Ratiometric fluorescence sensor based on chiral europium-doped carbon dots for specific and portable detection of tetracycline

The persistent residual of tetracycline (TC) in animal-derived food has posed a significant threat to human health, so the sensitive and specific detection of TC has extraordinary significance for food quality evaluation. However, most current methods were inevitably interfered by the highly similar structures of TCs family. To improve the specificity of TC detection, a novel ratiometric fluorescence sensor based on chiral europium-doped carbon dots (Eu-L/D-CDs) was designed for the sensing of TC. The blue fluorescence of Eu-L/D-CDs could be reduced by TC through static quenching (SQE) and internal filtering effects (IFE), while the red fluorescence could be enhanced through antenna effect (AE). The sensor achieved the rapid and sensitive detection of TC through fluorescence and colorimetric methods with detection limits as low as 2.82 nM and 3.74 nM, respectively. Importantly, the Eu-L-CDs-loaded test strips and hydrogel microspheres achieved the portable and visual detection of TC with the assistance of smartphone sensing platform. Additionally, the sensor could rapidly screen TC adjuvants in bacteria, providing a new approach to enhance the sensitivity of resistant bacteria to drugs. Therefore, this sensor not only proposed new insights into the sensitive and portable monitoring of TC, but also expanded the application of chiral CDs in the fields of biomedical sensing.