Facile route to γ-Fe2O3/SiO2 nanocomposite used as a precursor of magnetic fluid

Maghemite (γ-Fe2O3) nanoparticles (NPs) homogeneously dispersed in silica matrix were obtained via a three-step chemical procedure at mild conditions. The acid-treated solids were obtained using silica NPs, Fe(NO3)3·9H2O and acetic acid. The nanocomposites with various contents of maghemite were prepared by heating the acid-treated solids at 80 °C for 2 h and then at 400 °C for 1 h. The acid-treated solids were studied by means of Fourier Transform infrared spectroscopy (FT-IR) and thermogravimetry (TG). The morphology and particle size of the magnetic nanocrystallites were evaluated by the transmission electron microscopy (TEM) technique, while the nature of the obtained nanocomposites was studied using X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM), showing that the acid treatment played a critical role for the magnetic-phase formation and the maximum saturation magnetization (Ms) of the obtained nanocomposite was 37.78 emu g−1. However, when FeCl3·6H2O was used as precursor instead of Fe(NO3)3·9H2O, pure hematite (α-Fe2O3) particles dispersed in silica matrix were obtained. Magnetic fluid (MF) was prepared using the maghemite/silica nanocomposites by high-energy ball milling and was characterized by UV–vis, Gouy magnetic balance and rotating rheometer.