Physical Sciences and Mathematics Commons^™

Crystal Structure And Hirshfeld Surface Analysis Of Cyclo-Tetrabromido-1k2br,3k2br-Tetrakis(Pi2-2-{[(Pyridin-2-Yl)Methyl]Amino}Ethane-1-Thiolato-Krystal Structure And Hirshfeld Surface Analysis Ofcyclo-Tetrabromido-1j2br,3j2br-Tetrakis(L2-2-{[(Pyridin-2-Yl)Methyl]Amino}Ethane-1-Thiolato-K3n,S:S)Tetramercury(Ii), I. D. Thomas, K. R. Kocher, J. A. Viehweg, Robert Pike, Deborah Bebout

Arts & Sciences Articles

The macrometallacyclic title compound, [Hg4Br4(C8H11N2S)4] or [((HgL2)(HgBr2))2] (1) where HL = 2-{[(pyridin-2-yl)meth­yl]amino}­ethane-1-thiol, was prepared and structurally characterized. The Hg2+ complex crystallizes in the P21/c space group. The centrosymmetric Hg4S4 metallacycle is constructed from metal ions with alternating distorted tetra­hedral Br2S2 and distorted seesaw N2S2 primary coordination environments with pendant pyridyl groups. The backfolded extended chair metallacycle conformation suggests inter­actions between each of the bis-chelated mercury atoms and Br atoms lying above and below the central Hg2S4 plane. Supra­molecular inter­actions in 1 include a fourfold aryl embrace and potential hydrogen bonds with bromine as the acceptor. Hirshfeld surface analysis indicates that …

Modeling Titan’S Atmosphere Through Investigation Of Low-Temperature Kinetics And Branching Of N (^2d) And C2h4 Towards Cyclic-2h-Azirine (C-Ch2nch), Ruby Neisser, Sophia Haile

Undergraduate Research Awards

Excerpt from paper: "Understanding the rate coefficients and branching of reactions in extraterrestrial atmospheres is of vital importance because it allows us to build a more complete picture of the overall chemical makeup and photochemical behavior in these alien environments. Gaining insight into these exotic reactions is crucial not only for understanding extraterrestrial environments, but also for providing a better understanding of reactions on Earth. The atmosphere of Titan, Saturn’s largest moon, is notably rich in nitrogen compounds and chemical reactions, which makes it an immensely important environment to study.1 Titan’s reducing atmosphere resembles that of early Earth (the first …

The Roles Of Tidal Marshes In The Estuarine Biochemical Processes: A Numerical Modeling Study, Xun Cai

VIMS Articles

Observations suggest that the existence of tidal marsh can alter the oxygen and nutrient dynamics in adjacent water bodies, but assessing the impacts of large tidal marshes on an estuary is challenging. In this study, we use a modeling approach to investigate the roles of tidal marshes on the estuarine biochemical processes. The marsh model, which simulates the ecological functions of marshes at seasonal and annual time-scales, is embedded inside an unstructured-grid three-dimensional hydrodynamic and eutrophication model (SCHISM-ICM). This modeling system simulates the growth and metabolism of the tidal marshes and links biological processes to nutrient dynamics in the water …

Gas-Phase Proton Affinities Of Proline- And Pipecolic Acid-Containing Dipeptides, Trinh Ton

Dissertations, Theses, and Masters Projects

Mass spectrometry (MS) is one of the most used techniques in proteomics because it allows for both high-throughput and quantitative analyses. Bottom-up MS-based proteomics involves breaking down proteins into smaller chains of amino acids called peptides, ionizing and fragmenting the peptides, and identifying the fragments using sequencing databases. These databases depend on the random fragmentation at the backbone peptide bond of the peptides, as predicted by the mobile proton model. Research has shown that peptides containing proline or pipecolic acid have selective fragmentations that could lead to incorrect identification in the sequencing algorithms. These selective cleavages are called “the proline …

