Ageing in the inorganic nanoworld: Example of magnetite nanoparticles in aqueous medium

Etelka Tombácz, Erzsébet Illés, Andrea Majzik, Angéla Hajdú, Nóra Rideg, Márta Szekeres

Research output: Contribution to journalArticle

43 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)503-515
Number of pages13
JournalCroatica Chemica Acta
Issue number3-4
Publication statusPublished - Dec 1 2007


  • Colloidal stability
  • Magnetic fluids
  • Recrystallization
  • Solubility
  • Surface charging
  • pH-dependence

ASJC Scopus subject areas

  • Chemistry(all)

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