Edge enriched cobalt ferrite nanorods for symmetric/asymmetric supercapacitive charge storage

CoFe2O4 Hollow Spheres-Decorated Three-Dimensional rGO Sponge for Highly Efficient Electrochemical Charge Storage Devices

The energy demand, the crisis of fossil fuels, and the increasing popularity of portable and wearable electronics in the global market have triggered the demand to develop high-performance flexible all-solid-state supercapacitors that are capable of delivering high energy at high power density as well as being safely entrenched in those electronics. Herein, we have designed a nanocomposite, 80CF_hs-20rGO_sp, which exhibits a high specific capacitance (C _S) value of 1032 F g^-1 at 3 A g^-1. Utilizing this nanocomposite as the cathode and reduced graphene oxide sponge (rGO_sp) as the anode, a flexible all-solid-state asymmetric device has been fabricated. In this device, poly(vinyl alcohol) (PVA) gel embedded with a mixture of 3 M KOH and 0.1 M K₄[Fe(CN)₆] was used as an electrolyte cum separator. The fabricated device showed the capability to deliver an energy density of 65.8 W h kg^-1 at a power density of 1500 W kg^-1 and retained its capability even after various physical deformations. The device also exhibited a long cycle life and retained ∼96% of its C _S value after 5000 cycles. Moreover, the fabricated flexible all-solid-state device successfully illuminated light-emitting diodes, which proved its potential use in real-life supercapacitor applications. The obtained results revealed the excellent electrochemical performances of the fabricated device and rendered it a promising candidate in the energy sector.

Novel Polyimide/Copper-Nickel Ferrite Composites with Tunable Magnetic and Dielectric Properties

Heat-resistant magnetic polymer composites were prepared by incorporating cerium-doped copper-nickel ferrite particles, having the general formula Ni_1-xCu_xFe_1.92Ce_0.08O₄ (x: 0.0, 0.3, 0.6, 1.0), into a polyimide matrix. The effects of particle type and concentration on the thermal, magnetic, and electrical properties of the resulting composites were investigated. The samples were characterized by FTIR, scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis, differential scanning calorimetry, vibrating sample magnetometer, and broadband dielectric spectroscopy. The composites exhibited high thermal stability, having initial decomposition temperatures between 495 and 509 °C. Saturation magnetization (M_s), magnetic remanence (M_r), and coercivity (H_c) were found in range of 2.37–10.90 emu g⁻¹, 0.45–2.84 emu g⁻¹, and 32–244 Oe, respectively. The study of dielectric properties revealed dielectric constant values of 3.0–4.3 and low dielectric losses of 0.016–0.197 at room temperature and a frequency of 1 Hz.

Shape Anisotropic Iron Oxide-Based Magnetic Nanoparticles: Synthesis and Biomedical Applications

Research on iron oxide-based magnetic nanoparticles and their clinical use has been, so far, mainly focused on the spherical shape. However, efforts have been made to develop synthetic routes that produce different anisotropic shapes not only in magnetite nanoparticles, but also in other ferrites, as their magnetic behavior and biological activity can be improved by controlling the shape. Ferrite nanoparticles show several properties that arise from finite-size and surface effects, like high magnetization and superparamagnetism, which make them interesting for use in nanomedicine. Herein, we show recent developments on the synthesis of anisotropic ferrite nanoparticles and the importance of shape-dependent properties for biomedical applications, such as magnetic drug delivery, magnetic hyperthermia and magnetic resonance imaging. A brief discussion on toxicity of iron oxide nanoparticles is also included.

Vanadium-Incorporated Metallic (1-T) Molybdenum Sulfide Nanoroses for High-Energy-Density Asymmetric Supercapacitors

The metallic phase (1T) of molybdenum sulfide is critical, pertaining to its exceptional interlayer structure and metastability, but forms up with low content. Herein, 1T-phase-prominent vanadium-incorporated MoS₂ (MVS) nanoroses were synthesized through a hydrothermal process. A significant increase in 1T content (50 %) occurred with the addition of vanadium, enhancing the prompt diffusion of lithium ions by two orders. More exposed electroactive basal planes increased the number of redox active sites to 84 %, suggesting an excellent charge storage of 451 F g^-1 at 1 A g^-1 . On assembling MVS with MnO₂ to form an asymmetric cell (MnO₂ ∥MVS), a high energy density (62.7 Wh kg^-1 at 428 W kg^-1 ) with a threefold increment from the MVS‖MVS symmetric cell (21.8 Wh kg^-1 at 255 Wkg^-1 ) was achieved. The asymmetric cell also exhibited a superior cycling stability with 98 % retention of its capacitance after 10 000 cycles.

Enhanced supercapacitive performance of the CoFe2O4/CoFe2S4 composite nanoflake array induced by surface sulfidation

The CoFe₂O₄/CoFe₂S₄ composite nanoflake array was prepared by surface sulfidation and exhibited outstanding electrochemical performance.