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Articles 511 - 540 of 1553
Full-Text Articles in Chemistry
Inhibition Of The Flavin-Dependent Monooxygenase Siderophore A (Sida) Blocks Siderophore Biosynthesis And Aspergillus Fumigatus Growth, Julia S. Martín Del Campo, Nancy Vogelaar, Karishma Tolani, Karina Kizjakina, Kim Harich, Pablo Sobrado
Inhibition Of The Flavin-Dependent Monooxygenase Siderophore A (Sida) Blocks Siderophore Biosynthesis And Aspergillus Fumigatus Growth, Julia S. Martín Del Campo, Nancy Vogelaar, Karishma Tolani, Karina Kizjakina, Kim Harich, Pablo Sobrado
Chemistry Faculty Research & Creative Works
Aspergillus fumigatus is an opportunistic fungal pathogen and the most common causative agent of fatal invasive mycoses. The flavin-dependent monooxygenase siderophore A (SidA) catalyzes the oxygen and NADPH dependent hydroxylation of l-ornithine (l-Orn) to N5-l-hydroxyornithine in the biosynthetic pathway of hydroxamate-containing siderophores in A. fumigatus. Deletion of the gene that codes for SidA has shown that it is essential in establishing infection in mice models. Here, a fluorescence polarization high-throughput assay was used to screen a 2320 compound library for inhibitors of SidA. Celastrol, a natural quinone methide, was identified as a noncompetitive inhibitor of SidA with a MIC value …
Elucidating The Effects Of Fluoro And Nitro Substituents On Halogen Bond Driven Assemblies Of Pyridyl-Capped Π-Conjugated Molecules, Suong T. Nguyen, Arnold L. Rheingold, Gregory S. Tschumper, Davita L. Watkins
Elucidating The Effects Of Fluoro And Nitro Substituents On Halogen Bond Driven Assemblies Of Pyridyl-Capped Π-Conjugated Molecules, Suong T. Nguyen, Arnold L. Rheingold, Gregory S. Tschumper, Davita L. Watkins
Chemistry Faculty Research & Creative Works
Among recent advances toward efficient semiconducting materials, rational design guidelines have emerged focusing on the synergy between various intermolecular interactions to improve the solid-state order of π-conjugated molecules in organic electronic devices. Herein, we focus our attention on halogen bonding (XB) interactions and the crucial role of electron withdrawing substituents (e.g., nitro and fluoro) toward influencing solid-state properties via secondary interactions. Employing iodoethynyl benzene derivatives (F2BAI and (NO2)2BAI) and thiophene/furan-based building blocks equipped with pyridyl groups as self-assembling domains (PyrTF and PyrT2), co-crystals driven by XB, and π-stacking interactions were formed and studied. Spectroscopic and thermal analysis of 1:1 mixture …
The Structure Of The Antibiotic Deactivating, N-Hydroxylating Rifampicin Monooxygenase, Li Kai Liu, Heba Abdelwahab, Julia S. Martin Del Campo, Ritcha Mehra-Chaudhary, Pablo Sobrado, John J. Tanner
The Structure Of The Antibiotic Deactivating, N-Hydroxylating Rifampicin Monooxygenase, Li Kai Liu, Heba Abdelwahab, Julia S. Martin Del Campo, Ritcha Mehra-Chaudhary, Pablo Sobrado, John J. Tanner
Chemistry Faculty Research & Creative Works
Rifampicin monooxygenase (RIFMO) catalyzes the N-hydroxylation of the natural product antibiotic rifampicin (RIF) to 2′-N-hydroxy-4-oxo-rifampicin, a metabolite with much lower antimicrobial activity. RIFMO shares moderate sequence similarity with well characterized flavoprotein monooxygenases, but the protein has not been isolated and characterized at the molecular level. Herein, we report crystal structures of RIFMO from Nocardia farcinica, the determination of the oligomeric state in solution with small angle x-ray scattering, and the spectrophotometric characterization of substrate binding. The structure identifies RIFMO as a class A flavoprotein monooxygenase and is similar in fold and quaternary structure to MtmOIV and OxyS, which are enzymes …
Mechanism Of Rifampicin Inactivation In Nocardia Farcinica, Heba Abdelwahab, Julia S.Martin Del Campo, Yumin Dai, Camelia Adly, Sohby El-Sohaimy, Pablo Sobrado
Mechanism Of Rifampicin Inactivation In Nocardia Farcinica, Heba Abdelwahab, Julia S.Martin Del Campo, Yumin Dai, Camelia Adly, Sohby El-Sohaimy, Pablo Sobrado
Chemistry Faculty Research & Creative Works
A novel mechanism of rifampicin (Rif) resistance has recently been reported in Nocardia farcinica. This new mechanism involves the activity of rifampicin monooxygenase (RifMO), a flavin-dependent monooxygenase that catalyzes the hydroxylation of Rif, which is the first step in the degradation pathway. Recombinant RifMO was overexpressed and purified for biochemical analysis. Kinetic characterization revealed that Rif binding is necessary for effective FAD reduction. RifMO exhibits only a 3-fold coenzyme preference for NADPH over NADH. RifMO catalyzes the incorporation of a single oxygen atom forming an unstable intermediate that eventually is converted to 20-N-hydroxy-4-oxo-Rif. Stable C4a-hydroperoxyflavin was not detected by rapid …
Competition Between Hydrophilic And Argyrophilic Interactions In Surface Enhanced Raman Spectroscopy, John T. Kelly, Annie K. Mcclellan, Lynn V. Joe, Ashley M. Wright, Lawson T. Lloyd, Gregory S. Tschumper, Nathan I. Hammer
Competition Between Hydrophilic And Argyrophilic Interactions In Surface Enhanced Raman Spectroscopy, John T. Kelly, Annie K. Mcclellan, Lynn V. Joe, Ashley M. Wright, Lawson T. Lloyd, Gregory S. Tschumper, Nathan I. Hammer
Chemistry Faculty Research & Creative Works
The competition for binding and charge-transfer (CT) from the nitrogen containing heterocycle pyrimidine to either silver or to water in surface enhanced Raman spectroscopy (SERS) is discussed. The correlation between the shifting observed for vibrational normal modes and CT is analyzed both experimentally using Raman spectroscopy and theoretically using electronic structure theory. Discrete features in the Raman spectrum correspond to the binding of either water or silver to each of pyrimidine's nitrogen atoms with comparable frequency shifts. Natural bond orbital (NBO) calculations in each chemical environment reveal that the magnitude of charge transfer from pyrimidine to adjacent silver atoms is …
Room-Temperature Electrochemical Reduction Of Epitaxial Bi₂O₃ Films To Epitaxial Bi Films, Zhen He, Jakub Adam Koza, Ying-Chau Liu, Qingzhi Chen, Jay A. Switzer
Room-Temperature Electrochemical Reduction Of Epitaxial Bi₂O₃ Films To Epitaxial Bi Films, Zhen He, Jakub Adam Koza, Ying-Chau Liu, Qingzhi Chen, Jay A. Switzer
Chemistry Faculty Research & Creative Works
This work reports a new facile approach to fabricate high-quality epitaxial Bi thin films by direct electrochemical reduction of epitaxial δ-Bi2O3 thin films on Au single crystals in aqueous solution at room-temperature. The as-produced Bi thin films (without any post-annealing process) exhibit large grain sizes, continuous microstructures, and enhanced magnetotransport properties.
