Nanoparticles Of Co Research Articles

PMS activation by magnetic cobalt-N-doped carbon composite for ultra-efficient degradation of refractory organic pollutant: Mechanisms and identification of intermediates

Refractory organic pollutant effluent has led to severe water pollution. In this study, magnetic Co–N-doped carbon hybrid catalysts (Co-NC-x) were fabricated using a facile cation exchange combined pyrolysis and self-reduction technique to activate peroxymonosulfate (PMS) for rehabilitation of the water environment. Factors affecting the catalytic activity of the Co-NC-850 were comprehensively examined. 100% of RhB degradation efficiency within 20 min was achieved in the Co-NC-850/PMS system at the optimum conditions (C0 = 80 mg L−1, catalyst loading 0.025 g L−1, PMS concentration 0.8 mM, native pH and 25 °C). The electron paramagnetic resonance measurements and competitive quenching tests demonstrated that a sulfate radical (SO4•-) and singlet oxygen (1O2) account for RhB degradation in the Co-NC-850/PMS system, and 1O2 contributed ~86.2% to RhB removal. The synergistic effect of Co0 nanoparticles (NPs) and NC on Co-NC-850 might induce a predominant non-radical route to trigger PMS activation for RhB degradation. Direct oxidation of O2•- by a hydroxyl radical (•OH) might be the crucial process for forming 1O2. Magnetic response and successive cycles verified that Co-NC-850 has superior separable performance and reusability. This innovative magnetic Co-NC-850 hybrid catalyst for PMS activation delivered vast potential for disintegration of refractory organic contaminants.

Sm-substituted copper-cobalt ferrite nanoparticles: Preparation and assessment of structural, magnetic and photocatalytic properties for wastewater treatment applications

The nanoparticles of Co0.5Cu0.5SmxFe2−xO4 (0 ≤x ≤ 0.15) (CCS) were synthesized with the citrate combustion approach and then exploited to remove the noxious Rhodamine B (RhB) dye from the pollutant water. Before this mission of RhB disposal began, the CCS ferrite nanoparticles were comprehensively characterized by progressing analysis; as XRD, FTIR, STEM, VSM, DRS. The average crystallite size estimated using Williamson-Hall (W–H) method is in the range (75–45 nm). FTIR spectra exhibits the two finger print bands υ1 (~572) and υ2 (~375) of spinel ferrites. The STEM-EDX micrographs confirmed the purity, nanocrystalline nature of the CCS samples and existence of all the constituents' elements; Co, Cu, Sm, Fe and O ions without any other impurities. A gradual decrease for Ms values is remarked with further Sm3+ ions substitution; from MS= 55.373 emu/g (at x = 0.0) to MS= 43.981 emu/g (at x = 0.15). Coercivity shows a distinct behavior; increased from 892.81 Oe at pristine Co–Cu sample reaching a maximum value 1112.70 Oe (at x = 0.09) and then decreased to 983.09 Oe (for x = 0.15). The microwave frequency of the CCS nanoferrites is in the range 12.25–9.73 GHz. The pristine Co–Cu nanoparticles has band gap 1.57 eV, whereas all Sm3+ substituted nanoferrites have lower band gap values as 1.51, 1.55, 1.44, 1.51 and 1.36 eV with further Sm3+ ion substitution process. The photocatalytic activity of the nano-Co0.5Cu0.5SmxFe2−xO4 catalysts were scrutinized by the degradation of RhB dye using simulated sunlight source. Astonishingly, maximum degradation percentage was aggrandized to be 94.36%, under 270 min, for the nanoferrite with x = 0.15. Therefore, it is concluded that Sm doped Co–Cu nanoferrites is more convenient candidate for wastewater treatment applications besides switching, and high frequency absorption applications in microwave region.

