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A novel hybrid process of hydrothermal or supercritical water oxidation and TiO2 photocatalysis was developed to examine the degradation of chlorobenzene as a model of the oxidative decomposition of organic pollutants. Aqueous solutions of chlorobenzene containing H2O2 as the oxidizing agent and/or colloidal TiO2 nanoparticles as catalyst, were fed into the reactor with the temperature and the pressure controlled to be T = 25–400°C and P = 30 MPa, respectively. Chlorobenzene was considerably decomposed in the presence of H2O2 under hydrothermal conditions for T ≧ 300°C. It appeared that photocatalytic decomposition of chlorobenzene takes place at all temperatures by colloidal TiO2 nanoparticles under irradiation with near-UV light. We have realized the synergic decomposition of chlorobenzene by the coexistence of H2O2 and TiO2 in which maximum conversion is more than 80% under irradiation at T = 200°C.

The photocatalytic reduction of Ag+ ions by TiO2 nanoparticles was examined in water under high-temperature high-pressure conditions of T = 25–400°C and P = 30 MPa. The analysis of the reaction by uv-vis absorption spectroscopy, the atomic absorption spectrometry, and TEM observations revealed that the efficient photocatalytic activity compared with that at room temperature remained even under hydrothermal and supercritical conditions. These results could open the way to new applications of TiO2 under extreme environments which have never been explored before.

The photoreduction of Ag+ ions at the surface of colloidal TiO2 nanoparticles has been investigated. Irradiation of an aqueous solution containing TiO2 and Ag+ ions with near-UV light brings about the growth of a sharp absorption band of colloidal silver in absorption spectrum. The photoreduction of Ag+ ions by TiO2 is optically sensitized by a simple cyanine dye, 3,3′-disulfopropyl-5,5′-dichloro-thiacyanine sodium salt (TC). TC molecules are adsorbed at the surface of TiO2 nanoparticles in the form of the J-aggregate (JA). Visible-light irradiation of the solution containing TiO2, Ag+ ions, and TC causes the growth of a broad absorption band of the colloidal silver and the decrease of whole absorption bands of TC. Experimental results have been interpreted in terms of electronic energy levels of the colloidal silver and the TC aggregate, as well as energy bands of TiO2. In the sensitized photoreduction, TiO2 could play the role of a medium to facilitate efficient electron transfer from the excited TC aggregate to Ag+ ions adsorbed at the surface.

Formation and aggregation of photolytic silver nanoparticles at the surface of silver salt of carboxymethylcellulose films (CMCAg films) have been investigated. Detailed X-ray photoelectron spectroscopy (XPS) study and field emission type scanning electron microscopy (FE-SEM) observation have been carried out to characterize silver nanoparticles at the film surface. When the CMCAg films were irradiated with UV light in wet air at room temperature for 30–60 min, silver nanoparticles of ca. 10 nm size were formed at the irradiated surface. According to the FE-SEM observation, the growth of the particle diameter and aggregation of nanoparticles took place after prolonged irradiation, and finally, the irradiated side of the film surface was densely covered with the silver nanoparticles of ca. 35 nm size. Chemical composition analysis by the XPS measurements has confirmed the increase in the atomic concentration of silver with irradiation time. It is suggested that silver atoms and clusters can move in the film and precipitate at the irradiated surface.

CO 2 reforming of CH 4 was studied over Fe, Co and Ni catalysts supported on cerium oxide at atmospheric pressure. Ni catalyst gave the highest activity; equilibrium conversion of methane was attained under the conditions of 1123 K, 1 g h/mol, and CO 2 /CH 4 =1, and the composition of syngas formed was almost H 2 /CO=1. Carbon deposition was not observed, and the catalytic activity and the syngas selectivity were stable for 24 h over the catalyst. It was found that the high temperature treatment of the catalyst at 1123 K is important for such an excellent catalytic performance. Co catalyst exhibited an activity nearly equal to that of Ni catalyst when reduced sufficiently, whereas Fe catalyst showed a poor activity.

