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Three kinds of cationic aromatic alkenes, trans-stilbazolium derivatives: trans-4-[2-[4-phenyl]ethenyl]-1-pyridinium chloride (1a), trans-4-[2-[4-phenyl]ethenyl]-1-methylpyridinium bromide (1b), and trans-4-[2-[4-(4′-hexadecyloxy)phenyl]ethenyl]-1-methylpyridinium bromide (1c), were each cointercalated with a cationic polyfluorinated surfactant (C3F-S) within the interlayer of cation-exchangeable clay (SSA) to form hybrid compounds (C3F-S/SSA hybrids). The molecular orientations of the intercalated cationic molecules within the C3F-S/SSA hybrids were investigated photochemically using the stilbazolium derivatives as probes. Compound 1a exhibited selective excimer emission, indicating that at least two 1a molecules take on proximal orientations. However, the major photoproduct from 1a was the cis-isomer, and photodimer production was negligible. Absorption spectroscopic analysis showed that cointercalated 1a molecules were deprotonated within the C3F-S/SSA hybrid. These results suggested that deprotonated 1a was situated in a hydrophobic environment formed by the alkyl chains of C3F-S molecules. Compound 1b also exhibited selective excimer emission and both syn-head-to-head and syn-head-to-tail cyclodimers were obtained, suggesting that 1b could be competitively coadsorbed with C3F-S up to the amount of 100% vs CEC of SSA to form parallel conformational aggregates on the same side of the SSA surface. The amount of 1b that was directly adsorbed on the SSA surface was proportional to the sum of all cationic molecules present (1b and C3F-S). The remaining 1b molecules were solubilized as aggregates in the long alkyl chain “forest” of C3F-S in an antiparallel manner. Compound 1c exhibited predominantly monomer emission, and the cis-isomer was observed as the major photoproduct. These results indicated that cationic 1c was adsorbed as isolated monomers in the C3F-S/SSA hybrids because of the formation of hydrophobic interactions with the substituted long alkyl chains of 1c and C3F-S molecules. Thus, it was revealed that C3F-S/SSA provides a unique microenvironment for guest molecules, such as cationic stilbazolium derivatives, through a delicate balance among (1) electrostatic interactions exerted by the negatively charged SSA surface, (2) hydrophobic interactions from the long alkyl chain of C3F-S, and (3) both hydrophobic and lipophobic interactions from the perfluoropropyl chains of C3F-S that form a polyfluorinated “wall”.

The catalytic methanation of CO2 with ammonia over Ni, Pt, and Ru catalysts impregnated on γ-alumina was carried out in a fixed-bed reactor under atmospheric pressure at 573–873 K. The methanation of CO2 with NH3 is considered to occur in two stages –NH3 decomposition into H2/N2 followed by CO2 methanation with H2. 1 wt% Pt/γ-Al2O3 exhibited low activity for NH3 decomposition and CO2 methanation with H2. Both 5 wt% Ni/γ-Al2O3 and 1 wt% Ru/γ-Al2O3 showed high activity for NH3 decomposition and CO2 methanation with H2, but Ru/γ-Al2O3 was much more active. For CO2 methanation with ammonia, only Ru/γ-Al2O3 was significantly active. The yield of CH4 increased with increased Ru loading and reaction temperature, but was limited by thermodynamic equilibrium at higher temperatures. Ammonia decomposition is more facile than CO2 methanation on the Ru/γ-Al2O3 catalyst and CO2 methanation is the rate limiting step.

An international round-robin inter-comparison of the spectral responsivity (SR) and current-voltage (I-V) characteristics for dye-sensitized solar cells (DSCs) and crystalline silicon solar cells is reported for the first time. The crystalline silicon cells with various spectral responsivities were also calibrated by AIST to validate this round-robin activity. On the basis of the remarkable consistency in Pmax (within ±1.4% among participants) and Isc (within ±1.2% compared to the primary calibration of AIST) of the silicon specimens, the discrepancy in the SR and photovoltaic parameters of five DSCs among three national laboratories can be verified and diagnosed. Recommendations about sample packages, SR and I-V measurement methods as well as the inter-comparison protocol for improving the performance characterization of the mesoscopic DSCs are presented according to the consolidated data and the experience of the participants.

