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Ultrahigh molecular weight polyethylene (UHMWPE) is an aliphatic polymer made from ethylene monomers with an extraordinary high mechanical strength. With its excellent properties, this kind of material is widely used in mechanics, medical applications, military etc. Even though the final fiber product is extremely strong with a modulus as high as 7 GPa, there is still a lot potential to further improve this mechanical strength based on theoretical calculation. The strength of the fiber is currently mainly determined by the microstructure which is influenced by the fiber manufacturing process rather than by the intrinsic properties of the polymer chains. Plenty of studies so far have focused on the influence of various process parameters such as temperature, fiber draw ratio etc. Far less insights are available on the detailed UHMWPE polymer growth mechanism into the final powder particles and the molecular scale organization of the polymer chains into the final fiber. The main reason for this lack of insight is the absence of techniques that allow to directly observe the polymer distribution in the growing polymer particles and the processed fiber at the nanoscale in three dimensions. This research focuses on building new analytical tools for polyethylene to observe how the polymer is organized in the polymer particle and fiber in 3D dimensions separately. Both the UHMWPE powders and fibers are provided by DSM company. For the first part of the study, UHMWPE powders are labelled by fluorescent dye molecules. These fluorescent dyes are preloaded on the accessible active sites. Next the typical PE polymerization in heptane. The dye molecules hence allow tracing the distribution of the PE chains formed at the initially active sites throughout the final UHMWPE polymer product. The polymerization process was interrupted at different degrees of polymerization. By mapping out the distribution of these fluorescent dyes throughout the UHMWPE powder particles by using Stimulated Emission Depletion microscopy and Stimulated Raman Scattering microscope, will shed light on the catalytic process and yield a better understanding of the particle growth mechanism. For the second part, we will focus on the processed UHMWPE fibers. Here, unlabeled the typical UHMWPE is physically mixed with trace amounts of fluorescent dye molecules during the extrusion process. During gel spinning and further drawing, the individual UHMWPE chains will increasingly organize into crystalline domains. As a result, the fluorescent dye will remain in the non-crystalline domains of the imaged undrawn yarn fiber. By using the same microscopy techniques as for the UHMWPE powders, we mapped out the non-crystalline fiber domains both at the cross-section of the fiber as well as along the fiber length. The applied optical microscopic imaging approach combining different high-resolution molecular imaging techniques is novel in this field. For the UHMWPE powders, the catalyst fragmentation is the combination of shrinking core model and continuous bisection model and the polymer growth is via the multigrain model. For the UDY UHMWPE fiber, the contour of the non-crystalline domains was observed at the nanoscale. The images of the cross-section for fiber show nonhomogeneous distribution domains from the center to the edge. The images of the longitudinal section for fiber show the decisive location of domains and voids layer by layer, which can be used to guide industrial processing.

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Zilver beladen zeolieten worden sinds enkele decennia onderzocht omwille van hun katalytische eigenschappen, recent werd ook aangetoond dat ze heel efficiënt zichtbaar licht kunnen uitzenden wanneer ze met onzichtbaar ultravioletlicht worden bestraald. Dit maakt het interessante materialen om te gebruiken als fosformateriaal verlichtingstoepassingen, zoals TL-lampen, LED verlichting, etc. Zilverzeolieten hebben van nature uit geen lichtgevend eigenschappen. Het is dus noodzakelijk deze zilverzeolieten te behandelen om hen de gewenste fosfore eigenschappen te geven, deze behandeling wordt ook wel de activeringsstap genoemd. Tot voor dit onderzoek waren er slechts twee verschillende activeringsprocessen aangetoond die effectief zorgen voor lichtuitstralende zilverzeolieten. Het eerste activeringsproces is een proces dat gebaseerd is op een hittebehandeling van deze zilverzeolieten. Zilverzeolieten worden hierbij opgewarmd in een oven tot 450°C, bij dit proces is het mogelijk om op gramschaal te activeren. Het tweede reeds bekende activeringsproces is gekend als fotoactivering. Deze methode is gebaseerd op een (lokale) bestraling van het zilverzeoliet staal met intens UV-licht, en dit was tot op heden enkel aangetoond op zeer kleine schaal in een microscoop.In dit onderzoek werd voor de eerste keer aangetoond dat deze UV-licht activatie ook mogelijk is op grote schaal. Hierdoor werd het voor de eerste keer mogelijk om op een gedetailleerde manier beide activeringsprocessen, hittebehandeling en fotoactivering, met elkaar te vergelijken. Deze vergelijking toonde aan dat er grote gelijkenissen, maar ook enkele significante verschillen tussen de bekomen geactiveerde zilverzeolieten aan.Naast een gedetailleerde studie van het (bulk) fotoactivatieproces werd in dit onderzoek ook gekeken naar heterogeniteiten aanwezig in de geactiveerde stalen. Wanneer het geactiveerde zilverzeolietpoeder in detail onder een microscoop wordt bekeken dan zijn er duidelijk verschillen tuss...

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In deze studie wordt onderzoek verricht naar de fotokatalytische degradatie van fenol met behulp van ijzergebaseerde metaal-organische roosters (MOFs). Het belangrijkste voordeel van deze materialen ten opzichte van conventionele TiO2-katalysatoren is de lagere bandgap. Hierdoor absorberen deze materialen ook zichtbaar licht, waardoor de fotokatalysator-efficiëntie hoger zal liggen bij gebruik van de zon als lichtbron.Na een karakterisatieluik waarin de bandgap, kristalliniteit en morfologie van de MOF-materialen bepaald wordt, wordt de fotokatalytische activiteit voor fenolafbraak bestudeerd. Aanvankelijk worden deze reacties op kleine schaal, in cuvetten, uitgevoerd bij belichting met monochromatisch blauw licht, waarbij de fenolconcentratie gemonitord wordt met behulp van een spectrofluorimeter. Hierbij komen MIL-53(Fe), MIL-88B(Fe) en MIL-101(Fe).NH2 als beste kandidaten naar voor. In een volgende stap wordt het proces opgeschaald in grotere fotoreactorvaten waarbij blauw licht of gesimuleerd zonlicht als lichtbron werd gebruikt. Hierbij worden de fenolconcentraties bepaald via HPLC. Deze opschaling bracht een verlies aan fotokatalytische activiteit met zich mee, dat vermoedelijk te wijten is aan de manier waarop de stalen belicht worden in deze fotoreactoropstelling. Om dit te controleren werden additionele experimenten uitgevoerd waarin wijzigingen aangebracht werden in belichtingsintensiteit en belichtingsoppervlakte van de stalen. Deze experimenten zijn echter nog niet voldoende uitgewerkt om dit proces volledig te begrijpen. Gezien het belang van deze parameter op de degradatie-efficiëntie is verder onderzoek vereist.Naast deze belichtingsexperimenten is er ook onderzocht wat het effect van de zuurtegraad van de fenoloplossing was op de fotokatalytische activiteit. Een verlaging van de pH zorgt immers voor protonatie van de functionele groepen van fenol en het katalysatoroppervlak. Hierdoor werden wijzigingen in adsorptie en afbraak waargenomen afhanke...

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Metal-organic frameworks (MOFs) are a class of hybrid solid materials, built up by coordinative bonds between a wide variety of inorganic metal ion or cluster nodes and organic linking molecules. Their highly ordered three-dimensional architectures are often crystalline and porous, with pore sizes ranging from a few Ångström to ten nanometers. Owing to their large chemical versatility and highly porous architectures, MOFs have been thoroughly investigated over the last two decades as highly tailorable materials with unique structure-property relations for a wide scope of applications. This partly organic nature of MOFs involves the possibility of photoluminescence, which can be applied in lighting applications or can be an easy read-out mechanism for advanced sensing devices. Even more, biomolecules that play key roles in nature can be applied as building blocks for MOFs: for instance amino acids and nucleobases. This dissertation mainly resolves around the changing optical properties of adenine-containing MOFs, so-called bio-MOFs, by introduced silver and copper species and their applications in LED devices. Additionally, the interactions of amino acids in the pores of water-stable MOFs were studied for adsorption and recovery purposes from protein-rich waste streams.In a first part, the mixed-linker carboxylate- and adenine-containing bio-MOF-1 framework is introduced. It was proven that the presence of silver ions greatly influences the crystalline structure of this material, which is transformed to a purely carboxylate framework MOF-69A. With this MOF-to-MOF structural transformation, the photoluminescent properties also change remarkably, as luminescent silver-adeninate species are formed under the correct reducing environment provided by a ratio of ethanol and water in the silver nitrate solution. A wide range of spectroscopic and microscopy techniques were applied to visualize this process for bio-MOF-1. In the second part, the structure of a new mixed-linker adeninate MOF, BDC bioMOF, was elucidated based on diffraction-based techniques and solid-state nuclear magnetic resonance spectroscopy. The cation-loading of BDC bioMOF is further discussed, along with its optical properties. In contrast to bio-MOF-1, this BDC bioMOF remains stable in the presence of silver ions, but the optical properties again change drastically when silver is loaded on this material from a reducing environment in the form of alcohol solutions.In the second and third part, the latter two photoluminescent MOF materials were investigated for their electroluminescent properties as primary light source in lighting devices (LEDs). The investigation of MOF electroluminescence is a very recent research topic, but possibly of large interest for applications in LED lighting. Various silver- and lanthanide-loaded versions of bio-MOF-1 and BDC bioMOF were tested. It was observed that the introduction of silver ions and the presence of defects on the inorganic node of the MOF greatly improved the electroluminescent behavior of these materials compared to the as synthesized versions. The role of (defects at) the inorganic node is also crucial, as they localize the electron-hole recombination and electroluminescent emission, while the presence of silver enhances the materials' electrical conductivity.In the next part, cuprous (I) iodide clusters were successfully introduced by sublimation at 250 °C into various microporous zeolites and MOFs, including adenine-containing frameworks. The strong and distinct red luminescence from these CuII clusters is very peculiar, as it could possibly replace rare earths as efficient red phosphors in lighting applications. Similar to the case of silver-loading from solution, cupper (I) introduction through sublimation strongly influences the structure of bio-MOF-1, while BDC bioMOF remains stable. Thermally stable Al3+- and Zr4+-MOFs performed even better than the adeninate MOFs, displaying the strong red CuII cluster emission. Zeolites with pores consisting of ring structures larger than 10- and 12-membered T-atom rings also showed strong CuII cluster emission, while the zeolites with small 8-membered ring pores showed mass transfer limitations and no CuII emission.In the final part, water-stable MOFs were probed for the adsorption and separation of another type of biomolecules from aqueous solutions, namely amino acids. In particular aromatic amino acids (l-tryptophan, l-phenylalanine and l-tyrosine) were investigated, as they are expected to have strong dispersive interactions through their aromatic ring structures with the aromatic linkers present in MOFs. The Zr-MOF MIL-140C was found to display the largest affinity for l-tryptophan and l-tyrosine over l-phenylalanine by additional hydrogen bonding of the functional groups in the former two aromatic amino acids with the inorganic unit of MIL-140C. This was visualized with FT-IR and vibrational analysis. Finally, these aromatic amino acids, along with l-glutamic acid and l-aspartic acid, were successfully separated from a complex mixture of all 20 amino acids present in protein. With this result it was proven that MOFs could potentially be used as selective adsorbents in the recovery of high-value and important essential amino acids from protein waste streams.

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The richness and complexity of physical and chemical processes in perovskites make correlative investigations necessary for a comprehensive understanding on perovskites and their optoelectronic devices. That includes surface, morphology, chemical composition, photoluminescence, electroluminescence, electrical responses and so on. A major drawback of most perovskite materials, however, lays in their instability under operating conditions, which is not a secret. Next to the great importance of surface engineering to in stabilizing perovskites, it is also beneficial in improving their physical properties.Besides the importance of surfaces and interfaces, crystal morphology (in particular at the nanoscale) and local stoichiometry also greatly influence the material properties. By doing the work on surface and interface engineering for perovskite optoelectronic nanomaterials, revenues in stability improvements and in property engineering can be envisaged.