Catalytic Asymmetric Transfer Hydrogenation of Acylboronates: BMIDA as the Privileged Directing Group.

Developing a general, highly efficient, and enantioselective catalytic method for the synthesis of chiral alcohols is still a formidable challenge. We report in this article the asymmetric transfer hydrogenation (ATH) of N-methyliminodiacetyl (MIDA) acylboronates as a general substrate-independent entry to enantioenriched secondary alcohols. ATH of acyl-MIDA-boronates with (het)aryl, alkyl, alkynyl, alkenyl, and carbonyl substituents delivers a variety of enantioenriched α-boryl alcohols. The latter are used in a range of stereospecific transformations based on the boron moiety, enabling the synthesis of carbinols with two closely related α-substituents, which cannot be obtained with high enantioselectivities using direct asymmetric hydrogenation methods, such as the (R)-cloperastine intermediate. Computational studies illustrate that the BMIDA group is a privileged enantioselectivity-directing group in Noyori-Ikariya ATH compared to the conventionally used aryl and alkynyl groups due to the favorable CH-O attractive electrostatic interaction between the η6-arene-CH of the catalyst and the σ-bonded oxygen atoms in BMIDA. The work expands the domain of conventional ATH and shows its huge potential in addressing challenges in symmetric synthesis.

Regio- and Stereoselective Transfer Hydrogenation of Aryloxy Group-Substituted Unsymmetrical 1,2-Diketones: Synthetic Applications and Mechanistic Studies.

Developing a general method that leads to the formation of different classes of chiral bioactive compounds and their stereoisomers is an attractive but challenging research topic in organic synthesis. Furthermore, despite the great value of asymmetric transfer hydrogenation (ATH) in both organic synthesis and the pharmaceutical industry, the monohydrogenation of unsymmetrical 1,2-diketones remains underdeveloped. Here, we report the aryloxy group-assisted highly regio-, diastereo-, and enantioselective ATH of racemic 1,2-diketones. The work produces a myriad of enantioenriched dihydroxy ketones, and further transformations furnish all eight stereoisomers of diaryl triols, polyphenol, emblirol, and glycerol-type natural products. Mechanistic studies and calculations reveal two working modes of the aryloxy group in switching the regioselectivity from a more reactive carbonyl to a less reactive one, and the potential of ATH on 1,2-diketones in solving challenging synthetic issues has been clearly demonstrated.

LncRNA HEM2ATM improves obesity-associated adipose tissues meta-inflammation and insulin resistance by interacting with heterogeneous nuclear ribonucleoprotein U.

Obesity is a complicated metabolic disease characterized by meta-inflammation in adipose tissues. In this study, we explored the roles of a new long non-coding RNA (lncRNA), HEM2ATM, which is highly expressed in adipose tissue M2 macrophages, in modulating obesity-associated meta-inflammation and insulin resistance. HEM2ATM expression decreased significantly in adipose tissue macrophages (ATMs) obtained from epididymal adipose tissues of high-fat diet (HFD)-induced obese mice. Overexpression of macrophage HEM2ATM improved meta-inflammation and insulin resistance in the adipose tissues of HFD-fed mice. Functionally, HEM2ATM negatively regulated the production of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in macrophages. Mechanistically, HEM2ATM bound to heterogeneous nuclear ribonucleoprotein U (hnRNP U), suppressed hnRNP U translocation from the nucleus to the cytoplasm, hindered the function of cytoplasmic hnRNP U on TNF-α and IL-6 mRNA stabilization, and decreased the secretion of TNF-α and IL-6. Collectively, HEM2ATM is a novel suppressor of obesity-associated meta-inflammation and insulin resistance.

A High-Efficiency Side-Scan Sonar Simulator for High-Speed Seabed Mapping.

