Evaluation of Cu-ZSM-5 zeolites as QCM sensor coatings for DMMP detection

Nanosized Cu-ZSM-5 zeolites are used as novel and selectively sensitive materials for the detection of the nerve agent stimulant gas dimethyl methylphosphonate (DMMP). ZSM-5 and Cu-ZSM-5 zeolites, containing different amounts of copper cations, are synthesized and self-assembled on the surface of sensitive quartz crystal microbalance (QCM) films. The results demonstrate that Cu-ZSM-5 zeolite shows good selectivity and high sensitivity to DMMP vapor. Cu-ZSM-5 zeolite shows sensitivity of up to 8.8 Hz/ppm with a detection limit of 0.1 ppm, thus proving that these materials are preferable for DMMP detection. Five Cu-ZSM-5 zeolite samples containing different copper ion contents are synthesized and tested to explore the influence of copper ions on the detection of DMMP. The results indicate that sensitivity increases in proportion to the copper content before saturation. A novel desorption method for strong polar molecule DMMP using high frequency alternative electric fields is proposed. Compared with the thermal desorption method, desorption time decreases from 30 min to 25 s. Good repeatability is obtained under these conditions as well.