Vol. 7, Issue 2, Part C (2025)

In the last decade, the possible development of hybrid gas sensors based on carbon nanotube (CNT), titanium nanotube (TiO₂ NT), and conducting polymer (e.g., polyaniline, PANI, and polypyrrole, PPy) makes them intriguing gaps to fill for temperature-sensitivity replacement on conventional metal oxide sensors at high temperature. They offer operation at room temperature, high sensitivity, and possible engineered selectivity. Focusing on multi-component architectures, this report first details the roles of materials and sensing mechanisms (chemiresistive, photocatalytic, polymer doping and heterojunctions), and then fabrication techniques (Arc, CVD, laser, hydrothermal) and their effects on microstructure and performance. Additionally, other important performance parameters such as sensitivity, limit of detection (LOD), response/recovery times, selectivity, stability and repeatability are presented including test procedures and uncertainty analysis. The final judgement is that ternary systems (for example CNT/PANI/TiO₂ or 2D/CNT/PANI) and CNT/PANI composites own a relatively more competitive sensitivity, selectivity and stability during the actual humid atmospheres. What the future holds is reducing the tests protocols, making the chalcogenides resistant to humidity and creating scalable manufacturing methods.