Formation Of Cobalt Oxide Nanoparticles Research Articles

Biological Synthesis of Cobalt Oxide Nanoparticles Using Ziziphus oenopolia Leaf Extract

In this article, cobalt oxide nanoparticles were synthesized from the leaf extract of Ziziphus oenopolia by using cobaltous chloride hexahydrate. The prepared samples were characterized and subjected to the antimicrobial activity of some pathogens. The first confirmation of the formation of the cobalt oxide nanoparticles resulted from the reaction mixture’s color change from light brown to dark brown at room temperature. Further, UV-Visible spectrum analysis showed a strong absorption band at the visible region around 269 nm, confirming the formation of stable cobalt oxide nanoparticles. From the FT-IR spectrum, the peaks at 3626, 2978, 1689,1519,1396 and 578 cm-1 show the presence of OH stretching, C=O group, C=C stretching, C-C bonds and cobalt oxide nanoparticles. The X-ray diffraction showed their crystalline nature with a face-centered cubic structure; the surface morphology revealed an irregular shape. The antibacterial studies have been carried out against four bacterial strains such as Staphylococcus aureus, Streptococcus aureus, Escherichia coli and Klebisella pneumonia; E. coli showed the highest zone of inhibition. The antifungal studies were exhibited against Candida albicans, Candida vulgaris, Aspergillus flavus and Aspergillus niger; Aspergillus niger showed the highest zone of inhibition.

Synthesis of cobalt oxide nanoparticles coated with carbon and its catalytic applications in organic reactions

Cobalt oxide nanoparticles coated with carbon were prepared by the modified flame pyrolysis method. The preparation was carried out by simply exposing the cobalt nitrate salt onto a spatula to gas flame, the flame temperature converted the cobalt nitrate into cobalt oxide, which further get coated by carbon produced from the combustion of fuel gas. The obtained product from the flame pyrolysis was characterized using techniques viz. XRD, FTIR and SEM. SEM data show that the short length rod shaped nanoparticles coated with carbon ranging from 0.3 to 1 µm µm formed during the process. XRD and FTIR data also support the formation of cobalt oxide nanoparticles coated with carbon particles. Cobalt oxide NPs were utilized for the catalytic N-formylation reaction of amines at 70–80 °C. The optimization of the catalyst as well as temperature have been done carefully. The product of the reaction were characterized by various techniques viz. FTIR, HRMS and 1H NMR which confirmed the formation of the product.

Cobalt oxide nanoparticles by flame pyrolysis for efficient removal of mixed dyes

The cobalt oxide nanoparticles were prepared by low cost, gram scalable and environment friendly flame pyrolysis method by directly burning ethanolic solution of cobalt chloride. The cobalt oxide formation, functional group identification, morphology and particles size of as-synthesized nanoparticles were carried out using routine techniques viz. XRD, FTIR, FE-SEM, HR-TEM, Raman Spectroscopy and Vibrating Sample Magnetometer (VSM) analysis. The XRD pattern ensured the formation of Cobalt Oxide nanoparticles (CoO NPs). It also emphasized that synthesized CoO NPs are pure, crystalline and single phased. EDS ensured the purity of CoO NPs which contained only cobalt and oxygen. FE-SEM exhibited spherical morphology with particles size of around 30 nm aligned with Debye–Scherrer’s calculated average crystallite size of 20 nm. The optical direct band gap of CoO NPs was estimated using Kubelka - Munk function to be 2.97 eV. The magnetic behavior examined at room temperature by VSM confirmed the formation of CoO NPs with weak ferromagnetic nature. The CoO NPs were utilized successfully for the removal of mixed dye solutions. The CoO NPs showed excellent efficiency for the removal of mixture of hazardous dyes from the aqueous solutions. This makes CoO NPs valuable for removal of industrial dyes and colorants for the waste water treatment processes.

