Made available in DSpace on 2017-07-21T20:42:47Z (GMT). No. of bitstreams: 1 Katieli Tives Micene.pdf: 4623642 bytes, checksum: 36b44944e6ba4a03ed1e2905ac60f954 (MD5) Previous issue date: 2014-08-31 / The technique of remelting superficial laser (RSL) has been set up as a tool of increasing interest in recent years because of its ability to improve the corrosion performance of aluminum alloys, as a result of the formation of thin melting layers, with refined microstructures and practically free of intermetallic precipitates and inclusions. The laser treated samples are much more chemically homogeneous than the base material. This technique is promising versatile and it can be used to modify the surface region by melting and rapid solidification processes without affecting the property of the base material. In this study we used the RSL technique in a media without gas protection and with 2 kW Yb-fiber laser (IPG YLR-2000S), it was applied to the hypereutectic alloy Al-2.0 wt%Fe in order to analyze the changes caused by the treatment, therefore the resultant microstructure was evaluated, as well as, the surface quality (roughness), hardness and corrosion resistance in the aerated media 25ºC, solution of H2SO4 0.1 mol/L. The study of corrosion was analyzed by different techniques such as corrosion potential measurement, cyclic voltammetry and potentiodynamic polarization tests (micro and macro polarization) and the technique of electrochemical impedance spectroscopy (EIS). By EIS technique, the characterization of the electrochemical behavior of the treated layer was performed and the values of the equivalent circuit, composed of resistors, capacitors and inductors. Therefore equivalent electrical circuits were generated according to the results presented by EIS using computational mathematical tools and Matlab software (tools toolbox) was used to perform this step. These results showed that the laser surface treatment performed on the alloy Al-2.0 wt%Fe resulted to the formation of a more compact structure, homogeneous and finer microstructure, producing an increase in microhardness at about 60.7% compared to the base material, reducing roughness, and corrosion rates was of approximately 11 lower smaller when compared to the untreated alloy, the laser treated layer has behaved passively in a wide range of potential, the polarization resistance of the treated layer was higher in relation to the untreated sample, by the EIS technique at high frequencies the samples had capacitive behavior, however, at low frequencies the samples had an inductive behavior. The treated layer thus evidence the effectiveness of treatment RSL to improve the surface quality of the samples and wear and corrosion resistance. / A técnica de Refusão Superficial a Laser (RSL) tem se configurado como uma ferramenta de crescente interesse nos últimos anos, por sua capacidade de melhorar o desempenho à corrosão das ligas de alumínio, tendo como resultado a formação de camadas fundidas finas com microestruturas refinadas que são praticamente isentos de precipitados intermetálicos e inclusões. As amostras tratadas com laser são muito mais homogêneas quimicamente do que o material base. Esta técnica é versátil e promissora e pode ser utilizado para modificar a região superficial por processos de fusão e solidificação rápida sem afetar a propriedade da amostra base. No presente trabalho utilizou-se a técnica de RSL sem proteção a gás com 2 kW Yb-fibra laser (IPG YLR-2000S) que foi aplicado na liga hipereutética Al-2%Fe a fim de analisar as modificações causadas pelo tratamento, para tanto foram avaliadas a microestrutura resultante, qualidade superficial (rugosidade), dureza e a resistência à corrosão em meio aerado à 25ºC em solução de H2SO4 0,1 mol/L. O estudo da corrosão foi analisado por diferentes técnicas tal como o monitoramento do potencial de corrosão, voltametria cíclica e ensaios de polarização potenciodinâmicas (micro e macropolarização), além da técnica de espectroscopia da impedância eletroquímica (EIE). Através da EIE, pôde-se caracterizar o comportamento eletroquímico da camada tratada e estipular os valores do circuito equivalente formado por resistores e capacitores e indutores. Para tanto foram gerados circuitos elétricos equivalentes aos dados apresentados pela EIE utilizando ferramentas matemáticas computacionais, sendo o software Matlab com ferramentas (toolbox) escolhido para realização desta etapa. Os resultados desta pesquisa indicaram que o tratamento superficial a laser efetuado na liga Al-2%Fe conduziu à formação de uma estrutura com microestrutura mais compacta, homogênea e refinada, levando ao aumento de dureza superficial em torno de 60,7% em relação ao material base, redução de rugosidade e taxas de corrosão de aproximadamente 11 vezes menor quando comparada com a liga não tratada, evidenciando assim a eficiência do tratamento RSL para melhorar a qualidade superficial das peças em termos de resistência ao desgaste à corrosão.

