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Nanoscale Ag-loaded sunflower-like In2O3 hierarchical nanostructures are developed for HCHO detection.

Zn 0.95 − x Co 0.05 Al x O  (x=0,0.01,0.03) powders were prepared from the acetate-derived precursor by the sol-gel route. The structural and magnetic properties of the powders were investigated. X-ray absorption spectroscopy and high-resolution transmission electron microscope analyses indicate that Co2+ substitute for Zn2+ without changing the wurtzite structure. The powder shows paramagnetic behavior at 5K for x=0 sample. For x=0.01 and 0.03, the powders exhibit ferromagnetic behavior at 360K. It was demonstrated experimentally that high-temperature ferromagnetism in Co-doped ZnO powders can be obtained through increasing the carrier concentration which was realized by doping a few percent of Al.

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In this work, hierarchical flower-like tungsten trioxide (WO3) nanostructures assembled by needle-like single-crystalline nanosheets was fabricated synthesized via a facile and simple solvothermal method at a rather low temperature (100 o C) without any surfactants or templates. Time-dependent experiments are carried out to understand formation process which undergoes four stages-polymerizing, nucleating, assembling and growing from WO4 2to the flower-like WO3. The asprepared WO3 microflowers exhibit a good reversibility, fast response time (0.9 s)/recovery time (19 s) and well sensing selectivity at a relative lower working temperature (160 o C) after exposing to hydrogen sulfide (H2S). Such excellent performance can be attributed to the highly exposed surface area and the assembling of single-crystalline nanosheets. The sensing process is tentatively explained in terms of the adsorption-desorption mechanism and chemical kinetics theories in detail.

ZnO nanosheet (NS) arrays have been synthesized by a facile ultrathin liquid layer electrodeposition method. The ion concentration and electrode potential play important roles in the formation of ZnO NS arrays. Studies on the structural information indicate that the NSs are exposed with (100) facets. The results of Raman and PL spectra indicate that there existed a large amount of oxygen vacancies in the NSs. The gas sensing performances of the ZnO NS arrays are investigated: the ZnO NS arrays exhibited high gas selectivity and quick response/recovery for detecting NO2 at a low working temperature. High binding energies between NO2 molecules and exposed ZnO(100) facets lead to large surface reconstructions, which is responsible for the intrinsic NO2 sensing properties. In addition, the highly exposed surface and a large amount of oxygen vacancies existing in the NSs also make a great contribution to the gas sensing performance.

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