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In recent years, gas sensors have received considerable atten- tion driven by its practical applications in highly volatile and toxic gases detection. Among different sensor types, metal oxide semi- conductor (MOSs) gas sensors are the most popular type as it is more practical and market-oriented. A series of promising metal oxide, such as SnO2 , In2 O3 , ZnO, TiO2 , Fe2 O3 [6–10], and so on, has been used as sensing materials of gas sensors. They can test the toxic gases of ambient atmosphere through changes in the resistance of metal oxide. However, the gas response of single metal oxide is low. Recent researches to improve semiconductor oxide-based gas sensors are mainly based on two ways [11]. The first is doping rare metal oxides (PdO, NiO, CdO, etc. [12–14]) or noble metals (Au, Ag, Pt, Pd, etc. [15–18]). The second is to pre- pare composite sensing materials, such as binary or ternary metal oxides and organic-inorganic materials. For example, SnO2/ZnOcomposite nanofibers were synthesized recently by Khorami and co-workers, who reported highly sensitive toward ethanol [19]. It also has been reported that the response of SnO2-In2O3-CdO compounds toward 300ppm formaldehyde can reach 559 [20]. However, among them, there have been few researches devoting themselves to fabricate methanol gas sensors. Li’s research group synthesized ZnO/SnO2 complex nanostructures using a simple glucose-assisted hydrothermal method. The as-fabricated sensor toward 100 ppm of methanol was 9.6 [11]. Wang et al. reported the synthesis of SnO2 inverse opal with sol-gel method and the response of the SnO2 inverse opal sensor was as high as 95 for 500ppm methanol gas detection [21]. It should be mentioned that Han et al. also successfully prepared Ce-doped In2O3 porous nanospheres and showed excellent sensing performance toward methanol [22]. Although methanol gas sensors have been investi- gated by few groups, the gas responses of these gas sensors are too poor to meet the standard required. Furthermore, the sensors with high gas response to methanol have aroused tremendous interest on account of their highlighted roles in the areas of public safety and environmental monitoring.
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