Tellurium dioxide (TeO2) nanowires with a tetragonal structure have been grown by thermally evaporating tellurium metal at 400°C in air. The nanowires produced have diameters ranging from 30to200nm and have lengths of several tens of micrometers. Gas sensors were fabricated using the obtained TeO2 nanowires. The sensing behavior to NO2, NH3, and H2S gases at room temperature showed typical characteristics of a p-type semiconductor. The results demonstrate the potential to develop TeO2 nanowire based gas sensors with low power consumption.

Supported metallic catalysts have been widely used in catalytic reactions, as a function of hydrogenation, dehydrogenation, isomerization, 1 reforming, selective hydrocarbon oxidation, 2 and so on. Recently, nanostructured metallic catalysts 3À5 received widespread interest because of a large concentration of surface active sites. For FischerÀTropsch synthesis (FTS), the catalytic performance of cobalt based catalysts was strongly affected by the size of cobalt metal particles. 6À12 Conventional cobalt FT catalysts 6À14 were prepared by aqueous impregnation of supports with solutions of cobalt nitrates and followed by drying. After decomposition of the supported cobalt nitrates by calcination in the air atmosphere, the catalysts were reduced in pure hydrogen at higher temperature to generate metallic cobalt sites. However, Co crystalline size prepared from nitrates by these methods became as large as more than 20 nm. Chu et al. used glow-discharge nitrogen plasma and hydrogen plasma to pretreat cobalt catalyst, and then the catalysts were reduced in pure hydrogen at 673 K for 5 h to obtain a cobalt crystalline size of about 10 nm. 15 De Jong et al. decomposed cobalt or nickel nitrates in an NO/He atmosphere to obtain supported NiO and Co 3 O 4 particles with a diameter of 4À5 nm, and then the cobalt catalyst was reduced by H 2 /He at 823 K for 5 h. 16 Here, we present a novel surface impregnation autocombustion method to obtain uniform and nanostructured (Co size: 4À6 nm) Co/SiO 2 catalysts without further reduction and used directly in slurry phase Ficher-Tropsch synthesis. This technique was based on a chemical solÀgel process combined with a subsequent combustion process. 17 An aqueous solution containing the desired metal salts and organic fuel impregnated on the support, forming the xerogel through the solÀgel process, and then the xerogel was ignited to combust in the argon atmosphere, giving a voluminous and fluffy product with a large surface area. In this process, citric acid (noted as CA) was generally used as reductant and a kind of chelated agent providing complexing

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Cross-linked W nanopetals were synthesized by dealloying the sputtered W-Al alloy film in HNO 3 aqueous solution for 24 h under open circuit conditions. Scanning electron microscopy, X-ray diffraction, and transmission electron microscopy characterizations demonstrate that the W nanopetals are less than 100 nm in thickness and have a cubic crystal structure. The W nanopetals were transformed into monoclinic phase WO 3 nanopetals by a controlled thermal oxidation process at 500 °C in air. A gas sensor made using the WO 3 nanopetals showed promising NO 2 sensing performance. The present work indicates a new approach to fabricate high surface area oxide materials for applications such as gas sensors, catalysis, and photochemical devices.

The fern Athyrium yokoscense is known to be highly tolerant to lead toxicity, and is a lead hyperaccumulator that can accumulate over 1,000 microg g(-1) of lead in its dry matter. In this work, we examined whether the gametophytic generation of A. yokoscense also resists lead toxicity like the sporophytic generation. Spore germination in A. yokoscense was more tolerant to Pb2+, compared to that in other fern species, such as Pteridium aquilinum, Lygodium japonicum and Pteris vittata. In addition, the early gametophyte development of A. yokoscense was not much affected by 10 microM Pb2+, as evaluated from the prothallial growth and rhizoid development. We also showed that Athyrium gametophytes could accumulate more than 10,000 microg g(-1) of lead, and that the lead was localized in the cytosol and vacuole of rhizoidal cells, as determined by a transmission electron micrograph. These results indicate that Athyrium gametophytes have the ability to accumulate lead in the rhizoids. Furthermore, the gametophytes were found to include a large amount of proanthocyanidins (condensed tannins). Because proanthocyanidins have a latent ability to complex with lead ions, the possible roles of proanthocyanidins in the lead tolerance and accumulation of Athyrium gametophytes are discussed.