Ce travail de thèse est consacré au développement d’un dispositif autarcique pour le contrôle des amphétamines dans les égouts. Il a été conçu dans le cadre du projet européen MicroMole pour aider la police scientifique à résoudre des scènes concernant la localisation des laboratoires clandestins d’amphétamines et produits dérivés. Il est composé de trois volets : le premier volet est dédié au développement de deux générations de capteurs potentiométriques sélectifs à l’amphétamine en utilisant le ionophore commercial dibenzo-18-crown-6 éther dans un premier temps puis le ion-pair complexe [amphetamine-H]+[3,3’-Co(1,2-C2B9H11)2]- synthétisé comme sites actifs pour la reconnaissance sélective d’amphétamine. Le deuxième volet est consacré au développement d’un système microfluidique passif permettant de contrôler le flux d’échantillon arrivant à la partie sensible du capteur en utilisant des micro-filtres et micro-mélangeurs. Le troisième et dernier volet est dédié à la conception et fabrication d’un système autonome d’échantillonnage miniaturisé pour le stockage des échantillons dans les égouts lors des enquêtes menées par la police scientifique correspondant à la localisation de laboratoires clandestins d’amphétamines / The work in this thesis is devoted to the development of an autarkic device for real-time monitoring of amphetamines in sewage. It has been developed within the EU project Micromole to help Law Enforcement Agents (LEA) to solve forensic scenarios related to the production of amphetamines and amphetamine-type stimulants (ATS). It is composed of three main sections. The first section is devoted to the development of two generation of potentiometric sensors for the detection of amphetamines using first, the commercial ionophore dibenzo-18-crown-6 ether, then the synthesized ion-pair complex [amphetamine-H]+[3,3’-Co(1,2-C2B9H11)2]- as active sites for amphetamine recognition. The second section is dedicated to the fabrication of a passive microfluidic system integrated into a Lab-on-a-Chip to protect the sensor from the harsh environment through the control of the sample amount reaching the sensor. For this purpose, the microfluidic system formed a combination of passive micromixers, microfilters and microchannels. The final section was devoted to the development of an autarkic sample storage unit to help LEA to store spontaneous samples during forensic investigations related to the clandestine production of amphetamines in illegal laboratories

Made available in DSpace on 2014-12-17T15:42:08Z (GMT). No. of bitstreams: 1 EliasJL_DISSERT.pdf: 3301731 bytes, checksum: ed73b5da4a7dcfb4e0f473a7c83986b2 (MD5) Previous issue date: 2013-05-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The study of polymer blends has been an alternative method in the search field of new materials for obtaining materials with improved properties. In this work blends of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) doped with titanium dioxide (TiO2) were studied. The PEO is a polymer semicrystalline structure varying between, 70 and 84% crystallinity, while the PMMA exhibits behavior amorphous in their structure. The use of TiO2 is related to corrosion-resistant of titanium as well as good heat transfer and other characteristics. The study of these polymer blends doped TiO2 gives the properties junction organic (polymer) and inorganic (oxide) which leads to modification of the properties of the resultant material. The blends were doped TiO2 (POE/PMMA/TiO2) in different proportions of the PMMA with the PEO and TiO2 fixed. The ratios were: 90/10/0,1; 85/15/0, 1; 80/20/0,1, 75/25/0,1 and 70/30/0,1. The resulting material was obtained in powder form and being characterized by Fourier Transformed Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Electrochemical Impedance Spectroscopy (EIS). The infrared spectra (IR) for the blends in different ratios showed a band at 1744 cm-1, characteristic of the C=O stretching, which increases in intensity with increasing PMMA composition, while in the spectrum of pure PEO this band is absent. This may suggest that the interaction is occurring between the polymers. In