Ordering of Small Molecules on Hydrophobic Self-Assembled n -Alkanethiols: Delicate Balance of Interfacial and Intermolecular Interactions
Ordering of Small Molecules on Hydrophobic Self-Assembled n -Alkanethiols: Delicate Balance of Interfacial and Intermolecular Interactions
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疏水自组装正链烷硫醇上小分子的排序：界面和分子间相互作用的微妙平衡
DOI：
10.1021/acs.jpcc.1c06216
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Yang, Ding-Shyue
中科院分区：
文献类型：
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作者：
Ghosh, Mithun;Yang, Ding-Shyue
随着电子工业寻求新的机会和应用，具有所需顺序和取向的分子薄膜的生长已经变得与技术相关。然而，界面和分子间力的微妙平衡及其对薄膜生长的复杂影响仍然需要更多的了解。在这里，一个疏水性的自组装单层（SAM）表面上的四种常见的溶剂-乙腈，乙醇，甲醇和水的结晶的影响进行了研究。尽管没有显着的基板分子的力量，意想不到的定向生长观察到这些分子，除了水。乙腈和乙醇形成具有长程结晶结构的持续垂直组装顺序。小晶格失配的重合外延被发现是必不可少的这些排序，这是积极的青睐，但没有一个占主导地位的方位角取向。相比之下，一个优选的面内注册表的甲醇覆盖层观察到的一个小的标称厚度，并在稍厚的膜变得失去。这种依赖于厚度的顺序的甲醇组件可以解释与半相称的外延与一个拉伸应变为沿着氢键键合的链，其快速救济的结果在损失的顺序，甚至相的6.6%。这些丰富的观察表明，SAM表面提供了很好的机会，值得进一步研究的分子膜的选择性结晶。
Growth of molecular thin films with desired orders and orientations has become technologically relevant as the electronic industries seek new opportunities and applications. However, the delicate balance of interfacial and intermolecular forces and their complex influence on thin-film growths still require more understanding. Here, the effects of a hydrophobic self-assembled monolayer (SAM) surface on the crystallization of four common solvents—acetonitrile, ethanol, methanol, and water—are investigated. Despite the absence of significant substrate–molecule forces, unexpected oriented growth is observed for these molecules except water. Acetonitrile and ethanol form a sustaining vertical assembly order with long-range crystalline structures. Coincident epitaxy with small lattice mismatches is found to be essential to these orderings, which are energetically favored but without a dominant azimuthal orientation. In contrast, a preferred in-plane registry of methanol overlayers is observed for an ultrathin nominal thickness and becomes lost in slightly thicker films. Such thickness-dependent ordering of methanol assemblies can be explained with semi-commensurate epitaxy with a tensile strain of ∼6.6% along hydrogen-bonded chains, whose quick relief results in the loss of order and even the phase. These rich observations suggest that SAM surfaces offer good opportunities for selective crystallization of molecular films worthy of further investigations.