Gas sensing properties of Langmuir-Blodgett polypyrrole filminvestigated by surface acoustic waves

摘要

The gas sensing properties of organic polypyrrole (PPS) film,ndeposited onto LiNbO3 substrate by Langmuir-Blodgett (LB)ntechnique, have been monitored by surface acoustic wave (SAW) delaynlines and studied with respect to sensitivity, selectivity, responsentime, stability, repeatability, and aging. The SAW PPy elementsndemonstrate high sensitivity toward NH3 gas with highnselectivity against CH4, CO, H2, andnO2. The detectable threshold concentration has been estimatednas 20 ppm NH3 in air; the response time is in the 10s range,nand the recovery time is about 15 min; the repeatability of the SAWnresponse toward eight sequential NH3 gas exposures is withinn6%; the aging of the PPy film is within 4% over a month; and the effectnof humidity on SAW NH3 gas response is negligible for thentypical conditions at room ambient air. Partially reversible SAWnresponse recognizing NH3 gas as one component of anninterfering gases-mixture has been observed. Simultaneous chemoresponsesnof SAW phase and insertion loss have been performed in order toninvestigate the sensing mechanisms. By merging with electricalnconductivity gas response, the dominant SAW sensing effects for NH3n gas detection are defined as elastic loading