Enhanced ratiometric fluorescence molecularly imprinted nanosensor based on CDs for selective and visual detection of NOR in water samples

Norfloxacin plays an indispensable part in the field of the medical industry, stock raising, and aquaculture. However, excessive use of NOR can induce serious harmful effects on humans and antibiotic resistance of organisms. In this work, a novel fluorescence-enhanced ratiometric fluorescence imprinted sensor was constructed and used to realize selective and accurate detection of NOR. CdTe quantum dots encapsulated in silicon dioxide acted as the reference signal and CDs doped in the imprinted layer as the response signal. Under optimal conditions, NOR rapidly enhanced the fluorescence of CdTe@SiO 2 @FMIPs at 435 nm with 1 min and exhibited excellent linear relationships between the fluorescence enhancement efficiency and the NOR concentration over 10–90 nM with a detection limit of 3.28 nM. Due to the interaction of NOR and CDs through hydrogen bonding as well as π-π conjugation, the visual detection for NOR was achieved by distinguishing the color change from red to bright blue. Satisfied recovery rates of 93.4%–107.7% and RSD of 2.0%–3.6% were gained by actual sample experiments. Furthermore, CdTe@SiO 2 @FMIPs made it possible to reuse at least 5 times.