Abstract: The effects of the outer surface charge on the water transport behavior inside double-wall carbon nanotube (DWCNT) were examined using molecular dynamic simulation. It is shown that the bipolar dipole orientation of water molecules inside charged DWCNT prohibits the flipping of whole water chains, stabilizing the hydrogen bonds from these fluctuations and thus accelerating the water flux, compared to the neutral DWCNT. On the other hand, the introduction of electrostatic interactions between CNT and water molecules reduces the free energy barrier of water entry, which also enhances water flux. Above simulation results provide a molecular insight into the water transport through CNT, which is helpful for the design of CNT based materials and devices for water purification.

Key words: carbon nanotube, molecular simulation, nanomaterial, flow, transport

摘要： 采用分子动力学模拟方法考察了双壁碳纳米管外壁荷电性质对孔道内水分子运动行为的影响。模拟结果显示：外壁荷电的双壁碳纳米管中水分子链呈现“双偶极”分布，由此将水分子的偶极翻转限制在碳纳米管的中部，避免了整条水分子链的偶极翻转，加速了水分子运动。外壁负载电荷也增强了水分子与碳纳米管之间相互作用，降低了水分子进入碳纳米管的能量壁垒，增强了碳纳米管内水分子内的氢键稳定性，这些均有利于水分子加速进入碳纳米管并在其中连续运动。上述结果从分子水平上揭示了碳管中水分子流动机理，为设计新型水纯化膜材料提供了有益的启示。

关键词: 碳纳米管, 分子模拟, 纳米材料, 流动, 传递