Enzyme mimics can serve as efficient substitutes to address the challenges posed bynatural enzymes. Magnesium ferrite nanoparticles (MgFe2O4 NPs) have attracted interest as enzyme mimics because of their good catalytic activity and stability. Manganese and cerium ions are promising dopants because of the high reduction potentials of the Mn3+/Mn2+ and Ce4+/Ce3+ pairs, which can enhance the catalytic activity. In the present work, pristine and doped Mg0.8Mn0.2–xCexFe2O4+δ (x = 0.0, 0.1, and 0.2) NPs were synthesized by using the sol–gel method and assessed comparatively as polyphenol oxidase (PPO) and peroxidase mimics. The single-phase spinel structure was validated by the X-ray diffraction patterns. Transmission electron microscopy analysis confirmed that the size of the NPs was less than 30 nm. SEM displayed agglomeration of NPs, and Energy-Dispersive X-ray Spectroscopy confirmed the effective doping of MgFe2O4 NPs. Brunauer–Emmett–Teller analysis revealed that the surface area of ferrite NPs increased from 34.1 to 41.3 m2 g–1 upon doping. Electrochemical impedance spectroscopy revealed faster electron transfer in Mg0.8Mn0.2Fe2O4+δ NPs, which correlated with their best PPO and peroxidase-like activities. The effect of parameters, such as pH, temperature, enzyme mimic dose, and substrate concentration, was ascertained. The Mg0.8Mn0.2Fe2O4+δ NPs showed high enzyme mimic activity due to the efficient redox cycling of Mn3+/Mn2+. The lower activity of the Mg0.8Ce0.2Fe2O4+δ NPs is explained on the basis of slower charge transfer. Catechol, H2O2, and glucose were detected using the Mg0.8Mn0.2Fe2O4+δ NPs within linear ranges of 200–1000 μM, 20–1000 μM, and 20–1000 μM with detection limits of 7.7 μM, 7.0 μM, and 9.3 μM, respectively. The kinetic studies under optimal conditions showed a higher binding affinity for Mg0.8Mn0.2Fe2O4+δ than for pristine MgFe2O4 NPs. Mg0.8Mn0.2Fe2O4+δ NPs were successfully used for the estimation of the phenolic content and H2O2 in different samples. This work provides insights into the rational design of doped spinel ferrite nanozymes with tunable redox properties for advanced catalytic and sensing applications.
Singh et al. (Fri,) studied this question.