Phosphorescence liquid crystals

FIGURE 10.7 Power consumption simulation for a 2.2-in. full-color OLED display using Universal Display s phosphorescent OLEDs, small-molecule fluorescent devices, and polymer OLEDs along with a comparison of the power consumed by an active-matrix liquid crystal display backlight. R G B= 3 6 1, 50% polarizer efficiency, and 30% of pixels lit. (From Mahon, J.K., Adv. Imaging, June, 28, 2003. With permission.)... 

Self-assembly of Pt(II) complexes yielding luminescent liquid crystals (210,211,274) and AIE (275-279) have been already described, but metal complexes forming soft structures with such intense phosphorescence are very rare. 

The most straightforward way to produce partially oriented solute molecules is to orient them in anisotropic solvents. Good solute orientation can be achieved in stretched polymer sheets [94, 95, 96]. Homogeneously oriented nematic liquid crystals are perfectly clear and are thus excellently suited as anisotropic solvents for optical polarization experiments. Moreover, the liquid crystal method allows the performance of polarization experiments in fluid media. This unique feature of the liquid crystal method can be exploited for polarization studies of metastable molecular species (e.g. excited complexes) formed by a diffusion-controlled process. The ordered glasses produced by rapid cooling of a uniformly aligned nematic phase can be used for phosphorescence polarization experiments. 

The commonest form of phosphorus, and the one which is usually formed by condensation from the gaseous or liquid states, is the waxy, cubic, white form o -P4 (d 1.8232 gcm at 20°C). This, paradoxically, is also the most volatile and reactive solid form and thermodynamically the least stable. It is the slow phosphorescent oxidation of the vapour above these crystals that gives white phosphorus its most characteristic property. Indeed, the emission of yellow-green light from the oxidation of P4 is one of the earliest recorded examples of chemiluminescence, though the details of the reaction... 

The crystallization of zeolites from alkaline aluminosilicate gels was studied by luminescence and Raman spectroscopy. Trace amounts of Fe3+ ions substituted for Al3+in the tetrahedral aluminosilicate gel framework exhibit characteristic phosphorescence spectra, which have been used to follow the buildup of the zeolite framework. Phosphorescence spectra of exchanged Eui+ cations and Raman spectra of (CH N+ cations present in the solid phase of the gel indicate that no zeolitic cages exist in this phase during the induction period. Raman spectra of the liquid phase of the gel system show only the presence of Si02-(0H)2 and Al(OH)a anions. Our results demonstrate that crystallization of zeolites occurs within the solid phase of the gel, which is believed to consist of amorphous tetrahedral alumino-... 

In Linde A and sodalite syntheses the signal grew to about 20 times its initial intensity. In other systems, such as faujasite, the increase was somewhat smaller. The increase seemed to depend upon the Si/Al ratio of the resultant zeolite crystals—i.e., the smallest increase occurred for mordenite crystallizations having an Si/Al ratio of 5 (for Linde A and sodalite Si/Al = 1). No Fe3+ phosphorescence was observed in the liquid phase of the gel. In three experiments carried out under identical conditions Fe3+ phosphorescence studies of the growth kinetics gave identical results (induction periods equal within 5%, Fe3+ intensity increase on crystallization equal within 10%). 

Properties Crystals, waxlike, transparent solid, metastable with respect to red phosphorus, an impurity present in white allotrope. Bp 280C, vap d corresponds to formula P4, mp 44.1C, d (solid 20C), 1.82 d (liquid 44.5C) 1.745, Mohs hardness 0.5. High electrical resistivity. Insoluble in water and alcohol soluble in carbon disulfide, exhibits phosphorescence at room temperature. An essential dietary nutrient. 

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