Highly Sensitive Room Temperature CO Gas Sensor Based on MWCNT-PDDA Composite

In this work, a resistive sensor based on multiwalled carbon nanotube (MWCNT) - poly(diallyldi- methylammonium chloride) solution (PDDA) composite is proposed for highly sensitive carbon monoxide (CO) detection at room temperature. The surface of MWCNTs is functionalized with PDDA, and the functionalization is investigated by Fourier transform infrared and Raman spectroscopy. The MWCNT-PDDA composite is used as a sensing material with deposited interdigitated electrodes (IDE) of silver (Ag) on glass substrates. The resistance of the sensors changes due to charge transfer from CO to the positively charged quaternary ammonium group present on PDDA. The developed sensors are able to detect very low concentrations of CO gas ranging from 1 to 20 ppm with high sensitivity and limit of detection (LOD) of 127 ppb. The interference of other gases and volatile organic compounds is investigated, and the results are presented. The influence of humidity and temperature on the sensors is also explored. The stability and repeatability of the sensors are examined, and the sensors are almost stable for 2 months with excellent reproducibility. The sensors also follow the Langmuir adsorption/desorption model. The sensors have shown excellent potential for rapid CO gas sensing, and it can be used in wearable electronics applications.