Hydrothermal synthesis for high-quality glutathione-capped Cdx Zn1 - x Se and Cdx Zn1 - x Se/ZnS alloyed quantum dots and its application in Hg(II) sensing.

ABSTRACT

High-quality Cdx Zn1 - x Se and Cdx Zn1 - x Se/ZnS core/shell quantum dots (QDs) emitting in the violet-green spectral range have been successfully prepared using hydrothermal methods. The obtained aqueous Cdx Zn1 - x Se and Cdx Zn1 - x Se/ZnS QDs exhibit a tunable photoluminescence (PL) emission (from 433.5 nm to 501.2 nm) and a favorable narrow photoluminescence bandwidth [full width at half maximum (FWHM) 30-42 nm]. After coating with a ZnS shell, the quantum yield increases from 40.2% to 48.1%. These Cdx Zn1 - x Se and Cdx Zn1 - x Se/ZnS QDs were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared (FTIR) spectroscopy. To further understand the alloying mechanism, the growth kinetics of Cdx Zn1 - x Se were investigated through measuring the fluorescence spectra and X-ray diffraction spectra at different growth intervals. The results demonstrate that the inverted ZnSe/CdSe core/shell structure is formed initially after the injection of Cd2+ . With further heating, the core/shell structured ZnSe/CdSe is transformed into alloyed Cdx Zn1 - x Se QDs with the diffusion of Cd2+ into ZnSe matrices. With increasing the reaction temperature from 100 °C to 180 °C, the duration time of the alloying process decreases from 210 min to 20 min. In addition, the cytotoxicity of Cdx Zn1 - x Se and Cdx Zn1 - x Se/ZnS QDs were investigated. The results indicate that the as-prepared Cdx Zn1 - x Se/ZnS QDs have low cytotoxicity, which makes them a promising probe for cell imaging. Finally, the as-prepared Cdx Zn1 - x Se/ZnS QDs were utilized to ultrasensitively and selectively detect Hg2+ ions with a low detection limit (1.8 nM).