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.