Detection of citronellol in sweetpotato black spot disease using a quartz crystal microbalance (QCM) gas sensor based on Co/Zn-ZIF@MIP composite

Abstract Citronellol is a kind of terpene produced by plants in response to external stress; thus can be used as a gas biomarker to detect black spot Ceratocystis fimbriata infection in sweetpotato. However, many contemporary analytical methods, exemplified by gas chromatography-mass spectrometry, are technically demanding, time-consuming, and require complex sample preparation procedures. In this study, a quartz crystal microbalance (QCM)-based gas sensor fabricated via a surface molecular imprinting technique was modified with a Co/Zn-ZIF@MIP composite, in which cobalt–zinc bimetallic ZIF (Co/Zn-ZIF) served as the support material. A linear relationship was observed between the frequency shift and citronellol concentrations ranging from 0.88 to 22 mg/L, with a sensitivity of −6.08 Hz/(mg·L) and a limit of detection (LOD) of 1.35 mg/L. This result indicated that this sensor has excellent selectivity for citronellol and demonstrates high repeatability, as evidenced by R² value of 0.97. In evaluations with real samples, the sensor reliably identified citronellol among the complex volatile organic compounds (VOCs) emitted from black spot-infected sweetpotato, indicating a high level of selectivity. Our research achieved the rapid characterization of sweetpotato black spot disease within 4 min and provided new insights into the development of QCM-based gas sensors for the rapid assessment of agricultural product quality and safety.