Chemistry Commons^™

Reversing Interfacial Catalysis Of Ambipolar Wse2 Single Crystal, Zegao Wang, Hong-Hui Wu, Qiang Li, Flemming Besenbacher, Yanrong Li, Xiao Cheng Zeng, Mingdong Dong

Department of Chemistry: Faculty Publications

An improved understanding of the origin of the electrocatalytic activity is of importance to the rational design of highly efficient electrocatalysts for the hydrogen evolution reaction. Here, an ambipolar single-crystal tungsten diselenide (WSe2) semiconductor is employed as a model system where the conductance and carrier of WSe2 can be individually tuned by external electric fields. The field-tuned electrochemical microcell is fabricated based on the single-crystal WSe2 and the catalytic activity of the WSe2 microcell is measured versus the external electric field. Results show that WSe2 with electrons serving as the dominant carrier yields much higher activity than WSe2 with holes …

Understanding Interactions Of Citropin 1.1 Analogues With Model Membranes And Their Influence On Biological Activity, Nathalia Rodrigues De Almeida, Jonathan Catazaro, Maddeboina Krishnaiah, Yashpal Singh Chhonker, Daryl J. Murry, Robert Powers, Martin Conda-Sheridan

Department of Chemistry: Faculty Publications

The rapid emergence of resistant bacterial strains has made the search for new antibacterial agents an endeavor of paramount importance. Cationic antimicrobial peptides (AMPs) have the ability to kill resistant pathogens while diminishing the development of resistance. Citropin 1.1 (Cit 1.1) is an AMP effective against a broad range of pathogens. 20 analogues of Cit 1.1 were prepared to understand how sequence variations lead to changes in structure and biological activity. Various analogues exhibited an increased antimicrobial activity relative to Cit 1.1. The two most promising, AMP-016 (W3F) and AMP-017 (W3F, D4R, K7R) presented a 2- to 8-fold increase in …

A Panel Of Protein Kinase Chemosensors Distinguishes Different Types Of Fatty Liver Disease, Jon R. Beck, Fatima Cabral, Karuna Rasineni, Carol A. Casey, Edward N. Harris, Cliff I. Stains

Department of Chemistry: Faculty Publications

The worldwide incidence of fatty liver disease continues to rise, which may account for concurrent increases in the frequencies of more aggressive liver ailments. Given the existence of histologically identical fatty liver disease subtypes, there is a critical need for the identification of methods that can classify disease and potentially predict progression. Herein, we show that a panel of protein kinase chemosensors can distinguish fatty liver disease subtypes. These direct activity measurements highlight distinct differences between histologically identical fatty liver diseases arising from diets rich in fat versus alcohol and identify a previously unreported decrease in p38α activity associated with …

Systematic Optimization For Production Of The Anti-Mrsa Antibiotics Wap-8294a In An Engineered Strain Of Lysobacter Enzymogenes, Xusheng Chen, Shanren Li, Lingjun Yu, Amanda Miller, Liangcheng Du

Department of Chemistry: Faculty Publications

WAP-8294A is a group of cyclic lipodepsipeptides and considered as the first-in-class new chemical entity with potent activity against methicillin-resistant Staphylococcus aureus. One of the roadblocks in developing the WAP-8294A antibiotics is the very low yield in Lysobacter. Here, we carried out a systematic investigation of the nutritional and environmental conditions in an engineered L. enzymogenes strain for the optimal production of WAP-8294A. We developed an activity-based simple method for quick screening of various factors, which enabled us to optimize the culture conditions. With the method, we were able to improve the WAP-8294A yield by 10-fold in small-scale cultures and …

Computational Studies Of Thermal Properties And Desalination Performance Of Low-Dimensional Materials, Yang Hong

Department of Chemistry: Dissertations, Theses, and Student Research

During the last 30 years, microelectronic devices have been continuously designed and developed with smaller size and yet more functionalities. Today, hundreds of millions of transistors and complementary metal-oxide-semiconductor cells can be designed and integrated on a single microchip through 3D packaging and chip stacking technology. A large amount of heat will be generated in a limited space during the operation of microchips. Moreover, there is a high possibility of hot spots due to non-uniform integrated circuit design patterns as some core parts of a microchip work harder than other memory parts. This issue becomes acute as stacked microchips get …

