Compostos lamelares do tipo da hidrotalcita ou hidróxidos duplos lamelares (HDL), são materiais que possuem notáveis propriedades estruturais, químicas, eletrônicas, iônicas, ópticas e magnéticas. Em função dessas propriedades, os HDL apresentam uma diversidade de aplicações tais como adsorventes e catalisadores. Este trabalho tem por objetivo utilizar polímeros e macromoléculas na preparação e caracterização de HDL, visando melhorar as propriedades texturais dos HDL de MgAl-CO3 preparados em meio contendo polímeros orgânicos ou a intercalação direta de dendrímeros tipo PAMAM de gerações -0,5 e +0,5 em HDL do sistema Zn/Al. Os HDL de MgAl-CO3 foram preparados pela adaptação do método de coprecipitação a pH decrescente, com a presença de polímeros solubilizados no meio, como molde. Os materiais foram caracterizados por difração de Raios X, análise termogravimétrica, espectroscopia no infravermelho e medidas de área superficial por BET. Baseando-se nos resultados obtidos, pode-se concluir que propriedades texturais dos HDL preparados são modificadas, quando na presença de alguns polímeros. Na maioria dos casos, os valores calculados de área superficial específica foram mais elevados, em comparação com aquele obtido para o HDL preparado em meio reacional sem polímero. Isto pode ser explicado pela diminuição do tamanho de partículas e aumento no diâmetro médio de poros dos materiais preparados, provocada pela presença de polímeros no meio reacional. Os HDL intercalados com dendrímeros PAMAM G-0,5 e PAMAM G+0,5 foram preparados por duas rotas diferentes: coprecipitação a pH constante e troca iônica em fase dupla. Os materiais obtidos foram caracterizados por meio de difração de Raios X, análise de termogravimétrica associada à espectrometria de massas e espectroscopia no infravermelho. Utilizando os dois procedimentos de preparação, a intercalação de PAMAM G-0,5 deu origem a HDL com os mesmos espaçamentos basais, concordando com a intercalação dos ânions do dendrímero em um arranjo perpendicular à lamela do HDL, enquanto que para a intercalação do PAMAM G+0,5, espaçamentos basais muito menores do que o tamanho da molécula foram obtidos. A diferença entre a distância interlamelar observada e a esperada pode ser explicada por um arranjo peculiar das moléculas desse dendrímero em uma forma elipsoidal, devido às interações intramoleculares. Espectros no infravermelho confirmam a presença dos dendrímeros nos materiais Zn2Al-PAMAM G-0,5 e Zn2Al-PAMAM G+0,5. Finalmente, a presença destes dendrímeros foi confirmada por análise térmica associada com espectrometria de massas. Os estudos de Raios X com variação de temperatura in situ e as análises termogravimétricas revelaram que o material obtido pela intercalação do PAMAM G+0,5 é termicamente menos estável do que aquele intercalado com PAMAM G-0,5, concordando com a diferença de estabilidade entre os dendrímeros livres. / Hydrotalcite-like lamellar compounds or layered double hydroxides (LDH) are materials that present notable structural, chemical, electronic, ionic, optical and magnetic properties. Depending on these properties, the LDH present a great variety of applications such as adsorbents and catalysts. The aim of this work is to prepare and to characterize MgAl-CO3-LDH prepared in aqueous media containing organic polymer to improve textural properties, and to prepare HDL by intercalation of dendrimer (PAMAM) of generations -0.5 and +0.5 in ZnAl-HDL. MgAl-CO3-HDL samples were prepared by an adaptation of the coprecipitation method at decreasing pH, with the presence of polymers in the aqueous media as template. The materials were characterized by powder X-ray diffraction, termogravimetric analysis, infrared spectroscopy and BET isotherms. Based on the obtained results, it can be concluded that the textural properties of the prepared LDH were modified. The calculated values of specific surface area were higher in most of the cases compared with those obtained by the LDH prepared without polymer due to a decrease of the particle size and an increase in the average pore diameter of the prepared materials due to the presence of polymers. HDL with intercalated (PAMAM) dendrimers G-0.5 and G+0.5 were prepared by two different methods: coprecipitation at constant pH, and ionic exchange in double phase. The obtained materials were characterized by powder X-ray diffraction, thermal gravimetric analysis associated with mass spectrometry, and infrared spectroscopy. X-ray powder diffraction patterns exhibit the characteristic profiles of the lamellar materials with basal spacing depending on the nature of the dendrimer. For both preparation methods, the intercalation of PAMAM G-0.5 gives rise to LDH with basal spacing in agreement with the dendrimer molecules perpendicular to the layer of the host structure, while for PAMAM G+0.5 a basal spacing smaller than the molecule size was obtained. The difference between the obtained and the expected value is explained by an accommodation of the dendrimer molecule in an ellipsoidal shape, due to the intra-molecular interactions. Infrared spectra confirm the presence of dendrimers in the Zn2Al-PAMAM G-0.5 and Zn2Al-PAMAM G+0.5 materials. Finally, thermal analyses associated with mass spectrometry confirm the presence of these dendrimers. Powder X-ray diffraction with in situ temperature variation reveals that the material obtained by the PAMAM G+0.5 intercalation is thermally less stable than that prepared by PAMAM G-0.5 intercalation, in agreement with the difference in the thermal stability of the free dendrimers.

