Browsing by Author "Nielsen, Steven O."
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Item A Green Chemistry Approach to Designing Bio-based Resins for 3D Printing(May 2023) Sparacin, Marissa Lauren 1998-; Smaldone, Ronald A.; Nielsen, Steven O.; Stefan, Mihaela C.Sustainability has become a great topic of interest in recent years. Most associate sustainability with how a material is produced, consumed, and disposed of, and how this continuous cycle effects the environment. However, sustainability is a much more complex concept with nuance regarding its reach on societal issues such as resource inequality and access, as well as, economic availability and convenience. The reliance on petroleum-based materials, such as plastics, in modern day society has been discussed in great depth in relation to sustainability. This is due to fossil fuels being main contributors to environmental pollution, resource degradation, and rising global temperatures. On the other hand, the dependence on plastics in almost every industry is a result of their ease of production, favorable mechanical properties, and cost effectiveness. Because of this, it will be difficult to influence a shift from petroleum-based materials to more bio-based materials if these new materials do not perform similarity to industrially used plastics. It is also crucial to consider the manufacturing processed used to produce the materials. Competitive manufacturing techniques such as 3DP (3D printing) has become a desired technique due to its ability to fabricate complex, uniform, and flexible products without the use of molds or machining, its ability to provide fast, on-site production, and its cost-effective nature without wasting unnecessary materials or excessive waste production. The main goal of this research was to develop bio-based resins that are compatible with digital light processing 3D printing technologies (DLP 3DP) and optimize these materials such that they have comparable properties to commonly utilized plastics. Not only that, but a focus on designing materials that can be chemically recycled, thermally healed, and mechanically reprocessed while maintaining their mechanical properties, will help to produce a movement toward the implementation of more eco-friendly materials. Here, a background on the sustainability movement and its evolution, as well as, the issues associated with plastics will be discussed. Additionally, the implementation of bio-based feedstocks within the design of recyclable, self-healable, and reprocessable thermosets will be investigated and looked at through a green chemistry lens. The concepts explaining the various 3DP technologies, the pros of utilizing such techniques, and the fabrication of 3D printable resins will be explored. Finally, applications of such concepts utilizing bio-based feedstocks such as functionalized vanillin, guaiacol, and eugenol with scientific, peer-reviewed research with the reported findings will be presented.Item Effects Of Spherical Fullerene Nanoparticles On A Dipalmitoyl Phosphatidylcholine Lipid Monolayer: A Coarse Grain Molecular Dynamics Approach(Royal Society of Chemistry, 2012-07-30) Chiu, Chi-cheng; Shinoda, W.; DeVane, R. H.; Nielsen, Steven O.; Nielsen, Steven O.The effect of carbon-based nanoparticles (CNPs) on biological systems is currently of great concern. Yet, few experimental techniques are capable of directly imaging and probing the energetics of such nano-bio systems. Here, we use coarse grain molecular dynamics simulations to study spherical fullerene molecules interacting with dipalmitoyl phosphatidylcholine (DPPC) lipid membranes. Using free energy calculations we show that all the tested fullerene molecules can spontaneously diffuse into both a lipid bilayer and a lipid monolayer. In addition, we establish that large fullerene molecules tend to partition preferentially into bilayers, which affects the lipid monolayer-to-bilayer transition during the respiration cycle. Our results identify a possible CNP perturbation to the function of the pulmonary monolayer membrane and suggest a potential pathway for CNP entry into the body through lung inhalation.Item A Guiding Potential Method for Evaluating the Bending Rigidity of Tensionless Lipid Membranes from Molecular Simulation(2013-07-18) Kawamoto, Shuhei; Nakamura, Takenobu; Nielsen, Steven O.; Shinoda, Wataru; Nielsen, Steven O.A new method is proposed to estimate the bending rigidity of lipid membranes from molecular dynamics simulations. An external cylindrical guiding potential is used to impose a sinusoidal deformation to a planar membrane. The bending rigidity is obtained from the mean force acting on the cylinder by calibrating against a discretized Helfrich model that accounts for thermal fluctuations of the membrane surface. The method has been successfully applied to a dimyristoyl phosphatidylcholine bilayer simulated with a coarse-grained model. A well-converged bending rigidity was obtained for the tension-free membrane and showed reasonable agreement with that obtained from the height fluctuation spectrum.Item Hydrophilic Directional Slippery Rough Surfaces for Water Harvesting(Amer Assoc for the Advancement of Science) Dai, Xianming; Sun, Nan; Nielsen, Steven O.; Stogin, Birgitt Boschitsch; Wang, Jing; Yang, Shikuan; Wong, Tak-Sing; 0000-0001-5050-2867 (Dai, X); 308247739 (Dai, X); Dai, Xianming; Nielsen, Steven O.Multifunctional surfaces that are favorable for both droplet nucleation and removal are highly desirable for water harvesting applications but are rare. Inspired by the unique functions of pitcher plants and rice leaves, we present a hydrophilic directional slippery rough surface (SRS) that is capable of rapidly nucleating and removing water droplets. Our surfaces consist of nanotextured directional microgrooves in which the nanotextures alone are infused with hydrophilic liquid lubricant. We have shown through molecular dynamics simulations that the physical origin of the efficient droplet nucleation is attributed to the hydrophilic surface functional groups, whereas the rapid droplet removal is due to the significantly reduced droplet pinning of the directional surface structures and slippery interface. We have further demonstrated that the SRS, owing to its large surface area, hydrophilic slippery interface, and directional liquid repellency, outperforms conventional liquid-repellent surfaces in water harvesting applications.Item Investigating the Functional Impacts of Tetrel Bonding in the Reaction Mechanism of Methyltransferases and Screening of Peptidomimetic Inhibitors(May 2023) Douglas, Teri Arnelle 1995-; Stelling, Allison L.; Meloni, Gabriele; Ahn, Jung-Mo; Pantano, Paul; Nielsen, Steven O.While protein methyltransferases have important roles in many biological processes such as gene regulation and RNA processing, their dysregulation has been implicated in the progression of a number of diseases such as cancers and neurological conditions. These enzymes catalyze the methylation of lysine and arginine residues of target proteins using the cofactor and methyl donor, S-adenosyl methionine (SAM). A study of crystal structures of SAM-bound methyltransferases, along with computational studies using small molecule models, have revealed the presence of a type of non-covalent interaction termed a tetrel bond between the SAM methyl group and electron donating atoms of the target substrate. Since the tetrel-bonded complex in methyltransferase active site precedes the transition state in the SN2 methylation pathway, in this project it was hypothesized that methyltransferase active site promotes the formation of the tetrel-bonded complex, which is fundamental to the catalytic role of these enzymes. Using an optimized coupled fluorescent kinetic assay and site-directed mutagenesis to change a tyrosine residue to a phenylalanine in the active site of a model methyltransferase, SET7/9, a hydrogen bond which is believed to hold the tetrel- bonded complex in the correct orientation was removed, resulting in a 15-fold decrease in enzyme activity. Moreover, using this optimized fluorescence-based assay, ~80 peptidomimetic compounds were screened for inhibition of SET7/9, with the most potent compound, B21-2, having an IC50 value of 5.2 μM. Through understanding tetrel bonding and the use of lead compounds discovered, inhibitors may be designed to exploit unique interactions yielding potent and selective inhibitors for these enzymes.Item Magnetic and Catalytic Properties of Lanthanide Complexes(2021-05-01T05:00:00.000Z) Miller, Justin Todd; Stefan, Mihaela C.; Choudhary, Pankaj K.; Biewer, Michael C.; Nielsen, Steven O.; Pantano, PaulLanthanides are an intriguing family of elements possessing unique properties useful in many diverse applications. The first chapter of this work describes the origins of some of these properties and their catalytic and magnetic applications. The second chapter will highlight a highly unusual neodymium catalyst for diene polymerization. This coordination polymer catalyst contains no halides and makes use of no halide donor, yet produces desirable 96% 1,4- cis stereospecific material. The third chapter is concerned with the surprising formation and superparamagnetism of a neodymium-peroxide diimine cluster and the associated crystals. The cluster is formed by a rare example of anion-templated assembly in which the anion is derived from dissolved atmospheric oxygen. The resulting structural motif featured an array of tight three-metal clusters separated by a distance long enough to prevent long-range magnetic order, which resulted in superparamagnetic behavior in the solid state. This is believed to be the first report of superparamagnetism in a bulk crystal state. The fourth and final chapter is concerned with MRI contrast agents and presents an example of a new variety of potential next-generation agents composed of coordination polymers. The gadolinium diethylphosphate polymer features a far longer rotational coordination time than conventional small gadolinium complexes and thus offers dramatically improved T1 relaxation performance at low-fields common in clinical imaging applications. All of these lanthanide complexes are synthesized using an azeotropic distillation method. This method avoids the need for strict water-free techniques and also occasionally allows