Crystalisation of aqueous ferrofluids at the free liquid interface investigated by specular and off-specular x-ray reflectometry

Abstract

Abstract. Structural organization of nanoparticles from aqueous ferrofluids on free liquid surface was studied by X-ray reflectometry. The observed layered structure at interface is associated with the evaporation of the solvent. By orienting an external magnetic during evaporation of the aqueos ferrofluids their structural organization can be manipulated. For a magnetic field applied perpendicular to the surface a more pronounced ordering along the surface normal is observed as in the case of a parallel field. Independent on the orientation of the magantic field a ∼ 20 µm thick surface layer of depleted nanoparticle concentration is found at the interface.

Ferrofluids and bio-ferrofluids: looking back and stepping forward

“…Similar effects of 'oversaturation' can be observed at the interface 'air-ferrofluid' when drying the sample. This was done by X-ray reflectometry; 361 the formation and growth of a periodic structure was detected during the solvent evaporation. More extended studies with application of grazing incidence SAXS (GISAX) were performed 362 for evaporation-induced assembly during drop casting of superparamagnetic, oleate-capped γ-Fe 2 O 3 nanospheres dispersed in toluene.…”