Efficient, high-yield, ionized biopolymer-mediated fabrication of exfoliated MoSe2 nanosheets with reversible dispersion properties in water

Abstract

Using the environmentally friendly, water-soluble, biopolymer sodium-ion-grafted chitosan (Na-CMC), we achieved efficient exfoliation of bulk molybdenum diselenide (MoSe₂) into water-dispersible two-dimensional (2D) exfoliated nanosheets with tunable physical properties and multifunctional characteristics. We successfully developed Na-CMC through a simple, one-step synthetic process. Na-CMC exhibits high solubility and self-assembly properties in water, has strong affinity for the surface of MoSe₂, and assists exfoliation of MoSe₂ crystals in water on ultrasonic treatment. As the self-assembled Na-CMC structures tightly adhere to the surface of the nanosheets and confer excellent long-term dispersion stability in water, the exfoliated nanosheets possess several unique physical properties, including control over the content of the exfoliated nanosheets, the highest yield of up to 2.05 mg/mL, uniform few-layered sheet structures, and distinctive surface microstructural morphology. Importantly, Na-CMC/MoSe₂ solution can be converted into a stably preserved solid sample by freeze-drying, and easily redispersed in water through simple stirring. The redispersed solution maintains the same structure and physical properties as the original Na-CMC/MoSe₂ solution, even after multiple freeze-drying/redispersion cycles. The development of this efficient exfoliation technique for 2D nanomaterials based on a bio-based functional polymer offers significant potential to advance the processing and application of 2D nanomaterials.