Person:
Isasi Marín, Josefa

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

Identifiers

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Now showing 1 - 10 of 28

Structural and magnetic studies of NiFe2O4 and NiFe2O4@SiO2-Silane agent samples useful for the removal of Cu2+ ions
(Journal of Alloys and Compounds, 0021) Ferrer, Carlos; Arévalo, Pablo; Fernández-Ramos Miguel; Rapp, María; Alcolea, Mauricio; Marco, Jose; Martín-Hernández, Fátima; Isasi Marín, Josefa; Isasi Marín, Josefa; Science Citation Index Expanded
Nickel ferrite samples are currently investigated due to their potential technological applications. For this reason, the optimal synthesis conditions of nickel ferrite samples with small particle size were investigated here. First, a systematic study was carried out using urea as an additive, and varying reaction parameter such as the amount of urea added or the reaction temperature and time. For comparison purposes, another sample was synthesized using potassium hydroxide as an additive. The two pure nickel ferrite samples were coated with silica, functionalizing them with APTES and AEPMDS. X-rays, FTIR, Mössbauer spectroscopy, TEM and Ms vs. H and FC/ZFC curves were used for the characterization of samples and the evaluation of their properties. Square particles with an average size of 21.2 nm were observed in the TEM images of the sample synthesized with urea, while these are spherical of 6.2 nm in the sample prepared with potash. Their subsequent coating and functionalization give rise to an arrangement of particles within interlocking strands whose thickness increases with their size. Ms vs. H curves confirm the almost superparamagnetic behavior of all synthesized powders, although with a slight increase in the coercivity value of the samples prepared with urea. Preliminary tests carried out on the functionalized samples to evaluate the adsorption capacity in aqueous solution and their easy separation in presence of an external magnetic field, confirm that the sample syn thesized with urea and functionalized with AEPDMS is the most efficient for the Cu2+ ions removal.
Synthesis of new non-covered and silica-covered Y0.9Tm0.1-xYbxVO4 nanophosphors with emission in the visible and NIR ranges
(Journal of Luminescence, 0023) Lozano Yaiza; Fernández-Ramos Miguel; Rapp María; Alcolea Mauricio; Ortiz-Rivero Elisa; Muñoz-Ortiz Tamara; Isasi Marín, Josefa; Isasi Marín Josefa; Science Citation Index Expanded
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.
Project number: 3
Elaboración de material audiovisual de uso en asignaturas prácticas y teórico prácticas de grados y dobles grados que tratan la química
(2023) Isasi Marín, Josefa; Alcolea Palafox, Mauricio; Fernández-Ramos Humanes, Miguel; Rapp Diez de la Cortina, María; Hernán García, Esther; de la Lastra Martínez, Jaime; Alba Isasi, Pablo; Cáceres Ramos, Silvia; Alba Isasi, Carlos; Herranz Muñoz, Irene; Gordo Lozano, Marta; Luliana Ionita, Andrea; García Calvo, Elena; Espada Morán, Luis; Villa García, Mª Isabel; Martín Gandul, Mª del Carmen; Arévalo Cid, Pablo; Martinez Pacheco, Andrea; Boulahya, Khalid; Marco Arquero, Alexia; Arquero Avilés, María Del Rosario; Marco Arquero, Carla; Marco Arquero, María; Marco Cuenca, Gonzalo; Criado García, Mª Rosario; Sánchez Calero, Luisa
En el desarrollo del proyecto se han elaborado un total de 25 tutoriales que se convertirán en la guía con la que los estudiantes y el profesorado podrán recordar el funcionamiento de todos los softwares utilizados durante el grado (Excel, Origin, Avogadro, ChemSketch, Vesta, X´pert, Checkell, Hyperchem y Fullprof), pudiendo aprender además aquello que no se asimiló bien o lo que nunca se llegó a conocer de estos programas. Este material está ya a disposición de todos los estudiantes de la UCM y de otras universidades en el canal QuimIsasi (https://www.youtube.com/channel/UCNG3-lLP2AetTksEBC0hAw) en el espacio de título "Material audiovisual de uso en asignaturas prácticas de grados que tratan la Química", siendo de suma utilidad para el alumnado que vaya a cursar o que cursará diferentes asignaturas prácticas y teórico-prácticas incluidas en grados y dobles grados que tratan la Química. El análisis y evaluación del material audiovisual elaborado podrá permitir un aprendizaje más eficaz del manejo de distintos programas que, como se verá, va a permitir llevar a cabo: cálculos generales y estadísticos, creación de bases de datos, dibujos de moléculas y su simetría, representación de estructuras de compuestos inorgánicos/orgánicos y cálculos de parámetros de celdilla de esas estructuras o de sus momentos magnéticos.