Measurement and evaluation methods for the performance of dye-sensitized solar cells (DSCs), of which the mechanism for photocurrent generation is quite different from that of silicon-type solar cells, are reviewed here and a relevant method proposed. The slow response times and nonlinearity of DSC photocurrents against the light intensity (irradiance) at wavelengths of incident light are profoundly influenced by their characteristic working principles since photocurrent generation for DSCs is more complicated than for Si-type solar cells. DSCs work not only by the physical process of an electron in solid-state TiO 2 but also diffusion processes in the fluid electrolytes in contrast to only the simple solid-state physical process of a charge separation at the p–n junction of the interface for Si-type solar cells. In addition, newly developed DSCs are prepared by such elemental materials as sensitizers, electrolytes and semiconductors of diverse morphologies. In this respect, it is essential to establish a comprehensive and relevant method for the correct spectral measurement of the responsivity and performance of a wide range of DSCs which may include cells involving various kinds of electrolytic media. In this review, DSC electrolyte media with such disparate viscosities as a typical organic solvent, 3-methoxypropionitrile (Cell A), or an ionic liquid (Cell B) are introduced and analytical methods such as the AC method is compared with the DC method to gauge spectral responsivity. IPCE measurements were carried out by adjusting the chopping frequency low enough to obtain a steady state current under illumination conditions similar to those under practical use. Our studies revealed that when sufficient time is allowed for complete photocurrent generation, especially for DSCs involving an ionic liquid, I – V measurements which take this time allowance into consideration show them to perform satisfactorily. In fact, in an extreme example, I – V measurements of a DSC with an ionic liquid electrolyte can take over 50 min before correct data can be obtained. Thus, standards for the evaluation of DSCs need to be established separately from those for Si-type solar cells to avoid incorrect and incomplete comparisons.

UV-light induced redox reactions between cationic porphyrins (H 2 TMPyP) and methyl viologen (MV 2+ ) separately incorporated in titania nanosheets (TNS) and cubic -mesoporous silica (MPS) integrated films, respectively, were investigated. In this system, the following two modified hybrids, i.e ., the normally stacked (MV 2+ –TNS)/(H 2 TMPyP–MPS) on a FTO electrode and the inversely stacked (H 2 TMPyP–MPS)/(TNS) films on a FTO electrode were examined. In accordance with the expected electron flow from H 2 TMPyP to MV 2+ , cathodic photocurrents were observed for the normally stacked film in acetonitrile (CH 3 CN) under a negative bias voltage of −0.4 V. However, under the influence of a positive bias voltage of +0.3 V, anodic photocurrents were observed even in CH 3 CN. On the other hand, anodic photocurrents were also observed in water for the normally stacked films at both bias voltages of +0.3 and −0.4 V due to photoreduction followed by proton abstraction of the H 2 TMPyP molecules from H 2 O within the MPS nano-cavities. In addition, ca. 0.98 mC of the photocurrents were determined in water for the inversely stacked (H 2 TMPyP–MPS)/(TNS) films without MV 2+ , of which ca. 50% resulted in the oxidative consumption of H 2 TMPyP in the MPS cavities.

