Cobalt Acetate Research Articles

Preparation of GdCoO3 by Sol-Gel Method and Its Photocatalytic Activity

Using gadolinium nitrate, cobalt acetate, citric acid as main raw materials, GdCoO3 was successfully prepared by sol-gel method. The prepared samples were characterized by thermogravimetric differential scanning analysis (TG-DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy(FT-IR). Using methyl orange solution as simulated sewage, it was investigated that the effects of synthesis temperature and illumination time on photocatalytic activity of GdCoO3. The results show that the pure cubic perovskite GdCoO3 samples can be prepared at calcination temperature of 700 °C to 1000 °C. The GdCoO3 calcined at 900 °C has uniform particles and an average grain size of about 0.5 μm to 1 μm. The photocatalytic performance of GdCoO3 calcined at 900 °C sample was the best. Under the condition of UV-light for 120 min, the photocatalytic degradation rate of methyl orange reached more than 96% in presence GdCoO3 calcined at 900 °C. This indicates that GdCoO3 has good photocatalytic performance.

Method of obtaining multicomponent fine-grained powders for boron carbide matrix ceramics production

The paper presents a low-temperature method for the synthesis of tungsten boride containing ultra-fine powders of boron carbide matrix ceramics constituting an important class of superhard materials with diversity of industrial applications. Wet chemical method was used to prepare preceramic precursors. The technique provides annealing of a viscous paste of the mixture of ammonium paratungstate–zirconium(IV) oxide–cobalt acetate tetrahydrate–sucrose–amorphous boron at 200 °C in air and then at 600 °C in argon atmosphere for 2 h with the further grinding and additional annealing of the obtained powders at 800–1500 °C. Hot pressing of the complex ceramic powders at 1000–1700 °C was realized by using the SPS method. It was established that at 600 °C there were formed WO3–x, Co3O4, CoO, and amorphous carbon. The XRD data confirmed low temperature (800–1000 °C) formation of WC–Co, ZrB2, B4C, and W2B5. Tungsten carbide was completely converted into tungsten boride. Structural-morphological characteristics of the obtained samples were studied by using the SEM.

Exploring the studies of charge transportation of an aromatic acid based Co(II)-Metallogel scaffold fabricated Schottky device

An efficient supramolecular metallogel of Cobalt(II) has been synthesized through the ultra-sonication technique. Cobalt(II)-salt (Cobalt acetate tetrahydrate), organic acid like terephthalic acid along with N,N-dimethyl formamide solvent are the key ingredients of the Co(II)-metallogel. The rheology-based experimental values of storage and loss modulus of the Co(II)-metallogel prove the mechanical efficiency of the metallogel-material. The chemical compositions are found through elemental investigations. The infrared spectral results help to realize the metallogel formation strategy. The electrical characteristics of the synthesized metallogel have been properly investigated. The semiconducting feature of the metallogel-material has been experimentally verified. The measured current-voltage characteristics of Cobalt(II)-metallogel (Co-TA) based thin film type metal-semiconductor (MS) junction-device shows a non-linear rectifying behaviour, representing a Schottky diode (SD) performance with promising electronic charge transport property.

Synthesis, crystal structure, Hirshfeld surface analysis, spectroscopic characterizations and electrical properties of the new complex of cobalt (III) and the Schiff-base of dihydroxycoumarin

A new cobalt (III) complex, the [3,3′-{ethane-1,2-diylbis[(azanylylidene)eth-1-yl-1-ylidene]}bis [4-(hydroxy)-2H-1-benzopyran-2-onato]]-[bis(pyridine)]-cobalt chloradioxirane-1,1-dione hydrate, promising for its fluorescent and electrical properties was synthesized by the reaction of the Schiff-base '4-hydroxy-3-((E)-1-(2-((E)-1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylideneamino) ethylimino) ethyl)-2H-chromene-2-one' and cobalt(II) acetate tetrahydrate under an oxygen-rich atmosphere. The structure was determined by single crystal X-ray diffraction and confirmed by FT-IR and UV-visible spectroscopies. Hirshfeld's surface analysis indicates that the most important inter-molecular hydrogen bond within crystal packing is O-H⋯O interaction and the presence of a π-π stack was evident by the shape index and the curvature. It was also characterized for its high green emission in polar aprotic solvents using spectrofluorimetry. Dielectric constant (ε′), dielectric loss (tan δ) and conductivity (σ) were studied as a function of temperature and frequency. The results could be very significant in electronic and optoelectronic device applications.

