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Metal oxide nanostructures and their gas sensing properties: a review.

Sun YF, Liu SB, Meng FL, Liu JY, Jin Z, Kong LT, Liu JH - Sensors (Basel) (2012)

Bottom Line: When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them.Besides, doping is also an effective method to decrease particle size and improve gas sensing properties.The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Automotive Engineering, Anhui Polytechnic University, Wuhu 241000, China. sunyufeng118@126.com

ABSTRACT
Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

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(a) and (b) FESEM images of CuO-doped SnO2 hollow spheres, (c) and (d) TEM images of CuO-doped SnO2 hollow spheres. Reprinted with permission from [116]. Copyright (2009) Springer.
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f12-sensors-12-02610: (a) and (b) FESEM images of CuO-doped SnO2 hollow spheres, (c) and (d) TEM images of CuO-doped SnO2 hollow spheres. Reprinted with permission from [116]. Copyright (2009) Springer.

Mentions: If the doping is integrated into a high-sensitive nanostructure, the sensitivity will be further improved. Xue et al. have prepared n-type SnO2 nanorods uniformly coated with p-type CuO nanoparticles via a hydrothermal method which exhibited super-high sensitivity to H2S [113]. Besides, both the gold- or Pt-doped In2O3 nanowires have revealed higher sensitivity than the bare ones [114,115]. He et al. further improved the sensing properties to H2S of CuO-doped SnO2 material by replacing SnO2 nanorods with SnO2 hollow spheres. The CuO-doped SnO2 hollow spheres as shown in Figure 12 exhibited a ppb-leveled detection limit at a relatively low working temperature of 35 °C [116]. Besides, high selectivity was also acquired as shown in Figure 13, from which it can be seen that CuO-doped SnO2 hollow spheres could distinguish a small amount of (10 ppm) H2S among large amount of other gases including 1000 ppm of H2, NH3, ethanol and benzene.


Metal oxide nanostructures and their gas sensing properties: a review.

Sun YF, Liu SB, Meng FL, Liu JY, Jin Z, Kong LT, Liu JH - Sensors (Basel) (2012)

(a) and (b) FESEM images of CuO-doped SnO2 hollow spheres, (c) and (d) TEM images of CuO-doped SnO2 hollow spheres. Reprinted with permission from [116]. Copyright (2009) Springer.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376589&req=5

f12-sensors-12-02610: (a) and (b) FESEM images of CuO-doped SnO2 hollow spheres, (c) and (d) TEM images of CuO-doped SnO2 hollow spheres. Reprinted with permission from [116]. Copyright (2009) Springer.
Mentions: If the doping is integrated into a high-sensitive nanostructure, the sensitivity will be further improved. Xue et al. have prepared n-type SnO2 nanorods uniformly coated with p-type CuO nanoparticles via a hydrothermal method which exhibited super-high sensitivity to H2S [113]. Besides, both the gold- or Pt-doped In2O3 nanowires have revealed higher sensitivity than the bare ones [114,115]. He et al. further improved the sensing properties to H2S of CuO-doped SnO2 material by replacing SnO2 nanorods with SnO2 hollow spheres. The CuO-doped SnO2 hollow spheres as shown in Figure 12 exhibited a ppb-leveled detection limit at a relatively low working temperature of 35 °C [116]. Besides, high selectivity was also acquired as shown in Figure 13, from which it can be seen that CuO-doped SnO2 hollow spheres could distinguish a small amount of (10 ppm) H2S among large amount of other gases including 1000 ppm of H2, NH3, ethanol and benzene.

Bottom Line: When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them.Besides, doping is also an effective method to decrease particle size and improve gas sensing properties.The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Automotive Engineering, Anhui Polytechnic University, Wuhu 241000, China. sunyufeng118@126.com

ABSTRACT
Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

Show MeSH
Related in: MedlinePlus