Ce mémoire de thèse est consacré au développement d'anodes et de photonanodes efficaces pour l'oxydation électrocatalytique et photocatalytique de l'eau à base de nanocomposites dans lesquels des nanoparticules d'oxyde de nickel ou de cobalt ont été insérées dans un film de poly(pyrrole-alkylammonium) chargé positivement. Les anodes nanocomposites renferment des petites nanoparticules d'oxydes de nickel ou de cobalt avec une excellente nanostructuration induite par le film polypyrrole, et des performances catalytiques très élevées par rapport à des anodes sur lesquelles des oxydes de nickel et de cobalt ont été directement déposés sans polypyrrole. Ces électrodes nanocomposites surpassent les anodes à base de nickel de la littérature (non dopées par du fer) et celles utilisant des oxydes de métaux précieux, tels que RuO2 et IrO2.Cette stratégie a été étendue avec succès à la conception de photoanodes hybrides en introduisant un chromophore de pérylène diimine dans ces nanocomposites d’oxydes de nickel ou de cobalt. Ces photoanodes présentent une densité de photocourant très élevé avec l'oxyde de nickel et l'oxyde de cobalt sous irradiation dans le visible avec une stabilité relativement bonne dans le temps. Ces valeurs de photocourant dépassent largement celles obtenues par des photoanodes hybrides similaires de la littérature combinant un colorant organique et un oxyde métallique comme catalyseur, démontrant les grandes potentialités de notre approche pour élaborer des cellules (photo)électrochimiques dédiées à la dissociation de l’eau en H2 et O2. / This thesis is focused on the development of efficient anodes and photonanodes for electrocatalytic and photocatalytic water oxidation based on nanocomposite materials in which nickel or cobalt oxide nanoparticles have been inserted in a positively charged poly(pyrrole-alkylammonium) film.The nanocomposite anodes exhibit small nanoparticles of nickel or cobalt oxides and high nanostructuration induced by the polypyrrole matrix leading to very high catalytic performance in comparison with bare anodes on which nickel and cobalt oxides have been deposited without polypyrrole. These nanocomposite electrodes outperform the nickel-based anodes of the literature (undoped by iron) and those using precious metal oxides, such as RuO2 and IrO2.This strategy has been successfully extended to the design of hybrid photoanodes by introducing a perylene diimine chromophore in these nickel or cobalt oxide nanocomposite materials. These photoanodes display very high photocurrent density with nickel oxide and cobalt oxide under visible light illumination along with a relatively good stability over time. These photocurrent density values largely exceed those reached by similar hydrid photoanodes of literature combining an organic dye and a metal oxide as catalyst, demonstrating the great potentialities of our approach to implement (photo)electrochemical cells devoted to water splitting into H2 and O2.

There is currently a great interest to develop and market organic electronic devices, and theoretical models are needed to provide physical insight and quality predictions when designing these materials. Many organic molecules absorb in the UV-vis region of light, and therefore, UV-vis spectroscopy is a relatively simple tool that can help experimentalists "see" the packing arrangements of the molecules within each material, as long as there is a solid theoretical understanding of the photophysics that links the interactions between molecules to changes in optical features. For example, the Kasha spectral shifts have been used for decades to identify J-aggregate and H-aggregate packing arrangements from red- and blue- spectral shifts, respectively. The innate presence of vibronic coupling in organic molecules gives rise to a unique set of additional spectral signatures that are far more reliable than the Kasha spectral shifts for inferring packing arrangements. Moreover, the Kasha shifts are based entirely on Coulomb coupling between molecules, which leads to the creation of delocalized Frenkel excitons. For many π-conjugated organic molecules, however, dispersion forces in π-conjugated chromophores encourage close packing distances of about 3.5-4 Å between organic monomers, which further introduces intermolecular couplings beyond the Coulomb coupling, due to intermolecular charge transfer (CT). Therefore, much theoretical research has focused on incorporating all these effects through a Frenkel-CT-Holstein Hamiltonian, in order to better understand how different packing arrangements within a given material can be identified through specific changes in steady-state absorption and photoluminescence features. In this thesis, the Frenkel-CT-Holstein model is specifically applied to study the absorption and photoluminescent spectra of various derivatives of perylene diimide (PDI), which are of great interest as non-fullerene acceptors in organic photovoltaic design. PDIs display a plethora of packing arrangements and corresponding spectral signatures just by varying the substituents within the PDI core. This thesis first aims to understand the exciton band structure of two different PDI micro-crystals that both experience similar Frenkel-CT interference, but with one system displaying dominant Coulomb interactions while the other undergoes dominant Frenkel-CT coupling. Both are close to what is called a “null”-point, and the work in this thesis explores the photoluminescent signature as a reliable means to track which side of the “null”-point the Frenkel-CT interference lies. While the Frenkel-CT-Holstein model is successful in modeling mostly absorption spectra of aggregates composed of PDI monomers, one challenge has been that aggregates of PDIs often exhibit so-called excimer features in their photoluminescence spectra, which the model cannot account for. Systems that emit broad, structureless and red-shifted excimer peaks typically display inefficient exciton transport in organic semiconductors. The bulk of this thesis has been to expand the model to account for excimer emission, which is made possible by utilizing a Holstein-Peierls (HP) Hamiltonian that incorporates the effects of both local vibronic coupling and nonlocal Frenkel-CT coupling to intermolecular motions within a dimer. The experimental spectra for two different PDI dimer systems that display different excimer features is successfully reproduced with the new theory. This thesis concludes by analyzing how nonlocal coupling, which account for changes in the Frenkel-CT mixing along an intermolecular vibrational mode, can lead to various types of excimers. Different phase relations within the electron and hole nonlocal coupling parameters can combine with different phase relations within the electron and hole Frenkel-CT coupling parameters, leading to a rich array of excimer properties, especially when combined with the additional effects of Coulomb coupling, as well as local intermolecular vibronic coupling, which can either enhance or diminish the excimer photoluminescence. Overall, the Holstein-Peierls approach offers insight into the roles of Frenkel and CT excitons in excimer formation, and highlights the importance of the magnitude and phase of the intermolecular electron and hole transfer integrals in the ground and excited state geometries in producing distinct excimer features. The model provides further insight into the origin of excimers, which lays a foundation for future theoretical and experimental studies in designing organic materials. / Chemistry