for novel structures to be obtained, as demonstrated in Chapter 3 in particular.Item Molecular Dynamics Investigation of Fluoride Ion Permeation and Mechanism in Fluoride Export Protein Bordetella Pertussis (Bpe)(December 2022) Akintayo, Abiola Damilare; Torabifard, Hedieh; Stefan, Mihaela C.; Nielsen, Steven O.; Meloni, GabrieleMicroorganisms struggle to survive numerous chemical threats, one of which is fluoride ions to which they developed fluoride channels (Fluc) for exporting fluoride out of their cytoplasm. The crystallographic structure and previous studies have spotted an unusual tetrahedrally coordinated non-transported central sodium cation and highlighted certain conserved polar residues along the Fluc pores. However, the exact coordination number of the central sodium and the mechanism of fluoride permeation in relation to these conserved polar residues remains elusive. In this study, we applied the all-atoms molecular dynamics method on WT Fluc-Bpe (Bordetella pertussis) with single fluoride in its pore and with four fluorides alongside its arginine mutants (R23A and R23K). We investigated the possible hydration of central sodium ion to ascertain its coordination, the role of arginine 23, which is an important conserved polar residue, and the permeation mechanism of fluoride. We found out using the watershell analysis that sodium was anhydrous in the WT Fluc and its mutants but hydrated to form a 5-ligand coordination in WT Fluc systems with single fluoride in Fo and F2 binding sites. The dihedral analysis of arginine 23 revealed that it plays a pivotal role in the stabilization of fluoride ions by electrostatic non-bonded interactions made possible by its guanidinium side chain which undergoes dihedral shift for fluoride permeation and efflux. The mechanism of fluoride export for each protein system under study provides insight into the structural dynamics of Fluc’s important arginine polar residue.Item Molecular Dynamics Simulations of Protic Ionic Liquids(2017-12) Taghavi Nasrabadi, Amir; Gelb, Lev D.; Nielsen, Steven O.This dissertation concerns the study of protic ionic liquids (PILs) by means of molecular dynamics (MD) simulations. PILs are a subset of ionic liquids in which cations possess an acidic proton. They have been a focus of intense research in the past decade mainly due to their promising properties. In this dissertation, we first begin with an introduction to PILs, and briefly review their properties and applications in Chapter 1. In Chapter 2, the main features of MD simulations are explained. Empirical force fields used in simulation studies of ILs have often failed to correctly describe their dynamics and transport properties. Chapter 3 describes how to improve the ability of well-known empirical force fields to describe the dynamical properties of tertiary ammonium triflate PILs, by scaling the atomic partial charges of ions using an optimal scaling factor derived from experimental data. Our results show that this method successfully enhances the dynamics of the simulated PILs, and improves the computed transport coefficients without increasing the computational cost. The degree of proton transfer in PILs, which indicates the percentage of ions formed from the reactant acid and base molecules, is a key quantity in this field. However, the effects of this quantity on PIL properties are still not well-understood. In Chapter 4, we try to understand these effects by simulating a family of alkylammonium acetate PILs over the entire range of the degree of proton transfer. Our results show that properties of PILs change dramatically with varying degree of proton transfer. We also use the data obtained to estimate the degree of proton transfer in experimental PILs by comparison with simulation. In Chapter 5, we introduce a rigorous thermodynamic approach by which to calculate the degree of proton transfer and equilibrium constants in PIL media. Our approach is based on a thermodynamic cycle and uses constrained MD simulations to obtain the free energy change associated with the proton transfer reaction. We apply this scheme to trimethylammonium acetate, a tertiary ammonium acetate PIL known for their low degree of proton transfer. Our results show that the proton transfer takes place only partially in this PIL, which is in good agreement with experiment. This approach can effectively be used to predict the degree of proton transfer and equilibrium constant in PILs with variety degrees of proton transfer, which is difficult to assess experimentally. In Chapter 6, we briefly summarize our findings and elaborate on possible future applications of the computational approaches used in this dissertation.Item Molecular Dynamics Simulations to Study Molecular Interactions at Biologically and Mechanically Important Surfaces(2021-04-23) Ranathunga, Dineli Thakshila Sarasavi; Nielsen, Steven O.In this dissertation molecular dynamics computer simulations (MD) were used to explore molecular scale behavior in order to interpret experimental results and guide challenging experimental work. In Chapters 2, 3 and 4 MD simulations were utilized to study a new immunointeractive surface approach to induce