Chemistry Commons^™

Development Of A Liquid Contacting Method For Investigating Photovoltaic Properties Of Pbs Quantum Dot Solids, Vitalii Alekseevich Dereviankin

Dissertations and Theses

Photovoltaic (PV) devices based on PbS quantum dot (QD) solids demonstrate high photon-to-electron conversion yields. However, record power conversion efficiencies remain limited mainly due to bulk and interfacial defects in the light absorbing material (QD solids). Interfacial defects can be formed when a semiconductor, such as QD solid, is contacted by another material and may predetermine the semiconductor/metal or semiconductor/metal-oxide junction properties. The objective of the work described in this dissertation was set to explore whether electrochemical contacting using liquid electrolytes can provide sufficient means of contacting the QD solids to investigate their PV performance without introducing the unwanted interfacial …

Electron Transfer To Nitrogenase In Different Genomic And Metabolic Backgrounds, Saroj Poudel, Daniel R. Colman, Kathryn R. Fixen, Rhesa N. Ledbetter, Yanning Zheng, Natasha Pence, Lance C. Seefeldt, John W. Peters, Caroline S. Harwood, Eric S. Boyd

Chemistry and Biochemistry Faculty Publications

Nitrogenase catalyzes the reduction of dinitrogen (N₂) using low-potential electrons from ferredoxin (Fd) or flavodoxin (Fld) through an ATP-dependent process. Since its emergence in an anaerobic chemoautotroph, this oxygen (O₂)-sensitive enzyme complex has evolved to operate in a variety of genomic and metabolic backgrounds, including those of aerobes, anaerobes, chemotrophs, and phototrophs. However, whether pathways of electron delivery to nitrogenase are influenced by these different metabolic backgrounds is not well understood. Here, we report the distribution of homologs of Fds, Flds, and Fd-/Fld-reducing enzymes in 359 genomes of putative N₂ fixers (diazotrophs). Six distinct lineages …

Extraction Of Potassium Bromide On Polymeric Sulphate Ku-2 * 8 Under Conditions Of Nonsubstitutional Absorption, Kh.T. Trobov, N.B. Ferapontov, A.M. Qurbanov, G.Kh. Tursunova

Scientific Journal of Samarkand University

Based on heterogeneous model of the structure of sewed polielectrolytes grain the separation mechanism of strong electrolytes solutions by ion-exchanger is shown. The reasons of separation were determined. Examples of separation of strong electrolytes mixture on anion -exchanger APA-4 in Cl form is given.

Implications Of Monomer Deformation For Tetrel And Pnicogen Bonds, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

A series of TF₄ and ZF₅ molecules (T = Si, Ge, Sn and Z = P, As, Sb) were allowed to engage in tetrel and pnicogen bonds, respectively, with NH₃, pyrazine, and HCN. The interaction energies are quite large, approaching 50 kcal mol^-1 in some cases. The formation of each complex is accompanied by substantial geometrical deformation of the Lewis acid to accommodate the approaching base. The energy associated with this monomer rearrangement is the largest for the smaller central atoms Si and P, where it exceeds 20 kcal mol^-1. The total reaction …

Greer Studies, Teaches How To Improve Medicines, Aldemaro Romero Jr.

Publications and Research

“As a child, I was interested in asking questions. Like why different substances work the way they do and why they have some effect on our bodies. I was fascinated by hydrogen-peroxide and how it decomposes when you pour it on the wound. I would ask why it happens, what is the reason?” That’s how Dr. Edyta Greer explains how she became interested in science. A native of Poland, Greer received her master’s from Warsaw University and her doctorate from the Graduate Center of the City University of New York. Today she is an associate professor in the Department of …

Steric Crowding In Tetrel Bonds, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The tetravalent character of tetrel atoms leaves only limited room for an incoming nucleophile to approach and engage in a noncovalent bond with a tetrel atom. Any such approach can only occur at the expense of internal geometric distortions. The balance between attractive forces and repulsive steric crowding was studied for a series of Lewis acids of the type FTR₃ (T = Si, Ge, Sn, Pb) which were allowed to interact with various bases. The strength and other properties of the tetrel bond are examined as the R groups are made progressively larger, varying from H and CH_{3 …}

