One-step room temperature synthesis of very small g-Fe2O3 nanoparticles

O. MOSCOSO LONDOÑO; M. S. CARRIAO; C. COSIO CASTAÑEDA; V. BILOVOL; R. MARTINEZ SANCHEZ; E. J. LEDE; L. M. SOCOLOVSKY; R. MARTINEZ GARCIA

MATERIALS RESEARCH BULLETIN

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2013 vol. 48 p. 3474 - 3478

0025-5408

Very small maghemite nanoparticles (~3 nm) are obtained through a one-step synthesis at room temperature. The fast neutralization reaction of a ferric solution in a basic medium produces an intermediate phase, presumably two-line ferrihydrite, which in oxidizing conditions is transformed to maghemite nanoparticles. The synthesis of maghemite, as final product of the reaction, was characterized by High-Resolution Transmission Electron Microscopy (HR-TEM), X-ray Absorption Fine Structure (XAFS), Mössbauer spectroscopy, and magnetometry. The XAFS technique allowed the analysis of the crystallographic variations into maghemite nanoparticles as a result of modification in its surface/volume ratio. Mössbauer spectroscopy at low temperature (4.2 K) confirms the presence of Fe(III) in tetrahedral and octahedral interstices, in the stoichiometry corresponding to maghemite. The specific magnetization, M vs H (3 K and 300 K, up to 7 T) and temperature dependence of the magnetization (50 Oe by ZFC mode, 2 K < T < 300 K) indicate that maghemite nanoparticles of 3 nm are in superparamagnetic state with a blocking temperature close to 36 K. http://dx.doi.org/10.1016/j.materresbull.2013.05.042