Synthesis of Highly Crystalline CdSe@ZnO Nanocrystals via Monolayer-by-Monolayer Epitaxial Shell Deposition

In principle, nanometer thick, metal oxide shells provide a robust passivation layer that can minimize chemical and photochemical corrosion of semiconductor nanocrystals. Here, formation of single crystal, wurtzite ZnO shells by thermal decomposition of zinc acetylacetonoate is demonstrated. As an example, a simple, one-pot protocol for the preparation of CdSe@ZnO core–shell nanocrystals is presented. The CdSe photoluminescence quantum yield increases 6-fold from 1.4% to 8.6%, while the lifetime increases from 8.7 to 60 ns upon deposition of the ZnO shell and peaks for 5 monolayers of ZnO. High-resolution transmission electron microscopy reveals the core–shell particles to be single crystals with the wurtzite structure. The polydipsersity is maintained at less than σ < 5% for deposition of up to four monolayers of ZnO.