Tuning nanozyme property of Co@NC via V doping to construct colorimetric sensor array for quantifying and discriminating antioxidant phenolic compounds

Through V2O5 etching of ZIF-67 and subsequent pyrolysis in an argon flow, the V doped [email protected] (V/[email protected]) with mixed-valence Co(II)/Co(III) and V(III)/V(IV) was successfully obtained. V doping plays an important role in regulating the enzyme-like activity of [email protected] Specifically, the [email protected] has both oxidase-like activity and peroxidase-mimic activity, while the V/[email protected] possesses the specific oxidase-like activity. Benefiting from the elevated Co2+ level due to electrons transfer from the reduced V(III) to Co3+ and recyclable redox reactions between the Co(III)/Co(II) and V(IV)/V(III) couples, the V/[email protected] displays 4-fold increase in the oxidase-like activity, smaller Km (0.18 mM) and larger Vmax (4.01 × 10−8 M s−1) toward TMB relative to [email protected] The origin of V/[email protected] as oxidase mimic is likely attributed to the generation of 1O2 and •OH. Different phenolic compounds (PC), like gallic acid, kaempferol, caffeic acid, quercetin, and catechin, have distinct antioxidant capacity, showing a differential inhibiting effect on the V/[email protected] system. The different PC antioxidants in the V/[email protected] system lead to unique decrease in the absorbance at 652 nm (A652), resulting in a unique absorbance signal response mode. By choosing different combinations of A652 signals at various time points, multichannel information can be extracted from a single nanozyme for pattern recognition. Based on this, a colorimetric array sensing platform for the identification of PC is established successfully. Furthermore, the constructed sensor array can be used for quantifying and discriminating multiple PC antioxidants.