Polyethylenimine-polyethylene glycol/multi-walled carbon nanotubes bilayer structure for carbon dioxide gas sensing at room temperature

Abstract This work aims to fabricate polyethylenimine (PEI)-polyethylene glycol (PEG)/multi-walled carbon nanotubes (MWCNTs) bilayer-structure devices for CO2 gas sensors. The devices are composed of two layers; the first layer is made of MWCNTs, which act as the electron transport layer, whereas the second layer is made of PEI-PEG blender which can functionalize MWCNTs and acts as the CO2 adsorption material. Both layers are sequentially spray-coated on the screen-printed carbon electrodes. After functionalization, the resistance of the device is increased due to the functionalization effect by the PEI-PEG blender. Using air as background gas, the bilayer-structure devices provide 3.25% sensitivity under 5 vol% CO2. Moreover, the devices show excellent stability and reversibility under multiple cycle tests for 400 min.