Preparation of Cobalt Nanoparticles

Magnetic cobalt nanoparticles embedded in a carbonaceous hydrogel for the activation of peroxymonosulfate to degrade azo dyes and organic pollutants

Heterogeneous cobalt-based catalysts have recently gained attention as persulfate activators to degrade dyes and organic pollutants in sulfate radical-based advanced oxidation processes (SR-AOPs). This study fabricated magnetic cobalt nanoparticles embedded in a carbonaceous hydrogel (Co@C) using high-temperature pyrolysis of the Co2+-embedded chitosan-graft-poly(acrylic acid) (Co2+-embedded CTS-g-PAA) hydrogel. Subsequently, the prepared Co@C was evaluated as a peroxymonosulfate (PMS) activator for degrading azo dyes. The catalyst showed the highest performance toward reactive red 141 (RR141) than Congo red, methyl orange, direct yellow 50, and reactive black 5. RR141 was completely degraded within 10 min, with a 3.20 min-1 pseudo-first-order rate constant. The degradation rate increased with higher catalyst dosage, PMS dosage, and temperature. The pH of the solution had a minimal effect on the degradation of RR141, indicating that the catalyst could be effective across a wide pH range. Moreover, the quenching experiment and the electron paramagnetic resonance analysis indicated that the catalytic system generated SO4•-, HO•, O2•-, and 1O2. The RR141 degradation was slightly affected by Cl-, NO3-, and SO42-. The catalyst demonstrated high efficiencies in real water samples. The catalyst could be easily recovered using a magnet and reused for ten cycles with only a 10% degradation efficiency loss. Furthermore, the catalyst could effectively degrade other organic pollutants, including tetracycline and 4-nitrophenol. This study demonstrates that the Co@C catalyst can effectively purify wastewater via SR-AOPs.

Tuning the Selectivity of Catalytic Nitrile Hydrogenation with Phase-Controlled Co Nanoparticles Prepared by Hydrosilane-Assisted Method

Cobalt (Co) is a promising candidate to replace noble metals in the hydrogenation process, which is widely employed in the chemical industry. Although the catalytic performance for this reaction has been considered to be significantly dependent on the Co crystal phase, no satisfactory systematic studies have been conducted, because it is difficult to synthesize metal nanoparticles that have different crystalline structures with similar sizes. Here we report a new method for the synthesis of cobalt nanoparticles using hydrosilane as a reducing agent (hydrosilane-assisted method). This new method uses 1,3-butanediol and propylene glycol to successfully prepare fcc and hcp cobalt nanoparticles, respectively. These two types of Co nanoparticles have similar sizes and surface areas. The hcp Co nanoparticles exhibit higher catalytic performance than fcc nanoparticles for the hydrogenation of benzonitrile under mild conditions. The present hcp Co catalyst is also effective for highly selective benzyl amine production from benzonitrile without ammonia addition, whereas many catalytic systems require ammonia addition for selective benzyl amine production. Mechanistic studies revealed that the fast formation of the primary amine and the prevention of condensation and secondary amine hydrogenation promote selective benzonitrile hydrogenation for benzylamine over hcp Co nanoparticles.

Green synthesis of silver nanoparticles and its environmental sensor ability to some heavy metals

This study marks a pioneering effort in utilizing Vachellia tortilis subsp. raddiana (Savi) Kyal. & Boatwr., (commonly known as acacia raddiana) leaves as both a reducing and stabilizing agent in the green "eco-friendly" synthesis of silver nanoparticles (AgNPs). The research aimed to optimize the AgNPs synthesis process by investigating the influence of pH, temperature, extract volume, and contact time on both the reaction rate and the resulting AgNPs' morphology as well as discuss the potential of AgNPs in detecting some heavy metals. Various characterization methods, such as UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), Zeta sizer, EDAX, and transmitting electron microscopy (TEM), were used to thoroughly analyze the properties of the synthesized AgNPs. The XRD results verified the successful production of AgNPs with a crystallite size between 20 to 30 nm. SEM and TEM analyses revealed that the AgNPs are primarily spherical and rod-shaped, with sizes ranging from 8 to 41 nm. Significantly, the synthesis rate of AgNPs was notably higher in basic conditions (pH 10) at 70 °C. These results underscore the effectiveness of acacia raddiana as a source for sustainable AgNPs synthesis. The study also examined the AgNPs' ability to detect various heavy metal ions colorimetrically, including Hg2+, Cu2+, Pb2+, and Co2+. UV-Vis spectroscopy proved useful for this purpose. The color of AgNPs shifts from brownish-yellow to pale yellow, colorless, pale red, and reddish yellow when detecting Cu2+, Hg2+, Co2+, and Pb2+ ions, respectively. This change results in an alteration of the AgNPs' absorbance band, vanishing with Hg2+ and shifting from 423 to 352 nm, 438 nm, and 429 nm for Cu2+, Co2+, and Pb2+ ions, respectively. The AgNPs showed high sensitivity, with detection limits of 1.322 × 10-5 M, 1.37 × 10-7 M, 1.63 × 10-5 M, and 1.34 × 10-4 M for Hg2+, Cu2+, Pb2+, and Co2+, respectively. This study highlights the potential of using acacia raddiana for the eco-friendly synthesis of AgNPs and their effectiveness as environmental sensors for heavy metals, showcasing strong capabilities in colorimetric detection.

A New Approach to the Synthesis of Nanocrystalline Cobalt Boride in the Course of the Thermal Decomposition of Cobalt Complexes [Co(DMF)6]2+ with Boron Cluster Anions

In the course of the study, nanocrystalline cobalt monoboride was prepared by thermal decomposition of precursors [Co(DMF)₆][An], where [An] = [B₁₂H₁₂]^2- (1), [trans-B₂₀H₁₈]^2- (2) or [B₁₀Cl₁₀]^2- (3) in an argon atmosphere. Three new salt-like compounds 1-3 were prepared when Co(NO₃)₂ was allowed to react with (Et₃NH)₂[An]. Compound 1 is new; the structures of compounds 2 and 3 have been previously reported. Samples 1-3 were annealed at 900 °C in argon to form samples 1a-3a, which were characterized by single crystal XRD for 1 and powder XRD for 1-3. Powder XRD on the products showed the formation of BN and CoB for 1a in a 1:1 ratio; 2a gave a higher CoB:BN ratio but an overall decreased crystallinity. For 3a, only CoB was found. IR spectra of samples 1a-3a as well as X-ray spectral fluorescence analysis for 3a confirmed these results. The nanoparticular character of the decomposition products 1a-3a was shown using TEM; quite small particle sizes of about 10-15 nm and a quite normal size distribution were found for 1a and 2a, while the decomposition of 3 gave large particles with 200-350 nm and a broad distribution.

Advances of Cobalt Nanomaterials as Anti-Infection Agents, Drug Carriers, and Immunomodulators for Potential Infectious Disease Treatment

Infectious diseases remain the most serious public health issue, which requires the development of more effective strategies for infectious control. As a kind of ultra-trace element, cobalt is essential to the metabolism of different organisms. In recent decades, nanotechnology has attracted increasing attention worldwide due to its wide application in different areas, including medicine. Based on the important biological roles of cobalt, cobalt nanomaterials have recently been widely developed for their attractive biomedical applications. With advantages such as low costs in preparation, hypotoxicity, photothermal conversion abilities, and high drug loading ability, cobalt nanomaterials have been proven to show promising potential in anticancer and anti-infection treatment. In this review, we summarize the characters of cobalt nanomaterials, followed by the advances in their biological functions and mechanisms. More importantly, we emphatically discuss the potential of cobalt nanomaterials as anti-infectious agents, drug carriers, and immunomodulators for anti-infection treatments, which might be helpful to facilitate progress in future research of anti-infection therapy.

Current Methods for Synthesis and Potential Applications of Cobalt Nanoparticles: A Review

Cobalt nanoparticles (CoNPs) are promising nanomaterials with exceptional catalytic magnetic, electronic, and chemical properties. The nano size and developed surface open a wide range of applications of cobalt nanoparticles in biomedicine along with those properties. The present review assessed the current environmentally friendly synthesis methods used to synthesize CoNPs with various properties, such as size, zeta potential, surface area, and magnetic properties. We systematized several methods and provided some examples to illustrate the synthetic process of CoNPs, along with the properties, the chemical formula of obtained CoNPs, and their method of analysis. In addition, we also looked at the potential application of CoNPs from water purification cytostatic agents against cancer to theranostic and diagnostic agents. Moreover, CoNPs also can be used as contrast agents in magnetic resonance imaging and photoacoustic methods. This review features a comprehensive understanding of the synthesis methods and applications of CoNPs, which will help guide future studies on CoNPs.

Synthesis of Cobalt-Nickel Nanoparticles via a Liquid-Phase Reduction Process

Cobalt-nickel nanoparticles (Co-Ni-NPs) show promising electrochemical performance in oxygen and hydrogen evolution reactions (OER and HER) due to their physicochemical properties such as electronic configuration and great electrochemical stability. Therefore, developing new economically and environmentally friendly methods of synthesizing Co-Ni-NPs has become a practical requirement. Co-Ni-NPs were produced by employing the liquid-phase reduction method. Nickel and cobalt sulfate solutions in hydrazine monohydrate with various mixing ratios were used as raw materials. Nickel plays an important role in the nucleation process via increasing the reduction reaction rate throughout the formation of Co-Ni-NPs. Furthermore, the acceleration of the Co-Ni-NPs formation process may be attributed to the partial dissolution of Ni(OH)2 in the presence of N2H4 and/or citrate-anions and the formation of the Ni-N2H4 or Ni-Cit complexes in contrast to Co(OH)2.