Size effects and active state formation of cobalt oxide nanoparticles during the oxygen evolution reaction

Water electrolysis is a key technology to establish CO2-neutral hydrogen production. Nonetheless, the near-surface structure of electrocatalysts during the anodic oxygen evolution reaction (OER) is still largely unknown, which hampers knowledge-driven optimization. Here using operando X-ray absorption spectroscopy and density functional theory calculations, we provide quantitative near-surface structural insights into oxygen-evolving CoOx(OH)y nanoparticles by tracking their size-dependent catalytic activity down to 1 nm and their structural adaptation to OER conditions. We uncover a superior intrinsic OER activity of sub-5 nm nanoparticles and a size-dependent oxidation leading to a near-surface Co–O bond contraction during OER. We find that accumulation of oxidative charge within the surface Co3+O6 units triggers an electron redistribution and an oxyl radical as predominant surface-terminating motif. This contrasts the long-standing view of high-valent metal ions driving the OER, and thus, our advanced operando spectroscopy study provides much needed fundamental understanding of the oxygen-evolving near-surface chemistry.

Reductive N-methylation of alkanolamines with paraformaldehyde in the presence of cobalt catalysts

Herein a simple method for N-methylation of ethanolamines with paraformaldehyde as a dual methylation and reducing agent has been investigated. Two new cobalt complexes, Co[Methyl 6-(morpoline methyl) picolinate]2Cl2 and Co(2,6 bis morpholine methyl pyridine)Cl2 were prepared and applied as homogeneous catalyst in reductive methylation reaction. All experiments have progressed with excellent conversion and selectivity toward N,N dimethyl ethanolamine. On the other hand, Pyrolysis of prepared cobalt complexes on activated carbon at 550 °C leads to the formation of cobalt oxide nano-particles. These heterogeneous catalysts were shown similar activities in this reaction. Single-crystal X-ray crystallography, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used for characterization of prepared catalysts.

In situ formation of Co3O4 nanoparticles embedded N-doped porous carbon nanocomposite: a robust material for electrocatalytic detection of anticancer drug flutamide and supercapacitor application.

Theone-step synthesis of heteroatom-doped porous carbons is reportedwith the in situ formation of cobalt oxide nanoparticles for dual electrochemical applications (i.e., electrochemical sensor and supercapacitor). A single molecular template of zeolitic imidazole framework-67 (ZIF-67) was utilized for the solid-state synthesis of cobalt oxide nanoparticle-decorated nitrogen-doped porous carbon (Co3O4@NPC) nanocomposite through a facile calcination treatment. For the first time, Co3O4@NPC nanocomposite derived from ZIF-67 has been applied as an electrode material for the efficient electrochemical detection of anticancer drug flutamide (FLU). The cyclic voltammetry studies were performed in the operating potential from 0.15 to - 0.65V (vs. Ag/AgCl). Interestingly, the fabricated drug sensor exhibited a very low reduction potential (- 0.42V) compared to other reported sensors. The fabricated sensor exhibited good analytical performance in terms of low detection limit (12nM), wide linear range (0.5 to 400μM), and appreciable recovery results (~ 98%, RSD 1.7% (n= 3)) in a human urine sample. Hereafter, we also examined the supercapacitor performance of the Co3O4@NPC-modified Ni foam in a 1M KOH electrolyte, and noticeable a specific capacitance of 525Fg-1 at 1.5 A g-1 was attained, with long-term cycling stability. TheCo3O4@NPC nanocomposite supercapacitor experiments outperform the associated MOF-derived carbons and the Co3O4-based nanostructure-modified electrodes.

Optimisation of Cobalt Oxide Nanoparticles Synthesis as Bactericidal Agents.

AIM:With the increased bacterial resistance and the resulting problems in recent years, it seems necessary to find new biocompatible compounds to confront this problem. This research was conducted to optimise the synthesis of cobalt oxide nanoparticles with the highest antibacterial activity.METHODS:In the present study, 9 experiments were designed using the Taguchi method. The effect of three factors of cobalt nitrate, KOH and the stirring time in the synthesis of cobalt oxide nanoparticles with the highest antibacterial activity was investigated. The bactericidal effect of synthesised nanoparticles was evaluated using the colony-forming unit (CFU) and disk diffusion methods. The characteristics of nanoparticles were studied using the Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and the scanning electron microscopy (SEM).RESULTS:The results indicated that all three evaluated factors were effective on the antibacterial properties of the synthesised nanoparticles. The best antibacterial activity of cobalt oxide nanoparticles was observed in experiment 9 (cobalt nitrate 0.6 M, KOH 2M and stirring time 60 min). The study of nanoparticles synthesised by FTIR, XRD, and SEM confirmed the formation of cobalt oxide nanoparticles with size (24 nm) and a proper structure (spinel structure).CONCLUSION:Due to the optimal antibacterial properties of the synthesised cobalt oxide nanoparticles, they can be used in the fabrication of dental and medical equipment with antibacterial properties.

