Dissertations / Theses on the topic 'Electroactive Molecules'

This thesis deals with the synthesis of electroactiveorganic compounds. The synthesis of ethylenedioxy-benzodioxinstri-dioxin and tetra-dioxin are described. These molecules wereprepared with the aim of creating donor molecules for cationicradical salts. The symmetric analogs of tri-dioxin,methylenedioxy-derivative and ethylenedioxy-naphthalene werealso synthesized. Three different cation radical salts with 2:1stoichiometries were obtained from tri-dioxin, whiletetra-dioxin merely provided polycrystalline materials.Tri-dioxin and tetra-dioxin were also successful as operationalmatrixes in PALDI-TOF.

Tetrathiafulvalenes with the2-dialkyl-amino-1,3-dithiolium-4-thiolate mesoion asbuilding-block was also synthesized. A series of doublyalkylthiol-substituted TTFs were prepared with the aim offorming self-assembly monolayers on gold surfaces in theapplication of organic thin film field-effect transistors.Film-formation for two TTFs were studied and they providedrelatively dense packed monolayers with a discrete distance ofthe TTF moiety from the gold surface.

The mesoionic compound was also for the first time used inanumpolungreaction. The electrophile obtained in situ bytreatment of mesoion with sulfuryl chloride was reacted with avariety of electron-rich aromatic compounds. From the receivedproducts three new arylthio-substituted TTFs weresynthesized.

Keywords:Synthesis, Benzodioxin, Tetrathiafulvalene,Mesoion, Organic Conductor, Cation Radical Salt, CyclicVoltammetry, Electrocrystallization, Self-Assembly Monolayer,SAM, Organic Field-Effect Transistor, OFET

El objetivo fundamental de los circuitos eléctricos es la miniaturización utilizando moléculas, de manera individual o el conjunto de ellas, como bloques de construcción electrónicos. Se espera que el pequeño tamaño de los componentes electrónicos reduzca el consumo de energía a la vez que aumente la sensibilidad y el rendimiento del dispositivo. Los esfuerzos que se hacen en investigación están orientados en dos direcciones: la primera está enfocada en el estudio, a nivel fundamental, de nuevas moléculas con propiedades o funcionalidades específicas, que proporcionan un conocimiento más profundo de la estructura molecular, dinámica y reactividad. El segundo se dedica al desarrollo de nuevas técnicas para la implementación de estas moléculas in dispositivos electrónicos. A menudo, para fabricar un dispositivo molecular se necesita depositar las moléculas o materiales en un sustrato adecuado. Es importante controlar cómo afecta el disolvente, el sustrato o la funcionalización molecular en el ensamblaje molecular final y las interacciones moleculares, ya que el ordenamiento y el empaquetamiento de las moléculas son aspectos clave para el funcionamiento de los dispositivos. Esta Tesis Doctoral está enfocada en el desarrollo de nuevos dispositivos moleculares electrónicos basados en monocapas auto-ensambladas de moléculas electroactivas, y en el estudio electroquímico de los procesos de transferencia electrónica asociados a ellos. En la primera parte de la Tesis, se describe el uso de diferentes moléculas redox inmovilizadas en sustratos de oro como interruptores moleculares. El estado de los compuestos electroactivos se puede modular aplicando un potencial específico sobre el sustrato, y se ha implementado satisfactoriamente la respuesta en capacitancia como señal de salida del interruptor. Es importante destacar que se han obtenido estos interruptores moleculares eléctricos usando también geles iónicos como electrolitos sólidos, demostrando la viabilidad de integrar estos sistemas en futuros dispositivos electrónicos y/o flexibles. En la segunda parte de la Tesis, se presenta el estudio del mecanismo de transferencia electrónica, por medios electroquímicos, en una familia de compuestos derivados de radicales de policlorotrifenilmetilos (PTM), enlazados a sustratos de oro. La familia de moléculas de PTM contiene un grupo tiol en el extremo conectado al PTM a través de una cadena alquílica de distintas longitudes. Se ha estudiado el proceso de transferencia electrónica a través de SAMs de PTM en distintos medios electrolíticos y en función del grado de recubrimiento de la superficie del sustrato de oro modificado. Por lo tanto, se ha demostrado que la interacción de los disolventes juega un papel importante en el carácter adiabático del proceso redox. Además, el acoplamiento electrónico entre centros de moléculas de PTM adyacentes favorece la disminución de la constante de transferencia electrónica. Finalmente, en la última parte de la Tesis, se han fabricado transistores orgánicos de efecto campo (OFETs) utilizando un gel iónico como material dieléctrico, y se han estudiado sus propiedades. Los OFET se fabricaron con geometrías tipo “top-gate” y “side-gate”, donde el gel iónico se colocó encima del sustrato con el canal semiconductor. Las propiedades de estos transistores con gel iónico se compararon con estructuras similares como referencia, las cuales están basadas en oxido de silicio convencional, resultando ser bastante interesantes para aplicarlos en transistores orgánicos flexibles y económicos.
The ultimate goal of electrical circuits is miniaturization by using single molecules or collections of single molecules as electronic building blocks. It is expected that the smaller size of the electronic components will decrease the power consumption while increasing the sensitivity and the performance of the device. Research efforts are concentrated in two directions. The first one is focused in the study, at a fundamental level, of new molecules with specific properties or functionalities, which provides a deeper understanding of molecular structure, dynamics and reactivity. The second one is dedicated to develop new techniques for the implementation of these molecules in electronic devices. Often, to construct a molecular device it is necessary to deposit molecules or material on a suitable substrate. Since the ordering and packing of the molecules are crucial aspects for the operation of the devices, it is important to have a good control of how solvent, substrate or molecular functionalization influences on the resulting molecular assemblies and the intermolecular interactions. The present Doctoral Thesis is focused on the development of new molecular electronic devices based on electroactive self-assembled monolayers (SAMs), and on the electrochemical study of the electron transfer phenomena associated to them. In the first part of the Thesis, it is described the use of different redox molecules immobilized on gold substrates as molecular switches. The state of the electroactive compounds can be tuned when a specific potential is applied to the substrate, and the capacitance response has been successfully implemented as the read-out of the switch. It is important to highlight that these electrical molecular switches have been also obtained using ion gels as solid electrolytes, demonstrating the feasibility to integrate these systems in future electronic and/or flexible devices. In the second part of the Thesis, it is reported the electron transfer (ET) mechanism study, by electrochemical means, in a family of polychlorothriphenylmethyl radical (PTM) derivative compounds attached to gold substrates. The family of PTM molecules contains a thiol terminal group connected to the PTM through an alkyl chain with different lengths. It has been studied the ET process through PTM-SAMs in different organic electrolytic media and as a function of the surface coverage of the modified gold substrate. Hence, it was demonstrated that the interaction with the solvent plays an important role in the adiabaticity character of the redox process. Further, with neighbouring molecules, the intermolecular electronic coupling between PTM centers promotes a reduction of the ET constant rate. Finally, in the last part of the thesis, it has been fabricated a functioning OFET using an ion gel as gate dielectric, and its properties has been examined. The OFETs were prepared with top-gate and side-gate geometries, where the ion gel was placed on top of the substrate with the semiconductor channel. The ion gel gated OFET properties were compared with a reference OFET structure, which had a conventional SiO2 gate dielectric, demonstrating that the ion gels are highly attractive to be applied in low cost and flexible organic transistors.

Dans cette thèse, la fonctionnalisation redox du MoS₂ a été considérée pour le développement de dispositifs électrocommutables. Des monocouches de MoS₂ exfoliées mécaniquement ont été fonctionnalisées avec du 6-(ferrocényl)hexanethiol et caractérisées de manière approfondie par un large éventail de techniques expérimentales. La combinaison de ces techniques à de la modélisation théorique a permis d’accéder à une meilleure connaissance des propriétés électroniques du MoS₂ fonctionnalisé par du ferrocène. De plus, une étude de microscopie électrochimique (SECM) a permis de mieux comprendre l’alignement des bandes d’énergie à l’interface MoS₂/électrolyte. Enfin, des nanofeuillets de MoS₂ ont été fonctionnalisés par du ferrocène et une autre molécule électroactive donnant lieu à deux processus redox réversibles, le tétrathiafulvalène (TTF). Le succès de la fonctionnalisation a été confirmé par des techniques de caractérisations à plusieurs échelles. Les mesures électriques des dispositifs à base de TMD ont conduit à des résultats prometteurs vers l’objectif de la mise en oeuvre de dispositifs électrocommutables à partir de MoS₂ fonctionnalisé par des molécules électroactives
In this thesis, the molecular functionalization of MoS₂ with electroactive molecules was explored for the development of electroswitchable devices. Mechanically exfoliated MoS₂ monolayers were functionalized with 6-(ferrocenyl)hexanethiol and thoroughly characterized by a broad range of techniques. The electronic properties of the ferrocene-functionalized MoS₂ were investigated through the combination of multiple experimental techniques and theoretical modeling. Further insights on the energy band alignment at the MoS₂/ electrolyte interface were gained through scanning electrochemical microscopy (SECM) investigations. Finally, solution-processed MoS₂ nanosheets were functionalized with ferrocene and multiredox tetrathiafulvalene (TTF) derivatives. The successful functionalization was confirmed by multiscale characterization techniques. Electrical measurements of TMD-based devices showed promising results toward the goal of the implementation of electrochemically switchable devices from redox-functionalized MoS₂

