Thesis (Ph.D.)--University of Wollongong, 2007. / Typescript. Includes bibliographical references: leaf 206-217.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Peter F. Green. Vita. Includes bibliographical references.

abstract: As sunlight is an ideal source of energy on a global scale, there are several approaches being developed to harvest it and convert it to a form that can be used. One of these is though mimicking the processes in natural photosynthesis. Artificial photosynthetic systems include dye sensitized solar cells for the conversion of sunlight to electricity, and photoelectrosynthetic cells which use sunlight to drive water oxidation and hydrogen production to convert sunlight to energy stored in fuel. Both of these approaches include the process of the conversion of light energy into chemical potential in the form of a charge-separated state via molecular compounds. Porphyrins are commonly used as sensitizers as they have well suited properties for these applications. A high potential porphyrin with four nitrile groups at the beta positions, a β-cyanoporphyrin (CyP), was investigated and found to be an excellent electron acceptor, as well as have the necessary properties to be used as a sensitizer for photoelectrosynthetic cells for water oxidation. A new synthetic method was developed which allowed for the CyP to be used in a number of studies in artificial photosynthetic systems. This dissertation reports the theories behind, and the results of four studies utilizing a CyP for the first time; as a sensitizer in a DSSC for an investigation of its use in light driven water oxidation photoelectrosynthetic cells, as an electron acceptor in a proton coupled electron transfer system, in a carotene-CyP dyad to study energy and electron transfer processes between these moieties, and in a molecular triad to study a unique electron transfer process from a C60 radical anion to the CyP. It has been found that CyPs can be used as powerful electron acceptors in molecular systems to provide a large driving force for electron transfer that can aid in the process of the conversion of light to electrochemical potential. The results from these studies have led to a better understanding of the properties of CyPs, and have provided new insight into several electron transfer reactions. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

The understanding of self-assembly processes is important for fabrication of well-defined structures with new functionalities for applications in the area of biomedical sciences, material sciences and electronics. In this thesis, two types of self-assembly processes are described: (1) self-assembly of fullerene derivatives in water and (2) self-assembly on surfaces using layer-by-layer (LbL) approach. The various interactions and parameters involved in the self-assembly are detailed in the introductory chapter 1. The various internal parameters like molecular geometry, intramolecular and intermolecular forces that guides the self-assembly process of amphiphiles in water are discussed. The experimental procedures used in the present thesis for the fabrication of nanostructures via self-assembly approach are also described. In the later part of the chapter, the LbL technique for fabrication of thin films and microcapsules is reviewed where various interactions involved in the growth of LbL assembly are discussed. The effect of ionic strength and pH on the growth and property of LbL assemblies is elaborated. A brief discussion of the materials used in the thesis ‒ fullerene, bovine serum albumin (BSA) and nanocrystalline cellulose (NCC) is also provided The self-assembly behaviour of amphiphilic fullerene derivatives are described in chapter 2. Fullerene is anisotropically substituted with five polar hydroxyl groups using organo-copper reagent. The derivative can interact in water via the van der Waals and hydrophobic interactions of the fullerene moiety as well as the intermolecular hydrogen bonding among the hydroxyl groups and also with water. The penta-hydroxy fullerene derivative self-assembles in water as vesicular structures. The size of these vesicles can be varied by modifying the kinetics of self-assembly which was done by changing the rate of addition of non-solvent (water) to the solution of the fullerene derivative. In the second derivative, the hydroxyl groups are substituted with less polar methoxy groups. The penta-methoxy fullerene derivative cannot participate in inter-molecular hydrogen bonding formation unlike the penta-hydroxy derivative but there is possibility of hydrogen bond formation with water where oxygens on methoxy group can act as hydrogen bond acceptor. The penta-methoxy fullerene does not show any vesicle formation in water. The computational simulation studies were carried out on the two fullerene derivatives to understand the self-assembly behaviour of these two derivatives. Furthermore, the vesicle structures formed by the penta-hydroxy fullerene derivative are used for entrapment of hydrophobic polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and also hydrophilic dye, Rhodamine B. In both the cases, fluorescence quenching is observed due to electron transfer reaction with fullerene and hence these fullerene