Fluorescence and colorimetric dual-mode detection of tetracycline antibiotics based on Eu and the peroxidase mimetic activity of a FeO@MoS nanocomposite.

A sensitive fluorescence and colorimetric dual-mode detection method based on Eu and FeO@MoS nanocomposites was constructed. In this technique, tetracycline antibiotics (TCs) chelated with Eu to form a Eu-TCs complex which emits red fluorescence at 620 nm through the antenna effect. At the same time, Eu-TCs complex enhances the peroxidase-like activity of FeO@MoS to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) that can produce a colorimetric signal. This proposed strategy has been used to detect three antibiotics including oxytetracycline (OTC), tetracycline (TC), and chlortetracycline hydrochloride (HCl-CTC). The linear ranges of the new assay for OTC, TC, and HCl-CTC were 0.1-25 μM, 0.5-25 μM, and 0.05-5 μM with the detection limits of 0.016 μM, 0.039 μM, and 0.036 μM, respectively. Meanwhile, this new method was fast and convenient which can complete the detection in 22 min. The assay has been effectively applied to TCs detection in tap water, lake water and honey with satisfactory recoveries of 90.55-109.86%.