Sample preparation is the most error-prone step in chemical analysis. A great deal of efforts has been made to develop efficient techniques and protocols for sample preparation to accomplish important goals such as miniaturization and implementation of green analytical methodologies. Solid-phase microextraction (SPME) has successfully eliminated the use of hazardous organic solvents in extraction sampling, sample preparation, preconcentration and sample introduction to the analytical instrument in an effective manner. Ensuring thermal- and solvent-instability of traditional SPME extraction phases represented one of their main drawbacks. This was solved by the introduction of sol-gel SPME phases characterized by enhanced thermal-, solvent-, and stability over a wide pH range. Sol-gel SPME phases (sorbents) facilitated excellent preconcentration effects for a wide range of analytes. In this dissertation, hydrolytic and nonhydrolytic sol-gel routes were explored for the creation of zirconia-, titania-, and niobia-based novel hybrid organic-inorganic sorbents using sol-gel active polymeric ligands. These sorbents were prepared in the form of surface coatings for capillary microextraction and preconcentration of biologically important molecules such as catecholamine neurotransmitters and phosphopeptides. In comparison with other sorbents made only of inorganic transition metal oxides, the presented sol-gel sorbents facilitated efficient desorption of the extracted analytes by LC-MS compatible mobile phases. The sol-gel zirconia- and titania-based hybrid sorbents provided pH-stable (pH range: 0 - 14) and derivatization-free extraction media that effectively overcame the major drawbacks of traditional sorbents for the analysis of catecholamines (silica-based sorbents suffer from narrow operational pH window while polymer-based sorbents require additional sample derivatization steps). The modification of the terminal hydroxy groups in PPO with ZrCl4 or TiCl4 provided an enhanced sol-gel reactivity of the polymer modified-terminals. Such a modification procedure allowed for an efficient incorporation of the polymeric ligand into the evolving sol-gel network. The effectiveness of the PPO modification was also evaluated by a systematic thermogravimetric investigation exploring the loading of the ligand in sol-gel hybrid sorbents, which revealed an enhanced ligand-loading achieved via the nonhydrolytic sol-gel route used with modified-PPO. Sol-gel hybrid sorbents prepared by the nonhydrolytic sol-gel (NHSG) pathway provided excellent microextraction performance for catecholamines: low detection limits (5.6 – 9.6 pM), enhanced run-to-run reproducibility (RSD 0.6 – 5.1 %), excellent desorption efficiency (95.0 – 99.5 %) and high enrichment factors (EF) for epinephrine (EF ~ 1480) and for dopamine (EF ~ 2650) extracted from aqueous and synthetic urine samples at pH 10.5. Run-to-run and capillary-to-capillary reproducibility remained below 5 % when the peak area or the sorbent-mass was used as the reproducibility criterion. Niobia-based sol-gel sorbents prepared with and without organic ligand (polyethylenimine) were utilized as microextraction media for the enrichment of phosphorylated and nonphosphorylated tetrapeptide VYKA. Sol-gel niobia-based sorbents with covalently anchored polyethylenimine showed excellent selectivity toward the phosphopeptide compared to analogous titania-based sorbents. Specific extraction (SE) values were higher by 97.0 % when obtained by niobia-based sorbents. Excellent run-to-run peak area reproducibility (RSD < 5.1 %) and high EF of ~ 4000 were achieved. The sol-gel niobia-based coating facilitated excellent desorption efficiency (97.5 %), which suggests that the surface of the niobia sorbent possesses moderate-strength Lewis acid sites that avoided the need for special elution solvents that are conventionally used for the desorption of phosphorylated molecules from titania-based sorbents. The sol-gel pathway for the creation of microextraction phases is versatile and capable to provide unique control on the characteristics of the sorbents that are critically important for many sample preparation applications.

