Classification of chemical warfare agents using thick film gas sensor array

Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets such as impregnation, physical mixing (ball-milling) and co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by the SEM, XRD and BET, respectively. Response characteristics are examined for test gases with temperature in the range 200-400 °C, with different gas concentrations. Test gases are dimethyl methyl phosphonate (DMMP), dipropylene glycol methyl ether (DPGME), acetonitrile, and dichloromethane which are used simulant gases of chemical warfare agents. These sensors showed sensitivities higher than 50% in 500 ppb of test gases and also good repetition behaviour. Four sensing materials are selected with good sensitivity and stability and are fabricated as a sensor array. And then, principal component analysis (PCA) is adapted to classify objective gas among the four simulant gases. The thick film array sensor shows high sensitivity to CWA gases and four CWA gases are classified by using a sensor array composed of four sensing devices through PCA.