Fotocromismo refere-se ao fenômeno reversível no qual um material altera sua coloração quando irradiado com luz. Neste trabalho, é analisada a estrutura de materiais híbridos formada por poliânions de ácido 12-tungstofosfórico (H3PW12O40, HPW) HPW) inseridos em uma matriz de silicatos orgânico-inorgânica (ormosil). Estes materiais apresentam atividade fotocrômica na faixa do UV (~200nm). Os complexos analisados correspondem a formulações contendo 3-aminopropiltrietóxisilano (APTS), butironitrilatrietoxisilano (BUT), feniltrietóxisilano (FTS), tetraetilortosilicato (TEOS) e 3-glicidoxipropilltrimetóxisilano (GLYMO), com concentrações variadas dos precursores, objetivando o controle da resposta fotocrômica, visando a aplicação destes materiais em dosímetros de UV de baixo custo. Os complexos são constituídos de três componentes principais: a matriz inorgânica de silicatos, responsável pelas propriedades mecânicas dos complexos; os grupos orgânicos, que fornecem elétrons para a redução do HPW; e o poliânion de HPW, que é responsável pelo efeito fotocrômico. O objetivo deste trabalho é obter uma descrição da estrutura das três partes do híbrido e a da interação entre elas, que permita avançar na compreensão do fenômeno fotocrômico e oriente no processo de preparação destes complexos. Foi utilizada a técnica da Ressonância Magnética Nuclear (RMN) de alta resolução em estado sólido de 31P, 29Si e 13C para analisar, respectivamente, os ambientes de coordenação do poliânion, a distribuição de espécies de silicatos na rede inorgânica e o estado dos grupos orgânicos vinculando a rede com os poliânions. Através de técnicas como a ressonância dupla de eco de spin (SEDOR) entre 1H e 31P, e a correlação heteronuclear (HETCOR) 1H-29Si, foi obtida informação de mais longo alcance sobre o ambiente de coordenação do HPW e da distribuição relativa de espécies da rede inorgânica. Os resultados de 31P-RMN mostram que em todos os complexos analisados os poliânions de HPW se mantêm íntegros e estão diluídos na matriz ormosil, sem existir segregação em ambientes hidratados. Mediante a RMN de 31P, não foram constatadas diferenças estruturais significativas com relação à interação dos grupos amina e nitrila com o poliânion. Os resultados de RMN de 29Si revelam uma matriz amorfa do ormosil, contendo espécies tetraédricas SiO4 e grupos de organosilicatos com uma e duas ligações Si-C. A conectividade média da matriz de ormosil é invariante entre os diferentes complexos. Os experimentos de 13C-RMN mostram que o GLYMO é o único precursor cujo grupo funcional sofre algum tipo de reação, resultando em grupos diol que restringem a mobilidade do poliânion. Foi demonstrada pela primeira vez a possibilidade de analisar o processo fotocrômico através de RMN de 31P em amostras irradiadas, verificando a reversibilidade do processo a nível atômico. / The photocromic effect is the reversible change in the color of a material upon irradiation in the range UV-VIS-IR. In this work, the structure of photochromic ormosils complexes based on 12-phosphotungstic acid (H3PW12O40, HPW) was analyzed. These hybrid materials exhibit photochromic response in the UV range (~200nm). The analyzed compositions contain 3- aminopropyltriethoxysilane (APTS), butyronitriletriethoxysilane (BUT) and phenyltriethoxysilane (PhTS), tetraethylortosilicate (TEOS) and 3- Glycidoxypropyltrimethoxysilane (GLYMO), which where developed aiming to control the photochromic response for application of these materials in low-cost UV dosimeters. The structure of these complexes has three main building blocks: the inorganic silica matrix, responsible for mechanical properties; the HPW polyanion, responsible for the photochromic response; and the organic functionalities, providing electrons to the HPW during the reduction process induced by irradiation. The aim of this work is to obtain a structural description of these parts of the hybrid complexes, and their mutual interaction. This picture is relevant to the comprehension of the photochromic effect and to improve the preparation routes for these materials. High-resolution solid-state Nuclear Magnetic Resonance (NMR) techniques of 31P, 29Si and 13C NMR were applied to analyze, respectively, the polyanion coordination environment, the distribution of silicate species in the inorganic network, and the state of the organic functionalities linking the network with the polyanions. Using techniques based on the heteronuclear dipolar coupling, such as -31P Spin-Echo Double Resonance (SEDOR), and -29Si heteronuclear correlation (HETCOR), structural information on the 1H environment around 31P and the relative distribution of silicon species was obtained. The 31PNMR results show the chemical integrity of HPW polyanions in all complexes and the absence of segregation of these species in hydrated compounds. No significant differences were detected in the interaction of the polyanion with amine or nitride groups. The 29Si-NMR results reveal an amorphous ormosil matrix containing tetrahedral SiO4 species and organosilicates with one and two Si-C bonds. The average connectivity of the ormosil matrix is the same in all complexes. The 13C-NMR experiments show that GLYMO is the only reactive organic component, generating diol groups restricting the mobility of the HPW polyanion. Also, the possibility to analyze the photochromic process by 31P-NMR was demonstrated, verifying the reversibility of the process at atomic level.