The isomerization and zinc-chelation of spironaphthoxazine (SNO) during the course of the sol–gel–xerogel transitions of the tetraethylorthosilicate (TEOS) system and the mixture systems of TEOS and octyltriethoxysilane (OcTES) have been investigated by measuring the fluorescence and excitation spectra as a function of time. The influence of the hydrophobic octyl groups on the spectroscopic behavior of SNO in the TEOS and TEOS–OcTES systems containing zinc ions have been discussed. A fluorescence spectrum at around 430 nm, observed just after the preparation of the TEOS system, was similar to that of SNO observed in protic highly-polar solvents due to the presence of the ethanol solvent in the system. A weak fluorescence spectrum was observed at around 400 nm just after the preparation of the TEOS–OcTES systems. This spectrum corresponded to that of SNO in low-polar solvents due to the hydrophobicity of OcTES. The fluorescence spectra in both systems were gradually red-shifted to around 450 nm along with the progress of the sol–gel transition, indicating that SNO (ring-closed form) interacts with silanol groups generated by the hydrolysis of the alkoxides. A spectrum due to the zinc complex of the SNO-derivative, merocyanine (MC, ring-open form), also appeared at around 540 nm during the initial stage of the sol–gel–xerogel transitions (around the gelation point) for both systems. SNO molecules and zinc ions were concentrated in prestructural pores and easily interacted with each other. The fluorescence intensity of the complex in the TEOS–OcTES systems, however, was remarkably lower than that in the TEOS system due to the hydrophobicity of the system. Depending on changes in the polarity and volume of the space containing the species, the complex fluorescence intensity increased and decreased. In the TEOS–OcTES systems, the non-complex band was blue-shifted around the gelation point since the polymerization of the silanol groups preferentially occurred and the polarity decreased in the system containing hydrophobic groups. In the gel of the TEOS system and the sol of the TEOS–OcTES system, a photochromic reaction was observed, i.e., SNO formed the MC–Zn complex during UV irradiation, whereas a change was hardly observed during visible irradiation. In the xerogel of the TEOS system and in the gel and xerogel of the TEOS–OcTES system, a reversible photochromic reaction was observed, i.e., the MC–Zn complex was associated and dissociated by UV and visible irradiation, respectively.

Chelation of spironaphthoxazine (SNO) with zinc ions in the course of the sol–gel–xerogel transitions in the tetraethylorthosilicate (TEOS) systems has been investigated by monitoring the fluorescence and excitation spectra as a function of time. A fluorescence spectrum was observed at around 430 nm, just after the mixing SNO with zinc ions in TEOS, which was similar to that of SNO observed in protic high-polar solvents due to the existence of the considerable amounts of ethanol content in the TEOS systems. The fluorescence maxima were gradually red shifted to around 450 nm with the progress of the sol–gel reaction. This result indicates that SNO (ring-closed form) can interact by hydrogen bonding with SiOH groups generated by the hydrolysis of TEOS. Some of these SNO molecules formed the non-planar zwitterion as the C O bond was cleaved. A spectrum originating from the zinc complex of the SNO-derivative, merocyanine (MC, ring-open form), also appeared at around 540 nm near the gelation point. This complexation occurred because SNO molecules and zinc ions were concentrated in the prestructural pores and easily interact with each other. The hydrogen-bonding species and the chelate species decreased during the drying process of the wet gel due to growth of the silica networks including zinc along with the condensation of SiOH groups. As the gel converted to the xerogel, the SNO molecules were more strongly adsorbed on the surface of the pores in the xerogel than in the wet gel due to the evaporation of solvent and a contraction of the space. The SNO molecules, therefore, form not only the MC–Zn complex again, but also the MC–SiOH complex. The photochromic behavior including the ring opening and association of the MC–Zn or MC–SiOH complex, and its dissociation and ring-closure were observed by UV and visible light irradiations in the xerogel systems.

Dicetyl phosphate (DCP) ions incorporated into layered double hydroxide (LDH) clays to form a DCP/LDH hybrid were prepared and structurally characterized by X-ray diffraction analysis, scanning electron microscopy, thermogravimetry, and differential thermal analyses. DCP was concluded not only to form well-aligned bilayer structures along the vertical axis of the LDH layers but also to be arranged in a distorted hexagonal packing orientation in the lateral planes within the DCP/LDH hybrid interlayers.