Cobalt-benzene-1,4-dicarboxylic acid coordination polymer for efficient removal of anionic and cationic dyes

Dye removal from wastewater is an important research area due to the stability, toxicity, and potential carcinogenic properties of dyes. Herein, cobalt-benzene-1,4-dicarboxylic acid (Co-BDC) coordination polymer was precipitated from DMF solution of cobalt acetate and benzene-1,4-dicarboxylic acid (BDC) at room temperature. EDX, XPS, ICP-OES, and elemental analyses confirmed the composition of the prepared coordination polymer. SEM image showed microparticles with 200–400 nm. Physical adsorption of Congo red (CR) and methyl orange (MO) as anionic and methylene blue (MB) and malachite green (MG) as cationic dyes with Co-BDC was investigated. The experimental data exhibited higher removal efficiency of Co-BDC towards anionic rather than cationic dyes probably due to its stronger π-π stacking and electrostatic interactions. The removal efficiency of Co-BDC towards CR reaches 84% only after 2 minutes. The XRD and FT-IR analyses confirmed the preservation of the Co-BDC structure even after a long time. The removal efficiency of the prepared Co-BDC toward anionic dyes remained unchanged after two cycles and showed minor loss after three and four cycles. Therefore, the strategy of selecting adsorbents based on the structural properties is efficient for designing and preparing high-performance adsorbents.

Mutational property of newly identified mutagen l-glutamic acid γ-hydrazide in Escherichia coli.

We previously found that an l-glutamine analog l-glutamic acid γ-hydrazide has high mutagenic activity through the high-throughput laboratory evolution of Escherichia coli. In this study, mutagenicity and mutational property of l-glutamic acid γ-hydrazide were examined by the Ames test and mutation accumulation experiments using E. coli. The Ames test revealed that l-glutamic acid γ-hydrazide showed higher mutagenic activity without metabolic activation than known mutagens 2-aminoanthracene, and cobalt(II) acetate tetrahydrate. This result indicates that l-glutamic acid γ-hydrazide does not require metabolic activation for mutagenic activity in E. coli. Mutation accumulation experiments and whole-genome sequencing analysis revealed the number and spectrum of the accumulated mutations with or without l-glutamic acid γ-hydrazide. In the presence of l-glutamic acid γ-hydrazide, MDS42 strain accumulated 392.3 ± 116.2 point mutations during 30 passages corresponding to 777 generations, while MDS42 strain accumulated 1.5 ± 2.5 point mutations without l-glutamic acid γ-hydrazide during 50 passages corresponding to 1341 generations. The mutational spectrum of l-glutamic acid γ-hydrazide was G/C to A/T transition (82.2 ± 4.3 %) and A/T to G/C transition (17.4 ± 4.3 %). These results indicated that l-glutamic acid γ-hydrazide has a strong mutagenic activity.

