Can the Morphology of Biconcave Metal Sulfide Nanoplatelets Be Preserved during Cation Exchange?

Cation exchange (CE) has become a central strategy for preparing many previously unavailable semiconductor nanocrystals (NCs). However, general understanding of mechanisms governing morphology preservation or evolution upon CE reaction remains limited. In this study, we carried out CE starting from biconcave Cu_1.94S nanoplatelet (NPl) templates, whose relatively complex structure both provides opportunities to lower overall surface energy by shape evolution and facilitates observation of any shape evolution that occurs. From these templates, we prepared NCs of binary and ternary metal sulfides including CdS, ZnS, CuInS₂, MnS, SnS, PbS, and SnS₂. This study reveals that preservation of the template morphology depends upon compatibility of the anionic sublattices (hcp vs fcc) of the template and final product and produces biconcave NPls of several compositions for which this morphology has not previously been reported. In addition, we probed the morphology-dependent optical responses of different anisotropic CdS nanostructures produced by this approach, providing insight into the optical properties of a previously unreported morphology of CdS.