Zinc oxide thin films for a room temperature dual carbon dioxide and carbon monoxide sensor

Abstract

Zinc oxide was grown onto glass substrates by the spray-pyrolysis technique inorder to obtain thin films of different thicknesses to test their sensing characteristicstowards CO2 and CO at room temperature (21 C). The different filmsshowed a diverse surface reactivity towards these gases due to the dominantcrystallographic orientation of grains. The working temperature allows thesensor to operate without the need of maintaining the film heated, greatlyreducing its energy needs and building costs. A 2% signal decrease to 2000 ppmof CO2 is achieved within 120 s (t50 time) with a recovery time of approximately290 s. The detection limit is estimated to be at 400 ppm. This sensor can alsodetect harmful concentration of CO (above 50 ppm) since its response can beclearly differentiated from its CO2 response, thus behaving as a dual sensor.