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    20 May 1985, Volume 3 Issue 2
    ADSORPTION OF PHOTOGRAPHIC SPECTRAL SENSITIZING DYES AND THEIR COMBINATIONS ON THE SURFACE OF SILVER BROMIDE AND ENTHALPIES OF ADSORPTION MEASUREMENTS
    ZHANG WEN-MING, SHEN JIE-EU, ZHANG ZU-XUN, ZHONG GUANG-XUE
    1985, 3(2):  1-8.  DOI: 10.7517/j.issn.1674-0475.1985.02.1
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    The light absorption and adsorption properties of three cyanine dyes Ⅰ, Ⅱ and Ⅲ were studied in solution and in their adsorbed states for each dye alone and for their combinations.Adsorption isotherms of dyes to suspended AgBr at 25℃ and the absorption (reflection) spectra of dyes in solutions and in adsorbed states were obtained. Very small heat effects (< 10 mcal) accompanying dye adsorption were measured with the Versatile Model BD-1 Precision Semiconductor Calorimetric System developed by us using a calorimetric unit specially designed for this adsorption system. The precision temperature control of the thermostat to 25±0.0001℃ was implemented by a microcomputer system. The isosteric molar enthalpy of I adsorption to AgBr in water was obtained to be - (33.5±2.5) kJ/mol (Surface coverage 0000=94%). Also from dye combination studies, the obtained spectra, isotherms as well as appreciable heat of adsorption all indicate further adsorption of dye Ⅰ to AgBr dyed with Ⅱ and/or Ⅲ, forming possibly multilayers over the first layer of Ⅱ and/or Ⅲ, while no (or very little) adsorption of Ⅲ and/or Ⅲ can take place over dye Ⅰ. This clarifies the fact that in the photographic emulsion production, the green sensitive dyes Ⅱ and Ⅲ must foe added prior to the adding of I to ensure supersensitization. The results show that enthalpy measurements in combination with spectrascopy may be helpful for studying the sensitizing effect in photographic emulsion production.
    STUDY OF ADSORPTION OF SENSITIZING DYES ON SILVER BROMIDE BY CYCLIC VOLTAMMETRY
    DUAN MING-XING, JIANG LONG
    1985, 3(2):  9-18.  DOI: 10.7517/j.issn.1674-0475.1985.02.9
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    The adsorption of various types of dye on silver bromide was investigated by cyclic voltammetry and electronmicroscope in this paper. The electrode used was built by depositing silver bromide on the platinum substrate as a model for photographic emulsion. It was shown that adsorption behavior of dyes on AgBr/Br- surface was different depending on the electric charge of dyes. As soon as the positive dyes adsorbed, a sparingly soluble surface complex may be formed, while with negative dyes a soluble complex is formed, and no complex formation with negative noncyanine dyes because of the electrical repulsion between them. Therefore, with cyclovoltammetry it is possible to assess the tendency of adsorption of different dyes. The authors have also studied the roles of adsorption in supersensitization and "potenzierung" suggested by Eiester. The results showed that the state of arrangement of dyes on AgBr surface depends considerably on the strength of adsorption, The mechanism of potentiator by Riester has been proved to be reliable in our work.
    MODIFIED GELATIN AS COAGULATING AGENT IN EMULSION-MAKING
    LIU XUAN-YA, CHEN LI-JUAN, PENG BI-XIAN
    1985, 3(2):  19-25.  DOI: 10.7517/j.issn.1674-0475.1985.02.19
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    The coagulation method is of great importance in preparation of concentrated emulsion. The present study is devoted to the following items:1. Synthesis of different modified gelatins2. Evaluation of physical property3. Coagulating performance4. Recovery per cent of PA gelatin and silver halide5. Sensitometric characteristic of emulsion prepared with PA gelatin Modified gelatin is superior to other kinds of copolymer coagulating agent such as polystyrene sulfonate resin due to low cost, shorter induction period to start coagulation, narrower coagulating pH range, less loss of silver halide and better sensitometric property of the emulsion.
    SYNTHESIS OF POLYMERIC METALLOPORPHYRINS SENSITIZERS AND THEIR ABILITY OF SINGLET OXYGEN PRODUCTION
    CHEN XIAN-ZONG, YU YUE-TING
    1985, 3(2):  26-31.  DOI: 10.7517/j.issn.1674-0475.1985.02.26
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    A series of polymeric metalloporphyrins sensitizers were synthesized with chloro-methylated styrene resins, tetra-(pera-aminophenyl) porphyrin and their metal coplexes. The relative efficiency of photosensitized oxidation for 9, 10-dimethlanthrancene was determined with these sensitizers. The order of the sensitizing ability is: Mg2+ porphyrin > metal-free porphyrin>Cd2+ porphyrin>Ni2+ porphyrin>Cu2+ ponphyrin. The polymeric Mg2+ porphyrin is a good sensitizer for generating 1O2. The others, in particular the porphyrins containdnig paramagnetic Ni2+ and Cu2+, remarkably depress the formation of 1O2.
    CHARGE-TRANSFER POLYMERIZATION——THE PHOTOPOLYMERIZATION OF ACRYLONITRILE INITIATED BY ARYL ETHERS
    CAO WEI-XIAO, FENG XIN-DE
    1985, 3(2):  32-36.  DOI: 10.7517/j.issn.1674-0475.1985.02.32
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    The aryl ethers can initiate the polymerization of acrylonitrile under irradiation. The ethers substituted with positive groups on the benzene ring show higher initiating abilities than that substituted with negative groups. A tentative mechanism with the formation of exciplex was proposed.
