Purification and In Situ Ligand Exchange of Metal-Carboxylate-Treated Fluorescent InP Quantum Dots via Gel Permeation Chromatography.

Recently the addition of M2+ Lewis acids (M = Cd, Zn) to InP quantum dots (QDs) has been shown to enhance the photoluminescence quantum yield (PL QY). Here we investigate the stability of this Lewis acid layer to postsynthetic processing such as purification and ligand exchange. We utilize gel permeation chromatography to purify the quantum-dot samples as well as to aid in the ligand-exchange reactions. The Lewis-acid-capped particles are stable to purification and maintain the enhanced luminescence properties. We demonstrate successful ligand exchange on the quantum dots by switching the native carboxylate ligands to phosphonate ligands. Changes in the optical spectra after exposure to ambient environment indicate that both carboxylate- and phosphonate-capped QDs remain air-sensitive.