Search

Carbon dioxide, CO2 reduction and utilization for organic compounds synthesis are the potential technologies in environmental science and technology. In order to establish efficient CO2 utilization technologies, an effective catalyst for CO2 reduction and utilization is necessary. Among various catalysts, the biocatalyst is one of promising catalysts because it has excellent selectivity for the reaction and substrate. In this review, focusing on biocatalyst “formate dehydrogenase FDH” catalyzing CO2 reduction to formic acid, representative examples of properties, types, structure of active-site of FDH and, reaction mechanism of formic acid oxidation and CO2 reduction with FDH are outlined. A genetic engineering modified FDH and FDH immobilized various support for improving CO2 reduction catalytic activity also are introduced. Moreover, chemical and electrochemical system of CO2 reduction to formic acid with FDH, aqueous homogenous system of visible-light driven CO2 reduction to formic acid with FDH and device for visible-light driven CO2 reduction to formic acid with FDH are also introduced as an application of FDH.

Photochemical and enzymatic production of methanol from CO2 was investigated with the system formate (FDH), aldehyde (AldDH) and alcohol (ADH) dehydrogenases, and methylviologen (MV2+) photoreduction by the visible light photosensitization of organo-photocatalyst, water-soluble porphyrin, tetraphenylporphyrin tetrasulfonate (H2TPPS) in the presence of triethanolamine (TEOA) as an electron donating reagent. To improve the methanol production from CO2, the kinetic parameters for methanol production with ADH and dithionite-reduced MV2+ were clarified. When the sample solution consisting of H2TPPS (100 μM), MV2+ (2.0 mM), TEOA (0.3 M), FDH (2.0 μM), AldDH (2.0 μM) and ADH (2.0 μM) in CO2 saturated 50 mM sodium pyrophosphate buffer was irradiated, continuous methanol production from CO2 was observed and methanol concentration produced was estimated to be 6.8 μM after 100 min irradiation.

Formate dehydrogenase (FDH) is an attractive biocatalyst for converting CO 2 to formic acid in ambient conditions. FDH is applied to the catalyst for the visible-light induced CO 2 – formic acid conversion system consisting of an electron donor, a photosensitizaer and an electron carrier. For improvement of the formic acid production efficiency with this system, the enhancement of electron relay processes among a photosensitizer, an electron carrier and FDH has been needed. We aimed to solve this problem by developing novel electron carrier based on the viologen derivative instead of methylviologen (MV), widely used as an electron carreir. In this study, viologen derivatives with carbamoyl group, 1,1′-dicarbamoylmethyl-4,4′-bipyridinium diiodide (CV) and 1-carbamoylmethyl-1′-methyl-4,4′-bipyridinium diiodide (CMV) were synthesized and applied to the electron carrier for photoinduced CO 2 -formic acid conversion system consisting of triethanolamine, water-soluble zinc porphyrin and FDH. By using CV and CMV, the effective formic acid production in the system of water-soluble zinc porphyrin and FDH was improved compared with that of MV.

Singlet and triplet excited states dynamics of the photosynthetic pigment chlorophyll a in various solvents have been investigated by sub-ns pump-probe spectroscopic measurements with a sub-ns time resolution and a temporal window up to 400 μs. The singlet and triplet lifetimes of chlorophyll a were determined respectively to be 5.2–7.0 ns and 1.2–12 μs, depending on solvents. On a basis of a global analysis of time-resolved spectroscopic data, we estimated an yield of the intersystem crossing from the singlet to triplet excited states chlorophyll a to be about 30% depending not on surrounding environments. The value is much lower than the previously reported values.

Molecular conversion reaction system containing a dye and a biocatalyst catalyzing a reaction of a carbon–carbon bond formation from CO2 as a feedstock were constructed. For example, NADP-malic enzyme (ME, EC1.1.1.40) catalyzes the reaction of introducing CO2 as a carboxy group to pyruvate (C3 compound) to form malate (C4 compound) via oxaloacetate in the presence of natural co-enzyme NADPH. In a recent study, visible light-induced oxaloacetate production from pyruvate and CO2 with the system consisting an electron donor, a photosensitizer, diphenylviologen (PV2+) derivative as an electron mediator and ME was reported. However, the visible light-induced reduction properties of PV2+ with water-soluble Zn porphyrin have not been clarified. In this study, chemical and photo-redox properties of PV2+ were studied. In addition, to produce malate, CO2 saturated reaction solution containing triethanolamine, tetraphenylporphine tetrasulfonate (H2TPPS), pyruvate, PV2+ and ME in the presence of Mg2+, co-factor for ME was irradiated with visible-light, the oxaloacetate and malate were produced.

Acid phosphatase (APase) was immobilized in discrete mesospaces of an assembly of silica nanoparticles (SiO2NPA) to be used as a heterogeneous catalyst for the hydrolysis of organophosphates often found as pesticide residues in agricultural products. APase immobilized in SiO2NPA exhibited higher catalytic activity than APase supported on conventional porous supports for the hydrolysis of p-nitrophenyl phosphate (p-NPP) with quantitative yield of p-nitrophenol below pH 5.5 due to the efficient diffusion of substrates in the SiO2NPA. Especially, a heterogeneous catalyst prepared by the co-accumulation method, in which silica nanoparticles (SiO2NPs) dispersion containing APase was simply dried to assemble a composite catalyst (APase/SiO2NPA), exhibited four times faster rate for the hydrolysis of p-NPP than the catalyst prepared by the equilibrium adsorption of APase in pre-assembled SiO2NPA. The catalytic stability of immobilized APase above pH 6.0 was enhanced by surface modification of SiO2NPs with 3-aminopropyltriethoxysilane (APase/SiO2NPA-NH2) due to the strong electrostatic interaction between APase and the protonated amino groups at the pH condition. Such stability enhancement was hardly obtained by cross-linking treatment of SiO2NPA to improve the robustness. These results suggest that electrostatic interaction between APase and SiO2NPs is crucial to enhance catalytic stability in the wide range of pH as well as preparation methods for the stable encapsulation.

