Abstract
The detection of heavy metals in aqueous solutions has always attracted much attention from all over the world. A fluorescent probe of CdSe/CdS core-shell quantum dots (QDs) was designed to detect trace Cd(2+) in aqueous solutions using the OFF-ON mode rapidly and efficiently, likely based on adsorption and desorption reactions between ethylenediaminetetraacetic acid disodium salt (EDTA) and CdSe/CdS QDs. In the OFF mode, the optical shielding function of EDTA results in fluorescence quenching owing to the strong adsorption ability of EDTA with Cd(2+) on the sites of CdSe/CdS QDs surface. In the ON mode, the introduction of Cd(2+) promotes the desorption of EDTA from the EDTA-CdSe/CdS QDs and restores the fluorescence intensity. There were two linear response ranges which were 0.1-20 µmol/L and 20-90 µmol/L for the EDTA-CdSe/CdS system to detect Cd(2+). The detection limit was 6 nmol/L, and the standard deviation was below 4% for the detection of Cd(2+) concentration in tap water.