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SUMMARY New methods for recycling lithium-ion batteries (LIBs) are needed because traditional recycling methods are based on battery pulverization, which requires pre-treatment of tedious and non-eco-friendly discharging and results in low efficiency and high waste generation in post-treatment. Separating the components of recycled LIB cells followed by reuse or conversion of individual components could minimize material cross-contamination while avoiding excessive consumption of energy and chemicals. However, disposing of charged LIB cells is hazardous due to the high reactivity of lithiated graphite towards cathode materials and air, and the toxicity and flammability of the electrolytes. Here we demonstrate that the disassembly of charged jellyroll LIB cells in water with a single main step reveals no emissions from the cells and near perfect recycling efficiencies that exceed the targets of the US Department of Energy and Batteries Europe. The precise non-destructive mechanical method separates the components from jellyroll cell in water, avoiding both uncontrollable reactions from the anode and burning of the electrolyte, while allowing only a limited fraction of the anode lithium to react with water. Recycling in this way allows the recovery of materials with a value of ∼7.14 $ kg−1 cell, which is higher than that of physical separation (∼5.40 $ kg−1 cell) and much greater than the overall revenue achieved using element extraction methods (

Zinc ion batteries have been extensively studied with an aqueous electrolyte system. However, the batteries suffer from a limited potential window, gas evolution, cathode dissolution, and dendrite formation on the anode. Considering these limitations, we developed an alternative electrolyte system based on deep eutectic solvents (DESs) because of their low cost, high stability, biodegradability, and non-flammability, making them optimal candidates for sustainable batteries. The DES electrolyte enables reversible Zn plating/stripping and effectively suppresses zinc dendrite formation. Furthermore, in-depth characterizations reveal that the energy storage mechanism can be attributed to [ZnCl]

Synaptic devices based on non-volatile resistive random access memory (RRAM) have inspired increasing opportunities, including in-memory computing and neural engines, while typical filamentary-based RRAM is subjected to large switching current and causes huge power consumptions. In this work, a low-power memristor based on vertically stacked two-dimensional (2D) layered materials, achieved by plasma-assisted vapor reaction, as the switching material, with which the copper and gold metals as electrodes featured by reversible polymorphous phase changes from a conducting 1T-phase to a semiconducting 2H-one once copper cations interacted between vertical lamellar layers and vice versa was demonstrated. Here, molybdenum diselenide (MoSe2) was chosen as the switching material and the reversible polymorphous phase changes activated by the intercalation of Cu cations were confirmed by pseudo-operando Raman scattering, transmission electron microscopy and scanning photoelectron microscopy under high and low resistance states, respectively. The switching can be activated at about ± 1 V with critical currents less than 10 𝜇A with an on/off ratio of approaching 100 after 100 cycles and low power consumption of ~0.1 microwatt as well as linear weight updates controlled by the amount of intercalation. The work opens alternative feasibility of reversible and all-solid-state metal interactions, which benefits monolithic integrations of 2D materials into operative electronic circuits.

Resistive random access memory (RRAM) is vital to neuromorphic computing applications. However, filamentary RRAM cells are affected by transitions from abrupt switching to analog switching. In this...

A conductive-bridge random access memory (CBRAM) has been considered a promising candidate for the next-generation nonvolatile memory technology because of its excellent performance, for which the resistive switching behavior depends on the formation/dissolution of conducting filaments in an electrolyte layer originated by the cation injection from the active electrode with electrochemical reactions. Typically, the controllability of cations into the electrolyte layer is a main issue, leading to stable switching reliability. In this work, an architecture combining spike-shaped Ag electrodes created by Al2O3 nanopillar arrays as a physical diffusion barrier by glancing angle deposition technology was proposed to localize Ag cation injection for the formation of controllable filaments inside TiOx as the switching layer. Interestingly, the dimension of the Ag plugs defined by the topography of Al2O3 nanopillar arrays can control Ag cation injection to influence the dimensionality of conductive filaments. Compared to the typical planar-Ag/TiOx/Pt device, the spiked-Ag/Al2O3 nanopillar arrays/TiOx/Pt device shows improvement of endurance and voltage disturbance. With enhanced multilevel characteristics, the spiked active-metal-based CBRAM device can be expected to serve as an analogue synapse for neuromorphic applications.