Esta dissertação versa sobre o estudo de filmes híbridos orgânicos-inorgânicos do tipo ormosil com heteropoliânions do tipo Keggin. O heteropoliânion usado nesse trabalho foi: H3PW12O40 enquanto o ormosil foi obtido a partir do processo sol-gel usando tetraetilortossilicato (TEOS) como agente formador da rede 3D de silicatos e organossilanos contendo grupos oxirana e grupos básicos de Lewis nitrogenados. Realizaram-se testes do uso de Poli (dimetilsiloxano), bis (3-aminopropil) terminados (PDMSa) como agentes modificadores nos filmes. Foram obtidos filmes autossuportados e suportados em lâminas de vidro aluminossilicato. O PDMSa e o silano contendo o grupo oxirana levaram a uma queda na rugosidade média quadrática dos filmes como demonstrado nas micrografias obtidas por Microscopia Eletrônica de Varredura (MEV). Medidas de ângulos de contato estático da água sobre os filmes e de Espectroscopia de Fotoelétrons Excitados por Raios-X mostraram que há segregação do PDMSa ou do silano contendo o grupo oxirana na superfície dos filmes, entretanto os filmes com maior ângulo de contato são aqueles contendo PDMSa. Medidas de Espectroscopia de Absorção na Região do Infravermelho (IV) e Espectroscopia de Ressonância Magnética Nuclear com Rotação em Ângulo Mágico no Estado Sólido (RMN) mostraram que ormosis contendo silanos com grupo amino levam a parcial decomposição dos heteropoliânions, enquanto ormosis contendo silanos com o o grupo nitrila resultam em menor taxa de decomposição. Nos ormosis contendo igual proporção em número de moles destes dois silanos observou-se que estes dois grupos devem estar muito próximos e interagindo entre si via ligação de hidrogênio o que resultou numa queda ainda maior da taxa de decomposição. Os ormosis com silanos dotados de grupos oxirana e nitrila apresentaram maior sensibilidade a radiação UV, ou seja, a maior variação de absorbância e menor tempo de retorno à cor original. Estes filmes mostraram reprodutibilidade e não perderam sua atividade fotocrômica após serem submetidos a 10 ciclos sucessivos de irradiação com UV. Os filmes mostraram resposta linear da função de refletância com a dose de radiação UVB na faixa de 0,80 até 69 MED. Desta forma nós demonstramos a possibilidade de se obter filmes fotocrômicos reprodutíveis e estáveis e como controlar sua sensibilidade usando o processo sol-gel. / This thesis aim to study the organic-inorganic hybrid films of the organosilanes with heteropolyanions of the Keggin type. The heteropolyanion used in this study was H3PW12O40 while the ormosil was obtained by the sol-gel process using tetraethylortossilicate (TEOS) to build the 3D silicate network and organosilanes bearing the oxirane and Basic Lewis nitrogenated groups. Poly (dimethylsiloxane), terminated with (3-aminopropyl) groups, (PDMSa) was essayed as modifiers agents in the film. The films were supported on aluminosilicate glass substrates and self-suported ones. PDMSa or oxirane bearing silanes addition results on smoother filmes reporting lower mean square root roughness based on electron micrographies obtained by Scanning Electron Microscopy (SEM). Water static contact angle measurements and X-ray Photoemission Spectroscopy (XPS) pointed out the surface segregation of the PDMSa and oxirane bearing silane, however higher contact angles were observed for the PDMSa based films. InfraRed Absorption Spectroscopy (IR) and Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy (MAS NMR) results demonstrate that in ormosis with silanes bearing amino groups there was phosphotungstic acid decomposition while in ormosis with nitrile groups such decomposition is much less pronounced. For mixed ormosis with even proportion of amino and nitrile bearing silanes those functional groups are close enough to interact through hydrogen bonding resulting on even lower decomposition of the Phosphotungstate oxocluster. Those films with nitrile functional groups showed higher photochromic activity and faster bleaching time. The films showed high reproducibility and did not loose their photochromic activity after ten cycles of UV irradiation. The films bearing nitrile functionality showed linear response of the reflectance function as a function of the irradiation dose between 0,80 and 69 MED. Therefore, it was demonstrated the possibility to use sol-gel process to obtain photochromic ormosis.

