Nitrogen-doped carbon quantum dots for turn-off fluorescence detection of Aflatoxin B1 and Fumonisin B1: FRET versus aggregation-caused quenching.

Developing rapid and sensitive methods for monitoring of multiple mycotoxins is crucial for food safety. In this study, nitrogen-doped carbon quantum dots (N-CQDs) were synthesized via hydrothermal treatment of fumaronitrile and applied as a fluorescent "turn-off" probe for Aflatoxin B1 (AFB1) and Fumonisin B1 (FB1). For AFB1, the sensor shows high sensitivity through a Förster resonance energy transfer (FRET) mechanism, achieving a limit of detection (LOD) of 0.046 ng/mL and a linear range of 0.3-180 ng/mL. Meanwhile, the detection of FB1 follows an Aggregation-Caused Quenching (ACQ) mechanism with a working range of 40-250 ng/mL and a practical quantitation limit (PQL) of 50 ng/mL (RSD < 40%) for semi-quantitative screening. DFT calculations suggesting that N-CQDs may facilitate stronger π-π stacking and electrostatic interactions compared to O-CQDs. This work provides a promising analytical platform for ultra-trace mycotoxin detection and offers insights into tailoring carbon nanomaterials for sensing applications.