Facile synthesis of high-quality water-soluble N-acetyl-L-cysteine-capped Zn(1-x)Cd(x)Se/ZnS core/shell quantum dots emitting in the violet-green spectral range.

In this paper, we report a new facile method to synthesize water-soluble Zn(1-x)Cd(x)Se and core/shell Zn(1-x)Cd(x)Se/ZnS quantum dots (QDs) emitting in the violet-green spectral range, using N-acetyl-L-cysteine (NAC) as a stabilizer. The influence of various experimental variables, including the precursor Zn/Cd/Se/NAC molar ratios, the pH of original solution and the refluxing time on optical properties were explored systematically. The obtained aqueous Zn(1-x)Cd(x)Se QDs exhibit a tunable photoluminescence (PL) emission (from approximately 415 nm to 506 nm) and a favorable narrow PL bandwidth (FWHM: 27-38 nm). After coating with a ZnS shell, the PL emission intensity of the formed core/shell Zn(1-x)Cd(x)Se/ZnS QDs is greatly increased (PL quantum yield (QY): approximately 30%). These resulting Zn(1-x)Cd(x)Se and core/shell Zn(1-x)Cd(x)Se/ZnS QDs were further characterized by transmission electron microscopy (TEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). In addition, the cytotoxicity and the fluorescence imaging of Zn(1-x)Cd(x)Se/ZnS QDs to MCF-7 cells were preliminarily investigated. The experimental results show that the as-prepared violet-green-emitting Zn(1-x)Cd(x)Se/ZnS QDs have low cytotoxicity, which makes them an ideal inorganic fluorescent probe for biolabeling and cell imaging.