Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.     

高碳铬铁在氢氧化钠水溶液中电化学氧化过程

铬铁电化学氧化法是一种新的制备铬酸钠的方法,然而高碳铬铁在NaOH水溶液中的电化学氧化过程尚不明确。 采用循环伏安法(CV)、稳态极化法(LSV)等电化学测试方法对金属铬、高碳铬铁在NaOH水溶液中的电化学氧化过程进行研究,通过扫描电子显微镜(SEM)、能量散射谱(EDS)和X射线光电子能谱(XPS)对高碳铬铁电解后固相产物表征,判断固相产物的组成。 结果表明,高碳铬铁不同于金属铬的电氧化过程,它在NaOH溶液中通过Cr(0)→Cr(Ⅵ)的电氧化方式生成铬酸钠,中间产物Cr(OH)₃和Fe(0)发生电化学反应生成稳定的FeCr₂O₄。 随着NaOH浓度的增加,电势较低时,受高碳铬铁中Fe(0)的影响,高碳铬铁容易在NaOH水溶液中发生钝化;当电势足够正时,钝化膜溶解,生成铬酸钠、氢氧化铁和亚铬酸亚铁,同时,阳极表面有氧气析出。 高碳铬铁电化学氧化制备铬酸钠的适宜条件:碱浓度≥2 mol/L,阳极电势≥1.6 V(vs.SCE)。     

聚对氨基苯磺酸/石墨烯电化学修饰电极检测药物中氧氟沙星

基于石墨烯纳米材料和循环伏安法技术制备了聚对氨基苯磺酸/石墨烯修饰电极并研究了氧氟沙星(OFL)在该修饰电极上的电化学行为,建立了一种简单快速灵敏测定氧氟沙星的电化学分析方法。 结果表明,与玻碳电极相比,对氨基苯磺酸/石墨烯电化学修饰电极能显著提高氧氟沙星的峰电流。 在优化条件下,其检测线性范围为1~600 μmol/L,最低检测限为(S/N=3)0.33μmol/L。 该修饰电极具有较好的重现性和稳定性,用于实际样品氧氟沙星滴眼液的测定,效果良好。     

基于“1+2”模式的结构化学课程在线教学实践

Since the outbreak of novel coronavirus pneumonia (NCP) at the beginning of this year, Chinese government acted immediately and made some regulations to control the epidemic NCP and promote the recovery of society and industry including education. Chinese universities stayed on the online courses without suspension on teaching and learning. Herein, we report online teaching of structural chemistry course based on the teaching mode of online live broadcast platform, online course resources and management platforms ("1 + 2" mode). This may promote online teaching, and take advantage of online live broadcast and massive open online courses, which achieves good teaching and learning experiences on structural chemistry course.     

Design of Two Pyrazole-Based Sensors with Similar Configuration and Different Fluorescent Response to Anions

Two simple fluorescent anion receptors based on 1-phenyl-3-methylpyrozole-5-one-4-one phenylhydrazone (L1) and 1-phenyl-3-methylpyrozole-5-one-4-one p-nitrophenylhydrazone (L2) were designed, synthesized and characterized with ¹H NMR, COSY spectrum, ¹³C NMR, ESI-mass and elemental analyse. Interestingly, two receptors with similar configuration exhibited different anion binding behaviors in DMSO solution. The results of Job plots and ESI-mass spectrum indicate that L1 bind anions such as F⁻, AcO⁻, H₂PO₄⁻ to form 2:1 host-guest complexation, while L2 bind anions to form 1:1 host-guest complexation in the solution.     

Ratiometric and Selective Fluorescent Sensor for F<Superscript>−</Superscript> Based on Intramolecular Charge Transfer (ICT)

A simple colorimetric and ratiometric fluorescent anion sensor 1, was rationally designed and synthesized by facile one-step condensation on basis of the mechanism of intramolecular charge transfer (ICT). The sensor 1 shows more highly and selectively ability to F⁻ that induced the color changes from little yellow to purple, absorption-transferred to long wavelength and emission-transferred to short wavelength. Accordingly, ¹H NMR analysis reveals that the F⁻-induced colorimetric and fluorometric responses of 1 are simply driven by hydrogen bonding interaction between the NH protons and F⁻ ions.     

Analysis and Comparison Constituent of the Essential Oil from Three Different Species of Achillea L. in the Northern Slope of Tianshan Mountains

Moscow University Chemistry Bulletin - The genus Achillea L. (Family: Asteraceae) is a kind of perennial plant, mostly distributed in north western region of China, especially in Tianshan Mountains...     

Selective synthesis of monoclinic and tetragonal phase LaVO<Subscript>4</Subscript> nanorods via oxides-hydrothermal route

Pure monoclinic (m-) and tetragonal (t-) LaVO₄ nanorods are successfully obtained via a facile oxides-hydrothermal method, in which V₂O₅ and La₂O₃ bulk powders are directly utilized as precursors without pretreatment. It is found that ethylenediamine tetraacetic disodium salt (EDTA) is a key factor for synthesizing t-LaVO₄. The as-obtained products are characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED). The FTIR spectra of VO₄ around 800 cm⁻¹ are suggested as an effective auxiliary means to identify the crystal phase of LaVO₄. UV–Visible spectra of LaVO₄ nanomaterials are obvious blue shift compared with the bulk m-LaVO₄ materials. The different photoluminescent properties of Eu³⁺ doped m- and t-LaVO₄ are demonstrated. A dissolution–precipitation mechanism is mainly responsible for the anisotropic morphology and phase control evolution of the LaVO₄ nanocrystals. The oxides-hydrothermal system is also applicable to prepare other pure LnVO₄ (Ln³⁺: Nd³⁺, Y³⁺, Sm³⁺) and doped LnVO₄ nanomaterials.     

ICF瞄准定位系统的设计

将"神光Ⅱ"装置的原瞄准定位系统改为全反射式,可以用各波长的三倍频激光打靶.本文介绍一个双球面的反射系统的光学设计和测试结果.     

相移测量技术中相移器研究

本文介绍一种用于相移测量技术的相移器。该相移器由计算机通过Ｄ／Ａ接口板自动控制输出电压幅度，其电路采用闭环控制，位移由压电晶体产生，具有很高的电压稳定度（０１％）和较小的相移误差（小于３°）。描述相移器的结构、驱动源工作原理及相移器标定方法