The mesoporous silica nanoparticle@carbon dots-Eu 3+ based ratiometric fluorescence probe for the point-of-care testing of tetracycline

The development of a sensitive and facile method for the detection of tetracycline (TC) is crucial for food safety and environmental protection, as TC residues pose a major threat to human health and the ecological environment. In this work, a ratiometric fluorescence probe containing mesoporous silica nanoparticle (MSNs) encapsulated CDs (MSNs@CDs) and Eu 3+ is constructed for the detection of TC. With the addition of TC into MSNs@CDs-Eu 3+ solution, the internal filter effect (IFE) of the TC to MSNs@CDs induces the quenching of the blue fluorescence emission at 430 nm of the MSNs@CDs, while the antenna effect (AE) of Eu 3+ to β-diketone structure of TC amplifies the red fluorescence emission at 617 nm of the Eu 3+. Therefore, based on the ratio changes of the two fluorescence signals (I 616 /I 430 ), a sensitive and selective method for the detection of TC is established. The detection range of this method is from 0 to 50 μM with detection limit of 24 nM. Since there are obvious color changes throughout the TC detection process, a 3D-printing device based on the smartphone is designed for digital image detection of TC. The picture of solution is taken by smartphone and the color signal is converted into digital signal by color recognition software, thus realizing the visual and rapid quantitative detection of TC. The linear regression equation is R/(G + B) = 0.01C TC +0.49, and the detection limit is 40 nM. This method is applied for the detection of TC in the real sample with recoveries from 93.58 % to 108.1 %, which provides a new strategy for rapid and on-site detection of TC in actual water samples for environmental protection.