Physical Chemistry Commons^™

Hollow Nickel-Iron Nanoshells As Electrocatalysts For The Oxygen Evolution Reaction, Jonathan Batey

Chemistry & Biochemistry Undergraduate Honors Theses

The development of highly active and affordable catalysts for the oxygen evolution reaction is crucial to achieve a future where hydrogen is generated cleanly using renewable methods. Ni-Fe nanocatalysts show great promise in this area, as they are affordable and highly active. However, to overcome the industrial dominance of steam methane reforming, their activity needs improvement. This work aims to increase the activity of Ni-Fe nanocatalysts by making hollow nanostructures. Hollow Ni-Fe nanostructures were synthesized by coating a Cu template with Ni and Fe, followed by the etching of the Cu template. This left hollow Ni-Fe nanoshells, which were used …

Fret Studies On The Binding Of Fibroblast Growth Factor (Fgf) Proteins To The Hard Corona Of Cuins2-Based Quantum Dots, Colette Robinson

Graduate Theses and Dissertations

Fibroblast Growth Factor (FGF) has been shown to be an important protein in angiogenesis, which is critical in developmental biology and wound healing but has also been implicated in cancer metastasis. FGF interacts with an FGF Receptor (FGFR) to signal the onset of angiogenesis but the detailed mechanism of angiogenesis, and particularly its regulation, is still largely unknown. Imaging the interaction of FGF with FGFR in biologically-relevant environments, such as directly in cells, is key towards furthering this understanding and may eventually aid in the development of better cancer treatments. CuInS2/ZnS quantum dots (QDs) are an attractive fluorescent probe to …

Effects Of Varying Ph, Temperature, And Sucrose Concentration On The Activity Of Invertase Enzyme, B. Rainwater, S. Pratihar

Journal of the Arkansas Academy of Science

The purpose of this research is to study the factors that affect the enzymatic activity of invertase, extracted from baker’s yeast, on hydrolysis of sucrose in aqueous medium. Invertase, a glycoprotein, is an enzyme in the glycoside hydrolase family. It catalyzes the hydrolysis of sucrose producing equimolar mixture of a-D-glucose and b-D-fructose. Invertase shows high affinity for the substrate, and is capable of both cleaving the glycosidic linkage in sucrose and transferring ab-D-O-fructofuranoside residue to an acceptor substrate. (Toledo et al. 2019). A detailed mechanism of the action of invertase was postulated by Shall et al. (Shall et al. 1971). …

Synthesis And X-Ray Characterization Of Nickel Phosphide Nanostructures For Water Oxidation, David Thompson

Graduate Theses and Dissertations

The pursuit of earth-abundant 3d transition metal catalysts for alkaline water electrolysis remains an active area of research. While NiFe layered double hydroxides (LDH) are currently the most active catalysts for the oxygen evolution reaction (OER), doping Ni-based catalysts with phosphorus to form Ni metal phosphides has emerged as a promising alternative. However, the complex crystalline and amorphous phases of NiP_x have hindered their characterization, and the OER mechanism and origin of activity remain unclear. This dissertation aims to elucidate the synthesis, OER performance, and in situ reconstruction of amorphous NiP_x-based nanomaterials, with a focus on in …

Molecular Insights: Advances In Single Molecule And Single Particle Detection For Analysis Of Chemical, Physical, And Biological Phenomena, James Ethan Batey

Chemistry & Biochemistry Undergraduate Honors Theses

This thesis is focused on recent advancements made in the field of chemical imaging, optical microscopy, and recent developments that have improved spatial, temporal, or spectral resolution or have made certain techniques more accessible and cost effective for their wider adoption. This thesis is organized based on the systems of interest we studied with each new technique. Although, it is important to note that many of the methods here can be used with a multitude of systems even if not explicitly mentioned. The first chapter of this thesis will discuss the current state of chemical imaging, common terminology, and important …

Using Gaussian Process Regression To Learn Thermodynamic Equations Of State With Uncertainty Quantification, Austen T. Lee