The Coordination chemistry and cyclic voltammetry exploration of Cu(II), Co(II), Ni(II) and Zn(II) complexes of novel (E)-3,4-dichloro-N-(2-(1-(pyridin-2-yl)ethylidene)hydrazine-1-carbonothioyl) benzamide ligand

Abstract A novel thiosemicarbazone derivative (DEHC-H), (E)-3,4-dichloro-N-(2-(1-(pyridin-2-yl)ethylidene) hydrazine-1-carbonothioyl) benzamide was synthesized after three steps. Firstly, the reaction between acetyl pyridine with hydrazine hydrate at room temperature obtaining (E)-2-(1-hydrazonoethyl)pyridine. Secondly, 3,4-dichlorobenzoyl chloride was refluxed with potassium thiocyanate in acetonitrile solvent forming 3,4-dichlorobenzoyl isothiocyanate. The last step of the reaction is summarized by the refluxing the mixture of (E)-2-(1-hydrazonoethyl) pyridine and 3,4-dichlorobenzoyl isothiocyanate in acetonitrile solvent. A series of eight new metal complexes, Copper(II), Cobalt(II), Nickel(II) and Zinc(II) chloride and acetate complexes of the thiosemicarbazone ligand (DEHC-H) were accomplished in DMF/H2O or CHCl3/CH3OH mixture solvents. The {[(DEHC)CuCl], [(DEHC)CoCl], [(DEHC)NiCl], [(DEHC-H)ZnCl2], [(DEHC-H)2Cu](CH3COO)2, [(DEHC-H)2Co](CH3COO)2, [(DEHC-H)2Ni](CH3COO)2 and [(DEHC-H)2Zn](CH3COO)2} were prepared by the reaction of the free ligand with chloride and acetate metal salts, CuCl2.2H2O, CoCl2.6H2O, NiCl2.6H2O, ZnCl2, Cu(CH3COO)2.H2O, Co(CH3COO)2.4H2O, Ni(CH3COO)2.4H2O and Zn(CH3COO)2.2H2O. The preparation of the metal complexes was achieved in 1:1 and 1:2 mole ratios of (Metal salt : free Ligand). The identities of the (DEHC-H) ligand and its metal chloride and acetate complexes were characterized and confirmed by 1HNMR, 13CNMR, UV-visible, Infrared, mass spectroscopy, elemental analysis, solubility test, magnetic moments and conductivity measurements. The spectroscopic techniques and measurements indicate that metal chloride complexes were formed with the neutral structural formula [(DEHC)MCl], where M= Copper(II), Cobalt(II) and Nickel(II) and with the neutral structural formula [(DEHC-H)ZnCl2] for Zinc(II) complexes in spite of two mole ratios were examined. Moreover, the acetate complexes were formed as anionic formula [(DEHC-H)2M](CH3COO)2. The employed techniques indicate that thiosemicarbazone chloride complexes with formula [(DEHC)MCl], one tridentate [(DEHC) ligand coordinating in the thiole form with the metal ion and the fourth site was the chloride anion to form square planar geometry. While Zinc(II) complex [(DEHC-H)ZnCl2] show coordinating of the one tridentate [(DEHC-H) ligand as thione where the fourth and the fifth sites coordinating with the Zinc(II) ion to adopt a square pyramidal geometry. The characterization of the all acetate complexes [(DEHC-H)2M](CH3COO)2 pointed to two moles of tridentate [(DEHC-H) ligands in thione form coordinating with the metal ions to fill six sites forming octahedral geometry as well as to two moles of acetate ions as counter ions. It is worth noting that tridentate thiosemicarbazone [(DEHC-H) ligand coordinates through the nitrogen pyridyl, thionic sulfur and the azomethine nitrogen atoms. The observed magnetic moments data exhibit diamagnetic properties of Zinc(II) chloride and acetate complexes and Nickel(II) square planar chloride complexes. While Cu(II) and Co(II) square planar chloride compounds and Copper(II), Cobalt(II) and Nickel(II) octahedral acetate complexes appeared as paramagnetic species. The electrochemical behavior of a set Copper(II), Cobalt(II) and Nickel(II) chloride and acetate complexes of free ligand were recorded using cyclic voltammetry technique. The voltammetric analysis of Copper(II) chloride and acetate complexes displays a quasi-reversible one electron reduction in the range –1.0728 to –1.1439 volt versus Fc/Fc+ ascribable to the Copper(II)/Copper(I) redox couple. The Co(II) and Ni(II) chloride and acetate compounds display one and two irreversible oxidation processes respectively in the range +0.419 to +0.479 in Co(II) compounds and +0.449 to +0.491 as well as to +0.656 to +0.721 volt versus Fc/Fc+ in Ni(II) compounds.

