Throughout the study of polymer adsorption at the air/water and solid/water interfaces, surface tension measurements and surface plasmon resonance (SPR) spectroscopy have been identified as key methods for the acquisition of structural and thermodynamic information. These techniques were used to determine air/water and cellulose/water interfacial properties of pullulan (P) and pullulan cinnamates (PCs), 2-hydroxypropyltrimethylammonium xylans (HPMAXs), and hydroxypropyl xylans (HPXs). Hydrophobic modification of pullulan with cinnamate groups promoted adsorption onto model surfaces of regenerated cellulose. In order to understand the relative contributions of hydrophilic and hydrophobic interactions towards PC adsorption, PC adsorption onto self-assembled monolayers (SAMs) with different functional groups was also studied. As the degree of cinnamate substitution increased, greater adsorption onto cellulose, methyl-terminated SAMs (SAM-CH3), and hydroxyl-terminated SAMs (SAM-OH) was observed. This study showed that hydrogen bonding alone could not provide a complete explanation for PC adsorption onto cellulose. The adsorption of cationic 2-hydroxypropyltrimethylammonium (HPMA) xylans with different degrees of substitution (DS) onto SAMs and regenerated cellulose was studied by SPR. Surface concentration (Р) exhibited a maximum (Рmax) for HPMAX adsorption onto carboxylic acid-terminated SAMs (SAM-COOH) at an intermediate HPMA DS of 0.10. This observation was indicative of a relatively flat conformation for adsorbed HPMAXs with higher HPMA DS because of higher linear charge densities along the polymer backbone. Рobserved for HPMAX adsorption onto regenerated cellulose and SAM-OH surfaces was relatively low compared to HPMAX adsorption onto SAM-COOH surfaces. Surface tension measurements for aqueous solutions of HPX by the Wilhelmy plate technique showed that surface tension changes ("γ = γwater " γHPX(aq)) increased and critical aggregation concentrations generally decreased with increasing hydroxypropyl (HP) DS. Hence, even though HP substitution was necessary to induce aqueous solubility, excessive hydroxypropylation promoted aggregation in water. SPR studies indicated that HPXs did not adsorb significantly onto regenerated cellulose or SAM-OH surfaces (submonolayer coverage). In contrast, HPX did adsorb (~monolayer coverage) onto SAM-CH3 surfaces. Collectively, these studies showed natural polymers could be chemically modified to produce surface modifying agents with sufficient chemical control, whereby the surface properties of the resulting systems could be explained in terms of chemical structure and intermolecular interactions. / Ph. D.

Interactions between biomolecules and cellulose films at solid/liquid interfaces was studied by surface plasmon resonance spectroscopy (SPR), quartz crystal microbalance with dissipation monitoring (QCM-D) and in situ atomic force microscopy (AFM) measurements. This dissertation shows the porous character of nanocrystalline cellulose films as the key feature for enhanced adsorption of chemically modified polysaccharides and provides quantitative analysis of polymer supported phospholipid structures as a stable platform for studying membrane-related processes. Smooth cellulose I films were prepared by spincoating cellulose nanocrystal suspensions onto positively charged self-assembled monolayers on gold. The adsorption of pullulan cinnamate (PC) onto cellulose surfaces increased with increasing degree of cinnamate substitution. The interactions between PCs with higher degree of substitution (DS) and porous nanocrystalline cellulose (NC) films presumably generated looped multilayer PC structures that adsorbed more than twice as much onto NC films than onto regenerated cellulose (RC) films. PC chains not only covered the NC surface but also penetrated into the porous film. The porous features of NC film are responsible for the greater adsorption of polymer chains relative to tightly packed RC films. Adsorption of phospholipid vesicles onto RC and NC films was also studied. Aggregates of intact vesicle were observed on NC surfaces with high water content ~ 84 % by mass. Phospholipid patches with smooth features were found to assemble onto RC surfaces with a lower degree of hydration ~ 30 % by mass. Vesicle membrane breakage was triggered by a destabilizing agent, LysoPC. The great mass decrease, and changes in dissipation and degree of hydration for phospholipid structures