cell fabricated by this kind of sample is 4.05%.

Bis(8-quinolinolato)copper(II) immobilized onto amino-modified SBA-15 for the selective oxidation of benzyl alcohol

Bis(8-quinolinolato)copper(II) immobilized onto amino-modified SBA-15 catalyst has been synthesized through a stepwise procedure. The characterization results indicated that the BET surface area, total pore volume and average pore width decrease after stepwise modification of SBA-15, while the structure remains intact. The molar ratio of Cu2+/8-quinolinol is ca. 1/2 in the synthesized material. Catalytic tests showed that Cu-Q-SBA-15 catalyzes the oxidation reaction well with 36.2 % conversion of benzyl alcohol and 85.2 % selectivity to benzaldehyde when water is used as the solvent.

A Copper(II) Schiff base complex immobilized onto SBA-15 silica for selective oxidation of benzyl alcohol

A copper(II) Schiff base complex has been immobilized onto SBA-15 silica through a stepwise procedure and tested as an oxidation catalyst. BET surface area, total pore volume and average pore width of the SBA-15 all decrease after stepwise modification of SBA-15, while the structure of the support remains intact. The molar ratio of Cu2+/Schiff base is ca. 1/2 in the synthesized material. Catalytic tests showed that the supported copper complex catalyzes the oxidation of benzyl alcohol with 30 % conversion and 89 % selectivity to benzaldehyde when water is used as the solvent.

Preparation of Nano-Copper Oxide and Removal of Hydrogen Sulfide under Room Temperature

In this paper, nanocopper oxide is prepared by complexing-precipitate, and the influence of different process parameters on the removal of H2S performance are studied, and make a comparison for two other methods. The results indicate that different complexing agent, the molar ratio of Cu2+/OH- and calcination temperature, etc., effect the desulfurization activity of nanocopper oxide. nanocopper prepared under optimum conditions (the complexing agent is ammonia, the molar ratio of Cu2+/OH- is 1:3.0, calcination temperature is 400 °C) exhibits best desulfurization activity with a H2S breakthrough time of 235 min, this is much longer than that prepared by hydrothermal method and sol-gel method with breakthrough time of H2S only 20 min and 50 min, respectively; XRD analysis shows that the big grain size of nanocopper oxide and low purity are not in favor of H2S adsorption at room temperature.

Dendrimer-encapsulated copper as a novel oligonucleotides label for sensitive electrochemical stripping detection of DNA hybridization

This paper describes the synthesis and characterization of a novel electrochemical label for sensitive electrochemical stripping detection of DNA hybridization based on dendrimer-encapsulated copper. The generation 4.5 (G 4.5) carboxyl-terminated poly(amidoamine) dendrimer with a trimesyl core was used as a template for synthesis of Cu2+/dendrimer nanocomposites (Cu-DNCs). Ratios of Cu2+/dendrimer were optimized in order to obtain stable nanocomposites with maximal copper loading in the interior of a polymeric shell. Cu-DNCs labeled DNA probe was employed for determining a target ssDNA immobilized on multi-walled carbon nanotubes-modified glassy carbon electrode (GCE) based on a specific hybridization reaction. The hybridization events were monitored by electrochemical detection of Cu anchored on the hybrids after the release in a diluted nitric acid by anodic stripping differential pulse voltammetry (ASDPV). The results showed that only a complementary sequence could form a dsDNA with the Cu-DNCs DNA probe and give an obvious electrochemical signal. The non-complementary sequence exhibited negligible signal change compared with the blank measurement (means: the electrode containing no target DNA incubating in hybridization buffer solution containing Cu-DNCs DNA probe for a certain time). The use of Cu encapsulated-dendrimer as tags and ASDPV for the detection of the released Cu ions could enhance the hybridization signal, and result in the increase of the sensitivity for the target DNA. Under the conditions employed here, the detection limit for measuring the full complementary sequence is down to pM level.

