Search

Liquid metal‐based printing techniques are emerging as an exemplary platform for harvesting non‐layered 2D materials with a thickness down to a few nanometres, leading to an ultra‐large surface‐area‐to‐volume ratio that is ideal for sensing applications. In this work, the synthesis of 2D tin dioxide (SnO2) by exfoliating the surface oxide of molten tin is reported which highlights the enhanced sensing capability of the obtained materials to ammonia (NH3) gas is reported. It is demonstrated that amperometric gas sensors based on liquid metal‐derived 2D SnO2 nanosheets can achieve excellent NH3 sensing performance at low temperature (150 °C) with and without UV light assistance. Detection over a wide range of NH3 concentrations (5–500 ppm) is observed, revealing a limit of detection at the parts per billion (ppb) level. The 2D SnO2 nanosheets also feature excellent cross‐interference performance toward different organic and inorganic gas species, showcasing a high selectivity. Further, ab initio DFT calculations reveal the NH3 adsorption mechanism is dominated by chemisorption with a charge transfer into 2D SnO2 nanosheets. In addition, a proof of concept for prototype flexible ammonia sensors is demonstrated by depositing 2D SnO2 on a polyimide substrate, signifying the high potential of employing liquid metal printed SnO2 for realizing wearable gas sensors. [ABSTRACT FROM AUTHOR]

Significant progress has been made in recent years in the development of liquid metal alloy catalysts. This article provides an overview of the state‐of‐the‐art research pertaining to liquid metal alloy catalysis, including alloy synthesis, reactor design, and theoretical calculations. Different alloy synthesis methods are discussed with a focus on strategies that can achieve colloidal intermetallic structures in liquid metal alloys. Current reactors for liquid metal‐based electrocatalytic and thermochemical processes are summarized. The application of theoretical tools, such as machine learning and computational chemistry to further liquid metal alloy design, is discussed. Finally, an outlook on the technological challenges and our perspective on future research opportunities for liquid metal alloy catalysis are presented. [ABSTRACT FROM AUTHOR]

Availability of computing will be strongly limited by global energy production in 1–2 decades. Computing consumes 4–5% of global electricity supply and continues to increase. This is underpinned by memory and switching devices encountering leakage as they are downscaled. Two‑dimensional (2D) materials offer a potential solution to the fundamental problem owing to carrier confinement which significantly reduces scattering events. Herein, a mixed ionic‑electronic transport is used in layered black phosphorus (BP) based vertically stacked resistance change memories. The memory device relies on a unique interplay between the oxygen and silver ion diffusion through the stack which is generated using a combination of bottom (electrochemically active silver) and top (indium tin oxide) electrodes. The use of a transparent top‐electrode enabled for the first time to conduct spectroscopic characterization of the device and experimentally reveal fundamental mechanisms. Endurance of the devices are observed to be >104 switching cycles, with ON/OFF current ratio of >107 and standby power consumption of <5 fW, which effectively suppresses leakage current and sneak paths in a memory array. By undertaking detailed microscopic and spectroscopic investigations, supported by theoretical calculations, this work opens opportunities to enhance resistive switching performances of 2D materials for next‑generation information storage and brain‑inspired computation. [ABSTRACT FROM AUTHOR]

The structural characteristics of biological specimens, such as wet proteins and fixed living cells, can be conveniently probed in their host aqueous media using soft X‐rays in the water window region (200–600 eV). Conventional X‐ray detectors in this area exhibit low spatial resolution, have limited sensitivity, and require complex fabrication procedures. Here, many of these limitations are overcome by introducing a direct soft X‐ray detector based on ultrathin tin mono‐sulfide (SnS) nanosheets. The distinguishing characteristic of SnS is its high photon absorption efficiency in the soft X‐ray region. This factor enables the fabricated soft X‐ray detectors to exhibit excellent sensitivity values on the order of 104 μCGyVac−1 cm−2 at peak energies of ≈600 eV. The peak signal is found to be sensitive to the number of stacked SnS layers, with thicker SnS nanosheet assemblies yielding a peak response at higher energies and with peak sensitives of over 2.5 × 104 μCGyVac−1 cm−2 at 1 V. Detailed current–voltage and temporal characteristics of these detectors are also presented. These results showcase the excellent performance of SnS nanosheet‐based soft X‐ray detectors compared to existing direct soft X‐ray detectors, including that of the emerging organic–inorganic perovskite class of materials. [ABSTRACT FROM AUTHOR]

Boronium cation‐based ionic liquids (ILs) have demonstrated high thermal stability and a >5.8 V electrochemical stability window. Additionally, IL‐based electrolytes containing the salt LiTFSI have shown stable cycling against the Li metal anode, the "Holy grail" of rechargeable lithium batteries. However, the basic spectroscopic characterisation needed for further development and effective application is missing for these promising ILs and electrolytes. In this work, attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy and density functional theory (DFT) calculations are used in combination to characterise four ILs and electrolytes based on the [NNBH2]+ and [(TMEDA)BH2]+ boronium cations and the [FSI]− and [TFSI]− anions. By using this combined experimental and computational approach, proper understanding of the role of different ion‐ion interactions for the Li cation coordination environment in the electrolytes was achieved. Furthermore, the calculated vibrational frequencies assisted in the proper mode assignments for the ILs and in providing insights into the spectroscopic features expected at the interface created when they are adsorbed on a Li(001) surface. A reproducible synthesis procedure for [(TMEDA)BH2]+ is also reported. The fundamental findings presented in this work are beneficial for any future studies that utilise IL based electrolytes in next generation Li metal batteries. [ABSTRACT FROM AUTHOR]

