Underscreening in concentrated electrolytes
Underscreening in concentrated electrolytes
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DOI：
10.1039/c6fd00250a
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发表时间：
2017-07-01
影响因子：
3.4
通讯作者：
Perkin, Susan
中科院分区：
文献类型：
--
作者：
Lee, Alpha A.;Perez-Martinez, Carla S.;Perkin, Susan
在从生物分子相互作用到能量存储的场景中，通过电解液筛选表面电荷以及所产生的带电物体之间的相互作用能量是至关重要的。传统的观点认为，相互作用能随着物体的分离呈指数衰减，衰减长度是离子浓度的递减函数；因此，在浓缩液中，相互作用可以忽略不计。与传统的看法相反，我们通过表面力测量表明，对于浓缩的电解液，衰变长度是离子浓度和Bjerrum长度的递增函数。在本文中，我们报道了通过表面力测量来直接测试筛分长度与Bjerrum长度之间的比例关系。此外，我们确定了这种屏蔽长度的浓度依赖关系和活度系数和微分电容的经验测量之间的关系。屏蔽长度与离子浓度和Bjerrum长度的关系可以用一个简单的标度猜想来解释，该猜想基于一种物理直觉，即在浓缩的电解液中，溶剂分子而不是离子是电荷载流子。
Screening of a surface charge by an electrolyte and the resulting interaction energy between charged objects is of fundamental importance in scenarios from biomolecular interactions to energy storage. The conventional wisdom is that the interaction energy decays exponentially with object separation and the decay length is a decreasing function of ion concentration; the interaction is thus negligible in a concentrated electrolyte. Contrary to this conventional wisdom, we have shown by surface force measurements that the decay length is an increasing function of ion concentration and Bjerrum length for concentrated electrolytes. In this paper we report surface force measurements to test directly the scaling of the screening length with Bjerrum length. Furthermore, we identify a relationship between the concentration dependence of this screening length and empirical measurements of activity coefficient and differential capacitance. The dependence of the screening length on the ion concentration and the Bjerrum length can be explained by a simple scaling conjecture based on the physical intuition that solvent molecules, rather than ions, are charge carriers in a concentrated electrolyte.