Zeolite Sensor for Nitrogen Monoxide Detection at High Temperature

Development of new NO{sub x} sensors, which would be sensitive, selective, inexpensive and stable at elevated temperature, will greatly contribute to the reduction of the air pollution. In this paper, synthesis and performance of zeolite film applied for gas sensing are reported. Zeolite thin films (Cu ion-exchanged ZSM-5) were synthesized on the gold electrode at AT-cut quartz platelet by hydrothermal synthesis. In order to probe the target molecule (NO) selectively, Na in as-synthesized ZSM-5 film was ion-exchanged with Cu. The films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The synthesis condition for orientation to (0 x 0) face, on which the straight pores of ZSM-5 are opening, was optimized. The bulk type quartz oscillator coated with Cu-ZSM-5 thin layer was tested as NO sensor in a flowing stream of He. This sensing system could be operated at high temperature because of the thermal stability of the ZSM-5 film and the gold electrode. As a result, NO was successfully detected at 348 K.