Atomically thin oxide semiconductors are significantly expected for next-generation cost-effective, energy-efficient electronics. A high-performance p-channel oxide thin-film transistor (TFT) was developed using an atomically thin p-type tin monoxide, SnO channel with a thickness of ∼1 nm, which was grown by a vacuum-free, solvent-free, metal-liquid printing process at low temperatures, as low as 250 °C in an ambient atmosphere. By performing oxygen-vacancy defect termination for the bulk-channel and back-channel surface of the ultrathin SnO channel, the presented p-channel SnO TFT exhibited good device performances with a reasonable TFT mobility of ∼0.47 cm2 V-1 s-1, a high on/off current ratio of ∼106, low off current of

A new type of two-dimensional (2D) SnO2 semiconductor-based gate-tunable memristor, that is, a memtransistor, an integrated device of a memristor and a transistor, was demonstrated to advance next-generation neuromorphic computing technology. The polycrystalline 2D-SnO2 memristors derived from a low-temperature and vacuum-free liquid metal process offer several interesting resistive switching properties such as excellent digital/analog resistive switching, multistate storage, and gate-tunability function of resistance switching states. Significantly, the gate tunability function that is not achievable in conventional two-terminal memristors provides the capability to implement heterosynaptic analog switching by regulating gate bias for enabling complex neuromorphic learning. We successfully demonstrated that the gate-tunable synaptic device dynamically modulated the analog switching behavior with good linearity and an improved conductance change ratio for high recognition accuracy learning. The presented gate-tunable 2D-oxide memtransistor will advance neuromorphic device technology and open up new opportunities to design learning schemes with an extra degree of freedom.

Titanium dioxide (TiO2) has been acknowledged as one of the efficient photocatalysts in the UV region. To extend the photo-absorption region toward visible lights, the TiO2 nanowires enclosed with carbon shells (TiO2@carbon core-shell nanowires) were synthesized by a chemical vapor deposition technique at various temperatures from 650 to 950 °C. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses revealed that TiO2 cores and carbon shells are rutile and graphitic structures, respectively. From Raman spectra, the peak intensity of the Eg mode was observed to be redshifted with elevated growth temperatures due to the increase in oxygen vacancies in the TiO2@carbon core-shell nanowires. From X-ray photoelectron spectroscopy (XPS) results, the oxygen vacancies were strongly related to the Ti3+ ions. The UV–visible spectroscopic studies show a possible decrease in photocatalytic energy from 3.1 to 2.7 eV for the TiO2@carbon core-shell nanowires, indicating that the light absorption was enhanced in the visible-light region. The optical absorbance results confirmed the presence of the mid-gap states due to the oxygen vacancies, which are responsible for the visible-light absorption. The photocatalytic activity of the TiO2@carbon core-shell nanowires studied by methylene blue (MB) dye degradation is effective under visible lights.

Sodium-selenium (Na-Se) batteries have aroused enormous attention due to the large abundance of the element sodium as well as the high electronic conductivity and volumetric capacity of selenium. In this battery system, some primary advances in electrode materials have been achieved, mainly involving the design of Se-based cathode materials. In this Review, the electrochemical mechanism is discussed, thus revealing the main challenges in Na-Se batteries. Then, the advances in the design of Se-based cathode materials for Na-ion storage are systemically summarized, classified, and discussed, including Se/carbon composite, Se/polar material/carbon composites, and hybrid SexSy alloys. Some potential strategies enabling the improvement of crucial challenges and enhancement of electrochemical performance are also proposed to provide guidelines for the enhancements of Na-ion storage. An outlook for future valuable research directions is proposed to understand more deeply the electrochemical mechanism of Na-Se batteries and promote their further developments in full cell performance and commercialization.

Over the past decade, lead halide perovskite materials have emerged as a promising candidate for third-generation solar cells and have progressed extremely rapidly. The tunable band gap, strong absorption, high power conversion efficiency, and low cost of perovskite solar cells makes them highly competitive compared to current commercialized silicon-based and thin film-based photovoltaic technologies. However, commercial products unavoidably result in large amounts of waste and end-of-life devices which can cause serious environmental impacts. To address this issue, recycle and recovery technologies of perovskite solar cells should be researched and developed proactively. In this review, the development of perovskite solar cells and their necessary materials are first introduced. Subsequently, the potential environmental impacts of perovskite solar cells are discussed, including their stability and lifetime, use of critical materials (i.e., indium, tin, and lead), and toxicity. Accordingly, the present recycle and recovery technologies are reviewed, providing information and recommendations of key strategies for recycling and recovering. Finally, future works and strategies for recycling and recovering perovskite solar cells are proposed.

Here, a current-accelerated phase cycling by an in situ current-induced oxidation process was demonstrated to reversibly switch the local metallic Cu and semiconducting Cu2O phases of patterned polycrystalline copper nanobelts. Once the Cu nanobelts were applied by a direct-current bias of ∼0.5 to 1 V in air with opposite polarities, the resistance between several hundred ohms and more than MΩ can be manipulated. In practice, the thickness of 60 nm with a moderate grain size inhibiting both electromigration and permanent oxidation is the optimized condition for reversible switching when the oxygen supply is sufficient. More than 40% of the copper localized beneath the positively biased electrode was oxidized assisted by the Joule heating, blocking the current flow. On the contrary, the reduction reaction of Cu2O was activated by the thermally assisted electromigration of Cu atoms penetrating the interlayer at the reverse bias. Finally, based on a high on/off ratio, the fast switching and the scalable production, reusable feasibility based on copper nanobelts such as the memristor array was demonstrated.

