Effect of the Functionalization of Porous Silicon/WO₃ Nanorods with Pd Nanoparticles and Their Enhanced NO₂-Sensing Performance at Room Temperature

The decoration of noble metal nanoparticles (NPs) on the surface of metal oxide semiconductors to enhance material characteristics and gas-sensing performance has recently attracted increasing attention from researchers worldwide. Here, we have synthesized porous silicon (PS)/WO₃ nanorods (NRs) functionalized with Pd NPs to enhance NO₂ gas-sensing performance. PS was first prepared using electrochemical methods and worked as a substrate. WO₃ NRs were synthesized by thermally oxidizing W film on the PS substrate. Pd NPs were decorated on the surface of WO₃ NRs via in-situ reduction of the Pd complex solution by using Pluronic P123 as the reducing agent. The gas-sensing characteristics were tested at different gas concentrations and different temperatures ranging from room temperature to 200 °C. Results revealed that, compared with bare PS/WO₃ NRs and Si/WO₃ NRs functionalized with Pd NPs, the Pd-decorated PS/WO₃ NRs exhibited higher and quicker responses to NO₂, with a detection concentration as low as 0.25 ppm and a maximum response at room temperature. The gas-sensing mechanism was also investigated and is discussed in detail. The high surface area to volume ratio of PS and the reaction-absorption mechanism can be explained the enhanced sensing performance.