Physical Sciences and Mathematics Commons^™

Agricultural Aerosols: The Impact Of Farming Activity On Ice Nucleating Particles, Joseph Robinson

The Journal of Purdue Undergraduate Research

Farming activities cause particles such as soil dust and plant material to be emitted into the air. Some of these aerosols can become ice nucleating particles (INPs), serving as seeds for ice and mixed-phase clouds. While there have been ground-based studies of these particles in the western Great Plains and a single air-based study in Indiana, there is a distinct lack of ground-based studies in the Midwest. In Indiana, over two-thirds of the state is farmland, with over 75% of land in Tippecanoe County used for agriculture. Despite farming being such an essential part of life in Indiana, the connection …

National Chemistry Week: From Irl To The Web, Ilayda Kelley, Daniela Mesa Sanchez

Purdue Journal of Service-Learning and International Engagement

National Chemistry Week, an outreach program initiated by the American Chemical Society (ACS), encourages scientists to bring their love of chemistry to their community. Celebrated nationwide, ACS invites businesses, schools, and individuals to organize and participate in community events to promote the value of chemistry in everyday life. The Purdue graduate student chapter of Iota Sigma Pi, a national honor society for women in chemistry, annually organizes one such celebration. On a normal year, this event is a large logistical undertaking in which 100+ volunteers go directly to over 70 local elementary school classrooms and perform a series of activities …

Temperature-Dependent Exciton Dynamics Of Superacid Treatment In Monolayers Of The Metal Dichalcogenide Mos2, Mingwei Zhou, Long Yuan, Jordan Snaider, Libai Huang

The Summer Undergraduate Research Fellowship (SURF) Symposium

To improve optoelectronic semiconductor materials, one of the most efficient research areas is the two-dimensional (2D) transition-metal dichalocogenides (TMDCs). It has been shown that organic nonoxidizing superacid bis(trifluoromethane)sulfonamide (TFSI) treatment of molybdenum disulfide (MoS₂) monolayer could uniformly enhance its photoluminescence by more than two orders of magnitude and also extend the lifetime of excitons. This could greatly improve the efficiency of the solar energy usage, but the mechanism behind it has not been fully understood. Extreme low temperatures (approximately 7K), which slow the surface exciton mobility, were applied to investigate the changes of treated MoS₂ monolayer surfaces. …

Applying Machine Learning To Computational Chemistry: Can We Predict Molecular Properties Faster Without Compromising Accuracy?, Hanjing Xu, Pradeep Gurunathan, Lyudmila Slipchenko

The Summer Undergraduate Research Fellowship (SURF) Symposium

Non-covalent interactions are crucial in analyzing protein folding and structure, function of DNA and RNA, structures of molecular crystals and aggregates, and many other processes in the fields of biology and chemistry. However, it is time and resource consuming to calculate such interactions using quantum-mechanical formulations. Our group has proposed previously that the effective fragment potential (EFP) method could serve as an efficient alternative to solve this problem. However, one of the computational bottlenecks of the EFP method is obtaining parameters for each molecule/fragment in the system, before the actual EFP simulations can be carried out. Here we present a …

Raman Spectroscopy Of Oxygen Evolution Catalysts And Psii Manganese Model Compounds, Sergei Shmakov, Daniel A. Hartzler, Alireza Karbakhsh Ravari, Yulia Pushkar

The Summer Undergraduate Research Fellowship (SURF) Symposium

Photosynthesis is the basis of life on earth, and oxygen evolution catalysts are key components of this complicated, yet not fully understood process. Photosystem II, a large membrane bound pigment-protein complex, is the key system that facilitates oxygenic photosynthesis via the oxygen evolving complex (a natural oxygen evolving catalyst). It is a key component in oxygen producing catalysts, which can be used in fields such as energy production and biomimetic catalysts. The oxygen evolution cycle, or Kok cycle going within it is still not studied completely. In this project, we were studying the vibrational (and structural) state of a Manganese …

Ultraviolet And Infrared Spectroscopy Of Synthetic Foldamers, Aib Homopeptides, And Solvated 1,2-Diphenylethane In The Gas Phase, Joseph R. Gord

Open Access Dissertations

The work presented here implements a supersonic jet expansion source to funnel the population of model peptides and solvated-bichromophore clusters into their low lying structural minima and to collisionally cool these minima to their respective zero-point vibrational levels. Single-conformation ultraviolet and infrared spectroscopy techniques are then used to probe these systems and investigate their electronic properties and uncover their intrinsic conformational preferences in the gas phase.

Model β/γ-peptides known as synthetic foldamers and aminoisobutyric acid (Aib) homopeptides incorporate structural constraints that are designed/known to impose particular structural motifs. Here the ability of a β/γ-dipeptide to replicate the backbone length of …

Advances In Raman Hyperspectral Compressive Detection Instrumentation For Fast Label Free Classification, Quantitation And Imaging, Bharat R. Makani

Open Access Dissertations

Multiple prototypes of hyperspectral compressive detection (CD) Raman spectrometers have previously been constructed in the Ben-Amotz lab and have proven to be useful for fast, label-free chemical identification, quantitation and imaging. The CD spectrometer consists of a volume holographic grating (VHG) that linearly disperses the Raman photons into its component wavelengths and all wavelengths are focused onto a digital micromirror devise (DMD). The DMD is an optical modulator that consists of an array of programmable 10μm mirrors that can reflect photons in either +12° or -12° to the incoming light. The DMD is tilted such that the +12° photons go …

Single-Conformation Spectroscopy Of Hydrogen Bonding Networks: Solvation, Synthetic Foldamers, And Neurodegenerative Diseases, Patrick S. Walsh

Open Access Dissertations

The hydrogen bond is one of the most important interactions in natural processes ranging from protein folding to chemical reactions. Two complementary methodologies are applied to understanding this important interaction: top-down and bottom-up. Top-down methods use large molecules, such as proteins, revealing secondary structure information. Bottom-up experiments are performed on small molecules, utilizing high-resolution spectroscopy to reveal underlying quantum mechanical effects. The complexity gap is formed between these two experimental regimes; between large and small molecules; between bulk and individual solvent molecules; between classical mechanics calculations and quantum chemical calculations. This dissertation will focus on the application of gas phase, …

Catalytic Conversion Of Chlorite To Chlorine Dioxide By Non-Heme Complexes, Manasa Ramachandra

Open Access Theses

The oxyanions of chlorine (ClOx-, x=1-4) have diverse applications and are used in a variety of commercial products. They are very stable in an aqueous environment leading to water contamination, thereby posing a concern for the environment and human health. At the microbial level, the enzyme perchlorate reductase catalyzes the reduction of perchlorate (ClO4-) to chlorite (ClO2-) and chlorite dismutase further reduces chlorite to innocuous chloride (Cl -) and dioxygen (O2). Two non-heme complexes [Fe III-TAML]- (Tetraamido Macrocyclic Ligand), and [Mn II-(BnTPEN)] in the presence of peracetic acid (PAA) have been studied as catalysts for chlorite dismutation under ambient conditions. …

Energy Transfer And Localization In Molecular Crystals, Mitchell A. Wood

Open Access Dissertations

With the aim of developing new technologies for the detection and defeat of energetic materials, this collection of work was focused on using simulations to characterize materials at extremes of temperature, pressure and radiation. Each branch of the work here is collected by which material response is potentially used as the detectable signal.

Where the chemical response is of interest, this work will explore the possibility of non-statistical chemical reactions in condensed-phase energetic materials via reactive molecular dynamics (MD) simulations. We characterize the response of three unique high energy density molecular crystals to different means of energy input: electric fields …

Studies Of Optical And Electronic Properties Of Nanoparticles For Solar Energy Conversion, Caitlin Kruse, Libai Huang

The Summer Undergraduate Research Fellowship (SURF) Symposium

The higher energy needs for today's technological society requires sustainable and renewable energy source, such as solar energy. This study focuses on using semiconducting quantum dots and fluorescent dyes as light absorbers for solar energy conversion devices such as solar cells. Quantum dots are small nanocrystals (usually 2-10 nm in diameter) with tunable absorbing properties. The smaller the dot, the shorter the wavelength being absorbed. Quantum dots are extremely efficient light absorbers and emitters. Fluorescent dyes have a high quantum yield. In order to examine the energy conversion, cadmium selenide (CdSe) quantum dots and Rhodamine 6G (R6G) dye were spin …

Mass Spectrometric Characterization Of Peptide Radical Ions And Implication For Radical Chemistry, Lei Tan

Open Access Dissertations

Gas-phase radical ion chemistry has attracted increasing research interest from the mass spectrometry (MS) society because it provides new capabilities in bio-analysis which often complements traditional MS methods developed from even-electron ions. Fundamental studies of biomolecule related radical species are essential to broadening the scope of radical chemistry and pushing the frontiers of its analytical applications. This dissertation mainly discusses the gas-phase chemistry of peptide sulfinyl radicals (-SO·), which has been rarely studied before. In order to establish an effective research approach, a method that can generate site-specific peptide sulfinyl radical ion has been developed. This method is based on …

A Bracketing Method For Proton Affinity Measurements Of Dehydro-And Didehydropyridines, Guannan Li

Open Access Theses

Proton affinity (PA) is a fundamental property that is related to the structure and reactivity of a molecule. Currently, very few experimental PA values are available for organic radicals and none for biradicals. Equilibrium methods cannot be used for these measurements. The traditional bracketing method is based on monitoring reactions of different reference bases with known proton affinities with the protonated analyte for the occurrence of exothermic proton transfer to determine the upper and lower limits of proton affinity. However, the energy deposited into the precursor ions upon CAD when forming protonated radicals may cause endothermic proton transfer reactions occur …

Quantification Of Molecular Aggregation Equilibria Using Spectroscopic Measurements And Random Mixing Modeling, Blake M. Rankin

Open Access Dissertations

Molecular aggregation equilibria, such as the binding of ligands to a central solute molecule, are prevalent throughout biological processes and energy storage devices. However, both the sign and magnitude of hydrophobic and ionic interactions remains a subject of theoretical debate, and has yet to be experimentally determined. Here, Raman vibrational spectroscopy is combined with multivariate curve resolution (Raman-MCR) to experimentally quantify both the number of hydrophobic contacts between alcohol molecules in water and the affinity of ions for molecular hydrophobic interfaces. Furthermore, a generalized theoretical model is developed based on random statistics in which it is assumed that the concentration …

Supersonic Jet Spectroscopy Of Synthetic Foldamers, Multichromophores, And Their Water Containing Clusters, Evan Gardner Buchanan

Open Access Dissertations

A central theme specific to this dissertation concerns the conformation-specific spectroscopy of flexible molecules in an effort to bridge the complexity gap. Generally, molecules in the complexity gap have several flexible coordinates yet conformational isomerization still occurs along a simple reaction coordinate on the potential energy surface. Molecules in this regime benefit greatly from experiments probing the potential energy surfaces and provide a means to develop and test new theories in an effort to explain more complex system. These measurements are possible through the utilization of a supersonic jet expansion to collisionally cool molecules into their vibrational zero-point levels, collapsing …

Determination Of Disulfide Bond Connecting Patterns Via Tandem Mass Spectrometry (Msn) And Biomolecular Ion/Radical Reactions, Kirt Lenroy Durand

Open Access Dissertations

Disulfide bond formation is one of the most common post translational modifications to occur in proteins and naturally occurring peptides. Disulfide bond formation plays a critical role in stabilizing their three-dimensional structure; therefore, it is very important to pinpoint the correct disulfide bond connecting pattern in order to fully understand the biological functions of these proteins and peptides. To fully characterize an analyte containing disulfide bonds, the sequence must first be known followed by the disulfide bond connecting pattern. This presents an analytical challenge as there are very few methodologies that can produce those essential pieces of information. The gold …

Excited States Of Chromophores And Vibronic Interactions, Benjamin T. Nebgen

Open Access Dissertations

The main focus of my Ph.D. work has been on building a vibronic coupling model for multichromophores and extending that model to more general systems. This Dissertation serves as both a summary of this work as well as a manual for the two vibronic coupling programs I have written. It is my hope that the instructions written here are complete enough for any who would like to replicate my work on vibronic coupling on other systems. ^ Additionally, I have also worked on a few purely computational projects not directly related to the vibronic coupling work. The status of these …

Characterization Of Water-Solid Interactions In Crystalline Ingredients And Development Of Deliquescence Measurement Recommendations, Matthew C. Allan

