Thèses sur le sujet « Shape controlled synthesis »

The work presented in this dissertation is a composite of experiments in the growth of gold nanoparticles with specific optical properties of interest. The goal is to synthesize these gold nanoparticles using soybean extract for not only shape control, but for propensity as a biocompatible delivery system. The optical properties of these nanoparticles has found great application in coloring glass during the Roman empire and, over the centuries, has grown into its own research field in applications of nanoparticulate materials. Many of the current functions include use in biological systems as biosensors and therapeutic applications, thus making biocompatibility a necessity. Current use of cetyltrimethylammonium bromide leads to rod-shaped gold nanoparticles, however, the stability of these gold nanoparticles does not endure for extended periods of time in aqueous media. In my research, two important components were found to be necessary for stable, anisotropic growth of gold nanoparticles. In the first experiments, it was found that bromide played a key role in shape control. Bromide exchange on the gold atoms led to specific packing of the growing crystals, allowing for two-dimensional growth of gold nanoparticles. It was also discerned that soybean lecithin contained ligands that blocked specific gold facets leading to prismatic gold nanoparticle growth. These gold nanoprisms give a near infrared plasmon absorption similar to that of rod-shaped gold nanoparticles. These gold nanoprisms are discovered to be extremely stable in aqueous media and remain soluble for extended periods of time, far longer than that of gold nanoparticles grown using cetyltrimethylammonium bromide. Since soy lecithin has a plethora of compounds present, it became necessary to discover which compound was responsible for the shape control of the gold nanoprisms in order to optimize the synthesis and allow for a maximum yield of the gold nanoprisms. Many of these components were identified by high performance liquid chromatography and liquid chromatography-mass spectrometry. However, re-spike of these components into growth solutions did not enhance the growth of gold nanoprisms. Upon separating the shapes of the gold nanoparticles using gel electrophoresis, addition of KCN to the separated gold nanoparticles allowed us to extract the culpable ligands for shape control. Analysis of these ligands by mass spectrometry elucidated the identity of PA and upon re-spike of the PA into a growth solution of PC95, the growth of a near-infrared plasmon absorption was seen. The stability of these gold nanoparticles was tested with and without the addition of decane thiol and it was concluded that addition of the thiol allowed for improved stability of the gold nanoparticles towards cyanide. It was determined that at a concentration of 2 μM decanethiol, spherical gold nanoparticles remained stable to cyanide at the expense of the prismatic gold nanoparticles. However, at 5 μM decanethiol, both spherical and prismatic gold nanoparticles retained stability to cyanide in aqueous conditions.

Mesoporous nanostructured materials are useful for a widespread field of applications, such as gas storage; selective molecular adsorption; confined chemical reactions and catalysis. In this work, periodic mesoporous silica and organosilica materials, thanks to their high surface area, narrow pore size distribution and high regular structure, have been exploited to obtain nanostructured porous materials with different chemical nature, such as polymer or carbon. Periodic mesoporous silica objects with defined micrometric shape have been obtained by template synthesis in aqueous medium. A change in synthesis condition of temperature, time and acidity leads to the generation of different shapes such as gyroids, spheres and hollow tubes. Mesoporous silica particles have been exploited for confined polymerization of different monomers (styrene, methylmethacrylate and acrylonitrile) to obtain morphological polymeric nanocomposites. The nanocomposite with polyacrylonitrile has been then heated at high temperature in non-oxidative atmosphere to induce polymer carbonization until the formation of a graphitic-like carbon structure. The silica matrix has been then removed by chemical etching to obtain nanostructured porous materials in polymer and graphitic-like carbon with high surface area and the same micrometric morphology of starting silica matrix (shape replica effect). Afterwards, a periodic mesoporous organosilica system, with phenylene groups directly linked in the wall structure and organized on the molecular scale, has been synthesised, exploited as selective gas adsorption system and heated in non-oxidative atmosphere to obtain a new mesoporous carbon material with high surface area, very regular mesoporous structure and graphitic-like pore walls. Characterization of these materials has been conduced with X-ray diffraction, calorimetric techniques (DSC and TGA), adsorption of gases and vapours and advanced mono- and bi-dimensional NMR experiments to investigate the interaction between the organic and the inorganic moieties. Thermal evolutions of polyacrylonitrile and phenylene-organosilica have been studied with spectroscopic techniques of ATR and Raman, while the shape replica effect and the high regular pore structure have been directly seen with SEM and TEM microscopies.

Size and Shape Controlled Synthesis and Superparamagnetic Properties of Spinel Ferrites Nanocrystals Qing Song 216 pages Directed by Dr. Z. John Zhang The correlationship between magnetic properties and magnetic couplings is established through the investigations of various cubic spinel ferrite nanocrystals. The results of this thesis contribute to the knowledge of size and shape controlled synthesis of various spinel ferrites and core shell architectured nanocrystals as well as the nanomagnetism in spinel ferrites by systematically investigating the effects of spin orbital coupling, magnetocrystalline anisotropy, exchange coupling, shape and surface anisotropy upon superparamagnetic properties of spinel ferrite nanocrystals. A general synthetic method is developed for size and shape control of metal oxide nanocrystals. The size and shape dependent superparamagnetic properties are discussed. The relationship between spin orbital coupling and magnetocrystalline anisotropy is studied comparatively on variable sizes of spherical CoFe2O4 and Fe3O4 nanocrystals. It also addresses the effect of exchange coupling between magnetic hard phase and soft phase upon magnetic properties in core shell structured spinel ferrite nanocrystals. The role of anisotropic shapes of nanocrystals upon self assembled orientation ordered superstructures are investigated. The effect of thermal stability of molecular precursors upon size controlled synthesis of MnFe2O4 nanocrystals and the size dependent superparamagnetic properties are described.

Le contrôle de la taille et de la morphologie de nanocristaux d’oxydes métalliques simples, d’oxydes mixtes et d’oxydes métalliques hybrides est un sujet de grand intérêt. La dépendance de leur propriétés physio-chimiques avec leurs taille et morphologies, génèrent une variété de leur applications dans plusieurs domaines. Cependant, le dévellopement des nanocristaux en controllant la taille, la forme, l’assemblage et l’homogénéité de la composition chimique pour l’optimisation de propriété spécifiques demandent la combinaison de nombreux parametres de synthèse. Les trois différentes approches ont été développées dans le cadre de la thèse pour la synthèse d’une variété de nouveaux nanomatériaux d’oxydes simples, d’oxydes mixtes et d’oxydes métalliques hybrides dont la taille et la forme ont été bien controllées. Ces méthodes ont été nommées comme des méthodes solvo-hydrothermiques assistées par des molécules structurantes à l’état monophasique (eau ou eau/éthanol) et à l’état biphasique (eau-toluène). Nos approches de synthèse ont permi de préparer des nanocristaux des oxydes de métaux de transition (V, Cr, Mn, Co, Ni, In), et des terres rares (Sm, Ce, La, Gd, Er, Ti, Y, Zr), ainsi que des oxydes métalliques mixtes (tungstate, orthovanadate, molybdate). Ces nanomatériaux sont sous forme colloïdale mono-dispersée qui présente une cristallinité élevée. La taille et la forme de tels nanocristaux peuvent facilement être contrôlées par une simple variation des paramètres de synthèse telle que la concentration de précurseurs, la nature de la molécule structurante, la température et le temps de réaction. A large variété de techniques a été utilisée pour la caracterisation de ces nanomatériaux telles que TEM/HRTEM, SEM, SAED, EDS, XRD, XPS, FTIR, TGA-DTA, UV-vis, photoluminescence, BET. Les propriétés catalytiques de ces matériaux ont aussi été étudiées. Dans ce travail, le contrôle de la cinétique de croissance des nucléides ainsi que le mécanisme gouvernant la forme qui conduit à la taille et la morphologie finale du nanocrystal ont été proposé. L’effet de la taille et de la forme des nanoparticules d’oxyde métallique hybrides sur les propriétés catalytiques pour la réaction d’oxydation du CO et la photo-dégradation du bleue de méthylène a été aussi étudié. Car les catalyseurs existant actuellement à base de métaux nobles sont très couteux et en plus très sensibles à l’empoisonnement par le gas H2S ou les émissions polluantes de SOx. L’activité catalytique des nanocristaux d’oxydes métallique hybrides Cu@CeO2 de formes cubiques dans l’oxydation de CO et de Ag@TiO2 de formes de ceinture dans la photo dégradation du bleue de méthylène ont montré la dépendance de la taille et la forme des nanocristaux avec leur propriétés catalytiques.
The ability to finely control the size and shape of metal oxide, mixed metal oxide, hybrid metal/oxide nanocrystals has become an area of great interest, as many of their physical and chemical properties are highly dependent on morphology, and the more technological applications will be possible for their use. Large-scale synthesis of such high-quality nanocrystals is the first and key step to this area of science. A tremendous effort has recently been spent in attempt to control these novel properties through manipulation of size, shape, structure, and composition. Flexibly nanocrystal size/shape control for both monodisperse single and multiple-oxide nanomaterial systems, however, remains largely empirical and still presents a great challenge. In this dissertation, new synthetic approaches have been developed and described for the synthetic design of a series of colloidal monodisperse metal oxide, mixed metal oxide, hybrid metal-oxide nanocrystals with controlled size and shape. These materials were generally characterized using TEM/HRTEM, SEM, SAED, EDS, XRD, XPS, FTIR, TGA-DTA, UV-vis, photoluminescence, BET techniques. Effect of the size and shape of these obtained hybrid metal-oxide nanocrystals on the catalytic properties is illustrated. We have developed three different new surfactant-assistant pathways for the large-scale synthesis of three types of nanomaterials including metal oxide, mixed metal oxide, hybrid noble-metal-oxide colloidal monodisperse nanocrystals. Namely, the solvo-hydrothermal surfactant-assisted methods in one-phase (water or water/ethanol) and two-phase (water-toluene) systems were used for the synthesis of metal oxide (transition metal-V, Cr, Mn, Co, Ni, In and rare earth-Sm, Ce, La, Gd, Er, Ti, Y, Zr) and mixed metal oxide (tungstate, orthovanadate, molybdate). The seed-media growth with the assistant of bifunctional surfactant was used for the synthesis of hybrid noble metal@oxide (Ag@TiO2, (Cu or Ag)@CeO2, Au/tungstate, Ag/molybdate, etc.) nanocrystals. A significant feature of our synthetic approaches was pointed out that most resulting nanocrystal products are monodisperse, high crystallinity, uniform shape, and narrow distribution. The size and shape of such nanocrystals can be controlled easily by simple tuning the reaction parameters such as the concentration of precursors and surfactants, the nature of surfactant, the temperature and time of synthetic reaction. The prepared nanocrystals with the functional surface were used as the building blocks for the self-assembly into hierarchical mesocrystal microspheres. The effective ways how to control the growth kinetics of the nuclei and the shape-guiding mechanisms leading to the manipulation of morphology of final products were proposed. Our current approaches have several conveniences including used nontoxic and inexpensive reagents (most using inorganic metal salts as starting precursors instead of expensive and toxic metallic alkoxides or organometallics), relatively mild conditions, high-yield, and large-scale production; in some causes, water or ethanol was used as environmentally benign reaction solvent. Catalytic activity and selectivity are governed by the nature of the catalyst surface, making shaped nanocrystals ideal substrates for understanding the influence of surface structure on heterogeneous catalysis at the nanoscale. Finally, this work was concentrated on demonstration of heterogeneous catalytic activity of hybrid metal-oxide nanomaterials (Cu@CeO2, Ag@TiO2) as a typical example. We synthesized the high-crystalline titanium oxide and cerium oxide nanocrystals with control over their shape and surface chemistry in high yield via the aqueous surfactant-assist method. The novel hybrid metal-oxide nanocrystals were produced by the depositing noble metal ion (Cu, Ag, Au) precursors on the pre-synthesized oxide seeds via seed-mediated growth. The catalytic activity of these metal-oxide nanohybrids of Cu@CeO2 nanocubes for CO oxidation conversion and Ag@TiO2 nanobelts for Methylene Blue photodegradation with size/shape-dependent properties were verified.

Le contrôle de la taille et de la morphologie de nanocristaux d’oxydes métalliques simples, d’oxydes mixtes et d’oxydes métalliques hybrides est un sujet de grand intérêt. La dépendance de leur propriétés physio-chimiques avec leurs taille et morphologies, génèrent une variété de leur applications dans plusieurs domaines. Cependant, le dévellopement des nanocristaux en controllant la taille, la forme, l’assemblage et l’homogénéité de la composition chimique pour l’optimisation de propriété spécifiques demandent la combinaison de nombreux parametres de synthèse. Les trois différentes approches ont été développées dans le cadre de la thèse pour la synthèse d’une variété de nouveaux nanomatériaux d’oxydes simples, d’oxydes mixtes et d’oxydes métalliques hybrides dont la taille et la forme ont été bien controllées. Ces méthodes ont été nommées comme des méthodes solvo-hydrothermiques assistées par des molécules structurantes à l’état monophasique (eau ou eau/éthanol) et à l’état biphasique (eau-toluène). Nos approches de synthèse ont permi de préparer des nanocristaux des oxydes de métaux de transition (V, Cr, Mn, Co, Ni, In), et des terres rares (Sm, Ce, La, Gd, Er, Ti, Y, Zr), ainsi que des oxydes métalliques mixtes (tungstate, orthovanadate, molybdate). Ces nanomatériaux sont sous forme colloïdale mono-dispersée qui présente une cristallinité élevée. La taille et la forme de tels nanocristaux peuvent facilement être contrôlées par une simple variation des paramètres de synthèse telle que la concentration de précurseurs, la nature de la molécule structurante, la température et le temps de réaction. A large variété de techniques a été utilisée pour la caracterisation de ces nanomatériaux telles que TEM/HRTEM, SEM, SAED, EDS, XRD, XPS, FTIR, TGA-DTA, UV-vis, photoluminescence, BET. Les propriétés catalytiques de ces matériaux ont aussi été étudiées. Dans ce travail, le contrôle de la cinétique de croissance des nucléides ainsi que le mécanisme gouvernant la forme qui conduit à la taille et la morphologie finale du nanocrystal ont été proposé. L’effet de la taille et de la forme des nanoparticules d’oxyde métallique hybrides sur les propriétés catalytiques pour la réaction d’oxydation du CO et la photo-dégradation du bleue de méthylène a été aussi étudié. Car les catalyseurs existant actuellement à base de métaux nobles sont très couteux et en plus très sensibles à l’empoisonnement par le gas H2S ou les émissions polluantes de SOx. L’activité catalytique des nanocristaux d’oxydes métallique hybrides Cu@CeO2 de formes cubiques dans l’oxydation de CO et de Ag@TiO2 de formes de ceinture dans la photo dégradation du bleue de méthylène ont montré la dépendance de la taille et la forme des nanocristaux avec leur propriétés catalytiques.
The ability to finely control the size and shape of metal oxide, mixed metal oxide, hybrid metal/oxide nanocrystals has become an area of great interest, as many of their physical and chemical properties are highly dependent on morphology, and the more technological applications will be possible for their use. Large-scale synthesis of such high-quality nanocrystals is the first and key step to this area of science. A tremendous effort has recently been spent in attempt to control these novel properties through manipulation of size, shape, structure, and composition. Flexibly nanocrystal size/shape control for both monodisperse single and multiple-oxide nanomaterial systems, however, remains largely empirical and still presents a great challenge. In this dissertation, new synthetic approaches have been developed and described for the synthetic design of a series of colloidal monodisperse metal oxide, mixed metal oxide, hybrid metal-oxide nanocrystals with controlled size and shape. These materials were generally characterized using TEM/HRTEM, SEM, SAED, EDS, XRD, XPS, FTIR, TGA-DTA, UV-vis, photoluminescence, BET techniques. Effect of the size and shape of these obtained hybrid metal-oxide nanocrystals on the catalytic properties is illustrated. We have developed three different new surfactant-assistant pathways for the large-scale synthesis of three types of nanomaterials including metal oxide, mixed metal oxide, hybrid noble-metal-oxide colloidal monodisperse nanocrystals. Namely, the solvo-hydrothermal surfactant-assisted methods in one-phase (water or water/ethanol) and two-phase (water-toluene) systems were used for the synthesis of metal oxide (transition metal-V, Cr, Mn, Co, Ni, In and rare earth-Sm, Ce, La, Gd, Er, Ti, Y, Zr) and mixed metal oxide (tungstate, orthovanadate, molybdate). The seed-media growth with the assistant of bifunctional surfactant was used for the synthesis of hybrid noble metal@oxide (Ag@TiO2, (Cu or Ag)@CeO2, Au/tungstate, Ag/molybdate, etc.) nanocrystals. A significant feature of our synthetic approaches was pointed out that most resulting nanocrystal products are monodisperse, high crystallinity, uniform shape, and narrow distribution. The size and shape of such nanocrystals can be controlled easily by simple tuning the reaction parameters such as the concentration of precursors and surfactants, the nature of surfactant, the temperature and time of synthetic reaction. The prepared nanocrystals with the functional surface were used as the building blocks for the self-assembly into hierarchical mesocrystal microspheres. The effective ways how to control the growth kinetics of the nuclei and the shape-guiding mechanisms leading to the manipulation of morphology of final products were proposed. Our current approaches have several conveniences including used nontoxic and inexpensive reagents (most using inorganic metal salts as starting precursors instead of expensive and toxic metallic alkoxides or organometallics), relatively mild conditions, high-yield, and large-scale production; in some causes, water or ethanol was used as environmentally benign reaction solvent. Catalytic activity and selectivity are governed by the nature of the catalyst surface, making shaped nanocrystals ideal substrates for understanding the influence of surface structure on heterogeneous catalysis at the nanoscale. Finally, this work was concentrated on demonstration of heterogeneous catalytic activity of hybrid metal-oxide nanomaterials (Cu@CeO2, Ag@TiO2) as a typical example. We synthesized the high-crystalline titanium oxide and cerium oxide nanocrystals with control over their shape and surface chemistry in high yield via the aqueous surfactant-assist method. The novel hybrid metal-oxide nanocrystals were produced by the depositing noble metal ion (Cu, Ag, Au) precursors on the pre-synthesized oxide seeds via seed-mediated growth. The catalytic activity of these metal-oxide nanohybrids of Cu@CeO2 nanocubes for CO oxidation conversion and Ag@TiO2 nanobelts for Methylene Blue photodegradation with size/shape-dependent properties were verified.

Les composés à réseau moléculaire organo-métalliques (MOFs) ont émergé comme de nouvelles classes de matériaux hybrides organo-inorganiques avec des potentialités significatives en séparation, stockage de gaz, catalyse et support de médicaments. Ces matériaux sont formés par un processus d’assemblage dans lequel les ions métalliques sont liés entre eux via un ligand organique, ce qui génère une surface de l’ordre de 6500 m2g−1 et des volumes de pores supérieurs à 4.3 cm3g−1. Dans cette thèse trois différentes approches ont été développées pour la synthèse des nanocristaux MOFs à deux modes micro-mésoporeux, ainsi que des nanocristaux MOFs à taille et forme contrôlable. En plus, ces nanocristaux MOFs ont été utilisé comme un agent structurant pour la synthèse de nanocomposite hybride platine-oxyde de titane (metal-oxide-TiO2-PtOx) qui ont été utilisé comme photocatalyseurs pour la production d’hydrogène à partir de l’eau sous la lumière visible. Dans ce travail: (i) La première approche implique une méthode utilisant un surfactant, suivi de traitement solvo-thermale en présence d’acide acétique pour former des nanocristaux MOFs micro-mésoporeux. L’utilisation de surfactant non-ionique tell que F127 (EO97PO69EO97) pour induire une structure mésoporeuse provoque labilité de la cristallisation du mur des pores de la structure MOF. Tandis que la présence de l’acide acétique contrôle la vitesse de cristallisation du réseau MOFs pour former une mésostructure bien définie à l’intérieur des nanocristaux MOFs. En utilisant cette approche des nanocristaux de [Cu3(BTC)2] et [Cu2(HBTB)2] de structure mésoporeuse avec des diamètres de pores autour de 4.0 nm et des micropores intrinsèques ont été synthétisés. (ii) La méthodologie de modulation de la coordination a été développée pour contrôler la forme et la taille des nanocristaux MOFs. Des nanocubes et nanofeuilles de [Cu2(ndc)2(dabco)]n de la structure MOFs ont été synthétisés en utilisant simultanément l’acide acétique et la pyridine ou la pyridine uniquement, respectivement comme modulateurs sélectifs. Ces nanocristaux MOFs possèdent une cristallinité élevée et une grande capacité d’adsorption. La morphologie a été aussi étudiée en fonction de la capacité d’adsorption de CO2. (iii) La synthèse hydrothermale en contrôlant la taille de nanocristaux de carboxylates de structure MOFs, en utilisant simultanément des réactifs stabilisants et des réactifs contrôlant la déprotonation a été démontrée. Dans le cas de Fe-MIL-88B-NH2, la molécule triblock copolymer a été utilisée comme un réactif stabilisant en coordonnant avec le métal et contrôlant la croissance en formant des nanocristaux. L’acide acétique joue le rôle comme un agent déprotonant des liants carboxyliques en variant sa concentration dans le milieu réactionnel, ainsi il régule la vitesse de nucléation, conduisant à aussi contrôler la taille ainsi que le rapport longueur/largeur des nanocristaux. (iv) Finalement, des nanocomposites hybrides Fe2O3-TiO2-PtOx de forme creuse possédant l’activité photocatalytique performante ont été développés en utilisant des nanocristaux Fe-MIL-88B composés de centres Fe3(μ3-O) liés par coordination insaturée comme template solide. Ce type de nanocomposites non seulement absorbe la lumière visible mais aussi améliore la séparation des électrons et des trous photo-générés, due à l’épaisseur de paroi mince et les deux co-catalyseurs (Fe2O3 and PtOx) localisés sur deux opposites surfaces du creux. En conséquence, l'efficacité en photocatalyse de ce type de nanocomposites est élevée pour la production d'H2 à partir de l'eau sous la lumière visible.
Metal-organic frameworks (MOFs) have emerged as an important new class of porous inorganic-organic hybrid solids with the potential for a significant impact on separation, gas storage, catalysis and biomedicine. These materials are formed by assembly process in which metal ions are linked together by rigid organic ligands, which creates enormous surface areas (up to 6500 m2g−1) and high pore volumes (up to 4.3 cm3g−1). In this thesis, three different synthetic approaches have been developed to achieve bimodal micro/mesoporous MOF nanocrystals as well as nanosized MOFs with controlled size and shape. In addition, using the synthesized MOF nanocrystals as templates, a new hollow hybrid metal-oxide-TiO2-PtOx nanocomposite has also been prepared, and used as the visible-light driven photocatalyst for the hydrogen production from water. In this work, (i) the first approach involves nonionic surfactant-templated solvothermal synthesis in the presence of acetic acid toward hierarchically micro-mesoporous MOF nanocrystals. The use of a nonionic surfactant such as F127 (EO97PO69EO97) as mesostructure template induces the ability to crystallize a MOF structure of pore wall, while the presence of acetic acid allows control of the crystallization rate of the framework to form well-defined mesostructures within the crystalline MOF nanocrystals. Using this approach, [Cu3(BTC)2] and [Cu2(HBTB)2]-based MOF nanocrystals containing mesopores with diameter around 4.0 nm and intrinsic micropores have been successfully synthesized. (ii) Secondly, the coordination modulation methodology has been developed to control shape and size of MOF crystals at the nanoscale. Nanocubes and nanosheets of [Cu2(ndc)2(dabco)]n MOF have been rationally synthesized by using simultaneously acetic acid and pyridine or only pyridine, respectively, as selective modulators. These MOF nanocrystals exhibit high crystallinity and high CO2 sorption capacity. Their morphology-dependent CO2 sorption property has also been demonstrated. (iii) Thirdly, the size-controlled hydrothermal synthesis of uniform carboxylate-based MOF nanocrystals using simultaneously stabilizing reagent and deprotonation-controlled reagent has been demonstrated. In case of Fe-MIL-88B-NH2, the molecular triblock copolymers as stabilizing reagents coordinate with the metal ions and thus stabilize nuclei, which suppress the crystal growth to form nanocrystals. Acetic acid as deprotonation-controlled reagent adjusts the deprotonation of the carboxylic linker via varying its concentration in the reaction mixture, and thus regulates the rate of nucleation, leading to tailoring the size and aspect ratio (length/width) of the nanocrystals. (iv) Finally, a new hollow hybrid metal-oxide-TiO2-PtOx nanocomposite as an efficient photocatalyst has been developed by using iron-based MIL-88B nanocrystals consisting of coordinatively unsaturated Fe3(μ3-O) clusters as template. The hollow nanocomposite not only absorbs visible light, but also enhances the separation between photogenerated electrons and holes because of its thin wall and the surface separation of two distinct functional cocatalysts (Fe2O3 and PtOx) on two different surface sides of the hollow. As a result, the efficient photoactivity of the nanocomposite photocatalysts has been found for the H2 production from water under visible light irradiation.

Les composés à réseau moléculaire organo-métalliques (MOFs) ont émergé comme de nouvelles classes de matériaux hybrides organo-inorganiques avec des potentialités significatives en séparation, stockage de gaz, catalyse et support de médicaments. Ces matériaux sont formés par un processus d’assemblage dans lequel les ions métalliques sont liés entre eux via un ligand organique, ce qui génère une surface de l’ordre de 6500 m2g−1 et des volumes de pores supérieurs à 4.3 cm3g−1. Dans cette thèse trois différentes approches ont été développées pour la synthèse des nanocristaux MOFs à deux modes micro-mésoporeux, ainsi que des nanocristaux MOFs à taille et forme contrôlable. En plus, ces nanocristaux MOFs ont été utilisé comme un agent structurant pour la synthèse de nanocomposite hybride platine-oxyde de titane (metal-oxide-TiO2-PtOx) qui ont été utilisé comme photocatalyseurs pour la production d’hydrogène à partir de l’eau sous la lumière visible. Dans ce travail: (i) La première approche implique une méthode utilisant un surfactant, suivi de traitement solvo-thermale en présence d’acide acétique pour former des nanocristaux MOFs micro-mésoporeux. L’utilisation de surfactant non-ionique tell que F127 (EO97PO69EO97) pour induire une structure mésoporeuse provoque labilité de la cristallisation du mur des pores de la structure MOF. Tandis que la présence de l’acide acétique contrôle la vitesse de cristallisation du réseau MOFs pour former une mésostructure bien définie à l’intérieur des nanocristaux MOFs. En utilisant cette approche des nanocristaux de [Cu3(BTC)2] et [Cu2(HBTB)2] de structure mésoporeuse avec des diamètres de pores autour de 4.0 nm et des micropores intrinsèques ont été synthétisés. (ii) La méthodologie de modulation de la coordination a été développée pour contrôler la forme et la taille des nanocristaux MOFs. Des nanocubes et nanofeuilles de [Cu2(ndc)2(dabco)]n de la structure MOFs ont été synthétisés en utilisant simultanément l’acide acétique et la pyridine ou la pyridine uniquement, respectivement comme modulateurs sélectifs. Ces nanocristaux MOFs possèdent une cristallinité élevée et une grande capacité d’adsorption. La morphologie a été aussi étudiée en fonction de la capacité d’adsorption de CO2. (iii) La synthèse hydrothermale en contrôlant la taille de nanocristaux de carboxylates de structure MOFs, en utilisant simultanément des réactifs stabilisants et des réactifs contrôlant la déprotonation a été démontrée. Dans le cas de Fe-MIL-88B-NH2, la molécule triblock copolymer a été utilisée comme un réactif stabilisant en coordonnant avec le métal et contrôlant la croissance en formant des nanocristaux. L’acide acétique joue le rôle comme un agent déprotonant des liants carboxyliques en variant sa concentration dans le milieu réactionnel, ainsi il régule la vitesse de nucléation, conduisant à aussi contrôler la taille ainsi que le rapport longueur/largeur des nanocristaux. (iv) Finalement, des nanocomposites hybrides Fe2O3-TiO2-PtOx de forme creuse possédant l’activité photocatalytique performante ont été développés en utilisant des nanocristaux Fe-MIL-88B composés de centres Fe3(μ3-O) liés par coordination insaturée comme template solide. Ce type de nanocomposites non seulement absorbe la lumière visible mais aussi améliore la séparation des électrons et des trous photo-générés, due à l’épaisseur de paroi mince et les deux co-catalyseurs (Fe2O3 and PtOx) localisés sur deux opposites surfaces du creux. En conséquence, l'efficacité en photocatalyse de ce type de nanocomposites est élevée pour la production d'H2 à partir de l'eau sous la lumière visible.
Metal-organic frameworks (MOFs) have emerged as an important new class of porous inorganic-organic hybrid solids with the potential for a significant impact on separation, gas storage, catalysis and biomedicine. These materials are formed by assembly process in which metal ions are linked together by rigid organic ligands, which creates enormous surface areas (up to 6500 m2g−1) and high pore volumes (up to 4.3 cm3g−1). In this thesis, three different synthetic approaches have been developed to achieve bimodal micro/mesoporous MOF nanocrystals as well as nanosized MOFs with controlled size and shape. In addition, using the synthesized MOF nanocrystals as templates, a new hollow hybrid metal-oxide-TiO2-PtOx nanocomposite has also been prepared, and used as the visible-light driven photocatalyst for the hydrogen production from water. In this work, (i) the first approach involves nonionic surfactant-templated solvothermal synthesis in the presence of acetic acid toward hierarchically micro-mesoporous MOF nanocrystals. The use of a nonionic surfactant such as F127 (EO97PO69EO97) as mesostructure template induces the ability to crystallize a MOF structure of pore wall, while the presence of acetic acid allows control of the crystallization rate of the framework to form well-defined mesostructures within the crystalline MOF nanocrystals. Using this approach, [Cu3(BTC)2] and [Cu2(HBTB)2]-based MOF nanocrystals containing mesopores with diameter around 4.0 nm and intrinsic micropores have been successfully synthesized. (ii) Secondly, the coordination modulation methodology has been developed to control shape and size of MOF crystals at the nanoscale. Nanocubes and nanosheets of [Cu2(ndc)2(dabco)]n MOF have been rationally synthesized by using simultaneously acetic acid and pyridine or only pyridine, respectively, as selective modulators. These MOF nanocrystals exhibit high crystallinity and high CO2 sorption capacity. Their morphology-dependent CO2 sorption property has also been demonstrated. (iii) Thirdly, the size-controlled hydrothermal synthesis of uniform carboxylate-based MOF nanocrystals using simultaneously stabilizing reagent and deprotonation-controlled reagent has been demonstrated. In case of Fe-MIL-88B-NH2, the molecular triblock copolymers as stabilizing reagents coordinate with the metal ions and thus stabilize nuclei, which suppress the crystal growth to form nanocrystals. Acetic acid as deprotonation-controlled reagent adjusts the deprotonation of the carboxylic linker via varying its concentration in the reaction mixture, and thus regulates the rate of nucleation, leading to tailoring the size and aspect ratio (length/width) of the nanocrystals. (iv) Finally, a new hollow hybrid metal-oxide-TiO2-PtOx nanocomposite as an efficient photocatalyst has been developed by using iron-based MIL-88B nanocrystals consisting of coordinatively unsaturated Fe3(μ3-O) clusters as template. The hollow nanocomposite not only absorbs visible light, but also enhances the separation between photogenerated electrons and holes because of its thin wall and the surface separation of two distinct functional cocatalysts (Fe2O3 and PtOx) on two different surface sides of the hollow. As a result, the efficient photoactivity of the nanocomposite photocatalysts has been found for the H2 production from water under visible light irradiation.

Esta Tesis doctoral está enfocada en la síntesis de nanopartículas de platino (Pt) con forma controlada para la oxidación de amoniaco, un compuesto que puede ser utilizado como combustible para pila de combustibles y que asegura varios beneficios incluyendo cero emisiones de CO2, la posibilidad de la obtención de tecnología inspirada en el reciclaje de aguas residuales y sensores de amoniaco. Teniendo en cuenta estos beneficios, diversas investigaciones se han enfocado el estudio de los catalíticos más activos para la oxidación de amoniaco y han encontrado que las nanopartículas de Pt preferencialmente cúbicas son la que mayor actividad catalítica presentan. Sin embargo, desde un punto de vista aplicado, todavía faltan metodologías fáciles, baratas y escalables. Durante los últimos años, se ha trabajado, en esta Tesis Doctoral, la síntesis, caracterización y determinación de la actividad catalítica de las nanopartículas de Pt con formas preferenciales. La innovación en este trabajo ha sido en el método de síntesis que consiste en una microemulsión de agua en aceite, con la peculiaridad de agregar ácidos como agentes modificadores de la estructura. En este trabajo se ha propuesto hallar una alternativa que cumpla con la posibilidad de que puedan sintetizarse nanopartículas a gran escala para poder introducirlas en aplicaciones comerciales. En el primer trabajo publicado, se utilizaron distintas concentraciones de HCI en la fase acuosa de la microemulsión para estudiar el efecto modificado, de dicho compuesto. En este artículo, se reportó por primera vez, la síntesis de nanopartículas de platino preferencialmente cúbicas, utilizando el método de microemulsión de agua en aceite que, a diferencia de los métodos más conocidos, esta puede ser escalable. Este control de la forma / estructura de la superficie está determinado por la concentración de HCI en la fase acuosa de la microemulsión. Los resultados demostraron que el porcentaje óptimo de HCI fue aproximadamente 25% con la cual se logró obtener la mayor concentración de nanoestructuras de Pt preferencialmente cúbicas. Los resultados mostraron que las nanopartículas de Pt cúbicas preferenciales sintetizadas eran el mejor catalizador para la oxidación del amoniaco. El segundo artículo publicado abarca la síntesis de (100) nanopartículas de Pt de orientación preferencial, con un tamaño de partícula de aproximadamente 9 nanómetros, mediante el uso del mismo método de síntesis, pero en este caso, la estructura de las nanopartículas fue inducida con la presencia de H2SO4 en la fase acuosa de la microemulsión. Los resultados informados en este artículo mostraron como grandes cantidades de H2SO4 (hasta un 25%) conducen a la formación de nanopartículas de Pt que contienen una mayor cantidad de (100) sitios en su superficie y consecuentemente una forma preferencialmente cúbica. En la tercera publicación, también se utilizó la microemulsión de agua en aceite, pero en presencia de varios modificadores y precursores metálicos para obtener nanopartículas de Pt con orientación preferencial. Las nanopartículas cúbicas enriquecidas en sitios (100), se prepararon utilizando concentraciones específicas de HCI, HBr, H2S04 y H3PQ4. En cuanto a la utilización de ácido cítrico y oxálico como agentes modificadores, un aumento en la cantidad de (111) sitios, fue reportada. Esta faceta es más característico en nanopartículas con estructura octahedral. Las nanopartículas se caracterizaron electroquímicamente con adsorción/desorción de hidrógeno y germanio, así como por adsorción de CO. Finalmente, se evaluó la actividad electrocatalítica de las nanopartículas con el mayor porcentaje de sitios (100) para determinar la oxidación de amoniaco, lo que confirmó los resultados de la caracterización electroquímica. Las nanopartículas de Pt modificadas con HCI al 15% y sintetizadas utilizando K2PtCl4 como el precursor de Pt, mostraron Ia mayor cantidad de sitios (100) (46.7%) y obtuvieron una actividad catalítica más alta sobre la oxidación de amoníaco. De los trabajos no publicados, se han obtenido resultados interesantes incluyendo la síntesis de nanopartículas bimetálicas Pt/Rh de forma controlada utilizando el método similar al utilizado para la síntesis de las nanopartículas de Pt preferencialmente cúbicas. Las nanopartículas que se sintetizaron Pt75/Rh25 y Pt90/Rh10 con 20% de HCI en la fase acuosa, mostraron una actividad superior para la oxidación del etanol con mayor densidad de corriente y un desplazamiento del potencial de inicio a potenciales más bajos. En cuanto a la actividad catalítica presentada para la oxidación de amoníaco, las nanopartículas todas las nanopartículas Pt/Rh sintetizadas, presentaron una disminución en la actividad catalítica, sin embargo, hubo mejoras en el desplazamiento del potencial de inicio con valores menos positivos, para las muestras Pt75/Rh25 y Pt90/Rh10. La caracterización de superficie determinada por el análisis del microscopio de transmisión de electrones (TEM) y dispersión de electrones por rayo X (EDX), confirmó la modificación estructural por la presencia de los ácidos. Las imágenes TEM de las nanopartículas tenían una estructura preferencialmente cúbica. El análisis por EDX confirmó que la composición de cada uno de los metales en las de las nanoestructuras bimetálicas fue cercano a los valores con los que se prepararon las nanopartículas experimentalmente. De este trabajo se propone la realización de una nueva publicación. Finalmente, un estudio preliminar con monocristales de Pt fue realizado para explicar el efecto de los cloruros en inducir la formación de estructuras de Pt preferencialmente cúbicas en la síntesis de microemulsión agua en aceite. Para la realización de estos experimentos se tomaron los monocristales de Pt con planos de base [Pt (100), Pt (111) y Pt (110)] y Pt poliorientado [Pt(poly)]. En este estudio se pudo realizar un análisis del comportamiento electroquímico de los monocristales de Pt en concentraciones elevadas tanto de HCI como de H2S04. Sin embargo, pese a los distintos experimentos realizados, este estudio requiere de más investigación para poder llegar a conclusiones que den lugar al objetivo del estudio. Por último, en esta Tesis Doctoral se destacan varias colaboraciones, científicas realizadas con el propósito de determinar el rendimiento catalítico del material preparado. La primera colaboración ha sido con el grupo de investigación Micro-G que también es dirigido por mi director en la Universidad de Puerto Rico, el Dr. Carlos cabrera. En este proyecto, colaboramos con la preparación del catalizador para aumentar el rendimiento en las densidades de corriente de la oxidación de amoníaco en condiciones de microgravedad. Las medidas cronoamperométricas se realizaron durante 30 parábolas en el avión C9 de la NASA conocido como 'The Weightless Wonder', en enero de 2016 desde Ellington Field en Houston, Texas. Una publicación en la revista 'Microgravity Science and Technology' en 2017 fue producto de dicha colaboración. Otra colaboración realizada fue la preparación de electrodos para la determinación del rendimiento en un sistema microbiano de células en media­celda. Esta colaboración fue parte de un proyecto de investigación doctoral de la Dra. Myreisa Morales de la Universidad de Puerto Rico en Río Piedras. Este proyecto consistió en la deposición de nanopartículas de Pt preferencialmente cúbicas junto con el crecimiento de la bacteria P Vulgaris, en un electrodo de preparado con hebras de fibras de carbono, para la oxidación de amoníaco en un sistema bio-electroquímico. Esta colaboración también está en proceso de poder publicarse. Finalmente, se realizó otra colaboración con el grupo de investigación Micro-G mediante la preparación del procedimiento experimental de oxidación de amoníaco en nanocubos de Pt que sería enviado a la Estación Espacial Internacional (ISS). Se espera que el sistema sea lanzado fuera al espacio exterior en noviembre de 2019. Los resultados podrán ser comparados con los obtenidos para determinar los efectos de la gravedad cero. Se espera que la colaboración realizada logré otra publicación científica.

Rubber compounds enhance their mechanical properties when a rigid solid particulate (filler) is finely dispersed in the rubber structure, particularly in case of nanostructured silica. In fact, most of nanosilica properties that impact on rubber compounds have been investigated, in particular the size of the nanoparticle, its state of aggregation and surface chemistry. An extensive effort was paid to understand how nanostructured silica exert a reinforcing action on the resulting silica/rubber nanocomposite material. The intrinsic difficulty in obtaining silica nanoparticles with well defined shape has limited the discussion to nanoparticles different from silica, for example carbon nanotubes, nanoclays, thermoplastic polymeric fibres, cellulose nanowhiskers, ecc. It is therefore necessary to create a model system in which silica nanoparticle shape can be tuned adequately and its influence on the reinforcing mechanism can be worked out. In this context, the aim of the thesis is to investigate the impact of the anisotropic silica particles on the dynamic-mechanical behavior of model SBR nanocomposites, considering first the networking of differently shaped nanoparticles, and second the formation of the nanoscale rigid rubber at the filler interface. Silica nanoparticles featuring different shapes were obtained by sol-gel method, using a structuring agent based on an acqueous micellar solution of surfactant CTAB, that allowed to control the growth of the particles giving them different anisotropies, including spherical and rod-like particles with aspect ratio ranging between 2 and 7. Nanocomposites of silica nanoparticles and styrene butadiene rubber (SBR) were prepared by compounding methods, in order to evaluate the effect of shape on the mechanical properties of the material. The nanocomposites morphology and its effect on the dynamic-mechanical behavior were studied by a multi-technique approach. The combined use of TEM and AFM tapping mode analyses revealed that in all the nanocomposites spherical and anisotropic NPs are surrounded by a layer of about 15 nm of immobilized rubber. Spherical or nearly spherical particles show small contact zones sharing thin rubber layers. Anisotropic particles show instead oriented domains of rods preferentially aligned along the main axis separated by several layers of immobilized rubber. The formation of these self assembled domains causes an increase of rubber fraction trapped between the aligned particles. Low field 1H NMR measurements evidences that polymer chain dynamics of the rubber layers tightly bound to the silica particles are restricted by the interaction with the filler, increasing the stiffness with respect to that of polymer far from the particles. Dynamic- Mechanical measurements confirm that anisotropic particles with higher aspect ratio give a high reinforcement, as a result of spontaneous alignment of anisotropic particles that implies higher amounts of immobilized rubber, when compared to the system containing spherical particles. A similar approach was applied to anisotropic nanoparticles based on Sepiolite, a naturally occurring nanostructured silicate. Nanorods were prepared by a surface modification methodology and successfully compared with the model system proposed before showing improved reinforcement, particularly related to energy dissipation, that makes them potentially interesting for an industrial application. To conclude, the reinforcement mechanism passes through the immobilization of rubber on the surface of the nanoparticles, and it was found that the self-assembly of particles in anisotropic domains is crucial in order to further immobilize rubber and ensure a high reinforcement. The study confirmed that the control of filler morphology is mandatory to adequately modulate the nanocomposite mechanical properties.

碩士
國立中正大學
化學暨生物化學研究所
99
Monodispersed magnetic nanoparticles ( NPs ) recently have been actively studied due to their potential applications in data storage and magnetic resonance imaging (MRI). Cobalt nanostructures were prepared by thermal decomposition of dicobalt octacarbonyl, Co2(CO)8, in o-xylene and n-decane in this study. Significantly monodiapersed Co nanoparticles were obtained by tuning the reaction conditions such as precursor : surfactant ( oleylamine : oleic acid ) mole ratio, the reaction temperature and reaction time. Interestingly, the crucial role of the precursor: surfactant ( oleylamine : oleic acid ) mole ratio on the shape of the nanoparticles was demonstrated by altering the ratio from 1:10:1 ( spherical particles ) to 1:10:2 at 175°C leading to rectangular particles. Besides the observations of spherical particles in the former case with precursor: surfactant mole ratio of 1:10:1, the lowering the reaction temperature to 165°C led to formation of rectangular particles. This observation was explained by the controlled growth of the nanocrystals at lower temperature lead to special structures. Further examination by tuning the mole ratio to 1:12:1.2 at 165°C led to elongated rectangular particles. Characterization of the cobalt nanoparticles was conducted by transmission electron microscope ( TEM ) and EDS. The crystal structures of the nanoparticles were analyzed by powder x-ray diffraction and electron diffraction from the HR-TEM images. Hysteresis curve was found in magnetism analysis of Co nanoparticles.

碩士
國立臺灣師範大學
化學系
96
The shapes and sizes of nanoscaled materials have attracted extensive attention in recent years, due to their strong effects on the physical and chemical properties of materials. Copper particles have been widely studied because of its high electrical conductivity, thermal conducting and excellent catalytic property. The synthesis of stable, monodisperse, well-defined copper nanoparticles is difficult, partially because of copper’s propensity for oxidation. This report describes the findings of an investigation of the synthesis of copper nanoparticles in organic chemical reduction and controlled shapes including 100% cuboctahedral, 34.20% rods and 85.54% cubes by manipulate surfactant. The different shapes of copper nanoparticles are characterized using SEM, TEM, XRD, XPS and UV-Vis. From the result, we demonstrated the synthesis mechanism combination of the selective formation of uniform seeds by HDA and a selective growth direction due to the preferential adsorption of TOPO on the certain nanocrystal 100 face is believed to lead formation of cube-shaped particles. The synthesis copper nanoparticles have high stable catalytic property from the TPR results.

碩士
中國醫藥大學
藥用化妝品學系碩士班
101
This study successfully established a green process that can synthesize multi-functional metal nanomaterials. This study investigated the effect of various experimental parameters on the synthesis of nanomaterials, such as the amount of seed, seed sizes, hyaluronic acid (HA) concentration, the weight ratio of metal ion and HA , metal ion concentration and the reaction temperature. The results obtained in the experiment were analyzed by ultraviolet light-visible- near-infrared light spectrophotometer, high-resolution transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffractometer. The results showed that the the amount of seed control the shape of nanogold from plate-like to polyhedral shape, seed size control the size of nanogold, hyaluronic acid concentration control the particle size distribution uniformity of nanogold, he weight ratio of metal ion and HA control the the dimensions structure of nanogold; reaction temperature control the growth rate of nanogold, metal ion concentration control the yield of nanogold nanosilver. This study explored the catalytic activity and surface-enhanced Raman scattering (SERS) of the nanoflower and polyhedral gold nanocrystals. The nanoflower exhibited good catalytic reduction and SERS enhancing capabilities. The cytotoxicity test results displayed gold nanocrystals are non-toxic on human mammary epithelial cells, but it showed selectively inhibition on breast cancer cell viability. We also used this green process to prepare the nanosilver (Ag) and silver-gold (Ag@Au). The Ag and Ag@Au exhibited high antibacterial activity for against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae. This study expects the multi-functional metal nanomaterials synthesized via this green process have efficiency potential on catalytic, anticancer, SERS and antibacterial applications.

Magnetorheological fluids (MRFs) are non-colloidal stable suspensions of polarizable mesoscale soft magnetic particles, usually metallic Fe-particles, in a carrier liquid such as oil or water; the solidity of which can be tuned by varying the applied magnetic field strength. Magnetorheological fluids are agile candidates for impact mitigation due to their tunable “solidity”, quick and complete reversibility of physical states, durability and reusability in comparison to their mechanical counterparts. The highly desirable property of an MRF is its yield strength and hence the conventional MRFs are Fe-based. However, uncoated Fe-particles suffer from poor chemical and thermo-oxidative stabilities, poor sedimentation stability and redispersibilities necessitating the coatings / additives; which always lead to compromised performance when used in MRFs. An alternative (to Fe) magnetic filler phase is the use of magnetic oxide particles. Soft magnetic spinel ferrites and garnets (though with moderate yield strength in an MRF) with their excellent chemical, thermo-oxidative and sedimentation stabilities, ready-redispersibility, less stringent synthesis and preservation conditions, lower cost, need no stabilizers and additives make them potential contenders for use in MRFs which can provide reliable MR performance. As the microstructure and magnetic nature of particles have direct influence on the MR property, the effects of these were studied by preparing MRFs with magnetic oxide particles of different sizes and shapes. These MRFs were simple bi-phasic as magnetic oxide particles were dispersed in versatile carrier fluid (silicone oil) without any additives; where the magnetic fill fraction was decided based on off state viscosity and the wettability criteria. As the MRFs in a device can undergo different stress / strain conditions of varying amplitudes and frequencies during their service, such a response was studied in laboratory using magnetorheometer via different modes of operation which mimic the service conditions. By varying the applied magnetic field strength and applied shear conditions, the performance of MRFs was evaluated and correlated to the physical and magnetic properties of the particles. Such a study provides a basis for the choice of magnetic phase in MRFs and their required concentration in the base fluid to provide highest efficiency. The dynamic yield strengths (field dependent yield stress) of MRFs extracted from steady shear measurements showed that the yield strength was strongly dependent on the saturation magnetization as well as on the microstructure of the particles used in MRF. The yield strength scaled with the saturation magnetization, magnetic fill fraction and applied magnetic field strength due to stronger magnetic column formation. The stability of MRFs (via the absence of wall slip) was found to depend predominantly on the microstructure of magnetic particles in the fluid such that MRFs containing structured particles showed the absence of wall slip while the MRFs containing irregular shaped powder particles showed poor stability via the occurrence of wall slip. The steady shear tests highlight the importance of using particles of definite shape with superior magnetic properties at a certain magnetic fill fraction for an efficient and reliable MR performance. The MRFs subjected to different oscillatory shear conditions showed that sturdier structures form in-field (exhibited via high gain modulus or low loss factor) when the particles have certain shapes (and size distribution) which result in high surface contact and are highly magnetic. Hence, the MRF containing Fe3O4 micro-octahedrons with high magnetization and large surface area for contact with other octahedron showed the large value of gain modulus and low loss factor compared to all other MRF samples. Poly-dispersity in spheres was found to be advantageous over monodisperse spherical magnetic particles due to void-bridging effects that strengthen the magnetic structuration. The irregular shaped particles based MRFs showed lower gain (higher loss factor) due to weak structuration. Anomalously high loss factor observed for rod shaped LZFP particles based MRF at medium strains and low field strengths is attributed to the rotation hindrance and low density of particles. The polydisperse particles based MRFs showed need for higher applied field strengths to decrease the loss and irregular particles based MRFs showed noisy response. The magnetosweep results showed that shape anisotropic particles based MRFs respond faster to applied field manifested as a faster decrease in loss factor with field. With magnetorheological parameters showing high dependence on the physical and magnetic nature of particles, oscillatory shear tests can serve as a means to select and assess the suitability of these particles for magnetorheological fluid for specific applications. The time dependent magneto-mechanical behaviour such as creep-recovery in MRFs showed that the strain recovery was dependent on the microstructure and magnetic nature of the particles such that fluids containing structured particles with high saturation magnetization showed higher recovery (due to better in-field structuration) compared to the irregular shaped and lower magnetization particles based MRF counterparts. The endurance of the MRFs (sustenance of strength of the MRF) under sustained stress conditions were estimated by a novel method which showed that MRFs containing ‘structured’ particles with high saturation magnetization showed high creep strength. In case of spherical particles based MRFs, the polydispersity of particles was found to aid in better column strength due to void-filling. The high surface contact between rod-shaped particles in the fluid resulted in good creep-strength among all MRFs. Among all the particles, the octahedron shaped Fe3O4 particles with large surface contact coupled with high saturation magnetization makes the Fe3O4 micro-octahedron particles based MRF the best amongst all the MRFs studied in this work. In case of irregular shaped particles based MRFs, the creep strength lagged behind the yield strength suggesting that such MRFs are not suitable for applications which demand sustained strength over prolonged action of stresses. Thus, the present work highlights the importance of considering the physical and magnetic properties of magnetic particles while selecting them for application specific MRFs where high endurance is sought. The stress relaxation behaviour of MRFs showed an overall high strength (via relaxation moduli) for MRFs containing particles with definite shape and high magnetization values (increased structure strength). However, the rod shaped particles based MRF did not witness increased strain limit with increased field strength, probably due to the mass flow in fluid due to higher inter-particle interaction than the interaction with applied field. The observation of increase in critical strain with increase in field for MRFs containing irregular shaped particles is only due to the higher number of particles resulting in overall increase in viscosity with field. Among all the MRFs, octahedron Fe3O4 particles with superior magnetic properties and large surface contact between facets showed highest critical strain for flow, which is in corroboration with other magnetorheological studies discussed so far. The creep-recovery and stress relaxation behaviours of MRFs are rarely studied, yet very important when selecting an MRF for an application which seeks high retention of MR strength over prolonged action of stress or strains. A comparison of particle shapes used in the MRFs suggests that although both octahedron shaped and rod shaped particles make high surface contact during structuration, the former is better due to lack of rotation hindrance, thus useful for preparing quickly responding MRFs. The inadequacies in th e conventio nal FOMs are address ed by a new FOM which is based o n a wholistic approach formulated consideri ng all relev ant physical and magnetic paramete rs of the particles. Also, the individ ual terms of this FOM help in selecting a particular MRF for a specific application. The FOM is as follows: λ – sedimentation constant (time taken by the MRF to sediment to about 1/eth of its total volume) With the MRFs containing octahedron shape d Fe3O4 pa rticles showing the highest FOM followed by s pheres (mod erate value ) which are succeeded by irregular powder samples based MRFs, the FO M observed in all MRF cases follow the same trend as observed by results from different magnetorheologi cal studies. Hence, the highest F4 (or FAB) observed for Fe3O4 octahedron particles based MR F in comparison to a ll other MR Fs (including Fe-based) is justified by the o Mbserved large yield strength, creep-resistance, low density and ready-redispersibilities, validating the FOM. The entire thesis is organized as follows. Chapter 1 details the motivation for the present research work, introduction to the material of interest (Magnetorheological fluid) with overview of different areas of potential applications, important properties of MRF, the current status of MRF, the challenges / issues needed to be addressed followed by choice of alternate materials for addressal of these drawbacks faced by conventional (Fe based) MRFs. Chapter 2 explains the synthesis of magnetic-oxide particles of different sizes and shapes by following different synthesis techniques. This is followed by the structural, microstructural and magnetic properties characterizations carried out by employing different, standard characterization techniques. The procedure for preparation of MRFs from the synthesized magnetic oxide particles is discussed. The basis of carrier fluid selection and magnetic particle concentration in MRF is explained. Chapter 3 gives a background to magnetorheology, in terms of the instrumentation (magnetorheometer), the relation between the magnetorheological parameters and the instrumental parameters (conversion factors), the different operating modes and the relevance of characterization modes in terms of practical applications, the procedure of different characterizations and the standard response behavior of MRFs to the characterizations. Chapter 4 is comprehensive characterization of all the MRFs subjected to steady shear conditions at various applied fields. The detailed analyses in terms of MR response are given with respect to the structure, microstructure, magnetic nature, and magnetic fill fraction of the magnetic particle in the fluid. Chapter 5 is extensive study of all the MRFs subjected to dynamical shear conditions at various applied fields. The magnetorheological responses of MRFs under different dynamical conditions (amplitude sweep, frequency sweep and magnetosweep) are analyzed in regard to role of microstructure, magnetic nature and magnetic fill fraction of the magnetic particle in the fluid. Chapter 6 explains the creep-recovery response of MRFs for the best magnetic fill fraction, decided from the steady and dynamical shear responses for all concentrations of MRFs. The recovered strain is analyzed with respect to a range of applied field strength and stress values. The creep strength determined from this study is correlated to the microstructure and magnetic nature of particles constituting the MRFs. Chapter 7 elaborates the stress relaxation behaviour of MRFs for the best magnetic fill fraction, decided from the steady and dynamical shear responses for all concentrations of MRFs. The stress relaxation (plateau values) moduli for the MRFs extracted at various applied field strength and strain values are analyzed to estimate the critical stress for flow in MRFs. This relationship between the critical stress that an MRF can withstand and the microstructure and magnetic nature of the particles in the fluid are investigated. Chapter 8 is about the study of sedimentation stability (and the redispersibility) of magnetic oxide particles based MRFs and the comparison of these properties with Fe- based MRFs. The role of mass-density and microstructure of particles in the fluid on sedimentation rate is briefly explained. Chapter 9 compares the important outcome of all the magnetorheological characterizations for all the studied MRFs in terms of extent and speed of response, the sedimentation stability and eases of redispersibility, and relates the observations to the physical and magnetic properties of the magnetic particles. The method of developing a new figure of merit based on a wholistic approach for assessing the efficiency and reliability of MRF is discussed which overcomes the shortcomings of conventional figures of merit. Chapter 10 summarizes the important findings of research work and highlights the validity of the new figure of merit in assessing ‘reliability and performance’ of MRFs.

Magnetorheological fluids (MRFs) are non-colloidal stable suspensions of polarizable mesoscale soft magnetic particles, usually metallic Fe-particles, in a carrier liquid such as oil or water; the solidity of which can be tuned by varying the applied magnetic field strength. Magnetorheological fluids are agile candidates for impact mitigation due to their tunable “solidity”, quick and complete reversibility of physical states, durability and reusability in comparison to their mechanical counterparts. The highly desirable property of an MRF is its yield strength and hence the conventional MRFs are Fe-based. However, uncoated Fe-particles suffer from poor chemical and thermo-oxidative stabilities, poor sedimentation stability and redispersibilities necessitating the coatings / additives; which always lead to compromised performance when used in MRFs. An alternative (to Fe) magnetic filler phase is the use of magnetic oxide particles. Soft magnetic spinel ferrites and garnets (though with moderate yield strength in an MRF) with their excellent chemical, thermo-oxidative and sedimentation stabilities, ready-redispersibility, less stringent synthesis and preservation conditions, lower cost, need no stabilizers and additives make them potential contenders for use in MRFs which can provide reliable MR performance. As the microstructure and magnetic nature of particles have direct influence on the MR property, the effects of these were studied by preparing MRFs with magnetic oxide particles of different sizes and shapes. These MRFs were simple bi-phasic as magnetic oxide particles were dispersed in versatile carrier fluid (silicone oil) without any additives; where the magnetic fill fraction was decided based on off state viscosity and the wettability criteria. As the MRFs in a device can undergo different stress / strain conditions of varying amplitudes and frequencies during their service, such a response was studied in laboratory using magnetorheometer via different modes of operation which mimic the service conditions. By varying the applied magnetic field strength and applied shear conditions, the performance of MRFs was evaluated and correlated to the physical and magnetic properties of the particles. Such a study provides a basis for the choice of magnetic phase in MRFs and their required concentration in the base fluid to provide highest efficiency. The dynamic yield strengths (field dependent yield stress) of MRFs extracted from steady shear measurements showed that the yield strength was strongly dependent on the saturation magnetization as well as on the microstructure of the particles used in MRF. The yield strength scaled with the saturation magnetization, magnetic fill fraction and applied magnetic field strength due to stronger magnetic column formation. The stability of MRFs (via the absence of wall slip) was found to depend predominantly on the microstructure of magnetic particles in the fluid such that MRFs containing structured particles showed the absence of wall slip while the MRFs containing irregular shaped powder particles showed poor stability via the occurrence of wall slip. The steady shear tests highlight the importance of using particles of definite shape with superior magnetic properties at a certain magnetic fill fraction for an efficient and reliable MR performance. The MRFs subjected to different oscillatory shear conditions showed that sturdier structures form in-field (exhibited via high gain modulus or low loss factor) when the particles have certain shapes (and size distribution) which result in high surface contact and are highly magnetic. Hence, the MRF containing Fe3O4 micro-octahedrons with high magnetization and large surface area for contact with other octahedron showed the large value of gain modulus and low loss factor compared to all other MRF samples. Poly-dispersity in spheres was found to be advantageous over monodisperse spherical magnetic particles due to void-bridging effects that strengthen the magnetic structuration. The irregular shaped particles based MRFs showed lower gain (higher loss factor) due to weak structuration. Anomalously high loss factor observed for rod shaped LZFP particles based MRF at medium strains and low field strengths is attributed to the rotation hindrance and low density of particles. The polydisperse particles based MRFs showed need for higher applied field strengths to decrease the loss and irregular particles based MRFs showed noisy response. The magnetosweep results showed that shape anisotropic particles based MRFs respond faster to applied field manifested as a faster decrease in loss factor with field. With magnetorheological parameters showing high dependence on the physical and magnetic nature of particles, oscillatory shear tests can serve as a means to select and assess the suitability of these particles for magnetorheological fluid for specific applications. The time dependent magneto-mechanical behaviour such as creep-recovery in MRFs showed that the strain recovery was dependent on the microstructure and magnetic nature of the particles such that fluids containing structured particles with high saturation magnetization showed higher recovery (due to better in-field structuration) compared to the irregular shaped and lower magnetization particles based MRF counterparts. The endurance of the MRFs (sustenance of strength of the MRF) under sustained stress conditions were estimated by a novel method which showed that MRFs containing ‘structured’ particles with high saturation magnetization showed high creep strength. In case of spherical particles based MRFs, the polydispersity of particles was found to aid in better column strength due to void-filling. The high surface contact between rod-shaped particles in the fluid resulted in good creep-strength among all MRFs. Among all the particles, the octahedron shaped Fe3O4 particles with large surface contact coupled with high saturation magnetization makes the Fe3O4 micro-octahedron particles based MRF the best amongst all the MRFs studied in this work. In case of irregular shaped particles based MRFs, the creep strength lagged behind the yield strength suggesting that such MRFs are not suitable for applications which demand sustained strength over prolonged action of stresses. Thus, the present work highlights the importance of considering the physical and magnetic properties of magnetic particles while selecting them for application specific MRFs where high endurance is sought. The stress relaxation behaviour of MRFs showed an overall high strength (via relaxation moduli) for MRFs containing particles with definite shape and high magnetization values (increased structure strength). However, the rod shaped particles based MRF did not witness increased strain limit with increased field strength, probably due to the mass flow in fluid due to higher inter-particle interaction than the interaction with applied field. The observation of increase in critical strain with increase in field for MRFs containing irregular shaped particles is only due to the higher number of particles resulting in overall increase in viscosity with field. Among all the MRFs, octahedron Fe3O4 particles with superior magnetic properties and large surface contact between facets showed highest critical strain for flow, which is in corroboration with other magnetorheological studies discussed so far. The creep-recovery and stress relaxation behaviours of MRFs are rarely studied, yet very important when selecting an MRF for an application which seeks high retention of MR strength over prolonged action of stress or strains. A comparison of particle shapes used in the MRFs suggests that although both octahedron shaped and rod shaped particles make high surface contact during structuration, the former is better due to lack of rotation hindrance, thus useful for preparing quickly responding MRFs. The inadequacies in th e conventio nal FOMs are address ed by a new FOM which is based o n a wholistic approach formulated consideri ng all relev ant physical and magnetic paramete rs of the particles. Also, the individ ual terms of this FOM help in selecting a particular MRF for a specific application. The FOM is as follows: λ – sedimentation constant (time taken by the MRF to sediment to about 1/eth of its total volume) With the MRFs containing octahedron shape d Fe3O4 pa rticles showing the highest FOM followed by s pheres (mod erate value ) which are succeeded by irregular powder samples based MRFs, the FO M observed in all MRF cases follow the same trend as observed by results from different magnetorheologi cal studies. Hence, the highest F4 (or FAB) observed for Fe3O4 octahedron particles based MR F in comparison to a ll other MR Fs (including Fe-based) is justified by the o Mbserved large yield strength, creep-resistance, low density and ready-redispersibilities, validating the FOM. The entire thesis is organized as follows. Chapter 1 details the motivation for the present research work, introduction to the material of interest (Magnetorheological fluid) with overview of different areas of potential applications, important properties of MRF, the current status of MRF, the challenges / issues needed to be addressed followed by choice of alternate materials for addressal of these drawbacks faced by conventional (Fe based) MRFs. Chapter 2 explains the synthesis of magnetic-oxide particles of different sizes and shapes by following different synthesis techniques. This is followed by the structural, microstructural and magnetic properties characterizations carried out by employing different, standard characterization techniques. The procedure for preparation of MRFs from the synthesized magnetic oxide particles is discussed. The basis of carrier fluid selection and magnetic particle concentration in MRF is explained. Chapter 3 gives a background to magnetorheology, in terms of the instrumentation (magnetorheometer), the relation between the magnetorheological parameters and the instrumental parameters (conversion factors), the different operating modes and the relevance of characterization modes in terms of practical applications, the procedure of different characterizations and the standard response behavior of MRFs to the characterizations. Chapter 4 is comprehensive characterization of all the MRFs subjected to steady shear conditions at various applied fields. The detailed analyses in terms of MR response are given with respect to the structure, microstructure, magnetic nature, and magnetic fill fraction of the magnetic particle in the fluid. Chapter 5 is extensive study of all the MRFs subjected to dynamical shear conditions at various applied fields. The magnetorheological responses of MRFs under different dynamical conditions (amplitude sweep, frequency sweep and magnetosweep) are analyzed in regard to role of microstructure, magnetic nature and magnetic fill fraction of the magnetic particle in the fluid. Chapter 6 explains the creep-recovery response of MRFs for the best magnetic fill fraction, decided from the steady and dynamical shear responses for all concentrations of MRFs. The recovered strain is analyzed with respect to a range of applied field strength and stress values. The creep strength determined from this study is correlated to the microstructure and magnetic nature of particles constituting the MRFs. Chapter 7 elaborates the stress relaxation behaviour of MRFs for the best magnetic fill fraction, decided from the steady and dynamical shear responses for all concentrations of MRFs. The stress relaxation (plateau values) moduli for the MRFs extracted at various applied field strength and strain values are analyzed to estimate the critical stress for flow in MRFs. This relationship between the critical stress that an MRF can withstand and the microstructure and magnetic nature of the particles in the fluid are investigated. Chapter 8 is about the study of sedimentation stability (and the redispersibility) of magnetic oxide particles based MRFs and the comparison of these properties with Fe- based MRFs. The role of mass-density and microstructure of particles in the fluid on sedimentation rate is briefly explained. Chapter 9 compares the important outcome of all the magnetorheological characterizations for all the studied MRFs in terms of extent and speed of response, the sedimentation stability and eases of redispersibility, and relates the observations to the physical and magnetic properties of the magnetic particles. The method of developing a new figure of merit based on a wholistic approach for assessing the efficiency and reliability of MRF is discussed which overcomes the shortcomings of conventional figures of merit. Chapter 10 summarizes the important findings of research work and highlights the validity of the new figure of merit in assessing ‘reliability and performance’ of MRFs.

Significant progress has already been made in developing synthetic methods for synthesizing nanoparticles of various sizes and morphologies over the last few decades, and a considerable number of recent studies have been devoted to the characterization and applications of metal nanoparticles. This research has looked into the synthesis of gold nanoparticles using the polymer poly(N-vinyl-2-pyrrolidone) (PVP). PVP's ability to reduce and capping nanoparticles determines their ultimate form after wet chemical synthesis. The conjugation behaviour of polymer PVP with solvent molecules and halide ions can change its ambient nature. Different shaped gold nanospheres, nanotriangles, and nano stars were synthesized by tweaking the reduction of gold precursor (Hydro-Chloroauric acid (HAuCl4.3H2O) by PVP. The synthesized nanoparticles were characterized using UV–Vis absorption spectra, Transmission Electron Microscopy (TEM), and X ray diffraction studies. Peaks in absorption spectra originating from localized surface plasmon resonance (LSPR) were well correlated with electron microscope images and reaction kinetics. Diffraction peaks obtained in XRD studies confirm the crystallization of nanoparticles in the fcc structure, while other structural parameters calculated reveal the differential shape growth.

博士
國立清華大學
材料科學工程學系
98
摘要 本論文主要著重於四氧化三鐵和鐵鉑-四氧化三鐵核殼結構磁性奈米微粒之合成、形狀控制、鑑定、與其應用之研究。 首先，我們利用高溫注入前驅物的方法來製備四氧化三鐵的奈米微粒，注射時的反應溶液溫度為290 °C。我們發現溶液中鐵單體的濃度會影響著四氧化三鐵奈米微粒的形狀。當前驅物注射速度只有10 mL/h時，所還原出的有限鐵單體將優先成長於具有較高能量的晶面，而造成具有最低能量的{100}晶面變成主要外露面，最終得到立方體形的奈米微粒。然而，當注射速度增加到20 mL/h時，增加的鐵單體濃度會改變各主要晶面的相對成長速率。因此原本具有第二低能量的{110}晶面，也和{100}晶面一樣變成了主要外露面之一，最後形成了削菱截角立方體(Rhombicuboctahedron)。在我們的實驗中，這兩種四氧化三鐵奈米微粒的粒徑大約都在16奈米左右，並且都可以在TEM銅網上和矽基板上自組裝成具有優選晶體方向的奈米微粒超晶格結構。 第二部分的研究主要是製備具由核殼結構的鐵鉑-四氧化三鐵奈米立方體。我們利用上述之高溫注入前驅物的方法搭配晶種成長法，來製備具有球形鐵鉑核和立方體形四氧化三鐵殼的複合式磁性奈米微粒。此複合式奈米微粒的最終形狀主要取決於四氧化三鐵殼的成長條件。並且經由HRTEM的分析可得知，鐵鉑核和四氧化三鐵殼並不需具備磊晶成長關係，此結果表示內核的材料並不需要具備與外殼四氧化三鐵相近之晶體常數。因此，不同材料的核可被選用來製備具有核殼結構的四氧化三鐵奈米立方體，以增進其應用價值。 最後一部分則是探討四氧化三鐵和鐵鉑-四氧化三鐵奈米立方體的特性和前瞻應用。我們利用XMCD來量測鐵離子在四氧化三鐵內不同位置的分佈情形。在立方體形的四氧化三鐵奈米微粒內，我們發現三價鐵離子佔有八面體位置的比率比一般四氧化三鐵塊材還來的高。然而，在削菱截角立方體形的四氧化三鐵奈米微粒內，其鐵離子在不同位置上的分佈情形就比較接近於四氧化三鐵塊材。此鐵離子分佈位置的不同可能是由於這兩種形狀的奈米微粒具有不同的比表面積和外露面所致，此結果也將有助於進一步研究四氧化三鐵的催化特性。最後，我們也發現鐵鉑-四氧化三鐵奈米微粒能顯著地增強MRI影像對比，並且效果優於目前市售之影像顯影劑，此顯著效果應歸因於鐵鉑核的高單位磁化量。另外具有自組裝排列的鐵鉑-四氧化三鐵奈米立方體有機會成為前瞻性多頻譜的影像增強劑。

碩士
國立宜蘭大學
機械與機電工程學系碩士班
107
The electro-Fenton method can effectively degrade the organic sewage wastewater, when the system is reacted, it can generate extremely active hydroxyl radicals (•OH). Thereby interrupting the chemical chain of the organic sewage and degrading the organic sewage. The cathode electrode plays an important role in electro-Fenton system. In this study, the carbon felt with high specific surface area, good electrochemical performance and chemical stability was used as the substrate; and the zinc oxide (ZnO) with non-toxicity, high chemical stability and price was used to modify the substrate. The low-temperature wet chemical synthesis method was used to prepare three kinds of different textures of zinc oxide, which were spindle-shaped, flake-like and rod-shaped. After the solution was prepared into a solution, the carbon felt electrode was modified by immersion method. To analysis the degradation efficiency and electrochemical properties for electrodes, the activated carbon black (RB 5) was used as reagent to measure the effect in electro-Fenton system. The experiment including: (1) linear sweep voltammetry (LSV) analysis of the redox and hydrogen peroxide generation of the electrode; (2) cyclic voltammetry (CV) to observe the electrochemically active area of the electrode; (3) scanning Electron microscopy (SEM) to observe the surface morphology of the electrode; (4) X-ray diffraction (XRD) analysis of zinc oxide powder crystal phase; (5) hydrophilicity test to measure the contact angle of the electrode surface with water droplets; 6) Decolorization efficiency of FT5 dye degradation by electro-Fenton system; (7) Total organic carbon (TOC) analysis of organic carbon content of RB 5 dye after electro-Fenton system degradation. The results showed that carbon felt modified with flake-based ZnO had the best electrochemical characteristics, the electrode obtained the highest electrochemical active surface area and hydrogen peroxide production capacity. The decolorization rate of the flake -based ZnO/C electrode for the RB 5 dye for 120 mins was 73.94 % in the electro-Fenton system, and the total organic carbon (TOC) removal rate was 25.16 %, and the decolorization test showed 1.40 times than the unmodified carbon felt in time of 30 mins. It showed that the carbon felt modified by zinc oxide as the cathode, the efficiency for the system can be improved, and it has the development value of the cathode electrode material applied to the electro-Fenton system in the future.

碩士
國立清華大學
化學系
104
This study examines the facet-dependent optical properties of size-tunable Ag–Cu2O core–shell nanocrystals with 38, 42, and 50 nm cubic Ag cores. The Ag cores were prepared from octahedral Au seeds. The Cu2O shells are single-crystalline. In the case of Au@Ag–Cu2O nanocrystals with 42 nm Ag cores, the Ag surface plasmon resonance (SPR) absorption band at 485 nm has been widely red-shifted to 730, 755, and 775 nm for rhombic dodecahedra, truncated octahedra, and cuboctahedra, respectively, after forming the Cu2O shells. The Ag SPR band positions are mostly fixed despite large changes in the shell thickness, showing the presence of facet-dependent optical properties. Due to the strong Ag SPR band absorption, all samples exhibit a better photothermal activity than that of Au–Cu2O nanocrystals. Facet-dependent heat transmission may be present for particles with Ag SPR band much deviated from the laser wavelength, but this phenomenon is lost for particles with SPR band approaching the excitation wavelength as the particles become highly photothermally efficient to give solution temperatures of 80–95 ºC within 3 min of laser irradiation.

碩士
國立中興大學
化學工程學系所
104
Organic-based memory devices have received extensive scientific interest due to their advantages of flexibility, scalability, and material variety. A typical type of charge-trapping OFET memory is organic floating-gate memory. In OFET device, charges are stored in a metal or in a semiconducting layer called a floating gate, located within the insulating gate dielectric, and completely surrounded by insulator. However, there is no systematic study on the above structure effects. In this thesis, we’ll control the concentration of floating gate in the dielectric layer, and investigate the effect of the device. We have developed a facile synthetic route to star-shaped polymers featuring a metal complex of phthalocyanine (MPc) core by arm-first method using combination of atom transfer radical polymerization (ATRP) and cyclization reaction with metal ions. A phthalonitrile with an ATRP initiating group was firstly synthesized, followed by polymerization of styrene to obtain a phthalonitrile-bearing polystyrene (Pn-PS). We prepared Pn-PS with three different molecular weights using ATRP to control the lengths of the arms of resulting star polymers. Pc-cored four-armed star-shaped polymers with metal centers of copper or zinc, CuPc-PS4 and ZnPc-PS4, were synthesized via cyclization of Pn-PS with metal ions of Cu2+ or Zn2+ under the presence of base. Resulting MPc-cored star-shaped polymers showed unique aggregation behaviors in solvents and film states, which can be utilized in optoelectronic applications such as organic memory devices. The OFET memory device employing CuPc-PS4, ZnPc-PS4 shows significant hole-trapping characteristics with a high memory ON/OFF current ratio of 106, long retention ability of over 105 s, which is attributed to a flash-type memory. Especially, we try to modify the polymer chain length of phthalocyanine-core star-shape polymer to control the concentration of phthalocyanine core which form nano-floating gate by π-π interaction in the polymer matrix, also change the memory window and retention time of those memory device. The novel polymer design is a promising candidate for nano floating gates in nonvolatile OFET memory.

碩士
國立清華大學
化學系
95
Thermal Aqueous Solution Approach for the Synthesis of Ultra-Small Gold Nanoplates We report a study on the thermal aqueous solution approach of ultrasmall triangular gold nanoplates with average widths of 40 ± 7 and 58 ± 10 nm. Because of their relatively uniform sizes, these tiny nanoplates can spontaneously self-assemble into some ordered 2-dimensional structures such as the hexagonally arranged pattern. UV-vis absorption spectroscopy showed that these nanoplates exhibit a strong absorption band at 590-602 nm and a weak and broadband centered at ~775-900 nm. Controlled Synthesis of Bipyramid-Shaped Gold Nanoparticles by Seed-Mediated Growth and Their Transformation into Star Fruit-Shaped Branched Nanocrystals We report a study on the synthesis of bipyramid-shaped gold nanoparticles by a seed-mediated approach and their transformation into star fruit-shaped branched nanocrystals by adding a certain amount of Ag+ ions to different solutions in the process. The colloidal of AgCl and AgBr nearby the side surfaces of gold seeds make the growth slowly, and gold atoms deposit at the twin boundaries and led to their unsymmetrical growth, all of which is the source of forming star fruit-shaped branched nanocrystals.