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The accelerated evolution of the Internet of Things has brought new challenges to the gas sensors, which are required to work persistently under harsh conditions, like high humidity. However, currently, it is quite challenging to solve the hindrance of the trade-off between gas-sensing performance and anti-humidity ability of the chemiresistive gas sensors. Herein, hydrophobic inorganic CeO2/SnO2heterostructure films were prepared by depositing the CeO2layers with a thickness of a few nanometers onto the SnO2film via a magnetron sputtering method. The sensors based on the CeO2/SnO2heterostructure films demonstrated excellent gas-sensing performance toward trimethylamine (TEA) with high response, wide detection range (0.04–500 ppm), low record detection limit (0.04 ppm), ideal reproducibility, and long-term stability, while concurrently possessing promising anti-humidity ability. A portable, wireless TEA-sensing system containing the CeO2/SnO2sensor was constructed to realize the real-time monitoring of trace concentration of the volatiles released from a fish. This work provides a novel strategy to prepare advanced chemiresistive gas sensors for humidity-independent detection of harmful gases and vapors and will accelerate their commercialization process in the field of food safety and public health.

Currently, the exploration of wearable strain sensors that can work under subzero temperatures while simultaneously possessing anti-interference capability toward temperature is still a grand challenge. Herein, we present a low-temperature wearable strain sensor that is constructed via the incorporation of a Ag nanowires/graphene (Ag NWs/G) composite into the polydimethylsiloxane (PDMS) polymer. The Ag NWs/G/PDMS strain sensor exhibits promising flexibility at a very low temperature (−40 °C), outstanding fatigue resistance with low hysteresis energy, and near-zero temperature coefficient of resistance (TCR). The Ag NWs/G/PDMS strain sensor shows excellent sensing performance under subzero temperatures with a very high gauge factor of 9156 under a strain of >36%, accompanied by a noninterference characteristic to temperature (−40 to 20 °C). The Ag NWs/G/PDMS strain sensor also demonstrates the feasibility of monitoring various human movements such as finger bending, arm waving, wrist rotation, and knee bending under both room temperature and low-temperature conditions. This work initiates a new promising strategy to construct next-generation wearable strain sensors that can work stably and effectively under very low temperatures.

Rechargeable aqueous Zn-ion batteries (ZIBs) have recently attracted much attention due to their low cost and superior safety. Unfortunately, their low capacity and poor cycle life still hinder their practical application. Here, we have developed a general synthesis strategy for ultrasmall spinel oxide nanodots (Mn3O4, CoMn2O4, MnCo2O4.5, Co3O4, and ZnMn2O4) with abundant oxygen vacancies and highly active surface. Among them, 6.0-nanometer-sized Mn3O4nanodots deliver the best Zn-ion storage ability with a high reversible capacity of 386.7 mA h g–1at 0.1 A g–1, excellent rate performance, and a long-term stability of 500 cycles at 0.5 A g–1. Taking advantage of the highly activated surficial atoms, shortened transfer pathway, and introduction of numerous oxygen vacancies, an ultrahigh Zn2+diffusion coefficient of 2.4 × 10–10cm2s–1has been detected during the discharge process. This value is more than 2 orders of magnitude higher than that of other spinel oxide nanostructures in previous reports and also the highest one in all of the as-reported ZIB cathode materials to date. Our finding offers promising opportunities for the development of ZIB cathode materials with high energy density, long-term cycling stability, excellent flexibility, and wearability.

The realization of high-performance anode materials with high capacity at fast lithiation kinetics and excellent cycle stability remains a significant but critical challenge for high-power applications such as electric vehicles. Two-dimensional nanostructures have attracted considerable research interest in electrochemical energy storage devices owing to their intriguing surface effect and significantly decreased ion-diffusion pathway. Here we describe rationally designed metastable CoSeO3·H2O nanosheets synthesized by a facile hydrothermal method for use as a Li ion battery anode. This crystalline nanosheet can be steadily converted into amorphous phase at the beginning of the first Li+discharge cycling, leading to ultrahigh reversible capacities of 1100 and 515 mAh g–1after 1000 cycles at a high rate of 3 and 10 A g–1, respectively. The as-obtained amorphous structure experiences an isotropic stress, which can significantly reduce the risk of fracture during electrochemical cycling. Our study offers a precious opportunity to reveal the ultrafast lithiation kinetics associated with the rapid amorphization mechanism in layered cobalt selenide nanosheets.

