Part per trillion level DMMP gas sensor based on calixarene modified organic thin film transistor

Dimethyl methylphosphonate (DMMP) is a simulant of nerve agent sarin, which still remains a great challenge to detect due to lack of sensitive, selective and stable sensor. In this work, calixarenes are designed to apply on organic thin film transistor (OTFT) to form a high-performance gas sensor for DMMP detection. The theoretical calculation indicates that the binding energy between calixarene (4-tert-Butylcalix[6]arene, denote as TB6) and DMMP is stronger (-25.34 kcal/mol) than that of poly(3-hexylthiophene-2,5-diyl) (semiconductor layer of this OTFT sensor, denote as P3HT) (-10.83 kcal/mol), which could bring significant improvement to the sensitivity of this sensor. The experimental result confirms that the limit of detection (LOD) of TB6-P3HT based sensor can be as high as 10 ppt which is about four orders of magnitude higher than pristine P3HT. The drain current changes after exposure to 50 ppm DMMP, ethyl acetate, toluene, isopmpanol and nitrogen dioxide are 39.0%, 2.9%, 2.7%, 2.1% and 1.3%, which also suggests the good selectivity of this sensor. Besides, the TB6-P3HT based sensor exhibits a better stability (14.1% degradation after one month) than pristine P3HT (55.8%) because of the better antioxidant capacity of this bilayer structure. Further, this sensor shows its ability to work in different relative humidity and temperatures, which demonstrates the potential application in complex environment. We anticipate this general approach could offer solutions for high performance gas detection.