Gas Sensor with Reduced Humidity Response, Based on Metal Oxide Nanoparticles Synthesized by Spark Discharge

The most part of gas sensors based on tin dioxide semiconductor sensing material are fabricated by using sol-gel synthesis of SnO2. This process leads to the formation of highly sensitive sensing material; however, it forms hydroxyl groups on the surface of tin dioxide, leading, in turn, to strong parasitic sensitivity of the sensor to changing humidity. This sensitivity can be reduced by calcination of sensing material, but this treatment also reduces considerably the total response of the sensor to target gases. In this work, we investigated the possibility of the dry synthesis of tin dioxide nanoparticles by gas phase spark discharge. After the annealing at 610 degrees C, the specific area of the material synthesized by spark discharge was about 40 m(2)/g. The sensing layer resistance of the sensor decreases by only 20%, when relative humidity of a carrier air increases from 40 to 100%. At the same time, the hydrogen response of the sensor remains the same as for the material prepared by sol-gel synthesis, that is factor of 8 at 100 ppm concentration of H-2. Very important property of the sensor is short response time of similar to 1-2 s to both hydrogen and humidity.