Synthesis and characterization of uncoated and gold-coated magnetite nanoparticles
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Synthesis and characterization of uncoated and gold-coated magnetite nanoparticles L. León-Félix · J. Chaker · M. Parise · J. A. H. Coaquira · L. De Los Santos Valladares · A. Bustamante · V. K. Garg · A. C. Oliveira · P. C. Morais
© Springer Science+Business Media Dordrecht 2013
Abstract 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 Fe3 O4 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 Fe3 O4 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 Fe3 O4 nanoparticles. Zero-field–cooled and
Proceedings of the Thirteenth Latin American Conference on the Applications of the Mössbauer Effect, (LACAME 2012), Medellín, Colombia, 11–16 November 2012. L. León-Félix · M. Parise · J. A. H. Coaquira (B) · V. K. Garg · A. C. Oliveira · P. C. Morais Núcleo de Física Aplicada, Institute of Physics, University of Brasília, Brasília, DF 70910-900, Brazil e-mail: [email protected] J. Chaker Faculdadede Ceilândia, University of Brasília, Brasília, DF 72220-140, Brazil L. De Los Santos Valladares Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK A. Bustamante Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima, Perú
L. León-Félix et al.
field-cooled curves of both samples show irreversibilities which are consistent with a superparamagnetic behavior of interacting nanoparticles. Keywords Au-coated magnetite nanoparticles · Mössbauer spectroscopy · Superparamagnetism
1 Introduction Magnetite (Fe3 O4 ) is one of the iron oxide phases of great interest for technological applications due to its high saturation magnetization, the highest ordering temperature among spinel ferrites and its low toxicity [1]. Magnetite nanoparticles (NPs) are interesting systems to be used in biomedical applications, bioseparation, magnetic recording media, target drug delivery, biochemical sensors, among others [2]. Therefore, the stability of iron oxide particles is impeded notably by the occurrence of spontaneous oxidation surface [3]. Recently, it has been revealed the possibility
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