Rational design of MoS QDs and Eu as a ratiometric fluorescent probe for point-of-care visual quantitative detection of tetracycline via smartphone-based portable platform.

The abuse of the antibiotic tetracycline (TC) has resulted in its residues in the environment and animals, which has caused irreversible damage to public health safety and environments. Therefore, it is urgently needed to develop alternative sensitive and low-cost for quickly and accurately detection the TC residues in the environments. We innovatively rational design of MoS QDs and Eu to construct ratiometric fluorescent probe to detect TC. In general, TC coordinates Eu to form Eu-TC coordination compound with weak luminescence. However, MoS QDs with exceptional fluorescence characteristics are a good energy donors and acceptors, MoS QDs can transfer energy with Eu-TC coordination compound, which can greatly enhance the luminous ability of Eu-TC coordination compound while accompanied by a decline of its initial fluorescence intensity. MoS QDs can be used as an indicator and enhancer in the MoS-Eu ratiometric probe, which can greatly improve limit of detection and accuracy of quantitation for TC. The detection of TC by fluorescent intensity ratio (F/F) of MoS QDs-Eu shows a good linear response in the range of 10 nM-60 μM TC, with the limit of detection (LOD) toward TC is calculated to be 2 nM (3σ/slope), the recovery is 94.4-108.4%, and the RSD is less than 5.36. The smartphone-based portable platform with the RGB color recognition software is designed for point-of-care visual quantitative detection of TC. The portable detection system shows a low detection limit (0.05 μM) and excellent reproducibility in the range of 1-40 μM TC. This work has provided a sensitive, rapid, real-time detection of environmental pollutants.