Simulation of Subnanometer Contrast in Dynamic Atomic Force Microscopy of Hydrophilic Alkanethiol Self-Assembled Monolayers in Water
Simulation of Subnanometer Contrast in Dynamic Atomic Force Microscopy of Hydrophilic Alkanethiol Self-Assembled Monolayers in Water
复制标题
亲水性烷硫醇在水中自组装单分子层的动态原子力显微镜亚纳米对比度模拟
DOI：
10.1021/acs.langmuir.9b03655
复制
发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
Martini, Ashlie
中科院分区：
文献类型：
--
作者：
Hu, Xiaoli;Yang, Quanpeng;Ye, Tao;Martini, Ashlie
在液体环境中使用原子力显微镜（AFM）的表面的原子分辨率成像是具有挑战性的再现性和测量解释。为了了解这些挑战的起源，我们使用AFM在水中的亲水性自组装单分子膜（SAMs）上的分子动力学模拟。模型AFM针尖上的力被计算为相对于SAM表面的横向和垂直位置的函数。分析了水和自组装膜对总作用力的贡献，水的贡献与水的密度分布有关。然后，动态原子力显微镜建模的驱动振幅振荡的尖端。结果发现，在表面上的不同横向位置处的振幅之间的对比度依赖于尖端的垂直位置。最后，在恒定高度的两个垂直位置产生振幅图，捕获原子分辨率的能力与针尖上的力有关。这些结果提供了一个解释，观察到的不稳定性，原子尺度成像使用AFM和更普遍地提供洞察液体环境中获得的表面图像的对比度机制。
Atomic resolution imaging of surfaces in liquid environments using atomic force microscopy (AFM) is challenging in terms of both reproducibility and measurement interpretation. To understand the origins of these challenges, we used molecular dynamics simulations of AFM on hydrophilic self-assembled monolayers (SAMs) in water. The force on the model AFM tip was calculated as a function of lateral and vertical position relative to the SAM surface. The contributions of the water and SAMs to the overall force were analyzed, and the former was correlated to the water density distribution. Then, dynamic AFM was modeled by oscillating the tip at a driving amplitude. It was found that the contrast between amplitudes at different lateral positions on the surface was dependent on the vertical position of the tip. Lastly, amplitude maps were produced for two vertical positions at constant height, and the ability to capture atomic resolution was related to the force on the tip. These results offer an explanation for the observed instability in atomic scale imaging using AFM and more generally provide insight into the contrast mechanisms of surface images obtained in liquid environments.