Silver Cobalt Research Articles

In situ activated CoAg bimetallic catalyst for selective hydrodeoxygenation of syringol to cyclohexanol

Development of highly effective catalysts for selective hydrodeoxygenation (HDO) of syringol, a model compound of lignin, to cyclohexanol (CYHAOL) is a challenge due to the intricate molecular structure of syringol. Herein, we have synthesized an in–situ activated cobalt–silver bimetallic catalyst, CoAg/SiO2, through a simple incipient–wetness impregnation method. The catalyst without pre–reduction treatment attained a complete conversion with 93.8 mol% CYHAOL selectivity under moderate reaction conditions. Characterizations including HRTEM, XPS, XRD, NH3–TPD, and H2–TPR unanimously revealed the structure–activity relationship of the catalyst. In the reaction system, Ag promoted the in–situ reduction of Co3O4 to form a polycrystalline–structure complex (CoOx) containing oxygen vacancies. Ag also combines with Co to construct strong acid sites. The synergy of CoOx, oxygen vacancies, Ag, and acid sites demonstrates a high–efficiency HDO of syringol to CYHAOL. CoAg/SiO2 exonerates the pre–reduction treatment, simplifying the preparation and maintenance process and preventing severe sintering of the metals.

Photostability, cytotoxicity, and photothermal impact of AgNPs, CoAgNC, and IOAgNC on HEp-2 laryngeal carcinoma cells

Magnetic nanoparticles have shown promise in various medical applications, including cancer treatment and diagnostics. The objective of this study is to attain mastery over the synthesis of silver nanoparticles (AgNPs), Cobalt silver nanocomposite (CoAgNC) and magnetite silver nanocomposite (IOAgNC), while also examining their photostability, cytotoxicity, and photothermal impact on Human Laryngeal Carcinoma Cell line (HEp-2). The preparation and characterization of AgNPs, CoAgNC, and IOAgNC were described, including the assessment of their photostability and cytotoxicity on HEp-2 cell line. The photostability of these nanomaterials was determined by subjecting them to different light sources, while their morphology and magnetic properties were characterized using a spectrophotometer, Transmission Electron Microscopy (TEM), and Vibrating Sample Magnetometer (VSM). The results of the characterization of AgNPs, CoAgNC, and IOAgNC showed that the prepared nanomaterials have distinct optical and morphological properties. The synthesized nanomaterials were stable in aqueous solutions and exhibited magnetic properties. The cytotoxicity tests on HEp-2 cells showed that the nanomaterials were not toxic in the dark, but their toxicity increased under light exposure, with IOAgNC showing the most significant toxicity. CoAgNC was found to be photostable under UV light and Light Emitting Diode (LED) irradiation due to the little lattice mismatch between cobalt and silver. Nanocomposite systems of high magnetic moment, such as IOAgNC and CoAgNC, have potential for tumor treatment through magnetic fluid hyperthermia. The photostability, chemical stability, and biocompatibility of AgNPs, CoAgNC, and IOAgNC were investigated and found to be non-toxic even at high concentrations. These nanomaterials have multiple optical and magnetic functionalities and are promising candidates for biomedical applications.

Growth of AgCoS@CNTs composite on nickel foam to enrich the redox active sites for battery-supercapacitor hybrid energy storage device

Supercapacitors are recognized as reliable energy storage technologies, despite obstacles such as inadequate energy density and comparatively small capacitance. In this study, we employed a hydrothermal synthesis method to fabricate silver cobalt sulfide (AgCoS) and doped it with carbon nanotubes (CNTs). The surface area of 19.35 m2/g was achieved with AgCoS@CNT//AC using BET measurements. The galvanostatic charge-discharge (GCD) measurements revealed a specific capacity of 1023 C/g for AgCoS@CNT. To construct an asymmetric device (AgCoS@CNT//AC), the best-performing AgCoS@CNT composite was employed as the positive electrode, while activated carbon (AC) served as the negative electrode. The specific capacity of the asymmetric device AgCoS@CNT//AC was measured to be 104 C/g, accompanied by a high power density of 750 W/kg and an impressive energy density of 32 Wh/kg. Notably, the columbic efficiency of the AgCoS@CNT//AC device reached 100% after 5000 consecutive cycles, while maintaining a capacity retention of 82%. These findings indicate that the AgCoS@CNT composite might serve as an intriguing material as an electrodes for supercapacitor applications.

