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An electrochemical sensor for anti-inflammatory drug flufenamic acid, based on cobalt oxide (Co3O4) modified carbon paste electrode (CPE), has been fabricated. Co3O4 NPs was synthesized and characterized by UV-visible spectrophotometry, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The novel 0.5%(w/w)Co3O4/CPE sensor was also evauatedusing the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It showed a much-enhanced electroactive surface area and low charge transfer resistance (Rct), revealing that it has greatly enhance electron transfer process. Square wave voltammetry (SWV) was utilized as a sensitive method for the determination of very low concentrations of flufenamic acid. Under the optimized conditions, the limits of detection (LOD) and quantification (LOQ) of 0.5%Co3O4(w/w)/CPE were 4.8×10–9 M (1.35 ng/mL) and 1.6×10–8 M (4.50 ng/mL), respectively. After validation of the fabricated sensor, it was successfully applied for sensitive and selective determination of the drug in spiked human serum with LOD and LOQ of 4.5×10–8 M (12.65 ng/mL) and 1.5×10–7 M (42.18 ng/mL). [ABSTRACT FROM AUTHOR]

The design of hybrid electrocatalysts with abundant active sites and long term stability is crucial for efficient oxygen evolution reaction (OER) application. Cobalt oxide is considered as one of the most promising electrocatalysts to replace noble metal due to its low cost, availability, and electrocatalytic activity towards the oxygen evolution reaction in alkaline media. However, nano-scale cobalt oxide suffers from severe surface self-agglomeration during the OER process, so that leading to poor activity and durability. Herein, ultra-small cobalt oxide nanoparticles are anchored on the surface of nitrogen doped porous 3D graphitic carbon nano-spheres (N-ACS@Co 3 O 4) to increase the amount of exposed active site and avoid the self-agglomeration. The obtained electrocatalyst (N-ACS@Co 3 O 4) is enriched with abundant oxygen vacancies and exhibits a superior OER activity (Overpotential of 237 mV at 10 mA.cm−2) and exceptional stability for at least 30 h in alkaline electrolyte (1 M KOH). The DFT calculations demonstrate that the strong adsorption of Co 3 O 4 on N-doped graphene can prevent its agglomeration, and therefore improves the stability of Co 3 O 4 nanoparticles during OER process in line with the experimental results. • Cobalt oxide nanoparticles are synthesized on the surface of nitrogen doped carbon. • The hybrid composite enhances the conductivity, charge transfer and generate additional defect active sites. • The N-ACS@Co 3 O 4 exhibits a superior OER activity and exceptional long-term durability. • DFT calculations demonstrate a strong adsorption of Co 3 O 4 on N-doped graphene. • The strong adsorption of Co 3 O 4 prevents its agglomeration, and improves the stability. [ABSTRACT FROM AUTHOR]

Senna auriculata flower extract was utilized in this study for the bio generation of cobalt oxide (Co 3 O 4) nanoparticles. Powder X-ray diffraction (XRD), Fourier Transformed Infrared spectra (FTIR), UV–Visible spectroscopic analysis, and field-emission scanning electron microscopy (FESEM) were used to analyze the resulting Co 3 O 4 nanoparticles. These nanoparticles having a crystallite size of 31.94 nm were highly crystalline and had a cubic spinal structure, as indicated by the high-intensity peaks of the XRD spectra. The Co 3 O 4 nanoparticle's remarkable dispersion and spherical shape are highlighted in the FESEM image. Additionally, these biosynthesized Co 3 O 4 nanoparticles have shown efficient antibacterial efficacy against gram (+) and gram (−) bacteria, including Staphylococcus aureus, Streptococcus mutans, Klebsilla pneumonia, and E. coli, along with antifungal efficacy against Aspergillus flavus and Aspergillus Niger under in-vitro environmental conditions. The observed zone of inhibition values against all bacteria and fungi ranged from 22 ± 0.61 mm to 26 ± 0.81 mm and 20 ± 0.42 mm to 33 ± 0.67 mm, respectively. The Senna auriculata flower extract-assisted Co 3 O 4 nanoparticles showed minimum inhibitory concentration values that ranged from 8 to 20 μg/ml against isolated bacteria. This result shows that the Co 3 O 4 nanoparticles exhibited high antibacterial and anti-fungal behaviour with significant differences between other synthesize procedures and the control (Positive control). [ABSTRACT FROM AUTHOR]

