Microwave-Assisted Synthesis of Graphene–SnO2 Nanocomposites and Their Applications in Gas Sensors
2017
Kim, Hyoun Woo | Na, Han Gil | Kwon, Yong Jung | Kang, Sung Yong | Choi, Myung-Sik | Bang, Jae Hoon | Wu, Ping | Kim, Sang Sub
We obtained extremely high and selective sensitivity to NO₂ gas by fabricating graphene–SnO₂ nanocomposites using a commercial microwave oven. Structural characterization revealed that the products corresponded to agglomerated structures of graphene and SnO₂ particles, with small secondary SnOₓ (x ≤ 2) nanoparticles deposited on the surfaces. The overall oxygen atomic ratio was decreased with the appearance of an SnOₓ (x < 2) phase. By the microwave treatment of graphene–SnO₂ nanocomposites, with the graphene promoting efficient transport of the microwave energy, evaporation and redeposition of SnOₓ nanoparticles were facilitated. The graphene–SnO₂ nanocomposites exhibited a high sensor response of 24.7 for 1 ppm of NO₂ gas, at an optimized temperature of 150 °C. The graphene–SnO₂ nanocomposites were selectively sensitive to NO₂ gas, in comparison with SO₂, NH₃, and ethanol gases. We suggest that the generation of SnOₓ nanoparticles and the SnOₓ phase in the matrix results in the formation of SnO₂/SnO₂ homojunctions, SnO₂/SnOₓ (x < 2) heterojunctions, and SnO₂/graphene heterojunctions, which are responsible for the excellent sensitivity of the graphene–SnO₂ nanocomposites to NO₂ gas. In addition, the generation of surface Sn interstitial defects is also partly responsible for the excellent NO₂ sensing performance observed in this study.
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