Hierarchical engineering of Mn2O3/carbon nanostructured electrodes for sensitive screening of acetylcholine in biological samples

Abstract

Enzymeless electrochemical sensors have received considerable interest for the direct, sensitive, and selective monitoring of biomolecules in a complex biological environment. Here, we designed a nonenzymatic electrochemical sensor based on Mn₂O₃ nanolayers (NLs)/carbon (C) and Mn₂O₃ flower-like (FL)/C structure to detect acetylcholine (ACh) molecules in human fluids. The sensing properties and electrochemical activity varied based on the structural and chemical composition of Mn₂O₃-based materials. The Mn₂O₃NLs/C structure of two-dimensional NLs was arranged in parallel with a heterogeneous surface texture, stair-like step-by-step layer formation, and cracked layers that formed free spaces. Mn₂O₃FL/C was formed with an FL structure. The parallel and perpendicular buildup of sheets from the bottom to top and sheets spreading in all directions formed the FL structure of Mn₂O₃ with multi-structural defects and edges, and heterogeneous surface texture. This unique surface property of Mn₂O₃FL/C and composition facilitated target diffusion through the inner/outer surface and shortened the distance pathway. Moreover, the presence of carbon on the surface of Mn₂O₃ induced sensitivity and stability of Mn₂O₃, enhanced the electrochemical activity with high catalytic activity, hastened electron diffusion, and high loading of ACh molecules. The nonenzymatic ACh sensors of Mn₂O₃NLs/C and Mn₂O₃FL/C showed a good sensor design with low limits of detection (2 and 7 μM, respectively) and a linear range of 0.1–7 mM. The fabricated sensors provided high stability and selectivity, easy fabrication, multi-usage, and fast response motioning of ACh in a complex mixture of human fluids. The designed nonenzymatic sensors of Mn₂O₃NLs/C and Mn₂O₃FL/C signaled the ACh molecules with high stability and selectivity and can be used to investigate and follow up on several neuronal disorders.