Surface-protective assistance of ultrasound in synthesis of superparamagnetic magnetite nanoparticles and in preparation of mono-core magnetite-silica nanocomposites

Abstract

Ultrasound was throughout employed to enhance the co-precipitation process for the synthesis of magnetite nanoparticles (Fe3O4) and the Stöber approach for the preparation of magnetite-silica nanocomposites (Fe3O4/SiO2). The synthesised magnetite nanoparticles exhibited single-domain nanocrystallites with a uniform spherical morphology, a narrow size distribution (ca. 10 nm), and negligible coercive field (∼5 Oe). The prepared magnetite-silica nanocomposites possessed a mono core-shell structure with spherical morphology, biologically coherent size (ca. 100 nm), and discrete mono-domain behaviour. The crystalline structure-magnetic behaviour relationships of the nanomaterials were investigated to imply the presence of a surface protection at nanoscale. The speculation indicated that shock waves took place as the surface-protective role rather than the original mechanical interaction of ultrasound with a larger scope of impact. Keywords: Fe3O4 nanoparticles, Fe3O4@SiO2 nanocomposites, Shock-wave, Ultrasonic assistance, Co-precipitation, Stöber method, Crystalline structure-magnetic behaviour relationships