Dispersion Technique May Change Structure and Bio-Oxidative Activity of Magnetic MOF Nanoparticles

The overlooked influence of routine operations on hydrophobic nanosuspensions can induce polymorphic transformation, a critical factor that contributes to their instability and significantly limits their applications. Techniques such as ultrasonication are commercially employed for producing nanosuspensions. However, the impact of routine operations, including mechanical grinding and ultrasound, on obtaining stable suspensions has not received sufficient attention, despite their potential to alter microstructure, morphology, and consequently, functional properties. In this study, Fe3O4-asсorbic acid/ metal-organic coordination polymer (MOF) MIL-88b (Fe3O4-AA-MOF) nanoparticles (NPs) were subjected to grinding in a mortar (GM). Subsequently, 1.0 wt.% of aqueous suspensions were ultrasonicated (GM+US) for 3 min at 30 kHz and 37 °C. The structure and oxidative properties of the homogenized suspensions were investigated using X-ray diffraction technique, dynamic light scattering (DLS), and scanning electronic microscope (SEM), with native NPs serving as a control. Homogenization treatment significantly affected the microstructure and oxidative behavior of Fe3O4-AA-MOF NPs. The combination of milling and ultrasound led to a change in the stoichiometry of magnetite, partial destruction of MOF, and simultaneously, an acceleration of the Fenton reaction and increased stability of NPs in suspension. These findings underscore that the influence of routine sample preparation operations on the functional properties of NPs cannot be underestimated.