Side scan sonar (SSS) is a multi-purpose ocean sensing technology, but due to the complex engineering and variable underwater environment, its research process often faces many uncertain obstacles. A sonar simulator can provide reasonable research conditions for guiding development and fault diagnosis, by simulating the underwater acoustic propagation and sonar principle to restore the actual experimental scenarios. However, the current open-source sonar simulators gradually lag behind mainstream sonar technology; therefore, they cannot be of sufficient assistance, especially due to their low computational efficiency and unsuitable high-speed mapping simulation. This paper presents a sonar simulator based on a two-level network architecture, which has a flexible task scheduling system and extensible data interaction organization. The echo signal fitting algorithm proposes a polyline path model to accurately capture the propagation delay of the backscattered signal under high-speed motion deviation. The large-scale virtual seabed is the operational nemesis of the conventional sonar simulators; therefore, a modeling simplification algorithm based on a new energy function is developed to optimize the simulator efficiency. This paper arranges several seabed models to test the above simulation algorithms, and finally compares the actual experiment results to prove the application value of this sonar simulator.

Enhancement of Visible-Light-Driven Hydrogen Evolution Activity of 2D π-Conjugated Bipyridine-Based Covalent Organic Frameworks via Post-Protonation.

Photocatalytic hydrogen (H2 ) evolution represents a promising and sustainable technology. Covalent organic frameworks (COFs)-based photocatalysts have received growing attention. A 2D fully conjugated ethylene-linked COF (BTT-BPy-COF) was fabricated with a dedicated designed active site. The introduced bipyridine sites enable a facile post-protonation strategy to fine-tune the actives sites, which results in a largely improved charge-separation efficiency and increased hydrophilicity in the pore channels synergically. After modulating the degree of protonation, the optimal BTT-BPy-PCOF exhibits a remarkable H2 evolution rate of 15.8 mmol g-1 h-1 under visible light, which surpasses the biphenyl-based COF 6 times. By using different types of acids, the post-protonation is proved to be a potential universal strategy for promoting photocatalytic H2 evolution. This strategy would provide important guidance for the design of highly efficient organic semiconductor photocatalysts.

Low-Energy Hydrogen Ions Enable Efficient Room-Temperature and Rapid Plasma Hydrogenation of TiO2 Nanorods for Enhanced Photoelectrochemical Activity.

Hydrogenation is a promising technique to prepare black TiO2 (H-TiO2 ) for solar water splitting, however, there remain limitations such as severe preparation conditions and underexplored hydrogenation mechanisms to inefficient hydrogenation and poor photoelectrochemical (PEC) performance to be overcome for practical applications. Here, a room-temperature and rapid plasma hydrogenation (RRPH) strategy that realizes low-energy hydrogen ions of below 250 eV to fabricate H-TiO2 nanorods with controllable disordered shell, outperforming incumbent hydrogenations, is reported. The mechanisms of efficient RRPH and enhanced PEC activity are experimentally and theoretically unraveled. It is discovered that low-energy hydrogen ions with fast subsurface transport kinetics and shallow penetration depth features, enable them to directly penetrate TiO2 via unique multiple penetration pathways to form controllable disordered shell and suppress bulk defects, ultimately leading to improved PEC performance. Furthermore, the hydrogenation-property experiments reveal that the enhanced PEC activity is mainly ascribed to increasing band bending and bulk defect suppression, compared to reported H-TiO2 , a superior photocurrent density of 2.55 mA cm-2 at 1.23 VRHE is achieved. These findings demonstrate a sustainable strategy which offers great promise of TiO2 and other oxides to achieve further-improved material properties for broad practical applications.

Multifunctional MoS2 Transistors with Electrolyte Gel Gating.

MoS2 , one of the most valued 2D materials beyond graphene, shows potential for future applications in postsilicon digital electronics and optoelectronics. However, achieving hole transport in MoS2 , which is dominated by electron transport, is always a challenge. Here, MoS2 transistors gated by electrolyte gel exhibit the characteristics of hole and electron transport, a high on/off ratio over 105 , and a low subthreshold swing below 50 mV per decade. Due to the electrolyte gel, the density of electrons and holes in the MoS2 channel reaches ≈9 × 1013 and 8.85 × 1013 cm-2 , respectively. The electrolyte gel-assisted MoS2 phototransistor exhibits adjustable positive and negative photoconductive effects. Additionally, the MoS2 p-n homojunction diode affected by electrolyte gel shows high performance and a rectification ratio over 107 . These results demonstrate that modifying the conductance of MoS2 through electrolyte gel has great potential in highly integrated electronics and optoelectronic photodetectors.

