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    20 February 1987, Volume 5 Issue 1
    PHOTOCONDUCTION EFFECT OF SEVERAL SENSITIZING DYES ADSORBED ON AgBr CRYSTAL
    DUAN MING-XING, LI XING-CHANO, JIANG LONG
    1987, 5(1):  1-7.  DOI: 10.7517/j.issn.1674-0475.1987.01.1
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    The mechanism of sensitization and spectral response of dyes were investigated by photoconductivity method using AgBr crystal as a model of AgBr emulsion. AgBr crystal with good transparency was prepared by the "crucible-step-down" method. The processes of chemical treatment and the polish of the crystal piece were studied. Results of photoconductivity measurements of AgBr crystal adsorbing dyes used in practice was consistent with the spectral response of photographic emulsion. Moreover it was found that 5, 5’, 6, 6’-tetrachloro-l, 1’, 3, 3’-tetraethylbenzimidazolocarbocyanine apparently differs from other dyes. The results of photoconductivity of AgBr having adsorbed combined dyes with different electric charges showed that the position and height of photocurrent peak in the photoconductivity diagram changed markedly due to the order of adsorption of dyes on AgBr surface, which would be significant for the preparation of photographic emulsion.
    ESR SPECTRA OF SENSITIZING DYES ABSORBED ON THE SURFACES OF AgBr GRAINS
    Guo JIN-LIANG, WANG XIU-HUA
    1987, 5(1):  8-14.  DOI: 10.7517/j.issn.1674-0475.1987.01.8
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    Electron transfer processes between sensitizing dyes and AgBr grains were studied by ESR technique. Neither sensitizing dyes nor AgBr grians under exposure to light gave ESR signal. The AgBr grains absorbing dyes gave no signal in the dark. The ESR signals were observed for the dyes whose highest occupied levels were 0.7 eV higher than the top of the valence band of AgBr. Paramagnetic centre was formed by the positive hole of dyes (Dye©). The stronger the dye shows its ESR signal the more it desensitizes AgBr crystals.
    NOVEL PHOTOREDUCTION REACTION OF 4, 4’-DIMETHYLBENZOPHENONE IN THE SOLID-STATE
    MENG JI-BEN, MATSUURA T.
    1987, 5(1):  15-20.  DOI: 10.7517/j.issn.1674-0475.1987.01.15
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    A novel photoreduction reaction of 4,4’-dimethylbenzophenone in the solid-state was investigated. The crystal lattice arrangement of 4,4’-dimethylbenzophenone was adequate for the requirement of the abstraction of hydrogen atoms from adjacent molecules. Photochemistry of 4,4* dimethylbenzophenone in the solid-state was distinct from that in solution, and 4-(P-methylben-zoyl)benzyl-bis-(P-methyl)phenyl-methanol has been obtained. The mechanism of the solid-state photochemical reaction of 4,4’-dimethylbenzophenone was discussed simultaneously.
    CIS-TRANS PHOTOISOMERIZATION OF OCIMENE
    SHEN YU-QUAN, Liu HUI-PING, CAO YI
    1987, 5(1):  21-24.  DOI: 10.7517/j.issn.1674-0475.1987.01.21
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    Evidence of the dual isomerization mechanism is given for the cis-and trans-ocimene formed from c-pinene sensitized by xanthone. The quenching rate constant of triplet excitedxanthone by cis-ocimene was determined experimently to be 1.87×1010 (mol/dm3)-1s-1 which is muchfaster than the quenching rate constant of the excited state by aaaaaaaaaaaaa-pinene. Therefore, the paper points out that the conversion of the isomerization reaction is limited by the preferential quenching process of the products.
    THE METHOD OF CONJUNCTION OF SPIN TRAPPING TECHNIQUE——HIGH PRESSURE LIQUID CHROMATOGRAPHY-ESR SPECTROSCOPY TO STUDY THE ACTIVE INTERMEDIATES
    ZHOU JIAN-WEI, Xu GUANG-ZHI, TANG YOU-QI
    1987, 5(1):  25-29.  DOI: 10.7517/j.issn.1674-0475.1987.01.25
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    The conjunction of spin trapping technique——high pressure liquid chromatography-ESRhas been used to study the photolysis process of Ph3P, in which there are several kinds of active intermediates formed during photolysis. Each spin adduct presented in the system is separated by high pressure liquid chromatography and rapidly identified by its ESR spectrum.
    THE SOLARIZATION EFFECT OF EXTENSION DEFORMATION ON THE SILVER HALIDE GRAINS
    LlU QUAN
    1987, 5(1):  30-33.  DOI: 10.7517/j.issn.1674-0475.1987.01.30
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    An investigation has been made for the effect of extension deformation on the D-log ER curve in the solarization region. With the effect, pf extension, the density increases under a given exposure. The micrographs have shown for examining the latensification by extension. The results are discussed in terms of the expected dislocation produced by deformation. The other micrographs have revealed the distribution of photolytic silver in the interior of the grains and in the undeformed solarization region.
