Atomically Thin Metal Sulfides

We developed a method to colloidally synthesize atomically thin metal sulfides (ATMS). Unlike conventional 2D systems such as MoS₂ and graphene, none of the systems developed here are inherently layered compounds nor have known layered polymorphs in their bulk forms. The synthesis proceeds via a cation-exchange reaction starting from single- and multi-layer Ag₂S and going to various metal sulfides. The synthesized ATMS retain their size and shape during the cation-exchange reaction and are either single-layer or a few-layer, depending on the starting Ag₂S samples. They have lateral dimensions on the order of 5-10 nm and are colloidally stabilized by Z- and L-type ligands. Here, we demonstrate the synthesis of single-layer and a few-layer ZnS, CdS, CoS₂, and PbS. We find that the optical properties of these ATMS are quite distinct from the platelet or quantum-dot versions of the same metal sulfides.