Tesis sobre el tema "Ionic aggregation"

Nanoparticles present a myriad of physical, optical, electrical, and chemical properties that provide valuable functionality to thin-film technologies. In order to successfully exploit these aspects of nanoparticles, appropriate dispersion and stability measures must be implemented. In this dissertation, different types of nanoparticles are coated with polymer and metallic layers to enable their effectiveness in both anti-reflection coatings (ARCs) and organic photovoltaics (OPVs). Ionic self-assembled multilayers (ISAMs) fabrication of poly(allylamine hydrochloride) (PAH) and silica nanoparticles (SiO2 NPs) results in highly-transparent, porous ARCs. However, the ionic bonding and low contact area between the film constituents lack sufficient mechanical and chemical stability necessary for commercial application. Chemical stability was established in the film by the encapsulation of SiO2 NPs by a photo-crosslinkable polyelectrolyte, diazo-resin (DAR) to make modified silica nanoparticles (MSNPs). UV-irradiation induced decomposition of the diazonium group and the development of covalent bonds with polyanions. Crosslinked MSNP/poly(styrene sulfonate) (PSS) ISAMs exhibited excellent anti-reflectivity (transmittance >98%, reflectance <0.2% in the visible range) and chemical stability against dissolution in a ternary solvent. Mechanical stability was also achieved by the incorporation of two additional PAH and poly(acrylic acid) (PAA) layers to create PAH/PAA/PAH/SiO2 NP interlayer ISAM ARCs. Thermal crosslinking of PAH and PAA facilitates the formation of covalent amide bonds between the two polyelectrolytes, as confirmed by FTIR. Since PAH and PAA are both weak polyelectrolytes, adjustment of the solution pH causes significant variations in the polymer chain charge densities. At low PAA pH, the decreased chain charge densities caused large SiO2 NP encapsulation thicknesses in the film with great mechanical stability, but poor anti-reflection (≤97% transmittance). At high PAA pH, the high chain charge densities induced thin encapsulation layers, insufficient mechanical stability, but excellent anti-reflection. At trade-off between the two extremes was founded at a PAA pH of 5.2 with excellent anti-reflection (less than 99% transmittance) and sufficient mechanical stability. The normal force required for scratch initiation was increased by a factor of seven for films made from a pH of 5.2 compared to those made from a pH of 6.0. Organic photovoltaics (OPVs) are an attractive area of solar cell research due to their inexpensive nature, ease of large-scale fabrication, flexibility, and low-weight. The introduction of the bulk heterojunction greatly improved charge transport and OPV performance by the blending of the active layer electron donor and acceptor materials, poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), into an interpenetrating network with high interfacial area between adjacent nanodomains. However, constrained active layer thicknesses restrict the total optical absorption and device performance. The localized surface plasmon resonance (LSPR) of plasmonic nanoparticles, such as anisotropic silver nanoplates (AgNPs), provides large local field enhancements and in coupling with the active layer, substantial optical absorption improvements can be realized. AgNPs were first integrated into the hole-transport layer (PEDOT:PSS) by ISAM deposition. Here, PEDOT:PSS was used as a negatively-charged ISAM layer. Encapsulation of the AgNPs by PAH (ENPs) provided a positive surface charge and allowed for the creation of ENP/PEDOT:PSS ISAMs. Stability against acidic etching by PEDOT:PSS was imparted to the AgNPs by coating the edges with gold (AuAgNPs). The AuAgNP ISAMs substantially improved the optical absorption, but were ineffective at increasing the device performance. The dispersion effects of functionalized polymer coatings on AgNPs were also deeply investigated. Functionalized AgNPs were dispersed in methanol and spin-coated onto the active layer. When the AgNPs possessed hydrophilic properties, such as unfunctionalized or functionalized by poly(ethylene glycol) methyl ether thiol (PEG-SH), they formed large aggregates due to unfavorable interactions with the hydrophobic P3HT:PCBM layer. However, the hydrophobic functionalization of AgNPs with thiol-terminated polystyrene (PS-SH) (PS-AgNPs) resulted in excellent dispersion, optical absorption enhancements, and device performance improvements. At a PS-AgNP concentration of 0.57 nM, the device efficiency was increased by 32% over the reference devices.
Ph. D.
Investigations are presented on the quality of distribution or dispersion of functional inorganic (composed of silicon dioxide or silver) particles that have dimensions of less than 100 nanometers, called nanoparticles. The nanoparticle surfaces were covered with polymer layers, where polymers are organic materials with repeating molecular structures. The study of these nanoparticle distribution effects were first examined in anti-reflection coatings (ARCs). ARCs induce transparency of windows or glasses through a reduction in the reflection of light. Here, the ARCs were fabricated as self-assembled thin-films (films with thicknesses ranging from 1 to 2000 nanometers). The self-assembly process here was carried out by immersing a charged substrate (microscope slide) into a solution with an oppositely-charged material. The attraction of the material to the substrate leads to thin-film growth. The process can continue by sequentially immersing the thin-film into oppositely-charged solutions for a desired number of thin-film layers. This technique is called ionic self-assembled multilayers (ISAMs). ARCs created by ISAM with charged polymers (polyelectrolytes) and silicon dioxide nanoparticles (SiO2 NPs) can lead to highly-transparent films, but unfortunately, they lack the stability and scratch-resistance necessary for commercial applications. In this dissertation, we address the lack of stability in the ISAM ARCs by adding additional polyelectrolyte layers that can develop strong, covalent bonds, while also examining nanoparticle dispersive properties. First, SiO2 NP surfaces were coated in solution with a polyelectrolyte called diazo-resin, which can form covalent bonds by UV-light exposure of the film. After tuning the concentration for the added diazo-resin, the coated SiO2 NPs were used to make ARCs ISAM films. The ARCs had excellent nanoparticle dispersion, high levels of transparency, and chemical stability. Chemically stability entails that the integrity of the film was unaffected by exposure to polar organic solvents or strong polyelectrolytes. In a second method, two additional v polyelectrolyte layers were added into the original polyelectrolyte/SiO2 NP design. Here, heating of the film to 200 oC temperatures induced strong covalent bonding between the polyelectrolytes. Variation of the solution pH dramatically changed the polyelectrolyte thickness, the nanoparticle dispersion, the scratch-resistance, and the anti-reflection. An optimum trade-off was discovered at a pH of 5.2, where the anti-reflection was excellent (amount of transmitted light over 99%), along with a substantially improved scratch-resistance. A change of pH from 6.0 (highest tested pH) to 5.2 (optimal) caused a difference in the scratch-resistance by a factor of seven. In these findings, we introduce stability enhancing properties from films composed purely of polyelectrolytes into nanoparticle-containing ISAM films. We also show that a simple adjustment of solution parameters, such as the pH value, can cause substantial differences in the film properties. Nanoparticle dispersion properties were next investigated in organic photovoltaics (OPVs) OPVs use semiconducting polymers to convert sunlight into usable electricity. They have many advantages over traditional solar cells, including their simple processing, low-cost, flexibility, and lightweight. However, OPVs are limited by their total optical absorption or the amount of light that can potentially be converted to electricity. The addition of plasmonic nanoparticles into an OPV device is a suitable way to increase optical absorption without changing the other device properties. Plasmonic nanoparticles, which are composed of noble metals (such as silver or gold), act as “light antennas” that concentrate incoming light and radiate it around the particle. In this dissertation, we investigate the dispersion and stability effects of polymer or metallic layers on silver nanoplates (AgNPs). The stability of the AgNPs was found to be greatly enhanced by coating the nanoparticle edges with a thin gold layer (AuAgNPs). AuAgNPs could then be introduced into a conductive, acidic layer of the OPVs (PEDOT:PSS) to increase the overall light absorption, which otherwise would be impossible with uncoated AgNPs. Next, the AgNPs were distributed on top of the photoactive layer or the layer that is responsible for absorbing light. Coating the AgNPs with a polystyrene polymer layer (PS-AgNPs) allowed for excellent dispersion on this layer and contrastingly, dispersion of the uncoated AgNPs was poor. An increased amount PS-AgNPs added on top of the photoactive layer progressively increased the optical absorption of the OPV devices. However, trends were quite different for the power conversion efficiency or the ratio of electricity power to sunlight power in the OPV device. The greatest PCE enhancements (27 – 32%) were found at a relatively low coverage level (using a solution concentration of 0.29 to 0.57 nM) of the PS-AgNPs on the photoactive layer.

