High performance of 1-D ZnO microwire with curve-side hexagon as ethanol gas sensor

ZnO microwires of two different cross-sectional profiles were synthesized by chemical vapor deposition, and their morphologies were characterized by scanning electron microscopy. Their cross-sectional hexagonal profile could be tuned from straight to curved sides, by regulating the ZnO:graphite powder ratio used during synthesis. The ZnO microwires had hexagonal profiles with curved sides at a higher graphite ratio, and hexagonal profiles with straight sides at a lower graphite ratio. The higher graphite ratio was speculated to lower the growth rate from center to hexagonal sides, relative to the corners. The ZnO microwires were fabricated into gas sensors, and their sensing characteristics towards ethanol gas were investigated. The sensor based on a ZnO microwire with curved sides exhibited superior ethanol sensing performance than that based on a microwire with straight sides, which was attributed to the higher surface-to-volume ratio of the curved-side microwire. The sensor based on a ZnO microwire with curved sides was stable, and exhibited rapid response and recovery times. The straight-forward and economical fabrication of the gas sensor at room temperature makes it attractive for practical application.