Construction of ratiometric fluorescence MIPs probe for selective detection of tetracycline based on passion fruit peel carbon dots and europium

A new type of ratiometric molecularly imprinted fluorescence probe (B-CQDs@Eu/MIPs) based on biomass carbon quantum dots (B-CQDs) and europium ions (Eu³⁺) has been prepared to recognize and detect tetracycline (TC). In the experiment, the fluorescent material B-CQDs were prepared using passion fruit peels through microwave-assisted method, which by the meantime achieves the reuse of biomass waste. TC can block the transition of some parts of electrons in the prepared B-CQDs from the excited state to the ground state, resulting in the weakening of its blue light (Ex = 394 nm, Em = 457 nm), while TC can be chelated by Eu³⁺ and emit red characteristic fluorescence (Ex = 394 nm, Em = 620 nm) due to the antenna effect. Thus, a ratiometric fluorescence response to TC is the result of the combined B-CQD and Eu³⁺ . Based on this, we established the ratiometric fluorescent molecularly imprinted (MIP) probe for the detection of TC. The prepared B-CQDs@Eu/MIPs is aimed at catching the fluorescence changes of target tetracycline (TC) sensitively with the special combination of the specific recognition cavities and TC. The linear fluorescence quenching range of TC in milk using the fluorescent probe was 25–2000 nM, and the detection limit was 7.9 nM. The recoveries of this method for TC were 94.2–103.7%, and the relative standard deviations (RSDs) were 1.5–5.3%. Owing to the predetermined nature of MIP technology and the special response of ratio fluorescence, the interference of common substances is eliminated completely, which greatly improved the selectivity of its practical applications. Graphical abstract: