Nanoporous materials have been widely used in the fields of biological and chemical sensing, chemical separation, heterogeneous catalysis and biomedicine due to their merits of high surface area-to-volume ratio, chemical and thermal stabilities, and flexible surface modification. However, as the nature of nanoporous materials, they are inherently heterogeneous in the micro- and nanoenvironments. The environmental heterogeneity plays a decisive role in determining the performance of various applications of nanoporous materials. In order to provide an in-depth understanding of the nanoporous materials, it is of great interest to investigate the environmental heterogeneity in them. Single molecule spectroscopy, combined the quantitative confocal fluorescence imaging which possesses the capability of optical sectioning, has demonstrated to be a powerful tool to approach the environmental heterogeneity inside nanoporous materials. Single molecule spectroscopy is an ultrasensitive technique for probing molecular transport and properties of individual molecules. This technique has been extensively used in the research of environmental heterogeneity in nanoporous materials since it removes the issues of ensemble averaging and directly approaches detailed information that is obscured in ensemble measurements. In order to proficiently interpret single molecule data, we developed a comprehensive methodology – single molecule counting – for characterizing molecular transport in nanoporous silica. With this methodology as a tool, the nanoenvironmental heterogeneity inside the nanopores of C18-derivatized silica particles was explored by probing single molecular diffusion inside the pores. By employing single molecule ratiometric spectroscopy and a solvatochromic fluorophore as viii reporter of local environment, the gradient in nanopolarity as well as the nanoviscosity along the C18 layer after the inclusion of solvent was uncovered. The chemical properties of solute molecules at the nanopore surface are ultimately controlled by the energetics of the solute-interface interactions. The imaging of distribution of energies would be a decisive approach to assess the fundamental heterogeneity of the interface. To this end, we investigated the ΔG distribution of C18-derivatized nanoporous silica particles with quantitative confocal imaging. The pixel-to-pixel and particle-to-particle analysis showed the existence of ΔG heterogeneity between particles as well as within individual particles. The heterogeneity in ΔG could be partially responsible for band broadening in chemical separations and significantly affect overall reaction yield when using nanoporous materials as solid support for heterogeneous catalysis.

Thesis (Ph.D.)--McMaster University, 2006. / Supervisor: Yingfy Li. Includes bibliographical references (leaves 151-167).

Boronic acids play an important role in the design and synthesis of chemosensors for carbohydrates due to their ability to reversibly bind with diol-containing compounds. Along this line, the availability of boronic acids that change fluorescence upon sugar binding is critical to a successful sensor design effort. Here, two boronic acids that show strong fluorescent intensity changes upon sugar binding are reported: isoquinoline-7-boronic acid (7-IQBA) and phenoxathiin-4-boronic acid (4-POBA).

The design and development of a versatile time resolved fluorescence spectroscopy (TRFS) system capable of near real time data acquisition and processing for potential clinical diagnostic applications is reported. The TRFS apparatus is portable, versatile and compatible with the clinical environment. The main excitation source is a UV nitrogen laser with a nanosecond pulse width and the detection part consists of a dual grating spectrograph coupled with an MCP-PMT. The nitrogen laser also has a dye module attached to it, which enables broadband excitation of the sample. This setup allows rapid acquisition (250 ms for fluorescence decay at a wavelength) of time resolved fluorescence data with a high spectral (as low as 0.5 nm) and temporal (as low as 25 picoseconds) resolution. Alternatively, a state diode pumped pulsed laser can be used for excitation to improve data collection speed. The TRFS system is capable of measuring a broad range of fluorescence emission spectra (visible to near infra-red) and resolving a broad range of lifetimes (ranging from a few hundred picoseconds to several microseconds). The optical setup of the system is flexible permitting the connection of different light sources as well as optical fiber based probes for light delivery/collection depending on the need of the application. This permits the use of the TRFS apparatus in in vitro, ex vivo and in vivo applications. The system is fully automated for real-time data acquisition and processing, facilitating near-real time clinical diagnostic applications.

Time-resolved fluorescence spectroscopy (TRFS) is a powerful analytical tool for quantifying the biochemical composition of organic and inorganic materials. The potentials of TRFS as nondestructive clinical tool for tissue diagnosis have been recently demonstrated. To facilitate the translation of TRFS technology to the clinical arena, algorithms for online TRFS data analysis are of great need. A fast model-free TRFS deconvolution algorithm based on the Laguerre expansion method has been previously introduced, demonstrating faster performance than standard multiexponential methods, and the ability to estimate complex fluorescence decay without any a-priori assumption of its functional form. One limitation of this method, however, was the need to select, a priori, the Laguerre parameter a and the expansion order, which are crucial for accurate estimation of the fluorescence decay. In this thesis, a new implementation of the Laguerre deconvolution method is introduced, in which a nonlinear least-square optimization of the Laguerre parameter is performed, and the selection of optimal expansion order is attained based on a Minimum Description Length (MDL) criterion. In addition, estimation of the zero-time delay between the recorded instrument response and fluorescence decay is also performed based on a normalized means square error criterion. The method was fully validated on fluorescence lifetime, endogenous tissue fluorophores, and human tissue. The automated Laguerre deconvolution method is expected to facilitate online applications of TRFS, such as clinical real-time tissue diagnosis.

In the first part of this study, 4-(2,5-di-2-thiophen-2-yl-pyrrol-1-yl)-phthalonitrile (SNS-PN) was synthesized by utilizing 1,4-di(2-thienyl)-1,4- butadione (SOOS) and 4-aminophthalonitrile via Knorr-Paal Reaction. Nuclear magnetic resonance (1H NMR and 13C NMR) and fourier transform infrared (FTIR) spectroscopies were utilized for the characterization of this compound. SNS-PN monomer was then electrochemically polymerized in acetonitrile/0.2 M LiClO4 solvent/electrolyte couple. Characterizations of the resulting polymer P(SNS-PN) were carried out by cyclic voltammetry (CV), UV&ndash / vis and FTIR spectroscopic techniques. Spectroelectrochemical studies revealed that P(SNS-PN) has an electronic band gap of 2.5 eV and exhibits electrochromic behaviour. The switching ability of polymer was also monitored. It was also found that P(SNS-PN) was fluorescent and its fluorescence intensity enhanced in the presence of cations. In the second part, novel tetrakis (4-(2,5-di-2-thiophen-2-yl-pyrrol-1-yl)) substituted metal-free (H2Pc-SNS), zinc (ZnPc-SNS) and nickel phthalocyanine (NiPc-SNS) complexes were synthesized and characterized by elemental analysis, FTIR and UV-Vis spectroscopies. The solution redox properties of these complexes were also studied by using CV and differential pulse voltammetry. All of the complexes showed two reversible reduction peaks having ligand-based character and one irreversible oxidation peak. Also, the electrochemical polymerization of these complexes was performed in dichloromethane/tetrabutylammonium perchlorate solvent/electrolyte couple. Resulting polymer films were characterized by UV&ndash / vis and FTIR spectroscopic techniques and their electrochemical behaviors were investigated utilizing CV. In-situ spectroelectrochemical investigations revealed that all the polymer films could be reversibly cycled and exhibit electrochromic behavior. Furthermore, the band gap of P(H2Pc-SNS), P(ZnPc-SNS) and P(NiPc-SNS) were calculated as 2.38 eV, 2.25 eV and 2.69 eV, respectively. Moreover, the fluorescence property of the P(ZnPc-SNS) was investigated in dimethyl sulfoxide and toluene.

Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : [56]-59).

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Different optical and calorimetric techniques were utilized to gain a better understanding of aggregated macromolecules. This research looked at two different macromolecules: poly(9,9'-dioctylfluorene), a conjugated polymer that forms aggregates in organic solvents; and bovine insulin, which forms amyloid fibrils. Conjugated polymers are of increasing interest due to their thermal stability and ease of solution processing for use in devices. A member of the polyfluorene family, poly(9,9'-dioctylfluorene) (PFO), has been studied due to its blue-emitting spectral properties. However, PFO has been found to form aggregates in solution, which is detected by the presence of a red-shifted absorption peak. This peak is caused when a section of the backbone planarizes forming the [beta]-phase. The [beta]-phase can be removed from the solution upon heating and will not return until the solution is cooled, making it a non-equilibrium process. The dissolution and reformation of the -phase were monitored using absorption spectroscopy and differential scanning calorimetry. Atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) were able to probe the aggregates in films. It is important to understand polymer properties in solution in order to understand film morphology. Amyloid fibrils contribute to over 20 different neurodegenerative diseases, in which cures have yet to be found. The fibrils form when a soluble protein misfolds and self-assembles to form insoluble protein aggregates, and the cause of the fibril formation in vivo has still yet to be determined. Spectroscopy studies have been made possible with the use of fluorescent dyes: thioflavin T (ThT), BTA-2, and Congo red (CR). These dyes bind to amyloid fibrils and exhibit changes in their spectral properties. However, the exact mechanism for the binding of these dyes has only recently been studied. Through the use of calorimetry, the forces involved with binding of ThT and CR to amyloid fibrils can be determined. Absorption and fluorescence spectroscopy techniques were employed to study the spectral properties of these dyes. Polarized NSOM was used to determine the ThT or BTA-2's orientation with an individual fibril. Understanding how these dyes bind to fibrils will enable researchers to use spectroscopy to study the early stages of fibril formation. / text

Autofluorescence spectroscopy can improve the early detections of oral cancer. Biochemical and structural changes associated with dysplastic progression alter the optical properties of oral mucosa and cause diagnostically significant differences in spectra from normal and neoplastic sites. This dissertation describes experimental and modeling studies aimed at revealing biological reasons for the diagnostically significant differences observed in depth-resolved fluorescence spectra from normal and neoplastic oral mucosa. An experimental approach, based on high-resolution fluorescence imaging, is used to study the autofluorescence patterns of oral tissue. At UV excitation, most of the epithelial autofluorescence originates from cells occupying the basal and intermediate layers, while stromal signal originates from collagen and elastin crosslinks. With dysplasia, epithelial autofluorescence increases, while autofluorescence from subepithelial stroma drops significantly. Benign lesions also display a drop in autofluorescence from subepithelial stroma, but have different epithelium fluorescence patterns compared to dysplasia. Optical probes that measure mostly stromal fluorescence, may reveal a similar loss of fluorescence intensity and thus fail to distinguish benign inflammation from dysplasia. These results emphasize the importance of using probes with enhanced detection of epithelial fluorescence for improved diagnosis of different types of oral lesions. The second part of this work presents a Monte Carlo model that predicts fluorescence spectra of oral mucosa obtained using a depth-selective probe as a function of tissue optical properties. A model sensitivity analysis determines how variations in optical parameters associated with neoplastic development influence the intensity and shape of spectra, and elucidates the biological basis for differences in spectra from normal and premalignant oral mucosa. Spectra of oral mucosa collected with the depthselective probe, are affected by variations in epithelial optical properties and to a lesser extent by changes in superficial stromal parameters, but not by changes in the optical properties of deeper stroma. Changes in parameters associated with dysplastic progression lead to a decreased fluorescence intensity and a shift of the spectra to longer emission wavelengths. Decreased fluorescence is due to a drop in detected stromal photons, whereas the shift of spectral shape is attributed to an increased fraction of detected photons arising in the epithelium.