Structure of self-assembled monolayers of semifluorinated alkanethiols on gold and silver substrates
Structure of self-assembled monolayers of semifluorinated alkanethiols on gold and silver substrates
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DOI：
10.1560/0k18-2rla-gaqd-nhru
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发表时间：
2000-01-01
影响因子：
3.2
通讯作者：
Lee, TR
中科院分区：
文献类型：
--
作者：
Frey, S;Heister, K;Lee, TR
用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半氟化烷基硫醇（SFATs）CF 3（CF2）（9）（CH 2）（n）SH（F10 HnSH：n = 2，11和17）在多晶Au和Ag表面形成的自组装单分子膜。发现SFAT在两种衬底上形成高度有序和密集的自组装膜。该分子通过其硫头基以与常规烷乙氧基化物（AT）自组装膜相同的方式牢固地键合到基底上。吸附的SFAT的烃（除了n = 2）和碳氟化合物部分保留预期的平面锯齿形和螺旋构象的相应的散装材料。碳氟化合物链的取向不依赖于基底。这些实体在F10 H2S/Au和F10 H2S/Ag中几乎垂直于基底，并且在具有较长烃部分的SFAT SAM中变得稍微更倾斜。然而，SFAT膜的烷基部分表现出的倾斜角和扭曲角是类似于那些正常的烷醇聚醚薄膜上的银和Au基板，尽管减少的堆积密度在SFAT膜相比，正常的AT SAM。我们认为，基板相关的倾斜和扭转角的差异，这两个系统与不同字符的头基基板键合Au和Ag。
Self-assembled monolayers (SAMs) formed from semifluorinated alkanethiols (SFATs) CF3(CF2)(9)(CH2)(n)SH (F10HnSH: n = 2, 11, and 17) on polycrystalline Au and Ag were characterized by X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and near edge X-ray absorption fine structure spectroscopy. SFATs were found to form highly ordered and densely packed SAMs on both substrates. The molecules are strongly bonded to the substrates via their sulfur head groups, in the same manner as conventional alkanethiol (AT) SAMs. The hydrocarbon (except for n = 2) and fluorocarbon parts of the adsorbed SFATs retain the expected planar zigzag and helical conformations of the respective bulk materials. The orientation of the fluorocarbon chains does not depend on the substrate. These entities are almost perpendicular to the substrate in F10H2S/Au and F10H2S/Ag and become slightly more tilted in SFAT SAMs with longer hydrocarbon moieties. However, the alkyl parts of the SFAT films exhibit tilt and twist angles that are similar to those of normal alkanethiol films on Ag and Au substrates despite the reduced packing density in the SFAT films as compared to normal AT SAMs. We suggest that the substrate-related differences in tilt and twist angles for both systems are associated with the different character of the headgroup-substrate bonding on Au and Ag.