FACILE SYNTHESIS AND CHARACTERIZATION OF STRUCTURAL AND MAGNETIC PROPERTIES OF Fe3O4 AND Fe3O4@SiO2 NANOPARTICLES

Abstract

This study aimed to synthesize silica-coated magnetic nanoparticles (Fe₃O₄@SiO₂) via a simple hydrothermal process and investigate their structural and magnetic properties. Fe₃O₄ nanoparticles were prepared by reducing Fe(NO₃)₃·9H₂O with NaBH₄ under alkaline conditions (pH 9) at 160 °C for 24 h. The surface of Fe₃O₄ was subsequently coated with silica using tetraethyl orthosilicate (TEOS) as a precursor through hydrolysis and condensation reactions, resulting in a silica content of approximately 38 wt%. X-ray diffraction (XRD) analysis confirmed that Fe₃O₄ possessed a well-defined inverse spinel structure, while the silica coating did not alter its crystal phase. Fourier transform infrared (FTIR) spectra revealed the presence of Si-O-Si and Si-OH stretching vibrations, confirming the formation of an amorphous silica shell and increased surface hydrophilicity after coating. Vibrating sample magnetometry (VSM) measurements at room temperature indicated that both Fe₃O₄ and Fe₃O₄@SiO₂ nanoparticles exhibited superparamagnetic behavior. The saturation magnetization (M_s) decreased from 70.14 emu/g for Fe₃O₄ to 34.23 emu/g after silica coating, attributed to the non-magnetic mass contribution and spin disorder at the surface. These results demonstrate that the simple hydrothermal synthesis route effectively produces The Fe₃O₄ nanoparticles possessed high crystallinity, and the Fe₃O₄@SiO₂ composites retained the core's crystallinity while demonstrating an amorphous silica shell, both of which have good stability and good magnetic properties, making them suitable for various applications and efficient.