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Octahedral molecular sieves (OMSs) based on MnO

With the rapid development of miniaturization, high power and high integration of electronic components, multifunctional materials have attracted tremendous attention. Herein, the multifunctional aramid nanofibers@polypyrrole (ANF@PPy) composite films are prepared through a facile vacuum filtration method after the an in-situ polymerization of PPy on the surface of ANF, which are applied in broadband frequency electromagnetic interference (EMI) shielding, wearable sensor, Joule heating, photothermal conversion. ANF@PPy-4 composite film with thin thickness of 46 µm displays excellent EMI shielding effectiveness (EMI SE) of 35 dB for C-band, X-band, Ku-band and K-band of electromagnetic wave. Furthermore, the relative resistance variation of ANF@PPy-4 composite film can be recorded for monitoring human motions, such as finger, wrist, elbow, knee, ankle, forearm and throat (vocal cord vibration). In addition, the saturation temperature of ANF@PPy-4 composite film is about 77 ºC at a low working voltage of 5.0 V. Moreover, temperature of ANF@PPy-4 composite film can reach to 54 ºC via the photothermal conversion under one sun irradiation. Multifunctional ANF@PPy composite films show enormous potential application of broadband frequency EMI shielding, wearable sensor, personal thermal management.

Controlling the magnetic anisotropy of ferromagnetic materials plays a key role in magnetic switching devices and spintronic applications. Examples of spin-orbit torque devices with different magnetic anisotropy geometries (in-plane or out-of-plane directions) have been demonstrated with novel magnetization switching mechanisms for extended device functionalities. Normally, the intrinsic magnetic anisotropy in ferromagnetic materials is unchanged within a fixed direction, and thus, it is difficult to realize multifunctionality devices. Therefore, continuous modulation of magnetic anisotropy in ferromagnetic materials is highly desired but remains challenging. Here, we demonstrate a gate-tunable magnetic anisotropy transition from out-of-plane to canted and finally to in-plane in layered Fe5GeTe2 by combining the measurements of the angle-dependent anomalous Hall effect and magneto-optical Kerr effect with quantitative Stoner-Wohlfarth analysis. The magnetic easy axis continuously rotates in a spin-flop pathway by gating or temperature modulation. Such observations offer a new avenue for exploring magnetization switching mechanisms and realizing new spintronic functionalities.

GeP5, as the most representative phosphorus-based material in two-dimensional layered phosphorous compounds, has shown a fairly bright application prospect in the field of energy storage because of its ultrahigh electrical conductivity. However, high-yield exfoliation methods and effective structure construction strategies for GeP5 nanosheets are still missing, which completely restricts the further application of GeP5-based nanocomposites. Here, we not only improved the yield of GeP5 nanosheets by a liquid nitrogen-assisted liquid-phase exfoliation technique but also constructed the GeP5@RuO2 nanocomposites with the 0D/2D heterostructure by in situ introduction of ultrafine RuO2 nanoparticles on highly conductive GeP5 nanosheets using a simple hydrothermal synthesis method, and then applying it to micro-supercapacitors (MSCs) as electrode materials through a mask-assisted vacuum filtration technique. It is precisely because of the synergy of the electrical double-layer material, GeP5 nanosheets and the pseudocapacitance material RuO2 nanoparticles that endows the GeP5@RuO2 electrode with outstanding electrochemical performance in micro-supercapacitors with a large specific capacitance of 129.5 mF cm-2/107.9 F cm-3, high energy density of 17.98 μWh cm-2, remarkable long-term cycling stability with 98.4% capacitance retention after 10 000 cycles, the exceptional mechanical stability, outstanding environmental stability, and excellent integration features. This work opens up a new avenue to construct GeP5-based nanocomposites as a most promising novel electrode material for practical application in flexible portable/wearable micro-nanoelectronic devices.

Bimetallic sulfides are expected to realize efficient CO2 electroreduction into formate over a wide potential window, however, will undergo in situ structural evolution under the reaction conditions. Therefore, clarifying the structural evolution process, the real active site and the catalytic mechanism appear significance. Here, taking Cu2SnS3 as an example, we unveiled that Cu2SnS3 occurred self-adapted phase separation toward forming the stable SnO2@CuS and SnO2@Cu2O heterojunction during the electrochemical process. Theoretical calculations illustrated that the strongly coupled interfaces as real active sites driven the electron self-flow from Sn4+ to Cu+, thereby promoting the delocalized Sn sites to combine HCOO* with H*. Cu2SnS3 nanosheets achieve over 83.4% formate selectivity in a wide potential range from -0.6 V to -1.1 V. Our findings provide insight into the structural evolution process and performance-enhanced origin of ternary sulfides under the CO2 electroreduction.

