Luminescence shift

For cyclic oxidation, the roughness of the TOO increases with thermal cycles, and the interfacial separation gradually accumulates as a result of TOO rumpling (Fig. 15) [88]. Concurrently, the cracks and rumpling cause a steady decrease of the stresses in the TOO. It should be emphasized that the magnitude of the luminescence shift alone is insufficient to characterise the degradation of the TGO-BC interface, since the stresses in the TGO also depend on processing parameters, temperatures, bond coat, TGO microstructure etc [88]. For this reason, no unique relationship currently exists between the absolute value of the shift and the cyclic life. 

The luminescence spectrum of yellow sillimanite at 300 K is characterized by a broad band in the red with a half-width (A) of 100 nm peaking at approximately 765 nm with a very long decay time of 3.8 ms (Fig. 5.80a). At 77 K the luminescence shifts to 760 nm and narrows (A = 80 nm) (Fig. 5.80b). This luminescence excitation has two maxima situated at 450 and 590 nm (Fig. 5.80c) (Gaft et al. 2012). Such broad band luminescence with long decay time found in yellow and brown samples is typical for forbidden d-d electron transitions in a Fe center in tetrahedral coordination. The luminescence is coimected to the forbidden " Ti(G)- Ai(S) electronic transition, whereas the excitatimi arises from the... 

The changes in the Imninescence A.max during the TMOS sol-gel processes depend on the catalytic conditions (Matsui, 1997) as shown in Figure 20-15. The change in the A.max is slower for the acidic system than for the basic system. Gelation times were a 1/2, 2, and 6 days from the initial mixing for the basic, neutral, and acidic samples. The large luminescence shift is seen on the next day after preparation for the basic sample while the shift is completed more than 10 days after preparation for the acidic sample. 

P.D. Horn and Y.M. Gupta, Wavelength Shift of the Ruby Luminescence R Lines Under Shock Compression, Appl. Phys. Lett. 49, 856-858 (1986). 

For copolymers of structure I, for both types of side-chains, there is a striking similarity with the optical properties of the corresponding models the absorption and photoluminescence maxima of the polymers arc only 0.08-0.09 eV red-shifted relative to those of the models, as shown in Figure 16-9 (left) for the octyloxy-substituted compounds. The small shift can be readily explained by the fact that in the copolymers the chromophorcs are actually substituted by silylene units, which have a weakly electron-donating character. The shifts between absorption and luminescence maxima are exactly the same for polymers and models and the width of the emission bands is almost identical. The quantum yields are only slightly reduced in the polymers. These results confirm that the active chro-mophores are the PPV-type blocks and that the silylene unit is an efficient re-conjugation interrupter. 

A comparison of the absorption and emission spectra of Ooct-OPV5 with those of the fully conjugated, similarly substituted polymer Ooct-PPV shows that the absorption and luminescence maxima of the five-ring model compound are only slightly blue-shifted relative to those of the polymer (see Fig. 16-11). Hence, the... 

The bioluminescence systems of Phengodidae (railroad worms) and Elateroidae (click beetles) are basically identical to that of Lampyridae (fireflies), requiring firefly luciferin, ATP, Mg2+ and a luciferase for light emission. However, there seem to be some differences. Viviani and Bechara (1995) reported that the spectra of the luminescence reactions measured with the luciferases of Brazilian fireflies (6 species) shift from the yellow-green range to the red range with lowering of the pH of the medium, like in the case of the Photinus pyralis luciferase (see Section 1.1.5), whereas the spectra... 

Another notable feature of the in vivo bacterial luminescence is seen in their emission spectra. Although the emission peak of in vitro bacterial luminescence is normally at about 490 nm, the in vivo emission peaks of various bacterial species and strains are significantly shifted from 490 nm, ranging from the shortest wavelength of 472 nm to over 500 nm. Some expanded notes concerning in vivo bacterial luminescence are given below. 

The second procedure is to measure the luminescence intensities at various Ca2+ concentrations and plot log (light intensity) against —log [Ca2+] for each aequorin. Examples of this method are shown in Fig. 4.1.14. This method provides more detailed information on the sensitivity of each aequorin. Generally, an increase in Ca2+ sensitivity shifts the curve to the left. 

Fig. 7.3.2 Comparison between the in vivo luminescence spectrum of a freshly exuded slime of Diplocardia longa and the in vitro luminescence spectrum measured with partially purified preparations of Diplocardia luciferin and luciferase. Reproduced from Bellisario et al., 1972, with permission from the American Chemical Society. Note that the in vitro emission maximum shifts to 490 nm when a sample of pure luciferin is used (Ohtsuka et al., 1976).

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