Georgia Papaefthymiou

Publications (109) View all

• Source

  Available from: Ioannis Rabias

  Article: Gummic acid stabilized γ-Fe2O3 aqueous suspensions for biomedical applications

  G. C. Papaefthymiou, I. Rabias, M. Fardis, E. Devlin, N. Boukos, D. Tsitrouli, G. Papavassiliou
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  ABSTRACT: Biomedical applications of magnetic nanoparticles depend critically on their preparation as aqueous colloidal suspensions, or ferrofluids, with long term stability under physiological conditions. Dispersion of the magnetic nanoparticles is generally achieved by the use of protein cages, polysaccharide, polypeptide and charged macromolecular coatings, which minimize interparticle magnetic interactions, particle agglomeration and precipitation. The synthesis and characterization of gummic-acid stabilized maghemite ferrofluids is reported. X-ray diffraction, transmission electron microscope and dynamic light scattering measurements give a γ-Fe2O3 magnetic core diameter of 8nm and a nanocomposite particle hydrodynamic diameter of 50nm. Mössbauer and magnetization measurements indicate the presence of isolated, sterically stabilized superparamagnetic nanoparticles resistant to aging, and thus, promising agents for the production of novel magneto-pharmaceuticals.
  Hyperfine Interactions 04/2009; 190(1):59-66. · 0.21 Impact Factor
• Conference Proceeding: Gummic acid stabilized γ-Fe2O3 aqueous suspensions for biomedical applications

  G. C. Papaefthymiou, I. Rabias, M. Fardis, E. Devlin, N. Boukos, D. Tsitrouli, G. Papavassiliou
  Isiame 2008: Proceedings of the International Symposium on the Industrial Applications of the Mossbayer Effect, Budapest, Hungary; 08/2008
• Chapter: Hybrid magnetic nanoparticles derived from wüstite disproportionation reactions at the nanoscale

  G. C. Papaefthymiou, F. X. Redl, C. T. Black, R. L. Sandstrom, M. Yin, C. B. Murray, S. P. O’Brien
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  ABSTRACT: We present Mössbauer studies of hybrid iron-oxide nanoparticles obtained by the disproportionation of oleic acid stabilized wüstite (FexO) nanoparticles produced by selective oxidation of iron pentacarbonyl in high boiling temperature organic solvents. The results support X-ray diffraction and Transmission Electron Microscope studies of the presence of mixed FexO and Fe3O4 phases within the nanoparticles whose relative content can be altered through heat treatment in nitrogen atmosphere. Furthermore, the Mössbauer study gives evidence of the presence of an amorphous, spin-glass like phase due to spin frustration at the FexO/Fe3O4 interface.
  12/2007: pages 239-245;
• Article: Deuterium isotope effects on iron core formation in ferritin

  G. C. Papaefthymiou, A. J. Viescas, R. Horn, E. Carney, G. Zhao, N. D. Chasteen, J. Lee, S. M. Gorun
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  ABSTRACT: We present comparative Mössbauer investigations of nanosized FeOOH and FeOOD biomineral phases nucleated within the 7-nm diameter cavity of horse-spleen apoferritin in order to assess deuterium isotopic effects on nanoscale, bioinorganic lattice structures with extended hydrogen bond networks. Differences in magnetic anisotropy energy, packing density and degree of crystallinity in the resulting iron oxo-hydroxide nanophases obtained via D2O (heavy water) vs. H2O (light water) solution chemistry are noted. These observations point to the possibility of stabilizing new thermodynamic states in the solid-state by utilizing isotope effects, with important implications for new synthetic pathways to novel nano materials.
  Hyperfine Interactions 08/2005; 165(1):333-338. · 0.21 Impact Factor
• Article: Subsite-differentiated analogs of native iron sulfide [4Fe-4S]2+ clusters: preparation of clusters with five- and six-coordinate subsites and modulation of redox potentials and charge distributions

  S. Ciurli, M. Carrie, J. A. Weigel, M. J. Carney, T. D. P. Stack, G. C. Papaefthymiou, Richard H. Holm
  04/2002;