Single-atom cobalt catalysts as highly efficient oxidase mimics for time-based visualization monitoring the TAC of skin care products.

• SA-Co/NC is obtained by wet chemical method combined pyrolysis process. • Theoretical calculations and experiments prove oxidase-like activity of SA-Co/NC. • A time-based visualization scheme for TAC detection is proposed. • TAC monitoring of skin care products is achieved by smartphone platform. Reactive oxygen species (ROS) are an important cause of oxidative skin aging and can be removed by adding some antioxidant ingredients to skin care products. However, total antioxidant capacity (TAC) assays generally require sophisticated laboratory equipment, which greatly limits their daily application. Fortunately, the adoption and development of portable smartphone platforms could promises to solve this challenge. Herein, we report a cobalt single atom-based portable smartphone platform which can realize dynamic-time visualization monitoring the TAC of skin care product. Theoretical calculations and specific experimental results show that single-atom cobalt catalysts (SA-Co/NC) present excellent oxidase-like activity and can effectively convert dissolved oxygen into strongly oxidizing reactive oxygen species. More interestingly, based on the unique sacrificial inhibition catalytic mechanism of ascorbic acid (AA), it can be combined with a portable smartphone platform to detect the TAC of real samples by fitting a time-color-concentration standard curve and recording the change of color RGB values during the reaction. Compared with the traditional scheme, this scheme is convenient, low cost, and can realize visual detection of mobile terminals. This work provides a new scheme for miniaturization, convenience and home-based of TAC detection. [ABSTRACT FROM AUTHOR]