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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) TEM images of the precursor nanowires, (b) HRTEM image taken on the single precursor nanowire, (c) TEM and (d) HRTEM image of highly porous CdO nanowires. Reprinted with permission from [80]. Copyright (2008) IOP Publishing Ltd.
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f7-sensors-12-02610: (a) TEM images of the precursor nanowires, (b) HRTEM image taken on the single precursor nanowire, (c) TEM and (d) HRTEM image of highly porous CdO nanowires. Reprinted with permission from [80]. Copyright (2008) IOP Publishing Ltd.

Mentions: Nanowires as a kind of important one-dimensional nanostructures have been used in many field [66,67]. Many kinds of semiconductor nanowires, such as SnO2 [68–70], In2O3 [71,72], ZnO [73–75], TiO2 [76,77] and so on, have been widely applied in gas sensors. However, smooth nanowires only adsorb gases at their surfaces which results in a great obstacle to achieve highly-sensitive properties. Porous nanowires have attracted great interests due to their high surface-to-volume ratio and porous structure which allows adsorbing gases not only on the surface but also throughout the bulk. Wang et al. [78,79] have prepared porous SnO2 nanowires based on glycolate precursors under mild conditions which showed good sensitivity to some gases such as C2H5OH, CO and H2. Guo et al. have prepared highly porous CdO nanowires as shown in Figure 7 by calcining the hydroxy- and carbonate-containing cadmium compound precursor nanowires [80]. The precursor converted into porous CdO nanowires, which were polycrystalline structure, through heat treatment in air without changing the wire-like topography. Due to the highly porous structure, the highly porous CdO nanowires showed rapid response, low detection limit, high signal-to-noise ratio and selectivity to nitrogen oxide which is one of the most dangerous air pollutants.


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) TEM images of the precursor nanowires, (b) HRTEM image taken on the single precursor nanowire, (c) TEM and (d) HRTEM image of highly porous CdO nanowires. Reprinted with permission from [80]. Copyright (2008) IOP Publishing Ltd.
© Copyright Policy
Related In: Results  -  Collection

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

f7-sensors-12-02610: (a) TEM images of the precursor nanowires, (b) HRTEM image taken on the single precursor nanowire, (c) TEM and (d) HRTEM image of highly porous CdO nanowires. Reprinted with permission from [80]. Copyright (2008) IOP Publishing Ltd.
Mentions: Nanowires as a kind of important one-dimensional nanostructures have been used in many field [66,67]. Many kinds of semiconductor nanowires, such as SnO2 [68–70], In2O3 [71,72], ZnO [73–75], TiO2 [76,77] and so on, have been widely applied in gas sensors. However, smooth nanowires only adsorb gases at their surfaces which results in a great obstacle to achieve highly-sensitive properties. Porous nanowires have attracted great interests due to their high surface-to-volume ratio and porous structure which allows adsorbing gases not only on the surface but also throughout the bulk. Wang et al. [78,79] have prepared porous SnO2 nanowires based on glycolate precursors under mild conditions which showed good sensitivity to some gases such as C2H5OH, CO and H2. Guo et al. have prepared highly porous CdO nanowires as shown in Figure 7 by calcining the hydroxy- and carbonate-containing cadmium compound precursor nanowires [80]. The precursor converted into porous CdO nanowires, which were polycrystalline structure, through heat treatment in air without changing the wire-like topography. Due to the highly porous structure, the highly porous CdO nanowires showed rapid response, low detection limit, high signal-to-noise ratio and selectivity to nitrogen oxide which is one of the most dangerous air pollutants.

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