IMAGING SCIENCE AND PHOTOCHEMISTRY

INFLUENCE OF SULFITE ON THE COLOR IMAGING PROCESS

ZHAO WEN-FANG, HE PEI-WEN, HU PING, REN XIN-MIN

1992, 10(2): 97-102. DOI: 10.7517/j.issn.1674-0475.1992.02.97

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The influences of sulfite in color developer on the color image formation process in an incorporated cyan coupler photographic system were investigated. The results indicated that sulfite can promoted the formation of silver image, but it decreased the apparent coupling efficiency of the coupler and increased the unwanted absorption of cyan dye image. The influences of sulfite in color developer on the microscopic structure of the dye cloud were also observed.

THE FUNCTION OF GOLD IN DIRECT-POSITIVE PROCESS WITH AN INTERNALLY 1RIDIUM SENSITIZED EMULSION

FU YU-HUA, JI SU-XUE, ZHOU BEN-MAO, REN XIN-MIN

1992, 10(2): 103-108. DOI: 10.7517/j.issn.1674-0475.1992.02.103

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Silver bromide emulsions with monodisperse cubic grains, which were sensitized internally by iridium, were prepared. The emulsions were fogged by thiourea dioxide and gold salt. It was found that if the fogging proceeds with gold, fog centers may form predominantly on the grain surface, and if fogging proceeds without gold salt, fog centers may form predominantly in the interior of the grain. The emulsion grains were etched with Na₂S₂O₃ solution for different times and spatial distribution curves of fog centers were obtained. When emulsions were fogged by (1) a small amount of thiourea dioxide and gold salt, fog centers distributed on the grain surface and sub-surface; (2) a more amount of thiourea dioxide and a small amount of gold salt, fog centers distributed on the grain surface and interior, but from the surface to the center, fog centers became less and less; (3) a more amount of thiourea dioxide, fog centers mainly distributed in the grain interior. It is clear that the function of gold in the direct-positive process is to suppress the internal fogging which in turn to eliminate the competition in hole trapping and to increase the reversal efficiency.

THE INDUCTION PERIOD CONDITIONS FOR LITH DEVELOPMENT

JI SU-XUE, MA FENG-YUN, REN XIN-MIN

1992, 10(2): 109-114. DOI: 10.7517/j.issn.1674-0475.1992.02.109

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Lith effect appears only when the induction period conditions are strictly controlled. The conditions required can be achieved with the aid of the corabination of the two actions: development acceleration and development inhibition. The development acceleration caused by semi-quinone shortens the induction period of the grains bearing larger latent-image leading to the narrow distribution of the induction period among grains. The passivation of the development centers lengthens the induction period of the grains bearing smaller latent-image resulting in the dependance between the apparent induction period and exposure. Lith effect appears as the consequence of the different affected degree of the two actions in different exposures.

KINETICS OF DIFFUSION WITH CHEMICAL REACTION IN A GELATIN LAYER (Ⅴ) THE COUPLING REACTION OF A SOLVENT DISPERSION COUPLER WITH QDI

ZHAO WEN-FANG, Mo YI-BO, XIA PEI-JIE, REN XIN-MIN

1992, 10(2): 115-122. DOI: 10.7517/j.issn.1674-0475.1992.02.115

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A flow-apparatus and a numerical model for simulating diffusion with a reaction on surface of droplets which were dispersed in a gelatin layer were employed for investigating the kinetic process of the coupling reaction of QDI with dispersion coupler in the gelatin layer. The results showed that the kinetic curves obtained from both the experiments and the numerical model were in quite good agreement. This suggested that the coupling reaction took place do-minantly at the interface between droplets and gelatin-aqueous solution and that the reaction was dependant on the size of droplets, specific rate constant, concentrations of coupler in the organic medium and of QDI on the surface of droplets, which was closely related to the diffusion coefficient of QDI in the gelatin layer. Some valuable parameters and influences of temperature on kinetics of the coupling reation were observed.

PHOTOCHROMISM SYSTEM OF N,N,N,’N’-TETRAMETHYL-P-PHENYLENEDIAMINE VIA ELECTRON TRANSFER

HE JUN-HUI, SUN JUN, WANG ER-JIAN

1992, 10(2): 123-130. DOI: 10.7517/j.issn.1674-0475.1992.02.123

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Photoreaction and thermal stability of the electron transfer photochromism system composed of N,N,N’,N’-tetramethyl-p-phenylenediamine (TMPD)/electron acceptor were studied in solutions and polymer films. Experimental results showed that this kind of photochromism system has high sensitivity of photoresponse. In the arylamine/onium salt (DPIOC) systems, it could be observed that rate of electron transfer increases with the decrease of oxidation potential of the arylamines, i.e., TMPD>DMA>TPA>DPA. The relationships between photoreac-tion rates and concentrations of reactants were obtained with exponents 0.66 (TMPD) and 0.16 (DPIOC) respectively. In TMPD/halogenated alkane systems, it could be found that halogena-ted alkanes having weaker C-X bonds exhibit higher rates of photochromism reaction, due to the decrease of back electron transfer reactions resulted from further decomposition of the reaction intermediate (RX^-). Efficiencies of photoinduced coloration in PMMA films are much higher than those in solutions. The thermal stability data indicated that the color stability is dependent significantly on the temperature, and coloration ability of the system reduces about a half via a circle of alternate photocoloration and thermal decoloration.

