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931.
932.
Wenjuan Yan Mengyuan Liu Jinyao Wang Jian Shen Shuxia Zhang Xiaoqiang Xu Shuaishuai Wang Jie Ding Xin Jin 《Chemical record (New York, N.Y.)》2020,20(3):230-251
Molybdenum complexes are versatile and efficient for liquid phase olefin epoxidation reactions. Rational design of catalysts is critical to achieve high atom efficiency during epoxidation processes. Although liquid phase epoxidation has been a popular topic for decades, three key issues, (a) rational control of morphology of molybdenum nanoparticles, (b) manipulating metal‐support interaction and (c) altering electronic configuration at molybdenum center remains unsolved in this area. Therefore, in this paper, we have critically revised recent research progress on heterogeneous molybdenum catalysts for facile liquid phase olefin epoxidation in terms of catalyst synthesis, surface characterization, catalytic performance and structure‐function relationship. Furthermore, plausible reaction mechanisms will be systematically discussed with the aim to provide insights into fundamental understanding on novel epoxidation chemistry. 相似文献
933.
Xing‐Cai Huang Jia‐Xin Li Yong‐Zhi Chen Wen‐Yan Wang Rui Xu Jin‐Xia Tao Dong Shao Yi‐Quan Zhang 《化学:亚洲杂志》2020,15(9):1469-1477
Tuning the magnetic anisotropy of metal ions remains highly interesting in the design of improved single‐molecule magnets (SMMs). We herein report synthetic, structural, magnetic, and computational studies of four mononuclear CoII complexes, namely [Co(hfac)2(MeCN)2] ( 1 ), [Co(hfac)2(Spy)2] ( 2 ), [Co(hfac)2(MBIm)2] ( 3 ), and [Co(hfac)2(DMF)2] ( 4 ) (MeCN=acetonitrile, hfac=hexafluoroacetylacetone, Spy=4‐styrylpyridine, MbIm=5,6‐dimethylbenzimidazole, DMF=N,N‐dimethylformamide), with distorted octahedral geometry constructed from hexafluoroacetylacetone (hfac) and various axial ligands. By a building block approach, complexes 2 – 4 were synthesized by recrystallization of the starting material of 1 from various ligands containing solution. Magnetic and theoretical studies reveal that 1 – 4 possess large positive D values and relative small E parameters, indicating easy‐plane magnetic anisotropy with significant rhombic anisotropy in 1 – 4 . Dynamic alternative current (ac) magnetic susceptibility measurements indicate that these complexes exhibit slow magnetic relaxation under external fields, suggesting field‐induced single‐ion magnets (SIMs) of 1 – 4 . These results provide a promising platform to achieve fine tuning of magnetic anisotropy through varying the axial ligands based on Co(II) bis(hexafluoroacetylacetonate) complexes. 相似文献
934.
A facile hybrid assembly between Ti3C2Tx MXene nanosheets and (3‐aminopropyl) triethoxylsilane‐modified Si nanoparticles (NH2?Si NPs) was developed to construct multilayer stacking of Ti3C2Tx nanosheets with NH2?Si NPs assembling together (NH2?Si/Ti3C2Tx). NH2?Si/Ti3C2Tx exhibits a significantly enhanced lithium storage performance compared to pristine Si, which is attributed to the robust crosslinking architecture and considerably improved electrical conductivity as well as shorter Li+ diffusion pathways. The optimized NH2?Si/Ti3C2Tx anode with Ti3C2Tx: NH2?Si mass ratio of 4 : 1 displays an enhanced capacity (864 mAh g?1 at 0.1 C) with robust capacity retention, which is significantly higher than those of NH2?Si NPs and Ti3C2Tx anodes. Furthermore, this work demonstrates the important effect of the MXene‐based electrode architecture on the electrochemical performance and can guide future work on designing high‐performance Si/MXene hybrids for energy storage applications. 相似文献
935.
Aiguo Song Xin Shen Tian Feng Shouchang Gai Haiqing Wei Xinxin Li Hui Chen 《化学:亚洲杂志》2020,15(9):1464-1468
GSTP1 has been considered to be a marker for malignancy in many tissues. However, the existing GST fluorescent probes are unfavorable for in vivo imaging because of the limited emission wavelength or insufficient fluorescence enhancement (six‐fold). The limited fluorescence enhancement of GST fluorescent probes is mainly ascribed to the high background signals resulting from the spontaneous reaction between GSH and the probes. In this work, a highly specific GST probe with NIR emission has been successfully developed through optimization of the essential unit of the probe to repress the spontaneous reaction. The novel GST probe exhibits over 100‐fold fluorescence enhancement upon incubation with GSTP1/GSH and high selectivity over other potential interference. In addition, the probe has been proved to be capable of tracking endogenous GST in A549 cells. Finally, the in vivo imaging results demonstrate that the probe can be used for effective imaging of endogenous GST activity in subcutaneous tumor mouse with high contrast. 相似文献
936.
