Original scientific paper

Ageing in the Inorganic Nanoworld: Example of Magnetite Nanoparticles in Aqueous Medium

Etelka Tombácz ; Department of Colloid Chemistry, University of Szeged, Szeged, Hungary
Erzsébet Illés ; Department of Colloid Chemistry, University of Szeged, Szeged, Hungary
Andrea Majzik ; Department of Colloid Chemistry, University of Szeged, Szeged, Hungary
Angéla Hajdú ; Department of Colloid Chemistry, University of Szeged, Szeged, Hungary
Nóra Rideg ; Department of Colloid Chemistry, University of Szeged, Szeged, Hungary
Márta Szekeres ; Department of Colloid Chemistry, University of Szeged, Szeged, Hungary

Abstract

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.

Keywords

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

Hrčak ID:

18674

URI

https://hrcak.srce.hr/18674

Publication date:

30.11.2007.

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