Covalent chemical functionalization of semiconducting layered chalcogenide nanosheets

Layered chalcogenides are a diverse class of crystalline materials that consist of various covalently bound building blocks held together by van der Waals forces. Among these materials are the transition metal dichalcogenides (TMDCs) which can be exfoliated into two-dimensional (2D) nanosheets, and the pnictogen chalcogenides (PCs) which can be exfoliated into one-dimensional (1D) nanoribbons and 2D nanosheets. The chemical functionalization of 1D and 2D nanomaterials is an important enabling step for tuning their properties and forming interfaces with other materials and structures. However, broadly applicable chemical tools to functionalize a wide range of layered chalcogenides are lacking. Here we show the covalent functionalization of nanosheets of the representative TMDCs MoS2, WS2, MoSe2, and WSe2, and of the representative PCs Sb2S3 and Bi2S3 using aryl diazonium salts. Covalent bonds are formed on the basal planes of both mechanically exfoliated and liquid phase dispersed nanosheets, and the chemical and morphological changes upon functionalization are verified using a combination of spectroscopic and microscopic techniques. This work demonstrates that the aryl diazonium chemistry is a versatile and powerful approach to covalent functionalization of the 2D nanosheets of a diverse set of semiconducting layered chalcogenide materials.