Composite particles consisting of liposomes loaded with silver or gold ultrafine particles have been prepared by UV irradiation (λ=253.7 nm) of AgClO 4 or NaAuCl 4 aqueous solutions in the presence of l-α-dimyristoyl phosphatidylcholine liposomes. The diameter of the metal particles was

The J-aggregates of thiacarbocyanine dyes and naphthothiacarbocyanine dyes having bulky meso-substituent; 5,5′-dichloro-3,3′-diethyl-9-methyl-thiacarbocyanine chloride (dye I), 5,5′-dichloro-3,3′,9-triethyl-thiacarbocyanine chloride(dye II), 5,5′-dichloro-3,3′-diethyl-9-phenyl-thiacarbocyanine chloride(dye III), 3,3′-diethyl-9-methyl-4,5,4′,5′-naphthothiacarbocyanine bromide(dye IV), 3,3′,9-triethyl-4,5,4′,5′-naphthothiacarbocyanine chloride(dye V), 3,3′-dimethyl-9-phenyl-4,5,4′,5′-naphthothiacarbocyanine chloride(dye VI), in monolayer assemblies have been fabricated. From the viewpoints of steric requirement and electronic requirement proposed by us, it has been expected that mixed assemblies, donor/acceptor/arachidic acid(C20), which incorporate two kinds of thiacarbocyanine dyes or naphthothiacarbocyanine dyes in the same layer plane, could form the homogeneous aggregate of amalgamation type (HA-aggregate), which is characterized by a single J-band and accompanying resonance fluorescence distinct from corresponding peaks of each dye. We have really observed the HA-aggregate in the combinations of dye II dye III , dye IV dye VI and dye V dye VI . On the other hand, in spite of similar molecular structure, the dye I/dye III/C20 assembly does not form the HA-aggregate, but produces the separate aggregate or mosaic aggregate.

An aqueous silver perchlorate–sodium dodecylsulfate (SDS)–benzophenone (BP) solution was photolyzed with either UV or near-UV light. Irradiation with 253.7 nm light, which was absorbed by both BP and silver ions, brought about the formation of collidal silver and the photobleach of BP. Peptization of colloidal silver agglomerates after prolonged irradiation was ascribed to electron injection from the benzophenone ketyl radical (BPK). The formation of colloidal silver and the photobleach of BP were also caused by irradiation with 365 nm light, which was absorbed solely by BP (sensitized reaction). A simple reaction scheme was introduced and the initial rates for the sensitized photoreduction of silver ions and the photobleach of BP were expressed in closed forms. Suitable combinations of the kinetics parameters and the extinction coefficient of colloidal silver were proposed in order to interpret the dependences of the initial rates on the reactant concentrations.

An application of chitosan for the polymer support to fabricate thin gold films was examined. When a thin film of chloroauric acid salt of chitosan was irradiated with UV-light in air, a clear gold mirror was formed. It is suggested that the gold mirror is made of aggregated colloidal gold particles stabilized by chitosan.

A Raman signal arising from carboxylate ions in thin films of silver salt of carboxymethylcellulose (CMCAg film) was fairly increased, when the CMCAg film was photolyzed with UV-light. The maximum enhancement was achieved in the CMCAg film irradiated for 180 min. It is likely that the intensity enhancement of the carboxylate ions reflects the contribution of surface-enhanced Raman scattering (SERS).

