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Upcoming Dissertations

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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.

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.

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. 

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.

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. 

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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. 

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

Grain growth by Ordered Coalescence of crystallites in Ceramics : Grain Growth Mechanisms, Microstructure Evolution and Sintering

Grain growth and densification process play the two most crucial roles on the microstructure evolution and the achieved performances during sintering of ceramics. In this thesis, the grain growth of SrTiO3, BaTiO3-SrTiO3 solid solutions and Si3N4 ceramics during spark plasma sintering (SPS) were investigated by electron microscopy.

SrTiO3 ceramics starting from nanopowders were fabricated by SPS. A novel grain growth mechanism was discovered and named as ordered coalescence (OC) of nanocrystals. This mechanism involved nanocrystals as building blocks and is distinguished from atomic layer epitaxial growth (AEG) in classical sintering theory. The results also revealed that the dominant grain growth mechanism can be changed by varying heating rates. Low rate (10°C/min) gives AEG, whereas high rates (≥ 50°C/min) yields three-dimensional coalescence of nanocrystals, i.e. OC.

BaTiO3-SrTiO3 sintered bodies were made by SPS of BaTiO3 and SrTiO3 nanopowders mixtures. A novel Sr1-xBaxTiO3 “solid solution” with mosaic-like single crystal structure was manufactured by OC of the precursor crystallites. This reveals a new path for preparation of solid solution grains or composites.  

Si3N4 ceramics were prepared from α- or β-Si3N4 nanopowders at the same SPS conditions. The anisotropic OC of precipitated β-Si3N4 crystallites gives elongated β-Si3N4 grains at 1650°C using α-Si3N4 nanopowder. In contrast, AEG leads to the equi-axed β-Si3N4 grains using β-Si3N4 nanopowder. The metastable α- to β-Si3N4 phase transformation and OC accelerates anisotropic grain growth.

Grain motions contribute to the densification process during pressureless sintered 3Y-ZrO2 (>87%TD) or SPS of SrTiO3 (>92%TD) ceramics. This extends the sintering range for active grain re-arrangement over that predicted by classical theory.

In this thesis a new grain growth mechanism (OC) is proved by using SPS and nanopowders. By OC the microstructural evolution can be manipulated.

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.

Chloromethane Complexation by Cryptophanes : Host-Guest Chemistry Investigated by NMR and Quantum Chemical Calculations

Host–guest complexes are widely investigated because of their importance in many industrial applications. The investigation of their physico–chemical properties helps understanding the inclusion phenomenon. The hosts investigated in this work are cryptophane molecules possessing a hydrophobic cavity. They can encapsulate small organic guests such as halo–methanes (CH2Cl2, CHCl3). The encapsulation process was investigated from both the guest and the host point of view. With the help of Nuclear Magnetic Resonance (NMR), the kinetics of complex formation was determined. The information was further used to obtain the activation energies of the processes. Having done this on five different cryptophanes, it is possible to relate the energies to structural differences between the hosts. Via the dipolar interaction between the guest’s and host’s protons, one can get information on the orientation of the guest inside the cavity. Moreover, the dynamics of the guest can be further investigated by its relaxation properties. This revealed restricted motion of the guest inside the host cavity. Not only the nature of the guest plays an important role. The host is also changing its properties upon encapsulation. All the cryptophanes investigated here can exchange rapidly between many conformers. These conformers have different–sized cavities. Quantum chemical optimization of the structure of the conformers makes volume estimation possible. Not only the cavity volumes, but also the quantum-chemically obtained energies and the calculated chemical shifts of the carbon–13 atoms can be helpful to follow the changes of the host upon complex formation. The host cannot be considered as a rigid entity. Analysis of variable temperature proton and carbon-13 spectra shows that the encapsulation can be considered as a mixture of conformational selection and induced fit. The structures of the formed complexes are further investigated by means of two-dimensional nuclear Overhauser spectroscopy (NOESY). The complex formation, its kinetics and thermodynamics are found to be a complicated function of structure elements of the host, the cavity size and the guest size and properties.

Radiosynthesis of Perfluoroalkyl Substances : Chemical analysis, uptake, distribution, and partitioning studies

Perfluoroalkyl substances (PFASs) are widely utilized manmade chemicals. Their properties have made them highly appreciated in a variety of industrial and consumer product applications, including fire-fighting foams, hydraulic fluids, as well as in cookware and food contact papers.

However, some of the PFASs are highly persistent in the environment and their toxicological profiles are of concern. Voluntary and regulatory efforts have been taken to reduce the environmental levels of PFASs. These actions have resulted in a reduction of PFASs in human milk from Stockholm as presented in this thesis.

The radiosyntheses of 35S-PFOS, 35S-PFBS, and 14C-PFOA presented herein were applied for distribution studies in mice but also for solubility and adhesion experiments of common laboratory solvents and buffers. The radiosynthesis employed reactive Grignard reagents, perfluoroalkyliodides, and 35S-sulfur dioxide or 14C-carbon dioxide. The distribution studies were performed with 35S-PFOS on both pregnant mice and their offspring as well as on male mice. The mice were subjected to whole-body autoradiography and the tissues were analyzed by liquid scintillation counting. Liver and lungs were the target organs for 35S-PFOS in the dams. The fetuses and pups had remarkable high levels of 35S-PFOS in their lungs as well as in the brain. The male mice were given a high dose and a more environmental relevant dose of 35S-PFOS. PFOS was transferred from the blood to the tissues as the dose increased.

In another study the distribution pattern of the shorter homologue PFBS was compared to PFOS. 35S-PFBS was utilized and demonstrated a 5-40 fold lower tissue levels in comparison to PFOS.

The pharmacokinetic parameters determined for PFHxS in mice, rats, and monkeys will provide valuable insight in establishing a proper risk assessment for this compound. The study confirms the common species differences in serum elimination half-life that are associated with PFASs.

A structural investigation into the complexity of mesoporous silica crystals : From a view of curvature and micellar interaction to quasicrystallinity

Mesoporous silica crystals have a large variety of structures mainly due to the versatility of their structure template. The configuration and the chemical state of the templating micellar surfactants, together with the kinetic process of silica will determine the final outcome of the synthesis. Increasing the understanding of the complex formation processes involved will enable a possibilityto fine tune the material for specific uses, today focused into the fields of photoniccrystals, drug delivery, catalysis and separation technology.

In this thesis emphasis is put on (1) increasing the understanding the formation mechanism yielding the different species of mesoporous silica crystals through an in depth study of quasicrystallinity (2) Characterization and description of the structural complexity through various characterization techniquesand also by studying the kinetic structural transformation phenomenon related to the minimal G- and D-surfaces. (3) The structural studies of the versatile surfactant liquid crystals for establishing a thermodynamically stable basis to evaluate the kinetic mesoporous silica growth processes. Furthermorethe thesis both enlightens the possibilities of and contributes to the developmentof electron microscopy characterization techniques.

In these studies, electron microscopy is largely employed in the characterization to give a thorough picture of the mesoporous structures. This is combined with the sample preparation techniques cross-section polishing and ionslicing. Low voltage scanning electron microscopy is utilized for studying the surfaces and cross-sections of various materials at the limit of the resolution. Here, a deep understanding of the electron beam-material interaction is used for a better interpretation of the detected signals. Transmission electron microscopyis combined with electron crystallographic reconstruction to yield a three dimensional structural model. For determination of the quasicrystallinity level for a structure of dodecagonal tiling, revealed in the scope of this study,a phason strain analysis was made.

Templating and self-assembly of biomimetic materials

This thesis focuses on the use of biomolecular assemblies for creating materials with novel properties. Several aspects of biomimetic materials have been investigated, from fundamental studies on membrane shaping molecules to the integration of biomolecules with inorganic materials.

Triply periodic minimal surfaces (TPMS) are mathematically defined surfaces that partition space and present a large surface area in a confined space. These surfaces have analogues in many physical systems. The endoplasmic reticulum (ER) can form intricate structures and it acts as a replica for the wing scales of the butterfly C. rubi, which is characterized by electron microscopy and reflectometry. It was shown to contain a photonic crystal and an analogue to a TPMS. These photonic crystals have been replicated in silica and titania, leading to blue scales with replication on the nanometer scale. Replicas analyzed with left and right handed polarized light are shown be optically active.

A macroporous hollow core particle was synthesized using a double templating method where a swollen block copolymer was utilized to create polyhedral nanofoam. Emulsified oil was used as a secondary template which gave hollow spheres with thin porous walls. The resulting material had a high porosity and low thermal conductivity.

The areas of inorganic materials and functional biomolecules were combined to create a functional nanoporous endoskeleton. The membrane protein ATP synthase were incorporated in liposomes which were deposited on nanoporous silica spheres creating a tight and functional membrane. Using confocal microscopy, it was possible to follow the transport of Na+ through the membrane.

Yop1p is a membrane protein responsible for shaping the ER. The protein was purified and reconstituted into liposomes of three different sizes. The vesicles in the 10-20 nm size range resulted in tubular structures. Thus, it was shown that Yop1p acts as a stabilizer of high curvature structures.

Particle interactions at the nanoscale : From colloidal processing to self-assembled arrays

Nanostructured materials are the next generation of high-performance materials, harnessing the novel properties of their nanosized constituents. The controlled assembly of nanosized particles and the design of the optimal nanostructure require a detailed understanding of particle interactions and robust methods to tune them. This thesis describes innovative approaches to these challenges, relating to the determination of Hamaker constants for iron oxide nanoparticles, the packaging of nanopowders into redispersible granules, the tuning of the wetting behavior of nanocrystals and the simulation of collective magnetic properties in arrays of superparamagnetic nanoparticles.

The non-retarded Hamaker constants for iron oxides have been calculated from their optical properties based on Lifshitz theory. The results show that the magnitude of vdW interactions in non-polar solvents has previously been overestimated up to 10 times. Our calculations support the experimental observations that oleate-capped nanoparticles smaller than 15 nm in diameter can indeed form colloidally-stable dispersions in hydrocarbons. In addition, a simple procedure has been devised to remove the oleate-capping on the iron oxide nanoparticles, enabling their use in fluorometric assays for water remediation, with a sensitivity more than 100 times below the critical micelle concentration for non-ionic surfactants.

Nanosized particles are inherently more difficult to handle in the dry state than larger micron-sized powders, e.g. because of poor flowability, agglomeration and potential toxicity. The rheology of concentrated slurries of TiO2 powder was optimized by the addition of sodium polyacrylate, and spray-dried into fully redispersible micron-sized granules. The polymer was embedded into the granules, where it could serve as a re-dispersing aid.