Fulgides and fulgimides comprise one class of thermally irreversible photochromic organic compounds. Light dependent isomerization, has made these organic molecules promising materials for several applications, including optical memory devices, and switches. Hydrolytic stability of fulgides and fulgimides is crucial for their practical applications in biological systems and humid environments. Fulgimides, the most important derivative of fulgides, have a succinimide ring, which, unlike the anhydride ring, of fulgides, is resistant to hydrolytic degradation. A novel N-alkylindolylfulgimide was synthesized and copolymerized with acrylamide. The photochromic and hydrolytic properties of the copolymer in phosphate (pH 7.4) and acetate (pH 5.0) buffer solutions were characterized. The N-alkylindolylfulgimide based copolymer exhibited significantly enhanced hydrolytic stability (50 times better in phosphate buffer) and similar photochromic properties as a copolymer containing an N-arylindolylfulgimide.

Ce projet de thèse consiste dans un premier temps à synthétiser des systèmes moléculaires multifonctionnels possédants un grand nombre d’entités fluorescentes et photochromes. De telles architectures nécessitent ensuite une étude photophysique poussée pour caractériser leurs propriétés d’émission photo-activée pour jouer le rôle de sondes moléculaires fluorescentes super-résolutives en imagerie de fluorescence. En effet, l’accès aux observations nanométriques par microscopie optique est actuellement un domaine de recherche extrêmement actif et prometteur. Ici, la combinaison astucieuse de molécules photochromes (de type diaryléthène) et fluorescentes (de type dicyanométhylène pyranes ou benzophénoxazines) à l’échelle nanométrique, grâce à des plateformes moléculaires telles que des oligosaccharides et des peptides fonctionnalisés par “chimie click”, doit permettre d’obtenir des structures aux géométries variées avec des distances et orientations inter-chromophores diverses, dont l’optimisation doit conduire à des interactions efficaces menant à l’émergence d’effets collectifs coopératifs. Pour ces assemblages moléculaires mixtes, il est attendu que la présence d’une unité photochrome puisse engendrer l’extinction de fluorescence de plusieurs fluorophores lorsque ces entités sont situées à une distance appropriée pour que le transfert d’énergie ait lieu de manière amplifiée. Par ailleurs, même une faible conversion des photochromes doit permettre d’atteindre un contraste de fluorescence extrêmement efficace avoisinant 100% et ainsi obtenir des super-molécules dont la photo-commutation serait rapide et économe en photons. Il s’agira enfin de démontrer que les systèmes moléculaires multichromophoriques ainsi optimisés présentent le comportement souhaité à l’échelle de la molécule unique pour l’imagerie de fluorescence super-résolution. / The synthesis of photoswitchable emissive molecular system still represents a challenge, in order to develop fluorescence-based devices for nanotechnologies. In the last decade, excitation energy transfer processes (EET) have been advantageously employed to design photoswitchable fluorescent molecular systems between a photochromic dye and an appropriate fluorescent molecule. More recently, photochromic dyes of particular interest, showing no emission in the open-form (P-OF) but a strong emission signal in the closed-form (P-CF), have been developed. Such molecules allow a multi-emission switch when combined with a fluorescent moiety. In this project, we will design and synthesize fluorescent photochromic diarylethene covalently linked to different fluorophores, such as benzothiadiazole (BTD) and BODIPY derivatives. By choosing a fluorophore moiety with blue/green emission (F) and a photochromic moiety with orange/red emission in closed-form (P-CF), EET can occur between F and P-CF leading to photoswitchable multi-emission properties. Photophysical characteristics of dyads will be studied by spectroscopy with the aim of presenting their light-controllable optical properties and the intramolecular EET processes between fluorescent and photochromic moieties.

No description available.

No description available.