Photochemical synthesis of ethanol from acetate was investigated with the system aldehyde (AldDH) and alcohol (ADH) dehydrogenases from Yeast, and methylviologen (MV2+) photoreduction by the visible light photosensitization of chlorophyll derivative, chlorin-e6 of zinc complex (ZnChl-e6) in the presence of NADPH as an electron donating reagent. Irradiation of a solution containing NADPH, ZnChl-e6, MV2+, AldDH, ADH and sodium acetate with visible light resulted in ethanol synthesis. The concentration of ethanol produced was 1.4 mM after 150 min irradiation under the condition of NADPH (3.3 mM), ZnChl-e6 (100 μM), MV2+ (12 mM), AldDH (0.22 μM), ADH (6.7 nM) and sodium acetate (30 mM) in 50 mM of sodium pyrophosphate buffer pH 7.4).

Effect of chemical structures of some 2,2′-bipyridinium salts (BP2+) as the electron carrier molecules on the visible-light induced conversion of CO2 to formic acid with the system consisting of water-soluble zinc tetraphneylporphyrin tetrasulfonate (ZnTPPS) and formate dehydrogenase (FDH) in the presence of triethanolamine (TEOA) as an electron donor molecule was investigated. Irradiation of a CO2 saturated solution containing TEOA, ZnTPPS, BP2+ and FDH with visible light resulted in production of formic acid. By using 1,1′-ethylene-2,2′-bipyridinium dibromide (DB2+) as an electron carrier molecule, the effective formic acid production was observed compared with the other 2,2′-bipyridinium salt derivatives.

Zinc chlorophyll a derivatives were synthesised for use as photosensitizers. Herein, we report a system for photoinduced hydrogen production with colloidal platinum via photoreduction of methylviologen (MV2+) using the photosensitization of a Zn pyropheophorbide a (ZnPyOH) dimer connected by lysine (ZnPy-K(ZnPy)OH) as a special pair model in the photosynthetic reaction centre in the presence of NADPH as an electron donor.

Hydrogen and formic acid as a hydrogen energy storage material productions system coupling the glucose oxidation with glucose dehydrogenase (GDH), and hydrogen and formic acid productions with platinum nano-particle and formate dehydrogenase (FDH) as a catalyst combination of visible light-induced photoreduction of methylviologen (MV2+) by water soluble zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS) via the NADP+/NADPH redox cycle in the carbon dioxide saturated solution is developed. After 90 min irradiation to above system, the amount of hydrogen and formic acid productions in the system were estimated to be 4.3 and 0.2 μmol, respectively. Hydrogen gas and formic acid as a hydrogen gas carrier molecule were simultaneously produced from the glucose as a biomass and carbon dioxide by using this system.

An optical oxygen sensor was developed as a pressure-sensitive paint (PSP) to measure time-varying surface pressure in aerodynamic testing. A silica nanoparticle dispersion (slurry) was used as the binder for the sensor, with a pressure-sensitive dye dissolved in the slurry. The dye slurry was deposited onto arbitrary surfaces via spray coating. Thin porous silica films were successfully formed without any organic additives. The pressure and temperature sensitivity of common pressure-sensitive dyes platinum tetra(pentafluorophenyl)porphyrin (PtTFPP)and tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II)dichloride ([Ru(dpp) 3 ]Cl 2 ) with a silica/toluene slurry were tested, in addition to the temporal response. The pressure sensitivity was −0.94%/kPa for PtTFPP and −0.64%/kPa for [Ru(dpp) 3 ] 2+ , which was comparable to the sensitivity of common PSPs. The sensor had good photostability, although it exhibited substantial temperature sensitivity (ca. 1.5%/°C). The response time was less than 0.1 ms for a step rise in pressure obtained using a shock tube.

Photosynthesis dye chlorophyll derivative chlorin-e 6 , viologen (electron carrier) and platinum nano-particle immobilized onto silica gel based thin layer substrate is for photoinduced hydrogen production is developed. When the chlorin-e6, viologen and platinum nano-particle immobilized onto substrate is irradiated with 100 mWcm -2 visible light in the presence of NADPH as an electron donor, the hydrogen production is observed. After 2 h irradiation, 6.0×10 -8 mol of hydrogen is produced.

Cellulase obtained from Aspergillus niger was used to hydrolyze a mixture of saccharides containing sucrose, maltose, and cellobiose; the reduced form of nicotinamide-adenine dinucleotide (NAD+), which is NADH, was produced during hydrolysis of the mixture of saccharides in the presence of NAD+ and glucose dehydrogenase (GDH). We have developed a visible-light-induced enzymatic biohydrogen production system involving the combination of cellulase-mediated hydrolysis of the mixture of saccharides and hydrogen production by platinum nanoparticles using photosensitization of Mg chlorophyll-a (Mg Chl-a). Continuous production of hydrogen gas was observed when the reaction mixture containing saccharides, cellulase, GDH, NAD+, Mg Chl-a, methylviologen (MV2+, an electron donor), and platinum nanoparticles was irradiated by visible light. After 120 min of irradiation, the amount of hydrogen produced from the mixture of saccharides was approximately 2.8 μmol.

To develop the visible light-induced hydrogen and oxygen production based on the water photolysis, 2,6-dichloroindophenol (DCIP) reduction based on the photoinduced water oxidation with oxygen evolved centre (OEC) of PSII in photosynthesis organ, grana from spinach was studied. It noted that manganese–calcium (4Mn–Ca) cluster consisted of four manganese and one calcium ions in OEC, and the role and effect of manganese (III) and calcium ions on the DCIP reduction were investigated. By addition of manganese (III) acetate up to 80 μmol dm −3 , the concentration of the reduced DCIP with irradiation was increased compared with the system in the absence of manganese (III) acetate. The activity of DCIP reduction in the presence of 80 μmol dm −3 manganese (III) acetate was 4.7 times higher than that in the absence of manganese (III) acetate. This result shows that the DCIP photoreduction with grana was promoted by addition of manganese (III) ion. In contrast, the activity of DCIP reduction in the presence of 120 μmol dm −3 manganese (III) acetate was 1.5 times higher than that in the absence of manganese (III) acetate, indicating that photoreduction of DCIP activity of grana was inhibited under higher concentration of manganese (III) ion or acetate anion. By addition of 80 μmol dm −3 calcium chloride, on the other hand, 5.9 μmol dm −3 of reduced DCIP was produced and the reduction ratio of the reduced DCIP to DCIP was 8.6% after 240 min irradiation. The activity of DCIP reduction in the presence of 80 μmol dm −3 calcium chloride was almost the same in the absence of calcium chloride. This result shows the no effect on the DCIP photoreduction based on the water oxidation with grana by addition of calcium ion.

We studied the photochemical and enzymatic synthesis of methanol from HCO3− using formate dehydrogenase (FDH) isolated from Candida boidinii, aldehyde dehydrogenase (AldDH) and alcohol dehydrogenase (ADH) isolated from yeast, and the photoreduction of methyl viologen (MV2+) by the visible-light sensitization using zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS) in the presence of triethanolamine (TEOA). When a sample solution containing ZnTPPS, MV2+, FDH, AldDH, ADH, TEOA, and NaHCO3 in potassium phosphate buffer solution (pH 8) was irradiated, the amount of methanol produced increased with the irradiation time. After irradiation for 3 h, 4.5 μmol dm−3 of methanol was produced from 100 μmol dm−3 NaHCO3. The conversion ratio of HCO3− to methanol was approximately 4.5%. This result indicates that a system for the photochemical synthesis of methanol from HCO3− can be developed by using three dehydrogenases (FDH, AldDH, and ADH) and for the photoreduction of MV2+ through the photosensitization of ZnTPPS in aqueous media.

To develop the visible light induced hydrogen and oxygen production based on the water photolysis, 2,6-dichloroindophenol (DCIP) reduction based on the photoinduced water oxidation with oxygen evolved centre (OEC) of PSII in photosynthesis organ, grana from spinach was studied. It noted that manganese cluster consisted of four manganese ions in OEC, and the role and effect of manganese(II) and (III) ions on the DCIP reduction were investigated. By addition of manganese(III) acetate up to 80 μmol dm −3 , the concentration of the reduced DCIP with irradiation was increased compared with the system in the absence of manganese(III) acetate. The activity of DCIP reduction in the presence of 80 μmol dm −3 manganese(III) acetate was 4.7 times higher than that in the absence of manganese(III) acetate. In contrast, the concentration of the reduced DCIP with irradiation was increased by addition of manganese(II) acetate up to 40 μmol dm −3 compared with the system in the absence of manganese(II) acetate. These results show that the DCIP photoreduction with grana was promoted by addition of manganese(III) or (II) ion.

The visible light-operated saccharide–O2 biofuel cell consisting of zinc chlorin-e6 (ZnChl-e6) adsorbed on nanocrystalline TiO2 layer coated onto optical transparent conductive glass electrode (OTE) as an anode, platinum-coated OTE as a cathode, and the fuel solution containing sucrose as a saccharide, invertase, glucose dehydrogenase (GDH) and NAD+ is studied as a new type biofuel cell. The short-circuit photocurrent (ISC) and the open-circuit photovoltage (VOC) of this cell are 9.0 μA cm−2 and 415 mV, respectively. The peaks in the photocurrent action spectrum of this cell are observed at 400 and 800 nm and the incident photon-to-current efficiency (IPCE) values at 400 and 800 nm are estimated to be ca. 17.3% and 10.6%. Thus, a new type of visible light-operated saccharide–O2 biofuel cell with the visible and near IR photosensitization of ZnChl-e6 molecules on nanocrystalline TiO2 film electrode is accomplished.