Monte Carlo (MC) simulations have been applied to the collective magnetic behavior of nanoparticle arrays of various thicknesses. The decrease in magnetic susceptibility with the thickness observed experimentally was reproduced by the simulations. Ferromagnetic couplings in the arrays are enhanced by the finite thickness, and decrease in strength with increasing thickness. The simulations indicate the formation of vortex states with increasing thickness, along with a change in their orientation, which becomes more and more isotropic as the thickness increases.

Open-Framework Germanates : Synthesis, Structure, and Characterization

Novel open-framework germanates and open low-dimensional structures were synthesized and characterized. Their crystal structures were solved by single crystal X-ray diffraction or X-ray powder diffraction combined with other techniques. Although related open-framework materials, such as zeolites, are of interest for the ability to selectively accommodate guest species in their rings, pores and channels, germanates are primarily of interest for their unique structural properties. Compared to aluminosilicate-based zeolites, germanium oxides readily form frameworks with extra-large rings and low framework density. The formation of elegant germanate architectures is attributed to the unique Ge-O bond geometries compared to Si-O, and the tendency to form large clusters.

This thesis is to serve as an introduction to germanate synthesis, structures and characterization. Structures are categorized in accordance to their building units; the Ge7X19 (Ge7), Ge9X25-26 (Ge9) and Ge10X28 (Ge10) (X = O, OH, or F) clusters. Structure determination techniques as well as the characterization techniques used to examine the properties of the materials are presented. While most of the discussed techniques have routinely been used to study crystalline open-frameworks, we introduce the use of infrared spectroscopy for the identification of cluster types, valuable for structure determination by X-ray powder diffraction. Structures and properties of the novel materials ASU-21, SU-62, SU-63, SU-64, SU-65, SU-66, SU-71, SU-72, SU-73, SU-74, SU-75 and SU-JU-14 are described and put into context with previously known structures. The novel structures are all built of the Ge7, Ge9 or Ge10 clusters, and vary from a framework with novel topology to the first open zero-dimensional germanate cavities built of such clusters.

Open-Framework Germanates and Nickel Germanates : Synthesis and Characterization

Microporous materials have a wide range of important applications in separation, gas adsorption, ion-exchange and catalysis. Open-framework germanates are a family of microporous compounds and are of particular interest. This thesis focuses on the synthesis and characterization of new open-framework germanates as well as introducing the transition-metal nickel into germanate structures.

One new microporous germanosilicate, SU-78 and four new open-framework germanates, SU-74, SU-75, SU-69 and SU-76 have been obtained by using organic molecules as structure directing agents (SDAs). The incorporation of nickel and organic SDAs in the synthesis resulted in five novel nickel germanates, SUT-1, SUT-2, SUT-3, SUT-4 and SUT-5, in which nickel complexes act either as framework-forming components or as structure directing agents.

The general synthesis route is described and the variables that affect the synthesis products are summarized. Different techniques applied on the characterization of chemical and physical properties of the products are also introduced.

Metal-Organic Frameworks (MOFs) for Heterogeneous Catalysis : Synthesis and Characterization

Metal-organic frameworks (MOFs) are crystalline hybrid materials with interesting chemical and physical properties. This thesis is focused on the synthesis and characterization of different MOFs and their use in heterogeneous catalysis.

Zeolitic imidazolate frameworks (ZIFs), including ZIF-4, ZIF -7 and ZIF -62, Ln(btc)(H2O) (Ln: Nd, Sm, Eu, Gd, Tb, Ho, Er and Yb), Ln2(bpydc)3(H2O)3, (Ln: Sm, Gd, Nd, Eu, Tb, Ho and Er), MOF-253-Ru and Zn(Co-salophen) MOFs were synthesized. Various characterization techniques were applied to study the properties of these MOFs. X-ray powder diffraction (XRPD), single crystal X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were extensively used.

The effect of synthesis parameters, such as batch composition and temperature, on the formation and morphology of ZIF-7 and ZIF-62 was studied. Structural transformation and flexibility of two series of lanthanide-based MOFs, Ln(btc)(H2O) (Ln: Nd, Ho and Er) and Ln2(bpydc)3(H2O)3, (Ln: Sm and Gd) upon drying and heating were characterized. Relations between metal coordination, structure flexibility and thermal stability among the Sm2(bpydc)3(H2O)3, Nd(btc)(H2O) and MOF-253 were investigated.

Salophen- and phenanthroline-based organic linkers were designed, synthesized and characterized. Metal complexes were coordinated to these linkers to be used as catalytic sites within the MOFs.

Catalytic studies using two MOF materials, Ln(btc) and MOF-253-Ru, as heterogeneous catalysts in organic transformation reactions were performed. The heterogeneous nature and recyclability of these MOFs were investigated and described.

Synthesis and modification of potential CO2 adsorbents : Amine modified silica and calcium carbonates

The prospect of rapid changes to the climate due to global warming is subject of public concern. The need to reduce the emissions of atmospheric green house gases and in particular carbon dioxide is greater than ever. Extensive research is performed to find new solutions and new materials, which tackles this problem in economically benign way. This thesis dealt with two potential adsorbents for post combustion  carbon capture, namely, amine modified silica and calcium carbonates. We modified porous silica with large surface area by propyl-amine groups to enhance the carbon dioxide adsorption capacity and selectivity. Experimental parameters, such as reaction time, temperature, water content, acid and heat treatment of silica substrate were optimized using a fractional factorial design. Adsorption properties and the nature of formed species upon reaction of CO2 and amine-modified silica were studied by sorption and infrared spectroscopy. Physisorbed and chemisorbed amount of adsorbed CO2 were, for the first time, estimated directly in an accurate way. The effects of temperature and moisture on the CO2 adsorption properties were also studied.

Crystallization of calcium carbonate as a precursor to calcium oxide, which can be used as carbon dioxide absorbent, was studied in the second part of this thesis. Structure of different amorphous phases of calcium carbonate was studied in detail. Crystallization of calcium carbonate with and without additives was studied. Parameters like stirring rate, temperature, pH and polymer concentration showed to be important in selection of phase and morphology. An aggregation mediated crystallization was postulated to explain the observed morphologies. 

Structure-Property-Composition Correlations in Rare-Earth Alumino-silicate Glasses

Rare earth (RE) alumino-silicate (AS) glasses exhibit favorable physical, mechanical and optical properties, such as high values of the glass transition temperature, Vickers hardness, and refractive index. RE2O3-Al2O3-SiO2 glasses have found several industrial applications, for example as components of optical amplifiers and lasers. Many of these features stem from the high cation field-strength (CFS) of the trivalent RE ions (proportional to the valence of the ion divided by the square of its radius), which affects not only the physical properties of the glass, but also their structures.

This thesis deals with investigations of four different RE2O3-Al2O3-SiO2 systems, where RE represents either of La, Y, Lu or Sc. The glass forming regions of the latter two were reported by us for the first time. Within each system, glasses were prepared for variable RE, Si and Al contents.

The glass structures were investigated by solid-state 29Si and 27Al nuclear magnetic resonance (NMR) spectroscopy that informs about the local Si and Al environments in the glass network, which is built from interlinked SiO4 and AlO4 groups. Higher Al coordination numbers were also revealed by 27Al NMR: their amounts were observed to increase markedly as the CFS of the RE ion increases, i.e., along the series La<Y<Lu<Sc. This thesis discusses such structure/composition relationships, as well as the correlations between the glass composition and its physical properties of density, molar volume, compactness, glass transition temperature, Vickers hardness and refractive index. Some of these properties, for example the glass transition temperature and Vickers hardness, were observed to enhance as the RE3+ CFS increased.

Characterizing cavity containing materials using electron microscopy : A study of metal oxides, mesoporous crystals and porous material containing nanosized metal-particles

This thesis concerns the characterization of novel materials by utilizing electron microscopy techniques. The examined materials contain cavities with certain attributes that enables desired properties for applications such as gas separation, catalysis and fuel cells. The specimens concerned herein belong to the following groups of materials: Metal oxides in the Sb-W-Mo-O system; ordered mesoporous silicas and carbons; hollow spheres containing Au-nanoparticles; zeolite LTA incorporated with mesopores; metal organic frameworks doped with nickel.

With scanning electron microscopy (SEM) and transmission electron microscopy (TEM) you get vast possibilities within the field of characterization. This thesis utilizes conventional electron microscopy techniques such as imaging, energy-dispersive spectroscopy and electron diffraction as well as reconstruction techniques, such as exit-wave reconstruction, electron tomography and electron crystallography. Furthermore, the sample preparation technique cross-section polishing has been used in conjunction with low voltage SEM studies.

The scientific approach is to gain knowledge of nano-sized cavities in materials, in particular their shape, size and content. The cavities often have irregularities that originates from the synthesis procedure. In order to refine the synthesis and to understand the properties of the material it is required to carefully examine the local variations. Therefore average characterization techniques such as crystallography needs to be combined with local examination techniques such as tomography. However, some of the materials are troublesome to investigate since they to some extent bring limitations to or gets easily damaged by the applied characterization technique. For the development of novel materials it is essential to find means of overcoming also these obstacles.

Methodology for hemoglobin adduct measurement : Fetal exposures to acrylamide and other genotoxic agents

There is increasing evidence that exposure to toxic chemicals during the prenatal period constitute a higher health risk than exposure during adulthood. To characterize exposure and identify risk factors, sensitive methods for analysis of chemicals in vivo with biomarker methods are needed. Adducts to hemoglobin (Hb) have been shown useful as biomarkers of dose in blood of reactive compounds/metabolites, which are toxic due to reactions with biomacromolecules.

The aim of this thesis was to develop a new method for the analysis of Hb adducts suitable for analysis of large sample series, and then to apply the method for measurements of Hb adducts from exposure to acrylamide, glycidamide and ethylene oxide in mother/cord blood samples from five European countries.

A new method for measurements of N-terminal Hb adducts, denoted the adduct FIRE procedure, was developed using the fluorescein isothiocyanate Edman reagent. With the new procedure, optimized for LC/MS analysis, a high sensitivity and reproducibility was achieved. The new method made it possible to perform measurements of low exposures to the studied genotoxic compounds in approximately 1350 maternal and cord blood samples.

The results show that the fetus is exposed to a similar in vivo dose of the studied compounds as the mother. The measured Hb adduct levels show that acrylamide exposure from food intake is higher for the participating mothers fromUK compared to the mothers from the other countries. The measured Hb adduct levels form a basis for evaluations of relationships between exposure and health risks, and ongoing studies indicate associations between acrylamide Hb adduct levels and birth weight.