In this study, rosemary leaf extract was effectively used to synthesize cobalt oxide nanoparticles (Co3O4 NPs) using a rapid, low-cost, and environmentally friendly approach. The prepared Co3O4 NPs were examined using various analytical techniques. However, UV spectrum analysis displayed two sharp absorption peaks at ~350 and 745 nm. The dynamic light scattering and zeta potential measurements were used to evaluate the particle size and the effective stabilization of the synthetic nanoparticles in the suspensions. A semi-triangular pyramidal shape of the Co3O4 NPs with a wide particle-size distribution could be observed in the scanning electron microscopy images. The energy-dispersive X-ray spectrum confirmed their successful synthesis, as the experimental atomic percentages agreed with the theoretical values. Moreover, X-ray diffraction analysis revealed that the synthesized Co3O4 NPs had a cubic crystalline structure corroborating that of theoretical Co3O4. Additionally, the Co3O4 NPs were not toxic at ≤62.5 µg/mL for Hep G2 and at ≤31.25 µg/mL for Mcf7. Therefore, these unique environmentally friendly Co3O4 NPs at this safe concentration could be studied in the future for their therapeutic activity. [ABSTRACT FROM AUTHOR]

The green, sustainable, and inexpensive creation of novel materials, primarily nanoparticles, with effective energy-storing properties, is key to addressing both the rising demand for energy storage and the mounting environmental concerns throughout the world. Here, an orange peel extract is used to make cobalt oxide nanoparticles from cobalt nitrate hexahydrate. The orange peel extract has Citrus reticulata, which is a key biological component that acts as a ligand and a reducing agent during the formation of nanoparticles. Additionally, the same nanoparticles were also obtained from various precursors for phase and electrochemical behavior comparisons. The prepared Co-nanoparticles were also sulfurized and phosphorized to enhance the electrochemical properties. The synthesized samples were characterized using scanning electron microscopic and X-ray diffraction techniques. The cobalt oxide nanoparticle showed a specific capacitance of 90 F/g at 1 A/g, whereas the cobalt sulfide and phosphide samples delivered an improved specific capacitance of 98 F/g and 185 F/g at 1 A/g. The phosphide-based nanoparticles offer more than 85% capacitance retention after 5000 cycles. This study offers a green strategy to prepare nanostructured materials for energy applications. [ABSTRACT FROM AUTHOR]

One of the most important problems facing the restorer in stained glass restoration is the completion of missing glass pieces to which vitreous paints containing metal oxides were applied that require a high temperature for installation, starting from 550 °C and increasing according to the colored oxide nature and the smelter used. The present paper discusses the preparation of blue vitreous paint for nanoparticles Co3O4 to improve its thermal and color properties. It compares the color prepared from the cobalt nano oxide Co3O4 and cobalt oxide CoO mainly used to color the glass blue since the pharaonic periods. Examination and analysis methods, i.e., XRD, FTIR, SEM, EDX, and TEM, were used in characterizing the cobalt nano oxide. STEM, SEM, and stereo microscope were used to study the prepared color samples. Results showed that the particles size of the prepared Co3O4 of 0.78 nm gave an excellent blue color when applied to the glass at a temperature of 620 °C compared to the color resulting from CoO, which was installed at a temperature of 700 °C according to mixing rates. That paved the way for reducing the proportion of the smelter in the color mixture to increase color resistance to weathering deterioration factors, especially moisture. [ABSTRACT FROM AUTHOR]

Zinc-substituted cobalt oxide nanoparticles (Zn x Co 3-x O 4, 0 ≤ x ≤ 0.5) were produced by microwave refluxing technique. The structural, microstructural and magnetic properties of these samples were studied using X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and magnetic property measurement system (MPMS) respectively. XRD and TEM analyses confirmed the single phase nature for all the samples. Rietveld analysis of the samples further confirmed the substitution of Zn-ions into the Co 3 O 4 lattice. The chemical states of the elements were studied using X-ray photoelectron spectroscopy (XPS), which suggest the presence of Zn2+, Co2+, and Co3+ ions in the samples. The maximum saturation magnetization (M S) values of 0.33 Am2/kg was obtained for x = 0.01 sample, and then it continuously reduced with increased Zn content. The dielectric property of the samples was studied in the frequency range of 40 Hz–110 MHz. The samples x = 0.05 and 0.5 displayed the lowest conductivity due to the narrow size distribution of grains. [ABSTRACT FROM AUTHOR]

