Browsing by Author "Morris, John R."

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    Ab initio and Direct Quasiclassical Trajectory Study of the F + CH₄ → HF + CH₃ and F + C₂H₆ → HF + C₂H₅ Reactions
    Weiss, Paula (Virginia Tech, 2007-09-25)
    The reparametization of semiempirical Hamiltonians is an emerging method used in direct dynamics studies. The use of semiempirical Hamiltonians in direct dynamics studies diminishes the computational cost of trajectory calculations and negates the need for an analytical potential energy surface when performing reaction dynamics studies. The reparametization of semiempirical Hamiltonians increases the agreement with experiment and high level ab initio theory. We have chosen to create one set of new parameters that apply to two related reactions, F + CH₄ → HF + CH₃ and F + C₂H₆ → HF + C₂H₅. We have performed an electronic structure study for these reactions. The ab initio data obtained from the electronic structure study is then used as the reference for a reparametization of the PM3 Hamiltonian. The reparametization has improved the ab initio and PM3 reaction energy and potential energy surface scan agreement. This new set of parameters for PM3 (SRP-PM3) is used to perform a direct quasiclassical trajectory study of the reactions. The vibrational and rotational HF distributions calculated using SRP-PM3 are compared with experiments. We have observed an improvement in the agreement with experimental vibrational distributions but have seen no change in the rotational distributions.
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    Ab initio Calculations of Optical Rotation
    Tam, Mary Christina (Virginia Tech, 2006-04-18)
    Coupled cluster (CC) and density functional theory (DFT) are highly regarded as robust quantum chemical methods for accurately predicting a wide variety of properties, such as molecular structures, thermochemical data, vibrational spectra, etc., but there has been little focus on the theoretical prediction of optical rotation. This property, also referred to as circular birefringence, is inherent to all chiral molecules and occurs because such samples exhibit different refractive indices for left- and right- circularly polarized light. This thesis focuses on the theoretical prediction of this chiroptic property using CC and DFT quantum chemical models. Several small chiral systems have been studied, including (S)-methyloxirane, (R)-epichlorohydrin, (R)-methylthiirane, and the conformationally flexible molecules, (R)-3-chloro-1-butene and (R)-2-chlorobutane. All predicted results have been compared to recently published gas-phase cavity ringdown polarimetry data. When applicable, well-converged Gibbs free energy differences among confomers were determined using complete-basis-set extrapolations of CC energies in order to obtain Boltzmann-averaged specific rotations. The overall results indicate that the theoretical rotation is highly dependent on the choice of optimized geometry and basis set (diffuse functions are shown to be extremely important), and that there is a large difference between the CC and DFT predicted values, with DFT usually predicting magnitudes that are larger than those of coupled cluster theory.
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    Adsorption Studies of Polysaccharides and Phospholipids Onto Cellulose
    Du, Xiaosong (Virginia Tech, 2011-12-12)
    Interactions between biomolecules and cellulose films at solid/liquid interfaces was studied by surface plasmon resonance spectroscopy (SPR), quartz crystal microbalance with dissipation monitoring (QCM-D) and in situ atomic force microscopy (AFM) measurements. This dissertation shows the porous character of nanocrystalline cellulose films as the key feature for enhanced adsorption of chemically modified polysaccharides and provides quantitative analysis of polymer supported phospholipid structures as a stable platform for studying membrane-related processes. Smooth cellulose I films were prepared by spincoating cellulose nanocrystal suspensions onto positively charged self-assembled monolayers on gold. The adsorption of pullulan cinnamate (PC) onto cellulose surfaces increased with increasing degree of cinnamate substitution. The interactions between PCs with higher degree of substitution (DS) and porous nanocrystalline cellulose (NC) films presumably generated looped multilayer PC structures that adsorbed more than twice as much onto NC films than onto regenerated cellulose (RC) films. PC chains not only covered the NC surface but also penetrated into the porous film. The porous features of NC film are responsible for the greater adsorption of polymer chains relative to tightly packed RC films. Adsorption of phospholipid vesicles onto RC and NC films was also studied. Aggregates of intact vesicle were observed on NC surfaces with high water content ~ 84 % by mass. Phospholipid patches with smooth features were found to assemble onto RC surfaces with a lower degree of hydration ~ 30 % by mass. Vesicle membrane breakage was triggered by a destabilizing agent, LysoPC. The great mass decrease, and changes in dissipation and degree of hydration for phospholipid structures after exposure to LysoPC corresponded to the transformation from vesicles to layered structures. Initial binding of LysoPC micelles to unruptured vesicles was clearly resolved in SPR, whereas the huge mass decrease associated with bound water hides the initial adsorption of LysoPC onto vesicles in QCM-D experiments. The intitial binding of LysoPC micelles onto vesicle membranes lasted for 200 seconds with a maximal increase of 14 % by mass prior to vesicle collapse. The role of cholesterol in phospholipid interactions with model cellulose surfaces was also considered. Supported vesicle layers over RC surfaces were observed for vesicle membranes containing ≥ 6.3 % by mole cholesterol, whereas phospholipid or phospholipid with lower cholesterol content formed disconnected lipid islands on RC surfaces. Meanwhile, intact vesicles were always observed on NC surfaces for phospholipid/cholesterol blends regardless of the cholesterol content. The intact vesicles on cellulose surfaces were attributed to the ability of cholesterol to accommodate vesicle deformation. These studies showed the impact of mesoscale structure of cellulose films on adsorbates. It sheds light on the role of the lignin-carbonhydrate-complex in plant cell wall structure and will inform the next generation of biomimetic nanocomposites. The designed polymer supported biomimetic membranes provide a perfect platform to develop intact and ruptured protoplast systems for the study of plant cell wall self-assembly.
