Co3O4 spinel nanoparticles decorated graphite electrode: Bio-mediated synthesis and electrochemical H2O2 sensing

Co3O4/fluoro-copolymer nanocomposite modified boron-doped diamond electrode non-enzymatic sensor for the determination of skeletal muscle relaxant drug cyclobenzaprine in biological fluids

Electrochemical sensors have revolutionized pharmaceutical analysis by providing enhanced speed, selectivity, and cost-effectiveness. This study presents the development of a highly sensitive, non-enzymatic electrochemical sensor for Cyclobenzaprine (CBZ) determination. The sensor features a boron-doped diamond electrode (BDDE) modified with a novel Cobalt Oxide/Nafion-based nanocomposite (Co₃O₄/Nafion), synthesized and optimized for superior performance. The electroactive surface was fabricated by drop-casting a Co₃O₄/Nafion suspension onto the BDDE. Characterization techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR), confirmed the crystallinity, morphology, and functional groups of the nanocomposite. Electrochemical analyses, comprising electrochemical impedance spectroscopy (EIS), square wave voltammetry (SWV), and cyclic voltammetry (CV), demonstrated enhanced charge transfer properties and a one-electron/proton oxidation mechanism for Cyclobenzaprine (CBZ) detection. The sensor demonstrated optimal performance in BR buffer at pH 5.6, with a linear response to CBZ concentrations ranging from 2.49 μg/L to 19.61 μg/L, achieving a LOD of 2.08 μg/L and LOQ of 6.96 μg/L. Practical applicability was established by successfully quantifying CBZ in various biological matrices, including human blood serum (37.8 %), artificial blood serum (35.6 %), artificial sweat (-28.9 %), and urine (-8.9 %), with excellent recovery rates in pharmaceutical formulations (99.75 %) and human blood serum (100.16 %). The sensor exhibited high specificity, unaffected by common interferents such as ions, carbohydrates, and heavy metals. This work introduces, for the first time, a Co₃O₄/Nafion-modified BDDE sensor for CBZ determination, offering rapid, selective, and interference-free analysis with potential applications in therapeutic drug monitoring and pharmaceutical quality control.

Recent advances in electrochemical approaches for detection of nitrite in food samples

Nitrite is a common ingredient in the industry and agriculture; it is everywhere, like water, food, and surroundings. Recently, several approaches have been developed to measure the nitrite levels. So, this review was presented as a summary of many approaches utilized to detect the nitrite. Furthermore, the types of information that may be acquired using these methodologies, including optic and electrical signals, were discussed. In electrical signal methods, electrochemical sensors are usually developed using different materials, including carbon, polymers, oxides, and hydroxides. At the same time, optic signals receiving techniques involve utilizing fluorescence chromatography, absorption, and spectrometry instruments. Furthermore, these methodologies' benefits, drawbacks, and restrictions are examined. Lastly, due to the efficiency and fast means of electrochemical detectors, it was suggested that they can be used for detecting nitrite in food safety. Futuristic advancements in the techniques used for nitrite determination are subsequently outlined.

From green chemistry to biomedicine: the sustainable symphony of cobalt oxide nanoparticles

Deciphering the importance of nanostructures in advanced technologies for a broad application spectrum has far-reaching implications for humans and the environment. Cost-effective, abundant cobalt oxide nanoparticles (NPs) are among the most attractive and extensively utilized materials in biomedical sciences due to their high chemical stability, and biocompatibility. However, the methods used to develop the NPs are hazardous for human health and the environment. This article precisely examines diverse green synthesis methods employing plant extracts and microbial sources, shedding light on their mechanism, and eco-friendly attributes with more emphasis on biocompatible properties accompanied by their challenges and avenues for further research. An in-depth analysis of the synthesized cobalt oxide NPs by various characterization techniques reveals their multifaceted functionalities including cytotoxicity, larvicidal, antileishmanial, hemolytic, anticoagulating, thrombolytic, anticancer and drug sensing abilities. This revelatory and visionary article helps researchers to contribute to advancing sustainable practices in nanomaterial synthesis and illustrates the potential of biogenically derived cobalt oxide NPs in fostering green and efficient technologies for biomedical applications.