EFFECTS OF CALCIUM IONS ON CHEMICAL AND SPECTRAL SENSITIZATION OF AgBr(I) EMULSION

XIANG YAN, WANG SU-E

1992, 10(2): 131-137. DOI: 10.7517/j.issn.1674-0475.1992.02.131

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A series of photographic properties including sensitivity, fog, spectral sensitivity, light absorption and Dember effect of AgBr(I) emulsions with different concentrations of calcium ions ([Ca²⁺]) has been mearsured for studying effects of calcium ions on chemical, and particularly on spectral sensitization. The results show that the sensitivities and fogs of emulsions are decreased with the increase of [Ca²⁺] at the same short digestion time. While the digestion limes of emulsions with even more [CaCa³⁺] were prolonged, their highest speed can be reached almost with the same value. The reason that the calcium ions retard the process of chemical sensitization at shorter digestion time and that the same highest speed with different [Ca²⁺] can be,obtained by prolonged digestion is due to the reaction of calcium ions with a part of AgS₂O₃^- (intermediate of sulfur sensitization) to produce less insoluble Ca(AgS₂O₃)₂ than Ag₂S.An information which has scarcely been reported was obtained by studying the spectral sensitization and Dember effect. As electron trap, calcium ions may inhibit spectral sensitization at long wavelength, and restrain intrinsic desensitization of AgX emulsion, because the adhering of calcium ions to the surface of AgX grains can prevent the intrinsic latent images from oxidization by dye holes.

THE AGGREGATED STATE OF SOME THIACARBOCYANINE DYES ADSORBED ON THE AgBr(I) EMULSION

YU PE-XIA, ZHANG SHI-PING

1992, 10(2): 138-143. DOI: 10.7517/j.issn.1674-0475.1992.02.138

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The aggregated state of eight thiacarbocyanine dyes adsorbed on three kinds of AgBr(I) emulsion (cubic, octahedral and tabulargrain) was investigated. Experimental results showed that the formation of J-aggregate mainly depends on the dye structure, secondly depends on the property of the crystal of AgX-emulsion. Three different kinds of surfactants affected on the formation of the aggregates of dyes. Amphoteric surfactant is the strongest, secondly anionic surfactant, neutral surfactant is rather weak. The aggregated states of two meso-methyl-sub-stituted thiacarbocyanine dyes are evidently influenced by surfactants, giving very strong J-aggregate. But aggregates for other six dyes are influenced slightly.

INTRAMOLECULAR ENERGY TRANSFER AND PHOTOINDUCED ELECTRON TRANSFER IN A COVALENTLY LINKED PORPHYRIN-PHTHALOCYANINE

ZHOU QING-FU, TIAN HONG-JIAN, SHEN SHU-YIN, XU HUI-JUN, CHEN DE-WEN

1992, 10(2): 144-150. DOI: 10.7517/j.issn.1674-0475.1992.02.144

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A covalently linked porphyrin-phthalocyanine heterodimer was synthesied, the absorption spectra, fluorescence spectra, fluorescence lifetime and redox potantials were determined. There is a considerable overlap between the fluorescence spectrum of porphyrin and the ground state absorption spectrum of phthalocyanine, indicating that energy transfer should be extremly efficient. The efficiency and rate constant of intramolecular energy transfer (lEnT) from porphyrin moiety to phthalocyaneine in each model was measured in polar and non-polar solvent. Neither fluorescence quenching by dipole-dipole interaction, nor quenching by collision occurs in dilute mixture of monomers (1/1 mixture of TTP & PC). In contrast, selective excitation at 420nm of the heterodimer, a decrease of the porphyrin fluorescence, concomitant with a slight increase of phthalocyanine fluorescence occurs, indicating IEnT reaction takes place. The efficiency and rate constant of IEnT depends on heterodimer.Selective excitation of the phthalocyanine chromophore in heterodimer, intramolecular electron transfer (IET) takes place only. The efficiency of IET is rather high (38%). IEnT and IET process takes place in competition with different solvent. IEnT process is a very efficient in non-polar solvent, but IET process is a very efficient in polar solvent.

INTERACTION OF METAL PHTHALOCYANINE EXCITED STATES WITH MOLECULAR OXYGEN

ZHOU QING-FU, RAN JIAN-XIAN, SHEN SHU-YIN, XU HUI-JUN,CHEN DE-WEN

1992, 10(2): 151-158. DOI: 10.7517/j.issn.1674-0475.1992.02.151

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In this paper, the ability of photo generation of singlet oxygen as well as superoxide radical sensitized by metal phchalocyanines was evaluated. The results show that the ability of photo-generation of singlet oxygen is correlated with the triplet yield and tripet life time of the sen-sitizer The activity decreases in the order Zn>Ga>Cu>H₂>Al>Co. The ability of photogene-ration of superoxide radical depends not only on the triplet yield and triplet life time but also the excited energy and redox potential of the sensitizer. The ability decreases in the order Ga> Al>Cu>Zn. The fluorescence of metal phthalocyanine is quenched by tyrosine via electron transfer. Quenching of Ga phthalocyanine triplet state in deaerated solution by tyrosine giving rise to GaPc^- at 560nm. In oxygenated solution, subsequent electron transfer to oxygen occurs to give superoxide radical.

