Dissertations / Theses on the topic 'Colloidal silica'
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Gill, Michael. "Polyaniline-silica colloidal nanocomposites." Thesis, University of Sussex, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239632.
Full textCorradi, Roberto. "Conducting polymer-silica colloidal composites." Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263866.
Full textRamli, Nor Hanuni. "Ultrafiltration of polydisperse colloidal silica." Thesis, Swansea University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678552.
Full textYuan, Zheng. "Impact of Colloidal Silica on Silicone Oil-Silica Mixed Antifoams." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562587653182.
Full textSpencer, Laura Marie. "Evaluation of sand treated with colloidal silica gel." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37131.
Full textWeisen, Albree Rae. "Thermorheological Dynamics of Glycerol-Based Colloidal Silica Suspensions." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1626785313712582.
Full textSinclair, Luke Alexander. "Development of a silica scaling test rig." Thesis, University of Canterbury. Mechanical Engineering, 2012. http://hdl.handle.net/10092/7002.
Full textLe, Thai Van. "Silica colloidal crystals as new materials for biomolecule separations." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 117 p, 2007. http://proquest.umi.com/pqdlink?did=1251902811&Fmt=7&clientId=79356&RQT=309&VName=PQD.
Full textLesaine, Arnaud. "Structural and mechanical properties of dried colloidal silica layers." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS597/document.
Full textDrying a colloidal suspension results in the formation of a more or less porous solid layer. This procedure is central to many applications such as sol-gel processes, the design of paints and lacquers... As the solvent evaporation induces shrinkage of the material, large stresses can develop in these layers, making them prone to fracture. A crucial challenge is thus to understand the role of the control parameters, such as drying rate, film thickness and particle size, on the structural and mechanical properties of the final layer. In this thesis work, Ludox (colloidal silica) was used as a model system to study the effect of the drying rate on the structural and mechanical properties of the resultant solid. The effect of the drying rate on the structural properties of the dry layers was studied using porosity measurements as well as atomic force microscopy and small-angle X-ray scattering. We could evidence the importance of initial suspension dispersity and particle aggregation on the structure of the dry layers. Using ultrasound measurements, we determined the tensorial elasticity (bulk and shear moduli) of the dry layers. The elastic moduli can be related to the material porosity and the particle size. Thus, the experimental data was used to test several homogeneization schemes (Mori-Tanaka and self-consistent) as well as Kendall's model for the Young’s modulus, which considers the effect of adhesive forces between particles. Finally, hardness and fracture toughness of the materials were inferred from Vickers indentation tests. The fracture properties of the layers in their dry, final state were related to their packing fraction, the evaporation rate, and the density of the cracks formed during the desiccation process
Hamderi, Murat Gallagher Patricia M. "Pilot-scale modeling of colloidal silica delivery to liquefiable sands /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3285.
Full textSellou, Linda. "Structure in colloidal silica and its influence on abrading surfaces." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479526.
Full textBean, Keith Howard. "Stability studies of colloidal silica dispersions in binary solvent mixtures." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251536.
Full textLin, Yuanzhi Gallagher Patricia M. "Colloidal silica transport mechanisms for passive site stabilization of liquefiable soils /." Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1162.
Full textEgas, Proaño David Alexis. "Colloidal Silica as a Platform for Trace Protein Analysis and Recovery." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202703.
Full textSalguero, C., C. Salguero, L. Castaneda, J. Rodríguez, and E. Carrera. "Eco-Concrete for Hydraulic Structures with Addition of Colloidal Nano-Silica." Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/651739.
Full textTAGLIARO, IRENE. "NOVEL COLLOIDAL APPROACH TO PREPARE HIGHLY-LOADED SILICA-BASED ELASTOMERIC NANOCOMPOSITES." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241175.
Full textSustainability has become a field of great interest in the world industry. For the scientific community the challenge lies in the identification of green synthetic approaches and new alternatives to petroleum-based materials. In the case of the tyre industry, the challenge is to identify possible design strategies and alternatives to reduce the environmental impact throughout the life cycle of tyres, by means of both the use of environmentally friendly materials and the development of innovative products, having reduced energy consumption and CO2 emissions. In this context, this PhD thesis is focused on the preparation of eco-friendly silica-based nanocomposites by using a colloidal approach to increase the dispersion of hydrophilic fillers in line with the new requirements of sustainability from the EU policies. The colloidal approach aims at compounding nanocomposites with hydrophilic fillers, whose efficient dispersion through traditional mixing still remains a challenging issue, due to their poor compatibility with the organic matrix. This technique aims at increasing the filler dispersion without any expensive surface modification, with the elimination of the volatile component released during mixing, producing significant benefits for environment and workers. Two different colloidal approaches were applied: i) latex compounding technique (LCT) and ii) in situ emulsion polymerization to prepare highly-loaded nanocomposite rubber materials containing silica-based fillers, silica and sepiolite (Sep) clay, considered a promising filler candidate for the polymer strengthening due to its fibrous structure and high particle aspect ratio (AR). The concentration, the charge and the shape of silica-based nanofillers were studied as relevant parameters on stabilization and destabilization of natural and synthetic polyisoprene latexes. An effective LCT procedure was established to produce eco-friendly composites, namely masterbaches (MBs), by incorporating silica or Sep into natural rubber latex (i.e. emulsion in water of cis-1,4-polyisoprene), through the flocculation (i.e. aggregation resulting from the bridging of polymer particles) of the silica-based nanofillers/rubber mixed aqueous system. LCT showed to favour a homogeneous dispersion of hydrophilic Sep fibers in the rubber matrix. The main physicochemical parameters which control aggregation processes in the aqueous medium, i.e. pH, -potential, concentration, as well as the morphological features of the final Sep-natural rubber MBs, were comprehensively investigated helping to figure out the Sep-NR interactions and to propose a flocculation mechanism, based on electrostatic and depletion attraction forces, remarkably connected both to the high content (50 wt.%) and to the peculiar anisotropy of Sep fibers. Furthermore, the MBs with high filler loadings were used to produce environmentally friendly composites, by combining LTC and melt mixing. This combined approach could take advantage of the good filler distribution and prevents dust from floating in the air during processing. In situ Pickering polymerization was considered as an alternative colloidal approach to produce eco-friendly nanocomposites. Polyisoprene/silica-based structured particles were synthesized on the base of the stabilizing effects of inorganic fillers which act like surfactants lowering the interfacial tension and stabilizing the emulsion. On the basis of our results, we suggested a possible mechanism for emulsion polymerizations stabilized by solid particles. In conclusion, the colloidal approach, based on both LTC and in situ Pickering emulsion polymerization, can be considered as green, simple and effective method suitable for high-performance technological applications. The outcomes indicate the suitability of the adopted strategies as a sustainable procedure for the production of high-loaded silica based-rubber nanocomposites.
Singhon, Rattiya. "Adsorption of Cu(II) and Ni(II) Ions on Functionalized Colloidal Silica Particles Model Studies for Wastewater Treatment." Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2077/document.
Full textThis study is focused on the preparation of three types of silica-based composites for the capture of Cu(II) and Ni(II) ions. The first strategy consists in coating chitosan on colloidal fumed silica after acidic treatment yielding the composite SiO2+CS. The second strategy can be separated into two routes: the first one involves surface grafting of silica with aminopropyltriethoxysilane to obtaining silica particles covered by amino groups (SiO2(NH2)). The second one involves in surface condensation of triethoxysilylbutyronitrile, followed by acidic hydrolysis of the surface-bound nitrile groups affording silica particles covered by carboxyl groups (SiO2(CO2H)). In the last step, chitosan has been grafted on the surface bound NH2 or -CO2H groups yielding the composites SiO2(NH2)+CS or SiO2(CO2H)+CS. The third strategy involves in the modified CS surface with -CO2H groups, followed by coating onto the non-modified silica nanoparticles to obtain the composite SiO2+CS(CO2H). The novel hybrid materials were characterized by IR spectroscopy, scanning electron microscopy, atomic force microscopy, and zeta potential measurements. Batch experiments were conducted to study the sorption performance of these composites for Cu(II) and Ni(II) removal from aqueous solution at optimum pH at 298 K. The kinetics were evaluated utilizing pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all types of adsorbents. The adsorption isotherms were evaluated utilizing Langmuir, Freundlich, and Temkin models. The best interpretation for equilibrium data was given by Langmuir isotherm model. This study demonstrates that the adsorption capacities for Cu(II) ion is more efficient for the SiO2+CS (256 mg g-1) compared to SiO2(NH2) (75 mg g-1). However, the carboxyl grafted CS-coated silica (SiO2+CS(CO2H) exhibited an excellent adsorption capacity (333 mg g-1). In case of Ni(II), based on Langmuir isotherm the maximum adsorption capacity found to be 182 mg g-1for SiO2+CS, and 210 mg g-1 for SiO2(CO2H) + CS. Using single-metal solutions, these adsorbents were found to have an affinity for metal ions in order as Cu(II) > Ni(II). The adsorption of Cu(II) ion by SiO2+CS was affected by the nature of the respective anion. Application of these composite materials to remove Cu(II) and Ni(II) from aqueous solution was shown to be more efficient than the adsorption capacities of many sorbents probed by other research groups
Zhang, Guangqun. "Effects of alkali ions on the dielectric properties of porous silica prepared by a colloidal processing method." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19037.
Full textWalker, Richard John. "Behaviour of nanocolloidal particles on mica : investigations using atomic force microscopy." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4633.
Full textBethea, Tomika R. C. "Silica Colloidal Crystals as Porous Substrates for Total Internal Reflection Fluorescence Microscopy." Thesis, The University of Arizona, 2006. http://hdl.handle.net/10150/193371.
Full textAlireza, S., K. N. Fatemeh, and S. Hossein. "Improving thermo-mechanical properties of tabular alumina castables via using nano structured colloidal silica." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20571.
Full textRose-Hélène, Maureen. "Aspects thermodynamiques et cinétiques de la complexation de cations métalliques (Cu²+ et Ni²+) par la 5-phénylazo-8-hydroxyquinoline (5Ph8HQ) et le cyclame greffés sur des nanoparticules de silice en suspension colloïdale." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10060/document.
Full textWe considered both the thermodynamic and kinetic aspects of metal ions (Cu2+ and Ni2+) complexation by 5-phenylazo-8-hydroxyquinoline (5Ph8HQ) and cyclam grafted onto silica nanoparticles in colloidal dispersion. Fumed silicas with specific areas of respectively 200 and 390 m2/g were selected to get stable colloidal suspensions. We demonstrated the ability of these colloids to extract trace elements (at micromolar level). We used the ultrafiltration process to separate the dispersed silica phase from the aqueous phase. We also showed interest of our solid dispersed phases instead of a pseudo micellar one. We described complexation kinetics by stopped flow technique for the fastest reactions. The influence of metal cation concentration, counter-ion nature (acetate or chloride), ionic strength and pH on observed rate constant has been investigated. To describe the Ni2+ kinetics with grafted 5Ph8HQ, we took into account the spectrophotometric properties of the complex on silica nanoparticles. This is an original behaviour of 5Ph8HQ on silica since the optical densities of solutions containing 5Ph8HQ solubilised in micelles or cyclam grafted onto silica follow the Beer-Lambert's law. The study of grafted cyclam whether the kinetics or equilibrium is complicated due to the release of the latter in solution
Malkin, Douglas Scott, and Douglas Scott Malkin. "An Investigation of a Novel Monolithic Chromatography Column, Silica Colloidal Crystal Packed Columns." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/193936.
Full textKrsmanovic, Jody Lynn. "Adsorption of Novel Block Copolymers for Steric Stabilization and Flocculation of Colloidal Particles in Aqueous Environments." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26029.
Full textPh. D.
Conlee, Carolyn T. Gallagher Patricia M. "Dynamic properties of colloidal silica soils using centrifuge model tests and a full-scale field test /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3248.
Full textHuang, Yuan. "STUDY OF PORE SIZE EFFECT IN CHROMATOGRAPHY BY VIBRATIONAL SPECTROSCOPY AND COLLOIDAL ARRAYS." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/196108.
Full textGiovannini, Giorgia. "Preparation of silica nanoparticles for biomedical applications : bacterial detection, oral drug delivery and colloidal stability." Thesis, University of Kent, 2017. https://kar.kent.ac.uk/66561/.
Full textGallagher, Patricia M. "Passive Site Remediation for Mitigation of Liquefaction Risk." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29610.
Full textPh. D.
Peterson, Alisha. "Understanding the Role of Colloidal Particles in Electroporation Mediated Delivery." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5823.
Full textJUSTICE, RYAN SCOTT. "SMALL-ANGLE SCATTERING FROM NANOCOMPOSITES: ELUCIDATION OF HIERARCHICAL MORPHOLOGY/PROPERTY RELATIONSHIPS." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1196088584.
Full textRemeš, Hynek. "Trvanlivost a sanace vnějších tepelně izolačních kompozitních systémů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-233786.
Full textBradbury, Andrew James. "A study of the effect of particle size polydispersity on the properties of concentrated aqueous colloidal silica suspensions." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240548.
Full textCromey, Tyler. "Effect of elevated temperature on ceramic ultrafiltration of colloidal suspensions." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51778.
Full textVenkataraman, Manoj. "THE EFFECT OF COLLOIDAL STABILITY ON THE HEAT TRANSFER CHARACTERISTICS OF NANOSILICA DISPERSED FLUIDS." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3656.
Full textM.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
Abbas, Khan Zaheer [Verfasser]. "Fabrication and characterisation of multilayer thin film using self assembly of colloidal gold and silica nanoparticles / Zaheer Abbas Khan." München : GRIN Verlag, 2016. http://d-nb.info/1180622979/34.
Full textGao, Weihong. "The fabrication of structurally coloured textile materials using uniform spherical silica nanoparticles." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-fabrication-of-structurally-coloured-textile-materials-using-uniform-spherical-silica-nanoparticles(c2815c09-5353-4667-a1a3-1b31b62f8787).html.
Full textBarek, Jaroslav. "Vliv koloidního oxidu křemičitého na vybrané vlastnosti cementových past a malt." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240488.
Full textCiardi, Giovanni [Verfasser], Joachim [Akademischer Betreuer] Stahlmann, and Claudia [Akademischer Betreuer] Madiai. "Effects of high-diluted colloidal silica mixtures on the mechanical behavior of potentially liquefiable sand / Giovanni Ciardi ; Joachim Stahlmann, Claudia Madiai." Braunschweig : Technische Universität Braunschweig, 2021. http://d-nb.info/122503826X/34.
Full textCiardi, Giovanni Verfasser], Joachim [Akademischer Betreuer] [Stahlmann, and Claudia [Akademischer Betreuer] Madiai. "Effects of high-diluted colloidal silica mixtures on the mechanical behavior of potentially liquefiable sand / Giovanni Ciardi ; Joachim Stahlmann, Claudia Madiai." Braunschweig : Technische Universität Braunschweig, 2021. http://d-nb.info/122503826X/34.
Full textQuant, Carlos Arturo. "Colloidal chemical potential in attractive nanoparticle-polymer mixtures: simulation and membrane osmometry." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7616.
Full textFrise, Anton. "Nano-segregated soft materials observed by NMR spectroscopy." Doctoral thesis, KTH, Fysikalisk kemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-30337.
Full textQC 20110225
Dorget, Michel. "Propriétés rhéologiques des composés silice/silicone." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10194.
Full textMannix, Oonagh. "Etude de complexes de nanoparticules et polysaccharides par diffusion de rayons X aux petits angles." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAV068.
Full textThe macroscopic properties and long-term stability of a colloidal suspension are controlled by its microstructure. Inter-particle interactions determine the microstructure and dynamics of the system. Colloidal systems are often metastable and so the inter-particle correlations can change with time (and so change the microstructure, and macroscopic properties of the system). As smaller colloidal particles can be used to form larger structures with different properties it is necessary to examine a system across various size scales.In this PhD thesis a combination of small and ultra-small angle x-ray scattering (U)SAXS and x-ray photon correlation spectroscopy (XPCS) techniques are used to investigate colloidal complexation across both time and space. Spatial scales from nanometers (si{nanometre}) to microns (si{micrometre}) and time scales from milliseconds (si{millisecond}) to months were examined to elucidate the formation pathway and structural evolution of the complexes. To uncover general mechanisms of broad relevance this work uses technical-grade, non-ideal materials. The study is on the complexation of silica nanoparticles and chitosan, a bio-sourced, cationic polysaccharide.First, a new description for scattering data of polydisperse silica nanoparticles using a fractal model is employed. An investigation into the small-angle scattering of chitosan by neutrons and x-rays, and static light scattering reveals significant differences that are not readily explained. The investigation of nanoparticle and polysaccharide complexes uses kinetic SAXS measurements to study the formation pathways of the complexes, with rapid mixing experiments to access shorter times (stopped-flow apparatus). Combined USAXS and SAXS data are analysed to provide information on the complex structure within a state diagram. Salt was removed from the system using dialysis, and the subsequent behaviour of the system was investigated. It was found that the behaviour of the dialysed system differed to the behaviour of the non-dialysed system over long timescales. In the dialysed system the growth of crystallites of colloidal silica was observed. These results, along with an investigation into the temperature dependency of the system lead to some understanding of the microstructure of this type of colloidal complex
Moura, Sérgio de Paula. "Bicamadas catiônicas em sílica: adsorção e estabilidade coloidal a baixa força iônica." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-20112006-014013/.
Full textThe study of adsorption of model-membranes on the surface of solid partic1es is an important line of research in rapidly developing research areas such as biosensors design, building up of immunological kits or design ofbiocompatible materiais. In this work, interactions between hidrophilic silica particles and cationic liposomes made up of dioctadecyldimethylammonium bromide (DODAB) were evaluated from a physicochemical point of view. The challenge of breaking open rigid bilayer vesicles upon contact with silica particles was circumvented by using a dioctadecyldimethylammonium bromide (DODAB) dispersion consisting of open, nanosized bilayer fragments instead of vesicles. At low ionic strength and pH 6.5, DODAB adsorption from bilayer fragments on silica was quantified from adsorption isotherms at 0, 0.1, 0.5,1.0 and 10.0 mM KCI. Adsorption increased as a function of KCI concentration and surface charge density on particles. Isotherms shape was typical of competitive adsorption with a maximum possibly due to hydrophobic attraction between adsorbed and free bilayer fragments. Upon adsorption as fiat patches on particles, the fragments did not apparently seal into a continuous and closed bilayer surrounding the particle, instead interacted via hydrophobic edges with free fragments in dispersion. At pH 6.5, over a range of DODAB (0 - 1.0mM) and KCI concentrations (0.1 - 10.0 mM), from particle sizing, zeta-potential analysis, photographs of the mixtures and particle sedimentation kinetics, colloid stability of particles in the mixtures was govemed by the ratio R of total surface areas for bilayers Ab and partic1es Ap, R= Ab/Ap. At R ~ 0.5, mean zeta-potential ( ζ ) was zero, mean particle diameter (Dz) was at maximum, sedimentation was rapid and colloid stability was at minimum; at R > 1, ζ was positive, Dz was minimized, sedimentation was absent and colloid stability was high. At low ionic strength ([KCI] < 10 mM), high colloid stability for particles in presence of cationic bilayer fragments was achieved at or above R=I, i.e., from the equivalence of total surface areas for bilayer fragments and particles.
Ogundare, Ojo Oluwaseun. "Optimization and Analysis of a Slow-Release Permanganate Gel for TCE Plume Treatment in Groundwater." Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou161797021188483.
Full textHubert, Céline. "Ingénierie de particules et assemblages à l’échelle colloïdale." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0185/document.
Full textThe synthesis and the assembly of colloidal particles with original morphology and functionality should allow the fabrication of next-generation materials. This study deals with the synthesis of hybrid silica/polystyrene particles by an emulsion polymerization of styrenes eeded by surface functionalized silica particles. These particles, made by a silica coredecorated by a controlled number of polystyrene nodules, has been used as templates for thesynthesis of goldnanocages morphologically controlled. Theses gold nanocages has been characterized structurally and optically. We have also investigated the self-assembly of hybrid silica/polystyrene particles by generating interaction between polystyrene nodules due to the control of the solvent quality for polystyrene. Particles with one polystyrene nodule self assemble in little clusters and particle with two nodules in chains
Paula, Amauri Jardim de 1984. "Produção de veículos moleculares à base de nanoestruturas de sílica porosa para carreamento de compostos hidrofóbicos." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249035.
Full textTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Partindo-se do método de Stöber, um elegante e eficiente processo de síntese de partículas coloidais de SiO2, adaptações foram feitas para que fosse possível produzir nanopartículas porosas (50-80 nm) com alto valor de área de superfície (~1000 m g), volume de poros (~1,5 m g) e alta estabilidade coloidal. As nanoestruturas são compostas de nanopartículas coloidais de sílica hierarquicamente funcionalizadas, com poros internos com estrutura desordenada e diâmetros que vão de 1,8 a 10 nanômetros, funcionalizados com grupos fenil, e superfície externa recoberta com grupos propilmetilfosfonato ionizáveis. A funcionalização hierárquica e quimicamente antagônica (hidrofóbica = poros internos; hidrofílica = superfície externa) permite que moléculas hidrofóbicas (baixa solubilidade em água) sejam facilmente incorporadas nas cavidades porosas hidrofóbicas, ao passo que as partículas se mantêm de forma estável dispersas em água por meses. Moléculas hidrofóbicas foram incorporadas pelas nanopartículas porosas de SiO2 em concentração de até 3% (m/m) através da mistura de suspensões coloidais aquosas desses nanomateriais e as moléculas insolúveis (pós). A capacidade de incorporação da molécula hidrofóbica em questão (camptotecina) foi significantemente maior que outros sistemas porosos de SiO2 que estão sendo atualmente usados. A eficiência dos veículos moleculares foi comprovada através do carreamento da camptotecina, um potente agente antitumoral que levou à inibição do crescimento de células leucêmicas humanas. Além disso, as abordagens sintéticas usadas nessa Tese também possibilitaram a funcionalização da superfície externa das nanopartículas com outros grupos orgânicos hidrofílicos e reativos, como o propilamina. Consequentemente, as características dessas nanopartículas de SiO2 aqui mostradas preenchem uma série de demandas científicas atuais: a necessidade de nanoestruturas porosas de sílica com ampla distribuição de tamanho de poro, com morfologia homogênea, estreita distribuição de tamanhos e com real dispersibilidade em água (coloidais). Assim, o conjunto de propriedades apresentado abre perspectivas envolvendo o uso desse sistema como uma plataforma tecnológica suscetível a várias aplicações, servindo como um veículo para dispersão e liberação de moléculas hidrofóbicas em meio aquoso
Abstract: Based on the Stöber method, an elegant and efficient process for synthesizing SiO2 colloidal nanoparticles, modifications were done in order to produce porous nanoparticles (50-80 nm) with high surface area (~1000 mg), volume of pores (~1,5 m g) and high colloidal stability. The nanostructures are made of hierarchically functionalized colloidal silica nanoparticles, with internal pores with disordered structure and diameters ranging from 1.8 to 10 nanometers, functionalized with phenyl groups; and external surface covered with ionizable propylmethylphosphonate groups. The hierarchical and chemically antagonistic functionalization (hydrophobic = internal pores; hydrophilic = external surface) allows hydrophobic molecules (low solubility in water) to be easily incorporated in the hydrophobic porous cavities, whereas particles maintain stably dispersed in water for months. Hydrophobic molecules were incorporated by the porous SiO2 nanoparticles in concentrations up to 3% (w/w) simply by mixing colloidal aqueous suspensions of these nanomaterials and insoluble molecules (powders). The uptake capacity for a specific hydrophobic molecule (camptothecin) was significantly higher than in other porous systems of SiO2 that have been currently used. The efficiency of the molecular vehicles was evidenced through the transportation of camptothecin, a potent antitumoral agent which led to the growth inhibition of human leukemic cells. Besides, the synthetic approach used in this thesis also made possible the functionalization of the external surface of nanoparticles with other hydrophilic and reactive organic groups, such as propylamine. Consequently, the characteristics of these SiO2 nanoparticles here shown fulfill several current scientific demands: necessity of porous silica nanostructures with a wide distribution of pore sizes, homogeneous morphology, narrow size distribution and real dispersibility in water (colloidal). Thereby, this set of properties opens up perspectives involving the use of this system as a technological platform susceptible to several applications, acting as a vehicle for the dispersion and liberation of hydrophobic molecules in aqueous media
Doutorado
Quimica Inorganica
Doutor em Ciências
Benoit, Florence. "Développement de cristaux photoniques par voie sol-gel pour des applications laser de puissance." Thesis, Tours, 2015. http://www.theses.fr/2015TOUR4029/document.
Full textThree-dimensional photonic crystals (PCs) are periodic materials with a modulated refractive index on a length scale close to the light wavelength. This optical property allows the preparation of specific optical components like highly reflective mirrors. Moreover, these structured materials might have a high laser-induced damage threshold (LIDT) in the sub-nanosecond range compared to multi-layered dielectric mirrors. This property is obtained because only one high LIDT material (silica) is used. In this work, we present the development of 3D PCs with narrow-sized colloidal silica particles, prepared by sol-gel process and deposited with Langmuir- Blodgett technique. Different syntheses routes have been investigated and compared regarding the optical properties of the PCs. A numerical model based on an ideal opal network including defect influence is used to explain these experimental results
Dieudonné, Xavier. "Etude d'empilements multicouches colloidaux préparés par voie sol-gel : propriétés optiques et mécaniques." Thesis, Tours, 2011. http://www.theses.fr/2011TOUR4022/document.
Full textMain optical deposition processes, physical vapor deposition or sol-gel, exhibit difficulties of achieving thick coatings (>1 µm) and to build multilayer stacks (dielectric mirrors, polarizers). For these reasons, we have studied the conditions to enable a significative increase of deposited sol-gel films thickness. Three main parameters have been evidenced enabling the control of the stacking ability : single layer deposited thickness, chemical interactions beetween nanoparticles and coating drying time. We have shown that these parameters depend on the sol composition and on deposition conditions (process) and that the microstructure of single material stacking is influenced. Optical and mechanical properties of sol-gel films have been studied and optimized regarding these different material and process parameters. For this reason, optical and mechanical characterization techniques have been specifically developed and can now be used for fragile and thin film characterization. In controlling all these parameters, it is now possible to prepare multilayer colloidal stack with high thicknesses enabling the fabrication of high-performance mirrors and polarizers
Enarsson, Lars-Erik. "Polyelectrolyte adsorption on oppositely charged surfaces - Conformation and adsorption kinetics." Licentiate thesis, Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4059.
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