Coupled and decoupled dual quantum systems in one semiconductor nanocrystal.

Dual quantum systems, 0-dimensional quantum dot, and 2-dimensional quantum wells were constructed in one II-VI semiconductor nanocrystal by the epitaxial growth of a barrier (ZnS) layer between the systems in solution. By alteration of the thickness of the barrier layer, the two quantum systems were controlled to either electronically coupled or decoupled. Evidence of optical coupling between the two band gap emissions was also observed. The position and relative intensity of the two emissions can be independently tuned by reaction conditions. Total photoluminescence quantum efficiency of the dual emitting bands reached as high as 30% at room temperature under synthetic conditions not optimized for high emission.