Synthesis of nanoparticles under restricted environments offered by water-in-oil microemulsions provides excellent control over particle size and shape and interparticle spacing. These environments have been used in the synthesis of silica nanoparticles with a ZnFe2O4 magnetic core. First, aqueous magnetic fluids constituted of zinc ferrite nanoparticles with a size ranging between 4 and 6 nm have been synthesized using a soft chemical approach. Chemical analysis has shown that the zinc ferrite nanoparticles are nonstoichiometric with the estimated formula Zn 0.87Fe2.09X0.04O4 (X represents vacancies). The obtained silica nanoparticles (40-60 nm) with a zinc ferrite magnetic core (4-6 nm) have been characterized by X-ray diffraction, electron microscopy, and magnetization measurements. Preliminary magnetic measurements have inferred that the magnetic properties of these nanoparticles at low temperature are essentially governed by the interface particle-habitat.

International audienceCommercial zinc oxide nanoparticles (20–30 nm) were coated by aminopropyltriethoxysilane (APTES) under varying environments. Three different processes, acidic, basic and toluene were used. The effects of coating conditions (acidic, basic and toluene) on the grafting, structural and optical properties of these nanoparticles were studied. In the three cases, it was possible to control the coating and according to X-ray diffraction, BET, TEM and SEM results, it is clear that the APTES coating plays a role of growth inhibitor even at 800 °C..