Regulating electronic states of porous branched core-shell Pd@PtCo nanozyme by Co-doping for boosting colorimetric...

A total antioxidant capacity index is critical for assessing antioxidant quality and oxidative stress in foods, beverages, and pharmaceuticals, typically measured through colorimetric detection of antioxidants such as ascorbic acid (AA). Herein, porous branched core-shell Pd@PtCo nanozyme was prepared by a one-pot wet-chemical co-reduction method. The Co-doping greatly improved the catalytic activity due to regulating electronic states of Pd@PtCo nanozyme. Its peroxidase (POD)-like activity was investigated by catalyzing 3,3',5,5'-tetramethylbenzidine (TMB) oxidation in the presence of hydrogen peroxide (H₂O₂). Its affinity for both TMB and H₂O₂ substrates was evaluated by kinetics analysis, unveiling the Michaelis-Menten constants (K_m) of 3.38 mM and 5.88 mM, and maximum initial velocities (V_max) of 16.26 × 10^-8 M s^-1 and 3.52 × 10^-8 M s^-1, respectively. By virtue of the superior POD-like catalytic property, a colorimetric sensor was built for sensitive determination of H₂O₂ and AA. The sensor exhibited good linear ranges of 50-5000 μM and 20-600 μM for AA and H₂O₂, respectively, coupled with low detection limits of 14.8 μM (H₂O₂) and 1.7 μM (AA). Furthermore, the sensor was successfully employed in the assays of commercial tablets and juices, with satisfactory results through the recovery tests. The Pd@PtCo nanozyme holds a promising potential for bioanalysis and related food analysis.