Cobalt

About: Cobalt is a research topic. Over the lifetime, 69899 publications have been published within this topic receiving 1242058 citations. The topic is also known as: Co & Element 27.

Biological evaluation of non-steroidal anti-inflammatory drugs-cobalt(II) complexes

Abstract: Cobalt(II) complexes with the non-steroidal anti-inflammatory drug mefenamic acid in the presence or absence of nitrogen donor heterocyclic ligands (2,2′-bipyridine, 1,10-phenanthroline or pyridine) have been synthesized and characterized with physicochemical and spectroscopic techniques. The experimental data suggest that mefenamic acid acts as deprotonated monodentate ligand coordinated to Co(II) ion through a carboxylato oxygen. The crystal structures of tetrakis(methanol)bis(mefenamato)cobalt(II), 1 and (2,2′-bipyridine)bis(methanol)bis(mefenamato)cobalt(II), 2 have been determined by X-ray crystallography. The EPR spectra of complexes 1 and 2 in frozen solution reveal that they retain their structures. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA and bis(methanol)bis(pyridine)bis(mefenamato)cobalt(II) exhibits the highest binding constant. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB. The cyclic voltammograms of the complexes recorded in dmso solution and in the presence of CT DNA in 1 : 2 dmso : buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that they can bind to CT DNA by the intercalative binding mode. Mefenamic acid and its cobalt(II) complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values. The antioxidant activity of the compounds has been evaluated indicating their high scavenging activity against hydroxyl free radicals and superoxide radicals.

Effects of cobalt on plants

Abstract: Cobalt, a transition element, is an essential component of several enzymes and co-enzymes. It has been shown to affect growth and metabolism of plants, in different degrees, depending on the concentration and status of cobalt in rhizosphere and soil. Cobalt interacts with other elements to form complexes. The cytotoxic and phytotoxic activities of cobalt and its compounds depend on the physico-chemical properties of these complexes, including their electronic structure, ion parameters (charge-size relations) and coordination. Thus, the competitive absorption and mutual activation of associated metals influence the action of cobalt on various phytochemical reactions. The distribution of cobalt in plants is entirely species-dependent. The uptake is controlled by different mechanisms in different species. Biosorption involves ion-exchange mechanism in algae, but in fungi both metabolism-independent and -dependent processes are operative. Physical conditions like salinity, temperature, pH of the medium, and presence of other metals influence the process of uptake and accumulation in algae, fungi, and mosses. Toxic concentrations inhibit active ion transport. In higher plants, absorption of Co2+ by roots involves active transport. Transport through the cortical cells is operated by both passive diffusion and active process. In the xylem, the metal is mainly transported by the transpirational flow. Distribution through the sieve tubes is acropetal by complexing with organic compounds. The lower mobility of Co2+ in plants restricts its transport to leaves from stems. Cobalt is not found at the active site of any respiratory chain enzymes. Two sites of action of Co2+ are found in mitochondrial respiration since it induces different responses toward different substrates like α-keto glutarate and succinate. In lower organisms, Co2+ inhibits tetraphyrrole biosynthesis, but in higher plants it probably participates in chlorophyll b formation. Exogenously added metal causes morphological damage in plastids and changes in the chlorophyll contents. It also inhibits starch grain differentiation and alters the structure and number of chloroplasts per unit area of leaf. The role of cobalt in photosynthesis is controversial. Its toxic effect takes place by inhibition of PS2 activity and hence Hill reaction. It inhibits either the reaction centre or component of PS2 acceptor by modifying secondary quinone electron acceptor Qb site. Co2+ reduces the export of photoassimilates and dark fixation of CO2. In C4 and CAM plants, it hinders fixation of CO2 by inhibiting the activity of enzymes involved. Cobalt acts as a preprophase poison and thus retards the process of karyokinesis and cytokinesis. The action of cobalt on plant cells is mainly turbagenic. Cobalt compounds act on the mitotic spindle, leading to the formation of chromatin bridges, fragmentation, and sticky bridges at anaphase and binucleate cells. High concentrations of cobalt hamper RNA synthesis, and decrease the amounts of the DNA and RNA probably by modifying the activity of a large number of endo- and exonucleases. The mutagenic action of cobalt salts results in mitochondrial respiratory deficiency in yeasts. In cytokinesis-deficient mutant of Chlamydomonas it increases the amount of sulfhydryl compounds. Cobalt has been shown to alter the sex of plants like Cannabis sativa, Lemna acquinoclatis, and melon cultivars. It decreases the photoreversible absorbance of phytochrome in pea epicotyl and interferes with heme biosynthesis in fungi. Low concentration of Co2+ in medium stimulates growth from simple algae to complex higher plants. Relatively higher concentrations are toxic. A similar relationship is seen with crop yield when the metal is used in the form of fertilizer, pre-seeding, and pre-sowing chemicals. Toxic effect of cobalt on morphology include leaf fall, inhibition of greening, discolored veins, premature leaf closure, and reduced shoot weight. Being a component of vitamin B12 and cobamide coenzyme, Co2+ helps in the fixation of molecular nitrogen in root nodules of leguminous plants. But in cyanobacteria, CoCl2 inhibits the formation of heterocyst, ammonia uptake, and nitrate reductase activity. The interaction of cobalt with other metals mainly depends on the concentration of the metals used. For example, high levels of Co2+ induce iron deficiency in plants and suppress uptake of Cd by roots. It also interacts synergistically with Zn, Cr, and Sn. Ni overcomes the inhibitory effect of cobalt on protonemal growth of moss, thus indicating an antagonistic relationship. The beneficial effects of cobalt include retardation of senescence of leaf, increase in drought resistance in seeds, regulation of alkaloid accumulation in medicinal plants, and inhibition of ethylene biosynthesis. In lower plants, cobalt tolerance involves a cotolerance mechanism. The mechanism of resistance to toxic concentration of cobalt may be due to intracellular detoxification rather than defective transport. In higher plants, only a few advanced copper-tolerant families showed cotolerance to Co2+. Tolerance toward Co2+ may sometimes determine the taxonomic shifting of several members of Nyssaceae. Due to the high cobalt content in serpentine soil, essential element uptake by plants is reduced, a phenomenon known as “serpentine problem,” for New Caledonian families like Flacourtiaceae. Large amounts of calcium in soil may compensate for the toxic effects of heavy metals in adaptable genera grown in this type of soil. The biomagnification of potentially toxic elements, such as cobalt from coal ash or water into food webs, needs additional study for effective biological filtering.