Photoactive MOF-Derived Bimetallic Silver and Cobalt Nanocomposite with Enhanced Antibacterial Activity

Conventional antibiotic-based treatment of bacterial infections remains one of the most difficult challenges in medicine because of the threat of multidrug resistance caused by indiscriminate abuse. To solve these problems, it is essential to develop an effective antibacterial agent that can be used at a small dose while minimizing the occurrence of multiple resistance. Metal-organic frameworks (MOFs), which are hyper-porous hybrid materials containing metal ions linked by organic ligands, have recently attracted attention because of their strong antibacterial activity through metal-ion release, unlike conventional antibiotics. In this study, we developed a photoactive MOF-derived cobalt-silver bimetallic nanocomposite (Ag@CoMOF) by simply depositing silver nanoparticles on a cobalt-based MOF through nanoscale galvanic replacement. The nanocomposite structure continuously releases antibacterial metal ions (i.e., Ag and Co ions) in the aqueous phase and exhibits a strong photothermal conversion effect of Ag nanoparticles, accompanied by a rapid temperature increase of 25-80 °C under near-infrared (NIR) irradiation. Using this MOF-based bimetallic nanocomposite, superior antibacterial activities were achieved by 22.1-fold for Escherichia coli and 18.3-fold for Bacillus subtilis enhanced inhibition of bacterial growth in a liquid culture environment compared with the generally used chemical antibiotics. In addition, we confirmed the synergistic enhancement of the antibacterial ability of the bimetallic nanocomposite induced by NIR-triggered photothermal heating and bacterial membrane disruption even when using a small amount of the nanocomposites. We envision that this novel antibacterial agent using MOF-based nanostructures will replace traditional antibiotics to circumvent multidrug resistance and present a new approach to antibiotic development.

Active manipulation of radiated fields by a magnetoplasmonic half-wave dipole nanoantenna.

We demonstrate a concept for the active manipulation of radiated fields by a magnetoplasmonic half-wave dipole nanoantenna. Our idea comprises a two arms nanoantenna, made of metallic ferromagnetic cobalt-silver alloy (Co6Ag94), inspired by the analogous radio frequency half-wave dipole antenna design. Numerical results, obtained under the magnetization saturation condition, indicate a tilting of the radiated beam depending on the magnitude and sense of the magnetization of the ferromagnetic material. Significantly, we obtained tilting angles as large as ±9.7∘ around the y axis for the magnetization placed along the x or z axes, respectively. Results in this work not only open up a new, to the best of our knowledge, way to dynamically manipulate the beam steering at the chip-scale, but also contribute to unveil novel magneto-optical effects at the nanoscale.

Facile hydrothermal synthesis of high-performance binary silver-cobalt-sulfide for supercapattery devices