Fischer-Tropsch Synthesis: The Characterization and Testing of Pt-Co/SiO2 Catalysts Prepared with Alternative Cobalt Precursors

Different low-cost cobalt precursors (acetate, chloride) and thermal treatments (air calcination/H2 reduction versus direct H2-activation) were investigated to alter the interaction between cobalt and silica. H2-activated catalysts prepared from cobalt chloride had large Co0 particles (XRD, chemisorption) formed by weak interactions between cobalt chloride and silica (temperature programmed reduction (TPR), TPR with mass spectrometry (TPR-MS), TPR with extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectroscopy (XANES) techniques) and retained Cl-blocked active sites, resulting in poor activity. In contrast, unpromoted Co/SiO2 catalysts derived from cobalt acetate had strong interactions between Co species and silica (TPR/TPR-MS, TPR-EXAFS/XANES); adding Pt increased the extent of the Co reduction. For these Pt-promoted catalysts, the reduction of uncalcined catalysts was faster, resulting in larger Co0 clusters (19.5 nm) in comparison with the air-calcined/H2-activated catalyst (7.8 nm). Both catalysts had CO conversions 25% higher than that of the Pt-promoted catalyst prepared in the traditional manner (air calcination/H2 reduction using cobalt nitrate) and three times higher than that of the traditional unpromoted Co/silica catalyst. The retention of residual cobalt carbide (observed in XANES) from cobalt acetate decomposition impacted performance, resulting in a higher C1–C4 selectivity (32.2% for air-calcined and 38.7% for uncalcined) than that of traditional catalysts (17.5–18.6%). The residual carbide also lowered the α-value and olefin/paraffin ratio. Future work will focus on improving selectivity through oxidation–reduction cycles.

Microwave-assisted thin reduced graphene oxide-cobalt oxide nanoparticles as hybrids for electrode materials in supercapacitor

In recent times, microwave synthetic strategies have been considered as one of the facile methods for the development of efficient supercapacitor electrodes. Reduced graphene oxide containing cobalt oxide (rGO@Co3O4/CoO) hybrids were synthesized via single-step microwave irradiation in which the uniform Co3O4/CoO nanoparticles were attached in thin layers of rGO nanosheets. During short time of single-step microwave irradiation process, three kind of phenomena occurs as (i) reduction and exfoliation of graphite oxide into rGO nanosheets, (ii) decomposition of cobalt(II) acetate into Co3O4/CoO nanoparticles and (iii) rGO nanosheets covers the Co3O4/CoO nanoparticles. The BET surface area and pore diameter range of rGO@Co3O4/CoO hybrids were 133.2 m2g−1 and 5–45 nm, respectively, which shows the mesoporous structure formation of hybrids. Electrochemical evaluations of rGO@Co3O4/CoO hybrids as electrode materials for supercapacitor shows specific capacitance of 276.1 F g−1 (scan rate of 5 mV s−1) and long-term cycling stability as 82.37% capacitance retention after 10,000 cycles (scan rate of 60 mV s−1) in 0.1 M KOH electrolyte solution. The Co3O4/CoO nanoparticles with conducting scaffolds rGO structure will pave an encouraging alternative for electrode materials and suggesting good potential for supercapacitors applications.

