On the origin of the synergy between the Pt nanoparticles and MnO₂ nanosheets in Wonton-like 3D nanozyme oxidase mimics

We describe a 3-dimensional scaffold nanocomposite oxidase nanozyme (termed PtNPs@MnO₂) formed from 2-dimensional MnO₂ nanosheets grown on the surface of large platinum nanoparticles (PtNPs). The two components act synergistically in the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), due to the intimate contact between the two components and mutual electron transfer phenomena. The Wonton-like 3-dimensional structure of the nanocomposite is highly stable and was characterized by cryogenic electron microscopy (cryo-EM). The PtNPs@MnO₂ nanocomposite was employed in a sensing assay for the determination of glutathione (GSH) and dopamine (DA) with a linear range of 0.2 μM–11 μM for GSH and 0.1 μM–1.1 μM for DA. The limit of detection (LOD) and limit of quantification (LOQ) of GSH are 0.05 μM (S/N = 3) and 0.17 μM (S/N = 10), respectively. The LOD and LOQ for DA were estimated as 0.025 μM and 0.083 μM. The method was applied to analyze GSH in human serum samples and DA in pharmaceuticals.