Structural, morphological, and magnetic study of low temperature synthesized Co0.75Ni0.25Fe1.95Dy0.05O4 nano ferrite

The nanoparticles of Co0.75Ni0.25Fe2−zDyzO4 (z = 0.0 and 0.05) were prepared by the sol-gel auto-combustion method. The cation distribution was calculated from the Rietveld refinement of the XRD pattern to confirm a mixed inverse spinel structure. The crystallite size was calculated by the Debye–Scherrer method, modified Scherrer method, Williamson Hall plot method, and size-strain plot method for prepared samples. The variation in crystallite size was observed due to the contribution of lattice strain on line peak broadening. From Fourier transform infrared (FT-IR) spectrum the absorption bands appeared at 574.79 cm−1 and 414.70 cm−1 reveals spinel ferrite structure for Co0.75Ni0.25Fe1.95Dy0.05O4. The particle size from a high-resolution scanning electron microscope (HR-SEM) the image was found to be 46.99 nm for Co0.75Ni0.25Fe1.95Dy0.05O4. Energy-dispersive X-ray spectrum (EDS) was confirmed the purity of the sample with good stoichiometry. The coercivity, retentivity, and saturation magnetization were estimated at 841.97 Oe, 30.95 emu g−1 and 61.80 emu g−1 respectively for Co0.75Ni0.25Fe1.95Dy0.05O4. The squareness ratio for Co0.75Ni0.25Fe1.95Dy0.05O4 nanoferrite was found to be 0.5 which is the ideal Stoner—Wohlfarth value. The experimental estimated net magnetic moment () per formula was less than the theoretical value calculated from Neel’s two sublattice model for prepared samples.

Synthesis, structural, magnetic and dielectric studies of aluminum substituted cobalt-copper ferrite

Nano-particles of Co0.5 Cu0.5 Alx Fe2-x O4 ferrite compounds with compositions (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were prepared using co-precipitation method. The IR spectra of the samples showed the main characteristic bands of the spinel ferrite. X-ray diffraction patterns confirmed the formation of a single spinel phase for all the samples except the compound with composition x = 0.4. The particle size of the samples confirmed the nano-size, which found in the range of 30–54 nm. The saturation magnetization and coercivity showed a decreasing trend with the increase of Al-content. The electrical and dielectric properties of the samples were investigated through the DC and AC measurements of the ferrite samples. Moreover, dielectric properties of the samples, such as dielectric constant, dielectric loss, and loss tangent, exhibited decreasing behavior with the increase of frequency, which explained in terms of the possible polarization process in ferrite.

Fabrication of CoNPs-embedded porous carbon composites based on morphochemical imprinting strategy for detection of H2O2 released from living cells

Rational construction of biosensor to determine reactive oxygen species (ROS) generated from living cells is one of the great challenges in physiological and pathological fields. Herein, for the first time, a novel Co nanoparticles (CoNPs) embedded walnut-like N-doped porous carbon microsphere (Co@NCS) can be synthesized using dual imprinting strategy by pyrolysis and acid leaching. The distinct morphology and chemical characteristic of melamine cyanurate (MC) aggregates can be imprinted in the carbon source derived from glucose during the pyrolysis process. According to our research, with synergistic effect of CoNPs and NCS, the Co@NCS shows an excellent electrochemical activity toward the reduction of hydrogen peroxide (H2O2). The Co@NCS modified electrode exhibits a wider linear detection response with the range from 0.5 μM to 7500 μM and a low detection limit of 88 nM (S/N = 3). Moreover, with desirable selectivity, decent reproducibility and satisfied anti-interference performance, the fabricated biosensor can be applied to determine H2O2 in human serum samples and that released from living cell, indicating the potential applications in the fields of pathological and physiological sensing.

Construction of a novel electrochemical sensor for the determination of tellurium in soil and water samples by Co nanoparticles-modified electrode

ABSTRACT The spherical Co nanoparticles (Co-NPs) were successfully fabricated through a facile one-step reduction approach. Due to the large specific surface area and excellent electronic conductivity, Co-NPs displayed excellent electrochemical performance and exhibited high sensitivity towards the detection of Tellurium (IV). The electroanalysis of Tellurium (IV) on the modified electrode was investigated by differential pulse anodic stripping voltammetry. The peak currents of Tellurium (IV) increased proportionally within the range of 0.02–1.8 and 1.8–400 mg L−1 in the 0.1 M H2SO4 solution, under the optimal conditions. The detection limit was 0.2 μg L−1 (S/N = 3). Moreover, the proposed method was successfully applied to determine Tellurium (IV) in real samples with satisfactory results. The Co-NPs/GCE not only showed good reproducibility, stability and anti-interference but also supplied a viable way for designing low toxic, environment-friendly and low-cost sensors to detect Tellurium (IV).

