Visual detection of ciprofloxacin using a multi-emission ratiometric fluorescence sensor based on the molecularly...

Ciprofloxacin (CIP) is a commonly used antibiotic, but its abuse may cause bacterial resistance, posing a high risk to the environment and human health. Herein, based on the molecular imprinting technology, this study proposed a ratiometric fluorescence sensor employing the "post-doping" strategy, which aims to be rapid, selective, and visually easy-to-use for CIP detection to address antibiotic residues and environmental risks. Specifically, by exploiting the "antenna effect" of lanthanide metal ions (Ln³⁺), terbium (III) (Tb³⁺) chosen as a fluorescence-assisted functional monomer as well as the red emitting CdTe quantum dots (QDs) as the internal reference signal were introduced into multi-emission Tb³⁺-CdTe@SiO₂@MIPs (TbMIPs). With the increase of CIP concentration, the variations among the fluorescence peaks within a multi-emission ratiometric fluorescence sensor not only induce a broader range of color changes, but also produce a more sensitive and stable effect through self-internal standard correction. The sensor showed a good trend in a wide concentration range within 0.08-50 μM and provided a satisfactory detection limit of 0.018 μM, which had lower detection limit for CIP than most of methods. It had demonstrated exceptional selectivity and had been successfully used to efficiently detect CIP in real samples including seawater, river water, milk and urine. Furthermore, when integrated with smartphone-based data processing capabilities, this sensor enabled highly sensitive visual detection under the 365 nm UV lamp device. Through innovative development, the wide color transition observed with the sensor makes it highly suitable for practical applications, enhancing its usability for further real-time monitoring.