Synthesis of ultrasmall CdSe nanoclusters by cation exchange and subsequent growth

Fuyan Ma, Khalil Abboud, Chenjie Zeng

Department of Chemistry, University of Florida

The intriguing and tunable optical properties of cadmium selenide (CdSe) quantum dots afford their broad applications in imaging and lighting. Despite the advancements in the past four decades, controllable synthesis of CdSe nanoclusters remains challenging due to the complexity of the nanoscale reactions. Here, we report the synthesis of ultrasmall CdSe nanoclusters through a transformative pathway. Cation exchange has been widely used to generate large colloidal nanocrystals with diverse compositions and morphologies, in which the size and shape of the starting material can be preserved. Applying cation exchange to a well-defined nanocluster and a Cd(II) coordination complex, a CdSe nanocluster was produced with its core inherited from the templating cluster. The transformation process was unveiled by in-situ absorption spectroscopy. The resulting CdSe cluster can further grow into two larger sizes in a quantized manner via digestive ripening, revealing the high reactivity and selectivity in such systems. These results demonstrate a new strategy to construct binary semiconducting nanoclusters with desired core sizes and surface ligands.