One-step self-assembly economical synthesis of hierarchical ZnO nanocrystals and their gas-sensing properties

Hierarchical ZnO pine needles were successfully fabricated via a novel economical one-step self-assembly synthesis. The influences of the amount of metallic zinc powder added and reaction time on the size and morphology of the ZnO were studied in detail. The gas-sensing performance of the hierarchical ZnO pine needles was observed carefully, and it indicated that the sensor based on hierarchical ZnO pine needles showed a high selectivity, quick response and stability for a long time for ethanol gas. Furthermore, AC impedance spectroscopy of the sensor was also examined at different temperatures and in atmospheres of different gases to understand the gas-sensing mechanism, and the results indicate that the sensor has the lowest potential barrier height for the transition of space charges and the minimum resistance when it is exposed to ethanol gas at 400 °C.