titanium implant osseointegration, using the constructive inflammatory effects of high mobility group box 1 (HMGB1) protein. First, in Chapter 2 the protein, ion and water interactions with the rutile (110) TiO2 surface induced by surface hydroxylation were investigated. In an aqueous environment, we show the direct binding of HMGB1 to the TiO2 surface regardless of its hydroxylation state, which causes structural changes to the protein, thereby affecting its biological function. Hence, to find a compromise between stable adsorption and preservation of protein activity in Chapter 3 we study the advantages of dicationic imidazolium-based ionic liquids (IonLs) containing amino acid anions to serve as a vehicle for delivering proteins on the surface of TiO2 implants. A strongly bound well structured IonL coating formed on the TiO2 surface effectively blocking HMGB1 from direct adsorption on the implant. Additionally, the protein is immobilized due to IonL cations and anions which bind to oppositely charged amino acids on the protein surface. In order to account for the different biological roles of HMGB1, the different HMGB1 isoforms were studied in Chapter 4. Once the IonL/HMGB1 coating on the TiO2 surface comes into contact with water, the protein release mechanism and the integrity of its receptor binding sites were investigated. Imidazolium based IonLs are becoming increasingly popular not only in bioengineering but also in many other fields due to their promising properties. Because of the large number of cation and anion combinations available, it is not feasible to experimentally measure IonL properties over a wide range of composition and operating conditions. Therefore, fast and reliable methods such as molecular modeling tools are needed to acquire these properties. However, to validate and tune the molecular modeling approach some experimental data is required. Therefore, in Chapter 5 by combining experiments with molecular modeling we explore the properties of a series of IonLs. In Chapter 6, we used MD simulations to study vapor condensation which is an area with a wide range of industrial applications. We provide molecular insight into the condensation mechanism as a function of surface wettability using surfaces chemisorbed with alkanethiol self-assembled monolayers. By changing the alkanethiol head group chemistry, the surface wettability was tuned and the role of surface wettability on the rate of water condensation was studied. We show that decreasing surface hydrophobicity significantly increases the electrostatic forces between water molecules and the surface, thus increasing the water condensation rate. We also provide connections with other microscopic and macroscopic interfacial characterizations. In Chapter 7, we used MD simulations to link experimentally observed anion sensing, specifically towards nitrate, nitrite, iodide, and thiocyanate by polyvinylpyrrolidone (PVP) polymer, to anion interactions on the polymer surface and concomitant changes in the polymer aggregation state. Supporting the experimental observations, our results suggest that anions associating most strongly to the surface of PVP quench its fluorescence to the greatest extent.Item Nano-biothiol Interactions of Engineered Nanoparticles(December 2021) Zhou, Qinhan; Zheng, Jie; Kesden, Michael; Gnade, Bruce E.; Nielsen, Steven O.; Meloni, Gabriele; D'Arcy, SheenaNanomedicines have been extensively studied in the past decades at the fundamental level because they could potentially make a paradigm shift in human healthcare. Nano-bio interactions play a central role in the precise control of the benefit and hazards of nanomedicines, but current studies mainly focus on how nanoparticles are taken up by cells and interact with different receptors. There is still not enough investigation of how the physiological environment transforms engineered nanoparticles through a variety of biochemical reactions. This dissertation aims to fundamentally understand the nanoparticle-biochemical interactions and the in vivo transport of engineered nanoparticles modulated by these interactions. In Chapter 1 of this dissertation, an overall review is given on the current understanding of nanobio interactions at the molecular and chemical levels, particularly. In Chapter 2, we systematically investigated how the nanoparticle size, the thiols species, and the protein binding affect the interactions between the nanoparticles and thiols at the in vitro level. In Chapter 3, we focused on unraveling the relation between the nanoparticle-biothiol interactions in vitro and the nanoparticle-biothiol interactions in vivo. In Chapter 4, we explored the nanoparticle-biothiol interactions in the diseased mice model and illustrated the application of nanoparticle-biothiol interactions in disease diagnosis. Finally, in Chapter 5, we present the summary and outlook. These new understanding on nano-biochemical interactions at both in vitro and in vivo levels will help further advance physiology at the nanoscale as well as open new pathways to early disease diagnosis and treatment.Item Nested Sampling of Isobaric Phase Space for the Direct Evaluation of the