Fabrication And Research Of Binary Metal Oxides Loaded Graphene-based NO₂ Sensors

Nitrogen dioxide（NO₂）,one of the most toxic air pollutants,has caused serious environmental problems and respiratory diseases.Various methods have been investigated for monitoring NO₂,among which gas sensor is regarded as the primary and effective NO₂ detector because of its high sensitivity,facile fabrication and low cost.Metal oxide semiconductors（MOS）-based sensors have been widely employed in application.The sensing performance of MOS-based gas sensors can be improved by the heterostructure constructed by binary metal oxides.However,MOS-based sensors still suffer from poor room-temperature sensing issue（100-400°C）due to the low electron mobility,which severely limits its practical application.A room temperature NO₂ sensor with low energy consuming is of particular interest to wide application scenarios in real world.Various methods,such as surface modification and combination with high conductive materials have been proposed to realize high-performance MOS-based gas sensors at room temperature.Graphene is an intrinsic low-noise two dimensional material with superior electrical conductivity and huge specific surface area,which is available as a substrate for hosting MOS nanomaterials.Incorporation of MOS with graphene can not only significantly increase the electronic transport property but also improve the accessible surface area exposed to target gases.It has been proved that MOS/graphene composites exhibit high performance sensing properties owing to the enhanced electron transport and the decrease of operating temperature caused by the introduction of graphene.Therefore,conjugating binary metal oxides with graphene is expected to realize efficient sensing performance with high response signal at the reduced work temperature.In this work,a new type gas sensor based on SnO₂-CuO binary metal oxides supported by reduced graphene oxide（rGO）nanosheets is prepared through a facile hydrothermal method.CuO nanopetals covered by SnO₂ nanoparticles are tightly combined with rGO,forming the porous structure of the tenary composite.The sensing performances of the as-synthesized composite towards NO₂ are comprehensively investigated through a home-made sensing test system.Response of SnO₂-CuO/rGO towards 50 ppm NO₂ is 8-15 times higher than those of CuO/rGO and SnO₂/rGO counterparts.Meanwhile,good selectivity（6 times higher response over other inorganic gases）,long-term stability（decay<5%for 7 days）and low limit of detection（150 ppb）are achieved.Herein a high-performance room-temperature NO₂ sensor based on binary MOS and reduced graphene oxide（rGO）is demonstrated,which can be interpreted by the the introduction of p-n heterostructure and synergistic effect enabled at the solid/solid interface.The outcomes of this work suggest that binary MOS/graphene exhibits great potential to achieve good room-temperature sensing performance.