after exposure to LysoPC corresponded to the transformation from vesicles to layered structures. Initial binding of LysoPC micelles to unruptured vesicles was clearly resolved in SPR, whereas the huge mass decrease associated with bound water hides the initial adsorption of LysoPC onto vesicles in QCM-D experiments. The intitial binding of LysoPC micelles onto vesicle membranes lasted for 200 seconds with a maximal increase of 14 % by mass prior to vesicle collapse. The role of cholesterol in phospholipid interactions with model cellulose surfaces was also considered. Supported vesicle layers over RC surfaces were observed for vesicle membranes containing ≥ 6.3 % by mole cholesterol, whereas phospholipid or phospholipid with lower cholesterol content formed disconnected lipid islands on RC surfaces. Meanwhile, intact vesicles were always observed on NC surfaces for phospholipid/cholesterol blends regardless of the cholesterol content. The intact vesicles on cellulose surfaces were attributed to the ability of cholesterol to accommodate vesicle deformation. These studies showed the impact of mesoscale structure of cellulose films on adsorbates. It sheds light on the role of the lignin-carbonhydrate-complex in plant cell wall structure and will inform the next generation of biomimetic nanocomposites. The designed polymer supported biomimetic membranes provide a perfect platform to develop intact and ruptured protoplast systems for the study of plant cell wall self-assembly. / Ph. D.

L'oxydoréduction des monocouches auto-assemblées («Self-assembled monolayers ou SAMs) de ferrocenyldodecanethiolates sur une surface d'or (Fc(CH2)12SAu) dans des solutions aqueuses de n-alkyle sulfate de sodium (6, 8, 10 et 12 atomes de carbone) est étudiée par spectroscopie de résonance des plasmons de surface («Surface Plasmons Resonance ou SPR) couplée avec de la voltampérométrie cyclique (VC). La technique SPR est utilisée pour suivre en temps réel l'adsorption des tensioactifs en fonction du potentiel appliqué. Elle permet de quantifier l'épaisseur et le recouvrement des molécules adsorbées pour déterminer l'organisation des tensioactifs anioniques sur la SAM. La VC est utilisée afin de caractériser l'oxydation du groupement ferrocène en présence des n-alkyle sulfate de sodium qui s'associent à la SAM grâce à l'appariement entre le ferrocénium et le groupement sulfate. Des mélanges binaires d'alkylesulfates de différentes compositions sont utilisés dans le but de déterminer l'organisation induite par une réaction d'oxydoréduction. L'effet de la longueur de la chaîne d'hydrocarbures sur la quantité de tensioactifs anioniques adsorbés ainsi que les affinités relatives d'appariement des anions alkyle sulfate aux ferrocéniums sont rapportés dans ce mémoire. Ces surfaces électrosensibles permettront la détection de molécules amphiphiles et la compréhension du comportement de mélanges binaires de tensioactifs. Ainsi, ces travaux apporteront une avancée sur la modulation électrochimique de l'organisation de matériaux sur des substrats solides basée sur l'appariement d'ions. / The redox-induced pairing from aqueous solution of a homologous series of sodium n-alkyl sulfate (6, 8, 10 and 12 carbon atoms) to self-assembled monolayers (SAMs) of ferrocenyldodecanethiolates on a gold surface (Fc(CH2)12SAu) is investigated by spectroscopy of surface plasmon resonance (SPR) coupled with the cyclic voltammetry (CV). The SPR technique is used to monitor in real time the adsorption of surfactant in function of the applied potential. It quantifies the adsorbed layer thickness and surface coverage to determine the organization of anionic surfactants on SAM. CV is used to characterize the oxidation of ferrocene group in the presence of sodium n-alkyl sulfates that associate with SAM through matching between the ferrocenium and sulfate group. Binary mixtures of alkylesulfates of different compositions are used to determine the structure induced by a redox reaction. The effect of the length of the hydrocarbon chain on the amount of anionic surfactants adsorbed and the relative affinities of matching the ferroceniums alkyl sulfate anions are reported in this thesis. These electrosensitive surfaces allow the detection of amphiphilic molecules and the understanding the behavior of binary mixtures of surfactants. Thus, this work will result in progress on the electrochemical modulation organizing materials on solid substrates based on the ion-pairing.

Im Mittelpunkt dieser Arbeit stand die Darstellung sensitiver Blockcopolymere und deren Gele, die als Ausgangsmaterialien in Sensor- und Aktorsystemen einsetzbar sind. Die Vereinigung verschiedener Ansprechparameter stellt erhöhte Anforderung an die Synthese. Geringe Ansprechzeiten lassen sich mit einer Gelgröße im µm-Bereich erreichen. Hydrogele dieser Größenordnungen können durch nachträgliche Vernetzung funktioneller linearer Polymere ermöglicht werden. Die Makroinitiatormethode ermöglichte den Aufbau verschiedener linearer photovernetzbarer Blockcopolymere. Zum Einen wurde das temperatursensitive P(n-BuAc)-block-P(PNIPAAm-co-DMIAAm) erhalten, des Weiteren gelang die Darstellung der multi-sensitiven Blockcopolymere P2VP-block-P(NIPAAm-co-DMIAAm) und P4VP-block-P(NIPAAm-co-DMIAAm). Die Blockcopolymere wurden mit variierenden Blocklängen und Verhältnissen sowie mit unterschiedlichem Vernetzergehalt dargestellt. Die Charakterisierung der Blockcopolymere erfolgte mittels 1H-NMR-Spektroskopie, GPC-Messungen (Zusammensetzung) und DSC-Messungen (thermische Eigenschaften). Das Löslichkeitsverhalten in wässrigen Medien wurde durch Dynamische Lichtstreuung bestimmt. Die Beschreibung des Quellverhaltens der vernetzten Schichten erfolgte durch vornehmlich durch optische Methoden (SPR/OWS, WAMS, Ellipsometrie). Die Veränderung des E-Moduls in Abhängigkeit äußerer Parameter konnte mittels AFM untersucht werden. Die Reaktion der Schichten wurde gegenüber Temperatur, pH-Wert und Salzkonzentrationen getestet. Die charakterisierten Filme konnten im Anschluss als sensitive Schichten in piezoresistiven Sensorsystemen verwendetet werden.

Im Mittelpunkt dieser Arbeit stand die Darstellung sensitiver Blockcopolymere und deren Gele, die als Ausgangsmaterialien in Sensor- und Aktorsystemen einsetzbar sind. Die Vereinigung verschiedener Ansprechparameter stellt erhöhte Anforderung an die Synthese. Geringe Ansprechzeiten lassen sich mit einer Gelgröße im µm-Bereich erreichen. Hydrogele dieser Größenordnungen können durch nachträgliche Vernetzung funktioneller linearer Polymere ermöglicht werden. Die Makroinitiatormethode ermöglichte den Aufbau verschiedener linearer photovernetzbarer Blockcopolymere. Zum Einen wurde das temperatursensitive P(n-BuAc)-block-P(PNIPAAm-co-DMIAAm) erhalten, des Weiteren gelang die Darstellung der multi-sensitiven Blockcopolymere P2VP-block-P(NIPAAm-co-DMIAAm) und P4VP-block-P(NIPAAm-co-DMIAAm). Die Blockcopolymere wurden mit variierenden Blocklängen und Verhältnissen sowie mit unterschiedlichem Vernetzergehalt dargestellt. Die Charakterisierung der Blockcopolymere erfolgte mittels 1H-NMR-Spektroskopie, GPC-Messungen (Zusammensetzung) und DSC-Messungen (thermische Eigenschaften). Das Löslichkeitsverhalten in wässrigen Medien wurde durch Dynamische Lichtstreuung bestimmt. Die Beschreibung des Quellverhaltens der vernetzten Schichten erfolgte durch vornehmlich durch optische Methoden (SPR/OWS, WAMS, Ellipsometrie). Die Veränderung des E-Moduls in Abhängigkeit äußerer Parameter konnte mittels AFM untersucht werden. Die Reaktion der Schichten wurde gegenüber Temperatur, pH-Wert und Salzkonzentrationen getestet. Die charakterisierten Filme konnten im Anschluss als sensitive Schichten in piezoresistiven Sensorsystemen verwendetet werden.

[pt] Sensores baseados na espectroscopia de ressonância de plásmons de superfície (SPR) são dispositivos fotônicos amplamente usados para a detecção ultra sensível de gases e analitos (bio) químicos sem marcadores. O mecanismo de sensoriamento baseia-se na sensitividade do campo eletromagnético evanescente associado aos Polaritons de Plásmon de Superfície (SPP) propagando-se na interface metal-dielétrica, o qual age como uma eficiente nanosonda no meio exterior. Mesmo com resultados excelentes em aplicações de sensoriamento em tempo real, a espectroscopia SPR encontra severas limitações nas caracterizações elipsométricas de filmes finos com espessuras maiores que alguns nm. As limitações são principalmente associadas a instabilidade no longo prazo das propriedades físico-químicas das interfaces metal-dielétricas dos dispositivos SPR, a qual prejudica a acurácia na determinação simultânea da espessura e do índice de refração dos filmes finos que estão sendo investigados. Por estas razões, a primeira parte da tese é dedicada ao estudo da degradação e do processo de estabilização das interfaces metal-dielétricas de diferentes plataformas de sensoriamento SPR, tanto no ar como em ambiente aquoso. As plataformas de sensoriamento foram monitoradas por espectroscopia SPR e microscopia de força atômica (AFM). Diferentes configurações de interfaces metal-dielétricas foram analisadas, tanto em termos de camadas de adesão, tipo de metal que suporta a onda de plasma, e supercamadas, com o objetivo de otimizar a estabilidade e a sensitividade de plataformas SPR monomodais e multimodais. As melhores performances foram obtidas quando uma interface metal-dielétrica com baixo amortecimento eletromagnético é criada através da deposição de uma monocamada adesiva de (3-Mercaptopropyl) trimethoxysilane (MPTS), e quando uma monocamada de grafeno (SLG) é transferida como supercamada na cima de um filme fino metálico de ouro. O estudo do processo de estabilização das plataformas SPR foi a base para o desenvolvimento da segunda parte da tese, onde nós mostramos as potencialidades da espectroscopia SPR na configuração Kretschmann para a acurada caracterização elipsométrica de três classes de materiais deferentes: nanopartículas de ouro (AuNPs), filmes finos de materiais orgânicos luminescentes, e grafeno. Para determinar simultaneamente a espessura e o índice de refração dos filmes finos, foram adoptados os métodos das duas cores e/ou dois modos, esse último realizado através do uso de guias de onda carregadas por dielétricos (DLWGs) com interfaces simétricas do tipo Au/MPTS/SiO2. Por fim, estas três classes de materiais foram usadas no desenvolvimento de novos sensores ópticos SPR de interesse biológico e ambiental. A prova de conceito de um dosímetro de raios UVA baseado em espectroscopia SPR é demonstrado através do monitoramento das modificações da espessura e índice de refração induzidas pela radiação em filmes finos de tris (8-hydroxyquinoline) (Alq3) e tris (dibenzoylmethane) mono (1,10-phenanthroline) europium (III) (Eu (dbm)3Phen). AuNPs com um diâmetro nominal de 15nm estabilizadas por citrato de sódio, foram usadas para demonstrar o princípio de funcionamento de medidores de tamanho de partículas e contadores superficiais de AuNPs baseados na espectroscopia SPR de duas cores. Neste último caso, nós mostramos experimentalmente que as DLWG podem ser usadas como acurados nanocontadores para densidades superficiais entre 20 e 200 NP/um2, com importantes resultados para a metrologia óptica e a emergente espectroscopia SPR amplificada por nanopartículas (PA-SPR). Por último, mostramos o utilizo da interface Au/SLG para a detecção ultra-sensível de íons de metais pesados de interesse ambiental, com um limite de detecção (LoD) sem precedentes da ordem de uma parte por bilhão (ppb). Os resultados experimentais suportam as previsões teóricas sobre a afinidade de sítios particulares do grafeno infinito para íons de metais pesados, e