Natural composites like wood are scale-integrated structures that range from molecular to the macroscopic scale. Inspired by this design, layer-by-layer (LbL) deposition technique was used to create lignocellulosic composites from isolated wood polymers namely cellulose and lignin, with a lamellar architecture. In the first phase of the study, adsorption of alkali lignin onto cationic surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Complete coverage of the cationic surface with alkali lignin occured at low solution concentration; large affinity coefficients were calculated for this system at differing pH levels. Adsorption studies with organosolv lignin in an organic solvent, and spectroscopic analysis of mixtures of cationic polymer with alkali lignin revealed a non-covalent interaction. The work demonstrated how noncovalent interactions could be exploited to molecular organize thin polyphenolic biopolymers on cationic surfaces. The second phase of the study examined the adsorption steps during the LbL assembly process to create novel lignocellulosic composites. LbL assembly was carried out using oxidized nanocellulose (NC) and lignin, along with a cationic polymer poly(diallyldimethylammonium chloride) (PDDA). QCM-D was used to follow the sequential adsorption process of the three different polymers. Two viscoelastic models, namely Johannsmann and Voigt, were respectively used to calculate the areal mass and thickness of the adsorbed layers. Atomic force microscopy studies showed a complete coverage of the surface with lignin in all the disposition cycles, however, surface coverage with NC was seen to increase with the number of layers. Free-standing composite films were obtained when the LbL process was carried out for 250 deposition cycles (500 bilayers) on a cellulose acetate substrate, following the dissolution of the substrate in acetone. Scanning electron microscopy of the cryo-fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle was estimated to be 17 nm. The third phase of the study investigated the effect of LbL ordering of the polymers versus a cast film composed of a blended mixture of the polymers, using dynamic mechanical analysis. A tan ï ¤ peak was observed in the 30 – 40 ºC region for both films, which was observed in the neat NC film. Heating of the samples under a compressive force produced opposite effects in the films, as the LbL films exhibited swelling, whereas the cast films showed densification. The apparent activation energy of this transition (65 – 80 kJ mol-1) in cast films, calculated based on the Arrhenius equation was found to be coincident to those reported for the ï ¢ transition of amorphous cellulose. The peak was seen to disappear in case of LbL films in the second heat, whereas it was recurring in case of cast films of the blended mixture, and neat NC films. Altogether, the together the work details a novel path to integrate an organized lignin and cellulose molecular structure, albeit modified from their native form, into a three-dimensional composite material. / Ph. D.

Systemisch applizierte Therapeutika können erhebliche Nebenwirkungen auslösen, welche auf Grund eines unspezifischen Transports oder einer hohen Dosis von appliziertem Wirkstoff auftreten. Daher bedarf es der Entwicklung neuartiger Wirkstoff-Transportsysteme (Drug Delivery Systems) welche in der Lage sind, Wirkstoffe in genau definierbaren Dosen gezielt in die adressierte Zelle zu transportieren. Ein vielversprechender Ansatz, welcher diesen Anforderungen nachkommt, findet sich in der Layer-by-Layer-Technik (LbL), d.h. der wechselseitigen Assemblierung von Polymeren/Wirkstoffen auf soliden sphärischen Templaten, eines funktionellen Supported Lipid Bilayers sowie der Oberflächenfunktionalisierung mit spezifischen Antikörpern. Dabei ist die Homogenität und Regularität des Supported Lipid Bilayers von großer Bedeutung, um in biomedizinischen Anwendungen eine ungewollte Interaktion mit Serumkomponenten sowie eine Opsonierung zu verhindern. Insbesondere die funktionelle Lipidkomponente besitzt allerdings maßgebliche Auswirkungen auf diese Parameter. In dieser Arbeit wurde die Idee der Oberflächenfunktionalisierung von LbL-beschichteten Silica-Mikropartikeln (SiO2) mit einem funktionellen Supported Lipid Bilayer aufgegriffen und weiterentwickelt, wobei insbesondere die Homogenität des Supported Lipid Bilayers auch auf sehr kleinen Längenskalen (wenige Nanometer) bestimmt wurde. In einem letzten Schritt konnte anhand zweier verschiedener Zelllinien (3T3 und Vero) die Adaptivität und Effektivität des entwickelten Drug Delivery Systems nachgewiesen werden.