Chemical Characterization Of Fine Particulate Matter Emitted By Peat Fires In Central Kalimantan, Indonesia, During The 2015 El Niño, Thilina Jayarathne, Chelsea E. Stockwell, Ashley A. Gilbert, Kaitlyn Daugherty, Mark A. Cochrane, Kevin C. Ryan, Erianto I. Putra, Bambang H. Saharjo, Ati D. Nurhayati, Israr Albar, Robert J. Yokelson, Elizabeth A. Stone

Chemistry and Biochemistry Faculty Publications

Fine particulate matter (PM2:5) was collected in situ from peat smoke during the 2015 El Niño peat fire episode in Central Kalimantan, Indonesia. Twenty-one PM samples were collected from 18 peat fire plumes that were primarily smoldering with modified combustion efficiency (MCE) values of 0.725-0.833. PM emissions were determined and chemically characterized for elemental carbon (EC), organic carbon (OC), water-soluble OC, water-soluble ions, metals, and organic species. Fuel-based PM2:5 mass emission factors (EFs) ranged from 6.0 to 29.6 g kg1 with an average of 17:36:0 g kg1. EC was detected only in 15 plumes and comprised 1% of PM mass. …

Preventing Crossover In Redox Flow Batteries Through Active Material Oligomerization, Susan A. Odom

Chemistry Faculty Publications

No abstract provided.

Effect Of Molecular Side Groups And Local Nanoenvironment On Photodegradation And Its Reversibility, Nicole Quist, Mark Li, Ryan Tollefsen, Michael Haley, John Anthony, Oksana Ostroverkhova

Chemistry Faculty Publications

Degradation of organic semiconductors in the presence of oxygen is one of the bottlenecks preventing their wide-spread use in optoelectronic devices. The first step towards such degradation in functionalized pentacene (Pn) derivatives is formation of endoperoxide (EPO), which can either revert back to the parent molecule or proceed to molecule decomposition. We present the study of reversibility of EPO formation through probing the photophysical properties of functionalized fluorinated pentacene (Pn-R-F8) derivatives. Experiments are done in solutions and in films both at the single molecule level and in the bulk. In solutions, degradation of optical absorption and its partial recovery after …

Ultrahigh Resolution Ft-Icr Ms Data Of Long-Range Transported Free Tropospheric Aerosol Collected At The Pico Mountain Observatory In The Azores, Simeon K. Schum, Lynn Mazzoleni

Department of Chemistry Publications

This dataset and the methods used to obtain it were described in “Molecular and physical characteristics of aerosol at a remote marine free troposphere site: Implications for atmospheric aging” submitted to Atmospheric Chemistry and Physics in February 2018. Briefly, three long-range transported organic aerosol samples were analyzed using negative mode electrospray ionization Fourier transform ion cyclotron mass spectrometry (FT-ICR MS) with a mass resolving power of 400,000 (defined at m/z 400). FLEXPART retroplume simulations indicated that two of the samples (PMO-1 & PMO-3) were influenced by North American wildfire emissions transported in the free troposphere and one (PMO-2) by North …

Amide Neighbouring Group Effects In Peptides: Phenylalanine As Relay Amino Acid In Long‐Distance Electron Transfer, U. Wille, J. Nathanael, L. Gamon, M. Cordes, Paul R. Rablen, T. Bally, K. Fromm, B. Giese

Chemistry & Biochemistry Faculty Works

Nature uses proteins as medium for long‐distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single‐step superexchange or through a multi‐step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long‐distance electron hole transfer through peptides. The considerably increased susceptibility of the aromatic ring to oxidation is caused by the lone pairs of neighbouring amide carbonyl groups, which stabilize the Phe radical cation. This neighbouring amide group effect helps to better understand …