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    Aerosolization and Atmospheric Transformation of Engineered Nanoparticles
    Tiwari, Andrea Jean (Virginia Tech, 2014-04-04)
    While research on the environmental impacts of engineered nanoparticles (ENPs) is growing, the potential for them to be chemically transformed in the atmosphere has been largely ignored. The overall objective of this work was to assess the atmospheric transformation of carbonaceous nanoparticles (CNPs). The research focuses on C₆₀ fullerene because it is an important member of the carbonaceous nanoparticle (CNP) family and is used in a wide variety of applications. The first specific objective was to review the potential of atmospheric transformations to alter the environmental impacts of CNPs. We described atmospheric processes that were likely to physically or chemically alter aerosolized CNPs and demonstrated their relevance to CNP behavior and toxicity in the aqueous and terrestrial environment. In order to investigate the transformations of CNP aerosols under controlled conditions, we developed an aerosolization technique that produces nano-scale aerosols without using solvents, which can alter the surface chemistry of the aerosols. We demonstrated the technique with carbonaceous (C₆₀) and metal oxide (TiO₂, CeO₂) nanoparticle powders. All resulting aerosols exhibited unimodal size distributions and mode particle diameters below 100 nm. We used the new aerosolization technique to investigate the reaction between aerosolized C₆₀ and atmospherically realistic levels of ozone (O₃) in terms of reaction products, reaction rate, and oxidative stress potential. We identified C₆₀O, C₆₀O2, and C₆₀O3 as products of the C₆₀-O3 reaction. We demonstrated that the oxidative stress potential of C₆₀ may be enhanced by exposure to O3. We found the pseudo-first order reaction rate to be 9 x 10⁻⁶ to 2 x 10⁻⁵ s⁻¹, which is several orders of magnitude lower than the rate for several PAH species under comparable conditions. This research has demonstrated that a thorough understanding of atmospheric chemistry of ENPs is critical for accurate prediction of their environmental impacts. It has also enabled future research in that vein by developing a novel technique to produce nanoscale aerosols from nanoparticle powders. Results of this research will help guide the formulation of appropriate environmental policy concerning the regulation of ENPs.
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    AFM-Assisted Nanofabrication using Self-Assembled Monolayers
    Jang, Chang-Hyun (Virginia Tech, 2003-12-19)
    This study describes the covalent and the electrostatic attachment of molecules, nano-particles, and proteins to patterned self-assembled monolayers. A scanning probe nanografting technique was employed to produce patterns of various sizes, down to 10 nm. Thus, we are able to demonstrate a degree of surface patterning which is an order of magnitude smaller than that used in the semiconductor industry. One efficient strategy for creating chemically specific nanostructures is to use the extraordinary catalytic properties of enzymes. However, as the dimension of a catalyst patch is reduced down to nanometer scale, it is difficult to detect the very low concentration of product. This study resolves the problem by developing a new strategy: the surface trapping of a product generated by a nanometer-scale patch of surface-bound enzyme. An array of proteins finds use when the array contains a number of different proteins. Toward this end, a new and convenient method for immobilizing enzymes is developed, which will allow the preparation of thin films containing several different catalytically-active enzymes on the nanoscale. The disadvantage of scanning probe nanografting technique is that the AFM tip loses resolution through wear during the patterning procedure. This study examines the possibility of developing a new AFM lithographic method to avoid wear: the use of enzymes covalently attached to a tip as a site-specific catalyst.
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    Atomic-Level Structural Dynamics of Polyoxoniobates during DMMP Decomposition
    Wang, Qi; Chapleski, Robert C. Jr.; Plonka, Anna M.; Gordon, Wesley O.; Guo, Weiwei; Thuy-Duong Nguyen-Phan; Sharp, Conor H.; Marinkovic, Nebojsa S.; Senanayake, Sanjaya D.; Morris, John R.; Hill, Craig L.; Troya, Diego; Frenkel, Anatoly I. (Springer Nature, 2017-04-10)
    Ambient pressure in situ synchrotron-based spectroscopic techniques have been correlated to illuminate atomic-level details of bond breaking and formation during the hydrolysis of a chemical warfare nerve agent simulant over a polyoxometalate catalyst. Specifically, a Cs-8[Nb6O19] polyoxoniobate catalyst has been shown to react readily with dimethyl methylphosphonate (DMMP). The atomic-level transformations of all reactant moieties, the [Nb6O19](8)-polyanion, its Cs+ counterions, and the DMMP substrate, were tracked under ambient conditions by a combination of X-ray absorption fine structure spectroscopy, Raman spectroscopy, and X-ray diffraction. Results reveal that the reaction mechanism follows general base (in contrast to specific base) hydrolysis. Together with computational results, the work demonstrates that the ultimate fate of DMMP hydrolysis at the Cs-8[Nb6O19] catalyst is strong binding of the (methyl) methylphosphonic acid ((M) MPA) product to the polyanions, which ultimately inhibits catalytic turnover.
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    Biochar Surface Oxygenation by Ozonization for Super High Cation Exchange Capacity
    Kharel, Gyanendra; Sacko, Oumar; Feng, Xu; Morris, John R.; Phillips, Claire L.; Trippe, Kristin; Kumar, Sandeep; Lee, James W. (2019-10-07)
    Biochar cation exchange capacity (CEC) is a key property central to better retention of soil nutrients and reduction of fertilizer runoff. This paper reports a breakthrough process to improve biochar CEC value by a factor of nearly 10 through biochar surface oxygenation by ozonization. The CEC value of the untreated biochar was measured to be anywhere between 14 and 17 cmol/kg. A 90 min dry ozonization treatment resulted in an increased biochar CEC value of 109-152 cmol/kg. Simultaneously, the biochar ozonization process resulted in a reduction of biochar pH from 9.82 to as low as 3.07, indicating the formation of oxygen-functional groups including carboxylic acids on biochar surfaces. Using the technique of X-ray photoelectron spectroscopy (XPS), the formation of oxygen-functional groups including carboxylic acids on biochar surfaces have been observed at a nanometer molecular scale following the ozonization treatment. The molar O/C ratio (0.31:1) on ozonized biochar surface as analyzed by XPS was indeed significantly higher than that (0.16:1) of the control biochar surface. The molar O/C ratio from the elemental analysis data also showed an increase from the nonozonized sample (0.077:1) to the dry-ozonized sample (0.193:1). Fourier-transform infrared (FTIR) spectroscopy analysis also showed an increase in the content of oxygen-functional groups in the form of carbonyl groups on biochar surfaces upon ozonization, which can also produce certain amount of oxygenated biochar molecular fragments that may be solubilized by liquid water, potentially leading to greater effects upon application of biochar in soil.
