Evolution and growth mechanism of hexagonal ZnO nanorods and their LPG sensing response at low operating temperature

Abstract

Liquefied Petroleum Gas (LPG) response of ZnO nanorods synthesized by a simple and low cost colloidal method is presented here. The morphology of ZnO was controlled by changing the refluxing time from 3 h to 48 h. The nanorods synthesized were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) for structural and morphological studies. The FESEM images shows hollow and solid nanorods with hexagonal cross-section on varying the reflux time. The origin and evolution of epitaxial growth along the (002) plane is explained by a two-step growth processes. The nanorods of different morphologies were exposed to low concentrations (below 100 ppm) of LPG and their sensing behavior was recorded over a range of operating temperatures from 120 °C to 200 °C. Hollow ZnO nanorods showed remarkable sensing characteristics such as higher gas sensitivity ˜ 49%, rapid response time (˜ 39 s) and recovery time (˜ 46 s). The nanorods were able to detect as low as 20 ppm of LPG at operating temperature of 120 °C. These results shows that the ZnO nanorods prepared by simple colloidal method could be a promising material for the fabrication of highly sensitive LPG sensor at low operating temperatures.