Chemistry Commons^™

Detection Of 2,4,6-Trinitrotoluene Using A Colorimetric Gold Nanoparticle Air Cassette Filter, Andrea I. Ferrer Vega

Theses and Dissertations

Trinitrotoluene (TNT) is an explosive commonly used during military and terrorist activities. Current methods to identify this compound require sampling, transport and analysis at a forensic lab using analytical instrumentation. However, on-site detection is needed to assist efforts to prevent detonation. Gold nanoparticles have been used as sensors throughout the years due to their versatility and surface enhanced Raman scattering properties in the presence of an analyte and low limits of detection. By taking advantage of the Meisenheimer complex that TNT forms in the presence of amines, it is possible to determine its presence at picogram levels. Subsequently, adhering amine …

Information Architecture For A Chemical Modeling Knowledge Graph, Adam R. Luxon

Theses and Dissertations

Machine learning models for chemical property predictions are high dimension design challenges spanning multiple disciplines. Free and open-source software libraries have streamlined the model implementation process, but the design complexity remains. In order better navigate and understand the machine learning design space, model information needs to be organized and contextualized. In this work, instances of chemical property models and their associated parameters were stored in a Neo4j property graph database. Machine learning model instances were created with permutations of dataset, learning algorithm, molecular featurization, data scaling, data splitting, hyperparameters, and hyperparameter optimization techniques. The resulting graph contains over 83,000 nodes …

Computational Study Of Radical Cation Rearrangements, Mi'kayla D. Word

Theses and Dissertations

A radical cation is a molecule that has one unpaired electron that holds a positive charge. The unpaired electron within a radical cation causes the molecule to be reactive. The high reactivity of these species allows for radical cations to be commonly studied experimentally using mass spectrometry and other multi-mass imaging techniques. However, these methods often cannot resolve the reaction mechanisms for these fast reactions. Specifically, radical cation rearrangement mechanisms are particularly unresolved within experiments. For this reason, radical cation rearrangements are computationally investigated to explain complex reaction pathways for processes to understand reactions leading to the initiation of detonation …

Gas-Phase Studies Of Nucleophilic Substitution Reactions: Halogenating And Dehalogenating Aromatic Heterocycles, Leah L. Donham

Theses and Dissertations

Halogenated heterocycles are common in pharmaceutical and natural products and there is a need to develop a better understanding of processes used to synthesize them. Although the halogenation of simple aromatic molecules is well understood, the mechanisms behind the halogenation of aromatic heterocycles have been more problematic to elucidate because multiple pathways are possible. Recently, new, radical-based mechanisms have been proposed for heterocycle halogenation. In this study, we examine and test the viability of possible nucleophilic substitution, S_N2@X, mechanisms in the halogenation of anions derived from the deprotonation of aromatic heterocycles. All the experiments were done in a …

Development Of Photocatalysts Supported On Graphitic Carbon Nitride For The Degradation Of Organic Water Pollutants, Atanu Giri

Theses and Dissertations

Graphitic carbon nitride (g-C₃N₄) heterojunction composites with the semiconducting metal oxides, CeO₂, ZnO and TiO₂ are prepared in situ by co-calcination of the precursor materials or by a solvothermal method. The structural, morphological and the optical properties of the prepared materials are studied using various microscopy and spectroscopy techniques. The synthesized composite materials, CeO₂/g-C₃N₄, ZnO/g-C₃N₄ and TiO₂/g-C₃N₄ are more efficient in the photocatalytic degradation of the water pollutants indigo carmine (IC) and atrazine than the pure metal oxide, g-C …

Separation Of Transition And Heavy Metals Using Stationary Phase Gradients And Chelation Thin Layer Chromatography / Evaluation Of The Effectiveness Of Pogil-Pcl Workshops, Stacy L. Stegall

