Tailoring the d‐Band Centers Enables Co4N Nanosheets To Be Highly Active for Hydrogen Evolution Catalysis

Endowing materials with specific functions that are not readily available is always of great importance, but extremely challenging. Co₄N, with its beneficial metallic characteristics, has been proved to be highly active for the oxidation of water, while it is notoriously poor for catalyzing the hydrogen evolution reaction (HER), because of its unfavorable d‐band energy level. Herein, we successfully endow Co₄N with prominent HER catalytic capability by tailoring the positions of the d‐band center through transition‐metal doping. The V‐doped Co₄N nanosheets display an overpotential of 37 mV at 10 mA cm^?2, which is substantially better than Co₄N and even close to the benchmark Pt/C catalysts. XANES, UPS, and DFT calculations consistently reveal the enhanced performance is attributed to the downshift of the d‐band center, which helps facilitate the H desorption. This concept could provide valuable insights into the design of other catalysts for HER and beyond.     

Precise measurement of the micron-scale spot of ultrashort laser pulse based on film scanning

A novel and precise micron-scale nanosecond laser spot measurement based on film-scanning method is presented. The method can be used to measure the spot size, beam profile, and intensity distribution of the pulse.     

Effect of Monomer Composition on the Performance of Polymer‐Stabilized Liquid Crystals with Two‐Step Photopolymerization

Polymer‐stabilized cholesteric liquid crystal (PSCLC) films with broadband reflection based on two‐step photopolymerization are fabricated. Owing to the helical twisting power (HTP) value of the chiral dopant (CD) decreasing with increasing temperature, PSCLC films with broadband reflection are obtained by two‐step polymerization anchoring helical pitch of different length at two different temperature points. The effect of monomer composition on the PSCLC reflection properties before and after polymerization was studied. The results show that the free‐radical monomers with appropriate concentration and cationic monomers with sufficient concentration are vital for the formation of PSCLC films with broadband reflection. In addition, the experiments show that the increase in the functionality and rigidity of the cationic monomer has a positive effect on the broadening of the reflection band. This study can provide guidance and reference for the selection of monomer species and concentration in PSCLC preparation. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1126–1132     

Simultaneous enhancement of efficiency and stability of OLEDs with thermally activated delayed fluorescence materials by modifying carbazoles with peripheral groups

Science China Chemistry - Albeit their high efficiencies, the operational stability of the organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters is...     

Electrochemiluminescence Studies of Phosphorescent Dopant and Host Molecules of Polymer Light-emitting Diodes

Electrochemiluminescence (ECL) from tris(2‐phenylpyridine)irdium [Ir(ppy)₃] was investigated following cross reaction of its anion with oxidized poly(N‐vinyl‐carbazole) (PVK) and its cation with reduced 2‐(4‐biphenylyl)‐5‐(4‐tert‐butyl‐phenyl)‐1,3,4‐oxadiazole (PBD). Both cross reactions show Ir(ppy)₃ emission and the cross reaction of PVK^+·/Ir(ppy)⁻₃ showed the highest ECL intensity. The comparisons of the reaction enthalpy and the energy of Ir(ppy)₃ light emitting shows that reaction between PVK^+· and Ir(ppy)⁻₃ is energy sufficient to populate metal‐to‐ligand charge transfer (MLCT) excited singlet (3.04 eV) of Ir(ppy)₃, while the reaction between Ir(ppy)⁺₃ and PBD^{− ·} is energy efficient to populate MLCT excited triplet (2.4 eV). The ECL result in solution reveals that the energy released from charge transfer between the Ir(ppy)₃ and PVK or PBD is sufficient to produce the excited state of Ir(ppy)₃ in solid polymer light‐emitting diodes (PLEDs) based on PVK:PBD hosts doped by Ir(ppy)₃. These results obtained will provide further insight into charge‐transfer excitation in PLEDs.     

一种多孔配位聚合物的氢键协同客体响应

由硝酸锌、 吡唑-3,5-二羧酸（H₃pzdc）和2-氨基对苯二甲酸（H₂abdc）在溶剂热条件下反应得到一种多孔配位聚合物(Me₂NH₂)[Zn₂(pzdc)(abdc)]·H₂O·DMF(1·g), 其中Me₂NH₂⁺由溶剂N,N-二甲基甲酰胺（DMF）水解得到, 1可视为平行排列的平整带状{Zn₂(pzdc)}⁺链被abdc^2-柱子交错支撑而成的三维多孔框架. 通过脱附/吸附溶剂分子, 中心对称的配位聚合物1·g可以可逆转变成手性的(Me₂NH₂)[Zn₂(pzdc)(abdc)](1′). 单晶结构分析表明, 在客体响应过程中, 基于框架、 抗衡离子和客体分子之间的氢键协作与竞争, 抗衡离子发生了显著的移动 和转动, 导致{Zn₂(pzdc)}⁺链扭曲和转动, 伴随着超过10%的晶胞体积和孔洞率变化. 气体吸附测试表明, 化合物1'对N₂和CO₂存在不同的结构响应行为.     

浅谈实验室自动测试软件的管理

自动测试软件已经成为各检测/校准实验室开展测试工作的重要手段之一,因此如何进一步加强实验室自动测试软件的管理,提高自动测试软件的可靠性,成为各检测/校准实验室急需解决的问题。针对目前各检测/校准实验室自动测试软件开发、使用过程中普遍存在的问题,提出了具体的解决措施。     

Cellulose acetate polymer film modified microstructured polymer optical fiber towards a nitrite optical probe

A novel microstructured polymer optical fiber (MPOF) probe for nitrites (NO₂⁻) detection was made by forming rhodamine 6G (Rh 6G)-doped cellulose acetate (CA) on the side wall of array holes in a MPOF. It was found that the MPOF probe only have a response to nitrites in a certain concentration of sulfuric acid solution. The calibration graph of fluorescence intensity versus nitrites concentration was linear in the range of 2.0 × 10^− 4 g/ml-5.0 × 10^− 3 g/ml. The method possesses ease of chemical modification, low cost design, and potential for direct integration with existing instrumentation, and has been applied to the determination of nitrites in real samples with satisfactory results.     

Applications of Variational Method to Impulsive Fractional Differential Equations with Two Control Parameters

In this paper, we study the existence of the impulsive fractional di?erential equation. Based on a previous paper [2], we give more accurate condition to guarantee the impulsive fractional di?erential equation has at least three solutions under certain assumptions by using variational methods and critical point theory. Moreover, some recent results are generalized and signi?cantly improved.