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Title: ENGINEERING 2D PHOTO-REACTING COF FOR PATTERNING AND DRUG DELIVERY
Creator: Chen, Kuo Hao
Date: 2017, 2017-07
Description: Covalent Organic Frameworks (COFs) are 2-dimensional polymers that exhibit rigid and large surface area as well as porous architectures....
Show moreCovalent Organic Frameworks (COFs) are 2-dimensional polymers that exhibit rigid and large surface area as well as porous architectures. Currently, COFs are tailored for gas storage applications, drug delivery, catalysis and they are used as filtering membranes for water treatment. It is well documented that at the nano/micro scale, COFs can form multi-layered architecture with respect to the basic molecular building blocks. In this picture, it is possible that the 2D intra-layer and 3D inter-layer interactions of the basic molecular units COFs may dictate the overall efficiency of the aforementioned applications. To understand the dimensionality-function relationship of COFs, we are engineering hybrid 1D-2D organic polymers. This hybrid architecture will allow us to study the propagation of energy/exciton transfer within the resulting materials among other applications such as drug delivery and light-induced nano/micro-patterning. To achieve our objectives, I exploited the photo-reacting properties of two molecular systems: The first system is used to prepare the 2D COF of interest and the other system is used to engineer a 1D crystalline solid. Although I have not tested the energy/exciton propagation with the desired material, I have successfully engineered a 1D crystalline solid and synthesized the expected 2D COFs. Using a combination of synthetic strategies, I prepared and characterized photoreacting tetra-phenyl ketone building block that was used to form the desired polymer. I have also engineered 1D needle-like crystals of bisphenyl cyclopropenone compound. Moreover, the two materials were characterized by optical and electron microscopy methods. This thesis will detail the synthesis and characterization of all precursors of the basic molecular units that were used to engineer the 1D crystalline solid and 2D COF materials. Condignly, the optical and scanning electron microscopy images highlight the microscale features of the materials of interest. I am certain that this preliminary investigation will pave the way to study the dimensionality of energy/exciton transfer and reaction propagation in the many organic materials.
M.S. in Chemistry, July 2017
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Title: CHEMISTRY OF BUCKYBOWL FROM CLOSED-SHELL TO OPEN-SHELL
Creator: Li, Jingbai
Date: 2019
Description: Buckybowl is an open geodesic polyaromatic molecule with unevenly distributed π-electron on its convex and concave surface, which leads to a...
Show moreBuckybowl is an open geodesic polyaromatic molecule with unevenly distributed π-electron on its convex and concave surface, which leads to a readily accessible π-surface for substitution reactions and complexation with various metals. Despite the diverse structures of buckybowl complexes observed in the previous experimental study, our computational work has shown that the π-surface of buckybowl always plays the most important role in the bonding. Modification of the π-surface by changing the size of conjugation and the curvature enable us to tune the bonding preference of the buckybowl surface and the stability of the complex. Our continued study has shown similar importance of the π-surface in functionalization of buckybowl with different electrophilic groups. Surprisingly, our investigation on buckybowl cations intrigued an original perspective of aromatic behavior of the π-surface. Our results have revealed an intrinsic nature of aromatic stabilization in polyaromatic cations, which is mainly attributed to the depletion of anti-aromaticity at the center ring. Further study showed an explicit correlation between the curvature of π-surface and the stability of adducts, aromatic behavior at center ring, as well as the spin distribution over polyaromatic moiety. By curving the π-surface, we have proposed several buckybowl radical adducts and confirmed their stability. These models provide an alternative strategy of developing polyaromatic spin carriers, which have a great potential in the manufacture of quantum bits. We believe our comprehensive theoretical study on versatile chemistry of buckybowl and related polyaromatic hydrocarbons can offer fundamental understanding and essential guidance for developing buckybowl-based electrode materials in the lithium-ion battery, organometallic building block, and spin electronic devices.
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Title: NANOSTRUCTURED SULFUR COMPOSITE CATHODES FOR LITHIUM-SULFUR BATTERIES
Creator: Dunya, Hamza
Date: 2018
Description: Since the high demand for clean and efficient energy is the main motivation in the research of renewable energy, there have been extensive...
Show moreSince the high demand for clean and efficient energy is the main motivation in the research of renewable energy, there have been extensive studies on secondary lithium batteries. As a part of this initiative, lithium-ion batteries (LIBs) were introduced by Sony Corporation in 1991. Currently, LIBs are exclusively used in portable devices, such as laptops and cell phones. In the last decade, LIBs have also been widely used in hybrid electric vehicles (HEVs). However, state of the art has reached its limitation barriers due to high cost and low specific energy density. Lithium-sulfur batteries (LSBs) are considered promising next-generation energy storage systems due to high theoretical specific capacity and specific energy,1675 mAh g-1 and 2500 Wh g-1, respectively. The elemental sulfur as cathode material in LSBs is inexpensive, nontoxic, and abundant on the earth.Although LSBs have many advantages mentioned above, there are many challenges for commercialization of LSBs. The main roadblock is polysulfide shuttle (PSS), which is the migration of discharged lithium polysulfide intermediates from the cathode to the anode, leading to fast capacity fading and low Coulombic efficiency. Other important issues include volume change of sulfur during discharge (~80% expansion) and the insulating nature of sulfur.This dissertation describes two different approaches to achieve a decreased polysulfide shuttle effect for lithium-sulfur batteries; first approach, major focus, is nanostructured dual core-shell sulfur cathode composites and second is to design and synthesize new solvents as the electrolyte additives. For the cathode study, we synthesized two shells in the core-shell design. The inner shell was used as the carbon material (nanospheres and nanorods) to enhance the electrical conductivity of the cathode matrix. The outer shell was polysulfide retention materials (g-C3N4, TiO2, AlF3, and MnO2). g-C3N4, TiO2, and AlF3 coatings were used with hollow carbon nanospheres and MnO2 was coated on the nitrogen-doped hollow carbon nanorods. Significant enhancement in capacity retention was observed for all polysulfide resistant coated materials. g-C3N4-coated composite displayed the highest specific capacity among the materials with hollow nanosphere design. The nitrogen-doped hollow carbon nanorod coated with MnO2 displayed one of the highest initial discharge capacities reported in the literature. For electrolyte study, we designed and synthesized four new fluoroether sulfones as the electrolyte via Michael addition reaction of divinyl sulfone and fluoro alcohols to decrease the dissolution of polysulfides intermediates.