Characterizing Molecular Environments In Acrylic Paint Via Single-Sided Nmr, Lyndi Kiple

Dissertations, Theses, and Masters Projects

Acrylic paint is a modern artistic material made of colored pigment and polymeric binder. Acrylic binder requires fundamental study at the molecular level to understand its physical properties for purposes of art conservation and general polymer chemistry. The research presented in this thesis uses single-sided nuclear magnetic resonance (NMR) as a non-invasive and non-destructive way to measure relaxation and self-diffusion, which provide insight to molecular mobility and physical properties of proton-containing samples. Specifically, this study relies on T2 relaxation to gain insight to regions within acrylic paint with different molecular mobilities. In both dry and wet paint, relaxometry data revealed …

Chemical Analysis Of Organic Compounds In Dew Water, Monica Dibley

Undergraduate Honors Theses

Water films on outdoor surfaces, such as dew, can act as a reservoir for organic molecules deposited from the atmosphere and they present a potential reactive medium for chemical transformations. To better understand the flux of volatile organic compounds from evaporating films, the composition and reactivity of the complex mixture of dissolved organic material (DOM) found in these films need to be characterized. Previous studies have measured the salts and the small organic molecules in dew collected on clean Teflon surfaces or condensers. Here, we expand on this by probing the organic chemicals found on natural outdoor surfaces covered in …

Differential Protein Expression In Bacteriophages Crimd And Larva, Daria Moody

Undergraduate Honors Theses

Proteomics studies allow us to answer questions about differential protein expression across different systems. Mass spectrometry is a powerful tool in these studies due to the distinct masses of the amino acids that compose proteins. In our experiment, we used a bottom-up approach and focused on two bacteriophages found on the William & Mary campus, CrimD and Larva. The infection of Mycobacterium smegmatis, a nonpathogenic model for tuberculosis, by these two bacteriophages was frozen at five different timepoints, and our goal was to compare the differential protein expression across the samples in order to gain a greater understanding of …

Gas-Phase Proton Affinities For Twenty Of The Proline-Containing Dipeptides, Henry Cardwell

Undergraduate Honors Theses

Peptide fragmentation plays a crucial role in the analysis of proteins through mass spectrometry-based proteomics. Most proteomics experiments take place in the low-energy regime and are governed by the mobile proton model which predicts random cleavages along the peptide backbone; however, there sometimes arise circumstances where the mobile proton model fails causing sequencing algorithms to misidentify peptides. One such example is noted in the “proline effect” wherein proline-containing peptides preferentially fragment N-terminal. While it has been established that the “proline effect” is due to the rigidity and basicity of the proline N-terminus, a further understanding of the factors influencing the …

Honey As A Biomonitor For Air Pollutant Deposition In The Eastern United States Using Ion Chromatography And Scanning Electron Microscopy, Cole Cochran

Undergraduate Honors Theses

Anthropogenic activities generate metal, acid, and particulate air pollutants which negatively impact human and ecological health. In the United States, power plant, industrial, and vehicle emissions are leading causes of air pollution, however, the measurement of air pollution at high-resolution spatial regimes remains a challenge. Honey has emerged as a powerful biomonitoring tool to effectively quantify contaminants without the need for a large array of monitoring instruments. I hypothesized that honey could be used to effectively measure and map modern air pollutant spatiotemporal relationships over the Eastern U.S. Using ion chromatography with sulfate as an indicator for air pollution and …

Geologic Controls On 137cs Cycling By Terrestrial Vegetation In The Eastern U.S., Kathleen Chellman

Undergraduate Honors Theses

¹³⁷Cs is a radioactive trace metal (T_1/2 = 30 y) that was dispersed globally by nuclear weapons testing in the 1950s-1960s. Prevailing winds and precipitation systems caused some areas far from the test sites to receive significant fallout, which is still easily measured in soils, sediments and even some vegetation in the Eastern United States. Recent work near Chernobyl and Fukushima indicates that trace levels of ¹³⁷Cs can harm insects, pollination services, and other ecological functions. In areas with low soil potassium, ¹³⁷Cs is cycled in vegetation; however, soil potassium alone doesn't consistently predict the ^{137 …}