Co7se8 Nanostructures As Catalysts For Oxygen Reduction Reaction With High Methanol Tolerance, Jahangir Masud, Manashi Nath
Co7se8 Nanostructures As Catalysts For Oxygen Reduction Reaction With High Methanol Tolerance, Jahangir Masud, Manashi Nath
Chemistry Faculty Research & Creative Works
Co7Se8 nanostructures electrodeposited on glassy carbon (GC) electrodes show high efficiency for oxygen reduction reaction (ORR) with high methanol tolerance as compared to Pt electrocatalysts. In the presence of methanol, the onset potential for the ORR at Pt/GC is shifted from 0.931 V (vs reversible hydrogen electrode (RHE)) to 0.801 V (vs RHE), whereas it remains the same (0.811 V vs RHE) at Co7Se8/GC in the presence and absence of methanol in 0.5 M H2SO4 solution. The Co7Se8/GC electrodes also showed high cyclability in the presence …
Single Particle Icp-Ms Method Development For The Determination Of Plant Uptake And Accumulation Of Ceo2 Nanoparticles, Yongbo Dan, Xingmao Ma, Weilan Zhang, Kun Liu, Chady Stephan, Honglan Shi
Single Particle Icp-Ms Method Development For The Determination Of Plant Uptake And Accumulation Of Ceo2 Nanoparticles, Yongbo Dan, Xingmao Ma, Weilan Zhang, Kun Liu, Chady Stephan, Honglan Shi
Chemistry Faculty Research & Creative Works
Cerium dioxide nanoparticles (CeO2NPs) are among the most broadly used engineered nanoparticles that will be increasingly released into the environment. Thus, understanding their uptake, transportation, and transformation in plants, especially food crops, is critical because it represents a potential pathway for human consumption. One of the primary challenges for the endeavor is the inadequacy of current analytical methodologies to characterize and quantify the nanomaterial in complex biological samples at environmentally relevant concentrations. Herein, a method was developed using single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) technology to simultaneously detect the size and size distribution of particulate Ce, particle concentration, …
The First Potential Energy Surfaces For The C₆Hˉ-H₂ And C₆Hˉ-He Collisional Systems And Their Corresponding Inelastic Cross Sections, Kyle M. Walker, Fabien Dumouchel, François Lique, Richard Dawes
The First Potential Energy Surfaces For The C₆Hˉ-H₂ And C₆Hˉ-He Collisional Systems And Their Corresponding Inelastic Cross Sections, Kyle M. Walker, Fabien Dumouchel, François Lique, Richard Dawes
Chemistry Faculty Research & Creative Works
Molecular anions have recently been detected in the interstellar and circumstellar media. Accurate modeling of their abundance requires calculations of collisional data with the most abundant species that are usually He atoms and H2 molecules. In this paper, we focus on the collisional excitation of the first observed molecular anion, C6H-, by He and H2. Theoretical calculations of collisional cross sections rely generally on ab initio interaction potential energy surfaces (PESs). Hence, we present here the first PESs for the C6H--H2 and C6H--He van …
A New Set Of Potential Energy Surfaces For Hco: Influence Of Renner-Teller Coupling On The Bound And Resonance Vibrational States, Steve Alexandre Ndengué, Richard Dawes, Hua Guo
A New Set Of Potential Energy Surfaces For Hco: Influence Of Renner-Teller Coupling On The Bound And Resonance Vibrational States, Steve Alexandre Ndengué, Richard Dawes, Hua Guo
Chemistry Faculty Research & Creative Works
It is commonly understood that the Renner-Teller effect can strongly influence the spectroscopy of molecules through coupling of electronic states. Here we investigate the vibrational bound states and low-lying resonances of the formyl radical treating the Renner-Teller coupled X2A' and Ã2A" states using the MultiConfiguration Time Dependent Hartree (MCTDH) method. The calculations were performed using the improved relaxation method for the bound states and a recently published extension to compute resonances. A new set of accurate global potential energy surfaces were computed at the explicitly correlated multireference configuration interaction (MRCI-F12) level and yielded remarkably close agreement with experiment in this …
