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Ambient-condition acetylene hydrogenation to ethylene (AC-AHE) is a promising process for ethylene production with minimal additional energy input, yet remains a great challenge due to the difficulty in the coactivation of acetylene and H2 at room temperature. Herein, we report a highly efficient AC-AHE process over robust sulfur-confined atomic Pd species on tungsten sulfide surface. The catalyst exhibits over 99% acetylene conversion with a high ethylene selectivity of 70% at 25 oC, and a record space-time yield of ethylene of 1123 molC2H4 molPd−1 h−1 under ambient conditions, which is nearly four times that of the typical Pd1Ag3/Al2O3 catalyst, and exhibiting superior stability of over 500 h. We demonstrate that the confinement of Pd-S coordination induces positively-charged atomic Pdδ+, which not only facilitates C2H2 hydrogenation but also promotes C2H4 desorption, thereby enabling a high conversion of C2H2 to C2H4 at room temperature while suppressing over-hydrogenation to C2H6. Ambient-condition acetylene hydrogenation to ethylene (AC-AHE) is a promising process for ethylene production yet remains a challenge. Here the authors report a highly efficient AC-AHE process over robust sulfur-confined atomic Pd species on tungsten sulfide surface, achieving over 99% conversion and 70% selectivity, with a record-breaking ethylene yield and excellent stability exceeding 500 h at 25 °C. [ABSTRACT FROM AUTHOR]

Flexible capacitive pressure sensors play a crucial role in wearable electronics and robotics. However, their susceptibility to environmental noise poses challenges to sensing precision. To mitigate the impact of environmental influences, a sensor capable of producing signals orders of magnitudes larger than the noise becomes essential. One straightforward method to enhance capacitance values involves reducing the thickness of the dielectric layer. Yet, when this reduction reaches nanometer scale, the dielectric layer may become mechanically vulnerable and more importantly, their charge storage capability is compromised due to electron tunneling. To address these challenges, here the naturally formed alumina (Al2O3) on aluminum (Al) surface is employed as a stable and ultra‐thin dielectric layer. Simultaneously, the Schottky effect at the Al‐Al2O3‐carbon black (CB) interface is harnessed to prevent electron tunneling. These strategies collectively yielded a large unit‐area capacitance (UAC) of 50 nF cm−2 and demonstrated high electrical and environmental stability. Furthermore, hollow hemispherical microstructures are incorporated at the interface, resulting in a flexible pressure sensor with high sensitivity (8.6 kPa−1) and a linear response up to 50 kPa. With its simple two‐layer structure, this sensor can be seamlessly integrated in situ and offers commercial‐grade resolution at mN‐level for monitoring human biomechanical signals. [ABSTRACT FROM AUTHOR]

Atomically doping in thin film poses a significant challenge due to the potential for dopant precipitation caused by self‐purification effects. This challenge is particularly pronounced in the case of doping monolayers of photoluminescent transition metal dichalcogenides, where high energy barriers are also required to break the in‐plane bonds between the transition metal (TM) and chalcogen atoms. To address this issue, this study introduces hydroxide ions to adsorb onto the surface of WS2 monolayers. This results in a significant reduction in the formation energy of the TM─S bonds, enabling them to substitute for W sites and overcoming the self‐purification effect of WS2 monolayers. The in‐plane doping of TMs including Cr, Mn, Fe, Co, and Ni atoms is confirmed through precise atomic‐scale chemical imaging using scanning transmission electron microscopy with electron energy loss spectroscopy mapping. Photoluminescence measurements reveal that the band structure of WS2 monolayers can be systematically modulated by different doping metals, owing to their distinct atomic sizes. In addition, the atomically‐doped WS2 monolayers exhibit room‐temperature ferromagnetism, which has never been seen in pristine WS2 monolayers. The modulation of the band structure and the emergence of magnetism in TMs‐doped WS2 monolayers hold significant promise for optoelectronic and magnetoelectric applications. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenides (TMDs) exhibit remarkable properties that are strongly influenced by their atomic structures, as well as by various types of defects and interfaces that can be precisely engineered and controlled. These features make 2D TMDs and TMD‐based materials highly promising for a wide range of applications in electronics, optoelectronics, magnetism, spintronics, catalysis, energy, etc. By providing a comprehensive approach to understand the structure–property–functionality relationship in materials at the atomic scale, electron microscopy, and spectroscopy techniques have emerged as invaluable tools for studying both the static characteristics and dynamic evolutions of 2D TMDs. In this review, the primary focus lies in exploring intrinsic and artificial structures in TMDs and their heterostructures, along with their corresponding properties, through cutting‐edge aberration‐corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). Additionally, recent advancements in the field of in situ visualization and manipulation of 2D TMDs using electron beams are highlighted. It is anticipated that the up‐to‐date overview provided, along with a glimpse into the future development of STEM‐based techniques, will make a substantial contribution to advancing research on 2D materials. [ABSTRACT FROM AUTHOR]

