A Eu3+-based high sensitivity ratiometric fluorescence sensor for determination of tetracycline combining bi-functional carbon dots by surface functionalization and heteroatom doping

A ratiometric fluorescence sensor based on Cu-CDs–COOH–Eu was proposed and used to highly sensitive detection of Tetracycline (TC) residues in complex samples. Combination with surface functionalization of carboxyl group and heteroatom doping of Cu2+, the bi-functional carbon dots (Cu-CDs-COOH) were prepared, which exhibited an outstanding fluorescence properties and optical stability. Thanks to the Cu-CDs-COOH rich in carboxyl groups, Eu3+ can effectively chelate with Cu-CDs-COOH which still maintained excellent optical properties (denoted as Cu-CDs–COOH–Eu). When TC was presented in the sensing system of Cu-CDs–COOH–Eu, the strong blue emission of Cu–COOH was quenched at 467 nm based on inner filter effect while the characteristic peak of Eu3+ at 625 nm was enhanced via antenna effect. Herein, a ratiometric fluorescence sensor was built, which was able to detect TC in the range of 0.4–60 μM with a low limit detection of 36.1 nM. The proposed method also showed a satisfactory result of determination TC reliably and accurately in complex samples.