Exploring The Photophysics Of Brown Carbon Chromophores Using Laser-Based Spectroscopy And Computational Methods, Megan Elizabeth Alfieri

Dissertations, Theses, and Masters Projects

Atmospheric aerosols are made up of suspended liquids and solids in the atmosphere. These aerosols play a very important role in the solar energy exchange in Earth’s atmosphere as well have dramatic impact on human health. Different aerosols have different effects on the atmosphere depending on the physical properties of the aerosols.

The purpose of this research project is to understand how the structure of molecular chromophores impacts the solar absorption properties of aerosols. We propose a series of laboratory studies to investigate the outcomes from solar absorption of brown carbon chromophores: 1-phenylpyrrole, 2-phenyl-1-H-pyrrole, 2-phenylimadazole, as well as water complexes. …

Comparison Of Electrochemical Polishing Treatments Between Phosphoric Acid And A Deep Eutectic Solvent For High-Purity Copper, Tarek M. Abdel-Fattah, Jon Derek Loftis

VIMS Articles

This study investigated and compared the acid-free electropolishing of copper with the state-of-the-art acidic electropolishing process. The acid-free medium used in this study is based on a deep eutectic solvent comprised of 2:1 ethylene glycol and choline chloride. The electrochemical study included voltammetry and chronoamperometry tests during the electropolishing process. The characterization techniques used were atomic force microscopy (AFM) and digital microscopy, and surface morphology comparisons summarized the electropolishing efficiency of phosphoric acid and acid-free deep eutectic solvent treatments for high-purity copper. Electropolishing copper with a deep eutectic solvent resulted in a mirror finish and a post-treatment surface that was …

Developing Iron Complexes For Electrocatalytic Hydrogen Generation, Benjamin Travis

Undergraduate Honors Theses

Artificial photosynthesis systems convert solar energy into chemical fuels such as hydrogen gas. Photocatalytic hydrogen generation systems have previously been developed, but reliance on expensive metal catalysts limits the viability of these systems. In order for artificial photosynthesis to be used as a large-scale clean energy solution, it is crucial to discover more active and cost-efficient catalysts.

To this end, several novel iron polypyridyl complexes were synthesized using relatively inexpensive reactants. Electrochemical testing revealed that these complexes are active electrocatalysts for the reduction of protons to generate hydrogen gas. Furthermore, a naphthalene-terminated iron polypyridyl complex was found to be an …

Polyaromatic-Terminated Iron Polypyridyl Complexes For The Functionalization Of Carbon Surfaces And Electrocatalytic Hydrogen Generation, Caroline Marie Margonis

Dissertations, Theses, and Masters Projects

Artificial Photosynthesis (AP) focuses on developing methods for the conversion of solar energy into chemical fuel in the form of H2 and O2. Heterogeneous photocatalytic systems incorporating carbon nanotubes (CNTs) have shown much promise but are currently limited and expensive due to their reliance on noble metals. To that end, this work focuses on the development and synthesis of cheaper naphthalene- and pyrene-terminated iron polypyridyl complexes for use in the simultaneous functionalization of carbon surfaces, electrocatalytic proton reduction, and eventual incorporation in photocatalytic systems. Cyclic voltammetry was used to characterize the adsorption behavior of each complex on the surface of …

Evaluating Epoxy Cure And Adhesion Strength Through Single-Sided Nmr Measurements Of Molecular Mobility, Kayla Copeman

