Search results

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

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.
Show less

Title: ORGANOFUNCTIONALIZED OXOMETALATES: SYNTHESIS, STRUCTURE, AND PROPERTIES OF A NEW CLASS OF MIXED-METAL TETRAMETALATE CLUSTERS
Creator: Shuaib, Damola Taye
Date: 2022
Description: Oxometalates (OMs) are metal-oxide clusters with addenda mental atom mainly V, Mo, and W and bridged by oxide anions. Prototypical examples...
Show moreOxometalates (OMs) are metal-oxide clusters with addenda mental atom mainly V, Mo, and W and bridged by oxide anions. Prototypical examples like polyoxometalates (POMs) are completely inorganic. While clusters with nuclearities ranging from 6 to 18 are common for purely inorganic examples, those with less than nuclearity 6 are rare. Therefore, functionalization by covalent interaction with organic moiety via self-assembly has been utilized as a viable route for making compact clusters with nuclearity of 4 and below. These compounds constitute the organo-functionalized examples of the purely inorganic structure ([XMaOb]n-) POM. Reports of organo-functionalized tetrametalates (TMs), ([MxOyLz])n- (where M = metal, x = 4 and L represents an organic ligand) are sparse. Mixed metal species are especially interesting as potential redox active materials as they contain energetically distinct potential redox centers. OMs have ability to accept electrons in a chemically reversible manner through the terminal oxo-ligand (M=Ot) leading to dπ–pπ electron transfer. Considering the rich structural and electronic properties of these complexes, four neutral mixed-metal (M-V) tetrametalate clusters, [(CoIICl)2(VIVO)2{((HOCH2CH2)(H)N(CH2CH2O))(HN(CH2CH2O)2}2] (1), [(ZnIICl)2(VIVO)2{((HOCH2CH2)(H)N(CH2CH2O))(HN(CH2CH2O)2}2] (2), [CoII2(VIVOF)2{((HOCH2CH2)(H)N(CH2CH2O))(HN(CH2CH2O)2)}2] (3), and [ZnII2(VIVOF)2{((HOCH2CH2)(H)N(CH2CH2O))(HN(CH2CH2O)2)}2] (4) containing unprecedented oxometallocyclic {M2V2X2N4O8}(M = Co, Zn; X = F, Cl) frameworks decorated with diethanolamine ligand in bidentate and tridentate manners. The type of halo-ligand has direct influence on the geometry of the metal M and UV-Vis reflectance spectra revealed changes in electronic structure consistent with charge transfer processes expected. Computational and magnetic properties studies revealed that the ground state multiplicity of 1 is confirmed as an open-shell singlet with a prediction of an isotropic exchange coupling of -6.6 cm-1 but less clear for 2. The vanadium centers are best described as a V(IV) center and the cobalt centers are high-spin Co(II) centers. Less orbital destabilization was observed due to weaker interaction of Cl- ligand on Co than what was observed for O2- ligand on V centers. In 2, there are four weakly coupled spin centers, where the isotropic exchange couplings are defined as J1, J2’, and J2’’. These couplings are approximated as J1 = 1.5/+11.7 cm-1, J2’ = -22.1/-14.8 cm-1, and J2’’ = +4.2/+4.8 cm-1. Although J2’’ is predicted to be weakly ferromagnetic in nature, whereas the fit suggested a weak antiferromagnetic interaction for each of the V(IV)-Co(II) couplings. The low-temperature magnetic susceptibility suggests a Type III spin frustration present in the system. However, competing magnetic interactions are known to be operative in tetranuclear system which is even observed to be more prominent in the mixed-metal tetranuclear system considering the edge-sharing consequence on magnetic behavior. A new route to metal complex synthesis via in situ ligand transformation from diethanolamine to bicine by disproportionation and oxidation reactions yielded three isostructural mononuclear clusters Bis[N,N-bis(2-hydroxyethyl)glycinato]-Cobalt(II) 5, Bis[N,N-bis(2-hydroxyethyl)glycinato]-Nickel(II) 6, and Bis[N,N-bis(2-hydroxyethyl)glycinato]-Copper(II) 7. The observed transformation is predicted to proceed through nucleophilic substitution (SN2) as expected for substituted ammines. These metal complexes are characterized by various analytical techniques such as, FT-IR and UV-Vis spectroscopies, single crystal and powdered X-ray diffraction analyses, Energy-Dispersed X-ray spectroscopy, magnetic properties measurements, thermal gravimetric analysis, bond valence sum calculations etc. Based on their features and detailed structure-property-application analyses, the clusters showed great potentials for catalysis, materials for digital tools, chemical sensing, molecular magnets and precursors as molecular building blocks for extended open frameworks.
Show less

