Insight into peroxidase and polyphenol oxidase mimic activity of spinel ferrite nanoparticles and their GO composites

Abstract

Present work reports the comparative evaluation of MFe2O4 (M = Mn, Co and Cu) nanoparticles (NPs), graphene oxide (GO) and their nanocomposite (NC) for their intrinsic peroxidase and polyphenol oxidase (PPO) mimic activity of followed by the catalytic sensing of H2O2. Pure and doped MFe2O4 NPs were screened initially for peroxidase and PPO mimic activity. Among the tested metal ferrite NPs, MnFe2O4 NPs showed the highest enzyme mimic activity for both the enzymes. Thus, MnFe2O4-GO NC was synthesized by the facile ultrasonication method and characterized using FT-IR and XRD techniques. TEM micrographs of NC showed that MnFe2O4 NPs were anchored on GO sheets with lesser agglomeration than bare ferrite NPs. SEM-EDX confirmed the presence of MnFe2O4 and GO in NC. The greater surface area of NC as compared to pristine NPs was confirmed from BET analysis. MnFe2O4 NPs displayed highest peroxidase and PPO mimic activity followed by NC and GO. The results were correlated with the facile inter-conversion of Mn2+-Mn3+ ions. Thus, ease of inter-conversion of oxidation state was the dominating factor of highest activity of MnFe2O4 NPs rather than the surface area. The colorimetric detection of H2O2 was also achieved in the range 0.2 mM–1.0 mM H2O2. In-situ trapping experiments confirmed that OH. radicals were major active species involved in peroxidase mimic activity. The reaction mechanisms for both the reactions were proposed. Kinetic studies were performed and data was analysed using Michaelis Menten equation. The values of Vmax and Km for both the reactions proved MnFe2O4 NPs as potential oxidase mimic for a wide range of potential applications.