green synthesis of the nanocomposites of MnO/graphene as an oxidase mimic for sensitive colorimetric and electrochemical dual-mode biosensing.

Herein we report the colorimetry and an electrochemical for the determination of dopamine (DA) by using MnO nanoparticles and graphene nanosheets composite (MnO@G) that display oxidase mimicking property. MnO@G could directly oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into a blue product (oxTMB) without extra oxidants such as HO. Nevertheless, the presence of DA will inhibit the TMB oxidation due to the presence of the competitive reaction of MnO@G and DA, giving a product color change from blue to colorless.