Institute of Materials, École Polytechnique Fédérale de Lausanne (EPFL), Station 12, 1015 Lausanne, Switzerland.
Nanoscale. 2018 Dec 13;10(48):23027-23036. doi: 10.1039/c8nr07657j.
Surface coatings are becoming an integral part of materials. In recent years, molecular coatings have found larger acceptance and uses. Among them, self-assembled monolayers (SAMs) are attractive due to their inherent versatility, manufacturability, and scale up ease. Understanding their structure-properties relationships in realistic conditions remains a major challenge. Here we present a methodology based on simultaneous topographical and nanomechanical characterization of SAMs using a commercially available setup for bimodal atomic force microscopy (AFM). It allows for accurate and quantitative measurement of surface elasticity, which is correlated to molecular ordering through topographical imaging. Our results indicate that effective surface elasticity (E*) scales with monolayer formation-time and ligand-length, parameters known to affect ligand ordering. The method developed, is extended to provide localization of the chemical species present in thiolated binary SAMs. Within the systems tested phase separation down to ∼10 nm domains could be observed both in the topography and in the elasticity channel.
表面涂层正在成为材料不可或缺的一部分。近年来，分子涂层得到了更大的认可和应用。其中，自组装单层（SAMs）由于其固有的多功能性、可制造性和易于规模化而具有吸引力。在实际条件下了解它们的结构-性能关系仍然是一个主要挑战。在这里，我们提出了一种基于商用双模态原子力显微镜（AFM）同时对 SAMs 进行形貌和纳米力学特性表征的方法。它允许对表面弹性进行准确和定量的测量，而表面弹性通过形貌成像与分子有序性相关联。我们的结果表明，有效表面弹性（E*）与单层形成时间和配体长度相关，这些参数已知会影响配体的有序性。所开发的方法还扩展到提供硫醇化二元 SAMs 中存在的化学物质的定位。在所测试的系统中，在形貌和弹性通道中都可以观察到低至约 10nm 域的相分离。
