Co₃O₄ Nanowires on Flexible Carbon Fabric as a Binder-Free Electrode for All Solid-State Symmetric Supercapacitor

Developing portable, lightweight, and flexible energy storage systems has become a necessity with the advent of wearable electronic devices in our modern society. This work focuses on the fabrication of Co₃O₄ nanowires on a flexible carbon fabric (CoNW/CF) substrate by a simple cost-effective hydrothermal route. The merits of the high surface area of the prepared Co₃O₄ nanostructures result in an exceptionally high specific capacitance of 3290 F/g at a scan rate of 5 mV/s, which is close to their theoretical specific capacitance. Furthermore, a solid-state symmetric supercapacitor (SSC) based on CoNW/CF (CoNW/CF//CoNW/CF) was fabricated successfully. The device attains high energy and power densities of 6.7 Wh/kg and 5000 W/kg. It also demonstrates excellent rate capability and retains 95.3% of its initial capacitance after 5000 cycles. Further, the SSC holds its excellent performance at severe bending conditions. When a series assembly of four such devices is charged, it can store sufficient energy to power a series combination of five light-emitting diodes. Thus, this SSC device based on a three-dimensional coaxial architecture opens up new strategies for the design of next-generation flexible supercapacitors

Neutralizing the Charge Imbalance Problem in Eu³⁺-Activated BaAl₂O₄ Nanophosphors: Theoretical Insights and Experimental Validation Considering K⁺ Codoping

In recent years, rare-earth-doped nanophosphors have attracted great attention in the field of luminescent materials for advanced solid-state lighting and high-resolution display applications. However, the low efficiency of concurrent red phosphors creates a major bottleneck for easy commercialization of these devices. In this work, intense red-light-emitting K⁺-codoped BaAl₂O₄:Eu³⁺ nanophosphors having an average crystallite size of 54 nm were synthesized via a modified sol–gel method. The derived nanophosphors exhibit strong red emission produced by the ⁵D₀ → ⁷F<i>_J</i> (<i>J</i> = 0, 1, 2, 3, 4) transitions of Eu³⁺ upon UV and low-voltage electron beam excitation. Comparative photoluminescence (PL) analysis is executed for Eu³⁺-activated and K⁺-coactivated BaAl₂O₄:Eu³⁺ nanophosphors, demonstrating remarkable enhancement in PL intensity as well as thermal stability due to K⁺ codoping. The origin of this PL enhancement is also analyzed from first-principles calculations using density functional theory. Achievement of charge compensation with the addition of a K⁺ coactivator plays an important role in increasing the radiative lifetime and color purity of the codoped nanophosphors. Obtained results substantially approve the promising prospects of this nanophosphor in the promptly growing field of solid-state lighting and field emission display devices