Person:
Fernández Sánchez, Paloma

First Name

Paloma

Last Name

Fernández Sánchez

URI

https://hdl.handle.net/20.500.14352/74998

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Física de Materiales

Area

Ciencia de los Materiales e Ingeniería Metalúrgica

Identifiers

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Now showing 1 - 10 of 22

Fabrication and characterization of ZnO:CuO electronic composites for their application in sensing processes
(IEEE sensors journal, 2021) Ramos Ramos, D.J.; Sotillo Buzarra, Belén; Urbieta Quiroga, Ana Irene; Fernández Sánchez, Paloma
Sensing behaviour of samples belonging to the system ZnO:CuO has been investigated. Samples with different proportions of ZnO and CuO have been sintered and exposed to a reducing agent as ethanol (C_2H_5OH). All the samples have been characterized not only from the point of view of the sensing properties but also regarding morphology, composition, crystallinity and luminescent properties in order to correlate these properties to the sensing behaviour. Sensitivity, response times, recovery and stability have been measured under exposure to ethanol vapour in concentrations 800, 4700 and 16000 ppm. Sensing cycles have been performed at three different temperatures: 25, 50 and 100 degrees C.
Dual regimes of ion migration in high repetition rate femtosecond laser inscribed waveguides
(IEEE Photonics technology letters, 2015) Teddy Fernández, Toney; Sotillo Buzarra, Belén; del Hoyo, Jesús; Valles, Juan Antonio; Martínez Vázquez, Rebeca; Fernández Sánchez, Paloma; Solis, Javier
Ion migration in high repetition rate femtosecond laser inscribed waveguides is currently being reported in different optical glasses. For the first time, we discuss and experimentally demonstrate the presence of two regimes of ion migration found in laser written waveguides. Regime-I corresponds to the initial waveguide formation mainly via light element migration (in our case atomic weight < 31 u), whereas regime-II majorly corresponds to the movement of heavy elements. This behavior brings attention to a problem which has never been analyzed before and that affects the laser written active waveguides, in which active ions migrate changing their local spectroscopic properties. The migration of active ions may in fact detune the predesigned optimal values of active photonic devices. This letter experimentally demonstrate this problem and provides solutions to avert it.
Control of waveguide properties by tuning femtosecond laser induced compositional changes
(Applied physics letters, 2014) Del Hoyo Muñoz, Jesús; Martínez Vázquez, Rebeca; Sotillo Buzarra, Belén; Teddy Fernández, Toney; Siegel, Jan; Fernández Sánchez, Paloma; Osellame, Roberto; Solís Céspedes, Francisco Javier
Local compositional changes induced by high repetition rate fs-laser irradiation can be used to produce high performance optical waveguides in phosphate-based glasses. The waveguide refractive index contrast is determined by the local concentration of La, which can be changed by the action of the writing laser pulses. In this work, we have investigated the degree of control that can be exerted using this waveguide writing mechanism over the cross-section of the guiding region, and the local refractive index and compositional changes induced. These variables can be smoothly controlled via processing parameters using the slit shaping technique with moderate Numerical Aperture (NA 0.68) writing optics. The combined use of X-ray microanalysis and near field refractive index profilometry evidences a neat linear correlation between local La content and refractive index increase over a broad Δn interval (>3 x 10^2). This result further confirms the feasibility of generating efficient, integrated optics elements via spatially selective modification of the glass composition.
Competition effects during femtosecond laser induced element redistribution in Ba- and La-migration based laser written waveguides
(Materials, 2021) Macías Montero, Manuel; Moreno Zárate, Pedro; Muñoz, Francisco; Sotillo Buzarra, Belén; García Pardo, Marina; Serna, Rosalia; Fernández Sánchez, Paloma; Solís, Javier
Fs-laser induced element redistribution (FLIER) has been a subject of intensive research in recent years. Its application to various types of glasses has already resulted in the production of efficient optical waveguides, tappers, amplifiers and lasers. Most of the work reported on FLIER-based waveguides refers to structures produced by the cross-migration of alkali (Na, K) and lanthanides (mostly La). The latter elements act as refractive index carrying elements. Herein, we report the production of Ba-based, FLIER-waveguides in phosphate glass with an index contrast > 10^(-2). Phosphate glasses modified with the same amount of Na_2O and K_2O, and variable amounts of BaO and/or La_2O_3 were used to produce the FLIER-waveguides with Ba and or La acting as index carriers. Ba-only modified glasses show a waveguide writing threshold and light guiding performance comparable to that of La-based structures. However, mixed Ba-La glasses show a much higher element migration threshold, and much smaller compositionally modified regions. This behavior is consistent with a competition effect in the cross-migration of both elements (Ba and La) against the alkalis. Such an effect can be applied to inhibit undesired element redistribution effects in fs-laser processing applications in multicomponent glasses.
