Piezoelectric sensor for ethylene based on silver(I)/polymer composite

The postharvest stability of fruits is influenced by the atmospheric ethylene. Thus, it is important to detect ethylene accumulation in the fruit environment to avoid economic losses due to premature rotting. In this study, an ethylene sensor was fabricated by drop-casting a AgBR4/polyvinylpyrrolidone composite onto a quartz crystal microbalance (QCM). Upon exposure to ethylene, the oscillation frequency of the QCM decreased immediately, and reached steady state after 10 min. This response could be attributed to the binding of ethylene to immobilized Ag(I), causing a change in the surface mass of the sensor. The sensor can be regenerated by purging it with nitrogen gas, indicating reversibility of the response. The response was repeatable with RSD of <5% (n = 11) against 25% ethylene. The mole ratio of Ag(I) to monomer unit and the amount of coating material influenced the sensor response, and were optimized. The sensor exhibited a linear working range from 1 to 7 ppm (R = 0.9896) with RSD of <15% (n = 3). The sensitivity and limit of detection were determined to be 51 Hz ppm(-1) and 420 ppb, respectively. The sensor also produced responses to higher ethylene level (from 10 ppm to 1,000,000 ppm) but with a much lower sensitivity. The sensor output correlated well with the results of gas chromatograhic measurements. Good selectivity to ethylene was shown against other volatile organic compounds. The sensing paradigm for ethylene based on AgBF4/PVP coated QCM can be applied to ethylene monitoring in post-harvest technology. (C) 2017 Elsevier B.V. All rights reserved.