Silicon (Si) anode materials have attracted substantial interest due to its high theoretical capacity. Here, the growth of helical Si@Cu3Si nanorod arrays via glancing angle deposition (GLAD) followed by an annealing process was reported. The pre-deposited Cu atoms were driven into Si-nanorods and successfully reacted with Si to form Si-Cu alloy at a high temperature. Through varying the rotation rate and annealing temperature, the resultant Si@Cu3Si nanorod arrays showed a reasonably accessible surface area with precise control spacing behavior in favor of accommodating Si volume expansion. Meanwhile, the Si@Cu3Si anode materials showed higher electrical conductivity, facilitating the Li+ ion diffusion and electron transfer. The Si@Cu3Si nanorod arrays in half cell exhibited a volumetric capacity as high as 3350.1 mAh cm−3 at the rate of 0.25 C and could maintain 1706.7 mAh cm−3 after 100 cycles, which were superior to pristine Si materials. This facile and innovative technology provided new insights into the development of Si-based electrodes materials.

Real-time, daily health monitoring can provide large amounts of patient data, which may greatly improve the likelihood of diagnosing health conditions at an early stage. One potential sensor is a flexible humidity sensor to monitor moisture and humidity information such as dehydration. However, achieving a durable functional nanomaterial-based flexible humidity sensor remains a challenge due to partial desorption of water molecules during the recovery process, especially at high humidities. In this work, we demonstrate a highly stable resistive-type Pd/HNb3O8 humidity sensor, which exhibits a perdurable performance for over 100 h of cycle tests under a 90% relative humidity (RH) without significant performance degradation. One notable advantage of the Pd/HNb3O8 humidity sensor is its ability to regulate hydroniums due to the strong reducibility of H atoms dissociated on the Pd surface. This feature realizes a high stability even at a high humidity (99.9% RH). Using this superior performance, the Pd/HNb3O8 humidity sensor realizes wireless monitoring of the changes in the fingertip humidity of an adult under different physiological states, demonstrating a facile and reliable path for dehydration diagnosis.

The presence of two-dimensional (2D) layer-stacking heterostructures that can efficiently tune the interface properties by stacking desirable materials provides a platform to investigate some physical phenomena, such as the proximity effect and magnetic exchange coupling. Here, we report the observation of antisymmetric magnetoresistance in a van der Waals (vdW) antiferromagnetic/ferromagnetic (AFM/FM) heterostructure of MnPS3/Fe3GeTe2 when the temperature is below the Neel temperature of MnPS3. Distinguished from two resistance states in conventional giant magnetoresistance, the magnetoresistance in the MnPS3/Fe3GeTe2 heterostructure exhibits three states, of high, intermediate, and low resistance. This antisymmetric magnetoresistance spike is determined by an unsynchronized magnetic switching between the AFM/FM interface layer and the bulk of Fe3GeTe2 during magnetization reversal. Our work highlights that the artificial vdW stacking structure holds potential to explore some physical phenomena and spintronic device applications.

Transition metal dichalcogenides (TMDCs) have recently attracted a tremendous amount of attention owing to their superior optical and electrical properties as well as the interesting and various na...

In this work, we demonstrated nano-scaled Laue diffractions by a focused polychromatic synchrotron radiation beam to discover what happens in MoS2 when van der Waals epitaxy is locally invalid. A stronger exciton recombination with a local charge depletion in the density of 1 × 1013 cm-2, extrapolated by Raman scattering and photoluminescence, occurs in grains, which exhibits a preferred orientation of 30° rotation with respect to the c-plane of a sapphire substrate. Else, the charge doping and trion recombination dominate instead. In addition to the breakthrough in extrapolating mesoscopic crystallographic characteristics, this work opens the feasibility to manipulate charge density by the selection of the substrate-induced disturbances without external treatment and doping. Practically, the 30° rotated orientation in bilayer MoS2 films is promoted on inclined facets in the patterned sapphire substrate, which exhibits a periodic array of charge depletion of about 1.65 × 1013 cm-2. The built-in manipulation of carrier concentrations could be a potential candidate to lateral and large-area electronics based on 2D materials.

