Highly efficient persistent luminescent nanozymes-based luminescence-colorimetric dual-mode sensor for total antioxidant capacity assay

Total antioxidant capacity (TAC) is a vital parameter to assess the gross antioxidant activity in biological and food matrices. Accurate determination of TAC has become increasingly important for health monitoring and dietary guidance. Here, we report a persistent luminescent nanozyme (ZGO-Pt) based luminescence-colorimetric dual-mode sensor for selective determination of TAC. ZGO-Pt was fabricated based on ZnGa2O4:Cr nanoparticles (ZGO) with platinum nanoflower as synthetic additive. The prepared ZGO-Pt exhibited fascinating peroxidase-mimetic activity and persistent luminescence, and enabled effectively catalysis of the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB. Meanwhile, the generated oxTMB gave strong absorption at 652 nm to quench the luminescence of ZGO-Pt at 700 nm via the inner filter effect. Antioxidants could compete with the oxidable TMB or reduce oxTMB to TMB, resulting in the simultaneous variations of blue color and luminescence to provide the basis for dual-mode assay for TAC. The highly efficient catalysis of ZGO-Pt (Km, 3.12 mM for H2O2, 0.592 mM for TMB) allows the dual-mode sensor to realize precise determination of TAC with a wide linear range (0.5-200 μM and 1-300 μM for colorimetric and luminescence mode, respectively) and low limit of detection (LOD, 0.05 μM and 0.78 μM for colorimetric and luminescence mode, respectively). The developed dual-mode sensor was successfully applied to the determination of TAC in vitamin tablet, beverages and fruits. This work provides an efficient persistent luminescent nanoparticle-based nanozyme for a facile TAC assay with further vision in biosensing and food technology.