ELECTROCHEMISTRY

Author: ROSEL PEREZ MORALES MARTA.
Year: 2004.
University: CÓRDOBA [www.uco.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The present report examines the molecular organization of organic compounds, such as derivatives of porphyrins and C60, in Langmuir films formed at the interface aire-agua. There have also been deposited films derived from porphyrin on ITO electrodes using electrochemical methods. Lastly, have studied the properties of fluorescent films porphyrin prepared by various methods, for subsequent application to the preparation of devices electroluminiscentes. The Doctoral thesis consists of five chapters: Introduction, which reviews the methods of preparation of organic thin films, characterization techniques employed, and the theoretical models for the characterization espectroscópica and electrochemistry of the films studied, and a brief description on the preparation and characterization of OLEDs. A second chapter devoted to the pilot, and three chapters that cover all of the results and their discussion distribuidosa tending to the various specific issues that may come:-Organization of thin films formed at the interface aire-agua. The study of the molecular organization of Langmuir films of two porphyrins soluble in water, and a derivative anfifílico of C60, has been carried out by conducting isotherm pressure superficial-área, reflection and FTIR spectroscopy, Brewster angle microscopy (BAM), and elipsometría image. The use of these techniques, along with the use of theoretical models, allows the elucidation of factors such as molecular aggregation and guidance, so as the calculation of the index refraccióny thickness of the film. Electrodes-modified porphyrins through electroplating. By voltametría cyclical (VC) have been modified electrodes óptícamente transparent (ITO) porphyrins metaladas water soluble, investigating the structure of these electrodepósitos through VC and various spectroscopic techniques. We have also studied the mediators and catalytic properties of the films of porphyrins electrodepositadas in oxido-reducción other films deposited on them by technical Langmuir-Blodgett. - Fluorescent properties of thin films of porphyrin. Devices electroluminiscentes. There will always be a study of the properties of fluorescent porphyrins not metaladas water soluble, dissolution and forming part of films. Have also been prepared and characterized OLEDs based on cationic porphyrin. In order to improve the injection of charges from the electrodes, are given various materials with good properties injectors of holes and electrons, measuring curves IV AND L-Vy analizandolas properties grinding of each device.

Author: MARTÍN SOLÁNS SANTIAGO.
Year: 2004.
University: ZARAGOZA [www.unizar.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The work presented in the thesis falls within one of the lines of inquiry Area Química-Física, Department of Chemistry Orgánica-Química Physics and includes a study on the characterization of both the topcoat formed at the interface aire-agua as for the LB films of two compounds with interesting properties for use in applications rabid today as the electrodes are modified and non-linear optics. It shows mainly studying topcoat ionised a bipiridina disustituida (better known as viológenos), specifically dibromide 1.1 Â'-dioctadecil 4.4 Â'-bipiridilo, at the interface aire-agua and through suitable modification of the subfase with the introduction of organic anion (aqueous solutions of salts organic tetracianoquinodimetano (TCNQ)) preparation of the corresponding hybrid films in view of their possible application as modified electrodes. The topcoat ionised formed at the interface aire-agua have been characterized by techniques such as the potential surface, the reflection spectroscopy and Brewster angle microscopy. These topcoats have been transferred onto hard substrates obtaining relevant films hybrid viológeno / TCNQ. These films were characterized using standard techniques such as ultraviolet spectroscopy (UV-vis) and infrared (IR) and more complex problems such as scanning electron microscopy and atomic force. Finally, we have obtained the electrochemical properties of the same through the voltametría cyclical. This study has shown that the incorporation of these organic anions (TCNQ) to the film LB significantly modified their electrochemical properties. In the second part of the thesis is the study of a derivative of stilbene, 4-dioctadecilamino 4Â'- nitroestilbeno. These materials presented nonlinear optical properties and, since the assembly of molecules through the technical LB power applications such, this study seeks LB films of these materials with a view to its possible application in the field of optics nonlinear.

Author: VILÀ CUSCÓ NEUS.
Year: 2005.
University: AUTÓNOMA DE BARCELONA [www.uab.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: In this dissertation describes the electrochemical study of a series of comprehensive and diaminas aliphatic amines. It is known the ability of aliphatic amines to modify surfaces of carbon and metal surfaces through their electrochemical oxidation. However, the mechanism through which the process of change occurs is unclear. One objective of this dissertation is to determine the mechanism through which the change occurs. To do this it is necessary first to know the mechanism of electrochemical oxidation of aliphatic amines, ie whether it is a sequential mechanism or concerted and then determine which is the species responsible for the attack on the surface, or the radical cation radical formed in the phase chemistry after the electronic transfer. Cyclic voltammetry experiments have revealed that the aliphatic amines which have links in CH position on the amino group are oxidized through a sequential CE, ie the stage where electronic transfer and chemical reaction associated prime happen in stages. Experiments Electrolysis Controlled potential to demonstrate that the chemical reaction associated with the electronic transfer phase is the desprotonción of radical cation through the breaking of the link CH position. The evolution of radical formed leads to obtaining the amine lower order and the corresponding aldehyde. Once you know the mechanism of electrochemical oxidation characterization of the surfaces modified by XPS confirm allow the formation of metal-link nitrogen. Experiments IRRAS species deuteradas show that the radical is formed in the post-stage chemistry electronic transfer the responsibility for the attack to the surface. The reactivity associated with the presence of links-type CH involves a change in position clear mechanistic level cation radical in the case of amines which have no such links. In the case of aliphatic amines secondary tertiary carbons in position on the amino group has found that the generation of catalytic amounts of the cation radical is sufficient to give rise to obtaining diaminas aliphatic highly prevented some yields higher than those obtained in the chemical synthesis in cases where this has been described. Obtaining these diaminas led to the study of electrochemical behavior. Here is observed for the first time broken links CC level radical cation which in this case compete with the already described rupture C -Hy that will result in obtaining product heterocyclic ionic ( "ionic liquids") with good yields .

Author: VIDAL IGLESIAS FRANCISCO JOSÉ.
Year: 2005.
University: ALICANTE [www.ua.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: UNIVERSIDAD DE ALICANTE.

Summary: This thesis presents a study of the oxidation of ammonia in the midst basic platinum surfaces. The esttudio of this process on superficiese monocristalinas platinum, has highlighted the high sensitivity of this platinum to the sites with geometry (100), which almost exclusively on the reaction takes place. In turn, and by surfaces staggered sensitivity has been observed not only at sites with geometry (100), with respect to the other two planes based platinum. From a more applied after the study of this reaction surfaces monocristalinas spent working with nanoparticles. On one side were sinterizadoy characterized nanoparticles with an orientation preferential (100), which results have been very interesting reaction to this very sensitive to the sites with this geometry, thus demonstrating the importance of technical preperación of nanoparticles in the they surface and therefore in its catalytic activity in many reactions sensitive to the structure. Lastly, Bimetal nanoparticles have been synthesized in which the combination of platinum with other metal has not proved very interesting from the point of view voltamétrico although it has seen slight declines in the potential of ammonia oxidation.

Author: ABDELGHANI BENYOUCEF.
Year: 2005.
University: ALICANTE [www.ua.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: It has been oxidized electroquímicamente isomers orto-, meta and para-acid aminobenzoico on electrodes of platinum, gold, graphite and coal flint. The oxidation of these substances produces anódica depositing electroactivas polymeric films on the surfaces of the respective electrodes. These films were characterized by electrochemical techniques, spectroscopic and microscopic. Unlike the polianilina, polymers obtained maintain electroactividad until pH values as high as 5 thanks to the presence of the carboxylate group in its chemical structure. There have also been synthesized and characterized the co-polímeros of aniline with acids aminobenzoicos, noting that the characteristics are improved solubility and response to the pH of the polianilina traditional.

Author: PINTO LLONA ANTONIO.
Year: 2005.
University: BARCELONA [www.ub.es].
Place of defense: UNIVERSIDAD DE BARCELONA.
Place of preparation: FACULTAT DE QUÍMIQUES. UNIVERSITAT DE BARCELONA.

