Fully printed, rapid-response sensors based on chemically modified graphene for detecting NO2 at room temperature

Reduced graphene oxide (RGO) has proven to be effective in trace gas detection at room temperature ambient conditions. However, the slow response-recovery characteristic is a major hurdle for the RGO-based gas sensors. Herein, we report a gravure-printed chemoresistor-type NO2 sensor based on sulfonated RGO (S-RGO) decorated with Ag nanoparticles (Ag-S-RGO). Large amounts of silver nanoparticles with an average particle size of 10-20 nm were uniformly assembled on flat S-RGO surfaces. The printed Ag-S-RGO sensor possesses a high sensitivity and fast response-recovery characteristic over NO2 concentrations ranging from 0.5 to 50 ppm. Upon exposure to 50 ppm NO2 at room temperature, the Ag-S-RGO sensor shows a sensitivity of 74.6%, a response time of 12 s and a recovery time of 20 s. In addition, the Ag-S-RGO sensors exhibit satisfactory flexibility with an almost constant resistance after 1000 bending cycles. The printed and high-performance Ag-S-RGO sensors described here will be a good prospect in environmental monitoring of NO2.