This thesis describes a study of the aggregational behaviour of egg yolk lecithin (EYL), a natural lecithin, and bile salt mixtures especially with respect to an increase of the ionic strength of the solvent. Mixtures of two amphiphiles with very different spontaneous curvature as EYL lecithin and bile salt form mixed micelles and vesicles in aqueous solution. Their properties have been well-studied under physiological conditions, i.e. 150 mM electrolyte concentration and pH 7- 8, while other conditions are still hardly explored. Upon increasing ionic strength the formed structures and the transitional pathways (micelles, coexistence of micelles and vesicles, and vesicles) change the generated structures completely from those observed under physiological conditions. We quantitatively determined these structures formed in a broad range of electrolyte concentrations with various scattering techniques, x-ray, light and neutron scattering and calorimetry. With calorimetry, phase diagrams in the EYL and bile salt concentration phase plane were determined at various ionic strength ranging from physiological salt concentration to up to 1000 mM. Additionally a new electrochemical approach using functionalised electrodes, i.e. sensitive and selective to bile salt, and thus to control the bile salt concentration in solution (concentrations below the critical micellar concentration (cmc)) was attempted, since bile salt removal or injection drives the micelle-to-vesicle or the vesicle-to-micelle transition, respectively, of the mixed aggregational system of EYL/bile salt. Although this control was not achieved within the framework of this thesis, promising results show directions for future experiments.

Matrix glass transition temperature depression through internal plasticization of a styrene-sodium methacrylate ionomer resulted in enhanced clustering at low plasticization levels (up to ca. 20 mole%). At higher plasticization levels, ion aggregation was strongly disrupted. Matrix polarity effects were studied by nitrating the styrene units of the same ionomer. A sample with a relaxed dielectric constant comparable to acrylate polymers showed no decrease in clustering. Similarly, plasticization with nitrobenzene resulted in typical nonpolar diluent behavior. Polarity was, therefore, not a significant parameter affecting ion aggregation. New styrene copolymers with substituents R = $-$(CH$ sb2$)$ sb{ rm n}$COOMe (n = 1, 5, 10) or R = $-$O(CH$ sb2$)$ sb{ rm n}$COOMe (n = 1, 4, 10) in the para- position were synthesized, to form a systematic investigation of ionic group spacing effects on the dynamic mechanical properties of ionomers. The results were rationalized in terms of bulkiness and rigidity of the units supporting the ionic groups, and polymer backbone immobilization efficiency. Ion solvation effects were also suggested for the ether derivatives.

