Facile realization of Ag functionalized W18O49@PPy core–shell nanorods for multieffect modulation on gas sensing response

Surface modification and core–shell heterostructure are all proved effective in improving gas-response performance of a semiconductor sensor. Here Ag nanoparticles (Ag NPs) modified W18O49@PPy core–shell nanorods (Ag/CSNRs) prepared by a cost-effective process are investigated for enhanced NH3-sensing response. In present process, surface modification by Ag NPs is achieved in parallel to the PPy-shell formation via chemical polymerization of Py on W18O49 nanorods with AgNO3 as an oxidant. The distribution (partial or total embedding in PPy-shell) and amount of the modified Ag NPs are revealed to be decided by Py polymerization duration, and affect the gas response of corresponding Ag/CSNRs sensor. The sensor based on Ag/CSNRs exhibits significantly enhanced response. The sample modified with partially embedded Ag NPs is capable of detection to rarefied NH3 as low as 100 ppb at room temperature. However, long duration of polymerization induces a full coverage of Ag NPs by PPy film and thus seriously weakens the modification effect to gas response. A sensing mechanism model was proposed and the response feature of Ag/CSNRs was analyzed with the perspective of co-contribution of chemical sensitization and electronic sensitization, which is further correlated to the distribution of attached Ag NPs.