L’objectif de cette thèse est de contrôler les propriétés optiques des nanoparticules d’or greffées de polymère en modulant les propriétés structurales de la couche protectrice de polymères. Des nanoparticules greffées de polymères thermosensibles avec une large gamme de masse molaire et différents degrés d’hydrophobicité sont synthétisées par la méthode de « grafting-to ». La DNPA est utilisée pour caractériser les propriétés structurales de la couche protectrice de polymère. Les spectres d’absorption sont modélisés en utilisant la théorie de Mie. Nous démontrons que la sensibilité de la SPR à la propriété diélectrique du solvant diminue progressivement avec la fraction volumique de la couche de polymère jusqu’à devenir quasi-nulle; dans ce dernier cas de figure, la SPR est dite « gelée » par la couche de polymère. Un déplacement significatif de la bande de SPR vers le rouge est induit (un changement de couleur se produit) dû à une transition de collapse de la couche de polymère avec la température. La gamme de température pour induire ce déplacement dépend du degré d’hydrophobicité du polymère et de la salinité. Une partie important de cette thèse est également consacrée aux propriétés des nanoparticules d’or greffées de polymères à l’interface air-eau. La technique de Langmuir est utilisée pour former des films minces dont la distance entre particule est contrôlée par la compression, la longueur des chaînes du polymère greffé et la température. Les propriétés structurales des films minces sont étudiées en déterminant la conformation de la couche de polymère greffée et l’organisation du cœur de l’or par la réflectivité de neutron et de X, respectivement. Les mesures de réflectivité nous permettent également d’évaluer et d’améliorer la stabilité des films minces pour un meilleur control de la distance entre particule, aspect important pour l’optimisation de la SPR. Enfin, les propriétés optiques des nanoparticules d’or à l’interface sont mesurées par des mesures de transmission. / In this thesis, the objective is to control the polymer-grafted gold nanoparticles optical properties (SPR) by tuning the protecting polymer shell structural properties. Gold nanoparticles grafted with thermosensitive polymers with a large range of molecular masses and different degrees of hydrophobicity are synthesized by “grafting-to” technique. SANS is employed to characterize the protecting polymer shell structural properties. The absorption spectra are modeled using the Mie Dipolar theory. It is shown that the gold nanoparticle sensitivity to external solvent is progressively reduced with increasing polymer volume fraction of the nanocomposite until the SPR is frozen by the polymer shell. In this case, the SPR mode becomes insensitive to the dielectric properties of the solvent. SPR is also red-shifted (a color change occurs) by thermally inducing the collapse of the polymer shell. The temperature and the extent of the red-shift are controlled by the graft polymer hydrophobicity and salinity. An important part of this thesis is also dedicated to the polymer-protected gold nanoparticles behaviour at the air-water interface. The Langmuir balance technique is used to build interfacial layers whose interparticle distance is modulated by compression, polymer graft chain length and temperature. The interfacial layer structural properties are determined by studying both the polymer graft layer conformation and the gold core organization with neutron and X-ray reflectivities. These reflectivitity measurements also enable us to evaluate and ameliorate the surface layers stability for a better control of the interparticle distance that is important for optimizing the SPR of the surface layer.

No description available.

No description available.

No description available.

No description available.

