Chemistry Commons^™

Structural And Functional Studies Of Nicotinamide Adenine Dinucleotide And Streptolysin S Biosynthesis Proteins From Streptococcus Pyogenes, William T. Booth

Theses and Dissertations

Invasive infections caused by Streptococcus pyogenes, also known as Group A Strep (GAS), results in approximately 600,000 deaths annually. With evidence of antibiotic-resistant strains of this bacterium on the rise, there is a need for the identification of new drug targets to control these infections. In our approach we target the quinolinate-salvage pathway (QSP) and the streptolysin S (SLS) biosynthesis pathway. The QSP provides a secondary pathway for NAD+ biosynthesis within this organism; the SLS pathway leads to the formation of a quorum sensing molecule (SLS). We hypothesize that inhibition of the pathways will lead to GAS cell death or …

Applications Of Molecular Modelling And Structure Based Drug Design In Drug Discovery, Sreya Mukherjee

USF Tampa Graduate Theses and Dissertations

Calcium ions have important roles in cellular processes including intracellular signaling, protein folding, enzyme activation and initiation of programmed cell death. Cells maintain low levels of calcium in their cytosol in order to regulate these processes. When activation of calcium-dependent processes is needed, cells can release calcium stored in the endoplasmic reticulum (ER) into the cytosol to initiate the processes. This can also initiate formation of plasma membrane channels that allow entry of additional calcium from the extracellular milieu. The change in calcium levels is referred to as calcium flux. A key protein involved in initiation of calcium flux is …

Ligand-Induced Magnetic Changes In Metal Thin Films, Fiona Senta Oberbeck-Oxsher

Theses and Dissertations

The investigation of magnetic properties of thin films whose surfaces were modified by organic molecules shows that the addition of any functional group to the surface measurably changes the magnetic properties. The effect often scales with ligand strength and is not limited to surfaces with ferromagnetic properties. Improving upon the technique developed by Knaus et al. [1], a stable and sensitive device was developed to measure this magnetic effect using the planar Hall effect (PHE) in order to shed light onto controversial questions of purported paramagnetism of thiolated gold. There is a measureable non-diamagnetic response of thin gold layers when …

Quantum Dot Metrics For Preparative Chemistry And Fluorescence Applications, Yi Shen

Theses and Dissertations

Colloidal semiconductor quantum dots (QDs) are considered to be a promising candidate for bio-imaging and solar cells because of their extraordinary photo-physical properties. The ultimate goal of this dissertation is to design a reliable matrix and a reproducible method to prepare QDs-based biocompatible probe for fluorescence applications. Synthesis of quantum dots requires a large amount of ligands to improve the stability at high temperature. However, for further application and surface modification of QDs, excess ligands must be removed. In this dissertation, I will first describe using gel permeation chromatography (GPC) as a media to purify different types of QDs. A …

The Development Of A High Resolution Deep-Uv Spatial Heterodyne Raman Spectrometer, Nirmal Lamsal

Theses and Dissertations

Raman spectroscopy is a light scattering technique that has a huge potential for standoff measurements in applications such as planetary exploration because a Raman spectrum provides a unique molecular fingerprint that can be used for unambiguous identification of target molecules. For this reason, NASA has selected a Raman spectrometer as one of the major instruments for its new Mars lander mission, Mars 2020, in the search for biomarkers that would be the indicators of past or present life. Raman scattering is strongest at UV wavelengths because of the inherent increase in the Raman cross section at shorter wavelengths and because …

Electrospinning Of Polymeric Solutions Using Opuntia Ficus-Indica Mucilage And Iron Oxide For Nanofiber Membranes For Treating Arsenic Contaminated Water, Venkatesh Eppili

