Physical Sciences and Mathematics Commons^™

A Study Of The Effects Of Titanium Dioxide Nanoparticles On The Fluorescent Intensity Of Fluorescent Compounds In The Presence Of Known Quenchers., Vivian Dzigbodi Koka

Electronic Theses and Dissertations

Titanium Dioxide is a naturally occurring oxide of titanium. It has a wide range of uses in commercial products for providing whiteness and opacity. It has photocatalytic properties and can also be used to produce electricity in its nanoparticles form. This research is focused on investigating the effect of titanium dioxide nanoparticles in analysis of compounds using luminescence-based techniques. Quenching, which is one of the basic problems of fluorescent measurements, was studied in the presence of molecular oxygen and methyl iodide. The rutile phase of titanium dioxide nanoparticles was synthesized by the acid hydrolysis of titanium isobutoxide at low temperatures …

Novel Near-Infrared Cyanine Dyes For Fluorescence Imaging In Biological Systems, Nilmi T. Fernando

Chemistry Dissertations

Heptamethine cyanine dyes are attractive compounds for imaging purposes in biomedical applications because of their chemical and photophysical properties exhibited in the near-infrared region. A series of meso amino-substituted heptamethine cyanine dyes with indolenine, benz[e]indolenine and benz[c,d]indolenine heterocyclic moieties were synthesized and their spectral properties including fluorescence quntum yield were investigated in ethanol and ethanol/water mixture. Upon substitution with amines, the absorption maxima of the dyes shifted to the lower wavelength region (~600 nm), showed larger Stokes shifts and stronger fluorescence which can be attributed to an excited state intramolecular charge transfer (ICT). High quantum yields …

The Thioflavin T Fluorescence Assay For Amyloid Fibril Detection Can Be Biased By The Presence Of Exogenous Compounds, Sean A. Hudson, Heath Ecroyd, Tak W. Kee, John A. Carver

Heath Ecroyd

Thioflavin T (ThT) dye fluorescence is used regularly to quantify the formation and inhibition of amyloid fibrils in the presence of anti-amyloidogenic compounds such as polyphenols. However, in this study, it was shown, using three polyphenolics (curcumin, quercetin and resveratrol), that ThT fluorescence should be used with caution in the presence of such exogenous compounds. The strong absorptive and fluorescent properties of quercetin and curcumin were found to significantly bias the ThT fluorescence readings in both in situ real-time ThT assays and single time-point dilution ThT-type assays. The presence of curcumin at concentrations as low as 0.01 and 1 uM …

Removal Of Disinfection By-Product Precursors Using Magnetic Ion Exchange (Miex(R)): The Effects Of Ph And Source Water Variability, Sarah Cousins

Graduate Theses and Dissertations

Disinfection by-products (DBPs) form as an unintended result of drinking water disinfection, from chemical reactions between disinfectants (e.g., free chlorine) and naturally occurring dissolved organic matter (DOM). At present, 11 DBPs are regulated in treated drinking waters due to potential adverse health effects, including four trihalomethanes (THMs). Despite nearly 40 years of DBP research, compliance with DBP regulations remains a challenge for many drinking water treatment plants (DWTPs), including the four DWTPs located on the Beaver Lake Reservoir in Northwest Arkansas. Due to the high net negative surface charge on DOM, anion exchange is one potentially viable method for removing …

Fluorescence Probes For Cellular Thiol And Disulfide Detection: Sythesis And Biophysical Characterization, Timothy Jonhera

Dissertations (1934 -)

The total concentration of cellular thiols is about 30 mM, and use of current fluorescent chemical probes to quantitate these thiols inside cells is impractical. We recently reported fluorescent dithio probes (donor-S-S-acceptor, DSSA) with unusually low reduction potential (- 0.6 V) that can detect changes in intracellular thiols and cross membranes of bacterial and mammalian cells, but they could not quantify thiol redox state. Here we report a new variant of the DSSA series, which has hydroxy coumarin (Ex: 320 nm, Em: 460 nm) as donor and fluorescein (Ex: 485 nm, Em: 520 nm) as acceptor. The probe was characterized …

Quenching Of The Fluorescence Of Tris (2 2-Bipyridine) Ruthenium(Ii) [Ru(Bipy)3]2+ By A Dimeric Copper(Ii) Complex., Kevin E. Cummins

Electronic Theses and Dissertations

The quenching of the [Ru(bipy)₃]²⁺ by Cu₂L²⁺ was studied and the data were plotted with the Stern-Volmer equation. The plot showed a break and was divided into 2 regions, <0.5 and >0.5 Cu₂L²⁺: [Ru(bipy)₃]²⁺ molar ratio. Quenching above the 0.5 Cu₂L²⁺: [Ru(bipy)₃]²⁺ molar ratio was slower (330 x 10^-6 M^-1s^-1) than the quenching rate reaction below 0.5 ratio (387 x 10^-6 M^-1s^-1).

