Exploring the Impact of Zn Substitution on the Physicochemical Properties of Cobalt Ferrite Nanoparticles

Abstract

This research applied an advanced solvothermal synthesis approach that enabled precise control over the size, shape, surface functionalization, and stoichiometry of cobalt ferrite nanoparticles (CFO NPs), thanks to the bridging bidentate interaction of oleic acid (OA) and surface metal atoms. By relying on it, we systematically investigated the effect of Zn substitution in the CFO lattice (Co<inf>1-x</inf>Zn<inf>x</inf>Fe<inf>2</inf>O<inf>4</inf>, x = 0, 0.1, 0.3, 0.5) to reveal the structure-property relationship in spinel ferrites. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterization confirmed monodisperse spherical NPs (5 ± 1 nm) with the pure spinel phase. Fourier transform infrared (FTIR) and Raman spectroscopy revealed Zn incorporation in the lattice by the changes in metal-oxygen vibration modes (e.g., F<inf>2g</inf>(3) and A<inf>1g</inf>(1), with x(Zn) > 0.1 as a threshold for detectable changes). The matching of nominal and real stoichiometry of the NPs was confirmed by the inductively coupled plasma atomic emission spectrometry (ICP-AES) method. Magnetic studies performed at 5 K demonstrated tunable properties with magnetization change from 94.6 ± 0.4 A m²/kg for pristine CFO to 102.7 ± 0.3 A m²/kg for x(Zn) = 0.5 and simultaneous drop of coercivity from 1.13 ± 0.01 to 0.60 ± 0.01 T, thus highlighting the role of Zn in modulating magnetic properties. Beyond advancing synthesis precision, this study provides a framework for tailoring multifunctional NPs, bridging the gap between atomic-scale doping and macroscopic properties. The versatility of the approach, coupled with demonstrated control over interfacial chemistry and magnetism, positions it as a key tool for materials design with relevance to biomedical systems, magnetic storage, and catalytic applications. By elucidating substitution-driven property evolution in spinel ferrites, this study contributes to the rational design of next-generation functional materials.