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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.

Cobalt oxide nanoparticles (Co 3 O 4 -NPs) and cobalt sulfide nanoparticles (Co 9 S 8 -NPs) have shown extensive potential in electrochemical sensing, catalysis, specific drug targeting, and resonance imaging. However, Co 9 S 8 -NPs have been rarely explored for biomedical applications as compared to their oxide counterparts. Thus, in the current study, biocompatible PEGylated Co 9 S 8 -NPs and Co 3 O 4 -NPs are explored and compared for biological and photocatalytic properties. PEGylation of both the NPs is achieved using a simple chemical co-precipitation method followed by characterization using UV visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and pH-responsive dispersion study. After thorough characterization, the NPs are evaluated and compared for various biological applications including antibacterial, antifungal, antileishmanial, antioxidant, and biocompatibility as well as photo-catalytic dye degradation studies. Both the NPs have shown excellent biological applications; however, Co 9 S 8 -NPs exhibit comparatively better antibacterial, antifungal, and antioxidant properties except antileishmanial potential where Co 3 O 4 -NPs show slight superiority. Furthermore, Co 3 O 4 -NPs indicate a higher degradation potential of methylene blue (MB) up to 46.93%. In comparison, Co 9 S 8 -NPs have a degradation ability of up to 42%, at 20 mg/ml within 3 h, which indicates considerable remediation potential of the NPs. Interestingly, both the NPs exhibit non-hemolytic behavior, thus demonstrating a compatible and bio-safe nature of both the NPs. Graphical Abstract

BackgroundColorectal cancer (CRC) ranks as the third most common cancer globally and the second leading cause of cancer-related mortality. Traditional chemotherapy, while effective, often results in significant side effects, highlighting the need for more efficient cancer therapies. Recent advancements in nanotechnology have led to the development of strategies that aim to minimize toxicity to normal cells by more precise targeting of cancer cells. In this context, cobalt oxide nanoparticles (Co3O4 NPs) have shown promising anticancer potential. Our study focuses on evaluating the antioxidant, antibacterial, and anticancer properties of Co3O4 NPs synthesized using Vibrio sp. VLC, a bioluminescent bacterium.ResultsXRD and FTIR analyses confirmed the successful synthesis of Co3O4 NPs, which displayed spherical morphology with an average diameter of 60 nm. The nanoparticles demonstrated significant antioxidant and antibacterial activities. The MTT assay indicated that the NPs caused dose- and time-dependent toxicity against CT26 cells, while exhibiting relatively lower toxicity towards normal cells. In vivo experiments further confirmed the significant tumor suppressive effects in BALB/c mice, with minimal side effects on the liver, spleen, and kidney tissues compared to the widespread toxicity of cisplatin.ConclusionThis study verifies the successful synthesis of Co3O4 NPs and their potent antioxidant, antibacterial, and anticancer activities. The biosynthesized Co3O4 NPs represent a promising targeted method for CRC therapy. However, further research is needed to elucidate their mechanism of action and also their application in the clinical phase.

Cobalt oxide (Co3O4) nanoparticles supported on olive stone biochar (OSBC) was used as an efficient sorbent for rifampicin (RIFM) and tigecycline (TIGC) from wastewater. Thermal stabilities, morphologies, textures, and surface functionalities of two adsorbents; OSBC and Co-OSBC were compared. BET analysis indicated that Co-OSBC possesses a larger surface area (39.85 m2/g) and higher pore-volume compared to the pristine OSBC. FT-IR analysis showed the presence of critical functional groups on the surface of both adsorbents. SEM and EDX analyses showed the presence of both meso- and macropores and confirmed the presence of Co3O4 nanoparticles on the adsorbent surface. Batch adsorption studies were controlled using a two-level full-factorial design (2k-FFD). Adsorption efficiency of Co-OSBC was evaluated in terms of the % removal (%R) and the sorption capacity (qe, mg/g) as a function of four variables: pH, adsorbent dose (AD), drug concentration, and contact time (CT). A %R of 95.18% and 75.48% could be achieved for RIFM and TIGC, respectively. Equilibrium studies revealed that Langmuir model perfectly fit the adsorption of RIFM compared to Freundlich model for TIGC. Maximum adsorption capacity (qmax) for RIFM and TIGC was 61.10 and 25.94 mg/g, respectively. Adsorption kinetics of both drugs could be best represented using the pseudo-second order (PSO) model.

