Efficient and Green Strategy of Ultrasound-Assisted Liquid-Phase Exfoliation of MoS2 Nanosheets

Two-dimensional molybdenum disulfide (2D MoS2) holds significant promise for the development of various photoelectric devices due to its unique atomic thin layer and band gap characteristics. Numerous techniques have made strides in exfoliating 2D MoS2 nanosheets from their bulk counterparts. However, achieving environmentally benign and efficient preparation of high-quality MoS2 nanosheets remains challenging. Here, we develop a green and efficient approach to preparing MoS2 nanosheets through ultrasound-assisted liquid-phase exfoliation using sustainable alcohol solvents. Systematic investigations reveal that solvent selection critically governs both the exfoliation efficiency and structural preservation of MoS2 nanoflower precursors synthesized via hydrothermal methods. Comprehensive characterization confirms that ethanol-mediated exfoliation yields intact 2H phase nanosheets. For other solvents, however, chemical doping during exfoliation resulted in the emergence of the 1T phase within the nanosheets. Notably, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and isopropanol (IPA) induce detrimental aggregation and methanol (MeOH) causes structural fragmentation, leading to the least effective exfoliating outcome. Through first-principles calculations and considering the efficiency of chemical doping, ethanol (EtOH) was identified as the optimal solvent for the exfoliation of MoS2 nanosheets. This work establishes an eco-friendly pathway for producing phase-modulated MoS2 nanosheets, demonstrating remarkable potential for sustainable manufacturing of 2D materials.