Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Nanoscale. 2018 Jun 21;10(24):11657-11669. doi: 10.1039/c8nr02016g.
The adsorption and transport of water in an open cylindrical mesopore with two different inner surface arrangements of hydrophilicities were examined by molecular simulations. The first model has a weak hydrophilic surface at both entrances of the pore and a stronger hydrophilic surface in the mid-section. The second pore has stronger hydrophilic surfaces at the entrances and weaker in the middle region. The simulation results show that the water adsorption isotherms obtained from Grand Canonical Monte Carlo simulations and pore filling curves acquired from Grand Canonical Molecular Dynamics simulations change depending on the arrangement of the strong and weak hydrophilic surfaces. In the first model, water condensation focuses on the mid-section forming a liquid bridge or a film, which creates a concave meniscus accelerating subsequent adsorption within the pore. Two bridges form in the entrance regions, where a cavity naturally occurs in between the films, in the second model. The different filling and emptying mechanisms clearly change the adsorption-desorption characteristics for the two pore types, but the second type generally showed faster transitions overall. Flux and meniscus analysis also reveals a circulating flow at the menisci of the interfaces within the pore. The results are expected to be valuable in understanding the effects of interior surface modification of nanopores in future applications.
通过分子模拟研究了具有两种不同亲水内表面排列的开放圆柱形介孔中水分的吸附和传输。第一个模型在孔的两端具有较弱的亲水表面，而在中部具有较强的亲水表面。第二个孔在入口处具有较强的亲水表面，而在中部区域较弱。模拟结果表明，通过巨正则蒙特卡罗模拟获得的水分吸附等温线和通过巨正则分子动力学模拟获得的孔隙填充曲线取决于强亲水表面和弱亲水表面的排列方式而发生变化。在第一种模型中，水分凝结集中在中部形成液桥或薄膜，这会在孔内形成凹形弯月面，从而加速随后的吸附。在第二种模型中，在入口区域形成了两个桥，在薄膜之间自然形成了一个空腔。不同的填充和排空机制明显改变了两种类型的孔隙的吸附-解吸特性，但总体而言，第二种类型通常显示出更快的转变。通量和弯月面分析还揭示了孔隙界面弯月面处的循环流动。这些结果有望在未来的应用中理解纳米孔内部表面修饰的影响方面具有重要价值。
