Cylindrical droplet of aqueous ionic liquids on smooth and pillared graphite surface: A molecular dynamics study

Liquid-solid interaction is ubiquitous and has many applications, such as condensation, boiling, and lubrication. It is crucial to get insight into the wettability of aqueous ILs on different surface topographies at the nano-scale. Here, we have conducted molecular dynamics (MD) simulation on aqueous 1-Ethyl-3-Methylimidazolium Tet-rafluoroborate [EMIM] [BF4], 1-Hexyl-3-Methylimidazolium Tetrafluoroborate [HMIM] [BF4] and 1-Ethyl-3-Methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM] [NTF2] at different concentration (10 and 30 wt%) on a both smooth and pillared graphite surface. The contact angle values are estimated to explore the effect of surface texture on the wettability of the aqueous-IL droplet. We ensured that our simulation attained equi-librium by examining the droplet-substrate interaction. Further, we have calculated the distribution of IL mol-ecules through a density contour and, lastly, hydrogen bond (HB) calculation for both hydrophilic ([EMIM] [BF4]) and hydrophobic ([HMIM] [BF4] and [EMIM] [NTF2]) ILs, has been performed to elucidate the structural relationship of ILs.