Research Highlights

Professor Joon Hak Oh Develops Liquid-Phase Sensors with High Sensitivity and Selectivity

2015-07-29 369
Joon Hak Oh

A research team consisting of Prof. Joon Hak Oh, Moo Yeol Lee (Department of Chemical Engineering, POSTECH), and Prof. Bumjoon J. Kim (Department of Chemical and Biomolecular Engineering, KAIST) has developed highly sensitive and selective liquid-phase sensors based on a solvent-resistant organic semiconducting layer. The research outcome was highlighted as the cover article in Advanced Materials which is a renowned international journal in the field of materials.
Sensors based on organic field-effect transistor (OFET) platform have attracted great interest due to their use as light-weight, low-cost, flexible electronics. Although various OFET-based sensors have been demonstrated for sensing a various types of analytes, sensors for detecting liquid-phase analytes have not been reported because of the poor resistance of the organic semiconductors in common organic solvents. From this critical drawback, OFET-based sensors have only frequently been demonstrated with organic vapor- or aqueous-phase analytes.
By introduction of chemically crosslinkable organic semiconductor (P3HT-azide) to the OFET-based sensors, high resistance of the devices toward liquid-phase organic solvents was achieved. Moreover, calix[8]arene which is a well-known container molecule was adopted to enhance the sensitivity and selectivity of the sensor device. Calix[8]arene molecules on the surface of the semiconducting layer facilitated the interactions with target analytes, providing selectivity of the sensors. As a result, the sensors device showed higher resistance toward toluene and methanol compared with those with uncrosslinked semiconducting layers. Moreover, the sensors with cailix[8]arene showed 1 vol% of detection limit for detecting methanol, ethanol, and n-hexane in toluene based medium. Computational study has also been conducted and the calculated results well matched with experimental results.
Prof. Oh emphasized,“This research demonstratesaviable methodology for the fabrication of OFET-based sensors that can detect liquid-phase organic solvents, and extends the range ofpractical applications of OFET-based sensors.”
This research was supported by the Global Frontier Research Center for Advanced Soft Electronics and Mid-Career Researcher program under the Ministry of Science, ICT & Future Planning.