FeS nanoparticles embedded in 2D carbon nanosheets as novel nanozymes with peroxidase-like activity for colorimetric and fluorescence assay of H₂O₂ and antioxidant capacity

Nanozymes with high catalytic performance play a vital role in the construction of advanced biosensors for the signal detection and analysis of complicated biological samples. Herein, FeS nanoparticles (NPs) embedded in 2D carbon nanosheets (denoted as FeS@CNs) are demonstrated to serve as excellent nanozymes with high catalytic activity. Notably, the introduction of mesoporous carbon substrate could effectively improve the enzymatic peroxidase-like catalytic ability of embedded FeS nanozymes, especially in the fluorescence catalytic system. Based on the high peroxidase-like activity of proposed FeS@CNs nanozymes, a facile method was then designed for H₂O₂ assay with detection limit as low as 0.78 μM and 0.86 μM for the colorimetric and fluorescence method, respectively. The oxidation of the colorimetric and fluorescence substrates could be ascribed to the hydroxyl radical (·OH) produced by catalytic reaction of H₂O₂ with FeS@CNs nanozymes. Thus, the FeS@CNs nanozymes-based H₂O₂ sensing platform was further constructed to evaluate the antioxidant capacity of glutathione (GSH), cysteine (Cys), and gallic acid (GA). Notably, FeS@CNs nanozymes can keep the functionality in a broad pH range (2.0 ~ 9.0) for catalytic reaction, delivering a great potential in the fabrication of advanced biosensors.