Protein (mis)folding into highly ordered, fibrillar structures, amyloid fibrils, is a hallmark of several, mainly neurodegenerative, disorders. The mechanism of this supra-molecular self-assembly reaction, as well as its relationship to protein folding are not well understood. In particular, the molecular origin of the metastability of the soluble state of proteins with respect to the aggregated states has not been clearly established. In this dissertation, it is demonstrated, that highly accurate kinetic experiments, using a novel biosensing method, can yield fundamental insight into the dynamics of proteins in the region of the free energy landscape corresponding to protein aggregation. First, a section on Method development describes the extension and elaboration of the previously established kinetic assay relying on quartz crystal microbalance measurements for the study of amyloid fibril elongation (Chapter 3). This methodology is then applied in order to study in great detail the origin of the various contributions to the free energy barriers separating the soluble state of a protein from its aggregated state. In particular, the relative importance of residual structure, hydrophobicity (Chapter 4) and electrostatic interactions (Chapter 5) for the total free energy of activation are discussed. In the last part of this thesis (Chapter 6), it is demonstrated that this biosensing method can also be used to study the binding of small molecules to amyloid fibrils, a very useful feature in the framework of the quest for potential inhibitors of amyloid formation. In addition, it is shown that Thioflavin T, to-date the most frequently employed fluorescent label molecule for bulk solution kinetic studies, can in the presence of potential amyloid inhibitor candidates be highly unreliable as a means to quantify the effect of the inhibitor on amyloid formation kinetics. In summary, the work in this thesis contributes to both the fundamental and the applied aspects of the field of protein aggregation.

L’encapsulation dans des nanomatériaux de polymères de colorants ioniques à l’aide de contre-ions hydrophobes volumineux apparaît être une méthode très efficace pour générer des nanoparticules (NPs) fluorescentes ultra-brillantes pour la bioimagerie. Nous avons d’abord étendu cette approche par contre-ions aux colorants cyanine opérant dans la gamme du bleu au proche infra-rouge. A partir de NPs chargés en cyanines, une methode de code-barre multicolore pour le traçage cellulaire à long terme a été développé. Ensuite, le rôle des contre-ions hydrophobes volumineux dans l’auto-assemblage des colorants cationiques à l’intérieur des NPs de polymères a été étudié en testant une large collection d’anions. Nous avons montré qu’une forte hydrophobicité du contre-ion augmente l’encapsulation du colorant, régule son clustering et empêche l’agrégation de nanoparticules, alors qu’une grande taille empêche l’auto-inhibition de fluorescence. Enfin, nous avons introduit les contre-ions à base d’aluminates et de barbiturates, qui sur-performent les tetraphénylborates fluorés. Ce travail procure une base solide au concept d’émission et d’encapsulation augmentées par contre-ions pour la préparation de NPs chargés en colorants fluorescents
Encapsulation of ionic dyes with help of bulky hydrophobic counterions into polymer nanomaterials emerged as powerful method for generating ultrabright fluorescent nanoparticles (NPs) for bioimaging. Here, this counterion-based approach is extended to cyanine dyes, operating from blue to near-infrared range. Based on cyanine-loaded NPs, a multicolour cell barcoding method for long-term cell tracking is developed. Second, the role of bulky hydrophobic counterion in self-assembly of cationic dyes inside polymeric NPs is studied by testing a large library of anions. We show that high hydrophobicity of a counterion enhances dye encapsulation, prevents particle aggregation and tunes dye clustering, while large size prevents dyes from self-quenching. Third, counterions based on aluminates and barbiturates are shown to outperform fluorinated tetraphenylborates. This work provides a solid basis for counterion-enhanced encapsulation and emission concept in preparation of dye-loaded fluorescent NPs