The (CuTl)0.5Ba2Ca2Cu3O10−δ {CuTl-1223} superconducting phase was synthesized by a well-established solid-state reaction route and the semiconducting antiferromagnetic cobalt oxide (Co3O4) nanoparticles were prepared by a chemical sol–gel method. The final (Co3O4)x/(CuTl)-1223; (x = 0–2.0 wt.%) nanoparticles–superconductor composites were obtained by adding Co3O4 nanoparticles in CuTl-1223 phase of the CuTl-based superconducting family. A temperature range of 77–298 K was chosen for frequency-dependent electric modulus spectroscopy measurements of (Co3O4)x/(CuTl)-1223 composites to interpret the dynamical aspects of electrical transport phenomena, such as ac-conductivity, carrier hopping rate, etc. The influence of grains as well as the grain boundaries on the ac-conduction properties was witnessed from the complex electric modulus spectra of these composite samples. The grain boundaries showed higher capacitance compared with the grains. This behavior of capacitance was decreased for grain boundaries and increased for grains with higher values of operating temperature in all the superconducting composite samples. The shifting of peaks towards a lower frequency regime in imaginary parts of the electric modulus spectra with increasing Co3O4 nanoparticle contents showed the presence of non-Debye-type relaxation within the material. The effects of these semiconducting antiferromagnetic Co3O4 nanoparticles on the ac-conduction mechanism of the host CuTl-1223 phase were studied, particularly in the perspective of the capacitive resistance contribution via electric modulus spectroscopy measurements. [ABSTRACT FROM AUTHOR]

Abstract Three-dimensional (3D) carbon foams (CF) surrounded by carbon nanotubes (CNTs) and Co-Co 3 O 4 nanoparticles (NPs) (CF@Co-Co 3 O 4 /CNT) nanocomposites were prepared by a two-step method for stable lithium-ion batteries (LIBs). The low-cost melamine foams pre-soaked in cobalt nitrate solution were firstly carbonized under nitrogen atmosphere to form 3D CF surrounded by a large number of CNTs and Co NPs (CF@Co/CNT). Subsequently, the CF@Co/CNT was transformed into CF@Co-Co 3 O 4 /CNT nanocomposites by calcination in air. Here, Co NPs, CNT and 3D CF all improved the electrical conductivity of CF@Co-Co 3 O 4 /CNT nanocomposites. In addition, a large number of uniformly-dispersed small Co 3 O 4 NPs effectively increased Li+ storage capacity of nanocomposites. At the same time, the 3D macroporous carbon frameworks surrounded by CNT could also relieve the volume deformation of Co 3 O 4 NPs to some extent. When it was employed as anode materials for LIBs, CF@Co-Co 3 O 4 /CNT nanocomposites exhibited the stable reversible capacities of about 500 mAh g−1 at 0.5 A g−1, larger than that of commercial graphite and some other Co-based materials. The two-step preparation method was simple and convenient for large-scale production. Graphical abstract Image 1 Highlights • Three-dimensional macroporous carbon frameworks surrounded by CNTs and Co/Co 3 O 4 were prepared. • The CF@Co-Co 3 O 4 NPs/CNT was prepared by carbonizing melamine pre-soaked in cobalt nitrate solution. • A large number of highly-dispersed small Co 3 O 4 NPs effectively increased Li+ storage capacity. • The CoNPs, CNTs and 3D carbon frameworks itself ensured excellent electrical conductivity. • The CF@Co-Co 3 O 4 NPs/CNT exhibited stable reversible capacity of about 505 mAh g−1 at 0.5 A g−1. [ABSTRACT FROM AUTHOR]

Abstract This research article describes the synthesis of cobalt-oxide nanoparticles by simple precipitation technique and their environmental application. The prepared Co 3 O 4 nanoparticles were characterised by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, selected area diffraction, and energy-dispersive X-ray spectroscopy, along with elemental mapping analysis. The characterisation images revealed that as-synthesised nanomaterial had a hexagonal sheet-like morphology with average particle size 10–20 nm and was crystalline in nature. The nano-adsorbent displayed its efficiency in methyl orange adsorption from aqueous solution. Several adsorption factors such as pH, initial concentration, time, and temperature were examined, and isotherm, kinetic, and thermodynamic data were observed. The adsorption rate was fast and followed a pseudo–second-order kinetic model. The adsorption isotherm could be suited with both Langmuir and Freundlich isotherms. The adsorption process turned out to be spontaneous and exothermic. The effects of the various factors for methyl orange removal were analysed using the Box–Behnken design. A second-order quadratic model was used to project the response. Analysis of variance analysed the significance of the factors and their interactions. Three-dimensional response surface plots were used to determine the interactive effects of the independent factors on methyl orange adsorption capacity. The successful regeneration of Co 3 O 4 nanoparticles suggested their usefulness in wastewater treatment and various other industrial settings. The reusability and efficient adsorptive capacity of nano-adsorbent for environmental management represent the importance of this work. [ABSTRACT FROM AUTHOR]