Protein adsorption at the solid/liquid interface is of wide ranging importance in many different areas of science such as biomaterial design, the fate of nanoparticles and in the food industry. As a result, many studies have been undertaken with varying foci but there still remains a lack of agreement between many working in this field and fundamental questions regarding the adsorption of proteins at the solid/liquid interface. Neutron reflectivity is a powerful technique for probing the properties of adsorbed layers at interfaces due to its high structural resolution and the possibility of using isotopic substitution to distinguish between components of a mixture. In this work, neutron reflectivity has been used as the primary technique for the investigation of proteins adsorbed sequentially or from a binary mixture. Initially, the adsorption of four proteins (carbonic anhydrase II, lysozyme, human serum albumin and maltose binding protein) onto a clean silica surface was investigated which revealed the importance of electrostatic interactions and entropic contributions to the driving forces for adsorption. Most of the adsorbed layers were described by a 2-layer model with a thinner, denser layer adjacent to the surface and a thick, diffuse layer extending into the bulk solution. The presence of impurities is also shown to have a significant impact on the adsorption of HSA. A study of the HSA/myristic acid system shows that the presence of small amphiphiles can inhibit HSA adsorption and also remove a pre-adsorbed layer. A comparison was made between the protonated and deuterated forms of two proteins, HSA & MBP, showing the deuterated proteins to have a higher affinity for the surface with adsorption occurring in a 3:1 ratio when from a 1:1 mixture. Likewise, d-MBP displaced h-MBP more readily than vice versa in an investigation into the effect of incubation time on the properties of the protein layer. The extent of desorption into protein free buffer is not affected by incubation time but the extent to which d-MBP was displaced by h-MBP showed a clear trend of decreased exchange with increasing incubation time indicating an active exchange process was occurring. This was also observed to a lesser extent for the sequential adsorption of binary protein systems, HSA & LYS and HSA & MBP. When investigating binary protein mixtures the higher propensity for deuterated proteins to adsorb is observed. LYS dominates when adsorbed from a mixture with h-HSA but from a d-HSA & LYS mix both proteins were adsorbed. The marked difference between the adsorption characteristics of perdeuterated proteins and their protonated counterparts provides a good case study for testing the neutron reflectivity technique when investigating systems with more than one component. This thesis assesses the limitations of the methodology of contrast variation for investigating mixtures as well as using different solvent contrasts. A comparison of neutron reflectivity and dual polarisation interferometry (DPI) shows that the two techniques are similar and any small differences can be attributed to the small change in surface chemistry. This comparison also highlights the advantages of DPI; high throughput of samples and detailed information but the restriction to using a 1-layer model limits its use.

Dans le cadre du retraitement des déchets nucléaires et du recyclage de métaux critiques, l'extraction par solvant est l'une des technologies les plus utilisées. L'interface liquide entre deux fluides non miscibles est considérée comme une région où de multiples phénomènes physiques et chimiques sont à prendre en compte et peuvent limiter ou favoriser le transfert d'espèces entre les deux fluides. La structure de ces interfaces doit être connue en fonction de plusieurs paramètres thermodynamiques pour pouvoir déterminer le paysage énergétique associée. La réflectivité de neutrons et de rayons est un des outils appropriés pour sonder ce genre d'interfaces enfouies et fluctuantes à l'échelle nanométrique et à l'équilibre. Pour cette étude, une nouvelle cellule a été construite