Surface Structural Study on Ionic Liquids Using Metastable Atom Electron Spectroscopy
Surface Structural Study on Ionic Liquids Using Metastable Atom Electron Spectroscopy
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DOI：
10.1021/jp9056797
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发表时间：
2009-11-05
影响因子：
3.7
通讯作者：
Ouchi, Yukio
中科院分区：
文献类型：
--
作者：
Iwahashi, Takashi;Nishi, Toshio;Ouchi, Yukio
采用紫外光电子能谱（UPS）和亚稳态原子电子能谱（MAES）研究了n = 4，8和10的离子液体1-CnH 2n +1-3-甲基咪唑四氟硼酸盐（BF 4-）、三氟甲磺酸盐（OTf）和双（三氟甲磺酰基）酰胺（TFSA）的表面结构。MAES光谱表明，阴离子和阳离子共享的室温离子液体（RTIL）的表面与较短的烷基链在n = 4，虽然烷基链层往往覆盖在最外表面的情况下，RTIL与较长的烷基链的n = 8和10。UPS和MAES谱的比较表明，非极性基团如烷基链和CF 3基团指向真空侧，而极性基团如SO 3和SO2基团指向体相侧。根据这些观察，提出了在表面的双层结构，它由烷基链层和含有阴离子和咪唑环的极性层组成。
The surface structures of ionic liquids 1-CnH2n+1-3-methylimidazolium tetrafluoroborate (BF4-), trifluoromethanesulfonate (OTf) and bis(trifluoromethylsulfonyl)amide (TFSA) with n = 4, 8, and 10 were investigated by ultraviolet photoemission spectroscopy (UPS) and metastable atom electron spectroscopy (MAES). The MAES spectra reveal that the anions and cations share the surface of the room-temperature ionic liquids (RTILs) with a shorter alkyl chain at n = 4 although the alkyl chain layer tends to cover the outermost surface in the case of RTILs with longer alkyl chains of n = 8 and 10. Comparison of UPS and MAES spectra demonstrates that the nonpolar groups such as the alkyl chain and the CF3 group Point toward the vacuum side, while the polar groups such as the SO3 and SO2 groups face toward the bulk side. A double-layered structure at the Surface, which consists of an alkyl chain layer and a polar layer containing anions and imidazolium rings, is proposed from these observations.