Cobalt (Co) is an essential trace element for humans and other animals, but high doses can be harmful to human health. It is present in some foods such as green vegetables, various spices, meat, milk products, seafood, and eggs, and in drinking water. Co is necessary for the metabolism of human beings and animals due to its key role in the formation of vitamin B12, also known as cobalamin, the biological reservoir of Co. In high concentrations, Co may cause some health issues such as vomiting, nausea, diarrhea, bleeding, low blood pressure, heart diseases, thyroid damage, hair loss, bone defects, and the inhibition of some enzyme activities. Conversely, Co deficiency can lead to anorexia, chronic swelling, and detrimental anemia. Co nanoparticles have different and various biomedical applications thanks to their antioxidant, antimicrobial, anticancer, and antidiabetic properties. In addition, Co and cobalt oxide nanoparticles can be used in lithium-ion batteries, as a catalyst, a carrier for targeted drug delivery, a gas sensor, an electronic thin film, and in energy storage. Accumulation of Co in agriculture and humans, due to natural and anthropogenic factors, represents a global problem affecting water quality and human and animal health. Besides the common chelating agents used for Co intoxication, phytoremediation is an interesting environmental technology for cleaning up soil contaminated with Co. The occurrence of Co in the environment is discussed and its involvement in biological processes is underlined. Toxicological aspects related to Co are also examined in this review.

Background Detoxification of heavy metal pollutants in wastewater has become a serious problem to surrounding environment. This research was conducted to utilize a potential heavy metal-resistant bacterium for the remediation of cobalt metal and simultaneous synthesis of cobalt oxide nanoparticles in the form of powder for various industrial applications. Metal oxide nanoparticles have great applications in electrochemical devices such as supercapacitors, biosensors, and batteries. Method A heavy metal-resistant bacterium Microbacterium sp. MRS-1 isolated from electroplating industrial effluent reduced cobalt ions from an initial concentration of 200 mg/L to 26 mg/L were analyzed by atomic absorption spectroscopy. Instrumental analysis of bacterially synthesized Co 3 O 4 has been characterized. Cytotoxicity of synthesized nanoparticles was assessed by MTT assay. Results Microbacterium sp. MRS-1 isolated from electroplating industrial effluent was found to be suitable for cobalt oxide nanoparticles as it showed tolerance towards high concentration of metal. The nutrient broth containing metal solution and Microbacterium sp. MRS-1 showed color change from light pink to dark pink indicated the formation of extracellular nanoparticles. It also converted soluble cobalt salts into less soluble cobalt oxide nanoparticles outside the cell which allows easy recovery of nanoparticles without the destruction of cells and simultaneous detoxification of toxic metal ions. Electron microscopic imaging verified that nanoparticles were predominantly surrounding the bacterial cells and SEM imaging revealed that the produced particles were in the range of 10–100 nm in size. XRD spectrum exhibited 2 θ values were corresponding to cubic face-centered cobalt oxide (Co 3 O 4 ) nanoparticles. Conclusion The present study investigated new prospective for eco-friendly detoxification of toxic heavy metal Co from metal-polluted sites and the production of cobalt oxide nanoparticles in powder form for clinical and other industrial applications.

HighlightsA multicomponent Co@CNTs|Ru catalyst has been rationally designed, in which Co nanoparticles are in-situ confined inside CNTs while trace Ru loading is uniformly deposited on their exterior walls.Co and Ru nanoparticles spatially confined by the inner and outer surface of CNTs, respectively, would induce charge redistribution and a synergistic electron coupling.Co@CNTs|Ru catalyst exhibits an unprecedented hydrogen evolution reaction (HER) activity in all pH-range, representing a new record among all the previously reported HER catalysts.Exploring highly active but inexpensive electrocatalysts for the hydrogen evolution reaction (HER) is of critical importance for hydrogen production from electrochemical water splitting. Herein, we report a multicomponent catalyst with exceptional activity and durability for HER, in which cobalt nanoparticles were in-situ confined inside bamboo-like carbon nanotubes (CNTs) while ultralow ruthenium loading (~ 2.6 µg per electrode area ~ cm−2) is uniformly deposited on their exterior walls (Co@CNTsǀRu). The atomic-scale structural investigations and theoretical calculations indicate that the confined inner Co and loaded outer Ru would induce charge redistribution and a synergistic electron coupling, not only optimizing the adsorption energy of H intermediates (ΔGH*) but also facilitating the electron/mass transfer. The as-developed Co@CNTsǀRu composite catalyst requires overpotentials of only 10, 32, and 63 mV to afford a current density of 10 mA cm−2 in alkaline, acidic and neutral media, respectively, representing top-level catalytic activity among all reported HER catalysts. The current work may open a new insight into the rational design of carbon-supported metal catalysts for practical applications.