vesicles can be used to study the effect of confinement on electron transfer reactions and other chemical dynamics. The layer-by-layer self-assembly approach for the fabrication of biopolymeric thin films and microcapsules is discussed in the chapters 3 to 6. The biocompatible nanoparticles and nanofibers were used as the components of the assembly. In chapter 3, we have described fabrication of thin film of bovine serum albumin (BSA) nanoparticles via LbL approach using biopolymer chitosan as the complementary polymer. The driving force for the assembly growth of the assembly was the electrostatic and complementary hydrogen bond formation between the two components. The idea of incorporating nanoparticles in the thin film was that the nanoparticles can act as reservoirs for functional materials. The films were loaded with anticancer drug doxorubicin and show pH dependent release of the drug. The various interactions involved in the LbL assembly of BSA nanoparticles and polymers were investigated towards understanding the growth mechanism of the assembly in chapter 4. The understanding of the interactions involved in the assembly formation is important in order to modify the conditions of the assembly for enhancing the growth. It is inferred from the study reported in this chapter that not only the interaction of nanoparticles with polymers but also the inter-particle interactions are important factors in determining the growth of LbL assembly of nanoparticles/polymers. The growth of the assembly is enhanced on minimizing the inter-particle repulsions, which was achieved in case of BSA nanoparticles by modifying the pH of the assembly. We also utilized the LbL self-assembly approach for the delivery of lipophilic drugs. The lipophilic drugs are difficult to administer in the body due to their poor water solubility and hence show poor pharmacokinetic profile. The methods for incorporating hydrophobic drugs in LbL assembled thin films and microcapsules are described in chapters 5 and 6. In chapter 5, hydrophobic molecules binding property of albumin has been exploited for solubilisation of a water-insoluble molecule, pyrene (model drug) and hydrophobic drug, curcumin, by preparation of non-covalent conjugates with BSA. The interaction with BSA provided negative zeta potential to the previously uncharged molecules and hence they can be incorporated in the LbL assembled thin films and microcapsules using electrostatic as well as hydrogen bonding interaction with biopolymer, chitosan. The fabrication of protein encapsulated stable microcapsules with hydrophobic molecules incorporated in the shell of the microcapsules has also been demonstrated. The microcapsules were further capable of loading hydrophilic molecules like Rhodamine B. Thus, this approach can be employed for fabrication of multi-agent carrier for hydrophobic and hydrophilic drugs as well as therapeutic macromolecules. In chapter 6, we have incorporated nanocrystalline cellulose (NCC) LbL assembled thin films and microcapsules. The assembly formed was porous in nature due to the nano-fibrous morphology of NCC. The nanoassemblies can act as potential drug delivery carrier, which has been demonstrated by loading anticancer drug doxorubicin, and a lipophilic drug, curcumin. Doxorubicin hydrochloride, the salt form of the drug, doxorubicin, has good water solubility and hence can be postloaded in the assembly by diffusion from its aqueous solution. In the case of curcumin, which has limited solubility in water, a stable aqueous dispersion of the drug was prepared via noncovalent interaction with NCC prior to incorporation in the LbL assembly. The interaction of various other lipophilic drugs with NCC was analysed computationally.

Afin d'obtenir une meilleure compréhension de l'étape clé du système photosynthétique (la formation d’un état à charges séparées), une nouvelle famille de systèmes donneur-accepteur supramoléculaires a été préparée.Nous avons notamment acquis une meilleure compréhension de la nature des interactions π-π entre le C60 et les porphyrines (résultant d'un processus régi principalement par des forces de van der Waals) et de l'affinité des éthers couronnes vis-à-vis des fullerènes (résultant d'une combinaison entre interactions π-π, n-π et CH-π). Les propriétés supramoléculaires des dimères de porphyrines ont été aussi explorées, prouvant leur communication électronique à travers leurs sous-unités. Finalement, la coopérativité chélate d'un de nos systèmes a été évaluée par la molarité efficace. / In order to gain a better understanding of the key step of the photosynthetic system (formation of a charged separated stated), a series of new supramolecular crown ether containing donnor-aceptor ensembles have been obtained.Notably we have gained further insight in the nature of π-π stacking between C60 and porphyrins (arising from a process mainly governed by van der Waals forces) and the affinity of crown ethers towards fullerenes(arising from an interplay of π-π, n-π and CH-π interactions). The properties of porphyrin arrays have been explored, evidencing the electronic communication through subunits. Finally, the chelate cooperativity of one our systems has also been assessed through the effective molarity.

