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 nano-crystals (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 Cu1.94S 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 anisotro...