the micrographs of the blends also observed change in their surfaces with variation of the composition of PMMA, contributing to the change of the electrical properties of the material. The EIS data showed that the material exhibited conductivity of the order of 10-6 S.cm-1. The blend in the ratio B2(85/15/0, 1) showed better conductivity, σ = 1.56 x 10-6 S.cm-1. It was observed that the diffusion coefficient for the blends, B5(70/30/0, 1) was the largest, 1.07 x 10-6 m2.s-1. The XRD data showing that, with the variation in the composition of the PMMA blend crystallinity of the material is decreased reaching a minimum B3(80/20/0,1), and then increases again. Thermal analysis suggests that blends made from the material obtained can be applied at room temperature / O estudo de blendas polim?ricas tem sido um m?todo alternativo no campo de pesquisa de novos materiais para obten??o de materiais com melhores propriedades. Neste trabalho blendas de poli(metacrilato de metila) (PMMA) e poli(?xido de etileno) (POE) dopadas com di?xido de tit?nio (TiO2) foram estudadas. O POE ? um pol?mero de estrutura semicristalina com varia??o entre, 70 e 84% de cristalinidade, enquanto o PMMA apresenta comportamento amorfo em sua estrutura. O uso do TiO2 est? relacionado ? alta resist?ncia a corros?o do tit?nio, assim como a boa transfer?ncia de calor, al?m de outras caracter?sticas. Uma das suas aplica??es ? a fotocat?lise. O estudo destas blendas polim?ricas dopadas com TiO2 proporciona a jun??o das propriedades org?nica (pol?meros) e inorg?nica (?xido), o que leva a modifica??o das propriedades do material resultante. As blendas foram dopadas com TiO2 (POE/PMMA/TiO2) em diferentes propor??es do POE e PMMA com o TiO2 fixo. As propor??es foram: 90/10/0,1; 85/15/0,1; 80/20/0,1; 75/25/0,1 e 70/30/0,1. O material resultante obtido foi em forma de p? sendo caracterizado por Espectroscopia de Infravermelho por Transformada de Fourier (FTIR), Microscopia de Varredura Eletr?nica (MEV), Difra??o de Raios X (DRX), Termogravimetria (TG/DTG) e Espectroscopia de Imped?ncia Eletroqu?mica (EIE). Os espectros de infravermelho (IV) para as blendas em diferentes propor??es apresentaram uma banda em 1744 cm-1, caracter?stica do estiramento C=O, que aumenta de intensidade com o aumento da composi??o do PMMA, enquanto no espectro do POE puro esta banda est? ausente. Isto pode sugerir que est? ocorrendo ? intera??o entre os pol?meros. Nas micrografias das blendas, tamb?m, observa-se mudan?a em suas superf?cies com a varia??o da composi??o do PMMA o que pode contribuir na mudan?a das propriedades el?tricas do material. Os dados de EIE mostraram que o material apresentou condutividade da ordem de 10-6 S.cm-1. A blenda na propor??o B2(85/15/0,1) apresentou melhor condutividade, σ = 1,56 x 10-6 S.cm-1. Observou-se que o coeficiente de difus?o para as blendas, a B5(70/30/0,1) foi o maior, 1,07 x 10-6 m2.s-1. Os dados de DRX mostram que, com a varia??o na composi??o de PMMA na blenda a cristalinidade do material vai diminuindo atingindo um m?nimo em B3(80/20/0,1) e, ent?o, volta a aumentar. An?lise t?rmica realizada das blendas sugere que o material obtido pode ser aplicado em temperatura ambiente

Made available in DSpace on 2014-12-17T15:42:13Z (GMT). No. of bitstreams: 1 WilliamGM_DISSERT.pdf: 1986302 bytes, checksum: 71e6a449a8f77e2f64a9c3908ab5410d (MD5) Previous issue date: 2013-07-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / A new self-sustainable film was prepared through the sol-gel modified method, previously employed in our research group; sodium alginate was used as the polymer matrix, along with plasticizer glycerol, doped with titanium dioxide (TiO2) and tungsten trioxide (WO3). By varying WO3 concentration (0,8, 1,6, 2,4 and 3,2 μmol) and keeping TiO2 concentration constant (059 mmol), it was possible to study the contribution of these oxides on the obtained films morphological and electrical properties. Self-sustainable films have analyzed by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XDR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Electrochemical Impedance Spectroscopy (EIS). By the IR specters, it