Non-noble metal catalysts now play a key role in promoting efficiently and economically catalytic reduction of CO

Silicon semiconductor technology is approaching its downscaling limit in state-of-the-art electronics. Atomically thin two-dimensional (2D) semiconductors allow exceptional gate electrostatics in field-effect transistors (FETs), thus holding potential as the candidate channel materials beyond silicon. However, it remains challenging to integrate ultrathin and uniform high-κ dielectrics on 2D materials to fabricate FETs with large gate capacitances, though this is highly required to reduce the device operating voltage toward the energy-efficient electronics. Here we report a versatile two-step approach to integrating high-quality dielectric film with sub-1-nm equivalent oxide thickness (EOT) on 2D materials. Inorganic molecular crystal Sb2O3 is homogeneously deposited on 2D materials as a van der Waals buffer layer, which forms a high-quality oxide-to-semiconductor interface and offers a highly hydrophilic surface, enabling the integration of diverse high-κ dielectrics via atomic layer deposition. Using such an approach, we can fabricate monolayer molybdenum disulfide-based FETs with the ever-reported thinnest EOT (0.67 nm). The transistors exhibit an on/off ratio of over 106 using an ultralow operating voltage of 0.4 V, i.e., an unprecedentedly high gating efficiency not matched by any previous FETs. Our results may pave the way for the applications of 2D materials in the future low-power ultra-scaling electronic devices.

Low dimensional semiconductors can be used for various electronic and optoelectronic devices because of their unique structure and property. In this work, one-dimensional Sb2S3 nanowires (NWs) with high crystallinity were grown via chemical vapor deposition (CVD) technique on SiO2/Si substrates. The Sb2S3 NWs exhibited needle-like structures with inclined cross-sections. The lengths of Sb2S3 nanowires changed from 7 to 13 μm. The photodetection properties of Sb2S3 nanowires were comprehensively and systematically characterized. The Sb2S3 photodetectors show a broadband photoresponse ranging from ultraviolet (360 nm) to near-infrared (785 nm). An excellent specific detectivity of 2.1 × 1014 Jones, high external quantum efficiency of 1.5 × 104 %, sensitivity of 2.2 × 104 cm2W−1 and short response time of less than 100 ms was achieved for the Sb2S3 NW photodetectors. Moreover, the Sb2S3 NWs showed outstanding switch cycling stability that was beneficial to the practical applications. The high-quality Sb2S3 nanowires fabricated by CVD have great application potential in semiconductor and optoelectronic fields.

2D functional materials, such as 2D magnet and superconductor, spark massive interests from synthesis, manipulation to application. Especially, FeTex with multi-phases provides an ideal platform to explore the possible superconducting, ferromagnetic or antiferromagnetic properties and even their functional heterostructures. Herein, we report a facile chemical vapor deposition (CVD) approach to synthesize ultrathin tetragonal FeTe (down to monolayer), hexagonal FeTe (down to 2.3 nm), and Fe-rich hexagonal FeTe with superlattice by tuning the growth temperature according to the phase diagram. Scanning transmission electron microscopy (STEM) is further performed to confirm the difference among these various FeTe phases. Magneto-transport illustrates that the tetragonal device displays a high linear magnetoresistance (LMR) up to 10.5% at 1.9 K, and the LMR of hexagonal FeTe reaches 5.8% at 1.9 K. Interestingly, O doped tetragonal thick FeTe displays a superconducting transition at 9 K, which can persist even at 16 T. In summary, this study illustrates a phase-selective synthesis of FeTex ultrathin crystals, providing promising opportunities to construct complicated devices such as ferromagnet/antiferromagnet, magnet/superconductor heterostructures.

Manipulating the catalyst-electrolyte interface to push reactants into the inner Helmholtz plane (IHP) is highly desirable for efficient electrocatalysts, however, it has rarely been implemented due to the elusive electrochemical IHP and inherent inert catalyst surface. Here, we propose the introduction of local force fields by the surface hydroxyl group to engineer the electrochemical microenvironment and enhance alkaline hydrogen evolution activity. Taking a hydroxyl group immobilized Ni/Ni

Pressure, as an independent thermodynamic parameter, is an effective tool to obtain novel material system and exotic physical phenomena not accessible at ambient conditions, because it profoundly modifies the charge, orbital and spin state by reducing the interatomic distance in crystal structure. However, the studies of magnetoelectricity and multiferroicity are rarely extended to high pressure dimension due to properties measured inside the high pressure vessel being a challenge. Here we reported the temperature-magnetic field-pressure magnetoelectric (ME) phase diagram of Y type hexaferrite Ba