In this project self-supporting foils with focus on the element yttriumhave been fabricated by means of evaporation and magnetron sputtering.The goal was to see if it was possible to make photochromic selfsupportingyttrium foils. Multiple self-supporting foils were made andsome had suitable properties to be further investigated. The first foilof interest was a plain carbon foil, the second was yttrium layered ontop of a carbon foil, the third was a yttrium-only foil and the fourthwas a yttrium oxyhydride foil. The foils were then subsequentlycharacterized with a newly developed Medium Energy Ion Scattering -Elastic Recoil Detection Analysis (MEIS - ERDA) technique. Thistechnique measures energy loss and recoils (kicked out atoms) of heavyions passing through the self-supporting foils. The measurements weremade with three ion projectile energies, 250, 300 and 320keV. Theprojectiles sent were argon ions. It was noted that the yttriumoxyhydride foil had more hydrogen and oxygen than the yttrium foil. Withoptical measurements it was also possible to confirm that the yttriumoxyhydride foil had photochromic properties. With the knowledge of theparameters used to fabricate these foils, the conclusion is that furtherresearch on self-supporting yttrium oxyhydride is encouraged.

Three-dimensional (3D) optical data storage based on two-photon processes provides highly confined excitation in a recording medium and a mechanism for writing and reading data with less cross talk between multiple memory layers, due to the quadratic dependence of two photon absorption (2PA) on the incident light intensity. The capacity for highly confined excitation and intrinsic 3D resolution affords immense information storage capacity (up to 1012 bits/cm3). Recently, the use of photochromic materials for 3D memory has received intense interest because of several major advantages over current optical systems, including their erasable/rewritable capability, high resolution, and high sensitivity. This work demonstrates a novel two-photon 3D optical storage system based on the modulation of the fluorescence emission of a highly efficient two-photon absorbing fluorescent dye (fluorene derivative) and a photochromic compound (diarylethene). The feasibility of using efficient intermolecular Förster Resonance Energy Transfer (RET) from the non-covalently linked two-photon absorbing fluorescent fluorene derivative to the photochromic diarylethene as a novel read-out method in a two-photon optical data storage system was explored. For the purpose of the development of this novel two-photon 3D optical storage system, linear and two-photon spectroscopic characterization of commercial diarylethenes in solution and in a polymer film and evidence of their cyclization (O→C) and cycloreversion (C→O) reactions induced by two-photon excitation were undertaken. For the development of a readout method, Resonance Energy Transfer (RET) from twophoton absorbing fluorene derivatives to photochromic compounds was investigated under one and two-photon excitation. The Förster's distances and critical acceptor concentrations were determined for non-bound donor-acceptor pairs in homogeneous molecular ensembles. To the best of my knowledge, modulation of the two-photon fluorescence emission of a dye by a photochromic diarylethene has not been reported as a mechanism to read the recorded information in a 3D optical data storage system. This system was demonstrated to be highly stable and suitable for recording data in thick storage media. The proposed RET-based readout method proved to be non-destructive (exhibiting a loss of the initial fluorescence emission less than 20% of the initial emission after 10,000 readout cycles). Potential application of this system in a rewritable-erasable optical data storage system was proved. As part of the strategy for the development of diarylethenes optimized for 3D optical data storage, derivatives containing Ï€-conjugated fluorene molecules were synthesized and characterized. The final part of this reasearch demonstrated the photostability of fluorine derivatives showing strong molecular polarizability and high fluorescence quantum yields. These compounds are quite promising for application in RET-based two-photon 3D optical data storage. Hence, the photostability of these fluorene derivatives is a key parameter to establish, and facilitates their full utility in critical applications.

