High performance gas sensors based on in-situ fabricated ZnO/polyaniline nanocomposite: The effect of morphology on the sensing properties

Abstract

ZnO nanoparticles, nanorods and nanosheets were in-situ deposited on the interdigitated gold electrodes by hydrothermal treatment of electrospun nanofibers containing zinc salt precursors and seed-induced solution growth of ZnO. The nanostructured ZnO was further covered with polyaniline (PANI) via vapor phase polymerization of aniline or dip-coating with water-dispersible PANI to prepare ZnO/PANI nanocomposites. The morphology and structure of the nanocomposites were investigated by scanning electron microscopy, X-ray diffraction patterns and Fourier transform infrared spectroscopy. The electrical responses of the nanocomposites toward NH3 have been examined at room temperature, and the nanocomposite revealed much better gas sensing properties than ZnO or PANI alone. The morphology of the nanocomposites had a great effect on their sensing properties. Specifically, the composite of ZnO nanosheets covered with vapor phase polymerized aniline demonstrated optimal sensing performance, featuring high response magnitude (relevant resistance change of ∼2150% towards NH3 as low as 10 ppm), ultralow limit of detection (∼5 ppb), good repeatability and excellent selectivity. It is proposed that the morphology and the interactions between p-type PANI and n-type ZnO are responsible for the highly desirable sensing properties of the nanocomposites.