Chapter 1. A Brief Overview of Low Molecular Mass Gels and their Applications This chapter deals with molecular gels derived from the self-assembly of small organic molecules (typical molecular weight < 2000 daltons), endowed with appropriate functions to promote anisotropic growth of supramolecular aggregates, by means of various non-covalent interactions like van der Waals, π-πstacking, H-bonding etc., leading to a self-assembled fibrillar network (SAFIN). Several representative examples from the literature (Chart 1) are discussed to demonstrate the structural diversity of the gelator molecules which form self-assembled organogels or hydrogels. Chart 1 Besides emphasizing on the diverse molecular structures of the gelators, applications of gel phase materials as functional nanostructures are also discussed (Scheme 1). Some of the aspects that have been elaborated in this context include the use of gels as reaction media, as sensors, in light harvesting, as biomaterials and in optoelectronic applications. Scheme 1 Chapter 2. Supramolecular Chirality in Organogels: Spectroscopic, Morphological and Rheological Investigations of Gels/Xerogels derived from Alkyl Pyrenyl Urethanes This chapter addresses the formation of chiral supramolecular structures in the organogels derived from chiral 1R (or 2R), and its mixture with its enantiomer (1S) and a series of achiral analogues (3-9) by extensive circular dichroism (CD) spectroscopic measurements (Chart 2). Morphological studies by atomic force microscopy (AFM) and scanning electron microscopy (SEM) were complemented by the measurements of their bulk properties by thermal stability and rheological studies. Specific molecular recognition events (1/3 vs 2/3) and solvent effects (isooctane vs dodecane) were found to be critical in the formation of the chiral aggregates. Computational studies were carried out to understand the interactions responsible for the formation of chiral superstructures. Chapter 3. Self-assembled Composite Organogels based on a Thermo-reversible Photoactive n-Acene Fibrillar Scaffold and Organic Ligand stabilized ZnO Nanoparticles Organic/inorganic composite organogels were obtained in n-BuOH by the self-assembly of 2,3-di-n-decyloxyanthracene (DDOA, Chart 3) in this solvent in the presence of ZnO nanoparticles (NPs) capped with different organic ligands (Chart 4). When ligands (oleic acid or 2,3-substituted anthracenic acid/oleic acid mixed shell) having structural similarity with the gelator molecule were used to cap the NPs, a homogeneous dispersion of the NPs in the gel matrix was obtained, as confirmed by microscopy (TEM and confocal fluorescence microscopy) experiments. The efficient integration of these NPs into the gel fibers resulted in a significant quenching (20-25%) of DDOA emission, even with extremely small loading of these NPs (~ 10-4mol% compared to DDOA) into the gel fibers. The mechanical properties (rheology were unaffected relative to the pristine DDOA organogel. However, the presence of the NPs lowered the critical gelation concentration and accelerated the gelation kinetics. Attempts to disperse these NPs (the ones without fluoro capping) on the aerogel fibers of DDOA by dissolving both DDOA and the NPs in supercritical (sc) CO2 were not successful (Fig. 1), since the NPs could not be dissolved in scCO2. Figure 1. (a) TEM images of DDOA aerogels obtained from scCO2, containing A23-NPs, scale bar 200 nm; (b) SEM image of DDOA aerogel obtained in the presence of OL-NPs, scale bar 10 µm. Chapter 4. Donor-Acdeptor Interaction Promoted Gelation Of Organic Fluids by Anthracene Carboxamides/2,4,7-Trinitrofluorenone Tris Carboxamides of anthracene were found to form charge-transfer driven organogels in a range of aliphatic alcohols in the presence of an equivalent of (electron-deficient) 2,4,7-trinitrofluorenone (TNF) (Chart 5). Intense color developed in the gel state during the sol to gel phase transition process (Fig 2) Besides, none of these carboxamides were able to form gel in the absence of TNF, suggesting the importance of charge-transfer