Performance comparison of CTAB-modified NiO, ZnO, and SnO2 sensors for CO and CH4 detection in environmental and health applications

In industrial and environmental monitoring, high-sensitivity and response-time sensors are a major challenge. In this research, ZnO, NiO, and SnO₂ nanostructures were prepared via a Surfactant (CTAB)-assisted hydrothermal process. Surfactant improves surface activity and porosity for controlled development. A stable p-n heterojunction was formed by including PEDOT: PSS in n-type oxides. The fabricated sensors were put through an intensive testing procedure for the detection of CO and CH₄ at ambient temperature (30 °C) and at different concentrations (2-10 ppm). The maximum sensitivity of the PEDOT: PSS/SnO₂ heterojunction was 92.3% for CO and 90.8% for CH₄. Its response and recovery times were 10/5 s and 15/8 s, respectively. The developed sensors exhibited a linear response pattern and excellent repeatability across a 24-h evaluation, with five testing cycles of 250 s each. Characterization of structural and surface properties (XRD, EDS, BET, UV, JV, and EIS) confirmed that high crystallinity, nanoscale structure, and enhanced surface area were responsible for enhanced sensing performance. Based on the results, PEDOT: PSS heterojunction assembly combined with CTAB-assisted hydrothermal synthesis may be employed to synthesize high-performance, low-cost gas sensors for real-time detection of harmful and inflammable gases.