Physical Sciences and Mathematics Commons^™

Hyperstructures In Chemical Hyperstructures Of Redox Reactions With Three And Four Oxidation States, Fakhry Asad Agusfrianto, Sonea Andromeda, Mariam Hariri

All Works

Hyperstructures find numerous applications across various disciplines. One notable application is in chemistry, particularly in the context of chemical reactions. In 2014, Davvaz introduced the concept of bi-hyperstructures, but their application specifically in chemical reactions, has yet to be thoroughly explored in previous studies. Thus, the primary aim of this paper is to examine and analyze the different types of bi-hyperstructures present within chemical hyperstructures. The scope of this study focuses on two types of chemical hyperstructures: redox reactions and reactions in electrochemical cells. Within these chemical hyperstructures, we investigate the possibility of bi-hyperstructures among bi-semihypergroups, bi-hypergroups, bi-H_v-semigroups, and bi-H_v-groups. …

Additivity Of Diene Substituent Gibbs Free Energy Contributions For Diels–Alder Reactions Between Me2c=Cme2 And Substituted Cyclopentadienes, Thomas M. Gilbert, Austin S. Flemming, Brendan C. Dutmer

Faculty Peer-Reviewed Publications

Systematic computational studies of pericyclic Diels–Alder reactions between (H3C)2C═C(CH3)2, 1, and all permutations of substituted cyclopentadienes c-C5R1R2R3R4R5aR5b (R = H, CH3, CF3, F) allowed isolation of substitutional effects on Gibbs free energy barrier heights and reaction Gibbs free energies. “Average Substitution Gibbs Free Energy Correction” ΔGASC#‡/ΔGASC# values for each substituent in each position appeared to be additive. Substituent effects on barriers showed interesting contrasts. Methyl substitution at positions 5a and 5b increased barriers significantly, while substitution at all other positions had essentially no impact. In contrast, fluoro substitution at positions 5a and 5b lowered barriers more than substitution at other …

Tie Dye Activity Plans, Admin Stem For Success

STEM for Success Showcase

OVERVIEW:

The STEM for success ambassador program will provide high school students the opportunity to participate in STEM activities that challenge them to learn topics covered in most high school chemistry and physics courses in an environment that cultivates leadership, STEM advocacy, and the 21st century skills of creativity and collaboration. High school students will learn tie-dye science and the chemistry and physics of slime and use their learning experiences to create hands-on activities for Pre-K through 8th grade students. High school students will form teams and venture out into their communities to explore the activities they have created in …

Slime Lesson Plans, Admin Stem For Success

STEM for Success Showcase

The STEM for success ambassador program will provide high school students the opportunity to participate in STEM activities that challenge them to learn topics covered in most high school chemistry and physics courses in an environment that cultivates leadership, STEM advocacy, and the 21st century skills of creativity and collaboration. High school students will learn tie-dye science and the chemistry and physics of slime and use their learning experiences to create hands-on activities for Pre-K through 8th grade students. High school students will form teams and venture out into their communities to explore the activities they have created in local …

Synthesis Of Highly Reactive Sulfone Iminium Fluorides And Their Use In Deoxyfluorination And Sulfur Fluoride Exchange Chemistry, James A. Vogel, Rania Hammami, Ara Ko, Hiya Datta, Yael N. Eiben, Karley J. Labenne, Ellis C. Mccarver, Ebrar Z. Yilmaz, Patrick R. Melvin

Chemistry Faculty Research and Scholarship

We report the synthesis of sulfone iminium fluorides (SIFs), a reactive class of sulfur(VI) molecules. The synthesis is tolerant of a variety of substituents on the sulfur and nitrogen components. The SIF reagents were applied to the deoxyfluorination of alcohols and carboxylic acids, providing high yields of fluorinated products in 60 s at room temperature. The SIF reagents were then utilized in sulfur fluoride exchange (SuFEx), creating the first ionic SuFEx products to date.

Catalytic Transfer Hydrogenation Reactions Of Lipids, Alexander Asiedu

Civil & Environmental Engineering Theses & Dissertations

Catalytic transfer hydrogenation (CTH) of lipids was investigated using 2-propanol as hydrogen donor for producing liquid hydrocarbons, e.g. jet fuels. The main sources of lipids selected in this study were waste cooking oil (WCO) and oil-laden algae-derived biofuel intermediate (BI). Two different catalysts were employed in this study, namely activated carbon and trimetallic-doped zeolite.