Chemical Engineering Undergraduate Honors Theses

This study investigates the use of derivative-informed Gaussian Process (GP) models to estimate thermodynamic behavior across temperature and density by building a Helmholtz-based equation of state. Argon, a stable monatomic gas, was chosen as a case study within the vapor region. The GP model was trained using values of experimentally measurable properties found by taking first and second derivatives of the original potential function. Results show that while the GP model offered uncertainty quantification and informed thermodynamic behavior, it predicted values that deviated from the ground truth depending on the property. The model exhibited high confidence in regions with substantial …

Molecular Dynamics Investigation Of The Influenza Hemagglutinin Conformational Changes In Acidic Ph, Shadi A. Badiee, Vivek Govind Kumar, Mahmoud Moradi

Chemistry & Biochemistry Faculty Publications and Presentations

The surface protein hemagglutinin (HA) of the influenza virus plays a pivotal role in facilitating viral infection by binding to sialic acid receptors on host cells. Its conformational state is pH-sensitive, impacting its receptor-binding ability and evasion of the host immune response. In this study, we conducted extensive equilibrium microsecond-level all-atom molecular dynamics (MD) simulations of the HA protein to explore the influence of low pH on its conformational dynamics. Specifically, we investigated the impact of protonation on conserved histidine residues (H106₂) located in the hinge region of HA2. Our analysis encompassed comparisons between nonprotonated (NP), partially protonated …

Substrate Interference And Strain In The Second-Harmonic Generation From Mose2 Monolayers, Sudeep Puri, Sneha Patel, Jose Luis Cabellos, Luis Enrique Rosas-Hernandez, Kaitlin Reynolds, Hugh O.H. Churchill, Salvador Barraza-Lopez, Bernardo S. Mendoza, Hiroyuki Nakamura

Physics Faculty Publications and Presentations

Nonlinear optical materials of atomic thickness, such as non-centrosymmetric 2H transition metal dichalcogenide monolayers, have a second-order nonlinear susceptibility (χ⁽²⁾) whose intensity can be tuned by strain. However, whether χ⁽²⁾ is enhanced or reduced by tensile strain is a subject of conflicting reports. Here, we grow high-quality MoSe₂ monolayers under controlled biaxial strain created by two different substrates and study their linear and nonlinear optical responses with a combination of experimental and theoretical approaches. Up to a 15-fold overall enhancement in second-harmonic generation (SHG) intensity is observed from MoSe₂ monolayers grown on SiO₂ when …

Selective Hydrolysis Of Heterooligosaccharides By Poly(Acrylate) Gel Catalysts, Susanna Striegler

Chemistry & Biochemistry Faculty Publications and Presentations

Natural glycoside hydrolases are distinguished by their ability to hydrolyze glycosidic bonds with high efficiency and selectivity. This feature is achieved through specific interactions in the active site during catalytic turnover and is not just facilitated by two catalytically active amino acids. Intrigued by these features, a biomimetic α-galactosidase mimic was developed using an empirical catalyst design. Starting with a library of 704 gels of which 250 have a unique composition synthesized from TEGDMA cross-linker and 7 selected monomers, 238 monomodal gels are evaluated for their ability to hydrolyze the 1→6 α-glycosidic bond in the disaccharide melibiose. Among those, 13 …

Deciphering The Interdomain Coupling In A Gram-Negative Bacterial Membrane Insertase, Adithya Polasa, Shadi A. Badiee, Mahmoud Moradi

Chemistry & Biochemistry Faculty Publications and Presentations

YidC is a membrane protein that plays an important role in inserting newly generated proteins into lipid membranes. The Sec-dependent complex is responsible for inserting proteins into the lipid bilayer in bacteria. YidC facilitates the insertion and folding of membrane proteins, both in conjunction with the Sec complex and independently. Additionally, YidC acts as a chaperone during the folding of proteins. Multiple investigations have conclusively shown that Gram-positive bacterial YidC has Sec-independent insertion mechanisms. Through the use of microsecond-level all-atom molecular dynamics (MD) simulations, we have carried out an in-depth investigation of the YidC protein originating from Gram-negative bacteria. This …

Differential Behavior Of Conformational Dynamics In Active And Inactive States Of Cannabinoid Receptor 1, Ugochi H. Isu, Adithya Polasa, Mahmoud Moradi