USF Tampa Graduate Theses and Dissertations

Water is the essential part of every organism and it is also a vital constituent of healthy living and diet. Unfortunately water contamination over the past decade has increased dramatically leading to various diseases. As technology advances, we are detecting many pollutants at smaller levels of concentrations. Arsenic (As) is one of those major pollutants, and Arsenic poisoning is a condition caused due to excess levels of arsenic in the body. The main basis for Arsenic poisoning is from ground water which naturally contains high concentrations of arsenic. A case study from 2007 states that over 137 million people in …

Gold Nanoparticle-Based Colorimetric Sensors For Detection Of Dna And Small Molecules, Pingping Liang

FIU Electronic Theses and Dissertations

Biosensors have proven to be a powerful tool for detecting diverse targets, such as proteins, DNA, and small molecules representing disease biomarkers, toxins, drugs and their metabolites, environmental pollutants, agrichemicals, and antibiotics with high sensitivity and specificity.

The major objective of the research described in this dissertation was to develop low cost, low sample volume, highly sensitive and specific AuNP-based colorimetric sensor platforms for the detection of DNA and small molecules. With this in mind, we propose an instrument-free approach in chapter three for the detection of NADH with a sensor constructed on a paper substrate, based on the target-induced …

Aggregation-Induced Emission Enhancement In Boron Difluoride Complexes Of 3-Cyanoformazanates, Ryan R. Maar, Joe Gilroy

Chemistry Publications

Boron difluoride (BF₂) complexes of 3-cyanoformazanates exhibit aggregation-induced emission enhancement in THF-water mixtures due to their severely twisted N-aryl substituents which restrict intramolecular motion and π stacking upon aggregation.

Communication: Visualization And Spectroscopy Of Defects Induced By Dehydrogenation In Individual Silicon Nanocrystals, Dmitry A. Kislitsyn, Jon M. Mills, Vancho Kocevski, Sheng-Kuei Chiu, William J.I. Debenedetti, Christian F. Gervasi, Benjamen N. Taber, Ariel E. Rosenfield, Olle Eriksson, Ján Rusz, Andrea Mitchell Goforth, George V. Nazin

Chemistry Faculty Publications and Presentations

We present results of a scanning tunneling spectroscopy (STS) study of the impact of dehydrogenation on the electronic structures of hydrogen-passivated silicon nanocrystals (SiNCs) supported on the Au(111)surface. Gradual dehydrogenation is achieved by injecting high-energy electrons into individual SiNCs, which results, initially, in reduction of the electronic bandgap, and eventually produces midgap electronic states. We use theoretical calculations to show that the STS spectra of midgap states are consistent with the presence of silicon dangling bonds, which are found in different charge states. Our calculations also suggest that the observed initial reduction of the electronic bandgap is attributable to the …

Synthesis, Structural Diversity, And Redox Control Of Cyclometalated Monoruthenium Complexes, Zhong-Liang Gong, Jiang-Yang Shao, Zhong Yu-Wu

Journal of Electrochemistry

Cyclometalated ruthenium complexes have received increasing attractions recently due to their excellent redox and photophysical properties. One structural feature of these complexes is that there is a ruthenium-carbon (Ru-C) σ bond presented in the molecule. Three common methods, namely, the “late metalation”, “early metalation”, and “transmetalation” methods, for the synthesis of cyclometalated ruthenium complexes are discussed and summarized. General strategies for the design of cyclometalating ligand and cyclometalated ruthenium complexes are introduced. By using different ancillary ligands, such as pyridine, imidazole, triazole, and pyrimidine, a great number of ruthenium complexes can be prepared. The presence of the Ru-C bond significantly …

Electrochemical And In Situ X-Ray Absorption Fine Structure Study Of Li-Rich Cathode Materials, Meng-Yan Hou, Hong-Liang Bao, Ke Wang, Jian-Qiang Wang, Yong-Yao Xia

Journal of Electrochemistry

A series of the lithium-rich and manganese-based layered structure xLi₂MnO₃•(1-x)LiMn_1/3Ni_1/3Co_1/3O₂ (x = 0.3，0.5，0.7) materials were synthesized by a co-precipitation method, and followed by a solid-state reaction process. By comparing the first cycle efficiency, the reversible discharge capacity, the cycling stability and the voltage decay during the charge/discharge cycling process, the material with the composition of 0.5Li₂MnO₃•0.5LiMn_1/3Ni_1/3Co_1/3O₂was found to show the best electrochemical performance. The lithium storage mechanism and thermal stability of the de-lithiated compound were also investigated …

The Electrochemical Behavior Of Li+ In Lif-Baf2-Licl Molten Salt System, Shao-Hua Yang, Jun Wang, Xiao-Hui Lai, Hao-Ran Wang

Journal of Electrochemistry

The electrochemical reduction process and rate determining step of Li ion on a tungsten electrode at 1203 K in a LiF-BaF₂-LiCl molten system were studied by cyclic voltammetry, chronoamperometry and chronopotentiometry methods using a three-electrode system and electrochemical workstation AUTOLAB. The results showed that the reduction potential of Li ion was at around -1.0 V on a tungsten electrode as compared with a platinum electrode. The reduction process of Li ion on a tungsten electrode occurred in a single step with the exchange of one electron. Chronoamperograms indicated that the cathode process was controlled by the diffusion step …

Electrochemiluminescence Immunosensor Based On Platinum Nanoparticles For The Determination Of Apolipoprotein A1, Liao Ni, Zhuo Ying, Yuan Ruo

Journal of Electrochemistry

In this paper, a novel electrochemiluminescence (ECL) immunosensor for the detection of apolipoprotein A1 was constructed based on flower-like platinum nanoparticles (PtNFs) via a one-pot chemical synthesis method. The PtNFs was used to immobilize the secondary antibody and enzyme (GOD). Then the prepared bioconjugates were introduced onto the electrode via sandwich immunoreactions. Accordingly, the ECL luminophore peroxydisulfate (S₂O₈^2- ) was presented in the working buffer solution containing an appropriate amount of glucose. Through the ECL responses of S₂O₈^2- and O₂, a dramatically amplified ECL signal was obtained for the reason …

The Progress Of Order-Structured Membrane Electrode Assembly, Shang-Feng Jiang, Bao-Lian Yi

Journal of Electrochemistry

Performances of proton exchange membrane fuel cells (PEMFCs) have been recently improved. However, the cost and Pt loading must be further reduced for the commercialization of PEMFCs. Previous researches have proved that the order-structured electrode is beneficial to the effective utilization of Pt-based catalysts, decreasing the Pt loading and increasing the three-phase boundary for reaction. Especially, the nanostructure thin films (NSTFs) electrode, an ultra-thin catalytic layer developed by 3M Company, demonstrates high performance and durability. Besides, some other researchers have employed the high conductive carbon nanotube arrays or high stable metal oxide arrays as the order-structured catalyst supports for fundamental …

Recent Progress In Solid-State Nmr Study Of Electrode/Electrolyte Materials For Lithium/Sodium Ion Batteries, Gui-Ming Zhong, Zi-Geng Liu, Da-Wei Wang, Qi Li, Ri-Qiang Fu, Yong Yang

Journal of Electrochemistry

Solid state NMR technique is a powerful tool for characterizing the local structure and compositions of solid materials quantitatively. A comprehensive understanding of the structure evolution during the electrochemical reactions of the materials for lithium/sodium ion batteries will be obtained with the combination of solid state NMR, XRD, and XAS methods. Through analyzing solid state NMR spectra, we can obtain the compositions, local structures and ion diffusion dynamics of electrodes, electrolytes and surface layers for lithium/sodium ion batteries, providing an important theoretical support for the design and development of high-performance materials for batteries. In this paper, we review the recent …

