Ageing in the Inorganic Nanoworld: Example of Magnetite Nanoparticles in Aqueous MediumReportar como inadecuado

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Croatica Chemica Acta, Vol.80 No.3-4 November 2007. -

Changes in the inherent solid phase and aqueous interfacial properties of magnetite nanoparticles

in a Massart type magnetic fluid were investigated. Magnetite nanoparticles were synthesized,

purified, dialyzed against 0.001 mol dm–3 HCl and then stored at 4 °C for 6 years. The

solid phase transformation of magnetite to maghemite and formation of akageneite shell on the

magnetic core, as well as a slight increase in particle size were proved, causing no change in

the superparamagnetic features of nanoparticles after storage as long as 6 years. The aqueous

interfacial properties, however, were altered in a strange way. Surprisingly, neither the surface

charge density nor the particle charge in acidic region showed significant changes, except for a

definite decrease in pHpzc and pHiep from pH ~ 8 to ~ 7. Coalescence of akageneite shell during

recrystallization resulted in a significant decrease of the specific surface area of the aged sample,

and probably contributed to its declining colloidal stability.

magnetic fluids; pH-dependence; surface charging; solubility; recrystallization; colloidal stability

Autor: Etelka Tombácz - ; Department of Colloid Chemistry, University of Szeged, Szeged, Hungary Erzsébet Illés - ; Department of Col



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