Photosensitivity of holographic recording media based on films of polymer compositions with cadmium sulfide nanoparticles

The effect of doping with CdS nanoparticles of recording medium films for the thermoplastic holographic recording process, which are based on photosemiconductors (oligomers and cooligomers of glycidylcarbazole) and a dielectric (a styrene copolymer with octyl methacrylate) containing a photoconductivity sensitizer, on their photosensitivity was studied. The enhancement of photosensitivity of films by doping with nanoparticles is associated with the appearance of an additional channel for transport of electrons generated from sensitizer molecules. A difference in informational properties between the oligomer and the polymer films was revealed.     

Effects of the Structural Rigidity of Polymethine Dye Molecules on Quenching of Their Photoluminescence by an Electric Field and Charge Photogeneration in Poly(N-epoxypropylcarbazole)

For photoconducting poly(N-epoxypropylcarbazole) films doped with cationic polymethine dyes used as an example, it was found that an increase in dye molecular rigidity increased the photoconductivity of the films in the region of dye absorption, quenching effect of an electric field on photoluminescence, and concentration ratio of photogenerated triplet electron–hole pairs to singlet pairs. The effects were enhanced by an increase in the quantum energy of excitation light. The results are explained by a decrease in the dissipation rate of the electronic excitation energy of dye molecules upon growing their rigidity, which accelerates singlet–triplet intersystem crossing in the photogenerated electron–hole pairs via the spin–lattice relaxation mechanism.     

Photolysis of Aminoanthraquinones in Matrices

The efficiency of photolysis of aminoanthraquinones in cellulose and cellulose-like matrices depends not only on the chemical nature of the substrate but also on the energy of the excitation radiation and reaction conditions; the latter factors govern the mechanism of photochemical degradation of aminoanthraquinones: reductive (under the action of a labile hydrogen atom of the medium at a carbinol carbon atom) or oxidative (under the action of generated singlet oxygen).     

Photogeneration of holes and electrons in amorphous molecular semiconductors with neutral and ionic organic dyes

Photoconducting properties of amorphous molecular semiconductors based on polystyrene films doped with tetranitrofluorenone and merocyanine or an anionic polymethine dye, or with epoxypropylcarbazole and merocyanine or a cationic polymethine dye were studied. The former type of the films is characterized by electron conductivity, whereas the latter type by hole conductivity. The activation energy for photogeneration of mobile charge carriers increases on passing from a merocyanine dye to ionic dyes and decreases with a growth in quantum energy of excitation light for the films of the former type, but does not depend on the light quantum energy for the films of the latter type. It was concluded that the activation energy of photogeneration is determined by electrostatic interaction of a photogenerated charge carrier with the ionized photogeneration site or a counterion for neutral and ionic dyes, respectively. At low dissipation rates of the excess thermal energy of excited dye molecules via electron-nucleus interaction, photogenerated electrons have a possibility to travel over a long distance from the photogeneration site as compared with holes.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 3, 2005, pp. 195–203.Original Russian Text Copyright © 2005 by Davidenko, Derevyanko, Zabolotnyi, Ishchenko, Kuvshinskii, Studzinskii.     

Effect of the Structural Rigidity of Polymethine Dye Molecules on Quenching of Their Photoluminescence by an Electric Field in Poly-N-epoxypropylcarbazole Films

For the example of cationic thiacarbocyanines, we have observed that quenching of their photoluminescence in photoconducting films of poly-N-epoxypropylcarbazole on exposure to an external electric field is enhanced when the structural rigidity of the dye molecules increases. Quenching of the luminescence of these films is also enhanced when the wavelength of the excitation light is decreased. We propose a kinetic model for the observed effects in which we consider the possibility of acceleration of singlet-triplet conversion in photogenerated electron-hole pairs according to a spin-lattice relaxation mechanism.     

On the mechanisms of photogeneration of charge carriers in PEPC-C60 composites

Photogeneration of electric charge carriers at high strengths of the external electric field and the temperature of transition to the viscous-flow state (T _visc) of thin PEPC-C₆₀ composite films obtained by casting from a toluene solution have been studied. The rheology of the composite films has been investigated by the nondestructive optical method. The consistent correlated change in the values of T _visc and the effective temperature in the expression for the photogeneration quantum yield (T ₀) in the Meltz representation with variations in the C₆₀ concentration has been established. The difference between T _visc and T ₀ in thin composite films does not exceed 2–3% of T _visc (T ₀).     

Photodegradation of Aminoanthraquinones and Dyes Derived from Them in the Presence of Complexones

Photodegradation of model aminoanthraquinones and dyes derived from them was studied. Addition of organic complexones having carboxy or phosphinoyl groups to substrate solutions which simulate cellulose or to colored cellulose-containing fabrics accelerates photobleaching of the dyes.     

Electro-optical properties and photopolarization anisotropy of methacrylic azopolymer films

We have synthesized polymethacrylates with azobenzene side moieties and “spacers” of different lengths. We have studied the spectra and kinetics of the electro-optical effect appearing in films of such azopolymers after they are exposed to linearly polarized light. The nature of the electro-optical effect is explained by the appearance of photoinduced optical anisotropy in the films, due to a change in the ratio of the concentrations of trans and cis isomers of the azobenzene moieties. The characteristic time required for establishment and relaxation of photoinduced optical anisotropy correlates with the times required for a change in the dielectric characteristics of the studied films when exposed to linearly polarized light. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 307–310, March–April, 2009.     

Chemistry of furanidine series ketones

For the first time, oxacyclic ketones and-diketones are reacted with diazoacetic ester in the presence of a Lewis acid. It is found that 2,2, 5, 5-tetramethylfuranid-3-one(I) and 2, 2, 5, 5-tetramethylfuranidine-3, 4-dione (IV) undergo ring enlargement between the third and fourth carbon atoms in the ring, to give, respectively, 4-ethoxycarbonyl-2,2, 6, 6-tetramethyltetrahydropyrone-3 (II) and 4-ethoxycarbonyl-2, 2, 6, 6-tetramethyltetrahydropyran-3, 5-dione (V), with the characteristic properties of ß-ketoesters.For Part III see [17].