Among the various reported post synthetic modifications of colloidal nanocrystals, cation exchange is one of the most promising and versatile approaches for the synthesis of new nanostructures that cannot be directly synthesized from their constitutive precursors.  A number of studies have reported on the qualitative analysis of these reactions, but rigorous quantitative study of the thermodynamics of cation exchange is still lacking.  We demonstrate, using isothermal titration calorimetry (ITC), the thermodynamics of the cation exchange reaction between cadmium selenide (CdSe) nanocrystals and silver (or copper) can be quantified.  We discuss the influence of solvent, diameter of the CdSe nanocrystal, surface chemistry via different stabilizing ligands, temperature and silver salts with different anions on the thermodynamics of the exchange reaction.  The results obtained from ITC provide a detailed description of the overall thermodynamic parameters.  Furthermore, we established a correlation between the enthalpy of reaction of CdSe with Ag<sup>+</sup> and the coordination ability index for the anions of the different silver salts used.  The disparities between the experimental and theoretical values of the free energy change during the exchange suggests that all the above factors play significant roles in these chemical conversions that are not accounted in simple theoretical models.

Thermochemical measurements of cation exchange in cadmium selenide nanocrystals using isothermal titration calorimetry

254th National Meeting (2017)

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