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[EN] Temperature plays a critical role in regulating body mechanisms and indicating inflammatory processes. Local temperature increments above 42 °C are shown to kill cancer cells in tumorous tissue, leading to the development of nanoparticle-mediated thermo-therapeutic strategies for fighting oncological diseases. Remarkably, these therapeutic effects can occur without macroscopic temperature rise, suggesting localized nanoparticle heating, and minimizing side effects on healthy tissues. Nanothermometry has received considerable attention as a means of developing nanothermosensing approaches to monitor the temperature at the core of nanoparticle atoms inside cells. In this study, a label-free, direct, and universal nanoscale thermometry is proposed to monitor the thermal processes of nanoparticles under photoexcitation in the tumor environment. Gold-iron oxide nanohybrids are utilized as multifunctional photothermal agents internalized in a 3D tumor model of glioblastoma that mimics the in vivo scenario. The local temperature under near-infrared photo-excitation is monitored by X-ray absorption spectroscopy (XAS) at the Au L-edge (11 919 eV) to obtain their temperature in cells, deepening the knowledge of nanothermal tumor treatments. This nanothermometric approach demonstrates its potential in detecting high nanothermal changes in tumor-mimicking tissues. It offers a notable advantage by enabling thermal sensing of any element, effectively transforming any material into a nanothermometer within biological environments.

This paper explores the possibility to measure changes in internal stress in ferromagnetic steels using magnetostatic methods. The device consists of a permanent magnet placed close to the steel piece and a magnetic probe between both elements. The magnetostatic field measured by using the probe is partially due to the magnetization of the steel piece. Internal stress variations in the steel alter its magnetic permeability due to the magnetoelastic effect, varying the magnetostatic field measured by using the probe. For the device we present here, the relative variation of the measured magnetic field is of the order of 1.7 × 10-5/MPa of internal stress.

[EN] In this report, a method is proposed for determining the fluctuations of physical and structural properties in metallic ferromagnetic samples by magnetic scanning. The method is based on the shielding of a circular loop electromagnetic field source using a ferromagnetic and metallic sheet. The shielding of the electromagnetic field depends on the field frequency and amplitude as well as the electrical conductivity and magnetic permeability of the sheet. The proposed method does not require winding around the sheet. The experimental AC shielding results are reported.

[EN] The increasing environmental protection demand has prompted thedevelopment of passive thermal regulation systems that reduce temperaturefluctuations in buildings. Here, it is demonstrated that the heat generated bythe sun can trigger a spin crossover (SCO) in a molecule-base material,resulting in a concomitant color variation (from pink to white) and a phasetransition. This leads to a cooling effect with respect to other thermochromicmaterials. In addition, when the material is cooled, a dampening of thetemperature decrease is produced. Therefore, these materials can potentiallybe implemented for passive temperature control in buildings. Furthermore,SCO materials are remarkably stable upon cycling and highly versatile, whichallows for the design of compounds with properties tailored for the desiredclimatic conditions and comfortable temperature.

We show the efficiency in the preparation of >95 % dense ZnO ceramics by cold sintering process through the incorporation of ZnO nanoparticles in the 1−10 wt% range at temperatures of 170 °C, pressures of 750 MPa and a pellet height/diameter ratio of 0.38. Morphological, structural and physical properties are dependent on the amount of ZnO nanoparticles incorporated into the system. After the densification by cold sintering process, ZnO ceramics show a reduction of the average valence indicating the deficiency of oxygen, similar to ceramics sintered by the conventional route. Besides, the generation of structural disorder and modifications into the ZnO lattice are identified in sintered ceramics, inducing intrinsic defects related to the loss of oxygen ions, the diffusion of zinc and zinc vacancies, which depend on the sintering process and the starting powders. These characteristics influence the final functional properties of the sintered ZnO ceramics, such as the visible photoluminescence signal.

