Engineering porous Co–Mn oxide nanosheets with abundant oxygen vacancy as an efficient oxidase-like mimic for heparin colorimetric sensing

Defects engineering as an effective strategy was widely utilized to modulate catalytic performance for heterogeneous catalysts through tuning surface electronic surface and creating more active sites. In this work, porous Co-Mn oxide nanosheets with abundant oxygen vacancies (OVs-CMO NSs) were prepared via a simple "one-stone-two-birds" method. OVs were verified by various characterizations and found more favorable for O2 absorption and activation to produce more reactive O2•- radical, resulting in an improved oxidase-like activity in initiating 3,3',5,5'-tetramethylbenzidine (TMB) oxidation, with a lower Km value of 0.00717 mM and a higher Vmax of 2.086 × 10-7 M/s. Since heparin (Hep) shows an inhibition effect on OVs-CMO NSs-TMB chromogenic system due to strong absorption, a colorimetric sensing platform for Hep detection was established. The present colorimetric detection shows high sensitivity, good selectivity and reliability for normal goat serum. This work not only provides a high-performance non-precious metal oxidase mimic prepared by simple surface defect engineering, but also builds a sensitive colorimetric method for Hep detection.