The developed method was also used for identification of an unknown Hb adduct, which was shown to originate from methyl vinyl ketone (MVK), a highly reactive and toxic compound. The identity of the adduct was confirmed with synthesized standards. There exist both natural and anthropogenic sources to MVK, and to what extent the MVK-adduct reflects exogenous exposure is yet not clarified.

Cob(I)alamin as a Quantitative Tool for Analysis, Metabolism and Toxicological Studies of Electrophilic Compounds : Butadiene Epoxides, Glycidamide and Sucralose

Vitamin B12 can be reduced to cob(I)alamin [Cbl(I)], which is one of the most powerful nucleophiles known and referred to as a “supernucleophile”. Cbl(I) was applied as a tool in toxicological studies of the air pollutant 1,3-butadiene (BD), the toxicant acrylamide (AA) present in many foods, and the artificial sweetener sucralose.

BD, a human carcinogen, is metabolised to genotoxic epoxides, two monoepoxides and the most potent diepoxybutane (DEB). AA, classified as a probable human carcinogen, is metabolised to the genotoxic epoxide glycidamide (GA). Due to their reactivity, quantitative analysis of the epoxides presents an analytical challenge. By using Cbl(I) for trapping, a sensitive and accurate method to quantify the epoxides as alkylcobalamins by LC-MS/MS in metabolism studies was developed and validated.

Using the Cbl(I) method, enzyme kinetic parameters, Vmax and Km, were determined for the metabolic steps associated with the BD epoxides and with the formation of GA from AA, in liver S9 fractions of human, mouse and rat.

An approach to estimate dose in vivo (i.e. area under concentration time curve, AUC) of BD epoxides by scaling the enzyme kinetic data was designed. The AUCs obtained from in vitro were evaluated by comparing with AUCs in vivo that were calculated from published haemoglobin adduct data. The AUCs from in vitro and in vivo showed to be in agreement with each other for mouse and rat, and this evaluation allowed prediction of the unknown AUC of DEB in human from BD exposure. This approach has a potential to reduce animal experiments in the future.

Sucralose is of concern due to its chlorinated structure and persistence in the aquatic environment. It was demonstrated that Cbl(I) reacts with sucralose, also under in vitro physiological conditions, which might have toxicological significance. The demonstrated reaction also suggested a potential role for Cbl(I) in dehalogenation/degradation of sucralose. This was evaluated and shown possible using heptamethyl cobyrinate, a model compound for cobalamin.

Shaping Macroporous Ceramics : templated synthesis, X-ray tomography and permeability

Macroporous ceramic materials have found widespread technological application ranging from particulate filters in diesel engines, tissue engineering scaffolds, and as support materials in carbon capture processes. This thesis demonstrates how the pore space of macroporous alumina can be manipulated, analysed in three-dimensions (3D) using visualisation techniques, and functionalised with a CO2-adsorbing material.

A novel method was developed to produce macroporous alumina materials: by combining sacrificial templating with thermally expandable polymeric microspheres and gel-casting of an alumina suspension. This method offers a versatile production of macroporous ceramics in which the level of porosity and the pore size distribution can easily be altered by varying the amount and type of spheres. The permeability to fluid flow could be regulated by controlling the connectivity of the pore space and the size of the smallest constrictions between the pores. Sacrificial templating with particle-coated expandable spheres significantly increased the fraction of isolated pore clusters and reduced both the sizes and the numbers of connections between neighbouring pores, compared to templating with un-coated spheres.

The macroporous alumina materials were characterised with X-ray micro-computed tomography (μ-CT). The 3D data-sets obtained by X-ray μ-CT were used to calculate the spatial variation in porosity, the throat and pore size distributions and to calculate the permeability to fluid flow. The throat and pore size distributions were also able to be accurately quantified in only one extrusion and intrusion cycle with water-based porosimetry; a relatively novel and simple characterisation technique. The pore walls of the macroporous alumina materials were also coated with zeolite films by a colloidal processing technique. The CO2-uptake of the coated alumina materials and of hierarchically porous monoliths of zeolites was evaluated and compared.

New Cu-I cluster compounds with luminescent properties

The aim of this thesis has been to investigate how the synthesis route, choice of solvent and counter-ions effects the crystallization of Cu(I)I systems, and to investigate the correlation between the structure and luminescence properties of the systems.

In order to do so a series of compounds based on an anion containing Cu(I)I, stabilized by organic cations have been produced. The crystal structures have been determined by single crystal X-ray crystallography. The luminescence properties have been quantified by laser confocal microscopy or by fluorescence spectrophotometry. We have also performed quantum mechanical calculations (Time Dependent Density Functional Theory (TDDFT)) to increase the understanding of the luminescence properties of the title system.

Incorporation of tetraalkylammonium with different chain-size showed that the size of the counter-ion matters, where small counter-ion give rise to formation of infinite chains and large and bulky counter-ion tends to form discrete anion. However, the effect of incorporation of different phosphonium based cations was not as consistent, hence the conclusion must be that the size of the cation matters only sometimes. Two different synthesis routes have been employed during this study, the solvolysis method and the hydrothermal method. The latter method showed to be very efficient for this system. Hydrothermal conditions do, however, tend to give rise to the formation of the thermodynamically most stable product and the combination of the two approaches is beneficial for a wider scan of the phase space.

Chemical reactivities as a mirror of environmental transformations - method development and assessment of some selected organohalogens

The assement of chemical persistence is an important part of legislative protection of the environment and human health. Of the vast number of chemicals on the market today few have been properly assessed. The coordination between testing guidelines from different frameworks is limited and especially the methods for determination of biodegradation show poor reproducibility because of their highly complex nature.

In order to circumvent the multifactorial assessment methods that involve the use of e.g. soils and sediments an attempt to create a new approach to chemicals assessment was postulated by Green and Bergman in 2005. This approach puts the focus on testing the chemical reactivity of the compound in environmentally relevant transformation/degradation reactions, i.e. reduction, oxidation, hydrolysis-substitution-elimination (hse), radical reactions, and photolysis. These tests are to be performed in controlled abiotic laboratory experiments ensuring that the results reflect the transformation rate of the intended type of reaction for the investigated substance. To achieve an assessment of the presistence of the compound, the test results are then combined with data on physicochemical properties of the compound and a mathematic matrix describing the reactive power of the different types of reactions in each environmental compartment (air, water, soil, and sediment).

Thus far methods for testing of oxidation, photolysis, and hydrolysis-substitution-elimination reactions have been developed. Within this thesis a method for determining reduction was developed and further utilised to determine transformation products from reductive debromination of the three nonabrominated diphenyl ethers. The previously established method for hse was evaluated and further developed in a study of selected chlorobenzenes. Some novel brominated flame retardants were investigated using the previously developed photolysis method, and transformation products and quantum yields were determined. All of the papers presented within this thesis intend to build on the project of a new persistency assessment model. The results presented also contributes important information on the properties and transformation of some common organohalogen pollutants.

Trends and exposure of naturally produced brominated substances in Baltic biota - with focus on OH-PBDEs, MeO-PBDEs and PBDDs

The semi-enclosed and brackish Baltic Sea has become heavily polluted by nutrients, anthropogenic organic and inorganic chemicals via human activities. Persistent organic pollutants (POPs) have been thoroughly investigated due to their linkage to toxic effects observed in Baltic biota. There has been far less focus on semi-persistent pollutants e.g. naturally produced oraganohalogen compounds (NOCs) and their disturbances in the environment. This thesis is aimed on assessment of levels and trends of naturally produced brominated compounds in Baltic biota; more specifically on hydroxylated polybrominated diphenyl ethers (OH-PBDEs), methoxylated PBDEs (MeO-PBDEs) and polybrominated dibenzo-p-dioxins (PBDDs). These, NOCs, may originate from production in algae and cyanobacteria. OH-PBDEs and MeO-PBDEs may also be formed as metabolites of polybrominated diphenyl ethers (PBDEs), i.e. well-known commercial flame retardants.

High levels of OH-PBDEs, MeO-PBDEs and PBDDs are shown within Baltic biota (cyanobacteria, algae, mussels, fish), often in much higher concentrations than PBDEs which are possible anthropogenic precursors of OH- and MeO-PBDEs. The levels of OH-PBDEs, MeO-PBDEs and PBDDs are higher in the Baltic Sea than on the west coast of Sweden. Temporal and seasonal variations show fluctuations in concentrations of OH-PBDEs, MeO-PBDEs and PBDDs, possibly related with macroalgal life-cycles. OH-PBDEs, MeO-PBDEs and PBDDs are present in several filamentous macroalgae species, but considering the levels quantified, the time of peak exposure and the species life-cycle the macroalgae, Pilayella, Ceramium and Cladophora are suggested as major natural producers of OH-PBDEs and PBDDs.

The high levels of OH-PBDEs, MeO-PBDEs and PBDDs in the Baltic Sea may affect numerous organisms in the ecosystem. The toxic effects of OH-PBDEs and PBDDs are of particular concern. This thesis stress the importance of assessing and monitoring these substances, since the exposure to OH-PBDEs and PBDDs, during summer, may cause acute effects in Baltic fish and wildlife.

Assessment of Environmental Pollutants in Humans from Four Continents : Exposure levels in Slovakia, Guinea-Bissau, Nicaragua and Bangladesh

Humans are continuously exposed to complex mixtures of anthropogenic chemicals. This thesis focus on human exposure to persistent organic pollutants (POPs). POPs ability to bioaccumulate and biomagnify together with the extensive historical use of POPs in e.g. agriculture and industry have resulted in detection of these compounds in humans and animals from all over the world. Adverse health effects caused by POPs are of particular concern for newborns and young individuals.

The objective of this thesis is to assess human exposure to a selected set of POPs and their metabolites. More specifically, one aim of my thesis is to determine the exposure to polychlorinated biphenyls (PCBs) and in particular their methylsulfonyl and hydroxylated metabolites in humans from a “hot-spot” area of PCB contamination in eastern Slovakia. The maternal transfer of these chemicals is studied. Further, another specific aim is to determine occurrence, levels and, when possible, temporal trends of POPs in children and adults from three developing countries, Nicaragua, Guinea-Bissau and Bangladesh.

