Preparation And NH₃ Gas-sensing Characteristic Research Of Graphene-polyaniline Composite Films

Graphene possesses high specific surface area and excellent electrical properties,which has shown great application prospects in electronics, sensors, new energy materials and devices, optical, biomedicine and many other areas. In this paper, the graphene-polyaniline binary complex film and reduced graphene oxide loaded SnO2–polyaniline ternary complex film were prepared. The morphology and structure of prepared thin films were characterized by scanning electron microscopy(SEM) and UV-vis spectroscopy. The composite thin film ammonia(NH3) sensors were prepared based on micro- interdigital electrodes, and their gas-sensing performances were tested at room temperature. The effects of graphene mass and preparation process on NH3-sensitive sensing properties of sensors were investigated, and the gas-sensing mechanism of composite thin film sensors was analyzed. The main results are as follows:1.The graphene-polyaniline composite film(1-GR-PANI) was fabricated by in situ self-assembly method. The influence of graphene mass on gas-sensing properties of composite thin films was investigated and NH3-sensing performances of graphene-polyaniline composite thin film and graphene/polyaniline layered film(1-GR/PANI). The results revealed that the composite thin film exhibited nanofiber network morphology, which was more uniform and had larger pores and specific surface area compared with single PANI thin film. Therefore, the composite thin film showed superior gas-sensing properties. The optimum gas characteristic of 1-GR-PANI composite thin film sensor was obtained with 0.002 mol aniline and 1mg graphene.Experimental results showed that the preparation process had a great impact on gas sensing properties of films. The gas sensing properties of 1-GR-PANI composite thin film sensor was significantly obviously superior than the 1-GR/PANI layered film, and it was speculated that graphene not only provides a matrix for polymerization of aniline,and increases the specific surface area of composite film, but also has a doping effect on polyaniline. A π-π conjugated structure formed in the composite film is beneficial to the carrier transportation.2. The reduced graphene oxide loaded SnO2–polyaniline ternary composite(30-GS-PANI) was prepared by the in situ oxidation polymerization. Furthermore, thesingle PANI film, the bare GS film(30-GS) and the 30-GS-PANI composite film were developed by spin coating process, and NH3-sensing properties were studied. Surface morphology and UV-Vis analysis of 30-GS-PANI showed that there was not physical mixture merely between PANI and GS, but certain chemical interactions occured when the composite material was formed. PANI growing around GS nanosheets resulted in a uniform nanofiber structure. The effect of GS mass on the sensing performances of composites was studied, and the optimum gas-sensing properties of the nanocomposite thin film sensor was obtained with 30 mg GS and 0.002 mol aniline. The hybrid thin film was also prepared by physical mixed method, and NH3-sensing characteristics of hybrid and composite thin films were compared and analyzed. The results revealed that the composite film had showed more excellent gas sensing properties than hybrid film,and it might be due to more contact fully interface among ternary composite material and multiple heterojunction effect generated between interfaces, which were beneficial to the adsorption and response of gas molecules.