Here, we developed a photoinduced biohydrogen production system coupling saccharide hydrolysis with hydrogen production. A mixture of three different saccharides (sucrose, maltose, and cellobiose) was hydrolyzed by three enzymes (invertase, glucoamylase, and cellulase) and glucose dehydrogenase (GDH). Hydrogen production was performed with colloidal platinum as a catalyst, using visible light-induced photosensitization of Mg chlorophyll a (Mg Chl a ). Irradiation of the sample solution containing the saccharides, enzymes, GDH, NAD + , Mg Chl a , methyl viologen (MV 2+ ), and colloidal platinum resulted in continuous hydrogen production. Approximately 2.9 μmol hydrogen was produced after 2 h of irradiation, and the total yield was approximately 8.8%.

Chlorophyll- a (Chl- a ) assembled in hydrophobic domain by fatty acid with long alkyl hydrocarbon chain such as myristic acid (Myr), stearic acid (Ste) and cholic acid (Cho) modified onto nanocrystalline TiO 2 electrode is prepared and the photovoltaic properties of the nanocrystalline TiO 2 film by Chl- a are studied. Incident photon to current efficiency (IPCE) value at 660 nm in photocurrent action spectrum of Chl- a /Ste-TiO 2 , Chl- a /Myr-TiO 2 and Chl- a /Cho-TiO 2 electrodes are 5.0%, 4.1% and 4.1%, respectively. Thus, the IPCE is maximum using Chl- a /Ste-TiO 2 electrode. From the results of photocurrent responses with light intensity of 100 mW cm −2 irradiation or monochromatic light with 660 nm, generated photocurrent increases using Chl- a /Ste-TiO 2 electrode compared with the other Chl- a assembled TiO 2 electrodes. These results show that the hydrophobic domain formed by stearic acid with long alkyl hydrocarbon chain is suitable for fixation of Chl- a onto TiO 2 film electrodes and photovoltaic performance is improved using Chl- a onto Ste-TiO 2 film electrode.

Visible light and enzymatic induced synthesis of malic acid from pyruvic acid and HCO 3 - with malic enzyme (ME) and NADP+ photoreduction by the visible light photosensitization of chlorophyll derivative, zinc chlorin-e6 (Zn Chl-e6) in the presence of NADH as an electron-donating reagent was investigated. When the sample solution containing NADH, Zn Chl-e6, methylviologen (MV2+), pyruvic acid, NaHCO3, NADP+, ferredoxine-NADP+-reductase (FNR) and ME was irradiated with visible light (>390 nm), malic acid was produced. The produced malic acid was 0.65 mmol dm−3 after 3 h visible light irradiation.

Photovoltaic conversion using zinc chlorin-e6 (ZnChl-e6), which is zinc chlorophyll-a derivative, and fatty acid (myristic acid or cholic acid) co-adsorbed nanocrystalline TiO2 layer onto ITO glass (OTE) electrode is developed. The maximum peaks of photocurrent action spectrum of the ZnChl-e6 adsorbed TiO2 layer onto OTE (ZnChl-e6/TiO2) are 400, 660 and 800 nm, respectively. Especially the IPCE value at 800 nm (7.5%) is larger than that of 660 nm (6.9%). This result indicates that ZnChl-e6 molecules is aggregated or formed dimer on a nanocrystalline TiO2 layer onto OTE and the absorption band is shifted to near IR region. The photocurrent action spectrum of ZnChl-e6 and cholic acid adsorbed TiO2 layer onto OTE (ZnChl-e6–Cho/TiO2) is similar to that of the UV–vis absorption spectrum in methanol solution, and IPCE values at 400 and 660 nm (8.1%) increase and the IPCE value at 800 nm (4.1%) decreases, indicating that the aggregation of ZnChl-e6 molecules on the TiO2 is suppressed by cholic acid. By using ZnChl-e6–Cho/TiO2, the short-circuit photocurrent density and open-circuit photovoltage also increase compared with that of ZnChl-e6 adsorbed nanocrystalline TiO2 electrode.

Zn chlorophyll- a derivative, Zn chlorin-e 6 (ZnChl-e 6 ) and carotenoid derivative, crocetin (Cro) adsorbed onto a nanocrystalline TiO 2 film (ZnChl-e 6 -Cro/TiO 2 ) electrode was prepared and the photovoltaic properties of ZnChl-e 6 -Cro/TiO 2 electrode were studied. Incident photon to current efficiency (IPCE) value at 640 nm in photocurrent action spectrum of ZnChl-e 6 -Cro/TiO 2 electrode was ca. 2.50%. In contrast, IPCE value at 640 nm in ZnChl-e 6 /TiO 2 electrode was ca. 1.27%. Thus, the IPCE value increases by co-adsorbed crocetin and ZnChl-e 6 onto TiO 2 film electrode. From the results of photocurrent responses with light intensity of 100 mW cm −2 irradiation, generated photocurrents in the ZnChl-e 6 -Cro/TiO 2 and ZnChl-e 6 /TiO 2 electrodes are 380 and 180 μA cm −2 , respectively. Photocurrent increases using ZnChl-e 6 -Cro/TiO 2 electrode compared with that of ZnChl-e 6 /TiO 2 electrode.

Photoinduced hydrogen production with Mg chlorophyll- a (MgChl- a ) from spirulina as a visible-light photosensitizer by use of three component system consisting of NADH as an electron donor, methylviologen (MV 2+ ) as electron relay reagent and colloidal platinum as hydrogen production catalyst in cationic surfactant, alkyltrimethyl bromide with different methylene chain length (CH 3 (CH 2 ) n N + (CH 3 ) 3 ·Br − ; n = 9, 13 and 15) micellar media is investigated. Consequently, the effective MV 2+ photoreduction and hydrogen production system is accomplished using MgChl- a in CH 3 (CH 2 ) 15 N + (CH 3 ) 3 ·Br − micellar media.

