Exploiting Cation Exchange to Synthesize Well-Defined Three-Component CuInS₂ Nanocrystals

Cation exchange has emerged as a compelling strategy for crafting nanocrystals with intriguing compositions and structures, overcoming limitations inherent in direct-synthesis approaches. However, well-defined synthesis of multi-component nanocrystals with a single phase by finely tuning cation exchange kinetics remains challenging. Multi-component nanocrystals, such as CuInS₂ and CuInSe_2, have attracted significant interest owing to their diverse applications in optics, electronics, and catalysis. Utilizing Cu_2-xS nanocrystals as the host precursors and In³⁺ as the exchange cation, we successfully synthesized monodisperse CuInS₂nanocrystals with tunable size, morphology, and near-infrared luminescence properties. An in-depth exploration into the impact of size variations and Cu vacancies of host nanocrystals on cation exchange kinetics was conducted. Larger-size Cu_2-xS nanocrystals exhibit reduced vacancy density, leading to a slower rate of cation exchange and facilitating the formation of heterostructures during the cation exchange process. Comparative analysis with directly synthesized CuInS₂ nanocrystals highlighted the controllability achieved through cation exchange. This work provides valuable insights for synthesizing multi-component nanocrystals with attractive properties.