[Display omitted] • The facile and outstanding route were introduced for decorating Co 3 O 4 on GQDs to form the X% (Co 3 O 4)/GQDs composites. • The Co 3 O 4 nanoparticles with ultra-small sizes were uniformly decorated on the GQDs. • The resultant composites are applied as the robust photocatalysts for the conversion of N 2 to NH 3. • The kinetics and the concentration of produced ammonia on the surface of X% (Co 3 O 4)/GQDs composites were studied in details. • The mechanism of ammonia production is discussed in details. The crises related to energy and pollutants in the present century have led to the special look toward clean and sustainable energies. Material science plays a significant role in the way to achieve the world's envisioned sustainability. This paper introduces an outstanding and facile route for decorating cobalt oxide (Co 3 O 4) on graphene quantum dots (GQDs) to form the X% (Co 3 O 4)/GQDs composites. The 5% Co 3 O 4 /GQDs, 10% Co 3 O 4 /GQDs, and 20% Co 3 O 4 /GQDs composites are formed with the aid of ultrasound irradiation, followed by the pyrolysis of citric acid employing a bottom-up approach. Decoration of Co 3 O 4 nanoparticles with various weight percentages of 5%, 10%, and 20% is uniformly performed into the GQDs with the size distribution of 4.4, 4.6, and 4.8 nm, respectively. The resultant composites are applied as the robust photocatalysts for the conversion of N 2 to NH 3. In this report, GQDs decorated by three ratios of 5%, 10%, and 20% of Co 3 O 4 are formed to evaluate the effect of decorated Co 3 O 4 weight percentage on the production of ammonia. In addition, the kinetics and the concentration of the produced ammonia are studied using these composites. Based on the comparative analysis, the 5% Co 3 O 4 /GQDs photocatalyst not only optimizes the production of ammonia related to 10% Co 3 O 4 /GQDs, and 20% Co 3 O 4 /GQDs photocatalysts but also indicates the faster kinetics of ammonia production. These results can be attributed to the more uniform distribution and the lower size of nanoparticles in 5% Co 3 O 4 /GQDs photocatalyst. [ABSTRACT FROM AUTHOR]

Cobalt oxide (Co3O4) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase were prepared by sol-gel and solid-state reaction methods, respectively. Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223, x = 0-2.0 wt.%, nanoparticles-superconductor composites. The unchanged crystal structure of the host CuTl-1223 superconducting phase (i.e. tetragonal) revealed that Co3O4 nanoparticles were settled at the grain boundaries. Superconducting properties of the CuTl-1223 phase were overall suppressed due to hole-charge carriers interaction at the grain boundaries. The dielectric properties of (Co3O4)x/CuTl-1223 composites were investigated by varying the test frequencies from 40 Hz to 100 MHz and operating temperatures from 77 to 298 K. The values of dielectric properties were found maximal at lower frequencies and started to decrease at higher frequencies. So, the dielectric properties of the CuTl-1223 superconducting phase can be tuned by varying the contents of (Co3O4) nanoparticles, test frequencies as well as operating temperatures. [ABSTRACT FROM AUTHOR]

Chemically prepared cobalt oxide nanoparticles (NPs) were added to biodegradable carboxymethyl cellulose (CMC) (20%)/polyvinyl alcohol (PVA) (80%) blend films. The structural properties of these films were investigated by X-ray diffraction, Fourier transformation infrared spectroscopy (FTIR) and differential thermal analysis (DTA). Co3O4/(CMC + PVA) films show a semi-crystalline structure and the degree of crystallinity decreases with adding Co3O4 NPs. FTIR confirms the good interaction between the blend chains and Co3O4 NPs. The melting temperature Tm for CMC/PVA is about 212 °C then decreased with increasing Co3O4 content, due to some decrease in the ordered association of the blend which results in a decrease in the blend crystallinity. Positron annihilation lifetime spectroscopy (PALS) measurements were carried out with a conventional fast-fast coincidence spectrometer. It was found that ortho-positronium lifetime τ3 and free volume Vf increase while o-Ps intensity I3 still constant as Co3O4 concentration increases. This is because adding Co3O4 NPs encourages the formation of o-Ps. The swelling ratio SR% as a function of Co3O4 concentration was also studied and its value increases with Co3O4 addition. The optical study illustrated the decrease of the transmittance T of the films from 87 to 35.5% with increasing Co3O4 content from 0 to 0.9 wt%. Also, both the direct and indirect optical band gaps of the films red-shifted from 4.05 to 3.75 eV and 3.3 to 2.75 eV, respectively. The influence of Co3O4 on the refractive index of the films is also reported. [ABSTRACT FROM AUTHOR]

