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From hydrothermal carbonization to blue hydrochars and activated carbons : Adsorption of volatile organic compounds and heavy metals

Hydrothermal carbonization of carbohydrate and biomass is a straightforward method for preparing hydrochars at low temperature. Hydrochars are more carbonized than their precursors. Hydrochars themselves are carbon precursors for preparing activated carbons. Activated carbons are porous materials that can be used for water and air purification. In my first study (Paper I), I have focused on hydrothermal carbonization of glucose in presence of iron (II)sulfate. By changing the concentration of iron (II) sulfate, with a catalytic amount, blue hydrochars were formed at the bottom of the autoclave. The blueness was related to thin film interference. The thin film hydrochars were more carbonized than spherical hydrochars and the yield of HTC has increased in presence of iron (II)sulfate. The second study (Paper II) is focused on the activation of hydrochars with H3PO4 and H3PO4+FeCl3. We showed that ultramicroporsity and impregnated iron phosphate species enhance the adsorption of VOCs at low pressure. The ACs were impregnated with Fe(PO3)2 and it is shown that Fe(PO3)2 acts as an activation agent which opens up for future studies. In the third study (Paper III), H3PO4 activated carbons were prepared and impregnated with FeS and FeSe. ACs were used for the removal of Cd2+ and Pb2+ in the third study. The uptake of heavy metals by FeS/AC and FeSe/ACs was significantly increased compared to other studies in the literature. In the last study (Paper IV), prickly pear seed biomass from agro sector in Tunisia was hydrothermal carbonized. The hydrochars were then activated into ACs by CO2 activation. The life cycle assessment of the HTC and activation process was investigated.

Mesoporous Silica Particles for a Potential Therapeutic Application

Mesoporous silica particles (MSPs) have a high surface area, pore volume, and tunable pore size and surface properties, which makes them ideal for advanced therapeutic, biocatalytic, separation, and drug delivery applications. The work in this thesis shows that MSPs can be employed for therapeutic applications with minimal risk of adverse consequences. The MSPs in the study are of the SBA-15 type.

Obesity is a serious health problem caused by an excess of adipose tissue (body fat) as a result of inadequate energy expenditure. Both in developed and developing countries, the prevalence is increasing rapidly. Type 2 diabetes (T2D) mellitus is going to be one of the most destructive consequences of the global obesity pandemic. Obesity and diabetes are anticipated to affect 783 million people by 2045, with diabetes being the leading cause of death for an estimated 6.7 million people in 2021 (according to International Diabetes Federation, IDF Diabetes Atlas 10th edition, 2021). People who are overweight or have diabetes are more likely to trigger other physiological conditions such as the development of dyslipidemia. Dyslipidemia is defined by a combination of risk factors for cardiovascular disease, including excessive plasma free fatty acids, cholesterol, and triglycerides; low levels of high density lipoprotein (HDL); and aberrant low-density lipoprotein (LDL). Public health expenditures and initiatives are under severe strain as a result of these situations. Researching therapies that are both safe and effective is in dire need.

MSPs were produced at bench scale, and scaled to pilot (100L) and then at a relatively large demonstration scale (100-1000L) and tested in vitro, in vivo, ex vivo, and clinically. The results from these studies have shown that when administered orally, MSPs adsorb enzymes that break down carbohydrates and lipids (amylase and lipase), physically separating them from their large substrates. When administered orally, this consequently reduces the breakdown of carbohydrates and fats, leading to a lowering of the total energy intake in animals and humans. This occurs when the MSP has pore sizes which is typically in the range of 8–13 nm that are slightly larger than the food-digesting enzymes. The research carried out as part of this thesis showed that when the MSPs are in the micron size range, they operate locally in the gastrointestinal tract (GIT) and exit in the fecal mass without being absorbed by the body. The adsorbed enzymes aid in the safe transit of MSPs through the gastrointestinal system. Furthermore, the presence of these digestive enzymes within the pores was shown to have no effect on enzymatic function. It was also observed that when a large substrate (starch) was used to measure the activity of α-amylase adsorbed in the pores of MSPs, the activity appeared reduced. However, this was not related to an inactivation of α-amylase but to the fact that starch was molecularly too large to enter the pores of the MSPs.

Pressure-Induced Amorphization and Distinct Amorphous States of Clathrate Hydrates

This thesis summarizes a study on the pressure-induced amorphization (PIA) and structures of amorphous states of clathrate hydrates (CHs).

PIA involves the transition of a crystalline material into an amorphous solid in response of mechanical compression at temperatures well below the melting point. The first material observed to undergo PIA was hexagonal ice. More recently it was shown that compounds of water undergo the same phenomenon without decomposition, despite the presence of solutes. CHs, which are crystalline inclusion compounds consisting of water molecules encaging small guest species, undergo PIA at ca. 1–4 GPa below 145 K. The obtained amorphous CH phase can be further densified on isobaric heating at high pressure. This annealing step enables to retain an amorphous material on pressure release. There has been a significant amount of studies into the understanding of the nature of PIA and transformations between amorphous phases of pure ice. The aim of this thesis has been the understanding of the PIA in CHs and its relation to pure ice. New information on the nature of PIA and subsequent amorphous-amorphous transitions in CH systems were gained from structural studies and in situ neutron diffraction played pivotal role due to the sensitivity of neutrons to the light element hydrogen. Here a generalized understanding of the PIA in CHs and a clear image of amorphous CH structures are presented.

Biomass-derived nanoscopic catalysts for water treatment : Structure-property relationship investigation

Green Chemistry has received widespread interest due to its capacity to meet environmental and economic objectives. The Twelve Principles were proposed to better perform Green Chemistry and have become the guideline for solving many environmental issues. Water contamination has become a major global challenge in the 21st century. Millions of people die from diseases caused by drinking contaminated water. Nitrate, metal ions and dye are the most frequent contaminants. Nitrate in drinking water, after ingestion, is reduced to nitrite by the gastrointestinal tract and threatens human health. Dye-polluted water is usually nonbiodegradable and poisonous: the main criticism is that it is harmful to human health and hampers the photosynthesis rate of aquatic life. Metal ions generally lead to biological and physiological complications when they bind to cellular macromolecules. Therefore, efficient and eco-friendly purification technology is pressing to provide solutions for water purification. 

This thesis is set out to investigate the electro-/photo- catalytical water purification techniques using different catalysts. Efficient nitrate electrochemical reduction was achieved by using NDC materials, and the active sites were determined with the help of a comprehensive solid-state NMR supported by theoretical calculation and DFT calculations. Furthermore, the photochemical dye degradation was performed using cellulose-based hybrid bio-inorganic catalysts. The intentional maintenance of the surface functional groups on cellulose-based materials can promote dye degradation performance and, most importantly, achieve simultaneous removal of heavy metal ions aside from photo dye degradation. Additionally, this thesis proposed two possible synthesis strategies to obtain electro-/photo- catalysts using cellulose-based materials as renewable resources. The Twelve Principles of Green Chemistry guided the optimization of the synthesis route and raw material selectivity. Notably, the low-temperature synthesis of hybrid photocatalysts maintained the surface functional groups and preserved the kinetic mechanism of contaminants' adsorption on bio-substrate.  This research is likely to contribute to a deeper understanding of renewable materials with green synthesis methods for catalysts targeting water contamination treatment.

Functional hybrid and composite porous membranes derived from imidazolium-type poly(ionic liquid)

Poly(ionic liquid)s (PIL)s, as a subclass of polyelectrolytes, are composed of polymeric backbones with ionic liquid (IL)-based species in each repeating unit. Recent studies have deepened the understanding of the PIL concept in terms of characteristics, functions and applications in comparison to classical ILs and traditional polyelectrolytes. During the past two decades, PILs have developed themselves into an interdisciplinary subject among various research areas such as polymer science, materials science, catalysis, separation and sensing. Currently, the chemistry and applications of conventional polyelectrolytes are being expanded forward by the PIL concept. 

This PhD thesis deals with PIL-based porous hybrid and composite membranes. It is motivated by the growing demand on functional porous polymer membranes, in particularly, porous polyelectrolyte membranes in both industry and academia. By applying PILs as building blocks in membranes, the as-prepared porous PIL membranes combine certain desirable properties of ILs and common polymers with a wider potential to satisfy this demand. As a step further, the incorporation of functional guest substances on a molecular or nanoscale can enable new functionalities of porous membranes and broaden their application scope. 

The aim of this thesis is to develop synthetic approaches to fabricate porous PIL-based membranes based on hybridization and composition of a cationic PIL and a guest substance, and explore their diverse functions. Herein, fabrication methods based on two mechanisms were proposed and investigated. First, electrostatic complexation between a cationic hydrophobic PIL and a weak poly-/multi-acid. Second, ice-assisted phase separation of a hydrophobic PIL in water when in contact with a multi-acid compound as an ionic crosslinker. In following, task-specific functions were built up in porous PIL membranes via addition of specific metal-containing substances. This thesis content is inherently interdisciplinary, as it combines polymer chemistry and processing, membrane fabrication and materials science to secure its success in implementation, and this thesis advances the design and application scope of porous polyelectrolyte membranes.

Exploring The Versatility Of Ionic Liquids : From fundamental understanding to materials inspired from ionic liquids

Ionic liquids (ILs) have gained popularity as “green” and safe replacements for conventional organic solvents. They are defined as ionic salts displaying a melting point below 100 °C. Some of their unique characteristics also include negligible vapour pressure, good electrical conductivity as well as good thermal and chemical stability. While their “green” nature has since been disputed, they can be used and applied in many additional fields, such as solar energy production, new lighting technology and much more. 

In this thesis, the aim is to gain fundamental knowledge on ILs, specifically their structures and behaviour, in order to design materials tailored for specific applications. We also aim to use ILs to access otherwise difficult to synthesize materials and study their properties and applications.

The thermal properties of ILs are one of their most important characteristics. However, it is still poorly understood how the structural aspects of ILs influence their particular thermal behaviour. By studying different systems, we derived relationships between the structure and the thermal behaviour of ILs. Hydrogen bonding and other supramolecular interactions play a major role in controlling both the melting temperature and the IL's ability to support a liquid crystalline mesophase. This control was shown both in a series of ILs based on 1-alkyl-3-dodecylimidazolium bromide and in a series of ILs based on azobenzene-imidazolium compounds.

The stability issues associated with the electrolytes used in dye-sensitized solar cells (DSSCs) present a major disadvantage. We tested using ILs as electrolytes to avoid this problem. In our study, we used 1,3-dialkyltriazolium ILs as electrolytes in combination with the iodide redox couple, and not only was the stability of the DSSC improved but also the performance of IL-based DSSCs.

Efficient luminescent materials are always sought after. Using ILs in combination with lanthanides, we achieved highly luminescent compounds as well as some magnetic ones. ILs can also be used to access anhydrous forms of otherwise hydrophilic species, such as ions of the lanthanides. We have used acetate ILs to attain water free complexes of the ions from the whole lanthanide series, starting from the hydrated species. This simple process could be applied to more species of hydrophilic metals that are otherwise known to form hydrates.

Finally, the ligand obtained through ILs, 1,3-diethylimidazole-2-thione was used to aid in the studying of phase transitions when combined with zinc chloride (ZnCl2). It helped to reveal a yet unseen amorphous step in the solid-solid phase transition from a single crystal into another one, where morphology of the particle was preserved. I forsee that more fundamental structural studies can be conducted by forcing the coordination of the soft-donor nitrogen onto lanthanides by using dicyanamide ILs in the future.

Modified and hybrid cellulose-based materials for water purification

The need for clean water has led to the development of several different water treatment methods as well as to a large number of organic, inorganic, hybrid and/or composite materials that are used in these methods. Cellulose, being a highly abundant biopolymer with meritorious properties, such as high mechanical strength, tunable surface chemistry, high aspect ratio and surface area, to mention a few, is exploited in the current thesis for water treatment applications. Cellulose and its nanoscaled derivatives (i.e. cellulose nanocrystals and cellulose nanofibers) are modified or hybridized to achieve multiple functionalities.

Cellulose and lignocellulose nanocrystals were successfully prepared by mechanical treatment from the residue of bioethanol production and were decorated with zwitterionic polymer grafts through controlled radical polymerization reactions. The presence of residual lignin and polymer grafts was investigated which showed that especially the polymer grafting can significantly improve the antibacterial and antifouling performance of nanocellulose.

Functional cellulose-based membranes were prepared in a one-step water-based process. The membranes were evaluated as adsorbents for the removal of dyes and metal ions as well as metal-free catalysts for the decolorization of dyes Methylene Blue (MB) and Rhodamine B (RhB). The membranes exhibited maximum adsorption capacity of 78.6 mg/g for Co2+, up to 100 % of MB removal efficiency and up to 3-fold increase in the decolorization of MB.

Both in-situ and ex-situ growth of ZIF-8 crystals was performed on the surface of cellulose and nanocellulose and cellulose/ZIF hybrid membranes were manufactured. The adsorption capacity of the membranes was tested with Cd2+, Cu2+, Fe3+, and Pb2+, exhibiting a maximum adsorption capacity of 354 mg/g for Cu2+. Furthermore, the membranes showed potential for use as self-standing electrode for the detection of Pb2+.

Processing of cellulose/alginate composite hydrogels in the form of highly porous beads was successful. The surface of the beads was modified via in-situ TEMPO oxidation for the introduction of carboxyl groups. Adsorption of cationic contaminants as dyes and metal ions (MB and Cd2+ were used as models, respectively) was enhanced with in-situ modification. Removal of metal ions from the mining industry wastewater using modified cellulose/alginate hydrogel beads confirmed the potential of the adsorbent in complex water sources.

All-cellulose flat sheets (100 × 20 cm) were produced via a water-based process using a Formette dynamic sheet former. The sheets exhibited excellent mechanical properties attributed to the alignment of the micro and nanofibers that this process offers. The adsorption performance of the sheets was evaluated both with Irgalite Blue RL and Irgalite Violet H dyes, which are highly used in paper and pulp industries as dyes models, and Fe3+, Mg2+, Cd2+, Co2+, Cr3+, and Mn2+ as metal ion models. A maximum removal efficiency of 83% for IB RL and maximum adsorption capacity of 737 mg/g for Mg2+.

The work shows the potential of cellulose as a sustainable and scalable platform for the tailoring of multifunctional materials for water treatment with cationic pollutants removal, antifouling, antibacterial and sensing capabilities.

Evaluation of NMR Knight shifts in metallic nanoparticles and topological matter

Elucidating the surface electron states of transition metal compounds is of primary importance in main heterogeneous catalytic processes, such as the hydrogen and oxygen evolution reactions.  Key property in all these processes is the position of the energy of the d-band center relative to the Fermi-level of the catalyst; it must be shifted close to the Fermi level to achieve balance between adsorption and desorption of the catalyst and the adsorbate. Often, these processes involve expensive metals such as Ru or Pt, limiting their applicability. The Nickel Phosphide (NixPy) family has recently emerged as an important catalyst family replacing noble metals; in these systems the surface electronic properties, may be tailored by doping with different transition metals, decreasing size, or by controlling the nanoparticle shape (facet engineering). It is thus crucial to be able to simultaneously monitor the evolution of the morphology as well as the electronic structure of the NP particles while scaling down the size.

In most of these materials, surface electron states are extremely sensitive to local disturbances, such as impurities, surface defects, as well as surface termination. In contrast, 3D topological insulators like Bi2Se3, or Bi2Te3, exhibit exceptionally robust metallic surface electron states while the bulk interior is insulating. These extraordinary properties, which become dominant by reducing the system size to the nanometers, have been tied to enhancement of the Seebeck effect, i.e., the conversion of heat into electricity, catalytic activity, and electrochemical performance, the latter of these effects has been pursed in this thesis as well. An important question that has eluded however is the presence of the Dirac electrons themselves and to which extend the Dirac electrons penetrate the nanoparticles, controlling thus the overall electronic properties.

In contrast to the TIs, Weyl semimetals (WSMs), another category of topological materials, host protected electron states in the bulk interior. The bulk conduction and valence bands of these systems cross linearly in pairs of conjugate nodal points, the so-called Weyl points, forming characteristic double cones. Remarkably, in specific WSMs, such as the WTe2 and MoTe2, known as type-II WSMs, the Weyl cones are strongly tilted, leading to the formation of electron and hole pockets at the Fermi level, strongly influencing their electronic properties. However, energy bands in these systems are shown to disperse in a very tiny region, rendering standard experimental techniques, such as Angle Resolved Photoemission Spectroscopy obsolete in detecting the Weyl bands. 

In this thesis all the issues mentioned for each case, were tackled by employing solid-state nuclear magnetic resonance (ssNMR) spectroscopy under various temperatures and magnetic fields, combined with high-resolution transmission electron microscopy and density functional theory calculations.

New solid-state NMR methods for exciting and separating anisotropic interactions of spin I=1 nuclei

Solid-state NMR has become an essential tool for structural characterisation of materials, in particular systems with poor crystallinity and structural disorder. In recent years, a surge of interest has been observed for the study of paramagnetic systems, in which the interaction between nuclei and unpaired electrons allows to probe the electronic structure and properties of materials more directly. However, simultaneously this interaction leads to very broad resonances, which are difficult to acquire and interpret. While significant advancements in both NMR instrumentation and methodology have paved the way for the study of spin I=1/2 nuclei in these systems, still many issues remain to be resolved for routine investigation of quadrupolar nuclei I>1/2. In this Thesis we focus on improving both the excitation of the broad resonances and the resolution in the spectra of spin I=1 nuclei. The latter problem is addressed by developing methods for separation of the shift and the quadrupolar interactions. We introduce two new methods under static conditions, which have the advantage over previous experiments of both suppressing spectral artefacts and exhibiting a broader excitation bandwidth. Furthermore, we demonstrate for the first time an approach for separation of the anisotropic parts of the shift and quadrupolar interaction under magic-angle spinning. Secondly, to achieve broadband excitation we develop a new theoretical formalism for phase-modulated pulse sequences in rotating solids, which are applicable to nuclear spins with anisotropic interactions substantially larger than the spinning frequency, under conditions where the radio-frequency amplitude is smaller than or comparable to the spinning frequency. We apply the framework to the excitation of double-quantum spectra of 14N and design new pulse schemes with γ-encoded properties. Finally, we employ some of the new sequences together with density functional theory calculations to resolve the electronic structure of barium titanium oxhydride.

Probing Paramagnetic Systems by Solid-State NMR Spectroscopy

Paramagnetic systems have a wide range of applications ranging from energy storage or conversion to catalytic processes, metalloproteins and light-emitting materials. Over the recent years nuclear magnetic resonance (NMR) spectroscopy has become an established tool for studying the structural and electronic properties of these systems, largely because it can provide a link between the structure and the bulk properties. This progress was only possible due to improved probe technology and better radiofrequency irradiation schemes, since the hyperfine interaction between nuclei and the unpaired electrons generally hampers both the acquisition and interpretation of the spectra and, therefore, techniques that are standard for diamagnetic systems often perform poorly when applied to paramagnetic systems.

The aim of the present thesis is to continue the development of solid-state paramagnetic NMR and address some of the remaining limitations and bottlenecks in the acquisition and spectral interpretation. One specific area for which great improvements have been seen is the development of new broadband excitation and inversion sequences for systems under Magic-Angle Spinning (MAS) which employ adiabatic pulses. In this work, we provide a more rigorous understanding of the adiabatic pulses in solid-state MAS NMR applicable to both the design of new and improved pulse schemes, and their application in studies of an increased variety of systems, whilst avoiding potential implementation pitfalls.

We also demonstrate how a thorough understanding of the hyperfine interaction combined with quantum chemistry calculations can link bulk magnetic properties and magnetic resonance signatures both in solid-state NMR and Electron Paramagnetic Resonance (EPR), thus providing an accurate description of the geometry and electronic configuration of an organoytterbium complex with applications in heterogeneous catalysis.

Lastly, we explore the development of methods suitable for quadrupolar nuclei (spin I>1/2) in paramagnetic systems which have, so far, lagged behind their spin 1/2 counterparts. We focus more specifically on half-integer quadrupoles for which we propose a new method of processing Multiple-Quantum and Satellite-Transition MAS spectra which permits the separation of shift and quadrupolar interactions into orthogonal dimensions and evaluate the performance and limitations of the state-of-the-art methods for extraction of both quadrupolar and shift anisotropy tensor parameters on structurally complex systems.

We anticipate that the work developed throughout this thesis can help extend the fields of application of solid-state paramagnetic NMR.

Nanopolysaccharide coatings for functional surfaces in water-treatment materials : From mechanisms to process scalability

In this thesis, materials from renewable resources were used to develop functionalized surfaces for water treatment. The work is thus inspired by, and contributes to, the United Nations sustainable goals of: (i) clean water and sanitation, (ii) climate action, (iii) responsible consumption and production, (iv) life below water, and (v) partnerships for the goals.

Nanopolysaccharides, most specifically nanocellulose and nanochitin, are great candidates for functional and renewable materials for multiple applications, including the treatment of water and wastewater. This thesis focused on the formulation of different types of nanopolysaccharide-based coatings to enhance the performance of commercially available membranes and cellulose fabrics. We developed a simple waterborne layer-by-layer cellulose nanocrystals (CNC) and TEMPO-oxidized cellulose nanofibrils (T-CNF) coating for commercially available membranes. By changing the surface and pore structure of the membrane, the coating tuned which substrates could pass through the membrane, improved antifouling performanced, and when derived from T-CNF, it was harmful to bacterial colonization. Considering the observed T-CNF’s effect on bacteria, we developed a chemically crosslinked T-CNF/Poly(vinyl) alcohol (PVA) coating with outstanding antibiofouling performance, ion adsorption/rejection combined with size exclusion, and with dimensional and pH stability. Furthermore, we used a surface-impregnation approach based on bio-based nanotechnology which resulted in highly efficient, with improved mechanical properties, and fully bio-based high-flux water filtration membranes using commercially available nonwoven fabrics. Membranes with coatings prepared from CNC, chitin nanocrystals (ChNC) and T-CNF separated particles in the size range of bacteria and viruses, and those prepared from also T-CNF showed high microplastic filtration efficiency. Moreover, membrane coating based on ChNC and T-CNF had outstanding antibacterial properties.

Overall, we demonstrated that nanopolysaccharide coatings on membranes could provide a significant reduction in organic fouling and biofilm formation while enabling the adsorption of ions and separation of microplastics. In the case of biofilm formation, the functional group and surface charge of the different nanopolysaccharides determined the effect over bacteria, indicating that surfaces could be tailored against microbes. In addition, we directly compared the effect of the different nanopolysaccharides of interest (CNC, T-CNF, ligno-celullose nanocrystals (L-CNC), and ChNC) on bacterial viability and biofilm formation, and found a great difference between the different types of nanocellulose and a different mechanism for nanochitin. Thorough, none of the nanopolysaccharides displayed cytotoxic effects while in indirect contact with the bacterial cells. Nevertheless, T-CNF, ChNC and L-CNC showed a cytostatic effect on bacterial proliferation. Furthermore, the nanomechanical properties of the bacterial cells and interacting forces between the nanopolysaccharides and Escherichia coli (E. coli) were affected when in direct contact with the nanopolysaccharide surfaces.

Lastly, we upscaled one of our coating processes, demonstrating that the method could be easily implemented at an industrial level. The impact of this thesis relies on the effectiveness of the coatings, the different types of functionalities observed, the demonstrated fast implementation at an industrial scale, and the potential to extrapolate this technology to other applications.

Three-dimensional electron diffraction for studying order, disorder and flexibility in metal-organic frameworks

Metal-organic frameworks (MOFs) represent a class of 3D crystalline porous materials composed of organic linkers and metal nodes. Over the years, tens of thousands of MOF architectures have been developed, addressing various applications such as gas storage and separation, catalysis, chemical sensing, ion exchange and drug delivery. One of the most fascinating properties of MOFs lies in their flexible character responsible, for example, for the rotational dynamics of linkers. Three-dimensional electron diffraction (3D ED) has shown to be a powerful tool to solve the structure of nano- or submicrometer-sized crystals coexisting in mixtures, overcoming the limitations of x-ray diffraction.  In this thesis the great potential of one continuous 3D ED protocol, namely continuous rotation electron diffraction (cRED), for the investigation of MOFs is described. cRED has routinely been used in the past decade for obtaining accurate atomic coordinates and perform structure determination of MOFs. In this thesis it is introduced how the limits of the classical approaches for structure determination by cRED can be tackled by individually adjusting the strategies to the requirements of the structures. Thanks to these approaches, full determination of complex structures and fine structural features previously considered impossible to retrieve by 3D ED data, can now be achieved. The complete structure determination of MOFs with highly complex structures, low crystallinity, sensitivity to electron beam and high-vacuum, displacive disorder and long-range structural dynamics is presented. Specifically, in this thesis it is shown how it was possible to achieve the ab initio full determination of MIL-100, an architecture with a unit cell of several hundred thousand cubic Ångstroms, and the discovery of a new class of materials (M-HAF-2), with a connectivity between those of MOFs and hydrogen-bonded organic frameworks. Additionally, the displacive disorder and dynamics in UiO-67 and MIL-140C were investigated showing for the first time that 3D ED can be applied for probing displacive disorder and molecular motion by analyzing the anisotropic displacement parameters. Methods to obtain maximum structure information from anisotropic atomic displacement parameters are also provided through careful investigations of the refinement of ZIF-EC1, MIL-140C and Ga(OH)(1,4-ndc).

Magnetic frustration and low-dimensional magnetism : in transition metal fluorophosphates and square-lattice intermetallic compounds

Solids can display a variety of vastly different magnetic properties. Besides the generally well known ferromagnets, antiferromagnets with their antiparallel arrangements of magnetic moments can exhibit a wide range of complex magnetic behavior such as magnetic frustration or low-dimensional antiferromagnetism. Magnetic frustration emerges from competing magnetic interactions and typically leads to unusual magnetic ground states such as incommensurate or non-collinear magnetic structures or spin glasses. Low-dimensional magnetic behavior occurs if the magnetic interactions within a solid become negligible in at least one dimension in space. These magnetic phenomena are not restricted to certain compound classes but commonly linked to structural features such as the magnetic ion lattice geometry or the topology of the crystal structure. Effects of magnetic frustration are most pronounced in materials with high crystal symmetries and commonly observed in antiferromagnets with certain magnetic ion lattices such as triangular or square nets. Low-dimensional magnetic interactions may arise from a spacial separation of the magnetic ions within the unit cell. Furthermore, complex magnetic properties may also arise from intricate magnetic ion lattices with unusual topologies, as it is often the case in open framework materials. This thesis focuses on the magnetic properties of a series of transition metal (T) fluorophosphates (T = Fe, Co, Ni) that display a variety of crystal structure topologies, the cubic perovskite (NH4)CoF3 as well as the intermetallic phases LaMn2(Ge1-xSix)2 and LaMn2-xAu4+x in which the Mn atoms form square nets.

Ionothermal reactions, a soft-chemistry approach based on ionic liquids (ILs), was employed to synthesize the above mentioned transition metal phosphates and fluoride. Ionic liquids are salts with melting points below 100 C that typically contain organic cations. Task-specific ILs may be designed to fulfill multiple purposes within an ionothermal synthesis. Thus, an IL may be the solvent, mineralizer, fluorine source and structure directing agent all in one. Thanks to the unique properties of ILs, ionothermal syntheses enable the formation of a wide range of crystal structure topologies from low-dimensional motifs to open frameworks. Furthermore, kinetics plays an important role during the crystal structure formation in an ionothermal reaction and may lead to metastable phases.

Nearly all presented compounds display some type of complex magnetic behavior including magnetic frustration on the triangular and square lattices, incommensurate and/or non-collinear magnetic structures, spin glass behavior and low-dimensional magnetism of a spin dimer or chain. The magnetic properties were studied using magnetization measurements in combination with other techniques such as powder neutron and X-ray diffraction (PND, PXRD) and specific heat measurements. Temperature dependent PND measurements were employed to determine the magnetic structures and phase transitions in selected frustrated systems. A number of incommensurate and/or non-collinear arrangements of the magnetic moments including the 120, canted ferromagnetic, helical, conical and the so-called hedgehog spin-vortex crystal (SVC) state were observed. Density functional theory (DFT) calculations were performed to determine the total energies of possible magnetic structure solutions that cannot be distinguished from PND. Furthermore, some magnetic phase diagrams were established.

Investigating polymorphism in small molecules using three-dimensional electron diffraction

For scientific, regulatory and intellectual property reasons, the discovery and characterisation of polymorphic systems is an integral aspect of the development process of any solid-formulated drug product. Yet, these studies are often hindered by crystal quality and size, poor yields and the generation of mixtures of phases. Three-dimensional electron diffraction (3D ED) is a technique capable of structure determination from individually selected, nanometre-sized crystals. In this thesis, 3D ED is applied to investigate polymorphism in small molecules. The unique advantages of the method are highlighted across numerous studies to demonstrate how 3D ED can broaden the scope of polymorphism discovery and characterisation in the screening and selection of pharmaceutical crystal forms. 

3D ED is first applied to reveal that two crystallisation methods believed for 47 years to produce Form δ of the pharmaceutical compound indomethacin result in two different polymorphs, highlighting the power of the method for polymorphism discovery. The polymorphic crystal structures of a small molecule are then determined directly from melt-grown compact spherulites for the first time to show how 3D ED can widen the application of melt crystallisation in polymorph screening, where polycrystalline spherulites are common products. Furthermore, 3D ED is combined with on-the-grid crystallisation and plunge freezing to follow the polymorph evolution of glycine during crystallisation from an aqueous solution to demonstrate the ability of the method to monitor crystallisation processes in situ. The final part of the thesis explores how a high-throughput method combining 3D ED data collection in batch mode with semi-automated data processing can be applied for the phase analysis of complex melt crystallisation products to improve the efficiency and accuracy of polymorph screening.

Nanocellulose based 3D printed hydrogel scaffolds for cartilage and bone regeneration : Tuning of composition, pore structure and functions

Biobased-materials with customized scaffolds have played a prominent role in the success of tissue engineering (TE). Cellulose nanomaterials (CNM) isolated from the abundant biopolymer, cellulose, is explored in this thesis for TE engineering due to its versatile properties such as biocompatibility, high specific strength, surface functionality and water retention capacity. Hydrogel formation capability of CNM at low concentrations (1–2 wt%) and shear thinning behavior has facilitated its use in 3-dimensional (3D) printing as a fabrication technique for 2-dimensional (2D) and 3D scaffolds. This technique offers 3D scaffolds with tailored, controlled and complex geometries having precise micro and macro scaled structures. The current work focuses on CNM-based 3D printed hydrogel scaffolds with tuned composition and pore structure for cartilage and bone regeneration. Design of CNM hydrogel formulations with suitable rheological properties, hydrogel inks capable of ex-situ crosslinking, print resolution during printing due to swelling and mechanical and dimensional stability of the printed scaffolds in moist environment are key challenges that were addressed.

Inspired by the hierarchical and gradient nature of natural tissues 3D printed hydrogel scaffolds with gradient pore structure and composition are reported for the first time with focus on cellulose nanocrystals (CNC) and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-oxidized cellulose nanofibers (TOCNF) based hydrogel ink printing for advanced and functional scaffolds.

CNC-based hydrogel ink was used to 3D print uniform and gradient porous cubic scaffolds for cartilage regeneration. This work highlighted the importance of nozzle movement to obtain high resolution scaffolds with higher z-axis. The anisotropic rigid CNC aligned themselves along the printing direction due to the shear induced orientation that was quantified between 61–76%. To obtain adequate mechanical properties (0.20–0.45 MPa) suitable for cartilage regeneration, the hydrogel ink solid content was increased almost two-fold (5.4 wt% to 9.9 wt%) while exhibiting and mimicking the viscoelasticity of natural cartilage tissues. To improve the bioactivity of the CNC-based 3D printed scaffolds, a surface treatment through dopamine coating was performed. This coating enhanced the hydrophilicity and capability of 3D printed scaffolds to bind bioactive molecules such as fibroblast growth factor (FGF-18) for soft TE scaffolds.

Surface functionality of TOCNF was utilized to fabricate functional hybrid scaffolds (CelloZIF-8) through one-pot in- situ synthesis of Metal-Organic frameworks (MOFs) with varied ZIF-8 loadings (30.8–70.7%). The inherent porosity of the ZIF-8 was used for loading and stimuli-responsive (pH-dependent) releasing of drug molecule such as curcumin. The developed CelloMOF system was extended to other MOFs (MIL-100) and drugs (methylene blue). The shear thinning property of TOCNF was reserved after MOFs hybridization and was used to 3D print porous scaffolds with excellent shape fidelity. In Cello-Apatite, TOCNF was also used as template for in-situ synthesis of hydroxyapatite (HAP) where the HAP loading was 67 wt% to mimic the bone composition. In an attempt to address both cartilage and bone regeneration, a biphasic osteochondral 3D printed hydrogel scaffold has been introduced with tuned composition, pore structure and mechanical properties.

The work presents a sustainable, cost effective and scalable approach for TE using biobased and toxic free water-based formulations using low temperature processes that are extendable to other biomaterials as well as to other applications, such as water treatment.

Crystalline Porous Materials Inspired by Metallodrugs

Inspiration for developing robust porous materials from sustainable reagents was acquired by determining the crystal structures of bismuth subsalicylate and bibrocathol, two long-used and commonly available bismuth-based pharmaceuticals. From these insights, a number of coordination polymers and metal-organic frameworks (MOFs) were developed, facilitating the synthesis of robust porous materials from sustainably sourced reagents. The structural investigations were carried out using advanced transmission electron microscopy techniques, including three-dimensional electron diffraction.

Using Bi3+ to synthesize MOFs, a previously unreported type of the so-called ‘breathing effect’ was observed in two materials. The breathing originates in the inorganic part of the obtained metal-organic structures and was thoroughly investigated for the bismuth-carboxylate framework SU-100. Taking further inspiration from bismuth-based metallodrugs, pseudo-polymorphs of the metallodrug bismuth subgallate were prepared, yielding coordination networks of varying periodicities. Following this line of work, a bismuth-phenolate MOF was prepared using ellagic acid—a phenolic molecule isolated from plant-based waste. The resulting material, SU-101, can be synthesized in water under ambient conditions and exhibits excellent chemical robustness, remaining crystalline upon exposure to harsh aqueous solutions and toxic gases. A second metal-ellagate framework, SU-102, was prepared using zirconium, yielding an equally robust framework. The material was evaluated for the capture and degradation of pharmaceutical pollutants from the effluent of a wastewater treatment plant, showing a selectivity towards cationic pharmaceuticals. This work highlights the potential of using natural products to create high-performing and chemically robust porous materials, for use in applications such as water remediation and the adsorption of toxic gases.

Sustainable recycling of Li-ion batteries

Lithium-ion batteries (LIBs) play a key role in today’s energy storage sector, finding applications in everyday use electronic devices, like smartphones, laptops or electric vehicles. Despite very good properties, such as high electric capacity and high number of charge-discharge cycles, eventually each battery in the world will be disposed and stored in a landfill, waiting for the opportunity to be recycled. Until then, spent LIBs are a serious hazard to the natural environment because of their toxic constituents, like organic electrolytes or transition metal based electrodes, and unfortunately, the majority of those used batteries will never be recycled due to a lack of profitable and sustainable methods for the recovery of battery components.

The demand for the production of new batteries is caused by the increase in the number of electronic devices being sold to end customers every year, and battery waste is an important and promising source of valuable metals, so far essential for manufacturing new electrode materials. However, the existing industrial methods for the recovery of metals from batteries, despite high yields and purity of obtained products, usually are associated with high energy demand, implementation or in situ generation of toxic chemicals, and generation of additional, non-recyclable fractions – therefore they can not be considered as sustainable.

This thesis summarizes the approaches taken during Author’s doctoral studies towards green LIBs recycling, implementing various techniques, like adsorption and electrochemistry, as well as the valorisation of spent LIBs towards environmental applications. The first and second works implement adsorption for the recovery of metal ions present in the battery cathode materials from aqueous solutions. The third work implements the production of a cobalt catalysts made from scrap LIBs cathode materials with further testing towards hydrogen evolution reaction from sodium borohydride. The fourth work implements hydrometallurgical treatment of spent LIBs cathode materials via leaching and electrochemical separation of metals. The aim is to show the possibilities for the recovery and reuse of spent battery cathode materials, as well as the environmental importance of recycling.

Enrichment of biogenic and anthropogenic organic substances on sea spray aerosols

The world’s oceans are the source of one of the most abundant types of natural aerosols, namely sea spray aerosols (SSA). By scattering solar radiation, SSA play a significant role in controlling the Earth’s radiation budget, while they are also involved in the formation of clouds, acting as cloud condensation nuclei (CCN). To understand the connection between biogeochemical processes occurring in the ocean and in the atmosphere, it is crucial to gain better insight into the detailed chemical composition of SSA, which broadly consists of sea salt and marine organic matter. The aim of this thesis is to (1) better understand the impact of ocean biological activity on the chemical composition of SSA and (2) improve the knowledge on the ability of SSA to transport different organic pollutants to the atmosphere. In Paper I it was shown that changes in the composition of marine organic matter during a phytoplankton bloom in the North Atlantic were clearly reflected in the composition of generated SSA. Increased chlorophyll a concentration in seawater was correlated with the presence of lipid-like compounds with high H/C and low O/C atomic ratios, and a consistent trend in chemical composition was observed for subsurface water, the surface microlayer, and generated SSA. Although the effect of biological processes on the composition of SSA organic matter was clear, in Paper II it was shown that during the phytoplankton bloom, the abundance of organic matter in SSA was fairly constant, without any significant influence on their CCN activity or the particle production flux. Paper III provided a mechanistic understanding of the enrichment of different cationic surfactants (CSs) in SSA through experiments conducted using a sea spray simulation chamber. It was shown that enrichment of the CSs was primarily driven by the alkyl chain length of the CSs but also affected by the different functional groups in the CSs. The highest enrichment of CSs on SSA was observed for quaternary amines followed by primary and tertiary amines. Interaction with dissolved humic acid was shown to decrease the enrichment of longer-chain amines while the enrichment was increased for shorter-chain ones. When the plunging jet flow rate was increased, enrichment in SSA was shown to increase, especially for lower water concentrations of surface-active compounds. The purpose of Paper IV was to improve the understanding of the enrichment behavior of perfluoroalkyl acids (PFAAs), which are strong anionic surfactants. Similar to CSs, it was shown that increasing the plunging jet flow increased the enrichment on SSA, from 43-88% for different PFAAs. The effect of different inorganic salts present in seawater on enrichment was also tested. Compared to chamber experiments prepared with ~35% NaCl water matrix, it was shown that the presence of other seawater ions, namely Ca2+ and Mg2+, increased the enrichment of some PFAAs, especially for those with longer perfluoroalkyl chains.

In Light of Ionic Materials : A short exploration of ionic materials for light-related applications

Ionic liquids (ILs) have been one of the most attractive classes of materials of the last decades. The reason behind this is their peculiar set of properties, which enable their possible application in several research fields. ILs are salts that exhibit a very low melting point, which has been arbitrarily defined to be below 100 °C. Due to their ionic nature, ILs have little to no vapor pressure and they often demonstrate good electrical conductivity and high thermal and electrochemical stability. In this work, the focus is directed toward the exploitation of ILs for the engineering of materials that can have a primary role in light-emitting or light-absorbing devices. Materials belonging to the first type are explored in Papers I-III, while the ones belonging to the second are tackled in Papers IV and V.

There has always been a struggle to find a balance between costs and the efficiency of emitting materials for application in dedicated devices. In Papers I-III, two strategies are taken into account to address this issue. Finding inspiration from ionic complexes of Mn(II), newly designed ionic materials and ILs emitting green light are proposed as an alternative to the more expensive heavy metals-based ones such as Ir(III) and Pt(II). Coming closer to an ideal compromise of cost and performance, fully organic and extremely cheap low-melting salts based on the 8-hydroxyquinoline unit were prepared. These compounds revealed efficient fluorescence in the blue region of the spectrum for such simple molecules, paving the way for the preparation of possibly inexpensive light-emitting devices.

In Paper IV, direct absorption of light is taken into consideration with photoresponsive ionic liquids, which undergo cis-trans isomerization. Due to this feature and their ionic nature, these materials could be adopted into photoswitches. Additionally, the effect of functional groups on the isomerization of the ILs and on the ability of the materials to undergo mesophase formation was studied.

One of the key components of dye-sensitized solar cells is the electrolytic mediator sandwiched between two electrodes. This has been a matter of intense study due to issues regarding its stability, which impair the device's performance. ILs can be adopted in devices to solve this issue. In Paper V, triazolium ILs allowed the manufacturing of devices with higher efficiencies and longer lifetimes than the ones realized with imidazolium relatives. These materials allowed for the stability of the ionic couple I-/I3- and moisture resistance due to their non-hygroscopic nature.

Structural characterization of complex inorganic materials using solid-state NMR spectroscopy

Over the past decades, advancements in technology have relied greatly on the development of new functional inorganic materials. Detailed structural characterization of these materials is key for the understanding and also prediction of chemical and physical properties. The structural characterization of complex inorganic materials is typically conducted by a combination of multiple methods. Solid-state NMR brings several advantages because it is element-specific, non-destructive and allows local-chemical-structure elucidation for composite materials, disordered and interfacial structures. This thesis focuses on the application of solid-state NMR for structural characterization of two classes of complex inorganic materials. 

Calcium phosphate cements (CPCs) have been widely applied as bone-substitution materials. The structures of the setting cements are vital for understanding their behaviors in setting and bone-regeneration processes and functions of different additives. In this thesis two types of CPCs, with different additives, were investigated. The different components in the cements could be identified and quantified with solid-state NMR. Correlation spectra were established that helped in probing the structural relationship between different phases. 

Mixed-anion perovskite compounds AB(O,X)3 (X = N, F, H, OH, etc.) have been intensively investigated because of their unique properties for different applications as introduced by the mixed anion environment for the transition metal component B. Because of the lability of hydride oxyhydrides emerged as versatile precursors for the synthesis of other mixed-anion compounds and oxynitrides are extensively investigated for their photocatalytic activity and dielectric properties. In this thesis the oxyhydrides BaTiO3-xHx and SrVO2H were synthesized and their subsequent conversions to oxynitrides were investigated. Solid-state NMR was used to probe the local chemical environments of H and N incorporated in the perovskite anion substructure. 1H NMR proved especially to be useful in the quantification of H which is very difficult to accomplish by other methods.

Assemblies of Colloidal Hydrochar Nanoparticles and their Derived Activated Carbons for CO2 Sorption

Carbon-rich colloids are of great fundamental and technological interest and in this thesis, I tested a range of hypotheses and studied aspects of small hydrochar-based colloids and their colloidal and material chemistry. Crude hydrochar dispersions were synthesized by hydrothermal carbonization of glucose and purified by dialysis. After the purification, stable and monodisperse dispersions of colloidal hydrochar particles in water were obtained. Evaporation of water from the colloidal hydrochar dispersion led to that the hydrochar particles deposited into repeated strip patterns on glass substrates, or underwent directed assembly into macroscopic rods or yarn-shaped objects at the glass-water-air interface.

In one study, we studied the strip patterns that comprised dense assemblies of hydrochar particles formed through directed assembly on the substrates during evaporation of water as a function of the sodium dodecylsulfate (SDS) addition, pH of the dispersion, geometry of the substrates, and concentration of the colloidal particle. The mechanisms were presented. In the published paper included in the thesis, the formation of the macroscopically large and assembled rods was studied during evaporation of water from the colloidal hydrochar dispersions. This assembly was studied along with the electrostatic stability of the dispersions at various pH and ion strengths and the redispersability of the assembled rods into the constituting colloidal particles. For matters of applications of the rod assemblies, pyrolysis and templating silicon carbide -tricopper silicide ((SiC-Cu3Si) by reactive infiltration with a copper silicon alloy by reaction infiltration were introduced.

In two manuscripts, aspects of the dispersions of hydrochar particles were studied with means of KHCO3 activation into activated carbons (ACs). In one study, hydrochar particles were activated, and then the ACs were dispersed in a solvent after physical grinding. The morphology, porosity, and CO2 sorption properties, etc. of the activated carbons prepared by chemical activation were studied for freeze-dried hydrochar particles and the long bent yarn assemblies pretreated under different conditions. ACs of electrospun nanofibers of polyvinylpyrrolidone (PVP) and colloidal hydrochar were oxidized and chemically activated with KHCO3 or K2CO3 and studied for the adsorption of CO2.

On the accuracy of crystal structural analysis and the potential of unraveling structural details by 3D electron diffraction

Knowing the atomic crystal structures of ordered porous solids is essential in understanding their behaviors and properties, developing new applications, and designing new porous materials. Electrons have a much shorter wavelength and much stronger interaction with atoms in a crystal compared with X-ray. Therefore, electron crystallography can effectively determine the structures of nano- and micro-sized crystals. Three-dimensional electron diffraction (3D ED) methods have been developed for the structure determination of various types of complex crystal structures. Continuous rotation electron diffraction (cRED) has unique aspects in both fast data collection and accurate structure determination. 

This thesis focused on the accuracy of crystal structure analysis and the potential of unraveling structural details by cRED. The cRED method was first applied for the ab initio structure determination of a beam-sensitive biocomposite metal-organic framework (MOF), BSA@ZIF-CO3-1. The atomic structure of BSA@ZIF-CO3-1 obtained by cRED was the same compared to that obtained by single crystal X-ray diffraction (SCXRD). Accurate atomic structures could be obtained by cRED. The sample of BSA@ZIF-CO3-1 was initially regarded as a pure new phase, however, during the cRED data collection and processing procedure, two distinct crystal systems and unit cells were revealed. BSA@ZIF-CO3-1  was identified as the major phase in the sample, and a new MOF, denoted ZIF-EC1, as the minor phase. ZIF-EC1 has a dense 3D framework with high N and Zn densities, which is a promising candidate for electrocatalysis. The discovery of ZIF-EC1 was followed by investigating the effects of improving 3D ED data completeness on the structural analysis. I successfully solved the structures of ZIF-EC1 from each individual dataset with the lowest completeness of 44.5% and refined to a high precession (better than 0.04 Å). Then I merged ten datasets to obtain a high data completeness, the structural model is improved, peaks appear more spherical in the electrostatic potential maps. 

The next part of this thesis was focused on unraveling structural details. By applying cRED, each non-Hydrogen atom from guest molecules can be separately localized from the difference Fourier map for two open framework germanates, SU-8 and SU-68. The atomic structure of both the framework and the guest molecules obtained by cRED is as reliable and accurate as that obtained by SCXRD. In the last part, the application of cRED into determining structures for new materials are highlighted. The structure of two new MOFs, Cd-MOF and Pb-MOF are successfully determined by cRED.

Chemometrics : Unravelling information from complex data generated by modern instruments

Chemometrics is a discipline dedicated to solving problems arising from complicated analytical systems, combining statistics, mathematics, and computational programming languages.

This thesis is based on the work developed in four scientific projects published as papers in scientific journals. The studies developed in these projects have been essentially focused on a data analysis perspective, interpreting complicated data by means of algorithms, employing chemometrical methodologies. Several chemometrical approaches, based on multivariate data analysis and signal processing algorithms have been studied and employed in each project. Most of the data analysis problems studied these projects are related to liquid chromatography hyphenated to mass spectrometry systems, including tandem mass spectrometry. One of the projects has been related to spectrophotometric data.

Chromatographic peak shifts have been attributed to lack of control of the nominal chromatographic parameters. The purpose of the work presented in Paper I was to study retention time data, obtained experimentally by provoking peak shifts with controlled effects, to demonstrate that there are patterns associated with such changing factors affecting chromatographic processes. PCR (Principal Component Regression) models were calculated for each compound (98 compounds), using the retention time data of each compound as responses (y), and the retention time data of the remaining compounds as regressors (X). The results demonstrate that the peak shifts of each compound across samples are correlated with the peak shifts of the other compounds in the chromatographic data. This work confirmed a previous work, where an algorithm was developed to improve alignment of peaks in large number of complex samples, based on peak shift patterns.

Partial Least Squares (PLS) is one of the mostly used chemometrics techniques. In the work presented in Paper II, a previously reported modified PLS algorithm was studied. This algorithm was developed with the purpose of not generating overfitting models with increasing noise in X, which happens with the classical PLS. However, the results in less-noisy data were not as good as the classical PLS. From this study, we have developed another modified algorithm that does not overfit with increasing noise in X, and it converges with the solutions of the classical PLS in less-noisy data.

DNA adductomics is a recent field in omics that studies modifications in the DNA. The goal of the project in Paper III was to develop a program with a graphical interface to interpret LC-MS/MS using a data independent acquisition method, to identify adducts in DNA nucleosides. The results were compared with those performed manually. The program detected over 150 potential adducts whereas manually, in a previous work, only about 25 were found. This program can detect adducts automatically in a matter of seconds.

Cancer has been associated with processes that are related to exposure to pollutants and the consumption of certain food products. This process has been related to electrophilic compounds that react with DNA (adducts). When DNA modifications occur, often defense mechanisms in the cell are triggered often leading to the rupture of the cell. Fragments of DNA (micronuclei) are then roaming in the blood stream. In this work (Paper IV), electrophilic additions to hemoglobin (adducts) and the expression of micronuclei in blood samples from 50 children were studied. One of the goals of the project was to find correlations between the adducts in hemoglobin and the expression of micronuclei. PLS was used to model the data. However, the results were not conclusive (R2 =  0.60), i.e., there may be some trends, but there are other variables not modelled that may influence the variance in expression of micronuclei. 

