The development of future electronics depends on the availability of suitable functional materials. Printed electronics, for example, relies on access to highly conductive, inexpensive and printable materials, while strong light absorption and low carrier recombination rates are demanded in photocatalysis industry. Despite all efforts to develop new materials, it still remains a challenge to have all the desirable aspects in a single material. One possible route towards novel functional materials, with improved and unprecedented physical properties, is to form composites of different selected materials. In this work, we report on hydrothermal growth and characterization of graphene/zinc oxide (GR/ZnO) nanocomposites, suited for electronics and photocatalysis application. For conductive purposes, highly Al-doped ZnO nanorods grown on graphene nanoplates (GNPs) prevent the GNPs from agglomerating and promote conductive paths between the GNPs. The effect of the ZnO nanorod morphology and GR dispersity on the nanocomposite conductivity and GR/ZnO nanorod bonding strength were investigated by conductivity measurements and optical spectroscopy. The inspected samples show that growth in high pH solutions promotes a better graphene dispersity, higher doping and enhanced bonding between the GNPs and the ZnO nanorods. Growth in low pH solutions yield samples characterized by a higher conductivity and a reduced number of surface defects. In addition, different GR/ZnO nanocomposites, decorated with plasmonic silver iodide (AgI) nanoparticles, were synthesized and analyzed for solar-driven photocatalysis. The addition of Ag/AgI generates a strong surface plasmon resonance effect involving metallic Ag0, which redshifts the optical absorption maximum into the visible light region enhancing the photocatalytic performance under solar irradiation. A wide range of characterization techniques including, electron microscopy, photoelectron spectroscopy and x-ray diffraction confirm a successful formation of photocatalysts. Our findings show that the novel proposed GR-based nanocomposites can lead to further development of efficient photocatalyst materials with applications in removal of organic pollutants, or for fabrication of large volumes of inexpensive porous conjugated GR-semiconductor composites.

As environmental awareness raises the expectations to reduce emission of modern diesel engines are growing as well. Fuel diversity and the advanced injector systems requires even more attention on an ever existing problem which is called nozzle hole fouling. Recent literature and observations at Scania indicate the phenomena is connected to fuel filter plugging caused by metal carboxyl contaminants through the formation of “soft particles”. This report begins with a literature review about the nature of agglomerates in biodiesel. Followed by the evaluation of six particle sizing equipment. This include one ensemble technique based on Brownian motion, namely dynamic light scattering. The remaining five techniques are single particle counters, including a high speed camera system, light blocking system, Nano tracking analysis and two different approaches using light microscope. To characterise the structure and chemical components of the particles SEM, EDX, FT-IR and ICP-OES were used. From the above mentioned methods optical microscopy was chosen to be the best method to evaluate the particle distribution. The main reasons for this is the ability to measure particles in the solution in the desired size range and the possibility to couple it with a Raman spectrometer, providing possibilities for future studies. Besides finding the best technique to measure the particles, a secondary result is the negation of Zinc-neodecanoate creating particles in the fuel. It opposes the assumption made in the literature about filter blocking, and it finds the need for deeper understanding of the nature of soft particles.

<p>Magnetotactic bacteria (MTB) are ubiquitous, multi-phylogenetic bacteria that actively synthesize chains of magnetic, membrane bound; single domain magnetite (Fe₃O₄) or greigite (Fe₃S₄) crystals, termed magnetosomes in order to better navigate to their preferred chemical environment using the Earth’s magnetic field. Discovered in 1963, the field is now focused on understanding magnetosome chain formation and associated processes through genetic studies as well as analytical techniques such as Transmission Electron Microscopy (TEM) and Scanning Transmission X-ray Microscopy – X-ray Magnetic Circular Dichroism (STXM-XMCD).</p> <p>This thesis performed studies on <em>Candidatus Magnetovibrio blakemorei</em> strain MV-1 using STXM at the C 1s, O 1s, Ca 2p and Fe 2p edges. STXM-XMCD was used to determine the magnetism of individual magnetosomes and quantitatively determine magnetic properties such as the magnetic moment of individual chains. A sub-population of MV-1 cells was identified as having anomalous magnetic orientations of magnetosome sub-chains when separated spatial gaps. The frequency of this event and the underlying implications to magnetosome formation are discussed.</p> / Master of Science (MSc)

<p>Fabrication of microarrays using sol-gel immobilization has been utilized as an approach to develop high density biosensors. Microarray fabrication using various printing techniques including pin-printing and piezoelectric ink jet printing methods has been demonstrated. However, only limited characterization to understand the encapsulated biomolecule-material interface has been reported. Herein, Chemical characterization using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) on pin-printed microarrays of sol-gel derived acetylcholinesterase (AChE) microarrays is reported. Furthermore, the <em>in situ</em> fabrication of microarrays following the sol-gel process using piezoelectric ink jet printing methods was explored. Through techniques measuring solution viscosity, surface tension and particle size, important aspects of bio-ink formulation for piezoelectric ink jet printing were identified. Combined, a greater understanding towards the fabrication and characterization of sol-gel derived microarrays was achieved through this exploratory research.</p> / Master of Science (MSc)

Recently, the production of lithium-ion batteries (LIB) has grown rapidly, highlighting the need for efficient and environmentally friendly recycling of LIB waste. In this work, the usage of so-called deep eutectic solvents (DESs) for the leaching of the LIB cathode material lithium cobaltoxide is investigated. The initial DESs investigated are mixtures of poly(ethylene glycol) (PEG200) and an organic acid: tartaric, ascorbic, citric, oxalic or succinic acid (PEG:TA (4:1), PEG:AA (8:1), PEG:CA (4:1), PEG:OA (2:1) and PEG:SA (6:1), the molar ratio in parenthesis). Thermogravimetric analysis shows that the solvents are stable up to 180-190 °C. DESs were analyzed with FTIR spectroscopy, pH was measured using a pH-meter and viscosity using a rolling-ball viscometer. The highest leaching efficiency was obtained using PEG:AA followed by PEG:OA, both having the ability to reduce Co(III). This ability was dominant over pH and viscosity influence. For the other three solvents, leaching efficiency increases in the order of decreasing pH (PEG:TA&gt;PEG:CA&gt;PEG:SA). More investigations of leaching as a function of time are needed to determine the impact of viscosity. PEG:CA and PEG:AA are used to study the impact of solid-to-liquid ratio. For PEG:AA the optimal S/L-ratio is 20 mg/g. For PEG:CA the optimal S/L-ratio is different for Li and Co. Three additional CA based DESs are made using ethylene glycol (EG) and choline chloride (ChCl): EG:CA, ChCl:EG:CA and ChCl:PEG:CA. Adding ChCl to EG:CA and PEG:CA increases the leaching efficiency from ca 5 and 10 to ca 30% and the color changes from pink to blue, indicating the formation of tetrachlorocobalt complexes. This reaction may produce chlorine gas, although none was detected using potassium iodide starch paper. Study of leaching as afunction of time of ChCl:EG:CA shows the reaction slows down significantly after 24 h, indicating that the reaction has reached or is near equilibrium at this point. Antisolvent crystallization of this solvent using ethanol was not succesful.

Imposing dimensional restrictions on graphene sheets and adding impurities can give rise to carbon nanostructures with magnetic properties. In this work, zigzag graphene nanoribbons, zGNRs, with nitrogen and fluorine adatoms are investigated for magnetic properties of interest for spin devices. Geometry optimizations were done determining which position along a zGNR electrode that N and F would favorably attach to. Edge positions were determined as the most stable attachment site. M-cell zGNR electrodes (M = 1-3) edge-functionalized by N and F adatoms were investigated with respect to their band structures and spin densities in antiferromagnetic and ferromagnetic, AFM and FM, configurations. Focus was placed on band structures showing spin gaps, indicating potential for magnetoresistive devices. Devices were modeled for 2-cell and 3-cell electrodes with nitrogen adatoms, and the respective transmission spectra were compared. Attaching N adatoms to zGNRs turned out to be a mode of controlled manipulation of their spin configurations. Spin gaps were identified in units based on 3-cell-zGNR electrodes.

Semiconductors play an integral part in modern society. From computing to LEDs their use is ubiquitous, and no field is more reliant on them than that of power generation. Current political movements have seen a push to decrease reliance on traditional forms of power generation, which relies on fossil fuels, to renewable sources such as solar power. However, current commercial solar panels, based on silicon, are lacking in efficiency, only reaching between 18% and 22% efficiency.1 In recent years, materials called perovskites have been garnering significant attention as possible replacements for silicon cells due to their favorable optoelectronic properties.2 However, the most widely researched perovskite, lead-halide perovskites, have obvious problems with stability.3 This instability, coupled with their use of lead, can lead to the leaching of lead into the environment. Several ideas have been proposed to mitigate this problem including better encapsulation of the lead halide perovskite, substitution of lead with other elements, and non-perovskite structures. In this work, we explore the synthesis and ion exchange of ternary bismuth chalcogenides with the goal of creating a split-anion perovskite.4 To accomplish this, we first synthesize inorganic bismuth chalcogenide ABiS2 nanocrystals, where A is a +1 cation. Following the synthesis of these nanocrystals, we suspend them in solution and add trimethylsilyliodide (TMSI) which reacts with the sulfur in the nanocrystal replacing it with iodide. By modulating the amount of TMSI in the reaction, we believe we can create a perovskite-like nanocrystal that incorporates nanocrystals with anions of differing oxidation states, enabling a greater variety of elements that could adopt the perovskite phase. In this work we focused on crystals where A = Ag+ and Cs+, with which we were able to demonstrate the ion exchange.

The solar cells used today have a performance rate of about 30% in theory, but most solar cells on the market only utilize about 20% of the energy provided by sunrays. A prominent reason that the performance rate is far from 100% is the large variety of energies and corresponding wavelengths in white light. Tandem solar cells utilize two different solar cells, where the light not absorbed by the top cell travels through the top cell and onto the bottom cell. This can lead to an efficiency upward of 40%.    The purpose of this thesis was to evaluate how to use the machine Bentham PVE300 optimally for measurements of transmittance, reflectance and EQE (external quantum efficiency) with the aim to calculate the IQE (Internal quantum efficiency).   To optimize the efficiency of the tandem cells, the reflectance, transmittance and EQE needed to be measured. To do this Bentham PVE300 was used. The properties of Bentham PVE300 were explored beforehand to get a better understanding of the equipment. By reading the instrument manual and simultaneously working on the instrument, methods for the measurement of EQE, reflectance and transmittance were compiled into a manual.   The results of measurements performed by Bentham PVE300 were compared to results from other equipment to determine if the measurements were viable. Agilent Cary 7000 was used to validate the measurements of reflectance and transmittance. Bentham PVE300 was ultimately determined to be reliable and in most cases more reliable than the currently used instruments.

The particle size distribution of a powder plays a crucial role in the performance of bat- teries with powder-based electrodes and requires reliable and practical analysis. The aim of this project was therefore to develop a protocol for analysis of the particle size dis- tribution and composition of powders used in the electrodes of Nilar’s batteries. The analytical methods described in the protocol permits practical applications, such as com- paring the particle size distribution and composition of pristine and reclaimed powders with the manufacturer’s data as quality control.  A literature survey was initially conducted to select appropriate analysis methods for this project. After performing several practical trials, X-ray diffraction, X-ray fluorescence, laser diffraction analysis, and scanning electron microscopy were the techniques included in the protocol. X-ray diffraction showed potential in obtaining the crystallite size of the powders, but other techniques are required to confirm the results. X-ray fluorescence analysis was found to produce fairly similar values as those given by the manufacturer. Scanning electron microscopy was used to analyse the particle size distribution with the help of an image processing software. Complementary data of the smaller particle sizes was obtained using laser diffraction analysis.

This thesis investigates the lithium-ion dynamics and structural changes in the novel cathode material LiFeV2O7 by solid-state NMR spectroscopy and density functional theory (DFT). With the escalating demand for high-performance lithium-ion batteries (LIBs), exploring cathode materials that can offer superior energy density, cycle stability, and safety is crucial. LiFeV2O7 presents a fascinating structure because it incorporates two transition metals capable of undergoing redox processes, a feature highly beneficial for lithium-ion batteries. The research employs advanced DFT calculations to predict the electronic structure and 7Li NMR shifts. These theoretical insights are essential for understanding how structural disorder influences NMR results and how the oxidation state of transition metal impacts the Fermi contact shift. Experimental techniques, including solid-state NMR spectroscopy and diffraction methods, are applied to study the lithium-ion exchange process and structural evolution during electrochemical cycling. Selective inversion NMR experiments were used to quantify the exchange rates relative to lithiation levels, and in combination with diffraction methods and DFT calculations, enabled the development of a structure model that elucidates the corresponding phase changes in the material. Moreover, the thesis discusses the impact of structural modifications on the lithium-ion dynamics within Li1.71FeV2O7, revealing a direct link between specific crystallographic changes and enhanced lithium mobility. The integration of DFT calculations with experimental observations provides a comprehensive understanding of the material's behavior, paving the way for improvements in cathode design. Overall, this research contributes significantly to the field of LIBs, offering novel insights into the complex interplay between structure, dynamics, and electrochemical performance in cathode materials. / Thesis / Doctor of Science (PhD) / This thesis explores the lithium-ion dynamics and structural changes in the new cathode material LiFeV2O7 using solid-state NMR spectroscopy and density functional theory (DFT). As the demand for high-performance lithium-ion batteries (LIBs) grows, discovering cathode materials with better energy density, stability, and safety becomes crucial. LiFeV2O7 is particularly interesting due to its structure, which includes two transition metals that undergo redox processes. This study combines advanced DFT calculations with experimental techniques to understand how structural disorder and the oxidation state of transition metals affect NMR results. Solid-state NMR spectroscopy and diffraction methods are used to examine lithium-ion exchange and structural changes during battery cycling. The research identifies how specific crystallographic changes enhance lithium mobility, providing insights that can improve cathode design. This comprehensive study contributes to the development of more efficient and stable LIBs by revealing the complex interplay between structure, dynamics, and electrochemical performance.