The C-H Stretching Features At 3.2-3.5 Μm Of Polycyclic Aromatic Hydrocarbons With Aliphatic Sidegroups, Xuejuan Yang, Aigen Li, Rainer Glaser, Jianxin Zhong
The C-H Stretching Features At 3.2-3.5 Μm Of Polycyclic Aromatic Hydrocarbons With Aliphatic Sidegroups, Xuejuan Yang, Aigen Li, Rainer Glaser, Jianxin Zhong
Chemistry Faculty Research & Creative Works
The so-called "unidentified" infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm are ubiquitously seen in a wide variety of astrophysical regions. The UIE features are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials, e.g., polycyclic aromatic hydrocarbon (PAH) molecules. The 3.3 μm aromatic C-H stretching feature is often accompanied by a weaker feature at 3.4 μm. The latter is generally thought to result from the C-H stretch of aliphatic groups attached to the aromatic systems. The ratio of the observed intensity of the 3.3 μm aromatic C-H feature to that of the 3.4 …
Coupling Between Magnetic Exchange And Charge Activation In Cu-Doped Lafeo3, Emir Dogdibegovic, Qingsheng Cai, William Joseph James, William B. Yelon, Harlan U. Anderson, Jin Bo Yang, Xiao Dong Zhou
Coupling Between Magnetic Exchange And Charge Activation In Cu-Doped Lafeo3, Emir Dogdibegovic, Qingsheng Cai, William Joseph James, William B. Yelon, Harlan U. Anderson, Jin Bo Yang, Xiao Dong Zhou
Chemistry Faculty Research & Creative Works
Material research on perovskite-type oxides (ABO3) has been driven by the recognition of their unique properties primarily attributed to the presence of oxygen octahedron (BO6). Since 2003, the discovery of strong coupling in TbMnO3 and BiFeO3 has stimulated new interests in understanding the relationship between magnetic and electric properties in perovskites. In this article, we report our recent work on the magnetic superexchange interaction and charge formation in copper-doped LaFeO3 using high-temperature neutron diffraction and thermoelectric measurements. In situ neutron diffraction measurements show a loss of antiferromagnetic ordering above 450°C. With an increase …
Water Quality In Selected Small Drinking Water Systems Of Missouri Rural Communities, Bin Hua, Ruipu Mu, Honglan Shi, Enos Inniss, John Yang
Water Quality In Selected Small Drinking Water Systems Of Missouri Rural Communities, Bin Hua, Ruipu Mu, Honglan Shi, Enos Inniss, John Yang
Chemistry Faculty Research & Creative Works
Small drinking water treatment systems (serving < 10,000 population) in rural communities frequently encounter multiple challenges in water quality and federal regulatory compliance, especially the disinfection byproduct (DBP) regulations, due to source water variations, limited resources, and aging infrastructures. Unlike most studies on the DBP control using synthetic water in laboratory settings, this research aimed to identify the major water quality issues confronting small systems in the state of Missouri (MO), the United States of America (USA). Three small systems were selected based on source water and geographic locations. Water samples were collected quarterly from each major treatment process during the period of May 2012 to March 2013 and analyzed to identify the treatment effectiveness and potential water quality issues in each small system. Results of water quality characterization showed that the major water quality issue in the selected small systems was the low efficiency of dissolved organic carbon (DOC) removal, especially the DOC species that are considered as the DBP precursors. Most collected water samples had a higher trihalomethane formation potential (THMFP) than the United States Environmental Protection Agency (USEPA) maximum contaminant limit (MCL) (80 µg/L). Based on the analysis of the treatment efficiency in each system, several strategies for water quality improvement were recommended, and a few of which have been implemented in the small systems, leading to improved drinking water quality and compliance with the USEPA DBP regulations. This study would provide a valuable aid to small system operators and local water authority in context of water quality improvement and the regulatory compliance.
