Synthesis And Gas-Sensing Properties Of Polyaniline/Carbon Nanotubes Nanocomposites And P-N Junctions Nanomaterials

With the attention to the human health and environment increasing, people have proposed higher criteria in environmental monitoring. The development of new materials with good sensing properties becomes a main task for researchers. Recently, nanomaterials have got much research interest because of their special structure and properties. It is also found that the nanomaterials have potential application in gas sensor materials. Have this in mind, we do the following works:1) Synthesis of nanocomposites for NH₃ detection. Previous works have demonstrated that carbon nanotubes (CNTs) is an ideal candidate for sensing material. However, gas sensors based on pristine CNTs have some limitations, such as low sensitivity, lack of selectivity to analytes for which they have low adsorption energy or low affinity. In order to improve the gas sensitivity of CNTs, we focus on the functionalization of CNTs with PANI. In this paper, polyaniline-coated multi-wall carbon nanotubes (PANI-coated MWNTs) were prepared by in situ polymerization method. Sensors were fabricated by spin-coating, and ammonia gas sensing properties of the as-prepared PANI-coated MWNTs were studied. The results showed a good response and reproducibility towards ammonia at room temperature. In addition, PANI-coated MWNTs exhibited a linear response to ammonia in the range of 0.2–15 ppm. The effects of the thickness of PANI coatings on the gas sensing properties were also investigated in detail.2) An effort has been made to develop a new kind of SnO₂–CuO gas sensor which could detect an extremely small amount of H₂S gas at relative low working temperature. The sensor nanomaterials were prepared from SnO₂ hollow spheres (synthesized by employing carbon microspheres as temples) and Cu precursor by dipping method. The composition and structural characteristics of the as-prepared CuO-doped SnO₂ hollow sphere were studied by X-ray photoelectron spectroscopy, X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. Gas sensing properties of CuO-doped SnO₂ hollow sphere were also investigated. It was found that the sensor showed good selectivity and high sensitivity to H₂S gas. A ppb level detection limit was obtained with the sensor at the relatively low temperature of 35oC. Such good performances are probably attributed to the hollow sphere nanostructures. Our results imply that materials with hollow sphere nanostructured are promising candidates for high-performance gas sensors.