Density-dependent of gas-sensing properties of Co3O4 nanowire arrays

Well-oriented Co3O4 nanowire arrays were synthesized in-situ on Al2O3 substrates via a simple hydrothermal method without seed layers. The phase structure and array morphology of Co3O4 nanowire arrays were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was revealed that the array density of Co3O4 nanowire arrays could be controlled by the concentration of ammonium fluoride. The gas-sensing measurement revealed that the array structure on the surface of gas sensors exerted great impact on their performances. It was found the response value enhanced and then decayed with the increased array density of Co3O4 nanowires. We concluded that the Co3O4 nanowire arrays with moderate array density can possess highly exposed effective surface area to provide more pathways for gas diffusion than other samples. Our studies can provide a significant guidance on array design to fabricate high performance gas sensors. Moreover, the as-designed Co3O4 nanowire arrays have potential application in trimethylamine (TEA) detection.