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Your search keyword '"Zhang, Ke‐Feng"' showing total 131 results
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131 results on '"Zhang, Ke‐Feng"'

4. Highly Selective Fluorescent Sensor for Detection of Al3+ Based on Schiff-Base of 2-Hydroxy-1-Naphthaldehyde and 8-Aminoquinoline and Its Applications.

Author

Cai, Su-Qian, Zhang, Ke-Feng, and Cai, Xiao-Hua

Subjects
*CHINESE medicine, *DETECTORS, *FLUORESCENT probes
Abstract

Aluminum is a widely distributed element and plays an indispensable role in our lives, but excessive intake of Al3+ can cause potential harm to human health. Highly selective methods for the rapid detection of Al3+ are urgently needed. Here, a novel "turn on" fluorescent probe L based on Schiff-base of 2-hydroxy-1-naphthaldehyde and 8-aminoquinoline was obtained in an excellent yield. Probe L presents significant properties such as rapid response, good stability, wide pH range, simple synthetic operation, and provides an efficient strategy for the highly selective detection of Al3+ in an aqueous solution of DMSO/H2O (7:3, v:v). According to Job's curve and fluorescence titration, probe L with Al3+ forms a 2:1 ratio of complex, and the lowest limit of detection is 3.23 × 10−8 mol/L. The possible combination mode for probe L with Al3+ was proposed by comparison with the changes of 1H NMR and FTIR spectra of L and its complex. In addition, the potent applicants for probe L were also investigated, and indicated that it could conveniently be made into a series of sensor strips and applied to rapidly detect trace Al3+ in traditional Chinese medicine. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Regiodivergent enantioselective C–H functionalization of Boc-1,3-oxazinanes and application to the synthesis of β2 and β3-amino acids

Author

Lin, Weilong, Zhang, Ke-Feng, and Baudoin, Olivier

Subjects
Article
Abstract

β2- and β3-Amino acids are important chiral building blocks for the design of new pharmaceuticals and peptidomimetics. Here we report a straightforward regio- and enantiodivergent access to these compounds using a one-pot reaction composed of sparteine-mediated enantioselective lithiation of a Boc-1,3-oxazinane, transmetallation to zinc and direct or migratory Negishi coupling with an organic electrophile. The regioselectivity of the Negishi coupling was highly ligand-controlled and switchable to obtain the C4- or the C5-functionalized product exclusively. High enantioselectivities were achieved on a broad range of examples, and a catalytic version in chiral diamine was developed using the (+)-sparteine surrogate. Selected C4- and C5-functionalized Boc-1,3-oxazinanes were subsequently converted to highly enantio-enriched β2- and β3-amino acids with the (R) or (S) configuration, depending on the sparteine enantiomer employed in the lithiation step.

Published
2019

23. Ligand-controlled selectivity in palladium(0)-catalyzed C(sp2)-C(sp3) Negishi cross-coupling reactions

Author

Zhang, Ke-Feng, Baudoin, Olivier, and Leroux, Frédéric

Abstract

Over the past decades, transition-metal-catalyzed cross-coupling reactions have witnessed considerable growth and emerged as a powerful tool for the construction of carbon-carbon bonds. These reactions have found numerous applications in assembling structurally complex molecules ranging from medicines to materials. While the C(sp2)-C(sp2) cross-coupling reactions have seen a tremendous development, less effort has been devoted to the more challenging C(sp2)-C(sp3) couplings. The selectivity control in the palladium(0)-catalyzed cross-coupling of alkyl nucleophiles is an important topic of research in the Baudoin group. Both direct and migrative cross-couplings can be achieved by simply switching the ligand involved. Following the long-standing interest in this field, we firstly extended the migrative cross-coupling reactions to simple and easily available secondary alkyl bromides under Barbier conditions. Moreover, the terminal-selective functionalization of simple alkanes could be achieved when this reaction was coupled to a non-selective radical monobromination process. On the other hand, a series of azole-based bulky phosphine ligands was designed and applied to direct C(sp2)-C(sp3) Barbier-Negishi cross-coupling reactions, successfully preventing the β-hydride elimination process while favouring the direct reductive elimination. Finally, the ‘‘ligand-controlled selectivity’’ strategy was applied to the divergent synthesis of enantioenriched β-amino acid derivatives.

