Room Temperature NH₃ Selective Gas Sensors Based on Double-Shell Hierarchical SnO₂@polyaniline Composites

Morphology and structure play a crucial role in influencing the performance of gas sensors. Hollow structures, in particular, not only increase the specific surface area of the material but also enhance the collision frequency of gases within the shell, and have been studied in depth in the field of gas sensing. Taking SnO₂ as an illustrative example, a dual-shell structure SnO₂ (D-SnO₂) was prepared. D-SnO₂@Polyaniline (PANI) (DSPx, x represents D-SnO₂ molar content) composites were synthesized via the in situ oxidative polymerization method, and simultaneously deposited onto a polyethylene terephthalate (PET) substrate to fabricate an electrode-free, flexible sensor. The impact of the SnO₂ content on the sensing performance of the DSPx-based sensor for NH₃ detection at room temperature was discussed. The results showed that the response of a 20 mol% D-SnO₂@PANI (DSP20) sensor to 100 ppm NH₃ at room temperature is 37.92, which is 5.1 times higher than that of a pristine PANI sensor. Moreover, the DSP20 sensor demonstrated a rapid response and recovery rate at the concentration of 10 ppm NH₃, with response and recovery times of 182 s and 86 s.