57Fe-Mössbauer study and methylene blue decomposing effect of nanoparticle mixtures composed of metallic iron and maghemite

Balázs Kobzi, Yuka Watanabe, Kazuhiko Akiyama, E. Kuzmann, Z. Homonnay, Stjepko Krehula, Mira Ristić, Tetsuaki Nishida, Shiro Kubuki

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A relationship between local structure and methylene blue degradation ability of nanoparticle (NP) mixtures composed of metallic iron (Fe0) and maghemite (γ-Fe2O3) was studied by means of 57Fe-Mössbauer spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry-differential thermal analysis (TG-DTA), ultraviolet–visible light absorption spectroscopy (UV–Vis) and electrospray ionization mass spectroscopy (ESI-MS). Organic compounds decomposing behaviour of NPs was evaluated by 10-day degradation test with methylene blue (MB) aqueous solution. (Fe0 + γ-Fe2O3) NPs with a molar ratio of 1: 3 showed a remarkable decrease in the MB concentration from 20.0 to 0.85 μM with the largest first-order rate constant (kMB) of 2.84 day−1. The ESI-MS spectrum of MB aqueous solution after 1-day reaction with the (Fe0 + γ-Fe2O3) NPs (1:3) showed several peaks at the m/z values of 109, 129 and 165 etc. indicating that MB was decomposed by the NP mixture. Mössbauer spectrum of the NP mixture measured after 1-day degradation test, composed of two relaxation spectra (sextets): one with isomer shift (δ) of 0.35±0.01 mm s−1 and internal magnetic field (Hint) of 36.3±0.1 T, which was ascribed to tetrahedral Fe3+, and the other with δ of 0.65±0.01 mm s−1 and Hint of 33.1±0.1 T due to octahedral Fe2.5+. The precipitation of Fe3O4 NPs was also confirmed by the Mössbauer spectrum of the same sample measured at 78 K. Isothermal annealing of the Fe3O4 NPs at 250 and 450 °C proved an NP formation of γ-Fe2O3, suggesting that the (Fe0 + γ-Fe2O3) NPs could be applied as the environmental purifying material.

Original languageEnglish
Pages (from-to)94-100
Number of pages7
JournalJournal of Alloys and Compounds
Publication statusPublished - Jan 1 2017



  • Fe-Mössbauer spectroscopy
  • Maghemite
  • Metallic iron
  • Methylene blue decomposing effect
  • Nano particles

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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