▎ 摘　　要

In this study, we report a switchable fluorescence probe based on nitrogen-doped graphene quantum dots (N-GQDs) to detect the presence of tetracycline and L-Cystence. Strong blue emissive N-GQDs were successfully prepared by the hydrothermal treatment of urea and benzophenone, with a quantum yield of 34.9%. Both transmission electron microscopy and atomic force microscope images reveal a nearly monodispersed N-GQDs with spherical morphologies, and provide evidences of 1-3 layered structures of N-GQDs. Meanwhile, the obtained N-GQDs can be utilized for fluorescent labelling due to their superior optical stability and favourable biological compatibility. A strong fluorescence quenching was observed for the presence of tetracycline. The following addition of L-Cysteine can motivate the regeneration of fluorescence. Therefore, a simple strategy for the detection of tetracycline and L-Cystence in natural water was developed due to the relevant sensitivity of N-GQDs nanosensor.