N,S co-doped Co3O4 core–shell nanospheres with high peroxidase activity for the fast colorimetric detection of catechol†

It is necessary to develop nanoperoxidases with high activity to construct a fast and cheap sensing platform for real-time detection of some pollutants. In this study, the as-prepared N and S co-doped core–shell cobaltosic oxide nanospheres (N,S-Co₃O₄) exhibit excellent peroxidase-like activity. The oxidation reaction of the colorless chromogenic substrate TMB by H₂O₂ is used to evaluate the peroxidase-like behaviors of N,S-Co₃O₄. As expected, the N,S-Co₃O₄ nanospheres accelerated the oxidation of TMB accompanied by a blue shift only in 1 min. Thus, the N,S-Co₃O₄ nanoperoxidase exhibits high affinity towards TMB (K_m = 0.072 mM) and H₂O₂ (K_m = 3.78 mM). Moreover, as the catalytic process of N,S-Co₃O₄ can be inhibited in the presence of catechol, a fast inexpensive colorimetric sensor of catechol with high sensitivity and good selectivity was constructed. The enhanced catalytic activity of N,S-Co₃O₄ is attributed to some active species, including h⁺ and ˙O₂^?, owing to the more active sites on N,S-Co₃O₄. The colorimetric method has been validated by detecting catechol in real water samples for practical application.