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    Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles
    Geng, Xi (Virginia Tech, 2017-06-16)
    Anisotropic plasmonic noble metallic nanoparticles (APMNs) have received enormous attention due to their distinct geometric features and fascinating physicochemical properties. Owing in large part to their tailored localized surface plasmon resonance (LSPR) and the intensive electromagnetic field at the sharp corners and edges, APMNs are exceptionally well suited for biomedical applications such as biosensing, bioimaging, diagnostics and therapeutics. Although a rich variety of surfactant-assisted colloidal routes have been developed to prepare well-defined APMNs, biomedical applications necessitate tedious and rigorous purification processes for the complete removal of toxic surfactants. In this dissertation, we aim to develop generic bioenabled green synthetic methodologies towards APMNs. By applying a series of thermodynamic, kinetic and seed quality control, a series of APMNs with varied morphologies such as branched nanostars and triangular nanoprisms have been successfully prepared. We first presented the preparation of gold nanostars (Au NSTs) through a two-step approach utilizing a common Good's buffer, HEPES, as a weak reducing agent. Single crystalline Au NSTs with tunable branches up to 30 nm in length were produced and the halide ions rather than the ionic strength played a significant roles on the length of the branches of Au NSTs. Then consensus sequence tetratricopetide repeat (CTPR) proteins with increasing number of repeats were used as model proteins to probe the effects of concentration as well as the protein shape on the morphology and resulting physicochemical properties of plasmonic gold nanoparticles. Since the underlying growth mechanism for the biomimetic synthesis of APMNs remains elusive and controversial, the other objective is to elucidate the molecular interactions between inorganic species and biopolymers during the course of NP evolution. Fluorescent quenching and 2D NMR experiments have confirmed the moderate binding affinity of CTPR to the Au(0) and Au(III). We observed that the initial complexation step between gold ions and CTPR3 is ionic strength dependent. Furthermore, we also found that NPs preferentially interact with the negatively charged face of CTPR3 as observed in 2D NMR. Knowledge of binding behavior between biospecies and metal ions/NPs will facilitate rational deign of proteins for biomimetic synthesis of metallic NPs. A modified seed-mediated synthetic strategy was also developed for the growth of silver nanoprisms with low shape polydispersity, narrow size distribution and tailored plasmonic absorbance. During the seed nucleation step, CTPR proteins are utilized as potent stabilizers to facilitate the formation of planar-twinned Ag seeds. Ag nanoprisms were produced in high yield in a growth solution containing ascorbic acid and CTPR-stabilized Ag seeds. From the time-course UV-Vis and transmission electron microscopy (TEM) studies, we postulate that the growth mechanism is the combination of facet selective lateral growth and thermodynamically driven Ostwald ripening. By incorporation of seeded growth and biomimetic synthesis, gold nanotriangles (Au NTs) with tunable edge length were synthesized via a green chemical route in the presence of the designed CTPR protein, halide anions (Br⁻) and CTPR-stabilized Ag seeds. The well-defined morphologies, tailored plasmonic absorbance from visible-light to the near infrared (NIR) region, colloidal stability and biocompatibility are attributed to the synergistic action of CTPR, halide ions, and CTPR-stabilized Ag seeds. We also ascertained that a vast array of biosustainable materials including negatively charged lignin and cellulose derivatives can serve as both a potent stabilizers and an efficient nanocrystal modifiers to regulate the growth of well-defined Ag nanoprisms using a one-pot or seeded growth strategy. The influential effects of reactants and additives including the concentration of sodium lignosulfonate, H2O2 and NaBH4 were studied in great detail. It implies that appropriate physicochemical properties rather than the specific binding sequence of biomaterials are critical for the shaped-controlled growth of Ag NTs and new synthetic paradigms could be proposed based on these findings. Last but not the least, we have demonstrated the resulting APMNs, particularly, Au NSTs and Ag NTs exhibit remarkable colloidal stability, enhanced SERS performance, making them promising materials for biosensing and photothermal therapy. Since the Ag nanoprisms are susceptible to morphological deformation in the presence of strong oxidant, they also hold great potential for the colorimetric sensing of oxidative metal cation species such as Fe3+, Cr3+, etc.
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    Cation and Anion Transport in a Dicationic Imidazolium-Based Plastic Crystal Ion Conductor
    Kidd, Bryce Edwin (Virginia Tech, 2013-07-10)
    Here we investigate the organic ionic plastic crystal (OIPC) 1,2-bis[N-(N\'-hexylimidazolium-d2(4,5))]C2H4 2PF6- in one of its solid plastic crystal phases by means of multi-nuclear solid-state (SS) NMR and pulsed-field-gradient (PFG) NMR. We quantify distinct cation and anion diffusion coefficients as well as the diffusion activation energies (Ea) in this dicationic imidazolium-based OIPC. Our studies suggest a change in transport mechanism for the cation upon varying thermal and magnetic treatment (9.4 T), evidenced by changes in cation and anion Ea. Moreover, variable temperature 2H SSNMR lineshapes further support a change in local molecular environment upon slow cooling in B0. Additionally, we quantify the percentage of mobile anions as a function of temperature from variable temperature 19F SSNMR, where two distinct spectral features are present. We also comment on the pre-exponential factor (D0), giving insight into the number of degrees of freedom for both cation and anion as a function of thermal treatment. In conjunction with previously reported conductivity values for this class of OIPCs and the Stokes-Einstein relation, we propose that ion conduction is dominated by anion diffusion between crystallites (i.e., grain boundaries). Using our experimentally determine diffusion coefficient and previously reported PF6- hydrodynamic radius (rH), viscous (" = 4.1 Pa " s) ionic liquid (IL) is present with a cation rH of 0.34 nm. NMR measurements are very powerful in elucidating fundamental OIPC properties and allow a deeper understanding of ion transport within such materials.
