We developed a novel one-pot polyol approach for the synthesis of biocompatible CdSe quantum dots (QDs) using poly(acrylic acid) (PAA) as a capping ligand at 240°C. The morphological and structural characterization confirmed the formation of biocompatible and monodisperse CdSe QDs with several nanometers in size. The encapsulation of CdS thin layers on the surface of CdSe QDs (CdSe/CdS core–shell QDs) was used for passivating the defect emission (650 nm) and enhancing the fluorescent quantum yields up to 30% of band-to-band emission (530–600 nm). Moreover, the PL emission peak of CdSe/CdS core–shell QDs could be tuned from 530 to 600 nm by the size of CdSe core. The as-prepared CdSe/CdS core–shell QDs with small size, well water solubility, good monodispersity, and bright PL emission showed high performance as fluorescent cell labels in vitro. The viability of QDs-labeled 293T cells was evaluated using a 3-(4,5-dimethylthiazol)-2-diphenyltertrazolium bromide (MTT) assay. The results showed the satisfactory (>80%) biocompatibility of as-synthesized PAA-capped QDs at the Cd concentration of 15 μg/ml.
HDA-capped CdS nanoparticles were synthesized at 150°C using the cadmium complex. Optical properties of the nanoparticles were investigated by UV-vis and photoluminescence spectroscopy at room temperature () and show CdS nanoparticles with excitonic features at 420nm and emission at 559nm. The CdS nanoparticles showed quantum size effect which is manifested as a blue shift in their absorption band edges in comparison to that of the bulk.
Synthesis of zinc sulphide nanoparticles by thiourea ..
For their in vitro cell labeling studies, the cultured human embryonal kidney cell line 293T cells were incubated with the PAA-capped CdSe/CdS core–shell QDs (λem max = 559 nm, about 3 nm in size) with the concentration of 5 μg/mL for 4 h at 37°C. After 4 h, the cells were washed thrice with PBS to remove extra nanoparticles that were not uptaken by the cells and imaged using a laser scanning confocal microscope. Figure shows the typical labeling images of 293T cells with PAA-capped CdSe/CdS core–shell QDs. From these images, the bright green optical signal can be clearly observed from the cell interior. The result demonstrated that the as-synthesized quantum dots can be quickly uptaken by the 293T cells within 4 h. Moreover, we did not observe any signs of morphological damage to the cells after the treatment with PAA-capped CdSe/CdS core–shell QDs. This preliminary result indicates that the as-prepared QDs had promising applications as fluorescent biological labels.