Influence of Surface Functionalization on the Colloidal Stability and Magnetic Properties of Ferrite Nanoparticles

Magnetite ferrite (Fe3O4) nanoparticles have attracted considerable interest due to their tunable physico-chemical properties and relevance in functional materials. In this work, uncoated Fe3O4 nanoparticles and surface-modified Fe3O4 nanoparticles coated with polyethylene glycol (PEG-6000) and citric acid (CA) were synthesized via a chemical co-precipitation method. The effect of surface functionalization on the structural, spectroscopic, magnetic, and colloidal properties of the nanoparticles was systematically investigated. X-ray diffraction analysis confirmed the formation of phase-pure Fe3O4 with an inverse spinel structure for all the samples. Fourier transform infrared and Raman spectroscopy verified successful surface modification while preserving the Fe-O framework of the magnetite core. Dynamic light scattering and zeta potential measurements indicated improved dispersion and colloidal stability for the surface-modified nanoparticles. Magnetization studies performed at room temperature revealed superparamagnetic behaviour for all samples, accompanied by a coating-dependent reduction in saturation magnetization. Overall, the results emphasize the critical role of surface chemistry in tailoring the physicochemical, magnetic, and colloidal behaviour of Fe3O4 nanoparticles. Keywords: Fe3O4 nanoparticles, PEG, Citric acid, Co-precipitation, Surface functionalization, Zeta potential, Colloidal stability, Magnetic properties