Aluminum-sulfur batteries (ASBs) have attracted substantial interest due to their high theoretical specific energy density, low cost, and environmental friendliness, while the traditional sulfur cathode and ionic liquid have very fast capacity decay, limiting cycling performance because of the sluggishly electrochemical reaction and side reactions with the electrolyte. Herein, we demonstrate, for the first time, excellent rechargeable aluminum-selenium batteries (ASeBs) using a new deep eutectic solvent, thiourea-AlCl3, as an electrolyte and Se nanowires grown directly on a flexible carbon cloth substrate (Se NWs@CC) by a low-temperature selenization process as a cathode. Selenium (Se) is a chemical analogue of sulfur with higher electronic conductivity and lower ionization potential that can improve the battery kinetics on the sluggishly electrochemical reaction and the reduction of the polarization where the thiourea-AlCl3 electrolyte can stabilize the side reaction during the reversible conversion reaction of Al-Se alloying processes during the charge-discharge process, yielding a high specific capacity of 260 mAh g-1 at 50 mA g-1 and a long cycling life of 100 times with a high Coulombic efficiency of nearly 93% at 100 mA g-1. The working mechanism based on the reversible conversion reaction of the Al-Se alloying processes, confirmed by the ex situ Raman, XRD, and XPS measurements, was proposed. This work provides new insights into the development of rechargeable aluminum-chalcogenide (S, Se, and Te) batteries.

Hierarchical nano-/microstructured photocatalysts have drawn attention for enhanced photocatalytic performance. Deep eutectic solvents (DESs) have been used as a green sustainable media to act as both solvent and structure-inducing agent in the synthesis of hierarchical nanomaterials. In this work, the DESs-assisted synthesis of flower-structured BiOCl/BiVO4 (BOC/BVO) with g-C3 N4 (BOC/BVO/g-CN) ternary heterojunctions was achieved by using a simple wet-chemical method, providing good acidic and alkaline oxygen evolution reaction (OER) catalysts. BOC/BVO/g-CN-15 achieved an enhanced photocatalytic activity for OER with an overpotential of 570 mV in 1 m H2 SO4 and 220 mV in 1 m KOH electrolyte at a current density of 10 mA cm-2 with excellent stability and extraordinary durability of the catalyst. The ternary heterojunctions displayed extended lifetimes for photogenerated charges and enhanced the separation efficiency of photogenerated electron-hole pairs, which is helpful to enhance the photocatalytic OER. Furthermore, the photocatalytic performance of the ternary heterojunctions in aqueous solution was demonstrated through photocatalytic dye degradation of methyl orange (MO) as a model pollutant, resulting in 95 % degradation of 20 ppm of MO in 210 min under the irradiation of a 35 W Xe arc lamp. This work not only provides new insight into the design of catalysts by using green solvents but also into the design of highly efficient metal-free OER photocatalysts for applications in acidic and alkaline media.

In this study, we, for the first time, demonstrate a general solid-phase pyrolysis method to synthesize hybrid transition metal nanocrystal-embedded graphitic carbon nitride nanosheets, namely M-CNNs, as a highly efficient oxygen electrocatalyst for rechargeable Zn–air batteries (ZABs). The ratios between metallic acetylacetonates and the g-C3N4 precursor can be controlled where Fe-CNNs−0.7, Ni-CNNs−0.7 and Co-NNs−0.7 composites have been optimized to exhibit superior ORR/OER bifunctional electrocatalytic activities. Specifically, Co-CNNs−0.7 exhibited not only a comparable half-wave potential (0.803 V vs. RHE) to that of the commercial Pt/C catalyst (0.832 V) with a larger current density for the ORR but also a lower overpotential (440 mV) toward the OER compared with the commercial IrO2 catalyst (460 mV), revealing impressive application in rechargeable ZABs. As a result, ZABs using Co-CNNs−0.7 as the cathode exhibited an excellent peak power density of 85.3 mW cm−2 with a specific capacity of 675.7 mA h g−1 and remarkable cycling stability of 1000 cycles, outperforming the commercially available Pt/C + IrO2 catalysts. This study highlights the synergy from heterointerfaces in oxygen electrocatalysis, thus providing a promising approach for advanced metal–air cathode materials.

A multifunctional ion-sensitive floating gate Fin field-effect transistor (ISFGFinFET) for hydrogen and sodium detection is demonstrated. The ISFGFinFET comprises a FGFET and a sensing film, both of which are used to detect and improve sensitivity. The sensitivity of the ISFGFinFET can be adjusted by modulating the coupling effect of the FG. A nanoseaweed structure is fabricated via glancing angle deposition (GLAD) technology to obtain a large sensing area to enhance the sensitivity for hydrogen ion detection. A sensitivity of 266 mV per pH can be obtained using a surface area of 3.28 mm2 . In terms of sodium ion detection, a calix[4]arene sensing film to monitor sodium ions, obtaining a Na+ sensitivity of 432.7 mV per pNa, is used. In addition, the ISFGFinFET demonstrates the functionality of multiple ions detection simultaneously. The sensor arrays composed of 3 × 3 pixels are demonstrated, each of which comprise of an FGFET sensor and a transistor. Furthermore, 16 × 16 arrays with a decoder and other peripheral circuits are constructed and simulated. The performance of the proposed ISFGFinFET is competitive with that of other state-of-the-art ion sensors.

