Person:
Isasi Marín, Josefa

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First Name
Josefa
Last Name
Isasi Marín
URI
https://hdl.handle.net/20.500.14352/76120
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Inorgánica
Area
Química Inorgánica
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    Superparamagnetic and light-emitting bifunctional nanocomposites of iron oxide and erbium or thulium doped yttrium orthovanadate
    (Journal of Alloys and Compounds, 2022) Rapp Díez de la Cortina, María; Lozano Vilches, Yaiza; Fernández Ramos, Miguel; Isasi Marín, Josefa; Alcolea Palafox, Mauricio
    Advances in biomedical research have increased interest in obtaining and studying new bifunctional materials for use in theragnostic. Here we describe in detail the preparation of new magnetic-fluorescent bifunctional (Y0.9Ln0.1VO4/Fe3O4)@SiO2 and [(Y0.9Ln0.1VO4 @SiO2)/Fe3O4)@SiO2] nanocomposites with Ln = Er or Tm. In addition, their magnetic and optical properties were carefully analyzed. The influence of Fe3O4 content and the silica shell thickness on the fluorescent emission in the VIS-NIR region of Y0.9Ln0.1VO4 cores was evaluated as well as their use as display systems with the possibility of directing them by means of external magnetic fields. Samples were prepared using wet chemistry methods involving low temperatures and short reaction times. Y0.9Ln0.1VO4 samples that are not easily oxidizable were prepared by a hydrothermal method, while Fe3O4 sample was synthesized by a coprecipitation process in which the mixture of precursors was treated at very low temperature to avoid oxidation. The powder amalgamation of both Y0.9Ln0.1VO4 and Fe3O4 samples was possible due to the silica polymeric network synthetized by a modified Stöber method. The purity of all samples was ensured by XRD and FTIR techniques. Diffraction profiles of Y0.9Ln0.1VO4 samples show diffraction maxima that can be indexed to a tetragonal symmetry of space group I41/amd, compatible with the zircon structure-type of YVO4 host. All reflections present in the diffraction profile of Fe3O4 sample can be indexed to a cubic symmetry of space group Fd3̅m, characteristic of an inverse spinel structure-type. The amorphous silica incorporation on the samples was also evaluated by TEM images. Studies of the magnetic behavior and luminescent emission intensity of the investigated samples showed their dependence on both, the silica coating thickness, and the contact or not between the luminescent samples and the magnetic powder.
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    New magnetic-fluorescent bifuntional (Y0.9Ln0.1VO4/Fe3O4)@SiO2 and [(Y0.9Ln0.1VO4@SiO2)/Fe3O4@SiO2] materials
    (Ceramics International, 0022) Fernández-Ramos, Miguel; Isasi Marín, Josefa; Alcolea Palafox, Mauricio; Muñoz-Ortiz, Tamara; Ortiz-Rivero, Elisa
    The preparation and study of new bifunctional (Y0.9Ln0.1VO4/Fe3O4)@SiO2 and [(Y0.9Ln0.1VO4@SiO2)/ Fe3O4@SiO2] samples with Ln = Nd or Tb is described in detail. The influence of Fe3O4 content and silica coating on Y0.9Ln0.1VO4@SiO2 samples is analyzed to decide on their potential utility. Materials of this type are currently of great interest in the biomedicine field based on their potential use as bifunctional materials. On the one hand, because they can be directed using an external magnetic field and, on the other, because they can allow the visualization of diseased cells after appropriate functionalization. Y0.9Ln0.1VO4 samples with Ln = Nd or Tb were prepared by a hydrothermal process, while Fe3O4 sample was prepared by the coprecipitation method. These samples and different mixtures of them were treated with tetraethyl orthosilicate (TEOS) to proceed with their silica coating. All diffraction maxima of Y0.9Ln0.1VO4 samples were indexed on a tetragonal symmetry of space group I41/amd, compatible with a zircon structure-type. In the case of Fe3O4 sample, all reflections were indexed to a cubic symmetry of space group Fd 3 m, characteristic of an inverse spinel structure-type. These results also agreed well with the FTIR spectra of the investigated samples. For the first time, the experimental FTIR study of Y0.9Ln0.1VO4 samples was complemented with a theoretical vibrational study based on the YVO4 structure. To carry out this theoretical study, different density functional theory (DFT) methods and different basis sets were used. Silica presence in samples was clearly verified in both, the XRD profiles and the FTIR spectra. Elongated and spherical particles are found in TEM images of these samples. The study of PL emission and magnetic behavior showed that [(Y0.9Ln0.1VO4@SiO2)/Fe3O4@SiO2] samples are the most suitable for use as bifunctional materials.