This thesis presents work done to improve the switching speed and contrast performance of electrochromic devices. Layer-by-Layer (LbL) assembly was used to deposit thin electrochromic films of materials ranging from organic, inorganic, conducting polymers, etc. The focus was on developing new materials with high contrast and long lifecycles. A detailed switching-speed study of solid-state EC devices of already-developed (PEDOT (Poly(3,4-ethylenedioxythiophene)), polyviologen, inorganic) materials and some new materials (Prodot-Sultone) was performed. Work was done to achieve the optimum thickness and number of bilayers in LbL films resulting in high-contrast and fast switching. Device sizes were varied for comparison of the performance of the lab-made prototype device with the commercially available "small pixel" size displays. Symmetrical EC devices were fabricated and tested whenever conducting polymers are used as an EC material. This symmetrical configuration utilizes conducting polymers as an electroactive layer on each of two ITO-coated substrates; potential is applied to the two layers of similar conducting polymers and the device changes color from one redox state to another. This method, along with LbL film assembly, are the main factors in the improvement of switching speed results over already-published work in the literature. PEDOT results show that EC devices fabricated by LbL assembly with a switching speed of less than 30 ms make EC flat-panel displays possible by adjusting film thickness, device size, and type of material. The high contrast value (84%) for RuP suggests that its LbL films can be used for low-power consumption displays where contrast, not fastest switching, is the prime importance. In addition to the electrochromic work, this thesis also includes a section on the application of LbL assembly in fabricating electromechanical bending actuators. For bending actuators based on ionic polymer metal composites (IPMCs), a new class of conductive composite network (CNC) electrode was investigated, based on LbL self-assembled multilayers of conductive gold (Au) nanoparticles. The CNC of an electromechanical actuator fabricated with 100 bilayers of polyallylamine hydrochloride (PAH)/Au NPs exhibits high strain value of 6.8% with an actuation speed of 0.18 seconds for a 26 µm thick IPMC with 0.4 µm thick LbL CNCs under 4 volts. / Ph. D.

Made available in DSpace on 2016-06-02T20:36:10Z (GMT). No. of bitstreams: 1 DissFTS.pdf: 2833638 bytes, checksum: 674f7848802feac6027a9471c4dcc7e0 (MD5) Previous issue date: 2003-05-19 / Universidade Federal de Minas Gerais / In this work, the electrochemical characterization of a self-assembled film containing two conductive polymers, poly(o-methoxyanilina)(POMA) and poly(3- thiophene acetic acid)(PTAA), is presented. The technique that allows to obtain these films is known as layer-by-layer (LBL) deposition. It consists in a spontaneous adsorption of species with opposite charges. The technique used for the electrochemical characterization was cyclic voltammetry coupled with mass variation using an electrochemical quartz crystal microbalance (EQCM), which allows the characterization of the LBL film mass/charge transport during the redox process. Electroacoustic impedance experiments of the LBL films with different number of bilayers show that the viscoelastic and mechanic tension properties do not change significantly in the potential range studied. Therefore, allowing the use of the Sauerbrey equation for converting the frequency values in mass values. The charge compensation mechanism was determined using the species flux (ions+solvent molecules) compared with POMA those casting films. The POMA-PTAA LBL film presents a charge compensation mechanism due to simultaneous intercalation of cations and anions. This behavior suggests the existence of a pseudo-self-doping mechanism related to carboxilic lateral groups interactions through the alternating layers structure of POMA-PTAA. The charge in the deprotonated carboxilic groups neutralize the charge generation of the imina groups present in the POMA backbone, which gives a decrease of the total mass change of the film. In this sense, the LBL technique could be an alternative method to