Physical Sciences and Mathematics Commons^™

The High Pressure Dependence Of X-Ray Induced Decomposition Of Cadmium Oxalate, Adrian F. Lua Sanchez, Petrika Cifligu, Marc Graff, Michael Pravica, Pradip K. Bhowmik, Changyong Park, Egor Evlyukhin

Physics & Astronomy Faculty Research

The high proclivity of x rays to destabilize and distort molecular structures has been previously utilized in the synthesis of novel compounds. Here, we show that x-ray induced decomposition of cadmium oxalate induces chemical and structural transformations only at 0.5 and 1 GPa. Using x-ray diffraction and Raman spectroscopy, the synthesized product is identified as cadmium carbonate with cadmium oxalate remnants, which is stable under ambient conditions. At ambient and >1 GPa pressures, only degradation of the electronic density distribution is observed. The transformation kinetics are examined in terms of Avrami’s model, which demonstrates that despite the necessity of high …

Stoichiometric Determination Of Hydride Materials At Extreme Conditions, Gregory Alexander Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

Hydrogen was predicted to be a high-temperature superconductor at near-megabar conditions in 1968,[1] but only recently was been experimentally observed.[2] This is due to the extraneous metrological constraint of requiring 5 megabars of pressure to stabilize. A more practical approach for synthesis of high-temperature superconductors has been pro-posed through the use of hydride compounds. Recently, a surge of rare earth hydrides have achieved critical superconducting transition temperatures (T_C ) close to room temperature.[3, 4, 5, 6] However, due to limitations of the necessary instrumentation to achieve megabar pressures, many techniques traditionally used to measure stoichiometry are unavailable.Three works presented in …

Development Of A Novel Ionic Liquid-Coated Adsorbent For Treating Emerging Contaminants In Recycled Water On The International Space Station, Madeline Carroll, Gabson Baguma, Savanna Vacek

Undergraduate Research Symposium Posters

Synthesize at least 3 biobased ionic liquids. Optimize method for conducting liquid-liquid extractions. Analyze and quantify how much DMSO2 is removed by the ionic liquids. Coat biochar with the most effective biobased ionic liquids.

Groundwater Remediation Using Modified Biochar, Kers Ung-Watson, Ismail Abdulraheem, Nikki Tibayan, Suraj Pochampally

Undergraduate Research Symposium Posters

Biochar, a lightweight black residue made of carbon, has proved to be an effective adsorbent to remove TCE from groundwater. Not only is it an economical substitute for conventional adsorbents but it can be created by using a variety of organic materials. For this project, it will rely on walnut shell feedstock to create biochar as this had the best ability to adsorb TCE.

Trapping And Cooling Of Ca+ For Cold Ion-Radical Collisions, Bernardo Gutierrez

Undergraduate Research Symposium Posters

Free radicals are molecules that contain an unpaired valence electron which induces high reactivity. Ion radical reactions are typically exothermic and have low (or zero) activation energy. It is for these reasons that ion-radical reactions are believed to dominate in interstellar clouds where temperatures hover around 3-10K. State-to-state measurements require precision control of both reactants.

What Can General Chemistry Students Learn From External Representations Of Acid- Base Titrations?, Nicole Baldwin

UNLV Theses, Dissertations, Professional Papers, and Capstones

Laboratory activities are a prevalent and essential part of chemistry learning because of their potential to help students develop problem solving abilities, visualize chemistry concepts learned in lecture, and gain practical skills. However, learning in the laboratory environment is not without its challenges. For example, cookbook-style chemistry laboratories can promote superficial learning, and cognitive overload can result from the study of new concepts and the use of new procedures in this environment. Multiple pedagogies and supports have been developed to address challenges such as these. The current research focuses upon external representations that are commonly used to support learning in …

Characterization Of The Isothermal Titration Calorimetry Single Injection Method Using T4 Polynucleotide Kinase As A Model System For Kinases, Rebecca Chaehee Lim

UNLV Theses, Dissertations, Professional Papers, and Capstones

Kinases are an important class of enzymes involved in the regulation of different cellular processes. The dysfunctional activity, either hyperactivity or inactivity, of kinases has been associated with many types of diseases, making kinases a major therapeutic target. As of 2020, more than 80 kinase inhibitors have been FDA-approved and have revolutionized the treatment for progressive disorders such as cancers and Alzheimer's diseases. However, there is always the possibility of developing severe side effects or resistance to drugs so the search for new therapeutics must continue with efficiency and accuracy.Isothermal titration calorimetry (ITC) is a state-of-the-art technique specialized in detecting …