High-performance ß-Ga2O3 thickness dependent solar blind photodetector.

Gallium oxide (Ga2O3) has been studied as one of the most promising wide bandgap semiconductors during the past decade. Here, we prepared high quality ß-Ga2O3 films by pulsed laser deposition. ß-Ga2O3 films of different thicknesses were achieved and their crystal properties were comprehensively studied. As thickness increases, grain size and surface roughness are both increased. Based on these ß-Ga2O3 films, a series of ultraviolet (UV) photodetectors with interdigital electrodes structure were prepared. These devices embrace an ultralow dark current of 100 fA, and high photocurrent on/off ratio of 10E8 under UV light illumination. The photoresponse time is 4 ms which is faster than most of previous works. This work paves the way for the potential application of Ga2O3 in the field of UV detection.

Reliable resistive switching of epitaxial single crystalline cubic Y-HfO2 RRAMs with Si as bottom electrodes.

Previous studies have mainly focused on the resistive switching (RS) of amorphous or polycrystalline HfO2-RRAM. The RS of single crystalline HfO2 films has been rarely reported. Yttrium doped HfO2 (YDH) thin films were fabricated and successful Y incorporation into HfO2 was confirmed by x-ray photoemission spectroscopy. A pure cubic phase of YDH and an abrupt YDH/Si interface were obtained and verified by x-ray diffraction, Raman spectroscopy and transmission electron microscopy. A Pt/YDH/n++-Si heterostructure using Si as the bottom electrode was fabricated, which shows stable RS with an ON/OFF ratio of 100 and a reliable data retention (104 s). The electron transport mechanism was investigated in detail. It indicates that hopping conduction is dominating when the device is at a high resistance state, while space charge limited conduction acts as the dominant factor at a low resistance state. Such behavior, which is different from devices using TiN or Ti as electrodes, was attributed to the Y doping and specific YDH/Si interface. Our results demonstrate a proof of concept study to use highly doped Si as bottom electrodes along with single crystalline YDH as insulator layer for such RRAM applications as wireless sensors and synaptic simulation.

High-Performance Photovoltaic Detector Based on MoTe2 /MoS2 Van der Waals Heterostructure.

Van der Waals heterostructures based on 2D layered materials have received wide attention for their multiple applications in optoelectronic devices, such as solar cells, light-emitting devices, and photodiodes. In this work, high-performance photovoltaic photodetectors based on MoTe2 /MoS2 vertical heterojunctions are demonstrated by exfoliating-restacking approach. The fundamental electric properties and band structures of the junction are revealed and analyzed. It is shown that this kind of photodetectors can operate under zero bias with high on/off ratio (>105 ) and ultralow dark current (≈3 pA). Moreover, a fast response time of 60 µs and high photoresponsivity of 46 mA W-1 are also attained at room temperature. The junctions based on 2D materials are expected to constitute the ultimate functional elements of nanoscale electronic and optoelectronic applications.

Ultrahigh photoresponsivity MoS2 photodetector with tunable photocurrent generation mechanism.

Photodetectors with two-dimensional (2D) materials on a SiO2/Si substrate have been extensively explored. However, these photodetectors often suffer from a large gate voltage and relatively low photoresponsivity due to the low efficiency light absorption of 2D materials. Here, we develop a MoS2 photodetector based on the Al2O3/ITO (indium tin oxide)/SiO2/Si substrate with ultrahigh photoresponsivity of 2.7 × 104 A W-1. Most of the incident light is reflected by the interface of stacked Al2O3/ITO/SiO2 substrate, which significantly increases the light absorption of 2D materials. With the help of thinner and high-κ Al2O3 dielectric, the current ON/OFF ratio could exceed 109 with a gate voltage no more than 2 V. Enhanced gate regulation also brings about a relatively high mobility of 84 cm2 V-1 s-1 and subthreshold swing of 104 mV dec-1. Additionally, two different photocurrent generation mechanisms have also been revealed by tuning the gate voltage. The reflection-enhancement substrate assisted MoS2 photodetector provides a new idea for improving the performance of 2D material photodetectors, which can be perfectly combined with other methods.