Tetra( p -sulfonatophenyl)porphinatomanganese(III) anions, [Mn(III)TSPPCl] 4− were intercalated into the interlayer spaces of Mg–Al-layered double hydroxide (LDH) and studied as a catalyst for the oxidation of 2,4,6-trichlorophenol (TCP). The Mn(III)TSPP anions could be efficiently intercalated into the LDH interlayers as a perpendicular Mn(III)TSPP/LDH complex by adsorbing the guest molecules, which is a characteristic for easy handling and a high catalytic activity.

The hybridization of poly(ethylene terephthalate) (PET) with montmorillonite (Mont) was investigated by using hydroxypentyltrimethylammonium iodide (HPTA) as an ionic anchor monomer capable of being adsorbed onto clay surfaces by ion exchange. The HPTA/Mont hybrid films copolymerized with bis (hydroxyethyl) terephthalate (BHET) exhibited favorable characteristics such as improved tensile strength as well as optical transparency.

In order to achieve the effective removal and decomposition of n-nonylphenol (Np), an endocrine disruption chemical with poor solubility, tenuously dispersed in environmental water, the synthesis and characterization of a hydrophobic clay (HpC) with copper-phthalocyanine (CuPC) were investigated. The HpC powders were prepared by intercalating the cetyltrimethylammonium cations (CTA + ) into montmorillonite (Mont) interlayers. The HpC compound incorporated with CTA + molecules and equal to the cation-exchangeable capacity (CEC) of Mont were found to adsorb almost completely the Np molecules from the aqueous solution by the hydrophobic interaction between the alkyl chains of the CTA + and Np molecules. The CuPC molecules were incorporated with the HpC compound in order to add the photodecomposition properties of CuPC to the HpC compound. This HpC/CuPC hybrid efficiently adsorbed the Np molecules from the polluted water, too. Visible-light irradiation of the Np aqueous HpC/CuPC hybrid suspension under O2 atmosphere at 620 nm decomposed the Np molecules having been adsorbed at the hydrophobic spaces of the HpC/CuPC hybrid materials, forming quinonmethane molecules by the singlet oxygen produced by the photosensitization reaction of the cointercalated CuPC molecules. © 2002 Elsevier Science B.V. All rights reserved.

Self-organized porous TiO 2 particle layers were fabricated by simple calcination of a Ti substrate in air. The TiO 2 particle layers were formed by calcination at 800 °C for 24 h or 900 °C for 1 h. Calcination at 900 °C for more than 6 h, or at more than 1000 °C for more than 20 min, gives not only the formation of TiO 2 particle layers, but also spontaneous delamination of the TiO 2 particle layers from the substrate on cooling to room temperature. The crystal phase of the TiO 2 particle layers is rutile. Cross-section scanning electron microscopy (SEM) images revealed that the TiO 2 particle layers after spontaneous delamination have porous structure between the TiO 2 particle layers. The thicknesses of the TiO 2 layers increase with increasing calcination temperature and time. The sizes of the TiO 2 particles depend on the calcination temperature and time.

The transition behavior from stationary to oscillatory thermocapillary flow was experimentally studied with a liquid bridge of molten tin (Prandtl number Pr=0.01) of 1.5 mm in radius. The experimental difficulties such as preventing oxidation of the melt surface and detecting a small amplitude of surface temperature fluctuation without any external disturbances on the flow field were successfully solved by employing a high vacuum condition, ion etching to remove the oxide film on the surface and a high resolution radiation thermometer. A temperature fluctuation was first observed at a Marangoni number Ma of 43.3. Frequency and amplitude of the fluctuation were 0.08 Hz and 0.3 K, respectively, which is significantly larger than temperature resolution of the radiation thermometer used. The temperature oscillation developed with increasing temperature difference imposed between the upper and lower ends of the liquid column and then observed a standing wave of 0.42 Hz with very strong amplitude at a Marangoni number of 91. The flow transition was directly proved by a surface flow visualization experiment. Tin-oxide particles, which were pre-mixed with molten tin, were observed to repeat oscillatory movement along the circumferential direction with 0.5 s interval after the onset of the oscillation. Those results are the first and clear experimental evidence for the transition to oscillatory flow in a low Pr fluid by a non-contact diagnostic, which has never been observed yet. Validity of the experimentally determined critical Marangoni number and the frequency of the standing wave were discussed by comparing with a numerical result.