From Intramolecular (Circular) In An Isolated Molecule To Intermolecular Hole Delocalization In A Two‐Dimensional Solid‐State Assembly: The Case Of Pillarene, Maxim V. Ivanov, Denan Wang, Tushar S. Navale, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

To achieve long‐range charge transport/separation and, in turn, bolster the efficiency of modern photovoltaic devices, new molecular scaffolds are needed that can self‐assemble in two‐dimensional (2D) arrays while maintaining both intra‐ and intermolecular electronic coupling. In an isolated molecule of pillarene, a single hole delocalizes intramolecularly via hopping amongst the circularly arrayed hydroquinone ether rings. The crystallization of pillarene cation radical produces a 2D self‐assembly with three intermolecular dimeric (sandwich‐like) contacts. Surprisingly, each pillarene in the crystal lattice bears a fractional formal charge of +1.5. This unusual stoichiometry of oxidized pillarene in crystals arises from effective charge distribution within the …

Nepal Ambient Monitoring And Source Testing Experiment (Namaste): Emissions Of Particulate Matter From Wood-And Dung-Fueled Cooking Fires, Garbage And Crop Residue Burning, Brick Kilns, And Other Sources, Thilina Jayarathne, Chelsea E. Stockwell, Prakash V. Bhave, Puppala S. Praveen, Chathurika M. Rathnayake, Robiul Md Islam, Arnico K. Panday, Sagar Adhikari, Rashmi Maharjan, J. Douglas Goetz, Peter F. Decarlo, Eri Saikawa, Robert J. Yokelson, Elizabeth A. Stone

Chemistry and Biochemistry Faculty Publications

The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) characterized widespread and under-sampled combustion sources common to South Asia, including brick kilns, garbage burning, diesel and gasoline generators, diesel groundwater pumps, idling motorcycles, traditional and modern cooking stoves and fires, crop residue burning, and heating fire. Fuel-based emission factors (EFs; with units of pollutant mass emitted per kilogram of fuel combusted) were determined for fine particulate matter (PM2.5), organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals, and organic species. For the forced-draft zigzag brick kiln, EFPM2.5 ranged from 12 to 19gkg-1 with major contributions from OC (7%), sulfate …

Nmr Resonance Assignments Of Rnase P Protein From Thermotoga Maritima, Danyun Zeng, Benjamin P. Brown, Markus W. Voehler, Sheng Cai, Nicholas J. Reiter

Chemistry Faculty Research and Publications

Ribonuclase P (RNase P) is an essential metallo-endonuclease that catalyzes 5′ precursor-tRNA (ptRNA) processing and exists as an RNA-based enzyme in bacteria, archaea, and eukaryotes. In bacteria, a large catalytic RNA and a small protein component assemble to recognize and accurately cleave ptRNA and tRNA-like molecular scaffolds. Substrate recognition of ptRNA by bacterial RNase P requires RNA-RNA shape complementarity, intermolecular base pairing, and a dynamic protein-ptRNA binding interface. To gain insight into the binding specificity and dynamics of the bacterial protein-ptRNA interface, we report the backbone and side chain ¹H, ¹³C, and ¹⁵N resonance assignments of the …

Preparation Of Polymeric Materials From Bio-Renewable Sources, Jason Douglas Smith

Theses and Dissertations

The focus of this project was to develop methodologies for the preparation of novel polymeric materials from bio-renewable sources. In order to complete this task we needed (a) unfettered access to bio-based materials and ways to convert them to value needed chemicals, as well as, (b) reaction protocols that would allow greater diversity during the synthesis of polymeric compounds so as to affect the properties of these materials.