Quantum Chemical Calculations Applied To Somo–Homo Conversion And Vibrationally Averaged Nmr Shielding Parameters, Erik Johnson

Department of Chemistry: Dissertations, Theses, and Student Research

The inversion of frontier orbitals of free radicals was studied using density functional theory calculations in Gaussian 09. Comparisons of images of orbitals in GaussView was used to assess the relative positions of singly occupied and doubly occupied orbitals and to determine which was the highest in energy. A variety of organic free radicals were studied including several radical anions and also a neutral radical. It was found that cross-conjugation appears to be a factor in whether or not molecules show SOMO-HOMO conversion. Cross-conjugation is when two unsaturated groups are conjugated to a third unsaturated group but are not conjugated …

Design And Synthesis Of Stable Aminyl And Nitroxide Radical Precursors, Joshua Bryan Lovell

Department of Chemistry: Dissertations, Theses, and Student Research

Aminyl diradicals with sterically-hindered tert-butyl groups have yet to be fully investigated for their increased stability due to their difficulty in synthesis. The first chapter of this thesis details design and synthesis towards sterically-hindered aminyl radical and diradical precursors.

Structural features effecting nitroxide radical stability have been well investigated except for the impact on the ring-size of stability of nitroxides towards reduction by ascorbate. Two 7-membered nitroxides derived from TEMPONE and TEMPOL have been synthesized and characterized. The alcohol nitroxide shows increased stability towards reduction by ascorbate compared to the corresponding TEMPOL, while the other nitroxide shows decreased stability compared …

Phosphonate-Directed Catalytic Asymmetric Hydroboration: Synthesis Of Functionalized Chiral Secondary And Tertiary Boronic Esters And Mechanistic Insights, Suman Chakrabarty

Department of Chemistry: Dissertations, Theses, and Student Research

Over the past 30 years, catalytic asymmetric hydroboration (CAHB) of alkenes has emerged as a leading methodology to access chiral primary and secondary boronic esters. However, it wasn’t until 2015 that directed-CAHB was for the first time shown to efficiently access chiral tertiary boronic esters. The latter are excellent precursors to synthetically challenging structural motifs such as chiral tertiary alcohols, carbinamines and all-carbon quaternary stereocenters via stereospecific C-B bond substitutions. This dissertation focuses on phosphonate-directed CAHB of diverse alkene substrates, including challenging stereodefined trisubstituted alkenes, to efficiently access multifunctional chiral secondary and tertiary boronic esters. Mechanistic insights obtained via deuterium …

Optimization Of Protein Entrapment In Affinity Microcolumns Using Hydrazide-Activated Silica And Glycogen As A Capping Agent, John Vargas-Badilla, Saumen Poddar, Shiden Azaria, Chenhua Zhang, David S. Hage

David Hage Publications

Several approaches were compared for the entrapment of proteins within hydrazide-activated silica for use in affinity microcolumns and high performance affinity chromatography. Human serum albumin (HSA) and concanavalin A (Con A) were used as model proteins for this work. Items considered in this study included the role played by the solution volume, amount of added protein, and use of slurry vs. on-column entrapment on the levels of solute retention and extent of protein immobilization that could be obtained by means of entrapment. The levels of retention and protein immobilization were evaluated by injecting warfarin or 4-methylumbellipheryl α-D-mannopyranoside as solutes with …

Electropolymerization And Characterization Of Thin Film Dielectrics, Christopher White Ii

Department of Chemistry: Dissertations, Theses, and Student Research

Graphene is a two-dimensional allotrope of carbon, with several superlative properties, including high electron and hole conductivities, high tensile strength, and chemical robustness. Its chemical and physical properties make it attractive for in use in a myriad of applications, including transistors. However, graphene’s chemical inertness and its physical and electrical properties’ dependency on its conjugated structure make building composite materials with graphene difficult. In 2015, Lipatov, et. al. demonstrated that a film derived from electropolymerized phenol could be used as a dielectric layer on transistor devices fabricated from exfoliated graphene. This thesis extends that research, detailing experiments of phenol and …

