Ionic Liquid Crystals Confining Ultrathin MoS2 Nanosheets: A High-Concentration and Stable Aqueous Dispersion

To realize the application potential of molybdenum disulfide (MoS2) in aqueous environments, scalable and efficient methods for the preparation of high-concentration and stable dispersions need to be developed. In this paper, ultrathin MoS2 successfully was synthesized using an in situ-exfoliated bulk MoS2 method in water using ionic liquid crystals (ILCs) as green exfoliating/dispersing agents. The ILCs containing hydrophobic cations and hydrophilic anions not only help to exfoliate bulk MoS2 into ultrathin MoS2 nanosheets but also prevent the re-agglomeration of the ultrathin MoS2 nanosheets in water. MoS2 nanosheets were confined by the ILCs through π–π and C–H···π interactions, preventing direct contact of MoS2 with water. The ILC–MoS2 dispersion exhibited remarkable dispersion stability exceeding 8 months at room temperature. Moreover, the ILC–MoS2 dispersion has been successfully proven to be an excellent water-based lubricant, where the ILCs form a lubricant film on the friction surface through electrostatic interactions and MoS2 increases the load-bearing capacity of the lubricant film due to its high modulus, resulting in an 84.9% reduction in the coefficient of friction compared to pure water. The method is expected to provide a new idea for the preparation and application of MoS2.