was possible identify the TiO2, and posteriorly WO3, addition has provided dislocation of alginate characteristics bands to smaller vibrations frequencies indicating an electrostatic interaction between the oxides and the polymer matrix. Diffractograms show predominance of the amorphous phase in the films. SEM, along with EDX, analysis revealed self-sustainable films showed surface with no cracks and relative dispersion of the oxides throughout the polymer matrix. From Impedance analysis, it was observe increasing WO3 concentration to 2,4 μmol provided a reduction of films resistive properties and consequent improvement of conductive properties / Um novo filme autossustent?vel foi preparado, atrav?s do m?todo sol-gel modificado, anteriormente empregado no nosso grupo de pesquisa, utilizando como matriz polim?rica o alginato de s?dio, juntamente com o plastificante glicerol, dopado com di?xido de tit?nio (TiO2) e tri?xido de tungst?nio (WO3). Variando as concentra??es do WO3 (0,8, 1,6, 2,4 e 3,2 μmol), e mantendo constante a concentra??o do TiO2 (0,59 mmol), foi poss?vel estudar a contribui??o destes ?xidos nas propriedades morfol?gicas e el?tricas dos filmes obtidos. Os filmes autossustent?veis foram caracterizados atrav?s das t?cnicas de Espectroscopia de Infravermelho com Transformada de Fourier (FTIR), Difratometria de Raios X (DRX), Microscopia Eletr?nica de Varredura (MEV), Espectroscopia de Raios X por Dispers?o de Energia (EDS) e Espectroscopia de Imped?ncia Eletroqu?mica (EIE). Atrav?s dos espectros de FTIR foi poss?vel identificar que a adi??o do TiO2 e, posteriormente, do WO3 proporciona deslocamento das bandas caracter?sticas do alginato para menores frequ?ncias de vibra??o, indicando uma intera??o eletrost?tica dos ?xidos com a matriz polim?rica. Os difratogramas evidenciaram a predomin?ncia do comportamento amorfo nos filmes. As an?lises de MEV, juntamente com as de EDS, revelaram que os filmes autossustent?veis apresentam uma superf?cie sem trincamento e de relativa dispers?o dos ?xidos ao longo da matriz polim?rica. Atrav?s da EIE observouse que o aumento da concentra??o de WO3 at? 2,4 μmol proporcionou uma redu??o do comportamento resistivo dos filmes, e consequente melhoria em suas propriedades condutoras

Philosophiae Doctor - PhD / Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate ((PSNP-OSO3) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3 −) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10−8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were <100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 μA/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 μM NO2 −, were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3 −; respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors. / South Africa

La conservation du circuit secondaire des réacteurs à eau sous pression pendant les périodes d’arrêts nécessite la mise en oeuvre de conditions spécifiques afin de limiter les phénomènes de corrosion des aciers au carbone, qui composent en grande majorité ce circuit. Les méthodes de conservation impliquent une mise en oeuvre contraignante et couteuse lors des arrêts de tranche. L’injection d’amines filmantes (AF), en fonctionnement avant les phases d’arrêt, constitue une voie d’étude intéressante afin de protéger les composants en acier au carbone tout en simplifiant la mise en oeuvre de la conservation à l’arrêt. Le but de ce travail de thèse est d’étudier le comportement et l’efficacité d’une AF pour la protection des aciers au carbone dans les conditions représentatives des centrales REP. Pour mener à bien ces travaux, la spectroscopie d’impédance électrochimique a été utilisée en appui à des observations de surface par microscopie optique et microscopie électronique à balayage et à des analyses de surface par spectroscopie de photoelectrons X. Tout d’abord, des films d’AF formés sur un acier au carbone à basse température (80 °C) dans des conditions de dépôts optimisées ont été caractérisés (épaisseur, permittivité) et leurs propriétés inhibitrices de corrosion évaluées en milieu Na2SO4 à pH proche de 10. Cette première étude a permis de valider une