Preparation of intercalation compounds using H 3 PO 4 electrolyte solution in mesophase-pitch-based carbon fibers successfully carried out by electrolysis in less than 10 mol/dm 3 of its electrolyte solution. Structural changes with preparation of intercalation compounds of carbon fibers were confirmed by a peak appeared around 2 θ =8° observed after electrolysis, which corresponds to an interlayer spacing of about 0.9 nm through XRD pattern (anticathode: Cu Kα). This new peak was reasonably supposed to be due to the intercalation into interspacing of carbon layers. Suitable synthesis condition of the intercalation compounds was determined to be the concentration of electrolyte of 5 mol/dm 3 at the electrolysis. It was also confirmed by morphology changes through SEM, that is carbon fibers, which treated low electrolyte concentration synthesized the intercalation compounds easily, and then it revealed markedly morphology changes such as fibrils. It could become exfoliation as well as them treated by other acid treatment through rapid heat-treatment. The formation of graphite oxide was suggested when the kind of intercalate was analyzed with elementary and TPD analysis.

Photochemical and enzymatic formic acid synthesis from CO 2 gas system with the combination of formate dehydrogenase (FDH) from Saccharomyces cerevisiae and methylviologen (MV 2+ ) reduction by the visible light photosensitisation of Mg chlorophyll- a (Mg Chl- a ) is developed. Photochemical formic acid produced from CO 2 by adding FDH to the MV 2+ photoreduction system using photosensitisation of Mg Chl- a in the presence of NADPH as an electron donating reagent, and 56 μM of formic acid from CO 2 gas is produced after 4 h irradiation (1.0 M = 1.0 mol dm −3 ).

Biohydrogen production with the light-harvesting function of grana from spirulina by use of three-component system consisting of NADH, methylviologen ( MV 2 + ) and colloidal platinum was investigated. The decay rate of chlorophyll included in grana was suppressed by addition of NADH and little degradation was observed in 120 min irradiation. The biohydrogen production system was developed using the light-harvesting function of grana and platinum colloid in the presence of NADH and MV 2 + and the amount of hydrogen produced was estimated to be 0.14 μ mol after 4 h irradiation.

In order to investigate photoluminescence behaviour of an ordered molecular porphyrin monolayer and its quenching properties by oxygen gas, a porphyrin with long alkyl chains, 5,10,15,20-tetrakis[4-(11-carboxylundecane-1-oxy)phenyl]porphyrin ( 4 ), was synthesized and adsorbed onto an indium-tin oxide (ITO) substrate by a chemical dipping method. Cyclic voltammetry was used to analyze the ITO electrode coated with 4 . The peak current of the first oxidation was proportional to the sweep rate, and the surface coverage was estimated to be 2.3–2.5 × 10 −10 mol cm −2 . The UV–vis spectrum of the monolayer showed a broadened Soret band, which shifted to longer wavelength. These features suggest that the porphyrin moieties of 4 are packed to form a J -type structure. The oxygen quenching ratio of the porphyrin 4 monolayer on the ITO electrode, I 0 / I 100 , was estimated to be 1.25, where I 0 and I 100 are, respectively, luminescence intensity values in 100% argon and 100% oxygen. On repeated step cycling between 100% argon and 100% oxygen atmospheres, the response times of luminescence quenching were 10 s (argon to oxygen) and 23 s (oxygen to argon). These findings suggest that a monolayer of sensing dye is applicable for oxygen sensing system without deterioration of size-accuracy of models.

A new optical CO 2 sensor based on luminescence intensity changes of tetraphenylporphyrin (TPP) due to the absorption change of pH indicator dye (α-naphtholphthalein) with CO 2 is developed and its CO 2 sensing properties in pure water are investigated. The observed luminescence intensity from TPP at 650 nm increased with increasing the CO 2 concentration in pure water. The ratio I 100 / I 0 , where I 0 and I 100 represent the detected luminescence intensities from a layer exposed to 100% argon and 100% CO 2 , respectively, that we takes the sensitivity of the sensor is estimated to be 430. The response times of the sensing film are 42.6 s for switching from argon to CO 2 , and 88.8 s for switching from CO 2 to argon in pure water. The signal changes are fully reversible and no hysterisis is observed during the measurements.

An optical CO(2) sensor based on the overlay of the CO(2) induced absorbance change of pH indicator dye alpha-naphtholphthalein in poly(isobutyl methacrylate) (polyIBM) layer with the fluorescence of tetraphenylporphyrin (TPP) in polystyrene layer is developed. The observed luminescence intensity from TPP at 655nm increased with increasing the CO(2) concentration. The ratio I(100)/I(0) value of the sensing film consisting of alpha-naphtholphthalein in polyIBM and TPP in polystyrene layer, where I(0) and I(100) represent the detected luminescence intensities from a layer exposed to argon and CO(2) saturated conditions, respectively, that the sensitivity of the sensor, is estimated to be 192. The response and recovery times of the sensing film are less than 6.0s for switching from argon to CO(2), and for switching from CO(2) to argon. The signal changes are fully reversible and no hysterisis is observed during the measurements. The highly sensitive optical CO(2) sensor based on fluorescence intensity changes of TPP due to the absorption change of alpha-naphtholphthalein in polyIBM layer with CO(2) is achieved.

