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The Unique Electrochemical Reactivity Of Small Metal Nanoparticles., Rafael A. Masitas

Electronic Theses and Dissertations

This dissertation describes the factors controlling metal nanoparticle (NP) oxidation, using Au oxidation in Br- and Ag oxidation in acid as model systems. We found that the oxidation potential depends on size, surface charge, and electrode material. Size has a dramatic effect, shifting about 200 mV from > 200 nm diameter down to 4 nm diameter. The shift is more dramatic below 4 nm. 2.3 nm average diameter Au NPs oxidized in the 300-500 mV range and 1.5 nm average diameter Au NPs displayed several sharp peaks from 200 mV to as low as -200 mV. These smallest Au NPs show …

Electrochemical Formation Of One-Dimensional Metal Nanostructures Across Microgaps Electrodes For Resistive Switching And Optical Sensing Applications., Nidhi Shah

Electronic Theses and Dissertations

This dissertation focuses on the electrochemical formation of one-dimensional (1D) Ag nanostructures (in particular nanowires and nanochains) directly on electrode surfaces or gap of two electrodes. Ag nanowires (NWs) and nanorods (NRs) grow directly on glass/indium tin oxide (ITO) surfaces from electrode-attached Au nanoparticle seeds in the presence of cetyltrimethylammonium bromide (CTAB) at appropriate potentials with a 5-15 % yield and the average length ranging from 100 nm to 3 µm for growth times of 30 to 120 min. This method failed when trying to grow Ag NRs/NWs across 5 µm Au electrode gaps. Interestingly, applying voltage in air leads …

Method Development For Vitamin C Quantification In Two Complex Matrices, Hannah D. Hutt

Electronic Theses and Dissertations

The following liquid chromatographic (LC) method developments and applied research studies were done using two complex food matrices, potatoes and elderberries, which are common to the state of Maine. Potatoes are Maine’s largest agricultural crop, a staple food in most U.S. households, and are, from an analytical standpoint, considered a complex matrix due to the high starch content that can be difficult to remove without degrading or removing nutrients in the process. Elderberries are an emerging crop in the U.S. because of their antioxidant and anti-viral properties and are found growing wild, throughout Maine. Elderberries are also considered a complex …

Detection Of Iron (Iii) Using Magnetic Nanoparticles, Kaiya Hansen

Electronic Theses and Dissertations

The goal of this work was to develop an iron (III) sensor which can be mounted on buoys and gliders and automatically measure iron (III) in the ocean. The method investigated in this thesis was based on anchoring the iron (III) chelator desferrioxamine B (DFB) to magnetic particles. DFB selectively binds iron (III), resulting in a complex which produces a broad absorbance band at 430 nm. This band can be measured via UV-Vis spectroscopy (UV-Vis). However, measuring oceanic iron (III) directly in solution is difficult because the concentrations can be very low, sometimes less than 1 nM. This problem could …

Synthesis Of Phenothiazinium Derivatives, Selorm J. Fanah

Electronic Theses and Dissertations

Photodynamic therapy (PDT) employs photosensitizing drugs for treating cancer. Once introduced into the body and localized in tumor cells, these photosensitizers are irradiated with light to produce active singlet oxygen radicals which kill cancer cells. The current drugs used in PDT have low quantum yield and always require a high energy radiation (normally laser). There is always a need for more effective drugs that have a high quantum yield and can be activated by visible light, in order to eliminate side effects caused by laser radiations.

