Academic literature on the topic 'Total Internal Reflection Raman Spectroscopy'

Laser Raman spectroscopy has been used very effectively for some time to probe heterogeneous catalytic reactions in situ. TIR Raman is a variant of non-resonant Raman spectroscopy which uses a totally internally reflected light, i.e. an evanescent electric field acts as the excitation source. TIR Raman reduces or avoids some key limitations of bulk Raman spectroscopy, including reduction of laser induced sample damage. This thesis has therefore been investigating the possible application of TIR Raman spectroscopy to studying heterogeneous catalysts, in particular films of size controlled metal nanoparticle catalysts. Potential catalytic materials (such as platinum, supported either on optical elements or in mesoporous silica) were synthesised, characterised by techniques such as TEM, UV-VIS, deposited on substrates both at monolayer and thicker coverages, and subjected to both conventional and TIR Raman spectroscopy. This included a significant amount of synthetic development, in particular of copper nanoparticles. Results indicated that TIR Raman enables acquisition of spectra with improved sensitivity, compared to bulk Raman, below the damage threshold of the materials, even at low levels of surface coverage. Specifically, Raman bands indicating the presence and removal (by plasma cleaning) of organic capping agents on nanoparticles have been detected for a number of systems. This was not achieved using confocal Raman spectroscopy. This was extended to develop a system for studying gas/solid catalytic reactions in situ using a specially constructed gas cell to enable application of the technique under reaction conditions. Finally, the nanoparticles synthesised primarily for the TIR Raman study have also been demonstrated as catalysts in improving the understanding of several catalysed reactions, in particular direct amide bond formation from amines and alcohols, cascade oxidations, and selective furfural hydrogenation.

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.<br>Title from electronic title page (viewed Mar. 27, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.

The study of the binding between estrogen receptors (ER) and their ligands in vitro has long been of interest mainly because of its application in anti-estrogen drug discovery for breast cancer treatment as well as in the screening of environmental contaminants for endocrine disruptors. Binding strength was conventionally quantified in terms of equilibrium dissociation constant (KD). Recently, emphasis is shifting towards kinetics rate constants, and off-rate (koff) in particular. This thesis reported a novel method to measure such binding kinetics based on fluorescence polarization complemented with total internal reflection fluorescence (FP-TIRF). It used tethered receptors in a flow cell format. For the first time, the kinetics rate constants of the binding of full-length human recombinant ERα with its standard ligands were measured. koff was found to range from 1.3 10-3 to 2.3 10-3 s-1. kon ranged from 0.3 105 to 11 105 M-1 s-1. The method could also be used to screen potential ligands. Motivated by recent findings that ginsenosides might be functional ligands of nuclear receptors, eleven ginsenosides were scanned for binding with ER and peroxisome proliferator-activated receptor gamma (PPAR). None of the ginsenosides showed significant binding to ER, but Rb1 and 20(S)-Rg3 exhibited significant specific binding with PPAR.

The accurate and safe diagnosis of breast cancer is a significant societal issue, with annual disease incidence of 48,000 women and around 370 men in the UK. Early diagnosis of the disease allows more conservative treatments and better patient outcomes. Microcalcifications in breast tissue are an important indicator for breast cancers, and often the only sign of their presence. Several studies have suggested that the type of calcification formed may act as a marker for malignancy and its presence may be of biological significance. In this work, breast calcifications are studied with FTIR, synchrotron FTIR, ATR FTIR, and Raman mapping to explore their disease specific composition. From a comparison between vibrational spectroscopy and routine staining procedures it becomes clear that calcium builds up prior to calcification formation. Raman and FTIR indicate the same size for calcifications and are in agreement with routine staining techniques. From the synchrotron FTIR measurements it can be proven that amide is present in the centre of the calcifications and the intensity of the bands depends on the pathology. Special attention is paid to the type of carbonate substitution in the calcifications relating to different pathology grades. In contrast to mammography, Raman spectroscopy has the capability to distinguish calcifications based on their chemical composition. The ultimate goal is to turn the acquired knowledge from the mapping studies into a clinical tool based on deep Raman spectroscopy. Deep Raman techniques have a considerable potential to reduce large numbers of normal biopsies, reduce the time delay between screening and diagnosis and therefore diminish patient anxiety. In order to achieve this, a deep Raman system is designed and after evaluation of its performance tested on buried calcification standards in porcine soft tissue and human mammary tissue. It is shown that, when the calcification is probed through tissue, the strong 960 cm-1 phosphate band can be used as a pseudo marker for carbonate substitution which is related to the pathology of the surrounding tissue. Furthermore, the first study in which human breast calcifications are measured in bulk tissue with a thickness of several millimetres to centimetres is presented. To date, measurements have been performed at 41 specimens with a thickness up to 25 mm. Measurements could be performed through skin and blue dye. The proposed deep Raman technique is promising for probing of calcifications through tissue but will need refinement before being adopted in hospitals.

This thesis focuses on investigations of transient dark states of fluorescentmolecules using spectroscopic techniques. The main purpose is to show andconvince the reader that transient dark states are not always a nuisance, butalso represent an additional source of information. Several studies with fluorescencecorrelation spectroscopy were performed, all related to non-fluorescentstates such as triplet state or isomerized states.Photobleaching is one of the main problems in virtually all of the fluorescencetechniques. In this thesis, mechanisms that retard photobleaching arecharacterized. Several compounds, antioxidants and triplet state quenchers,which decrease photobleaching, are studied, and guidelines for achieving optimalfluorescence brightness using these compounds are presented.Triplet state quenching by several compounds was studied. Detailed investigationsof the fluorescence quencher potassium iodide demonstratedthat for some of fluorophores, except of quenching, there is fluorescence enhancementmechanism present. In agreement with the first publication inthis thesis, antioxidative properties were found to play an important role inthe fluorescence enhancement. Quenching of the triplet state is proposedas a tool for monitoring diffusion mediated reactions over a wide range offrequencies.Specially designed fluorophores combining high triplet yields with reasonablefluorescence brightness and photostability were characterized forpossible applications in novel super-resolution imaging techniques based onfluorescence photoswitching. Except of benefits for imaging techniques, photoinducedswitching to non-fluorescent states could be used for monitoringmolecular diffusion, which was also demonstrated in this thesis.Studies of the triplet state kinetics of fluorophores close to dielectric interfaceswere performed using fluorescence spectroscopy. The analysis of thetriplet state kinetic can provide information about the local microenvironmentand electrostatic interactions near dielectric interfaces.<br>QC 20100414