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    Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers
    Kittle, Joshua Daniel (Virginia Tech, 2012-04-02)
    As the two most abundant natural polymers on earth, cellulose and chitin have attracted increasing attention as a source of renewable energy and functional materials. Thin films of cellulose and chitin are useful for studying interactions of these materials with other natural and synthetic molecules via techniques such as quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR). Because of the difficulty of extracting native cellulose, regenerated cellulose (RC), sulfated nanocrystalline cellulose (SNC), and desulfated nanocrystalline cellulose (DNC) thin films are often studied in its place. In this work, QCM-D solvent exchange studies showed that water contents of RC, SNC and DNC films were proportional to the film thickness (d). Accessibility and degradation of the films was further analyzed via substrate exposure to cellulase. Cellulase adsorption onto RC films was independent of d, whereas cellulase adsorption onto SNC and DNC films increased with d. Enhanced access to guest molecules for SNC and DNC films relative to RC films revealed they are more porous. The porosity of these cellulose films aided in understanding the observed differences of xyloglucan (XG) adsorption onto their surfaces. Xyloglucan adsorption onto RC, SNC, and DNC was studied by QCM-D and SPR. The amount of adsorbed XG increased in the order RC < SNC < DNC. XG adsorption onto RC films was independent of d, whereas XG adsorption was weakly dependent upon d for SNC films and strongly dependent upon d for DNC films. However, XG adsorbed onto "monolayer" thin films of RC, SNC, and DNC in approximately the same amount. These results suggested that the morphology and surface charge of the cellulose substrate had a limited effect upon XG adsorption and that accessible surface area of the cellulose film may be the factor leading to apparent differences in XG adsorption for different surfaces. The porosity and surface charge of SNC films presented a unique opportunity to examine polyelectrolyte adsorption and subsequent dewatering of the SNC substrate. The adsorption of a series of cationically derivatized dextran (cDex) polyelectrolytes with various degrees of substitution (DS) onto SNC was studied using QCM-D and SPR. As the hydrophobic character of the cDex samples increased, the water content of the adsorbed cDex layer decreased. For cDex with the greatest hydrophobic content, nearly 50% by mass of the initial water present in the porous SNC film was removed upon cDex adsorption. This study indicated that the water content of the film could be tailored by controlling the DS and hydrophobic character of the polyelectrolyte. This work also presents the first report of smooth, homogeneous, ultrathin chitin films, opening the door to surface studies of binding interactions, adsorption kinetics, and enzymatic degradation. The chitin films were formed by spincoating trimethylsilyl chitin onto gold or silica substrates, followed by regeneration to a chitin film. The utility of these chitin films as biosensors was evident from QCM-D and SPR studies that revealed bovine serum albumin adsorbed as a monolayer.
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    Computational Investigations at the Gas-Surface Interface: Organic Surface Oxidation and Hydrolysis of Chemical Warfare Agents and Simulants
    Chapleski Jr, Robert Charles (Virginia Tech, 2017-04-25)
    Motivated by recent experiments in gas-surface chemistry, we report our results from computational investigations of heterogeneous systems relevant to atmospheric chemistry and protection against chemical weapons. To elucidate findings of ultra-high vacuum experiments that probe the oxidation of carbon-carbon double bonds on model surfaces, we used electronic structure and QM/MM methods to study the reaction of ozone with C60-fullerene and the products of nitrate addition to a vinyl-terminated self-assembled monolayer. In the first system, we followed a reaction pathway beginning with primary ozonide formation through the formation of stable products. Theoretical vibrational spectra were used to identify a ketene product in prior experimental work. Next, through the construction of a multilayer model for the initial addition product of a nitrate radical to a chain embedded within a self-assembled monolayer, we report theoretical spectra that are consistent with experimental results. We then examined the fundamentals of the hydrolysis mechanism for nerve agents by a catalyst of interest in the development of filtration materials for chemical-warfare-agent defense. By following the gas-surface reaction pathway of the nerve agent Sarin on the Lindqvist polyoxoniobate Cs8Nb6O19, we determined that the rate-limiting step is the transfer of a proton from an adsorbed water molecule to the niobate surface, concomitant with the nucleophilic addition of the nascent hydroxide to the phosphorus atom in Sarin. Our results support a general base hydrolysis mechanism, though high product-adsorption energies suggest that thermal treatment of the system is required to fully regenerate the catalyst. We report similar mechanisms for the simulants dimethyl methylphosphonate and dimethyl chlorophosphate, though the latter may serve as a better simulant in studies of this type. Finally, an investigation of Sarin hydrolysis with solvated Cs8Nb6O19 shows an increase in the rate-limiting barrier relative to the gas-surface system, revealing the role of Cs counterions in the reaction. Then, we further increased explicit solvation to model the homogeneous solution-phase reaction, finding a different mechanism in which a water molecule adds to phosphorus in the rate-limiting step and protonation of the niobate surface occurs in a subsequent barrierless step. By examining the rate-limiting barrier for protonation, we suggest that specific base hydrolysis is also likely in the homogeneous system.
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    Coupled-Cluster Methods for Large Molecular Systems Through Massive Parallelism and Reduced-Scaling Approaches
    Peng, Chong (Virginia Tech, 2018-05-02)
    Accurate correlated electronic structure methods involve a significant amount of computations and can be only employed to small molecular systems. For example, the coupled-cluster singles, doubles, and perturbative triples model (CCSD(T)), which is known as the ``gold standard" of quantum chemistry for its accuracy, usually can treat molecules with 20-30 atoms. To extend the reach of accurate correlated electronic structure methods to larger molecular systems, we work towards two directions: parallel computing and reduced-cost/scaling approaches. Parallel computing can utilize more computational resources to handle systems that demand more substantial computational efforts. Reduced-cost/scaling approaches, which introduce approximations to the existing electronic structure methods, can significantly reduce the amount of computation and storage requirements. In this work, we introduce a new distributed-memory massively parallel implementation of standard and explicitly correlated (F12) coupled-cluster singles and doubles (CCSD) with canonical bigO{N^6} computational complexity ( C. Peng, J. A. Calvin, F. Pavov{s}evi'c, J. Zhang, and E. F. Valeev, textit{J. Phys. Chem. A} 2016, textbf{120}, 10231.), based on the TiledArray tensor framework. Excellent strong scaling is demonstrated on a multi-core shared-memory computer, a commodity distributed-memory computer, and a national-scale supercomputer. We also present a distributed-memory implementation of the density-fitting (DF) based CCSD(T) method. (C. Peng, J. A. Calvin, and E. F. Valeev, textit{in preparation for submission}) An improved parallel DF-CCSD is presented utilizing lazy evaluation for tensors with more than two unoccupied indices, which makes the DF-CCSD storage requirements always smaller than those of the non-iterative triples correction (T). Excellent strong scaling is observed on both shared-memory and distributed-memory computers equipped with conventional Intel Xeon processors and the Intel Xeon Phi (Knights Landing) processors. With the new implementation, the CCSD(T) energies can be evaluated for systems containing 200 electrons and 1000 basis functions in a few days using a small size commodity cluster, with even more massive computations possible on leadership-class computing resources. The inclusion of F12 correction to the CCSD(T) method makes it converge to basis set limit much more rapidly. The large-scale parallel explicitly correlated coupled-cluster program makes the accurate estimation of the coupled-cluster basis set limit for molecules with 20 or more atoms a routine. Thus, it can be used rigorously to test the emerging reduced-scaling coupled-cluster approaches. Moreover, we extend the pair natural orbital (PNO) approach to excited states through the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) method. (C. Peng, M. C. Clement, and E. F. Valeev, textit{submitted}) We simulate the PNO-EOM-CCSD method using an existing massively parallel canonical EOM-CCSD program. We propose the use of state-averaged PNOs, which are generated from the average of the pair density of excited states, to span the PNO space of all the excited states. The doubles amplitudes in the CIS(D) method are used to compute the state-averaged pair density of excited states. The issue of incorrect states in the state-averaged pair density, caused by an energy reordering of excited states between the CIS(D) and EOM-CCSD, is resolved by simply computing more states than desired. We find that with a truncation threshold of $10^{-7}$, the truncation error for the excitation energy is already below 0.02 eV for the systems tested, while the average number of PNOs is reduced to 50-70 per pair. The accuracy of the PNO-EOM-CCSD method on local, Rydberg and charge transfer states is also investigated.
