Colloidal quantum dots generally include a shell of organic ligands bound to atoms at the semiconductor surface. The ligand shell composition is tunable, and can impact a number of quantum dot properties, including the photoluminescence quantum yield, solubility, and interactions with other molecules or quantum dots. Understanding the structure of the ligand shell is therefore of interest in modulating quantum dot properties. In this work, CdSe/CdS quantum dots with a known ligand shell are synthesized and the ligand shell composition is varied by a ligand exchange and quantified via NMR.  We investigate an apparent order/disorder transition in these mixed ligand shells of CdSe/CdS quantum dots via techniques including visible and infrared spectroscopies. We show a change in phase transition temperature and width as a function of ligand shell composition, which can then be related to models of first-order phase transitions. This study highlights the potential importance of ligand-ligand interactions in understanding quantum dot properties.

Ligand ordering phase transitions in mixed ligand shells of CdSe/CdS quantum dots

255th National Meeting (2018)

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