Ce travail de thèse s’inscrit dans un projet plus large qui vise à développer avec le laboratoire Ampère et l’Etablissement Français du Sang un microsystème capable de réaliser un phénotypage plaquettaire pour le diagnostic de la thrombopénie néonatale. Ce microsystème doit permettre d’isoler les plaquettes du sang total et de détecter les antigènes plaquettaires présents à leur surface. L’isolation des plaquettes se fera grâce à un module de magnétophorèse et un module de diélectrophorèse. La détection sera électrochimique. Le cœur de ce travail de thèse a donc consisté à développer des nanoparticules magnétiques pour le module de magnétophorèse. Ces nanoparticules doivent permettre la capture spécifique des plaquettes et servir de marqueur pour la détection électrochimique. Pour ce faire, des nanoparticules magnétiques ont donc été doublement fonctionnalisées en une seule étape avec un anticorps anti-CD32 dirigé contre l’antigène CD32 présent à la surface des plaquettes et avec une molécule électroactive. Après optimisation des différents paramètres de greffage, les propriétés électrochimiques de ces particules ont été caractérisées. Leurs propriétés de bioreconnaissance ont été testées sur l’antigène purifié puis sur plaquettes entières. Enfin la faisabilité de la manipulation des structures nanoparticules/plaquettes par magnétophorèse avec des micro-aimants a été démontrée
Fetal/neonatal alloimmune thrombocytopenia (F/NAIT) represents a great threat to new-borns or fetus. It occurs when a woman becomes alloimmunized against fetal platelet antigens. With the aim to improve fetal and neonatal survival, in collaboration with Ampere Laboratory and Etablissement Français du Sang, we plan at developing a Point-of-Care (POC) platform for platelet phenotyping. The final POC microsystem will be able to perform magnetophoresis and dielectrophoresis for platelets isolation from whole blood, and their selective electrochemical detection allowing for their phenotyping. The development of nanoparticles (NPs) with magnetic, electrochemical and bio-selection properties is a key issue. Herein, we have focused on the elaboration of magnetic NPs bearing 1) anti-CD32 antibody for specific interaction with CD32 antigen, which is present at the surface of platelets and 2) ferrocene carboxylic acid, an electroactive molecule for detection. To achieve this, the coupling reactions of this electroactive molecule and this antibody were optimized and a one-pot reaction for double functionalization was developed. The bioactivity of the immobilized antibody was tested at the molecular and cellular level. The dual-functionalized NPs voltammetric signals were also investigated. Finally the feasibility of platelets capture and actuation by magnetophoresis with micro-magnet array were demonstrated

Des molecules polyeniques conjuguees de differentes longueurs et comportant des groupes pyridinium aux deux extremites ont ete synthetisees. Ces composes qui reunissent les caracteristiques structurales des carotenoides et des viologenes ont ete designes sous le terme de caroviologenes. Des molecules de ce type, suffisamment longues pour traverser une membrane lipidique, sont susceptibles de presenter des proprietes de fil moleculaire conducteur, c'est-a-dire de pouvoir transferer des electrons a travers la membrane a l'aide des groupes electroactifs terminaux qui changent les electrons, et de la chaine conjuguee qui permet leur propagation. Leur incorporation dans les membranes bicouches phospholipidiques des vesicules a ete realisee. En utilisant un reducteur externe et un oxydant interne appropries, l'aptitude de caroviologenes zwitterioniques de longueur adequate a transferer des electrons du reducteur externe vers l'oxydant interne a pu etre etablie. Des molecules polyeniques donneur-accepteur de taille croissante et comportant differents groupes electrodonneurs et electroattracteurs a leurs extremites ont ete preparees. L'etude de leur solvatochromie permet de mettre en evidence l'existence de transition de transfert de charge intramoleculaire. Dans ces composes, le segment polyenique joue le role de fil conducteur moleculaire assurant le transfert de charge d'une extremite a l'autre de la molecule. Ces composes presentent des proprietes tres interessantes dans le domaine de l'optique non lineaire

