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排序方式: 共有1435条查询结果,搜索用时 31 毫秒
981.
Wei Zhao Shengping Dou Qin Zhong Licheng Wu Qian Wang Aijian Wang 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(13):2489-2494
V2O5/S-doped TiO2 was prepared by the sol-gel and impregnation methods. The adsorption of NO, NH3, and O2 over the catalyst was studied by in situ DRIFTS spectroscopy to elucidate the reaction mechanism of the low-temperature selective catalytic reduction of NO with NH3. Exposing the catalyst to O2 and NO, three types of nitrates species appeared on the surface. The introduction of S to TiO2 could generate large amounts of acid sites for ammonia adsorption on the catalyst, which was believed to be an important role in the SCR reaction and hereby improved the catalytic activity. The results indicated two possible SCR reaction pathways for catalyst. One was that NO was absorbed to form nitrite species, which could react with NH3 on Lewis acid sites, producing N2 and H2O. Another way was that NH3 was adsorbed, then reacted with gas phase NO (E–R) and nitrite intermediates on the surface (L–H). 相似文献
982.
Theoretical investigation on the performance of DNA electrophoresis under programmed step electric field strength: Two‐step condition 下载免费PDF全文
Yi Ni Chenchen Liu Qinmiao Chen Xifang Zhu Xiaoming Dou 《Journal of separation science》2015,38(20):3638-3644
Programmed step electric field strength is a simple‐to‐use technique that has already been reported to be effective to enhance the efficiency or speed of DNA electrophoresis. However, a global understanding and the details of this technique are still vague. In this paper, we investigated the influence of programmed step electric field strength by theoretical calculation and concentrated on a basic format named as two‐step electric field strength. Both subtypes of two‐step electric field strength conditions were considered. The important parameters, such as peak spacing, peak width, resolution, and migration time, were calculated in theory to understand the performance of DNA electrophoresis under programmed step electric field strength. The influence of two‐step electric field strength on DNA electrophoresis was clearly revealed on a diagram of resolution versus migration time. Both resolution and speed of DNA electrophoresis under two‐step electric field strength conditions are simply expressed by the shape of curves in the diagram. The possible shapes of curve were explored by calculation and shown in this paper. The subtype II of two‐step electric field strength brings drastic variation on the resolution. Its limitations of enhancement and deterioration of resolution were predicted in theory. 相似文献
983.
Synthesis and Characterization of Co3O4/Multiwalled Carbon Nanotubes Nanocomposite for Amperometric Sensing of Hydrazine 下载免费PDF全文
Jie Zhang Haijing Liu Meiling Dou Feng Wang Jingjun Liu Zhilin Li Jing Ji 《Electroanalysis》2015,27(5):1188-1194
Co3O4 nanoparticles (NPs) were synthesized and decorated on the multi‐walled carbon nanotubes (MWCNTs) through a simple hydrothermal procedure. The deposited Co3O4 NPs on the sidewalls of MWCNTs were found to be cubic crystal structure and homogenously dispersed with a narrow particle size distribution centered at around 6 nm. The Co3O4/MWCNTs nanocomposite was then utilized for the electrochemical detection of hydrazine, and exhibited a high sensitivity of 34.5 µA mM?1, a low detection limit of 0.8 µM (S/N=3), a wide linear range of 20 µM to 1.1 mM along with a short response time of less than 5 s. 相似文献
984.
Sulfur‐Doped Graphene Derived from Cycled Lithium–Sulfur Batteries as a Metal‐Free Electrocatalyst for the Oxygen Reduction Reaction 下载免费PDF全文
Zhaoling Ma Shuo Dou Anli Shen Li Tao Prof. Liming Dai Prof. Shuangyin Wang 《Angewandte Chemie (International ed. in English)》2015,54(6):1888-1892
Heteroatom‐doped carbon materials have been extensively investigated as metal‐free electrocatalysts to replace commercial Pt/C catalysts in oxygen reduction reactions in fuel cells and Li–air batteries. However, the synthesis of such materials usually involves high temperature or complicated equipment. Graphene‐based sulfur composites have been recently developed to prolong the cycling life of Li–S batteries, one of the most attractive energy‐storage devices. Given the high cost of graphene, there is significant demand to recycle and reuse graphene from Li–S batteries. Herein, we report a green and cost‐effective method to prepare sulfur‐doped graphene, achieved by the continuous charge/discharge cycling of graphene–sulfur composites in Li–S batteries. This material was used as a metal‐free electrocatalyst for the oxygen reduction reaction and shows better electrocatalytic activity than pristine graphene and better methanol tolerance durability than Pt/C. 相似文献
985.
