Experimental Evaluation of Kinetic and Thermodynamic Reaction Parameters of Colloidal Nanocrystals

The unique properties of colloidal semiconductor nano crystals, or quantum dots, have attracted enormous interest in a wide range of applications, including energy, lighting, and biomedical fields. However, widespread implementation is hampered by the difficulty of developing large-scale and inexpensive synthesis routes, mainly due to our limited knowledge of formation reaction parameters. We report here a simple yet powerful method to experimentally determine critically important reaction parameters such as rate constants, activation barriers, equilibrium constants and reaction enthalpies. This method was applied to wurtzite cadmium: selenide nanocrystals, yielding activation energies for growth and dissolution of 14 +/- 6 kJ mol(-1) and 27 +/- 8 kJ mol(-1), respectively, and a reaction enthalpy for nanocrystal growth of -15 +/- 7 kJ mol(-1). Moreover, the Gibbs free energy for growth was found to be negative at low temperatures, whereas dissolution becomes the spontaneous process above 150 degrees C.