a possibilidade de aumentar a sensibilidade dos dispositivos SPR através da transferência de elétrons assistida por plásmons entre o filme de metal e o SLG. / [en] Surface Plasmon Resonance (SPR) Spectroscopy based sensors have emerged as a versatile and widely used optical tool for the label free ultrasensitive detection of gas and (bio) chemical analytes. The sensing mechanism is relying on the sensitivity of the evanescent field of the Surface Plasmon Polariton (SPP) wave propagating at metal dielectric interface, which acts as an efficient optical nanoprobe in the external medium. Despite the excellent results in the real-time sensing applications, SPR Spectroscopy has found limited applications in the accurate ellipsometric characterization of thin films with thickness higher than a few nm. The limitations are mainly associated with the long-time instability of the metal-dielectric interfaces of the SPR devices, which deteriorates the accuracy in the simultaneous determination of thickness and refractive index of the thin films under investigation. For these reasons, the first part of the dissertation is dedicated to the study of the degradation and stabilization process of the metal-organic interfaces of different SPR sensing platforms, in both air and water environment. The sensing platforms were monitored by SPR spectroscopy and atomic force microscopy (AFM). Different metal-dielectric interfaces configurations were analyzed, in terms of both adhesion layers, type of metal supporting the plasma wave and super-layers, with the aim to optimize the stability and the sensitivity of both monomodal and multimodal SPR platforms. The best performances were obtained when a low damping metal-dielectric interface is created through the self-assembling of a monolayer of (3-Mercaptopropyl) trimethoxysilane (MPTS), and a single layer graphene (SLG) is transferred as a super-layer on the gold (Au) thin film. The study of the process of stabilization of the SPR platforms was the base for the development of the second part of the dissertation, where we demonstrate the potentialities of the SPR spectroscopy in the Kreschtmann configuration for the accurate ellipsometric characterization of a class of three different materials: gold nanoparticles (AuNPs), organic luminescent materials, and graphene. To obtain the simultaneous determination of both the thickness and refractive index of the thin films, a two-color and/or two-mode approach was adopted, the latter performed by the use of dielectric loaded waveguides (DLWG) with symmetric Au/MPTS/SiO2 interfaces. Finally, the three class of materials have been used for the development of novel SPR optical sensors with environmental or biological interest. The proof of principle of an SPR based UVA dosimeter is demonstrated via the monitoring of the radiation induced modifications of the thickness and refractive index of luminescent thin film of tris(8-hydroxxyquinoline) (Alq3) and tris(dibenzoylmethnae) mono(1,10-phenanthroline) europium (III) (Eu(dbm)3Phen). Sodium Citrate stabilized AuNPs with a nominal diameter of about 15 nm were used to show the principle work of a two-color SPR spectroscopy nanosizer and nanocounter. In the latter case, we demonstrate experimentally that DLWGs can be used as accurate nanocounters in the range of surface density between 20 and 200 NP/um2, with results important for both optical metrology and the emerging particle amplified PA-SPR spectroscopy. Finally, we show the use of the Au/SLG interface for the ultrasensitive detection of heavy metal ions of environmental interest, with an unprecedented limit of detection (LoD) of the order of part per billion (ppb). The experimental results support the theoretical predictions about the affinity of particular sites of the infinite graphene to heavy metal ions, and the possibility to enhance the sensitivity of SPR devices by the plasmon assisted electron transfer between the metal film and the SLG.