The activity of Zn precursors determines the cation exchange reaction kinetics with Ag2S: Zn-doped Ag2S or Ag2S@ZnS QDs

Cation exchange (CE) has been emerged as a promising post-synthesis strategy of colloidal nanocrystals. However, it is unclear how the cation precursor affects the CE process and the final colloidal nanocrystals. Herein, we utilized two Zn-B Lewis acid-base adduct complexes (B = oleylamine (OAM) and methanol (MeOH)) as Zn precursors for CE with Ag2S quantum dots (QDs). Our study revealed that the steric hindrance and complexing capabilities of Zn precursor significantly affect the CE kinetics. As a result, the Zn-doped Ag2S (Zn:Ag2S) and Ag2S@ZnS core-shell QDs were successfully obtained with enormous enhancement of their photoluminescence (PL) intensities. Theoretical simulation showed that the Zn-OAM with higher desolvation energy and spatial hindrance tended to form doped Zn:Ag2S QDs due to the inefficient cation exchange. Whereas the Zn-MeOH with lower exchange barrier promoted the conversion of Ag-S to Zn-S, thus forming Ag2S@ZnS core-shell QDs. We anticipate that this finding will enrich the regulatory approaches of post-synthesis of colloidal nanocrystals with desirable properties.

Automated summary

Cation exchange (CE) is a promising post-synthesis strategy for colloidal nanocrystals, and the choice of cation precursor significantly affects the CE process and the final nanocrystals. In this study, two Zn-B Lewis acid-base adduct complexes were used as Zn precursors for CE with Ag2S quantum dots. The results showed that the steric hindrance and complexing capabilities of the precursor greatly influenced the CE kinetics and led to the formation of Zn-doped Ag2S and Ag2S@ZnS core-shell quantum dots. Theoretical simulation provided insights into the formation mechanisms of these nanocrystals.