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Trabajo presentado al International Flow Battery Forum (IFBF), celebrado en London (UK) del 7 al 9 de julio de 2021.

Carbon materials have a high electronic conductivity and low density, which make them essential additives in electrodes for electrochemical storage devices[1]. However, the use of nanocarbon material suspensions in the electrolyte of such devices is also attracting for two aspects: increasing total electrode active surface area and/or building percolation networks for electrons[2]. For these reasons nanocarbons have been considered as components in semi-solid electrolytes, which can be considered one class of nanofluids. Furthermore, the introduction of multiredox couples dispersed in the electrolyte can also lead to remarkable improvements, as seen in Li/air batteries[3]. These redox couples can act both as redox mediators and catalysts for the oxygen reduction or evolution reactions (ORR, OER) that take place during the battery cycling. Polyoxometalate clusters or other nanoparticles such as IrOx are already known by their catalytic activity in O2 reduction and reoxidation processes[5]. In this work we show the influence of carbon black nanocarbons and redox couples in organic media for the cathode of metal-air batteries, i.e. O2 reduction electrolytes. The addition of nanocarbons or mediators separately does not result on an impedance decrease or a clear effect on terms of current densities and overpotentials. Nevertheless, we observe a synergy between the redox and the conducting components added simultaneously, giving rise to enhanced currents, lower overpotentials and lower impedances for the charge transfer and diffusion processes. The relevant parameters and hypothesis for a mechanism will be discussed based on impedance analysis.

Resumen del trabajo presentado a la XXXVII Reunión Bienal de la Real Sociedad Española de Física celebrada en Zaragoza, del 15 al 21 de julio de 2019.

Trabajo presentado a la Applied Superconductivity Conference (ASC), celebrada en Washington State Convention Center (US) del 28 de octubre al 2 de noviembre de 2018.

Resumen del trabajo presentado al 13th Workshop on Low Temperature Electronics (WOLTE-13), celebrado en Sorrento (Italia) del 10 al 13 de septiembre de 2018., Transition Edge Sensors (TESs) are used as extremely sensitive thermometers in a wide range of applications. When coupled to a suitable absorber, they can detect, with unprecedented energy resolution, electromagnetic radiation from microwaves to gamma rays. To achieve this performance, they need to operate at very low temperatures, in the range of 100mK. In order to achieve superconductors with tunable critical temperature (Tc), bilayers made out of few nanometers of a superconductor and a normal metal are used. Depending on the selected materials and thicknesses, the Tc and normal resistance Rn of the device can be selected, which will impact their performance. Different groups worldwide develop TES for soft X-rays detection, mainly for future space missions. In Europe, SRON is developing Ti/Au sensors which are characterized under AC bias, adequate for the frequency domain multiplexing of several pixels. ICMA/ICMAB is developing sensors made of Mo/Au bilayers which are characterized under DC bias. Comparison of performances of the two types of sensors and the two operating conditions is basic for future development and optimization of this technology. In this communication we report on the comparison of Ti/Au and Mo/Au devices characterized under DC bias at ICMA facilities. We analyse the evolution of TES parameters at different operation points taking into account the differences between both materials and fabrication procedures., Work financed by the Spanish Ministerio de Economía y Competitividad (MINECO, projects ESP2014-59306-JIN, ESP2014-53672-C3-2-P, ESP2016-76683-C3-2-R), the European Space Agency (ESA, CTP Contract “Optimization of a European TES array”) and the European Commission (H2020 project AHEAD: Integrated Activities for the high energy astrophysics domain”). Personnel from ICMAB acknowledge financial support from MINECO, through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-04969. RMJ wishes to thank MINECO for her FPI contract. We also thank PTB for providing the SQUIDs.

Trabajo presentado en el HETERONANOCARB: Advances and applications in carbon related nanomaterials: From pure to doped structures including heteroatom layers, celebrado en Benasque (Zaragoza) del 11 al 15 de diciembre de 2017.

