Ionic-liquid-assisted one-pot synthesis of Cu2O nanoparticles/multi-walled carbon nanotube nanocomposite for high-performance asymmetric supercapacitors

β-Cyclodextrin-Stabilized CuO/MXene Nanocomposite as an Electrode Material for High-Performance Supercapacitors

Supercapacitors are the best energy storage systems due to their high power density, quick charge/discharge rate, and long-term reliability. In this study, β-cyclodextrin-stabilized CuO nanoparticles (CuO@βCD NPs) were synthesized through a simple reduction method and anchored on the surface of MXene nanosheets in three different proportions (1:1, 4:1, and 1:4) to obtain CuO@βCD/MXene nanocomposites through the wet-impregnation method. The formation of CuO@βCD NPs and their physicochemical characteristics were verified by XRD, XPS, FE-SEM, and HR-TEM analysis. The actual focus is on the evaluation of the electrochemical performances of CuO@βCD, MXene, and CuO@βCD/MXene nanocomposites for supercapacitor applications. The cyclic voltammetry and galvanostatic charge-discharge analysis revealed the pseudocapacitance and an improved specific capacitance of 1693.43 F g-1 at 0.90 A g-1 for the CuO@βCD/MXene (1:1) nanocomposite. The electrochemical impedance analysis displays superior electrical conductivity with a low charge transfer resistance value on incorporating CuO@βCD between the MXene layers. Furthermore, the CuO@βCD/MXene (1:1) nanocomposite exhibited improved long-term cycling stability by retaining 86% of its initial specific capacitance even after the 10,000th cycle at the current density of 4.54 A g-1. Based on the electrochemical performance, the CuO@βCD/MXene (1:1) nanocomposite proves its suitability as an electrode material for supercapacitor application with long-term cycling stability and rate capability.

A Conformable, Gas-Permeable, and Transparent Skin-Like Micromesh Architecture for Glucose Monitoring

Monitoring the concentration of useful biomarkers via electronic skins (e-skins) is highly important for the development of wearable health management systems. While some biosensor e-skins with high flexibility, sensitivity, and stability have been developed, little attention has been paid to their long-term comfortability and optical transparency. Here, a conformable, gas permeable, and transparent skin-like Cu₂ O@Ni micromesh structural glucose monitoring patch is reported. With its self-supporting micromesh structure, the skin-like glucose monitoring patch exhibits excellent shape conformability, high gas permeability, and high optical transmittance. The skin-like glucose biosensor achieves real-time monitoring of glucose concentrations with high sensitivity (15 420 µA cm^{- 2} mM^{- 1} ), low detection limit (50 nM), fast response time (＜2 s), high selectivity, and long-term stability. These desirable performance properties arise from the synergistic effects of the self-supporting micromesh configuration, high conductivity of the metallic Ni micromesh, and high electrocatalytic activities of the Cu₂ O toward glucose. This work presents a versatile and efficient strategy for constructing conformable, gas permeable, and transparent biosensor e-skins with excellent practicability towards wearable electronics.

Ultra-High Energy Density Hybrid Supercapacitors Using MnO2/Reduced Graphene Oxide Hybrid Nanoscrolls

Manganese oxide (MnO2) is a promising material for supercapacitor applications, with a theoretical ultra-high energy density of 308 Wh/kg. However, such ultra-high energy density has not been achieved experimentally in MnO2-based supercapacitors because of several practical issues, such as low electrical conductivity of MnO2, incomplete utilization of MnO2, and dissolution of MnO2. The present study investigates the potential of MnO2/reduced graphene oxide (rGO) hybrid nanoscroll (GMS) structures as electrode material for overcoming the difficulties and for developing ultra-high-energy storage systems. A hybrid supercapacitor, comprising MnO2/rGO nanoscrolls as anode material and activated carbon (AC) as a cathode, is fabricated. The GMS/AC hybrid supercapacitor exhibited enhanced energy density, superior rate performance, and promising Li storage capability that bridged the energy-density gap between conventional Li-ion batteries (LIBs) and supercapacitors. The fabricated GMS/AC hybrid supercapacitor demonstrates an ultra-high lithium discharge capacity of 2040 mAh/g. The GMS/AC cell delivered a maximum energy density of 105.3 Wh/kg and a corresponding power density of 308.1 W/kg. It also delivered an energy density of 42.77 Wh/kg at a power density as high as 30,800 W/kg. Our GMS/AC cell's energy density values are very high compared with those of other reported values of graphene-based hybrid structures. The GMS structures offer significant potential as an electrode material for energy-storage systems and can also enhance the performance of the other electrode materials for LIBs and hybrid supercapacitors.