abstract: A clean and sustainable alternative to fossil fuels is solar energy. For efficient use of solar energy to be realized, artificial systems that can effectively capture and convert sunlight into a usable form of energy have to be developed. In natural photosynthesis, antenna chlorophylls and carotenoids capture sunlight and transfer the resulting excitation energy to the photosynthetic reaction center (PRC). Small reorganization energy, λ and well-balanced electronic coupling between donors and acceptors in the PRC favor formation of a highly efficient charge-separated (CS) state. By covalently linking electron/energy donors to acceptors, organic molecular dyads and triads that mimic natural photosynthesis were synthesized and studied. Peripherally linked free base phthalocyanine (Pc)-fullerene (C60) and a zinc (Zn) phthalocyanine-C60 dyads were synthesized. Photoexcitation of the Pc moiety resulted in singlet-singlet energy transfer to the attached C60, followed by electron transfer. The lifetime of the CS state was 94 ps. Linking C60 axially to silicon (Si) Pc, a lifetime of the CS state of 4.5 ns was realized. The exceptionally long-lived CS state of the SiPc-C60 dyad qualifies it for applications in solar energy conversion devices. A secondary electron donor was linked to the dyad to obtain a carotenoid (Car)-SiPc-C60 triad and ferrocene (Fc)-SiPc-C60 triad. Excitation of the SiPc moiety resulted in fast electron transfer from the Car or Fc secondary electron donors to the C60. The lifetime of the CS state was 17 ps and 1.2 ps in Car-SiPc-C60 and Fc-SiPc-C60, respectively. In Chapter 3, an efficient synthetic route that yielded regioselective oxidative porphyrin dimerization is presented. Using Cu2+ as the oxidant, meso-β doubly-connected fused porphyrin dimers were obtained in very high yields. Removal of the copper from the macrocycle affords a free base porphyrin dimer. This allows for exchange of metals and provides a route to a wider range of metallporphyrin dimers. In Chapter 4, the development of an efficient and an expedient route to bacteriopurpurin synthesis is discussed. Meso-10,20- diformylation of porphyrin was achieved and one-pot porphyrin diacrylate synthesis and cyclization to afford bacteriopurpurin was realized. The bacteriopurpurin had a reduction potential of - 0.85 V vs SCE and λmax, 845 nm. / Dissertation/Thesis / Ph.D. Chemistry 2014

O objetivo desta dissertação é estudar os efeitos estruturais e eletrônicos em fulerenos menores e C60 causados pela dopagem substitucional com boro e nitrogênio para aplicações em eletrônica molecular. Estudamos as propriedades eletrônicas e estruturais de possíveis retificadores moleculares formados por pares de fulerenos menores dopados com boro e nitrogênio. A molécula C@C59N foi estudada e suas propriedades estruturais e eletrônicas comparadas com as do endofulereno N@C60. No estudo da dopagem dos fulerenos utilizamos o método semiempírico Parametric Method 3 (PM3). Foram calculadas as geometrias de equilíbrio e os calores de formação, que serviram para investigar a estabilidade relativa dessas moléculas. Para cada dopante identificamos os sítios de substituição que mais favorecem à estabilidade termodinâmica das moléculas. Dentre todos os fulerenos menores estudados os isômeros do C5o atingiram a maior estabilidade quando comparados com o C60. Com os pares de moléculas mais estáveis obtidas no trabalho anterior, montamos os retificadores em uma estrutura do tipo D-ponte-A, onde D e A representam doador e aceitador de elétrons. Para as moléculas isoladas, calculamos as estruturas eletrônicas através da Teoria do Funcional da Densidade (DFT) com o funcional BLYP e a base 6-31G*. No caso dos pares usamos o método DFT com o funcional BSLYP e a base 3-21G* para obter as geometrias de equilíbrio e as estruturas eletrônicas. Aplicando um campo elétrico sobre as moléculas, investigamos a facilidade de transferência de cargas entre fulerenos. Concluímos que fulerenos menores possuem um grande potencial para construção de um diodo molecular. As propriedades da molécula hipotética C@C59N foram comparadas com as bem Conhecidas C60, C59N e N@C60. A energia de ligação por átomo da molécula é comparável às energias de ligação dos outros fulerenos, em particular do seu isômero N@C60. Devido à tendência dos azafulerenos em formar dímeros, verificamos a estabilidade da molécula N@C60 quando comparada com o dímero N@C60 )2. . Tanto as geometrias quanto as estruturas eletrônicas foram calculados via DFT, BSLYP/6-31G*. Concluímos deste estudo que a molécula C@Ge¡/ é estável energeticamente, como também a interessante possibilidade do uso do dímero (C@C59N)2 como um bit quântico. / The present dissertation is devoted to the study of the effects on small