Luminescence and excitation energy transfer of the J-aggregate of cyanine dyes: 5,6,5',6'-dibenzo-1,1'-diethyl-2,2'-cyanine chloride (dye I), 5,5'-dichloro-3,3'-diethyl-9-phenyl-thiacarbocyanine chloride (dye II), 3,3'-dimethyl-9-phenyl-4,5,4',5'-naphthothiacarbocyanine chloride (dye III), 1,1'-diethyl-2,2'-cyanine iodide (dye IV), in the monolayer assemblies have been studied. Sensitization of resonance fluorescence of the acceptor aggregate (dyes II and III) by the donor aggregate (dyes I and IV) is evident in the mixed assemblies, donor: acceptor, which contain two kinds of the J-aggregates in the same layer plane. The dependence of sensitization efficiency on the composition of the dye I: dye II assembly has been interpreted in terms of an empirical Perrin relation. The slope of the Perrin type plot of sensitized fluorescence is consistent with the model that the dye I aggregate and the dye II aggregate are distributed at random in the layer plane as if each of them were a large supermolecule.

A bright silver mirror was formed by photolysis of silver salt of carboxymethylcellulose with 253.7 nm light. The silver metal film was proved to be useful for the substrate to deposit dye monolayers. Fluorescence quenching of rhodamine B on the silver metal film was interpreted in terms of excitation energy transfer.

Simulation of the absorption spectra of the 2D amalgamation-type molecular aggregates consisting of two kinds of cyanine dyes is being investigated. These aggregates are modeled by the brick-stone structure in the extended dipole approximation of Kuhn et al. The simulation takes into account the vector properties of the transition dipole moment, its orientation, diagonal disorder and the composition of the aggregate. A good fit with the experiment is obtained for the dipole tilt angle θ =90°− α =30°, dipole moment μ =10 D and the disorder parameter of 750 cm −1 for various molar fractions of two dyes.

Multilayer assemblies incorporating the J-aggregate of 3,3′-disulfopropyl-5,5′-dichloro-thiacyanine dye were fabricated up to 50 layers by the alternate adsorption technique to examine their luminescence properties. Fluorescence spectra as well as fluorescence lifetime of multilayer assemblies remarkably depend on the number of layers. The result is interpreted in terms of the interaction between dye layers within a limited distance, as well as the luminescence reabsorption effect.

Photochemical formation of colloidal silver, colloidal gold and silver-gold (Ag-Au) composite colloids under mild conditions has been studied. Irradiation of either aqueous AgCIO4 or HAuCI4 solution in the presence of sodium alginate (SA) with 253.7 nm light yielded colloidal silver or gold, whose particle diamter was 10-30 nm or 40-60 nm, respectively. The Ag-Au composite colloids consisting of mixtures of silver and gold domains (particle diameter 30-150 nm) have been prepared and their extinction spectra have been examined on the basis of a conventional Mie theory in combination with an effective medium theory to estimate the optical constants of these colloids. It has been shown that the extinction spectra of the Ag-Au composite colloids are completely different from those of Ag-Au alloy colloids, in that the former have two extinction maxima close to the colloidal extinction bands of pure silver and gold, in contrast to a single extinction maximum of the latter. The importance of natural, high-molecular carboxylic acids such as alginic acid in the photochemical formation of metal colloids and thin films has been stressed.

Luminescence and excitation energy transfer of organic dye molecules in monolayer assemblies have been studied. Three cyanine dyes: 5,6,5′,6′-dibenzo-1, 1′-diethyl-2, 2′-cyanine chloride (dye I), 5,5′-dichloro-3, 3′-diethyl-9-phenyl-thiacar-bocyanine chloride (dye II), 3,3′-dimethyl-9-phenyl-4,5,4′,5′-naphthothiacarbocyanine chloride (dye III) are organized into the J-aggregate which consists of large arrays of densely packed chromophores and is characterized by an intense absorption band (J band) and a sharp resonance fluorescence. Sensitization of resonance fluorescence of the acceptor aggregate (dye II, dye III) by the donor aggregate (dye I) is evident in the monolayer assemblies in which donor and acceptor layers are in direct contact with one another. Dependence of energy transfer efficiency on the layer separation has yielded an empirical formula of exponential decay type. Excitation energy transfer between the J-aggregates is also observed when both donor (dye I) and acceptor (dye II) aggregates are incorporated into the same layer plane of the monolayer assembly.