Self-Assembled Magnetically Isolated Co Nanoparticles Embedded Inside Carbon Nanotubes

We investigate the influence of carbon nanotubes (CNTs) aligned array on the magnetic properties of an ensemble of densely packed Co nanoparticles (NPs) embedded inside CNTs. Samples are synthesized by chemical vapor deposition activated by current discharge plasma and hot filament. Each CNT contained only one NP of Co, which had preliminarily been formed on the surface of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si substrate. Co NPs are elongated along the CNT axis. The reference Co NPs ensemble and Co NPs embedded inside CNTs behave differently in a magnetic field. In the former case, Co NPs are strongly coupled by the dipole-dipole interaction (DDI); the easy axis plane is oriented parallel to the substrate. For Co-CNT samples, Co NPs are magnetically isolated. The reason for suppressing the contribution of the DDI is the magnetic anisotropy. It increases significantly because of the peculiar morphology of Co embedded in CNT and stresses. We evaluate the values of shape, magnetocrystalline, and magnetoelastic anisotropy constants. The magnetoelastic anisotropy is estimated for both the crystalline structures of Co, fcc and hcp, observed in Co NPs. The maximum stresses are reached in the case of hcp Co, when the hexagonal axis is oriented along the radial CNT direction. The influence of stresses onto the magnetic structure of Co inclusions is investigated by the micromagnetic simulations.

Metal-organic frameworks derived reverse-encapsulation Co-NC@Mo2C complex for efficient overall water splitting

Developing low-cost, highly active, and stable bifunctional electrocatalysts is a challenging issue in electrochemical water electrolysis. Herein, we develop a simple metal organic frameworks (MOFs) based approach to prepare bifunctional Co-NC@ Mo2C complex catalysts. Differently from traditional carbon encapsulated functional nanomaterials, herein the carbon-based framework derived carbonitride and Co nanoparticles (Co-NC) are encapsulated with Mo2C. Benefiting from the unique reverse-encapsulation structure and synergetic effects of Mo2C and Co-NC, the Co-NC@Mo2C catalyst shows superior hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance. In alkaline media, it affords the current density of 10 mA cm−2 at low overpotentials of 99 mV and 347 mV for HER and OER, respectively. Interestingly, due to a reversed encapsulation structure where Co nanoparticles are protected by Mo2C, it leads to an outstanding HER catalytic activity (a low overpotential of 143 mV) and stability in acidic solutions. Remarkably, when employed as both the cathode and anode for overall water splitting, a low cell voltage of 1.685 V is required to reach the current density of 10 mA cm−2 in alkaline media with excellent stability, making the Co-NC@Mo2C an efficient non noble metal bifunctional electrocatalyst toward water splitting.

Cobalt nanoparticles mechanically deposited on α‐Al2O3: a competitive catalyst for the production of hydrogen through ethanol steam reforming

AbstractBACKGROUNDCobalt (Co)‐containing materials are promising catalysts for Ethanol Steam Reforming (ESR) allowing renewable hydrogen production. Usually, complex catalysts are used where Co, produced by impregnation or coprecipitation, is supported on oxide or carbon‐based materials. Here Co nanoparticles (CoNPs) mechanically mixed with α‐Al2O3 are prepared and tested for ESR.RESULTSCoNPs mechanically mixed with α‐Al2O3 are very active catalysts in ESR at 773 K, even when retaining amorphous structure for Co. After annealing at 773 K, CoNPs crystallize into a cubic structure. These materials are even more active in ESR at 773 K with hydrogen yields ≈70% and nearly stable performances after 8 h on‐stream. Hydrogen yield is limited by the formation of some CH4, probably as a result of acetaldehyde formation and successive decomposition. Two kinds of Co particles are found in the used but still active catalysts: the former ones interacting with alumina and embedded in graphitic carbon, that are probably the most active components, whereas the latter are ‘isolated’ and partly aggregated CoNPs embedded in carbon nanotubes, which are probably less active in ESR.CONCLUSIONSMechanical mixing of CoNPs with α‐Al2O3 produced active and stable catalysts for ESR. The ‘chemical’ interaction of CoNPs with the support may not be an important factor for ESR catalysts. © 2018 Society of Chemical Industry

Cobalt–carbon nanocomposite catalysts of gas-phase hydrodechlorination of chlorobenzene

