Porphyrin modified ZnCo2O4 nanospheres as the excellent peroxidase/oxidase dual nanozymes for colorimetric sensing of cholesterol

5,10,15,20-Tetrakis(4-carboxyl phenyl)porphyrin (H₂TCPP) modified ZnCo₂O₄ nanospheres (H₂TCPP-ZnCo₂O₄) were prepared by a two-step hydrothermal method. Compared with pure ZnCo₂O₄, H₂TCPP-ZnCo₂O₄ possessed higher peroxidase-like activity and fast catalyze the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) into oxTMB by H₂O₂ with a blue change. The catalytic behaviors of H₂TCPP-ZnCo₂O₄ is consistent with the Michaelis–Menten equation. Several techniques including electrochemical, fluorescent probes and capture agents were used to investigate the catalytic mechanism, which was identified as electron transfer and superoxide radical (•O₂⁻), due to the synergetic effect between porphyrin molecules and ZnCo₂O₄. Based on the nanoperoxidase activity of H₂TCPP-ZnCo₂O_4, a facile colorimetric sensing platforms was designed for the determination of H₂O₂ and cholesterol. The linear range for H₂O₂ determination is 100–200 μM, with a detection limit of 76.297 μM as well as cholesterol is 100–900 μM, with a detection limit of 40.027 μM