Green-precursor carbon dots as effective “off” fluorescence sensors for detecting MnO4− ion in environmental water quality monitoring

Developing carbon dots as a fluorescent probe specifically for detecting residual permanganate ion (MnO 4 − ion) in water is crucial for effective environmental water quality monitoring. In this study, nitrogen-doped carbon dots (N-CDs) were successfully synthesized using purslane as a green precursor and ortho-phenylenediamine (OPD) as a nitrogen source via a simple one-step hydrothermal method. These N-CDs exhibited a maximum emission wavelength of 486 nm when excited at 358 nm. They demonstrated significant antioxidative properties in various concentrations of H 2 O 2 and showed high photostability and resistance to photobleaching under different pH, ionic strength, and UV irradiation conditions. Furthermore, the N-CDs were validated as highly selective and sensitive fluorescence sensors for MnO 4 − ion, demonstrating a linear relationship within the concentration range of 0.5–168 uM with a detection limit of 41.8 nM. The sensor successfully detected MnO 4 − ion in spiked tap and river waters, achieving satisfactory recovery.