Advances in green carbon quantum dots: heteroatom doping strategies for pesticide detection

Carbon quantum dots (CQDs) have emerged as promising nanomaterials due to their tunable photoluminescence, biocompatibility, and facile synthesis. The green synthesis of CQDs using biomass-derived precursors provides a sustainable and economical alternative for developing sensors, particularly relevant to address pesticide contamination in food and water. Heteroatom doping with nitrogen, sulfur, phosphorus, or boron enhances the optical and electronic properties of CQDs, thereby significantly improving their fluorescence-based sensing capabilities. This review discusses advances in the green synthesis of doped CQDs and the effects of single-, dual-, and triple-heteroatom doping on quantum yield and sensing performance. Mechanistic pathways, including photoinduced electron transfer (PET), Förster resonance energy transfer (FRET), static/dynamic quenching, and the inner filter effect (IFE), are examined. Case studies reveal the potential of doped CQDs to detect pesticides at nanomolar levels in complex matrices. Key challenges and design principles for next-generation eco-friendly CQD-based sensors are also addressed.