Water/supercritical CO2 microemulsions were prepared by using ammonium carboxylate perfluoropolyether (PFPE) as a surfactant. The de-aggregation of the J-aggregate of cyanine dyes and the formation of fairly small silver particles in these microemulsions would indicate the realization of the chemical reactions in the small space. In this sense, the water/supercritical microemulsion is regarded as a novel “microreactor” of the nanometer size.

We fabricated the mixed J-aggregate consisting of 5,5′-dichloro-3,3′-diethyl-9-phenyl-thiacarbocyanine chloride and 3,3′-dimethyl-9-phenyl-4,5,4′,5′-naphthothiacarbocyanine chloride. Based on intrinsic optical spectra and the coherent potential approximation (CPA) method, the formation of the amalgamation-type J-aggregate is proposed.

Quantum yields ranging from 0.084 to 0.191 were obtained for the reduction of Ag+ by irradiation of light at 365 nm on a TiO2 surface in aqueous solutions containing 1×10−4 to 1×10−2 mol dm−3 AgClO4. Some features of the reduction were preliminarily examined with the aid of an electrochemical measurement of TiO2 sinter. It is proposed that some conduction-band electrons, produced in the TiO2 by irradiation, transfer to Ag+ adsorbed on the TiO2 surface and that positive holes react with water molecules. The photoreduction of Ag+ is optically sensitized by addition of Uranine. The apparent quantum yield (the number of reacted ions/the number of photons incident to the suspension) of the dye-sensitized photoreduction of Ag+ is 0.01.

The electronic structures of several aliphatic carbonyls, X2CO, CH3COX, and (XCO)2 (X=H, F, CN, CH3), have been investigated by the INDO method. Variations in the calculated electron density, the nπ*-excitation energy, the electron affinity, and the ionization potential with α-X substitution are explained qualitatively in terms of the σ-attracting and π-donating character of F, the π-attracting nature of CN and XCO, and the σ,π-donating property of CH3. The lowest 3nπ* excitation energies and ionization potentials calculated by the UHF method are in reasonable agreement with the experimental values in most cases. The partitioning of the total energy suggests that the C–O bonds of X2CO compounds in the lowest 3nπ* state and the radical anions derived from them are somewhat longer than those of the parent molecules, primarily because of the decrease in the electron-core attraction. The C–C bonds in some (XCO)2 compounds appear to be cloven as easily as the C–X one on thermal activation and electron impact.

Quantum yields of from 0.235 to 0.385 have been determined for the reduction of Ag+ by the irradiation of 365 nm light on a ZnO surface in aqueous solutions containing 5×10−5 to 1×10−3 M AgClO4. It is proposed that these results can be interpreted by a reaction scheme based on the assumption that some conduction-band electron produced in the ZnO by the irradiation transfers to the Ag+ adsorbed on the ZnO surface. The surface-energy barrier under the present experimental conditions was discussed with the aid of the electrochemical measurement of the ZnO sinter. The photoreduction of Ag+ is optically sensitized by the addition of xanthene dyes, such as Uranine and Rhodamine B. In this case, it is observed that the photoreduction of Ag+ is accompanied by the photolysis of dye molecules. The apparent quantum yields (the number of reacted molecules/the number of photons absorbed in the suspension) of the dye-sensitized photoreduction of Ag+ and the photolysis of dye molecules are 0.015 and 0.007 for Uranine, a...

We have constructed a photochemical storage battery with an n-GaP Photoelectrode. A two-compartment cell, n-GaP|aqueous K3[Fe(CN6]–K4[Fe(CN)6||aqueous NiSO4|Pt, is capable of being charged by the irradiation of the photoelectrode. The current efficiency of nickel deposition on the storage electrode was 80%. When we drew electrical energy out of the dattery, the deposited nickel could act as a Ni electrode in the Ni2+ solution. The power efficiency of the storage battery amounted to about 2%. We could recharge the battery more than five times after discharge.