Isothermal-Isobaric Partition Function of Atomic Systems(American Institute of Physics) Wilson, Blake A.; Gelb, Lev D.; Nielsen, Steven O.; Wilson, Blake A.; Gelb, Lev D.; Nielsen, Steven O.Nested Sampling (NS) is a powerful athermal statistical mechanical sampling technique that directly calculates the partition function, and hence gives access to all thermodynamic quantities in absolute terms, including absolute free energies and absolute entropies. NS has been used predominately to compute the canonical (NVT) partition function. Although NS has recently been used to obtain the isothermal-isobaric (NPT) partition function of the hard sphere model, a general approach to the computation of the NPT partition function has yet to be developed. Here, we describe an isobaric NS (IBNS) method which allows for the computation of the NPT partition function of any atomic system. We demonstrate IBNS on two finite Lennard-Jones systems and confirm the results through comparison to parallel tempering Monte Carlo. Temperature-entropy plots are constructed as well as a simple pressure-temperature phase diagram for each system. We further demonstrate IBNS by computing part of the pressure-temperature phase diagram of a Lennard-Jones system under periodic boundary conditions.Item Novel Monomer Designs for 2D Polymeric Materials With Directed Supramolecular Interactions(December 2022) Boardman, Samuel R; Smaldone, Ronald; Stefan, Mihaela C.; Nielsen, Steven O.; Gassensmith, Jeremiah J.Covalent organic frameworks (COFs) are a class of polymers that have garnered significant attention in recent years for their unique physical properties. Consisting exclusively of lightweight elements (C, N, O, B, H, etc.), COFs possess highly crystalline, low-density, and permanently porous architectures. Their synthesis is carried out under thermodynamic control, where through solvothermal approaches directionally oriented dynamic covalent bonds form between monomeric units. Diversity in the successful incorporation of boron ester, imine, azine, and hydrazone linkages in tandem with stabilization forces such as dipolar and π-π stacking interactions has demonstrated the crystallization problem can be overcome to confer COFs with highly crystalline structures. Reticular methodologies afford COFs with atomically precise molecular assembly, providing the ability to predefine pore size, geometry, and dimensionality. This fascinating feature of COF design suggests great advancements in long-range order, surface area, pore size, and sorption capabilities are possible. Thus, the goal of this research details the efforts made to leverage the ‘customizable’ utility of COF design, both in regards to the monomers employed in their fabrication and with respect to the stabilization of supramolecular complexes, for the purpose of improving materials properties of 2D-COFs and broadening the practical scope of COF materials in the future. In the first chapter, COF design is discussed through the lens of scientific literature. Progress in the underlying mechanisms of formation, monomer design, and COF application as materials in gas storage are discussed. In the second chapter, two novel monomers with intended application in 2D COFs are synthesized and discussed. The first monomer, 2,4,6-trihydroxy-1,3,5-tris(p-formylphenyl)benzene, possesses out-of-plane hydroxyl groups that may participate in interlayer hydrogen bonding to improve the stability between 2D COF sheets. The second monomer, N,N',N''-(benzene-1,3,5-triyl)tris(1,1-diphenylmethanimine), is a stable benzophenone imine protected analog of 1,3,5-triaminobenzene and is suitable for use in the synthesise of a 2D imine-linked COF. In the third chapter, preliminary reactions using the novel monomer discussed in Chapter 2 are detailed and the resultant polymers are characterized.Item Selective Chemical Bath Deposition of Copper Sulfides and Tin Sulfides on Functionalized Self-assembled Monolayers(December 2022) Estrada, Tania Guadalupe; Walker, Amy V; Hong, Liang; Nielsen, Steven O.; Balkus Jr., Kenneth J.; Stefan, Mihaela C.The deposition of select chemical phases of semiconducting materials is an industrially complex problem. Moreover, the currently practiced deposition methods that employ harsh conditions, such as high temperature (>100oC), limit the ability to deposit onto polymer or organic substrates. The development of low temperature methods is necessary for the future of flexible electronic applications. In this work chemical bath deposition (CBD), is employed towards selective compositional deposition of copper sulfide and tin sulfide phases on alkanethiolate self- assembled monolayers (SAMs) substrates. SAMs are model organic systems with tunable surface chemistry. This work shows selective compositional deposition of copper sulfide, Cu2S or CuS, on -COOH, -OH, and -CH3 terminated SAMs when using thiourea as a sulfur precursor deposited at pH 9 and CuS deposited at pH 12. The selectivity of the deposit is dependent on the bath pH and surface chemistry. Area selective deposition of CuS is also observed when using thioacetamide as a sulfur precursor for copper sulfide CBD. Tin sulfides are also