The ever‐growing demands for electrical energy storage have stimulated the pursuit of alternative advanced batteries. Zn‐ion batteries (ZIBs) are receiving increased attentions due to the low cost, ...high safety, and high eco‐efficiency. However, it is still a big challenge to develop suitable cathode materials for intercalation of Zn ions. This review provides a timely access for researchers to the recent activities regarding ZIBs. First, cathode materials including various manganese oxides, vanadium compounds, and Prussian blue analogs are summarized with details in crystal structures and Zn ion storage mechanisms. Then, the electrolytes and their influences on the electrochemical processes are discussed. Finally, opinions on the current challenge of ZIBs and perspective to future research directions are provided.
Recent advances in zinc‐ion batteries, especially the cathode materials including Mn‐based, V‐based, and Prussian blue analogs based materials, are comprehensively summarized here. The relationships between crystal structure, reaction mechanism, and electrochemical performance are elaborated.
Abstract
Recently, three-terminal synaptic devices have attracted considerable attention owing to their nondestructive weight-update behavior, which is attributed to the completely separated ...terminals for reading and writing. However, the structural limitations of these devices, such as a low array density and complex line design, are predicted to result in low processing speeds and high energy consumption of the entire system. Here, we propose a vertical three-terminal synapse featuring a remote weight update via ion gel, which is also extendable to a crossbar array structure. This synaptic device exhibits excellent synaptic characteristics, which are achieved via precise control of ion penetration onto the vertical channel through the weight-control terminal. Especially, the applicability of the developed vertical organic synapse array to neuromorphic computing is demonstrated using a simple crossbar synapse array. The proposed synaptic device technology is expected to be an important steppingstone to the development of high-performance and high-density neural networks.
The unique properties of hybrid heterostructures have motivated the integration of two or more different types of nanomaterials into a single optoelectronic device structure. Despite the promising ...features of organic semiconductors, such as their acceptable optoelectronic properties, availability of low‐cost processes for their fabrication, and flexibility, further optimization of both material properties and device performances remains to be achieved. With the emergence of atomically thin 2D materials, they have been integrated with conventional organic semiconductors to form multidimensional heterostructures that overcome the present limitations and provide further opportunities in the field of optoelectronics. Herein, a comprehensive review of emerging 2D–organic heterostructures—from their synthesis and fabrication to their state‐of‐the‐art optoelectronic applications—is presented. Future challenges and opportunities associated with these heterostructures are highlighted.
The hybridization of 2D materials and organic materials represents a promising domain for the realization of improved or unprecedented features in comparison to those of semiconductor devices. This comprehensive review focuses on emerging 2D–organic heterostructures (from their synthesis and fabrication to their state‐of‐the‐art optoelectronic applications) and highlights the future challenges and opportunities associated with these heterostructures.
Recently, MXenes, which are 2D early transition metal carbides and carbonitrides, have attracted wide attention because of their excellent conductivities. Here, the electrode applications of ...Ti2C(OH)xFy, one member of the MXene family, in WSe2 and MoS2 field effect transistors (FETs) are assessed. Kelvin probe force microscopy analysis is performed to determine its work function, which is estimated to be ≈4.98 eV. Devices based on WSe2/Ti2C(OH)xFy and MoS2/Ti2C(OH)xFy heterostructures are fabricated with the mechanical transfer method and their electronic performances evaluated. The temperature‐dependent current–voltage transfer characteristics of the devices are determined to extract their Schottky barrier heights. The hole barrier between WSe2 and Ti2C(OH)xFy is estimated to be ≈0.23 eV and the electron barrier between the MoS2 band and Ti2C(OH)xFy is ≈0.19 eV, which indicates that the pinning effect occurs at the MoS2/Ti2C(OH)xFy interface but not at the WSe2/Ti2C(OH)xFy interface; this difference arises because of the difference between the band structures of WSe2 and MoS2. A complementary metal–oxide–semiconductor inverter based on these electrode properties of Ti2C(OH)xFy with MoS2 (n‐channel) and WSe2 (p‐channel) is fabricated, which demonstrates that Ti2C(OH)xFy is a promising electrode for future nanoelectronics applications.
By using Ti2C(OH)xFy as an electrode for the integration of 2D p‐FET (WSe2) and n‐FET (MoS2), the heights of the hole barriers of WSe2/Ti2C(OH)xFy and MoS2/Ti2C(OH)xFy are determined to be 0.23 eV and 0.19 eV, respectively. A complementary metal–oxide–semiconductor inverter is fabricated, which demonstrates that Ti2C(OH)xFy is a promising electrode for future nanoelectronics applications.
Sessile plants are exposed throughout their existence to environmental abiotic and biotic stress factors, such as cold, heat, salinity, drought, dehydration, submergence, waterlogging, and pathogen ...infection. Chromatin organization affects genome stability, and its dynamics are crucial in plant stress responses. Chromatin dynamics are epigenetically regulated and are required for stress-induced transcriptional regulation or reprogramming. Epigenetic regulators facilitate the phenotypic plasticity of development and the survival and reproduction of plants in unfavorable environments, and they are highly diversified, including histone and DNA modifiers, histone variants, chromatin remodelers, and regulatory non-coding RNAs. They contribute to chromatin modifications, remodeling and dynamics, and constitute a multilayered and multifaceted circuitry for sophisticated and robust epigenetic regulation of plant stress responses. However, this complicated epigenetic regulatory circuitry creates challenges for elucidating the common or differential roles of chromatin modifications for transcriptional regulation or reprogramming in different plant stress responses. Particularly, interacting chromatin modifications and heritable stress memories are difficult to identify in the aspect of chromatin-based epigenetic regulation of transcriptional reprogramming and memory. Therefore, this review discusses the recent updates from the three perspectives-stress specificity or dependence of transcriptional reprogramming, the interplay of chromatin modifications, and transcriptional stress memory in plants. This helps solidify our knowledge on chromatin-based transcriptional reprogramming for plant stress response and memory.