Chemistry & Biochemistry Faculty Publications and Presentations

Cannabinoid receptor 1 (CB1) is a G protein-coupled receptor that regulates critical physiological processes including pain, appetite, and cognition. Understanding the conformational dynamics of CB1 associated with transitions between inactive and active signaling states is imperative for developing targeted modulators. Using microsecond-level all-atom molecular dynamics simulations, we identified marked differences in the conformational ensembles of inactive and active CB1 in apo. The inactive state exhibited substantially increased structural heterogeneity and plasticity compared to the more rigidified active state in the absence of stabilizing ligands. Transmembrane helices TM3 and TM7 were identified as distinguishing factors modulating the state-dependent dynamics. TM7 …

Developing Catalysts For The Hydrolysis Of Glycosidic Bonds In Oligosaccharides Using A Spectrophotometric Screening Assay, Susanna Striegler

Chemistry & Biochemistry Faculty Publications and Presentations

In a proof-of-concept study, a method for the empirical design of polyacrylate gel catalysts with the ability to cleave 1→4 α-glycosidic bonds in di- and trisaccharides was elaborated. The study included the synthesis of a 300-gel member library based on two different cross-linkers and 10 acrylate monomers, identification of monomodal gels by dynamic light scattering, and a 96-well plate spectrophotometric screening assay to monitor the hydrolysis of chromophore-free maltose into glucose units. The composition of the matrix of the most efficient catalysts in the library was found to enable CH−π, hydrophobic, and H-bond accepting interactions during the hydrolysis as typically …

Simulation Of Linear And Cyclic Alkanes With Second-Order Møller–Plesset Perturbation Theory Through Adaptive Force Matching, Alexei Nikitin, Feng Wang

Chemistry & Biochemistry Faculty Publications and Presentations

Predicting ensemble properties, such as density and heat of vaporization, of small hydrocarbons is challenging due to the dispersion-dominated weak interactions between these molecules. With the adaptive force matching (AFM) method, the bonded and short-range nonbonded interactions are fitted to second-order Møller–Plesset perturbation theory (MP2) references computed with the def2-TZVP basis set. The dispersion is modeled using symmetry adapted perturbation theory (SAPT) at MP4 accuracy using the def2-TZVPD basis set. A new charge matrix decomposition technique is described to obtain partial charges in AFM. Although the models developed do not have any empirical parameters, several properties of the resulting models …

Water Potential From Adaptive Force Matching For Ice And Liquid With Revised Dispersion Predicts Supercooled Liquid Anomalies In Good Agreement With Two Independent Experimental Fits, Raymond Weldon, Feng Wang

Chemistry & Biochemistry Faculty Publications and Presentations

A revised version of the Water potential from Adaptive force matching for Ice and Liquid (WAIL) was developed by using the previous data set for fitting the WAIL model but with a dispersion term calculated using symmetry adapted perturbation theory (SAPT). The model has no adjustable parameters and relies solely on fitting first-principles information. The new model, named revised WAIL (rWAIL), shows improved predictions of most properties of water when compared to the previously published WAIL model. The rWAIL model also compares favorably to other first-principles-derived water models, such as MB-Pol, at only a fraction of the computational cost. The …

Ionically Crosslinked Cellulose Nanocrystals By Metal Nitrates For The Preparation Of Stable Emulsions With Tunable Interface Properties, Joseph Batta-Mpouma, Gurshagan Kandhola, Jin-Woo Kim

Materials Science and Engineering Faculty Publications and Presentations

Biologically extracted cellulose nanocrystals (CNCs) are rod-like and amphiphilic materials with surface-exposed (hydrophilic sites) and hidden (hydrophobic sites) hydroxyl groups. These physicochemical characteristics make CNCs suitable for use as emulsifying agents to stabilize emulsions. Stable oil-in-water emulsions, using sulfated (i.e., – SO₃−) CNCs that were ionically crosslinked with alkaline-earth (i.e., Mg ²⁺) or transition-d-block (i.e., Zn ²⁺) metal cations, were developed without the use of any synthetic surfactants or prior functionalization of pure CNCs with hydrophobic molecules. Various emulsion surface properties such as interfacial tension, surface charge, surface chemistry, as well as rheology were characterized. Ionically …