The development of stable and low-cost catalysts with high reactivity to replace Pt-based ones is the central focus but challenging for hydrogen evolution reaction (HER). The incorporation of single atoms into two-dimensional (2D) supports has been demonstrated as an effective strategy because of the highly active single atomic sites and extremely large surface area of two-dimensional materials. However, the doping of single atoms is normally performed on the surface suffering from low stability, especially in acidic media. Moreover, it is experimentally challenging to produce monolayered 2D materials with atomic doping. Here, we propose a strategy to incorporate single foreign Fe atoms to substitute W atoms in sandwiched two-dimensional WS2. Because of the charge transfer between the doped Fe atom and its neighboring S atoms on the surface, the proximate S atoms become active for HER. Our theoretical prediction is later verified experimentally, showing an enhanced catalytic reactivity of Fe-doped WS2 in HER with the Volmer-Heyrovsky mechanism involved. We refer to this strategy as proximity catalysis, which is expected to be extendable to more sandwiched two-dimensional materials as substrates and transition metals as dopants.

Li2MnO3, as one traditional member of lithium-rich layered cathodes, gives batteries with large specific capacity. However, it suffers from unexpected severe capacity fading and discharge voltage d...

Two-dimensional (2D) magnetic CrI3 has received considerable research attention because of its intrinsic features, including insulation, Ising ferromagnetism, and stacking-order-dependent magnetism, as well as potential in spintronic applications. However, the current strategy for the production of ambient-unstable CrI3 thin layer is limited to mechanical exfoliation, which normally suffers from uncontrollable layer thickness, small size, and low yet unpredictable yield. Here, via a confined vapor epitaxy (CVE) method, we demonstrate the mass production of flower-like CrI3 monolayers on mica. Interestingly, we discovered the crucial role of K ions on the mica surface in determining the morphology of monolayer CrI3, reacting with precursors to form a KIx buffer layer. Meanwhile, the transport agent affects the thickness and size of the as-grown CrI3. Moreover, the Curie temperature of CrI3 is greatly affected by the interaction between CrI3 and the substrate. The monolayer CrI3 on mica could act as a magnetic substrate for valley Zeeman splitting enhancement of WSe2. We reckon our work represents a major advancement in the mass production of monolayer 2D CrI3 and anticipate that our growth strategy may be extended to other transition metal halides.

As an emerging ultrathin semiconductor material, Bi2O2Se exhibits prominent performances in electronics, optoelectronics, ultrafast optics, etc. However, until now, the in-plane growth of Bi2O2Se thin films is mostly fulfilled on atomically flat mica substrates with interfacial electrostatic forces setting obstacles for Bi2O2Se transfer to fabricate functional van der Waals heterostructures. In this work, controlled growth of inclined Bi2O2Se ultrathin films is realized with apparently reduced interfacial contact areas upon mica flakes. Consequently, the transfer of Bi2O2Se could be facile by overcoming weaker electrostatic interactions. From cross-sectional characterizations at the Bi2O2Se/mica interfaces, it is found that there are no oxide buffer layers in existence for both in-plane and inclined growths, while the un-neutralized charge density is apparently decreased for inclined films. By mechanical pressing, inclined Bi2O2Se could be transferred onto SiO2/Si substrates, and back-gated Bi2O2Se field effect transistors are fabricated, outperforming previously reported in-plane Bi2O2Se devices transferred with the assistance of corrosive acids and adhesive polymers. Furthermore, Bi2O2Se/graphene heterostructures are fulfilled by a probe tip to fabricate hybrid phototransistors with pristine interfaces, exhibiting highly efficient photoresponses. The results in this work demonstrate the potential of inclined Bi2O2Se to act as a building block for prospective van der Waals heterostructures.

Silicon phosphide (SiP) has attracted a great deal of attention in the field of energy storage because of its unique properties of stable semiconducting two-dimensional structure and promising theo...

In spite of extremely high strength and hardness, the property of brittleness is tightly linked to diamond. In the deformation of diamond at room temperature, the plasticity of the diamond is normally considered hard to occur because of the domination of catastrophic brittle fracture. Herein, we employed in-situ transmission electron microscopy to reveal the diamond room-temperature plastic behavior, and compared it with a recent report (Adv. Mater. 2020, 1906458) on transformation-induced room-temperature plasticity of diamond nanopillars. Our present in-situ uniaxial compression tests in sub-micron-sized diamond pillars indicate that the plasticity in diamond is carried out by dislocations slipping instead of phase transformation and the initiation of plasticity highly depends on the stress state. On the other hand, we noted that a high proportion of amorphous surface layer in the diamond pillars with a diameter of less than 20 nm may be a significant factor leading to the plasticity.