A three-dimensional (3D) composite consisting of nickel-cobalt (Ni-Co) dual hydroxide nanoneedles (NCDHNs) grown on a carbon nanotube (CNT) material, denoted as CNTs@NCDHNs, was designed using a facile one-step hydrothermal method. This composite was further fabricated into electrodes, which exhibited high rate capability and long cycle life. Comparative analysis of the electrochemical performance between 3D CNTs@NCDHNs electrodes and Ni-Co hydroxide electrodes revealed that the high rate capability and long cycle life of the CNTs@NCDHNs are due to a synergistic effect. The CNTs@NCDHNs exhibited a high specific capacitance of 1823 F g-1 at a current density of 1 A g-1, and more than 77.6% of the capacitance was retained at a charge-discharge rate of 20 A g-1. To evaluate the functional behavior of the CNTs@NCDHNs, quasi-solid-state cells using CNTs@NCDHNs as the positive electrode and rGO-Fe2O3 as the negative electrode were assembled and tested. These devices presented ultrafast charge-discharge rates of up to 20 A g-1 with high rate capabilities and excellent long-term cyclic stability. The corresponding quasi-solid-state device presented a high energy density of up to 54.6 Wh kg-1 at a power density of 1.13 kW kg-1 and an energy density of 35.8 Wh kg-1 at 12.4 kW kg-1 when a voltage in the range 0-1.6 V was applied. Moreover, the device exhibited optimal flexibility, stability, and safety under different extreme conditions.

The development of flexible Cu(In, Ga)Se2 (CIGS) solar cells opens new markets for indoor and outdoor applications, and thus has become one of the major directions for present research. Although the efficiency gap between glass and flexible substrates can now be reduced on a flexible polyimide through KF post-deposition treatment, it still seems difficult to transfer research-level technologies to industrial applications. Therefore, in this article, except for the progress made on different flexible materials, we discuss the feasibility of laser scribing and durability of transparent electrodes on flexible substrates. Finally, we provide an overview of the emerging technologies including cracked selenium sources and lift-off processes that may be applied for other flexible low-temperature substrates in the future.

Doping nonmetal atoms into layered transition metal dichalcogenide MX2 structures has emerged as a promising strategy for enhancing their catalytic activities for the hydrogen evolution reaction. In this study, we developed a new and efficient one-step approach that involves simultaneous plasma-induced doping and exfoliating of MX2 bulk into nanosheets–such as MoSe2, WSe2, MoS2, and WS2 nanosheets–within a short time and at a low temperature (ca. 80 °C). Specifically, by utilizing active plasma that is generated with an asymmetric electrical field during the electrochemical reaction at the surface of the submerged cathode tip, we are able to achieve doping of nitrogen atoms, from the electrolytes, into the semiconducting 2H-MX2 structures during their exfoliation process from the bulk states, forming N-doped MX2. We selected N-doped MoS2 nanosheets for demonstrating their catalytic hydrogen evolution potential. We modulated the electronic and transport properties of the MoS2 structure with the synergy of ...

Direct growth of hierarchically interconnected Ni3S2 nanofibers as binder-free electrodes for high-performance sodium (Na+)-ion batteries was demonstrated by a facile one-step hydrothermal method on a nickel (Ni) foam. The hierarchically interconnected Ni3S2 nanofibers can effectively relieve volume expansion of Ni3S2 and shorten diffusion paths of Na+ ions that can enhance the high electronic conductivity during the electrochemical reaction, yielding high specific capacitance, excellent cycling stability, and outstanding rate capability. As a result, a high discharge specific capacity of 584.2 mAh g–1 at a current density of 0.2 A g–1 in the first sodiation process with a capacity retention of 91.9% after 100 cycles (retains 536.9 mAh g–1) can be achieved. The asymmetric Na+-ion capacitor based on the hierarchically interconnected Ni3S2 nanofibers as binder-free anode materials and the activated carbon as a cathode material exhibits high energy and power density. Interestingly, the conversion reaction me...

Multifunctional electronics featuring optical transparency, portability, mechanical flexibility, light-weight and environment-friendly are of great demands for next-generation smart electronics. Memristor represents one of the important chains in next-generation devices as the information computing and storage component. Here, we design the transparent flexible structure based on van der Waals heteroepitaxial AZO/NiO/AZO/muscovite (ANA/muscovite) for a memristor application. The (ANA/muscovite) memristor satisfies all the hardest requirements of a transparent soft device such as optical transparency over 80% in visible light and high performance with a ON/OFF resistance ratio > 105, stable endurance to 103 cycles and long retention time of 105 s. In addition, the ANA/muscovite memristor can work at various bending radii down to 5 mm, a mechanical bending after 1000 cycles at a curvature with a radius of 6.5 mm and a high temperature up to 185 °C, which deliver a pathway for future applications in flexible transparent smart electronics.

