Incorporation of Electron-Deficient Sites into Luminescent Complexes: Photochromism and Chlortetracycline Detection

Chlortetracycline (CTE) is a kind of tetracycline antibiotic against Gram-positive and negative bacteria. However, the overuse and excessive discharge of CTE would be harmful to the environment and human beings inevitably. Herein, to achieve sensitive and specific detection of CTE, an electron-deficient site (i.e., viologen segment) is incorporated into the construction of two isostructural multifunctional lanthanide-based complexes. Besides the distinct photochromism coupled with light-modulated typical Eu³⁺/Sm³⁺ luminescence, Eu-CP also shows a significant luminescence quenching behavior toward the specific antibiotic CTE with a detection limit of 0.19 μM, which is superior to most reported Eu³⁺-based fluorescence chemosensors for CTE. Moreover, thanks to the sensitive CTE-detection of Eu-CP, a portable test strip Eu-CP@PAN is further obtained for evaluating the residual antibiotic content in fresh food and the corresponding RGB value can be real-time determined by a smartphone.