Nanozymes are nanomaterials exhibiting intrinsic enzyme-like activity. They have found applications in various fields, such as biosynthesis, environmental protection, and bioelectronic sensing devices [1]. However, artificially designed biomimetic nanomaterials mostly exhibit poor dispersion and low catalytic activity. Therefore, the search for new approaches to designing inexpensive biomimetic materials is inevitable. To this end, a nanocomposite containing magnetite nanoparticles and the poly-N-vinylpyrrolidone (PVP) polymer—Fe3O4/PVP—was synthesized by the solvothermal method. The peroxidase activity of the synthesized Fe3O4/PVP nanocomposite as a function of concentration was studied; the colorometric detection of hydrogen peroxide was simulated in accordance with the developed standard [2].figureFig 1. (A) Colorometric study of the dependence of peroxidase activity on the concentration of the Fe3O4/PVP nanocomposite and (B) dose–response curve for H2O2 Fe3O4/PVP Figure 1 shows results of the studies; the observed increase in absorbance as a function of the magnetite nanoparticle concentration suggests that the enzyme-like nanocomposite exhibits the peroxidase activity, while the increase in absorbance as a function of hydrogen peroxide concentration in the presence of the nanocomposite makes it possible to use this catalytic process to detect the presence of H2O2 in various objects, such as rainwater.