Póster presentado al Encuentro RIA-SpaceTec: Nuevas perspectivas en el desarrollo de instrumentación astronómica en España, organizadas por la red SpaceTec-CM (Desarrollo de nuevas tecnologías para instrumentación espacial en la Comunidad de Madrid: S2013/ICE-2822 con el apoyo y la financiación de la Red de Infraestructuras en Astronomía (RIA-MINECO). Las jornadas se celebraron del 10 al 12 de febrero de 2016, en la Sede Central del CSIC (Serrano 117, Madrid)., The so-called Transition Edge Sensors (TES) , whose basic element is a superconducting film operating at cryogenic temperatures (~100mK), constitute high performance detectors for a very wide radiation range. Thus, they are considered essential for extremely sensitive astronomic instruments, either on ground or in space, such as EDELWEISS, CRESST, BICEP2, SCUBA2, ACTPol, SAFARI and ATHENA’s X-IFU, as well as for other applications in science and industry. TES X-ray detectors with extremely high spectral resolution have been fabricated by NASA and SRON, using respectively Mo/Au or Ti/Au bilayers as the sensing element and Bi or Au as absorber. We report here our progress in the fabrication of TES X-ray detectors based on Mo/Au bilayers, within the framework of the initiative to develop a european backup for the X-IFU detector. Mo/Au TES are fabricated on SiN membranes in Ultra High Vacuum conditions through a two-step deposition process, using sputtering and electron-beam deposition, followed by dry etching photolithography. Superconducting Nb wiring is used. Electrodeposited Bi is being developed as absorber. An advanced specific characterization setup has been implemented, involving complex impedance and I-V curve measurements using superconducting electronics in a dilution refrigerator (base temperature, Work financed by the Spanish Ministerio de Economía y Competitividad (projects ESP2013-48637-C2-1-P, ESP2014-53672-C3-2-P and ESP2014-59309-JIN) and the European Commission (project AHEAD: Integrated Activities for the High Energy Astrophysics Domain ); RJ wishes to thank MINECO for her contract BES-2015-072733. We acknowledge also ESA contract No. 4000114932/15/NL/BW “Optimization of a European Transition Edge Sensor Array”.

Trabajo presentado en el Latest Advances on Nanomaterials for Biomedical Applications (Nanobioapp), celebrado en Barcelona, España, del 21 al 23 de septiembre de 2015

Trabajo presentado en la 5th Zing Conference in BioNanomaterials, celebrada en Carvoeiro, Portugal, del 25 al 28 de abril de 2015, Intercalation materials that have been shown biocompatible in neural systems, are nanostructured for their use as electrodes. As the materials undergo faradaic reactions themselves, upon electric field application, they prevent radical formation and interfacial heating, while allowing cell growth and full functionality. Iridium oxide, IrOx, and conducting polymers are the basic materials that have been hybridized with carbon nanotubes, graphene, and graphite, graphene oxide and conducting PEDOT and polypyrrole polymers, in various forms1-5. Electrodeposition mechanisms are elucidated, while control of the multiple variables have allowed to reach optimal preprations on platinum. Charge storage capacities are increased in different magnitudes, while a clear difference is observed for some of the polymeric materials in terms of biocompatibility. Optimal behavior of cells is always observed on IrOx based materials, with respect to blank glass or platinum, while graphene and carbon nanotubes hybrids of IrOx are among the ones with best charge storage capacities an lower impedance up to middle frequencies.

Trabajo presentado en la 15th edition of Trends in Nanotechnology International Conference, celebrada en Barcelona, España, del 27 al 31 de octubre de 2014

[ES]: En este trabajo se describe la oxidación anódico de electrodos de plata y de cobre en medios básicos. Se han utilizado tanto medios acuosos como hidróxidos fundidos (eutéctico NaOH/KOH). Los procesos de oxidación se han estudiado mediante voltametría cíclica y cronoamperometría, y las fases resultantes han sido caracterizadas por difracción de Rayos X. Los rangos de estabilidad encontrados para cada uno dependen del medio utilizado. Además de óxidos conocidos de cobre y de plata, se ha aislado un nuevo óxido de plata., [EN]: The anodic oxidations of copper and silver electrodes in basic media are reported. Experiments were conducted both in aqueous NaOH solutions and in a flux of molten NaOH/KOH eutectic. The oxidation processes were studied by means of cyclic voltammetry and chronoamperometries and the phases obtained were systematically characterized by x-ray diffraction. The ranges of stability of each phase in the different media studied are reported. In addition to known oxides of copper or silver, a new silver oxide was isolated., This work was funded by the MCyT(Spain), Plan Nacional de Materiales (MAT2001-1709-C04-01 and MAT2002-04529-C03, MAT96- 1057-c02-01and PGC PB98-0491). We also thank the Ministry of Education and Culture (Spain) for a predoctoral fellowship awarded to EMT-R.