A triple read-out visible biosensing platform based on multifunctional nanozyme and bipolar electrode for multi-mode detection and imaging of CEA

In this paper, a proposal of closed bipolar electrode (BPE) and nanozyme based multi-mode biosensing platform is first presented. As a novel integrated chip, multi-mode-BPE (MMBPE) combines enzyme-linked immunoassay (ELISA), electrochemiluminescence (ECL), ECL imaging and light emitting diode (LED) imaging, enabling highly sensitive triple read-out visible detection of cancer embryonic antigen (CEA). The ECL probe Ab2@Au@Co3O4/CoFe2O4 hollow nanocubes (HNCs) with excellent peroxidase (POD) activity is introduced into the BPE cathode through immune adsorption. The Au@Co3O4/CoFe2O4 HNCs can increase the rate of hydrogen peroxide oxidation of TMB, thus promoting the reaction, and can be used for ELISA detection of CEA at different concentrations. The modification of the BPE sensing interface and reporting interface involved the introduction of the luminescent reagent Ru(bpy)32+ to the BPE anode. The decomposition rate of H2O2 increased under the catalytic action of Au@Co3O4/CoFe2O4 HNCs nanozyme, leading to an accelerated electron transfer rate in the MMBPE system and an enhanced ECL signal from Ru(bpy)32+. The LED imaging technology further provides a convenient and visible approach for CEA imaging in which no additional chemicals are needed. The integration of nanoenzymes as the catalytic core in MMBPE system provides impetus, while the combination of nanozymes with BPE expands the application of nanoenzymes in the field of biological analysis. The integration of intelligent chips with multiple modes of detection shows portable, miniaturized, and integrated excellent properties which meets the requirements of modern detection devices and thus offers a flexible approach for determination of nucleic acids, proteins, and cells.

PO6 geometric configuration unit enhanced electrocatalytic performance of Co3O4 in acidic oxygen evolution

It is challenging to develop high-efficient and stable nonprecious metal-based electrocatalyst for oxygen evolution reaction (OER) in acid for proton exchange membrane (PEM) water splitting. Herein, P atoms were introduced into the lattice of spinel Co₃O₄ (P-Co₃O₄) to replace with octahedral coordinated Co³⁺ via a hydrothermal process following a thermal treatment. The formation of PO₆ geometric configuration unit in Co₃O₄ can trigger electron rearrangement around Co ions, which resulted in the high-active Co²⁺ site on the surface, significantly decreasing the energy barrier of rate-determining step for OER. Moreover, the weaker covalency of the Co 3d-O 2p bond and higher formation energy of oxygen vacancy around Co²⁺ in P-Co₃O₄ inhibited the participation of lattice oxygen during OER process, enabling that P-Co₃O₄ can work stably in acidic media. The obtained P-Co₃O₄ afforded satisfying stability over 30 h in a PEM electrolysis device with an overpotential of 400 mV@10 mA/cm² in 0.1 M HClO₄.

Co3O4/CoFe2O4 Hollow Nanocube Multifunctional Nanozyme with Oxygen Vacancies for Deep-Learning-Assisted Smartphone Biosensing and Organic Pollutant Degradation

Although the application of nanozymes has been widely studied, it is still a huge challenge to develop highly active and multifunctional nanozyme catalysts with a wider application prospect. Co₃O₄/CoFe₂O₄ hollow nanocubes (HNCs) with oxygen vacancies were proposed in this study, which had a porous oxide heterostructure with CoFe₂O₄ as the core and Co₃O₄ as the shell. The Co₃O₄/CoFe₂O₄ HNCs had three enzyme activities: peroxidase-like, oxidase-like, and catalase-like. Combining XPS depth profiling with density functional theory (DFT), the catalytic mechanism of peroxidase-like activity was explored in depth, which was mainly originated from ·OH produced by the synergistic effect between the outer oxygen and inner oxygen and electron transfer between Co and Fe. A colorimetry/smartphone dual sensing platform was designed based on the peroxidase-like activity. Especially, a multifunctional intelligent sensing platform based on deep learning-YOLO v3 algorithm-assisted smartphone was constructed to realize real-time and rapid in situ detection of l-cysteine, norfloxacin, and zearalenone. Surprisingly, the detection limit of norfloxacin was low at 0.015 μM, which was better than that of the newly published detection method in the field of nanozymes. Meanwhile, the detection mechanism of l-cysteine and norfloxacin was successfully investigated by in situ FTIR. In fact, it also showed outstanding applications in detecting l-cysteine in the food environment and norfloxacin in drugs. Furthermore, Co₃O₄/CoFe₂O₄ HNCs also could degrade 99.24% of rhodamine B, along with good reusability even after 10-cycle runs. Therefore, this work provided an in-depth understanding of the synergistic effect between the outer and inner oxygen in the reaction mechanism and an efficient method for establishing a deep-learning-assisted intelligent detection platform. In addition, this research also offered a good guideline for the further development and construction of nanozyme catalysts with multienzyme activities and multifunctional applications.

