Selective ratiometric fluorescent detection of chlortetracycline in environmental water based on hydrolysis-induced emission.

For specific determination of chlortetracycline (CTC) among tetracycline antibiotics (TCs), the current study focused on the hydrolysis effect of TCs. In water, CTC was hydrolyzed into isochlortetracycline (iso-CTC) along with blue fluorescence, but other TCs remained stable without blue fluorescence. CTC was thus identified within TCs based on hydrolysis-induced emission. To improve signal stability, Mn-doped ZnS (Mn:ZnS) quantum dots (QDs) that exhibited red luminescence were introduced to achieve ratiometric sensing. After adding CTC to Mn:ZnS QDs, the red emission of Mn:ZnS QDs was decreased owing to inner filter effect and dynamic quenching effect, whereas blue emission was observed due to the hydrolysis of CTC. This ratiometric method quantified CTC in the concentration range 0.3-50 μM with a response time of 60 min and a detection limit of 94 nM. This ratiometric method was employed to detect CTC in environmental water. A sensing platform that combined test strips and a smartphone was constructed to visualize the determination of CTC. This work proposes a hydrolysis-based mechanism for selective recognition of CTC among TCs, which facilitates to assess the hazard rating of the environmental water polluted by TCs.