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

Abstract

To realize the application potential of molybdenum disulfide (MoS 2 ) in aqueous environments, scalable and efficient methods for the preparation of high-concentration and stable dispersions need to be developed. In this paper, ultrathin MoS 2 successfully was synthesized using an in situ-exfoliated bulk MoS 2 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 MoS 2 into ultrathin MoS 2 nanosheets but also prevent the reagglomeration of the ultrathin MoS 2 nanosheets in water. MoS 2 nanosheets were confined by the ILCs through π−π and C−H•••π interactions, preventing direct contact of MoS 2 with water. The ILC−MoS 2 dispersion exhibited remarkable dispersion stability exceeding 8 months at room temperature. Moreover, the ILC−MoS 2 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 MoS 2 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 MoS 2 .

Synthetic Kilogram Carbon Dots for Superior Friction Reduction and Antiwear Additives

“…This may be attributed to the fact that small CDs were easily filled into the friction gap. With the deformation and failure of CDs, the remaining CDs will immediately supplement the friction gap, play a self-repairing role, and form a self-lubricating carbon film at the contact surface, showing relatively stable lubrication. − The average friction coefficient and wear scar width of CDs with different concentrations are shown in Figure b. Compared with pure sunflower oil, the addition of CDs significantly reduced the average friction coefficient and wear scar width.…”

Effect of Sodium Salicylate on Improving the Lubricating Properties of [C18imC9]Br Wormlike Micelles in Glycerol/Propylene Glycol at Low Temperatures

“…With the increasing environmental pollution and energy problems, it has become a trend that oil-based lubricants are gradually replaced by environment-friendly lubricants . Ionic liquids and polar organic solvents are considered ideal lubricant fluids because of their high viscosity index, high flash point, high boiling point, low volatility, and low freezing point. − In addition to their use as solvents, ionic liquids can be used as neat anticorrosion and antiwear lubricants with good lubricating properties. The ionic liquids can form strong structural boundary layers with low dissipation even at high pressures through van der Waals, electrostatic, and H-bonding interactions, which can act as a shield and buffer. − The solid–IL interface can be divided into three different regions: the boundary layer, the transition zone, and the bulk phase .…”

Efficient Green Synthesis of Highly Concentrated and Stable Carbon Nanotube Aqueous Dispersions for Photothermal Textile Fabrication

“…In contrast to common surfactants, ILCs are green molten salts containing long flexible alkyl chains (C > 12), consisting of anions and cations. Their own low volatility, wide range of liquids, and non-flammability confer them great potential for application. , Especially, imidazolium-based ILCs possess excellent thermal stability due to the unique imidazole ring structure . In addition, Yan et al found that the imidazole ring of ILC can form cation−π bonds with graphene-like materials with π-conjugated structures and successfully constructed the reversible solution-processable hydrogels of g-C 3 N 4 .…”

“…20,21 Especially, imidazolium-based ILCs possess excellent thermal stability due to the unique imidazole ring structure. 22 In addition, Yan et al found that the imidazole ring of ILC can form cation−π bonds with graphene-like materials with π-conjugated structures and successfully constructed the reversible solution-processable hydrogels of g-C 3 N 4 . 23 Furthermore, ILC-assisted exfoliation of graphite fluoride was reported to achieve simultaneous exfoliation and non-covalent functionalization of fluorinated graphene (FG), in which ILCs were attached to the surface of FG, enabling stable dispersion of the exfoliated FG.…”