Copper(II) Adsorptive Removal from Solutions with Sunflower Straw-Modified by Phosphoric Acid

Straw active carbon was manufactured from sunflower straw by phosphoric acid. The adsorption was studied by considering the effects of various parameters on the removal rate of Cu2+ such as the dosage of absorbent, adsorption time, temperature and pH. The results showed that the absorbent was efficient, the removal ratio of Cu2+ up to 98.3% with an adsorbent dosage of 16 g•L-1, a pH of 6.0, at 25°C and absorption time of 4 hours. The Langmuir and Freundlich equations can describe the adsorption equilibrium well. The negative values of the adsorption enthalpy △H and the absolute values>42 kJ•mol-1 indicate the exothermic chemical adsorption character. The negative changes in free energy (△G) indicate that the adsorption is a spontaneous process, The negative values of the adsorption entropy △S indicate the more restricted mobility of the Cu2+ on the carbon surface than in solution.

Effect of Cu2+ on the Stability of Xanthophylls in Acetone

Investigations were conducted on the stability of lutein, zeaxanthin, and β-cryptoxanthin during incubation with CuSO4·5H2O. For this purpose, a method for simultaneous determination of lutein, zeaxanthin, and β-cryptoxanthin stereoisomers by HPLC-DAD and APcI-MS was developed. (all-E)-Lutein, (all-E)-zeaxanthin, and (all-E)-β-cryptoxanthin were baseline separated and identified using chromatographic retention times; UV/Vis absorption spectra and positive mass spectra were compared with literature data. It was found that Cu2+ exhibited a rapid isomerization induction of (all-E)-xanthophylls to their (Z)-isomers exceeding 4/1 mass ratio of Cu2+/pigments, and after the incubation time exceeding 8 h, the concentration of the formation (Z)-xanthophylls decreased, indicating that the Cu2+ also exhibited isomerization of (Z)-isomers. The (13-Z)-lutein and (13′-Z)-lutein were identified as the major (Z)-isomers of (all-E)-lutein treated by Cu2+, and the (9-Z)-zeaxanthin was identified as the major isomerization product of (all-E)-zeaxanthin, and an unidentified (Z)-β-cryptoxanthin was also detected.

Study on Technology of Simultaneous Removal of Copper Ion and Crystal Violet in Aqueous Solution by Foam Separation

A system for the removal of Cu2+ and crystal violet from aqueous solution by foam separation was used. The goal of this work was to explore a method for simultaneous desalination and decolorization by foam separation. In the aqueous solution of this work, Cu2+ was used for studying desalination and crystal violet was used for studying decolorization, respectively, and dodecyl benzene sulfonic acid (DBSA) (C18H29SO3H) was used as a surfactant. The effect of surfactant concentration, pH, superficial velocity, and foam height on the removal percentage and the enrichment ratio were studied to optimize the conditions. Under the optimum conditions, the removal percentage of Cu2+ and crystal violet were 96.5% and 96.3%, respectively, and the enrichment ratio of Cu2+ and crystal violet were 3.7 and 3.6, respectively.

Syntheses of copper complexes of nicotinohydroxamic and isonicotinohydroxamic acids.

Nicotinohydroxamic acid (NHA) and isonicotinohydroxamic acid (INHA) were synthesized, characterized by electronic and spectral studies,magnetic measurements and their pKa determined spectrophotometrically as 8.68 ± 0.02 in aqueous medium of 0.1mol dm-3 I=ionic strength. The composition of the complexes was determined by Job’s plot. The ratios of Cu2+ to ligands under investigation were ML2. The formation constants obtained and the possible binding modes for the complexes in solid states are discussed. Spectral studies of the isolated complexes indicate tetragonally distorted octahedral geometry via (O,O) and (N,O) coordination modes. The magnetic moments obtained for the complexes are in the range 1.57-1.79B.M. Microbial sensitivity test carried out on the ligands and their isolated complexes showed no activity on the microorganisms under investigation. Keywords: Nicotinohydroxamic acid, isonicotinohydroxamic acid, IR spectra, ionic strength, Job’s plot, pKa, microbial sensitivity.

