Coordination of Quantum Dots in a Polar Solvent by Small-Molecule Imidazole Ligands

Colloidal quantum dots (QDs) are attractive fluorophores for bioimaging and biomedical applications because of their favorable and tunable optoelectronic properties. In this study, the native hydrophobic ligand environment of oleate-capped sphalerite CdSe/ZnS core/shell QDs was quantitatively exchanged with a set of imidazole-bearing small-molecule ligands. Inductively coupled plasma-optical emission spectroscopy and ¹H NMR were used to identify and quantify three different ligand exchange processes: Z-type dissociation of the Zn(oleate)₂, L-type association of the imidazole, and X-type anionic exchange of oleate with Cl^-, all of which contributed to the overall ligand exchange.