Monolayer Triphosphates Mp3 (M = Sn, Ge) With Excellent Basal Catalytic Activity For Hydrogen Evolution Reaction, Hong-Hui Wu, He Huang, Jie Zhong, Song Yu, Qiaobao Zhang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Atomically thin two-dimensional (2D) materials have received intense research interest due to their novel properties and promising applications in nanodevices. By using density functional theory (DFT) calculations, we investigate catalytic activities of several newly predicted two-dimensional (2D) triphosphides GeP₃, SnP₃ and InP₃ monolayers for hydrogen evolution reaction (HER). The calculation results show that GeP₃ and SnP₃ monolayers are active catalysts for HER with suitable free energy of hydrogen adsorption in the basal plane. In particular, the Gibbs free energy of hydrogen adsorption (ΔG_H*) of GeP₃ is 0.024 eV, a value even …

Putting The I In Science, Naomi Kirkvold

Honors Program: Expanded Learning Clubs

This club gets kids interested in science in ways that they may not have experienced in a classroom by doing weekly experiments.

Development Of Nanomaterial Supports For The Study Of Affinity-Based Analytes Using Ultra-Thin Layer Chromatography, Allegra Pekarek

Department of Chemistry: Dissertations, Theses, and Student Research

Ultra-thin layer chromatography (UTLC) is a growing field in analytical separations. UTLC is a branch of planar and liquid chromatography that is related to thin layer chromatography. The main advantage of UTLC compared to other techniques is it uses much less material, allowing for faster and more sensitive separations to take place. The UTLC devices fabricated in this project used either silicon oxide or silicon nanopillars deposited on a glass slide using glancing angle deposition (GLAD). Even a thin layer of these nanopillars deposited on a glass slide provide a large surface area for the analyte to be separated. GLAD …

Analysis Of Drug–Protein Interactions During Diabetes By High-Performance Affinity Chromatography, Pingyang Tao

Department of Chemistry: Dissertations, Theses, and Student Research

High-performance affinity chromatography (HPAC) is a type of liquid chromatography in which solutes are separated based on their binding to a stationary phase that is a biologically-related agent. Sulfonylurea drugs have significant binding to proteins in blood, with most of this binding is believed to occur with human serum albumin (HSA). HSA is known to be modified as a result of the high serum levels of glucose that is present during diabetes, which may also alter the function of HSA as a binding agent for many drugs in circulation. Some modifications of HSA that can occur during diabetes involves early …

Slips-Teng: Robust Triboelectric Nanogenerator With Optical And Charge Transparency Using A Slippery Interface, Wanghuai Xu, Xiaofeng Zhou, Chonglei Hao, Huanxi Zheng, Yuan Liu, Xiantong Yan, Zhengbao Yang, Michael Leung, Xiao Cheng Zeng, Ronald X. Xu, Zuankai Wang

Xiao Cheng Zeng Publications

Energy harvesting devices that prosper in harsh environments are highly demanded in a wide range of applications ranging from wearable and biomedical devices to self-powered and intelligent systems. Particularly, over the past several years, the innovation of triboelectric nanogenerators (TENGs) that efficiently convert ambient kinetic energy of water droplets or wave power to electricity has received growing attention. One of the main bottlenecks for the practical implications of such devices originates from the fast degradation of the physiochemical properties of interfacial materials under harsh environments. To overcome these challenges, here we report the design of a novel slippery lubricant-impregnated porous …

An Overview Of Capillary Electrophoresis (Ce) In Clinical Analysis, David S. Hage

David Hage Publications

The development and general applications of capillary electrophoresis (CE) in the field of clinical chemistry are discussed. It is shown how the early development of electrophoresis was closely linked to clinical testing. The rise of gel electrophoresis in clinical chemistry is described, as well as the eventual developments that lead to the creation and the use of modern CE. The general principles of CE are reviewed and the potential advantages of this method in clinical testing are examined. Finally, an overview is presented of several areas in which CE has been developed and is currently being explored for use with …

