Yutaka Amao

Characterization of an ultrathin polymer optode and its application to temperature sensors based on luminescent europium complexesElectronic supplementary information (ESI) available: surface plasmon curves and X-ray diffraction pattern of p(DDA-Eu(TTA)3Phen) LB films. See http://www.rsc.org/suppdata/jm/b3/b307309b/

This paper focuses on an ultrathin polymer optode containing europium complexes (p(DDA-Eu(TTA)3Phen)). Ultrathin films were prepared by the Langmuir–Blodgett (LB) technique; a mixed solution of poly(N-dodecylacrylamide) n(pDDA) and tris(4,4,4-trifluoro-1-(2-thienyl)-1,3-butanediono)-1,10-phenanthroline europium(III) n(Eu(TTA)3Phen) was spread onto a water subphase and the condensed monolayer was transferred onto a solid substrate. The spectroscopic properties and layer structure of p(DDA-Eu(TTA)3Phen) LB films were investigated by UV-Vis spectroscopy, fluorescence spectroscopy, time-resolved luminescence decay measurement, X-ray diffraction, and surface plasmon spectroscopy. It was found that europium complexes were uniformly distributed in the ultrathin films compared with a cast film. The p(DDA-Eu(TTA)3Phen) optodes showed efficient sensitivity to temperature in the range of 320 to 370 K. The findings demonstrate that the p(DDA-Eu(TTA)3Phen) optode is a good candidate for temperature sensitive sensors.

Artificial leaf device for solar fuel production

Solar fuels, such as hydrogen gas produced from water and methanol produced from carbon dioxide reduction by artificial photosynthesis, have received considerable attention. In natural leaves the photosynthetic proteins are well-organized in the thylakoid membrane. To develop an artificial leaf device for solar low-carbon fuel production from CO2, a chlorophyll derivative chlorin-e6 (Chl-e6; photosensitizer), 1-carboxylundecanoyl-1-methyl-4,4-bipyrizinium bromide, iodide (CH3V(CH2)9COOH; the electron carrier) and formate dehydrogenase (FDH) (the catalyst) immobilised onto a silica-gel-based thin layer chromatography plate (the Chl-V-FDH device) was investigated. From luminescence spectroscopy measurements, the photoexcited triplet state of Chl-e6 was quenched by the CH3V(CH2)9COOH moiety on the device, indicating the photoinduced electron transfer from the photoexcited triplet state of Chl-e6 to the CH3V(CH2)9COOH moiety. When the CO2-saturated sample solution containing NADPH (the electron donor) was flowed onto the Chl-V-FDH device under visible light irradiation, the formic acid concentration increased with increasing irradiation time.

Photoluminescent oxygen sensing using palladium tetrakis(4-carboxyphenyl)porphyrin self-assembled membrane on alumina

An optical oxygen sensor based on the photoluminescent quenching of palladium tetrakis(4-carboxyphenyl)porphyrin (PdTCPP) self-assembled membrane on an alumina plate has been developed. The luminescence intensity of PdTCPP membrane decreased with increase of oxygen concentration, indicating that this membrane is a highly sensitive device for oxygen concentration. The signal changes of this membrane are large enough to allow quantification of oxygen with good sensitivity (I0/I100 > 3). The response times of the sensor are 36 s on going from argon to oxygen and 148 s from oxygen to argon. This is a photostable sensing membrane that exhibits minimal decrease (ca 5%) in initial intensity after continuous irradiation for 24 h.

Novel optical oxygen sensing material: platinum porphyrin–styrene–pentafluorostyrene copolymer film

A new fluoropolymer, poly(styrene-co-pentafluorostyrene) [copoly(styrene/PFS)], is synthesized and applied to the matrix of optical oxygen sensing using phosphorescence quenching of platinum octaethylporphyrin (PtOEP) by oxygen. The phosphorescence intensity of PtOEP–poly(styrene-co-PFS) film decreased with increase of oxygen concentration. The ratio I0/I100 is used to describe the 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. The I0/I100 of PtOEP–poly(styrene-co-PFS) film is estimated to be 18.0 and a large Stern–Volmer constant is obtained compared with PtOEP–polystyrene film (I0/I100=4.5). The response times of PtOEP–poly(styrene-co-PFS) film are 5.66 s on going from argon to oxygen and 30.0 s from oxygen to argon. This result indicates that PtOEP–copoly(styrene/PFS) film is a highly sensitive device for oxygen.

Formate dehydrogenase–viologen-immobilized electrode for CO2 conversion, for development of an artificial photosynthesis system

Formate dehydrogenase (FDH)–viologen with a long alkyl chain (CH3V(CH2)nCOOH) immobilized on an indium–tin oxide (ITO) electrode, with the function of reduction of CO2 to formic acid, was investigated as an artificial photosynthesis device based on CO2 reduction. The amount of formic acid produced by use of FDH–CH3V(CH2)nCOOH immobilized on ITO in CO2-saturated buffer solution, on application of a potential, as a result of one-electron reduction of viologen, depends on the carbon chain length of CH3V(CH2)nCOOH. When a CH3V(CH2)9COOH–FDH/ITO electrode was used, production of formic acid was estimated to be 23xa0μmol after 3xa0h.