In-situ transmission electron microscopy (TEM) has been demonstrated to be a powerful method in resolving challenging problems such as interactions among various defects. To take advantage of the atomic resolution of advanced TEMs, a compact five-degree-of-freedom nanomanipulator was integrated with an indenter that was made of nanotwinned diamonds, for both the in-situ mechanical testing and double tilting of TEM samples. As a demonstration, in-situ bending tests were performed on the (111), (110) and (100) single-crystal diamond needles. The tests revealed the {111} cleavage to be the dominant failure mode. The in-situ indentation on a diamond nanoplate led to curved cracks consisting of nanometer-scale steps, which were identified to be atomic flat {111} facets. The atomic-scale observation of the deformation and failure of diamonds demonstrated the stability of the entire system and the durability of the indenter. We expect that more delicate research can be carried out by means of this holder in the near future, including in-situ stimulation, atomic characterization, and tomography.

The ordering of hydrogen bonds plays a vital role in breaking space inversion symmetry and inducing the paraelectric to ferroelectric phase transition in metal–organic frameworks (MOFs). Magnetic f...

Si poisoning on Al-5Ti-B master alloys has been restraining the effectiveness of grain refinement of hypoeutectic Al-Si casting alloys for over 60 years, and yet the underlying mechanism of this phenomenon remains unclear. In this work, Si poisoning in Al-Si/Al-5Ti-B system was systematically investigated by combining state-of-the-art electron microscopy, first-principles calculations and thermodynamic calculations. Different from the common belief that silicides coat and therefore poison TiB2, this study demonstrates that the segregation of Si atoms at the TiB2/α-Al interface is likely the cause of Si poisoning. Silicide was found to be thermodynamically unfavorable to form even in an alloy with 10 wt.%Si. On the other hand, an appreciable amount of Si (5∼20 at. %) was found to segregate in the TiAl3 two-dimensional compound (2DC) which is critical for triggering the nucleation of α-Al on TiB2. The formation of Ti-Si covalent bond within TiAl3 2DC disturbs its lattice and reduces its chemical interaction with α-Al, which both obstruct the epitaxial nucleation of α-Al and hence leads to Si poisoning. This study suggests that composition engineering of TiAl3 2DC and TiB2 with elements less attractive to Si could be a viable way to mitigate Si poisoning.

A molecule-confined two-dimensional (2D) hybrid superlattice is emerging for uncovering the chemical properties as well as distinctive physical phenomenon arising from the interface electronic stat...

The structures of the various phases endow In2Se3 unique properties as well as a broad range of potential applications. However, the controversy on the structures of In2Se3 strongly hinders the exp...

Domain boundaries in ferroelectric materials exhibit rich and diverse physical properties distinct from their parent materials and have been proposed for broad applications in nanoelectronics and quantum information technology. Due to their complexity and diversity, the internal atomic and electronic structure of domain boundaries that governs the electronic properties remains far from being elucidated. By using scanning tunneling microscopy and spectroscopy (STM/S) combined with density functional theory (DFT) calculations, we directly visualize the atomic structure of polar domain boundaries in two-dimensional (2D) ferroelectric β'-In

Encapsulation is critical for devices to guarantee their stability and reliability. It becomes an even more essential requirement for devices based on 2D materials with atomic thinness and far inferior stability compared to their bulk counterparts. Here a general van der Waals (vdW) encapsulation method for 2D materials using Sb

Oxygen-based anionic redox reactions have recently emerged as a lever to increase the capacity of Mn-rich layered oxide cathodes in addition to the charge compensation based on cationic redox reactions for sodium-ion batteries. Unfortunately, the irreversibility of anionic redox often aggravates irreversible structure change and poor cycling performance. Here, a stable anionic redox is achieved through substituting Na ions by Mg ions in P2-type Na

