Nanoparticles have gained significant attention as a cost-effective and robust alternative to natural enzymes. Their stability makes them suitable for a wide range of applications in medicine, science, and industry. Horseradish peroxidase (HRP) plays vital roles in biological systems by catalyzing substrate oxidation in the presence of hydrogen peroxide (H₂O₂). However, HRP is affected by harsh conditions of pH and temperature. In this work, carbon dots doped with metals (X-CDs) are utilized as nanozymes, mimicking the function of horseradish peroxidase (HRP) to some extent. Cobalt (Co), Nickel (Ni), Iron (Fe), and Copper (Cu) are used as the carbon dot-doping materials. X-CDs are synthesized from inexpensive chemicals in just a few steps, saving time and costs and showing better robustness. A total of 0.25 m mole of metal acetate was mixed with 87 mg L-Arginine, 80.6 µL Amine, and 100 µL distilled water at 240°C, for 3 minutes, and was then purified by a 0.5-1 kDa MWCO membrane against 1 liter of distilled water for five days. The peroxidase- like activity of the nanozymes was investigated by measuring the absorbance of TMB solution at 652 nm in the presence of H₂O₂. The results showed that X-CDs had a maximum ability to catalyze TMB in acidic buffer media at pH=4. High temperatures did not destroy the internal system of the X-CDs. Also, the X-CDs did not lose their activity after 3 months of storage at 4 C. To conclude, nanozymes exhibit evident peroxidase activity, which in some ways can be compared to the activity of horseradish peroxidase (HRP), with excellent stability at harsh pH and high temperature. They maintain their activity even after months, and they do not need to be stored at low temperature, nor do they need stabilizers. These features can be employed in biosensing by conjugating nanozymes to antibodies, where they appear in color as a sign of their presence.