Effect of metal ions on the quenching of photoluminescent CdTe QDs and their recovery

• A simple TGA–CdTe QD sensor is constructed for detecting Cu2+.
• The detection limit of 0.04 nM for Cu2+ is achieved.
• Ammonium solution can recover the fluorescence of QDs quenched by metal ions.

Herein, we report a simple, rapid and low-cost method as a probe for ultrasensitive Cu2+ detection by using CdTe quantum dots. For the detection of Cu2+, we simply synthesized three different sizes of thioglycolic acid (TGA) stabilized CdTe quantum dots (QDs) by tuning the refluxing time. A rapid and reliable detection of Cu2+ with a detection limit as low as 0.04 nM (1 × 10−9 mol/L) is obtained, to our knowledge, which was the lowest concentration for detection of Cu2+ by using CdTe QDs. And we also found that copper (II) ions, other than other metal ions, can quench the fluorescent of quantum dots with excellent selectivity in the linear response range of 0.25–617.53 nM. Moreover, the ammonium solution was used to recover the fluorescence quenched by metal ions for the first time. Mechanism for turn-off-on of photoluminescence (PL) in CdTe QDs was also systematically discussed.