[EN] In this study, we evaluate the magnetic properties and cytotoxic effect of magnetic nanoparticles (MNPs) based on magnetite and Mn, Co and Ni ferrites, obtained by electrochemical synthesis. These nanoparticles have almost spherical shape and an mode size of 9±1 nm. The electrochemical synthesis produces a single crystallographic phase with a spinel-like structure in all cases. Magnetization saturation at room temperature varies with the composition of the ferrites from M S (Fe3O4) > M S (MnFe2O4) > M S (CoFe2O4) > M S (NiFe2O4). Ferrite MNPs present low magnetic remanence indicating a superparamagnetic-like response at room temperature. However, the different values of magnetic anisotropy and size produce variations in the values of coercivity and susceptibility of the ferrite MNPs. The cytotoxicity of the different ferrites was evaluated by internalizing MNP in HeLa cancer cells. Although magnetite and Mn ferrite present low toxicity for all the concentrations studied, significant cytotoxic effect were observed when incubating the cells with high concentration of Co and Ni ferrites.

It is shown that magnetic forces as the force exerted on electron spins at rest, account for both the transverse spin imbalance typical of spin Hall effect and the transverse charge imbalance associated with pure spin currents (inverse spin Hall effect). Considering that for stationary currents the laboratory reference frame, and those for which the spin up and spin down carriers are at rest, are inertial systems one can easily find the forces exerted by the lattice on both spin sub-bands, as well as the force between sub-bands.

©2019 American Physical Society This work was supported by the Spanish Ministry of Innovation, Science, and Technology and the Spanish Ministry of Economy and Competitiveness through Research Projects No. CSD2009-00013, No. TSI-020100-2011-280, No. MAT2011-23068, No. MAT2012-37109-C02-01, No. MAT2014-54372-R, and No. MAT2017-86450-C04-R., We describe here a type of magnetoresistance that takes place in naturally layered and outstanding ordered single phase manganites that may be mediated by magnon excitation. In particular, we show the effect for the Ruddlesden-Popper compound, LaSr2Mn2O7 synthesized by ceramic method. This material exhibits, besides the conventional colossal magnetoresistance, another type of magnetoresistance at low temperature, associated with breaking of the A-type antiferromagnetic coupling of Mn-containing planes. Excitation of magnons or application of a magnetic field breaks this antiparallel alignment so that some electrons, initially confined on the planes, become itinerant along the interplain directions through a double exchange mechanism, giving rise to resistance variations of the order of similar to 60% for polycrystalline samples. The effect described here might be present in other types of manganites exhibiting a natural layered structure, opening up the possibility of developing magnetoresistive devices based on antiferromagnetic oxide materials without requiring artificial multilayered structures., Ministerio de Economia y Competitividad (MINECO), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

[EN] We describe here a type of magnetoresistance that takes place in naturally layered and outstanding ordered single phase manganites that may be mediated by magnon excitation. In particular, we show the effect for the Ruddlesden-Popper compound, LaSr2Mn2O7 synthesized by ceramic method. This material exhibits, besides the conventional colossal magnetoresistance, another type of magnetoresistance at low temperature, associated with breaking of the A-type antiferromagnetic coupling of Mn-containing planes. Excitation of magnons or application of a magnetic field breaks this antiparallel alignment so that some electrons, initially confined on the planes, become itinerant along the interplain directions through a double exchange mechanism, giving rise to resistance variations of the order of~60% for polycrystalline samples. The effect described heremight be present in other types of manganites exhibiting a natural layered structure, opening up the possibility of developing magnetoresistive devices based on antiferromagnetic oxide materials without requiring artificial multilayered structures.

[EN] Efficient and low cost detection of harmful volatile organic compounds (VOCs) is a major health and environmental need in industrialized societies. For this, tailor-made porous coordination polymers are emerging as promising molecular sensing materials thanks to their responsivity to a wide variety of external stimuli and could be used to complement conventional sensors. Here, a non-porous crystalline 1D Fe(ii) coordination polymer acting as a porous acetonitrile host is presented. The desorption of interstitial acetonitrile is accompanied by magneto-structural transitions easily detectable in the optical and electronic properties of the material. This structural switch and therefore its (opto)electronic readout are reversible under exposure of the crystal to acetonitrile vapor. This simple and robust iron-based coordination polymer could be ideally suited for the construction of multifunctional sensor devices for volatile acetonitrile and potentially for other organic compounds.

