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Synaptic devices based on 2D materials are being considered as potential solutions to mimic the behavior of synapses in neuromorphic computing.

High-performance silicon anodes with stable cycling and favorable flexibility are achieved by surface modification and structural design.

Molybdenum disulfide (MoS2) based electronic devices, particularly field effect transistors, have outstanding performance.

An optical blackbody is an ideal absorber for all incident optical radiation, and the theoretical study of its radiation spectra paved the way for quantum mechanics (Planck’s law). Herein, we propose the concept of an electron blackbody, which is a perfect electron absorber as well as an electron emitter with standard energy spectra at different temperatures. Vertically aligned carbon nanotube arrays are electron blackbodies with an electron absorption coefficient of 0.95 for incident energy ranging from 1 keV to 20 keV and standard electron emission spectra that fit well with the free electron gas model. Such a concept might also be generalized to blackbodies for extreme ultraviolet, X-ray, and γ -ray photons as well as neutrons, protons, and other elementary particles.

Low-dimensional materials are bringing significant innovations to

The bottom-up approach to directly synthesizing low-dimensional materials with outstanding performance has extended the material basis for the next generation integrated circuit industry. All the low-dimensional semiconductors, metals, dielectrics, and their heterojunctions are very promising bricks to build faster and more efficient chips because of their atomically smooth surface and interfaces. The greatest challenge in the synthesis of nanomaterials is how to precisely control the structure, crystalline orientation, defects, dimensions, etc. In past decades, both the methodology and the mechanism of synthesis have been systematically investigated to improve the controllability. However, few studies focused on sensing the synthesis processes in situ and responding to the synthesis immediately. Here, we propose the concept of intelligent synthesis in which the final product can be automatically fine-controlled by a closed loop including in situ monitoring and real-time interventions. As a model system, a high-temperature-tolerant circuit is fabricated on the single-walled carbon nanotube (SWCNT) growth substrate for sensing and responding to the synthesis processes. As a result, either highly pure semiconducting (s-) SWCNT arrays or metallic-semiconducting (m-s) junction arrays with different junction positions is simply synthesized by programming the responding signal. The intelligent synthesis shows much higher efficiency and controllability compared to conventional methods and will lead to the next leap in nanotechnology.

As a sister compound of MnBi2Te4, the high-quality MnSb2Te4 single crystals are grown via solid-state reaction where prolonged annealing and narrow temperature window play critical roles on account of its thermal metastability. Single-crystal X-ray diffraction (SCXRD) analysis on MnSb2Te4 illustrates a crystal model that is isostructural to MnBi2Te4, consisting of Te-Sb-Te-Mn-Te-Sb-Te septuple layers (SLs) stacking in an ABC sequence. However, MnSb2Te4 reveals a more pronounced cation intermixing in comparison with MnBi2Te4, comprising 28.9(7)% Sb antisite defects on the Mn (3a) site and 19.3(6)% Mn antisite defects on the Sb (6c) site, which may give rise to novel magnetic properties in emerging layered MnBi2Te4-family materials. Unlike the antiferromagnetic (AFM) nature in MnBi2Te4, MnSb2Te4 exhibits a glassy magnetic ground state below 24 K and can be easily tuned to a ferromagnetic state under a weak applied magnetic field. Its magnetic hysteresis, anisotropy, and relaxation process are investigated in detail via static and dynamic magnetization measurements. Moreover, anomalous Hall effect as a p-type conductor is demonstrated with transport measurements. This work grants MnSb2Te4 a possible access to the future exploration of exotic quantum physics by removing the odd/even layer number restraint in realizing quantum transport phenomena in intrinsic AFM MnBi2Te4-family materials, as a result of the crossover between its magnetism and potential topology arising from the Sb-Te layer.

Low-dimensional semiconductors have shown great potential in switches for their atomically thin geometries and unique properties. It is significant to achieve new tunneling transistors by the efficient stacking methodology with low-dimensional building blocks. Here, we report a one-dimensional (1D)-two-dimensional (2D) mixed-dimensional van der Waals (vdW) heterostructure, which was efficiently fabricated by stacking an individual semiconducting carbon nanotube (CNT) and 2D MoS2. The CNT-MoS2 heterostructure shows specific reconfigurable electrical transport behaviors and can be set as a nn junction, pn diode, and band-to-band tunneling (BTBT) transistor by gate voltage. The transport properties, especially BTBT, could be attributed to the electron transfer from MoS2 to CNT through the ideal vdW interface and the 1D nature of the CNT. The progress suggests a new solution for tunneling transistors by making 1D-2D heterostructures from the rich library of low-dimensional nanomaterials. Furthermore, the reconfigurable functions and nanoscaled junction show that it is prospective to apply CNT-MoS2 heterostructures in future nanoelectronics and nano-optoelectronics.

We report the design and simple spray coating fabrication process of a perfect absorber based on carbon nanotubes (CNTs) and carbon black particles with omnidirectional high absorption efficiency beyond 99.9% over the broad wavelength range from 400 nm to 20 μm. The carbon black particles are introduced into the CNT solution to form multi-scale all-carbon-based nanomaterials, effectively modifying the morphology of the sprayed layer to improve the light absorption. The promising absorption characteristics of the CNT–carbon black layer are attributed to not only the intrinsic optical properties of the carbon nanomaterials but also the unique surface nanostructures that efficiently trap light. In addition to serving as absorbers in the coating layer, the CNTs, more importantly, act as connectors between carbon black particles for absorber preparation at a large scale, which is the key to modifying the surface morphology. The all-carbon-based coating layer is also shown to be effective for solar thermal harvesting and self-cleaning function. The developed mixing method for CNTs and carbon black particles in solutions opens a new path for the realization of multi-functional sprayed layers based on CNTs and advances the technology of CNT coatings for scale-up to industry applications.

Lithium metal anodes have a high theoretic capacity and are considered the promising electrodes for high energy density rechargeable batteries. However, the uneven deposition of lithium and lithium dendrites hinders the practical usage of lithium metal anodes. In order to solve this problem, carbon nanotube aerogels coated with amorphous carbon (AC@CNT aerogels) are used as the host, and molten lithium infuses into the carbon aerogels to obtain composite lithium metal anodes. The self-standing, porous AC@CNT aerogels provide a solid structure for lithium deposition/stripping and effectively reduce the local current density, so that lithium dendrites are suppressed and better electrochemical performances are achieved. Compared with the bare lithium metal anodes, the AC@CNT aerogel/lithium metal (AC@CNT/Li) anodes exhibit a longer cycling life of 500 h at deposition/striping capacity of 1 mAh cm−2 on symmetric cells, better cycling performance of 152 mAh g−1 at 0.1C in lithium cobalt oxide/lithium (LCO/Li) cells, and 120.3 mAh g−1 at 1 C in lithium iron phosphate/Li (LFP/Li) cells, demonstrating the potential of the AC@CNT/Li electrodes in developing high-performance lithium-metal batteries.

MoS2 nanomaterials show excellent high theoretical performance in energy storage and hydrogen evolution reaction (HER), whereas they typically suffer from agglomeration and poor electrical conducti...

A much stronger interfacial gating effect was observed in the graphene/HfO2/Si photodetector when compared with that in the graphene/SiO2/Si photodetector. We found that this improvement was due to the higher interface state density at the HfO2/Si interface and the higher dielectric constant of the HfO2 layer. The photoresponsivity of the graphene/HfO2/Si photodetector is as high as 45.8 A W-1. Germanium and amorphous MoS2 (a-MoS2) were used to prepare graphene/HfO2/Ge and graphene/HfO2/a-MoS2 photodetectors, further demonstrating the high efficiency of the interfacial gating mechanism for photodetection. Because of the 0.196 eV bandgap of a-MoS2, which was verified in our previous report, the graphene/HfO2/a-MoS2 photodetector realized ultrabroadband photodetection over the range from 473 nm (visible) to 2712 nm (mid-infrared) at room temperature with photoresponsivity as high as 5.36 A W-1 and response time as fast as 68 μs, which represent significant improvements from the corresponding properties of the pure a-MoS2 photodetectors in our previous report and are comparable with those of state-of-the-art broadband photodetectors. By taking full advantage of the interfacial gating mechanism, a fast response, high photoresponsivity and ultrabroadband photodetection were achieved simultaneously. These interfacial gated graphene photodetectors also offer simple fabrication and full semiconductor process compatibility. The advantages described here indicate that the proposed photodetectors have significant potential for use in electronic and optoelectronic applications and offer a new path toward the development of ultrabroadband photodetectors.

