Edge-on adsorption of multi-chain functional alkanes stabilizes noncovalent monolayers on MoS2

Abstract

Modified long-chain alkanes are often used to functionalize graphene and MoS₂ noncovalently, with the goal of controlling the substrate electronic structure or interactions with the environment. Alkyl chain adsorption enthalpy is lower on MoS₂ than on graphite; the decreased molecule–substrate interaction strength suggests utility for monolayer structures that increase stability through other means. Previously, we have found that diyne phospholipid monolayers on HOPG are more stable toward solution processing than monolayers of single-chain amphiphiles. Here, we show that this is also true for assembly on MoS₂, but that the additional stability appears to arise from edge-on adsorption, producing monolayers in which alkyl chains form two stacked layers on the substrate.