Nitrogen-Doped Carbon Nanoflowers Decorated with PtNi Nanoparticles for Colorimetric Detection of Total Antioxidant Capacity

A total antioxidant capacity (TAC) assay plays an essential role in evaluating antioxidant behaviors. It mainly involves examining the dosages of antioxidants such as ascorbic acid (AA), while TAC can be measured by nanozyme with peroxidase-like activity. Herein, nitrogen-doped carbon nanoflowers decorated with uniform PtNi nanoparticles (PtNi/NCFs) were fabricated by a simple pyrolysis strategy. The obtained PtNi/NCFs showed high peroxidase-mimicking activity to catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation by generating rich hydroxyl radicals (·OH) in the H2O2 system. By virtue of the PtNi/NCFs nanozyme, a visual colorimetric sensor was developed for assays of H2O2 and AA. The limits of detection were as low as 45.3 and 0.94 μM for determination of H2O2 and AA with linear ranges of 100–1000 and 1.0–20.0 μM, respectively. Moreover, such sensor was also successfully employed to detect AA and H2O2 in real tablets and juices. The PtNi/NCFs nanozyme holds great potential for practical applications.