Molecular dynamics investigation of wetting-dewetting behavior of reline DES nanodroplet at model carbon material

Deep eutectic solvents (DESs) have emerged as a promising class of solvents for application in nanotechnology, particularly for designing new functional nanomaterials based on carbon. Here, we have employed molecular dynamics simulations to understand the structuring of choline chloride and urea-based DES, reline, nanodroplets on carbon sheets with varying strength of the DES-sheet interaction potentials. The wetting-dewetting nature of reline has been investigated by analyzing simulated contact angles formed by its nanodroplets on the carbon sheets. Through this investigation, we find that at the lowest DES-sheet interaction strength, the contact angle formed by the reline nanodroplet on the carbon surface exceeds 150°, indicating that the surface is supersolvophobic. On the other hand, at the higher interaction potentials, reline DES wets the surface of the sheets, forming an adlayer primarily consisting of urea molecules. The choline cation and urea molecules are observed to exhibit stronger interactions with the carbon surface as compared to that of chloride anions. At the supersolvophobic carbon surface, the urea molecules have relatively higher density in the bulk of the nanodroplet, whereas the choline cation and chloride have major contributions to the outer layers of the droplets. Moreover, at the solvophilic surfaces, urea molecules are present in the adlayer, as well as in the bulk of the droplets, whereas the reline-vapor interface majorly consists of choline and chloride ions.