Water-Soluble Nanocomposites Containing Co3O4 Nanoparticles Incorporated in Poly-1-vinyl-1,2,4-triazole

New water-soluble nanocomposites with cobalt oxide nanoparticles (Co₃O₄NPs) in a poly(1-vinyl-1,2,4-triazole) (PVT) matrix have been synthesized. The PVT used as a stabilizing polymer matrix was obtained by radical polymerization of 1-vinyl-1,2,4-triazole (VT). The polymer nanocomposites with Co₃O₄ nanoparticles were characterized by ultraviolet-visible, Fourier-transform infrared spectroscopy, atomic absorption spectroscopy, transmission electron microscopy, dynamic light scattering, gel permeation chromatography, and simultaneous thermogravimetric analysis. The resulting polymer nanocomposites consist of spherical isolated cobalt nanoparticles with a diameter of 1 to 13 nm. The average hydrodynamic diameters of macromolecular coils are 15-112 nm. The cobalt content in nanocomposites ranges from 1.5 to 11.0 wt.%. The thermal stability of nanocomposites is up to 320 °C.

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.

Evaluating the antibacterial effect of cobalt nanoparticles against multi-drug resistant pathogens

This study aimed to estimate the effect of cobalt nanoparticles (Co NPs) with different concentrations against multidrug-resistant (MDR) pathogenic bacteria. Three isolates of Staphylococcus aureus (gram-positive), Proteus spp. (gram-negative), and Escherichia coli (gram-negative) bacteria were extracted from various clinical examples utilizing routine methods on bacteriological culture media. The antibacterial sensitivity of commercial antibiotics such as Ciprofloxacin, Cefotaxime, Gentamycin, and Amoxicillin was broken down on a Muller Hinton agar plate and evaluated using the disk diffusion method. The study results demonstrated the antibacterial effect of the Co NPs against the bacterial isolates with three different concentrations utilized in the study. The results indicated that the Co NPs showed the highest antibacterial activity when utilizing 100 μg/ml against Escherichia coli followed by Proteus spp and Staphylococcus aureus with zones of inhibition measured as 22.2±0.1 mm, 20.3±0.15 mm, and 15.8±0.1 mm; respectively. Co NPs at a 100 μg/mL concentration showed higher inhibition zones than several common antibiotics except for Ciprofloxacin, which demonstrated better antibacterial activity against the bacterial isolates employed in this study. Scanning Electron Microscope (SEM)and X-Ray diffraction (XRD)studies confirmed that Cobalt nanoparticles (Co NPs) were synthesized from cobalt sulphate solution with a size ranging from 40 nm to 60 nm. The nanoparticles showed a crystalline structure with a round shape and smooth surface. The antibacterial resistance of Co NPs against three common bacteria such as Staphylococcus aureus, Proteus spp, and Escherichia coli was assessed in this study. The optimum concentration of the Co NPs was identified as 100 μg/ml, which could provide a similar or higher antibacterial effect.

Green Synthesis of Transition-Metal Nanoparticles and Their Oxides: A Review

In recent years, many researchers have begun to shift their focus onto the synthesis of nanomaterials as this field possesses an immense potential that may provide incredible technological advances in the near future. The downside of conventional synthesis techniques, such as co-precipitation, sol-gel and hydrothermal methods, is that they necessitate toxic chemicals, produce harmful by-products and require a considerable amount of energy; therefore, more sustainable fabrication routes are sought-after. Biological molecules have been previously utilized as precursors for nanoparticle synthesis, thus eliminating the negative factors involved in traditional methods. In addition, transition-metal nanoparticles possess a broad scope of applications due to their multiple oxidation states and large surface areas, thereby allowing for a higher reactivity when compared to their bulk counterpart and rendering them an interesting research topic. However, this field is still relatively unknown and unpredictable as the biosynthesis of these nanostructures from fungi, bacteria and plants yield undesired diameters and morphologies, rendering them redundant compared to their chemically synthesized counterparts. Therefore, this review aims to obtain a better understanding on the plant-mediated synthesis process of the major transition-metal and transition-metal oxide nanoparticles, and how process parameters—concentration, temperature, contact time, pH level, and calcination temperature affect their unique properties such as particle size, morphologies, and crystallinity.