In this work we synthesized derivatives of phenothiazine and phenothiazinium chromophores from the commercially …

Candida Albicans Hyphal Mannan Is Structurally Distinct From Yeast Mannan, Francis Kwofie

Electronic Theses and Dissertations

C. albicans is a polymorphic fungal pathogen which has the ability to shift from yeast to hyphae. C. albicans cell wall is composed of glucan, chitin, mannoprotein and mannan. It is not possible, using standard extraction methods, to isolate mannan from C. albicans hyphae. To isolate hyphal mannan, we developed a simplified alkali extraction method. Using this method it was determined that hyphal mannan has a much lower molecular weight, a smaller polymer distribution and altered conformation structure when compared to yeast mannan. The hyphal mannan was found to contain little to no acid-labile portion with only α-Man-PO₄ groups …

Application Of Surface Chemistry At The Interface Of Mesoporous Tio2 Films For Stable And High Efficiency Dye-Sensitized Solar Cells., Tulashi Luitel

Electronic Theses and Dissertations

Solar energy is widely believed to be the most promising renewable energy source to fulfill the ever-increasing energy demand from human society now and into the future. Dye-sensitized solar cells (DSSCs) have been explored as a potentially low-cost alternative to silicon solar cell technology due to their lower fabrication costs compared to crystalline semiconductor photovoltaics. However, the optimized efficiency for DSSCs has not been achieved yet, and the chemical stability between dye and semiconductor has also not been addressed completely. In this research, we applied the following four main strategies to prepare photoanodes used in DSSCs with the aim of …

Methodology Study Of N-Deacetylation Of 4-Acetamido-Perfluoroalkylbenzenesulfonimide, Grace Abban

Electronic Theses and Dissertations

In order to improve the synthetic route for diazonium perfluoroalkyl benzenesulfonylimide (PFSI) zwitterionic monomers, N-deacetylation of the coupling product was proposed to replace the reduction of aromatic amine intermediates. A series of hydrolysis methods, such as acid and base catalyzed refluxing, were explored for the N-deacetylation to obtain the PFSI aromatic amine. Factors such as temperature, concentration of acid/base and the time needed for the reaction to take place were investigated in an attempt to optimize the reaction condition. The basic hydrolysis was preferred since it was expected to carry out the N-deacetylation and debromination in one …

Linkage Analysis And Compositional Studies Of Β-Glucan From Saccharomyces Cerevisiae And Compositional Studies Of Mannan From Candida Albicans, Clara Arthur

Electronic Theses and Dissertations

The efficacy of a novel carbohydrate extraction procedure was investigated with methylation analysis and alditol acetate method by Gas Chromatography-Mass Spectrometry. A published extraction procedure for β-glucans was compared to one developed in house. Both procedures gave a dominant glucose peak in the Gas chromatogram indicative of successful β-glucan isolation. Further linkage studies showed four linkage positions for β-glucans isolated with the published method; terminal, 1,3-linkage, 1,6-linkage and 1,3,6-linkage, while β-glucans isolated using the new method showed six linkage positions; terminal, 1,3-linkage, 1,6-linkage, 1,4-linkage, 1,2,3-linkage and 1,3,6-linkage. Diminishing β-glucan linkage peaks in the chromatogram for the published method indicated structure …

Phosphinimine Zinc Complexes And Neutral Phosphinimines For Ring Opening Polymerization Of Lactides., Rajesh Thapa

Electronic Theses and Dissertations

Achiral arenesulfonates ligands having a (NNN) or (NNO) side arm have been developed (Chapter 2) and their respective zinc ethyl complexes, NNNZnEt 3.2 and NNOZnEt 3.3, have been synthesized and characterized using spectroscopic methods (Chapter 3). NNNZnEt as well as NNOZnEt complexes are stable under nitrogen atmosphere. In the NNOZnEt 3.3 complex the protons associated with the pendant (dimethylamino)ethyl arm are broad indicating that a fluxional process is operative, most likely dissociation of the (dimethylamino)ethyl arm at 25 °C in CD2Cl2. The fluxional behavior present in the 1H NMR spectrum of 3.2 could be arrested by cooling the CD2Cl2 solution …

Optical And Sensing Properties Of Various Shaped Gold Nanoplates And Highly Controlled Asymmetric Gold Nanoplate/Nanosphere Coupled Assemblies., Aiqin Fang

Electronic Theses and Dissertations

With the development of a strategy to correlate the dark-field light scattering spectra of individual nanostructures with scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the same nanostructures, we were able to investigate several interesting optical properties of Au nanoplates (NPs) and asymmetrically-coupled Au nanospheres (NSs) attached to Au NPs with a high level of control. The light scattering spectra of the NP/NS coupled structures depend strongly on the location of NS attachment on the NP. Attachment of multiple NSs at the edge/vertex sites leads to a unique synergistic effect. In contrast to the uniform distribution of …

Effects Of Select Vitamin E Isoforms On The Production Of Polyunsaturated Fatty Acid Metabolites In Colorectal Cancer, Martha A. Borketey

Electronic Theses and Dissertations

Vitamin E exhibits anti-tumor activity by regulating pathways in cancer cells, potentially the lipoxygenase (LOX) pathway. We studied the effects of alpha tocopherol (AT), gamma tocopherol (GT), gamma tocotrienol (GT3), and an alpha-gamma tocopherol mixture (ATGT) on the production of the LOX metabolites 13-hydroxyoctadecaenoic acid (HODE), 15-hydroxyeicosatetraenoic acid (HETE), 12-HETE, and 5-HETE in colorectal cancer. These metabolites were examined in the HCT-116 cell line after 24 h treatment with select vitamin E isoforms and quantified by LC/MS/MS. Under physiological conditions, we find that treatment with varying vitamin E isoforms have different effects on the production of 13-HODE, 15-HETE, 12-HETE, and …

Analysis Of Anacardic Acid On The Surface Of Pelargonium × Hortorum Using Matrix Assisted Laser Desorptoin Ionization Mass Spectrometry Imaging., Bryan Edward Wessel 1989-

Electronic Theses and Dissertations

The biosynthetic pathway leading to the production of anacardic acids (AnAcs) in glandular trichomes on the surface of geranium plants remains unclear. Anacardic acids are salicylic acid derivatives known to possess various medicinal benefits. Gene silencing techniques, such as RNA interference, could be useful in determining specific enzymes involved in the synthesis of AnAcs. However, it is first necessary to develop methodologies to image AnAcs. In this project, both fluorescence (FL) and mass spectral imaging (MSI) were tested. Our results indicate that cellular imaging of AnAcs, via FL, is not suitable because the spectral ranges of absorption and emission of …

Optimized Acid/Base Extraction And Structural Characterization Of Β-Glucan From Saccharomyces Cerevisiae, Shardrack O. Asare

Electronic Theses and Dissertations

β-glucan is a major component of the fungal cell wall consisting of (1→3)-β linked glucose polymers with (1→6)-β linked side chains. The published classical isolation procedure of β-glucan from Saccharomyces cerevisiae is expensive and time-consuming. Thus, the aim of this research was to develop an effective procedure for the extraction of glucans. We have developed a new method for glucan extraction that will be cost effective and will maintain the native structure of the glucan. The method that we developed is 80% faster and utilizes ¹/₃ of the reagents compared to the published classical method. Further, the method …

Sulfur-Oxidation Enhances Nitrile Hydration In Bioinspired Ruthenium Complexes : Catalytic, Kinetic, And Dft Investigations., Davinder Kumar

Electronic Theses and Dissertations

The current dissertation focuses on the effects of sulfur‒oxidation on nitrile hydration activity of a series of ruthenium(II) complexes inspired by nitrile hydratase (NHase). NHase catalytically hydrates nitriles to amides at a low spin non‒heme Fe(III) or non‒corrin Co(III) metal center. The active‒site employs a N2S3X type donor set using two carboxamido nitrogens and three cofacial cysteinic sulfurs that are present in distinct oxidation states as sulfinate (RSO2¯), sulfenate (RSO¯), and thiolate (RS¯). The apical site is occupied by substrate or solvent. A lack of sulfur‒oxidation renders the enzyme inactive. Three precatalysts, LnRuPPh3 (n = 1‒3), are employed to assess …

A Study Of The Catalytic And Chemical Properties Of Palladium And Palladium-Silver Monolayer Protected Clusters., Luther Benjamin Hutcherson