GeP

Carbon is likely the most fascinating element of the periodic table because of the diversity of its allotropes stemming from its variable (sp, sp2, and sp3) bonding motifs. Exploration of new forms of carbon has been an eternal theme of contemporary scientific research. Here we report on novel amorphous carbon phases containing high fraction of sp3 bonded atoms recovered after compressing fullerene C60 to previously unexplored high pressure and temperature. The synthesized carbons are the hardest and strongest amorphous materials known to date, capable of scratching diamond crystal and approaching its strength which is evidenced by complimentary mechanical tests. Photoluminescence and absorption spectra of the materials demonstrate they are semiconductors with tunable bandgaps in the range of 1.5-2.2 eV, comparable to that of amorphous silicon. A remarkable combination of the outstanding mechanical and electronic properties makes this class of amorphous carbons an excellent candidate for photovoltaic applications demanding ultrahigh strength and wear resistance., 40 pages, 17 figures

The observation of fracture behaviors in perfect and twinned B

Pressure, as an independent thermodynamic parameter, is an effective tool to obtain novel material system and exotic physical phenomena not accessible at ambient conditions, because it profoundly modifies the charge, orbital and spin state by reducing the interatomic distance in crystal structure. However, the studies of magnetoelectricity and multiferroicity are rarely extended to high pressure dimension due to properties measured inside the high pressure vessel being a challenge. Here we reported the temperature-magnetic field-pressure magnetoelectric (ME) phase diagram of Y type hexaferrite Ba0.4Sr1.6Mg2Fe12O22 derived from static pyroelectric current measurement and dynamic magnetodielectric in diamond anvil cell and piston cylinder cell. We found that a new spin-driven ferroelectric phase emerged at P = 0.7 GPa and sequentially ME effect disappeared around P = 4.3 GPa. The external pressure may enhance easy plane anisotropy to destabilize the longitudinal conical magnetic structure with the suppression of ME coefficient. These results offer essential clues for the correlation between ME effect and magnetic structure evolution under high pressure.

Bimetallic sulfides are expected to realize efficient CO

Structural defects play an important role in exploitation of two-dimensional layered materials (2DLMs) for advanced biosensors with the increasingly high sensitivity and low detection limit. Grain boundaries (GBs), as an important type of structural defect in polycrystalline 2DLM films, potentially provide sufficient active defect sites for the immobilization of bioreceptor units via chemical functionalization. In this work, we report the selective functionalization of high-density GBs with complementary DNA receptors, via gold nanoparticle (AuNP) linkers, in wafer-scale polycrystalline monolayer (1L) W(Mo)S

Emerging two-dimensional (2D) layered materials have been attracting great attention as sensing materials for next-generation high-performance biological and chemical sensors. The sensor performance of 2D materials is strongly dependent on the structural defects as indispensable active sites for analyte adsorption. However, controllable defect engineering in 2D materials is still challenging. In the present work, we propose exploitation of controllably grown polycrystalline films of 2D layered materials with high-density grain boundaries (GBs) for design of ultra-sensitive ion sensors, where abundant structural defects on GBs act as favorable active sites for ion adsorption. As a proof-of-concept, our fabricated surface plasmon resonance sensors with GB-rich polycrystalline monolayer WS2 films have exhibited high selectivity and superior attomolar-level sensitivity in Hg2+ detection owing to high-density GBs. This work provides a promising avenue for design of ultra-sensitive sensors based on GB-rich 2D layered materials., Here, the authors report the controlled growth of polycrystalline WS2 films with high density of grain boundaries to realize surface plasmon Hg2+ ion sensors exhibiting attomolar sensitivity and enhanced selectivity.

With the rapid development of wearable electronic and smart electronic devices, the flexible supercapacitors have attracted special attention in energy storage and conversion. Indium selenide (InSe) as a novel two-dimensional layered material has been widely investigated in photodetector, solar cell, and so on due to high electron mobility, anomalous optical response and tuning the bandgap. InSe nanoflakes are obtained from bulk layered InSe materials via a liquid-exfoliation technique and used as electrodes materials of supercapacitors. Flexible all-solid-state supercapacitors (ASSPs) with sandwich structure using InSe nanoflakes have a volumetric capacitance of 3.48 F cm−3 at a scan rate of 0.005 V s−1. For improving the performance of ASSPs based on InSe, highly conductive carbon nanotubes (CNTs) are added into InSe nanoflakes to enhance the conductivity of InSe/CNTs composites used as electrodes of ASSPs. InSe/CNTs (mass ratio 6:1) ASSPs deliver high volumetric capacitance of 25.1 F cm−3 at a scan rate of 0.005 V s−1, good mechanical properties (93.2% capacitance at 180° bending) and long cycle stability (88.3% capacitance after 10000 cycles). In addition, ASSPs based on InSe/CNTs composites exhibit a high power density of 410.15 W cm−3 and a superior energy density of 3.48 mWh cm−3. The InSe/CNTs composite is expected to have a potential candidate in high-performance electrochemical energy storage devices.