[ES]: El fosfato de vanadilo es bien conocido como una fase inorgánica laminar capaz de intercalar una gran variedad de moléculas orgánicas. Mediante la polimerización in-situ, de anilina o pirrol, en la fase inorgánica es posible preparar materiales híbridos orgánico-inorgánicos en los que el polímero queda intercalado. Se describe la síntesis y caracterización de este tipo de híbridos y algunos resultados preliminares de su aplicación como materiales activos de cátodo en celdas reversibles de litio., [EN]: Vanadyl phosphate is a well known layered inorganic phase, capable of intercalating a great variety of organic molecules. By means of an in-situ polymerisation of aniline or pyrrole between the layers of the inorganic phase, it is possible to obtain organic-inorganic hybrids. We describe the synthesis and characterization of these type of hybrids, and some preliminary results of their application as active cathodic materials for positive electrodes in reversible lithium cells., Agradecemos la financiación de este trabajo a través de los proyectos MAT2001-709-C04-01 y MAT2002-04529-C03, y al Consejo Nacional de Ciencia y Tecnología de México (CONACYT) por la concesión de una beca predoctoral a A.K Cuentas-Gallegos.

Póster presentado en el 15º Congreso Nacional de la Sociedad Española de NeuroCiencia, celebrado del 25 al 27 de septiembre de 2013 en Oviedo (España)

The mixed silver–copper oxide, Ag2Cu2O4 has been previously synthesized by electrochemical oxidation of suspensions of the precursor Ag2Cu2O3 and also by direct oxidation/coprecipitation of soluble salts. This work shows how the transformation from Ag2Cu2O3 to Ag2Cu2O4 can take place in solid state at room temperature by ozonization of the precursor. The final phase is overstoichiometric in oxygen but shows the same structural features of the firstly described phase Ag2Cu2O4. The maximum content of oxygen achieved is 4.34 per unit formula. SEM micrograph of Ag2Cu2O4 nanocrystals obtained by room temperature ozonization of a Ag2Cu2O3 suspension, The authors thank Dr. F. Bardé and Prof. JM. Tarascon (LRCS, Univ. Picardie, Amiens, France) for access to equipment and financing from Spanish Ministry of Science and Education (PGC PB98-0491, MAT2002-04529-C03 and fellowship for DMR).

Fecha de solicitud: 30.05.2003.- Titular: Consejo Superior de Investigaciones Científicas (CSIC)., [EN]The invention relates to the preparation of novel copper- and silver-oxide-based catalysts and the use thereof in oxidation reactions. More specifically, the inventive materials and methods involve the development of novel catalysts based on mixed silver-copper oxides. The aforementioned materials are used as oxidation catalysts and, in particular, as catalysts in the partial oxidation of alcohols, with the purpose of combining the catalytic activity of both metals at a molecular level into one single compound. Moreover, said materials exhibit good catalytic activity for the above-mentioned reactions even at temperatures as low as 170 DEG C. To date, there has been no precedent of mixed silver-copper oxides, or synthetic compounds or natural minerals, and the catalysts outlined above constitute the first of said type. [ES]Los materiales y procedimientos patentados involucran el desarrollo de nuevos catalizadores basados en óxidos mixtos de cobre y plata. Dichos materiales se utilizan como catalizadores de oxidación y, en particular, como catalizadores en la oxidación parcial de alcoholes con el fin de combinar la actividad catalítica de ambos metales a nivel molecular en un solo compuesto. Dichos materiales muestran una buena actividad catalítica para dichas reacciones incluso a temperaturas bajas de tan sólo 170 DEG C. De hecho, no ha habido hasta la fecha ningún precedente de óxidos mixtos de cobre y plata, ni compuestos sintéticos ni minerales naturales, y los catalizadores presentados aquí constituyen los primeros de este tipo.

