Molybdenum disulfide (MoS2) nanosheets (NSs) with an 8.1 Å interlayer spacing were heavily loaded with cerium(III) ions by a one-step hydrothermal method. The material thus obtained has a strong peroxidase-like (POx-like) activity. The introduction of the large Ce(III) ion enlarges the interlayer distance of MoS2NSs. It also supports shuttling and transport of substrate, intermediates and electrons. It also increases the specific surface of MoS2. This results in a larger number of active sites, accelerates the contact between substrate and catalytic surface, and improves the kinetics of the catalytic reaction. The nanomaterial catalyzes the oxidation of colorless 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide (H2O2 ) to give a blue-green product with an absorption maximum at 652 nm. The assay has a linear response in the 1-50 μM H2O2 concentration range and a 0.47 μM limit of detection. The colorimetric method was applied to real milk samples, and high recoveries (98.4%-108.0%) and repeatability were obtained. Graphical abstractMolybdenum disulfide nanosheets loaded with cerium(III) catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide to give a blue-green product with an absorption maximum at 652 nm.
Keywords: Catalytic mechanism; Colorimetric assay; Enzyme mimics; One-pot synthesis; Peroxidase mimic; TMB-H2O2 system.