Optimization of the surface coverage of metal nanoparticles on nanowires gas sensors to achieve the optimal sensing performance

The functionalization of noble metal nanoparticles (NPs) is a highly efficient method for increasing the sensing performance of metal oxide nanowire (NWs) gas sensors. Despite the well-established strategy, the level of the optimal functionalization for obtaining the maximum sensing response has rarely been reported. Herein, the surfaces of SnO2 NWs were functionalized with N and Pd NPs, and the gas sensing characteristics were then investigated using NO2 as an example gas. The sensing responses obtained at the optimal temperature showed a bell-shaped dependency on the proportion of surface coverage by Pd and N NPs. The sensing mechanism is explained and the results were also fitted to a simple theoretical model based on modulation in the conduction channel via the chemical and electronic sensitization on NWs. This study provides guidelines on the amount of metal NPs for achieving the optimal sensing responses in metal oxide NWs gas sensors.