Aqueous Synthesis of ZnSe Nanocrystals by Using Glutathione As Ligand: The pH-Mediated Coordination of Zn2+ with Glutathione

Abstract

A series of ZnSe nanocrystals was synthesized in the range of pH 6.5−11.5 in aqueous solution by using glutathione (γ-glutamyl-cysteinyl-glycine, GSH) as ligand. The photoluminescence quantum yields (PLQYs) of the ZnSe nanocrystals were dependent on the pH of the reaction solutions, which increased from 0.5 to 23% as the pH increased from 6.5 to 11.5. It is identified that Zn2+ primarily coordinates with thiol group of the cysteine residual at low pH (6.5−8.3); then, the deprotonated amino group of the glutamyl residue also contributed to the coordination at medium pH (8.3−10.3). With increasing pH to >10.3, N atom of the amide bond further took part in the coordination after its deprotonation. As a result, the growth rate of the ZnSe nanocrystals increased with increasing pH, indicating the improved activity of the Zn2+ precursors with increased pH. At pH 10.3, the as-prepared nanocrystals were identified to have ZnSe...