CdS QDs: Facile synthesis, design and application as an “on–off” sensor for sensitive and selective monitoring Cu2+, Hg2+ and Mg2+ in foods

Abstract

A new yellow CdS quantum dots (CdS QDs) with 59% quantum yield were synthesized successfully by one-pot method using thioglycolic acid as stabilizer, thiourea and sodium sulfide as double reducing agents. Based on CdS QDs, a novel “on–off” sensor for detecting Cu2+, Hg2+ and Mg2+ in foods has been constructed in the presence of glutathione (GSH). The fluorescence intensity of CdS QDs is improved about 1.5-fold by GSH, then quenched linearly by Cu2+, Hg2+ and Mg2+ owning to the electron transfer or ligand competition. Interestingly, without GSH, CdS QDs has no fluorescence response to Hg2+ at all, and with GSH, linear ranges of Cu2+ and Mg2+ is not only broader, but sensitivities are improved 16.9-fold for Cu2+ and 8.5-fold for Mg2+. GSH-CdS QDs sensor discloses a more sensitive, efficient and selective methodology for monitoring Cu2+, Hg2+ and Mg2+ in further heavy metal pollution and food safety.