Willey Trevor M, Vance Andrew L, van Buuren T, Bostedt C, Nelson A J, Terminello L J, Fadley C S
Department of Physics, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.
Langmuir. 2004 Mar 30;20(7):2746-52. doi: 10.1021/la036073o.
Carboxyl-terminated self-assembled monolayers (SAMs) are commonly used in a variety of applications, with the assumption that the molecules form well-ordered monolayers. In this work, near-edge X-ray absorption fine structure measurements verify that well-ordered monolayers can be formed using acetic acid in the solvent. Disordered monolayers with unbound molecules present in the film result using only ethanol. A stark reorientation occurs upon deprotonation of the end group by rinsing in a KOH solution. This reorientation of the end group is reversible with tilted-over, hydrogen-bound carboxyl groups while the carboxylate ion end groups are upright. C(1s) photoemission shows that SAMs formed and rinsed with acetic acid in ethanol have protonated end groups, while SAMs formed without acetic acid have a large fraction of carboxylate-terminated molecules.
羧基封端的自组装单分子层（SAMs）通常用于各种应用中，其前提假设是分子能形成有序的单分子层。在这项工作中，近边X射线吸收精细结构测量证实，在溶剂中使用乙酸可以形成有序的单分子层。仅使用乙醇时，薄膜中会出现含有未结合分子的无序单分子层。通过在KOH溶液中冲洗使端基去质子化后会发生明显的重新取向。当羧基离子端基直立时，端基的这种重新取向对于倾斜的、氢键结合的羧基是可逆的。C(1s)光发射表明，在乙醇中用乙酸形成并冲洗的SAMs具有质子化的端基，而没有乙酸形成的SAMs有很大一部分是羧基封端的分子。
