2D Hybrid Nanomaterials for Selective Detection of NO 2 and SO 2 Using "Light On and Off" Strategy.

In order to distinguish NO2 and SO2 gas with one sensor, we designed a paper chip assembled with a 2D g-C3 N4 /rGO stacking hybrid fabricated via a layer-by-layer self-assembly approach. The g-C3 N4 /rGO hybrid exhibited a remarkable photoelectric property due to the construction of a van der Waals heterostructure. For the first time, we have been able to selectively detect NO2 and SO2 gas using a "light on and off" strategy. Under the "light off" condition, the g-C3 N4 /rGO sensor exhibited a p-type semiconducting behavior with a low detection limit of 100 ppb of NO2 , but with no response toward SO2 . In contrast, the sensor showed n-type semiconducting behavior which could detect SO2 at concentration as low as 2 ppm under UV light irradiation. The effective electron transfer among the 2D structure of g-C3 N4 and rGO nanosheets as well as highly porous structures could play an important role in gas sensing. The different sensing mechanisms at "light on and off" circumstances were also investigated in detail.