SnO2 nanowire gas sensors have been fabricated on Cd−Au comb-shaped interdigitating electrodes using thermal evaporation of the mixed powders of SnO2 and active carbon. The self-assembly grown sensors have excellent performance in sensor response to hydrogen concentration in the range of 10 to 1000 ppm. This high response is attributed to the large portion of undercoordinated atoms on the surface of the SnO2 nanowires. The influence of the Debye length of the nanowires and the gap between electrodes in the gas sensor response is examined and discussed.

The gasochromic effect has important applications in energy savings, for example, in a smart window. This study reveals evidence of the existence of localized water molecules in colored WO 3 nanowires and their important role in the gasochromic effect. Such water molecules can be moved out from the nanowires. The coexistence of the water molecules and oxygen vacancies in nanowires leads to a defect band in the band gap. Coloration is attributed to absorptions of photons involving this defect band. These findings deepen the understanding of the physical mechanism underlying the gasochromic effect of WO 3 .

Hydrogen sulfide (H2S) plays a vital role in Al3+ stress resistance in plants, but the underlying mechanism is unclear. In the present study, pretreatment with 2 μM of the H2S donor NaHS significantly alleviated the inhibition of root elongation caused by Al toxicity in rice roots, which was accompanied by a decrease in Al contents in root tips under 50 μM Al3+ treatment. NaHS pretreatment decreased the negative charge in cell walls by reducing the activity of pectin methylesterase and decreasing the pectin and hemicellulose contents in rice roots. This treatment also masked Al-binding sites in the cell wall by upregulating the expression of OsSATR1 and OsSTAR2 in roots and reduced Al binding in the cell wall by stimulating the expression of the citrate acid exudation gene OsFRDL4 and increasing the secretion of citrate acid. In addition, NaHS pretreatment decreased the symplasmic Al content by downregulating the expression of OsNRAT1, and increasing the translocation of cytoplasmic Al to the vacuole via upregulating the expression of OsALS1. The increment of antioxidant enzyme [superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD)] activity with NaHS pretreatment significantly decreased the MDA and H2O2 content in rice roots, thereby reducing the damage of Al3+ toxicity on membrane integrity in rice. H2S exhibits crosstalk with nitric oxide (NO) in response to Al toxicity, and through reducing NO content in root tips to alleviate Al toxicity. Together, this study establishes that H2S alleviates Al toxicity by decreasing the Al content in the apoplast and symplast of rice roots.

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Porous nonprecious metal-based nanomaterials have gained considerable attention in heterogeneous catalysis owing to their low price, high specific surface area, efficient mass/electron transfer, tunable pore structure, and unique physicochemical properties. Controlling the phase and compositions of these porous nonprecious metal-based materials is critical to their applications. Porous nonprecious transition-metal borides (TMBs), typical metal−metalloid alloys, have recently received much interest because of their optimized electronic structure, adjustable crystal phase, and abundant active site. The controlled tuning of the porous structure of TMBs, exploring the relationship between the structure and performance, and understanding the function of B are essential for developing catalysts with excellent performance; however, these factors have rarely been reviewed. Herein, a detailed summary of the synthesis methods of porous TMBs is provided by precisely defining their shape, composition, and pore size/structure. Incorporating B into metals can significantly alter their performance due to the unique metalloid properties of B. Further, we focus on the key roles of B in porous TMBs for related heterogeneous catalytic applications, including phase control, regulated electronic structure, optimized adsorption of reaction intermediates, and enhanced charge transfer and stability. Finally, we outline the shortcomings, challenges, and possible development of porous TMBs, which need to be further explored to increase TMBs' contribution to heterogeneous catalyst applications and beyond.

H 2 sensors able to operate at room temperature are very important for safe detection of H 2 leakage. We report the large electrical response to H 2 of Pt-coated WO 3 (Pt-WO 3 ) nanowire films without the need of using an external heater. More important, hydrogen sensing processes have been investigated under various conditions, including in air, vacuum filled with pure gas, and a mixture of H 2 and other gases. This is carried out with both electrical and optical methods. The evidence shows that hydrogen will inject into the nanowire and create oxygen vacancy, in addition to reducing adsorbed oxygen at the surface, as is often recognized. It is experimentally demonstrated that the increase of electrical conductivity resulting from the reaction with hydrogen is hampered by coadsorption of O 2 , while N 2 has no such effect. A model has been developed to combine these new findings to give a clearer understanding of the mechanism responsible for H 2 sensing behavior.

No abstract

A fiber laser resonantly pumped 1.645 μm passively Q-switched Er:YAG laser is reported. Graphene on a silicon carbide was used as the saturable absorber for the Q-switching. The pulse energy of the 1.645 μm Q-switched Er:YAG laser was 7.05 μJ, with a pulse repetition rate of 35.6 kHz and an average output power of 251 mW.