The presence of nitrates (NO3-) in groundwater is a worldwide concern. The high energy demand and environmental impact of available technologies requires investigating new technologies. This thesis was focused on investigating the usage of bioelectrochemical systems (BES) for treating nitrate-polluted groundwater. BES uses microorganisms able to catalyze oxidation/reduction processes by delivering/obtaining electrons from an electrode. In this thesis, microorganisms able to use the electrode as an electron donor (biocathode) to reduce nitrates into dinitrogen gas (inert) were investigated. As a result, a process could be patented, in which BES are able to treat nitrates at high denitrification rates (up to 700 gN•m-3NCC•d-1), with a competitive energy demand (0.68•10-2 – 1.27•10-2 kWh•gN-1treated), without sludge generation nor chemical dosing. Moreover, the microorganisms were electrochemically characterized, and the key subcommunities of the process were elucidated. In summary, bioelectrochemical systems have the potential for becoming a competitive alternative for the treatment of nitrate-polluted groundwater
La presència de nitrats (NO3-) en aigües subterrànies és una preocupació global. L’alt cost energètic i ambiental de les tecnologies actuals requereixen la investigació de noves estratègies. Aquesta tesi ha investigat la utilització de sistemes bioelectroquímics (BES) pel tractament d’aigües subterrànies contaminades per nitrats. Les BES es basen en microorganismes capaços de realitzar oxidacions/reduccions tot alliberant/captant electrons d’un elèctrode. Aquesta tesi ha investigat l’ús de bactèries capaçes d’utilitzar l’elèctrode com a donador d’electrons (biocàtode) per reduir el nitrat a dinitrogen gas (compost inert). Com a resultat, s’ha patentat un procés que permet desnitrificar a altes velocitats (700 gN•m-3NCC•d-1), a un cost energètic competitiu (0.68•10-2 – 1.27•10-2 kWh•gN-1tractat), sense generar fangs ni addicionar substàncies químiques. També s’ha caracteritzat electroquímicament els microorganismes i s’ha elucidat les subcomunitats microbianes responsables de la desnitrificació. En definitiva, aquesta tesi demostra que els sistemes bioelectroquímics poden esdevenir una alternativa competitiva pel tractament d’aigües subterrànies contaminades per nitrats

L'objectif de ce travail est, d'une part, de comprendre les mecanismes mis en jeu lors de l'electrochimie de complexes a base de cyclodextrine et de molecules electroactives et, d'autre part, de realiser la synthese de polymeres conducteurs encapsules. Le premiere axe presente l'etude en presence de cyclodextrine d'une molecule electroactive, le 4-amino n,n-diphenylamine (adpa). Differentes etudes spectroscopiques montrent la formation d'un complexe d'inclusion. L'etude electrochimique du complexe conclut a un mecanisme redox reversible faisant intervenir deux electrons et deux protons et precise que le complexe ne participe pas a la reaction redox. Des etudes par spectroscopie d'absorption in situ et par modelisation moleculaire montrent que l'espece oxydee de l'adpa est complexee par la cyclodextrine avec une meilleure affinite que l'espece reduite. Par ailleurs, la complexation induit la deprotonation de l'espece oxydee a ph quasiment neutre. Le second axe de ce travail est consacre a l'etude d'un second complexe d'inclusion forme entre la biphenylamine (bpa) et la cyclodextrine. La formation d'un complexe d'inclusion est confirmee par des etudes spectroscopiques qui precisent que la forme neutre de la bpa est mieux complexee que sa forme protonee. La modelisation moleculaire montre que la bpa, en raison de sa structure allongee, est entierement incluse dans la cavite de la cyclodextrine. L'etude electrochimique du bpa en milieu aqueux permet de definir un mecanisme redox irreversible impliquant deux electrons et deux protons et montre que le complexe se dissocie lors de son oxydation. La polymerisation electrochimique du bpa en presence de cyclodextrine donne des produits solubles observes a proximite de l'electrode. Leur caracterisation par spectroscopie d'absorption et par spectrometrie de masse a determine que ce sont des oligomeres du bpa et qu'ils sont encapsules dans une ou plusieurs molecules de cyclodextrine.

