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21.
发现含有二氯二茂钛与取代水杨酸的氯仿溶液在水存在下可以发生反应,由此合成了六个二茂钛衍生物,经元素分析、IR及^1HNMR对基结构进行了表征,并对反应机理进行了探讨。 相似文献
22.
Controlled growth and field emission of vertically aligned AlN nanostructures with different morphologies 下载免费PDF全文
The controllable growth of three different morphologies of AlN
nanostructures (nanorod, nanotip and nanocrater) arrays are
successfully realized by using chemical vapour deposition (CVD)
technology. All three nanostructures are of single crystal h-AlN
with a growth orientation of [001]. Their growth is attributed to
the vapour-liquid-solid (VLS) mechanism. To investigate the factors
affecting field emission (FE) properties of AlN nanostructures, we
compare their FE behaviours in several aspects. Experimental results
show that AlN nanocrater arrays possess the best FE properties, such
as a threshold field of 7.2~V/μm and an emission current
fluctuation lower than 4%. Moreover, the three AlN nanostructures
all have good field emission properties compared with a number of
other excellent cathode nanomaterials, which suggests that they are
future promising FE nanomaterials. 相似文献
23.
Xiu-An Zheng Hua-Shan Huang Rui Kong Wei-Jie Chen Shan-Shan Gong Qi Sun 《Tetrahedron》2018,74(49):7095-7101
In the past decade, synthetic oxidized 5-MedC nucleosides and their derivatives have become essential tools for epigenetic research. The low efficacy of both conventional and newly reported BOP methods on C4-amination of these specific oxidized 5-MedU substrates urged us to systematically investigate how the nature of onium salt-based coupling reagents affects the C4-amination of pyrimidine nucleobases and lead us to the findings that different onium coupling reagents result in the formation of distinctive activation intermediates and PyAOP is much more potent than BOP in both activation and aminolysis steps. Direct amination without the need of ribose protection, ultrafast activation, tolerance to aqueous N-nucleophiles, and excellent yields for diverse oxidized 5MedC derivatives are the advantages of this PyAOP-based C4-amination method. 相似文献
24.
Gong Wei-Jie Yang Zhan-Yong Hong Yu-Xuan Liu Dong Niu Zheng Braunstein Pierre Lang Jian-Ping 《中国科学:化学(英文版)》2022,65(10):1867-1872
Science China Chemistry - In the context of the highly desirable design and preparation of smart materials with adjustable properties based on photoreactive compounds, we report two unique... 相似文献
25.
Four divalent metal thiocyanate coordination compounds containing a rigid functional pyridine ligand
Lin Kong Wei-Jie Li Xian-Lei Li Wen-Qian Geng Fu-Ying Hao Jie-Ying Wu Hong-Ping Zhou Jia-Xiang Yang Yu-Peng Tian Bao-Kang Jin 《Polyhedron》2010
A series of new coordination compounds Zn(SCN)2L2 (1), Co(SCN)2L2 (2), [Cd(SCN)2L2·2L]n (3) and [CdHg(SCN)4L2]n (4) have been prepared by self-assembly of a rigid functional pyridine ligand, trans-4-[4′-(N-methyl-N-hydroxyethyl)amimo]styryl pyridine (abbreviated as L) with M(SCN)x (M: Zn, Co, Cd, CdHg; x: 2, 4). The crystal structures indicate that 1 and 2 are mononuclear compounds while 3 and 4 are coordination polymers. O–H?N, C–H?O, O–H?π and C–H?π hydrogen bonds play significant roles in the final crystal structures. The solid-state luminescence properties have been measured. The results indicate that the photoluminescence spectra of all the compounds can be changed by the frameworks and introducing of different metal ions. 相似文献
26.
Ultrafast third-order nonlinear optical response of bulk 6H-SiC undoped and doped with different nitrogen concentrations are investigated utilizing femtosecond Z-scan and optical Kerr effect (OKE) techniques at the wavelength of 800hm. The Z-scan measurement shows that the third-order nonlinear optical susceptibilities of the doped samples are improved in comparison to the intrinsic sample. The OKE results additionally reveal that the instantaneous nonlinear optical response of the samples can be ascribed to the distortion of the electron cloud. The ultrafast transient spectroscopic measurements with the one-color and two-color pump-probe techniques demonstrate that the ultrafast recovery process in subpicosecond domain is induced by two-photon absorption process, while the slow relaxation component reflects the carrier dynamics of the excited electrons. 相似文献
27.
It is widely believed that the power-law is a proper probability distribution being effectively applied for evolution in τ-EO (extremal optimization), a general-purpose stochastic local-search approach inspired by self-organized criticality, and its applications in some NP-hard problems, e.g., graph partitioning, graph coloring, spin glass, etc. In this study, we discover that the exponential distributions or hybrid ones (e.g., power-laws with exponential cutoff) being popularly used in the research of network sciences may replace the original power-laws in a modified τ-EO method called self-organized algorithm (SOA), and provide better performances than other statistical physics oriented methods, such as simulated annealing, τ-EO and SOA etc., from the experimental results on random Euclidean traveling salesman problems (TSP) and non-uniform instances. From the perspective of optimization, our results appear to demonstrate that the power-law is not the only proper probability distribution for evolution in EO-similar methods at least for TSP, the exponential and hybrid distributions may be other choices. 相似文献
28.
Meng-Zhao Qin & Wei-Jie Zhu 《计算数学(英文版)》1994,12(4):352-356
IntroductionWhenweconstructahigherorderschemeforsystemsofordinarydifferentialequations:y,=f(y)(1)(wherey=y(x),andxisavariable),weoftenusethe"Tayorseriesexpanding"method,butsometimesthismethodisverytediouswhenitisaPpliedtogethigherorderschemes.Thereisanothermethod:Lieseries,itisthemethodweuseinthispaPer.J.Dragt,F,Neri,andStaulySteinberghavedonealotofworkindevelopingthismethod.Fordetails,onecanreferto[4,6,8].WejustaPplythismethodtoourproblem,anddonotneedtocomputeouttheexacttermsofthe"Lieser… 相似文献
29.
VPO catalysts are widely used in selective oxidation of n-butane into maleic anhydride (MA)[1-2]. In the recent years, there is an obvious trend worldwide that the selectivity of a target product is more emphasized than the overall conversion, to decrease the undesired by-products. In this study, different approaches have been tried to generate more environmentally friendly VPO catalysts, with high MA selectivity and improved n-butane conversion. The moderated catalyst was prepared in aqueous phase[3]. For comparison, the moderators were also introduced by impregnating the VPO precursor synthesized in organic medium. The supported VPO systems on the MCM-41 mesopore materials were prepared by employing the reaction of V2O5 with isobutanol in the presence of MCM-41 fine powder with different Si/Al ratios. The catalysts were evaluated at 385-425℃ and characterized by XRD, XPS and TPR etc. 相似文献
30.
VPO超微粒子的制备和表征 总被引:5,自引:0,他引:5
以V2O5和浓H3PO4为原料,浓HCl和柠檬酸作还原剂,以含量不同金属离子为助剂,采用超临界流体干燥法制备了VPO超微粒子.应用BET、XRD、TEM及XPS等手段考察了VPO超微粒子的物性、结构及助剂对其物性的影响.实验结果表明,超临界流体干燥法可显著增大样品的比表面积,且可使粒子大小达到纳米尺度.实验发现,超微样品的晶相结构为一种尚未鉴定的未知物相.而表面V离子价态则基本上为+4价. 相似文献