IMAGING SCIENCE AND PHOTOCHEMISTRY

THE PHOTOPHYSICAL BEHAVIORS OF HYPOCRELLIN A IN MICELLES

HE HUI-ZHU, JIANG XIAN-FENG, WANG DUO-YUAN

1992, 10(3): 193-199. DOI: 10.7517/j.issn.1674-0475.1992.03.193

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In this paper the solubilization and the photophysical properties of HA in micelles (Triton X-100, TDPB, SDS) were investigated. Experimental results proved that HA can be solu-bilized into different kind of micellar aqueous solution, the abilities of solubilization for HA are as showing: Triton X-100 > TDPB > SDSThe concentration of HA in the range of 10^-5-10^-4 mol/L in micelles can be easily prepared. It provided a condition to search for an excited state’s behaviors of HA in aquenous system. The tautomerization of HA in micelles were observed at lower occupancy number and the enconter complex of HA at high occupancy number in ground state was formed in TDPB micelle at λ_max 630nm, corresponding to λ_max 670nm for an excimer of HA in excited state.

SYNTHESIS AND LUMINESCENCE OF EU(DMBM)₂ (2,2’-bipy)NO₃

WANG MING-ZHAO, JIN LIN-PEI, HUANG SHI-HUA, QIN WEI-PING

1992, 10(3): 200-206. DOI: 10.7517/j.issn.1674-0475.1992.03.200

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The title compound, Eu(DMBM)₂(2,2’-bipy)NO₃(DMBM=di-p-methoxy-benzoylmetha-ne,2,2’-biby=2,2’-bipyridine),was synthesized and characterized with elemental analysis, thermal analysis, molar conductance, IR-Raman spectra and ¹HNMR spectra. Its high-resolution laser-excited excitation and luminescence spectra were measured at 77K. Two Eu(Ⅲ) ion sites have been probed. A detailed analysis of spectra reveales that there are two types of slightly unequivalent coordinated Eu(Ⅲ) ion moities with asymmetric C₁ or C_a or C₂ symmetry, differing in the distortion or more than one configurations of three types of ligand, experiencing slightly different crystal field effects in the compound.

A STUDY OF FORMATION OF J-AGGREGATES IN MONOLA- YERS BY COSPREADING OF LIPID AND WATER- SOLUBLE CYANINE DYE

LI BAO-FANG, DIETMAR MOBIUS

1992, 10(3): 207-212. DOI: 10.7517/j.issn.1674-0475.1992.03.207

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Authors report on formation of J-aggregate monolayers of two cyanine dyes with the same chromophore, however, having a different net charge, after cospreading with the appropriate lipid. Authors had measured surface pressure/area, surface potential/area isotherms, reflection spectra and absorption spectra. It was found that the cationic dye in monolayers with arachidic acid showed a surface pressure dependent equilibrium between dimers and J-aggregate. The second cyanine dye with a net negative charge was spread with eicosylamine and formed the J-aggregate at very low surface pressures. The monolayers with dye B is optically anisotropic in the layer plane.

STUDY ON THE DIRECT PHOTOLYSIS AND SENSITIZED PHOTOLYSIS OF SUBSTITUTED PHENYL DIAZONIUM SALTS

ZHENG JIU-TIAN, Wu SHI-KANG

1992, 10(3): 213-221. DOI: 10.7517/j.issn.1674-0475.1992.03.213

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In this work, a series of substituted phenyl diazonium salts have been synthesized. Results in the direct photolysis indicated that the diazonium salt with electron-repulsive group possesses higher rate of photolysis reaction. But in the sensitized photolysis it was found that the diazonium salts which contain electron-withdrawing group possess stronger abilities than that with electron-repulsive group either in the sensitized photolysis or in the process of fluorescence quenching of sensitizers. It indicated evidently that the process of sensitization was realized by the reaction of electron transfer. It was also found it this work that the charge transfer complex (CTC) between diazonium salts and N,N-dimethyl aniline can be formed in the ground state. According to the results obtained from the Benesi-Hildebrand equation, the formed complex was the 1:1 charge transfer complex.

A STUDY ON THE PHOTOSTABILIZING MECHANISM OF FLUORO-CONTAINING β-DIKETONE IN PROTONIC SOLVENT

MOU YING, WU SHI-KANG

1992, 10(3): 222-229. DOI: 10.7517/j.issn.1674-0475.1992.03.222

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The destruction of intramolecular hydrogen bond, hemiacetal formation and their kinetics for fluoro-containing β-diketone compounds in protonic solution have been studied by absorption and ¹H NMR spectroscopy. The processes of photo-irradiation which induces the hemiacetal going back to the original intramolecular hydrogen bond structure and the hemiacetal formation for the system after irradiation in the dark have also been investigated. Although the reason of hemiacetal destruction by irradiation is not clear yet, this kind of β-diketone with -CF₃ group which will return to intramolecular hydrogen bond under irradiation can be used as photostabilizer in the protonic solvents. The photostability of these compounds has been confirmed in this work.