High concentrations of PCBs and their metabolites are shown in men and women from Michalovce in eastern Slovakia. Placental transfer of methylsulfonyl-metabolites of PCBs and 4,4’-DDE was observed for the first time. Decreasing temporal trends of the majority of POPs are shown in serum from a cohort of policemen from Guinea-Bissau. In contrast, the levels of polybrominated diphenyl ethers (PBDEs) show an increasing time trend. Within five years, decreasing levels of POPs were also shown in children working and living at a waste disposal site in Nicaragua. Children working and living at waste disposal sites in Bangladesh have considerably lower levels of POPs compared to the children from Nicaragua except for 4,4’-DDT and 4,4’-DDE that are present at very high concentrations, indicating ongoing use of technical DDT.

There are many studies on levels and trends of environmental pollutants from the developed industrial countries in the world, whereas data from developing countries is still scarce. This thesis contributes to partly fill this data gap since it includes assessments of POPs in children and adults from four countries on four continents.

Thermoelectric Properties of Antimony Based Networks

With the retreating sources of carbon based fuels, thermoelectric materials can play an important role in the future of environmentally friendly power generators. Sb based framework have in some cases shown some promising properties as thermoelectric materials. The physical properties may be modified with doping or incorporation of new elements. Zn4Sb3 and Cd4Sb3 are structurally related with a Sb-based network and Zn/Cd occupying the rest of the positions. Both structures undergo order-disorder αβ transition of the Zn/Cd positions, at 254 K and ~355 K respectively. The previously ordered interstitial atoms become distributed in the structure and the two high temperature phases are isostructural (R-3c). Cd4Sb3 was synthesized from melt-quench, flux synthesis with Sn, Bi and In. The syntheses made with In resulted in interstitial-free β-Cd4Sb3 with the composition Cd11.7In1.5Sb10. This compound exhibits no phase transitions until decomposition. ZnSnSb2 and InSb both exhibit the cubic sphalerite structure. ZnSnSb2 is metallic and InSb narrow band-gap semiconductor. Attempts were made to fine-tune the electrical properties by probing the mutual solid solubility range. The formula [ZnSnSb2]x[2(InSb)]1-xSn4 and 0<X<1 with 0.1 increments for the whole composition range was used. Resistivity changes from semiconducting to metallic conduction between x=0.9 and x=0.8. In the attempt to dope Zn4Sb3 by In a novel metastable compound with the composition Zn9Sb6In2 was found. Another novel phase was discovered with the composition Zn5Sb4In2-δ (δ=0.15).  The two phases have the same Sb-framework with a CuAl2 structure. Zn and In arrangements fill the square antiprisms formed by the stacking of 32434 nets in anti configuration. The filling of the antiprisms in the two phases are different, in Zn9Sb6In2 the antiprisms have two filling arrangements, an In or Zn3 triangles. In Zn5Sb4In2-δ the antiprisms are filled with an In and a Zn that occupies a split position to form a hetero-atomic dimers.

Organohalogen contaminants in Greenland shark (Somniosus microcephalus)

The remote sub-Arctic/Arctic environment has due to human activities become a sink for organohalogen contaminants (OHCs). These OHC include traditional contaminants such as polychlorinated biphenyls (PCBs), DDTs and technical mixtures of polybrominated diphenyl ethers (PBDEs), all included in the Stockholm Convention list of persistent organic pollutants (POPs). Other OHCs, currently under evaluation to be included among the POPs i.e. short chain chlorinated paraffins (SCCPs) and hexabromocyclododecane (HBCDD) are also found in these environments as well as a whole range of other OHCs.

The main objective of this thesis is to increase the knowledge about the presence of OHCs in a high trophic Arctic shark species, the Greenland shark (Somniosus microcephalus). The Greenland shark is an opportunistic feeder, occasionally feeding at the top of the Arctic marine food chain. Furthermore may this species have a life span in excess of 100 years and is probably among the oldest of any fish species. These traits make the shark prone to accumulate elevated concentrations of OHCs.

This has shown to be true for the Greenland sharks studied and most of the targeted OHCs were determined in the species. The highest concentrations were observed for the DDTs, ranging up to 26 μg/g fat. Other OHCs reported that are of special interest are SCCPs and brominated flame retardants used as replacement products to PBDEs; pentabromoethylbenzene (PBEB) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE). Also a range of OHCs whose origin is assumed to be natural, were shown to be present in Greenland sharks.

This thesis is stressing the fact that even though the use of certain OHCs has been banned for decades they are still present at high concentrations in the deep waters of the Arctic. Therefore it is of major importance to continue to monitor the fate of traditional and emerging OHCs in the environment, and for this purpose the Greenland shark is an excellent species.

3D Electron crystallography : Real space reconstruction and reciprocal space tomography

Electron crystallography is an important technique for studying micro- and nano-sized materials. It has two important advantages over X-ray crystallography for structural studies: 1) crystals millions of times smaller than those needed for X-ray diffraction can be studied; 2) it is possible to; focus the electrons to form an image. The local atomic arrangement can be seen directly by high-resolution transmission electron microscopy (HRTEM). The crystallographic structure factor phases, which are lost in recording diffraction patterns, are present in HRTEM images and can be determined experimentally. The main disadvantages of electron crystallography compared to X-ray diffraction are that the data are difficult to collect, often incomplete and suffer from dynamic scattering. New methods need to be developed to overcome these problems. In this work, structure determination of several unique and complex porous materials including zeolites and mesoporous silica is demonstrated. None of the structures of these materials could be solved by X-ray crystallography. New techniques are also developed in order to overcome the disadvantages of electron crystallography. The new techniques include a digital sampling method for collecting precession electron diffraction data and a rotation method for automatic collection of complete 3D electron diffraction data. A number of practical issues concerning data collection and data processing are described and the data quality is analysed.

Identification of brominated organic compounds in aquatic biota and exploration of bromine isotope analysis for source apportionment

Brominated organic compounds (BOCs) of both natural and anthropogenic origin are abundant in the environment. Most compounds are either clearly natural or clearly anthropogenic but some are of either mixed or uncertain origin. This thesis aims to identify some naturally produced BOCs and to develop a method for analysis of the bromine isotopic composition in BOCs found in the environment.

Polybrominated dibenzo-p-dioxins (PBDDs) in the Baltic Sea are believed to be of natural origin although their source is unknown. Since marine sponges are major producers of brominated natural products in tropical waters, BOCs were quantified in a sponge (Ephydatia fluviatilis) from the Baltic Sea (Paper I). The results showed that the sponge does not seem to be a major producer of PBDDs in the Baltic Sea. In this study, mixed brominated/chlorinated dibenzo-p-dioxins were however discovered for the first time in a background environment without an apparent anthropogenic source.

The use of nuclear magnetic resonance spectroscopy (NMR) is unusual in analytical environmental chemistry due to its sample requirements. Preparative capillary gas chromatography was used to isolate a sufficient amount of an unidentified BOC from northern bottlenose whale (Hyperoodon ampullatus) blubber (Paper II) to enable NMR analysis for identification of the compound.

The bromine isotopic composition of BOCs may give information on the origin and environmental fate of these compounds. The first steps in this process are the development of a method to determine the bromine isotope ratio in environmentally relevant BOCs (Paper III) and measuring the bromine isotope ratio of several standard substances to establish an anthropogenic endpoint (Paper IV).

Molecular Modeling of Cardiolipin

Biological membranes are assembled from many different lipids. Our understanding of membrane function and morphology is dependent on linking the properties of the lipids to the properties of the membranes. In the inner mitochondrial membrane, one of the main lipids is cardiolipin, which is involved in the formation of high curvature tubular regions. In this thesis a series of molecular models of cardiolipin is presented, with the aim of providing a bottom-up understanding for its influence on model and biological membranes. The models allow detailed control over the headgroup charge and the chain volumes, which experimentally have shown to be important for the packing, mechanical, and electrostatic properties of membranes.To achieve these aims, three levels of detail were used: i) quantum chemical calculations for the cardiolipin headgroup, ii) atomistic united atom molecular dynamics simulations for cardiolipin and phosphatidylcholine lipid mixtures, and iii) coarse grained molecular dynamics simulations for larger lipid systems, including phase transitions between the micellar, lamellar, and inverse hexagonal phases, as well as mixtures of cardiolipin with zwitterionic lipids. These models are presented in the context of various experiments on cardiolipin systems done by others, and some basic theory of electrostatics and mechanics of membranes are discussed.The simple coarse grained model gave lipid phase preferences in agreement with experimental data. Relatively small amounts of partially neutralized cardiolipin molecules introduced mechanical instability in phosphatidylcholine bilayers, and showed some evidence of domain formation due to curvature frustration. The small effective headgroup volume of cardiolipin induced order in the hydrocarbon chains, partly due to strong sodium ion binding. Different types of intramolecular hydrogen bond networks in cardiolipin were described, and proton transfer between the phosphate groups within a cardiolipin molecule was estimated to have a 4-5 kcal/mol barrier. Such transfer might play a role in the surface conduction of protons at the inner mitochondrial membrane.

Improved basis for cancer risk assessment of acrylamide from food : Determination of glycidamide in vivo doses

Acrylamide is formed in heat processing of many common foods. According to animal cancer tests acrylamide is a carcinogen. To estimate the cancer risk from exposure via food, the response at high doses in the cancer tests with rats has to be extrapolated to the exposure levels in humans. Acrylamide is biotransformed to the epoxide glycidamide, which is assumed to be the cancer-risk increasing agent. Therefore in vivo doses of both acrylamide and glycidamide should be measured in rats and humans and related to the acrylamide intake. In vivo doses (area under the time-concentration curve, AUC) of reactive compounds can be determined from measured reaction products, adducts, to hemoglobin (Hb).

A study in mice showed that the food matrix does not have an influence on the absorbed amount of acrylamide from food. There was a linear dose-response of Hb-adduct levels from acrylamide and glycidamide.

For cancer risk assessment it is important to describe variations between individuals in intake and in AUC. Hb-adduct levels of acrylamide and glycidamide were studied in two large groups. In non-smokers the acrylamide and glycidamide-adduct levels varied with a factor of 5 and 8, respectively. The influence of other compounds in the diet on metabolic formation/elimination of glycidamide was demonstrated by associations between the ratio of glycidamide-to-acrylamide-adduct levels and alcohol intake. Furthermore, a non-linearity between glycidamide and acrylamide-adduct levels was shown at low exposure levels. AUCs from acrylamide and glycidamide in rats exposed as in the cancer tests were measured and compared with AUCs in humans exposed to acrylamide through food. The AUC of glycidamide per given dose of acrylamide was somewhat higher in humans than in the rats. Altogether the generated data could be used to improve the cancer risk estimate of acrylamide in food. The obtained data strengthen earlier preliminary cancer risk estimates of acrylamide.

