How Is Diffusion of Neutral and Charged Tracers Related to the Structure and Dynamics of a Room-Temperature Ionic Liquid? Large Deviations from Stokes鈥揈instein Behavior Explained

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• 作者：Juan C. Araque ; Sharad K. Yadav ; Michael Shadeck ; Mark Maroncelli ; Claudio J. Margulis
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：June 11, 2015
• 年：2015
• 卷：119
• 期：23
• 页码：7015-7029
• 全文大小：1348K
• ISSN：1520-5207

文摘

The deviations from Stokes鈥揈instein hydrodynamics of small solutes are more pronounced in ionic liquids than in conventional solvents (J. Phys. Chem. B 2013 117 (39), 11697). Small neutral solutes diffuse much faster than expected, whereas small charged solutes diffuse much slower. This article attempts to establish a link between the local friction experienced by tracer solutes and the polar/apolar structure of ionic liquids. We find that small neutral solutes probe locally 鈥渟tiff鈥?(mostly charged, high electrostriction) regions and locally 鈥渟oft鈥?(mostly apolar, low electrostriction) regions. These regions of high and low friction are associated with cage and jump regimes. Enhanced neutral tracer mobility in the low friction regions associated with the cationic apolar component has an important bearing on the large positive deviations from Stokes鈥揈instein behavior. In contrast, diminished charged tracer mobility involves long caging dynamics separated by jump events often triggered by the loss and recovery of counterions.