The CTH reaction was between WCO and 2-propanol in a continuous flow reactor over a packed-bed activated carbon at near atmospheric pressure. Results revealed a high level of alkenes and aromatics compounds, which are not stable and are not environmentally unfriendly. To reduce these compounds in …

Metal-Organic Frameworks With Metal Catecholates For O2/N2 Separation, Samuel J. Stoneburner, Hakan Demir, Wooseok Jeong, Debmalya Ray, Xuan Zhang, Omar K. Farha, Christopher J. Cramer, Ilja Siepmann, Laura Gagliardi

Educator Scholarship

Oxygen and nitrogen are widely produced feedstocks with diverse fields of applications, but are primarily obtained via the energy-intensive cryogenic distillation of air. More energy-efficient processes are desirable, and materials such as zeolites and metal-organic frameworks (MOFs) have been studied for air separation. Inspired by recent theoretical work identifying metal-catecholates for enhancement of O2 selectivity MOFs, in this work the computation-ready experimental (CoRE) database of MOF structures was screened to identify promising candidates for incorporation of metal catecholates. Based on structural requirements, preliminary Grand-Canonical Monte Carlo simulations, and further constraints to ensure the computational feasibility, over 5,000 structures were eliminated …

Size And Site Dependence Of The Catalytic Activity Of Iridium Clusters Towards Ethane Dehydrogenation, Yingbin Ge, Hao Jiang, Russell Kato, Prasuna Gummagatta

All Faculty Scholarship for the College of the Sciences

This research focuses on optimizing transition metal nanocatalyst immobilization and activity to enhance ethane dehydrogenation. Ethane dehydrogenation, catalyzed by thermally stable Ir_n (n = 8, 12, 18) atomic clusters that exhibit a cuboid structure, was studied using the B3LYP method with triple-ζ basis sets. Relativistic effects and dispersion corrections were included in the calculations. In the dehydrogenation reaction Ir_n + C₂H₆ → H−Ir_n−C₂H₅ → (H)₂−Ir_n−C₂H₄, the first H-elimination is the rate-limiting step, primarily because the reaction releases sufficient heat to facilitate …

Kinetic Isotope Effect Of The ¹⁶O+³⁶O₂ And ¹⁸O+³²O₂ Isotope Exchange Reactions: Dominant Role Of Reactive Resonances Revealed By An Accurate Time-Dependent Quantum Wavepacket Study, Zhigang Sun, Dequan Yu, Wenbo Xie, Jiayi Hou, Richard Dawes, Hua Guo

Chemistry Faculty Research & Creative Works

The O + O₂ isotope exchange reactions play an important role in determining the oxygen isotopic composition of a number of trace gases in the atmosphere, and their temperature dependence and kinetic isotope effects (KIEs) provide important constraints on our understanding of the origin and mechanism of these and other unusual oxygen KIEs important in the atmosphere. This work reports a quantum dynamics study of the title reactions on the newly constructed Dawes-Lolur-Li-Jiang-Guo (DLLJG) potential energy surface (PES). The thermal reaction rate coefficients of both the 18O + 32O₂ and 16O + 36O₂ reactions obtained using the …

Synthesis Of Novel Dienes And Cyclic Compounds Via Olefin Metathesis Reactions Catalyzed By The Second Generation Grubbs Catalyst, Patrick Joseph Carey

Honors Theses

Transition metal-catalyzed olefin metathesis reactions play a significant role in chemical synthesis. These reactions are currently applied across several disciplines, and their full potential has not yet been reached. This project details the synthesis of spiro[3-cyclopentene-1,9’-[9H]fluorene], 1-(1-amino-2-methylpropyl)-3-cyclopentenol, and the eugenol dimer via olefin metathesis reactions catalyzed by the second generation Grubbs catalyst. The unique structural properties of each compound help demonstrate the widespread abilities of these reactions. Also reported are the novel three-dimensional crystal structures of both spiro[3-cyclopentene-1,9’-[9H]fluorene] and the eugenol dimer. These structures were determined via X-ray diffraction crystallography methods using a Bruker SMART X2S Single Crystal Diffractometer. Both …

Theoretical Examination Of Solvent And R Group Dependence In Gold Thiolate Nanoparticle Synthesis, Suzanne M. Neidhart, Brian M. Barngrover, Christine M. Aikens

Faculty Publications

The growth of gold thiolate nanoparticles can be affected by the solvent and the R group on the ligand. In this work, the difference between methanol and benzene solvents as well as the effect of alkyl (methyl) and aromatic (phenyl) thiols on the reaction energies and barrier heights is investigated theoretically. Density functional theory (DFT) calculations using the BP86 functional and a triple ζ polarized basis set show that the overall reaction favors methylthiol over phenylthiol with reaction energies of −0.54 and −0.39 eV in methanol, respectively. At the same level of theory, the methanol solvent is favored over the …

