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Coordination polymers, a broad class of porous hybrid materials resulting from the connection of metal ions with organic ligands, showcase enduring porosity, well-organised crystalline structures, and open metal active sites that augment their metal ions' redox activity. This investigation focuses on examining a nanocomposite composed of cobalt carbide/reduced graphene oxide (Co3C/rGO) prepared through the copolymer method, serving as an electrode material for supercapacitor devices. The nanocomposite's structure and hollow cubic morphology were confirmed through X-ray diffraction, Raman spectroscopy, and field emission scanning electron microscopy (FESEM) analysis. Electrochemical properties were thoroughly assessed using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge in 6M KOH with a voltage window of 0 V to 0.5 V. The Co3C/rGO electrode exhibited notable electrochemical performance, displaying a specific capacitance of 486.6 F g-1 at 1 mV s-1 and a low internal resistance of 0.58 Ω, surpassing existing literature due to its porous morphology. Additionally, to evaluate the nanocomposite's cycling stability, 5000 charge/discharge cycles were conducted, revealing a capacitive retention of 82% of its original capacitance after 5000 cycles. This underscores its excellent long-term durability as a high-performance material for supercapacitor applications.

Background: The discharge of effluents from the textile and dyeing industries has been a worldwide concern. Although reduced graphene oxide/titanium dioxide (rGO/TiO2) nanocomposite is a potential candidate for wastewater treatment, the influence of graphene oxide (GO) content on its physico-chemical characteristics and its subsequent photocatalytic capabilities in degrading the organic contaminants has not been well established.Objective: The primary objective of this study was to assess the use of rGO/TiO2 nanocomposites with various GO contents for the removal of toxic methylene blue (MB) dye from aqueous solution.Method: In the present study, rGO/TiO2 nanocomposites were fabricated using various GO contents through a one-step solvothermal method. The effect of GO content on the nanocomposite formation was investigated by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The resulting nanocomposites were evaluated against MB degradation under artificial solar light illumination.Results: Based on the photocatalytic results, the highest removal percentage of MB was achieved by 0.15rGO/TiO2, which was about 1.7 times higher than that of 0.01rGO/TiO2.Conclusion: The enhanced removal efficiency of MB by the nanocomposite with the highest GO content (0.15 g) was attributed to the increased active adsorption sites, which greatly promoted the π- π interaction between the aromatic rings of MB dye and the graphitic skeleton of rGO, as well as the electrostatic interaction between the cationic center of MB molecules and the residual oxygen functionalities of rGO.

Achieving a high energy density and long-cycle stability in energy storage devices demands competent electrochemical performance, often contingent on the innovative structural design of materials under investigation. This study explores the potential of transition metal selenide (TMSe), known for its remarkable activity, electronic conductivity, and stability in energy storage and conversion applications. The innovation lies in constructing hollow structures of binary metal selenide (CoNi-Se) at the surface of reduced graphene oxide (rGO) arranged in a three-dimensional (3D) morphology (CoNi-Se/rGO). The 3D interconnected rGO architecture works as a microcurrent collector, while porous CoNi-Se sheets originate the active redox centers. Electrochemical analysis of CoNi-Se/rGO based-electrode reveals a distinct faradic behavior, thereby resulting in a specific capacitance of 2957 F g–1(1478.5 C g–1), surpassing the bare CoNi-Se with a value of 2149 F g–1(1074.5 C g–1) at a current density of 1 A g–1. Both materials exhibit exceptional high-rate capabilities, retaining 83% of capacitance at 10 A g–1compared to 1 A g–1. In a two-electrode coin cell system, the device achieves a high energy density of 73 Wh kg–1at a power density of 1500 W kg–1, stating an impressive 90.4% capacitance retention even after enduring 20,000 cycles. This study underscores the CoNi-Se/rGO composite’s promise as a superior electrode material for high-performance energy storage applications.

Background: Owing to their remarkable chemical, physical and biological properties, silver nanoparticles have been widely used in water purification, electronics, bio-sensing, clothing, food industry, paint and medical devices. Various approaches, such as using harsh reducing and stabilising agents for reverse micelle and thermal decomposition, were proposed for silver nanoparticle production. However, these methods are not eco-friendly. Thus, the aim of this paper is to synthesise silver nanoparticles through a cost-effective and environmentally friendly approach. Materials and Methods: A green approach was presented for the synthesis of silver nanoparticles. This approach involved the treatment of silver nitrate and hibiscus leaf extract, which acts as reducing and capping agent. The synthesis was performed at room temperature. The resulting silver nanoparticles were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and Fourier transform infrared (FTIR) spectroscopy. Results: Spherical, rod-like, hexagonal and triangular silver nanoparticles were obtained through the proposed synthesis method. The crystalline nature of each nanoparticle was revealed by XRD and selected area electron diffraction (SAED). The average spherical size of the silver nanoparticles produced in this route was 44.3 nm. The obtained FTIR band at 1622 cm-1 corresponded to the C=O stretch in the amine I group, which is commonly found in protein. Thus, the protein was believed to serve as capping agent that was responsible for the stabilisation of silver nanoparticles. Conclusion: In conclusion, silver nanoparticles had been successfully synthesised using hibiscus leaf extract and a plausible formation mechanism of silver nanoparticles was proposed.

Porous coordination polymers (PCPs) and metal-organic frameworks (MOFs) have emerged as promising materials for nanostructuring inorganic functional materials with applications in energy storage. In this study, our aim was to synthesize CoNi-carbide (CoNi-C)/reduced graphene oxide (rGO) hybrids by annealing CoNi-cyanide bridged coordination polymers (CoNi-CP) under a nitrogen atmosphere. The resulting CoNi-C/rGO hybrids exhibited exceptional electrochemical performance, surpassing the individual components (CoNi-C and rGO). The hybrids demonstrated a specific capacitance of 1177 F g−1and an electroactive surface area of 130.87 m2 g−1. By optimizing the CoNi-C/rGO ratio, we achieved the highest specific capacitance. Furthermore, we constructed a coin cell using CoNi-C/rGO-2 as the positive electrode and rGO as the negative electrode, which showed excellent performance with an energy density of 31.6 Wh kg−1at a power density of 750 W kg−1and capacitive retention of 84 % over 8000 charging cycles. Our findings provide valuable insights into designing and developing high-performance electrode materials for energy storage, with potential applications in various devices.

Silver nanoparticles were successfully synthesised at room temperature from silver nitrate using unripe Carica papaya fruit extract as a reducing and capping agent. PH of the reaction solution was adjusted with the addition of sodium hydroxide from pH 5.6 (original pH of the broth) to pH 6.5, pH 7.5 and pH 8.5. Quasi spherical silver nanoparticles were obtained across the studied pH range. The average particle size obtained decreased from 34 nm to 15 nm as the pH of the solution increased from 5.6 to 8.5. From the observations and ultra violet-visible spectrophotometer analysis, the rate of reduction and formation of silver nanoparticles increased as the pH increased. The crystalline nature of the as-synthesised silver nanoparticles in a cubic structure was confirmed by the peaks in X-ray diffraction and selected area electron diffraction. From Fourier transform infrared spectra, it was found that proteins in unripe papaya fruit extract were strongly bounded to the surface of silver nanoparticles as a capping agent. The thin layer of protein coating also further confirmed under high resolution transmission electron microscope. A plausible formation mechanism has been briefly proposed.