Facile synthesis, physiochemical characterization and bio evaluation of sulfadimidine capped cobalt nanoparticles

Due to their less expensive, environment friendly nature, and their natural abundance of cobalt have attained more significant attention for the synthesis of cobalt nanoparticles. In the present study, we report the facile synthesis of cobalt nanoparticles using a straight forward chemical reduction approach of cobalt chloride with sodium borohydride and capping of sulfadimidine. sulfadimidine has strong capping eligibility on the surface of nanoparticles due to its chemical stability and is an applicable as stabilizer due to the existence of an amine bond. The as-synthesized sulfadimidine stabilized cobalt nanoparticles (Co-SD NPs) were characterized by using various spectroscopic and microscopic analysis like UV-Visible spectroscopy (UV-Vis), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), High-Resolution Transmission electron microscopy (HR-TEM), and Fourier-transform infrared spectroscopy (FT-IR). The XRD analysis exhibited the triclinic crystal structure of the as-synthesized cobalt nanoparticles and FT-IR analysis confirmed the capping of sulfadimidine via monodentate interaction. The HR-TEM analysis displayed the size of the cobalt nanoparticles approximately 3-5 nm. The antibacterial properties of the sulfadimidine stabilized cobalt nanoparticles (Co-SD NPs) were tested against various bacterial strains such as Klebsiella pneumonia (KP), Escherichia coli (EC) and Pseudomonas syringae (PS) by using agar disc diffusion approach. The results of sulfadimidine capped cobalt nanoparticles displayed the enhanced biological properties against the tested gram-negative bacteria.

Optimum synthesis of polyhydroxybutyrate-Co3O4 bionanocomposite with the highest antibacterial activity against multidrug resistant bacteria

Increased multidrug resistant (MDR) bacteria are considered one of the most challenging problems of the present century. The present study aimed to identify the optimum conditions for synthesis of Polyhydroxybutyrate-Co3O4 bionanocomposite with the highest antibacterial activity via in situ synthesis. Nine experiments with different amounts of polyhydroxybutyrate (PHB) biopolymer and Co3O4 nanoparticles and different stirring times were designed using Taguchi method. The antibacterial activity of synthesized nanocomposites against Staphylococcus aureus and Escherichia coli was evaluated using colony forming units (CFU) and disc diffusion methods. The characterizations of products were studied by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The synthesized bionanocomposites completely prevented the growth of bacteria under the conditions of experiments 5 (Co3O4 4 mg/ml, PHB 1 mg/ml and stirring time: 90 min) and 9 (Co3O4 8 mg/ml, PHB 2 mg/ml and stirring time: 60 min). The results showed that nanocomposite formation improved structural properties, thermal stability and antibacterial activity. PHB-Co3O4 bionanocomposite can be used in various fields of pharmacy, medicine and dentistry due to its desirable antibacterial properties.

Fabrication and characterization of cobalt hyaluronic acid nanostructure via gamma irradiation for improving biomedical applications

Aqueous dispersed cobalt hyaluronic acid nanostructure (CoHANs) was synthesized using cobalt ion (Co⁺²) as precursor and natural polysaccharide hyaluronic acid (HA) as stabilizing agent and gamma irradiation as reducing agent. The synthesized CoHANs are characterized by UV-Vis. spectroscopy, Dynamic light scattering (DLS), X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT-IR). The morphology and surface appearance of CoHANs has been observed by SEM images. The particles size and shape of CoHANs were estimated by TEM images and was found to be 12.0 nm. XRD analysis of the CoHANs confirmed the formation of crystalline nanoparticles. The nucleation and growth mechanism of CoHANs was also discussed. The size of nanoparticles was found to be influenced by certain parameters such as the choice of stabilizer and cobalt ion concentration and the absorbed dose. The results indicated the CoHANs possesses high activity than cobalt ion and HA. The present study explored the positive role of CoHANs as an antitumor agent on different cell carcinoma in vitro. Excellent bactericidal spatially against pathogenic bacteria and fungicidal activity was shown by the CoHANs.

