title: Perfect Composition Depth Profiling of Ionic Liquid Surfaces Using High-resolution RBS/ERDA.
abstract: In order to reveal the surface structures of large molecular ionic liquids (ILs), the near-surface elemental depth distributions of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([CnC1Im][Tf2N], n = 2, 6, 10) were studied using high-resolution Rutherford backscattering spectroscopy (HRBS) in combination with high-resolution elastic recoil detection analysis (HR-ERDA). The elemental depth profiles of all constituent elements, including hydrogen, were derived from HR-ERDA/HRBS measurements, so that the profiles would reproduce both HR-ERDA and HRBS spectra simultaneously. The derived elemental depth profiles agree with state-of-the-art molecular dynamics simulations, indicating the feasibility of this method. A controversy concerning the preferential orientation of [C2C1Im] at the surface has been resolved by this new combination analysis; namely, the [C2C1Im] cation has a preferential orientation with the ethyl chain pointing towards the vacuum in the topmost molecular layer.
authors.affiliation: Department of Micro Engineering, Kyoto University.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Nakajima
authors.forename: Enkhbayar
authors.initials: E
authors.lastname: Zolboo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Ohashi
authors.forename: Martin
authors.initials: M
authors.lastname: Lísal
authors.forename: Kenji
authors.initials: K
authors.lastname: Kimura