    PHOTOISOMERIZATION OF BILADIENE a,b
    MA JIN-SHI, Pu YU-MING, FANG JOAN, JIANG LI-JIN
    1987, 5(1):  34-39.  DOI: 10.7517/j.issn.1674-0475.1987.01.34
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    For understanding the natural configuration and the function of phycoerythrobilin a model compound of biladiene a, b, dihydromesobiliviolin IXa dimethyl ester, was irradiated with visible light or UV radiation. The absorption change from 565 nm to 610 nm and the 1H NMR studies on the chemical shifts of C-5 H and C-10 H indicated that a configurational change from Z type to E type at the double bond of C-10 bridge may take place. The molecule has a more closed spiral configuration before irradiation and a more extended configuration after irradiation.
    SENSITIZED PHOTO-REDOX REACTION IV. DETERMINATION OF THE QUANTUM YIELD OF THE PORPHYRIN SENSITIZED PHOTOREDUCTION OF METHYL VIOLOGEN
    Wu GUO-ZHANG, Hu MING, LIANG XIAO-GUANG
    1987, 5(1):  40-46.  DOI: 10.7517/j.issn.1674-0475.1987.01.40
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    Sensitized photoreduction of methyl viologen produces a cation radical, MV+, the absorption spectrum (λmax 605, ε/ =1.1×104, λmax395, s=3.3×104) of which overlaps with that of the porphyrin sensitizer. As the MVt starts building up upon irradiation, it competes with the sensitizer for the incoming photons. Therefore, the quantum yield φ, determined experimentally decreases with irradiation time, and deviates considerably from the "real" value. Employing an expression developed by Rougee and coworkers: where f(P, MV+) =factor of light absorbed by P where MV+ is the only other species absorbing at the region.We developed a way of estimating the fraction of light absorbed by the sensitizer. All the data can be processed in an APPLE Ⅱ microprocessor. This method promised to be generally applicable to other photoreactions with the product having an absorption spectrum overlapping with the light absorbing species.
    KINETICS AND MECHANISM OF COPPER PHYSICAL DEVELOPMENT——AN ELECTROCHEMICAL APPROACH
    XI XIAO-BING, REN XIN-MIN(JEN HSIN-MIN)
    1987, 5(1):  47-53.  DOI: 10.7517/j.issn.1674-0475.1987.01.47
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    The polarization curves of copper physical development (CuPD) system were obtained by transient constant current step method on copper plated platinum electrode. The results showed that the cathode polarization curve for the reduction of Cu2+ and the anode polarization curve for the oxidation of BH4- have a crossing point, which corresponds to a mixed potential (Emp) of -715 mV and a current density (iR) of 8.9×10-4 Acm-2. These values are approximately the same as determined directly on the CuPD system, i.e. Emp=-720 mV and iR=8.7×10-4 Acm-2, respectively. This implies that the mixed potential approach is reasonable. In the CuPD system, there is little influence between the cathode reduction of Cu2+ and the anode oxidation of BH4-. When the electrode was coated with gelatin, the reaction rate was lowered, r=6.09 μgmin-1cm-2. This value is more approximate to the rate determined on the photographic layer, i.e. 4.82 μg min-1cm-2. The rate determined on clean electrode is much higher, 17.12 μg min-1cm-2. This showed the profound influence of gelatin on the physical development. The transfer coefficient a was obtained from the Tafel equation, and has a value of 0.48. This implies that the deposition of copper proceeds via two single electron transfer reactions, provided that the transfer of the first electron is rate-limiting.
    THE RELATION BETWEEN ACTIVITIES AND STRUCTURES OF THE CYAN COUPLERS OF PHENOLIC TYPE
    CHEN YUE, ZHU ZHENG-HUA, YAO ZU-GUANG, WANG SU-YINC
    1987, 5(1):  54-60.  DOI: 10.7517/j.issn.1674-0475.1987.01.54
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    Using T. S. S. (4-Amino-N, N-Diethylaniline sulfate) as a developing agent, the cyan couplers were developed in the positive film. The photographic data had been shown to fit the Elveg-ard equation. The superdelocalizabilities (Sr(K)) proposed by Fukui at the coupling sites of these couplers were calculated with HMO method as the chemical activities of the couplers. It has beem found that the Sr(K) is a good parameter characterizing the chemical activity of the coupler. The o-substituent to the coupling site of the couplerwould have a steric effect on the coupling reaction.
    THE PREPARATION OF PARA-BIS (BICYCLO[2.2.1]-2,5-HEPTADIENE-2-CARBAMOYL) BENZENE
    Hu QING-YU, LUAN HE-LIN
    1987, 5(1):  61-63.  DOI: 10.7517/j.issn.1674-0475.1987.01.61
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    Para-bis(bicyclo[2. 2. 1] -2,5-heptadiene-2-carbamoyl) benzene was synthesized and its molecular structure was identified by IR, MS, 1H-NMR and elementary analysis.