Light stabilisation of photochromic dyes is seen as the most challenging part in the development of photochromic dyes. The aim of this research is to compare stabilisation methods and their effect on the lifetime of a photochromic print on textile. The vision is to create a textile UV-sensor that detects current UV light exposure in the surroundings and alarms the wearer by showing colour. The developed inks have been formulated for ink-jet printing as a novel production method with resource saving properties. UV-LED light curable ink formulations were prepared for two dye classes; a non-commercial spirooxazine, a commercial spirooxazine (Oxford Blue) and a commercial naphthopyran (Ruby Red). Two different stabilisation methods were applied; chemically by incorporation of hindered amine light stabilisers and physically by polyurethane coating. Fatigue tests were performed to evaluate and compare the stabilisation methods. The tests included were household washing, multiple activations and intensive sun-lamp exposure. As a result it was found that Oxford Blue and spirooxazine had an initial better resistance to photodegradation than Ruby Red. The coating reduced the ability of colour development in higher extend for Oxford Blue and spirooxazine compared to Ruby Red. Moreover, the photocolouration increased with the number of activations for Oxford Blue and spirooxazine in particular. In general, the physically stabilised samples showed a better or similar fatigue resistance compared to chemically stabilised samples. On the other hand the results are weak in significance. It is concluded that the developed coating method in combination with further optimising has potential.

Organic electronics has evolved into a well-established research field thanks to major progresses in material sciences during recent decades. More attention was paid to this research field when “the discovery and development of conductive polymers” was awarded the Nobel Prize in Chemistry in 2000. Electronic devices that rely on tailor-made material functionalities, the ability of solution processing and low-cost manufacturing on flexible substrates by traditional printing techniques are among the key features in organic electronics. The common theme while exploring organic electronics, and the focus of this thesis, is that (semi-)conducting polymers serve as active materials to define the principle of operation in devices. This thesis reviews two kinds of organic electronic devices. The first part describes electrochemical devices based on conducting polymers. Active matrix addressed displays that are printed on flexible substrates have been obtained by arranging electrochemical smart pixels, based on the combination of electrochemical transistors and electrochromic display cells, into cross-point matrices. The resulting polymer-based active-matrix displays are operated at low voltages and the same active material is used in the electrochemical transistors as well as in the electrochromic display cells, simply by employing the opto-electronic properties of the material. In addition to this first part, a switchable optical polarizer based on electrochromism in a stretch-aligned conducting polymer is described. The second part reports switchable charge traps in polymer diodes. Here, a device based on a solid-state blend of a conjugated polymer and a photochromic molecule has been demonstrated. The solid state blend, sandwiched between two electrodes, provide a polymer diode that allows reversible current modulation between two different charge transport mechanisms via externally triggered switching of the charge trap density.