Published
2018

27. Growth and terahertz characterization of Hg1-xCdxTe crystal

Author

Zhang Li-Ping, Lu Ye, Liu Xiangyang, Shao Xiu-Hua, Zhang Ke-Feng, Jiao Cui-Ling, Ge Jin, Dai Ning, Lin Xing-Cao, HU Shu-Hong, and Wang Reng

Subjects
Crystal, Crystallography, Materials science, Terahertz radiation, Crystal growth, Atomic and Molecular Physics, and Optics, Characterization (materials science)
Published
2012

28. Calculation of Terahertz Pulse Propagation and Detection in〈331〉 ZnTe Single Crystal

Author

王仍 WANG Reng, 林杏潮 LIN Xing-chao, 张丽萍 ZHANG Li-ping, 张可锋 ZHANG Ke-feng, 焦翠玲 JIAO Cui-ling, 陆液 LU Ye, 邵秀华 SHAO Xiu-hua, 陆荣 LU Rong, 葛进 GE Jin, 胡淑红 HU Shu-hong, and 戴宁 DAI Ning

Subjects
Atomic and Molecular Physics, and Optics
Abstract

根据光整流效应辐射太赫兹理论,计算了〈331〉晶向ZnTe单晶的太赫兹辐射性能.通过与〈110〉、〈111〉晶向对比,当晶体方位角为0°或180°时,利用〈331〉晶向ZnTe单晶辐射太赫兹信号可以与〈111〉晶向相当,强于〈110〉晶向.利用电光取样原理,计算了〈331〉晶向ZnTe单晶的太赫兹探测性能,通过理论计算为〈331〉晶向ZnTe 晶体有效辐射太赫兹波提供理论依据.

Published
2010

30. Dark Energy Model with Canonical Scalar Field and Non-Linear Born–Infeld Type Scalar Field

Author

Zhang Ke-Feng, Fang Wei, and Lu Hui-qing

Subjects
Physics, Nonlinear system, Physics and Astronomy (miscellaneous), De Sitter universe, General Mathematics, Quantum mechanics, Attractor, Scalar (mathematics), Dark energy, Sigma, Lambda, Scalar field
Abstract

In this paper, we propose the non-linear Born–Infeld scalar field and canonical scalar field dark energy models with the potential \(\frac{\lambda }{4}( {\phi ^2 - \sigma ^2 })^2 + V_0\), which admits late time de Sitter attractor solution. The attractor solution corresponds to an equation of state ω_φ → − 1 and a cosmic density parameter Ω_φ → 1, which are important features for a dark energy model that can meet the current observations. dark energy; canonical scalar field, non-linear Born–Infeld type scalar field, attractor solution.

Published
2006

38. High Current Matching over Full-Swing and Low-Glitch Charge Pump Circuit for PLLs

Author

Wang, De-zhi, Zhang, Ke-feng, Zou, Xue-cheng, Wang, De-zhi, Zhang, Ke-feng, and Zou, Xue-cheng

Abstract

A high current matching over full-swing and low-glitch charge pump (CP) circuit is proposed. The current of the CP is split into two identical branches having one-half the original current. The two branches are connected in source-coupled structure, and a two-stage amplifier is used to regulate the common-source voltage for the minimum current mismatch. The proposed CP is designed in TSMC 0.18µm CMOS technology with a power supply of 1.8 V. SpectreRF based simulation results show the mismatch between the current source and the current sink is less than 0.1% while the current is 40 µA and output swing is 1.32 V ranging from 0.2 V to 1.52 V. Moreover, the transient output current presents nearly no glitches. The simulation results verify the usage of the CP in PLLs with the maximum tuning range from the voltage-controlled oscillator, as well as the low power supply applications.

Published
2013

46. Growth and terahertz characterization of Hg1-xCdxTe crystal

Author

WANG, Reng, primary, LIN, Xing-Cao, additional, ZHANG, Li-Ping, additional, ZHANG, Ke-Feng, additional, JIAO, Cui-Ling, additional, LU, Ye, additional, SHAO, Xiu-Hua, additional, LI, Xiang-Yang, additional, GE, Jin, additional, HU, Shu-Hong, additional, and DAI, Ning, additional

Published
2012
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