Effective thermal management has become extremely urgent for electronics due to the massive heat originated from the ever-rising power density. With the merits of high thermal conductivity, good chemical stability and desirable mechanical properties, carbon nanotubes (CNTs) are considered to have great potential to be widely used in heat dissipation devices. This article describes the progress on thermal conductivity of CNT-reinforced composites, aligned CNT materials (aligned CNT arrays, films/buckypapers and fibers) as high thermal conductors, experimental and theoretical results of CNT-substrate interface resistance, and utilizations of CNTs in the passive heat dissipation (natural convection, heat radiation, and phase-change heat transfer). Finally, the challenges and prospects are discussed to provide some hints in the future studies. It is believed that CNTs can play an important role in thermal management of electronics, especially in the portable electronic devices.

Aluminum is one of the most promising candidates for metal–air batteries due to its abundance, high specific energy and theoretical voltage. However, the Al–air battery is hindered by a high corrosion rate in an aqueous alkaline solution. In this work, a new type of hybrid device is presented, which combines sandwich-like hydrocapacitor and Al–air battery together using a common polyaniline composite/carbon nanotube (PANI/CNT) electrode. This device works under an all-solid-state condition without adding the electrolyte in advance, which could reduce corrosion greatly, control the initiation and cessation of reactions, and prevent harmful leakage or deformation of the electrolyte completely when it is not used. It could provide a maximum open-circuit voltage of 1.5 V within one minute after adding only a drop of tap water instead of using alkaline and saline electrolyte and maintain over 1 V for more than 3 hours. When another drop of tap water was added, it could start working again. Moreover, daily measurements of the open-circuit voltage of the same device were tested repeatedly for a month and the maximum 1 V could be maintained, which shows circularity and stability. In addition, the integration of the device was also demonstrated using three devices to light up a light-emitting-diode. The performance could still maintain at a high level under bending conditions. The working mechanism is also discussed in this work.

Ultrathin and flexible layers containing BaTiO3 (BTO) nanoparticles, graphene oxide (GO) sheets, and carbon nanotube (CNT) films (BTO/GO@CNT) are used to trap solvated polysulfides and alleviate the shuttle effect in lithium-sulfur (Li-S) batteries. In the functional layers, the CNT films build a conductive framework, and the GO sheets form a support membrane for the uniform dispersion of BTO nanoparticles. BTO nanoparticles without ferroelectricity (nfBTO) can trap polysulfides more effectively by chemical interaction compared to BTO nanoparticles with ferroelectricity (fBTO). A Li-S cell with the nfBTO/GO@CNT functional layer exhibits a reversible capacity of 824.5 mA h g-1 over 100 cycles at 0.2 C. At a high sulfur loading of 5.49 mg cm-2, an electrode with the functional layer shows an areal capacity of 5.15 mA h cm-2 at 0.1 C, demonstrating the nfBTO/GO@CNT functional layer's potential in developing high-performance Li-S batteries.

By using superaligned carbon nanotube (SACNT) macrostructures as reinforcements, the one-step homoepitaxial growth of SACNT/graphite composites was achieved with a home-built experimental setup at temperatures as high as 2600 °C. Compared with traditional furnace heating method, this approach offers the advantages of increased convenience, high throughput and energy efficiency. This high-temperature homoepitaxy strategy was applied to three kinds of structures: SACNT yarn, SACNT film, and SACNT array. Because of the high temperature which exceeded 1800 °C, the samples after high-temperature homoepitaxy showed increased G/D peak area ratios in the Raman spectra, enhanced mechanical properties and improved thermal properties, all of which can meet the requirements of various applications.