Developments Of Photo-Assisted Fuel Cells, Ling-Ling Zhang, Shao-Jun Dong

Journal of Electrochemistry

The exploitation and utilization of fossil fuels have led to serious energy crisis and environmental pollution. In this case, the development of renewable energy is an alternative to traditional energy consumption. Fuel cells (FCs) can convert chemical energy into electricity via the electrochemical reaction, which is green and environment-friendly. Photo-assisted FCs integrate photo-responsive components into FCs, leading to the dual routes of energy conversion including light energy to electricity and chemical energy to electricity, and thus, improving the energy utilization efficiency. The development of photo-assisted FCs is significant for practical application and promising to solve the coming energy crisis. In …

Reduced Graphene Oxide (Rgo) Hollow Network Cages For High-Performance Electrochemical Energy Storage, Chi Zhang, Xu-Jun He, Gao-Ren Li

Journal of Electrochemistry

The reduced graphese oxide (RGO) hollow network cages were synthesized via zinc oxide (ZnO) template-assisted electrodeposition. The as-prepared RGO hollow network cages exhibited the multi-level architectures, from nano sheets, porous structures, networks, to 3D microscaled hollow cages, which can simultaneously optimize transport of electroactive species, utilization rate of electrode material, and super capacitive performance. Electrochemical measurements confirmed the superior performance of RGO hollow network cages for supercapacitors (SCs), such as high Csp (393 F•g^-1 at 1.0 A•g^-11), excellent rate capability (21.2% Csp loss from 1.0 to 20 A•g^-1), and superior cycling stability (< 1% Csp loss after 10000 cycles).

3, 4-Ethylenedioxythiophene Monomer As Safety-Enhancing Additive For Lithium Ion Batteries, Wei-Xiao Ji, Feng Wang, Jiang-Feng Qian, Yu-Liang Cao, Xin-Ping Ai, Han-Xi Yang

Journal of Electrochemistry

Safety concern is a major obstacle hindering the wide applications of large-capacity lithium ion batteries (LIBs) in electric vehicles. In this paper, a polymerizable monomer of 3, 4-ethylenedioxythiophene (EDOT) was proposed and tested as an electrolyte additive for enhancing the safety of LIBs. The electro-oxidative polymerization behaviors and influence of PEDOT additive on the thermal behavior of LiCoO₂ cathode, as well as the safety performance and electrochemical properties of LiCoO₂-based LIBs were investigated. The results from cyclic voltammetry (CV) and transmission electron microscope (TEM) characterizations indicated that the monomer additive can be electro-oxidatively polymerized to form a …

Uniform Nanoshells For Functional Materials：Constructions And Applications, Shu-Yi Duan, Wei Zhang, Jun-Yu Piao, An-Min Cao, Li-Jun Wan

Journal of Electrochemistry

As a significant protocol for materials treatment, surface modification has found broad applications in different fields including catalyst, photochemistry, and electrochemistry. Herein, we introduced the representative synthetic methodologies for the constructions of different functional materials with a focus on their core-shell structures. By taking the electrode materials in lithium ion batteries as an example, we demonstrated the importance of surface modification on the electrode materials. Different coating materials ranging from metal oxides, metal phosphates to carbon have been discussed. We also showed that an accurate control on the surface layer can be crucial for optimizing the electrochemical performances of the …

Spatially Directional Resorcin[4]Arene Cavitand Glycoconjugates For Organic Catalysis In Aqueous Media, Ali Husain Husain

USF Tampa Graduate Theses and Dissertations

Resorcin[4]arenes and their rigid structures “cavitands” offer a unique molecular structure scaffolds suitable for attaching and orienting multi-ligands on their upper rims. Their remarkable structure properties, the relative ease of chemical modification on their either rims or through the multiple phenolic hydroxyl (-OH) groups, manipulating their cavity size and the role of spatial directionality provided by their cores, led synthetic chemist to explore their utilities in the synthesis of valuable resorcin[4]arene/cavitand assemblies with wide range of applications in many research areas such as supramolecular chemistry, host-guest chemistry, glycoconjugates, polymer chemistry, host-guest chemistry, micro-reactors in chemical catalysis and others. In particular, …