A Solid-State NMR Study Reveals Structure and Dynamics in Copper(ii)-Binding to Alzheimer's Beta-Amyloid Fibrils

β-amyloid (Aβ) peptide associated with Alzheimer's diseases exhibit neural toxicity upon aggregation. One of the most widespread hypotheses on the origin of the toxicity of Aβ aggregates is the binding of Cu2+ ions to Aβ fibrils and subsequent generation of reactive oxygen species (ROS) such as H2O2 by Cu2+-bound Aβ. Although a variety of studies have been performed on Cu2+-binding to Aβ, the proposed binding sites or models have been controversial partly because non-crystalline and insoluble nature of Aβ fibrils have limited access to site-specific structure and dynamic properties on Cu2+-bound Aβ fibrils. Here, we examine the effect of Cu2+ binding to amyloid fibrils of 40-residue Aβ(1-40) by UV-VIS spectroscopy and solid-state NMR (SSNMR). Specifically, we will answer the following questions (i) Is the Cu2+ binding is site specific? (ii) If so, which sites are involved in binding? (iii) Are there any major structural changes introduced by Cu2+ binding or oxidization due to Cu2+?UV-VIS spectroscopy showed that Cu2+ binds to Aβ(1-40) fibrils almost completely when the ratio of Cu2+ to Aβ(1-40) is less than 1. Based on the result, we performed high-resolution SSNMR experiments on Cu2+-bound Aβ(1-40) fibrils. First, the 13C T1 paramagnetic relaxation enhancement (PRE) due to Cu2+ binding on Aβ was measured for different residues; the PRE data highlight possible binding sites, where the relaxation enhancements are notable. The analysis indicates that the binding is specific, and Cu2+ most likely binds to His-13/14 and His-6. Second, the comparison of 2D 13C/13C correlation spectra of Aβ fibrils with and without Cu2+ revealed that the secondary structure of Aβ(1-40) fibrils is largely unaltered by Cu2+ binding. Third, we tested a previously proposed hypothesis that Met-35/Gly-33 can be oxidized[4] by Cu2+ to produce ROS by SSNMR.

Catalytic Combustion of Toluene with a Novel Mixed Cu.Mn Oxides Catalyst Supported on Cordierite

The catalytic combustion of toluene over mixed Cu–Mn oxides supported on cordierite is investigated in this paper. The catalysts were prepared by the incipient wetness method and characterized by XRD, BET and TEM. Five kinds of cordierite-type compounds containing different amounts of Cu2+ and Mn2+ ions were prepared (the mole ratio of Cu2+:Mn2+ varied as follows: 1 : 1, 1 : 2, 1 : 4, 2 : 1 and 4 : 1). Calcination of the precursors at 500°C resulted in mixed oxides and all calcined materials proved extremely active in catalytic combustion of toluene, in which the Cu2+:Mn2+=1 : 2 (forming CuMn2O4) was found to have the highest activity for toluene oxidation and T90% was about 200°C. The objective of this study was to investigate the catalytic properties of Cu–Mn/cordierite catalysts prepared at different mole ratios, in order to obtain some information to prepare an efficient and highly active catalyst for catalytic combustion of volatile organic compounds at low temperature.

Copper Binding Extrinsic to the Octarepeat Region in the Prion Protein

Current research suggests that the function of the prion protein (PrP) is linked to its ability to bind copper. PrP is implicated in copper regulation, copper buffering and copper-dependent signaling. Moreover, in the development of prion disease, copper may modulate the rate of protein misfolding. PrP possesses a number of copper sites, each with distinct chemical characteristics. Most studies thus far have concentrated on elucidating chemical features of the octarepeat region (residues 60-91, hamster sequence), which can take up to four equivalents of copper, depending on the ratio of Cu2+ to protein. However, other sites have been proposed, including those at histidines 96 and 111, which are adjacent to the octarepeats, and also at histidines within PrP's folded C-terminal domain. Here, we review the literature of these copper sites extrinsic to the octarepeat region and add new findings and insights from recent experiments.

Synthesis and Characterization of Cu<sub>2</sub>O/TNTs Nanocomposites

Cu2O/TNTs(Titanium-based Nanotubes) composites were prepared by a simple “soak-deoxidize” method by using hydrazine hydrate as the reducing agent. The Cu2O/TNTs composites particles was made by changing pH and the mol ratio of Cu2+:N2H4H2O. The obtained composites were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV-Vis Diffuse reflectance spectra(DRS). The results of UV-Vis diffuse reflectance spectra indicate that the absorption edge of Cu2O/TNTs shows a shift to visible-light region, followed by an obvious absorption peak at 500–700 nm.