Employing Synergetic Effect Of Doping And Thin Film Coating To Boost The Performance Of Lithium-Ion Battery Cathode Particles, Rajankumar L. Patel, Yingbing Jiang, Amitava Choudhury, Xinhua Liang
Employing Synergetic Effect Of Doping And Thin Film Coating To Boost The Performance Of Lithium-Ion Battery Cathode Particles, Rajankumar L. Patel, Yingbing Jiang, Amitava Choudhury, Xinhua Liang
Chemistry Faculty Research & Creative Works
Atomic layer deposition (ALD) has evolved as an important technique to coat conformal protective thin films on cathode and anode particles of lithium ion batteries to enhance their electrochemical performance. Coating a conformal, conductive and optimal ultrathin film on cathode particles has significantly increased the capacity retention and cycle life as demonstrated in our previous work. In this work, we have unearthed the synergetic effect of electrochemically active iron oxide films coating and partial doping of iron on LiMn1.5 Ni0.5O4 (LMNO) particles. The ionic Fe penetrates into the lattice structure of LMNO during the ALD process. …
Big Changes For Small Noncovalent Dimers: Revisiting The Potential Energy Surfaces Of (P2)2 And (Pccp)2 With Ccsd(T) Optimizations And Vibrational Frequencies, Eric Van Dornshuld, Gregory S. Tschumper
Big Changes For Small Noncovalent Dimers: Revisiting The Potential Energy Surfaces Of (P2)2 And (Pccp)2 With Ccsd(T) Optimizations And Vibrational Frequencies, Eric Van Dornshuld, Gregory S. Tschumper
Chemistry Faculty Research & Creative Works
This article details the re-examination of low-lying stationary points on the potential energy surfaces (PESs) of two challenging noncovalent homogeneous dimers, (P2)2 and (PCCP)2. The work was motivated by the rather large differences between MP2 and CCSD(T) energetics that were recently reported for these systems (J. Comput. Chem. 2014, 35, 479-487). The current investigation reveals significant qualitative and quantitative changes when the CCSD(T) method is used to characterize the stationary points instead of MP2. For example, CCSD(T) optimizations and harmonic vibrational frequency computations with the aug-cc-pVTZ basis set indicate that the parallel-slipped (PS) structure is …
A 1-D Coordination Polymer Route To Catalytically Active Co@C Nanoparticles, Anand Pariyar, Siddharth Gopalakrishnan, Joseph Stansbery, Rajankumar L. Patel, Xinhua Liang, Nikolay Nikolaevich Gerasimchuk, Amitava Choudhury
A 1-D Coordination Polymer Route To Catalytically Active Co@C Nanoparticles, Anand Pariyar, Siddharth Gopalakrishnan, Joseph Stansbery, Rajankumar L. Patel, Xinhua Liang, Nikolay Nikolaevich Gerasimchuk, Amitava Choudhury
Chemistry Faculty Research & Creative Works
Pyrolysis of a 1-D polymeric cobalt(ii) coordination complex ([Co(BDC)(Mim)2]n, H2BDC = benzenedicarboxylic acid; Mim = N-methylimidazole) results in the formation of carbon embedded fcc cobalt nanoparticle composites, Co@C. The as-prepared Co@C shows an agglomerated secondary structure with a highly embedded carbon shell comprising of cobalt nanoparticles of 20-100 nm. These Co@C particles show excellent catalytic activity in the reduction of nitrophenol to aminophenol, studied as a model reaction, and evolves as a promising candidate for the gas phase reduction process.
The Ideal And Real Gas Heat Capacity Of Potassium Atoms At High Temperatures, Louis Biolsi, Michael Biolsi
The Ideal And Real Gas Heat Capacity Of Potassium Atoms At High Temperatures, Louis Biolsi, Michael Biolsi
Chemistry Faculty Research & Creative Works
The Ideal Gas Heat Capacity, Cp, of Potassium Atoms is Calculated to High Temperatures using Statistical Mechanics. Since There Are a Large Number of Electronic Energy Levels in the Partition Function (Boltzmann Sum) Below the First Ionization Potential, the Partition Function and Cp will become very large as the Temperature Increases Unless the Number of Energy Levels Contributing to the Partition Function is Constrained. Two Primary Categories of Arguments Are Used to Do This. First, at High Temperatures, the Increased Size of the Atoms Constrains the Sum (Bethe Method). Second, an Argument based on the Existence of Interacting …
In Crystallo Capture Of A Covalent Intermediate In The Udp-Galactopyranose Mutase Reaction, Ritcha Mehra-Chaudhary, Yumin Dai, Pablo Sobrado, John J. Tanner
In Crystallo Capture Of A Covalent Intermediate In The Udp-Galactopyranose Mutase Reaction, Ritcha Mehra-Chaudhary, Yumin Dai, Pablo Sobrado, John J. Tanner
Chemistry Faculty Research & Creative Works
UDP-galactopyranose mutase (UGM) plays an essential role in galactofuranose biosynthesis in pathogens by catalyzing the conversion of UDP-galactopyranose to UDP-galactofuranose. Here we report the first crystal structure of a covalent intermediate in the UGM reaction. The 2.3 Å resolution structure reveals UDP bound in the active site and galactopyranose linked to the FAD through a covalent bond between the anomeric C of galactopyranose and N5 of the FAD. The structure confirms the role of the flavin as nucleophile and supports the hypothesis that the proton destined for O5 of galactofuranose is shuttled from N5 of the FAD via O4 of …
Neutron And Magnetic Studies Of La₀.₇Sr₀.₃Mn₁₋ₓcrₓo₃(X ≤ 0.7): A Homogeneous Charge-Ordered System, Thomas F. Creel, Jinbo Yang, Satish K. Malik, Sylvio Quezado, Oran Allan Pringle, William B. Yelon, William Joseph James
Neutron And Magnetic Studies Of La₀.₇Sr₀.₃Mn₁₋ₓcrₓo₃(X ≤ 0.7): A Homogeneous Charge-Ordered System, Thomas F. Creel, Jinbo Yang, Satish K. Malik, Sylvio Quezado, Oran Allan Pringle, William B. Yelon, William Joseph James
Physics Faculty Research & Creative Works
Structural and magnetic properties of La0.7Sr0.3Mn1-xCrxO3 (0 < x ≤ 0.7) have been studied in order to determine the effect of substitution of Cr3+ for Mn3+. The data consist of neutron and x-ray powder-diffraction and magnetization measurements. We previously suggested these systems transition from ferromagnetic to antiferromagnetic ordering with the intermediate concentrations containing coexisting ferromagnetic and antiferromagnetic domains. Upon further detailed examination, we find that the neutron data can be fit using a single homogeneous long-range magnetically ordered state and compositionally dependent charge ordering. The magnetic structures are controlled by the competition between Mn-Mn, Mn-Cr, and Cr-Cr interactions (double exchange and superexchange). The metal to …
Calculated Vibrational States Of Ozone Up To Dissociation, Steve Alexandre Ndengué, Richard Dawes, Xiaogang Wang, Tucker Carrington Jr., Zhigang Sun, Hua Guo
Calculated Vibrational States Of Ozone Up To Dissociation, Steve Alexandre Ndengué, Richard Dawes, Xiaogang Wang, Tucker Carrington Jr., Zhigang Sun, Hua Guo
Chemistry Faculty Research & Creative Works
A new accurate global potential energy surface for the ground electronic state of ozone [R. Dawes et al., J. Chem. Phys. 139, 201103 (2013)] was published fairly recently. The topography near dissociation differs significantly from previous surfaces, without spurious submerged reefs and corresponding van der Waals wells. This has enabled significantly improved descriptions of scattering processes, capturing the negative temperature dependence and large kinetic isotope effects in exchange reaction rates. The exchange reactivity was found to depend on the character of near-threshold resonances and their overlap with reactant and product wavefunctions, which in turn are sensitive to the potential. Here …
Metabolic Disorders, Drug Development, Drug Design And Biomarkers, Gjumrakch Aliev, Ramon Cacabelos, V. Prakash Reddy
Metabolic Disorders, Drug Development, Drug Design And Biomarkers, Gjumrakch Aliev, Ramon Cacabelos, V. Prakash Reddy
Chemistry Faculty Research & Creative Works
No abstract provided.
