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Research Interests: Materials Engineering, Physics, Condensed Matter Physics, Materials Science, Chemistry, and 15 moreNanoparticle, Nanotechnology, Medicine, Thin Film, Iron Oxide, Iron, Exchange Bias, Nanoclusters, Oxide, Magnetization, Low Temperature, Ferromagnetism, X ray Absorption, Spin Canting, and Antiferromagnetism
We describe various molecular switching processes occurring in several types of inorganic solids: spin cross-over (SC) compounds, photomagnetic Prussian blue analogs (PBAs), and valence-tautomeric system. Their thermo-, photo-, piezo-,... more
We describe various molecular switching processes occurring in several types of inorganic solids: spin cross-over (SC) compounds, photomagnetic Prussian blue analogs (PBAs), and valence-tautomeric system. Their thermo-, photo-, piezo-, and magneto-chromic properties are illustrated by recent examples. A common description of their static properties by a two-level model is given.
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... Sylvie Létard, Xavier Solans, Nieves Menéndez, Antoine Goujon, François Varret, and José Antonio Real*. ... Chandrasekar Rajadurai, Frank Schramm, Susan Brink, Olaf Fuhr, Mohamed Ghafari, Robert Kruk, and Mario Ruben. Inorganic... more
... Sylvie Létard, Xavier Solans, Nieves Menéndez, Antoine Goujon, François Varret, and José Antonio Real*. ... Chandrasekar Rajadurai, Frank Schramm, Susan Brink, Olaf Fuhr, Mohamed Ghafari, Robert Kruk, and Mario Ruben. Inorganic Chemistry 2006 45 (25), 10019-10021. ...
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A new series of double perovskites of stoichiometry Sr2-xCexFeMoO6 (0<= x <= 1) has been prepared by a wet chemistry procedure yielding very reactive precursors, which were subsequently annealed under reducing conditions. The compounds... more
A new series of double perovskites of stoichiometry Sr2-xCexFeMoO6 (0<= x <= 1) has been prepared by a wet chemistry procedure yielding very reactive precursors, which were subsequently annealed under reducing conditions. The compounds have been studied by X-ray (XRD), neutron powder diffraction (NPD), Mössbauer spectroscopy, magnetic and magnetotransport measurements in polycrystalline samples, aiming to investigate the effect of electron doping in the parent perovskite Sr2FeMoO6. The evolution of the crystal structure has been analyzed from NPD data; a transition from tetragonal (I4/m) to monoclinic (P21/n) has been observed at 0.2<= x <= 0.4 as a result of the decrease of the tolerance factor due to the electron injection on B
sites and the reduction in ionic size at A positions of the ABO3 perovskite. A bond valence study shows that an important fraction of the injected electrons is localized at Mo sites, which promotes the occurrence of antisite disordering between Fe and Mo cations. The magnetic properties are characteristic of ferromagnetic materials, with an ordering temperature of around 400 K, showing a non-monotonic behavior along the series, which is understood as a compromise between the steric and the electron injection effects. The introduction of a magnetic rare-earth in the Sr sublattice improves the magnetoresistive response at low temperatures, as a result of the
polarization of the Ce3+ moments: a magnetoresistance (MR) factor of 45% is observed at 5 K for the x = 0.6 sample. For the first time we show that the introduction of a magnetic element in the A sublattice of a double perovskite can be used as an effective way to enhance the magnetoresistive response in this attractive family of oxides.
sites and the reduction in ionic size at A positions of the ABO3 perovskite. A bond valence study shows that an important fraction of the injected electrons is localized at Mo sites, which promotes the occurrence of antisite disordering between Fe and Mo cations. The magnetic properties are characteristic of ferromagnetic materials, with an ordering temperature of around 400 K, showing a non-monotonic behavior along the series, which is understood as a compromise between the steric and the electron injection effects. The introduction of a magnetic rare-earth in the Sr sublattice improves the magnetoresistive response at low temperatures, as a result of the
polarization of the Ce3+ moments: a magnetoresistance (MR) factor of 45% is observed at 5 K for the x = 0.6 sample. For the first time we show that the introduction of a magnetic element in the A sublattice of a double perovskite can be used as an effective way to enhance the magnetoresistive response in this attractive family of oxides.
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We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic... more
We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic Belt) in an extreme acidic ecosystem (pH∼2.3) with high concentration of dissolved iron, sulphate and heavy metals. Iron biominerals were found at the cellular level in tissues of root, stem and leaf both in collected and laboratory-cultivated plants. Iron accumulated in this plant as a mix of iron compounds (mainly as jarosite, ferrihydrite, hematite and spinel phases) was characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy (MS), magnetometry (SQUID), electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX; TEM-EDX; HRSTEM). A low fraction of phosphorous was detected in this iron hyperaccumulator plant. Root and rhizomes tissues present a high proportion of ferromagnetic iron oxide c...
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... Sylvie Létard, Xavier Solans, Nieves Menéndez, Antoine Goujon, François Varret, and José Antonio Real*. ... Chandrasekar Rajadurai, Frank Schramm, Susan Brink, Olaf Fuhr, Mohamed Ghafari, Robert Kruk, and Mario Ruben. Inorganic... more
... Sylvie Létard, Xavier Solans, Nieves Menéndez, Antoine Goujon, François Varret, and José Antonio Real*. ... Chandrasekar Rajadurai, Frank Schramm, Susan Brink, Olaf Fuhr, Mohamed Ghafari, Robert Kruk, and Mario Ruben. Inorganic Chemistry 2006 45 (25), 10019-10021. ...