shown to be compositionally dependent on bath pH and substrate chemistry and deposit as either SnS, SnS2, or Sn2S3.Item Studying the RNA Surveillance Activity of Mtr4 and the Tramp Complex Using Hydrogen Deuterium Exchange Mass Spectrometry(2021-08-01T05:00:00.000Z) Zhang, Naifu; Efromovich, Sam; D'Arcy, Sheena; Meloni, Gabriele; Dodani, Sheel; Nielsen, Steven O.Mtr4 is an essential ribonucleic acid (RNA) helicase that plays a central role in RNA processing and degradation as an activator of the nuclear exosome. Mtr4 can carry out its function alone or in the Trf4/Air2/Mtr4 Polyadenylation complex (TRAMP). While recent structures highlight the pathway of RNA through the helicase core, the limited resolution of these studies precludes a detailed description of Mtr4-RNA interactions and how these change with different RNA substrates. The molecular arrangement and mechanism of the TRAMP complex are also unknown. To fill these gaps, we performed an extensive series of hydrogen-deuterium exchange (HDX), binding and activity assays with Mtr4, the TRAMP complex, and different RNA substrates. Our study reveals important RNA interactions that span multiple domains of the Mtr4 helicase, including the Kyprides-Ouzounis-Woese (KOW) motif (or fist) of the Arch domain. Different RNA substrates engage the KOW motif to different extents when they bind Mtr4, and this engagement correlates with RNA binding and unwinding activity. Interactions between the KOW motif and RNA also induce a large conformational change of the arm of the Arch domain. These data support a substrate-specific role for the Arch domain in RNA recognition. We further uncover molecular details about the arrangement and function of TRAMP. We show the path of RNA binding in the Air2-Trf4 sub-complex and identify novel interfaces between Air2-Trf4 and Mtr4. Air2 in fact binds to the Arch domain of Mtr4 and causes Mtr4 to adopt a conformation that resembles an RNA-bound complex. Experiments with RNA and TRAMP also show that RNAbinding by Air2-Trf4 and Mtr4 is similar when the proteins are alone or in TRAMP. This, combined with functional assays, clearly implies competition between the polyadenylation active site of Trf4 and the helicase active site of Mtr4. Consistently, we show that Mtr4 will prevent unregulated RNA polyadenylation by Trf4-Air2. Altogether our data shows that Mtr4 helicase activity is regulated by the RNA substrate, as well as protein binding partners.Item Supercapacitor Electrode Materials Comprising Uniformly Dispersed Chromium Nitride/ Carbon Fiber Composite(2022-05-01T05:00:00.000Z) Rifat, Samia; Ferraris, John P.; Balkus Jr., Kenneth J.; Nielsen, Steven O.; Pantano, PaulNowadays, researchers and industrial designers are looking for an eco-friendly alternative energy source to fulfill the increasing need for energy and reduce environmental pollution. Electricity based on energy storage devices can be a way of solving the crisis. Among different energy storage devices, the faster charging and discharging speeds or higher power densities, working in a wider range of temperatures, and longer cycle life of supercapacitor make them attractive for several applications. The commercially available supercapacitors are mostly electric double-layer capacitors (EDLCs) and to a lesser degree of pseudocapacitors. Recently, researchers have been focusing on hybrid supercapacitors (HSCs) due to their ability to combine the properties of both EDLCs and pseudocapacitors to expand the applications. Engineered carbon nanofibers can be coupled with conductive metal nitrides to form composites and used as electrode materials for supercapacitor applications. In this work, a new hybrid nanocomposite of carbon fibers and chromium nitride (CFs/CrN) was fabricated as electrode materials, where polyacrylonitrile (PAN) was utilized as the carbonizing materials and polymethyl methacrylic acid (PMAA) as the sacrificial agents. Here, pore-forming agents, PMAA, assisted in improving the supercapacitor's performance by increasing the electrode materials' surface area. Also, growing CrN nanoparticles in the fiber contributed by the pseudocapacitance from proton adsorption. Furthermore, the chelation ability of the PMAA might be beneficial for the homogeneous distribution of CrN all over the CFs. Furthermore, the use of aqueous electrolytes and comparatively low-cost transition metal materials lowered the fabrication costs, and the utilization of the electrospinning technique makes CFs/metal nitrides composite electrodes freestanding and readily produced. Chapter 1 describes a detailed introduction to supercapacitors, including a brief description of the storage principle of EDLCs, pseudo capacitors, and hybrid supercapacitors and their advantages and disadvantages. It also describes the basics of the electrospinning process, thermal treatments, and aqueous electrolytes, all of which were applied to fabricate the supercapacitors using CFs and metal nitrides composite-based electrodes. Chapter 2 represents the fabrication of CFs and chromium nitrides composites using polymer blends containing PAN and PMAA and Cr precursor as a source of chromium. This chapter also describes