Carbon dots (CDs) combined with a nanomaterial-based quencher has created an innovative way for designing promising sensors. Herein, a novel fluorescent-sensing platform was designed for sensitive detection of organophosphorus pesticides (OPs). The preparation of CDs was based on one-step hydrothermal reaction of 3-aminobenzeneboronic acid. The fluorescence of CDs can be quenched by manganese dioxide (MnO) nanosheets via the Förster resonance energy transfer (FRET). In the presence of butyrylcholinesterase (BChE) and acetylthiocholine, the enzymatic hydrolysate (thiocholine) can efficiently trigger the decomposition of MnO nanosheets, resulting in the recovery of CDs fluorescence. OPs as inhibitors for BChE activity can prevent the generation of thiocholine and decomposition of MnO nanosheets, accompanying the fluorescence "turn-off" of the system. So the BChE-ATCh-MnO-CDs system can be utilized to detect OPs quantitatively based on the fluorescence turn "on-off". Under the optimum conditions, the present FRET-based approach can detect paraoxon ranging from 0.05 to 5 ng mL with a detection limit of 0.015 ng mL. Meanwhile, the present strategy also showed a visual color change in a concentration-dependent manner. Thus, the proposed assay can potentially be a candidate for OPs detection.

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