méthode de caractérisation des films à travers l’analyse des données d’impédance à haute fréquence. Puis, cette méthode a été utilisée pour suivre et caractériser la formation de films d’AF d’une part, sur de la magnétite électrodéposée dans les conditions de dépôt optimisées, et d’autre part, sur des coupons d’acier au carbone polis dans les conditions thermo-chimiques du circuit secondaire à 120 °C, 220 °C et 275 °C en fixant la concentration en AF en solution à 2 ppm. Les suivis par impédance au cours du temps de l’acier au carbone traité avec l’AF ont permis de tester l’efficacité des films pendant une phase de conservation humide. Les résultats mettent en évidence l’influence des conditions de formation des films d’AF (température, concentration en AF, temps de traitement et nature du substrat) sur leur efficacité contre la corrosion en conservation. D’après nos résultats, seul le traitement réalisé à 120 °C a abouti à la formation d’un film d’AF pour lequel la protection de l’acier au carbone a été confirmé à l’issu d’une conservation humide de 30 jours. Les films formés sur l’acier au carbone nu à basse température ont montré une forte susceptibilité à la désorption au cours du temps, de même que pour les films d’AF déposés à 220 °C, et ce même avec une forte concentration en AF de 25 ppm. Enfin, pour les dépôts effectués à 275 °C, la cause la plus probable de la diminution de l’efficacité contre la corrosion observée entre 2 h et 24 h de traitement viendrait de la dégradation thermique de l’AF, détectée en solution au-delà de 2 h d’exposition à cette température. / The preservation of the secondary circuit of pressurized water reactors during layup periods requires the implementation of specific conditions in order to limit the corrosion phenomena of carbon steels, which constitute the major part of this circuit. These conservation methods are costly and very demanding for the operating. The injection of film-forming amines (FFA), in operation in before shutdown phases, is an interesting route of study to protect carbon steel components while simplifying the conservations. The aim of this thesis work is to study the behavior and the efficiency of an FFA for the protection of carbon steels in the representative conditions of PWRs. To carry out this work, electrochemical impedance spectroscopy was used with surface observations by optical microscopy and scanning electron microscopy and surface analysis by X-ray photoelectron spectroscopy. First, FFA films formed on a carbon steel at low temperature (80 ° C) under optimized deposition conditions were characterized (thickness and permittivity) and their corrosion inhibiting properties evaluated in an Na2SO4 medium at pH close to 10. This study allowed to validate a method for the film characterization through the analysis of the high frequency part of the impedance data. Then, this method was used to follow and characterize the FFA film formation on electrodeposited magnetite in optimized deposition conditions in one hand, and on a carbon steel under the thermo-chemical conditions of the secondary circuit at 120 °C, 220 ° C and 275 °C using FFA concentrations fixed at 2 ppm on the other hand. Impedance monitoring over time of the FFA-treated carbon steel allowed the effectiveness of the films to be followed during humid conservation. The results highlight the influence of FFA film formation conditions (temperature, FFA concentration, treatment time and nature of the substrate) on their efficiency against corrosion during conservation. According to our results, only the treatment at 120 °C resulted in the formation of an FFA film that could protect the carbon steel from corrosion in humid conservation during 30 days. The films formed on bare carbon steel at low temperature showed a high susceptibility to desorption over time, as well as for FFA films deposited at 220 °C, even with a high FFA concentration of 25 ppm. Finally, for FFA deposition made at 275 °C, the decrease of the efficiency against corrosion observed over time would come from the thermal degradation of the FFA, detected in solution beyond 2 hours of exposure to this temperature.