The rapid depletion of fossil fuel resources, along with rising energy consumption, has prompted the development of renewable energy storage systems. More focus must be placed on renewable and sustainable energy sources in order to reduce the reliance on fossil fuels for energy production. Because of their tremendous energy and great power density, batteries and supercapacitors are being intensively researched in renewable energy storage systems. In this work. We used a one-step simple hydrothermal approach to synthesize silver sulfide, cobalt sulfide, and their binary compound silver cobalt sulfide with a 50/50 weight ratio. X-ray diffraction (XRD) and scanning electron microscopy (SEM) examined the materials' crystallinity and surface morphology. Electrochemical behavior of silver sulfide AgS (S1) cobalt sulfide CoS (S2), and silver cobalt sulfide (AgCoS) was investigated in the three-electrode assembly. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) have been carried out to explore its electrochemical characteristics. The electrochemical analysis reveals that silver sulfide AgS (S1) provides a specific of 402 C/g at 3 mV/s while cobalt sulfide CoS (S2) provides the specific capacity of 289C/g at 3 mV/s. when combined silver sulfide and cobalt sulfide in a 50/50 weight ratio specific capacity achieved with silver cobalt sulfide AgCoS (S3) is 701.01C/g at a low scan rate of 3 mV/s. An asymmetric device (AgCoS//AC) was developed by employing activated carbon as the negative electrode and the best silver cobalt sulfide as the positive electrode. This asymmetric supercapacitor has been investigated through CV, GCD, and stability tests for 1000 consecutive cycles. The device delivered a high energy density of 22.34 Wh/kg in parallel to the high power density of 899.2 W/kg. After 1000 consecutive cycles, the columbic efficiency of this device increases to 105% while maintaining capacity retention of 82%. This study indicates that silver cobalt can be an efficient electrode material for supercapattery devices.

Structure, magnetic properties and giant magnetoresistance of granular cobalt–silver films

Structure, magnetic properties and giant magnetoresistance of granular cobalt–silver films

An easy synthesis of carbon-supported silver–cobalt bimetallic nanoparticles to study the electrocatalytic performance in alkaline borohydride fuel cell

An easy synthesis of carbon-supported silver–cobalt bimetallic nanoparticles to study the electrocatalytic performance in alkaline borohydride fuel cell

Catalytic Ozonation of Reactive Black 5 Over Silver–Cobalt Composite Oxide Catalyst

Catalytic ozonation was carried out using the silver–cobalt composite catalyst. Co-precipitation method was followed for the preparation of the catalyst, and characterization of the catalyst was carried out by XRD, BET and SEM with EDX. The percentage of total organic carbon removal was 75% employing silver–cobalt composite catalyst with ozonation, against 34% employing ozonation without any catalyst. The parameters such as amount of catalyst, initial concentration of the dye, ozone flow rate and the solution pH were found to affect the catalytic ozonation process. Degradation mechanism identified employing hydroxyl radical scavenger. The cyclic use of the synthesized catalyst indicated that the catalytic activity of Ag–Co–O is not much deteriorated after three cycles. Further, the kinetic suggests pseudo-first-order kinetics for the process.

AgCoO2−Co3O4/CMC Cloudy Architecture as High Performance Electrodes for Asymmetric Supercapacitors

AbstractThis work represents the design of superior supercapacitor electrode that comprised of 3D cloud like silver cobalt oxide/cobalt oxide (AgCoO2−Co3O4) and carbon architecture. AgCoO2−Co3O4/C architecture can be fabricated from Co−Ag nitrate precursors with the addition of carboxymethyl cellulose followed by annealing. Mesoporous 3D cloudy architecture provides higher specific capacitance (575 F g−1 at a scan rate of 2 mV s−1) and rate performance (666 F g−1 at a current density of 1 A g−1). The combined effect of AgCoO2 embedded Co3O4 and carboxymethyl cellulose (carbon) highly favors for outstanding cycle life (around 1 % capacitance degradation even after 5000 cycles). Presence of such porous 3D architecture with carbon backbone delivers admirable energy/power density. Also, an advanced asymmetric supercapacitor with an operating range of 1.2 V is designed by utilizing this porous 3D cloudy architecture as positive electrode and activated carbon as negative electrode. The fabricated design shows a robust energy density of 17 W h kg−1 with a high power density of 166 W kg−1 at a current density of 1 A g−1. The findings of the current study underline the potential of AgCoO2−Co3O4/C electrodes for supercapacitor applications.

