Co-MOF-derived Co₃O₄ sensors for efficient 3-octanone biomarker monitoring in wheat mildew

3-octanone has been widely identified as a primary biomarker for mold and insect infestation in wheat. Nevertheless, to date, no chemiresistive sensor based on a metal oxide semiconductor with excellent sensing properties for 3-octanone has been developed. In light of the extensively reported superior efficacy of Co₃O₄-based sensors for ketone detection, we designed Co₃O₄ samples with various hierarchical morphologies (hollow sphere, multi-wall sphere, flower-like, and urchin-like), which were determined by regulating solvent and organic ligand. The sensing properties of four as-fabricated Co₃O₄-based sensors were systematically evaluated, verifying their potential for efficient 3-octanone monitoring. The adsorption behavior of 3-octanone was studied by DFT simulation, and the preferential adsorption of the hydroxyl functional group in 3-octanone at Co sites was verified. Among the four samples, the hollow spherical Co₃O₄ demonstrated the highest sensitivity for 3-octanone (173.88 ± 5.59@50 ppm), which can be attributed to the larger specific surface area (SSA, 60.164 m²/g), lower energy gap (1.306 eV), and the superior concentration of chemisorbed oxygen (23.8 %). Furthermore, the practical value of this sensor in agricultural product inspection and environmental monitoring applications was validated by testing its response to the complex gases emitted from wheat stored for different periods.