Structural and cathodoluminiscent properties of Zr0.95Ce0.05O2 nanopowders prepared by sol–gel and template methods
(Journal of Luminescence, 2011) Fernández Castillo, Jesús; Isasi Marín, Josefa; Pérez Estébanez, Marta; Aldama, Iván; Arévalo, Pablo; Díaz-Guerra Viejo, Carlos
Nanopowders of Zr0.95Ce0.05O2 composition have been prepared by a standard Pechini-type sol–gel process and by means of a colloidal crystal template approach. In the latter method, inverse opal Zr0.95Ce0.05O2 powders were fabricated employing poly(methylmethacrylate) (PMMA) colloidal crystals as a template.The effects of the two different synthesis routes on the structure and microstructural characteristics of the prepared nanopowders were evaluated by X-ray diffraction and scanning electron microscopy. For both preparation routes, the X-ray diffraction analysis has shown that a tetragonal fluorite structure is formed with a crystallite size of 35–40 nm. The scanning electron microscopy measurements indicate that the powder obtained by the sol–gel Pechini-type process is comprised of nanoparticles that are arranged in agglomerates with shape and size relatively uniform whereas the inverse opal Zr0.95Ce0.05O2 nanopowders exhibit the formation of macropores with a mean size of 100 nm. The cathodoluminescence spectra of the prepared Zr0.95Ce0.05O2 nanomaterials have been measured in the 300–800 nm wavelength range. The powder prepared by sol–gel method yields a broad emission band centered at 482nm whereas the emission from the inverse opal preparation is considerably less intense.
A systematic study of Nasicon-type Li1+xMxTi2-x(PO4)3 (M:Cr, Al, Fe) by neutron diffraction and impedance spectroscopy
(Solid State Ionics, 2014) Pérez Estébanez, Marta; Isasi Marín, Josefa; Rivera Calzada, Alberto Carlos; Tobbens, Daniel; León Yebra, Carlos
A systematic study of Li1+ xMxTi2 − x(PO4)3 with M=Al, Cr and Fe and 0 ≤ x ≤ 1 has been carried out by X-ray and neutron powder diffraction and by impedance spectroscopy. The analysis of the diffraction data allowed us to describe the disposition of the lithium atoms within the structure. They were found to occupy two different positions, the well-known M1 and a new position called M2′. The addition of trivalent metals into the LiTi2(PO4)3 compound, even in small amount, gives rise to the liberation of the M1 sites and simultaneous occupation of the M2′ sites. This situation becomes more pronounced as the substituent content increases, meaning a higher delocalization of lithium atoms within the structure.Moreover, rising temperature also provokes the movement of lithium fromM1 to M2′. The impedance spectroscopy measurements allowed us to relate the electrical properties to the observations of the crystal structure. Both dc bulk and grain boundary ionic conductivity showa thermally activated behavior, and their values increase with substituent content until compositions of x= 0.2–0.3. The activation energy for bulk dc conductivity hardly changes with the substitution, and the main factor affecting the variation of the ionic conductivity is the pre-exponential factor. We find indeed a correlation between the pre-exponential factor and the degree of disorder of the lithium atoms in the structure as determined from neutron diffraction data. The highest conductivity was found in the sample Li1.3Al0.3Ti1.7(PO4)3 with a value of 6.2 × 10−3 S cm−1 at room temperature and activation energy of 0.30 eV, which is comparable with those measured in the best ionic conductors reported to date.