    6-HYDROXY-1, 4-CIS, CIS-CYCLOOCTADIENE REACTS WITH SINGLET OXYGEN
    WANG DUO-YUAN, HE HUI-CHU, LI QIONG-YAO, ZHANG LIN-HUA, XIAO XU-LING
    1985, 3(2):  37-41.  DOI: 10.7517/j.issn.1674-0475.1985.02.37
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    Singlet oxygenation of 6-hydroxy-1, 4-cis, cis-cyclooctadiene (Ⅰ) which is formed in the photosensitized oxygenation of 1, 5-cis, cis-cyclooctadiene by sodium lamp illumination is described.Thermal decomposation of triphenylphosphite ozonide(Ⅱ) generate efficiently singlet oxygen, the yield of singlet oxygen increase from 70% to 98% dependence on the procedure used(Ⅰ) reacts readily with singlet oxygen generated by thermal decomposation of (Ⅱ) via abstraction of hydrogen atom from the doubly activited methylenic group at quasi-axial position, then predominantly undergoes “ene”reaction to give reduced product 5, 8-dihydroxy-1, 3-cis, cis-cyclooctadiene (Ⅲ) and 6-hydroxy-4-cis-cyclooctenone (Ⅳ) after thermal rearrangement of (Ⅲ), their spectral data are identical with literature.This result can be explained by both the existence of comformation favorable for concerted "ene" reaction and the existence of strengthened π-π intermolelar interaction in compound (Ⅰ). π4s + π2S cycloaddition is suppressed due to unfavorable molecular orbital interaction.
    A STUDY OF PHOTOCATALYTIC CLEAVAGE OF WATER BY ZINC TETRACARBOXYLPHTHALOCYANINE
    ZHU YAN-NING, XIAO XU-RUI, XU HUI-JUN
    1985, 3(2):  42-48.  DOI: 10.7517/j.issn.1674-0475.1985.02.42
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    A new photocatalytic system for producing hydrogen using zinc tetracarboxylph-thalocyanine as sensitizer has been investigated. It was found that the presence of ca-tionic surface active agent in aqueous solution was in favor of the reduction of concentration of zinc tetracarboxylphthalocyanine dimers which was the inactive species in the photo reaction. It could also improve the charge seperation so as to increase the efficiency of photocatalytic reaction in the four-component system. The mechanism of evolution of hydrogen in the four-component system has been briefly discussed.
    ELECTRON-TRANSFER FLUORESCENCE QUENCHING AND EXCIPLEXES OF CYANOANTHRACENES
    CAO YI, CHEN JIAN-XIN, ZHANG BAO-WEN, MING YANG-FU
    1985, 3(2):  49-56.  DOI: 10.7517/j.issn.1674-0475.1985.02.49
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    The values of the fluorescence quenching rate constants kq, for 9, 10-dicyanoanthra-cene (DCA) and 9-cyanoanthracene (CNA) in different solvents by a series of compounds were determined and the exciplex emission was observed for the DCA/2, 5-dime-thylfuran system. A plot of kq vs. calculated free energy change AG gave a very good correlation with the theoretical line calculated by Rehm and Weller for an electron-transfer process. Solvent polarity and solvent viscosity has great influence upon fluorescence quenching reactions: For strong electron donors the main factor which influences the kq, values is the solvent viscosity and the kq values of weak electron donors depend strongly on solvent polarity. The kq of oxygen molecule coincide with the solvent diffusion rate constants kdiff.
    PHOTOCHEMICAL REACTION BETWEEN CARBAZOLE AND CHLOROALKANES
    CHEN SHANG-XIAN, BAI FENG-LIAN
    1985, 3(2):  57-61.  DOI: 10.7517/j.issn.1674-0475.1985.02.57
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    In this paper, the interaction between the excited carbazole and chloro-alkanes has been studied. Photochemical reaction in these systems has been proved by the emission, excitation spectra and the color change in the carbazole and chloro-alkane solution mixed with dimethyl yellow after illumination. The photochemical reaction may proceed through the formation of exciplex which can be verified by quenching and phosphoreoe-nce. A reaction mechanism at the initial gtage has been suggested.
    QUANTUM CHEMISTRY STUDY OF THE PHOTOCYCLOAD- DITION BETWEEN 8-METHOXYPSORALEN AND OLEFINES
    ZHU JIN-CHANG, LAI ZHU-GEN, LIANG DE-SHENG
    1985, 3(2):  62-64.  DOI: 10.7517/j.issn.1674-0475.1985.02.62
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    In this paper the Wiberg bond index of olefinic double bond in 8-methoxypsoralen and tetramethylethylene, 1, 1-methylethylene, trimethylethylene and acrylonitrile have been calculated by using CNDO/2 method. The calculated results indicate that the rate of photocyeloaddition varies linearly with the Wiberg bond index of olefinic double bond. It shows that the reaction rate is determined by the Wiberg bond index of olefinic double bond.
    1985, 3(2):  64-64.  DOI: 10.7517/j.issn.1674-0475.1985.02.64
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