Dithizone-etched CdTe nanoparticles-based fluorescence sensor for the off-on detection of cadmium ion in aqueous media

In the present study, a new fluorescence probe based on dithizone-etched CdTe nanoparticles was designed for the sensitive and selective detection of cadmium ions in environmental samples via a reversible off-on fluorescence mode. At first, the initial bright fluorescence of L-cysteine-capped CdTe NPs could be effectively quenched in the presence of dithizone (DZ) due to the chemical etching effect, which results from the breaking of Cd-thiol layers by DZ, thus leading to a decrease in the NPs surface passivation. Then, upon the addition of Cd2+, the weak fluorescence of the CdTe NPs-DZ system gradually recovered, owing to the occurrence of Cd-thiol passivation layers on the surface of the NPs. Under optimal conditions, a good linear relationship was obtained in the range from 0.4 mM to 15.4 mM for Cd2+, with a detection limit of 0.13 mM. In addition, this CdTe NPs-based nanosensor presents remarkable selectivity for Cd2+ over other metal ions and was successfully applied for the detection of Cd2+ in real water samples with satisfactory results, demonstrating its potential application for the determination of Cd2+ in the environment.