Tight Binding of Carboxylate, Phosphonate, and Carbamate Anions to Stoichiometric CdSe Nanocrystals

R' reacts with oleic acid, n-octadecylphosphonic acid, or carbon dioxide to form surface bound n-alkylammonium oleate, phosphonate, and carbamate ion pairs that bind with greater affinity than primary n-alkylamines. The results indicate that nanocrystal dispersions solely stabilized by neutral donor ligands are relatively unstable compared to those stabilized by adsorbed metal carboxylate or phosphonate complexes or by ion pairs. The challenge of differentiating between the neutral ligand bound form and adsorbed ion pairs is discussed.