Single Carbon Nanotube Based Ion Sensor for Gas Detection

This paper presents a new method for carbon nanotube based gas sensing. Instead of sensing the gas directly, the gas molecules are first ionized and then the ionized molecules are sensed by the single carbon nanotube based ion sensor. The adsorption of ionized gas molecule on the carbon nanotube surface introduces electrons into the material and consequently changes the current of the sensor. Once the electron of an ionized gas molecule is desorbed and transported to the electrode, the gas molecule is released from the carbon nanotube and another ionized gas molecule is adsorbed onto the carbon nanotbue surface. In this way, the response of the sensor is much faster than the traditional carbon nanotube based gas sensors which directly sense the gas molecules. A single carbon nanotube based ion sensor is fabricated and assembled to verify this theory. The electrical behavior of a single multiwall carbon nanotube is measured and analyzed. Experimental results show the responses of the ion sensor to oxygen ions. It is shown that the sensor exhibits a reversible response with a recovery time of couple seconds, which is much less than the traditional gas sensors´ recovery time of several minutes to couple hours.