To elucidate the role of cardiolipin (CL) on redox behavior of cytochrome c (cyt c (III)), the photoreduction of cyt c using the photosensitization of zinc tetraphenylporphyrin in presence of triethanolamine (TEOA) as a sacrificial electron-donating reagent in various lipid media were studied. The initial rate of cyt c (III) photoreduction in various lipid, CL, l -α-phosphatidic acid (PA), dimethyldipalmitoylammonium bromide (DMPA) and Triton X-100 media were 1.0, 0.73, 0.80 and 0.67 μmol dm−3 min−1, respectively. The cyt c (III) photoreduction rate slightly increased by the addition of CL.

An optical CO 2 sensor based on the overlay of the CO 2 induced absorbance change of pH indicator dye α-naphtholphthalein in poly(trimethylsiliypropyne) (poly(TMSP))layer with the fluorescence of tetraphenylporphyrin (TPP) in polystyrene layer is developed. The observed luminescence intensity from TPP at 655 nm increased with increasing the CO 2 concentration. The ratio I 100 / I 0 value of the sensing film, where I 0 and I 100 represent the detected luminescence intensities from a layer exposed to 100% argon and 100% CO 2 , respectively, that the sensitivity of the sensor, is estimated to be 10.3. The response and recovery times of the sensing film are less than 3.0 s for switching from argon to CO 2 , and for switching from CO 2 to argon. The signal changes are fully reversible and no hysteresis is observed during the measurements. The highly sensitive and fast responsible optical CO 2 sensor based on fluorescence intensity changes of TPP due to the absorption change of α-naphtholphthalein with CO 2 is achieved using poly(TMSP) film.

Visible light-induced enzymatic hydrogen production coupling the enzymatic oligosaccharide degradation and hydrogen production with platinum colloid using the photosensitization of Mg chlorophyll-a (Mg Chl-a) has been developed. The continuous hydrogen gas production was observed when the reaction mixture containing oligosaccharide (sucrose or maltose), invertase, glucose dehydrogenase, nicotinamide adenine dinucleotide (NAD+), Mg Chl-a, methylviologen (MV2+, an electron relay reagent) and platinum colloid was irradiated by visible light. After 420 min irradiation, the amounts of hydrogen production from sucrose and from maltose were estimated to be 4.3 and 0.40 μmol , respectively.

A dye-sensitized solar cell using the visible light sensitization of chlorophyll-a derivative, chlorine-e 6 (Chl-e 6 ) immobilized on TiO 2 film was developed. From fluorescence spectrum of Chl-e 6 immobilized on TiO 2 film, the emission of Chl-e 6 was effectively quenched by TiO 2 , indicating that the effective electron injection from the excited singlet state of Chl-e 6 into the conduction band of TiO 2 occurred. The short-circuit photocurrent density ( I SC ), the open-circuit photovoltage ( V OC ), and the fill factor (FF) of solar cell consisting of Chl-e 6 immobilized on TiO 2 film electrode and platinum-coated substrate electrode were estimated to be 1.47 mA cm −2 , 425 mV, and 57.0%, respectively. IPCE values were reached a maximum around the wavelength of absorption maximum (11.0% at 400 nm, 4.7% at 541 nm and 7.9% at 661 nm), indicating that the dye-sensitized solar cell using visible light sensitization of TiO 2 film by Chl-e 6 was developed.

A new optical CO2 sensor based on the overlay of the CO2 induced absorbance change of pH indicator dye α-naphtholphthalein with the fluorescence of tetraphenylporphyrin (TPP) was developed. The observed luminescence intensity from TPP at 655 nm increased with increasing the CO2 concentration. The ratio I100/I0 values of the sensing films consisting of α-naphtholphthalein in ethyl cellulose layer and TPP in polystyrene layer, where I0 and I100 represent the detected luminescence intensities from a layer exposed to 100% nitrogen and 100% CO2, respectively, that the sensitivity of the sensor, are more than 53.9. The response and recovery times of the sensing films consisting of α-naphtholphthalein in ethyl cellulose layer and TPP in polystyrene layer were less than 5 s for switching from nitrogen to CO2, and for switching from CO2 to nitrogen. The signal changes were fully reversible and no hysterisis was observed during the measurements. The highly sensitive optical CO2 sensor based on fluorescence intensity changes of TPP due to the absorption change of α-naphtholphthalein with CO2 was achieved.

Oxygen sensing properties of optical sensor using layer of 1-pyrenedecanoic acid and perfluorodecanoic acid chemisorbed onto anodic oxidized aluminium plate was investigated. The ratio I 0 / I 100 , where I 0 and I 100 represent the detected fluorescence intensities from a substrate exposed to 100% argon and 100% oxygen, respectively, is used as an indicator of the sensitivity of the sensing film. The I 0 / I 100 value of 1-pyrenedecanoic acid and perfluorodecanoic acid layer chemisorbed onto the anodic oxidized aluminium plate is estimated to be 18.6. On the other hand, the I 0 / I 100 value of 1-pyrenedecanoic acid chemisorbed onto the anodic oxidized aluminium plate is 20.2. The response time of the 1-pyrenedecanoic acid layer is 8.5 s on going from argon to oxygen and the recovery time is 40 s on going from oxygen to argon, respectively. In contrast, the response and recovery times of the 1-pyrenedecanoic acid and perfluorodecanoic acid chemisorbed layer are 3.0 and 22 s, respectively. Thus, the optical oxygen sensor using 1-pyrenedecanoic acid and perfluorodecanoic acid chemisorbed layer has rapid response and recovery times.

