Effect Of Cobalt Ions Research Articles

Impact of Cobalt Doping on the Structural, Optical, and Dielectric Properties of MgAl2O4 Spinel Material.

Nanomaterials (NMs) with structural, optical, and dielectric properties are called functional or smart materials and have favorable applications in various fields of material science and nanotechnology. Pure and Co-doped MgAl2O4 were synthesized by using the sol-gel combustion method. A systematic investigation was carried out to understand the effects of the Co concentration on the crystalline phase, morphology, and optical and dielectric properties of Co-doped MgAl2O4. X-ray diffraction confirmed the cubic spinel structure with the Fd3̅m space group, and there was no impurity phase, while the surface morphology of the samples was investigated by scanning electron microscopy. The dielectric properties of the synthesized material are investigated using an LCR meter with respect to the variation in frequency (1-2 GHz), and their elemental composition has been examined through the energy-dispersive X-ray technique. The existence of the metal-oxygen Mg-Al-O bond has been confirmed by Fourier transform infrared spectroscopy. The value of the dielectric constant decreases with the increasing frequency and Co concentration. The optical behaviors of the Co2+-doped MgAl2O4 reveal that the optical properties were enhanced by increasing the cobalt concentration, which ultimately led to a narrower band gap, which make them exquisite and suitable for energy storage applications, especially for super capacitors. This work aims to focus on the effect of cobalt ions in different concentrations on structural, optical, and dielectric properties.

Effect of Co‐Doping on the Structural and Dielectric Properties of La0.8K0.2MnO3 Perovskite

In this work, the effect of cobalt ions on the structural and dielectric properties of La0.8K0.2MnO3 manganite prepared via the simplest sol–gel route is studies. The X‐ray diffractions analyses reveal that our perovskites, with the general formula La0.8K0.2Mn1−xCoxO3 (x = 0, 0.03, 0.06), crystallized by a rhombohedral structure with space group. Rietveld refinement indicates that each octahedron (Mn, Co)O6 has little deformation and that the θ(Mn, Co)–O–(Mn, Co) bond angles decrease with increasing Co content. From the conductance measurements, it is noticed that the substitution into the Mn site of the LaKMnO3 material by cobalt increases its conductivity. However, the electrical conductance of our perovskites is well described by the universal Jonscher's law. It is deduced that the conduction process of the present structures occurs between neighboring sites. In addition, the dielectric constant and loss tangent can be explicated based on Maxwell–Wagner polarization. Finally, the Nyquist diagram is fitted by an adequate equivalents circuit, the obtained results depict a non‐Debye relaxation process in these materials.

Structural, Optical, and Magnetic Properties of Cobalt-Doped ZnAl2O4 Nanosheets Prepared by Hydrothermal Synthesis

Nanomaterials with collective optical and magnetic properties are called smart or functional materials and have promising applications in many fields of science and technology. Undoped and Co-doped ZnAl2O4 were prepared using a co-precipitation-assisted hydrothermal method. A systematic investigation was carried out to understand the effects of the Co concentration on the crystalline phase, morphology, and optical and magnetic properties of Co-doped ZnAl2O4. X-ray diffraction confirmed the cubic spinel structure with the Fd3m space group, and there was no impurity phase. X-ray photoelectron spectroscopy of Co-doped ZnAl2O4 confirmed the existence of Zn, Al and O, and the Co in the optimized sample of ZAO-Co-3 confirmed the oxidation state of cobalt as Co2+. Transmission electron microscopy of pure and Co-doped ZnAl2O4 revealed micro-hexagons and nanosheets, respectively. The optical absorption results showed that the bandgap of ZnAl2O4 decreased with increasing Co concentration. The hysteresis loop of Co-doped ZnAl2O4 revealed clear ferromagnetic behavior at room temperature. The as-prepared materials are suitable for energy storage applications, such as in supercapacitors and fuel cells. This work aims to focus on the effect of cobalt ions in different concentrations on structural, optical and magnetic properties.

Effects of cobalt ions and cobalt nanoparticles on transient expression of gus gene in catharanthus roseus suspension cultures

Agrobacterium tumefaciens mediated transformation is a major tool in plant biotechnology. Catharanthus roseus suspension cultures were inoculated with A. tumefaciens strain carrying β-glucuronidase...

Effect of cobalt ions on chemokine expression: Case report of immune cell infiltration in patient undergoing replacement of a metal-on-metal implant

Effect of cobalt ions on chemokine expression: Case report of immune cell infiltration in patient undergoing replacement of a metal-on-metal implant

The Effect of Cobalt Ions on Thermooxidation and Photooxidation of Polyethylene Containing Modified Montmorillonite

Nanocatalysts obtained by applying cobalt salts to modified montmorillonite significantly accelerate the thermal oxidation and photooxidation of polyethylene. It is important that even short-term irradiation accelerates the thermal oxidation at 23°C. This makes it possible to obtain polymer materials with a regulated lifetime.

Effect of cobalt ions on the interaction between macrophages and titanium.

Inflammation and bone reduction around dental implants are described as peri‐implantitis and can be caused by an inflammatory response against bacterial products and toxins. Titanium (Ti) forms aggregates with serum proteins, which activate and cause release of the cytokine interleukin (IL‐1β) from human macrophages. It was hypothesized that cobalt (Co) ions can interact in the formation of pro‐inflammatory aggregates, formed by titanium. To test this hypothesis, we differentiated THP‐1 cells into macrophages and exposed them to Ti ions alone or in combination with Co ions to investigate if IL‐1β release and cytotoxicity were affected. We also investigated aggregate formation, cell uptake and human biopsies with inductively coupled plasma atomic emission spectroscopy and electron microscopy. Co at a concentration of 100 µM neutralized the IL‐1β release from human macrophages and affected the aggregate formation. The aggregates formed by Ti could be detected in the cytosol of macrophages. In the presence of Co, the Ti‐induced aggregates were located in the cytosol of the cultured macrophages, but outside the lysosomal structures. It is concluded that Co can neutralize the Ti‐induced activation and release of active IL‐1β from human macrophages in vitro. Also, serum proteins are needed for the formation of metal‐protein aggregates in cell medium. Furthermore, the structures of the aggregates as well as the localisation after cellular uptake differ if Co is present in a Ti solution. Phagocytized aggregates with a similar appearance seen in vitro with Ti present, were also visible in a sample from human peri‐implant tissue. © 2018 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2518–2530, 2018.

Enhanced magneto-optical and photo-catalytic properties of transition metal cobalt (Co2+ ions) doped spinel MgFe2O4 ferrite nanocomposites

In this study, spinel magnesium cobalt ferrite (CoxMg1−xFe2O4: x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanocomposites were synthesized successfully by modified sol-gel combustion method. Magnesium nitrate, cobalt nitrate and iron nitrate were used as the source of divalent (Mg2+ and Co2+) and trivalent (Fe3+) cations, respectively and urea were used as the reducing (fuel) agent. The effects of cobalt ions on morphology, structural, optical, magnetic and photo-catalytic properties of spinel CoxMg1−xFe2O4 nanocomposites were investigated. Various characterization methods, including X-ray powder diffraction (XRD), high resolution scanning electron microscope (HR-SEM), transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared (FT-IR) spectroscopy, vibrating sample magnetometer (VSM) and photo-catalytic degradation (PCD) activity were used to study the phase purity, microstructure, particle size, elemental composition, functional group determination, band gap calculation, magnetic properties and degradation efficiency of nanoparticles, respectively. The observed results showed that the final products consists cubic spinel phase with sphere-like nanoparticles morphologies. Furthermore, spinel Co0.6Mg0.4Fe2O4 nanocomposite showed highest PCD efficiency (98.55%) than other composition of ferrite nanoparticles.

