title: Molecular dynamics simulation study of the structural characteristics of water molecules confined in functionalized carbon nanotubes.
abstract: Molecular dynamics (MD) simulations were performed to study the structural properties of water molecules confined in functionalized carbon nanotubes (CNTs). Four CNTs, two armchair-type (6, 6), (7, 7) and two zigzag-type (10, 0), (12, 0) CNTs, representing different helicities and different diameters, were chosen and functionalized at their open ends by the hydrophilic -COOH and the hydrophobic -CH3 groups. The structural properties of water molecules inside the functionalized CNTs, including the orientation distributions of dipole moment and O-H bonds, the length of the single-file water chain, and the average number of hydrogen bonds, were analyzed during a process of simulations. MD simulation results in this work showed that the -CH3 functional groups exert little special effects on the structural properties of water molecules. It is mainly due to the relatively small size of the -CH3 group and its hydrophobic nature, which is consistent with hydrophobic CNTs. For CNTs functionalized by -COOH groups, the configurations of -COOH groups, incurvature or excurvature, determine whether water molecules can enter the CNTs. The incurvature or excurvature configurations of -COOH groups are the results of synergy effects of the CNTs' helicity and diameter and control the flow direction of water molecules in CNTs.
authors.affiliation: College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing, 210009, PR China.
authors.forename: Liang-Liang
authors.initials: LL
authors.lastname: Huang
authors.forename: Lu-Zheng
authors.initials: LZ
authors.lastname: Zhang
authors.forename: Qing
authors.initials: Q
authors.lastname: Shao
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Ling-Hong
authors.initials: LH
authors.lastname: Lu
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Lu
authors.forename: Shao-Yi
authors.initials: SY
authors.lastname: Jiang
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Shen