Dissolution And Electrochemical Recovery Of Uo2, Uo3, And U3o8 In Ionic Liquids, Katherine Iolani Thornock Luebke

UNLV Theses, Dissertations, Professional Papers, and Capstones

This research explores a novel method of increasing the solubility of uranium oxides and other actinide oxides in room temperature ionic liquids (IL) using direct dissolution. The goal is to further expand our knowledge of actinide dissolution and possible nuclear fuel cycle material applications using ionic liquids. The novelty of the methods is focused on the use of oxidizing gas generated using air passed through an ozone generator. While examples of dissolution exist in IL using acidic functionalized ionic liquids, the solubility of all possible oxide species was not demonstrated. Also, the addition of aqueous acid to IL containing actinide …

The Dissolution And Recovery Of Critical Materials (Li2co3 And Uf6) From Ionic Liquid, Cassara Higgins

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lithium and uranium are critical materials in both the energy industry and for national security. Lithium is necessary for the next generation of batteries and 6Li is valuable for the production of tritium necessary for both fusion energy and to maintain our nuclear stockpiles. Uranium is a fuel source or precursor fuel source for commercially operating nuclear fission power. The monitoring of uranium hexafluoride (UF6) enrichment at foreign facilities is important for the monitoring of nuclear safeguards and enforcement of non-proliferation treaties. Recovery methods for lithium at the end of life of batteries are necessary to ensure abundance of the …

Low-Cost Adsorbent For Disinfection Byproduct Removal From Drinking Water, Savanna Vacek, Suraj Pochampally

Undergraduate Research Symposium Posters

Disinfection byproducts (DBPs) are harmful contaminants that are unintentionally created in disinfected water after chlorination. Activated carbon, often expensive and difficult to acquire in low-income and rural areas, has previously been used to remove DBPs from drinking water. Biochar is made from agricultural waste (i.e. feedstock) and has been identified as a low-cost yet effective adsorbent to remote contaminants from drinking water. This work focuses on the efficacy of biochar and activated carbon to remove DBPs from drinking water for the purpose of treating drinking water after emergency chlorination. This study has the potential to help water distributors and disadvantaged …

Identification Of Lipid Species: Potential Biomarkers For Early Detection Of Hepatocellular Carcinoma, Kit Yee Leung, Kaylee Freitas

Undergraduate Research Symposium Posters

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. HCC is associated with cirrhosis. Poor survival rate of HCC is due to diagnosis of HCC at late stage.

Biochar Hydrophilicity Characterization By A Smartphone-Based Apparatus: Design, Construction, And Measurement Calibration, Emma Letourneau, Suraj Pochampally

Undergraduate Research Symposium Posters

Water contact angles are used to determine hydrophilicity, which is a material's attraction to water. A water contact angle of greater than 90 degrees indicates a hydrophobic material that repels water, whereas a contact angle of less than 90 degrees indicates a hydrophilic material [Fig. 1]. Water contact angles are measured through a goniometer, which can cost between $2000 to $10,000.

Biochar is a porous carbon material created from biological waste products, that is pyrolyzed (i.e. burned) in a low-oxygen, high heat environment. Biochar can be used to remove contaminants from water and remediate soil while reusing waste, making it …

Synthesis Of Modified Walnut Shell Biochar And Material Characterization In Ground Water Treatment, Maaike Parajes, Suraj Pochampally

Undergraduate Research Symposium Posters

Biochar (BC) is a carbon-rich material synthesized from the pyrolysis of biomasses and developed to remove soil and wastewater contaminants. The pyrolysis process involves thermally decomposing the organic materials in the absence of oxygen. Biochar has the potential to be an eco-friendly and effective adsorbent for heavy metals and toxic organic compounds. An adsorbent is a material that attracts other substances on its surface, chemically and physically. Walnut shells were chosen for the biochar modification to improve the surface morphology, pore structure, and adsorption capability.

An Approach For Material Model Identification Of A Composite Coating Using Micro-Indentation And Multi-Scale Simulations, Pouya Shojaei, Riccardo Scazzosi, Mohamed Trabia, Brendan O’Toole, Marco Giglio, Xing Zhang, Yiliang Liao, Andrea Manes

Mechanical Engineering Faculty Research

While deposited thin film coatings can help enhance surface characteristics such as hardness and friction, their effective incorporation in product design is restricted by the limited understand-ing of their mechanical behavior. To address this, an approach combining micro-indentation and meso/micro-scale simulations was proposed. In this approach, micro-indentation testing was conducted on both the coating and the substrate. A meso-scale uniaxial compression finite element model was developed to obtain a material model of the coating. This material model was incorporated within an axisymmetric micro-scale model of the coating to simulate the indentation. The proposed approach was applied to a Ti/SiC metal …

What Do General And Organic Chemistry Students Consider When Making Decisions About Acids And Bases? A Phenomenographic Study, Sarah Wood

UNLV Theses, Dissertations, Professional Papers, and Capstones

Chemistry students often struggle in organic chemistry courses. In fact, these courses are viewed by some as “weed-out” classes. There are many fundamental concepts covered in general chemistry that contribute to students’ ability to succeed in organic chemistry. One of those fundamental topics, and the focus of this study, is the topic of acids and bases. Acid–base topics are featured in both general and organic chemistry courses, and the interests of this study lie not only within the realm of organic chemistry but also general chemistry.

