3D porous flower-like ZnO microstructures loaded by large-size Ag and their ultrahigh sensitivity to ethanol.

3D porous flower-like ZnO microstructures loaded by large-size Ag were successfully synthesized via a simple two-stage method. XRD and XPS results proved that the synthesized Ag/ZnO was a pure phase. SEM and TEM results showed that the Ag nanoparticles with large size (about 400 nm) were successfully loaded on the porous flower-like ZnO. The sensitivity of Ag/ZnO was 268 to 200 ppm ethanol at 300 °C, which was 6 times higher than that of pure ZnO. In addition, the sensor of Ag/ZnO exhibited a faster response/recovery behavior and a lower detection limit. The enhanced gas sensing performance of Ag/ZnO has been explained from three aspects: the "spillover effect" of Ag, the formation of metal-semiconductor heterojunction and the role of "electronic sensitization". • A new method to synthesize large-size Ag nanoparticles (400 nm) and loaded it on 3D porous flower-like ZnO. • Ag/ZnO gas sensor displays higher gas response and faster response/recover time. • This paper explains the enhanced gas sensing mechanism from three aspects. [ABSTRACT FROM AUTHOR]