What is the impact of solvent polarity and viscosity on the dynamic equilibrium of ligands in colloidal metal chalcogenide QDs?

The dynamic equilibrium of ligands, where they are bound to the QD surface and in equilibrium with the surrounding solvent, is influenced by ligand-solvent interactions. These interactions are more pronounced in aliphatic, rather polar solvents, which promote ligand solvation and, consequently, their displacement from the QD surface. Additionally, ligand-ligand interactions, more significant in larger QDs, help stabilize ligand bonding at the QD surface. DOSY measurements revealed that both toluene-d8 and dichlorobenzene-d4, which are aromatic solvents, resulted in broader, more downfield-shifted resonances and slower diffusion compared to other solvents.

The dynamic equilibrium of ligands in colloidal metal chalcogenide QDs is significantly affected by solvent polarity and viscosity. Aliphatic and more polar solvents enhance ligand solvation and their displacement from the QD surface, while aromatic solvents lead to broader NMR resonances and slower ligand diffusion. Conversely, aliphatic solvents such as dichloromethane-d2, chloroform-d, and hexane-d14 produced relatively narrow resonances.