Wettability Scope of MoS2-Ionic Liquid Interfaces and Their Modification toward Novel Superhydrophobic Boundaries.

Abstract

In the past two decades, much interest has been given to properties and applications of 2D materials, mainly molybdenum disulfide (MoS2). Understanding how liquids (particularly green liquids) interact with and wet the surfaces of the 2D materials has become essential to engineering synthesis methods and their applications. We used molecular dynamics (MD) simulation to model the wetting behavior and interfacial structure of imidazolium-based ([BMIM][BF4] and [BMIM][NTf2]) ionic liquid (IL) nanodroplets on various (1T-, 2H-, 3R-, and P-) MoS2 crystal surfaces. The extent of the hydrophobicity, structure of the crystal surface, and anion types lead to a significantly different spreading mechanism and wetting behavior at room temperature. [BMIM][BF4] IL spreads well on any MoS2 surface, showing high and low spreading rates on 3R-MoS2 and P-MoS2, respectively. The slow spreading rate and wetting behavior on P-MoS2 are influenced by the morphology and unique atom organization in terms of cavities and kinks. The equilibrated configuration for hydrophobic [BMIM][NTf2] IL displayed an abnormal no-spreading structure on any MoS2 surface. Conclusively, the newly developed P-MoS2 structure found to possess a surface with stronger hydrophobicity than that of other crystal structures of MoS2. We elucidate and present detailed aspects of surface modification of P-MoS2 with a selected fluorooctylsilane coating to reach a superhydrophobic surface. In addition to assessing the fluorooctylsilane features by quantum chemical calculations in favor of film stability, the coating quality and suitability were vastly confirmed by the simulation of IL wetting behavior and the calculated contact angle (CA) of more than 150°. Therefore, the results of this work shed light on composite materials to generate a novel 2D superhydrophobic surface via a qualified fluorooctylsilane coating on the P-MoS2 substrate.