化学学报 ›› 2011, Vol. 69 ›› Issue (24): 2901-2907.DOI: 10.6023/A1108113    下一篇

研究论文

离子通过碳纳米管的拉伸分子动力学模拟

贺仲金, 周健*   

  1. (华南理工大学化学与化工学院 绿色化学产品技术广东省重点实验室 广州 510640)
  • 收稿日期:2011-08-11 修回日期:2011-08-30 出版日期:2011-12-28 发布日期:2011-09-05
  • 通讯作者: 周健 E-mail:jianzhou@scut.edu.cn
  • 基金资助:

    国家自然科学基金;教育部新世纪优秀人才支持计划

Steered Molecular Dynamics Simulations of Ions Traversing Through Carbon Nanotubes

HE Zhong-Jin, ZHOU Jian   

  1. (Guangdong Provincial Key Laboratory for Green Chemical Product Technology, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640)
  • Received:2011-08-11 Revised:2011-08-30 Online:2011-12-28 Published:2011-09-05
  • Contact: Jian Zhou E-mail:jianzhou@scut.edu.cn

采用拉伸分子动力学模拟研究了Na+, K+和Cl通过(6,6), (7,7), (8,8), (9,9)和(10,10)碳纳米管的过程, 利用伞形取样法计算了离子通过碳管的平均力势能, 并对离子在管中和本体相中的水化作了比较. 结果表明, 离子通过管径较窄的碳管时, 在入口处遇到较大的阻力, 从出口进入本体相较容易|而通过管径相对较宽的碳管则几乎无阻碍. 离子通过碳管的能垒随管径的增大而降低, 不同离子的能垒各不相同, 表明碳管具有固有的离子选择性|离子通过碳管时, 不仅其配位数改变了, 而且配位层中水分子的取向也有所改变, 这两者共同决定了离子进入碳管时的去水化能, 进而影响离子通过碳管的能垒和碳管的离子选择性. 本工作将有助于理解离子通道蛋白中疏水区域的功能作用, 并可以为基于碳纳米管的纳流控系统的设计提供指导.

关键词: 碳纳米管, 离子选择性, 离子水化, 拉伸分子动力学, 伞形取样

In this work, steered molecular dynamics simulations were performed to study the process of Na+, K+ and Cl traversing through (6,6), (7,7), (8,8), (9,9) and (10,10) carbon nanotubes (CNTs). The potential of mean forces (PMF) of ions passing through CNTs were calculated with the umbrella sampling method. Ion hydration in CNTs and in bulk solution was analyzed and compared. Simulation results show that ions are hindered from entering narrow CNTs at the entrance|however, it is easy for ions to leave narrow CNTs into bulk solution at the exit. There is almost no hindrance for ions to translocate through wide CNTs. The free energy barriers for ions translocating through CNTs decrease sharply with the increase of diameter. Different free energy barriers of Na+, K+ and Cl entering CNTs indicate that CNTs have an inherent ion selectivity. When ions traverse through CNTs, coordination numbers and preferential orientation of water molecules in coordination shells of ions are different from those in bulk, which determine the dehydration energies of ions and affect free energy barriers of ions traversing CNTs and the ion selectivity of CNTs. Studies on ions traversing through the hydrophobic pores of CNTs assist in understanding the function of hydrophobic regions of ion-channel proteins and provide guidance for the design of CNT-based nano- fluidic devices.

Key words: carbon nanotube, ion selectivity, ion hydration, steered molecular dynamics, umbrella sampling

中图分类号: