Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review

Department of Mechanical and Automotive Engineering, Anhui Polytechnic University, Wuhu 241000, China.
Sensors (Impact Factor: 2.25). 12/2012; 12(3):2610-31. DOI: 10.3390/s120302610
Source: PubMed


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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    • "Over the past decades, the design and development of gas sensors with high sensing performance has been a research hotspot due to its profound influence on human health and environmental protection [1]. Thanks to the advances in nanotechnologies and synthetic methods, various kind of sensing materials, such as metal-oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials, have been developed and applied in gas sensors [2] [3] [4] [5]. Among them, the sensors based on metaloxide semiconductors have triggered great interest owing to their attractive characteristics such as low cost, high sensitivity, and controllable preparation [6] [7] [8]. "
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    Sensors and Actuators B Chemical 12/2015; 220. DOI:10.1016/j.snb.2015.05.038 · 4.10 Impact Factor
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    • "However, the morphology and structure of the sensing materials significantly influence their sensing performances, therefore various nanostructured metal oxides have been prepared to improve gas sensing properties [8] [9] [10] [11] [12]. In particular, ZnO based nanostructures such as nanowires [13] [14], nanorods [15] [16] [17], nanosheets [18] and nanospheres [19] have been used as gas sensing materials because of the excellent electronic and photonic properties of ZnO [20] [21] [22] [23] [24]. "
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    Sensors and Actuators B Chemical 11/2015; 219. DOI:10.1016/j.snb.2015.04.132 · 4.10 Impact Factor
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    • "HE investigation of metal oxide semiconductor (MOS) gas sensors is yet of a great relevance in the scientific and industrial community due to their cost effectiveness, efficiency, compatibility and portability [1]. Over decades both p and n type metal oxides such as SnO 2 , NiO, CuO, WO 3 , ZnO, TiO 2 Manuscript received July 7, 2014; accepted September 3, 2014. "
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    ABSTRACT: The optical and conductometric responses of sol-gel-based ZnO thin films with embedded 5% mol. Au or Pt nanoparticles (NPs) have been compared at different operating temperatures, to assess the effect of noble metal additions on to H 2 , CO and NO 2 gases sensors response. The scanning electron microscopy and X-ray diffraction techniques have been utilized for morphological characterization of the crystal structures of the films after annealing at 400 °C for 30 min and the effect of Au and Pt NPs additions on crystallite growth is discussed. Au NPs additions is effective to enhance the optical response to H 2 and CO at 390 nm and in the 500–700-nm wavelength range at 300-°C temperature. No optical response to NO 2 gas, even at low concentrations has been measured in the optical mode. The catalytic action of Pt NPs additions powerfully improves both the optical to H 2 and CO at 390 nm, and the conductometric gas responses. Detection limits as low as 20-ppb NO 2 and 50-ppm H 2 , in line with the best performances reported to the best of our knowledge in literature for ZnO-based sensors, have been measured in the conduction mode. Response times have been also compared, highlighting the positive effects played by Pt additions.
    IEEE Sensors Journal 02/2015; 15(2). DOI:10.1109/JSEN.2014.2356252 · 1.76 Impact Factor
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