Abstract
Carbon materials have been widely used as nanozymes in bioapplications, attributing to their intrinsic enzyme-like activities. Nitrogen (N)-doping has been explored as a promising way to improve the activity of carbon material-based nanozymes (CMNs). However, hindered by the intricate N dopants, the real active site of N-doped CMNs (N-CMNs) has been rarely investigated, which subsequently retards the further progress of high-performance N-CMNs. Here, a series of porous N-CMNs with well-controlled N dopants were synthesized, of which the intrinsic peroxidase (POD)like activity has a positive correlation with the pyridinic N content. Density functional theory calculations also reveal that pyridinic N boosts the intrinsic POD-like activity of N-CMNs. Pyridinic-N dopant can effectively promote the first H2O desorption process in comparison with the graphitic and pyrrolic N, which is the key endothermic reaction during the catalytic process. Then, utilizing the optimized nanozymes with high pyridinic N content (NP-CMNs) and superior POD-like activity, a facile total antioxidant capacity (TAC) assay was developed, holding great promise in the quality assessment of medicine tablets and antioxidant food for healthcare and healthy diet.
Highlights
Nanomaterial-based enzyme mimics, defined as nanozymes, have emerged and attracted considerable attention recently
Using silica colloid as hard templates, N-Carbon material-based nanozymes (CMNs)-1 were synthesized via a pyrolysis process in the presence of glucosamine, targeting the simultaneous formation of porous structures and dispersed N dopants (Figure 1(a))
As can be seen from the high-resolution transmission electron microscopy (TEM) (HRTEM) image in Figure 1(c), NP-CMNs consist of the curved graphene layers with a low crystallinity deduced from the unclear lattice fringes of graphitic carbon, which is consistent with the selected area electron diffraction (SAED) result
Summary
Nanomaterial-based enzyme mimics, defined as nanozymes, have emerged and attracted considerable attention recently. As emerging substitutes of natural enzymes, nanozymes possess exceptional features including high stability, durability under harsh conditions, and simple preparation with low costs [1,2,3,4,5,6,7,8,9]. As metal-free catalysts, pure CMNs have been endowed with moderate catalytic activities, which are still far from meeting the requirements of high catalytic activity. To address this issue, heteroatom (N, B, P, S, or Se) doping is an efficient method to improve the catalytic activities of carbon materials [17,18,19,20,21,22,23]. N-doping has been extensively studied due to the fact that a similar atomic radius of nitrogen as carbon makes it easier to incorporate into the graphitic lattice [10, 24]
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