interaction in the gel formation. Importantly, most of these gels formed only through rapid cooling of the hot solution, otherwise, leading to the precipitation of the CT complex from the solvent. This result indicated that the kinetics is very important for the formation of these gels. Optimum stoichiometry of the donor and acceptor was found to be 1:1. At this molar ratio of the donor and the acceptor, the gels not only showed the highest thermal stability (thermal gel melting experiments), they also displayed the highest values of the mechanical strength and the yield stress (rheology experiments). All the gels showed extensive quenching of the emission of the monomeric anthracenic donor. For the gels derived from the 2-substituted donor, a low energy emission at high wavelength indicated the formation of an emissive CT exciplex. X-ray powder diffraction studies of these xerogels revealed the presence of layered, fibrillar structures in the xerogel phase. (For structural formula pl see the abstract file)

>Magister Scientiae - MSc / Organic-inorganic lead-based perovskite has exhibited great performance in the past few years. However, the lead (Pb) embedded in those compounds is a significant drawback to further progress, due to its environmental toxicity. As an alternative, tin (Sn) based-perovskites have demonstrated promising results in terms of electrical and optical properties for photovoltaic devices, but the oxidation of tin ion- from stannous ion (Sn2+) to stannic ion (Sn4+) presents a problem in terms of performance and stability when exposed to ambient conditions. A more feasible approach may be in a Pb-Sn binary metal perovskite in pursuit of efficient, stable perovskite solar cells (PSCs) with reduced Pb-content, as compared to pure Pb- or Sn-based PSCs. Here, we report on the deposition of a Pb-Sn binary perovskite by sequential chemical vapor deposition.

Orientador: Celso Valentim Santilli / Banca: Leila Aparecida Chiavacci Favorin / Banca: Eduardo Ferreira Molina / Resumo: Neste trabalho a metodologia sol-gel foi utilizada para a preparação de materiais híbridos orgânico-inorgânicos (HOI) à base de óxido de poli-etileno (PEO), ligado de forma covalente com o agente acoplador 3(isocianatopropil) - trietoxisilano (IsoTREOS) conjugados com um material zeolítico do tipo MFI, visando aplicações como catalisador para a reação de acetilação do glicerol e assim agregar valor a esse coproduto gerado na produção do biodiesel. O objetivo desta dissertação é demonstrar que o sinergismo entre híbridos do tipo siloxano-poliéter e as zeólitas pode ser explorado na produção de hidrogéis com atividade catalítica. As análises por Microscopia Eletrônica de Varredura (MEV) evidenciaram a homogeneidade na dispersão do material zeolítico na matriz híbrida Os difratogramas de raios-X apresentaram os picos característicos da estrutura cristalina da zeolita ZSM-5 após a conjugação com a matriz U-PEO. Os resultados de Calorimetria Diferencial de Varredura (DSC) revelaram que não ocorre uma mudança significativa na temperatura de transição vítrea (Tg), após a conjugação da matriz híbrida com a zeólita e revelaram uma diminuição do pico endotérmico associado à fusão dos domínios cristalinos do PEO1900, indicando uma possível interação matriz-zeólita. As análises por Espectroscopia no Infravermelho com Transformada de Fourier (FTIR) confirmaram a interação entre a matriz híbrida e a zeólita pelo deslocamento das bandas associadas ao oxigênio tipo éter não coordenado. Medid... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work the sol-gel methodology was used for the preparation of organic-inorganic hybrid (HOI) materials based on polyethylene oxide (PEO) - covalently bonded with the coupling agent 3 (isocyanatopropyl) triethoxysilane (IsoTREOS) conjugate with a zeolitic material of the MFI type, aiming at applications as catalyst for glycerol acetylation reaction and thus add value to this byproduct generated in biodiesel production. The objective of this dissertation is to demonstrate that the synergism between siloxane-polyether hybrids and zeolites can be explored in the production of catalytic activity hydrogels. Scanning Electron Microscopy (SEM) analyzes showed homogeneity in the dispersion of zeolite material in the hybrid matrix. XDR patterns showed the characteristic peaks of the ZSM-5 zeolite crystal structure after conjugation with the U-PEO matrix. Differential Scanning Calorimetry (DSC) results revealed that no significant change in glass transition temperature (Tg) occurs after conjugation of hybrid matrix with zeolite and revealed a decrease in endothermic peak associated with fusion of crystalline domains of PEO1900., indicating a possible matrix-zeolite interaction. Fourier Transform Infrared Spectroscopy (FTIR) analyzes confirmed the interaction between the hybrid matrix and zeolite by shifting the bands associated with uncoordinated ether oxygen. Small-angle X-ray Scattering (SAXS) measurements showed that the starting reagents in the solketal production reaction w... (Complete abstract click electronic access below) / Mestre

Nano-structured materials are widely applied for various applications like photovoltaics, electrochromics and sensors. A challenging task in all these fields is the functionalization of these materials with a molecule of interest for the desired application. This work demonstrate the post grafting of the most important and commonly used nano-structured material, mesoporous TiO2, with different bifunctional molecular linkers. These compounds basically have two functional groups, the phosphonic acid group which coordinates to the TiO2 surface and a positive and negative head group which controls the surface charge and the potential interaction of the surface with species in solution. These two groups are systematically separated by alkyl group of different chain length which controls the hydrophobicity of the surface. It is shown that the new surface modification technique simplifies the molecular requirements for functional surface modifiers considerably. Using a limited set of organic anchors with adjustable head group charge and hydrophobicity, broad range of molecules can be adsorbed onto TiO2. Different applications based on such modified surfaces were explored and demonstrated. The modified surfaces can be used to incorporate different charged guest molecules, electrochromophores and dyes which enable to probe their electrochemistry and photovoltaic properties on the surface. Supra-molecular self assembly inside the modified pores is possible which can be monitored by different methods. The study includes the prepartaion of the modified surfaces and their characterization using different electrochemical methods, FTIR spectroscopy, Quartz Crystal Microbalance, Contact angle and Scanning Electron Microscopy measurements.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20405号 / 工博第4342号 / 新制||工||1673(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 大北 英生, 教授 赤木 和夫, 教授 木村 俊作 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Computational modeling of organic interface formation on semiconductors poses a challenge to a density functional theory-based description due to structural and chemical complexity. A hierarchical approach is presented, where parts of the interface are successively removed in order to increase computational efficiency while maintaining the necessary accuracy. First, a benchmark is performed to probe the validity of this approach for three model reactions and five dispersion corrected density functionals. Reaction energies are generally well reproduced by generalized gradient approximation-type functionals but accurate reaction barriers require the use of hybrid functionals. Best performance is found for the model system that does not explicitly consider the substrate but includes its templating effects. Finally, this efficient model is used to provide coverage dependent reaction energies and suggest synthetic principles for the prevention of unwanted growth termination reactions for organic layers on semiconductor surfaces.

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