AuPd nanoparticles functionalized core-shell CoO/ZnO@ZnO for ultra-sensitive toluene detection.

In this work, core-shell AuPd nanoparticles (NPs) sensitized CoO/ZnO@ZnO ellipsoid nanoparticles was successfully synthesized via a simple liquid phase synthesis method. SEM and TEM characterization results showed that the as-prepared samples have core-shell ellipsoid morphology and the size of the nanoparticles were uniform. Systematic gas sensing characterization was carried out to obtain the gas sensing property of AuPd NPs decorated CoO/ZnO@ZnO. It was found that the gas sensing property could be significantly enhanced after noble metal decoration with Au, Pd and AuPd NPs, respectively. The optimal gas sensing performance was achieved by AuPd NPs functionalized CoO/ZnO@ZnO based gas sensor. The maximum response reached 256-100 ppm toluene at 250 °C, which is 50 °C lower than pure ZnO. The detection limit of AuPd functionalized CoO/ZnO@ZnO was as low as 100 ppb. The enhanced sensing mechanism was mainly attributed to the synergistic effect of Au and Pd, which was detailly discussed in gas sensing mechanism part.