Photoreduction of [UO₂(dma)₅] (ClO₄)₂ (dma=N, N-dimethylacetamide) has been studied in DMA and acetone. It was found that Uv was stable in acid-free organic solvents in the dark. The molar extinction coefficient of a Uv-DMA complex at 760 nm was determined to be 45.4+0.8 mol-1. dm3cm-1 by utilizing disproportionation reaction of Uv by perchloric acid. It was concluded that Uv was formed by an intramolecular reaction from the following results: (1) the quantum yield of Uv formation was constant irrespective of the DMA concentration in acetone (2) CHBCON CHOCHe was produced by irradiation of [UO₂(dma)₅] (ClO₄)₂in acetone-dB at 170°C. The lower limit of the rate constant of the intramolecular reaction was estimated to be 5 x106s-1 from the lifetime of excited uranyl ions by using laser flash photolysis. The results of quantum yield of Uv formation at various wavelengths of incident light led to be the conclusion that the photoreduction of [UO₂(dma)₅] (ClO₄)₂ occurred in the triplet state of uranyl ions.

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Irradiation with visible light (>420nm) has induced a remarkable effect on the reactivity of the metal-carbon bond in metalloporphyrins such as ethyl(N-methyltetraphenylporphinato)zinc (NMTPPZnEt) and ethyl(tetraphenylporphinato)aluminium (TPPAlEt) which have an alkyl group bound to the metal via c bond as an axial ligand. NMTPPZnEt underwent the homolytic cleavage of the ethyl-zinc group in dichloromethane resulting in the substitution of a chlorine for an ethyl group. In dibromomethane or diiodomethane the reaction proceeded more rapidly, while in benzene the homolysis proceeded only with difficulty. Irradiation of visible light also showed a dramatic effect on the reactivity of NMTPPZnEt and TPPAlEt in the substitution reaction with, hindered phenols such as 2, 6-di-t-butyl-4-methylphenol, to form the metalloporphyrins with the corresponding phenoxyl group bound to the central metal atom. The reactivity of the ethyl group bound to the central metal atom is considered to be increased via photoexcitation of the porphyrin moiety.

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Potential difference across poly(methacrylic acid) membrane having spirobenzopyran pendant groups was measured under visible light irradiation (γ>470 nm) and in the dark. The membrane potential was found to decrease by visible light irradiation in the low NaCl concentration region (C<5×10^-2mol·dm^-3), while it increased in the high concentration region. The photoinduced membrane potential change was reversible and in good correlation with the change in absorbance of spirobenzopyran pendant groups at 513 nm. Salt concentration dependence of the membrane potential and maximum membrane potential change at pH of 6.7have suggested that the photoinduced change in the high NaC1 concentration region is caused by the change of ion transport number resulted from the conformational change of polymer chains, while in the low concentration region the membrane potential change is caused by the charge density change of the membrane derived from photoisomerization of spirobenzopyran pendant groups.

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The anodic photocurrent on the CdS single crystal electrode increased up to twice when formate was added to a neutral electrolyte solution. During the current doubling reaction, there was a constant flow of the photocurrent. From analysis of the electrolyte solution, neither Cd2+ nor S were found, but the current efficiencies for both CO₂ and H⁺ formations were nearly 100%. Therefore, the photoanodic reaction is indicated to be: HC00^- p⁺→H⁺ CO₂ + e^-. By using these results and the fact that the onset potential of the photocurrent was shifted to cathodic, an electrochemical photocell was constructed in which the CdS photoanode was connected with a platinum cathode in a neutral electrolyte solution containing formate. The current-potential curves for the photocell were measured. Electric energy from the outer load and hydrogen gas from the Pt. cathode were obtained. The characteristics of the photocell were improved when the pH in the compartment of the cathode electrode was changed into acid.

