Positioning a Carbon–Fluorine Bond over the π Cloud of an Aromatic Ring: A Different Type of Arene Activation

It is known that the fluoro group has only a small effect on the rates of electrophilic aromatic substitutions. Imagine instead a carbon–fluorine (C?F) bond positioned tightly over the π cloud of an aryl ring—such an orthogonal, noncovalent arrangement could instead stabilize a positively charged arene intermediate or transition state, giving rise to novel electrophilic aromatic substitution chemistry. Herein, we report the synthesis and study of molecule 1 , containing a rigid C?F???Ar interaction that plays a prominent role in both its reaction chemistry and spectroscopy. For example, we established that the C?F???Ar interaction can bring about a >1500 fold increase in the relative rate of an aromatic nitration reaction, affording functionalization on the activated ring exclusively. Overall, these results establish fluoro as a through‐space directing/activating group that complements the traditional role of fluorine as a slightly deactivating aryl substituent in nitrations.     

多元络合物显色反应的研究——Ⅰ.稀土-铬天青S-1, 10-邻菲啰啉-溴化十六烷基三甲铵体系

近年来在分析化学中广泛使用多元络合物,它的优越性在于提高了反应的灵敏度和选择性.在三元络合物中,一般说来,混合配位体络合物(混配络合物)的选择性较好,而胶束增溶络合物(胶溶络合物)的灵敏度较高,这在稀土多元络合物的显色反应中也表现得很明显.为了提高多元络合物显色反应的灵敏度和改善选择性,我们设想把混配络合物和胶溶络合物统一在一个多元络合物体系中.胶溶络合物中以三苯甲烷染料研究最多,其中应用较广的是铬天青S和铬菁R,因此,我们对稀土-铬天青S-1,10-邻菲啰啉-溴化十六烷基三甲铵四元络合物的显色反应进行系统的研究.     

Shape‐directed platinum nanoparticle synthesis: nanoscale design of novel catalysts

Platinum‐based catalytic materials have received significant attention, particularly in the shape and size control of faceted materials for catalysis. More recently, there has been a rapid increase in the number of reports of successful preparations in this field; however, a fundamental understanding of controlled growth towards catalytic material design is essential for future implementation and broad application. In this review, we provide an overview of the recent findings reported since 2009, focusing on methods for shape control as well as the effects of exposed surface facets on select catalytic reactions. Copyright © 2013 John Wiley & Sons, Ltd.     

载Ag二氧化钛纳米线的制备及其光催化性能

利用水热合成法,制备出了二氧化钛纳米线,通过葡萄糖还原Ag(NH3)+2,在制备出的二氧化钛纳米线表面负载了 Ag纳米颗粒.利用透射电镜(TEM)、高分辨透射电镜(HRTEM)、X射线光电子能谱(XPS)和紫外-可见光谱(UV-Vis)对产物进行了表征.结果表明:该Ag/TiO2纳米线在可见光区域表现出较强的吸收性能.测试了样品降解酸性红3R溶液的活性.结果表明,TiO2纳米线表面负载Ag纳米颗粒对提高其光催化性能具有积极的作用.     

β-AgVO3一维材料的制备及其光学性能

以AgNO3和 NH4VO3为原料,采用水热法,通过调控反应体系pH值,制备了β-AgVO3纳米线、亚微米线及微米棒.采用X射线衍射(XRD)和场发射扫描电子显微镜(FE-SEM)对样品的组成和表面形貌进行了表征.紫外-可见光吸收测试表明所制得的不同尺寸的β-AgVO3一维材料均具有较宽的紫外-可见光吸收范围,通过计算得出β-AgVO3纳米线、亚微米线及微米棒的光学带隙分别为2.21 eV,2.17 eV和2.12 eV.     

Cd对纤锌矿ZnO极化特性的影响以及Zn0.75Cd0.25O/ZnO界面能带偏差的第一性原理研究

基于第一性原理GGA+U方法研究了Zn1-xCdxO合金的品格常数以及自发极化随Cd组分x的变化关系,其中极化特性的计算采用Berry-phase方法,同时计算了禁带宽度随Cd组分x的变化关系,并得到了能隙弯曲参数0.69.此外,通过计算宏观平均静电势的方法得到了(5 +3)Cd0.25Cd0.750/ZnO超晶格界面处的价带偏差为0.13 eV,导带偏差与价带偏差的比值为4/13,并且Zn1-xCdxO/ZnO界面两侧能带呈现Ⅰ型排列,这些研究结果将对Zn1-xCdxO/ZnO界面二维电子气的设计与优化起到重要作用.