Project number: 198
Aula de juegos para el fomento del aprendizaje autónomo y la creatividad
(2016) Fernández Sánchez, Paloma; López Orozco, José Antonio; Maestre Varea, David; Hidalgo Alcalde, Pedro; Besada Portas, Eva; Sotillo Buzarra, Belén; Neira Gómez, Andrea Paulette; Pereyra Ocampo, Laura Victoria; de las Heras de la Campa, Pablo
El juego como modo de aprendizaje es algo inherente no sólo al ser humano sino, en general, al reino animal. Para cualquier mamífero el juego constituye la forma de aprendizaje fundamental. A través del juego se aprende a luchar, a defenderse y las normas básicas de convivencia en la manada. Sin embargo en el ser humano, juego y aprendizaje se han ido desligando progresivamente, excepto en las etapas iniciales de crecimiento, en las que los niños siguen aprendiendo los comportamientos más básicos a través de juegos. A medida que vamos avanzando en la escuela, se va abandonando el juego, contraponiendo las actividades lúdicas a las estrictamente relacionadas con el trabajo, con un aprendizaje más costoso. De esta forma al llegar a la etapa universitaria, el juego se ha abandonado por completo como forma de aprendizaje. No es fácil definir lo que es el juego o cuáles son sus características. Tiene una fuerte componente cultural, actividades que unas culturas pueden considerar eminentemente lúdicas, no lo serán en contextos culturales distintos. No obstante, una vez admitida la importancia del juego en el desarrollo de la personalidad, sí podemos establecer algunas de las funciones básicas que el juego desempeña en el ser humano, en relación con el perfeccionamiento y adquisición de habilidades tanto cognitivas como sociales o conductuales. El juego facilita la integración de experiencias en la conducta, contribuye a inhibir conductas no admitidas socialmente y a reforzar aquéllas con una mayor aceptación dentro del marco cultural de referencia. Mejora considerablemente la interacción social y la adquisición de las habilidades básicas necesarias para que se produzca dicha interacción de modo satisfactorio. En el caso de juegos competitivos, enseña a manejar situaciones desfavorables, a soportar y superar la frustración. Tradicionalmente, los juegos se han usado en los niveles iniciales de enseñanza, sin embargo son una poderosa herramienta también en el nivel universitario, especialmente para promover el aprendizaje activo y la adquisición de variadas competencias profesionales. En este proyecto se plantea la elaboración de una herramienta para la creación de simuladores de juegos de mesa con fines didácticos.
Project number: 104
Diseño de herramientas de dinamización del aula adaptables a distintos escenarios de docencia (presenciales o en línea)
(2022) Fernández Sánchez, Paloma; Arroyo Bujase, Alex Miguel; Díaz-Guerra Viejo, Carlos; Fernández Jiménez, Rubén; Garrido Díaz, Esther; Hidalgo Alcalde, Pedro; Panis Maramba, Carlo Dexter; Romero Izquierdo, Carlos; Sotillo Buzarra, Belén; Urbieta Quiroga, Ana Irene
Preferential Growth of ZnO Micro- and Nanostructure Assemblies on Fs-Laser-Induced Periodic Structures
(Nanomaterials, 2020) Sotillo Buzarra, Belén; Ariza García, Rocío; Siegel, Jan; Solis, Javier; Fernández Sánchez, Paloma
In this work, we demonstrate the use of laser-induced periodic surface structures (LIPSS) as templates for the selective growth of ordered micro- and nanostructures of ZnO. Different types of LIPSS were first produced in Si-(100) substrates including ablative low-frequency spatial (LSF) LIPSS, amorphous-crystalline (a–c) LIPSS, and black silicon structures. These laser-structured substrates were subsequently used for depositing ZnO using the vapor–solid (VS) method in order to analyze the formation of organized ZnO structures. We used scanning electron microscopy and micro-Raman spectroscopy to assess the morphological and structural characteristics of the ZnO micro/nano-assemblies obtained and to identify the characteristics of the laser-structured substrates inducing the preferential deposition of ZnO. The formation of aligned assemblies of micro- and nanocrystals of ZnO was successfully achieved on LSF-LIPSS and a–c LIPSS. These results point toward a feasible route for generating well aligned assemblies of semiconductor micro- and nanostructures of good quality by the VS method on substrates, where the effect of lattice mismatch is reduced by laser-induced local disorder and likely by a small increase of surface roughness.
