Finding luminescent materials with narrow-band emissions, high stability, and high photoluminescence quantum yield (PLQY), yet relatively fast radiative decay rates, has been an outstanding research challenge. This thesis aims to develop different luminescent materials and examine their structural and optical properties for light-emitting applications. The first part of this thesis covers the controversy regarding the origin of emission in zerodimensional perovskites (0D), Cs4PbBr6 and Cs4PbI6, through a comparative analysis between 0D and three-dimensional (3D) perovskites. A series of optical studies excluded the 3D phases as the origin of emission in these materials. In parallel, the results from the DFT proposed the defects as a possible origin of emission. The second part of the thesis addresses the shortcoming of lead-based perovskites in terms of toxicity and stability, motivated by the high demand for sustainable materials with analogous electrical and structural properties. Thus, a series of solid-state Zn-based and Mn-based ternary compounds were investigated with and without doping. The compounds' photoluminescence peaks were between 520 nm – 525 nm, with PLQY between 34% -60%. Finally, CsMnBr3 NCs were synthesized revealing an intense red PL peak centered at 650 nm and a PLQY as high as 54% along with a remarkable excitation spectrum and surprisingly short lifetimes. The single crystals of this composition were also reported with a PL peak at 640 nm and a relatively high PLQY of 6.7% under the excitation at 360 nm. Further, a combination of structural and optical analysis attributed the green and red luminescence to the tetrahedral and octahedral environment of Mn2+, respectively. These materials represent a milestone towards lead-free luminescent materials with interesting optical properties. This dissertation aims at engineering different materials to address critical aspects in the field including stability and good luminescence properties while simultaneously examining the photophysics and mechanisms of the corresponding properties. This work paves the way for finding sustainable light-emitting materials for the next generation of light-emitting applications.

The present study was designed to investigate the role of pre- and postnatal manganese (Mn) exposure on hydroxyl radical (HO•) formation in the brains of dopamine (DA) partially denervated rats (Parkinsonian rats). Wistar rats were given tap water containing 10,000 ppm manganese chloride during the duration of pregnancy and until the time of weaning. Control rat dams consumed tap water without added Mn. Three days after birth, rats of both groups were treated with 6-hydroxydopamine at one of three doses (15, 30, or 67 µg, intraventricular on each side), or saline vehicle. We found that Mn content in the brain, kidney, liver, and bone was significantly elevated in dams exposed to Mn during pregnancy. In neonates, the major organs that accumulated Mn were the femoral bone and liver. However, Mn was not elevated in tissues in adulthood. To determine the possible effect on generation of the reactive species, HO• in Mn-induced neurotoxicity, we analyzed the contents of 2.3- and 2.5-dihydroxybenzoic acid (spin trap products of salicylate; HO• being an index of in vivo HO• generation), as well as antioxidant enzyme activities of superoxide dismutase (SOD) isoenzymes and glutathione S-transferase (GST). 6-OHDA-depletion of DA produced enhanced HO• formation in the brain tissue of newborn and adulthood rats that had been exposed to Mn, and the latter effect did not depend on the extent of DA denervation. Additionally, the extraneuronal, microdialysate, content of HO• in neostriatum was likewise elevated in 6-OHDA-lesioned rats. Interestingly, there was no difference in extraneuronal HO• formation in the neostriatum of Mn-exposed versus control rats. In summary, findings in this study indicate that Mn crosses the placenta but in contrast to other heavy metals, Mn is not deposited long term in tissues. Also, damage to the dopaminergic system acts as a “trigger mechanism,” initiating a cascade of adverse events leading to a protracted increase in HO• generation, and the effects of Mn and 6-OHDA are compounded. Moreover, HO• generation parallels the suppression of SOD isoenzymes and GST in the brains of rats lesioned with 6-OHDA and/or intoxicated with Mn—the most prominent impairments being in frontal cortex, striatum, and brain stem. In conclusion, ontogenetic Mn exposure, resulting in reactive oxygen species, HO• formation, represents a risk factor for dopaminergic neurotoxicity and development of neurodegenerative disorders.

No description available.

The effect of neonatal manganese (Mn) exposure in a 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease was investigated. Pregnant Wistar rats were given drinking water with 10,000ppm of Manganese (MnCl2.4H2O) from the time of conception until weaning on the 21st day after delivery. Control rats consumed tap water. Three days after the birth, other groups of neonatal rat pups were pretreated with desipramine (20mg/kg ip 1h) prior to bilateral ICV administration of 6-OHDA or its vehicle, saline-ascorbic (0.1%) (control). Two months after the birth, striatal dopamine and homovanilic acid efflux measured by an in vivo microdialysis method were reduced in rats lesioned with 6-OHDA. Co-exposure to perinatal Mn did not modify neurotransmission alterations. However, there were prominent abnormalities in behavioral testing in rats perinatally exposed to Mn and treated neonatally with 6-OHDA. These findings demonstrate that although Mn did not further damage neurotransmitter activity in the neostriatum, ontogenetic exposure to Mn enhances the behavioral toxicity to 6-OHDA.

Rats lesioned shortly after birth with 6-hydroxydopamine (6-OHDA; 134 μg icv) represent a near-ideal model of severe Parkinson's disease because of the near-total destruction of nigrostriatal dopaminergic fibers. There are scarce data that in Parkinson's disease, activity of the central histaminergic system is increased. The element manganese, an essential cofactor for many enzymatic reactions, itself in toxic amount, replicates some clinical features similar to those of Parkinson's disease. The aim of this study was to examine the effect of neonatal manganese exposure on 6-OHDA modeling of Parkinson's disease in rats, and to determine effects on histamine content in the brain of these rats in adulthood. Manganese (MnCl 2•4H 2O; 10,000 ppm) was included in the drinking water of pregnant Wistar rats from the time of conception until the 21st day after delivery, the age when neonatal rats were weaned. Control rats consumed tap water. Other groups of neonatal rat pups, on the 3rd day after birth, were pretreated with desipramine (20 mg/kg ip 1 h) prior to bilateral icv administration of 6-OHDA (60 or 134 μg) or its vehicle saline-ascorbic (0.1%) (control). At 2 months after birth, in rats lesioned with 60 or 134 μg 6-OHDA, endogenous striatal dopamine (DA) content was reduced, respectively, by 92 and 98% (HPLC/ED), while co-exposure of these groups to perinatal manganese did not magnify the DA depletion. However, there was prominent enhancement of histamine content in frontal cortex, hippocampus, hypothalamus, and medulla oblongata of adult rat brain after 6-OHDA (60 and 134 μg) injection on the day 3rd postnatal day. These findings indicate that histamine and the central histaminergic system are altered in the brain of rats lesioned to model Parkinson's disease, and that manganese enhances effects of 6-OHDA on histamine in brain.

In situ chemical oxidation using permanganate is an approach to organic contaminant site remediation. Manganese dioxide particles are products of permanganate reactions. These particles have the potential to deposit in the subsurface and impact the flow-regime in/around permanganate injection, including the well screen, filter pack, and the surrounding subsurface formation. Control of these particles can allow for improved oxidant injection and transport and contact between the oxidant and contaminants of concern. The goals of this research were to determine if MnO2 can be stabilized/controlled in an aqueous phase, and to determine the dependence of particle stabilization on groundwater characteristics. Bench-scale experiments were conducted to study the ability of four stabilization aids (sodium hexametaphosphate (HMP), Dowfax 8390, xanthan gum, and gum arabic) in maintaining particles suspended in solution under varied reaction conditions and time. Variations included particle and stabilization aid concentrations, ionic content, and pH. HMP demonstrated the most promising results, as compared to xanthan gum, gum arabic, and Dowfax 8390 based on results of spectrophotometric studies of particle behavior, particle filtration, and optical measurements of particle size and zeta potential. HMP inhibited particle settling, provided for greater particle stability, and resulted in particles of a smaller average size over the range of experimental conditions evaluated compared to results for systems that did not include HMP. Additionally, HMP did not react unfavorably with permanganate. These results indicate that the inclusion of HMP in a permanganate oxidation system improves conditions that may facilitate particle transport.

Two types of (polymer-imaging agent-drug) complexes were prepared and characterized. These included block and graft copolymer complexes with magnetite nanoparticles and manganese ions. Magnetite block ionomer complexes (MBICs) were formed through binding of a portion of the anionic segment of poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA) block copolymers with the magnetite nanoparticle surfaces. The remainder of the carboxylic acids were utilized to bind with high concentrations of the cationic antibiotic gentamicin (31 wt%). A near zero-order release of gentamicin (pH 7.4 in PBS) that reached ~35 wt% of the initial gentamicin within 10 hours was observed, and this was followed by slower release of another 7 % by 18 hours. These nanoparticles were efficiently taken up by macrophages and appeared to enhance intracellular antimicrobial activities of gentamicin. To increase the complex sizes and NMR T2 relaxivities, amine functional MBICs (MBICs-NH2) were first assembled by adsorbing the polyacrylate block of an aminofunctional poly(ethylene oxide)-b-poly(acrylic acid)) (H2N-PEO-b-PAA) copolymer onto magnetite nanoparticles. Amines at the tips of the H2N-PEO corona were then linked through reaction with a PEO diacrylate oligomer to yield MBIClusters where the metal oxides in the precursor nanoparticles were distinctly separated by the hydrophilic polymer. These MBIClusters with hydrophilic intra-cluster space had transverse relaxivities (r2's) that increased from 190 to 604 s-1 mM Fe-1 measured at 1.4 T and 37°C as their average sizes increased. The clusters were loaded with up to ~38 wt% of the multi-cationic drug gentamicin. MRI scans focused on the livers of mice demonstrated that these MBIClusters are very sensitive contrast agents. These results indicate that these complexes could be potential theranostic agents for dual imaging and drug delivery. Manganese graft ionomer complexes (MaGICs) comprised of Mn ions and a novel polyaminobisphosphonate-g-PEO copolymer were developed for use as T1 weighted MRI positive contrast agents. The graft copolymers were prepared by free radical copolymerization of ammonium bisphosphonate methacrylate monomers with PEO-acrylate macromonomers. The complexes exhibited good colloidal stability without release of free manganese and did not show any in vitro toxicity against mouse hepatocytes. The T1 relaxivities of the MaGICs were 2-10 times higher than that of a commercial manganese based contrast agent MnDPDP. These MaGICs with encapsulated anticancer drugs including doxorubicin, cisplatin and carboplatin have encapsulation efficiencies of 80-100 %. Drug release was sustained and depended on environmental pH, drug structure and drug concentration in the MaGICs. Moreover, these drug-loaded complexes exhibited high anticancer efficacy against MCF-7 breast cancer cells. The prominent MRI relaxivities and high anticancer efficacy suggest that these MaGICs have potential as effective dual imaging and chemotherapeutic agents. / Ph. D.

Thallium (Tl) is a rare heavy metal in drinking water, but its extreme toxicity makes its removal crucial to consumer health. Traditional treatment methods do not work for Tl in sources with high concentrations of ions like calcium (Ca+2) and potassium (K+), as they are removed preferentially to Tl. A treatment method that specifically targets Tl must be applied. Pilot studies conducted in Park City Utah found that pyrolusite, a manganese oxide ore, will remove Tl to very low concentrations in the presence of competing ions but because this method is not common, further study was required. This study investigated the mineral composition of the pyrolusite and where, within the material, Tl was held. Calcite is known to accumulate Tl so tests were done looking at Tl accumulation onto pyrolusite with and without calcite on the surface in three water qualities: one with high pH and chlorine (Cl2) and low concentrations of the interfering ions Ca, K, chloride (Cl-) predicted to promote Tl removal, one with low pH and Cl2 and high concentrations of interfering ions predicted to limit Tl removal, and one with a moderate pH used for comparison. The likelihood of this Tl to stay on the media surface with changes in water chemistry was also tested. It was seen that Tl does accumulate in calcite on the media surface. Both pyrolusite media showed a high capacity for Tl and media without calcite exhibited a preference for Tl over K. Calcite dissolved with changes in pH which led to the conclusion that its formation on the media surface must be closely monitored as it may increase the risk Tl release into the drinking water system.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第21386号 / エネ博第374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基礎科学専攻 / (主査)教授 片平 正人, 教授 森井 孝, 准教授 小瀧 努 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

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