Summary: The work has been studied in five reactors, (a reactor and four commercial electrochemical reactors designed specifically) electrochemical decomposition of nitrogen-a pollutant wastewater difficult to eliminate. In commercial aircraft, type of filter press single cell has been used four different pairs of electrodes. The resulting reactors have been designated as: Reactor MPC1, anode Ti / Pt and cathode steel reactor MPC 2, cathode, anode Cu/SnO2-PbO2 and steel reactor MPC 3 anode and cathode of PBO2 porous and steel reactor MPC 4, Ti anode / cathode Pt and diffusion of O2. In the four reactors design specific electrodes used were respectively: Reactor DIS 1, anode PbO2 and cathodes of Ti, Reactors CRP 2, anodes and cathodes of graphite reactor CIL 1, Ti anode and cathode Cu, and Reactor CIL 2 anode and cathode Ag steel. In four of these reactors were also tested different geometries: a gradation from geometry to flat geometry cilíndirca. Thus, in commercial aircraft, parallel electrodes can be considered infinite cylinder radio, in one of the reactor design, reactor DIS 1, the disposal of its electrodes is approaching the cylindrical geometry and two other reactors, CIL 1 and CIL 2, the electrodes are arranged in a concentric cylinders. Reactors with graphite electrodes, MPC 4 and CRP 2, were used for the decomposition of the compound studied by a reaction phase homogeneous type Electro-Fenton. These reactors were mounted on three different facilities. In treatments in the different reactors, we studied the influence of pH and intensity of flow in the evolution of the conversion of nitroceno. On the other hand, monitoring the cell voltage was used to determine energy consumption. Finally, we compared the results with each other reactors in the same facility. The comparison results show the advantages and disadvantages of each reactor. The ability to achieve combustion electrochemical (complete oxidation to CO2) was found in some cases by analyzing the evolution of the Total Carbon, CT, and Total Organic Carbon, TOC. In general are higher conversions at acid pH. Comparing the evolution of the conversion of nitrobenzene in the commercial aircraft with different intensities and anode current of 4 A (with a value of current density of 40 mA.cm-2) were obtained conversions fastest in the anodes PbO2 and Cu/SnO2-PbO2. The mathematical models explaining the evolution of the conversion and demonstrate the importance of the reactions in homogeneous phase especially in the reactor cathodes diffusion of O2 and in the reactor cylindrical ándodo of Ag and steel cathode. Intermediate products obtained, particularly in the case of cylindrical reactor suggest that the degradation of nitrobenzene in a reactor compartments without separation occurs with a reduction before aniline subsequently oxidizes. Comparing yields farádicos of reactors studied the best results offer the reactor cylindrical anode and cathode of Ag and reactor graphite anodes and cathodes.

Author: BONASTRE CANO JOSÉ ANTONIO.
Year: 2006.
University: POLITÉCNICA DE VALENCIA [www.upv.es].
Place of defense: Dep. Ingenieria Textil y Papelera.
Place of preparation: Universidad Politécnica de Valencia.

Author: LEON MOHEDANO BERNARDO.
Year: 2006.
University: CÓRDOBA [www.uco.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: This report provides the results of the study of electrode materials in cells ión-litio. Among the materials studied included the use of materials anódicos of fosfuro tin that exceeds the storage capacity of lithium carbon. This compound is interesting to present two elements electroactivos They can study the mechanism of insertion of lithium. As cathode ray equipment are proposed structure type spinel oxides and phosphates. Within the former, have been studied and lithium manganese spinel composition incorporating varied very small amounts of metals such as doping that can improve the performance of existing ones. Within phosphates, we have focused on iron phosphate and lithium conducting various methods of studying their behavior electrochemical synthesis. The selected materials are combined in high capacity cells seeking to present better benefits for a possible applicability gives industrial level.

Author: PADILLA MARTÍNEZ JAVIER.
Year: 2006.
University: POLITÉCNICA DE CARTAGENA [www.upct.es].
Place of defense: UNIVERSIDAD POLITÉCNICA DE CARTAGENA.
Place of preparation: UNIVERSIDAD POLITÉCNICA DE CARTAGENA.

