Dimethyl Sulfide (CH3SCH3, DMS) is the most important natural sulfur compound emitted from the ocean and its oxidation in the atmosphere has been proposed to play an important role in climate modification because some products from DMS oxidation become non-volatile and could participate in particle formation and growth processes. Although it has been demonstrated that aqueous phase reactions are potentially important for understanding DMS oxidation, the kinetics database for aqueous phase transformations is rather limited. In this work, a laser flash photolysis (LFP) ??ng path UV-visible absorption (LPA) technique was employed to investigate the kinetics of the aqueous phase reactions of four organic sulfur compounds produced from DMS oxidation, i.e., dimethylsulfoxide (DMSO), dimethyl-sulfone (DMSO2), methanesulfinate (MSI) and methanesulfonate (MS), with four important aqueous phase radicals, OH, SO4 and #8722;, Cl and Cl2 and #8722;. The temperature-dependent kinetics of the OH and SO4 and #8722; reactions with DMSO, DMSO2 and MS were studied for the first time. OH is found to be the most reactive, while Cl2 and #8722; is the least reactive toward all the sulfur species studied. The less oxidized DMSO and MSI are found to be more reactive than the more oxidized DMSO2 and MS for each radical. The kinetic data have been employed in a Trajectory Ensemble Model to simulate DMS oxidation in the marine atmosphere as a means of assessing the contribution of aqueous phase reactions to the growth of particulate matter. For the first time, oxidation of organic sulfur compounds by SO4 and #8722;, Cl and Cl2 and #8722; are included in the model to simulate DMS chemistry. Our simulations suggest that aqueous phase reactions contribute >97% of MS and ~90% of NSS (Non-Seasalt Sulfate) production, and aqueous phase reactions of the organic sulfur compounds contribute 30% of total particle mass growth. When our kinetic data for the MS + OH reaction were used in the model, it was found that MS + OH could consume ~20% of MS and produce ~8% of NSS, within 3 days under typical marine atmospheric conditions.

The discovery of the ocular hypotensive effect of topically applied prostaglandins (PGs) has raised a number of questions about the mechanisms of action involved. The aim of the present thesis was to answer some of these questions. PGs reduce the intraocular pressure (IOP) by increasing uveoscleral flow through the ciliary muscle, but the exact mechanism is not known. Morphological changes may be involved. PGs are also involved in the inflammatory response. In the first study the aim was to investigate the effect of latanoprost, a prostaglandin F2 a-analogue, on the blood-aqueous barrier and the IOP restoration after long-term treatment. 26 glaucoma patients were treated with latanoprost (50 pg/ml) once daily for 6-12 months. Aqueous protein concentration was followed with a laser flare meter in 16 patients throughout this period. No change was observed. IOP increased slowly after withdrawal of treatment. It was concluded that latanoprost has no clinically significant effect on the permeability of the blood-aqueous barrier and that the IOP will return to pretreatment levels within a few weeks, indicating that any changes in the ciliary muscle morphology are reversible. In 20 healthy volunteers it was attempted to prevent the ocular hypotensive effect of latanoprost by inhibiting uveoscleral flow by a pronounced ciliary muscle contraction. For this purpose a high dose of the cholinergic agonist, physostigmine (1 drop 8 mg/ml alternate hours) was used. However, the effects on IOP of the two drugs were mainly additive most likely due to a short-lasting effect of physostigmine on the ciliary muscle. The progressive IOP reduction by physostigmine in the second study raised the question as to whether the drug reduces aqueous flow apart from enhancing outflow. On the contrary, in the third study repeated administrations of physostigmine, in 20 normal subjects, increased aqueous flow, measured with fluorophotometry, by about 25%. From studies of patients it is known that latanoprost twice daily has less ocular hypotensive effect than once daily. This was the subject of the two remaining studies. The possibility that latanoprost causes a short-lasting increase in aqueous flow was examined in 18 healthy volunteers. Application of a second drop in the morning would blunt some of the early IOP lowering effect of latanoprost. Once or twice daily applications had similar effect on aqueous flow, a tendency to an increase without any difference between the dose regimens. The next study confirmed the difference in effect on IOP between once and twice daily applications in 40 normal subjects. The difference remained even when one of the two applications was omitted after two weeks’ treatment. The results indicate that applying latanoprost twice daily induces a modest receptor desensitisation. / <p>Diss. Umeå : Umeå universitet, 1997, härtill 5 uppsatser.</p> / digitalisering@umu

Thèse--Louvain. / Bibliography: p. 207-238.

Aqueous zinc ion storage system has been deemed as one of the most promising alternatives due to its high capacity of zinc metal anode, low cost, and high safety characteristics. Recently, significant attempts have been made to produce highperformance aqueous Zn batteries. (AZBs) and great progress has been achieved. Yet there are a lot of issues still exist and need to be further optimized. In this thesis, we proposed several strategies to tackle these challenges and finally optimize the overall battery performance, including metal anode protection, cathode structural engineering, and rational electrolyte design. In the present thesis, we first developed the ZnF2 layer coated Zn metal anode via a simple plasma treatment method. The plasma treated Zn anode leads to dendrite-free Zn electrodeposition with lower overpotential. Density function theory calculation results demonstrate that the Zn diffusion energy barrier can be greatly reduced on the ZnF2 surface. Benefiting from these merits, the symmetric cell and full cell exhibited much improved electrolchemical performance and stability. Afterthen, We synthesised a layered Mg2+-intercalated V2O5 as the cathode material for AZBs. The large interlayer spacing reachs up to 13.4 A, allowing for efficient Zn2+ (de)insertion. As a result, the porous Mg0.34V2O5・nH2O cathodes can provide high capacities as well as long-term durability. We then recongnized that most of the parasitic side reactions are related to the aqueous electrolyte. We therefore further designed a hybrid electrolyte to realize the anode-free Zn metal batteries. It is demonstrated that in the presence of propylene carbonate, triflate anions are involved in the Zn2+ solvation sheath structure. The unique solvation structure results in the reduction of anions, thus forming a hydrophobic solid electrolyte interphase. Consequently, in the hybrid electrolyte, both Zn anodes and cathodes show excellent stability and reversibility. More importantly, we design an anode-free Zn metal battery, which exhibits good cycling stability (80% capacity retention after 275 cycles at 0.5 mA cm–2).

The growing renewable energy consumption has stimulated the rapid development of diverse energy storage systems (ESSs) in our electronic society. As a successful representative, lithium-ion batteries (LIBs) play a vital role in meeting today's energy storage demand. However, LIBs are plagued by intrinsic unsafety and detrimental environmental contamination. In this respect, rechargeable aqueous zinc-ion batteries (ZIBs) and supercapacitors (SCs) as potential alternatives have attracted considerable attention due to their characteristics such as innate safety, environmental friendliness, cost-effectiveness, competitive gravimetric energy density, and loose fabrication process. Inspired by these merits, massive efforts have been devoted to designing and exploring high-performance aqueous Zn-based energy storage devices. The key for advanced Zn-based energy storage devices is to exploit high-performance cathode materials. Covalent organic frameworks (COFs) are an emerging class of organic polymer with periodic skeletons showing attractive properties in structural tunability, well-defined porosity, functional versatility, and high chemical stability. The distinguishing features of COFs make them promising electrode materials for electrochemical energy storage applications. However, the electrochemical storage capability and charge storage mechanism of COF materials have been rarely investigated, and their potential applications have not been evaluated yet so far. In this thesis, COFs are proposed as cathode materials for rechargeable aqueous Zn-ion energy storage. Initially, a new phenanthroline COF (PA-COF) material was synthesized and used as an electrode for Zn-ion supercapatteries (ZISs) for the first time. The as-synthesized PA-COF shows abundant nucleophilic sites and suitable pore structure, demonstrating the efficient storage capability of Zn2+ and H+. Further, hexaazatriphenylene-based COF (HA-COF) material with and without precisely grafted quinone functional groups has been proposed to understand structure-activity relationships. In this chapter, the influence of quinone groups on the electrochemical performance of HA-COF has been systematically studied, disclosing an enhancement coordination capability of Zn ions against protons in the quinone-functionalized HA-COF. Lastly, we synthesized a radical benzobisthiazole COF (BBT-COF) and deeply investigated the electrochemical performance. As expected, this COF electrode shows an ultrastable cycling performance and demonstrates a radical reaction pathway.

The wide applications of energy storage systems in consumer electronics, electric vehicles, and grid storage in the recent decade has created an enormous market globally. The electrochemical flow system has many applications in Li-ion battery recycling and energy storage system design. First, research work on a scalable electrochemical flow system is presented to effectively restore the lithium concentration in end-of-life Li-ion cathode materials. An effective recycling process for end-of-life lithium-ion batteries could relieve the environmental burden and retrieve valuable cathode battery materials. The design is validated in a static configuration with both cathode loose powder and cathode electrode sheet. Materials with comparable electrochemical performance to virgin cathode materials are produced after post heat treatment. Second, research contributions in sulfur-based flow battery systems for long-duration energy storage are presented. Sulfur-based redox flow batteries are promising due to their high theoretical capacity, low cost, and high abundance. The speciation of aqueous sulfur solutions with different nominal concentrations, sulfur concentrations, and pH are studied by Raman spectroscopy. Next, a promising aqueous manganese catholyte to couple with the sulfur anolyte for a full flow battery is investigated. Test protocols and quantification metrics for the catholyte are developed. The stability of the catholyte, including self-discharge rate and precipitation rate, is measured via ex-situ characterizations. The electrochemical performance of the catholyte is investigated and optimized via in-situ experiments. The reaction pathway for the precipitation of catholyte is discussed and several mitigation strategies are proposed. Finally, a semi-solid sodium-sulfur flow battery is developed. The electrochemical performance of the sodium-sulfur battery is studied first in a static configuration at an intermediate temperature (150°C). Then a Na-S semi-solid flow cell is assembled and cycled under the two-aliquots and three-aliquots intermittent flow. / Doctor of Philosophy / The market of energy storage systems has been expanding dramatically in recent years due to their wide applications in portable electronics, electric vehicles, and large-scale grid storage. First, the research on the development of an electrochemical flow system in the Li-ion batteries (LIB) recycling process is presented. The improper disposal of end-of-life LIBs will generate flammable hazardous waste. Recycling spent LIBs could ease the environmental burden and replenish valuable resources such as lithium, cobalt, and nickel, and reduce the cost of battery manufacturing. In this study, an electrochemical flow system is designed to restore the end-of-life cathode materials in LIBs. The design has the potential to scale up and is validated with a static configuration. The recycled materials show comparable electrochemical performance to virgin battery cathode materials. Life cycle analysis shows that the recycling process consumes less energy and is more environmentally friendly. Second, the research contribution in sulfur-based flow battery systems for long-duration energy storage is presented. The aqueous sulfur solutions with different nominal concentrations, sulfur concentrations, and pH are studied by Raman spectroscopy. Next, a promising aqueous manganese catholyte to couple with the sulfur anolyte for a full redox flow battery is investigated. The chemical stability of the catholyte, including self-discharge rate and precipitation rate, is measured via ex-situ characterizations. The electrochemical performance of the catholyte is studied and optimized via in-situ experiments. The reaction mechanisms for the precipitation of aqueous manganese solutions are discussed. Finally, a semi-solid sodium-sulfur (Na-S) flow battery is developed. The electrochemical performance of the sodium-sulfur battery is studied first in a static cell at intermediate temperature. Then a Na-S semi-solid flow cell is demonstrated and cycled under the two-aliquots and three-aliquots intermittent flow.

During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

The semiconductor industry is continually challenged to maintain the trend identified in 1965 by Gordon Moore of increasing the density of transistors on an integrated circuit. These advances have been achieved by increasing the resolution that can be printed with photolithography, traditionally by decreasing the exposure wavelength. Decreasing the exposure wavelength from 193 nm, the current state of the art, presents significant technical challenges. To circumvent these challenges, resolution can be increased by enabling increases in numerical aperture (without changing the exposure wavelength), using immersion lithography. In immersion lithography, the air gap between the photoresist-coated wafer and lens is replaced with a high refractive index fluid. Immersion lithography has been demonstrated with water as the immersion fluid. With water immersion lithography at 193 nm, the maximum resolution that can be printed can be decreased from 65 nm to 45 nm. To enable further resolution increases, immersion fluids with a higher index than water are needed. The requirements for next generation high index fluids are: an index of refraction higher than water, high transparency, and physical properties similar to water. A variety of methods to identify a high index fluid were completed. First, the optical properties of aqueous solutions of metal cations with varying anions were tested. A series of linear, cyclic, and polycyclic alkanes were also studied, since saturated systems have electronic transitions at wavelengths less than 200 nm, to provide the necessary transparency at 193 nm. Large alkane groups were also incorporated into either the cation or anion of a salt to develop an aqueous solution with the optical properties of a saturated hydrocarbon. In addition to these empirical surveys, a modeling approach was used to develop “designer” absorbance spectra that would correspond to fluids with a high index and low absorbance at 193 nm. Additionally, in Appendix D, the results of an electrochemical study of the diffusion coefficient of ferrocene methanol in poly(ethylene glycol) diacrylate hydrogels of varying molecular weight and water content will be presented. The results of these mass transport studies can be used to qualitatively understand the mass transport characteristics of additional species in the hydrogel. / text

With the proliferation of renewable energy sources, there has been a growing interest in battery chemistries for grid scale energy storage. Aqueous sodium ion batteries are particularly interesting for large scale energy storage because of their low cost and high safety, however, they tend to show poor long term stability. NaTi2(PO4)3 shows promise as an anode for these systems with excellent long term stability when cycled quickly. When cycled slowly, NaTi2(PO4)3 shows rapid capacity fade. The reasons for this rate depend capacity fade is poorly understood and is the topic of this document. It has been found that the products of the hydrogen evolution reaction, H2(g) and OH-, are the two largest contributors to capacity fade. High electrolyte pH caused by generation of OH- promotes dissolution of NTP during extend cycling, this is exacerbated when the pH increase above 11. The single greatest cause of apparent capacity fade for this material is loss of electrochemical surface area due to hydrogen gas entrapment within the porous structure of the electrode. Capacity lost in this manner can be recovered through reinfiltration of the electrode. The detrimental effects of gas entrapment within the electrode can be partially mitigated through compositing of the electrode with activated carbon and enhancing the wettability of the pores through addition of a surfactant to the electrolyte.