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Three-Dimensional Graphene Hydrogel Decorated with SnO₂ for High-Performance NO₂ Sensing with Enhanced Immunity to Humidity

Wu, Jin, Wu, Zixuan, Ding, Haojun, Wei, Yaoming, Huang, Wenxi, Yang, Xing, Li, Zhenyi, Qiu, Lin, Wang, Xiaotian
ACS applied materials & interfaces 2020 v.12 no.2 pp. 2634-2643
ambient temperature, deformation, detection limit, engineering, graphene, graphene oxide, humidity, hydrogels, immunity, liquid crystals, nanoparticles, nitrogen dioxide, polymers, tin dioxide
A facile, one-step hydrothermal route was exploited to prepare SnO₂-decorated reduced graphene oxide hydrogel (SnO₂/RGOH) with three-dimensional (3D) porous structures for NO₂ gas detection. Various material characterizations demonstrate the effective deoxygenation of graphene oxide and in situ growth of rutile SnO₂ nanoparticles (NPs) on 3D RGOH. Compared with the pristine RGOH, the SnO₂/RGOH displayed much lower limit of detection (LOD) and an order of magnitude higher sensitivity, revealing the distinct impact of SnO₂ NPs in improving the NO₂-sensing properties. An exceptional low theoretical LOD of 2.8 ppb was obtained at room temperature. The p–n heterojunction formed at the interface between RGOH and SnO₂ facilitates the charge transfer, improving both the sensitivity in NO₂ detection and the conductivity of hybrid material. Considering that existing SnO₂/RGO-based NO₂ sensors suffer from great vulnerability to humidity, here we employed integrated microheaters to effectively suppress the response to humidity, with nearly unimpaired response to NO₂, which boosted the selectivity. Notably, a flexible NO₂ sensor was constructed on a liquid crystal polymer substrate with endurance to mechanical deformation. This work indicates the feasibility of optimizing the gas-sensing performance of sensors by combining rational material hybridization, 3D structural engineering with temperature modulation.