et un programme spécifique d'analyse de données a été élaboré.Nous avons également porté notre étude sur deux différents systèmes bi-phasiques (eau / dodécane) contenant des sels de lanthanides et deux différents ligands non ioniques (ou extractants) : une diamide de type DMDBTDMA et de type DMDOHEMA, ces deux extractants étant connus pour avoir des comportements différents dans un processus d'extraction de cations métalliques en phase organique. Bien que la structure amphiphile des deux diamides soit bien connue, la structure de l'interface liquide / liquide semble être différente de celle que l'on pourrait s'attendre avec des tensioactifs classiques. L'organisation de ces ligands à l'interface est en effet plus complexe, varie en fonction de leurs concentrations dans la phase organique (seules des concentrations inférieures à la concentration d'agrégation critique ont été étudiées) et en fonction de la concentration d'acide et de sel dans la phase aqueuse. Une organisation de type monocouche n'est pas l'organisation principale de ces systèmes à l'équilibre mais on observe plutôt une couche épaisse de ligands.Plus précisément, dans le cas de la DMDBTDMA, cette région plus épaisse (environ trois à quatre fois la longueur du ligand) crée une région interfaciale où les molécules d'huile et d'eau peuvent se mélanger ainsi que les sels. Le système DMDOHEMA, présente une structuration différente avec également une épaisse couche de ligand (environ deux fois la longueur du ligand) mais située plus à l'intérieur de la phase huileuse et distinct de la distribution des sels à l'interface. Ces différentes structures interfaciales de DMDBTDMA et DMDOHEMA peuvent permettre d'expliquer les différents régimes de transfert ionique qualifiés soit de diffusionnel ou de cinétique. / In the frame of the nuclear waste reprocessing and various kinds of critical metals recycling methods, solvent extraction is one of the most used technological processes. The liquid interface between two immiscible fluids is considered as a region where many physical and chemical phenomena take place and can limit or promote the transfer of species between both fluids. The structure of these interfaces has to be known as a function of several thermodynamical parameters to be able to determine the associated energy landscape. X-ray and neutron reflectivity are suitable techniques to probe such kind of fluctuating and buried interfaces at the nanometer scale and at equilibrium. For this study, a new cell has been built and a specific data analysis procedure was established.We have focused our study on two different biphasic systems (water/dodecane) containing lanthanides salts and two different nonionic ligands or extractant molecules: DMDBTDMA and DMDOHEMA diamides. These ligands are known to have different behaviour in the lanthanides extraction process. Although the amphiphilic chemical structure of both diamides is well known, the structure of the liquid/liquid interface appears to be different as those expected for a classical surfactant molecule. This structure looks more complex, varies as a function of the ligand concentration in the organic phase (below the critical aggregation concentration) and as a function of the proton and salt concentration of the aqueous phase. A monolayer organization does not appear as the main interfacial structuration and a thicker organic layer with an excess of salt has to be considered.In the case of the DMDBTDMA, this thicker region (approximatively three or four times the length of the ligand) creates an interfacial region where oil and water molecules as well as some salts can mix in. The DMDOHEMA system shows a different structuration where we can roughly observe also a thick layer of the ligand (approximatively two times the length of the ligand) but located more within the oil phase and forming a barrier to the salt distribution. These different interfacial structures made of DMDBTDMA and DMDOHEMA could allow to explain the diffusive or kinetic regime of ion transfer observed respectively in similar systems by others authors.

No description available.

Submitted by CARLA MARIA GOULART DE MORAES (carlagm) on 2015-04-06T13:09:19Z No. of bitstreams: 1 SolangeGarcesCienciasSociais.pdf: 3864176 bytes, checksum: 23aecc60f6bb1199f8fc531e51b0828e (MD5) / Made available in DSpace on 2015-04-06T13:09:19Z (GMT). No. of bitstreams: 1 SolangeGarcesCienciasSociais.pdf: 3864176 bytes, checksum: 23aecc60f6bb1199f8fc531e51b0828e (MD5) Previous issue date: 2012 / Universidade de Cruz Alta / O objetivo foi analisar como se constituem os espaços sociais para vivenciar a velhice e as sociabilidades que geram identidade e potência aos idosos, transformando-os em atores sociais. O referencial metodológico foi qualitativo. Os sujeitos foram vinte e dois idosos. Os entrevistados foram indicados por conhecidos, via método bola de neve: cada entrevistado apresentou referências/indicações de outros indivíduos elegíveis para participarem do estudo em questão. O instrumento foi um roteiro de pesquisa com questões abertas, e a interpretação foi a partir de análise de conteúdo. A partir dos resultados afirma-se que os idosos vivenciam diferentes dinâmicas de vida e não querem ser vistos como doentes ou coitadinhos. Os tipos ideais encontrados foram: Idosas Viúvas e Solitárias; Idosos Militantes Políticos; Idosos engajados em movimentos culturais;Idosos espiritualizados e solidários e Idosos que trabalham e estudam a questão do envelhecimento. Mas são os espaços de sociabilidades que permitem a que os idosos se potencializem e adquiram identidade pela suas ações. É nos processos de interação (sociação), que se constituem como sujeitos atuantes e constroem as diferentes velhices (tipos ideais) que se encontra hoje na esfera pública. Os idosos, que participam de diferentes sociações enriquecem o seu círculo social e também seu próprio desenvolvimento, intensificando diferentes interações, seja na forma política, cultural ou religiosa. A movimentação na esfera pública acontece quando suas ações impulsionam-se pela subjetividade, possibilitando maior reflexividade, a partir dos movimentos sociais. Essa reflexividade lhe estimula para suas escolhas, para o engajamento e participação política ou para o hedonismo e a religiosidade e os conselhos de direitos têm o dever e obrigação de possibilitar acesso a esses conhecimentos, assim como também às Universidades. Os idosos detentores de engajamento político, apresentam uma liderança e um carisma que os potencializa para a ação em suas comunidades, que constituem seus territórios de ação e trazem esse conhecimento a mão em suas trajetórias de vida. O idoso ainda é representado por políticos, intelectuais e demais pessoas interessadas em tirar proveito da questão social do envelhecimento. Aos poucos vão se acordando para essa realidade e iniciam sua participação, mas pelo elevado número de idosos do Brasil, essa participação política ainda é irrisória e por isso se diz que os idosos ainda não são legitimamente protagonistas na esfera pública, pois a sua movimentação ainda é uma novidade até mesmo entre os próprios idosos. / The purpose was to analyze how the social spaces are constituted to experience the old age and the sociability that generate identity and power to the elderly, transforming them into social actors. The methodological referential was qualitative. The subjects were 22 elderly. The interviewed were indicated by known people, via snow ball method: each interviewed showed references/indications from other closeable individuals to participate in the study in question. The instrument was a research guide with open questions and the interpretation was from analyzes of categories. From the results we can affirm that the elderly experience different dynamics of life and they don?t want to be seen as sick or poor people. The ideal types found were: lonely and widow female elderly; Military Politician elderly; elderly engaged in cultural movements; spiritualized and solidary elderly and elderly who work and study the question of aging. But the sociability spaces are what allow that the elderly who potentiate and acquire identity by their actions. Its in the interaction processes (association) that are going to be constituted as acting subjects and building the different old ages (ideal kinds) that we find today in the public sphere. The elderly who participate in different associations enrich their social circle and also their own development, intensifying different interactions, in the political, cultural or religious means. The movement in the public sphere happens when its actions are boosted by the subjectivity, what enable it to have more reflectivity, from the social movements. This reflectivity stimulates it to its choices, to the engagement and political participation or to the hedonism and the religiosity and the advices of right have duty and the obligation to enable the access to this knowledge, as well as the Universities. The elderly who have political engagement present a leadership and charisma that potentiate them to the action and bring this knowledge to the hand on their life journey. The elderly is still represented by politicians, intellectuals and other people interested in benefiting from the aging social question. Few people are going to waking up to this reality and they start their participation, but by high number of elderly in Brazil, this political participation is still negligible and so we can say that the elderly aren?t the real protagonists in the public sphere yet, because their movementaction is still something new even among the elderly themselves.

Ultrafast carrier dynamics studies have been carried out on samples with single layers of self-assembled In0.4Ga0.6As/GaAs quantum dots (QDs). Measurements were made using femtosecond degenerate pump-probe differential reflectivity with an 800-nm, 28-fs Ti-sapphire oscillator as the source. The QDs were grown via modified Stranski-Krastanov growth. This modified growth process consists of two steps: low-temperature growth and high-temperature annealing. Specifically, the InGaAs QD structures are fabricated on n-type GaAs(001) using molecular beam epitaxy. The InGaAs layer is deposited at 350-3700C followed by QD self assembly at 420-4900C. Finally, these QDs are capped with 10 nm or 100 nm of GaAs. The measured width and height of these QDs are typically 25 nm and 8 nm, respectively. Dots annealed at higher temperature have larger base area (width and length) and reduced height, as compared to those annealed at lower temperature. We have used a model consisting of a linear combination of an exponential decaying function to describe the carrier dynamics and fit the reflectivity data, revealing trends in the carrier capture and relaxation times associated with the InGaAs layer versus laser excitation level and QD morphology. Capture times are ~ 1 ps for the 100-nm capped samples, but slightly shorter for the 10-nm capped thin samples, indicating carrier transport plays a role in dynamics. The carrier dynamics in 10-nm capped samples are correlated with sample annealing temperature, indicating QD morphology affects carrier capture. Versus laser intensity, and thus carrier excitation level, the dynamics generally become slower, suggesting state filling is important in both the capture and relaxation of excited carriers in these samples.