Platinum Nanoparticles Loaded Graphitic Carbon Nitride Nanosheets with Enhanced Peroxidase-like Activity for H 2 O 2 and Oxidase-Based Sensing.

Platinum nanoparticles (PtNPs) are classical peroxidase-like nanozyme; self-agglomeration of nanoparticles leads to the undesirable reduction in stability and catalytic activity. Herein, a hybrid peroxidase-like nanocatalyst consisting of PtNPs in situ growing on g-C 3 N 4 nanosheets with enhanced peroxidase-mimic catalytic activity (PtNP@g-C 3 N 4 nanosheets) was prepared for H 2 O 2 and oxidase-based colorimetric assay. g-C 3 N 4 nanosheets can be used as carriers to solve the problem of poor stability of PtNPs. We observed that the catalytic ability could be maintained for more than 90 days. PtNP@g-C 3 N 4 nanosheets could quickly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), and the absorbance of blue color oxidized TMB (oxTMB) showed a robust linear relationship with the concentration of H 2 O 2 (the detection limit (LOD): 3.33 μM). By utilizing H 2 O 2 as a mediator, this strategy can be applied to oxidase-based biomolecules (glucose, organophosphorus, and so on, that generate or consume hydrogen peroxide) sensing. As a proof of concept, a sensitive assay of cholesterol that combined PtNP@g-C 3 N 4 nanosheets with cholesterol oxidase (ChOx) cascade catalytic reaction was constructed with an LOD of 9.35 μM in a widespread range from 10 to 800 μM (R 2 = 0.9981). In addition, we also verified its ability to detect cholesterol in fetal bovine serum. These results showed application prospect of PtNP@g-C 3 N 4 nanosheets-based colorimetry in sensing and clinical medical detection.