Iron-doped carbon nitride with enhanced peroxidase-like activity for smartphone-based colorimetric assay of total antioxidant capacity.

The facile detection of total antioxidant capacity (TAC) is limited by in-situ analysis, because it usually requires complex laboratory equipments. Here, a colorimetric assay for TAC detection is developed based on the peroxidase-like activity of iron-doped carbon nitride (Fe/NC) and the smartphone platform. The peroxidase-like activity of carbon nitride is greatly improved by the introduction of Fe atoms, and the active sites turn to Fe-N x coordination groups in the Fe/NC. The inhibition mechanism of the chromogenic reaction for different kinds of antioxidants is also studied. The colorimetric assay is fabricated by the relationship of absorbance-color-antioxidant content and applied successfully to the TAC detection of several fruit juicesand commercial beverages. This work not only provides a promising approach for convenient in-situ TAC assay without the use of large instruments, but also expands the application of nanozymes in nutritional value assessment of foods. The Fe atom-containing carbon nitride shows greatly improved peroxidase-like activity and can be conveniently used for the on-site smartphone-based colorimetric assay of total antioxidant capacity of foods. [Display omitted] • The peroxidase-like activity of C 3 N 4 is greatly improved by Fe atom doping. • The newly formed Fe-N x serve as the main active sites in the Fe/NC nanozyme. • The antioxidants content are tested and different mechanisms are proposed for AA or GSH/Cys. • RGB model of smartphone can be used for on-site colorimetric assay of TAC in food samples. [ABSTRACT FROM AUTHOR]