Facile, sensitive, and ratiometric detection of mercuric ions using GSH-capped semiconductor quantum dots

Glutathione (GSH) capped CdTe semiconductor quantum dots (QDs) are applied for detecting mercuric ions (Hg(2+)) of trace quantity. The synthesis of GSH-capped CdTe (CdTe@GSH) QDs is cost-efficient and straightforward. We observed that Hg(2+) can quantitatively quench the fluorescence of CdTe@GSH QDs and further induce the slight redshift of emission peaks due to the quantum confinement effect. Detailed studies by spectroscopy, dynamic light scattering (DLS), and electrospray ionization mass spectrometry (ESI-MS) demonstrated that the competitive Hg(2+) binding with GSH makes the surface of CdTe QDs exposed, results in gradual aggregation, and quantitatively changes the photophysical properties of QDs. The whole procedure for detecting Hg(2+) by this protocol took less than 10 min. The experimental limit of detection (LOD) of Hg(2+) can be as low as 5 nM using CdTe@GSH with a low concentration (0.5 nM) because of the excellent fluorescent properties of QDs. This strategy may become a promising means to simply detect Hg(2+) in water with high sensitivity.