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 affected by the presence of sulphate species on the surface due to the formation of superacidic sites. The potential advantages of this new method of selectivity control of SnO2 gas sensors are described with respect 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 loss of activity upon exposure to humidity. The evidence obtained from instrumental techniques such as XRD, TG-DTA, SEM, IR and TDS indicate that these superacid species exert considerable influence on the sensitivity by modulating the adsorption characteristics along with microstructural changes.