A porous hierarchical In2O3 micro-/nanostructure was prepared by oxidizing In2S3 precursors for gas sensor applications. The formation mechanism of the porous structure was investigated systemically by means of simultaneous thermogravimetry and differential thermal analysis, conventional X-ray diffraction, and energy-dispersive XRD cooperated with field-emission scanning electronic microscopy observations. In gas-sensing measurements with noxious volatile organic compounds as target gases, the gas sensor based on porous hierarchical In2O3 micro-/nanostructures showed a sensitive performance with a large detecting concentration range. Besides, the as-fabricated gas sensor also exhibited significant selectivity toward each target gas. Both the sensitivity and the selectivity of the porous hierarchical In2O3 micro-/nanostructure-based gas sensor enable it to be potentially applied for environmental monitoring toward noxious volatile organic compounds. Furthermore, the gas-sensing mechanism was also demonstrated from the kinetic process of gas adsorption−desorption.

A novel leaf-like CdS micro-/nanostructure was prepared via a hydrothermal method using dimethyl sulfoxide as the growth template. The as-synthesized hierarchical micro-/nanostructures were characterized by field emission scanning electronic microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectrometry (XPS). The elemental mapping and the line scans were also performed in the high-angle annular dark-field (HAADF) mode on the same TEM. The growth mechanism was demonstrated from the aspects of time-dependent growth processes and different influencing factors including temperatures and templates. In gas-sensing measurements, typical volatile organic compounds at a series of concentrations were employed as the target analytes, including ether, methanol, acetone and isopropanol. We found that the gas sensor based on the special leaf-like CdS micro-/nanostructures exhibited a fascinating performance including high response, short response/recovery times and good recognition ability towards different analytes. The detecting limits towards ether, methanol, acetone and isopropanol could be lower than 25, 50, 50, and 10 ppb, respectively. By comparing with a conventional spherical structure, the leaf-like micro-/nanostructure was revealed to possess an improved ability for diffusion and adsorption/desorption. The structure could be generally significant for developing some other novel materials which possess a morphology inspired from nature for specific applications, such as sensors, energy transfer and storage devices, and catalysts.