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It has been found that niobium oxide is an effective catalyst under UV irradiation for converting olefin into other olefins. The niobium oxide catalyst supported on porous Vycor glass catalyzed propene metathesis under UV irradiation (Fig.1). The catalyst was also active for ethene dimerization, in which very high selectivity to 1-butene formation was observed (Fig.3). The catalyst was activated by UV irradiation in the presence of ethene, but not without ethene (Fig.2). When the catalyst was reduced in the presence of hydrogen either under UV irradiation or at high temperature, it was activated to catalyze ethene dimerization (Fig.4). Both metathesis and dimerization on the catalyst were poisoned when a little amount of oxygen gas was mixed in the reactant gas. The wavelength of UV light effective for the activation of the catalyst corresponded to the UV absorption spectrum of niobium(V) oxide (Table 1). It is therefore suggested that a certain reduced state produced from niobium (V) oxide by the photoreduction is active for both of the reactions. It was observed that the catalytic activity for propene metathesis and ethene dimerization individually depends in a different manner upon the amount of niobium loaded on the support (Fig.7). Therefore, the type of the active site for dimerization is different from that for metathesis. It has been suggested that metathesis proceeds in the same reaction mechanism as proposed for the propene photometathesis by molybdenum oxide, and dimerization was catalyzed by niobium(IV) species produced by the photoreduction of niobium(V) oxide in the presence of ethene. It was found that on the activated catalyst oligomerization of ethene proceeded as well as its dimerization, and also 1-butene was isomerized to 2-butenes (Figs.6, 8). It became clear that ethene dimerization and oligomerization proceeded on the niobium oxide supported on various supports (Figs.9, 10).

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A series of TiO₂ powders was prepared by calcining titanium(N) hydroxide slurry, which was provided by hydrolysis of titanium(N) sulfate, in the temperature range (To) of 170 to 1000°C. The content of anatase (CA) in the TiO₂ powder and the corresponding crystallite size (LA) increased with increasing To up to 700°C (Fig.1). The transition from anatase to rutile occurred at 740-830°C. The BET surface area (S) of the TiO₂ powder was directly proportional to the content of amorphous TiO₂ (CAM) (Fig.2). The residual sulfate ions in the TiO₂ powder decreased linearly with increasing To, disappearing almost completely above 800°C (Fig.4). The amount of hydroxyl groups located on the TiO₂ surface decreased monotonously with increasing To (Fig.6). The To dependence of the photocatalytic activity of Pt (5 wt%)loaded TiO₂ (Fig.9), with reference to the above structural characteristics of the TiO₂, suggested that the anatase, but not the rutile, has a sufficient photocatalytic activity to reduce 11+ and oxidize 2-propanol when loaded with a small amount of platinum black (Pt)(see also Fig.8).
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However, in another reaction system consisting of 2-propanol and silver salts, even the rutile TiO₂ without Pt could effectively photocatalyze the reduction of Ag+ to Ag metal onto the TiO₂ and oxidation of 2-propanol to acetone (Table 1).

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The rates of formic acid decarboxylation and of dichromate reduction both on titanium (IV)oxide photocatalysts were investigated as a function of temperature. In the former reaction, the logarithmic rate depended linearly on the reciprocal absolute temperature up to ca.60°C beyond which a tendency of saturation was observed. In the latter, however, no appreciable temperature dependence of the reaction rate was observed. The observed temperature dependences of the reaction rates were discussed on the basis of electrochemical processes involved in these heterogeneous reactions. In the case of formic acid decarboxylation, the anodic process seems to control the reaction rate at least above 60°C. The same mechanism was also assumed in the dichromate reduction over the entire temperature range investigated.

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Quantum efficiency was measured for the photolysiA of gaseous water over NaOH-coated Pt; TiO₂ catalysts and it was maximized by improving the method of platinization and selecting the crystal structure and the manufacturer of TiO₂. The preparation methods of Pt/TiO₂ catalysts were photo-electrochemical deposition, NaBH4 reduction, HCOONa reduction, and impregnation followed, by hydrogen reduction. It was found that the catalysts were activated by illuminating them in a wet state and then in a dry state in the presence of gaseous water. The stoichiometry of the products (H₂/O₂=2) was well established after the activation of the catalysts.
The results show that the photocatalytic activity is little affected by the preparation method, but strongly depends on the crystal structure and the source of TiO₂. Anatase is more active than rutile irrespective of its source. The activity of anatase seems to be affected by the impurity, the degree of crystal growth, and the grain size, while that of rutile seems to depend on the grain size alone. The maximum quantum efficiency, 17%, was attained when MCB anatase was used. It was also found that the rate of the thermal back reaction (H₂+1/2O₂→H₂O) on Pt/TiO₂ is proportional to the pressure of hydrogen and the net rate of water photolysis is independent of the pressures of the products within the pressure range observed.

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Exposure of acidic solutions (pH 1-3) containing decatungstate (VI) and alcohols to nearultravilet light resulted in the electron transfer from alcohols to decatungstate(VI). The photoreduced decatungstate could be coupled with the reduction of water to hydrogen. When colloidal Pt was coexistent, the quantum yield (∅) of hydrogen increased and was optimal, 0=0.03, with [W₁₀O₃₂^4-]=0.03 mmoldm^-3, [CH2OH] =12.4 mol. dm-3, [Pt] =O.07 mmoldm-3at pH 2.5. The turnover number for hydrogen molecules per decatungstate(V) was more than 100.
Flash photolysis experiments revealed that W₁₀O₃₂^4- was produced by an electron transfer from. alcohol to W₁₀O₃₂^4- and that the protonated W₁₀O₃₂^4- underwent the disproportionation to yield the two-electron reduced and protonated species H₂W₁₀O₃₂^4-. These reduced decatungstates reduced, readily H+ to yield hydrogen.

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Liquid-phase catalytic dehydrogenation of cyclohexanol has been performed for a long period under visible light irradiation with a rodium porphyrin complex, chloro(tetraphenylporphynato)rodium(III). Photocatalysis was pursued for 530 h at the refluxing temperature (161.1°C). The reaction rate decreased slightly (Fig.2), the total turnover number of 3430 being estimated to attain.
The observed gradual decrease in the photocatalytic reaction rate seems to be caused partly by the kinetical product retardation (Fig.3). Electronic absorption (Fig.5) and C-13NMR (Fig.6) observations revealed, however, that the rate decrease was caused additionally by the change of the photocatalyst concentration, since the porphyrin ligand was hydrogenated partially during the reaction.
Even at the high concentration range, where all the incident photons were absorbed, the reaction rate varied in parallel to the catalyst concentration (Table 1) as was found for 2-propanol dehydrogenation with the same catalyst. The reaction scheme, proposed for 2-propanol previously, seems to be applicable to cyclohexanol as well. On the basis of the photohydrogenation enhancement in the acidic media, the abrupt decrease of the photocatalytic reaction rate after the addition of the hydrochloric acid solution (Fig.4) was well interpreted.

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In order to elucidate the determining factors which control the reactivity of particulate semiconductor photocatalyst and to exploit a new material for the efficient photocatalyst, the relation between the electronic structure of the particle and the reactivity was studied through the hydrogen production from water-ethanol mixture and methane production from acetic acid. For H₂ production, Fe2O3 and WO₃, whose conduction band edge are below H+/H₂, are poor photocatalysts in spite of their deep valence band positions. Si and GaP have conduciton band high enough for H2 production, but valence band positions are not deep. For this reason, they are also poor photocatalysts for H₂ production from water-ethanol mixture. CdS, TiO₂ and MoS₂ have conduciton bands colse to H+H₂ and, furthermore, have moderate valence band position. These are efficient photocatalysts for H2 production by visible and UV light. The activity of methane production from acetic acid could also be explained in the same Manner.
Electron microscopic investigation of platinized TiO₂ particle revealed that platinum is deposited on the TiO₂ particle as many small spots, like a body of Leopard, the size of which are about 100 Å. The XPS spectrum showed that the edge of the filled state density distribution of Pt valence band coincides with the Fermi level of TiO₂. The oxidizing site, TiO₂, and reducing site, Pt, are very close to each other. Accordingly, if a molecule in solution is oxidized irreversibly into a stable chemical species, then the corresponding electron can be effectively used for the 142 production. The effect of this surface structure was observed in the decomposition of acetic acid to form methane, where "the redox mechanism" is dominant on the TiO₂ with highly dispersed Pt. Finally, the characteristic feature of small particlulate photocatalyst is compared with that of bulky semiconductor photoelectrode.

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Semiconductor Photocatalysis has been studied for the hydroxylation of benzene and other aromatic compounds. Anatase (TiO₂( a )) was usually used as a catalyst for this purpose. Attempts have been made to enhance the yield of phenol by loading a series of metals and their oxides on TiO₂( a ) and also by adding to the reaction solution (CH₂CN±H₂O-1-benzene)appropriate additives such as inorganic acids and metal sulfates. Hydroxylation of benzene was conducted at 30°C under 1 atm of O₂ by irradiation with a 500 W Xe lamp. The effects of the loading and additives are expressed in terms of "relative activity" in reference to the phenol formation rate obtained for the nonloaded TiO₂( a) in the additive-free solution (Table 2-7). The phenol formation was accelerated by the addition of most acids including H₂SO₄(Table 2). In the reaction solution acidified with H₂SO₄, the relative activity was slightly enhanced further by the addition of some metal sulfates (Table 3). The TiO₂( a) catalysts loaded with Pd, Pt, Cu (Table 4), RuO_x, PdOs, IrO_x, RhO_x, and PtO_x. (Table 5) exhibited the quite high relative activities ranging from 3.0 to 4.3 when used in the H₂SO₄-added solution. The highest relative activity (4.8) was obtained with the RuO_x/TiO₂( a ) catalyst in the H₂SO₄-acidified solution containing 4-methyl-2-pentanone. The selectivity to phenol from benzene in this reaction system attained to 38%.

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Effect of electrical potential floating of titanium(N) oxide (TiO2) particles (radius was ca.1 pm) dispersed in liquid on photocatalytic reaction was studied. The electrical charges of n-type TiO₂ (reduction treated) particles in benzene and toluene were changed from the positive charges of 240 e and 390 e (e: elemental charge) to the negative charges of 450 e and 380 e by illumination, respectively. In the case of platinized TiO2 (Pt/TiO₂) particles, sudh a large negative shift of the charge by illumination was not observed. Oleyl alcohol-treated TiO₂ particles in benzene-olive oil mixture showed good dispersion property, but did not show any photocatalytic property. Such a negative shift of the particle's charge is explained in terms of consumption of the photogenerated holes by the reaction with liquids, and the shift causes an increase in the energy of electrons on the particle and enables to reduce species whose potential is more negative than the flat band potential of TiO2.

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The effect of ZnO surface on the sensitized photoreduction of Ag+ by xanthene dyes (Uranin and Rhodamine B) was investigated. Though the apparent quantum yields of Ag+ reduction (the number of reduced ions/the number of photons incident to the reaction system) in the homogeneous aqueous solutions of both dyes were rather low, they were conciderably improved by suspending ZnO powder in the solutions. The photochemical action spectra of the reaction in the ZnO suspensions were in accordance with the reflection spectra of the corresponding suspensions. In this reaction, ZnO seems to play the role of a medium to facilitate the efficient electron-transfer from excited dye molecules to Ag+ adsorbed on the surface. Such a phenomenon is interesting as a typical example of a surface effect in photochemical electrontransfer reactions. A large difference was found in quantum yield of the Ag+ reduction between the two dyes, i. e., Uranin has larger sensitizing ability than Rhodamine B. We have observed that the flat-band potential of the ZnO sinter electrode in the indifferent electrolyte solution was not affected by addition of Rhodamine B, but shifted to a more negative value by addition of Uranin. Uranin molecules seems specifically adsorbed in the Helmholtz layer on the surface of ZnO in contrast to Rhodamine B. This is consistent with the fact that Uranin is anionic dye and Rhodamine B is cationic one. The difference in the sensitizing ability between these dyes may reflect such physicochemical properties inherent to them. The photobleach of Uranin proceeds simultaneously with Ag+ reduction. However, the total amount of the photoreduced silver during 4 h irradiation was about five times as large as that of Uranin which exists in the suspention at the beginning.

