Investigation of Ag doping and ligand engineering on green synthesized CdS quantum dots for tuning their optical properties

We present a green route for the colloidal synthesis of undoped and silver (Ag) doped cadmium sulfide (CdS) quantum dots (QDs). We have used olive oil as the reaction medium, which acted as a source of oleic acid (OA) ligand in the green synthesis of CdS QDs. With the increase in OA concentration, the dispersibility of CdS QDs improved. The water-dispersible CdS QDs were prepared via exchanging OA’s associated ligand with 3-mercaptopropionic acid (MPA). The MPA-capped CdS QDs showed the disappearance of the S-H peak as characterized via FTIR. The crystal and optical properties of Ag-doped CdS QDs were investigated, and the spectral red shift in the absorption spectra was observed. The CdS QDs with low Ag doping concentration increased the lifetime of excitons, but the average lifetime was suppressed at a higher concentration. We also discussed the variation in the properties of the CdS QDs through ligand engineering and Ag doping. These doped and undoped QDs have the potential for applications in photocatalysis, water splitting, solar cells, etc. In addition, water dispersible QDs can be helpful for bioimaging, and drug delivery applications