EFFECT OF SURFACE MODIFICATION DUE TO SUPERACID SPECIES IN CONTROLLING THE SENSITIVITY AND SELECTIVITY OF SNO2 GAS SENSORS

The sensitivity and selectivity of SnO2 gas sensors are found to be af fected by the presence of sulphate species on the surface due to the f ormation of superacidic sites. The potential advantages of this new me thod of selectivity control of SnO2 gas sensors are described with res pect to the sensing of carbon monoxide, ammonia, ethanol, acetone and LPG. Although an increase in sensitivity is observed in the range 3-60 ppm for a few of these gases, these modified materials show a slow lo ss of activity upon exposure to humidity. The evidence obtained from i nstrumental techniques such as XRD, TG-DTA, SEM, IR and TDS indicate t hat these superacid species exert considerable influence on the sensit ivity by modulating the adsorption characteristics along with microstr uctural changes.