Sustainable, aqueous exfoliation of MoS2via bio-inspired avenues

Abstract

Two dimensional (2D) nanosheets of MoS₂ were succesfully produced by an exfoliation process in aqueous media with the support from peptides and sonication. The exfoliation process assisted by uncapped MoSBP1 peptides was found to have enhanced efficiency in comparison to the capped counterpart. MoS₂ nanosheets obtained using uncapped MoSBP1 have thinner structures containing one layer of MoS₂, while in capped version of peptides, MoS₂ nanosheets tend to form multilayer (up to 4) structures of exfoliated sheets. Molecular dynamics simulations indicate that inter-sheet gaps generated by sonication in MoS₂ nanostacks cannot be maintained by water only; the gaps closed after ∼11 ns. Both capped CMoSBP1 and uncapped MoSBP1 were seen to spontaneously insert into the gap in nanostacks of MoS₂ and they can ultimately maintain the inter-sheet gap for longer (≥20 ns). Potential of mean force profiles for the association of two MoS₂ nanosheets decorated with CMoSBP1 and MoSBP1 versions of peptides revealed that uncapped MoSBP1 peptides provide good protection from MoS₂ nanosheet re-unification. Such protection can prevent the nanosheets from reassociation and subsequent aggregation, whereas the capped CMoSBP1 peptides can offer protection, but over a shorter range. These simulation results could explain the experimental observation of greater efficiency of exfoliation in uncapped MoSBP1 peptides.