Due to intriguing electrical and optical properties, two-dimensional MoS2 has gained significant attention and emerged as a promising material in photonic and optoelectronic fields. Nevertheless, the intrinsic optical absorption of monolayer MoS2 is limited in the visible region only, restricting applications toward near-infrared (NIR) photodetection. Herein, we engineered the optical properties of MoS2 via alloying with Se to extend its optical absorption to the NIR region, and the phototransistor was fabricated based on monolayer MoS2(1−x)Se2x (x = ∼0.1). When under 780 nm (∼1.59 eV) illumination, the device delivered a photoresponsivity of 75.38 A/W, a specific detectivity of ∼1012 Jones, and an external quantum efficiency up to 11 230%. Additionally, it was revealed by density functional theory calculations that NIR absorption originated from the transition of valence states of sulfur vacancy (Vs) interband energy states between +1 and 0, providing an interband energy level of 1.58 eV away from the conduction band minima. Moreover, alloying of Se can suppress deep-level defects formed via Vs, further boosting device performance. This work has demonstrated high-performance NIR phototransistors based on ternary monolayer MoS2(1−x)Se2x, providing both a viable solution and fundamental mechanisms for NIR-blind MoS2 with extended optical absorption. [ABSTRACT FROM AUTHOR]

The discovery of layered magnetic semiconductor materials has stimulated a search for the magnetic order of atomically thin‐layered materials. However, layer‐controlled growth is difficult because of the high nucleation barrier of the material surface during the few‐layer formation of 2D materials. Herein, a seeding solution method is demonstrated that changes the nucleation mode of seed crystals on the substrate surface by precisely controlling the concentration of metal precursors and promoting the formation of cluster seed nuclei to ensure a sufficient source of metal for subsequent reactions. It is studied that the kinetic and thermodynamic synergy through temperature control is readily to grow VS2 with a tunable layer number. Monolayer VS2 exhibits strong ferromagnetic ordering with a saturation magnetization strength (Ms) of 37 emu per cc and a coercivity (Hc) of 135 Oe at 300 K. Notably, the ferromagnetism of VS2 has layer‐dependent performance of the saturation magnetization and coercivity decreases with increasing number of layers. Monolayer VS2 exhibits typical semiconductor properties in Hall devices. This study broadens the chemical pathway for the tunable synthesis of 2D layered magnetic materials and provides the possibility for the construction of novel spintronic and magnetoelectronic devices. [ABSTRACT FROM AUTHOR]

Two-dimensional materials have been demonstrated as promising toolboxes for optoelectronics. Transition metal carbides and nitrides (MXenes), members of an emerging family of two-dimensional materials, have drawn extensive attention in optoelectronics owing to their excellent conductivity and tunable electronic properties. Herein, a photodetector based on the two-dimensional van der Waals heterostructure of Ti3C2Tx MXene and a MoS2 monolayer was constructed to observe the ambipolar photoresponse, which showed a positive photoresponse in the visible spectrum (500–700 nm) and a negative photoresponse at longer wavelengths (700–800 nm). The device exhibited a high negative responsivity of 1.9 A/W and a detectivity of 2.1 × 1010 Jones under 750 nm light illumination. Detailed experiments demonstrate that the negative photoresponse arises from the heterostructure-induced trap energy level, which confines the excited photoelectrons and leads to an inverse current. This work demonstrates a unique optoelectronic phenomenon in MoS2/MXene heterostructures and provides valuable insights into the development of new photodetection materials. [ABSTRACT FROM AUTHOR]

Monolayer transition metal dichalcogenides (TMDs) show promising potential for next-generation optoelectronics due to excellent light capturing and photodetection capabilities. Photodetectors, as important components of sensing, imaging and communication systems, are able to perceive and convert optical signals to electrical signals. Herein, the large-area and high-quality lateral monolayer MoS2/WS2 heterojunctions were synthesized via the one-step liquid-phase chemical vapor deposition approach. Systematic characterization measurements have verified good uniformity and sharp interfaces of the channel materials. As a result, the photodetectors enhanced by the photogating effect can deliver competitive performance, including responsivity of ~ 567.6 A/W and detectivity of ~ 7.17 × 1011 Jones. In addition, the 1/f noise obtained from the current power spectrum is not conductive to the development of photodetectors, which is considered as originating from charge carrier trapping/detrapping. Therefore, this work may contribute to efficient optoelectronic devices based on lateral monolayer TMD heterostructures. [ABSTRACT FROM AUTHOR]