In‐depth understanding of the catalytic active sites is of paramount importance for the design of efficient electrocatalysts for CO2 conversion. Here we highlight the structural evolution of SnO2 nanosheets for electrocatalytic CO2 reduction. The transformation of SnO2 into metallic Sn would occur on the surface of catalyst during the catalytic process, followed by enhanced selectivity and activity for the conversion of CO2 to HCOOH. Electrocatalytic characterization and structural analysis demonstrate that the metallic Sn derived from structural evolution plays a dominant role in the CO2 reduction to HCOOH. This work deepens the understanding of the catalytic mechanism and provides a new pathway for the rational design of advanced electrocatalysts for CO2 reduction. 相似文献
937.
Xiao‐Tong Wang Zhen‐Yi Gu Wen‐Hao Li Xin‐Xin Zhao Jin‐Zhi Guo Kai‐Di Du Xiao‐Xi Luo Xing‐Long Wu 《化学:亚洲杂志》2020,15(18):2803-2814
As the power supply of the prosperous new energy products, advanced lithium ion batteries (LIBs) are widely applied to portable energy equipment and large‐scale energy storage systems. To broaden the applicable range, considerable endeavours have been devoted towards improving the energy and power density of LIBs. However, the side reaction caused by the close contact between the electrode (particularly the cathode) and the electrolyte leads to capacity decay and structural degradation, which is a tricky problem to be solved. In order to overcome this obstacle, the researchers focused their attention on electrolyte additives. By adding additives to the electrolyte, the construction of a stable cathode‐electrolyte interphase (CEI) between the cathode and the electrolyte has been proven to competently elevate the overall electrochemical performance of LIBs. However, how to choose electrolyte additives that match different cathode systems ideally to achieve stable CEI layer construction and high‐performance LIBs is still in the stage of repeated experiments and exploration. This article specifically introduces the working mechanism of diverse electrolyte additives for forming a stable CEI layer and summarizes the latest research progress in the application of electrolyte additives for LIBs with diverse cathode materials. Finally, we tentatively set forth recommendations on the screening and customization of ideal additives required for the construction of robust CEI layer in LIBs. We believe this minireview will have a certain reference value for the design and construction of stable CEI layer to realize desirable performance of LIBs. 相似文献
938.
This paper studies the contact vibration problem of an elastic half-space coated with functionally graded materials (FGMs) subject to a rigid spherical punch. A static force superimposing a dynamic time-harmonic force acts on the rigid spherical punch. Firstly, we give the static contact problem of FGMs by a least-square fitting approach. Next, the dynamic contact pressure is solved by employing the perturbation method. Lastly, the dynamic contact stiffness with different dynamic contact displacement conditions is derived for the FGM coated half-space. The effects of the gradient index, coating thickness, internal friction, and punch radius on the dynamic contact stiffness factor are discussed in detail. 相似文献
939.
风机大型化是我国海上风电技术发展的重要方向. 东南沿海是我国海上风电发展的重要基地, 这一区域频繁发生的台风对海上风机的影响不可忽略. 台风风场与常规大风风场有不同的湍流特性, 同时台风期间较高的风速会引起巨大的台风浪. 本文考虑台风经过期间独特的风场及波浪场, 开展风浪联合作用对大型单桩海上风机影响的研究. 基于DTU 10 MW大型单桩风机, 运用一体化分析软件SIMA建立风浪联合作用下大型单桩风机的耦合数值模型, 研究台风经过不同阶段大型风力机的动力响应特性. 计算结果显示, 叶片变桨能有效降低台风经过时风机叶片所受风载荷, 变桨状态下单桩风机所受风载荷主要来源于塔筒. 在台风经过的不同阶段, 大型单桩海上风机结构表现出不同的动力特性. 台风全过程塔筒运动均受波浪激发一阶频率控制, 塔基上方结构动力载荷以惯性载荷为主, FOVS至FEWS阶段及BOVS阶段至BEWS阶段塔筒运动一阶频率处响应能量增长较小, 响应能量向低频及波频转移. 塔基下方泥面线处剪力响应受波频控制, 弯矩响应受一阶频率控制. 相似文献
940.
An independent set S of a graph G is said to be essential if S has a pair of vertices distance two apart in G. We prove that if every essential independent set S of order k ≥ 2 in a k-connected graph of order p satisfies max {deg v:v ϵ S} ≥ ½ p, then g is hamiltonian. This generalizes the result of Fan (J. Combinatorial Theory B 37 (1984), 221–227). If we consider the essential independent sets of order k + 1 instead of k in the assumption of the above statement, we can no longer assure the existence a hamiltonian cycle. However, we can still give a lower bound to the length of a longest cycle. © 1996 John Wiley & Sons, Inc. 相似文献