Physical Sciences and Mathematics Commons^™

Uv-Light-Tunable P-/N-Type Chemiresistive Gas Sensors Based On Quasi-1d Tis3 Nanoribbons: Detection Of Isopropanol At Ppm Concentrations, Victor V. Sysoev, Andrey V. Lashkov, Alexey Lipatov, Ilya A. Plugin, Michael Bruns, Dirk Fuchs, Alexey S. Varezhnikov, Mustahsin Adib, Martin Sommer, Alexander Sinitskii

Chemistry Department: Faculty Publications

The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS₃) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS₃ nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors. These sensors were exposed to isopropanol as a model analyte, which was mixed with air at low concentrations of 1–100 ppm that are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit. The tests were performed at room temperature (RT), as …

Development Of An Automated Platform For Sensing And Differentiating Vapor-Phase Btex Constituents, Jonathan Samuelson

USF Tampa Graduate Theses and Dissertations

Light aromatic hydrocarbons are an inevitable byproduct of fossil fuel extraction, refinement, distribution, and use. The four lightest and most prevalent of these are benzene, toluene, ethylbenzene, and xylene, which are known collectively as BTEX. In spite of their chemical similarity these species have markedly different effects on human health and substantially different concentrations are permitted by OSHA in workplaces and by the EPA in ambient air and groundwater. Real-time detection, identification, and quantification of these species is therefore of great importance wherever they see industrial use.This work represents the continuation and advancement of a line of research in which …

Mixed Quantum/Classical Theory For Collisional Quenching Of Pahs In The Interstellar Media, Bikramaditya Mandal, Carolin Joy, Alexander Semenov, Dmitri Babikov

Chemistry Faculty Research and Publications

A computationally affordable methodology is developed to predict cross sections and rate coefficients for collisional quenching and excitation of large molecules in space, such as PAHs. Mixed quantum/classical theory of inelastic scattering (MQCT) is applied, in which quantum state-to-state transitions between the internal states of the molecule are described using a time-dependent Schrodinger equation, while the scattering of collision partners is described classically using mean-field trajectories. To boost the numerical performance even further, a decoupling scheme for the equations of motion and a Monte Carlo sampling of the initial conditions are implemented. The method is applied to compute cross sections …

Development Of Standard Operating Procedure With Modified Method To Quantify Benzene And Other Volatile Organic Compounds In Air Samples Using Gas Chromatography, Heather Hall

Electronic Theses and Dissertations

Stephen F. Austin State University (SFASU) Department of Environmental Science has recently invested in a gas chromatograph which can be used to analyze air samples for volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylenes (BTEX). The goal of this project was to develop a standard operating procedure (SOP) and modify the current method for the detection of VOCs associated with oil and gas drilling activity to accommodate the equipment and capabilities of SFASU Environmental Assessment Lab. This study aims to provide the framework for future research in air quality monitoring in the Eagle Ford Shale area. An …

Gas Phase Reactions Of Cyclopentadiene With Ch And Oh Radicals, Kacee Lynn Caster

Graduate Theses, Dissertations, and Problem Reports

The formation of polycyclic aromatic hydrocarbons (PAHs) and carbon-based nanoparticles in combustion environments is driven by the pyrolysis and oxidation of abundant fuel molecules. The subsequent growth of these pyrolytic byproducts is then propagated by reactions with small free radical species like OH, CH, O atoms, and C₂H. Cyclopentadiene (C₅H₆) is a significant five-member combustion intermediate that has been detected in many high temperature reactions, such as in the pyrolysis of jet fuels like JP-10. Experimental and theoretical investigations in the reactions of cyclopentadiene with these small free radical species are necessary towards understanding …

Synthesis Of Graphene By Liquid Precursors At Lower Temperatures, Clayton Hansen

Physics Capstone Projects

Benzene, toluene, and xylene can be liquid precursors for graphene and carbon nanotube synthesis. However, the growth mechanisms can have greater variances for different carbon allotropes. In the case of graphene, Cu can be the catalyst for dehydrogenation and provides a weakly-coupled substrate for 2-dimensional graphene nucleation and growth. In the case of carbon nanotubes, Fe nanoparticles are essential to catalyze the C-C bonds breaking and dissolve carbon before the precipitation of a graphene cap over the catalyst particle where a tube forms. Controlling the precursor feed rate is crucial for a successful synthesis. In this research, we developed a …

Investigations Of Electronic Cigarette Chemistry: 1. Formation Pathways For Degradation Products Using Isotopic Labeling; And 2. Gas/Particle Partitioning Of Nicotine And Flavor Related Chemicals In Electronic Cigarette Fluids, Kilsun Kim

Dissertations and Theses

Use of electronic cigarettes (e-cigarettes) is rapidly growing around the world. E-cigarettes are commonly used as an alternative nicotine delivery system, and have been advocated as generating lower levels of harmful chemicals compared to conventional cigarettes. Cigarette smoke-like aerosols are generated when e-cigarettes heat e-liquids. The main components of e-cigarette liquids are propylene glycol (PG) and glycerol (GL) in a varying ratio, plus nicotine and flavor chemicals. Both PG and GL are considered safe to ingest in foods and beverages, but the toxicity of these chemicals in aerosols is unknown. Current studies of e-cigarettes have mainly focused on dehydration and …

Oxidation Of Substituted Catechols At The Air-Water Interface: Production Of Carboxylic Acids, Quinones, And Polyphenols, Elizabeth A. Pillar, Marcelo I. Guzman

Chemistry Faculty Publications

Anthropogenic activities contribute benzene, toluene, and anisole to the environment, which in the atmosphere are converted into the respective phenols, cresols, and methoxyphenols by fast gas-phase reaction with hydroxyl radicals (HO(•)). Further processing of the latter species by HO(•) decreases their vapor pressure as a second hydroxyl group is incorporated to accelerate their oxidative aging at interfaces and in aqueous particles. This work shows how catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol (all proxies for oxygenated aromatics derived from benzene, toluene, and anisole) react at the air-water interface with increasing O3(g) during τc ≈ 1 μs contact time and contrasts their …

Benzene Formation In Electronic Cigarettes, James F. Pankow, Kilsun Kim, Kevin J. Mcwhirter, Wentai Luo, Jorge O. Escobedo, Robert M. Strongin, Anna K. Duell, David H. Peyton

Chemistry Faculty Publications and Presentations

The heating of the fluids used in electronic cigarettes (“e-cigarettes”) used to create “vaping” aerosols is capable of causing a wide range of degradation reaction products. We investigated formation of benzene (an important human carcinogen) from e-cigarette fluids containing propylene glycol (PG), glycerol (GL), benzoic acid, the flavor chemical benzaldehyde, and nicotine.

Contributions Of Wood Smoke And Vehicle Emissions To Ambient Concentrations Of Volatile Organic Compounds And Particulate Matter During The Yakima Wintertime Nitrate Study, Graham Vanderschelden, Benjamin De Foy, Courtney Herring, Susan D. Kaspari, Tim Vanreken, Bertram Jobson

All Faculty Scholarship for the College of the Sciences

A multiple linear regression (MLR) chemical mass balance model was applied to data collected during an air quality field experiment in Yakima, WA, during January 2013 to determine the relative contribution of residential wood combustion (RWC) and vehicle emissions to ambient pollutant levels. Acetonitrile was used as a chemical tracer for wood burning and nitrogen oxides (NOx) as a chemical tracer for mobile sources. RWC was found to be a substantial source of gas phase air toxics in wintertime. The MLR model found RWC primarily responsible for emissions of formaldehyde (73%), acetaldehyde (69%), and black carbon (55%) and mobile sources …

Isotopic Abundance Analysis Of Biofield Treated Benzene, Toluene And P-Xylene Using Gas Chromatography-Mass Spectrometry (Gc-Ms), Mahendra Trivedi, Alice Branton, Dahryn Trivedi, Gopal Nayak, Gunin Saikia, Snehasis Jana

Mahendra Kumar Trivedi

Theoretical Examination Of Solvent And R Group Dependence In Gold Thiolate Nanoparticle Synthesis, Suzanne M. Neidhart, Brian M. Barngrover, Christine M. Aikens

Faculty Publications

The growth of gold thiolate nanoparticles can be affected by the solvent and the R group on the ligand. In this work, the difference between methanol and benzene solvents as well as the effect of alkyl (methyl) and aromatic (phenyl) thiols on the reaction energies and barrier heights is investigated theoretically. Density functional theory (DFT) calculations using the BP86 functional and a triple ζ polarized basis set show that the overall reaction favors methylthiol over phenylthiol with reaction energies of −0.54 and −0.39 eV in methanol, respectively. At the same level of theory, the methanol solvent is favored over the …

Prediction Of Nonradical Au (0)-Containing Precursors In Nanoparticle Growth Processes, Brian M. Barngrover, Timothy J. Manges, Christine M. Aikens

Faculty Publications

This density functional theory (DFT) investigation examines the formation of nonradical Au(0) species from the reduction of Au(I) species. The Au(I) complexes of interest are AuCl₂^–, AuBr₂^–, AuI₂^–, AuClPH₃, and AuCl(H)SCH₃⁽⁻⁾, which are precursors for gold nanoparticle and cluster formation. Reaction of two of the Au(I) species with a hydride results in ejection of two of the ligands and formation of Au₂ with two ligands still attached. AuX₂^– (where X = Cl, Br, or I) reactions eject two halides and form Au_{2 …}

A Theoretical And Experimental Investigation Of The Physical And Chemical Properties Of Solid Nanoscale Interfaces, Jeronimo Matos

Electronic Theses and Dissertations

With the emerging interest in nanoscale materials, the fascinating field of surface science is rapidly growing and presenting challenges to the design of both experimental and theoretical studies. The primary aim of this dissertation is to shed some light on the physical and chemical properties of selected nanoscale materials at the interface. Furthermore, we will discuss the effective application of cutting edge theoretical and experimental techniques that are invaluable tools for understanding the systems at hand. To this effect, we use density functional theory (DFT) with the inclusion of van der Waals (vdW) interactions to study the effect of long-range …

The Atmosphere Can Be A Source Of Certain Water Soluble Volatile Organic Compounds In Urban Streams, Scott J. Kenner, David A. Bender, James F. Pankow, John S. Zogorski

Chemistry Faculty Publications and Presentations

Surface water and air volatile organic compound (VOC) data from 10 U. S. Geological Survey monitoring sites were used to evaluate the potential for direct transport of VOCs from the atmosphere to urban streams. Analytical results of 87 VOC compounds were screened by evaluating the occurrence and detection levels in both water and air, and equilibrium concentrations in water (C-w(s)) based on the measured air concentrations. Four compounds (acetone, methyl tertiary butyl ether, toluene, and m- & p-xylene) were detected in more than 20% of water samples, in more than 10% of air samples, and more than 10% of detections …

The Typical Organic Pollutants Health Risk Research Of The Main Source Water In Yellow River Basin, Gao Jijun

International Conference on Hydroinformatics

Although the contamination of the organic pollutants had been reported to occur in the Yellow River basin, few studies had been done on the source water contamination and health risk of Yellow River basin. To understand the typical organic pollutant contamination status of the main source water in Yellow River basin, samples were collected from fifty source water points (including reservoir and river) in Yellow River basin. The samples were analyzed for the representative organic pollutants, including Benzene homology, Chlorobenzene compounds, organophosphorous pesticides, and Nitrobenzene compounds, total 17 compounds. It was observed that the concentrations of the 17 compounds in …

Public Perception On The State Of Air Quality In Malta, Nikolas Cassar

Masters Theses, 2010-2019

Public perception on the state of air quality is an unclear and hazy concept whereby every individual has different opinions and views. In fact, the state of air quality is a major concern in many countries, including in Malta. This problem arises from the emissions of a number of pollutants to the atmosphere from a host of processes such as the combustion of fuel to generate electricity and the internal combustion engines to manoeuvre cars. Amongst these pollutants, there are benzene and nitrogen dioxide, which are very hazardous since they cause problems related to human health and contribute in the …

Binding Energies And Solvation Of Organic Molecular Ions, Reactions Of Transition Metal Ions With, And Plasma Discharge Ionization Of Molecular Clusters, Isaac Kwame Attah

Theses and Dissertations

In this dissertation, different approaches have been employed to address the quest of understanding the formation and growth mechanisms of carbon-containing molecular ions with relevance to astrochemistry. Ion mobility mass spectrometry and DFT computations were used to investigate how a second nitrogen in the pyrimidine ring will affect the formation of a covalent bond between the benzene radical cation and the neutral pyrimidine molecule, after it was shown that a stable covalent adduct can be formed between benzene radical cation and the neutral pyridine. Evidence for the formation of a more stable covalent adduct between the benzene radical cation and …

Acid-Free Nitration Of Benzene And Toluene In Zeolite Nazsm-5, Scott Kirkby

Scott J. Kirkby

Volatilization Of Benzene In A River, Eric Dunlop

Undergraduate Journal of Mathematical Modeling: One + Two

Benzene is a volatile organic compound: when it contaminates a river, some of the substance will evaporate as it flows through. We examine the volumetric flow rate to find how volatilization affects the concentration levels of benzene as the substance flows through several consecutive sections of a river, using a specific example to illustrate the general method.

Interaction Mechanism Of Benzene And Phenanthrene In Condensed Organic Matter: Importance Of Adsorption (Nanopore-Filling), Ke Sun, Yong Ran, Yu Yang, Baoshan Xing, Jingdong Mao

Chemistry & Biochemistry Faculty Publications

Although microporosity and surface area of natural organic matter (NOM) are crucial to mechanistic evaluation of the sorption process for nonpolar organic contaminants (NOCs), they have wrongly been estimated by the N₂ adsorption technique. Nuclear magnetic resonance spectroscopy (¹³C NMR), and benzene, carbon dioxide, and nitrogen adsorption techniques were used to characterize structural and surface properties for different condensed NOM samples, which were related to the sorption behavior of phenanthrene (Phen). It was found that the revised Freundlich model by taking the chemical activity into account can well describe the isotherms for benzene and Phen. The benzene …

Slides: Colorado Law: Protecting Water Quantity And Quality, Alan E. Curtis

Monitoring and Protecting Groundwater During Oil and Gas Development (November 26)

Presenter: Alan E. Curtis, White & Jankowski, LLP

23 slides

The Loss Of Carbon Dioxide From Activated Perbenzoate Anions In The Gas Phase: Unimolecular Rearrangement Via Epoxidation Of The Benzene Ring, David G. Harman, Aravind Ramachandran, Michelle Gracanin, Stephen J. Blanksby

Stephen Blanksby

The unimolecular reactivities of a range of perbenzoate anions (X−C6H5CO3-), including the perbenzoate anion itself (X = H), nitroperbenzoates (X = para-, meta-, ortho-NO2), and methoxyperbenzoates (X = para-, meta-OCH3) were investigated in the gas phase by electrospray ionization tandem mass spectrometry. The collision-induced dissociation mass spectra of these compounds reveal product ions consistent with a major loss of carbon dioxide requiring unimolecular rearrangement of the perbenzoate anion prior to fragmentation. Isotopic labeling of the perbenzoate anion supports rearrangement via an initial nucleophilic aromatic substitution at the ortho carbon of the benzene ring, while data from substituted perbenzoates indicate that …

Agenda: Drafting Model Laws On Indoor Pollution For Developing And Developed Nations, University Of Colorado Boulder. Center For Energy & Environmental Security, Colorado Natural Resources, Energy And Environmental Law Review

Drafting Model Laws on Indoor Pollution for Developing and Developed Nations (July 12-13)

On July 12 and 13, 2012, experts convened at Colorado Law to demonstrate the extent to which a model law could help address the global problem of indoor air pollution from inefficient cook stoves. The air pollution that results from inefficiently burning biomass as fuel for cooking has serious health and climatic consequences. The workshop produced two sets of Model Laws and commentaries to help nations solve the problem, and the commentaries were published in the Colorado Natural Resources, Energy, and Environmental Law Review.