Title: Unraveling the Factors Affecting Virus Adhesion to Food Contact Materials and Virus-Virus Interaction – A Nanoscopic Study
Creator: Guo, Ao
Date: 2020
Description: Food safety is a worldwide issue nowadays since pathogens cause diseases, even death. Human enteric viruses are a major cause of non-bacterial...
Show moreFood safety is a worldwide issue nowadays since pathogens cause diseases, even death. Human enteric viruses are a major cause of non-bacterial foodborne gastroenteritis. In the United States, they are the most life-threatening pathogenic agents for the foodborne illnesses. The fecal-oral route is responsible for the attachment and transmission of such foodborne pathogens, which lead to contamination of food-contact materials (FCMs) during food preparation, enhancing the risk of transmission. The interaction between viruses and contact surface is the source of virus adhesion.Due to lack of knowledge on virus adhesion to various FCMs, this thesis aims to reveal the key factors that mediate the virus-FCM and virus-virus interactions in order to effectively prevent virus infection or spread. The objectives are (1) to identify the physical and chemical features of a material surface that affect virus adhesion to determine an optimal FCM, (2) to reduce virus adhesion via nanofabrication of a material’s surface; (3) to investigate the effect of thermal inactivation (heat treatment) on virus-virus interaction toward the establishment of a non-culture-based infectivity assay for laboratory assessment of the effectiveness of disinfection methods. In this study, virus adhesion on various FCMs, including glass, polyvinyl chloride (PVC), polyethylene (PE) and graphite which have been widely used in food storages, food packages and utensil handling during food preparations, was investigated. Male-specific coliphage (MS2) was used as a virus surrogate of the highly infectious human enteric virus with similar physiochemical properties. Atomic force microscopy (AFM) was predominantly used in quantitative analyses of the strength of MS2 adhesion to various food-contact surfaces. Dynamic light scattering (DLS) was applied in MS2 dimensional analysis in aqueous suspension. Moreover, surface modification, such as nanofabrication, was employed to create controllable surface textures to reduce virus adhesion on FCM. Thermal inactivation was employed as a disinfection method. A comparative study was carried out to differentiate the active and inactivated MS2 in the virus-FCM and the virus-virus interactions. The results of this examination indicate that a material’s surface property, such as topography, hydrophobicity and surface charge, contributed to virus adhesion in aqueous phase at neutral pH (=7.4). Each surface feature played a distinctive role; however, the combined effect as well as the chemical signature of a virion’s surface determined the virus-FCM interaction. A delicate control of a surface’s chemical affinity and physical feature is expected to effectively reduce/interfere virus adhesion. It was also discovered that thermally inactivated MS2 particles became larger, softer, and more hydrophobic. These properties can be utilized in developing a non-culture-based assay to assess the effectiveness of disinfection methods for human enteric viruses, which can hardly be cultured in laboratory.
Show less

Title: ATOMIC LAYER DEPOSITION STUDIES OF GOLD AND TUNGSTEN DISULFIDE
Creator: Liu, Pengfei
Date: 2020
Description: In the last few decades, atomic layer deposition (ALD), as a vapor deposition technique and a powerful thin film fabrication method, has...
Show moreIn the last few decades, atomic layer deposition (ALD), as a vapor deposition technique and a powerful thin film fabrication method, has received more and more attention in many fields. A variety of materials can be made by ALD; however, the progress of ALD application is still necessary. Meanwhile, in the process of film fabrication by ALD, the interfacial chemistry is interesting and well worth studying. This dissertation mainly described the process of exploring two materials, gold and tungsten disulfide, fabrication and related content.For the portion of applying ALD in gold thin film deposition, a relatively comprehensive process was explored, studied, analyzed and discussed. Start with the synthesis of the gold precursor, Me2Au(S2CNEt2), the synthetic reaction was explored. By modified the conditions, such as solvent system, twice the yield as previously reported in the literature were achieved. Next, the application of in situ microbalance and infrared spectroscopic technique illuminate the organometallic chemistry during the gold thermal ALD process with Me2Au(S2CNEt2) and ozone. In situ quartz crystal microbalance (QCM) studies give an explanation for the nucleation delay and island growth of gold on a freshly prepared aluminum oxide surface. In situ infrared spectroscopy provides insight to study the surface chemistry during the process, which supports an oxidized gold surface mechanism. The epitaxy of gold thin film was explored by X-ray diffraction. The thermal ALD gold on various substrates reveals out-of-plane orientation, however, in-plane orientation was only existed in the gold film on mica. For the portion of applying ALD in tungsten disulfide fabrication, the early work started with studying the effect of interfaces upon crystallinity. The sulfuration of indium thin film with different interface was explored. Then the idea of “interfaces” was brought into the process of tungsten compounds fabrication. Due to this “indirect” method which made tungsten disulfide by sulfurizing ALD made tungsten compounds (eg. tungsten oxide and tungsten nitride) could not reduce the reaction temperature of tungsten disulfide synthesis to less than 400 °C. Sequently, the “direct” way of tungsten disulfide fabrication which directly utilized tungsten precursor and H2S in ALD system was tested and explored. With the tungsten precursors developed by our group, finally, tungsten disulfide could be fabricated at the temperature as low as 125 °C.
Show less

