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. 2012 Aug 17;2:588. doi: 10.1038/srep00588

Figure 3. Gas sensing properties.

Figure 3

(a), (b) Dynamic sensing transients of the dense-planar (a) and nanocolumnar WO3 thin film sensor (b) to 5 ppm NO2 with changing applied bias from 1 to 5 V. Measurements were carried out without external heating. (c) Sensing transients of the dense-planar and nanocolumnar WO3 thin film sensors to 1−5 ppm NO2 at an applied bias voltage of 5 V. (d) Response of the dense-planar and nanocolumnar WO3 thin film sensors as a function of gas concentration for various target gases. (e) Detection limits of the nanocolumnar WO3 thin film sensor to various gases. Ambient air quality standard (AAQS) levels of European Union (EU), United States (US), and Korea for NO2, SO2, and CO are presented for comparison. The averaging periods of AAQSs for NO2, SO2, and CO are 1 year, 1 hour, and 8 hours, respectively (see Supplementary Table S1 for details). (f) Change of response of nanocolumnar thin film sensor to 5 ppm NO2 for 48 days. Inset: response to 10 consecutive pulses of 5 ppm NO2 after 48 days of operation.