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91.
Jinxia Deng Jun Chen Ranbo Yu Guirong Liu Xianran Xing Songbai Han Yuntao Liu Dongfeng Chen Linfeng He 《Solid State Sciences》2009,11(1):170-175
Microwave dielectric powder Ba(Ca1/3Nb2/3)O3 with high B-site cation ordering was synthesized by the molten salt method. Neutron powder diffraction (NPD) and Raman scattering spectra were introduced to investigate the variable ordering degree during the sintering process. It was revealed that the as-synthesized Ba(Ca1/3Nb2/3)O3 powder had a nearly completely ordered structure, and the sintered Ba(Ca1/3Nb2/3)O3 presented a bit higher ordering degree based on the detailed quantitative NPD Rietveld full profile fitting. The complete Raman mode assignment for the Ba(Ca1/3Nb2/3)O3 was presented. The phonon bands could also confirm the order–disorder structural model and increasing ordering degree with the increasing sintering temperature. Final microwave dielectric measurements on sintered samples showed the present compound to tailor other dielectric materials for microwave applications with the dielectric properties of ?r = 47.11, and Qf = 1389 GHz, and τf was about 113 ppm/°C. 相似文献
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94.
Lei Tang Zechao Lin Qiwei WangXiaobei Wang Linfeng CunWeicheng Yuan Jin ZhuJingen Deng 《Tetrahedron letters》2012,53(30):3828-3830
As an efficient catalyst for asymmetric transfer hydrogenation reaction (ATH reaction) of α,β-unsaturated ketones, Rh-Cp∗-TsDPEN (Cp∗ = 1,2,3,4,5-pentamethylcyclopenta-1,3-diene, TsDPEN = N-(p-toluenesulfonyl)-1,2-diphenyl- ethylenediamine) shows high chemoselectivity on CO and CC reduction. In our method, both CO and CC bonds in a variety of chromenone derivatives were reduced efficiently in aqueous media, resulting in at least 98% ee and up to 99% yields in a convenient way without further purification. The product was a useful intermediate for deriving chiral chroman-4-amine, which was reported as an effective agent against hypotension and inflammatory pain by inhibiting human bradykinin B1 receptor. 相似文献
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How to integrate individual nanostructures into macroscopic thin films has become one of the most intriguing fields in nanoscience and nanotechnology due to the unique properties and important applications of these functional films. Since being discovered in 2004, oil-water interfacial self-assembly of nanostructures has become a novel strategy for fabrication of nanofilms. It is a powerful bottom-up approach for film fabrication due to the low cost and high efficiency, and is simple and universal for almost all low-dimensional nanostructures. In this article, we provide a critical review of the state-of-the-art research activities in this burgeoning self-assembly strategy. We first discuss the thermodynamic mechanism of the oil-water interfacial self-assembly, then the self-assembly of various low-dimensional nanostructures including nanoparticles, one-dimensional (1D) nanostructures, two-dimensional (2D) nanostructures at an oil-water interface developed so far to fabricate high-quality nanofilms. Finally, we present some progress on the construction of functional nanofilm-based nanodevices from this novel strategy based on our research. We conclude this review with critical comments on advantages and the experimental challenges, and further propose the future research and development of this self-assembly strategy for nanodevice construction (105 references). 相似文献
97.
G Tian SJ Teat Z Zhang L Rao 《Dalton transactions (Cambridge, England : 2003)》2012,41(38):11579-11586
Glutarimidedioxime (H(2)A), a cyclic imide dioxime ligand that has implications in sequestering uranium from seawater, forms strong tridentate complexes with UO(2)(2+). The stability constants and the enthalpies of complexation for five U(vi) complexes were measured by potentiometry and microcalorimetry. The crystal structure of the 1?:?2 metal-ligand complex, UO(2)(HA)(2)·H(2)O, was determined. The re-arrangement of the protons of the oxime groups (-CH[double bond, length as m-dash]N-OH) and the deprotonation of the imide group (-CH-NH-CH-) results in a conjugated system with delocalized electron density on the ligand (-O-N-C-N-C-N-O-) that coordinates to UO(2)(2+)via its equatorial plane. 相似文献
98.
A one‐pot synthesis of alkynyl sulfide from terminal alkyne has been reported via lithiation of the alkyne, oxidative addition of sulfur, consecutively followed by the nucleophilic substitution of lithium alkynyl thiolate to various halides. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:105–110, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20745 相似文献
99.
Linfeng WANG 《数学年刊B辑(英文版)》2012,33(5):715-736
In this paper,quasi-almost-Einstein metrics on complete manifolds are studied.Two examples are given and several formulas are established.With the help of these formulas,the author proves rigid results on compact or noncompact manifolds,in which some basic tools,such as the weighted volume comparison theorem and the weak maximum principle at infinity,are used.A lower bound estimate for the scalar curvature is also obtained. 相似文献
100.
Self-assembled monolayers (SAMs) of 4,4'-thiobisbenzenethiol (TBBT) can be formed on Au surface spontaneously. The structural characteristics and adsorption behavior of TBBT SAMs on Au have been investigated by surface enhanced Raman scattering (SERS), electrochemical cyclic voltammetry (CV), ac impedance spectroscopy (EIS), and atomic force microscopy (AFM). It is demonstrated that TBBT adsorbed on Au by losing a H atom, forming one Au-S bond, and the other mercapto group is free at the surface of the monolayer owing to the presence of the nu(S-H) at 2513 cm(-1) and the delta(C-S-H) at 910 cm(-1) in SERS. The enhancement of the vibration of C-S (1064 cm(-1)), the aromatic C-H vibration (3044 cm(-1)), and the absence of the vibration of S-S illustrate TBBT adsorbed on Au forming a monolayer with one benzene ring tilted with respect to the Au surface. The interpretation of the observed frequencies is aided by ab initio molecular orbital (MO) calculations at the HF/6-31G level of theory. Electrochemical CV and EIS indicate TBBT monolayers can passivate the Au effectively for its low ratio of pinhole defects (theta = 99.6%). AFM studies give details about the surface morphology. The applications of TBBT SAMs have been extensively investigated by exposure of Cu2+ ion to TBBT SAMs on Au and covalent adsorption of metal nanoparticles. Electrochemical, X-ray photoelectron spectroscopic, and SERS results indicate that Cu2+ can react with TBBT SAMs and present on TBBT SAMs as Cu(I). A scanning electron microscopic image of Ag nanoparticles on TBBT/Au and the Raman spectrum of TBBT in smooth macroscopic Au/TBBT SAMs/Ag nanoparticle sandwich structure indicate that metal nanoparticles can be adsorbed on TBBT SAMs effectively through covalent linkage. 相似文献