Evaluation of a silica-coated magnetic nanoparticle for the immobilization of a His-tagged lipase

Magnetic particles of size 10 nm have been coated with silica to a mean diameter of 40 nm and charged with Cu2+ ions via a multidentate ligand, iminodiacetic acid (IDA), for the immobilization of His-tagged Bacillus stearothermopilus L1 lipase. Microporous (average pore diameter of 60 Å) silica gel with a mean particle diameter of 115 µm has been used as a comparative support material. The molar ratio of Cu2+ to IDA was found to be 1:1.14 and 1:1.99 in the silica gel and the silica-coated magnetic nanoparticles (SiMNs), respectively. The specific activity of the immobilized enzyme was found to conform to the following order: Cu2+-charged SiMN>SiMN>Cu2+-charged silica gel>silica gel. When it was immobilized on the Cu2+-charged SiMNs, over 70% of the initial activity of the lipase remained after it had been reused five times. However, only 20% of the initial activity remained after the enzyme immobilized on the Cu2+-charged silica gel had been reused five times. For the enzyme immobilized on supports without Cu2+ cations, all activity was lost after threefold reuse. The differences in the specific activities and the efficiencies of reuse of the enzymes immobilized on the various support materials are discussed in terms of immobilization mechanisms (physical adsorption vs. coordination bonding), mass transfer of a substrate and a product of the enzyme reaction, and the status of the Cu (Cu bound to the IDA on the silica layer vs. Cu directly adsorbed on the silica layer).

Complex with fullerenol and copper (II)

Polyhydroxy fulleren derivates have significant potential in nanomedical application. Research of polyanion nanoparticle fullerenol C60(OH)24 is of high significance for interpretation of biological mechanisms. This paper investigated the properties of polyanion nanoparticle fullerenol C60(OH)24 as a potential polydentat ligand. Fullerenol C60(OH)24 water solutions were added in solution of [Cu(NH3)4]2+ in order to form a dark brown complex. Absorbance of [Cu(NH3)4]2+ solution was decreasing with increasing concentration of polyanion nanoparticle nanoligand fullerenol. This relation was determined in all investigated concentrations of [Cu(NH3)4]2+. The ratio of Cu2+ complex composer to polyanion polydentat nanoligand fullerenol had an increase from 1.5 to 9, proportional to the increase of the complex composer concentration and decrease of polyanion polydentat nanoligand fullerenol in the alkali medium. The thermogram TGA-DTA of fullerenol and fullerenol and CuSO4 complex, clearly show endothermic effects (which are the result of dehydratation and dehydroxylation) and exothermic effects (as the result of degradation of C60(OH)24 molecules and processes of oxidation in CO, CO2. At the beginning of TGA-DTA fullerenol thermogram, there is a very well defined endothermic peak of water loss at 100?C, followed by mass decrease as a consequence of lost hydroxyl groups, covalent bounded for C60. The influence of the complex composer is manifested in the moving of thermal stability towards lower temperatures. The complex composer is a catalyst of the process of polyanion polydentat nanoligand fullerenol oxidation to CO and CO2. The temperature peak of fullerenol oxidation is at 490?C and in the case of complex oxidation two peaks were detected at 380 and 410?C.

Effect of Cu2+ on the magnetic properties and reducibility of Fe2TiO5

Abstract Ferrites have been studied for several years due to their wide use as magnetic materials for telecommunications, audio and video, power transformers and many other applications. Equimolar mixtures of Fe2O3 and TiO2 were fired in a muffle furnace at 1200 °C for 4 h. Mixed samples were prepared by replacing TiO2 with calculated amounts of CuO (x = 0.2, 0.4, 0.6, 0.8 and 1 mol). The synthesized samples were characterized with X-ray diffraction and their magnetic properties were measured using vibrating-sample magnetometer. The microstructure of the sample was examined using reflected light microscope and scanning electron microscope. The formation of Fe2TiO5, Fe5CuO8, Cu2TiO3 and CuFeO2 phases were detected whereas their magnetic properties increased with increasing the added mole ratio of Cu2+ ions. The isothermal reduction kinetics of synthesized nanocrystallites Ti–Cu mixed ferrite compacts were studied at 500 °C using hydrogen gas. It was found that the reduction rate and the reduction extent increased with increasing the extent of Cu2+ (0.2–1) whereas the maximum reduction extent (100%) was detected for pure Cu ferrite (Cu2+) while the minimum reduction extent (12%) was detected for pure iron titanate (Cu2+ = 0). The magnetic properties showed a drastic improvement upon reduction with hydrogen gas.