2D Hybrid Nanomaterials for Selective Detection of NO₂ and SO₂ 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-C₃N₄/rGO stacking hybrid fabricated via a layer-by-layer self-assembly approach. The g-C₃N₄/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-C₃N₄/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-C₃N₄ 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.