Effect of conducting polymers on nitrogen-doped multiwalled carbon nanotube for the detection of chemical warfare agent simulant

Chemical warfare agents (CWAs) have inflicted significant harm to human lives, from World War I to present-day conflicts, including armed battles, terrorist incidents, and civil wars. To explore the possibility of early detection of CWAs to prevent loss of life, we developed various composite materials for sensing these agents using a hydrothermal process. The surface acoustic wave (SAW) sensor was employed as a detector for dimethyl methyl phosphonate (DMMP), a well-known simulant of the nerve agent sarin. Nitrogen doped multiwalled carbon nanotube (N-MWCNT) was used as a precursor, with polymers such as carboxymethyl cellulose (CMC), polyaniline (PANI), and polypyrrole (PPy) added to enhance sensitivity to DMMP concentrations ranging from 2 to 10 parts per million (ppm). The N-MWCNT@CMC composite demonstrated exceptional performance exhibiting frequency response (Δf) of ∼1212 Hz at a concentration of 10 ppm DMMP. The composite materials showed excellent sensitivity to DMMP with minimal effect of potential interferences during selectivity test. Specifically, the N-MWCNT@CMC showed excellent coefficients of determination (R²) of 0.990, with a limit of detection (LOD) of 1.33 ppm. In the relative humidity test from 30–70 %, the N-MWCNT@CMC exhibited the highest Δf, measuring ∼137 Hz. However, it showed lowest Δf difference of ∼16 % in temperature tests conducted from 25–75 °C. The Brunauer-Emmett-Teller (BET) results revealed that the addition of CMC to the N-MWCNT increased the pore size (adsorption = 36.9 nm, desorption = 40.0 nm) of the composite, which enhanced its sensitivity to DMMP during both adsorption and desorption. Based on these findings, it can be concluded that synthesized composites show potential as candidates for detecting the nerve agent sarin.