Effect of bromine substituent on optical properties of aryl compounds

Substituents significantly affect optical properties of organic compounds. In this study, a series of organic compounds were synthesized. Ultraviolet‐visible and cyclic voltammetry spectra were determined. The relationships between the number of π electron in an aryl ring and the redshift (and molecular orbital energy levels) were studied. To investigate mechanisms of the bromine substituent effects, theoretical calculations were carried out. Ultraviolet‐visible spectra of bromine‐containing compounds exhibit obvious redshifts (0.04‐0.17 eV) of the maximal absorption wavelengths and enhanced absorbance (11%‐57%) compared with corresponding reference compounds. The lowest unoccupied and highest occupied molecular orbital energy levels of compounds containing bromine substituents are 0.05 to 0.60 and 0.02 to 0.40 eV lower than that of corresponding reference compounds. On the whole, the redshifts and the reduced molecular orbital energy levels caused by bromine substituent decrease with the increase in the number of π electron in an aryl ring. The effects would be attributed to strong p‐π conjugation between p electron in the bromine substituent and π electrons in aryl rings. Therefore, this paper suggests a useful way for tuning optical absorption and molecular orbital energy levels of aryl compounds.     

A three‐crystal spectrometer for high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy and X‐ray emission spectroscopy at SSRF

A Johann‐type spectrometer for the study of high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy, X‐ray emission spectroscopy and resonant inelastic X‐ray scattering has been developed at BL14W1 X‐ray absorption fine structure spectroscopy beamline of Shanghai Synchrotron Radiation Facility. The spectrometer consists of three crystal analyzers mounted on a vertical motion stage. The instrument is scanned vertically and covers the Bragg angle range of 71.5–88°. The energy resolution of the spectrometer ranges from sub‐eV to a few eV. The spectrometer has a solid angle of about 1.87 × 0^?3 of 4π sr, and the overall photons acquired by the detector could be 10⁵ counts per second for the standard sample. The performances of the spectrometer are illustrated by the three experiments that are difficult to perform with the conventional absorption or emission spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of hierarchical Na<Subscript>2</Subscript>FeP<Subscript>2</Subscript>O<Subscript>7</Subscript> spheres with high electrochemical performance via spray drying

Hierarchical Na₂FeP₂O₇ spheres with nanoparticles were successfully fabricated by a facile spray drying method. A relatively low drying temperature was introduced in order to form a carbon layer on the surface. As a cathode material for sodium-ion batteries, it delivered a reversible capacity of 84.4 mAh g^?1 at 0.1 C and showed excellent cycling and rate performance (64.7 mAh g^?1 at 5 C). Furthermore, a full sodium battery was fabricated using SP-Na₂FeP₂O₇ as the cathode and hard carbon as the anode, suffering almost no capacity loss after 400 cycles at 1 C. Due to its superior electrochemical property and the low materials cost, Na₂FeP₂O₇ is becoming a promising cathode material for large-scale energy storage systems.     

Vortex glass phase and flux creep in YBa2Cu3O y epitaxial film

Nonlinear I–V characteristics of YBa₂Cu₃O _y epitaxial film at different temperatures in a magnetic field of up to 5T and angles between the direction of the field and the a–b plane of 0°, 30°, 45°, 60°, and 90° were measured. We find that there are the vortex glass phase and vortex liquid phase in the mixed state. The flux creep exists in the vortex glass phase, and it obviously appears in the area around the boundary between the vortex glass phase and the vortex liquid phase.     

DNA damage induced by laser-hematoporphyrin derivative

Irradiation caused DNA single-strand breaks in S180 cells in the presence oflaser-hematoporphyrin derivative(HPD).The number of single strand breaks was 3.69 ×10~(10)break dolton~(-1).The analysis of base composition of DNA showed that the effect of laser-HPDirradiation on guanine was the highest,being 5-12 times as high as those of the three others(adenine,cytosine and thymine).It was different from the nature of DNA damage caused by γ-ray irradiation.     

双路输出超宽谱高功率微波驱动源Tesla变压器

为实现25 GW级双路输出超宽谱高功率微波驱动源的小型化,选择研制了一种与双筒脉冲形成线(Blumlein线)相配一体化的带有开路磁芯的Tesla变压器,作为初级脉冲功率源。进行了Tesla变压器的理论分析,利用简化的磁路模型研究了Tesla变压器初次级线圈电感等电参数的估算方法,给出了Tesla变压器磁芯截面的估算和磁芯制作方法。该Tesla变压器最大输出电压880 kV,充电时间约20 s,耦合系数约0.95,实验结果与理论设计相符。     

First-principles study on the geometric and electronic structures and phase transition of PbZr1-xTixO3 solid solutions

With first-principles virtual-crystal approximation calculations, we systematically investigate the geometric and elec- tronic structures as well as the phase transition of lead zirconate titanate (PbZr1-xTixO3 or PZT) as a function of Ti content for the whole range of 0 ≤ x Ti ≤ 1. It can be found that, with the increase of the Ti content, the PbZr1-xTixO3 solid solu- tions undergo a rhombohedral-to-tetragonal phase transition, which is consistent with the experimental results. In addition, we also show the evolution in geometric and electronic structures of rhombohedral and tetragonal PbZr1-x TixO3 with the increasing content of Ti.     

Simulation of near-infrared photodiode detectors based on β-FeSi_2/4H-SiC heterojunctions

In this paper,we propose a near-infrared p-type β-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide(β-FeSi2) as the active region for the first time.The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature.The results show that the photodetector has a good rectifying character and a good response to near-infrared light.Interface states should be minimized to obtain a lower reverse leakage current.The response spectrum of the β-FeSi2/4H-SiC detector,which consists of a p-type β-FeSi2 absorption layer with a doping concentration of 1×1015cm-3 and a thickness of 2.5 μm,has a peak of 755 mA/W at 1.42 μm.The illumination of the SiC side obtains a higher responsivity than that of the β-FeSi2 side.The results illustrate that the β-FeSi2/4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices.     

饱和铁芯型超导限流器对距离保护的影响

饱和铁芯型超导限流器SCFCL(Saturated Core Superconducting Fault Current Limiter)是一种较为理想的高电压限流器,利用其技术特点可以实现无时限的明显限流作用,有着广泛的运用前景。距离保护能够很好的满足高电压复杂网络快速、精确切除故障的要求,其主要元件阻抗继电器是现阶段普遍应用的高性能继保装置。SCFCL在高压输电网络的接入会对距离保护产生很大影响,运用PSCAD搭建500kV输电线路模型,详细分析限流器接入前后不同短路故障类型及故障距离对线路距离保护的影响。