Figure 1.

Schematic representation of a CIS NC surface depicting the chemical processes that can take place during a ZnS shelling reaction. (A) [ZnS] monomers form homogeneously in solution from Zn- and S-precursors. (B) Alloying: Zn²⁺ from adsorbed [ZnS] monomer units diffuses inward, while Cu⁺ and/or In³⁺ ions diffuse outward. (C) Heteroepitaxial shell overgrowth. A stable ZnS phase grows on the CIS surface. (D) Cation exchange: upon adsorption of Zn-R species at the CIS surface a place exchange reaction can take place, through which Zn²⁺ is incorporated in the NC, while Cu⁺ or In³⁺ cations are extracted as M-R species. (E) Etching: chemical species in the reaction medium can promote the partial dissolution of the CIS NC by extracting cations and/or S^2- from the lattice. (F) Homogeneous nucleation: [ZnS] monomers can form ZnS NCs through homogeneous nucleation.