This article surveys the intercalation characteristics of a number of clay minerals which can be utilized as host materials for photofunctional organic–inorganic hybrid systems as well as photochemical anisotropic reaction fields. The introduction of this review describes the chemical compositions and the structural features of various kinds of artificial as well as naturally produced clays. The chemical structures of these clays are often considered to be complicated due to their unfamiliar names which are sometimes taken from the areas where they originate although, structurally, only slight differences actually exist. The second chapter summarizes the adsorption and aggregation properties of typical organic dyes in clays. The aggregation behavior is sensitive to the kind and amount of metallic ions present in the lattice of the clays, the amount of adsorbed water as well as the structure of the organic guests to be intercalated. All of these factors are discussed in relation to the adsorption and aggregation behavior. In the third chapter, the photochemical reactions of excited metal complexes adsorbed in clays are discussed. Electron transfers for [Ru(bpy)3]2+ in clays are described, showing that the clay layers provide reaction fields which stabilize the resulting charge separated species. This article aims to provide important insights into the fundamental mechanisms and properties of anisotropic reaction fields for the applications in design of promising, new photochemical and photobiological systems and processes.

The photochromism of 1,2-bis(2-methyl-3-thiophenyl)perfluorocyclo-pentene bearing two pyridinium substituents at each thiophenyl ring (1) in smectite clay thin films is the subject of the present study. In order to prepare oriented thin films with photochromic characteristics, the hybridization of cationic diarylethene molecules, 1, into the layered clay was carried out, and the structure and photochromic properties of these hybrid materials were investigated. Clay intercalated diarylethene exhibited typical photochromic behavior. Polarized spectroscopic data has confirmed the diarylethenes inside the clay to be present as a tilted monolayer. Although the photochromic efficiency of these hybrid materials gradually decreased upon repeated irradiation with alternative UV and visible light, photochromic degradation could be dramatically improved by the cointercalation of cationic surfactant molecules such as dodecylpyridinium ions.

Photopolymerizations of intercalated 4-vinylbenzoate (VBA) and p-(or m-) phenylenediacrylates (PDA) were investigated in the presence of an anion exchange clay, hydrotalcite. UV irradiation of clay powder adsorbing VBA and 4-benzoylbenzoate (BBA) ions gave rise to the cyclodimerization of the olefin and a radical polymerization to form polyvinylbenzoate. The degree of the polymerization was 10–103. The stereoregularity was investigated by NMR analysis and is discussed in relation to the state of molecular aggregation in the clay interlayers. In contrast to VBA, photoreaction of the intercalated PDAs resulted in the formation of oligomers in [2+2] cycloaddition manner, of which the polymerization degrees were rather low (up to ten at most). The stereochemistry of the oligomer was revealed to be of a syn-head-to-head structure by NMR analysis. Dianionic molecules such as PDAs showed an interesting intercalation behavior in contrast to monoanions, i.e. just one double-negatively charged molecule was estimated to occupy three anion exchange sites of the hydrotalcite layer. Also, the relatively low polymerization degrees of the PDAs were found to be due to the above intercalation characteristics. Powder X-ray diffraction analysis showed that the molecular aggregation state was remarkably changed by desiccating the clay composite in vacuum, thus suppressing the efficiency of the photoreaction.

The Norrish type II reactions of a number of aromatic ketocarboxylate ions, p -CH 3 C 6 H 4 CO(CH 2 ) n CO 2- (1, n = 4–10), were studied under the conditions of intercalation in the anion-exchange clay, hydrotalcite. Photolysis of 1 adsorbed in aqueous hydrotalcite suspension yielded the type II products p -methylacetophenone and alkenecarboxylates (E), and/or cyclobutanols (C) in variable yields depending on the length of the alkyl chains ( n ). The ratios C/E decreased with increasing n and hence became negligibly small when n ≥ 6, in contrast with the photolysis of 1 in homogeneous aqueous solutions. The effect of coadsorbates was significant in the acceleration of the type II reaction, but the product distributions remained unchanged. These results will be discussed in terms of the conformational flexibility of the aromatic ketocarboxylate ions imposed by the interlayer space of hydrotalcite clays.

