Directing Long-Range Molecular Ordering in Ionic Liquid Films: A Tale of Two Interfaces
Directing Long-Range Molecular Ordering in Ionic Liquid Films: A Tale of Two Interfaces
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DOI：
10.1021/acs.jpcc.8b12575
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发表时间：
2019-04-11
影响因子：
3.7
通讯作者：
Shaw, Scott K.
中科院分区：
文献类型：
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作者：
Anaredy, Radhika S.;Shaw, Scott K.
我们报道了两种离子液体，1-丁基-1-甲基吡咯烷鎓四氰硼酸盐（P14 B（CN)）(4)）和1-丁基-1-甲基吡咯烷鎓二氰酰胺(P14 N（CN)(2)）的表面依赖的远程有序行为。离子液体被支撑成液体膜，并使用振动光谱和椭偏光谱对其进行了检测。两种体系中阴离子的主要偶极子取向的红外峰分布特征都发生了变化，但所观察到的变化是在不同的光谱区域。具体来说，四氰硼酸盐表现出B-C模式的变化，二氰酰胺表现出C - N和N-C模式的变化。令人惊讶的是，B(CN)(4)诱导了与固液界面取向相同的最终膜环境。然而，N(CN)(2)表明气液界面环境通过薄膜向固体衬底传播。P14 N(CN)(2)和P14 B(CN)(4)在膜内的有序程度分别达到0.4和1.1 μ m。这一观察结果很有趣，因为它提出了通过调节基本的分子间相互作用在100秒纳米尺度上控制分子（再）取向的可能性。这些关于氰基官能化阴离子的研究结果应该普遍应用于其他体系，直接有助于更好地理解和设计在分子电子学、润滑和储能装置中的应用。
We report surface-dependent, long-range ordering behavior of two ionic liquids, 1-butyl-1-methylpyrrolidinium tetracyanoborate (P14 B(CN)(4)) and 1-butyl-1-methylpyrrolidinium dicyanamide (P14 N(CN)(2)). The ionic liquids are supported as liquid films and examined using vibrational spectroscopy and spectroscopic ellipsometry. Both systems show changes in the infrared peak profile characteristic of major dipole reorientations for both anions, but the changes observed are in different spectral regions. Specifically, tetracyanoborate shows changes in the B-C stretching modes, and dicyanamide displays changes in the C N and N-C modes. Surprisingly, B(CN)(4) induces a final film environment, which is identical to the solid-liquid interfacial orientation. However, the N(CN)(2) indicates propagation of the gas-liquid interfacial environment through the film toward the solid substrate. The extent of ordering within the films extends to 0.4 and 1.1 mu m for P14 N(CN)(2) and P14 B(CN)(4), respectively. This observation is intriguing as it presents a possibility for controlling molecular (re)orientations at 100 s of nanometer scales by tuning fundamental intermolecular interactions at surfaces. These results for the cyano-functionalized anions should be generally applied for other systems, contributing directly to a better understanding and design for applications in molecular electronics, lubrication, and energy storage devices.