Physical Chemistry Commons^™

Enhancing Upconversion Nanoparticle Performance Of Nayf4: Yb,Tm With Doping Optimization And Shell Addition And Of Nayf4: Yb,Er With Yb,Nd Shell Addition, Ashleigh M. Chov

Honors Thesis

Upconversion (UC), is a phenomenon that occurs when low-energy excitation (usually near-infrared (NIR)) results in higher-energy emission. Upconversion nanoparticles (UCNPs) are particles less than 100 nm in size that are synthesized using rare earth metals such as Yb, Er, Tm, and Y. UCNPs have important applications in a variety of fields, including bio-imaging, security printing, and latent fingerprint development. Traditional methods for latent fingerprint development such as fluorescent powder dusting have several drawbacks including low contrast, high background interference, and autofluorescence. NIR-to-NIR UCNPs are composed of NaYF₄: Yb, Tm and emit 800 nm light under 980 nm excitation …

Improving Biodiesel Through Pyrolysis: Direct Dynamics Investigations Into Thermal Decomposition Of Methyl Linoleate, Michael Bakker

Graduate Theses/Dissertations

Dependence on petroleum and petrochemical products is unsustainable as it is both a finite resource and environmentally hazardous. Biodiesel is a proposed alternative, but has complications including possessing poor cold weather operability and lacking the ability to supplement other petrochemical products (e.g., ethylene, hexane, etc.) relied upon in society. Pyrolysis of biodiesel has demonstrated the formation of smaller hydrocarbons comprising many of these petrochemical products. Our aim is to computationally simulate the pyrolysis of methyl linoleate, the most prevalent component in biodiesel formed in the US (from soybean). We make use of unimolecular direct dynamics describing intramolecular processes, introducing Temperature …

Hot Electron Chemistry On Bimetallic Plasmonic Nanoparticles, Bryn E. Merrill, Bingjie Zhang, Jerry Larue

Student Scholar Symposium Abstracts and Posters

Catalysis provides pathways for efficient and selective chemical reactions through the lowering of energy barriers for desired products. Gold nanoparticles (AuNP) show excellent promise as plasmonic catalysts. Localized surface plasmon resonances are oscillations of the electron bath at the surface of a nanoparticle that generate energetically intense electric fields and rapidly decay into energetically excited electrons. The excited electrons have the potential to destabilize strongly bound oxygen atoms through occupation of accessible anti-bonding orbitals. Tuning the anti-bonding orbitals to make them accessible for occupancy will be achieved by coating the AuNP in a thin layer of another transition metal, such …

Raman Spectroscopic And Quantum Chemical Investigation Of The Effects Of Tri-Methylamine N-Oxide (Tmao) On Hydrated Urea, Hydrated Guanidinium, And Hydrogen Bonded Networks, Genevieve Verville

Honors Theses

Trimethylamine N-Oxide (TMAO), guanidinium, and urea are three important

osmolytes with their main significance to the biophysical field being in how they

uniquely interact with proteins. TMAO is known to stabilize and counteract the

destabilizing effects of both urea and guanidinium. The exact mechanisms by which

TMAO stabilizes and both guanidinium and urea destabilize folded proteins continue

to be debated in the literature. Some studies suggest that solvent interactions do not

play a large role in TMAO’s stabilizing effects and therefore advocate direct

stabilization, whereas others suggest that TMAO counteracts denaturation primarily

through an indirect effect of strong solvent interactions. …

Computational Modeling Of Photolysis And Catalysis Reactions In Vitamin B12-Dependent Enzymes., Abdullah Al Mamun

Electronic Theses and Dissertations

Vitamin B₁₂ is a complex organometallic molecule, the derivatives of which such as adenosylcobalamin (AdoCbl) and methylcobalamin (CH₃Cbl) act as a cofactor in numerous enzymatic reactions. These two biologically active cofactors contain a unique organometallic Co-C σ bond. Important feature of this Co-C bond is that it can be activated by both thermally and photolytically inside the enzymatic environment as well as in the solution. In the case of enzymatic reactions where AdoCbl molecule act as a cofactor, the cleavage of the Co-C bond constitutes the key catalytic step. The most intriguing features of this cleavage is …

Computational Quantum Study Of Intermediates Formed During The Partial Oxidation Of Melatonin, Oladun Oladiran

Electronic Theses and Dissertations

Melatonin is a neurohormone produced by the pineal gland in the brain. It functions as an antioxidant to scavenge free radicals. Free radicals are reactive species; they often oxidize the cells leading to oxidative stress which may lead to severe health complications. Reaction of melatonin with free radicals is known to be stepwise, as such the stability of the intermediates can be examined. Thus, the possibility of using melatonin as an in vivo spin trap can be determined. Spin traps allow characterization of unstable radical species using electron spin resonance spectroscopy. In this research, ab initio quantum chemistry techniques were …

Determining Particle Size Of Polymeric Micelles In Thermothickening Aqueous Solutions, Jessica Diane Bruer

Graduate Theses/Dissertations

Many active pharmaceutical ingredients (APIs) are poorly soluble and cause inadequate drug absorption. Soluplus^®, a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer, is a commercial excipient (BASF Corp) that enhances the solubility and bioavailability of many APIs. The mechanism of enhancement is related to the ability to form polymeric micelles in solution. These micelles store insoluble APIs in their hydrophobic interior and transport them to targeted sites in the body. An important characteristic of solubility enhancers is the particle size exhibited in solution before and after loading with APIs. This is most commonly determined by dynamic light scattering (DLS) …

Understanding Ice Mixtures Under Pluto Simulated Conditions And Their Implications For Geophysical Processes, Caitlin Joannah Ahrens

Graduate Theses and Dissertations

New Horizons at Pluto has given the planetary science community the first images of Pluto’s surface, including geologic wonders and compositional variability. Methane, nitrogen, and carbon monoxide make up the bulk of the volatile plutonian surface along with water ice. In this work, these three main volatiles are specifically investigated in the laboratory setting to understand the spectral properties and behavior of binary and ternary mixtures. The spectra are taken in the near-infrared wavelengths (1 – 2.5 µm) using Fourier transform infrared (FTIR) spectroscopy techniques utilizing the Pluto Simulation Chamber housed at the University of Arkansas, which can reach conditions …

Chemical And Electronic Surface Structure Of Chalcopyrite-Based Thin Films For Solar Water Splitting, James C. Carter

UNLV Theses, Dissertations, Professional Papers, and Capstones

In recent years, various thin film solar devices have reached markedly high efficiencies on both the laboratory and large area scale. To further evaluate their potential, and help drive device optimization of efficient solar devices, a detailed understanding of the chemical and electronic structure of the surfaces and interfaces is required. It is these interfaces that play a pivotal role in dictating aspects of device performance. Chalcopyrite-based materials, such as Cu(In,Ga)S2 (CIGS) are regarded as one of the most promising absorber materials for use in highly efficient solar devices. In the context of photoelectrochemical (PEC) hydrogen generation, the tunability of …

Investigations Of Technetium Metal And The Synthesis Of Binary Technetium Nitrides Under Extreme Conditions, Emily Siska

UNLV Theses, Dissertations, Professional Papers, and Capstones

Technetium (Tc) is the lightest of the radioactive elements and has no stable isotopes. Significant quantities of Tc are not naturally occurring on earth. However, technetium is found in high fission yield in nuclear reactors and produced for medical imaging. With its long half life, and high mobility in the environment make it of particular interest. To that end, the fundamental chemistry of Tc and Tc compounds is not as well understood compared to neighboring elements on the periodic table. Therefore, fundamental studies designed to better understand this transition metal, coupled with more targeted investigation at high temperature and pressure …

Spectroscopic And Computational Studies Of The Agricultural Active Ingredient Dicamba, James Johnson

Honors Theses

3,6-dichloro-2-methoxy benzoic acid, more commonly known as Dicamba, is the active ingredient in an array of pesticides used on farmlands across the globe. Dicamba’s mode of action works by mimicking the plant hormone auxin, which is synonymous to growth hormones in mammals. The mimicking of auxin results in excessive elongation and growing, which is eventually fatal for plants when the rate of growth can no longer be sustained. Dicamba has risen in prominence in recent years due to drift damage as a result of Dicamba’s high volatility. Having the ability to identify Dicamba is crucial for the agricultural industry. The …

Surface Chemistry And Surface Properties Of Energetic Nitrocellulose (Nc), Henry Grau

Seton Hall University Dissertations and Theses (ETDs)

This research describes an investigation into the wettability of nitrocellulose (NC), most importantly to nitroglycerin (NG), which are key components of formulations used to propel military ammunition. NG demonstrates complete wetting of NC and, overtime, NG sweats on the NC surface and leaks out. The leaking out of NG from the solid formulation is a known cause of fires and explosions resulting from storage. The origin of this research is inspired by the need to engineer a solution to leakage problems of energetic plasticizer in NC based propellant. While searching for a viable material for a specific application, we journeyed …

Materials, Micro-Stacks And Related Applications Of Single-Chamber Solid Oxide Fuel Cells, Zhe Lv, Bo Wei, Zhi-Hong Wang, Yan-Ting Tian

Journal of Electrochemistry

Single-chamber solid oxide fuel cell (SC-SOFC) is a special type of fuel cells, in which both an anode and a cathode are placed in one chamber. Its working principle relies on the selective catalytic activity of the electrodes towards fuel and oxidant in a gas mixture, leading to the generation of an electromotive force. Because of its unique principle and structure, SC-SOFC has many advantages such as sealing-free, easy stacking, quick start-up and no carbon deposition, thus, it possesses large potential in application. Herein, the principles and characteristics of SC-SOFC are introduced. Furthermore, the SC-SOFC materials, micro-stack design, degeneration mechanisms …

Electrochemical Performance Improvement Of Li2Mno3 Cathode Materials By Mgf2 Coating, Du-Dan Wang, Fei Wang, Huan-Huan Zhai, Yu-Peng Li, Na-Chuan Yang, Kang-Hua Chen

Journal of Electrochemistry

Cathode material Li₂MnO₃ has received more and more attention owing to its high theoretical capacity (459 mAh·g ^-1). However, the low initial coulombic efficiency and the poor cycle stability hamper its practical application in lithium-ion batteries. Herein, we investigated the crystal structure and electrochemical performance of Li₂MnO₃ by introducing MgF₂ coating layer. The results indicated that the conversion of partial layer Li₂MnO₃ to spinel phase induced by MgF₂ coating could reduce the initial irreversible capacity and improve the first cycle efficiency. The initial coulombic efficiencies of the 0.5wt.%, …

Syntheses And Properties Of Ta5+ Doped Li7La3Zr2O12, Feng-Feng Peng, Shi-You Li, Tong-Tong Geng, Chun-Lei Li, Shuang-Wei Zeng

Journal of Electrochemistry

The tantalum ion (Ta ⁵⁺) doped garnet-type inorganic solid electrolyte Ta-LLZO was prepared by solid state reaction, and the effect of doping amount on the properties of the materials was investigated. The materials were characterized by X-ray diffraction (XRD), field emission electron scanning microscopy (FESEM) and electrochemical impedance spectroscopy (EIS). And the cycle stability was tested by assembly of LiFePO₄//LLZTO//Li all solid lithium battery. The results show that with the increase of Ta ⁵⁺ doping amount, the material appeared to form a single cubic phase structure. When the Ta ⁵⁺ doping content became 14.09wt.%, x=0.3, the …

Recent Advances Of Co2 Electrochemical Reduction In Solid Oxide Electrolysis Cells, Yi-Hang Li, Chang-Rong Xia

Journal of Electrochemistry

Solid oxide electrolysis cells (SOECs) have stimulated wide interests for their promising application in the reduction of CO₂ emissions and the storage of renewable energy. Here, the advances made in the development of cathode materials including cermets and perovskite oxides in our research group, are summarized, along with the design of cell configurations. The electrochemical kinetics and performances of cathodes and cells are discussed and analyzed. It is expected that this brief review offers critical insights and useful guidelines for developing superior electrodes and SOECs in the future.

Cyclic Voltammetry Coupled With Faradic Adsorption/Desorption Processes: A Finite Element Simulation, Jia-Yao Guo, Duan Chen, Jie Zhang, Dong-Ping Zhan

Journal of Electrochemistry

Heterogeneous electron transfer (HET) coupled with Faradic adsorption/desorption is the fundamental processes involved in hydrogen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and methanol oxidation reaction. However, the electrochemical behaviors of HET coupled with Faradic adsorption/desorption are complicated, and difficult to get the interface reaction kinetics quantitatively. In this paper, finite element method was adopted to simulate the cyclic voltammetric behaviors of HET coupled with Faradic adsorption/desorption processes by using the Fick’s second law and Langmuir isotherm. The cyclic voltammograms when reactant or product adsorbed weakly or strongly were simulated, and they agreed well with the classical results. …

Preparation And Characterization Of Cathode Supported Solid Oxide Fuel Cell, Xiao-Nan Bao, Guang-Jun Zhang, Shao-Rong Wang

Journal of Electrochemistry

A site deficient (La_0.8Sr_0.2)_0.95MnO₃ (LSM95) powder was synthesized by solid state reaction as a cathode material. The commercial Zr_0.9Sc_0.1SO_1.95 (SSZ) was selected as an electrolyte material and La_0.8Sr_0.2Cr_0.5Mn_0.5O₃- (LSCrM) was synthesized by sol-gel method as an anode material. Accordingly, single cells of LSCrM-CeO₂|SSZ|3YSZ-LSM95 were prepared by tape casting, sintering and impregnation. The single cell test results for LSCrM-CeO₂|SSZ|3YSZ-LSM95 with 0.11 g·cm ^-2 CeO₂ and using CH₄ as a fuel showed the power …

Direct Carbon Solid Oxide Fuel Cells, Jiang Liu, Xiao-Min Yan

Journal of Electrochemistry

Carbon is richly reserved in coal, biomasses, and many other nature resources. It is usually used as an energy source through oxygen oxidation reaction. The oxidation is generally realized through combustion which causes serious air pollution. Besides, the conversion efficiency of generating electricity through the combustion process is limited by Carnot efficiency. A direct carbon solid oxide fuel cell (DC-SOFC) is a solid oxide fuel cell (SOFC) directly operated with solid carbon as the fuel. It can convert the chemical energy of carbon into electricity with high efficiency. The concentration of produced CO₂ from a DC-SOFC is so high …

Research Progress Of Fuel Electrode In Oxide-Ion Conducting Solid Oxide Electrolysers, Ling-Ting Ye, Kui Xie

Journal of Electrochemistry

Solid oxide electrolysers are now attracting much more attentions because they can efficiently produce fuels by electrolyzing H₂O/CO₂. In this paper, a comprehensive introduction to the recent progress in the development of fuel electrode (cathode) materials is provided. The advantages, disadvantages and development trend towards various cathode materials are pointed out. The key scientific and technological problems in this field are emphasized.