Electrospray Ionization Deposition of Ultrathin Ionic Liquid Films: [C8C1Im]Cl and [C8C1Im][Tf2N] on Au(111)
Electrospray Ionization Deposition of Ultrathin Ionic Liquid Films: [C8C1Im]Cl and [C8C1Im][Tf2N] on Au(111)
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DOI：
10.1021/la404429q
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发表时间：
2014-02-04
期刊：
影响因子：
3.9
通讯作者：
Maier, Florian
中科院分区：
文献类型：
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作者：
Rietzler, Florian;Piermaier, Marius;Maier, Florian
介绍了一种在超高真空条件下，利用电喷雾离子化沉积（ESID）技术在表面制备纳米离子液体薄膜的新方法。与在UHV下的离子液体的物理气相沉积（PVD）相反，ESID甚至允许离子液体的沉积，其易于热分解。作为概念的证明，我们首先通过角分辨X射线光电子能谱（ARXPS）研究了在Au（111）上的双[C（8）C（1）Im][Tf 2N]（=1-甲基-3-辛基咪唑鎓双（三氟甲基）酰亚胺）膜。发现通过ESID获得的膜与通过标准PVD生长的膜几乎相同。此后，研究了[C（8）C（1）Im]Cl在Au（111）上的ESID，作为否则不能制备为SOI膜的IL的第一实例。[C（8）C（1）Im]Cl形成具有棋盘排列的润湿层，其中阳离子咪唑环和氯阴离子彼此相邻地吸附在基底上，并且烷基链指向真空。润湿层内的这种排列类似于对[C（8）C（1）Im][Tf 2N]观察到的排列，尽管具有更高的烷基链有序度。[C（8）C（1）Im]Cl的进一步沉积导致润湿层顶部上的明显岛状生长，这通过ARXPS和原子力显微镜独立地证实。该行为与[C8 C，Itn][Tf 2N]的生长行为形成对比，其中观察到在润湿层顶部上的逐层生长。这两种离子液体之间的显着差异是由于在阳离子/阴离子相互作用的差异，并在两个离子液体的润湿层的程度。
We introduce a new method for preparing ultrathin ionic liquid (IL) films on surfaces by means of electrospray ionization deposition (ESID) under ultraclean and well-defined ultra-high-vacuum (UHV) conditions. In contrast to physical vapor deposition (PVD) of ILs under UHV, ESID even allows deposition of ILs, which are prone to thermal decomposition. As proof of concept, we first investigated ultrathin [C(8)C(1)Im][Tf2N] (=1-methyl-3-octyl imidazolium bis(trifluoromethyl)imide) films on Au(111) by angle-resolved X-ray photoelectron spectroscopy (ARXPS). Films obtained by ESID are found to be virtually identical to films grown by standard PVD. Thereafter, ESID of [C(8)C(1)Im]Cl on Au(111) was studied as a first example of an IL that cannot be prepared as ultrathin film otherwise. [C(8)C(1)Im]Cl forms a wetting layer with a checkerboard arrangement with the cationic imidazolium ring and the chloride anion adsorbed next to each other on the substrate and the alkyl chain pointing toward vacuum. This arrangement within the wetting layer is similar to that observed for [C(8)C(1)Im][Tf2N], albeit with a higher degree of order of the alkyl chains. Further deposition of [C(8)C(1)Im]Cl leads to a pronounced island growth on top of the wetting layer, which is independently confirmed by ARXPS and atomic force microscopy. This behavior contrasts the growth behavior found for [C8C,Itn][Tf2N], where layer-by-layer growth on top of the wetting layer is observed. The dramatic difference between both ILs is attributed to differences in the cation anion interactions and in the degree of order in the wetting layer of the two ILs.