The demand for electric vehicles is increasing rapidly as the world is preparing for a fossil fuel-free future in the automotive field. Lithium battery technologies are the most effective options to replace fossil fuels due to their higher energy densities. However, safety remains a major concern in using lithium as the anode, and the development of non-volatile, non-flammable, high conductivity electrolytes is of great importance. In this dissertation, a gel polymer electrolyte (GPE) consisting of ionic liquid, lithium salt, and a polymer has been developed for their application in lithium batteries. A comparative study between GPE and ionic liquid electrolyte (ILE) containing batteries shows a superior cyclic performance up to 5C rate and a better rate capability for 40 cycles for cells with GPE at room temperature. The improvement is attributed to GPE’s improved stability voltage window against lithium as well as higher lithium transference number. The performance of the GPE in lithium-sulfur battery system using sulfur-CNT cathodes shows superior rate capability for the GPE versus ILE for up to 1C rates. Also, GPE containing batteries had higher capacity retention versus ILE when cycled for 500 cycles vii at C/2 rate. Electrochemical impedance spectroscopy (EIS) studies reveal interfacial impedances for ILE containing batteries grew faster than in GPE batteries. The accumulation of insoluble Li2S2/Li2S on the electrodes decreases the active material thus contributes to capacity fading. SEM imaging of cycled cathodes reveals cracks on the surface of cathode recovered from ILE batteries. On the other hand, the improved electrochemical performance of GPE batteries indicates better and more stable passivation layer formation on the surface of the electrodes. Composite GPE (cGPE) containing micro glass fillers were studied to determine their electrochemical performance in Li batteries. GPE with 1 wt% micro fillers show superior rate capability for up to 7C and also cyclic stability for 300 cycles at C/2 rate. In situ, EIS also reveals a rapid increase in charge transfer resistance in GPE batteries, responsible for lowering the capacity during cycling. Improved ion transport properties due to ion-complex formations in the presence of the micro fillers, is evidenced by improved lithium transference number, ionic conduction, and ion-pair dissociation detected using Raman spectroscopy.

Ce travail a permis dans un premier temps, l’élaboration de composites semi-conducteurs à base de nanoobjetspossédant des caractéristiques électrochimiques spécifiques en fonction du type d’inclusion (siliciumdopé N ou dopé P et oxydes métalliques, ZnO, SnO2, NiO). Ces composites ont permis d’obtenir avec succèsdes encres de sérigraphie présentant un comportement électrique semi-conducteur qui ont servi à laréalisation d’électrodes par dépôt sur divers supports et notamment des films plastiques souples. Lamodification chimique des supports réalisés a été étudiée en vue de pouvoir utiliser ce type de matériaucomme transducteurs électrochimiques en les intégrant dans des dispositifs de types capteurs et biocapteurs.Dans un second temps, un composite photostructurable conducteur a également été développé en se basantsur la technologie SU-8, et en y incluant des particules de graphite ou des nanoparticules de carbone noir.Ce photocomposite a été par la suite fonctionnalisé avec succès par des dérivés diazonium, tel que lebromobenzène diazonium ou le nitrobenzène diazonium dont les greffages ont été suivis par spectroscopied’impédance. Enfin, le greffage d’oligonucléotides via la chimie des sels d’aryldiazonium a également étéeffectué avec succès et utilisé pour la détection de séquences cibles à des concentrations de 100 pM à 200nM. / The first part of this study report the development of semiconducting composites consisting ofsemiconducting nano-objects (N doped, P doped silicon or metals oxides, ZnO, SnO2, NiO) held together inan insulating polymeric matrix and exhibiting typical semiconductor impedance signals according to thecharge used and with clear differentiation between the two fundamental type of semiconductor, n-type and ptype.This new composites have been used as screen-printing ink. Electrodes on various substrates (PVC,glass) have been successfully prepared following this cost-effective method. Surface functionalization ofthese electrodes by chemicals compounds and biomolecules was studied using impedance spectroscopy andchemiluminescent detection in order to assess their integration as electrochemical transducers in sensorsand biosensors microdevices.The second part of this work consisted in photopatternable conductive composite elaboration using a simpleand straightforward route based on SU-8 epoxy-based negative photoresist matrix mixed with carbon filler.The electrodes, obtained by the classical photolithography method, and after an electrochemical pretreatment,exhibited very good electrochemical behaviors, opening the path to various electrochemicaldetections and grafting possibilities. Finally, the direct electrografting of biomolecules was demonstratedusing aniline modified oligonucleotide probes. The grafted probes were shown to be available for targethybridization and the material compatible with a chemiluminescent detection of the interactions between theimmobilized single stranded DNA and its complementary sequence in a 100 pM to 200 nM range.

