The gas sensing properties of zeolite modified zinc oxide

The illicit manufacture of drugs in the 21st century presents a danger to first responders, bystanders and the environment, making its detection important. Electronic noses based on metal oxide semiconducting (MOS) sensors present a potential technology to create devices for such purposes. An array of four thick film MOS gas sensors was fabricated, based on zinc oxide inks. Production took place using a commercially available screen printer, a 3 × 3 mm alumina substrate containing interdigitated electrodes and a platinum heater track. ZnO inks were modified using zeolite β, zeolite Y and mordenite admixtures. The sensors were exposed to four gases commonly found in the clandestine laboratory environment; these were nitrogen dioxide, ethanol, acetone and ammonia. Zeolite modification was found to increase the sensitivity of the sensor, compared to unmodified ZnO sensors, all of which showed strong responses to low ppm concentrations of acetone, ammonia and ethanol and to ppb concentrations of nitrogen dioxide. Machine learning techniques were incorporated to test the selectivity of the sensors. A high level of accuracy was achieved in determining the class of gas observed.