Conselho Nacional de Desenvolvimento Científico e Tecnológico
This work reports the study of the molecular structure influence of ionic liquid (IL) derived from 1,8-bis(3-methylimidazolium-1-yl)octane in the aggregates formation in a solution ethanol in water (4,75%) and in ethanol (95%). Was varied the anions (Br-, NO3-, BF4-, SCN- e NTf2-) of IL and the aggregation behavior was investigated by various methods, such as differential scanning calorimetry (DSC), conductivity, surface tension, fluorescence and dynamic light scattering (DLS). In the ethanol in water solution (4,75%), the critical aggregation concentration values (cac) (114 to 205 mM), free energy of aggregation (ΔG°a) ( 15 to 18 kJ/mol) and ionization degree (α) (0,37 a 0,44) for the IL with Br-, NO3-, BF4-, SCN- significantly decreased with the increase of anion hydrophobicity. In ethanol, the cac values (165 to 500 mM) and ΔG°a ( 9 to 11 kJ/mol) also decreased with the increase of anion size and hydrophobicity. The free energy adsorption data (ΔG°ads) (-35 to -39 kJ/mol) demonstrated that the ILs, in general, have a good surfactant activity and this property improve with the decrease in the hydrophobic characteristics of anions. In general, in the solvents used in this study, the hydrodynamic radius (Rh) of aggregates ranged between 200 and 500 nm for all the ILs. The critical packing parameter was determined using data from the X-Ray (of IL 4) and surface tension, and showed that aggregates are micelar. The cac data was obtained by the techniques of conductivity, fluorescence and surface tension. Where, was observed that increasing the anion hydrophobicity of dicationic ILs structure favored the formation of aggregates, while less hydrophobic anions improved the surfactant properties of the IL structures.
Este trabalho relata o estudo da influência da estrutura molecular de líquidos iônicos (LI) dicatiônicos, derivados do cátion 1,8-bis(3-metilimidazolil-1-íneo)-octano, na formação de agregados em uma solução etanol em água (4,75%) e em etanol (95%). Variaram-se os ânions (Br-, NO3-, BF4-, SCN- e NTf2-) dos LI e o comportamento de agregação foi investigado através das técnicas de calorimetria exploratória diferencial (DSC), condutividade, tensão superficial, fluorescência e espalhamento de luz dinâmico (DLS). Na solução etanol em água (4,75%), os valores de concentração de agregação crítica (cac) (114 a 205 mM), energia livre de agregação (ΔG°a) ( 15 a 18 kJ/mol) e grau de ionização do contra-íon (α) (0,37 a 0,44) para os LI contendo os ânions Br-, NO3-, BF4-, SCN- diminuíram significativamente com o aumento da hidrofobicidade do ânion. Em etanol, os dados de cac (165 a 500 mM), ΔG°a ( 9 a 11 kJ/mol) para os LI com os ânions Br-, SCN- e NTf2- também diminuíram com o aumento do volume e hidrofobicidade dos ânions. Dados de energia livre de adsorção (ΔG°ads) (-35 a -39 kJ/mol) demonstraram que os LI dicatiônicos, de forma geral, possuem boa atividade tensoativa e esta propriedade aumenta com a diminuição das características hidrofóbicas dos ânions. Em geral, nos solventes utilizados no estudo, o raio hidrodinâmico (Rh) dos agregados variou entre 200 e 500 nm para todos os LI. Valores de parâmetro de empacotamento crítico (Pc) determinados a partir de dados de raios-X e tensão superficial indicaram que os agregados formados são micelares. Os dados de cac obtidos por condutividade, fluorescência e tensão superficial apresentaram-se de forma concordante. Observou-se que o aumento da hidrofobicidade da estrutura do ânion do LI dicatiônico favoreceu a formação dos agregados, enquanto que ânions menos hidrofóbicos melhoraram as propriedades tensoativas das estruturas dos LI.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This paper presents the study of influence of molecular structure of ionic liquid-type Gemini imidazolium ìn the formation of aggregates in aqueous solution. The aggregation behavior was investigated through differential scanning calorimetry, conductivity, surface tension, fluorescence, dynamic light scattering techniques and transmission electron microscopy. Among the obtained data, it is possible to highlight the critical aggregation concentration (cac) determination, that is, a concentration range where a variation in physical and chemical properties of the solution emerging from the formation of aggregates can be observed. Differential scanning calorimetry showed that the aggregation can be detected by means of thermal events, characteristics of pure LI. Through the conductivity, it was possible to determine thermodynamic parameters, as the aggregate free energy (ΔG°a), the binding degree of the counterion to the aggregate (α), and the process equilibrium constant (Ka). Surface tension measurements provided data regarding the activity of the surfactant LI studied, while fluorescence, dynamic light scattering and transmission electron microscopy were important to obtain information on the aggregates' size. Critical packing parameter was determined throughout data obtained from X-ray diffraction and surface tension. This parameter allowed the prediction of LI micellar form currently in study. It was observed that the values of cac determined by the methods employed are consistent with each other and it was found that the increase of the carbon chain used as a spacer group promoted the aggregates formation, as well as caused an improvement in the surfactant LI properties.
Este trabalho apresenta o estudo da influência da estrutura molecular dos líquidos iônicos (LI) dicatiônicos derivados do imidazolíneo na formação de agregados em solução aquosa. O comportamento de agregação foi investigado pelas técnicas de calorimetria exploratória diferencial, condutividade, tensão superficial, fluorescência, espalhamento de luz dinâmico e microscopia eletrônica de transmissão. Dentre os dados obtidos, destaca-se a determinação da concentração de agregação crítica, que trata-se de uma faixa de concentração onde pode ser observado a variação nas propriedades físicas e químicas da solução emergente da formação de agregados. Por calorimetria exploratória diferencial observou-se que a agregação pode ser detectada por meio de eventos térmicos característicos dos LI puros. Através da condutividade foi possível determinar parâmetros termodinâmicos como a energia livre de agregação (ΔG°a), grau de ligação do contraíon ao agregado (α) e constante de equilíbrio do processo (Ka). As medidas de tensão superficial forneceram dados a respeito da atividade tensoativa dos LI em estudo enquanto que a fluorescência, espalhamento de luz dinâmico e microscopia eletrônica de transmissão foram importantes para obter informações a sobre o tamanho dos agregado. O parâmetro de empacotamento crítico foi determinado, para isto utilizou-se dados provenientes da difratometria de raios-X e tensão superficial. Este parâmetro possibilitou a previsão da forma micelar para os LI em estudo. Foi observado que os valores de cac determinados pelos métodos empregados são concordantes entre si e verificou-se que o aumento da cadeia carbônica utilizada como grupo espaçador tanto favoreceu a formação dos agregados como também provocou uma melhora nas propriedades tensoativas dos LI.

