A dual-emission ratiometric fluorescent probe based on carbon quantum dots and a lanthanide MOF for the selective detection of TNT and Fe³⁺ in aqueous phase

Water contamination by explosive compounds and heavy metal ions poses serious risks to ecosystems and human health worldwide. Among them, 2,4,6-trinitrotoluene (TNT), a persistent nitroaromatic explosive, is frequently found in military and industrial wastewater, as well as residues from civilian blasting activities. Ferric ions (Fe³⁺), commonly discharged through various industrial processes, also present a significant environmental threat. Therefore, the development of effective detection methods for both TNT and Fe³⁺ in aquatic environments is of great importance for environmental monitoring and pollution control. Herein, we report a novel dual-emission ratiometric fluorescent probe, CNQDs/Eu-MOF-76, capable of simultaneously and selectively detecting both TNT and Fe³⁺ in aqueous environments. The probe combines blue-green fluorescence from carbon quantum dots (CNQDs, 496 nm) and red fluorescence from Eu-MOF-76 (618 nm), enabling a distinct ratiometric response upon analyte recognition. It exhibits high sensitivity, with a detection limit for TNT as low as 0.4 nM and a linear range from 0 to 6.3 nM. Moreover, the probe shows excellent selectivity toward TNT and Fe³⁺ over various common ions. Its practical applicability was validated in real water samples (river, tap, and drinking water), demonstrating satisfactory recoveries and good reproducibility. This strategy offers a rapid, cost-effective, and reliable tool for environmental monitoring and water quality protection.