Two-dimensional (2D) hydroxide nanosheets can exhibit exceptional electrochemical performance owing to their shortened ion diffusion distances, abundant active sites, and various valence states. Herein, we report ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets (thickness ∼30 nm) which crystallize in a layered structure and exhibit a high specific capacitance of 3946.5 F g–1at 3 A g–1for an electrochemical pseudocapacitor. ZnCo1.5(OH)4.5Cl0.5·0.45H2O was synthesized by a homogeneous precipitation method and spontaneously crystallized into 2D nanosheets in well-defined hexagonal morphology with crystal structure revealed by synchrotron X-ray powder diffraction data analysis. In situgrowth of ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheet arrays on conductive Ni foam substrate was successfully realized. Asymmetric supercapacitors based on ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets @Ni foam// PVA, KOH//reduced graphene oxide exhibits a high energy density of 114.8 Wh kg–1at an average power density of 643.8 W kg–1, which surpasses most of the reported all-solid-state supercapacitors based on carbonaceous materials, transition metal oxides/hydroxides, and MXenes. Furthermore, a supercapacitor constructed from ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets@PET substrate shows excellent flexibility and mechanical stability. This study provides layered bimetallic hydroxide nanosheets as promising electroactive materials for flexible, solid-state energy storage devices, presenting the best reported performance to date.

Two-dimensional LDH nanosheets recently have generated considerable interest in various promising applications because of their intriguing properties. Herein, we report a facile in situ nucleation strategy toward in situ decorating monodispersed Ni–Fe LDH ultrafine nanosheets (UNs) on graphene oxide template based on the precise control and manipulation of LDH UNs anchored, nucleated, grown, and crystallized. Anion-exchange behavior was observed in this Ni–Fe LDH UNs@rGO composite. The Ni–Fe LDH UNs@rGO electrodes displayed a significantly enhanced specific capacitance (2715F g–1at 3 A g–1) and energy density (82.3 Wh kg–1at 661 W kg–1), which exceeds the energy densities of most previously reported nickel iron oxide/hydroxides. Moreover, the asymmetric supercapacitor, with the Ni–Fe LDH UNs @rGO composite as the positive electrode material and reduced graphene oxide (rGO) as the negative electrode material, exhibited a high energy density (120 Wh kg –1) at an average power density of 1.3 kW kg –1. A charge transfer from LDH layer to graphene layer, which means a built in electric field directed from LDH to graphene can be established by DFT calculations, which can significantly accelerate reaction kinetics and effectively optimize the capacitive energy storage performance.

As an emerging star in the family of two-dimensional (2D) materials, 2D transition metal carbides, carbonitrides and nitrides, collectively referred to as MXenes, have large specific surface area, rich active sites, metallic conductivity and adjustable surface chemical properties. These features make MXenes promising candidates for gas-sensing materials. For the past few years, MXene-based sensors have drawn increasing attention due to their enhanced sensor performance. Based on this, this review systematically represents the structure, synthesis methods and properties of MXenes, and summarizes their applications in gas sensors. Firstly, the types, structure, main synthesis methods and properties of MXenes are introduced in a comprehensive way. Next, the corresponding design principle and working mechanism of MXene-based gas sensor are clarified. Subsequently, the sensing performances of pristine MXenes and the MXene-based nanocomposite are discussed. Finally, some future opportunities and challenges of MXene-based sensors are pointed out.

Latent heat of phase change materials (PCMs) has long been regarded as constant. In this work, it is found that this parameter can be altered when they are in nanoscale. We designed and assembled a nanocapsule-confinement system with stearic acid (SA) sealed in silica nanoshells to investigate the thermodynamics and kinetics of their phase transition in nanoscale. It is interesting that heat storage capacity of the obtained SA@SiO2nanocapsules (NCs) could be increased up to 374.2 kJ/kg, about 36.9% more than that of the unconfined SA (273.3 kJ/kg). This is because the high superimposed stress from the curvature effect inside SiO2nanoshells would significantly shorten the intermolecular spacing of SA as compared to their unconfined state, which will especially strengthen hydrogen bonds of SA, forming multiple stable hydrogen bond networks. Therefore, breaking and reforming of these hydrogen bonds will no doubt contribute to latent heat of SA when they change from solid to liquid. Our results not only are helpful for understanding phase transition behaviors of phase change materials in nanocapsule interface confinement conditions but also provide a good example to develop new types of heat energy storage composite materials.