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

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 transform...

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Bibliographic Details
Published inCroatica Chemica Acta Vol. 80; no. 3-4; p. 503
Main Authors Tombácz, Etelka, Illés, Erzsébet, Majzik, Andrea, Hajdú, Angéla, Rideg, Nóra, Szekeres, Márta
Format Paper
LanguageEnglish
Published Hrvatsko kemijsko društvo 30.11.2007
Subjects
colloidal stability
magnetic fluids
pH-dependence
recrystallization
solubility
surface charging
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Summary: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.
Bibliography:18674
ISSN:0011-1643
1334-417X