Structure and dynamics of water inside endohedrally functionalized carbon nanotubes

Abstract

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.

Translocation of Bioactive Molecules through Carbon Nanotubes Embedded in the Lipid Membrane

“…Sometimes CNTs may be present with negatively charged ends, where the ends are functionalized with some acidic groups. 45 We consider −COOH-functionalized CNT, where both the open ends of the CNT are terminated with −COOH functional groups. The procedure is given in the Methods section and in Figure S12 in the Supporting Information.…”

Solvation of narrow pores of graphene-like plates in simple dipolar liquids: Wetting and dewetting behavior and solvent dynamics for varying pore width and solute–solvent interaction

“…For example, there are studies which have considered water near atomistically modeled flat slab shaped graphitic plates or structureless smooth surfaces and also in the confined hydrophobic environments of nonpolar cavity of fullerene or in the cylindrical nanopores of http://dx.doi.org/10.1016/j.chemphys.2015.05.009 0301-0104/Ó 2015 Elsevier B.V. All rights reserved. single and multi-walled carbon nanotubes as well as in the surface of proteins [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Our focus of the present study has been on the solvation of hydrophobic surfaces in simple dipolar liquids without any complexities of hydrogen bonding.…”

Wetting behavior of nonpolar nanotubes in simple dipolar liquids for varying nanotube diameter and solute-solvent interactions

“…Almost all the existing simulation work on solvation of carbon nanotubes involve explicit water models as the solvent. 35,36,[38][39][40][41][42][43][44][45]47,[52][53][54][55][56][57][58] However, water is a complex solvent with its hydrogen bonded network greatly determining its structural, thermodynamic, and dynamical behavior and it would be instructive to look at the structural and dynamical behavior of simple polar liquids in nanotubes where there are no hydrogen bonds in the solvent. Clearly, the motivation to look at this aspect comes from hydrophobic interactions where water hydrogen bonds are considered to play key roles.…”