An “off-on”type fluorescent probe with zinc doped carbon quantum dots(Zn-CQDs) was established for the selective and sensitive detection of glutathione(GSH).A stable and water soluble Zn-CQDs with high fluorescence quantum yield were prepared by one step hydrothermal method using citric acid

ethylenediamine and zinc acetate as precursors.The structures and optical properties of the Zn-CQDs were characterized by transmission electron microscopy(TEM)

X ray diffraction(XRD)

Fourier transform infrared spectroscopy(FT-IR)

ultraviolet-visible absorption spectroscopy(UV-Vis) and fluorescence spectroscopy.Results showed that the fluorescence of Zn-CQDs was quenched by Cu2+

the fluorescence signal of the system was in the “off” state

while the fluorescence of Zn-CQDs-Cu2+ system was recovered because of the presence of reduced glutathione(GSH)

and the fluorescence signal of the system was in the “on” state.The effects of pH value and reaction time on the fluorescence recovery system were investigated.The effects of small organic molecules and ions in fruits and vegetables on the fluorescence intensity of Zn-CQDs-Cu2+ system were also investigated.Under the optimal conditions

the fluorescence recovery rate of Zn-CQDs was linearly correlated with the concentration of GSH in the range of 0.05-80 μmol/L with the detection limit of 63 nmol/L.The probe was applied in the detection of GSH in fruits and vegetables with the recoveries of 98.6%-101% and the relative standard deviations(RSD) of 1.8%-3.1%

and the results were satisfactory.