Organic Field-effect Transistor Based VOCs Gas Sensors

Volatile organic compounds(VOCs)pollution is becoming a great threat to human health in recent years.Thus,it is an urgent need to monitor ppb level VOCs in order to evaluate indoor/outdoor air quality and health condition.Gas chromatography is a traditional strategy for VOCs vapor detection,which has the advantages including high sensitivity,high selectivity and could achieve quantitative analysis.But this method is also troubled by the efficiency and cost problems,which cannot meet the need of rapid and real-time VOCs detection.In this case,it is necessary to develop a miniature,portable,sensitive and rapid VOCs gas sensors.Traditional gas sensors are mainly based on metal oxide semiconductor materials.But they are all troubled by the poor sensitivity and selectivity for VOCs detection.Unlike inorganic materials,the rich functional groups of organic semiconductor materials could bring non-covalent interactions with VOCs molecules including ?-?interactions,hydrogen bonds and charge transfer adsorptions.These effects could be helpful for enhancing sensitivity and selectivity to some VOCs molecules.Organic field-effect transistor(OFET)is a kind of new devices which is easy to fabricate,low cost and printable.In recent years,OFETs have been widely concerned by researchers in this area.In this paper,a series of OFET gas sensors based on organic semiconductor materials are fabricated and investigated for typical toxic and harmful VOCs detection.The dynamic gas testing system is also built,and the abilities of dynamic toluene and dimethyl methylphosphonate(DMMP)detection for our sensors are approved.The research contents in detail are listed as follow:1.In order to solve the selectivity problem of some VOCs gases detection,OFET gas sensors based on pentacene and poly(3-hexylthiophene)(P3HT)were fabricated.The ? conjugate adsorption between organic semiconductor and conjugated structure molecules could help improve the selectivity and sensitivity of benzene series gas sensors.The electrical characteristics of the OFET devices and sensing properties were studied.These results indicated that ? conjugate adsorption can effectively improve the selectivity and sensitivity of benzene series gas sensors.2.In order to achieve DMMP trace detection,the OFET gas sensors modified by calixarene was fabricated,and their electrical properties and gas sensitivities to DMMP were studied.The research results show that hydrogen bond interaction between calixarene and DMMP molecules can significantly improve the gas sensing performance of OFET based gas sensors.3.Based on our previous researches,dynamic sensing system was built in order to simulate the dynamic toluene and DMMP detection in natural environment.According to these results,we found that the sensing materials and device structures of OFET based gas sensors were still needs to be optimized to meet the needs of practical applications.