Reaction Mechanism Between Small-Sized Ce Clusters And Water Molecules: An Ab Initio Investigation On CeN+H2O, Rulong Zhou, Yang Yang, Seema Pande, Bingyan Qu, Dongdong Li, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Reactions of small-sized cerium clusters Ce_n (n = 1–3) with a single water molecule are systematically investigated theoretically. The ground state structures of the Ce_n/H₂O complex and the reaction pathways between Ce_n + H₂O are predicted. Our results show the size-dependent reactivity of small-sized Ce clusters. The calculated reaction energies and reaction barriers indicate that the reactivity between Ce_n and water becomes higher with increasing cluster size. The predicted reaction pathways show that the single Ce atom and the Ce₂ and Ce₃ clusters can all easily react with H …

Role Of Water On The Rotational Dynamics Of The Organic Methylammonium Cation: A First Principles Analysis, Ross D. Hoehn, Joseph S. Francisco, Sabre Kais, Ali Kachmar

Department of Chemistry: Faculty Publications

Understanding the degradation mechanisms of lead-halide perovskites (CH₃NH₃PbI₃) under exposure to liquid/aerosol water is an essential problem within the photovoltaic community. Herein we investigate both the static and the dynamic properties of the methylammonuim cation (MA) as it coordinates with invading water molecules (MA.(H₂O)_n, n = 1, 2, 3, 4) using both stationary state quantum mechanics and first principle molecular dynamics simulations. Various solvation structures of MA were characterized by their stabilization energies, dipoles, and Maximally-Localized Wannier Function (MLWF) centers. Calculation – and analysis – of vibrational shifts in the …

Structural Basis Of 7sk Rna 5′ Γ-Phosphate Methylation And Retention By Mepce, Yuan Yang, Catherine D. Eichhorn, Yaqiang Wang, Duilio Cascio, Juli Feigon

Department of Chemistry: Faculty Publications

Among RNA 5′-cap structures, γ-phosphate monomethylation is unique to a small subset of noncoding RNAs, 7SK and U6 in humans. 7SK is capped by methylphosphate capping enzyme (MePCE), which has a second non-enzymatic role as a core component of the 7SK RNP that is an essential regulator of RNA transcription. We report 2.0 and 2.1 Å X-ray crystal structures of human MePCE methyltransferase domain bound to S-adenosylhomocysteine (SAH) and uncapped or capped 7SK substrates, respectively. 7SK recognition is achieved by protein contacts to a 5′ hairpin-single-stranded RNA region, explaining MePCE specificity for 7SK and U6. The structures reveal SAH and …

Molecular Insights Into Cage Occupancy Of Hydrogen Hydrate: A Computational Study, Rui Ma, Hong Zhong, Jinxiang Liu, Jie Zhong, Youguo Yan, Jun Zhang, Jiafang Xu

Department of Chemistry: Faculty Publications

Density functional theory calculations and molecular dynamics simulations were performed to investigate the hydrogen storage capacity in the sII hydrate. Calculation results show that the optimum hydrogen storage capacity is ~5.6 wt%, with the double occupancy in the small cage and quintuple occupancy in the large cage. Molecular dynamics simulations indicate that these multiple occupied hydrogen hydrates can occur at mild conditions, and their stability will be further enhanced by increasing the pressure or decreasing the temperature. Our work highlights that the hydrate is a promising material for storing hydrogen.

Brush-Arm Star Polymer Imaging Agents And Uses Thereof, Jeremiah A. Johnson, Hung Vanthanh Nguyen, Andrzej Rajca

Department of Chemistry: Faculty Publications

Disclosed are methods, compositions, reagents, systems, and kits to prepare nitroxide-functionalized brush-arm star polymer organic radical contrast agent (BASP-ORCA) as well as compositions and uses thereof. Various embodiments show that BASP-ORCA display unprecedented per-nitrox-ide and per-molecule transverse relaxivities for organic radical contrast agents, exceptional stability, high water solubility, low in vitro and in vivo toxicity, and long blood compartment half-life. These materials have the potential to be adopted for tumor imaging using clinical high-field ¹H MRI techniques.

