Ratiometric system based on graphene quantum dots and Eu³⁺ for selective detection of tetracyclines

In this study, a system was established for the detection of tetracyclines (TCs) by simply mixing graphene quantum dots (GQDs) and Eu³⁺. The GQDs-Eu³⁺ system exhibits both strong emission of GQDs and weak characteristic emission of Eu³⁺ upon 360 nm excitation. In the presence of TCs, the luminescence of GQDs was quenched, while the luminescence of Eu³⁺ was significantly enhanced. It is worth to mention that the GQDs we prepared possess a lot of carboxyl groups on the surface and edge. This carboxyl groups play an important role in fluorescent enhancement of Eu³⁺. On the basis of this effect, a novel label free ratiometric sensor was developed for the detection of TCs. Under the optimized conditions, linear concentration ranges from 0 to 20 μM for tetracycline was found, and the detection limits was 8.2 nM. This system also exhibited excellent selectivity toward TCs over other antibiotics. In addition, it was successfully applied to the determination of tetracycline in river water and milk samples. The proposed system was simple in design, fast in operation, rapid in response and cost-effective. In view of the advantages, the developed system demonstrates great potential for the detection of TCs in environmental and biological samples.