Probing liquid behaviour by helium atom scattering: surface structure and phase transitions of an ionic liquid on Au(111)

Probing liquid behaviour by helium atom scattering: surface structure and phase transitions of an ionic liquid on Au(111)
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通过氦原子散射探测液体行为:Au(111) 上离子液体的表面结构和相变

DOI:
10.1039/c3sc52237g
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发表时间:
2014
期刊:
Chem. Sci.
影响因子:
--
通讯作者:
McIntosh E
McIntosh E
中科院分区:
--
文献类型:
--
作者:
McIntosh E

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我们展示了氦原子散射技术在离子液体表面的应用,特别是研究在超高真空下吸附到单晶金(Au)(111)表面上的离子液体1-乙基-3-甲基咪唑双(三氟甲磺酰基)酰亚胺[C2 C1 Im][Tf 2N]层的结构和相变。我们观察到形成连续有序层的离子对吸附过程中的[C2 C1 Im][Tf 2N],并发现,需要一个剂量相当于三层的离子对润湿的表面。氦衍射扫描中的弹性衍射峰的存在和位置表明,在[C2 C1 Im][Tf 2N]的甚至厚的吸附膜(>8层或约36 μ m)的表面层与Au(111)衬底之间存在配准,其中[C2 C1 Im][Tf 2N]结构由矩阵符号(3 2,−6 8)描述。对于衬底温度在150和320 K之间,镜面反射氦的强度和衍射峰揭示了从结晶相到液体的相变,熔化发生在270和280 K之间,高于体相。我们发现从固体和液体表面的散射之间没有显着的差异,并找到一个Debye-Waller因子为这个系统2 W 1。
We demonstrate the application of the helium atom scattering technique to ionic liquid surfaces, specifically to study structure and phase transitions in layers of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C2C1Im][Tf2N] adsorbed onto the (111) surface of single crystal gold (Au) in UHV. We observe the formation of successive ordered layers of ion pairs during adsorption of [C2C1Im][Tf2N] and find that a dose equivalent to three layers of ion pairs is needed to wet the surface. The presence and position of the elastic diffraction peaks in helium diffraction scans indicates that there is registry between the surface layer of even thick adsorbed films (>8 layers or ∼36 Å) of [C2C1Im][Tf2N] and the Au(111) substrate, with the [C2C1Im][Tf2N] structure described by the matrix notation (3 2, −6 8). For substrate temperatures between 150 and 320 K, the intensity of specularly reflected helium and the diffraction peaks reveal a phase transition from a crystalline phase to a liquid, with melting occurring between 270 and 280 K, higher than in the bulk. We find no significant difference between scattering from the solid and liquid surfaces, and find a Debye–Waller factor for this system 2W ∼ 1.
DOI: --
发表时间: 2013
影响因子: 8.6
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DOI: --
发表时间: 1971
期刊:
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