Title: Development of Metal Oxide-Based Phosphors for Luminescence Thermometry
Creator: Jahanbazi, Forough
Date: 2023
Description: Temperature is both a thermodynamic property and a fundamental unit of measurement; one of the seven base quantities of the international...
Show moreTemperature is both a thermodynamic property and a fundamental unit of measurement; one of the seven base quantities of the international system of units (SI). It can be seen simply as the degree of hotness or coldness, a qualitative definition built on the bodily sensation of heat and cold. Today it is readily defined from the principles of classical thermodynamics as the parameter of state that has the same value for any systems which are in thermal equilibrium, and from statistical mechanics as a direct measure of the average kinetic energy of noninteracting particles. Temperature is an intensive quantity, meaning that its value does not depend on the amount of the substance for which it is measured. It is important because it is something we feel and because it influences the smallest aspects of our daily life, from how to adjust our housing and clothing to what we eat for supper. It affects the life cycles of plants and animals, governs rates of chemical reactions, influences tides and so on. For these reasons, it is by far the most measured physical quantity; sensors of temperature account for 80% of all sensors worldwide at present and they are used across a broad spectrum of human activities, such as in medicine, home appliances, meteorology, agriculture, and industrial and military contexts, to mention some of the most significant areas. Thus, the market demand for temperature sensors is increasing due to their extending applications in human activities. Traditional “contact” temperature measurements, which are mainly based on the expansion and contraction of an employed material, encounter difficulties when used in some emerging technologies and environments, such as nanotechnology and biomedicine. Today, an immediate need exists for the “non-contact” thermometry of moving or contact-sensitive objects, difficult to access pieces, bodies in hazardous locations, objects of nano-size dimensions, or living cells and organisms. However, the properties of existing thermometers and sensor platforms limit their use in such environments. Non-contact sensors measure object temperature without the need for physical contact between sensors and objects. Therefore, they have been considered as a great interest for hardly accessible objects. As non-contact thermometry methods, besides pyrometers and radiation thermometers, optical thermometers have drawn extensive attention nowadays. Specifically, among all the optical based thermometry methods, including Raman scattering, optical interferometry, and near field optical scanning microscopy, the one having drawn the most attention is luminescence thermometry in which the temperature detection is based on the luminescent signal accompanied with acceptable spatial resolution.In luminescence thermometry method, temperature can be determined from different features of luminescence using luminescence thermometers. Depending on the temporal nature of these features, the principles of their measurements are classified as either time-integrated (steady-state) or time-resolved ones. The temperature measurement based on the excitation and emission band positions and bandwidths, emission band intensities, luminescence/fluorescent intensity ratio (LIR or FIR, the ratio of the intensities of two emission bands) are classified as time-integrated methods. The temperature measurements based on the emission decay- or rise-times are classified as time-resolved ones. Temperature readouts from LIR and emission lifetime are by far the most exploited methods. Both readouts are self-referenced, so they are not affected by fluctuations in excitation and signal detection. Moreover, thermal sensing ability of many lanthanide-based luminescent materials is not limited to only one read-out method. Some of them can be used as dual/multiple modes via utilizing a combination of two or more read-out methods for temperature measurement. Non-contact luminescence thermometry based on LIR read-out method has attracted much attention due to its excellent accuracy and sensitivity. The intensity ratio is independent of undesirable factors that makes this luminescence thermometry more appropriate. Moreover, the method is self- referencing which removes the need for a temperature standard. In principle, it can be realized with any combinations of the emission lines from lanthanides and transition metallic ions with different temperature dependencies, either from single or multiple luminescent centers. It is the most reported luminescence thermometric read-out method in the past few years. In the past years, researchers have done a lot of work on developing high-efficient LIR thermometers by employing a single center emitting. This ratiometric method is mainly performed based on the principle that governs thermally coupled energy level of the luminescent