Drafting Model Laws On Indoor Pollution For Developing And Developed Nations Workshop, July 12-13, 2012, Boulder, Colorado: Introduction, Lakshman Guruswamy

Drafting Model Laws on Indoor Pollution for Developing and Developed Nations (July 12-13)

11 pages.

"This Essay introduces the framework for deliberation and legislative drafting undertaken at the workshop: Drafting Model Laws on Indoor Pollution for Developing and Developed Nations on July 12-13, 2012, in Boulder, Colorado. There are a number of fundamental premises upon which the workshop was based, and this Essay refers to the most salient among them."-- Excerpted from 24 Colo. Nat. Resources, Energy & Envtl. L. Rev. 319 (2013).

Products Of The Benzene + O(3p) Reaction, Craig A. Taatjes, David L. Osborn, Talitha M. Selby, Giovanni Meloni, Adam J. Trevitt, Evgeny Epifanovsky, Anna I. Krylov, Baptiste Sirjean, Enoch Dames, Hai Wang

Adam Trevitt

No abstract provided.

Reactions Of The Cn Radical With Benzene And Toluene: Product Detection And Low-Temperature Kinetics, Adam J. Trevitt, Fabien Goulay, Craig A. Taatjes, David L. Osborn, Stephen R. Leone

Adam Trevitt

Low-temperature rate coefficients are measured for the CN + benzene and CN + toluene reactions using the pulsed Laval nozzle expansion technique coupled with laser-induced fluorescence detection. The CN + benzene reaction rate coefficient at 105, 165, and 295 K is found to be relatively constant over this temperature range, (3.9−4.9) × 10−10 cm3 molecule−1 s−1. These rapid kinetics, along with the observed negligible temperature dependence, are consistent with a barrierless reaction entrance channel and reaction efficiencies approaching unity. The CN + toluene reaction is measured to have a rate coefficient of 1.3 × 10−10 cm3 molecule−1 s−1 at 105 …

Slides: Hydrofracking: Air Issues And Community Exposure, Debra A. Kaden

Air Quality Impacts from Oil and Gas Development (January 27)

Presenter: Debra Kaden, Ph.D., Toxicologist, ENVIRON International Corporation, discusses air concentrations of chemicals of potential health concern surrounding oil and gas development activities, as well as temporal and spatial patterns of these chemicals in the ambient environment. Such information is necessary to evaluate possible health impacts of the drilling process on air in surrounding communities.

19 slides

Developing Slow-Release Persulfate Candles To Treat Btex Contaminated Groundwater, Ann Kambhu, Steve D. Comfort, Chanat Chokejaroenrat, Chainarong Sakulthaew

School of Natural Resources: Faculty Publications

The development of slow-release chemical oxidants for sub-surface remediation is a relatively new technol­ogy. Our objective was to develop slow-release persulfate-paraffin candles to treat BTEX-contaminated ground­water. Laboratory-scale candles were prepared by heating and mixing Na₂S₂O₈ with paraffin in a 2.25 to 1 ra­tio (w/w), and then pouring the heated mixture into circular molds that were 2.38 cm long and either 0.71 or 1.27 cm in diameter. Activator candles were prepared with FeSO₄ or zero-valent iron (ZVI) and wax. By treat­ing benzoic acid and BTEX compounds with slow-release persulfate and ZVI candles, we observed rapid …

Three Unique Coordination Geometries Involving 1,2-Dimethoxy-4,5-Bis(2-Pyridylethynyl)Benzene, Jeffrey E. Fiscus, Sandra Shotwell, Ralph C. Layland, Mark D. Smith, Hans Conrad Zur Loye, Uwe H. F. Bunz

Hans Conrad zur Loye

Reaction of the new ligand 1,2-dimethoxy-4,5-bis(2-pyridylethynyl) benzene with different metal centers under similar reaction conditions led to three distinct structure formation processes: molecular ring closure, dimerization, and polymer formation.