A visual colorimetric detection strategy is reported for total antioxidant capacity (TAC) assay by using 3,3',5,5'-tetramethylbenzidine (TMB) oxidation as chromogenic substrate based on gold nanoparticle-decorated MoSe₂ nanosheets (Au@MoSe₂). Au@MoSe₂ nanostructures exhibit high peroxidase-like activity and can catalyze H₂O₂ to oxidize TMB. Based on inhibition effect of ascorbic acid (AA) on TMB oxidation, a facile and sensitive colorimetric method was developed for AA detection. Under optimal conditions, the proposed method showed a sensitivity for AA in a concentration range from 2 to 120 μM and limit of detection was 0.41 μM. Furthermore, the method was employed for TAC assay in actual samples, including commercial beverages and vitamin C tablets. This work represents a model in nanostructure design and will lead to further development of TAC assay in evaluation of antioxidant food quality.

We report a colorimetric method for glucose detection based on Au nanoparticle-decorated WSe₂ (Au@WSe₂) hybrid nanostructures. These hybrid structures are easily synthesized by simply stirring HAuCl₄ precursor with WSe₂ nanosheets in aqueous solution. Owing to strong synergistic catalytic effects of Au nanoparticles and WSe₂ nanosheets, the Au@WSe₂ hybrid nanostructures exhibit enhanced peroxidase-like activity (about 2-fold higher compared to WSe₂ nanosheets alone) for 3, 3', 5, 5'-tetramethylbenzidine oxidation by H₂O₂. Based on the highly catalytical property, the colorimetric method for glucose detection is established by coupling glucose oxidase (GOx). The detection limit of glucose is 3.66 μM. Moreover, the proposed colorimetric method is applicable to glucose detection in serum samples and is promising for applications in biomedical fields.