The catalytic efficiency of three different cobalt–carbon composites has been compared in the gas-phase hydrodechlorination (HDC) of chlorobenzene (CB) in a flow type fixed bed reactor. The Co@C composite was synthesized by evaporation of overheated liquid drop of Co in the flow of an argon–butene mixture; the Co/C composite – by pyrolysis of sawdust impregnated with Co(NO3)2 water solution, and the Co/CNT composite – by the impregnation of carbon nanotubes with Co(NO3)2 water solution. Different oxidation states of cobalt were observed in the studied composites according to XPS, TPR, and in situ vibrating sample magnetometry results: predominantly Co0 in Co@C, CoO in Co/C, and Co3O4 in Co/CNT. TPR showed the possibility of the reduction of Co3O4 to CoO and even to Co0 under conditions of HDC and established the temperatures of these transitions. TEM revealed that Co0 nanoparticles in the Co@C composite are encapsulated by the thin carbon shell, CoO nanoparticles in Co/C are immersed in the carbon matrix, and Co3O4 nanoparticles in Co/CNT are located both on the surface and inside the channels of CNTs. All the composites demonstrated activity in HDC of CB. The efficiency of not only Co0 but CoO in the CB HDC was shown. The CB conversion at 150–250 °C for Co/C and Co/CNT composites, containing predominantly cobalt oxides, was higher than that for Co@C one, containing Co0 nanoparticles coated with the thin carbon shell. The Co/C composite with the lowest Co content (1.3 wt.%) was more effective in HDC than Co/CNT (14.6 wt.% of Co) and Co@C (79 wt.% of Co) ones. High CB conversion for the Co@C composite at 350 °C resulted from the catalytic action of the graphene shell of Co particles, activated by subsurface Co0.

In-Situ Synthesis of Amorphous Co Nanoparticles Supported onto TiO₂ Nanofibers as a Catalyst for Hydrogen Generation from the Hydrolysis of Ammonia Borane.

Co0 nanoparticles supported on TiO2 nanofibers (nanocomposite) were prepared using a simple electrospinning technique and In-Situ chemical reduction. The synthesized nanocomposite was used to generate hydrogen from ammonia borane (AB). Standard characterization techniques revealed dense distribution of Co0 nanoparticles (Co NPs) onto the TiO2 nanofibers (TiO2 NFs) in the prepared nanocomposite. The introduced nanocomposite has been showed a good catalytic activity as compared to those unsupported Co NPs. As, the hydrogen evolutions for the nanocomposite and Co NPs were 3 mol in 23 min and 47 min, respectively. Furthermore, both the nanocomposite concentration and the temperature have a significant catalytic activity in the AB dehydrogenation. The nanocomposite also showed low effective activation energy of ~26.03 KJ · mol-1.

Effect of Ce3+ Ion on Structural and Hyperfine Interaction Studies of Co0.5Ni0.5Fe2−xCexO4 Ferrites: Useful for Permanent Magnet Applications

Nanoparticles of Co0.5Ni0.5Fe2−xCexO4 (where x = 0.0, 0.01, 0.015 and 0.02) ferrites are prepared by the modified solution combustion method using a mixture of fuels and are characterized to understand their structural, microstructural and magnetic properties. The X-ray diffraction is used to confirm the formation of a single-phase cubic spinel structure. The average crystallite sizes are calculated using the Scherrer formula and are found to be less than 50 nm. The microstructural features are obtained by the scanning electron microscopy, and the compositional analysis is done by using the energy-dispersive spectroscopy. The transmission electron microscopy (TEM) investigations show that the synthesized ferrites are made up of very fine spherical nanoparticles. The influence of a rare-earth element (Ce3+) on the magnetic properties of the samples was studied using the Mossbauer spectroscopy. The Mossbauer spectroscopy reveals the formation of broadened Zeeman lines and quadrupole-split lines and the presence of the Fe3+ charge state at B sites in the samples. The quadrupole splitting shows that the orientation of the magnetic hyperfine field with respect to the principle axes of the electric field gradient was random. The magnetic hyperfine field values indicate that the A sites have more A-O-B superexchange interactions than the B sites. The coexistence of magnetic sextet and a doublet component on the room-temperature spectra suggests superparamagnetic properties of the nanoparticles. The low-temperature (15 K) Mossbauer spectroscopy explores the paramagnetic relaxation in the nanoparticles. The area under the sextet refers to Fe3+ concentrations in the tetrahedral and octahedral sites of the ferrite. This study confirms that the Ce3+ substitution of Fe3+ only for octahedron sites causes the decrease in Fe-O-Fe arrangement. The effect of Ce3+ doping on the magnetic properties of Co0.5Ni0.5Fe2O4 is examined from the vibrating sample magnetometry (VSM) spectra. Saturation magnetization values are decreased initially and then increased, as result of Ce3+ doping. This can be explained by Neel’s two-sub-lattice model. Further, the value of coercivity is found to be increasing with increasing Ce3+ concentration. The obtained results of M-H loop with improved coercivity (from 851 to 1039 Oe) by Ce3+ doping of Co0.5Ni0.5Fe2O4 demonstrate the usefulness for permanent magnet applications.