[EN] We analyze the contribution of the inhomogeneous magnetic field induced by an electrical current to the spin Hall effect in metals. The Zeeman coupling between the field and the electron spin leads to a spin dependent force, and to spin accumulation at the edges. We compare the effect of this relativistic correction to the electron dynamics to the features induced by the spin-orbit interaction. The effect of current induced magnetic fields on the spin Hall effect can be comparable to the extrinsic contribution from the spin-orbit interaction, although it does not require the presence of heavy elements with a strong spin-orbit interaction.

In this paper Co/CoO thick layers (hundreds of nanometers) of different porosity and oxidation degree were prepared in a magnetron sputtering deposition process by tailoring the DC sputtering power, as well as the process gas and target composition. The control of the synthesis parameters allowed the nanostructuration of the films with a singular distribution of closed pores and a controlled amount of CoO. We observed an exchange bias field of 2.8 KOe for porous Co/CoO composites, similar to Co/CoO bilayers but for coatings thicker than 300 nm. Besides, it was observed that the coating presents bistable magnetic features when cooled under zero field conditions as a result of the unusual exchange coupling.

En esta tesis se han estudiado dos tipos de sistemas cuyas propiedades proceden del comportamiento colectivo de los electrones en la banda de conducción, como son los superconductores y los sistemas plasmónicos. Ambos son ejemplos paradigmáticos de fenómenos colectivos en la banda de conducción y resultan de un gran interés tanto en el terreno de la investigación fundamental como de cara a aplicaciones tecnológicas. Mientras que en el caso de los superconductores hay una interacción mutua entre electrones, ésta no existe para los plasmones. Así, aunque ambos efectos se originan en la banda de conducción, las propiedades características de cada uno de estos sistemas son muy diferentes. Los superconductores estudiados han sido monocristales dopados con níquel del compuesto BaFe2As2. Estos cristales forman parte de la clase de superconductores descubierta más recientemente, los nicturos de hierro. En este tipo de materiales la superconductividad se consigue a partir del dopado del compuesto padre (p. ej. el BaFe2As2 en nuestro caso), de forma análoga a otros sistemas superconductores bien conocidos como son los cupratos. Sin embargo, al contrario que en estos últimos compuestos, la presencia de átomos ferromagnéticos (como el propio hierro, o elementos dopantes como el níquel y el cobalto) en la estructura cristalina no suprime la superconductividad..., In this thesis, two different kinds of systems whose properties arise from a colective behavior of conduction band electrons have been studied. These systems are superconductors and plasmonic materials, both being paradigmatic examples of colective phenomena in the conduction band. These systems are of great interest in the fields of basic research and techonological applications. While for superconductors there is a mutual interaction between electrons, that is not the case for plasmons. Therefore, even when both effects emerge from the conduction band, the characteristic features of each system are quite different. The superconductors studied in this thesis are nickel-doped single crystals of the BaFe2As2 compound. These crystals belong to the most recently discovered group of superconductors: the iron pnictides. In these materials, superconductivity is achieved through doping of the parent compound (i. e. BaFe2As2 in our case), in a similar way than in other wellknown superconducting systems as cuprates. However, the presence of ferromagnetic atoms (such as iron in the parent structure or dopants like nickel and cobalt) in the iron pnictides does not suppress superconductivity, as it happens in cuprates...