ELECTROCHEMICAL STUDIES ON THE BLEACHING PROCESS Ⅰ. THE KINETICS OF THE REACTION BETWEEN Fe (Ⅲ)EDTA AND SILVER

LIU CHUN-YAN, ULRICH NICKEL

1992, 10(3): 230-236. DOI: 10.7517/j.issn.1674-0475.1992.03.230

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The silver rotating disc electrode was used to study the redox reaction: Fe(Ⅲ)-complex + Ag° + X^-→ Fe(Ⅱ)-complex + AgXThe redox reaction could be followed by galvanostatic reduction of AgX. The galvanostatic reduction time (τ) can easily be determined because of the jump at the end of the reduction of the silver halide. The kinetics of the reaction between Fe(Ⅲ)-complex and silver electrode in the presence of halide would be studied varing oxidation time, the concentration of the reactants and the rotation frequency of silver disc electrode.The redox reaction is a diffusion controlled reaction and is first order with respect to the Fe(Ⅲ)-complex and halide respectively. The initial rate of formation of silver bromide decreases with increasing pH.The diffusion coefficient of Fe(Ⅲ)EDTA was determined from the dependence of the limiting current on both the concentration of Fe(Ⅲ)-complex and square root of the rotation frequency of silver disc electrode.

EPR STUDIES OF THE PHOTOCATALYTIC DEHYDROGE-NATION FOR AQUEOUS ETHANOL SOLUTIONS

FENG LIANG-BO, WANG HAN-QING

1992, 10(3): 237-242. DOI: 10.7517/j.issn.1674-0475.1992.03.237

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By employing different spin trapping agents: POBN (α-(4-pyridyl-N-oxide)-N-tert-butyl nitrone), MV2+ (methylviologen), TCNQ (7, 7, 8, 8-tetracyano-p-qui-nodimethane) and NB (nitrosobenzene), EPR spectroscopy was used to probe the photocatalytic dehydrogenation pathway of aqueous ethanol solution suspended by Pt/CdS powder under the irradiation of visible light (λ≥450nm). The results indicated that the amount of hydrogen produced from the system of Pt/CdS-CH₃CH₂OH/H₂O was relatively high (0.0136 mmol) upon irradiation for 3 hours. However adding in POBN to this system resulted in the decreasing of the amount of hydrogen to 2/3 of the value, suggesting that the CH₃CHOH was trapped and it was easier to produce hydrogen via H⁺ decomposed from CH₃CHOH than from water. For the system adding TCNQ or NB, no hydrogen has been detected, probably due to the trapping of electron or H radical, and indicating that the dehydrogenation mechanism of aqueous ethanol solution catalyst upon irradiation was vis: H⁺+e^-→Ñ→1/2H₂.

IONIC CONDUCTIVITY OF EPITAXIAL AgCI/AgBr(I) CUBIC EMULSION GRAINS

WANG YAN-MEI, YUE JUN, TAO CHUN, XU XU-GUO

1992, 10(3): 243-247. DOI: 10.7517/j.issn.1674-0475.1992.03.243

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Three monodispersed tetradecahedra AgBr (Ⅰ) host grains were prepared by microcomputer-controlled balance double-jet method at the condition of various pAg values. After that three monodispersed epitaxial AgCl/AgBr (Ⅰ) cubic emulsion grains also were prepared successfully by epitaxial deposition of AgCl on (Ⅲ) surface of host grains. The dielectric loss curres of epitaxial grains showed two separative peaks corresponding to the contributions of ionic conductivities of AgBr (Ⅰ) and AgCl. Both host and epitaxial grains, their ionic conductivities varied differently with pAg values.

STUDY ON THE PHOTOSENSITIZATION OF CARENE BY AROMATIC CYANIDE Ⅰ. THE FLUORESCENCE QUENCHING BEHAVIOR OF 9,10-DICYANOAN THRACENE BY CARENE

HE HUI-ZHU, XIE JIE, WANG DUO-YUAN

1992, 10(3): 248-252. DOI: 10.7517/j.issn.1674-0475.1992.03.248

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The fluorescene quenching properties of DCA by Carene in different solvents and the influence of solvent polarity on quenching rate constant as well as the temperature effect were investigated. The quenching rate constant k_q, and △G values in acetonitrile coincide with the Rehm-Weller’s theoretical results, Therefore the fluorescence quenching of DCA by Carene is of electron transfer dynamic quenching characteristic.