Open Access Theses

There are five major mechanisms of water-solid interactions. The primary focus of this thesis was on two of these: deliquescence and hydrate formation. Many crystalline food ingredients are deliquescent compounds (e.g., NaCl, sucrose, and ascorbic acid) and some are both deliquescent and hydrate formers (e.g., glucose, thiamine HCl, citric acid). Deliquescence is the first order phase transformation of a crystalline solid to a solution above a critical relative humidity (RH) known as the deliquescence point (RH0). A crystalline hydrate is a pseudo-polymorph in which water is incorporated into the crystal structure, altering the molecular formula and the physical properties.^ To …

Gas-Phase Ion/Ion Reactions Of Biomolecules: An Examination Of Carboxylate Reactivity And Arginine Based Non-Covalent Complexes, Nathan Zachary Barefoot

Open Access Theses

The advent of Electrospray Ionization with the ability to generate multiply charges ions has contributed significantly to the study of gas-phase ion/ion reactions. With the tools available in mass spectrometry it has been shown that these reactions are effective at transforming one type of gaseous ion into another through a series of reactions. This work examines some of these reactions and their application to field of proteomics specifically focusing on the amino acids of arginine and lysine. NHS reagents have been shown to react to both of these molecules with in the gas-phase under different conditions but have relies on …

Fundamental Studies On Copper Zeolites For Catalytic No X Abatement, Anuj Arun Verma

Open Access Dissertations

Stringent regulations in mobile NOx emissions have resulted in the development of Standard Selective Catalytic Reduction (SCR) as the dominant NOx abatement technology in lean burn diesel engines. Standard SCR is a reaction of nitric oxide (NO) with ammonia (NH₃), in the presence of oxygen (O ₂) to form nitrogen (N₂) and water (H₂O). Copper containing zeolites show commercially viable SCR performance. Cu-SSZ-13 (CHA framework), a member of this family, is a preferred catalyst for SCR applications because it shows exceptional hydrothermal stability in addition to commercially viable SCR performance. Our work focuses …

Investigation Of Isotope Effects Of Ozone As A Function Of Temperature, Daniel J. Mcmahon

Open Access Theses

Ozone is an important oxidizer in the atmosphere and plays a crucial role as a cleanser, removing various compounds such NOx and SOx. It also is intriguing to those that study stable isotopes as it has a unique signature found in no other oxygen containing molecule. Ozone is observed to fractionate mass independently, which means it does not follow the typical δ 17 O /δ18 O = 0.52 ratio expected for molecules enriched with 17 O and 18 O. The magnitude of ozone's mass independent enrichment has been studied in laboratory experiments and atmospheric observations but its explanation is still …

Reactivity Studies Of Tridhydropyridine Radical Cautions By Using Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry And Advancement Of Mass Spectrometric Analysis Of Asphaltenes And Degradation Products, Mohammad Sabir Aqueel

Open Access Dissertations

Aromatic organic molecules which have unpaired electrons play an important role in a variety of applications in the fields of organic synthesis, organic magnets, and biological activity of organic compounds. Several studies have been published on σ- type carbon-centered mono- and biradicals. Reactive intermediates with three formally unpaired electrons are known as triradicals. They can be defined as species with three electrons distributed in three degenerate or nearly degenerate orbitals, based on Salem's definition of biradicals from the electronic structure point of view. Very little is known about the reactivity of carbon-centered σ,σ,σ- triradicals due to the complexity of studying …

Investigating Intermolecular Interactions In Crystalline Aspirin Using Cdft, Nicholas Turner, Tonglei Li, Mingtao Zhang

The Summer Undergraduate Research Fellowship (SURF) Symposium

Drugs today are widely administered in their crystalline form, namely via tablets and capsules. The crystal structure of a drug molecule affects important drug qualities such as solubility, bioavailability, shelf life, and compaction properties. In order to form a basis for crystal structure prediction, it is necessary to first understand how intermolecular interactions cause molecules to pack in certain ways. Being able to predict and perhaps even control a drug molecule’s crystal structure will lead to the development of higher quality drugs that perform more consistently. Scientists and engineers do not fully understand the reasons for a molecule assuming a …

Investigation Of Major Intermolecular Interactions In 7,8-Dihydrobenzo(K)Phenanthridin-6(5h)-One Crystal Using Quantum Calculations And Crystallographic Visualization Programs, Zhiwei Liao, Tonglei Li, Mingtao Zhang

