Light-Responsive Carbon Nitride Based Atomic Cu(I) Oxidase Mimics for Dual-Mode Total Antioxidant Capacity Assay

External light stimuli strategy under conventional conditions achieves a sustainable future due to its controllable spatial and temporal precision coupled with environmental friendliness. Herein, atomic Cu(I)-carbon nitride (Cu-CN) was synthesized and served as specific light-stimuli oxidase mimics for total antioxidant capacity (TAC) assay. Singlet oxygen (1O2) and hydroxyl radical (·OH) are the main intermediates, which can oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) into its blue oxidant and therefore improve photothermal signal generation. Based on the intrinsic light responsiveness and photothermal conversion property, we established a colorimetric and photothermal dual-mode sensing platform. The proposed dual-mode assay presented a specific assay of ascorbic acid with LOD of 0.28 μM and 0.15 μM, respectively. This platform was further successfully applied to assess TAC of fruits and beverages. It is believed that the intelligently modulated activity and dual-mode detection function of such atomic enzyme mimics can offer a promising strategy for other analytical assays in high repeatability and reproducibility.