Layered Double Hydroxide Nanosheets with Multiple Vacancies Obtained by Dry Exfoliation as Highly Efficient Oxygen Evolution Electrocatalysts

Layered double hydroxides (LDHs) with two-dimensional lamellar structures show excellent electrocatalytic properties. However, the catalytic activity of LDHs needs to be further improved as the large lateral size and thickness of the bulk material limit the number of exposed active sites. However, the development of efficient strategies to exfoliate bulk LDHs into stable monolayer LDH nanosheets with more exposed active sites is very challenging. On the other hand, the intrinsic activity of monolayer LDH nanosheets can be tuned by surface engineering. Herein, we have exfoliated bulk CoFe LDHs into ultrathin LDH nanosheets through Ar plasma etching, which also resulted in the formation of multiple vacancies (including O, Co, and Fe vacancies) in the ultrathin 2D nanosheets. Owing to their ultrathin 2D structure, the LDH nanosheets expose a greater number of active sites, and the multiple vacancies significantly improve the intrinsic activity in the oxygen evolution reaction (OER).     

Generation of Quantum States for Atomic Ensemble via Cavity QED

A scheme is proposed for generating quantum states of atomic ensemble. In this scheme, a beam of three-level atoms in the Λ configuration is trapped in a cavity, then squeezed vacuum state and squeezed coherent state of the atomic ensemble are prepared by choosing different initial states of the system. The scheme is based on the off-resonant interaction between the atom and cavities, so the high-level of the atom is eliminated adiabatically.     

圆弧刃刀具刀尖圆弧精密测量

圆弧刃刀具刀尖圆弧参数会影响加工尺寸精度、表面质量和刀刃耐用度,研磨和测量的精度要求已达微米甚至亚微米级别;针对其本底噪声强、圆弧刃直线刃过度不明显等问题,提出结合形态学闭运算、滑动窗口三点定圆和空间矩法,分步实现圆弧初、精定位;实验结果表明,算法具有较强的抗噪能力,可快速对0.2~0.8 mm的刀尖进行直线刃与圆弧刃正确分离,圆弧半径、圆度误差测量精度达亚微米量级,角度测量精度达0.1°。     

Achieving Pure Green Electroluminescence with CIEy of 0.69 and EQE of 28.2% from an Aza‐Fused Multi‐Resonance Emitter

Pure green emitters are essential for realizing an ultrawide color gamut in next‐generation displays. Herein, by fusing the difficult‐to‐access aza‐aromatics onto B (boron)–N (nitrogen) skeleton, a hybridized multi‐resonance and charge transfer (HMCT) molecule AZA‐BN was successfully synthesized through an effective one‐shot multiple cyclization method. AZA‐BN shows pure green fluorescence with photoluminance quantum yield of 99.7 %. The corresponding green device exhibits a maximum external quantum efficiency and power efficiency of 28.2 % and 121.7 lm W^?1, respectively, with a full width half maximum (FWHM) of merely 30 nm and Commission Internationale de l'Eclairage (CIE) coordinate y of 0.69, representing the purest green bottom‐emitting organic light‐emitting diode.     

Comparison of headspace solid‐phase microextraction and solvent extraction method for the simultaneous analysis of various soil fumigants in soil or water by gas chromatography–mass spectrometry

The quantity of soil fumigants has increased globally that has focused attention on their environmental behavior. However, simultaneous analysis of traces of fumigant residues is often unreported because analysis methods are not readily available to measure them at low concentrations. In this study, typical solvent extraction methods were compared with headspace solid‐phase microextraction methods. Both methods can be used for simultaneously measuring the concentrations of five commonly used soil fumigants in soil or water. The solvent extraction method showed acceptable recovery (76–103%) and intraday relative standard deviations (0.8–11%) for the five soil fumigants. The headspace solid‐phase microextraction method also showed acceptable recovery (72–104%) and precision rates (1.3–17%) for the five soil fumigants. The solvent extraction method was more precise and more suitable for analyzing relatively high fumigant residue levels (0.05–5 μg/g) contained in multiple soil samples. The headspace solid‐phase microextraction method, however, had a much lower limits of detection (0.09–2.52 μg/kg or μg/L) than the solvent extraction method (5.8–29.2 μg/kg), making headspace solid‐phase microextraction most suitable for trace analysis of these fumigants. The results confirmed that the headspace solid‐phase microextraction method was more convenient and sensitive for the determination of fumigants to real soil samples.     

Supramolecular Nanofibers/Hydrogels of the Conjugates of Nucleobase,Saccharide, and Amino Acids

Three new hydrogelators based on the conjugates of three naturally occurring biological building blocks: nucleobase, saccharide, and amino acids, were explored. Being synthesized via a facile solid phase peptide synthesis route, the hydrogelators self‐assemble in water to afford supramolecular nanofibers and hydrogels. Transmission electron microscopy, oscillation rheometry, and circular dichroism reveal that the hydrogels consist of largely helix‐based nanofibers of the widths of 5–12 nm and exhibit storage moduli up to 1 kPa. These hydrogelators also exhibit excellent cell‐compatibility. This work illustrates a new platform for constructing molecular soft materials for nanobiotechnology.     

Super-parallel holographic correlator with optical fixing

Seven thousand five hundred holograms are stored in 15 locations within a bar of Zn:Mn:Fe:LiNbO₃, using a signal beam that propagates along the long axis of the bar. At each location, angular multiplexing is performed with the reference light changing its orientation in two-dimensional space. The same angular multiplexing is repeated at different locations along the long axis of the Zn:Mn:Fe:LiNbO₃ bar. When operating as a holographic correlator, an input image is compared simultaneously with the records stored in all locations within the bar and is recalled accurately.     

Rhodium‐Catalyzed Synthesis of 4‐Bromo‐1,2‐dihydroisoquinolines: Access to Bromonium Ylides by the Intramolecular Reaction of a Benzyl Bromide and an α‐Imino Carbene

Highly functionalized 4‐bromo‐1,2‐dihydroisoquinolines were synthesized from readily available 4‐(2‐(bromomethyl)phenyl)‐1‐sulfonyl‐1,2,3‐triazoles. A bromonium ylide is proposed as the key intermediate, which can be formed by the intramolecular nucleophilic attack of the benzyl bromide on the α‐imino rhodium carbene formed in the presence of the rhodium catalyst.     

无人水面艇模型辨识及其航向非线性控制的研究

为了实现无人艇的自动航向控制,本文采用Z型和回转实验数据,通过递推最小二乘对无人艇的数学模型进行辨识,然后将模型的仿真实验与实船数据进行对比,验证了模型的正确性和合理性.基于Backstepping方法设计非线性航向控制器,借助Lyapunov 函数证明了闭环系统的稳定性.仿真结果表明系统的实际航向能实时的跟踪设定航向,控制器具有良好的动静态特性和鲁棒性.