Facile synthesis of high-quality CdTe/CdS core/shell quantum dots in aqueous phase by using dual capping ligands

Abstract

To overcome the low emission efficiency and poor photo and colloidal stability of quantum dots (QDs) prepared in aqueous media, the main challenge is to find suitable capping reagents to obtain stable QD/ligand complexes. Adenosine 5′-monophosphare (AMP) appears very promising for the stabilization and the further functionalization of QDs because AMP has multiple functionalities that can chelate metal cations. Herein, we synthesized high-quality CdTe/CdS core/shell nanostructures in aqueous media, in which AMP and thiopropionic acid (MPA) acting as dual stabilizing agents were introduced directly on the surface of QDs. With the combination of AMP and MPA ligands, it was found that dual ligands could accelerate the reaction kinetics, accompanied by possessing high emission efficiency of QDs. The prepared water-soluble AMP/MPA-QDs exhibit narrow size distribution and nearly spherical morphology. Most importantly, the resultant water-soluble AMP/MPA-QDs exhibit superior photo and colloidal stability, solving the problem of deterioration for biological applications. To demonstrate the targeting capability of QDs, we have used folate-receptor targeting to show good selectivity to tumor cells.