Excitation Power Dependence Of Blinking In Copper-Indium-Sulfide Quantum Dots, Nicholas Chambers

Physics Undergraduate Honors Theses

Under continuous excitation, quantum dots exhibit random transitions between fluorescent ON states and non-fluorescent OFF states --- a phenomenon known as blinking. A physical description of the mechanism responsible for blinking that applies broadly to many types of quantum dots remains under debate. We study the blinking behavior of the non-toxic CuInS2 quantum dot, a system that has seen little investigation at the single-particle level. In particular, the optical properties of CuInS2 quantum are often improved by adding ZnS to the nanoparticles, but this addition leads to complex structural-optical property relationships that are even less understood. To probe the relationship …

Detection Of Nitrogen Dioxide Via Graphene-Enhanced Raman Scattering, Spencer Hazeslip

Chemistry & Biochemistry Undergraduate Honors Theses

This paper presents the development of a nitrogen dioxide (NO₂) sensor that utilizes the phenomenon of graphene-enhanced Raman scattering (GERS). The sensor consists of monolayer graphene on a silicon wafer, functionalized noncovalently with Copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuTTPc) via the solution soaking method. A custom sensing chamber was constructed to enable Raman spectra to be collected during NO₂ exposure. The response of the sensor was found to be linear between 10 and 100 ppm NO₂, indicating that it could be used for both detection and quantification. Furthermore, the sensor was shown to be reusable after …

Carbon Dioxide Reduction On Large Area Liquid Metal Gallium-Indium Electrocatalysts, Thomas Hollis

Chemistry & Biochemistry Undergraduate Honors Theses

Carbon dioxide (CO₂) is widely known as a greenhouse gas that contributes to global warming due to the burning of fossil fuels. The carbon dioxide reduction reaction (CO₂RR) is widely studied to reutilize CO₂ to useful products, including methane, ethane, and carbon monoxide. This project studies the use of liquid metal gallium-indium as an electrocatalyst to perform CO₂ reduction to carbon monoxide (CO) or possibly solid carbon in various solutions. Gallium-indium is characterized and studied through its “wetting” properties and adhesion to substrate foil through the measurement of contact angles inside solution. These liquid …

High Order Structures Formed By The Natural Aromatic Amino Acids, Gabriel Alexander Kupovics, Zeina Alraawi

Inquiry: The University of Arkansas Undergraduate Research Journal

Excessive concentrations of the natural aromatic amino acids phenylalanine and tyrosine are characteristic of the severe genetic abnormalities known as phenylketonuria (PKU) and tyrosinemia, respectively. Within this context, this feature article authenticates claims that tryptophan can form amyloid-like supramolecular structures in vitro and is the first to propose potential mechanisms of tryptophan self-assembly, including hydrophobic and electrostatic interactions. Thioflavin T (ThT) fluorescence kinetics and transmission electron microscopy (TEM) data suggest the formation of amyloid-like fibrillar structures by natural aromatic amino acids in vitro. Additionally, the propensity of amino acid aggregation increases in the presence of sodium dodecyl sulfate (SDS). The …

Surface-Driven Instabilities At Oil-Water Interfaces, Anelisse Claros Mendieta

Graduate Theses and Dissertations

Fluid-fluid interactions are such a wide area and can be observed in different scenarios such as geothermal systems, waterflooding of reservoirs, oil recovery, and water treatment processes. This thesis aims to deepen the understanding of fluid-fluid interactions which include Marangoni flows, charge related instabilities, and surface activity. This thesis studied the interactions of micrometer-sized droplets of an oil (toluene) with surfactant Di-(2-ethylhexyl) phosphoric acid (DEHPA) in the aqueous phase. One of the main goals is to understand several surface-driven instabilities and how those can be manipulated for future applications.Furthermore, this thesis aims to use these oil-surfactant droplets as a medium …

Introduction Of Human Acidic Fibroblast Growth Factor (Fgf1) Variant With Increased Stability And Bioactivity, Azadeh Tavousi Tabatabaei