The purpose of this study was to determine both undergraduate general and organic chemistry …

Statistical Measurements Of Dispersion Measure Fluctuations Of Frbs, Siyao Xu, David H. Weinberg, Bing Zhang

Physics & Astronomy Faculty Research

Extragalactic fast radio bursts (FRBs) have large dispersion measures (DMs) and are unique probes of intergalactic electron density fluctuations. By using the recently released First CHIME/FRB Catalog, we reexamined the structure function (SF) of DM fluctuations. It shows a large DM fluctuation similar to that previously reported in Xu & Zhang, but no clear correlation hinting toward large-scale turbulence is reproduced with this larger sample. To suppress the distortion effect from FRB distances and their host DMs, we focus on a subset of CHIME catalog with DM < 500 pc cm-3. A trend of nonconstant SF and nonzero correlation function (CF) at angular separations θ less than 10 is seen, but with large statistical uncertainties. The difference found between SF and that derived from CF at θ ≲ 10 can be ascribed to the large statistical uncertainties or the density inhomogeneities on scales on the order of 100 Mpc. The possible correlation of electron density fluctuations and inhomogeneities of density distribution should be tested when several thousands of FRBs are available.

Thermal Analysis Of Benzotriazolium Perrhenate And Its Implication To Rhenium Metal, James Louis-Jean, Harry Jang, Andrew J. Swift, Frederic Poineau

Chemistry and Biochemistry Faculty Research

The thermal analysis behavior of C6H6N3[ReO4] was studied by simultaneous thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) up to 700 °C under argon. Such analysis afforded rhenium metal, which was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. XRD peak broadening due to crystallite size and lattice strain was analyzed by both Williamson-Hall (W-H) and Debye-Scherrer (D-S) methods. Efforts to isolate Re metal from the thermal treatment of benzotriazole (BTA = C6H5N3) with NH4ReO4 and Re2O7 under various atmospheres and temperatures are also reported. The results provide a significant insight into …

Inelastic, Exchange, And Reactive Processes In Rovibrationally Excited Collisions Of Hd With H, Boyi Zhou, Benhui Yang, Balakrishnan Naduvalath, B. K. Kendrick, Maodu Chen, P. C. Stancil

Chemistry and Biochemistry Faculty Research

The HD molecule is an important coolant in early universe chemistry models and a tracer of H2 in star-forming regions. Rate coefficients for collisional excitation and de-excitation of HD rotational and vibrational levels form important ingredients in astrophysical models. While collisions with He, H2, and H are the most important, available data for H + HD collisions are largely limited to temperatures less than 1000 K for the vibrational ground state, low-lying rotational levels of the v = 1 HD vibrational level, or computed without reactive contributions. Here, through explicit quantum scattering calculations, we report extensive data for rovibrational transitions …

Controllable Co2 Electrocatalytic Reduction Via Ferroelectric Switching On Single Atom Anchored In2se3 Monolayer, Lin Ju, Xin Tan, Xin Mao, Yuantong Gu, Sean Smith, Aijun Du, Zhongfang Chen, Changfeng Chen, Liangzhi Kou

Physics & Astronomy Faculty Research

Efficient and selective CO2 electroreduction into chemical fuels promises to alleviate environmental pollution and energy crisis, but it relies on catalysts with controllable product selectivity and reaction path. Here, by means of first-principles calculations, we identify six ferroelectric catalysts comprising transition-metal atoms anchored on In2Se3 monolayer, whose catalytic performance can be controlled by ferroelectric switching based on adjusted d-band center and occupation of supported metal atoms. The polarization dependent activation allows effective control of the limiting potential of CO2 reduction on TM@In2Se3 (TM = Ni, Pd, Rh, Nb, and Re) as well as the reaction paths and final products on …

Vacancy Control In Acene Blends Links Exothermic Singlet Fission To Coherence, Clemens Zeiser, Chad Cruz, David R. Reichman, Michael Seitz, Jan Hagenlocher, Eric L. Chronister, Christopher J. Bardeen, Roel Tempelaar, Katharina Broch

