Plasmonic Copper Sulfide-Based Materials: A Brief Introduction to Their Synthesis, Doping, Alloying, and Applications

Plasmonic copper sulfide-based colloidal nanocrystals (NCs) have attracted considerable attention due to their unique and versatile optical and electronic properties. In this Feature Article, we first introduce the optical properties of these p-type semiconductor nanostructures, particularly localized surface plasmon resonance (LSPR). We then discuss nanostructures of copper sulfides [CuS and Cu_2-xS, (0 ≤ x < 1)] with different crystal structures and optical properties. In addition to the synthesis and transformation between these copper sulfide phases, we review their doping or alloying with extrinsic cations, which can produce homogeneous alloy nanostructures, new crystal phases, and multidomain (e.g., core-shell or dimer) NCs. In general, divalent cations (e.g., Zn, Hg, Cd) do not form a homogeneous phase upon incorporation into copper sulfide NCs, but trivalent and tetravalent cations (e.g., In, Sn, Ga) can do so. Filling of the Cu vacancies responsible for p-type doping results in red-shifting and damping of the LSPR upon incorporation of extrinsic elements. Finally, we present some emerging applications of copper sulfide-based nanomaterials.