En los últimos años el estudio y aplicación de las nanopartículas magneto-plasmónicas ha despertado un enorme interés en la comunidad científica. El uso de este tipo de materiales en aplicaciones biomédicas abre la puerta a un gran número de nuevas técnicas de diagnóstico y tratamiento. Sin embargo existe una carencia de materiales biocompatibles que presenten propiedades magneto-plasmónicas adecuadas. En la presente tesis se abordará en primer lugar la síntesis y caracterización de estructuras magneto-plasmónicas híbridas basadas en nanocilindros de Au, nanopartículas magnéticas de diferentes ferritas y sílice. La síntesis de estas nanoestructuras se realizó desarrollando un nuevo método de hibridación que aprovecha el entrecruzamiento que tiene lugar entre las moléculas de polietilenglicol y el ácido cítrico cuando se incluyen en los procesos de crecimiento de sílice como mecanismo de autoensamblado. Para ello la superficie de los nanocilindros de Au y de las nanopartículas de ferritas fueron recubiertas con polietilenglicol y ácido cítrico respectivamente y sometidas a un proceso de silanización conjunta. La estructura obtenida al final del proceso consiste en una geometría núcleo-satélite con los nanocilindros de Au en el centro y las nanopartículas de ferrita alrededor embebidas en una matriz de sílice. La síntesis individual de los componentes magnético y plasmónico, permitió ajustar individualmente sus propiedades antes de ser hibridizados en una estructura común. Sin embargo, aunque este tipo de nanoestructuras evitan la intercara entre las fases, aparece un cierto grado de interacción que obliga a considerar los posibles cambios en las propiedades magneto-plasmónicas del material resultante..., In the recent years, magneto-plasmonic nanoparticles have attracted increasing attention from the scientific community due to their promising properties and high applicability. Thanks to the development of new synthesis routes, it has been possible to use this kind of nanostructures in different biomedical applications such as dual imaging, combined treatments or biodetection. However, there is still a lack of biocompatible materials with suitable magneto-plasmonic features to translate all these advances to clinical studies. In this thesis, I propose a new sythesis to produce hybrid magneto-plasmonic nanoparticles based on Au nanorods, ferrite nanospheres and silica. The synthesis developed takes advantage of the cross-linking process between polyethilenglycol and citric acid during sol-gel reactions of sylanization, to drive the self-assembly between Au nanorods and ferrite nanospheres. Following such method, it was possible to obtain hybrid nanostructures composed by a Au nanorod in the core and ferrite nanospheres in satellite positions imbibed in a silica matrix. The individual synthesis of the components before hybridization enabled the fine tuning of their magnetic and plasmonic properties. Besides in this geometry there are not common interfaces between Au and ferrite, avoiding a direct interaction between them. However, due to the close proximity of the phases, it was important to study the effect of the short-distance interaction in the magneto-plasmonic properties...

[EN] We present here a study on the modification of morphological and plasmonic properties of Ag thin films deposited on glass substrates upon annealing in air at different temperatures. Initially, Ag films are continuous and exhibit extended surface plasmons with a resonant absorbance that depends on the film thickness. The dewetting process promotes the formation of nanoparticles with different sizes, shapes, and agglomerations states, besides a partial oxidation from Ag to AgO at surface level. The final Ag-AgO nanostructures are dependent on the annealing temperature and initial film thickness. The optical properties evolve from those typical of metallic films with high reflectivity and extended surface plasmon resonance toward localized surface plasmons characteristic of nanoparticles. The optical evolution and the final plasmonic response are evaluated according to the morphological and structural features of nanostructures.

Nanocrystalline textured EuO thin films are prepared by an oxygen loss process from a pure EuO bulk ceramic target through pulsed laser deposition in vacuum at room temperature. X-ray diffraction spectra evidence a well-defined diffraction peak corresponding to the EuO phase textured along the (1 1 0) direction. Analysis of the XRD peak profile indicates that the films are nanocrystalline (average crystallite size of 11 nm) with a compressive residual strain. The formation of stoichiometric EuO is further confirmed by a strong signal from Eu in the X-ray photoelectron spectra. The complex refractive index in the near infrared has been determined by spectroscopic ellipsometry and shows that the EuO films have a high transparency (k < 10) and a refractive index of 2.1. A band-gap shift of 0.25 eV is found with respect to the EuO bulk. These films, deposited by an accessible and efficient method, open a new route to produce EuO films with optical quality, suitable for NIR optoelectronic components.