Theses and Dissertations

Gradient surfaces exhibit a variation in functionality along the length of the surface. One method for preparing gradients is controlled-rate infusion (CRI). In Part 1 of this work, CRI was used to prepare gradients for the purpose of separating transition and heavy metals. Initial work on this project was focused on controlling the retention of the metal ions by varying the number of amine groups, aminoalkoxysilane concentration, and the infusion time. The retention factors of four metal ions varied predictably with increasing number of amine groups, increasing aminoalkoxysilane concentration, and increasing infusion time, producing small but useful changes in the …

Versatile Synthesis Of Transition Metal Phosphides: Emerging Front-Runners For Affordable Catalysis, April C. Mattei

Theses and Dissertations

Transition metal phosphide materials have found themselves at the forefront of research revolving around energy applications. Due to the vast range of properties possessed by marginally different phase compositions, binary and ternary metal phosphides are utilized as catalysts, semi-conductors and magnetocaloric materials along with many others. These attractive properties, which are highly phase dependent, call for a versatile and cost effective synthesis route for various phosphide materials without sacrificing properties important at the nanoscale such as particle size and morphology.

The primary focus outlined in the work of this dissertation pertains to a versatile wet chemical synthesis capable of producing …

Gas-Phase Reactions And Mechanistic Details Of Gold, Silver, And Iridium Complexes, Christopher Swift

Theses and Dissertations

The ever increasing demand for more efficient and environmentally benign routes for synthesizing target compounds, has led to the use of organometallic catalysts. This demand has created the need to understand the mechanistic details that are at work in these organometallic catalytic cycles. Along with this, there is a demand for new organometallic catalysts that are tailored for specific transformations. This presents a myriad of challenges for organometallic chemists. Unfortunately, it is often difficult to gain an understanding of the reaction mechanisms at work when the intermediates are too short lived to be observed in the condensed phase. It is …

Electronic Principles Governing The Stability And Reactivity Of Ligated Metal And Silicon Encapsulated Transition Metal Clusters, Marissa B. Abreu

Theses and Dissertations

A thorough understanding of the underlying electronic principles guiding the stability and reactivity of clusters has direct implications for the identification of stable clusters for incorporation into clusters-assembled materials with tunable properties. This work explores the electronic principles governing the stability and reactivity of two types of clusters: ligated metal clusters and silicon encapsulated transition metal clusters. In the first case, the reactivity of iodine-protected aluminum clusters, Al₁₃I_x^- (x=0-4) and Al₁₄I_y^- (y-0-5), with the protic species methanol was studied. The symmetrical ground states of Al₁₃I_x^- showed no reactivity …

Light Mediated Drug Delivery Using Photocaged Molecules And Photoswitchable Peptides, Deboleena Mitra

Theses and Dissertations

There are many different types of targeted therapy for cancer treatment. The method of light mediated targeted therapy that we have developed uses photocaged molecules and photoswitchable peptides.

In photocaging, a biologically active molecule is made inactive by the attachment of a photocleavable blocking group. On exposure to UV radiation the photocleavable entity is removed and the biologically active molecule is released. Using this concept we have designed a prodrug that consists of a cell impermeable hydrophilic molecule attached to a photocaged doxorubicin. Upon irradiation with UV light the photosensitive group is removed and cytotoxic doxorubicin is released at the …

Investigations Into The Fluorescent Covalent Labeling Of Biomolecules Utilizing Rhodamine Dyes, Electrophilic Leaving Groups And Mrna Display., Susan D. Selaya

Theses and Dissertations

The discovery of a method by which proteins of interest can selectively be labeled with a probe of choice intracellularly is a longstanding goal in chemical biology research. Conventional labeling techniques have utilized large domain tags but despite the development of small labeling molecules there have been no short peptide sequences known to covalently label a small molecule without the aid of an enzymatic process or metal chelation. We aimed to find a sequence of nucleophilic peptides that reacted covalently and specifically with electrophilic small labeling molecules using mRNA display. Our goal was to show that an electrophilic small labeling …