Electronic Theses and Dissertations

This thesis describes a study of the ligand chemistry of Pd Monolayer-Protected Clusters (MPCs) synthesized in the presence of octylamine. MPCs consists of a metal core surrounded by various organic stabilizers. Pd MPCs coated with alkanethiols, alkylamine, dendrimers, surfactants, and polymers have recently been explored for catalysis applications.Pd MPCs coated with alkylamines are more catalytically active than alkanethiols for hydrogentation/isomerization of allyl alcohol, but at shorter chain lengths are unstable in H2. We explored Pd MPCs synthesized in the presence of octylamines and discovered that the ligands attach to Pd as octanenitrile. This amine to nitrile conversion is catalyzed by …

Synthesis And Characterization Of Five New Tetrakis(N-Phenylacetamidato) Dirhodium(Ii) Amine Complexes And One Molybdenum Cofactor Described Crystallographically, Cragin K. Harris

Electronic Theses and Dissertations

Six new crystal structures were determined using a Rigaku Mercurcy 375/MCCD(XtaLab mini) diffractometer. The structure of a molybdenum cofactor was solved resulting in an R1 (R1 = Σ ||Fo| - |Fc|| / Σ |Fo|) of 3.61% despite the presence of a disordered DMSO molecule. New Tetrakis(N-phenylacetamidato) Dirhodium(II) complexes were synthesized and characterized. Two 2,2-cis-[Rh2(NPhCOCH3)4]•(C3H4N2)x where x= 1 or 2 were successfully crystallized and solved with R1 values below 5%. Additional studies were conducted via NMR to observe formation of both products. Three potential catalysts were synthesized starting with 3,1-[Rh₂(NPhCOCH₃)₄]. The resulting compounds were a …

Chemical Analysis, Databasing, And Statistical Analysis Of Smokeless Powders For Forensic Application, Dana-Marie Dennis

Electronic Theses and Dissertations

Smokeless powders are a set of energetic materials, known as low explosives, which are typically utilized for reloading ammunition. There are three types which differ in their primary energetic materials; where single base powders contain nitrocellulose as their primary energetic material, double and triple base powders contain nitroglycerin in addition to nitrocellulose, and triple base powders also contain nitroguanidine. Additional organic compounds, while not proprietary to specific manufacturers, are added to the powders in varied ratios during the manufacturing process to optimize the ballistic performance of the powders. The additional compounds function as stabilizers, plasticizers, flash suppressants, deterrents, and opacifiers. …

Synthesis Of Fluorene-Based Derivatives, Characterization Of Optical Properties And Their Applications In Two-Photon Fluorescence Imaging And Photocatalysis, Grace Githaiga

Electronic Theses and Dissertations

The two-photon absorption (2PA) phenomenon has attracted attention from various fields ranging from chemistry and biology to optics and engineering. Two of the common NLO applications in which organic materials have been used are three-dimensional (3D) fluorescence imaging and optical power limiting. Two-photon absorbing materials are, therefore, in great demand to meet the needs of emerging technologies. Organic molecules show great promise to meet this need as they can be customized through molecular engineering, and as the development of two-photon materials that suit practical application intensifies, so does research to meet this need. However, there remains some uncertainty in the …

Fabrication And Study Of Graphene-Based Nanocomposites For Sensing And Energy Storage, Matthew Mcinnis

Electronic Theses and Dissertations

Graphite is an allotrope of carbon made up of atomically thin sheets, each covalently bound together, forming a π-conjugated network. An individual layer, called graphene, has extraordinary electrical, thermal and physical properties that provide the opportunity for innovating new functional composites. Graphene can be produced directly on a metallic substrate by chemical vapor deposition or by chemical oxidation of graphite, forming a stable aqueous suspension of graphene oxide (GO), which allows for convenient solution processing techniques. For the latter, after thermal or chemical reduction, much of the properties of the starting graphene re-emerge due to the reestablishment of π-conjugation. The …

Development Of A Nano-Sensing Approach And A Portable Prototype For Real-Time Detection And Quantification Of Free Mercury In Stream-Flow: Combining Science And Engineering In Pro Of The Environment, Warinya Chemnasiri