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Some polymeric photosensitizers with the pendant photosentitizer and chloromethyl groups were synthesized by the partial reaction of poly(chloromethylstyrene) with the photosensitizer compounds such as potassium p-nitrophenoxyacetate and potassium 4-(p-nitrophenoxy)butyrate. The remaining chloromethyl groups were allowed to react with cinnamic acid derivatives to give self-sensitized photosensitive polymers. The glass transition temperature (Tg), photochmical reactivity and practical photosensitivity of the polymers were measured. The introduction of the flexible spacer between the polymer skelton and the functional groups such as photosensitizing and photosensitive groups lowered the Tg of the polymers. The self-sensitized polymers showed a higher practical photosensitivity than the photosensitive polymers prepared from the corresponding homopolymer with the pendant photosensitive group and low molecular weight photosensitizers. The apparent rates of disappearance of the C=C bonds in the former polymers were, however, slower than the latter polymers. In the film state, the self-sensitized polymers are considered to assume a different conformation by the effect of the pendant photosensitizing group from the homopolymer with only pendant photosensitive group. Then, intermolecular photodimerizations should occur selectively in the former polymer. The polymers with the pendant p-nitrophenoxyl (NP) group as a photosensitizer showed the highest photochemical reactivity and practical photoreactivity at about 30 mol% of the pendant NP group. The Tg of the polymer decreased with the increasing pendant NP group. The polymers with the pendant 4-nitro-l-naphthyloxyl (NN) group had the highest photochemical reactivity and practical photosensitivity at about 15 mol% and 20-30 mol% of the pendant NN group, respectively.

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Relative quantum efficiency of spectral sensitization (∅_r) is one of the most important properties for the understanding of the mechanism of spectral sensitization in photography. Then, temperature dependence of ∅_r in silver bromide emulsions was studied with a series of spectrally sensitizing dyes with variation of their electronic energy levels. It was found that the dyes with high efficiency exhibited small temperature coefficient, and that the reverse was also ture. High efficiency of spectral sensitization and its small temperature coefficient was achieved by using the dyes whose lowest vacant levels were high, and by using a supersensitizer. It has been suggested that the acceleration of the dissociation of molecular excitons in dye aggregate results in high efficiency and low temperature dependence of spectral sensitization.

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Since positive type photoresist softens at a baking temperature of 120-140°C, there must be an improvement in thermal resistance in dry etching. By adding a Deep UV-sensitive bisazide to a positive type photoresist, we have obtained the following results. When exposed to UV, the bisazide-containing photoresist shows not only a positive type characteristic at lower exposure dose but also a negative one at higher dose. By the addition of bisazide, the sensitivity is reduced to 62%, but the thermal resistance is improved up to 200°C or more. Resistance to a plasma etching is also improved.

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Photopolymers which have cationically polymerizable group in side chain were obtained by radical polymerization of glycidyl methacrylate or 2, 3-epithiopropyl methacrylate. These polymer films sensitized with either diazonium salt or polyhalogen derivatives showed a remarkable photosensitivity for ultraviolet and visible lights. In the presence of a few initiators, the range of the spectral sensitivity was extended up to 500 nm, and the sensitivity was 1 mJ/cm²for ultraviolet light and 10 mJ/cm² for 488 nm laser exposure. These photopolymers followed the reciprocity law under a laser scanning exposure at very high intensity. By the addition of iodoform and Michler's thioketone, the range of spectral sensitivity was extended toward longer wavelength (620 nm), and photosensitivity reached 12 mJ/cm2 for 488 nm argon ion laser light. The photopolymer systems showed no oxygen effect, indicating the cationic polymerization mechanism. The sensitivity was amplified by heating after exposure. From the crosslinking efficiency of gelation for two polymers sensitized with diazonium salt, it was concluded that the photoreactivity of the epithio ring was over 6 tim es higher than that of the epoxy ring.

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Investigations were carried out on the effect of photoirradiation on the alkali metal ion permeability of poly(vinyl chloride) (PVC) membranes entrapping photoresponsive crown ethers 3, 4-(1, 4, 7, 10, 13-pentaoxatridecane-1, 13-diyl)benzyl p-(phenylazo)benzoate [1] and 4, 4'-bis (3, 4-(1, 4, 7, 10, 13-pentaoxatridecane-1, 13-diyl) benzyloxycarbonyl azobenzene[2]). The photoresponsive crown ethers [ 1 ] and [2] were isomerized from trans-form to cis-form and vice versa in the PVC membranes by ultraviolet (UV) and visible (VIS) light irradiation, respectively (Figures 2 and 3). The PVC1trans-[2] membrane was found to permeate alkali metal picrates with the selectivity in order of K⁺>Rb⁺>Na⁺>Cs⁺ (Tables 4 and 5). The permeation rate of K⁺ was accelerated by UV irradiation, while the acceleration for the other cations was not pronounced. The acceleration of K⁺ permeation rate was explicated in terms of enhancement of the K⁺ concentration in the membrane. On the other hand, in the case of the PVC/[ 1 ] membrane, photoirradiation had little influence on the permeability for alkali metalions (Table 3). In order to estimate the cation-binding abilities of [1 ] and [ 2 ] the liquid-liquid extractions were carried out before and after irradiation (Tables[ 1] and [2]). The K⁺selectivities in extraction (K⁺/Na⁺) of 1.7 and 2.2 were observed for trans-[2] and UV-irradiated [2], respectively. The cation binding ability of [1 ] was not affected by UV irradiation. These results suggest that cis-[2] effectively binds K⁺ ion as an intramolecular sandwich-type complex.