STUDY ON CHEMICAL FORMS OF IRON IN PHOTOGRAPHIC GELATIN USED IN COLOR FILM MAKING

YUE JUN, HUANG BI-XIA, XIONG FANG, MENG DONG-FANG, AI JING-YUAN, LIN SHU-QIN, CHEN SHU-YU, YUE AI-BING

1992, 10(2): 159-164. DOI: 10.7517/j.issn.1674-0475.1992.02.159

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Chemical forms of iron in photographic gelatin used in color film making were studied by means of gel filtration-atomic absorption spectrum method. It is shown that most of the iron in photographic gelatin coordinate with protein to form stable large molecular compounds and a litter one is small molecular. The trace inorganic iron salt added in the gelatin exists as protein-free iron form only. The foreign iron pollution, therefore, should be paid special attention when iron content in photographic gelatin is very low. Both total iron content and iron chemical form in photographic gelatin should be considered in photographic emulsion making.

BIOMIMETIC PHOTO-ELECTRIC CONVERSION PORPHYRIN TETRAD

QIAN WEN-YUAN, ZHANG BAO-WEN, BAI JIAN-WBI, CAO YI, JIA JIAN-GUANG, XIAO XU-RUI

1992, 10(2): 165-168. DOI: 10.7517/j.issn.1674-0475.1992.02.165

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In recent years, intramolecular electron transfer reactions have been investigated intensively in relation to the imitation of photosynthesis. Photosynthesis in green plants and bacteria is carried out by highly ordered system. Therefore, it is important to study artificial photosynthesis in well organized form at the level of molecules.

PHOTOBLEACHING OF FLUORESCEIN IN GELATIN FILMS

ZHAO JING-QUAN

1992, 10(2): 169-173. DOI: 10.7517/j.issn.1674-0475.1992.02.169

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The current work was done for the study of the absorption and photostability of fluores-cein in gelatin films. Some interesting phenomina were observed. The films with high dye concentration showed the absorption maxima at about 503 nm under proper base concentration, but the absorption maxima would be changed into 490 nm or even lower with the decrease of the absorbance at the same time after illumination or dilution. The dye films with absorption maxima at about 503 nm had little fluorescence but would be induced to have fluorescence by intense light. From the natures and reported results in literatures, the state was thought most likely to be the dimer of the fluorescein dianions.

MEASUREMENT OF SECOND-ORDER POLARIZABILITY OF SUBSTITUTED 2-PYRAZOLINES BY SOLVATOCHROMIC METHOD

YANG GUO-QIANG, WU SHI-KANG

1992, 10(2): 174-179. DOI: 10.7517/j.issn.1674-0475.1992.02.174

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Second-order polarizabilities of 1,3-diphenl-2-pyrazoline and 1-(4’-nitrophenyl)-3-phenyl -2-pyrazoline have been measured by a solvarochromic method. The results show that electro-withdrawing substituent (such as nitro group) at the phenyl group linked with the C-3 atom gives rise to large second order polarizabiliy. It is accordant with the results of quantum mechanics calculation. The results also show that the studied substituted pyrazolines can be applied as a kind of high efficiency second order harmonic generation (SHG) materials.

STUDIES ON THE PHOTOELECTROCHEMICAL REDUCTION OF CARBON DIOXIDE ON P⁺/P-SILICON ELECTRODE

CHUN YU BAO-CHU, LIU JUN-FU

1992, 10(2): 180-184. DOI: 10.7517/j.issn.1674-0475.1992.02.180

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The photoelectrochemical reduction of carbon dioxide on P⁺/P-silicon electrode in aqueous solution was reported. The effects of cathodic polarization potential, electrolysis time and electrolyte pH, were studied by means of electrochemical voltammetry and prolonged electrolysis. The cathodic reduction products were formic acid and a small amount of formaldehyde. A power energy conversion efficiency of 4.0% of carbon dioxide reduction was achieved. Also the photoelectrochemical reduction process of carbon dioxide was discussed.

SYNTHESIS OF 5-NITRO-SPIRO-INDOLINO-NAPHTHOXAZINE AND ITS PHOTOCHROMISM

WU WEI, WANG YONG-MIN, CHEN HONG-FENG, ZHANG JIAN-CHENG

1992, 10(2): 185-188. DOI: 10.7517/j.issn.1674-0475.1992.02.185

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A new photochromic compound-5-nitro-spiro-indolino-naphthoxazine(Ⅱ) was synthesized. Some photochromic properties of (Ⅱ) and spiro-indolino-naphthoxazine were compared in polar and nonpolar solvents. An unexpected hypsochromic effect of the absorption maximum was observed by the substitution of nitro group in compound(Ⅱ).

1992, 10(2): 189-192. DOI: 10.7517/j.issn.1674-0475.1992.02.189

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