Excimer intensity

Figure 6. Comparison of excimer intensity for free and tagged pyrene in novolac films. Film composition ( ) free pyrene in novolac (A) pyrene tagged novolac (o) 19.6 mol% pyrene tagged novolac mixed with untagged novolac. The inset is an expansion of the graph for low pyrene concentrations.

Fig. 14 Plot of polarity parameter (h/h) and excimer intensity of pyrene at various concentrations of BC-20 (CMC = 8.0 x 10 M, Cjviex = 5.0 x 10 M)...

Figure 10. Excimer intensity of polymer bonded pyrenyl groups. Film 1 ( ), Film 2 (o), excitation at 344 nm. "Reproduced with permission from Ref. 17.

Solvent Degree of, Esterificationz Absorption Spectrum Excimer Intensity Fe/Fm Contact Angle to Water (°)... 

Figure 14. Plots of + and excimer intensity versus the concentration of (l -pyrenyUmethyl acetate. < cv+ (o) (The reaction conditions are the same as Table IV, run 4), Fe/Fm in the absence of LCV ( ). "Reproduced with permission from Ref 17. Copyright 1983, John Wiley Sons, Inc. "...

Finally, we performed similar experiments for the various copolymers. As shown in Figure 12 for one of the copolymers, despite a large (70%) decrease in excimer intensity, the thermal behavior is qualitatively identical, and an Arrhenius plot of the monomer intensity data. Figure 13, gives the same activation energy, vl30-150cm . ... 

Excimer Emission and CPF Spectra Fluorescence spectra of the two polypeptides in TMP solution are shown in Figure 7 (lower curves). Small excimer emissions are observed in the two polymers. The monomer/excimer intensity ratio was independent of the polymer concentration at least down to [pyr] = 1x10 mol L, suggesting an intramolecular character of the excimer. Since the interchromo-phore distances in the most probable conformations predicted from the conformational energy calculation are much longer than the exci-mer-forming distance, the excimers should be formed at the point where conformations of the main chain and/or the side chain are largely distorted. 

The addition of -CD to an aqueous naphthalene solution caused the growth of its molecular fluorescence and the appearance of excimer emission [130]. By lowering the temperature of the solution, the excimer intensity grew at the expense of that of the monomer. The excimer emission was attributed to the association of 1 1 complexes to give 2 2 / -CD-naphthalene inclusion compounds. In air-saturated solutions, the three species have the following lifetimes 40 ns (free naphthalene), 48 ns (1 1 complex), and 68 ns (2 2 complex). The quenching rate constants derived from these lifetimes by the addition of I" were 6x 10 dm mol s , 3.9x 10 dm mol s , and 1.8 x 10 dm mol s , respectively, which confirmed the protection furnished by the cavity to the included molecules. 

From the practical point of view, the ratio of monomer to excimer intensity has been used very frequently ... 

Pyrene Monomer and Excimer Emission. The emission of locally isolated excited pyrenes ( monomer emission, intensity Im) is characterized by a well-resolved spectrum with the [0, 0] band at 378 nm. The emission of pyrene excimers (intensity Ie), centered at 480 nm, is broad and featureless. Excimer formation requires that an excited pyrene (Py ) and a pyrene in its ground state come into close proximity within the Py lifetime. The process is predominant in concentrated pyrene solutions or under circumstances where microdomains of high local pyrene concentration form, even though the total pyrene concentration is very low. This effect is shown for example by... 

Hydrophobic association is also enhanced in polymer systems. Although polymer surfactants are considered to form micelles via intrapolymer hydrophobic interaction, our recent study (2r,s) revealed that a polyionene bearing anthryl groups as the hydrophobic domain showed a clear cmc UHtical micelle concentration) at the segment concentration around 3 x 10 5m. Reference experiments with a polyionene without anthryl groups and the monomer and dimer model compounds have indicated that the cmc is particularly low for the polymer. Taking the excimer intensity of anthracene fluorescence as an index of interchromophore interaction, we confirmed the existence of interpolymer association by the concentration dependent excimer intensity. Under the same condition to the polymer, any model systems either monomeric or dimeric do not associate intermolecularly. 

The interpolymer association is a distinctively different property of exciplex forming polymers from that of excimer forming polymers. The reason must be attributed to the presence of the ground state interaction in the former polymers. Interpolymer excimer formation is, however, facilitated by the aid of hydrophobic interaction in water. Polyionenes bearing anthryl groups (J2) form both inter- and intrapolymer excimer in water (2s). The excimer intensity decreases with increasing hydrophobic interaction. All experimental results indicate that weak intermolecular interactions almost undetectable in small molecule systems are amplified enormously in polymer systems in dilute solutions. 

The polyesters bearing 1-naphthyl or 9-anthryl groups exhibit concentration dependence in their excimer intensity in the concentration region of 10 2m. The concentration dependence is stronger than that of the monomer or dimer model compounds indicating the participation... 

The meso and racemic isomers of III Fig. 31 exhibit some important differences in fluorescence behaviour. In the rac nic comiKmnd excimer intensity is smaller than that in the meso, and the IdAm the meso ccmpound is wavelength depend ,... 

The fluorescent probe methods were used to determine miCToviscosity (T ,) of potassium A-acylalaninates and potassium A-acylvalinates micelles. The results obtained show that 11 on the micellar surface is larger in A-acylalaninates than in 7V-acylvalinates, whereas in the micellar core remains same in the micelles of the two surfactant series. The values of 11 of SDS, lithium dodecyl sulfate (LDS), CTACl, and CjjEg, determined at 15°C by monomer/excimer intensity ratio and excimer lifetime of dipyrenylpropane dissolved in micelles, are 19, 19, 39, and 57 cP, respectively. The fluorescent probe technique was used to determine r m values of SDS, CTABr, and CTACl micelles at different applied pressure. The derived values of SDS, CTABr, and CTACl micelles at 25°C and atmospheric pressure are 12,47, and 27 cP, respectively. The addition... 

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