In pulsed laser deposition, the laser irradiation wavelength and the substrate nature and temperature crucially affect the composition, crystallinity, structure and magnetic properties of the grown deposits. In this work, cobalt ferrite (CoFeO) thin films were deposited on Si (1 0 0) and SrTiO (1 0 0) single crystal substrates at room temperature and 770 K using laser wavelengths of 213, 532 and 1064 nm. The deposited films were characterized by atomic force microscopy to determine the surface morphology, by X-ray diffraction to examine their crystallinity, and by micro-Raman, scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray photoelectron and Mössbauer spectroscopies to investigate their composition and stoichiometry. Magnetic characterization was carried out by superconducting quantum interference device magnetometry. At 770 K and 1064 nm, the films consisted of single-crystal CoFeO ((1 0 0) orientation) when grown on SrTiO, and of polycrystalline CoFeO when grown on Si. The composition of the films became more complex at shorter wavelengths as they contained magnetite and other minority phases in different concentrations. The crystalline quality of the films also decreased with decreasing wavelength even including superparamagnetic species. In general, for the same wavelength, the deposits obtained at room temperature were less crystalline than those produced with the substrate heated at 770 K.

We here present a simple model of a vibrating sample magnetometer (VSM). The system allows recording magnetization curves at room temperature with a resolution of the order of 0.01 emu and is appropriated for macroscopic samples. The setup can be mounted with different configurations depending on the requirements of the sample to be measured (mass, saturation magnetization, saturation field, etc.). We also include here examples of curves obtained with our setup and comparison curves measured with a standard commercial VSM that confirms the reliability of our device.

En esta tesis se han estudiado dos tipos de sistemas cuyas propiedades proceden del comportamiento colectivo de los electrones en la banda de conducción, como son los superconductores y los sistemas plasmónicos. Ambos son ejemplos paradigmáticos de fenómenos colectivos en la banda de conducción y resultan de un gran interés tanto en el terreno de la investigación fundamental como de cara a aplicaciones tecnológicas. Mientras que en el caso de los superconductores hay una interacción mutua entre electrones, ésta no existe para los plasmones. Así, aunque ambos efectos se originan en la banda de conducción, las propiedades características de cada uno de estos sistemas son muy diferentes. Los superconductores estudiados han sido monocristales dopados con níquel del compuesto BaFe2As2. Estos cristales forman parte de la clase de superconductores descubierta más recientemente, los nicturos de hierro. En este tipo de materiales la superconductividad se consigue a partir del dopado del compuesto padre (p. ej. el BaFe2As2 en nuestro caso), de forma análoga a otros sistemas superconductores bien conocidos como son los cupratos. Sin embargo, al contrario que en estos últimos compuestos, la presencia de átomos ferromagnéticos (como el propio hierro, o elementos dopantes como el níquel y el cobalto) en la estructura cristalina no suprime la superconductividad...

En los últimos años el estudio y aplicación de las nanopartículas magneto-plasmónicas ha despertado un enorme interés en la comunidad científica. El uso de este tipo de materiales en aplicaciones biomédicas abre la puerta a un gran número de nuevas técnicas de diagnóstico y tratamiento. Sin embargo existe una carencia de materiales biocompatibles que presenten propiedades magneto-plasmónicas adecuadas. En la presente tesis se abordará en primer lugar la síntesis y caracterización de estructuras magneto-plasmónicas híbridas basadas en nanocilindros de Au, nanopartículas magnéticas de diferentes ferritas y sílice. La síntesis de estas nanoestructuras se realizó desarrollando un nuevo método de hibridación que aprovecha el entrecruzamiento que tiene lugar entre las moléculas de polietilenglicol y el ácido cítrico cuando se incluyen en los procesos de crecimiento de sílice como mecanismo de autoensamblado. Para ello la superficie de los nanocilindros de Au y de las nanopartículas de ferritas fueron recubiertas con polietilenglicol y ácido cítrico respectivamente y sometidas a un proceso de silanización conjunta. La estructura obtenida al final del proceso consiste en una geometría núcleo-satélite con los nanocilindros de Au en el centro y las nanopartículas de ferrita alrededor embebidas en una matriz de sílice. La síntesis individual de los componentes magnético y plasmónico, permitió ajustar individualmente sus propiedades antes de ser hibridizados en una estructura común. Sin embargo, aunque este tipo de nanoestructuras evitan la intercara entre las fases, aparece un cierto grado de interacción que obliga a considerar los posibles cambios en las propiedades magneto-plasmónicas del material resultante...