L'objectif de cette thèse est d'analyser la structure microscopique des mélanges de liquide avec des solvants utilisés comme électrolytes dans les dispositifs électrochimiques afin de caractériser l'effet de l'agrégation des ions sur les propriétés de transport de ces systèmes. En utilisant la simulation de dynamique moléculaire, les systèmes suivants ont été étudiés: (i) les solutions de LiPF6 dans le mélange carbonate de diméthyle / carbonate d'éthylène (1:1), (ii) les solutions de SBPBF4 dans l'acétonitrile, et (iii) les mélanges de liquides ioniques (ILs) C4mimX à température ambiante (X= BF4-, PF6-, TFO-, TFSI-) avec des solvants aprotiques dipolaires tels que l'acétonitrile, la γ-butyrolactone et le carbonate de propylène.Pour tous les systèmes, l'analyse des agrégats a montré la formation d'un réseau ionique continu avec l'augmentation de la concentration de l'électrolyte. Ceci affecte significativement la diffusivité et la viscosité dans ces solutions.L'analyse des polyèdres de Voronoi des mélanges ILs-solvants a montré qu'en dessous de la fraction molaire IL d'environ 0.2, les ions sont bien solv atés par les molécules de solvant, mais au-dessus de cette fraction molaire, ils commencent à former des paires de contact, tandis que les molécules de solvant, expulsées du voisinage des ions, s'autoassocient
The objective of this thesis is to analyze the microscopic structure of the series ion-molecular systems that widely used for practical electrochemistry and to characterize the effect of the ion aggregation on the transport properties of these systems. By using molecular dynamics simulation, the following systems were investigated: (i) the solutions of LiPF6 in dimethyl carbonate / ethylene carbonate mixture (1:1), (ii) the solutions of SBPBF4 in acetonitrile, and (iii) the mixtures of room-temperature ionic liquids (ILs) C4mimX (X= BF4-, PF6-, TFO-, TFSI-) with dipolar aprotic solvents such as acetonitrile, γ-butyrolactone and propylene carbonate.For all the systems the aggregate analysis showed the formation of the ionic continuous network with the increase of electrolyte concentration. This affects significantly diffusivity and viscosity in these solutions.Voronoi polyhedra analysis of ILs-solvent mixtures showed that below the IL mole fraction of about 0.2, the ions are well solvated by the solvent molecules, but above this mole fraction they start to form contact pairs, while the solvent molecules, expelled from the vicinity of the ions, self-associates

En œnologie, la formation de trouble d'origine protéique dans les vins blancs est un défaut visuel inacceptable d'un point de vue commercial. Il est attribué à des modifications lentes de la conformation des protéines (présentes à une concentration de 15 à 330 mg.L-1), conduisant à des phénomènes d'agrégation. Ce phénomène est accéléré par une exposition du vin à des températures élevées pendant le transport ou le stockage. Il peut aussi se développer dans des conditions de stockage conventionnelles mais suivant des cinétiques très lentes (> 12 mois). Il est aussi influencé par la composition du vin en ions, polyphénols et polysaccharides. Pour éviter ce problème, des tests et traitements efficaces mais non spécifiques sont appliqués avant embouteillage. Il en résulte une diminution de la qualité organoleptique du vin ainsi qu'une perte non négligeable de produit.L'objectif des travaux présentés dans cette thèse est de progresser dans l'identification des mécanismes physico-chimiques impliqués dans le développement de troubles protéiques. Pour cela, les expérimentations ont été réalisées sur des systèmes modèles et des systèmes réels (vin) dans différentes conditions de température, pH et force ionique. Les résultats ont permis de mettre en évidence les protéines impliquées dans le trouble ainsi que le rôle déterminant du pH et de la force ionique sur les mécanismes d'agrégation, les caractéristiques des agrégats et le trouble final. Les polysaccharides du vin modulent le phénomène d'agrégation mais ne le préviennent pas. Par ailleurs, des modifications de la conformation des protéines du vin induites par le pH ont été mises en évidence. Ces résultats permettent d'apporter des informations supplémentaires pour le développement de tests et de traitements alternatifs plus spécifiques
In enology, the haze formation in white wine is a visual defect, related to the presence of proteins. This problem is inacceptable for the consumer. It is attributed to a slow unfolding of protein conformation (in white wine at a concentration ranging from 15 to 330 mg.L-1), leading to their aggregation. This phenomenon is accelerated by an exposure to excessive temperature during the storage or the transport. It can also develop on conventional storage conditions but following very slow kinetics (> 12 months). It is influenced by the wine composition in non proteinaceous compounds such as ions, polyphenols and polysaccharides. To prevent this problem, some tests and treatments are used before bottling. However, even if they are efficient, they are non specific to proteins and lead to a diminution of wine organoleptic quality and a non negligible loss of product. The aim of this work is to progress on the identification of physico-chemical mechanisms involved in aggregation. To this end, experiments were performed on model systems and wine, at different conditions of temperature, pH, ionic strength. Results evidenced that specific wine proteins were involved in haze formation whereas others were not. The main role played by pH and ionic strength on aggregation mechanisms, aggregates characteristics and final haze was highlighted. The impact of wine polysaccharides was studied. They modulated the aggregation phenomenon but did not prevent it. Moreover, conformational modifications induced by low pH of some wine proteins were highlighted. These results give some supplementary information for the development of news tests and treatments alternatives, more specific

