Low-temperature and highly selective NO-sensing performance of WO3 nanoplates decorated with silver nanoparticles

For improving the low-temperature response and selectivity of WO3-based sensors, Ag nanoparticles (AgNPs) have been used to modify the WO3 nanoplates. Ag@plate-WO3 nanocomposites with various amounts of AgNPs were synthesized by growing AgNPs on WO3 nanoplates. XRD, SEM, TEM and XPS spectrum were used to characterize the Ag@plate-WO3 samples. The gas-sensing properties were evaluated at r.t. −250 °C using NO gases with various concentrations (0.5-50 ppm). AgNPs enhance the low-temperature response and selectivity of the Ag@plate-WO3 sensors for NO detection, and the amounts of AgNPs influence the NO-sensing performance of the Ag@plate-WO3 sensors. The sample with 0.5% AgNPs shows the best performance. Its optimum operating temperature is around 170 °C, but it shows response even at room temperature. The Ag@plate-WO3 sensors have a high selective response to NO gas, among various gases (i.e., H2 and CO) and organic vapors (i.e., alcohol, acetone, methanol and benzene). The morphologies of WO3 nanocrystals also influence the NO-sensing properties of the Ag@WO3 sensors, and the plate-like WO3 samples are better than the particle-like WO3 samples in improving NO-sensing performance. The NO-sensing enhancement should result from the synergistic effects of AgNPs and the loose house-of-card structure of plate-like WO3 aggregates.