Esta tesis presenta el uso de nuevos complejos [Mo3S7L3]2-, en el que L es un ligando electroquímicamente activo (ditioleno, diselenoleno o dioxoleno), como precursores para la preparación de semiconductores multifuncionales unimoleculares basados en unidades clúster magnéticas. Se han investigado las propiedades redox de estos clústeres dianiónicos y se han determinado sus estructuras cristalinas mediante difracción de rayos x en monocristal, así como calculado sus estructuras electrónicas utilizando métodos DFT. La abstracción de azufre de [Mo3S7L3]2- resulta en clústeres con unidad Mo3S4 que presentan una estructura de cubo incompleto. Todos los clústeres dianiónicos con ligandos ditioleno o diselenoleno poseen un orbital HOMO con simetría "e1" que se encuentra deslocalizado sobre los ligandos y la unidad clúster. La fragmentación de los compuestos con unidad M3Q7 (M = Mo, W; Q = S, Se) da lugar a especies dinucleares M2O2(μ-Q)2, mientras que el autoensamblaje de la unidad Mo3S7 conduce a un nanoclúster de fórmula {[Mo3S7I3]4(μ-I)6I}3- con estructura tipo adamantano. La electrooxidación de moléculas orgánicas dadoras como ET o I2-EDT-TTF en presencia de aniones Mo3Q7 conlleva a la formación de nuevas sales de ión radical con empaquetamientos peculiares de las moléculas dadoras y con propiedades semiconductoras o metálicas.

The work embodied in this dissertation is specifically focused on the evanescent interaction of light with thin-films which has lead to two related instrument based projects: i) the Electroactive Fiber-Optic Chip (EA-FOC) and ii) Attenuated Total Reflectance (ATR) spectroscopy of novel materials. The EA-FOC combines the sensitivity of an electroactive total internal reflection element (20 to 50 times more sensitive than a transmission experiment) with the ease of use of fiber-optic based CCD spectrometers. A side-polished optical fiber, in a V-groove glass mount, forms the planar platform, which allows access to the evanescent field escaping from the fiber core. The exposed evanescent field, which was used to probe molecules or molecular assemblies supported by the platform, has an interaction area ca. 0.05 cm squared. Thin-film and bulk absorbing samples, and waveguide modeling calculations were initially used to evaluate the sensitivity of the FOC platform, which was found to be analogous to ATR instrumentation. The wavelength range of the FOC platform was increased to include the near-UV and applied to monitor adsorption of a protein film. Fluorescence applications of the FOC were demonstrated using a fluorescence bioassay and a drop cast nanoparticle film. Finally, a transparent conducting oxide film, ITO, was added to the surface of the platform to complete the EA-FOC for spectroelectrochemical applications. A methylene blue redox couple and an electrodeposited ultra-thin PEDOT film were used to probe the capabilities of the EA-FOC. The EA-FOC was shown to be a multifunctional platform for advanced sensor technologies requiring absorbance, fluorescence, and electrochemical detection or a combination thereof.ATR spectroscopy of novel materials included the evaluation of two architectures: i) a pH sensitive polyelectrolyte film and ii) surface capture of a nanoparticle film. Absorbance spectra of a polyaniline/polyacetic acid self-assembled bilayer were evaluated with respect to pH and potential using ATR spectroscopy; the ultimate application of the polymer signal transduction layer was to monitor proton transport across a lipid-bilayer. Additionally, ATR spectroscopy was used to monitor adsorption of pyridine capped nanoparticles on a silyl-propyl-thiol modified surface.

Nesta tese investigamos o comportamento eletroquímico da matriz lamelar de xerogel de pentóxido de vanádio(V) hidratado (VXG), visando desenvolver interfaces moleculares e eletrodos modificados. A partir da suspensão do gel de V2O5.nH2O, geramos os filmes lamelares de VXG sobre a superfície do eletrodo de trabalho. Inicialmente, os filmes de VXG consistem de regiões heterogêneas, que podem ser diferenciadas espectroeletroquimicamente. Após tratamento eletroquímico, esses filmes atingem uma condição eletroquímica estacionária, sofrendo um colapso e formando uma estrutura tipo banda uniforme. Esses filmes de VXG condicionados, foram utilizados como interfaces de espécies moleculares eletroativas. Em paralelo, interagimos o VXG com a argila bentonita, e obtivemos um xerogel floculento verde em solução aquosa, denotado BV, cuja evidência mais forte dessa interação foi obtido pelo espectro de FTIR, em função do surgimento de um forte pico em 835 cm-1, atribuído ao estiramento V-O-Si. A interação com a zeólita13X, resultou num sólido amarelo devido à troca de íons Na+ pelo grupo VO3+, denotado ZV. A troca iônica foi evidenciada pela análise de ICP-AES, que determinou uma quantidade grande de íons Na+ na solução sobrenadante, aproximadamente 225 mg/L contra 28 e 25,4 mg/L das soluções originais de VXG e zeólita13X, respectivamente. Eletroquimicamente, os compósito BV e ZV, despontam como materiais modificadores de eletrodos muito atraentes, combinando a boa condutividade dos filmes de VXG com as propriedades de troca iônica e de intercalação das argilas e das zeólitas.
The electrochemical behavior of hydrated vanadium(V)-oxide xerogels (denoted VXG), has been investigated, aiming the development of molecular interfaces and modified electrodes. Layered vanadium(V)- oxide xerogel films have been generated, in a controlled way, by the direct deposition de precise amounts of the polyvanadic acid solution onto the electrode surface. Initially, the layered VGX films consist of heterogeneous regions, which can be differentiated spectroelectrochemically. However, after the electrochemical treatment, those films reach a stationary electrochemical condition, collapsing into a uniform band type structure. The conditioned layered VXG films have been utilized as interfaces of electroactive molecular species. In parallel, the VXG suspension has been combined with a montmorillonite clay, yielding a green flocculent xerogel in suspension, here denoted BV. Strong evidence of polyvanadate-bentonite interaction has been provided by the FTIR spectra, from the appearance of a strong peak in 835 cm-1, ascribed to the a new V-O.-Si stretching vibration. The VXG suspension has also been combined with zeolite 13X, resulting a yellow solid, envolving ionic exchange of Na+ ions by VO3+; this solid has been denoted ZV. Ionic exchange has been evidenced by ICP-AES analyses. A promissing use of the new materiaIs as molecular interfaces has been demonstated, exploiting the good conductivity and intercalation properties of VXG and BV, as well as, the ion exchange properties of ZV.

This dissertation has focused on i) optimizing charge transfer rates at indium-tinoxide (ITO) electrodes, and ii) characterization of the supramolecular structure and properties of ultra thin surface modifier films on modified electrodes for various device applications. Commercial ITO surfaces were modified using conducting polymer thin film architectures with and without various chemical activation procedures. Ferrocene derivatives were used as redox probes, which showed dramatic changes in electron transfer rate as the SA-PANI/PAA layers were added to the ITO surface. Highest rates of electron transfer were observed for DMFc, whose oxidation potential coincides with the potential region where these SA-PANI/PAA films reach their optimal electroactivity. Apparent heterogeneous electron transfer rate constants, kS, measured voltammetrically, were ca.10 x higher for SA-PANI/PAA films on ITO, versus clean ITO substrates. These films also showed linear potentiometric responses with retention of the ITO transparency with the capability to create smoothest films using an aqueous deposition protocol, which proved important in other applications. ITO electrodes were also modified via chemisorption of carboxy functionalized EDOTCA and electropolymerization of PEDOTCA/PEDOT copolymers, when properly optimized for thickness and structure, enhance voltammetrically determined electron transfer rates (kS) to solution probe molecules, such as dimethylferrocene (DMFc). Values of kS ≥ 0.4 cm•sec⁻¹, were determined, approaching rates seen on clean gold surfaces. ITO activation combined with formation of these co-polymer films has the effect of enhancing the electroactive fraction of electrode surface, versus a non-activated, unmodified ITO electrode, which acts as a “blocked” electrode. The electroactivity and spectroelectrochemistry of these films helped to resolve the electron transfer rate mechanism and enabled the construction of models in combination with AFM, XPS, UPS and RAIRS studies. The surface topography, structure, composition, work function and contact angle, also revealed other desirable properties for molecular electronic devices. The carboxylic functionality of the EDOTCA molecule adds more desirable properties compared to normal PEDOT films, such as favoring the deposition of smooth films, increasing the optical contrast, participating in hydrogen-bonding, chemisorption to oxide surface, self-doping and providing a linker for incorporation of different functional groups, new molecules, or nanoparticles. Periodic sub-micron electrode arrays can be created using micro-contact printing and electropolymerization. The sinusoidal modulation of the refractive index of such confined conducting polymer nanostructures or nanoparticle stripes allows efficient visible light diffraction. The modulation of the diffraction efficiency at PANI and PEDOT gratings in the presence of an analytical stimulus such as pH or potential demonstrate the sensing capability at these surfaces. The template stripped gold surfaces that are being developed in our lab demonstrate several advantages over commercially available evaporated gold films especially for nanoscale surface modification.