Assembly and alignment in cellulose nanomaterial-based composite dispersions and thermally insulating foams

Research on nanoparticles extracted from renewable and highly available sources is motivated by both the development of functional nanomaterials and the drive to replace widely used materials based on fossil resources. In particular, cellulose, in the form of cellulose nanomaterials (CNM), has attracted increased attention for the development of sustainable and high performance products, thanks to properties that include high specific mechanical strength, chemical versatility and anisotropic thermal conductivity. Ice-templated CNM foams display super-insulating properties across the direction of the aligned particles (radially) and could potentially compete with fossil-based insulation materials. This thesis investigates the alignment and co-assembly of widely available inorganic nanomaterials with CNM in aqueous dispersions, and the relative importance of phonon scattering in anisotropic thermally insulating composite foams.

Time resolved small-angle X-ray scattering (SAXS) experiments have been conducted to study assembly and alignment in composite aqueous dispersions containing cellulose nanocrystals (CNC) and montmorillonite (MNT) clay nanoplatelets. The co-assembly of CNC and MNT in slowly evaporating levitating droplets was dominated by the interactions between the dispersed CNC particles but MNT promoted gelation and assembly at lower total volume fractions than in CNC-only droplets. Combining SAXS with rotational rheology showed that shear induced a high degree of orientation of CNC in both the CNC-only and mixed CNC:MNT dispersions. The shear-induced CNC orientation relaxed quickly in the CNC-only dispersion but relaxation was strongly retarded and partially inhibited in the mixed CNC:MNT dispersions.

Analysis of previous works suggests that anisotropic and multiscale CNM-based foams with a high number of interfaces can favour heat dissipation by phonon scattering within the foam walls. Measurements and theoretical estimates of the thermal conductivities of CNC-only ice-templated foams over a wide range of densities confirmed the importance of phonon scattering to achieve super-insulating radial thermal conductivity values. 

Ice-templated CNC:MNT composite foams displayed a lower radial thermal conductivity compared to CNC-only foams, which suggests that the introduction of heterogeneous interfaces between the biopolymer and the clay enhanced the dissipation of heat through phonon scattering. Composite ice-templated foams of colloidal silica and TEMPO-oxidised cellulose nanofibrils (TCNF) were significantly stronger under mechanical compression and less sensitive to moisture uptake than TCNF-only foams, and maintained radial thermal conductivities that are comparable with widely used thermally insulating materials. These examples could pave the way towards the development of super-insulating, strong and moisture-resilient CNM-based composite foams.

Push the limitations of crystal structure determination by 3D electron diffraction : From inorganic porous materials to biomolecules

Structure elucidation is fundamental to understanding the chemical and physical properties of a material. Three-dimensional electron diffraction (3D ED) has shown great power for structure determination of nanometer- or submicrometer-sized crystals that are either too small or too complex for X-ray diffraction. 3D ED can be applied to a wide range of crystalline materials from inorganic materials, small organic molecules, to macromolecules. In this thesis, continuous rotation electron diffraction (cRED), also known as micro-crystal electron diffraction (MicroED) in macromolecular crystallography, has been applied for the determination of interesting novel crystal structures. New methods and protocols have been developed to push the current limitations of crystal structure determination by 3D ED.

The structure of silicate zeolite PST-24 is highly disordered. A combination of cRED with high-resolution transmission electron microscopy (HRTEM) revealed its unique channel system with varying dimensionality from 2D to 3D. The aluminum metal-organic framework CAU-23 nanocrystals form aggregates and are very beam sensitive. Its structure, as determined by cRED, is built by twisted helical Al-O chains connected by TDC2- linkers, forming a chiral structure with square channels. The unique structure of CAU-23 provides high stability and high water adsorption capacity, making it an ideal material for ultra-low temperature adsorption driven chillers.

A simple pressure-assisted specimen preparation method, denoted Preassis, has been developed to overcome the challenges in the application of MicroED on biological samples with high viscosity and low crystal concentration. It has been successfully applied for the specimen preparation of several bio-molecular crystals including a novel R2lox metalloenzyme, which was crucial for its structure determination. Furthermore, an investigation of the influence of radiation damage on lysozyme crystals was performed to improve the data quality and final structural model. Finally, the crystal structure of acetylated amyloid-β fragment Ac-Aβ16-20, related to Alzheimer’s disease, has been studied. The crystal has an active optical wave-guiding property with an excitation wavenumber of 488 nm due to its unique packing of Ac-KLVFF β–sheets.

Thermal Conductivity of Hygroscopic Foams Based on Cellulose Nanomaterials

Biobased super-insulating materials could mitigate climate change by minimizing the use of petroleum-based materials, creating artificial carbon sinks and minimizing the energy needed to maintain pleasant interior conditions. Cellulose nanomaterials (CNM) produced from abundantly available cellulose sources constitute versatile, highly anisotropic raw materials with tunable surface chemistry and high strength. This thesis includes the evaluation of the thermal conductivity of isotropic and anisotropic CNM-based foams and aerogels and analysis of the dominant heat transfer mechanisms. 

We have developed a customized measurement cell for hygroscopic materials in which the humidity and temperature are carefully controlled while the thermal conductivity is measured. Anisotropic cellulose nanofibrils (CNF) foams with varying diameters showed a super-insulating behavior perpendicular (radial) to the nanofibril direction, that depended non-linearly on the relative humidity (RH) and foam density. Molecular simulations revealed that the very low thermal conductivity is related to phonon scattering due to the increase of the inter-fibrillar gap with increasing RH that resulted in a 6-fold decrease of the thermal boundary conductance. The moisture-induced swelling exceeds the thermal conductivity increase due to water uptake at low and intermediate RH and resulted in a minimum thermal conductivity of 14 mW m-1 K-1 at 35% RH and 295 K for the foams based on the thinnest CNF.

The density-dependency of the thermal conductivity of cellulose nanocrystal (CNC) foams with densities of 25 to 129 kg m-3 was investigated and a volume-weighted modelling of the solid and gas thermal conductivity contributions suggested that phonon scattering was essential to explain the low radial thermal conductivity, whereas the replacement of air with water and the Knudsen effect related to the nanoporosity in the foam walls had a small effect. Intermediate-density CNC foams (34 kg m-3) exhibited a radial thermal conductivity of 24 mW m-1 K-1 at 295 K and 20% RH, which is below the value for air.

The moisture uptake of foams based on CNMs with different degree of crystallinity and surface modifications decreased significantly with increasing crystallinity and temperature. Molecular simulations showed that the narrow pore size distribution of the amorphous cellulose film, and the relatively low water adsorption in the hydration cell around the oxygen of the carboxyl group play an important role for the moisture uptake of amorphous and crystalline CNM-based materials.

Isotropic CNF- and polyoxamer based foams as well as CNF-AL-MIL-53 (an aluminum‑based metal-organic framework) foams were both moderately insulating (>40 mW m-1 K-1) and comparable with commercial expanded polystyrene. The thermal conductivity of CNF and polyoxamer foams displayed a very strong RH dependency that was modelled with a modified Künzel’s model. The presence of hydrophobic AL-MIL-53 decreased the moisture uptake of CNF-AL-MIL-53 aerogels by 42% compared to CNF-polyoxamer foams.

Solid and gas conduction are the main heat transfer mechanisms in hygroscopic nanofibrillar foams and aerogels that depend on the interfacial phonon scattering, Knudsen effect and water uptake. It is essential that the thermal conductivity measurements of hygroscopic CNM-based foams and aerogels are determined at controlled RH and that parameters such as the temperature, density, nanoporosity, fibril dimensions and alignment are characterized and controlled for systematic development and upscaling of biobased foams for applications in building insulation and packaging.

Functional Nanocellulose–Tannin Materials Inspired by Nature and Traditional Processes

Renewable and biodegradable alternatives to fossil-based materials are essential as concerns over depleting finite resources and the pollution of our ecosystems are growing. Abundant, highly anisotropic, and mechanically strong cellulose nanofibrils (CNF) are attractive building blocks for the fabrication of high-performance biobased materials that can compete with their conventional fossil-based counterparts. This thesis presents potential solutions to key challenges in the production and properties of CNF and CNF-based materials, such as low moisture resistance and energy-intense processing, by using the physicochemical properties of tannins. The benchmarking of CNF to improve energy-efficient production was investigated and the ability of plant-derived tannins to precipitate proteins, react with nucleophiles when oxidized, and coordinate to metal ions was exploited to produce multifunctional films and foams that were inspired by Nature or traditional processes.

Wet strong, antioxidant, and UV-blocking CNF-based films were produced by mimicking the traditional process of leather tanning. Oxidized CNF were grafted with gelatin that was precipitated with a water-soluble tannin. The polyphenolic tannin provided the films with good radical scavenging properties and efficient blocking of light in the UV-B/UV-C range. The insoluble gelatin–tannin complexes conferred upon the material wet mechanical properties that were comparable to the dry mechanical performance of fossil-based packaging films. So far, there is no universally accepted approach to account for how the swelling of a hygroscopic CNF-based film influences its mechanical properties in humid or wet conditions. Here, a best practice for determining and reporting wet strength is suggested.

Inspired by the sclerotization of insect cuticle, a scalable route towards moisture-resilient, strong, and thermally insulating CNF-based foams was developed. The CNF were modified with a polyamine, ice-templated, treated with an oxidized tannin, solvent-exchanged to ethanol, and evaporatively dried. The cross-linked structure had a high compressive modulus and a thermal conductivity close to that of air, even at high relative humidities.

A method to produce micron-sized patterns on CNF films based on the traditional Bògòlanfini dyeing technique is presented. The films were pre-impregnated with a tannin and patterned using microcontact printing with a metal-salt-soaked stamp. The line and dot patterns were analyzed and their colors were tuned by changing the metal ion in the printing ink or the pH.

The final part of the thesis describes a novel approach to assess the degree of CNF fibrillation during energy-efficient grinding by analyzing the structure and properties of anisotropic foams. The optimal energy input during fiber disintegration that produced CNF foams with the best mechanical and thermal insulation properties, as well as the highest CNF and foam cell wall orientation, was identified.

Following nanoparticle self-assembly in real-time : Small-angle X-ray scattering and quartz crystal microbalance study of self-assembling iron oxide nanocubes

Self-assembly of nanoparticles is a widely used technique to produce nanostructured materials with crystallographic coherence on the atomic scale, i.e. mesocrystals, which can display useful collective properties. This thesis focusses on the underlying mechanism and dynamics of mesocrystal formation by using real-time techniques. Quartz-crystal microbalance with dissipation monitoring (QCM-D) as well as small-angle X-ray scattering (SAXS) in combination with optical microscopy were used to probe the temporal evolution of growing mesocrystals to elucidate the growth mechanism.

Time-resolved small-angle X-ray scattering was used to probe the formation and how the structure and defects of the growing mesocrystals in levitating droplets evolve with time. Probing self-assembly of oleate-capped iron oxide nanocubes during evaporation-driven poor-solvent enrichment (EDPSE) showed that a low particle concentration in combination with a short nucleation period can generate large and well-ordered mesocrystals. Information on the formation and transformation of defects in mesocrystals were obtained by analysis of the temporal evolution of crystal strain. A transition from a rapidly increasing isotropic strain to a decreasing anisotropic strain towards the end of the growth stage was observed. The occurrence of anisotropic strain was assigned to the formation of stress-relieving dislocations in the crystal, which were induced by large internal stresses caused by superlattice contraction.

Directed assembly of superparamagnetic iron oxide nanocubes, subjected to a weak magnetic field, produced one-dimensional mesocrystal fibers. Real-time SAXS as well as optical microscopy revealed a two-stage growth mechanism. The primary stage involved the growth of cuboidal mesocrystals by nanocube self-assembly. In a secondary stage, the cuboidal mesocrystals were assembled and aligned into fibers by the magnetic field. Evaluation of the magnetic dipole-dipole and van der Waals interactions showed that the dipolar forces arising between two nanocubes in a weak magnetic field are negligible compared to the van der Waals forces, but become the dominant force for larger mesocrystals, which drives the formation of fibers.

QCM-D combined with optical microscopy provided simultaneously information on the rheological properties as well as on the mass of an adsorbed self-assembled layer of iron oxide nanocubes. We show that the iron oxide nanocubes rapidly assembled into an array with primarily viscous characteristics. This fluid-like behaviour can be assigned to a layer of solvent surrounding the nanocubes inside the assembly. Expulsion of the thin solvent layer from the assembled array is responsible for the increase in rigidity observed shortly after the beginning of self-assembly.

A journey towards complete structure determination of zeolites by electron crystallography methods

Electron crystallography has recently become very successful for structural studies of materials with sub-micrometer sized crystals. In this thesis two major techniques have been applied for structure elucidation – 3-dimensional electron diffraction (3D ED) and high-resolution transmission electron microscopy (HRTEM) imaging. Both can provide information about the structure at the atomic level and have been used for structure determination. During the last decade, two 3D ED methods have been used in our group; the stepwise rotation electron diffraction (RED) method developed in our lab and continuous rotation electron diffraction (cRED) where improvements on the already existing RED method were implemented. Both 3D ED methods can be used for fast structure determination of ordered crystalline materials. HRTEM imaging is very useful for structure determination of more complex and severely disordered materials. For complex structures it is often necessary to combine several methods including powder X-ray diffraction (PXRD).

   Zeolites are microporous crystalline materials. They have complex structures and often synthesized as polycrystalline powders. The aforementioned electron crystallography methods have unique advantages in elucidation of atomic structures of such zeolites. In this thesis, the development of 3D ED methods, especially from RED to cRED, is described through the journey of structure determination of four zeolites; a known pure silicate silicalite-1 for testing the RED method, and three new zeolites. The new zeolites include two extra-large pore germanosilicates ITQ-56 and SYSU-3 and one small-pore aluminosilicate EMM-37. The thesis shows the limitations and advantages of the RED and cRED methods and how different challenges in the structure determination of zeolites are tackled by the advances of 3D ED methods. Finally the thesis presents a detailed structural study of disorders in an aluminosilicate zeolite ITQ-39 by combining HRTEM, RED with sample preparation by ultramicrotomy. The structure of ITQ-39 was determined in 2012 by our group. Here three new zeolite polytypes of ITQ-39 were identified from the HRTEM images and their structure models are proposed.

   A complete structure determination of zeolites includes elucidation of the framework structure, guest species such as structure directing agent (SDA) molecules and ions in the pores, and any structural disorder in the crystal. This thesis reflects to all of these structural characteristics of zeolites, presenting the power of electron crystallography.

Design of new materials with crystal structure-related properties : The role of lone pair cations

Non-centrosymmetry and low-dimensional arrangements, e.g. chains or layers, are very attractive structural characteristics of crystalline compounds since they are linked to some physical properties including nonlinear optical activity, ferroelectricity and magnetic frustration. The insertion of a lone-pair cation, equipped with a stereochemically active electron pair into a compound may increase its structural variety and induce the aforementioned characteristics.

In this thesis some novel oxide and oxohalide compounds are described. They contain a transition metal and also a p-element lone-pair cation. Relevant synthesis details, crystal structure and physical properties of the compounds will be presented.

Chemical systems containing iodate ions and either Cu2+ or Sc3+ have been explored in an effort to find new non-centrosymmetric compounds. The compounds contain also K+ due to its tendency to form highly coordinated asymmetric units. The new iodates are KCu(IO3)3 and the non-centrosymmetric compounds K3Sc(IO3)6 and KSc(IO3)3Cl.

Only a few oxofluoride compounds that contain lone-pair cations have been reported in the literature, mainly due to synthetic difficulties. In this work new oxofluoride compounds containing the transition metals Cu2+, Co2+, or Sc3+ and the lone pair cations Bi3+ or Se4+ have been synthesized, where the transition metal octahedra form low-dimensional arrangements in form of chains or layers. The electronegative F ̶ anions behave like O2 ̶  and bridge in between different building blocks. The new oxofluorides are Cu2SeO3F2, CoBi2O2F4 and ScBi2O3F3. The first is a framework-like compound and the latter two are layered and belong to the Aurivillius family with one perovskite like layer. The inclusion of F made it possible to broaden this Aurivillius family to contain low-oxidation state transition metals. 

The magnetic properties of the new compounds containing Cu2+ and Co2+ were characterised and the Sc3+ containing non-centrosymmetric iodates were found to show non-linear optical properties.

Additive metallurgy - Thermal influences on structure and properties of stainless steel 316L

Additive manufacturing (AM) as a manufacturing process has, in recent years, become widely accepted as capable of manufacturing parts that will be used in end products. In this thesis, stainless steel grade 316L parts are manufactured using two different powder bed fusion techniques, selective laser melting (SLM) and electron beam melting (EBM). It is recognized that parts made using these processes will have unique microstructures and mechanical properties that have not been seen in bulk parts produced with other methods. The driving force behind the formation of these structures is the fast cooling speed that induces segregation of elements, forming an inhomogeneous microstructure. How these structures react to thermal treatment is less well known and an essential aspect in many applications. Parts manufactured using SLM was treated with hot isostatic pressing (HIP) to investigate if the material retains its unique features. Two different HIP cycles were used, one with 1150 °C and one with 1040 °C. In both cases, the cellular sub-grain structure fades. The cycle utilizing the high temperature is found to coarsen the grain structure and thus lowering the mechanical properties significantly. As manufactured parts show yield strength (615±1 MPa), tensile strength (725±2 MPa) and microhardness (211±10 Hv), compared to values of yield strength (284±2 MPa), tensile strength (636±1 MPa) and microhardness (178±8 Hv) after 1150 °C HIP. Using HIP at 1040 °C, the material will retain a finer grain structure resulting in higher yield strength (417±7 MPa) compared to 1150 °C HIP temperature, while the UTS and hardness have a similar value. It is also observed that the dispersed inclusions formed during SLM are still present after HIP to increase the mechanical properties compared to a conventionally annealed bar (TS: 515 MPa, YS: 205 MPa). Samples manufactured using EBM was investigated to understand the influence of the in-situ heat treatment that is present in the EBM process. The material possesses a long-range heterogeneous structure in addition to the cellular structure, where the cellular structure is present at the top and disappears further down the sample. Samples with different geometries were produced to study the effect of heat flux, cooling speed and the elevated temperature of 800 °C that is present during the EBM process. The thickness of the cell boundaries is measured in different areas, revealing that geometry and size of manufactured parts have a significant impact on the evolving microstructure. It is also revealed that the tensile strength (562±4 MPa) and microhardness (161±11 Hv) is not affected by the change in microstructure, resulting in a very homogeneous material concerning these parameters. Heat treating the material at 800 °C show that the cellular structure becomes diffuse after several hours, but the grain morphology stays the same.

Nanocellulose: Energy Applications and Self-Assembly

Technologies based on renewable materials are required to decrease the environmental cost and promote the development of a sustainable society. In this regard, nanocellulose extracted from wood finds many applications thanks to its intrinsic mechanical and chemical properties as well as the versatility in its manufacturing processes. In this thesis, I present the results of the investigations on carboxylated cellulose nanofibres (CNF) as ionic conductive membranes and electrode component in fuel cells and lithium ion batteries. Moreover, I also show the results of the assembly of CNF suspension and cellulose nanocrystals (CNC) - lepidocrocite nanorods (LpN) hybrids.

The fuel cell performance of CNF-based proton conductive membranes was evaluated as a function of intrinsic material parameters such as membrane thickness and surface charge density as well as extrinsic parameters such as the relative humidity (RH). It was found that the proton conductivity is about 2 mS cm-1 at 30 °C between 65 and 95 % RH. At the same time, the water uptake of the membrane was measured and correlated with the structural evolution of the membrane using small angle X-ray scattering.

The performance of the CNF-based separator in lithium ion batteries was investigated as a function of membrane porosity and protonation of the functional groups. The Li-ion battery assembled with the protonated separators showed stable and good rate performance.

The CNF was also tested as binder in lithium ion battery, showing that the morphology and mechanical properties of the cathode depend on the nanofibre surface charge and degree of defibrillation. In particular, high surface charge and medium degree of defibrillation give the best electrochemical performance.

Pyrolysed CNF (cCNF) improved the electrochemical performance of silicon nanoparticles-based anode thanks to the carbon network derived from the nanofibres. Si-cCNF has a capacity retention of 72.2 % after 500 cycles at 1 C and better performance rate than the pristine silicon nanoparticles.

Regarding the assembly of nanocellulose, the nematic order of CNF suspension at different nanofibre concentrations (0.5 – 4.9 wt%) was studied by small angle X-ray scattering, polarized optical microscopy and rheological measurements. The order parameter reaches a maximum value of 0.8 depending on the CNF concentration. Small angle neutron scattering with contrast matching experiments reveals that the natural alignment of CNC and LpN can be switched using a combination of magnetic fields of up to 6.8 T and varying the amount of LpN incorporated in the CNC.

Unraveling the structures of complex nanocrystalline materials by combining TEM and XRPD – development and application

Knowledge of the three-dimensional (3D) atomic structure of materials is essential to a fundamental understanding of their properties. The key to understanding the functionality of many materials, particularly those of commercial and industrial interest, is often hidden in the details at the nanoscale. For this reason, it is very important to choose the right strategy to analyze the structure of challenging materials with complex disordered framework structures, or of the layered materials that are the subject of this thesis. Structure analysis of beam-sensitive or uniquely disordered materials can be complicated. Although there are already existing methods such as X-ray powder diffraction (XRPD), the data may exhibit reflection overlap or other problems that make structure determination difficult. To overcome these limitations for nanocrystalline materials, complementary characterization techniques can be used. Here, I will focus on 3D electron crystallography (continuous rotation electron diffraction and high-resolution electron microscopy) methods that have grown during the past years as hybrid methods for structure determination. Based on the presented materials, I will also emphasize that any kind of challenges can be a driving force for method development.  Furthermore, some of the insights gained lead to better understanding of how to collect and process 3D electron diffraction data, which could be applied to make data collection of challenging samples easier and obtain higher quality structure refinements from the data. Finally, I will try to describe the general procedures for ab initio structure elucidation of disordered nanocrystals and layered materials.

Aqueous Exfoliation of Transition Metal Oxides for Energy Storage and Photocatalysis Applications : Vanadium Oxide and Molybdenum Oxide Nanosheets

Two-dimensional (2D) transition metal oxides (TMOs) are a category of materials which have unique physical and chemical properties compared to their bulk counterparts. However, the synthesis of 2D TMOs commonly includes the use of environmental threats such as organic solvents. In this thesis, we developed environmentally friendly strategies to fabricate TMO nanosheets from the commercially available bulk oxides. In particular, hydrated vanadium pentoxide (V2O5∙nH2O) nanosheets and oxygen deficient molybdenum trioxide (MoO3-x) nanosheets were prepared.  The V2O5∙nH2O nanosheets were drop-cast onto multi-walled carbon nanotube (MWCNT) paper and applied as a free-standing electrode (FSE) for a lithium battery. The accessible capacity of the FSE was dependent on the electrode thickness; the thickest electrode delivered the lowest accessible capacity.  Alternatively, a composite material of V2O5∙nH2O nanosheets with 10% MWCNT (VOx-CNT composite) was prepared and two types of electrodes, FSE and conventionally cast electrode (CCE), were employed as cathode materials for lithium batteries. A detailed comparison between these electrodes was presented. In addition, the VOx-CNT composite was applied as a negative electrode for a sodium-ion battery and showed a reversible capacity of about 140 mAh g-1. On the other hand, the MoO3-x nanosheets were employed as binder-free electrodes for supercapacitor application in an acidified Na2SO4 electrolyte. Furthermore, the MoO3-x nanosheets were used as photocatalysts for organic dye degradation. The simple eco-friendly synthesis methods coupled with the potential application of the TMO nanosheets reflect the significance of this thesis in both the synthesis and the energy-related applications of 2D materials.

Rechargeable Aqueous Batteries Based on Available Resources : Investigation and Development towards Efficient Battery Performance

Batteries employing water based electrolytes enable extremely low manufacturing costs and are inherently safer than Li-ion batteries. Batteries based on zinc, manganese dioxide, iron, and air have high energy relevancy, are not resource restricted, and can contribute to large scale energy storage solutions. Zinc has a rich history as electrode material for primary alkaline Zn–MnO2 batteries. Historically, its use in secondary batteries has been limited because of morphological uncertainties and passivation effects that may lead to cell failure. Manganese dioxide electrodes are ineffective as rechargeable electrodes because of failure mechanisms associated with phase transformations during cycling. The irreversibility of manganese dioxide is strongly correlated to the formation of the electrochemically inactive spinel, Mn3O4/ZnMn2O4. The development of the iron electrode for Fe–air batteries was initiated in late the 1960s and these batteries still suffer from charging inefficiency, due to the unwanted hydrogen evolution reaction. Meanwhile, the air electrode is limited in long-term operation because of the sluggish oxygen evolution and reduction kinetics. These limitations of the Fe–air battery yield poor overall efficiencies, which bring vast energy losses upon cycling.

Herein, the limitations described above were countered for rechargeable Zn–MnO2 and Fe–air batteries by synthesizing electrode materials and modifying electrolyte compositions. The electrolyte mixture of 1 M KOH + 3 M LiOH for rechargeable alkaline Zn–MnO2 batteries limited the formation of the inactive spinels and improved their cycle life significantly. Further, the formation of the inactive spinels was overcome in mildly acidic electrolytes containing 2 M ZnSO4, enabling the cells to cycle reversibly at lower pH via a distinctive reaction mechanism. The iron electrodes were improved with the addition of stannate, which suppressed hydrogen evolution. Furthermore, optimal charge protocols of the iron electrodes were identified to minimize the hydrogen evolution rate. On the air electrode, the synthesized NiCo2O4 showed excellent bifunctional catalytic activity for oxygen evolution and reduction, and was incorporated to a flow assisted rechargeable Fe–air battery, in order to prove the practicability of this technology. Studies of the electrode materials on the micro, macro, nano, and atomic scales were carried out to increase the understanding of the nature of and interactions between of these materials. This included both in operando and ex situ characterization. X-ray and neutron radiation, and analytical- and electrochemical methods provided insight to improve the performance and cycle life of the batteries.

The chemical nature of CO2 adsorption in zeolite A

The climate changes are accelerated by increasing levels of carbon dioxide in the atmosphere connected to the fossil-fuel-based energy system. Substantial reforms of the system are needed immediately and could include the implementation of carbon capture and storage (CCS) technologies. Adsorption-driven CO2 capture is one of the most promising post-combustion CO2 capture techniques, which aim to remove CO2 from N2 in flue gas.

The nature of adsorption of CO2 can vary. The process can act as physisorption with intermolecular interactions of the van der Waals type or as chemisorption with a significantly perturbed electronic structure of CO2 and for example the formation of CO32- and HCO3- species. The molecular details were elucidated by MAS NMR and IR studies for a zeolite, and the placement of adsorbed molecules was revealed by in situ diffraction data analysis.

Adsorption-driven processes can be implemented only if highly functional adsorbent materials have been developed. Zeolite A seems to be a promising candidate. This thesis broadly discussed the potential enhancement of the selectivity of CO2 over N2 and CH4 by replacing Na+ with larger monovalent cation e.g. K+ in pore apertures of zeolite A. The positions of the extra-framework cations were analyzed by in situ X-ray diffraction using synchrotron light source. The cations were positioned at the 4- and 6-rings and the 8-ring apertures of the aluminosilicate framework of zeolite A. K+ was favored at the 8-ring sites, and this cation did also gradually substitute the 6-ring sites with and increasing x in |Na12-xKx|-A. Large cations did not fit the mirror plane of the 6-ring and were placed on both its sides. K+ at both positions, in 8-rings and 6-rings, seems to have tailored the size of pore openings.

The effective pore aperture size was shown to depend on the K+ content and to partition small CO2 molecules from large N2 and CH4 because of, likely, differences in diffusivities. Various compositions of |Na12-xKx|-A demonstrated gradual decrease of CO2 uptake with x and an exclusion of N2 and CH4 already for low x. Although already absorbed CO2 molecules were revealed by in situ neutron diffraction to be coordinated mainly by the 8-ring cation or bridging adjacent 8-ring sites. Adsorbed CO2 molecules displaced the cations into the a-cages and resulted in a slight contraction of the overall distribution of extra-framework cations upon the adsorption of CO2.

The kinetically-enhanced separation of CO2 from N2/CH4 seemed to be associated by a restrained diffusion also for the CO2 molecules. This is problematic for pressure swing adsorption processes. However, it could potentially be addressed by the reduction of size of zeolite crystals to increase the extent of accessible porous space over limited time.

3D Electron Microscopy Methods and Applications : Structures from Atomic Scale to Mesoscale

The crystal structure determines the physical properties of a material. The structure can be analysed at different levels, from atomic level, mesoscale level, all the way up to the macroscale level. Transmission Electron Microscope (TEM) is a powerful tool for studying the structure of materials at atomic scale level and mesoscale level because of the short wavelength of the electrons. At atomic scale level, structure determination using TEM can be performed in diffraction mode. The recent developments in 3D electron diffraction methods make structure determination from nano- and micron-sized crystals much easier than before. However, due to the strong interactions, electrons can be scattered multiple times through the crystal, causing the measured intensities to be less accurate than that in the X-ray case.

In this thesis, we use the continuous rotation electron diffraction (cRED) developed in our group to investigate the structure of materials and the accuracy of this method. In the third chapter, we use cRED method to determine the structure of two aluminophosphate zeolites, PST-13 and PST-14. We presented that these structures can be built from two pairs of enantiomeric structural building units. In the fourth chapter, we show that despite the inaccuracy in measured intensities originated from dynamical effect, it is still possible to determine the structure accurately. We show that the atomic coordinates of ZSM-5 and sucrose crystal structure determined by multiple electron diffraction datasets is identical to that determined from X-ray data or neutron data. We also assessed the linearity between calculated structure factor and observed structure factor and use this as a coarse assessment indicator for diffraction data quality for protein crystals.

Apart from atomic structure, mesoscale structures, such as mesopores, can also determine the property of materials. For the 3D structures of these nanoscale structures, we can also use TEM electron tomography techniques to investigate. In chapter five, we performed electron tomography for two different materials with mesoporous structure and illustrated the formation mechanism of mesoporous magnesium carbonate and the internal tunnel structure of hierarchical TS-1 zeolite.

Modeling of biomembranes: from computational toxicology to simulations of neurodegenerative diseases

It was known from the middle of the last century that a cell-membrane is a lipid bilayer. Since that time a large number of experimental studies has been done in order to see how a certain molecule can penetrate through a membrane. Due to the complexity of laboratory experiments computational chemistry became a convenient tool for investigations involving this process. In a real life a compound has to pass through several membranes of different chemical composition before reaching the actual target. Such a diversity in constitution gives a various selectivity to cell-membranes: some molecules will penetrate through them and others will not. That is why the development and a choice of suitable models for lipid bilayers are important steps in such a research. In this thesis new all-atomistic models for polyunsaturated phospholipids in cis conformations have been derived and added to the SLipids force field. After a successful force field validation, the new lipid models were used in molecular dynamics and well-tempered metadynamics simulations of several problems, such as toxicity of hydroxylated polybrominated diphenyl ethers (OH-PBDE), behavior of cholesterol in various membranes, an aggregation of amyloid-β (Aβ) peptides. The significance of the presence of lipid unsaturation has been demonstrated by all computations. 2’-OH-BDE68 (ortho) showed the affinity to saturated lipid bilayer, but had more conformational variations in the center of the unsaturated membrane. Cholesterol did not exhibit the preference to polynsaturated lipid bilayers from free energy calculations, but the diversity in orientations of this molecule, depending on its locations was observed. The behavior of Aβ peptides was dependent on membrane saturation as well. The insertion of Aβ peptides was detected in lipid bilayers containing higher amounts of polyunsaturated phospholipids, while in systems with more saturated membranes amyloids aggregated on membrane surfaces. Moreover, a comparison of simulations for quadro- and mono-component lipid bilayers showed that the membrane built of 18:0-22:6 PC can serve as a good model for the ’healthy’ tissue of a human brain. Also the lipid bilayer built of 14:0-14:0 PC exhibited similar features as the quadro-lipid membrane representing the brain tissue affected by Alzheimer’s disease. Good agreement of some computational results with available experimental findings demonstrated the applicability of computer simulations to real life problems.

Atomistic simulations of structural and dynamical properties of liquids under geometric constraints

The statistical-mechanical description of liquids represents a formidable problem in physic due to the absence of the analytical theory of the liquid state. Atomistic simulations represent a unique source of information in this respect and can be implemented in order address macroscopically measurable liquid properties, including its structure and dynamics, based on the information of the interactions between its constituent molecules. A particularly intriguing challenge is represented by the problem of studying liquids under geometric constraints like surfaces, or where the dimensionality is strongly suppressed like for liquids in 2 dimensions. Experimental measurements cannot access to these regions due to the resolution limitations. In this thesis the study of confined liquids is achieved by particle-based simulations at different level of theory. In particular 3 study cases are considered: the first is the characterization of solid-liquid interfaces. The problem of adsorbing surfaces is treated as a specific case of inorganic surfaces in contact with liquid water. TiO2, chosen as reference material, is studied in its polymorphic structures in aqueous conditions. The surface reactivity and its influence on the liquid structure is solved considering the quantum nature of the system. The mechanism of a solute adsorbing at the interface, considering the interfacial liquid properties, is also addressed. New advanced analysis tools for determining the structural and dynamical properties of water under a surface confinement and the thermodynamic associated to relative adsorption processes are developed. We are confident that this study will represent a mile stone for a systematic study of complex environments as bio-inorganic interfaces. As second case a liquid confined in a 2D surface is studied. Simple liquids having spherically symmetric interaction are very powerful in order to understand the relevant degrees of freedom that governs a certain physical process. Here we expand the definition of 2D hexatic phases to smectic systems in 3D. Finally the self-assembly of a triply periodic mesophase having a Fddd space symmetry group is fully characterized for a simple liquid. This phase can be thought as a geometrical reduction to a two-dimensional separation surface. The possibility of generating such complex network with simple particles, like in colloids, opens the frontiers for the exploration of new materials and applications.

Development of rotation electron diffraction as a fully automated and accurate method for structure determination

Over the past decade, electron diffraction methods have aroused more and more interest for micro-crystal structure determination. Compared to traditional X-ray diffraction, electron diffraction breaks the size limitation of the crystals studied, but at the same time it also suffers from much stronger dynamical effects. While X-ray crystallography has been almost thoroughly developed, electron crystallography is still under active development. To be able to perform electron diffraction experiments, adequate skills for using a TEM are usually required, which makes ED experiments less accessible to average users than X-ray diffraction. Moreover, the relatively poor data statistics from ED data prevented electron crystallography from being widely accepted in the crystallography community.

The thesis focused on both application and method development of continuous rotation electron diffraction (cRED) technique. The cRED method was first applied to a beam sensitive metal-organic framework sample, Co-CAU-36, and the structure was determined and refined within one working day. More importantly, the guest molecules in the pores were also located using only electron diffraction data. To facilitate general users to perform cRED data collection for useful data, software was developed to automate the overall data collection procedure. Through combination of hierarchical cluster analysis tools, the automatically collected data showed comparable quality to those from recent publications, and thus were useful for structure determination and even phase identification. To deal with dynamical refinement for ED data, a frame orientation refinement algorithm was designed to calculate accurate frame orientations for rotation data. Accuracy for the method was validated and compared to an existing software, and the behavior of TEM goniometer was studied by applying the method to an experimental data set.

Structure-property investigation of ZnSb, ZnAs, and SiB3 : - binary semiconductors with electron poor framework structures

In today’s society, where energy conservation and green energy are buzz words, new scientific discoveries in green energy harvesting is key. This work focuses on materials capable of recycling low value thermal energy. Low value thermal energy, waste heat, is for free, and can be transformed into valuable electricity via thermoelectric technology. A thermoelectric device cleanly converts heat into electricity through the Seebeck effect. Thermoelectric devices can play an important role in satisfying the future global need for efficient energy management, however, the primary barrier of improving thermoelectric devices is the materials themselves.

The aim of this thesis is to identify new compositions and structures for thermoelectric materials. In particular, the concept of “electron poor framework semiconductors” is explored. Electron Poor Framework Semiconductors (EPFS) are materials at the border between metals and non-metals, which often show intricate and unique structures with complex bonding schemes. Generally, constituting elements should be from group 12(II) (Zn, Cd), 13(III) (B, Al, Ga, In), 14(IV) (Si, Ge, Sn, Pb), 15(V) (Sb, Bi), and 16(VI) (Te), i.e. elements which have a similar electronegativity (between 1.5-2.0). All EPFS materials have in common highly complex crystal structures, which are thought to be a consequence of their electron-poor bonding patterns. EPFS materials have an intrinsically very low – glass like - lattice thermal conductivity. The focus of this thesis is on combinations of group 12(II) (Zn) with 16 (V) (As, Sb), and 13(III) (B) with 14(IV) (Si).

ZnSb possesses a simple structure with 8 formula units in an orthorhombic unit cell, it is considered a stoichiometric compound without noticeable structural disorder. In this thesis ZnSb is used as a model system to establish more broadly structure–property correlations in Sb based EPFS materials.

ZnSb was established to possess an impurity band that determines electrical transport properties up to 300–400 K. Doping of ZnSb with Ag seems to enhance the impurity band by increasing the number of acceptor states and improving charge carrier density by two orders of magnitude. ZT values of Ag doped ZnSb are found to exceed 1 at 350 K. The origin of the low thermal conductivity of ZnSb was traced back to a multitude of localized low energy optic modes, acting as Einstein-like rattling modes.

ZnAs was accessed through high pressure synthesis. The compound is isostructural to ZnSb and possess an indirect band gap of 0.9 eV, which is larger than that for ZnSb (0.5 eV). The larger band gap is attributed to the higher polarity of Zn-As bonds. The electrical resistivity of ZnAs is higher and the Seebeck coefficient is lower compared to ZnSb. However, ZnAs and ZnSb exhibit similarly low lattice thermal conductivity, although As is considerably lighter than Sb. This was explained by their similar bonding properties.

Lastly, the longstanding mystery of SiB3 phases was resolved. The formation of metastable and disordered α-SiB3-x is fast and thus kinetically driven, whereas formation of stable β-SiB3 is slow and not quantitative unless high pressure conditions are applied. This thesis work established reproducible synthesis routes for both materials. The fast kinetics can be exploited for simultaneous synthesis and sintering of α -SiB3-x specimens in a SPS device. It is suggested that α -SiB3-x represents a promising refractory thermoelectric material.

Unveiling Catalytic Species in Suspension/Solution-Based Reactions by In Situ X-Ray Absorption Spectroscopy : Evolution of Palladium and Ruthenium Species

The palladium (Pd) and ruthenium (Ru) species in several attractive catalysts have been probed using X-ray absorption spectroscopy (XAS). The study of catalyst evolution in suspension- and solution-based reactions was the primary aim. It was achieved by performing in situ XAS experiments on Pd and Ru over the course of the reactions. A custom-made reactor was employed which allowed the catalysts to be mixed with other reaction components under desired conditions.

The first system investigated was the Heck coupling reaction catalyzed by Pd(II) complexes embedded on metal-organic frameworks. It was realized that the as-synthesized catalysts go through an instant ligand substitution process when added to the reaction mixture. Mononuclear Pd complexes are the active species at the first stage of the measurement which then gradually transform into Pd nanoclusters. At a later stage of the measurement, chloride ligands start to bind to surface atoms of the Pd nanoclusters, leading to a deactivation of the catalyst. Following the first successful in situ XAS experiment, Pd(II) carbene complexes catalyzing undirected C–H acetoxylation of benzene in the presence of an oxidant were explored. A gradual ligand substitution occurs, and the mean oxidation state of Pd increases at the same time. At a later stage, Pd nanoclusters form, while the mean oxidation state of Pd returns to the start value. Deactivation of a heterogeneous Pd(II) catalyst during cycloisomerization of acetylenic acids was then investigated using in situ XAS. The choice of substrates showed to significantly influence the nature of Pd species, and the reduction of Pd(II) forming Pd(0) aggregates causes the deactivation. Moreover, strategies of reactivating the catalyst and prevention of the deactivation were developed and examined. In the end, the activation process of a Ru catalyst was studied and the structure of the intermediate was determined by in situ XAS. It was demonstrated that an electron-donating substituent on the cyclopentadiene ligand exhibits a promoting effect on the activation, while an electron-withdrawing substituent inhibits the activation.

Cellulose Nanofibril-based Hybrid Materials : Eco-friendly design towards separation and packaging applications

Nanocellulose has been lately considered as the “Holy-Grail” in the design of sustainable materials due to its bio-origin and an unprecedented combination of prominent features, including good mechanical properties, anisotropy and versatile surface chemistry. In addition, nanocellulose in the form of cellulose nanofibrils, can adopt variable structures and morphologies depending on the processing technique, such as aerogels, films and monoliths.

However, there are limitations that hinder the implementation of cellulose nanofibrils in “real-life applications”, such as inherent interaction with bacteria and proteins, thus leading to surface-fouling; and loss of integrity due to water-induced swelling. A way to overcome these challenges, and provide further functionality, is through hybridization strategies, at which the multiple components act synergistically towards specific properties and applications. In this thesis, the aim is to present multiple strategies for the synthesis of novel cellulose nanofibril-based hybrid materials, in the form of 2D-films and 3D-foams, towards their employment for separation applications or active food packaging.

A novel strategy to surface-functionalize cellulose nanofibril-membranes is proposed via grafting zwitterionic polymer brushes of poly (cysteine methacrylate). The modification can suppress the absorption of proteins in an 85%, as well as decreasing the adhesion of bacteria in an 87%, while introducing antimicrobial properties, as demonstrated against S. aureus.

The spontaneous formation of functional metal oxide nanoparticles occurring in situ on cellulose nanofibrils-films during the adsorption of metal ions from water is investigated, which occurs without the additional use of chemicals or temperature. Notably, this process not only enables the upcycling of materials through multi-stage applications, but also provides a cost-effective method to prepare multifunctional hybrid materials with enhanced dye-removal/antimicrobial activity.

The processing of functional composite films from cellulose nanofibril-stabilized Pickering emulsions and their suitability to be used as active edible barriers was demonstrated. The presence of oil in the films fine-tuned the properties of the films, as well as acted as the medium to encapsulate bio-active hydrophobic compounds, providing further functionality such as antioxidant and antimicrobial properties.

Anisotropic porous hybrid foams with ultra-high loading capacity of sorbents (e.g., zeolites and metal-organic frameworks) were produced via unidirectional freeze-casting method using cellulose nanofibrils/gelatin as template material. The foams indeed exhibited ultra-high loading capacity of sorbent nanomaterials, a linear relationship between sorbent content and CO2 adsorption capacity, and high CO2/N2 selectivity.

Understanding Composition–Structure–Bioactivity Correlations in Bioactive Glasses

Bioactive glasses integrate with bone/tooth tissues by forming a layer of hydroxy-carbonate apatite (HCA), which mimics the composition of bone mineral. In the current thesis, we investigated composition–structure–bioactivity correlations of phosphosilicate and borophosphosilicate (BPS) glasses. Bioactive phosphosilicate glasses extend the compositional space of the ”45S5 Bioglass®”, which has been in clinical use for decades. Recently developed bioactive BPS glasses with SiO2→B2O3 substitutions transform more completely into HCA and their glass dissolution behaviors can be tuned by varying the relative contents of B and Si. 

It is known that the average silicate network connectivity NSi and the phosphate content (x(P2O5)) affect the apatite formation (in vitro bioactivity) of phosphosilicate glasses, but the details remain poorly explored. Three series of phosphosilicate glasses were designed by independently varying NSi and x(P2O5). After immersion of the glasses in a simulated body fluid (SBF) for 24 hours, different degrees of their apatite formation were quantified by Fourier-transform infrared (FTIR) spectroscopy. The results revealed that a high P content widened the NSi range that generated optimum amounts of apatite and also mitigated the detrimental effects associated with using glass particles with < 50 μm. The amounts of apatite derived from FTIR agreed with those from 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The growth of apatite at bioactive glass surfaces was found to follow a sigmoidal growth model, in which the precursor phase, amorphous calcium phosphate (ACP), formed in the induction period and then crystallized into HCA in the following proliferation period, with an improvement in the structural ordering of HCA in the maturation period. This formation process closely resembles the apatite precipitated spontaneously from supersaturated Ca/P-containing solutions. The simultaneous growth of ACP and HCA is discussed in conjunction with a previously proposed mechanism for explaining in vitro bioactivity and apatite growth from bioactive glasses. 

The short- and medium- range structures of bioactive borophosphosilicate (BPS) glasses were investigated by solid-state MAS NMR. Two series of BPS glasses were designed by gradually replacing SiO2 with B2O3 in the 45S5 glass, as well as another base glass featuring a more condensed glass network. As the B2O3 content is increased, the glass networks become more polymerized, together with decreased fractions of the dominating BO3 and orthophosphate units. Borate groups are homogeneously mixed with the isolated orthophosphate groups, while the remaining phosphate groups exhibit a slight preference for bonding to BO4 over SiO4 units. Linkages among borate groups are dominated by B[3]–O–B[4] linkages at the expenses of B[3]–O–B[3] and B[4]–O–B[4] linkages, with the latter B[4]–O–B[4] motifs disfavored yet abundant. A similar fashion of borate mixing was observed in P-free Na/Ca-based borosilicate glasses that span a large compositional space. The content of B[4]–O–B[4] linkages was found to be controlled by the relative fractions of BO4 groups and non-bridging oxygen ions.

Design, processing and properties of lightweight foams from cellulose nanofibers

Foams are applied in many areas including thermal insulation of buildings, flotation devices, packaging, filters for water purification, CO2 sorbents and for biomedical devices. Today, the market is dominated by foams produced from synthetic, non-renewable polymers, which raises serious concerns for the sustainable and ecological development of our society. This thesis will demonstrate how lightweight foams based on nanocellulose can be processed and how the properties in both the wet and dry state can be optimized.

Lightweight and highly porous foams were successfully prepared using a commercially available surface-active polyoxamer, Pluronic P123TM, cellulose nanofibers (CNFs), and soluble CaCO3 nanoparticles. The stability of wet and dry composite foams was significantly improved by delayed aggregation of the CNF matrix by gluconic acid-triggered dissolution of the CaCO3 nanoparticles, which generated a strong and dense CNF network in the foam walls. Drying the Ca2+-reinforced foam at 60 °C resulted in moderate shrinkage but the overall microstructure and pore/foam bubble size distribution were preserved after drying. The elastic modulus of Ca2+-reinforced composite foams with a density of 9 – 15 kg/m3 was significantly higher than fossil-based polyurethane foams.

Lightweight hybrid foams have been prepared from aqueous dispersions of a surface-active aminosilane (AS) and CNF for a pH range of 10.4 – 10.8. Evaporative drying at a mild temperature (60 °C) resulted in dry foams with low densities (25 – 50 kg/m3) and high porosities (96 – 99%). The evaporation of water catalyzed the condensation of the AS to form low-molecular linear polymers, which contributed to the increase in the stiffness and strength of the CNF-containing foam lamella.

Strong wet foams suitable for 3D printing were produced using methylcellulose (MC), CNFs and montmorillonite clay (MMT) as a filler and tannic acid and glyoxal as cross-linkers. The air-water interface of the foams was stabilized by the co-adsorption of MC, CNF and MMT. Complexation of the polysaccharides with tannic acid improved the foam stability and the viscoelastic properties of the wet foam for direct ink writing of robust cellular architectures. Glyoxal improved the water resistance and stiffened the lightweight material that had been dried at ambient pressure and elevated temperatures with minimum shrinkage. The highly porous foams displayed a specific Young’s modulus and yield strength that outperformed other bio-based foams and commercially available expanded polystyrene.

Unidirectional freezing, freeze-casting, of nanocellulose dispersions produced cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment with X-ray diffraction showed high orientation of CNF and short and stiff cellulose nanocrystals (CNC).

Synthesis, characterization and applications of hierarchical porous inorganic materials: a multi-dimensional approach

Zeolites are a type of microporous crystalline materials that have been widely used in industrial applications including separation, adsorption, and catalysis. However, great limitations on diffusion through these materials can arise due to the small pores present in mircoporous frameworks, and this can impact catalytic reactions in particular. The synthesis of hierarchical zeolites has solved the diffusion problem. In this thesis, various hierarchically porous materials have been synthesized and tested as catalysts.

In the first part of this thesis, a titanium-containing hierarchically porous silicate material has been constructed from double-four-ring (D4R) units as building blocks.

In the second part of this thesis, hierarchical MWW zeolites were synthesized by swelling and pillaring of a lamellar MWW zeolitic precursor (MCM-22) using D4R building units. The synthesis procedure has been carefully studied by various characterization methods, such as PXRD, TEM, N2 adsorption–desorption etc.

In the last part of this thesis, MFI zeolites with controllable hierarchical pore systems have been prepared. Firstly, hierarchical ZSM-5 and TS-1 with open pores were generated using a temperature programmed dissolution–recrystallization post-synthesis treatment and tested as catalysts for benzyl alcohol self-etherification and cyclohexanone ammoximation. Secondly, single-crystalline hierarchical shell-like ZSM-5 has been synthesized via a dissolution–recrystallization post-treatment of mesoporous ZSM-5. The post-treatment increased the catalytic activity of the ZSM-5 zeolite for the aldol condensation of bulky substrates.

Sustainable porous organic materials : Synthesis, sorption properties and characterization

The resources available to us humans, including metals, minerals, biomass, air, water, and anything else on the planet, are being used at an increasing rate. This anthropogenic use of resources both depletes the resources and has negative impacts on other resources, e.g. the biosphere. Thus, developing (more) sustainable chemical and industrial processes are of the utmost importance for the well-being of the creatures of Earth and for the long-term sustainability of human society.

This thesis focuses on organic porous materials, and more specifically their synthesis and characterization. Porous materials are, for example, used in detergents, water treatment, bio gas upgrading, carbon dioxide capture, as catalysts, in sensors, and in various biological applications. The application of porous materials can contribute to the drive towards a more sustainable society. However, porous materials are typically not sustainable themselves. Thus, there is a need to develop more sustainable porous materials. The synthesis and characterization of three different groups of porous organic materials are described in this thesis.

In pulp- and paper manufacturing, lignin is separated from desirable products and is typically combusted for heat. In one section of this thesis, lignin was used to produce bio-oil for potential use in fuels and chemicals. However, the bio-oil process produced a solid by-product. The by-product was used to synthesize and study activated carbons with very high porosities and magnetic properties, a combination of properties that may prove to be useful in applications.

Sugar is known to produce solid and unwanted compounds through reactions with acids. It is shown here that it is possible to produce highly microporous humins, i.e. organic porous materials with a large amount of small pores, using sulphuric acid and a range of saccharides and bio-based polymers. This work supports that solid by-products in a wide range of biomass conversion processes can be of high value, both economically and as replacements for less sustainable alternatives.

The biosphere contains vast amounts of molecules with aromatic structures. The last section of this thesis shows how such aromatic molecules can be used to produce highly porous materials through Friedel-Crafts type chemistry using sulfolane as a solvent and iron chloride as a catalyst. This synthesis strategy produces high-performance materials, improves upon the sustainability of traditional Friedel-Crafts chemistry, and makes use of typically underutilized and abundant bio-based molecules.

Nanocellulose and Its Biohybrids for Water Purification : Atomic Force Microscopy as a Tool to Probe Surface Properties and Interactions

Nanocellulose has been explored extensively in recent years as an adsorbent due to its promising performance in the removal of charged contaminants from water. In this thesis, various atomic force microscopy (AFM) techniques are used to understand the surface characteristics and specific interactions of nanocellulose with water contaminants (heavy metal ions and dyes) and nanoscale entities (Graphene Oxide (GO) and Graphene Oxide nanocolloids (nanoGO)), and explain the mechanisms related to adsorption, metal ion clustering, self-assembly and mechanical reinforcement.

AFM probes functionalised with microscale and nanoscale celluloses were used as colloidal probes to study specific surface interactions with heavy metal ions and dyes in the aqueous medium. This approach enabled quantitative measurements of the adhesion force between nanocellulose and the water pollutants under in situ conditions by direct or in-direct methods. Adhesion forces, including the piconewton range, were measured, and the forces depended on the surface groups present on the nanocellulose.

AFM imaging in dry and/or wet conditions was successfully used to investigate the adsorption, self-assembly, morphology and mechanical properties of nanocellulose and its bio-hybrids. The self-assembly, the metal nanolayer and the nanoclusters on the surface of nanocellulose and its biohybrids after adsorption were confirmed and explained by advanced microscopy, spectroscopy and computational modelling.

The adhesion and stiffness measurement of single nanocellulose fibers using in situ PeakForce Quantitative Nanomechanical (PF-QNM) characterization confirmed the adsorption of metal ions on the surface in the liquid medium. PF-QNM mapping of the freestanding biohybrid membranes also revealed the enhanced modulus of the biohybrid membrane compared with the TEMPO(2,2,6,6-tetramethylpiperidine-1-oxylradical)-mediated oxidation nanofibers (TOCNF) membrane, which explained the hydrolytic stability and recyclability of these membranes.

The established methodology, which combines advanced microscopy with spectroscopy and modelling techniques, can be extended to other biobased macromolecular systems to investigate the adsorption behaviour and/or surface interactions in bio nanotechnology.

Development of metal hydride surface structures for high power NiMH batteries : Also extended cycle-life and lead to more effective recycling methods

By combining alkaline etching of hydrogen storage alloys or their hydrides with a controlled oxidation, it was possible to improve reaction kinetics and accelerate activation of MH-electrodes. Both AB5 and AB2 alloys were studied where A is mixtures of rare earth elements for AB5 alloys and titanium and/or vanadium, zirconium for AB2 alloys; nickel contributes the major part of B. With SEM and TEM studies the surface could be described as consisting of several phases where an interphase with active Ni-containing cluster protected the inner metallic hydrogen storage part of the powder particles. These catalytic Ni-clusters presumably lead to the fast activation and high discharge capacity of alloy.

This interphase was observed to be stable enough to allow us to develop a method, where we could add pure oxygen to a NiMH battery pack in order to regenerate the amount of electrolyte that was lost during long time cycling of the battery. Meanwhile, the method will rebalance the electrodes mitigating excessive pressures during over charge. Therefore, the internal resistance of cells can be reduced and cycle life will increase.

It was also shown that the stable interphase could survive a mild ball milling or sonication which enabled us to upcycle material from spent NiMH batteries into a better working MH-electrodes with improved kinetics and activation properties. Reuse of ball-milled or sonicated material could serve as a simple recycling alternative to energy-demanding metallurgical smelting methods and chemical consuming hydrometallurgical recycling processes, where the possibilities of up-scaling further favour the less complex mechanical treatments. The stable but catalytic interphase protecting the inner particles indicates that the MH-electrode material may perform better in its second life in a new NiMH battery.

Nanocellulose-based materials: from colloidal assembly to functional films

The assembly of nature-based nanomaterials into complex architectures is both a design principle of biological composites, e.g., wood and nacre with outstanding properties and a promising route for developing functional macroscopic materials. This thesis aims to investigate and understand the colloidal and self-assembly behaviour of nanocellulose in aqueous dispersions. Moreover, composite films of nanocellulose and nanoclay/lignin with diverse functionalities, e.g., mechanical and optical properties, are fabricated by tailoring the electrostatic interactions of these building blocks.

The evaporation induced assembly of sulfonated cellulose nanocrystal (CNC) has been followed in either an aqueous droplet on substrates or a levitated droplet by real-time small angle X-ray scattering. The evolution of structural features, e.g., an isotropic phase, biphasic phase, fully liquid crystalline and contracted helical structures of drying CNC dispersions were related to the power-law scaling of the particle separation distance (d) with concentrations (c, from 1 vol% to 38 vol%). Below 2 vol%, CNC dispersions consolidated isotropically with a scaling of d c-1/3, while the fully cholesteric liquid crystalline phase showed a unidimensional contraction of the nematic structure (d c-1) with increasing concentrations. Competition between gelation and the ordered assembly of CNC was quantitatively evaluated in nanoscale for the first time, which was reflected by a scaling of d c-2/3.

The rheology of composite dispersions of carboxylated cellulose nanofibril (CNF) and nanoclay was investigated, which was influenced by the surface charge of CNF, the morphology of nanoclays and interactions between CNF and clay particles. Optically transparent films of synthetic aminoclay (50 wt%) and CNF were fabricated, of which tensile strength and strain to failure (205 MPa and 7.5%) were significantly higher than those of nacre and other nacre-mimicking nanocellulose-based materials, e.g., montmorillonite-CNF films, due to the formation of ionic bonding between the cationic clay and anionic CNF.

Lignin nanoparticles were testified to enhance the colloidal stability and dispersity of carboxylated CNF in dispersions, and showed a remarkable strengthening and stiffening effect on the matrix of CNF. The mechanical properties of lignin-CNF films were superior to previously reported polymer/nanoparticle-CNF composites, such as polyvinyl alcohol-CNF films and even reduced graphene oxide-CNF films.

Local structure of perovskite ferroelectric ceramics as revealed by 3D electron diffuse scattering : A walk in between the Bragg peaks

Local structural disorder in crystalline materials plays a crucial role in understanding their properties. The means to study structural disorder is diffuse scattering (DS). Even though DS was observed since the early days of X-ray diffraction the weak intensity and the sheer number of different kinds of disorder hindered the development of a unique solution strategy. However, the advent of X-ray and neutron synchrotron sources together with recent advances in automated electron diffraction techniques have unraveled a new world in between Bragg peaks where a wealth of information is available.

In this thesis electron diffraction is used to explore the different kinds of DS in three-dimensions, for several perovskite ferroelectric ceramics. Based on the information presented in the reconstructed 3D reciprocal space volumes, disordered atomic structures were proposed and verified by the calculated electron diffraction patterns. A complex structural model for the local disorder in 85Na0.5Bi0.5TiO3-10K0.5Bi0.5TiO3-5BaTiO3 piezoceramic was developed by analyzing the morphology and intensity of electron DS in 3D. Next, the influence of potassium-content on the octahedral-tilt disorder for three different piezoceramics was studied by a combination of dark-field imaging and electron diffraction. Further on, the temperature-dependence of electron DS for 95Na0.5Bi0.5TiO3-5BaTiO3 piezoceramic revealed a local structural phase transition that was correlated with the depolarization mechanism. Lastly, strong electron DS was recorded from a Pb-based relaxor and simulations of disordered atomic structures showed that the local structure resembles a dipolar glass state. These demonstrate that electron diffraction is a powerful tool for the study of local structural disorder in crystalline materials, especially for ceramics. The major advantage is that we are able to record single-crystal electron diffraction data from individual grains. Moreover, since we are analyzing a 3D reciprocal volume several orientations can be studied simultaneously and we are not limited to zero-Laue zones. Finally, the models for local structural disorder provided valuable insight into how macroscopic properties are influenced by local structural disorder, in addition to the average structure.

Water splitting by heterogeneous catalysis

A sustainable solution for meeting the energy demands at our planet is by utilizing wind-, solar-, wave-, thermal-, biomass- and hydroelectric power. These renewable and CO2 emission-free energy sources are highly variable in terms of spatial and temporal availability over the Earth, introducing the need for an appropriate method of storing and carrying energy. Hydrogen has gained significant attention as an energy storage- and carrier media because of the high energy density that is exploited within the ‘power-to-gas’ process chain. A robust way of producing sustainable hydrogen is via electrochemical water splitting.

In this work the search for new heterogeneous catalyst materials with the aim of increasing energy efficiency in water splitting has involved methods of both electrochemical water splitting and chemical water oxidation. Some 21 compounds including metal- oxides, oxofluorides, oxochlorides, hydroxide and metals have been evaluated as catalysts. Two of these were synthesized directly onto conductive backbones by hydrothermal methods. Dedicated electrochemical cells were constructed for appropriate analysis of reactions, with one cell simulating an upscale unit accounting for realistic large scale applications; in this cell gaseous products are quantified by use of mass spectrometry. Parameters such as real time faradaic efficiency, production of H2 and O2 in relation to power input or overpotentials, Tafel slopes, exchange current density and electrochemical active surface area as well as turnover numbers and turnover frequencies have been evaluated.

Solubility, possible side reactions, the role of the oxidation state of catalytically active elements and the nature of the outermost active surface layer of the catalyst are discussed. It was concluded that metal oxides are less efficient than metal based catalysts, both in terms of energy efficiency and in terms of electrode preparation methods intended for long time operation. The most efficient material was Ni-Fe hydroxide electrodeposited onto Ni metal foam as conductive backbone. Among the other catalysts, Co3Sb4O6F6 was of particular interest because the compound incorporate a metalloid (Sb) and redox inert F and yet show pronounced catalytic performance.

In addition, performance of materials in water splitting catalysis has been discussed on the basis of results from electron microscopy, solubility experiments and X-ray diffraction data.

3D Electron Diffraction : Application and Development towards High-quality Structure Determination

Electron crystallography has been proven to be effective for structure determination of nano- and micron-sized crystals. In the past few years, 3D electron diffraction (3DED) techniques were used for the structure solution of various types of complex structures such as zeolites, metal-organic frameworks (MOF) and pharmaceutical compounds. However, unlike X-ray crystallography, electron diffraction has not yet become an independent technique for a complete structure determination due to relatively poorer diffraction intensities and often powder X-ray diffraction data are used for structure validation and refinement.

Electron beam damage to the structures that are sensitive to high energy electrons and dynamical scattering are important factors to lead to the deviation of electron diffraction intensities from the squared amplitudes of the structure factors. In this thesis, we investigate various aspects around the 3D electron diffraction data quality and strategies for obtaining better data and structure models. We combined 3D electron diffraction methods and powder X-ray diffraction to determine the structure of an open-framework material and discussed the difficulties and limitations of electron diffraction for beam sensitive materials. Next, we illustrated the structure determination of a pharmaceutical compound, bismuth subgallate, using 3D electron diffraction. While severe beam damage and diffuse scattering were observed in the dataset collected with the conventional rotation electron diffraction (RED) method, the continuous rotation electron diffraction (cRED) method coupled with sample cooling significantly improved the data quality and made the structure solution possible. In order to better understand the potentials and limitations of the continuous rotation method, we collected multiple datasets from different crystals of a known structure and studied the data quality by evaluating the accuracy of the refined structure models. To tackle dynamical scattering in electron diffraction data, we explored a routine for structure refinement with dynamical intensity calculation using RED data from a known structure and discussed its potentials and limitations.

Investigating Hydrogenous Behavior of Zintl Phases : Interstitial Hydrides, Polyanionic Hydrides, Complex Hydrides, Oxidative Decomposition

This thesis is an investigation into the hydrogenous behavior of Zintl phases. Zintl phases are comprised of an active metal (i.e alkali, alkaline earth, and rare earth) and a p-block element. The discussion gives an overview of the influence hydrogen affects the electronic and geometric structure of Zintl phases and subsequent properties. Incorporation of hydrogen into a Zintl phase is categorized as either polyanionic or interstitial Zintl phase hydrides. In the former the hydrogen covalently bonds to the polyanion and in the latter the hydrogen behaves hydridic, coordinates exclusively with the active metal, leading to an oxidation of the polyanion. Synthesis of hydrogenous Zintl phases may be through either a direct hydrogenation of a Zintl phase precursor or by combining active metal hydrides and p-block elements. The latter strategy typically leads to thermodynamically stable hydrides, whereas the former supports the formation of kinetically controlled products. 

Polyanionic hydrides are exemplified by SrAlGeH and BaAlGeH. The underlying Zintl phases SrAlGe and BaAlGe have a structure that relates to the AlB2 structure type. These Zintl phases possess 9 valence electrons for bonding and, thus, are charge imbalanced species. Connected to the charge imbalance are superconductive properties (the Tc of SrAlGe and BaAlGe is 6.7 and 6.3 °C, respectively). In the polyanionic hydrides the hydrogen is covalently bonded as a terminating ligand to the Al atoms. The Al and Ge atoms in the anionic substructure [AlGeH]2- form corrugated hexagon layers. Thus, with respect to the underlying Zintl phases there is only a minimal change to the arrangement of metal atoms. However, the electronic properties are drastically changed since the Zintl phase hydrides are semiconductors. 

Interstitial hydrides are exemplified by Ba3Si4Hx (1 < x < 2) which was obtained from the hydrogenation of the Zintl phase Ba3Si4. Ba3Si4 contains a Si46- “butterfly” polyanion. Hydrogenation resulted in a disordered hydride in which blocks of two competing tetragonal structures are intergrown. In the first structure the hydrogen is located inside Ba6 octahedra (I-Ba3Si4H), and in the second structure the hydrogen is located inside Ba5 square pyramids (P-Ba3Si4H2). In both scenarios the “butterfly anions appear oxidized and form Si44- tetrahedra.

Hydrogenation may also be used as a synthesis technique to produce p-block element rich Zintl phases, such as silicide clathrates. During hydrogenation active metal is removed from the Zintl phase precursor as metal hydride. This process, called oxidative decomposition, was demonstrated with RbSi, KSi and NaSi. Hydrogenation yielded clathrate I at 300 °C and 500 °C for RbSi and KSi, respectively. Whereas a mixture of both clathrate I and II resulted at 500 °C for NaSi. 

Low temperature hydrogenations of KSi and RbSi resulted in the formation of the silanides KSiH3 and RbSiH3. These silanides do not represent Zintl phase hydrides but are complex hydrides with discrete SiH3- complex species. KSiH3 and RbSiH3 occur dimorphic, with a disordered α-phase (room temperature; SG Fm-3m) and an ordered β-phase (below -70 °C; SG = Pnma (KSiH3); SG = P21/m ( RbSiH3)). During this thesis the vibrational properties of the silyl anion was characterized. The Si–H stretching force constants for the disordered α-phases are around 2.035 Ncm-1 whereas in the ordered b-forms this value is reduced to ~1.956 Ncm-1. The fact that SiH3- possesses stronger Si-H bonds in the α-phases was attributed to dynamic disorder where SiH3- moieties quasi freely rotate in a very weakly coordinating alkali metal ion environment.

Lanthanide Metal-Organic Frameworks and Hierarchical Porous Zeolitic Imidazolate Frameworks : Synthesis, Properties, and Applications

This thesis presents the synthesis, properties, and applications of two important classes of metal-organic frameworks (MOFs); lanthanide MOFs and hierarchical porous zeolitic imidazolate frameworks (ZIFs). The materials have been characterized using a wide range of techniques including diffraction, imaging, various spectroscopic techniques, gas sorption, dynamical light scattering (DLS) and thermogravimetric analysis (TGA).

In Chapter 1, the unique features of MOFs and ZIFs as well as their potential applications are summarized. In Chapter 2, different characterization techniques are presented.

Chapter 3 describes a family of new isoreticular lanthanide MOFs synthesized using tri-topic linkers of different sizes, H3L1-H3L4, denoted SUMOF-7I-IV (Ln) (SU; Stockholm University, Ln = La, Ce, Pr, Nd, Sm, Eu and Gd, Paper I). The SUMOF-7I-III (Ln) contain permanent pores and exhibit exceptionally high thermal and chemical stability. The luminescence properties of SUMOF-7IIs are reported (Paper II). The influences of Ln ions and the tri-topic linkers as well as solvent molecules on the luminescence properties are investigated. Furthermore, the potential of SUMOF-7II (La) for selective sensing of Fe (III) ions and the amino acid tryptophan is demonstrated (Paper III). 

Chapter 4 presents a simple, fast and scalable approach for the synthesis of hierarchical porous zeolitic imidazolate framework ZIF-8 and ZIF-67 using triethylamine (TEA)-assisted approach (Paper IV). Organic dye molecules and proteins are encapsulated directly into the ZIFs using the one-pot method. The photophysical properties of the dyes are improved through the encapsulation into ZIF-8 nanoparticles (Paper IV). The porosity and surface area of the ZIF materials can be tuned using the different amounts of dye or TEA. To further simplify the synthesis of hierarchical porous ZIF-8, a template-free approach is presented using sodium hydroxide, which at low concentrations induces the formation of zinc hydroxide nitrate nanosheets that serve as in situ sacrificial templates (Chapter 5, Paper V). A 2D leaf-like ZIF (ZIF-L) is also obtained using the method. The hierarchical porous ZIF-8 and ZIF-L show good performance for CO2 sorption.

Prussian blue analogue copper hexacyanoferrate : Synthesis, structure characterization and its applications as battery electrode and CO2 adsorbent

Prussian blue (PB) and Prussian blue analogues (PBAs) are compounds with potential applications in a large variety of fields such as gas storage, poison antidotes, electrochromism, electrochemistry and molecular magnets. The compounds are easy to synthesize, cheap, environmentally friendly and have been pursued for both fundamental research and industrial purposes. Despite the multifunctionality of PB and PBAs, they have complicated compositions, which are largely dependent on the synthesis methods and storage conditions. Thus, performing investigations on such compounds with defined composition, stoichiometry and crystal structure is essential.

This thesis has focused on synthesis and detailed structure characterization of copper hexacyanoferrate (CuHCF) via X-ray powder diffraction (XRPD), neutron powder diffraction (NPD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), inductively coupled plasma-optical emission spectroscopy (ICP-OES), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Mössbauer spectroscopy, extended X-ray absorption fine structure (EXAFS), infrared (IR) and Raman techniques. In addition, kinetics of thermal dehydration process, CO2 adsorption and CO2 adsorption kinetics were investigated. Moreover, in operando synchrotron X-ray diffraction experiments were performed to gain insight into the structure-electrochemistry relationships in an aqueous CuHCF/Zn battery during operation.

Modification of zeolites and synthesis of SAPO-templated carbon

Zeolites are crystalline aluminosilicates with diverse structures and uniform porosities. They are widely used as catalysts, adsorbents and ion-exchangers in industry. Direct or post modifications optimize the performance of zeolites for different applications. In this thesis, IZM-2 and TON-type zeolites were synthesized, modified and studied. In addition, FAU-type zeolite and silicoaluminophosphate (SAPO) molecular sieves were applied as templates for the preparation of microporous carbons.

In the first part of this thesis, the IZM-2 zeolite with an unknown structure was synthesized. We focused on the increasing the secondary porosity and the varied framework compositions upon post modifications.

The structure determination of this IZM-2 zeolite was hindered by the small size of crystals. In the second part of this thesis, the synthesis composition was directly modified in order to increase the crystal sizes. IZM-2 crystals were enlarged by excluding the aluminium atoms from the framework. The micropores of the obtained pure-silica polymorphs were activated by ion-exchanging alkali-metal ions with protons.

Typically, TON-type zeolites that are synthesized at hydrothermal conditions under stirring have needle-shaped crystals. In the third part of this thesis, snowflake-shaped aggregates were produced by using static hydrothermal conditions for the synthesis of TON-type zeolites. The effects of synthesis parameters on the growth and morphology of crystals were discussed in detail.

In the last part of this thesis, microporous carbons with a structural regularity were prepared by chemical vapour deposition (CVD) of propylene using a silicoaluminophosphate (SAPO-37) template. Compared to the conventional zeolite templates, the SAPO template could be removed under mild conditions, without using hydrofluoric acid, and the generated carbons had a large specific surface area and a high fraction of ultrasmall micropores.

Hydrogen incorporation in Zintl phases and transition metal oxides- new environments for the lightest element in solid state chemistry

This PhD thesis presents investigations of hydrogen incorporation in Zintl phases and transition metal oxides. Hydrogenous Zintl phases can serve as important model systems for fundamental studies of hydrogen-metal interactions, while at the same time hydrogen-induced chemical structure and physical property changes provide exciting prospects for materials science. Hydrogen incorporation in transition metal oxides leads to oxyhydride systems in which O and H together form an anionic substructure. The H species in transition metal oxides may be highly mobile, making these materials interesting precursors toward other mixed anion systems. 

Zintl phases consist of an active metal, M (alkali, alkaline earth or rare earth) and a more electronegative p-block metal or semimetal component, E (Al, Ga, Si, Ge, etc.). When Zintl phases react with hydrogen, they can either form polyanionic hydrides or interstitial hydrides, undergo full hydrogenations to complex hydrides, or oxidative decomposition to more E-rich Zintl phases. The Zintl phases investigated here comprised the CaSi2, Eu3Si4, ASi (A= K, Rb) and GdGa systems which were hydrogenated at various temperature, H2 pressure, and dwelling time conditions. For CaSi2, a regular phase transition from the conventional 6R to the rare 3R took place and no hydride formation was observed. In contrast, GdGa and Eu3Si4 were very susceptible to hydrogen uptake. Already at temperatures below 100 ºC the formation of hydrides GdGaH2-x and Eu3Si4H2+x was observed. The magnetic properties of the hydrides (antiferromagnetic) differ radically from that of the Zintl phase precursor (ferromagnetic). Upon hydrogenating ASi at temperatures around 100 oC, silanides ASiH3 formed which contain discrete complex ion units SiH3-. The much complicated β – α order-disorder phase transition in ASiH3 was evaluated with neutron powder diffraction (NPD), 2H NMR and heat capacity measurements. 

A systematic study of the hydride reduction of BaTiO3 leading to perovskite oxyhydrides BaTiO3-xHx was done. A broad range of reducing agents including NaH, MgH2, CaH2, LiAlH4 and NaBH4 was employed and temperature and dwelling conditions for hydride reduction examined. Samples were characterized by X-ray powder diffraction (XRPD), thermal gravimetric analysis and 1H NMR. The concentration of H that can be incorporated in BaTiO3-xHx was found to be very low, which is in contrast with earlier reports. Instead hydride reduction leads to a high concentration of O vacancies in the reduced BaTiO3. The highly O-deficient, disordered, phases - BaTiO3-xHy(x-y) with x up to 0.6 and y in a range 0.05 – 0.2 and (x-y) > y – are cubic and may represent interesting materials with respect to electron and ion transport as well as catalysis.

Structure determination of beam sensitive crystals by rotation electron diffraction : the impact of sample cooling

Electron crystallography is complementary to X-ray crystallography. Single crystal X-ray diffraction requires the size of a crystal to be larger than about 5 × 5 × 5 μm3 while a TEM allows a million times smaller crystals being studied. This advantage of electron crystallography has been used to solve new structures of small crystals. One method which has been used to collect electron diffraction data is rotation electron diffraction (RED) developed at Stockholm University. The RED method combines the goniometer tilt and beam tilt in a TEM to achieve 3D electron diffraction data. Using a high angle tilt sample holder, RED data can be collected to cover a tilt range of up to 140o

Here the crystal structures of several different compounds have been determined using RED. The structure of needle-like crystals on the surface of NiMH particles was solved as La(OH)2. A structure model of metal-organic layers has been built based on RED data. A 3D MOF structure was solved from RED data. Two halide perovskite structures and two newly synthesized aluminophosphate structures were solved. For those beam sensitive crystals characterized here, sample cooling down to -170oC was used to reduce the beam damage. The low temperature not only reduces electron beam damage, but also keeps the structure more stable in the high vacuum in a TEM and improves the quality of the diffraction data. It is shown that cooling can improve the resolution of diffraction data for MOFs and zeolites, for samples undergoing phase changes at low temperature, the data quality could be worse by cooling. In summary, cooling can improve the ED data quality as long as the low temperature does not trigger structural changes. 

Sub-grain structure in additive manufactured stainless steel 316L

The thesis focuses on exploring the sub-grain structure in stainless steel 316L prepared by additive manufacturing (AM). Two powder-bed based AM methods are involved: selective laser melting (SLM) and electron beam melting (EBM). It is already known that AM 316L has heterogeneous property and hierarchy structure: micro-sized melt pools, micro-sized grains, nano-sized sub-grain structure and nano-sized inclusions. Yet, the relation among these structures and their influence on mechanical properties have not been clearly revealed so far. Melt pool boundaries having lower amount of sub-grain segregated network structures (Cellular structure) are weaker compared to the base material. Compared with cell boundaries, grain boundaries have less influence on strength but are still important for ductility. Cell boundaries strengthen the material without losing ductility as revealed by mechanical tests. Cellular structure can be continuous across the melt pool boundaries, low angle sub-grain boundaries, but not grain boundaries. Based on the above understanding, AM process parameters were adjusted to achieve customized mechanical properties. Comprehensive characterization were carried out to investigate the density, composition, microstructure, phase, magnetic permeability, tensile property, Charpy impact property, and fatigue property of both SLM and EBM SS316L at room temperature and at elevated temperatures (250°C and 400°C). In general, SLM SS316L has better strength while EBM SS316L has better ductility due to the different process conditions. Improved cell connection between melt pools were achieved by rotating 45° scanning direction between each layer compared to rotating 90°. Superior mechanical properties (yield strength 552 MPa and elongation 83%) were achieved in SLM SS316L fabricated with 20 µm layer thickness and tested in the building direction. Y2O3 added oxide dispersed strengthening steel (ODSS) were also prepared by SLM to further improve its performance at elevated temperatures. Slightly improved strength and ductility (yield strength 574 MPa and elongation 90%) were obtained on 0.3%Y2O3-ODSS with evenly dispersed nanoparticles (20 nm). The strength drops slightly  but ductility drops dramatically at elevated temperatures. Fractographic analysis results revealed that the coalescence of nano-voids is hindered at room temperature but not at elevated temperatures. The achieved promising properties in large AM specimens assure its potential application in nuclear fusion. For the first time, ITER first wall panel parts with complex inner pipe structure were successfully fabricated by both SLM and EBM which gives great confidence to application of AM in nuclear industry. 

Crystallization on the Mesoscale : Self-Assembly of Iron Oxide Nanocubes into Mesocrystals

Self-assembly of nanoparticles is a promising route to form complex, nanostructured materials with functional properties. Nanoparticle assemblies characterized by a crystallographic alignment of the nanoparticles on the atomic scale, i.e. mesocrystals, are commonly found in nature with outstanding functional and mechanical properties. This thesis aims to investigate and understand the formation mechanisms of mesocrystals formed by self-assembling iron oxide nanocubes.

We have used the thermal decomposition method to synthesize monodisperse, oleate-capped iron oxide nanocubes with average edge lengths between 7 nm and 12 nm and studied the evaporation-induced self-assembly in dilute toluene-based nanocube dispersions. The influence of packing constraints on the alignment of the nanocubes in nanofluidic containers has been investigated with small and wide angle X-ray scattering (SAXS and WAXS, respectively). We found that the nanocubes preferentially orient one of their {100} faces with the confining channel wall and display mesocrystalline alignment irrespective of the channel widths. 

We manipulated the solvent evaporation rate of drop-cast dispersions on fluorosilane-functionalized silica substrates in a custom-designed cell. The growth stages of the assembly process were investigated using light microscopy and quartz crystal microbalance with dissipation monitoring (QCM-D). We found that particle transport phenomena, e.g. the coffee ring effect and Marangoni flow, result in complex-shaped arrays near the three-phase contact line of a drying colloidal drop when the nitrogen flow rate is high. Diffusion-driven nanoparticle assembly into large mesocrystals with a well-defined morphology dominates at much lower nitrogen flow rates. Analysis of the time-resolved video microscopy data was used to quantify the mesocrystal growth and establish a particle diffusion-based, three-dimensional growth model. The dissipation obtained from the QCM-D signal reached its maximum value when the microscopy-observed lateral growth of the mesocrystals ceased, which we address to the fluid-like behavior of the mesocrystals and their weak binding to the substrate. Analysis of electron microscopy images and diffraction patterns showed that the formed arrays display significant nanoparticle ordering, regardless of the distinctive formation process. 

We followed the two-stage formation mechanism of mesocrystals in levitating colloidal drops with real-time SAXS. Modelling of the SAXS data with the square-well potential together with calculations of van der Waals interactions suggests that the nanocubes initially form disordered clusters, which quickly transform into an ordered phase.

Design and characterization of nanoparticles and their assemblies : Transmission electron microscopy investigations from atomic to mesoscopic length scales

Transmission electron microscopy (TEM) is a powerful and versatile tool for investigating nanomaterials. In this thesis, various transmission electron microscopy techniques are used to study the chemical and structural features of different types of inorganic nanoparticles of well-defined morphologies as well as their assemblies. The synthesis of spherical and anisotropic nanoparticles (iron oxide nanocubes and other morphologies, gadolinium orthophosphate nanorods, tungsten oxide nanowires and nanorods, palladium nanospheres, and facetted iron-manganese oxides hybrid nanoparticles) using thermal decomposition of metal complex precursors in high-boiling point organic solvents and hydrothermal process are described in details.

Electron diffraction tomography (3D EDT) is a recently developed technique that is used to investigate the 3D structure of crystalline materials. Reciprocal space volume reconstruction of 3D EDT data of thin WO3 nanowires assembled into nanorods revealed single crystal domains of hexagonal symmetry. Moreover, the use of 3D EDT enabled to identify and solve the structures of individual GdPO4 nanorods in a mixed phase powder. The use of 3D EDT was extended using small-angle diffraction mode to investigate the packing arrangements and defects in nanoparticle assemblies. A high concentration of planar defects found in different nanoparticle assemblies highlights the competition between the fcc and hcp arrangements during the assembly process.

Iron-manganese oxides hybrid nanoparticles with different three-dimensional configurations, i.e. core|shell and asymmetric facetted dimers, were investigated using a combination of several electron microscopy techniques (HRTEM, SAED, STEM-HAADF, EFTEM, EELS). The growth of the facetted cubic MnO phase onto preformed Fe3O4 seed particles occurs preferentially along the Fe3O4 nanocube edges forming a well-oriented crystalline interface despite the lattice mismatch and defects. Atomic resolution monitoring of the structural changes in Mn3O4|Fe3O4 and Fe3O4|Mn3O4 core|shell nanoparticles induced by the electron beam revealed a strain relief mechanism at the interface involving inhomogeneous diffusion of cations and defects creation.

Structural study of nano-structured materials: electron crystallography approaches

The structural analysis serves as a bridge to link the structure of materials to their properties. Revealing the structure details allows a better understanding on the growth mechanisms and properties of materials, and a further designed synthesis of functional materials. The widely used methods based on X-ray diffraction have certain limitations for the structural analysis when crystals are small, poorly crystallized or contain many defects. As electrons interact strongly with matter and can be focused by electromagnetic lenses to form an image, electron crystallography (EC) approaches become prime candidates for the structural analysis of a wide range of materials that cannot be done using X-rays, particularly nanomaterials with poor crystallinity.

Three-dimensional electron diffraction tomography (3D EDT) is a recently developed method to automatically collect 3D electron diffraction data. By combining mechanical specimen tilt and electronic e-beam tilt, a large volume of reciprocal space can be swept at a fine step size to ensure the completeness and accuracy of the diffraction data with respect to both position and intensity. Effects of the dynamical scattering are enormously reduced as most of the patterns are collected at conditions off the zone axes. In this thesis, 3D EDT has been used for unit cell determination (COF-505), phase identifications and structure solutions (ZnO, Ba-Ta3N5, Zn-Sc, and V4O9), and the study of layer stacking faults (ETS-10 and SAPO-34 nanosheets).

High-resolution transmission electron microscope (HRTEM) imaging shows its particular advantages over diffraction by allowing observations of crystal structure projections and the 3D potential map reconstruction. HRTEM imaging has been used to visualize fine structures of different materials (hierarchical zeolites, ETS-10, and SAPO-34). Reconstructed 3D potential maps have been used to locate the positions of metal ions in a woven framework (COF-505) and elucidate the pore shape and connectivity in a silica mesoporous crystal.

The last part of this thesis explores the combination with X-ray crystallography to obtain more structure details.

Structure of Rare-Earth Aluminosilicate Glasses Probed by Solid-State NMR Spectroscopy and Quantum Chemical Calculations

Aluminosilicate glasses incorporating rare earth elements feature highly beneficial physical and chemical properties, at the level beyond that accessible for compositions based on alkali and/or alkaline earth metals. Extraordinary hardness, high glass transition temperatures and indices of refraction, favorable coefficients of thermal expansion, as well as excellent chemical durability, result in many potential technological applications. However, in contrast to the systematically explored and commercially exploited aluminosilicate glasses that contain Na, K, and Ca elements, their rare earth counterparts were sparsely investigated, although exhibit several unique structural features.

This thesis explored the short- and medium-range structural organization of glasses belonging to the ternary RE2O3—Al2O3—SiO2 systems, where RE denotes one of the trivalent and diamagnetic rare earth metal ions of scandium (Sc), yttrium (Y), lanthanum (La), and lutetium (Lu). Comprehensive multinuclear solid-state nuclear magnetic resonance studies complemented with atomistic molecular dynamics computer simulations and quantum chemical calculations provided detailed insight into local environments of the glass networkforming elements (Si, Al), oxygen species, as well as the rare earth ions, thereby offering a deeper understanding of the glass structure.

Stainless steels fabricated by laser melting : Scaled-down structural hierarchies and microstructural heterogeneities

Additive manufacturing is revolutionizing the way of production and use of materials. The clear tendency for shifting from mass production to individual production of net-shape components has encouraged using selective laser melting (SLM) or electron beam melting (EBM). In this thesis, austenitic, duplex and martensitic stainless steel parts were fabricated by laser melting technique using fixed laser scanning parameters. The fabricated steel parts were characterised using XRD, SEM, TEM/STEM, SADP and EBSD techniques. Mechanical properties of the fabricated steel parts were also measured. The mechanism of the evolution of microstructure during laser melting as well as the mechanism of the effect of developed microstructure on the mechanical properties was investigated. It was found that the intense localized heating, non-uniform and asymmetric temperature gradients and subsequently fast cooling introduces unique high level structural hierarchies and microstructure heterogeneities in laser melted steel parts. A unique structural hierarchy from the millimetre scale melt pools down to the sub-micron/nano scale cellular sub-grains was observed. The cellular sub-grains were 0.5-1μm with Molybdenum enriched at the sub-grain boundaries in SLM 316L. The Mo enriched cell boundaries affected the chemical and microstructure stability of the post heat treated samples. Well dispersed and large concentration of dislocations around the cell boundaries and well distributed oxide nano inclusions, imposed large strengthening and hardening effect that led to relatively superior tensile strength (700 MPa), yield strength (456 MPa), and microhardness (325Hv) compared to those of HIP 316L steel. The in-situ formation of oxide nano inclusions provided a unique way for preparation of oxide dispersion-strengthened (ODS) steel in a single process. The formation of oxide nano inclusions in the very low oxygen partial pressure of laser chamber was thermodynamically explained. High concentration of nano size dislocation loops, formation of nitride phases along with nitrogen enriched islands and oxide nano inclusions lead to strong dislocation pinning effect which strengthened the laser melted duplex stainless steel with a total tensile strength of 1321 MPa, yield strength of 1214 MPa and microhardness of 450HV. The grade 420 stainless steel was laser melted in Ar and N2 atmosphere which also showed a two level hierarchy with nanometric martensite lathes embedded in parental austenite cellular grains. The Ar treated sample had relatively higher retained austenite, lower YS (680-790 MPa) and UTS (1120-1200 MPa) compared to those treated in N2 (YS= 770-1100 MPa, UTS=1520-1560 MPa). The mechanism of the effect of atmosphere on phase transformation was explained.

Structure Determination and Prediction of Zeolites : A Combined Study by Electron Diffraction, Powder X-Ray Diffraction and Database Mining

Zeolites are crystalline microporous aluminosilicates with well-defined cavities or channels of molecular dimensions. They are widely used for applications such as gas adsorption, gas storage, ion exchange and catalysis. The size of the pore opening allows zeolites to be categorized into small, medium, large and extra-large pore zeolites. A typical zeolite is the small pore silicoaluminophosphate SAPO-34, which is an important catalyst in the MTO (methanol-to-olefin) process. The properties of zeolite catalysts are determined mainly by their structures, and it is therefore important to know the structures of these materials in order to understand their properties and explore new applications.

Single crystal X-ray diffraction has been the main technique used to determine the structures of unknown crystalline materials such as zeolites. This technique, however, can be used only if crystals larger than several micrometres are available. Powder X-ray diffraction (PXRD) is an alternative technique to determine the structures if only small crystals are available. However, peak overlap, poor crystallinity and the presence of impurities hinder the solution of structures from PXRD data. Electron crystallography can overcome these problems. We have developed a new method, which we have called “rotation electron diffraction” (RED), for the automated collection and processing of three-dimensional electron diffraction data. This thesis describes how the RED method has been applied to determine the structures of several zeolites and zeolite-related materials. These include two interlayer expanded silicates (COE-3 and COE-4), a new layered zeolitic fluoroaluminophosphate (EMM-9), a new borosilicate (EMM-26), and an aluminosilicate (ZSM-25). We have developed a new approach based on strong reflections, and used it to determine the structure of ZSM-25, and to predict the structures of a series of complex zeolites in the RHO family. We propose a new structural principle that describes a series of structurally related zeolites known as “embedded isoreticular zeolite structures”, which have expanding unit cells. The thesis also summarizes several common structural features of zeolites in the Database of Zeolite Structures.

Computer Simulations of Membrane–Sugar Interactions

Carbohydrate molecules are essential parts of living cells. They are used as energy storage and signal substances, and they can be found incorporated in the cell membranes as attachments to glycoproteins and glycolipids, but also as free molecules. In this thesis the effect of carbohydrate molecules on phospholipid model membranes have been investigated by the means of Molecular Dynamics (MD) computer simulations.

The most abundant glycolipid in nature is the non-bilayer forming monogalactosyldiacylglycerol (MGDG). It is known to be important for the membrane stacking typical for the thylakoid membranes in plants, and has also been found essential for processes related to photosynthesis. In Paper I, MD simulations were used to characterize structural and dynamical changes in a lipid bilayer when MGDG is present. The simulations were validated by direct comparisons between dipolar couplings calculated from the MD trajectories, and those determined from NMR experiments on similar systems. We could show that most structural changes of the bilayer were a consequence of lipid packing and the molecular shape of MGDG.

In certain plants and organisms, the enrichment of small sugars such as sucrose and trehalose close to the membrane interfaces, are known to be one of the strategies to survive freezing and dehydration. The cryoprotecting abilities of these sugar molecules are long known, but the mechanisms at the molecular level are still debated. In Papers II–IV, the interactions of trehalose with a lipid bilayer were investigated. Calculations of structural and dynamical properties, together with free energy calculations, were used to characterize the effect of trehalose on bilayer properties. We could show that the binding of trehalose to the lipid bilayer follows a simple two state binding model, in agreement with recent experimental investigations, and confirm some of the proposed hypotheses for membrane–sugar interactions. The simulations were validated by dipolar couplings from our NMR investigations of TRH in a dilute liquid crystal (bicelles). Furthermore, the assumption about molecular structure being equal in the ordered and isotropic phases was tested and verified. This assumption is central for the interpretation of experimentally determined dipolar couplings in weakly ordered systems.

In addition, a coarse grain model was used to tackle some of the problems with slow dynamics that were encountered for trehalose in interaction with the bilayer. It was found that further developments of the interaction models are needed to properly describe the membrane–sugar interactions. Lastly, from investigations of trehalose curvature sensing, we concluded that it preferably interacts in bilayer regions with high negative curvature.

Rapid sintering of ceramics by intense thermal radiation

Sintering is an important processing step for obtaining the necessary mechanical stability and rigidity of ceramic bulk materials. Both mass and heat transfer are essential in the sintering process. The importance of radiation heat transfer is significantly enhanced at high temperatures according to the well-known Stefan-Boltzmann’s law. In this thesis, we modified the pressure-less spark plasma sintering set-up to generate intense thermal radiation, aiming at rapid consolidation of ceramic bulk materials. This approach was named as “Sintering by Intense Thermal Radiation (SITR)” as only thermal radiation contributed.

Firstly, the heat and mass transfer mechanisms during the SITR process were studied by choosing zirconia ceramics as references. The results revealed that the multiple scattering and absorption of radiation by the materials contributed to the heat diffusion. The observed enhanced densification and grain growth can be explained by a multiple ordered coalescence of zirconia nanocrystals using high heating rates.

Secondly, the temperature distribution during the SITR process was investigated by both numerical simulation and experimental verifications. It showed that the radiator geometry, sample geometry and radiating area were influencing factors. Besides, the change of material and geometry of the radiators resulted in an asymmetric temperature distribution that favored the formation of SiC foams. The foams had gradient structures with different open porosity levels and pore sizes and size distributions.

Finally, ceramic bulk materials were successfully fabricated by the SITR method within minutes. These materials included dense and strong ZrO2 ceramics, Si3N4 foams decorated with one-dimensional nanostructures, and nasal cavity-like SiC-Si3N4 foams with hierarchical heterogeneities. Sufficient densification or formed strong necks were used for tailoring these unique microstructures. The SITR approach is well applicable for fast manufacture of ceramic bulk materials because it is clean and requires low energy consumption and properties can be controlled and tuned by selective heating, heating speed or temperature distribution.

Fabrication of nanocellulose-based materials : Liquid crystalline phase formation and design of inorganic–nanocellulose hybrids

The increasing need to replace fossil fuels as a source of energy and raw material is resulting in extensive research efforts towards identifying and developing high performance materials and devices based on renewable sources. Cellulose being the most versatile and abundant biopolymer in nature is one of the obvious choices. Cellulose, due to its properties that arise from the hierarchical structure, has been used for millennia by mankind although it is currently used, in the form of microfibers, mainly in the paper and pulp industry. However, many efforts are being directed towards retrieving even smaller cellulose constituents such as nanofibers and nanocrystals (i.e., nanocellulose), which can actually be used in high performance materials. In order to do so, a better understanding of the behavior and interactions between these novel nanomaterials are required. Moreover, the combination of nanocellulose with inorganic nanoparticles bears a great potential that can open the door to multifunctional materials based on a renewable component.

In this work, the anisotropic behavior, i.e., the formation of a chiral nematic phase, of cellulose nanocrystals (CNC) initially dispersed in aqueous media spanning a wide volume fraction range has been studied by small angle X-ray scattering (SAXS) and laser diffraction. The analysis shows that the twist angle between neighboring CNCs increased from ~1° up to ~4° as the CNC volume fraction increased from 2.5 to 6.5 vol%.

Also, the drying of an aqueous CNC droplet immersed in a binary toluene/ethanol mixture was studied and monitored in-situ by polarized video microscopy, where the influence of the water dissolution rate on the morphology of the resulting microbeads was investigated by scanning electron microscopy. The morphology of the microbeads depends not only on the drying speed but also on the initial starting CNC volume fraction. In this regard, the influence of the degrees of liquid crystallinity on the formation of a chiral nematic phase on films has also been studied.

Lastly, the fabrication and various properties of hybrids and composites prepared from cellulose nanofibers (CNF) and inorganic constituents are presented. The structure and chemistry of a museum sample of a traditional African textile (Bogolan) is analyzed and the chemical foundation of the dyeing method is outlined. This Bogolan dyeing method was used to pattern CNF films, and to study the details of how the surface-bound iron-tannin complexes are formed on the cellulose surface.

Also, the formation of transparent, hard and flexible films based on CNF-titania (anatase) nanoparticle hybrids was studied, where the influence of the composition of the hybrids on the optical and mechanical properties is discussed on the basis of results from electron microscopy, spectrophotometry and nanoindentation.

Composition-Structure Correlations of Bioactive Glasses Explored by Multinuclear Solid-state NMR Spectroscopy

This PhD thesis presents a study of structure-composition correlations of bioactive glasses (BGs) by employing solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.

Silicate-based Na2O−CaO−SiO2−P2O5 BGs are utilized clinically and are extensively investigated for bone regeneration purposes. Once implanted in the human body, they facilitate bone regeneration by partially dissolving in the body fluids, followed by the formation of a biomimetic surface-layer of calcium hydroxy-carbonate apatite (HCA). Eventually, the implanted BG totally integrates with the bone. The bioactivity of melt-prepared BGs depends on their composition and structure, primarily on the phosphorus content and the average silicate-network connectivity (NC). We explored these composition-structure relationships for a set of BGs for which the NC and phosphorus contents were varied independently.

The short-range structural features of the glasses were explored using 29Si and 31P magic-angle-spinning (MAS) NMR spectroscopy. 31P MAS NMR revealed that the orthophosphate content is directly proportional to the total P content of the glass, with a linear correlation observed between the orthophosphate content and the silicate network connectivity. The bearings of the results for future BG design are discussed.

By using multiple-quantum coherence-based 31P NMR experiments, the spatial distribution of orthophosphate groups was probed in the melt prepared BGs, as well as in two mesoporous bioactive glasses prepared by an evaporation-induced self-assembly technique. The results evidence randomly distributed orthophosphate groups in the melt-prepared BGs, whereas the pore-walls of the mesoporous bioactive glasses constitute nanometer-sized clusters of calcium phosphate. The distribution of Na+ ions among the phosphate/silicate groups were studied by heteronuclear dipolar-based 23Na−31P NMR experiments, verifying that sodium is dispersed nearly randomly in the glasses.

The phosphorus and proton environments in biomimetically grown HCA were investigated by using 1H and 31P MAS NMR experiments. Our studies revealed that the biomimetic HCA shared many local structural features with synthetic and well-ordered hydroxy-apatite.

Multiscale Modeling of Molecular Sieving in LTA-type Zeolites : From the Quantum Level to the Macroscopic

LTA-type zeolites with narrow window apertures coinciding with the approximate size of small gaseous molecules such as CO2 and N2 are interesting candidates for adsorbents with swing adsorption technologies due to their molecular sieving capabilities and otherwise attractive properties. These sieving capabilities are dependent on the energy barriers of diffusion between the zeolite pores, which can be fine-tuned by altering the framework composition. An ab initio level of theory is necessary to accurately describe specific gas-zeolite interaction and diffusion properties, while it is desirable to predict the macroscopic scale diffusion for industrial applications. Hence, a multiscale modeling approach is necessary to describe the molecular sieving phenomena exhaustively.

In this thesis, we use several different modeling methods on different length and time scales to describe the diffusion driven uptake and separation of CO2 and N2 in Zeolite NaKA. A combination of classical force field based modeling methods are used to show the importance of taking into account both thermodynamic, as well as, kinetic effects when modeling gas uptake in narrow pore zeolites where the gas diffusion is to some extent hindered. For a more detailed investigation of the gas molecules’ pore-to-pore dynamics in the material, we present a procedure to compute the free energy barriers of diffusion using spatially constrained ab initio Molecular Dynamics. With this procedure, we seek to identify diffusion rate determining local properties of the Zeolite NaKA pores, including the Na+-to-K+ exchange at different ion sites and the presence of additional CO2 molecules in the pores. This energy barrier information is then used as input for the Kinetic Monte Carlo method, allowing us to simulate and compare these and other effects on the diffusion driven uptake using a realistic powder particle model on macroscopic timescales.

Extreme water catalyzed transformations of SiO2, TiO2 and LiAlSiO4

The dramatic change in properties of water near its critical point (i.e. T = 374 °C and p = 22.1 MPa, note: 100 MPa = 0.1 GPa = 1 kbar ≈ 1000 atm) has been a subject of numerous studies and also lead to the development of various applications (e.g. in waste destruction, biomass processing, and the synthesis of advanced ceramic materials). However, comparatively little is known about the behavior of water at gigapascal pressures. The present study attempts to explore catalytical properties and reactivity of extreme water with respect to several oxide systems: SiO2, TiO2 and LiAlSiO4. “Extreme water” here is defined as existing at p,T conditions of 0.25–10 GPa and 200–1000 °C, thus considering both supercritical fluid and hot compressed ice. The study shows that extreme water can make high pressure mineral phases accessible at relatively mild T conditions. At the same time, high pressure aqueous environments appear efficient in stabilizing novel metastable structures and may be considered as a general route for synthesizing new materials.

The hydrothermal treatment of SiO2 glass at 10 GPa and 300–550 °C yielded an unusual ultrahydrous form of stishovite with up to 3% of structural water. At the same time, the extreme water environment enhanced notably the kinetics of stishovite formation, making it accessible at unprecedentedly low temperatures. Thus, for the SiO2–H2O system water acts as both catalyst and reactant. For TiO2 a hydrothermal high pressure treatment proved to be of high importance for overcoming the kinetical hindrance of the rutile – TiO2-II transformation. 6 GPa and 650 °C were established as the mildest conditions for synthesizing pure TiO2-II phase in less than two hours. The crystallization of LiAlSiO4 glass in an extreme water environment yielded a number of different phases. In the low pressure region (0.25 – 2 GPa) mainly a zeolite (Li-ABW) and a dense anhydrous aluminosilicate (α-eucryptite) were obtained. At pressures above 5 GPa the formation of novel pyroxene-like structures with crystallographic amounts of structural water was observed.

The overall conclusion of this study is that extreme water environments show a great potential for catalyzing phase transitions in oxide systems and for stabilizing novel structures via structural water incorporation.

Biomarkers of internal exposure/dose : Methods to quantify adducts to protein and DNA by LC/MS studied with benzo[a]pyrene and isocyanates

This thesis focuses on methods for quantification by liquid chromatography/mass spectrometry (LC/MS) of specific biomarkers for internal dose of chemicals which induce toxicity through their electrophilic reactivity. In vivo such compounds are short-lived, and could feasibly be measured as their reaction products (adducts) with biomacromolecules. Analysis by MS methods of stable adducts offers the specificity and accuracy required to generate data on internal dose useful in risk estimation.

The primary aim was to develop a method for quantification by LC/MS of bulky adducts to serum albumin (SA) from polycyclic aromatic hydrocarbons, using the genotoxic diolepoxide (DE) of benzo[a]pyrene (BP) as a model. A method for analysis of the BPDE adducts to His146 in SA was developed which is robust, easy-to-use, has good reproducibility and which reached a high sensitivity. A method for quantification of BPDE adducts to N2-deoxyguanosine (dG) in DNA by LC/MS was also established.

In mice exposed to BP, adducts to SA and DNA from stereoisomers of BPDE were identified and quantified. The adduct level was shown to be >400 times higher in DNA than in SA, which from an in vitro study could be concluded to mainly depend on a large difference in the rates of adduct formation to His in SA and to dG in DNA. BPDE adduct levels to SA and DNA, and a biomarker of genotoxic effect (frequency of micronuclei), were compared in BP-exposed mice. The results were used to evaluate how these methods could be used in procedures for cancer risk estimation.

An LC/MS method for analysis of valine hydantoins (VH) formed as adducts from isocyanates to N-termini in haemoglobin was established. VH, formed from urea/isocyanic acid, was investigated in mice as a potential biomarker of renal failure and for dose adjustment during treatment with a radioactive cytostatic drug. The kidney dysfunction was not severe enough to give a significant increase of VH in the experiment. 

On the nature of self-assembly in low-density condensed matter : A classical molecular dynamics approach

The study of the physics of self-assembly in low-density condensed matter is an extremely interesting, mostly unexplored field of scientific research. The contribution reported in this thesis explains how this problem can be addressed using molecular dynamics simulation of 3D systems composed by simple, identical particles, interacting via a spherically symmetric pair potential, which belongs to the class of Dzugutov potentials. Such approach resulted in four, self-assembled archetypal structures, which are reported in the included papers I, II, III, IV. In order to produce the reported results, a major effort of software development has been done by the author, both in the simulation and the analysis programs used. This thesis will start with a brief introduction to the field, highlighting the important aspects needed to have a more complete, general understanding of the reported scientific results. Some conclusions will be drawn, together with some possible future endeavors.

Development of Metal–Organic Frameworks for Catalysis : Designing Functional and Porous Crystals

Metal–organic frameworks, or MOFs, have emerged as a new class of porous materials made by linking metal and organic units. The easy preparation, structural and functional tunability, ultrahigh porosity, and enormous surface areas of MOFs have led to them becoming one of the fastest growing fields in chemistry. MOFs have potential applications in numerous areas such as clean energy, adsorption and separation processes, biomedicine, and sensing. One of the most promising areas of research with MOFs is heterogeneous catalysis.

This thesis describes the design and synthesis of new, carboxylate-based MOFs for use as catalysts. These materials have been characterized using diffraction, spectroscopy, adsorption, and imaging techniques. The thesis has focused on preparing highly-stable MOFs for catalysis, using post-synthetic methods to modify the properties of these crystals, and applying a combination of characterization techniques to probe these complex materials.

In the first part of this thesis, several new vanadium MOFs have been presented. The synthesis of MIL-88B(V), MIL-101(V), and MIL-47 were studied using ex situ techniques to gain insight into the synthesis–structure relationships. The properties of these materials have also been studied.

In the second part, the use of MOFs as supports for metallic nanoparticles has been investigated. These materials, Pd@MIL-101–NH2(Cr) and Pd@MIL-88B–NH2(Cr), were used as catalysts for Suzuki–Miyaura and oxidation reactions, respectively. The effect of the base on the catalytic activity, crystallinity, porosity, and palladium distribution of Pd@MIL-101–NH2(Cr) was studied.

In the final part, the introduction of transition-metal complexes into MOFs through different synthesis routes has been described. A ruthenium complex was grafted onto an aluminium MOF, MOF-253, and an iridium metallolinker was introduced into a zirconium MOF, UiO-68–2CH3. These materials were used as catalysts for alcohol oxidation and allylic alcohol isomerization, respectively.

Exploring Protein Functions by Molecular Modelling

Proteins are one of the most important families of biological macromolecules. Proteins can assume many different structures. This makes them perfect to serve a wide range of functions in all organisms. In the last decades, molecular modeling has become an important and powerful tool in the investigation of biological systems. Adopting different computational methods many protein functions and structure related problems can be explored.

This thesis focuses on three different protein issues. The structural changes induced by high temperature on a large enzyme were investigated simulating the denaturation of glucose oxidase. Molecular dynamics (MD) simulations at different high temperatures were performed. The transition state of the denaturation process was found and the relative ensemble of structures characterized. Different protein properties were analyzed and found in agreement with experimental and theoretical data. Moreover the breaking points of the protein were localized and point mutations on the protein sequence were suggested.

Antifreeze proteins (AFP) allow different organisms to survive in subzero environments. These proteins lower the freezing point of physiological fluids. MD simulations of the snow flea AFP (sfAFP) in water have shown partial instability of the protein structure. When attached to different ice planes at the ice/water interface, the sfAFP induces local ice melting. AFPs are divided into two categories: hyperactive and moderately active depending on their antifreeze power. The water diffusion profile of ice/water systems containing one protein from each family were compared. The ice/water interface width was found to be broadened to different extent by the two proteins, while a control protein (ubiquitin) did not affect the interface thickness.

Hemoglobin is the oxygen carrier in all vertebrates. Mutation along the protein sequence can alter the protein functionality and its capability of binding molecular oxygen. Density Functional Theory methods were applied in the calculation of the oxygen binding energy of the wild type hemoglobin and four other variants. Evaluations on the electronic structures and on the binding energies of the different hemoglobin variants suggest that perhaps none of the mutated hemoglibins efficiently bind oxygen.

Processing and performance of zeolites for efficient carbon dioxide separation

We have structured zeolites from powders of zeolite 13X and 4A into hierarchically porous monoliths for efficient carbon dioxide capture by tailoring the pore dimensions to facilitate rapid gas uptake and release. Freeze-casting was used for the first time to shape adsorbents into a lamellar structure. Lamellar walls with thicknesses and spacing in the range of 10 µm were found to be the best combination between rapid gas transport and a short diffusion distance in the zeolite-containing walls for rapid carbon dioxide uptake and release.

Compressive strength measurements of the freeze-cast zeolite-based monoliths showed that monoliths with small pores, thin walls and a lot of interconnectivity between the walls were stronger than monoliths with large pores and thick walls. Image analysis of the structures together with modelling of the deformation behavior suggests that the failure mechanism of freeze-cast monoliths is dominated by buckling.

Binder-free zeolite Y and ZSM-5 -based monoliths were produced by pulsed current processing (PCP) into strong, hierarchically porous monoliths with minimal loss of crystallinity. Ranges for the maximum PCP processing temperatures for the zeolites with different aluminium contents were identified by powder x-ray diffraction (PXRD) with full-profile fitting analysis.

Matching the thermal expansion behavior of the supports with the zeolite film is important to minimize the risk of thermally induced cracking of zeolite membranes. Zeolite supports with a macroporous structure was prepared by PCP and the thermal expansion coefficient was determined by PXRD and compared to traditional alumina substrates. It was found that the slightly negative thermal expansion coefficient of the zeolite supports matched the thermal expansion of the zeolite films very well, whereas the alumina support would induce large stresses upon fluctuating temperatures.

Methylcellulose-directed synthesis of zeolite 4A produced nano-sized crystals with a narrow size distribution, which could be tuned by adjusting the methylcellulose content. The crystallinity of the synthesized 4A was controlled by PXRD and found to be very high, and the gas uptake capability performed well in comparison with available micron-sized zeolites.

Structure and Phase Stability of CaC2 Polymorphs, Li2C2 and Lithium Intercalated Graphite : A Revisit with High Pressure Experiments and Metal Hydride–Graphite Reactions

Alkali (A) and alkaline earth (AE) metals can form carbides and intercalated graphites with carbon. The carbides mostly represent acetylides which are salt-like compounds composed of C22− dumbbell anions and metal cations. Both the acetylide carbides and intercalated graphites are technologically important. Superconductivity has been observed in several intercalated graphites such as KC8 and CaC6. Li intercalated graphites are a major ingredient in Li ion batteries. CaC2 is an important commodity for producing acetylene and the fertilizer CaCN2.

In spite of the extensive research on A–C and AE–C compounds, phase diagrams are largely unknown. The thermodynamic and kinetic properties of both carbides and intercalalated graphites are discussed controversially. Recent computational studies indicated that well-known carbides, like CaC2 and BaC2, are thermodynamically unstable. Additionally, computational studies predicted that acetylide carbides will generally form novel polymeric carbides (polycarbides) at high pressures. This thesis is intended to check the validity of theoretical predictions and to shed light on the complicated phase diagrams of the Li–C and the Ca–C systems.

The Li–C and the Ca–C systems were investigated using well-controllable metal hydride–graphite reactions. Concerning the Li–C system, relative stabilities of the metastable lithium graphite intercalation compounds (Li-GICs) of stages I, IIa, IIb, III, IV and Id were studied close to the competing formation of the thermodynamically stable Li2C2. The stage IIa showed distinguished thermal stability. The phase Id showed thermodynamic stability and hence, was included in the Li–C phase diagram. In the Ca–C system, results from CaH2–graphite reactions indicate compositional variations between polymorphs I, II and III. The formation of CaC2  I was favored  only  at  1100  ◦C or  higher  temperature  and  with  excess calcium, which speculates phase I as carbon deficient CaC2−δ .

To explore the potential existence of polycarbides, the acetylide carbides Li2C2 and CaC2 were investigated under various pressure and temperature conditions, employing diamond anvil cells for in situ studies and multi anvil techniques for large volume synthesis. The products were characterized by a combination of diffraction and spectroscopy techniques. For both Li2C2 and CaC2, a pressure induced structural transformation was observed at relatively low pressures (10–15 GPa), which was followed by an irreversible amorphization at higher pressures (25–30 GPa). For Li2C2 the structure of the high pressure phase prior to amorphization could be elucidated. The ground state with an antifluorite Immm structure (coordination number (CN) for C22− dumbbells = 8) transforms to a phase with an anticotunnite Pnma structure (CN for C22− dumbbells = 9). Polycarbides, as predicted from theory, could not be obtained.

The synergistic role of hierarchical macro- and mesoporous implant surface and microscopic view of enhanced osseointegration

The trend for designing of a titanium implant explored using different chemical compositions and crystallinity materials until people realized that the implant surface character was another important factor affecting the rate and extent of osseointegartion. Titanium received a macroporous titania surface layer by anodization, which contains open pores with average pore diameter around 5μm. An additional mesoporous titania top layer was created that followed the contour of the macropores and having 100–200 nm thickness and a pore diameter of 10 nm. Thus, a coherent laminar titania surface layer was obtained producing a hierarchical macro- and mesoporous surface. The interfacial bonding between the surface layers and the titanium matrix was characterized by a scratch test that confirmed a stable and strong bonding of the laminar titania surface layers upon titanium. The wettability to water and the effects on the osteosarcoma cell line (SaOS-2) proliferation and mineralization of the formed titania surface layers were studied systematically by cell culture and scanning electron microscopy (SEM). A synergistic role of the hierarchical macro- and mesoporosities was revealed in terms of enhancing cell adhesion, proliferation and mineralization, when compared with the titania surface with solo porosity scale topography.

For the in vivo results of the evaluation of osseointegration, an argon ion beam polishing technique was applied to prepare the cross sections of implants feasible for the high resolution SEM investigation. The interfacial microstructure between newly formed bone and implants with four modified surfaces including the new hierarchical macro- and mesoporous implant surface retrieved after in vivo tests were characterized. By this approach it has become possible to directly observe early bone formation, the increase of bone density, and the evolution of bone structure. The two bone growth mechanisms, distant osteogenesis and contact osteogenesis, can also be distinguished. These direct observations give, at microscopic level, a better view of osseointegration and explain the functional mechanisms of various implant surfaces for osseointegration.

Imine/azo-linked microporous organic polymers : Design, synthesis and applications

Microporous organic polymers (MOPs) are porous materials. Owing to their high surface area, tunable pore sizes and high physicochemical stability, they are studied for applications including gas capture and separation and heterogeneous catalysis. In this thesis, a series of imine/azo-linked MOPs were synthesized. The MOPs were examined as potential CO2 sorbents and as supports for heterogeneous catalysis.

The MOPs were synthesized by Schiff base polycondensations and oxidative couplings. The porosities of the imine-linked MOPs were tunable and affected by a range of factors, such as the synthesis conditions, monomer lengths, monomer ratios. All the MOPs had ultramicropores and displayed relatively high CO2 uptakes and CO2-over-N2 selectivities at the CO2 concentrations relevant for post-combustion capture of CO2. Moreover, the ketimine-linked MOPs were moderately hydrophobic, which might increase their efficiency for CO2 capture and separation.

The diverse synthesis routes and rich functionalities of MOPs allowed further post-modification to improve their performance in CO2 capture. A micro-/mesoporous polymer PP1-2, rich in aldehyde end groups, was post-synthetically modified by the alkyl amine tris(2-aminoethyl)amine (tren). The tethered amine moieties induced chemisorption of CO2 on the polymer, which was confirmed by the study of in situ infrared (IR) and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. As a result, the modified polymer PP1-2-tren had a large CO2 capacity and very high CO2-over-N2 selectivity at low partial pressures of CO2.

Pd(II) species were incorporated in the selected MOPs by means of complexation or chemical bonding with the imine or azo groups. The Pd(II)-rich MOPs were tested as heterogeneous catalysts for various organic reactions. The porous Pd(II)-polyimine (Pd2+/PP-1) was an excellent co-catalyst in combination with chiral amine for cooperatively catalyzed and enantioselective cascade reactions. In addition, the cyclopalladated azo-linked MOP (Pd(II)/PP-2) catalyzed Suzuki and Heck coupling reactions highly efficiently.

The Role of Tetrahedral Building Blocks in Low-Dimensional Oxohalide Materials

The structural architecture found in low-dimensional materials can lead to a number of interesting physical properties including anisotropic conductivity, magnetic frustration and non-linear optical properties. There is no standard synthesis concept described thus far to apply when searching for new low-dimensional compounds, and therefore control on the design of the new materials is of great importance.This thesis describes the synthesis, crystal structure and characterization of some new transition metal oxohalide compounds containing p-elements having a stereochemically active lone-pair. First row transition metal cations have been used in combination with SeIV, SbIII and TeIV ions as lone-pair elements and Cl- and Br- as halide ions. The lone-pairs do not participate in covalent bonding and are responsible for an asymmetric one-sided coordination. Lone-pair elements in combination with halide ions have shown to be powerful structural spacers that can confine transition metal building blocks into low-dimensional arrangements. The halide ions and lone-pairs reside in non-bonded crystal volumes where they interact through weak van der Waals forces. The transition metal atoms are most often arranged to form sheets, chains or small clusters; most commonly layered compounds are formed.To further explore the chemical system and to separate the transition metal entities even more the possibility to include tetrahedral building blocks such as phosphate-, silicate-, sulphate- and vanadate building blocks into this class of compounds has been investigated. Tetrahedral building blocks are well known for their ability of segmenting structural arrangements by corner sharing, which often leads to the formation of open framework structures. The inclusion of tetrahedral building blocks led to the discovery of interesting structural features such as complex hydrogen bonding, formation of unusual solid solutions or faulted stacking of layers.Compounds for which phase pure material could be synthesized have been characterized in terms of their magnetic properties. Most compounds were found to have antiferromagnetic spin interactions and indications of magnetic frustration could be observed in some of them.

Refining of hydrochars/ hydrothermally carbonized biomass into activated carbons and their applications

Hydrothermally treated biomass could not only be used as a fuel or a fertilizer but it can also be refined into high-value products. Activated carbons are one of those. In the studies of this thesis, four different hydrothermally carbonized (HTC) biomasses, including horse manure, grass cuttings, beer waste and biosludge, have been successfully made into activated carbons. The activated carbon materials were in the forms of powdered activated carbons, powdered composites of activated carbon and iron oxide nano-crystals, and activated carbon discs.

The HTC biomasses and the activated carbons were characterized and analyzed using several methods. The biomasses were carbonized to different extent during the hydrothermal treatment, which depended on the different natures of the biomasses. The HTC biomasses were activated into powdered activated carbons by both physical activation, using CO2, and by chemical activation, using H3PO4. Full factorial design matrices were applied to design experiments and study the influence of different parameters used during both physical and chemical activation. Activated carbons with embedded iron oxide nanoparticles were synthesized through hydrothermal carbonization followed by CO2 activation. These composites had high surface areas and showed a strong magnetism, and the powders could be separated from liquid phase by applying a magnetic field. Strong and dense activated carbon discs were also prepared from powdered HTC beer waste by pulsed current processing (PCP) and a subsequent CO2 activation procedure. The potential for carbon dioxide separation from nitrogen, and methylene blue adsorption in aqueous solution, were assessed for the powdered activated carbons produced from HTC biomasses. They showed good performance in both applications. 

Open-framework Structures Built by Inorganic Clusters : Synthesis and Characterization

Novel open-framework germanates and vanadoborates, which are constructed from typical types of clusters, have been synthesized based on different strategies. The crystal structures are solved by using single crystal X-ray diffraction (SXRD) technique or by combined techniques. Additionally, the structures of two open-framework materials, PKU-3 and PKU-16, are determined from nano-sized crystals by rotation electron diffraction (RED) combined with powder X-ray diffraction (PXRD).

This thesis serves as an introduction to synthesis of open-framework germanates and vanadoborates based on different design strategies. Two germanates are obtained; SU-74 is achieved by employing a novel structure directing agent (SDA), SUT-8 is achieved by assembling the novel structure building units (SBUs) of Co@Ge14 with the introduction of cobalt ions in the synthesis. Four strategies are successfully used in construction of open-framework vanadoborates: using metal-oxo polyhedra as the linkages in SUT-6; applying the scale chemistry approach in SUT-7; employing metal-organic complexes as the linkages in SUT-12, SUT-13, SUT-14; and introducing covalent bond organic linkages into SUT-10 and SUT-11. Single crystal X-ray diffraction is used to conduct the structure determination in combination with other techniques.

Furthermore, the structures of two open-framework materials, an aluminoborate PKU-3 and a germanosilicate PKU-16, are solved from nano-sized crystals using RED data. The structures are further confirmed by Rietveld refinement against PXRD data. The advantages of the RED techniques are demonstrated in two aspects. In PKU-3, the presence of seriously preferred orientation and light elements in the structure makes it difficult for structure determination by PXRD, but it is easier by RED. In PKU-16, the RED technique is used to determine its structure from the as-synthesized multi-phasic sample containing nano-sized crystals. After the structure of PKU-16 has been solved, the synthesis of this interesting phase can be optimized and pure PKU-16 can be obtained.

Keywords: Open-framework, germanates, vanadoborates, aluminoborates, germanosilicates, crystal structure, hydrothermal synthesis, single crystal X-ray diffraction, rotation electron diffraction, powder X-ray diffraction

Dissolving the Rocks : Solubility Enhancement of Active Pharmaceutical Ingredients using Mesoporous Silica

Poor aqueous solubility is one of the greatest barriers for new drug candidates to enter toxicology studies, let alone clinical trials. This thesis focuses on contributing to solving this problem, evaluating the oral toxicity of mesoporous silica particles, and enhancing the apparent solubility and bioavailability of active pharmaceutical ingredients in vitro and in vivo using mesoporous silica particles.

Toxicological studies in rats showed that two types of mesoporous silica particles given by oral administration were well tolerated without showing clinical signs of toxicity. Solubility enhancement, including in vivo bioavailability and in vitro intracellular activity, has been evaluated for selected drug compounds. Mesoporous silica was shown to effectively increase drug solubility by stabilizing the amorphous state of APIs, such as itraconazole (anti-fungal), dasatinib (anti-cancer), atazanavir (anti-HIV) and PA-824 (anti-tuberculosis). Itraconazole was successfully loaded into a variety of porous silica materials showing a distinct improvement in the dissolution properties in comparison to non-porous silica materials (and the free drug). Microporosity in SBA-15 particles has advantages in stabilizing the supersaturation state of dasatinib. Small pore sizes show better confinement of atazanavir, contributing to a higher dissolution of the drug compound. In the in vivo animal studies, NFM-1 loaded with atazanavir shows a four-fold increase in bioavailability compared to free crystalline atazanavir. PA-824 has a higher dissolution rate and solubility after loading into AMS-6 mesoporous particles. The loaded particles show similar antibacterial activity as the free PA-824.

This thesis aims at highlighting some of the important factors enabling the selection of adequate mesoporous structures to enhance the pharmacokinetic profile of poorly water-soluble compounds, and preparing the scientific framework for uncovering the effects of drug confinement within mesopores of varying structural properties.

Persistent halogenated pollutants in mothers´ milk

Persistent organic pollutants (POPs) are substances that degrade slowly, are distributed wotldwide, bioaccumulate and are harmful to both animals and humans. The release of POPs to the environment was the preamble to human background contamination. In the mid-20th century it became clear to scientists and policy makers that even the mothers´ milk was contaminated by POPs. This led to national and global monitoring programs to assess the extent of contamination and subsequently to ban several POPs via the Stockholm Convention.

The concentrations of dioxin, polychlorinated dibenzodioxins (PCDD), -furans (PCDF) and dioxin like polychlorinated biphenyls (DL-PCB) is analysed in a retrospektive time trend study. The findings show a faster decrease of dioxin concentrations 2002-2011, compared to the whole series, 1972-2011. The transfer of polybrominated diphenyl ethers from mother to child via the milk is investigated and a relationship between both the PBDE molecule’s size and time post partum of the sampling and the ability to transfer to the milk is found. A literature review concerning the POPs in human milk finds, in addition to accounting for POP concentrations; that some substances are investigated more thoroughly than others; DDT and PCB compared to Aldrine and Toxaphene and that certain geographical areas are more well-studied than others, e.g. Europe compared to Africa. The study also shows a strong over all need for better reporting protocols. To understand the current and emerging POPs present in mothers´ milk screening of a larger than normal sample of mothers´ milk can give new insights. The development of a method designed to tackle the problems of large fat rich sample and still to be as benign as possible to the analytes was undertaken. The method is subsequently applied to a both Swedish and Chinese pooled sample to show the differences in POP exposure between countries.

Transition metal oxofluorides comprising lone pair elements : Synthesis and Characterization

Within the family of transition metal oxochlorides/bromides containing lone pair elements, the transition metal cations often adopt a low-dimensional arrangement such as 2D layers, 1D chains or 0D clusters. The reduced dimensionality is attributed to the presence of stereochemically active lone pairs which are positioned in the non-bonding orbital and will not participate in bond formation and instead act as structural spacers that help to separate coordination polyhedra around transition metal cations from forming three dimensional networks. On the other hand, the chlorine and bromine ions also play an important role to open up the crystal structure because of their low coordination number. However, fluorine has been rarely used in this concept due to the difficulties in synthesis.

This thesis is focused on finding new compounds in the M-L-O-F system (M = transition metal cation, L= p-block lone pair elements such as Te4+, Se4+, or Sb3+) in order to study the structural character of fluorine. Hydrothermal reactions have been adopted instead of conventional chemical transport reactions that are commonly used for synthesizing compounds in the M-L-O-(Cl, Br) family. A total of 8 new transition metal oxofluorides containing lone pair elements have been synthesized and their structures have been determined via single crystal X-ray diffraction. Bond valence sum calculations are used to distinguish in between fluorine and oxygen due to their very similar X-ray scattering factors.

Inorganic and Metal-Organic Framework Materials : Synthesis and structure characterization

Inorganic and metal-organic framework materials possessing accessible and permanent pores are receiving tremendous attention. Among them, zeolites are the most famous class due to their wide applications on petrochemistry and gas separation. Besides zeolites, the other oxide framework materials are also intensively investigated because of their diverse structures and compositions. Metal-organic frameworks are built from metal clusters and organic linkers. By rational designing the reagent, the network with desired topology and functionality can be synthesized.

For all of the framework materials mentioned above, to explore novel framework structures is important for improving properties and discovering new applications. This thesis includes the synthesis of zeolites and structure characterization for various types of inorganic framework materials. The zeolite synthesis conditions was exploited. With the optimized condition, the zeolite ITQ-33 was synthesized as single crystals. From the single crystal X-ray diffraction data, the disorder in the structure is discovered and explained. Following the topic of disorder and twinning, we proposed a novel method of solving structure of pseudo-merohedric twinning crystal by using an example of a metal-organic complex crystal. Then we also showed methods for solving structures of high complexity and nano-crystal by using mainly powder X-ray diffraction and transmission electron microscopy. Four examples were shown in chapter 4 including open-framework germanates and metal-organic frameworks.

Narrow-pore zeolites and zeolite-like adsorbents for CO2 separation

A range of porous solid adsorbents were synthesised and their ability to separate and capture carbon dioxide (CO2) from gas mixtures was examined. CO2 separation from flue gas – a type of exhaust gas from fossil fuel combustion that consists of CO2 mixed with mainly nitrogen and biogas (consists of CO2 mixed with mainly methane) were explicitly considered. The selected adsorbents were chosen partly due to their narrow pore sizes. Narrow pores can differentiate gas molecules of different sizes via a kinetic separation mechanism: a large gas molecule should find it more difficult to enter a narrow pore. CO2 has the smallest kinetic diameter in zeolites when compared with the other two gases in this study. Narrow pore adsorbents can therefore, show enhanced kinetic selectivity to adsorb CO2 from a gas mixture.

The adsorbents tested in this study included mixed cation zeolite A, zeolite ZK-4, a range of aluminophosphates and silicoaluminophosphates, as well as two types of titanium silicates (ETS-4, CTS-1). These adsorbents were compared with one another from different aspects such as CO2 capacity, CO2 selectivity, cyclic performance, working capacity, cost of synthesis, etc. Each of the tested adsorbents has its advantages and disadvantages. Serval phosphates were identified as potentially good CO2 adsorbents, but the high cost of their synthesis must be addressed in order to develop these adsorbents for applications.

Computer Simulations of Heterogenous Biomembranes

Molecular modeling has come a long way during the past decades and in the current thesis modeling of biological membranes is the focus. The main method of choice has been classical Molecular Dynamics simulations and for this technique a model Hamiltonian, or force field (FF), has been developed for lipids to be used for biological membranes. Further, ways of more accurately simulate the interactions between solutes and membranes have been investigated.

A FF coined Slipids was developed and validated against a range of experimental data (Papers I-III). Several structural properties such as area per lipid, scattering form factors and NMR order parameters obtained from the simulations are in good agreement with available experimental data. Further, the compatibility of Slipids with amino acid FFs was proven. This, together with the wide range of lipids that can be studied, makes Slipids an ideal candidate for large-scale studies of biologically relevant systems.

A solute's electron distribution is changed as it is transferred from water to a bilayer, a phenomena that cannot be fully captured with fixed-charge FFs.  In Paper IV we propose a scheme of implicitly including these effects with fixed-charge FFs in order to more realistically model water-membrane partitioning. The results are in good agreement with experiments in terms of free energies and further the differences between using this scheme and the more traditional approach were highlighted.

The free energy landscape (FEL) of solutes embedded in a model membrane is explored in Paper V. This was done using biased sampling methods with a reaction coordinate that included intramolecular degrees of freedom (DoF). These DoFs were identified in different bulk liquids and then used in studies with bilayers. The FELs describe the conformational changes necessary for the system to follow the lowest free energy path. Besides this, the pitfalls of using a one-dimensional reaction coordinate are highlighted.

Laser sintered materials with Non-equilibrium structures

This thesis is focused on achieving materials with non-equilibrium structures fabricated by high-energy laser sintering. The chosen precursor materials have rigid and inert structures like high-melting point ceramics or metals. It was necessary to use real-time monitoring of temperature and spectrum profiles for selecting the optimal laser parameters for the laser sintering process. This monitoring was done by an off-axial setup that also controls the surface morphologies during the laser irradiation process. The laser focal spot receives very high temperatures and subsequent extreme cooling rates within a short time period. New non-equilibrium structures will emerge ruled by kinetics, huge temperature gradients or stresses and freeze by quenching in solid state. These material structures were found to form at different length scales from nano- to macro-level, frequently by a hierarchical ordering. This opens a method to engineer materials with both hierarchical and non-equilibrium structures by a single operation in both metal and ceramics by laser sintering. In the Co-Cr-Mo alloy system, structures on three levels of lengths were observed, namely i) nano-level structures dominated by the grain boundary segregation; ii) micron-level structures characterized by the interlocked clusters of columns; and iii) macro-level structures defined by the selected laser scan patterns. The non-equilibrium structures of the Co-Cr-Mo alloy are related to mechanical, corrosion and bio-compatibility properties. In ZrO2 ceramics, the final product had a non-equilibrium nano- and micron-sized structure created by uneven absorption of laser energy and rupture. The structure inside the micron-sized grains is formed through ordered coalescence of nano-crystals. Properties of the laser sintered materials were established and related to the observed structures. The materials properties might be tailored by controlling the structures in different levels and potential applications of the new materials will be given.

Structuring porous adsorbents and composites for gas separation and odor removal

Porous zeolite, carbon and aluminophosphate powders have been colloidally assembled and post-processed in the form of monoliths, flexible free standing films and coatings for gas separation and odor removal. Zeolite 13X monoliths with macroporosites up to 50 vol% and a high CO2 uptake were prepared by colloidal processing and sacrificial templating. The durability of silicalite-I supports produced in a binder-free form by pulsed current processing (PCP) were compared with silicalite-I supports produced using clay-binders and conventional thermal treatment. Long-term acid and alkali treatment of the silicalite-I substrates resulted in removal of the clay binder and broadened the size-distribution of the interparticle macropores. Furthermore, strong discs of hydrothermally treated beer waste (HTC-BW) were produced by PCP and the discs were activated by physical activation in CO2 at high temperatures. The activated carbon discs showed high strength up to 7.2 MPa while containing large volume of porosities at all length scales. PCP was further used to structure aluminomphosphate powders (AlPO4-17 and AlPO4-53) into strong functional monoliths. The aluminophosphate monoliths had strengths of 1 MPa, high CO2 uptake and were easy to regenerate. Zeolite Y, silicalite and ZSM5 were selected as potential zeolite adsorbents for removal of sulfur containing compound, e.g. ethyl mercaptan (EM) and propyl mercaptan (PM). A novel processing procedure was used to fabricate free-standing films and coatings of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite; 89 w/w% and 96 w/w%, respectively. Thin flexible free-standing films and coatings of zeolite-CNF on paperboards with thickness around 100 µm and 40 µm, respectively, were produced. Headspace solid phase microextraction (SPME) coupled to gas chromatography- mass spectroscopy (GC/MS) analysis showed that the zeolite-CNF films can efficiently remove considerable amount of odors below concentration levels that can be sensed by the human olfactory system.

Characterization of crystalline materials by rotation electron diffraction : Phase identification and structure determination

Electron crystallography is powerful for determination of complex structures. The newly-developed 3D electron diffraction (ED) methods make structure determination from nano- and micron-sized crystals much easier than using other methods, for example X-ray diffraction. Almost complete 3D ED data can be collected easily and fast from crystals at any arbitrary orientations. Dynamical effects are largely reduced compared to zonal ED patterns. 3D ED is powerful for phase identification and structure solution from individual nano- and micron-sized crystals, while powder X-ray diffraction (PXRD) provides information from all phases present in the samples. 3D ED methods and PXRD are complementary and their combinations are promising for studying multiphasic samples and complicated crystal structures.

In this thesis, the feasibility and capability of 3D ED methods, specifically rotation electron diffraction (RED), in phase identification and structure determination of different kinds of crystalline materials with nano- or submicrometer-sized crystals are investigated. Experimental conditions for RED data collection and data processing in relation to data quality, as well as the challenges in the applications of RED are discussed.

RED was combined with PXRD to identify phases from as-synthesized samples and to characterize atomic structures of eleven crystalline compounds. It was shown to be possible to identify as many as four distinct compounds within one sample containing submicron-sized crystals in a Ni-Se-O-Cl system. RED was also used to determine unit cell and symmetry of isoreticular metal-organic frameworks (SUMOF-7) and solve five zeolite structures with new frameworks, ITQ-51, ITQ-53, ITQ-54, EMM-23 and EMM-25 and that of a metal-organic framework (MOF), SUMOF-7I. The structure of an open-framework germanate SU-77 was solved by combining RED with PXRD. The structures of the zeolites and SU-77 were confirmed by Rietveld refinement against PXRD. High-resolution transmission electron microscopy was used to confirm the structure models of ITQ-51, EMM-25 and SUMOF-7I.

Structural study of zeolites utilizing novel electron crystallographic methods : A voyage into the world of zeolite structures

Electron crystallography has evolved as a powerful method for structural characterization of a wide range of materials. It has two significant advantages over other methods for structure determination, e.g. X-ray diffraction. Electrons interact much more strongly with matter compared to X-rays and they can be focused by electromagnetic lenses to form images with atomic resolution. These advantages make electron crystallography a unique tool for characterization of crystalline materials suffering from small crystal size and complex or disordered structures.

     Zeolites are a class of microporous materials with significance in several applications. They often possess complex and disordered structures, which demand large efforts in the structure determination.

     Over the last years, two new electron crystallographic methods have been developed; the rotation electron diffraction (RED) and the structure projection reconstruction from a through-focus series of high resolution transmission electron microscopy (HRTEM) images. In this thesis, they will be applied for structure determination of four new zeolite structures, including EMM-25 and EMM-23 with two ordered structures, and ITQ-39 and ITQ-38 with disordered structures. Each of the structure solutions have different challenges to overcome. The high silica borosilicate EMM-25 was solved by the RED method. The aluminosilicate EMM-23 was solved by a combination of HRTEM and RED. The structure solution of two materials with disordered structures, ITQ-39 and ITQ-38, will be described. For materials containing disorders, structure projection images are of utmost importance.

     Furthermore, the mesoporosity inside hierarchically porous ZSM-5 crystals was studied by a combination of focused ion beam (FIB) and HRTEM imaging. The last part of this thesis explores STEM imaging for use in structure determination from 3D reconstruction.

Synthesis of organobromines as a tool for their characterisation and environmental occurrence assessment

Polybrominated diphenyl ethers (PBDEs) have been intensively used as flame retardants (FRs) and have become ubiquitous environmental pollutants. PBDEs form hydroxylated PBDEs (OH-PBDEs) as metabolites. Further, some OH-PBDEs and methoxy-PBDEs (MeO-PBDEs) are natural products. These are all compounds of environmental and health concern and it is therefore important to confirm their identity and to assess their environmental levels and toxicities. Hence, it is vital to obtain authentic reference standards of individual PBDEs and OH/MeO-PBDEs. The thesis main aim was to develop synthesis methods of congener specific PBDEs, OH- and MeO-PBDEs. The second aim was to identify and quantify PBDEs, OH- and MeO-PBDEs in environmental samples. The third was to propose an abbreviation system for FRs.

O-Arylation of brominated phenols, using either symmetrical or unsymmetrical brominated diphenyliodonium salts, was selected for synthesis of PBDEs and OH-/MeO-PBDEs. A total of 16 MeO-PBDEs, 11 OH-PBDEs, 1 diMeO-PBDE and 1 EtO-MeO-PBDE were synthesised. Three novel unsymmetrical diaryliodonium triflates were synthesised and used in synthesis. Optimisations were made to construct a reliable general method for congener specific PBDE synthesis, which was used in the synthesis of 8 representative PBDE congeners. The products were generally characterised by electron ionisation mass spectrometry (EIMS) and nuclear magnetic resonance (NMR) spectroscopy.

Identification of PBDEs and OH-PBDEs in various matrixes was based on gas chromatographic and mass spectrometric analyses. Fourteen OH-PBDE congeners were identified in a pooled human blood sample. One previously uncharacterised natural PBDE analogue was identified as 6-OH-6’-MeO-BDE-194, and quantified in Swedish blue mussels. PBDE congeners and other BFRs were identified and quantified in workers and dust from a smelter in Sweden.

A structured and practical abbreviation system was developed for halogen- and phosphorus containing FRs.

Multiscale simulations of soft matter: systematic structure-based coarse-graining approach

The soft matter field considers a wide class of objects such as liquids, polymers, gels, colloids, liquid crystals and biological macromolecules, which have complex internal structure and conformational flexibility leading to phenomena and properties having multiple spacial and time scales. Existing computer simulation methods are able to cover these scales, but with different resolutions, and ability to link them together performing a multiscale simulation is highly desirable.

The present work addresses systematic multiscaling approach for soft matter studies, using structure-based coarse-graining (CG) methods such as iterative Boltzmann inversion and inverse Monte Carlo. A new software package MagiC implementing these methods is introduced. The software developed for the purpose of effective CG potential derivation is applied for ionic water solution and for water solution of DMPC lipids. A thermodynamic transferability of the obtained potentials is studied.

The effective inter-ionic solvent mediated potentials derived for NaCl successfully reproduce structural properties obtained in explicit solvent simulation, which indicates the perspectives of using the structure-based coarse-graining for studies of ion-DNA and other polyelectrolytes systems. The potentials have temperature dependence, dominated mostly by the electrostatic long-range part which can be described by temperature dependent effective dielectric permittivity, leaving the short-range part of the potential thermodynamically transferable.

For CG simulations of lipids a 10-bead water-free model of dimyristoylphosphatidylcholine is introduced. Four atomistic reference systems, having different lipid/water ratio are used to derive the effective bead-bead potentials, which are used for subsequent coarse-grained simulations of lipid bilayer. A significant influence of lipid/water ratio in the reference system on the properties of the simulated bilayers is noted, however it can be softened by additional angle-bending interactions. At the same time the obtained bilayers have stable structure with correct density profiles. The model provides acceptable agreement between properties of coarse-grained and atomistic bilayer, liquid crystal - gel phase transition with temperature change, as well as realistic self-aggregation behavior, which results in formation of bilayer, bicell or vesicle from a dispersed lipid solution in a large-scale simulation.

Transition Metal Hydride Complexes and Hydrogenated Gallium Clusters : Synthesis and Structural Properties

Synthesis and structural characterisation of metal hydrides in two important systems are presented. The first system presented is low valent cobalt and nickel complex hydrides with the compositions BaMg5Co2H10, RbMg5CoNiH10, SrMg2CoH7and Sr4Mg4Co3H19 featuring nickel with oxidation state of 0 and cobalt with oxidation state +I and -I. The second system presented is polyanionic gallium complex hydrides with the compositions RbGaH2, RbxK(1−x)GaH2 (0.5≤x≤1), CsxRb(8−x)Ga5H15 (0≤x≤8) and Cs10Ga9H25 featuring novel hydrogenous polyanionic gallium hydride clusters mimicking common hydrocarbons. The syntheses of the compounds were performed at elevated temperatures and at moderate hydrogen pressures (50-100 bar). The structural investigations were mainly done by X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD). The metal-hydrogen bond was investigated by vibrational spectroscopy using Fourier Transform IR-spectroscopy (FTIR) and Inelastic Neutron Scattering (INS).By subtle changes in the compositions of the hydrides it was possible to induce major changes in band gaps, oxidation states and structures.

Building crystals out of crystals : Synthesis, structure and magnetic properties of iron oxide nanoparticles and self-assembled mesocrystals

This thesis is focused on the fabrication and characterization of self-assembled arrays of magnetic iron oxide (Fe3O4, γ-Fe2O3 and Fe1-xO) nanoparticles. The synthesis of spherical and cubic iron oxide nanocrystals, with sizes between 5 and 30 nm and narrow size distributions, is demonstrated, along with a rigorous morphological characterization of the cubic nanoparticles. The transformation of core|shell Fe1-xO|Fe3-δO4 particles into single-phase Fe3-δO4 particles is studied in detail. It is found that anti-phase boundaries in the particles result in the emergence of anomalous magnetic properties i.e. exchange bias, and a reduced saturation magnetization compared to that of bulk Fe3O4. Cubic nanocrystals are assembled into arrays possessing an exceptionally high degree of translational ordering and a high degree of crystallographic alignment. A combination of electron microscopy and small-angle X-ray scattering is used in the characterization of the 3D nanostructures. The directional (anisotropic) interactions in the 3D structures are modeled in an attempt to find a link between the nanocrystal morphology and the corresponding mesostructure. Here, the cohesive van der Waals energy is estimated for a system of nanocubes with a variable truncation. The assembly of nanocubes in magnetic fields of various strengths is systematically investigated. A perturbed mesocrystal growth habit is observed at intermediate fields, whereas at high field strengths, the assembly is dominated by ferrohydrodynamic instabilities. Last, magnetometry is used to study the collective magnetic properties of self-assembled nanocrystals. The magnetic susceptibility in a weak magnetic field is studied as a function of film thickness and particle size. An increase in the tendency to form ferromagnetic couplings  with decreasing film thickness can be established. This 2D to 3D crossover of the magnetic properties of the nanoparticle arrays can be related to a change in the magnetic vortex states.

Fast Dynamic Processes in Solution Studied by NMR Spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy is capable to deliver a detailed information about the dynamics on molecular level in a wide range of time scales, especially if accompanied by suitably chosen theoretical tools. In this work, we employed a set of high-resolution NMR techniques to investigate dynamics processes in several weakly interacting molecular systems in solution.

Van der Waals interactions play an important role in inclusion complexes of cryptophane-C with chloroform or dichloromethane. The complex formation was thoroughly investigated by means of 1H and 13C NMR experiments along with the quantum-chemical density functional theory (DFT) calculations. We characterized kinetics, thermodynamics, as well as fine details of structural rearrangements of the complex formation.

Internal dynamics of oligo- and polysaccharides presents a considerable challenge due to possible coupling of internal and global molecular motions. Two small oligosaccharides were investigated as test cases for a newly developed integrated approach for interpreting the dynamics of the molecules with non-trivial internal flexibility. The approach comprised advanced theoretical tools, including stochastic modeling, molecular dynamics (MD) simulations, and hydrodynamic simulations.

A biologically important bacterial O-antigenic polysaccharide from E. Coli O91 was addressed employing selective isotope labeling and multiple-field 13C relaxation experiments. The complex dynamics of the polysaccharide is characterized by the conformational motion of the exocyclic groups of the sugars, superimposed to the breathing motion of the polymeric chain.

Hydrogen bonding is another major non-covalent interaction. Dilute solutions of ethanol were chosen as a model of liquid systems containing extensive hydrogen-bonded networks. We developed a new methodology consisting of NMR diffusion measurements, DFT calculations, and hydrodynamic modeling and utilized it to determine average size of the molecular clusters of ethanol at given conditions.

Electrostatic Interactions in Coarse-Grained Simulations : Implementations and Applications

Electrostatic interactions between charged species play a prominent role in determining structures and states of physical system, leading to important technological and biological applications. In coarse-grained simulations, accurate description of electrostatic interactions is crucial in addressing physical phenomena at larger spatial and longer temporal scales.

In this thesis, we implement ENUF method, an abbreviation for Ewald summation based on non-uniform fast Fourier transform technique, into dissipative particle dynamics (DPD) scheme. With determined suitable parameters, the computational complexity of ENUF-DPD method is approximately described as O(N logN). The ENUF-DPD method is further validated by investigating dependence of polyelectrolyte conformations on charge fraction of polyelectrolyte and counterion valency of added salts, and studying of specific binding structures of dendrimers on amphiphilic membranes.

In coarse-grained simulations, electrostatic interactions are either explicitly calculated with suitable methods, or implicitly included in effective potentials. The effect of treatment fashion of electrostatic interactions on phase behavior of [BMIM][PF6] ionic liquid (IL) is systematically investigated. Our systematic analyses show that electrostatic interactions should be incorporated explicitly in development of effective potentials, as well as in coarse-grained simulations to improve reliability of simulation results.

Detailed image of microscopic structures and orientations of [BMIM][PF6] at graphene and vacuum interfaces are investigated by using atomistic simulations. Imidazolium rings and alkyl side chains of [BMIM] lie preferentially flat on graphene surface. At IL-vacuum interface, ionic groups pack closely together to form polar domains, leaving alkyl side chains populated at interface and imparting hydrophobic character. With the increase of IL filmthickness, orientations of [BMIM] change gradually from dominant flat distributions along graphene surface to orientations where imidazolium rings are either parallel or perpendicular to IL-vacuum interface with tilted angles. The interfacial spatial ionic structural heterogeneity formed by ionic groups also contributes to heterogeneous dynamics in interfacial regions.

Properties in New Complex Perovskite-Related Materials, a Matter of Composition and Structure

This PhD thesis presents investigations of perovskite-related compounds in systems of interest for applications in components in solid oxide fuel cells. The compound compositions derive from substitutions in the parent compounds LaCoO3, LaCrO3 and SrFeO3.

Novel phases La2Co1+z(MgxTi1-x)1-zO6 were synthesized and investigated with regard to structure, thermal expansion, electronic and magnetic properties. The study focused on the composition lines La2Co(MgxTi1-x)O6 (z=0), where the oxidation state of Co nominally changes from +2 (x=0.0) to +3 (x=0.5), and La2Co1+z(Mg0.5Ti0.5)1-zO6, with a varying fraction of Co3+ ions. XANES data show that the Co ions in the system have discrete oxidation states of +2 and +3. The TEC increases with increasing x due to an increasing contribution from spin state transitions of the Co3+ ions. Novel compounds La2Cr(M2/3Nb1/3)O6 with M=Mg, Ni, Cu were synthesized and characterized with respect to structure and magnetic properties. XRPD and NPD data indicate Pbnm symmetry; however, SAED patterns and HREM images indicate a P21/n symmetry for M=Mg, and Cu. The magnetic measurements results were rationalized using the Goodenough-Kanamori rules.

Oxygen-deficient phases with x≥0.63 in SrxY1-xFeO3-δ and Sr0.75Y0.25Fe1-yMyO3-δ (M=Cr, Mn, Ni and y=0.2, 0.33, 0.5), were synthesized and characterized with respect to structure, oxygen content, thermogravimetry, TEC, conductivity and magnetic properties. Powder patterns of phases agree with cubic  perovskite structures. NPD data for x=0.75 reveal anisotropic displacement for the O atom, related to local effects from Fe3+/Fe4+ ions. SAED patterns for x=0.75 reveal the presence of an incommensurate modulation. The compounds start to lose oxygen in air at ~ 400°C. The TEC up to ~400°C for x=0.75 is ~10.5 ppm/K and increase to ~17.5 ppm/K at higher temperatures. The conductivity for x=0.91 is 164 S/cm at 400°C. Partial substitution of Fe by Cr, Mn or Ni does not increase the conductivity or decrease TEC.

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