A new ratiometric AIE fluorescent probe for detecting cysteine in food samples and imaging in the biological system

•A ratiometric fluorescent probe NFA with AIE property for the determination of Cys was developed.•The probe NFA showed sensitive (0.21 μM), rapid (within 2 min) response to Cys and could distinguish Cys from Hcy and GSH.•Probe NFA was used for the detection of Cys in real food samples.•Probe NFA has been successfully applied to visualize endogenous and exdogenous Cys in living HeLa cells and zebrafish.