Preparation of high quantum yield nitrogen-doped carbon quantum dots via solid-phase pyrolysis for highly sensitive “on-off-on” fluorescence probe detection of silver ions and glutathione

In this study, folic acid-driven nitrogen-doped carbon quantum dots (N-FA-CQDs) were synthesized via solid-phase pyrolysis and utilized as a highly sensitive “on-off-on” fluorescence probe for the detection of silver ions (Ag + ) and glutathione (GSH). The N-FA-CQDs exhibit strong blue fluorescence with a quantum yield of up to 48.51 % and demonstrate excellent optical stability. The detection mechanism is based on the fluorescence of N-FA-CQDs being quenched by Ag + through an aggregation-caused quenching mechanism, followed by recovery of fluorescence via competitive binding of GSH with Ag + . The detection ranges for Ag + and GSH are 0–70 μM and 0–140 μM, respectively, with detection limits of 1.07 μM and 0.15 μM, respectively. Importantly, satisfactory recovery rates were achieved in the spiked recovery tests of real samples, indicating the potential practical application value of the prepared fluorescence probe. In summary, the “on-off-on” detection method based on N-FA-CQDs exhibits dual functionality and higher sensitivity and selectivity compared to traditional “on-off” probes, making it a promising new approach for the fluorescence analysis of Ag + and GSH.