[ES]: Recientemente se ha sintetizado en nuestro laboratorio el primer óxido mixto de cobre y plata. Tal síntesis ha sido posible gracias a la utilización de métodos de química suave y baja temperatura, que impiden que los óxidos de plata se descompongan. En este trabajo se describe el estudio llevado a cabo sobre el comportamiento electroquímico del óxido mixto de cobre y plata, Ag2Cu2O3 ,mediante voltametría cíclica y electrólisis tanto para los procesos de oxidación como de reducción. Dicho compuesto sufre varios procesos redox cuando es reducido, obteniéndose plata metálica y cobre metálico como productos finales, sin que se dé regeneración del óxido al volver a oxidar a éstos. En cambio al ser oxidado el Ag2Cu2O3, se observa la formación de una fase oxidada de estequiometría Ag2Cu2O4±δ a partir de la cual se puede regenerar el compuesto original., [EN]: The first silver-copper mixed oxide was recently synthesized in our laboratory. Such synthesis has been possible using soft chemistry methods and low temperatures, which prevent the decomposition of silver oxides. The present work describes the electrochemical behaviour of the silver-copper mixed oxide, Ag2Cu2O3, as studied by cyclic voltametry and electrolysis, both for oxidation and for reduction reactions. This compound undergoes several redox processes when it is reduced, yielding metallic silver and metallic copper as final products. The initial oxide is not regenerated upon re-oxidation. On the other hand, when Ag2Cu2O3 is oxidized a new phase with stoichiometry Ag2Cu2O4±δ appears.The original compound can be regenerated after a new reduction., Los autores quieren agradecer al Ministerio Español de Ciencia y Tecnología por la financiación de este trabajo a través del proyecto CICYT MAT96-1057-c02-01, PB98-0491 y de becas predoctorales de D. Muñoz y E. Tejada.

The synthesis of several substituted and unsubstituted derivatives of the series of layered perovskitesLn2Ba2Cu2Ti2O11by a sol–gel method is reported. Reduced synthesis temperatures were attained for La, Nd (750°C), and Eu (900°C) derivatives, whereas Tb derivatives could not be obtained by this method. The products were characterized by small particle sizes of 30–100 nm (compared to 800 nm for samples prepared by the classical ceramic method). Furthermore,in situoxidation of the samples took place leading to oxidized products, such as La2Ba2Cu2.15Ti2O11, which earlier could have been obtained only by high oxygen pressure (5 kbar) annealing.

Además de la necesidad de mejoras técnicas en las baterías actuales, los usuarios deben saber que los elementos que las componen son altamente contaminantes, especialmente el plomo y el cadmio, y que en el caso de este último, los procesos de reciclado no están bien establecidos. Sin embargo, la demanda del mercado de baterías recargables es previsible que siga creciendo tanto a corto como a medio plazo. Así, la búsqueda de baterías más ligeras y de mayor densidad de energía para el mercado de la electrónica de consumo es ya una necesidad urgente (¿a quién le gustaría comprar un equipo electrónico en el que la batería ocupara la mayor parte del espacio?).

Control of structure and order in oxides is essential for the design of new superconducting cuprates. The intergrowth of perovskite and rock salt layers, as found in bismuth, thallium and, very recently, the record breaking mercury cuprates, is just one way to induce bidimensionality. Defect “all perovskite” oxides, such as Ln2Ba2C2Ti2O11 (Ln = La, Nd, Eu) are discussed as examples of a crystal -chemical approach to the induction of bidimensionality and order in mixed perovskite oxides of copper., This work was supported by the spanish CICYT (MAT90-1020-C02-01) and the MIDAS Program (92–1592). We thank the Departament ďEnsenyament de la Generalitat de Catalunya for a predoctoral fellowship awarded to M. R. P.

Simultaneous electrodeposition of Y, Ba and Cu from solution is achieved in presence of complexing agents, using metal wires as substrates. The resulting wire is superconducting after thermal treatment at 900 °C. The main problem is the presence of excess copper in the deposit that may be easily overcome using cyanide as a complexing agent which inhibits copper deposition in DMSO. On the other hand, deposition of YBa2Cu3O7-δ particles by electrophoresis yields superconducting wires with preferential orientation and high critical currents.

Electrochemical oxidation of La2CuO4 in aqueous OHMIN yield superconducting materials with Tc values that depend on the degree of oxidation and the temperature. The chemical nature of the charge carriers changes with temperature, yielding notable changes in Tc values. For the maximum oxidation of 0.15 holes per copper, an internal redistribution of holes between Cu and O is proposed from RT to 100 °C. Partial derivatives of magnetic susceptibility vs susceptibility show the existence of several coexisting phases with distinct Tc's, possibly within each grain.