Surface-Confined Fabrication of Ultrathin Nickel Cobalt-Layered Double Hydroxide Nanosheets for High-Performance Supercapacitors

Abstract: The design and fabrication of 2D nanostructure electrodes with desired electrochemical activities is highly demanded for electrocatalysis and supercapacitors. Herein, the tuned fabrication of ultrathin and tortuous nickel/cobalt-layered double hydroxide (NiCo-LDH) nanosheets via a graphene oxide (GO) surface-confined strategy is reported, yielding nanosheets with a thickness of 1.7–1.8 nm that is duplicated from the graphene oxides in terms of both the lateral size and the shape. It has been found that the C/O functional groups on the GO surface have functioned to promote the oxidation of Co2+ to Co3+, and to transform the β-phase NiCo-hydroxide (NiCo-OH) into the LDH-phase with tuned homogenous composition and geometry. The ultrathin NiCo-LDH nanosheets mimic the morphology and size of the graphene due to the surface-confined and/or surface-guided growth. The as-obtained NiCo-LDH-graphene (NiCo-LDH-G) nanosheets exhibit a superior electrocatalytic activity for oxygen evolution reaction, evidenced by a small overpotential of 0.337 V (@10 mA cm−2 in 0.1 m KOH electrolyte), and a high charge storage capability of 1489 F g−1 as electrodes for supercapacitors. This 2D surface-confined growth strategy may pave a way for the fabrication of ultrathin 2D materials including but not limited to transition metal hydroxides for high-performance electrochemical applications.

Synthesis and Optical Properties of Two Cobalt Oxides (CoO and Co3O4) Nanofibers Produced by Electrospinning Process

Abstract: In the present study, cobalt(II) oxide (CoO), which is hard to synthesize because of the chemical activity of cobalt metal, and the popular cobalt(II, III) oxide (Co3O4) have been successfully produced in smooth and continuous nanofibrous form by using the electrospinning technique. An aqueous cobalt acetate tetrahydrate and poly(vinyl alcohol) mixture has been electrospun and vacuously dried at 80 °C. Pure, smooth and solid Co3O4 nanofibers were produced when the dried nanofiber mats were calcined in air atmosphere at 700 °C. Water gas has been prepared by a novel technique to produce pure CoO nanofibers from the original cobalt acetate/poly(vinyl alcohol) nanofiber mats. The nanofiber mats have been hydrothermally treated in the presence of carbon at 300 °C in an especially designed reactor. The invoked physiochemical analyses have affirmed formation of both oxides in nanofibrous shape. The optical properties of the obtained nanofibers have been studied. UV−visible absorbance spectra have indicated that...

Comparison of cobalt-based nanoparticles as electrocatalysts for water oxidation.

Abstract: The controlled synthesis of e-Co, CoO, and Co3O4 nanoparticles with the same stabilizers and with nearly identical particle size and shape allows comparisons of the inherent catalytic properties of these materials in the oxygen evolution reaction (OER). The nanoparticle electrodes exhibit relatively low overpotentials and very similar catalytic activities under basic conditions. The latter observation indicates that all three catalysts operate with similar catalytic mechanisms.