Le couplage de la spectroscopie d’impédance électrochimique(EIS) et de la spectroscopie photoélectronique à rayonnement X(XPS) a permis d’étudier en profondeur le lien entre la structure etles propriétés électrochimiques d’électrolytes solides en couchesminces, ainsi que de l’interface formée avec le matériau d’électrodepositive LiCoO2. L’incorporation d’azote dans la structure duLiPON, électrolyte solide de référence dans les microbatteries, estcaractérisée par la formation de lacunes de lithium et d’oxygènesfavorables au transport des ions lithium. Un électrolyte solideLiPOS a été développé par pulvérisation cathodique radiofréquencevia l’incorporation de soufre dans la structure initiale Li3PO4. Laprésence d’une interface solide/solide entre le LiPON et LiCoO2 estcaractérisée par une réduction partielle du cobalt et une oxydationdu LiPON à son voisinage, vraisemblablement responsable del’augmentation de la résistance de transfert de charges entre lesdeux matériaux. / The link between the structure and the electrochemicalproperties of thin-film electrolytes and the interface formed withthe cathode material LiCoO2 has been intensively studied bycoupling Electrochemical Impedance Spectroscopy (EIS) and X-rayPhotoelectron Spectroscopy (XPS). Nitrogen incorporation intoLiPON, reference solid-state electrolyte for microbatteries, ischaracterized by the formation of lithium and oxygen vacancies,increasing the lithium ions transport. A sulfide based thin filmelectrolyte called LiPOS has been developed by radiofrequencysputtering, with the incorporation of sulfur into the initial Li3PO4structure. The solid/solid interface between LiPON and LiCoO2 ischaracterized by a partial reduction of cobalt and oxidation ofLiPON, which is in all probability responsible of the increase of thecharge transfer resistance between the two materials.

<p>In the presented work, immunosensors for detection of Aflatoxin B1 based on different immobilization platforms were studied. Synthesis of an electroactive hydrogel was also carried out. Aflatoxins are a group of mycotoxins that have deleterious effects on humans and are produced during fungal infection of plants or plant products. Electrochemical immunosensor for the determination of Aflatoxin B1 (AFB1) was developed with anti-aflatoxin B1 antibody immobilized on Pt electrodes modified with polyaniline (PANi) and polystyrene sulphonic acid (PSSA). Impedimetric analysis shows that the electron transfer resistances of Pt/PANi-PSSA electrode, Pt/PANi-PSSA/AFB1-Ab immunosensor and Pt/PANi-PSSA/AFB1-Ab incubated in BSA were 0.458, 720 and 1066 k&Omega / , respectively. These results indicate that electrochemical impedance spectroscopy (EIS) is a suitable method for monitoring the change in electron-transfer resistance associated with the immobilization of the antibody. Modelling of EIS data gave equivalent circuits which showed that the electron transfer resistance increased from 0.458 k&Omega / for Pt/PANi-PSSA electrode to 1066 k&Omega / for Pt/PANi-PSSA/AFB1-Ab immunosensor, indicating that immobilization of the antibody and incubation in BSA introduced an electron transfer barrier. The AFB1 immunosensor had a detection limit of 0.1 mg/L and a sensitivity of 869.6 k &Omega / L/mg.</p>