Convenient and Mild Epoxidation of Alkenes Using Heterogeneous Cobalt Oxide Catalysts

A general epoxidation of aromatic and aliphatic olefins has been developed under mild conditions using heterogeneous Cox Oy -N/C (x=1,3; y=1,4) catalysts and tert-butyl hydroperoxide as the terminal oxidant. Various stilbenes and aliphatic alkenes, including renewable olefins, and vitamin and cholesterol derivatives, were successfully transformed into the corresponding epoxides with high selectivity and often good yields. The cobalt oxide catalyst can be recycled up to five times without significant loss of activity or change in structure. Characterization of the catalyst by XRD, TEM, XPS, and EPR analysis revealed the formation of cobalt oxide nanoparticles with varying size (Co3 O4 with some CoO) and very few large particles with a metallic Co core and an oxidic shell. During the pyrolysis process the nitrogen ligand forms graphene-type layers, in which selected carbon atoms are substituted by nitrogen.

Convenient and Mild Epoxidation of Alkenes Using Heterogeneous Cobalt Oxide Catalysts

AbstractA general epoxidation of aromatic and aliphatic olefins has been developed under mild conditions using heterogeneous CoxOy–N/C (x=1,3; y=1,4) catalysts and tert‐butyl hydroperoxide as the terminal oxidant. Various stilbenes and aliphatic alkenes, including renewable olefins, and vitamin and cholesterol derivatives, were successfully transformed into the corresponding epoxides with high selectivity and often good yields. The cobalt oxide catalyst can be recycled up to five times without significant loss of activity or change in structure. Characterization of the catalyst by XRD, TEM, XPS, and EPR analysis revealed the formation of cobalt oxide nanoparticles with varying size (Co3O4 with some CoO) and very few large particles with a metallic Co core and an oxidic shell. During the pyrolysis process the nitrogen ligand forms graphene‐type layers, in which selected carbon atoms are substituted by nitrogen.

Amperometric detection of acetaminophen by an electrochemical sensor based on cobalt oxide nanoparticles in a flow injection system

This paper reports the use of a carbon ceramic electrode as a highly-porous substrate for the electrochemical formation of cobalt oxide nanoparticles. The electrocatalyst was characterized by energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry techniques, and it was used in a homemade flow injection analysis (FIA) system for acetaminophen determination using 0.1 M KOH as the carrier solution. The rate constant ( k s) and charge transfer coefficient ( α) were calculated for the electron exchange reaction of the modified film. The kinetic parameters and the mechanism of acetaminophen electrooxidation at the electrode surface were studied by cyclic voltammetry and chronoamperometry. The effects of working potential and flow rate on the performance of the FIA system were studied. Under optimized conditions, the electrode response due to the electrocatalytic oxidation of acetaminophen at 450 mV (vs. SCE) is proportional to the concentration of acetaminophen over a 5–35 μM range with an associated detection limit (S/N = 3) of 0.37 μM and a sensitivity of 0.0296 μA/μM. The relative standard deviation (RSD) was 1.6% for eight replicate measurements. The modified electrode was used to determine the acetaminophen content in tablet samples.

Constrained synthesis of cobalt oxide nanomaterials in the 12-subunit protein cage from Listeria innocua.

The protein cage of the 12-subunit ferritin-like protein from Listeria innocua has been utilized as a size and shape constrained reaction environment for the synthesis of two cobalt oxide minerals, Co(3)O(4) and Co(O)OH. Reaction of Co(II) with H(2)O(2) at pH 8.5 under either elevated temperature (65 degrees C) or ambient temperature (23 degrees C) resulted in the formation of cobalt oxide nanoparticles encapsulated within the protein cage. At elevated temperatures, Co(3)O(4) was formed while at lower temperature the oxyhydroxide Co(O)OH was found. Mineral particles, commensurate in size with the internal dimensions of the protein (5 nm), were imaged by transmission electron microscopy and shown to be surrounded by the intact protein cage. The minerals were investigated by electron diffraction and revealed a crystalline Co(3)O(4) phase and an amorphous Co(O)OH phase. Further investigation of these composite materials using size exclusion chromatography, gel electrophoresis, dynamic light scattering, and zeta potential measurements indicated that the mineral was encapsulated within the protein cage giving rise to properties of both the mineral and protein components.