Os corantes ciânicos (CC) são compostos orgânicos que possuem uma estrutura facilmente variável, permitindo obter-se as características fotofísicas desejáveis. Devido a sua alta afinidade por estruturas biológicas, baixa citotoxicidade no escuro, alta solubilidade em meio aquoso e fotoatividade os CC são considerados compostos promissores para aplicações no tratamento do câncer por terapia fotodinâmica (TFD). CC possuem uma forte tendência de se agregar em meio aquoso, que modifica suas características fotofísicas, reduzindo os rendimentos quânticos de fluorescência e do estado tripleto, diminuindo assim sua eficiência em suas aplicações como sonda fluorescente e na TFD, todavia, a agregação aumenta a eficiência da conversão da sua energia de excitação em calor, que é importante para sua aplicação na terapia por hipertermia (HT). Sendo introduzido num organismo o CC se encontra no ambiente onde ele vai interagir com sais e estruturas nano-heterogêneas (membrana celular, ácidos nucléicos etc.), interações que podem influenciar na sua agregação. Nesse trabalho investigamos o fenômeno da agregação dos CC em suas interações com sistemas nano-heterogêneos naturais (DNA) e sintéticos (micelas) em função da sua própria estrutura, da estrutura destes sistemas e da composição da solução: as concentrações do corante e do sistema nano-heterogêneo e a força iônica. Entre os CC, escolhemos como modelos a Acridina Laranja (AL) e os corantes com dois cromóforos (BCD) que se diferem pelo ângulo formado entre seus cromóforos. Utilizamos técnicas espectroscópicas estacionárias e com resolução temporal de absorção óptica, fluorescência, espalhamento ressonante e dinâmico da luz e fotólise por pulso relâmpago. Descobrimos que em soluções aquosas homogêneas os sais induzem a agregação dos CC. No caso da AL, os sais suprimem sua fluorescência pelo aumento da agregação da AL e pela formação de um exciplexo entre a AL em seu estado excitado singleto e o ânion do sal. A interação dos CC com estruturas nano-organizadas é complexa. Observamos que na interação do CC com o DNA aparecem várias espécies em equilíbrio, tais como monômeros de CC livres e ligados ao DNA, agregados de CC ligados ao DNA e agregados de DNA ligados com os monômeros de CC. A ligação da AL ao DNA reduz a probabilidade do contato da AL com outras moléculas. Contudo, na presença do DNA os sais reduzem a agregação da AL devido à redução da constante de ligação da AL com o DNA. Na presença do dodecil sulfato de sódio (SDS), observamos que em baixas concentrações este estimula a agregação do CC. O aumento da concentração de SDS induz a desagregação do CC. Identificamos que os agregados dos CC com SDS apresentam uma dinâmica que pode perdurar por diversas horas. Durante esse período os agregados trocam suas formas H e J. Investigamos uma possível aplicação prática da agregação numa terapia de HT, identificando que a agregação protege o CC da fotodecomposição e aumenta a eficiência da geração de calor. Os resultados obtidos são importantes para avaliar o potencial de aplicação do CC como fotossensibilizadores em terapia fotodinâmica, fotohipertermia e sondas fluorescentes em diagnóstico por fluorescência.
Cyanine dyes (CD) are organic compounds that have an easily variable structure, thus allowing obtain desirable photophysical characteristics. Due to their high affinity to biological structures, low cytotoxicity in the dark, high solubility in aqueous medium and photoactivity the CD are promising materials for application as photosensitizers in cancer treatment by photodynamic therapy (PDT) and as fluorescence probes in fluorescence diagnostics (FD). CD have a strong tendency to aggregate in aqueous media, which modify their photophysical characteristics, reducing its fluorescence and triplet state quantum yields, thus decreasing their efficiency in applications in PDT and FD. At the same time, aggregation increases the probability of excitation energy conversion into heat, which is important for application in hyperthermia (HT) therapy. Being introduced into organism, CD will interact with salts and nano-heterogeneous structures (cell membrane, nucleic acids etc.). These interactions can affect its aggregation. In this work we have investigated the CD aggregation phenomenon at its interactions with natural (DNA) and synthetic (micelles) nano-heterogeneous systems in function of their own structure, structure of the nano-heterogeneous system and the solution characteristics like dye and nano-heterogeneous system concentrations and ionic strength. Among CD, we have chosen as models Acridine Orange (AO) and cyanine dyes with two chromophores (BCD) that differ by the angle between chromophores. Stationary and time-resolved optical absorption, fluorescence, resonant and dynamic light scattering spectroscopies and flash photolysis were used. We have found that in homogeneous aqueous solutions salts induce the CD aggregation. In the case of AO, the salts quench the AO fluorescence by increasing its aggregation and by forming an exciplex between the AO molecule in its singlet excited state and the salt anion. Interaction of CD with nano-organized systems is complex. We observed that at CD interaction with DNA there appear several species in equilibrium, such as CD monomers free and bound to DNA, CD aggregates bound to DNA and DNA aggregates bound to CD monomers. The aggregation of DNA molecules around AO monomers reduces the probability for AO contact with other molecules. In the presence of DNA salts reduce AO aggregation due to reduction of the AO binding constant to DNA. Sodium dodecyl sulfate (SDS) in low concentrations induces CD aggregation, while higher SDS concentrations stimulate CD disaggregation. The process of CD aggregation in the presence of SDS can continue for several hours. During this period, the form of aggregates may modify from H to J or from J to H depending on the dye structure. The irradiation of dye solutions with visible light increases the solution temperature. Aggregation protected CD from photodecomposition and increased heat generation. The results obtained may help in evaluation the potential of CD as photosensitizers in photodynamic therapy, photohyperthermia and fluorescent probes in fluorescence diagnostics.