the characterization of synthesized PAM-PMAA-CrN electrode materials and their electrochemical performance and analysis. The highest capacitance was obtained from PANPMAA-CrN based electrode 159 F/g at 5 mV/s. Also, the highest energy densities of 13.26 Wh/Kg at 1.2 V were obtained from the PAN-PMAA-CrN and CNFs based asymmetric device. Furthermore, the PAN-PMAA-CrN electrode showed higher stability with 80.4% capacitance retention after 10000 cycles.Item Synthesis and Characterization of ScMGa₅ (M = Fe, Co, Ni) and Yb₁₋ₓScₓCoGa₅ (0 ≤ x ≤ 1)(2020-08) Green, Lance M; Ferraris, John P.; Nielsen, Steven O.The crystal structures of ScMGa5 (M = Fe, Co, Ni) have been determined by single crystal X-ray diffraction for crystals grown from a gallium self-flux. The synthesis and characterization of Yb₁₋ₓScxCoGa₅ (0 ≤ x ≤ 1) is first reported here. ScMGa₅ (M = Fe, Co, Ni) adopts the HoCoGa5-structure type and crystallizes in the tetragonal space group P4/mmm (No. 123), Z = 1, a = 4.1367(7) Å and c = 6.6422(17) Å for ScFeGa₅, a = 4.1290(11) Å and c = 6.6034(16) Å for ScCoGa₅, and a = 4.1466(6) Å and c = 6.492(2) Å for ScNiGa₅. As the transition metal atomic size increases, from Ni to Fe, the volume of the unit cell increases from 111.63(5) ų to 113.66(4) ų. The compounds consist of alternating MGa₂ edgesharing rectangular prisms interweaved with face-sharing cuboctahedra of ScGa₃ that stack in the [001] direction. ScMGa₅ (M = Fe, Co, Ni) can be structurally compared to materials adopting the AuCu₃-structure type. Yb₁₋ₓScₓCoGa₅ (0 ≤ x ≤ 1) also adopts the HoCoGa₅-structure type and crystallizes in the tetragonal space group P4/mmm. The volume of the unit cell decreases linearly with increasing Sc concentration. Inhomogeneity was found to be maximized when the nominal molar ratios of Yb and Sc were equal.Item Synthetic Design of Cerium-Based Intermetallics(2021-05-01T05:00:00.000Z) Weiland, Ashley; Chan, Julia; Xuan, Zhenyu; Zheng, Jie; Nielsen, Steven O.; Walker, Amy V.Ce-based highly correlated systems are of interest due to Ce3+ (S=1/2) providing an ideal f-electron system to study the interplay of localized magnetic moments and conduction electrons. The growth of high-quality single crystals is of utmost importance to ensure the determination of intrinsic anisotropic properties. This dissertation presents the single crystal growth and d etailed characterization of Ce-containing intermetallics. Motivated by the search for new spintronic devices based on topological materials, the first study highlights the incorporation of Bi in the topological parent compound, CeSbTe. Sb net containing CeSbTe has been studied to show the interplay of magnetism and topology. Inserting Bi, a larger element, provides the opportunity to change the Fermi surface while preserving topologically relevant features. We show the band structure engineering of potential topological materials LnSb1-xBixTe (Ln = La, Ce, Pr; x ~ 0.2) and CeBiTe. Continuing our search for novel quantum materials, our elucidation of crystal growth parameters of Ce-based intermetallics, led to the identification of a new intermetallic homologous series An+1MnX3n+1 (A = rare earth; M = transition metal; X = tetrels; n = 1 – 6) built up of structural subunits such as AlB2, AuCu3, and BaNiSn3. The homologous series serves as a model system for studying the coupling between localized f-electrons and conduction electrons. Additionally, the stacking of heterostructural subunits is an exciting way to modify physical properties of related phases, highlighting the importance of structural building blocks as a new avenue to study magnetism and topology. Crystal growth, detailed single crystal structural modeling, and magnetic and transport properties of Ce5Co4+xGe13-ySny (n = 4), Ce6Co5+xGe16-ySny (n = 5), and Ce7Co6+xGe19-ySny (n = 6), are presented. The similarities between the synthetic profiles used to grow n = 4 – 6 brought about new questions which led to our work investigating phase formation. Finally, the process for designing in situ synchrotron experiments, including a new sample environment and furnace apparatus for the use with flux grown intermetallics, is presented.Item Towards an Understanding of Structure-Nonlinearity Relationships in Triarylamine-based Push-Pull Electro-Optic Chromophores: The Influence of Substituent and Molecular Conformation on Molecular Hyperpolarizabilities(Royal Soc Chemistry, 2014-02-17) Wu, Jingbo; Wilson, Blake A.; Smith, Dennis W., Jr.; Nielsen, Steven O.; 2012052347 (Smith, DW); Smith, Dennis W., Jr.; Nielsen, Steven O.We calculated the second-order hyperpolarizability (beta) of a series of triarylamine (TAA) based donor-bridge-acceptor (D-π-A) push-pull type nonlinear optical (NLO) chromophores with different electron donor moieties and the same thiophene π-bridge and dicyanovinyl electron acceptor using a time-dependent Hartree-Fock (TDHF) approach within the software package MOPAC 2012. NLO chromophores with various quantities and positions of methoxy groups in the TAA donor moiety were investigated. The relationship between NLO properties and the electronic or geometric structures of the TAA donor subunit is discussed through the