Single-Molecule MoS₂–Polymer Interaction\nand Efficient Aqueous Exfoliation of MoS₂ into Single Layer

Abstract

Single molecule\nforce spectroscopy (SMFS) was utilized to\nstudy single-molecule interactions between synthesized polymers and\nMoS₂ surfaces that provide the guidance to determine candidate\npolymers for efficient aqueous exfoliation of bulk MoS₂ into single-layer nanosheets. The technique allowed the direct quantification\nof the adhesion force of single polymer molecules with both basal\nand edge surfaces of MoS₂. Compared with two studied neutral\npolymers, highly water-soluble cationic poly­(vinylbenzyl trimethyl\nammonium chloride) (PVBTA) was shown to be more promising for MoS₂ exfoliation as a result of strong single-molecule interactions\nwith both basal and edge surfaces of MoS₂. In 1 mM NaCl\nsolution of pH around 5.5, the measured single-molecule adhesion forces\non basal and edge surfaces were around 59 and 51 pN, respectively.\nSuch strong adhesion force led to high performance of PVBTA in exfoliating\nMoS₂ bulk material into single-layer sheets. Compared with\nreported approaches in the literatures, an order of magnitude higher\nconcentration of single-layer MoS₂ sheets in water was\nprepared using an order of magnitude less treatment time in this study.\nThis research demonstrated that SMFS is a powerful tool to select\nappropriate surface-active polymers for effective exfoliation of MoS₂, which could be applied to a variety of practical applications,\nsuch as water adhesion and dispersing.