Self-standing MWCNTs based gas sensor for detection of environmental limit of CO2

In this work, we have demonstrated multi walled carbon nanotubes (MWCNTs) based CO2 gas sensor using a reliable and low cost gel-cast method with MWCNT concentration of 0.6, 1.0, 1.5, 2.0 and 3.0 by wt% in alumina Al2O3 sol which acts as a host matrix for the composite. Sensing response of the as prepared highly uniform selfstanding MWCNTs film was measured at room temperature by exposure to different CO2 concentrations, ranging from 50 ppm to 450 ppm. The adsorption effect of CO2 on the varying concentration of CNTs was investigated by measuring a significant change in the resistance. Upon exposure to CO2 molecules, the device shows a drastic increase in resistance attributed to the charge transfer between CNTs and CO2 molecules. High sensor response of 7.3% with a response time of 53.7 s exhibited by sensor S3 (1.5 wt% of MWCNTs) is reported when the concentration of CO2 is 450 ppm in ambient conditions. In addition, different recovery modes were examined and the results reveal that there is a significant decrease in the recovery time of sensor upon UV light exposure and heat application. Besides being fast recoverable with heat energy, the fabricated gas sensor shows favorable stability in response over multiple exposure of analyte gas.