The estimated sizes and concentrations of the quantum dots were determined from their absorption measurements (Figure ) based on empirical determined extinction coefficients. Calculations for quantum dot sizes and concentrations can be found in the Supporting Information, alongside luminescence measurements (Figures ) and raw isothermal titration calorimetry plots (Figure ). In general, as nanocrystal size increases, the titrations become more endothermic. In previous work, self-consistent fitting of a modified Ising model with other metal halide salts indicate that the change in head binding energy in this reaction is exothermic. 51 However, the net endothermicity is ascribed to a greater endothermic contribution from the breaking of surface ligand van der Waals interactions between the aliphatic chains as indium trimyristate is displaced by zinc chloride. Reactions with stearate (C18H35O2) capped indium phosphide quantum dots are generally more endothermic than those capped with myristate (C14H27O2). This finding is consistent with previous reports which found that coordinating ligands with longer aliphatic chains require more energy to displace as a result of stronger van der Waals interactions. Figure . Quantitative 1 H NMR measurements of the bound ligands per quantum dot during the titration of zinc chloride into samples of indium phosphide quantum dots capped with (A) myristate ligands (C14H27O2) and (B) stearate ligands (C18H35O2). Note that an organic ligand is considered as one indium tri-carboxylate unit, as this is the unit that is being displaced by zinc chloride. Again, the two samples capped with indium myristate are very close in size (to 0.1 nm in diameter), however, the rightmost sample is slightly larger based on the sizing calculations.