Decorated‐Induced Oxygen Vacancy Engineering for Ultra‐Low Concentration Nonanal Sensing: A Case Study of La‐Decorated Bi₂O₂CO₃

La-decorated Bi₂O₂CO₃ (BCO-La) microspheres are synthesized using a facile wet chemical strategy for sensing low-concentration nonanal (C₉H₁₈O) at room temperature. These BCO-La gas sensors are applied to evaluate agricultural product quality, specifically for cooked rice. The sensitivity of the BCO-6La sensor significantly surpassed that of the pure BCO sensor, achieving a response value of 174.6 when detecting 30 ppm nonanal gas. Notably, the BCO-6La sensor demonstrated a faster response time (36 s) when exposed to 18 ppm of nonanal. Additionally, the selectivity toward nonanal gas detection is higher (approximately 4-24 times) compared to interfering gases (1-octanol, geranyl acetone, linalool, hexanal, 2-pentyfuran, and 1-octen-3-ol) during cooked rice quality detection. The gas sensing mechanism and the factors contributing to the enhanced sensing performance of the BCO-La microspheres are demonstrated through in situ FT-IR spectra and DFT analysis while the realistic detection scenario is carried out. In a broader context, the reported sensors here represent a novel platform for the detection and monitoring of gases released by agricultural products during storage.