We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single-crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity.

Powders of (LaSr)MnO (LSM85) and (LaSr)MnO (LSM80) perovskites have been synthesized and characterized in detail, and then sintered to evaluate their electrical and magnetic properties at low temperatures and at near room temperature. Microstructural observations/analyses after the dilatometric essays show that the perovskites have compositions that deviate from the nominal ones. Furthermore, magnetic characterization of both samples reveals a ferromagnetic behavior with a Curie temperature above 300 K for LSM80 and of 260 K for LSM85. In addition, LSM85 is insulator from 15 up to 300 K, whereas LSM80 is metallic up to 160 K and insulator up to 300 K. This significant discrepancy of behaviour is attributable to structural and compositional differences between the two perovskites.

La presente invención se refiere a un material cerámico vítreo de albita y / o anortita, que presenta una sensación de calor térmico y su proceso de producción. Además, la presente invención se refiere al uso de este material vitrocerámico para la fabricación de productos cerámicos industriales, estructurales y ornamentales.

We explore here the effect of x-ray irradiation (7.7 keV) on Co-phthalocyanine (CoPc) thin films using surface plasmon resonance (SPR). We have found a small and partially reversible modification of the SPR spectra of CoPc in CoPc/Au bilayers upon irradiation. For a beam intensity of ∼10 photons • s • mm and an irradiation time of the order of 1 h, we estimate small variations of the order of ∼1-5% in the refractive index associated with the scattering of the x-rays with the soft matter. A Raman study of the irradiated regions did not show structural modifications, suggesting that the observed variations in the optical properties of the CoPc films are related to modifications of their electronic configuration.

The present invention relates to an albite and/or anorthite glass ceramic material, which exhibits a sensation of thermal warmth and its production process. Furthermore, the present invention relates to the use of this glass-ceramic material for the manufacturing of industrial, structural and ornamental ceramic products.

Magnetic nanobeads are synthesized by coprecipitation of hollow iron oxide nanoparticles and an amphiphilic polymer. The resulting nanobeads can be tuned in diameter and nanoparticle content. X-ray absorption near-edge structure (XANES) spectroscopy and superconducting quantum interferometer device (SQUID) characterization of the nanobeads reveal that they exhibit an increased effective magnetic anisotropy as compared to the individual nanoparticles, despite that no structural changes of the particles had occurred during the embedding process into the polymer. The spin-spin relaxation times of the pristine hollow nanoparticles and of the final magnetic nanobeads reveal a high R2 relaxivity of 206 s-1 mM-1 for the magnetic nanobeads. This result should enable their application as negative contrast enhancing agents in magnetic resonance imaging.

In this work, surface plasmon resonance (SPR) spectroscopy has been employed as a probe to study modifications in nanostructured systems based on Au. Those modifications include a) structural and morphological changes induced by annealing and b) electronic modifications upon X-ray irradiation. The use of SPR spectroscopy to follow the evolution of modifications in nanostructures (especially, in situ and in real time) has been scarcely explored and its study results interesting and relevant for the plasmonic technology. In this first part of the work, we have grown nanostructures from Au films and Au/Fe bilayers which have been later annealed under different conditions. These nanostructures have been characterized morphologically and analyzed by SPR spectroscopy, in order to follow the morphological changes of the systems varying the sample features (i.e., initial thickness) and the annealing conditions. With the purpose of studying changes induced upon X-ray irradiation using SPR as a probe, we have designed and developed a SPR system based on the Kretschmann-Raether configuration compatible with a X-ray absorption spectroscopy (XAS) beamline (SPR-XAS setup). Using this device, a study of the effects of the X-rays on glasses and Co-Phthalocyanines (CoPcs) has been carried out. For the study on glasses, two different types are analyzed: soda-lime and silica substrates, and for the case of the CoPcs, these have been grown varying the film thickness and the growth conditions

