Highly sensitive and selective H2 and NO2 gas sensors based on surface-decorated WO3 nanoigloos

WO3 nanoigloos decorated with Ag-, Pd-, and Au nanoparticles are fabricated by soft-template method and self-agglomeration of metal films. The responses of WO3 nanoigloos decorated with metal nanoparticles to various gases such as NO2, CH3COCH3, C2H5OH, and H2 are much higher than those of bare WO3 nanoigloos. According to the surface decoration, WO3 nanoigloos show significantly different behaviors in the response enhancement, revealing that Pd-decorated WO3 nanoigloos exhibit the highest response to H2 together with fast response time to H2, C2H5OH, and CH3COCH3 (below 10 s), Au-decorated WO3 nanoigloos exhibit the highest response to NO2. The catalytic effect of Ag is relatively weaker than Pd and Au nanoparticles, however, it exhibit the fastest response time to NO2. These are attributed to not only the varied catalytic activities of the metal nanoparticles, but also the different work function energies of them. Our results show that highly sensitive and selective WO3 nanoigloos decorated with metal nanoparticles can be an effective platform to fabricate an electronic nose for the further application of semiconducting metal oxide gas sensors.