Morphological Control of Metal Oxide for Semiconductor-Based Gas Sensor †
1
Faculty of Advanced Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan
2
Graduate School of Science and Technology, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555, Japan
3
Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
*
Author to whom correspondence should be addressed.
†
Presented at the 8th GOSPEL Workshop. Gas Sensors Based on Semiconducting Metal Oxides: Basic Understanding & Application Fields, Ferrara, Italy, 20–21 June 2019.
Proceedings 2019, 14(1), 7; https://doi.org/10.3390/proceedings2019014007
Published: 19 June 2019
(This article belongs to the Proceedings of The 8th GOSPEL Workshop. Gas Sensors Based on Semiconducting Metal Oxides: Basic Understanding & Application Fields)
Morphological control of metal oxide (MO) is important for enhancement of sensing properties such as sensor response and response-recovery characteristics. Our research group has been developed MO based gas sensors fabricated by WO3 and SnO2 nanocrystals synthesized by hydrothermal method for high sensor response to NO2 or H2 [1,2]. On the other hand, shuttle-shape SnO2 showed the sensor response to NO2 and H2S at room temperature.
The film sensor with cuboid-shape monoclinic WO3 nanocrystal (Figure 1a) showed sensor response (Rg/Ra) of 102–104 to 0.05–1 ppm NO2 at 200 °C (Figure 1c). In contrast, the sensor with hexagonal-shape hexagonal WO3 nanocrystal (Figure 1b) showed sensor response lower one order of magnitude than that with cuboid-shape monoclinic WO3 in above same detection condition (Figure 1d). This difference was related to surface states. XPS spectra of O1s showed that the content of OH- was larger for hexagonal-shape hexagonal WO3 (O2−/OH−/H2O (in %) = 60.0/38.1/1.9, in Figure 1e) than for cuboid-shape monoclinic WO3 (80.4/4.9/14.7, in Figure 1f). The results suggested that the high content of oxygen adsorbate (O2−) on the surface of WO3 could be contributed to higher sensor response.
References
- Meng, Z.; Fujii, A.; Hashishin, T.; Wada, N.; Sanada, T.; Tamaki, J.; Kojima, K.; Haneoka, H.; Suzuki, T. Morphological and crystal structural control of tungsten trioxide for highly sensitive NO2 gas sensors. J. Mater. Chem. C 2015, 3, 1134–1141. [Google Scholar] [CrossRef]
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Figure 1.
FE-SEM images of (a) cuboid-shape monoclinic WO3 nanocrystal and (b) hexagonal-shape hexagonal WO3 nanocrystal. Sensor response as a function of NO2 concentration for (c) cuboid-shape WO3 and (d) hexagonal-shape WO3. XPS spectra of O 1s on the surface of (e) as-prepared cuboid-shape WO3 and (f) hexagonal-shape WO3.
Figure 1.
FE-SEM images of (a) cuboid-shape monoclinic WO3 nanocrystal and (b) hexagonal-shape hexagonal WO3 nanocrystal. Sensor response as a function of NO2 concentration for (c) cuboid-shape WO3 and (d) hexagonal-shape WO3. XPS spectra of O 1s on the surface of (e) as-prepared cuboid-shape WO3 and (f) hexagonal-shape WO3.
Figure 2.
FE-SEM images of (a) SnO2 nanocubes annealed at 250 °C for 3 h and (b) commercial SnO2 nanoparticles calcined at 1100 °C. Response- recovery transients of (c) and (d) to respective gas mixture of 1000 ppm H2 and air.
Figure 2.
FE-SEM images of (a) SnO2 nanocubes annealed at 250 °C for 3 h and (b) commercial SnO2 nanoparticles calcined at 1100 °C. Response- recovery transients of (c) and (d) to respective gas mixture of 1000 ppm H2 and air.
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MDPI and ACS Style
Hashishin, T.; Sun, J.; Sato, K.; Kubota, H. Morphological Control of Metal Oxide for Semiconductor-Based Gas Sensor. Proceedings 2019, 14, 7. https://doi.org/10.3390/proceedings2019014007
AMA Style
Hashishin T, Sun J, Sato K, Kubota H. Morphological Control of Metal Oxide for Semiconductor-Based Gas Sensor. Proceedings. 2019; 14(1):7. https://doi.org/10.3390/proceedings2019014007
Chicago/Turabian StyleHashishin, Takeshi, Jian Sun, Kazuyoshi Sato, and Hiroshi Kubota. 2019. "Morphological Control of Metal Oxide for Semiconductor-Based Gas Sensor" Proceedings 14, no. 1: 7. https://doi.org/10.3390/proceedings2019014007
