Hexagonal ZnO nanorings: synthesis, formation mechanism and trimethylamine sensing properties

A one-step hydrothermal method assisted by polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) was developed to synthesize hexagonal ZnO nanorings. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to characterize the as as-prepared ZnO nanorings and deduce the possible formation mechanism. The as-prepared ZnO nanorings showed the well-defined hexagonal shape with a width of 0.75-1.4 mu m, a thickness of 0.17-0.33 mu m and a hollow size of 0.2-1 mu m. The trimethylamine (TMA) sensing performance of the hexagonal ZnO nanorings was tested. The results indicated that the hexagonal ZnO nanorings showed a high response (47 to 100 ppm TMA), fast response/recovery rate (less than 23 s and 37 s, respectively), wide linearity in a relatively wide range (1-200 ppm TMA), low detectable TMA minimum concentration (less than 5 ppm) and good selectivity to TMA. In addition, the TMA-sensing mechanism of the hexagonal ZnO nanorings was also discussed.