Herein, Co3O4 nanoparticles/nitrogen-doped carbon (Co3O4/NPC) composites with different structures were prepared via a facile method. Structure control was achieved by the rational morphology design of ZIF-67 precursors, which were then pyrolyzed in air to obtain Co3O4/NPC composites. When applied as catalysts for the oxygen evolution reaction (OER), the M-Co3O4/NPC composites derived from the flower-like ZIF-67 showed superior catalytic activities than those derived from the rhombic dodecahedron and hollow spherical ZIF-67. The former M-Co3O4/NPC composite displayed a small overpotential of 0.3 V, low onset potential of 1.41 V, small Tafel slope of 83 mV dec-1, and a desirable stability. (94.7% OER activity was retained after 10 h.) The excellent performance of the flower-like M-Co3O4/NPC composite in the OER was attributed to its favorable structure. [ABSTRACT FROM AUTHOR]

In this study, a new Co3O4nanoparticles (NPs) coated with sodium dodecyl sulphate (SDS) is developed for preconcentration of trace amounts of cadmium ions (Cd2+) as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The effects of various parameters, including pH of sample solution, amount of sorbent, flow rates of solution and eluent, sample volume, type, and least amount of the eluent for elution of the Cd2+from Co3O4NPs were studied and optimized. Experimental conditions for effective separation of trace levels of the Cd2+were optimized with respect to different experimental parameters in Column method. Under the best experimental conditions, the calibration curve was linear in the range of 1.0–500.0 ng.mL−1of cadmium (Cd) withR2 = 0.999. The detection limit was 0.4ng.mL−1in the original solution (3Sb/m) and the relative standard deviation for eight replicate determination of 0.1µg.mL−1Cd was ±2.1%. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was successfully applied to the extraction and determination of Cd in water and food samples with satisfactory results. [ABSTRACT FROM AUTHOR]

In this study, co-precipitation synthesis of natural clay (NC) with Co 3 O 4 nanoparticles (NPs) is carried out to elaborate the super NC@Co 3 O 4 nanocomposites with admirable salinity confrontation, environmental stability and reusability, to eliminate heavy metal pollution such as toxic Pb(II) and Cd(II) ions. The advantages of using the NC@Co 3 O 4 adsorbent are easy synthesis and biocompatibility. In addition, NC@Co 3 O 4 can keep an excellent adsorption capacity by taking into account various environmental parameters such as the pH solution, NC@Co 3 O 4 dose, adsorption process time and the initial heavy metals concentration. Furthermore, FTIR, XRD, TGA, SEM-EDS, TEM and AFM analyses were performed to confirm NC@Co 3 O 4 nanocomposites synthesis and characterisation. The adsorption efficiencies of Pb(II) and Cd(II) ions by NC@Co 3 O 4 nanocomposites were demonstrated to be up to 86.89% and 82.06% respectively. Regarding the adsorption from water onto the NC@Co 3 O 4 nanocomposites, kinetics data were well fitted with PSO kinetic model, whereas a good agreement was found between the equilibrium adsorption and theoretical Langmuir isotherm model leading to maximum adsorption capacities of 55.24 and 52.91 mg/g, for Pb(II) and Cd(II) respectively. Monte Carlo (MC) simulations confirmed the spontaneous of this adsorption based on the negative values of E ads. The MC simulations were performed to highlight the interactions occurring between heavy metal ions and the surface of NC@Co 3 O 4 nanocomposites, these were well correlated with the experimental results. Overall the study showed that NC@Co 3 O 4 nanoadsorbents have strongly versatile applications and are well designed for pollutant removal from wastewater due to their unique adsorptive properties. [Display omitted] • Synthesis of sustainable nanocomposites of natural clay (NC) with Co3O4 nanoparticles (NPs). • Removal of Pb(II) and Cd (II) ions using NC@Co 3 O 4 nanocomposites. • NC@Co 3 O 4 has Qm of 55.24 mg/g for Pb(II) and 52.91 mg/g for Cd (II) ions. • MC simulations were used to clarify adsorption properties of nanocomposites. • The NC@Co 3 O 4 nanocomposites are reusable for 5 consecutive cycles. [ABSTRACT FROM AUTHOR]