Synergistic Effects of Co3O4-CeO2 Nanoparticles towards Catalytic Oxidation of Aromatic Hydrocarbons: A Study in Association with Carbon Monoxide and Humidity

In this study, a series of Co3O4-CeO2 nanocomposites with various Co3O4 loading were fabricated by the impregnation method using cobalt(II) acetate as the cobalt precursor for the treatment of benzene, toluene, ethylbenzene, and xylene (BTEX). The as-prepared Co3O4-CeO2 nanocomposites were thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brumauer-Emmett-Teller (BET), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed desorption (O2-TPD). The excellent reproduction of active oxygen species caused by the high dispersion of Co3O4 crystals on the CeO2 supports was established. In addition, the reduction peaks of Co3O4-CeO2 nanocomposites were found at much lower temperatures compared to pure CeO2, considering their unique redox property influencing on the high catalytic activity. Among the characterized materials, the 5.0 wt.% Co3O4 supported on CeO2 (5.0Co–Ce) was the best system for catalytic oxidation of xylene, along with excellent performances in the cases of benzene, ethylbenzene, and toluene. Its catalytic activity increased in the order: benzene < xylene < ethylbenzene < toluene . Furthermore, the addition of carbon monoxide (CO) as a coreactant permitted to improve the catalytic performances in such oxidations as well as the stability of as-prepared catalysts, even under humid conditions.

Ultralow Co Loading Phenanthroline‐based Porous Organic Polymer as a High‐efficient Heterogeneous Catalyst for the Fixation of CO2 to Cyclic Carbonates at Ambient Conditions

AbstractThe exploration of cost‐effective and efficient catalysts for the transformation of CO2 into chemicals at room temperature and low CO2 pressure is a key challenge. Here, a green synthesis method of porous organic polymer was developed, which was obtained by the Scholl coupling reaction via polycondensation of 1,3,5‐triphenylbenzene and 1,10‐phenanthroline at room temperature. The polymer has a large surface area (1074 m2 g−1) and exhibited excellent CO2 capture of 77.26 cm3 g−1 at 273.15 K and 1.00 bar. After loading cobalt acetate, an ultralow Co loading phenanthroline‐based porous organic polymer was obtained with very high catalytic efficiency in TOF of 263 h−1 for the fixation of CO2 to cyclic carbonates at room temperature and atmospheric with free‐solvent, which is over six‐fold than that of a molecular analogue, 1,10‐phenanthroline‐Co(OAc)2. This work provided a facile, powerful, green, and efficient strategy for designing porous organic polymers as high‐efficient heterogeneous catalysts in the fixation of carbon dioxide.

Electrochemical Studies Of Novel 3,4-Dichloro-N-((5-ChloroPyridin-2-yl)Carbamothioyl)Benzamide Based On Its Complexes With Copper(II), Cobalt(II), Nickel(II) and Zinc(II) ions

The synthesis of novel N,Nʹ-disubstituted benzoyl thiourea ligand [3,4-dichloro-N-((5-chloropyridin-2-yl)carbamothioyl) benzamide] (L) is achieved in two steps. First step by refluxing KSCN with 3,4-dichloro benzoyl chloride in CH3CN solvent and the other step by the reaction of the resulting filtrate from the first step with 2-amino-5-chloropyridine. The copper(II), Cobalt(II), Nickel(II) and Zinc(II) chloride and acetate salts were coordinated with L ligand in the 1:1 and 1:2 mole ratios (M:L) in the solvent mixture of DMF/H2O or CHCl3/methanol to form the complexes with structural formulas {[LMCl2] and [L2M](CH3COO)2, M= Copper(II), Cobalt(II), Nickel(II) and Zinc(II) ions}. Two mole ratios of the starting materials, 1:1 and 1:2 (M:L) were experimented to form chloride complexes, the product was with structural formula [LMCl2] while acetate complexes with [L2M](CH3COO)2 formula are resulted with the same conditions. Ligand L and its complexes [LCuCl2], [LCoCl2], [LNiCl2], [LZnCl2], [L2Cu](CH3COO)2, [L2Co](CH3COO)2, [L2Ni](CH3COO)2 and [(L)2Zn](CH3COO)2 have been characterized by mass spectrometry, elemental analysis, magnetic moments, conductivity measurements, solubility test, UV-visible, FTIR, 1H and 13C NMR spectroscopies. Electrochemical studies were probed by using cyclic voltammetry technique(CV). The data reflect the quasi-reversible reductive nature for the Copper(II) complexes with one electron transfer process while Nickel(II) and Cobalt(II) complexes exhibited two consecutive irreversible reductive nature. The observed UV-visible, elemental analysis, molar conductivity, magnetic moment measurements and solubility test revealed that the metal ion in the all prepared complexes adopted four coordinated square planar structures and [LCuCl2], [LCoCl2], [LNiCl2], [LZnCl2], are formed as neutral complexes while [L2Cu](CH3COO)2, [L2Co](CH3COO)2, [L2Ni](CH3COO)2 and [(L)2Zn](CH3COO)2 adopted anion complexes. The observed magnetic moments show diamagnetic properties of Zinc(II) and Nickel(II) complexes while Copper(II) and Cobalt(II) appeared as paramagnetic species. FT-IR analysis confirmed the coordination sites between the central metal ion with ligand L through two sites, the nitrogen atom in pyridyl ring and the sulphur atom in C=S group

