Post-modified metal-organic framework as ratiometric fluorescence-scattering probe for trace ciprofloxacin residue based on competitive coordination

The abuse of ciprofloxacin (CIP) in stock industries causes the residue in food stuffs and the leakage in the environment, impairing human health and ecological balance. Based on the competitive coordination of CIP with Al3+ and the inherent fluorescence of CIP, Al-based metal-organic framework NH2-MIL-53 was herein prepared as the ratiometric probe for CIP residue by integrating fluorescence with scattering signals. Considering the overlapped emission of NH2-MIL-53 with CIP, 8-hydroxy-2-quinolinecarboxaldehyde (HQCA) was further modified on NH2-MIL-53 via Schiff base reaction to produce non-fluorescent HQCA-MIL-53, for reducing the background signal and improving the detection sensitivity. After adding CIP to HQCA-MIL-53, the competitive coordination of CIP with Al3+ made HQCA-MIL-53 decomposed, reducing the second-order scattering signal at 660 nm, while the inherent emission of CIP made the fluorescence signal at 425 nm observed. And expectably, HQCA-MIL-53 displayed high sensitivity toward CIP and the limit of detection was determined as low as 52 nM ascribed to HQCA-reduced background signal. HQCA-MIL-53 was finally applied to analyzing the CIP residue in basa fish, tap water and human urine. Overall, this work develops a ratiometric probe for the sensitive detection of CIP residue, also paves the way to construct ratiometric CIP probes with the fluorescence-scattering strategy. [Display omitted] •HQCA-MIL-53 was prepared from the modification of NH2-MIL-53(Al) with HQCA.•HQCA-MIL-53 acted as a ratiometric fluorescence-scattering probe of ciprofloxacin.•The sensing mechanism was the competitive coordination of ciprofloxacin with Al3+.•The grafting of HQCA reduced background signal and improved detection sensitivity.•HQCA-MIL-53 was applied to detecting CIP in basa fish, tap water and human urine.