Influence of Superexchange Interaction on the Ferromagnetic Properties of Manganites and Cobaltites

The role of superexchange interaction in the formation of the ferromagnetic state of cobaltites in the La0.5Sr0.5Co1–xMexO3 (Me = Cr, Ga, Fe) systems and manganites La0.7Sr0.3Mn0.85M0.15O3 (M–Nb, Mg) with a perovskite structure has been studied. It was found that the ferromagnetic state in cobaltites can be implemented in some compositions without the mixed-valence effect of cobalt ions. The initial compound (x = 0) is ferromagnetic (ТС = 247 K) with the saturation magnetization close to 2μB (at T = 30 K) per formular unit. It has been shown that the chemical substitution of cobalt by chromium reduces the spontaneous magnetization to 0.3μB (at х = 0.2), while the substitution of cobalt by iron ions (х = 0.2) does not alter the magnetization. The obtained data are interpreted in the model of positive superexchange interactions between cobalt and iron ions and negative ones between cobalt and chrome. It has been shown that the La0.7Sr0.3Mn0.85Nb0.15O3 composition is ferromagnetic with ТС=145K, with a magnetic moment of 3.1 μB/Mn at 10 K, and no evidence of a cooperative orbital ordering in the manganite compounds has been revealed. Partial chemical substitution of Nb5+ ions by Mg2+ ones leads to the formation of Mn4+ ions, while it does not strengthen the ferromagnetic state. The strengthening of the structural distortions reduces the ferromagnetic component. It is assumed that the ferromagnetic state is caused by a significant hybridization of eg-orbitals of the manganese and oxygen ions, which strengthens the positive component of the superexchange interactions.

The effect of cobalt ion on the hydrogen evolution reaction in sulfate solution

The effects of cobalt ion on the hydrogen evolution reaction (HER) in sulfate solution were studied by several electrochemical measurements, such as linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry. The charge transfer resistance and the apparent activation energy can be decreased with the cobalt ion adding into the sulfate solution. The calculated values of apparent activation energy are 43.4 kJ mol−1 and 31.9 kJ mol−1 for HER in the MnSO4(NH4)2SO4 solution without and with cobalt ion respectively. At the same temperature, the charge transfer resistances become smaller when the cobalt ion present in the solution. The charge transfer resistance of HER decreases with the increasing concentration of cobalt ion. The results of X ray diffraction (XRD), Energy Dispersive Spectrometer (EDS) and scanning electron microscopy (SEM) indicate that metallic cobalt electrodeposited on the surface of the electrode. As a result of the cobalt electrodeposition, the surface property of the cathode is changed significantly and thus the hydrogen evolution reaction is promoted.

Synthesis, investigation on structural and electrical properties of cobalt doped Mn–Zn ferrite nanocrystalline powders

Abstract Synthesis of CoxMnyZnyFe2O4 (x = 0.1, 0.5, 0.9 and y = 0.45, 0.25, 0.05) nanocrystalline powders was done by chemical co-precipitation method. The crystal structure was determined by using X-ray diffraction (XRD) studies. The crystallite size and lattice parameters were calculated from the XRD data. The XRD results revealed that the crystallite size of the nanocrystalline powder was found to decrease from 37 nm to 28 nm with the substitution of cobalt. The effect of cobalt ions on the crystallization process, the lattice parameters and electrical properties of Mn–Zn ferrites has been also investigated. The AC conductivity increased with an increase in frequency but it decreased with an increase in cobalt content. The complex impedance analysis of the data showed that the resistive and capacitive properties of the Co–Mn–Zn ferrite are predominant due to the fact that the processes are associated with the grains and grain boundaries. The dielectric constant and dielectric loss dependence on doping level and frequency at room temperature were also studied.

The effects of cobalt ions and cobalt-chromium-wear debris on TGF-beta patterns in osteoblast-like MG63 cells

The effects of cobalt ions and cobalt-chromium-wear debris on TGF-beta patterns in osteoblast-like MG63 cells

Doping Effect of Cobalt Ions Incorporated into NaTaO3 Nanocrystalline

A series of cobalt ions doped NaTaO3 photocatalysts are prepared. XRD patterns confirmed the doping of cobalt ions lead to NaTaO3 cell expansion. UV-vis diffuse reflectance spectra clearly displayed the red-shift in the series of cobalt doped NaTaO3 catalysts, indicating a decrease in the band gap of NaTaO3 caused by the substitution of Co2+ ions at Ta5+ site. The red-shift increased with the increase of cobalt doping concentration in NaTaO3. Density functional calculations revealed that the narrowed band gap originated from an impurity level formed via cobalt ions replace tantalum ions in the NaTaO3 lattice.