Comparison of the effects of silver nanoparticles and silver cobalt nanoparticles on function tests and liver tissue changes in adult male rats

Objective(s): This study aimed to compare impacts of silver nanoparticles and silver cobalt nanoparticles on the hepatic function tests and changes in liver tissues in adult male rats.Materials and Methods: This study was conducted on 49 adult male Wistar rats, each weighing approximately 180-220 gr. The rats were randomly assigned to seven groups of seven including one control group and six experimental groups. The experimental groups 1 and 2 respectively received 25 and 100 mg/kg of silver nanoparticles synthesized for 75 sec intraperitoneally for 14 days. Experimental group 3 received silver nanoparticles that were synthesized at 300 sec which were administered intraperitoneally in a 25 mg/kg dose for 14 days. The experimental groups 4 and 5 received silver cobalt nanoparticles, whereby silver nanoparticles were synthesized at 75 sec and were administered intraperitoneally in a 25 and 100 mg/kg dose for 14 days, respectively. Finally, experimental group 6 received a 25 mg/kg dose of silver cobalt nanoparticles, intraperitoneally for 14 days, with the silver nanoparticles synthesized for 300 sec. At the end of this period, the serum levels of hepatic enzymes, albumin, and total protein were measured and tissue changes were evaluated in this study.Results: The mean serum levels of AST, total protein, and albumin in the experimental groups 1 and 3 increased significantly compared to the control group. Similarly, the mean serum levels of ALT and ALP in the experimental group 3 showed a significant increase in comparison with the control group. The mean of liver weight in all experimental groups was significantly higher than the control group(P<0.05). Furthermore, the necrosis of the liver tissue was observed in the recipients of silver nanoparticles. However, liver necrosis was not observed in the groups receiving silver cobalt nanoparticles.Conclusion: The use of silver nanoparticles can boost the serum levels of hepatic enzymes and increase liver tissue necrosis, as well. However, the silver cobalt nanoparticles did not change the levels of hepatic enzymes and liver tissue.

Synthesis and Structure of New Mixed Silver Cobalt(II)/(III) Diphosphate - Ag3.68Co2(P2O7)2. Silver(I) Transport in the Crystal

Synthesis and Structure of New Mixed Silver Cobalt(II)/(III) Diphosphate - Ag3.68Co2(P2O7)2. Silver(I) Transport in the Crystal

Synthesis, structural characterization and antimicrobial activities of polyindole stabilized Ag-Co3O4 nanocomposite by reflux condensation method

Polyindole stabilized silver‒cobalt oxide (Pind/Ag‒Co3O4) nanocomposites were synthesized, characterized and evaluated for their antibacterial and antifungal activities. Polyindole, cobalt oxide and Pind/Ag‒Co3O4 were prepared by chemical oxidative polymerization, co-precipitation and reflux condensation method, respectively. Colloidal nanoparticles of polyindole, cobalt oxide and nanocomposite were characterized by Fourier transform infrared spectrophotometer (FT-IR), X-ray diffraction pattern (XRD), scanning electron microscope with energy dispersive X-ray diffraction study (SEM-EDAX) and high resolution transmission electron microscope with selected area diffraction (HRTEM-SAED). FTIR spectra revealed the functional group’s transformation of cobalt oxide nanoparticles. The crystalline nature of the samples was confirmed by XRD study. The SEM images revealed the various shapes and surface morphology of the nanocomposites. Further, the elemental composition was confirmed by EDAX. The HRTEM images showed shapes such as spherical, cylindrical, rectangular, rods, oval and square. The average particle size of the nanocomposites found to be ∼20 nm which is in good agreement with XRD analysis in terms of the size of the crystalline. The Pind/Ag‒Co3O4 nanocomposites exhibited improved antibacterial and antifungal activities against pathogenic bacteria and fungi. Hence, these nanocomposites could be used as a potential candidate for the biomedical applications.

Crystal structure of a silver-, cobalt- and iron-based phosphate with an alluaudite-like structure: Ag1.655Co1.64Fe1.36(PO4)3.

