Fung Y K Catherine, Perkin Susan
Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK.
Faraday Discuss. 2023 Oct 12;246(0):370-386. doi: 10.1039/d3fd00042g.
The observation of long-range interactions across ionic liquids and highly concentrated electrolytes, extending far beyond the Debye-Hückel prediction and beyond the range predicted in liquid state theory, has been called 'anomalous underscreening'. A number of theoretical and experimental works have explored this phenomenon over recent years, although its origin is not yet fully understood. Most of the experimental studies of anomalous underscreening until now involved aprotic ionic liquids, and so it is of interest to explore interactions in protic ionic liquids where the distribution of charge in the fluid is different in nature. Here we present direct measurements of the interaction force as a function of separation distance, measured using a surface force balance, across solutions of a protic ionic liquid ethylammonium nitrate (EAN) and its mixtures with water over a range of volume fractions from 10 vol% to 100 vol% EAN. The results reveal intricate details about near-surface ordering and dynamics at the EAN-mica interface as well as anomalous underscreening consistent with that observed in the past with aprotic ionic liquids.
跨越离子液体和高浓度电解质的长程相互作用的观察结果，远远超出了德拜-休克尔预测范围以及液态理论所预测的范围，这一现象被称为“异常欠屏蔽”。近年来，许多理论和实验研究都探讨了这一现象，尽管其起源尚未完全明了。到目前为止，大多数关于异常欠屏蔽的实验研究都涉及非质子离子液体，因此，研究质子离子液体中的相互作用很有意义，因为质子离子液体中流体的电荷分布本质上有所不同。在此，我们展示了使用表面力天平测量的，作为分离距离函数的相互作用力的直接测量结果，该测量跨越了质子离子液体硝酸乙铵（EAN）及其与水的混合物在10体积%至100体积% EAN范围内的一系列体积分数的溶液。结果揭示了EAN-云母界面处近表面有序性和动力学的复杂细节，以及与过去在非质子离子液体中观察到的一致的异常欠屏蔽现象。
