Continuous Detection of Cobalt Ions and Pyrophosphates by NAC-CdTe Quantum Dots Fluorescence Probes

In this work, a simple and sensitive N-acetyl-L-cysteine (NAC)-covered CdTe quantum dots (NAC-CdTe QDs) fluorescence probe for continuous detection of Co²⁺ and pyrophosphate ions (PPi, P₂O₇^4-) was synthesized. The fluorescence of the quantum dots was significantly quenched by Co²⁺ through the coordination of Co²⁺ and the carboxyl groups on the NAC-CdTe quantum dots. Interestingly, the combination of NAC-CdTe quantum dots with Co²⁺ yields a new fluorescence probe of Co²⁺-modified NAC-CdTe QDs (Co²⁺@NAC-CdTe). The addition of PPi restored the fluorescence due to the competition between PPi and carboxyl groups with Co²⁺ causing Co²⁺ to detach from the surface of Co²⁺@NAC-CdTe quantum dots. Thus, a sensitive and reversible detection of Co²⁺ and PPi had been successfully established. The Co²⁺@NAC-CdTe quantum dots fluorescence probe exhibits excellent selectivity and high sensitivity toward PPi detection with low detection limit of 0.28 μM. In addition, the novel fluorescence probe was successfully applied to detect the concentration of PPi in environmental water samples and in-vitro cells imaging.