The most popular and effective synthesis processes for Co3O4 nanoparticles and their benefit in preventing corrosion

Cobalt oxide nanostructures are gaining popularity in the scientific community because they are reasonably priced, easy to develop, and have unique properties that make them valuable for coating, corrosion inhibitors, supercapacitors, photocatalysis, and other applications. In this review, the most well-known and effective synthetic methods are mentioned along with their particle size. A description of the main experimental methods used to describe the nanoparticles is also provided. In addition, the green production of cobalt oxide nanoparticles using plant extract is summarized. In particular with regard, we mentioned the use of cobalt oxide nanoparticles in the construction of nanocomposites coatings and future prospective approaches.

Biosynthesis and Characterization of Co3O4NPs Utilizing Prickly Pear Fruit Extract and its Biological Activities

In the current research, there is a low level of research and information about the interaction of cobalt oxide nanoparticles (Co3O4NPs) in biological systems. This research creates a very simple and cost-effective preparation of cobalt oxide nanoparticles by using prickly pear fruit extract as a reducing agent, which may be further used for biological applications like antimicrobial, antioxidant, DNA interaction and in-vitro anticancer activity. The use of prickly pear fruit extract acts as a good reducing agent and is responsible for easy preparation and reducing the toxicity of cobalt oxide nanoparticles. The fabricated biogenic nanoparticles were confirmed by microscopic and spectroscopic analytical techniques like Ultra Violet-Visible spectrometer, Fourier transforms infrared spectrometer (FTIR), X-ray Diffraction Method (XRD), Energy-dispersive X-ray spectroscopy (EDS), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The average size of the synthesized nanoparticles is 36.24 nm. In the MTT assay, the prepared cobalt oxide NPs haspotential mechanisms of cytotoxicity and in-vitro anticancer activity in Hepatocellular carcinoma cancer cells (HepG2). The microbial activities like antibacterial and antifungal studies of the biosynthesized nanoparticles were performed by the Disc method. The Co3O4NPs with DNA interaction were examined by UV-Visible and fluorescence spectroscopic methods. The binding constant value of biogenic Co3O4NPs with CT-DNA was observed by UV-Visible spectroscopy with a result of 2.57x105mol-1. The binding parameters and quenching constants were observed by fluorescence spectroscopic methods having values of Ksv=7.1x103, kq=7.1x108, Ka=3.47.1x105, n=0.9119. From the findings, Co3O4NPs may be utilized as a medicinal aid for their antibacterial, antifungal, antioxidant, DNA binding and in-vitro anticancer activities.

Co3O4 Nanoparticles Uniformly Dispersed in Rational Porous Carbon Nano-Boxes for Significantly Enhanced Electrocatalytic Detection of H2O2 Released from Living Cells

A facile and ingenious method to chemical etching-coordinating a metal-organic framework (MOF) followed by an annealing treatment was proposed to prepare Co₃O₄ nanoparticles uniformly dispersed in rational porous carbon nano-boxes (Co₃O₄@CNBs), which was further used to detect H₂O₂ released from living cells. The Co₃O₄@CNBs H₂O₂ sensor delivers much higher sensitivity than non-etching/coordinating Co₃O₄, offering a limit of detection of 2.32 nM. The wide working range covers 10 nM-359 μM H₂O₂, while possessing good selectivity and excellent reproducibility. Moreover, this biosensor was used to successfully real-time detect H₂O₂ released from living cells, including both healthy and tumor cells. The excellent performance holds great promise for Co₃O₄@CNBs’s applications in electrochemical biomimetic sensing, particularly real-time monitor H₂O₂ released from living cells.

Green Synthesis of Iron-Doped Cobalt Oxide Nanoparticles from Palm Kernel Oil via Co-Precipitation and Structural Characterization

In this study, a bio-derived precipitating agent/ligand, palm kernel oil, has been used as an alternative route for the green synthesis of nanoparticles of Fe-doped Co3O4 via the co-precipitation reaction. The palm oil was extracted from dried palm kernel seeds by crushing, squeezing and filtration. The reaction of the palm kernel oil with potassium hydroxide, under reflux, yielded a solution containing a mixture of potassium carboxylate and excess hydroxide ions, irrespective of the length of saponification. The as-obtained solution reacts with an aqueous solution containing iron and cobalt ions to yield the desired metallo-organic precursor, iron cobalt carboxylate. Characterization of the precursors by IR and gas chromatography (GC) attests to the presence of carboxylate fatty acids in good agreement with the proportion contained in the oil, and ICP confirms that the metallic ratios are in the proportion used during the synthesis. Analysis of the products thermally decomposed between 400 °C and 600 °C by XRD, EDX, TEM and ToF-SIMS, established that cobalt iron oxide nanoparticles (Co(1-x)Fex)3O4 were obtained for x ≤ 0.2 and a nanocomposite material (Co(1-x)Fex)3O4/Fe3O4 for x ≥ 0.2, with sizes between 22 and 9 nm. ToF-SIMS and XRD provided direct evidence of the progressive substitution of cobalt by iron in the Co3O4 crystal structure for x ≤ 0.2.

