Specific features of photoconductivity in a polymer composite with a heterometallic Copper(II)/Vanadium(V) complex

The dark conductivity and the photoconductive properties of polymer film composites based on polyvinyl butyral doped with various amounts of the heterometallic complex (H₃O)₂(H₂en)[Cu(en)₂(H₂O)₂][V₁₀O₂₈] · 3H₂O (where en is ethylenediamine) have been studied. It has been found that the activation energy of photocurrent in the films increases with an increase in applied electric field strength. An increase in the applied electric field strength has been assumed to result in the release of charge carriers from deeper energy traps that can occur in the heterometallic complex.     

Spectroscopic study of the photolysis of bismuth(III) chlorides

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 3, pp. 442–445, March, 1988.     

Effect of a d.c. electric field on the fluorescence spectra of cationic polymethine dyes in a polymer film

We have observed that in an external d.c. electric field, in the differential fluorescence spectra of both symmetric and asymmetric polymethine dyes in a polymer film, the intensity of the emission in the long-wavelength region of the band increases while the intensity in the short-wavelength region decreases. In symmetric polymethines, these effects are opposite to those in the differential absorption spectra, while in asymmetric polymethines they are symbatic. The spectral effects were interpreted by a change in the probability of the vibronic transitions due to redistribution of electron density in the chromophore, in the ground state and the excited state of the dye, in an external electric field. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 343–347, November–December, 2008.     

Sensitization of photosensitivity of photothermoplastic holographic recording media by metal (Zinc, Dysprosium) mono-and diphthalocyanines in the presence of praseodymium sesquioxide

Holographic properties, dark conductivity, and photoconductivity of films based on carbazolyl-containing cooligomer doped with zinc 2,3,9,10,16,17,23,24-octabutylphthalocyanine (Pc^BuZn), double-decker dysprosium phthalocyanine (Dy(Pc)₂), and Pr₂O₃ particles were studied. The films with Pc^BuZn are characterized by higher photoconductivity, which is due to photogeneration of long-lived triplet charge pairs. The presence of Dy in the sensitizer molecules or Pr₂O₃ in the films enhances their photoconductivity, a change that is attributed to an increase in the rate of the singlet-triplet intersystem crossing of the charge pairs.     

Specific features of the photoconductivity of polymer film composites containing a heterometallic iron(II)/zinc(II) complex

The specific features of electric conductivity and photoconductivity in films of composites based on poly(vinyl alcohol) doped with the complex [Fe(bipy)₃][Zn(NCS)₄] (where bipy is 2,2′-bipyridyl) and the effect of magnetic field on these properties were studied. It was found that photocurrent decreases with an increase in the magnetic field strength up to 5.5 kOe. It was assumed that the photoconductivity of these composites and its dependence on magnetic field are affected by paramagnetic iron(III) complex particles produced as a result of internal photoelectric effect. The effect of magnetic field on the photoconductivity is associated with the spin-dependent recombination of photogenerated charge pairs.     

Photolysis of Optical Whiteners in the Presence of Haloarenes

Halobenzenes and sodium salts of halobenzenesulfonic acids decelerate photochemical degradation of optical whiteners in aqueous 2-propanol or in a polyvinyl alcohol matrix owing to T-T transfer of the electronic excitation energy from the substrate to the additive and also to the quenching effect of the heavy atom of the additive. In all the cases, the efficiency of deceleration of luminophore photodegradation grows in going from chloro to bromo and then iodo derivatives.     

Effect of the interaction of azobenzene groups in polymeric composites on their electrooptical characteristics

New azo polymers and a polymeric complex with cobalt based on them were created, and the effect of interaction of the chromophores on the electrooptical effect in films of these materials was investigated. It was established that with increase in the length of the “spacer” and with the possibility of the formation of hydrogen bonds between the substituents in the azobenzene groups the time of the changes in the optical characteristics of the films decreases and their magnitude increases under the influence of the electric field. A phenomenological model of the effect of aggregates of the azobenzene groups attached to the main polymer chain by the spacers on the electrooptical characteristics of the films is proposed.     

Photoconducting and photodielectric properties of heterostructures based on poly-n-epoxypropylcarbazole and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] doped with zinc octabutylphthalocyanine

We have studied the photoconducting and photodielectric properties of heterostructures based on poly-N-epoxypropylcarbazole and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] doped with zinc 2,3,9,10,16,17,23,24-octabutylphthalocyanine located between SnO₂ :In₂O₃ and Ag electrical contacts, in the absorption region of the metal complex. We have observed that the photosensitivity is higher when the poly-N-epoxypropylcarbazole films are deposited on a SnO₂ :In₂O₃ electrode. The increased photosensitivity of the heterostructures compared with monolayers of the films is explained by the high efficiency of dissociation of the photogenerated electron–hole pairs and the decrease in the effect of traps for nonequilibrium charge carriers at the film interfaces.     

Anomalous photoconductivity effects of poly-N-epoxypropylcarbazole films with a high concentration of an anionic polymethine dye

Photoluminescence quenching in an external electric field increases and a long-wavelength photoluminescence band and photoconductivity appear in the visible spectrum with increasing concentration of anionic polymethine dye in poly-N-epoxypropylcarbazole films. Associated species containing dye ion pairs are formed with increasing dye concentration. The kinetics found for the growth and relaxation of the photocurrent in these composite films is anomalous for photosemiconductor materials: the time required for growth of the photocurrent is much greater than the time for its relaxation after switching off the light. A prior irradiation memory effect of the films was discovered.     

Photodecomposition of Optical Bleaching Agents in the Presence of Arenes and Arenesulfonic Acids

Addition of arenes and arenesulfonic acids to optical bleaching agents in the liquid system 2-propanol-water or in a polyvinyl alcohol matrix affects the rate of their photodecomposition via T-T transfer of the electronic excitation energy. The relative arrangement of the triplet levels of the luminophore and added compound is responsible for acceleration or deceleration of the process.