Water-Soluble N-Acetyl-L-cysteine-Capped CdTe Quantum Dots Application for Hg(II) Detection

A simple, rapid, and specific method for Hg(II) detection has been proposed based on the fluorescence change of N-acetyl-L-cysteine-capped CdTe quantum dots (QDs). The presence of Hg(II) ions could quench the fluorescence of QDs at 565 nm and meanwhile produce new peak in 700-860 nm wavelength range. The linear response range is 20-430 nM with the detection limit at 8.0 nM Hg(II). It was found that the position of the new peak was irrelevant to the size of QDs. Furthermore, the mechanism of the quenching of QDs fluorescence by Hg(II) and the appearance of new peak in near-infrared area were also discussed and deduced through ultraviolet absorption spectrum, fluorescence spectrum, and X-ray photoelectron spectrum.