Thesis (M.S.)--University of Nevada, Reno, 2005. / "December, 2005." Includes bibliographical references (leaves 50-53). Online version available on the World Wide Web.

Thesis (M.S.)--State University of New York at Binghamton, Department of Chemistry, 2006. / Includes bibliographical references.

This thesis is dedicated to the study of fluorescent conjugated polymers made of fluorene labelled with rylene moieties. Those polymers are important candidates for use in Organic Light Emitting Devices (OLEDs). The dyes present in the polymers were studied at the single-molecule level. The first part of the work is devoted to the construction and validation of an epi-fluorescent confocal/widefield/Total Internal Reflection microscope. The ensemble properties of the samples are first measured in solution. The combination of steady-state and time-resolved spectroscopies allows us to unravel the photophysics of the conjugated polyfluorene polymer containing perylenediimides in its backbone. Energy transfer is found to occur between the polyfluorene and the perylenediimide units. Beside energy transfer, a photoinduced electron transfer is also supposed to take place. Widefield microscopy is used to measure the end-to-end distance in single polymer chains. From those measurements the polymer is shown to present a quasi linear shape inside its host matrix. From the simulation of the end-to-end distance distribution, a conjugation length of 4-6 fluorene units is found. The introduction of a new subtraction method associated with defocused imaging allows us to study a more complicated polymer containing more perylenediimide units. The location and the 3D orientation of the incorporated dyes were measured at the same time by this new technique named SPIDER. Finally, the sequential two-color measurements allow us to get useful informations concerning the energy transfer occurring between polyfluorene backbone and perylenediimide units at the single molecule level.

In recent years, application of fluorescent conjugated polymers to sense chemical and biological analytes has received much attention owing to its technological significance. Water soluble conjugated polymers are interesting towards the developing sensors for biomolecules. In this present contribution, we describe the syntheses and characterization of a series of water soluble conjugated polymers with sulfonic acid groups in the side chain. Such anionic conjugated polymers are designed to interact with biomolecules such as cytochrome-C. All polymers are water soluble and showed strong blue emission. Significant quenching of the fluorescence from our functionalized PPP was observed upon addition of viologen derivatives or cytochrome -C. / Singapore-MIT Alliance (SMA)

Fluorescent labeling of biological materials using small organic dyes is widely employed in the life sciences and have been used in a variety of applications that include diagnostics and imaging. Quantum dots have the potential to overcome problems encountered by organic molecules and have been exploited for applications in biological imaging and in single particle tracking studies. The dithiolane ring can be exploited to attach a diversity of organic compounds to CdSe–ZnS core–shell nanoparticles. The introduction of spectroscopic labels as trans-azobenzene chromophores offers the opportunity to quantify the average number of dithiolane anchoring groups attached to each quantum dot. The transition from monomeric ligands with a single dithiolane anchor to polymeric ligands with multiple dithiolane anchoring groups can be exploited to raise the number of chromophoric labels adsorbed on each quantum dot. Systems showing FRET have been developed on the basis of supramolecular association of BODIPY based dyes or quantum dots as donors and organic chromophores as acceptors. Amino - terminated dyes and quantum dots associate with the chromophores through an ammonium moiety on addition of acid, thereby bringing them closer. Addition of base increases back the fluorescence intensity of the donor completely because of the dissociation. However a similar system with quantum dots as donor, show a very small restoration of fluorescence possibly due to non-specific interaction. In the next project, introduction of spectroscopic labels, in the form of BODIPY dye within the ligands offered the opportunity to quantify the average number of dithiolane anchoring groups attached to each quantum dot. Both fluorescence resonance energy transfer and electron transfer mechanisms are responsible for the quenching of quantum dot fluorescence and unfortunately does not make the system suitable for pH sensing. In the final project, BODIPY-oxazine based fluorophore – photochrome dyad has been assembled by a connecting triazole ring, such that the emission of the former can be modulated by the electronic and structural changes caused by the photoinduced transformations of the later. Further experiments need to be conducted on the fluorophore – photochrome dyads to switch the luminescence of the former with optical inputs.

Fluorescence microscopy offers the opportunity to image noninvasively biological samples in real time. However, the phenomenon of diffraction limits the resolution of conventional fluorescence microscopes to submicrometer dimensions in both the horizontal and vertical directions. This limitation can be overcome by photoswitchable fluorescent probes able to undergo reversible saturable optically linear fluorescence transitions (RESOLFT). In this study, firstly, a photoswitchable fluorescent probe based on BODIPY fluorophore and Spiropyran photochrome were designed and its photophysical and photochemical properties were investigated in organic and aqueous environments. Also, its imaging with patterned illumination was showed by trapping them in PMMA matrix. Secondly, photochromic [1,3]oxazines with different substituents as well as polymers incorporating them were synthesized and their photochemical and photophysical properties were investigated. Thirdly, to improve the switching speeds and fatigue resistance of the BODIPY-Spiropyran conjugate, the photochromic part was replaced by [1,3]oxazines and dyads incorporating BODIPY fluorophore and [1,3]oxazine photochromes were synthesized. Lastly, a new strategy was designed to switch the fluorescence of fluorophores by a modular approach. It is based on photoinduced elongation of the absorption wavelength of a fluorescent chromophore with the aid of an appended photochromic auxochrome.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xii, 146 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 134-146).

M.S. / Applied Physics / A new method of measuring the level of 8-methoxypsoralen in blood serum was developed for the reasons of speed, accuracy, and cost. This new method uses laser induced fluorescence of the psoralen to determine the concentration in serum. The fluorescence is analyzed with an optical multichannel analyzer coupled to an intensified photodiode array detector. Research was first attempted on samples with ethanol as the solvent to confirm that the method would work. Sample concentrations of 8-methoxypsoralen in serum are determined by comparing the fluorescence signal obtained from previously known concentrations. Levels down to 200ng per milliliter of serum can be measured with this technique.

A new molecular imaging modality has been developed to detect and locate positive axillary and sentinel lymph nodes non-invasively in breast cancer patients undergoing lymphoscintigraphy. The modality is based on fluorescent photon detection to locate the presence of indocyanine green (ICG) in the lymph subsequent to peritumoral injection of ICG into the breast. The imaging system consists of a gain-modulated intensified charge-coupled device (ICCD) camera, which captures low-intensity, near-infrared, and frequency-modulated photons. A four-fold ‘optical lymphography’ study was conducted to (1) examine fluorescence depth penetration and ICCD system accuracy at clinically relevant depths, (2) compare image quality of the ICCD system vs. conventional gamma imaging, (3) measure ICG pharmacokinetics in vivo, and (4) develop a clinical protocol while examining pre-clinical factors such as the outcome of combining ICG with sulfur colloids used in lymphoscintigraphy. The frequency-domain ICCD system was found to precisely detect modulation amplitude, IAC, and phase, θ, at depths up to 9 cm and with IAC accuracy less than 20% and θ less than 2º using an 80-mW laser incident on phantoms having ranging tissue optical properties. Significant differences in the mean depth of penetration owing to 0.62-ns lifetime and 100-MHz frequency increases were detected. An in vivo optical vs. nuclear image quality comparison demonstrated statistically similar (α=0.05) target-to-background ratios for optical (1.4+/-0.3) and nuclear (1.5+/-0.2). Alternatively, resulting image signal-to-noise ratios (SNR) from the ICCD system were greater than that achieved with a conventional gamma camera (pvalue<<0.01). Analysis of SNR versus contrast showed greater sensitivity of optical over nuclear imaging for subcutaneous tumors. In vivo and rapid detection of ICG in the blood-stream of nude mice was accomplished with a home-built avalanche photodiode dynamic fluorescence measurement system. Intensity data upon i.v. injection were regressed with a pharmacokinetic model describing the partitioning of ICG from the blood to the surrounding tissues. ICG blood-clearance was detected approximately 15 min after injection. Lastly, a human subject protocol was written, practiced, and federally approved for the application of optical lymphography. Furthermore, ICG was unaffected when mixed with sulfur colloids thus supporting the feasibility for combining fluorescence imaging with lymphoscintigraphy in breast cancer patients.

Diffusion can be classified as either normal or anomalous. A variety of experimental systems are evaluated to classify diffusion. Potential regressions and step size distributions are analysed. Nor-mal diffusion holds except where flocculation takes place, or where concentrations of cationic starches are high or with cationic starches and latex together. In these cases, subdiffusion takes place. Furthermore, limiting values are used to calculate diffusion coefficients. Diffusion of non-spherical particles is covered as well, here tested on microcrystalline cellulose.