Thermodynamics of ligand exchange in CdSe NCs

The nanocrystals (NCs) surface and their ligand layer have a significant contribution in controlling the NCs size, shape and optoelectronic properties, as well as for their applicability for biological tagging, photocatalysis, electronic devices and more. Yet, the NC surface properties and the interactions with the ligands still remain under-explored.

In this work we combined calorimetric measurements together with basic surface characterization for studying the interaction on the NC surface during ligand exchange process. Isothermal titration calorimetry (ITC) measurements were applied on oleic acid capped CdSe NCs during their ligand exchange with alkanethiols. A complete set of thermodynamic parameters was extracted for this process and the effects of both temperature and chain lengths were studied. A complementary study on the effect of temperature and the ligand chain length on the yield of the ligand exchange process was conducted by thermogravimetric analysis (TGA).

This work is a starting point for achieving fundamental understanding of the surface physico-chemical properties and their dependence on a variety of SC NC parameters. The insights of the presented research will pave the way for smart NC surface design that can impact NCs applications considering the central role that surface passivation and chemical processing through surface control plays on the NCs functionality.