Summary: The devices electrocrómicos transmission variable are able to modulate the light passing through it, through the passage of an electric current. Their most important applications pass through the windows of intelligent design in architecture, mirrors or anti automotive vision systems adapted for use in sport, professional or military. These cells are electrochemical devices composite materials for the reduction or oxidation processes cause color changes: materials electrocrómicos. Within materials with these features, drivers organic polymers are presented as excellent candidates compared with inorganic metal transition, because of its great versatility in terms of attainable colors, ease of processing, and low cost. A cell configuration in which the two electrodes are active electrocrómicamene, dual configuration is presented as a good option in the face to improve the performance of the device. The work carried out in this thesis aims to emphasize the relationships between electrochemical process and changes color based on two aspects: a study of the individual constituent materials, and study the dual system. The goal is the optimization of both the optical and electrochemical processes, systems dual polymer conductors, obtaining experimental methodologies able to characterize, predict theoretically, and finally designing devices electrocrómicos dual optimal. The first part of the study focuses on the development of methodology in obtaining the optical characterization of a material electrocrómico according to their electrochemical characteristics, such as the burden redox total consumed during the process of oxidation or reduction, and the potential window where these processes occur. The materials used are the drivers polymers poly-3 ,4-etilendioxitiofeno (PEDOT) and poly-3 ,6-bis (2 - (3,4-etilendioxi) tienil) -N-metilcarbazol (PBEDOT-NMCz). The first one is colored by reducing, while the latter makes during oxidation, besides introducing complementary colors, and can therefore be used in a device electrocrómico dual. Based on the results obtained during the second part takes place a desk review, together with its experimental verification, on the optical responses resulting in a system that includes several layers electrocrómicas. Relationships obtained can predict the configuration maximum constraste for a dual system, based on the electrochemical characteristics of each individual component. The dual system studied is PEDOT / PBEDOT-NMCz. In a third section, and intends to develop an experimental methodology capable of recording the statements of each individual electrode oxidation during operation of a dual device, obtaining a direct information on the performance of the device. This allows the study of the influence that a number of variables, such as load redox ratio between the two films constituents, the potential applied to the device, and the initial state of oxidation of polymers have on the performance of the device. The ultimate goal is to build devices electrocrómicos that can be used outside the academic realm. To do this, and for reasons of security for the end user, it is necessary to use means solid electrolytic cell. It is also necessary to manufacture devices of a size appropriate. In the next section, is studying the construction of such devices for the system PEDOT / PBEDOT-NMCz. The information obtained in the preceding sections is used to determine combinations with the highest contrast possible. We discuss problems relating to the deposition of polymers in supermarkets (about 30 cm2), optimizing speed color change when using a me 8 gave sóli a3d do, as well as the ability to adjust and color retention in absence of applied potential. It proposes a method for quick and easy assembly consisting of the solidification of the gel by ultraviolet curing. Finally, it proposes a simple and rapid electrochemical technique to detect possible faulty devices. The devices electrocrómicos constructed presents a surface active 30 cm2, with a contrast of 30% and a rate of change of color less than 1 s. The last section includes the study of two new polymers, poli-dibencil-ProDOT (PDiBz-ProDOT) and poli-bifenilmetiloximetil-ProDOT (PBPMOM-ProDOT) coloreables catódicamente and individually have a higher contrasts that PEDOT. For this reason, we studied the effect of replacement by the two new polymers in dual systems with PBEDOT-NMCz. This repeats the individual characterizations with the methodology used for the system PEDOT / PBEDOT-NMCz. Also, the desk study was performed to calculate maximum contrast of each system. With the information obtained will be built in solid state devices, and it is found that the two systems PDiBz-ProDOT/PBEDOT-NMCz and PBPMOM-ProDOT/PBEDOT-NMCz higher contrasts the system PEDOT / PBEDOT-NMCz. The values obtained were 46 and 52% for systems PBPMOM-ProDOT/PBEDOT-NMCz and PDiBz-ProDOT/PBEDOT-NMCz respectively. Finally, throughout the study proposes the use of optical quantities comparable to any study electrocrómico. To that end, it is proposed to use securities fotópicos in place of the securities referred to a single wavelength. The measures fotópicas are standardized by the Commission Internationale de l'Eclairge (ICE), and correspond to the real feelings that the human eye perceives, whose sensitivity is different for each wavelength.