The addition of Co2+ enhances the catalytic efficiency and thermostability of recombinant glucose isomerase from Thermobifida fusca

Glucose isomerase is an important industrial enzyme that catalyzes the reversible isomerization of glucose to fructose. In this study, the effect of cobalt ions (Co2+) on the catalytic efficiency and thermostability of recombinant glucose isomerase from Thermobifida fusca was analyzed. The activity of glucose isomerase from engineered Escherichia coli supplemented with 1mM Co2+ (C-GI) reached 41U/ml, 2.1-fold higher than enzyme prepared from E. coli without additive (GI). The purified C-GI also exhibited an increased specific activity (23.8U/mg compared to 12.1U/mg for GI) and a greater thermostability (half-life of 17h at 75°C, 11.3-fold higher than GI (1.5h)). The optimal temperature for C-GI shifted from 80°C to 85°C and demonstrated higher activity over pH 7.0–9.0. The kcat/Km value of C-GI (89.3M−1s−1) for the isomerization of glucose to fructose was nearly 1.75-fold higher than that of GI. In addition, the engineered cells were immobilized with the method of flocculation-cross linking. The immobilized cells supplemented with 1mM Co2+ (C-IGI) had a better operational performance than cells without additives (IGI); at the end of 6 cycles, the conversion rate of C-IGI was still 43.1%, meeting the conversion rate requirement.

Effects of cobalt doping on the microstructure and magnetic properties of Mn–Zn ferrites prepared by the co-precipitation method

Abstract Mn–Zn ferrite nanoparticles with various amounts of cobalt doping have been synthesized by the co-precipitation method. The structure and morphology of the nanoparticles have been characterized by X-ray diffraction and transmission electron microscopy. The effects of cobalt ions on the crystallization behavior, lattice parameters and magnetic properties of Mn–Zn ferrites have been investigated. All the Co-doped ferrite nanoparticles calcined at 1150 °C possess a simple spinel structure and have an approximately spherical shape. The lattice parameters increase almost linearly with increasing Co content. The studies of magnetic properties show that the saturation magnetization Ms strongly depends on the Co content, having a maximum Ms value of 73 emu/g at a Co content of 1.0 at%, and all the Co-doped ferrites, with the average crystallite sizes ranging from 24.5 to 27.0 nm, exhibit superparamagnetism at room temperature.

Cobalt reverses vanadate inhibition of rat kidney alkaline phosphatase

Vanadate ion (VO43-) is an established inhibitor of alkaline phosphatase (ALP) and inorganic phosphate transport across biologic membranes. The concentration-dependent effects of Co2+ and VO43- on rat kidney ALP activity were carried out over a range of 3.33 – 25.67 mM p–NPP concentrations. The investigation revealed Co2+ as an activator of rat kidney ALP, while vanadate inhibited the enzyme. The activatory effect of cobalt ion on ALP was compared with that of magnesium ion when vanadate-inhibited ALP was exposed to both cobalt and magnesium ions at both 2 and 4 mM concentrations. The results revealed that cobalt ion at these concentrations significantly reversed (P < 0.05) vanadate inhibition of rat kidney ALP activity while magnesium ion was significantly deficient (P < 0.05) in this regard. In the light of the foregoing, cobalt may be a better activator of rat kidney ALP in the presence of inhibitors of ALP. This reversal of ALP inhibition by Co2+could be employed as a protector with a potential physiological relevance in cells. Key words: Cobalt, vanadate inhibition, alkaline phosphatase.

