A relationship between the force curve measured by atomic force microscopy in an ionic liquid and its density distribution on a substrate
A relationship between the force curve measured by atomic force microscopy in an ionic liquid and its density distribution on a substrate
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DOI：
10.1039/c7cp06948k
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发表时间：
2017-12-07
影响因子：
3.3
通讯作者：
Sakka, Tetsuo
中科院分区：
文献类型：
--
作者：
Amano, Ken-ichi;Yokota, Yasuyuki;Sakka, Tetsuo
离子液体在衬底上形成特征的溶剂化结构。例如，当衬底表面带负电荷或正电荷时，阳离子和阴离子层在表面上交替排列。这种溶剂化结构与扩散速度慢、电容量大以及界面化学反应密切相关。为了分析溶剂化结构的周期性，经常使用原子力显微镜。测得的力曲线一般是振荡的，其特征振荡长度不是对应于离子直径，而是对应于离子对直径。然而，力曲线不是溶剂化结构。因此，有必要了解作用力曲线与溶剂化结构之间的关系。为了在这种关系中找到物理本质，我们使用了简单离子液体的统计力学。我们发现，基本关系可以用一个简单的方程来表示，并解释了振荡长度与离子对直径相对应的原因。此外，我们还发现Derjaguin近似适用于离子液体体系。
An ionic liquid forms a characteristic solvation structure on a substrate. For example, when the surface of the substrate is negatively or positively charged, cation and anion layers are alternately aligned on the surface. Such a solvation structure is closely related to slow diffusion, high electric capacity, and chemical reactions at the interface. To analyze the periodicity of the solvation structure, atomic force microscopy is often used. The measured force curve is generally oscillatory and its characteristic oscillation length corresponds not to the ionic diameter, but to the ion-pair diameter. However, the force curve is not the solvation structure. Hence, it is necessary to know the relationship between the force curve and the solvation structure. To find physical essence in the relationship, we have used statistical mechanics of a simple ionic liquid. We found that the basic relationship can be expressed by a simple equation and the reason why the oscillation length corresponds to the ion-pair diameter. Moreover, it is also found that Derjaguin approximation is applicable to the ionic liquid system.