Effects of single-wall carbon nanotube confinement on triazolium-based ionic liquid/water mixtures

In this work, we have performed molecular dynamics (MD) simulations to investigate the effects of confinement in a (20,20) single-wall carbon nanotube (SWCNT) on the behavior of a mixture of water and 1-n-propyl-4-amino-1,2,4-triazolium bromide ([part][Br]) ionic liquid (IL). The effects of water mole fraction were examined on the structural and dynamical properties of water/IL mixture and confined water/IL mixture. The total energy, the interaction energy between molecules and the radial distribution functions (RDFs) were calculated and compared at different water mole fractions for both water/IL mixture and confined water/IL mixture. The obtained results show that for the confined water/IL mixtures, the most interaction energy value is observed in pure water and pure IL systems. The analysis of the RDFs between different atoms of IL, water and SWCNT shows that the presence of SWCNT leads to a stronger spatial correlation between the water and IL molecules. Also, investigating the dihedral angle between the surface of SWCNT and the cation ring plane shows that the cations tend to orient their rings mainly parallel to the SWCNT surface. Finally, we calculated and compared the dynamics of the water molecules, anions, and cations at different water mole fractions in water/IL mixture and confined water/IL mixture. Two different regimes were observed for the confined and the bulk mixtures in low and high water mole fractions.