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Arsenic (As) appears in the environment as various As species, which may vary in plant uptake and toxicity. Moreover, As exposure may vary between habitat due to availability and speciation, both of which are influenced by redox potential. To decrease As uptake, addition of silicate may be a tool. The aim of the study was to investigate how the external factors As availability, plant habitats, silicon and oxygen level, influenced the accumulation and speciation of As in plants for food and phytoremediation in a temperate region. The external factors were chosen due to their previously showed influence on As in plants. The risks with dietary As was investigated by plant As accumulation and speciation in carrot, lettuce and spinach grown in alum shale and glassworks soils, and by the influence of silicon on As accumulation in lettuce in hydroponics. Suitable plants for As phytoremediation was investigated by analysing plants from various habitats, and by the O2 influence on phytofiltration. The results showed that vegetables accumulated more As in soils with higher As extractability, and the As extractability in the rhizosphere was higher than in bulk soil. Also, the As concentration in lettuce was higher in hydroponics than in soil, but silicon reduced the accumulation of As in lettuce in hydroponics. Also, the more toxic inorganic As were the main As species detected in vegetables, compared with the less toxic organic As. For phytoremediation, the results showed a low As accumulation in emergent and terrestrial plants. Submerged plants had had a higher shoot As concentration. In general, the habitat had a major influence on the As accumulation in plants. The results also showed that the As accumulation properties in Elodea canadensis was reduced at higher O2. In conclusion, consumption of vegetables cultivated in As polluted soils can result in an elevated intake of inorganic As, and E. canadensis is a promising candidate for As phytofiltration in a temperate region. / <p>At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 2: Manuscript; Paper 4: Manuscript; Paper 5: Manuscript.</p>

<div> <p>Fluorescent proteins and the biosensors created with them have been used extensively to monitor chemical species inside and outside of the cell. They have been used to increase our knowledge of cellular function in normal and diseased states. Fluorescent biosensors are advantageous because they can be genetically encoded, do not require exogenous reagents, and can be quantitative. Fluorescent biosensors are also able to measure analytes with high spatial and temporal resolutions, enabling measurements at the scale of physiological events. In this thesis efforts have made to increase the available fluorescent biosensor tools for imaging cellular events. This work includes creation of new sensors for two molecules not yet detectable via fluorescent protein biosensor, acetylcholine and adenosine diphosphate. Efforts were also made to improve the current available biosensors for adenosine triphosphate and cellular redox, to make them more compatible with multiplex and deep tissue imaging. Here I present my work to design, characterize and utilize these fluorescent biosensors.</p> </div> <br>

Indigo N,N’-diarylimine (Nindigo) and indigo N-arylimine (Mindigo) are redox-active ligands which exhibit near-infrared absorption and can accommodate up to five ligand charge states. This dissertation explores the coordination chemistry of these ligands to further understand the role that metal-ligand combinations play on ligand-centered properties, which include electrochemical potentials, UV-Vis-NIR absorption, pKa values, hydricities, and NH bond strengths at different ligand charge states. A series of cis-Nindigo palladium complexes containing acetylacetonate (acac) and hexafluoroacetylacetonate (hfac) ligands were synthesized. The acac complexes were easier to oxidize by 0.11 to 0.16 V and absorbed at lower wavelengths compared to their hfac analogues. Complexes using indigo bis(4-methylphenylimine) were more easily reduced than complexes of indigo bis(2,6-dimethylphenylimine). Cis- and trans-Mindigo complexes of palladium acac and hfac were synthesized as the first coordination complexes of Mindigo. Trans-Mindigo complexes were more difficult to reduce by 0.33 to 0.37 V and absorbed at lower wavelengths than their cis-Mindigo counterparts. Cis-Mindigo complexes were easier to reduce and harder to oxidize than the corresponding cis-Nindigo complexes. The NH bond strengths of cis-Nindigo complexes containing Pd(acac) and Ru(bipy)2 (bipy = 2,2’-bipyridyl) fragments were determined through a potential-pKa diagram in tetrahydrofuran and acetonitrile, respectively. The NH bond strength and hydricity values of the Pd(acac) complex were comparable to the values of diaryl amines. The NH bond strength and hydricity of the Ru(bipy)2 complex were substantially smaller due to the lower oxidation potentials of this complex. In both cases, the ligand’s NH bond strengths were not affected greatly by the ligand’s charge state. Ru(acac)2 complexes of neutral, aprotic cis-Nindigo and cis-Mindigo ligands were synthesized. The Nindigo/Mindigo ligand could be protonated, and the resulting complexes demonstrated substantial temperature dependence of some of their 1H NMR chemical shifts. The NH bond strengths and hydricities of the Ru(acac)2 complexes were determined using cyclic voltammetry and pKa measurements. The NH bond strengths and hydricities of these complexes are substantially smaller than the Pd(acac) and Ru(bipy)2 complexes. Collectively, these results show that Nindigo and Mindigo can act as both a proton and electron reservoirs, and the thermodynamics of proton and electron transfer can be tuned through the choice of metal and ligand combinations. / Graduate / 2020-07-17

INTRODUCTION: Physiologic and pathophysiologic inflammation is mediated, at least in part, by the generation and release of reactive oxygen species into the local tissue milieu. The chronic inflammation observed in patients with inflammatory bowel disease (IBD) is thought to begin in the lining of the intestine and may progress to involve the entire bowel wall.In an effort to assess disease activity, clinicians rely on costly and technically invasive procedures such as colonoscopies. As such, there is currently a need for the development of less invasive and more cost-effective methods for use in the diagnosis and interval assessment of children and adults with these chronic intestinal inflammatory disorders. OBJECTIVES: The objective of this study was to first determine if ambient redox status can be reliably measured in the stool of patients with IBD. A second aim of the study was to determine if ambient stool redox status was related to underlying diagnosis, clinical disease activity, or response to therapy in patients with IBD . METHODS: We first our ability to measure redox redox standards using three different commercially available devices. Once demonstrated, we then the process of performing sample analysis under various conditions (room tempererture, refrigerated, frozen, or spun/unspun) to determine the conditions under which we were able to achieve the most stable redox assessments. Finally, we conducted a small pilot cohort study in hospitalized pediatric patients with IBD to assess if stool redox status informed about disease activityWe collected stool samples from seven patients admitted to the inpatient gastrointestinal service at Boston Children’s Hospital during a period extending from November of 2018 to March of 2019. RESULTS: Preliminary studies confirmed our ability to accurately measure relative redox status (RRS) using three different apparatuses. Furthermore, we were able to generate dilution curves using juices known to include oxidants, with linear regression r2 values of 0.99. In our patient population, we confirmed our ability to generate a reliable readings and consistent RRS measurements over. Frozen samples displayed less stable and higher RRS than those either refrigerated or kept at room temperature for up to 8-hours. This suggests that freeze-thaw cycles may impact adversely on the stability of oxidants and antioxidants in our samples. The RRS measurements from stool samples collected from patients who were exhibiting active symptoms of their IBD measured about -400 mV, while samples collected from hospitalized patients without IBD manifest RRS readings of about 100 mV. CONCLUSION: This preliminary study demonstrates our ability to measure RRS in the stool of patients with and without IBD. The stability we observed in samples that were either stored at room temperature or refrigerated demonstrated that these represented optimal storage options. Additionally, measurements from homogenized stool samples appeared to be more variable when compared to the relatively smaller range from centrifuged samples. Initial studies indicated a strong difference in RRS measurements between patients with inflammatory and non-inflammatory GI disease or inactive IBD. This difference suggests that measurements of RRS could provide a quantitative real-time assessments of disease activity and response to therapy in patients with IBD.

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Thesis advisor: Udayan Mohanty / Rechargeable batteries, especially lithium ion batteries, have greatly transformed mobile electronic devices nowadays. Due to the ever-depletion of fossil fuel and the need to reduce CO2 emissions, the development of batteries needs to extend the success in small electronic devices to other fields such as electric vehicles and large-scale renewable energy storage. Li-ion batteries, however, even when fully developed, may not meet the requirements for future electric vehicles and grid-scale energy storage due to the inherent limitations related with intercalation chemistry. As such, alternative battery systems should be developed in order to meet these important future applications. This dissertation presents our successes in improving Li-O2 battery performance for electric vehicle application and integrating a redox flow battery into a photoelectrochemical cell for direct solar energy storage application. Li-O2 batteries have attracted much attention in recent years for electric vehicle application since it offers much higher gravimetric energy density than Li-ion ones. However, the development of this technology has been greatly hindered by the poor cycling performance. The key reason is the instability of carbon cathode under operation conditions. Our strategy is to protect the carbon cathode from reactive intermediates by a thin uniform layer grown by atomic layer depostion. The protected electrode significantly minimized parasitic reactions and enhanced cycling performance. Furthermore, the well-defined pore structures in our carbon electrode also enabled the fundamental studies of cathode reactions. Redox flow batteries (RFB), on the other hand, are well-suited for large-scale stationary energy storage in general, and for intermittent, renewable energy storage in particular. The efficient capture, storage and dispatch of renewable solar energy are major challenges to expand solar energy utilization. Solar rechargeable redox flow batteries (SRFBs) offer a highly promising solution by directly converting and storing solar energy in a RFB with the integration of a photoelectrochemical cell. One major challenge in this field is the low cell open-circuit potential, mainly due to the insufficient photovoltages of the photoelectrode systems. By combining two highly efficient photoelectrodes, Ta3N5 and Si (coated with GaN), we show that a high-voltage SRFB could be unassistedly photocharged and discharged with a high solar-to-chemical efficiency. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.