| In recent years, with the fast development of science and technology, it provides tremendous convenience to human beings. But at the same time, it has seriously polluted the enviroment. Owing to the toxic and flammable gases threat to our health and wealth, human beings call for a high-qualiy environment. So it becomes more and more important in the study of gas sensor to detect and inspect the toxic and flammable gases. Recently nanomaterials and nanotechnology provide new opportunities for improving the performance of gas sensors.In the past several decades, the sensing properties of porous nanomaterials semiconductor metal oxide nanomaterials and CNT-basd nanocomposites have been widely investigated. Owing to the existence of the large activated surface areas, it could cause the detected gas samples to easily diffuse and interact with sensing materials. Therefore, the syntheses of porous nanomaterials and CNT-basd nanocomposites would be of importance for improving gas sensing properties. Aiming at solving the problem mentioned above, the follows:(1) Porous nanosheets, nanospheres and hollow core-shell nanosperes of SnO2 have been prepared via a solvethermal approach in DMF/water solution by changing the ratio of DMF to total mixture volume. These nano-materials have been thoroughly characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and nitrogen adsorption-desorption. The gas-sensing properties of samples were studied. Results show all the SnO2-based gas sensors are realized the detection of organic vapors with high sensitivity and short response-recovery time. But the obtained SnO2 porous nanosheet exhibit high selectivetity to ethanol vapor and the SnO2 hollow core-shell structures exhibit high sensitivity to ethanol and methanol vapors, while the SnO2 porous nanospheres exhibit high sensitivity to acetone, toluene, tetrahydrofuran and dichloromethane vapors.(2) We described here a simple approach to the synthesis of hierarchical polyaniline/multiwalled carbon nanotube (MWCNT) nanocables by in situ chemical polymerization directed by the cationic surfactant cetyltrimethylammonium bromide (CTAB). Morphological and structural characteristics, thermal stability, as well as gas-sensing properties of the hybrid nanocomposites were characterized by using various techniques; including Fourier transform infrared spectroscopy (FT-IR), UV-visible absorption spectra (UV-vis), scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), thermogravimetric analyzer and gas-sensing measurement. The results indicate that the as-prepared PANI/MWCNT is uniform with needle-like PANI shell with the thickness as about 20nm. The sensors based on PANI/MWCNT nanocomposites and pure PANI was tested for ammonia gas. The results show that the as-prepared PANI/MWCNT nanocomposites sensors have higher sensitivity and repeatability, and better response/reproducibility towards ammonia at room temperature. Compare with reported PANI/MWCNT with no needle-like PANI, the as-prepared PANI/MWCNT also exhibits the higher sensitivity.(3) A convenient method of sonochemical route in an aqueous solution is reported to synthesize CdS/MWCNT with thioacetamide and cadmium acetate as raw materials at 60℃. The obtained samples are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and selected area electon diffraction (SAED). The results indicate that the as-prepared CdS/MWCN are uniform with cubic CdS shell thickness of about 30-40 nm. The applications in gas sensors for the SnO2 nanomaterials reveal that the obtained CdS/MWCNT nanocomposites exhibit high sensitivity and better selectivity to ethanol vapors. |
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