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. These materials have recently been extensively studied for their intriguing electronic, optical, and chemical properties. 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 and versatile chemical tools that can effectively functionalize a wide range of layered chalcogenide compositions without disruptive pre-treatments need further advancement. Here we show the covalent functionalization of nanosheets of the representative TMDC materials MoS₂, WS₂, MoSe₂, and WSe₂, and of the representative PC materials 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 builds on previous demonstrations of diazonium functionalization of 2D materials like MoS₂, and expands it to five additional compositions. Thus, the aryl diazonium chemistry is shown to be a versatile and powerful approach to covalent functionalization of the 2D nanosheets of a diverse set of semiconducting layered chalcogenide materials.