Detection of enrofloxacin by flow injection chemiluminescence immunoassay based on cobalt hydroxide nanozyme

The emergence and development of low-cost and high-efficiency nanozymes are promising to replace natural enzymes promoting the application of chemiluminescence immunoassays. Herein, a rapid and highly sensitive flow injection chemiluminescence immunoassay based on cobalt hydroxide (Co(OH)₂) nanozyme was established to detect enrofloxacin (ENR) residues in food. In this system, Co(OH)₂ nanosheets act as nanozymes to catalyze and amplify the chemiluminescence signal of the luminol-PIP-H₂O₂ system, as well as a carrier for immobilizing antibodies to form stable immunoprobes. In addition, carboxyl resin beads with good stability and biocompatibility were used as the base of the immunosensor to carry more coating antigens, based on the principle of competitive immunity and to achieve the rapid detection of ENR. Under optimal conditions, the linear working range is 0.0001 ~ 1000 ng/mL, and the limit of detection (LOD) is 0.041 pg/mL (S/N = 3). The method has been successfully applied to the analysis of aquatic products and poultry food. A non-enzyme immunosensor using Co(OH)₂ nanosheets as antibody-conjugated carriers and peroxidase mimics for catalytic amplification of the chemiluminescence signal of luminol and using carboxyl resin beads as platform was designed to detect ENR residues in food.

Bio-inspired PtNPs/Graphene nanocomposite based electrocatalytic sensing of metabolites of dipyrone

Noble metal nanoparticles are known to electrocatalyze various redox reactions by improving the electron transfer kinetics. In the present study, we have introduced a facile bioinspired synthesis of PtNPs and their integration for the formation of PtNPs/graphene nanocomposite using Psidium guajava (guava) leaves extract. Graphene used in nanocomposite formulation was synthesized by exfoliation of graphite in water/acetone (25:75 v/v) mixture followed by mechanical shearing using ultrasonication and microwave irradiation. PtNPs/graphene nanocomposite was drop-cast onto a glassy carbon electrode (GCE, 3 mm dia). The electrocatalytic activity of PtNPs/graphene nanocomposite was tested in a three-electrode system for sensing of metabolic products of dipyrone (DIP) formed through 1 e^- and 2 e^- transfer reactions. The modified electrode exhibited almost 50% reduction in electrode resistance. The limit of detection was found to be 0.142 μM with sensitivities of 0.820 and 0.445 μA․μM^-1cm^-2 for DIP concentration below and above 100 μM, respectively, using square wave voltammetry. The signal of sensing of metabolites of DIP was almost invariant in the presence of glucose, dopamine, uric acid, and ciprofloxacin; however, the response current was decayed by 20% within the 10th cycle. The sensing of DIP spiked in treated sewage-water and running tap-water samples was ∼100% recoverable and comparable with HPLC.

Green fabrication of Co and Co3O4 nanoparticles and their biomedical applications: A review

Nanotechnology is the fabrication, characterization, and potential application of various materials at the nanoscale. Over the past few decades, nanomaterials have attracted researchers from different fields because of their high surface-to-volume ratio and other unique and remarkable properties. Cobalt and cobalt oxide nanoparticles (NPs) have various biomedical applications because of their distinctive antioxidant, antimicrobial, antifungal, anticancer, larvicidal, antileishmanial, anticholinergic, wound healing, and antidiabetic properties. In addition to biomedical applications, cobalt and cobalt oxide NPs have been widely used in lithium-ion batteries, pigments and dyes, electronic thin film, capacitors, gas sensors, heterogeneous catalysis, and for environmental remediation purposes. Different chemical and physical approaches have been used to synthesize cobalt and cobalt oxide NPs; however, these methods could be associated with eco-toxicity, cost-effectiveness, high energy, and time consumption. Recently, an eco-friendly, safe, easy, and simple method has been developed by researchers, which uses biotic resources such as plant extract, microorganisms, algae, and other biomolecules such as starch and gelatin. Such biogenic cobalt and cobalt oxide NPs offer more advantages over other physicochemically synthesized methods. In this review, we have summarized the recent literature for the understanding of green synthesis of cobalt and cobalt oxide NPs, their characterization, and various biomedical applications.

Three-dimensional composite of Co3O4 nanoparticles and nitrogen-doped reduced graphene oxide for lignin model compound oxidation

3D composite of Co₃O₄ nanoparticles and N-doped reduced graphene oxide can effectively catalyze the oxidation of lignin model compounds.