文章基本信息

标题：Molecular mechanism of water reorientational slowing down in concentrated ionic solutions
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作者：Qiang Zhang ; TianMin Wu ; Chen Chen 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：38
页码：10023-10028
DOI：10.1073/pnas.1707453114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Water dynamics in concentrated ionic solutions plays an important role in a number of material and energy conversion processes such as the charge transfer at the electrolyte–electrode interface in aqueous rechargeable ion batteries. One long-standing puzzle is that all electrolytes, regardless of their “structure-making/breaking” nature, make water rotate slower at high concentrations. To understand this effect, we present a theoretical simulation study of the reorientational motion of water molecules in different ionic solutions. Using an extended Ivanov model, water rotation is decomposed into contributions from large-amplitude angular jumps and a slower frame motion which was studied in a coarse-grained manner. Bearing a certain resemblance to water rotation near large biological molecules, the general deceleration is found to be largely due to the coupling of the slow, collective component of water rotation with the motion of large hydrated ion clusters ubiquitously existing in the concentrated ionic solutions. This finding is at variance with the intuitive expectation that the slowing down is caused by the change in fast, single-molecular water hydrogen bond switching adjacent to the ions.
关键词：ion specificity ; water rotation ; ionic solution ; femtosecond infrared ; structure dynamics