Synthesis, Characterization and In Vitro Cytotoxic Effects of Cu:Co3O4 Nanoparticles Via Microwave Combustion Method

An electrochemical sensing potential of cobalt oxide nanoparticles towards citric acid integrated with computational approach in food and biological media

Although citric acid (CA) has antioxidant, antibacterial, and acidulating properties, chronic ingestion of CA can cause urolithiasis, hypocalcemia, and duodenal cancer, emphasizing the need for early detection. There are very few documented electrochemical-based sensing methods for CA detection due to the challenging behavior of electrode fouling caused by reactive oxidation products. In this study, a novel, non-enzymatic, and economical electrochemical sensor based on cobalt oxide nanoparticles (CoOxNPs) is successfully reported for detection CA. The CoOxNPs were synthesized through a simple thermal decomposition method and characterized by SEM, FT-IR, EDX, and XRD techniques. The proposed sensing platform was optimized by various parameters, including pH (7.0), time (15 min), and concentration of nanoparticles (100 mM) etc. In a linear range of 0.05-2500 μM, a low detection limit (LOD) of 0.13 μM was achieved. Theoretical calculations (ΔRT), confirmed hydrogen bonding and electrostatic interactions between CoOxNPs and CA. The detection method exhibited high selectivity in real media like food and biological samples, with good recovery values when compared favorably to the HPLC method. To facilitate effective on-site investigation, such a sensing platform can be assembled into a portable device.

CuO nanoparticles: green combustion synthesis, applications to antioxidant, photocatalytic and sensor studies

The use of metal oxide nanoparticles for heterogeneous photodegradation is a prominent method for the removal of organic dyes from water resources. Compared to conventional approaches to treat polluted water, it is a more preferable method because of its environmental friendliness, low cost, and no requirement of extreme temperature and pressure. Among all the nanoparticles, CuO is a prominent material. Therefore, this study reports on the biogenic preparation of CuO nanoparticles by adopting a combustion method and Samanea saman pod extract as fuel. The synthesized nanoparticles were characterized through X-ray diffraction spectroscopy to confirm the crystallinity of CuO; the surface morphology of the material was studied using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) and the purity of the material was confirmed by energy dispersive X-ray spectroscopy. The degradation efficiency of CuO nanoparticles towards methylene blue dye, a model pollutant present in water resources, was assessed and found to be 97% after 90 minutes of light exposure. The synthesized CuO nanoparticles were also examined for antioxidant and electrochemical sensing studies using cyclic voltammetry. Results showed that CuO nanoparticles function as a strong antioxidant and are a very effective electrochemical sensor.

Regulated electrochemical performance of manganese oxide cathode for potassium-ion batteries: A combined experimental and first-principles density functional theory (DFT) investigation

Potassium-ion batteries (KIBs) are promising energy storage devices owing to their low cost, environmental-friendly, and excellent K⁺ diffusion properties as a consequence of the small Stoke's radius. The evaluation of cathode materials for KIBs, which are perhaps the most favorable substitutes to lithium-ion batteries, is of exceptional importance. Manganese dioxide (α-MnO₂) is distinguished by its tunnel structures and plenty of electroactive sites, which can host cations without causing fundamental structural breakdown. As a result of the satisfactory redox kinetics and diffusion pathways of K⁺ in the structure, α-MnO₂ nanorods cathode prepared through hydrothermal method, reversibly stores K⁺ at a fast rate with a high capacity and stability. It has a first discharge capacity of 142 mAh/g at C/20, excellent rate execution up to 5C, and a long cycling performance with a demonstration of moderate capacity retention up to 100 cycles. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) simulations confirm that the K⁺ intercalation/deintercalation occurs through 0.46 K movement between Mn^IV/Mn^III redox pairs. First-principles density functional theory (DFT) calculations predict a diffusion barrier of 0.31 eV for K⁺ through the 1D tunnel of α-MnO₂ electrode, which is low enough to promote faster electrochemical kinetics. The nanorod structure of α-MnO₂ facilitates electron conductive connection and provides a strong electrode-electrolyte interface for the cathode, resulting in a very consistent and prevalent execution cathode material for KIBs.

Solvent-free synthesis of NiCo2S4 having the metallic nature

Nickel-cobalt sulfide (NiCo2S4) is a prominent member of bimetallic transition metal sulfides. It is being widely used for a variety of applications such as electrode material, photocatalysis, and energy storage devices (like pseudo capacitors, supercapacitors, solar cells, and fuel cells) due to its better electronic conductivity, manageable morphology, and high capacitance. This work presents the one-step solventless synthesis of NiCo2S4 sheet-like nanostructures and then explores their metallic nature. Scanning electron microscopy (SEM) and transmission electron microscopic (TEM) analysis show the sheet-like grown morphology. Few nanorods are also seen. Except for a recent study (Xia et al. 2015) that shows metallic behavior, most of the reports show that NiCo2S4 is a semiconductor with claimed bandgap between 1.21 and 2.4 eV. In this study, we observe from UV-Vis and diffuse reflectance spectroscopy (DRS) that NiCo2S4 has a specific band gap value between 2.02 and 2.17 eV. However, IV characteristics in the temperature range of 300-400 K show that NiCo2S4 is a metal with a positive temperature coefficient of resistance consistent with a recent report. Furthermore, we see the ohmic conduction mechanism. The Arrhenius plot is drawn, and the activation energy is calculated to be 3.45 meV. The metallic nature is attributed to the coupling of two metal species (nickel and cobalt), which accounts for its superior conductivity and performance in a variety of essential applications.