Electrolytes that can enable the use of a Li metal anode at a vast 3860 mAh/g, in place of currently used graphite anodes (372 mAh/g), are required for the advancement of next‐generation rechargeable Li batteries. Both quaternary ammonium and boronium (trimethylamine)(dimethylethylamine)dihydroborate [NNBH2]+ cation‐based ionic liquids (ILs) show high electrochemical stability windows and thermal stability for use in Li batteries. Cyclization of the former cation shows improved electrolyte stability compared to the open‐chain counterpart. However, it is not known whether this is the case for the cyclic derivative of [NNBH2]+, N,N,N',N'‐tetramethylethylenediamine)dihydroborate [(TMEDA)BH2]+. Here, the details of the initial stages of solid−electrolyte interphase (SEI) layer formation on a lithium metal surface, Li(001), for the [(TMEDA)BH2]+ based ILs are revealed using density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. These indicate that [(TMEDA)BH2]+ remains intact, displaying a similarly weak interaction with the Li metal surface as the open‐chain analogue. The chemical stability shown by the boronium cation indicates spontaneous and unwanted side reactions with the Li anode are unlikely to occur, which could help to facilitate long‐term cycling stability of the battery. Altogether, the findings suggest the [(TMEDA)BH2]+ ILs, like their [NNBH2]+ IL counterparts, are viable candidates for rechargeable Li metal batteries. [ABSTRACT FROM AUTHOR]

Among the family of elemental 2D materials, antimonene is predicted to have a desirable combination of bandgap tunability and exceptional physical properties. However, there is a lack of a facile synthesis technique to prepare high‐quality antimonene with large aspect ratios on standard SiO2 substrates, hindering wide scale exploration of this material. Here, a physical vapor deposition process to controllably achieve millimeter‐scale, β‐phase, monocrystalline antimonene nanosheets on a SiO2 dielectric substrate is reported. The temperature gradient across the deposition tube is exploited to realize either large‐area nanosheets or single antimonene crystals on‐demand. The composition and quality of the nanosheets and crystals is assessed using spectroscopy, diffraction, and microscopy techniques which suggest the formation of the β‐phase allotrope. The band structure of as‐synthesized nanosheets which matches the theoretically calculated values is experimentally extracted. Finally, contrary to earlier reports, the oxidation of antimonene under ambient conditions over a period of time indicating the need for further experimental studies of the material's stability is revealed. The reported controllable growth of antimonene nanosheets and single crystals on conventional dielectric substrates opens a spectrum of possible applications of this material in electronics and optoelectronics devices. [ABSTRACT FROM AUTHOR]

Calculating vibrational properties of crystals using quantum mechanical (QM) methods is a challenging problem in computational material science. This problem is solved using complementary machine learning methods that rapidly and reliably recapitulate entropy, specific heat, effective polycrystalline dielectric function, and a non‐vibrational property (band gap) for materials calculated by accurate but lengthy QM methods. The materials are described mathematically using property‐labeled materials fragment descriptors. The machine learning models predict the QM properties with root mean square errors of 0.31 meV per atom per K for entropy, 0.18 meV per atom per K for specific heat, 4.41 for the trace of the dielectric tensor, and 0.5 eV for band gap. These models are sufficiently accurate to allow rapid screening of large numbers of crystal structures to accelerate material discovery. [ABSTRACT FROM AUTHOR]

Preharvest sprouting of grains causes significant losses to growers and buyers. The problem occurs throughout the world, and economic losses can be millions of dollars. Visual assessment of germination is ineffective because even grains showing no external signs (e.g., having a visible shoot) may still have germinated sufficiently so that it is no longer possible for high-quality products to be made from them. Current procedures to determine whether a grain has germinated are based around measuring enzyme or starch levels. However, despite protracted efforts to develop enhanced ways to measure germination over the last 50 years, there are currently no sufficiently accurate or reliable approaches available. The present work assesses the potential for infrared spectroscopy-based metabolomic profiling to assess the germination of barley and wheat. The results indicate that mid- and near-infrared spectroscopy are able to determine if the grain has germinated and give an indication of how long the germination process has been occurring. Both techniques are already well established in the grain industry and have the potential to form the basis of a simple, fast dockside test that would allow segregation of sound and mildly sprouted grain. [ABSTRACT FROM AUTHOR]

Optoelectronics: Multifunctional Optoelectronics via Harnessing Defects in Layered Black Phosphorus (Adv. Funct. In article number 1901991, Taimur Ahmed, Sumeet Walia, and co-workers exploit the defect engineering in layered black phosphorus to showcase new opportunities for optoelectronics. Black phosphorus, defect engineering, negative photocurrent, optoelectronics. [Extracted from the article]

Layered black phosphorus (BP), a promising 2D material, tends to oxidize under ambient conditions. While such defective BP is typically considered undesirable, defect engineering has in fact been exploited in contemporary materials to create new behaviors and functionalities. In this spirit, new opportunities arising from intrinsic defect states in BP, particularly through harnessing unique photoresponse characteristics, and demonstrating three distinct optoelectronic applications are demonstrated. First, the ability to distinguish between UV‐A and UV‐B radiations using a single material that has tremendous implications for skin health management is shown. Second, the same device is utilized to show an optically stimulated mimicry of synaptic behavior opening new possibilities in neuromorphic computing. Third, it is shown that serially connected devices can be used to perform digital logic operations using light. The underpinning photoresponse is further translated on flexible substrates, highlighting the viability of the technology for mechanically conformable and wearable systems. This demonstration paves the way toward utilizing the unexplored potential offered by defect engineering of 2D materials for applications spanning across a broad range of disciplines. [ABSTRACT FROM AUTHOR]