A Computational And Experimental Study Of Thieno[3,4-B]Thiophene As A Proaromatic Π-Bridge In Dye-Sensitized Solar Cells, Phillip Brogdon, Fabrizio Giordano, George A. Puneky, Amala Dass, Shaik M. Zakeeruddin, Mohammad Khaja Nazeeruddin, Michael Grätzel, Gregory S. Tschumper, Jared H. Delcamp
A Computational And Experimental Study Of Thieno[3,4-B]Thiophene As A Proaromatic Π-Bridge In Dye-Sensitized Solar Cells, Phillip Brogdon, Fabrizio Giordano, George A. Puneky, Amala Dass, Shaik M. Zakeeruddin, Mohammad Khaja Nazeeruddin, Michael Grätzel, Gregory S. Tschumper, Jared H. Delcamp
Chemistry Faculty Research & Creative Works
Four D-π-A dyes (D=donor, A=acceptor) based on a 3,4-thienothiophene π-bridge were synthesized for use in dye-sensitized solar cells (DSCs). The proaromatic building block 3,4-thienothiophene is incorporated to stabilize dye excited-state oxidation potentials. This lowering of the excited-state energy levels allows for deeper absorption into the NIR region with relatively low molecular weight dyes. The influence of proaromatic functionality is probed through a computational analysis of optimized bond lengths and nucleus independent chemical shifts (NICS) for both the ground- and excited- states. To avoid a necessary lowering of the TiO2 semiconductor conduction band (CB) to promote efficient dye-TiO2 electron …
Electrodeposition And Characterization Of Metals And Metal Oxides For Energy Conversion And Storage, Ying-Chau Liu
Electrodeposition And Characterization Of Metals And Metal Oxides For Energy Conversion And Storage, Ying-Chau Liu
Doctoral Dissertations
"This dissertation investigates the electrodeposition of metal and metal oxide thin films applicable to solar water splitting cells. Paper I describes the synthesis of cobalt hydroxide, ß-Co(OH)2, by electrochemically reducing tris(ethylenediamine)cobalt(III) in alkaline solution. Paper II presents a scheme to convert the ß-Co(OH)2 to CoOOH and Co3O4 and compares their catalytic activity for the oxygen evolution reaction. Co3O4 appears to be a more active catalyst than CoOOH based on Tafel analysis. However, when the observed current densities are corrected for the measured electrochemically active surface area, the linear region of the …
Calculating Potential Energy Curves With Fixed-Node Diffusion Monte Carlo: Co And N₂, Andrew D. Powell, Richard Dawes
Calculating Potential Energy Curves With Fixed-Node Diffusion Monte Carlo: Co And N₂, Andrew D. Powell, Richard Dawes
Chemistry Faculty Research & Creative Works
This study reports on the prospect for the routine use of Quantum Monte Carlo (QMC) for the electronic structure problem, applying fixed-node Diffusion Monte Carlo (DMC) to generate highly accurate Born-Oppenheimer potential energy curves (PECs) for small molecular systems. The singlet ground electronic states of CO and N2 were used as test cases. The PECs obtained by DMC employing multiconfigurational trial wavefunctions were compared with those obtained by conventional high-accuracy electronic structure methods such as multireference configuration interaction and/or the best available empirical spectroscopic curves. The goal was to test whether a straightforward procedure using available QMC codes could …
Tracking Silver, Gold, And Titanium Dioxide Nanoparticles Through Drinking Water Systems By Single Particle - Inductively Coupled Plasma - Mass Spectrometry, Ariel Renee Donovan
Tracking Silver, Gold, And Titanium Dioxide Nanoparticles Through Drinking Water Systems By Single Particle - Inductively Coupled Plasma - Mass Spectrometry, Ariel Renee Donovan
Masters Theses
"Single particle (SP)-ICP-MS methods were developed to characterize and quantify Ti-containing, titanium dioxide, silver, and gold NP concentration, size, size distribution and dissolved metal element concentration in surface water and treated drinking water. The effectiveness of conventional drinking water treatments (including lime softening, alum coagulation, filtration, and disinfection) to remove NPs from surface water was evaluated using six-gang stirrer jar test simulations. Six-gang stirrers were used to simulate drinking water treatments including lime softening, alum coagulation, powdered activated carbon sorption, filtration, and disinfection by free chlorine. Lime softening effectively removed most nanoparticles added. Source and drinking waters from three large …
The Onset Of Electron-Induced Proton-Transfer In Hydrated Azabenzene Cluster Anions, Yi Wang, Xinxing Zhang, Svetlana Lyapustina, Michael M. Nilles, Shoujun Xu, Jacob D. Graham, Kit H. Bowen, John T. Kelly, Gregory S. Tschumper, Nathan I. Hammer
The Onset Of Electron-Induced Proton-Transfer In Hydrated Azabenzene Cluster Anions, Yi Wang, Xinxing Zhang, Svetlana Lyapustina, Michael M. Nilles, Shoujun Xu, Jacob D. Graham, Kit H. Bowen, John T. Kelly, Gregory S. Tschumper, Nathan I. Hammer
Chemistry Faculty Research & Creative Works
The prospect that protons from water may be transferred to N-heterocyclic molecules due to the presence of an excess electron is studied in hydrated azobenzene cluster anions using anion photoelectron spectroscopy and computational chemistry. In the case of s-triazine (C3H3N3), which has a positive adiabatic electron affinity, proton transfer is not energetically favored nor observed experimentally. Heterocyclic rings with only 1 or 2 nitrogen atoms have negative electron affinities, but the addition of solvating water molecules can yield stable negative ions. In the case of the diazines (C4H4N2: …
Sub-Millisecond Response Time In A Photorefractive Composite Operating Under Cw Conditions, Jong-Sik Moon, Tyler E. Stevens, Todd C. Monson, Dale L. Huber, Sung-Ho Jin, Jin-Woo Oh, Jeffrey G. Winiarz
Sub-Millisecond Response Time In A Photorefractive Composite Operating Under Cw Conditions, Jong-Sik Moon, Tyler E. Stevens, Todd C. Monson, Dale L. Huber, Sung-Ho Jin, Jin-Woo Oh, Jeffrey G. Winiarz
Chemistry Faculty Research & Creative Works
Extensive study of photorefractive polymeric composites photosensitized with semiconductor nanocrystals has yielded data indicating that the inclusion of such nanocrystals enhances the charge-carrier mobility, and subsequently leads to a reduction in the photorefractive response time. Unfortunately, the included nanocrystals may also act as a source of deep traps, resulting in diminished diffraction efficiencies as well as reduced two beam coupling gain coefficients. Nonetheless, previous studies indicate that this problem is mitigated through the inclusion of semiconductor nanocrystals possessing a relatively narrow band-gap. Here, we fully exploit this property by doping PbS nanocrystals into a newly formulated photorefractive composite based on …
The Virtual Atomic And Molecular Data Centre (Vamdc) Consortium, Marie-Lise Dubernet, B. K. Antony, Ernesto Quintas-Sánchez, For Full List Of Authors, See Publisher's Website.
The Virtual Atomic And Molecular Data Centre (Vamdc) Consortium, Marie-Lise Dubernet, B. K. Antony, Ernesto Quintas-Sánchez, For Full List Of Authors, See Publisher's Website.
Chemistry Faculty Research & Creative Works
The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for …
Blended Learning In Chemistry Laboratory Courses: Enhancing Learning Outcomes And Aligning Student Needs With Available Resources, Shayna Brianne Burchett
Blended Learning In Chemistry Laboratory Courses: Enhancing Learning Outcomes And Aligning Student Needs With Available Resources, Shayna Brianne Burchett
Doctoral Dissertations
"Freshman science courses are intended to prepare students for the rigor and expectations of subsequent college science. While secondary education aims to prepare students for the college curriculum, many incoming freshman lack the sense of responsibility for their own learning that is essential for success in a college-level course. The freshman general-chemistry laboratory course at Missouri University of Science and Technology (Missouri S&T) was identified as a bottleneck course with a demand beyond accommodation capacity. To address the bottleneck and develop a sense of learner responsibility, a decision was made to investigate laboratory course delivery strategies. As a result of …
Continuous Flow Reactor For Carbonic Acid Hydrolysis/Pretreatment Of Microalgal Biomass To Produce Bioethanol, Nicholas Dudenhoeffer
Continuous Flow Reactor For Carbonic Acid Hydrolysis/Pretreatment Of Microalgal Biomass To Produce Bioethanol, Nicholas Dudenhoeffer
Doctoral Dissertations
"In order to maximize bioethanol production an efficient pretreatment method for the hydrolysis of polysaccharides to fermentable sugars is necessary. Commonly used pretreatment methods are the slow enzymatic hydrolysis and the corrosive mineral acid hydrolysis process that requires a post-treatment neutralization step and generates waste stream. We investigated the high temperature water with carbonic acid catalyst as an alternative method. Carbonic acid generated from dissolved CO2 is inexpensive and environmentally benign, and easily removed by decompression. A high pressure continuous flow reactor that can continuously process the wet biomass stream and perform the carbonic acid hydrolysis in-situ using the …