Role of the La/K Compositional Ratio in the Properties of Waveguides Written by Fs-Laser Induced Element Redistribution in Phosphate-Based Glasses
(Materials, 2020) Moreno-Zarate, Pedro; Muñoz, Francisco; Sotillo Buzarra, Belén; Macias-Montero, Manuel; Atienzar, Julia; Garcia-Pardo, Marina; Fernández Sánchez, Paloma; Serna, Rosalia; Solis, Javier
The local modification of the composition of glasses by high repetition femtosecond laser irradiation is an attractive method for producing photonic devices. Recently, the successful production of waveguides with a refractive index contrast (Δn) above 10−2 by fs-laser writing has been demonstrated in phosphate glasses containing La2O3 and K2O modifiers. This large index contrast has been related to a local enrichment in lanthanum in the light guiding region accompanied by a depletion in potassium. In this work, we have studied the influence of the initial glass composition on the performance of waveguides that are produced by fs-laser induced element redistribution (FLIER) in phosphate-based samples with different La and K concentrations. We have analyzed the contribution to the electronic polarizability of the different glass constituents based on refractive index measurements of the untreated samples, and used it to estimate the expected index contrast caused by the experimentally measured local compositional changes in laser written guiding structures. These estimated values have been compared to experimental ones that are derived from near field images of the guided modes with an excellent agreement. Therefore, we have developed a method to estimate before-hand the expected index contrast in fs-laser written waveguides via FLIER for a given glass composition. The obtained results stress the importance of considering the contribution to the polarizability of all the moving species when computing the expected refractive index changes that are caused by FLIER processes.
Influence of Indium doping in the morphology of ZnS nanostructures grown by a vapor-solid method
(CrystEngComm, 2013) Sotillo Buzarra, Belén; Ortega Villafuerte, Yanicet; Fernández Sánchez, Paloma; Piqueras De Noriega, Francisco Javier
Pure and In-doped ZnS structures have been grown using a VS method. Thermal treatments have been performed at temperatures ranging from 1000 to 1200 °C, during 15 to 17 hours in a N2 overpressure environment. Nanowires and nanoribbons are the main kind of structures obtained for pure ZnS, depending on the deposition temperature. In the case of ZnS:In, nano- and microswords, nanoribbons, hierarchical structures and nanoplates are obtained, depending on the In content in the starting material and on the deposition temperature. Nanoplates are the dominant structures for the higher In content. The influence of the impurity incorporation on the morphology of the structures has been studied by transmission electron microscopy. While in pure ZnS wires and ribbons two main growth directions are observed ([0001] and [10-10]), indium doped structures show a greater variety of morphologies associated with different growth behavior.
LTA zeolite particles functionalized with nanomagnetite for effective recovery of dysprosium from liquid solutions
(Microporous and Mesoporous Materials, 2024) Alcaraz, Lorena; Sotillo Buzarra, Belén; Iglesias, Carlos; López, Félix A.; Fernández Sánchez, Paloma; Belviso, Claudia; Urbieta Quiroga, Ana Irene
Rare earth elements (REEs) as Dysprosium (Dy) are critical elements for the fabrication of components in many green energy technologies, from electric vehicles to wind turbines. Consequently, there is an increasing interest in creating sustainable and effective materials for the recovery and recycling of these elements. Zeolite materials have demonstrated a high affinity and selectivity for REEs. Thus, this paper aims to study the use of a synthetic LTA zeolite functionalized with nanomagnetite for Dy absorption, including a complete characterization of the synthetic zeolite, the kinetics and the factors affecting the adsorption efficiency. The maximum adsorption capacity reaches a value around 35 mg of Dy per gram of zeolite. The results from the adsorption isotherms and kinetic study revealed a good agreement with both Langmuir and Temkin models and pseudo-second-order kinetics. Furthermore, the thermodynamic analysis suggests that the adsorption of Dy onto the zeolite is a spontaneous and favorable process. The findings from this work could provide insights into the design and optimization of zeolite-based processes for REE recovery and recycling, contributing to the development of a more sustainable and circular economy.