Este trabalho tem como principal objetivo comparar as respostas de biossensores amperomé-tricos preparados a partir do uso de uma enzima, a tirosinase (polifenoloxidase, PFO), quando nas formas purificada e adquirida comercialmente e de extrato bruto enzimático do fruto do abacate (Persea Americana). As soluções de PFO apresentaram valores de atividades enzimá-ticas de 479 unidades de enzimas ativas por mililitro (UA mL-1) (purificada) e 259 UA mL-1 (extrato bruto). A enzima nas duas formas (pura e como extrato bruto) foi imobilizada quimi-camente em substratos de Au modificados com monocamadas automontadas (self-assembly monolayers, SAMs) de ácido mercaptopropiônico (MPA) pela técnica de impressão por mi-crocontato (CP). Os biossensores foram preparados sobre substratos de Au modificados por CP com um molde elastomérico de polidimetilsiloxano (PDMS), cujas trilhas paralelas de 100 m foram produzidas pela cura polimérica sobre um molde mestre de GaAs. A réplica de PDMS se mostrou fiel em relação ao molde mestre nos picos e vales, mas apresentou defeitos na borda dos moldes. Com o objetivo de otimizar o funcionamento dos biossensores, eles fo-ram caracterizados pelas técnicas de voltametria cíclica e cronoamperometria com um sistema de análise de injeção em fluxo (FIA) em meio de catecol a diferentes concentrações. Os po-tenciais de oxidação do catecol nos eletrodos de Au modificados foram observados em 418 e 365 mV, em pHs ótimos de funcionamento de 7,0 e 7,2, e com limites de detecção de 6,65 nmol L-1 e 4,65 nmol L-1 para os biossensores com a enzima purificada e com o extrato bruto, respectivamente. A saturação dos sensores teve início a uma concentração de catecol de 0,02 mol L-1. Com estes resultados, mostramos que é possível o preparo de biosensores com um baixo custo, eficientes e miniaturizadas a partir do uso da PFO na forma extrato bruto do fruto do abacate para a detecção de compostos fenólicos, tal como catecol, abrindo assim a possibi-lidade de uso destes biossensores na análise e no monitoramento de pesticidas presentes no solo e na água. / The main objective of this master thesis is to compare the performance of amperometric biosensors prepared using the purified tirosinase (PPO) enzyme, (commercially acquired) and the PPO present in the enzymatic crude extract from the avocado fruit (Persea Americana). The PPO solutions had 479 units of active enzyme per milliliter (UA mL-1) (purified) and 259 UA mL-1 (crude extract). Both forms of the enzyme (purified and crude extract) were chemically immobilized on gold substrates patterned with 3-mercaptopropionic acid (MPA) self assembled monolayers (SAMs), using the microcontact printing (CP) technique. The biosensors were prepared on gold subtracts patterned using CP with a polydimethylsiloxane (PDMS) elastomeric mold, that was shaped in the form as tracks using a gallium arsenate master mold. The PDMS mold was quite similar to the master mold in its peaks and valleys, but defects were found on the edges. In order to optimize the parameters of the biosensors , they were characterized using cyclic voltammetry and chronoamperometry techniques in a FIA system by cathecol injections at different concentrations. The oxidation potentials for the cathecol analysis using the patterned biosensors were observed at 418 and 365 mV, the optimum pH were 7,0 and 7,0, with detection limits of 6,65 nmol L-1 and 4,65 nmol L-1 for the purified enzyme and crude extract biosensors, respectively. The biosensors saturation point started at 0,02 mol L-1 of cathecol concentration. With this results, we demonstrate that it is possible to use miniaturized, efficient, low cost biosensors based on tyrosine from the avocado´s fruit crude extract to detect phenolic compounds, as the cathecol. This expands the possibility of using this biosensors in the analysis and monitoring pesticides in water and soil.

L’objectif de cette thèse de doctorat vise à développer des monocouches organiques auto-assemblées (SAMs) destinées à mieux comprendre la transposition depropriétés macroscopiques observées en solution vers le milieu confiné. Dans le cadre de notre étude, nous avons synthétisé des précurseurs électroactifs (i.e. dérivés du thiophène, du pérylènediimide et du tétrathiafulvalène) comportant des mécanismes électrochimiques (i.e. schéma carré, EDimE) et des propriétés optiques (absorption et/ou émission de fluorescence) spécifiques. L’immobilisation des précurseurs sur substrats d’or à l’aide de fonctions disulfures a permis d’élaborer des SAMs. L’étude des électrodes modifiées par des méthodes électrochimiques (voltammétrie cyclique) et spectroélectrochimiques a permis d’établir des relations de type structure/propriétés et structure/réactivité. / This thesis is devoted to the elaboration of new organic self-assembled monolayers (SAMs) for a better understanding of the transposition of macroscopic properties that are well-known in solution onto metallic surface. In our study we have synthesised electroactive precursors (i.e. thiophene, perylene diimide and tetrathiafulvalene derivatives) with electrochemical mechanisms (i.e. squared scheme, EDimE) and specific optical properties (absorption and/or emission of fluorescence). The immobilization of the precursors on gold substrates was achieved using disulphide moieties to form SAMs. The study of the modified electrodes by electrochemical techniques (cyclic voltammetry) and spectroelectrochemistry helped to establish detailed structure-properties and structure-reactivity relationships, especially on mixed SAMs.

L'insertion de couches minces d'oxyde métallique (MO) à l'interface entre les électrodes conductrices (FTO / ITO, Métaux) et la couche active (polymère, pérovskite) constitue une solution prometteuse pour améliorer les performances des dispositifs photovoltaïques organiques et hybrides. La procédure consiste à introduire des couches MO fonctionnalisées par des monocouches auto-assemblées dipolaires (SAMs) à l'interface entre l'électrode conductrice et la couche active. Les couches SAMs supportant des dipôles perpendiculaires à la surface peuvent avoir un impact important sur les dispositifs électroniques à la fois en affectant la croissance et l'organisation de la couche organique active et en accordant le travail de sortie des couches MO. Dans ce travail, nous montrons que le greffage des molécules dipolaires sur des couches minces de MO peut affecter considérablement les performances des cellules photovoltaïques. Cet impact dépend fortement de l'orientation du dipôle permanent situé sur la molécule SAM. / The insertion of very thin metal-oxide (MO) layers at the interface between the conductive electrodes (FTO/ITO, Metals) and the active layer (polymer, perovskite) presents a promising solution to improve the performances of organic and hybrid photovoltaic devices. The procedure is about introducing MO layers functionalized by dipolar self-assembling monolayer’s (SAMs) at the interface between the conductive electrode and the active layer. The SAM layers bearing dipoles perpendicular to the surface that can have a large impact on the electronic devices both by affecting the growth and organization of active organic layer and by tuning the work function of the MO layers. In this work we show that the grafting of dipole molecular on top of MO thin films can considerably affect the performance of the photovoltaic cell. The impact on these performances depends strongly on the orientation of the permanent dipole lying on the SAM molecule.

This thesis deals with the synthesis and characterization ofnovel polyhydroxyl surfactants. The first part describes thesynthesis of a number of stereoisomers of a polyhydroxylsurfactant, and the second part concerns surface chemicalcharacterization. A stereodivergent route for preparation of the hydrophilichead group was developed, featuring consecutive stereoselectivedihydroxylations of a diene. This afforded in total fourdifferent polyhydroxyl head groups. These surfactant headgroups were natural and unnatural sugar analogues, and wereused for the coupling with two different hydrophobic tailgroups. Three of these surfactants were used to investigate thechiral discrimination in Langmuir monolayers at an air-waterinterface. The isotherms showed a remarkable difference incompressibility between surfactants of diastereomericrelationship and also a pronounced chiral discriminationbetween racemic and enantiomerically pure surfactants favoringheterochiral discrimination. / <p>NR 20140805</p>

A dimensionality controlled metal insulator transition in epitaxial [LaNiO3 (d nm)/LaAlO3(2nm)]10 (100) superlattices (thereafter [d/2]10 SLs) is demonstrated for decreasing LaNiO3 single layer thickness from 4nm down to 1.2 nm. The [4/2]10 SL shows metallic behavior with positive resistivity temperature coefficient, while the [2/2]10 SL shows a metal-insulator transition with crossover from 3D to two-dimensional single-layer dimensionality. Strong localization appears for the [1.2/2]10 SL with the resistivity being dominated by two-dimensional variable range hopping with a localization length of about 0.035 nm.

In this paper, a nanometer-sized gold electrode with an effective radius around several tens of nanometers has been modified with a monolayer of alkanethiols. There are pinholes in the monolayer, and the pinholes can be used as very small electrode. Our evaluation shows that it is possible to have only one pinhole on the monolayer covered electrode. The single pinhole electrode has been used to study the electrochemical behaviors of fast and slow electrochemical reactions. Our results show that the electrochemical response of a slow electrochemical reaction is not a Butler-Volmer response if the electrode is small enough.

Partitioning of poly(ethyleneglycol) (PEG) molecules in 2-D and 3-D systems is presented as a self-assembly approach for controlling non-specific adsorption of proteins at interfaces. Lateral restructuring of multi-component Langmuir monolayers to accommodate adsorbing proteins was investigated as a model 2-D system. Ferritin adsorption to monolayers containing cationic, nonionic, and PEG bearing phospholipids induced protein sized binding pockets surrounded by PEG rich regions. The number, size, and distribution of protein imprint sites were controlled by the molar ratios, miscibility, and lateral mobility of the lipids. The influence of PEG chain length on the ternary monolayer restructuring and protein distribution was also investigated using DSPE-PEGx (x= 7, 16, 22). Monolayer miscibility analysis demonstrated that longer PEG chains diminished the condensed phase formation for a fixed ratio of lipids. Thus, incorporation of longer PEG chains, intended to diminish protein adsorption outside of the imprint sites of cationic / non-ionic lipids, leads to dramatic changes in monolayer phase behavior and protein distribution in this 2-D system. The assembly of PEG-amphiphiles at elastomer surfaces and subsequent protein adsorption was investigated as a model 3-D system. Polydimethylsiloxane (PDMS) substrates were modified with block copolymers comprised of PEG and PDMS segments by two methods: (1) the block copolymer was mixed with PDMS during polymerization; (2) the block copolymer diffused into solvent swollen PDMS monoliths. Hydrophilic surfaces resulted for both approaches that, for 600 D block copolymer, exhibited up to 85% reduction in fibrinogen adsorption as compared to native PDMS. Higher MW block copolymers (up to 3000 D) resulted in less hydrophilic surfaces and greater protein adsorption, presumably due to diffusion limitations of copolymer in the PDMS monolith. All modified PDMS surfaces were dynamic and restructured when cycled between air and water. PDMS transparency also decreased with increase in block copolymer concentration for both methods, limiting this modification protocol for applications requiring high polymer transparency. The 2-D system presents a bottom-up approach, where adsorbing protein constructs the binding site, while the 3-D system presents a top down approach, where protein-binding elements may be introduced into the PEG-bearing polymer for fabrication of surfaces with controlled protein adsorption.

La conception de surfaces "intelligentes" sensibles aux stimuli externes (lumière, champ électromagnétique, environnement chimique ...) attire un intérêt considérable en raison de leur potentiel pour une large gamme d'applications. Dans ce contexte, nous étudions les propriétés de transfert de photos d'une monocouche de photochromes organiques immobilisés sur des surfaces de silicium.Les groupes Fulgimide sont ancrés par liaison covalente au-dessus de monocouches alkyliques fonctionnalisées greffées sur des surfaces Si (111) exemptes d'oxyde. La composition des monocouches dans les états stationnaires photo EPS-UV et EPS-Vis est déterminée à partir de l'analyse quantitative de l'intensité de la bande infrarouge caractéristique des isomères ouverts (E, Z) et fermés (C). La photocommutation de surface UV-Vis est surveillée par des mesures infrarouge à transformée de Fourier in situ en temps réel lors de l'éclairage UV-Vis. Les études de dépendance temporelle de la photocommutation montrent une diminution de l'efficacité quantique pendant la commutation. Cette diminution de l'efficacité quantique dépend faiblement de la densité de fulgimide et n'est pas observée en solution. Cependant, les mesures de PC en fonction du flux de photons ont permis de déterminer une section efficace de la PC (σ) de la majorité des molécules commutables. Les études de photocommutation dépendantes de la polarisation montrent une forte dépendance de σ par rapport au champ électrique local de la lumière excitante d'isomérisation.Les modèles analytiques et les simulations de Monte Carlo basées sur les interactions des voisins les plus proches sont effectuées pour obtenir une meilleure compréhension des observations expérimentales. Ces simulations expliquent qualitativement la dépendance à la température de la cinétique de commutation, diminuant l'efficacité quantique et la faible densité de surface de la photocommutation.Il a été montré dans cette thèse que σ dépend du champ électrique local. À l'instar de la spectroscopie Raman améliorée en surface, le champ électrique local sur les surfaces augmente en raison du plasmon des nanoparticules d'or. Le plasmon de la monocouche de nanoparticules d'or et ainsi l'amélioration du champ électrique dépend de la longueur d'onde de l'irradiation externe. L'exploitation de cet effet améliore significativement la cinétique de la commutation en fonction de la longueur d'onde de l'irradiation. Cette amplification dépendant de la longueur d'onde de la cinétique de la commutation s'explique par la même amplification dépendante de la longueur d'onde du champ électrique. / The design of “smart” surfaces responsive to external stimuli (light, electromagnetic field, chemical environment…) is attracting considerable interest because of their potential for a wide range of applications. Within this context we are studying the photoswitching properties of a monolayer of organic photochromes immobilized onto silicon surfaces.Fulgimide groups are anchored through covalent linkage atop of functionalized alkyl monolayers grafted on oxide free Si(111) surfaces. The monolayers composition at the photo stationary states PSS-UV and PSS-Vis is determined from quantitative analysis of the infrared band intensity characteristic of open (E,Z) and closed (C) isomers. The UV-Vis surface photocommutation is monitored by in-situ real time FTIR measurements during UV-Vis illumination. Time dependence studies of photocommutation evidence decreasing quantum efficiency during the commutation. This decrease in quantum efficiency only weakly depends on fulgimide density and is not observed in solution. However, PC measurements as a function of photon flux enabled determining a PC cross section (σ) of the majority of switching molecules. Polarization dependent photocommutation studies show the strong dependence of σ with respect to the local electric field of the isomerization-exciting light.Analytical models and Monte Carlo simulations based on nearest neighbor interactions are performed to gain deeper insight in the experimental observations. These simulations qualitatively explain the temperature dependence of the commutation kinetics, decreasing quantum efficiency and weak surface density dependence of the photocommutation.It has been shown in this thesis that σ depends on the local electric field. Similar to the Surface Enhanced Raman Spectroscopy the local electric field at surfaces is increased due to the plasmon of gold nanoparticles. The plasmon of the gold nanoparticle monolayer and thereby the enhancement of the electric field depends on the wavelength of the external irradiation. Exploitation of this effect improves the photo switching kinetics significantly depending on the wavelength of the irradiation. This wavelength dependent amplification of the switching kinetics is explained by the same wavelength dependent enhancement of the electric field.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23897号 / 工博第4984号 / 新制||工||1778(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 杉村 博之, 教授 山田 啓文, 教授 邑瀬 邦明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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