碩士
國立中山大學
材料與光電科學學系研究所
101
Restricted intramolecular rotation (RIR) of the non-coplanar aromatic fluorophores has been proven in several instances as the operative mechanism leading to the aggregation-enhanced emission (AEE) property. Besides using the bulky substituent as structural moiety of AEE-active materials, ionic bond interaction is also considered to be effective in reinforcing RIR. In this study, ionic ammonium sulfonate bond was used to introduce long chain orientation order and thus to impose effective RIR to generate emission enhancement on AEE-active organic fluorophores. With this aspect, a surfactant (surf) molecule of weakly-luminescent dodecylbenzenesulfonic acid (DBSA) was used to complex to different amines of varied structures and certain diamines (piperazine (PZ) and poly(ethyleneimine (PEI)) with right geometry to generate orientated dodecyl chains in the ionic products result in the further emission intensifications of the complex systems. Additionally, long-chain dodecylamine (DA) was used to react with weakly-fluorescent biphenyldisulfonate (BPS) and poly(styrene sulfonate) (PSS) to generate AEE-active materials with required orientation order and strong fluorescence due to the active RIR effect. An interesting aggregation-enhanced excimer emission (AEEE) was observed specifically for PSS(DA)1 complex system. Several complex systems (such as DBSA(PZ)x, DBSA(PEI)X, BPS(DA)x and PSS(DA)x ) were found to self-assemble into well-ordered supramolecular lamellar structures with the preferable orientation orders among their long aliphatic chains. RIR in relation to orientation order is therefore the main focus of this research.

碩士
國立中山大學
材料與光電科學學系研究所
102
Abstract-1 A fluorescent biological sensor utilizing aggregation-enhanced emission (AEE) property was developed in our laboratory. First, anAIE-active fluorescent tetraphenylthiophene (TP) unit was synthetically connected to poly(N-isopropylacrylamide) by covalent and ionic bonds, resulting in the respective c- and i-TP-PNIPAM for the detection and quantification of the bovine serum albumin (BSA) model protein. When bind to BSA, the ionic i-TP-PNIPAM shows much better fluorescence (FL) sensitivity compared to c-TP-PNIP AM. The fluorescence (FL) intensity of i-TP-PNIAPM displays a good linear dependence on concentration of BSA (0 – 1 mg/mL), indicating quantitative fluorimetric protein detection can be achieved. Further addition of anionic surfactant ofsodium dodecylsulfate (SDS) considerably raised the FL intensity of the complexsolution. All the FL response was discussed in term of conformational freedom of the TP unit under different environmental constraints. Abstract-2 A water-soluble fluorophore containing four anionicsulfonated groups, sodium tetraphenylthiophenesulfonate (TPS), was sythesizedand characterized to have aggregation-enhanced emission (AEE) property. One the other hand, acidified Jeffamine (diammonium-terminated poly(propylene glycol) and Jeffamine-included β-cyclodextrin (β-CD) were separatedly prepared. Through the facile ionic interaction between sulfonate anion in TPS and ammonium cation in Jeffamine (or in Jeffamine-included β-CD), fluorescent ionic complex of iTP-JA (or iTP-CD-JA) can be prepared and their emission behavior was correlated with the degree of restricted intramolecular rotation (RIR), as the main mechanism responsible for AEE phenomenon, in each system of different molecular structures. When bind to polymeric Jeffamine, iTP-JA complex emits with higher intensity than the small-mass TPS. Use of β-CD rigidify the flexible Jeffamine, therefore, iTP-CD-JA complex is the most efficient emitter among all three samples.