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Title: DESIGN, SYNTHESIS AND CHARACTERIZATION OF NOVEL MATERIALS TO CONSTRUCT HIGH-ENERGY-DENSITY RECHARGEABLE CELLS
Creator: Yue, Zheng
Date: 2018
Description: ABSTRACTRechargeable electrical energy storage cells, especially lithium-ion cells, are the critical technology that realized the great...
Show moreABSTRACTRechargeable electrical energy storage cells, especially lithium-ion cells, are the critical technology that realized the great development of the portable electronic devices, such as laptop computers and cell phones. But in some other areas, such as the renewable energy industries and electrical vehicles, which are developing fast and more and more important for environment protection, the current rechargeable energy storage cells cannot meet their requirements, because of their limited energy density.Two types of cells, lithium sulfur batteries (LSBs) and supercapacitors, are attracting peoples’ attention for their potential to be developed as the future high-energy-density rechargeable cells. However, Li-S batteries are suffering from the fast discharging capacity fading, which is still a barrier for the large-scale commercialization. Although supercapacitors have been widely used in various areas, their energy density is much lower than current lithium-ion batteries, which limited their application only in assistant systems, such as regenerative brakes.To solve these problems, novel design for both the electrode material and electrolytes are required. In this thesis work, we focused our study in four areas: (1) New electrolytes for LSBs; (2) Cathode material for LSBs; (3) Activated carbon electrodes for electrical double layer capacitors (EDLCs); and (4) Electrolyte formulations for EDLCs. We investigated three types of new compounds as a co-solvent for the electrolyte of LSBs: fluorinated ethers, fluoroether sulfones and sulfonium ILs, which have improved the discharging capacity and cycling stability of LSBs. A novel S@HCN@MnO2 cathode material was designed and synthesized, which performed excellent long-term performance. A novel porous AC material with very high SSA was synthesized, and EDLCs with new electrolyte formulations were tested, which showed wide electrochemical potential window and high energy density.
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Title: Efficiency of Stratification for Ensemble Reduction based on docking scores
Creator: Zhang, Hexi
Date: 2018
Description: Molecular docking has been widely used in structure-based drug design to virtually screen large chemical libraries to predict the prefer...
Show moreMolecular docking has been widely used in structure-based drug design to virtually screen large chemical libraries to predict the prefer conformations ligands that could bind the target site. Protein flexibility is a major issue that could be solved by ensemble docking which is docking to ‘ensemble’ of protein rigid conformations, such as snapshots obtained by molecular dynamics simulations. Our group has developed a method called ‘Efficiency of Stratification’ to evaluate a number of common snapshot selection strategies using a quality metric from stratified sampling (Xie et al. [19]). Docking was performed to four proteins and with each ligand numbers sets of up to five hundred ligands. In this paper, we generated distance matrices based on docking score to analysis the performance of the efficiency of stratification method. We observed that most docking score based score-based distance matrices have had better performance than structure-based distance matrices and with including any structure-based component overwhelms the docking-score component. Only a few ligands are required to get a good distance matrix.
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Title: Small Molecule Ligands and Antibody Drug Conjugates for Potential Application in Targeted Cancer Therapy and PET Imaging
Creator: Ren, Siyuan
Date: 2020
Description: Cancer has been a deadly disease threatening humans. Traditional treatment methods such as chemotherapy with non-specific targeting may cause...
Show moreCancer has been a deadly disease threatening humans. Traditional treatment methods such as chemotherapy with non-specific targeting may cause severe side effects to normal cells and tissues. Novel and better methods for treatment and imaging of cancer has been eagerly sought. We wanted to develop new small molecule inhibitors and antibody drug conjugates for targeted cancer therapy and imaging. Theranostic conjugates combining therapeutic entity and imaging agent are useful in treatment and diagnosis of cancer. We designed a theranostic conjugate containing iron chelating anti-tumor agent and optical imaging probe. Novel iron chelator CAB-NE3TA displayed significant anti-proliferation activity against several cancer cell lines and was conjugated to targeting antibody panitumumab (PAN). The therapeutic conjugate exhibited excellent anti-tumor efficacy and targeting ability to EGFR overexpressed on cancer cells such as skin cancer (A431). The theranostic conjugate CAB-NE3TA-PAN loaded with a near IR fluorescent dye provided promising anti-tumor efficacy and optical imaging in tumor-bearing mice. Tetrahydroisoquinoline (THIQ) analogues were synthesized and evaluated for cytotoxicity against different cancer cell lines. Our in vitro studies showed that the THIQ analogues exhibited anti-proliferative activities against multiple cancer cell lines. Cytotoxicity study revealed that anti-tumor activity of THIQ analogues are structure-dependent. Binding affinity between THIQ analogues and a potential target Tdp1 was determined. Positron emission tomography (PET) has been used in diagnosis of cancer. In this study, small molecules and chelators with potential donor groups were evaluated systematically for complexation with 89Zr for PET imaging. New ligands with different donors were evaluated for radiolabeling efficiency and complex stability with 89Zr. The theranostic conjugate (CAB-NE3TA-PAN-IR800) and small molecule THIQs and 89Zr-chelators showed encouraging results for potential applications in for therapy and imaging of cancer.
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Title: HIGH SURFACE AREA CARBONS FOR ENERGY STORAGE TECHNOLOGIES
Creator: Lee, Youngjin
Date: 2021
Description: Energy storage systems play a pivotal role in harvesting energy from various sources and converting it to the energy forms required for...
Show moreEnergy storage systems play a pivotal role in harvesting energy from various sources and converting it to the energy forms required for applications in several sectors, such as utility, industry, building and transportation. The outstanding growth of portable electronic devices and electric vehicle/hybrid electric vehicles (EVs/HEVs) has promoted the urgent and increasing demand for high‐power energy resources. The most common electrical energy‐storage device is the battery due to the large amount of energy stored in a relatively small volume and weight while providing suitable levels of power for many applications and requirements of everyday life. These days, lithium-sulfur batteries (LSBs) have been drawing attention with their potential to provide 3-5 times more energy than that of current lithium-ion batteries (LIBs) at lower cost. Thus, realization of a practical Li-S technology can move the U.S. rapidly toward a more sustainable transportation future. The electrochemical double-layer capacitor (EDLC) is also an emerging technology, which really plays a key part in fulfilling the demands of electronic devices and systems, for present and future. The EDLC technology strongly depends on the properties of electrode materials. Activated carbons play an important role in developing new electrodes for both LSB and supercapacitor technologies. For example, carbon electrode-based supercapacitors require very high specific surface area and superior pore size distribution for easy accessibility of ions. Thus, the primary objective of this study is to develop a new high surface area carbon material and assess its applicability for both LSB and supercapacitor technologies. In this thesis work, we have designed and synthesized several active carbon materials. One of them displayed very high surface area (1,832 m2/g) and excellent pore diameter (3.6 nm). We investigated the applicability of this carbon material for supercapacitor electrodes. We have also modified this carbon material with a nickel-rich phosphide in order to make it suitable for LSB cathode applications.
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Title: THE INTERACTION BETWEEN COINAGE OR ALKALI METALS AND POLYAROMATIC HYDROCARBONS
Creator: Liu, Shuyang
Date: 2020
Description: Theoretical study on versatile chemistry of buckybowls and related polyaromatic hydrocarbons has been comprehensively accomplished and...
Show moreTheoretical study on versatile chemistry of buckybowls and related polyaromatic hydrocarbons has been comprehensively accomplished and documented. Polyaromatic hydrocarbons from simple double bond to fullerene C60, as one of major family in buckybowls has shown a wide potential in development of various specifically purposed materials. Complexes with coinage metals evidenced tunable donor ability of related polyaromatic systems’ π-surface. Moreover, functionalization with small ligands cations interact with these π-surface also show some patterns which have certain enlightenment to the experiment. By adding the methyl group on corannulene, to pursue the relationship between geometry and stabilization which provide an alternative strategy of developing. Further study of alkali metals interacts with annulene, continuously adding with crown ether to mimic experiment environment display an interesting pattern. In the end, extended topics of some applications with computational chemistry, such as the help of Raman spectrum of L-focus.
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Title: NANOMATERIALS FOR ADVANCED BATTERY CATHODES
Creator: Moazzen, Elahe
Date: 2020
Description: Cathode materials are key components that directly determine the power density of a battery. One of the most effective ways of developing high...
Show moreCathode materials are key components that directly determine the power density of a battery. One of the most effective ways of developing high power density cathodes is bringing them into the nano-scale world, which results in many expected and unexpected properties. Some of the desired characteristics include faster charge/discharge kinetics, improved capacity retention and structural stability due to the higher surface to volume ratio and shorter ion diffusion paths. In this dissertation a number of uniquely designed nano-sized cathode materials and nanocomposites are developed and investigated for alkaline aqueous and lithium ion battery applications. Nickel hydroxide (Ni(OH)2), which is one of the most important cathode materials in alkaline batteries, suffers from low conductivity, which usually leads to inefficient discharge and incomplete utilization of the material. A series of Ni(OH)2/Co(OH)2 core/shell nanoplatelets were synthesized and systematically investigated as cathode materials. Structure-property correlations revealed that electrochemical behavior and reversibility of Co(OH)2 redox conversion depended non-linearly on the average shell thickness, with the best performance (99.6% of theoretical capacity of the composite material) achieved at shell thickness of 1.9 ± 0.3 nm. Two fundamental phenomena were suggested to be responsible for the superior performance: templated shell deposition and galvanic coupling of core and shell materials.Manganese (IV) oxide (MnO2), which is another practical cathode that has a great potential to be utilized for a variety of energy storage systems, still has some major challenges including reversible cycling in rechargeable batteries. One of the most crucial challenges is the fact that polymorphs of MnO2 have different electrochemical activities as aqueous and Li-ion battery cathodes. However, most synthetic samples contain a mixture of polymorphs, which makes the structure-property correlations more complicated. This dissertation reports on systematic studies correlating synthesis, thermal and mechanical processing, and composite formation with polymorph composition, electrochemical performance and ion intercalation mechanisms. Among all the results, several main conclusions were reached: 1) Through control of the synthesis parameters and post-processing, desired phase compositions and nanoparticle morphologies, which optimize MnO2 performance in aqueous alkaline electrolyte, can be achieved. Nanoparticles with higher fraction of the akhtenskite polymorph showed higher reversible capacities in LiOH electrolyte (~210 mAh g-1), with stable performance for over 50 cycles. The effects of sub-nanoparticle organization of MnO2 polymorphs by thermal treatment without any morphology change on cycling performance, phase activation, and charge/discharge mechanisms in LiOH electrolyte as well as the detailed mechanism of the polymorph conversion during annealing were studied and for the first time, demonstrating that the electrochemical activity of MnO2 material strongly depends not only on the lattice structure of individual polymorphs but also on the sub-nanoparticle polymorph architecture and interphases.2) Several processing strategies, including thermal and mechanical processing, and composite fabrication were utilized to develop functional MnO2 cathodes for Li-ion batteries. Improvements in capacity and cycling performance were correlated to the presence of the pyrolusite phase of MnO2 and the crystallite size. Composite fabrication by graphene oxide wrapping also provided significant performance improvements through polymorph composition control and improved conductivity.
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Title: Silkworm silk - CNT composite fibers: fabrication, characterization and application in cell stimulation for tissue regeneration
Creator: Zheng, Shuyao
Date: 2019
Description: Silk fibroin, a structural protein of the Bombyx mori cocoons, is widely studied for biomedical applications because of its strong mechanical...
Show moreSilk fibroin, a structural protein of the Bombyx mori cocoons, is widely studied for biomedical applications because of its strong mechanical property, biocompatibility, low degradation rate and ease of processing. In this study, we incorporated functionalized CNT in silkworm silk proteins to generate biocomposite fibers by electrospinning. The electro-spun (E-spun) fibers were unidirectionally aligned with a diameter at the sub-micrometer scale, mimicking the locally oriented ECM proteins in native tissues. The addition of a minute amount of CNT not only reinforced the stability and the mechanical strength of the flexible scaffolds, but also rendered the fibers electrical conductivity to not only facilitate the E-spun fiber formation but also grant the fibers an additional functionality that can be utilized for cell stimulation. It is known that endogenous electric field is present in the human body at various locations and plays critical physiological roles through its effect on cell proliferation, migration and activation mediated by its interference with growth factor secretion and intracellular signaling pathways. Electrical stimulation (ES) has been widely investigated as a potential method to regulate cell functions for the treatment of a number of diseases. It has been reported that in dermal fibroblasts, ES induces the secretion of FGF-1 and FGF-2 which promotes cell proliferation, contraction, migration, and activation/differentiation into myofibroblasts for increased collagen synthesis in favor of tissue repair. In this work, the modulation effect of the aligned E-spun SWS-CNT fibers was examined by their application in inducing polarization and activation of fibroblasts with cellular deficit, like those from pelvic organ prolapse (POP) patients. These cells are characterized by low productivity of collagen with abnormally high COLI/COLIII ratio, leading to a loose and fragile collagen network, decreased integration among the tissue constituents and reduced tissue strength. Electrical stimulation boosted the collagen productivity by 20 folds in cells on silk-CNT than on pure silk due to silk-CNT’s high electrical conductivity. The developed approach can be potentially utilized to remedy the dysfunctional fibroblasts for therapeutic treatment of diseases and health conditions associated with collagen disorder.
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Title: Nanopore Detection of Heavy Metal Ions
Creator: MohammadiRoozbahani, Golbarg
Date: 2019
Description: Nanopore sensing is an emerging analytical technique for measuring single molecules. Under an applied potential bias, analyte molecules are...
Show moreNanopore sensing is an emerging analytical technique for measuring single molecules. Under an applied potential bias, analyte molecules are transported through the nanopore and cause ionic current modulations. Accordingly, the fingerprint of the analyte is reflected in the signature of the current blockage events. Due to its advantages such as lable-free and multi-analyte detection, nanopore sensing technology has been utilized as an attractive versatile tool to study a variety of topics, including biosensing of different species, such as DNA, RNA, proteins, peptides, anions, and metal ions.Metal ions play a crucial role in human health and environmental safety. Although metal ions are essential for numerous biological processes, the presence of the wrong metal, or even the essential metals in the wrong concentration or location, can lead to undesirable results and serious health concerns, including antibiotic resistance, metabolic disorders, mental retardation, and even cancer. Therefore, it is still of prime importance to develop highly sensitive and selective sensors for metal ions.In this dissertation, various nanopore sensing strategies to detect metal ions will first be discussed. These include: a) construction of metal ion binding sites in the nanopore inner surface; b) utilization of a biomolecule as a ligand probe; and c) employing enzymatic reactions. Then, three projects will be summarized. Among them, two projects are involved with detection of non-essential metal ions: uranyl and thorium ions, while the other is targeted at essential element, zinc ion. To be more specific, uranyl and thorium ions are detected by taking advantage of peptide molecules as ligand probes. In this case, the event signatures of peptide molecules in the nanopore are significantly different in the absence and presence of metal ions, which might be attributed to the conformational change of the biomolecules induced by the metal ion-biomolecule interaction. On the other hand, zinc ion is detected based on enzymatic reaction: without Zn2+, ADAM17 (a zinc dependent protease) is inactive and cannot cleave peptide substrate molecules; in contrast, with Zn2+ ion in the solution, the enzyme was activated, and its cleavage of the peptide substrate produced new types of blockage events with smaller residence time and amplitude values than those the peptide substrate.
