[×ÊÔ´] ¡¶Science¡·(»¯Ñ§¡¢²ÄÁÏ)Á¬ÔØ----(15 August 2008)

Science (15 August 2008) CHEMISTRY: Halogen Versus Hydrogen P. Metrangolo and G. Resnati Science 15 August 2008: 918-919. Use of noncovalent interactions involving halogen atoms opens up new ways to manipulate molecular recognition processes. MATERIALS SCIENCE: Directing Self-Assembly Toward Perfection Rachel A. Segalman Science 15 August 2008: 919-920. A combination of self-assembled block copolymers with templated substrates can be used for precision lithographic applications. Optical Negative Refraction in Bulk Metamaterials of Nanowires Jie Yao, Zhaowei Liu, Yongmin Liu, Yuan Wang, Cheng Sun, Guy Bartal, Angelica M. Stacy, and Xiang Zhang Science 15 August 2008: 930. An array of silver nanowires placed in a porous alumina matrix forms a three-dimensional material that negatively refracts visible light. Density Multiplication and Improved Lithography by Directed Block Copolymer Assembly Ricardo Ruiz, Huiman Kang, Fran ois A. Detcheverry, Elizabeth Dobisz, Dan S. Kercher, Thomas R. Albrecht, Juan J. de Pablo, and Paul F. Nealey Science 15 August 2008: 936-939. An appropriate substrate pattern can direct an even finer pattern of a block copolymer, improving the resolution for lithography by a factor of four, beyond the usual limits. Graphoepitaxy of Self-Assembled Block Copolymers on Two-Dimensional Periodic Patterned Templates Ion Bita, Joel K. W. Yang, Yeon Si 122812829 08:55:57 k Jung, Caroline A. Ross, Edwin L. Thomas, and Karl K. Berggren Science 15 August 2008: 939-943. A substrate patterned with a sparse array of nanoscale posts can direct the self-assembly of block copolymers to create a finely ordered lithographic array, even over a large area. X-ray Diffraction and Computation Yield the Structure of Alkanethiols on Gold(111) A. Cossaro, R. Mazzarello, R. Rousseau, L. Casalis, A. Verdini, A. Kohlmeyer, L. Floreano, S. Scandolo, A. Morgante, M. L. Klein, and G. Scoles Science 15 August 2008: 943-946. The structure of self-assembled monolayers (SAMs) of long-chain alkyl sulfides on gold(111) has been resolved by density functional theory¨Cbased molecular dynamics simulations and grazing incidence x-ray diffraction for hexanethiol and methylthiol. The analysis of molecular dynamics trajectories and the relative energies of possible SAM structures suggest a competition between SAM ordering, driven by the lateral van der Waals interaction between alkyl chains, and disordering of interfacial Au atoms, driven by the sulfur-gold interaction. We found that the sulfur atoms of the molecules bind at two distinct surface sites, and that the first gold surface layer contains gold atom vacancies (which are partially redistributed over different sites) as well as gold adatoms that are laterally bound to two sulfur atoms. Download: http://www.namipan.com/d/b4fab97 ... 20e67752c6af3341e00 PS: ´Ë×ÊÔ´ÄËÊÇ´úzdq0110·¢£¬ËùÓеõ½µÄ½ð±Ò½±Àø»òÕßÆÀ¼ÛÈ«²¿¹ézdq0110ËùÓУ¬µ½Ê±ºòÓÐÀÍ°æÖ÷´úת£¬Ð»Ð»

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