One-Pot Synthesis of Ratiometric Fluorescent Europium (III)−Functionalized Polymer Nanodots for Amplified Detection of Tetracyclines

Rapid and sensitive detection of tetracyclines (TCs) is an urgent requirement for effective food safety control and human health protection. Herein, we presented an approach utilizing europium (III−functionalized fluorescent polyethylenimine-based nonconjugated polymer nanodots (PEI-PDs-Eu3+) for ratiometric and signal-amplified sensing of TCs. The PEI-PDs-Eu3+ were synthesized via a simple one-pot one-step reaction of PEI, Eu3+, and l-ascorbic acid (AA). PEI-PDs not only served as a reference signal but also as nanocarriers chelating response signal Eu3+ on matrix of nanodots. The Eu3+ doping could lead to the increase in size of nanodots. In this protocol, the red fluorescence of the Eu3+ complex could be effectively enhanced by TCs through the antenna effect (AE), while the blue fluorescence of PEI-PDs almost remained. The PEI-PDs-Eu3+−based nanoprobe exhibited good detection limits as low as 5.6, 5.9, and 10.8 nM for tetracycline (TET), oxytetracycline (OXY), and doxycycline (DOX), respectively. The high sensitivity was attributed to the dense chelation of the Eu3+ complex on the nanomatrix of PEI-PDs endowing the PEI-PDs-Eu3+−based nanoprobe realization of a signal amplification effect for sensing of TCs. The application of the assay platform for the detection of TET in milk samples was demonstrated. Accordingly, the as-developed nanoprobe demonstrated the advantages of low cost, easy preparation, and desirable specificity and sensitivity.