Eco-friendly synthesis of Cobalt oxide nanoparticles (Co 3 O 4 NPs) was assessed by the aqueous extract of red algae and their utilization as cytotoxicity, antioxidant, anticoagulant, antibacterial, and anti-cancer properties. UV–vis, SEM, TEM, FTIR, EDAX, XRD, and TGA are tools used for characterization purposes. The size of the Co 3 O 4 NPs crystal of 28.2 ± 7.8 nm was measured based on the X-ray diffraction analysis. Biosynthesized Co 3 O 4 NPs showed uniform spherical morphology with an average diameter of 29.8 ± 8.6 nm according to TEM and SEM images. Furthermore, Co 3 O 4 NPs biological properties such as determination of the antibacterial properties of Co 3 O 4 NPs by the zone of inhibition method and the minimum inhibitory concentration (MIC) were determined using a dilution broth agar test. Co 3 O 4 NPs indicated higher antibacterial than oxytetracycline standard antibiotics. On the other hand, a scavenging free radical DPPH study was done to determine the propensity for antioxidants that showed a similar capacity for antioxidants in Co 3 O 4 NPs. The biosynthesized Co 3 O 4 NPs are effective erythrocyte viability dose-dependently and indicated this method was nontoxic. Moreover, bioinspired Co 3 O 4 NPs has promising results against HepG2 cancer cells (IC50: 41.4 μg/ml). Most notably, biogenic Co 3 O 4 NPs have anticoagulant and thrombolytic activities by the addition of nanoparticles to human blood samples under practical conditions. According to these context findings, Co 3 O 4 NPs would be used as a medicinal aid along with its anti-cytotoxic, antioxidant, and effects on bacteria, and cancer.

Samples of well-controlled nanoparticles consisting of alloys of cobalt and nickel of different atomic ratios were synthesized using wet chemical methods with oleylamine as the solvent and the reducing agent. These materials were characterized by a variety of techniques, including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Small amounts of heterogenized catalysts were prepared using alumina as the support. However, the potential for use of Co–Ni catalysts in CO hydrogenation was explored using a larger amount of Co–Ni/alumina catalyst prepared from standard aqueous impregnation methods and tested in a continuously stirred tank reactor (CSTR) for Fischer–Tropsch synthesis (FTS). Results are compared to a reference catalyst containing only cobalt. The heterogenized catalysts were characterized using synchrotron methods, including temperature programmed reduction with extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge spectroscopy (TPR-EXAFS/XANES). The characterization results support intimate contact between Co and Ni, strongly suggesting alloy formation. In FTS testing, drawbacks of Ni addition included decreased CO conversion on a per gram catalyst basis, although Ni did not significantly impact the turnover number of cobalt, and produced slightly higher light gas selectivity. Benefits of Ni addition included an inverted induction period relative to undoped Co/Al2O3, where CO conversion increased with time on-stream in the initial period, and the stabilization of cobalt nanoparticles at a lower weight % of Co.

Nanomedical applications have increased significantly. This work aimed to fabricate and characterize cobalt oxide nanoparticles (CoOnps) synthesized biologically via aqueous Alhagi maurorum extract and evaluate their cytotoxic and antimicrobial impacts. Green-synthesized CoOnps were prepared and analyzed using UV–Vis spectrophotometer UV–vis, Scanning electron microscopy (SEM), Transmission electron microscopy TEM, Energy dispersive X-ray analysis EDAX, Fourier transform infrared, FTIR, and X-ray diffraction (XRD). In vitro traits of green-synthesized CoOnps were studied on ovarian cancer cells (SKOV3) using a Sulforhodamine B (SRB) method. The cytotoxic effect and IC50 were estimated. Moreover, concentrations of 10, 30, 40, 70, 100, 200, 300, 400 and 500 μg/mL CoOnps were applied to investigate their antimicrobial effect against Listeria , Staphylococcus aureus and Streptococcus as gram +ve pathogenic bacteria, Bifidobacterium bifidum 2203, Bifidobacterium bifidum LMG 10,645, Bifidobacterium breve LMC 017, Bifidobacterium angulatum 2238 and Bifidobacterium longum ATCC 15,707 as probiotics , E. coli as gram −ve bacterial model and yeast strain Candida albicans . CoOnps showed anti-ovarian cancer effects at 24.02 μg/mL. Furthermore, it exerted antimicrobial activity versus Listeria , Streptococcus, S. aureus, and E. coli were 31.66 ± 0.88, 24.33 ± 2.08, 25.66 ± 0.33, and 33.00 ± 6.08; however, they did not suppress the growth of Candida albicans and all tested Bifidobacterial strains up to concentrations of 500 μg/mL with significant difference compared to all concentrations p < 0.05. Green synthesis of CoOnps is a low-cost, eco-friendly and easily prepared method. Its impressive features as cytotoxic SKOV3, a cell line ovarian cancer and antibacterial effect for some gram +ve and −ve bacteria, besides maintaining probiotics, could candidate them as competitive agents for medical, pharmacological, agricultural and food applications.