Low-dimensional semimetal–semiconductor (Sm-S) van der Waals (vdW) heterostructures have shown their potentials in nanoelectronics and nano-optoelectronics recently. It is an important scientific issue to study the interfacial charge transfer as well as the corresponding Fermi-level shift in Sm-S systems. Here we investigated the gate-tunable contact-induced Fermi-level shift (CIFS) behavior in a semimetal single-walled carbon nanotube (SWCNT) that formed a heterojunction with a transition-metal dichalcogenide (TMD) flake. A resistivity comparison methodology and a Fermi-level catch-up model have been developed to measure and analyze the CIFS, whose value is determined by the resistivity difference between the naked SWCNT segment and the segment in contact with the TMD. Moreover, the relative Fermi-level positions of SWCNT and two-dimensional (2D) semiconductors can be efficiently reflected by the gate-tunable resistivity difference. The work function change of the semimetal, as a result of CIFS, will naturally introduce a modified form of the Schottky–Mott rule, so that a modified Schottky barrier height can be obtained for the Sm-S junction. The methodology and physical model should be useful for low-dimensional reconfigurable nanodevices based on Sm-S building blocks.

Three dimensional TiO2–Au cross-nanoporous structure (3D TiO2–Au CNS) as an efficient photoelectrocatalytic system was fabricated using superaligned carbon nanotube films as etching masks and electron-beam evaporation. The 3D TiO2–Au CNS exhibited a broad absorption band in the visible region, and the incident photon-to-current conversion efficiency of 3D TiO2–Au CNS/Ti electrode was 3–4 times higher than that of pure TiO2 electrode. The photocurrent density of the 3D TiO2–Au CNS device was 0.079 mA cm−2 at 0 V vs. Ag/AgCl with a solar irradiance of 100 mW cm−2. This developed preparation method was simple, of high flexibility and can be adopted for mass production due to its low cost and good compatibility with other processing technologies. The 3D TiO2–Au CNS and its preparation method have important value in design of photoelectrocatalytic system for research and practical applications, which may have a potential utility in photocatalytic and other photoelectrocatalytic reactions.

Heat dissipation is a serious limitation for increasingly miniaturized and functionalized electronics, resulting in the continuous need for developing highly efficient cooling methods. Here, utiliz...

Harvesting energy from water movement directly has played a critical role, as water is one of the most common resources in our daily life as well as in our bodies. In this work, a kind of sandwich-...

A strategy to produce sulfur (S) cathodes with ultrahigh areal capacity for lithium-sulfur (Li–S) batteries is proposed. Porous carbon nanotube (CNT) aerogel@Li2S8 cathodes are obtained by dropping Li2S8 solution into the CNT aerogels that are prepared through a freeze-drying method. The three-dimensional (3D) porous structure of the CNT aerogel provides a complete electron transport network and rapid ion transport channels. Moreover, the rich mesoporous structure has an extreme capillary action on the electrolyte. Numerical simulation shows that in a surprisingly short time (2 μs), the electrolyte can be absorbed into the mesopores by capillary action and reach a stable state, limiting the “shuttle effect” of polysulfides. Based on these unique characteristics, the CNT aerogel@Li2S8 cathode exhibits excellent electrochemical performance. With an extremely high areal S loading of 20 mg cm−2, the cathode shows an ultrahigh areal specific capacity of 22.9 mAh cm−2. For the pouch cell with an areal S loading of 10 mg cm−2 and a low electrolyte/sulfur (E/S) ratio of 7.8 μL mg−1, the areal specific capacity reaches a high value of 10.4 mAh cm−2.

It is of great importance to develop new micro-actuators with high performance by optimizing the structures and materials. Here we develop a VO2/Al2O3/CNT eccentric coaxial nanofiber, which can be potentially applied as a micro-actuator. The specific eccentric coaxial structure was efficiently fabricated by conventional thin film deposition methodology with individual CNT templet. Activated by thermal and photothermal stimuli, the as-developed actuator delivers a bidirectional actuation behavior with large amplitudes and an ultra-fast response, ∼ 2.5 mS. A tweezer can be further made by assembling two such nanofibers symmetrically onto a tungsten probe. Clamping and unclamping can be realized by laser stimulus. More experimental and simulation investigations indicated that the actuation behaviors could be attributed to the nanostructured eccentric coaxial geometry, the thermal coefficient mismatch between layers and the fast phase transition of VO2. The micro-actuators will have potentials in micro manipulators, nanoscaled switches, remote controls and other autonomous systems. Furthermore, a large variety of coaxial and eccentric coaxial nanofibers with various functions can also be developed, giving the as-developed methodology more opportunities.