Cobalt-embedded carbon nanofiber derived from a coordination polymer as a highly efficient heterogeneous catalyst for activating oxone in water

Carbon fiber (CF) supported cobalt nanoparticles (NPs) are promising catalysts for activating Oxone because carbon is non-metal and earth-abundant, and CF-based catalysts exhibit a high aspect ratio, which affords more accessible and dense catalytic sites. Nevertheless, most of CF-supported catalysts are fabricated by post-synthetic methods, which involve complicated preparations. More importantly, metallic NPs are attached to the outer surface of CF rather than embedded within CF. However, there is still a great demand for developing Co-bearing carbon fibers for Oxone activation via simple and effective methods. Thus, this study proposes to develop a cobalt NP-embedded carbon nanofiber (CCNF) by a simple hydrothermal reaction of Co and nitrilotriacetic acid (NA), followed by one-step carbonization. Owing to the coordinative structure of CoNA, the derivative CCNF exhibits a fibrous carbon matrix embedded with evenly distributed and densely packed Co3O4 and magnetic Co0 nanoparticles. The fibrous structure, magnetism and embedded Co NPs enable CCNF to be a promising catalyst for Oxone activation. As degradation of Rhodamine B (RhB) is selected as a model reaction, CCNF not only rapidly activates Oxone to fully degrade RhB but also shows a much higher catalytic activity than the most common Oxone activator, Co3O4. CCNF also exhibits the lowest activation energy than any reported catalysts for Oxone activation to degrade RhB. In addition, CCNF could be re-used to activate Oxone for RhB degradation. These results indicate that CCNF is a conveniently prepared and highly effective fibrous Co/C hybrid material for activating Oxone to oxidize contaminants in water.

Fine Co Nanoparticles Encapsulated in a N-Doped Porous Carbon Matrix with Superficial N-Doped Porous Carbon Nanofibers for Efficient Oxygen Reduction.

Herein, we develop a novel method to synthesize evenly dispersed fine Co nanoparticles (CoNPs) (particle size of ∼42 nm) encapsulated in a N-doped porous carbon matrix (NPCM) with superficial N-doped porous carbon nanofibers (NPCNF) (denoted as Co@NPCM/CNF-850) as an oxygen reduction reaction (ORR) electrocatalyst. Such an electrocatalyst is the direct pyrolysis product of the novel pine needle-like ZIF-67-based metal-organic framework nanowire array (MOFNWA) prepared using an inorganic cobalt carbonate hydroxide (Co(CO3)0.5(OH)·0.11H2O) nanowire array as a linear sacrificial template, which is totally different from the traditional method, that is, using inorganic salts to synthesize MOF particles. Because of the high dispersibility of the effective fine N-doped carbon-wrapped CoNPs (rather than the overlarge CoNP aggregates); the unique linear MOF-derived assemblies, which are beneficial to electronic transmission; the high degree of graphitization, which is attributed to the superficial NPCNF and carbon layers wrapping the CoNPs; as well as the high porosity, our catalyst showed remarkable ORR activity (Eonset of 1.033 V vs the reversible hydrogen electrode) in alkaline solution. Besides, our catalyst revealed excellent stability and tolerance of methanol. Furthermore, on the basis of the X-ray absorption near-edge structure, extended X-ray absorption fine structure, and linear sweep voltammetry data, we first provided proof that a catalyst devoid of obvious Co-Nx can have superior ORR activity.

Localized Plasmon resonance in metal nanoparticles using Mie theory

In this work, scattering light by colloidal metal nanoparticles with spherical shape was studied. Optical properties such as diffusion efficiencies of extinction and absorption Qext and Qabs were calculated using Mie theory. We employed a MATLAB program to calculate the Mie efficiencies and the radial dependence of electric field intensities emitted for colloidal metal nanoparticles (MNPs). By UV-Vis spectroscopy we have determined the LSPR for Cu nanoparticles (CuNPs), Ni nanoparticles (NiNPs) and Co nanoparticles (CoNPs) grown by laser ablation technique. The peaks of resonances appear in 590nm, 384nm and 350nm for CuNPs, NiNPs and CoNPs respectively suspended in water. Changing the medium to acetone and ethanol we observed a shift of the resonance peaks, these values agreed with our simulations results.

The impact of support surface area on the SMSI decoration effect and catalytic performance for Fischer-Tropsch synthesis of Co-Ru/TiO2-anatase catalysts

A series of Co-Ru/TiO2 catalysts (10wt% Co, 0.5wt% Ru, nominal loadings) were prepared by impregnation of TiO2-anatase supports synthesized with different specific surface areas (Ti-L: 53m2/g, Ti-M: 117m2/g, and Ti-H: 148m2/g) by tuning the conditions of the hydrothermal synthesis and/or the calcination treatments. The most relevant physicochemical properties of supports and catalysts were determined by a set of techniques including ICP-OES, XRD, N2 physisorption, electron microscopy (FESEM, HAADF-STEM, HR-TEM), H2-TPR, H2 chemisorption, and IR-CO. Oxidized precursors were reduced in-reactor under flowing pure H2 at 400°C for 10h and evaluated for Fischer-Tropsch synthesis (FTS) in a fixed bed reactor at 220°C, 2.0MPa, and H2/CO molar ratio of 2. These catalysts exhibited the well-known strong metal-support interaction (SMSI) effect reported for TiO2 materials by which partially reduced TiOx species formed during the catalyst reduction step migrate and decorate the surface of the supported metal phases. The extent to which the SMSI effect occurred was found to increase with the surface area of the TiO2-anatase carrier, as supported by H2 chemisorption, TEM, and IR-CO surface titration experiments. As a consequence, the activity per total mass of cobalt or cobalt-time-yield (CTY) of the Co-Ru/TiO2 catalysts gradually declined with the increase in support surface area: Co-Ru/Ti-L>Co-Ru/Ti-M>Co-Ru/Ti-H. The catalysts, however, displayed similar initial TOFs, implying a negligible influence of the SMSI effect on the initial intrinsic activity of the surface Co0 sites. The high surface area Co-Ru/Ti-H catalyst exhibiting the most pronounced SMSI also presented the lowest C5+ selectivity. This behavior was explained by considering the contribution of two effects: the lower resistance to the intraparticle diffusion of α-olefins when increasing the support surface area, as inferred from the olefin-to-paraffin ratios and the values of the diffusion-related parameter χ, and the reduction in size of the cobalt ensembles on the terraces of Co0 nanoparticles, connected to the extent of SMSI, on which chain growth events are favored.

Nanoparticles of WC-Co, WC, Co and Cu of relevance for traffic wear particles – Particle stability and reactivity in synthetic surface water and influence of humic matter

Studded tyres made of tungsten carbide cobalt (WC-Co) are in the Northern countries commonly used during the winter time. Tungsten (W)-containing nano- and micron-sized particles have been detected close to busy roads in several European countries. Other typical traffic wear particles consist of copper (Cu). The aims of this study were to investigate particle stability and transformation/dissolution properties of nanoparticles (NPs) of WC-Co compared with NPs of tungsten carbide (WC), cobalt (Co), and Cu. Their physicochemical characteristics (primarily surface oxide and charge) are compared with their extent of sedimentation and metal release in synthetic surface water (SW) with and without two different model organic molecules, 2,3- and 3,4-dihydroxybenzoic acid (DHBA) mimicking certain sorption sites of humic substances, for time periods up to 22 days. The WC-Co NPs possessed a higher electrochemical and chemical reactivity in SW with and without DHBA molecules as compared with NPs of WC, Co, and Cu. Co was completely released from the WC-Co NPs within a few hours of exposure, although it remained adsorbed/bonded to the particle surface and enabled the adsorption of negatively charged DHBA molecules, in contrast with the WC NPs (no adsorption of DHBA). The DHBA molecules were found to rapidly adsorb on the Co and Cu NPs. The sedimentation of the WC and WC-Co NPs was not influenced by the presence of the 2,3- or 3,4-DHBA molecules. A slight influence (slower sedimentation) was observed for the Co NPs, and a strong influence (slower sedimentation) was observed for the Cu NPs in SW with 2,3-DHBA compared with SW alone. The extent of metal release increased in the order: WC < Cu < Co < WC-Co NPs. All NPs released more than 1 wt-% of their metal total mass. The release from the Cu NPs was most influenced by the presence of DHBA molecules.