Electronic Theses and Dissertations

Mercury (Hg) is a well-known hazardous environmental contaminant existing in several forms, but all are toxic to human in one way or the others. Since Hg usually settles into water polluting the environment and accumulating in living organisms, it is crucial to monitor Hg levels in the aquatic ecosystem. Although there are many well established techniques currently used to detect Hg, most of them require elaborate and time-consuming sample preparation and pre-concentration procedures, as well as costly and bulky equipment that limit their practical application in the field. In order to overcome the existent limitations in Hg determination methods, Hernandez …

Optimization Of Molecular Beacon-Based Multicomponent Probes For Analysis Of Nucleic Acids, Maria Stancescu

Electronic Theses and Dissertations

Detection of single nucleotide substitutions (SNS) in DNA and RNA has a growing importance in biology and medicine. One traditional approach for recognition of SNS takes advantage of hybridization probes that bind target nucleic acids followed by measuring ?Tm, the difference in melting temperatures of matched and mismatched hybrids. The approach enables SNS differentiation at elevated temperatures (usually 40-65oC) often only in a narrow range of < 10oC and requires high-resolution melting devices. Here we demonstrate that a specially designed DNA probe (X sensor) can broaden ?Tm from ~10oC to ~16oC and distinguish SNS in the interval of ~5-40oC. Therefore, there is no need for heating or measuring Tm for accurate SNS differentiation. Our data indicate that this wide differentiation range is in part due to the non-equilibrium hybridization conditions. Further we explored the idea that it is possible to improve the performance of an X sensor operable in close to equilibrium conditions by shifting its operability to non-equilibrium conditions. One way to achieve this is to introduce as many as possible structured ligands in analyte's dissociated state. Here we show that by introducing the maximum possible conformational constraints in X probe it is possible to shift its operation to non-equilibrium conditions and to improve its selectivity at temperatures < 15oC. Thus, this work points towards a new strategy for the design of highly selective hybridization sensors which operate in non-equilibrium conditions at close to room temperature. The X sensors could be utilized in qPCR, microarrays, as well as RNA analysis in living cells and for ambient temperature point-of-care diagnostics. In the last part of this work, X sensors were used in real time detection of PCR products. The sensors were optimized to operate in PCR buffer with optimal Mg2+ concentration. They were able to detect the target amplicon together with nonspecific products. The results presented here suggest that X sensors might be adopted for real time PCR format.

Synthesis, Linear And Nonlinear Photophysical Characterization Of Two Symmetrical Pyrene-Terminated Squaraine Derivatives In Solution, Alfonso Ballestas Barrientos

Electronic Theses and Dissertations

Two indole-based squaraine dyes bonded to two pyrenyl groups through vinyl- and ethynyl- linkers were synthesized with the aim of enhancing the intramolecular charge transfer interaction in addition to improving their optical properties. The absorption and emission properties of these derivatives were determined in order to gain an insight into the intensity of this type of interaction, their aggregation behavior and compare them with results obtained through quantum chemical calculations. Both compounds presented high photochemical stability in THF, and the linear spectroscopic characterization revealed high extinction coefficients, large fluorescence quantum yields and relatively low tendency of forming excimers in several …

Strategies For Enhanced Genetic Analysis Of Trace Dna From Touch Dna Evidence And Household Dust, Katherine Farash

Electronic Theses and Dissertations

In forensic casework it is often necessary to obtain genetic profiles from crime scene samples that contain increasingly smaller amounts of genetic material, called Low Template DNA (LTDNA). Two examples of LTDNA sources are touch DNA evidence and dust bunnies. Touch DNA refers to DNA that is left behind through casual contact of a donor with an object or another person. Touch DNA can be used to prove a suspect was present at a crime scene. Dust bunnies, or dust conglomerates, typically contain trapped shed skin cells of anyone in the vicinity along with fibers, dirt, hair, and other trace …

Investigating New Guaiazulenes And Diketopyrropyrroles For Photonic Applications, Ebrahim Ghazvini Zadeh

Electronic Theses and Dissertations

?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced photophysical and optoelectronic characteristics, the azulene framework has been under-appreciated despite its unique electronic and optical properties. Among several attributes, azulenes are vibrant blue naturally occurring hydrocarbons …

Photophysics Of Organic Probes And Their Applications In Bioimaging & Photodynamic Therapy, Bosung Kim

Electronic Theses and Dissertations

Over the past several decades the phenomenon of luminescence (divided into fluorescence and phosphorescence) has received great attention in the field of biological science. This quest has motivated scientists for a variety of applications, including fluorescence imaging. Fluorescence microscopy techniques that provide unique advantages, such as high spatial resolution and superior sensitivity, have been regarded as attractive tools in biophotonics. With the progress of ultrafast laser sources, two-photon absorption (2PA), in which a molecule absorbs two photons simultaneously, has opened possibilities of using it for various applications. Two-photon fluorescence microscopy (2PFM), which affords deeper tissue penetration and excellent three-dimensional (3D) …

Folate Conjugated Hyperbranched Polyester Nanoparticles For Prostate Tumor-Targeted Delivery Of A Cytotoxic Peptide Via Prostate Specific Membrane Antigen, Orielyz Flores-Fernandez

Electronic Theses and Dissertations

Prostate Cancer is the second most deadly cancer in men, after lung cancer. The need for new and effective therapeutics that can constrain prostate cancer progression are challenged by the lack of suitable delivery strategies that target prostate cancer tissue. To study CT20p as potential chemotherapeutic agent in the treatment of prostate cancer we proposed the use of targetable hyperbranched polyester (HBPE) based nanoparticles as delivery system. Folic acid was conjugated to the nanocarrier to improve the selectivity of the nanoparticle towards specific cell surface targets in prostate cancer cell lines. Specifically we evaluated LNCaP that up-regulated the PSMA receptor. …

Structure-Property Relationship Of The Two-Photon Circular Dichroism Of Compounds With Axial And Helical Chirality, Carlos Diaz

Electronic Theses and Dissertations

Back in 1894 Lord Kelvin coined the term "chiral" in order to refer to molecules whose mirror images were not superimposable with themselves. Over the years, research has demonstrated the important role that chiral molecules play in life, chemistry, and biology as well as their importance in the development of new drugs and technologies. The efforts to understand chiral systems have been mainly driven by spectroscopic methods that leverage on the opposite responses that enantiomers have to linear or circularly polarized light of both handedness. More specifically, Electronic Circular Dichroism (ECD) which measures the differences in linear absorption of left …

Quantum Chemical Studies For The Engineering Of Metal Organic Materials, Hector Javier Rivera Jacquez

Electronic Theses and Dissertations

Metal Organic Materials (MOM) are composed of transition metal ions as connectors and organic ligands as linkers. MOMs have been found to have high porosity, catalytic, and optical properties. Here we study the gas adsorption, color change, and non-linear optical properties of MOMs. These properties can be predicted using theoretical methods, and the results may provide experimentalists with guidance for rational design and engineering of novel MOMs. The theory levels used include semi-empirical quantum mechanical calculations with the PM7 Hamiltonian and, Density Functional Theory (DFT) to predict the geometry and electronic structure of the ground state, and Time Dependent DFT …

Synthesis And Characterization Of New Probes For Use In Fluorescence And X-Ray Ct Bioimaging, Simon Tang

Electronic Theses and Dissertations

The pursuit of more suitable drugs intended for possible biological applications are a continuously growing topic of research within the scientific community. One of these suitable qualities includes the need for hydrophilicity and or some appropriate delivery system for the drug to enter into biological systems. A system of analyzing and following these compounds would then, however, be necessary to conduct any kind of mechanistic or interaction studies for he said drug within the biological system. Just to name a few, fluorescence and X-ray computed tomography (CT) methods allow for imaging of biological systems but require the need of compounds …