The use of ex-situ nitrogen-doped olive oil-derived carbon nano-onions for application in chemi-resistive gas sensors to detect acetone at room temperature

This study reports on the synthesis of carbon nano-onions (CNOs; ca. d ≤ 55 nm) and nitrogen-doped CNOs (N-CNOs) using a facile pyrolysis method and ex-situ doping of the CNOs. Elemental analysis of the N-CNOs revealed that their nitrogen content depended on the ammonia flow rate. Analysis of the N-CNOs revealed that they all exhibited structural defects. After the successful synthesis of CNOs and N-CNOs, polyvinylpyrrolidone (PVP):CNOs/N-CNOs:MnO₂-nanorods (MONRs) composites were prepared and used as active sensing materials. In every case, the PVP polymer was used to stabilize the MONRs for acetone detection at 25 °C. The chemi-resistive gas sensors that showed the highest acetone sensitivity (pS = 2.0 × 10⁻⁴ ppm⁻¹) was fabricated using a pristine CNOs (pCNOs) based composite. However, the N-CNOs based sensor (a_1.5S) presented the lowest acetone limit of detection (LoD) at 1.2 ppm. The study implicated the effect of the nitrogen and oxygen content of the CNOs surfaces on the acetone detection. Thus, a higher sensitivity with lower LoD was observed at room temperature using the pCNOs based sensor, when compared to earlier literature reports.