Facile synthesis of high-quality water-soluble N-acetyl-L-cysteine-capped Zn1-xCdxSe/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 Zn1-xCdxSe and core/shell Zn1-xCdxSe/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 Zn1-xCdxSe QDs exhibit a tunable photoluminescence (PL) emission (from similar to 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 Zn1-xCdxSe/ZnS QDs is greatly increased (PL quantum yield (QY): similar to 30%). These resulting Zn1-xCdxSe and core/shell Zn1-xCdxSe/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 Zn1-xCdxSe/ZnS QDs to MCF-7 cells were preliminarily investigated. The experimental results show that the as-prepared violet-green-emitting Zn1-xCdxSe/ZnS QDs have low cytotoxicity, which makes them an ideal inorganic fluorescent probe for biolabeling and cell imaging. (C) 2010 Elsevier Inc. All rights reserved.