In this diploma thesis were investigated in terms of microviscosity liquid and condensed systems composed of hyaluronan (Hya) and cationic surfactant cetyltrimethylammonium bromide (CTAB). The excitation and emission spectra, lifetime, steady-state fluorescence anisotropy and time-resolved fluorescence anisotropy of the samples were measured. First, was studied the formation of hydrophobic domains in the system Hya-CTAB at concentration of CTAB lower than its critical micelle concentration in an aqueous solution and 0.15M NaCl. It was found that in an aqueous solution small hydrophobic domains linked to chains Hya are formed. Then an increasing concentration of CTAB leads to phase separation and formation of gel. Due to the addition of NaCl then leads to the reorganization of this system and probably the formation of free micelles in the solution. Were also studied condensed phase of system Hya-CTAB-NaCl at high concentrations of surfactant during fourteen days of ageing. It was found that the microviscosity of hydrophobic domains is constant, but the microviscosity of hydrophilic parts gradually decreases.

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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Energy storage is a necessity for the electrification of the modern world and the progression towards renewable energy. Designing new and innovative energy storage alternatives is one of the many challenges taken on by the Nuckolls group at Columbia University. More precisely, organic materials for energy storage with facile synthesis methods, non-toxic materials, and compatibility with aqueous electrolytes are a focus of this research. For this purpose, Perylenediimide (PDI) is the chosen primary molecular building block, that has enabled design of redox active materials due to its versatility as a structural unit, as well as its remarkable electrochemical performance. In this thesis 3 classes of materials based on PDI - small molecules, polymer networks, and COF materials - are compared; providing insights into how their design impacts electrochemical performance. Chapter 1 provides an overview of existing organic materials for energy storage. In particular, explaining the limitations, challenges, current landscape, and future of organic materials for battery and pseudocapacitive applications. This research area confronts current traditional energy storage strategies, such as lithium-ion batteries, with new organic alternatives that offer opportunities that could be more eco-friendly alternatives to lithium-ion batteries in specific applications. Chapter 2 describes the synthesis and characterization of PHATN, the highest performing aqueous n-type pseudocapacitor based on the PDI molecular backbone integrated into a 3-dimensional polymer network, and the relationship between electrochemical performance and structural contortion generated because of the molecular design. This is accomplished by benchmarking against a non-contorted linear polymer and comparing their electrochemical properties. This work provides the foundation for chapters 3 and 4. Chapter 3 expands on the use of molecular contortion as a design principle for molecular electronics, associating molecular contortion to electrochemical performance by generating helical inspired PDI polymers. This design reveals that the helical motif allows for enhanced electronic communication between the redox moieties and leads to higher device performance. Chapter 4 utilizes linear PDI polymers as a non-contorted control in comparison to the helical inspired polymers described in chapter 3. This linear motif reveals the competing design principle of increased surface area for electrolyte access to redox sites which is shown to increase device performance. Chapter 5 discusses a COF inspired redox active 2-dimensional polymers (RA-2DP) based on PDI materials and how the structural motif and conductive linkers can improve electrochemical performance. This chapter validates the design criteria outlined in chapter 4 and explains how these RA-2DPs and similar structures can enhance energy storage in organic materials. Collectively, this work provides a structured story of PDI materials, their potential as energy storage materials, and the design principles that have led to increased performance. The work completed in this thesis points towards structured and porous redox active organic materials as next generation energy storage alternatives. With the consideration of renewable energy and challenges with existing energy storage options, it is our hope that organic materials will contribute to this ever evolving and growing research area to create a more sustainable and environmentally friendly future.

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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.