Department of Micro Engineering, Kyoto University, Kyoto-daigaku-Katsura, Nishikyo, Kyoto 615-8549, Japan.
J Chem Phys. 2013 Dec 14;139(22):224701. doi: 10.1063/1.4838376.
Surface structures of binary mixtures of imidazolium-based ionic liquids having a common anion (bis(trifluoromethanesulfonyl)imide ([TFSI]), namely [C2MIM]1-x[C10MIM]x[TFSI] (x = 0.5 and 0.1), are studied using high-resolution Rutherford backscattering spectroscopy (HRBS) and time of flight secondary ion mass spectroscopy (TOF-SIMS). Although both measurements show surface segregation of [C10MIM] the degrees of the segregation are different. The surface fraction xsurf of [C10MIM] is estimated to be 0.6 ± 0.05 and 0.18 ± 0.02 by HRBS for x = 0.5 and 0.1, respectively. On the other hand, TOF-SIMS indicates much stronger surface segregation, namely xsurf = 0.83 ± 0.03 and 0.42 ± 0.04 for x = 0.5 and 0.1, respectively. The observed discrepancy can be attributed to the difference in the probing depth between HRBS and TOF-SIMS. The observed surface segregation can be roughly explained in terms of surface tension.
使用高分辨率卢瑟福背散射光谱（HRBS）和飞行时间二次离子质谱（TOF-SIMS）研究了具有常见阴离子（双（三氟甲烷磺酰基）亚胺（[TFSI]）的基于咪唑鎓的离子液体二元混合物的表面结构，即[C2MIM]1-x[C10MIM]x[TFSI]（x = 0.5 和 0.1）。尽管这两种测量都表明[C10MIM]的表面偏析，但偏析程度不同。通过 HRBS 分别估算出 x = 0.5 和 0.1 时[C10MIM]的表面分数 xsurf 为 0.6 ± 0.05 和 0.18 ± 0.02。另一方面，TOF-SIMS 表明表面偏析要强得多，即 xsurf = 0.83 ± 0.03 和 0.42 ± 0.04，分别为 x = 0.5 和 0.1。观察到的差异可归因于 HRBS 和 TOF-SIMS 之间的探测深度差异。观察到的表面偏析可以根据表面张力大致解释。