The ambipolar evolution of a high-performance WSe2 transistor assisted by a ferroelectric polymer.

In recent years, the electrical characteristics of WSe2 field-effect transistors (FETs) have been widely investigated with various dielectrics. Among them, being able to perfectly tune the polarity of WSe2 is meaningful and promising work. In this work, we systematically study the electrical properties of bilayer WSe2 FETs modulated by ferroelectric polymer poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)). Compared to traditional gate dielectric SiO2, the P(VDF-TrFE) can not only tune both electron and hole concentrations to the same high level, but also improve the hole mobility of bilayer WSe2 to 265.96 cm2 V-1 s-1 under SiO2 gating. Its drain current on/off ratio is also improved to 2 × 105 for p-type and 4 × 105 for n-type driven by P(VDF-TrFE). More importantly, the ambipolar behaviors of bilayer WSe2 are effectively achieved and maintained because of the remnant polarization field of P(VDF-TrFE). This work indicates that WSe2 FETs with P(VDF-TrFE) gating have huge potential for complementary logic transistor applications, and paves an effective way to achieve in-plane p-n junctions.

Graphene Dirac point tuned by ferroelectric polarization field.

Graphene has received numerous attention for future nanoelectronics and optoelectronics. The Dirac point is a key parameter of graphene that provides information about its carrier properties. There are lots of methods to tune the Dirac point of graphene, such as chemical doping, impurities, defects, and disorder. In this study, we report a different approach to tune the Dirac point of graphene using a ferroelectric polarization field. The Dirac point can be adjusted to near the ferroelectric coercive voltage regardless its original position. We have ensured this phenomenon by temperature-dependent experiments, and analyzed its mechanism with the theory of impurity correlation in graphene. Additionally, with the modulation of ferroelectric polymer, the current on/off ratio and mobility of graphene transistor both have been improved. This work provides an effective method to tune the Dirac point of graphene, which can be readily used to configure functional devices such as p-n junctions and inverters.

Interfacial memristors in Al-LaNiO3 heterostructures.

Memristive devices are promising circuit elements that enable novel computational approaches which go beyond the von-Neumann paradigms. Here by tuning the chemistry at the Al-LaNiO3 (LNO) interface, a metal-metal junction, we engineer good switching behavior with good electroresistance (ON-OFF resistance ratios of 100), and repeatable multiple resistance states. The active material responsible for such a behavior is a self-formed sandwich of an AlxOy layer at the interface obtained by grabbing oxygen by Al from LNO. Using aberration corrected electron microscopy and transport measurements, it is confirmed that the memristive hysteresis occurs due to the electric field driven O2- (or ) cycling between LNO (reservoir) and the interlayer, which drives the redox reactions forming and dissolving Al nanoclusters in the AlxOy matrix. This work provides clear insights into and details on precise oxygen control at such interfaces and can be useful for newer opportunities in oxitronics.

Ferroelectric switching of elastin.

Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 µC/cm(2), whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications.

When Nanowires Meet Ultrahigh Ferroelectric Field-High-Performance Full-Depleted Nanowire Photodetectors.

One-dimensional semiconductor nanowires (NWs) have been widely applied in photodetector due to their excellent optoelectronic characteristics. However, intrinsic carrier concentration at certain level results in appreciable dark current, which limits the detectivity of the devices. Here, we fabricated a novel type of ferroelectric-enhanced side-gated NW photodetectors. The intrinsic carriers in the NW channel can be fully depleted by the ultrahigh electrostatic field from polarization of P(VDF-TrFE) ferroelectric polymer. In this scenario, the dark current is significantly reduced and thus the sensitivity of the photodetector is increased even when the gate voltage is removed. Particularly, a single InP NW photodetector exhibits high-photoconductive gain of 4.2 × 10(5), responsivity of 2.8 × 10(5) A W(-1), and specific detectivity (D*) of 9.1 × 10(15) Jones at λ = 830 nm. To further demonstrate the universality of the configuration we also demonstrate ferroelectric polymer side-gated single CdS NW photodetectors with ultrahigh photoconductive gain of 1.2 × 10(7), responsivity of 5.2 × 10(6) A W(-1) and D* up to 1.7 × 10(18) Jones at λ = 520 nm. Overall, our work demonstrates a new approach to fabricate a controllable, full-depleted, and high-performance NW photodetector. This can inspire novel device structure design of high-performance optoelectronic devices based on semiconductor NWs.

Highly sensitive visible to infrared MoTe2 photodetectors enhanced by the photogating effect.

Two-dimensional materials are promising candidates for electronic and optoelectronic applications. MoTe2 has an appropriate bandgap for both visible and infrared light photodetection. Here we fabricate a high-performance photodetector based on few-layer MoTe2. Raman spectral properties have been studied for different thicknesses of MoTe2. The photodetector based on few-layer MoTe2 exhibits broad spectral range photodetection (0.6-1.55 µm) and a stable and fast photoresponse. The detectivity is calculated to be 3.1 × 10(9) cm Hz(1/2) W(-1) for 637 nm light and 1.3 × 10(9) cm Hz(1/2) W(-1) for 1060 nm light at a backgate voltage of 10 V. The mechanisms of photocurrent generation have been analyzed in detail, and it is considered that a photogating effect plays an important role in photodetection. The appreciable performance and detection over a broad spectral range make it a promising material for high-performance photodetectors.

Visible to short wavelength infrared In2Se3-nanoflake photodetector gated by a ferroelectric polymer.

Photodetectors based on two-dimensional (2D) transition-metal dichalcogenides have been studied extensively in recent years. However, the detective spectral ranges, dark current and response time are still unsatisfactory, even under high gate and source-drain bias. In this work, the photodetectors of In2Se3 have been fabricated on a ferroelectric field effect transistor structure. Based on this structure, high performance photodetectors have been achieved with a broad photoresponse spectrum (visible to 1550 nm) and quick response (200 µs). Most importantly, with the intrinsic huge electric field derived from the polarization of ferroelectric polymer (P(VDF-TrFE)) gating, a low dark current of the photodetector can be achieved without additional gate bias. These studies present a crucial step for further practical applications for 2D semiconductors.

Flexible ferroelectric polymer devices based on inkjet-printed electrodes from nanosilver ink.

High-quality silver (Ag) patterns were inkjet-printed with nanosilver ink on a flexible polyethylene terephthalate (PET) substrate. All-solution-processed flexible ferroelectric polymer devices that use inkjet-printed Ag to create their bottom and top electrodes were demonstrated. The active layer, a poly (vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) thin film, was spin-coated from solution. The devices have a remanent polarization of 8.03 µC cm(-2) and a coercive field of 68.5 MV m(-1), which is comparable to the device with evaporated-Ti electrodes on a silicon substrate. Based on the results presented in this paper, mass production of flexible ferroelectric devices is predictable.

Polarization photodetectors with configurable polarity transition enabled by programmable ferroelectric-doping patterns.

Advances in symmetry-breaking engineering of heterointerfaces for optoelectronic devices have garnered significant attention due to their immense potential in tunable moiré quantum geometry and enabling polarization light detection. Despite several proposed approaches to breaking the symmetry of low-dimensional materials, there remains a lack of universal methods to create materials with prominent polarization detection capabilities. Here, we introduce a reliable strategy for manipulating the symmetry of low-dimensional materials through a programmable ferroelectric-doping patterns technique. This method introduces a spontaneous photocurrent and enables the detection of linearly polarization light in isotropic 2H-MoTe2. The 2H-MoTe2 photodetector exhibits a significant short-circuit photocurrent intensity (Jsc = 29.9 A/cm2) and open-circuit voltage Voc of 0.12 V ( ~ 3 × 105 V/cm). Under a specific bias, the polarization ratio transitions from 1 to ∞/-∞, shifting from a positive state (unipolar regime) to a negative state (bipolar regime). These findings underscore the potential of ferroelectric-doping patterns as a promising approach to creating composite materials with artificial bulk photovoltaic effect and achieving high-performance polarization light detection.