含硅路易斯酸的发展及其在有机合成中的应用

综述了含硅路易斯酸R₃SiX [X＝I, OTf, NTf₂, C(C₆F₅)Tf₂等]和(R₃SiX＋ML_n)的发展、合成以及它们在有机合成中的应用. 它们主要被用来催化Aldol, 烯丙基化, Diels-Alder, Ene和Friedel-Crafts等反应. 催化剂的用量一般为0.5～20 mol%, 并随着催化剂的活性不同, 反应产率从一般到良好不等. 催化剂活性顺序为R₃SiNTf₂＞R₃SiOTf, (R₃SiX＋ML_n)＞R₃SiX. 也对近年出现的手性含硅路易斯酸的发展和应用进行了概述, 当手性双-(多氟甲磺酰)-亚胺基硅烷用于催化环戊二烯和丙烯酸甲酯的Diels-Alder反应时, ee值高达54%.     

新型氨基甲酸含氮杂环甲基酯的合成及生物活性研究

常规加热或微波照射下, 含氮杂环1与多聚甲醛反应以良好的产率生成含氮杂环基甲醇3, 反应物物质的量的比、反应温度等对反应产率有影响, 微波条件下的反应时间比常规加热下大大缩短. 化合物3和异氰酸酯4在常规加热或微波照射下生成相应的氨基甲酸含氮杂环甲基酯5a～5m. 反应温度、反应物物质的量的比、反应时间、微波辐射功率等对反应产率都有一定的影响, 与常规加热相比微波条件下的反应时间大大缩短. 化合物5的结构经过IR, ¹H NMR, MS, 元素分析测定, 部分化合物经过¹³C NMR测定. 测定了化合物5的杀虫和除草活性, 结果表明其杀虫活性较低, 除草活性高于杀虫活性, 5a, 5d, 5e和5m对苋菜和黄瓜的防除率高达100%.     

Synthesis and photocatalytic properties of core–shell TiO~2@ZnIn_2S_4 photocatalyst

A novel core–shell TiO2@ZnIn2S4composite has been synthesized successfully by a simple and flexible hydrothermal route using TiO2as precursors.The as-synthesized samples were characterized by X-ray diffraction,UV–vis diffuse reflectance spectra and transmission electron microscopy.The photocatalytic properties of samples were tested by degradation of aqueous methylene blue（MB）under visible light irradiation.It was found that the as-synthesized TiO2@ZnIn2S4photocatalyst was more effcient than TiO2and ZnIn2S4in the photocatalytic degradation of MB.Moreover,TEM images confrmed the TiO2@ZnIn2S4nanoparticles possessed a well-proportioned core–shell morphology.     

Effect of microstructure on thermoelectric properties of CSD-grown Bi2Sr2Co2Oy thin films

Three Bi₂Sr₂Co₂O_y thin films with different microstructures have been prepared by chemical solution deposition on LaAlO₃(001) through varying the annealing temperature. With the decrease in the annealing temperature, both the size and c-axis alignment degree of grains in the film decrease as well, leading to an increase in the film resistivity. In addition, the decrease in the annealing temperature also results in a slight increase in the seebeck coefficient due to the enhanced energy filtering effect of small-grain film. The nanostructured Bi₂Sr₂Co₂O_y film with the average grain size of about 100 nm shows a power factor comparable to that of the films with larger grains. Since the thermal conductivity of the nanostrcutured films can be depressed due to the enhanced phonon scattering by grain boundary, a higher figure of merit is expected in Bi₂Sr₂Co₂O_y thin film with grains in nanometer size.     