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Title: HETEROGENEOUS CATALYST FOR ALKANE DEHYDYGENATION AND IMPLEMENTING TO SOLID OXIDE FUEL CELL
Creator: Xu, Yunjie
Date: 2019
Description: In the past decade, shale gas has become the most import source of natural gas in the United States. Large amounts of light alkanes in shale...
Show moreIn the past decade, shale gas has become the most import source of natural gas in the United States. Large amounts of light alkanes in shale gas, such as methane, ethane, and propane are available as an industrial source of chemicals through the catalyzed, on-purpose light alkane dehydrogenation to olefins. Therefore, it is obvious there is a benefit to developing catalysts to directly convert shale gas to olefins. However, alkane dehydrogenation and non-oxidative methane coupling are thermodynamically unfavorable reactions at low temperatures. The energy requirements make these reactions less attractive for shale gas utilization. In principle, consuming the hydrogen product with a fuel cell can drive the thermodynamically unfavorable reaction by reducing the hydrogen partial pressure in the anode and by heat generating by the fuel cell, while also generating electricity in the process. Moreover, catalyst integration with fuel cell can facilitate the transfer of charge in anode which is rate determine step in the fuel cell. This thesis will focus on catalyst development for alkane dehydrogenation and exploring a way to integrate these catalysts with fuel cells.Chapters 2, 3 and 4 focus on designing, characterizing, and studying catalysts for non-oxidative coupling of methane (NOCM) and propane dehydrogenation (PDH). PtM (M is a transition metal) alloys were found to efficiently decrease the desorption energy of olefin products and avoid deeper C-H bond activation compared to metallic Pt. Based on the previous study of single cobalt on silica, a novel synthesis of PtCo3 was developed to further increase the activity of the PDH reaction. The Pt bimetallic catalyst made by novel synthesis route was proven to be one of several types of alloy. It was observed that extremely high conversion of PDH and high selectivity of target olefin were catalyzed by PtCo3/SiO2. Ga, as another promotor to replace Co, was also investigated. As expected, PtGa3 alloy was formed by a similar synthesis, and it showed extraordinary stability and activity for propane dehydrogenation. A Mo-Pt dual-metal catalyst was found to catalyze methane coupling even though Pt-Mo bimetallic alloys do not form. We hypothesize that Pt catalyzed C-H bond cleavage of CH4 to form methyl radical, and a MoOC species, formed by MoO3 reacting with CH4, could effectively facilitate methyl radical coupling to form larger alkanes and alkenes. Pt-Mo dual-metal catalyst had higher catalytic activity for methane coupling than a physical mixture of Pt and Mo and genuine PtMo alloy. Chapter 5 details our efforts to transplant PtM catalysts from silica support to target fuel cell material--(La,Sr)(Cr,Fe)O3 as a support. Different catalyst structures were observed, and, in this case, second transition metals become a barrier to prevent Pt aggregation. When using propane as fuel for fuel cell, we observed electrochemical redox reactions occurred via electrochemical analysis. However, the resistance of cell is comparatively high and limited overall system performance. Chapter 6 details a study of the impact of the electrode oxide phase on overall cell performance. In this case, we conducted a fundamental study of degradation of cathode material, (La,Sr)(Co,Fe)O3. We found that raw material and cells can degrade even under room temperature. Thus, the storage of raw powder and fabricated cells is critical for performance studies. This also indicates that our high cell resistance in previous electrochemical measurements could come from the insulating compound formation during storage. Some directions for future research on catalyst integration and electrochemical testing are outlined.
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Title: DOPING OF SODIUM CHROMIUM OXIDE CATHODE MATERIALS TO ENHANCE ELECTROCHEMICAL PERFORMANCE FOR SODIUM-ION BATTERIES
Creator: wang, ziyong
Date: 2019
Description: In this project, we investigated the effects of doping several types of metals to NaCrO2 on its electrochemical performance. The doping method...
Show moreIn this project, we investigated the effects of doping several types of metals to NaCrO2 on its electrochemical performance. The doping method is aiming to stabilize the O3-type structure by partial substituting some of Cr with other metals during intercalation/deintercalation by suppressing Cr6+ migration to alkaline slab, and thus facilitate long-term cycle performance and reversible capacity. All doped NaCrO2 powders were hereby denoted to NaMe0.1Cr0.9O2 (Me=Al, Co, Ni, Mn). To achieve metal-doped NaCrO2 powders, sodium, chromium and dopant sources were mixed with various metal oxides and then subjected to 6-hour high energy ball milling, followed by heating in flow-Ar tube at 900℃ for 1 hour. Pristine NaCrO2 powder synthesized in the same process was to make comparisons with doped ones. To understand the mechanism of doping, field emission scanning microscopy (FESM) and energy Disperse Spectroscopy (EDS), as well as X-ray diffractometer (XRD), were employed to analyze the morphology and composition of final products. Benefiting from Ni doping, NaNi0.1Cr0.9O2 cell exhibited a high reversible capacity of 132 mAh g-1 at the initial cycle in a potential region between 2.0 and 3.6 V vs. Na/Na+, and 78 % of capacity retention over 70 cycles. For NaMn0.1Cr0.9O2, reversible capacity at first discharge is about 30 mAh g-1, lower than that of Ni-doped and pristine NaCrO2, while the cycle retention stays at nearly 100% after 100 cycles. The opposite charge/discharge behaviors from Ni- and Mn-doped NaCrO2 provide us a potential method for the optimization of cathode materials with the best electrochemical performance in the future.
