Composite materials based on disordered carbon as supercapacitor electrodes

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Química Inorgánica, leída el 28-06-2019Los condensadores electroquímicos de doble capa (EDLC), comunmente denominados supercondensadores, son dispositivos de almacenamiento electroquímico de energía capaces de proporcionar más energía que un condensador común y cargarse o descargarse más rápido que una batería. Hoy en día, este tipo de dispositivos ha atraído un gran interés debido a tener una excelente reversibilidad, una capacidad de ciclado prácticamente ilimitada (>1,000,000 ciclos) y un modo de operación sencillo,ofreciendo soluciones en aplicaciones donde se requiere un aporte instantáneo de energía. Los esfuerzos e investigaciones actuales tienen como objetivo aumentar su densidad de energía sin perder potencia, para obtener nuevos dispositivos que alcancen o incluso superen la densidad de energía de una batería manteniendo las ventajas propias de los supercondensadores...Electrochemical double layer capacitors (EDLC), commonly referred as supercapacitors, are electrochemical energy storage devices that can provide more energy than a common capacitor and deliver or capture it faster than a battery. Nowadays, this type of devices have attracted considerable interest because they have excellent reversibility, practically unlimited cyclability (> 1,000,000 cycles) and a simple operation mode, offering solutions in applications where a rapid energy boost is required. Current efforts and research are aimed at increasing their energy density without losing power, in order to obtain new devices that reach or even surpass the energy density of a battery while simultaneously maintaining the advantages of supercapacitors...Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEunpu

Artificial neural network model for automatic code generation in graphical interface applications

Introduction: Currently, the software development industry is living in its golden age due to the progress in areas related to machine learning, which is part of AI techniques. These advances have allowed tasks considered exclusively human to be solved using a computer. However, the complexity and the extensive area covered by new projects that must be developed using programming languages have slowed down project delivery times and affected the company's productivity. Objective: This research presents the methodology carried out for constructing a recurrent neural network model for the automatic generation of source code related to graphical user interfaces using Python programming language. Method: By constructing a natural language-related dataset for describing graphical interfaces programmed in Python, a deep neural network model is built to generate automatic source code. Results:  The trained model achieves loss and perplexity values of 1.57 and 4.82, respectively, in the validation stage, avoiding overfitting in the model's training. Conclusions: A neural network model is trained to process the natural language related to the request to create graphical interfaces using the Python programming language to automatically generate source code that can be executed through the Python interpreter.Introduction: Currently, the software development industry is living in its golden age due to the progress in areas related to machine learning, which is part of AI techniques. These advances have allowed tasks considered exclusively human to be solved using a computer. However, the complexity and the extensive area covered by new projects that must be developed using programming languages have slowed down project delivery times and affected the company's productivity. Objective: This research presents the methodology carried out for constructing a recurrent neural network model for the automatic generation of source code related to graphical user interfaces using Python programming language. Method: By constructing a natural language-related dataset for describing graphical interfaces programmed in Python, a deep neural network model is built to generate automatic source code. Results:  The trained model achieves loss and perplexity values of 1.57 and 4.82, respectively, in the validation stage, avoiding overfitting in the model's training. Conclusions: A neural network model is trained to process the natural language related to the request to create graphical interfaces using the Python programming language to automatically generate source code that can be executed through the Python interpreter

Evaluación de variables implicadas en las lesiones en fútbol

Este Trabajo de Fin de Grado se encuadra en la temática de la evaluación de variables implicadas en las lesiones deportivas. En él se ha realizado una revisión bibliográfica sobre las variables implicadas en las lesiones en fútbol y un estudio descriptivo sobre las lesiones que han afectado a 15 jugadores de fútbol. En la metodología empleada en este trabajo se ha utilizado un protocolo de evaluación de lesiones basado en una entrevista semiestructurada y una encuesta diseñada específicamente para este propósito, que permite la evaluación de las lesiones que han afectado a un jugador de fútbol en su trayectoria deportiva. Tal y como se observa en los resultados de nuestro trabajo así como en otros estudios hay variables que pueden estar asociadas a la ocurrencia de lesiones en fútbol, pero también hemos obtenido resultados acerca de variables de las que no hay estudios hasta el momento que pueden o no estar relacionadas con la aparición de lesiones. La principal conclusión a la que hemos llegado es la necesidad de seguir realizando estudios en una línea similar cuyos resultados puedan contribuir a diseñar actividades de carácter informativo, formativo y de asesoramiento con jugadores y entrenadores de fútbol dirigidas a la prevención y reducción de la probabilidad de lesiones en este deporte

Hf/porphyrin-based metal-organic framework PCN-224 for CO2 cycloaddition with epoxides

Herein, we describe for the first time the synthesis of the highly porous Hf-tetracarboxylate porphyrinbased metal-organic framework (MOF) (Hf)PCN-224(M) (M ¼ H2, Co2þ). (Hf)PCN-224(H2) was easily and efficiently prepared following a simple microwave-assisted procedure with good yields (56e67%; spacetime yields: 1100e1270 kg m3 $day1 ), high crystallinity and phase purity by using trifluoromethanesulfonic acid and benzoic acid as modulators in less than 30 min. By simply introducing a preliminary step (10 min), 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin linker (TCPP) was quantitatively metalated with Co2þ without additional purification and/or time consuming protection/deprotection steps to further obtain (Hf)PCN-224(Co). (Hf)PCN-224(Co) was then tested as catalyst in CO2 cycloaddition reaction with different epoxides to yield cyclic carbonates, showing the best catalytic performance described to date compared to other PCNs, under mild conditions (1 bar CO2, room temperature, 18 e24 h). Twelve epoxides were tested, obtaining from moderate to excellent conversions (35e96%). Moreover, this reaction was gram scaled-up (x50) without significant loss of yield to cyclic carbonates. (Hf)PCN-224(Co) maintained its integrity and crystallinity even after 8 consecutive runs, and poisoning was efficiently reverted by a simple thermal treatment (175 C, 6 h), fully recovering the initial catalytic activityS.C. acknowledges the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie (MSCA-COFUND) grant agreement No 754382 (GOT Energy Talent). S.C. and P.H. acknowledge "Comunidad de Madrid" and European Regional Development Fund-FEDER 2014-2020-OE REACT-UE 1 for their financial support to VIRMOF-CM project associated to R&D projects in response to COVID-19. The authors acknowledge H2020-MSCA-ITN-2019 HeatNMof (ref. 860942), the M-ERA-NET C-MOF-cell (grant PCI2020-111998 funded by MCIN/AEI /10.13039/ 501100011033 and European Union NextGenerationEU/PRTR) project, and Retos Investigacion MOFSEIDON (grant PID2019- 104228RB-I00 funded by MCIN/AEI/10.13039/501100011033) project. This work has been also supported by the Regional Government of Madrid (Project ACES2030-CM, S2018/EMT-4319) and the Universidad Rey Juan Carlos IMPULSO Project (grant MATER M 3000). S.K acknowledges the Flemish Fund for Scientific Research (FWO Vlaanderen) through a PhD research grant (1181122 N

Electrochemical Stability of Rhodium-Platinum Core-Shell Nanoparticles : An Identical Location Scanning Transmission Electron Microscopy Study

Rhodium-platinum core-shell nanoparticles on a carbon support (Rh@Pt/C NPs) are promising candidates as anode catalysts for polymer electrolyte membrane fuel cells. However, their electrochemical stability needs to be further explored for successful application in commercial fuel cells. Here we employ identical location scanning transmission electron microscopy to track the morphological and compositional changes of Rh@Pt/C NPs during potential cycling (10 000 cycles, 0.06-0.8 V, 0.5 HSO) down to the atomic level, which are then used for understanding the current evolution occurring during the potential cycles. Our results reveal a high stability of the Rh@Pt/C system and point toward particle detachment from the carbon support as the main degradation mechanism

The design of magneto-plasmonic nanostructures formed by magnetic Prussian Blue-type nanocrystals decorated with Au nanoparticles

We have developed a general protocol for the preparation of hybrid nanostructures formed by nanoparticles (NPs) of molecule-based magnets based on Prussian Blue Analogues (PBAs) decorated with plasmonic Au NPs of different shapes. By adjusting the pH, Au NPs can be attached preferentially along the edges of the PBA or randomly on the surface. The protocol allows tuning the plasmonic properties of the hybrids in the whole visible spectrum

Two-Dimensional CdSe-PbSe Heterostructures and PbSe Nanoplatelets: Formation, Atomic Structure, and Optical Properties

Cation exchange enables the preparation of nanocrystals (NCs), which are not reachable by direct synthesis methods. In this work, we applied Pb2+-for-Cd2+ cation exchange on CdSe nanoplatelets (NPLs) to prepare two-dimensional CdSe-PbSe heterostructures and PbSe NPLs. Lowering the reaction temperature slowed down the rate of cation exchange, making it possible to characterize the intermediary NCs ex situ with atomically resolved high-angle annular dark-field scanning transmission electron microscopy and optical spectroscopy. We observe that the Pb2+-for-Cd2+ cation exchange starts from the vertices of the NPLs and grows into the zinc blende CdSe (zb-CdSe) lattice as a rock salt PbSe phase (rs-PbSe), while the anion (selenium) sublattice is being preserved. In agreement with previous works on CdTe-PbTe films, the interfaces between zb-CdSe and rs-PbSe consist of shared {001} and {011} planes. The final PbSe NPLs are highly crystalline and contain protrusions at the edges, which are slightly rotated, indicating an atomic reconfiguration of material. The growth of PbSe domains into CdSe NPLs could also be monitored by the emission peak shift as a function of the exchange time. Temperature-dependent emission measurements confirm a size-dependent change of the band gap energy with temperature and reveal a strong influence of the anisotropic shape. Time-resolved photoluminescence measurements between 4 and 30 K show a dark-bright exciton-state splitting different from PbSe QDs with three-dimensional quantum confinement

Metal Nanoparticle-Functionalized Three-Dimensional Graphene: a versatile platform towards sensors and energy-related applications

We demonstrate the first successful functionalization of epitaxial three-dimensional graphene with metal nanoparticles. The functionalization is obtained by immersing the 3D graphene in a nanoparticle colloidal solution. This method is versatile and here is demonstrated for gold and palladium, but can be extended to other types and shapes of nanoparticles. We have measured the nanoparticle density on the top-surface and in the porous layer volume by Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. Samples exhibit a high coverage of nanoparticles with minimal clustering. High quality graphene has been demonstrated to promote the functionalization leading to higher nanoparticle density, both on the surface and in the pores. X-ray Photoelectron Spectroscopy allowed to verify the absence of contamination after the functionalization process. Moreover, it confirmed the thermal stability of the Au- and Pd-functionalized three-dimensional graphene up to 530{\deg}C. Our approach opens up new avenues for utilizing three-dimensional graphene as a versatile platform for catalytic applications, sensors, and energy storage and conversion

Cristales, cristalización y difracción: Nuevo material audiovisual para la enseñanza de la cristalografía

El objetivo de este proyecto es la creación de nuevo material didáctico para la enseñanza de la cristalografía. En concreto, se presentan videoclips divulgativos sobre la forma y estructura de los cristales, los procesos básicos de cristalización y sobre la difracción de las ondas por los cristales. Estos videoclips están dirigidos tanto a estudiantes de ciencias como al público general y su intención es presentar de manera clara y visualmente atractiva una serie de conceptos físicos y cristalográficos que han resultado tradicionalmente difíciles de transmitir mediante clases teóricas. Además, los videoclips van acompañados de textos explicativos con el fin de que sirvan como material de estudio