Controllable synthesis of MnO nanoparticles supported on porous carbon as a highly active oxidase mimic for dopamine detection

Mn(II) ion has emerged as a cofactor in heme-copper oxidase to confer O2 reduction to H2O, which shares the similar mechanism with oxidase mimicking reaction, so it is fascinating and interesting to explore the oxidase mimetic activity of Mn(II) compound. Here, MnO nanoparticles supported on porous carbon (MnO NPs/PC) was controllably prepared via in-situ conversion of MnO2 nanobelts supported on porous carbon (MnO2 NBs/PC). The oxidase mimetic activity of MnO NPs/PC was investigated using 3,3′,5,5′-tetramethyl-benzidine (TMB) as chromogenic substrate. MnO NPs/PC shows excellent oxidase mimetic activity with a low kinetic parameter Km of 0.0214 mM and a high Vmax of 7.21 × 10−7 M/s. Due to the inhibition effect on TMB color reaction, dopamine (DA) can be detected using MnO NPs/PC-TMB chromogenic system, even in human serum samples. This work not only provides a controllable synthetic method for small-sized MnO NPs, but also throws the light on MnO oxidase mimetic activity for the first time.