The new silver-, cobalt- and iron-based phosphate, silver cobalt iron tris(ortho-phosphate), Ag1.655Co1.64Fe1.36(PO4)3, was synthesized by solid-state reactions. Its structure is isotypic to that of Na2Co2Fe(PO4)3, and belongs to the alluaudite family, with a partial cationic disorder, the AgI atoms being located on an inversion centre and twofold rotation axis sites (Wyckoff positions 4a and 4e), with partial occupancies of 0.885 (2) and 0.7688 (19), respectively. One of the two P atoms in the asymmetric unit completely fills one 4e site while the Co and Fe atoms fill another 4e site, with partial occupancies of 0.86 (5) and 0.14 (5), respectively. The remaining Co2+ and Fe3+ cations are distributed on a general position, 8f, in a 0.39 (4):0.61 (4) ratio. All O atoms and the other P atoms are in general positions. The structure is built up from zigzag chains of edge-sharing [MO6] (M = Fe/Co) octa-hedra stacked parallel to [101]. These chains are linked together through PO4 tetra-hedra, forming polyhedral sheets perpendicular to [010]. The resulting framework displays two types of channels running along [001], in which the AgI atoms (coordination number eight) are located.

Failure mechanisms in cobalt welded with a silver–copper filler

Cobalt silver–copper (Co–AgCu) weldments approximate the stresses and failure mechanisms of beryllium aluminum–silicon (Be–AlSi) welds, which have strategic importance but are hazardous to study. Failure tests of these surrogate Co–AgCu welds, examined in tension and four-point bending, show that residual stresses and post-welding heat treatment have little or no effect on strength, whereas weld quality and geometry are extremely important. Scanning electron microscopy images reveal abundant defects in poor welds, which usually fail through propagation of preexisting cracks. Fracture surfaces show a variety of morphologies, ranging from dimples in the AgCu filler, to cleavage steps in the CoCu peritectic, and suspected intergranular fracture in the cobalt base. Spatially resolved acoustic spectroscopy reveals significant changes in microstructure near the base–filler interface, whereas wavelength dispersive analysis shows high Cu concentrations in this area.. Contrary to finite element predictions, these welds were found to be stronger during face bending than root bending, likely resulting from the increased number of cracks and imperfections in the Co base. These computations correctly predict that weld strength depends on geometry and that welds fail either in the cobalt base, or along the base–filler interface. Crack compliance measurements show that the largest residual stresses are located along this interface. However, these stresses are unlikely to influence failure due to their direction, whereas stresses in the weld root are too small to have observable effects on failure. The strength of Co–AgCu welds depends strongly on geometry, penetration, and weld quality, but little on residual stresses, and this conclusion is tentatively extended to Be–AlSi welds.

Silver–Cobalt Oxides Derived from Silver Nanoparticles Deposited on Layered Double Hydroxides for Methane Combustion

AbstractAg nanoparticles (Ag NPs) have been deposited successfully on CoAl‐layered double hydroxide (CoAl‐LDH) layers through a simple and facile self‐redox process to give Ag‐CoAl‐LDHs. Furthermore, the CoAl‐LDHs and the Ag‐CoAl‐LDHs are calcined in air at different temperatures (500, 600, and 700 °C) to give CoAlO‐X and Ag‐CoAlO‐X catalysts for methane combustion (X=500, 600, and 700). The catalytic and characterization results reveal that Ag‐CoAlO‐600 has the highest catalytic activity as it has the highest low‐temperature reducibility and the most abundant surface Co3+ and surface adsorbed oxygen species. In addition, the Ag NP sizes on Ag‐CoAlO and the morphology changes of the CoAlO nanosheet supports affect the catalytic activity of methane combustion.

