2D van der Waals (vdW) magnets, which present intrinsic ferromagnetic/antiferromagnetic ground states at finite temperatures down to atomic‐layer thicknesses, open a new horizon in materials science ...and enable the potential development of new spin‐related applications. The layered structure of vdW magnets facilitates their atomic‐layer cleavability and magnetic anisotropy, which counteracts spin fluctuations, thereby providing an ideal platform for theoretically and experimentally exploring magnetic phase transitions in the 2D limit. With reduced dimensions, the susceptibility of 2D magnets to a large variety of external stimuli also makes them more promising than their bulk counterpart in various device applications. Here, the current status of characterization and tuning of the magnetic properties of 2D vdW magnets, particularly the atomic‐layer thickness, is presented. Various state‐of‐the‐art optical and electrical techniques have been applied to reveal the magnetic states of 2D vdW magnets. Other emerging 2D vdW magnets and future perspectives on the stacking strategy are also given; it is believed that they will excite more intensive research and provide unprecedented opportunities in the field of spintronics.
2D van der Waals (vdW) magnets, which present intrinsic ferromagnetic/antiferromagnetic ground states down to atomiclayer thicknesses, open a new horizon in materials science. Recent state‐of‐the‐art characterization and tuning of the magnetic properties of 2D vdW magnets are outlined. Future perspectives and emerging 2D vdW magnets are also discussed, to provide unprecedented opportunities in the fields of spintronics.
Although only a few 2D materials have been predicted to possess ferroelectricity, 2D ferroelectrics are expected to play a dominant role in the upcoming nano era as important functional materials. ...The ferroelectric properties of 2D ferroelectrics are significantly different than those of traditional bulk ferroelectrics owing to their intrinsic size and surface effects. To date, 2D ferroelectrics have been reported to exhibit diverse properties ranging from bulk photovoltaic and piezoelectric/pyroelectric effects to the spontaneous valley and spin polarization. These properties are either dependent on ferroelectric polarization or coupled with it for easy electric control, thus making 2D ferroelectrics applicable to multifunctional nanodevices. At present, cumulative efforts are being made to explore 2D ferroelectrics in theories, experiments, and applications. Herein, such theories and methods are briefly introduced. Subsequently, intrinsic and extrinsic origins of 2D ferroelectricity are separately summarized. In addition, invented or laboratory‐validated 2D ferroelectric‐based applications are listed. Finally, the existing challenges and prospects of 2D ferroelectrics are discussed.
2D ferroelectrics are expected to play a dominant role in the upcoming nano era as important functional materials. Relevant theories, as well as intrinsic and extrinsic 2D ferroelectrics, are outlined. Further, the existing challenges and prospects of the exploration in 2D ferroelectrics are also discussed, which should provide unprecedented opportunities in the fields of electronics, spintronics, optoelectronics, and valleytronics.
Atomically ordered intermetallic nanoparticles exhibit improved catalytic activity and durability relative to random alloy counterparts. However, conventional methods with time‐consuming and ...high‐temperature syntheses only have rudimentary capability in controlling the structure of intermetallic nanoparticles, hindering advances of intermetallic nanocatalysts. We report a template‐directed strategy for rapid synthesis of Pd‐based (PdM, M=Pb, Sn and Cd) ultrathin porous intermetallic nanosheets (UPINs) with tunable sizes. This strategy uses preformed seeds, which act as the template to control the deposition of foreign atoms and the subsequent interatomic diffusion. Using the oxygen reduction reaction (ORR) as a model reaction, the as‐synthesized Pd3Pb UPINs exhibit superior activity, durability, and methanol tolerance. The favored geometrical structure and interatomic interaction between Pd and Pb in Pd3Pb UPINs are concluded to account for the enhanced ORR performance.
This template‐directed synthetic strategy is a universal route for shape‐controlled synthesis of intermetallic nanocrystals and will provide new opportunities for intermetallic nanocatalysts.