Prediction Of Nonradical Au (0)-Containing Precursors In Nanoparticle Growth Processes, Brian M. Barngrover, Timothy J. Manges, Christine M. Aikens

Faculty Publications

This density functional theory (DFT) investigation examines the formation of nonradical Au(0) species from the reduction of Au(I) species. The Au(I) complexes of interest are AuCl₂^–, AuBr₂^–, AuI₂^–, AuClPH₃, and AuCl(H)SCH₃⁽⁻⁾, which are precursors for gold nanoparticle and cluster formation. Reaction of two of the Au(I) species with a hydride results in ejection of two of the ligands and formation of Au₂ with two ligands still attached. AuX₂^– (where X = Cl, Br, or I) reactions eject two halides and form Au_{2 …}

Analysis Of Localized Diabatic States Beyond The Condon Approximation For Excitation Energy Transfer Processes, Ethan Alguire, Shervin Fatehi, Yihan Shao, Joseph E. Subotnik

Chemistry Faculty Publications and Presentations

In a previous paper [Fatehi, S.; et al. J. Chem. Phys. 2013, 139, 124112], we demonstrated a practical method by which analytic derivative couplings of Boys-localized CIS states can be obtained. In this paper, we now apply that same method to the analysis of triplet–triplet energy transfer systems studied by Closs and collaborators [Closs, G. L.; et al. J. Am. Chem. Soc.1988, 110, 2652]. For the systems examined, we are able to conclude that (i) the derivative coupling in the BoysOV basis is negligible, and (ii) the diabatic coupling will likely change little over the configuration space explored …

Theoretical And Computational Studies Of Diffusion Of Adatom Islands And Reactions Of Molecules On Surfaces, Syed Islamuddin Shah

Electronic Theses and Dissertations

The work presented in this dissertation focuses on the study of post deposition spatial and temporal evolution of adatom islands and molecules on surfaces using ab initio and semiemperical methods. It is a microscopic study of the phenomena of diffusion and reaction on nanostructured surfaces for which we have developed appropriate computational tools, as well as implemented others that are available. To map out the potential energy surface on which the adatom islands and molecules move, we have carried out ab initio electronic structure calculations based on density functional theory (DFT) for selected systems. For others, we have relied on …

Oxidation Of Gold Clusters By Thiols, Brian M. Barngrover, Christine M. Aikens

Faculty Publications

The formation of gold–thiolate nanoparticles via oxidation of gold clusters by thiols is examined in this work. Using the BP86 density functional with a triple ζ basis set, the adsorption of methylthiol onto various gold clusters Au_n^Z (n = 1–8, 12, 13, 20; Z = 0, −1, +1) and Au₃₈⁴⁺ is investigated. The rate-limiting step for the reaction of one thiol with the gold cluster is the dissociation of the thiol proton; the resulting hydrogen atom can move around the gold cluster relatively freely. The addition of a second thiol can lead to H_{2 …}

Pump Dependence Of The Dynamics Of Quantum Dot Based Waveguide Absorbers, T. Piwonski, Jaroslaw Pulka, Guillaume Huyet, Et. Al.

Physical Sciences Publications

The nonlinear two stage recovery of quantum dot based reverse-biased waveguide absorbers is investigated experimentally and analytically as a function of the initial ground state occupation probability of the dot. The latter is controlled experimentally by the pump pulse power. The slow stage of the recovery is exponential and its basic timescale is independent of pump power. The fast stage of the recovery is a logistic function which we analyze in detail. The relative strength of slow to fast components is highlighted and the importance of higher order absorption processes at the highest pump level is demonstrated.

The Golden Pathway To Thiolate-Stabilized Nanoparticles: Following The Formation Of Gold (I) Thiolate From Gold (Iii) Chloride, Brian M. Barngrover, Christine M. Aikens

Faculty Publications

Pathways for the formation of gold thiolate complexes from gold(III) chloride precursors AuCl₄^– and AuCl₃ are examined. This work demonstrates that two distinct reaction pathways are possible; which pathway is accessible in a given reaction may depend on factors such as the residue group R on the incoming thiol. Density functional theory calculations using the BP86 functional and a polarized triple-ζ basis set show that the pathway resulting in gold(III) reduction is favored for R = methyl. A two-to-one ratio of thiol or thiolate to gold can reduce Au(III) to Au(I), and a three-to-one ratio can lead …

Synthetic And Mechanistic Studies On The Cross-Coupling Reactions Catalyzed By Ruthenium Complexes, Ruili Gao

Dissertations (1934 -)

Transition metal catalyzed C-H bond activation reaction is a powerful synthetic method for forming functionalized products directly from unreactive hydrocarbons, and has enormous synthetic potentials for developing chemical processes ranging from petroleum products to pharmaceutical agents. In an attempt to mimic the high stereo selectivity and region selectivity of catalytic reactions by transition metal catalysts, recent research has focused on design and synthesis of transition metal complex and the application on the coupling reactions involving C-H bond activation.