Les polymères ferroélectriques et plus récemment les matériaux électrostrictifs ont attiré l’attention de la communauté scientifique en raison de leur capacité de conversion d’une excitation électrique en une réponse mécanique et vice versa. La synergie entre les propriétés électro actives de ces polymères et leurs propriétés physico-chimiques intrinsèques (souplesse, légèreté, grande résistance mécanique, facilité de mise en œuvre etc.) en font des candidats de choix pour des applications de types capteurs et actionneurs souples. Cette thèse vise à déterminer de façon systématique le comportement électromécanique des terpolymères P (fluorure de vinylidène-trifluoréthylène-chlorotrifluoroéthylène) [P (VDF-TrFE-CTFE)] par des techniques de cristallisation et de technologies additives et entend étendre ces terpolymères à l'application des dispositifs de type capteur de force électromécanique. L'influence du traitement thermique sur la réponse électromécanique et la microstructure des terpolymères a d'abord été étudiée. Il a été mis en évidence que la déformation électrostrictive transversale S31 pour chaque terpolymère traité thermiquement suit une loi quadratique avec le champ électrique. Par ailleurs il a été démontré que la déflexion d’un actionneur unimorphe est maximisée pour une fraction de phase cristalline de 39,3%. La dynamique moléculaire des terpolymères cristallisés a également été étudiée par spectroscopie diélectrique à large bande. Une dynamique segmentaire contrainte a été observée dans le terpolymère contenant la fraction cristalline la plus élevée pour laquelle une distribution étroite du temps de relaxation a été mise en évidence. En outre, il a été démontré que l’ajout d’agent plastifiant permet d’augmenter de manière significative la réponse électromécanique des terpolymères fluorés, ouvrant la voie vers de nouveaux matériaux électrostrictifs hautes performances fonctionnant sous faible champ électrique. De plus, la réponse diélectrique et électromécanique accrue du terpolymère dopé a été étudiée par microscope à force atomique et spectroscopie diélectrique dynamique. Ces analyses ont permis de lier l’augmentation de la réponse électromécanique de ces mélanges à un effet de polarisation interfaciale intensifié lors de l’augmentation de mobilité moléculaire de la phase amorphe rigide de ces terpolymères fluorés. Enfin, des dispositifs électromécaniques basés sur le polymère ferroélectrique P (VDF-TrFE) et le terpolymère électrostrictif P (VDF-TrFE-CTFE) ont été élaborés. Un procédé de fabrication additive utilisant la technologie d'impression jet d'encre a permis de concevoir et valider la faisabilité de réalisation de capteurs de force dynamique. Il a alors été démontré que les propriétés pseudo-piézoélectriques du terpolymère électrostrictif sont équivalentes à celles du copolymère ferroélectrique pour un faible champ électrique de biais de 7,5 V /μ
Electromechanical coupling effect has been paid the increasing attention due to ability to realize conversion between electric excitation and mechanical response and vice versa. Thanks to their flexibility, light weight, relatively low mechanical strength, ease of processability into large-area films, and ability to be molded into desirable geometric dimensions, polymers materials which possess an electromechanical coupling effect have been emerging recently. This thesis aims to systematically determine the electromechanical behavior of the P(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] terpolymers via crystallization and additive technology approaches and intend to extend such terpolymers to the electromechanical force sensor devices application. The influence of the thermal processing on the electromechanical response and microstructure of the terpolymers were firstly investigated. Cantilever unimorph bending measurement found the tip displacement δ and transverse strain S_31 for each thermally treated terpolymer followed a quadratic correlation with the electric field. δ was maximized at a 39.3% crystal content, instead of S_31 peaking at lowest crystal content, showing an exponential decay against the crystal fraction increasing. The dynamics of crystallized terpolymers were additionally studied via broadband dielectric spectroscopy. Constrained segmental dynamics was observed in the terpolymer containing the highest crystal fraction for which a narrow relaxation time distribution was found. Moreover, the enhanced dielectric and electromechanical response of DEHP doped terpolymer were interpreted via morphology microstructure and molecular mobility analysis. Interfacial polarization shifted to the high frequency by one decade because of dopant DEHP. Finally, electromechanical devices based on ferroelectric P(VDF-TrFE) and electrostrictive P(VDF-TrFE-CTFE) towards the dynamic force sensor implementation were designed and fabricated via inkjet printing technology. The bias electric field for terpolymer sensor was much lower than the poling electric field for a copolymer sensor. And the piezoelectric properties equivalent to the corresponding copolymer sensor can be obtained for a bias as low as 7.5 V/μ