calculation results. Both substituent and conformational effects affect the delocalization of the nitrogen lone pair into the aryl rings, leading to a dramatic influence on the nonlinear optical properties. Introduction of methoxy groups at the ortho positions of the TAA moiety has a larger influence on the molecular hyperpolarizability and dipole moment than the introduction of methoxy group at the para or meta positions. Our calculation results demonstrate how to improve the NLO properties of TAA based chromophores while meeting practical device requirements.Item Towards Understanding the Roles of Organic Bath Additives in Copper Electroless Deposition on Self-assembled Monolayers(December 2022) Vienes, Jevalyne Satparam; Walker, Amy; Makarenkov, Oleg; Gelb, Lev D.; Nielsen, Steven O.; Stefan, Mihaela C.Organic bath additives are commonly used in solution-based deposition techniques to improve the properties of the desired material. However, despite their wide application, studies on understanding the roles of these additives are limited. In this dissertation, we employed multiple surface characterization techniques including X-ray photoelectron spectroscopy (XPS), time-of- flight secondary ion mass spectrometry (TOF SIMS), Raman spectroscopy, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), atomic force microscopy (AFM), and optical microscopy to investigate the effect monoethanolamine, diethanolamine, triethanolamine, urea, guanidine, and thiourea as bath additives in the electroless deposition of copper on self-assembled monolayers (SAMs). Using XPS and TOF SIMS, we observed that electrolessly deposited copper is more adherent on the –CH3 terminated SAMs. TOF SIMS spectra also showed that the mono- and triethanolamine interact with the –CH3 terminated SAM via the amine functional group while diethanolamine adsorbs flat on the SAM surface. These interactions allowed the deposition of copper wires via electroless nanowire deposition on micropatterned substrates (ENDOM). Fragment ions in the TOF SIMS spectra showed various interactions of the hydroxyl group of ethanolamines with the –OH terminated SAMs. This indicates that polar ethanolamines interact strongly with the hydroxyl-terminated SAM surface. We also demonstrated a switch from copper electroless deposition at low concentrations of thiourea to copper sulfide deposition at high concentrations of thiourea. We synthesized copper wires using thiourea as bath additive in ENDOM. A method of depositing Cu/CuxS layer via a two-step solution-based technique is also presented. The electron-donating property of the heteroatom in bath additives (urea, guanidine, and thiourea) influences its stabilizing ability. Thiourea inhibited the electroless deposition process which allowed the deposition of small particles resulting in smooth copper film. Also, regardless of the bath additive heteroatom, smoother films were deposited at pH 9. At pH 12, we observed two layers of deposit: (a) ion-by-ion growth of the underlayer and (b) cluster-by-cluster growth of the overlayer. Copper wires deposited using guanidine as bath additive at pH 9 are more uniform. Lastly, we proposed methods to optimize the crossbar wire synthesis using multiple ENDOM processes.Item Ultrafast Pulsed Laser Induced Nanocrystal Transformation in Colloidal Plasmonic Vesicles(Wiley-VCH Verlag) Karim, Mohammad R.; Li, Xiuying; Kang, Peiyuan; Kang, Peiyuan; Randrianalisoa, J.; Ranathunga, Dineli; Nielsen, Steven O.; Qin, Zhenpeng; Qian, Dong; 0000-0003-3406-3045 (Qin, Z); 295272933 (Qian, D); Karim, Mohammad R.; Li, Xiuying; Ranathunga, Dineli; Nielsen, Steven O.; Qin, Zhenpeng; Qian, DongPlasmonic vesicle consists of multiple gold nanocrystals within a polymer coating or around a phospholipid core. As a multifunctional nanostructure, it has unique advantages of assembling small nanoparticles (< 5 nm) for rapid renal clearance, strong plasmonic coupling for ultrasensitive biosensing and imaging, and near-infrared light absorption for drug release. Thus, understanding the interaction of plasmonic vesicles with light is critically important for a wide range of applications. In this paper, a combined experimental and computational study is presented on the nanocrystal transformation in colloidal plasmonic vesicles induced by the ultrafast picosecond pulsed laser. Experimentally observed merging and transformation of small nanocrystals into larger nanoparticles when treated by laser pulses is first reported. The underlying mechanisms responsible for the experimental observations are investigated with a multiphysics computational approach featuring coupled electromagnetic/molecular dynamics simulation. This study reveals for the first time that combined nanoparticle heating and laser-enhanced Brownian motion is responsible for the observed nanocrystal merging. Correspondingly, laser fluence, interparticle distance, and presence of water are identified as the most important factors governing the nanocrystal transformation. The guidelines established from this study can be employed to design a host of biomedical and nanomanufacturing applications involving laser interaction with plasmonic nanoparticles.