Structure and Orientation of Interfacial Water Determine Atomic Force Microscopy Results: Insights from Molecular Dynamics Simulations
Structure and Orientation of Interfacial Water Determine Atomic Force Microscopy Results: Insights from Molecular Dynamics Simulations
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DOI：
10.1021/nn103454m
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发表时间：
2011-03-01
期刊：
影响因子：
17.1
通讯作者：
Striolo, Alberto
中科院分区：
文献类型：
--
作者：
Argyris, Dimitrios;Ashby, Paul D.;Striolo, Alberto
采用大规模全原子分子动力学模拟来研究 α-Al2O3 (0001) 表面附近的水合力，该水合力是在环境条件下使用 (28,0) 单壁碳纳米管作为尖端进行的假设 AFM 力谱实验中采样的。结果提供了作用在碳纳米管尖端上的力，以及界面水的详细特性，作为纳米管表面距离的函数。当尖端接近固体基质时，界面水会发生构象和结构变化。这些变化导致了力分布中观察到的特征，包括力的测量范围（最多两个水合壳）、AFM 尖端所经历的力的强度及其振荡特性。我们的详细分析表明，异质表面化学成分会导致明显不同的力分布。这一观察结果可以解释即使在原子级光滑的基底上，AFM 数据采样水合力的可变性。此外，我们的结果表明，足够精确的 AFM 力谱可用于研究水合力如何依赖于表面异质特性以及界面水的方向和局部密度，这可以帮助我们理解界面现象并带来重大的科学突破。
Massive all-atom molecular dynamics simulations were employed to study hydration forces near alpha-Al2O3 (0001) surfaces as sampled during a hypothetical AFM force spectroscopy experiment conducted using, a (28,0)single-walled carbon nanotube as the tip at ambient conditions. The results provide the-force acting on the carbon nanotube tip, as well as detailed properties of interfacial water, as a function of the nanotube-surface distance. As the tip approaches the solid substrate, interfacial water undergoes conformational and structural changes. These changes are responsible for the features observed in the force profiles, including the range at which forces can be measured (up to two hydration shells), the intensity of the forces experienced by the AFM tip, and their oscillatory,character. Our detailed analysis shows that heterogeneous surface chemical composition results in appreciably different force profiles. This observation may explain the variability of AFM data sampling hydration forces even on atomically smooth substrates. In addition, our results suggest that sufficiently accurate AFM force spectroscopy could be used to study how hydration forces depend on surface heterogeneous properties and on the orientation and local density of interfacial water, which could aid our understanding of interfacial phenomena and lead to significant scientific breakthroughs.