Magnetic hydrophobic nanocomposites: Silica aerogel/maghemite

Magnetic hydrophobic aerogels (MHA) in the form of nanocomposites of silica and maghemite (γ-Fe2O3) were prepared by one step sol-gel procedure followed by supercritical solvent extraction. Silica alcogels were obtained from TEOS, MTMS, methanol and H2O, and Fe(III) nitrate as magnetic precursor. The hydrophobic property was achieved using the methytrimethoxysilane (MTMS) as co-precursor for surface modification. The so produced nanocomposite aerogels are monolithic, hydrophobic and magnetic. The interconnected porous structure hosts ∼6 nm size γ-Fe2O3 particles, has a mean pore diameter of 5 nm, and a specific surface area (SSA) of 698 m²/g. Medium range structure of MHA is determined by SAXS, which displays the typical fractal power law behavior with primary particle radius of ∼1 nm. Magnetic properties of the nanoparticle ensembles hosted in them are studied by means of dc-magnetometry.