A calorimetric study of ligand exchange on silver nanoparticles

Calorimetric measurements were conducted to study ligand exchange from stearic acid to dodecane thiol on silver nanoparticles. The shape of the enthalpy curves and the linear correlation between the thiol amount and enthalpy, obtained with small amounts of thiol, agreed with the model of direct ligand exchange on uniform surface sites. On the contrary, excess amounts of thiol yielded enthalpy curves with distinct behavior in the longtime regime, indicating the coexistence of ligand exchange and other processes producing heat. Enthalpy, reaction rate and equilibrium constants, Gibbs free energy, and entropy of the ligand exchange reaction were estimated from the calorimetric data using a kinetic model.