Synthesis of dandelion-like NiO hierarchical structures assembled with dendritic units and their performances for ethanol gas sensing

Dandelion-like NiO hierarchical structures are successfully synthesized by a simple one-step hydrothermal method without any surfactant. The structures and morphologies of the samples are investigated by different kinds of techniques, including X-ray diffraction, field-emission electron scanning microscopy, and transmission electron microscopy. Morphology analysis reveals that as-synthesized dandelion-like NiO hierarchical structures with diameters of similar to 1.8 mu m are assembled with dendritic units and possess abundant gaps. The gas sensing properties for ethanol of the as-synthesized materials are investigated. The sensors have been shown to exhibit a high sensitivity and rapid response-recovery speed to the ethanol gas at the optimum operating temperature of 240 degrees C. The response and recovery time are 2 s and 12 s with the gas concentration of 100 ppm, respectively. The unique dandelion-like architecture and a high specific area are applied to explain the rapid response-recovery speed. Moreover, Raman and UV-vis spectra of the dandelion-like NiO hierarchical structures are also investigated.