In this work, we create plasma-engineered-1T/2H 3D-hierarchical WSe2 nanoscrews derived from WOx 3D-hierarchical nanoscrews through a low-temperature plasma-assisted selenization process with controlled shapes grown using a glancing angle deposition (GLAD) system. Through a detailed investigation of chemical bonding in WSe2 by XPS and TEM, it was found that hybrids of 1T and 2H phases can be engineered, depending on substrate temperatures under plasma treatment. The GLAD system was exploited to achieve 1D nanostructures to enhance the surface-area-to-volume ratio compared to that of flat films, thus increasing the capacity for sensing applications. Here, WSe2 was chosen as the best sensing material for nitric oxide (NO) gas detection because of its p-type semiconducting properties and effective charge transfer with NO molecules. The performance of WSe2 nanoscrew gas sensors which was closely associated with 1T–2H phases was investigated where the barrier height decreased by the heterojunction of 1T/2H phases in WSe2 exhibiting the best sensing capability at a ratio of 0.41 between 1T and 2H phases was found. The plasma-engineered-1T/2H WSe2 3D-hierarchical nanoscrews exhibited a highly sensitive performance with a response over 40% at 60 ppb at room temperature with a detection limit of approximately ∼15 ppb. Finally, ∼100% response in air using the plasma-engineered-1T/2H WSe2 3D-hierarchical nanoscrews was demonstrated, proving their potential for application as next-generation high-performance gas sensors.

Utilization of light to boost the performance of gas sensors allows us to operate sensor devices at room temperature. Here, we, for the first time, demonstrated an indoor light-activated 3D cone-shaped MoS2 bilayer-based NO gas sensor with ppb-level detection operated at room-temperature. Large-area cone-shaped (CS)-MoS2 bilayers were grown by depositing 2 nm-thick MoO3 layers on a 2'' three-dimensional (3D) cone-patterned sapphire substrate (CPSS) followed by a sulfurization process via chemical vapor deposition. Because the exposed area of MoS2 bilayers is increased by 30%, the CS-MoS2 gas sensor (GS) demonstrated excellent performance with a response of ∼470% and a fast response time of ∼25 s after exposure to 1 ppm of NO gas illuminated by ultraviolet (UV) light with a wavelength of 365 nm. Such extraordinary performance at room temperature is attributed to the enhanced light absorption because of the light scattering effect caused by the 3D configuration and photo-desorption induced by UV illumination. For NO concentrations ranging from 2 ppm down to 0.06 ppm, the CS-MoS2 GS demonstrated a stable sensing behavior with a high response and fast response time (470% and 25 s at 2 ppm NO) because of the light absorption enhanced by the 3D structure and photo-desorption under constant UV illumination. The CS-MoS2 GS exhibits a high sensitivity (∼189.2 R% ppm-1), allowing the detection of NO gas at 0.06 ppm in 130 s. In addition, the 3D cone-shaped structure prolonged the presence of sulfur vapor around MoO3, allowing MoO3 to react with sulfur completely. Furthermore, the CS-MoS2 GS using an indoor lighting to detect NO gas at room temperature was demonstrated for the first time where the CS-MoS2 GS exhibits a stable cycling behavior with a high response (165% at 1 ppm NO) in 50 s; for concentration as low as ∼0.06 ppm, the response of ∼75% in 150 s can be achieved.

Introducing an anti-reflective coating (ARC) is the last step of fabricating Cu(In,Ga)Se2 solar cells with enhanced photo-generated current by reducing the reflectance of visible light. The use of nanostructures in ARC has been intensively investigated because this can prolong the optical path length by a scattering effect or by the formation of a refractive index gradient. Herein, we proposed the use of TiO2 helical nanostructures using glancing angle deposition (GLAD), and then synthesized SiO2 surrounding the helical nanostructures to further decrease the reflectance by producing a refractive index gradient. The optimized values of TiO2 and SiO2 thicknesses are 150 nm and 3 nm determined by the finite-difference time-domain (FDTD) simulation on Cu(In,Ga)Se2 solar cells. The suppression of reflectance led to enhanced light absorption across a broad wavelength range, and boosted the JSC from 20.66 to 22.51 mA cm−2, resulting in improved power conversion efficiency (PCE) from 6.32 to 7.00% after applying the TiO2–SiO2 core–shell nanostructures as the ARC. This 10.75% PCE enhancement suggests that the novel TiO2–SiO2 core–shell nanostructures have great potential as ARC for Cu(In,Ga)Se2 solar cells, and it would be beneficial for development in the photovoltaic field in both research and applications.

