Functionalisation of alkali-resistant nanoporous glass via Au nanoparticle decoration using alkaline impregnation: catalytic activity for CO removal.

The concerted use of nano-metal particles with catalytic functions and nanoporous materials holds promise for effective air purification and gas sensing; however, only a few studies have used porous glasses as supports for Au nanoparticles. Furthermore, Au/nanoporous glasses with activities comparable to that of Au/TiO2, which is a typical Au catalyst, have not been reported to date. This study demonstrates that a nanoporous glass, which is highly acid- and alkali-resistant and chemically stable, can be decorated with Au nanoparticles using an alkali impregnation method. The resulting composite exhibits high catalytic activity in CO oxidation. The catalysts reported herein are as active as Au/TiO2 catalysts per active site. Further optimisation of the pore properties of the glass and sizes of the Au nanoparticles is expected to result in excellent catalytic systems for CO removal and sensing.

Triplet-triplet annihilation upconversion through triplet energy transfer at a nanoporous solid-liquid interface.

We report the triplet-triplet annihilation (TTA) upconversion (UC) through triplet energy transfer (TET) from a sensitiser fixed on a solid surface to free emitters dissolved in solution. A carboxylic-acid derivative of Pt-porphyrin was used as the sensitiser fixed on an amino-treated surface of continuous nanoporous glass without aggregation. UC emission was observed under photoexcitation of 532 nm for porphyrin-fixed glass immersed in an emitter solution of 9,10-diphenylanthracene (DPA), showing that TET occurs through the solid-liquid interface. The dynamics of TET was analysed through both phosphorescence decay of the sensitiser and UC emission rise from the emitter. Two TET components with different rate constants were found, slower than diffusion-controlled reactions in solution by 1-2 orders of magnitude. Nevertheless, the solid surface TET rates were fast enough to obtain a high quantum yield over the solid-liquid interface. By melting DPA and soaking it into sensitiser-fixed porous glass, we fabricated an all-solid system enabling TTA-UC through the bulk interface.

Enhanced phosphorescence properties of a Pt-porphyrin derivative fixed on the surface of nano-porous glass.

The room-temperature phosphorescence chromophore, Pt(ii) coproporphyrin I (PtCP), was fixed on the surface of a 3D-network of nanoscale pores of porous glass through ion-exchange reaction. The absorption and phosphorescence spectra indicated that PtCP can be loaded while maintaining monomeric dispersion at concentrations well beyond solubility limits of PtCP in solution. The phosphorescence quantum yield of PtCP fixed on the surface was also found to have double the enhancement of solution. The extended lifetime of phosphorescence of PtCP bonded on the surface compared to that in solution clearly indicated that suppression of nonradiative deactivation plays a key role in high quantum yield and long triplet lifetime. This hybridization with nano-porous glass provides opportunities for various potential applications.

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.

Hydrogen evolution from glycerol aqueous solution under aerobic conditions over Pt/TiO2 and Au/TiO2 granular photocatalysts.

Hydrogen was efficiently evolved from glycerol aqueous solution upon vertical photoirradiation of a Pt/TiO2 or Au/TiO2 bed under aerobic conditions. Granular photocatalysts were easily deposited, leading to high H2 selectivity (80-95%), whereas glycerol oxidation with CO2 evolution became dominant when suspended powder photocatalysts were used.

Oxygen-Evolving Porous Glass Plates Containing the Photosynthetic Photosystem II Pigment-Protein Complex.

The development of artificial photosynthesis has focused on the efficient coupling of reaction at photoanode and cathode, wherein the production of hydrogen (or energy carriers) is coupled to the electrons derived from water-splitting reactions. The natural photosystem II (PSII) complex splits water efficiently using light energy. The PSII complex is a large pigment-protein complex (20 nm in diameter) containing a manganese cluster. A new photoanodic device was constructed incorporating stable PSII purified from a cyanobacterium Thermosynechococcus vulcanus through immobilization within 20 or 50 nm nanopores contained in porous glass plates (PGPs). PSII in the nanopores retained its native structure and high photoinduced water splitting activity. The photocatalytic rate (turnover frequency) of PSII in PGP was enhanced 11-fold compared to that in solution, yielding a rate of 50-300 mol e(-)/(mol PSII·s) with 2,6-dichloroindophenol (DCIP) as an electron acceptor. The PGP system realized high local concentrations of PSII and DCIP to enhance the collisional reactions in nanotubes with low disturbance of light penetration. The system allows direct visualization/determination of the reaction inside the nanotubes, which contributes to optimize the local reaction condition. The PSII/PGP device will substantively contribute to the construction of artificial photosynthesis using water as the ultimate electron source.

CoS-Graphene Composite Counter Electrode for High Performance Dye-Sensitized Solar Cell.

