疏水性可调的功能化纳米管的水传输
Water transport through functionalized nanotubes with tunable hydrophobicity
摘要：
分子动力学模拟被用来研究水通过由疏水和亲水原子组成的纳米管的占据和流动，纳米管被布置在蜂窝晶格上以模拟官能化的碳纳米管（CNT）。我们考虑TIP 3 P水通过具有不同亲水原子分数（f）的（6，6）CNT的窄通道的单列运动。亲水性原子的各种排列被用来产生沿着管具有单独的疏水/亲水域以及两种类型的原子的随机混合物的异质纳米管。发现纳米管通道内的水占有率作为f的函数非线性地变化，并且一小部分亲水原子（f ~ 0.4）足以诱导纳米管的自发和连续填充。有趣的是，通道内水分子的平均数量和通过纳米管的水通量对亲水原子的特定排列的敏感性低于对分数f的敏感性。对于水通量对f的依赖性，观察到两种不同的状态-对于f < 0.4，通量作为f的函数近似线性增加，并且对于更高的f值，通量几乎没有变化，类似于水占有率的变化。我们能够定义纳米管原子和水的氧之间的有效相互作用强度，基于疏水性和亲水性纳米管原子和水之间的相互作用强度的线性组合，可以定量地捕获所观察到的行为。
英文摘要：
Molecular dynamics simulations are used to study the occupancy and flow of water through nanotubes comprised of hydrophobic and hydrophilic atoms, which are arranged on a honeycomb lattice to mimic functionalized carbon nanotubes (CNTs). We consider single-file motion of TIP3P water through narrow channels of (6,6) CNTs with varying fractions (f) of hydrophilic atoms. Various arrangements of hydrophilic atoms are used to create heterogeneous nanotubes with separate hydrophobic/hydrophilic domains along the tube as well as random mixtures of the two types of atoms. The water occupancy inside the nanotube channel is found to vary nonlinearly as a function of f, and a small fraction of hydrophilic atoms (f ~ 0.4) are sufficient to induce spontaneous and continuous filling of the nanotube. Interestingly, the average number of water molecules inside the channel and water flux through the nanotube are less sensitive to the specific arrangement of hydrophilic atoms than to the fraction, f. Two different regimes are observed for the water flux dependence on f - an approximately linear increase in flux as a function of f for f < 0.4, and almost no change in flux for higher f values, similar to the change in water occupancy. We are able to define an effective interaction strength between nanotube atoms and water's oxygen, based on a linear combination of interaction strengths between hydrophobic and hydrophilic nanotube atoms and water, that can quantitatively capture the observed behavior.
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