Achieving a desirable combination of solid-like properties and fast self-healing is a great challenge due to slow diffusion dynamics. In this work, we describe a design concept that utilizes weak but ...abundant coordination bonds to achieve this objective. The designed PDMS polymer, crosslinked by abundant Zn(II)-carboxylate interactions, is very strong and rigid at room temperature. As the coordination equilibrium is sensitive to temperature, the mechanical strength of this polymer rapidly and reversibly changes upon heating or cooling. The soft-rigid switching ability σ, defined as G'
/G'
, can reach 8000 when ΔT = 100 °C. Based on these features, this polymer not only exhibits fast thermal-healing properties, but is also advantageous for various applications such as in orthopedic immobilization, conductive composites/adhesives, and 3D printing.
As an emerging subclass of 2D materials, Xenes (e.g., borophene, silicene, germanene, stanene, phosphorene, arsenene, antimonene, and bismuthene) consist of one single element and have opened the ...door for various important applications. Benefiting from their impressive characteristics, including ultrathin folded structure, ultrahigh surface–volume ratio, excellent mechanical strength and flexibility, Xenes are considered as promising electrode materials in the field of electrochemical energy with large capacity, high rate, and high safety. This review provides a comprehensive summary of selected properties, synthetic challenges, and the latest theoretical and experimental advances in the energy‐related applications of Xenes, including Li/Na ion batteries, Li–S batteries, electrocatalysis, and supercapacitors. Finally, the challenges and outlook of this emerging field are discussed.
The 2D monoelemental family (Xenes) and their fundamental electrochemistry are comprehensively reviewed and discussed. Strategies and challenges on engineering heterostructures, defects, encapsulation, modification of Xenes are deeply summarized. The relationship/interaction among fundamental electrochemistry, electrocatalysis, and energy storage (Li/Na ion batteries, Li/Na air batteries, supercapacitors, Li–S battery) is concluded and outlooked.
Type II porous liquids are demonstrated to be promise porous materials. However, the category of porous hosts is very limited. Here, a porous host metal–organic polyhedra (MOP‐18) is reported to ...construct type II porous liquids. MOP‐18 is dissolved into 15‐crown‐5 as an individual cage (5 nm). Both the molecular dynamics simulations and experimental gravimetric CO2 solubility test indicate that the inner cavity of MOP‐18 in porous liquids is unoccupied by 15‐crown‐5 and is accessible to CO2. Thus, the prepared porous liquids show enhanced gas solubility. Furthermore, the prepared porous liquid is encapsulated into graphene oxide (GO) nanoslits to form a GO‐supported porous liquid membrane (GO‐SPLM). Owing to the empty cavity of MOP‐18 unit cages in porous liquids that reduces the gas diffusion barrier, GO‐SPLM significantly enhances the permeability of gas.
A type II porous liquid is constructed by using MOP‐18 and 15‐crown‐5 as the porous host and bulky solvent, respectively. The existence of permanent porosity in porous liquid is confirmed by both the molecular dynamics simulations and experimental date. The unoccupied cavity in the porous liquid can be used for gas storage and facilitating the gas transportation.
The in‐depth understanding of ions' generation and movement inside all‐inorganic perovskite quantum dots (CsPbBr3 QDs), which may lead to a paradigm to break through the conventional von Neumann ...bottleneck, is strictly limited. Here, it is shown that formation and annihilation of metal conductive filaments and Br− ion vacancy filaments driven by an external electric field and light irradiation can lead to pronounced resistive‐switching effects. Verified by field‐emission scanning electron microscopy as well as energy‐dispersive X‐ray spectroscopy analysis, the resistive switching behavior of CsPbBr3 QD‐based photonic resistive random‐access memory (RRAM) is initiated by the electrochemical metallization and valance change. By coupling CsPbBr3 QD‐based RRAM with a p‐channel transistor, the novel application of an RRAM–gate field‐effect transistor presenting analogous functions of flash memory is further demonstrated. These results may accelerate the technological deployment of all‐inorganic perovskite QD‐based photonic resistive memory for successful logic application.