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Title: Novel Chelating Agents for Positron Emission Tomography Imaging and Theranostic Applications
Creator: Zhang, Shuyuan
Date: 2022
Description: Positron emission tomography (PET) is a molecular imaging technology that can be used to detect various diseases including cancer. Zirconium...
Show morePositron emission tomography (PET) is a molecular imaging technology that can be used to detect various diseases including cancer. Zirconium-89 (t1/2 = 78.4 h) is one of the positron-emitting radionuclides that has been widely explored for PET imaging because its half-life matches the long biological half-life of antibody. Research efforts have been devoted to the development of chelation chemistry for 89Zr, a bone-seeking radionuclide. Deferoxamine (DFO) is the most frequently used chelator for 89Zr in both clinical and preclinical trials. DFO can rapidly sequester 89Zr to form 89Zr-DFO complex. However, DFO is not an ideal ligand for 89Zr because 89Zr-labeled DFO-antibody conjugate showed high bone uptake in mice. We wanted to develop novel small molecule donors and novel chelators for 89Zr. We discovered N-methyl-N-(pyridin-2-yl)hydroxylamine (Py-HA) and 2,6-bis(N-methylhydroxylamino)pyridine (Py-BHA) as small molecule donors for 89Zr. Based on the new small molecule donors (Py-HA and Py-BHA), we have designed and synthesized a series of novel macrocyclic chelators containing TACN (1,4,7-triazacyclononane), CYCLEN (1,4,7,10-tetraazacyclododecane), and a diaza-crown ether backbone for 89Zr-based PET imaging applications. Moreover, bifunctional chelators (BFCs) structured on TACN and diaza-18-crown-6 were synthesized for conjugation to antibody. Theranostics contains a diagnostic agent and a therapeutic drug that can be used for simultaneous therapy and imaging of diseases. Radiotheranostics includes radiometal complexes for both therapy and imaging. 177Lu is a promising radiotheranostic metal because it can emit gamma radiation for single photon emission computed tomography (SPECT) imaging and emit β radiation for radiotherapy. A radioisotope pair with complementary emission such as 64Cu/67Cu and 86Y/90Y, can be used for PET imaging and radiotherapy. In this study, we synthesized nonfunctional TACN and diaza crown ether-backboned chelators containing different donor groups for 177Lu, 64Cu/67Cu, and 86Y/90Y. Finally, two bifunctional chelators were synthesized for coupling with hydroxamic acid-based small molecule as a potential histone deacetylase (HDAC) inhibitor to generate a small molecule ligand-chelator conjugate (SMLC) for theranostic applications.
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Title: Investigation of Novel Solid Polymer Electrolytes and Lithium Salts for Rechargeable Lithium Batteries
Creator: Zhao, Wendy
Date: 2021
Description: Lithium-ion batteries (LIBs) are extensively used in many consumer electronic products. LIBs have great potential for application in electric...
Show moreLithium-ion batteries (LIBs) are extensively used in many consumer electronic products. LIBs have great potential for application in electric vehicles by virtue of their high power density and charge cycles. Research and development in this area has been focused on all around the globe. The major challenges include high cost, safety issues of the solvent based electrolytes, and low conductivities at ambient temperature of the solid polymer electrolytes (SPEs).This dissertation describes four novel electrolyte systems and a series of low lattice energy lithium salts synthesized and characterized for applications in LIBs. First, a new SPE has been derived from oligomeric poly(ethylene oxide) (PEO)-grafted crosslinked polystyrene (XPS) microspheres containing 1-2 lithium sulfonate moieties. This SPE possesses amorphous character with a glass transition temperature (Tg) around 135 ºC, displayed a good electrochemical stability with excellent ionic conductivity in excess of 10^-4 S/cm at 25ºC, and no significant thermal decomposition until 420 ºC. Second, a hybrid composite polymer electrolyte (CPE) was constructed with a gel matrix formed through hydrogen bonding by incorporating nanoparticles of fumed silica into the nanoscale network of PEO-XPS. Fumed silica with large surface modification group like polysiloxane formed an ideal gel structure offering significant high mechanical strength above 10^4 Pa, and a good ionic conductivity at 25°C. Third, a nonvolatile x-linked gel membrane electrolyte was synthesized with amino methacrylate, to introduce hemi-labile ligands as ionic liquid, into the polymer network. This new material exhibited improved salt solubility and ionic conductivity, due to the fast ligand exchange that facilitates the lithium ion structural transport, and also displayed an excellent electrochemical stability(4.8 V vs, Li/Li+). Fourth, a self-healing and thermal reversible polymer electrolyte designed based on Diels-Alder conjugation between multi-maleimides (2M-3M) and multi-furans (2F-4F) was synthesized. The reversible x-linking was realized through Diels-Alder (DA) and Retro-DA reactions by applying heating (>130°C)/cooling (<90°C) cycles. Last, new lithium salts with star and branch structures containing 1-4 of imide or methide moieties were synthesized and evaluated in PEO electrolyte system. These salts demonstrated good ambient temperature ionic conductivity at low concentrations, and the electrochemical stabilities were equal to or better than the most commonly used lithium salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Synthesis and characterization, including electrochemical properties, thermal and electrochemical stabilities, mechanical behaviors and surface morphologies of these new materials are described and discussed.
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Title: Organo-Functionalized Polyoxometalates
Creator: Alsaleh, Musaed Riyadh A
Date: 2023
Description: Polyoxometalates (POM) or transition metal oxide clusters are a sub-class of metal oxide-based materials of contemporary interest. POMs are...