Two-dimensional (2D) heterostructures based on the combination of transition metal dichalcogenides (TMDs) and transition metal oxides (TMOs) have aroused growing attention due to their integrated merits of both components and multiple functionalities. However, nondestructive approaches of constructing TMD-TMO heterostructures are still very limited. Here, we develop a novel type of lateral TMD-TMO heterostructure (NbS2-Nb2O5-NbS2) using a simple lithography-free, direct laser-patterning technique. The perfect contact of an ultrathin TMO channel (Nb2O5) with two metallic TMDs (NbS2) electrodes guarantee strong electrical signals in a two-terminal sensor. Distinct from sensing mechanisms in separate TMOs or TMDs, this sensor works based on the modulation of surface conduction of the ultrathin TMO (Nb2O5) channel through an adsorbed layer of water molecules. The sensor thus exhibits high selectivity and ultrahigh sensitivity for room-temperature detection of NH3 (ΔR/R = 80% at 50 ppm), superior to the reported NH3 sensors based on 2D materials, and a positive temperature coefficient of resistance as high as 15%–20%/°C. Bending-invariant performance and high reliability are also demonstrated in flexible versions of sensors. Our work provides a new strategy of lithography-free processing of novel TMD-TMO heterostructures towards high-performance sensors, showing great potential in the applications of future portable and wearable electronics.

We report the design and simple fabrication process of a perfect absorber based on carbon nanotube films, which enable omnidirectional high absorption efficiency over the wavelength range from 250 nm to 20 μm with polarization independence. The absorber is fabricated using layers of super-aligned carbon nanotube (SACNT) films assembled in a unique manner, which could be easily prepared on stretchable or rigid substrates or suspended. The promising absorption characteristics of the SACNT films were attributed to not only the intrinsic optical properties of the carbon nanomaterials but also the unique surface nanostructures that efficiently trapped light. Moreover, the absorber and its fabrication method exhibit excellent compatibility with various composed materials and treatment processes. Through combination with ultraviolet-curable resist, a robust, ultrathin, and ultralight absorber with good mechanical properties was fabricated on stretchable substrates. The developed fabrication method opens a new path to realize high absorption performance using carbon nanomaterials and the obtained absorber has broad prospects in aerospace and military applications.

Mixed-dimensional van der Waals (vdW) heterostructures composed of one-dimensional (1D) and two-dimensional (2D) materials have exhibited great potential in nanoelectronics and nano-optoelectronics...

Molybdenum dioxide (MoO2) and molybdenum disulfide (MoS2) are considered as promising non-precious metal electrocatalysts for the hydrogen evolution reaction (HER). However, the thermodynamic inactivity of MoO2 and poor conductivity of MoS2 result in unsatisfactory catalytic activities for individual materials. Here we developed a high-performance HER hetero-electrocatalyst of high-valence-cation doped MoS2/MoO2 composites incorporated in carbon nanotube (CNT) foam by a simple one-step synthesis. MoO2 is stably attached and partially sulfurized into MoS2 on CNT foam, which couples the features of abundant active sites of MoS2, good conductivity of MoO2, flexibility and porosity of the CNT foam matrix, and unique doping effects of high-valence cations to synergistically enhance the HER activity. This delicately designed hetero-electrocatalyst thus exhibits low overpotential (62 mV @ η10), small Tafel slope (44 mV dec−1), and extremely high double-layer capacitance (217.9 mF cm−2). The performance remains almost unchanged after hundreds/thousands of times of bending/CV scans, and shows long-term stability at both low and high currents. Experiments and density functional theory calculations suggest that the high-valence-cation doping improves both electrical conductivity and catalytic activity of the materials. This state-of-the-art electrocatalyst can be directly used as an easily processable, flexible, free-standing, and cost-effective electrode without binders in diverse environments.

