| In the past few years, the development of nanomaterials and nanotechnologies provided new opportunities for improving the properties of gas sensors. Recently, the sensing properties of porous MOS nanostructured materials and CNTs-based nanocomposites have been widely studied, owing to the great surface activity provided by their enormous surface areas for chemical reaction and effective diffusion of gases into the materials. Hence, the preparation of porous MOS nanomaterials and CNTs-based nanocomposites would be of significance for improving the gas sensor's performance. In view of this problems, this paper mainly do the following work:(1) A nanocomposite(PPy/F-MWCNTs) has been successfully synthesized by the in-situ chemical oxidation polymerization with acid-treated multi-walled carbon nanotubes(F-MWCNTs) and polypyrroles(PPy). The asprepared composiste was characterized by Fourier transformed infrared spectra (FT-IR), UV-vis diffuse reflection spectroscopy(UV-vis DRS), Thermal gravimetric analysis(TGA), X-ray diffraction study(XRD), Branauer-Emmett-Teller analysis(BET), Field-emission scanning electron microscopy(FE-SEM) and Transmission electron microscopy (TEM). The results has revealed that the F-MWCNTs was well-coated with about 25-40 nm thickness of polypyrrole, and the surface specific areas of PPy/F-MWCNTs is about three times than that of pure PPy. The sensors fabricated by PPy/F-MWCNTs exhibited a higher sensitivity, better response/reproduc-ibility towards NH3 vapor at room temperature than by pure PPy or F-MWCNTs. The sensitivity was 1.9 even to 200 ppm of NH3 and the response time was 135s. In addition, compared with MWCNTs untreated with acid, the as-prepared PPy/F-MWCNTs also exhibits higher sensitivity than that prepared without acid-treated MWCNTs.(2) In this paper, the porous single-crystalline Zinc oxide (ZnO) nanoplates were fabricated from the thermal-decomposition of layered basic zinc carbonate (LBZC) precursors, which were synthesized by an urea hydrothermal method used PVP as surfactant in the solution of water. The structure and morphology of the as-synthesized samples were characterized by means of X-ray powder diffraction(XRD), Fourier transform infrared(FT-IR), Thermogravimetric-differential scanning calorimetry analysis(TGA-DSC), Field-emission scanning electron microscopy(FE-SEM), Transmission electron microscopy(TEM), Selected area electron diffraction (SAED) pattern and Nitrogen adsorption-desorption isotherm analysis. The results showed that the average diameter of as-prepared porous ZnO nanoplates were about several hundred nanometers and the thickness of the nanoplates was about 15 nm. The sensors fabricated from the porous ZnO nanoplates exhibited good sensitivity, high selectivity, rapid response-recovery times to ethanol vapors at 300℃and would be good candidate for gas sensing materials.Moreover, it is believed that the solution-based approach could be extended to fabricate other porous metal oxide materials with a unique morphology.(3) Hierarchical porous Tin oxide (SnO2) nanorods that composed of numerous single-crystalline SnO2 nanoparticles with about 15.9 nm in diameter were synthesized by a facile hydrothermal method with the help of the surfactant DMF followed by calcination in air atmosphere.The structure and morphology of resulting samples were characterized by means of X-ray powder diffraction (XRD), Fourier transform infrared(FT-IR), Thermogravimetric-differential thermalgravimetric analysis(TGA-DTA), Feld-emission scanning electron, Transmission electron microscopy(TEM), selected area electron diffraction (SAED) pattern and Branauer-Emmett-Teller analysis. The results showed that the as-synthesized porous nanorods were about 5-6μm in length. The sensors fabricated from the porous SnO2 nanorods exhibited good sensitivity, high selectivity, long-term stability and rapid response-recovery times to ethanol vapors at 240℃. |
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