Fluorescence Visualization Quantitative Detection of Tetracycline and Nitrofurantoin in Food and Natural Water by...

Quantitative detection of tetracycline (TC) and nitrofurantoin (NFT) in food and water is of importance for food safety and environmental protection. Herein, Zn²⁺ was introduced into a europium metal-organic framework Eu-bpdc (H₂bpdc = 2,2'-bipyridyl-5,5'-dicarboxylic acid) to prepare a composite of Zn²⁺@Eu-bpdc, which was developed as a fluorescence sensor for TC and NFT. The fluorescence mechanism concerns with bpdc^2- ligand-to-Eu(III) charge transfer, and the detection mechanism is the inner filter effect. Zn²⁺@Eu-bpdc is a ratiometric fluorescence sensor for TC with the linear fitting equation of I₅₂₀/I₆₁₈ = 1.94 × 10⁴ M^-1C_TC, whose limit of detection (LOD) is 0.148 μmol·L^-1 (μM); it is also a fluorescence "turn-off" sensor for NFT with the fitting equation of (I₀-I)/I = 3.62 × 10⁴ M^-1C_NFT and LOD = 0.0792 μM. Zn²⁺@Eu-bpdc can detect TC or NFT in lake water, honey, and milk with high accuracy. The emission color changes of paper-based Zn²⁺@Eu-bpdc depending on C_TC or C_NFT reveal the visualization detections of TC and NFT. With the red and green values as input signals, smartphone-assisted on-site detection is utilized to recognize the antibiotic residuals of TC and NFT by a self-programmed APP. Zn²⁺@Eu-bpdc is promising in a smartphone-assisted intelligent platform for on-site detection of TC and NFT.