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    Design and Construction of a High Vacuum Surface Analysis Instrument to Study Chemistry at Nanoparticulate Surfaces
    Jeffery, Brandon Reed (Virginia Tech, 2011-04-21)
    Metal oxide and metal oxide-supported metal nanoparticles can adsorb and decompose chemical warfare agents (CWAs) and their simulants. Nanoparticle activity depends on several factors including chemical composition, particle size, and support, resulting in a vast number of materials with potential applications in CWA decontamination. Current instrumentation in our laboratory used to investigate fundamental gas-surface interactions require extensive time and effort to achieve operating conditions. This thesis describes the design and construction of a high-throughput, high vacuum surface analysis instrument capable of studying interactions between CWA simulants and nanoparticulate surfaces. The new instrument is small, relatively inexpensive, and easy to use, allowing for expeditious investigations of fundamental interactions between gasses and nanoparticulate samples. The instrument maintains the sample under high vacuum (10?⁷-10?⁹ torr) and can reach operating pressures in less than one hour. Thermal control of the sample from 150-800 K enables sample cleaning and thermal desorption experiments. Infrared spectroscopic and mass spectrometric methods are used concurrently to study gas-surface interactions. Temperature programmed desorption is used to estimate binding strength of adsorbed species. Initial studies were conducted to assess the performance of the instrument and to investigate interactions between the CWA simulant dimethyl methylphosphonate (DMMP) and nanoparticulate silicon dioxide.
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    Design and Synthesis of Mixed-Metal Supramolecular Complexes Incorporating Specialized Light Absorbing Units to Investigate Processes Relevant to Catalyst Function
    Wagner, Alec T. (Virginia Tech, 2015-06-15)
    The goal of this research was to develop a series of mixed-metal supramolecular complexes with specialized light absorbing units to probe perturbation of excited-state properties by ligand deuteration and long-term complex stability via racemization of initially enantiopure light absorbing subunits. Varying bidentate polypyridyl terminal ligands (TL), bridging ligands (BL), reactive metal center (RM), or number of Ru(II) light absorbers (LA) tunes the electrochemical, spectroscopic, photophysical, and photochemical properties within the supramolecular architecture. Ru(II) monometallics of the design [(bpy)2Ru(prolinate)](PF6) utilize prolinate as a chiral directing ligand to impart chirality to the Ru(II) LAs in the synthesis of more sophisticated supramolecular complexes. Ru(II) monometallics of the design [(TL)2Ru(BL)](PF6)2 (TL = bpy or d8-bpy; BL = dpp or d10-dpp; bpy = 2,2′-bipyridine; dpp = 2,3-bis(2-pyridyl)pyrazine) covalently couple two TLs and one BL to a central Ru(II) metal center forming a LA subunit. Larger bi- and trimetallic complexes are formed by coupling an additional Ru(II), Rh(III), or Pt(II) metal center to an existing Ru(II) LA through a BL. Ru(II),Ru(II), Ru(II),Rh(III), and Ru(II),Pt(II) bimetallics of the design [(TL)2Ru(BL)Ru(TL)2](PF6)4, [(TL)2Ru(BL)RhCl2(TL′)](PF6)3, and [(TL)2Ru(BL)PtCl2](PF6)2 (TL/TL′ = bpy or d8-bpy; BL = dpp or d10-dpp) couple only one Ru(II) LA to a Ru(II), Rh(III), or Pt(II) metal center through the BL. Ru(II),Rh(III),Ru(II) trimetallics of the design [{(TL)2Ru(BL)}2RhCl2](PF6)5 (TL = bpy or d8-bpy; BL = dpp or d10-dpp) covalently couple two Ru(II) LAs to a central Rh(III) RM through polyazine BLs. The complexes discussed herein are synthesized using a building block approach, permitting modification of the supramolecular architecture through multiple synthetic steps. Electrochemical analysis of the mono-, bi-, and trimetallic complexes displays several common features: a Ru-based HOMO and either a bridging ligand or Rh-based LUMO. TL and BL modification by ligand deuteration does not affect the electrochemistry of the Ru(II), Ru(II),Ru(II), Ru(II),Rh(III), or Ru(II),Rh(III),Ru(II) complexes. Likewise, utilizing a single enantiomer of the LA subunit does not modify the redox behavior of Ru(II), Ru(II),Pt(II), or Ru(II),Rh(III),Ru(II) complexes. All of the mono-, bi-, and trimetallic complexes are efficient light absorbers throughout the UV and visible with π→π* intraligand (IL) transitions in the UV and Ru(dπ)→ligand(π*) metal-to-ligand charge transfer (MLCT) transitions in the visible. Ligand deuteration does not affect the light absorbing properties of the complexes, while incorporation of chiral LA subunits imparts a preference for circularly polarized light (CPL) absorbance into supramolecular complexes. Photoexcitation of the Ru(dπ)→dpp(π*) 1MLCT results in near unity population of short-lived, weakly emissive Ru(dπ)→dpp(π*) ³MLCT excited state. In the Ru(II), Ru(II),Ru(II), and Ru(II),Pt(II) complexes, the 3MLCT excited state relaxes to the ground state by emission of a photon or vibrational relaxation processes. In the Ru(II),Rh(III) and Ru(II),Rh(III),Ru(II) complexes, the 3MLCT excited state is efficiently quenched by intramolecular electron transfer to populate a non-emissive Ru(dπ)→'Rh(dσ*) metal-to-metal charge transfer (3MMCT) excited state. Utilizing a deuterated BL, the excited-state lifetimes and quantum yield of emission (Φem) are increased for Ru(II), Ru(II),Ru(II), Ru(II),Rh(III) and Ru(II),Rh(III),Ru(II) complexes. The Ru(II),Rh(III) and Ru(II),Rh(III),Ru(II) complexes have previously been shown to be exceptional photochemical molecular devices (PMD) for photoinitiated electron collection (PEC). The ability of these complexes to undergo multiple redox cycles, efficiently absorb light, populate reactive excited states, and collect electrons at a reactive Rh metal center fulfills the requirements