Bimetallic NiCo metal-organic frameworks for efficient non-Pt methanol electrocatalytic oxidation

Bimetallic NiCo-MOF was synthesized via the one-pot synthesis method by using 2,2′-bipyridine-5,5′-dicarboxylic acid as the building block with nickel acetate and cobalt acetate as the mixed precursors. Co and Ni ions were concurrently coordinated with carboxyl groups and pyridyl nitrogen donors. Basic characterizations of the series of MOFs were investigated by diverse techniques. The developed NiCo-MOF consisted of mixed-valence Co(II)/Co(III) and Ni(II)/Ni(III) and rich functional groups. The MOF exhibited a large specific surface area, evenly distributed nanocubes, and high electrocatalytic activity. Compared with the Ni-MOF, Co-MOF, and commercial Pt/C(20 %), the NiCo-MOF catalyst had improved electrocatalytic activity toward methanol oxidation reaction (MOR). High current density of 225 mA cm−2 at the potential of 1.6 V versus RHE in alkaline medium was achieved. Moreover, remarkable cycling stability in the MOR conditions was observed and only showed a slight decline after 5000 s. The catalytic mechanism of NiCo-MOF toward MOR was provided.

Self-template synthesis of hollow Fe-doped CoP prisms with enhanced oxygen evolution reaction activity

The development of efficient, durable and low cost electrocatalysts is crucial but extremely challenging for the oxygen evolution reaction (OER). Herein, we develop a self-template strategy to synthesize hollow Fe-doped CoP prisms (Fe-CoP) via ion exchange of cobalt acetate hydroxide with [Fe(CN)6]3- and phosphorization-induced transformation of CoFe-PBA (Co/Fe-containing prussian blue analogue) prisms in N2 atmosphere. The obtained Fe-CoP not only inherits the hollow prism-like morphology of CoFe-PBA, but also forms rich mesoporous channel. The Fe-CoP prisms exhibit extraordinary OER performances in 1.0 M KOH, with a low overpotential of 236 mV to deliver a current density of 10 mA cm−2 and a low Tafel slope of 32.9 mV dec–1. Moreover, the presented electrocatalyst shows good long-term operating durability and activity. The XPS and TEM analysis confirm that Fe-CoP has undergone surface reconstruction in the process of electrocatalytic OER, and the in situ formed oxides and oxyhydroxides are the real active species to boost OER. This work provides a promising pathway to the design and synthesis of efficient and robust electrocatalysts with hierarchical hollow structure for boosting OER.

Buffered Coordination Modulation as a Means of Controlling Crystal Morphology and Molecular Diffusion in an Anisotropic Metal-Organic Framework.