Activation and Inactivation of Horseradish Peroxidase by Cobalt Ions

The effect of cobalt ions (Co2+) on horseradish peroxidase (HRP) was studied in vitro by enzymatic activity assay, electronic absorption spectra, intrinsic fluorescence spectra and 8-anilo-1-naphthalenesulfonate(ANS)-binding fluorescence spectra. Co2+ at concentrations below 0.1 mM mildly increased the HRP activity, whereas higher concentrations of Co2+ significantly inactivated HRP in a time and concentration-dependent manner. Steady-state kinetic studies show that Co2+ was a noncompetitive inhibitor of o-dianisidine oxidation by HRP. The Ki value dropped as the incubation time increased. Furthermore, Co2+ was found to be an uncompetitive inhibitor of H2O2. These results suggested that Co2+ would slowly bind to the enzyme and progressively induce conformational changes. Spectroscopic analysis showed that even for high Co2+ concentrations, the structure of HRP as a whole only changed slightly; however, there were significant conformational changes near or in the active site of HRP. Based on the above results, we suggest that Co2+ may bind with some amino acids near or in the active site of HRP and the conformational changes of HRP induced by such binding should be the main reason for activation and inactivation effect of Co2+. The potential binding sites of Co2+ were also proposed.

EFFECT OF COBALT IONS ON THE PERFORMANCE OF LEAD ANODES USED FOR THE ELECTROWINNING OF COPPER—A LITERATURE REVIEW

The effect of cobalt ions in the electrolyte on the performance of lead alloy anodes used for oxygen evolution during electrolysis of copper/sulfuric acid solutions has been studied extensively over the past 90 years. A review of the literature has confirmed that cobalt both as constituent of the anode material and present as ions in the electrolyte reduces the rate of corrosion of the anodes, lowers the overpotential for the evolution of oxygen, and reduces lead contamination of the copper cathodes. Despite the fact that these effects have been developed into widespread applications in the electrowinning industry, a fundamental understanding of the mechanism of the action of cobalt ions remains a point of debate. A selection of the most relevant literature on this phenomenon has been reviewed and the data and proposed mechanisms critically evaluated.

Molecular Mechanism of the Inhibitory Effect of Cobalt Ion on Thermolysin Activity and the Suppressive Effect of Calcium Ion on the Cobalt Ion-dependent Inactivation of Thermolysin

Thermolysin activity in the hydrolysis of N-[3-(2-furyl)acryloyl]-glycyl-l-leucine amide (FAGLA) and FA-l-leucyl-l-alanine amide (FALAA) was examined at various Co(2+) and Ca(2+) concentrations. It decreased to 28% with increasing [Co(2+)] up to 18 mM. The Co(2+)-dependent inactivation was in part suppressed by adding Ca(2+) ion up to 0.5 mM, but 33% of the activity remained to be inactivated even with a sufficient concentration of Ca(2+) (>0.5 mM). The Co(2+)-dependent inactivation was shown to be composed of Ca(2+)-sensitive and Ca(2+)-insensitive parts. In the latter part which is observed at [Ca(2+)] >0.5 mM, Co(2+) plays as a competitive inhibitor. On the other hand, the Co(2+)-dependent inactivation in the Ca(2+)-sensitive part observed at [Ca(2+)] <0.5 mM proceeds time-dependently following second-order kinetics, and the time-course is in good agreement with that of decrease in the thermolysin band due to autolysis in SDS-PAGE. This indicates that Co(2+) accelerates the autolysis. Here, we describe the co-regulation of thermolysin activity by Co(2+) and Ca(2+) ions and propose a molecular mechanism for the inhibition of thermolysin by Co(2+) and suppressive effect of Ca(2+) on the Co(2+)-dependent inhibition. Co(2+) ion inhibits thermolysin activity not only as a competitive inhibitor but also promoting the autolysis.

Effect of cobalt ions on the metabolism of some volatile and polar compounds in the marine invertebrates Mytilus galloprovincialis and Actinia equina

The compositions of the volatile and polar fractions from two coexisting Black Sea invertebrates, the mussel Mytilus galloprovincialis and the beadlet anemone Actinia equina, were established. The main metabolites in the volatile fraction from the investigated animals appeared to be methyl esters of fatty acids and fatty aldehydes. In the polar fraction from both animals low concentrations of free acids and nitrogen-containing compounds were obtained. Free carbohydrates were in much higher concentrations in M. galloprovincialis than in A. equina. Some sterols, probably as polar conjugates, were identified mainly in A. equina. Significant changes among all compounds appeared after treatment of both invertebrates with two different concentrations of cobalt ions. The variety of changes in each invertebrate could be due to their different evolutionary status. The effect of cobalt ions was often stronger at medium cobalt-ion concentrations.