CuO-decorated bismuth subcarbonate p–n heterostructured micro-flowers for high-selectivity VOC gas sensor arrays and cooked rice quality assessment

A gas sensor system with high sensitivity and excellent selectivity is essential for accurately evaluating the quality of cooked rice and optimizing agricultural storage conditions in real time. Detecting large molecular volatile organic compounds (VOCs) emitted from cooked rice presents several challenges, including low volatility, interference from complex sample matrices, and limited selectivity. In this study, we propose using CuO/Bi₂O₂CO₃ (Cu–BC) p–n heterostructure micro-flowers as a substrate to create a four-channel gas sensor array that converts voltage to resistance. The individual Cu<i>x</i>–BC sensors (<i>x</i> = 10, 20, 30, and 40) exhibit a strong response to nonanal, benzaldehyde, and 1-octen-3-ol at room temperature (25±2 °C), with detection specificity confirmed through principal component analysis (PCA). This integrated gas sensor array effectively identifies and distinguishes the quality of cooked rice, including both freshly prepared rice and rice stored for one to six weeks. The sensing mechanism relies on increased oxygen vacancies and improved electron mobility. Additionally, we explore the adsorption and diffusion mechanisms of the target gas molecules and oxygen on the surface of the materials using molecular dynamics (MD) simulations. Overall, the gas sensor array demonstrates significant potential in accurately assessing the quality of agricultural products at different storage stages.