Ratiometric fluorescent sensor for sensitive visualization of full-spectrum fluoroquinolone antibiotic residues in the environment

Misuse of fluoroquinolone antibiotics (FQs) leads to environmental residues that threaten human health and ecosystems. Therefore, the development of efficient and sensitive micro-residue detection techniques for FQs is crucial for the environment and human health. Here, we developed a functionalised ratiometric fluorescence sensor for sensitive, rapid and intuitive detection and analysis of FQs residues in the environment. The sensor was constructed from green fluorescent carbon dots (GCDs) and red fluorescent europium metal–organic frameworks (Eu-MOFs). After the addition of FQs, the carboxyl group on the surface of FQs combined with the amino group on the surface of GCDs to form an amide bond, which was facilitated by the sensitisation effect and energy transfer, resulting in the fluorescence from green to red, and the detection limit of 4.3 nM, detection time within 1 s, which enables rapid micro-detection of FQs. Combined with 3D printing technology, we designed a hand-held fluorescent needle for direct quantification of FQs residues in real samples with a detection limit of 4.9 nM. This technology provides an innovative scientific approach to the rapid detection of trace levels of environmental contaminants, helping to reduce the health and environmental hazards of FQs.