Hybrid metal‐ion capacitors (MICs) (M stands for Li or Na) are designed to deliver high energy density, rapid energy delivery, and long lifespan. The devices are composed of a battery anode and a ...supercapacitor cathode, and thus become a tradeoff between batteries and supercapacitors. In the past two decades, tremendous efforts have been put into the search for suitable electrode materials to overcome the kinetic imbalance between the battery‐type anode and the capacitor‐type cathode. Recently, some transition‐metal compounds have been found to show pseudocapacitive characteristics in a nonaqueous electrolyte, which makes them interesting high‐rate candidates for hybrid MIC anodes. Here, the material design strategies in Li‐ion and Na‐ion capacitors are summarized, with a focus on pseudocapacitive oxide anodes (Nb2O5, MoO3, etc.), which provide a new opportunity to obtain a higher power density of the hybrid devices. The application of Mxene as an anode material of MICs is also discussed. A perspective to the future research of MICs toward practical applications is proposed to close.
Hybrid metal‐ion capacitors are found to deliver high energy density and rapid energy delivery. The material design strategies particularly in pseudocapacitive oxide anodes in Li‐ion and Na‐ion capacitors (LICs and NICs) are systematically discussed. A perspective on the challenges and opportunities of LIC and NIC devices is also presented.
Exploring highly efficient and low‐cost electrocatalysts for electrochemical water splitting is of importance for the conversion of intermediate energy. Herein, the synthesis of dual‐cation (Fe, ...Co)‐incorporated NiSe2 nanosheets (Fe, Co‐NiSe2) and systematical investigation of their electrocatalytic performance for water splitting as a function of the composition are reported. The dual‐cation incorporation can distort the lattice and induce stronger electronic interaction, leading to increased active site exposure and optimized adsorption energy of reaction intermediates compared to single‐cation‐doped or pure NiSe2. As a result, the obtained Fe0.09Co0.13‐NiSe2 porous nanosheet electrode shows an optimized catalytic activity with a low overpotential of 251 mV for oxygen evolution reaction and 92 mV for hydrogen evolution reaction (both at 10 mA cm−2 in 1 m KOH). When used as bifunctional electrodes for overall water splitting, the current density of 10 mA cm−2 is achieved at a low cell voltage of 1.52 V. This work highlights the importance of dual‐cation doping in enhancing the electrocatalyst performance of transition metal dichalcogenides.
Dual‐cation incorporation makes NiSe2 nanosheet a more effective catalyst. Introducing both Fe and Co atoms with an optimal ratio into porous NiSe2 nanosheets causes evident lattice distortion and strong electronic interaction, leading to a more efficient bifunctionality in overall electrochemical water splitting.
Developments in semiconductor technology are propelling the dimensions of devices down to 10 nm, but facing great challenges in manufacture at the sub-10 nm scale. Nanotechnology can fabricate ...nanoribbons from two-dimensional atomic crystals, such as graphene, with widths below the 10 nm threshold, but their geometries and properties have been hard to control at this scale. Here we find that robust ultrafine molybdenum-sulfide ribbons with a uniform width of 0.35 nm can be widely formed between holes created in a MoS2 sheet under electron irradiation. In situ high-resolution transmission electron microscope characterization, combined with first-principles calculations, identifies the sub-1 nm ribbon as a Mo5S4 crystal derived from MoS2, through a spontaneous phase transition. Further first-principles investigations show that the Mo5S4 ribbon has a band gap of 0.77 eV, a Young's modulus of 300GPa and can demonstrate 9% tensile strain before fracture. The results show a novel top-down route for controllable fabrication of functional building blocks for sub-nanometre electronics.
Recently, research interest in brain‐inspired neuromorphic computing based on robust and intelligent artificial neural networks has surged owing to the ability of such technology to facilitate ...massive parallel, low‐power, highly adaptive, and event‐driven computing. Here, a photosynaptic device with a novel weight updating mechanism for high‐speed and low‐power optoelectronic spike processing is proposed, wherein a synaptic weight is controlled by a mixed spike consisting of voltage and light spikes; the light spike, in particular, boosts up the probability of electron detrapping from graphene oxide charge‐trapping layer to the photosensitive indium–gallium–zinc oxide charge‐transporting layer. Compared to electrically operating synaptic device, the magnitude of conductance change in the proposed photosynaptic device increases remarkably from 2.32 to 5.95 nS without degradation of the nonlinearity (potentiation/depression values are changed from 4.24/8 to 5/8). Owing to this enhancement of synaptic operation, the recognition rates for the Modified National Institute of Standards and Technology digit patterns improve from 36% and 49% to 50% and 62% in artificial neural networks using long‐term potentiation/depression characteristics with 20 and 100 weight states, respectively. The proposed photosynaptic device technology capable of optoelectronic spike processing is expected to play a crucial role in the implementation of neuromorphic computing in the future.
A photosynaptic device with a novel weight updating mechanism using a mixed (light + voltage) spike is proposed. The photosynaptic device shows a remarkable increase in the conductance change (∆G) from 2.32 to 5.95 nS in 100 weight states without degradation of the nonlinearity, resulting in the improvement of the recognition rates for the digit patterns from 49% to 62%.
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