Institute of Physics, Academia Sinica, 11529, Taipei, Taiwan.
Phys Chem Chem Phys. 2018 Sep 19;20(36):23522-23527. doi: 10.1039/c8cp02309c.
Investigating interfacial water ordering on solid surfaces with different hydrophobicities is fundamentally important. Here, we prepared hydrophilic mica substrates with some areas covered by mildly hydrophobic graphene layers and studied the resulting hydration layers using three-dimensional (3D) force measurements based on frequency-modulation atomic force microscopy. Hydration layers of 0.3-0.6 nm were detected on bare graphene regions; these layers were considerably larger than the spacing measured on mica (0.2-0.3 nm). On the graphene-covered regions, we also observed the formation of special ordered structures of adsorbates over time, on which, surprisingly, no prominent hydration layers were detected. Based on these findings, we present one possible scenario to describe the formation process of the ordered interfacial structures and the enhanced oscillation period in the force profiles. This work also demonstrates the capability and significance of 3D force measurements in probing hydration behaviors on a heterogeneous substrate with a lateral resolution smaller than several nanometers.
研究具有不同疏水性的固体表面上的界面水分子有序化具有重要的意义。在这里，我们制备了具有部分被轻度疏水性石墨烯层覆盖的亲水云母基底，并使用基于调频原子力显微镜的三维（3D）力测量技术研究了由此产生的水化层。在裸露的石墨烯区域检测到 0.3-0.6nm 的水化层；这些层的厚度明显大于云母（0.2-0.3nm）上测量的间距。在石墨烯覆盖的区域，我们还观察到吸附物的特殊有序结构随时间形成，令人惊讶的是，在这些结构上没有检测到明显的水化层。基于这些发现，我们提出了一种可能的情景来描述有序界面结构的形成过程和力谱中增强的振荡周期。这项工作还展示了 3D 力测量在探测具有小于几个纳米的横向分辨率的异质基底上的水化行为的能力和重要性。