In this paper, an energetic coordination compound namely pentamminenitratocobalt(III) nitrate, [Co(NH 3)5(NO3)](NO3)2, was used as a new precursor for the preparation of Co3O4 nanoparticles.  e results showed that the complex is easily decomposed into the Co3O4 nanoparticles at low temperature (200 °C) without employing a surfactant or solvent and any complicated equipment.  e product was characterized by diff erential scanning calorimetry (DSC), X-ray diff raction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). Optical and magnetic properties of the product were studied by UV-visible (UV-vis) spectroscopy and a vibrating sample magnetometer (VSM), respectively. FT-IR, XRD and EDS analyses con rmed the formation of highly pure spinel-type Co3O4 phase with cubic structure. TEM images showed that the Co3O4 nanoparticles are approximately in the range of 10 to 24 nm with a mean size of around 17 nm.  e optical spectrum of the Co3O4 nanoparticles revealed the presence of two band gaps at 3.45 and 2.20 eV which are blue-shi ed relative to reported values for the bulk sample.  e magnetic measurement of the product showed a weak ferromagnetic order at room temperature. [ABSTRACT FROM AUTHOR]

In this work, thermal decomposition of the [Co(NH3)5(H2O)] (NO3)3 precursor complex was investigated under solid state conditions. Thermal analysis (TG/DTA) showed that the complex was easily decomposed into the Co3O4 nanoparticles at low temperature (175 °C) without using any expensive and toxic solvent or a complicated equipment. The obtained product was identified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). Optical and magnetic properties of the products were studied by UV-visible spectroscopy and a vibrating sample magnetometer (VSM), respectively. FT-IR, XRD and EDX analyses confirmed the formation of highly pure spinel-type Co3O4 phase with cubic structure. SEM and TEM images showed that the Co3O4 nanoparticles have a sphere-like morphology with an average size of 17.5 nm. The optical absorption spectrum of the Co3O4 nanoparticles showed two band gaps of 2.20 and 3.45 eV, which in turn confirmed the semiconducting properties. The magnetic measurement showed a weak ferromagnetic order at room temperature. Photocatalytic degradation of methylene blue (MB) demonstrated that the as-prepared Co3O4 nanoparticles have good photocatalytic activity under visible-light irradiation. [ABSTRACT FROM AUTHOR]

The synthesis of crystalline, nonagglomerated, and perfectly dispersible Co3O4 nanoparticles with an average size of 3-7 nm using a solvothermal reaction in tert-butanol is reported. The very small size and high dispersibility of the Co3O4 nanoparticles allow for their homogeneous deposition on mesoporous hematite layers serving as the photoactive absorber in the light-driven water splitting reaction. This surface treatment leads to a striking photocurrent increase. While the enhancement of hematite photoanode performance by cobalt oxides is known, the preformation and subsequent application of well-defined cobalt oxide nanoparticles are novel and allow for the treatment of arbitrarily complex hematite morphologies. Photoelectrochemical and transient absorption spectroscopy studies show that this enhanced performance is due to the suppression of surface electron-hole recombination on time scales of milliseconds to seconds. [ABSTRACT FROM AUTHOR]

• Arishta leaves extract assisted Co3O4 nanoparticles were synthesized by sol gel auto combustion method at different annealing temperature. • The crystallite size, lattice constant, dislocation density and lattice strain were determined using XRD. • Annealing temperature increased the crystalline nature of Co3O4 nanoparticles. • The purity of the synthesized nanoparticles was confirmed by EDX analysis. • The antibacterial and antifungi behaviour of Co3O4 nanoparticles was observed in all samples. A novel biosynthesis of cobalt oxide nanoparticles (Co 3 O 4 NPs) attains using Arishta leaves (Neem leaves) extract at disparate annealing temperature, (Untreated (RT), 200 °C, 400 °C, 600 °C, and 800 °C) was analysed. The structural and morphological analysis has been carried out by using different characterization techniques. The characterization techniques such as X ray diffraction and scanning electron microscopy reveals that the Arishta leaves extract act as a fundamental, oxidation-reductant in addition to mediated preserving compound. Also the transparent and nonporous pyramid like crystalline structure of Co 3 O 4 is confirmed. The antibacterial and antifungal behaviour of synthesized nanoparticles was analysed against S taphylococcus aureus, Streptococcus mutans, Klebsilla pneumonia and Escherichia coli as well as Aspergillus species of A. flavus and A. Niger fungi by agar disc diffusion process. Because of the pH, reaction temperature, reaction time, and extract clustering during the synthesis of Co 3 O 4 NPs, the synthesized neem Co 3 O 4 NPs have a strong antibacterial and antifungal activity. These findings show that the leaf extract may effectively operate as a dynamic response medium for the formation of Co 3 O 4 NPs, and that it can be used in a variety of biomedical by-products and nano devices due to its low cost and high efficiency. [ABSTRACT FROM AUTHOR]

