Photochemical reactions, luminescent materials

Apart from forming catalysts for photochemical reactions, some rare-earth ion complexes may also form efficient luminescent materials after incorporation into microporous crystals. Alvaro et al. loaded a europium complex into zeolite Y,111831 mordenite, and ZSM-5. Because of their confinement in the zeolite framework, the chance for the luminescent centers to decay nonradiationally is reduced, and as a result the lifetime is increased in comparison with that in solution. In the meantime, upon formation of the complex, the luminescence intensity of Eu3+ ion is distinctly increased. Therefore, it is possible to prepare valuable composite luminescent materials using microporous crystals as hosts and complexes as guests. 

One of the most interesting aspects of the physics and chemistry of organic solids is their ability to conduct optical excitation energy within the crystal or even in amorphous material and to transfer it. Energy which is absorbed at one place in the solid can be transported to another place where it can be used to induce various processes which require energy. Such processes include sensitised luminescence, the generation of free charge carriers and photochemical reactions. 

Instrumentation. A cell design employing reticulated vitreous carbon as the working electrode material that enables both UV-Vis absorption and luminescence measurements has been described [47]. A thin-layer cell with a platinum working electrode has been developed [69]. The luminescence of the electrooxidation products of o-tolidine as a function of electrode potential was studied. A simplified flow cell design has been reported [70]. Luminescence spectra and fluorescence intensity for various aromatic compounds and their electrochemical and photochemical reaction products were observed as a function of flow rate, current and time after the potential step. In the latter study the electrooxidation of p-phenylenediamine (PPD) was examined. The cyclic voltammogram showed two oxidation peaks the first one is assumed to be caused by the formation of the radical cation according to... 

Topics which have formed the subjects of reviews this year include photosubstitution reactions of transition-metal complexes, redox photochemistry of mononuclear and polynuclear" complexes in solution, excited-state electron transfer processes, transition-metal complexes as mediators in photochemical and chemiluminescence reactions, lanthanide ion luminescence in coordination chemistry, inorganic photosensitive materials," and photocatalytic systems using light-sensitive co-ordination compounds. Reviews have also appeared on the photoreduction of water.Finally, various aspects of inorganic photochemistry have been reviewed in a single issue of the Journal of Chemical Education. 

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