  We have used molecular dynamics simulations to study the effect of water on
the wetting behavior and the interfacial structure of ionic liquid (IL)
1-ethyl-3-methylimidazolium boron tetrafluoride[EMIM][BF4] droplets on graphite
surfaces which, is a prerequisite for the new IL-based applications in the
field of chemical engineering. A slight decrement in the value of the contact
angle has been found while adding water up to 20wt%; afterward, the contact
angle starts to increase. The non-monotonic behavior of contact angle of IL
droplet with the addition of water molecules was examined through several key
parameters, such as the interaction energies between the graphite and IL
molecules, density distributions, cluster formation, and the number of formed
hydrogen bonds (HBs) for the different weight percentages of water molecules.
The results indicate that the hydrogen bond network and the cluster formation
among the water molecules play a vital role during the transition from IL rich
medium to water-rich medium of the droplet.