A bio-photovoltaic conversion device based on dye-sensitised solar cell (DSSC) using the visible light sensitisation of chlorine-e6 (Chl-e6) derived from chlorophyll from Spirulina adsorbed on a nanocrystalline TiO2 film was developed. Form fluorescence spectrum of Chl-e6 adsorbed on a nanocrystalline TiO2 film, the emission of Chl-e6 was effectively quenched by TiO2 nanocrystalline indicating that the effective electron injection from the excited singlet state of Chl-e6 into the conduction band of TiO2 particles occurred. The short-circuit photocurrent density (ISC), the open-circuit photovoltage (VOC), and the fill factor (FF) of solar cell using Chl-e6 adsorbed on a nanocrystalline TiO2 film electrode were estimated to be 0.305±0.012 mA cm−2, 426±10 mV, and 45.0%, respectively. IPCE values were reached a maximum around the wavelength of absorption maximum (7.40% at 400 nm; 1.44% at 514 nm and 2.91% at 670 nm), indicating that the DSSC using visible light sensitisation of nanocrystalline TiO2 film by Chl-e6 was developed.

Effect of micellar species on the photostability of Mg chlorophyll-a and the photoinduced hydrogen production with Mg chlorophyll-a by use of three component system consisting of NADPH, methylviologen and colloidal platinum was investigated. Triton X-100 and CTAB solublized Mg chlorophyll-a solution were rapidly bleached by irradiation and 50% of Mg chlorophyll-a was degraded in 90 min irradiation. On the other hand, the decay rate of Mg chlorophyll-a concentration in the presence of NADPH was suppressed and the degradation rate was 15% in 90 min irradiation. The effective hydrogen production system was developed using CTAB solubilized Mg chlorophyll-a ( 2.7 μmol in 4 h ), compared with that using Triton X-100 solubilized Mg chlorophyll-a ( 0.1 μmol in 4 h ) .

Photochemical synthesis of formic acid was investigated from hydrogen carbonate ion with formate dehydrogenase (FDH) from Saccharomyces cerevisiae and methylviologen (MV2+) photoreduction by the visible light photosensitisation of zinc tetrakis(4-methylpyridyl) porphyrin (ZnTMPyP) in the presence of triethanolamine (TEOA) as an electron donating reagent. Irradiation of a solution containing TEOA, ZnTMPyP, MV2+, sodium hydrogen carbonate and FDH with visible light resulted in formic acid synthesis. The concentration of formic acid was 62 μM after 3 h irradiation under the condition of 30 μM MV2+, 20 units FDH and pH 8.

Photochemical hydrogen production with the system containing triethanolamine, zinc tetraphenylporphyrin tetrasulfonate, methylviologen and hydrogenase in cationic surfactant, cetyltrimethylammonium bromide (CTAB) was investigated. The effective photoreduction of methylviologen and an effective hydrogen production with hydrogenase were accomplished in the presence of CTAB micellar system by optimizing the reaction condition.

A new optical CO2 sensor based on the overlay of the CO2 induced absorbance change of pH indicator dye thymol blue with the luminescence of europium(III) complex, tris(thenoyltrifluoroacetonato) europium(III) dihydrate complex [(Eu(tta)3)] was developed. The observed luminescence intensity from [(Eu(tta)3)] at 613 nm increased with the increasing CO2 concentration. The response times of the sensing film were 4.0 s for switching from nitrogen to CO2, and 36 s for switching from CO2 to nitrogen, respectively. The signal changes were fully reversible and hysterisis was not observed during the measurements.

Controlling the excimer formation of pyrene-1-butylic acid (PBA) chemisorption layer onto nano-porous anodic oxidized aluminium plate by myristic acid layer was attempted and the optical oxygen-sensitivity using PBA and myristic acid co-chemisorption layer was controlled by varying the molar ratio of myristic acid to PBA. When the [myristic acid]/[PBA] value increased, the fluorescence intensities at 376 and 396 nm attributed to monomer emission increased and the intensity at 474 nm attributed to excimer emission decreased, indicating that the excimer formation between PBA molecules onto nano-porous anodic oxidized aluminium plate was suppressed by the myristic acid layer. The oxygen-sensitivity is changed by controlling the excimer formation of PBA by co-chemisorption of myristic acid.