Dissertations, Theses, and Masters Projects

Commonly used in aerospace, automotive, marine, defense, electronic, and manufacturing industries, epoxy adhesives offer advantages over mechanical joints by providing stronger and/or more flexible bonds, more uniform stress distribution, low shrinkage, and lightweight connections between materials. Determination of curing kinetics and properties of interfaces between epoxy and inorganic substrates provides insight that is useful for quality control and defect detection for such applications. Single-sided NMR provides a nondestructive and inexpensive method for probing epoxy materials and spatially resolving the decay of spin-lattice and spin-spin relaxation times (T1 and T2) during and after curing of epoxy resins onto substrates. In this …

Investigating Charge Transfer Complexes In Brown Carbon Aerosols, Brianna Peterson

Undergraduate Honors Theses

Aerosols are suspensions of particles in the air, commonly seen as dust or fog in the atmosphere. Brown carbon is a particular classification of carbonaceous atmospheric aerosol that increases in absorption from the visible to ultraviolet region, making it important for radiative forcing models. Elucidating the structures of brown carbon chromophores has been difficult as brown carbon is a broad category and the chromophore type can change depending on emission source, temperature, humidity, and season. Twisted intramolecular charge transfer (TICT) molecules have been identified as potential brown carbon chromophores. TICT molecules are those that allow charge transfer to occur between …

Molecular Cluster Fragment Machine Learning Training Techniques To Predict Energetics Of Brown Carbon Aerosol Clusters, Emily E. Chappie

Undergraduate Honors Theses

Density functional theory (DFT) has become a popular method for computational work involving larger molecular systems as it provides accuracy that rivals ab initio methods while lowering computational cost. Nevertheless, computational cost is still high for systems greater than ten atoms in size, preventing their application in modeling realistic atmospheric systems at the molecular level. Machine learning techniques, however, show promise as cost-effective tools in predicting chemical properties when properly trained. In the interest of furthering chemical machine learning in the field of atmospheric science, I have developed a training method for predicting cluster energetics of newly characterized nitrogen-based brown …

Proteomic Analysis Of Mycobacteriophage Crimd, William Moeller

Undergraduate Honors Theses

Bacteriophages represent a large portion of the biomatter on our planet, and many of them have yet to be fully characterized. Here we discuss the proteomic analysis of a particular Bacteriophage, Mycobacteriophage CrimD. This phage was discovered on the Campus of William & Mary and has had its genome characterized. We took the next logical step of proteomic analysis.

In our analyses we made use high pressure liquid chromatography paired with linear ion trap mass spectrometry to analyze the proteome of CrimD at specific time points after the infection of its host, Mycobacterium smegmatis. Additionally, we used nanospray ionization with …

Analytical Chemistry Of Plastic Debris: Sampling, Methods, And Instrumentation, Robert C. Hale, Meredith E. Seeley, Ashley E. King, Lehuan H. Yu

VIMS Books and Book Chapters

Approaches for the collection and analysis of plastic debris in environmental matrices are rapidly evolving. Such plastics span a continuum of sizes, encompassing large (macro-), medium (micro-, typically defined as particles between 1 μm and 5 mm), and smaller (nano-) plastics. All are of environmental relevance. Particle sizes are dynamic. Large plastics may fragment over time, while smaller particles may agglomerate in the field. The diverse morphologies (fragment, fiber, sphere) and chemical compositions of microplastics further complicate their characterization. Fibers are of growing interest and present particular analytical challenges due to their narrow profiles. Compositional classes of emerging concern include …

Investigating The Electron Transfer Dynamics Of Eosin Y Photosensitizers Using Single Molecule Spectroscopy, Kelly Margaret Kopera

Dissertations, Theses, and Masters Projects

Growing global energy demands have necessitated the search for alternative sources of renewable fuels. Dye-sensitized photocatalysis (DSP) is a promising low cost, sustainable method that directly converts solar energy to readily usable forms of energy such as hydrogen fuel. While DSP is a promising technology, its efficiency is limited by back electron transfer and kinetic redundancy. In order to fully understand these processes, single-molecule spectroscopy (SMS) is used to probe the electron transfer (ET) dynamics of photosensitizers. In particular, eosin Y (EY), a brominated fluorescein derivative that undergoes intersystem crossing prior to injection, is investigated using SMS. In this approach, …

Electronic Effects In A Cyclization Cascade To Diversified, Polycyclic, Helical Molecules, Caleb Lee Burns

Dissertations, Theses, and Masters Projects

Heterocyclic aromatic compounds and their derivatives are ubiquitous in the pharmaceutical and photochemical industries. Naphthochromene derivatives in particular have garnered great interest for their photochemical properties and biological activity. Herein, the effects of electronics on a three-step cascade reaction between aryl substituted 2-(4-aryl-3-((triethylsilyl)oxy)but-1-yn-1-yl)phenols and structurally diverse aldehydes is explored. The cascade is initiated by alkynyl substrate addition to BF3-activated aldehydes. The aldehyde undergoes condensation with the substrate phenol moiety forming an oxocarbenium ion, this initiates the alkynyl-Prins cyclization forming a new six-membered heterocyclic ring with an internal alkenyl cation. The cation is subsequently trapped by a Friedel-Crafts (FC) reaction by …

Mass Spectrometry-Based Proteomics: An Experimental Study Of Differential Bacteriophage Protein Expression And A Computational Investigation Of The Effects Of Proton Affinity On The Fragmentation Of Proline-Containing Dipeptides, Hao Qian

Dissertations, Theses, and Masters Projects

After decades with the development of genetics study, the next step of molecular biology had already been moved onto proteomics. The proteomics study provides an innovative aspect to deduct the relationship between genes and proteins. Meanwhile, research that focuses on the mechanism of protein interactions and intrinsic properties of proteins never cease. The mass spectrometry-based proteomics approaches have already shown their versatile and superior in studying the whole proteome of complicated organisms. This study focuses on practicing bottom-up method in determining and characterizing the expressed proteome of two mycobacteriophages, CrimD and Larva. The expressed proteins of CrimD and Larva in …

Indoor Chemistry: Development Of An Indoor Surface Extractor, Hannah Rose Przelomski

Dissertations, Theses, and Masters Projects

People spend around 90% of their time indoors. This means that indoor air can have an impact on human health. One of the main factors that makes indoor air differ from outdoor air is indoor areas have a higher surface area to volume ratio than outdoor areas. Surfaces give aerosol particles a place to deposit where they can stick or react. Some of this material can leave the surface and reenter the air. Being able to analyze the material on different indoor surfaces will help further the understanding of indoor surfaces’ impact on indoor air. A surface extractor was developed …

Comparison Of Electropolishing Of Aluminum In A Deep Eutectic Medium And Acidic Electrolyte, Tarek M. Abdel-Fattah, Jon Derek Loftis

VIMS Articles

Research advances in electropolishing, with respect to the field of metalworking, have afforded significant improvements in the surface roughness and conductivity properties of aluminum polished surfaces in ways that machine polishing and simple chemical polishing cannot. The effects of a deep eutectic medium as an acid-free electrolyte were tested to determine the potential energy thresholds during electropolishing treatments based upon temperature, experiment duration, current, and voltage. Using voltammetry and chronoamperometry tests during electropolishing to supplement representative recordings via atomic force microscopy (AFM), surface morphology comparisons were performed regarding the electropolishing efficiency of phosphoric acid and acid-free ionic liquid treatments for …

Isotopes In The Estuary: Conception And Application Of Stable And Radioactive Carbon, Derek Detweiler

Reports

Grades: 9-12 Subjects: Chemistry | Environmental Science | Oceanography

In this interactive estuary-focused activity, students will examine stable and radioactive isotope data which provide information about the source and age of environmental samples such as plant and soil matter. Students will calculate average isotope ratios from five reference land types (forest, wetland, agriculture, industry, aquatic) and an unknown site within an estuary. Students will graph their calculated ratios and determine the land type that most impacts their estuary based on reference-to-unknown comparisons.