prepare conducting polymer films modifying their electrochemistry properties. / Este trabalho tem como objetivo a caracterização dos processos eletroquímicos em filmes automontados contendo dois polímeros condutores, a poli (o-metoxianilina)(POMA) e o poli(ácido-3-tiofeno acético)(PTAA). A técnica que permite a obtenção destes filme é conhecida como layer by layer (LBL) e consiste na adsorção espontânea de espécies carregadas com cargas espaciais opostas. A caracterização eletroquímica foi realizada utilizando a técnica de voltametria cíclica acoplada à microbalança de cristal de quartzo eletroquímica (MCQE). Através dela foi possível analisar os processos de transferência de massa e carga que ocorrem nos filmes LBL durante o processo redox. Além disso, medidas de impedância eletroacústica revelaram que os filmes LBL com diferente número de multicamadas não apresentam variações consideráveis em suas propriedades viscoelásticas e mecânicas, justificando o uso da Equação de Sauerbrey. As espécies que participam do mecanismo de compensação de carga puderam ser determinadas com o auxílio das curvas de fluxo de espécies (íons+moléculas do solvente), permitindo a comparação com filmes de poli(o-metoxianilina) obtidos por evaporação do solvente. O filme LBL de POMA-PTAA apresentou um mecanismo de compensação de carga diferente do observado em filme de POMA obtido por evaporação do solvente. Neste caso, o mecanismo de compensação de carga no filme LBL apresentou uma participação simultânea de espécies catiônicas e aniônicas durante o processo redox. Este comportamento sugere a presença de uma pseudo-autodopagem relacionada com as interações dos grupos carboxílcos laterais através da estrutura das multicamadas alternadas de POMA-PTAA. A carga presente nos grupos carboxilatos auxiliam na compensação de cargas geradas nos grupos imina da POMA, proporcionando uma diminuição da massa transportada da solução para manter a condição de eletroneutralidade. Os resultados obtidos demonstraram que a técnica de automontagem pode ser um método alternativo na fabricação de filmes de polímeros condutores com modificações em suas propriedades eletroquímicas.

Des couches fonctionnelles hybrides organiques/inorganiques ont été générées à une interface solide/liquide à l’aide d’une nouvelle technique de fabrication ascendante (bottomup) dénommée Croissance de Couche à partir d’une Surface (Surface Grown Layers - SgL)grâce à une modulation très fine de l’interaction électrostatique entre nano-objets decharges opposés en fonction de la force ionique de la dispersion aqueuse. Différents nanoparticules/tubes à la fois cationiques et anioniques et très stables vis-à-vis d’un environnement fortement salin ont été développés. La complexation électrostatique entre ces nanomatériaux a été étudiée en solution et près d’une interface au travers du concept de “transition de dessalage”. Dans un deuxième temps la croissance de couches hybrides à partird’un substrat a été étudiée en comparant l’approche SgL et la méthode classique d’adsorption séquentielle couche par couche (Layer by layer - LbL). Des expériences préliminaires ont montré le potentiel de cette approche dans le développement de substrats fonctionnels. / In this manuscript, one-step bottom-up fabrication of “smart organic-inorganic hybridfunctional layers” at a liquid/solid interface were fabricated via a novel surfacefunctionalization pathway termed as “Surface Grown Hybrid Functional Layers” or SgLthrough fine tuning of electrostatic interaction between “highly stable” and oppositelycharged nanomaterials as a function of ionic strength of the dispersion. Cationic and anionicnanomaterials based on different hybrid nanoparticles/nanotubes that are very stable towardshigh saline environment have been formulated. The electrostatic complexation between theseoppositely charged nanomaterials has been studied in bulk and at an interface through theconcept of “desalting transition” pathway. In a second step, the growth of functional hybridlayers directly from a substrate via the novel SgL approach was then compared with theconventional Layer-by-Layer approach (LbL). Finally the preliminary experiments haveshown the potential applications of generated functional surfaces.