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Meso-IX-C_n, and Zn-meso-IX-C_n with long hydrocarbon chains were synthesized (Scheme 1)to investigate the photoinduced charge separation process in the DPPC liposomal membrane from the inner EDTA (electron donor) to the outer MV2+ (electron acceptor) via excited porphyrins (Fig.1). There were three types of porphyrins in the forms of monomer, oligomer, and aggregated solid in the membrane (Figs.6, 7, and 8), and the monomer was the most efficient form for the photoelectron transfer through the membrane. The optimum concentration ratio of pigment/lipid was found to be-1/100 (Fig.9). From the result of temperature dependency measurements of photoelectron transfer efficiency, meso-IX-C_n's were classified into three types (Fig.4). Among these, the Type II porphyrins exhibited higher activities at low temperature range. Incorporation of the Type II porphyrins in the membrane caused an increase in fluidity at the microenvironment of the pigment (Fig.5), and the efficiency of photoelectron transfer increased with fluidity (Figs.8 and 9). The optimum chain length was found to be around C. (Fig.4).
The position of the prophyrin in the membrane had also a significant effect on the transfer efficiency (Fig.10 and Table 1), and a large efficiency was observed with the porphyrin positioned mainly at the hydrophilic region in the membrane. The effect of the membrane potential induced by the transport of K⁺ with Val was not so large as that was reported by Glavin et al.; because, in the present work, the porphyrin, meso-IX-C_n used as the photosensitizer was found to act as a proton carrier, and this canceled efficiently the potential imbalance induced by the electron transfer (Figs.12, 13, and 14). It was suggested that the photoelectron transfer through the membrane occurred by the electron-exchange mechanism between the inner excited porphyrin and the porphyrin cation radical photoproduced at the outer interface.

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Photochemical reaction of the skin-photosensitizing 8-methoxypsoralen (8-MOP) has been discussed in various kinds of solvents on the basis of the effect of the moiety on the electronic spectra and photochemical reaction-product and of the effect on the triplet quenchers such as nucleic acid bases, aromatic amino acids, and oxygen. It was found that the absorption maximum at 340 nm, which appears in less polar solvents and in dimyristoyllecithin liposome, almost coincides with the action spectrum of PUVA photochemotherapy.
The flourescence maximum energy and the fluorescence quantum yield of 8-MOP markedly depended on solvent polarity; i. e., with decreasing solvent polarity, the emission maximum shifted toward shorter wavelength with simultaneous decrease in the intensity of emission, and no fluorescence was observed at ε≤ 2. The result can be interpreted by assuming the presence of a triplet state, T(n, π*) state, which is located close to the S, (π, π*) state.
The quenching of phosphorescence of 8-MOP was also investigated in the presence of nucleic acid bases (thymine, cytosine, uracil, adenine), aromatic amino acids (tryptophan, tyrosine, phenylalanine), or oxygen in water matrix at 77 K. High quenching efficiency and slight decrease of lifetime were observed with these quenchers, except for phynylalanine. It is suggested that the T(n, π*) state or unrelaxed T(n, π*) state is effectively quenched by the quenchers neighbouring 8-MOP at the liquid nitrogen temperature. The quenching efficiencies to triplet excited 8-MOP of oxygen and that of aromatic amino acid were almost the same. Under UV-A irradiation, the photochemical reaction of an aqueous or SDS micelle 8-MOP solutions gave a weakly fluorescent photoproduct. However, no reaction between 8-MOP in ground or in excited state and nucleic acid bases was observed in such a polar atmosphere as water. From the above results it is concluded that 8-MOP in vivo locates in a less polar atmosphere than in water, and the reactive excited 8-MOP is supposed to be the triplet excited state including T(n, π*) state.

