Performance of F-CNTs sensors towards ethanol vapor using different functional groups

Ethanol vapor sensors utilizing functionalized carbon nanotubes as sensing elements have been successfully built. The Au microelectrodes on the silicon substrate were fabricated by MEMS technology and the carbon nanotubes connection was achieved by DEP manipulation. Chemical oxidation method was used to graft functional groups such as COOH and OH on multi-walled nanotubes (MWNTs). Sensor performance using COOH-MWNTs and OH-MWNTs were compared in terms of various aspects, such as I-V curve, responsivity, sensor performance under different input current and time constant. Both sensors showed negative Temperature Coefficient of Resistance (TCR) and sharp resistance increase upon exposure to the ethanol vapor. Moreover, we observed the trends of decreased response and prolonged response time while the activation current was raised gradually. In addition, COOH-MWNTs based sensors have proved to be more sensitive towards ethanol vapor compared to OH-MWNTs.