Miniaturizing van der Waals (vdW) ferroelectric materials to atomic scales is essential for modern devices like nonvolatile memory and sensors. To unlock their full potential, their growth mechanisms, interface effects, and stabilization are preferably investigated, particularly for ultrathin 2D nanosheets with single‐unit cell thickness. This study focuses on Bi2TeO5 (BTO) and utilizes precise control over growth kinetics at the nucleation temperature to create specific interfacial reconfiguration layers. Ultrathin BTO nanosheets with planar ferroelectricity at a single‐unit cell thickness are successfully grown. Atomic‐scale characterization reveals a disordered distribution of elements in the interfacial layer, which buffers strain from lattice mismatch. The theoretical calculations support these observations. Furthermore, this strategy also can be extended to the growth of a variety of 2D ternary oxide nanosheets. This work contributes to a better understanding of growth and stability mechanisms in 2D ultrathin nanosheets. [ABSTRACT FROM AUTHOR]

Highlights: Due to the Se composition and thickness gradient within single MoS2(1−x)Se2x domains, the bandgap of MoS2(1−x)Se2x is gradually tuned from 1.83 to 1.73 eV. The homojunction phototransistors at zero bias deliver a photoresponsivity of 311 mA W−1, a specific detectivity up to ~ 1011 Jones, and an on/off ratio up to ~ 104. The biased devices yield a champion photoresponsivity of 191.5 A W−1, a specific detectivity up to ~ 1012 Jones, and a photoconductive gain of 106–107. Ternary transition metal dichalcogenide alloys with spatially graded bandgaps are an emerging class of two-dimensional materials with unique features, which opens up new potential for device applications. Here, visible–near-infrared and self-powered phototransistors based on spatially bandgap-graded MoS2(1−x)Se2x alloys, synthesized by a simple and controllable chemical solution deposition method, are reported. The graded bandgaps, arising from the spatial grading of Se composition and thickness within a single domain, are tuned from 1.83 to 1.73 eV, leading to the formation of a homojunction with a built-in electric field. Consequently, a strong and sensitive gate-modulated photovoltaic effect is demonstrated, enabling the homojunction phototransistors at zero bias to deliver a photoresponsivity of 311 mA W−1, a specific detectivity up to ~ 1011 Jones, and an on/off ratio up to ~ 104. Remarkably, when illuminated by the lights ranging from 405 to 808 nm, the biased devices yield a champion photoresponsivity of 191.5 A W−1, a specific detectivity up to ~ 1012 Jones, a photoconductive gain of 106–107, and a photoresponsive time in the order of ~ 50 ms. These results provide a simple and competitive solution to the bandgap engineering of two-dimensional materials for device applications without the need for p–n junctions. [ABSTRACT FROM AUTHOR]

The discovery of layered magnetic semiconductor materials has stimulated a search for the magnetic order of atomically thin‐layered materials. However, layer‐controlled growth is difficult because of the high nucleation barrier of the material surface during the few‐layer formation of 2D materials. Herein, a seeding solution method is demonstrated that changes the nucleation mode of seed crystals on the substrate surface by precisely controlling the concentration of metal precursors and promoting the formation of cluster seed nuclei to ensure a sufficient source of metal for subsequent reactions. It is studied that the kinetic and thermodynamic synergy through temperature control is readily to grow VS2 with a tunable layer number. Monolayer VS2 exhibits strong ferromagnetic ordering with a saturation magnetization strength (Ms) of 37 emu per cc and a coercivity (Hc) of 135 Oe at 300 K. Notably, the ferromagnetism of VS2 has layer‐dependent performance of the saturation magnetization and coercivity decreases with increasing number of layers. Monolayer VS2 exhibits typical semiconductor properties in Hall devices. This study broadens the chemical pathway for the tunable synthesis of 2D layered magnetic materials and provides the possibility for the construction of novel spintronic and magnetoelectronic devices. [ABSTRACT FROM AUTHOR]

Evaporation power generators (EPGs) based on natural water evaporation can directly convert heat energy from the surrounding environment into electrical energy. Nevertheless, the commercialization of EPGs faces challenges due to the low charge generation and transport efficiency of single material systems, leading to unsatisfactory open-circuit voltages and short-circuit currents. Here, we systematically prepared molybdenum sulfide (MoS 2 )/porous carbon nanofiber (PCNF) heterogeneous systems by electrospinning and hydrothermal methods. Electron microscope measurements have confirmed the uniform coating of high-crystalline quality MoS 2 nanosheets on PCNF fabrics, and the uneven concave-convex surface increased the specific surface area. MoS 2 covered PCNF fabrics retained excellent hydrophilicity, which was suitable for absorbing water and keeping the surface wet during long-term evaporation. Moreover, layered MoS 2 with rich surface charge improved the charge transfer of the MoS 2 /PCNF fabrics. As a result, the open-circuit voltage and short-circuit current of the EPGs fabricated with MoS 2 /PCNF fabrics were enhanced to 0.25 V and 75 μ A, respectively, in comparison to those based on PCNF fabrics, which demonstrated that the MoS 2 coatings improved the interaction area with water and the charge transfer effect of the EPGs. This heterogeneous combination strategy provides ideas for the preparation of high-performance EPG materials., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)