Liquid/solid interface of ultrathin ionic liquid films: [C1C1Im][Tf2N] and [C8C1Im][Tf2N] on Au(111) |
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Authors: | Cremer T Stark M Deyko A Steinrück H-P Maier F |
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Institution: | Lehrstuhl fu?r Physikalische Chemie II and Erlangen Catalysis Resource Center, Friedrich-Alexander-Universita?t, Erlangen-Nu?rnberg Egerlandstrasse 3, 91058 Erlangen, Germany. |
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Abstract: | Ultrathin films of two imidazolium-based ionic liquids (IL), C(1)C(1)Im]Tf(2)N] (= 1,3-dimethylimidazolium bis(trifluoromethyl)imide) and C(8)C(1)Im]Tf(2)N] (= 1-methyl-3-octylimidazolium bis(trifluoromethyl)imide) were prepared on a Au(111) single-crystal surface by physical vapor deposition in ultrahigh vacuum. The adsorption behavior, orientation, and growth were monitored via angle-resolved X-ray photoelectron spectroscopy (ARXPS). Coverage-dependent chemical shifts of the IL-derived core levels indicate that for both ILs the first layer is formed from anions and cations directly in contact with the Au surface in a checkerboard arrangement and that for C(8)C(1)Im]Tf(2)N] a reorientation of the alkyl chain with increasing coverage is found. For both ILs, geometry models of the first adsorption layer are proposed. For higher coverages, both ILs grow in a layer-by-layer fashion up to thicknesses of at least 9 nm (>10 ML). Moreover, beam damage effects are discussed, which are mainly related to the decomposition of Tf(2)N](-) anions directly adsorbed at the gold surface. |
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