碩士
高雄醫學大學
醫藥暨應用化學研究所
100
In this study, we have developed a new attenuated total reflection infrared (ATR-IR) spectroelectrochemical cell in which a nanoporous gold wire spiraled over the ZnSe crystal was used as the working electrode. With this system we can observe not only spectroelectrochemical behavior of target species but also the concentration fluctuation of reactants and products simultaneously. By monitoring the absorption bands variation of [Fe(CN)6]3- and [Fe(CN)6]4- at constant potential , a simple, effective and direct spectroelectrochemical sensing method is provided. In addition, the result demonstrates that the signal of ATR-IR can be increased with about 60% when a pontential was applied at the gold wire electrode. Further application on discriminating each individual component from the mixture of gallic acid and n-propyl gallate has been carried out. These two antioxidants are often used as additives in food industry. To singly use infrared spectrometer or electrochemical method is unable to distinguish the two compounds. However, to use the spectorelectrochemical method will be simple, effective and low cost method to achieve qualitative and quantitative analysis for the two compounds.

碩士
中原大學
化學研究所
98
In this study, a series of elctroactive polyimide-titania hybrid sol-gel materials were first successfully prepared under the incorporation of small basic molecules-catalyzed route through conventional thermal imidization reactions. Typically, tetraethyl orthotitanate (Ti(OEt)4) was used as inorganic sol-gel precursor reacting with coupling agent (acetylacetone; ACAC) to give inorganic solution. Subsequently, amine-capped aniline trimer (ACAT) functioned as small organic base catalyst for sol-gel reaction and diamine monomer for the preparation of electroactive polyimide was incorporated into inorganic solution. Dianhydride (BSAA) was then introduced into the previous solution to give electroactive poly(amic acid)/titania hybrid solution, followed by thermal imidization to give a series of electroactive polyimide/titania hybrid membranes. Morphology of titania particles existed in hybrid membranes was investigated by transmission electron microscopy (TEM) and exhibited approximate ~ 15 nm in diameter. It should be noted that the hybrid coatings was found to reveal better corrosion protection as compared to that of neat electroactive polyimide based on a series of electrochemical corrosion measurements in saline conditions. Effects of material composition on the mechanical strength, thermal stability, gas permeability, surface wettability of as-prepared elctroactive polyimide-titania materials were also investigated by DMA, TGA, DSC, GPA and contact-angle measurements, respectively. Redox behavior of as-prepared hybrid materials was identified by electrochemical CV studies.

碩士
中原大學
化學研究所
99
In this study, a series of elctroactive epoxy-titania hybrid sol-gel materials were first successfully prepared under the incorporation of small basic molecules-catalyzed route through conventional thermal curing reactions. Typically, tetraethyl orthotitanate (Ti(OC4H9)4) was used as inorganic sol-gel precursor reacting with coupling agent (acetylacetone; ACAC) to give inorganic solution. Subsequently, amine-capped aniline trimer (ACAT) functioned as small organic base catalyst for sol-gel reaction and diamine monomer as hardener for the preparation of electroactive epoxy was incorporated into inorganic solution. Bisphenol A diglycidyl ether (DGEBA) was then introduced into the previous solution to give electroactive epoxy /titania hybrid solution, followed by thermal epoxy-ring opening polymerization to give a series of electroactive epoxy/titania hybrid materials. Morphology of titania particles existed in hybrid membranes was investigated by transmission electron microscopy (TEM) and exhibited approximate 100 nm in diameter. It should be noted that the hybrid coatings was found to reveal better corrosion protection as compared to that of neat electroactive epoxy based on a series of electrochemical corrosion measurements in saline conditions. Effects of material composition on the thermal stability of as-prepared elctroactive epoxy-titania materials were also investigated by TGA and DSC, respectively. Redox behavior of as-prepared hybrid materials was identified by electrochemical CV studies. Enhancement of corrosion protection of as-prepared hybrid coating might be attributed to the electroactivity of epoxy resin and increase of gas barrier property of composite membrane resulted from the incorporation of titania particles. The passive metal oxide layer was formed onto the metallic surface due to the redox catalytic property of electroactive epoxy resin, which can be identified by scanning electron microscopy (SEM) and ESCA.