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991.
Zhiyuan Qian Luke Galuska William W. McNutt Michael U. Ocheje Youjun He Zhiqiang Cao Song Zhang Jie Xu Kunlun Hong Rene B. Goodman Simon Rondeau‐Gagn Jianguo Mei Xiaodan Gu 《Journal of Polymer Science.Polymer Physics》2019,57(23):1635-1644
Thermomechanical properties of polymers highly depend on their glass transition temperature (T g). Differential scanning calorimetry (DSC) is commonly used to measure T g of polymers. However, many conjugated polymers (CPs), especially donor–acceptor CPs (D–A CPs), do not show a clear glass transition when measured by conventional DSC using simple heat and cool scan. In this work, we discuss the origin of the difficulty for measuring T g in such type of polymers. The changes in specific heat capacity (Δc p) at T g were accurately probed for a series of CPs by DSC. The results showed a significant decrease in Δc p from flexible polymer (0.28 J g?1 K?1 for polystyrene) to rigid CPs (10?3 J g?1 K?1 for a naphthalene diimide‐based D–A CP). When a conjugation breaker unit (flexible unit) is added to the D–A CPs, we observed restoration of the Δc p at T g by a factor of 10, confirming that backbone rigidity reduces the Δc p. Additionally, an increase in the crystalline fraction of the CPs further reduces Δc p. We conclude that the difficulties of determining T g for CPs using DSC are mainly due to rigid backbone and semicrystalline nature. We also demonstrate that physical aging can be used on DSC to help locate and confirm the glass transition for D‐A CPs with weak transition signals. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1635–1644 相似文献
992.
993.
Dawei Xu Li Zheng Xinhong Cheng Gang Wang Qian Wang Wenbo Xin Peiyi Ye Lingyan Shen Yuehui Yu 《Physics letters. A》2019,383(25):3134-3137
The efficient passivation of in situ NH3-plasma pre-treatment and its regulation of the band alignment between HfO2 and 4H-SiC have been investigated by XPS. With in situ NH3-plasma passivation by PEALD, a VBO of 0.72 eV and a CBO of 1.54 eV can be obtained across the HfO2/4H-SiC interface. The Si-O bonds components reduction in the passivated interface layers will lead to band bending or band shift at the interface and regulate the band alignments between HfO2 and 4H-SiC. The physical mechanism investigation of band alignments can be a cornerstone for the application of HfO2/4H-SiC heterojunctions in the high-power devices. 相似文献
994.
The steam-assistant heteroatoms of sulfur and phosphorus dual-doped graphene film fabricated via an ice-template and thermal-activation approach demonstrates an excellent pseudocapacitive behavior in flexible electrochemical capacitors. 相似文献
995.
Li Xuetian Shao Zhongbao Liu Kuiren Zhao Qing Liu Guangfu Xu Binshi 《Journal of Solid State Electrochemistry》2019,23(2):465-473
Journal of Solid State Electrochemistry - Li1-xNbxFePO4/C has been prepared by wet mechanical stirring–assisted high-temperature ball milling route. Wet mechanical stirring was considered to... 相似文献
996.
Xiaomin Xu Xiaohong Ding Bo Yuan Weiwei Li Yimei Wang Yi Jin Haiyan Xu 《Biomedical chromatography : BMC》2019,33(6)
A rapid, simple and sensitive LC–MS/MS method was established and validated for simultaneous quantification of ticagrelor and its active metabolite AR‐C124910XX in human plasma. After plasma samples were deproteinized with acetonitrile, the post‐treatment samples were chromatographed on a Dikma C18 column interfaced with a triple quadrupole tandem mass spectrometer. Electrospray negative ionization mode and multiple reaction monitoring were adopted to assay ticagrelor and AR‐C124910XX. Acetonitrile and 5 mΜ ammonium acetate was used as the mobile phase with a gradient elution at a flow rate of 0.5 mL/min. The method was linear in the range of 0.781–800 ng/mL for both ticagrelor and AR‐C124910XX with a correlation coefficient ≥0.994. The intra‐ and inter‐day precisions were within 12.61% in terms of relative standard deviation and the accuracy was within ±7.88% in terms of relative error. The LC–MS/MS method was fully validated for its sensitivity, selectivity, stability, matrix effect and recovery. This convenient and specific LC–MS/MS method was successfully applied to the pharmacokinetic study of ticagrelor and AR‐C124910XX in healthy volunteers after an oral dose of 90 mg ticagrelor. 相似文献
997.
