▎ 摘　　要

A highly sensitive gas sensor based on novel hybrid structures composed of 2D graphene and 2D NiO nanosheets (NSs) is fabricated using a low-cost, low temperature and large area scalable solution-based process. The highly developed hierarchically porous structures of 2D NiO sheets are grown on reduced graphene oxide (RGO) surfaces. Sensors fabricated with hybrid structures showed a responsivity and sensitivity two orders higher than that of a NiO NS alone toward NO2 even at 1 ppm level. This is attributed to the effective carrier transfer from NiO NS to graphene and to the well-developed 2D NiO structure. The sensing results are similar when reducing gases such as H-2, NH3 and H2S are tested, but the responsivity toward NO2 was highest among all the gases tested. (C) 2013 Elsevier B.V. All rights reserved.