Soft magnetic property and enhanced microwave absorption of nanoparticles of Co0.5Zn0.5Fe2O4 incorporated in MWCNT

Nanoparticles of Co0.5Zn0.5Fe2O4 (CZFO) are prepared by coprecipitation method where CoCl2·H2O, ZnCl2·6H2O and FeCl3 are used as precursor materials. To enhance the microwave absorption, nanoparticles of CZFO are incorporated in the matrix of multiwall carbon nanotubes (MWCNT). X-ray diffractogram (XRD) and its analysis confirmed the formation of the desired crystallographic phase of the sample. The average crystallite size is evaluated by using the Debye-Scherrer formula. Micrographs observed in high resolution transmission electron microscope confirm the successful incorporation of CZFO in the matrix of MWCNT. Results obtained from the high resolution lattice fringe and selected area electron diffraction patterns are in good agreement with the findings extracted from the XRD analysis. Analysis of Raman spectra confirms the presence of CZFO and MWCNT in the nanocomposite sample. Magnetic properties recorded in SQUID magnetometer confirm the presence of mixed state of superparamagnetic and ferrimagnetic nanoparticles. Reflection losses in X (8–12GHz) and Ku (12–18GHz) bands of microwave region are significantly high (~−38.2dB at 16.9GHz). High magnetization (~36.5emu/g at 300K), low coercive field (~30.1Oe at 300K) and high reflection loss of CZFO-MWCNT would be suitable for application in microwave devices.

Characterization of a Porous Carbon Material Functionalized with Cobalt-Oxide/Cobalt Core-Shell Nanoparticles for Lithium Ion Battery Electrodes

ABSTRACTA nanoporous carbon (C) material, functionalized with Cobalt-Oxide/Cobalt (CoO/Co) core-shell nanoparticles (NPs), was structurally and chemically characterized with transmission electron microcopy (TEM) while its electrochemical response for Lithium ion battery (LIB) applications was evaluated as well. The results herein show that the nanoporous C material was uniformly functionalized with the CoO/Co core-shell NPs. Further the NPs were crystalline with fcc-type lattice on the Co2+ oxide shell and hcp-type core of metallic Co0. The electrochemical study was carried out by using galvanostatic charge/discharge cycling at a current density of 1000 mA g−1. The potential of this hybrid material for LIB applications was confirmed and it is attributed to the successful dispersion of the Co2+/ Co0 NPs in the C support.

The Protective Effect of Bafilomycin A1 Against Cobalt Nanoparticle-Induced Cytotoxicity and Aseptic Inflammation in Macrophages In Vitro.

Co ions released due to corrosion of Co nanoparticles (CoNPs) in the lysosomes of macrophages may be a factor in the particle-induced cytotoxicity and aseptic inflammation accompanying metal-on-metal (MOM) hip prosthesis failure. Here, we show that CoNPs are easily dissolved under a low pH, simulating the acidic lysosomal environment. We then used bafilomycin A1 to change the pH inside the lysosome to inhibit intracellular corrosion of CoNPs and then investigated its protective effects against CoNP-induced cytotoxicity and aseptic inflammation on murine macrophage RAW264.7 cells. XTT {2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide} assays revealed that bafilomycin A1 can significantly decrease CoNP-induced cytotoxicity in RAW264.7 cells. Enzyme-linked immunosorbent assays showed that bafilomycin A1 can significantly decrease the subtoxic concentration of CoNP-induced levels of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), but has no effect on anti-inflammatory cytokines (transforming growth factor-β and interleukin-10) in RAW264.7 cells. We studied the protective mechanism of bafilomycin A1 against CoNP-induced effects in RAW264.7 cells by measuring glutathione/oxidized glutathione (GSH/GSSG), superoxide dismutase, catalase, and glutathione peroxidase levels and employed scanning electron microscopy, transmission electron microscopy, and energy dispersive spectrometer assays to observe the ultrastructural cellular changes. The changes associated with apoptosis were assessed by examining the pAKT and cleaved caspase-3 levels using Western blotting. These data strongly suggested that bafilomycin A1 can potentially suppress CoNP-induced cytotoxicity and aseptic inflammation by inhibiting intracellular corrosion of CoNPs and that the reduction in Co ions released from CoNPs may play an important role in downregulating oxidative stress in RAW264.7 cells.