for H2O reduction photocatalysts. Photolysis of the Ru(II),Rh(III) and Ru(II),Rh(III),Ru(II) complexes with 470 nm light in the presence of a sacrificial electron donor and H2O substrate yields photocatalytic H2 production. Varying the BL from dpp to d10-dpp in the bimetallic architecture results in enhanced, although relatively low, catalyst efficiency producing 40 ± 10 μL H2 with dpp and 80 ± 10 μL H2 with d10-dpp in a CH3CN solvent system after 48 h photolysis. The trimetallic architecture showed no enhancement in photocatalytic efficiency and produced 210 ± 20 μL H2 with dpp and 180 ± 20 μL H2 with d10-dpp in a DMF solvent system after 20 h photolysis. The Ru(II),Rh(III) and Ru(II),Rh(III),Ru(II) complexes' behavior differs in that the excited state lifetime is the most important factor for bimetallic catalyst functioning, but intramolecular electron transfer is the most important factor for the trimetallic photocatalysts. Another important property to understand with these catalysts is their long-term stability in solution. In order for these mixed-metal complexes to be industrially useful, they must perform for long periods of time without degradation in the presence of H2O substrate and electron donors in solution. Previous examinations of Ru(II),Rh(III),Ru(II) photocatalysts have found that they can perform for ca. 50 h of photolysis, but are not as effective as the initial few hours. Special care was taken to synthesize enantiopure LA subunits and incorporate them into Ru(II),Pt(II) and Ru(II),Rh(III),Ru(II) architectures to study their photolytic stability by monitoring how long the complexes retained their chirality using electronic circular dichroism (ECD) spectroscopy. After photolyzing for longer than 200 hours with an LED light source, the quantum yield for racemization (Φrac) for the Ru(II),Pt(II) and Ru(II),Rh(III),Ru(II) architectures is 2.6 ⨉ 10⁻⁸ and 0.72 ⨉ 10⁻⁸ respectively. Also, by photolyzing in the presence of free bpy, the bi- and trimetallic complexes racemize via a non-dissociative trigonal twist mechanism. This dissertation reports the detailed analysis of the electrochemical, spectroscopic, photophysical, and photochemical properties of a series of selectively deuterated [(TL)2Ru(BL)](PF6)2, [(TL)2Ru(BL)Ru(TL)2](PF6)4, [(TL)2Ru(BL)RhCl2(TL′)](PF6)3, and [{(TL)2Ru(BL)}2RhCl2](PF6)5 (TL = bpy or d8-bpy; BL = dpp or d10-dpp; bpy = 2,2′-bipyridine; dpp = 2,3-bis(2-pyridyl)pyrazine) supramolecular complexes and a series of [(bpy)2Ru(prolinate)](PF6), [(bpy)2Ru(dpp)](PF6)2, [(bpy)2Ru(dpp)PtCl2](PF6)2, and [{(bpy)2Ru(dpp)}2RhCl2](PF6)5 supramolecular complexes with enantiopure light absorbing subunits. The design of the supramolecular architecture and intrinsic properties of each subunit contribute to the function of these systems. The careful design, synthesis and purification, thorough characterizations, and experimentation have led to deeper understanding of the molecular properties required for efficient H2O reduction.
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    Design and synthesis of Ni-rich and low/no-Co layered oxide cathodes for Li-ion batteries
    Yang, Zhijie (Virginia Tech, 2023-02-23)
    Li-ion batteries (LIBs) have achieved remarkable success in electric vehicles (EVs), consumer electronics, grid energy storage, and other applications thanks to a wide range of electrode materials that meet the performance requirements of different application scenarios. Cathodes are an essential component of LIBs, which governs the performance of commercial LIBs. Layered transition metal oxide, i.e., LiNixCoyMn1-x-yO2 (NMC), is one family of cathodes that are widely applied in the prevailing commercial LIBs. With increasing demand for high energy density, the development of layered oxide cathodes is towards high Ni content because Ni redox couples majorly contribute to the battery capacity. Meanwhile, the battery community has been making tremendous efforts to eliminate Co in layered cathodes due to its high cost, high toxicity, and child labor issues during Co mining. However, these Ni-rich Co-free cathodes usually suffer from low electrochemical and structural stability. Several strategies are adopted to enhance the stability of Ni-rich Co-free cathodes, such as doping, coating, and synthesizing single crystal particles. However, the design principles and synthesis mechanisms of these approaches have not been fully understood. Herein, we design and synthesize stable Ni-rich and low/no-Co layered oxide cathodes by manipulating the chemical and structural properties of cathode particles. Our studies reveal the cathode formation mechanisms and shed light on the cathode design through complementary synchrotron microscopic and spectroscopic characterization methods. In Chapter 1, the motivation for LIB research is introduced from the perspective of its indispensable role in achieving carbon neutrality. We then comprehensively introduce the status of LIBs at present, including assessing their sustainability, worldwide supply chain and manufacturing, and cathode materials. Subsequently, we focus on the Co-free layered oxide cathodes and discuss their structure, limitations, and strategies to address the challenges. Finally, we discuss single crystal Ni-rich layered oxide cathodes and the challenges and strategies associated with their synthesis. In Chapter 2, we investigate the dopant redistribution, phase propagation, and local chemical changes of layered oxides at multiple length scales using a multielement-doped LiNi0.96Mg0.02Ti0.02O2 (Mg/Ti-LNO) as a model platform. We observed that dopants Mg and Ti diffuse from the surface to the bulk of cathode particles below 300 °C long before the formation of any layered phase, using a range of synchrotron spectroscopic and imaging diagnostic tools. After calcination, Ti is still enriched at the cathode particle surface, while Mg has a relatively uniform distribution throughout cathode particles. Our findings provide experimental guidance for manipulating the dopant distribution upon cathode synthesis. In Chapter 3, we synthesized Mn(OH)2-coated single crystal LiNiO2 (LNO) and used it as the platform to monitor the Mn redistribution and the structural and chemical evolution of the LNO cathode. We use in situ transmission X-ray microscopy (TXM) to track the Mn tomography inside the LNO particle and Ni oxidation state evolution at various temperatures below 700 °C. We further reveal chemical and structural changes induced by different extents of Mn diffusion at ensemble-averaged scale, which validates the results at the single particle scale. The ion diffusion behavior in the cathode is highly temperature dependent. Our study provides guidance for ion distribution manipulation during cathode modification. In Chapter 4, we successfully fabricated a surface passivation layer for NMC particles via a feasible quenching approach. A combination of bulk and surface structural characterization methods show the correlation of surface layer with bulk chemistry including valence state and charge distribution. Our design enables high interfacial stability and homogeneous charge distribution, impelling superior electrochemical performance of NMC cathode materials. This study provides insights into the cathode surface layer design for modifying other high-capacity cathodes in LIBs. In Chapter 5, we use statistical tools to identify the significance of multiple synthetic parameters in the molten salt synthesis of single crystal Ni-rich NMC cathodes. We also create a prediction model to forecast the performance of synthesized single crystal Ni-rich NMC cathodes from the input of synthetic parameters with relatively high prediction accuracy. Guided by the models, we synthesize single crystal LiNi0.9Co0.05Mn0.05O2 (SC-N90) with different particle sizes. We find large single crystals show worse capacity and cycle life than small single crystals especially at high current rates due to slower Li kinetics. However, large single crystal has higher thermal stability potentially because of smaller specific surface area. The findings of particle size effect on the performance provide insights into size engineering while developing next-generation single crystal Ni-rich NMC cathodes. The statistical and prediction models developed in this study can guide the molten salt synthesis of Ni rich cathodes and simplify the optimization process of synthetic parameters. Chapter 6 summarizes our efforts on the novel design and fundamental understanding of the state-of-the-art cathodes. We also provide our future perspectives for the development of LIBs.
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    Design and Synthesis of Photoactive Metal-Organic Frameworks for Photon Upconversion and Energy Transfer Studies
    Rowe, Jennifer Maria (Virginia Tech, 2018-07-06)
    The synthesis, characterization and photophysical properties of three Zr-based Metalorganic frameworks (MOFs) assembled from 2,6-anthracenedicarboxylic acid (2,6-ADCA, 2,6- MOF) and 1,4-anthracenedicarboxylic (1,4-ADCA, 1,4-MOF), and 9,10-anthracenedicarboxylic acid (9,10-ADCA, 9,10-MOF) are described. The crystal structure of the 9,10-MOF was elucidated by synchrotron powder X-ray diffraction (PXRD) analysis and is isostructural with the well-known UiO-66 framework. The 2,6-MOFs also form highly crystalline, octahedral-shaped structures and was characterized by PXRD. Le Bail refinement of the powder pattern revealed that the 2,6-MOF also has UiO-type crystal structure. Conversely, incorporation of the 1,4-ADCA ligand results in large rod-shaped crystals. The excited-state properties of the MOFs were examined using steadstate diffuse reflectance, steady-state emission spectroscopy and time-correlated single photon counting (TCSPC) spectroscopy and are compared to those of the corresponding ligand in solution. Both the unique fluorescent properties of the ligand as well as individual framework structure, result in distinctive luminescent behavior and dictate the extent of intermolecular interactions. Specifically, the 2,6-MOF displays monomeric emission with a fluorescence lifetime (t) of 16.6 ± 1.1 and fluorescence quantum yield (Ff). On the other hand, the 1,4-MOF displays both monomeric and excimeric emission, with corresponding lifetime values of 7.5 ± 0.01 and 19.9 ± 0.1, respectively and a quantum yield of 0.002 ± 0.0001. The propensity for photon upconversion through sensitized triplet-triplet annihilation (TTA-UC) was probed in the three anthracene-based MOFs. The MOFs were surface-modified with Pd(II) mesoporphyrin IX (PdMP) as the triplet sensitizer. Upconverted emission from the 9,10-MOF was observed, with a quantum efficiency (FUC) of 0.46 % and a threshold intensity (Ith) of 142 mW/cm2 . The variation of the spacing between the anthracene units in the MOFs was found to have significant impact on TTA-UC. As a result, upconverted emission is only displayed by the 9-10-MOF. The distance between anthracene linkers in the 2,6-MOF are too large for TTA to occur, while the short distances in the 1,4-MOF inhibit upconversion through competitive excimer formation. To further explore the effects of chromophore spacing on energy transfer processes, a series of zinc-based mixed-ligand MOF were constructed from Zn(II) tetrakis(4- carboxyphenyl)porphyrin (ZnTCPP) and pyrazine, 2,2′-bipyridine (pyz) or 4,4′-bipyridyl (bpy) or 1,4-di(4-pyridyl)benzense (dpbz), comprising ZnTCPP/Zn paddlewheel layers. Across this series, the porphyrin spacing was approximately 6 Å, 11 Å and 16 Å for pyz, bpy and dpbz, respectively. The photophysical properties of the MOFs were explored using stead-state diffuse reflectance spectroscopy and steady-state and time-resolved emission spectroscopies. Florescence quenching studies examined the correlation between porphyrin spacing and efficiency of energy transfer.
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    Development and Application of Coupled Cluster Ground- and Excited-State Models
    Smith, Christopher Edward (Virginia Tech, 2006-04-24)
    We give an overview of quantum chemical methods with a particular emphasis on the development of high-accuracy quantum chemical models. The reliability of these methods often hinges on whether enough electron correlation is included in the truncated wave function. As an example, we investigate the structures of m-benzyne and its fluorinated derivative, tetrafluoro-m-benzyne where the inclusion of triple excitations is paramount to correctly describe through-bond delocalization of the monocyclic form. At the CCSDT/6-31G** level of theory, the C1–C3 distance of the minimum energy form of m-benzyne is 2.0°A and the profile of the PES along the C1–C3 distance is that of an asymmetric, single-well, in agreement with previous density-functional theory and coupled cluster studies. In addition, the calculated CCSD(T) fundamental frequencies are in excellent agreement with the measured infrared frequencies, thus confirming the monocyclic form of m-benzyne. For tetrafluoro-m-benzyne, however, the increased eclipsing strain between the ring-external Câ X bonds stabilizes the bicyclo[3.1.0]hexatriene form: the C1–C3 distance is calculated at the CCSD(T)/cc-pVTZ level to be approximately 1.75 °A, which is in the range of elongated CC bonds. Computed harmonic vibrational frequencies compare reasonably well with the experimental neon-matrix difference spectrum and provide further evidence for the existence of a bicyclic form. We also report an extension of the coupled cluster iterative-triples model, CC3, to excited states of open-shell molecules, including radicals. We define the method for both spin-unrestricted Hartree-Fock (UHF) and spin-restricted open-shell Hartree-Fock (ROHF) reference determinants and discuss its efficient implementation in the PSI3 program package. The program is streamlined to use at most O(N7) computational steps and avoids storage of the triple-excitation amplitudes for both the ground-and excited-state calculations. The excitation-energy program makes use of a Lowdin projection formalism (comparable to that of earlier implementations) that allows computational reduction of the Davidson algorithm to only the single- and double-excitation space, but limits the calculation to only one excited state at a time. However, a root-following algorithm may be used to compute energies for multiple states of the same symmetry. Benchmark applications of the new methods to the lowest valence 2B1 state of the allyl radical, low-lying states of the CH and CO+ diatomics, and the nitromethyl radical show substantial improvement over ROHF- and UHF-based CCSD excitation energies for states with strong double-excitation character or cases suffering from significant spin contamination. For the allyl radical, CC3 adiabatic excitation energies differ from experiment by less than 0.02 eV, while for the 2§+ state of CH, significant errors of more than 0.4 eV remain. Finally, ground- and excited-state dipole moments are derived diagramatically and were recently developed within the PSI3 quantum chemistry package. However, convergence problems with computing the left-hand excited-state has prevented us from reporting any meaningful results. Thus, future work includes solving this convergence problem before the effects of triple excitations on one-electron properties can be reported with certainty.
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    Development of a Knudsen Cell Reactor for Measuring the Uptake of Atmospheric Gases on Particulate Matter
    Rockhold, Thomas Hall Jr. (Virginia Tech, 2011-04-20)
    Heterogeneous reactions between mineral dust aerosols and gas phase volatile organic compounds have the potential to impact important atmospheric chemical processes. However, little is known about the uptake and reactivity of volatile organic compounds on particulates found in the environment. A Knudsen cell was designed and constructed for providing precise measurement of reaction probabilities within these systems. The instrument was validated through a series of experiments. After validating the Knudsen cell against several key benchmarks, the instrument was used to measure the uptake coefficient for ethanol on particulate silicon dioxide. The uptake coefficient of ethanol on silicon dioxide, a common compound in mineral dust aerosols, was determined to be 7 x 10-7. Therefore, uptake of ethanol on silicon dioxide would be competitive with the loss of other volatile organic compounds on silicon dioxide, which show similar rates of uptake. The Knudsen cell was validated and measured the uptake of ethanol on silicon dioxide, and future work with the Knudsen cell will study the uptake of chemical warfare agent simulants on metal oxides.
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    Development of an Ionically-Assembled On-Column Enzyme Reactor for Capillary Electrophoresis
    Hooper, Stephanie Elaine (Virginia Tech, 2007-06-26)
    This work describes the integration of a separation capillary for capillary electrophoresis (CE) with an on-column enzyme reactor for selective determination of the enzyme substrate. The enzyme reaction occurs during a capillary separation, allowing selective determination of the substrate in complex samples without the need for pre- or post- separation chemical modification of the analyte. The overall goal of this work is to develop a system in which sample introduction, separation of the analyte/substrate from other biological species, enzymatic conversion of the analyte/substrate into a detectable product, and sensitive detection are all included within a single analysis scheme. Immobilization of the enzyme is achieved by electrostatic assembly of poly(diallydimethylammonium chloride) (PDDA) followed by adsorption of a mixture of the negatively charged enzyme glucose oxidase (GOx) and anionic poly(styrenesulfonate) (PSS). The reaction of glucose with the immobilized glucose oxidase produces H2O2 which migrates the length of the capillary under the influence of electroosmotic flow and is detected amperometrically at the capillary outlet. The optimal response, kinetics, and stability for the enzyme reactor are determined through characterization of several parameters including the concentration ratio of PSS:GOx, applied separation voltage, and the inner diameter of the separation capillary. Various analyte mixtures containing the substrate and other biological species were evaluated to illustrate selective separation and determination of the substrate from other biomolecules. Optimization of this electrostatically assembled capillary enzyme reactor lead to application of these parameters to similar enzymes such as glutamate oxidase. Future application to similar enzymes like L-amino acid oxidase and possible microfluidic systems is a long-term goal of the system.
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    Development, Characterization, and Fundamental Studies on Molecular Ionic Composites and PBDT Hydrogels
    Zanelotti, Curt Joseph (Virginia Tech, 2022-01-28)
    This dissertation aims to develop, characterize, and fundamentally understand a new class of materials termed "molecular ionic composites" (MICs). MICs show promise as next-generation solid electrolytes for batteries. MICs form when mixing a rigid polyanion with purely ionic fluids, and they behave mechanically as a solid but contain a high density of ions that move nearly as in a neat liquid. Specifically, prototypical MICs are based on solutions of the rigid-rod polyelectrolyte poly(2,2'-disulfonyl-4,4'-benzideneterephthalamide) (PBDT), which forms a double helix, combined with imidazolium-based ionic liquids (ILs). The IL comprises 75-97 wt% of the final solid, even though the Young's modulus can reach ~ 2 GPa at 80 wt% IL. We propose that these properties are driven by a biphasic internal structure in MICs corresponding to IL-rich "puddles" (an interconnected liquid phase) and PBDT-IL associated "bundles" where IL ions form the collective electrostatic associations that cause the MICs to be a solid. Through this dissertation I will discuss a wide variety of MICs that have been created through the use of two different formation processes, the "ingot" method and the "solvent casting" method, which allow for the use of many different ionic fluid sources to further tune MIC properties. The following chapters build to the fundamental knowledge and our current understanding of the wide variety of materials that can be created from PBDT and IL.