Synthesis of floral assembly with single crystalline ZnO nanorods and its CO sensing property

In the present work, two types of flower-like ZnO microstructures composed of nanorod bundles with different thickness was successfully synthesized by a polyethylene glycol (PEG)-assisted hydrothermal route. Hexagonal wurtzite structure of ZnO was confirmed by X-ray diffraction (XRD) in both cases. Scanning electron microscope (SEM), showed individual rods of flower-like ZnO synthesized in ethanol medium has 10 μm length and 400–500 nm diameter whereas in water medium it has 10 μm length and 1–1.5 μm diameter. Transmission electron microscope (TEM) studies showed that the surface of ZnO nanorods were smooth and diameter was uniform throughout. The single crystalline nature of individual rod of flower-like ZnO, in both cases, was confirmed by selected area electron diffraction (SAED) pattern. The ZnO microstructures composed of thinner rods exhibited excellent CO-sensing properties at reduced working temperature, which could still respond to 10 ppm CO at 200 °C. Whereas sensing property of flower-like ZnO composed of thicker rods was very poor at every testing temperatures. It was found that difference in response of these two flower-like ZnO was due to difference in diameter of individual ZnO nanorods.