Optical oxygen sensor based on the fluorescence quenching of pyrene derivatives with carboxyl group, pyrene-1-decanoic acid, pyrene-1-dodecanoic acid and pyrene-1-butyric acid chemisorption layers onto alumina plate were developed. The fluorescence intensity of pyrene derivatives layer decreased with increasing of oxygen concentration, indicating that the pyrene derivatives layer can be used as an optical oxygen sensing device based on fluorescence quenching by oxygen. The ratio I0/I100, where I0 and I100 represent the detected fluorescence intensities from a layer exposed to 100% argon and 100% oxygen, respectively, as a sensitivity of the sensing layers are estimated to be 50.7 for pyrene-1-decanoic acid, 44.7 for pyrene-1-dodecanoic acid and 73.4 for pyrene-1-butyric acid, showing that the pyrene-1-butyric acid layer is highly sensitive device for oxygen concentration. These samples obeyed Stern–Volmer plots with multi-site model and possessed good operational stability. Response times are 10 s for pyrene-1-decanoic acid, 5.0 s for pyrene-1-dodecanoic acid and 5.0 s for pyrene-1-butyric acid for argon saturated to oxygen saturated conditions and 50.0 s for pyrene-1-decanoic acid, 50.0 s for pyrene-1-dodecanoic acid and 50.0 s for pyrene-1-butyric acid for the reverse conditions. These are stable sensing layers against irradiation that exhibit minimal decrease (ca. 7%) in initial intensity after continuous irradiation for 24 h.

The optical oxygen sensors were prepared using the some Ru(II) polypyridyl complexes, tris(4,7′-diphenyl-1,10′-phenanthroline) ruthenium(II) dichloride (Ru(ph2phen)32+), tris(1,10′-phenanthroline) ruthenium(II) dichloride (Ru(phen)32+) and tris(2,2′-bipyridine) ruthenium(II) dichloride (Ru(bpy)32+), electrostatically attached to anionic polymer, poly(acrylic acid) and poly(sodium-4-styrene sulfonate) chemisorption thin film onto alumina plate. These sensing films were good linearity using modified Stern–Volmer plot based on two-site model (oxygen-accessible site and oxygen-difficult accessible site) in total oxygen concentration region. These results show that Ru(II) polypyridyl complexes attached to anionic polymer films onto alumina plate can be developed for a highly sensitive device for oxygen sensing. Especially, the superior oxygen sensors are developed using Ru(II) polypyridyl complex in poly(sodium 4-styrene sulfonate) film.

An optical oxygen-sensing material based on the fluorescence intensity changes of pyrene-1-butyric acid (PBA) chemisorption film has been developed and characterised. The fluorescence intensity of PBA film decreased with increase of oxygen concentration. The I 0 / I 100 value of PBA film is estimated to be 6.14±0.15 and large Stern–Volmer constant ( K SV =0.028±0.13 Torr −1 ) is obtained. After irradiation for 24 h with 150 W tungsten lamp, little changes of oxygen-sensing properties were observed. These results indicate that PBA film is highly oxygen-sensitive and photostability device. The response times of the PBA chemisorption film were 10.0 s for switching from argon to oxygen, and 53.0 s for switching from oxygen to argon. Moreover, the optical sensor based on the PBA chemisorption film was applied to the measurement of oxygen concentration in aqueous solution.

An optical oxygen sensor based on the fluorescence quenching of 1-pyrenedecanoic acid chemisorption film was developed. The I 0 / I 100 value, where I 0 and I 100 represent the detected fluorescence intensities from a film exposed to 100% argon and 100% oxygen, respectively, of 1-pyrenedecanoic acid film is estimated to be 36.6. The 1-pyrenedecanoic acid chemisorption film onto alumina plate is a highly sensitive device for oxygen compared with the other oxygen sensor using pyrene compounds.

Photoinduced hydrogen production with the system containing triethanolamine, zinc tetraphenylporphyrin tetrasulfonate, methylviologen and hydrogenase in various nonionic surfactant micellar was investigated. The effective photoreduction of methylviologen and an effective hydrogen production with hydrogenase were accomplished in the presence of various nonionic surfactants (Triton X-100, Triton X-305, Nonidet P-40, Triton N-101, Tween-20 and Tween-40) micellar system. Especially, the hydrogen production rate was increased by an addition of Tween-40 dramatically.

A series of new fluorine-containing poly(aryl ether ketone)s (8F-PEKEK(Ar); Ar: 2-2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (6FBA), 2,2-bis(4-hydroxyphenyl)propane (BA), 2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane (3,4′-BA) or 9,9′-bis(4-hydroxyphenyl)fluorine (HF)) are synthesized and applied to the matrix of optical oxygen sensing using phosphorescence quenching of metalloporphyrins, platinum and palladium octaethylporphyrin, (PtOEP and PdOEP) by oxygen. The phosphorescence intensity of PtOEP and PdOEP in 8F-PEKEK(Ar) films decreased with increase of oxygen concentration. The ratio I0/I100 is used as a sensitivity of the sensing film, where I0 and I100 represent the detected phosphorescence intensities from a film exposed to 100% argon and 100% oxygen, respectively. For PtOEP in 8F-PEKEK(Ar) film, I0/I100 values are more than 20.0 and large Stern–Volmer constants more than 0.19%−1 are obtained compared with PtOEP in polystyrene film. For PdOEP in 8F-PEKEK(Ar) film, on the other hand, the large I0/I100 values more than 143 are obtained. However, the Stern–Volmer plots of PdOEP in 8F-PEKEK(Ar) films exhibit considerable linearity at lower oxygen concentration range between 0% and 20%. These results indicate that PtOEP and PdOEP films are useful optical oxygen sensor at the oxygen concentration range between 0% and 100% and between 0% and 20%, respectively. The response times of PtOEP and PdOEP dispersed in 8F-PEKEK(Ar) films are 5.6 and 3.0 s on going from argon to oxygen and 110.1 and 160.0 s from oxygen to argon, respectively.