Colloidal semiconductor quantum dots (QDs) synthesized with an organic ligand shell for stabilization and monodispersity typically require ligand exchange reactions in order to alter their solubility or allow functionalization, especially for further application in a biological environment. Studies on the binding of ligands to the surface of QDs allow for optimization of the interactions between the nanocrystals and surrounding media, as well as physical properties of the QDs themselves such as photoluminescence quantum yield. Isothermal titration calorimetry (ITC) is a highly sensitive technique normally used for full thermodynamic characterization of specified binding events in biological systems in an aqueous phase. We have used ITC to study the sequential chemistry involved in quantitative QD ligand exchange reactions. A procedure has been developed for ITC to analyze highly purified QDs in a single phase during a complete ligand exchange reaction. I will describe the mechanistic factors considered for a more comprehensive interpretation of the thermodynamic parameters of the ligand exchange process as measured by ITC. A proposed isotherm model describing ligand exchange equilibrium constants, coupled with NMR characterization of ligand density and extent of adsorption/desorption to the QD surface will also be presented.

Thermodynamic analysis of quantum dot ligand exchange reaction using isothermal titration calorimetry

246th National Meeting (2013)

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