Show morePolyoxometalates (POM) or transition metal oxide clusters are a sub-class of metal oxide-based materials of contemporary interest. POMs are molecular systems which contain highly symmetrical structures and are characteristics of group 5 and 6 metals, especially V, Mo, and W. Typical POM clusters have nuclearities ranging from 6 to 18 metal centers and are purely inorganic in their compositions. POMs can act as multielectron redox systems, while retaining their robust oxometallic framework structure. POMs have been receiving increasing attention, in part due to their potential as redox active materials for applications in various areas and their suitability as attractive molecular building units for making new functional materials of desirable properties and functions.In recent years, there has been a growing interest in the functionalization of polyoxometalates with organic moieties to synthesize organo-functionalized POMs. During the course of the work described in this thesis, we explored the synthesis of organo-functionalized polyoxometalates with special interest in polyoxovanadates incorporating heterometal center(s) in addition to vanadium in the structure. The focus of the work was on low nuclearity POMs. The thesis describes the synthesis and full characterization of a new organo-functionalized polyoxovanadate cluster - [(n-C4H9)4N]2[V6O13{(OCH2)3C (CH2CH3)}2]. The cluster compound has been characterized by a series of analytical techniques- FT-IR, Thermo Gravimetric Analysis, Bond Valence Sum calculations and complete single X-ray diffraction structure analysis. The hexavanadate cluster features {V6O19} oxometallate core composed of six edge sharing {VO6} octahedra defined by five bridging oxygen atoms and a terminal {V=Ot} oxo group. The {V6O19} oxometallic core of the cluster adopts the Lindqvist structure incorporating two 1,1,1-tris(hydroxymethyl)propane organic ligands. Six of the oxygens in the {V6O19} core come from the three alkoxy groups from two organic ligands. To the best of our knowledge, this organo-functionalized POM cluster has not been reported in the literature previously.
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Title: Critical Understanding of Multi-Mode Luminescence Properties of Eu3+ Doped LaAlO3
Creator: Alolayan, Abdulelah Abdulaziz H
Date: 2023
Description: Fluorescent anti-counterfeit materials with multi-luminescent modes under different external excitation sources are always advantageous over...
Show moreFluorescent anti-counterfeit materials with multi-luminescent modes under different external excitation sources are always advantageous over the conventional anti-counterfeit techniques. In the present thesis, our aim is to develop efficient Eu3+ doped LaAlO3 phosphor materials with different modes of luminescence properties such as down conversion-luminescence (DCL), persistent-luminescence (PersL), and optically stimulated luminescence (OSL), Thermo-luminescence (TL), radioluminescence (RL) Although, there are many reports on persistent-luminescence and optically stimulated luminescence based on Eu3+ doped matrices but the red persistent luminescence of Eu3+ ion on those matrices is not very long and the OSL intensities are also low. Herein, we report a long red persistent luminescence which lasted for 17 hrs. and the OSL intensity is very high. Furthermore, we have observed that the OSL property can be achieved even after 35 days of UV excitation and indicating its potential application for optical storage phosphor. From carrying out TSL studies we have found that three different types of traps namely Trap 1, Trap 2 and Trap 3 with trap depth 0.63 eV, 0.82 eV, 1.02 eV respectively are responsible for the persistent and OSL properties. It has been concluded that Trap 1 is mostly responsible for the persistent luminescence in short term while Trap 2 and Trap 3 are responsible for intermediate and long persistent luminescence. Further, Trap 2 and Trap 3 were also found to be present even after 35 days and responsible for the OSL properties. Anti-counterfeiting PersL composite has been developed in which AC real-life application is demonstrated.
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Title: AN EXPLORATION INTO THE EFFECTS OF CHROMATIN STRUCTURAL PROTEINS ON THE DYNAMICS AND ENERGETIC LANDSCAPE OF NUCLEOSOME ARCHITECTURES
Creator: Woods, Dustin C
Date: 2022
Description: Comprised of eight core histones wrapped around at least 147 base pairs of DNA, nucleosomes are the fundamental unit the chromatin fiber from...
Show moreComprised of eight core histones wrapped around at least 147 base pairs of DNA, nucleosomes are the fundamental unit the chromatin fiber from which long arrays are built to compact genetic information into the cell nucleus. Structural proteins, such as linker histones (LH) and centromere proteins (CENP), interact with the DNA to dictate the exact architecture of the fiber which can directly influence the regulation of epigentic processes. However, the mechanisms by which structural proteins affect these processes are poorly understood. In this thesis, I will explore the various way in which LHs and CENP-N affect nucleosome and, by extension, chromatin fiber dynamics. First, I present a series of simulations of nucleosomes bound to LHs, otherwise known as chromatosomes, with the globular domain of two LH variants, generic H1 (genGH1) and H1.0 (GH1.0), to determine how their differences influence chromatosome structures, energetics and dynamics. These simulations highlight the thermodynamic basis for different LH binding motifs, and details their physical and chemical effects on chromatosomes. Second, I examine how well the findings above translate from mono-nucleosomes to poly-nucleosome arrays. I present a series of molecular dynamics simulations of octa-nucleosome arrays, based on a cryo-EMstructure of the 30-nm chromatin fiber, with and without the globular domains of the H1 LH to determine how they influence fiber structures and dynamics. These simulations highlight the effects of LH binding on the internal dynamics and global structure of poly- nucleosome arrays, while providing physical insight into a mechanism of chromatin compaction. Third, I took a brief departure from LHs to study the effects that the centromere protein N (CENP-N) has on the poly-nucleosome systems. I present a series of molecular dynamics simulations of CENP-N and di-nucleosome complexes based on cryo- EM and crystal structures provided by Keda Zhou and Karolin Luger. Simulations were conducted with nucleosomes in complex with one, two, and no CENP-Ns. This work, in collaboration with the Karolin Luger Group (University of Colorado – Boulder) and the Aaron Straight Group (Stanford University), represents the first atomistic simulations of this novel complex, providing the foundation for a plethora of future research opportunities exploring centromeric chromatin the effect that its structure and dynamics have on epigenetics. Lastly, I return to the chromatosome to study how DNA sequence affects the free energy surface and detailed mechanism of LH transitions between binding modes. I used umbrella sampling simulations to produce PMFs of chromatosomes wrapped in three different DNA sequences: Widom 601, poly-AT, and poly-CG. This work, my final in the series, represents a culmination of my studies furthering the understanding of biophysical phenomena surrounding LHs and how they can be extrapolated towards epigentic mechanisms. I was able to report on the first PMFs illustrating a previously unknown transition and describe the transition mechanism as it depends on DNA sequence.
