Insects cause substantial damage to crops, with the FAO estimating up to 40 percent of global crop losses, totaling around USD 220 billion annually. This underscores the critical need for innovative insect detection methods. Green leaf volatiles (GLVs) are organic compounds emitted by plants in response to insect attacks, offering potential for early detection . Current detection methods like gas chromatography–mass spectroscopy (GC-MS) are costly and complex, limiting real-time monitoring. There is a pressing need for affordable, portable sensors with high sensitivity to monitor GLVs in real time to address this critical agricultural challenge.

Chemical analyte binding to sensing materials can lead to optical, mechanical, thermal, electrical, and mass changes. By utilizing a transducer capable of detecting these multidimensional changes, sensor performance, including sensitivity and selectivity, can be enhanced. In this study, we developed a novel sensor capable of capturing both piezoelectric and colorimetric signals for the sensitive and selective detection of hexanol, a well-known green leaf volatile. We used a piezoelectric micro quartz tuning fork (MQTF) as the transducer. The MQTF's two prongs were coated with a metal–organic framework (MOF)–thymol blue hybrid sensing material, enabling detection through both color change and resonating frequency shifts upon hexanol binding. MOFs offer a high surface area and tunable pore size, enhancing sensor sensitivity and selectivity. The sensor's frequency shift indicates mass change due to hexanol binding to MOFs, while colorimetric sensing relies on thymol blue's reaction with hexanol. Tests demonstrate the sensor's ability to detect hexanol from 60ppb to 250ppm with high sensitivity and selectivity. Its compact size, cost-effectiveness, simple fabrication, wide detection range, and accuracy make the MOF-based colorimetric–piezoelectric sensor an ideal choice for early insect herbivore attack detection in agriculture.