Fabrication of poly (p-phenylene) / zeolite composites as ammonia sensor

Abstract

Poly (p-phenylene) (PPP) is a one type of conductive polymers that has a potential as a gas sensing material because its optical and electrical property changes when exposed to particular gases. PPP was chemically synthesized via the oxidative polymerization of benzene and doped with FeCl3. Electrical conductivity response of doped PPP (dPPP) towards Co, H2 and NH3 was investigated. dPPP showed no reponse towards CO and H2, but it showed a definite negative response to NH3. The electricacl conductivity sensitivity of dPPP increased with increasing NH3 concentration. In order to improve sensitivity of the sensor, ZSM-5 zeolite was added into the conductive polymer matrix. The sensitivity of the sensor increased with increasing zeolite content up to 30%. Moreover, an effect of cation type containing in the zeolite pore was investigated, including Na+, K+, NH4+ and H+. The sensitivity of the composite with different cation containing in zeolite were organized; 50:1dPPP(90)/KZ23 <50:1dPPP(90)/NaZ23 <50:1dPPP(90)/NH4Z23<50:1dPPP(90)/HZ23. The sensitivity increase with changing cation type can be described in term of acidic properties. The 50:1 dPPP(90)/HZ23 possessed highest sensitivity of -0.36 due to H+ has highest acidity which induces more favorable NH3 adsorption and interaction with the conductive polymer.