Preparation of monolayer muscovite through exfoliation of natural muscovite

Abstract

The exfoliation of layered materials to two-dimensional (2D) nanosheets has sparked much attention since the emergence of graphene. These starting layered materials have strong in-plane bonds and weak van der Waals forces between layers. However, the exfoliation of layered materials with stronger interlayer forces has rarely been reported. Among them, natural muscovite is challenging to split into nanosheets due to its extreme interlayer forces. Here, stable monolayer muscovite was successfully prepared for the first time through weakening its layer attractions by enlarging the basal spacing followed by micromechanical cleavage to nanosheets. The XRD and IR results demonstrated that the crystalline structure of muscovite did not change, and that OTA⁺ exhibited a less ordered arrangement after exfoliation. HRTEM observation of the muscovite treated by our method revealed that it lost the periodicity in stacking, had hexagonal lattice fringes and was transparent to visible light, indicating that it was a highly crystalline 2D material. The smallest thickness of these 2D nanosheets confirmed by AFM was around 1.2 nm, demonstrating the existence of monolayer muscovite.