Ultrathin two-dimensional carbon nanosheets with highly active Cu-Nx sites as specific peroxidase mimic for determining total antioxidant capacity

Abstract

Cu,N-codoped carbon nanosheets (Cu-NC) with highly active Cu-N x sites were fabricated via a low-cost and facile nitrogen-doping strategy, and successfully demonstrated as a novel specific peroxidase mimic enzyme for determining total antioxidant capacity. • A facile strategy was proposed to fabricate Cu-NC specific peroxidase nanozyme. • Relative to Cu-C and N-C, Cu-NC shows 19.06 and 15.84-fold peroxidase activity rise. • A highly sensitive colorimetric biosensor was developed for glucose and H 2 O 2 . • The method was successfully applied to TAC quantification in drinks. We designed the Cu,N-codoped carbon (Cu-NC) nanosheets with highly active Cu-N x sites through a facile nitrogen-doping strategy that employed copper MOF as a precursor and dicyandiamide as a N source, respectively. The Cu-NC displayed an ultrathin two dimensional sheet structure. The ultrathin nanosheet structure and Cu,N-codoping endowed Cu-NC highly exposed active sites. The Cu-NC showed superior and specific peroxidase-like activity able to greatly promote TMB oxidation by H 2 O 2 . Relative to that of Cu doped carbon (Cu-C) and N doped carbon (N-C), the peroxidase mimic activity of the optimized Cu-NC-700 increased by 19.06-fold and 15.84-fold, respectively. The mechanism investigation revealed that the ·OH is the main active oxygen specie for the peroxidase-like activity of Cu-NC-700. The Cu-NC-700 showed high affinity to TMB and H 2 O 2 with K m values of 0.077 mM and 0.928 mM, which were 4.63 and 2.98 times lower than those of HRP, respectively. The high and specific peroxidase mimic activity enables the Cu-NC-700 for sensitively detecting H 2 O 2 , glucose, and ascorbic acid with limit detection of 10, 100 and 90 nM, respectively. The assay was successfully used to evaluate the total antioxidant capacity of real drinks.