A STUDY ON THE PHOTOVOLTAIC BEHAVIOURS OF ZINC-PHTHALOCYANINE DERIVATIVE L-B FILMS

XU JING-MEI, LIN YUAN, XIAO XU-RUI, DENG GANG, XU HUI-JUN

1992, 10(3): 253-258. DOI: 10.7517/j.issn.1674-0475.1992.03.253

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The SnO₂ electrodes were modified by phthalocyanine with different length of alkyl substitutes (ZnPcCH₂n+1,n=3,9,12,16) using L-B method. The formation of a stable monolayer on water and the characterics of phase transition were observed. The photovoltaic behaviours and adsorption spectra of monolayer assemblies were determined. The results showed that L-B films of ZnPcC₃H₇(i) which has horter chain of alkyl substitutes exhibit larger transfer ratio and better photovoltaic effects.

THE PROPERTIES OF SOME COLOR-SHIFTED DYES FOR SILVER-DYE-BLEACH PHOTOGRAPHY

PENG XIAO-JUN, YANG JIN-ZONG, YAO ZHENG-YANG

1992, 10(3): 259-265. DOI: 10.7517/j.issn.1674-0475.1992.03.259

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Color shifting and returning of diazo dyes used in silver dye bleach (SDB) photography were studied, focusing on the relationship between the properties and their molecular structure. The results showed that the dyes with coupling moieties of N-benzoyl J-acid, G-acid or chro-motropic acid could shift and return easily by benzoylation and debenzoylation, but those with coupling moieties of R-acid or N-acyl H-acid were difficult. Using the shifted dyes M-16 and C-20 in SDB photography, the sensitivity increased 3.8 and 6.3 times, respectively.

1992, 10(3): 266-274. DOI: 10.7517/j.issn.1674-0475.1992.03.266

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ELECTROCHEMICAL CHARACTERISTICS OF PLATINUM ELECTRODES COATED WITH CYANINE DYES MONOLAYERS

LI BAO-FANG, JIANG LONG

1992, 10(3): 275-278. DOI: 10.7517/j.issn.1674-0475.1992.03.275

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The electrochemical properties of cyanine dyes (A, B)-lipid monolayers attached onto platinum were investigated. These results indicate that the electrode reaction can be facilitated by monolayers of mixture of cyanine dyes and lipid on these electrode surfaces in comparison with lipid monolayers.

PHOTOCHEMICALLY INDUCED DYNAMIC NUCLEAR SPIN POLARIZATION OF AMINO ACIDS

CHENG LING-JIANG, Xu GUANG-ZHI, YAN BAO-ZHEN, YUAN HAN-CHENG

1992, 10(3): 279-283. DOI: 10.7517/j.issn.1674-0475.1992.03.279

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A photochemically induced dynamic nuclear spin polarization (photo-CIDNP) study was presented of the amino acids that are polarisable with vitamin B? In the amino acid-vitamin B?systems with light irradiation, strong emission for 3-H, 5-H and enhanced absorption for 2-H, 6-H at the benzene ring of N-acetyl-L-tyrosine and enhanced absorption for the protons at the imidazole ring of N-acetyl-L-histidine were observed. No polarization was observed for other protons or protons at other amino acids and deriveatives. The CIDNP evidence indicates that the hydrogen-atom abstraction is important in generating radical pairs in the vitamin B₂ sensitizing systems. Vitamin B₂ was considered to be an excellent sensitizer and probe for the surface amino acid residues of proteins and enzymes.

THE SENSITIZATION OF SILVER BROMIDE EMULSION WITH CROWN COMPOUND

Fu YU-HUA, ZHOU BEN-MAO, ZHANG CHEN-GONG, LI XIAO-LING, REN XIN-MIN, YANG JI-QIU, HU PEI-BIN, QIN YONG, LUO SHI-QIONG, LI SHENG-JIAN

1992, 10(3): 284-288. DOI: 10.7517/j.issn.1674-0475.1992.03.284

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In the present work, it was found that N-toluensulfonyl-7-aza-1, 4, 10, 13-te-trathiacyclohexadecane (NTsTTH) can sensitize AgBr emulsion and the sensitivity-can be increased from 3 to 12.5. The growth of AgBr crystals under the action of NTsTIH was studied with transmitance electron microscopy (TEM), and it was found that NTsTTH acts as a modifier in crystals growth. The ionic conductivity of AgBr emulsion sensitized with NTsTTH decreases with increasing amount of NTsTTH. When excess NTsTTH was added to the emulsion, fog was significantly-increased. According to the results, a hypothetical sensitization mechanism was suggested: when NTsTTH is added to the emulsion, it will combine with the positively charged kink sites (Ag⁺) on the silver bromide microcrystal forming complex (1) which is possible to become sensitization centers. During this process (1) a disproportionate reaction may occur (2) Ag⁺ + NTsTTH——Ag(NTsTTH)⁺ (1) 2Ag⁺ + NTsTTH——Ag(NTsTTH)²⁺ + Ag° (2) and the Ag atoms may aggregate to form fog centers or reduction sensitization centers.

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