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Chemisorption of an organic monolayer to tune the surface properties of a transparent conductive oxide (TCO) electrode can improve the performance of organic electronic devices that rely on efficient charge transfer between an organic active layer and a TCO contact. Here, a series of perylene diimides (PDIs) was synthesized and used to study relationships between monolayer structure/properties and electron transfer kinetics at PDI-modified indium-tin oxide (ITO) electrodes. In these PDI molecules, one of the imide substituents is a benzene ring bearing a phosphonic acid (PA) and the other is a bulky aryl group that is twisted out of the plane of the PDI core. The size of the bulky aryl group and the substitution of the benzene ring bearing the PA were both varied, which altered the extent of aggregation when these molecules were absorbed as monolayer films (MLs) on ITO, as revealed by both attenuated total reflectance (ATR) and total internal reflection fluorescence spectra. Polarized ATR measurements indicate that, in these MLs, the long axis of the PDI core is tilted at an angle of 33-42 degrees relative to the surface normal; the tilt angle increased as the degree of bulky substitution increased. Rate constants for electron transfer (k(s,opt)) between these redox-active modifiers and ITO were determined by potential-modulated ATR spectroscopy. As the degree of PDI aggregation was reduced, k(s,opt) declined, which is attributed to a reduction in the lateral electron self-exchange rate between adsorbed PDI molecules, as well as the heterogeneous conductivity of the ITO electrode surface. Photoelectrochemical measurements using a dissolved aluminum phthalocyanine as an electron donor showed that ITO modified with any of these PDIs is a more effective electron-collecting electrode than bare ITO.

Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide. A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface. Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2 surface. The results show strong influence of anchor and inserted spacer groups on adsorption and electronic properties. Also in these cases, the phosphonic acid anchor group was found to bind the dyes significantly stronger to the surface than the carboxylic acid anchor, while the interfacial electronic coupling was stronger for the carboxylic anchor. The estimated electron injection times were twice as fast for the carboxylic anchor compared to the phosphonic anchor. Moreover, the electronic coupling was affected by the choice of spacer group, where unsaturated spacer groups were found to mediate electron transfer more efficiently than saturated ones.

This thesis described the synthesis and characterization of new perylene diimide (PDI)-based photonic and electronic materials. In the first part of this thesis, PDI-based polynorbornenes, including PDI-grafted homopolymers and block-copolymers (BCPs) were synthesized and characterized as alternative acceptors for fullerenes for organic electronics. It was found that the PDIs on the polymer side-chains affect π-π stacking with the neighboring PDIs, which has implications for the use of these materials for organic field-effect transistors (OFETs) and organic photovoltaic devices (OPVs). It should be noted that the performance of solar cell based on these materials was poor, like other similar materials. The major reasons could be the challenge in controlling the molecular alignment of the PDI-based materials, which leads to lower electron mobilities in films compared to devices with fullerene-based acceptors. One PDI-grafted BCP showed better OPV performance compared to the other BCPs and respective homepolymer blends, presumably due to favorable morphology. In the second part of this thesis, photo-induced charge-separation in blends of poly-3-hexyl-thiophene (P3HT) and various PDI derivatives have been studied. Probing of long-lived photo-generated PDI radical anions provided insight on these photo-induced processes and their use for OPVs. In the third part of this thesis, the use of photo-generated PDI radical-anion absorption was shown to be effective for optical limiting of nanosecond laser pulses between 650 - 800 nm. In Chapter 5, an effective approach for two-photon absorption (2PA)-induced optical limiting using donor-PDI dyads through which donors and acceptors can be independently chosen to maximize optical suppression at particular wavelengths has been demonstrated. In Chapter 6, conjugated polymers with PDI pendants and poly(carbazole-alt-2,7-fluorene) main-chains were synthesized for optical limiting using the photo-generated PDI radical anion via PDI aggregate excitation and/or 2PA from the polymer backbones. It was also found that nitro-phenyl group or similar derivatives could be good candidates to incorporate into those donor-conjugated polymers, which have significant overlap between their 2PA band and respective polaron absorptions for 2PA-indced optical limiting. / Thesis advisor has approved the addition of errata to this item. Corrections were made to pages 95, 98 and 101.

