Plants are exposed to a variety of environmental stresses, ranging from insects and phytopathogens known as biotic stressors, to edaphic stressors including drought and salinity - clustered under the group of abiotic stresses. Facing these pernicious risks, plants have adopted several strategies to survive in stressful environments. With contemporary advances in technology and scientific research, it is possible to insert a specific gene or trait into a plant in order to confer salt tolerance. For example, a thiol methyltransferase enzyme in cabbage converts Cl¯ and other halide ions into their corresponding methyl halides, which are released directly into the air. Cloning the TMT1 gene and functionally expressing this gene into tobacco plants conferred salt tolerance on these plants. Although increased salt tolerance is a favourable and beneficial trait for plant productivity, the emission of methyl halides into the atmosphere can be noxious for the environment. Indeed, methyl halides are some of the factors contributing to climate change, widely believed to be the foremost environmental problem of the twenty-first century. Climate change is affecting all forms of life on earth and its impacts are often severe and irreversible. For that reason, it has been placed at the forefront of the international political agenda. The present study focused on two main physiological traits of stress resistance in tobacco plants which have been genetically engineered with the cabbage TMT1 gene: The production of methyl halides, particularly methyl chloride, as a way to confer salt tolerance; and synthesis of the stress hormone, ethylene. Both pathways share a common metabolite, S-adenosyl-L-methionine (SAM), for the synthesis of the final products. SAM, derived from the amino acid methionine (Met), is a universal methyl group donor. It plays essential roles in plant metabolism, by acting as a precursor for ethylene, polyamines, and vitamin B1 synthesis, and as a source of atmospheric dimethylsulphides. Therefore, it is important that the plant maintains the SAM pool at a level sufficient to serve all the different metabolic pathways. The present work set out to determine whether addition of another SAM-dependent pathway through TMT insertion in tobacco plants would negatively affect ethylene synthesis by lessening the amount of SAM available for ethylene biosynthesis. Detailed experimental studies were conducted, including in vitro and in vivo experiments, to examine the potential effect of TMT gene insertion on SAM availability for ethylene synthesis in tobacco plants. Three series of in vitro tests, differing by the number of leaf discs used, the final headspace volume in each flask, the incubation period in the different solutions and the time of introducing salt solutions, were carried out. Data obtained from two series of in vitro experiments revealed a decrease in ethylene emission when salt solutions were added at the beginning of the experiment and when leaves where incubated overnight in the presence of 0.1 M NaBr, coupled with the production of methyl halides, whereas the other series of in vitro tests as well as the in vivo results showed no alteration in ethylene accumulation because of TMT insertion when tobacco leaves were exposed to salt treatments. According to the results presented in this study, the amounts of available SAM in transformed tobacco are likely sufficient to serve both ethylene and methyl halides biosynthetic pathways. Besides, in vivo results indicate that inserting the TMT1 gene that improves salt stress resistance in tobacco should not dramatically alter ethylene synthesis, and therefore, would be unlikely to affect any physiological trait associated with ethylene production if this gene is used to engineer salt tolerance in high-value crops. Although TMT insertion does not alter ethylene emission in transgenic plants and tends to be an efficient tool to confer salt tolerance in halo-intolerant crops, its environmental cost is of great concern and, therefore, should be taken into consideration to mitigate the amounts of methyl halides emitted into the atmosphere because of this insertion.

Abstract Electron-ion coincidence spectroscopy has been used to study the fragmentation behaviour of small molecules in two distinct cases: to resolve the state specific fragmentation patterns of HgBr₂ and HgCl₂ subsequent to UV ionization, and to distinguish the dissociation behaviour of various chlorinated methanes (CH₃Cl, CH₂Cl₂, CHCl₃ and CCl₄) subsequent to X-ray irradiation. The mercury-compound work has revealed details on the electronic structure and dissociation dynamics of the valence states which were previously unknown. The study on the chlorinated methanes has found new details on the exact pathways of the appearance of a specific fragment and also investigates the speed of the dissociation in the four different chlorinated methane molecules. The results from the electron-ion coincidence spectroscopic experiments are presented and analysed together with theoretical and computational support.

This thesis examines the depiction of female characters as New Women in a comparative analysis of the fiction of two authors from fin-de-siècle United States of America and late Ottoman/early Republican Turkey: Edith Wharton’s The House of Mirth (1905), The Custom of the Country (1913) and The Age of Innocence (1920), and Halide Edib Adıvar’s Raik’in Annesi (Raik’s Mother, 1909), Handan (Handan, 1912) and Kalp Ağrısı (Heartache, 1924). It argues that these novels can be read as examples of New Woman fiction, with their challenge to conventional fictional treatments of womanhood and their depiction of complex female heroines struggling against restrictive social roles, conventions and moral codes. Examining these texts together opens up a hitherto unexplored area of comparison into how the construct of New Womanhood was perceived and dealt with differently (and similarly) in the American and Turkish societies of the era. The thesis brings a new approach to the analysis of the novels under question not only by reading Wharton’s and Adıvar’s fiction in a comparative perspective but also by approaching New Woman fiction by means of Mikhail Bakhtin’s theories of dialogism, complemented by the work of feminist critics such as Dale M. Bauer, Gail Cunningham, Luce Irigaray and Lyn Pykett. A feminist dialogic approach informs my reading of the novels as texts that present a pluralistic exchange between multiple discourses and that resist a singular interpretation - instead offering multiple “readings”, with a surface narrative and counter narrative: whilst the surface narrative appears as authoritative and seeks to maintain the status quo (through voices that attempt to stabilise the New Woman and assert the authority of conventions and moral codes), this is disrupted and destabilised by the subversive marginal voices of the counter narrative. By attending in this way to the juxtaposition of a multiplicity of conflicting voices on the New Woman question in the texts - particularly as these are expressed in the heroines’ inner dilemmas and conflicts and around the issues of marriage, divorce and sexuality - I attempt to go beyond a reading of the texts as reflections of the biography of the authors or their views regarding a certain model of female identity, instead emphasising the problematisation and unfixing of identity in the novels and their depiction of New Women that are complex, fragmented and contradictory. Furthermore, influenced by the ideas of feminist thinkers such as Judi M. Roller and Elizabeth Bronfen, I propose that the unhappy endings of Wharton’s and Adıvar’s novels can be read as critiques of the oppressive effects of hegemonic discourses about women and a recognition of female agency and struggle. By examining these aspects of the novels, this comparative thesis aims to contribute to feminist studies focused upon the “woman question” and to the growing body of scholarly work on the New Woman.

Ink-based semiconductors that come to mind today include conjugated molecules and polymers, colloidal quantum dots, metal halide hybrid perovskites, and transition metal oxides. These materials form an ink (solution/ suspension/ sol-gel) that can be applied and dried in ambient air to form high-quality films for optoelectronic devices. In this study, we will introduce the current understanding of ink-based lead and lead-free hybrid perovskite and perovskite-inspired thin films. Examples will be presented through time-resolved studies of the solidification to link the solid-state microstructure and device figures of merit to the ink’s formulation, drying, and solidification process. The perovskite crystallization kinetics characterized in situ during the solution process indicates an essential role by the inclusion of Cs+ and K+ alkali metal cations in perovskite inks. The film and device characterizations indicate the functions of mixed cation and halides in determining the optoelectronic properties. The further sophisticated design of perovskite inks enables significantly optimized charge dynamics, including exciton separation, inter-grain charge transfer, trap density, charge mobility, and charge collection efficiency. The considerably improved optoelectronic properties lead to higher charge collection efficiency and, therefore, better open-circuit voltage and fill factor for the Cs+-containing 3D perovskite devices in contrast to the control FAPbI3 one. Recent developments in ink formulation and processing that enable scalable ambient fabrication of high-quality perovskite semiconductor films will also be presented. These findings raise the possibility of developing more controlled perovskites for systematically addressing both charge dynamics and degradation mechanisms in concert for the timely commercialization of perovskite solar cells.

In this thesis, we have developed a reproducible, safe, and scalable sequential thermal vapour deposition (STVD) method for the growth of quality 3D halide perovskite (HaP) thin films. High-quality methylammonium lead tri-bromide (MAPbBr3), methylammonium lead tri-iodide (MAPbI3), and methylammonium lead bromide-iodide (MAPb(I1-xBrx)3) thin films have been optimised using the STVD technique. The structural, optical, morphological, and electrical properties were tuned by varying the thicknesses of the organic (MAI, MABr) and inorganic (PbI2, PbBr2) precursor thin films and post-annealing times of the HaP. X-ray diffractograms confirmed the cubic MAPbBr3 structure with the Pm¯3 m space group, tetragonal MAPbI3 crystal structure with I4/mcm space group, and the tetragonal MAPbI3 structure being transformed to cubic MAPbBr3 system as MAPb(I1-xBrx)3 (x=0.89-0.95) forms. UV-Vis spectra revealed broad absorption bands with a redshift in absorption onset from 540 to 550 nm for MAPbBr3 and 750 to 780 nm for MAPbI3 as the thickness of respective organic precursors increased from 300 to 500 nm. The bandgap of MAPb(I1-xBrx)3 decreased from 2.21 to 2.14 eV as the thicknesses of MABr precursors increased from 300 to 500 nm. The crystallisation of the HaP started within the chamber, and prolonged post-annealing times exceeding 10 min caused the transformation of MAPbI3 to PbI2. Scanning Electron Micrographs show pin-hole-free and densely packed grains with an average size that increases as thicknesses increase. The charge carrier mobility increases while trap density decreases as the thickness of organic precursors increased. Besides, the thesis investigated the growth and stability of thin MAPbBr3 films at metal/MAPbBr3 interfaces. We studied the structure, morphology, and stability of the optimised MAPbBr3 perovskite on aluminium (Al), tin (Sn), silver (Ag), gold-zinc (Au-Zn) and gold (Au) electrodes, immediately and 60 days later. FE-SEM images show an average grain size that increased linearly with the work function from 294 nm for Al to 850 nm for Au. The MAPbBr3 grains remain glued to Sn, Ag, Au-Zn but delaminate quickly on Al. X-ray analysis of MAPbBr3 reveals variable crystallographic texturing for various metals and loss in intensity of prominent peaks at different rates over time. We found that the best thicknesses of 100 nm PbI2 and 500 nm MAI, and 100 nm PbBr2 and 500 nm MABr are needed for the preparation of quality MAPbI3 and MAPbBr3 thin films for solar cells, respectively. Quality thin MAPb(I0.11Br0.89)3 film is formed by inter-diffusion and halide exchange processes when optimised MAPbBr3 is grown on optimised MAPbI3 as a bottom layer. Al speeds up the degradation of MAPbBr3 at Al/MAPbBr3 while MAPbBr3 is relatively stable at Au-Zn/MAPbBr3 interfaces. / Thesis (PhD (Physics))--University of Pretoria, 2020. / University of Pretoria, the National Research Foundation/The World Academy of Sciences (NRF-TWAS), and NRF grant no N0115/115463 of the SARChI / Physics / PhD (Physics) / Restricted

The endeavor to have more efficient solar cells and as environmentally beneficial as possible are the driving forces for this work. The way to reach this is by research to better the understanding of the mechanisms and parameters that govern the performance of solar cells. New materials are essential to develop because the current ones lack stability and are water, temperature and UV-radiation sensitive. In this work the lead (Pb2+), which is poisonous and hazardous is intended to be replaced in the organic metal halide (OMH) perovskite structure. This is tested with gold or silver combined with bismuth and silver by itself. Also trimethylsulfonium gold or silver iodides are investigated. The methylammonium cation is also substituted to cesium. The perovskite material both absorbs light and transports charges in the solar cells. Materials based on AuI/AgI, BiI3 and CH3NH3I and AuI/AgI and [Me3S]I and AgI, BiI3 and CsI were synthesized and analyzed by XRD on thin film and mesoporous substrate and Raman spectroscopy to determine material structure and bonding. J-V measurements were performed to see the function in solar cells. After this conductivity and absorption parameters were determined by an electrical conductivity test and UV-vis absorption spectroscopy. XRD measurements indicate that the perovskite structure could have been obtained because the materials match with the XRD spectra of [20] foremost T3, T5 and T6, Cs1 and Cs2. In T7 some new structure is formed. The bismuth could be partially substituted by silver as the metal cation. The samples are quite amorphous, but still containing crystalline peaks, the product material could be a mixture of a crystalline and an amorphous phase. The crystalline phase could have the desired perovskite structure. To have mesoporous TiO2 as substrate seem to enhance a more crystalline structured material. All the materials seem to have formed some new structures because the pure reactants does not seem to be present, exceptions could be P1 and T1 that contained AuI. The change of cation from methylamine to cesium though results in a shift of the peak positions because of the change of cation size as in [20], but the structure is most likely the same. Raman spectroscopy indicate that there is a change in structure, some new bond being present, when increasing the methylamine ratio for the presumed methylammonium silver bismuth iodide perovskites. This concerns materials T5, T6, T7 with increasing ratio of methylamine. This new bond is most pronounced in T7 where the methylamine content is the highest. Both Silver and bismuth iodide bonds seem to be present and cannot be coupled to be the pure reactants recrystallizing and some new bonds of these are present in all materials to some extent. The organic bond vibration has low intensity and might indicate that there is not so much organic cation present in the product and thus the probability of having the desired product anion decreases. The solar cells made with Spiro-OMeTAD were 700-4000 times more efficient than those made with Sulphur polymer HTM. Solar cells made with Spiro-OMeTAD as HTM gives slightly higher efficiency when increasing the methylammonium cation ratio. For cesium as cation the combined metal cation constellation with bismuth and silver gives a little higher efficiency than bismuth alone. Methylammonium as cation gives a higher efficiency than cesium. Solar cells made with Sulphur polymer HTM show approximately 3-30 times higher efficiency with methylammonium as cation compared to cesium as cation. HTM material seem to affect the perovskite material making some of the cells completely transparent and some of them paler, water in the solvent chlorobenzene can be a possible explanation. The transparency can be the reason for the low efficiency obtained for the solar cells. Also the measurement methodology of these solar cells can also have been false, measuring the contacts, and the etching procedure could be another source of this. The solar cells had quite low efficiencies compared to [20], although same presumed material and procedure has been used and thus there might be something wrong in the accuracy of the manufacturing. The cells should probably been made several times and possible sources of error should be analyzed and corrected for. The materials were all relatively conductive. P1 gave the highest conductivity, almost three times higher than for methylammonium lead iodide that has a conductivity of 1,1x10-4 s/cm [3]. Increasing the methylammonium ratio gave an increase of the conductivity both with bismuth and silver as metal cations and silver alone. The increase of the methylammonium ratio might result in a new structure formed which has lattice planes that are more conductive. A change of gold to silver for the trimethylsulfonium iodide materials gave a large decrease in conductivity. The materials have different absorption curves meaning that they have different bandgaps and this indicates differences in structure. The bandgaps of all materials are indirect contrary to what is proven to be the case for perovskites that are believed to have direct bandgaps in general. To have indirect bandgaps requires a shift in momentum in the electronic transitions and is not as beneficial as having direct bandgaps. Compared to methylammonium lead iodide that has a direct bandgap of 1,6 eV, the bandgaps are at least 0,5 eV higher and range between 2,2-2,36 eV. P1 had a low bandgap of 1,6 eV meaning it absorbs a wide range of wavelengths. The conductivity does not seem to be the obstacle and the cells that are not transparent absorb light. It is highly possible that the low solar cell performance, at least to a certain extent, has to do with the production process. The low scan rate could also affect the low efficiencies and HTM Spiro-OMeTAD should be used. Currently the efficiency of the perovskite materials with silver/bismuth, gold/bismuth and silver are too low, and not able to substitute lead in the perovskite structure solar cells. Neither trimethylsulfonium gold or silver iodide cells nor cesium perovskites have enough efficiency at present. The conductivities for the materials are promising and the materials that are not completely transparent absorb light. / Strävan att utveckla effektivare solceller och så miljövänliga som möjligt är drivkrafterna för det här arbetet. För att uppnå detta krävs forskning för att förbättra förståelsen för vilka mekanismer och parametrar som styr hur väl solcellerna fungerar. Det är nödvändigt att ta fram nya material, då de nuvarande brister i stabilitet, de är framförallt känsliga för vatten, temperatur och UV-strålning. I det här arbetet är syftet att byta ut bly (Pb2+), som är giftig och kopplad till hälsorisker, i den organiska metall halid (OMH) perovskit strukturen. Detta görs med guld eller silver i kombination med vismut och silver självt. Även trimetylsulfonium- guld eller silver undersöks. Metylammonium katjonen substitueras också mot cesium. Perovskit material absorberar både ljus och transporterar laddningar i solceller. Material baserade på AuI/AgI, BiI3 och CH3NH3I and AuI/AgI och [Me3S]I and AgI, BiI3 and CsI syntetiserades. Dessa analyserades, med XRD på dels ett substrat av tunn film och dels ett mesoporöst och Raman spektroskopi, för att bestämma strukturen på materialet och bindningar. J-V mätningar utfördes för att se hur materialen fungerade som solceller. Efter detta utfördes mätningar av konduktiviteten och absorptions parametrar bestämdes genom ett elektriskt konduktivitetstest respektive UV-vis absorptions spektroskopi. XRD mätningarna indikerar att perovskit strukturen kan ha erhållits eftersom spektrumen överensstämmer med de i [20], framförallt för T3, T5 och T6, Cs1 och Cs2. I T7 bildas någon ny struktur. Vismut skulle kunna vara delvis utbytt mot silver som metalkatjon. Proven är relativt amorfa, men uppvisar kristallina toppar och produkten skulle kunna vara en blandning av en kristallin och amorf fas, där den kristallina fasen skulle kunna ha den eftersträvade perovskit strukturen. Mesoprös TiO2 som substrat verkar öka graden av kristallinitet hos materialen. Samtliga material verkar ha bildat någon ny struktur eftersom reaktanterna i sin rena form inte verkar finnas. Undantag skulle kunna vara P1 och T1, vilka innehåller AuI. Bytet av katjon från metylammonium mot cesium resulterar i ett skifte av topparna troligen beroende av skillnaden i storlek mellan katjonerna, liksom påvisas i [20], men strukturen är förmodligen densamma. Raman spektroskopin indikerar en förändring i strukturen, någon ny bindning finns, hos materialen när metylammonium andelen ökas för de förmodade metylammonium silver vismut jodid perovskiterna. Detta gäller materialen T5, T6, T7, där andelen metylammonium ökar. Den nya bindningen är mest uttalade i T7, där metylammonium andelen är den högsta. Både silver och vismut jodid bindningar verkar finnas och kan inte kopplas till att de rena reaktanterna har rekristalliserats och nya bindningar av dessa finns i alla material till en viss grad. Den organiska bindningens vibration har låg intensitet och kan tyda på att det inte finns så mycket organisk katjon i produkten och således minskar sannolikheten att ha den eftersträvade anjon produkten. Solcellerna gjorda med Spiro-OMeTAD var 700-4000 gånger mer effektiva än dom gjorda med Svavel polymer HTM. För solcellerna gjorda med Spiro-OMeTAD som HTM ger en ökning av metylammonium katjon andelen en ökad effektivitet. För cesium som katjon med den kombinerade metalkatjon konstellationen med vismut och silver, blir effektiviteten högre än om vismut är metalkatjon självt. Metylammonium som katjon ger en högre effektivitet än cesium. Solceller gjorda med Svavel polymer HTM visar ungefär 3-30 gånger högre effektivitet med metylammonium som katjon jämfört med cesium som katjon. HTM materialet verkar påverka perovskit materialet och göra några av cellerna helt transparenta och de andra blekare. Klor benzen användes som lösningsmedel och denna kan ha innehållit vatten och kan vara orsaken till färgskiftningen. Detta kan vara orsaken till den låga verkningsgraden som erhölls för solcellerna. En annan möjlig förklaring skulle kunna vara metoden för mätningarna. Denna kan ha varit felaktig, då kontakten troligen har varit det som har mätts och etsningsprocessen skulle kunna vara en orsak till detta. Solcellerna uppvisar ganska låg effektivitet i jämförelse med [20], trots att samma material och procedur har använts och således kan det vara något fel i precisionen av framställningen. Cellerna skulle förmodligen gjorts om ett antal gånger och möjliga felkällor borde utretts och åtgärdats. Materialen var överlag relativt konduktiva. P1 gav den högsta konduktiviteten, nära tre gånger högre än metylammonium bly jodid, som har en konduktivitet på 1,1x10-4 s/cm [3]. En ökning av andelen metylammonium gav en ökning av konduktiviteten både med vismut och silver som metalkatjon och silver självt. Ökningen av andelen metylammonium skulle kunna resultera i ett en ny struktur uppkommer som har plan som är mer konduktiva. Utbytet av guld mot silver för trimetylsulfonium jodid materialen gav en markant sänkning av konduktiviteten. Materialen har olika absorptionskurvor vilket innebär att de har olika bandgap och detta indikerar olikheter i strukturen. Bandgapen för alla material är indirekta, trots att bandgapen för perovskiter i regel är direkta. Att ha indirekta bandgap kräver ett skifte i momentum i de elektroniska energiöverföringarna och är inte så fördelaktigt som att ha direkta bandgap. I jämförelse med metylammonium bly jodid, som har ett direkt bandgap på 1,6eV, är bandgapen minst 0,5 eV högre och varierar mellan 2,2-2,36 eV. P1 hade ett lågt värde på bandgapet, 1,6 eV, vilket innebär absorption av ett brett spektrum av våglängder. Konduktiviteten verkar inte vara den faktor som är orsaken till den låga effektiviteten hos solcellerna och de celler som inte är transparenta absorberar ljus. Det är högst troligt att den låga effektiviteten har sin förklaring, åtminstone delvis, i produktionsprocessen för solcellerna. Den relativt låga skanningshastigheten kan också vara en orsak för den låga effektiviteten och HTM Spiro-OMeTAD bör användas. I dagsläget är effektiviteten för perovskitmaterialen med silver/vismut, guld/vismut och silver för låg och har inte möjlighet substituera bly i perovskit solceller. Inte heller trimetylsulfonium guld eller silver jodid cellerna och inte heller cesium perovskiternas effektivitet räcker till i dagsläget. Konduktiviteten för materialen är lovande och materialen som inte är transparenta absorberar ljus.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20391号 / 工博第4328号 / 新制||工||1671(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 中村 正治, 教授 辻 康之, 教授 小澤 文幸 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

It has been previously shown that micelles formed from surfactants with chiral head groups serve to induce a chiral reaction medium, leading to enhanced enantioselectivities in the reaction products. This utilization of chiral surfactants will offer an economical alternative to traditional chial solvents while simultaneously reducing organic waste. We have successfully dimethlated S-leucinol in an 85% yield, and have synthesized a hydrocarbon-based surfactant with this molecule as a head group. We have also formed polymeric surfactants that have polydimethylsiloxane as the hydrophobic portion with the (S)-dimethylleucinol as a head group. Tests of the solubility of these surfactants have been conducted. We also have done a reduction of a ketone in 95% ethanol and 1.3%-4% (w/v) surfactants, resulting in ee. 5.4%-6.6%.

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25287号 / 工博第5246号 / 新制||工||1999(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 杉村 博之, 教授 邑瀬 邦明, 准教授 小林 圭 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM