Barium hexaferrite nanoplatelets (BHF NPLs) are being investigated for a range of applications, including ferromagnetic fluids, liquid magnets, biomedical imaging, and contactless sensors. Spinel-structured iron oxide nanoparticles (IONPs) are widely used in catalysis, magnetic separation, and magnetic resonance imaging. Although ferrite nanoparticles are generally considered chemically stable, they may be released into the environment following their use. Understanding their chemical stability under environmentally relevant conditions is therefore important for assessing their potential environmental impact. In this study, we investigated the effects of naturally occurring complexing agents on the chemical stability of ferrite nanoparticles.

Our results show that catechol adsorption onto ferrite surfaces involves proton transfer and is further stabilized by hydrogen bonding between the ligand’s ortho-functional group and adjacent surface sites. The chemical stability of the functionalized nanoparticles was strongly influenced by both ligand structure and the pH during functionalization. Under acidic conditions, the presence of adsorbed ligands promoted the decomposition of BHF NPLs. In contrast, at neutral pH, the investigated natural complexing agents did not induce nanoparticle dissolution under the conditions studied. These findings provide new insights into the behaviour and stability of ferrite nanoparticles in natural aqueous environments and may contribute to the development of safer and more environmentally sustainable applications of these materials.