ions. The electronic distribution between electronic states of closely separated excited levels of the doped element follows the Boltzmann equation. The two excited levels of ions are thermally coupled with a maximum energy gap of 2000 cm-1, which is sufficiently small to allow electrons to transit to high energy level upon thermal excitation and at the same time large enough to have different electronic populations and high sensitivity value. In this case, both high and low excited states share the electronic population according to Boltzmann’s distribution. Therefore, the ratio of the number of electrons between the high and the low excited levels can be defined as follows for LIR-based thermometry utilizing single emitting centers. In addition to LIR between two thermally coupled energy levels of the luminescent ion, in some ions LIR between two other energy levels which are not coupled thermally were employed to reach to a high-sensitive thermometry. The quantitative evaluation of the thermometric performance of a temperature probe is defined by its absolute and relative thermal sensitivities, temperature resolution, and repeatability. The rate of change in thermometric parameters (indicated by Δ) over a temperature changing process (∂T) is defined as absolute thermal sensitivity (Sa). However, absolute sensitivity is not appropriate to compare the performance among thermometers with different employed materials or physical principles. The relative thermal sensitivity (Sr) is defined to eliminate the problem associated with comparison between the performance of thermometers with different natures. Sr of a luminescent thermometer is one of the most important factors which determine its temperature readout accuracy. The smallest temperature change resolvable by a thermometer is defined as temperature resolution or temperature uncertainty (indicated by δT) which is expressed in Kelvin and depends on the characteristic of measuring systems such as the experimental detection setup and the signal-to noise ratio: The reproducibility is defined as the change of the same measurement performed under different conditions such as different methods or devices. The repeatability (indicated by R) is the ability of a thermometer to provide the same result under different conditions. Regarding temperature resolution, most light detection systems, including thermometry systems, suffer from low resolution because of the scattering at both excitation and emission wavelengths. Light scattering of thermometric phosphors is induced by their grain size, shape, and surface roughness. This is a problem particularly associated with conventional phosphors which typically have micrometer grain size. On the other hand, the light scattering by nanoparticles (NPs) is close to zero, which leads to better resolution of luminescence thermometers using NPs. Consequently, nanothermometry has emerged as a hot research area of thermometers for new technological applications with high resolution. Accordingly, below in chapter 1, we discussed a host material, pyrochlore compound of La2Zr2O7, doped with Tb3+ and Eu3+, synthesized in nanoscale (~15 nm) that showed a great potential for LIR temperature sensing with a high resolution based on dual emitting centers. In chapter 2, another sample of this nano powder host, La2Zr2O7 doped with Pr3+, is discovered and discussed for LIR temperature sensing based on single emitting center. Beside the high-resolution thermometry by La2Zr2O7: Pr3+ nano powder, a broad-temperature sensing range was achieved using it. The broad temperature sensing range obtained only by using one LIR-read out mode originated from high-lying charge transfer states with slow thermal-quenching that will be elaborated in chapter 2. Multiple materials employed for luminescence thermometry application, such as organic dyes, quantum dots, metal–organic complexes and frameworks, among which lanthanide or transition metal ion-based phosphors, are most promising. The electronic states of lanthanides are characterized by partially filled 4f orbitals as they are gradually filling up from 4f0 for La3+ to 4f14 for Lu3+. Their luminescence emission occurs due to interconfigurational f-f transitions except some ions like Eu2+ and Ce3+ which have f-d allowed transition emissions. The partially filled 4f orbitals of lanthanide ions are shielded by 5s and 5p subshells from surrounding environment that leads to long lifetime and narrowband emission characteristics. Once excited with UV light, lanthanide-doped materials mostly emit light in visible/near infrared (NIR) range in a downshift (DS) photoluminescence (PL) mechanism. In DS emission, high energy photons are converted into phonons with lower energy. Overall, having excellent repeatability, reproducibility and photostability with thermally and chemically stable structures makes the lanthanide-based materials the most favorite choices for luminescent thermometry applications. Their luminescence is easy to identify and differentiate from other materials. Multiplexing is possible due to their narrow emission bands which are easily identifiable. Host materials also play a crucial role in thermal sensing properties of thermometric phosphors. Various hosts such as fluorides, ceramic oxides, nitrides, chalcogenides, and phosphides have been employed for luminescence thermometry. Ceramic hosts are composed of different elements, thus often require complex synthesis processes which would limit their applicability. Fluoride hosts have a level of toxicity which is harmful for living systems, so they are not environmentally friendly. Nitride compounds are commonly prepared in oxygen/water-free glove boxes and synthesized in harsh synthesis conditions under high pressure/temperature which restrict their large-scale production. Chalcogenides and phosphides may not be sufficiently stable. On the other hand, metal oxide phosphors possess the advantages of convenient preparation, non-toxicity, excellent chemical stability (capable of withstanding sustained exposure to high temperature), and low cost. Moreover, they are preferable in biomedical luminescence thermometry as applications for measuring long-wavelength emissions where tissues are optically transparent and are less affected by scattering and background luminescence. Considering all these aspects, metal oxide-based phosphors are more favorable for luminescent thermometry. One of the goals of research in luminescence thermometry field has been to push the limit of temperature measurement capability to higher temperatures. However, the development of luminescent phosphors with high thermal stability of emission and high sensing efficiency still is a paramount challenge. Thermal stability of photoluminescence (PL) is a property related to the chemical composition, electronic structure, and crystal structure rigidity of phosphors. It is commonly referred to as positive thermal quenching (TQ), that is, the loss of light emission with rising temperature. Most phosphors indicate positive TQ which stems from high non-radiative transition probability at elevating temperatures. This phenomenon severely limits the applications of luminescent phosphors and degrades their devices’ performance. To compensate for the thermally induced emission loss of phosphors, several strategies have been reported, while as will be discussed in chapter 3, mostly have negative impacts on their inherent luminescence properties. From the structural perspective, TQ caused by nonradiative relaxations is closely related to the crystal structure stability. A rigid structural framework with high lattice symmetry has reduced nonradiative transitions at elevated temperatures. As one of the rigid-type hosts, materials possessing a negative thermal expansion (NTE) property have been explored as suitable hosts for anti-TQ phosphors doped with lanthanides. NTE refers to the unique property of some unique and rare materials with their volume abnormally contracting with increasing temperature. Among various reported NTE families, compounds with the general formula of A2M3O12, where A is a trivalent rare earth ion and M stands for W6+ or Mo6+, are well-known with a broad range of compositions and have been explored for anti-TQ in the recent years. Some earlier works reported employing A2M3O12 host to obtain thermally enhanced upconversion (UC) emission. However, the upconversion emission is not the type of widely used emission as they produce weaker emissions mostly limited to a higher wavelength range than most-applicable visible range. Thus, NTE phosphors and thermally enhanced stronger downshift (DS) emissions on visible range are not yet high enough to fulfill their practical application. To explore the applicability of NTE idea for down-shift (DS) emitting phosphors, we reported the anti-TQ performance of single and co-doped samples of Sc2Mo3O12: Eu3+ and Sc2Mo3O12: Tb3+, Eu3+ in chapter 3 and 4, respectively. Specifically, we took advantage of the existence of interionic energy transfer in our NTE host, to achieve superior anti-TQ performance for DS luminescence that can be employed for efficient thermometry at high temperatures range. The structural shrinkage with rising temperature shortens the distance between the host and activator dopant ions, which enhances the host to activator ET and consequently the final emission intensity as will be elaborated in two last chapters. As a highly promising strategy, there is an urgent need to obtain more evidence on how NTE property, associates with the anti-TQ of luminescence that we tried to discover in our works. We explored these compound’s potential for high temperature luminescence thermometry. We tested both LIR and lifetime-based temperature sensing and revealed their great potential for an efficient temperature sensing at high temperature ranges. This study opens a new design strategy and perspective to obtain phosphors with thermally boosted luminescence based on NTE host materials to meet the serious demands for their broad applications at elevated temperatures and harsh conditions.
Show less

repository.iit

Search the repository

Enabled Filters

Refine Results

Date

Subject

Creator