fullerenes and 060 caused by the substitutional doping of boron and nitrogen for applications in molecular electronics. Electronic and structural properties of molecular rectifiers formed by small fullerenes doped with boron and nitrogen have been studied. The molecule C@C59 N has been investigated and its structural and electronic properties compared with those of the endofullerene N@C60 To study the doping of the fullerenes we used the semiempirical method Para­ metric Method 3 (PM3). Ground state conformations and heats of formation were obtained and used to investigate the relative molecular stability. We indentified the most favorable molecular substitution sites for the thermodynamic stability of each dopant. Among all small fullerenes investigated, the isomers of C50reached the largest stability when compared with 060 Molecular rectifiers with a structure of the type D-bridge-A, where D and A indicate electron donor and acceptor, respectively, were built with the most stable pairs found in the previous part of. The Density Functional Theory (DFT) with the functional BLYP and the base 6-31G* was used to calculate the electronic struc­ tures of the isolated molecules. Geometry optimizations and electronic structures of the pairs, were carried by DFT, B3LYP j3 21G*, method. The asymmetry of the charge transfer was assessed through the application of an externai electric field. We concluded that small fullerenes are promising candidates for the construction of molecular rectifiers. The properties of the hypothetical molecule C@C59 N were compared with those well known C60 , C59 N e N@C60 molecules. The binding energy of this molecule is comparable with that of the other fullerenes, in particular with that of its isomer N@C60 Due to the tendency of the azafullerene in forming dimers, the stability of the dimer (C@C59 N)2 was investigated. The molecular conformations and the electronic structures were obtained by the DFT, B3LYP/6-31G*, method. We con­ cluded that (C@C59 N) 2 molecule should be as stable as the azafullerene dimer. Our results point to the interesting possibility of using this system as a quantum bit.

Orientador: Douglas Soares Galvão / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-10T00:38:23Z (GMT). No. of bitstreams: 1 Troche_KarlaSouza_D.pdf: 4475542 bytes, checksum: 174644e87f1d2a1a584c4b840a379b95 (MD5) Previous issue date: 2007 / Resumo: Este trabalho apresenta o estudo teórico de nano-estruturas de carbono de interesse em nanociência. Ele envolve o estudo estrutural, eletrônico e mecânico de estruturas híbridas que são o resultado do encapsulamento de moléculas de carbono (em nosso caso: fulerenos e diamondóides) inseridas em nanotubos de carbono. Utilizando métodos clássicos de Dinâmica Molecular fizemos um estudo do ordenamento molecular dos fulerenos de simetria esférica como o C 60, fulerenos assimétricos C 70 e C78 e diamondóides. Para observar à dependência da ordenação molecular na simetria cilíndrica com o tamanho do nanotubo de carbono e simetria molecular da molécula inserida. Com simulações de dinâmica molecular investigamos as mudanças das propriedades mecânicas de nanotubos de carbono quando são preenchidos com moléculas de C60 e diamondoides. Previmos as mudanças no material e características promissoras das estruturas híbridas. Aplicamos o método Tight-binding baseado na teoria do funcional da densidade para determinar as propriedades eletrônicas dos novos híbridos Fulerenos@nanotubo de carbono. Previmos mudanças nas propriedades e potenciais aplicações em nanotecnologia / Abstract: This work presents a theoretical study of carbon nanostructures with great interest in nanoscience world. It is about the structural, electronic and mechanical study of hybrid structures that result from encapsulation of carbon molecules (fullerenes and diamondoids) introduced inside carbon nanotubes. Using classical methods of molecular dynamics we performed a study of molecular ordering of fullerenes with spherical geometry, C60, asymmetric fullerenes C70 and C78 and diamondoids. We observed dependence of the molecular ordering on cylindrical geometry with the carbon nanotube size and the geometry of the inserted molecule. Through molecular dynamics simulations, we investigated the change on mechanical properties of carbon nanotubes when filled with C60 molecules and diamondoids. We also predict changes on the material and promising characteristics of hybrid structures. We applied the Tight-binding method based on the theory of density functional to determine the electronic properties of the new hybrid fullerenes@carbon nanotube. We predict interesting properties and powerful applications on nanotechnology / Doutorado / Física da Matéria Condensada / Doutor em Ciências

