Highly Luminescent Nucleoside-Based N, P-Doped Carbon Dots for Sensitive Detection of Ions and Bioimaging

The efficient detection of Fe³⁺ and MnO₄ ^- in a water environment is very important and challenging due to their harmful effects on the health of humanity and environmental systems. Good biocompatibility, sensitivity, selectivity, and superior photophysical properties were important attributes of carbon dot-based CDs sensors for sensing applications. In this work, we synthesized N, P-co-doped carbon dots (N/P CDs) with guanosine 5'-monophosphate (GMP) as a green carbon source, with high fluorescence quantum yield in water (QY, 53.72%). First, the luminescent N/P CDs showed a three-state "on-off-on" fluorescence response upon the sequential addition of Fe³⁺ and F^-, with a low detection limit of 12 nM for Fe³⁺ and 8.5 nM for F^-, respectively. Second, the N/P CDs also exhibited desirable selectivity and sensitivity for toxic MnO₄ ^- detection with the limit of detection of 18.2 nM, through a turn-off mechanism. Moreover, the luminescent N/P CDs successfully monitored the aforementioned ions in environmental water samples and in Escherichia coli.