Significant advances have been made in the synthesis of chemically selective environments within metal-organic frameworks, yet materials development and industrial implementation have been hindered by the inability to predictively control crystallite size and shape. One common strategy to control crystal growth is the inclusion of coordination modulators, which are molecular species designed to compete with the linker for metal coordination during synthesis. However, these modulators can simultaneously alter the pH of the reaction solution, an effect that can also significantly influence crystal morphology. Herein, noncoordinating buffers are used to independently control reaction pH during metal-organic framework synthesis, enabling direct interrogation of the role of the coordinating species on crystal growth. We demonstrate the efficacy of this strategy in the synthesis of low-dispersity single-crystals of the framework Co2(dobdc) (dobdc4-= 2,5-dioxido-1,4-benzenedicarboxylate) in a pH 7-buffered solution using cobalt(II) acetate as the metal source. Density functional theory calculations reveal that acetate competitively binds to Co during crystallization, and by using a series of cobalt(II) salts with carboxylate anions of varying coordination strength, it is possible to control crystal growth along the c-direction. Finally, we use zero length column chromatography to show that crystal morphology has a direct impact on guest diffusional path length for the industrially important hydrocarbon m-xylene. Together, these results provide molecular-level insight into the use of modulators in governing crystallite morphology and a powerful strategy for the control of molecular diffusion rates within metal-organic frameworks.

Investigation of advanced catalytic effect of Co3O4 nanosheets modified carbon felts as vanadium flow battery electrodes

3D petal-like Co3O4 nanosheets with the mesoporous structure are produced successfully and coated firmly on carbon fibers by simply electrodepositing cobaltous acetate tetrahydrate and its subsequent calcination. The morphology of the precursor, which dominates the structure of the final product, evolves from layers of moss-like amorphous cobalt compounds to Co3O4 nanosheets with obvious lattice defects. Compared with Co3O4 nanoparticles synthesized by the traditional hydrothermal method, the nanosheet layered structure has a higher specific surface area and more active sites. The 3D Co3O4 nanosheets are further used as modification materials to fabricate electrodes with excellent electrocatalytic activity and good reversibility towards both the positive and negative vanadium redox reactions. With the Co3O4 nanosheets modified electrodes, the battery demonstrates remarkably improved performance and shows excellent long-term stability with a dischargeable capacity decay rate of only 2.9 mAh per cycle, which is 70% lower than that of the battery with unmodified electrodes.

Co(II) and Ni(II) bis(salamo)-based tetraoxime complexes: Syntheses, structural characterizations, fluorescence properties, and Hirshfeld analyses

Two new asymmetric complexes with the chemical structural formulas [{Co2(L)(μ 2-OH)}{Co2(L)(OAc)(CH3OH)}{Co2(L)(μ 2-OCH3)}{Co2(L)(μ 2-OAc)}]⋅4CH3OH and [Ni2(L)(μ 2-OAc)(CH3OH)]⋅CH2Cl2⋅3CH3OH have been synthesized from cobalt(II) acetate, nickel(II) acetate, and a bis(salamo)-based tetraoxime ligand derived from 3-bromo-5-chlorosalicylicaldehyde and 4-tert-butyl-2,6-diformylphenol, respectively, and characterized by elemental analyses, IR, UV–vis, fluorescence spectra, and single-crystal X-ray diffraction analyses. The Co(II) complex unit cell contained four crystallographically independent and chemically different heterotrinuclear complexes (molecules A, B, C, and D). The crystal structure included eight Co(II) ions, four completely deprotonated ligand (L)3− moieties, one bridging hydroxide, one monodentate acetate, one bridging methoxy, one bidentate chelating acetate, one coordinated methanol, and four crystallization methanol molecules. The Ni(II) complex had a dinuclear structure. The crystal structure of the Ni(II) complex included two Ni(II) ions, one completely deprotonated ligand (L)3−, one bidentate bridging acetate, one coordinated methanol, one crystallized dichloromethane, and three crystallized methanol molecules. Hirshfeld surface analyses showed that the complexes are stable. Furthermore, the fluorescence quenching of the Co(II) and Ni(II) complexes with H3L further confirmed the above experimental results.

