Understanding the increasing energy demands and probable utilization of mechanical energy harvesters, current research is highly focused on enhancing their performance/applicability in everyday life. Herein, we proposed a box-type hybrid nanogenerator (BT-HNG) consisting of acetone-dissolved microarchitectured strontium (Sr) doped silver niobate (ASNb)/ecoflex composite film as a highly efficient mechanical energy harvester. The simple and unique microarchitectured (MA) master mold was fabricated by immersing a plastic petri dish inside the acetone which was further utilized to obtain MA-composite films. The ASNb microparticles (MPs) with varying the Sr doping concentration were synthesized and further loaded inside the ecoflex film to enhance its dielectric properties. The MA-ASNb/ecoflex composite films were utilized as a negative triboelectric material and copper as a positive triboelectric material for the fabrication of HNG operating in a contact-separation mode. The ASNb filler concentration inside the ecoflex film was optimized in the aspect of Sr doping and filler concentrations to obtain the highest electricity from respective HNG. The highly efficient and stable electrical output produced by the HNG was further utilized to power various small-scale electronics. The BT-HNG producing unique direct current electrical output was developed by integrating five similar HNGs in it. The enhancement in the electrical output with successive addition of each HNG was thoroughly investigated. The proposed BT-HNG was successfully demonstrated as a real-time sensor that can be utilized to turn on the lamps situated at stairs, corridors, etc. in human presence. The enclosed BT-HNG along with a heavy weighing block was demonstrated to harvest vibrational/linear movements into electricity.

Novel near-white emission phosphors of single Pr3+-doped Ca2(Gd,Y)TaO6 double perovskites were successfully prepared. Their crystal structures, morphologies, elemental compositions, photoluminescence (PL) behaviors, internal quantum yields, thermal stabilities, etc. were systemically investigated. Interestingly, the chemical composition of Gd3+ ions replaced by Y3+ ions did not affect the crystal structure of the monoclinic structure in the P 21/n(14) space group. Particularly, the PL emission spectrum of the optimal Ca2YTaO6:Pr3+ phosphors showed different dominant peaks compared to the Ca2GdTaO6:Pr3+ phosphors due to the appearance of cross-relaxation. Note that the near-white region chromaticity coordinates/internal quantum yields of the optimal Ca2GdTaO6:Pr3+ and Ca2YTaO6:Pr3+ phosphors were (0.363, 0.438)/28.1 % and (0.350, 0.441)/27.4 %, respectively. Finally, the potential applications of single Pr3+-doped double-perovskite phosphors were expanded to luminescence lifetime thermometers and flexible safety film applications.

The novel transition metal vanadate materials with hierarchical nanostructures have attracted considerable attention due to their remarkable electrochemical properties in catalysis and energy storage/conversion systems. Herein, we report the zinc vanadate (Zn3V2O10) nanomaterials (ZVO NMs) by a simple one-step hydrothermal method. The synthesis of ZVO NMs is studied at different growth temperatures (100, 150, and 200 °C). Additionally, reduced graphene oxide (rGO) sheets are introduced into the optimized ZVO NM obtained at 150 °C (i.e., ZVO NM-150). The prepared materials are analyzed by various characterization techniques and the obtained properties of ZVO NM with rGO sheets are beneficial for energy storage devices. The ZVO NM-150@rGO electrode exhibits a high specific capacity (capacitance) of 95 mAh g−1 (677 F g−1) at 2 A g−1 with a rate capability of 82 % in 1 M KOH aqueous electrolyte solution. The ZVO NM-150@rGO electrode reveals superior capacity retention of 105 % with Coulombic efficiency (CE) of 98 % after completing 45,000 cycles. Furthermore, the assembled asymmetric supercapacitor (ASC) device demonstrated maximum energy and power densities of 19.06 Wh kg−1 and 2190.78 W kg−1, respectively. The ASC device also shows good cycling stability with excellent capacitance retention of 139 % and CE of 98 % after 80,000 cycles. Benefiting from these advantageous properties, the ZVO NM and ZVO NM-150@rGO electrode materials are very promising for high-performance SCs.

Two-dimensional (2D) materials have gained considerable attention in chemical sensing owing to their naturally high surface-to-volume ratio. However, the poor response time and incomplete recovery restrict their application in practical, high performance gas sensors. In this work, we fabricated air-stable ReS2/GaSe heterostructure-based NO2 gas sensors with excellent gas sensing response, recovery, selectivity and a low limit of detection (LOD) toward nitrogen dioxide (NO2). The ReS2/GaSe heterostructure was prepared via mechanical exfoliation and an all-dry transfer method. Before the sensing measurements, temperature-dependant transport measurements were carried out. The Schottky Barrier Height (SBH) of the ReS2/GaSe heterostructure was calculated and the corresponding transport mechanisms were discussed. The fabricated gas sensors showed a significant response enhancement with full reversibility toward ppm-level NO2 (response of ∼17% at 3 ppm, a LOD of ∼556 ppb) at an operating temperature of (33 °C). In particular, the total response and recovery time of the ReS2/GaSe was revealed to be less than 4 min (∼38 s and ∼174 s, respectively) for the 250 ppm concentration, which is one of the best response and recovery time toward ppm-level NO2. The excellent sensing performances and recovery characteristics of the ReS2/GaSe structure are attributed to its efficient charge separation, unique interlayer coupling and desirable band alignments. This atomically thin, ultrasensitive gas sensor that operates at room temperature is a strong technological contender to conventional metal oxide gas sensors, which often require elevated temperatures.