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Several acyl derivatives of the aureolic acid chromomycin A(3) were obtained via lipase-catalyzed acylation. Lipase B from Candida antarctica (CAL-B) was found to be the only active biocatalyst, directing the acylation regioselectively... more
Several acyl derivatives of the aureolic acid chromomycin A(3) were obtained via lipase-catalyzed acylation. Lipase B from Candida antarctica (CAL-B) was found to be the only active biocatalyst, directing the acylation regioselectively towards the terminal secondary hydroxyl group of the aglycone side chain. All new chromomycin A(3) derivatives showed antitumor activity at the micromolar or lower level concentration. Particularly, chromomycin A(3) 4&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-vinyladipate showed 3-5 times higher activity against the four tumor cell lines assayed as compared to chromomycin A(3).
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ABSTRACT
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Herein a facile and versatile one step synthesis of magnetite nanoparticles coated with polydopamine is described.
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The synthesis of two new iron dithiolene derivatives and the study of their physical properties are described.
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... MA Alario-Franco and U. Amador-Elizondo. Solid State Ionics 8688 (1996), pp. 811818. Article | PDF (674 K) | View Record in Scopus | Cited By in Scopus (7). 16. JB Goodenough. Magnetism and the Chemical Bond, Interscience, New York... more
... MA Alario-Franco and U. Amador-Elizondo. Solid State Ionics 8688 (1996), pp. 811818. Article | PDF (674 K) | View Record in Scopus | Cited By in Scopus (7). 16. JB Goodenough. Magnetism and the Chemical Bond, Interscience, New York (1963) p. 266 . 17. AF Reid and ...
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Two new oxynitride double perovskites of composition Sr2FeMoO6−xNx (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750°C and 650°C, respectively. The polycrystalline... more
Two new oxynitride double perovskites of composition Sr2FeMoO6−xNx (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750°C and 650°C, respectively. The polycrystalline samples have been characterized by chemical analysis, x-ray and neutron diffraction (NPD), Mössbauer spectroscopy and magnetic measurements. They exhibit a tetragonal structure with a=5.5959(1)Å, c=7.9024(2)Å, V=247.46(2)Å3 for Sr2FeMoO5.7N0.3; and
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Characterization of the MnLi ferrite system Li 1−0.5x Fe 1.5x+1 Mn 1−x O 4 (0.2 ≤ x ≤ 1). Mercedes Gracia*a, José F. Marcoa, J. Ramón Gancedoa, Juan Luis Gautierb, Edmundo I. Ríosb, Nieves Menéndezc and Jesús Torneroc. a Insto. de... more
Characterization of the MnLi ferrite system Li 1−0.5x Fe 1.5x+1 Mn 1−x O 4 (0.2 ≤ x ≤ 1). Mercedes Gracia*a, José F. Marcoa, J. Ramón Gancedoa, Juan Luis Gautierb, Edmundo I. Ríosb, Nieves Menéndezc and Jesús Torneroc. a Insto. de Química Física Rocasolano, CSIC. ...
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ABSTRACT
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ABSTRACT Nickel ferrite nanoparticles (NiFe2O4) were synthesized by electrochemical method and used as catalyst for direct oxidation of glucose, NADH and methanol. Characterization of these nanoparticles was carried out by X-ray... more
ABSTRACT Nickel ferrite nanoparticles (NiFe2O4) were synthesized by electrochemical method and used as catalyst for direct oxidation of glucose, NADH and methanol. Characterization of these nanoparticles was carried out by X-ray diffraction, Mössbauer spectroscopy, and colloidal properties such as hydrodynamic radius and Zeta potential. To evaluate the catalytic properties of these nanoparticles against the oxidation process, paste graphite electrodes mixing nickel ferrites and different conductive materials (graphite, carbon nanotubes) and binders agents (mineral oil, 1-octylpyridinium hexafluorophosphate (nOPPF6)) were used. The results prove good catalytic properties of these materials, with an oxidation potential around 0.75, 0.5 and 0.8 V for glucose, NADH, and methanol, respectively.
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ABSTRACT Iron nanoclusters have been deposited by the gas-phase aggregation technique to form multilayered structures with outstanding exchange-bias (HE) values up to HE = 3300 Oe at low temperatures. In order to explain the observed... more
ABSTRACT Iron nanoclusters have been deposited by the gas-phase aggregation technique to form multilayered structures with outstanding exchange-bias (HE) values up to HE = 3300 Oe at low temperatures. In order to explain the observed magnetic properties, composition and crystallographic phase have been determined by X-ray absorption spectroscopy. A metal-oxide core–shell arrangement has to be discarded to explain the large obtained values of HE since structural results show nanoclusters formed by the antiferromagnetic α-Fe2O3 oxide. Moreover, nanoparticles of few nanometers formed by substoichiometric α-Fe2O3 explain the observed weak ferromagnetism and let to understand the origin of large exchange bias by the interaction between different spin sublattice configurations provided by the low iron coordination at surface.
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... The structure of the complexes is discussed in terms of the Mössbauer quadrupole splitting and the tin-halogen stretching vibrations in the IR and Raman spectra. Article Outline. • References. ... 14. S. Calogero, U. Russo, G. Valle,... more
... The structure of the complexes is discussed in terms of the Mössbauer quadrupole splitting and the tin-halogen stretching vibrations in the IR and Raman spectra. Article Outline. • References. ... 14. S. Calogero, U. Russo, G. Valle, PWC Barnard and JD Donaldson. Inorg. Chim. ...
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From the observed jump in the isomer shift of Fe3+, we conclude that, in the double perovskite Sr2FeMoO6, for moderate levels of anti-site disorder at the Fe/Mo sites, the magnetic transition triggers a charge-transfer process between the... more
From the observed jump in the isomer shift of Fe3+, we conclude that, in the double perovskite Sr2FeMoO6, for moderate levels of anti-site disorder at the Fe/Mo sites, the magnetic transition triggers a charge-transfer process between the ordered and anti-site ...