In this paper, we reported a recyclable and highly active porous catalyst of titanate nanowires (TNWs) coated with well-distributed Co3O4 nanoparticles (NPs) (Co3O4/TNWs). Sodium ions of TNWs were exchanged with hydrogen ions in the dilute nitric acid, and this protocol was very suitable for capturing cobalt ions. X-ray diffraction (XRD) demonstrated the existence of Co3O4 phase with unique lattice planes, such as (220), (311) and (511). Electron microscopes (FE-SEM and TEM) indicated that the Co3O4 NPs with an average diameter of 22±3nm were coated uniformly on TNWs surface (average diameter: 37±5.5nm), and the Co3O4 NPs mainly exposed their (220) and (222) active planes. XPS analysis confirms the formation of Co3O4 phase by the presence of Co 2p peaks at 780.1eV (2p 3/2) and 795.5eV (2p 1/2). Methylene blue (MB) and other organic dyes (rhodamine B (RhB) and methyl orange (MO)) were chosen as target compounds for catalytic degradation under indoor scattering light. Compared to the original Co3O4/TNWs catalyst, the catalytic efficiency of nanoscaled catalyst with oxone for MB was about 15 times higher, and the MB solution (10mgL-1) was completely degraded within 8min. The catalytic activity of recycled catalyst used in the sixth run still remained very active, and the degradation time for MB was only 16min. The nanosized catalyst also had a high activity for dyes of RhB (10mgL-1) and MO (10mgL-1), as the degradation efficiencies of RhB and MO after 10min of contact time were about 90.2% and 92.6%, respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] The catalase-like activity of Co3O4 nanoparticles could be tunable by the pH. [•] Compared to catalase, Co3O4 nanoparticles had the efficient catalytic ability. [•] Hydroxyl radicals took part in the catalytic recycles. [•] Co3O4 nanoparticles were used as the amperometric sensor for the detection of H2O2. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt oxide (Co3O4) nanoparticles (NPs) assembled coating have been prepared by reactive pulsed laser deposition of Co, in O2 atmosphere, on Si or glass substrate ranging from room temperature to 250°C. The NPs, having narrow size distribution with average values of around 25–50nm, were characterized by Raman, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The Co3O4 NPs synthesized at 150°C comprise a mixed amorphous–nanocrystalline phase (that is unique property for catalysis) while complete crystallization of Co3O4 occurs at 250°C with formation of spinel structure. Photocatalytic properties of Co3O4 NPs assembled coating for degradation of methylene blue solution under visible light irradiation are reported. The effect of H2O2 concentration and effect of pH variation on dye degradation rate has been reported. The reusability of the Co3O4 NPs assembled thin coating catalyst was further evaluated in several recycling runs. The activity of heterogeneous Co3O4 NPs assembled thin coating catalyst was compared with homogenous catalyst producing Co+2 ions in methylene blue solution. [Copyright &y& Elsevier]

Abstract: Co3O4 nanoparticles have been obtained by stoichiometric combustion synthesis: in particular 4 nitrates-aspartic routes each with different fuel ratio (ranging 0.5-2.5) have been studied. It has been determined through XRD that the crystalline structure present in all obtained powders was the face-centered cubic corresponding to Co3O4 and it has been evaluated an average crystallite size ranging between 21 and 76nm. As regards to the effect of fuel ratio on physical properties, an increment on the crystallite average size and a drop on the specific surface area with the increase of the fuel ratio has been observed. [Copyright &y& Elsevier]

• Hierarchical Co 3 O 4 /rGO nanocomposites are synthesized by a facile one-pot microwave-assisted hydrothermal approach. • The size of Co 3 O 4 nanoparticles is effectively reduced to 8.5 nm by 35 wt% addition of rGO. • Co 3 O 4 /rGO composites exhibit a specific capacitance of 1031 F g−1 at 1 A g−1, and 78% capacitance retention at 10 A g−1. • The approach can be extended to synthesize other TMOs and carbonaceous nanocomposites for superior electrode materials. The composites composed of transition metal oxide and carbonaceous nanomaterials have been regarded as one of the promising electrode materials for high performance supercapacitors. How to develop effective hybridization of two components to deliver synergistic effect on electrochemical performance is a key question to be tackled. Herein, we successfully prepare three-dimensional hierarchical cobalt oxide (Co 3 O 4)/reduced graphene oxide (rGO) composites via a facile, rapid and cost-effective one-pot microwave assisted hydrothermal process. The effects of rGO content on morphology, chemical and crystalline structure, electrode performance are systematically investigated. Interestingly, it is noticed that by changing the addition of graphene oxide (GO), the size of Co 3 O 4 nanoparticles can be effectively controlled, which has a significant effect on the electrochemical properties of electrode materials. The as-prepared Co 3 O 4 /rGO with 23 wt% rGO exhibits an outstanding specific capacitance of 1031 F g−1 at 1 A g−1 and retains 78% of capacitance when current density increased to 10 A g−1, revealing that Co 3 O 4 /rGO composites prepared by this facile process can be an ideal candidate electrode for high performance supercapacitors. [ABSTRACT FROM AUTHOR]