Within the emerging methods of controlled free radical polymerization, the Reversible Addition-Fragmentation chain Transfer (RAFT) process has been recently established as a powerful technique to synthesize standard polymers with controlled characteristics (narrow polydispersity and predictable molar masses). This method is now employed to synthesize well-defined, reactive precursor polymers that are subsequently converted into speciality polymers such as fluorescent-labeled polycations. Those are suitable for Electrostatic Self-Assembly (ESA). The observation of the Förster Resonance Energy Transfer (FRET) in such films is established, contributing to the understanding of the self-organization during thin film growth. The RAFT process using Benzyl Dithiobenzoate (BDTB) is shown to enable the control of the free radical polymerization of vinylbenzyl chloride (VBC). The high tolerance of the method to functional groups allows the preparation of such reactive polymers with narrow polydispersities and predictable molar masses. The well-defined precursors are easily converted, for instance, to polycations. Also they are easily functionalized by fluorophores, here derived from coumarin and perylene. The fluorophores, as pendent side chains, served as label to investigate the alternating deposition process, while the influence of molecular variations on the self-assembly can be systematized. Furthermore, when using complementary fluorophores, Fluorescence Resonance Energy Transfer (FRET) studies in organized media become possible. The alternating deposition cycles are followed by UV-Vis spectroscopy, ellipsometry, and X-Ray reflectivity. Regular growth is observed for three complementarily labeled polycations. Noteworthy, fluorescence and UV-Vis studies reveal the formation of large fluorescent dye aggregates for one coumarin and for the perylene derivative in the ESA multilayers. When these polycations are used in mixed thin films, Förster Resonance Energy Transfer (FRET) between fluorophores is observed. The non-radiative nature of the different energy transfer was confirmed by fluorescence decay time measurements/ Parmi les récentes méthodes pour contrôler la polymérisation radicalaire, le procédé RAFT (Reversible Addition-Fragmentation chain Transfer) a été récemment établi et s'impose comme une méthode performante pour la synthèse de polymères standards possédant des caractéristiques contrôlées (faibles polydispersités et masses molaires prédictibles). Cette méthode est désormais utilisée pour la synthèse de précurseurs réactifs bien définis qui sont par la suite convertis en polymères spécialisés, par exemple en polycations marqués a l'aide de sondes fluorescentes. Ces polycations peuvent être ensuite auto-assemblés électrostatiquement afin d'élaborer des films minces. Le phénomène de transfert de fluorescence (Förster Resonance Energy Transfer –FRET-) dans de tels films a été établi, contribuant par là-même à une meilleure compréhension du phénomène d'auto-organisation durant la croissance des films. Le procédé RAFT, utilisant le dithiobenzoate de benzyle (BDTB), a démontré sa capacité à contrôler la polymérisation radicalaire du chlorométhlstyrène (VBC). La tolérance de cette méthode vis à vis des groupes fonctionnels permet la synthèse de polymères réactifs possédant de faibles polydispersités et des masses molaires prédictibles. Les précurseurs ainsi définis sont facilement convertis, en polycations par exemple. Ils sont tout aussi facilement fonctionnalisés par des fluorophores dérivés de la coumarine ou du pérylène. Les fluorophores en tant que chaînes pendantes servent de marqueurs pour étudier le processus de dépôts alternés, alors que l'influence des variations au niveau moléculaire peut être systématisée. De plus, en utilisant des fluorophores complémentaires, il devient possible de mener des études sur le transfert de fluorescence (FRET) au sein de milieux organisés. Les cycles de dépôts alternés ont été suivis par spectroscopie UV-Vis, éllipsométrie et reflexion des rayons X. Une croissance régulière est observée dans le cas des trois polycations marqués. Il convient de noter que les études UV-Vis et de fluorescence révèlent la formation de larges aggrégats de fluorophores au sein des multicouches, dans le cas d'une coumarine et du dérivé de pérylène. Lorsque les polycations complémentaires sont utilisés dans des films minces mixtes, le FRET est observé. La nature radiative ou non-radiative du processus de transfert d'énergie a été confirmée par des mesures de déclin de fluorescence.