Chemistry and Biochemistry Faculty Research

The fission of singlet excitons into triplet pairs in organic materials holds great technological promise, but the rational application of this phenomenon is hampered by a lack of understanding of its complex photophysics. Here, we use the controlled introduction of vacancies by means of spacer molecules in tetracene and pentacene thin films as a tuning parameter complementing experimental observables to identify the operating principles of different singlet fission pathways. Time-resolved spectroscopic measurements in combination with microscopic modelling enables us to demonstrate distinct scenarios, resulting from different singlet-to-triplet pair energy alignments. For pentacene, where fission is exothermic, coherent mixing between the …

Singlet Fission In Acene Blends, Katharina Broch, Clemens Zeiser, Chad Cruz, Luca Moretti, Margherita Maiuri, Eric Chronister, David Reichman, Roel Tempelaar, Giulio Cerullo, Christopher Bardeen

Chemistry and Biochemistry Faculty Research

Singlet fission (SF), the photophysical process converting an excited singlet exciton into two triplet excitons, is a promising approach to boost solar cell efficiencies. It is controlled by various parameters such as intermolecular interactions, energetics, entropy and vibronic coupling and a controlled modification of these parameters is key to a fundamental understanding. Blends of organic semiconductors present an interesting alternative to established methods of chemical functionalization and their potential for the study of SF pathways will be discussed using acene blends as example. Mixed thin films of SF chromophores and weakly interacting, high-bandgap spacer molecules allow one to study the …

Free-Free Absorption In Hot Relativistic Flows: Application To Fast Radio Bursts, Esha Kundu, Bing Zhang

Physics & Astronomy Faculty Research

Magnetic flares create hot relativistic shocks outside the light cylinder radius of a magnetized star. Radio emission produced in such a shock or at a radius smaller than the shock undergoes free–free absorption while passing through the shocked medium. In this work, we demonstrate that this free–free absorption can lead to a negative drift in the frequency-time spectra. Whether it is related to the downward drift pattern observed in fast radio bursts (FRBs) is unclear. However, if the FRB down-drifting is due to this mechanism then it will be pronounced in those shocks that have isotropic kinetic energies ≳1044 erg. …

A Proposed Change To Astronaut Exposures Limits Is A Giant Leap Backwards For Radiation Protection, Francis A. Cucinotta, Walter Schimmerling, Eleanor A. Blakely, Tom K. Hei

Health Physics & Diagnostic Sciences Faculty Publications

Addressing the uncertainties in assessing health risks from cosmic ray heavy ions is a major scientific challenge recognized by many previous reports by the National Academy of Sciences (NAS) and the National Council on Radiation Protection and Measurements (NCRP) advising the National Aeronautics and Space Administration (NASA). These reports suggested a series of steps to pursue the scientific basis for space radiation protection, including the implementation of age and sex dependent risk assessments and exposure limits appropriate for a small population of radiation workers, the evaluation of uncertainties in risk projections, and developing a vigorous research program in heavy ion …

Recovery Of High Specific Activity Molybdenum-99 From Accelerator-Induced Fission On Low-Enriched Uranium For Technetium-99m Generators, M. Alex Brown, Nathan Johnson, Artem V. Gelis, Milan Stika, Anna G. Servis, Alex Bakken, Christine Krizmanich, Kristin Shannon, Peter Kozak, Amanda Barnhart, Chad Denbrock, Nicolas Luciani, Terry Grimm, Peter Tkac

Chemistry and Biochemistry Faculty Research

A new process was developed to recover high specific activity (no carrier added) 99Mo from electron-accelerator irradiated U3O8 or uranyl sulfate targets. The process leverages a novel solvent extraction scheme to recover Mo using di(2-ethylhexyl) phosphoric acid following uranium and transuranics removal with tri-n-butyl phosphate. An anion-exchange concentration column step provides a final purification, generating pure 99Mo intended for making 99Mo/99mTc generators. The process was demonstrated with irradiated uranium targets resulting in more than 95% 99Mo recovery and without presence of fission products or actinides in the product.

Special Issue Editorial: Current Advances In Liquid Crystals, Pradip K. Bhowmik

Chemistry and Biochemistry Faculty Research

No abstract provided.