Our research group has a background in converting plant-based materials like cellulose into value added chemicals employing catalytic reactions. The polymerization of these monomers was then conducted utilizing the Baylis-Hillman reaction. The …

Atmospheric Chemistry Of Ch3Cho: The Hydrolysis Of Ch3Cho Catalyzed By H2So4, Ellen Mitchell, Xing-Feng Tan, Bo Long, Wei-Jun Zhang, Zheng-Wen Long

Chemistry Faculty Scholarship

Elucidating atmospheric oxidation mechanisms and the reaction kinetics of atmospheric compounds is of great importance and necessary for atmospheric modeling and the understanding of the formation of atmospheric organic aerosols. While the hydrolysis of aldehydes has been detected in the presence of sulfuric acid, the reaction mechanism and kinetics remain unclear. Herein, we use electronic structure methods with CCSD(T)/CBS accuracy and canonical variational transition state theory combined with small-curvature tunneling to study the reaction mechanism and kinetics of the hydrolysis of CH3CHO. The calculated results show that the hydrolysis of CH3CHO needs to overcome an energy barrier of 37.21 kcal …

Distinct Properties Underlie Flavin-Based Electron Bifurcation In A Novel Electron Transfer Flavoprotein Fixab From Rhodopseudomonas Palustris, H. Diessel Duan, Carolyn E. Lubner, Monika Tokmina-Lukaszewska, George H. Gauss, Brian Bothner, Paul W. King, John W. Peters, Anne-Frances Miller

Chemistry Faculty Publications

A newly recognized third fundamental mechanism of energy conservation in biology, electron bifurcation, uses free energy from exergonic redox reactions to drive endergonic redox reactions. Flavin-based electron bifurcation furnishes low-potential electrons to demanding chemical reactions, such as reduction of dinitrogen to ammonia. We employed the heterodimeric flavoenzyme FixAB from the diazotrophic bacterium Rhodopseudomonas palustris to elucidate unique properties that underpin flavin-based electron bifurcation. FixAB is distinguished from canonical electron transfer flavoproteins (ETFs) by a second FAD that replaces the AMP of canonical ETF. We exploited near-UV–visible CD spectroscopy to resolve signals from the different flavin sites in FixAB and to …

Semi-Synthesis Of A Novel Library Of Alkaloids As Potential Selective Analgesics, Brittany M. Gallagher

Theses and Dissertations

Semi-synthetic compounds are an important part of the therapeutic drug discovery process. The goals of the project were to synthesize different generations of matrine analogues in order to gain many opportunities to manipulate the core structure. The long-term goal was, by manipulating the structure, the possibility to increase the biological activity of the original compound while also decreasing the toxicity. The first-generation matrine analogue allows for a synthesis similar to the Striker reaction producing aminonitriles. An alkyne coupling reaction was also possible with the modification, producing propargyl-amines. Both of the reactions resulted in the addition of a triple bond substituent …

Biscyclic Guanidine Compound Compositions, Methods Of Use And Treatment Thereof, Lindsey Shaw, Renee Fleeman, Richard A. Houghten, Marc Giulianotti, Radleigh Santos, Adel Nefzi

Mathematics Faculty Proceedings, Presentations, Speeches, Lectures

The present disclosure provides compositions including a bis-cyclic guanidine compound, pharmaceutical compositions including a bis-cyclic guanidine compound, methods of treatment of a condition (e.g., bacterial infection) or disease, methods of treatment using compositions or pharmaceutical compositions, and the like.

Investigating Biomass Burning Aerosol Morphology Using A Laser Imaging Nephelometer, Katherine M. Manfred, Rebecca A. Washenfelder, Nicholas L. Wagner, Gabriela Adler, Frank Erdesz, Caroline C. Womack, Kara D. Lamb, Joshua P. Schwarz, Alessandro Franchin, Vanessa Selimovic, Robert J. Yokelson, Daniel M. Murphy

Chemistry and Biochemistry Faculty Publications

Particle morphology is an important parameter affecting aerosol optical properties that are relevant to climate and air quality, yet it is poorly constrained due to sparse in situ measurements. Biomass burning is a large source of aerosol that generates particles with different morphologies. Quantifying the optical contributions of non-spherical aerosol populations is critical for accurate radiative transfer models, and for correctly interpreting remote sensing data. We deployed a laser imaging nephelometer at the Missoula Fire Sciences Laboratory to sample biomass burning aerosol from controlled fires during the FIREX intensive laboratory study. The laser imaging nephelometer measures the unpolarized scattering phase …

