Fluorescence yield advantage

Besides the impressive difference in the chemiexcitation efficiency, also the fluorescence yield of the meta-pattemed emitter m-17 is by more than an order of magnitude ( ) higher than that of the para regioisomer p-17 . Evidently, crossed-conjugated emitters are advantageous for the design of efficient intramolecular CIEEL systems. In Sections V.A-V.C we shall consider additional internal (substrate structural effects) and external (medium influence) factors, which play an essential role in the development of efficient dioxetane-based analytical probes. 

Fluorescent photon counting is an alternative to electron yield (EY) [41]. The strongest advantage of fluorescence yield (EY) is that the mean free path of photons through solids is much longer than that of electrons. Therefore, EY mode reveals x-ray absorption from deeper into the film bulk ( 100 mn) than EY modes can measure (=10 nm). A comparison of EY and FY NEXAFS spectra can reveal surface... 

Sensitivity levels more typical of kinetic studies are of the order of lO molecules cm . A schematic diagram of an apparatus for kinetic LIF measurements is shown in figure C3.I.8. A limitation of this approach is that only relative concentrations are easily measured, in contrast to absorjDtion measurements, which yield absolute concentrations. Another important limitation is that not all molecules have measurable fluorescence, as radiationless transitions can be the dominant decay route for electronic excitation in polyatomic molecules. However, the latter situation can also be an advantage in complex molecules, such as proteins, where a lack of background fluorescence allow s the selective introduction of fluorescent chromophores as probes for kinetic studies. (Tryptophan is the only strongly fluorescent amino acid naturally present in proteins, for instance.)... 

Water-based flexo inks can be formulated with either a soluble toner or with the Day-Glo EPX Series which is a tme pigment and can be formulated like a conventional pigment dispersion. The Radiant Aquabest or the Day-Glo WST can be formulated in an alkaline water-soluble system to yield strong inks. They have limited shelf life and inferior fade, but do not necessarily requite additional binder. Day-Glo EPX must be formulated with a binder such as a hard resin or can be used with one of the soluble toners such as WST. The EPX Series has several advantages over soluble toners such as much superior fade, exceUent ink stabiHty, and some hiding power over kraft-type papers. A disadvantage of the EPX is its lower tinctorial strength than other fluorescent toners. 

A major advantage of fluorescence as a sensing property stems from the sensitivity to the precise local environment of the intensity, i.e., quantum yield (excited state lifetime (xf), and peak wavelength (Xmax). In particular, it is the local electric field strength and direction that determine whether the fluorescence will be red or blue shifted and whether an electron acceptor will or will not quench the fluorescence. An equivalent statement, but more practical, is that these quantities depend primarily on the change in average electrostatic potential (volts) experienced by the electrons during an electronic transition (See Appendix for a brief tutorial on electric fields and potentials as pertains to electrochromism). The reason this is more practical is that even at the molecular scale, the instantaneous electric... 

In this chapter, it was shown that filterFRET is an easy, intuitive and quantitative alternative to record sensitized emission and FRET efficiency. The major advantages of filterFRET over donor-based FRET detection methods (FLIM) are that it can be carried out with standard wide-held or confocal fluorescence microscopes that are available in most laboratories, and that it yields additional data on the acceptor population. FilterFRET is also fast, requiring just two confocal scans (if need be on a line-by-line basis) which minimizes the risk of artifacts due to, for example, organelle movement in living cells, and acquisition can be optimized for each channel independently. However, quantitative... 

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