Novel gas sensor based on nano-zeolite films for the nerve agent simulant dimethylmethylphosphonate detection

A novel gas sensor based on nanosized zeolite for the detection of nerve agent simulant gas dimethylmethylphosphonate (DMMP) is developed. Novel sensing membrane materials of nanosized zeolite films of ZSM-5 and of Ag⁺ modified ZSM-5 are immobilized on a QCM (quartz crystal microbalance) piezoelectric sensor device. A frequency shift with different concentrations of DMMP is measured. The gas sensor based on nanosized zeolite in resonating mode, whose resonant frequency shifts due to mass loading, has shown high sensitivity for detecting DMMP. The minimum detectable concentration of DMMP is 1 ppm in N₂ at 303 K. The frequency shift is about 60 Hz for 1 ppm DMMP. In order to improve the selectivity of the sensor to DMMP from other organic gases, different pore sized films, such as ZSM-5 zeolites and Ag⁺ modified ZSM-5 zeolites, are studied. The frequency shifts for two other organic gases, such as acetone and ethanol, at 1 ppm concentration are observed for the sensor selectivity detection. The relationship between frequency shift and temperature for 1 ppm DMMP has been studied. The best adsorption temperature is 303 K and the desorption temperature is at the DMMP boiling point, 473 K. Using principle component analysis (PCA); we can easily qualify and quantify the DMMP gas.