Staff directory

Publications

2016

  • Enhanced Spin Tunneling in a Molecular Magnet Mixed with a Superconductor

    Tejada J., Zarzuela R., García-Santiago A., Imaz I., Espin J., Maspoch D., Chudnovsky E.M. Journal of Superconductivity and Novel Magnetism; 29 (5): 1133 - 1137. 2016. 10.1007/s10948-016-3474-6. IF: 1.100

    We report characterization and magnetic studies of mixtures of micrometer-size ribbons of Mn12 acetate and micrometer-size particles of YBaCuO superconductor. Extremely narrow zero-field spin-tunneling resonance has been observed in the mixtures, pointing to the absence of the inhomogeneous dipolar broadening. It is attributed to the screening of the internal magnetic fields in the magnetic particles by Meissner currents flowing between superconducting grains surrounding the particles. © 2016, Springer Science+Business Media New York.


  • Narrowing the Zero-Field Tunneling Resonance by Decreasing the Crystal Symmetry of Mn12 Acetate

    Espín J., Zarzuela R., Statuto N., Juanhuix J., Maspoch D., Imaz I., Chudnovsky E., Tejada J. Journal of the American Chemical Society; 138 (29): 9065 - 9068. 2016. 10.1021/jacs.6b05380. IF: 13.038

    We report the discovery of a less symmetric crystalline phase of Mn12 acetate, a triclinic phase, resulting from recrystallizing the original tetragonal phase reported by Lis in acetonitrile and toluene. This new phase exhibits the same structure of Mn12 acetate clusters and the same positions of tunneling resonances on the magnetic field as the conventional tetragonal phase. However, the width of the zero-field resonance is at least 1 order of magnitude smaller - can be as low as 50 Oe - indicating very small inhomogeneous broadening due to dipolar and nuclear fields. © 2016 American Chemical Society.


2015

  • Resonant spin tunneling in randomly oriented nanospheres of Mn12 acetate

    Lendínez S., Zarzuela R., Tejada J., Terban M.W., Billinge S.J.L., Espin J., Imaz I., Maspoch D., Chudnovsky E.M. Physical Review B - Condensed Matter and Materials Physics; 91 (2, 024404) 2015. 10.1103/PhysRevB.91.024404. IF: 3.736

    We report measurements and theoretical analysis of resonant spin tunneling in randomly oriented nanospheres of a molecular magnet. Amorphous nanospheres of Mn12 acetate have been fabricated and characterized by chemical, infrared, TEM, x-ray, and magnetic methods. Magnetic measurements have revealed sharp tunneling peaks in the field derivative of the magnetization that occur at the typical resonant field values for the Mn12 acetate crystal in the field parallel to the easy axis. Theoretical analysis is provided that explains these observations. We argue that resonant spin tunneling in a molecular magnet can be established in a powder sample, without the need for a single crystal and without aligning the easy magnetization axes of the molecules. This is confirmed by reanalyzing the old data on a powdered sample of nonoriented micron-size crystals of Mn12 acetate. Our findings can greatly simplify the selection of candidates for quantum spin tunneling among newly synthesized molecular magnets. © 2015 American Physical Society.


  • Synthesis, culture medium stability, and in vitro and in vivo zebrafish embryo toxicity of metal-organic framework nanoparticles

    Ruyra A., Yazdi A., Espín J., Carné-Sánchez A., Roher N., Lorenzo J., Imaz I., Maspoch D. Chemistry - A European Journal; 21 (6): 2508 - 2518. 2015. 10.1002/chem.201405380. IF: 5.731

    Metal-organic frameworks (MOFs) are among the most attractive porous materials available today. They have garnered much attention for their potential utility in many different areas such as gas storage, separation, catalysis, and biomedicine. However, very little is known about the possible health or environmental risks of these materials. Here, the results of toxicity studies on sixteen representative uncoated MOF nanoparticles (nanoMOFs), which were assessed for cytotoxicity to HepG2 and MCF7 cells in vitro, and for toxicity to zebrafish embryos in vivo, are reported. Interestingly, there is a strong correlation between their in vitro toxicity and their in vivo toxicity. NanoMOFs were ranked according to their respective in vivo toxicity (in terms of the amount and severity of phenotypic changes observed in the treated zebrafish embryos), which varied widely. Altogether these results show different levels of toxicity of these materials; however, leaching of solubilized metal ions plays a main role. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.