Facile synthesis of porous M-doped Co3O4 as high-performance oxidase-mimicking nanozymes for colorimetric assay of L-cysteine

Abstract

Oxidase-mimicking nanozymes are more desirable for applications than peroxidase-mimicking ones owing to H₂O₂ can be omitted. In this work, a facile strategy was reported to prepare a series of Co-based bimetallic oxide nanosheets (Co–M–O NSs, M = Fe, Ni, Mn) derived from different isomorphism precursors. Herein, a comprehensive and systematic research of oxidase-like enzymes based on distinctions of elemental surface content and surface state has been undertaken. The porous Co–Mn–O NSs made of Mn-doping Co₃O₄ can lead to decrease the size of Co₃O₄ nanoparticle from 20–50 to 20–30 nm, and increase in oxygen vacancy from 20.7% to 21.8%. The Co–Mn–O NSs via the Mn-doping could highly enhanced the performance and efficiency of the oxidase-mimicking, which is 7.5 times than that of Co₃O₄ and other elements (Ni, Fe) doping Co₃O₄. Considering the features of Co–Mn–O NSs, a sensitive and selective colorimetric assay for the detection of L-cysteine (L-cys) was established. The system showed a linear absorbance response to L-cys concentrations ranging from 0.8 to 70 μM, with a detection limit of 0.79 μM. This facile and effective fabrication strategy of Co–Mn–O NSs has discovered a highly efficient oxidase-mimicking nanozyme useful in environmental protection, biotechnology, and clinical diagnosis.