Synthesis and Characterization of Functionalized Silica Mesoporous Crystals : Cationic Surfactant and Co-structure Directing Agent System

This dissertation has been focused on the synthesis and characterization of novel functionalized silica mesoporous crystals by using cationic surfactant and co–structure directing agents (CSDA), the central concept of the synthesis method is to build proper organic/inorganic interactions by introducing CSDA into the synthesis system.

By using cationic surfactant as template and anionic CSDA, carboxylic group functionalized mesoporous silicas were successfully synthesized. Well ordered 2D p6mm, cubic Fm-3m, mixture of CCP (Fm-3m) and HCP (P63/mmc), and cubic Fd-3m with uniform carboxylic group distribution have been obtained. Besides, we have investigated the Fm-3m/Fd-3m type intergrowth and new type defects observed in the Fd-3m structure using transmission electron microscopy (TEM) and proposed a “polyhedron packing” model.

New amphoteric, inorganic amino acid with highly ordered mesopores were synthesized. Uniform distribution of acid and base organic groups on the mesopore surfaces were formed by interactions between the counter charged surfactant head groups and ionic parts of CSDAs. It has been demonstrated that organic (–NH2 and –COOH) pairs incorporated in the mesopore walls behave as natural amino acids, collectively exhibiting an isoelectric point of ~6.0. Moreover, we have demonstrated that the inorganic amino acid is an efficient catalyst for the reaction between aldehydes and carbon nucleophiles.

Spark Plasma Sintering Enhancing Grain Sliding, Deformation and Grain Size Control : Studies of the Systems Ti, Ti/TiB2, Na0.5 K0.5 NbO3, and Hydroxyapatite

The unique features of the Spark plasma sintering (SPS) were used to investigate the sintering and deformation behaviour of titanium and titanium–titanium diboride composites, and to control the sintering and grain growth of ferroelectric Na0.5K0.5NbO3 (NKN) and of hydroxyapatite (HAp). In the SPS the samples experience a temperature different from that recorded by the thermocouple (pyrometer) used and this temperature difference has been estimated for Ti and NKN.

 

Sintering and deformation of titanium was investigated. Increasing heating rate and/or pressure shifted the sintering to lower temperatures, and the sintering and deformation rates changed when the α→β phase transition temperature was passed. Fully dense Ti/TiB2 composites were prepared. The Ti/TiB2 composites could be deformed at high temperatures, but the hardness decreased due to the formation of TiB. 

 

The kinetic windows within which it is possible to obtain fully dense NKN and HAp ceramics and simultaneously avoid grain growth are defined. Materials have a threshold temperature above which rapid and abnormal grain growth takes place. The abnormal grain growth of NKN is due to a small shift in the stoichiometry, which in turn impairs the ferroelectric properties. Fully transparent HAp nanoceramics was prepared, and between 900 and 1050 oC elongated grains are formed, while above 1050 oC abnormal grain growth takes place.NKN samples containing grains of the sizes 0.35–0.6 µm yielded optimum ferroelectric properties, i.e. a high remanent polarization (Pr = 30 µC/cm2) and high piezoelectric constant (d33= 160 pC/N). The ferroelectric domain structure was studied, and all grains exhibited a multi-domain type of structure.

Protein structure prediction : Zinc-binding sites, one-dimensional structure and remote homology

Predicting the three-dimensional (3D) structure of proteins is a central problem in biology. These computationally predicted 3D protein structures have been successfully applied in many fields of biomedicine, e.g. family assignments and drug discovery. The accurate detection of remotely homologous templates is critical for the successful prediction of the 3D structure of proteins. Also, the prediction of one-dimensional (1D) protein structures such as secondary structures and shape strings are useful for predicting the 3D structure of proteins and important for understanding the sequence-structure relationship. In addition, the prediction of the functional sites of proteins, such as metal-binding sites, can not only reveal the important function of proteins (even in the absence of the 3D structure) but also facilitate the prediction of the 3D structure.

Here, three novel methods in the field of protein structure prediction are presented: PREDZINC, a method for predicting zinc-binding sites in proteins; Frag1D, a method for predicting the 1D structure of proteins; and FragMatch, a method for detecting remotely homologous proteins. These methods compete satisfactorily with the best methods previously published and contribute to the task of protein structure prediction.

New approaches for synthesis and analysis of adducts to N-terminal valine in hemoglobin from isocyanates, aldehydes, methyl vinyl ketone and diepoxybutane

Human exposure to harmful compounds in the environment, from intake via food, occupational exposures or other sources, could have health implications. Exposure to reactive compounds/metabolites can be identified and quantified as hemoglobin (Hb) adducts by mass spectrometry. This thesis aimed at improved synthetic pathways for reference standards, and improved analytical methods for adducts to N-terminal valine in Hb from a range of reactive compounds; isocyanates, aldehydes, methyl vinyl ketone (MVK), and diepoxybutane (DEB).

Isocyanates form urea adducts with N-terminal valine by carbamoylation, which are detachable as hydantoins by hydrolysis. A new synthetic pathway for reference standards of adducts from isocyanates and a method for their analysis by liquid chromatography/mass spectrometry (LC/MS) were developed.

Aldehydes form reversible imines (Schiff bases) with N-termini in Hb. After stabilisation by reduction and detachment by isothiocyanates using modified Edman methods, these adducts could be analysed by gas chromatography/mass spectrometry (GC/MS) or LC/MS. 5-Hydroxymethylfurfural, its metabolites, and other aldehydes related to exposure via food, were studied with regard to analysis by these methods with synthesised standard references. A considerably improved analytical method for imines was developed. Many of the studied adducts are too short-lived in vivo or in vitro to be used for long-term biomonitoring. However, different approaches for the analysis were evaluated.

Through synthesised reference standards, an observed unknown adduct in blood was verified as the adduct from MVK. There exist both natural and anthropogenic sources for MVK.

DEB, metabolite of butadiene, forms a cyclic adduct to valine-N. A new approach using hydrazinolysis of protein and enrichment by molecularly imprinted solid-phase extraction was tested on synthesised reference DEB-adduct and gave promising results.

Synthesised standards were characterized by NMR, LC/MS and GC/MS.

Functionalization and processing of porous powders into hierarchically porous monoliths

Inorganic porous materials are widely used in a number of applications, where is a need to functionalize and produce materials with a multiscale porosity. The first part of the thesis describes how a novel and facile powder processing approach, using pulsed current processing (PCP) or, as it is commonly called, spark plasma sintering (SPS), has been employed to produce mechanically stable, hierarchically porous bodies from different porous powders.

Surfactant-templated mesoporous spheres were PCP-treated to yield meso/macro porous monoliths. The bimodal pore size can be tailored by choice of templating molecules in the aerosol-assisted synthesis process and by the particle size of the spheres. Diatomite powders were used to produce macro/macroporous monoliths. The densification behaviour of this inexpensive and renewable macroporous raw material was evaluated in detail, and an optimum temperature range was identified where the PCP process yields mechanically strong monoliths.

Binder-less, hierarchically porous zeolite monoliths were produced from various zeolite powders, e.g. silicalite-1, ZSM-5 and zeolite Y. Line-broadening analysis of X-ray powder diffraction data by the Rietveld method and electron microscopy showed that the formation of strong interparticle bonds during the PCP process is associated with a local amorphization reaction that is induced by the high contact stress and temperature. Xylene isomerisation studies showed that binder-less ZSM-5 monoliths display a high catalytic selectivity.

Direct (in-situ) nanoparticle functionalization of surfactant templated mesoporous silica particles has also been demonstrated. Pre-synthesized TiO2 nanoparticles were dispersed in a precursor solution, containing surfactant and silica source, and processed in an aerosol-generator to produce spherical nanoparticle-functionalized mesoporous particles.

 

Toxicologically important DDT metabolites : Synthesis, enantioselective analysis and kinetics

DDT was extensively and globally used as a pesticide in agriculture and for malaria vector control from the 1940’s until the 1970’s. Due to its heavy use, DDT became ubiquitously distributed throughout the environment. DDT and several DDT metabolites are persistent organic pollutants. Two DDT metabolites, 3-MeSO2-DDE and o,p’-DDD have been proved to be tissue specific toxicants in the adrenal cortex. They are bioactivated to reactive intermediates which bind covalently to the adrenal cortex causing cell death. Due to its tissue specific toxicity o,p’-DDD has been used as a chemotherapy drug for adrenal cancer in humans. The efficacy and potency is however low and o,p’-DDD treatment is associated with serious side effects. 3-MeSO2-DDE has been suggested as a potential alternative therapeutic agent.

A key aim of this thesis has been to improve the understanding of the kinetics of the two adrenocorticolytic compounds o,p’-DDD, its two enantiomers and 3-MeSO2-DDE. To meet this objective chemical synthesis and enantioselective analysis were required. Furthermore, in vitro toxicity of o,p’-DDD enantiomers and diastereomers were performed.

An 11 step synthesis of 3-SH-DDE has been developed to promote both labelled and unlabelled synthesis of 3-alkylsulfonyl-DDE. Toxicokinetic studies showed that 3-MeSO2-DDE and o,p’-DDD were accumulated in tissues and retained in adipose tissue in minipigs. 3-MeSO2-DDE however had a twice as long biological t1/2 and a considerably lower Vd compared to o,p’-DDD. Suckling offspring were more exposed to 3-MeSO2-DDE than their mothers who were given 3-MeSO2-DDE orally. Interindividual differences in enantiomer kinetics in minipigs were observed suggesting polymorphism among the minipigs. Preparative isolation of the o,p’-DDD enantiomers is presented allowing determination of the absolute structures of the o,p’-DDD enantiomers by X-ray. The pure enantiomer of o,p’-DDD showed significant differences in toxicity in human adrenocortical cells.

Formation mechanism of anionic-surfactant-templated mesoporous silica (AMS)

This dissertation is focused on synthesis, characterization and formation mechanism of anionic-surfactant-templated mesoporous silica (AMS).

Structural control mechanisms of AMS are investigated. First, different ionization degree of anionic surfactant affected by the acidity or alkalinity of the synthesis system gives rise to different charging density of micelles and therefore determines the organic/inorganic interface curvature, producing mesophases from cage-type to cylindrical, bicontinuous and lamellar. Second, mesocage/mesocage electrostatic repulsive interaction affects the formation of cage-type mesostructure, which is derived from a full-scaled synthesis-field diagram of AMS. The mesocage/mesocage interaction changes with charge density of mesocages and gives rise to their different packing manners. Third, the structural properties of AMS materials could be tuned by molecular features of surfactant and co-structure-directing agent (CSDA).

The pore size of AMS is found to be controlled by alkyl chain length, ionization degree of surfactant and the CSDA/surfactant ratio. Alkyl chain length of surfactant determines size of micelles and thus mesopores. Larger ionization degrees of anionic surfactant give rise to smaller pore sizes due to thermodynamic coiling of alkyl chains of surfactant. The hydrophobic interactions between the pendant organic groups of CSDA on the silica wall and the hydrophobic core of the micelles drive a contraction of the mesopores.

A mesoporous silica with novel bicontinuous cubic Pn-3m structure has been prepared using a diprotic anionic surfactant. 3d-reconstruction of the structure shows that it is bicontinuous composed of an enantiomeric pair of 3d mesoporous networks that are interwoven with each other, divided by a D surface. Inverse replication suggests the possible presence of ordered complimentary micropores in the material.

Harnessing Mesoporous Spheres - transport studies and biotechnological applications

Applications in controlled release and delivery calls for a good understanding of molecular transport within the carrier material and the dominating release mechanisms. It is clear that a better understanding of hindered transport and diffusion of guest molecules is important when developing new porous materials, e.g., surfactant templated silica spheres, for biotechnological applications. Confocal laser scanning microscopy was used to quantify the bulk release and intraparticle transport of small charged fluorescent dyes, and fluorescently-tagged neutral dextran, from mesoporous silica spheres. The time dependent release and the concentration profiles within the spheres have been used to analyze the release mechanisms using appropriate models. While the small, non-adsorbing anionic dye is released following a simple diffusion driven process, the concentration of the cationic dye varies radially within the spheres after loading. The release of the cationic dye is controlled by diffusion after an initial period of rapid release, which could be due to a significant fraction of the cationic dye that remains permanently attached to the negatively charged walls of the mesoporous silica spheres. The diffusion of dextran and the resulting flat concentration profiles could be related to the complex structural feature of the cylindrical pores close to the surface, and a possible conformational change of the dextran with the concentration. The stability and leaching of a catalytic enzyme, lipase, immobilized in hydrophobilized mesoporous support has also been quantified. Colloidal monodisperse mesoporous silica spheres were synthesized and transmission electron microscopy showed that the inner pore structure display a radially extending pores. The mesoporous spheres were used as solid supports for a lipid membrane incorporated with a multi-subunit redox-driven proton pump, which was shown to remain functional.

Comparison of experimentally and theoretically determined oxidation and photochemical transformation rates of some organohalogens to promote prediction of persistence

The diversity of choices we have to make everyday influence our environment and ourselves in more ways than most of us realise. Anthropogenic substances, such as flame retardants, date back as early as 450 BC when the Egyptians used alum to reduce flammability. The increasing demand for new articles has led to an increased production of chemical substances, for which many are commercially produced without complete knowledge on properties such as persistence, bioaccumulation and toxicology (PBT). Commercial compounds may be properly tested and denominated as “safe” regarding PBT properties, but their degradation products and/or metabolites may cause environmental impact.

The availability of uniform and accurate data for prediction of persistence is of key importance for the understanding of chemical fate. A method to determine the susceptibility of chemicals to undergo oxidation in water has been developed and applied on several organohalogens, including PBDEs and OH-PBDEs. The method was used to determine reaction rates and the group of OH-PBDEs were subsequently subjected to photolysis by use of UV-light. Hence, susceptibility to undergo both oxidation and photolysis for the OH-PBDEs were investigated and compared to previously reported degradation rates on PBDEs.

As a final step in promoting the prediction of persistence, Quantitative structure-property relationship (QSPR) models were performed on a set of compounds which had undergone photolytic degradation under similar conditions. The QSPRs were used as a preliminary step in predicting photolysis half-lives for chemical substances and to determine which physicochemical descriptors are of greatest importance thereof.

This thesis presents the possibility of performing and assessing oxidation transformations on compounds of low and high water solubility, photolysis transformations in various media and using obtained data to predict behaviour via QSPR models, to promote predictions of persistence.

Preparation, characterization and properties of nitrogen rich glasses in alkaline earth-Si-O-N systems

Nitrogen rich glasses in the systems Ca-Si-O-N, Sr-Si-O-N and AE-Ca-Si-O-N (AE = Mg, Sr and Ba) have been prepared using a novel glass-synthesis route. The limits of the glass forming regions in the Ca and Sr systems and substitution limits in the AE-Ca-Si-O-N systems have been determined and physical properties of the glasses measured.

Transparent glasses were obtained for a few specific compositions in the Ca-Si-O-N and Mg-Ca-Si-O-N systems. All other glasses were found to be translucent gray to opaque black, with the coloration of the glasses depending on the modifier. Small inclusions of Ca/Sr silicides and, in much smaller amounts, elemental Si are believed to be responsible for their poor transparency.

A large glass forming region was found for the Ca-Si-O-N system, with glasses retaining up to 58 e/o N and 42 e/o Ca. In comparison, a more narrow glass forming region was found for the corresponding Sr system, with glasses retaining up to 45 e/o N and 39 e/o Sr. The glass formation was found to depend on reaction kinetics and precursors used. A strong exothermic reaction was observed at temperatures 650–1000oC, providing improved conditions for reaction kinetics upon further heating.

Physical property measurements for the Ca and Sr glasses showed that glass transition and crystallization temperatures, viscosity, hardness, Young’s modulus and shear modulus depend strongly on the nitrogen content and that these properties increase approximately linearly with increasing nitrogen content. Glass density and refractive index are also dependent on the modifier element and content, in particular for the Sr glasses.

Glasses AE-Ca-Si-O-N, with approximately constant (Ca/AE): Si:O:N ratios, showed that mixed modifier glass properties, such as density, molar volume, glass transition temperature, hardness, refractive index can be related to the effective cation field strength of the modifiers.

Temporal and spatial trends of organohalogens in guillemot (Uria aalge) from North Western Europe

The Arctic and sub-Arctic region of the North Atlantic is a remote area, also in relations to environmental contaminants, such as POPs, BFRs and last but not least, PFCs. Both the BFRs and PFCs are considered emerging pollutants of significant environmental concern.

The main objective of this thesis is to increase the knowledge and understanding of organohalogen compound distribution in the Nordic environment, their occurrence in biota and change over time. The temporal change of environmental contaminants in the Baltic Sea was monitored over the years 1971 to 2001, with emphasis on BCPS. Further, the pollution profile of the Nordic region was investigated by using common guillemot eggs. Further, to investigate a single remote site, Iceland, in more depth, eggs from seven marine bird species were collected and analysed. Both the organohalogen compounds mentioned above and their metabolites were investigated. The study focused also on an inter-species difference in the bird’s capability of metabolising xenobiotics.

All environmental pollutants investigated in the Baltic Sea show decreasing levels over the time period investigated. BCPS showed a remarkably small change over time compared to other compounds. These results reinforce the previous findings, indicating the North Atlantic as remote where the concentrations of the organohalogens are lower compared to Europe in general. There are some exceptions however; the concentration of HCB is ubiquitously distributed across the study area. Further, the spatial trends of the PFCs are complicated and differ within the PFC group. When comparing bird species from Iceland, the concentration of organohalogens mainly depends on trophic level, while migration seems to contribute to a lesser extent. There are some similarities in the metabolism between the bird species investigated. However, the guillemot seems to distinguish itself from other marine birds, with a different composition of metabolites, indicating a different metabolic capacity.

In conclusion, even human populations living in remote areas need to minimise the release of pollutants to the environment. Long term, well organised, and extensive governmental monitoring programs are highly recommended to follow the quality the environment and to detect any immediate and/or new threats of chemical pollutants.

Structural Investigations of Complex Glasses by Solid-state NMR

This PhD thesis presents structural investigations of amorphous inorganic materials: oxide and oxynitride glasses and mesoporous bioactive glasses (MBGs), by solid-state Nuclear Magnetic Resonance (NMR).

Lanthanum oxide and oxynitride [La-Si-(Al)-O-(N)] glasses have a large number of potential applications due to their physical properties. In our work we have studied, compared to previous investigations, significantly expanded ranges of glass compositions (for oxynitride glasses, including samples of very high nitrogen content, up to 53 % out of the anions). We have estimated local environments of 29Si and 27Al structural units (their coordination, polymerization degree and number of N incorporated into tetrahedral units) in the materials. We have suggested a random Al/Si distribution along with almost uniform non-bridging oxygen atoms distribution in aluminosilicate glasses.

Silicon nitride was used as precursor in the oxynitride glass synthesis. We studied both α- and β-modifications of silicon nitride, 15N-enriched, as well as fully (29Si, 15N)-enriched samples. We have shown that the linewidths of 15N NMR spectra are dominated by J(29Si-15N) coupling in 29Si315N4 sample.

Mesoporous bioactive glasses in the CaO-SiO2-P2O5 system show superior bioactivity (the ability to form a hydroxycarbonate apatite layer on the glass surface when exposed to body fluids) compared to conventional bioactive glasses due to their large surface area and uniform pore-size distribution. Previous studies suggested a homogeneous cation distribution over the MBG samples on a 10−20 nm length-scale. From our results, on the other hand, we may conclude that Si and P is not intimately mixed. We propose a structural model, in which the pore walls of MBGs are composed of a silica network, and a phosphate phase is present as nanometer-sized clusters that are dispersed on the pore wall.

Synthesis and Characterization of Nitrogen-rich Calcium α-Sialon Ceramics

In this thesis, a synthesis concept has been developed, which uses nitrogen-rich liquid phases for sintering of Ca-α-sialon ceramics. First, keeping the Si/Al ratios constant, the effects of N/O ratio on the properties and microstructure were investigated through a liquid phase sintering process. Second, nitrogen-rich Ca-α-sialon ceramics, with nominal compositions: CaxSi12-2xAl2xN16, x < 2.0, was synthesized and characterized. Third, mechanical and thermal properties of nitrogen-rich Ca-α-sialons were investigated in terms of high temperature deformation resistance,reaction mechanism, phase stability and oxidation resistance, and further correlated to their phase assemblage and microstructure observation.

It has been found that increasing the N/O and Ca/Al ratio simultaneously in the materials could result in development of a microstructure with well shaped, high-aspect-ratio Ca-α-sialon grains, and an improvement in both toughness and hardness.

For the nitrogen-rich Ca-α-sialon, mono-phasic α-sialon ceramics were obtained for 0.51 ≤ x ≤ 1.32. The obtained Ca-α-sialon ceramics with elongated-grain microstructures show a combination of high hardness and high fracture toughness. Compared with the oxygen-rich Ca-α-sialons, the nitrogen-rich Ca-α-sialons exhibited approximately 150 oC higher deformation onset temperatures and decent properties even after the deformation.

The α-sialon phase was first observed at 1400 oC, however the phase pure Ca-α-sialon ceramics couldn’t be obtained until 1800 oC. The nitrogen-rich Ca-α-sialons were thermal stable, no phase transformation observed in the temperatures range1400-1600 oC. In general, mixed α/β-sialon showed better oxidation resistance than pure α-sialon in the low temperature range (1250-1325 oC), while α-sialons with compositions located at α/β-sialon border-line showed significant weight gains over the entire temperature range (1250-1400 oC).

NMR Studies of Inclusion Compounds

This thesis presents the application of some of the NMR methods in studying host-guest complexes, mainly in solution. The general focus of the work is on investigating the reorientational dynamics of some small molecules that are bound inside cavities of larger moieties. In the current work, these moieties belong to two groups: cryptophanes and cyclodextrins. Depending on the structure of the cavities, properties of the guest molecules and the formed complexes vary. Chloroform and dichloromethane are in slow exchange between the cage-like cavity of the cryptophanes and the solvent, on the chemical shift time scale, whereas adamantanecarboxylic acid, quinuclidine and 1,7-heptanediol in complex with cyclodextrins are examples of fast exchange. Kinetics and thermodynamics of complexation are studied by measuring exchange rates and translational self-diffusion coefficients by means of 1-dimenssional exchange spectroscopy and pulsed-field gradient (PFG) NMR methods, respectively. The association constants, calculated using the above information give estimates of the thermodynamic stability of the complexes. Carbon-13 spin relaxation data were obtained using conventional relaxation experiments, such as inversion recovery and dynamic NOE, and in some cases HSQC-type (Hetereonuclear Single Quantum Correlation Spectroscopy) experiments. Motional parameters for the free and bound guest, and the host molecules were extracted using different motional models, such as Lipari-Szabo, axially symmetric rigid body, and Clore models. Comparing the overall correlation times and the order parameters of the free and bound guest with the overall correlation time of the host molecule one can estimate the degree of the motional restriction, brought by the complexation, and the coupling between the motion of the bound guest and the reorientation of the host molecule. In one case, the guest motions were also investigated inside the cavities of a solid host material.

Probing Dynamics of Oligosaccharides by Interference Phenomena in NMR Relaxation

Oligosaccharides (carbohydrates) are a large class of biological molecules that are important as energy sources in the human body and have enormously varied biological functions. It is generally believed that biological activities of carbohydrates are related to their internal dynamics. The dynamic properties of some oligosaccharides in solution are studied in this thesis, by NMR relaxation. We have employed relaxation interference effects to investigate the conformational dynamics within oligosaccharides (in-tramolecular dynamics) and paramagnetic relaxation enhancement (PRE) as an experimental tool to study intermolecular dynamics. Most of the thesis concerns the dynamics of the methylene group in the two possibly mobile parts of the oligosaccharide: in the exocyclic hydroxymethyl moiety and in the glycosidic linkage position. To perform conformational dynamic studies, the more traditional auto-relaxation pa-rameters are combined with the relaxation interference terms or the cross-correlated relaxation rates (CCRRs). Some experimental schemes based on the initial-rate technique were developed for measuring CCRRs. The techniques are useful for labelled sugars as well as naturally abundant ones. Furthermore, various dynamical models ranging from the Lipari–Szabo approach to several more informative and complicated models such as the two-site jump model, restricted internal rotation and slowly relaxing local structure (SRLS), have been employed to interpret our experimental data. We have combined and com-pared different models; we have also developed a novel approach to existing models, by scaling dipolar coupling constants (DCC), to extract the dynamic behaviour and structural properties of the system. We found that the auto- and cross-correlated relaxation data analyses yield a consistent picture of the dynam-ics in all cases. Additionally, our investigations show that CCRRs are practically important for verifica-tion of certain dynamical and structural information that is difficult to be determined by other means. Moreover, the anisotropy of the carbon-13 chemical shielding tensor in the methylene group has been estimated, using the interference between dipole-dipole and chemical shift anisotropy.

This thesis also discusses using the PRE to investigate sugar dynamics relative to a paramagnetic MRI contrast agent in solution, which might be important in medicine. We have studied the intramolecu-lar dynamics of the trisaccharide raffinose in the presence of a gadolinium complex. We also investigated the effect of translational diffusion instead of rotational diffusion, which is normally more important in NMR. The paramagnetically enhanced spin–lattice relaxation rates of aqueous protons over a wide range of magnetic fields and of carbon-13 and protons of the sugar at high fields have been measured. The nuclear magnetic relaxation dispersion of water protons and the PREs of proton and carbon in the sugar are interpreted in terms of the model recently developed in our laboratory, allowing both outer- and inner-sphere PREs for water protons, but allowing only the outer sphere PRE for nuclei in the sugar. We found that the relative diffusion has a stronger effect on the PRE than the electron spin relaxation.

Synthesis and Characterisation of Carbide Derived Carbons

Carbide derived carbons (CDCs) have been synthesised through chlorination of VC, TiC, WC, TaC, NbC, HfC and ZrC at different temperatures. The aim of the investigation was to systematically study changes of structural and adsorption properties depending on the synthesis conditions. CDCs were characterised using nitrogen and carbon dioxide adsorption, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and electron energy loss spectroscopy. The studies revealed the CDCs structures to range from amorphous to ordered, from microporous to mesoporous. It was found that structural ordering and porosity can be modified by: i) synthesis temperature, ii) precursor, iii) density and volume of precursor, iv) catalysts, v) incorporation of nitrogen in to carbide structure, and CDCs can be tuned up to the demanded quality. They also exhibited a high potential for methane storage.

Modeling DNA Damage

In this thesis methods of computational chemistry have been used to examine DNA damaging processes initiated by ionizing radiation, free radicals, or Low-Energy Electrons (LEE).

The computational chemistry method based on quantum mechanics that has been mainly used here is the Density Functional Theory (DFT). The Car-Parrinello Molecular Dynamics (CPMD) method, which includes the dynamics of atoms, has also been used. For enabling calculations of large systems the hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) method has been applied by treating the chemically relevant part with quantum mechanics and the rest of the system with molecular mechanics.

Herein, several types of DNA damaging processes have been examined by performing calculations on models of sections of DNA. A detailed description of how DNA becomes damaged is of major importance for understanding and treating diseases such as cancer.

Hydrogen abstractions by nucleobase radicals have been investigated as an initial step leading to DNA strand break or base release. The nucleobase radicals that have been examined are uracil-5-yl, uracil-5-peroxyl, and hydroxyl-thymine. The uracil-5-yl radical was identified as the prominent hydrogen abstracting radical.

Secondary electrons with low energy, LEEs, produced in the tracks of ionizing radiation can reduce nucleotides in DNA and thereby create an unstable anion nucleotide radical. The aim of these studies has been to investigate the effect of LEE attachment on cytosine and guanine nucleotides in an aqueous environment. To verify the possibility of strand break in DNA the ruptures of the phosphodiester bonds, which link the deoxyriboses and the phosphate groups, were analyzed. This study revealed that strand break most likely would occur when a guanine nucleotide, compared with other nucleotides, becomes reduced by an LEE in an aqueous environment.

Synthesis of highly brominated diphenyl ethers and aspects on photolysis and indoor spreading

Adding chemicals to materials to decrease flammability can be dated back to as early as 450 BC when the Egyptians used alum to reduce flammability of wood. Almost 2500 years later brominated flame retardants (BFRs) are used to prevent ignition of textiles, electronics and polymers. BFRs in major use today are polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA), including derivatives. There have been three industrial PBDE mixtures produced. Extensive scientific reporting has shown increasing concentrations of PBDEs in wildlife and in humans. This in combination with reports on their physico-chemical characteristics and chemical reactivity have led to that two of the PBDE products have been classified as being persistent, bioaccumulative and toxic, which has led to legislative measures, in e.g. EU, Norway and the USA.

The availability of pure reference standards is a prerequisite for much toxicologically related research. Hence the main objective of this thesis was to develop additional methods for synthesis of highly brominated diphenyl ethers. Further, to quantify and identify photolysis products of decabromodiphenyl ether (decaBDE) and to perform a case study regarding PBDE exposure in aircrafts.

Synthesis of highly brominated BDE congeners by perbromination of mono- or diaminodiphenyl ethers followed by diazotization of the amino group(s) and introduction of hydrogen(s) in the molecules is a convenient route for synthesis of some octaBDEs and all nonaBDEs. Selective bromination of diaminodiphenyl ether, followed by diazotization of the amino groups and substitution with bromines yielded a hexaBDE or a heptaBDE which were then further brominated to octaBDE congeners.

Even though several studies have been performed on photolysis of decaBDE a new study with a more quantitative approach was performed as part of this thesis. Debrominated PBDE products were identified and quantified and a marker PBDE for UV degradation of DecaBDE was identified i.e., 2,2’,3,3’,5,5’,6,6-octabromodiphenyl ether (BDE-202). Polybrominated dibenzofuranes, methoxlated brominated dibenzofuranes, pentabromophenol and hydroxylated bromobenzenes were also detected. The PBDEs accounted for approximately 90% of the total amount of substances in each sample and the PBDFs for about 10%. Also, a case study on potential exposure to PBDEs in humans travelling long distances by aircraft was done. It was shown that PBDE concentrations in dust onboard aircrafts may be high and increased PBDE serum levels were indicated in a majority of the travellers.

The present thesis has contributed to make higher brominated diphenyl ethers available as reference standards, allowing better quantitative assessments possible regarding both abiotic studies and exposure assessments. New toxicological testing can also be pursued.

Low Temperature Structural and Property investigations in the Zn-Sb System

Thermoelectric Zn4Sb3 has a randomly disordered crystal structure at room temperature and undergoes a reversible sequence of phase transitions, β-α-α’/α, at low temperatures. During the transformations interstitial Zn atoms and Zn vacancies present in the β-phase become increasingly ordered. The low-temperature structures α and α’ can be described by differently stacked layers A (interstitial free) and B (containing five-atom Zn clusters).The Zn/Sb ratio can be slightly altered by small amounts of metal doping achieved by growing the crystals in a metal flux. The small doping amounts (< 1 at.%) have, however, a large impact on the structural low-temperature behavior. First principles calculations show β-Zn4Sb3 to be thermodynamically stable because of the large entropy contribution from the disordered Zn substructure and that ordered α-Zn4Sb3 is meatstable with respect to a decomposition into ZnSb and Sb. Resistivity, thermopower and charge carrier properties at low temperatures have been investigated for both binary and metal doped samples. Preliminary studies of the high pressure structural behavior of zinc antimonides have also been made. Both ZnSb and β-Zn4Sb3 showed to be stable up to 8 GPa, which is in disagreement with earlier reports. Amorphous Zn41Sb59 could be produced at 8 GPa and temperatures between 350 and 550 oC in a multi anvil apparatus.

Open-Framework Germanates : Crystallography, structures and cluster building units

This thesis is focussing on the crystallographic challenges and what knowledge we can gain from studying the different open-framework germanates. Five new open-framework germanates have been synthesized and the structures have been determined by single crystal X-ray diffraction. A thorough description is made of the different problems raised with the different compounds, whether it is choice of crystal system in SU-61, twinning and possible ordering in SU-46, superstructure and variation in elemental content in SU-57, template disorder in JLG-5 or framework disorder in SU-44.

Open-framework germanates are often built from one type of cluster, such as the Ge7 [Ge7X19], Ge8 [Ge8X20], Ge9 [Ge9Xn, n =25-26] and Ge10 [Ge10X28], (X =O, OH, F) clusters. The structures built by clusters containing different kinds of polyhedra are discussed, with a focus on the 4-coordinated Ge7 clusters, the larger cluster aggregate found in SU-8 and SU-44 and the structures built by the Ge10 clusters.

A structural study into the boundary surface and associated curvature of three-dimensional mesoporous silica crystals

Since their first discovery in the early 1990s, mesoporous crystals (MCs) have fascinated researchers in various fields because of their interesting structures and their potential uses. Electron crystallography (EC) gives the direct three-dimensional (3D) realization of a crystal as a reconstructed electrostatic potential map (EPM). Various 3D-EPMs of silica MCs with cubic symmetry have been previously obtained by EC.

The main task in this thesis is the development of structural analyses focusing on MCs and thus to evaluate the properties of periodic mesopores within EC data. How MC structures can be described and solved by EC is discussed in terms of the interpretation of the reconstructed 3D-EPM. Assuming a regime of an equi-potential surface (EPS), a structural description for MCs is suggested as a surface that optimizes the curvature elasticity evaluated on every EPS. The geometric properties of cubic MCs so far already reconstructed by EC, are then analyzed on the basis of the optimized EPSs. The analysis provides the property of the mesopores independently from gas adsorption measurements. A large cage-like MC is further studied by in-situ synchrotron powder X-ray diffraction to help understand the nitrogen adsorption process onto the mesopore wall.

As an additional study, a silica MC showing its crystal morphologies of icosahedron, decahedron, etc. is studied. Results by EC suggest that the spherical uni-modal cages form the cubic close packing. The morphologies observed are explained in terms of the multiple twinning, which is analogous to metal nanoparticles. The occurrence of multiple twinning in MCs is discussed in light of the synthesis condition and the shape of micelles.

Structural modeling of membrane transporter proteins

A fundamental process of all living organisms - the transport of molecules across cellular membranes through membrane transport proteins - is investigated.

After a brief review of general properties of biological membranes follows a recollection of the major methods of membrane transport that Nature utilizes (Chapter 1). This is followed by a description of important experimental (Chapter 2) and theoretical methods (Chapter 3) for structural studies of membrane proteins. The findings on membrane protein transport in papers I-IV are then summarized (Chapter 4) and important findings are discussed. The remaining text is a discussion on relevant theoretical and experimental methods.

A new synthetic strategy for low-dimensional compounds : Lone pair cations and alkaline earth spacers

Complex transition metals oxyhalides containing a lone pair element, such as tellurium (IV), form an attractive research field because there is a high probability of finding new low-dimensionally arranged compounds and, particularly, a low-dimensionally arranged transition metals substructures, leading to interesting physical properties. Tellurium (IV) can drive the formation of many unusual structures because of its stereochemically active lone pair electrons, E. It commonly takes a coordination of three or four oxygen atoms to form either a TeO3E square pyramid or a TeO3+1E trigonal bipyramid. These lone pairs are very important players involved in lowering the dimensionality of crystal structures. Previous studies in transition metal tellurium (IV) oxohalide quarternary systems revealed a family of compounds, many of which exhibit interesting properties e.g. magnetic frustration. The unique point of this thesis is to employ alkaline earth elements (AE) to augment this ability of lone pair elements to lower the dimensionality of the transition metal arrangements. By this double usage of “chemical scissors” (a lone pair element used in conjunction with alkaline earth elements) we obtained new types of low-dimensionally arranged compounds.

This thesis is focused on the syntheses and characterization of a series of compounds in the pentanary (five components) system AE-TeIV-TM-O-X (AE=alkaline earth metal, TM=transition metal and X=halogen), in which nine new compounds were found. The crystal structures of each of these compounds were determined by the single crystal X-ray diffraction data.

Sulfur-Related Conservation Concerns in Marine Archaeological Wood : The Origin, Speciation and Distribution of Accumulated Sulfur with Some Remedies for the Vasa

Synchrotron-based sulfur spectroscopy reveals a common concern for marine archaeological wood from seawater: accumulation of reduced sulfur compounds in two pathways. The distribution of sulfur species in the oak wood cell structure was mapped by scanning x-ray spectro-microscopy (SXM). Organically bound sulfur was found within lignin-rich parts, identified mainly as thiols and disulfides by sulfur K-edge x-ray absorption near edge structure (XANES) spectroscopy. Particles of iron sulfides, which may form in the presence of corroding iron, appeared in wood cavities. Cores scanned by x-ray fluorescence (XRF) show that high sulfur accumulation is restricted to the surface layers for the Swedish shipwreck Vasa, while the distribution is rather uniform throughout the hull timbers of the Mary Rose, U.K. Laboratory experiments, exposing fresh pine to simulated seabed conditions, show that the organically bound sulfur develop in reactions between lignin, exposed by cellulose-degrading erosion bacteria, and hydrogen sulfide produced in situ by scavenging sulfate reducing bacteria. With bacteria inoculated from shipwreck samples also iron sulfides formed. The iron sulfides oxidise in high humidity, and are the probable main cause of the numerous outbreaks on the Vasa’s hull of acidic sulfate salts, which were identified by x-ray powder diffraction (XRD). The iron ions catalyse several wood-degrading oxidative processes. Multi-elemental analyses were performed by scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (ESCA). The present amounts of total S remaining in the Vasa and the Mary Rose are estimated to at least 2 tonnes. After the Vasa´s spray treatment with polyethylene glycol solutions ceased in 1979, the continuing oxidation processes are estimated to have produced 2 tonnes of sulfuric acid in the wood. Laboratory experiments to gently neutralize acidic Vasa wood by ammonia gas have been conducted with promising results.

Synthesis and characterization of highly polybrominated diphenyl ethers

Polybrominated diphenyl ethers (PBDEs) make up an important class of brominated flame retardants. The present production is mainly concentrated to DecaBDE but until recently also a significant production of PentaBDE and OctaBDE took place, leaving us with a large number of different PBDE congeners. The PBDEs have become widespread pollutants abiotically and in biota, particularly in high trophic level wildlife and in humans. Accordingly, pure authentic reference standards have been required to promote high quality exposure assessments of wildlife and humans and analysis of abiotic matrices, to study both chemical and physical properties of the PBDEs and to allow toxicological studies. The objective of this thesis was to develop methods for synthesis of polybrominated diphenyl ether (PBDE) congeners and to characterize them. Further, some octabrominated DEs were determined with x-ray crystallography. Main focus has been to prepare highly brominated PBDE congeners, i.e. PBDEs substituted with six to nine bromine atoms.

A total number of twenty-three PBDE congeners were synthesized via reduction of decabromodiphenyl ether receiving nonaBDEs; perbromination and bromination of mono- and diaminodiphenyl ethers followed by diazotization of the amino group(s) and reduction of the diazonium ion(s) receiving octaBDEs and nonaBDEs; selective bromination of diaminodiphenyl ethers followed by diazotization of the amino groups and insertion of bromine receiving hexaBDEs and heptaBDEs; bromination of the latter PBDEs giving octaBDEs; and an improved coupling of symmetrical diphenyliodonium salts with bromophenols yielding tetraBDEs to octaBDEs. To enable these compounds to be synthesized three hexabromodiphenyl iodonium salts were prepared: 2,2’,3,3’,4,4’-, 2,2’,4,4’,5,5’- and 2,2’,4,4’,6,6’ - hexabromodiphenyliodonium salts. These iodonium salts are described for the first time which made it possible to synthesize PBDE congeners with 2,3,4-, 2,4,5- and 2,4,6-tribromo substitution in the phenyl rings originating from the diphenyliodonium salts. Among the PBDE congeners 18 are synthesized for the first time. The thesis includes an improved methodology for synthesis of polybromodiphenyl iodonium salts which is based on improved solubilization of both one of the reactants and the product formed. The present work on PBDE synthesis adds useful methods for synthesis of the most highly brominated diphenyl ether congeners.

Studies of inorganic crystal structures and gas adsorption process in mesoporous crystals : New approach through analysis of electron charge distribution by synchrotron powder X-ray diffraction

Using synchrotron powder XRD experiments, I studied (i) structures of silica mesoporous MCM-41 and MCM-48 crystals, (ii) gas adsorption processes of Ar and N2 in the mesopores of the mesoporous crystals, and (iii) bonding features of CaAl2-xZnx crystals through the analysis of electron charge density distributions.

In the case of mesoporous crystals, the following two different approaches were taken depending on the number of observed X-ray reflections

1. The analytical expression was chosen and further developed to study the size and shape of the mesopores with the plane group of p6mm by powder XRD experiments. For MCM-41, following the determination of the mesopores’ size and shape, and the thickness of the adsorbed gas layer as a function of the gas pressure were successfully observed. In addition, for carbon pipe mesoporous crystals CMK-5, the carbon pipe thickness was determined and the diffraction pattern was discussed quantitatively focusing on the “accidental extinction.”

2. Maximum entropy method (MEM) was used for the structural study of MCM-48 (3D bicontinuous Ia-3d ) and for the gas adsorption process within the mesopores.

By adopting the MEM approach, the study of “bonding electrons” and associated atomic displacements from the ideal Kagome net in the Laves phase CaAl2-xZnx were observed. In particular, the two Kagome nets in the C36 structure showed different feature in the electron density distributions between each other.

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