Depuis plusieurs années, une nouvelle génération de matériaux appelés “matériaux intelligents” et définis par leur capacité d’adaptation à leur environnement, est intensément développée. Des systèmes sensibles à différents stimuli tels que le pH, la lumière, ou encore une force mécanique, impliquée dans un grand nombre de processus naturels, comme l’adhésion et la prolifération cellulaire, ont été rapportés. Ce travail de thèse a ainsi été dédié au développement de matériaux mécano-sensibles. Plus précisément de matériaux transformant une contrainte mécanique en un signal chimique, en mimant le processus physique utilisé par la nature, à savoir des changements conformationnels de protéines. Nous avons donc cherché à atteindre ce but en greffant covalemment des protéines ou des enzymes sur un substrat élastomère. Etirer le substrat devant induire des modifications de structure des protéines, conduisant ainsi à des modulations de leurs propriétés. / Since many years, a new generation of materials called « smart materials » and defined by their capacity to adapt to their environment is intensively developed. Systems sensitive to different stimuli such as pH, light or ionic strength have been reported. One of these stimuli can also be a mechanical force which is involved in many reactions in nature such as, cells adhesion and proliferation, tissues growing or even plants developments. The aim of my thesis was dedicated to the elaboration of mechano-responsive materials. More precisely, materials that transform a stretching constraint into a chemical signal by mimicking the physical processes used by nature, namely protein conformational changes. We planned to achieve this goal by covalently grafting proteins or enzymes onto a stretchable substrate or incorporating them into cross-linked polymer networks. Stretching these materials should induce protein conformational changes leading to modifications of their properties.

Indiana University-Purdue University Indianapolis (IUPUI) / In this research thesis, copper indium gallium selenium (CIGS) nanoparticles were synthesized from metal chlorides, functionalized to disperse in water, and further used in layer by layer (LbL) nanoassembly of CIGS films. CIGS nanoparticles were synthesized through the colloidal precipitation in an organic solvent. The peak and average sizes of the synthesized particles were measured to be 68 nm and 75 nm in chloroform, and 30 nm and 115 nm in water, respectively. Two methods were used to disperse the particle in water. In the first method the stabilizing agent oleylamine (OLA) was removed through multiple cleaning processes, and in the second method ligand exchange was performed with polystyrene sulfonate (PSS). Zeta potential of CIGS nanoparticles dispersed in water was measured to be +61 mV. The surface charge of the nanoparticles was reversed by raising the pH of the solution, which was measured to be −43.3 mV at 10.5 pH. In a separate process, the CIGS nanoparticles dispersed in water were coated with PSS. The resulting dispersion was observed to be stable and the surface charge was measured to be −56.9 mV. The LbL deposition process of CIGS nanoparticles was characterized by depositing thin films on quartz crystal microbalance (QCM). LbL depositions was conducted using (i) oppositely charged CIGS nanoparticles, (ii) positively charged CIGS nanoparticles and PSS, and (iii) PSS-coated CIGS (CIGS-PSS) and polyethyleneimine (PEI). The average thickness of each bi-layer of the above mentioned depositions were measured to be 2.2 nm, 1.37 nm, and 10.12 nm, respectively. The results from the QCM have been observed to be consistent with the film thickness results obtained from atomic force microscopy (AFM). Various immersion times versus thickness of the film were also studied. For electrical characterization, the CIGS films were deposited on indium tindioxide (ITO)-coated glass substrates. Current versus voltage (I/V) measurements were carried out for each of the films using the Keithley semiconductor characterization instruments and micromanipulator probing station. It was observed that the conductivity of the films was increased with the deposition of each additional layer. The I/V characteristics were also measured under the light