Tunable size and cation distribution in cobalt ferrite nanoparticles via a scalable eco-friendly synthesis method

Advancing synthesis methods for cobalt ferrite nanoparticles with precise control over their structural properties-while simultaneously aligning with sustainable development goals-remains a persistent challenge. In this work, we report a simple oxidative precipitation route based on the air oxidation of an aqueous suspension containing Fe(OH) 2 and Co(OH) 2 , carried out entirely under ambient atmospheric conditions. In this approach, atmospheric oxygen diffuses into the reaction mixture and serves as the oxidizing agent, eliminating the need for forced air bubbling. By varying the parameter R=[OH − ]/([Co 2+ ]+[Fe 2+ ]) between 1.5 and 6, we achieved controlled particle size distributions in the 20–60 nm range while preserving a quasi-spherical morphology. Furthermore, R played a key role in tuning the crystallinity, stoichiometry, and cation distribution in the resulting nanoparticles. The optical band gap for direct electronic transitions, estimated using Tauc plots, was approximately 1.4 eV. High saturation magnetization values (~ 100 emu/g) were attributed to partial inversion in the spinel structure. These findings expand the applicability of a scalable, cost-effective, and environmentally friendly route for synthesizing iron oxide-based materials with multifunctional advanced applications.