Vibrational excitation of X2CO-type polyatomic molecules (X=F, Cl, Br, and H) on collision with an argon atom at temperatures 1000–3000 K was treated by the SSH-Tanczos method with a more tractable formula of average vibrational factor. Bending modes are more easily excited than bond-stretching modes in carbonyl halides. Excitation of the carbonyl stretching mode, the most difficult to occur in T–V process, becomes realizable when coupled with other modes to satisfy the near-resonance conditions.

The solid-state photogalvanic cells involving photochemically deposited metals as active materials are presented. As these cells have many excellent features as compared with usual photogalvanic cells in which both the cathodic and anodic materials are dissolved in solution, they will promise a novel storage system for the conversion of solar energy to electrical energy. A typical two-compartment cell: TiO2, aqueous Ce(SO4)2–Ce2(SO4)3||aqueous AgNO3, Pt could be charged by the irradiation of 300–400 nm light on TiO2. The deposited silver on a platinum black storage electrode has almost the same electrochemical properties as the silver metal electrode and is capable of recharging after a nearly complete discharge.

Sensitized photocurrent spectra of ZnO electrode show distinct peaks at the J-band of the two cyanine dyes, 1,1′-diethyl-2, 2′-quinocyanine chloride(dye I) and 3,3′-dimethyl-9-phenyl-4,5,4′,5′-naphthothiacarbocyanine chloride(dye II). Quantum efficiencies of the anodic photocurrent by dye I and the cathodic photocurrent by dye II have high values of about 1.0 under suitable conditions.

The multi-state semiclassical method proposed by Sharp and Rapp for calculating the vibrational transition probabilities of harmonic oscillators in collision was extended to Morse oscillators. Model calculations have been carried out for the excitation of a vibrational ground-state hydrogen molecule colliding with a helium atom at varying relative velocity. It has been shown that the Morse oscillator model gives greater transition probabilities than the corresponding harmonic oscillator model.

Charge-transfer complexations of carbonyl cyanide with furan, tetrahydrofuran, diethyl ether, and their sulfur homologs have been investigated in gaseous phase at temperatures 22–82°C. Thermodynamic data showed that the complexations are enthalpy-controlled in the temperature range studied and that the complexes formed from n-donors are fairly strongly bound. Both the transition and bonding energies could be interpreted in terms of the usual two-state resonance model. It has been deduced that the spatial arrangements of the components do not greatly differ for the various donors studied, despite the difference in precise nature of the bondings involved.

The novel Rhodamine B dyes having one or two long alkyl chains were synthesized. Monolayers of these dyes have been prepared at the air-water interface by spreading the mixture of dye molecules and matrix molecules. Absorption spectra of the dye films which were transferred from the water surface to the quartz plate by the Langmuir-Blodgett technique have been measured.They were comp ared with the dye layers which were prepared by adsorption of Rhodamine B molecules without having long alkyl chains from the subphase to the matrix monolayers.

A regenerative half cell presented here: TiO2(Ag)–Ag+ can be photochemically charged by irradiation of the TiO2 surface with sunlight. Electrical energy is extracted from it by connection through the load with a suitable half cell which has a more positive electrode potential than Ag–Ag+.

A near-infrared photocurrent has been observed in a sintered ZnO electrode whose surface was covered with Ag atoms. The photocurrent became more evident when silver deposition was carried out with a relatively large charging current. The importance of H+ reduction which competed with silver reduction is pointed out.

Colloidal silver and gold have been formed by irradiation of AgClO4 and HAuCl4 solutions with 253.7 nm light in the presence of protective agents such as sodium dodecylsulphate, sodium alginate and colloidal silica. Absorption maxima of colloidal silver and gold have been observed at 390–420 and 540–560 nm, respectively. Colloidal metals have been purified by dialysis and their amounts analysed quantitatively. The quantum yields of metal deposition are 0.053–0.15 for colloidal silver and 0.030–0.039 for colloidal gold. The quantum yield is increased several times by the use of protective agents, with the exception of a AgClO4–sodium alginate solution.