NO2 sensing properties of bead-like TeO2 nanostructures fabricated using different O2 flow rates

초록

Wereport the synthesis of bead-like TeO₂ nanowire (NW)-basedNO₂ gas sensors using differentO₂ flow rates. The performance of these sensors was compared with that of a sensor based on smooth TeO₂ NWs. The smooth TeO₂NWswere grown directly from Te powder by thermal evaporation in air (i.e., without usingO₂ gas), while the bead-like TeO₂NWswere synthesized by transporting the evaporated Te precursor indirectly using reactive O₂ gas at flow rates of 20-40 sccm. Scanning electron microscopy showed that the bead-like TeO₂ NWs had uneven surfaces on which protruding nanoparticles with sizes of 20-100 nm were attached. The nanoparticle size varied with the O₂ flow rate used. The responses of the gas sensors based on the multi-networked bead-like TeO₂ NWs were indicative of a higher change in their electrical resistance as well as better selectivity to NO₂ gas than those of the sensor based on the smooth TeO₂ NWs. The individual responses- to 50 ppm NO₂ gas at 350 °C-of the sensors based on TeO₂ NWs fabricated without using O₂, using O₂ at 20 sccm, using O₂ at 30 sccm, and using O₂ at 40 sccm were 113, 188, 220, and 345%, respectively. The underlying mechanisms responsible for the improved performances of the bead-like TeO₂ NW-based sensors are also discussed. © 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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