Porphyrin-Modified NiS₂ Nanoparticles Anchored on Graphene for the Specific Determination of Cholesterol

Exploring peroxidase-like nanozymes with high catalytic activity is an urgent task to construct a fast, convenient, and selective colorimetric sensing platform. In this work, a nanozyme, 5,10,15,20-tetrakis(4-carboxyl phenyl)porphyrin-functionalized NiS2 nanoparticles, anchored on the surface of graphene (Por-NiS2/GO) was designed. Compared with NiS2 nanoparticles anchored on the surface of graphene (NiS2/GO), Por-NiS2/GO had a higher peroxidase-like activity due to the introduction of porphyrin. The size of NiS2 nanoparticles was about 110–250 nm. The peroxidase-like behaviors of Por-NiS2/GO were evaluated using the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) with a fast-blue color change in less than 1 min. Electron spin resonance (ESR) data revealed that the excellent performance of Por-NiS2/GO was due to the active oxygen species produced, including hydroxyl radical (•OH) and superoxide radical (•O2–), during the catalytic reaction, owing to the synergetic effect among different components including porphyrin, NiS2, and GO. Thus, based on the enhanced peroxidase-like activity of Por-NiS2/GO, a fast, sensitive, and selective colorimetric sensing platform of H2O2 has been constructed, and furthermore, a sensing platform for cholesterol was also developed coupled with cholesterol oxidase (ChOx). The colorimetric sensing platform was validated by detecting cholesterol in serum samples.