Fluorescence molecular

Figure C 1.5.13. Schematic diagram of an experimental set-up for imaging 3D single-molecule orientations. The excitation laser with either s- or p-polarization is reflected from the polymer/water boundary. Molecular fluorescence is imaged through an aberrating thin water layer, collected with an inverted microscope and imaged onto a CCD array. Aberrated and unaberrated emission patterns are observed for z- and xr-orientated molecules, respectively. Reprinted with pennission from Bartko and Dickson [148]. Copyright 1999 American Chemical Society.

UV molecular absorption Vis molecular absorption molecular fluorescence IR molecular absorption IR molecular absorption IR molecular absorption atomic absorption molecular fluorescence... 

The basic design of instrumentation for monitoring molecular fluorescence and molecular phosphorescence is similar to that found for other spectroscopies. The most significant differences are discussed in the following sections. 

Molecular Fluorescence A typical instrumental block diagram for molecular fluorescence is shown in Figure 10.45. In contrast to instruments for absorption spectroscopy, the optical paths for the source and detector are usually positioned at an angle of 90°. 

The sample cells for molecular fluorescence are similar to those for optical molecular absorption. Remote sensing with fiber-optic probes (see Figure 10.30) also can be adapted for use with either a fluorometer or spectrofluorometer. An analyte that is fluorescent can be monitored directly. For analytes that are not fluorescent, a suitable fluorescent probe molecule can be incorporated into the tip of the fiber-optic probe. The analyte s reaction with the probe molecule leads to an increase or decrease in fluorescence. 

Molecular fluorescence and, to a lesser extent, phosphorescence have been used for the direct or indirect quantitative analysis of analytes in a variety of matrices. A direct quantitative analysis is feasible when the analyte s quantum yield for fluorescence or phosphorescence is favorable. When the analyte is not fluorescent or phosphorescent or when the quantum yield for fluorescence or phosphorescence is unfavorable, an indirect analysis may be feasible. One approach to an indirect analysis is to react the analyte with a reagent, forming a product with fluorescent properties. Another approach is to measure a decrease in fluorescence when the analyte is added to a solution containing a fluorescent molecule. A decrease in fluorescence is observed when the reaction between the analyte and the fluorescent species enhances radiationless deactivation, or produces a nonfluorescent product. The application of fluorescence and phosphorescence to inorganic and organic analytes is considered in this section. 

Selectivity The selectivity of molecular fluorescence and phosphorescence is superior to that of absorption spectrophotometry for two reasons first, not every compound that absorbs radiation is fluorescent or phosphorescent, and, second, selectivity between an analyte and an interferant is possible if there is a difference in either their excitation or emission spectra. In molecular luminescence the total emission intensity is a linear sum of that from each fluorescent or phosphorescent species. The analysis of a sample containing n components, therefore, can be accomplished by measuring the total emission intensity at n wavelengths. 

Molecular fluorescence is a more complicated phenomenon than atomic fluorescence (e.g., x-ray fluorescence). In molecular fluorescence, energy changes in the vibrational and rotational motions are involved, in addition to the electronic transitions. 

H H Willard, L L Merritt, J R Dean and F A Settle, Instrumental methods of analysis, Molecular Fluorescence and Phosphorescence Methods, 6th edn, Van Nostrand Reinhold, New York, 1981, Chapter 5... 

The active state of luminescence spectrometry today may be judged ly an examination of the 1988 issue of Fundamental Reviews of Analytical Chemistry (78), which divides its report titled Molecular Fluorescence, Phosphorescence, and Chemiluminescence Spectrometry into about 27 specialized topical areas, depending on how you choose to count all the subdivisions. This profusion of luminescence topics in Fundamental Reviews is just the tip of the iceberg, because it omits all publications not primarily concerned with analytical applications. Fundamental Reviews does, however, represent a good cross-section of the available techniques because nearly every method for using luminescence in scientific studies eventually finds a use in some form of chemical analysis. Since it would be impossible to mention here all of the current important applications and developments in the entire universe of luminescence, this report continues with a look at progress in a few current areas that seem significant to the author for their potential impact on future work. 

Detection in CC may be visually for coloured compounds. Different methods can be used to monitor colourless compounds (collecting fractions addition of an inorganic phosphor to the column adsorbent). The detector choice is quite limited, with UV, RI and molecular fluorescence (F) emission being the most popular. A fluorescent column adsorbent is extremely... 

Resch-Genger U, Grabolle M, Nitschke R, Nann T (2010) Nanocrystals and nanoparticles vs. molecular fluorescent labels as reporters for bioanalysis and the life sciences. A critical comparison. In Demchenko AP (ed) Advanced Fluorescence Reporters in Chemistry and Biology II. Springer Ser Fluoresc 9 3—40... 

Valeur B (2002) Molecular fluorescence principles and applications. Wiley-VCH, Wein-heim, Germany... 

Arimori S, Bell ML, Oh CS et al (2001) Molecular fluorescence sensors for saccharides. Chem Commun 18 1836—1837... 

Molecular Fluorescence Spectroscopy Photometric Titrations Analytical Applications of Interferometry Vol. 9 Ultraviolet Photoelectron and Photoion Spectroscopy... 

Yaleur, B. (2002). Molecular Fluorescence Principles and Applications. Wiley-VCH, New York. 

Valeur B., Molecular Fluorescence, Wiley-VCH, Weinheim, Germany, 2001. 

McGown, L.B., and Warner, I.M. (1990) Molecular fluorescence, phosphorescence, and chemiluminescence spectroscopy. Anal. Chem. 190, 255R. 

R.A. Bissell, AT. de Silva, H.QN. Gunaratne, P.LM. Lynch, G.EM. Maguire, K.R.A.S. Sandanayake, Molecular fluorescent signalling with fluor-spacer-receptor systems - approaches to sensing and switching devices via supramolecular photophysics , Chem. Soc Rev. 1992, 21, 187-195. 

Molecular fluorescence is a powerful tool for analysis and has many applications in chemistry, biological chemistry and in the health sciences. The schematic instrumental geometry is shown in Fig. 9.4. 

In addition to the spectrophotometric method discussed in section 12.1.1.1 Aznarez et al. [2] have described a method based on the molecular fluorescence of boron with dibenzoylmethane. The preliminary soil digestion and extraction procedures are identical to those described earlier. The reactive fluorescence intensity of the boron complex is measured at 400nm with excitation at 390nm and quinine sulphate as reference. 

Nanocrystals and Nanoparticles Versus Molecular Fluorescent Labels as Reporters for Bioanalysis and the Life Sciences ... 

Nanocrystals and Nanoparticles Versus Molecular Fluorescent Labels... 

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