Using the method of pyrolytic mass spectrometry in the study of biodegradable polymeric materials

The results of pyrolytic mass spectrometry studies of biodegradable polymeric materials based on polyolefins and segmented polyurethanes with various functional additives are summarized. The structure and composition of initial and after exposure in soil, climate chamber and after exposure to microorganisms (bacteria, yeast) composites are characterized. In the research presented, influence of acetates and complexonates of metals, including cobalt, copper and zinc, on the structural changes in the high pressure polyethylene (HPPE) occurring under the impact of factors such as temperature, humidity and UV-radiation is investigated. It was established, that samples of HPPE, modified by cobalt acetate and cobalt and copper complexonates are responsive and most sensitive to the action of above-mentioned physical factors. Investigation of a segmented polyurethanes (SPU) of a different chemical structure influenced by a factors, modeling of the environmental conditions was conducted. It was shown using pyrolytic mass-spectrometry method and monitoring of samples’ weight loss that under the influence of above-mentioned environmental factors in the SPU occurs processes, resulting to changing its micro heterogeneous structure. It is established that SPU having ester links in its structure and being exposured in soil for 120 days is predominantly attacked by microorganisms, then the main active factor appears to be soil’ pH value – after 300 days in soil with alkaline or acid solution SPU sample decomposes into a separate fragments. Features of the chemical structure of urethane polymers synthesized on the base of hydroxylated rapeseed oil (polyol) were examined. Analysis of the results showed that the macromolecular compounds obtained are segmented polyurethanes which thermal degradation occurs in two stages: hard blocks are destroyed at the first stage, while polyol part (soft blocks) decomposes at the second stage, allowing to identify the temperature area of polymer destruction and thus its temperature region of operation. It is shown that the most suitable from the viewpoint of environmental friendly is polyurethane composition containing more than 50% of polyol. Thermal mass-spectrometry (TMS) has been employed to investigate processes of thermal destruction of segmented polyurethane and it’s compositions filled by polysaccharides: starch, dextrin, chitosan. The features of thermal destruction for segmented polyurethane and related compositions before and after their storage in a soil have been determined. Application TMS is shown to permit the processes of biodegradation of polymeric materials to investigate.

FABRICATION OF ANTIBACTERIAL MATERIAL USING DIFFERENT ACETATE SALTS

Ammonium, Cadmium, Cobalt, Sodium and Magnesium acetates were diluted inside both distilled water and Isopropanol alcohol separately and then tested as antibacterial material against (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella sp. and Candida albicans). Among diluted salts in water only Cadmium and Cobalt acetate had inhibition zones. The particles sizes inside distilled water were 5.6 and 25.5 nm for diluted Cadmium and Cobalt acetate respectively as measured by particle size distribution test. The addition of all used acetate salts on Isopropanol alcohol increased its ability for killing tested bacteria. All diluted acetates in Isopropanol alcohol had inhibition zones, both Cadmium and Cobalt acetates had equal or larger inhibition zones than those diluted in water. Minimum bactericidal concentration (MBC), minimal inhibitory concentration (MIC) and biofilm inhibition% were measured for Cadmium acetate and cobalt acetate.

Effect of type and concentration of cobalt precursor on structural, optical and defect properties of ZnCoO nanoparticles

ZnO and ZnCoO nanoparticles were synthesized by hydrothermal route via various Cobalt precursors (cobalt chloride hexahydrate, cobalt nitrate hexahydrate, and cobalt acetate tetrahydrate) and different Cobalt precursor concentrations (10 %–30 %) in synthesis solution. Incorporation of Cobalt into the ZnO structure and its effect were examined by means of elemental, structural, optical and photoluminescence studies. It was observed that the outcome of cobalt incorporation varied according to the dopant source used in the synthesis solution. Besides, the dopant source not only affected the doping ratio but also the morphological, crystal, optical properties of synthesized nanoparticles. Once cobalt acetate tetrahydrate was determined as the adequate precursor, effects of doping on photoluminescence and point defects were studied for different precursor concentrations and reaction times. It was observed that cobalt doping significantly reduces concentration of point defects in nanoparticles.