Room temperature synthesis of aqueous soluble covellite CuS nanocrystals with high photothermal conversion

Abstract

Near-infrared plasmonic binary copper-based chalcogenides have found promising applications in photovoltaics and photothermal therapy. Here, we report a facile synthetic protocol for aqueous soluble covellite (CuS) nanocrystals (NCs) at room temperature. In contrast to previously reported routes, the present method involves the reaction of Cu precursors (e.g. CuCl₂, Cu(NO₃)₂, Cu(Ac)₂) with sulphur precursors (e.g. Na₂S and (NH₄)₂S) under ambient conditions in the presence of various ligands, requiring neither high temperature and high pressure nor an inert atmosphere. The as-synthesized CuS NCs, without any further ligand exchange, can be readily dispersed in water and exhibit well-defined near-infrared (NIR) plasmon absorbance. The scalability and reproducibility of the present procedure allow for the gram-scale production of CuS NCs in a one-pot reaction, which is elaborated by upscaling the amounts of precursors and solvents/ligands. In particular, when excited with an 806 nm laser (1.2 W cm⁻²), the aqueous soluble covellite NCs produce significant photothermal heating with a photothermal transduction efficiency of 20.3%, comparable to previously reported binary copper chalcogenides. Combined with good photothermal transduction properties, photostability and synthesis scalability, the present work provides a general and cost-effective synthetic protocol for not only Cu_2−xS but also other copper chalcogenides for promising photothermal applications.