Effect of NAC and MPA ligands on growth process and optical properties of CdTe quantum dots

This study explores the aqueous synthesis of cadmium telluride (CdTe) quantum dots (QDs) using 3-mercaptopropionic acid (MPA) and N-acetyl-l-cysteine (NAC) as stabilizing ligands, focusing on their combined effect on QD growth, optical properties, and stability. By systematically varying the Cd : MPA ratio and MPA : NAC combinations, we identified an optimal Cd : MPA ratio of 1 : 1.75, yielding a quantum yield (QY) of ∼44.8%, and an MPA : NAC ratio of 1 : 2, achieving a superior QY of 66% with enhanced QD monodispersity. The dual-ligand system resulted in smaller particle sizes, slower growth kinetics, and a bathochromic shift in photoluminescence (from 567 nm to 731 nm) over 5-180 minutes of synthesis time. The synthesized QDs exhibited excellent photostability, with QY variations of less than 3% under 29 hours of continuous laser irradiation. Transmission electron microscopy (TEM) confirmed spherical, crystalline nanoparticles with diameters of 3.4-3.6 nm. These findings highlight the potential of MPA and NAC in tailoring CdTe QD properties, offering insights for their application in optoelectronics and biomedicine.