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 μM to 15.4 μM for Cd2+, with a detection limit of 0.13 μM. 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.

In the present study, a novel and sensitive fluorescence probe method has been established for the determination of luteolin (LTL) based on the fluorescence quenching effect of LTL on glutathione (GSH)-capped Mn-doped CdTe quantum dots (QDs). GSH-capped Mn-doped CdTe QDs with a diameter of 6–8 nm were synthesized via a facile and inexpensive method in an aqueous system. The fluorescence of doped CdTe QDs at 541 nm was quenched in the presence of LTL with an excitation wavelength at 351 nm and the fluorescence quenching efficiency was closely related to the amount of LTL added to the QDs solution; they presented a linear relationship when the concentrations of LTL vary from 6 to 138 μM. The mechanism of the interaction between doped CdTe QDs and LTL was investigated and was confirmed to be a dynamic quenching mechanism. The proposed method was successfully applied to the determination of LTL, and satisfactory results were obtained.

Based on the quenching of the fluorescence intensity of thioglycolic acid (TGA)-capped core-shell CdTe/ZnS nanoparticles (NPs) by vanillin, a novel, simple and rapid method for the determination of vanillin was proposed. In aqueous medium, the functionalized core-shell CdTe/ZnS NPs were successfully synthesized with TGA as the capping ligand. TGA-capped core-shell CdTe/ZnS NPs were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Factors affecting the vanillin detection were investigated, and the optimum conditions were also determined. Under the optimum conditions, the relative fluorescence intensity of CdTe/ZnS NPs was linearly proportional to vanillin over a concentration range from 9.4 × 10−7 to 5.2 × 10−4 M with a correlation coefficient of 0.998 and a detection limit of 2.6 × 10−7 M. The proposed method was also employed to detect trace vanillin in cookies with satisfactory results.