Copper(I) Iodide-Based Chemical Sensor Materials In Gaseous And Aqueous Media, Matthew D. Kessler

Dissertations, Theses, and Masters Projects

Chemical detection is an area of great importance in the shift to more green approaches to industry. Some of the chemical species produced by assorted industries can be harmful, long lived, and challenging to differentiate. Copper(I) iodide (CuI) is a material that readily forms complexes of multiple colors, both under visible and ultraviolet (UV) light. The process of CuI reacting with dimethyl sulfide vapor to produce a color change (vapochromism) has been analyzed to propose mechanistic information about the process. Using the information obtained, a series of potential sensor materials were developed with CuI as the base. The complexes were …

Structural And Dosage Dependence Of Electron Transfer From Conjugated Polymer Nanoparticles, Jaclyn Rebstock

Dissertations, Theses, and Masters Projects

Conjugated polymer nanoparticles (CPNs or Pdots) have become popular fluorophores for a variety of fluorescence imaging applications due to their brightness, photostability, and aqueous compatibility. Recently, their ability to generate charged species has begun to be exploited in applications ranging from photocatalysis to photovoltaic cells. Upon excitation, CPNs can eject an electron via photoinduced electron transfer (PET) to oxygen or other acceptors. The competition between fluorescence and PET is undesirable in redox-based applications. However, CPNs are capable of the simultaneous generation and detection of reactive oxygen species, expanding their use in photodynamic therapy (PDT). We seek to determine the dependence …

Unravelling The Aggregation Of Eosin Y Photosensitisers For Solar Energy Conversion, Huw Richards

Dissertations, Theses, and Masters Projects

The impact of molecular aggregation on the photophysics of eosin y adsorbed to TiO₂ was investigated using diffuse reflectance spectroscopy, steady-state fluorescence and time correlated single photon counting (TCSPC) measurements. Deconvolution of the diffuse reflectance spectra of eosin y on TiO₂ revealed the formation of H-aggregates, with the extent of H-aggregation increasing with increasing dye-loading concentration. The resultant bathochromic shift from the monomer diffuse reflectance maximum is due to Charge-transfermediated H-aggregates The fluorescent maximum also shifts with increasing dye loading concentration starting at 537.5 nm at a dye loading concentration of 7.5x10^-7 M and shifting to 585 …

Complex Mixtures: Identifying And Characterizing Secondary Organic Aerosols, Emma Quinn Walhout

Dissertations, Theses, and Masters Projects

Complex organic mixtures in the environment can contain hundreds to thousands of different organic molecules, and their composition and reactivity can have important environmental implications. In addition to gases, the atmosphere is made of a variety of small liquids and solids called aerosols. These aerosols have large impacts on human health, climate, and atmospheric chemical reactions. Here, secondary organic aerosol (SOA) from the ozonolysis of α-pinene is characterized. The atmospheric lifetime of SOA is very uncertain, but recent laboratory and modeling studies have demonstrated that photolysis is potentially an important process for organic mass loss from aerosol particles.1-5 Photolysis modifies …

Investigating The Molecular Choreography Of Atmospherically Relevant Molecules: A Dynamics Study, Kenneth Jacob Blackshaw

Dissertations, Theses, and Masters Projects

Investigating and understanding the chemistry of the atmosphere has historically been an important research topic. This importance has only strengthened in the recent decades as technological advancements have drastically increased anthropogenic emissions of hydrocarbons and nitroaromatic compounds. Indeed, we are in an era of unprecedented change of the chemical composition of the troposphere and never before has an in-depth understanding of atmospheric chemical properties been more sought-after. This study seeks to fill that need by probing the molecular dynamics of atmospherically relevant molecules through the use of velocity map imaging (VMI). In particular, we utilize VMI to study the photolysis …