Novel artificial co-enzyme based on viologen skeleton for highly efficient CO2 reduction to formic acid with formate dehydrogenase

Formate dehydrogenase (FDH) is an attractive catalyst for the reduction of CO2 because CO2 is converted to formic acid by FDH at room temperature under normal pressure in neutral aqueous solution. The reduced form of methylviologen acts as an artificial co‐enzyme for FDH in the conversion of CO2 to formic acid. To improve the catalytic activity of FDH in reducing CO2, viologen derivatives with ionic groups were synthesized as effective artificial co‐enzymes for FDH. We used enzyme kinetic analysis to assess the effect of the ionic amino or carboxyl functional groups in the reduced form of the viologen derivatives on the catalytic activity of FDH with respect to the reduction of CO2. By using 1,1′‐diaminoethyl‐4,4′‐bipyridinium salt, which is the reduced form of a viologen derivative with two amino groups, we optimized the reduction of CO2 to formic acid with FDH. The catalytic efficiency value (kcat/Km) of the reduced form of 1,1′‐diaminoethyl‐4,4′‐bipyridinium salt was estimated to be more than 560u2005times larger than that of the natural co‐enzyme NADH. From the analysis result, the CO2 reduction was influenced by the ionic group of the viologen derivative.

Dye-sensitized solar cell with the near-infrared sensitization of aluminum phthalocyanine

The dye-sensitized solar cell (DSSC) using visible and near-infrared sensitization of nanocrystalline TiO2 films using a series of four aluminum phthalocyanines was developed and its photoelectrochemical properties were investigated. By using aluminum 2,9,16,23-tetrakis(phenyl-thio)-29H,31H-phthalocyanine chloride adsorbed on a nanocrystalline TiO2 film electrode, the ISC, VOC, FF, Pmax and η values were largest compared with the other DSSCs using aluminum phthalocyanines. For all the DSSCs using aluminum phthalocyanines, IPCE values at near-infrared region (700 nm) are larger than those at visible region (500 nm). Thus, the DSSC using near-infrared sensitization of nanocrystalline TiO2 film by aluminum phthalocyanines was developed.

Near-infrared sensitization solar cell with the electrode of aluminium phthalocyanine adsorbed on nanocrystalline titanium dioxide film

The dye-sensitized solar cell using visible and near-infrared sensitization of nanocrystalline TiO2 films by aluminium phthalocyanine, aluminium 2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine hydroxide (AlTPPc), was developed and its photoelectrochemical properties were investigated. The short-circuit photocurrent (ISC) was 0.026 mA cm-2, the open-circuit photovoltage (VOC) was 186 mV, and the fill factor (FF) of solar cell using AlTPPc adsorbed on nanocrystalline TiO2 film electrode was estimated to be 40.4%, respectively. By using AlTPPc adsorbed on nanocrystalline TiO2 film electrode, photovoltage and photocurrent were higher compared with that of only nanocrystalline TiO2 film electrode and were maintained under near-infrared irradiation. Thus, the solar cell using the near-infrared sensitization by AlTPPc adsorbed on nanocrystalline TiO2 film electrode was developed.

CO2 Photoreduction by Formate Dehydrogenase and a Ru-Complex in a Nanoporous Glass Reactor

In this study, we demonstrated the conversion of CO2 to formic acid under ambient conditions in a photoreduction nanoporous reactor using a photosensitizer, methyl viologen (MV2+), and formate dehydrogenase (FDH). The overall efficiency of this reactor was 14 times higher than that of the equivalent solution. The accumulation rate of formic acid in the nanopores of 50 nm is 83 times faster than that in the equivalent solution. Thus, this CO2 photoreduction nanoporous glass reactor will be useful as an artificial photosynthesis system that converts CO2 to fuel.

Biohydrogen Production from Sucrose Using the Light-Harvesting Function of Zinc Chlorophyll-a

A biohydrogen production system, has been developed that couples sucrose hydrolysis by invertase and glucose dehydrogenase (GDH) and hydrogen production with a platinum colloid as a catalyst. The system uses the visible light-harvesting function of artificial Zn chlorophyll-a (Zn Chl-o), prepared from Mg Chl-a (obtained from Spilurina). When a sample solution containing sucrose, invertase, nicotinamide adenine dinucreotide (NAD + ), Zn Chl-a, methyl-viologen (MV 2 + , an electron carrier), and platinum colloid was irradiated, continuous hydrogen production was observed with the irradiation time. The amount of hydrogen production was about 10.5 μmol after 4 h of irradiation under the optimum condition.