Orientador: Carlos José Leopoldo Constantino / Banca: Marystela Ferreira / Banca: Neri Alves / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Filmes finos do bis benzimidazo perileno (AzoPTCD) foram fabricados usando as técnicas de Langmuir, Langmuir-Blodgett (LB) e evaporação a vácuo (PVD). A estabilidade térmica durante a fabricação dos filmes PVD ('DA ORDEM DE' '400 GRAUS' a '10 POT. -6' Torr) e a integridade da estrutura molecular pela dissolução do AzoPTCD em ácidos fortes para a fabricação dos filmes de Langmuir e LB foram monitoradas pelo espalhamento Raman. Complementarmente a análise termogravimétrica revelou que a degradação térmica do AzoPTCD ocorre a '675 GRAUS'. Os filmes de Langmuir revelaram um alto empacotamento molecular do AzoPTCD sobre a subfase aquosa, onde as moléculas estão apoiadas sobre seu eixo maior ou menor. A adição de íons metálicos na subface aquosa revelou uma sensibilidade do AzoPTCD a presença destes íons, deslocando as isotermas para maiores valores de área molecular média. O crescimento dos filmes LB e PVD sobre substratos sólidos foi monitorado através da espectroscopia de absorção UV-Vis, e a morfologia dos filmes PVD foi estudada via microscopia de força atômica (AFM) em função da espessura em massa. A organização molecular dos filmes PVD foi determinada usando as regras de seleção de superfície aplicadas na espectroscopia de absorção no infravermelho (modos de transmissão e reflexão). Apesar da organização molecular, a difração de raios-x revelou que os filmes PVD são amorfos. Cálculos teóricos (Density functional theory -B3LYP) foram usados para atribuição dos modos vibracionais nos espectros de absorção no infravermelho e espalhamento Raman ressoante Nanoestruturas metálicas, capazes de ativar os fenômenos de amplificação em superfície foram usadas para estudos de espalhamento Raman ressonante amplificado em superfície (SERRS) e fluorescência amplificada em superfície (SEF) nos filmes LB e PVD. Através... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Thin solid films of bis benzimidazo perylene (AzoPTCD) were fabricated using Langmuir, Langmuir-Blodgett (LB) and physical vapor deposition (PVD) techniques. Thermal stability during the fabrication of PVD films ('DA ORDEM DE' '400 GRAUS' a '10 POT. -6' Torr) and chemical structure integrity by dissolution of the AzoPTCD in a strong acid were monitored by Raman scattering. Complementary thermogravimetric results showed that thermal degradation of AzoPTCD occurs at '675 GRAUS'. Langmuir films showed a high molecular packing with the molecules tilted onto the aqueous subphase. Besides, the AzoPTCD л-A isotherms were shifted to larger areas due to the addition of metallic ions in the subphase. The growth of the LB and PVD films were established through UV-Vis absorption spectroscopy, and the surface morphology in PVD films was probed by atomic force microscopy (AFM) as function of the mass thickness. The AzoPTCD molecular organization in the PVD films was determined using the selection rules of infrared absorption spectroscopy (transmission and reflection-absorption modes). Despite the molecular organization, X-ray diffraction revealed that the PVD films are amorphous. Theoretical calculations (Density Functional Theory, B3LYP) were used to assign the vibrational modes in the infrared and Raman spectra. Metallic nanostructures, able to sustain localized surface plasmons (LSP) were used to achieve surface-enhanced resonance Raman scattering (SERRS) and surface-enhanced fluirescence (SEF) in the LB and PVD films. The conductivity and rectifier character of the PVD films of AzoPTCD were determined by current as function of tension curves (I(V)) in dc measurements. The impedance spectroscopy in ac measurements was used to study the performance of PVD films of the AzoPTCD as transductor elements in sensing units applied to discriminate... (Complete abstract click electronic access below) / Mestre