Synthesis and characterization of uncoated and gold-coated magnetite nanoparticles

• Published in: Hyperfine interactions 2014, Vol.224 (1-3), p.179-188
• Main Authors: León-Félix, L., Chaker, J., Parise, M., Coaquira, J. A. H., De Los Santos Valladares, L., Bustamante, A., Garg, V. K., Oliveira, A. C., Morais, P. C.
• Format: Article
• Language: English
• Subjects: Atomic; Condensed Matter Physics; Hadrons; Heavy Ions; Molecular; Nuclear Physics; Optical and Plasma Physics; Physics; Physics and Astronomy; Surfaces and Interfaces; Thin Films
• ISSN: 0304-3843; 1572-9540
• DOI: 10.1007/s10751-013-0857-y

We report on the synthesis and characterization of uncoated and gold coated magnetite nanoparticles. Structural characterizations, carried out using X-ray diffraction, confirm the formation of magnetite phase with a mean size of ~7 and ~8 nm for the uncoated and gold covered magnetite nanoparticles, respectively. The value of the gold coated Fe 3 O 4 nanoparticles is consistent with the mean physical size determined from transmission electron microscopy images. Mössbauer spectra at room temperature are consistent with the thermal relaxation of magnetic moments mediated by particle-particle interactions. The 77 K Mössbauer spectra are modeled with four sextets. Those sextets are assigned to the signal of iron ions occupying the tetrahedral and octahedral sites in the core and shell parts of the particle. The room-temperature saturation magnetization value determined for the uncoated Fe 3 O 4 nanoparticles is roughly ~60 emu/g and suggests the occurrence of surface effects such as magnetic disorder or the partial surface oxidation. These surface effects are reduced in the gold-coated Fe 3 O 4 nanoparticles. Zero-field–cooled and field-cooled curves of both samples show irreversibilities which are consistent with a superparamagnetic behavior of interacting nanoparticles.