The development of novel non-enzyme mimics for (bio)sensing applications is of great practical importance. Herein, an efficient chemiluminescence (CL) system is presented according to the significant mimetic behavior of the copper metal-organic framework decorated with cobalt oxide nanoparticles (Co 3 O 4 @CuMOF). The catalytic activity of nanocomposite was proved by its strengthening effect on the CL emission of rhodamine B (RB)-hydrogen peroxide (H 2 O 2) reaction. More documents were also obtained using colorimetric and fluorometric peroxidase substrates. The presence of Cu and Co in the Co 3 O 4 @CuMOF structure, as well as the high porosity and great surface area of the obtained composite, was responsible for the observed synergetic catalytic activity. The Michaelis-Menten constant (K m) for the composite (0.108 mM) was remarkably lower than that of pristine CuMOF and Co 3 O 4 NPs, illustrating its superior affinity towards H 2 O 2. A linear correlation was found between the CL intensity and H 2 O 2 concentration in the extensive range of 1–250 nM, with a detection limit (3S) of 0.244 nM. Furthermore, the developed system was exploited as a reliable sensing device for individual measurement of cholesterol and glucose after their enzymatic oxidations. The obtained data verified the high sensitivity and selectivity of the probe, which could be linked to the presence of high-performance Co 3 O 4 @CuMOF and the accompanying enzymes, respectively. The designed method was appropriately applied to measure cholesterol and glucose levels in human serum samples, and its accuracy was validated by analyzing the standard materials. [Display omitted] • Synthesis of mimic Cu MOF/Co 3 O 4 nanoparticles composite (Co 3 O 4 @CuMOF). • Promoting effect of Co 3 O 4 @CuMOF on chemiluminescence emission of rhodamine B-H 2 O 2. • High porosity and surface area, as well as the presence of Cu and Co were responsible for the synergetic effect. • Sensitive measurement of cholesterol/glucose content of human serum. • Validation of the results by analyzing the certified reference materials. [ABSTRACT FROM AUTHOR]

• Er3+-doped boro-tellurite glasses containing cobalt oxide NPs are prepared by melt-quenching method. • SPR spectrum revealed two plasmon peaks that are related to the composition. • TEM images revealed the presence of Co 3 O 4 NPs. • VSM and EPR data revealed some different changes that are related to cobalt ions. • The mechanisms involving in magnetic properties are discussed. We report the cobalt oxide (Co 3 O 4) nanoparticles (NPs) assisted modifications of magnetic properties of melt-quench synthesized Er3+ doped sodium magnesium boro-tellurite glass. The changes in magnetic parameters are attributed to the difference in the content of Co 3 O 4 NPs. XRD pattern confirmed the amorphous nature of the newly doped glasses. Surface plasmon band of Co 3 O 4 NPs in the glass revealed two peaks which are corresponded to the characteristic of spinel-type cobalt oxide phase and TEM images manifest the occurrence of non-spherical Co 3 O 4 NPs having an average diameter 6.02 ± 0.10 nm. Magnetic study using Vibrating Sample Magnetometer (VSM) revealed the paramagnetic behavior of Co ion in boro-tellurite glass doped Er3+ contributes by the embedded Co 3 O 4 NPs. The lower value of squareness ratio in the sample is attributed by stronger interactions among grains implying the appearance of isotropic behavior, hence, making them as a multi-domain magnetic with the addition of Co 3 O 4 NPs. Electron Paramagnetic Resonance (EPR) spectra revealed three prominent value of g factor at ranges of 4.07–4.22, 2.97–3.02, 2.11–2.41. Furthermore, the tetrahedral symmetry contribution is increased as inferred from the oxidation states of Co2+ ions probed by EPR. [ABSTRACT FROM AUTHOR]

The Inside Cover picture illustrates that novel precious‐metal‐free cathode materials, Co3O4 nanoparticle‐incorporated mesoporous Beta zeolites, can show synergetic catalytic effects for the oxygen reduction reaction. More details can be found in the Article by J. Zhou et al. on page 1279 in Issue 6, 2017 (DOI: 10.1002/celc.201600858). [ABSTRACT FROM AUTHOR]