Structure of Self-Assembled Monolayers of Partially Fluorinated Alkanethiols with a Fluorocarbon Part of Variable Length on Gold Substrate
Structure of Self-Assembled Monolayers of Partially Fluorinated Alkanethiols with a Fluorocarbon Part of Variable Length on Gold Substrate
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DOI：
10.1021/jp405475h
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发表时间：
2013-09-19
影响因子：
3.7
通讯作者：
Zharnikov, Michael
中科院分区：
文献类型：
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作者：
Lu, Hao;Zeysing, Daniela;Zharnikov, Michael
用高分辨X射线光电子能谱、红外反射吸收谱和近边X射线吸收精细结构谱研究了不同碳氟链长度的部分氟化烷基硫醇（PFAT）F（CF 2）（n）（CH 2）（11）SH（FnH 11 SH，n = 6，8，10）在Au（111）表面形成的一系列自组装单分子膜（SAMs）.发现自组装膜是高度有序和密集的。堆积密度由采用该实体典型的螺旋构象的大体积氟碳链段决定。随着碳氟链段长度的减小，取向顺序逐渐恶化，伴随着包装密度略有下降，观察到在氟碳部分的FnH11SH自组装膜。碳氟化合物片段的构象在整个系列中是持久的，对于n = 8和6，可能只有轻微的恶化。然而，单分子膜的烃段不受碳氟化合物部分中取向顺序劣化的影响。它们持续显示出所有的反式平面构象，这是这些部分密集组装的典型，而它们的取向（由特征倾斜角和扭曲角给出）模仿了Au上未取代的烷硫醇盐自组装分子的取向（111）。这种行为是解释的弯曲电位的影响，它预先定义的烃链段的取向，即使它们被分开超过平衡间距的庞大的氟碳化合物部分。
A series of self-assembled monolayers (SAMs) formed on Au(111) from partially fluorinated alkanethiols (PFAT) with variable length of the fluorocarbon chain, viz. F(CF2)(n)(CH2)(11)SH (FnH11SH, n = 6, 8, and 10), was studied by high resolution X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and near edge X-ray absorption fine structure spectroscopy. The SAMs were found to be highly ordered and densely packed. The packing density was governed by the bulky fluorocarbon segments which adopted a helical conformation typical of this entity. With decreasing length of the fluorocarbon segment, progressive deterioration of the orientational order accompanied by a slight decrease in the packing density was observed in the fluorocarbon part of the FnH11SH SAMs. The conformation of the fluorocarbon segment was persistent through the series, with probably only a minor deterioration for n = 8 and 6. The hydrocarbon segments of the monolayers were, however, unaffected by the deterioration of the orientational order in the fluorocarbon part. They persistently exhibited all trans planar conformation, typical of densely packed assemblies of these moieties, while their orientation, given by the characteristic tilt and twist angles, mimicked that of the nonsubstituted alkanethiolate SAMs on Au(111). This behavior is explained by the effect of the bending potential which predefines the orientation of the hydrocarbon segments even if they are separated beyond the equilibrium spacing by the bulky fluorocarbon moieties.