CoS-graphene composite counter electrode for dye-sensitized solar cell (DSSC) was prepared by coating hydrothermal synthesized CoS with graphene onto the FTO conductive glass. SEM shows that CoS particles are uniformly dispersed in the graphene. The result confirms that the prepared composite counter electrode is of highly electrocatalytic activity towards iodine reduction, which is even better than Pt electrode. And cyclic voltammetry measurement also shows that the composite counter electrode has good stability after 100 scan cycles. DSSC with CoS-graphene as composite counter electrode achieves a maximum power conversion efficiency of 6.31%, which is better than Pt electrode.

Light-Driven Hydrogen Production by Hydrogenases and a Ru-Complex inside a Nanoporous Glass Plate under Aerobic External Conditions.

Hydrogenases are powerful catalysts for light-driven H2 production using a combination of photosensitizers. However, except oxygen-tolerant hydrogenases, they are immediately deactivated under aerobic conditions. We report a light-driven H2 evolution system that works stably even under aerobic conditions. A [NiFe]-hydrogenase from Desulfovibrio vulgaris Miyazaki F was immobilized inside nanoporous glass plates (PGPs) with a pore diameter of 50 nm together with a ruthenium complex and methyl viologen as a photosensitizer and an electron mediator, respectively. After immersion of PGP into the medium containing the catalytic components, an anaerobic environment automatically established inside the nanopores even under aerobic external conditions upon irradiation with solar-simulated light; this system constantly evolved H2 with an efficiency of 3.7 µmol H2 m(-2) s(-1). The PGP system proposed in this work represents a promising first step toward the development of an O2-tolerant solar energy conversion system.

Oriented nanostructured titanates array from low concentration alkaline solution via hydrothermal process.

Na2Ti2O5 x H2O nanowire/nanobelt array and other nanostructures were hydrothermally prepared on Ti substrate in low concentration NaOH solution (< 5 mol/L). Then the Na2Ti2O5 x H2O nanostructures were converted to H2Ti2O5 x H2O through an ion-exchange process and finally to TiO2 anatase by calcination at 450 degrees C without changing their nanostructures. The morphology of the prepared Na2Ti2O5 x H2O nanostructures could be controlled by varying the experimental parameters such as hydrothermal temperature and alkaline solution. The formation mechanism of the nanoarray was also discussed.

TiO2 mesoporous thick films with large-pore structure for dye-sensitized solar cell.

Large-pore mesoporous titania films with thickness up to 3.5 microm were prepared by dip-coating method using block copolymer Pluronic P123 as structure directing agent. The highly transparent multilayer mesoporous film shows a large pore size of 8.9 nm with surface area of 129.4 m2 x g(-1). The mesopore structure with continuous crystalline framework was maintained after being calcined at 400 degrees C. Dye-sensitized solar cell (DSSC) based on the large-pore mesoporous film exhibited an enhanced light-to-electricity conversion efficiency of 6.01%, due to the thick large-pore mesoporous film with continuous crystalline framework structure.

Alcohol-vapor inclusion in single-crystal adsorbents [M(II)2(bza)4(pyz)]n (M = Rh, Cu): structural study and application to separation membranes.

The vapor absorbency of the series of alcohols methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol was characterized on the single-crystal adsorbents [M(II)2(bza)4(pyz)]n (bza = benzoate, pyz = pyrazine, M = Rh (1), Cu (2)). The crystal structures of all the alcohol inclusions were determined by single-crystal X-ray crystallography at 90 K. The crystal-phase transition induced by guest adsorption occurred in the inclusion crystals except for 1-propanol. A hydrogen-bonded dimer of adsorbed alcohol was found in the methanol- and ethanol-inclusion crystals, which is similar to a previous observation in 2 x 2EtOH (S. Takamizawa, T. Saito, T. Akatsuka, E. Nakata, Inorg. Chem. 2005, 44, 1421-1424). In contrast, an isolated monomer was present in the channel for 1-propanol, 1-butanol, and 1-pentanol inclusions. All adsorbed alcohols were stabilized by hydrophilic and/or hydrophobic interactions between host and guest. From the combined results of microscopic determination (crystal structure) and macroscopic observation (gas-adsorption property), the observed transition induced by gas adsorption is explained by stepwise inclusion into the individual cavities, which is called the "step-loading effect." Alcohol/water separation was attempted by a pervaporation technique with microcrystals of 2 dispersed in a poly(dimethylsiloxane) membrane. In the alcohol/water separation, the membrane showed effective separation ability and gave separation factors (alcohol/water) of 5.6 and 4.7 for methanol and ethanol at room temperature, respectively.

Synthesis of TiO2-based nanotube on Ti substrate by hydrothermal treatment.

TiO2-based titanate nanotube film was directly synthesized by hydrothermal treatment of Ti substrate in NaOH solution. The prepared high aspect ratio nanotubes have diameter of 10 nm and pore size of 5 nm with length of several microns. The nanotubes show the same structure and component characteristics as the nanotubes prepared through hydrothermal treatment of TiO2. Other nanostructured titanate as oriented nanofiber film and translucent film were also prepared by adjusting the hydrothermal conditions. The formation mechanism of nanostructured titanate was discussed.