Two-dimensional quantum dots have received a lot of attention in recent years due to their fascinating properties and widespread applications in sensors, batteries, white light-emitting diodes, photodetectors, phototransistors, etc. Atomically thin two-dimensional quantum dots derived from graphene, layered transition metal dichalcogenide, and phosphorene have sparked researchers’ interest with their unique optical and electronic properties, such as a tunable energy bandgap, efficient electronic transport, and semiconducting characteristics. In this review, we provide in-depth analysis of the characteristics of two-dimensional quantum dots materials, their synthesis methods, and opportunities and challenges for novel device applications. This analysis will serve as a tipping point for learning about the recent breakthroughs in two-dimensional quantum dots and motivate more scientists and engineers to grasp two-dimensional quantum dots materials by incorporating them into a variety of electrical and optical fields.

Single crystal wafers, such as silicon, are the fundamental carriers of advanced electronic devices. However, these wafers exhibit rigidity without mechanical flexibility, limiting their applications in flexible electronics. Here, we propose a new approach to fabricate 1.5 in. flexible functional zinc oxide (ZnO) single crystal wafers with high electron mobility (>100 cm2 V-1 s-1) and optical transparency (>80%) by a combination of thin-film deposition, a chemical solution method, and surficial treatment. The uniformity of the flexible single crystal wafers is examined by an advanced scanning X-ray diffraction technique and photoluminescence spectroscopy. The transport properties of ZnO flexible single crystal wafers retain their pristine states under various bending conditions, including cyclability and endurability. This approach demonstrates a breakthrough in the fabrication of the flexible single crystal wafers for future flexible optoelectronic applications.

The rechargeable aluminum-ion battery (AIB) is a promising candidate for next-generation high-performance batteries, but its cathode materials require more development to improve their capacity and cycling life. We have demonstrated the growth of MoSe

Triboelectric nanogenerator (TENG) is a new energy technology, which can effectively convert ambient various mechanical energy into electricity by coupling effect of triboelectrification and electrostatic induction, yielding self-powered microelectronic devices. However, the surface charge density of triboelectric materials and the performance degradation and failure of TENG caused by wear are the key bottlenecks for its practical application. Here, we propose a high-performance and long-life TENG for harvesting wind energy that uses polyvinyl chloride/molybdenum disulfide (PVC/MoS2) composite membranes and polyamide (PA) membranes as matching triboelectric materials, and aluminum (Al) sheets with micro-nano structures as electrodes. Adding a small amount of MoS2 with excellent lubricating properties can not only effectively increase the surface charge density of composite films but also improve its wear resistance, which enhances the output performance and extends the life time of the TENG. The optimized TENG can generate an output voltage, current and maximum power up to 398 V, 40 μA and 1.23 mW, respectively, which can power tens of commercial light-emitting diodes (LEDs) and a water thermometer. Moreover, the friction coefficient of PVC after the doping of 2.5 wt % MoS2 is 0.29, which is 19.4% lower than that of pure PVC film, providing a new way to improve the surface charge density and the durability of triboelectric materials.

Thermal hysteresis (TH) is defined as the temperature difference between the melting points and crystallization temperatures of phase-change materials (PCMs). The magnitude of the TH is proportional to the energy loss in a system. In addition, the latent heats of the PCMs cannot be exploited if the TH is beyond the operation temperature range of a system. In this study, Zn/TiO2, Zn/Al2O3, and Zn/SiO2 core-shell microparticles were synthesized and the TH values of the microparticles were examined. The TH for the microparticles was mainly affected by the ramping rate in differential scanning calorimetry, the shell thermal resistance and the required temperature for heterogeneous nucleation. Given that Al2O3 possesses a superior thermal conductivity than that of TiO2 and SiO2, the Zn/Al2O3 core-shell microparticles provided the smallest TH among the three types of microparticles. The heat capacity of the salt can be enhanced by 6.7% by doping with 10 wt% Zn/Al2O3 microparticles while the viscosity increased from 1.3 to 3 cp. The study provided guidelines to modulate the TH of PCMs, and the concept learned from this study can be applied to enhancing the thermal energy storage in various thermal systems.

We demonstrate, for the first time, a new method of fabricating hybrid MoS2/poly(ethyleneimine)-modified graphene oxide (PEI-GO) composites assembled through electrostatically charged interaction between the negatively charged MoS2 nanosheets and positively charged PEI-GO in an aqueous solution. The GO can not only improve the electronic conductivity of the MoS2/PEI-GO composites, leading to an excellent charge-transfer network, but also hamper the restacking of MoS2 nanosheets. The composition ratios between MoS2 and PEI-GO were also optimized with the highest specific capacitance of 153.9 F g–1 where 96.0% of the initial specific capacitance remains after 6800 cycles. The specific capacitance of only 117.5 F g–1 was observed for the pure MoS2 nanosheets, and 68.2% of the initial specific capacitance was achieved after 5000 cycles. The excellent electrochemical performance of the hybrid MoS2/PEI-GO composites was demonstrated by establishing an asymmetric supercapacitor with a MoS2/PEI-GO-based negative ...

