Investigation of functionalization layers for NO2 detection

Functionalization layers are investigated for NO₂ detection using a highly sensitive and versatile potentiometric sensor platform for gas and vapor sensing applications. Work function changes were measured for different functionalization layers made of ln₂O₃ and SnO₂ thin films and ZnO nanowires deposited on a Si substrate. A sensitivity of ~0.36 mV/sec for surface work function change was found out for 70 ppm NO₂ concentration for isolated clusters of ZnO nanowires indicating that this technique is applicable even for nano-clusters of sensing materials where amperometric detection is impossible due to material discontinuity. A surface work function change of ~10 mV was observed in sub-ppm regime (600 ppb NO₂) for highly insulating ln₂O₃ (resistivity >1 TOmega / ). Graphene layers and nanocrystalline graphite (NG) were compared with the transition oxide based functionalization layer for sensing sub-ppm NO₂ (600 ppb) sensing. It was observed that NG shows much higher sensitivity and lower response times.