Mercury (Hg2+), one of the most dangerous toxins in water, is a heavy metal that causes organ damage from both short-term and chronic exposure. Conventional methods for detecting mercury such as atomic absorption spectrometry or Raman spectroscopy require bulky equipment with complicated procedures. In this work, we fabricated a highly sensitive, real-time thin-film sensor based on vertically aligned rhenium disulfide (ReS2). Its outstanding large surface area and the unique electronic appearance of its layered architecture make a ReS2 nanosheet a strong contender for such an application. The sensor exhibited a fast response speed (< 2 s) to Hg2+ and an ultralow detection limit of 4 nM, which is significantly less than that of the U.S. Environmental Protection Agency's (U.S. EPA) allowed utmost contamination limit for Hg2+ in drinking water (10 nM). It also exhibited strong selectivity for Hg2+ against other metal ions such as Na+, Zn2+, Fe3+, Cu2+, Ca2+, Ni2+, Ag+, Cd2+, Fe2+, and Pb2+. Because this nanosheet can be replaced with any secondary substrate and possibly patterned into a microscale size, the sensor can be integrated into multiple platforms such as portable devices or sensor nodes in a grid network.

Aqueous zinc-ion batteries (AZIBs) have received growing attention for comprehensive energy storage owing to their affordability and high safety. Still, cathode materials that usually exhibit low capacity or poor cycling performance have hindered the practical application of AZIBs. Herein, the selenium-incorporated sodium vanadate (Na2V6O16) (NVO@Se) nanobelts (NBs) were synthesized via a facile hydrothermal method, followed by calcination under N2 flow. As a cathode for AZIBs, the NVO@Se NBs electrode delivered a high discharge capacity value of 329.15 mA h g−1 at 2 A g−1 with ∼ 99 % coulombic efficiency and excellent rate capability (284.89 and 200.21 mA h g−1 at 4 and 5 A g−1, respectively). Mechanistic analyses of the intercalation reaction in the NVO@Se NBs after cycling using ex-situ X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy techniques revealed their good structural stability and electrochemical reversibility. Developing interactive properties, the NVO@Se NBs material was also studied as a battery-type electrode for hybrid supercapacitors (HSCs). By sandwiching the NVO@Se NBs and activated carbon, the fabricated HSC exhibited good power and energy density values, along with its verification for practical applications. From all the electrochemical characteristic results, the NVO@Se NBs material has good aspects for AZIBs and HSCs, which makes new prospects for the advancement of materials in energy storage applications.

Reddish-orange emitting CaLa4Ti4O15:Sm3+ phosphors were synthesized via a simple solid-state reaction. The synthesized CaLa4Ti4O15:Sm3+ phosphors revealed dominant excitation at 408 nm and emission at 601 nm with the 6H5/2 → 4F7/2 and 4G5/2 → 6H7/2 transitions, respectively. The transitions are governed by dipole-dipole interaction in the CaLa4Ti4O15:Sm3+ luminescent material. The morphology and crystal structure were investigated, and the material synthesis and chemical compositions were also confirmed. In a study of the effect of Sm3+ ion concentration on the luminescent properties of CaLa4Ti4O15:Sm3+ phosphors, the optimized concentration was found to be 5 mol%. The optimized phosphor powder exhibited Commission Internationale de l′Eclairage (CIE) chromaticity coordinate of (0.610, 0.390) under 408 nm illumination, and the thermal stability was also measured, exhibiting good thermal stability of about 81.7% at 423 K and 67.95% at 483 K. The white light-emitting diode (WLED) device was packaged using CaLa4Ti4O15:Sm3+ phosphors, together with commercial phosphors. The fabricated WLED device exhibited good correlated color temperature and color rendering index values of 5461 K and 83.97, respectively with (0.3341, 0.3997) CIE chromaticity coordinate. The CaLa4Ti4O15:Sm3+ materials as a reddish-orange emitting phosphor are expected to be a highly promising candidate for WLED applications.