Comparative study of core-shell nanostructures based on amino-functionalized Fe-4@SiO2 and CoFe2O4@SiO2 nanocomposites
(Journal of alloys and compounds, 2018) Arévalo Cid, Pablo; Isasi Marín, Josefa; Martín Hernández, Fátima
Fe3O4@SiO2 and CoFe2O4@SiO2 and their corresponding amino-functionalized nanocomposites were successfully synthesized by a process of two steps including the preparation by coprecipitation or hydrothermal synthesis of the corresponding magnetic cores, the coating of its surface with a silica coating followed by its subsequent functionalization with 3-aminopropyltriethoxysilane (APTES). All magnetic samples were characterized by XRD using FULPROFF program, FTIR analysis, TEM and M-H hysteresis loops. The results showed diffraction maxima indexed in a cubic symmetry of S. G. Fd-3m with Z = 8 compatible with an inverse spinel-type structure. FTIR spectra of all samples show the characteristic bands of the magnetic cores and others bands corresponding to the asymmetric vibration of O-Si-O and Si-O-Si bonds of silica. The TEM images confirm that all the nanoparticles are coated, finding the largest thickness of the coating in the Fe3O4 sample prepared hydrothermally, which are the smaller ones. An expected reduction of the saturation magnetization of the magnetic cores is achieved with the coating and functionalization, although the behaviour of the Fe3O4 -samples remains practically superparamagnetic while the corresponding ones of cobalt are still ferrimagnetic. Fe3O4 nanocomposites respond to more quickly in the presence of an external magnetic field, something important against the removal of contaminating species in aqueous media. UV-Vis spectroscopy studies confirm the adsorption capacity of Cu2+ in aqueous solutions of the prepared nanocomposites, having found that a small thickness of the coating leads a greater adsorption, so that the best adsorption is found for CPFe3O4@SiO2-APTES nanocomposite. (C) 2018 Elsevier B.V. All rights reserved.
Structural, magnetic and luminescent characteristics of Pr3+-doped ZrO2 powders synthesized by a sol–gel method
(Journal of Physics D: Applied physics, 2009) Isasi Marín, Josefa; Pérez Estébanez, Marta; Díaz-Guerra Viejo, Carlos; Fernández Castillo, Jesús; Correcher, Virgilio; Cuervo Rodríguez, María Rocío
The structural, magnetic and luminescence properties of praseodymium-doped zirconia powders of compositions Pr0.03Zr0.97O2 and Pr0.05Zr0.95O2 synthesized by a sol–gel process have been investigated. X-ray diffraction patterns indicate that these materials crystallize in a tetragonal fluorite-type structure. Scanning electron microscopy shows that the powders exhibit an agglomerated microcrystalline structure and the grain size may be in the order of 5–20μm. The study of the magnetic properties of these doped metal oxides indicates a Curie–Weiss behaviour in the temperature range (100–300)K that allow us to estimate an effective magnetic moment of 3.51μB, which indicates the presence of Pr3+ in the grown samples. Cathodoluminescence spectra recorded at temperatures between 85 and 295K show emission peaks that can be attributed to transitions between different states within the 4f2 configuration of Pr3+ ions incorporated in the zirconia crystal lattice. Thermoluminescence measured at temperatures ranging from 373 to 773K and at 550 nm wavelength show an intense and broad peak around 653K for the Pr-doped zirconia which is not observed in the undoped material.