Investigating S-wave bound states composed of two pseudoscalar mesons

In this study, we systematically investigated two-pseudoscalar meson systems with the Bethe-Salpeter equation in the ladder and instantaneous approximations. By solving the Bethe-Salpeter equation numerically with the kernel containing the one-particle exchange diagrams, we found that the \begin{document}$ K\bar{K} $\end{document}, \begin{document}$ DK $\end{document}, \begin{document}$ B\bar{K} $\end{document}, \begin{document}$ D\bar{D} $\end{document}, \begin{document}$ B\bar{B} $\end{document}, \begin{document}$ BD $\end{document}, \begin{document}$ D\bar{K} $\end{document}, \begin{document}$ BK $\end{document}, and \begin{document}$ B\bar{D} $\end{document} systems with \begin{document}$ I=0 $\end{document} can exist as bound states. We also studied the contributions from heavy meson (\begin{document}$ J/\psi $\end{document} and \begin{document}$\Upsilon $\end{document}) exchanges and found that the contributions from heavy meson exchanges cannot be ignored.     

Facile electrochemical synthesis of hexagonal Cu2O nanotube arrays and their application

Large-scale and highly oriented single-crystalline hexagonal Cu(2)O nanotube arrays have been successfully synthesized using a two-step solution approach, which involves the electrodeposition of oriented Cu(2)O nanorods and a subsequent dissolution technique along the c axis to form a tubular structure. Herein, NH(4)Cl was found to be an effectual additive, and it can successfully realize the dissolution process of Cu(2)O from nanorods to nanotubes. The dissolution mechanism of Cu(2)O from nanorods to nanotubes was illustrated in detail. These prepared Cu(2)O nanotube arrays were characterized by SEM, EDS, XRD, XPS, and TEM. The photoluminescence (PL) spectrum of Cu(2)O nanotube arrays was also measured, and it shows there is a greater fraction of copper or oxygen vacancies in these prepared Cu(2)O nanotubes. Finally, the applications of Cu(2)O nanotube arrays for gas sensors were investigated in this paper.     

Diversity-oriented synthesis and antifungal activities of novel pimprinine derivative bearing a 1,3,4-oxadiazole-5-thioether moiety

Molecular Diversity - Based on the strategy of diversity-oriented synthesis and the structures of natural product pimprinine and streptochlorin, two series of novel pimprinine derivatives...     

Analysis of bending and buckling of pre-twisted beams: A bioinspired study

Twisting chirality is widely observed in artificial and natural materials and structures at different length scales. In this paper, we theoretically investigate the effect of twisting chiral morphology on the mechanical properties of elas- tic beams by using the Timoshenko beam model. Particular attention is paid to the transverse bending and axial buckling of a pre-twisted rectangular beam. The analytical solution is first derived for the deflection of a clamped-free beam under a uniformly or periodically distributed transverse force. The critical buckling condition of the beam subjected to its self- weight and an axial compressive force is further solved. The results show that the twisting morphology can significantly improve the resistance of beams to both transverse bending and axial buckling. This study helps understand some phenomena associated with twisting chirality in nature and provides inspirations for the design of novel devices and structures.     

硫脲修饰ZnSe:Cu量子点的水相合成及荧光特性

以3-巯基丙酸为稳定剂在水相中合成了Cu掺杂的ZnSe量子点(QDs), 并利用硫脲(CH₄N₂S)对其进行表面修饰, 制备出核壳结构的ZnSe:Cu/ZnS 量子点. 制得的量子点呈闪锌矿结构, 尺寸约为5 nm, 有较好的分散性, 其荧光发射峰在460 nm左右. 经CH₄N₂S修饰后, 量子点表面形成了宽禁带的ZnS包覆层, 将电子和空穴限域在了ZnSe:Cu 核内, 减少了表面发生非辐射复合的载流子, 显著提高了量子点的荧光强度. 与Na₂S、硫代乙酰胺(TAA)等常用硫源相比, 以CH₄N₂S为硫源制得的ZnSe:Cu/ZnS 量子点壳层厚度可控, 表面钝化效果更好, 显示出更佳的荧光效率和稳定性. ZnSe:Cu/ZnS 量子点经过紫外线照射后消除了表面的悬空键, 进一步提高了其量子产率, 最终获到了具有较好荧光性质的ZnSe:Cu/ZnS量子点.