“…The two-dimensional materials are divided into four categories by their electrical conductivity and optical bandgap. The first type is metallic, e.g., semimetal graphene , and metallic MXenes. − Second is semiconducting materials, e.g., transition metal dichalcogenides − such as and monoelemental nanosheets such as borophene, phosphorene, and germanene . The typical transition metal dichalcogenides , refer to conventional MoS 2 , − MoSe 2 , WS 2 , WSe 2 , , and WTe 2 , and noble metal chalcogenides including PtS, PtS x , and PdSe 2 .…”