Confinement and surface effects of aqueous solutions within charged carbon nanotubes

Abstract

We have examined the structure of water and aqueous solutions in carbon nanotubes using molecular dynamics simulations. We find confinement changes the structure of water as well as the interactions between ions and their solvation shells. The density and orientation of water at the nanotube walls are strongly dependent on the surface charge and cations/anions present at the interfaces. Decreasing the nanotube diameter alters the ion hydration properties as well as hydrogen bonding structure and formation dynamics. The results indicate that fluid structure and hydrogen bond characteristics in nano-channels can be tuned through modification of tube charge and with ion selection.

Interaction of HF, HBr, HCl and HI Molecules with Carbon Nanotubes

“…Dipolar moments of all confined molecules are affected. At the parallel and perpendicular directions, HF molecule forms a stable system with the nanotubes (5,5) and (6,6). HCl, HBr and HI molecules placed perpendicular, form a stable complex with the CNT (6,6).…”

“…Theoretical calculations have been made to investigate the encapsulation of HF, HCl, HBr and HI molecules inside carbon nanotubes (3,3), (4,4), (5,5) and (6,6). Calculations are made using DFT/CAM-B3LYP functional with STO-3G basis sets.…”

“…35 Terminal carbon atoms are hydrogenated to saturate their valence. The formulas of the considered (3,3), (4,4), (5,5) and (6,6) carbon nanotubes are : C 36 H 12 , C 48 H 16 , C 60 H 20 and C 72 H 24 respectively. The optimized diameters of the chosen nanotubes are varying from 5.49 Å to 8.23 Å.…”

“…The same phenomena was observed for water which flow rate varies when the CNT diameter changes. 43 By increasing the carbon nanotube's diameter, only HI molecule leaves the CNT (5,5) at the perpendicular orientation. HF placed perpendicular forms a stable complex with the nanotubes (5,5) and (6,6) with a stabilization energy equal to -0.4017 kcal mol -1 and -0.1864 kcal mol -1 , respectively.…”

“…The greatest advantage of this SWCNTs is their hollow space which could confine numerous molecules in order to storage them [2][3][4][5][6] or to contain chemical reactions. 7 They are used to remove heavy metals in wastewater treatment 8 and in drug delivery.…”