Synthesis and characterization of silver nanoparticle-decorated cobalt nanocomposites (Co@AgNPs) and their density-dependent antibacterial activity

Magnetic cores loaded with metallic nanoparticles can be promising nano-carriers for successful drug delivery at infectious sites. We report fabrication, characteristic analysis and in vitro antibacterial performance of nanocomposites comprising cobalt cores (Co-cores) functionalized with a varied concentration of silver nanoparticles (AgNPs). A two-step polyol process synchronized with the transmetalation reduction method was used. Co-cores were synthesized with cobalt acetate, and decoration of AgNPs was carried out with silver acetate. The density of AgNPs was varied by changing the amount of silver content as 0.01, 0.1 and 0.2 g in the synthesis solution. Both AgNPs and Co-cores were spherical having a size range of 30-80 nm and 200 nm to more than 1 µm, respectively, as determined by scanning electron microscopy. The metallic nature and face-centred cubic crystalline phase of prepared nanocomposites were confirmed by X-ray diffraction. Biocompatibility analysis confirmed high cell viability of MCF7 at low concentrations of tested particles. The antibacterial performance of nanocomposites (Co@AgNPs) against Escherichia coli and Bacillus subtilis was found to be AgNPs density-dependent, and nanocomposites with the highest AgNPs density exhibited the maximum bactericidal efficacy. We therefore propose that Co@AgNPs as effective drug containers for various biomedical applications.

Mechanochemical Synthesis of Iron and Cobalt Magnetic Metal Nanoparticles and Iron/Calcium Oxide and Cobalt/Calcium Oxide Nanocomposites

We report an environmentally benign and cost-effective method to produce Fe and Co magnetic metal nanoparticles as well as the Fe/Cao and Co/CaO nanocomposites by using a novel, dry mechanochemical process. Mechanochemical milling of metal oxides with a suitable reducing agent resulted in the production of magnetic metal nanoparticles. The process involved grinding and consequent reduction of low-costing oxide powders, unlike conventional processing techniques involving metal salts or metal complexes. Calcium granules were used as the reducing agent. Magnetometry measurements were performed over a large range of temperatures, from 10 to 1273 K, to evaluate the Curie temperature, blocking temperature, irreversibility temperature, saturation magnetization, and coercivity. The saturation magnetizations of the iron and cobalt nanoparticles were found to be 191 and 102 emu g-1, respectively. The heating abilities of these nanoparticles suspended in several liquids under alternating magnetic fields were measured and the specific loss power was determined. Our results suggest that the dry mechanochemical process is a robust method to produce metallic nanoparticles and nanocomposites.

Magnetic, Structural, and Chemical Properties of Cobalt Nanoparticles Synthesized in Ionic Liquids

Cobalt nanoparticles (CoNPs) exhibit quite unique magnetic, catalytic, and optical properties. In this work, imidazolium-based ionic liquids (ILs) are successfully used to elaborate magnetically responsive suspensions of quite monodisperse CoNPs with diameters below 5 nm. The as-synthesized CoNPs adopt the noncompact and metastable structure of ϵ-Co that progressively evolves at room temperature toward the stable hexagonal close-packed allotrope of Co. Accordingly, magnetization curves are consistent with zero-valent Co. As expected in this size range, the CoNPs are superparamagnetic at room temperature. Their blocking temperature is found to depend on the size of the IL cation. The CoNPs produced in an IL with a large cation exhibit a very high anisotropy, attributed to an enhanced dipolar coupling of the NPs, even though a larger interparticle distance is observed in this IL. Finally, the presence of surface hydrides on the CoNPs is assessed and paves the way toward the synthesis for Co-based bimetallic NPs.

Magnetic Cobalt and Cobalt Oxide Nanoparticles in Hyperbranched Polyester Polyol Matrix

A series of cobalt (Co) and its oxides based nanoparticles were synthesized by using hyperbranched polyester polyol Boltorn H20 as a platform and sodium borohydride as a reducing agent. UV, FT-IR, XRD, NTA, and TEM methods were employed to obtain physicochemical characteristics of the products. The average diameter of Co nanoparticles was approximately 8.2±3.4 nm. Their magnetic properties, including hysteresis loop, field-cooled, and zero field-cooled curves were investigated. The nanoparticles exhibit superparamagnetism at room temperature, accompanied by magnetic hysteresis below the blocking temperature.

Environment friendly synthesis of polyvinylpyrrolidone nanofibers and their potential use as seed coats

Incorporation of urea and cobalt nanoparticles into electrospun biocompatible PVP seed coats leads to controlled release of ammonia.