博士
國立臺灣大學
化學研究所
98
Recently, the topics of substituting volatile organic solvents with ionic-liquids takes advantages of the flexibility in designed functionalities. Ionic-liquids improves the reaction capabilities with specific functionalities and also becomes more eco friendly. We have synthesized ionic liquids built-in with mononuclear, binuclear and multinuclear imidazolium cations and have probed the molecular interactions of monoimidazolium ionic liquids with 1H-NMR and TEM. We have found that the property of mesoscopic aggregation of ionic liquids are with two dominant forces, the hydrogen bonding (Brønsted acid-base pair) and the π-acid (Lewis acid-base pair) besides the charge attraction and repellence. The application on catalytic conversion of ROH to RBr with mononuclear ionic-liquids have been shown that the ionic-liquid catalysts could be recovered and reused for six times without loss of reactivity. In D2O at pH 7, we have found that the binuclear ionic liquids spontaneously form carbene species as an important intermeatiale on dynamic H-D exchange phenomena and are employed as initially agents for the caprolactone ring-open polymerization to synthesis the bio-degradation polycaprolactone. We have also developed a carbene derivative, N,N’-dimethylimidiazolium-2 -carboxylate (1-1-CO2, a masked carbene). According the TGA results, 1-1-CO2 would be sublimed instead of thermally decomposed at 130℃. Hence 1-1-CO2 was used in the CO2 fixation reaction, to catalyze the conversion of propylene epoxide into propylene carbonate, 1-1-CO2 being reused as catalyst for 10 times. Multinuclear imidazolium ionic-liquids could also be the catalyst for cycloaddition reaction of carbon dioxide and epoxy species, and have been reused for 8 times. Furthermore, this catalyst system fixed at high molecular weight skeleton is easy for the V separation of products by simple filtration utilizing SiO2. In conclusion, this exploratory work was being devoted to the capability of ionic-liquids, on catalytic halide substitution reaction for hydroxyl group of an alcohol, ring-open polymerization of caprolactone, and cycloaddition reaction with carbon dioxide and epoxide. The reactions are all improved to more friendly towards the environments.

碩士
國立中山大學
材料與光電科學學系研究所
104
Bulky camphorsulfonic acid (CSA) was used to complex with quinine (Qu) to impose the restricted intramolecular rotation (RIR) required for aggregation-induced emission (AIE) properties. After complexation with two equivalents of CSA, the non-emissive quinine (Qu) base can be protonated to result in ionic complex Qu(CSA)2 with AIE properties. AIE-active rhodamine-based luminogen was prepared by complexation reaction between non-emissive rhodamine hydrazide (RdH) and bulky camphorsulfonic acid (CSA). Besides acting to open the spirolactam ring of RdH, CSA also imposes rotational restriction on the resultant ionic complex RdH(CSA)x. The ionic bonds of Qu(CSA)2 and RdH(CSA)3 are sensitive to several external stimuli and therefore, it is a luminescent sensor for metal ions, organic amines, pH value and the blood protein of bovine serum albumin (BSA); through the use of Qu(CSA)2 and RdH(CSA)3, the unfolding process of the BSA chains was evaluated.

碩士
國立中正大學
化學暨生物化學研究所
103
The first research project－”Ionic liquids as potential inhibitors for aggregation of beta-amyloid peptides”－focused on the design, synthesis and screening of water-soluble ionic liquids for use as potential inhibitors for beta-amyloid peptides aggregation. Aromatic-based ionic liquids may interact with beta-amyloid peptides by intercalation to arrest peptide aggregation. The second research project－”Improved synthesis of bicyclic 1,2,3-triazolium ionic liquids and its application”－designed and synthesized targeted bicyclic triazolium ionic liquids with an aim to start with inexpensive reagents. Cyclization using iodosobenzene diacetate was found appropriate to scale up its preparation. As a new application, this triazolium ionic liquid conjugated with tetrazine was found valuable for alkene gas detection on quartz crystal microbalance. Appendix－”Exploring silver ionic liquids for reaction-based gas sensing on quartz crystal microbalance”－recorded the synthetic procedure of aminooxy-based ligand for silver ionic liquid, and proved its high reactivity with ketones.

碩士
國立中央大學
化學研究所
98
Abstract Ionic liquid (IL) is a very popular medium which has been explored in recent years. It has been widely employed in various research fields. Nanoscale transition metal catalysts have also attracted increasing intrests. It has been mainly the study of special physical and chemical properties of ILs in order to make use of metal ions. Alternatively, ILs can prevent the metal nanoparticles from aggregation. Pd-nanoparticles and Au-nanoparticles were synthesized by UV irradiation or microwave heating of respective metal halide anions PdBr2 and HAuCl4 in CDCl3 solution of 1-butyl-3-ethyl-1H-imidazol-3-ium bromide ,chloride(4-2Br and 4-2Cl), respectively. The 4-2 Br IL with 10 mol % metal salt in chloroform ionic liquid clustering exhibits at increasing concentration of 4-2 Br. After UV or microwave irradiation, the metal nanoparticles produced could serve as the contrasting agent on the TEM images, to correlate the concentrations of IL with the aggregation phenomena of IL. On a separate study, fluorescent dyes of 3-hydroxy chromone derivatives 2-(6-diethylaminobenzo[b]furan-2-yl)-3-hydroxychromone (FA) and 2-(4-(dimethylamino)phenyl)-3-hydroxy-4H-chromen-4-one (CF) have been used to extract structural information from the luminescence and excitation spectra, which also reflect the the aggregation of ionic liquid in chloroform. The chloroform solution of 4-2 Br and 10% PdBr2 under UV or microwave irradiation generated the Pd nanoparticles in IL layer of 4-2 Br which also protected the size of Pd nanoparticles from growing too fast. These Pd nanoparticles in IL were used in the Heck reactions. Initially ionic liquid layer with Pd NPs was added with organic materials for the two-phase catalytic Heck reactions, which could be carried out under mild conditions. The combinations of Pd nanoparticles and the IL conforms to goals of green chemistry in reducing environmental damages.