Graduate Theses and Dissertations

Human acidic Fibroblast Growth Factor 1 (FGF-1) involves in a broad spectrum of biological processes, including cell growth, proliferation, differentiation, migration, angiogenesis, wound healing, and embryonic development. hFGF1 non-selectively binds to cell surface hFGF receptor isoforms to elicit these cell-signaling processes. Since hFGF1 plays a significant role in tissue repair activity, that is a prime candidate for novel wound healing therapeutics. However, hFGF1 has been found to unfold near physiological temperature due to a strong electrostatic repulsion created by a dense cluster of positively charged amino acids near the c-terminus. The problem not only leads to proteolytic degradation of the …

Investigation Of The Binding Domain Interfaces Of The C-Terminus Of The Albino3 Insertase And The 43kda Chloroplast Signal Recognition Particle Subunit Via Single Molecule Förster Resonance Energy Transfer, Amanda Tomanek

Chemistry & Biochemistry Undergraduate Honors Theses

Fluorescent labeling is a technique used for visualizing functional groups contained in biomolecules by fluorescence imaging. This technique was used in this project to analyze post-translational targeting of light-harvesting chlorophyll-binding proteins (LHCP), which are the core complexes that harvest sunlight to drive photosynthetic electron transfer. This protein is synthesized in the cytosol and post-translationally targeted to the stroma of chloroplasts. CpSRP43 is a signal recognition particle (SRP) subunit unique to chloroplasts, which has been shown to interact with the stroma-soluble C-terminus of the thylakoid-bound Albino3 insertase (Alb3-Cterm). In the chloroplast stroma, targeting to thylakoids is performed via the cpSRP pathway …

Mechanisms Of Spontaneous Curvature Inversion In Compressed Graphene Ripples For Energy Harvesting Applications Via Molecular Dynamics Simulations, James M. Mangum, Ferdinand Harerimana, Millicent N. Gikunda, Paul M. Thibado

Physics Faculty Publications and Presentations

Electrically conductive, highly flexible graphene membranes hold great promise for harvesting energy from ambient vibrations. For this study, we built numerous three-dimensional graphene ripples, with each featuring a different amount of compression, and performed molecular dynamics simulations at elevated temperatures. These ripples have a convex cosine shape, then spontaneously invert their curvature to concave. The average time between inversion events increases with compression. We use this to determine how the energy barrier height depends on strain. A typical convex-to-concave curvature inversion process begins when the ripple’s maximum shifts sideways from the normal central position toward the fixed outer edge. The …

High Performance Mixed-Matrix Electrospun Membranes For Ammonium Removal From Wastewaters, Shu-Ting Chen, Sumith Ranil Wickramasinghe, Xianghong Qian

Chemical Engineering Faculty Publications and Presentations

Mixed-matrix electrospun membranes were developed to investigate ammonium removal from low ammonium concentration wastewaters for the first time. Particles derived from the inexpensive zeolite 13X were successfully incorporated into polyethersulfone (PES) matrices. The fabricated mixed-matrix electrospun membranes demonstrate high ammonium removal capacity reaching over 55 mg/g_zeolite, more than 2.5 times higher than the previously fabricated mixed-matrix membranes via non-solvent induced phase inversion. Moreover, the membranes fabricated exhibit high permeability and ease of regeneration. Over 90% of total ammonium nitrogen (TAN) can be removed from low TAN wastewaters such as aquaculture wastewaters. In addition to zeolite 13X, other zeolite …

Quantum Transport Of The 2d Surface State In A Nonsymmorphic Semimetal, Xue Liu, Jin Hu, Jiang Wei, Chunlei Yue, Sergey V. Erohin, Yanglin Zhu, Abin Joshy, Jinyu Liu, Ana M. Sanchez, David Graf, Pavel B. Sorokin, Zinqiang Mao

Physics Faculty Publications and Presentations

In a topological semimetal with Dirac or Weyl points, the bulk-boundary correspondence principle predicts a gapless edge mode if the essential symmetry is still preserved at the surface. The detection of such topological surface state has been considered as the fingerprint prove for crystals with nontrivial topological bulk band. On the contrary, it has been proposed that even with symmetry broken at the surface, a new surface band can emerge in nonsymmorphic topological semimetals. The symmetry reduction at the surface lifts the bulk band degeneracies and produces an unusual “floating” surface band with trivial topology. Here, we first report quantum …

