Up to now different nanozymes with oxidase-like, peroxidase-like, urease-like, and hydrolase-like activity were synthesized and applied for different applications, however, most nanozymes reveal significant peroxidase-like activity and can cleavage the peroxide bonds to produce active oxygen species such as hydroxyl radicals . The resulting radicals can react with peroxidase substrates such as TMB, DAB, and OPD and proceed their oxidation to producing the colored products. It is notable that the product of oxidation of TMB and OPD is a colored cation radical while DAB oxidation resulted in production a colored indamine polymer via an n-electron irreversible oxidation pathway.