Fluorescent Zn-PDC/Tb³⁺ Coordination Polymer Nanostructure: A Candidate for Highly Selective Detections of Cefixime...

Tb³⁺-doped zinc-based coordination polymer nanospindle bundles (Zn-PDC/Tb³⁺, or [Zn(2,5-PDC)(H₂O)₂]·H₂O/Tb³⁺) were synthesized by a simple solution precipitation route at room temperature, employing Zn(NO₃)₂, Tb(NO₃)₃, and 2,5-Na₂PDC as the initial reactants, and a mixture of water and ethanol with the volume ratio of 10:10 as the solvent. The as-obtained nanostructures presented strong fluorescent emission under the excitation of 298 nm light, which was attributed to the characteristic emission of the Tb³⁺ ion. It was found that the above-mentioned strong fluorescence of the nanostructures could be selectively quenched by cefixime (CFX) in aqueous solution. The other common antibiotics hardly interfered. Thus, as-obtained Zn-PDC/Tb³⁺ nanostructures could be prepared as a highly sensitive fluorescence probe for selective detection of CFX in an aqueous system. The corresponding detection limit reached 72 ppb. The theoretic calculation and UV-vis absorption experiments confirmed that the fluorescence quenching of Zn-PDC/Tb³⁺ nanostructures toward CFX should be attributed to the electron transfer and the fluorescence inner filter effect between the fluorescent matter and the analyte. In addition, the strong fluorescence of the nanostructures could also be selectively quenched by acetone in the water system.