Herein, we wish to report the highly effective coupling reactions involving C-H bond activation by using well-defined ruthenium catalysts. Ruthenium hydride complex …

Diffuse-Charge Dynamics Of Ionic Liquids In Electrochemical Systems, Hui Zhao

Mechanical Engineering Faculty Research

We employ a continuum theory of solvent-free ionic liquids accounting for both short-range electrostatic correlations and steric effects (finite ion size) [Bazant et al., Phys. Rev. Lett. 106, 046102 (2011)] to study the response of a model microelectrochemical cell to a step voltage. The model problem consists of a 1-1 symmetric ionic liquid between two parallel blocking electrodes, neglecting any transverse transport phenomena. Matched asymptotic expansions in the limit of thin double layers are applied to analyze the resulting one-dimensional equations and study the overall charge-time relation in the weakly nonlinear regime. One important conclusion is that our …

Secondary Enrichment Of Copper At The Madison Gold Skarn Deposit, Silver Star District, Montana, Christopher H. Gammons, Jill Sotendahl, Dan Everett

Geological Engineering

Secondary Enrichment of Copper at the Madison Gold Skarn Deposit, Silver Star District, Montana. This paper focuses on the chemical reactions responsible for secondary enrichment of copper...we argue that most of the secondary Cu enrichment occurred during a late hydrothermal event that replaced the high temperature skarn mineral assemblage with hematitic jasperoid. Evidence favoring this "hypogene" Cu enrichment hypothesis is presented.

High Order Well-Balanced Schemes And Applications To Non-Equilibrium Flow With Stiff Source Terms, Wei Wang, Chi-Wang Shu, H. C. Yee, Björn Sjögreen

United States National Aeronautics and Space Administration: Publications

The stiffness of the source terms in modeling non-equilibrium ow problems containing finite-rate chemistry or combustion poses additional numerical difficulties beyond that for solving non-reacting flows. A well-balanced scheme, which can preserve certain non-trivial steady state solutions exactly, may help minimize some of these difficulties. In this paper, a simple one dimensional non-equilibrium model with one temperature is considered. We first describe a general strategy to design high order well-balanced finite difference schemes and then study the well-balanced properties of the high order finite difference weighted essentially non-oscillatory (WENO) scheme, modified balanced WENO schemes and various TVD schemes. The advantages …

Intradot Dynamics Of Inas Quantum Dot Based Electroabsorbers, T. Piwonski, Jaroslaw Pulka, Gillian Madden, Guillaume Huyet, Et. Al.

Physical Sciences Publications

The carrier relaxation and escape dynamics of InAs/GaAs quantum dot waveguide absorbers is studied using heterodyne pump-probe measurements. Under reverse bias conditions, we reveal differences in intradot relaxation dynamics, related to the initial population of the dots’ ground or excited states. These differences can be attributed to phonon-assisted or Auger processes being dominant for initially populated ground or excited states, respectively.

Electron And Hole Dynamics Of Inas∕Gaasinas∕Gaas Quantum Dot Semiconductor Optical Amplifiers, I. O'Driscoll, T. Piwonski, C. F. Schleussner, J. Houlihan, G. Huyet, R. J. Manning

Physical Sciences Publications

Single-color and two-color pump-probe measurements are used to analyze carrier dynamics in InAs∕GaAs quantum dot amplifiers. The study reveals that hole recovery and intradot electron relaxation occur on a picosecond time scale, while the electron capture time is on the order of 10ps. A longer time scale of hundreds of picoseconds is associated with carrier recovery in the wetting layer, similar to that observed in quantum well semiconductor amplifiers.

Carrier Capture Dynamics Of Inas/Gaas Quantum Dots, T. Piwonski, I. O'Driscoll, J. Houlihan, G. Huyet, R. J. Manning, A. V. Uskov

Physical Sciences Publications

Carrier dynamics of a 1.3μm InAs∕GaAs quantum dot amplifier is studied using heterodyne pump-probe spectroscopy. Measurements of the recovery times versus injection current reveal a power law behavior predicted by a quantum dot rate equation model. These results indicate that Auger processes dominate the carrier dynamics.

Characterization Of Black Deposit Associated With Rock Paintings In Little Lost River Cave, Idaho Using Pyrolysis Gc, Sarah Therese Fezzey

Master's Theses and Doctoral Dissertations

A black, shiny coating overlies rock paintings in Little Lost River Cave no. 1, located in southeastern Idaho. If this coating is the result of human activity within the cave – a condensate from cooking fires, for example – then a radiocarbon date on the coating would provide a minimum age for the underlying paintings. The work reported here was undertaken to test the assumption that the coating has an anthropomorphic origin. Using pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) and thermally-assisted hydrolysis/methylation-GC-MS, we have compared samples of the black coating from Idaho to humic acid, a geologic material; an experimental cooking residue; …

Geminal Model Chemistry Ii. Perturbative Corrections, Vitaly A. Rassolov, Feng Xu, Sophya Garashchuk

Faculty Publications

We introduce and investigate a chemical model based on perturbative corrections to the product of singlet-type strongly orthogonal geminals wave function. Two specific points are addressed (i) Overall chemical accuracy of such a model with perturbative corrections at a leading order; (ii) Quality of strong orthogonality approximation of geminals in diverse chemical systems. We use the Epstein–Nesbet form of perturbation theory and show that its known shortcomings disappear when it is used with the reference Hamiltonian based on strongly orthogonal geminals. Application of this model to various chemical systems reveals that strongly orthogonal geminals are well suited for chemical models, …

An Ab Initio Study Of Specific Solvent Effects On The Electronic Coupling Element In Electron Transfer Reactions, Thomas M. Henderson '98, Robert J. Cave

All HMC Faculty Publications and Research

Specific solvent effects on the electronic coupling element for electron transfer are examined using two model donor–acceptor systems (Zn2+ and Li2+) and several model “solvent” species (He, Ne, H2O, and NH3). The effects are evaluated relative to the given donor–acceptor pair without solvent present. The electronic coupling element (Hab) is found to depend strongly on the identity of the intervening solvent, with He atoms decreasing Hab, whereas H2O and NH3 significantly increase Hab. The distance dependence (essentially exponential decay) is weakly affected by a single intervening solvent atom–molecule. However, when the donor–acceptor distance increases in concert with addition of successively …

A System Dynamics Model Of The Bioavailability Of Metals In Constructed Wetland Sediment, Timothy S. Wood

Theses and Dissertations

Constructed wetlands used for storm water treatment accumulate metals primarily in their sediment. This sediment has the potential to produce toxic effects in benthic organisms at some period in time. Bioavailability of metals in sediment is directly linked to pore water metal activity. The mechanisms that influence pore water metal activity are included in physical, chemical, and biological processes. A system dynamics model was developed to represent these processes and the major influences affecting pore water metal activity in a treatment wetland receiving storm water influent. The model structure and behavior was tested and validated using several system dynamics validation …

Calculation Of Electronic Coupling Matrix Elements For Ground And Excited State Electron Transfer Reactions: Comparison Of The Generalized Mulliken–Hush And Block Diagonalization Methods, Robert J. Cave, Marshall D. Newton

All HMC Faculty Publications and Research

Two independent methods are presented for the nonperturbative calculation of the electronic coupling matrix element (Hab) for electron transfer reactions using ab initio electronic structure theory. The first is based on the generalized Mulliken–Hush (GMH) model, a multistate generalization of the Mulliken Hush formalism for the electronic coupling. The second is based on the block diagonalization (BD) approach of Cederbaum, Domcke, and co-workers. Detailed quantitative comparisons of the two methods are carried out based on results for (a) several states of the system Zn2OH2+ and (b) the low-lying states of the benzene–Cl atom complex and its contact ion pair. Generally …

Factors Affecting Crop Response To Liming, Kenneth L. Wells, J. L. Sims

Soil Science News and Views

Soil acidity levels directly affect the rate, kinds, and degree of chemical reactions which take place in soil. Crops respond to varying degrees to these chemical reactions. For the most part, these reactions affect the solubility of mineral elements in soil and the activity of the soil's biological processes. As a result, the availability of many plant nutrient elements is regulated by soil acidity. The level of availability of plant required nutrients can be adequate, deficient, or toxic to the plant, depending on the nutrient, soil acidity, and the crop. That is why measurement of soil acidity is regarded by …