Automating Data Analysis For Two-Dimensional Gas Chromatography/Time-Of-Flight Mass Spectrometry Non-Targeted Analysis Of Comparative Samples, Ivan A. Titaley, O. Maduka Ogba, Leah Chibwe, Eunha Hoh, Paul H.-Y. Cheong, Staci L. Massey Simonich

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Non-targeted analysis of environmental samples, using comprehensive two‐dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC/ToF-MS), poses significant data analysis challenges due to the large number of possible analytes. Non-targeted data analysis of complex mixtures is prone to human bias and is laborious, particularly for comparative environmental samples such as contaminated soil pre- and post-bioremediation. To address this research bottleneck, we developed OCTpy, a Python™ script that acts as a data reduction filter to automate GC × GC/ToF-MS data analysis from LECO^® ChromaTOF^® software and facilitates selection of analytes of interest based on peak area …

Surface Thiolation Of Silicon For Antifouling Application, Xiaoning Zhang, Pei Gao, Valerie Hollimon, Dashan Brodus, Arion Johnson, Hongmei Hu

EKU Faculty and Staff Scholarship

Thiol groups grafted silicon surface was prepared as previously described. 1H,1H,2H,2H-perfluorodecanethiol (PFDT) molecules were then immobilized on such a surface through disulfide bonds formation. To investigate the contribution of PFDT coating to antifouling, the adhesion behaviors of Botryococcus braunii (B. braunii) and Escherichia coli (E. coli) were studied through biofouling assays in the laboratory. The representative microscope images suggest reduced B. braunii and E. coli accumulation densities on PFDT integrated silicon substrate. However, the antifouling performance of PFDT integrated silicon substrate decreased over time. By incubating the aged substrate in 10 mM TCEP·HCl solution for 1 h, the fouled PFDT …

The Meniscus-Guided Deposition Of Semiconducting Polymers, Xiaodan Gu, Leo Shaw, Kevin Gu, Michael F. Toney, Zhenan Bao

Faculty Publications

The electronic devices that play a vital role in our daily life are primarily based on silicon and are thus rigid, opaque, and relatively heavy. However, new electronics relying on polymer semiconductors are opening up new application spaces like stretchable and self-healing sensors and devices, and these can facilitate the integration of such devices into our homes, our clothing, and even our bodies. While there has been tremendous interest in such technologies, the widespread adoption of these organic electronics requires low-cost manufacturing techniques. Fortunately, the realization of organic electronics can take inspiration from a technology developed since the beginning of …

Using Natural Resources To Control The Fate Of Contaminants In The Environment, Lucia Rodriguez Freire

Sustainability Seminar Series

Environmental contamination poses an increased health risk to those communities living nearby impacted sites, and it is imperative to find sustainable remediation strategies to restore the natural systems. My research investigates natural biogeochemical processes and the use of ubiquitous materials to the design remediation solutions that are site-specific and take into consideration the needs of the affected communities. The first example is the investigation of uranium (U) accumulation in plants growing along the Rio Paguate, which flows through the Jackpile Mine, and open-pit U mine listed on the National Priority List as a Superfund site. Two villages of the Laguna …

Innovative Monte Carlo Methods For Sampling Molecular Conformations, Aliasghar Sepehri

LSU Doctoral Dissertations

Sampling molecular conformations is an important step in evaluating physical, mechanical, hydrodynamic, and optical properties of flexible molecules especially polymers. One powerful method for this purpose is configurational-bias Monte Carlo in which one random segment of a molecule is chosen, all segments toward one random end are removed, and then regrown segment by segment to produce a new geometry to be accepted/rejected according to probability laws. The advantage of this method is the ability to generate acceptable conformations that are favorable for intra- and intermolecular energies to save computational costs. However, when there are several interdependent energetic terms, trial generation …

Pi Tetrel Bonds, And Their Influence On Hydrogen Bonds And Proton Transfers, Yuanxin Wei, Qingzhong Li, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The positive region that lies above the plane of F2TO (T=C and Si) interacts with malondialdehyde (MDA), which contains an intramolecular H‐bond. The T atom of F2TO can lie either in the MDA molecular plane, forming a T⋅⋅⋅O tetrel bond, or F2TO can stack directly above MDA in a parallel arrangement. The former structure is more stable than the latter, and in either case, F2SiO engages in a much stronger interaction than does F2CO, reaching nearly 200 kJ mol−1. The π‐tetrel bond strengthens/weakens the MDA H‐bond when the bond is formed to the hydroxyl/carbonyl group of MDA, and causes an …

Highway Construction Or Stream Destruction: A Water Quality Analysis In The Black Warrior Basin, Walker County, Alabama, Cayla Baughn

Mahurin Honors College Capstone Experience/Thesis Projects

In 2012, residents along Freeman Branch Creek in Eldridge, Alabama observed unusual orange discoloration along the stream and on stream vegetation; an unprecendented black veneer coating pebbles along the streambed; and life in the stream seemed to have vanished. Freeman Branch Creek is located in Walker County, Alabama, which is known for its production of coal and natural gas from the underlying Pennsylvanian-aged Pottsville Formation, which is the uppermost geologic layer within the the Black Warrior Basin. Concerns for environmental safety related to intensive mining operations include the concern that shallow aquifers will be contaminated by mining in deep reservoir …

Expansion Of The (Bb)>Ru Metallacycle With Coinage Metal Cations: Formation Of B-M-Ru-B (M= Cu, Ag, Au) Dimetalacyclodiboryls†, Bennett J. Eleazer, Mark D. Smith, Alexey A. Popov, Dmitry V. Peryshkov

Faculty Publications

In this work, we introduce a novel approach for the selective assembly of heterometallic complexes by unprecedented coordination of coinage metal cations to strained single ruthenium–boron bonds on a surface of icosahedral boron clusters. M(I) cations (M ¼ Cu, Ag, and Au) insert into B–Ru bonds of the (BB)–carboryne complex of ruthenium with the formation of four-membered B–M–Ru–B metalacycles. Results of theoretical calculations suggest that bonding within these metalacycles can be best described as unusual three-center-two-electron B–M/Ru interactions that are isolobal to B–H/Ru borane coordination for M ¼ Cu and Ag, or the pairs of two-center-two electron B–Au and Au–Ru …

Reaction Chemistry Of Silver(I) Trifluoromethanesulfonate Complexes Of Nitrogen-Confused C-Scorpionates, James R. Gardinier, Kristin J. Meise, Fathiya Jahan, Sergey V. Lindeman

Chemistry Faculty Research and Publications

Two new C-scorpionate ligands with a bis(3,5-dimethylpyrazol-1-yl)methyl group bound to the 3 position of either an N-tosyl (^TsL*) or an N–H pyrazole (^HL*) ring have been prepared. The silver(I) complexes of these new ligands and the two previously reported analogous ligands with unsubstituted bis(pyrazol-1-yl)methyl groups (^TsL and ^HL) in both 1:1 and 2:1 ligand/metal ratios were investigated to explore the effects of ligand sterics on their physical and chemical properties. The structurally characterized derivatives of the type [Ag(L)₂](OTf) are four-coordinate, where the confused pyrazolyl is not bound to the …

Comparison Of Processed And Non-Processed Biomass Digestion, Richard Bruce Clark Iii

Graduate Theses - Chemistry and Biochemistry

Lignocellulosic ethanol is the main focus of second-generation biofuels [1]. Because cellulose is the most abundant organic material on earth, second-generation biofuels are a more sustainable option than the classical first-generation biofuels that use foodstuffs as the main feedstock in ethanol production [1]. Furthermore, biofuel can be produced not only from unprocessed biomass such as corn husks but also from processed material like paper [1]. Ionic liquids have shown to be quite effective in dissolving naturally occurring, and traditionally insoluble, polymers such as cellulose into solution, and cellulase enzymes have been shown to effectively digest cellulose into simple sugars [2]. …