Boosting Gaseous Acetone Detection by Nanoheterojunctions of p‑TypeMWCNTs/PANI Integrated into 3D Flame-Synthesized n‑Type ZnO

Accurate methods for detecting volatile organic compounds (VOCs) are essential for non-invasive disease diagnosis, with breath analysis providing a simpler, user-friendly alternative to traditional diagnostic tools. However, challenges remain in low-temperature VOC solid-state sensors, especially concerning the selectivity and functionality at room temperature. Herein, we present key insights into optimizing multi-walled carbon nanotubes (MWCNTs)/polyaniline (PANI) and ZnO nanocomposites for efficient, light-free selective acetone sensing. We showcased novel nanocomposites prepared by integrating p-type MWCNTs/PANI into a porous 3D network of n-type ZnO nanoparticles, synthesized via flame spray pyrolysis, and varying the weight ratios between ZnO and MWCNTs/PANI (namely 1:1, 8:1, 32:1, 64:1). The 32:1 nanocomposite exhibited superior acetone selectivity over toluene and ethanol, resulting promising even at room temperature. As such, a potential sensing mechanism was proposed, which involves nanoheterojunctions formation between p-type MWCNTs/PANI and n-type ZnO, creating an accumulation layer that enhances the gas response. Moreover, the incorporation of MWCNTs improved the overall conductivity and carrier mobility. Hence, we believe that this work offers valuable insights for optimizing MWCNTs/PANI and ZnO nanocomposites for efficient, low temperature, light-free gas sensors.