RSC-ZPS.pdf 1. 扫描隧道显微术 (STM/S)只能 获取固体表层原子的外层电子谱（费米能级附近）； 2. XPS 获取固体表面几层和体内原子混合的内层电子谱 （体信息）； 3. ZPS 提取表层原子和缺陷周围两个原子范围内的价电子和芯能级谱（表面单原子层和点分辨信息, 如图示）; 4. ZPS 不仅克服 XPS 解谱的困难而且提供关于局域键长、键能、结合能、电荷极化和钉扎等以及它们的动力学过程的定量信息； 5. ZPS（2010美国专利） 有望成为材料科学、表面科学、和界面科学领域最为快捷有效的关键技术。 Zone-selective photoelectronic measurements of the local bonding and electronic dynamics associated with the monolayer skin and point defects of graphite RSC Adv DOI: 10.1039/c2ra00512c STM/S Profiles of point defects at graphite surface evidenced the BOLS expected high protrusion and the Ef resonant peaks as arising from th epolarization of the dangling bond electrons by the localy and densely entrapped core electrons of he lesscoordinated edge carbon atoms. Findings: 1) surface bonds are shorter and stronger (Ts) than those in the bulk (B); 2) defect bonds are even shorter and stronger (TD); 3) defect dangling bond electrons are polarized (P).
11 August 2010 Chinese chemists have successfully coupled aromatic molecules without the use of a transition metal catalyst - something that people have been trying to do for years with little success. Such cross-coupling reactions are crucial to organic synthesis and typically require expensive metals such as palladium. Efforts to find cheaper and more widely available alternatives have proved challenging. Now, Wei Liu, from Wuhan University, and colleagues appear to have succeeded by using an organic catalyst, DMEDA ( N,N '-dimethylethane-1,2-diamine) in the presence of the base potassium tert -butoxide. The team coupled unactivated benzene with a range of aryl iodides in the presence of the organic catalyst and the base. We have checked for contamination and excluded the involvement of trace amounts of transition metals - Aiwen Lei, Wuhan University The researchers suggest that the reaction proceeds via the formation of a radical, with the potassium salt initiating radical formation in the presence of DMEDA. 'In radical trap experiments the coupling was inhibited by a classical radical scavenger which suggested that radical species are involved,' says team member Aiwen Lei. Could trace amounts of transition metal have contaminated the experiment? 'Obviously this is one of the most important factors,' says Lei. 'We have checked the contamination of trace amounts of transition metals by ICP and excluded the involvement of small amounts of transition metals in this transformation.' In addition, the potassium tert -butoxide used in the work was purified by sublimation to remove any contaminants. Lei believes that the work could herald a new direction in organic synthesis. 'This is the first report of organocatalysis in carbon-carbon coupling or direct arylation between aryl halides and arenes, which could be considered as a conceptually different approach towards biaryl syntheses.' Commenting on the work, Carsten Bolm, an organic synthesis expert fromAachenUniversityinGermany, says, 'To be able to prepare cross-coupling products without the use of transition metals is an important scientific advance. Although at thepresent stage the substrate scope is by far too limited to make the process synthetically attractive, the findings illustrate that new reaction paths in direct C-H arylations are still to be discovered, and as such this work will be highly stimulating to the community.' Simon Hadlington Interesting? Spread the word using the 'tools' menu on the left. References W Liu et al , J. Am. Chem. Soc ., 2010, DOI: 10.1021/ja103050x http://www.rsc.org/chemistryworld/News/2010/August/11081002.asp
标签: C-C