illumination and after annealing to study the photovoltaic and annealing effects. It was observed that under light illumination, the resistivity of a 12-layer CIGS film decreased by 93% to 0.54 MΩ.m, and that of the same number of layers of PSS-coated CIGS and PEI film decreased by 60% to 0.97 MΩ.m under illumination. The resistivity of an 8-layer CIGS and PSS film decreased by 76.4% to 0.1 MΩ.m, and that of the same layers of PSS-coated CIGS and PEI decreased by 87% to 0.07 MΩ.m after annealing. The functionalized nanoparticles and the LbL CIGS films were implemented in the solar cell devices. Several configurations of CIGS films (p-type), and ZnO and CdS films (n-type) were considered. Poly(3,4-ethylenedioxythiophene) (PEDOT), molybdenum (Mo), and ITO were used as back contacts and ITO was used as front contact for all the devices. The devices were characterized the Keithley semiconductor characterization instruments and micromanipulator probing station. For a CIGS and n-ZnO films device with PEDOT as back contact and ITO as front contact, the current density at 0 V and under light illumination was measured to be 60 nA/cm2 and the power density was measured to be 0.018 nW/cm2. For a CIGS and CdS films device with ITO as both back and front contact, the current density at 0 V and under light illumination was measured to be 50 nA/cm2 and the power density was measured to be 0.01 nW/cm2. For a drop-casted CIGS and CdS films device with Mo as back contact and ITO as front contact, the current density of 50 nA/cm2 at 0 V and power density of 0.5 nW/cm2 under light illumination was measured. For the LbL CIGS and chemical bath deposited CdS films device with ITO as both back and front contact, the current density of 0.04 mA/cm2 at 0 V and power density of 1.6 μW/cm2 under light illumination was measured. Comparing to Device-III, an increase by 99% in the power density was observed by using the CIGS LbL film in the device structure. The novel aspects of this research include, (i) functionalization of the CIGS nanoparticles to disperse in water including coating with PSS, (ii) electrostatic LbL deposition of CIGS films using oppositely charged nanoparticles and polymers, and (iii) the utilization of the fabricated LbL CIGS films to develop solar cells. In addition, the n-type cadmium sulfide film (CdS) and zinc oxide (ZnO) buffer layer were also deposited through LbL process after the respective particles were functionalized with PSS coating in separate experiments.

[EN] Fiber grating sensors and devices have demonstrated outstanding capabilities in both telecommunications and sensing areas, due to their well-known advantageous characteristics. Therefore, one of the most important motivations lies in the potential of customized fiber gratings to be suitably employed for improving the interrogation process of optical fiber sensors and systems. This Ph.D. dissertation is focused on the study, design, fabrication and performance evaluation of customized fiber Bragg gratings (FBGs) and long period gratings (LPGs) with the double aim to present novel sensing technologies and to enhance the response of existing sensing systems. In this context, a technique based on time-frequency domain analysis has been studied and applied to interrogate different kind of FBGs-based sensors. The distribution of the central wavelength along the sensing structures has been demonstrated, based on a combination of frequency scanning of the interrogating optical pulse and optical time-domain reflectometry (OTDR), allowing the detection of spot events with good performance in terms of measurand resolution. Moreover, different customized FBGs have been interrogated using a technology inspired on the operation principle of microwave photonics (MWP) filters, enabling the detection of spot events using radio-frequency (RF) devices with modest bandwidth. The sensing capability of these technological platforms has been fruitfully employed for implementing a large scale quasi-distributed sensor, based on an array of cascaded FBGs. The potentiality of LPGs as fiber optic sensors has also been investigated in a new fashion, exploiting the potentials of MWP filtering techniques. Besides, a novel approach for simultaneous measurements based on a half-coated