SEMICONDUCTOR GAS SENSORS FOR DETECTION OF CHEMICAL WARFARE AGENTS AND TOXIC INDUSTRIAL CHEMICALS

Abstract

The sensors for detection of toxic and chemical warfare agents (CWA) should be sensitive to low concentrations of gases – considerably lower than ones immediately dangerous to life or health concentrations. The paper shortly discusses classical CWAs and toxic industrial sensors; makes a comparison between nuclear weapons and chemical agents and a toxicity comparison between real gases and simulants. Moreover, the paper analyzes the simulants for testing the sensor devices and semiconductor gas sensor' technique; shows sensitivity change with dimethyl methylphosphonate (DMMP) gas concentration for sensor made of SnO 2 . The MoO 3 , NiO, Al 2 O 3 , In 2 O 3 , Pt, ZnO and ZrO 2 additives are reported to exhibit enhanced sensitivity to dimethyl methylphosphonate (DMMP), and Al2O3, In2O3, ZrO 2 and ZnO additives – to exhibit enhanced sensitivity to dipropyleneglycol methylethylene (DPGME). SnO2 devices with ZrO 2 and ZnO additives exhibit high sensitivity to acetonitrile. The sensors made from Co-doped SnO 2 films demonstrate sensitivity to CWAs such as sarin and yperite. We performed the measurements at the operating temperature of 210 ºC, and found that the sensor exposed comparatively greater concentration of target gas (200 ppm sarin and 100 ppm yperite) and the SnO 2 <Co> sensor was sensitive to yperite starting from 25 ppm. Furthermore, the sensitivities to 50 ppm and 12.5 ppm sarin were found. The paper presents the results of our studies on tin oxide/ multiwall carbon nanotube film nanocomposite sensors of PG, dimethylformamide (DMF) and formaldehyde (FA) using hydrothermal synthesis and sol-gel methods. The investigations of response/recovery characteristics in the 50–300 o C operating temperature range reveal that the optimal operating temperature for the PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times, was 200–220 ºC. A sensor response dependence on gas concentration in all cases was linear. We measured the minimal PG, DMF and FA gas concentrations at which the perceptible signal was registered.