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Under UV excitation, a aqueous ZnO suspension showed in the visible region the same green luminescence band as the ZnO single crystals. The luminescence intensity showed the Stern-Volmer like dependence on the AgNO₃ concentration in the suspension. The green luminescence practically disappeared at the AgNO3 concentrations higher than 5 ×10^-5 mol·dm^-3. The mean quantum yield of the photoreduction of Ag⁺ which proceeded concurrently at the ZnO surface was about 0.1. A simple reaction scheme is proposed to explain the observed variation of the luminescence intensity with the incident light intensity.

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A simple method for the preparation of a pheophytin monolayer-coated optically transparent SnO₂ electrode has been developed. The electrode functions as a photocathode (see Fig.1) and the photocurrent spectrum at the electrode is in fair agreement with the visible absorption spectrum of a pheophytin monolayer (see Fig.2).

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Resin-immobilized colloidal platinum catalysts were prepared by refluxing the anion-exchange resin [2 ]- and chelate resin [3]-hexa chloroplatinate(IV) complexes in ethanol-water. The catalysts were active for visible light-induced hydrogen evolution in an EDTA/[Ru(bpy)₃]²⁺/MV²⁺ aqueous solution as shown in Table 1. Ternary photocatalyst was prepared by further immobilization of [Ru(bpy)₃]²⁺ and MV²⁺ on the chelate resin-immobilized platium catalyst with the electrostatic force. Irradiation of the ternary photocatalyst in simple aqueous solution of disodium salt of EDTA resulted in the hydrogen evolution as shown in Table 3. The hydrogen evolution rate depended on the pH of the solution as shown in Fig.2.

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The lifetime of the photolytic silver atom in photographic emulsions was measured by the multiflash exposure method which is a kind of intermittent exposure method. The lifetime at 20°C and the apparent activation energy were 2±0.2 s and 0.82±0.05 eV, respectively in a room air environment. In dry air and vacuum environment, however, the lifetime increased to 11±1 sec and 320±30s while the apparent activation energy decreased to 0.47±0.04eV and 0.44±0.04eV, respectively. These results show that the lifetime of the photolytic silver atom is determined by complicated chemical processes rather than a simple primary process such as the thermal ionization of the silver atom.

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A simple procedure to immobilize chloroplast using water-soluble poly(vinyl alchol) substituted with 1 mol% of 4-styrylpyridinium residue is described. An air-dried film of the photosensitive poly(vinyl alchol) containing chloroplast was reinforced by a polyester gauze and exposed to uv light for a few minutes. The chloroplast entrapped in the insolubilized film showed remarkable stability on storage in the dark. Co-immobilization. of glucose oxidase and catalase was performed to decrease the rate of the inactivation of the chloroplast on illumination.

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The hydrogenase extracted from sulfate-reducing bacteria (Desulfovibrio vulgaris) was immobilized in a photosensitive poly(vinyl alcohol) with 7-styrylpyridinium residue by exposing to UV light for a few minutes. The immobilized hydrogenase was 92%. The efficiency of hydrogen evolution of immobilized hydrogenase, methylviologen and sodium dithionite was observed. The resistivities of the immobilized film against the inactivation of air and the thermal treatment were 35 times stronger and 20°C higher than those before immobilization.

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Photodechlorination of polychlorinated anthraquinones such as 1, 2, 3, 4-tetrachloro-(Cl₄AQ), 1, 2, 3-trichloro-(Cl₃AQ), 1, 2-dichloro-(1, 2-O₂AQ), 2, 3-dichloro-(2, 3-Cl₂AQ), 1-chloro-(1-ClAQ), and 2-chloroanthraquinone (2-ClAQ) were investigated. All the a-substituted chlorine atoms in Cl₄AQ, Cl₃AQ, 1, 2-Cl₂AQ, and 1-ClAQ were dechlorinated on irradiation with the light of A =365 nm in ethanol, while 2, 3-Cl₂AQ and 2-CAQ having only β-substituted chlorine atoms did not suffer any photodechlorination even on prolonged irradiation of light.

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