Synthesis of Disk-Shaped Tungsten(VI) Oxide Particles with Various Physical Properties for Mineralization of Acetic Acid in Water Under Irradiation of Visible Light.

Disk-shaped tungsten(VI) oxide (D-WO3) particles were synthesized according to a previously reported method consisting of pyrolysis, precipitation, and calcination, and the calcination temperature was changed (200-600 °C). The samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, the Brunauer- Emmett-Teller single-point method, and diffuse reflectance spectroscopy. In addition, to evaluate the photocatalytic activities of the samples, the mineralization of acetic acid to carbon dioxide (CO2) was measured by loading Pt particles onto the surface of the samples by photodeposition and irradiating them in an aqueous suspension with a blue light-emitting diode. Increasing the calcination temperature was associated with several changes: the crystallites grew larger, increasing the crystallinity; the specific surface area decreased, decreasing the adsorption capacity; and the rate of the photocatalytic CO2 evolution reaction increased. Pt-loaded (0.1 wt%) D-WO3 calcined at 600 °C showed the highest activity with a CO2 evolution rate of 5.9 µmol h-1. These results indicated that improving the crystallinity of the D-WO3 samples was effective in increasing their photocatalytic activities.

Synthesis, structure, and fluorescence properties of a calcium-based metal-organic framework.

The solvothermal reaction of a mixture of calcium acetylacetonate and 1,4-naphthalenedicarboxylic acid (H2NDC) in a solution containing ethanol and distilled water gave rise to a metal-organic framework (MOF), {(H3O+)2[Ca(NDC)(C2H5O)(OH)]}4·1.1H2O. This MOF possesses a new structure composed of calcium clusters and H2NDC linker anions and shows a unique fluorescence property; it exhibits a fluorescence peak at 395 nm (λ ex = 350 nm) at room temperature, which is blue-shifted compared with that exhibited by the free H2NDC ligand. One of the possible mechanisms for this fluorescence is likely attributable to a ligand-to-metal charge transfer (LMCT) transition and is the first example of a calcium-based MOF exhibiting blue-shifted fluorescence due to LMCT.

Characterization of water-soluble dark-brown pigment from Antarctic bacterium, Lysobacter oligotrophicus.

Lysobacter oligotrophicus strain 107-E2(T) isolated from Antarctica produces dark-brown colored water-soluble pigment, in addition to hydrolases and lytic enzymes. The production of pigment is a common characteristic among members of the genus Lysobacter, but the identity of the pigments has been unknown. In this study, we identified the pigment from L. oligotrophicus as melanin pigment (Lo-melanin) by chemical and spectroscopic analyses. Although melanin is generally insoluble in both aqueous and organic solvents, the results in this study revealed that Lo-melanin shows water-solubility by means of the added polysaccharide chain. Lo-melanin production of L. oligotrophicus was increased by ultraviolet (UV) exposure, and survival rate of Escherichia coli under UV-irradiated condition was increased by the addition of Lo-melanin to the medium.