LPG has been proposed and demonstrated. Finally, the feasibility of FBGs as selective wavelength filters has been exploited in sensing applications; an alternative approach to improve the response and performance of Brillouin distributed fiber sensors has been studied and validated via experiments. The performance of the reported sensing platforms have been analyzed and evaluated so as to characterize their impact on the fiber sensing field and to ultimately identify the use of the most suitable technology depending on the processing task to be carried out and on the final goal to reach. / [ES] Los sensores y dispositivos en fibra basados en redes de difracción han mostrado excepcionales capacidades en el ámbito de las telecomunicaciones y del sensado, gracias a sus excelentes propiedades. Entre las motivaciones más estimulantes destaca la posibilidad de fabricar redes de difracción ad-hoc para implementar y/o mejorar las prestaciones de los sensores fotónicos. Esta tesis doctoral se ha enfocado en el estudio, diseño, fabricación y evaluación de las prestaciones de redes de difracción de Bragg (FBGs) y de redes de difracción de periodo largo (LPGs) personalizadas con el fin de desarrollar nuevas plataformas de detección y a la vez mejorar la respuesta y las prestaciones de los sensores fotónicos ya existentes. En este contexto, una técnica basada en el análisis tiempofrecuencia se ha estudiado e implementado para la interrogación de sensores en fibra basados en varios tipos y modelos de FBGs. Se ha analizado la distribución de la longitud de onda central a lo largo de la estructura de sensado, gracias a una metodología que conlleva el escaneo en frecuencia del pulso óptico incidente y la técnica conocida como reflectometria óptica en el dominio del tiempo (OTDR). De esta manera se ha llevado a cabo la detección de eventos puntuales, alcanzando muy buenas prestaciones en términos de resolución de la magnitud a medir. Además, se han interrogado varias FBGs a través de una técnica basada en el principio de operación de los filtros de fotónica de microondas (MWP), logrando así la detección de eventos puntuales usando dispositivos de radio-frecuencia (RF) caracterizados por un moderado ancho de banda. La capacidad de sensado de estas plataformas tecnológicas ha sido aprovechada para la realización de un sensor quasi-distribuido de gran alcance, formado por una estructura en cascada de muchas FBGs. Por otro lado, se han puesto a prueba las capacidades de las LPGs como sensores ópticos según un enfoque novedoso; para ello se han aprovechados las potencialidades de los filtros de MWP. Asimismo, se ha estudiado y demostrado un nuevo método para medidas simultáneas de dos parámetros, basado en una LPG parcialmente recubierta por una película polimérica. Finalmente, se ha explotado la viabilidad de las FBGs en cuanto al filtrado selectivo en longitud de onda para aplicaciones de sensado; para ello se ha propuesto un sistema alternativo para la mejora de la respuesta y de las prestaciones de sensores ópticos distribuidos basados en el scattering de Brillouin. En conclusión, se han analizado y evaluado las prestaciones de las plataformas de sensado propuestas para caracterizar su impacto en el ámbito de los sistemas de detección por fibra y además identificar el uso de la tecnología más adecuada dependiendo de la tarea a desarrollar y del objetivo a alcanzar. / [CA] Els sensors i dispositius en fibra basats en xarxes de difracció han mostrat excepcionals capacitats en l'àmbit de les telecomunicacions i del sensat, gràcies a les seus excel¿lents propietats. Entre les motivacions més estimulants destaca la possibilitat de fabricar xarxes de difracció ad-hoc per a implementar i/o millorar les prestacions de sensors fotònics. Esta tesi doctoral s'ha enfocat en l'estudi, disseny, fabricació i avaluació de les prestacions de xarxes de difracció de Bragg (FBGs) i de xarxes de difracció de període llarg (LPGs) personalitzades per tal de desenvolupar noves plataformes de detecció i al mateix temps millorar la resposta i les prestacions dels sensors fotònics ja existents. En este context, una tècnica basada en l'anàlisi temps-freqüència s'ha estudiat i implementat per a la interrogació de sensors en fibra basats en diversos