La recherche présentée dans cette thèse traite de la synthèse, propriétés et applications optoélectroniques de matériaux nanohybrides basés sur le greffage d’une porphyrine donneur d’électron et d’un dérivé du fullerène sur des nanoparticules de ZnO.Ces molécules sont accrochées à la surface de l’oxyde métallique grâce à une fonction acide carboxylique. L'effet du rapport molaire porphyrine / fullerène, de la polarité du solvant et la forme des nanoparticules sur les propriétés optiques des nanohybrides ont été étudiés. Les interactions porphyrine / fullerène à l’échelle moléculaire apparaissent pour un rapport de 1:2 à l'état co-greffé sur des nanobâtonnets de ZnO. Cela est indiqué par le fort décalage bathochrome du pic de Soret des porphyrines et de l’extinction de sonémission de fluorescence. Toutefois, à cette valeur du rapport, le complexe de transfert de charge n'est pas détectable. La formation de ce complexe requiert à la fois les molécules donneur et accepteur d’électron d'être d’être maintenues à proximité, ce qui est réalisableen augmentant le rapport stoechiométrique à 1:3 et au-delà. Dans l’acétonitrile, une bande d’absorption de transfert de charge de faible intensité apparaît vers 700-800 nm, ainsi qu’une bande d'émission à 800 nm, caractérisant la complexation supramoléculaire à la surface de l’oxyde métallique. Lorsqu'ils sont utilisés pour la fabrication de la couche active dans une cellule solaire à hétérojonction hybride, les nanobâtonnets de ZnO fonctionnalisés montrent une efficacité de conversion lumineuse pour des valeurs faibles du rapport porphyrine / fullerène, mais l’augmentation du taux de fullerène tend à diminuer le rendement de conversion photovoltaïque. Cet effet a été relié à l’apparition de défauts morphologiques dans les films minces induite par l’agrégation des nanotubeslié au taux et rapport de greffage des molécules organiques. / The research presented in this dissertation deals with the synthesis, properties andoptoelectronic applications of the nanohybrids based on dye and fullerene functionalizedZnO nanoparticles. These molecules being acid functionalized, were co-grafted on thesurface of ZnO nanoparticles. The effect of changing ratio of donor to acceptor, polarityof the solvent and shapes of the nanoparticles on porphyrin/fullerene interaction werestudied. The molecules were found appreciably interacting at a ratio of 1:2 under the cograftedstate on ZnO nanorods. This was indicated by the strong bathochromic shift of thesoret peak of porphyrin and quenching of its fluorescence however, at this ratio chargetransfer complex is not detectable. The complex formation requires both the donors andacceptors to be enough close to each other to undergo Van der Waal’s type interactionwhich is achievable by raising the stoichiometric ratio to 1:3 and beyond. Weak CTabsorption (700-800 nm) and emission bands (800 nm) characterizing supramolecularcomplexation, were noticed only in polar solvent acetonitrile. When applied as acomponent of the active layer in bulk heterojunction hybrid solar cells, the dyefunctionalized ZnO nanoprods raised the efficiency of the solar cells at lowconcentrations but addition of fullerene had an inverse effect. This was investigated to bedue to the morphological defects induced by the clusterization of nanorods.

In situ Raman spectroscopy was used to explore etching of carbon nanotubes as well as their growth from C60. The thesis is in three parts: (1) C60 seed particles were partially oxidized in air and were used to grow carbon nanotubes and other nanocarbon structures. Seed oxidization was characterized by monitoring the evolution of the Raman Ag(2) peak and the D band, and oxidation temperature was found to be critical to nanotube growth. (2) To further explore oxidation, carbon nanotubes were thermally oxidized in air at different temperatures, while the evolution of different Raman bands was tracked. Etching dynamics and band intensity evolution were tracked in situ. Notably, metallic species were found to etch much more rapidly than semiconducting species of similar diameter. (3) To confirm and expand on this, a novel, simultaneous two-laser Raman spectroscopy setup was used to track the thermal oxidation of carbon nanotubes in O2 and CO2 gases at different temperatures. Metallic species were resonant with one laser line, while semiconducting species were resonant with the other, so changes to sample metallicity could be tracked unambiguously in two separate spectra. Again, metals were found to etch more rapidly. In situ Raman spectroscopy can track the evolution of nanotubes in real time and provide insight into processing. In general, detailed process monitoring like this can help in the development of selective synthesis and processing.