986.
Jianglin Liu Guifang Dou Xiaona Dong Dan Yuan Xiwei Ji Zhuona Wu ZhiYun Meng 《Biomedical chromatography : BMC》2010,24(9):935-940
In this study, a sensitive, selective and reproducible liquid chromatography–tandem mass spectrometry method for the simultaneous determination of 1,5‐dicaffeoylquinic acid (1,5‐DCQA) and its active metabolites, 1‐caffeoyl‐5‐feruoylquinic acid and 1,5‐O‐diferuoylquinic acid, in human plasma, using puerarin as internal standard, was developed and validated. Analytes were extracted from plasma samples by liquid–liquid extraction with ethyl acetate, separated on a C18 reversed‐phase column with water containing 5 mM ammonium acetate and acetonitrile as the mobile phase and detected by electrospray ionization mass spectrometry in negative selected reaction monitoring mode. The accuracy and precision of the method were acceptable and linearity was good over the range 1–200 ng/mL for each analyte. In addition, the selectivity, extraction recovery and matrix effect were satisfactory too. The validated LC‐MS/MS method was successfully applied to phase II clinical pharmacokinetic study of 1,5‐DCQA in patients. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
987.
Phonon energies in cobaltite/manganites A(Co1/2Mn1/2)O3, where A is a lanthanide, have been determined by far-infrared spectroscopy. The phonon energies systematically shift and split and new modes appear as the mass of the lanthanide is increased through the series A=La, Nd, Dy, Ho, Yb. The behavior of the phonon modes correlates with the magnetic properties of this series of compounds, in particular with the appearance of metamagnetism for the compounds with smaller ions on the A site. 相似文献
988.
989.
Three dinuclear copper(I) complexes, [Cu2(µ‐Cl)2(1,2‐(PPh2)2‐1,2‐C2B10H10)2]·2CH2Cl2 ( 1 ), [Cu2(µ‐Br)2(1,2‐(PPh2)2‐1,2‐C2B10H10)2]·2THF ( 2 ) and {Cu2(µ‐I)2[1,2‐(PPh2)2‐1,2‐C2B10H10]2} ( 3 ) have been synthesized by the reactions of CuX (X = Cl, Br and I) with the closo ligand 1,2‐(PPh2)2‐1,2‐C2B10H10. All these complexes were characterized by elemental analysis, FT‐IR, 1H and 13C NMR spectroscopy and X‐ray structure determination. Single crystal X‐ray structure determinations show that every complex contained di‐µ‐X‐bridged structure involving a crossed parallelogram plane formed by two Cu atoms and two X atoms (X = Cl, Br, I). The geometry at the Cu atom was a distorted tetrahedron, in which two positions were occupied by two P atoms of the PPh2 groups connected to the two C atoms of carborane (Cc), and the other two resulted from two X atoms which bridged the other Cu atom at the same time. To the best of our knowledge, this is the first example of copper(I) complexes with 1,2‐diphenylphosphino‐1,2‐dicarba‐closo‐dodecaborane as ligand characterized by X‐ray diffraction. The catalytic property of the complex 3 for the amination of iodobenzene with aniline was also investigated. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
990.
Diffraction fields in the focal space of some lens is investigated by using ray tracing and Stratton-Chu formulas. Two formulas are used. One is surface integration formula, and for another a line integration is added. Comparison of two calculation results is given. It is shown that for hyperbolic lens two calculations results are same and for extended hemi-ellipsoidal lens there are a lilt difference between them. 相似文献