tipus i models de FBGs. S'ha analitzat la distribució de la longitud d'ona central al llarg de l'estructura de sensat, gràcies a una metodologia que comporta l'escaneig en freqüència del pols òptic incident i la tècnica coneguda com reflectometria òptica en el domini del temps (OTDR). D'esta manera s'ha dut a terme la detecció d'esdeveniments puntuals, aconseguint molt bones prestacions en termes de resolució de la magnitud a mesurar. A més, s'han interrogat diverses FBGs a través d'una tècnica basada en el principi d'operació dels filtres de fotònica de microones (MWP), aconseguint així la detecció d'esdeveniments puntuals utilitzant dispositius de ràdio-freqüència (RF) caracteritzats per un moderat ample de banda. La capacitat de sensat d'aquestes plataformes tecnològiques ha sigut aprofitada per a la realització d'un sensor quasi-distribuït a llarga escala, format per una estructura en cascada de moltes FBGs. D'altra banda, s'han posat a prova les capacitats de les LPGs com a sensors òptics segons un enfocament nou; per a això s'han aprofitat les potencialitats dels filtres de MWP. Així mateix, s'ha estudiat i demostrat un nou mètode per a mesures simultànies de dos paràmetres, basat en una LPG parcialment recoberta per una pel¿lícula polimèrica. Finalment, s'ha explotat la viabilitat de les FBGs pel que fa al filtrat selectiu en longitud d'ona per a aplicacions de sensat; per això s'ha proposat un sistema alternatiu per a la millora de la resposta i de les prestacions de sensors òptics distribuïts basats en el scattering de Brillouin. S'han analitzat i avaluat les prestacions de les plataformes de sensat propostes per a caracteritzar el seu impacte en l'àmbit dels sistemes de detecció per fibra i a més identificar l'ús de la tecnologia més adequada depenent de la tasca a desenvolupar i de l'objectiu a assolir. / Ricchiuti, AL. (2016). Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/66343 / TESIS / Premios Extraordinarios de tesis doctorales

The research presented in this dissertation is focused on the construction of complex molecular structures on planar gold and silicon dioxide surfaces using a variety of surface modification techniques, along with thorough surface characterization at each modification step. The dissertation is structured into six separate chapters. In Chapter 1, an introduction to the importance and implications of molecular level surface modification, commonly employed surface modification methods, and available surface characterization techniques is presented. Chapter 2 shows applications of novel methodologies for the functionalization of gold surfaces using alkane dithiol self-assembled monolayers and thiol-ene click chemistry. The resulting functionalized gold substrates demonstrate higher chemical stability than alkanethiol self-assembled monolayers alone and allow spatially controlled functionalization of gold surfaces with light. In Chapter 3, work on tunable hydrophobic surfaces is presented. These surfaces are prepared using a combination of organosilane chemistry, layer-by-layer polyelectrolyte deposition, and thiol-ene chemistry. These hydrophobic surfaces demonstrate high mechanical and chemical stability, even at low pH (1.68). The pinning of water droplets could be tuned on them by the extent of their thermal treatment. Comprehensive surface characterization using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), spectroscopic ellipsometry, atomic force microscopy, and water contact angles was carried out on the molecular assemblies prepared on gold and silicon dioxide surfaces. Chapters 4 and 5 are focused on the application, data interpretation, and enhancement in sensitivity of different surface characterization methods. In Chapter 4, XPS, ToF-SIMS, and principal components analysis are used to probe a real world corrosion-type problem. This systemic study showed the destruction of a protective coating composed of a nitrilotris(methylene)triphosphonic acid by a low-intensity fluorine plasma. In Chapter 5, enhancement in ToF-SIMS signals is shown via bismuth metal deposition. These surfaces are also probed by spectroscopic ellipsometry using the interference enhancement method. Finally, Chapter 6 concludes this dissertation by describing possible future work.