Β -Technetium: An Allotrope With A Nonstandard Volume-Pressure Relationship, Emily Siska, Dean Smith, Christian Childs, Daniel Koury, Paul M. Forster, Keith V. Lawler, Ashkan Salamat

Chemistry and Biochemistry Faculty Research

We report the synthesis and structure of the second allotrope of technetium, β-Tc. Transformative pathways are accessed at extreme conditions using the laser-heated diamond anvil cell and confirmed with in situ synchrotron x-ray diffraction and Raman spectroscopy. β-Tc is fully recoverable to ambient conditions, although counter to our DFT calculations predicting a face-centered-cubic lattice, we observe a tetragonal structure (I4/mmm) that exhibits further tetragonal distortion with pressure. β-Tc has an expanded volume relative to the hcp ground state phase, that when doped with nitrogen has an unexpected volume lowering. Such anomalous behavior is possibly indicative of a rare electronic phase …

Colossal Density-Driven Resistance Response In The Negative Charge Transfer Insulator Mns2, Dylan Durkee, Nathan Dasenbrock-Gammon, G. Alexander Smith, Elliot Snider, Dean Smith, Christian Childs, Simon A.J. Kimber, Keith V. Lawler, Ranga P. Dias, Ashkan Salamat

Chemistry and Biochemistry Faculty Research

A reversible density driven insulator to metal to insulator transition in high-spin MnS2 is experimentally observed, leading with a colossal electrical resistance drop of 108 ω by 12 GPa. Density functional theory simulations reveal the metallization to be unexpectedly driven by previously unoccupied S22- σ3p∗ antibonding states crossing the Fermi level. This is a unique variant of the charge transfer insulator to metal transition for negative charge transfer insulators having anions with an unsaturated valence. By 36 GPa the emergence of the low-spin insulating arsenopyrite (P21/c) is confirmed, and the bulk metallicity is broken with the system returning to an …

Pressure- And Temperature-Dependent Inelastic Neutron Scattering Study Of The Phase Transition And Phonon Lattice Dynamics In Para-Terphenyl, Qingan Cai, Michael Mcintire, Luke L. Daemen, Chen Li, Eric Chronister

Chemistry and Biochemistry Faculty Research

Inelastic neutron scattering has been performed on para-terphenyl at temperatures from 10 to 200 K and under pressures from the ambient pressure to 1.51 kbar. The temperature dependence of phonons, especially low-frequency librational bands, indicates strong anharmonic phonon dynamics. The pressure- and temperature-dependence of the phonon modes suggest a lack of phase transition in the region of 0-1.51 kbar and 10-30 K. Additionally, the overall lattice dynamics remains similar up to 200 K under the ambient pressure. The results suggest that the boundary between the ordered triclinic phase and the third solid phase, reported at lower temperatures and higher pressures, …

Steep Sulfur Gradient In Cztsse Solar Cells By H2s-Assisted Rapid Surface Sulfurization, Teoman Taskesen, Devendra Pareek, Dirk Hauschild, Alan Haertel, Lothar Weinhardt, Wanli Yang, Timo Pfeiffelmann, David Nowak, Clemens Heske, Levent Gütay

Chemistry and Biochemistry Faculty Research

Sulfur/selenium grading is a widely used optimization strategy in kesterite thin-film solar cells to obtain a bandgap-graded absorber material and to optimize optical and electrical properties of the solar-cell device. In this work, we present a novel approach to introduce a [S]/([S] + [Se]) grading for Cu ZnSn(S,Se) solar cells. In contrast to commonly used methods with slow process dynamics, the presented approach aims to create a fast sulfurization reaction on the surface of pure selenide kesterite absorbers by using highly reactive H S gas and high sulfurization temperatures in a rapid flash-type process. With a combination of X-ray photoelectron …

Poly(Pyridinium Salt)S Containing 2,7-Diamino-9,9'-Dioctylfluorene Moieties With Various Organic Counterions Exhibiting Both Lyotropic Liquid-Crystalline And Light-Emitting Properties, Pradip K. Bhowmik, Tae S. Jo, Jung J. Koh, Jongwon Park, Bidyut Biswas, Ronald Carlo G. Principe, Haesook Han, András F. Wacha, Matti Knaapila

Chemistry and Biochemistry Faculty Research

A series of poly(pyridinium salt)s-fluorene main-chain ionic polymers with various organic counterions were synthesized by using ring-transmutation polymerization and metathesis reactions. Their chemical structures were characterized by Fourier Transform Infrared (FTIR), proton (1H), and fluorine 19 (19F) nuclear magnetic resonance (NMR) spectrometers. These polymers showed a number-average molecular weight (Mns) between 96.5 and 107.8 kg/mol and polydispersity index (PDI) in the range of 1.12-1.88. They exhibited fully-grown lyotropic phases in polar protic and aprotic solvents at different critical concentrations. Small-angle X-ray scattering for one polymer example indicates lyotropic structure formation for 60-80% solvent fraction. A lyotropic smectic phase contains 10 …