Growth Of Carbon Dioxide Whiskers, Avinash Kumar Both, Chin Li Cheung

Department of Chemistry: Faculty Publications

We report the growth of carbon dioxide (CO₂) whiskers at low temperatures (–70 °C to –65 °C) and moderate pressure (4.4 to 1.0 bar). Their axial growth was assessed by optical video analysis. The identities of these whiskers were confirmed as CO₂ solids by Raman spectroscopy. A vapor– solid growth mechanism was proposed based on the influence of the relative humidity on the growth.

Role Of Water On The Rotational Dynamics Of The Organic Methylammonium Cation: A First Principles Analysis, Ross D. Hoehn, Joseph S. Francisco, Sabre Kais, Ali Kachmar

Department of Chemistry: Faculty Publications

Understanding the degradation mechanisms of lead-halide perovskites (CH₃NH₃PbI₃) under exposure to liquid/aerosol water is an essential problem within the photovoltaic community. Herein we investigate both the static and the dynamic properties of the methylammonuim cation (MA) as it coordinates with invading water molecules (MA.(H₂O)_n, n = 1, 2, 3, 4) using both stationary state quantum mechanics and first principle molecular dynamics simulations. Various solvation structures of MA were characterized by their stabilization energies, dipoles, and Maximally-Localized Wannier Function (MLWF) centers. Calculation – and analysis – of vibrational shifts in the …

Indole Reverses Intrinsic Antibiotic Resistance By Activating A Novel Dual-Function Importer, Yan Wang, Tian Tian, Jingjing Zhang, Xin Jin, Huan Yue, Xiao-Hua Zhang, Liangcheng Du, Fan Bai

Department of Chemistry: Faculty Publications

Bacterial antibiotic resistance modulation by small signaling molecules is an emerging mechanism that has been increasingly reported in recent years. Several studies indicate that indole, an interkingdom signaling molecule, increases bacterial antibiotic resistance. However, the mechanism through which indole reduces antibiotic resistance is largely unknown. In this study, we demonstrated a novel mechanism for indole-mediated reversal of intrinsic antibiotic resistance in Lysobacter. This reversal was facilitated by a novel BtuD-associated dual-function importer that can transfer both vitamin B₁₂ and antibiotics. Indole stimulated btuD overexpression and promoted efficient absorption of extracellular vitamin B₁₂; meanwhile, the weak selectivity …

Facile Access To Functionalized Chiral Secondary Benzylic Boronic Esters Via Catalytic Asymmetric Hydroboration, Suman Chakrabarty, Hector Palencia, Martha D. Morton, Ryan O. Carr, James M. Takacs

James M. Takacs Publications

Allylic and homoallylic phosphonates bearing an aryl or heteroaryl substituent at the γ- or δ-position undergo rhodium-catalyzed asymmetric hydroboration by pinacolborane to give functionalized chiral secondary benzylic boronic esters in yields up to 86% and enantiomer ratios up to 99 : 1. Compared to minimally-functionalized terminal and 1,1-disubstituted vinyl arenes, there are relatively few reports of efficient catalytic asymmetric hydroboration (CAHB) of more highly functionalized internal alkenes. Phosphonate substrates bearing a variety of common heterocyclic ring systems, including furan, indole, pyrrole and thiophene derivatives, as well as those bearing basic nitrogen substituents (e.g., morpholine and pyrazine) are tolerated, …

High Initial Reversible Capacity And Long Life Of Ternary Sno2‑Co‑Carbon Nanocomposite Anodes For Lithium‑Ion Batteries, Pan Deng, Jing Yang, Shengyang Li, Tian-E Fan, Hong-Hui Wu, Yun Mou, Hui Huang, Qiaobao Zhang, Dong-Liang Peng, Baihua Qu

Department of Chemistry: Faculty Publications

The two major limitations in the application of SnO₂ for lithium-ion battery (LIB) anodes are the large volume variations of SnO₂ during repeated lithiation/delithiation processes and a large irreversible capacity loss during the first cycle, which can lead to a rapid capacity fade and unsatisfactory initial Coulombic efficiency (ICE). To overcome these limitations, we developed composites of ultrafine SnO₂ nanoparticles and in situ formed Co(CoSn) nanocrystals embedded in an N-doped carbon matrix using a Co-based metal–organic framework (ZIF-67). The formed Co additives and structural advantages of the carbon-confined SnO₂/ Co nanocomposite effectively inhibited Sn coarsening …

Au60–: The Smallest Gold Cluster With The High-Symmetry Icosahedral Core Au13, Seema Pande, Xingao Gong, Lai-Sheng Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Among coinage metal nanoclusters with 55 atoms, only Ag₅₅^– and Cu₅₅^– are the geometric magic-number clusters, as both exhibit icosahedral symmetry. Au₅₅^–, however, exhibits much lower symmetry due largely to the strong relativistic bonding effect. In this study, we collect a much larger population (>10,000 isomers) of low-energy isomers of Au₅₅^– to Au₆₀^– by using the combined density-functional theory and basin-hopping global optimization method. We also include the spin−orbit effect in the density-functional theory computation to achieve simulated photoelectron spectra in quantitative fashion. Remarkably, we uncover that the …

Highly Stable And Efficient All-Inorganic Lead-Free Perovskite Solar Cells With Native-Oxide Passivation, Min Chen, Ming-Gang Ju, Hector F. Garces, Alexander D. Carl, Luis K. Ono, Zafer Hawash, Yi Zhang, Tianyi Shen, Yabing Qi, Ronald L. Grimm, Domenico Pacifici, Xiao Cheng Zeng, Yuanyuan Zhou, Nitin P. Padture

Department of Chemistry: Faculty Publications

There has been an urgent need to eliminate toxic lead from the prevailing halide perovskite solar cells (PSCs), but the current lead-free PSCs are still plagued with the critical issues of low efficiency and poor stability. This is primarily due to their inadequate photovoltaic properties and chemical stability. Herein we demonstrate the use of the lead-free, allinorganic cesium tin-germanium triiodide (CsSn_0.5Ge_0.5I₃) solid-solution perovskite as the light absorber in PSCs, delivering promising efficiency of up to 7.11%. More importantly, these PSCs show very high stability, with less than 10% decay in efficiency after 500 h …

Urease Is An Essential Component Of The Acid Response Network Of Staphylococcus Aureus And Is Required For A Persistent Murine Kidney Infection, Chunyi Zhou, Fatema Bhinderwala, Mckenzie K. Lehman, Vinai C. Thomas, Sujata S. Chaudhari, Kelsey J. Yamada, Kirk W. Foster, Robert Powers, Tammy Kielian, Paul D. Fey

Department of Chemistry: Faculty Publications

Staphylococcus aureus causes acute and chronic infections resulting in significant morbidity. Urease, an enzyme that generates NH₃ and CO₂ from urea, is key to pH homeostasis in bacterial pathogens under acidic stress and nitrogen limitation. However, the function of urease in S. aureus niche colonization and nitrogen metabolism has not been extensively studied. We discovered that urease is essential for pH homeostasis and viability in urea-rich environments under weak acid stress. The regulation of urease transcription by CcpA, Agr, and CodY was identified in this study, implying a complex network that controls urease expression in response to changes …

Machine Learning Enabled Prediction Of Mechanical Properties Of Tungsten Disulfide Monolayer, Xinyu Wang, Dan Han, Yang Hong, Haiyi Sun, Jingzhi Zhang, Jingchao Zhang

Department of Chemistry: Faculty Publications

One of two-dimensional transition metal dichalcogenide materials, tungsten disulfide (WS₂), has aroused much research interest, and its mechanical properties play an important role in a practical application. Here the mechanical properties of h-WS₂ and t-WS₂ monolayers in the armchair and zigzag directions are evaluated by utilizing the molecular dynamics (MD) simulations and machine learning (ML) technique. We mainly focus on the effects of chirality, system size, temperature, strain rate, and random vacancy defect on mechanical properties, including fracture strain, fracture strength, and Young’s modulus. We find that the mechanical properties of h-WS₂ surpass those of …