Dr. Lei He Prof. Wen-Cui Li Shuang Xu Prof. An-Hui Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3209-3218
Microporous carbons afford high surface areas, large pore volumes, and good conductivity, and are fascinating over a wide range of applications. Traditionally synthesized microporous carbon materials usually suffer from some limitations, such as poor accessibility and slow mass transport of molecules due to the micrometer-scale diffusion pathways and space confinement imposed by small pore sizes. Two-dimensional microporous carbon materials, denoted as microporous carbon nanosheets (MCNs), possess nanoscale thickness, which allows fast mass and heat transport along the z axis; thus overcoming the drawbacks of their bulk counterparts. Herein, recent breakthroughs in the synthetic strategies for MCNs are summarized. Three typical methods are discussed in detail with several examples: pyrolysis of organic precursors with 2D units, a templating method that uses wet chemistry, and the molten salt method. Among them, molecular-based assembly of MCNs in the liquid phase shows more controllable morphology, thickness, and pore size distribution. Finally, challenges in this research area are discussed to inspire future explorations. 相似文献
998.
Jian Wang Jinjin Zhou Yu Xu Bingqi Zhu Huiyi Li 《Rapid communications in mass spectrometry : RCM》2019,33(17):1410-1419
999.
Zhangxin Chen Chang Su Xiaogang Zhu Ruoteng Xu Lihuan Xu Cheng Zhang 《Journal of polymer science. Part A, Polymer chemistry》2018,56(22):2574-2583
A novel organic conjugated polymer based on star-shaped triazine-functional triphenylamine framework poly[1,3,5-tris(4-diphenylamino-phenyl)triazine] (PTDAPTz) is designed and synthesized successfully by FeCl3-catalysted chemical oxidative polymerization. The polymer PTDAPTz powder exhibits a compactly packed pleated skirt shape-like morphology with a high surface area (~930 m2 g−1) and a bimodal pore size distribution ranging from micropores (~0.55 nm) to small diameter mesopores (~2–6 nm). As explored as the cathode material, the obtained PTDAPTz presents the double charge–discharge process characteristics of both the free radical redox of triphenylamine unit and the bipolar redox of triazine unit in the polymer and a well-defined multistage charge/discharge voltage plateau (~3.8 V for p-doped and ~2.0 V for n-doped) during the charge–discharge process. Also, the PTDAPTz demonstrates an improved capacity (stabilized at 123 mA h g−1 until 50th cycle) and the enhanced rate performance compared to polytriphenylamine (PTPAn). Specially, the discharge curve for the part of triphenylamine unit presents an obviously improved discharge plateau (~3.8 V for PTDAPTz compared to ~3.6 V for PTPAn) due to the electron-withdrawing effect of the triazine unit to triphenylamine. The elaborate structural design and created micro-/mesoporous morphology with the double charge–discharge process make PTDAPTz a potential candidate as the performance-improved cathode of Li-organic battery. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2574–2583 相似文献
1000.
Ytterbium, erbium, aluminum tri-doped zinc oxide crystal was synthesized, which can turn color from red to green up-conversion luminescence through adjusting aluminum content. When the aluminum concentration reached 4?mol%, the color of up-conversion emission first turn from red to green. Meanwhile, the ratio of red to green emission reduced from 25.32 to 0.26, and the coordinates of chromaticity coordinate calculation changes from (0.5749, 0.3378) to (0.2190, 0.7169) with aluminum concentration range from 0 to 4?mol%. The up-conversion emission peaks at 521, 542, and 660?nm of sample originate from the transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of erbium ions, respectively. X-ray diffraction patterns perform the better crystallization degree with increasing aluminum concentration. The scanning electron microscopy images show the porous and lamellar structures with different aluminum concentrations. A convenient but effective design to obtain ytterbium, erbium, aluminum tri-doped zinc oxide up-conversion luminescence is reported, which can turn color from red to green. 相似文献