Supramolecular assemblies in ternary systems of alkyldimethylamine oxide (C n DAO, n = 12, 16)/cinnamic acid/D 2 O were investigated by small-angle neutron scattering. In the C 12 DAO/cinnamic acid/D 2 O system, prolate ellipsoidal micelles with axial ratios of 1.3 and 2.4 were formed at mixing molar ratios X ([cinnamic acid]/[C n DAO]) of 0 and 0.2, respectively. For the C 16 DAO/cinnamic acid/D 2 O system, lamellar layers with a bilayer thickness of 30 A existed in a solution at X = 0, while rodlike micelles with a cross-sectional diameter of 50 A were constructed at X = 0.2. Vesicles in solutions at X = 0.5–1 had multilamellar layers. The bilayer thickness was 23–30 and 35–36 A for C 12 DAO/cinnamic acid and C 16 DAO/cinnamic acid vesicles, respectively. The thinner bilayer thickness suggests that the tilt or random orientation of alkyl chains may occur in lamellar bilayers and membrane bilayers. The comb-shaped arrangement is also possible in membrane bilayers by C n DAO/cinnamic acid complex.

Oxidation of vitamin A alcohol (1) by peracetic acid in tetrahydrofuran at room temperature affords an amorphous product, which on purification by the column chromatography gives 11,12-epoxy vitamin A aldehyde (5; 45%) whose structure was determined on the basis of IR, UV, NMR and mass spectra. This reaction is compared with oxidations with other oxidants.

Diphenyl ether (Ia) was converted to o-phenylphenol (IIa, 20·4%), p-phenylphenol (IIIa, 12·7%) and a small amount of phenol (IVa, ca. 0·4%) by irradiation with UV light in various solvents. p,p′-Ditolyl ether (Ib) was similarly converted to 2-(p-tolyl)-4-methylphenol (IIb, 14%) and p-cresol (IVb, 7%), indicating that the photochemical rearrangement proceeds via CO bond cleavage and recombination of the radical fragments. These reactions are intramolecular and occur via an excited singlet state or via a short-lived triplet. The combined yields of o- and p-rearrangement products were increased from 1 to 18% by an increase of the ratio of ethyl ether to ethanol, implying the facilitation of CO bond fission by the H- bonding of ethanol to diphenyl ether (Ia) or the stabilization of quinoid intermediates (VIII and IX).

The photochemical reaction of benzyl methyl ketone (I) has been studied in n-hexane and t-butanol. The rearrangement products, o -methylacetophenone (II) and/or p -methylacetophenone (III), are obtained in poor yield, together with a reductive dimerization product, substituted pinacol (IV), and derivatives of benzyl radical, bibenzyl (V) and tolune (VI). The ratio of III to V tends to increase with lowering concentrations of reactants, but it is little affected by the irradiation time and reaction temperature.

Irradiation of 1-alkyl-3,4-dihydroisoquinolines( Ia, b ) containing γ-hydrogen afforded 1-methyl-3,4-dihydroisoquinolines( IIa, b ) in poor yields. The elimination is analogous to the type II cleavage of ketone. The similarity between this photoreaction and the electron-impact fragmentation was observed. Ethyl 3,4-dihydroisoquinoline-1-acetate( Ic ) without γ-hydrogen is stable photochemically in an inert solvent, but it was readily photodecomposed to yield IIa in a good yield in excess HCl aq. Ic is stable in the dark at room temperature, but Ic decomposes quantitatively into IIa by refluxing 50° HCl aq. A reaction pathway is presented and discussed.