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Title: Synthesis and Photophysical Characterization of Novel Aromatic Triplet Dyes for Photodynamic Therapy Applications
Creator: Morgan, Jayla A
Date: 2022
Description: Photodynamic therapy is a biomedical approach to treating specific types of cancerous tumor cells and harmful bacteria. The core principle of...
Show morePhotodynamic therapy is a biomedical approach to treating specific types of cancerous tumor cells and harmful bacteria. The core principle of photodynamic therapy involves the usage of a photosensitizer, which is an agent with the capability of transforming molecular, triplet state oxygen, into a reactive oxygen species upon a reaction with near-infrared (NIR) light. The reactive oxygen species has been demonstrated to cause apoptosis among harmful cells without damaging cancer free cells. The effectiveness of photodynamic is highly dependent upon the identity of the photosensitizer; a powerful and efficient photosensitizer should be non-toxic, exhibit high light absorption capabilities, and should produce large amounts of the reactive oxygen species. A novel chromophore bis-iodo-dipyrrolonaphthyridine-dione was demonstrated to have all vital characteristics of an ideal photosensitizer, however produced low amounts of the reactive oxygen species of interest due to the chemical instability of a carbon-halogen bond present in the molecule. Various subsequent halogenations (bis-bromo and bis-chloro) completed in order to remedy this instability revealed specific regioselectivity in regards to the dipyrrolonaphthyridinedione parent that are exhibited upon substituents effects by the substrate, electronic effects exhibited by the reagents of interest, and overall photophysical characterization of the molecules.
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Title: SYNTHESIS AND APPLICATION OF ORGANOMETALLIC PRECURSORS FOR TUNGSTEN AND MOLYBDENUM SULFIDE
Creator: Liu, Bo
Date: 2021
Description: Transition metal chalcogenides (TMCs) have unique properties. They are promising materials for the next generation electrical devices due to...
Show moreTransition metal chalcogenides (TMCs) have unique properties. They are promising materials for the next generation electrical devices due to their suitable band gap, outstanding electron mobility, and controllable atomic thickness. In the last few decades, atomic layer deposition (ALD) has been one of the hottest research frontiers for the fabrication of TMCs films. Signification progress has been made on the varieties of material grown by ALD and the improvement of ALD equipment. However, the fast-evolving microelectronic industry set higher requirements for the ALD application. In the potential electronic fabrication process, low-temperature preparation and non-corrosive procedure are critical for the advanced device architecture. Thus the novel precursor development and the investigation of reaction mechanism are necessary. In addition, as the comprehensive research of film deposition, the prevailing crystallographic defects on the as-prepared films are another appealing thing for us to think about and try to eliminate for better film quality. Therefore, this dissertation will describe the precursor ligand design and its effect on the morphology, the development of W/Mo precursors for tungsten/molybdenum disulfide, and the defect passivation of tungsten diselenide films.In chapter 2, a series of heteroleptic tungsten precursors of tetrathiotungstates (WS42-) were prepared through the facile ligand transfer method. Ligand variation has a significant effect on the crystallinity of the resulting tetrathiotungstate products. Crystalline tetrathiotungstates with preferred orientation were prepared from the reaction of synthesized precursors with H2S at room temperature. Results indicated the morphologies and crystallinities of the tetrathiotungstates can be well controlled by their ligand behaviors which give us a better understanding of the growth mechanism. Chapters 3 and 4 focus on the development of W and Mo precursors for W/Mo disulfide and their performance in wet chemistry reactions and ALD. WS2 can be synthesized at the ambient temperature in solution by the non-redox reaction. WS2 film growth can be achieved at the exciting low temperature of 125°C by ALD. Based on the performance of the tungsten precursor, a new molybdenum dimer precursor with improved reactivity was synthesized, and MoSx can be prepared at the ambient temperature in seconds. X-ray absorption spectroscopy (XAS) was also utilized to investigate the interaction between the organometallic precursor and the SiO2 surface. Chapter 5 will focus on the defect passivation of WSe2 films for the improvement of their electrical performance. Precursors were synthesized, and the wet chemistry method was designed for oxidation removal and vacancy healing. Raman spectroscopy was used as the express characterization method to reveal the treatment results. A promising healing reagent was screened out, and the repaired films were fabricated to field-effect transistors (FETs) for electrical measurements. The final results showed the electrical performance of the WSe2 films was improved after the convenient chemical treatment.
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