Remote Performance Modulation Of Ultrafiltration Membranes By Magnetically And Thermally Responsive Polymer Chains, Arijit Sengupta, Anh Vu, Xianghong Qian, Sumith R. Wickramasinghe

Chemical Engineering Faculty Publications and Presentations

Ultrafiltration membranes, that respond to an external magnetic field and local temperature have been developed. Surface-initiated activator-generated electron transfer (AGET) atom transfer radical polymerization (ATRP) has been used to graft poly(N-isopropylacrylamide) (PNIPAm) from the surface of 300 kDa regenerated cellulose membranes. The polymerization initiator was selectively attached to the entire membrane surface, only the outer membrane surface or only the inner pore surface. A superparamagnetic nanoparticle was attached to the end of the polymer chain. The DI water flux as well as the flux and rejection of bovine serum albumin were investigated in the absence and presence of a 20 …

Blood Driven Biopower Cells: Acquiring Energy From Reverse Electrodialysis Using Sodium Concentrations From The Flow Of Human Blood, Efecan Pakkaner, Chase Smith, Christina Trexler, Jamie Hestekin, Christa Hestekin

Chemical Engineering Faculty Publications and Presentations

With the growth of the healthcare industry, small scale power sources are needed to support advancements in medical implants, artificial organs, and sensors throughout the body. However, it remains a challenge to find safe, reliable, and stable power sources for these devices. In this study, a miniaturized reverse electrodialysis (RED) biopower cell design using physiological salinity concentration differences between renal bloodstreams is explored for its potential to be used as a power supply for implantable medical devices. Two small scale RED devices produced consistent power for up to three to ten days, depending on the device design. A two-fold decrease …

Development And Validation Of A Dft-Based Force Field For A Hydrated Homoalanine Polypeptide, Ying Yuan, Zhonghua Ma, Feng Wang

Chemistry & Biochemistry Faculty Publications and Presentations

A new force field has been created for simulating hydrated alanine polypeptides using the adaptive force matching (AFM) method. Only density functional theory calculations using the Perdew–Burke–Ernzerhof exchange–correlation functional and the D3 dispersion correction were used to fit the force field. The new force field, AFM2020, predicts NMR scalar coupling constants for hydrated homopolymeric alanine in better agreements with experimental data than several other models including those fitted directly to such data. For Ala₇, the new force field shows about 15% helical conformations, 20% conformation in the β basin, and 65% polyproline II. The predicted helical population of …

Effects Of Resin Chemistries On The Selective Removal Of Industrially Relevant Metal Ions Using Wafer-Enhanced Electrodeionization, Humeyra B. Ulusoy Erol, Christa N. Hestekin, Jamie A. Hestekin

Chemical Engineering Faculty Publications and Presentations

Wafer-enhanced electrodeionization (WE-EDI) is an electrically driven separations technology that occurs under the influence of an applied electric field and heavily depends on ion exchange resin chemistry. Unlike filtration processes, WE-EDI can be used to selectively remove ions even from high concentration systems. Because every excess ion transported increases the operating costs, the selective separation offered by WE-EDI can provide a more energy-efficient and cost-effective process, especially for highly concentrated salt solutions. This work reports the performance comparison of four commonly used cation exchange resins (Amberlite IR120 Na⁺, Amberlite IRP 69, Dowex MAC 3 H⁺, and …

Predicting The Hydration Free Energy Of Small Alkanes And Alcohols From Custom, Electronic Structure-Based Force Fields, T. Ryan Rogers

Graduate Theses and Dissertations

Mathematical theories reveal the fundamental physics involved in experimentalphenomena. Computer models of such theories are routinely used to corroborate or explain experiments and predict properties of chemical systems. Therefore, an important effort in computational chemistry is the development of more accurate and efficient chemical models. Current-generation models are only beginning to approach experimental-quality predictions of hydration free energies (HFEs).Using computations of quantum mechanical (QM) forces and classical simulations based on these forces, I investigate models to predict several properties of solutes and solutions. This dissertation is a collection of projects exemplifying methods used to gain insight into chemical systems.

Simulations …