Resistive random‐access memory (RRAM) and RRAM‐functionalized field‐effect transistors (FETs) based on photon tunable CsPbBr3 quantum dots are demonstrated. The formation and annihilation of metal conductive filaments and bromine‐vacancy filaments in CsPbBr3 quantum dot arrays can be realized under an electric field and light irradiation. The devices exhibit multilevel data storage using light tuning, which may accelerate the technological deployment of all‐inorganic perovskite QD‐based photonic memory.
Chiral perovskites have emerged as a significant class of materials showing promising optoelectronic and spintronic applications. Reports of chiral perovskite ferroelectrics, however, have been ...scarce. In this work, we have successfully synthesized homochiral lead–iodide perovskite ferroelectrics (R)‐N‐(1‐phenylethyl)ethane‐1,2‐diaminiumPbI4 and (S)‐N‐(1‐phenylethyl)ethane‐1,2‐diaminiumPbI4 by introducing a methyl group into the organic cation of the parent (N‐benzylethane‐1,2‐diaminium)PbI4. Vibrational circular dichroism spectra identify the chiral mirroring relationship. They both undergo 222F2‐type paraelectric–ferroelectric behavior at around 378 K coupled with clear ferroelastic domain “ON/OFF” switching. Besides, they exhibit an evident thermochromism with color change from orange–yellow to orange–red. To our knowledge, the discovery of integrated ferroelectricity, ferroelasticity, and reversible thermochromism in chiral perovskites is unprecedented.
2D homochiral lead‐iodide perovskites were constructed by the introduction of a chiral center. The perovskites exhibit coexisting ferroelectricity, ferroelasticity, and reversible thermochromism, offering great application prospects for next‐generation smart devices.
The demands for waste heat energy recovery from industrial production, solar energy, and electronic devices have resulted in increasing attention being focused on thermoelectric materials. Over the ...past two decades, significant progress is achieved in inorganic thermoelectric materials. In addition, with the proliferation of wireless mobile devices, economical, efficient, lightweight, and bio‐friendly organic thermoelectric (OTE) materials have gradually become promising candidates for thermoelectric devices used in room‐temperature environments. With the development of experimental measurement techniques, the manufacturing for nanoscale thermoelectric devices has become possible. A large number of studies have demonstrated the excellent performance of nanoscale thermoelectric devices, and further improvement of their thermoelectric conversion efficiency is expected to have a significant impact on global energy consumption. Here, the development of experimental measurement methods, theoretical models, and performance modulation for nanoscale OTE materials are summarized. Suggestions and prospects for the future development of these devices are also provided.
Organic thermoelectric (OTE) devices play an important role in developing novel thermoelectric devices. Here, the progresses of nanoscale OTE devices from the aspects of structural, materials, measurement, and theoretical methods, as well as some typical optimization strategies are reviewed, and an outlook is given to provide an inspiration for the future development of OTE devices.
Existing weakly supervised semantic segmentation (WSSS) methods usually utilize the results of pre-trained saliency detection (SD) models without explicitly modelling the connections between the two ...tasks, which is not the most efficient configuration. Here we propose a unified multi-task learning framework to jointly solve WSSS and SD using a single network, i.e. saliency and segmentation network (SSNet). SSNet consists of a segmentation network (SN) and a saliency aggregation module (SAM). For an input image, SN generates the segmentation result and, SAM predicts the saliency of each category and aggregating the segmentation masks of all categories into a saliency map. The proposed network is trained end-to-end with image-level category labels and class-agnostic pixel-level saliency labels. Experiments on PASCAL VOC 2012 segmentation dataset and four saliency benchmark datasets show the performance of our method compares favorably against state-of-the-art weakly supervised segmentation methods and fully supervised saliency detection methods.
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