A General Approach To Study the Thermodynamics of Ligand Adsorption to Colloidal Surfaces Demonstrated by Means of Catechols Binding to Zinc Oxide Quantum Dots

A general strategy to study the thermodynamics of ligand adsorption to colloidal surfaces was established. The versatility of our approach is demonstrated by means of catechols binding to ZnO quantum dots (QDs). First, isothermal titration calorimetry (ITC) was used to extract all relevant thermodynamic parameters, namely association constant, enthalpy, entropy, and free energy of ligand binding. Noteworthy, the determined ΔG of −20.3 ± 0.4 kJ mol–1 indicates a strong, reproducible, and exothermic interaction between the catechol anchor group and the oxide particle surface. To confirm the characterization of ligand binding by measuring the heat of adsorption, the free energy was cross-validated by mass-based adsorption isotherms. A combination of inductively coupled plasma optical emission spectroscopy (ICP-OES) and UV/vis spectroscopy was developed to quantitatively determine the mass of bound catechols with respect to the available particle surface. The association constant K was determined by a Langmui...