Seed-mediated growth of gradient Cu–In–Zn–S alloyed nanocrystals by balancing cation exchange and shelling reaction

The interplay between ZnS shelling reaction and cation exchange affected the genuine nanostructure of the multinary Cu–In–S-based nanocrystals (NCs), which arose from the dosage and injection speed of Zn precursors as well as the surface of the seed NCs. The effects of Zn precursors on the growth of Cu–In–Zn–S NCs have been previously reported. However, effective control of cation exchange based on the surface of seed NCs is still lacking. Herein, a seed-mediated growth method was developed to eliminate the instability of free ligands and ions on the seed NCs. The clean surface of seed NCs was critical for balancing the internal cation exchange and epitaxial shelling reaction of NCs. Importantly, the photoluminescence quantum yield of the Cu–In–Zn–S NCs has been improved without peak shift through this method. In this dynamic balanced process, the as-obtained Cu–In–Zn–S NCs were confirmed to be gradient alloyed structures rather than core-shell structures. Furthermore, this method can be used to synthesize green- and red-emission Cu-In-Zn-S NCs as well. This seed-mediated strategy through simple redispersion may pave a way toward the controllable synthesis of NCs with gradient alloyed structures.