A Highly Sensitive Nitrogen Dioxide Gas Sensor Using Horizontally Aligned SWCNTs Employing MEMS and Dielectrophoresis Methods

This article introduces sensing of nitrogen dioxide (NO
₂
) gas using horizontally aligned single walled carbon nanotubes (SWCNTs) in between gold interdigitated electrodes (IDEs). The fabrication process employed microelectromechanical system (MEMS), photolithography, thin film metallization, and dielectrophoresis (DEP) methods. Gold IDEs were fabricated using photolithography and thin film metallization techniques onto Si/SiO
₂
substrate, and then, SWCNTs were horizontally aligned in between IDE using DEP. The fabricated sensor was characterized for sensing of NO
₂
gas in the range 1 to 5 ppm. The cardinal sensing principle involves the reduction of NO
₂
molecules on interaction with horizontally aligned SWCNTs. This reduction of NO
₂
molecules is attributed to intratube and intertube electron modulation and charge transfer mechanisms on SWCNTs surface, which is manifested in terms of change in resistance of the SWCNTs. Therefore, change in resistance of SWCNTs on changing the concentration of NO
₂
gas was considered as the detection signal. The sensitivity of the present NO
₂
gas sensor is found to be ~70%, which is better than the reported ones. The additional advantages of present study are that it is highly efficient, portable, compact, and cost effective technique for sensing of NO
₂
gas, which possesses potential applications in environmental monitoring of NO
₂
gas and space flight demonstration.