Metal/non-metal doped graphene quantum dots as dual fluorescent probes for detection of pesticide residues and heavy metal ions.

Heavy metals (Fe) and pesticides (diquat) pose serious threats to the environment and human health, necessitating the development of efficient detection technologies. In this study, metal/non-metal doped graphene quantum dots (GQDs) were developed. Given excellent sensitivity, stability and selectivity, it was used as a fluorescent probe with multiple functions for simultaneous detection of two pollutants. Nitrogen-doped (N-GQDs-1/2), magnesium‑nitrogen co-doped (Mg-N-GQDs), and aluminum‑nitrogen co-doped (Al-N-GQDs) materials were synthesized via the hydrothermal method, and their morphology, composition, and optical properties were characterized using TEM, XPS, and PL systems. The results show that heteroatom doping significantly modulates the bandgap (3.76-3.93 eV) and fluorescence intensity of GQDs, with N-GQDs-2 and Mg-N-GQDs exhibiting strong blue fluorescence (fluorescence intensity order: N-GQDs-2 > Mg-N-GQDs > N-GQDs-1 > Al-N-GQDs), with effective detection ranges for Fe of 100-600 μg/mL (R = 0.9636) and 150-450 μg/mL (R = 0.9459), respectively, and a response range for diuron of 10-10 M. This demonstrates that the surface functional groups of GQDs (-COOH, -OH, -NH) and the Fe chelation and π-π stacking pesticide recognition mechanism endow this material with application potential in environmental sensing, providing a new strategy for simultaneous detection of multiple pollutants. The GQDs prepared in this study are a promising candidate for portable detection systems in ecological monitoring or agricultural residue screening.