In this study, we presented a colorimetric sensor based on CeO2 nanostructures to detect glutathione (GSH), which is an important biological thiol in cells that is involved in many physiological processes in the organism and regulates the pathological processes of cells [1]. Therefore, the nanostructures of CeO2 were synthesized using a hydrothermal method. The synthesized nanostructures showed good peroxidase-like activity, which was confirmed by the oxidation of 3,3,5,5 -tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) in a few seconds with change of color from colorless to blue. The presence of GSH can inhibit the peroxidase-like activity of CeO2 and lead to the disappearance of the blue color of TMBox. Thus, the adsorption of GSH on the surface of nanostructures lead to a decrease in the absorbance of the UV–vis spectra. The possible catalytic mechanism of TMBox conversion to TMB by GSH was proposed and based on the GSH concentration can be estimated by this method, which is known as turn-off sensor. All of experimental data were obtained using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis absorption spectroscopy. The detection limit of GSH was in the micromolar range. Moreover, the proposed colorimetric method is feasible, simple, and inexpensive, and will have promising applications in the analysis of biological samples.
