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Síntese, dinâmica de formação, caracterização e propriedades ópticas de nanobastões de ouro dispersos em meio aquoso e matrizes orgânicas / Synthesis, characterization, dynamic formation and optical properties of gold nanorods dispersed in aqueous phase and organic matricesSilva, Monique Gabriella Angelo da 12 April 2010 (has links)
In this work, different colloidal gold nanorods were prepared dispersed in different liquid matrices. All gold nanorods were prepared from the acid tethrachloroauric (HAuCl4) in the presence of a reducing agent, using the seed mediated method. The cetyltrimethylammonium bromide (CTAB) was employed as director growth agent. The variable concentration of CTAB in the medium was evaluated in order to verify the selectivity in the formation of nanorods. In addition, we performed a kinetic study to obtain information about the formation mechanism of these particles. Colloid containing gold nanorods in organic matrices such as castor oil and hexafluorophosphate ionic liquid butylmethylilimidazolium (BMIM.PF6) were prepared in order to obtain colloid systems with different physico-chemical characteristics, however among same particles. These new colloids were obtained using the transfer technique of particles, which were synthesized in aqueous medium and then dispersed, after separation, for the desired organic matrix. All colloids were characterized by absorption spectroscopy at ultraviolet and visible (UV-Vis) and nanoparticles characterized by Transmission Electron Microscopy (TEM) / Neste trabalho, diferentes colóides contendo nanobastões de ouro dispersos em diferentes matrizes líquidas foram preparados a partir do ácido tetracloroáurico (HAuCl4), em presença de um agente redutor adequado, através do método mediado por sementes. O brometo de cetiltrimetilamônio (CTAB) foi empregado como agente direcionador de crescimento. A variável concentração de CTAB no meio foi avaliada com o objetivo de verificar a seletividade na formação de nanobastões. Além disso, foi realizado um estudo cinético para obter informações sobre o mecanismo de formação dessas partículas. Coloides contendo nanobastões de ouro em matrizes orgânicas como óleo de mamona e o líquido iônico hexafluorofosfato de butilmetilimidazólio (BMIM.PF6) foram preparados a fim de obter sistemas coloidais com diferentes características fisico-químicas porém com as mesmas partículas. Esses novos colóides foram obtidos através da técnica de transferência de partículas, as quais foram sintetizadas em meio aquoso e posteriormente dispersas, após separação, para a matriz orgânica desejada. Todos os colóides preparados foram caracterizados por Espectroscopia de absorção na região do ultravioleta e visível (UV-Vis) e as nanopartículas caracterizadas por Microscopia na eletrônica de transmissão (MET)
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Structures and silica forming properties of insoluble organic matrices from diatomsPawolski, Damian 31 August 2018 (has links)
Since the 18th-century scientists are studying diatoms, fascinated by their beauty and
diversity. Their nano- and micropatterned biosilica cell walls are outstanding examples of
biologically controlled mineral formation. Although the knowledge about diatom cell wall
formation increased over the last 60 years, the process is still far away from being completely
understood. Diatom cell walls exhibit highly interesting material properties, making them
appealing to material scientists. Due to those properties, diatom cell walls are on the brink of
becoming powerful tools in nanotechnology. However, the production of tailored silica
structures for nanotechnology requires a much better understanding of the processes and
components involved in cell wall morphogenesis. Recent studies set the focus on insoluble
organic matrices as important parts of this process, suggesting that they act as templates in
silica morphogenesis. Therefore, in this study, the occurrence of insoluble organic matrices
and their possible silica precipitation activity was analyzed in the three diatom species T.
pseudonana, T. oceanica and C. cryptica.
For all three species girdle band and valve derived insoluble organic matrices could be
identified. The extracted insoluble organic matrices exhibited structural features present in the
corresponding biosilica cell walls. The highest similarities were found in the valve derived
matrices of C. cryptica. Accessibility studies showed that the biosilica associated insoluble
organic matrices of T. pseudonana were only partially accessible, arguing for an entrapment
of insoluble organic matrices in the silica, rather than an attachment to the surface of the cell
wall. All examined insoluble organic matrices of the three species exhibited intrinsic silica
precipitation activity. The most intriguing structures were formed by the insoluble organic
matrices of C. cryptica, yielding a porous silica pattern. The addition of biosilica derived
soluble components or long-chain polyamines promoted this process and moreover lead to the
reconstitution of biosilica-like hierarchical silica pore patterns. The generated silica structures
were templated by the underlying structure of the insoluble organic matrix.
The result presented in this thesis make this the first study reporting the in vitro
generation of diatom biosilica-like hierarchical silica pore patterns using all natural cell wall
components. It supports the hypothesis of microplates acting as templates for biosilica
morphogenesis and introduces an interesting experimental setup for silica-based in vitro
studies on the mechanism of pore formation in diatoms.
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