A Nano Sensor Array for Methyl Salicylate Detection in Gaseous Form

Abstract

Pathogenic plant diseases can be recognized through volatile organic compounds (VOC) chemical markers that are emitted from the plant surface upon distress. The ability to detect biomarkers from distressed plants sensitively, selectively, accurately, and rapidly could be of enormous benefit to the agricultural industry and crop growers. Among the various VOC, Methyl Salicylate (MeSa) has been identified to be a fingerprint compound that can be used as chemical marker for early detection of diseased crops1,2. Carbon nanotube (CNT) based sensors have been long used in detection of molecular species, due to their extremely high surface to volume ratio, and their p-type semiconducting behavior when connected to metallic electrode3. In this work the development of a CNT-based amperometric gas sensor for MeSa has been undertaken. The CNT gas adsorption capabilities result from their hollow structure and nanometric dimensions. These properties are important for sensitivity as it allows for several molecules to adsorb on to the surface of the sensor. The detection of MeSa is done by monitoring the current flowing through the CNT under specific gate-drain and source-drain potentials. These potentials are determined by careful examination of the change in current under different gate potentials (Trans-conductance) and the change in current under different source-drain potentials. When the MeSa molecule is adsorbed to the CNT surface it behaves as an additional gate potential source and therefore changes the current in the CNT. Selectivity can be achieved with different surface modifications of the CNT. The surface modifications will change the potential the MeSa induces on the CNT, and thus gives a different current profile for the adsorption and desorption of the MeSa molecules to and from the CNT surface.