With Cu₂L²⁺ being a dimeric complex the …

Characterization Of The Desorption Electrospray Ionization Mechanism Using Microscopic Imaging Of The Sample Surface, Michael Craig Wood

Theses and Dissertations

Desorption electrospray ionization (DESI) is an ambient ionization technique for mass spectrometry. This solvent based desorption ion source has wide applicability in surface analysis with minimal sample preparation. Interest in improving detection limits, broadening applications, and increasing the spatial resolution for chemical imaging has led to studies of the DESI mechanism. An inverted microscope has been used to image interactions between the DESI spray and test analytes on a glass surface. Microscopic images recorded with millisecond time resolution have provided important insights into the processes governing analyte transport and desorption. These insights are the basis of a rivulet-based model for …

Design And Syntheses Of Fluorescent Cytosine Analogues, David W. Dodd

Electronic Thesis and Dissertation Repository

The avid hybridization of peptide nucleic acid (PNA) to DNA and RNA along with the molecule’s biological stability has led it to be used in both antisense and antigene capacities. PNA acts against translation via a steric blockade mechanism. It is therefore reasonable to assume that increased heteroduplex stability could lead to increased potency. Two ways of doing this were explored. I) N-Terminal attachment of a platinous chloride chelating moiety to PNA complementary to Xenopus noggin was synthesized with the objective of selective, covalent platination of the target transcript in vivo. Phenotypes consistent with knockdown of the selected …

Drug Design, Biological Activity, And Metabolic Consequences Of Cytotoxic Platinum Compounds: Utilizing Fluorescent Tagging To Understand Drug Action And Metabolism, Brad Benedetti

Theses and Dissertations

Platinum drugs are among the most commonly used chemotherapeutics for the treatment of testicular, head and neck, ovarian, small cell lung, and colorectal carcinomas. Although the current set of platinum chemotherapeutics has proven somewhat successful, the overall success of platinum based drugs is limited due to acquired drug resistance and a limited range of tumor types that are treatable with the current regime. The development of novel cytotoxic platinum based compounds, both trans- and polynuclear, provides for the promising treatment of clinical platinum drug resistant tumors. While the cytotoxic activity of platinum drugs provides for a hopeful outlook, the ultimate …

Experimental And Molecular Dynamics Investigation Into The Amphiphilic Nature Of Sulforhodamine B, Baris E. Polat, Shangchao Lin, Jonathan D. Mendenhall, Brett Vanveller, Robert Langer, Daniel Blankschtein

Brett VanVeller

Sulforhodamine B (SRB), a common fluorescent dye, is often considered to be a purely hydrophilic molecule, having no impact on bulk or interfacial properties of aqueous solutions. This assumption is due to the high water solubility of SRB relative to most fluorescent probes. However, in the present study, we demonstrate that SRB is in fact an amphiphile, with the ability to adsorb at an air/water interface and to incorporate into sodium dodecyl sulfate (SDS) micelles. In fact, SRB reduces the surface tension of water by up to 23 mN/m, and the addition of SRB to an aqueous SDS solution induces …

Self-Assembly And Photophysics Of Selected Organic Materials And Two-Photon Bioimaging With Profluorescent Nitroxides, Polyelectrolyte Nanoparticles, And Squaraine Probes, Hyo Yang Ahn

Electronic Theses and Dissertations

Two-photon absorption and upconverted fluorescence has been utilized in a variety of applications in pure science and engineering. Multiphoton-based techniques were used in this research in order to understand photophysical and chemical characteristics of several fluorescent dyes and to demonstrate some of their key applications. Two-photon fluorescence microscopy (2PFM) has become a powerful technique in bio-photonics for non-invasive imaging in the near-infrared (NIR) region (700~1000 nm) that often results in less photobleaching. In Chapter 1, there is a brief introduction to fluorescence, examples of fluorescence materials, and a discussion of the advantages of two-photon absorption. 2PFM imaging was utilized in …

Electronic Interactions Within Composites Of Polyanilines Formed Under Acidic And Alkaline Conditions. Conductivity, Esr, Raman, Uv-Vis And Fluorescence Studies, L Dennany, P C. Innis, S T. Mcgovern, Gordon G. Wallace, Robert J. Forster

Faculty of Science - Papers (Archive)

The properties of two forms of polyaniline (PAni) synthesised under acidic and basic conditions have been investigated both individually and as combined complexes. The PAni polymerised within alkaline media was redox inactive and non-conducting while the PAni emeraldine salt (ES) was electroactive and conducting. Raman, electron spin resonance, UV-Vis and fluorescence spectroscopies were used to monitor the changes in electronic properties of these conducting polymer composites. Solution cast films of alkaline synthesised (A-PAni) with the PAni ES resulted in an increase in the high spin polaron population suggesting that it acts as a pseudodopant. The ability of the A-PAni to …

Preparation And Studies Of Ratiometric Fluorescent Chemosensors Based On The Attenuation Of Excitation Energy Transfer, Jiba Raj Acharya

LSU Doctoral Dissertations

Molecular devices possessing pi-electron conjugated scaffold demonstrate unique capabilities as fluorescent chemosensors for the trace detection of analytes in a variety of environments. Important properties of these compounds such as charge transport and exciton migration, emission intensity etc. can be simply attenuated by external stimuli or analyte binding, leading to considerable changes in observable signals. The main goal of this Ph.D. dissertation was to study the possibility to control excitation energy migration in conjugated systems. Towards this goal, we designed surface-immobilized monodispersed oligo(p-phenylene ethynylene)s (OPEs) as a general basis for thin-film ratiometric fluorescent chemosensors. The sensor molecules have been functionalized …

Pyrenyl-Appended Imidazolium Receptor For Selective Fluorescence Sensing Of Oxalic Acid, Md Wasi Ahmad, Sung Hong Kim, Hong Seok Kim

Dr. Mohammad Wasi Ahmad (Md Wasi Ahmad)

A new fluorescent imidazolium-based cholestane receptor 4 bearing a pyrene moiety was synthesized. The binding ability of 4 toward various dicarboxylic acids was examined by UV–vis and fluorescence spectroscopy. Receptor 4 showed the highest binding constant for oxalic acid among all the tested dicarboxylic acids. Oxalic acid formed a complex with 4 with a 1:2 ratio in ethanol.