Anthracene sensitized delayed fluorescence

Fig. 33. Dependence of the rhodamine sensitized delayed fluorescence in anthracene on the magnetic field oriented parallel to the 001 surface of anthracene. (2 x 10-7 M rhodamine and 10 1 NaHSC>3 in aqueous solution) 9°)...

There are two mechanisms by which the sensitized delayed fluorescence from anthracene can be produced ... 

Fig. 22. Sensitized delayed fluorescence spectra of anthracene in 10 SM phenan-threne solution.38 Intensity of exciting light was approximately 2.7 X 10-8 einstein cm. 2 sec. 1 at 3.19m-1 (313 dim)- Delayed emission spectra with anthracene concentrations of (1) 10 8Af, (2) 5 X 10 W, (3) 10-W, (4) 10- M, (5) 10 9M. Curve (6) Fluorescence emission spectrum of solution 1 at 260 times less sensitivity. (Owing to variation in the shapes of the cylindrical optical cells, the relative intensities of the delayed emission are only approximately proportional to 9A/fF.)...

Fig. 23. Sensitized delayed fluorescence of naphthacene. 5 X 10-5M anthracene and 10 W naphthacene in ethanol at 20°C. Rate of light absorption was approximately 4 X 10- einstein liter-1 sec. L at 366 m/i. (a) Fluorescence at sensitivity 1X. (6) Delayed fluorescence at sensitivity 3300X.

Fig. 17. Delayed fluorescence spectrum of 5 X 10-63/ anthracene in ethanol.84 Half-bandwidth of analyzing monochromator was 0.05 ju-1 at 2.5 n K Intensity of exciting light was approximately 1.4 X 10 einstein cm. a sec.-1 at 2.73m-1 (366 mju). (1) Normal fluorescence spectrum (distorted by self-absorption). (2) Delayed emission spectrum at sensitivity 260 times greater than for curve 1. (3) Spectral sensitivity of instrument (units of quanta and frequency).

Fig. 26. Sensitized anti-Stokes delayed fluorescence from anthracene.60 Normal fluorescence (curve 1) and delayed fluorescence (curve 2) from a solution containing 10- Af proflavine hydrochloride and 5 X 10-4M anthracene in ethanol excited by 436 m/ , 3 X 10-4 einstein liter-1 sec.-1 absorbed. Curve 1 at a sensitivity 3000 times less than curve 2. Temperature was — 66°C. 3°C.

Sensitized P-Type Delayed Fluorescence phenanthrene/anthracene, anthracene/naphthacene, phenanthrene/naphthalene, proflavine hydro-chloride/anthracene. Undoubtedly, many more examples will soon be found. 

This phenomenon is possible in molecules like naphthalene, anthracene and Pyrene, each of which happens to have the lowest singlet energy level about twice hat of the respective triplet. For the generation of these triplets in high concentrations (T — T) type energy transfer from a suitable donor is necessary. Delayed fluorescence in naphthalene has been sensitized by phenanthrene. according to the following scheme ... 

In the last study it was shown that the ODMR lineshape is a sensitive detector of the mobility of triplet excitation in crystals. An extensive study has been reported on the spin-forbidden non-radiative decay of anthracene, acridine, and phenazine using delayed fluorescence detection of magnetic resonance.383 It was shown that, in anthracene, the spin states Tx and Ty (axis system is x long axis,... 

Excitation fluorescence is the principle of the fluorescence techniques used for studying polymer blends. The method comprises of three steps incorporation of an excimer, its excitation, and recording the excitation delay. The excimer can be an aromatic polymer component of the blend (viz., PS, poly(viny 1-dibenzyl), polyvinylnaphthalene, an aromatic group grafted onto the macromolecular chain, etc.), or it can be added as probe molecule (e.g., anthracene). There are three possibilities for the aromatic rings to form excimers intramolecular adjacent, intramolecular nonadjacent, and intermolecular types. Each of these types is sensitive to different aspects of the chain conformation and environment, thus, sensitive to blend miscibility effects. The most important of these for studies of polymer blends is the intermolecular, usually identified from concentration measurements (Wiruiik et al. 1988). 

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