Na‐Cation‐Assisted Exfoliation of MX₂ (M = Mo, W; X = S, Se) Nanosheets in an Aqueous Medium with the Aid of a Polymeric Surfactant for Flexible Polymer‐Nanocomposite Memory Applications

Abstract

Abstract 2D nanosheets of transition metal dichalcogenides (TMDCs) have been attracting attention due to their sizable band gap. Facile and effective Na‐cation‐assisted exfoliation of TMDC (MX 2 , M = Mo, W; X = S, Se) nanosheets in an aqueous medium and their application as a composite filler in a polyvinyl alcohol (PVA) matrix are explored in this work. The presence of Na cations is highly beneficial for exfoliating defect‐free and few‐layer MX 2 nanosheets in water in the presence of small‐sized micelles of polymeric surfactant, and significantly elevates the exfoliation yield by more than one order of magnitude compared to a conventional surfactant‐assisted exfoliation. The strategy suggested in this work is very advantageous compared to both Li cation intercalation in organic solvents and conventional low‐yield surfactant‐assisted exfoliations. As an application of the exfoliated nanosheets, the fabrication of memory devices with the configuration of Ga‐doped ZnO/MX 2 –PVA/Ag is demonstrated, and they exhibit bistable and write‐once‐read‐many‐times resistive switching behavior with a high ON/OFF current ratio of 3 × 10 3 at −1.0 V (for WS 2 ) and 2.0 V (for MoS 2 ). Furthermore, MX 2 –PVA nanocomposite fibrous films and mats are successfully fabricated using an electrospinning technique, which can expand the use of TMDC nanofillers in applications involving highly flexible polymer‐based MX 2 composites.