Pyrene phosphorescence emission

Figure 14. Phosphorescence emission of pyrene on decanol covered silica gel surface at 60°K. The excitation wavelength 360 nm.

A significant property of Stmcture 6 is the intercalation of polycyclic arenes to form binary stacks of alternating 6 and arene. The stmcture of the mixed stack of 6 and pyrene is shown in Fig. 5. The photophysical properties of these compounds are significant, and the binary stacked compounds with pyrene, naphthalene, and biphenyl exhibit strong phosphorescent emissions in the red. green, and blue regions, respectively. ... 

Another factor affecting phosphorescent emission of 4 and 5 may be the different dilution degrees in 4 and 5 as stated in the cocrystal structures section. The A B B A- B - B arrangement in 5 imphes a lower concentration than the A B A B arrangement in 4, resulting in a more efficient prevention of the pyrene-pyrene interactions in 5, as can be seen from Figs. 4 and 5, and thus stronger phosphorescent emission is observed for 5. 

P-type delayed fluorescence is so called because it was first observed in pyrene. The fluorescence emission from a number of aromatic hydrocarbons shows two components with identical emission spectra. One component decays at the rate of normal fluorescence and the other has a lifetime approximately half that of phosphorescence. The implication of triplet species in the mechanism is given by the fact that the delayed emission can be induced by triplet sensitisers. The accepted mechanism is ... 

Kim and Webber studied delayed emission spectra of poly(vinyl carbazole) that was doped with dimethylterephthalate and pyrene [252]. On the basis of their results, they concluded that at room temperature dimethylterephthalate does not completely quench the triplet excitation state of poly (vinyl carbazole). They also concluded that phosphorescent states of poly(vinyl carbazole)-dimethylterephthalate are similar, implying a significant charge-transfer character in the former. 

Bradley et al. [69] have extended the sonochemical polymer latex formation technique to synthesise fluorescent and phosphorescent latex particles. The method, schematically shown in Fig. 2.9, simply involved the ultrasonic emulsification of methylmethacrylate monomer in an aqueous surfactant solution where a fluorescence or phosphorescent solute was pre-dissolved in the monomer phase. When pyrene was used as a fluorescent solute, the dielectric constant of the latex particles could be evaluated. Due to the incorporation of the fluorescence solutes into the polymer latex matrix, the interaction between excited state and ground state monomer could be avoided resulting in the lack of dimer emission and domination of monomer emission. 

Using the ratio between band intensities of pyrene emission at specific wavelengths, the dielectric constant of the latex could he evaluated. Phosphorescent poly-MMA particles were also produced using 1-hromonaphthalene. 

Excimer fluorescence is often observed from 2 1 complexes (structure VII or VIII) [10] and 2 2 complexes (structure X) [11,12] of pyrene and naphthalene derivatives. Also, intramolecular exciplex emission from 1 1 complex of the structure in [21] and room temperature phosphorescence or exciplex emission from 1 1 1 (structure IX) and 1 1 2 (structure XI) ternary complexes have been reported [22]. Systems exhibiting the room temperature emission were recently reviewed [22]. 

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