Synthesis of loofah sponge carbon supported bimetallic silver–cobalt nanoparticles with enhanced catalytic activity towards hydrogen generation from sodium borohydride hydrolysis

We demonstrate a functionalized carbonaceous material derived from the hydrothermal carbonization of natural loofah sponge can be served as an effective scaffold for anchoring bimetallic AgCo nanoparticles (NPs). The resulting loofah sponge carbon (LSC) supported AgCo NPs (LSC/AgCo) exhibits excellent performance for the catalytic hydrolysis of NaBH4 towards hydrogen generation. It is experimentally proved that the existed AgCo NPs mainly contribute to the catalytic activity, while the employed LSC support make them more effective in LSC/AgCo catalytic systems. The catalytic activities of the LSC/AgCo catalysts are also strongly dependent on the Ag/Co ratio, where LSC/Ag0.1Co0.9 is most active among all of the catalysts, and even more than five times that of monometallic LSC/Co, revealing that the Ag and Co compositions in LSC/AgCo catalysts show excellent synergy to catalyze NaBH4 hydrolysis for hydrogen generation. The present experimental study provides a promising pathway for the economical and sustainable implementation of biomass for the chemical hydrogen storage.

Corrosion Properties of Cobalt–Silver Alloy Electroplates

We establish the relationship between the corrosion resistance and composition of Co–Ag alloy electroplates with different contents of alloy-forming components. According to the results of analysis of the histograms of distribution of heights and inclination angles and the 2D- and 3D-maps of the surfaces, it is shown that the Co–Ag alloy electroplate is dense and has homogeneous structure. It grains have ellipsoidal shape and their size varies within the range 80–100 nm. It is experimentally shown that cobalt–silver alloys are characterized by a high corrosion resistance in alkaline media.

Structure, sintering and electrical properties of new ionic conductor Ag4Co7(AsO4)6

Abstract A new silver–cobalt arsenate, Ag 4 Co 7 (AsO 4 ) 6 , is synthesized by solid state reaction method and characterized by X-ray diffraction and impedance spectroscopy. The phase crystallizes in the monoclinic space group C2/m with a = 10.755(2) A, b = 14.937(2) A, c = 6.731(2) A, and β = 106.17(3)°. The structure is described as a three-dimensional anionic framework having interconnecting tunnels running along [1 0 0] and [0 1 0]. The former contains the silver cations. Ball milling is used as mechanical means to reduce the particles sizes of the as synthesized powder. At the optimal sintering temperature of 1173 K, dense ceramics (96% of the relative density) are obtained. Their microstructure is characterized by scanning electron microscopy. The conductivity of the ceramics is studied at different relative densities over a temperature interval from 437 to 773 K. The high conductivity at 210 °C (3.3 × 10 − 5 S cm − 1 ) and the activation energy ( Ea = 0.45 eV) show that Ag 4 Co 7 (AsO 4 ) 6 is a fast ionic conductor.

Measurement of the giant magnetoresistance effect in cobalt–silver magnetic nanostructures: nanoparticles

Cobalt–silver (Co–Ag) core–shell nanoparticles with different silver thicknesses were prepared by the microemulsion method in a two-step reduction process. Transmission electron microscopy (TEM) characterization revealed the almost monodispersity and nanometric size (in the range 3–5 nm depending on the shell thickness) of the synthesized nanoparticles. However, it was the use of high-resolution TEM that revealed the correct core–shell formation of the nanometric material. The selected area electron diffraction pattern indicated the fcc (face-centered cubic) and hcp (hexagonal close packed) nature for silver and cobalt, respectively. Cyclic voltammetry also allowed the correct core–shell formation to be assured. The magnetic properties revealed the presence of both superparamagnetic and ferromagnetic contributions. Because of the lack of methodology, it was necessary to develop a method to measure the magnetotransport properties of the prepared nanoparticles. The strategy which followed was successful as it was possible to measure these properties: giant magnetoresistance values of 0.1% at room temperature were obtained. The numerical analysis of magnetic and magnetoresistance data indicated the presence of superparamagnetic particles showing interaction among the magnetic moments.