Paul Sanjib, Abi T G, Taraphder Srabani
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
Department of Chemistry, Sacred Heart College Thevara, Kochi 682013, India.
J Chem Phys. 2014 May 14;140(18):184511. doi: 10.1063/1.4873695.
We have carried out classical molecular dynamics simulations on the formation of extended water chains inside single-walled carbon nanotubes (SWCNTs) in water in the presence of selected functional groups covalently attached to the inner wall of the tube. Analogues of polar amino acid sidechains have been chosen to carry out the endohedral functionalization of SWCNTs. Our results show a spontaneous and asymmetric filling of the nanotube with dynamical water chains in all the cases studied. The presence of Asp- and Glu-like sidechains is found to result in the formation of well-ordered water chains across the tube having the maximum number of water molecules being retained within the core with the largest residence times. The presence of methyl or methylene groups along the suspended chain is observed to disrupt the formation of water chains with higher length and/or longer residence times. The importance of hydrogen bonding in forming these water chains is assessed in terms of the relaxations of different hydrogen bond correlation functions. For a given dimension of the hydrophobic nanopore, we thus obtain a scale comparing the ability of carboxylic, alcohol, and imidazole groups in controlling the structure and dynamics of water in it. Our results also suggest that SWCNTs of varying lengths, endohedrally functionalized with Asp- and Glu-like sidechains, may be used as design templates in CNT-based water storage devices.
我们对存在共价连接于碳纳米管内壁的特定官能团时，单壁碳纳米管（SWCNT）内延伸水链的形成进行了经典分子动力学模拟。已选择极性氨基酸侧链类似物来对SWCNT进行内包官能化。我们的结果表明，在所研究的所有情况下，纳米管都会自发且不对称地被动态水链填充。发现存在类似天冬氨酸和谷氨酸的侧链会导致在管中形成排列有序的水链，其中最大数量的水分子被保留在核心区域且停留时间最长。观察到沿着悬挂链存在甲基或亚甲基会破坏具有更长长度和/或更长停留时间的水链的形成。根据不同氢键相关函数的弛豫情况评估了氢键在形成这些水链中的重要性。因此，对于给定尺寸的疏水纳米孔，我们得到了一个比较羧基、醇基和咪唑基控制其中水的结构和动力学能力的尺度。我们的结果还表明，用类似天冬氨酸和谷氨酸的侧链进行内包官能化的不同长度的SWCNT，可用作基于碳纳米管的储水装置的设计模板。