For iron vanadium-based lithium (Li)-ion batteries (LIBs), enhancing solidity as well as exploring storage mechanism is important. Herein, a facile hydrothermal method is employed to fabricate N-doped reduced graphene oxide-wrapped porous iron vanadate (FVO@N-rGO) hybrid composite nanostructures (HCNSs), followed by the calcination under the N2 atmosphere. The as-prepared FVO@N-rGO HCNSs are used as an anode material for LIBs. The FVO@N-rGO HCNSs electrode delivers a high reversible specific capacity of 711 mA h g−1 at 100 mA g−1 and durable cycling life (226 mA h g−1 at 3000 mA g−1). The Li+ intercalation kinetics (from cyclic voltammetry analysis) reveal that the Li storage capacity of FVO@N-rGO HCNSs is normally dominated via a pseudo-capacitive behavior. A full cell using commercial LiNi0.3Mn0.3Co0.3O2 (NMC111) as a cathode and pristine FVO nanospheres and FVO@N-rGO HCNSs as an anode is also fabricated. The obtained good reversible capacity, stability, and rate capability may be due to the synergetic result of three-dimensional HCNSs construction and porous morphology with a large surface area, which offers void space to shield size expansion/contraction along with reducing the diffusion coefficient for Li ions/electrons in the cycling process. Thus, this study gives a deep understanding of improving the cell performance of iron vanadium-based LIBs.

We have synthesized the hierarchical FeCo-MIL-88 (FC-MOF) derived CoFe2O4 and NiMn2O4 (CFO@NMO) composite using a hydrothermal route. The combination and formation process were presented. The prepared composite of CFO@NMO is studied using XRD, XPS, FESEM with EDS, HRTEM, and nitrogen adsorption and desorption isotherm. The formation of composite with CoFe2O4 (CFO) and NiMn2O4 (NMO) may effectively boost the conductivity thereby enhance the performance of electrochemical activity. Benefitting from the formation of composite, the hybrid CFO@NMO electrode achieved a high specific capacity (i.e., 353.6 mAh/g), 86.1 % retention in capacity after 5000 galvanostatic charging and discharging (GCD) cycles. To utilize the advantages of ultra-long cycling stability and high specific capacity, the aqueous electrolyte-based hybrid supercapacitor (HSC) device with AC//NF as a negative electrode and CFO@NMO//NF as a positive electrode was fabricated. The assembled HSC device provided a specific capacitance 312.8 F/g, 88.4 % retention in capacitance after 10,000 GCD cycles along with high energy density (90.3 Wh/kg) and power density (12.9 kW/kg). An easy and cost-effective preparation of CFO@NMO composite with outstanding supercapacitor performance demonstrates an excessive potential for utilization in the near future.

Recently, for energy storage materials, various surfactant-less synthesis methods have been attaining extensive attention from researchers. Herein, we utilized the wasted desoldering copper wicks (E-waste) as the base substrate to synthesize hierarchical core–shell maze-corn-like nickel selenide/copper oxide (NiSe/Cu4Ox) architectures by a facile two-step synthesis process. Initially, the Cu4Ox nanorods (NRs) were grown directly over the surface of the flat braided E-waste copper wicks by thermal oxidation, followed by a facile electrodeposition method to coat the pre-existing Cu4Ox NRs with NiSe nanoparticles. The optimized NiSe-120/Cu4Ox-3 electrode exhibited superior electrochemical characteristics (138.27 µAh cm−2 at 4 mA cm−2) compared to the other electrodes, owing to the contribution of core and shell materials, and sustained an ultra-long cycling test of 50,000 charge/discharge cycles with an excellent capacity retention of 98.7%. Inspired by commercially available AA battery, the as-synthesized working electrode was coupled with activated carbon-coated nickel foam to fabricate a cylindrical-type (C-type) hybrid supercapacitor (HSC) device, with an areal capacitance of 233.1 mF cm−2 accompanied by an extraordinary cycling efficiency of 99.1%. Furthermore, the C-type HSC device exhibited maximum energy and power densities of 70.9 µWh cm−2 and 14,000 µW cm−2, respectively and it was tested by powering portable electronics for real-time application.