The inhibitory effect of glutathione (GSH) molecules on the nanozymatic activity of peroxidase-like N-doped carbon dots was evaluated by calculating their nanozymatic activity in the presence and absence of glutathione molecules. The UV-visible spectra of the oxidation product of TMB in the presence and the absence of glutathione molecules as an inhibitor are shown in Figure , revealing that the absorbance at 662 nm was significantly reduced by introducing GSH into the reaction media. Based on this investigation it can be concluded that N-doped CDs reveal high intrinsic peroxidase-like activity of N-doped carbon dots, however, this intrinsic peroxidase-like activity significantly inhibit by glutathione molecules. However, to provide a better view of the inhibitory effect of glutathione molecules on the nanozyme's activity, the inhibitory effect of glutathione molecules on their nanozymatic activity was evaluated as a function of enzyme-like residual activity in the presence of glutathione molecules. The results (Figure ) reveal that the relative activity of nanozymes was inhibited by increasing the glutathione concentration in the reaction media and reached its minimum value (45%) when glutathione concentration is 14 µM and then leveled off, revealing a strong inhibitory effect of glutathione molecules on the nanozymatic behavior of peroxidase-like N-doped carbon dots. Herein, the effect of the glutathione molecules (a possible inhibitor) on the peroxidaselike activity of the enzyme-like N-doped carbon dots was evaluated. To do this investigation, the enzyme-like activity of N-doped carbon dots was evaluated toward peroxidase-mediated oxidation of TMB as a common peroxidase substrate, revealing high intrinsic peroxidase-like activity of N-doped carbon dots. However, the intrinsic peroxidase-like activity of the N-doped carbon dot was significantly inhibited by the introduction of the glutathione molecules in the reaction media. Hence, the inhibitory effect of glutathione molecules on their nanozymatic activity was evaluated as a function of enzyme-like residual activity in the presence of glutathione molecules. The results reveal that the relative activity of nanozymes was inhibited by increasing the glutathione concentration in the reaction media and reached its minimum value (45%) when the glutathione concentration was 14 µM and then leveled off.