Selenium (Se) is one of the potential candidates as photodetector because of its outstanding properties such as high photoconductivity (∼8 × 104 S cm–1), piezoelectricity, thermoelectricity, and nonlinear optical responses. Solution phase synthesis becomes an efficient way to produce Se, but a contamination issue that could deteriorate the electric characteristic of Se should be taken into account. In this work, a facile, controllable approach of synthesizing Se nanowires (NWs)/films via a plasma-assisted growth process was demonstrated at the low substrate temperature of 100 °C. The detailed formation mechanisms of nanowires arrays to thin films at different plasma powers were investigated. Moreover, indium (In) layer was used to enhance the adhesive strength with 50% improvement on a SiO2/Si substrate by mechanical interlocking and surface alloying between Se and In layers, indicating great tolerance for mechanical stress for future wearable devices applications. Furthermore, the direct growth of Se NWs...

In this work, the discovery of an abnormal p-type conductivity in SnSe2 thin films synthesized by a plasma-assisted chemical vapor reaction (PACVR) at a low temperature as low as 150 °C was reported. Due to a thermodynamically driven mechanism, three distinct phases including homogeneous SnSe2 and SnSe as well as a SnSe2/SnSe heterostructure were demonstrated. The SnSe2 homogeneous film was prepared by the PACVR from a thin Sn prelayer at a high substrate temperature on a glass substrate. The SnSe homogeneous film was prepared at a low temperature on a mica substrate regardless of the Sn prelayer thickness. Furthermore, the SnSe2/SnSe heterostructure film was prepared from a thick Sn prelayer on the glass substrate. All of the phases exhibit p-type conducting behavior because of hydrogen doping at the vapor–solid reaction interface during the PACVR. Furthermore, the first experimental evidence of intrinsic thermal conductivities of SnSe2 and SnSe thin film of 2.15 W/(m K) and 0.18 W/(m K), respectively, together with an interfacial thermal conductance of 11.32 MW m−2 K−1 in between, was measured by Raman scattering behaviors. The low thermal conductivity make PACVR-synthesized SnSe2-based thin films feasible for thermoelectric applications. In particular, the SnSe2/SnSe heterostructure is the optimized phase for use in thermoelectric generators owing to not only its low thermal conductivity but also the strong accumulation of holes and phonons near the surface.

Here, we demonstrate the successful synthesis of (1T/2H) MoS2/α-MoO3 heterostructured nanoflowers at a low temperature of 200 °C by a one-step hydrothermal method. By tuning the reaction time under the influence of thiourea and hydrazine hydrate, we established a complete phase-engineered MoS2 with 1T and 2H phases on the surface of α-MoO3. Active sites associated with the phase-engineered (1T/2H) MoS2/α-MoO3 hybrid nanoflowers enable them to exhibit dual roles as a superior dye adsorbent and an electrocatalyst towards the hydrogen evolution reaction. The 2H-rich (1T/2H) MoS2/α-MoO3 hybrid heterostructured nanoflowers prepared at 16 h achieved a high surface area of 37.97 m2 g−1, and 97% of the RhB dye with an initial concentration of 47.9 mg L−1 was removed within 10 min through the adsorption process, which is the highest known removal efficiency reported in the literature. As a hydrogen evolution reaction (HER) electrocatalyst in acidic solution, the 1T-rich (1T/2H) MoS2/α-MoO3 hybrid heterostructured nanoflowers prepared at 12 h exhibited a highly efficient catalytic activity by achieving a low overpotential of 232 mV at a current density of 10 mA cm−2, which is comparable to those of previously reported HER catalysts based on MoS2. Moreover, this sample reached a low Tafel slope of 81 mV dec−1 and was stable when operated for more than 1000 cycles.

A suitable electrocatalyst plays an essential role in room-temperature Na–S (RT/Na–S) batteries owing to the more severe dissolution of polysulfides and sluggish kinetics of the conversion of polysulfides during charging and discharging processes. In this study, a novel MoS2/MoN heterostructure synthesized via NH3 annealing was introduced as an electrocatalyst into RT/Na–S batteries to promote the evolution of polysulfides in the catholyte with an initial specific capacity of 703 mA h g–1 and retains 392 mA h g–1 after 300 cycles. The density-functional theory (DFT) calculations, ex-situ XPS and Raman spectra were utilized to reveal moderate anchoring and the fast redox kinetics of polysulfides, significantly enhancing the cycling performance and electrochemical performance of the RT-Na/S batteries when compared with those of the RT-Na/S batteries containing pure MoS2 or MoN as the catalyst. The work provides a new strategy for guiding the design of high‐performance catalysts with manipulated chemical components and optimized adsorption ability.