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

초록

Wereport the synthesis of bead-like TeO<inf>2</inf> nanowire (NW)-basedNO<inf>2</inf> gas sensors using differentO<inf>2</inf> flow rates. The performance of these sensors was compared with that of a sensor based on smooth TeO<inf>2</inf> NWs. The smooth TeO<inf>2</inf>NWswere grown directly from Te powder by thermal evaporation in air (i.e., without usingO<inf>2</inf> gas), while the bead-like TeO<inf>2</inf>NWswere synthesized by transporting the evaporated Te precursor indirectly using reactive O<inf>2</inf> gas at flow rates of 20-40 sccm. Scanning electron microscopy showed that the bead-like TeO<inf>2</inf> NWs had uneven surfaces on which protruding nanoparticles with sizes of 20-100 nm were attached. The nanoparticle size varied with the O<inf>2</inf> flow rate used. The responses of the gas sensors based on the multi-networked bead-like TeO<inf>2</inf> NWs were indicative of a higher change in their electrical resistance as well as better selectivity to NO<inf>2</inf> gas than those of the sensor based on the smooth TeO<inf>2</inf> NWs. The individual responses- to 50 ppm NO<inf>2</inf> gas at 350 °C-of the sensors based on TeO<inf>2</inf> NWs fabricated without using O<inf>2</inf>, using O<inf>2</inf> at 20 sccm, using O<inf>2</inf> at 30 sccm, and using O<inf>2</inf> at 40 sccm were 113, 188, 220, and 345%, respectively. The underlying mechanisms responsible for the improved performances of the bead-like TeO<inf>2</inf> NW-based sensors are also discussed. © 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

키워드