A PCB Based Chemiresistive Carbon Dioxide Sensor Operating at Room Temperature Under Different Relative Humidity

A chemiresistive type carbon dioxide (CO
₂
) gas sensor comprised of polyethersulfone (PES)/ ethylenediamine (EDA)-functionalized multi-wall carbon nanotubes (e-MWCNTs) composite has been developed by fabricating on the printed circuit board (PCB) using drop casting method. Composite with different volumetric ratios of PES/e-MWCNTs were prepared as a sensing element to evaluate the CO
₂
gas sensing properties at room temperature under different relative humidity (30 - 70% RH). The sensing mechanism mainly depends on the interaction between primary amino groups present in EDA and CO
₂
gas molecules at room temperature under different relative humidity where the formation of bicarbonate ions (HC0
₃
-) protonates amino groups and changes the total conductivity of the composite based fabricated sensors. In evaluation of sensing properties, PES/e-MWCNTs based sensor having a volumetric ratio of 1:4 showed high sensitivities (2.1 × 10
^-3
to 2.94 × 10
^-3
% ppm
^-1
) with fast responses towards entire CO
₂
gas concentration (500 - 5000 ppm) under 30 - 70% RH as compared to other volumetric ratios. These results indicate that fabricated sensors are capable of CO
₂
gas detection at various concentrations for environmental as well as human safety.