One-pot aqueous synthesis of near infrared emitting PbS quantum dots

In this study, we report the synthesis of PbS quantum dots (QDs) using an aqueous route with L-cysteine (L-Cys) as the capping ligands. The as-prepared PbS QDs were characterized by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD), the results indicated that the QDs were about 7 nm in size and dispersed well. There was L-Cys on the surface of QDs, which was confirmed by Fourier transform infrared (FT-IR) spectrometry. Various synthesis parameters affecting on the photoluminescent (PL) properties of the PbS QDs were discussed in detail. These parameters include the reaction time, the molar ratio of L-Cys/Pb or S/Pb, pH value and different sulfur source compounds. Furthermore, we found the as-synthesized QDs were still keeping highly PL properties not only in their original solution but also in deinoized (DI) water and phosphate buffer saline (PBS) solution during the period of 30 days, which indicated that the L-Cys capped PbS QDs could be important to the application in biomedical field in the future.