Platinum is the most used catalyst in electrodes for fuel cells due to its high catalytic activity. Polymer electrolyte and direct methanol fuel cells usually include Pt as catalyst in their electrodes. In order to diminish the cost of such electrodes, different Pt deposition methods that permit lowering the metal load whilst maintaining their electroactivity, are being investigated. In this work, the behaviour of electron beam Pt (e-beam Pt) deposited electrodes for fuel cells is studied. Three different Pt loadings have been investigated. The electrochemical behaviour by cyclic voltammetry in H2SO4, HClO4 and in HClO4+MeOH before and after the Pt deposition on carbon cloth has been analysed. The Pt improves the electrochemical properties of the carbon support used. The electrochemical performance of e-beam Pt deposited electrodes was finally studied in a single direct methanol fuel cell (DMFC) and the obtained results indicate that this is a promising and adequate method to prepare fuel cell electrodes.

In this work, surface plasmon resonance (SPR) spectroscopy has been employed as a probe to study modifications in nanostructured systems based on Au. Those modifications include a) structural and morphological changes induced by annealing and b) electronic modifications upon X-ray irradiation. The use of SPR spectroscopy to follow the evolution of modifications in nanostructures (especially, in situ and in real time) has been scarcely explored and its study results interesting and relevant for the plasmonic technology. In this first part of the work, we have grown nanostructures from Au films and Au/Fe bilayers which have been later annealed under different conditions. These nanostructures have been characterized morphologically and analyzed by SPR spectroscopy, in order to follow the morphological changes of the systems varying the sample features (i.e., initial thickness) and the annealing conditions. With the purpose of studying changes induced upon X-ray irradiation using SPR as a probe, we have designed and developed a SPR system based on the Kretschmann-Raether configuration compatible with a X-ray absorption spectroscopy (XAS) beamline (SPR-XAS setup). Using this device, a study of the effects of the X-rays on glasses and Co-Phthalocyanines (CoPcs) has been carried out. For the study on glasses, two different types are analyzed: soda-lime and silica substrates, and for the case of the CoPcs, these have been grown varying the film thickness and the growth conditions, En este trabajo se ha empleado la espectroscopía de resonancia de plasmones de superficie (SPR) para estudiar modificaciones en sistemas nanoestructurados basados en Au. Estas modificaciones incluyen a) cambios estructurales y morfológicos inducidos mediante tratamientos térmicos y b) modificaciones electrónicas bajo irradiación con rayos X. El uso de la espectroscopía de SPR para seguir la evolución de modificaciones en nanoestructuras (especialmente, in situ y en tiempo real) ha sido escasamente explorado y su estudio resulta interesante y relevante para el campo de la plasmónica. En la primera parte de este trabajo se ha llevado a cabo la fabricación de nanoestructuras a partir de películas de Au y bicapas Au/Fe tratadas térmicamente bajo diferentes condiciones. Estas nanoestructuras han sido caracterizadas morfológicamente y analizadas mediante espectroscopía de SPR con el fin de estudiar los cambios estructurales inducidos en las muestras al variar parámetros como el espesor y las condiciones del tratamiento térmico. Con el objetivo de estudiar modificaciones inducidas en la materia bajo irradiación con rayos X usando la SPR como sonda, se ha diseñado y desarrollado un sistema experimental de SPR basado en la configuración de Kretschmann-Raether y compatible con la espectroscopía de absorción de rayos X (dispositivo SPR-XAS). Mediante este montaje experimental se han analizado los efectos inducidos por los rayos X en vidrios y en Ftalocianinas de Co (CoPcs), in situ y en tiempo real. Para el caso de los vidrios, dos tipos diferentes han sido empleados como substratos: sodicocálcicos y de sílice. Por otro lado, las CoPcs estudiadas han sido crecidas variando su espesor y las condiciones de crecimiento

Discoveries of room-temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier-mediated versus defect-mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO-based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor.