abstract: A Fundamental study of bulk, layered, and monolayers bromide lead perovskites structural, optical, and electrical properties have been studied as thickness changes. X-Ray Diffraction (XRD) and Raman spectroscopy measures the structural parameter showing how the difference in the thicknesses changes the crystal structures through observing changes in average lattice constant, atomic spacing, and lattice vibrations. Optical and electrical properties have also been studied mainly focusing on the thickness effect on different properties where the Photoluminescence (PL) and exciton binding energies show energy shift as thickness of the material changes. Temperature dependent PL has shown different characteristics when comparing methylammonium lead bromide (MAPbBr3) to butylammonium lead bromide (BA2PbBr4) and comparing the two layered n=1 materials butylammonium lead bromide (BA2PbBr4) to butylammonium lead iodide (BA2PbI4). Time-resolved spectroscopy displays different lifetimes as thickness of bromide-based perovskite changes. Finally, thickness dependence (starting from monolayers) Kelvin Probe Force Microscopy (KPFM) of the layered materials BA2PbBr4, Butylammonium(methylammonium)lead bromide (BA2MAPb2Br7), and molybdenum sulfide (MoS2) were studied showing an exponential relation between the thickness of the materials and their surface potentials. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19740号 / 工博第4195号 / 新制||工||1647(附属図書館) / 32776 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 阿部 竜, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第21315号 / エネ博第371号 / 新制||エネ||73(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 松田 一成, 教授 佐川 尚, 教授 大垣 英明 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22780号 / 工博第4779号 / 新制||工||1747(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 田中 勝久, 教授 陰山 洋, 教授 藤田 晃司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The goal of the dissertation was to optimize synthetic parameters to tune the properties of two layered materials, MoS2 and MnO2 for applications such as antibacterial, energy storage and water remediation. Two aspects of the materials were investigated. Firstly, the synthetic parameters were tuned to prepare material with different morphologies and then the effect of morphology and structure on interaction with bacterial cells was studied. In the second part, the research was focused on tuning the synthetic parameters to improve the intrinsic conductivity of the material for electrocatalytic applications. This dissertation work primarily focuses on understanding the catalytic and antibacterial activity of layered MnO2 and MoS2. One research effort was focused on the antibacterial mode of action of layered nanosheets of MnO2 and MoS2 toward Gram-positive and Gram-negative bacteria. Bacillus subtilis and Escherichia coli bacteria were chosen as model organisms, which were treated individually with randomly oriented and vertically aligned nanosheets. Viability measurements of bacteria, by flow cytometry and fluorescence imaging, showed that vertically aligned MnO2 and MoS2 nanosheets revealed the highest antimicrobial activity and that Gram-positive bacteria showed a higher loss in membrane integrity, compared to Gram-negative bacteria. Moreover, scanning electron microscopy images suggested that the nanosheets compromised the cell wall upon interaction, which led to significant bacterial morphological changes. We propose that the peptidoglycan mesh in the bacterial wall is likely the primary target of the 2D layered nanomaterials. Another focus of the dissertation research investigated the effect of structural and geometrical changes of layered materials on the properties which affect the intrinsic conductivity of material. In the first study, the electrocatalytic activity of layer-by-layer (LbL) deposited 1T'-MoS2 (metallic phase) on a fluorine-doped tin oxide (FTO) substrate was investigated for the hydrogen evolution reaction (HER) as a function of layer number. Conversion of the deposited 1T'-MoS2 to the semiconducting 2H-MoS2 phase via exposure to 532 nm wavelength light, confirmed by Raman spectroscopy and scanning tunneling spectroscopy (STS), allowed a direct comparison of the HER activity of the two phases at a constant mass loading and surface area on the same substrate. The morphology, thickness and roughness of the deposited MoS2 layers as a function of the number of deposition cycles were investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results showed that the average roughness of the surface increased with the number of deposition cycles, indicating that the thickness of the deposited layered material became heterogeneous with increasing cycle number. For a given number of deposition cycles (i.e., similar mass loading), 1T'-MoS2 exhibited a lower overpotential for the HER than the 2H-MoS2 phase. For example, at a sample thickness of 19.7 ± 2.8 nm (20 LbL cycle) the overpotentials for the HER for 1T'-MoS2 and 2H-MoS2 were 0.54 and 0.61 V, respectively (at a current density of -2 mA/cm2). Overall, the overpotential for HER associated with both MoS2 phases decreased as the mass loading increased. Our study revealed the heterogenous formation of few layer 1T'-MoS2 on the surface, providing a novel approach to improve HER activity towards water splitting applications. A further research effort studied birnessite, focusing on the activity of exfoliated birnessite and the role of birnessite defects for water oxidation. The catalytic activity of layered MnO2 has been studied widely. Birnessite has the lowest oxygen evolution reaction (OER) activity in alkaline media compared to other manganese oxide phases. A motivation for the study was to investigate the OER activity of exfoliated-restacked birnessite sheets which can lead to a better understanding of the birnessite catalytic performance. Synthesized birnessite was exfoliated into monolayer sheets via a cation exchange method. Characterization of the birnessite monolayer sheets using AFM and scanning tunneling microscopy (STM) revealed the presence of the holes and point defects. The phase and conductivity of monolayer sheets were measured by STS. Electrochemical characterizations of exfoliated birnessite have shown that nanosheets of birnessite expose a great number of active sites and exhibit facile electrode kinetics as a result of the defective sheets. In particular, the overpotential of exfoliated birnessite synthesized at 400°C was 450 mV compared to 550 mV for the exfoliated birnessite synthesized at 1000°C. The results indicate that the defective exfoliated sheets have higher conductivity and higher OER activity compared to defect free exfoliated sheets. Additional research of birnessite focused on its activity for the arsenite (i.e., As(III)) oxidation reaction. Birnessite polytypes were synthesized by decomposition of KMnO4 at different temperatures, and three polytypes including two-layer orthogonal (2O), two-layer hexagonal (2H) and three-layer rhombohedral (3R) were identified in the samples. The synthetic temperature controlled the phase formation and heterogeneity of the phases. Birnessite synthesized at 600°C contained 2H/3R phases which showed the highest activity with first order rate constant of the 0.741 h-1 which is 3.6 and 24 times higher than Birnessite synthesized at 800 and 1000°C, respectively. The structural change of the polytype birnessite after As(III) oxidation was studied by pair distribution function experiment. Results indicated that Mn4+ in the birnessite was reduced to Mn3+ and that this reduced species migrated from the in-layer position to the interlayer region. Furthermore, we report the results of in-situ AFM of birnessite sheets exposed to arsenite which provides a detailed understanding of the arsenite oxidation reaction at the birnessite surface. The reductive dissolution of birnessite was shown to be more active on the edges compared to the basal plane of birnessite. Our findings have important implications for material design aimed at removal of arsenite in purification processes. / Chemistry

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外科手術後の癒着防止を目的としてゼラチンを使用した新規癒着防止材を開発した。ゼラチンを数種類の形状に加工し、その有用性を従来製材との比較のもとに検討した。実験により①熱架橋を行うことで性質を制御でき、様々な形状にも容易に加工できる。②創傷治癒を阻害することなく十分な癒着防止効果を持ち、従来製材では禁忌とされていた環境でも使用が可能である。③腹腔鏡手術でも使用可能な材型にも加工できるとの結果を得た。 / To prevent adhesion after surgical operation, we developed a new anti-adhesive material that is made of gelatin. We processed gelatin into several kinds of shapes and examined its usefulness compared with conventional materials. We got the result that ① it can be controlled properties by thermal crosslinking, and easily processed into various shapes ② It has sufficient anti-adhesive effects without inhibiting wound healing, and can be used the sites which are typically contraindicated for conventional materials. ③ it can be processed into a shapes that can be used also in laparoscopic surgery. / 博士(理学) / Doctor of Philosophy in Science / 同志社大学 / Doshisha University

Purpose: The purpose of this study was to evaluate the fracture strength of monolithic FDPs of multi-layered zirconia (YML) with different connector dimensions and placement in the disc. Material and method: Forty 3-unit monolithic anterior FDPs were produced, 212223, and divided in four groups (n=10) based on the different connector dimensions and strategies for placement in KATANATM Zirconia Yttria Multi-Layered (YML)-disc. The groups were as follows: EB12, produced with 12 mm  connector dimension and EB7, with 7 mm  connector dimension which were both placed in Enamel layer and Body layer 1 (flexural strength: 750 and 1000 MPa, respectively) in the disc, BB12, with 12 mm  connector dimension and BB7, produced with 7 mm  connector dimension both placed in Body layer 2 and 3 (both with 1100 MPa) in the disc. The specimens were artificially aged by 10 000 cycles in thermocycling. Then, one random specimen was selected from each group (4 in total) and cemented onto the model, subsequently loaded to fracture using a universal testing machine. The result was compiled and reported descriptively. Result: The FDP in group BB12 remained intact and fracturing only occurred in this model at 893 N. The FDP in group BB7 demonstrated the highest fracture strength (972 N), followed by EB12 (842 N) and EB7 which showed the lowest fracture strength (465 N). All these three FDPs broke mesially on the pontics. Conclusion: Within the limitations of this pilot study, the following conclusions can be drawn: the fracture strength of monolithic FDPs of multi-layered zirconia is affected by the connector dimension. Placement of FDPs with a small connector area should be avoided in the layers with lower strength. The choice of model material affects the result. / Syfte: Syftet med föreliggande pilotstudie var att undersöka brotthållfastheten påmonolitiska broar av flerskiktad zirkonia (YML) med olika konnektordimensioneroch placering i disken. Material och metod: Totalt framställdes 40 stycken 3-leds monolitiska anteriorabroar, 212223. Broarna delades in i 4 grupper (n=10) efter olikakonnektordimensionering och placering i KATANATM Zirconia YttriaMulti-Layered (YML)-disken. Grupperna var enligt följande: EB12 med 12 mm²konnektordimension och EB7 med 7 mm² konnektordimension där broarnaplacerades i både Enamel Layer och Body Layer 1 (med 750 respektive 1000 MPai böjhållfasthet) i disken. Broarna i grupperna BB12 med 12 mm²konnektordimension och BB7 med 7 mm² konnektordimension placerades i BodyLayer 2 och Body Layer 3 (med 1100 MPa böjhållfasthet för respektive lager) idisken. Broarna genomgick termocykling, 10 000 cykler. Därefter valdes fyrabroar slumpmässigt ut, en bro från varje grupp, och cementerades på modell.Slutligen genomfördes ett brotthållfasthetstest med en universaltestmaskin tillsfraktur uppstod. Resultatet sammanställdes och redovisades deskriptivt. Resultat: Bron i grupp BB12 förblev intakt och fraktur skedde enbart i modellen(893N). Bron i grupp BB7 visade högst brotthållfasthet: 972N, följt av bron igrupp EB12 som visade brotthållfasthet på 842N och bron i grupp EB7 påvisadeden lägsta brotthållfastheten: 465N. Dessa tre broar frakturerade mesialt på dethängande ledet. Slutsats: Inom ramen för föreliggande pilotstudies begränsningar kan följandeslutsatser dras: brotthållfastheten på monolitiska broar i flerskiktad zirkoniapåverkas av konnektordimensioneringen. Placering av broar med mindrekonnektorarea än rekommendationen ska undvikas i skikten med lägre hållfasthet.Valet av modellmaterial har betydelse och påverkar resultatet.

A green synthesis method for the synthesis of hydrotalcite has been previously developed but this process has not yet been optimised. The main focus of this dissertation was on aluminium-based LDHs. The purpose of this investigation were; to determine optimum synthesis conditions for the formation of hydrotalcite using the dissolution-precipitation method and to determine the possibility of partial substituting the divalent metal species in hydrotalcite and hydrocalumite with other metal species. During the optimisation process for the formation of hydrotalcite using the dissolution precipitation method, the formation of hydromagnesite was proved to be dominant reaction at lower reaction temperatures. With the increase in reaction time and temperature the decomposition of hydromagnesite occurred to form magnesite. At low temperatures the formation of Mg-Al-CO3 LDH is limited due to the low solubility of gibbsite. Mg-Al-CO3 LDH formation of 80 % was achieved at 140 oC after 2 hours reaction time, but crystallinity was low. To achieve an Mg-Al-CO3 LDH conversion higher than 96 % a reaction temperature of 160 oC for a minimum of 4 hours is required, but is achieved within 1 hour at 180 oC. A 99.37 % conversion was achieved at 180 oC for 5 hours with a high crystallinity and homogeneity. The surface area for Mg-Al-CO3 LDH at 180 oC after 5 hours reaction time proved to be 9.19 m2/g. The average particle size obtained for a high crystalline LDH was in the range of approx. 3 μm and 6.8 μm at temperatures of 160 oC and above for a minimum of 3 hours reaction time. The following are recommended for future work:  Determine the effect of mixing speed on the shape of the platelets.  Determine the difference between freshly precipitated metal oxides/hydroxides as reagents compared to aged metal oxides/hydroxides. The presence of Mg(OH)2 and Ca(OH)2 in solution (respectively) did increase the pH enough for the dissolution of gibbsite and most of the Mx+ metal species. A reaction time and temperature of 5 hours at 180 oC in a carbonate environment proved to be close to the ideal conditions for the formation of Mg/Mo-Al-CO3 LDH and Mg/Zn-Al-CO3 LDH. The results for the formation of Mg/Ti-Al-CO3 LDH were inconclusive. Isolation of the possible Mg/Ti-Al-CO3 LDH is recommended to determine the degree of substitution. The conditions for the dissolution of the metal species for the following experiments were proven to be successful:  Ca/Mn(lV)-Al  Ca/Mo-Al  Ca/Ni-Al  Ca/Ti-Al The following recommendations are made for the improvement on the formation of an Mx+-impregnated LDH/precursor:  Determine the effect of different reaction time and temperature.  Determine the effect of adding the carbonate source at temperatures above 100 oC under pressure.  Determine the effect of synthesising at different pH conditions. Cobalt and tin showed no/negligible amount of possible solubility. / Dissertation (MSc)--University of Pretoria, 2014. / Chemical Engineering / MSc / Unrestricted

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