Large-scale synthesis of flower-like ZnO nanorods via a wet-chemical route and the defect-enhanced ethanol-sensing properties

In this paper, flower-like zinc oxide (ZnO) nanorods were successfully synthesized via a simple, cost-effective and environment-friendly wet-chemical method at a relatively low temperature (90 °C). X-ray diffraction indicated that the ZnO nanorods are crystallized in a hexagonal wurtzite structure. Electron microscopy observations confirmed the nanorod assembled flower-like morphology. And, high-resolution transmission electron microscopy (HRTEM) images proved that plenty of defects exist on the surface of ZnO nanorods. Photoluminescence analysis showed that abundant intrinsic defects are present on the ZnO crystal surfaces, the content of which is far more than that of commercial ZnO powders. X-ray photoelectron spectrometry revealed that considerable oxygen species (23.29%) chemisorbs on the surface of the as-prepared ZnO nanorods. Gas sensors based on these ZnO nanorods exhibit high response, fast response-recovery and good selectivity to 1–1000 ppm ethanol vapor at 400 °C. The excellent ethanol-sensing performance, particularly high response values, is considered to be mainly originated from plenteous defects formed on ZnO surfaces.