Transition metal compounds are considered as competitive candidates for efficient noble-metal-free electrocatalysts in overall water splitting. However, a single material generally fails to maintain simultaneous activities in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we developed a hybrid electrocatalyst of a Fe-(NiS2/MoS2)/carbon nanotube (CNT) film by combining composite and doping strategies, followed by a microstructure design of laser-drilled micropores, for high-efficiency overall water splitting and pH-universal HER. The charge transfer between MoS2 and NiS2 synergistically enhances both the HER and OER, and the light Fe doping further promotes the synergistic effect. The microstructure with periodic pores favors the release of bubbles, ensuring long-term stabilities at both low and large current densities without activity degradation. Consequently, Fe-(NiS2/MoS2)/CNT exhibits an ideal voltage, even lower than that of noble-metal electrodes, of 1.51 V at 10 mA cm−2 for overall water splitting in 1 M KOH, with η10 of the HER/OER at 87/234 mV, respectively. As a cathode, it also delivers low η10 values of 98 mV in 0.5 M H2SO4 and 127 mV in 1 M PBS, showing a pH-universal HER activity. Our work provides a comprehensive strategy towards high-efficiency electrocatalysts for overall water splitting, which will find a broad range of green energy applications.

Recently, MnBi2Te4 has been discovered as the first intrinsic antiferromagnetic topological insulator (AFM TI), and will become a promising material to discover exotic topological quantum phenomena. In this work, we have realized the successful synthesis of high-quality MnBi2Te4 single crystals by solid-state reactions. The as-grown MnBi2Te4 single crystal exhibits a van der Waals layered structure, which is composed of septuple Te-Bi-Te-Mn-Te-Bi-Te sequences as determined by powder X-ray diffraction (PXRD) and high-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The magnetic order below 25 K as a consequence of A-type antiferromagnetic interaction between Mn layers in the MnBi2Te4 crystal suggests the unique interplay between antiferromagnetism and topological quantum states. The transport measurements of MnBi2Te4 single crystals further confirm its magnetic transition. Moreover, the unstable surface of MnBi2Te4, which is found to be easily oxidized in air, deserves attention for onging research on few-layer samples. This study on the first AFM TI of MnBi2Te4 will guide the future research on other potential candidates in the MBixTey family (M = Ni, V, Ti, etc.)., Comment: 16 pages, 10 figures

Dendrite formation is an important issue for the metal anode-based battery system. The traditional perception that Mg metal anode does not grow dendrite during operation has been challenged recently. Herein, we investigate the Mg electrodeposition behavior in a 0.3 M all-phenyl-complex (APC) electrolyte and confirm that Mg dendrites are readily formed at high current densities. A semiquantitative model indicates that the Mg-ion concentration on the electrode surface, limited by the intrinsic diffusion coefficient of the Mg cation group, decreases with increasing current density, resulting in an extra concentration polarization. However, Mg deposition at the tip of a protrusion on the electrode surface is hardly affected by the concentration polarization, and thus dendrite growth is more prone to occur at the tips. We find that the addition of LiCl in conventional APC electrolytes can suppress the Mg dendrite formation, mainly as a result of the enhanced Mg cation diffusion coefficient due to the influence of the LiCl additive, rather than the less pronounced electrostatic shield effect provided by Li cations.

As essential units in an artificial neural network (ANN), artificial synapses have to adapt to various environments. In particular, the development of synaptic transistors that can work above 125 °C is desirable. However, it is challenging due to the failure of materials or mechanisms at high temperatures. Here, we report a synaptic transistor working at hundreds of degrees Celsius. It employs monolayer MoS

A strategy of lattice-reversible binary intermetallic compounds of metallic elements is proposed for applications in flexible lithium-ion battery (LIB) anode with high capacity and cycling stability. First, the use of metallic elements can ensure excellent electronic conductivity and high capacity of the active anode substance. Second, binary intermetallic compounds possess a larger initial lattice volume than metallic monomers, so that the problem of volume expansion can be alleviated. Finally, the design of binary intermetallic compounds with lattice reversibility further improves the cycle stability. In this work, the feasibility of this strategy is verified using an indium antimonide (InSb) system. The volumetric expansion and lithium storage mechanism of InSb are investigated by in situ Raman characterization and theoretical calculations. The active material utilization is significantly improved and the growth of In whiskers is inhibited in the micron-sized ball-milled and carbon coated InSb (bInSb@C) anode, which exhibits a reversible capacity of 733.8 mAh g-1 at 0.2 C, and provides a capacity of 411.5 mAh g-1 after 200 cycles at 3 C with an average Coulombic efficiency of 99.95%. This strategy is validated in pouch cells, illustrating the great potential of lattice-reversible binary intermetallic compounds for use as commercial flexible LIB anodes.