Person:
Alcolea Palafox, Mauricio

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First Name
Mauricio
Last Name
Alcolea Palafox
URI
https://hdl.handle.net/20.500.14352/76202
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Física
Area
Química Física
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2022 - 20232
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Author: Muñoz-Ortiz, Tamara × Subject: 546 ×

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    Synthesis of new non-covered and silica-covered Y0.9Tm0.1-xYbxVO4 nanophosphors with emission in the visible and NIR ranges
    (Journal of Luminescence, 2023) Lozano, Yaiza; Fernández-Ramos, Miguel; Rapp, María; Alcolea Palafox, Mauricio; Ortiz-Rivero, Elisa; Muñoz-Ortiz, Tamara; Isasi Marín, Josefa
    The development of new materials of interest in the bioimaging field is a relevant topic in current research. We present and study here novel non-covered and silica-covered Y0.9Tm0.1-xYbxVO4 samples with x = 0, 0.01, 0.05 and 0.09 that were prepared by hydrothermal synthesis. For comparison purposes, the study of Y0.9Tm0.1VO4 sample synthesized by the sol-gel method was also included. The relationships between the synthesis method, dopant content and luminescence emission were systematically studied by X-ray diffraction (XRD), FTIR spectroscopy and transmission electron microscopy (TEM). XRD profiles and FTIR spectra confirm the zircon-type structure of the obtained samples. Particles of two different morphologies were found in TEM images of uncoated samples, some spherical with sizes between 42 and 50 nm and others elongated. A shell thickness between 8 and 13 nm was also observed in silica-covered samples. Photoluminescence studies of our samples revealed emission in the NIR and visible ranges. Under excitation at 790 nm, the spectra of thulium-doped samples showed the characteristic emission band of Tm3+ ions. Substitution of thulium by ytterbium successfully led to an up-conversion emission under excitation at 980 nm. Finally, the fluorescent emission study in the NIR of samples that could be more biocompatible demonstrated that they are suitable for use as luminescent thermometers in the physiological temperature range.
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    New magnetic-fluorescent bifuntional (Y0.9Ln0.1VO4/Fe3O4)@SiO2 and [(Y0.9Ln0.1VO4@SiO2)/Fe3O4@SiO2] materials
    (Ceramics International, 2022) 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.