Project number: PIMCD207/23-24
Ciencia en abierto: Química para remedios caseros
(2024) Isasi Marín, Josefa; Alba Isasi, Carlos; Alba Isasi, Pablo; Cáceres Ramos, Silvia; Espada Morán, Luis; Fernández-Ramos, Miguel; Hernán García, Esther; Iuliana Ionita, Andreea; Rapp Diez de la Cortina, María; Valera Fernández, José Ignacio; Villa García, Isabel; Megía López, Juan Antonio; Piedrabuena Martín, María; Isasi Marín, Josefa
En la convocatoria de proyectos de innovación 2023-2024 se recogía que el objeto principal de esa convocatoria era fomentar el esfuerzo de la comunidad universitaria hacia la mejora de la enseñanza y del aprendizaje de los estudiantes a partir del trabajo realizado por grupos de trabajo colaborativos. Nuestro equipo de trabajo es un grupo colaborativo que lleva años trabajando en la elaboración y puesta a punto de materiales digitales que evidencian el papel de la Química, sus contenidos y su investigación en ese escenario que nos proporciona hoy la Ciencia abierta o Ciencia de la ciudadanía. En su momento, se trabajó para poner en funcionamiento el canal de YouTube QuimIsasi. A lo largo de los años, a este canal se han ido subiendo distintos tipos de materiales digitales divulgativos que, agrupados en espacios de títulos diferentes, dan cuenta de experimentos sencillos de Química básica, de presentaciones explicativas que aluden al fundamento y utilidad de distintas técnicas de caracterización estructural de muestras de materiales o al desarrollo de investigaciones mucho más avanzadas. En esa misma línea y ahora para atraer la atención del estudiantado hacia la UCM, en el desarrollo de este proyecto hemos elaborado un conjunto de materiales digitales editados en formato de 10 vídeos tipo TikTok para evidenciar que la Química y sus acciones están no sólo en los laboratorios, sino que se puede encontrar incluso en casa ya que cualquier remedio casero está claramente emparentado con la Química y con su acción, hasta tal punto, que ya no se podrá pensar que es la magia la responsable del cambio. En opinión del equipo de trabajo, se necesita ser líderes en el desarrollo de propuestas de innovación que, con el sello Complutense, atraigan el interés de un público diversificado. Sin duda se trata de un proyecto innovador que va a repercutir de forma positiva en la mejora de la calidad docente al entenderse que nuestro equipo de trabajo ha sabido adaptarse a los tiempos, fomentando así el interés del alumnado por la Química y sus contenidos y haciendo posible que, en un futuro cercano, parte de ese alumnado no universitario pudiera elegir cursar grados en la UCM que tengan que ver con la Química.
Spark plasma versus conventional sintering in the electrical properties of Nasicon-type materials
(Journal of Alloys and Compounds, 2015) Pérez Estébanez, Marta; Isasi Marín, Josefa; Rivera Calzada, Alberto Carlos; León Yebra, Carlos; Nygren, Mats
Li1-xMxTi2-x(PO4)3 powders with x = 0 and 0.3 and M = Al, Cr and Fe have been sintered by conventional sintering (CS) and Spark Plasma Sintering (SPS), and the electrical properties have been compared. The use of SPS allows preparing samples with higher density at lower temperature and shorter time than the CS, avoiding segregation of secondary phases and with reduced crystallite size. Thei ntroduction of aluminum, chromium and iron in the LiTi2(PO4)3 (LTP) clearly enhances ionic conductivity even if the samples have similar densities. Despite the different level of density reached with CS and SPS, the activation energies of dc and grain boundary contributions are very similar and the differences in ionic conductivity are determined by pre-exponential factors. The samples produced by SPS showed a well-defined grain boundary meaning a more homogenous electrical contact.
Síntesis mediante química sol gel de compuestos Li_(1+x)M^(III)_(x)Ti_(2-x)(PO_(4))_(3) con estructura tipo Nasicon. Estudio de la relación microestructura-propiedades eléctricas
(Boletín de la Sociedad Española de Cerámica y Vidrio, 2010) Pérez Estébanez, Marta; Rivera Calzada, Alberto Carlos; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo; Isasi Marín, Josefa
Haciendo uso de la química sol-gel, se han preparado ortofosfatos de composición LiTi_(2)(PO_(4))_(3) y Li_(1.05)(Cr/Fe)_(0.05)Ti_(1.95)(PO_(4))_(3) a temperaturas moderadas mediante el método Pechini. Estas fases han sido caracterizadas estructural y microestructuralmente por difracción de rayos X de polvo y microscopía electrónica de barrido (SEM), encontrándose que todas cristalizan en una estructura tipo NASICON, con parámetros de red muy similares. El dopaje con Fe y Cr permite aumentar la densidad de las muestras en la sinterización, mejorando de forma apreciable su conductividad iónica. Se ha observado un incremento de hasta cuatro órdenes de magnitud en la conductividad a temperatura ambiente obteniéndose una energía de activación de 0.29 eV para el material dopado con Cr.