Fluorescence spectroscopic information

FBAs can also be estimated quantitatively by fluorescence spectroscopy, which is much more sensitive than the ultraviolet method but tends to be prone to error and is less convenient to use. Small quantities of impurities may lead to serious distortions of both emission and excitation spectra. Indeed, a comparison of ultraviolet absorption and fluorescence excitation spectra can yield useful information on the purity of an FBA. Different samples of an analytically pure FBA will show identical absorption and excitation spectra. Nevertheless, an on-line fluorescence spectroscopic method of analysis has been developed for the quantitative estimation of FBAs and other fluorescent additives present on a textile substrate. The procedure was demonstrated by measuring the fluorescence intensity at various excitation wavelengths of moving nylon woven fabrics treated with various concentrations of an FBA and an anionic sizing agent. It is possible to detect remarkably small differences in concentrations of the absorbed materials present [67]. 

In protein molecules with two or more tryptophan residues, it is necessary to obtain first the fluorescence decay curves for the individual residues. For this purpose, additional spectroscopic information is necessary. One can use the dependence of the decay curves on emission wavelength, apply selective fluorescence quenchers, or selectively modify one of the tryptophan residues. The results of Brochon et al. for the lac repressor(44) and those of Beechem et al. for alcohol dehydrogenase(45) provide evidence in favor of such approaches. 

It would be elegant to finish the part on photophysics and photochemistry of liquid alkanes by giving a picture that unifies the temperature- and energy-dependence results obtained in fluorescence and photodecomposition studies. However, the spectroscopic information available for alkane molecules is not sufficient to identify the exact excited states involved in the radiative and nonradiative processes [55]. Because of the lack of information, there are different views on the positions and identities of excited states involved [52,55,83,121,122]. 

In this work we investigate such interactions by fluorescence spectroscopy. Probe molecules such as 2-naphthol and its 5-cyano-derivative are effective chromophores for studying acid/base interactions since both are relatively strong photo-acids. In addition, 2-naphthol is a common solute for which SCF solubility and physical property data exist. Ultimately, spectroscopic information will be used to develop a clearer picture of the specific interactions which induce large cosolvent effects on solubility in SCF solutions. 

D-Fluorescence spectroscopic analysis has also been used for analysis of terrestrial and aquatic HS. Figure 16.40 shows an example of topographic and contour plot of 3D-fluorescence spectrum. In this case, the Fluorescence spectroscopy involved scanning and recording 17 individual emission spectra (260-700 nm) at sequential 10-nm increments of excitation wavelength between 250 and 410 nm (Parlanti et al., 2002). The authors used this technique to obtain structural information about HS and also used it in studies concerning their transformation processes. They reported that there were five major fluorescent components in bulk seawater based on 3D-fluorescence spectroscopy. They defined a and a (excitation at 330-350 nm and emission at 420-480 nm excitation at 250-260 nm and emission at... 

Given the challenges that are associated with creating BPs that can deliver active proteins and/or diversified xerogel-based sensor platforms for chemical sensor applications, we have developed automated systems that can rapidly prepare large numbers of BP or xerogel-based materials and rapidly obtain fluorescence-based spectroscopic information from these formulations. Ultimately, these laboratory... 

To obtain spectroscopic information, the radiant power transmitted, fluoresced, or emitted must be detected in some manner and converted into a measurable quantity. A detector is a device that indicates the existence of some physical phenomenon. Familiar examples of detectors include photographic film (for indicating the presence of electromagnetic or radioactive radiation), the pointer of a balance (for indicating mass differences), and the mercury level in a thermometer (for indicating temperature). The human eye is also a detector it converts visible radiation into an electrical signal that is passed to the brain via a chain of neurons in the optic nerve and produces vision. 

For the Advances in Photochemistry audience, familiarity with simple absorption and fluorescence spectroscopic principles is assumed. However, the beginning of the chapter reviews the basics of DNA structure and provides background information from other powerful techniques such as X-ray diffraction and nuclear magnetic resonance (NMR) experiments. Although these tech-... 

Essentially the spectroscopic information in this region arises from atomic and molecular transitions involving both inner and outer electrons together with vibrational transitions and rotational fine structure. In principle, the spectroscopic processes of emission, absorption, luminescence, and scattering should all be covered. Within the scope of these four topics, discussion will be confined to the UV-visible (absorption and fluorescence), the near-infrared... 

Sensitivity depends on the relative intensities of the analyte Raman bands compared with overlapping, interfering Raman bands and emissions from the sample. Raman analysis is often hindered by fluorescence by the sample or impurities with the laser excitation line being used. Fluorescence occurs when the excitation line is partially absorbed and reemitted. The quantum yield of the fluorescence process is often several orders of magnitude higher than that of the Raman process, and thus any useful spectroscopic information is lost, cfr. Fig. 1.19). Fluorescence interference does not normally occur in condensed phases with UV excitation wavelengths below 260 nm [357]. There is no single solution to the fluorescence problem in Raman spec-... 

Laser-induced fluorescence data provide a wide variety of detailed information about physical and chemical reactions. Laser-based time-resolved (picosecond) fluorescence spectroscopic techniques have been used to investigate the mechanism of photo-stabilisation by UVAs such as benzophenones, ben-zotriazoles and polymer-bound UV stabilisers [117]. Such ultrafast spectroscopic measurements can provide insight into the dynamics of the primary energy dissipation processes in polymers and polymer additives following light absorption. Excimer LIF spectra of plasticised PVC showed two distinct regions... 

Volume n/24 presents the spectroscopic data on diamagnetic and paramagnetic molecules as well as on molecular ions and radicals up to date considering the publications up to and partly including 1997. The spectroscopic information collected in this volume has been obtained principally from gas phase microwave measurements. In addition, gas phase data have been included derived from methods related to microwave spectroscopy by employing a coherent radiation source. These are molecular beam techniques, radio frequency spectroscopy, electron resonance spectroscopy, laser spectroscopy, double resonance and saturation techniques. Some other methods are considered if the accuracy of the derived molecular parameters is comparable to that of microwave spectroscopy owing to a good statistics in the analysis of data, and no microwave data are available. Examples would be Fourier infrared spectroscopy or laser induced fluorescence. 

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