Smartphone-assisted fluorescent sensor for the visualization and quantitative detection of doxycycline and L-arginine

A novel smartphone-assisted fluorescent sensor based on europium/zirconium metal-organic framework (Eu 0.5 /Zr 0.5 -MOF) was developed for the fast and sensitive determination of doxycycline (DOX) and L-arginine (Arg). After the addition of DOX, the fluorescence of Eu 0.5 /Zr 0.5 -MOF was quenched owing to the inner filter effect (IFE). When Arg was introduced into the Eu 0.5 /Zr 0.5 -MOF@DOX complex system, the fluorescence was recovered because the interaction between Arg and Eu 0.5 /Zr 0.5 -MOF@DOX weakened the IFE. Moreover, the Eu 0.5 /Zr 0.5 -MOF produced continuous fluorescence color changes for the visual measurement of DOX and Arg. The fluorescent probe for DOX and Arg offered broad linear ranges of 0.05–80 and 0.1–60 μg/mL, respectively, with detection limits as low as 2.07 and 67.5 ng/mL. The proposed method was successfully applied to monitor DOX in eggs and Arg in human serum. This work provides a powerful platform for the real-time and visual analysis of DOX and Arg in food and biological samples.