The Summer Undergraduate Research Fellowship (SURF) Symposium

Currently, tablets and capsules are the most common ways of delivering drugs. The active pharmaceutical ingredients and excipients used to make those tablets and capsules are in their crystalline form generally. However, a single molecule can form multiple different crystal structures because of different packing arrangements of the molecules. These different crystal structures have identical chemical composition but different properties such as solubility, density, stability, etc. This phenomenon is called polymorphism. Occurrence of polymorphism could be a disaster for both patients and pharmaceutical companies, as the drug could lose its efficacy due to changes in properties. Studying intermolecular interactions in …

Construction And Demonstration Of A Tandem Mass Spectrometer Based Instrument For Cold Ion Spectroscopy, James Gerhardt Redwine

Open Access Dissertations

A new instrument incorporating ion trap based tandem mass spectrometry and cold ion UV and UV-IR double resonance spectroscopy has been developed at Purdue University for the study of gas phase, biologically relevant ions. The instrument incorporates multiple quadrupole linear ion trap mass analyzers to prepare and isolate the precursor ions as well as to analyze the resultant photofragments. A 22-pole ion trap cooled to 5 K via a closed cycle helium cryostat is used to cool the ions for spectroscopic interrogation. Results show the vibrational and rotational temperature of a wide assortment of ions to be 12±2 K.

The …

Gas-Phase Covalent And Non-Covalent Ion/Ion Chemistry Of Biological Macromolecules, John Robert Stutzman

Open Access Dissertations

Gas-phase ion/ion chemistry involves the interaction of oppositely charged ions inside of the mass spectrometer. During this gas-phase chemistry, particle transfer (i.e., proton and electron) or synthesis can occur at rapid reaction rates. Particle transfer represents a mature area of ion/ion chemistry, while selective covalent modification represents a fairly new area of gas-phase chemistry. Gas-phase covalent chemistry is based on traditional solution phase organic chemistry.

The work demonstrated in this dissertation greatly involves gas-phase covalent and non-covalent Schiff base chemistry on peptide and protein ions. The reagent dianion, 4-formyl 1,3-benzene disulfonic acid, has been used to covalently modify unprotonated primary …

Spectroscopic Characterization Of The Water-Oxidation Intermediates In The Ru-Based Catalysts For Artificial Photosynthesis, Dooshaye Moonshiram

Open Access Dissertations

Utilization of sunlight requires solar capture, light-to-energy conversion and storage. One effective way to store energy is to convert it into chemical energy by fuel-forming reactions, such as water splitting into hydrogen and oxygen. Ruthenium complexes are among few molecular-defined catalysts capable of water splitting. Insight into the mechanism of their action will help to design future robust and economically feasible catalysts for light-to-energy conversion. Mechanistic insights about the design of such catalysts can be acquired through spectroscopic analysis of short-lived intermediates of catalytic water oxidation. Development of time-resolved approaches through stopped flow UV-Vis Spectroscopy to follow the catalysis of …

Specific Salt Effects On The Formation And Thermal Transitions Among Β-Lactoglobulin And Pectin Electrostatic Complexes, Stacey Ann Hirt

Open Access Theses

Factors of ion specificity and ionic strength (I~0-100) were studied in the electrostatic complex formation and protein particle formation by thermal treatment for a β-lactoglobulin and pectin system. ζ-potential showed β-lactoglobulin and pectin began to interact near pH 5.50 and interactions were strengthened with decrease in pH. Visible light turbidimetry and light scattering at 90° revealed a trend in critical pH transitions for electrostatic complex formation based on both the ionic strength and the anion of the salt species, while effects of the monovalent cation was insignificant. Critical pH values for complex formation and separation (pHc and pHΦ) decreased with …

Pickering Stabilization Of Oil-Water Interfaces By Heated B-Lactoglobulin/Pectin Particles, Laura Kathryn Zimmerer

Open Access Theses

The use of natural biopolymer particles as Pickering stabilizers for oil-in-water emulsions was investigated. B-lactoglobulin microgels and B-lactoglobulin/pectin complexes were created by heating appropriate biopolymer solutions at pH 5.8 and 4.75, respectively. Resultant particles exhibited spherical morphology with diameters of 100-300 nm and possessed significant negative surface charge. Particles were first homogenized with 1% corn oil at 0.05%, 0.1% or 0.25% (wt/ wt) particle concentrations. All emulsions appeared stable over seven days with only a thin, creamed ring forming after several hours. Corn oil emulsions were most stable with 0.25% heated complexes, with volume-weighted mean droplet diameter remaining around 480 …