Direct growth of redox-active noble metals and rational design of multifunctional electrochemical active materials play crucial roles in developing novel electrode materials for energy storage devices. In this regard, silver (Ag) has attracted great attention in the design of efficient electrodes. Inspired by the house/building process, which means electing the right land, it lays a strong foundation and building essential columns for a complex structure. Herein, we report the construction of multifaceted heterostructure cobalt-iron hydroxide (CFOH) nanowires (NWs)@nickel cobalt manganese hydroxides and/or hydrate (NCMOH) nanosheets (NSs) on the Ag-deposited nickel foam and carbon cloth (i.e., Ag/NF and Ag/CC) substrates. Moreover, the formation and charge storage mechanism of Ag are described, and these contribute to good conductive and redox chemistry features. The switching architectural integrity of metal and redox materials on metallic frames may significantly boost charge storage and rate performance with noticeable drop in resistance. The as-fabricated Ag@CFOH@NCMOH/NF electrode delivered superior areal capacity value of 2081.9 µA h cm−2 at 5 mA cm−2. Moreover, as-assembled hybrid cell based on NF (HC/NF) device exhibited remarkable areal capacity value of 1.82 mA h cm−2 at 5 mA cm−2 with excellent rate capability of 74.77% even at 70 mA cm−2 Furthermore, HC/NF device achieved maximum energy and power densities of 1.39 mW h cm−2 and 42.35 mW cm−2, respectively. To verify practical applicability, both devices were also tested to serve as a self-charging station for various portable electronic devices.

The rich redox chemistry of vanadate-based materials makes them a potential anode for the fabrication of advanced lithium-ion batteries (LiBs). However, poor electrical conductivity as well as volume variation of vanadate-based anode materials hinders practical applications. Herein, magnesium vanadate (MgV3O8) incorporated carbon nanofibers (CNFs) (MgVO@CNFs) composites were prepared via a simple and scalable electrospinning technique, followed by pyrolysis. The synergistic effect of MgVO and CNFs effectively offers a good conductive path and excellent integrity between the active particles with highly porous network. As an anode for LiBs, the MgVO@CNFs composite electrode exhibited good discharge capacity values of 457 mA h g−1 (over 300 cycles) and 245 mA h g−1 (over 500 cycles) at 0.1 and 0.5 A g−1, respectively and revealed excellent rate performance. The charge storage mechanism of MgVO@CNFs is contributed by both capacitive and diffusion-controlled behaviors. Consequently, this novel preparation process of the MgVO@CNFs may provide a new idea for the fabrication of different kinds of nanostructures for LiB applications.

A series of novel dysprosium(III) (Dy3+)-doped yellow-emitting double-perovskite A2BB’O6 (A = calcium(II) (Ca2+), B = lanthanum(III) (La3+), gadolinium(III) (Gd3+), and indium(III) (In3+); B′ = antimony(V) (Sb5+), tantalum(V) (Ta5+), and niobium(V) (Nb5+)) phosphors were synthesized. The ion substitution in B and B′ sites in the double-perovskite structure significantly affected its crystal structures and photoluminescence properties such as excitation spectrum, emission spectrum, thermal stability, color purity, luminescence dynamic, and quantum yield. Interestingly, the beneficial thermal stability of all the obtained samples (> 62% at 423 K with respect to the initial value at 303 K) implied their potential for solid-state lighting application. Among them, the Ca2LaTaO6:Dy3+ exhibited the best heat resistance (> 83% at 423 K) while the Ca2GdNbO6:Dy3+ had the highest internal quantum yield up to 35.17%. Furthermore, the possible mechanisms for the changes in luminescent properties relying on their chemical compositions were studied accordingly. Eventually, some fabricated light-emitting diode devices based on the obtained samples were tested for their application in warm solid-state lighting.

Hierarchical core–shell architectures constructed with zeolitic imidazolate frameworks (ZIFs) and binary metal oxides are attracting much attention as an efficient electrode material for supercapacitors (SCs). In this regard, we reported the ZIF-67 amorphous nanoparticles (NPs)@Cu2CoO3 (ZIF-67@CCO) via a two-step synthesis process. Initially, the CCO electrode material with soap nuts-like core–shell hollow sphere (SNHS) morphology was synthesized by a facile solvothermal method and post-annealing treatment. The optimized CCO SNHS (CCO-9 h (9 h growth time)) electrode demonstrated higher areal capacity (CA)/specific capacity (CS) values than the CCO-6 h and CCO-12 h electrodes. Next, ZIF-67 NPs were deposited on the CCO-9 h material using the solvothermal method. The resulting ZIF-67@CCO-9 h electrode exhibited improved electrochemical properties of CA = 176.3 μAh cm−2 (CS = 117.5 mAh g−1) at 1 mA cm−2 and superb cycling stability after 25,000 cycles (83.4% retention). The ZIF-67 layer on the CCO-9 h with SNHS structure may provide faster electron transfer as well as more active sites, benefiting the electrochemical characteristics. Furthermore, the hybrid supercapacitor (HSC) cell was assembled using ZIF-67@CCO-9 h and activated carbon/Ni foam as positive (+) and negative (−) electrodes, respectively. The as-constructed HSC cell revealed high energy density value of 25.2 Wh kg−1. Also, the commercial application of the fabricated HSC cell was verified by driving different electronic components.